National Toxicology Program

National Toxicology Program
https://ntp.niehs.nih.gov/go/2958

TDMS Study 05135-07 Pathology Tables

NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23

                                                         2 YEAR CHRONIC




       Facility:  Battelle Northwest

       Chemical CAS #:  78-79-5

       Lock Date:  03/13/96

       Cage Range:  All

       Reasons For Removal:    All

       Removal Date Range:     All

       Treatment Groups:       Include All




































                                                              Page   1


NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 6| 7| 7| 7| 7| 7| 5| 4| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 4| 3| 7| 7| 5|             
                             DAY ON TEST   | 3| 8| 3| 3| 3| 3| 3| 9| 8| 3| 3| 3| 3| 3| 5| 3| 3| 3| 3| 3| 5| 9| 3| 3| 8|             
                                           | 0| 4| 4| 5| 5| 5| 5| 6| 2| 4| 4| 4| 6| 5| 2| 6| 4| 5| 4| 4| 4| 8| 4| 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| 0|             
   FISCHER 344 RATS 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Basophilic Focus                     | X  X  X  X  X  X  X        X  X           X  X  X  X  X  X        X  X   |             
      Clear Cell Focus                     |             X                                                     X  X   |             
      Eosinophilic Focus                   |                                                       X                  |             
      Fatty Change                         |                         2                 2                              |             
      Hepatodiaphragmatic Nodule           |                                     X                                    |             
      Mixed Cell Focus                     |                      X                    X           X                  |             
      Bile Duct, Cyst                      |                                                                          |             
      Bile Duct, Hyperplasia               |                                                                          |             
      Centrilobular, Necrosis              |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               | +        +        +        +                                             |             
      Fat, Necrosis                        | 2        3        2        2                                             |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |       2  2  3  1        2        2  2                 2                  |             
      Basophilic Focus                     |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                           2                    2         |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                           2                              |             
                                            __________________________________________________________________________|             
   Tongue                                  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       | 2  1  2     1     1        1  2  1     1  2  1  2  1  2  2  1     1  2  1|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Degeneration, Cystic                 |                                                                          |             
      Hyperplasia                          |             2  2     2     2  2  2  2  2           2                 2  2|             
      Hypertrophy                          |                2                 2           2           2        1      |             
      Necrosis                             |                                                                          |             
      Vacuolization Cytoplasmic            | 2  2                       2                          2                  |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                              2                           |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   2                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 6| 7| 7| 7| 7| 7| 5| 4| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 4| 3| 7| 7| 5|             
                             DAY ON TEST   | 3| 8| 3| 3| 3| 3| 3| 9| 8| 3| 3| 3| 3| 3| 5| 3| 3| 3| 3| 3| 5| 9| 3| 3| 8|             
                                           | 0| 4| 4| 5| 5| 5| 5| 6| 2| 4| 4| 4| 6| 5| 2| 6| 4| 5| 4| 4| 4| 8| 4| 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| 0|             
   FISCHER 344 RATS 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                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                2                                                         |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           | 3                       2              2              2        2  4      |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      C-Cell, Hyperplasia                  |       1     1  2  2     2  2  2  1     1  1  2  1  2  1  1  1  1  2  2   |             
      Follicular Cell, Hyperplasia         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          | +  +  +  +  +  M  +  +  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                          3               |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 | 3              3                                                         |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                             4            |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A|             
      Myelofibrosis                        |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  +  M  +  +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  +  M  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  M  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             |                                                                         2|             
      Hematopoietic Cell Proliferation     |                         3                                   3  3         |             
      Hemorrhage                           |                                                                          |             
      Necrosis                             |                                                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Galactocele                          |                                                                          |             
      Hyperplasia                          |                      2                                                   |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst Epithelial Inclusion            |                               X                                          |             
      Inflammation, Chronic Active         |                                              1                           |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page   3                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 6| 7| 7| 7| 7| 7| 5| 4| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 4| 3| 7| 7| 5|             
                             DAY ON TEST   | 3| 8| 3| 3| 3| 3| 3| 9| 8| 3| 3| 3| 3| 3| 5| 3| 3| 3| 3| 3| 5| 9| 3| 3| 8|             
                                           | 0| 4| 4| 5| 5| 5| 5| 6| 2| 4| 4| 4| 6| 5| 2| 6| 4| 5| 4| 4| 4| 8| 4| 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| 0|             
   FISCHER 344 RATS 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|             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM - cont             |                                                                          |             
                                           |                                                                          |             
      Fibrous Osteodystrophy               |                                                                          |             
      Hyperostosis                         |                                  3                    2                  |             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                                +         |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Gliosis                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |       2  3  3  2  1        2  2  2  2  2     2  3  3  2  2        2  2   |             
      Alveolar Epithelium, Hyperplasia     |    1                                   1              1                  |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Foreign Body                         |                                                                          |             
      Inflammation, Suppurative            | 2              1  2                                                      |             
      Thrombosis                           |                                                                         2|             
      Olfactory Epithelium, Metaplasia     |                   1                                                      |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                     +                 +                  |             
      Cataract                             |                                     2                 4                  |             
      Retina, Atrophy                      |                                     3                 3                  |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                      1                                                   |             
      Nephropathy                          | 2  3  2  1  2  2  2  2  1  2  1  2  2  2  1  2  2  2  2  2        3  2  1|             
      Renal Tubule, Hyperplasia            |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Transitional Epithelium, Hyperplasia |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   4                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 7| 6| 6| 7| 6| 7| 5| 6| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6|            |
                             DAY ON TEST   | 2| 3| 2| 2| 3| 5| 7| 0| 5| 3| 8| 4| 3| 3| 3| 1| 2| 3| 3| 3| 3| 3| 3| 3| 7|            |
                                           | 9| 6| 7| 8| 6| 7| 1| 5| 7| 4| 0| 8| 6| 9| 4| 4| 7| 4| 6| 5| 4| 5| 5| 6| 0|      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     |
   FISCHER 344 RATS 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  I  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |                                        1                       3         |      2  2.0|
      Basophilic Focus                     |    X  X  X     X  X  X     X  X  X  X     X  X  X  X  X     X  X  X  X   |     36     |
      Clear Cell Focus                     |                      X     X                             X     X  X  X   |      9     |
      Eosinophilic Focus                   |                                                       X                  |      2     |
      Fatty Change                         | 3     1        2        3                          1                    3|      8  2.1|
      Hepatodiaphragmatic Nodule           |                                                                X         |      2     |
      Mixed Cell Focus                     |                   X                                                      |      4     |
      Bile Duct, Cyst                      |       2                                                                  |      1  2.0|
      Bile Duct, Hyperplasia               |                2                 1     1                                 |      3  1.3|
      Centrilobular, Necrosis              |                1              1  3              1                       1|      5  1.4|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                   +                    +        +     +              +   |   9        |
      Fat, Necrosis                        |                   2                    2        2     2              2   |      9  2.1|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              | 1  2     3        1  4                          1  2  1           1     1|     18  1.8|
      Basophilic Focus                     |                   X                                                      |      1     |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |          2                                                               |      1  2.0|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Necrosis                             |                3                                3                       3|      5  2.6|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Necrosis                             |                      2           2                                       |      3  2.0|
                                            __________________________________________________________________________|____________|
   Tongue                                  |                   +                                                      |   1        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       | 1  2  2     1           2  1        2     2  2  1  2  1     2  1  1  2   |     35  1.5|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Degeneration, Cystic                 |                                              3                           |      1  3.0|
      Hyperplasia                          | 2  2  2           2  1  2  1  2     2     2        2        2  2     2   |     25  1.9|
 __________________________________________________________________________________________________________________________________ 

  * : 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: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 7| 6| 6| 7| 6| 7| 5| 6| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6|            |
                             DAY ON TEST   | 2| 3| 2| 2| 3| 5| 7| 0| 5| 3| 8| 4| 3| 3| 3| 1| 2| 3| 3| 3| 3| 3| 3| 3| 7|            |
                                           | 9| 6| 7| 8| 6| 7| 1| 5| 7| 4| 0| 8| 6| 9| 4| 4| 7| 4| 6| 5| 4| 5| 5| 6| 0|      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     |
   FISCHER 344 RATS 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                   |                                                                          |            |
                                           |                                                                          |            |
      Hypertrophy                          |                                                       1  1  3  2         |      9  1.8|
      Necrosis                             |                                  2              3                        |      2  2.5|
      Vacuolization Cytoplasmic            |                                                                          |      4  2.0|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          | 2     2  1           2  3  2  2              3  2  2                     |     11  2.1|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hyperplasia                          |                                        3                                 |      2  2.5|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  M  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Pars Distalis, Hyperplasia           |             2           2     2        2  3     2                        |     12  2.3|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      C-Cell, Hyperplasia                  | 1     1  1  2  3  1     1  1  1     1  1  2  3  2  2  1  1  2     2  2  4|     40  1.6|
      Follicular Cell, Hyperplasia         |                                     1                                    |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Hyperplasia                          |                                                       2                  |      2  2.5|
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |             2                 3        2                                 |      5  2.6|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |                                                                          |      1  4.0|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Myelofibrosis                        |                                                 4                        |      1  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  M  M  +  +  +  +  +  +  +  +|  42        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  M  +  +  +  +  +  +  M  +  +  +  +  M  +  +  +  M  +  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  M  +  +  +  +  +  +  +  M  +  +  M  +  +  +  +  +  +  +  +  +|  44        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrosis                             |                2                       1     2                           |      4  1.8|
      Hematopoietic Cell Proliferation     |                                              3                           |      4  3.0|
      Hemorrhage                           |                         2                                                |      1  2.0|
      Necrosis                             |                                  4                                       |      1  4.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY 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: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 7| 6| 6| 7| 6| 7| 5| 6| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6|            |
                             DAY ON TEST   | 2| 3| 2| 2| 3| 5| 7| 0| 5| 3| 8| 4| 3| 3| 3| 1| 2| 3| 3| 3| 3| 3| 3| 3| 7|            |
                                           | 9| 6| 7| 8| 6| 7| 1| 5| 7| 4| 0| 8| 6| 9| 4| 4| 7| 4| 6| 5| 4| 5| 5| 6| 0|      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     |
   FISCHER 344 RATS 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|            |
 __________________________________________________________________________________________________________________________________ 
 INTEGUMENTARY SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Galactocele                          |                                                          4               |      1  4.0|
      Hyperplasia                          |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst Epithelial Inclusion            |                                                                          |      1     |
      Inflammation, Chronic Active         |                                                                          |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrous Osteodystrophy               |       1                                                                  |      1  1.0|
      Hyperostosis                         |                3        4           3                                3   |      6  3.0|
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Gliosis                              |    2                                                                     |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |    2  1     1     1        2        1     2        1  2  2  1  1  2  1   |     31  1.8|
      Alveolar Epithelium, Hyperplasia     |                                     1     1                              |      5  1.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Foreign Body                         |                                                                X         |      1     |
      Inflammation, Suppurative            |                                                       1        2         |      5  1.6|
      Thrombosis                           |                                                 3                        |      2  2.5|
      Olfactory Epithelium, Metaplasia     |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     | +                                               +              +         |   5        |
      Cataract                             | 3                                               3              3         |      5  3.0|
      Retina, Atrophy                      | 3                                               4              4         |      5  3.4|
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                                                                          |      1  1.0|
      Nephropathy                          | 2  1  4  1  2  2  1     3  3  1     2  1  2  1  2  3  1  2  2  4  2  3  1|     46  1.9|
 __________________________________________________________________________________________________________________________________ 

