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https://ntp.niehs.nih.gov/go/5154

TDMS Study 88070-03 Pathology Tables

NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25

                                                           CORE STUDY




       Facility:  Battelle Northwest

       Chemical CAS #:  115-11-0007

       Lock Date:  10/05/95

       Cage Range:  All

       Reasons For Removal:    All

       Removal Date Range:     All

       Treatment Groups:       Include All


































a  Number of animals examined microscopically at site and number of animals with lesion

                                                              Page   1

NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially In Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                21           25           15           23                                     
    Natural Death                                      6            5            2            5                                     
    Accidently Killed                                               1                                                               
  Survivors                                                                                                                         
    Terminal Sacrifice                                23           19           33           22                                     
  Animals Examined Microscopically                    50           50           50           50                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Esophagus                                          (50)         (50)         (50)         (50)                                   
      Inflammation, Suppurative                                                  1 (2%)                                             
   Intestine Large, Colon                             (49)         (50)         (49)         (49)                                   
      Inflammation, Acute                                           1 (2%)                                                          
      Parasite Metazoan                                5 (10%)                   1 (2%)       1 (2%)                                
   Intestine Large, Rectum                            (47)         (47)         (47)         (48)                                   
      Parasite Metazoan                                8 (17%)      5 (11%)      5 (11%)      3 (6%)                                
   Intestine Large, Cecum                             (48)         (49)         (48)         (49)                                   
      Inflammation, Acute                              1 (2%)       1 (2%)                                                          
      Parasite Metazoan                                5 (10%)      2 (4%)       4 (8%)       3 (6%)                                
   Intestine Small, Jejunum                           (47)         (47)         (48)         (47)                                   
      Inflammation, Acute                                           1 (2%)                                                          
      Necrosis                                                                   1 (2%)                                             
   Intestine Small, Ileum                             (46)         (47)         (48)         (47)                                   
      Inflammation, Acute                                           1 (2%)                                                          
      Parasite Metazoan                                                                       1 (2%)                                
   Liver                                              (50)         (50)         (50)         (49)                                   
      Angiectasis                                      1 (2%)       3 (6%)       4 (8%)       3 (6%)                                
      Basophilic Focus                                36 (72%)     36 (72%)     43 (86%)     36 (73%)                               
      Clear Cell Focus                                 6 (12%)      9 (18%)     12 (24%)      5 (10%)                               
      Cytomegaly                                                                              1 (2%)                                
      Degeneration, Cystic                                                       2 (4%)                                             
      Degeneration, Fatty                             12 (24%)     10 (20%)     12 (24%)     12 (24%)                               
      Eosinophilic Focus                               6 (12%)      6 (12%)      5 (10%)      9 (18%)                               
      Hematopoietic Cell Proliferation                                           1 (2%)                                             
      Hepatodiaphragmatic Nodule                       4 (8%)       7 (14%)      5 (10%)      3 (6%)                                
      Inflammation, Granulomatous                      1 (2%)                                                                       
      Mitotic Alteration                                            1 (2%)                                                          
      Mixed Cell Focus                                 7 (14%)     11 (22%)      9 (18%)      8 (16%)                               
      Necrosis                                         2 (4%)                    2 (4%)                                             
      Regeneration                                     1 (2%)       1 (2%)       2 (4%)       3 (6%)                                
      Thrombosis                                       1 (2%)                                                                       
      Bile Duct, Hyperplasia                           9 (18%)      5 (10%)      7 (14%)     10 (20%)                               
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    2                                                              
NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - CONT                                                                                                            
      Centrilobular, Necrosis                          4 (8%)       4 (8%)       5 (10%)      9 (18%)                               
   Mesentery                                          (8)          (10)         (12)         (7)                                    
      Thrombosis                                                                 1 (8%)                                             
      Artery, Inflammation, Chronic Active                                                    2 (29%)                               
      Fat, Hemorrhage                                  1 (13%)                                                                      
      Fat, Necrosis                                    8 (100%)    10 (100%)    12 (100%)     6 (86%)                               
   Pancreas                                           (50)         (50)         (49)         (49)                                   
