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TDMS Study 05185-04 Pathology Tables

NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02




       Facility:  I. I. T. Research Institute

       Chemical CAS #:  542-56-3

       Lock Date:  08/20/92

       Cage Range:  All

       Reasons For Removal:    All

       Removal Date Range:     All

       Treatment Groups:       Include All






































                                                              Page   1

NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 6| 5| 7| 6| 7| 0| 7| 6| 5| 7| 7|             
                             DAY ON TEST   | 3| 0| 2| 7| 3| 2| 3| 8| 2| 2| 2| 3| 3| 9| 9| 8| 3| 1| 2| 7| 3| 9| 8| 2| 2|             
                                           | 1| 9| 9| 2| 1| 9| 0| 9| 9| 9| 9| 1| 1| 0| 1| 5| 1| 3| 9| 1| 0| 1| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  A  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  A  +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  A  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  A  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |                                                                          |             
      Cytologic Alterations                |                                           3                              |             
      Eosinophilic Focus                   |                                                                          |             
      Fatty Change, Diffuse                |                               1                                          |             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Inflammation, Chronic                | 1                             1                                          |             
      Inflammation, Chronic Active         |       1                                               1                  |             
      Mixed Cell Focus                     |                   X                 X                                    |             
      Necrosis                             |                                                                          |             
      Fat, Necrosis                        |                                                             1            |             
      Hepatocyte, Necrosis                 |                                                             2            |             
      Periportal, Fatty Change             |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                                 +                 +     +|             
      Artery, Inflammation, Chronic        |                                                                          |             
      Fat, Necrosis                        |                                                 3                       3|             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                                                                         2|             
      Acinus, Atrophy                      |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 2     1  1  1  1  1  1        1  1  1  1  2  1  1     1     2  2  1  2  2|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular                |                                                                          |             
      Inflammation, Chronic                |                                                             1            |             
      Thrombosis                           |    1                                                                     |             
      Artery, Inflammation, Chronic        |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcapsular, Hyperplasia             | 3  2  2  1  3  2  3  2  3  2     2  1  2  2  2  2  2  2     2  2  1  2  2|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page   2                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 6| 5| 7| 6| 7| 0| 7| 6| 5| 7| 7|             
                             DAY ON TEST   | 3| 0| 2| 7| 3| 2| 3| 8| 2| 2| 2| 3| 3| 9| 9| 8| 3| 1| 2| 7| 3| 9| 8| 2| 2|             
                                           | 1| 9| 9| 2| 1| 9| 0| 9| 9| 9| 9| 1| 1| 0| 1| 5| 1| 3| 9| 1| 0| 1| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                  +                                       |             
      Hyperplasia, Focal                   |                                  2                                       |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  +  M  +  M  M  +  +  M  +  +  M  +  M  M  M  M  +  M  +  M  +  +  M  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  M|             
      Pars Distalis, Angiectasis           |                                                                          |             
      Pars Distalis, Cyst                  |                                  2                                       |             
      Pars Distalis, Hemorrhage            |                                                                          |             
      Pars Distalis, Hyperplasia           |                            2     3  1                       2  2         |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicle, Cyst                       |                                                             4            |             
      Follicular Cell, Hyperplasia, Diffuse|                                                                          |             
      Follicular Cell, Hyperplasia, Focal  |       4                       2                                          |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +|             
      Cyst                                 |                2                                      4              3   |             
      Infiltration Cellular, Lymphocyte    |                                                                          |             
      Interstitium, Hyperplasia            |                                                                          |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                3        2|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Cystic                  | 2  3  2  1  1  1  3     3  2  1  2  3     3  2  2  1  3     2  3  2      |             
                                            __________________________________________________________________________|             
   Vagina                                  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Degeneration, Fatty                  |    2                                                                     |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                      +                    +        +                     |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  +  +  M  +  +  M  M  +  +  M  +  +  M  M  M  +  +  +  +  M  M  +  M  M|             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                         2                                                |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |                         2                                                |             
      Hemorrhage                           |                                                                          |             
      Inflammation, Chronic Active         |                                                             2            |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                                                             3        2   |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page   3                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 6| 5| 7| 6| 7| 0| 7| 6| 5| 7| 7|             
                             DAY ON TEST   | 3| 0| 2| 7| 3| 2| 3| 8| 2| 2| 2| 3| 3| 9| 9| 8| 3| 1| 2| 7| 3| 9| 8| 2| 2|             
                                           | 1| 9| 9| 2| 1| 9| 0| 9| 9| 9| 9| 1| 1| 0| 1| 5| 1| 3| 9| 1| 0| 1| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Fibrosis                             |                                        2                                 |             
      Hematopoietic Cell Proliferation     | 1     1  2  1  1  1     1  3  1  1  2  1  2  1  1     1  1  1  1     1  1|             
      Hyperplasia, Lymphoid                |                         2     2                                      3   |             
      Pigmentation, Hemosiderin            | 1  1  1  1  1  1  1     1  1  1  1  1  1  1  1  1     1  1  1  1     1  1|             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  +  +|             
      Atrophy                              |                                        2  4  1           3        3      |             
      Hyperplasia, Lymphoid                |                                        2                                 |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                         1                                            1   |             
      Epithelium, Hyperplasia              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dysplasia                            | 2  3  1        4        2  1     3           3        1     1  2     1   |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Compression                          |                                                                          |             
      Mineralization                       | 2  2     2  2  1  1     1  2  3  1  1  1  3  1     2  1     2  2  2  2  2|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    | 1     1                          1                          1  1         |             
      Inflammation, Chronic Active         |                                                             1            |             
      Leukocytosis                         |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate                              |                                                                          |             
      Exudate, Serous                      |                                                                          |             
      Inflammation, Chronic Active         |                         1              2                                 |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                1                                1              1         |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         | 1  1                    1     1                 1                    1   |             
      Respiratory Epithelium, Hyperplasia  | 1                                            1                           |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |                                        1                                 |             
      Respiratory Epithelium, Ulcer        |                                        1                                 |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page   4                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 6| 5| 7| 6| 7| 0| 7| 6| 5| 7| 7|             
                             DAY ON TEST   | 3| 0| 2| 7| 3| 2| 3| 8| 2| 2| 2| 3| 3| 9| 9| 8| 3| 1| 2| 7| 3| 9| 8| 2| 2|             
                                           | 1| 9| 9| 2| 1| 9| 0| 9| 9| 9| 9| 1| 1| 0| 1| 5| 1| 3| 9| 1| 0| 1| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Amyloid Deposition                   |                                                                          |             
      Cyst                                 |                                                                          |             
      Hydronephrosis                       |                                                                          |             
      Infiltration Cellular, Lymphocyte    | 2        1  1  1  1           3  1           1  1           2  1         |             
      Renal Tubule, Degeneration, Hyaline  |                                                                          |             
      Renal Tubule, Dilatation             |                                                                          |             
      Renal Tubule, Hyperplasia, Focal     |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    | 2     1     1  1  1              3  1  1     1  1           2     1  2  1|             
 _____________________________________________________________________________________________________________________|             
                                                             Page   5                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 7| 7| 6| 6| 7|             
                             DAY ON TEST   | 3| 3| 2| 3| 7| 0| 2| 3| 3| 3| 2| 3| 3| 3| 3| 2| 3| 9| 3| 4| 2| 3| 9| 4| 3|             
                                           | 0| 1| 9| 8| 6| 9| 9| 0| 0| 5| 9| 0| 0| 0| 1| 9| 1| 5| 0| 9| 9| 0| 6| 3| 1|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    CONTROL                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  A  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  A  +  +  +  A  +  +  +  +  +  +  +  M  +  +  +  +  A  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  +  A  A  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |                                     X                       X            |             
      Cytologic Alterations                |                                              3                           |             
      Eosinophilic Focus                   |       X                                                                  |             
      Fatty Change, Diffuse                |                                                                          |             
      Hematopoietic Cell Proliferation     |                1                                                         |             
      Inflammation, Chronic                | 1  1                 1        1  1           1  2     1        1         |             
      Inflammation, Chronic Active         |                                                                          |             
      Mixed Cell Focus                     |                                     X                                    |             
      Necrosis                             |                                                 2                        |             
      Fat, Necrosis                        |                                                                          |             
      Hepatocyte, Necrosis                 |                                                                          |             
      Periportal, Fatty Change             |                                     2                                    |             
                                            __________________________________________________________________________|             
   Mesentery                               |                   +     +                       +  +                     |             
      Artery, Inflammation, Chronic        |                                                    3                     |             
      Fat, Necrosis                        |                   2     3                       3                        |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                                     2                          3        2|             
      Acinus, Atrophy                      |                                                                4         |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 2  2  1  1  1  2     2  1  1  1  2  3  3  1  2  2  1  1  2  2  2  1  1  2|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular                |             2                                                            |             
      Inflammation, Chronic                |                                                                          |             
      Thrombosis                           |                                                                          |             
      Artery, Inflammation, Chronic        |                                                    1                     |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcapsular, Hyperplasia             | 2  2  2  1  2  2  2  2  2  1  2  3  2  2  2  2  2  2  2     2  2  1  4  2|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  M  +        +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page   6                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 7| 7| 6| 6| 7|             
                             DAY ON TEST   | 3| 3| 2| 3| 7| 0| 2| 3| 3| 3| 2| 3| 3| 3| 3| 2| 3| 9| 3| 4| 2| 3| 9| 4| 3|             
                                           | 0| 1| 9| 8| 6| 9| 9| 0| 0| 5| 9| 0| 0| 0| 1| 9| 1| 5| 0| 9| 9| 0| 6| 3| 1|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    CONTROL                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                 +                        |             
      Hyperplasia, Focal                   |                                                 3                        |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  M  M  M  M  +  +  +  M  M  +  M  +  +  M  M  M  M  M  +  M  +  M  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
      Pars Distalis, Angiectasis           |                2                                                         |             
      Pars Distalis, Cyst                  |                                                                          |             
      Pars Distalis, Hemorrhage            |                                     2                                    |             
      Pars Distalis, Hyperplasia           | 1  4                    1     2     2                                    |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicle, Cyst                       |                                                                          |             
      Follicular Cell, Hyperplasia, Diffuse|                            4                                             |             
      Follicular Cell, Hyperplasia, Focal  |    2              2                                            2         |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +|             
      Cyst                                 | 3  4     2              2        3                                       |             
      Infiltration Cellular, Lymphocyte    |                                     2                                    |             
      Interstitium, Hyperplasia            |                   3                                                      |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Cystic                  | 2  3  3  1  3        2     3  4  4  3  2  4     2  1  3  1  3  1  2     1|             
                                            __________________________________________________________________________|             
   Vagina                                  |                                                                      +   |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Degeneration, Fatty                  |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                                                      +   |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  M  +  M  M  M  +  +  +  M  +  M  M  M  M  M  M  M  M  M  M  M  M  M  M|             
      Hyperplasia, Lymphoid                | 2                                                                        |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  M  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                                  2                                       |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Hemorrhage                           |                3                                                         |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |    2                             2  3                          2         |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page   7                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 7| 7| 6| 6| 7|             
                             DAY ON TEST   | 3| 3| 2| 3| 7| 0| 2| 3| 3| 3| 2| 3| 3| 3| 3| 2| 3| 9| 3| 4| 2| 3| 9| 4| 3|             
                                           | 0| 1| 9| 8| 6| 9| 9| 0| 0| 5| 9| 0| 0| 0| 1| 9| 1| 5| 0| 9| 9| 0| 6| 3| 1|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    CONTROL                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Fibrosis                             |                                                                          |             
      Hematopoietic Cell Proliferation     | 1  1  1  1  3  4  1  1  1  1        1  1  1  1  1  4  1  1  1  1  1  3  1|             
      Hyperplasia, Lymphoid                | 3  2                             2                                       |             
      Pigmentation, Hemosiderin            | 1  1  1  1     1  1  1  1  2  1  1  1  1  1  1  1     1  1  1  1  1     1|             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
      Atrophy                              |          3  2  4           3                                      3  3   |             
      Hyperplasia, Lymphoid                | 3                                                           2           2|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                            2                 2                           |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                   1  1        1  1                                       |             
      Epithelium, Hyperplasia              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dysplasia                            |          1        1  1           1  1  2        1                 1  1  1|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Compression                          |                            4                                             |             
      Mineralization                       | 2  2  2  2     2  1  2  2     2     1  2  2        1     2  1  2  3  2   |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    | 2  1  1        1  1  1  1     1  1  1  1  1  1  1     1  1  1  2        1|             
      Inflammation, Chronic Active         |          2                                                           1   |             
      Leukocytosis                         |             2                                                            |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate                              |                                  2                                       |             
      Exudate, Serous                      |                   1                                                      |             
      Inflammation, Chronic Active         |                               1     1                       1        1   |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                                                                          |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |                1  1  1        1     1     1  1     1  1     1            |             
      Respiratory Epithelium, Hyperplasia  |       1              1                    1                       1      |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |                               1     2                                1   |             
      Respiratory Epithelium, Ulcer        |                               1     2                                    |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page   8                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 7| 7| 6| 6| 7|             
                             DAY ON TEST   | 3| 3| 2| 3| 7| 0| 2| 3| 3| 3| 2| 3| 3| 3| 3| 2| 3| 9| 3| 4| 2| 3| 9| 4| 3|             
                                           | 0| 1| 9| 8| 6| 9| 9| 0| 0| 5| 9| 0| 0| 0| 1| 9| 1| 5| 0| 9| 9| 0| 6| 3| 1|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    CONTROL                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Amyloid Deposition                   |          4                                                               |             
      Cyst                                 | 2                                                                        |             
      Hydronephrosis                       |                                                                      2   |             
      Infiltration Cellular, Lymphocyte    | 1  3  1  2     1  1  1  1        1  1     1  1  1     2  1  1  1  1     1|             
      Renal Tubule, Degeneration, Hyaline  |             2                                                            |             
      Renal Tubule, Dilatation             |          3                                                        3      |             
      Renal Tubule, Hyperplasia, Focal     |                                                 1                        |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  A  +  +|             
      Infiltration Cellular, Lymphocyte    | 2  1  1  1     1  1  1     1  2  1  2  2  2  1  2     2     1           1|             
 _____________________________________________________________________________________________________________________|             
                                                             Page   9                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 0| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 9| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 1| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|                                            |      A     |
    CONTROL                                | 1| 1| 1| 1| 1| 1| 1| 1| 1| 2|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  A  +  +  +  +  +                                             |  55        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +                                             |  57        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +                                             |  57        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  A  +  +  +  +  +                                             |  51        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  A  +  +  +  +  +                                             |  53        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +                                             |  53        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Basophilic Focus                     |                                                                          |      2     |
      Cytologic Alterations                |                                                                          |      2  3.0|
      Eosinophilic Focus                   |                                                                          |      1     |
      Fatty Change, Diffuse                |                                                                          |      1  1.0|
      Hematopoietic Cell Proliferation     |                                                                          |      1  1.0|
      Inflammation, Chronic                |                                                                          |     11  1.1|
      Inflammation, Chronic Active         |                                                                          |      2  1.0|
      Mixed Cell Focus                     |                                                                          |      3     |
      Necrosis                             |                                                                          |      1  2.0|
      Fat, Necrosis                        |                                                                          |      1  1.0|
      Hepatocyte, Necrosis                 |                                                                          |      1  2.0|
      Periportal, Fatty Change             |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   7        |
      Artery, Inflammation, Chronic        |                                                                          |      1  3.0|
      Fat, Necrosis                        |                                                                          |      5  2.8|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                |                                                                          |      4  2.3|
      Acinus, Atrophy                      |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                | 1        2        1  1     1                                             |     49  1.4|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Tooth                                   |             +                                                            |   1        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Infiltration Cellular                |                                                                          |      1  2.0|
      Inflammation, Chronic                |                                                                          |      1  1.0|
      Thrombosis                           |                                                                          |      1  1.0|
      Artery, Inflammation, Chronic        |                                                                          |      1  1.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  10                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 0| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 9| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 1| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|                                            |      A     |
    CONTROL                                | 1| 1| 1| 1| 1| 1| 1| 1| 1| 2|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Subcapsular, Hyperplasia             | 1  1  1  1     1  1  1  2  1                                             |     56  1.9|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +     +  +  +                                             |  55        |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   2        |
      Hyperplasia, Focal                   |                                                                          |      2  2.5|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  M  +  +  +  +  +  M  +                                             |  28        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  M  +  +                                             |  56        |
      Pars Distalis, Angiectasis           |                                                                          |      1  2.0|
      Pars Distalis, Cyst                  |                                                                          |      1  2.0|
      Pars Distalis, Hemorrhage            |                                                                          |      1  2.0|
      Pars Distalis, Hyperplasia           |                                                                          |     10  2.0|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Follicle, Cyst                       |                                                                          |      1  4.0|
      Follicular Cell, Hyperplasia, Diffuse|                                                                          |      1  4.0|
      Follicular Cell, Hyperplasia, Focal  |                                                                          |      5  2.4|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Cyst                                 | 3        1                                                               |     10  2.7|
      Infiltration Cellular, Lymphocyte    |                                                                          |      1  2.0|
      Interstitium, Hyperplasia            |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Angiectasis                          |                                                                          |      2  2.5|
      Hemorrhage                           |                   2                                                      |      1  2.0|
      Hyperplasia, Cystic                  | 1  3  2  1     1  2  1  1  1                                             |     49  2.1|
                                            __________________________________________________________________________|____________|
   Vagina                                  |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Degeneration, Fatty                  |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   4        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  M  +                                             |  28        |
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +                                             |  58        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  11                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 0| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 9| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 1| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|                                            |      A     |
    CONTROL                                | 1| 1| 1| 1| 1| 1| 1| 1| 1| 2|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
      Hyperplasia, Lymphoid                |                                                                          |      2  2.0|
      Inflammation, Chronic Active         |             3                                                            |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Hematopoietic Cell Proliferation     |                                                                          |      1  2.0|
      Hemorrhage                           |                                                                          |      1  3.0|
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Hyperplasia, Lymphoid                |                                                                          |      6  2.3|
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Atrophy                              |             3                                                            |      1  3.0|
      Fibrosis                             |                                                                          |      1  2.0|
      Hematopoietic Cell Proliferation     | 1  1  1  1  1  1  1  1  1  1                                             |     54  1.3|
      Hyperplasia, Lymphoid                |                                                                          |      6  2.3|
      Pigmentation, Hemosiderin            | 1  1  1  1  1  1  1  1  1  1                                             |     54  1.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  M  +  +  +  +  +                                             |  56        |
      Atrophy                              |                                                                          |     11  2.8|
      Hyperplasia, Lymphoid                |                         3                                                |      5  2.4|
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Hyperplasia                          |                                                                          |      2  2.0|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                |                                                                          |      6  1.0|
      Epithelium, Hyperplasia              |                   1                                                      |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Dysplasia                            |    2                       1                                             |     24  1.6|
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  M  +  +  +  +  +                                             |  59        |
      Compression                          |                                                                          |      1  4.0|
      Mineralization                       |       1        1  1  1  1  2                                             |     45  1.7|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Infiltration Cellular, Lymphocyte    | 1        1              1  1                                             |     28  1.1|
      Inflammation, Chronic Active         |                                                                          |      3  1.3|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  12                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 0| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 9| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 1| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|                                            |      A     |
    CONTROL                                | 1| 1| 1| 1| 1| 1| 1| 1| 1| 2|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
      Leukocytosis                         |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Exudate                              |                                                                          |      1  2.0|
      Exudate, Serous                      |                                                                          |      1  1.0|
      Inflammation, Chronic Active         |                                                                          |      6  1.2|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |          1                                                               |      4  1.0|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |          1        1        1                                             |     19  1.0|
      Respiratory Epithelium, Hyperplasia  |                                                                          |      6  1.0|
      Respiratory Epithelium, Metaplasia,  |                                                                          |            |
           Squamous                        |                                                                          |      4  1.3|
      Respiratory Epithelium, Ulcer        |                                                                          |      3  1.3|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Amyloid Deposition                   |                                                                          |      1  4.0|
      Cyst                                 |                                                                          |      1  2.0|
      Hydronephrosis                       |                                                                          |      1  2.0|
      Infiltration Cellular, Lymphocyte    | 1  1     1     1        1                                                |     35  1.2|
      Renal Tubule, Degeneration, Hyaline  |                                                                          |      1  2.0|
      Renal Tubule, Dilatation             |                                                                          |      2  3.0|
      Renal Tubule, Hyperplasia, Focal     |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Infiltration Cellular, Lymphocyte    |          1     1  1  1  1  2                                             |     38  1.3|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  13                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 2| 9| 3| 3| 3| 3| 2| 2| 3| 2| 2| 3| 0| 2| 3| 3| 1| 4| 2| 3| 2| 3| 3| 3|             
                                           | 1| 9| 7| 0| 1| 1| 1| 9| 0| 1| 9| 8| 0| 7| 9| 0| 0| 4| 5| 9| 1| 9| 0| 1| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 8| 8| 8| 8| 8| 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  M|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Ectopic Tissue                       |                                                                          |             
      Proliferation Connective Tissue      |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                                                                          |             
      Proliferation Connective Tissue      |                                                                          |             
      Serosa, Inflammation, Chronic Active |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Clear Cell Focus                     |                                                 X                        |             
      Cytologic Alterations                |                                                                          |             
      Eosinophilic Focus                   |                X                                                         |             
      Hematopoietic Cell Proliferation     |                            1                                             |             
      Inflammation, Chronic                |       1  1                    1     1              1                     |             
      Inflammation, Chronic Active         |                                                                          |             
      Mitotic Alteration                   |                                     1                                    |             
      Mixed Cell Focus                     |                   X                                                      |             
      Necrosis                             |                            1                                             |             
      Proliferation Connective Tissue      |                                                                          |             
      Hepatocyte, Necrosis                 |                            1                                             |             
      Periportal, Hypertrophy              |                                     2                                    |             
                                            __________________________________________________________________________|             
   Mesentery                               | +     +              +                                                   |             
      Cyst                                 |       4                                                                  |             
      Proliferation Connective Tissue      |       X                                                                  |             
      Fat, Necrosis                        | 2     2              3                                                   |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             |                               4                                          |             
      Inflammation, Chronic Active         |                               4                                          |             
      Acinus, Atrophy                      |                               3                                          |             
      Duct, Dilatation                     |    3                                                                     |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 1  2     2  2  1     1  1  1  2  1  1  1  1  2  1        1  2  1     2  2|             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Proliferation Connective Tissue      |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Proliferation Connective Tissue      |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  14                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 2| 9| 3| 3| 3| 3| 2| 2| 3| 2| 2| 3| 0| 2| 3| 3| 1| 4| 2| 3| 2| 3| 3| 3|             
                                           | 1| 9| 7| 0| 1| 1| 1| 9| 0| 1| 9| 8| 0| 7| 9| 0| 0| 4| 5| 9| 1| 9| 0| 1| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 8| 8| 8| 8| 8| 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic        |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Focal                   |                      1                                                   |             
      Hypertrophy, Focal                   |                                                    1                     |             
      Subcapsular, Hyperplasia             | 2  2  2  3  2  2  1  1  2  2  2  3  2  2  3  2  2  2     2  1  2  1  2  2|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +  +  +|             
      Hyperplasia, Focal                   |                                                          2               |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                                          |             
      Hyperplasia, Focal                   |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  M  M  +  M  M  M  +  M  +  +  +  +  M  +  +  M  M  M  +  M  +  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +|             
      Pars Distalis, Cyst                  |                                                                          |             
      Pars Distalis, Hyperplasia, Focal    |                                                                          |             
      Pars Distalis, Hyperplasia           | 3              2              2           2  3           2               |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |                                                                          |             
      Follicle, Cyst                       |             2                                      3              2      |             
