ABSTRACT. A pinealoma (benign) was found in a 61-week-old male Crj:CD (SD) IGS rat. The neoplasm was located between the cerebral hemispheres and the cerebellum. Histologically, the tumor cells consisted of two cell types: large, pale-staining cells and small darkstaining cells. A fibrovascular stroma divided the tumor cells into incomplete lobules or nest structures. Relatively numerous mitoses were noted in the tumor cells. Ultrastructurally, the tumor cells contained dense-cored vesicles, approximately 120 nm in diameter.-KEY WORDS: Crj:CD (SD) IGS, pinealoma (benign), pinealoma (spontaneous).
ABSTRACT. To examine the effect on cell population in hepatocytes of phenobarbital (PB) and other barbiturates, PB, allobarbital (ALB), barbital sodium (BS) and barbituric acid (BA) were given orally to male rats for 7 consecutive days. Although there was no apparent change in non-promoting BA, hepatomegaly was induced by PB, BS and ALB, which are promoters of hepatocarcinogenesis. In PB-and BS-treated livers, hepatomegaly was attributable to hepatocyte proliferation and enzyme induction. In ALB-treated liver, it was attributable to enzyme induction. The level of cell proliferation was reduced to less than the control values following withdrawal of PB, ALB and BS. It seemed that the degree of suppression of cell proliferation following withdrawal of these compounds correlated to the degree of cell proliferation (PB>BS>ALB) during treatment. In PB-treated liver, apoptosis was induced during treatment, serving to eliminate the excess of hepatocytes. This suggests that short-term administration of PB neither induced suppression of apoptosis nor disturbed homeostasis of hepatocyte populations.-KEY WORDS: apoptosis, cell proliferation, liver, phenobarbital, rat.
Delayed-type hypersensitivity responses against bovine leukemia virus (BLV) envelope glycoprotein (gp60) were induced in the skin of sheep vaccinated with recombinant vaccinia virus (RVV) expressing BLV glycoprotein. The lesions were characterized by marked infiltration of lymphocytes, slight migration of neutrophils, eosinophils, and macrophages in the dermis to hypodermis, and partial intercellular edema in the reticular layer. Immunohistochemical analysis with monoclonal antibodies demonstrated that the lymphocytic infiltrates consisted mainly of CD8+ T cells (53.7-55.8% at 48 hours post-challenge of BLV), CD4+ T cells (24.7-26.7%), and B cells (11.5-16.9%). The role of CD4+ and CD8+ T cells in suppressing BLV growth in RVV-vaccinated animals is discussed.
Unilateral renal dysplasia was found in a male Std: Syrian hamster at 13 weeks of age. At necropsy, the kidney was markedly reduced in size (0.1539 g), and had a granular surface and pale color. The kidney had renal papillae. Histologically, the kidney had a distinct cortico-medullary junction. In the cortex, small glomeruli, poorly differentiated tubular epithelia, and flattened tubular epithelia were observed. The poorly differentiated epithelia were single-or multi-layered, and had nuclei of varying size and shape, i.e. round, oval or kidney-shaped. They were described as having moth-eaten basement membranes. In the medulla, flattened tubular epithelia were observed. Ultrastructurally, the small glomeruli were composed of well-differentiated cells, therefore they may not have been primitive, but rather immature. The poorly differentiated epithelia did not have lumina or brush borders, and were concluded to be primitive tissues. This case was characterized by immature glomeruli and primitive cortical tubular epithelia, and likely represents a developmental disorder. In conclusion, this case was diagnosed as renal dysplasia, but the histological features did not resemble those of human renal dysplasia. (J Toxicol Pathol 2001; 14: 309-312)
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