Skip to Main Navigation
Skip to Page Content
Share This:
https://ntp.niehs.nih.gov/go/5168

TDMS Study 88070-04 Pathology Tables

NTP Experiment-Test: 88070-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:10:34

                                                           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: 88070-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:10:34  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially In Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                13           16            6           13                                     
    Natural Death                                      5            3            5            4                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                32           31           39           33                                     
  Animals Examined Microscopically                    50           50           50           50                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Intestine Large, Rectum                            (45)         (45)         (47)         (48)                                   
      Artery, Inflammation, Chronic Active                                                    1 (2%)                                
   Intestine Small, Ileum                             (46)         (48)         (46)         (47)                                   
      Inflammation, Chronic Active                                               1 (2%)                                             
   Liver                                              (47)         (50)         (50)         (50)                                   
      Angiectasis                                      1 (2%)       1 (2%)                    1 (2%)                                
      Basophilic Focus                                 4 (9%)       4 (8%)       2 (4%)       5 (10%)                               
      Clear Cell Focus                                              4 (8%)       3 (6%)       4 (8%)                                
      Cyst                                             1 (2%)                                 1 (2%)                                
      Degeneration, Fatty                              2 (4%)       1 (2%)       5 (10%)      1 (2%)                                
      Eosinophilic Focus                              17 (36%)     11 (22%)     12 (24%)      7 (14%)                               
      Hematopoietic Cell Proliferation                                           1 (2%)       1 (2%)                                
      Mixed Cell Focus                                                                        1 (2%)                                
      Necrosis                                                      2 (4%)       3 (6%)       1 (2%)                                
      Tension Lipidosis                                1 (2%)       3 (6%)       1 (2%)                                             
      Bile Duct, Hyperplasia                                                     1 (2%)                                             
      Centrilobular, Necrosis                                                    1 (2%)       3 (6%)                                
   Mesentery                                          (7)          (8)          (8)          (10)                                   
      Artery, Inflammation                                          1 (13%)                   1 (10%)                               
      Fat, Inflammation, Chronic Active                                                       1 (10%)                               
      Fat, Necrosis                                    7 (100%)     6 (75%)      6 (75%)     10 (100%)                              
   Pancreas                                           (47)         (50)         (48)         (49)                                   
      Atrophy                                                                                 1 (2%)                                
      Basophilic Focus                                 1 (2%)       2 (4%)                                                          
      Lipomatosis                                      1 (2%)                                 1 (2%)                                
      Duct, Cyst                                       1 (2%)       1 (2%)                                                          
   Stomach, Forestomach                               (48)         (49)         (49)         (49)                                   
      Hyperplasia                                      2 (4%)       4 (8%)       1 (2%)       1 (2%)                                
      Inflammation, Acute                              1 (2%)       2 (4%)                                                          
   Stomach, Glandular                                 (46)         (48)         (48)         (49)                                   
      Necrosis                                                                   1 (2%)                                             
      Artery, Inflammation, Chronic Active                                                    1 (2%)                                
   Tooth                                                                        (1)          (1)                                    
      Malformation                                                               1 (100%)     1 (100%)                              
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    2                                                              
NTP Experiment-Test: 88070-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:10:34  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (50)         (50)         (50)         (50)                                   
      Cardiomyopathy                                  10 (20%)     10 (20%)     12 (24%)      8 (16%)                               
      Mineralization                                                1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (49)         (50)         (49)         (50)                                   
      Hematopoietic Cell Proliferation                 1 (2%)                    1 (2%)       1 (2%)                                
      Hyperplasia                                      3 (6%)       4 (8%)       3 (6%)       5 (10%)                               
      Hypertrophy                                      3 (6%)       1 (2%)       4 (8%)       2 (4%)                                
      Vacuolization Cytoplasmic                        1 (2%)       2 (4%)       1 (2%)       2 (4%)                                
   Adrenal Medulla                                    (48)         (49)         (49)         (49)                                   
      Hyperplasia                                                   3 (6%)                                                          
   Islets, Pancreatic                                 (47)         (49)         (48)         (49)                                   
      Hyperplasia                                      1 (2%)                    1 (2%)       3 (6%)                                
   Pituitary Gland                                    (49)         (49)         (49)         (49)                                   
      Pars Distalis, Hyperplasia                      13 (27%)     15 (31%)     19 (39%)     14 (29%)                               
   Thyroid Gland                                      (48)         (50)         (49)         (50)                                   
      Follicular Cell, Hyperplasia                    25 (52%)     16 (32%)     29 (59%)     30 (60%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Ovary                                              (48)         (50)         (48)         (50)                                   
      Angiectasis                                                   1 (2%)                    3 (6%)                                
