Cellular radiation effects and hyperthermia. Comparison of different treatment schedules and their relation to recovery processes in diploid yeast

Diploid yeast was chosen as a test system to study the influence of elevated temperatures (up to 500C) on cellular sensitivity to X-ray exposure in the presence and the absence of oxygen. Survival is always lower if the temperature is increased during irradiation but the difference between oxic and anoxic conditions is very small. There is an optimum incubation temperature (400C) for survival if the cells are held in nutrient medium after exposure at room temperature, but again there is no change in the extent of the oxygen effect. Liquid holding recovery, which is achieved by keeping the cells under non-nutrient conditions before plating, decreases with temperature, showing a more pronounced effect on cells irradiated under nitrogen. This leads to a considerable reduction of the oxygen effect with a liquid holding temperature of 400C. (author)