Induction of micronuclei in cultured murine splenocytes exposed to elevated levels of ferrous ions, hydrogen peroxide and ultraviolet irradiation.

The frequency of micronuclei in cultured mouse splenocytes increased positively and in a dose-related manner to exposure to ferrous ions and ultraviolet irradiation, but not to hydrogen peroxide. Combined treatments, especially when ferrous ions were present with hydrogen peroxide or with ultraviolet irradiation, led to a synergistic enhancement in micronucleus frequency. The results indicate that a significant level of chromosome damage is associated with exposure to ultraviolet light and to general cellular pro-oxidative stress, and indicate that under these conditions the micronucleus assay can provide an effective in vitro model for the study of genotoxicity in relation to oxygen-derived free radicals.

Zinc deficiency is associated with suppression of colonocyte proliferation in the distal large bowel of rats.

As zinc status may influence susceptibility to colon cancer, we examined the effect of dietary zinc deficiency on the proliferation of epithelial cells (colonocytes) in the large bowel of rats. When compared to feed-restricted rats, those with zinc deficiency showed a significant reduction in proliferation in the distal colon as assessed by accumulated metaphase arrest and crypt cell production rates in vivo. Zinc deficiency had no apparent effect on thymidine kinase activity in colonocytes but was accompanied by minor changes in fecal mass and fecal pH.

Zinc, ethanol, and lipid peroxidation in adult and fetal rats.

Studies were performed on adult and fetal rats receiving either a zinc-deficient (<0.5 ppm) diet and/or ethanol (20%) throughout pregnancy. Liver zinc levels were depressed in fetuses exposed toin utero zinc deficiency, but brain zinc levels were unchanged.

alpha-Adrenergic stimulation of trans-sarcolemma electron efflux in perfused rat heart. Possible regulation of Ca2+-channels by a sarcolemma redox system.

The role of trans-sarcolemma membrane electron efflux in the alpha-adrenergic control of Ca2+ influx in perfused rat heart was examined. Electron efflux was measured by monitoring the rate of reduction of extracellular ferricyanide and compared with changes in contractility, as an indirect assessment of changes in cytoplasmic Ca2+ concentration. Methoxamine and phenylephrine each increased the rate of ferricyanide reduction from 80 to approx.

Properties and regulation of a trans-plasma membrane redox system of perfused rat heart.

Ferricyanide was reduced to ferrocyanide by the perfused rat heart at a linear rate of 78 nmol/min per g of heart (non-recirculating mode). Ferricyanide was not taken up by the heart and ferrocyanide oxidation was minimal (3 nmol/min per g of heart). Perfusate samples from hearts perfused without ferricyanide did not reduce ferricyanide.

Properties and regulation of a trans-plasma membrane redox system in rat liver.

1. Regulation of the reduction of ferricyanide by the isolated perfused rat liver was studied. 2.

Evidence for the extracellular reduction of ferricyanide by rat liver. A trans-plasma membrane redox system.

1. Reduction of ferricyanide by the isolated perfused rat liver and by isolated rat hepatocytes was studied. 2.

Effects of variations in nucleoside pool sizes on comparisons of the incorporation of [3H]thymidine into isolated rat liver cells.

Isolated rat liver cells have been used to measure DNA repair synthesis induced by ultraviolet light and aflatoxin. Age, sex, and diet of the rats were found to influence DNA repair in rat liver cells, as measured by [3H]thymidine uptake by the cells. These effects were found to be due to variations in the thymidine pool size and should serve to indicate that high-specific-activity thymidine (i.

Induction of DNA repair by some selenium compounds.

Selenium compounds were found to induce DNA repair synthesis as a measure of DNA damage in both the isolated rat liver cell system and by Ames' Salmonella assay. In liver cells, DNA repair measured by uptake of [3H]thymidine was found to be greater with sodium selenite and selenate than with selenomethionine. In the bacterial culture system, selenomethionine inhibited the repair-deficient variant more than the selenite and selenate.