      Cyst                                            13 (27%)     14 (28%)     11 (23%)      8 (16%)                               
      Inflammation, Suppurative                        1 (2%)                                                                       
   Uterus                                             (49)         (50)         (50)         (50)                                   
      Angiectasis                                                                             1 (2%)                                
      Hydrometra                                       6 (12%)      7 (14%)      3 (6%)       4 (8%)                                
      Inflammation, Suppurative                                     1 (2%)       1 (2%)                                             
      Necrosis                                                                   1 (2%)                                             
      Thrombosis                                                                 1 (2%)                                             
      Endometrium, Hyperplasia, Cystic                                                        1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    3                                                              
NTP Experiment-Test: 88070-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:10:34  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (48)         (49)         (49)         (50)                                   
      Necrosis                                                      1 (2%)                                                          
   Lymph Node                                         (7)          (2)          (5)          (4)                                    
      Lumbar, Hemorrhage                               1 (14%)                                                                      
   Lymph Node, Bronchial                              (38)         (33)         (44)         (44)                                   
      Hyperplasia, Plasma Cell                         1 (3%)                                                                       
   Lymph Node, Mandibular                             (41)         (42)         (44)         (38)                                   
      Hyperplasia, Lymphoid                            1 (2%)                                                                       
      Infiltration Cellular, Mixed Cell                                          1 (2%)                                             
   Lymph Node, Mesenteric                             (46)         (48)         (47)         (49)                                   
      Angiectasis                                      1 (2%)       2 (4%)                                                          
      Infiltration Cellular, Plasma Cell                                                      1 (2%)                                
      Infiltration Cellular, Mixed Cell                                          1 (2%)                                             
   Lymph Node, Mediastinal                            (38)         (42)         (36)         (42)                                   
      Infiltration Cellular, Mixed Cell                                          1 (3%)                                             
   Spleen                                             (49)         (50)         (50)         (50)                                   
      Hematopoietic Cell Proliferation                 4 (8%)      12 (24%)      6 (12%)      5 (10%)                               
      Infarct                                                                                 1 (2%)                                
      Infiltration Cellular, Histiocyte                             1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Skin                                               (49)         (50)         (49)         (50)                                   
      Inflammation, Acute                                           1 (2%)                                                          
      Inflammation, Chronic Active                     1 (2%)       1 (2%)                    1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (49)         (50)         (50)         (50)                                   
      Inflammation, Chronic Active                                  1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (49)         (50)         (50)         (50)                                   
      Hemorrhage                                                    1 (2%)                                                          
      Infiltration Cellular, Histiocyte                                          1 (2%)       1 (2%)                                
      Inflammation, Granulomatous                                                             1 (2%)                                
      Metaplasia, Osseous                                           1 (2%)                                                          
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    4                                                              
NTP Experiment-Test: 88070-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:10:34  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
RESPIRATORY SYSTEM - CONT                                                                                                           
      Alveolar Epithelium, Hyperplasia                 4 (8%)       3 (6%)       3 (6%)       1 (2%)                                
   Nose                                               (47)         (50)         (49)         (50)                                   
      Inflammation, Chronic                                                                   1 (2%)                                
      Inflammation, Suppurative                                     1 (2%)       1 (2%)                                             
      Olfactory Epithelium, Atrophy                                 1 (2%)                                                          
      Olfactory Epithelium, Degeneration, Hyaline     17 (36%)     19 (38%)     24 (49%)     27 (54%)                               
      Respiratory Epithelium, Degeneration, Hyaline   21 (45%)     39 (78%)     41 (84%)     48 (96%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Eye                                                (1)          (1)                       (1)                                    
      Degeneration                                     1 (100%)                                                                     
      Cornea, Metaplasia, Squamous                                  1 (100%)                                                        
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (49)         (50)         (49)         (50)                                   
      Amyloid Deposition                               1 (2%)                                                                       
      Cyst                                                          1 (2%)                                                          
      Infarct                                          1 (2%)       2 (4%)       1 (2%)                                             
      Metaplasia, Osseous                              1 (2%)       1 (2%)       2 (4%)                                             
      Mineralization                                                             1 (2%)                                             
      Nephropathy                                     13 (27%)     14 (28%)     18 (37%)     12 (24%)                               
      Renal Tubule, Necrosis                                                     1 (2%)                                             
   Urinary Bladder                                    (45)         (49)         (49)         (50)                                   
