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TDMS Study 05185-04 Pathology Tables


                                     INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)
                                                       ISOBUTYL NITRITE (IBN)


NTP Experiment-Test: 05185-04                                                                                     Report: PEIRPT03
Study Type: CHRONIC                                                                                               Date: 05/20/95
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48




       Facility:  I. I. T. Research Institute

       Chemical CAS #:  542-56-3

       Lock Date:  08/20/92

       Cage Range:  All

       Reasons For Removal:    All

       Removal Date Range:     All

       Treatment Groups:       Include All
































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

                                                             Page   1

NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially In Study                          60           60           60           60                                     
  Scheduled Sacrifice                                  9            9            9           10                                     
  Early Deaths                                                                                                                      
    Natural Death                                     16            6            8           10                                     
    Moribund Sacrifice                                 3            3            6            2                                     
    Accidently Killed                                                                         1                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                32           42           36           37                                     
  Other                                                                          1                                                  
  Animals Examined Microscopically                    60           60           59           60                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Gallbladder                                        (55)         (55)         (54)         (51)                                   
      Dilatation                                                                              1 (2%)                                
      Inflammation, Chronic                                                      1 (2%)       1 (2%)                                
   Intestine Large, Rectum                            (57)         (60)         (59)         (57)                                   
      Dilatation                                                                 1 (2%)                                             
   Intestine Large, Cecum                             (57)         (58)         (59)         (55)                                   
      Dilatation                                                                 1 (2%)                                             
      Hyperplasia, Lymphoid                                                      1 (2%)                                             
   Intestine Small, Duodenum                          (51)         (59)         (58)         (52)                                   
      Ectopic Tissue                                                1 (2%)                                                          
      Proliferation Connective Tissue                               1 (2%)                                                          
   Intestine Small, Jejunum                           (53)         (59)         (56)         (55)                                   
      Hyperplasia, Lymphoid                                         1 (2%)                                                          
      Proliferation Connective Tissue                               1 (2%)                                                          
      Serosa, Inflammation, Chronic Active                          1 (2%)                                                          
   Intestine Small, Ileum                             (53)         (57)         (59)         (54)                                   
      Dilatation                                                                 1 (2%)                                             
   Liver                                              (60)         (60)         (59)         (60)                                   
      Angiectasis                                                                             1 (2%)                                
      Basophilic Focus                                 2 (3%)                                 1 (2%)                                
      Clear Cell Focus                                              1 (2%)       2 (3%)       1 (2%)                                
      Cytologic Alterations                            2 (3%)       1 (2%)       1 (2%)                                             
      Eosinophilic Focus                               1 (2%)       2 (3%)                                                          
      Fatty Change, Diffuse                            1 (2%)                                                                       
      Fibrosis                                                                   1 (2%)                                             
      Hematopoietic Cell Proliferation                 1 (2%)       1 (2%)       1 (2%)                                             
      Hemorrhage                                                                              1 (2%)                                
      Hyperplasia                                                                             2 (3%)                                
      Infarct                                                                    1 (2%)       1 (2%)                                
      Inflammation, Chronic                           11 (18%)      7 (12%)      6 (10%)      7 (12%)                               
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    2                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - CONT                                                                                                            
      Inflammation, Chronic Active                     2 (3%)       2 (3%)       4 (7%)                                             
      Mitotic Alteration                                            1 (2%)                                                          
      Mixed Cell Focus                                 3 (5%)       1 (2%)       1 (2%)       2 (3%)                                
      Necrosis                                         1 (2%)       2 (3%)       2 (3%)       1 (2%)                                
      Pigmentation                                                                            1 (2%)                                
      Proliferation Connective Tissue                               1 (2%)                                                          
      Fat, Necrosis                                    1 (2%)                                                                       
      Hepatocyte, Necrosis                             1 (2%)       1 (2%)       1 (2%)                                             
      Periportal, Fatty Change                         1 (2%)                    1 (2%)                                             
      Periportal, Hypertrophy                                       1 (2%)                                                          
   Mesentery                                          (7)          (4)          (3)          (2)                                    
      Cyst                                                          1 (25%)                                                         