      Follicular Cell, Hyperplasia, Focal  |                      2     2                    1                 1  3   |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          |                                                                          |             
      Dilatation                           |                                                                          |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                   3           4     3                    4     4     2   |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |    4                                                                     |             
      Hyperplasia, Cystic                  | 2     3     1  4  2  3     1  1  3  1  2  1  2  2  1  1  4  1            |             
      Hyperplasia                          |       4                                                                  |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |          2                                                               |             
      Myeloid Cell, Hyperplasia            |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node                              |    +  +                 +                       +                        |             
      Hyperplasia, Lymphoid                |    3                                                                     |             
      Pigmentation                         |                                                                          |             
      Iliac, Hyperplasia, Lymphoid         |       2                                                                  |             
      Pancreatic, Hyperplasia, Lymphoid    |                                                 4                        |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  15                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 2| 9| 3| 3| 3| 3| 2| 2| 3| 2| 2| 3| 0| 2| 3| 3| 1| 4| 2| 3| 2| 3| 3| 3|             
                                           | 1| 9| 7| 0| 1| 1| 1| 9| 0| 1| 9| 8| 0| 7| 9| 0| 0| 4| 5| 9| 1| 9| 0| 1| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 8| 8| 8| 8| 8| 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  M  +  +  +  +  +  +  +  +  +  M  M  +  +  M  M  M  M  +  M  +  M  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |    2                          4              2                           |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  M  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  M  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                                                                          |             
      Hyperplasia, Plasma Cell             |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | M  +  +  M  +  +  +  +  +  +  +  +  +  +  M  M  +  +  +  +  +  +  M  +  +|             
      Hyperplasia, Lymphoid                |       2                       2                    2                     |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Hematopoietic Cell Proliferation     | 3  1  1     1  1  1  1     3        1  2  1  1  1  2     1        2  1  1|             
      Hyperplasia, Lymphoid                |    2  1                                                           2      |             
      Pigmentation, Hemosiderin            | 1  1  1     1  1  1  1        1     1  1  1  1  1  1     1  1     1  2  1|             
      Proliferation Connective Tissue      |       X                                                                  |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                       2                  |             
      Hyperplasia, Lymphoid                |                      2     2  3                                         1|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                      2   |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                     1     1              3               |             
      Ulcer                                |                                                                          |             
      Epithelium, Hyperplasia              |                                              1                           |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Developmental Malformation           |                                                                          |             
      Dysplasia                            |    2  1                          1                 2  1  2        1     4|             
      Hyperostosis                         |                                                                          |             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                    +                     |             
      Proliferation Connective Tissue      |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Compression                          |                                                                      2   |             
      Mineralization                       | 2  1  2           1  3                 1                 2  2  1  3     2|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  16                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 2| 9| 3| 3| 3| 3| 2| 2| 3| 2| 2| 3| 0| 2| 3| 3| 1| 4| 2| 3| 2| 3| 3| 3|             
                                           | 1| 9| 7| 0| 1| 1| 1| 9| 0| 1| 9| 8| 0| 7| 9| 0| 0| 4| 5| 9| 1| 9| 0| 1| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 8| 8| 8| 8| 8| 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |             1  1                 1  1  1     1                           |             
      Inflammation, Chronic Active         |                                                                          |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |                      4                       4                           |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |                               2                                          |             
      Artery, Inflammation, Chronic        |                                                                      3   |             
      Fat, Mediastinum, Necrosis           |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate, Serous                      |                                                                          |             
      Inflammation, Chronic Active         | 1        1     1           1                    2                 2      |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                            1                    1                        |             
      Olfactory Epithelium, Metaplasia     |                            1  1  1                          1            |             
      Olfactory Epithelium, Metaplasia,    |                                                                          |             
           Squamous                        |          1                                                               |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |          2        1  1     1        1  1     1     1     1               |             
      Respiratory Epithelium, Hyperplasia  |                   1     1                                                |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        | 1                                               2                 2      |             
      Respiratory Epithelium, Ulcer        |                            1                    1                 1      |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |       +                                                                  |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    | 1  3  1           1        1        2  1     1                       1   |             
      Nephropathy                          |                            1                                             |             
      Renal Tubule, Dilatation             |                                                                      2   |             
      Renal Tubule, Pigmentation           |                                                                1         |             
      Renal Tubule, Regeneration           |                                                          2               |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                                  3                                       |             
      Infiltration Cellular, Lymphocyte    | 1  1     1     1  1  1     1     1     1  1        2     1  2  1     1  1|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  17                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 2| 2| 3| 2| 2| 3| 3| 2| 3| 8| 1| 2| 3| 3| 3| 3| 2| 2| 3| 2| 2| 2|             
                                           | 9| 9| 0| 9| 9| 1| 9| 9| 1| 0| 9| 0| 6| 2| 9| 0| 0| 0| 1| 9| 9| 0| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Ectopic Tissue                       |    X                                                                     |             
      Proliferation Connective Tissue      |    X                                                                     |             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                                                       3                  |             
      Proliferation Connective Tissue      |    X                                                                     |             
      Serosa, Inflammation, Chronic Active |    3                                                                     |             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Clear Cell Focus                     |                                                                          |             
      Cytologic Alterations                |             2                                                            |             
      Eosinophilic Focus                   |                               X                                          |             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Inflammation, Chronic                |          1                                      1                        |             
      Inflammation, Chronic Active         |                                                       2           2      |             
      Mitotic Alteration                   |                                                                          |             
      Mixed Cell Focus                     |                                                                          |             
      Necrosis                             |                   1                                                      |             
      Proliferation Connective Tissue      |    X                                                                     |             
      Hepatocyte, Necrosis                 |                                                                          |             
      Periportal, Hypertrophy              |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                  +                                       |             
      Cyst                                 |                                                                          |             
      Proliferation Connective Tissue      |                                                                          |             
      Fat, Necrosis                        |                                  2                                       |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
      Acinus, Atrophy                      |                            3                                             |             
      Duct, Dilatation                     |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |    2  2  1     1  1     1  1  1  1  1     1  2     2  1  2  3  1  1  1  1|             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Proliferation Connective Tissue      |    X                                                                     |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Proliferation Connective Tissue      |    X                                                                     |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  18                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 2| 2| 3| 2| 2| 3| 3| 2| 3| 8| 1| 2| 3| 3| 3| 3| 2| 2| 3| 2| 2| 2|             
                                           | 9| 9| 0| 9| 9| 1| 9| 9| 1| 0| 9| 0| 6| 2| 9| 0| 0| 0| 1| 9| 9| 0| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic        |                                                 4                        |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Focal                   |                                                       2                  |             
      Hypertrophy, Focal                   |                                                                          |             
      Subcapsular, Hyperplasia             | 2  2  2  1  2  3  2  1  1  3  3  2  1  1  2  2     1  1  3  1  2  1  2   |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +     +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Focal                   |                2                                                         |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                          +        +      |             
      Hyperplasia, Focal                   |                                                                   2      |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  +  M  +  M  +  +  +  +  +  +  +  M  M  +  M  M  +  +  +  M  M  M  M  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  I  +  +  +  +  +  +  +|             
      Pars Distalis, Cyst                  |                                                                         1|             
      Pars Distalis, Hyperplasia, Focal    |       2                                                                  |             
      Pars Distalis, Hyperplasia           | 3        2  2                       1           2              2         |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |                                  1                                       |             
      Follicle, Cyst                       |       4                                      2                           |             
      Follicular Cell, Hyperplasia, Focal  |                   2     3  1     3                                       |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          |                                                                   +      |             
      Dilatation                           |                                                                   3      |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |    4  3                 3     4  2  4  4                       3         |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                                                                          |             
      Hyperplasia, Cystic                  | 3  3  2  2  3  2  1  1  1  1  2     2  2  2  1  2  2  1  1  1  2  3  3  4|             
      Hyperplasia                          |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                          |             
      Myeloid Cell, Hyperplasia            |                                     4                                    |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                     +                                    |             
      Hyperplasia, Lymphoid                |                                                                          |             
      Pigmentation                         |                                     3                                    |             
      Iliac, Hyperplasia, Lymphoid         |                                                                          |             
      Pancreatic, Hyperplasia, Lymphoid    |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  19                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 2| 2| 3| 2| 2| 3| 3| 2| 3| 8| 1| 2| 3| 3| 3| 3| 2| 2| 3| 2| 2| 2|             
                                           | 9| 9| 0| 9| 9| 1| 9| 9| 1| 0| 9| 0| 6| 2| 9| 0| 0| 0| 1| 9| 9| 0| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  +  +  +  M  M  +  M  +  M  +  +  M  +  +  +  M  M|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |    4                                                                     |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                                                       2                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                                                                   2      |             
      Hyperplasia, Plasma Cell             |                                                       2                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                      2                                                   |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                2         |             
      Hematopoietic Cell Proliferation     | 1  1  1  1  1  1  2  1  1  1  1  1  3  1  2  3     1  1     1  1     1  1|             
      Hyperplasia, Lymphoid                |    3                                                        2     4  2   |             
      Pigmentation, Hemosiderin            | 1  1  1  1  1  1  1  1  1  1  1  1  1  2  1  1  1  1  1     1     1  1  1|             
      Proliferation Connective Tissue      |                                                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  M  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  M  +  +  +|             
      Atrophy                              |                                                                          |             
      Hyperplasia, Lymphoid                |       2  1                    1              2     2                 4   |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                     4                                    |             
      Ulcer                                |                                     4                                    |             
      Epithelium, Hyperplasia              |             2                                                            |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Developmental Malformation           |             X                                                            |             
      Dysplasia                            |                   2     1     1  1                 2  1        2  1  1  2|             
      Hyperostosis                         |                                                                         2|             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |    +                                                           +         |             
      Proliferation Connective Tissue      |    X                                                                     |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Compression                          |                                                                          |             
      Mineralization                       |       2  1           1  1  1  2  2  2        2              2            |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  20                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 2| 2| 3| 2| 2| 3| 3| 2| 3| 8| 1| 2| 3| 3| 3| 3| 2| 2| 3| 2| 2| 2|             
                                           | 9| 9| 0| 9| 9| 1| 9| 9| 1| 0| 9| 0| 6| 2| 9| 0| 0| 0| 1| 9| 9| 0| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    | 1     1     1     2              1                 1  1                 1|             
      Inflammation, Chronic Active         |    2                                      1        1                     |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |                                                                          |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |                                                                          |             
      Artery, Inflammation, Chronic        |                                                                          |             
      Fat, Mediastinum, Necrosis           |    3                                                                     |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate, Serous                      |                                                          1               |             
      Inflammation, Chronic Active         |          1              2  1                                             |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |    1                                                                     |             
      Olfactory Epithelium, Metaplasia     |    1                                                  1                  |             
      Olfactory Epithelium, Metaplasia,    |                                                                          |             
           Squamous                        |                                                                          |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         | 1  1  2     2     1  1  1  1  1  1  1     1     1     1  1        1      |             
      Respiratory Epithelium, Hyperplasia  |             1                                                            |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |                         1  1                                             |             
      Respiratory Epithelium, Ulcer        |          1                                                               |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |    1  1        1           1              1     2  1  1  1              1|             
      Nephropathy                          |                   1                                                      |             
      Renal Tubule, Dilatation             |                                                                          |             
      Renal Tubule, Pigmentation           |                                                                          |             
      Renal Tubule, Regeneration           |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                                                                          |             
      Infiltration Cellular, Lymphocyte    | 1  3     2  1  1  2  1        2  1  1     1  1  2  2  1     1        2   |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  21                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 1|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 8|                                            |            |
                                           | 8| 8| 8| 8| 8| 8| 8| 8| 8| 3|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|                                            |      A     |
    37.5 PPM                               | 3| 3| 3| 3| 3| 3| 3| 3| 3| 4|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  M  +  +  +  +  +                                             |  58        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  M  +  +  +  +  +  +  +                                             |  55        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  A                                             |  58        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  A                                             |  59        |
      Ectopic Tissue                       |                                                                          |      1     |
      Proliferation Connective Tissue      |                                                                          |      1     |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  M                                             |  59        |
      Hyperplasia, Lymphoid                |                                                                          |      1  3.0|
      Proliferation Connective Tissue      |                                                                          |      1     |
      Serosa, Inflammation, Chronic Active |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  A                                             |  57        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Clear Cell Focus                     |                                                                          |      1     |
      Cytologic Alterations                |                                                                          |      1  2.0|
      Eosinophilic Focus                   |                                                                          |      2     |
      Hematopoietic Cell Proliferation     |                                                                          |      1  1.0|
      Inflammation, Chronic                |                                                                          |      7  1.0|
      Inflammation, Chronic Active         |                                                                          |      2  2.0|
      Mitotic Alteration                   |                                                                          |      1  1.0|
      Mixed Cell Focus                     |                                                                          |      1     |
      Necrosis                             |                                                                          |      2  1.0|
      Proliferation Connective Tissue      |                                                                          |      1     |
      Hepatocyte, Necrosis                 |                                                                          |      1  1.0|
      Periportal, Hypertrophy              |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   4        |
      Cyst                                 |                                                                          |      1  4.0|
      Proliferation Connective Tissue      |                                                                          |      1     |
      Fat, Necrosis                        |                                                                          |      4  2.3|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Fibrosis                             |                                                                          |      1  4.0|
      Inflammation, Chronic Active         |                                                                          |      1  4.0|
      Acinus, Atrophy                      |                                                                          |      2  3.0|
      Duct, Dilatation                     |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                | 1     1     2     1                                                      |     44  1.4|
      Inflammation, Chronic Active         |                            2                                             |      1  2.0|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  22                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 1|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 8|                                            |            |
                                           | 8| 8| 8| 8| 8| 8| 8| 8| 8| 3|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|                                            |      A     |
    37.5 PPM                               | 3| 3| 3| 3| 3| 3| 3| 3| 3| 4|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM - cont                  |                                                                          |            |
                                           |                                                                          |            |
      Proliferation Connective Tissue      |                                                                          |      1     |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Proliferation Connective Tissue      |                                                                          |      1     |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Artery, Inflammation, Chronic        |                                                                          |      1  4.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Hyperplasia, Focal                   |                                                                          |      2  1.5|
      Hypertrophy, Focal                   |                                                                          |      1  1.0|
      Subcapsular, Hyperplasia             | 2  1  2  1  1  1  2  1  1                                                |     56  1.8|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Hyperplasia, Focal                   |                                                                          |      2  2.0|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   2        |
      Hyperplasia, Focal                   |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  M  +                                             |  37        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  M  +  +  +  +  +                                             |  56        |
      Pars Distalis, Cyst                  |                                                                          |      1  1.0|
      Pars Distalis, Hyperplasia, Focal    |                                                                          |      1  2.0|
      Pars Distalis, Hyperplasia           |                                                                          |     12  2.2|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Infiltration Cellular, Lymphocyte    |                                                                          |      1  1.0|
      Follicle, Cyst                       |                                                                          |      5  2.6|
      Follicular Cell, Hyperplasia, Focal  |                                                                          |      9  2.0|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          |                                                                          |   1        |
      Dilatation                           |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Cyst                                 | 2                                                                        |     15  3.3|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Dilatation                           |                                                                          |      1  4.0|
      Hyperplasia, Cystic                  | 2  1  2  2  1  2  2  2  2                                                |     51  1.9|
      Hyperplasia                          |                                                                          |      1  4.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  23                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 1|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 8|                                            |            |
                                           | 8| 8| 8| 8| 8| 8| 8| 8| 8| 3|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|                                            |      A     |
    37.5 PPM                               | 3| 3| 3| 3| 3| 3| 3| 3| 3| 4|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Atrophy                              |                                                                          |      1  2.0|
      Myeloid Cell, Hyperplasia            |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   5        |
      Hyperplasia, Lymphoid                |                                                                          |      1  3.0|
      Pigmentation                         |                                                                          |      1  3.0|
      Iliac, Hyperplasia, Lymphoid         |                                                                          |      1  2.0|
      Pancreatic, Hyperplasia, Lymphoid    |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | M  +  +  +  +  +  +  +  +  M                                             |  42        |
      Hemorrhage                           |                      2                                                   |      1  2.0|
      Hyperplasia, Lymphoid                |                                                                          |      4  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +                                             |  57        |
      Hemorrhage                           | 3                                                                        |      1  3.0|
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  A                                             |  59        |
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
      Hyperplasia, Plasma Cell             |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  M  M  +                                             |  51        |
      Hyperplasia, Lymphoid                |                                                                          |      4  2.0|
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Angiectasis                          |                                                                          |      1  2.0|
      Hematopoietic Cell Proliferation     | 1  1  1  1  3  1  1  1  1                                                |     49  1.3|
      Hyperplasia, Lymphoid                |                                                                          |      7  2.3|
      Pigmentation, Hemosiderin            | 1  1  1  1  1  1  1  1  1  2                                             |     52  1.1|
      Proliferation Connective Tissue      |                                                                          |      1     |
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +                                             |  56        |
      Atrophy                              |                            3                                             |      2  2.5|
      Hyperplasia, Lymphoid                |                                                                          |     10  2.0|
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Hyperplasia                          |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic Active         |                                                                          |      4  2.3|
      Ulcer                                |                                                                          |      1  4.0|
      Epithelium, Hyperplasia              |                                                                          |      2  1.5|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  24                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 1|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 8|                                            |            |
                                           | 8| 8| 8| 8| 8| 8| 8| 8| 8| 3|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|                                            |      A     |
    37.5 PPM                               | 3| 3| 3| 3| 3| 3| 3| 3| 3| 4|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 MUSCULOSKELETAL SYSTEM - cont             |                                                                          |            |
                                           |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Developmental Malformation           |                                                                          |      1     |
      Dysplasia                            |                                                                          |     18  1.6|
      Hyperostosis                         |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                                                                          |   3        |
      Proliferation Connective Tissue      |                                                                          |      1     |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Compression                          |                                                                          |      1  2.0|
      Mineralization                       | 1  1  2  1           1                                                   |     26  1.6|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +                                             |  58        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Infiltration Cellular, Lymphocyte    |                                                                          |     14  1.1|
      Inflammation, Chronic Active         |                                                                          |      3  1.3|
      Alveolar Epithelium, Hyperplasia,    |                                                                          |            |
           Focal                           |                                                                          |      2  4.0|
      Alveolus, Infiltration Cellular,     |                                                                          |            |
           Histiocyte                      |                                                                          |      1  2.0|
      Artery, Inflammation, Chronic        |                                                                          |      1  3.0|
      Fat, Mediastinum, Necrosis           |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Exudate, Serous                      |                                                                          |      1  1.0|
      Inflammation, Chronic Active         |                            1                                             |     10  1.3|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |                                                                          |      3  1.0|
      Olfactory Epithelium, Metaplasia     |                                                                          |      6  1.0|
      Olfactory Epithelium, Metaplasia,    |                                                                          |            |
           Squamous                        |                                                                          |      1  1.0|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |          1                                                               |     26  1.1|
      Respiratory Epithelium, Hyperplasia  |                                                                          |      3  1.0|
      Respiratory Epithelium, Metaplasia,  |                                                                          |            |
           Squamous                        |                                                                          |      5  1.4|
      Respiratory Epithelium, Ulcer        |                                                                          |      4  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  25                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 1|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 8|                                            |            |
                                           | 8| 8| 8| 8| 8| 8| 8| 8| 8| 3|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|                                            |      A     |
    37.5 PPM                               | 3| 3| 3| 3| 3| 3| 3| 3| 3| 4|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Infiltration Cellular, Lymphocyte    |                                                                          |     19  1.2|
      Nephropathy                          |                                                                          |      2  1.0|
      Renal Tubule, Dilatation             |                                                                          |      1  2.0|
      Renal Tubule, Pigmentation           |                                                                          |      1  1.0|
      Renal Tubule, Regeneration           |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Dilatation                           |                                                                          |      1  3.0|
      Infiltration Cellular, Lymphocyte    | 1  1     1     1  1  1  1                                                |     40  1.3|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  26                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 4| 7| 4| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 6| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 3| 2| 3| 3| 6| 2| 1| 3| 3| 3| 2| 3| 2| 6| 3| 5| 3| 6| 2| 0| 3| 3|             
                                           | 9| 9| 0| 1| 9| 4| 1| 0| 8| 9| 1| 0| 0| 9| 0| 9| 3| 0| 8| 0| 0| 9| 6| 0| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |             1                                                            |             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                3                                                         |             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                3                                                         |             
      Hyperplasia, Lymphoid                |                                     2                                    |             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                3                                                         |             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Clear Cell Focus                     |                                                                X         |             
      Cytologic Alterations                |                   2                                                      |             
      Fibrosis                             |                                                                          |             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Infarct                              |                4                                                         |             
      Inflammation, Chronic                |          1                                   1                 1     1   |             
      Inflammation, Chronic Active         |                   1                                                      |             
      Mixed Cell Focus                     |                                           X                              |             
      Necrosis                             |                         1  3                                             |             
      Hepatocyte, Necrosis                 |                                                                          |             
      Periportal, Fatty Change             |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                         +                                                |             
      Fat, Necrosis                        |                                                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Acinus, Atrophy                      |                               4                          3               |             
      Duct, Dilatation                     |                               3                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                              1                           |             
      Inflammation, Chronic                | 1        1        1        2  2  2     2     2     1        1     1     1|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Ulcer                                |                                                       2                  |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Thrombosis                           |                                                                          |             
      Artery, Hypertrophy                  |                                                             3            |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  27                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 4| 7| 4| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 6| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 3| 2| 3| 3| 6| 2| 1| 3| 3| 3| 2| 3| 2| 6| 3| 5| 3| 6| 2| 0| 3| 3|             
                                           | 9| 9| 0| 1| 9| 4| 1| 0| 8| 9| 1| 0| 0| 9| 0| 9| 3| 0| 8| 0| 0| 9| 6| 0| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |       1                       2                             3            |             
      Hypertrophy, Focal                   |                   1           1                                          |             
      Subcapsular, Hyperplasia             | 2  2  1  2  2  1  2  2     2     1  1  2  2  2  2  2     1  2  1  2  2   |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +     +  +     +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Focal                   |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                      +        +                             +            |             