      Artery, Inflammation, Chronic Active                                                    1 (2%)                                
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    5                                                              
NTP Experiment-Test: 88070-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:10:34  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially In Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Natural Death                                      6            9            3            9                                     
    Moribund Sacrifice                                16            9           20           13                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                28           32           27           28                                     
  Animals Examined Microscopically                    50           50           50           50                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Liver                                              (50)         (50)         (50)         (49)                                   
      Basophilic Focus                                 7 (14%)      8 (16%)      6 (12%)      5 (10%)                               
      Clear Cell Focus                                 9 (18%)      4 (8%)       6 (12%)     10 (20%)                               
      Cyst                                             1 (2%)       1 (2%)                                                          
      Degeneration, Fatty                              2 (4%)       1 (2%)       2 (4%)       5 (10%)                               
      Eosinophilic Focus                               5 (10%)      4 (8%)      11 (22%)      7 (14%)                               
      Mixed Cell Focus                                              2 (4%)       1 (2%)                                             
      Necrosis                                         1 (2%)       5 (10%)      2 (4%)       1 (2%)                                
      Vacuolization Cytoplasmic, Focal                 1 (2%)       1 (2%)                    1 (2%)                                
      Centrilobular, Necrosis                          2 (4%)                                                                       
   Mesentery                                          (4)          (2)          (4)          (2)                                    
      Fat, Inflammation, Chronic Active                1 (25%)                                                                      
      Fat, Necrosis                                    3 (75%)      2 (100%)     4 (100%)     2 (100%)                              
   Pancreas                                           (50)         (48)         (50)         (47)                                   
      Atrophy                                          1 (2%)                                                                       
      Basophilic Focus                                              1 (2%)                                                          
   Stomach, Forestomach                               (50)         (49)         (50)         (48)                                   
      Hyperplasia                                      2 (4%)                    1 (2%)       1 (2%)                                
      Inflammation, Acute                                                        1 (2%)       1 (2%)                                
   Stomach, Glandular                                 (49)         (47)         (49)         (46)                                   
      Inflammation, Acute                              1 (2%)                                                                       
      Necrosis                                                      2 (4%)       1 (2%)                                             
   Tooth                                              (7)          (14)         (9)          (16)                                   
      Malformation                                     6 (86%)     12 (86%)      7 (78%)     14 (88%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (50)         (50)         (50)         (50)                                   
      Cardiomyopathy                                  21 (42%)     18 (36%)     16 (32%)     19 (38%)                               
      Inflammation, Chronic                            1 (2%)                                                                       
      Thrombosis                                       1 (2%)                    1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    6                                                              
NTP Experiment-Test: 88070-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:10:34  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (49)         (49)         (50)         (49)                                   
      Hyperplasia                                     14 (29%)     10 (20%)     15 (30%)     16 (33%)                               
      Hypertrophy                                     32 (65%)     24 (49%)     24 (48%)     29 (59%)                               
   Adrenal Medulla                                    (49)         (49)         (50)         (49)                                   
      Hyperplasia                                                                1 (2%)       1 (2%)                                
   Islets, Pancreatic                                 (50)         (48)         (50)         (48)                                   
      Hyperplasia                                      1 (2%)                    1 (2%)       1 (2%)                                
   Pituitary Gland                                    (50)         (48)         (49)         (48)                                   
      Pars Distalis, Hyperplasia                       1 (2%)       4 (8%)       3 (6%)       4 (8%)                                
   Thyroid Gland                                      (50)         (50)         (50)         (49)                                   
      Follicular Cell, Hyperplasia                     5 (10%)      6 (12%)      3 (6%)       3 (6%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Epididymis                                         (50)         (50)         (50)         (50)                                   
      Granuloma Sperm                                               1 (2%)       1 (2%)       5 (10%)                               
   Penis                                                                        (2)                                                 
      Inflammation, Acute                                                        1 (50%)                                            
   Preputial Gland                                    (50)         (48)         (50)         (50)                                   
      Cyst                                                                       2 (4%)       1 (2%)                                
      Inflammation, Chronic Active                                  2 (4%)                    3 (6%)                                
   Prostate                                           (48)         (46)         (47)         (48)                                   
      Inflammation, Chronic Active                                  2 (4%)       4 (9%)       4 (8%)                                
   Seminal Vesicle                                    (49)         (47)         (50)         (47)                                   
      Necrosis                                                                   1 (2%)                                             
   Testes                                             (50)         (50)         (50)         (50)                                   
      Atrophy                                                                    1 (2%)       1 (2%)                                
