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Five kinds of plastics (3 polyvinyl chlorides, 1 polyhydroxyethyl metacrylate and 1 dimethyl polysiloxane) were implanted into subcutaneous tissues of Wistar rats of both sexes. Subcutaneous tumors developed in all experimental groups. The incidences of the tumors, however, differed from each other, although these materials were tested on the same experimental condition. This result indicates that chemical characters of the materials may influence the incidence of subcutaneous tumors. Histologically, most of these subcutaneous tumors were mesenchymal tumors with spindle cells arranged in a storiform pattern, with sheets of histiocyte-like cells or pleomorphic giant cells. Electron microscopy showed mixture of fibroblastic cells, histiocytic cells and undifferentiated cells in these tumors. From these histological and electron microscopical findings, many of the tumors were diagnosed as malignant fibrous histiocytomas.

M73101 and aspirin were evaluated for the effects on prenatal development of progeny in JW-NIBS strain rabbits. Pregnant females were given orally M73101 (0, 50, 120 and 300mg/kg/day) or aspirin (200mg/kg/day) on days 6 to 18 of gestation. They were sacrificed on days 29 of pregnancy and their fetuses were examined for abnormalities. The results were summarized as follows: 1. During the dosing period, females received 300mg/kg of M73101 showed pronounced body weight depression and decrease in food and water intake. But after the dosing period, these influences were not seen. Females received aspirin did not show such phenomena. 2. There were no adverse effects on number of implants, litter size, fetal mortality or fetal weight, and no malformed fetuses attributable to the drugs were seen in each group.

Spontaneous neoplastic and non-neoplastic lesions in 98 male and 100 female Slc: Wistar rats, which have been widely used in Japan for toxicological studies, were examined. As spontaneous tumors, the most frequent tumors in males were testicular interstitial cell tumors, followed by tumors of the hematopoietic organs, adrenal gland, thyroid gland, preputial gland, pituitary gland, liver and mammary gland. Those in females were tumors of the pituitary gland, mammary gland, hematopoietic organs, uterus and thyroid gland. The organ distribution and histological types of spontaneous tumors observed in Slc: Wistar rats were very similar to those in F-344/DuCrj rats, although the incidences of some tumors differed slightly in the two strains. Various non-neoplastic lesions were also observed in the heart, kidney, liver and many other organs. These results should be useful in evaluating the results of toxicological and carcinogenic studies on this strain of rat.

Spontaneous neoplastic and non-neoplastic lesions in 95 male and 96 female Donryu rats which were observed up to 120 weeks of age, were examined. The incidence of spontaneous tumors was 73.7% in males and 88.5% in females. In males, the most frequent tumors were pituitary adenomas, followed by pheochromocytomas and insulinomas. In females, uterine adenocarcinomas, mammary fibroadenomas and pituitary adenomas were the most common. Other tumors with relatively high incidences in both sexes included cortical adenomas of the adrenal gland, histiocytic sarcomas of the hematopoietic organs and granular cell tumors of the brain. Various tumors were also found in many other organs and/or tissues, although their incidences were low. The organ distribution and incidences of spontaneous tumors observed in Donryu rats were different from those in other strains of rats such as the ACI, Wistar, F344 or Sprague-Dawley strains. The main non-neoplastic lesions were observed in the lung, cervical lymph nodes and kidney of both sexes. In addition, lesions were also observed in the urinary bladder, prostate and peripheral nerves (spinal nerve roots and peripheral nerves) and/or femoralis muscle of males. Histologically, the most characteristic lesion was radiculoneuropathy with degeneration of the peripheral nerves.

Spontaneous tumors of the nervous system and associated organs and/or tissues in 346 male and 346 female F344/DuCrj rats and 200 male and 177 female Slc:Wistar rats were examined. The main neurogenic tumors observed were gliomas and neurinomas, which were detected in both strains of rats. Out of 7 gliomas, 6 were found in the brain and 1 in the spinal cord, and out of 4 neurinomas, 2 were in the trigeminal nerves and the other 2 were in the spinal nerves. In addition, other types of tumors (2 granular cell tumors in the brain, 1 pinealoma, 3 ganglioneuromas in the adrenal gland, 1 undifferentiated carcinoma in the nasal cavity and 1 chordoma in the posterior neck region) were observed.

A 50-year-old Japanese man had had abscesses and draining fistulas in the perianal region. These lesions recurred, despite surgical treatment such as incision and drainage over a 30 year period. "Sulfur granules" were found in the pus from the abscess and Actinomyces israelii was cultured. Ampicillin-cloxacillin treatment lead to healing. The patient died 4 months later with a hepatoma and multiple metastases.