Dissociation between cortisol-induced pycnosis and inhibition of [3H]uridine incorporation in rat thymocytes.

Treatment of rat thymocytes with cortisol induced an inhibition of [3H]uridine incorporation after 30-90 min, an accumulation of pycnotic cells after 90 min, and a decrease in cell viability after several hours. No cortisol-resistant cells could be distinguished, and dose-response curves for a number of glucocorticoids showed a correlation to the saturation of the glucocorticoid receptors. The pycnotic effect of cortisol increased between pH 5.2--7.0 in parallel with a stimulation of the spontaneous development of pycnotic cells. The cortisol-induced accumulation of pycnotic cells and inhibition of [3H]uridine incorporation varied independently as a function of the cell density, and in a glucose-salt medium only the pycnotic effect of cortisol became inhibited. The inhibition of [3H] uridine incorporation is therefore not an integral part of the pycnotic change of the cells. The glucocorticoid sensitivity was found to increase with the age of the animals, before the onset of thymus involution.     

Further Studies on the Influence of Oxygen on X-ray-induced rearrangement in Drosophila Oocytes

Summary

Alteration of the metabolism of Drosophila oocytes greatly affects the induction of structural changes by x-rays. Females 2–3 days of age contain oocytes whose chromosomes restitute and rearrange rapidly, whereas no evidence for restitution within the intervals studied was found in samples of oocytes from females 8–9 days old at the time of irradiation. The effect of nitrogen as a post- or inter-treatment showed, however, that for both young and old oocytes there was more restitution in air than in nitrogen. Both young and old oocytes show reduced rearrangement frequencies when irradiations were performed in nitrogen, and increased rearrangement frequencies when a fractionated irradiation was performed with the flies maintained in a nitrogen environment between irradiations. These different effects of anoxia are discussed.