      Proliferation Connective Tissue                               1 (25%)                                                         
      Artery, Inflammation, Chronic                    1 (14%)                                                                      
      Fat, Necrosis                                    5 (71%)      4 (100%)     2 (67%)      2 (100%)                              
   Pancreas                                           (60)         (60)         (59)         (60)                                   
      Fibrosis                                                      1 (2%)                                                          
      Inflammation, Chronic                            4 (7%)                                 3 (5%)                                
      Inflammation, Chronic Active                                  1 (2%)                                                          
      Acinus, Atrophy                                  1 (2%)       2 (3%)       3 (5%)       2 (3%)                                
      Duct, Dilatation                                              1 (2%)       1 (2%)                                             
   Salivary Glands                                    (60)         (60)         (59)         (60)                                   
      Atrophy                                                                    1 (2%)                                             
      Hemorrhage                                                                              1 (2%)                                
      Inflammation, Chronic                           49 (82%)     44 (73%)     33 (56%)     32 (53%)                               
      Inflammation, Chronic Active                                  1 (2%)                                                          
   Stomach, Forestomach                               (60)         (60)         (59)         (59)                                   
      Angiectasis                                                                             1 (2%)                                
      Developmental Malformation                                                              1 (2%)                                
      Proliferation Connective Tissue                               1 (2%)                                                          
      Ulcer                                                                      1 (2%)                                             
   Stomach, Glandular                                 (60)         (60)         (59)         (59)                                   
      Proliferation Connective Tissue                               1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (60)         (60)         (59)         (60)                                   
      Infiltration Cellular                            1 (2%)                                                                       
      Inflammation, Chronic                            1 (2%)                                                                       
      Thrombosis                                       1 (2%)                    1 (2%)                                             
      Artery, Hypertrophy                                                        1 (2%)                                             
      Artery, Inflammation, Chronic                    1 (2%)       1 (2%)                    1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    3                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (59)         (60)         (59)         (59)                                   
      Cyst                                                                       3 (5%)                                             
      Hyperplasia, Focal                                            2 (3%)                                                          
      Hypertrophy, Focal                                            1 (2%)       2 (3%)                                             
      Subcapsular, Hyperplasia                        56 (95%)     56 (93%)     54 (92%)     53 (90%)                               
   Adrenal Medulla                                    (55)         (58)         (54)         (57)                                   
      Hyperplasia, Focal                                            2 (3%)       1 (2%)                                             
   Islets, Pancreatic                                 (2)          (2)          (3)          (3)                                    
      Hyperplasia, Focal                               2 (100%)     1 (50%)      3 (100%)     2 (67%)                               
   Pituitary Gland                                    (56)         (56)         (59)         (57)                                   
      Cyst                                                                       1 (2%)                                             
      Pars Distalis, Angiectasis                       1 (2%)                    1 (2%)       2 (4%)                                
      Pars Distalis, Cyst                              1 (2%)       1 (2%)       1 (2%)       2 (4%)                                
      Pars Distalis, Hemorrhage                        1 (2%)                                                                       
      Pars Distalis, Hyperplasia                      10 (18%)     12 (21%)     12 (20%)      7 (12%)                               
      Pars Distalis, Hyperplasia, Focal                             1 (2%)                                                          
   Thyroid Gland                                      (60)         (60)         (59)         (60)                                   
      Ectopic Thymus                                                             1 (2%)                                             
      Infiltration Cellular, Lymphocyte                             1 (2%)                                                          
      Inflammation, Chronic                                                      3 (5%)                                             
      Follicle, Cyst                                   1 (2%)       5 (8%)       4 (7%)                                             
      Follicular Cell, Hyperplasia, Diffuse            1 (2%)                    1 (2%)                                             
      Follicular Cell, Hyperplasia, Focal              5 (8%)       9 (15%)      7 (12%)      5 (8%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Clitoral Gland                                                  (1)          (2)          (5)                                    
      Dilatation                                                    1 (100%)     1 (50%)      1 (20%)                               
      Pigmentation                                                                            3 (60%)                               
   Ovary                                              (58)         (59)         (55)         (59)                                   
      Angiectasis                                                                             1 (2%)                                
      Cyst                                            10 (17%)     15 (25%)     10 (18%)     13 (22%)                               
      Hemorrhage                                                                              1 (2%)                                
      Infiltration Cellular, Lymphocyte                1 (2%)                                 1 (2%)                                
      Interstitium, Hyperplasia                        1 (2%)                                                                       
   Uterus                                             (60)         (60)         (58)         (59)                                   
      Angiectasis                                      2 (3%)                                 1 (2%)                                