  * : 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: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 7| 6| 6| 7| 6| 7| 5| 6| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6|            |
                             DAY ON TEST   | 2| 3| 2| 2| 3| 5| 7| 0| 5| 3| 8| 4| 3| 3| 3| 1| 2| 3| 3| 3| 3| 3| 3| 3| 7|            |
                                           | 9| 6| 7| 8| 6| 7| 1| 5| 7| 4| 0| 8| 6| 9| 4| 4| 7| 4| 6| 5| 4| 5| 5| 6| 0|      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     |
   FISCHER 344 RATS 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|            |
 __________________________________________________________________________________________________________________________________ 
 URINARY SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
      Renal Tubule, Hyperplasia            |                            3                                   2  1  2   |      4  2.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Transitional Epithelium, Hyperplasia |                                                          3               |      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   8                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 6| 7| 7| 5| 6| 7| 7| 7| 7| 6| 7| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7|             
                             DAY ON TEST   | 0| 3| 3| 7| 0| 3| 3| 8| 8| 3| 3| 3| 3| 2| 3| 9| 3| 3| 3| 3| 3| 3| 3| 9| 2|             
                                           | 1| 6| 6| 0| 2| 4| 6| 7| 5| 4| 5| 5| 6| 2| 5| 5| 5| 5| 6| 5| 4| 6| 6| 4| 7|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   FISCHER 344 RATS 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|             
    220 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  I  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | A  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | A  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | A  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                    4           1         |             
      Basophilic Focus                     | X        X     X  X  X  X  X  X  X  X     X     X  X     X  X  X  X  X  X|             
      Clear Cell Focus                     |    X     X                 X                       X  X                  |             
      Degeneration, Cystic                 |                                                    2                     |             
      Degeneration, Fatty                  |                                                                          |             
      Eosinophilic Focus                   |                                                                          |             
      Fatty Change                         |             2        2                                               3   |             
      Hepatodiaphragmatic Nodule           |          X        X                                         X            |             
      Mixed Cell Focus                     |       X                       X                 X                        |             
      Regeneration                         |                                                                          |             
      Bile Duct, Cyst                      |                                                                          |             
      Bile Duct, Hyperplasia               | 1  1        2                 1        2     2              1            |             
      Centrilobular, Necrosis              |             2        1                       2                       1   |             
                                            __________________________________________________________________________|             
   Mesentery                               |             +           +                 +                              |             
      Fat, Necrosis                        |             2           2                 2                              |             
                                            __________________________________________________________________________|             
   Oral Mucosa                             |                                                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              | 2     2                                1  1           1  2               |             
      Hyperplasia                          |                                                                         3|             
      Metaplasia, Hepatocyte               |       2                                                                  |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |       2                                                                  |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Diverticulum                         |                                                                          |             
      Necrosis                             |                                                                      2   |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |             2        2                                                   |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       | 1  1  1  1        2  2     2     1        1        2  2     1  2  1     2|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Ectopic Tissue                       |                                                                   1      |             
      Hyperplasia                          |       2  2     3              1  2  2        2  2           2  2         |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   9                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 6| 7| 7| 5| 6| 7| 7| 7| 7| 6| 7| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7|             
                             DAY ON TEST   | 0| 3| 3| 7| 0| 3| 3| 8| 8| 3| 3| 3| 3| 2| 3| 9| 3| 3| 3| 3| 3| 3| 3| 9| 2|             
                                           | 1| 6| 6| 0| 2| 4| 6| 7| 5| 4| 5| 5| 6| 2| 5| 5| 5| 5| 6| 5| 4| 6| 6| 4| 7|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   FISCHER 344 RATS 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|             
    220 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                          |    2  1        2                                   2     1           1   |             
      Inflammation, Granulomatous          |                                           2                              |             
      Vacuolization Cytoplasmic            |                      2                                2                  |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          | 2                 2                                                  3   |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           |       3                    3  2        3  1              3  2           3|             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      C-Cell, Hyperplasia                  |    1  1  2  1  4           4  2  1  1  2  2              4  1  1  2  2  1|             
      Follicular Cell, Hyperplasia         |                         1                                                |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  M  +  +  +  +|             
      Hyperplasia                          |                                                 2                        |             
      Inflammation, Chronic Active         |                                        3                                 |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                               1     2                                    |             
      Inflammation, Granulomatous          |                                           3                              |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Histiocytic             |                                                                          |             
      Hyperplasia, Reticulum Cell          |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node                              |             +                          +     +                           |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  +  +  M  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  M  M  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  M  +  M  M  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             |       2                                                     1            |             
      Hematopoietic Cell Proliferation     |                      3              3                                   3|             
      Hemorrhage                           |                                                                          |             
      Metaplasia, Osseous                  |                                        2                                 |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  M  +  +  M  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Galactocele                          |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  10                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 6| 7| 7| 5| 6| 7| 7| 7| 7| 6| 7| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7|             
                             DAY ON TEST   | 0| 3| 3| 7| 0| 3| 3| 8| 8| 3| 3| 3| 3| 2| 3| 9| 3| 3| 3| 3| 3| 3| 3| 9| 2|             
                                           | 1| 6| 6| 0| 2| 4| 6| 7| 5| 4| 5| 5| 6| 2| 5| 5| 5| 5| 6| 5| 4| 6| 6| 4| 7|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   FISCHER 344 RATS 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|             
    220 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|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                   2                                                      |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperostosis                         | 2                    3                       3                       3   |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Degeneration, Focal                  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |    2     1        1  1     1  1  1  1     1     2  1     1     1  1      |             
      Alveolar Epithelium, Hyperplasia     |                               1  1                                       |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Foreign Body                         |                               X                                          |             
      Inflammation, Suppurative            |             2     2           1     1                                    |             
      Thrombosis                           |                                              1                           |             
      Olfactory Epithelium, Atrophy        |                                                       1                  |             
      Olfactory Epithelium, Metaplasia     |             2                                                            |             
      Respiratory Epithelium, Hyperplasia  |                                                                          |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |                                     1                                    |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     | +                                   +                                    |             
      Cataract                             | 2                                   3                                    |             
      Degeneration                         |                                                                          |             
      Retina, Atrophy                      | 3                                   3                                    |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hydronephrosis                       |                                                                          |             
      Infarct                              |                                        3                                 |             
      Nephropathy                          | 1  1  1  1  1  2  2  1  2  2  2  1  1     2  2  2  3  2  2  1  1  2  2  2|             
      Papilla, Necrosis                    |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  11                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 6| 7| 6| 6| 7| 7| 7| 7| 6| 3| 6| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 4| 7|            |
                             DAY ON TEST   | 2| 9| 3| 7| 6| 3| 3| 3| 3| 8| 7| 3| 2| 3| 4| 3| 3| 3| 3| 3| 1| 3| 3| 8| 3|            |
                                           | 6| 3| 5| 0| 4| 4| 6| 6| 6| 6| 0| 8| 7| 5| 3| 6| 6| 5| 5| 4| 4| 6| 4| 2| 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     |
   FISCHER 344 RATS 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     |
    220 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        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |                                                                          |      2  2.5|
      Basophilic Focus                     | X     X  X     X  X  X  X        X     X  X  X  X  X  X  X  X  X  X     X|     38     |
      Clear Cell Focus                     |                      X              X           X     X        X        X|     11     |
      Degeneration, Cystic                 |                                                                          |      1  2.0|
      Degeneration, Fatty                  |                            3                                             |      1  3.0|
      Eosinophilic Focus                   |       X     X                                                     X      |      3     |
      Fatty Change                         |                            3           2                    2            |      6  2.3|
      Hepatodiaphragmatic Nodule           |                                        X                                 |      4     |
      Mixed Cell Focus                     | X     X  X  X                    X        X     X                        |     10     |
      Regeneration                         |                                                          2               |      1  2.0|
      Bile Duct, Cyst                      |          2                                                               |      1  2.0|
      Bile Duct, Hyperplasia               |                                                 1  2                     |      9  1.4|
      Centrilobular, Necrosis              |                               1                                          |      5  1.4|
                                            __________________________________________________________________________|____________|
   Mesentery                               | +                    +              +     +              +  +     +      |  10        |
      Fat, Necrosis                        | 2                    2              2     2              2  2     2      |     10  2.0|
                                            __________________________________________________________________________|____________|
   Oral Mucosa                             |    +                                                                     |   1        |
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                   2  2     1                 1     1  1        1         |     13  1.4|
      Hyperplasia                          |                                                             2            |      2  2.5|
      Metaplasia, Hepatocyte               |                                                       1                  |      2  1.5|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Diverticulum                         |    X                                                                     |      1     |
      Necrosis                             |                            4                                             |      2  3.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Necrosis                             |             2                                                            |      3  2.0|
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       | 2     2  1        1  1     2     2  1  2  1  1  2  1  1  1     1     1  2|     33  1.4|
 __________________________________________________________________________________________________________________________________ 

  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        

                                                             Page  12                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 6| 7| 6| 6| 7| 7| 7| 7| 6| 3| 6| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 4| 7|            |
                             DAY ON TEST   | 2| 9| 3| 7| 6| 3| 3| 3| 3| 8| 7| 3| 2| 3| 4| 3| 3| 3| 3| 3| 1| 3| 3| 8| 3|            |
                                           | 6| 3| 5| 0| 4| 4| 6| 6| 6| 6| 0| 8| 7| 5| 3| 6| 6| 5| 5| 4| 4| 6| 4| 2| 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     |
   FISCHER 344 RATS 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     |
    220 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        |
      Ectopic Tissue                       |                                                                          |      1  1.0|
      Hyperplasia                          |       2                 2           2  2           2           2  2      |     17  2.0|
      Hypertrophy                          |          2           2  2  3     1           2              1           3|     14  1.8|
      Inflammation, Granulomatous          |                                                                          |      1  2.0|
      Vacuolization Cytoplasmic            |                2     2  2                       2                        |      6  2.0|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                         2           1                    1               |      6  1.8|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | M  +  +  +  +  +  +  +  M  +  +  +  M  +  +  M  +  +  +  +  +  +  M  +  M|  43        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Pars Distalis, Hyperplasia           |    3                 3              2  3     1  2        3     4         |     16  2.6|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      C-Cell, Hyperplasia                  |          1  1  4        1  2     1  2     1        2  1  2  1  1  1  1   |     32  1.7|
      Follicular Cell, Hyperplasia         |                                                                          |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Hyperplasia                          |                                     3  2              3                  |      4  2.5|
      Inflammation, Chronic Active         |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                2                                                         |      3  1.7|
      Inflammation, Granulomatous          |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hyperplasia, Histiocytic             |       2                                                                  |      1  2.0|
      Hyperplasia, Reticulum Cell          |                1                                                         |      1  1.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |    +                          +                             +            |   6        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  M  +  +  +  +  +  +  M  +  M  +  +  +  +  +  +  M  +  M  +  +  M  +  M|  37        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  M  +|  44        |
 __________________________________________________________________________________________________________________________________ 

