M. Sambasiva Rao

Mitogenic effect in mouse liver induced by a hypolipidemic drug, nafenopin

SummaryThe mitogenic effect of Nafenopin, a hypolipidemic hepatic peroxisome proliferator, in mouse liver has been studied in acute and chronically treated mice. After 1, 6 and 32 weeks of treatment, the total hepatic DNA was increased 1.5–2.0-fold over controls. Mitotic and labeling indices were also increased 3–4 fold after 5 days, 6 weeks and 32 weeks of treatment. The increased mitotic activity in nafenopin fed animals was not associated with liver cell necrosis. The nafenopin induced hepatomegaly therefore appears to arise from a combination of cell proliferation, as well as, cellular hypertrophy, which is associated with peroxisome proliferation.

Interstitial Cell Tumor, Testis, Rat

Interstitial or Leydig’s cell tumors in the rat testes vary in size, ranging up to 40 mm in diameter. When the tumors are small, they are usually present as multiple homogeneous nodules. Large tumors are well circumscribed and the cut surface is yellow to yellow- brown, which is clearly demarcated from the gray background of normal testis. These large tumors may replace the entire testis and usually contain multiple cystic areas filled with clear or hemorrhagic fluid (Fig. 214).

Experimental Carcinogenesis of Exocrine Pancreas: Animal Models, Neoplasms, and Current Understanding of Pathogenesis

The induction of neoplasms of the exocrine pancreas by chemical carcinogens has been achieved in several rodent species (Table 12). These have been the focus of research in a number of laboratories and have collectively contributed significantly to our understanding of pancreatic carcinogenesis. Although three rodent models have been identified, namely the rat, guinea pig, and Syrian golden hamster, the majority of research has been done with the rat and hamster. However, in an effort to be complete, all three models will be considered in this manuscript.

Testicular Feminization, Testes, and Testicular Tumors, Rat, Mouse

In both rats and mice with testicular feminization (Tfm/y), the entire reproductive tract, with the exception of small bilateral cryptorchid testes, is absent (Stanley et al. 1973). The undescended testes lie in the inguinal region or inside the abdominal cavity because the scrotum is not developed. The hairless portion of the scrotum also remains undeveloped in this syndrome. The cryptorchid testes, in both rats and mice with Tfm/y, are about one-fifth the testicular size of their normal littermates (Fig. 240). Leydig’s cell (interstitial cell) tumors develop in over 20% of the older male pseudohermaphrodite animals, usually between 1 and 3 years of age (Ohno 1974).