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TDMS Study 05150-02 Pathology Tables


                                     INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)
                                                   METHYLPHENIDATE HYDROCHLORIDE


NTP Experiment-Test: 05150-02                                                                                     Report: PEIRPT03
Study Type: CHRONIC                                                                                               Date: 05/20/95
Route: DOSED FEED                                                                                                 Time: 09:59:03




       Facility:  TSI Mason Research

       Chemical CAS #:  298-59-9

       Lock Date:  02/19/92

       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: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially In Study                          69           69           70           70                                     
  Scheduled Sacrifice                                 20           19           20           20                                     
  Early Deaths                                                                                                                      
    Natural Death                                      5            7            6                                                  
    Accidently Killed                                  1                                                                            
    Moribund Sacrifice                                 6            7            7            6                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                36           34           37           44                                     
    Natural Death                                      1            1                                                               
  Missing                                                           1                                                               
  Animals Examined Microscopically                    69           68           70           70                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Gallbladder                                        (64)         (56)         (63)         (68)                                   
      Dilatation                                                    1 (2%)                    1 (1%)                                
   Intestine Large, Cecum                             (67)         (63)         (65)         (70)                                   
      Edema                                                                      1 (2%)                                             
      Hyperplasia, Lymphoid                           30 (45%)     18 (29%)     18 (28%)     17 (24%)                               
   Intestine Small, Jejunum                           (65)         (63)         (65)         (70)                                   
      Hyperplasia, Lymphoid                                                      1 (2%)       1 (1%)                                
   Liver                                              (69)         (67)         (69)         (70)                                   
      Angiectasis                                      1 (1%)       1 (1%)       1 (1%)                                             
      Autolysis                                        1 (1%)                                                                       
      Basophilic Focus                                 2 (3%)       4 (6%)       3 (4%)       1 (1%)                                
      Clear Cell Focus                                              2 (3%)       2 (3%)                                             
      Congestion                                       1 (1%)                                                                       
      Eosinophilic Focus                               3 (4%)       3 (4%)      10 (14%)     27 (39%)                               
      Fatty Change                                     1 (1%)       1 (1%)       8 (12%)      5 (7%)                                
      Fatty Change, Focal                                                        2 (3%)                                             
      Hematopoietic Cell Proliferation                 1 (1%)       1 (1%)       2 (3%)                                             
      Hemorrhage                                                    1 (1%)                                                          
      Hyperplasia, Lymphoid                            2 (3%)       1 (1%)                                                          
      Necrosis, Focal                                  7 (10%)      4 (6%)       7 (10%)     13 (19%)                               
   Mesentery                                          (6)                       (1)          (2)                                    
      Fat, Necrosis                                    5 (83%)                                2 (100%)                              
   Pancreas                                           (68)         (67)         (69)         (70)                                   
      Inflammation, Chronic, Focal                     2 (3%)       2 (3%)       1 (1%)       1 (1%)                                
      Acinus, Atrophy                                               1 (1%)       1 (1%)       2 (3%)                                
      Duct, Ectasia                                    2 (3%)       1 (1%)                    2 (3%)                                
   Salivary Glands                                    (69)         (67)         (70)         (69)                                   
      Inflammation, Chronic, Focal                     6 (9%)       7 (10%)      7 (10%)      9 (13%)                               
   Stomach, Forestomach                               (67)         (68)         (69)         (70)                                   
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    2                                                              
NTP Experiment-Test: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - CONT                                                                                                            
      Abscess                                          1 (1%)                                                                       
      Diverticulum                                     1 (1%)                    1 (1%)                                             
      Ulcer                                            1 (1%)                    1 (1%)                                             
   Stomach, Glandular                                 (68)         (65)         (68)         (70)                                   
      Edema                                                         1 (2%)                                                          