      Developmental Malformation                                                 1 (2%)                                             
      Dilatation                                                    1 (2%)                                                          
      Hemorrhage                                       1 (2%)                                                                       
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    4                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
GENITAL SYSTEM - CONT                                                                                                               
      Hyperplasia                                                   1 (2%)                                                          
      Hyperplasia, Cystic                             49 (82%)     51 (85%)     50 (86%)     54 (92%)                               
      Inflammation, Chronic Active                                               1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (60)         (60)         (59)         (60)                                   
      Atrophy                                                       1 (2%)                                                          
      Degeneration, Fatty                              1 (2%)                                                                       
      Myeloid Cell, Hyperplasia                                     1 (2%)       3 (5%)                                             
   Lymph Node                                         (4)          (5)          (8)          (6)                                    
      Hyperplasia, Lymphoid                                         1 (20%)                                                         
      Pigmentation                                                  1 (20%)                                                         
      Iliac, Hemorrhage                                                          1 (13%)                                            
      Iliac, Hyperplasia, Lymphoid                                  1 (20%)                                                         
      Iliac, Inflammation, Chronic Active                                        1 (13%)                                            
      Iliac, Pigmentation                                                                     1 (17%)                               
      Inguinal, Pigmentation                                                                  1 (17%)                               
      Lumbar, Angiectasis                                                        1 (13%)                                            
      Lumbar, Hemorrhage                                                         1 (13%)                                            
      Lumbar, Hyperplasia, Lymphoid                                                           1 (17%)                               
      Pancreatic, Hyperplasia, Lymphoid                             1 (20%)                                                         
      Renal, Hemorrhage                                                          1 (13%)                                            
   Lymph Node, Bronchial                              (28)         (42)         (40)         (38)                                   
      Hemorrhage                                                    1 (2%)       1 (3%)                                             
      Hyperplasia, Lymphoid                            1 (4%)       4 (10%)                                                         
   Lymph Node, Mandibular                             (58)         (57)         (57)         (55)                                   
      Hemorrhage                                                    1 (2%)       2 (4%)       1 (2%)                                
      Hyperplasia, Lymphoid                            2 (3%)       1 (2%)       2 (4%)       1 (2%)                                
      Inflammation, Chronic Active                     1 (2%)                                                                       
   Lymph Node, Mesenteric                             (60)         (59)         (58)         (55)                                   
      Angiectasis                                                                             1 (2%)                                
      Hematopoietic Cell Proliferation                 1 (2%)                                                                       
      Hemorrhage                                       1 (2%)                    1 (2%)                                             
      Hyperplasia, Lymphoid                                         1 (2%)       1 (2%)       1 (2%)                                
      Hyperplasia, Plasma Cell                                      1 (2%)                                                          
      Inflammation, Chronic Active                     1 (2%)                                                                       
   Lymph Node, Mediastinal                            (58)         (51)         (52)         (53)                                   
      Hyperplasia, Lymphoid                            6 (10%)      4 (8%)       3 (6%)       3 (6%)                                
      Inflammation, Chronic Active                                               1 (2%)                                             
   Spleen                                             (60)         (60)         (59)         (59)                                   
      Angiectasis                                                   1 (2%)                                                          
      Atrophy                                          1 (2%)                                                                       
      Fibrosis                                         1 (2%)                                                                       
      Hematopoietic Cell Proliferation                54 (90%)     49 (82%)     54 (92%)     54 (92%)                               
      Hyperplasia, Lymphoid                            6 (10%)      7 (12%)      6 (10%)      3 (5%)                                
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    5                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - CONT                                                                                                         
      Pigmentation, Hemosiderin                       54 (90%)     52 (87%)     46 (78%)     57 (97%)                               
      Proliferation Connective Tissue                               1 (2%)                                                          
   Thymus                                             (56)         (56)         (57)         (51)                                   
      Atrophy                                         11 (20%)      2 (4%)       5 (9%)       6 (12%)                               
      Ectopic Parathyroid Gland                                                               1 (2%)                                
      Hemorrhage                                                                 1 (2%)                                             
      Hyperplasia, Lymphoid                            5 (9%)      10 (18%)      6 (11%)      2 (4%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (58)         (60)         (59)         (60)                                   
      Dilatation                                                                 1 (2%)       2 (3%)                                
      Hyperplasia                                      2 (3%)       1 (2%)       1 (2%)       2 (3%)                                
   Skin                                               (60)         (60)         (59)         (60)                                   
