Mutagenicity and carcinogenicity in relation to DNA adduct formation in rats fed leucomalachite green.

Leucomalachite green is a persistent and prevalent metabolite of malachite green, a triphenylmethane dye that has been used widely as an antifungal agent in the fish industry. Concern over the use of malachite green is due to the potential for consumer exposure, evidence suggestive of tumor promotion in rodent liver, and suspicion of carcinogenicity based on structure-activity relationships. Our previous study indicated that feeding rodents malachite or leucomalachite green resulted in a dose-related increase in liver DNA adducts, and that, in general, exposure to leucomalachite green caused an increase in the number and severity of changes greater than was observed following exposure to malachite green. To characterize better the genotoxicity of leucomalachite green, female Big Blue rats were fed leucomalachite green at doses of 0, 9, 27, 91, 272, or 543 ppm for up to 32 weeks. The livers were analyzed for lacI mutations at 4, 16, and 32 weeks and DNA adducts at 4 weeks. Using a 32P-postlabeling assay, we observed a dose-related DNA adduct in the livers of rats fed 91, 272, and 543 ppm leucomalachite green. A approximately 3-fold increase in lacI mutant frequency was found in the livers of rats fed 543 ppm leucomalachite green for 16 weeks, but significant increases in mutant frequencies were not found for any of the other doses or time points assayed. We also conducted 2-year tumorigenesis bioassays in female and male F344 rats using 0, 91, 272, and 543 ppm leucomalachite green. Preliminary results indicate an increasing dose trend in lung adenomas in male rats treated with leucomalachite green, but no increase in the incidence of liver tumors in either sex of rat. These results suggest that the DNA adduct formed in the livers of rats fed leucomalachite green has little mutagenic or carcinogenic consequence.

Resistance to the Sterne strain of B. anthracis: phagocytic cell responses of resistant and susceptible mice.

Inflammatory responses were compared in vivo, and host phagocytic cell functions compared in vitro, of mice resistant (CBA/J) and susceptible (A/J) to lethal infection with the Sterne strain of Bacillus anthracis. Polymorphonuclear leukocyte (PMN) and macrophage responses at the initial site of infection were slower in A/J mice than in CBA/J mice. Whereas in A/J mice, the number of PMN ultimately responding to infection was equal to, or greater than, that in CBA/J mice, fewer macrophages accumulated. A/J mice failed to clear relatively low doses of the organisms and died. In vitro, chemotactic responses to both serum- and bacteria-derived attractants were similar for macrophages from A/J and CBA/J mice but were reduced for PMN from A/J mice. PMN and macrophages from the two mouse strains phagocytosed and killed spores in vitro to a similar extent, although killing by A/J PMN could be blocked by prior uptake of large numbers of killed spores. Thus susceptibility to lethal infection with Sterne strain correlated with the delayed influx (PMN) and reduced accumulation (macrophages) of phagocytes at the initial site of infection, but not with defective in vitro uptake or killing of spores.

Effects of testosterone on the prevention of T-2 toxin-induced adrenocortical necrosis in mice.

To evaluate the effect of exogenous testosterone on the development of T-2 toxin-induced necrosis of adrenal glands, mice were allotted to 3 treatment groups. Each treatment group contained castrated male, and castrated and sexually intact female mice. Each mouse in group 1 was given 0.16 mg testosterone propionate at 48-hour intervals for a total of 12 injections, group-2 mice were given similar injections of only the vehicle, and group-3 mice were given no treatment. Twenty-four hours after the last injection, the mice in all 3 groups were exposed for 10 minutes to an aerosol of T-2 toxin. All mice alive at 24 hours after exposure were euthanatized and the adrenal glands and thymuses were examined histologically. Necrosis of the adrenal cortex was not found in any of the mice given preexposure treatment with exogenous testosterone, whereas all mice given vehicle only or no treatment had T-2 toxin-induced necrosis of the inner portion of the adrenal cortex. Lymphocytolysis in the cortex of the thymus confirmed that each mouse of all 3 treatment groups had experienced systemic mycotoxicosis. The uniform severity of the lesion in all mice suggests that the thymus was not protected by exogenous testosterone administration or by the castration status of the mice. We propose that T-2 toxin-induced adrenal necrosis in mice is prevented by the presence of testosterone.

Mycotoxicosis caused by aerosolized T-2 toxin administered to female mice.

Thymus, spleen, adrenal glands, and small intestine of female mice exposed to aerosolized T-2 mycotoxin were examined at postexposure hours (PEH) 0.25, 1, 2, 4, 6, 9, 12, and 24. Lymphocyte necrosis was observed at PEH 1 in the thymus, spleen, and lamina propria and Peyer patches of the small intestine. Necrosis of small intestinal crypt epithelial cells was observed at PEH 2, and necrosis of parenchymal cells and increased number of neutrophils were seen in sinusoids of the adrenal cortex at PEH 4. These results indicated that the earliest microscopic evidence of T-2 mycotoxicosis after aerosol exposure was necrosis of lymphocytes in the thymus, spleen, and lamina propria and Peyer patches of the small intestine.