      Erosion                                                       2 (3%)                                                          
      Inflammation, Chronic                                         1 (2%)       1 (1%)                                             
      Inflammation, Chronic, Focal                                               1 (1%)                                             
      Inflammation, Subacute                                                                  1 (1%)                                
      Muscularis, Hypertrophy                          1 (1%)                    1 (1%)                                             
   Tongue                                             (3)                                    (1)                                    
      Angiectasis                                      3 (100%)                               1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (68)         (68)         (69)         (70)                                   
      Artery, Inflammation, Chronic                                 1 (1%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (69)         (67)         (68)         (70)                                   
      Congestion                                       1 (1%)                                                                       
      Cytoplasmic Alteration, Focal                                 2 (3%)                                                          
      Fibrosis                                                                                1 (1%)                                
      Hematopoietic Cell Proliferation                 1 (1%)                                 1 (1%)                                
      Hyperplasia, Focal                               1 (1%)                                 1 (1%)                                
      Hypertrophy                                                   1 (1%)       2 (3%)                                             
      Capsule, Hyperplasia                             1 (1%)                                                                       
   Adrenal Medulla                                    (67)         (64)         (66)         (68)                                   
      Hyperplasia, Focal                               1 (1%)       1 (2%)                                                          
   Islets, Pancreatic                                 (68)         (67)         (69)         (70)                                   
      Hyperplasia                                      7 (10%)      9 (13%)     10 (14%)     11 (16%)                               
      Hypoplasia                                                                 1 (1%)                                             
   Pituitary Gland                                    (67)         (66)         (68)         (67)                                   
      Pars Distalis, Angiectasis                       1 (1%)       1 (2%)                    1 (1%)                                
      Pars Distalis, Hyperplasia, Focal               14 (21%)     10 (15%)     13 (19%)     11 (16%)                               
   Thyroid Gland                                      (69)         (66)         (68)         (69)                                   
      Inflammation, Acute, Focal                                                              1 (1%)                                
      Inflammation, Chronic                                         1 (2%)                                                          
      Follicle, Cyst                                                             2 (3%)       1 (1%)                                
      Follicular Cell, Hyperplasia, Focal              4 (6%)      11 (17%)      8 (12%)      5 (7%)                                
____________________________________________________________________________________________________________________________________
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    3                                                              
NTP Experiment-Test: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Clitoral Gland                                     (43)         (41)         (44)         (46)                                   
      Abscess                                                                    1 (2%)                                             
      Angiectasis                                                                             1 (2%)                                
      Cyst                                             1 (2%)                                                                       
      Dilatation                                       2 (5%)       1 (2%)                                                          
      Pigmentation, Hemosiderin                                                  1 (2%)                                             
   Ovary                                              (65)         (67)         (69)         (67)                                   
      Abscess                                                                    1 (1%)                                             
      Angiectasis                                                                1 (1%)                                             
      Cyst                                             7 (11%)     13 (19%)     13 (19%)      9 (13%)                               
      Mineralization, Focal                                         1 (1%)       1 (1%)                                             
      Thrombosis                                                    1 (1%)                                                          
   Uterus                                             (69)         (68)         (69)         (70)                                   
      Angiectasis                                      1 (1%)       3 (4%)       2 (3%)       2 (3%)                                
      Fibrosis, Focal                                                                         1 (1%)                                
      Hydrometra                                       6 (9%)       8 (12%)      6 (9%)      14 (20%)                               
      Inflammation, Suppurative                        1 (1%)                                 2 (3%)                                
      Thrombosis                                                                              1 (1%)                                
      Endometrium, Hyperplasia, Cystic                63 (91%)     62 (91%)     58 (84%)     61 (87%)                               
      Endometrium, Metaplasia, Squamous                             1 (1%)       2 (3%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (69)         (68)         (67)         (70)                                   
      Angiectasis                                                                             1 (1%)                                