  * : 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: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 6| 7| 6| 6| 7| 7| 7| 7| 6| 3| 6| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 4| 7|            |
                             DAY ON TEST   | 2| 9| 3| 7| 6| 3| 3| 3| 3| 8| 7| 3| 2| 3| 4| 3| 3| 3| 3| 3| 1| 3| 3| 8| 3|            |
                                           | 6| 3| 5| 0| 4| 4| 6| 6| 6| 6| 0| 8| 7| 5| 3| 6| 6| 5| 5| 4| 4| 6| 4| 2| 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     |
   FISCHER 344 RATS 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     |
    220 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               |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrosis                             |                            2  1                    2        2            |      6  1.7|
      Hematopoietic Cell Proliferation     |                                        3                             3   |      5  3.0|
      Hemorrhage                           |                            2  2                                          |      2  2.0|
      Metaplasia, Osseous                  |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  +|  45        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Galactocele                          |                                                             3            |      1  3.0|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |                                     4                                    |      2  3.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperostosis                         |    2              1        1           3                                 |      8  2.3|
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Degeneration, Focal                  | 3                                                                        |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |    1  1  1     1  2              1  1  1  1     1     1  1  1  1        1|     29  1.1|
      Alveolar Epithelium, Hyperplasia     |                      3     2                             1               |      5  1.6|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Foreign Body                         |                                                                          |      1     |
      Inflammation, Suppurative            | 3                                2                    1                 1|      8  1.6|
      Thrombosis                           |    2                                                                     |      2  1.5|
      Olfactory Epithelium, Atrophy        |                                                                          |      1  1.0|
      Olfactory Epithelium, Metaplasia     | 3                                                                        |      2  2.5|
      Respiratory Epithelium, Hyperplasia  |                                                                         1|      1  1.0|
      Respiratory Epithelium, Metaplasia,  |                                                                          |            |
           Squamous                        |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     | +        +                                                               |   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  14                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 6| 7| 6| 6| 7| 7| 7| 7| 6| 3| 6| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 4| 7|            |
                             DAY ON TEST   | 2| 9| 3| 7| 6| 3| 3| 3| 3| 8| 7| 3| 2| 3| 4| 3| 3| 3| 3| 3| 1| 3| 3| 8| 3|            |
                                           | 6| 3| 5| 0| 4| 4| 6| 6| 6| 6| 0| 8| 7| 5| 3| 6| 6| 5| 5| 4| 4| 6| 4| 2| 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     |
   FISCHER 344 RATS 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     |
    220 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|            |
 __________________________________________________________________________________________________________________________________ 
 SPECIAL SENSES SYSTEM - cont              |                                                                          |            |
                                           |                                                                          |            |
      Cataract                             | 1                                                                        |      3  2.0|
      Degeneration                         |          3                                                               |      1  3.0|
      Retina, Atrophy                      |                                                                          |      2  3.0|
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Hydronephrosis                       |                                     3                                    |      1  3.0|
      Infarct                              |                                                                          |      1  3.0|
      Nephropathy                          |    2  2  2  2  2  2  2  1  2  1  2  3  1  2  1  2  1  1     2  2  3  1  2|     47  1.7|
      Papilla, Necrosis                    |                                     2                                    |      1  2.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  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  15                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 5| 7| 7| 7| 1| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 5| 5|             
                             DAY ON TEST   | 6| 0| 3| 3| 3| 1| 3| 3| 1| 1| 3| 1| 3| 2| 3| 3| 3| 3| 3| 3| 1| 3| 9| 8| 4|             
                                           | 6| 8| 5| 5| 5| 1| 5| 5| 7| 3| 5| 0| 4| 7| 6| 4| 4| 5| 6| 5| 0| 6| 9| 0| 7|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   FISCHER 344 RATS 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|             
    700 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  A  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  A  A  +|             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                        1  2                              |             
      Basophilic Focus                     | X     X  X  X     X  X        X  X  X  X  X  X  X     X  X  X  X         |             
      Clear Cell Focus                     |       X  X                          X     X     X                        |             
      Eosinophilic Focus                   |                   X                                                      |             
      Fatty Change                         |                            3                                            3|             
      Hepatodiaphragmatic Nodule           |                                     X     X              X               |             
      Mixed Cell Focus                     |             X     X                       X              X  X        X   |             
      Regeneration                         |                                                                          |             
      Bile Duct, Hyperplasia               | 2     1     2        1                                                   |             
      Centrilobular, Necrosis              | 1  1                    1                                                |             
      Periportal, Infiltration Cellular,   |                                                                          |             
           Lymphocyte                      |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |    +                       +                 +                           |             
      Fat, Necrosis                        |    2                       2                 3                           |             
                                            __________________________________________________________________________|             
   Oral Mucosa                             |                                                                          |             
      Pharyngeal, Hyperplasia, Squamous    |                                                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |       2              2        1           1                    2         |             
      Basophilic Focus                     |                                                       X                  |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Squamous                |                                                                          |             
      Necrosis                             |                            4                                            2|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |                                                 1                        |             
      Necrosis                             | 2                                                                        |             
                                            __________________________________________________________________________|             
   Tongue                                  |                            +                                             |             
      Hyperplasia                          |                            1                                             |             
                                            __________________________________________________________________________|             
   Tooth                                   |                +                                                         |             
      Developmental Malformation           |                X                                                         |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |       2  2  2     2  2                 1  1  2     1  1  1     2  2  2   |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  16                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 5| 7| 7| 7| 1| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 5| 5|             
                             DAY ON TEST   | 6| 0| 3| 3| 3| 1| 3| 3| 1| 1| 3| 1| 3| 2| 3| 3| 3| 3| 3| 3| 1| 3| 9| 8| 4|             
                                           | 6| 8| 5| 5| 5| 1| 5| 5| 7| 3| 5| 0| 4| 7| 6| 4| 4| 5| 6| 5| 0| 6| 9| 0| 7|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   FISCHER 344 RATS 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|             
    700 PPM                                | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Degeneration, Cystic                 | 3                                                                        |             
      Hyperplasia                          |                   2        1  4              1     1  2  1     2         |             
      Hypertrophy                          |             3                 3              1  1                       2|             
      Vacuolization Cytoplasmic            |       1                                   2                              |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                   2  2     2                                             |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  M  +  M  +  +|             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           | 2     3                 2  3                                             |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +|             
      C-Cell, Hyperplasia                  | 1  1  1  1  1     1  1     3  2     1  2     1  1  4  2     1  2         |             
      Follicular Cell, Hyperplasia         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          | +  +  M  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                              2                    2      |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Myelofibrosis                        |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node                              |    +                       +                                            +|             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  M  +  M  +  M  +  M  M  +  +  +  M  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             | 2  2  1     2        2                                                   |             
      Hemorrhage                           |                            2                                            2|             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  M  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Galactocele                          |                                                       4                  |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  17                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 5| 7| 7| 7| 1| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 5| 5|             
                             DAY ON TEST   | 6| 0| 3| 3| 3| 1| 3| 3| 1| 1| 3| 1| 3| 2| 3| 3| 3| 3| 3| 3| 1| 3| 9| 8| 4|             
                                           | 6| 8| 5| 5| 5| 1| 5| 5| 7| 3| 5| 0| 4| 7| 6| 4| 4| 5| 6| 5| 0| 6| 9| 0| 7|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   FISCHER 344 RATS 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|             
    700 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|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperostosis                         |    1     3                    4        2                       3  3      |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         | 4     1     1     1     1     1           1     1  1     1     1     1   |             
      Alveolar Epithelium, Hyperplasia     |       1                             1           1              4         |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Foreign Body                         |                                        X                                 |             
      Inflammation, Suppurative            | 3                       1        1     1                                 |             
      Thrombosis                           |                                                                          |             
      Olfactory Epithelium, Atrophy        |                                                                          |             
      Olfactory Epithelium, Hyperplasia    | 3                                                                        |             
      Olfactory Epithelium, Metaplasia     |                                                                          |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |                                                                          |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                        +           +                     |             
      Cataract                             |                                        2           4                     |             
      Retina, Atrophy                      |                                        4           4                     |             
                                            __________________________________________________________________________|             
   Zymbal's Gland                          |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infarct                              |                                                                          |             
      Nephropathy                          | 1  2  1  2  2     2  2  1  2  3  2  2  1  1  2  2  2  2  1  2  2  2  2   |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Transitional Epithelium, Hyperplasia |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  18                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 5| 7| 4| 7| 7| 7| 7| 7| 7| 5| 7| 6| 6| 7| 7| 7| 7| 6| 7| 7| 6| 7| 7|            |
                             DAY ON TEST   | 3| 3| 8| 3| 2| 2| 3| 3| 3| 3| 3| 3| 2| 1| 3| 3| 3| 1| 3| 0| 3| 0| 7| 3| 3|            |
                                           | 5| 6| 1| 6| 7| 1| 4| 6| 5| 5| 4| 9| 3| 1| 8| 5| 6| 0| 6| 4| 5| 8| 2| 6| 5|      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     |
   FISCHER 344 RATS 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     |
    700 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        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|  46        |
      Inflammation, Chronic Active         |                         3                                                |      1  3.0|
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |                                                          2               |      3  1.7|
      Basophilic Focus                     |    X     X     X  X  X  X     X  X  X     X  X  X           X  X     X  X|     33     |
      Clear Cell Focus                     |                         X  X  X                 X     X                  |     10     |
      Eosinophilic Focus                   |                                                                          |      1     |
      Fatty Change                         |       3        2                    2  3  3        2  1        1  1      |     11  2.2|
      Hepatodiaphragmatic Nodule           |                      X                                               X   |      5     |
      Mixed Cell Focus                     |    X                             X              X        X               |     10     |
      Regeneration                         | 2  2                                                                     |      2  2.0|
      Bile Duct, Hyperplasia               |             2  2                    2     2                    2         |      9  1.8|
      Centrilobular, Necrosis              |                3                    1              1           1     1   |      8  1.3|
      Periportal, Infiltration Cellular,   |                                                                          |            |
           Lymphocyte                      |                      3                                                   |      1  3.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               |             +  +                             +                 +  +      |   8        |
      Fat, Necrosis                        |             2  2                             2                 2  2      |      8  2.1|
                                            __________________________________________________________________________|____________|
   Oral Mucosa                             |                                                                         +|   1        |
      Pharyngeal, Hyperplasia, Squamous    |                                                                         4|      1  4.0|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |    2        2              2        2                 3              1   |     11  1.8|
      Basophilic Focus                     |                               X                       X                  |      3     |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia, Squamous                |    2                                                                     |      1  2.0|
      Necrosis                             |       3                             3  3  3                    1         |      7  2.7|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Mineralization                       |                                                                          |      1  1.0|
      Necrosis                             |                3                                   2           1         |      4  2.0|
                                            __________________________________________________________________________|____________|
   Tongue                                  |                               +                                          |   2        |
      Hyperplasia                          |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Tooth                                   |                                                                          |   1        |
      Developmental Malformation           |                                                                          |      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  19                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 5| 7| 4| 7| 7| 7| 7| 7| 7| 5| 7| 6| 6| 7| 7| 7| 7| 6| 7| 7| 6| 7| 7|            |
                             DAY ON TEST   | 3| 3| 8| 3| 2| 2| 3| 3| 3| 3| 3| 3| 2| 1| 3| 3| 3| 1| 3| 0| 3| 0| 7| 3| 3|            |
                                           | 5| 6| 1| 6| 7| 1| 4| 6| 5| 5| 4| 9| 3| 1| 8| 5| 6| 0| 6| 4| 5| 8| 2| 6| 5|      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     |
   FISCHER 344 RATS 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     |
    700 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 - cont                  |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       | 1        2        2  2  2        2     1        2     1  2  1     3  1  1|     28  1.6|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Degeneration, Cystic                 |                                                                          |      1  3.0|
      Hyperplasia                          | 2  2     2        2  3  2     2     2           2              2  1     2|     20  1.9|
      Hypertrophy                          |                                           2  2        2                  |      8  2.0|
      Vacuolization Cytoplasmic            |          2                                                           2   |      4  1.8|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |             2                       2     2  2  2     1                  |      9  1.9|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |    3                                                                     |      1  3.0|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  M|  43        |
      Hyperplasia                          |                               2                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Pars Distalis, Hyperplasia           |                            2  3  3                                       |      7  2.6|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      C-Cell, Hyperplasia                  | 1     1     2  2  2  2  2  1  2  1  1  2  1  1  1  2  2        1  1  1  1|     38  1.5|
      Follicular Cell, Hyperplasia         |          1                                                               |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  M  +  +  +  +  +  +  +  +|  46        |
      Hyperplasia                          |                   2        2                                             |      2  2.0|
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |          2        2           3                                          |      5  2.2|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Myelofibrosis                        |          2                                                               |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                           +                              |   4        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | M  +  +  +  +  +  +  M  M  M  M  M  +  +  +  M  +  M  +  M  M  +  +  +  +|  34        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  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  20                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 5| 7| 4| 7| 7| 7| 7| 7| 7| 5| 7| 6| 6| 7| 7| 7| 7| 6| 7| 7| 6| 7| 7|            |
                             DAY ON TEST   | 3| 3| 8| 3| 2| 2| 3| 3| 3| 3| 3| 3| 2| 1| 3| 3| 3| 1| 3| 0| 3| 0| 7| 3| 3|            |
                                           | 5| 6| 1| 6| 7| 1| 4| 6| 5| 5| 4| 9| 3| 1| 8| 5| 6| 0| 6| 4| 5| 8| 2| 6| 5|      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     |
   FISCHER 344 RATS 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     |
    700 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               |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  M  +  +  +  +  +  +  M  +  +  M  +  M  M  +  +  +  M  +  +  +  +|  42        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrosis                             |                1     3                    1        2           2         |     10  1.8|
      Hemorrhage                           |       3                             2                                    |      4  2.3|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  M  +  +  +  M  +  M  M  M  M  +  +  +  +  +  +  +  +  +  +  +  +  M|  39        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Galactocele                          |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperostosis                         |                            2  3              2              2  4         |     11  2.6|
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |       1     1     1     1  1  1  1     1     1     1  1     1     1      |     25  1.1|
      Alveolar Epithelium, Hyperplasia     |                   1           2                 1     1           1  2   |     10  1.5|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Foreign Body                         |                                                                          |      1     |
      Inflammation, Suppurative            |                               1        1  2  1                           |      8  1.4|
      Thrombosis                           |                2                    3              3                     |      3  2.7|
      Olfactory Epithelium, Atrophy        |                                     1                             2      |      2  1.5|
      Olfactory Epithelium, Hyperplasia    |                                                                          |      1  3.0|
      Olfactory Epithelium, Metaplasia     |                                           2                              |      1  2.0|
      Respiratory Epithelium, Metaplasia,  |                                                                          |            |
           Squamous                        |                               1                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                                                      +   |   3        |
      Cataract                             |                                                                      3   |      3  3.0|
      Retina, Atrophy                      |                                                                      4   |      3  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  21                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 5| 7| 4| 7| 7| 7| 7| 7| 7| 5| 7| 6| 6| 7| 7| 7| 7| 6| 7| 7| 6| 7| 7|            |
                             DAY ON TEST   | 3| 3| 8| 3| 2| 2| 3| 3| 3| 3| 3| 3| 2| 1| 3| 3| 3| 1| 3| 0| 3| 0| 7| 3| 3|            |
                                           | 5| 6| 1| 6| 7| 1| 4| 6| 5| 5| 4| 9| 3| 1| 8| 5| 6| 0| 6| 4| 5| 8| 2| 6| 5|      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     |
   FISCHER 344 RATS 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     |
    700 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|            |
 __________________________________________________________________________________________________________________________________ 
 SPECIAL SENSES SYSTEM - cont              |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Zymbal's Gland                          |                   +                                                      |   1        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Infarct                              |                   2                                                      |      1  2.0|
      Nephropathy                          | 3  2  1  2  1  2  2  2  2  2  3  1  1  3  1  2  1  2  4  2  2  2  3  2  2|     48  1.9|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Transitional Epithelium, Hyperplasia |                            3                                             |      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  22                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 7| 7| 4| 7| 4| 7| 6| 6| 6| 7| 7| 7| 7| 4| 7| 7| 4| 7| 7| 7| 7| 5| 7|             
                             DAY ON TEST   | 1| 6| 3| 3| 3| 3| 1| 3| 2| 6| 2| 3| 3| 3| 3| 9| 3| 3| 8| 3| 3| 3| 3| 9| 3|             
                                           | 4| 4| 6| 5| 2| 6| 5| 4| 1| 4| 5| 5| 5| 5| 5| 7| 5| 6| 2| 4| 5| 4| 5| 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|             
   FISCHER 344 RATS 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|             
    7000 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                               1                                          |             
      Basophilic Focus                     |       X  X     X     X  X  X  X  X  X  X  X     X  X  X  X  X  X  X  X  X|             
      Clear Cell Focus                     |          X                          X           X        X  X  X         |             
      Degeneration, Cystic                 |    1                                                                     |             
      Eosinophilic Focus                   |                      X        X                             X            |             
      Fatty Change                         |                   2                                                      |             
      Fibrosis                             |                                                                          |             
      Hepatodiaphragmatic Nodule           |                                                       X           X      |             
      Inflammation, Granulomatous          |                                        2                                 |             
      Mixed Cell Focus                     |    X  X     X                                                            |             
      Necrosis                             |                                                          1               |             
      Regeneration                         |                                                                   2  4   |             
      Bile Duct, Hyperplasia               |                            1  2  1                                   2   |             
      Centrilobular, Necrosis              |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |       +                 +     +           +           +              +   |             
      Fat, Necrosis                        |       2                 2     2           3           2              2   |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                            2  2  2     1  1  2                       2   |             
      Basophilic Focus                     |          X           X                                                   |             
      Metaplasia, Hepatocyte               |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                              3                           |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             | 2                                                                        |             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
      Developmental Malformation           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       |       1  1  1  2     1     1  1  1     1  1  1  2  2  2  1  1  2  1     2|             
      Mineralization                       |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  23                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 7| 7| 4| 7| 4| 7| 6| 6| 6| 7| 7| 7| 7| 4| 7| 7| 4| 7| 7| 7| 7| 5| 7|             
                             DAY ON TEST   | 1| 6| 3| 3| 3| 3| 1| 3| 2| 6| 2| 3| 3| 3| 3| 9| 3| 3| 8| 3| 3| 3| 3| 9| 3|             
                                           | 4| 4| 6| 5| 2| 6| 5| 4| 1| 4| 5| 5| 5| 5| 5| 7| 5| 6| 2| 4| 5| 4| 5| 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|             
   FISCHER 344 RATS 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|             
    7000 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                   |                                                                          |             
                                           |                                                                          |             
      Degeneration, Cystic                 |                                                                          |             
      Hyperplasia                          |       2                       2     2           1        1     2         |             
      Hypertrophy                          |          2     1              2     2              3              2     2|             
      Necrosis                             |                                                                          |             
      Thrombosis                           |                                                                1         |             
      Vacuolization Cytoplasmic            | 2                    2                 1  2                 1            |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                 1        1        2  2   |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  M  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           |    3  2           3                             2  3                     |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      C-Cell, Hyperplasia                  | 2  1  1  1     2     1        1  1  1  1  1     1        2  2  1  1  1  2|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                     2                                    |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                     2              2  2                  |             
      Inflammation, Granulomatous          |       2                                                                  |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                  2                                       |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                   +                                                      |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  +  +  M  +  M  +  +  +  +  M  +  +  +  M  M  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | M  +  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  +  M  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  M  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             |                                                                   2  2   |             
      Hematopoietic Cell Proliferation     | 3                                                                        |             
      Necrosis                             |                                                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                         2|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  24                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 6| 7| 7| 4| 7| 4| 7| 6| 6| 6| 7| 7| 7| 7| 4| 7| 7| 4| 7| 7| 7| 7| 5| 7|             
                             DAY ON TEST   | 1| 6| 3| 3| 3| 3| 1| 3| 2| 6| 2| 3| 3| 3| 3| 9| 3| 3| 8| 3| 3| 3| 3| 9| 3|             
                                           | 4| 4| 6| 5| 2| 6| 5| 4| 1| 4| 5| 5| 5| 5| 5| 7| 5| 6| 2| 4| 5| 4| 5| 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|             
   FISCHER 344 RATS 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|             
    7000 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|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                   2     4                                                |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperostosis                         |          4              2                                            4   |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Degeneration, Focal                  |                                                                          |             
      Gliosis                              |                                        2                                 |             
                                            __________________________________________________________________________|             
   Spinal Cord                             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |          1  1        2  1        1     2           1     1        1  4  3|             
      Alveolar Epithelium, Hyperplasia     | 1              1           1                             1        2      |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Foreign Body                         |                                  X  X                          X         |             
      Inflammation, Suppurative            |    1                 1           2  1                          2     2   |             
      Thrombosis                           |                                                                          |             
      Olfactory Epithelium, Atrophy        | 2                                                                        |             
      Olfactory Epithelium, Metaplasia     |                                                                2         |             
      Respiratory Epithelium, Hyperplasia  |                                                                      1   |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |                                                 1                        |             
                                            __________________________________________________________________________|             
   Pleura                                  |    +                                                                     |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |          +                          +                                    |             
      Cataract                             |          4                          2                                    |             
      Degeneration                         |                                                                          |             
      Hemorrhage                           |                                                                          |             
      Retina, Atrophy                      |          4                          3                                    |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                                                          |             
      Nephropathy                          | 2  2  2  3  1  2  1  2  1  1     2  2  3  2  1  2  2     2  3  3  2  1  2|             
      Renal Tubule, Necrosis               |                                                                          |             
      Transitional Epithelium, Hyperplasia |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  25                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 5| 6| 6| 1| 7| 7| 7| 7| 6| 4| 7| 7| 4|            |
                             DAY ON TEST   | 5| 3| 3| 8| 3| 3| 1| 3| 2| 3| 3| 0| 9| 3| 5| 1| 1| 3| 3| 3| 8| 6| 3| 3| 9|            |
                                           | 2| 6| 6| 1| 6| 5| 3| 5| 7| 4| 4| 9| 4| 0| 3| 4| 3| 5| 6| 5| 1| 4| 4| 5| 0|      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     |
   FISCHER 344 RATS 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     |
    7000 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        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |             2           2     2                                          |      4  1.8|
      Basophilic Focus                     |    X     X     X     X  X        X        X     X  X  X  X  X        X   |     33     |
      Clear Cell Focus                     |    X                 X        X                       X  X               |     11     |
      Degeneration, Cystic                 |                                                                          |      1  1.0|
      Eosinophilic Focus                   |                               X                                          |      4     |
      Fatty Change                         | 2        2        2                 3     1     2           2           2|      9  2.0|
      Fibrosis                             |                                                 1                        |      1  1.0|
      Hepatodiaphragmatic Nodule           |                      X                             X     X              X|      6     |
      Inflammation, Granulomatous          |                                                                          |      1  2.0|
      Mixed Cell Focus                     |          X           X                                                   |      5     |
      Necrosis                             |                                                                          |      1  1.0|
      Regeneration                         |                                                                         2|      3  2.7|
      Bile Duct, Hyperplasia               | 2                 2              1     2                             1  2|     10  1.6|
      Centrilobular, Necrosis              | 1                                1     1                                 |      3  1.0|
                                            __________________________________________________________________________|____________|
   Mesentery                               | +                 +           +                          +  +            |  11        |
      Fat, Necrosis                        | 2                 3           2                          2  2            |     11  2.2|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              | 1           2  1  2     1           2  3  1     2  1  2              2  1|     20  1.7|
      Basophilic Focus                     |       X                                                                  |      3     |
      Metaplasia, Hepatocyte               |                   2                                                      |      1  2.0|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Necrosis                             |          4                                      2                        |      3  3.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Necrosis                             |                   2                       4     2              3        3|      6  2.7|
                                            __________________________________________________________________________|____________|
   Tooth                                   |                                              +                           |   1        |
      Developmental Malformation           |                                              X                           |      1     |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       | 2  2  1  3  2  2  2  2  1  1  2     2     2     1     2  1  1     1      |     37  1.5|
 __________________________________________________________________________________________________________________________________ 