      Atrophy                                          9 (18%)     11 (22%)     17 (35%)     10 (20%)                               
      Basophilic Focus                                 1 (2%)       4 (8%)       3 (6%)       2 (4%)                                
      Hyperplasia                                                   1 (2%)       1 (2%)                                             
      Metaplasia, Hepatocyte                           1 (2%)                                                                       
   Salivary Glands                                    (50)         (50)         (50)         (50)                                   
      Atrophy                                                       1 (2%)                    1 (2%)                                
   Stomach, Forestomach                               (50)         (50)         (50)         (50)                                   
      Hyperplasia, Basal Cell                                       1 (2%)                                                          
      Inflammation, Acute                              1 (2%)                                                                       
      Mineralization                                   1 (2%)                                                                       
      Necrosis                                         7 (14%)      7 (14%)      6 (12%)      5 (10%)                               
   Stomach, Glandular                                 (50)         (50)         (50)         (49)                                   
      Mineralization                                                             1 (2%)                                             
      Necrosis                                         3 (6%)       2 (4%)       1 (2%)       1 (2%)                                
   Tongue                                                          (1)                       (1)                                    
      Hyperplasia, Squamous                                                                   1 (100%)                              
   Tooth                                                                        (1)                                                 
      Necrosis                                                                   1 (100%)                                           
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (50)         (50)         (49)         (50)                                   
      Cardiomyopathy                                  30 (60%)     29 (58%)     37 (76%)     31 (62%)                               
      Atrium, Thrombosis                                                         1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (50)         (50)         (49)         (49)                                   
      Atrophy                                                       1 (2%)                    1 (2%)                                
      Degeneration, Cystic                             2 (4%)       2 (4%)       4 (8%)       2 (4%)                                
      Hyperplasia                                     15 (30%)     16 (32%)     24 (49%)     21 (43%)                               
      Hypertrophy                                     11 (22%)      8 (16%)      9 (18%)      9 (18%)                               
      Necrosis                                         2 (4%)                    3 (6%)       1 (2%)                                
      Thrombosis                                                    1 (2%)                                                          
      Vacuolization Cytoplasmic                                                               1 (2%)                                
   Adrenal Medulla                                    (50)         (50)         (49)         (49)                                   
      Hyperplasia                                     10 (20%)      5 (10%)      6 (12%)     10 (20%)                               
   Islets, Pancreatic                                 (50)         (50)         (49)         (49)                                   
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    3                                                              
NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ENDOCRINE SYSTEM - CONT                                                                                                             
      Hyperplasia                                                   1 (2%)                                                          
   Pituitary Gland                                    (50)         (49)         (50)         (49)                                   
      Angiectasis                                                                1 (2%)                                             
      Pars Distalis, Angiectasis                                    1 (2%)                    1 (2%)                                
      Pars Distalis, Cyst                                                                     1 (2%)                                
      Pars Distalis, Hyperplasia                       7 (14%)      7 (14%)     11 (22%)      5 (10%)                               
   Thyroid Gland                                      (50)         (50)         (49)         (49)                                   
      C-Cell, Hyperplasia                             37 (74%)     34 (68%)     38 (78%)     35 (71%)                               
      Follicular Cell, Hyperplasia                                  2 (4%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Clitoral Gland                                     (50)         (49)         (47)         (48)                                   
      Hyperplasia                                      1 (2%)                    5 (11%)      1 (2%)                                
      Inflammation, Chronic Active                                               1 (2%)                                             
   Ovary                                              (50)         (50)         (50)         (50)                                   
      Cyst                                             9 (18%)      4 (8%)       4 (8%)       2 (4%)                                
      Inflammation, Granulomatous                                                1 (2%)                                             
   Uterus                                             (50)         (50)         (50)         (50)                                   
      Fibrosis                                                                   1 (2%)                                             
      Inflammation, Chronic Active                                                            1 (2%)                                
      Necrosis                                                                                1 (2%)                                
      Cervix, Hypertrophy                                           1 (2%)                                                          