      Hyperplasia, Neutrophil                          2 (3%)       6 (9%)       5 (7%)       2 (3%)                                
      Myelofibrosis                                   25 (36%)     21 (31%)     22 (33%)     21 (30%)                               
   Lymph Node                                         (7)          (7)          (8)          (5)                                    
      Lumbar, Hematopoietic Cell Proliferation         1 (14%)                                                                      
      Lumbar, Lymphatic, Angiectasis                                             1 (13%)                                            
      Mediastinal, Hyperplasia, Lymphoid               1 (14%)                                                                      
      Mediastinal, Infiltration Cellular, Mixed                                                                                     
          Cell                                                                   1 (13%)                                            
      Pancreatic, Hyperplasia, Lymphoid                1 (14%)                   2 (25%)                                            
      Renal, Hematopoietic Cell Proliferation          1 (14%)                                                                      
   Lymph Node, Mandibular                             (67)         (61)         (68)         (68)                                   
      Congestion                                                    1 (2%)                                                          
      Hematopoietic Cell Proliferation                 1 (1%)                                                                       
      Necrosis                                                                   1 (1%)                                             
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    4                                                              
NTP Experiment-Test: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - CONT                                                                                                         
      Lymphatic, Angiectasis                                                                  1 (1%)                                
   Lymph Node, Mesenteric                             (65)         (66)         (67)         (67)                                   
      Congestion                                       1 (2%)                                                                       
      Depletion Lymphoid                               1 (2%)                                                                       
      Inflammation, Chronic                            1 (2%)                                                                       
      Lymphatic, Angiectasis                                        1 (2%)       3 (4%)       1 (1%)                                
   Spleen                                             (68)         (67)         (68)         (70)                                   
      Congestion                                       1 (1%)                    1 (1%)       2 (3%)                                
      Depletion Lymphoid                               1 (1%)       3 (4%)       3 (4%)       1 (1%)                                
      Hematopoietic Cell Proliferation                 8 (12%)     10 (15%)     13 (19%)      9 (13%)                               
      Hyperplasia, Lymphoid                            2 (3%)       1 (1%)       4 (6%)       2 (3%)                                
      Necrosis, Focal                                               1 (1%)       1 (1%)                                             
   Thymus                                             (65)         (66)         (67)         (69)                                   
      Angiectasis                                                                             1 (1%)                                
      Depletion Lymphoid                               1 (2%)       2 (3%)       2 (3%)                                             
      Hyperplasia, Lymphoid                            2 (3%)                                 1 (1%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (59)         (60)         (63)         (64)                                   
      Lactation                                        1 (2%)       2 (3%)       3 (5%)       2 (3%)                                
   Skin                                               (69)         (68)         (70)         (70)                                   
      Inflammation, Chronic                                                                   1 (1%)                                
      Ulcer                                            1 (1%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (69)         (68)         (70)         (70)                                   
      Hyperostosis                                                  1 (1%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (69)         (68)         (70)         (70)                                   
      Compression                                      1 (1%)                    1 (1%)                                             
      Hemorrhage, Focal                                             1 (1%)                                                          
      Mineralization                                  42 (61%)     38 (56%)     36 (51%)     38 (54%)                               
      Mineralization, Focal                            2 (3%)                    1 (1%)       1 (1%)                                
      Artery, Inflammation, Chronic                                 1 (1%)                                                          
   Spinal Cord                                                     (1)                                                              
      Artery, Inflammation, Chronic                                 1 (100%)                                                        
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    5                                                              
NTP Experiment-Test: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE FEMALE                        0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (68)         (68)         (69)         (70)                                   
      Congestion                                       1 (1%)       1 (1%)                                                          
      Hemorrhage, Focal                                2 (3%)       2 (3%)       1 (1%)                                             
      Inflammation, Chronic                            1 (1%)                    1 (1%)                                             
      Thrombosis                                                    1 (1%)                                                          