      Inflammation, Chronic                            6 (10%)                                4 (7%)                                
      Inflammation, Chronic Active                                  4 (7%)       2 (3%)                                             
      Ulcer                                                         1 (2%)                                                          
      Epithelium, Hyperplasia                          1 (2%)       2 (3%)       2 (3%)                                             
      Sebaceous Gland, Hyperplasia, Focal                                        1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (60)         (60)         (59)         (60)                                   
      Developmental Malformation                                    1 (2%)                                                          
      Dysplasia                                       24 (40%)     18 (30%)     25 (42%)     28 (47%)                               
      Hyperostosis                                                  1 (2%)                                                          
      Maxilla, Fracture                                                                       1 (2%)                                
   Skeletal Muscle                                                 (3)          (1)          (1)                                    
      Hemorrhage                                                                 1 (100%)                                           
      Proliferation Connective Tissue                               1 (33%)                                                         
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (59)         (60)         (59)         (60)                                   
      Compression                                      1 (2%)       1 (2%)       4 (7%)       2 (3%)                                
      Hemorrhage                                                                 2 (3%)       1 (2%)                                
      Mineralization                                  45 (76%)     26 (43%)     31 (53%)     27 (45%)                               
      Meninges, Inflammation, Chronic Active                                                  1 (2%)                                
   Spinal Cord                                                                               (1)                                    
      Inflammation, Chronic                                                                   1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    6                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Larynx                                             (60)         (58)         (59)         (59)                                   
      Artery, Inflammation, Chronic                                                           1 (2%)                                
   Lung                                               (60)         (60)         (59)         (60)                                   
      Infiltration Cellular, Lymphocyte               28 (47%)     14 (23%)     11 (19%)     23 (38%)                               
      Inflammation, Chronic Active                     3 (5%)       3 (5%)       1 (2%)                                             
      Leukocytosis                                     1 (2%)                                                                       
      Alveolar Epithelium, Hyperplasia, Focal                       2 (3%)      10 (17%)      8 (13%)                               
      Alveolus, Infiltration Cellular, Histiocyte                   1 (2%)       1 (2%)       2 (3%)                                
      Artery, Inflammation, Chronic                                 1 (2%)                                                          
      Fat, Mediastinum, Necrosis                                    1 (2%)                                                          
   Nose                                               (60)         (60)         (59)         (60)                                   
      Exudate                                          1 (2%)                                                                       
      Exudate, Serous                                  1 (2%)       1 (2%)       2 (3%)      23 (38%)                               
      Inflammation, Chronic Active                     6 (10%)     10 (17%)     12 (20%)     12 (20%)                               
      Olfactory Epithelium, Atrophy                                              1 (2%)      16 (27%)                               
      Olfactory Epithelium, Degeneration, Hyaline      4 (7%)       3 (5%)       5 (8%)       3 (5%)                                
      Olfactory Epithelium, Metaplasia                              6 (10%)      2 (3%)       2 (3%)                                
      Olfactory Epithelium, Metaplasia, Squamous                    1 (2%)                    1 (2%)                                
      Respiratory Epithelium, Degeneration, Hyaline   19 (32%)     26 (43%)     14 (24%)     19 (32%)                               
      Respiratory Epithelium, Hyperplasia              6 (10%)      3 (5%)       4 (7%)       1 (2%)                                
      Respiratory Epithelium, Metaplasia, Squamous     4 (7%)       5 (8%)                    6 (10%)                               
      Respiratory Epithelium, Ulcer                    3 (5%)       4 (7%)       3 (5%)       3 (5%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Eye                                                                                       (1)                                    
      Phthisis Bulbi                                                                          1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (60)         (60)         (59)         (60)                                   
      Amyloid Deposition                               1 (2%)                                                                       
      Cyst                                             1 (2%)                                                                       
      Glomerulosclerosis                                                                      1 (2%)                                
      Hydronephrosis                                   1 (2%)                    1 (2%)                                             
      Infarct                                                                                 1 (2%)                                
      Infiltration Cellular, Lymphocyte               35 (58%)     19 (32%)     19 (32%)     31 (52%)                               
      Nephropathy                                                   2 (3%)       1 (2%)                                             
      Renal Tubule, Degeneration, Hyaline              1 (2%)                                                                       
      Renal Tubule, Dilatation                         2 (3%)       1 (2%)       2 (3%)       1 (2%)                                
      Renal Tubule, Hyperplasia, Focal                 1 (2%)                                 1 (2%)                                
      Renal Tubule, Pigmentation                                    1 (2%)                                                          
      Renal Tubule, Regeneration                                    1 (2%)                    1 (2%)                                
   Urinary Bladder                                    (58)         (59)         (57)         (57)                                   
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    7                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
URINARY SYSTEM - CONT                                                                                                               
      Dilatation                                                    1 (2%)                                                          