   Vagina                                             (1)          (1)                       (1)                                    
      Inflammation, Suppurative                                                               1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (50)         (50)         (49)         (49)                                   
      Atrophy                                          1 (2%)       1 (2%)                    2 (4%)                                
      Hyperplasia, Histiocytic                                                                1 (2%)                                
      Hyperplasia, Reticulum Cell                                                1 (2%)                                             
   Lymph Node                                         (6)          (3)          (3)          (2)                                    
      Pancreatic, Ectasia                                           1 (33%)                                                         
   Lymph Node, Mandibular                             (44)         (46)         (47)         (47)                                   
      Infiltration Cellular, Plasma Cell                            1 (2%)                                                          
      Infiltration Cellular, Polymorphonuclear                                                1 (2%)                                
   Lymph Node, Mesenteric                             (50)         (50)         (49)         (49)                                   
      Infiltration Cellular, Plasma Cell                                         1 (2%)                                             
   Spleen                                             (50)         (50)         (49)         (50)                                   
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    4                                                              
NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - CONT                                                                                                         
      Accessory Spleen                                              1 (2%)                                                          
      Fibrosis                                                      3 (6%)       6 (12%)      2 (4%)                                
      Hematopoietic Cell Proliferation                 5 (10%)      2 (4%)       3 (6%)       2 (4%)                                
      Hemorrhage                                       1 (2%)                                 2 (4%)                                
      Inflammation, Granulomatous                                                             1 (2%)                                
      Necrosis                                         1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (50)         (50)         (50)         (50)                                   
      Galactocele                                      2 (4%)       2 (4%)       1 (2%)       2 (4%)                                
      Hyperplasia, Atypical                                                                   1 (2%)                                
      Inflammation, Acute                                                        1 (2%)                                             
      Inflammation, Chronic                            1 (2%)                                                                       
   Skin                                               (50)         (50)         (50)         (50)                                   
      Cyst Epithelial Inclusion                                     1 (2%)                                                          
      Hyperkeratosis                                   1 (2%)                                                                       
      Inflammation, Acute                                                        1 (2%)                                             
      Inflammation, Chronic Active                     1 (2%)                    1 (2%)       2 (4%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (50)         (50)         (50)         (50)                                   
      Hyperostosis                                     9 (18%)      7 (14%)     11 (22%)     15 (30%)                               
   Skeletal Muscle                                                                           (1)                                    
      Artery, Inflammation, Chronic                                                           1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (50)         (50)         (50)         (50)                                   
      Hemorrhage                                       1 (2%)                                                                       
      Artery, Inflammation, Chronic                                                           1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Larynx                                             (50)         (50)         (50)         (50)                                   
      Epiglottis, Metaplasia, Squamous                                                        2 (4%)                                
   Lung                                               (50)         (50)         (50)         (50)                                   
      Inflammation, Granulomatous                      7 (14%)      5 (10%)      9 (18%)     11 (22%)                               
      Inflammation, Suppurative                                     1 (2%)                                                          
      Alveolar Epithelium, Hyperplasia                 9 (18%)      9 (18%)      7 (14%)      6 (12%)                               
      Alveolus, Infiltration Cellular, Histiocyte                   1 (2%)                                                          
      Bronchiole, Hyperplasia                                                    1 (2%)                                             
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    5                                                              
NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
RESPIRATORY SYSTEM - CONT                                                                                                           
   Nose                                               (50)         (50)         (50)         (49)                                   
      Inflammation, Suppurative                        7 (14%)      2 (4%)       8 (16%)      8 (16%)                               
      Thrombosis                                       2 (4%)       3 (6%)       2 (4%)       3 (6%)                                
      Lateral Wall, Metaplasia, Squamous                                                      3 (6%)                                
      Olfactory Epithelium, Degeneration, Hyaline     44 (88%)     47 (94%)     48 (96%)     47 (96%)                               
