Background pathology in BDF1 mice allowed to live out their life-span.

Fifty male and 50 female BDF1 mice were observed allowing them to live out their life-span. Mortality up to 104 weeks of age was higher in males (42%) than in females (34%), and the 50% survival age was 112 weeks for males and 118 weeks for females. Body weight reached the peak at 82 weeks of age in males and 92 weeks of age in females, showing the mean body weight of 54.3 g for males and 48.0 g for females. The incidence of calculi and proteinaceous casts in the kidneys, that were not associated with exposure to chloroform, cell-alteration in the adrenal cortex, and islet cell hyperplasia in the pancreas was significantly higher in males than in females. On the other hand, hyaline droplet degeneration of the renal tubular epithelium, spindle cell proliferation in the adrenal cortex and milk-retention in the mammary glands occurred at a significantly higher incidence in females than in males. Cerebral mineralization in both sexes, atrophy and calcification of the testes and enlargement of the seminal vesicles of males, as well as cyst-formations in the ovary and endometrium of females developed at a very high incidence. Frequent neoplasms in males were hepatocellular adenomas and carcinomas, blood vessel tumours, pulmonary adenomas and carcinomas, and malignant lymphomas. In females, malignant lymphomas were the most common neoplasm, followed by blood vessel tumours, chromophobe pituitary adenomas and hepatocellular adenomas. Hepatocellular carcinomas developed only in males, whereas the histiocytic and lymphocytic types of malignant lymphomas and chromophobe cell adenomas arose solely or at a significantly higher incidence in females than in males.