      Hyperplasia, Focal                   |                      2        2                             3            |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  M  M  M  +  M  M  M  +  +  +  +  +  +  +  M  +  M  +  +  +  M  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |    2                                                                     |             
      Pars Distalis, Angiectasis           |                                                                          |             
      Pars Distalis, Cyst                  |                                                                2         |             
      Pars Distalis, Hyperplasia           | 3     2           2              2        3                          2   |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Ectopic Thymus                       |                                                                          |             
      Inflammation, Chronic                |                                              1                           |             
      Follicle, Cyst                       |                         4                                                |             
      Follicular Cell, Hyperplasia, Diffuse|                                                                          |             
      Follicular Cell, Hyperplasia, Focal  | 2                                                  1                     |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          |                                     +                                    |             
      Dilatation                           |                                     3                                    |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +|             
      Cyst                                 | 2  3  3              1              4                                2   |             
                                            __________________________________________________________________________|             
   Oviduct                                 |                         +                                                |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Developmental Malformation           |                                                                          |             
      Hyperplasia, Cystic                  | 1  1  1     2     1  1     1  1  3  3  2  2  3  1  2  2  2  3  2  1  3  1|             
      Inflammation, Chronic Active         |                            2                                             |             
                                            __________________________________________________________________________|             
   Vagina                                  |                         +                                                |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Myeloid Cell, Hyperplasia            |                2                                                         |             
                                            __________________________________________________________________________|             
   Lymph Node                              |             +  +                                      +           +      |             
      Iliac, Hemorrhage                    |                                                                          |             
      Iliac, Inflammation, Chronic Active  |                2                                                         |             
      Lumbar, Angiectasis                  |             2                                                            |             
      Lumbar, Hemorrhage                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  28                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 4| 7| 4| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 6| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 3| 2| 3| 3| 6| 2| 1| 3| 3| 3| 2| 3| 2| 6| 3| 5| 3| 6| 2| 0| 3| 3|             
                                           | 9| 9| 0| 1| 9| 4| 1| 0| 8| 9| 1| 0| 0| 9| 0| 9| 3| 0| 8| 0| 0| 9| 6| 0| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Renal, Hemorrhage                    |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  M  +  +  M  +  M  +  +  M  M  +  +  +  +  +  M  +  +  +  M  M  +  M  +|             
      Hemorrhage                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                               4                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                                              2                           |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                | 3                                                                    3   |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     | 1  1  1  1  1  4  3  1  2  1  3  1  1  1  1  1  1  1  1  1  1  1     1  1|             
      Hyperplasia, Lymphoid                |                                                                1     2   |             
      Pigmentation, Hemosiderin            | 1  1  1  1  1        2     1  1  1  1  1  1  1  1  1     1  2        1  1|             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                          |             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                            2                                1            |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                                                                          |             
      Hyperplasia                          |          1                                                               |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |    1                                                                     |             
      Epithelium, Hyperplasia              |                                                    1                     |             
      Sebaceous Gland, Hyperplasia, Focal  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dysplasia                            |    1        1                 1     2  1  1  1     1     1  2  2        1|             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                                          |             
      Hemorrhage                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Compression                          |                                                                   3      |             
      Hemorrhage                           |                                                                          |             
      Mineralization                       | 2  2  1  2  2  1  2     2  2  2     2     3     1              2  1      |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  29                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 4| 7| 4| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 6| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 3| 2| 3| 3| 6| 2| 1| 3| 3| 3| 2| 3| 2| 6| 3| 5| 3| 6| 2| 0| 3| 3|             
                                           | 9| 9| 0| 1| 9| 4| 1| 0| 8| 9| 1| 0| 0| 9| 0| 9| 3| 0| 8| 0| 0| 9| 6| 0| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    | 2                             1  1  1  1                    1  3         |             
      Inflammation, Chronic Active         |                   2                                                      |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |          3  3                 2                 4              4         |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      | 3                                                                        |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate, Serous                      |       1                                                                  |             
      Inflammation, Chronic Active         | 2                 1                       1  1              1            |             
      Olfactory Epithelium, Atrophy        | 2                                                                        |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                                                                          |             
      Olfactory Epithelium, Metaplasia     |                                                                1         |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         | 2              1        1     2        2  1        1              1      |             
      Respiratory Epithelium, Hyperplasia  |             1                 1                                          |             
      Respiratory Epithelium, Ulcer        | 1                                                                        |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hydronephrosis                       |                                                                1         |             
      Infiltration Cellular, Lymphocyte    | 1                 1           1  1  1     1                 1        1   |             
      Nephropathy                          |                                                                          |             
      Renal Tubule, Dilatation             |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    | 1           1              1     1     1           1     2              1|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  30                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 7| 7| 7| 4| 7| 7| 6| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5|             
                             DAY ON TEST   | 3| 3| 3| 2| 3| 1| 3| 3| 3| 8| 3| 3| 3| 2| 2| 2| 2| 3| 2| 2| 2| 3| 2| 0| 5|             
                                           | 0| 6| 0| 9| 1| 5| 0| 0| 9| 5| 0| 1| 0| 9| 9| 9| 9| 0| 9| 9| 9| 0| 9| 5| 8|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | M  +  +  +  +  A  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +     +|             
      Inflammation, Chronic                |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Dilatation                           |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Dilatation                           |                                                                          |             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Dilatation                           |                                                                          |             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Clear Cell Focus                     | X                                                                        |             
      Cytologic Alterations                |                                                                          |             
      Fibrosis                             |          3                                                               |             
      Hematopoietic Cell Proliferation     |                   2                                                      |             
      Infarct                              |                                                                          |             
      Inflammation, Chronic                |                                                          1        1      |             
      Inflammation, Chronic Active         |                   1                                            1        1|             
      Mixed Cell Focus                     |                                                                          |             
      Necrosis                             |                                                                          |             
      Hepatocyte, Necrosis                 |                                  1                                       |             
      Periportal, Fatty Change             |                                     1                                    |             
                                            __________________________________________________________________________|             
   Mesentery                               |                               +                                   +      |             
      Fat, Necrosis                        |                               2                                   2      |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Acinus, Atrophy                      |                                                 2                        |             
      Duct, Dilatation                     |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Atrophy                              |                                                                          |             
      Inflammation, Chronic                | 3  1     1        1  2        1  2  1  1  1     1  1     1     2  1     1|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Ulcer                                |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                    +                     |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Thrombosis                           |                                  3                                       |             
      Artery, Hypertrophy                  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  31                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 7| 7| 7| 4| 7| 7| 6| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5|             
                             DAY ON TEST   | 3| 3| 3| 2| 3| 1| 3| 3| 3| 8| 3| 3| 3| 2| 2| 2| 2| 3| 2| 2| 2| 3| 2| 0| 5|             
                                           | 0| 6| 0| 9| 1| 5| 0| 0| 9| 5| 0| 1| 0| 9| 9| 9| 9| 0| 9| 9| 9| 0| 9| 5| 8|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Cyst                                 |                                                                          |             
      Hypertrophy, Focal                   |                                                                          |             
      Subcapsular, Hyperplasia             | 3  2  2  2  4  1  2  2  1  1  2  2     2  1  2  1  3  3  2  2  1  1     1|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         |    +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Hyperplasia, Focal                   |                                              2                           |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                                          |             
      Hyperplasia, Focal                   |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  +  M  +  +  +  +  +  M  M  +  +  M  +  M  M  +  M  +  +  +     +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Cyst                                 |                                                                          |             
      Pars Distalis, Angiectasis           | 3                                                                        |             
      Pars Distalis, Cyst                  |                                                                          |             
      Pars Distalis, Hyperplasia           | 3        2        3                                3  2        2         |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Ectopic Thymus                       |                                                                   X      |             
      Inflammation, Chronic                |                                     3           1                        |             
      Follicle, Cyst                       |                      1           3     1                                 |             
      Follicular Cell, Hyperplasia, Diffuse|                                     4                                    |             
      Follicular Cell, Hyperplasia, Focal  |       2     1        2           2              2                        |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          |                                                                          |             
      Dilatation                           |                                                                          |             
                                            __________________________________________________________________________|             
   Ovary                                   | M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +     +|             
      Cyst                                 |    4        2                 2  2                                       |             
                                            __________________________________________________________________________|             
   Oviduct                                 |                                                                          |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Developmental Malformation           |             X                                                            |             
      Hyperplasia, Cystic                  | 1  2  2  2  1     4  2  1     3     3  2  1  1  2  4  4  2  2  1  3     1|             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Vagina                                  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Myeloid Cell, Hyperplasia            |                3  3                                                      |             
                                            __________________________________________________________________________|             
   Lymph Node                              |             +  +              +                                          |             
      Iliac, Hemorrhage                    |                                                                          |             
      Iliac, Inflammation, Chronic Active  |                                                                          |             
      Lumbar, Angiectasis                  |                                                                          |             
      Lumbar, Hemorrhage                   |                4                                                         |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  32                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 7| 7| 7| 4| 7| 7| 6| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5|             
                             DAY ON TEST   | 3| 3| 3| 2| 3| 1| 3| 3| 3| 8| 3| 3| 3| 2| 2| 2| 2| 3| 2| 2| 2| 3| 2| 0| 5|             
                                           | 0| 6| 0| 9| 1| 5| 0| 0| 9| 5| 0| 1| 0| 9| 9| 9| 9| 0| 9| 9| 9| 0| 9| 5| 8|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Renal, Hemorrhage                    |                4                                                         |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  M  M  M  +  +  +  M  M  +  +  M  +  M  +  M     +|             
      Hemorrhage                           |                2                                                         |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  M     +|             
      Hemorrhage                           |       2        4                                                         |             
      Hyperplasia, Lymphoid                |                                        2                                 |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +     +|             
      Hemorrhage                           |                2                                                         |             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +     +|             
      Hyperplasia, Lymphoid                |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Hematopoietic Cell Proliferation     | 1  1  1  1     4  4  1     1     2  2  1  1  1     1  2  1  1  1  1     1|             
      Hyperplasia, Lymphoid                |                                                 2        2     3         |             
      Pigmentation, Hemosiderin            |    1  1  1           1  2  3     2  2  1  1  1  1  1     1  1  1  1     2|             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  M  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +     +|             
      Atrophy                              |                4        3  1                                             |             
      Hemorrhage                           |                2                                                         |             
      Hyperplasia, Lymphoid                |                                                       2  2     2         |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Dilatation                           |                      2                                                   |             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Inflammation, Chronic Active         |             2                                                            |             
      Epithelium, Hyperplasia              |                                        1                                 |             
      Sebaceous Gland, Hyperplasia, Focal  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Dysplasia                            |    1  2     2        1  1     1  2  1  1     3              1           1|             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                            +                                             |             
      Hemorrhage                           |                            4                                             |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Compression                          |                      2           2           2                           |             
      Hemorrhage                           |                2           4                                             |             
      Mineralization                       |    2  2     1     2           1  1  1  1  2        2  1  2     1  1      |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  33                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 7| 7| 7| 4| 7| 7| 6| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5|             
                             DAY ON TEST   | 3| 3| 3| 2| 3| 1| 3| 3| 3| 8| 3| 3| 3| 2| 2| 2| 2| 3| 2| 2| 2| 3| 2| 0| 5|             
                                           | 0| 6| 0| 9| 1| 5| 0| 0| 9| 5| 0| 1| 0| 9| 9| 9| 9| 0| 9| 9| 9| 0| 9| 5| 8|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Infiltration Cellular, Lymphocyte    |    1                                1                 1        1         |             
      Inflammation, Chronic Active         |                                                                          |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |                                  3  2  3           2                     |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Exudate, Serous                      |                                     1                                    |             
      Inflammation, Chronic Active         |    1                 1     1                       1           1         |             
      Olfactory Epithelium, Atrophy        |                                                                          |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |             1              1              1     1     1                  |             
      Olfactory Epithelium, Metaplasia     |                                     1                                    |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |       1     1  1     1                             1     1               |             
      Respiratory Epithelium, Hyperplasia  | 1                             1                                          |             
      Respiratory Epithelium, Ulcer        |                      1                                         2         |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                             +           +|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Hydronephrosis                       |                                                                          |             
      Infiltration Cellular, Lymphocyte    | 1  1                             1  2           1     1        1        1|             
      Nephropathy                          |             2                                                            |             
      Renal Tubule, Dilatation             |                            1     2                                       |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +|             
      Infiltration Cellular, Lymphocyte    | 2  2     1     1        1        2  1  1        2     2        2  1     1|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  34                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 2| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 1| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 0| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|                                            |      A     |
    75 PPM                                 | 5| 5| 5| 5| 5| 5| 5| 5| 5| 6|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  A  +  +  +  +  +                                             |  54        |
      Inflammation, Chronic                |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Dilatation                           |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Dilatation                           |                                                                          |      1  3.0|
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +                                             |  58        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +                                             |  56        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Dilatation                           |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Clear Cell Focus                     |                                                                          |      2     |
      Cytologic Alterations                |                                                                          |      1  2.0|
      Fibrosis                             |                                                                          |      1  3.0|
      Hematopoietic Cell Proliferation     |                                                                          |      1  2.0|
      Infarct                              |                                                                          |      1  4.0|
      Inflammation, Chronic                |                                                                          |      6  1.0|
      Inflammation, Chronic Active         |                                                                          |      4  1.0|
      Mixed Cell Focus                     |                                                                          |      1     |
      Necrosis                             |                                                                          |      2  2.0|
      Hepatocyte, Necrosis                 |                                                                          |      1  1.0|
      Periportal, Fatty Change             |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   3        |
      Fat, Necrosis                        |                                                                          |      2  2.0|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Acinus, Atrophy                      |                                                                          |      3  3.0|
      Duct, Dilatation                     |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Atrophy                              |                                                                          |      1  1.0|
      Inflammation, Chronic                |       1  1     1     1     1                                             |     33  1.3|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Ulcer                                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Tooth                                   |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  35                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 2| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 1| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 0| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|                                            |      A     |
    75 PPM                                 | 5| 5| 5| 5| 5| 5| 5| 5| 5| 6|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Thrombosis                           |                                                                          |      1  3.0|
      Artery, Hypertrophy                  |                                                                          |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Cyst                                 |                                                                          |      3  2.0|
      Hypertrophy, Focal                   |                                                                          |      2  1.0|
      Subcapsular, Hyperplasia             | 1  2  2  2  1  1  1  2  1  1                                             |     54  1.7|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  M  +  +  +  +  +                                             |  54        |
      Hyperplasia, Focal                   |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   3        |
      Hyperplasia, Focal                   |                                                                          |      3  2.3|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  M  +  +  +  +  +  M  +  +                                             |  40        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Cyst                                 |                                                                          |      1  2.0|
      Pars Distalis, Angiectasis           |                                                                          |      1  3.0|
      Pars Distalis, Cyst                  |                                                                          |      1  2.0|
      Pars Distalis, Hyperplasia           |                                                                          |     12  2.4|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Ectopic Thymus                       |                                                                          |      1     |
      Inflammation, Chronic                |                                                                          |      3  1.7|
      Follicle, Cyst                       |                                                                          |      4  2.3|
      Follicular Cell, Hyperplasia, Diffuse|                                                                          |      1  4.0|
      Follicular Cell, Hyperplasia, Focal  |                                                                          |      7  1.7|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          |             +              M                                             |   2        |
      Dilatation                           |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +                                             |  55        |
      Cyst                                 |                                                                          |     10  2.5|
                                            __________________________________________________________________________|____________|
   Oviduct                                 |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Developmental Malformation           |                                                                          |      1     |
      Hyperplasia, Cystic                  | 2  2     2     2  2     2  2                                             |     50  1.9|
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  36                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 2| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 1| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 0| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|                                            |      A     |
    75 PPM                                 | 5| 5| 5| 5| 5| 5| 5| 5| 5| 6|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Vagina                                  |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Myeloid Cell, Hyperplasia            |                                                                          |      3  2.7|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |             +                                                            |   8        |
      Iliac, Hemorrhage                    |             2                                                            |      1  2.0|
      Iliac, Inflammation, Chronic Active  |                                                                          |      1  2.0|
      Lumbar, Angiectasis                  |                                                                          |      1  2.0|
      Lumbar, Hemorrhage                   |                                                                          |      1  4.0|
      Renal, Hemorrhage                    |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  M  +  +  M  +  +                                             |  40        |
      Hemorrhage                           |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +                                             |  57        |
      Hemorrhage                           |                                                                          |      2  3.0|
      Hyperplasia, Lymphoid                |                                                                          |      2  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Hemorrhage                           |                                                                          |      1  2.0|
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  M  +  +  +  M  +  M  +  +                                             |  52        |
      Hyperplasia, Lymphoid                | 4                                                                        |      3  3.3|
      Inflammation, Chronic Active         |             2                                                            |      1  2.0|
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Hematopoietic Cell Proliferation     | 1  1  1  1  3  1  1  1  1  1                                             |     54  1.4|
      Hyperplasia, Lymphoid                | 1                                                                        |      6  1.8|
      Pigmentation, Hemosiderin            | 2  1  2  2     2  1  1  2  2                                             |     46  1.3|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +                                             |  57        |
      Atrophy                              |    2        3                                                            |      5  2.6|
      Hemorrhage                           |                                                                          |      1  2.0|
      Hyperplasia, Lymphoid                | 2                                                                        |      6  1.8|
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Dilatation                           |                                                                          |      1  2.0|
      Hyperplasia                          |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Inflammation, Chronic Active         |                                                                          |      2  1.5|
      Epithelium, Hyperplasia              |                                                                          |      2  1.0|
      Sebaceous Gland, Hyperplasia, Focal  |                         2                                                |      1  2.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  37                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 2| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 1| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 0| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|                                            |      A     |
    75 PPM                                 | 5| 5| 5| 5| 5| 5| 5| 5| 5| 6|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 INTEGUMENTARY SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Dysplasia                            |          1                                                               |     25  1.3|
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                                                                          |   1        |
      Hemorrhage                           |                                                                          |      1  4.0|
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Compression                          |                                                                          |      4  2.3|
      Hemorrhage                           |                                                                          |      2  3.0|
      Mineralization                       |                1     2                                                   |     31  1.6|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Infiltration Cellular, Lymphocyte    |                                                                          |     11  1.3|
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
      Alveolar Epithelium, Hyperplasia,    |                                                                          |            |
           Focal                           |    1                                                                     |     10  2.7|
      Alveolus, Infiltration Cellular,     |                                                                          |            |
           Histiocyte                      |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Exudate, Serous                      |                                                                          |      2  1.0|
      Inflammation, Chronic Active         |    1  1                                                                  |     12  1.1|
      Olfactory Epithelium, Atrophy        |                                                                          |      1  2.0|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |                                                                          |      5  1.0|
      Olfactory Epithelium, Metaplasia     |                                                                          |      2  1.0|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |                                                                          |     14  1.2|
      Respiratory Epithelium, Hyperplasia  |                                                                          |      4  1.0|
      Respiratory Epithelium, Ulcer        |                                                                          |      3  1.3|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +                                             |  59        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   2        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  38                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 2| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 1| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 0| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|                                            |      A     |
    75 PPM                                 | 5| 5| 5| 5| 5| 5| 5| 5| 5| 6|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 URINARY SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Hydronephrosis                       |                                                                          |      1  1.0|
      Infiltration Cellular, Lymphocyte    |       1              1  1                                                |     19  1.1|
      Nephropathy                          |                                                                          |      1  2.0|
      Renal Tubule, Dilatation             |                                                                          |      2  1.5|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +                                             |  57        |
      Infiltration Cellular, Lymphocyte    |    1  1        1                                                         |     24  1.3|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  39                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 4| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 4| 7| 7| 7| 6|             
                             DAY ON TEST   | 2| 8| 2| 2| 3| 9| 2| 2| 3| 2| 3| 2| 2| 2| 2| 3| 2| 3| 2| 0| 8| 2| 3| 3| 9|             
                                           | 9| 3| 9| 9| 0| 4| 9| 5| 0| 9| 0| 9| 9| 9| 4| 0| 9| 0| 9| 3| 5| 9| 1| 1| 2|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  A  M  +  +  +|             
      Dilatation                           |                2                                                         |             
      Inflammation, Chronic                |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  A  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  A|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                               1                                          |             
      Basophilic Focus                     |             X                                                            |             
      Clear Cell Focus                     |                                                                          |             
      Hemorrhage                           |                                                             2            |             
      Hyperplasia                          |                                                                          |             
      Infarct                              |                                                 3                        |             
      Inflammation, Chronic                |       1                          1                                1      |             
      Mixed Cell Focus                     |                                                                          |             
      Necrosis                             |                                                             2            |             
      Pigmentation                         |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |          +                          +                                    |             
      Fat, Necrosis                        |          2                          3                                    |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                                                                   2      |             
      Acinus, Atrophy                      |                                     4  4                                 |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Inflammation, Chronic                | 1           1        1     1  1  1  1  2  1  2  1  1  2        1  1      |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Developmental Malformation           |                                        X                                 |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic        |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcapsular, Hyperplasia             | 2  2  2  2  2     2  1  2  2  2  3  1  1  2  2  2  3  2  2  1  2  2  2  2|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +     +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                +              +  +                                       |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  40                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 4| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 4| 7| 7| 7| 6|             
                             DAY ON TEST   | 2| 8| 2| 2| 3| 9| 2| 2| 3| 2| 3| 2| 2| 2| 2| 3| 2| 3| 2| 0| 8| 2| 3| 3| 9|             
                                           | 9| 3| 9| 9| 0| 4| 9| 5| 0| 9| 0| 9| 9| 9| 4| 0| 9| 0| 9| 3| 5| 9| 1| 1| 2|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
      Hyperplasia, Focal                   |                3              2                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  M  +  +  +  +  +  +  M  +  +  M  +  +  +  +  +  +  +  +  M  M  M  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  +|             
      Pars Distalis, Angiectasis           | 1                                         2                              |             
      Pars Distalis, Cyst                  |                                                                          |             
      Pars Distalis, Hyperplasia           |                   3        4                                             |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia, Focal  |                                              1                           |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          |                                  +     +                                 |             