      Respiratory Epithelium, Metaplasia, Squamous                  1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Eye                                                (4)          (4)          (6)          (4)                                    
      Cataract                                         4 (100%)     3 (75%)      6 (100%)     4 (100%)                              
      Retina, Atrophy                                  3 (75%)      3 (75%)      6 (100%)     4 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (50)         (50)         (49)         (49)                                   
      Infarct                                          1 (2%)                                 2 (4%)                                
      Nephropathy                                     46 (92%)     46 (92%)     46 (94%)     46 (94%)                               
      Renal Tubule, Hyperplasia                                     1 (2%)                                                          
   Urinary Bladder                                    (50)         (49)         (49)         (49)                                   
      Hemorrhage                                                                              1 (2%)                                
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    6                                                              
NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially In Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                39           40           37           41                                     
    Natural Death                                      4            5            7            1                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                 7            5            6            8                                     
  Animals Examined Microscopically                    50           50           50           50                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Esophagus                                          (50)         (50)         (50)         (50)                                   
      Inflammation, Suppurative                        1 (2%)       1 (2%)       2 (4%)                                             
   Intestine Large, Colon                             (49)         (48)         (48)         (49)                                   
      Diverticulum                                                               1 (2%)                                             
      Mineralization                                                                          1 (2%)                                
      Parasite Metazoan                                4 (8%)       1 (2%)       2 (4%)       2 (4%)                                
   Intestine Large, Rectum                            (47)         (49)         (49)         (49)                                   
      Necrosis                                                                   1 (2%)                                             
      Parasite Metazoan                                             2 (4%)       3 (6%)       3 (6%)                                
   Intestine Large, Cecum                             (48)         (47)         (49)         (49)                                   
      Inflammation, Acute                                                                     1 (2%)                                
      Necrosis                                                                   2 (4%)       1 (2%)                                
      Parasite Metazoan                                3 (6%)       2 (4%)       6 (12%)      4 (8%)                                
   Intestine Small, Duodenum                          (49)         (49)         (50)         (49)                                   
      Necrosis                                         2 (4%)                    2 (4%)                                             
   Liver                                              (50)         (50)         (50)         (50)                                   
      Angiectasis                                      3 (6%)       1 (2%)                    1 (2%)                                
      Basophilic Focus                                17 (34%)     14 (28%)     14 (28%)     22 (44%)                               
      Clear Cell Focus                                 3 (6%)       1 (2%)       3 (6%)       3 (6%)                                
      Cyst                                                                                    2 (4%)                                
      Degeneration, Cystic                            13 (26%)     10 (20%)     14 (28%)     16 (32%)                               
      Degeneration, Fatty                             14 (28%)     18 (36%)     18 (36%)     14 (28%)                               
      Eosinophilic Focus                               6 (12%)      2 (4%)       5 (10%)      5 (10%)                               
      Hepatodiaphragmatic Nodule                       4 (8%)       2 (4%)       1 (2%)       2 (4%)                                
      Inflammation, Granulomatous                                                1 (2%)                                             
      Mineralization                                                             1 (2%)       1 (2%)                                
      Mixed Cell Focus                                 3 (6%)       2 (4%)       4 (8%)                                             
      Necrosis                                                      2 (4%)       3 (6%)       1 (2%)                                
      Regeneration                                                                            2 (4%)                                
      Thrombosis                                       2 (4%)                                                                       
      Vacuolization Cytoplasmic, Focal                                           1 (2%)                                             
      Bile Duct, Hyperplasia                          23 (46%)     27 (54%)     23 (46%)     29 (58%)                               
      Centrilobular, Necrosis                         10 (20%)      9 (18%)     10 (20%)     15 (30%)                               
   Mesentery                                          (15)         (10)         (8)          (11)                                   
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    7                                                              
NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - CONT                                                                                                            
      Mineralization                                   1 (7%)                                                                       
      Pigmentation                                     1 (7%)                                                                       
      Artery, Inflammation, Chronic Active                          1 (10%)                   1 (9%)                                
