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TDMS Study 88070-04 Pathology Tables

NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32

                                                           CORE STUDY




       Facility:  Battelle Northwest

       Chemical CAS #:  115-11-0007

       Lock Date:  10/05/95

       Cage Range:  All

       Reasons For Removal:    All

       Removal Date Range:     All

       Treatment Groups:       Include All




































                                                              Page   1

NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 6| 7| 6| 7| 3| 7| 7| 7| 7| 6| 7| 7| 7| 7| 4| 7| 7| 7| 3| 7|             
                             DAY ON TEST   | 3| 3| 3| 0| 3| 2| 3| 0| 3| 2| 3| 3| 3| 3| 6| 3| 0| 3| 3| 4| 3| 3| 3| 7| 3|             
                                           | 5| 5| 9| 9| 5| 1| 5| 8| 5| 2| 5| 5| 5| 5| 7| 5| 9| 5| 5| 9| 5| 5| 5| 8| 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 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| 1| 1| 1| 1| 1| 1|             
    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  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | I  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
      Angiectasis                          |                                                                          |             
      Basophilic Focus                     |    X                             X                       X               |             
      Cyst                                 |                                                                          |             
      Degeneration, Fatty                  |                1                                                         |             
      Eosinophilic Focus                   | X        X  X     X              X  X                 X        X  X      |             
      Tension Lipidosis                    |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |    +  +                                +                          +     +|             
      Fat, Necrosis                        |    2  2                                2                          2     2|             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
      Basophilic Focus                     |                                                                          |             
      Lipomatosis                          |                                                                          |             
      Duct, Cyst                           |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
      Hyperplasia                          |                      2                          2                        |             
      Inflammation, Acute                  |                                                 2                        |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |       1  1  1     1                                   1                  |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Hyperplasia                          |                   1                                                      |             
      Hypertrophy                          |                                                             1            |             
      Vacuolization Cytoplasmic            |                                                                         2|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  I  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  M  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  M  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           |                                                             2  1  3      |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page   2                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 6| 7| 6| 7| 3| 7| 7| 7| 7| 6| 7| 7| 7| 7| 4| 7| 7| 7| 3| 7|             
                             DAY ON TEST   | 3| 3| 3| 0| 3| 2| 3| 0| 3| 2| 3| 3| 3| 3| 6| 3| 0| 3| 3| 4| 3| 3| 3| 7| 3|             
                                           | 5| 5| 9| 9| 5| 1| 5| 8| 5| 2| 5| 5| 5| 5| 7| 5| 9| 5| 5| 9| 5| 5| 5| 8| 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 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| 1| 1| 1| 1| 1| 1|             
    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                   |                                                                          |             
                                           |                                                                          |             
      Follicular Cell, Hyperplasia         | 1  2           1  2     2     1     2  2     1  2  3              3     1|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          | +  +  +  +  +  +  +  +  M  M  +  +  +  +  I  I  +  +  I  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
      Cyst                                 |       4        2  2     2     3                                         1|             
      Inflammation, Suppurative            |                                                                          |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hydrometra                           |             3           1                                      3         |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              | +           +                       +                                +   |             
      Lumbar, Hemorrhage                   |                                     4                                    |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  M  +  +  M  +  +  +  +  +  M  +  M  +  +  M  M  +|             
      Hyperplasia, Plasma Cell             |                                        4                                 |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  M  +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  +  M  +|             
      Hyperplasia, Lymphoid                |                                        4                                 |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  I  +  +  +  +  +  +  A  +|             
      Angiectasis                          |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  M  +  M  +  +  M  +  +  M  +  +  +  +  M  +  +  +  M  M  M  +  +  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |                                        3                                 |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  A  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  I  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar Epithelium, Hyperplasia     |                                                       3           3     2|             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page   3                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 6| 7| 6| 7| 3| 7| 7| 7| 7| 6| 7| 7| 7| 7| 4| 7| 7| 7| 3| 7|             
                             DAY ON TEST   | 3| 3| 3| 0| 3| 2| 3| 0| 3| 2| 3| 3| 3| 3| 6| 3| 0| 3| 3| 4| 3| 3| 3| 7| 3|             
                                           | 5| 5| 9| 9| 5| 1| 5| 8| 5| 2| 5| 5| 5| 5| 7| 5| 9| 5| 5| 9| 5| 5| 5| 8| 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 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| 1| 1| 1| 1| 1| 1|             
    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|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |          2  1                 1              2           1  1     2      |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |    2        2  2              2                    3  1     1           1|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                                          |             
      Degeneration                         |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
      Amyloid Deposition                   |                                                                          |             
      Infarct                              |                                                                          |             
      Metaplasia, Osseous                  |                                                                          |             
      Nephropathy                          |          1  1     1  1        1           1                              |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page   4                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 6| 2| 7| 7| 7| 6| 7| 7| 5| 7| 7| 7|            |
                             DAY ON TEST   | 2| 5| 3| 3| 3| 8| 3| 3| 3| 3| 3| 4| 3| 1| 3| 3| 3| 3| 6| 3| 3| 8| 3| 2| 3|            |
                                           | 3| 3| 5| 5| 6| 1| 6| 6| 6| 6| 6| 1| 6| 0| 0| 6| 6| 6| 7| 6| 6| 0| 6| 3| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    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|      L     |
                                           | 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  I|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  47        |
      Angiectasis                          |                                                                      2   |      1  2.0|
      Basophilic Focus                     |                                                             X            |      4     |
      Cyst                                 |                                                             3            |      1  3.0|
      Degeneration, Fatty                  |          2                                                               |      2  1.5|
      Eosinophilic Focus                   |    X        X  X     X  X                       X     X           X      |     17     |
      Tension Lipidosis                    |                   X                                                      |      1     |
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                       +  +               |   7        |
      Fat, Necrosis                        |                                                       2  3               |      7  2.1|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  47        |
      Basophilic Focus                     |                                              X                           |      1     |
      Lipomatosis                          |                   4                                                      |      1  4.0|
      Duct, Cyst                           |                   4                                                      |      1  4.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  48        |
      Hyperplasia                          |                                                                          |      2  2.0|
      Inflammation, Acute                  |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +|  46        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       |                                              1        1     2     2     1|     10  1.2|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
      Hematopoietic Cell Proliferation     |                                                       3                  |      1  3.0|
      Hyperplasia                          |                            1                    2                        |      3  1.3|
      Hypertrophy                          |             2     2                                                      |      3  1.7|
      Vacuolization Cytoplasmic            |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  47        |
 __________________________________________________________________________________________________________________________________ 
  * : 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   5                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 6| 2| 7| 7| 7| 6| 7| 7| 5| 7| 7| 7|            |
                             DAY ON TEST   | 2| 5| 3| 3| 3| 8| 3| 3| 3| 3| 3| 4| 3| 1| 3| 3| 3| 3| 6| 3| 3| 8| 3| 2| 3|            |
                                           | 3| 3| 5| 5| 6| 1| 6| 6| 6| 6| 6| 1| 6| 0| 0| 6| 6| 6| 7| 6| 6| 0| 6| 3| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    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|      L     |
                                           | 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                          |                                        3                                 |      1  3.0|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | M  +  +  M  M  +  +  M  +  +  M  M  +  M  A  +  +  +  M  M  +  +  +  M  +|  35        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +|  49        |
      Pars Distalis, Hyperplasia           |       2     4     2        3  1  2           3        1        1     3   |     13  2.2|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  48        |
      Follicular Cell, Hyperplasia         | 1     2     3  1  1  1     3  2     1  1           2        2            |     25  1.7|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  44        |
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  48        |
      Cyst                                 | 4           2  2        3  3                       2  2                  |     13  2.5|
      Inflammation, Suppurative            |                2                                                         |      1  2.0|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
      Hydrometra                           |                      2           2  2                                    |      6  2.2|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |    +     +                    +                                          |   7        |
      Lumbar, Hemorrhage                   |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | M  +  +  +  +  +  M  +  +  +  M  M  +  +  A  +  +  +  +  +  +  +  +  M  +|  38        |
      Hyperplasia, Plasma Cell             |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | M  +  +  +  +  +  M  +  +  +  M  +  +  +  A  +  +  M  +  +  +  +  +  +  +|  41        |
      Hyperplasia, Lymphoid                |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  46        |
      Angiectasis                          |          3                                                               |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  M  M  +  +  +  +  +  A  +  +  +  +  +  M  +  +  +  +|  38        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
      Hematopoietic Cell Proliferation     | 3                                3                    4                  |      4  3.3|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  47        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
      Inflammation, Chronic Active         |                                                                      2   |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 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   6                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 6| 2| 7| 7| 7| 6| 7| 7| 5| 7| 7| 7|            |
                             DAY ON TEST   | 2| 5| 3| 3| 3| 8| 3| 3| 3| 3| 3| 4| 3| 1| 3| 3| 3| 3| 6| 3| 3| 8| 3| 2| 3|            |
                                           | 3| 3| 5| 5| 6| 1| 6| 6| 6| 6| 6| 1| 6| 0| 0| 6| 6| 6| 7| 6| 6| 0| 6| 3| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    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|      L     |
                                           | 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|            |
 __________________________________________________________________________________________________________________________________ 
 MUSCULOSKELETAL SYSTEM - cont             |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
      Alveolar Epithelium, Hyperplasia     |                                     1                                    |      4  2.3|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  47        |
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         | 1        1  2     2           2        2        1        1           2  2|     17  1.5|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         | 1  1              3  1     1  3  1  2  2        3        1        2     2|     21  1.8|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  48        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                                                      +   |   1        |
      Degeneration                         |                                                                      4   |      1  4.0|
                                            __________________________________________________________________________|____________|
   Harderian Gland                         | +                                                                    +   |   2        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Amyloid Deposition                   |                                           4                              |      1  4.0|
      Infarct                              |    2                                                                     |      1  2.0|
      Metaplasia, Osseous                  |                               2                                          |      1  2.0|
      Nephropathy                          |                2                       2        1  1  2  2  1            |     13  1.3|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  I  +  M  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +|  45        |
 __________________________________________________________________________________________________________________________________ 
  * : 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   7                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 6| 6| 7| 7| 7| 6| 6| 6| 7| 7| 7| 7| 5| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 3| 9| 4| 3| 3| 3| 9| 9| 5| 2| 3| 3| 3| 0| 3| 3| 1| 3| 3| 3| 3| 3| 3| 3|             
                                           | 5| 9| 5| 9| 5| 5| 5| 5| 1| 3| 7| 1| 5| 5| 6| 5| 5| 1| 5| 5| 5| 5| 5| 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 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|             
    500 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                             | +  +  +  A  +  +  +  M  M  +  +  A  +  +  A  +  M  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  A  +  +  +  +  I  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  A  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  A  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Basophilic Focus                     |    X        X                                                            |             
      Clear Cell Focus                     |                                                                X     X  X|             
      Degeneration, Fatty                  |                                                                          |             
      Eosinophilic Focus                   |             X           X        X     X     X                 X  X      |             
      Necrosis                             |                               2                                          |             
      Tension Lipidosis                    |                            X     X                                       |             