  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        

                                                             Page  26                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 5| 6| 6| 1| 7| 7| 7| 7| 6| 4| 7| 7| 4|            |
                             DAY ON TEST   | 5| 3| 3| 8| 3| 3| 1| 3| 2| 3| 3| 0| 9| 3| 5| 1| 1| 3| 3| 3| 8| 6| 3| 3| 9|            |
                                           | 2| 6| 6| 1| 6| 5| 3| 5| 7| 4| 4| 9| 4| 0| 3| 4| 3| 5| 6| 5| 1| 4| 4| 5| 0|      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     |
   FISCHER 344 RATS 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     |
    7000 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              |                                                                          |            |
                                           |                                                                          |            |
      Mineralization                       |                                           2                              |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                                                 2                        |      1  2.0|
      Degeneration, Cystic                 |                2     2                                                  2|      3  2.0|
      Hyperplasia                          |                2     2        2           2           2  2           2   |     13  1.8|
      Hypertrophy                          | 2  2  2                 2                       2     2     3            |     14  2.1|
      Necrosis                             |                                                                         3|      1  3.0|
      Thrombosis                           |                                                                          |      1  1.0|
      Vacuolization Cytoplasmic            |                   2                                                      |      6  1.7|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |          2     1              2           2                       1      |      9  1.6|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                            4     2                                       |      2  3.0|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  M  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Pars Distalis, Hyperplasia           |             3                 2  3     2           2     3              1|     12  2.4|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      C-Cell, Hyperplasia                  | 1  1  2  1  1  1  4  2  1     1  2  3  1  2     1  1  1  2  1     2  3  1|     40  1.5|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Hyperplasia                          |                      2                                2                  |      3  2.0|
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                         2                                      1        3|      6  2.0|
      Inflammation, Granulomatous          |                                                    3                     |      2  2.5|
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              | +                                                                        |   2        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  M  +  M  +  +  +  +  M  +  +  +  +  +  +  M  +  M  +  M  M  M  M  +  +|  35        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  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  27                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 5| 6| 6| 1| 7| 7| 7| 7| 6| 4| 7| 7| 4|            |
                             DAY ON TEST   | 5| 3| 3| 8| 3| 3| 1| 3| 2| 3| 3| 0| 9| 3| 5| 1| 1| 3| 3| 3| 8| 6| 3| 3| 9|            |
                                           | 2| 6| 6| 1| 6| 5| 3| 5| 7| 4| 4| 9| 4| 0| 3| 4| 3| 5| 6| 5| 1| 4| 4| 5| 0|      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     |
   FISCHER 344 RATS 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     |
    7000 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               |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  M  +  M  +  +  +  +  +|  44        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrosis                             | 2                 2                                                      |      4  2.0|
      Hematopoietic Cell Proliferation     |                                                                          |      1  3.0|
      Necrosis                             |                                                                         2|      1  2.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  M  +  +  +|  46        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |       2                                                                  |      2  2.0|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |                                                                          |      2  3.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperostosis                         | 2                    2        3        2                                2|      8  2.6|
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Degeneration, Focal                  |                                                                         2|      1  2.0|
      Gliosis                              |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Spinal Cord                             |                                                                         +|   1        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |    1     1           1     1           4  1  1                 1         |     19  1.5|
      Alveolar Epithelium, Hyperplasia     |                               1     2                 1                  |      8  1.3|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Foreign Body                         |                                           X                              |      4     |
      Inflammation, Suppurative            |          2              1     2           2  2                    2      |     12  1.7|
      Thrombosis                           |                   3                                                      |      1  3.0|
      Olfactory Epithelium, Atrophy        |                                           2                              |      2  2.0|
      Olfactory Epithelium, Metaplasia     |                                                                          |      1  2.0|
      Respiratory Epithelium, Hyperplasia  |                                                                          |      1  1.0|
      Respiratory Epithelium, Metaplasia,  |                                                                          |            |
           Squamous                        |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Pleura                                  |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  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  28                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 5| 6| 6| 1| 7| 7| 7| 7| 6| 4| 7| 7| 4|            |
                             DAY ON TEST   | 5| 3| 3| 8| 3| 3| 1| 3| 2| 3| 3| 0| 9| 3| 5| 1| 1| 3| 3| 3| 8| 6| 3| 3| 9|            |
                                           | 2| 6| 6| 1| 6| 5| 3| 5| 7| 4| 4| 9| 4| 0| 3| 4| 3| 5| 6| 5| 1| 4| 4| 5| 0|      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     |
   FISCHER 344 RATS 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     |
    7000 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|            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                   +        +     +                                   +   |   6        |
      Cataract                             |                                  2                                   2   |      4  2.5|
      Degeneration                         |                            3                                             |      1  3.0|
      Hemorrhage                           |                   3                                                      |      1  3.0|
      Retina, Atrophy                      |                                  3                                   3   |      4  3.3|
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                   2                                                      |      1  2.0|
      Nephropathy                          | 2  2  2  3  2  2  2  2  3  2  3  2  1  2  4     3  2  2  2  1  1  2  2  2|     47  2.0|
      Renal Tubule, Necrosis               |                                                                2         |      1  2.0|
      Transitional Epithelium, Hyperplasia |                                                             2            |      1  2.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  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  29                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 3| 4| 7| 7| 7| 6| 5| 6| 7| 7| 2| 7| 7| 6| 7| 4| 4| 5| 6| 4| 7| 5| 7| 5|             
                             DAY ON TEST   | 5| 4| 5| 3| 3| 3| 7| 1| 5| 3| 2| 3| 3| 0| 0| 2| 6| 8| 9| 8| 4| 3| 4| 3| 3|             
                                           | 2| 2| 4| 3| 3| 4| 2| 8| 2| 3| 3| 5| 3| 4| 0| 8| 8| 2| 2| 6| 0| 3| 7| 3| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   FISCHER 344 RATS 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                                                          |             
      Necrosis                             |                                                 2                        |             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                               2                                          |             
      Basophilic Focus                     |       X     X              X           X  X              X  X  X     X  X|             
      Clear Cell Focus                     |                X           X                                             |             
      Degeneration, Cystic                 |          2     2                          1  4                           |             
      Eosinophilic Focus                   |             X                                                            |             
      Fatty Change                         | 2                 2  2  3     1           1              1  2     1     3|             
      Hematopoietic Cell Proliferation     |                                                                      2   |             
      Hepatodiaphragmatic Nodule           |                                                                          |             
      Mineralization                       |                                                                          |             
      Regeneration                         |                                                                          |             
      Bile Duct, Hyperplasia               |          2  2     2     2  1              1  3  2  2  2           1  1   |             
      Centrilobular, Necrosis              |                                              3        2                  |             
                                            __________________________________________________________________________|             
   Mesentery                               |       +           +  +                                                   |             
      Fat, Hemorrhage                      |                                                                          |             
      Fat, Necrosis                        |       2           2  2                                                   |             
                                            __________________________________________________________________________|             
   Oral Mucosa                             |          +                                                               |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |          2  2  3  2     3           2        2     1           3         |             
      Basophilic Focus                     |                                                                          |             
      Hyperplasia                          |          3                             2                                 |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                           1                              |             
      Necrosis                             |                2        3     3                       3  2  3     3      |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |                                                                      1  3|             
      Necrosis                             |                                              1                          3|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Blood Vessel                            |                                                                          |             
      Inflammation                         |                                                                          |             
      Endothelium, Hyperplasia             |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  30                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 3| 4| 7| 7| 7| 6| 5| 6| 7| 7| 2| 7| 7| 6| 7| 4| 4| 5| 6| 4| 7| 5| 7| 5|             
                             DAY ON TEST   | 5| 4| 5| 3| 3| 3| 7| 1| 5| 3| 2| 3| 3| 0| 0| 2| 6| 8| 9| 8| 4| 3| 4| 3| 3|             
                                           | 2| 2| 4| 3| 3| 4| 2| 8| 2| 3| 3| 5| 3| 4| 0| 8| 8| 2| 2| 6| 0| 3| 7| 3| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   FISCHER 344 RATS 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|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       | 2  1  1  3  2  2  1  1     2  2  1     3  2  3     1  1  2  2  1     2  2|             
      Artery, Mineralization               |                                                                          |             
      Atrium, Thrombosis                   |                                              4        2                  |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                          |             
      Hyperplasia                          | 2        1     2           2  2     2  1                 2  1     2     2|             
      Hypertrophy                          |          2              2     2                                2         |             
      Vacuolization Cytoplasmic            |                                                                      2   |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |          4  2  2  1                    2     2  1              3     2   |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                               2                                         2|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           |       3                    3                    2                        |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      C-Cell, Hyperplasia                  |             1  1  1     2  1  2           1  3  1        1  1     1      |             
      Follicular Cell, Hyperplasia         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Peritoneum                              |                                     +                                    |             
                                            __________________________________________________________________________|             
   Tissue NOS                              |                                  +                                       |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Granuloma Sperm                      |                                                                          |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         | 2                                                                 4      |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |          2                          2  2                                 |             
      Inflammation, Chronic Active         |                               4  4                                       |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                  2                                       |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                          3               |             
      Artery, Inflammation, Chronic Active |                                        3                 3     2         |             
      Interstitial Cell, Hyperplasia       |       2           4     2     2                 4                 1  2   |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                              +  +                    +   |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  31                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 3| 4| 7| 7| 7| 6| 5| 6| 7| 7| 2| 7| 7| 6| 7| 4| 4| 5| 6| 4| 7| 5| 7| 5|             
                             DAY ON TEST   | 5| 4| 5| 3| 3| 3| 7| 1| 5| 3| 2| 3| 3| 0| 0| 2| 6| 8| 9| 8| 4| 3| 4| 3| 3|             
                                           | 2| 2| 4| 3| 3| 4| 2| 8| 2| 3| 3| 5| 3| 4| 0| 8| 8| 2| 2| 6| 0| 3| 7| 3| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   FISCHER 344 RATS 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|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Iliac, Ectasia                       |                                                                      3   |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  M  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             |          2              1              2  1                              |             
      Hematopoietic Cell Proliferation     |       2                                                              2   |             
      Hemorrhage                           |                                                                          |             
      Necrosis                             |                         2                                                |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  M  +  +  M  +  M  +  +  +  +  +  +  M  +  +  +  M  +  +  +  +  +  +  +|             
      Galactocele                          |                                                                      3   |             
      Inflammation, Chronic                |                                                                          |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst Epithelial Inclusion            |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrous Osteodystrophy               |                                                                         1|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Degeneration, Focal                  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +  +  +  +|             
      Inflammation, Chronic Active         | 1        1  2  1           2        2        2     4           3     1   |             
      Alveolar Epithelium, Hyperplasia     |             1                       1                             1  1   |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Foreign Body                         |                                                                          |             
      Inflammation, Suppurative            |                   1                                1                     |             
      Thrombosis                           |                                                       1                  |             
      Olfactory Epithelium, Atrophy        |                                                                          |             
      Olfactory Epithelium, Metaplasia     |                                                    1                     |             
      Olfactory Epithelium, Metaplasia,    |                                                                          |             
           Squamous                        |                                                                          |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  32                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 3| 4| 7| 7| 7| 6| 5| 6| 7| 7| 2| 7| 7| 6| 7| 4| 4| 5| 6| 4| 7| 5| 7| 5|             
                             DAY ON TEST   | 5| 4| 5| 3| 3| 3| 7| 1| 5| 3| 2| 3| 3| 0| 0| 2| 6| 8| 9| 8| 4| 3| 4| 3| 3|             
                                           | 2| 2| 4| 3| 3| 4| 2| 8| 2| 3| 3| 5| 3| 4| 0| 8| 8| 2| 2| 6| 0| 3| 7| 3| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   FISCHER 344 RATS 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|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM - cont              |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                                          |             
      Cataract                             |                                                                          |             
      Retina, Atrophy                      |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |                                                                          |             
      Infarct                              |                                                                          |             
      Nephropathy                          | 3  1  1  3  3  3  3  3  3  2  4  1  2  4  2  3  2  2  2  4  2  3  3  3  4|             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
      Transitional Epithelium, Hyperplasia |                                  1                                       |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  33                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 5| 6| 7| 6| 5| 7| 7| 7| 7| 7| 5| 6| 7| 7| 5| 7| 7| 7| 6| 7| 5| 6| 7| 7| 6|            |
                             DAY ON TEST   | 5| 7| 3| 5| 9| 3| 3| 3| 3| 2| 5| 9| 3| 3| 6| 2| 3| 3| 0| 2| 0| 7| 3| 3| 6|            |
                                           | 5| 5| 3| 9| 7| 4| 3| 3| 4| 1| 1| 4| 4| 4| 4| 3| 4| 3| 4| 4| 2| 1| 3| 3| 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     |
   FISCHER 344 RATS 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        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  A  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Inflammation, Acute                  |       2                                                                  |      1  2.0|
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Inflammation, Acute                  |       2                                                                  |      1  2.0|
      Necrosis                             |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  A  +  A  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  A  +  A  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |                      2                                                   |      2  2.0|
      Basophilic Focus                     |       X        X     X  X           X  X        X                        |     17     |
      Clear Cell Focus                     |                      X  X              X           X                     |      6     |
      Degeneration, Cystic                 |    2  1                    2     2                    1                  |      9  1.9|
      Eosinophilic Focus                   |                                                                   X      |      2     |
      Fatty Change                         |                               2                          1  1        2  3|     15  1.8|
      Hematopoietic Cell Proliferation     |                                                                          |      1  2.0|
      Hepatodiaphragmatic Nodule           |                                                       X                  |      1     |
      Mineralization                       |       2                                                                  |      1  2.0|
      Regeneration                         |                   2                                                  2   |      2  2.0|
      Bile Duct, Hyperplasia               | 1  1  2  3     2           3  1  2        3  1        1        1  2      |     25  1.8|
      Centrilobular, Necrosis              |             2     1        2                          4           1      |      7  2.1|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                 +     +  +           +  +|   8        |
      Fat, Hemorrhage                      |                                                                         2|      1  2.0|
      Fat, Necrosis                        |                                                 2        2           2   |      6  2.0|
                                            __________________________________________________________________________|____________|
   Oral Mucosa                             |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              | 2     1  2     3           2     2              2     3     1            |     18  2.1|
      Basophilic Focus                     |                         X                                                |      1     |
      Hyperplasia                          |                                        2           3                     |      4  2.5|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                                                                2         |      1  2.0|
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Acute                  |                                                                          |      1  1.0|
      Necrosis                             |       3  1                 2  4           1           4                 3|     14  2.6|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Mineralization                       |       1                                1                                1|      5  1.4|
      Necrosis                             | 1        2                 2                                            3|      6  2.0|
 __________________________________________________________________________________________________________________________________ 