      Artery, Mineralization                           1 (7%)       1 (10%)                   1 (9%)                                
      Fat, Hemorrhage                                               1 (10%)                   1 (9%)                                
      Fat, Necrosis                                   14 (93%)      9 (90%)      8 (100%)     8 (73%)                               
   Pancreas                                           (50)         (50)         (50)         (50)                                   
      Atrophy                                         22 (44%)     17 (34%)     26 (52%)     18 (36%)                               
      Basophilic Focus                                 1 (2%)       1 (2%)       1 (2%)       2 (4%)                                
      Hyperplasia                                      4 (8%)       3 (6%)       4 (8%)       3 (6%)                                
      Artery, Inflammation                                                                    1 (2%)                                
      Artery, Mineralization                                                     1 (2%)       1 (2%)                                
   Salivary Glands                                    (50)         (50)         (50)         (50)                                   
      Artery, Mineralization                                        1 (2%)                                                          
   Stomach, Forestomach                               (50)         (50)         (50)         (50)                                   
      Inflammation, Chronic                                                                   1 (2%)                                
      Mineralization                                   1 (2%)       1 (2%)       1 (2%)       1 (2%)                                
      Necrosis                                        17 (34%)     16 (32%)     19 (38%)     10 (20%)                               
      Perforation                                                                1 (2%)                                             
   Stomach, Glandular                                 (50)         (49)         (50)         (50)                                   
      Mineralization                                   3 (6%)       3 (6%)       5 (10%)      4 (8%)                                
      Necrosis                                         8 (16%)      5 (10%)     11 (22%)      9 (18%)                               
   Tongue                                             (1)                                    (1)                                    
      Necrosis                                         1 (100%)                                                                     
   Tooth                                              (2)          (3)          (1)          (1)                                    
      Developmental Malformation                       2 (100%)     1 (33%)                   1 (100%)                              
      Inflammation, Chronic Active                                  2 (67%)      1 (100%)                                           
      Necrosis                                                      1 (33%)                                                         
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Blood Vessel                                       (2)          (2)          (2)          (2)                                    
      Aorta, Mineralization                            2 (100%)     2 (100%)     2 (100%)     2 (100%)                              
   Heart                                              (50)         (50)         (50)         (50)                                   
      Cardiomyopathy                                  39 (78%)     39 (78%)     41 (82%)     41 (82%)                               
      Artery, Mineralization                           3 (6%)       4 (8%)       4 (8%)       5 (10%)                               
      Atrium, Thrombosis                                            1 (2%)       3 (6%)       6 (12%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (50)         (49)         (50)         (50)                                   
      Atrophy                                          1 (2%)                                                                       
      Degeneration, Cystic                                                                    1 (2%)                                
      Hyperplasia                                     21 (42%)     23 (47%)     24 (48%)     23 (46%)                               
      Hypertrophy                                      7 (14%)      6 (12%)      7 (14%)      4 (8%)                                
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    8                                                              
NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ENDOCRINE SYSTEM - CONT                                                                                                             
      Necrosis                                                      1 (2%)       1 (2%)                                             
      Vacuolization Cytoplasmic                                     1 (2%)       3 (6%)                                             
   Adrenal Medulla                                    (50)         (49)         (50)         (50)                                   
      Atrophy                                          1 (2%)                                                                       
      Hyperplasia                                     14 (28%)     18 (37%)     28 (56%)     15 (30%)                               
      Bilateral, Hyperplasia                           1 (2%)       1 (2%)       2 (4%)       3 (6%)                                
   Islets, Pancreatic                                 (50)         (49)         (50)         (50)                                   
      Hyperplasia                                                   4 (8%)       3 (6%)       3 (6%)                                
   Parathyroid Gland                                  (49)         (50)         (49)         (47)                                   
      Hyperplasia                                      9 (18%)     11 (22%)     12 (24%)     10 (21%)                               
   Pituitary Gland                                    (50)         (49)         (50)         (49)                                   
      Angiectasis                                      1 (2%)                                                                       
      Pars Distalis, Hyperplasia                       5 (10%)      5 (10%)      3 (6%)       6 (12%)                               
      Pars Distalis, Thrombosis                        1 (2%)                                                                       
   Thyroid Gland                                      (48)         (48)         (48)         (50)                                   