                                            __________________________________________________________________________|             
   Mesentery                               |             +                                         +                 +|             
      Artery, Inflammation                 |                                                                          |             
      Fat, Necrosis                        |             2                                         2                 3|             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |                                                 X                        |             
      Duct, Cyst                           |                                                                         4|             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |          1                       3                                       |             
      Inflammation, Acute                  |                                  2                                       |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |                               1              1     1  1  1        1     1|             
      Mineralization                       |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |    2                                         2        2                  |             
      Hypertrophy                          |                                                                          |             
      Vacuolization Cytoplasmic            |                                                          3               |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  M  +  +  M  M  +  +  M  +  M  +  M  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           | 3     3                 2     3        2                       2  2  3   |             
 _____________________________________________________________________________________________________________________|             
                                                             Page   8                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 6| 6| 7| 7| 7| 6| 6| 6| 7| 7| 7| 7| 5| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 3| 9| 4| 3| 3| 3| 9| 9| 5| 2| 3| 3| 3| 0| 3| 3| 1| 3| 3| 3| 3| 3| 3| 3|             
                                           | 5| 9| 5| 9| 5| 5| 5| 5| 1| 3| 7| 1| 5| 5| 6| 5| 5| 1| 5| 5| 5| 5| 5| 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 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|             
    500 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                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia         | 2     3              2  2     1     1           1     2  4     1         |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Cyst                                 |                2                 3                       3  2  3     2   |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hydrometra                           |    2  2           2                                            2         |             
      Inflammation, Suppurative            |                               4                                          |             
                                            __________________________________________________________________________|             
   Vagina                                  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  +  M  M  +  +  M  +  M  +  +  +  +  +  +  +  M  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                      2                                                   |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |       3  2                    4                                          |             
      Infiltration Cellular, Histiocyte    |                                                                   2      |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  M  +  M  +  +  +  +  +  +  +  +  M  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                               4                                          |             
      Inflammation, Chronic Active         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                               2                                          |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page   9                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 6| 6| 7| 7| 7| 6| 6| 6| 7| 7| 7| 7| 5| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 3| 9| 4| 3| 3| 3| 9| 9| 5| 2| 3| 3| 3| 0| 3| 3| 1| 3| 3| 3| 3| 3| 3| 3|             
                                           | 5| 9| 5| 9| 5| 5| 5| 5| 1| 3| 7| 1| 5| 5| 6| 5| 5| 1| 5| 5| 5| 5| 5| 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 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|             
    500 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                 |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                                                          |             
      Metaplasia, Osseous                  |                                                                          |             
      Alveolar Epithelium, Hyperplasia     |                3                                2                        |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Suppurative            |                                                                          |             
      Olfactory Epithelium, Atrophy        |                                                                          |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                1  1  1        1  2  1        2     1              2      |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         | 1  2  1  2  1  2  1  2  1     3  1  2        1  1  1  2        1  2  1  2|             
                                            __________________________________________________________________________|             
   Pleura                                  |       +                                                                  |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                                          |             
      Cornea, Metaplasia, Squamous         |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                                                   2      |             
      Infarct                              |                                                                          |             
      Metaplasia, Osseous                  |                   2                                                      |             
      Nephropathy                          | 1  2  2                    1                             1               |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  10                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 6| 4| 6| 7| 7| 7| 7| 5| 5| 6| 7| 7| 7| 7| 7| 7| 5| 6| 7| 7| 7| 7| 7|            |
                             DAY ON TEST   | 5| 3| 1| 8| 3| 3| 3| 3| 3| 7| 9| 3| 3| 3| 3| 3| 3| 3| 6| 1| 3| 3| 3| 3| 3|            |
                                           | 3| 6| 1| 3| 9| 6| 6| 6| 6| 2| 4| 9| 6| 6| 6| 6| 6| 6| 7| 5| 6| 6| 6| 6| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    500 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|      L     |
                                           | 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M|  43        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  I  +  +  I  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |                                           3                              |      1  3.0|
      Basophilic Focus                     |                                              X                       X   |      4     |
      Clear Cell Focus                     |                               X                                          |      4     |
      Degeneration, Fatty                  |             1                                                            |      1  1.0|
      Eosinophilic Focus                   |             X           X                 X                       X      |     11     |
      Necrosis                             |                                           2                              |      2  2.0|
      Tension Lipidosis                    |                               X                                          |      3     |
                                            __________________________________________________________________________|____________|
   Mesentery                               |          +                                +     +                 +  +   |   8        |
      Artery, Inflammation                 |          3                                                               |      1  3.0|
      Fat, Necrosis                        |                                                 2                 3  2   |      6  2.3|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Basophilic Focus                     |                                                    X                     |      2     |
      Duct, Cyst                           |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hyperplasia                          | 1  3                                                                     |      4  2.0|
      Inflammation, Acute                  |    2                                                                     |      2  2.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       |                1                 1                    1                  |     10  1.0|
      Mineralization                       |                      1                                                   |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                                                 2                        |      4  2.0|
      Hypertrophy                          |                               2                                          |      1  2.0|
      Vacuolization Cytoplasmic            |                4                                                         |      2  3.5|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
 __________________________________________________________________________________________________________________________________ 
  * : 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: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 6| 4| 6| 7| 7| 7| 7| 5| 5| 6| 7| 7| 7| 7| 7| 7| 5| 6| 7| 7| 7| 7| 7|            |
                             DAY ON TEST   | 5| 3| 1| 8| 3| 3| 3| 3| 3| 7| 9| 3| 3| 3| 3| 3| 3| 3| 6| 1| 3| 3| 3| 3| 3|            |
                                           | 3| 6| 1| 3| 9| 6| 6| 6| 6| 2| 4| 9| 6| 6| 6| 6| 6| 6| 7| 5| 6| 6| 6| 6| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    500 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|      L     |
                                           | 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                          |    2        2                                                        2   |      3  2.0|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  M  +  M  +  +  +  +  +  +  M  +  +  +  M  +  +  +  M  +  +  +  +  +  +|  39        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Pars Distalis, Hyperplasia           |    2  1                 3        3        1  3              2            |     15  2.3|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Follicular Cell, Hyperplasia         |                         1                       1  1     2  2  2         |     16  1.8|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          | +  +  M  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |                                                          4               |      1  4.0|
      Cyst                                 |    2  2                 2        2  2              2        2  4         |     14  2.4|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hydrometra                           |                            1                             4              2|      7  2.1|
      Inflammation, Suppurative            |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Vagina                                  |                   +                                                      |   1        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Necrosis                             |                                           4                              |      1  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                           +              +               |   2        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | M  +  +  M  M  +  M  M  +  +  +  +  +  +  +  M  M  +  +  M  M  +  M  M  M|  33        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  M  M  +  +  +  +  +  +  +  M  +  +  +  M  +  M  M  +  +  +  +  +|  42        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Angiectasis                          |                               3                                          |      2  2.5|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | M  M  M  +  M  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +|  42        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hematopoietic Cell Proliferation     | 3     3     2  3     3           3                 2  2                 2|     12  2.7|
      Infiltration Cellular, Histiocyte    |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | M  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +|  44        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Acute                  |                                                                          |      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  12                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 6| 4| 6| 7| 7| 7| 7| 5| 5| 6| 7| 7| 7| 7| 7| 7| 5| 6| 7| 7| 7| 7| 7|            |
                             DAY ON TEST   | 5| 3| 1| 8| 3| 3| 3| 3| 3| 7| 9| 3| 3| 3| 3| 3| 3| 3| 6| 1| 3| 3| 3| 3| 3|            |
                                           | 3| 6| 1| 3| 9| 6| 6| 6| 6| 2| 4| 9| 6| 6| 6| 6| 6| 6| 7| 5| 6| 6| 6| 6| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    500 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|      L     |
                                           | 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               |                                                                          |            |
                                           |                                                                          |            |
      Inflammation, Chronic Active         |          3                                                               |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hemorrhage                           |          1                                                               |      1  1.0|
      Metaplasia, Osseous                  |                      3                                                   |      1  3.0|
      Alveolar Epithelium, Hyperplasia     |                   2                                                      |      3  2.3|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Suppurative            |                                     2                                    |      1  2.0|
      Olfactory Epithelium, Atrophy        |                                  2                                       |      1  2.0|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |                   2     1     1  1  1  1           1              1  1  1|     19  1.2|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         | 1  1  1     2     2  1  2     1  3  2  1     1  2  2  1     1  1     1  2|     39  1.5|
                                            __________________________________________________________________________|____________|
   Pleura                                  |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                           +                              |   1        |
      Cornea, Metaplasia, Squamous         |                                           4                              |      1  4.0|
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |    +                                      +                              |   2        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                                                                          |      1  2.0|
      Infarct                              |             3        3                                                   |      2  3.0|
      Metaplasia, Osseous                  |                                                                          |      1  2.0|
      Nephropathy                          | 1  1  2     3                                      1  1     1        1  2|     14  1.4|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
 __________________________________________________________________________________________________________________________________ 
  * : 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: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 7|             
                             DAY ON TEST   | 3| 3| 3| 3| 3| 3| 3| 4| 3| 3| 3| 3| 7| 3| 3| 3| 3| 3| 3| 3| 2| 3| 0| 3| 3|             
                                           | 5| 5| 5| 5| 5| 5| 5| 3| 5| 5| 5| 5| 7| 5| 5| 5| 5| 5| 5| 6| 0| 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 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   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|             
    2000 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                             | +  +  +  +  +  +  +  A  +  +  +  +  +  M  +  +  +  +  +  +  +  M  +  M  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |                                                                          |             
      Clear Cell Focus                     |                                        X  X                              |             
      Degeneration, Fatty                  |                      3                                         1         |             
      Eosinophilic Focus                   |       X  X     X                    X  X  X  X                           |             
      Hematopoietic Cell Proliferation     |          2                                                               |             
      Necrosis                             |             2                                                     2      |             
      Tension Lipidosis                    |                                                                          |             
      Bile Duct, Hyperplasia               |                                                                          |             
      Centrilobular, Necrosis              |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                              +           +               |             
      Fat, Necrosis                        |                                              2           2               |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |       2                                                                  |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                                                   1      |             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
