Intestinal microflora plays a crucial role in the genotoxicity of the cooked food mutagen 2-amino-3-methylimidazo [4,5-f]quinoline

We investigated the impact of the intestinal microflora on the genotoxicity of 2-amino-3-methylimidazo[4,5-f] quinoline (IQ), a mutagenic/carcinogenic heterocyclic amine commonly found in fried meats and fish. In parallel, we also examined the effect of the microflora on the protective effect of glucotropaeolin (GT), a glucosinolate contained in cruciferous vegetables, towards IQ-induced genotoxic effect. Conventional (NF), human flora associated (HFA) and germ free (GF) rats were treated either with 90 mg/kg IQ alone, 150 mg/kg GT alone or a combination of the two by gavage and DNA damage was determined in liver and colon cells using the alkaline single cell gel electrophoresis (SCGE) or comet assay. IQ caused a significant effect in both organs of all groups. However, DNA damage was most pronounced in NF animals. In colon cells, DNA migration was 6-fold more in IQ-exposed rats as compared with untreated controls. The effect measured with liver cells was similar. In comparison to NF rats, in HFA rats, tail length of the comets was 22 and 53% lower in liver and colon cells, respectively. Significantly weaker effects were seen in GF animals (66 and 75% lower damage in hepatocytes and colonocytes, respectively, than in NF animals). Pretreatment with GT led to a complete reduction of IQ-induced DNA damage regardless of the microbial status of the animals. In addition, a moderate decrease in spontaneous DNA damage was seen in animals that received GT alone. Our results show that the microflora has a strong impact on the genotoxic effects of IQ. We conclude that the alkaline SCGE assay with rats harbouring different flora opens new possibilities to investigate the role of intestinal bacteria on health risks caused by dietary carcinogens.

[Effects of thioglucoside on thyroid and iodine metabolism]

Swine, fed with fodder containing 8%-16% rape-seed meal, took 919.42-1416.02 mg of thioglucoside (glucosinolate) daily. After being fed with it for 120 consecutive days, swine's thyroid enlarged and their thyroid follicles and epithelial cells were prominently hyperplastic, lacking secretory granules and lysosome in thyroid cytoplasm, with microvilli condensed in apical cells, and a great number of vacuoles surrounding the colloid in the follicular cavity, with its secretory function vigorous and significantly increased T4 and ratio of T4 to T3, and showing hyperthyroidism. If iodine was supplied in the fodder and the antidotes were administered, the morphology and ultrastructure of the thyroid tissues in swine restored to normal, and their T4 and ratio of T4 to T3 tended to be normal, too.

5-Thio-D-glucose selectively potentiates hyperthermic killing of hypoxic tumor cells

To investigate the mechanisms by which heat affects cancer cells, we used 5-thio-D-glucose, an inhibitor of glycolysis in HeLa S-3 cells, under aerobic and hypoxic conditions at temperatures ranging from 37 degrees to 43 degrees C. Drug alone or heat alone killed a minimum number of cells under aerobic or hypoxic conditions. Exposure to drug and hyperthermia selectively increased the number of cells killed under hypoxic conditions at temperatures as low as 40.5 degrees C but had little effect on cells incubated under aerobic conditions. These results suggest that the glycolytic pathways is a primary site of hyperthermic damage leading to cell death.