      Alveolar Epithelium, Hyperplasia                                                        4 (6%)                                
      Peribronchial, Inflammation, Chronic             3 (4%)       1 (1%)       5 (7%)                                             
   Nose                                               (69)         (68)         (70)         (70)                                   
      Degeneration, Hyaline                            8 (12%)      4 (6%)       7 (10%)      8 (11%)                               
      Inflammation, Chronic                           54 (78%)     49 (72%)     51 (73%)     56 (80%)                               
      Inflammation, Chronic, Focal                    10 (14%)      8 (12%)     10 (14%)     10 (14%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Harderian Gland                                    (2)          (1)          (4)          (5)                                    
      Hyperplasia                                      1 (50%)                   1 (25%)      1 (20%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (69)         (67)         (70)         (70)                                   
      Congestion                                                    1 (1%)       1 (1%)                                             
      Fatty Change                                     2 (3%)                                                                       
      Glomerulosclerosis                               2 (3%)       2 (3%)                    1 (1%)                                
      Hemorrhage, Focal                                1 (1%)                                                                       
      Hyperplasia, Lymphoid                            1 (1%)       1 (1%)       1 (1%)                                             
      Infarct                                          2 (3%)                    2 (3%)       3 (4%)                                
      Inflammation, Chronic, Focal                                               1 (1%)                                             
      Mineralization                                   1 (1%)                                 1 (1%)                                
      Nephropathy                                                                1 (1%)       1 (1%)                                
      Renal Tubule, Degeneration, Granular             1 (1%)                    2 (3%)                                             
      Renal Tubule, Necrosis                                        2 (3%)                                                          
      Renal Tubule, Regeneration                       7 (10%)      3 (4%)       3 (4%)       3 (4%)                                
   Urinary Bladder                                    (63)         (59)         (64)         (70)                                   
      Inflammation, Chronic, Focal                     8 (13%)      7 (12%)      9 (14%)      9 (13%)                               
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    6                                                              
NTP Experiment-Test: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially In Study                          70           70           70           70                                     
  Scheduled Sacrifice                                 20           20           20           20                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                 2            2            4            4                                     
    Natural Death                                      3            3            2            5                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                45           45           43           41                                     
    Moribund Sacrifice                                                           1                                                  
  Animals Examined Microscopically                    70           70           70           70                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Gallbladder                                        (64)         (67)         (64)         (62)                                   
      Ulcer                                            1 (2%)                                                                       
   Intestine Large, Cecum                             (68)         (69)         (68)         (67)                                   
      Hyperplasia, Lymphoid                           33 (49%)     18 (26%)     23 (34%)     24 (36%)                               
   Intestine Small, Jejunum                           (68)         (68)         (67)         (66)                                   
      Hyperplasia, Lymphoid                            3 (4%)       1 (1%)       2 (3%)       1 (2%)                                
      Inflammation, Acute                              1 (1%)                                 1 (2%)                                
      Ulcer                                                         1 (1%)                                                          
   Intestine Small, Ileum                             (66)         (68)         (67)         (65)                                   
      Hyperplasia, Lymphoid                            1 (2%)                                                                       
   Liver                                              (70)         (70)         (70)         (70)                                   
      Angiectasis                                      4 (6%)       2 (3%)       1 (1%)                                             
      Basophilic Focus                                 1 (1%)       2 (3%)       5 (7%)       1 (1%)                                
      Clear Cell Focus                                 5 (7%)       3 (4%)       3 (4%)       6 (9%)                                
      Eosinophilic Focus                               6 (9%)       9 (13%)      9 (13%)     14 (20%)                               
      Fatty Change                                    12 (17%)     13 (19%)     13 (19%)     24 (34%)                               
      Fatty Change, Focal                              2 (3%)                                 2 (3%)                                
      Inflammation, Chronic, Focal                                  1 (1%)       1 (1%)       1 (1%)                                
      Necrosis, Focal                                  3 (4%)       1 (1%)       4 (6%)       6 (9%)                                
      Thrombosis                                       1 (1%)                    1 (1%)       1 (1%)                                
      Artery, Inflammation, Acute                                                             1 (1%)                                
   Mesentery                                          (2)          (3)          (1)          (2)                                    