      Dilatation                           |                                                                          |             
      Pigmentation                         |                                                                          |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Cyst                                 |                                  3     1        1              2         |             
      Hemorrhage                           |                                                                2         |             
      Infiltration Cellular, Lymphocyte    |                                                                          |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Hyperplasia, Cystic                  | 3  2  3  3  3  2  3  1  4  4  1  3  2  1  2  3  4  4  4  2     1  1  3   |             
                                            __________________________________________________________________________|             
   Vagina                                  |             +                    +                                       |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                +                          +                             +|             
      Iliac, Pigmentation                  |                2                                                         |             
      Inguinal, Pigmentation               |                2                                                         |             
      Lumbar, Hyperplasia, Lymphoid        |                                           2                              |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  +  +  +  +  +  +  M  +  +  M  +  +  M  M  M  +  M  M  +  +  M  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | M  +  +  +  +  +  +  +  +  +  +  +  M  +  +  M  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|             
      Angiectasis                          |                                     2                                    |             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
      Hematopoietic Cell Proliferation     | 1  1  1  1  2     1     1  1  1  1  1  1  1  2  1  1  2  1     3  1  1   |             
      Hyperplasia, Lymphoid                |       2                          3                                       |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  41                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 4| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 4| 7| 7| 7| 6|             
                             DAY ON TEST   | 2| 8| 2| 2| 3| 9| 2| 2| 3| 2| 3| 2| 2| 2| 2| 3| 2| 3| 2| 0| 8| 2| 3| 3| 9|             
                                           | 9| 3| 9| 9| 0| 4| 9| 5| 0| 9| 0| 9| 9| 9| 4| 0| 9| 0| 9| 3| 5| 9| 1| 1| 2|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Pigmentation, Hemosiderin            | 2  2  1  2  2  3  1  3  1  2  2  1  2  2  3  1  1  1  1  2     1  1  2   |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  M  +  M  +  +  +  +  +  M  +  +  +  +  +  +  A  M  +  +  M|             
      Atrophy                              |    3                          2           3                              |             
      Ectopic Parathyroid Gland            |                                                                      X   |             
      Hyperplasia, Lymphoid                |             2                                                            |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                      3                 2                                 |             
      Hyperplasia                          |    3                          1                                          |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                         1     1                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dysplasia                            | 2     2     2        2  2  1        2     1  1  1  1  2  1           1   |             
      Maxilla, Fracture                    |                                                                          |             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Compression                          |    X                          3                                          |             
      Hemorrhage                           |                                        2                                 |             
      Mineralization                       |          1              1  1              1  2  2                       2|             
      Meninges, Inflammation, Chronic      |                                                                          |             
          Active                           |       2                                                                  |             
                                            __________________________________________________________________________|             
   Peripheral Nerve                        |                                           +                              |             
                                            __________________________________________________________________________|             
   Spinal Cord                             |                                           +                              |             
      Inflammation, Chronic                |                                           2                              |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic        |                                                                          |             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    | 1     1  1        1     1  1        1  1        1  1                     |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |                                              2  1     4              4   |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |                                              2                       2   |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate, Serous                      | 2                 1        1     1     1  1  1  1  1     2               |             
      Inflammation, Chronic Active         |    1        2           2     1                       1              1   |             
      Olfactory Epithelium, Atrophy        | 2  2        2                          1     1  1                        |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  42                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 4| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 4| 7| 7| 7| 6|             
                             DAY ON TEST   | 2| 8| 2| 2| 3| 9| 2| 2| 3| 2| 3| 2| 2| 2| 2| 3| 2| 3| 2| 0| 8| 2| 3| 3| 9|             
                                           | 9| 3| 9| 9| 0| 4| 9| 5| 0| 9| 0| 9| 9| 9| 4| 0| 9| 0| 9| 3| 5| 9| 1| 1| 2|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
           Hyaline                         |                                                                          |             
      Olfactory Epithelium, Metaplasia     |    2                                                                 1   |             
      Olfactory Epithelium, Metaplasia,    |                                                                          |             
           Squamous                        |                                                                          |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         | 2        1        1  1  1     1           1     1  1                 1  1|             
      Respiratory Epithelium, Hyperplasia  |                                                                          |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |    1                 1  2     1                                      1   |             
      Respiratory Epithelium, Ulcer        |    1                                                                     |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Ear                                     |                                  +                                       |             
                                            __________________________________________________________________________|             
   Eye                                     |                         +                                                |             
      Phthisis Bulbi                       |                         4                                                |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                   +                             +                        |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Glomerulosclerosis                   |                                                                3         |             
      Infarct                              |                                                                      1   |             
      Infiltration Cellular, Lymphocyte    | 1     1  2  1           1  1        1     1  1  1  1           2     1   |             
      Renal Tubule, Dilatation             |                                                                3         |             
      Renal Tubule, Hyperplasia, Focal     |                                                                          |             
      Renal Tubule, Regeneration           |          1                                                               |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    | 1     1  1        1  1  1  1  1  1  1  2        2  2              1  1   |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  43                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 0| 7| 7| 0| 7| 7| 7| 7| 7| 1| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 3| 3| 3| 2| 3| 3| 2| 3| 3| 2| 6| 3| 2| 7| 3| 1| 2| 2| 2| 1| 2| 4| 2| 3|             
                                           | 1| 1| 0| 0| 9| 0| 0| 9| 0| 1| 9| 5| 1| 9| 1| 1| 6| 9| 9| 9| 4| 9| 6| 9| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  M  A  +  +  +  +  +  A  +  +|             
      Dilatation                           |                                                                          |             
      Inflammation, Chronic                |                                                                      2   |             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  A  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  A  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  A  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  A  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Basophilic Focus                     |                                                                          |             
      Clear Cell Focus                     |             X                                                            |             
      Hemorrhage                           |                                                                          |             
      Hyperplasia                          |                               3                                         3|             
      Infarct                              |                                                                          |             
      Inflammation, Chronic                |          1           1  1                                            1   |             
      Mixed Cell Focus                     |                            X                          X                  |             
      Necrosis                             |                                                                          |             
      Pigmentation                         |                                              2                           |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                                                          |             
      Fat, Necrosis                        |                                                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                2              2                                          |             
      Acinus, Atrophy                      |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           | 4                                                                        |             
      Inflammation, Chronic                |    1  1  1     2  2        1  3     1           1     1  1     2  1  1   |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                            2                                             |             
      Developmental Malformation           |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |                      +                                                   |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic        | 2                                                                        |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcapsular, Hyperplasia             | 2  2  2  2  2  3  2     2  2  2     2  2     2  2  2  2  2     2  2  2   |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +     +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  44                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 0| 7| 7| 0| 7| 7| 7| 7| 7| 1| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 3| 3| 3| 2| 3| 3| 2| 3| 3| 2| 6| 3| 2| 7| 3| 1| 2| 2| 2| 1| 2| 4| 2| 3|             
                                           | 1| 1| 0| 0| 9| 0| 0| 9| 0| 1| 9| 5| 1| 9| 1| 1| 6| 9| 9| 9| 4| 9| 6| 9| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
      Hyperplasia, Focal                   |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  M  M  +  M  M  M  +  +  M  M  M  +  +  +  +  +  +  M  M  +  +  M  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Angiectasis           |                                                                          |             
      Pars Distalis, Cyst                  |                               3                          1               |             
      Pars Distalis, Hyperplasia           |                                        2              1        3  2     2|             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia, Focal  |                2        2     1                                2         |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          |       +                                                                  |             
      Dilatation                           |       2                                                                  |             
      Pigmentation                         |       2                                                                  |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                              3                           |             
      Cyst                                 |    4  3        3              2        1                             2  3|             
      Hemorrhage                           |                                                                          |             
      Infiltration Cellular, Lymphocyte    |                   1                                                      |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Hyperplasia, Cystic                  | 1  3  4  1  1  1  2     1  3  2     4  4     4  1  3  2  3     4  4  3  2|             
                                            __________________________________________________________________________|             
   Vagina                                  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                +        +                                               +|             
      Iliac, Pigmentation                  |                                                                          |             
      Inguinal, Pigmentation               |                                                                          |             
      Lumbar, Hyperplasia, Lymphoid        |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  +  +  +  M  +  +  M  +  M  +  +  +  M  +  M  +  M  +  +  +  M  M  M  M|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  M|             
      Hemorrhage                           | 3                                                                        |             
      Hyperplasia, Lymphoid                |                                     3                                    |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  A  +  +|             
      Angiectasis                          |                                                                          |             
      Hyperplasia, Lymphoid                |                               2                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | M  +  +  +  +  +  +  +  +  +  +  M  M  +  +  +  +  M  +  M  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |          2                    3                                2         |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     | 1  1  1  1  1  1  2     2  1  2  1  1  1  1  1  2  2  1  1  1  1  1  1   |             
      Hyperplasia, Lymphoid                |                                                                2         |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  45                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 0| 7| 7| 0| 7| 7| 7| 7| 7| 1| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 3| 3| 3| 2| 3| 3| 2| 3| 3| 2| 6| 3| 2| 7| 3| 1| 2| 2| 2| 1| 2| 4| 2| 3|             
                                           | 1| 1| 0| 0| 9| 0| 0| 9| 0| 1| 9| 5| 1| 9| 1| 1| 6| 9| 9| 9| 4| 9| 6| 9| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Pigmentation, Hemosiderin            | 3  2  2  2  2  1  1  1  1  2  1  2  1  2  3  1  1  1  1  2  1  1  3  2   |             
                                            __________________________________________________________________________|             
   Thymus                                  | M  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                           2     4                 2      |             
      Ectopic Parathyroid Gland            |                                                                          |             
      Hyperplasia, Lymphoid                |                                                                      2   |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                                                                          |             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                                                    1                    1|             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dysplasia                            |    1  3                 1  2           2     4     1  2  2     2     1   |             
      Maxilla, Fracture                    |                                  X                                       |             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                    +                     |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Compression                          |                                                                          |             
      Hemorrhage                           |                                                                          |             
      Mineralization                       | 2  1  3  2  1  2  2  1                       2  1  2           1  2  1  2|             
      Meninges, Inflammation, Chronic      |                                                                          |             
          Active                           |                                                                          |             
                                            __________________________________________________________________________|             
   Peripheral Nerve                        |                                                                          |             
                                            __________________________________________________________________________|             
   Spinal Cord                             |                                                                          |             
      Inflammation, Chronic                |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic        | 2                                                                        |             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |    1  1     1  1  1     1  2  2     1              1     2     1         |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |                      1                       2                       2  1|             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate, Serous                      | 2        1     2  1                 1  1        1     1  2     1  2  2  1|             
      Inflammation, Chronic Active         |    1        1                                                            |             
      Olfactory Epithelium, Atrophy        | 1           2  2  1                    1                 2     1  2  2  1|             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  46                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 0| 7| 7| 0| 7| 7| 7| 7| 7| 1| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 3| 3| 3| 2| 3| 3| 2| 3| 3| 2| 6| 3| 2| 7| 3| 1| 2| 2| 2| 1| 2| 4| 2| 3|             
                                           | 1| 1| 0| 0| 9| 0| 0| 9| 0| 1| 9| 5| 1| 9| 1| 1| 6| 9| 9| 9| 4| 9| 6| 9| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
           Hyaline                         | 1  1                    1                                                |             
      Olfactory Epithelium, Metaplasia     |                                                                          |             
      Olfactory Epithelium, Metaplasia,    |                                                                          |             
           Squamous                        |                               1                                          |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |    2        1           1              1           1                     |             
      Respiratory Epithelium, Hyperplasia  |                                                    1                     |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |    1                                                                     |             
      Respiratory Epithelium, Ulcer        |    1                                                              1      |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Ear                                     |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                                          |             
      Phthisis Bulbi                       |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Glomerulosclerosis                   |                                                                          |             
      Infarct                              |                                                                          |             
      Infiltration Cellular, Lymphocyte    |    1  1     1  1  1     1  2  2     1        1  1  1  1  1     2  1     1|             
      Renal Tubule, Dilatation             |                                                                          |             
      Renal Tubule, Hyperplasia, Focal     |                                              4                           |             
      Renal Tubule, Regeneration           |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |    1  1     2  1  2  1     1        2  1     1     1  2  1     3  2     1|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  47                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 8| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |      A     |
    150 PPM                                | 7| 7| 7| 7| 7| 7| 7| 7| 7| 8|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  +  +  +  +  +  +                                             |  57        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +                                             |  51        |
      Dilatation                           |                                                                          |      1  2.0|
      Inflammation, Chronic                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +                                             |  56        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +                                             |  57        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +                                             |  55        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +                                             |  52        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +                                             |  55        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +                                             |  54        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Angiectasis                          |                                                                          |      1  1.0|
      Basophilic Focus                     |                                                                          |      1     |
      Clear Cell Focus                     |                                                                          |      1     |
      Hemorrhage                           |                                                                          |      1  2.0|
      Hyperplasia                          |                                                                          |      2  3.0|
      Infarct                              |                                                                          |      1  3.0|
      Inflammation, Chronic                |                                                                          |      7  1.0|
      Mixed Cell Focus                     |                                                                          |      2     |
      Necrosis                             |                                                                          |      1  2.0|
      Pigmentation                         |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   2        |
      Fat, Necrosis                        |                                                                          |      2  2.5|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                |                                                                          |      3  2.0|
      Acinus, Atrophy                      |                                                                          |      2  4.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Hemorrhage                           |                                                                          |      1  4.0|
      Inflammation, Chronic                |       1     1        1                                                   |     32  1.3|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Angiectasis                          |                                                                          |      1  2.0|
      Developmental Malformation           |                                                                          |      1     |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Tooth                                   |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Artery, Inflammation, Chronic        |                                                                          |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  48                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 8| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |      A     |
    150 PPM                                | 7| 7| 7| 7| 7| 7| 7| 7| 7| 8|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ENDOCRINE SYSTEM - cont                   |                                                                          |            |
                                           |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Subcapsular, Hyperplasia             | 2  2  1  2  1  1  1  2     2                                             |     53  1.9|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +                                             |  57        |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   3        |
      Hyperplasia, Focal                   |                                                                          |      2  2.5|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  M  +  +                                             |  40        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +                                             |  57        |
      Pars Distalis, Angiectasis           |                                                                          |      2  1.5|
      Pars Distalis, Cyst                  |                                                                          |      2  2.0|
      Pars Distalis, Hyperplasia           |                                                                          |      7  2.4|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Follicular Cell, Hyperplasia, Focal  |                                                                          |      5  1.6|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          |                +        +                                                |   5        |
      Dilatation                           |                                                                          |      1  2.0|
      Pigmentation                         |                2        2                                                |      3  2.0|
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Angiectasis                          |                                                                          |      1  3.0|
      Cyst                                 |    3     1                                                               |     13  2.2|
      Hemorrhage                           |                                                                          |      1  2.0|
      Infiltration Cellular, Lymphocyte    |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Angiectasis                          |                      2                                                   |      1  2.0|
      Hyperplasia, Cystic                  | 2  2  2  3  2  1  3  1  1  2                                             |     54  2.4|
                                            __________________________________________________________________________|____________|
   Vagina                                  |                                                                          |   2        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   6        |
      Iliac, Pigmentation                  |                                                                          |      1  2.0|
      Inguinal, Pigmentation               |                                                                          |      1  2.0|
      Lumbar, Hyperplasia, Lymphoid        |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  M  +  +  M  +  +                                             |  38        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +                                             |  55        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  49                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 8| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |      A     |
    150 PPM                                | 7| 7| 7| 7| 7| 7| 7| 7| 7| 8|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
      Hemorrhage                           |                                                                          |      1  3.0|
      Hyperplasia, Lymphoid                |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +                                             |  55        |
      Angiectasis                          |                                                                          |      1  2.0|
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +                                             |  53        |
      Hyperplasia, Lymphoid                |                                                                          |      3  2.3|
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Hematopoietic Cell Proliferation     | 1  2  1  2  1  1  1  1  1  1                                             |     54  1.2|
      Hyperplasia, Lymphoid                |                                                                          |      3  2.3|
      Pigmentation, Hemosiderin            | 2  2  2  2  2  2  2  2  2  2                                             |     57  1.7|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +                                             |  51        |
      Atrophy                              |                                                                          |      6  2.7|
      Ectopic Parathyroid Gland            |                                                                          |      1     |
      Hyperplasia, Lymphoid                |                                                                          |      2  2.0|
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Dilatation                           |                                                                          |      2  2.5|
      Hyperplasia                          |                                                                          |      2  2.0|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                |                                                                          |      4  1.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Dysplasia                            | 1        2        1                                                      |     28  1.6|
      Maxilla, Fracture                    |                                                                          |      1     |
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Compression                          |                                                                          |      2  3.0|
      Hemorrhage                           |                                                                          |      1  2.0|
      Mineralization                       | 2  1     2     1  1                                                      |     27  1.6|
      Meninges, Inflammation, Chronic      |                                                                          |            |
          Active                           |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Peripheral Nerve                        |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Spinal Cord                             |                                                                          |   1        |
      Inflammation, Chronic                |                                                                          |      1  2.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  50                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 8| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |      A     |
    150 PPM                                | 7| 7| 7| 7| 7| 7| 7| 7| 7| 8|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 NERVOUS SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Artery, Inflammation, Chronic        |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Infiltration Cellular, Lymphocyte    |             1                                                            |     23  1.1|
      Alveolar Epithelium, Hyperplasia,    |                                                                          |            |
           Focal                           |                                                                          |      8  2.1|
      Alveolus, Infiltration Cellular,     |                                                                          |            |
           Histiocyte                      |                                                                          |      2  2.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Exudate, Serous                      |                                                                          |     23  1.3|
      Inflammation, Chronic Active         |    1           1     1  1                                                |     12  1.2|
      Olfactory Epithelium, Atrophy        |                                                                          |     16  1.5|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |                                                                          |      3  1.0|
      Olfactory Epithelium, Metaplasia     |                                                                          |      2  1.5|
      Olfactory Epithelium, Metaplasia,    |                                                                          |            |
           Squamous                        |                                                                          |      1  1.0|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |       1        1     2                                                   |     19  1.2|
      Respiratory Epithelium, Hyperplasia  |                                                                          |      1  1.0|
      Respiratory Epithelium, Metaplasia,  |                                                                          |            |
           Squamous                        |                                                                          |      6  1.2|
      Respiratory Epithelium, Ulcer        |                                                                          |      3  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Ear                                     |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                                                          |   1        |
      Phthisis Bulbi                       |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   2        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Glomerulosclerosis                   |                                                                          |      1  3.0|
      Infarct                              |                                                                          |      1  1.0|
      Infiltration Cellular, Lymphocyte    | 1                                                                        |     31  1.2|
      Renal Tubule, Dilatation             |                                                                          |      1  3.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  51                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 8| 8| 8| 8| 8| 8| 8| 8| 8| 8|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |      A     |
    150 PPM                                | 7| 7| 7| 7| 7| 7| 7| 7| 7| 8|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 URINARY SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
      Renal Tubule, Hyperplasia, Focal     |                                                                          |      1  4.0|
      Renal Tubule, Regeneration           |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +                                             |  57        |
      Infiltration Cellular, Lymphocyte    |          1     1     1                                                   |     34  1.3|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  52                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 7| 4| 7| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 1| 2| 2| 2| 2| 5| 2| 2| 2| 2| 2| 2| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
                                           | 6| 2| 6| 5| 5| 5| 5| 6| 9| 6| 5| 6| 5| 8| 6| 5| 5| 6| 6| 6| 6| 5| 6| 6| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  A  +  A  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  A  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  A  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  A  +  M  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Basophilic Focus                     |                                                 X                       X|             
      Clear Cell Focus                     |                               X                                          |             
      Cytologic Alterations                |                                                                          |             
      Eosinophilic Focus                   |                                                       X                  |             
      Fatty Change, Focal                  |                                                                          |             
      Infarct                              |                4                                                         |             
      Necrosis                             | 1                                                                        |             
      Syncytial Alteration                 |             1           1  1        2     1           2        1        2|             
      Vacuolization Cytoplasmic            |                                                                          |             
      Centrilobular, Fatty Change          |                                                 1                        |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                                                             1            |             
      Acinus, Atrophy                      |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 1     1     1  1           2     1        1  2  2  1  1  1  2     1  1   |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |             +                                                            |             
      Dysplasia                            |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hypertrophy, Focal                   |       2     1              1  2                          2     2         |             
      Capsule, Accessory Adrenal Cortical  |                                                                          |             
          Nodule                           |                                                                          |             
      Subcapsular, Hyperplasia             | 3     4  1  1  1     1     2  1  1  2     2  1     1  3  1  1        4  2|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                       +              +  +|             
      Hyperplasia, Focal                   |                                                       2              3   |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  +  +  +  +  +  +  +  +  +  M  M  M  M  M  M  M  M  +  M  +  +  +  M  M|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  53                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 7| 4| 7| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 1| 2| 2| 2| 2| 5| 2| 2| 2| 2| 2| 2| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
                                           | 6| 2| 6| 5| 5| 5| 5| 6| 9| 6| 5| 6| 5| 8| 6| 5| 5| 6| 6| 6| 6| 5| 6| 6| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Cyst                  |                                              2                           |             
      Pars Distalis, Hyperplasia           |                      4                                                   |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia, Focal  |                1                                      1              1   |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                       2                  |             
                                            __________________________________________________________________________|             
   Penis                                   |    +                                                                     |             
      Inflammation, Chronic Active         |    3                                                                     |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +        +                 +  +  +     +        +     +  +        +  +   |             
      Dilatation                           | 4        4                 4  2  3     4        4     3  4        4      |             
      Inflammation, Chronic Active         |                                  4                    2           1  4   |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |    2                                                                     |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                            3        2     3  3                           |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Spermatocele                         |                                                                          |             