      Malformation                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |    1              2           1           1  1     1              1      |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |          3                                                               |             
      Hyperplasia                          |                                                                          |             
      Hypertrophy                          |                                                                          |             
      Vacuolization Cytoplasmic            |                                           4                              |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                          3               |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  M  +  M  +  A  +  +  +  +  +  +  M  +  +  +  +  +  +  M  +  M  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  14                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 7|             
                             DAY ON TEST   | 3| 3| 3| 3| 3| 3| 3| 4| 3| 3| 3| 3| 7| 3| 3| 3| 3| 3| 3| 3| 2| 3| 0| 3| 3|             
                                           | 5| 5| 5| 5| 5| 5| 5| 3| 5| 5| 5| 5| 7| 5| 5| 5| 5| 5| 5| 6| 0| 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 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   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|             
    2000 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                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           | 1  2                       3     2     3  1        2  2     2           3|             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia         | 1  2  1  4     2           1  4     1  2  4     1     3  2           1  3|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          | +  +  +  +  +  +  +  A  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |    3                                      2        2        3           2|             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hydrometra                           |       3                                                                  |             
      Inflammation, Suppurative            |                                                                          |             
      Necrosis                             |                                                                   4      |             
      Thrombosis                           |                         4                                                |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                  +                                       |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  +  +  M  +  M  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  M  M  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  M  A  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Mixed Cell    |          4                                                               |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  A  +  +  +  +  M  +  +  +  +  +  +  +  I  +  +  +  +|             
      Infiltration Cellular, Mixed Cell    |          4                                                               |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | M  +  M  +  M  +  +  M  +  +  +  +  +  +  M  +  +  +  +  +  +  +  M  +  +|             
      Infiltration Cellular, Mixed Cell    |          4                                                               |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |       2  3                                                               |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  A  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  15                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 7|             
                             DAY ON TEST   | 3| 3| 3| 3| 3| 3| 3| 4| 3| 3| 3| 3| 7| 3| 3| 3| 3| 3| 3| 3| 2| 3| 0| 3| 3|             
                                           | 5| 5| 5| 5| 5| 5| 5| 3| 5| 5| 5| 5| 7| 5| 5| 5| 5| 5| 5| 6| 0| 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 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   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|             
    2000 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, Histiocyte    |                                        1                                 |             
      Alveolar Epithelium, Hyperplasia     |                1                                                         |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Suppurative            |                                                                          |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         | 1        1  1  1  1     1  1           1  1        2  1        1     1  1|             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         | 1  2  2     3  2  1     1  2     1  1  2  2  2  2  2  2  2  1  2  1  2  2|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |    +                                                                     |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infarct                              |                                                                2         |             
      Metaplasia, Osseous                  |                               2                                          |             
      Mineralization                       |                                                             1            |             
      Nephropathy                          |    2  1                    1  1           1           1     2        1  1|             
      Renal Tubule, Necrosis               |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  16                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 6| 7|            |
                             DAY ON TEST   | 1| 3| 3| 3| 3| 3| 3| 3| 9| 2| 0| 3| 3| 3| 3| 7| 3| 3| 3| 8| 3| 3| 3| 0| 3|            |
                                           | 8| 6| 6| 6| 6| 6| 6| 6| 2| 8| 9| 6| 6| 6| 6| 5| 6| 6| 6| 6| 6| 6| 6| 0| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               ANIMAL ID   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|      A     |
    2000 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|      L     |
                                           | 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  A  +|  43        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | I  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  A  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  A  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  A  +|  46        |
      Inflammation, Chronic Active         |             3                                                            |      1  3.0|
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Basophilic Focus                     |                         X                             X                  |      2     |
      Clear Cell Focus                     |                                                       X                  |      3     |
      Degeneration, Fatty                  |                            1                       1                 2   |      5  1.6|
      Eosinophilic Focus                   |                         X     X           X  X     X                     |     12     |
      Hematopoietic Cell Proliferation     |                                                                          |      1  2.0|
      Necrosis                             |                                                                      2   |      3  2.0|
      Tension Lipidosis                    |                                                                X         |      1     |
      Bile Duct, Hyperplasia               |                                              2                           |      1  2.0|
      Centrilobular, Necrosis              | 2                                                                        |      1  2.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |    +                             +     +  +           +  +               |   8        |
      Fat, Necrosis                        |    2                                   2  2           2                  |      6  2.0|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hyperplasia                          |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|  48        |
      Necrosis                             |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Tooth                                   |          +                                                               |   1        |
      Malformation                         |          X                                                               |      1     |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       |    1                 1        1        1  1                              |     12  1.1|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hematopoietic Cell Proliferation     |                                                                          |      1  3.0|
      Hyperplasia                          |          2                                               2              3|      3  2.3|
      Hypertrophy                          |          3  2                             2     2                        |      4  2.3|
 __________________________________________________________________________________________________________________________________ 
  * : 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  17                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 6| 7|            |
                             DAY ON TEST   | 1| 3| 3| 3| 3| 3| 3| 3| 9| 2| 0| 3| 3| 3| 3| 7| 3| 3| 3| 8| 3| 3| 3| 0| 3|            |
                                           | 8| 6| 6| 6| 6| 6| 6| 6| 2| 8| 9| 6| 6| 6| 6| 5| 6| 6| 6| 6| 6| 6| 6| 0| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               ANIMAL ID   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|      A     |
    2000 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|      L     |
                                           | 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                   |                                                                          |            |
                                           |                                                                          |            |
      Vacuolization Cytoplasmic            |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|  48        |
      Hyperplasia                          |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  M  +  +  M  +  +  +  +  M  +  +  +  +  M  M  +  +  M  +  +  +  M  +|  37        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|  49        |
      Pars Distalis, Hyperplasia           |       3        3  3              2  2     4  2     1                    3|     19  2.3|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Follicular Cell, Hyperplasia         | 2     2  1        2     3     3  2  2     1     1     1     3  2        1|     29  2.0|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          | +  +  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Cyst                                 |             4                       2     4        3        1  1         |     11  2.5|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hydrometra                           |                            2              2                              |      3  2.3|
      Inflammation, Suppurative            |                                                       2                  |      1  2.0|
      Necrosis                             |                                                                          |      1  4.0|
      Thrombosis                           |                                                                          |      1  4.0|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |    +                          +                       +  +               |   5        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  44        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  M  +  +  +  +  +  +  +  +  M  +  +  M  +  +  +  +  +  +  +  +  +|  44        |
      Infiltration Cellular, Mixed Cell    |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Infiltration Cellular, Mixed Cell    |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | M  +  +  +  M  M  M  +  +  M  +  +  +  +  +  +  +  M  +  +  M  +  +  +  M|  36        |
      Infiltration Cellular, Mixed Cell    |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hematopoietic Cell Proliferation     | 3              2                                               2     3   |      6  2.5|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|  49        |
 __________________________________________________________________________________________________________________________________ 
  * : 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  18                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 6| 7|            |
                             DAY ON TEST   | 1| 3| 3| 3| 3| 3| 3| 3| 9| 2| 0| 3| 3| 3| 3| 7| 3| 3| 3| 8| 3| 3| 3| 0| 3|            |
                                           | 8| 6| 6| 6| 6| 6| 6| 6| 2| 8| 9| 6| 6| 6| 6| 5| 6| 6| 6| 6| 6| 6| 6| 0| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               ANIMAL ID   | 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5|      A     |
    2000 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|      L     |
                                           | 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               |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|  49        |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Infiltration Cellular, Histiocyte    |                                                                          |      1  1.0|
      Alveolar Epithelium, Hyperplasia     |                      1              1                                    |      3  1.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Inflammation, Suppurative            |                            1                                             |      1  1.0|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |             1  1  1  2              1  1  1                    1     1  1|     24  1.1|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |    2  2  1  1  2  1  1  1        2  1  2  2     2  1  1  1     2  2     2|     41  1.6|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Infarct                              |                                                                          |      1  2.0|
      Metaplasia, Osseous                  |                                           2                              |      2  2.0|
      Mineralization                       |                                                                          |      1  1.0|
      Nephropathy                          |             1        1        1     1  1           1  1           1  1   |     18  1.1|
      Renal Tubule, Necrosis               | 3                                                                        |      1  3.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
 __________________________________________________________________________________________________________________________________ 
  * : 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  19                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 6| 3| 5| 3| 3| 3| 7| 2| 3| 0| 2| 8| 3| 3| 3| 1| 3| 3| 2| 3| 3| 3| 3| 3| 3|             
                                           | 5| 5| 3| 5| 5| 5| 2| 9| 5| 1| 1| 3| 5| 5| 5| 5| 5| 5| 1| 5| 5| 5| 5| 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 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   | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
    8000 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                             | A  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  A  +  +  +  M  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic Active |                   3                                                      |             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | A  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                      3                                                   |             
      Basophilic Focus                     |                            X                    X                 X      |             
      Clear Cell Focus                     |       X              X                                      X            |             
      Cyst                                 |                                                                          |             
      Degeneration, Fatty                  |                                                                          |             
      Eosinophilic Focus                   |             X           X                                      X  X  X   |             
      Hematopoietic Cell Proliferation     |       3                                                                  |             
      Mixed Cell Focus                     |                                                                         X|             
      Necrosis                             |                                                                          |             
      Centrilobular, Necrosis              |       3                                               2                  |             
                                            __________________________________________________________________________|             
   Mesentery                               |       +  +        +     +                                   +        +   |             
      Artery, Inflammation                 |                   4                                                      |             
      Fat, Inflammation, Chronic Active    |       3                                                                  |             
      Fat, Necrosis                        |       3  2        3     2                                   3        2   |             
                                            __________________________________________________________________________|             
   Pancreas                                | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |    3                                                                     |             
      Lipomatosis                          |       3                                                                  |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Hyperplasia                          |                                                    2                     |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic Active |                   4                                                      |             
                                            __________________________________________________________________________|             
   Tongue                                  |                                                                          |             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