      Infiltration Cellular, Lymphocyte               38 (66%)     40 (68%)     24 (42%)     34 (60%)                               
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    8                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially In Study                          60           60           60           60                                     
  Scheduled Sacrifice                                 10           10           10            7                                     
  Early Deaths                                                                                                                      
    Natural Death                                     10            8           11           17                                     
    Accidently Killed                                  2                                      2                                     
    Moribund Sacrifice                                 1            7            4            4                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                37           35           35           30                                     
  Animals Examined Microscopically                    60           60           60           60                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Gallbladder                                        (51)         (50)         (51)         (53)                                   
      Inflammation, Chronic Active                                                            1 (2%)                                
   Intestine Large, Cecum                             (54)         (55)         (55)         (50)                                   
      Hyperplasia, Lymphoid                                         2 (4%)                                                          
   Intestine Small, Duodenum                          (53)         (55)         (55)         (50)                                   
      Proliferation Connective Tissue                               1 (2%)                                                          
   Intestine Small, Jejunum                           (52)         (55)         (56)         (50)                                   
      Hyperplasia, Lymphoid                                         1 (2%)                                                          
      Inflammation, Chronic Active                                  1 (2%)                                                          
   Liver                                              (60)         (60)         (60)         (60)                                   
      Abscess                                                                                 1 (2%)                                
      Angiectasis                                      1 (2%)       1 (2%)                                                          
      Basophilic Focus                                 3 (5%)       2 (3%)       2 (3%)       2 (3%)                                
      Clear Cell Focus                                 2 (3%)       3 (5%)       3 (5%)                                             
      Cytologic Alterations                            3 (5%)                    2 (3%)       2 (3%)                                
      Developmental Malformation                                    1 (2%)                                                          
      Eosinophilic Focus                               1 (2%)                    1 (2%)                                             
      Fatty Change, Focal                              1 (2%)                    1 (2%)                                             
      Hematopoietic Cell Proliferation                              1 (2%)       1 (2%)       1 (2%)                                
      Hyperplasia                                                                             1 (2%)                                
      Infarct                                          2 (3%)       2 (3%)       3 (5%)       2 (3%)                                
      Inflammation, Chronic                                         1 (2%)                    5 (8%)                                
      Inflammation, Chronic Active                                  1 (2%)       1 (2%)                                             
      Mixed Cell Focus                                              5 (8%)       1 (2%)       1 (2%)                                
      Necrosis                                         1 (2%)       3 (5%)       3 (5%)       4 (7%)                                
      Proliferation Connective Tissue                               1 (2%)                    1 (2%)                                
      Syncytial Alteration                            12 (20%)     14 (23%)     16 (27%)     11 (18%)                               
      Vacuolization Cytoplasmic                        1 (2%)                                                                       
      Bile Duct, Cyst                                                            2 (3%)                                             
      Bile Duct, Hyperplasia                                                     1 (2%)       1 (2%)                                
      Centrilobular, Fatty Change                      5 (8%)       6 (10%)      4 (7%)       1 (2%)                                
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    9                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - CONT                                                                                                            
      Centrilobular, Necrosis                                                                 2 (3%)                                
      Hepatocyte, Necrosis                                                                    1 (2%)                                
      Midzonal, Fatty Change                                        1 (2%)                                                          
      Periportal, Vacuolization Cytoplasmic                                                   1 (2%)                                
   Mesentery                                                       (1)          (5)          (2)                                    
      Artery, Inflammation, Chronic Active                                       1 (20%)                                            
      Fat, Necrosis                                                 1 (100%)     2 (40%)      2 (100%)                              
   Pancreas                                           (60)         (59)         (60)         (56)                                   
      Inflammation, Chronic                            3 (5%)                                 3 (5%)                                
      Inflammation, Chronic Active                                               1 (2%)                                             
      Proliferation Connective Tissue                                                         1 (2%)                                
      Acinus, Atrophy                                  1 (2%)       1 (2%)       1 (2%)       1 (2%)                                
      Duct, Cyst                                                                              1 (2%)                                
   Salivary Glands                                    (60)         (60)         (60)         (60)                                   
      Inflammation, Chronic                           36 (60%)     33 (55%)     29 (48%)     29 (48%)                               
   Stomach, Glandular                                 (59)         (59)         (59)         (56)                                   
      Dysplasia                                                                               1 (2%)                                
      Necrosis                                                      1 (2%)       1 (2%)       2 (4%)                                