      Seminiferous Tubule, Degeneration    |                                                                         2|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Myeloid Cell, Hyperplasia            |    2                                                                     |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                        +                                 |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  M  M  +  M  +  +  +  +  M  +  M     M  M  M  +  M  +  M  M  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  M  +  +  M  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  M|             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                     2                 2                  |             
      Hyperplasia, Lymphoid                |       2  3                    1                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  M  M  M  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  M  +  +  +|             
      Hemorrhage                           |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     | 1  3  1  2  1  3  1  1  2  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1|             
      Pigmentation, Hemosiderin            |          1     1  1     1  1     1     2  1  1  1  1  1     1     1  1  1|             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  M  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |    1                    3                                            2   |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  54                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 7| 4| 7| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 1| 2| 2| 2| 2| 5| 2| 2| 2| 2| 2| 2| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
                                           | 6| 2| 6| 5| 5| 5| 5| 6| 9| 6| 5| 6| 5| 8| 6| 5| 5| 6| 6| 6| 6| 5| 6| 6| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  +  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |       1                                                                  |             
      Fat, Necrosis                        |                                                                          |             
      Hair Follicle, Atrophy               |                                                                          |             
      Prepuce, Inflammation, Chronic Active|    3                                                                     |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Maxilla, Callus                      |                                                                          |             
      Maxilla, Fracture                    |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       | 2  2  2  2  2        1     1  3  2  3     1  2  2  1  2  1  2  2  3  2  2|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |                                                             1            |             
      Inflammation, Chronic Active         |                            1                          1                  |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                          1           1  1|             
      Olfactory Epithelium, Metaplasia     |                                                                          |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |             1                                                        1   |             
      Respiratory Epithelium, Hyperplasia  |             1           1  1        1     2                       1  1  1|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                      +                       +        +                 +|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                                             2            |             
      Hydronephrosis                       |    1                                                                     |             
      Infiltration Cellular, Lymphocyte    | 1     1                    1        1     2  1           1  1     1      |             
      Inflammation, Chronic Active         |                                                                          |             
      Metaplasia, Osseous                  |       1                                                                  |             
      Nephropathy                          |                         4                                                |             
      Renal Tubule, Dilatation             |                                                                          |             
      Renal Tubule, Hyperplasia, Focal     |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  55                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 7| 4| 7| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 1| 2| 2| 2| 2| 5| 2| 2| 2| 2| 2| 2| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
                                           | 6| 2| 6| 5| 5| 5| 5| 6| 9| 6| 5| 6| 5| 8| 6| 5| 5| 6| 6| 6| 6| 5| 6| 6| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
      Renal Tubule, Regeneration           |       1     2        1                    1  1                    1     1|             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |    3                                                                     |             
      Infiltration Cellular, Lymphocyte    |                                                                          |             
      Inflammation, Chronic Active         |    4                                                                     |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  56                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 0| 7| 7| 7| 7| 7| 7| 7| 7| 5| 1| 6| 7| 7| 7| 7| 5| 5| 5| 7| 4| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 0| 3| 0| 2| 2| 1| 2| 6| 7| 9| 2| 7| 2|             
                                           | 6| 6| 6| 1| 6| 6| 6| 6| 6| 6| 6| 5| 9| 6| 4| 5| 6| 1| 5| 3| 0| 4| 6| 9| 5|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  +  +  M  +  A  +  +  A  +  A  A  A  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  A  +  A  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  A  A  +  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  A  A  A  +  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  A  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                          3               |             
      Basophilic Focus                     |                                                       X                  |             
      Clear Cell Focus                     | X                                                                        |             
      Cytologic Alterations                |             3     2        4                                             |             
      Eosinophilic Focus                   |                                                                          |             
      Fatty Change, Focal                  |                                  2                                       |             
      Infarct                              |                                     4                                    |             
      Necrosis                             |                                                                          |             
      Syncytial Alteration                 |    2  1                 1        3                                       |             
      Vacuolization Cytoplasmic            | 1                                                                        |             
      Centrilobular, Fatty Change          |                                                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                               1              1                           |             
      Acinus, Atrophy                      |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 1  1  1     1  1  2  1  1  1  1  2        1        1  1     1     1     1|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |       +                                                     +            |             
      Dysplasia                            |                                                             3            |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hypertrophy, Focal                   |                                                                          |             
      Capsule, Accessory Adrenal Cortical  |                                                                          |             
          Nodule                           |                                     X                                    |             
      Subcapsular, Hyperplasia             |    2  1        1  2  2  2  1              1                 1     2     1|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |             +  +                                                         |             
      Hyperplasia, Focal                   |                2                                                         |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  +  +  +  M  +  M  +  +  M  M  +  +  +  M  +  +  +  M  +  +  +  M  +  M|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  57                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 0| 7| 7| 7| 7| 7| 7| 7| 7| 5| 1| 6| 7| 7| 7| 7| 5| 5| 5| 7| 4| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 0| 3| 0| 2| 2| 1| 2| 6| 7| 9| 2| 7| 2|             
                                           | 6| 6| 6| 1| 6| 6| 6| 6| 6| 6| 6| 5| 9| 6| 4| 5| 6| 1| 5| 3| 0| 4| 6| 9| 5|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +|             
      Pars Distalis, Cyst                  |                                                                          |             
      Pars Distalis, Hyperplasia           |                                                                          |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia, Focal  | 1                    1        1              1                          1|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Penis                                   |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Preputial Gland                         |       +                 +     +              +                          +|             
      Dilatation                           |       4                 3                                               4|             
      Inflammation, Chronic Active         |                               3                                         2|             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                                                                          |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Spermatocele                         |                                                                          |             
      Seminiferous Tubule, Degeneration    |                                                                   2      |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Myeloid Cell, Hyperplasia            |          3                                                     2         |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  M  +  M  M  M  +  M  +  M  M  +  +  +  M  M  +  M  +  +  M  +  M  +  M|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  M  +  +  M  +  M  +  +  +  +  +  +  +  +  +  M  +  +  M  +  M  M  +  +|             
      Hyperplasia, Lymphoid                |                                        2                                 |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  A  +  A  +  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  M  M  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                           3                              |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     | 1  1  1     2  1  1  1  1  1  1  1  2  1  4  1  1  1  1  2  1  2  1  2  1|             
      Pigmentation, Hemosiderin            |    1        1           1     1  1        1  1  1  1           1  1     1|             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +|             
      Atrophy                              |          2                          3     3  1  1  2     3  3  3     4   |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  58                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 0| 7| 7| 7| 7| 7| 7| 7| 7| 5| 1| 6| 7| 7| 7| 7| 5| 5| 5| 7| 4| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 0| 3| 0| 2| 2| 1| 2| 6| 7| 9| 2| 7| 2|             
                                           | 6| 6| 6| 1| 6| 6| 6| 6| 6| 6| 6| 5| 9| 6| 4| 5| 6| 1| 5| 3| 0| 4| 6| 9| 5|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  +  M  M  M  M  M  M  +  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                                                                          |             
      Fat, Necrosis                        |                1                                                         |             
      Hair Follicle, Atrophy               |          3                                                               |             
      Prepuce, Inflammation, Chronic Active|                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Maxilla, Callus                      |          3                                                               |             
      Maxilla, Fracture                    |          X                                                  X            |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |    3  2     2  1  3  2           2  2     2  3  3  3  2  1     1        2|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |                                                                          |             
      Inflammation, Chronic Active         |                                                       1                  |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |       1  2     1  1                    1                                 |             
      Olfactory Epithelium, Metaplasia     |                      1                    1                       1      |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |                                                                1     1   |             
      Respiratory Epithelium, Hyperplasia  |                                           1              1        1  1   |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                    +                     |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |             2                                                            |             
      Hydronephrosis                       |                                              1                           |             
      Infiltration Cellular, Lymphocyte    |       1                       1  2        1  1  1     1                 1|             
      Inflammation, Chronic Active         |                                                                4         |             
      Metaplasia, Osseous                  |                                                                          |             
      Nephropathy                          |                                                                          |             
      Renal Tubule, Dilatation             |                                                          1               |             
      Renal Tubule, Hyperplasia, Focal     |                                                 2                        |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  59                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 0| 7| 7| 7| 7| 7| 7| 7| 7| 5| 1| 6| 7| 7| 7| 7| 5| 5| 5| 7| 4| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 0| 3| 0| 2| 2| 1| 2| 6| 7| 9| 2| 7| 2|             
                                           | 6| 6| 6| 1| 6| 6| 6| 6| 6| 6| 6| 5| 9| 6| 4| 5| 6| 1| 5| 3| 0| 4| 6| 9| 5|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
      Renal Tubule, Regeneration           | 1           1                                   1                 1     1|             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                                  3              3     3              3  4|             
      Infiltration Cellular, Lymphocyte    |                               1                                          |             
      Inflammation, Chronic Active         |                                                                3         |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  60                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      A     |
    CONTROL                                | 5| 5| 5| 5| 5| 5| 5| 5| 5| 6|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +                                             |  51        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +                                             |  54        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +                                             |  53        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +                                             |  52        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +                                             |  55        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Angiectasis                          |                                                                          |      1  3.0|
      Basophilic Focus                     |                                                                          |      3     |
      Clear Cell Focus                     |                                                                          |      2     |
      Cytologic Alterations                |                                                                          |      3  3.0|
      Eosinophilic Focus                   |                                                                          |      1     |
      Fatty Change, Focal                  |                                                                          |      1  2.0|
      Infarct                              |                                                                          |      2  4.0|
      Necrosis                             |                                                                          |      1  1.0|
      Syncytial Alteration                 |                                                                          |     12  1.5|
      Vacuolization Cytoplasmic            |                                                                          |      1  1.0|
      Centrilobular, Fatty Change          | 1     1  1              2                                                |      5  1.2|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                |                                                                          |      3  1.0|
      Acinus, Atrophy                      |          4                                                               |      1  4.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                | 1  1           1  1                                                      |     36  1.2|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Tooth                                   |                                                                          |   3        |
      Dysplasia                            |                                                                          |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Mineralization                       |    1                                                                     |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Hypertrophy, Focal                   |                                                                          |      6  1.7|
      Capsule, Accessory Adrenal Cortical  |                                                                          |            |
          Nodule                           |          X                                                               |      2     |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  61                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      A     |
    CONTROL                                | 5| 5| 5| 5| 5| 5| 5| 5| 5| 6|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ENDOCRINE SYSTEM - cont                   |                                                                          |            |
                                           |                                                                          |            |
      Subcapsular, Hyperplasia             | 1     1           1  1                                                   |     33  1.6|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   5        |
      Hyperplasia, Focal                   |                                                                          |      3  2.3|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +                                             |  39        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  M  +  +  +  +  +  +                                             |  56        |
      Pars Distalis, Cyst                  |                                                                          |      1  2.0|
      Pars Distalis, Hyperplasia           |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Follicular Cell, Hyperplasia, Focal  |                                                                          |      8  1.0|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Penis                                   |                                                                          |   1        |
      Inflammation, Chronic Active         |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +           +  +                                                         |  19        |
      Dilatation                           | 3           4  4                                                         |     16  3.6|
      Inflammation, Chronic Active         |                                                                          |      6  2.7|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Dilatation                           |                                                                          |      4  2.8|
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Spermatocele                         |                            X                                             |      1     |
      Seminiferous Tubule, Degeneration    |                                                                          |      2  2.0|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Myeloid Cell, Hyperplasia            |                                                                          |      3  2.3|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  M  +  +  +  +  +  M  +                                             |  33        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +                                             |  49        |
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +                                             |  57        |
      Hemorrhage                           |                                                                          |      2  2.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  62                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      A     |
    CONTROL                                | 5| 5| 5| 5| 5| 5| 5| 5| 5| 6|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
      Hyperplasia, Lymphoid                |                                                                          |      3  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  M  M  +  +  M  +  +  +                                             |  48        |
      Hemorrhage                           |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Hematopoietic Cell Proliferation     | 1  1  1  1  1  1  1  1  1  1                                             |     59  1.2|
      Pigmentation, Hemosiderin            |       1  1  1     1  1  1                                                |     34  1.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +                                             |  55        |
      Atrophy                              |                                                                          |     13  2.4|
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | M  M  M  M  +  M  M  M  M  M                                             |   4        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                |                                                                          |      1  1.0|
      Fat, Necrosis                        |                                                                          |      1  1.0|
      Hair Follicle, Atrophy               |                                                                          |      1  3.0|
      Prepuce, Inflammation, Chronic Active|                                                                          |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Maxilla, Callus                      |                                                                          |      1  3.0|
      Maxilla, Fracture                    |                                                                          |      2     |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Mineralization                       | 1        1  3           1                                                |     41  2.0|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Infiltration Cellular, Lymphocyte    |                                                                          |      1  1.0|
      Inflammation, Chronic Active         |                                                                          |      3  1.0|
      Alveolar Epithelium, Hyperplasia,    |                                                                          |            |
           Focal                           |          3                                                               |      1  3.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic Active         |                                                                          |      8  1.1|
      Olfactory Epithelium, Metaplasia     |                                                                          |      3  1.0|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |                                                                          |      4  1.0|
      Respiratory Epithelium, Hyperplasia  |                         1                                                |     13  1.1|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  63                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      A     |
    CONTROL                                | 5| 5| 5| 5| 5| 5| 5| 5| 5| 6|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   5        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Cyst                                 |                                                                          |      2  2.0|
      Hydronephrosis                       |                                                                          |      2  1.0|
      Infiltration Cellular, Lymphocyte    |                                                                          |     17  1.1|
      Inflammation, Chronic Active         |                                                                          |      1  4.0|
      Metaplasia, Osseous                  |                                                                          |      1  1.0|
      Nephropathy                          |                                                                          |      1  4.0|
      Renal Tubule, Dilatation             |                                                                          |      1  1.0|
      Renal Tubule, Hyperplasia, Focal     |                                                                          |      1  2.0|
      Renal Tubule, Regeneration           |                                                                          |     12  1.1|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Dilatation                           |       3                                                                  |      7  3.1|
      Infiltration Cellular, Lymphocyte    |    1                                                                     |      2  1.0|
      Inflammation, Chronic Active         |                                                                          |      2  3.5|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  64                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 5| 7| 7| 7| 7| 1| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 5| 7| 7| 3| 6|             
                             DAY ON TEST   | 2| 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 6| 9| 2| 8| 2| 2| 7| 1|             
                                           | 5| 6| 5| 5| 1| 5| 9| 9| 5| 4| 4| 5| 5| 5| 5| 9| 5| 7| 2| 6| 1| 5| 6| 9| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  M  +  A  +  +  +  +  +  +  +  M  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |          2                                                               |             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
      Proliferation Connective Tissue      |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |       4                                                                  |             
      Basophilic Focus                     |                                                                          |             
      Clear Cell Focus                     |                                        X                          X      |             
      Developmental Malformation           |                                                                          |             
      Hematopoietic Cell Proliferation     |                                                                      1   |             
      Infarct                              |                                                                          |             
      Inflammation, Chronic                |                   1                                                      |             
      Inflammation, Chronic Active         |                                                                          |             
      Mixed Cell Focus                     |                                        X                                 |             
      Necrosis                             |                               2                             1            |             
      Proliferation Connective Tissue      |                                                                          |             
      Syncytial Alteration                 | 2  1     2  2  1              1     1           1                        |             
      Centrilobular, Fatty Change          |                                                                          |             
      Midzonal, Fatty Change               |                                        1                                 |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                                                   +      |             
      Fat, Necrosis                        |                                                                   3      |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Acinus, Atrophy                      |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 1  2  1  1        1  1  2     1  1     1  1           1  1        1      |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Necrosis                             |             2                                                            |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                  2  1                                    |             
      Hypertrophy, Focal                   | 1              1  2  1  1        1  2     2     1              1         |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  65                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 5| 7| 7| 7| 7| 1| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 5| 7| 7| 3| 6|             
                             DAY ON TEST   | 2| 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 6| 9| 2| 8| 2| 2| 7| 1|             
                                           | 5| 6| 5| 5| 1| 5| 9| 9| 5| 4| 4| 5| 5| 5| 5| 9| 5| 7| 2| 6| 1| 5| 6| 9| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
      Subcapsular, Hyperplasia             |    1     1  1     1  1           1     1  2  1  2        1  1           1|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                              +                           |             
      Hyperplasia, Focal                   |                                              2                           |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  +  +  +  +  M  +  M  M  +  M  +  +  +  +  M  +  +  +  +  M  M  M  M  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | M  +  +  +  +  M  +  +  +  M  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia, Focal    |                      2                                                   |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia, Focal  |          1        1     2                    1                    1      |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |       3                                                                  |             
      Spermatocele                         |                                     X                                    |             
                                            __________________________________________________________________________|             
   Penis                                   |                                                                         +|             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +  +  +  +     +                 +     +              +  +  +         |             
      Abscess                              | 4                                                                        |             
      Dilatation                           | 4  3  4     3     4                                      3  3  4         |             
      Inflammation, Chronic Active         |          2                          2     2                              |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |             3                                                            |             
      Inflammation, Chronic Active         |                                                                      3   |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |          2           2                    3  3                    2      |             
      Inflammation, Acute                  |             1                                                            |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Myeloid Cell, Hyperplasia            |                                                                      3  4|             
                                            __________________________________________________________________________|             
   Lymph Node                              |             +                                                        +   |             
      Lumbar, Hyperplasia, Lymphoid        |             2                                                            |             
      Renal, Hyperplasia, Plasma Cell      |                                                                      3   |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  M  M  +  +  +  +  +  +  +  M  +  +  +  M  M  +  M  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                   2                                                      |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                            2                                             |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Hemorrhage                           |                   2                          2                           |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  66                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 5| 7| 7| 7| 7| 1| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 5| 7| 7| 3| 6|             
                             DAY ON TEST   | 2| 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 6| 9| 2| 8| 2| 2| 7| 1|             
                                           | 5| 6| 5| 5| 1| 5| 9| 9| 5| 4| 4| 5| 5| 5| 5| 9| 5| 7| 2| 6| 1| 5| 6| 9| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Hyperplasia, Lymphoid                |          3                                                               |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | M  +  +  M  +  +  +  +  +  +  +  +  +  M  +     +  +  +  +  +  M  +  M  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     | 1  1  2     2  1     1  1  1  1  1  1  1  1  2  1  1  1  1     1  1  3  3|             
      Hyperplasia, Lymphoid                |          2        2                                                      |             
      Pigmentation, Hemosiderin            | 1                 1     1                    1     1  1  1     1  1      |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +|             
      Atrophy                              |       2  2  3                 2                       3     3        3   |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  +  M  M  M  M  M  M  M  M  M  M  M  M  A  M  M  M  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |    1                                                                     |             
      Ulcer                                |             3                                                            |             
      Epithelium, Hyperplasia              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperostosis                         |                                                                          |             
      Cartilage, Degeneration              |                                                                          |             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |       1        1  2     2        3        1  2  2  1  2  2  2  1  2  1  2|             
                                            __________________________________________________________________________|             
   Spinal Cord                             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                                       3                  |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |                                        2                                 |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           | 1                                                        1               |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |                      2                                                   |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         | 1                 2        1                       1                     |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |          1                       1                    1                  |             
      Olfactory Epithelium, Metaplasia     |                                     1                                    |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  67                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 5| 7| 7| 7| 7| 1| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 5| 7| 7| 3| 6|             
                             DAY ON TEST   | 2| 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 6| 9| 2| 8| 2| 2| 7| 1|             
                                           | 5| 6| 5| 5| 1| 5| 9| 9| 5| 4| 4| 5| 5| 5| 5| 9| 5| 7| 2| 6| 1| 5| 6| 9| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
      Respiratory Epithelium, Hyperplasia  |                1  1                    1  1  1              1  1  2      |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |                   1                                1                     |             
      Respiratory Epithelium, Ulcer        |                                           1                              |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                              +                           |             
      Inflammation, Chronic Active         |                                              4                           |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Amyloid Deposition                   |                                                       2                  |             
      Cyst                                 |                                                                          |             
      Hydronephrosis                       |             2                                                           1|             
      Infiltration Cellular, Lymphocyte    | 1  2                    1        1  1  1        1        1               |             
      Inflammation, Acute                  |             3                                                            |             
      Inflammation, Chronic Active         |                                                                      4   |             
      Nephropathy                          |       3                                                                  |             
      Renal Tubule, Dilatation             |                               1                             1            |             
      Renal Tubule, Regeneration           |    1           1              1                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Dilatation                           |          3                    4     3                                    |             
      Infiltration Cellular, Lymphocyte    |                                                          1               |             
      Inflammation, Acute                  |             4                                                            |             
      Inflammation, Chronic Active         |                                                                      2  4|             
      Transitional Epithelium, Hyperplasia |                                                                      4   |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  68                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 6| 7| 7| 7| 6| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 9| 6| 2| 2| 2| 9| 2| 2| 2| 0| 8| 2| 2| 2| 8| 2| 2| 2| 2| 2| 2| 8| 2| 2|             
                                           | 6| 9| 7| 5| 5| 6| 3| 6| 6| 6| 3| 4| 6| 6| 6| 2| 6| 5| 5| 6| 6| 6| 7| 5| 5|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  M  M  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  A  +  +  M  A  A  +  +  +  A  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  A  +  +  +  A  A  +  +  +  +  +  +  +  +  +  M  +  +  +|             
      Hyperplasia, Lymphoid                |                      2                                                   |             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Proliferation Connective Tissue      |                               X                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  A  +  +  +  A  A  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                      2                                                   |             
      Inflammation, Chronic Active         |          3                                                               |             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Basophilic Focus                     |                               X  X                                       |             
      Clear Cell Focus                     | X                                                                        |             
      Developmental Malformation           |       X                                                                  |             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Infarct                              |                               4     2                                    |             
      Inflammation, Chronic                |                                                                          |             
      Inflammation, Chronic Active         |                                                                   1      |             
      Mixed Cell Focus                     |          X                                               X           X   |             
      Necrosis                             |                                  2                                       |             
      Proliferation Connective Tissue      |                               X                                          |             
      Syncytial Alteration                 |          1                                            2  1  1  1     1   |             
      Centrilobular, Fatty Change          |    2                 1                                1                  |             
      Midzonal, Fatty Change               |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                                                          |             
