Abstract
Comparisons were made of body weights, survivals, and pathological changes between CRJ:CD-1 (ICR) and B6C3F1 mice dying in the course of the study as well as those survived for 104 weeks. The mean body weight curves of both sexes of B6C3F1 crossed between 65 to 70 weeks of age and thereafter the mean body weight of females was heavier than that of males. No such a finding was observed in ICR mice. At 104 weeks of age, survival was better in B6C3F1 than in ICR mice. The incidences of liver tumors were higher in both sexes of B6C3F1 than in ICR mice. Pulmonary tumors occurred more frequently in ICR males than in B6C3F1 males, whereas malignant lymphomas were more common in B6C3F1 females than in ICR females. The incidences of pelvic dilatation and cerebral mineralization were higher in ICR males than in B6C3F1 males. On the contrary, foci or areas of hepatocellular alteration, lithogeny in the renal tubules, spindle-cell proliferation in the adrenal cortex, and pancreatic islet-cell hyperplasia occurred more frequently in B6C3F1 males than in ICR males. In females, systemic amyloidosis, proteinaceous casts, cysts, pelvic dilatation and epithelial yellow pigment deposition in the kidney, and ovarian cysts were more common in ICR than in B6C3F1 mice, while hyperplasia of lymphatic follicles in the spleen, spindle-cell proliferation in the adrenal cortex, focal necrosis in the abdominal adipose tissue, and endometrial cystic hyperplasia in the uterus occurred more frequently in B6C3F1 mice.
