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TDMS Study 55301-06 Pathology Tables

NTP Experiment-Test: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97
Route: DOSED WATER                                                                                                Time: 12:18:24




       Facility:  TSI Mason Research

       Chemical CAS #:  110-86-1

       Lock Date:  12/13/94

       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: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97  
Route: DOSED WATER                                                                                                Time: 12:18:24  
____________________________________________________________________________________________________________________________________

         WISTAR OUTBRED RATS MALE                  0 PPM        100 PPM      200 PPM      400 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________

DISPOSITION SUMMARY                                                                                                                 

  Animals Initially In Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Natural Death                                     26           27           30           33                                     
    Moribund Sacrifice                                 2            9            9           10                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                22           14           11            7                                     

  Animals Examined Microscopically                    50           50           50           50                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Esophagus                                          (50)         (50)         (50)         (50)                                   
      Foreign Body                                                               1 (2%)       1 (2%)                                
      Inflammation, Acute                                                                     1 (2%)                                
      Ulcer                                                                                   1 (2%)                                
      Muscularis, Degeneration                                                                1 (2%)                                
   Intestine Large, Colon                             (35)         (39)         (36)         (33)                                   
      Mineralization                                                             1 (3%)       1 (3%)                                
      Parasite Metazoan                                                          1 (3%)                                             
   Intestine Large, Rectum                            (42)         (42)         (41)         (40)                                   
      Hemorrhage                                       1 (2%)                                                                       
      Mineralization                                                1 (2%)                                                          
      Parasite Metazoan                                                                       1 (3%)                                
      Ulcer                                                                                   1 (3%)                                
   Intestine Large, Cecum                             (32)         (37)         (29)         (27)                                   
      Congestion                                                                 1 (3%)                                             
      Edema                                                         1 (3%)                                                          
      Hemorrhage                                       1 (3%)       2 (5%)       1 (3%)                                             
      Inflammation, Acute                                           2 (5%)       2 (7%)       1 (4%)                                
      Inflammation, Chronic                                                      1 (3%)       1 (4%)                                
      Ulcer                                                         2 (5%)                    2 (7%)                                
      Artery, Mineralization                                        1 (3%)                                                          
   Intestine Small, Jejunum                           (37)         (36)         (34)         (35)                                   
      Inflammation, Chronic                                                                   1 (3%)                                
   Liver                                              (50)         (50)         (50)         (50)                                   
      Angiectasis                                      5 (10%)      9 (18%)      2 (4%)                                             
      Basophilic Focus                                                                        2 (4%)                                
      Cholangiofibrosis                                                                       1 (2%)                                
      Clear Cell Focus                                15 (30%)      7 (14%)      8 (16%)      8 (16%)                               
      Congestion                                      19 (38%)     12 (24%)      6 (12%)     17 (34%)                               
      Degeneration, Cystic                             7 (14%)     13 (26%)      9 (18%)      5 (10%)                               
      Eosinophilic Focus                              14 (28%)     12 (24%)      4 (8%)       2 (4%)                                
      Fibrosis                                         1 (2%)       5 (10%)     26 (52%)     31 (62%)                               
      Hemorrhage                                       1 (2%)       1 (2%)       5 (10%)      3 (6%)                                
      Hepatodiaphragmatic Nodule                       2 (4%)       1 (2%)       2 (4%)                                             

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

                                                             Page    2                                                              
NTP Experiment-Test: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97  
Route: DOSED WATER                                                                                                Time: 12:18:24  
____________________________________________________________________________________________________________________________________