      Fat, Necrosis                        |                                                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Acinus, Atrophy                      |                   1                                                      |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 1  1  1  1  1        1  1  2     1  1  1  1  1        1     1     1  1  1|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                                                          |             
      Hypertrophy, Focal                   |                      2                          2           1            |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  69                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 6| 7| 7| 7| 6| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 9| 6| 2| 2| 2| 9| 2| 2| 2| 0| 8| 2| 2| 2| 8| 2| 2| 2| 2| 2| 2| 8| 2| 2|             
                                           | 6| 9| 7| 5| 5| 6| 3| 6| 6| 6| 3| 4| 6| 6| 6| 2| 6| 5| 5| 6| 6| 6| 7| 5| 5|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
      Subcapsular, Hyperplasia             | 1                 1        2  1  1  2  1  2     1  1     1              1|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                                +         |             
      Hyperplasia, Focal                   |                                                                4         |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  M  M  M  M  M  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  M  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia, Focal    |                                                                          |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia, Focal  | 1  1     1     1        1  2        1     1        1  3              1  1|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                    2                     |             
      Spermatocele                         |                                                                          |             
                                            __________________________________________________________________________|             
   Penis                                   |                                                                          |             
                                            __________________________________________________________________________|             
   Preputial Gland                         |             +     +  +        +  +  +                    +        +      |             
      Abscess                              |             4                 3                                          |             
      Dilatation                           |                   4  3        4  4  4                    3               |             
      Inflammation, Chronic Active         |                   2  2                                            3      |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |          2                                                        2      |             
      Inflammation, Acute                  |                                                                          |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Myeloid Cell, Hyperplasia            |                   2                                               3     3|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                   +                                +     +               |             
      Lumbar, Hyperplasia, Lymphoid        |                                                                          |             
      Renal, Hyperplasia, Plasma Cell      |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  M  +  +  M  +  M  +  +  +  +  M  +  +  M  +  +  +  +  M  +  +  M  M  +|             
      Hemorrhage                           |                                                                         2|             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |                                                                   3      |             
      Hemorrhage                           |                   4                                   2                  |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  70                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 6| 7| 7| 7| 6| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 9| 6| 2| 2| 2| 9| 2| 2| 2| 0| 8| 2| 2| 2| 8| 2| 2| 2| 2| 2| 2| 8| 2| 2|             
                                           | 6| 9| 7| 5| 5| 6| 3| 6| 6| 6| 3| 4| 6| 6| 6| 2| 6| 5| 5| 6| 6| 6| 7| 5| 5|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  M  +  +  +  +  +  M  M  +  +  +  +  +  +  +  M  M  +  +  M  M  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     | 1  1  1  1     1  1  1  1     3  2  1  1  1  2  1     1     1  1  3  1  1|             
      Hyperplasia, Lymphoid                |                                                                          |             
      Pigmentation, Hemosiderin            |    1  1  1        1  1           1              1     1        1        1|             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  M  +  +  +|             
      Atrophy                              |    3                 1        4              2                          2|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                   4     4|             
      Ulcer                                |                                                                         4|             
      Epithelium, Hyperplasia              |                                        1                                 |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperostosis                         |                                                    2                     |             
      Cartilage, Degeneration              |                                                                         3|             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                   +                                                      |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |    2  1  2  1     2        2  2  2  1     2  2        2  1  2  2     2   |             
                                            __________________________________________________________________________|             
   Spinal Cord                             |    +                                                                     |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                                                          |             
      Inflammation, Chronic Active         |       1                                                                  |             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    | 2                                         1                              |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |                                           3           2                  |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |             2           1              1                          1      |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                                                                          |             
      Olfactory Epithelium, Metaplasia     |                                                                          |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         | 1           1              1                                             |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  71                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 6| 7| 7| 7| 6| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 9| 6| 2| 2| 2| 9| 2| 2| 2| 0| 8| 2| 2| 2| 8| 2| 2| 2| 2| 2| 2| 8| 2| 2|             
                                           | 6| 9| 7| 5| 5| 6| 3| 6| 6| 6| 3| 4| 6| 6| 6| 2| 6| 5| 5| 6| 6| 6| 7| 5| 5|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
      Respiratory Epithelium, Hyperplasia  |       1        1     1     1           1           1     1  1            |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |             1                                                            |             
      Respiratory Epithelium, Ulcer        |       1                                                                  |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Amyloid Deposition                   |                                                                          |             
      Cyst                                 |                      1                                                   |             
      Hydronephrosis                       |                                                                          |             
      Infiltration Cellular, Lymphocyte    |          1                 1  1     1  1  1  1        1  1              1|             
      Inflammation, Acute                  |                                                                          |             
      Inflammation, Chronic Active         |                1                                                  4      |             
      Nephropathy                          |                                                                          |             
      Renal Tubule, Dilatation             |                                                                          |             
      Renal Tubule, Regeneration           |    1                                         1                           |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |          3              4                       2                       2|             
      Infiltration Cellular, Lymphocyte    |                                           1     1                        |             
      Inflammation, Acute                  |                                                                          |             
      Inflammation, Chronic Active         |                                                                   3      |             
      Transitional Epithelium, Hyperplasia |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  72                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|                                            |      A     |
    37.5 PPM                               | 7| 7| 7| 7| 7| 7| 7| 7| 7| 8|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  +  +  +  +  +  +                                             |  56        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +                                             |  50        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +                                             |  55        |
      Hyperplasia, Lymphoid                |                                                                          |      2  2.0|
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +                                             |  55        |
      Proliferation Connective Tissue      |                                                                          |      1     |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +                                             |  55        |
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
      Inflammation, Chronic Active         |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +                                             |  55        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Angiectasis                          |                                                                          |      1  4.0|
      Basophilic Focus                     |                                                                          |      2     |
      Clear Cell Focus                     |                                                                          |      3     |
      Developmental Malformation           |                                                                          |      1     |
      Hematopoietic Cell Proliferation     |                                                                          |      1  1.0|
      Infarct                              |                                                                          |      2  3.0|
      Inflammation, Chronic                |                                                                          |      1  1.0|
      Inflammation, Chronic Active         |                                                                          |      1  1.0|
      Mixed Cell Focus                     |                X                                                         |      5     |
      Necrosis                             |                                                                          |      3  1.7|
      Proliferation Connective Tissue      |                                                                          |      1     |
      Syncytial Alteration                 |                                                                          |     14  1.3|
      Centrilobular, Fatty Change          | 1     1           1                                                      |      6  1.2|
      Midzonal, Fatty Change               |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   1        |
      Fat, Necrosis                        |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Acinus, Atrophy                      |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                |                      1                                                   |     33  1.1|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Necrosis                             |                                                                          |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  73                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|                                            |      A     |
    37.5 PPM                               | 7| 7| 7| 7| 7| 7| 7| 7| 7| 8|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Cyst                                 |                3                                                         |      3  2.0|
      Hypertrophy, Focal                   |       1           1  1                                                   |     16  1.3|
      Subcapsular, Hyperplasia             |       1                                                                  |     26  1.2|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                         +                                                |   3        |
      Hyperplasia, Focal                   |                         2                                                |      3  2.7|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | M  +  +  M  +  M  +  +  +  +                                             |  38        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +                                             |  56        |
      Pars Distalis, Hyperplasia, Focal    |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Follicular Cell, Hyperplasia, Focal  |                                                                          |     17  1.2|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic Active         |                                                                          |      2  2.5|
      Spermatocele                         |                                                                          |      1     |
                                            __________________________________________________________________________|____________|
   Penis                                   |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Preputial Gland                         |                +  +        +                                             |  22        |
      Abscess                              |                                                                          |      3  3.7|
      Dilatation                           |                                                                          |     14  3.6|
      Inflammation, Chronic Active         |                                                                          |      6  2.2|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Inflammation, Acute                  |                                                                          |      1  3.0|
      Inflammation, Chronic Active         |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Dilatation                           |                                                                          |      7  2.3|
      Inflammation, Acute                  |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Myeloid Cell, Hyperplasia            |                                                                          |      5  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   5        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  74                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|                                            |      A     |
    37.5 PPM                               | 7| 7| 7| 7| 7| 7| 7| 7| 7| 8|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
      Lumbar, Hyperplasia, Lymphoid        |                                                                          |      1  2.0|
      Renal, Hyperplasia, Plasma Cell      |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | M  +  +  +  +  +  +  +  +  +                                             |  45        |
      Hemorrhage                           |                                                                          |      1  2.0|
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  M  +  +  +  +  +  +                                             |  59        |
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  M  +  +  +  +                                             |  57        |
      Hematopoietic Cell Proliferation     |                                                                          |      1  3.0|
      Hemorrhage                           |                                                                          |      4  2.5|
      Hyperplasia, Lymphoid                |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +                                             |  47        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Hematopoietic Cell Proliferation     | 1  1  1  1  1  2  1  1  1  1                                             |     53  1.3|
      Hyperplasia, Lymphoid                |                                                                          |      2  2.0|
      Pigmentation, Hemosiderin            | 1  1  1  1  1  1  1                                                      |     26  1.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +                                             |  56        |
      Atrophy                              |                                                                          |     12  2.5|
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | M  M  M  M  M  M  M  M  +  +                                             |   3        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic Active         |                                                                          |      3  3.0|
      Ulcer                                |                                                                          |      2  3.5|
      Epithelium, Hyperplasia              |                                                                          |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Hyperostosis                         |                                                                          |      1  2.0|
      Cartilage, Degeneration              |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Mineralization                       |    2           1     2  1                                                |     36  1.7|
                                            __________________________________________________________________________|____________|
   Spinal Cord                             |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  75                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|                                            |      A     |
    37.5 PPM                               | 7| 7| 7| 7| 7| 7| 7| 7| 7| 8|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
      Inflammation, Acute                  |                                                                          |      1  3.0|
      Inflammation, Chronic Active         |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Infiltration Cellular, Lymphocyte    |                                                                          |      3  1.7|
      Alveolar Epithelium, Hyperplasia,    |                                                                          |            |
           Focal                           |                                                                          |      4  1.8|
      Alveolus, Infiltration Cellular,     |                                                                          |            |
           Histiocyte                      |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic Active         |                                                                          |      8  1.3|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |             1                                                            |      4  1.0|
      Olfactory Epithelium, Metaplasia     |                                                                          |      1  1.0|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |                                                                          |      3  1.0|
      Respiratory Epithelium, Hyperplasia  | 1     1  1           1                                                   |     20  1.1|
      Respiratory Epithelium, Metaplasia,  |                                                                          |            |
           Squamous                        |                                                                          |      3  1.0|
      Respiratory Epithelium, Ulcer        |                                                                          |      2  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   1        |
      Inflammation, Chronic Active         |                                                                          |      1  4.0|
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Amyloid Deposition                   |                                                                          |      1  2.0|
      Cyst                                 |                                                                          |      1  1.0|
      Hydronephrosis                       |                                                                          |      2  1.5|
      Infiltration Cellular, Lymphocyte    |                                                                          |     18  1.1|
      Inflammation, Acute                  |                                                                          |      1  3.0|
      Inflammation, Chronic Active         |                                                                          |      3  3.0|
      Nephropathy                          |                                                                          |      1  3.0|
      Renal Tubule, Dilatation             |                1                                                         |      3  1.0|
      Renal Tubule, Regeneration           |                         1                                                |      6  1.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Dilatation                           |                                                                          |      7  3.0|
      Infiltration Cellular, Lymphocyte    |                1                                                         |      4  1.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  76                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|                                            |      A     |
    37.5 PPM                               | 7| 7| 7| 7| 7| 7| 7| 7| 7| 8|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 URINARY SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
      Inflammation, Acute                  |                                                                          |      1  4.0|
      Inflammation, Chronic Active         |                                                                          |      3  3.0|
      Transitional Epithelium, Hyperplasia |                                                                          |      1  4.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  77                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 6| 7| 5| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 5| 6| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 1| 2| 5| 2| 2| 2| 0| 2| 2| 2| 2| 2| 2| 5| 6| 5| 2| 2| 2| 2|             
                                           | 6| 6| 6| 4| 6| 4| 6| 7| 6| 6| 6| 8| 5| 6| 9| 6| 5| 6| 8| 2| 8| 5| 5| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |                                        X                    X            |             
      Clear Cell Focus                     |                                                                          |             
      Cytologic Alterations                |                               X                    2                     |             
      Eosinophilic Focus                   |             X                                                            |             
      Fatty Change, Focal                  |                                                                          |             
      Hematopoietic Cell Proliferation     |                3                                                         |             
      Infarct                              |                               4                          4               |             
      Inflammation, Chronic Active         |                                                                          |             
      Mixed Cell Focus                     |                                                                          |             
      Necrosis                             |                                                                          |             
      Syncytial Alteration                 | 1  1              1     2                       2              1     2   |             
      Bile Duct, Cyst                      |                         3  3                                             |             
      Bile Duct, Hyperplasia               |                         1                                                |             
      Centrilobular, Fatty Change          |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |    +                             +                       +               |             
      Artery, Inflammation, Chronic Active |                                  3                                       |             
      Fat, Necrosis                        |                                                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
      Acinus, Atrophy                      |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 1  1        1              1           1  2  1  1        1  1     1  1  1|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |          1                                                               |             
      Ulcer                                |                                                                          |             
                                            __________________________________________________________________________|             
   Tooth                                   |                               +                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic Active |                                  1                                       |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  78                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 6| 7| 5| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 5| 6| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 1| 2| 5| 2| 2| 2| 0| 2| 2| 2| 2| 2| 2| 5| 6| 5| 2| 2| 2| 2|             
                                           | 6| 6| 6| 4| 6| 4| 6| 7| 6| 6| 6| 8| 5| 6| 9| 6| 5| 6| 8| 2| 8| 5| 5| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
      Hyperplasia                          |                                              3                           |             
      Hypertrophy, Focal                   |       1                    1        3                                1   |             
      Capsule, Accessory Adrenal Cortical  |                                                                          |             
          Nodule                           |             X                                                            |             
      Subcapsular, Hyperplasia             | 1     1     1  2  1                 1     1  3  4  1                 2   |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Focal                   |                                        3                                 |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                               +                       +                  |             
      Hyperplasia, Focal                   |                               3                       2                  |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  M  M  M  +  +  M  +  M  +  +  +  +  +  +  +  +  +  +  M  +  +  M  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  M  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +|             
      Pars Distalis, Hyperplasia, Focal    |                                                                          |             
      Pars Distalis, Hyperplasia           |                3                                                         |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Ultimobranchial Cyst                 |                                                                          |             
      Follicular Cell, Hyperplasia, Focal  |       1     1  1        1                 1  1        1        1         |             
      Follicular Cell, Hyperplasia         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Tissue NOS                              |                                  +                                       |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                   2                       1                              |             
                                            __________________________________________________________________________|             
   Penis                                   |          +                                                               |             
      Inflammation, Chronic Active         |          2                                                               |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +                       +     +        +        +  +              +      |             
      Abscess                              |                               4                                   2      |             
      Dilatation                           | 4                       4              4        4  3              2      |             
      Inflammation, Chronic Active         | 2                                                                        |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Focal                   |                                                 3                        |             
      Inflammation, Chronic Active         |          1                                                               |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |          2     2        3     4                    4                 4  4|             
      Inflammation, Chronic Active         |                   2                                                      |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |                            2                                             |             
      Tunic, Inflammation, Chronic         |                   2                                                      |             
      Tunic, Proliferation Connective      |                                                                          |             
          Tissue                           |                   X                                                      |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Blood                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  79                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 6| 7| 5| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 5| 6| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 1| 2| 5| 2| 2| 2| 0| 2| 2| 2| 2| 2| 2| 5| 6| 5| 2| 2| 2| 2|             
                                           | 6| 6| 6| 4| 6| 4| 6| 7| 6| 6| 6| 8| 5| 6| 9| 6| 5| 6| 8| 2| 8| 5| 5| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Myeloid Cell, Hyperplasia            |          3     4                 3                                      2|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                  +                       +              +|             
      Iliac, Infiltration Cellular,        |                                                                          |             
          Histiocyte                       |                                  2                                       |             
      Inguinal, Hyperplasia, Lymphoid      |                                  2                                      2|             
      Renal, Hyperplasia, Plasma Cell      |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  M  M  M  M  M  +  +  M  M  M  +  +  +  M  M  M  M  M  M  +  M  M  M  +|             
      Hyperplasia, Lymphoid                |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +|             
      Angiectasis                          |                                                                          |             
      Hematopoietic Cell Proliferation     |                2                                                         |             
      Hemorrhage                           |          4                                                  2  2  2      |             
      Hyperplasia, Plasma Cell             |                                  2                                       |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  M  +  +  M  +  +  +  M  +  M  +  M  M  +  +  +  +  +  +  +  +  +  M|             
      Hemorrhage                           |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     | 1  2  1  2  1     1  1  1  1  1  3  1  1  1  1  1  1  1  3  2  1  1  1  2|             
      Hematopoietic Cell Proliferation     |                                                                          |             
          Granulocytic                     |                4                                                         |             
      Pigmentation, Hemosiderin            | 1  1  1  1  1     1  1  1  1  1  1  1  1  1  1  1  1  2  2  1  1  1  1  1|             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  M  +  +  +  M  +  M  +  +  +  +  +  +  +  +  +  M  +  M  +  +  +|             
      Atrophy                              |                2              3  3                    2                  |             
      Hyperplasia, Lymphoid                |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                  4                                      4|             
      Epithelium, Hyperplasia              |                         1                                                |             
      Prepuce, Inflammation, Chronic Active|          4                                                               |             
      Prepuce, Ulcer                       |          4                                                               |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Developmental Malformation           |                               X                                          |             
      Dysplasia                            |                                                                          |             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                   +                                                      |             
      Inflammation, Chronic Active         |                   2                                                      |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  80                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 6| 7| 5| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 5| 6| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 1| 2| 5| 2| 2| 2| 0| 2| 2| 2| 2| 2| 2| 5| 6| 5| 2| 2| 2| 2|             
                                           | 6| 6| 6| 4| 6| 4| 6| 7| 6| 6| 6| 8| 5| 6| 9| 6| 5| 6| 8| 2| 8| 5| 5| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
      Mineralization                       |       1  2  1     2     1  2  1           1  2  3  3     2        1  1   |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |    1                                                                     |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           | 3                                      1        1                    1   |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |                   2                                                      |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate                              |                                                    1                     |             
      Inflammation, Chronic Active         |                               2           1        1                 1  1|             
      Olfactory Epithelium, Atrophy        |                                                    2                     |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                                                                          |             
      Olfactory Epithelium, Metaplasia     |                                     1                                    |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |                         1     2                                          |             
      Respiratory Epithelium, Hyperplasia  | 1  1  1                 1     1                 1  1     1  1        1   |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                                      +   |             
      Phthisis Bulbi                       |                                                                      X   |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                   +  +   |             
                                            __________________________________________________________________________|             
   Zymbal's Gland                          | +                                                                        |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                               3                                          |             
      Infarct                              |                                        1                       1         |             
      Infiltration Cellular, Lymphocyte    |    1        1              1           1  1  2                           |             
      Inflammation, Chronic Active         |          3     4                                                         |             
      Metaplasia, Osseous                  |                                                                          |             
      Mineralization                       |                         1                                                |             
      Artery, Inflammation, Chronic Active |                                  2                                       |             
      Renal Tubule, Hyperplasia, Focal     |                         3                                         2      |             
      Renal Tubule, Regeneration           |                                                 1                    1   |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |          3  3                    2  2     3                    4  4     3|             
      Infiltration Cellular, Lymphocyte    |                                                                          |             
      Inflammation, Chronic Active         |          3     4                 3                                       |             
      Transitional Epithelium, Hyperplasia |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  81                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 5| 7| 4| 7| 7| 7| 3| 7| 7| 6| 7| 6| 6|             
                             DAY ON TEST   | 2| 2| 0| 2| 2| 2| 2| 2| 8| 2| 2| 2| 7| 2| 8| 2| 2| 2| 0| 2| 2| 8| 2| 4| 1|             
                                           | 5| 5| 1| 9| 5| 5| 6| 6| 3| 6| 6| 5| 9| 6| 4| 5| 6| 5| 7| 6| 6| 1| 5| 7| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 9|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  M  +  +  A  M  +  +  +  +  A  +  +  M  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  A|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  A  +  A  +  +  +  +  +  +  +  +  +  A|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  A  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |                                                                          |             
      Clear Cell Focus                     |                X           X  X                                          |             
      Cytologic Alterations                |                                                                          |             
      Eosinophilic Focus                   |                                                                          |             
      Fatty Change, Focal                  |                2                                                         |             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Infarct                              |       4                                                                  |             
      Inflammation, Chronic Active         |                                                                          |             
      Mixed Cell Focus                     |                                                                          |             
      Necrosis                             |                   1                                            3         |             
      Syncytial Alteration                 | 1  1        1  1     1        1        2     1                    1      |             
      Bile Duct, Cyst                      |                                                                          |             
      Bile Duct, Hyperplasia               |                                                                          |             
      Centrilobular, Fatty Change          |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |             +                          +                                 |             
      Artery, Inflammation, Chronic Active |                                                                          |             
      Fat, Necrosis                        |             3                          3                                 |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                       3                  |             
      Acinus, Atrophy                      |    1                                                                     |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 1  1     1        1           1     1           1           1  1  1  1   |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +     +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +     +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                                                          |             
      Ulcer                                |                                                                2         |             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic Active |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +     +|             
      Cyst                                 |                                                          2               |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  82                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 5| 7| 4| 7| 7| 7| 3| 7| 7| 6| 7| 6| 6|             
                             DAY ON TEST   | 2| 2| 0| 2| 2| 2| 2| 2| 8| 2| 2| 2| 7| 2| 8| 2| 2| 2| 0| 2| 2| 8| 2| 4| 1|             
                                           | 5| 5| 1| 9| 5| 5| 6| 6| 3| 6| 6| 5| 9| 6| 4| 5| 6| 5| 7| 6| 6| 1| 5| 7| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 9|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
      Hyperplasia                          |                                                                          |             