      Ulcer                                                                      1 (2%)                                             
   Tooth                                              (3)                       (1)          (1)                                    
      Dysplasia                                        1 (33%)                                                                      
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (60)         (60)         (60)         (60)                                   
      Cardiomyopathy                                                                          1 (2%)                                
      Degeneration                                                                            1 (2%)                                
      Mineralization                                   1 (2%)                                                                       
      Thrombosis                                                                              1 (2%)                                
      Artery, Inflammation, Chronic Active                                       1 (2%)       1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (59)         (59)         (58)         (58)                                   
      Cyst                                                          3 (5%)       1 (2%)                                             
      Hyperplasia                                                                1 (2%)                                             
      Hypertrophy, Focal                               6 (10%)     16 (27%)     10 (17%)      9 (16%)                               
      Capsule, Accessory Adrenal Cortical Nodule       2 (3%)                    1 (2%)                                             
      Subcapsular, Hyperplasia                        33 (56%)     26 (44%)     18 (31%)     24 (41%)                               
   Adrenal Medulla                                    (59)         (59)         (58)         (58)                                   
      Hyperplasia, Focal                                                         2 (3%)                                             
   Islets, Pancreatic                                 (5)          (3)          (9)          (1)                                    
      Hyperplasia, Focal                               3 (60%)      3 (100%)     7 (78%)      1 (100%)                              
   Pituitary Gland                                    (56)         (56)         (54)         (54)                                   
      Pars Distalis, Cyst                              1 (2%)                                                                       
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   10                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ENDOCRINE SYSTEM - CONT                                                                                                             
      Pars Distalis, Hyperplasia                       1 (2%)                    1 (2%)                                             
      Pars Distalis, Hyperplasia, Focal                             1 (2%)       1 (2%)                                             
   Thyroid Gland                                      (60)         (60)         (60)         (60)                                   
      Ultimobranchial Cyst                                                       1 (2%)                                             
      Follicular Cell, Hyperplasia                                               1 (2%)                                             
      Follicular Cell, Hyperplasia, Focal              8 (13%)     17 (28%)     12 (20%)     20 (33%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Epididymis                                         (60)         (60)         (60)         (60)                                   
      Inflammation, Chronic Active                     1 (2%)       2 (3%)       3 (5%)       8 (13%)                               
      Spermatocele                                                  1 (2%)                                                          
   Penis                                              (1)          (1)          (1)          (5)                                    
      Congestion                                                                              1 (20%)                               
      Inflammation, Chronic Active                     1 (100%)                  1 (100%)     3 (60%)                               
   Preputial Gland                                    (19)         (22)         (18)         (14)                                   
      Abscess                                                       3 (14%)      2 (11%)      1 (7%)                                
      Dilatation                                      16 (84%)     14 (64%)     17 (94%)     11 (79%)                               
      Inflammation, Chronic Active                     6 (32%)      6 (27%)      5 (28%)      4 (29%)                               
   Prostate                                           (60)         (59)         (59)         (60)                                   
      Hyperplasia, Focal                                                         1 (2%)                                             
      Inflammation, Acute                                           1 (2%)                    2 (3%)                                
      Inflammation, Chronic Active                     1 (2%)       1 (2%)       4 (7%)       3 (5%)                                
   Seminal Vesicle                                    (60)         (60)         (60)         (60)                                   
      Dilatation                                       4 (7%)       7 (12%)     12 (20%)      3 (5%)                                
      Hyperplasia                                                                             1 (2%)                                
      Inflammation, Acute                                           1 (2%)                                                          
      Inflammation, Chronic Active                                               1 (2%)       1 (2%)                                
   Testes                                             (60)         (60)         (60)         (60)                                   
      Mineralization                                                             1 (2%)                                             
      Spermatocele                                     1 (2%)                                                                       
      Seminiferous Tubule, Degeneration                2 (3%)                                 1 (2%)                                
      Tunic, Inflammation, Chronic                                               1 (2%)                                             
      Tunic, Proliferation Connective Tissue                                     1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   11                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (60)         (60)         (59)         (59)                                   
      Infarct                                                                                 1 (2%)                                
      Myeloid Cell, Hyperplasia                        3 (5%)       5 (8%)       7 (12%)      9 (15%)                               
   Lymph Node                                         (1)          (5)          (5)          (5)                                    
      Iliac, Infiltration Cellular, Histiocyte                                   1 (20%)                                            
      Iliac, Inflammation, Chronic Active                                                     1 (20%)                               
      Inguinal, Hyperplasia, Lymphoid                                            2 (40%)                                            