         WISTAR OUTBRED RATS MALE                  0 PPM        100 PPM      200 PPM      400 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - CONT                                                                                                            
      Hypertrophy                                                                1 (2%)                                             
      Infarct                                                                    1 (2%)                                             
      Infiltration Cellular, Histiocyte                             1 (2%)       2 (4%)                                             
      Inflammation, Acute                              1 (2%)       1 (2%)       3 (6%)       1 (2%)                                
      Mineralization                                                1 (2%)       3 (6%)       3 (6%)                                
      Mixed Cell Focus                                 1 (2%)                    1 (2%)       1 (2%)                                
      Necrosis                                         6 (12%)      7 (14%)      6 (12%)      2 (4%)                                
      Pigmentation                                     6 (12%)     15 (30%)     34 (68%)     42 (84%)                               
      Regeneration                                                                            2 (4%)                                
      Tension Lipidosis                                                          1 (2%)                                             
      Thrombosis                                                                 1 (2%)                                             
      Vacuolization Cytoplasmic                       18 (36%)     18 (36%)     12 (24%)     15 (30%)                               
      Artery, Mineralization                                        1 (2%)                                                          
      Bile Duct, Cyst                                                            2 (4%)       3 (6%)                                
      Bile Duct, Dilatation                                         2 (4%)                                                          
      Bile Duct, Hyperplasia                          31 (62%)     33 (66%)     30 (60%)     27 (54%)                               
      Centrilobular, Cytomegaly                                     1 (2%)       1 (2%)       1 (2%)                                
      Centrilobular, Degeneration                      1 (2%)      15 (30%)     25 (50%)     33 (66%)                               
      Centrilobular, Hypertrophy                                    1 (2%)                                                          
      Centrilobular, Necrosis                          5 (10%)      6 (12%)      4 (8%)      23 (46%)                               
      Hepatocyte, Atrophy                              2 (4%)                    1 (2%)       1 (2%)                                
      Oval Cell, Hyperplasia                           1 (2%)                                                                       
      Periportal, Fibrosis                                                       5 (10%)      7 (14%)                               
      Sinusoid, Congestion                             1 (2%)                                                                       
   Mesentery                                          (7)          (1)          (2)          (2)                                    
      Mineralization                                   1 (14%)                                                                      
      Artery, Inflammation                             5 (71%)      1 (100%)                  1 (50%)                               
      Artery, Mineralization                           2 (29%)                                                                      
      Fat, Necrosis                                    1 (14%)                                1 (50%)                               
      Vein, Thrombosis                                                           2 (100%)                                           
   Oral Mucosa                                        (5)          (1)          (1)                                                 
      Hyperplasia, Squamous                                         1 (100%)     1 (100%)                                           
      Inflammation, Suppurative                        3 (60%)                                                                      
   Pancreas                                           (46)         (50)         (50)         (49)                                   
      Atrophy                                          2 (4%)       3 (6%)       3 (6%)       1 (2%)                                
      Basophilic Focus                                 1 (2%)                                                                       
      Edema                                                                      1 (2%)                                             
      Fibrosis                                                                   1 (2%)                                             
      Hemorrhage                                                    1 (2%)                                                          
      Hyperplasia                                     18 (39%)     18 (36%)      8 (16%)      8 (16%)                               
      Necrosis                                         1 (2%)                                                                       
      Acinus, Hyperplasia                              1 (2%)                    1 (2%)                                             
      Artery, Inflammation                             3 (7%)       5 (10%)      3 (6%)                                             
      Artery, Mineralization                           2 (4%)       6 (12%)      1 (2%)                                             
      Duct, Hyperplasia                                1 (2%)       1 (2%)       1 (2%)                                             
   Salivary Glands                                    (48)         (49)         (47)         (48)                                   
      Atrophy                                                                                 1 (2%)                                

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

                                                             Page    3                                                              
NTP Experiment-Test: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97  
Route: DOSED WATER                                                                                                Time: 12:18:24  
____________________________________________________________________________________________________________________________________