      Malformation                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |       1              1  1              1                                1|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |       3                                                                  |             
      Hyperplasia                          |                                           2              2               |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  20                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 6| 3| 5| 3| 3| 3| 7| 2| 3| 0| 2| 8| 3| 3| 3| 1| 3| 3| 2| 3| 3| 3| 3| 3| 3|             
                                           | 5| 5| 3| 5| 5| 5| 2| 9| 5| 1| 1| 3| 5| 5| 5| 5| 5| 5| 1| 5| 5| 5| 5| 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 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   | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
    8000 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                   |                                                                          |             
                                           |                                                                          |             
      Hypertrophy                          |                   1                                                      |             
      Vacuolization Cytoplasmic            |                         3  3                                             |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |             2                                                     3      |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  M  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           |          3           2                 2                 2  2     2      |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia         |    1  1     1  3        3  2  4  2  2  1     2     4     4  3  1  2  1  2|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          | +  +  M  M  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +  M  +  +  +|             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                4         |             
      Cyst                                 |       2  2                             2                                 |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                         4|             
      Hydrometra                           |                                                             3            |             
      Endometrium, Hyperplasia, Cystic     |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                               +  +           +                           |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  M  +  +  +  +  +  M  M  +  +  M  +  +  +  +  +  +  +  M  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Infiltration Cellular, Plasma Cell   |       3                                                                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  M  +  +  M  +  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |       3                                               4                  |             
      Infarct                              |                                                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  M  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                   4                                                      |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  21                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 6| 3| 5| 3| 3| 3| 7| 2| 3| 0| 2| 8| 3| 3| 3| 1| 3| 3| 2| 3| 3| 3| 3| 3| 3|             
                                           | 5| 5| 3| 5| 5| 5| 2| 9| 5| 1| 1| 3| 5| 5| 5| 5| 5| 5| 1| 5| 5| 5| 5| 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 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   | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
    8000 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|             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM - cont             |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Histiocyte    |                                                                          |             
      Inflammation, Granulomatous          |                                                                          |             
      Alveolar Epithelium, Hyperplasia     |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic                |                                                                          |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |       1     1     1  2  1  2  1  1     1  1  1  1  1  1  1  1  1     2   |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         | 2  2     3  3  2  2  3  3  2  2  2  3  2  3  2  3  3  3  3  3  3  2  2  2|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                              +                           |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                              +                           |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Nephropathy                          |    1                             1                                1     1|             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Artery, Inflammation, Chronic Active |                   3                                                      |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  22                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 5| 5| 7| 7| 6| 7| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7|            |
                             DAY ON TEST   | 3| 3| 9| 2| 3| 3| 4| 3| 3| 3| 0| 3| 8| 3| 3| 3| 0| 3| 1| 3| 3| 0| 3| 3| 3|            |
                                           | 6| 6| 6| 7| 6| 6| 5| 6| 6| 6| 9| 6| 7| 6| 6| 6| 3| 6| 7| 6| 6| 9| 6| 6| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               ANIMAL ID   | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|      A     |
    8000 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|      L     |
                                           | 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +|  43        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Artery, Inflammation, Chronic Active |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |                                                                          |      1  3.0|
      Basophilic Focus                     |                                                                   X     X|      5     |
      Clear Cell Focus                     |       X                                                                  |      4     |
      Cyst                                 |                                     2                                    |      1  2.0|
      Degeneration, Fatty                  |       2                                                                  |      1  2.0|
      Eosinophilic Focus                   |       X                                            X                     |      7     |
      Hematopoietic Cell Proliferation     |                                                                          |      1  3.0|
      Mixed Cell Focus                     |                                                                          |      1     |
      Necrosis                             |                2                                                         |      1  2.0|
      Centrilobular, Necrosis              |                   2                                                      |      3  2.3|
                                            __________________________________________________________________________|____________|
   Mesentery                               |          +                       +                       +     +         |  10        |
      Artery, Inflammation                 |                                                                          |      1  4.0|
      Fat, Inflammation, Chronic Active    |                                                                          |      1  3.0|
      Fat, Necrosis                        |          2                       2                       1     2         |     10  2.2|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Atrophy                              |                                                                          |      1  3.0|
      Lipomatosis                          |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hyperplasia                          |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Artery, Inflammation, Chronic Active |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Tongue                                  |                                                                +         |   1        |
                                            __________________________________________________________________________|____________|
   Tooth                                   |       +                                                                  |   1        |
      Malformation                         |       X                                                                  |      1     |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       |                               3                    1     1               |      8  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  23                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 5| 5| 7| 7| 6| 7| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7|            |
                             DAY ON TEST   | 3| 3| 9| 2| 3| 3| 4| 3| 3| 3| 0| 3| 8| 3| 3| 3| 0| 3| 1| 3| 3| 0| 3| 3| 3|            |
                                           | 6| 6| 6| 7| 6| 6| 5| 6| 6| 6| 9| 6| 7| 6| 6| 6| 3| 6| 7| 6| 6| 9| 6| 6| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               ANIMAL ID   | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|      A     |
    8000 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|      L     |
                                           | 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              |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hematopoietic Cell Proliferation     |                                                                          |      1  3.0|
      Hyperplasia                          |                      2                                            1  1   |      5  1.6|
      Hypertrophy                          |                                                                2         |      2  1.5|
      Vacuolization Cytoplasmic            |                                                                          |      2  3.0|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hyperplasia                          |       2                                                                  |      3  2.3|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  M  +  +  +  +  +  M  +  +  M  +  +  M  +  +  M  +  M  +  M  +  +  +  +|  41        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +|  49        |
      Pars Distalis, Hyperplasia           | 2     3     3  3     2        2     1                             2      |     14  2.2|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Follicular Cell, Hyperplasia         |    1        2     3     3  1     3     3        1  2           2  3     1|     30  2.1|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |             3                                                           2|      3  3.0|
      Cyst                                 |    4     4                       2                 2  3                  |      8  2.6|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |                                                                          |      1  4.0|
      Hydrometra                           | 3                                         3                       3      |      4  3.0|
      Endometrium, Hyperplasia, Cystic     |                         3                                                |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                     +                                    |   4        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  +  +  M  +  +  M  +  +  +  M  +  +  M  +  +  +  +  +  +  +  +|  44        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  M  +  M  +  +  M  +  +  +  +  +  +  +  M  +  +  +  +  +  +  M  M  +  M|  38        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Infiltration Cellular, Plasma Cell   |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  M  +  +  +  +  +  M  +|  42        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hematopoietic Cell Proliferation     |          3                    4                       3                  |      5  3.4|
 __________________________________________________________________________________________________________________________________ 
  * : 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  24                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 5| 5| 7| 7| 6| 7| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7|            |
                             DAY ON TEST   | 3| 3| 9| 2| 3| 3| 4| 3| 3| 3| 0| 3| 8| 3| 3| 3| 0| 3| 1| 3| 3| 0| 3| 3| 3|            |
                                           | 6| 6| 6| 7| 6| 6| 5| 6| 6| 6| 9| 6| 7| 6| 6| 6| 3| 6| 7| 6| 6| 9| 6| 6| 6|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               ANIMAL ID   | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|      A     |
    8000 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|      L     |
                                           | 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               |                                                                          |            |
                                           |                                                                          |            |
      Infarct                              |                               3                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  +|  46        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |                                                                          |      1  4.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Infiltration Cellular, Histiocyte    |                               1                                          |      1  1.0|
      Inflammation, Granulomatous          |             2                                                            |      1  2.0|
      Alveolar Epithelium, Hyperplasia     |                                                                      1   |      1  1.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic                |                                                                2         |      1  2.0|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |                               1           2  1  2  2        1  1  1     1|     27  1.2|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         | 1  2  2  1  3  3  2  2  2  2  2  1     3  2  2  2  2  2  3  3  1  2  1  2|     48  2.3|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                            +                                             |   2        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Nephropathy                          |       1  2              1  1        1        1        3              1   |     12  1.3|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Artery, Inflammation, Chronic Active |                                                                          |      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  25                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 4| 7| 7| 7| 7| 7| 6| 7| 7| 6| 7| 4| 6| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 6| 8| 3| 3| 3| 3| 3| 1| 3| 3| 8| 3| 2| 6| 1| 9| 3| 3| 3| 3| 3| 0| 3| 3|             
                                           | 3| 0| 3| 3| 3| 3| 3| 3| 0| 3| 3| 1| 3| 6| 4| 5| 5| 3| 3| 3| 3| 3| 9| 3| 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   | 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  +  +  +  +  +  +  +  +  M  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  A  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  A  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  A  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |                   X           X                       X                  |             
      Clear Cell Focus                     | X        X  X                       X                          X     X   |             
      Cyst                                 |                                                                          |             
      Degeneration, Fatty                  |                2                                                         |             
      Eosinophilic Focus                   |                                     X                                X   |             
      Necrosis                             |                                                                          |             
      Vacuolization Cytoplasmic, Focal     |                                                                          |             
      Centrilobular, Necrosis              |    4                                            1                        |             
                                            __________________________________________________________________________|             
   Mesentery                               |                         +                    +        +                  |             
      Fat, Inflammation, Chronic Active    |                                              4                           |             
      Fat, Necrosis                        |                         2                    4                           |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                   1                                                      |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                 1           1            |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                           2                              |             
                                            __________________________________________________________________________|             
   Tooth                                   | +                                   +              +           +         |             
      Malformation                         | X                                   X              X           X         |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |             1  1  1           1  1        1  1                           |             
      Inflammation, Chronic                |                                                                          |             
      Thrombosis                           |                                                 2                        |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                       2  2        2  3  2|             