      Hypertrophy, Focal                   |             2        2                 1     2              1     1      |             
      Capsule, Accessory Adrenal Cortical  |                                                                          |             
          Nodule                           |                                                                          |             
      Subcapsular, Hyperplasia             |                1              1        1           1        2            |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +     +|             
      Hyperplasia, Focal                   |                                                                         2|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |             +              +  +  +                       +     +  +      |             
      Hyperplasia, Focal                   |             2              2  2                          2        2      |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  M  M  +  M  M  M  +  M  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia, Focal    |          1                                                               |             
      Pars Distalis, Hyperplasia           |                                                                          |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Ultimobranchial Cyst                 |                                                                          |             
      Follicular Cell, Hyperplasia, Focal  |    3        1                                4              1            |             
      Follicular Cell, Hyperplasia         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Tissue NOS                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                   3      |             
                                            __________________________________________________________________________|             
   Penis                                   |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +        +                 +     +     +                          +     +|             
      Abscess                              |                                                                          |             
      Dilatation                           | 4        3                 4     3     3                          1     3|             
      Inflammation, Chronic Active         | 2        2                 1                                      2      |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Focal                   |                                                                          |             
      Inflammation, Chronic Active         |                            2                          2  2               |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           | 4           3                                            3        4  2   |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |                                                                          |             
      Tunic, Inflammation, Chronic         |                                                                          |             
      Tunic, Proliferation Connective      |                                                                          |             
          Tissue                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Blood                                   |                                     +                                    |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  83                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 5| 7| 4| 7| 7| 7| 3| 7| 7| 6| 7| 6| 6|             
                             DAY ON TEST   | 2| 2| 0| 2| 2| 2| 2| 2| 8| 2| 2| 2| 7| 2| 8| 2| 2| 2| 0| 2| 2| 8| 2| 4| 1|             
                                           | 5| 5| 1| 9| 5| 5| 6| 6| 3| 6| 6| 5| 9| 6| 4| 5| 6| 5| 7| 6| 6| 1| 5| 7| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 9|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
      Myeloid Cell, Hyperplasia            |                                                       2  3           3   |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                      +                                   +               |             
      Iliac, Infiltration Cellular,        |                                                                          |             
          Histiocyte                       |                                                                          |             
      Inguinal, Hyperplasia, Lymphoid      |                                                                          |             
      Renal, Hyperplasia, Plasma Cell      |                                                          3               |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  +  M  M  M  +  M  +  +  M  M  +  M  +  +  +  M  M  +  M  +  M  +  M  M|             
      Hyperplasia, Lymphoid                |                                        2                                 |             
      Inflammation, Chronic Active         |                                                       2                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |             1                                                            |             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Hemorrhage                           |                               2                                          |             
      Hyperplasia, Plasma Cell             |          2                                                               |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  M  +  +  M  +  A  M  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                   2                                                      |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     | 1  1  2  1  1  1  2     1  1  1  1  1  1     1  1  3  2  4  1  1  1  3  3|             
      Hematopoietic Cell Proliferation     |                                                                          |             
          Granulocytic                     |                                                                          |             
      Pigmentation, Hemosiderin            | 1  1  1  1  1  1  1     2  1  1  1  1  1     1  1  1  2  1  1  1  1  1   |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  M  +  M  +  +  +  +  +  +  M  A  +  +  +  M  M  M  +  +  +  +|             
      Atrophy                              |                         4                                      3         |             
      Hyperplasia, Lymphoid                |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  +  M  M  M  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
      Epithelium, Hyperplasia              |                                                                          |             
      Prepuce, Inflammation, Chronic Active|                                                                          |             
      Prepuce, Ulcer                       |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Developmental Malformation           |                                                                          |             
      Dysplasia                            |             2                                                            |             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  84                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 5| 7| 4| 7| 7| 7| 3| 7| 7| 6| 7| 6| 6|             
                             DAY ON TEST   | 2| 2| 0| 2| 2| 2| 2| 2| 8| 2| 2| 2| 7| 2| 8| 2| 2| 2| 0| 2| 2| 8| 2| 4| 1|             
                                           | 5| 5| 1| 9| 5| 5| 6| 6| 3| 6| 6| 5| 9| 6| 4| 5| 6| 5| 7| 6| 6| 1| 5| 7| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 9|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
      Mineralization                       | 1     1              1        2     2  2           1  2  3        2      |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Lymphocyte    |                      2                                                   |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |                            2  1        2                                 |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |                      2                                                   |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate                              |                                                                          |             
      Inflammation, Chronic Active         | 1                    1                                                   |             
      Olfactory Epithelium, Atrophy        |                                                                          |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |    1                                                                    1|             
      Olfactory Epithelium, Metaplasia     |                                                       1  1               |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |                                     1                                    |             
      Respiratory Epithelium, Hyperplasia  | 1  1              1           1        1     1           1  1            |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                                          |             
      Phthisis Bulbi                       |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                            +                                             |             
                                            __________________________________________________________________________|             
   Zymbal's Gland                          |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                              2                           |             
      Infarct                              |                                                                          |             
      Infiltration Cellular, Lymphocyte    |    1     1     1              1     1                                    |             
      Inflammation, Chronic Active         |                                                       4  4           4   |             
      Metaplasia, Osseous                  | 1                                                                        |             
      Mineralization                       |                                                                          |             
      Artery, Inflammation, Chronic Active |                                                                          |             
      Renal Tubule, Hyperplasia, Focal     |                                                                          |             
      Renal Tubule, Regeneration           |    1                                   1                                 |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
      Dilatation                           |    4                 4  2           2           4                 2      |             
      Infiltration Cellular, Lymphocyte    |                                                                          |             
      Inflammation, Chronic Active         |                                                       4  3               |             
      Transitional Epithelium, Hyperplasia |                                                          3               |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  85                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|                                            |      A     |
    75 PPM                                 | 9| 9| 9| 9| 9| 9| 9| 9| 9| 0|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  M  +  +  +  +  +  +  +  +                                             |  51        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +                                             |  58        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +                                             |  58        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +                                             |  55        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +                                             |  55        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +                                             |  56        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  M  +  +  +  +  +  M  +                                             |  53        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Basophilic Focus                     |                                                                          |      2     |
      Clear Cell Focus                     |                                                                          |      3     |
      Cytologic Alterations                |                                                                          |      2  2.0|
      Eosinophilic Focus                   |                                                                          |      1     |
      Fatty Change, Focal                  |                                                                          |      1  2.0|
      Hematopoietic Cell Proliferation     |                                                                          |      1  3.0|
      Infarct                              |                                                                          |      3  4.0|
      Inflammation, Chronic Active         |                            1                                             |      1  1.0|
      Mixed Cell Focus                     |                   X                                                      |      1     |
      Necrosis                             |                            1                                             |      3  1.7|
      Syncytial Alteration                 |                                                                          |     16  1.3|
      Bile Duct, Cyst                      |                                                                          |      2  3.0|
      Bile Duct, Hyperplasia               |                                                                          |      1  1.0|
      Centrilobular, Fatty Change          | 1              1     1  1                                                |      4  1.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   5        |
      Artery, Inflammation, Chronic Active |                                                                          |      1  3.0|
      Fat, Necrosis                        |                                                                          |      2  3.0|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic Active         |                                                                          |      1  3.0|
      Acinus, Atrophy                      |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                |    1  1     1        1  1                                                |     29  1.0|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Necrosis                             |                                                                          |      1  1.0|
      Ulcer                                |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Tooth                                   |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  86                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|                                            |      A     |
    75 PPM                                 | 9| 9| 9| 9| 9| 9| 9| 9| 9| 0|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |            |
                                           |                                                                          |            |
      Artery, Inflammation, Chronic Active |                                                                          |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Cyst                                 |                                                                          |      1  2.0|
      Hyperplasia                          |                                                                          |      1  3.0|
      Hypertrophy, Focal                   |                                                                          |     10  1.5|
      Capsule, Accessory Adrenal Cortical  |                                                                          |            |
          Nodule                           |                                                                          |      1     |
      Subcapsular, Hyperplasia             |    1        1                                                            |     18  1.4|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Hyperplasia, Focal                   |                                                                          |      2  2.5|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   9        |
      Hyperplasia, Focal                   |                                                                          |      7  2.1|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +                                             |  45        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | M  +  +  +  M  +  +  +  +  +                                             |  54        |
      Pars Distalis, Hyperplasia, Focal    |                                                                          |      1  1.0|
      Pars Distalis, Hyperplasia           |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Ultimobranchial Cyst                 |                            X                                             |      1     |
      Follicular Cell, Hyperplasia, Focal  |                                                                          |     12  1.4|
      Follicular Cell, Hyperplasia         |          1                                                               |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Tissue NOS                              |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic Active         |                                                                          |      3  2.0|
                                            __________________________________________________________________________|____________|
   Penis                                   |                                                                          |   1        |
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +        +     +        +                                                |  18        |
      Abscess                              |                                                                          |      2  3.0|
      Dilatation                           | 2        4     4        2                                                |     17  3.2|
      Inflammation, Chronic Active         |                                                                          |      5  1.8|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Hyperplasia, Focal                   |                                                                          |      1  3.0|
      Inflammation, Chronic Active         |                                                                          |      4  1.8|
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  87                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|                                            |      A     |
    75 PPM                                 | 9| 9| 9| 9| 9| 9| 9| 9| 9| 0|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
      Dilatation                           |                                                                          |     12  3.3|
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Mineralization                       |                                                                          |      1  2.0|
      Tunic, Inflammation, Chronic         |                                                                          |      1  2.0|
      Tunic, Proliferation Connective      |                                                                          |            |
          Tissue                           |                                                                          |      1     |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Blood                                   |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Myeloid Cell, Hyperplasia            |                                                                          |      7  2.9|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   5        |
      Iliac, Infiltration Cellular,        |                                                                          |            |
          Histiocyte                       |                                                                          |      1  2.0|
      Inguinal, Hyperplasia, Lymphoid      |                                                                          |      2  2.0|
      Renal, Hyperplasia, Plasma Cell      |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | M  +  +  +  +  M  +  +  +  +                                             |  26        |
      Hyperplasia, Lymphoid                |                                                                          |      1  2.0|
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +                                             |  57        |
      Angiectasis                          |                                                                          |      1  1.0|
      Hematopoietic Cell Proliferation     |                                                                          |      1  2.0|
      Hemorrhage                           |                                                                          |      5  2.4|
      Hyperplasia, Plasma Cell             |                                                                          |      2  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  M  +  +  +  +                                             |  48        |
      Hemorrhage                           |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Hematopoietic Cell Proliferation     | 1  1  1  1  1  1  1  1  1  4                                             |     57  1.4|
      Hematopoietic Cell Proliferation     |                                                                          |            |
          Granulocytic                     |                                                                          |      1  4.0|
      Pigmentation, Hemosiderin            | 2  1  1  1  1  1  1  2  2                                                |     55  1.1|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +                                             |  48        |
      Atrophy                              |                            2                                             |      7  2.7|
      Hyperplasia, Lymphoid                |       1                                                                  |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  M  M  M  M  M  M  M  M  M                                             |   2        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  88                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|                                            |      A     |
    75 PPM                                 | 9| 9| 9| 9| 9| 9| 9| 9| 9| 0|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 INTEGUMENTARY SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Inflammation, Chronic Active         |                                                                          |      2  4.0|
      Epithelium, Hyperplasia              |                                                                          |      1  1.0|
      Prepuce, Inflammation, Chronic Active|                                                                          |      1  4.0|
      Prepuce, Ulcer                       |                                                                          |      1  4.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Developmental Malformation           |                                                                          |      1     |
      Dysplasia                            |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                                                                          |   1        |
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Mineralization                       | 2  3  1  1     1  2     2                                                |     31  1.7|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +                                             |  59        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Infiltration Cellular, Lymphocyte    |                                                                          |      2  1.5|
      Alveolar Epithelium, Hyperplasia,    |                                                                          |            |
           Focal                           |                                                                          |      7  1.6|
      Alveolus, Infiltration Cellular,     |                                                                          |            |
           Histiocyte                      |                                                                          |      2  2.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Exudate                              |                                                                          |      1  1.0|
      Inflammation, Chronic Active         |                                                                          |      7  1.1|
      Olfactory Epithelium, Atrophy        |                                                                          |      1  2.0|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |                                                                          |      2  1.0|
      Olfactory Epithelium, Metaplasia     |                                                                          |      3  1.0|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |                                                                          |      3  1.3|
      Respiratory Epithelium, Hyperplasia  | 1                                                                        |     19  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                                                          |   1        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  89                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|                                            |            |
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|                                            |      A     |
    75 PPM                                 | 9| 9| 9| 9| 9| 9| 9| 9| 9| 0|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 SPECIAL SENSES SYSTEM - cont              |                                                                          |            |
                                           |                                                                          |            |
      Phthisis Bulbi                       |                                                                          |      1     |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   3        |
                                            __________________________________________________________________________|____________|
   Zymbal's Gland                          |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Cyst                                 |                                                                          |      2  2.5|
      Infarct                              |                                                                          |      2  1.0|
      Infiltration Cellular, Lymphocyte    |                      1  1                                                |     13  1.1|
      Inflammation, Chronic Active         |                                                                          |      5  3.8|
      Metaplasia, Osseous                  |                                                                          |      1  1.0|
      Mineralization                       |                                                                          |      1  1.0|
      Artery, Inflammation, Chronic Active |                                                                          |      1  2.0|
      Renal Tubule, Hyperplasia, Focal     |                                                                          |      2  2.5|
      Renal Tubule, Regeneration           |          1                                                               |      5  1.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Dilatation                           |                                                                          |     14  3.0|
      Infiltration Cellular, Lymphocyte    |                            1                                             |      1  1.0|
      Inflammation, Chronic Active         |                                                                          |      5  3.4|
      Transitional Epithelium, Hyperplasia |                                                                          |      1  3.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page  90                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 7| 7| 5| 7| 4| 7| 5| 6| 7| 7| 7| 5| 7| 5| 2| 7| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 4| 2| 2| 7| 2| 4| 2| 5| 6| 2| 2| 2| 5| 2| 4| 3| 2| 8| 2| 2| 2| 2|             
                                           | 5| 5| 6| 0| 5| 6| 5| 5| 3| 5| 3| 8| 5| 5| 5| 8| 6| 1| 5| 4| 8| 6| 9| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    150 PPM                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  A  A  +  A  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | A  +  +  A  +  +  +  +  A  +  +  A  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | A  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  A  +  +  A  +  A  +  +  A  +  +  M  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | A  +  +  A  +  +  +  +  A  +  +  A  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Abscess                              |                                        2                                 |             
      Basophilic Focus                     |                                        X  X                              |             
      Cytologic Alterations                |                2                                                         |             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Hyperplasia                          |                                                                          |             
      Infarct                              |                                           3  3                           |             
      Inflammation, Chronic                |                                        1  1                       1     1|             
      Mixed Cell Focus                     |                                                                          |             
      Necrosis                             |          2                    3  3                          2            |             
      Proliferation Connective Tissue      |                                                                          |             
      Syncytial Alteration                 |    1                                1           1        1              1|             
      Bile Duct, Hyperplasia               |                                                                          |             
      Centrilobular, Fatty Change          |                                                                          |             
      Centrilobular, Necrosis              |                   2        2                                             |             
      Hepatocyte, Necrosis                 |                                                                   1      |             
      Periportal, Vacuolization Cytoplasmic|                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                               +                       +                  |             
      Fat, Necrosis                        |                               3                       2                  |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
      Inflammation, Chronic                |                1                       1                                 |             
      Proliferation Connective Tissue      |                                                                          |             
      Acinus, Atrophy                      |                                                                          |             
      Duct, Cyst                           |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 1  1  1     2  1     2     1        1           1        1     1     1   |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
      Dysplasia                            |                                                                          |             
      Necrosis                             |          1                    1                                          |             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  91                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 7| 7| 5| 7| 4| 7| 5| 6| 7| 7| 7| 5| 7| 5| 2| 7| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 4| 2| 2| 7| 2| 4| 2| 5| 6| 2| 2| 2| 5| 2| 4| 3| 2| 8| 2| 2| 2| 2|             
                                           | 5| 5| 6| 0| 5| 6| 5| 5| 3| 5| 3| 8| 5| 5| 5| 8| 6| 1| 5| 4| 8| 6| 9| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    150 PPM                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |             
                                           |                                                                          |             
      Degeneration                         |                               1                                          |             
      Thrombosis                           |                                  2                                       |             
      Artery, Inflammation, Chronic Active |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  A  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
      Hypertrophy, Focal                   |    1  1        1  1                                                      |             
      Subcapsular, Hyperplasia             |       2     1  1  1  1                    1     1           2     2  1   |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  A  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                                          |             
      Hyperplasia, Focal                   |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  M  +  M  +  +  +  +  +  +  +  M  +  M  M  +  +  +  +  +  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  M  M  +  +  +  +  M  +  +  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia, Focal  |    3        3  1     1              2  2  2     1        1        1     1|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Coagulating Gland                       |                                                    A                     |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                      4                             4     2  2            |             
                                            __________________________________________________________________________|             
   Penis                                   |          +                             +                                 |             
      Congestion                           |                                                                          |             
      Inflammation, Chronic Active         |          2                                                               |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +              +  +  +                                            +     +|             
      Abscess                              |                                                                         3|             
      Dilatation                           | 4              4  4  2                                            4      |             
      Inflammation, Chronic Active         |                   2  2                                                   |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |          2                                               3               |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                                              3                       3   |             
      Hyperplasia                          |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Seminiferous Tubule, Degeneration    |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
      Infarct                              |                                              3                           |             
      Myeloid Cell, Hyperplasia            |                                        3     3                          2|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  92                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 7| 7| 5| 7| 4| 7| 5| 6| 7| 7| 7| 5| 7| 5| 2| 7| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 4| 2| 2| 7| 2| 4| 2| 5| 6| 2| 2| 2| 5| 2| 4| 3| 2| 8| 2| 2| 2| 2|             
                                           | 5| 5| 6| 0| 5| 6| 5| 5| 3| 5| 3| 8| 5| 5| 5| 8| 6| 1| 5| 4| 8| 6| 9| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    150 PPM                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node                              | +                       +                                                |             
      Iliac, Inflammation, Chronic Active  |                                                                          |             
      Inguinal, Inflammation, Chronic      |                                                                          |             
          Active                           |                                                                          |             
      Inguinal, Pigmentation               |                         2                                                |             
      Lumbar, Hemorrhage                   |                                                                          |             
      Lumbar, Hyperplasia, Histiocytic     |                                                                          |             
      Lumbar, Hyperplasia, Lymphoid        |                         3                                                |             
      Lumbar, Hyperplasia, Plasma Cell     |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  M  M  M  +  +  +  +  M  +  M  +  +  M  +  +  M  M  +  +  +  M|             
      Hyperplasia, Lymphoid                |                                                                          |             
      Infiltration Cellular, Histiocyte    |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  M  +  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                                                                          |             
      Pigmentation, Hemosiderin            |                         2                                                |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  M  +  M  M  +  +  +  M  +  M  +  +  +  +  +  M  M  +  +  +|             
      Hemorrhage                           |                               2                                          |             
      Hyperplasia, Lymphoid                |                                                                          |             
      Hyperplasia, Plasma Cell             |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
      Fibrosis                             |                      1                                                   |             
      Hematopoietic Cell Proliferation     | 3  1  1  1  1  1  2  1     3  3  2  1  2  1  3  1        1  3  3  1  1  4|             
      Hematopoietic Cell Proliferation     |                                                                          |             
          Granulocytic                     |                               3              3                           |             
      Pigmentation, Hemosiderin            | 1  1  1  1  1  2  1  1     1  1  1  1  1  1  2  1        2  1  1  1  2  1|             
      Lymphoid Follicle, Atrophy           |                                                          3               |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  M  +  A  +  M  +  +  +  +  M|             
      Atrophy                              |          2                    3  3                          2            |             
      Cyst                                 |                                                                      2   |             
      Ectopic Parathyroid Gland            |       X                                                                  |             
      Hyperplasia, Lymphoid                |                                           1                              |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                   1                             1                        |             
      Inflammation, Chronic Active         |                         4                    4                           |             
      Ulcer                                |                         4                                                |             
      Prepuce, Inflammation, Chronic Active|                                                                          |             
      Subcutaneous Tissue, Edema           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  93                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 7| 7| 5| 7| 4| 7| 5| 6| 7| 7| 7| 5| 7| 5| 2| 7| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 4| 2| 2| 7| 2| 4| 2| 5| 6| 2| 2| 2| 5| 2| 4| 3| 2| 8| 2| 2| 2| 2|             
                                           | 5| 5| 6| 0| 5| 6| 5| 5| 3| 5| 3| 8| 5| 5| 5| 8| 6| 1| 5| 4| 8| 6| 9| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    150 PPM                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Subcutaneous Tissue, Granuloma       |                                                                          |             
      Subcutaneous Tissue, Hemorrhage      |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fracture                             |                                                       X                  |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       | 2  2              1  1  1  1     2  2        1        1  1  1           1|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  M  +  +  +  M  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Congestion                           |                                  3                                       |             
      Infiltration Cellular, Lymphocyte    |                                                                          |             
      Leukocytosis                         |                               2                                          |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |       2     2  2                          2                          2   |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |                                  2                                       |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate, Serous                      |                1                                                         |             
      Inflammation, Chronic Active         |                                        1        1              1     1   |             
      Olfactory Epithelium, Atrophy        |                                                                          |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                                                                   1  1   |             
      Olfactory Epithelium, Metaplasia     |    1                                                                     |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |                                     1                                    |             
      Respiratory Epithelium, Hyperplasia  |    1                                                                     |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |                                                                          |             
      Respiratory Epithelium, Ulcer        |                                                                          |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                                          |             
      Phthisis Bulbi                       |                                                                          |             