  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        

                                                             Page  34                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 5| 6| 7| 6| 5| 7| 7| 7| 7| 7| 5| 6| 7| 7| 5| 7| 7| 7| 6| 7| 5| 6| 7| 7| 6|            |
                             DAY ON TEST   | 5| 7| 3| 5| 9| 3| 3| 3| 3| 2| 5| 9| 3| 3| 6| 2| 3| 3| 0| 2| 0| 7| 3| 3| 6|            |
                                           | 5| 5| 3| 9| 7| 4| 3| 3| 4| 1| 1| 4| 4| 4| 4| 3| 4| 3| 4| 4| 2| 1| 3| 3| 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     |
   FISCHER 344 RATS 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 - cont                  |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Blood Vessel                            |                                                       +                  |   1        |
      Inflammation                         |                                                       3                  |      1  3.0|
      Endothelium, Hyperplasia             |                                                       4                  |      1  4.0|
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       | 1  3  3     1  2  3  2  2     1  2  2  3     2  2  2     2     1  2  2  3|     41  1.9|
      Artery, Mineralization               |       1                                                                  |      1  1.0|
      Atrium, Thrombosis                   |                            4                          4                  |      4  3.5|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |       4                                                                  |      1  4.0|
      Hyperplasia                          | 2                 2  2  2     2     3  3     2  2        2        2  2   |     23  2.0|
      Hypertrophy                          |    2           2                       2           2                     |      8  2.0|
      Vacuolization Cytoplasmic            |                                           2                              |      2  2.0|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |    4           2     3                 2     2  2  3  2     1        2   |     19  2.2|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +|  48        |
      Hyperplasia                          |       3                                2                                1|      5  2.0|
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Pars Distalis, Hyperplasia           |    2                       1                                             |      5  2.2|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      C-Cell, Hyperplasia                  | 1           1  1     1  1  1  2        2  1  2  2  1     1  1  2  1  1  1|     30  1.3|
      Follicular Cell, Hyperplasia         |                                        2                                 |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Peritoneum                              |                                                       +                  |   2        |
                                            __________________________________________________________________________|____________|
   Tissue NOS                              |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Granuloma Sperm                      |                                                          3               |      1  3.0|
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |                                                                      4   |      3  3.3|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |    2     1     2     2           2  2  2                          2      |     11  1.9|
      Inflammation, Chronic Active         |                   4  2  2                                                |      5  3.2|
 __________________________________________________________________________________________________________________________________ 

  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        

                                                             Page  35                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 5| 6| 7| 6| 5| 7| 7| 7| 7| 7| 5| 6| 7| 7| 5| 7| 7| 7| 6| 7| 5| 6| 7| 7| 6|            |
                             DAY ON TEST   | 5| 7| 3| 5| 9| 3| 3| 3| 3| 2| 5| 9| 3| 3| 6| 2| 3| 3| 0| 2| 0| 7| 3| 3| 6|            |
                                           | 5| 5| 3| 9| 7| 4| 3| 3| 4| 1| 1| 4| 4| 4| 4| 3| 4| 3| 4| 4| 2| 1| 3| 3| 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     |
   FISCHER 344 RATS 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|            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Inflammation, Chronic Active         |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                                                                          |      1  3.0|
      Artery, Inflammation, Chronic Active |                                     3  3                                2|      6  2.7|
      Interstitial Cell, Hyperplasia       |          2  2     2     4           2     2                 2           3|     15  2.4|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                   +              +        +                              |   6        |
      Iliac, Ectasia                       |                                                                          |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  M  M  +  +  +|  44        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  M  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrosis                             |    2     2              2  2              3  2                    2      |     11  1.9|
      Hematopoietic Cell Proliferation     |                                                       3                  |      3  2.3|
      Hemorrhage                           |                                                                   2      |      1  2.0|
      Necrosis                             |                                           4  2                           |      3  2.7|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  M  +|  47        |
      Cyst                                 |                               2                                          |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  M  +  +  +  +|  42        |
      Galactocele                          |       3                                                                  |      2  3.0|
      Inflammation, Chronic                |                                                                   3      |      1  3.0|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst Epithelial Inclusion            |                                     X        X                           |      2     |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrous Osteodystrophy               |       3                                                                  |      2  2.0|
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Degeneration, Focal                  |                                                                   2      |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY 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  36                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 5| 6| 7| 6| 5| 7| 7| 7| 7| 7| 5| 6| 7| 7| 5| 7| 7| 7| 6| 7| 5| 6| 7| 7| 6|            |
                             DAY ON TEST   | 5| 7| 3| 5| 9| 3| 3| 3| 3| 2| 5| 9| 3| 3| 6| 2| 3| 3| 0| 2| 0| 7| 3| 3| 6|            |
                                           | 5| 5| 3| 9| 7| 4| 3| 3| 4| 1| 1| 4| 4| 4| 4| 3| 4| 3| 4| 4| 2| 1| 3| 3| 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     |
   FISCHER 344 RATS 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|            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Inflammation, Chronic Active         |       1        2  3  1  1  1        1  1        1  2  1                  |     21  1.6|
      Alveolar Epithelium, Hyperplasia     |                                  2                             1        1|      7  1.1|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Foreign Body                         |                   X                             X              X        X|      4     |
      Inflammation, Suppurative            | 1     1           2     1           2           2        1     1        3|     11  1.5|
      Thrombosis                           |                            3                                             |      2  2.0|
      Olfactory Epithelium, Atrophy        |                                                                         1|      1  1.0|
      Olfactory Epithelium, Metaplasia     |                   2     1           2           2              2        2|      7  1.7|
      Olfactory Epithelium, Metaplasia,    |                                                                          |            |
           Squamous                        |                                                             1            |      1  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                         +                                                |   1        |
      Cataract                             |                         3                                                |      1  3.0|
      Retina, Atrophy                      |                         3                                                |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                                                       4                 3|      2  3.5|
      Infarct                              |                                           3                              |      1  3.0|
      Nephropathy                          | 3  2  4  3  2  3  3  3  3  3  3  2  3  4  2  3  3  3  2  3  2  2  3  4  4|     50  2.8|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |                   2                                                      |      1  2.0|
      Transitional Epithelium, Hyperplasia |                                                                          |      1  1.0|
 __________________________________________________________________________________________________________________________________ 

  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        

                                                             Page  37                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 5| 7| 5| 7| 7| 6| 6| 7| 7| 6| 5| 7| 7| 7| 7| 3| 5| 7| 5| 6| 7| 6| 5|             
                             DAY ON TEST   | 3| 3| 5| 1| 9| 3| 3| 0| 9| 3| 2| 5| 9| 1| 3| 3| 3| 9| 1| 0| 4| 9| 3| 0| 3|             
                                           | 3| 8| 9| 4| 2| 4| 3| 4| 8| 4| 3| 7| 7| 9| 3| 3| 4| 8| 0| 2| 9| 3| 3| 2| 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|             
   FISCHER 344 RATS 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|             
    220 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Necrosis                             |                                                          1               |             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Basophilic Focus                     |                X              X        X  X                              |             
      Clear Cell Focus                     | X                 X     X                 X                       X      |             
      Degeneration, Cystic                 |                            2     1                             2         |             
      Eosinophilic Focus                   |                            X                                             |             
      Fatty Change                         |    1     2                    1        2              3                  |             
      Hepatodiaphragmatic Nodule           |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
      Inflammation, Granulomatous          |                                        1                                 |             
      Necrosis                             |                                                                          |             
      Bile Duct, Hyperplasia               |    2     2  2  1  1        2     2     1  1  1  2        2  2  2     2   |             
      Centrilobular, Necrosis              |    2     1                                               2  2  2     1  2|             
                                            __________________________________________________________________________|             
   Mesentery                               |    +              +                 +           +                        |             
      Fat, Hemorrhage                      |                                                                          |             
      Fat, Necrosis                        |                   2                 2           2                        |             
                                            __________________________________________________________________________|             
   Oral Mucosa                             |                                                 +                        |             
      Pharyngeal, Hyperplasia, Squamous    |                                                 4                        |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |       1     2  2     1  2     1     2     1     2                 2  1   |             
      Basophilic Focus                     |                X                                                  X      |             
      Hyperplasia                          |                2  3                                               3      |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Squamous                |       3                                                                  |             
      Necrosis                             |       2                          3                    3  2     3        3|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |                                                                          |             
      Necrosis                             |    3                                                     2           2   |             
                                            __________________________________________________________________________|             
   Tooth                                   |                                     +                                    |             
      Developmental Malformation           |                                     X                                    |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       | 2  2  1  2  1  3  2  2  2  2  1  2  2  2  2  3  2  2  2  2  2  1  2     2|             
      Atrium, Thrombosis                   |                                                                1     3   |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  38                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 5| 7| 5| 7| 7| 6| 6| 7| 7| 6| 5| 7| 7| 7| 7| 3| 5| 7| 5| 6| 7| 6| 5|             
                             DAY ON TEST   | 3| 3| 5| 1| 9| 3| 3| 0| 9| 3| 2| 5| 9| 1| 3| 3| 3| 9| 1| 0| 4| 9| 3| 0| 3|             
                                           | 3| 8| 9| 4| 2| 4| 3| 4| 8| 4| 3| 7| 7| 9| 3| 3| 4| 8| 0| 2| 9| 3| 3| 2| 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|             
   FISCHER 344 RATS 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|             
    220 PPM                                | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          | 2        2     1  2  2     2  2     2  1  2           1           2      |             
      Hypertrophy                          |          2                                      2              2         |             
      Vacuolization Cytoplasmic            |                                              2  3        1           2   |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                                                                          |             
      Hyperplasia                          | 3     3           1     2              3           1        2  3  3      |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +|             
      Cyst                                 |                                                                          |             
      Hyperplasia                          |                               2  2  2                                1   |             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           | 3                 2                                      3               |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      C-Cell, Hyperplasia                  | 3     1  1     1  1  3  1  1     1  1  1        1     1  1     3     2  1|             
      Follicular Cell, Hyperplasia         |                                                          1               |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Tissue NOS                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          | 2        1                 1  1           2     1                 3      |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                   3      |             
      Artery, Inflammation, Chronic Active |                                                                          |             
      Interstitial Cell, Hyperplasia       |                3     2        2                    2  2     2            |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Histiocytic             |                                        2                                 |             
                                            __________________________________________________________________________|             
   Lymph Node                              |    +                             +              +                    +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  M  M  +  M  +  +  +  M  +  +  +  M  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  M  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Plasma Cell   |                         4           4                                    |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  39                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 5| 7| 5| 7| 7| 6| 6| 7| 7| 6| 5| 7| 7| 7| 7| 3| 5| 7| 5| 6| 7| 6| 5|             
                             DAY ON TEST   | 3| 3| 5| 1| 9| 3| 3| 0| 9| 3| 2| 5| 9| 1| 3| 3| 3| 9| 1| 0| 4| 9| 3| 0| 3|             
                                           | 3| 8| 9| 4| 2| 4| 3| 4| 8| 4| 3| 7| 7| 9| 3| 3| 4| 8| 0| 2| 9| 3| 3| 2| 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|             
   FISCHER 344 RATS 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|             
    220 PPM                                | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             | 2                          2     2                          2  1     3   |             
      Hematopoietic Cell Proliferation     |                                                    2                     |             
                                            __________________________________________________________________________|             
   Thymus                                  | M  +  M  +  +  +  M  +  +  +  +  M  +  +  +  +  +  M  +  +  M  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  M  +  +  +  +  M  +  +  +  +  +  +  M  +  M  +  +  +  +  +  +|             
      Galactocele                          |                      2                                         3         |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrous Osteodystrophy               |                                  2                                       |             
      Hyperostosis                         |                                                                1         |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Gliosis                              |                                                                2         |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic, Focal         |                      4                                                   |             
      Inflammation, Chronic Active         | 1                                            2     1     1           1  4|             
      Thrombosis                           |                                                                         3|             
      Alveolar Epithelium, Hyperplasia     |                2           4  1  1        1                    1         |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Foreign Body                         | X                                                                 X     X|             
      Inflammation, Suppurative            | 1                       1           2           2                 1     1|             
      Thrombosis                           |                                                                      3  4|             
      Olfactory Epithelium, Metaplasia     |                                           2     2                        |             
      Respiratory Epithelium, Hyperplasia  |                                     1                                    |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |          +                                                           +   |             
      Cataract                             |                                                                      3   |             
      Cornea, Inflammation, Chronic Active |                                                                          |             
      Retina, Atrophy                      |          3                                                           4   |             
                                            __________________________________________________________________________|             
   Zymbal's Gland                          |                         +                                                |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  40                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 5| 7| 5| 7| 7| 6| 6| 7| 7| 6| 5| 7| 7| 7| 7| 3| 5| 7| 5| 6| 7| 6| 5|             
                             DAY ON TEST   | 3| 3| 5| 1| 9| 3| 3| 0| 9| 3| 2| 5| 9| 1| 3| 3| 3| 9| 1| 0| 4| 9| 3| 0| 3|             
                                           | 3| 8| 9| 4| 2| 4| 3| 4| 8| 4| 3| 7| 7| 9| 3| 3| 4| 8| 0| 2| 9| 3| 3| 2| 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|             
   FISCHER 344 RATS 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|             
    220 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|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infarct                              |                                                                4         |             
      Nephropathy                          | 4  2  3  3  2  3  2  3  2  3  4  4  2  4  3  2  3  1  3  2  2  4  3  2  2|             
      Renal Tubule, Hyperplasia            |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  41                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 5| 6| 4| 7| 7| 7| 7| 7| 6| 6| 4| 6| 5| 6| 7| 4| 6| 6| 7| 7| 6|            |
                             DAY ON TEST   | 5| 3| 3| 1| 8| 8| 2| 3| 3| 3| 3| 3| 5| 6| 9| 5| 8| 7| 3| 5| 2| 7| 0| 0| 3|            |
                                           | 7| 4| 3| 7| 8| 2| 0| 3| 3| 3| 3| 3| 7| 4| 9| 2| 1| 1| 3| 5| 9| 0| 2| 3| 5|      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     |
   FISCHER 344 RATS 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     |
    220 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        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  I|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Necrosis                             |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Basophilic Focus                     |             X  X     X     X  X  X              X     X              X   |     13     |
      Clear Cell Focus                     |                               X  X                    X        X         |      9     |
      Degeneration, Cystic                 |          2              3              2           2              2  2   |      9  2.0|
      Eosinophilic Focus                   | X              X                                                     X   |      4     |
      Fatty Change                         |             1     1     1     2        1                 1  1            |     12  1.4|
      Hepatodiaphragmatic Nodule           |                                                       X                  |      1     |
      Inflammation, Chronic Active         |                                                    2                     |      1  2.0|
      Inflammation, Granulomatous          |                                                                          |      1  1.0|
      Necrosis                             |                                     1                                    |      1  1.0|
      Bile Duct, Hyperplasia               | 2  2  2  2     1     1  2  1  1        1     2     2  1  1  2     1     2|     32  1.6|
      Centrilobular, Necrosis              | 1              2                             2              1            |     11  1.6|
                                            __________________________________________________________________________|____________|
   Mesentery                               |             +           +           +           +     +     +        +  +|  12        |
      Fat, Hemorrhage                      |                                     2                                    |      1  2.0|
      Fat, Necrosis                        |             2           2                       3     2     2        2  3|     10  2.2|
                                            __________________________________________________________________________|____________|
   Oral Mucosa                             |                                                                          |   1        |
      Pharyngeal, Hyperplasia, Squamous    |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |       1  2  2        2  2  1        2        1              2  2     2  3|     23  1.7|
      Basophilic Focus                     |                X              X                                          |      4     |
      Hyperplasia                          |                2        2  2                                             |      6  2.3|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia, Squamous                |                                                                          |      1  3.0|
      Necrosis                             |                                        4                          4      |      8  3.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Mineralization                       |    1                                                                     |      1  1.0|
      Necrosis                             |                                                                          |      3  2.3|
                                            __________________________________________________________________________|____________|
   Tooth                                   |                                                                          |   1        |
      Developmental Malformation           |                                                                          |      1     |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 

