A variety of neoplastic and non-neoplastic lesions in F344/DuCrj rats, which were used as control animals in chronic toxicity and carcinogenicity studies conducted at the Biosafety Research Center, Foods, Drugs and Pesticides over a 9 year period, are described. The causes of death of animals which were found dead or that were killed in a moribund condition, as well as age-associated differences in the incidence rate of various lesions at 31, 57, 83, and 109 weeks, were also analyzed. The average number of naturally-occurring tumors per rat was 1.68 in male and 0.92 in female rats. The incidence rate of malignant tumors in all animals was 12.5% in male and 11.4% in female rats. The most common tumors were leukemia and benign tumors of the endocrine and reproductive organs. As for the non-neoplastic lesions, chronic nephropathy occurred more frequently in male than in female rats. Other lesions commonly observed were atrophic changes in the thymus and reproductive organs, deposits of hemosiderin or ceroid-like materials in a variety of organs, proliferative or hyperplastic changes of the bile ducts, endocrine and reproductive organs, microgranuloma, angiectasis and dilated or cystic changes in a variety of organs, fatty change in the liver and adrenals, and hepatodiaphragmatic nodules of the liver. Nearly all of the above findings increased in both incidence and severity with age.

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Forty-five male Syrian golden hamsters out of 90 were given subcutaneous injections with N-nitrosodiethylamine (DEN) in saline twice a week for 20 weeks to induce tracheal hyperplasia and papilloma. These proliferative lesions were analysed by mitotic index (M.I.) and bromodeoxyuridine-labelling index (BrdU-L.I.), as well as by nucleolar organizer regions (NORs) count to determine the relationship between cell proliferation and (the tumorigenic process.) the tumorigenic process. Besides, the meaning and significance of NORs count was evaluated from the counts in the basal area of the lesions in comparison with M.I. and BrdU-L.I.. The mean M.I., BrdU-L.I., and NORs count in various tracheal lesions were as follows: 0.10%, 0.37%, and 2.12 in control tracheal epithelium, 0.25%, 2.50%, and 2.30 in non-lesional area, 0.37% (0, 27%), 2.15% (3.49%), and 2.33 (2.53) in hyperplasia, 0.23% (0.25%), 3.54% (5.65%), and 2.59 (2.97) in papilloma, respectively. Numbers in the parentheses indicate the values of the basal area. The elevation of NORs count surely reflected the high frequencies of proliferation in the preneoplastic and neoplastic changes as demonstrated by M.I. and BrdU-L.I., but in papilloma increased protein synthesis without cell division was indicated. These results showed that measurement of cell proliferation activity in the basal area could demonstrate the growth rate much more clearly than that in the whole area. Also, it was shown that analysis of distribution patterns of the NORs counts was a useful means for evaluating the biological behavior of the neoplastic lesions.

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Acute hepatotoxicity of T-2 toxin (10mg/kg b.w., p.o.) was examined up to 48 hours after injection (48 HAI). Blood biochemical parameters such as activities of GOT, GPT, and LDH and concentrations of glucose, lipids, and protein showed apparent changes from 8 to 24 hours, and, at 48 HAI, most of them exhibited values within normal ranges. On the other hand, hepatic aniline hydro-xylase activity decreased while hepatic lipid peroxide level increased continuously throughout the observation period of 48 hours. Histopathological changes of the liver were clearly detected 8 HAI and characterized by an increase in density and acidophilic stainability of hepatocyte cytoplasm with loss of glycogen. Such changes reached their maximal severity 16 HAI and thereafter became to locate in the perilobular area. Ultrastructural changes of hepatocytes were characterized by condensation and/or deformation of mitochondria, aberrations of rough endoplasmic reticulum with decrease in ribosomes, and depletion of glycogen. Subcellular changes of hepatocytes also showed a tendency to recover on and after 24 HAI. Thus, a sublethal dose of T-2 toxin could cause prominent but essentially transient hepatic damages, and blood chemical changes correlated well with histological ones.