      Hypertrophy                          | 2        3     1  2  2     1  2  2  2     1  2     2  2  2  3  2        2|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                2         |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  26                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 4| 7| 7| 7| 7| 7| 6| 7| 7| 6| 7| 4| 6| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 6| 8| 3| 3| 3| 3| 3| 1| 3| 3| 8| 3| 2| 6| 1| 9| 3| 3| 3| 3| 3| 0| 3| 3|             
                                           | 3| 0| 3| 3| 3| 3| 3| 3| 0| 3| 3| 1| 3| 6| 4| 5| 5| 3| 3| 3| 3| 3| 9| 3| 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   | 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                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           |                                                                         4|             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia         |                               2                                          |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  I  +|             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                                    +                     |             
      Pancreatic, Infiltration Cellular,   |                                                                          |             
           Plasma Cell                     |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  M  M  M  +  +  M  M  M  +  M  M  +  +  +  +  +  M  M  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | M  +  +  M  +  +  +  M  +  +  +  +  +  +  M  +  M  M  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                 2                        |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  M  M  +  M  +  +  M  +  M  +  +  M  +  +  +  +  +  M  +  M  M  +  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |                                              4  2                        |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  M  +  +  +  +  +  +  M  +  M  +  +  +  +  +  M  M  M|             
 _____________________________________________________________________________________________________________________|             
 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                                    | +  +  +  +  +  +  +  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                        2                                 |             
      Prepuce, Inflammation, Chronic Active|                                           4  3                           |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  27                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 4| 7| 7| 7| 7| 7| 6| 7| 7| 6| 7| 4| 6| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 6| 8| 3| 3| 3| 3| 3| 1| 3| 3| 8| 3| 2| 6| 1| 9| 3| 3| 3| 3| 3| 0| 3| 3|             
                                           | 3| 0| 3| 3| 3| 3| 3| 3| 0| 3| 3| 1| 3| 6| 4| 5| 5| 3| 3| 3| 3| 3| 9| 3| 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   | 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|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
      Thrombosis                           |                                                                          |             
      Alveolar Epithelium, Hyperplasia     |             2  3                          2                          2   |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Suppurative            |                                                                          |             
      Polyp, Inflammatory                  |                                                                          |             
      Olfactory Epithelium, Atrophy        |                                                                          |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                                                    1                     |             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |                1              1                                          |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                         +                                            +   |             
      Cornea, Inflammation, Chronic Active |                         3                                                |             
                                            __________________________________________________________________________|             
   Harderian Gland                         | +                       +                                                |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                     2                                    |             
      Infarct                              |                                                                          |             
      Metaplasia, Osseous                  |                                                                          |             
      Mineralization                       |                                        1                                 |             
      Nephropathy                          | 2  1     2  1  2  2  1  2     1     2        2              1  2  2  1  2|             
      Papilla, Inflammation, Suppurative   |                                                                          |             
      Pelvis, Dilatation                   |                                                                   3      |             
      Renal Tubule, Hyperplasia            |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                           3                              |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  28                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 5| 7| 6| 7| 7| 6| 5| 6| 6| 7| 7| 7| 7| 7| 3| 7| 7| 7| 5| 7| 7| 5| 6| 7| 3|            |
                             DAY ON TEST   | 2| 3| 5| 3| 3| 1| 8| 5| 0| 2| 3| 3| 0| 3| 8| 3| 3| 3| 9| 3| 3| 8| 9| 3| 9|            |
                                           | 7| 4| 3| 4| 4| 1| 0| 3| 8| 3| 4| 4| 8| 4| 7| 4| 4| 4| 2| 4| 4| 9| 5| 4| 9|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    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|      L     |
                                           | 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  M  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  A  +  +  A  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Basophilic Focus                     |                               X     X     X                             X|      7     |
      Clear Cell Focus                     |          X                       X                                   X   |      9     |
      Cyst                                 |       2                                                                  |      1  2.0|
      Degeneration, Fatty                  |                                                 1                        |      2  1.5|
      Eosinophilic Focus                   |                X                 X                                   X   |      5     |
      Necrosis                             |                                                                         3|      1  3.0|
      Vacuolization Cytoplasmic, Focal     |                                                       2                  |      1  2.0|
      Centrilobular, Necrosis              |                                                                          |      2  2.5|
                                            __________________________________________________________________________|____________|
   Mesentery                               |       +                                                                  |   4        |
      Fat, Inflammation, Chronic Active    |                                                                          |      1  4.0|
      Fat, Necrosis                        |       2                                                                  |      3  2.7|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                                                                          |      2  1.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +|  49        |
      Inflammation, Acute                  |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Tooth                                   | +                                   +                 +                  |   7        |
      Malformation                         |                                     X                 X                  |      6     |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       |    1  1  1  1  1           1  1        1     1  1  1     1           1  1|     21  1.0|
      Inflammation, Chronic                |                   2                                                      |      1  2.0|
      Thrombosis                           |                                                                          |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|  49        |
      Hyperplasia                          | 1        2  2           2  3           2        2                 2  2   |     14  2.1|
 __________________________________________________________________________________________________________________________________ 
  * : 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  29                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 5| 7| 6| 7| 7| 6| 5| 6| 6| 7| 7| 7| 7| 7| 3| 7| 7| 7| 5| 7| 7| 5| 6| 7| 3|            |
                             DAY ON TEST   | 2| 3| 5| 3| 3| 1| 8| 5| 0| 2| 3| 3| 0| 3| 8| 3| 3| 3| 9| 3| 3| 8| 9| 3| 9|            |
                                           | 7| 4| 3| 4| 4| 1| 0| 3| 8| 3| 4| 4| 8| 4| 7| 4| 4| 4| 2| 4| 4| 9| 5| 4| 9|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    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|      L     |
                                           | 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                   |                                                                          |            |
                                           |                                                                          |            |
      Hypertrophy                          |    2     2  2     2  1     2     1  2     2  2  2           2  1  2  2   |     32  1.9|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  I  +  +  +  M  +  M  M  +  +  M  M  +  +  +  +  +  M  +  +  M  +  +  +|  41        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Pars Distalis, Hyperplasia           |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Follicular Cell, Hyperplasia         |    1                 1                                      1     2      |      5  1.4|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |       +        +                       +                                 |   4        |
      Pancreatic, Infiltration Cellular,   |                                                                          |            |
           Plasma Cell                     |                                        3                                 |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  M  M  +  M  M  +  M  +  +  +  +  +  M  +  +  M  +  +  +  +  M  M  M|  30        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | M  +  M  +  +  +  +  M  +  +  M  M  +  +  +  M  M  M  +  +  +  M  M  +  +|  34        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Angiectasis                          |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  M  +  +  M  M  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +|  37        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hematopoietic Cell Proliferation     |                         3                                         2      |      4  2.8|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  M  +  +  +  M  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|  41        |
 _____________________________________________________________________________________________________________________|            |
 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                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Cyst                                 |                                                                          |      1  2.0|
      Prepuce, Inflammation, Chronic Active|       3              4              3     4                       3      |      7  3.4|
 __________________________________________________________________________________________________________________________________ 
  * : 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  30                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 5| 7| 6| 7| 7| 6| 5| 6| 6| 7| 7| 7| 7| 7| 3| 7| 7| 7| 5| 7| 7| 5| 6| 7| 3|            |
                             DAY ON TEST   | 2| 3| 5| 3| 3| 1| 8| 5| 0| 2| 3| 3| 0| 3| 8| 3| 3| 3| 9| 3| 3| 8| 9| 3| 9|            |
                                           | 7| 4| 3| 4| 4| 1| 0| 3| 8| 3| 4| 4| 8| 4| 7| 4| 4| 4| 2| 4| 4| 9| 5| 4| 9|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    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|      L     |
                                           | 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               |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Thrombosis                           |                                                                         1|      1  1.0|
      Alveolar Epithelium, Hyperplasia     |                                  3                                       |      5  2.4|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Suppurative            |                   2                                                      |      1  2.0|
      Polyp, Inflammatory                  | 4                                                                        |      1  4.0|
      Olfactory Epithelium, Atrophy        | 2                                                                        |      1  2.0|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |       1     1     1     1     1                                          |      6  1.0|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |             1     1     1        1                                       |      6  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                                                          |   2        |
      Cornea, Inflammation, Chronic Active |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                  +                                   +   |   4        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                                                                          |      1  2.0|
      Infarct                              |                                        2                                 |      1  2.0|
      Metaplasia, Osseous                  |                      2                                                   |      1  2.0|
      Mineralization                       |                                                                          |      1  1.0|
      Nephropathy                          |    1  2  2  2  2  2     3  2  2  2  1  2     2  1  2  1  2  2     1  2   |     36  1.7|
      Papilla, Inflammation, Suppurative   |                      2  2                                               1|      3  1.7|
      Pelvis, Dilatation                   |                                     2     2                              |      3  2.3|
      Renal Tubule, Hyperplasia            |    1                                                                     |      1  1.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +|  49        |
      Inflammation, Chronic Active         |                      3  3                                               2|      4  2.8|
 __________________________________________________________________________________________________________________________________ 
  * : 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  31                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 7| 7| 7| 4| 5| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 7| 7|             
                             DAY ON TEST   | 3| 3| 3| 6| 3| 3| 3| 0| 4| 3| 3| 3| 9| 3| 3| 3| 1| 3| 3| 3| 3| 3| 5| 3| 3|             
                                           | 3| 3| 3| 7| 3| 3| 3| 5| 6| 3| 3| 3| 6| 3| 3| 3| 5| 3| 3| 3| 4| 4| 2| 4| 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   | 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|             
    500 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  A  M  +  +  A  I  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  I  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  A  +  +  +  A  A  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  A  +  +  +  A  A  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  A  +  +  +  A  A  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |          X        X     X                                                |             
      Clear Cell Focus                     |                                        X                                 |             
      Cyst                                 |          2                                                               |             
      Degeneration, Fatty                  |                                                                          |             
      Eosinophilic Focus                   |                                  X              X        X     X         |             
      Mixed Cell Focus                     | X                                                                        |             
      Necrosis                             |                                                                          |             
      Vacuolization Cytoplasmic, Focal     |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                               +                                          |             
      Fat, Necrosis                        |                               2                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                                                          |             
                                            __________________________________________________________________________|             
   Tooth                                   |                   +              +     +     +              +  +  +  +   |             
      Malformation                         |                   X              X     X     X              X  X     X   |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |       1  2        1                             1        1           1  1|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |       3        2        1              2     2                    2      |             
      Hypertrophy                          | 2                       1  2     3     2  2  1        2  2  2  2     2   |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  M  +  +  +  +  M  +  +  M  +  +  +  +  +  +  M  +  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           |       2                                                     2            |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia         |    2                                            2  1     1               |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  32                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 7| 7| 7| 4| 5| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 7| 7|             