      Cyst                                                                       1 (100%)                                           
      Hemorrhage, Focal                                1 (50%)                                                                      
      Mineralization                                                                          1 (50%)                               
      Fat, Necrosis                                    1 (50%)      2 (67%)                   1 (50%)                               
   Pancreas                                           (70)         (69)         (69)         (70)                                   
      Hyperplasia, Focal                                            2 (3%)                                                          
      Inflammation, Chronic, Focal                                                            1 (1%)                                
   Salivary Glands                                    (70)         (70)         (70)         (70)                                   
      Inflammation, Chronic, Focal                     2 (3%)       7 (10%)      4 (6%)       8 (11%)                               
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    7                                                              
NTP Experiment-Test: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - CONT                                                                                                            
   Stomach, Forestomach                               (69)         (70)         (70)         (70)                                   
      Foreign Body                                     1 (1%)                                                                       
      Hyperkeratosis, Focal                                                      1 (1%)                                             
      Ulcer                                                                                   2 (3%)                                
   Stomach, Glandular                                 (68)         (69)         (70)         (67)                                   
      Erosion                                                       1 (1%)       2 (3%)       2 (3%)                                
      Hyperplasia                                                                             1 (1%)                                
      Inflammation, Acute                              1 (1%)                                                                       
      Inflammation, Chronic                            2 (3%)       1 (1%)       1 (1%)       3 (4%)                                
      Mucosa, Hyperplasia, Focal                                    1 (1%)                                                          
      Perivascular, Inflammation, Chronic                                        1 (1%)                                             
   Tongue                                             (3)                       (1)          (2)                                    
      Hemorrhage, Focal                                1 (33%)                                1 (50%)                               
      Hyperkeratosis, Focal                                                      1 (100%)                                           
      Pigmentation, Focal                              1 (33%)                                1 (50%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (70)         (70)         (70)         (70)                                   
      Inflammation, Chronic, Focal                                                            1 (1%)                                
      Mineralization                                                1 (1%)                                                          
      Ventricle, Hypertrophy                           1 (1%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (69)         (69)         (70)         (70)                                   
      Atrophy                                          2 (3%)                                                                       
      Fibrosis                                                                                1 (1%)                                
      Hyperplasia, Focal                              14 (20%)     18 (26%)     15 (21%)     13 (19%)                               
      Capsule, Hyperplasia                             1 (1%)                    1 (1%)       1 (1%)                                
      Capsule, Hyperplasia, Focal                                   1 (1%)                                                          
   Adrenal Medulla                                    (68)         (67)         (69)         (66)                                   
      Hyperplasia                                                   1 (1%)                                                          
      Hyperplasia, Focal                                                         2 (3%)                                             
   Islets, Pancreatic                                 (70)         (68)         (69)         (70)                                   
      Atrophy                                                                                 1 (1%)                                
      Hyperplasia                                     24 (34%)     27 (40%)     22 (32%)     20 (29%)                               
   Pituitary Gland                                    (68)         (68)         (64)         (64)                                   
      Pars Distalis, Cyst                              1 (1%)                                                                       
   Thyroid Gland                                      (70)         (69)         (69)         (70)                                   
      Follicle, Cyst                                   1 (1%)                                                                       
      Follicular Cell, Hyperplasia                     2 (3%)       1 (1%)                                                          
____________________________________________________________________________________________________________________________________
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    8                                                              
NTP Experiment-Test: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Epididymis                                         (70)         (70)         (70)         (70)                                   
      Atrophy                                          1 (1%)                    1 (1%)                                             
      Inflammation, Chronic                            1 (1%)                                                                       
      Spermatocele                                     1 (1%)       1 (1%)                                                          