         WISTAR OUTBRED RATS MALE                  0 PPM        100 PPM      200 PPM      400 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - CONT                                                                                                            
      Inflammation, Acute                                           1 (2%)                                                          
      Artery, Mineralization                           2 (4%)       3 (6%)                                                          
      Duct, Cyst                                       1 (2%)                    1 (2%)                                             
   Stomach, Forestomach                               (49)         (50)         (50)         (49)                                   
      Cyst                                                                       1 (2%)       2 (4%)                                
      Erosion                                          1 (2%)                                                                       
      Fibrosis                                                                                1 (2%)                                
      Foreign Body                                                               1 (2%)       2 (4%)                                
      Hemorrhage                                                                 1 (2%)                                             
      Hyperplasia, Squamous                            2 (4%)      13 (26%)     11 (22%)     10 (20%)                               
      Inflammation, Acute                              1 (2%)                                                                       
      Inflammation, Chronic                                                      1 (2%)       1 (2%)                                
      Inflammation, Chronic Active                                                            1 (2%)                                
      Mineralization                                   3 (6%)       5 (10%)      3 (6%)       1 (2%)                                
      Ulcer                                            2 (4%)       4 (8%)       3 (6%)       4 (8%)                                
      Ulcer, Chronic                                   1 (2%)                                                                       
   Stomach, Glandular                                 (49)         (50)         (48)         (48)                                   
      Erosion                                          3 (6%)       3 (6%)       2 (4%)       4 (8%)                                
      Fibrosis                                                      1 (2%)                                                          
      Hemorrhage                                                                 2 (4%)                                             
      Hyperplasia                                      1 (2%)                    1 (2%)                                             
      Inflammation, Chronic Active                                               1 (2%)                                             
      Mineralization                                   8 (16%)     25 (50%)     16 (33%)      6 (13%)                               
      Ulcer                                                                      1 (2%)                                             
      Artery, Mineralization                                                     1 (2%)       1 (2%)                                
      Serosa, Edema                                                 1 (2%)                                                          
   Tooth                                              (2)          (2)          (4)          (3)                                    
      Peridontal Tissue, Inflammation, Chronic                                                1 (33%)                               
      Peridontal Tissue, Inflammation, Chronic                                                                                      
          Active                                       1 (50%)                                1 (33%)                               
      Peridontal Tissue, Inflammation,                                                                                              
          Granulomatous                                             1 (50%)                                                         
      Peridontal Tissue, Inflammation, Suppurative     1 (50%)      1 (50%)      4 (100%)     1 (33%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Blood Vessel                                       (8)          (23)         (12)         (3)                                    
      Mineralization                                   6 (75%)      6 (26%)      1 (8%)                                             
      Aorta, Mineralization                            7 (88%)     21 (91%)     10 (83%)      3 (100%)                              
      Pulmonary Artery, Degeneration                                1 (4%)                                                          
      Pulmonary Artery, Mineralization                 3 (38%)      3 (13%)      5 (42%)      2 (67%)                               
   Heart                                              (50)         (50)         (50)         (50)                                   
      Cardiomyopathy                                  49 (98%)     49 (98%)     49 (98%)     47 (94%)                               
      Inflammation, Chronic                            1 (2%)                                                                       
      Mineralization                                   6 (12%)     17 (34%)     12 (24%)      3 (6%)                                
      Thrombosis                                       1 (2%)                    1 (2%)                                             

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

                                                             Page    4                                                              
NTP Experiment-Test: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97  
Route: DOSED WATER                                                                                                Time: 12:18:24  
____________________________________________________________________________________________________________________________________