  * : Total animals with tissue examined microscopically; total animals with lesion and mean severity grade                         
  + : Tissue examined microscopically                M : Missing tissue                        1-4 : Lesion qualified as:           
  X : Lesion present but not qualified               A : Autolysis precludes examination               1) Minimal  3) Moderate      
  I : Insufficient tissue                        BLANK : Not examined                                  2) Mild     4) Marked        

                                                             Page  42                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 5| 6| 4| 7| 7| 7| 7| 7| 6| 6| 4| 6| 5| 6| 7| 4| 6| 6| 7| 7| 6|            |
                             DAY ON TEST   | 5| 3| 3| 1| 8| 8| 2| 3| 3| 3| 3| 3| 5| 6| 9| 5| 8| 7| 3| 5| 2| 7| 0| 0| 3|            |
                                           | 7| 4| 3| 7| 8| 2| 0| 3| 3| 3| 3| 3| 7| 4| 9| 2| 1| 1| 3| 5| 9| 0| 2| 3| 5|      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     |
   FISCHER 344 RATS 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     |
    220 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              |                                                                          |            |
                                           |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       | 1  2  2  2  2     1  2  3  2  2  3  2  2     2     2  2  1     2  2  2   |     44  1.9|
      Atrium, Thrombosis                   | 2                                                                        |      3  2.0|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |    2           2           2     1     1  1     3  2  2  2     2         |     23  1.8|
      Hypertrophy                          |    2     1  1        2     2                                2  2        2|     11  1.8|
      Vacuolization Cytoplasmic            |                                  2                                      2|      6  2.0|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |    4                                                                     |      1  4.0|
      Hyperplasia                          |          2                 2  3  2  2  2     2     2              1  3   |     19  2.2|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                                                                      2   |      1  2.0|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  M  +  +  M  +  +  +|  46        |
      Cyst                                 | 3                                                                        |      1  3.0|
      Hyperplasia                          |                         3  2                                             |      6  2.0|
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Pars Distalis, Hyperplasia           |       3        2                                      3                  |      6  2.7|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      C-Cell, Hyperplasia                  | 1  1        1  3     1  1     1        1  1  2  1  1                 2   |     30  1.4|
      Follicular Cell, Hyperplasia         |                                                                          |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Tissue NOS                              |                                                 +                       +|   2        |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                                                       1                  |      1  1.0|
      Inflammation, Chronic Active         |                                                                   4      |      1  4.0|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |    3           2        3     3  3                                   3   |     13  2.2|
      Inflammation, Chronic Active         |                      2                                            1      |      2  1.5|
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +|  48        |
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                                                                          |      1  3.0|
      Artery, Inflammation, Chronic Active |                                        3                       3         |      2  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  43                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 5| 6| 4| 7| 7| 7| 7| 7| 6| 6| 4| 6| 5| 6| 7| 4| 6| 6| 7| 7| 6|            |
                             DAY ON TEST   | 5| 3| 3| 1| 8| 8| 2| 3| 3| 3| 3| 3| 5| 6| 9| 5| 8| 7| 3| 5| 2| 7| 0| 0| 3|            |
                                           | 7| 4| 3| 7| 8| 2| 0| 3| 3| 3| 3| 3| 7| 4| 9| 2| 1| 1| 3| 5| 9| 0| 2| 3| 5|      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     |
   FISCHER 344 RATS 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     |
    220 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|            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
      Interstitial Cell, Hyperplasia       |                   3        2           4  1     2        2  3            |     13  2.3|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia, Histiocytic             |                                                                          |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |       +                 +                                                |   7        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  M  M  M  +  +  M  M  +|  39        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +|  46        |
      Infiltration Cellular, Plasma Cell   |                                                                          |      2  4.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  M  M  +  +  M  +  +  +  +  +  +  M  +  +  +  +  +  +  +|  44        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrosis                             |    2           2     2  2              2                       2  1     2|     14  1.9|
      Hematopoietic Cell Proliferation     |          3                                      2                        |      3  2.3|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  44        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  I  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|  43        |
      Galactocele                          |                                        2                             2   |      4  2.3|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |             4                                                            |      1  4.0|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrous Osteodystrophy               |                                                                          |      1  2.0|
      Hyperostosis                         |                                                                          |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Gliosis                              |                                                                          |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic, Focal         |                                                                          |      1  4.0|
      Inflammation, Chronic Active         | 1  1     1        1     1  1  1  1              1                    1   |     16  1.3|
      Thrombosis                           |                                                                          |      1  3.0|
      Alveolar Epithelium, Hyperplasia     |       1     1                          1              1           1      |     11  1.4|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  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  44                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 7| 7| 7| 5| 6| 4| 7| 7| 7| 7| 7| 6| 6| 4| 6| 5| 6| 7| 4| 6| 6| 7| 7| 6|            |
                             DAY ON TEST   | 5| 3| 3| 1| 8| 8| 2| 3| 3| 3| 3| 3| 5| 6| 9| 5| 8| 7| 3| 5| 2| 7| 0| 0| 3|            |
                                           | 7| 4| 3| 7| 8| 2| 0| 3| 3| 3| 3| 3| 7| 4| 9| 2| 1| 1| 3| 5| 9| 0| 2| 3| 5|      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     |
   FISCHER 344 RATS 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     |
    220 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|            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
      Foreign Body                         |                      X                                                   |      4     |
      Inflammation, Suppurative            |             3        2                                1                  |      9  1.6|
      Thrombosis                           | 1                                                           2            |      4  2.5|
      Olfactory Epithelium, Metaplasia     |                                                                          |      2  2.0|
      Respiratory Epithelium, Hyperplasia  |                      1                                                   |      2  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |             +                                                            |   3        |
      Cataract                             |                                                                          |      1  3.0|
      Cornea, Inflammation, Chronic Active |             3                                                            |      1  3.0|
      Retina, Atrophy                      |                                                                          |      2  3.5|
                                            __________________________________________________________________________|____________|
   Zymbal's Gland                          |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Infarct                              |                                                                          |      1  4.0|
      Nephropathy                          | 3  3  3  3  2  3  1  3  4  4  4  2  3  3  2  2  2  4  2  2  2  3  4  3  2|     50  2.7|
      Renal Tubule, Hyperplasia            |                            4                                      3      |      2  3.5|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  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  45                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 5| 7| 7| 6| 7| 5| 6| 6| 7| 6| 5| 7| 7| 7| 7| 6| 5| 7| 4| 5| 4| 5| 5| 7|             
                             DAY ON TEST   | 5| 7| 3| 1| 6| 3| 4| 6| 9| 3| 8| 6| 2| 3| 3| 2| 7| 9| 3| 6| 2| 5| 1| 1| 0|             
                                           | 5| 6| 3| 2| 4| 4| 7| 7| 2| 4| 6| 6| 2| 4| 4| 7| 1| 1| 3| 9| 1| 4| 0| 8| 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|             
   FISCHER 344 RATS 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|             
    700 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  A  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  A  +  +  +  +  A  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +|             
      Diverticulum                         |                                                                          |             
      Mineralization                       |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                                                          |             
      Necrosis                             |                                                                         1|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  A  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  A  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                          |             
      Necrosis                             |                                                                          |             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                      1                                                   |             
      Basophilic Focus                     |       X              X           X        X  X                 X        X|             
      Clear Cell Focus                     |       X              X                                         X         |             
      Degeneration, Cystic                 |             2        2              4     1  2                          2|             
      Eosinophilic Focus                   |       X                 X                                                |             
      Fatty Change                         | 2                                                     1     1        3   |             
      Hepatodiaphragmatic Nodule           |             X                                   X                        |             
      Inflammation, Acute                  |                                                                          |             
      Necrosis                             |                                                                          |             
      Regeneration                         |                                     2                             4      |             
      Bile Duct, Hyperplasia               | 2  1     2  3  2  2  1  2  2  2     3                 2     1     2  1  1|             
      Centrilobular, Necrosis              | 2           2                 2                 2     2                  |             
                                            __________________________________________________________________________|             
   Mesentery                               |       +  +                       +  +     +                 +        +   |             
      Thrombosis                           |                                           4                              |             
      Artery, Mineralization               |                                  4                                       |             
      Fat, Hemorrhage                      |                                                                          |             
      Fat, Inflammation, Chronic Active    |                                                                      2   |             
      Fat, Necrosis                        |       2  2                       2  2                       2            |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |          2  1     2  2        2  2     2  2                             2|             
      Basophilic Focus                     |                                                                          |             
      Hyperplasia                          |    2  2              3        4                             2            |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia, Squamous                |                                                 1                        |             
      Inflammation, Acute                  |                                                                          |             
      Mineralization                       |                                  3                                       |             
      Necrosis                             | 2           3        4        3              3                       4   |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  46                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 5| 7| 7| 6| 7| 5| 6| 6| 7| 6| 5| 7| 7| 7| 7| 6| 5| 7| 4| 5| 4| 5| 5| 7|             
                             DAY ON TEST   | 5| 7| 3| 1| 6| 3| 4| 6| 9| 3| 8| 6| 2| 3| 3| 2| 7| 9| 3| 6| 2| 5| 1| 1| 0|             
                                           | 5| 6| 3| 2| 4| 4| 7| 7| 2| 4| 6| 6| 2| 4| 4| 7| 1| 1| 3| 9| 1| 4| 0| 8| 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|             
   FISCHER 344 RATS 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|             
    700 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 - cont                  |                                                                          |             
                                           |                                                                          |             
      Mineralization                       |                               1  4                                       |             
      Necrosis                             |                                              3  3                    3   |             
                                            __________________________________________________________________________|             
   Tongue                                  |                                                                          |             
      Hyperplasia                          |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Blood Vessel                            |                                  +                                       |             
      Aorta, Mineralization                |                                  4                                       |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       | 2  2  2  3  2  3     2  2  2  2  3  2  3  2  2     2  2  2  3  1  2  2  1|             
      Artery, Mineralization               |                                  3                                       |             
      Atrium, Thrombosis                   |                               2                       3                  |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          | 2  2  2                             2  2     2              2     1     2|             
      Hypertrophy                          |          4                          2     1                              |             
      Necrosis                             |                         2                                                |             
      Vacuolization Cytoplasmic            |                2     1                                                   |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |    2     2  3        4  2  2  2           2           2        1     2  2|             
      Bilateral, Hyperplasia               |                2                             3                           |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +|             
      Hyperplasia                          |                      2     2     4           3                           |             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Hyperplasia           |                                  3     3                    1            |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
      C-Cell, Hyperplasia                  | 1  2  3     1  1     2        1  1     1  1  1        2           3  1  1|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Peritoneum                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Granuloma Sperm                      |                                                                          |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                             4            |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |             2              2  2     1     3  3        1        3         |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  47                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 5| 7| 7| 6| 7| 5| 6| 6| 7| 6| 5| 7| 7| 7| 7| 6| 5| 7| 4| 5| 4| 5| 5| 7|             
                             DAY ON TEST   | 5| 7| 3| 1| 6| 3| 4| 6| 9| 3| 8| 6| 2| 3| 3| 2| 7| 9| 3| 6| 2| 5| 1| 1| 0|             
                                           | 5| 6| 3| 2| 4| 4| 7| 7| 2| 4| 6| 6| 2| 4| 4| 7| 1| 1| 3| 9| 1| 4| 0| 8| 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|             
   FISCHER 344 RATS 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|             
    700 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 - cont                     |                                                                          |             
                                           |                                                                          |             
      Atrophy                              |                                                                          |             
      Artery, Inflammation, Chronic Active |          3                                                               |             
      Interstitial Cell, Hyperplasia       | 2  1     2                                         3        2  2     1   |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              | +                                               +                 +      |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  M  +  +  M  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  +  +  +  +  M  +  +  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             |       2  1     4  3        2  3     2  2     1                          2|             
      Hematopoietic Cell Proliferation     |                                                                          |             
      Necrosis                             |                                                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +|             
      Galactocele                          |                                                                          |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                                                                      3   |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrous Osteodystrophy               |                      2           3                                       |             
      Hyperostosis                         |                               1                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |    1                    2  1  1           1     3     2           3     1|             
      Mineralization                       |                                  4                                       |             
      Alveolar Epithelium, Hyperplasia     |                                                          1           1   |             
      Artery, Mediastinum, Mineralization  |                                  3                                       |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
      Foreign Body                         |                                  X              X                        |             
      Inflammation, Suppurative            |                   2              2              2                        |             
      Thrombosis                           | 3           4                 2                       2                  |             
      Olfactory Epithelium, Atrophy        |                                  1           2                       2   |             
      Olfactory Epithelium, Metaplasia     |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  48                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 5| 7| 7| 6| 7| 5| 6| 6| 7| 6| 5| 7| 7| 7| 7| 6| 5| 7| 4| 5| 4| 5| 5| 7|             
                             DAY ON TEST   | 5| 7| 3| 1| 6| 3| 4| 6| 9| 3| 8| 6| 2| 3| 3| 2| 7| 9| 3| 6| 2| 5| 1| 1| 0|             
                                           | 5| 6| 3| 2| 4| 4| 7| 7| 2| 4| 6| 6| 2| 4| 4| 7| 1| 1| 3| 9| 1| 4| 0| 8| 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|             
   FISCHER 344 RATS 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|             
    700 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                 |                                                                          |             
                                           |                                                                          |             
      Respiratory Epithelium, Hyperplasia  |                                                                          |             
      Respiratory Epithelium, Metaplasia,  |                                                                          |             
           Squamous                        |                   1                                                      |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |                                  2                                       |             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |    +                       +                                             |             
      Cataract                             |    3                       3                                             |             
      Hemorrhage                           |                                                                          |             
      Cornea, Inflammation, Chronic Active |                                                                          |             
      Retina, Atrophy                      |    4                       3                                             |             
                                            __________________________________________________________________________|             
   Zymbal's Gland                          |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |       3                          2                                       |             
      Infarct                              |                                                                          |             