   Preputial Gland                                    (54)         (53)         (55)         (54)                                   
      Abscess                                          1 (2%)                    1 (2%)                                             
      Atrophy                                                                    1 (2%)                                             
      Cyst                                            36 (67%)     42 (79%)     42 (76%)     35 (65%)                               
      Depletion Cellular                                                                      1 (2%)                                
      Dilatation                                      28 (52%)     25 (47%)     25 (45%)     28 (52%)                               
      Hemorrhage, Focal                                1 (2%)                                                                       
      Infiltration Cellular, Plasma Cell                                                      1 (2%)                                
      Inflammation, Acute                              6 (11%)      8 (15%)      7 (13%)      4 (7%)                                
      Inflammation, Chronic                            9 (17%)      8 (15%)      9 (16%)      6 (11%)                               
   Prostate                                           (69)         (69)         (67)         (65)                                   
      Atrophy                                                                    2 (3%)       1 (2%)                                
      Inflammation, Acute                                                                     1 (2%)                                
      Inflammation, Chronic                                         1 (1%)       2 (3%)       2 (3%)                                
      Inflammation, Chronic, Focal                                               2 (3%)                                             
   Seminal Vesicle                                    (70)         (69)         (70)         (70)                                   
      Depletion Cellular                               4 (6%)       2 (3%)       3 (4%)       2 (3%)                                
      Dilatation                                       5 (7%)       5 (7%)       7 (10%)      3 (4%)                                
      Fibrosis                                                                   1 (1%)                                             
   Testes                                             (70)         (70)         (70)         (70)                                   
      Hypospermia                                      1 (1%)       1 (1%)       1 (1%)       2 (3%)                                
      Interstitial Cell, Hyperplasia                                                          1 (1%)                                
      Seminiferous Tubule, Atrophy                                               1 (1%)       2 (3%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (70)         (70)         (70)         (69)                                   
      Hyperplasia, Neutrophil                                       2 (3%)       1 (1%)       3 (4%)                                
      Myelofibrosis                                    1 (1%)                    1 (1%)       1 (1%)                                
   Lymph Node                                         (3)          (5)          (1)          (2)                                    
      Mediastinal, Infiltration Cellular, Plasma                                                                                    
          Cell                                                      1 (20%)                                                         
      Pancreatic, Hyperplasia                          2 (67%)                                                                      
      Renal, Lymphatic, Angiectasis                                                           1 (50%)                               
   Lymph Node, Mandibular                             (66)         (65)         (67)         (66)                                   
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    9                                                              
NTP Experiment-Test: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - CONT                                                                                                         
      Infiltration Cellular, Plasma Cell                                                      1 (2%)                                
   Lymph Node, Mesenteric                             (68)         (65)         (65)         (65)                                   
      Congestion                                       2 (3%)       3 (5%)       3 (5%)       2 (3%)                                
      Fibrosis                                                                                1 (2%)                                
      Hyperplasia                                      1 (1%)                    1 (2%)                                             
      Hyperplasia, Lymphoid                                         1 (2%)                                                          
      Infiltration Cellular, Plasma Cell                                                      1 (2%)                                
      Thrombosis                                       1 (1%)                                                                       
   Spleen                                             (69)         (69)         (69)         (70)                                   
      Congestion                                       1 (1%)       1 (1%)       1 (1%)                                             
      Cyst                                                          1 (1%)                                                          
      Depletion Lymphoid                               5 (7%)       3 (4%)       4 (6%)       1 (1%)                                
      Fibrosis, Focal                                  2 (3%)                                                                       
      Hematopoietic Cell Proliferation                 6 (9%)       7 (10%)      9 (13%)      8 (11%)                               
      Hyperplasia, Lymphoid                                         1 (1%)                    1 (1%)                                
      Infiltration Cellular, Plasma Cell                                                      1 (1%)                                
   Thymus                                             (58)         (60)         (58)         (56)                                   
      Cyst                                             1 (2%)                                                                       