                             DAY ON TEST   | 3| 3| 3| 6| 3| 3| 3| 0| 4| 3| 3| 3| 9| 3| 3| 3| 1| 3| 3| 3| 3| 3| 5| 3| 3|             
                                           | 3| 3| 3| 7| 3| 3| 3| 5| 6| 3| 3| 3| 6| 3| 3| 3| 5| 3| 3| 3| 4| 4| 2| 4| 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   | 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|             
    500 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|             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Granuloma Sperm                      |                                                                          |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M|             
      Inflammation, Chronic Active         |                                                             4            |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Congestion                           |                                                 3                        |             
                                            __________________________________________________________________________|             
   Lymph Node                              |       +                                   +                              |             
      Iliac, Infiltration Cellular, Plasma |                                                                          |             
          Cell                             |                                                                          |             
      Lumbar, Infiltration Cellular,       |                                                                          |             
          Plasma Cell                      |                                           2                              |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  +  +  +  +  +  +  M  M  +  +  +  M  +  M  +  M  +  +  M  +  +  +  M  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  M  M  M  +  +  M  M  +  M  M  +  +  M  +  +  +  M  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Plasma Cell   |                2                                                         |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  M  +  M  M  +  +  +  +  M  M  +  M  +  M  +  M  +  +  +  M  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |                                           2                              |             
      Infiltration Cellular, Histiocyte    |                                                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  M  +  +  +  +  +  +  +  M  +  M  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 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                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Prepuce, Inflammation, Chronic Active|                   4                             2                        |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Thrombosis                           |                                                                          |             
      Alveolar Epithelium, Hyperplasia     |             1                    3                                       |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  33                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 7| 7| 7| 4| 5| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 7| 7|             
                             DAY ON TEST   | 3| 3| 3| 6| 3| 3| 3| 0| 4| 3| 3| 3| 9| 3| 3| 3| 1| 3| 3| 3| 3| 3| 5| 3| 3|             
                                           | 3| 3| 3| 7| 3| 3| 3| 5| 6| 3| 3| 3| 6| 3| 3| 3| 5| 3| 3| 3| 4| 4| 2| 4| 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   | 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|             
    500 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                 |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Suppurative            |                                                                   3      |             
      Olfactory Epithelium, Atrophy        |                                                                   3      |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |                                        1              1                 1|             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |             1     1     1  1     1  2        1     2                     |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |       +                                                        +         |             
      Hyperplasia                          |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infarct                              |                                           2                              |             
      Inflammation, Chronic Active         |                                           4                              |             
      Mineralization                       |                                                                          |             
      Nephropathy                          | 1  2  1  2  2  1  1     1  1  1  1     1     1     1  1  1  2  2  1  2  1|             
      Papilla, Inflammation, Suppurative   |                                           2                              |             
      Pelvis, Dilatation                   |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                           3                              |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  34                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 6| 7| 6| 7| 6| 7| 7| 7| 5| 7| 5| 7| 5| 6| 7| 6| 7| 7| 7| 5| 7| 7|            |
                             DAY ON TEST   | 3| 1| 3| 3| 3| 9| 3| 6| 3| 3| 3| 1| 1| 6| 3| 2| 0| 3| 4| 3| 3| 0| 8| 3| 3|            |
                                           | 4| 1| 4| 9| 4| 8| 4| 7| 4| 4| 4| 2| 6| 2| 4| 2| 1| 4| 9| 4| 4| 9| 3| 4| 4|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    500 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|      L     |
                                           | 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A  A  M  +  +  +  +  +  +  +|  40        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +  +  +|  43        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +  +  +|  43        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Basophilic Focus                     |       X              X     X           X           X                     |      8     |
      Clear Cell Focus                     |             X           X                             X                  |      4     |
      Cyst                                 |                                                                          |      1  2.0|
      Degeneration, Fatty                  | 1                                                                        |      1  1.0|
      Eosinophilic Focus                   |                                                                          |      4     |
      Mixed Cell Focus                     |                         X                                                |      2     |
      Necrosis                             |    3                                   3     2  2                 4      |      5  2.8|
      Vacuolization Cytoplasmic, Focal     |                                           2                              |      1  2.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                   +                                                      |   2        |
      Fat, Necrosis                        |                   2                                                      |      2  2.0|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Basophilic Focus                     |                                                          X               |      1     |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Necrosis                             |                                                 1     2                  |      2  1.5|
                                            __________________________________________________________________________|____________|
   Tooth                                   | +     +     +           +                             +                 +|  14        |
      Malformation                         | X     X     X           X                                               X|     12     |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       | 1        2        1     1  1        1              1        1  1     1  1|     18  1.1|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hyperplasia                          |             3     2     2  2                                             |     10  2.1|
      Hypertrophy                          | 2     1              3  2  2  2  1        2     2        2     3        2|     24  2.0|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  M  +  M  +  +  +  +  +  +|  42        |
 __________________________________________________________________________________________________________________________________ 
  * : 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: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 6| 7| 6| 7| 6| 7| 7| 7| 5| 7| 5| 7| 5| 6| 7| 6| 7| 7| 7| 5| 7| 7|            |
                             DAY ON TEST   | 3| 1| 3| 3| 3| 9| 3| 6| 3| 3| 3| 1| 1| 6| 3| 2| 0| 3| 4| 3| 3| 0| 8| 3| 3|            |
                                           | 4| 1| 4| 9| 4| 8| 4| 7| 4| 4| 4| 2| 6| 2| 4| 2| 1| 4| 9| 4| 4| 9| 3| 4| 4|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    500 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|      L     |
                                           | 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                         | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Pars Distalis, Hyperplasia           |                               2                                      2   |      4  2.0|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Follicular Cell, Hyperplasia         |                                  1  1                                    |      6  1.3|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Granuloma Sperm                      |                                        2                                 |      1  2.0|
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Inflammation, Chronic Active         |                                                    2                     |      2  3.0|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  A  +  +  +  +  +  +  I  +  +  A  +  +  +  +  +  +  +  +  +|  46        |
      Inflammation, Chronic Active         |          3           3                                                   |      2  3.0|
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Mineralization                       |                                                                      2   |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Congestion                           |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |          +                                                               |   3        |
      Iliac, Infiltration Cellular, Plasma |                                                                          |            |
          Cell                             |          3                                                               |      1  3.0|
      Lumbar, Infiltration Cellular,       |                                                                          |            |
          Plasma Cell                      |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  M  +  +  M  M  +  M  +  +  +  +  M  +  +  +  +  M  +  +  M  +  M  M|  33        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  M  +  M  M  M  M  +  M  +  +  +  +  M  M  +  +  M  M  +  +  M  M|  29        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Infiltration Cellular, Plasma Cell   |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  M  +  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +|  38        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hematopoietic Cell Proliferation     |                                                    3              3      |      3  2.7|
      Infiltration Cellular, Histiocyte    |                                                             3            |      1  3.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  A  +  +  +  +  +  +  +  +  M  M  +  M  +  +  M  +  +  +  +|  42        |
 _____________________________________________________________________________________________________________________|            |
 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|            |
 __________________________________________________________________________________________________________________________________ 
  * : 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: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 6| 7| 6| 7| 6| 7| 7| 7| 5| 7| 5| 7| 5| 6| 7| 6| 7| 7| 7| 5| 7| 7|            |
                             DAY ON TEST   | 3| 1| 3| 3| 3| 9| 3| 6| 3| 3| 3| 1| 1| 6| 3| 2| 0| 3| 4| 3| 3| 0| 8| 3| 3|            |
                                           | 4| 1| 4| 9| 4| 8| 4| 7| 4| 4| 4| 2| 6| 2| 4| 2| 1| 4| 9| 4| 4| 9| 3| 4| 4|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    500 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|      L     |
                                           | 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               |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Prepuce, Inflammation, Chronic Active|          4           4                 4                       4         |      6  3.7|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Thrombosis                           |                                                                         1|      1  1.0|
      Alveolar Epithelium, Hyperplasia     |                            1  2                 1                       2|      6  1.7|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Inflammation, Suppurative            |                                                       3                  |      2  3.0|
      Olfactory Epithelium, Atrophy        |                                                                          |      1  3.0|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |                         1           1                 2              1   |      7  1.1|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         |    1        1     1     1  2        1  1  1     1     2              1   |     19  1.2|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                            +  +                                          |   4        |
      Hyperplasia                          |                               2                                          |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Infarct                              |                                           2                              |      2  2.0|
      Inflammation, Chronic Active         |                                                                          |      1  4.0|
      Mineralization                       |          1                                                               |      1  1.0|
      Nephropathy                          | 1     1     2     1  1  2  2  1           1     1  2  1  1  2  1  2  1  1|     39  1.3|
      Papilla, Inflammation, Suppurative   |          3           2                                                   |      3  2.3|
      Pelvis, Dilatation                   |                                  3                             2         |      2  2.5|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Inflammation, Chronic Active         |          4           4                                                   |      3  3.7|
 __________________________________________________________________________________________________________________________________ 
  * : 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: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 7| 7| 5| 5| 7| 5| 7| 7| 4| 5| 7| 7| 7| 7| 7| 7| 5| 6| 7| 3| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 3| 3| 5| 8| 3| 5| 3| 3| 8| 8| 3| 3| 3| 3| 3| 3| 1| 2| 3| 8| 3| 8| 3| 0|             
                                           | 7| 3| 3| 5| 4| 3| 9| 3| 3| 0| 3| 3| 3| 3| 3| 3| 3| 2| 8| 3| 7| 3| 1| 3| 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 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   | 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|             
    2000 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                             | +  +  +  +  A  I  +  +  +  A  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |    X                                   X           X        X            |             
      Clear Cell Focus                     |                X     X                 X                                 |             
      Degeneration, Fatty                  |                                                                          |             
      Eosinophilic Focus                   |                X        X     X  X  X                                X   |             
      Mixed Cell Focus                     |                                     X                                    |             
      Necrosis                             | 1                                                                        |             
                                            __________________________________________________________________________|             
   Mesentery                               |    +                                                        +            |             
      Fat, Necrosis                        |    2                                                        2            |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                          |             
      Inflammation, Acute                  |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                                                          |             
                                            __________________________________________________________________________|             
   Tooth                                   |                         +  +     +  +  +                       +     +   |             
      Malformation                         |                            X        X  X                       X     X   |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |    1                    1                 1  1     1                     |             
      Thrombosis                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |       2                 2              2  3  1        2                  |             
      Hypertrophy                          |    2     1     4                 2  3  2        2        1     2        2|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |          2                                                               |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                2         |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  +  +  +  M  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           |                                                 1                       2|             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