      Cornea, Inflammation, Chronic Active |                                                                          |             
      Lens, Cataract                       |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                            +                                   +         |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  94                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 7| 7| 5| 7| 4| 7| 5| 6| 7| 7| 7| 5| 7| 5| 2| 7| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 4| 2| 2| 7| 2| 4| 2| 5| 6| 2| 2| 2| 5| 2| 4| 3| 2| 8| 2| 2| 2| 2|             
                                           | 5| 5| 6| 0| 5| 6| 5| 5| 3| 5| 3| 8| 5| 5| 5| 8| 6| 1| 5| 4| 8| 6| 9| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    150 PPM                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Abscess                              |                                        4                                 |             
      Cyst                                 |                            2                 2                           |             
      Hydronephrosis                       |                                              2                           |             
      Infarct                              |                                                                          |             
      Infiltration Cellular, Lymphocyte    | 2           1     1  1              1     1                 2  1     1   |             
      Inflammation, Acute                  |          2                                                               |             
      Inflammation, Chronic Active         |                         4                    3                          2|             
      Renal Tubule, Dilatation             |                                  2                       2  1            |             
      Renal Tubule, Hyperplasia, Focal     |                1           1                                             |             
      Renal Tubule, Regeneration           |                                                             1            |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |                                     4  3  3     4        3               |             
      Infiltration Cellular, Lymphocyte    | 1  1                 1     1                                             |             
      Inflammation, Acute                  |          2                                                               |             
      Inflammation, Chronic Active         |                                              4                          3|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  95                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 3| 7| 7| 7| 7| 7| 7| 6| 5| 7| 7| 6| 7| 7| 7| 1| 5| 7| 7| 5|             
                             DAY ON TEST   | 2| 2| 2| 5| 1| 1| 2| 2| 2| 2| 2| 2| 9| 5| 2| 2| 9| 2| 2| 2| 0| 5| 2| 2| 3|             
                                           | 5| 5| 5| 8| 8| 6| 5| 9| 5| 5| 6| 5| 3| 2| 5| 6| 2| 5| 5| 6| 0| 6| 5| 6| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  +|             
      Inflammation, Chronic Active         |                1                                                         |             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  A|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Abscess                              |                                                                          |             
      Basophilic Focus                     |                                                                          |             
      Cytologic Alterations                |                                  3                                       |             
      Hematopoietic Cell Proliferation     |                1                                                         |             
      Hyperplasia                          |                               4                                          |             
      Infarct                              |                                                                          |             
      Inflammation, Chronic                |                               2                                          |             
      Mixed Cell Focus                     |                               X                                          |             
      Necrosis                             |                                                                          |             
      Proliferation Connective Tissue      |                                                 X                        |             
      Syncytial Alteration                 |    1                       1        1  2                 1        2      |             
      Bile Duct, Hyperplasia               |                               2                                          |             
      Centrilobular, Fatty Change          |                                                                          |             
      Centrilobular, Necrosis              |                                                                          |             
      Hepatocyte, Necrosis                 |                                                                          |             
      Periportal, Vacuolization Cytoplasmic|                               3                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                                                          |             
      Fat, Necrosis                        |                                                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                               1                                          |             
      Proliferation Connective Tissue      |                                                 X                        |             
      Acinus, Atrophy                      |                                              1                           |             
      Duct, Cyst                           |                                                             3            |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                | 1  1  1  1  1  1  1  1  1  1        1     1        1  1  1        2  1   |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dysplasia                            |                               2                                          |             
      Necrosis                             |                                                                          |             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |                                                 1                        |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  96                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 3| 7| 7| 7| 7| 7| 7| 6| 5| 7| 7| 6| 7| 7| 7| 1| 5| 7| 7| 5|             
                             DAY ON TEST   | 2| 2| 2| 5| 1| 1| 2| 2| 2| 2| 2| 2| 9| 5| 2| 2| 9| 2| 2| 2| 0| 5| 2| 2| 3|             
                                           | 5| 5| 5| 8| 8| 6| 5| 9| 5| 5| 6| 5| 3| 2| 5| 6| 2| 5| 5| 6| 0| 6| 5| 6| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |             
                                           |                                                                          |             
      Degeneration                         |                                                                          |             
      Thrombosis                           |                                                                          |             
      Artery, Inflammation, Chronic Active |                                        2                                 |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hypertrophy, Focal                   |    2                          1  1        1        1                     |             
      Subcapsular, Hyperplasia             | 2  1  1     2     2  1  2                    1                    1      |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                    +                     |             
      Hyperplasia, Focal                   |                                                    2                     |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  M  +  M  +  +  M  +  +  +  M  M  +  M  +  M  +  +  +  M  +  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  M  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia, Focal  | 1  1  1              1           1        2  1     1     1               |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Coagulating Gland                       |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |             3     3        2                    1                        |             
                                            __________________________________________________________________________|             
   Penis                                   |                                        +                                +|             
      Congestion                           |                                                                          |             
      Inflammation, Chronic Active         |                                        4                                4|             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +                          +                    +  +           +      |             
      Abscess                              |                                                                          |             
      Dilatation                           | 4  4                          4                    4  4                  |             
      Inflammation, Chronic Active         |                                                                   4      |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                                                          |             
      Inflammation, Chronic Active         |                1                                               3        2|             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           | 3                                                                        |             
      Hyperplasia                          |                                                 3                        |             
      Inflammation, Chronic Active         |                                                 3                        |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Seminiferous Tubule, Degeneration    |                                                 1                        |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infarct                              |                                                                          |             
      Myeloid Cell, Hyperplasia            |                4                 3     3                                3|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  97                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 3| 7| 7| 7| 7| 7| 7| 6| 5| 7| 7| 6| 7| 7| 7| 1| 5| 7| 7| 5|             
                             DAY ON TEST   | 2| 2| 2| 5| 1| 1| 2| 2| 2| 2| 2| 2| 9| 5| 2| 2| 9| 2| 2| 2| 0| 5| 2| 2| 3|             
                                           | 5| 5| 5| 8| 8| 6| 5| 9| 5| 5| 6| 5| 3| 2| 5| 6| 2| 5| 5| 6| 0| 6| 5| 6| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                +                    +                          +         |             
      Iliac, Inflammation, Chronic Active  |                                                                3         |             
      Inguinal, Inflammation, Chronic      |                                                                          |             
          Active                           |                                                                3         |             
      Inguinal, Pigmentation               |                                                                          |             
      Lumbar, Hemorrhage                   |                                     2                                    |             
      Lumbar, Hyperplasia, Histiocytic     |                                     2                                    |             
      Lumbar, Hyperplasia, Lymphoid        |                                                                          |             
      Lumbar, Hyperplasia, Plasma Cell     |                3                                                         |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  M  +  +  +  M  +  +  M  +  +  +  M  +  +  M  M  M  +  M  M  +  +  +  +|             
      Hyperplasia, Lymphoid                |          3                                                               |             
      Infiltration Cellular, Histiocyte    |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                      3                                                   |             
      Pigmentation, Hemosiderin            |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |             2                    2  2     2                    2        3|             
      Hyperplasia, Lymphoid                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | M  M  M  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Hyperplasia, Lymphoid                |                                              2  2                        |             
      Hyperplasia, Plasma Cell             |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             |                                                                          |             
      Hematopoietic Cell Proliferation     |    1  1  1  2  4  1  1  1  1  1  3  2  1     2  4  1  1  1  2  3  1  1  3|             
      Hematopoietic Cell Proliferation     |                                                                          |             
          Granulocytic                     |                                                                          |             
      Pigmentation, Hemosiderin            | 1  1  1  2  2  2  1  1  1  1  1  2  2  3  1  1  1  2  1  1  2  2  1  1  2|             
      Lymphoid Follicle, Atrophy           |             3                                                            |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  M  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  +|             
      Atrophy                              |          2     2     3                 3                       2         |             
      Cyst                                 |                                                                          |             
      Ectopic Parathyroid Gland            |                                                                          |             
      Hyperplasia, Lymphoid                |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                                                                          |             
      Inflammation, Chronic Active         |                                                                4         |             
      Ulcer                                | 3                                                                        |             
      Prepuce, Inflammation, Chronic Active|                4                                                         |             
      Subcutaneous Tissue, Edema           |                                                             2            |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  98                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 3| 7| 7| 7| 7| 7| 7| 6| 5| 7| 7| 6| 7| 7| 7| 1| 5| 7| 7| 5|             
                             DAY ON TEST   | 2| 2| 2| 5| 1| 1| 2| 2| 2| 2| 2| 2| 9| 5| 2| 2| 9| 2| 2| 2| 0| 5| 2| 2| 3|             
                                           | 5| 5| 5| 8| 8| 6| 5| 9| 5| 5| 6| 5| 3| 2| 5| 6| 2| 5| 5| 6| 0| 6| 5| 6| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Subcutaneous Tissue, Granuloma       |                                                                   3      |             
      Subcutaneous Tissue, Hemorrhage      |                                                             3            |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fracture                             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |    2              1  1              2  2        2        2     2     2   |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Congestion                           |                                                                          |             
      Infiltration Cellular, Lymphocyte    |          1              1                    1                           |             
      Leukocytosis                         |                                                                          |             
      Alveolar Epithelium, Hyperplasia,    |                                                                          |             
           Focal                           |    2                 2     2  1        3        2  3                 2   |             
      Alveolus, Infiltration Cellular,     |                                                                          |             
           Histiocyte                      |          2                                                               |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Exudate, Serous                      |                               1                                          |             
      Inflammation, Chronic Active         |             1     1                             1        1  1     1      |             
      Olfactory Epithelium, Atrophy        |                               1                                          |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                                                                          |             
      Olfactory Epithelium, Metaplasia     |                                                                          |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |                1                                                         |             
      Respiratory Epithelium, Hyperplasia  | 1  1  1  1           1                    1              1               |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |             1                                            2        1      |             
      Respiratory Epithelium, Ulcer        |       1                                                                  |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                             +     +      |             
      Phthisis Bulbi                       |                                                             X            |             
      Cornea, Inflammation, Chronic Active |                                                                   3      |             
      Lens, Cataract                       |                                                                   1      |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                      +                                   +        +  +   |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  99                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 3| 7| 7| 7| 7| 7| 7| 6| 5| 7| 7| 6| 7| 7| 7| 1| 5| 7| 7| 5|             
                             DAY ON TEST   | 2| 2| 2| 5| 1| 1| 2| 2| 2| 2| 2| 2| 9| 5| 2| 2| 9| 2| 2| 2| 0| 5| 2| 2| 3|             
                                           | 5| 5| 5| 8| 8| 6| 5| 9| 5| 5| 6| 5| 3| 2| 5| 6| 2| 5| 5| 6| 0| 6| 5| 6| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Abscess                              |                                                                          |             
      Cyst                                 |                                                                          |             
      Hydronephrosis                       |             2              4     1  2                                    |             
      Infarct                              |                                                       1                  |             
      Infiltration Cellular, Lymphocyte    | 1  1     1        1  1  1  2  3  1  1     1        1              1  2   |             
      Inflammation, Acute                  |                                                                2         |             
      Inflammation, Chronic Active         |                4                                                        4|             
      Renal Tubule, Dilatation             |                               2  1                                   3   |             
      Renal Tubule, Hyperplasia, Focal     |                                                                          |             
      Renal Tubule, Regeneration           |                      1        2              1                           |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
      Dilatation                           |             4              3                          3                  |             
      Infiltration Cellular, Lymphocyte    |                   1                                                      |             
      Inflammation, Acute                  |                                                                          |             
      Inflammation, Chronic Active         |                4                 4     3                       4        4|             
 _____________________________________________________________________________________________________________________|             
                                                             Page 100                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 3| 0| 4| 4| 4| 2| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 0| 9| 5| 5| 5| 9| 5| 5| 5| 5|                                            |            |
                                           | 0| 6| 7| 7| 7| 6| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |      A     |
    150 PPM                                | 1| 1| 1| 1| 1| 1| 1| 1| 1| 2|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  +  +  +  +  +  +                                             |  60        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +                                             |  53        |
      Inflammation, Chronic Active         |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  A  +  +  +  +                                             |  56        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | A  +  +  +  +  A  +  +  +  +                                             |  56        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | A  +  +  +  +  A  +  +  +  +                                             |  50        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | A  +  +  +  +  A  +  +  +  +                                             |  50        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | A  +  +  +  +  A  +  +  +  +                                             |  50        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | A  A  +  +  +  A  +  +  +  +                                             |  50        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Abscess                              |                                                                          |      1  2.0|
      Basophilic Focus                     |                                                                          |      2     |
      Cytologic Alterations                |                                                                          |      2  2.5|
      Hematopoietic Cell Proliferation     |                                                                          |      1  1.0|
      Hyperplasia                          |                                                                          |      1  4.0|
      Infarct                              |                                                                          |      2  3.0|
      Inflammation, Chronic                |                                                                          |      5  1.2|
      Mixed Cell Focus                     |                                                                          |      1     |
      Necrosis                             |                                                                          |      4  2.5|
      Proliferation Connective Tissue      |                                                                          |      1     |
      Syncytial Alteration                 |                                                                          |     11  1.2|
      Bile Duct, Hyperplasia               |                                                                          |      1  2.0|
      Centrilobular, Fatty Change          |                   1                                                      |      1  1.0|
      Centrilobular, Necrosis              |                                                                          |      2  2.0|
      Hepatocyte, Necrosis                 |                                                                          |      1  1.0|
      Periportal, Vacuolization Cytoplasmic|                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   2        |
      Fat, Necrosis                        |                                                                          |      2  2.5|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  A  +  +  +  +                                             |  56        |
      Inflammation, Chronic                |                                                                          |      3  1.0|
      Proliferation Connective Tissue      |                                                                          |      1     |
      Acinus, Atrophy                      |                                                                          |      1  1.0|
      Duct, Cyst                           |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic                |                                                                          |     29  1.1|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  A  +  +  +  +                                             |  56        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  A  +  +  +  +                                             |  56        |
      Dysplasia                            |                                                                          |      1  2.0|
      Necrosis                             |                                                                          |      2  1.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page 101                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 3| 0| 4| 4| 4| 2| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 0| 9| 5| 5| 5| 9| 5| 5| 5| 5|                                            |            |
                                           | 0| 6| 7| 7| 7| 6| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |      A     |
    150 PPM                                | 1| 1| 1| 1| 1| 1| 1| 1| 1| 2|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM - cont                  |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Tooth                                   |                            +                                             |   1        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Cardiomyopathy                       |                                                                          |      1  1.0|
      Degeneration                         |                                                                          |      1  1.0|
      Thrombosis                           |                                                                          |      1  2.0|
      Artery, Inflammation, Chronic Active |                                                                          |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Hypertrophy, Focal                   |                                                                          |      9  1.1|
      Subcapsular, Hyperplasia             |             1     1  1  1  1                                             |     24  1.3|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +                                             |  58        |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   1        |
      Hyperplasia, Focal                   |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +                                             |  46        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +                                             |  54        |
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Follicular Cell, Hyperplasia, Focal  |                                                                          |     20  1.4|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Coagulating Gland                       |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Chronic Active         |                                                                          |      8  2.6|
                                            __________________________________________________________________________|____________|
   Penis                                   |                +                                                         |   5        |
      Congestion                           |                3                                                         |      1  3.0|
      Inflammation, Chronic Active         |                                                                          |      3  3.3|
                                            __________________________________________________________________________|____________|
   Preputial Gland                         |          +  +                                                            |  14        |
      Abscess                              |                                                                          |      1  3.0|
      Dilatation                           |          3                                                               |     11  3.7|
      Inflammation, Chronic Active         |             1                                                            |      4  2.3|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Inflammation, Acute                  |                                                                          |      2  2.5|
      Inflammation, Chronic Active         |                                                                          |      3  2.0|
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +                                             |  60        |
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page 102                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 3| 0| 4| 4| 4| 2| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 0| 9| 5| 5| 5| 9| 5| 5| 5| 5|                                            |            |
                                           | 0| 6| 7| 7| 7| 6| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |      A     |
    150 PPM                                | 1| 1| 1| 1| 1| 1| 1| 1| 1| 2|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
      Dilatation                           |                                                                          |      3  3.0|
      Hyperplasia                          |                                                                          |      1  3.0|
      Inflammation, Chronic Active         |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Seminiferous Tubule, Degeneration    |                                                                          |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Infarct                              |                                                                          |      1  3.0|
      Myeloid Cell, Hyperplasia            | 4     2                                                                  |      9  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   5        |
      Iliac, Inflammation, Chronic Active  |                                                                          |      1  3.0|
      Inguinal, Inflammation, Chronic      |                                                                          |            |
          Active                           |                                                                          |      1  3.0|
      Inguinal, Pigmentation               |                                                                          |      1  2.0|
      Lumbar, Hemorrhage                   |                                                                          |      1  2.0|
      Lumbar, Hyperplasia, Histiocytic     |                                                                          |      1  2.0|
      Lumbar, Hyperplasia, Lymphoid        |                                                                          |      1  3.0|
      Lumbar, Hyperplasia, Plasma Cell     |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  +  M  +  +  M  M                                             |  39        |
      Hyperplasia, Lymphoid                |                                                                          |      1  3.0|
      Infiltration Cellular, Histiocyte    |    3                                                                     |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +                                             |  55        |
      Hemorrhage                           | 4                                                                        |      1  4.0|
      Hyperplasia, Lymphoid                |                                                                          |      1  3.0|
      Pigmentation, Hemosiderin            |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | A  +  +  +  +  +  +  +  +  +                                             |  56        |
      Hemorrhage                           |                                                                          |      6  2.2|
      Hyperplasia, Lymphoid                |          3                                                               |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  M  +  M  +                                             |  46        |
      Hemorrhage                           |                                                                          |      1  2.0|
      Hyperplasia, Lymphoid                |                                                                          |      2  2.0|
      Hyperplasia, Plasma Cell             | 3                                                                        |      1  3.0|
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +                                             |  58        |
      Fibrosis                             |                                                                          |      1  1.0|
      Hematopoietic Cell Proliferation     | 3  1  3  1  1  2  1  1  1  1                                             |     55  1.7|
      Hematopoietic Cell Proliferation     |                                                                          |            |
          Granulocytic                     |                                                                          |      2  3.0|
      Pigmentation, Hemosiderin            | 2     2  1  2  1  1  1  2  2                                             |     56  1.4|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page 103                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 3| 0| 4| 4| 4| 2| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 0| 9| 5| 5| 5| 9| 5| 5| 5| 5|                                            |            |
                                           | 0| 6| 7| 7| 7| 6| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |      A     |
    150 PPM                                | 1| 1| 1| 1| 1| 1| 1| 1| 1| 2|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
      Lymphoid Follicle, Atrophy           |                                                                          |      2  3.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  M  +  +  +  +                                             |  50        |
      Atrophy                              |                                                                          |      9  2.4|
      Cyst                                 |                                                                          |      1  2.0|
      Ectopic Parathyroid Gland            |                                                                          |      1     |
      Hyperplasia, Lymphoid                |                                                                          |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M                                             |            |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +                                             |  59        |
      Inflammation, Chronic                |                                                                          |      2  1.0|
      Inflammation, Chronic Active         |                                                                          |      3  4.0|
      Ulcer                                |                                                                          |      2  3.5|
      Prepuce, Inflammation, Chronic Active|                                                                          |      1  4.0|
      Subcutaneous Tissue, Edema           |                                                                          |      1  2.0|
      Subcutaneous Tissue, Granuloma       |                                                                          |      1  3.0|
      Subcutaneous Tissue, Hemorrhage      |                                                                          |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Fracture                             |                                                                          |      1     |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Mineralization                       | 1              1                                                         |     24  1.5|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +                                             |  57        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Congestion                           |                                                                          |      1  3.0|
      Infiltration Cellular, Lymphocyte    |                                                                          |      3  1.0|
      Leukocytosis                         |                                                                          |      1  2.0|
      Alveolar Epithelium, Hyperplasia,    |                                                                          |            |
           Focal                           |                                                                          |     13  2.1|
      Alveolus, Infiltration Cellular,     |                                                                          |            |
           Histiocyte                      |                                                                          |      2  2.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Exudate, Serous                      |                                                                          |      2  1.0|
      Inflammation, Chronic Active         |                                                                          |     10  1.0|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page 104                                                               
NTP Experiment-Test: 05185-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 04/18/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 09:58:02  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 3| 0| 4| 4| 4| 2| 4| 4| 4| 4|                                            |            |
                             DAY ON TEST   | 0| 9| 5| 5| 5| 9| 5| 5| 5| 5|                                            |            |
                                           | 0| 6| 7| 7| 7| 6| 7| 7| 7| 7|                                            |      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      O     |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|                                            |      T     |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|                                            |      A     |
    150 PPM                                | 1| 1| 1| 1| 1| 1| 1| 1| 1| 2|                                            |      L     |
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|                                            |            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
      Olfactory Epithelium, Atrophy        |                                                                          |      1  1.0|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |                                                                          |      2  1.0|
      Olfactory Epithelium, Metaplasia     |                                                                          |      1  1.0|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |             1                                                            |      3  1.0|
      Respiratory Epithelium, Hyperplasia  |                                                                          |      8  1.0|
      Respiratory Epithelium, Metaplasia,  |                                                                          |            |
           Squamous                        |                                                                          |      3  1.3|
      Respiratory Epithelium, Ulcer        |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +                                             |  59        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                                                          |   2        |
      Phthisis Bulbi                       |                                                                          |      1     |
      Cornea, Inflammation, Chronic Active |                                                                          |      1  3.0|
      Lens, Cataract                       |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   6        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +                                             |  60        |
      Abscess                              |                                                                          |      1  4.0|
      Cyst                                 |                                                                          |      2  2.0|
      Hydronephrosis                       |                                                                          |      5  2.2|
      Infarct                              |                                                                          |      1  1.0|
      Infiltration Cellular, Lymphocyte    |                                                                          |     23  1.3|
      Inflammation, Acute                  |                                                                          |      2  2.0|
      Inflammation, Chronic Active         | 4                                                                        |      6  3.5|
      Renal Tubule, Dilatation             |                                                                          |      6  1.8|
      Renal Tubule, Hyperplasia, Focal     |                                                                          |      2  1.0|
      Renal Tubule, Regeneration           |                                                                          |      4  1.3|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  A  +  +  +  +                                             |  57        |
      Dilatation                           |       2                                                                  |      9  3.2|
      Infiltration Cellular, Lymphocyte    |                                                                          |      5  1.0|
      Inflammation, Acute                  |                                                                          |      1  2.0|
      Inflammation, Chronic Active         | 2                                                                        |      8  3.5|
 __________________________________________________________________________________________________________________________________ 
  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        
                                                             Page 105                                                               
                             ------------------------------------------------------------                                           
                             ----------              END OF REPORT             ----------                                           
                             ------------------------------------------------------------