      Mineralization                       |                                  3                                       |             
      Nephropathy                          | 4  2  3  3  2  3  2  4  2  4  3  4  2  3  3  4  3  2  3  2  2  2  2  3  4|             
      Renal Tubule, Hyperplasia            |                      3           2                                   2   |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  49                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 6| 7| 7| 6| 7| 6| 7| 5| 5| 7| 7| 5| 5| 4| 6| 6| 7| 7| 7| 6| 5| 5| 7| 6|            |
                             DAY ON TEST   | 6| 6| 3| 3| 8| 2| 8| 3| 8| 3| 3| 3| 4| 6| 5| 2| 9| 3| 3| 3| 8| 5| 9| 3| 7|            |
                                           | 7| 8| 3| 3| 3| 8| 1| 3| 0| 7| 3| 3| 1| 6| 4| 1| 5| 3| 3| 3| 4| 5| 4| 3| 0|      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     |
   FISCHER 344 RATS 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     |
    700 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        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +|  46        |
      Inflammation, Acute                  |                   2                                            2         |      2  2.0|
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  46        |
      Diverticulum                         |                                  X                                       |      1     |
      Mineralization                       |                                  2                                       |      1  2.0|
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Inflammation, Acute                  |    3                                                                     |      1  3.0|
      Necrosis                             |                   2                                                      |      2  1.5|
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Inflammation, Chronic Active         |                                              4                           |      1  4.0|
      Necrosis                             |          4                                                               |      1  4.0|
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |             2     2                             1     2                  |      5  1.6|
      Basophilic Focus                     |                X  X              X        X           X  X               |     13     |
      Clear Cell Focus                     |                                  X     X           X        X            |      7     |
      Degeneration, Cystic                 |       1        1     3  1  2        2           2                       2|     14  1.9|
      Eosinophilic Focus                   |             X                                                            |      3     |
      Fatty Change                         |    2           2  3  1                                                  1|      9  1.8|
      Hepatodiaphragmatic Nodule           |                                                          X  X            |      4     |
      Inflammation, Acute                  |    3                                                                     |      1  3.0|
      Necrosis                             |    3                                                                     |      1  3.0|
      Regeneration                         |                                                                          |      2  3.0|
      Bile Duct, Hyperplasia               | 2  1  3  1  1  1  1  2     2  1  1  2        2  2  2     1  1  1  3  3   |     36  1.7|
      Centrilobular, Necrosis              | 1                          1        1                          1  1      |     10  1.5|
                                            __________________________________________________________________________|____________|
   Mesentery                               |                   +  +              +                          +         |  11        |
      Thrombosis                           |                                                                          |      1  4.0|
      Artery, Mineralization               |                                                                          |      1  4.0|
      Fat, Hemorrhage                      |                   2                                                      |      1  2.0|
      Fat, Inflammation, Chronic Active    |                                                                          |      1  2.0|
      Fat, Necrosis                        |                      2              2                          2         |      8  2.0|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |       1  2  2  2     2  2     1  1           2        1     2  2  2  2   |     23  1.8|
      Basophilic Focus                     |                                  X                                       |      1     |
      Hyperplasia                          |                      3        2                       2     3            |      9  2.6|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  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  50                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 6| 7| 7| 6| 7| 6| 7| 5| 5| 7| 7| 5| 5| 4| 6| 6| 7| 7| 7| 6| 5| 5| 7| 6|            |
                             DAY ON TEST   | 6| 6| 3| 3| 8| 2| 8| 3| 8| 3| 3| 3| 4| 6| 5| 2| 9| 3| 3| 3| 8| 5| 9| 3| 7|            |
                                           | 7| 8| 3| 3| 3| 8| 1| 3| 0| 7| 3| 3| 1| 6| 4| 1| 5| 3| 3| 3| 4| 5| 4| 3| 0|      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     |
   FISCHER 344 RATS 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     |
    700 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 - cont                  |                                                                          |            |
                                           |                                                                          |            |
      Hyperplasia, Squamous                |                                                                          |      1  1.0|
      Inflammation, Acute                  |    2                                                                     |      1  2.0|
      Mineralization                       |                                                 2                        |      2  2.5|
      Necrosis                             |                   4                    2     2                          3|     10  3.0|
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Mineralization                       |                                                 4     3                  |      4  3.0|
      Necrosis                             |                   2        2                                2  2         |      7  2.4|
                                            __________________________________________________________________________|____________|
   Tongue                                  |             +                                                            |   1        |
      Hyperplasia                          |             1                                                            |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Blood Vessel                            |                                                 +                        |   2        |
      Aorta, Mineralization                |                                                 4                        |      2  4.0|
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       |    2  2  2  2  2  2  3  2  2  3  3  2  1  2  2  3  2  3  2  2     2      |     44  2.2|
      Artery, Mineralization               |                                                 4                        |      2  3.5|
      Atrium, Thrombosis                   |                                                                3         |      3  2.7|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |    2     2  2              2  2  2              1  2     3  2            |     19  1.9|
      Hypertrophy                          |          2                                                               |      4  2.3|
      Necrosis                             |                                                                          |      1  2.0|
      Vacuolization Cytoplasmic            |                                                                      2   |      3  1.7|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          | 3     3           2        2  2  2           2     3  3  2        2  3  3|     25  2.3|
      Bilateral, Hyperplasia               |                                                                          |      2  2.5|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |                      2                             3  3                  |      3  2.7|
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  M  +  M  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +|  45        |
      Hyperplasia                          |                      2        2                 4     3                  |      8  2.8|
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Pars Distalis, Hyperplasia           |                               3     1        3        3     3        3   |      9  2.6|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      C-Cell, Hyperplasia                  |    1  1     2  1  1  1     1  1  2  1  2     3                    1  2  2|     30  1.5|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Peritoneum                              |                                        +                                 |   1        |
 _____________________________________________________________________________________________________________________|            |
 GENITAL 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  51                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 6| 7| 7| 6| 7| 6| 7| 5| 5| 7| 7| 5| 5| 4| 6| 6| 7| 7| 7| 6| 5| 5| 7| 6|            |
                             DAY ON TEST   | 6| 6| 3| 3| 8| 2| 8| 3| 8| 3| 3| 3| 4| 6| 5| 2| 9| 3| 3| 3| 8| 5| 9| 3| 7|            |
                                           | 7| 8| 3| 3| 3| 8| 1| 3| 0| 7| 3| 3| 1| 6| 4| 1| 5| 3| 3| 3| 4| 5| 4| 3| 0|      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     |
   FISCHER 344 RATS 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     |
    700 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|            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Granuloma Sperm                      |                                                                   3      |      1  3.0|
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |                                                                          |      1  4.0|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |       3  2     2                 2                 2     4     2         |     15  2.3|
      Inflammation, Chronic Active         |                                                       3                  |      1  3.0|
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                                                                3         |      1  3.0|
      Artery, Inflammation, Chronic Active |                                                                          |      1  3.0|
      Interstitial Cell, Hyperplasia       |                                                             3            |      8  2.0|
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |       +              +                                            +  +   |   7        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  +  +  +  M  +  +  +  M|  42        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  M  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  M|  45        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrosis                             |    1        2        2  2        2  2        1  2  2  2  2  2     2  2   |     24  2.0|
      Hematopoietic Cell Proliferation     |                                                             3            |      1  3.0|
      Necrosis                             | 2                          2                                             |      2  2.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +|  47        |
      Galactocele                          |       3     2                                                            |      2  2.5|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |    2                                                                     |      2  2.5|
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrous Osteodystrophy               |                      1                          3     2                 2|      6  2.2|
      Hyperostosis                         |                                                                          |      1  1.0|
 _____________________________________________________________________________________________________________________|            |
 NERVOUS 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  52                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 6| 6| 7| 7| 6| 7| 6| 7| 5| 5| 7| 7| 5| 5| 4| 6| 6| 7| 7| 7| 6| 5| 5| 7| 6|            |
                             DAY ON TEST   | 6| 6| 3| 3| 8| 2| 8| 3| 8| 3| 3| 3| 4| 6| 5| 2| 9| 3| 3| 3| 8| 5| 9| 3| 7|            |
                                           | 7| 8| 3| 3| 3| 8| 1| 3| 0| 7| 3| 3| 1| 6| 4| 1| 5| 3| 3| 3| 4| 5| 4| 3| 0|      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     |
   FISCHER 344 RATS 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     |
    700 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|            |
 __________________________________________________________________________________________________________________________________ 
 NERVOUS SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |          2     1     2  1     1  1  1     1  4     1     1  1     2      |     22  1.5|
      Mineralization                       |                                                 3                        |      2  3.5|
      Alveolar Epithelium, Hyperplasia     |    1                             1                                       |      4  1.0|
      Artery, Mediastinum, Mineralization  |                                                 4                        |      2  3.5|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Foreign Body                         |    X                                                                     |      3     |
      Inflammation, Suppurative            | 1              2  1           2           2     2                       1|     10  1.7|
      Thrombosis                           |       1                    3        2                 1        4     3   |     10  2.5|
      Olfactory Epithelium, Atrophy        |    2           2  2                    2                                2|      8  1.9|
      Olfactory Epithelium, Metaplasia     |                               2                                          |      1  2.0|
      Respiratory Epithelium, Hyperplasia  |                1                          1                              |      2  1.0|
      Respiratory Epithelium, Metaplasia,  |                                                                          |            |
           Squamous                        |                                                                          |      1  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Mineralization                       |                                                                          |      1  2.0|
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                               +                                          |   3        |
      Cataract                             |                               3                                          |      3  3.0|
      Hemorrhage                           |                               3                                          |      1  3.0|
      Cornea, Inflammation, Chronic Active |                               2                                          |      1  2.0|
      Retina, Atrophy                      |                               3                                          |      3  3.3|
                                            __________________________________________________________________________|____________|
   Zymbal's Gland                          |                                           +                              |   1        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                                                       2  2               |      4  2.3|
      Infarct                              |                               2                                3         |      2  2.5|
      Mineralization                       |                                                 4                        |      2  3.5|
      Nephropathy                          | 2  4  3  3  3  4  4  4  2  2  4  3  2  4  1  3  4  3  4  3  3  2  2  3  4|     50  2.9|
      Renal Tubule, Hyperplasia            |    2                 3                                2                  |      6  2.3|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  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  53                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 7| 4| 7| 0| 7| 7| 6| 6| 7| 6| 5| 7| 7| 7| 7| 6| 6| 7| 7| 6| 2| 5| 7| 7|             
                             DAY ON TEST   | 8| 2| 7| 3| 2| 3| 3| 2| 6| 3| 8| 8| 3| 3| 2| 2| 1| 8| 0| 3| 2| 2| 6| 3| 3|             
                                           | 8| 1| 8| 3| 6| 3| 4| 2| 4| 4| 5| 8| 3| 4| 7| 3| 8| 1| 9| 3| 1| 2| 6| 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|             
   FISCHER 344 RATS 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|             
    7000 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                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Acute                  |                                                                          |             
      Necrosis                             |                                                    1                     |             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  A  +  A  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Angiectasis                          |                         2  2                                             |             
      Basophilic Focus                     |          X     X  X        X  X                          X  X           X|             
      Clear Cell Focus                     |                X                                         X              X|             
      Degeneration, Cystic                 |                2  2  3  4     2           2                             2|             
      Eosinophilic Focus                   |                   X                                      X               |             
      Fatty Change                         | 2                    3  2     2              2     3        2            |             
      Hematopoietic Cell Proliferation     |                                           3                              |             
      Hepatodiaphragmatic Nodule           |                      X                          X                        |             
      Infarct                              |                                                       4                  |             
      Mixed Cell Focus                     |                                                                          |             
      Necrosis                             |                                                                2         |             
      Regeneration                         |                         4                             2              3   |             
      Artery, Inflammation, Chronic Active |                                                                4         |             
      Bile Duct, Hyperplasia               | 2  2           2        2  1     3  2  2     2     2  2        4  1  4   |             
      Centrilobular, Necrosis              |       2                          3        2     1                        |             
                                            __________________________________________________________________________|             
   Mesentery                               |    +           +                          +        +              +      |             
      Artery, Mineralization               |                                                                          |             
      Fat, Hemorrhage                      |                                                                          |             
      Fat, Inflammation, Chronic Active    |                                                                   2      |             
      Fat, Necrosis                        |    2           2                                   2                     |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |    3     1              2        1           2  2        2        2      |             
      Basophilic Focus                     |                               X        X                                 |             
      Hyperplasia                          |                            2                             1        2      |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrosis                             |                                                                          |             
      Hyperplasia, Squamous                |                                                                          |             
      Necrosis                             |       3           2              1                          3            |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Mineralization                       |                                                                          |             
      Necrosis                             |    1  2                                            1                     |             
                                            __________________________________________________________________________|             
   Tongue                                  |                                                             +            |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  54                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 7| 4| 7| 0| 7| 7| 6| 6| 7| 6| 5| 7| 7| 7| 7| 6| 6| 7| 7| 6| 2| 5| 7| 7|             
                             DAY ON TEST   | 8| 2| 7| 3| 2| 3| 3| 2| 6| 3| 8| 8| 3| 3| 2| 2| 1| 8| 0| 3| 2| 2| 6| 3| 3|             
                                           | 8| 1| 8| 3| 6| 3| 4| 2| 4| 4| 5| 8| 3| 4| 7| 3| 8| 1| 9| 3| 1| 2| 6| 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|             
   FISCHER 344 RATS 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|             
    7000 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|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |             
                                           |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Blood Vessel                            |                                                                          |             
      Aorta, Mineralization                |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cardiomyopathy                       | 2  2     3     3  2  3  2  2           2     3  1  2  2  2  2     2  2  2|             
      Artery, Mineralization               |                                                                          |             
      Atrium, Thrombosis                   |       2                                   4           3                  |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |                                                                   3      |             
      Degeneration, Cystic                 |                                                                          |             
      Hyperplasia                          |    2  2  1     2  1  2  2  2                 2           2  2        2   |             
      Hypertrophy                          |                                                                          |             
      Thrombosis                           |                                           2                              |             
      Vacuolization Cytoplasmic            |    2                          2                                          |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |          3     3  2  2        2  2  2     1              2           2   |             
      Thrombosis                           |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  M  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |                   3                                   4           1     2|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +|             
      Pars Distalis, Hyperplasia           |       2                          4        3        2  3                  |             