      C-Cell, Hyperplasia                             32 (67%)     36 (75%)     34 (71%)     26 (52%)                               
      Follicular Cell, Hyperplasia                                  2 (4%)                    1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Epididymis                                         (50)         (50)         (50)         (50)                                   
      Granuloma Sperm                                                            1 (2%)                                             
   Preputial Gland                                    (50)         (50)         (49)         (50)                                   
      Hyperplasia                                      2 (4%)       1 (2%)       2 (4%)       1 (2%)                                
      Inflammation, Acute                                           1 (2%)                                                          
      Inflammation, Chronic Active                     3 (6%)       3 (6%)                    2 (4%)                                
   Prostate                                           (50)         (49)         (50)         (50)                                   
      Hyperplasia                                      6 (12%)      6 (12%)      6 (12%)      7 (14%)                               
      Inflammation, Chronic Active                     4 (8%)       4 (8%)       4 (8%)       6 (12%)                               
   Seminal Vesicle                                    (50)         (47)         (50)         (50)                                   
      Inflammation, Chronic Active                     1 (2%)                    1 (2%)                                             
      Mineralization                                                1 (2%)       1 (2%)       1 (2%)                                
   Testes                                             (50)         (50)         (50)         (50)                                   
      Atrophy                                          7 (14%)                   3 (6%)       5 (10%)                               
      Necrosis                                                      3 (6%)                    1 (2%)                                
      Artery, Inflammation, Chronic Active             4 (8%)       2 (4%)       1 (2%)       3 (6%)                                
      Artery, Mineralization                                                                  1 (2%)                                
      Interstitial Cell, Hyperplasia                   4 (8%)       4 (8%)       4 (8%)       2 (4%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    9                                                              
NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (50)         (48)         (50)         (50)                                   
      Necrosis                                                                                1 (2%)                                
   Lymph Node                                         (4)          (11)         (10)         (10)                                   
      Hemorrhage                                       1 (25%)                                                                      
      Iliac, Ectasia                                                             1 (10%)                                            
      Renal, Hemorrhage                                             1 (9%)                                                          
   Lymph Node, Mandibular                             (47)         (47)         (49)         (49)                                   
      Hemorrhage                                                                 1 (2%)                                             
      Infiltration Cellular, Plasma Cell               1 (2%)       1 (2%)                    1 (2%)                                
      Infiltration Cellular, Polymorphonuclear         1 (2%)                                                                       
   Lymph Node, Mesenteric                             (50)         (50)         (49)         (50)                                   
      Ectasia                                          1 (2%)                    1 (2%)                                             
   Lymph Node, Mediastinal                            (46)         (42)         (44)         (45)                                   
      Hemorrhage                                                    1 (2%)                                                          
   Spleen                                             (50)         (49)         (50)         (50)                                   
      Accessory Spleen                                 1 (2%)                    1 (2%)       1 (2%)                                
      Fibrosis                                         9 (18%)      6 (12%)     10 (20%)     11 (22%)                               
      Hematopoietic Cell Proliferation                 2 (4%)       5 (10%)      4 (8%)       3 (6%)                                
      Hemorrhage                                       1 (2%)       1 (2%)                    1 (2%)                                
      Necrosis                                                                   2 (4%)       1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (41)         (41)         (40)         (44)                                   
      Galactocele                                      2 (5%)       7 (17%)      1 (3%)       4 (9%)                                
      Hyperplasia, Atypical                                         1 (2%)                                                          
      Inflammation, Chronic                            1 (2%)                    1 (3%)       1 (2%)                                
   Skin                                               (50)         (50)         (50)         (50)                                   
      Cyst Epithelial Inclusion                                     1 (2%)                                                          
      Hyperkeratosis                                   1 (2%)                    1 (2%)       1 (2%)                                
      Inflammation, Chronic Active                     1 (2%)                    1 (2%)       5 (10%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (50)         (50)         (50)         (50)                                   
      Fibrous Osteodystrophy                           9 (18%)      7 (14%)      9 (18%)      6 (12%)                               
      Hyperostosis                                                               1 (2%)       1 (2%)                                
   Skeletal Muscle                                    (1)                       (1)          (1)                                    
      Mineralization                                                                          1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   10                                                              
NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (50)         (50)         (50)         (50)                                   
      Angiectasis                                                   1 (2%)                                                          
      Hemorrhage                                                                 1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Larynx                                             (50)         (49)         (50)         (49)                                   
      Necrosis                                         1 (2%)       1 (2%)                                                          
      Epiglottis, Metaplasia, Squamous                                                        1 (2%)                                
   Lung                                               (50)         (50)         (50)         (50)                                   
      Cyst                                             1 (2%)                                                                       
      Hemorrhage                                       1 (2%)       1 (2%)                    1 (2%)                                
      Inflammation, Granulomatous                      9 (18%)      3 (6%)       1 (2%)       5 (10%)                               
      Inflammation, Suppurative                        1 (2%)                                 1 (2%)                                
      Metaplasia, Squamous                             1 (2%)                                                                       
      Mineralization                                   2 (4%)       2 (4%)       1 (2%)       1 (2%)                                
      Alveolar Epithelium, Hyperplasia                 9 (18%)      5 (10%)      7 (14%)      5 (10%)                               
      Alveolus, Infiltration Cellular, Histiocyte                                1 (2%)                                             
      Artery, Mediastinum, Mineralization              2 (4%)       2 (4%)       1 (2%)       1 (2%)                                
      Bronchiole, Hyperplasia                                                                 1 (2%)                                
      Mediastinum, Inflammation, Suppurative                                     1 (2%)                                             
   Nose                                               (49)         (49)         (50)         (49)                                   
      Inflammation, Suppurative                       14 (29%)     11 (22%)     16 (32%)      9 (18%)                               
      Thrombosis                                       4 (8%)       7 (14%)     10 (20%)      6 (12%)                               
      Lateral Wall, Metaplasia, Squamous               1 (2%)                                                                       
      Olfactory Epithelium, Atrophy                    3 (6%)                                                                       
      Olfactory Epithelium, Degeneration, Hyaline     43 (88%)     45 (92%)     46 (92%)     49 (100%)                              
      Olfactory Epithelium, Metaplasia                 4 (8%)                                                                       
      Respiratory Epithelium, Metaplasia, Squamous     1 (2%)                                                                       
   Trachea                                            (50)         (50)         (50)         (50)                                   
      Inflammation, Suppurative                        2 (4%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Eye                                                (3)                       (4)                                                 
      Cataract                                         2 (67%)                   3 (75%)                                            
      Degeneration                                     1 (33%)                                                                      
      Inflammation, Chronic Active                                               2 (50%)                                            
      Retina, Atrophy                                  1 (33%)                   3 (75%)                                            
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   11                                                              
NTP Experiment-Test: 88070-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:10:25  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (50)         (50)         (50)         (50)                                   
      Cyst                                             3 (6%)       3 (6%)                    1 (2%)                                
      Hydronephrosis                                   1 (2%)                                                                       
      Hyperplasia, Oncocytic                           1 (2%)                                                                       
      Infarct                                                       1 (2%)                    1 (2%)                                
      Mineralization                                   4 (8%)       2 (4%)       3 (6%)       4 (8%)                                
      Nephropathy                                     50 (100%)    48 (96%)     50 (100%)    50 (100%)                              
      Papilla, Necrosis                                                          1 (2%)                                             
      Pelvis, Inflammation, Acute                      1 (2%)       1 (2%)       2 (4%)       1 (2%)                                
      Renal Tubule, Hyperplasia                        2 (4%)       4 (8%)       3 (6%)       4 (8%)                                
      Transitional Epithelium, Hyperplasia             1 (2%)                                 2 (4%)                                
   Urinary Bladder                                    (50)         (49)         (50)         (50)                                   
      Hemorrhage                                       1 (2%)                    1 (2%)                                             
      Inflammation, Chronic Active                                  1 (2%)       3 (6%)       2 (4%)                                
      Inflammation, Suppurative                        1 (2%)                                                                       
      Necrosis                                         1 (2%)                                                                       
      Transitional Epithelium, Hyperplasia             1 (2%)       1 (2%)       1 (2%)       3 (6%)                                
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   12                                                              
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                             ----------              END OF REPORT             ----------                                           
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