         WISTAR OUTBRED RATS MALE                  0 PPM        100 PPM      200 PPM      400 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
CARDIOVASCULAR SYSTEM - CONT                                                                                                        
      Artery, Inflammation                                          1 (2%)                                                          
      Artery, Inflammation, Acute                                                             1 (2%)                                
      Artery, Mineralization                           4 (8%)      15 (30%)      9 (18%)      2 (4%)                                
      Artery, Thrombosis                               1 (2%)                                                                       
      Atrium, Dilatation                                                         1 (2%)       1 (2%)                                
      Atrium, Thrombosis                               4 (8%)       2 (4%)       5 (10%)      3 (6%)                                
      Valve, Inflammation                                                                     1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (50)         (50)         (50)         (50)                                   
      Accessory Adrenal Cortical Nodule                1 (2%)                                                                       
      Angiectasis                                      1 (2%)                    1 (2%)                                             
      Congestion                                                    2 (4%)                    1 (2%)                                
      Degeneration                                                  2 (4%)                                                          
      Hemorrhage                                       3 (6%)                                                                       
      Hyperplasia                                      1 (2%)       2 (4%)       1 (2%)       1 (2%)                                
      Hypertrophy                                      2 (4%)       2 (4%)       2 (4%)                                             
      Mineralization                                                1 (2%)                                                          
      Necrosis                                                                                2 (4%)                                
      Thrombosis                                                    1 (2%)                    1 (2%)                                
      Vacuolization Cytoplasmic                       17 (34%)     13 (26%)     12 (24%)      7 (14%)                               
   Adrenal Medulla                                    (50)         (50)         (50)         (50)                                   
      Hyperplasia                                      3 (6%)       4 (8%)       2 (4%)       1 (2%)                                
   Islets, Pancreatic                                 (47)         (50)         (49)         (49)                                   
      Hyperplasia                                      1 (2%)       1 (2%)       2 (4%)       1 (2%)                                
   Parathyroid Gland                                  (48)         (47)         (48)         (47)                                   
      Hyperplasia                                     16 (33%)     32 (68%)     29 (60%)     12 (26%)                               
      Inflammation, Chronic                            1 (2%)                                                                       
   Pituitary Gland                                    (49)         (49)         (50)         (50)                                   
      Angiectasis                                                                             1 (2%)                                
      Congestion                                                                              2 (4%)                                
      Cyst                                            17 (35%)     13 (27%)     18 (36%)     11 (22%)                               
      Hemorrhage                                                                 1 (2%)       1 (2%)                                
      Hyperplasia                                     13 (27%)     10 (20%)      7 (14%)      3 (6%)                                
      Hypertrophy                                                                             1 (2%)                                
      Pars Distalis, Hyperplasia                       2 (4%)       1 (2%)                                                          
   Thyroid Gland                                      (49)         (50)         (48)         (49)                                   
      Inflammation, Granulomatous                                                1 (2%)                                             
      C-Cell, Hyperplasia                                           1 (2%)       1 (2%)                                             
      Follicle, Cyst                                   2 (4%)       4 (8%)       5 (10%)      1 (2%)                                
      Follicular Cell, Hyperplasia                                  2 (4%)       1 (2%)                                             
____________________________________________________________________________________________________________________________________

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

                                                             Page    5                                                              
NTP Experiment-Test: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97  
Route: DOSED WATER                                                                                                Time: 12:18:24  
____________________________________________________________________________________________________________________________________

         WISTAR OUTBRED RATS MALE                  0 PPM        100 PPM      200 PPM      400 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Coagulating Gland                                  (48)         (42)         (45)         (45)                                   
      Inflammation, Acute                                           1 (2%)       1 (2%)                                             
      Inflammation, Chronic                                                                   1 (2%)                                
      Inflammation, Chronic Active                     1 (2%)                                                                       
      Artery, Mineralization                                        1 (2%)                                                          
   Epididymis                                         (50)         (49)         (49)         (50)                                   
      Arteriole, Mineralization                        1 (2%)                                                                       
      Artery, Inflammation                                                                    1 (2%)                                
      Epithelium, Hyperplasia                                                                 1 (2%)                                
   Preputial Gland                                    (50)         (48)         (50)         (50)                                   
      Atrophy                                                                    1 (2%)                                             
      Hyperplasia, Squamous                                                                   1 (2%)                                
      Inflammation, Chronic                            2 (4%)       2 (4%)       3 (6%)       1 (2%)                                
      Inflammation, Chronic Active                     1 (2%)                    1 (2%)                                             
      Inflammation, Suppurative                       12 (24%)      9 (19%)     10 (20%)      3 (6%)                                
      Duct, Cyst                                      49 (98%)     43 (90%)     46 (92%)     48 (96%)                               
   Prostate                                           (50)         (49)         (50)         (50)                                   
      Fibrosis                                                                   2 (4%)       1 (2%)                                
      Hemorrhage                                       1 (2%)                    1 (2%)                                             
      Hyperplasia                                      4 (8%)       4 (8%)       1 (2%)       2 (4%)                                
      Inflammation, Acute                              4 (8%)       1 (2%)                                                          
      Inflammation, Chronic                            3 (6%)       4 (8%)       5 (10%)      2 (4%)                                
      Inflammation, Chronic Active                     5 (10%)      5 (10%)      2 (4%)       2 (4%)                                
      Artery, Mineralization                           1 (2%)                                                                       
   Seminal Vesicle                                    (49)         (49)         (50)         (49)                                   
      Cyst                                                          1 (2%)                                                          
      Hyperplasia                                                   1 (2%)                                                          
      Inflammation, Chronic                                         1 (2%)                                                          
      Inflammation, Chronic Active                                               1 (2%)                                             
      Artery, Mineralization                                        1 (2%)                                                          
   Testes                                             (50)         (49)         (49)         (50)                                   
      Atrophy                                         20 (40%)     20 (41%)     18 (37%)      9 (18%)                               
      Congestion                                                                              1 (2%)                                
      Inflammation, Granulomatous                                                1 (2%)       1 (2%)                                
      Mineralization                                   6 (12%)      2 (4%)       9 (18%)      4 (8%)                                
      Artery, Inflammation                            24 (48%)     24 (49%)     14 (29%)     11 (22%)                               
      Artery, Mineralization                                        3 (6%)       2 (4%)                                             
      Interstitial Cell, Hyperplasia                   3 (6%)       4 (8%)       7 (14%)      7 (14%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    