                                                             Page  38                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 7| 7| 5| 5| 7| 5| 7| 7| 4| 5| 7| 7| 7| 7| 7| 7| 5| 6| 7| 3| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 3| 3| 5| 8| 3| 5| 3| 3| 8| 8| 3| 3| 3| 3| 3| 3| 1| 2| 3| 8| 3| 8| 3| 0|             
                                           | 7| 3| 3| 5| 4| 3| 9| 3| 3| 0| 3| 3| 3| 3| 3| 3| 3| 2| 8| 3| 7| 3| 1| 3| 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 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   | 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|             
    2000 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                   |                                                                          |             
                                           |                                                                          |             
      Follicular Cell, Hyperplasia         |                                              1  2                        |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Granuloma Sperm                      |                                                                2         |             
                                            __________________________________________________________________________|             
   Penis                                   |          +                                                               |             
      Inflammation, Acute                  |                                                                          |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                      3                                                   |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                       3           2      |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                                       3                  |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                                       +           +      |             
      Iliac, Infiltration Cellular, Plasma |                                                                          |             
          Cell                             |                                                       4                  |             
      Iliac, Infiltration Cellular,        |                                                                          |             
          Polymorphonuclear                |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  M  +  +  +  +  M  M  M  +  M  M  +  +  M  M  +  +  +  M  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | M  +  +  M  M  +  +  M  +  M  +  +  M  +  +  +  M  M  +  M  +  +  +  M  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
      Angiectasis                          |       1                                                                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  M  +  +  +  M  M  +  +  +  +  +  M  +  +  +  +  M  M  +  +  M  M  M  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |       2                                               4                  |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  M  M  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 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                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Prepuce, Inflammation, Chronic Active| 4                 4        4                 4        4     3     4      |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  39                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 7| 7| 5| 5| 7| 5| 7| 7| 4| 5| 7| 7| 7| 7| 7| 7| 5| 6| 7| 3| 7| 6| 7| 7|             
                             DAY ON TEST   | 2| 3| 3| 5| 8| 3| 5| 3| 3| 8| 8| 3| 3| 3| 3| 3| 3| 1| 2| 3| 8| 3| 8| 3| 0|             
                                           | 7| 3| 3| 5| 4| 3| 9| 3| 3| 0| 3| 3| 3| 3| 3| 3| 3| 2| 8| 3| 7| 3| 1| 3| 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 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   | 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|             
    2000 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|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |             2                                               2            |             
      Alveolar Epithelium, Hyperplasia     |                         2                                   2        1   |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Suppurative            |                            2     2                                       |             
      Olfactory Epithelium, Atrophy        |                                                                2         |             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |       1                 2                    2                 1     2  2|             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         |    1  1  1     1     1  2        3     1  1  2  2  1     1  1  2  1  3   |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                      +   |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infarct                              |                                                                         2|             
      Nephropathy                          |    1  1  2  2  1  1     3     3  2  1  1  2  2  1     2  1     1     1   |             
      Capsule, Inflammation, Chronic       |                                                                          |             
      Papilla, Inflammation, Suppurative   |                   2                                3  1           2      |             
      Pelvis, Dilatation                   |                   3                          2                           |             
      Renal Tubule, Hyperplasia            |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Calculus Gross Observation           |                                                    X                     |             
      Inflammation, Chronic Active         |                   3                                3  4           4      |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  40                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 4| 7| 5| 7| 4| 7| 7| 7| 7| 7| 6| 6| 7| 6| 3| 7| 7| 7| 7| 7| 6| 7| 6| 7|            |
                             DAY ON TEST   | 3| 9| 3| 1| 3| 2| 3| 3| 3| 3| 3| 3| 3| 3| 4| 8| 3| 3| 3| 2| 3| 5| 3| 8| 1|            |
                                           | 1| 9| 3| 2| 4| 8| 4| 4| 4| 4| 4| 6| 9| 4| 5| 9| 4| 4| 4| 9| 4| 3| 4| 6| 3|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    2000 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|      L     |
                                           | 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Basophilic Focus                     |                            X           X                                 |      6     |
      Clear Cell Focus                     |       X              X                                X                  |      6     |
      Degeneration, Fatty                  |                                              1        1                  |      2  1.0|
      Eosinophilic Focus                   |       X           X     X  X                    X                        |     11     |
      Mixed Cell Focus                     |                                                                          |      1     |
      Necrosis                             |                               1                                          |      2  1.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               | +                             +                                          |   4        |
      Fat, Necrosis                        | 2                             2                                          |      4  2.0|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                                                                   3      |      1  3.0|
      Inflammation, Acute                  |                                                                   3      |      1  3.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Necrosis                             |                                              3                           |      1  3.0|
                                            __________________________________________________________________________|____________|
   Tooth                                   |       +                                                              +   |   9        |
      Malformation                         |       X                                                              X   |      7     |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       |             1  1        1     1  1  1           1        2  1     1     1|     16  1.1|
      Thrombosis                           |                                                                2         |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                1  2     2     2  2                 2     2        2     2|     15  1.9|
      Hypertrophy                          | 1     2     1     2  1     2  2        2  1  1  1  2  2     2            |     24  1.8|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 __________________________________________________________________________________________________________________________________ 
  * : 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  41                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 4| 7| 5| 7| 4| 7| 7| 7| 7| 7| 6| 6| 7| 6| 3| 7| 7| 7| 7| 7| 6| 7| 6| 7|            |
                             DAY ON TEST   | 3| 9| 3| 1| 3| 2| 3| 3| 3| 3| 3| 3| 3| 3| 4| 8| 3| 3| 3| 2| 3| 5| 3| 8| 1|            |
                                           | 1| 9| 3| 2| 4| 8| 4| 4| 4| 4| 4| 6| 9| 4| 5| 9| 4| 4| 4| 9| 4| 3| 4| 6| 3|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    2000 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|      L     |
                                           | 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                          |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  M  +  M  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +  M  +  +  M|  42        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +|  49        |
      Pars Distalis, Hyperplasia           |                               3                                          |      3  2.0|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Follicular Cell, Hyperplasia         |                                                       1                  |      3  1.3|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Granuloma Sperm                      |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Penis                                   |                                  +                                       |   2        |
      Inflammation, Acute                  |                                  3                                       |      1  3.0|
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |             2                                                            |      2  2.5|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  M  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Inflammation, Chronic Active         |                                  2                       2               |      4  2.3|
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Necrosis                             |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                                           3                              |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lymph Node                              | +  +                             +        +                          +   |   7        |
      Iliac, Infiltration Cellular, Plasma |                                                                          |            |
          Cell                             |    2                                                                     |      2  3.0|
      Iliac, Infiltration Cellular,        |                                                                          |            |
          Polymorphonuclear                |                                  3                                       |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  M  M  +  M  +  +  M  +  +  +  +  +  +  M  +  +  M  M  +  +  +  +  M|  32        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  M  +  +  +  +  M  +  +  +  +  +  +  +  +  M  +  +  M  +  M  M  M|  33        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +|  48        |
      Angiectasis                          |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  M  +  +  +  M  +  +  +  +  M  M  +  +  +  +  M  +  +  +  +  +  +  +|  36        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hematopoietic Cell Proliferation     |          3                       3                                   4   |      5  3.2|
                                            __________________________________________________________________________|____________|
   Thymus                                  | M  +  +  +  M  M  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +  M  +  M  M|  38        |
 __________________________________________________________________________________________________________________________________ 
  * : 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  42                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 4| 7| 5| 7| 4| 7| 7| 7| 7| 7| 6| 6| 7| 6| 3| 7| 7| 7| 7| 7| 6| 7| 6| 7|            |
                             DAY ON TEST   | 3| 9| 3| 1| 3| 2| 3| 3| 3| 3| 3| 3| 3| 3| 4| 8| 3| 3| 3| 2| 3| 5| 3| 8| 1|            |
                                           | 1| 9| 3| 2| 4| 8| 4| 4| 4| 4| 4| 6| 9| 4| 5| 9| 4| 4| 4| 9| 4| 3| 4| 6| 3|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               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|      A     |
    2000 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|      L     |
                                           | 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               |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 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                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Prepuce, Inflammation, Chronic Active|                3              4  4  4                    3              4|     13  3.8|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hemorrhage                           |                2                                                         |      3  2.0|
      Alveolar Epithelium, Hyperplasia     |                                           2                              |      4  1.8|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Suppurative            |                                                                          |      2  2.0|
      Olfactory Epithelium, Atrophy        |                                                                          |      1  2.0|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         |             1        1  2                 2        1  2  1     2  2     2|     16  1.6|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         | 2     1     1     1  1  2              2  2     1  2     2  2            |     29  1.5|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         | +                                                              +        +|   4        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Infarct                              |    4        2                             3                              |      4  2.8|
      Nephropathy                          |    2  2  3  1  1  2  2  2  1  1  1     1        2  1  2     1  3  1  1  3|     38  1.6|
      Capsule, Inflammation, Chronic       |                1                                                         |      1  1.0|
      Papilla, Inflammation, Suppurative   |                                  2                       4               |      6  2.3|
      Pelvis, Dilatation                   |    3                                3                                    |      4  2.8|
      Renal Tubule, Hyperplasia            |                                                                3         |      1  3.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Calculus Gross Observation           |                                                                          |      1     |
      Inflammation, Chronic Active         |    3                             4                       4               |      7  3.6|
 __________________________________________________________________________________________________________________________________ 
  * : 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  43                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 3| 4| 6| 7| 7| 7| 7| 4| 7| 5| 6| 6| 6| 5| 7| 7| 6| 7| 7| 7| 5| 7| 7|             
                             DAY ON TEST   | 3| 2| 4| 9| 6| 3| 3| 3| 3| 5| 3| 4| 3| 8| 0| 6| 3| 3| 8| 3| 3| 3| 1| 3| 3|             
                                           | 3| 7| 1| 9| 7| 3| 3| 3| 3| 7| 3| 7| 3| 9| 8| 2| 3| 3| 2| 3| 3| 3| 2| 3| 3|             
 _____________________________________________________________________________________________________________________|             
                                           | 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   | 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6|             
    8000 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                             | +  +  A  +  M  +  +  +  M  +  M  M  +  A  I  +  +  +  A  M  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  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                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Basophilic Focus                     |                                     X                    X               |             
      Clear Cell Focus                     |                X     X        X                 X  X        X            |             
      Degeneration, Fatty                  |       1  1                             2                          2  1   |             
      Eosinophilic Focus                   | X                                                  X                     |             
      Necrosis                             |                                                                          |             
      Vacuolization Cytoplasmic, Focal     |                                                 4                        |             
                                            __________________________________________________________________________|             
   Mesentery                               | +                                               +                        |             
      Fat, Necrosis                        | 3                                               2                        |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                         4|             