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Acute and chronic toxicity of a synthetic sydnone derivative, 3-benzylsydnone-4-acetamide (BSA), was examined. Hepatotoxic effect of BSA given in drinking water at concentrations up to 0.2% for 4 weeks varies considerably in differing strains of mice, DDD is the most susceptible followed by C57BL/6, DBA, BALB/c, and ICR. C3H mice were resistant at the tested doses. Female mice were more susceptible than the males in all strains. In DDD females liver cell necrosis developed in 2 weeks with 0.05 to 0.2% BSA in drinking water. With continuous administration of 0.05% BSA liver cell nuclei with polyploid DNA contents (8c, 16c, and 32c) increased in 2 weeks. Then hepatocytes having diploid nuclei predominated in 4 weeks. In DDD female mice hepatocellular carcinoma developed within 12 months with 0.01% and 0.02% of BSA in the drinking water. The incidence was 11.8 and 46.2%, respectively. By whole body autoradiography of female DDD mice given orally 10μCi of [¹⁴C]-labeled BSA (about 60mg/kg body weight) the radioactivity was shown to concentrate in the liver after 45min and remained faintly but definitely up to 72 hrs, indicating the possible accumulation of the drug or its metabolite(s) in the liver.

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Natural vitamin E is widely used as an antioxidative food additive as well as a remedy for gerontological disorders. We have tested long term effects of natural vitamin E (E-mix 80: a mixture of natural tocopherols) in a strain of mice by the continuous oral administration from 8 weeks to 104 weeks of age. It was shown that the frequency of the spontaneous development of liver tumors was significantly elevated in a group fed with vitamin E diet. We have also tested effects of natural vitamin E on the carcinogenesis by N-nitrosodiethylamine. E-mix 80 exerted inhibitory effects on N-nitrosodiethylamine-induced hepatocarcinogenesis, and inhibited the effects of N-nitrosodiethylamine initiated lung and upper alimentary tract carcinogenesis. Taking these findings and other published data into consideration, we urge the careful re-evaluation of the use of this agent as an antioxidative food additive and a remedy.

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N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN), 7, 12-dimethylbenz(a)anthracene (DMBA), and N-methyl-N-nitro-N-nitrosoguanidine (MNNG) were given by gastric intubation, in sequence, to 6-week-old female SD rats. After receiving BBN (600mg/kg body wt.) three times, every other day, in the 1st week, the animals were administered a single dose of DMBA (50mg/kg body wt.) at the beginning of week 2 and MNNG (100mg/kg body wt.) three times every other day in the 3rd week. Groups were sacrificed at the end of weeks 12, 16, 20, and 24 of the experiment. The putative preneoplas-tic lesion, papillary or nodular hyperplasia as well as papillomas were found in the urinary bladder after week 16 but the incidences were very low. Adenocarcinoma in the mammary gland appeared after week 12 at a high incidence. Papilloma and carcinoma in the forestomach were induced after week 16. Pepsinogen isoenzyme 1 altered pyloric glands could be detected immunohistochemically after week 12. These results indicate that treatment with the three carcinogens given in sequence is effective for induction of preneoplastic and neoplastic lesions in the urinary bladder, mammary gland, forestomach, and glandular stomach of rats in a relative short-period.

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The present study was conducted to examine nephrotoxicity of β-cyclodextrin (β-C) in dogs. Five female Beagle dogs were divided into 3 groups: Group 1 (2 dogs treated with 0.9g/kg of β-C), Group 2 (2 dogs treated with 0.45g/kg of β-C), and Group 3 (1 dog treated with saline). Durations of β-C injection were 7 and 10 consecutive days in Groups 1 and 2. Histopathological and histo-chemical examinations of the kidney were performed. Following 0.9g/kg or long-term 0.45g/kg treatment with β-C, the animals showed marked fatigue and elevated BUN and Cr. Histopathologically, β-C treatment resulted in vacuolation, necrosis, and regeneration in the proximal tubules. Activities of succinic dehydrogenase, β-glucuronidase, and glucose-6-phosphatase decreased histochemically after β-C treatment. Because signs of nephrotoxicity represented were noted in dogs after β-C treatment, as has been reported in rats, it seems likely that dogs also can serve as a model of nephrosis. If this model is to be applied to the study of renal carcinogenesis, the present study suggests the optimum dosing regimen for β-C to be 7-day 0.45g/kg treatment.

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