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

                                                             Page    6                                                              
NTP Experiment-Test: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97  
Route: DOSED WATER                                                                                                Time: 12:18:24  
____________________________________________________________________________________________________________________________________

         WISTAR OUTBRED RATS MALE                  0 PPM        100 PPM      200 PPM      400 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (50)         (50)         (50)         (50)                                   
      Atrophy                                                       1 (2%)                    1 (2%)                                
      Erythroid Cell, Hyperplasia                                   1 (2%)                                                          
      Myeloid Cell, Hyperplasia                        2 (4%)       1 (2%)       1 (2%)                                             
   Lymph Node                                         (31)         (44)         (38)         (32)                                   
      Ectasia                                          2 (6%)       1 (2%)                                                          
      Hemorrhage                                       2 (6%)       1 (2%)                                                          
      Hyperplasia, Plasma Cell                         2 (6%)                                                                       
      Iliac, Ectasia                                   5 (16%)      3 (7%)       3 (8%)       1 (3%)                                
      Iliac, Hemorrhage                                1 (3%)       2 (5%)       2 (5%)       3 (9%)                                
      Iliac, Hyperplasia, Lymphoid                                  1 (2%)       2 (5%)       1 (3%)                                
      Iliac, Hyperplasia, Plasma Cell                               4 (9%)       2 (5%)       2 (6%)                                
      Inguinal, Atrophy                                1 (3%)                                                                       
      Inguinal, Ectasia                                1 (3%)                    1 (3%)                                             
      Inguinal, Hemorrhage                                          1 (2%)       1 (3%)       1 (3%)                                
      Inguinal, Hyperplasia, Lymphoid                                            1 (3%)                                             
      Inguinal, Infiltration Cellular, Histiocyte                                1 (3%)                                             
      Mediastinal, Atrophy                                          1 (2%)                                                          
      Mediastinal, Congestion                          1 (3%)       3 (7%)       2 (5%)       1 (3%)                                
      Mediastinal, Ectasia                             6 (19%)     12 (27%)      9 (24%)      6 (19%)                               
      Mediastinal, Hemorrhage                          8 (26%)     15 (34%)     10 (26%)      9 (28%)                               
      Mediastinal, Hyperplasia, Lymphoid                                                      1 (3%)                                
      Mediastinal, Hyperplasia, Plasma Cell                         2 (5%)       1 (3%)       1 (3%)                                
      Pancreatic, Ectasia                              2 (6%)       5 (11%)                   1 (3%)                                
      Pancreatic, Hemorrhage                           4 (13%)      5 (11%)      4 (11%)      7 (22%)                               
      Pancreatic, Hyperplasia, Lymphoid                2 (6%)       1 (2%)                    4 (13%)                               
      Pancreatic, Hyperplasia, Plasma Cell             1 (3%)                    2 (5%)       2 (6%)                                
      Pancreatic, Pigmentation                                                   1 (3%)                                             
      Renal, Ectasia                                  15 (48%)     20 (45%)     16 (42%)     10 (31%)                               
      Renal, Fibrosis                                               2 (5%)                                                          
      Renal, Hemorrhage                               10 (32%)     17 (39%)     19 (50%)     12 (38%)                               
      Renal, Hyperplasia, Lymphoid                                               1 (3%)       2 (6%)                                
      Renal, Hyperplasia, Plasma Cell                               1 (2%)       6 (16%)      2 (6%)                                
      Renal, Pigmentation                                                        3 (8%)                                             
   Lymph Node, Mandibular                             (48)         (49)         (47)         (48)                                   
      Congestion                                                    5 (10%)      1 (2%)       4 (8%)                                
      Ectasia                                         15 (31%)      8 (16%)     10 (21%)     10 (21%)                               
      Hemorrhage                                       3 (6%)       1 (2%)       3 (6%)       1 (2%)                                
      Hyperplasia, Lymphoid                                         1 (2%)                    1 (2%)                                
      Hyperplasia, Plasma Cell                         4 (8%)       8 (16%)      6 (13%)      4 (8%)                                
   Lymph Node, Mesenteric                             (46)         (50)         (50)         (50)                                   
      Atrophy                                                       6 (12%)      1 (2%)       2 (4%)                                
      Ectasia                                          5 (11%)      6 (12%)      6 (12%)      5 (10%)                               
      Hemorrhage                                      12 (26%)     14 (28%)     12 (24%)     12 (24%)                               
      Hyperplasia, Lymphoid                            1 (2%)       1 (2%)       2 (4%)       5 (10%)                               
      Hyperplasia, Plasma Cell                                      2 (4%)                    1 (2%)                                