      Inflammation, Acute                  |                                                                         3|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |                +  +     +              +        +        +  +  +        +|             
      Malformation                         |                X  X     X              X        X        X     X        X|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |             1           1                 1  1  1        1        1     1|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          | 2  2                    2     2                          2  2           1|             
      Hypertrophy                          | 1     1        3  3  2  2     2     2           2  3  2  2  3  2  2     1|             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                              3                           |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                         2|             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  +  M  +  +  +  +  M  +  +  +  +  +  +  +  +  M  +  +  +  M  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           |                                                       3                  |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Follicular Cell, Hyperplasia         |                                                                      1  2|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  44                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 3| 4| 6| 7| 7| 7| 7| 4| 7| 5| 6| 6| 6| 5| 7| 7| 6| 7| 7| 7| 5| 7| 7|             
                             DAY ON TEST   | 3| 2| 4| 9| 6| 3| 3| 3| 3| 5| 3| 4| 3| 8| 0| 6| 3| 3| 8| 3| 3| 3| 1| 3| 3|             
                                           | 3| 7| 1| 9| 7| 3| 3| 3| 3| 7| 3| 7| 3| 9| 8| 2| 3| 3| 2| 3| 3| 3| 2| 3| 3|             
 _____________________________________________________________________________________________________________________|             
                                           | 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   | 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6|             
    8000 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|             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Granuloma Sperm                      |             2                                   1                        |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                                                3         |             
      Inflammation, Chronic Active         |                                                    3                     |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |          3                                                               |             
                                            __________________________________________________________________________|             
   Lymph Node                              |             +                                                            |             
      Iliac, Infiltration Cellular, Plasma |                                                                          |             
          Cell                             |             3                                                            |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  M  M  +  +  +  +  +  M  +  +  +  M  +  +  +  M  +  +  +  +  M  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | M  +  M  +  +  +  +  +  +  +  +  M  +  +  +  +  M  M  M  +  M  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  M  +  +  M  M  +  M  +  M  M  +  +  M  +  +  M  +  +  M  +  M  M  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Infiltration Cellular, Histiocyte    |                                                          2               |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  M  +  +  +  +  +  +  +  +  +  +  +  A  M  +  +  +  +  M  +  +  M  +  +|             
 _____________________________________________________________________________________________________________________|             
 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                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Prepuce, Inflammation, Chronic Active|             4     3        4                                             |             
      Subcutaneous Tissue, Edema           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Peripheral Nerve                        |                                     +                                    |             
      Sciatic, Degeneration                |                                     3                                    |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar Epithelium, Hyperplasia     |                   2  1                                         1         |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  45                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 3| 4| 6| 7| 7| 7| 7| 4| 7| 5| 6| 6| 6| 5| 7| 7| 6| 7| 7| 7| 5| 7| 7|             
                             DAY ON TEST   | 3| 2| 4| 9| 6| 3| 3| 3| 3| 5| 3| 4| 3| 8| 0| 6| 3| 3| 8| 3| 3| 3| 1| 3| 3|             
                                           | 3| 7| 1| 9| 7| 3| 3| 3| 3| 7| 3| 7| 3| 9| 8| 2| 3| 3| 2| 3| 3| 3| 2| 3| 3|             
 _____________________________________________________________________________________________________________________|             
                                           | 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   | 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6|             
    8000 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                 |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Polyp, Inflammatory                  |                                                             3            |             
      Nasolacrimal Duct, Polyp,            |                                                                          |             
          Inflammatory                     |                                                                         3|             
      Olfactory Epithelium, Atrophy        |                                                             2           2|             
      Olfactory Epithelium, Degeneration,  |                                                                          |             
           Hyaline                         |    2                    1              1                    2  1     1  2|             
      Respiratory Epithelium, Degeneration,|                                                                          |             
           Hyaline                         | 2  2        3  3  2  2  2  2  2              1  2  3     2  2  2     1  2|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                                          |             
      Cataract                             |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         | +                                                              +         |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                                                          |             
      Metaplasia, Osseous                  |                2                                                         |             
      Nephropathy                          |    1     1  2  2  2  1  1  1  2     1     3  2  1  1     1  2  1  2  2  1|             
      Papilla, Inflammation, Suppurative   |             2                                                            |             
      Pelvis, Dilatation                   |                            2                                             |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |             4              1                                             |             
 _____________________________________________________________________________________________________________________|             
                                                             Page  46                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 6| 3| 3| 6| 7| 7| 6| 2| 6| 7| 7| 7| 7| 5|            |
                             DAY ON TEST   | 3| 3| 3| 3| 3| 3| 0| 3| 3| 3| 4| 7| 3| 8| 3| 3| 3| 9| 5| 3| 3| 3| 3| 3| 0|            |
                                           | 3| 4| 4| 4| 4| 4| 6| 4| 4| 4| 7| 0| 0| 6| 9| 4| 4| 5| 1| 1| 4| 4| 4| 4| 8|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               ANIMAL ID   | 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6|      A     |
    8000 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|      L     |
                                           | 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  A  +  +  +  M  A  A  A  +  +  +  +  +  +  M  +  +  +  M|  34        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  I  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  A  +  +  +  +  A  A  +  +  +  +  +  A  +  +  +  +  +  A|  42        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  A  A  A  +  +  +  +  A  +  +  +  +  +  A|  42        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  A  +  +  +  +  +  A|  43        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  A  +  +  +  +  A  A  +  +  +  +  +  A  +  +  +  +  +  A|  42        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Basophilic Focus                     |                                                    X                 X  X|      5     |
      Clear Cell Focus                     |       X                 X                       X                       X|     10     |
      Degeneration, Fatty                  |                                                                          |      5  1.4|
      Eosinophilic Focus                   |       X                 X                    X  X                 X      |      7     |
      Necrosis                             |                                                                         2|      1  2.0|
      Vacuolization Cytoplasmic, Focal     |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   2        |
      Fat, Necrosis                        |                                                                          |      2  2.5|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Hyperplasia                          |                                                                          |      1  4.0|
      Inflammation, Acute                  |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Tooth                                   |    +                    +  +     +           +  +           +            |  16        |
      Malformation                         |    X                       X     X           X  X           X            |     14     |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       | 1  2           1        1     1     1        1  1        1  1        1   |     19  1.1|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hyperplasia                          | 2  2  2        1           2  2           2  2                 2         |     16  1.9|
      Hypertrophy                          |       2  2  3  1  1  1  2  2                 2  2  1     1     2         |     29  1.9|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hyperplasia                          |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Hyperplasia                          |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | M  +  M  +  +  M  +  +  +  M  +  M  +  +  +  +  M  +  M  +  +  +  +  M  +|  37        |
 __________________________________________________________________________________________________________________________________ 
  * : 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  47                                                               
NTP Experiment-Test: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 6| 3| 3| 6| 7| 7| 6| 2| 6| 7| 7| 7| 7| 5|            |
                             DAY ON TEST   | 3| 3| 3| 3| 3| 3| 0| 3| 3| 3| 4| 7| 3| 8| 3| 3| 3| 9| 5| 3| 3| 3| 3| 3| 0|            |
                                           | 3| 4| 4| 4| 4| 4| 6| 4| 4| 4| 7| 0| 0| 6| 9| 4| 4| 5| 1| 1| 4| 4| 4| 4| 8|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               ANIMAL ID   | 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6|      A     |
    8000 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|      L     |
                                           | 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                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  I|  48        |
      Pars Distalis, Hyperplasia           | 1  2                                                                 1   |      4  1.8|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Follicular Cell, Hyperplasia         |                                                                      1   |      3  1.3|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Granuloma Sperm                      |    2                                                     4  2            |      5  2.2|
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                                                                          |      1  3.0|
      Inflammation, Chronic Active         |       2                 2                                                |      3  2.3|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|  48        |
      Inflammation, Chronic Active         |                   3              3        1              2               |      4  2.3|
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |    3                                                                     |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hemorrhage                           |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   1        |
      Iliac, Infiltration Cellular, Plasma |                                                                          |            |
          Cell                             |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  +  +  M  M  M  +  M  M  +  M  +  +  +  M  M  +  +  M  M  M  M|  32        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  M  +  +  +  M  +  +  M  +  M  M  M  +  +  M  +  +  +  +  +  +  +  +  M|  35        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  M  +  +  M  M  +  +  M  +  M  +  +  +  +  M  +  +  M  +  +  M  +|  31        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Hematopoietic Cell Proliferation     |                   3                       3              3              3|      4  3.0|
      Infiltration Cellular, Histiocyte    |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  M  +  +  +  +  +  +  +  M  M  +  M  +  +  +  +  +  +  +  +  +  +  +|  41        |
 _____________________________________________________________________________________________________________________|            |
 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|   1        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Prepuce, Inflammation, Chronic Active|                                  2     4  4        3  4  4               |      9  3.6|
 __________________________________________________________________________________________________________________________________ 
  * : 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: 88070-04                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:37:32  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 6| 3| 3| 6| 7| 7| 6| 2| 6| 7| 7| 7| 7| 5|            |
                             DAY ON TEST   | 3| 3| 3| 3| 3| 3| 0| 3| 3| 3| 4| 7| 3| 8| 3| 3| 3| 9| 5| 3| 3| 3| 3| 3| 0|            |
                                           | 3| 4| 4| 4| 4| 4| 6| 4| 4| 4| 7| 0| 0| 6| 9| 4| 4| 5| 1| 1| 4| 4| 4| 4| 8|      T (*) |
 _____________________________________________________________________________________________________________________|            |
                                           | 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|      O     |
   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|      T     |
                               ANIMAL ID   | 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6|      A     |
    8000 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|      L     |
                                           | 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, Edema           |                                        2                                 |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Peripheral Nerve                        |                                                                          |   1        |
      Sciatic, Degeneration                |                                                                          |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Alveolar Epithelium, Hyperplasia     |                                                                          |      3  1.3|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Polyp, Inflammatory                  |                                                                          |      1  3.0|
      Nasolacrimal Duct, Polyp,            |                                                                          |            |
          Inflammatory                     |                                                                          |      1  3.0|
      Olfactory Epithelium, Atrophy        |                                                                          |      2  2.0|
      Olfactory Epithelium, Degeneration,  |                                                                          |            |
           Hyaline                         | 1  2     1        2  2  1  1                       2              1     1|     17  1.4|
      Respiratory Epithelium, Degeneration,|                                                                          |            |
           Hyaline                         | 2  3  1  3  1     2  2  3  2     2  1  1  1  1  2  2     2  1  1  2  1  1|     39  1.8|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                         +                                            +   |   2        |
      Cataract                             |                                                                      3   |      1  3.0|
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                   +  +   |   4        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                2                                                         |      1  2.0|
      Metaplasia, Osseous                  |    2                                                                     |      2  2.0|
      Nephropathy                          | 2  1  2  2  1  2     2  2  1  3     2        2  1  1     2  2  2  2  2  2|     40  1.7|
      Papilla, Inflammation, Suppurative   |                   3              3                    2  3               |      5  2.6|
      Pelvis, Dilatation                   |                   3           4           3                              |      4  3.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|  46        |
      Inflammation, Chronic Active         |                   4              3                 1     4               |      6  2.8|
 __________________________________________________________________________________________________________________________________ 
  * : 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        
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