      Inguinal, Inflammation, Chronic Active                                                  1 (20%)                               
      Inguinal, Pigmentation                                                                  1 (20%)                               
      Lumbar, Hemorrhage                                                                      1 (20%)                               
      Lumbar, Hyperplasia, Histiocytic                                                        1 (20%)                               
      Lumbar, Hyperplasia, Lymphoid                                 1 (20%)                   1 (20%)                               
      Lumbar, Hyperplasia, Plasma Cell                                                        1 (20%)                               
      Renal, Hyperplasia, Plasma Cell                               1 (20%)      1 (20%)                                            
   Lymph Node, Bronchial                              (33)         (45)         (26)         (39)                                   
      Hemorrhage                                                    1 (2%)                                                          
      Hyperplasia, Lymphoid                                         1 (2%)       1 (4%)       1 (3%)                                
      Infiltration Cellular, Histiocyte                                                       1 (3%)                                
      Inflammation, Chronic Active                                               1 (4%)                                             
   Lymph Node, Mandibular                             (49)         (59)         (60)         (55)                                   
      Hemorrhage                                                                              1 (2%)                                
      Hyperplasia, Lymphoid                            1 (2%)       1 (2%)                    1 (2%)                                
      Pigmentation, Hemosiderin                                                               1 (2%)                                
   Lymph Node, Mesenteric                             (57)         (57)         (57)         (56)                                   
      Angiectasis                                                                1 (2%)                                             
      Hematopoietic Cell Proliferation                              1 (2%)       1 (2%)                                             
      Hemorrhage                                       2 (4%)       4 (7%)       5 (9%)       6 (11%)                               
      Hyperplasia, Lymphoid                            3 (5%)       1 (2%)                    1 (2%)                                
      Hyperplasia, Plasma Cell                                                   2 (4%)                                             
   Lymph Node, Mediastinal                            (48)         (47)         (48)         (46)                                   
      Hemorrhage                                       1 (2%)                    1 (2%)       1 (2%)                                
      Hyperplasia, Lymphoid                                                                   2 (4%)                                
      Hyperplasia, Plasma Cell                                                                1 (2%)                                
   Spleen                                             (60)         (60)         (59)         (58)                                   
      Fibrosis                                                                                1 (2%)                                
      Hematopoietic Cell Proliferation                59 (98%)     53 (88%)     57 (97%)     55 (95%)                               
      Hematopoietic Cell Proliferation Granulocytic                              1 (2%)       2 (3%)                                
      Hyperplasia, Lymphoid                                         2 (3%)                                                          
      Pigmentation, Hemosiderin                       34 (57%)     26 (43%)     55 (93%)     56 (97%)                               
      Lymphoid Follicle, Atrophy                                                              2 (3%)                                
   Thymus                                             (55)         (56)         (48)         (50)                                   
      Atrophy                                         13 (24%)     12 (21%)      7 (15%)      9 (18%)                               
      Cyst                                                                                    1 (2%)                                
      Ectopic Parathyroid Gland                                                               1 (2%)                                
      Hyperplasia, Lymphoid                                                      1 (2%)       1 (2%)                                
____________________________________________________________________________________________________________________________________
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   12                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Skin                                               (60)         (60)         (59)         (59)                                   
      Inflammation, Chronic                            1 (2%)                                 2 (3%)                                
      Inflammation, Chronic Active                                  3 (5%)       2 (3%)       3 (5%)                                
      Ulcer                                                         2 (3%)                    2 (3%)                                
      Epithelium, Hyperplasia                                       1 (2%)       1 (2%)                                             
      Fat, Necrosis                                    1 (2%)                                                                       
      Hair Follicle, Atrophy                           1 (2%)                                                                       
      Prepuce, Inflammation, Chronic Active            1 (2%)                    1 (2%)       1 (2%)                                
      Prepuce, Ulcer                                                             1 (2%)                                             
      Subcutaneous Tissue, Edema                                                              1 (2%)                                
      Subcutaneous Tissue, Granuloma                                                          1 (2%)                                
      Subcutaneous Tissue, Hemorrhage                                                         1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (60)         (60)         (60)         (60)                                   
      Developmental Malformation                                                 1 (2%)                                             
      Dysplasia                                                                  1 (2%)                                             
      Fracture                                                                                1 (2%)                                
      Hyperostosis                                                  1 (2%)                                                          
      Cartilage, Degeneration                                       1 (2%)                                                          
      Maxilla, Callus                                  1 (2%)                                                                       
      Maxilla, Fracture                                2 (3%)                                                                       
   Skeletal Muscle                                                 (1)          (1)                                                 