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

                                                             Page    7                                                              
NTP Experiment-Test: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97  
Route: DOSED WATER                                                                                                Time: 12:18:24  
____________________________________________________________________________________________________________________________________

         WISTAR OUTBRED RATS MALE                  0 PPM        100 PPM      200 PPM      400 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - CONT                                                                                                         
   Spleen                                             (49)         (50)         (49)         (49)                                   
      Angiectasis                                      1 (2%)                                                                       
      Atrophy                                          2 (4%)       1 (2%)       1 (2%)       1 (2%)                                
      Congestion                                       1 (2%)                    1 (2%)                                             
      Fibrosis                                                      1 (2%)       1 (2%)       1 (2%)                                
      Hematopoietic Cell Proliferation                 1 (2%)       2 (4%)                    2 (4%)                                
      Hyperplasia, Lymphoid                            1 (2%)                                                                       
      Necrosis                                         1 (2%)                                                                       
      Artery, Mineralization                           1 (2%)       1 (2%)                                                          
   Thymus                                             (48)         (49)         (49)         (50)                                   
      Atrophy                                         15 (31%)     29 (59%)     28 (57%)     24 (48%)                               
      Cyst                                             5 (10%)      6 (12%)      4 (8%)       6 (12%)                               
      Ectopic Parathyroid Gland                        3 (6%)       5 (10%)      1 (2%)       1 (2%)                                
      Ectopic Thyroid                                  1 (2%)                                                                       
      Fibrosis                                                                   1 (2%)                                             
      Hemorrhage                                       8 (17%)      6 (12%)      8 (16%)     14 (28%)                               
      Hyperplasia, Lymphoid                            1 (2%)                                                                       
      Hyperplasia, Squamous                                                                   2 (4%)                                
      Artery, Mineralization                                        1 (2%)                                                          
      Epithelial Cell, Hyperplasia                                               1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (48)         (46)         (44)         (46)                                   
      Cyst                                                          2 (4%)                    1 (2%)                                
      Hyperplasia                                      4 (8%)                    2 (5%)       4 (9%)                                
      Artery, Mineralization                           3 (6%)       5 (11%)                                                         
      Duct, Dilatation                                 6 (13%)      7 (15%)      5 (11%)      4 (9%)                                
   Skin                                               (50)         (50)         (50)         (50)                                   
      Cyst                                             1 (2%)       2 (4%)       1 (2%)                                             
      Hyperkeratosis                                   1 (2%)                                                                       
      Hyperplasia, Squamous                                         2 (4%)       1 (2%)       2 (4%)                                
      Inflammation, Chronic                            1 (2%)       2 (4%)                    1 (2%)                                
      Inflammation, Suppurative                                     1 (2%)                    1 (2%)                                
      Ulcer                                            1 (2%)       1 (2%)                    2 (4%)                                
      Hair Follicle, Cyst                              1 (2%)                                 1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (50)         (50)         (50)         (50)                                   
      Fibrous Osteodystrophy                          10 (20%)     21 (42%)     16 (32%)      6 (12%)                               
      Inflammation, Chronic Active                                  1 (2%)                                                          
      Osteosclerosis                                                             1 (2%)                                             
      Cartilage, Degeneration                                                                 1 (2%)                                
      Cranium, Fibrous Osteodystrophy                 10 (20%)     15 (30%)     13 (26%)      2 (4%)                                

