Vascular leiomyoma of the mesentery in a dog.

A 4-year-old male, miniature Schnauzer dog showed two large masses in the mesentery at necropsy. Histological examination of both masses revealed plain smooth muscle tumour cells intermingled with thick-walled blood vessels. The bundles of tumour cells often extended from the periphery of the vessels. Mitotic figures were rare. From these findings, the tumour was diagnosed as a vascular leiomyoma (angiomyoma), previously unreported in animals. The term, vascular leiomyoma, was proposed to describe this tumour in order to avoid confusion with hamartomatous angiomyoma.

Subchronic toxicity of Di(2-ethylhexyl)phthalate in common marmosets: lack of hepatic peroxisome proliferation, testicular atrophy, or pancreatic acinar cell hyperplasia.

To evaluate the toxicological effect, di(2-ethylhexyl)phthalate (DEHP) was administered orally at 100, 500, and 2500 mg/kg to four male and four female marmosets in each group for 13 weeks. Its potentials of hepatic peroxisome proliferation, testicular atrophy, and pancreatic acinar cell hyperplasia were evaluated more closely. Clofibrate, which potently causes peroxisome proliferation in rodents, was administered in like manner at 250 mg/kg as a reference drug. DEHP induced significant suppression of weight gain in males at 2500 mg/kg. However, the increase in liver mass and hypertrophy of hepatocytes were not detected in organ weight measurements or histopathological examination. The number of peroxisomes, volume density, peroxisome morphology, and peroxisomal enzyme activities were not different from those in the control group, though the males treated with 500 and 2500 mg/kg DEHP showed 1.3- and 1.4-fold increases in mean peroxisome volume, respectively. In contrast, clofibrate induced 2.2 (in male)- and 1.9-fold (in female) increases in hepatic cyanide-insensitive acyl CoA oxidation system activity, 1. 2 (in male)- and 1.7-fold (in female) increases in hepatic carnitine-dependent acetyltransferase activity, and 1.8 (in male)- and 3.0-fold (in female) increases of carnitine-dependent palmitoyltransferase activity. Cytochrome P-450 contents tended to increase in all males and females administered 500 and 2500 mg/kg of DEHP and clofibrate associated with the increase in hepatic microsomal protein content, suggesting a relationship with the treatment. The atrophic change in the testis or proliferative change in the pancreatic acinar cells seen in rodents were not seen histopathologically; also, no changes were observed in testes weight, testicular zinc level, blood levels of testosterone and estradiol, pancreas weight, and blood levels of cholecystokinin. Finally, no changes considered to be due to the administration of DEHP were noted in blood chemical examination or pathological examination of other organs.

Spontaneous lesions detected in the common cotton-eared marmosets (Callithrix jacchus).

Spontaneous lesions in the common cotton-eared marmosets (Callithrix jacchus), which were maintained in our laboratory or were purchased from a commercial breeder, were examined histopathologically. There were 39 males and 22 females, between the ages of 7 and 100 months. The most interesting finding noted was extramedullary hematopoiesis, which was observed in the mesenteric lymph nodes, spleen, liver, kidney, adrenal gland, and cerebral choroid plexus. Megakaryocytes were frequently observed in the blood vessels of the alveolar wall of the lung. It is important to distinguish extramedullary hematopoiesis which occurs accidentally from that induced by repeated blood sampling or that resulting from administration of chemicals. Extramedullary hematopoiesis was easily distinguishable from inflammation or hematopoietic neoplasms, because of the various cellular elements present, including megakaryocytes. In the weak and dead animals, enterocolitis was found at a high frequency. Other common findings included thymic involution, prominent vacuolation of liver sinusoidal cells, which were probably Ito-cells, and basophilic changes in the renal tubular epithelium. The liver and the kidney are frequently affected by toxic effects of chemicals. Therefore, it is important to distinguish the toxic changes from the spontaneous ones. Proliferation of apocrine glands in the cervical skin was an interesting finding; however, neither inflammatory change nor cellular atypia was noted in this structure. Although its function is unclear, this structure may be a marmoset-specific tissue.