      Hyperplasia, Lymphoid                                         1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Skin                                               (70)         (70)         (69)         (70)                                   
      Inflammation, Chronic                                                                   1 (1%)                                
      Ulcer                                                                      1 (1%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (70)         (70)         (70)         (70)                                   
      Hyperostosis                                                  1 (1%)                    1 (1%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (70)         (70)         (70)         (70)                                   
      Compression                                                                             1 (1%)                                
      Hemorrhage, Focal                                                                       1 (1%)                                
      Mineralization                                  36 (51%)     42 (60%)     34 (49%)     34 (49%)                               
      Mineralization, Focal                            5 (7%)       3 (4%)       4 (6%)       5 (7%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   10                                                              
NTP Experiment-Test: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (70)         (69)         (70)         (70)                                   
      Angiectasis                                      1 (1%)                                                                       
      Congestion                                                    1 (1%)       1 (1%)                                             
      Hemorrhage, Focal                                5 (7%)       1 (1%)       1 (1%)                                             
      Infiltration Cellular, Histiocyte                             1 (1%)                                                          
      Inflammation, Chronic                                         1 (1%)                    1 (1%)                                
      Alveolar Epithelium, Hyperplasia                 3 (4%)       1 (1%)       4 (6%)       3 (4%)                                
      Peribronchial, Inflammation, Chronic             4 (6%)       4 (6%)       7 (10%)      3 (4%)                                
   Nose                                               (70)         (70)         (70)         (70)                                   
      Degeneration, Hyaline                                                      3 (4%)       2 (3%)                                
      Inflammation, Chronic                           55 (79%)     53 (76%)     52 (74%)     52 (74%)                               
      Inflammation, Chronic, Focal                    11 (16%)      8 (11%)     10 (14%)     10 (14%)                               
      Metaplasia, Squamous                                          1 (1%)       1 (1%)       1 (1%)                                
      Olfactory Epithelium, Hyperplasia                                          1 (1%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Harderian Gland                                    (5)          (2)                       (2)                                    
      Hyperplasia                                                   1 (50%)                                                         
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (70)         (70)         (70)         (70)                                   
      Casts                                                                                   1 (1%)                                
      Cyst                                             1 (1%)       1 (1%)       1 (1%)       3 (4%)                                
      Glomerulosclerosis                               1 (1%)       1 (1%)       1 (1%)       1 (1%)                                
      Hemorrhage                                                    1 (1%)                                                          
      Hyperplasia, Lymphoid                            2 (3%)                    1 (1%)                                             
      Infarct                                          1 (1%)       2 (3%)       1 (1%)       1 (1%)                                
      Inflammation, Chronic, Focal                                  2 (3%)                    1 (1%)                                
      Metaplasia, Osseous                                                        1 (1%)                                             
      Mineralization                                  16 (23%)     14 (20%)     13 (19%)     18 (26%)                               
      Nephropathy                                      1 (1%)                    2 (3%)       1 (1%)                                
      Renal Tubule, Degeneration, Granular             1 (1%)                                 2 (3%)                                
      Renal Tubule, Regeneration                      38 (54%)     37 (53%)     40 (57%)     36 (51%)                               
   Urinary Bladder                                    (68)         (68)         (68)         (67)                                   
      Calculus Micro Observation Only                               1 (1%)                    1 (1%)                                
      Concretion                                                                 1 (1%)       1 (1%)                                
      Ectasia                                                                    1 (1%)                                             
      Inflammation, Chronic, Focal                     1 (1%)       6 (9%)       2 (3%)                                             
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   11                                                              
NTP Experiment-Test: 05150-02         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                   METHYLPHENIDATE HYDROCHLORIDE                               Date: 05/20/95  
Route: DOSED FEED                                                                                                 Time: 09:59:03  
____________________________________________________________________________________________________________________________________
         B6C3F1 MICE MALE                          0 PPM        50 PPM       250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
URINARY SYSTEM - CONT                                                                                                               
      Perivascular, Inflammation, Chronic              1 (1%)                                 1 (1%)                                
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   12                                                              
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