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

                                                             Page    8                                                              
NTP Experiment-Test: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97  
Route: DOSED WATER                                                                                                Time: 12:18:24  
____________________________________________________________________________________________________________________________________

         WISTAR OUTBRED RATS MALE                  0 PPM        100 PPM      200 PPM      400 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
MUSCULOSKELETAL SYSTEM - CONT                                                                                                       
      Joint, Arthrosis                                                                        1 (2%)                                
      Joint, Fibrosis                                                                         1 (2%)                                
      Joint, Inflammation, Chronic                                               1 (2%)       1 (2%)                                
      Mandible, Hyperplasia                                                                   1 (2%)                                
      Metacarpal, Inflammation, Chronic Active                                                1 (2%)                                
      Metatarsal, Hyperplasia                                                    1 (2%)                                             
      Metatarsal, Inflammation, Chronic Active                                                1 (2%)                                
      Periosteum, Hyperplasia                                                                 1 (2%)                                
      Rib, Callus                                                   1 (2%)                                                          
      Vertebra, Fibrous Osteodystrophy                              4 (8%)       2 (4%)                                             
      Vertebra, Inflammation, Chronic                                                         1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (50)         (49)         (50)         (50)                                   
      Degeneration                                                  1 (2%)                                                          
      Hemorrhage                                       1 (2%)       1 (2%)                                                          
      Hydrocephalus                                    1 (2%)       1 (2%)                                                          
   Peripheral Nerve                                   (1)          (4)          (2)          (5)                                    
      Degeneration                                     1 (100%)                                                                     
      Mineralization                                                2 (50%)      2 (100%)                                           
      Radicular Neuropathy                                          4 (100%)     1 (50%)      2 (40%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (50)         (50)         (50)         (50)                                   
      Congestion                                                    4 (8%)       2 (4%)       4 (8%)                                
      Edema                                                         2 (4%)                                                          
      Hemorrhage                                       2 (4%)       1 (2%)      10 (20%)      7 (14%)                               
      Inflammation, Acute                              1 (2%)       3 (6%)                                                          
      Inflammation, Chronic                            1 (2%)                    1 (2%)                                             
      Inflammation, Granulomatous                      4 (8%)       1 (2%)       5 (10%)      2 (4%)                                
      Mineralization                                                1 (2%)                                                          
      Necrosis                                         1 (2%)                    1 (2%)                                             
      Alveolar Epithelium, Hyperplasia                 1 (2%)                    2 (4%)                                             
      Alveolar Epithelium, Hypertrophy                              1 (2%)                                                          
      Alveolus, Infiltration Cellular, Histiocyte      8 (16%)      5 (10%)      4 (8%)                                             
      Alveolus, Mineralization                         2 (4%)                                                                       
      Artery, Mineralization                           2 (4%)       3 (6%)                                                          
      Bronchus, Inflammation, Acute                    1 (2%)                                                                       
      Bronchus, Mineralization                         1 (2%)                                                                       
      Interstitium, Fibrosis                           4 (8%)       6 (12%)      4 (8%)       1 (2%)                                
      Interstitium, Inflammation, Chronic                           2 (4%)                                                          
   Nose                                               (50)         (50)         (50)         (50)                                   
      Cyst                                             1 (2%)                                                                       

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

                                                             Page    9                                                              
NTP Experiment-Test: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97  
Route: DOSED WATER                                                                                                Time: 12:18:24  
____________________________________________________________________________________________________________________________________