      Inflammation, Chronic Active                                               1 (100%)                                           
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (60)         (60)         (60)         (60)                                   
      Mineralization                                  41 (68%)     36 (60%)     31 (52%)     24 (40%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Larynx                                             (60)         (60)         (59)         (57)                                   
      Inflammation, Acute                                           1 (2%)                                                          
      Inflammation, Chronic Active                                  1 (2%)                                                          
   Lung                                               (60)         (60)         (59)         (60)                                   
      Congestion                                                                              1 (2%)                                
      Infiltration Cellular, Lymphocyte                1 (2%)       3 (5%)       2 (3%)       3 (5%)                                
      Inflammation, Chronic Active                     3 (5%)                                                                       
      Leukocytosis                                                                            1 (2%)                                
      Alveolar Epithelium, Hyperplasia, Focal          1 (2%)       4 (7%)       7 (12%)     13 (22%)                               
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   13                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
RESPIRATORY SYSTEM - CONT                                                                                                           
      Alveolus, Infiltration Cellular, Histiocyte                   1 (2%)       2 (3%)       2 (3%)                                
   Nose                                               (60)         (60)         (60)         (60)                                   
      Exudate                                                                    1 (2%)                                             
      Exudate, Serous                                                                         2 (3%)                                
      Inflammation, Chronic Active                     8 (13%)      8 (13%)      7 (12%)     10 (17%)                               
      Olfactory Epithelium, Atrophy                                              1 (2%)       1 (2%)                                
      Olfactory Epithelium, Degeneration, Hyaline                   4 (7%)       2 (3%)       2 (3%)                                
      Olfactory Epithelium, Metaplasia                 3 (5%)       1 (2%)       3 (5%)       1 (2%)                                
      Respiratory Epithelium, Degeneration, Hyaline    4 (7%)       3 (5%)       3 (5%)       3 (5%)                                
      Respiratory Epithelium, Hyperplasia             13 (22%)     20 (33%)     19 (32%)      8 (13%)                               
      Respiratory Epithelium, Metaplasia, Squamous                  3 (5%)                    3 (5%)                                
      Respiratory Epithelium, Ulcer                                 2 (3%)                    1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Eye                                                                          (1)          (2)                                    
      Phthisis Bulbi                                                             1 (100%)     1 (50%)                               
      Cornea, Inflammation, Chronic Active                                                    1 (50%)                               
      Lens, Cataract                                                                          1 (50%)                               
   Harderian Gland                                    (5)          (1)          (3)          (6)                                    
      Inflammation, Chronic Active                                  1 (100%)                                                        
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (60)         (60)         (60)         (60)                                   
      Abscess                                                                                 1 (2%)                                
      Amyloid Deposition                                            1 (2%)                                                          
      Cyst                                             2 (3%)       1 (2%)       2 (3%)       2 (3%)                                
      Hydronephrosis                                   2 (3%)       2 (3%)                    5 (8%)                                
      Infarct                                                                    2 (3%)       1 (2%)                                
      Infiltration Cellular, Lymphocyte               17 (28%)     18 (30%)     13 (22%)     23 (38%)                               
      Inflammation, Acute                                           1 (2%)                    2 (3%)                                
      Inflammation, Chronic Active                     1 (2%)       3 (5%)       5 (8%)       6 (10%)                               
      Metaplasia, Osseous                              1 (2%)                    1 (2%)                                             
      Mineralization                                                             1 (2%)                                             
      Nephropathy                                      1 (2%)       1 (2%)                                                          
      Artery, Inflammation, Chronic Active                                       1 (2%)                                             
      Renal Tubule, Dilatation                         1 (2%)       3 (5%)                    6 (10%)                               
      Renal Tubule, Hyperplasia, Focal                 1 (2%)                    2 (3%)       2 (3%)                                
      Renal Tubule, Regeneration                      12 (20%)      6 (10%)      5 (8%)       4 (7%)                                
   Urinary Bladder                                    (60)         (58)         (59)         (57)                                   
      Dilatation                                       7 (12%)      7 (12%)     14 (24%)      9 (16%)                               
      Infiltration Cellular, Lymphocyte                2 (3%)       4 (7%)       1 (2%)       5 (9%)                                
      Inflammation, Acute                                           1 (2%)                    1 (2%)                                
      Inflammation, Chronic Active                     2 (3%)       3 (5%)       5 (8%)       8 (14%)                               
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   14                                                              
NTP Experiment-Test: 05185-04         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:48  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
URINARY SYSTEM - CONT                                                                                                               
      Transitional Epithelium, Hyperplasia                          1 (2%)       1 (2%)                                             
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   15                                                              
                             ------------------------------------------------------------                                           
                             ----------              END OF REPORT             ----------                                           
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