      Mineralization                                                1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (50)         (49)         (50)         (49)                                   
      Congestion                                                    1 (2%)                                                          
      Hemorrhage                                                                              1 (2%)                                
   Lymph Node                                         (4)          (3)          (7)          (1)                                    
      Iliac, Infiltration Cellular, Plasma Cell                     1 (33%)      2 (29%)      1 (100%)                              
      Iliac, Infiltration Cellular,                                                                                                 
          Polymorphonuclear                                                      1 (14%)                                            
      Lumbar, Infiltration Cellular, Plasma Cell                    1 (33%)                                                         
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    7                                                              
NTP Experiment-Test: 88070-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:10:34  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - CONT                                                                                                         
      Pancreatic, Infiltration Cellular, Plasma                                                                                     
          Cell                                         1 (25%)                                                                      
   Lymph Node, Mesenteric                             (48)         (49)         (48)         (49)                                   
      Angiectasis                                      1 (2%)                    1 (2%)                                             
      Infiltration Cellular, Plasma Cell                            1 (2%)                                                          
   Spleen                                             (50)         (49)         (50)         (48)                                   
      Hematopoietic Cell Proliferation                 4 (8%)       3 (6%)       5 (10%)      4 (8%)                                
      Infiltration Cellular, Histiocyte                             1 (2%)                    1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Skin                                               (49)         (50)         (50)         (50)                                   
      Cyst                                             1 (2%)                                                                       
      Prepuce, Inflammation, Chronic Active            7 (14%)      6 (12%)     13 (26%)      9 (18%)                               
      Subcutaneous Tissue, Edema                                                              1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Peripheral Nerve                                                                          (1)                                    
      Sciatic, Degeneration                                                                   1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (50)         (50)         (50)         (50)                                   
      Hemorrhage                                                                 3 (6%)                                             
      Thrombosis                                       1 (2%)       1 (2%)                                                          
      Alveolar Epithelium, Hyperplasia                 5 (10%)      6 (12%)      4 (8%)       3 (6%)                                
   Nose                                               (50)         (49)         (50)         (48)                                   
      Inflammation, Suppurative                        1 (2%)       2 (4%)       2 (4%)                                             
      Polyp, Inflammatory                              1 (2%)                                 1 (2%)                                
      Nasolacrimal Duct, Polyp, Inflammatory                                                  1 (2%)                                
      Olfactory Epithelium, Atrophy                    1 (2%)       1 (2%)       1 (2%)       2 (4%)                                
      Olfactory Epithelium, Degeneration, Hyaline      6 (12%)      7 (14%)     16 (32%)     17 (35%)                               
      Respiratory Epithelium, Degeneration, Hyaline    6 (12%)     19 (39%)     29 (58%)     39 (81%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    8                                                              
NTP Experiment-Test: 88070-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:10:34  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Eye                                                (2)                                    (2)                                    
      Cataract                                                                                1 (50%)                               
      Cornea, Inflammation, Chronic Active             1 (50%)                                                                      
   Harderian Gland                                    (4)          (4)          (4)          (4)                                    
      Hyperplasia                                                   1 (25%)                                                         
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (50)         (49)         (50)         (50)                                   
      Cyst                                             1 (2%)                                 1 (2%)                                
      Infarct                                          1 (2%)       2 (4%)       4 (8%)                                             
      Inflammation, Chronic Active                                  1 (2%)                                                          
      Metaplasia, Osseous                              1 (2%)                                 2 (4%)                                
      Mineralization                                   1 (2%)       1 (2%)                                                          
      Nephropathy                                     36 (72%)     39 (80%)     38 (76%)     40 (80%)                               
      Capsule, Inflammation, Chronic                                             1 (2%)                                             
      Papilla, Inflammation, Suppurative               3 (6%)       3 (6%)       6 (12%)      5 (10%)                               
      Pelvis, Dilatation                               3 (6%)       2 (4%)       4 (8%)       4 (8%)                                
      Renal Tubule, Hyperplasia                        1 (2%)                    1 (2%)                                             
   Urinary Bladder                                    (49)         (47)         (49)         (46)                                   
      Calculus Gross Observation                                                 1 (2%)                                             
      Inflammation, Chronic Active                     4 (8%)       3 (6%)       7 (14%)      6 (13%)                               
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    9                                                              
                             ------------------------------------------------------------                                           
                             ----------              END OF REPORT             ----------                                           
                             ------------------------------------------------------------