      Pars Intermedia, Hyperplasia         |                                                                          |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      C-Cell, Hyperplasia                  | 1  1  2  1     1  2  1     2  1  2        1  1        2     1        1  1|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Peritoneum                              |       +                                   +        M                     |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |    3                                                                     |             
      Inflammation, Chronic Active         |                                                                          |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hyperplasia                          |    3     3     2  2        4        2  2           2     2  1            |             
      Inflammation, Chronic Active         |                3  2                                         1     2      |             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  55                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 7| 4| 7| 0| 7| 7| 6| 6| 7| 6| 5| 7| 7| 7| 7| 6| 6| 7| 7| 6| 2| 5| 7| 7|             
                             DAY ON TEST   | 8| 2| 7| 3| 2| 3| 3| 2| 6| 3| 8| 8| 3| 3| 2| 2| 1| 8| 0| 3| 2| 2| 6| 3| 3|             
                                           | 8| 1| 8| 3| 6| 3| 4| 2| 4| 4| 5| 8| 3| 4| 7| 3| 8| 1| 9| 3| 1| 2| 6| 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|             
   FISCHER 344 RATS 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|             
    7000 PPM                               | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Myelofibrosis                        |                                                                          |             
      Necrosis                             |                                           2                              |             
                                            __________________________________________________________________________|             
   Lymph Node                              | +              +                       +        +                    +   |             
      Renal, Hemorrhage                    |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  M  +  +  +  +  +  M  M  +  M  +  M  +  +  M  M  +  +  M  +  +  M|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  M  +  +  +  +  +  +  M  +  +  +  M  +  M  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Infiltration Cellular, Plasma Cell   |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  M  +  M  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Depletion Cellular                   |                                                                          |             
      Fibrosis                             |                3  2  3  2        3  2  2  3           1           3     2|             
      Hematopoietic Cell Proliferation     |       3                                   3                              |             
      Necrosis                             |                                                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +|             
      Atrophy                              |             3                                                            |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  M  +  +  +  +  +  +  +  M  +  +  M  +  +  +  +  +  +  +  +  +|             
      Galactocele                          |                                                             2            |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst Epithelial Inclusion            |                                  X           X                           |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Fibrous Osteodystrophy               |                                                    1                     |             
      Hyperostosis                         |                                  1  1                                    |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Inflammation, Chronic Active         |                   1        1  1     1     1  1                       2  1|             
      Mineralization                       |                                                                          |             
      Thrombosis                           |                                                                          |             
      Alveolar Epithelium, Hyperplasia     |       2        1        1                    2           1               |             
      Artery, Mediastinum, Mineralization  |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Foreign Body                         |                                        X                                 |             
      Inflammation, Suppurative            |                   2                    2              1     1  2         |             
      Thrombosis                           |       4                                   3     1                        |             
      Olfactory Epithelium, Atrophy        |                               2                             2            |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  56                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 5| 7| 4| 7| 0| 7| 7| 6| 6| 7| 6| 5| 7| 7| 7| 7| 6| 6| 7| 7| 6| 2| 5| 7| 7|             
                             DAY ON TEST   | 8| 2| 7| 3| 2| 3| 3| 2| 6| 3| 8| 8| 3| 3| 2| 2| 1| 8| 0| 3| 2| 2| 6| 3| 3|             
                                           | 8| 1| 8| 3| 6| 3| 4| 2| 4| 4| 5| 8| 3| 4| 7| 3| 8| 1| 9| 3| 1| 2| 6| 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|             
   FISCHER 344 RATS 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|             
    7000 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                 |                                                                          |             
                                           |                                                                          |             
      Olfactory Epithelium, Metaplasia     |                                        2                                 |             
      Respiratory Epithelium, Hyperplasia  |    1                                                           1         |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                 +                        |             
      Cataract                             |                                                 3                        |             
      Retina, Atrophy                      |                                                 4                        |             
                                            __________________________________________________________________________|             
   Zymbal's Gland                          |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cyst                                 |          4                                                               |             
      Mineralization                       |                                                                          |             
      Nephropathy                          | 2  4  2  3     4  4  3  3  3  3  2  3  2  3  3  3  4  4  4  3  2  2  3  4|             
      Renal Tubule, Hyperplasia            |    4                       1                                             |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemorrhage                           |                                                                4         |             
      Inflammation, Acute                  |                                                                          |             
      Inflammation, Chronic Active         |                                                                          |             
      Necrosis                             |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  57                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 6| 3| 7| 7| 6| 6| 7| 5| 7| 5| 6| 7| 5| 6| 6| 7| 7| 5| 6| 7| 5| 6| 6|            |
                             DAY ON TEST   | 3| 1| 1| 6| 0| 3| 3| 8| 3| 4| 3| 8| 6| 3| 1| 8| 6| 2| 3| 8| 6| 2| 6| 6| 9|            |
                                           | 3| 2| 1| 1| 8| 3| 0| 6| 3| 8| 3| 1| 8| 4| 7| 0| 7| 7| 3| 1| 7| 1| 0| 4| 1|      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     |
   FISCHER 344 RATS 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     |
    7000 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        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Inflammation, Acute                  |                                                                2         |      1  2.0|
      Necrosis                             |                            1                                             |      2  1.0|
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Angiectasis                          |                1                                                         |      3  1.7|
      Basophilic Focus                     | X     X     X           X     X        X  X                    X         |     16     |
      Clear Cell Focus                     |                X  X     X                             X        X         |      8     |
      Degeneration, Cystic                 |       1     3  1  2  2  2     1                                2     1  1|     17  1.9|
      Eosinophilic Focus                   |                                                 X                        |      3     |
      Fatty Change                         |                   1                                      1  1           2|     11  1.9|
      Hematopoietic Cell Proliferation     |                                                                          |      1  3.0|
      Hepatodiaphragmatic Nodule           |                               X                                   X      |      4     |
      Infarct                              |                                                                          |      1  4.0|
      Mixed Cell Focus                     |                         X                                                |      1     |
      Necrosis                             |                                                                          |      1  2.0|
      Regeneration                         |    4     2                                                           4   |      6  3.2|
      Artery, Inflammation, Chronic Active |                                                                          |      1  4.0|
      Bile Duct, Hyperplasia               | 3  3  2     1     1  2  1     2     2           1  1  1  2  1        3   |     29  2.0|
      Centrilobular, Necrosis              |          2                          1        1  3                    2   |      9  1.9|
                                            __________________________________________________________________________|____________|
   Mesentery                               | +           +  +                             +     +        +            |  11        |
      Artery, Mineralization               | 1                                                           3            |      2  2.0|
      Fat, Hemorrhage                      |             3                                                            |      1  3.0|
      Fat, Inflammation, Chronic Active    |                                                                          |      1  2.0|
      Fat, Necrosis                        |                2                             2     2                     |      6  2.0|
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |             2              2           2           2     2  1           2|     15  1.9|
      Basophilic Focus                     |                                                       X                  |      3     |
      Hyperplasia                          |                               4           2           4              2   |      7  2.4|
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrosis                             |                   4                                                      |      1  4.0|
      Hyperplasia, Squamous                |                                                    1                     |      1  1.0|
      Necrosis                             |       2                    2                    3  1     3     2     3  3|     12  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  58                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 6| 3| 7| 7| 6| 6| 7| 5| 7| 5| 6| 7| 5| 6| 6| 7| 7| 5| 6| 7| 5| 6| 6|            |
                             DAY ON TEST   | 3| 1| 1| 6| 0| 3| 3| 8| 3| 4| 3| 8| 6| 3| 1| 8| 6| 2| 3| 8| 6| 2| 6| 6| 9|            |
                                           | 3| 2| 1| 1| 8| 3| 0| 6| 3| 8| 3| 1| 8| 4| 7| 0| 7| 7| 3| 1| 7| 1| 0| 4| 1|      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     |
   FISCHER 344 RATS 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     |
    7000 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 - cont                  |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Mineralization                       | 3           3                                               4  2         |      4  3.0|
      Necrosis                             |       1  1                 1                    2        2     2         |      9  1.4|
                                            __________________________________________________________________________|____________|
   Tongue                                  |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Blood Vessel                            | +           +                                               +            |   3        |
      Aorta, Mineralization                | 3           4                                               4            |      3  3.7|
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cardiomyopathy                       | 3     2     3  2  1  2  2  2  2  2  2  2  1  2     1  2  1  3  4  2      |     38  2.1|
      Artery, Mineralization               | 3           3                                               4  3         |      4  3.3|
      Atrium, Thrombosis                   |             2                                   2                        |      5  2.6|
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Atrophy                              |                                                                          |      1  3.0|
      Degeneration, Cystic                 |                                        3                                 |      1  3.0|
      Hyperplasia                          |             2  2     2  2              2  2     1                       1|     20  1.8|
      Hypertrophy                          |             4           2        2                    2                  |      4  2.5|
      Thrombosis                           |                                                                          |      1  2.0|
      Vacuolization Cytoplasmic            | 3                    2                       2                       2   |      6  2.2|
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |       2        2     2  1        1  3  3  3        4  2  3               |     21  2.2|
      Thrombosis                           |                                                 2                        |      1  2.0|
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      | +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Hyperplasia                          |       4     2           1  3           2     3     3        4  2         |     13  2.6|
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Pars Distalis, Hyperplasia           | 3           3        2     2                    3                    3   |     11  2.7|
      Pars Intermedia, Hyperplasia         |                                                             4            |      1  4.0|
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      C-Cell, Hyperplasia                  | 2  3     1  2  1  1  1  3           2     1  1  2  1  1  1     1  3     1|     34  1.4|
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Peritoneum                              |                                                 +                        |   3        |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  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  59                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 6| 3| 7| 7| 6| 6| 7| 5| 7| 5| 6| 7| 5| 6| 6| 7| 7| 5| 6| 7| 5| 6| 6|            |
                             DAY ON TEST   | 3| 1| 1| 6| 0| 3| 3| 8| 3| 4| 3| 8| 6| 3| 1| 8| 6| 2| 3| 8| 6| 2| 6| 6| 9|            |
                                           | 3| 2| 1| 1| 8| 3| 0| 6| 3| 8| 3| 1| 8| 4| 7| 0| 7| 7| 3| 1| 7| 1| 0| 4| 1|      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     |
   FISCHER 344 RATS 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     |
    7000 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|            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
      Hyperplasia                          |                                                                          |      1  3.0|
      Inflammation, Chronic Active         |       2     3                                               2            |      3  2.3|
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hyperplasia                          |       3                       2  1                       2  2     1     2|     17  2.1|
      Inflammation, Chronic Active         | 4  2                                                                     |      6  2.3|
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Myelofibrosis                        |             2                                                            |      1  2.0|
      Necrosis                             |                         2                                                |      2  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node                              |          +                 +                 +                       +   |   9        |
      Renal, Hemorrhage                    |                            2                                             |      1  2.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  M  +  +  +  +  +  M  +  M  M  +  M  +  +  +  +  M  +  +  +  +  +  +  +|  35        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M|  44        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Infiltration Cellular, Plasma Cell   |                                           3                              |      1  3.0|
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  M  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +|  44        |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Depletion Cellular                   |                                                                         3|      1  3.0|
      Fibrosis                             | 1  3        3           3     3     2  1           2  2  2           2   |     22  2.3|
      Hematopoietic Cell Proliferation     |                                  2        4     3                        |      5  3.0|
      Necrosis                             |                                     3                                    |      1  3.0|
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  M  +|  47        |
      Atrophy                              |                                                                          |      1  3.0|
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  M  +  +  +  +  +  +  +  M  +  +  +  +  M  +  +  +  +  +  +  +  +|  44        |
      Galactocele                          |                3  2                                                      |      3  2.3|
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst Epithelial Inclusion            |                                                                          |      2     |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Fibrous Osteodystrophy               | 2     2     2                                      2        4  2         |      7  2.1|
      Hyperostosis                         |                                                                          |      2  1.0|
 _____________________________________________________________________________________________________________________|            |
 NERVOUS 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  60                                                               
NTP Experiment-Test: 05135-07                  NONNEOPLASTIC LESIONS BY INDIVIDUAL ANIMAL                         Report: PEIRPT09
Study Type: CHRONIC                                              ISOPRENE                                         Date: 09/24/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:01:23  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 6| 3| 7| 7| 6| 6| 7| 5| 7| 5| 6| 7| 5| 6| 6| 7| 7| 5| 6| 7| 5| 6| 6|            |
                             DAY ON TEST   | 3| 1| 1| 6| 0| 3| 3| 8| 3| 4| 3| 8| 6| 3| 1| 8| 6| 2| 3| 8| 6| 2| 6| 6| 9|            |
                                           | 3| 2| 1| 1| 8| 3| 0| 6| 3| 8| 3| 1| 8| 4| 7| 0| 7| 7| 3| 1| 7| 1| 0| 4| 1|      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     |
   FISCHER 344 RATS 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     |
    7000 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|            |
 __________________________________________________________________________________________________________________________________ 
 NERVOUS SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Inflammation, Chronic Active         |                1     1        1                       1        1  1     1|     15  1.1|
      Mineralization                       |             2                                               4            |      2  3.0|
      Thrombosis                           |                                                 2                        |      1  2.0|
      Alveolar Epithelium, Hyperplasia     | 1           4  1              1           2                              |     10  1.6|
      Artery, Mediastinum, Mineralization  | 3                                                           3            |      2  3.0|
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Foreign Body                         |                X                                                         |      2     |
      Inflammation, Suppurative            |             2  1     2                    1                              |      9  1.6|
      Thrombosis                           |                      2                          4                        |      5  2.8|
      Olfactory Epithelium, Atrophy        |                                                                          |      2  2.0|
      Olfactory Epithelium, Metaplasia     |                                        1                                 |      2  1.5|
      Respiratory Epithelium, Hyperplasia  |                                                                          |      2  1.0|
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                               +                                          |   2        |
      Cataract                             |                               3                                          |      2  3.0|
      Retina, Atrophy                      |                               3                                          |      2  3.5|
                                            __________________________________________________________________________|____________|
   Zymbal's Gland                          |                                  +                                       |   1        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cyst                                 |                                        2                                 |      2  3.0|
      Mineralization                       | 2           2                                               3            |      3  2.3|
      Nephropathy                          | 4  2  4  1  4  4  4  3  4  4  3  2  3  4  2  4  3  4  3  2  4  4  2  4  4|     49  3.2|
      Renal Tubule, Hyperplasia            |       2     3  4           2                       4           4         |      8  3.0|
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hemorrhage                           |                                                                          |      1  4.0|
      Inflammation, Acute                  |    4                                                                     |      1  4.0|
      Inflammation, Chronic Active         | 4                                                                        |      1  4.0|
      Necrosis                             | 3                                                                        |      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  61                                                               
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NTP is located at the National Institute of Environmental Health Sciences, part of the National Institutes of Health.