         WISTAR OUTBRED RATS MALE                  0 PPM        100 PPM      200 PPM      400 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
RESPIRATORY SYSTEM - CONT                                                                                                           
      Erosion                                          1 (2%)                                                                       
      Foreign Body                                    11 (22%)      4 (8%)       6 (12%)      1 (2%)                                
      Hemorrhage                                       3 (6%)                    1 (2%)                                             
      Hyperplasia, Squamous                            1 (2%)                                                                       
      Inflammation, Acute                              7 (14%)      7 (14%)      4 (8%)       2 (4%)                                
      Inflammation, Chronic                            7 (14%)      1 (2%)       2 (4%)       1 (2%)                                
      Inflammation, Chronic Active                     4 (8%)       6 (12%)      5 (10%)      6 (12%)                               
      Metaplasia, Squamous                                          1 (2%)       1 (2%)       2 (4%)                                
      Thrombosis                                                                 1 (2%)                                             
      Ulcer                                                                      2 (4%)                                             
      Artery, Thrombosis                                                                      1 (2%)                                
      Olfactory Epithelium, Hyperplasia                1 (2%)                                                                       
      Olfactory Epithelium, Metaplasia                                           1 (2%)                                             
      Respiratory Epithelium, Hyperplasia             20 (40%)      9 (18%)     12 (24%)     15 (30%)                               
      Respiratory Epithelium, Metaplasia                            1 (2%)                                                          
      Respiratory Epithelium, Metaplasia, Squamous                               1 (2%)                                             
   Trachea                                            (50)         (50)         (50)         (50)                                   
      Cyst                                                          1 (2%)                                                          
      Foreign Body                                                               1 (2%)                                             
      Inflammation, Acute                                           1 (2%)                                                          
      Inflammation, Chronic Active                                                            1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Eye                                                                          (1)                                                 
      Cornea, Ulcer                                                              1 (100%)                                           
   Harderian Gland                                    (1)                       (4)          (1)                                    
      Inflammation, Chronic                                                                   1 (100%)                              
   Lacrimal Gland                                                               (1)                                                 
      Atrophy                                                                    1 (100%)                                           
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (50)         (50)         (50)         (50)                                   
      Congestion                                       4 (8%)                                 2 (4%)                                
      Cyst                                            21 (42%)     31 (62%)     19 (38%)     16 (32%)                               
      Hydronephrosis                                  19 (38%)     20 (40%)     30 (60%)     15 (30%)                               
      Inflammation, Acute                                           2 (4%)                    1 (2%)                                
      Mineralization                                   8 (16%)     17 (34%)      8 (16%)      5 (10%)                               
      Nephropathy                                     50 (100%)    50 (100%)    50 (100%)    50 (100%)                              
      Artery, Mineralization                           5 (10%)      8 (16%)      3 (6%)                                             
      Renal Tubule, Accumulation, Hyaline Droplet                                1 (2%)       1 (2%)                                
      Renal Tubule, Hyperplasia                        6 (12%)     17 (34%)      8 (16%)      5 (10%)                               
      Vein, Thrombosis                                              2 (4%)       1 (2%)       3 (6%)                                
   Urinary Bladder                                    (47)         (49)         (47)         (44)                                   

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

                                                             Page   10                                                              
NTP Experiment-Test: 55301-06         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                              PYRIDINE                                         Date: 10/08/97  
Route: DOSED WATER                                                                                                Time: 12:18:24  
____________________________________________________________________________________________________________________________________

         WISTAR OUTBRED RATS MALE                  0 PPM        100 PPM      200 PPM      400 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
URINARY SYSTEM - CONT                                                                                                               
      Dilatation                                                                 1 (2%)                                             
      Edema                                                         1 (2%)                                                          
      Hemorrhage                                                                 1 (2%)                                             
      Inflammation, Acute                                           1 (2%)                                                          
      Inflammation, Chronic                            1 (2%)                                                                       
      Inflammation, Chronic Active                                               1 (2%)                                             
      Ulcer                                                         1 (2%)                                                          
      Artery, Mineralization                                                     1 (2%)                                             
      Transitional Epithelium, Hyperplasia             1 (2%)       3 (6%)       1 (2%)                                             
                                                                                                                                    

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

                                                             Page   11                                                              
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