Survival and Recovery of Yeast Cells After Simultaneous Treatment of UV Light Radiation and Heat^¶

Abstract

Cell survival, synergistic interaction, liquid‐holding recovery (LHR) kinetics and inactivation forms after the simultaneous treatment with UV light (254 nm) and various high temperatures were studied in diploid yeast cells Saccharomyces cerevisiae. The synergistic interaction was observed within a certain temperature range in which there was a temperature that maximizes the synergistic effect. The LHR study revealed that both the extent and the rate of recovery greatly decreased with the increase in exposure temperature. A quantitative approach describing the LHR process as a decrease in the effective radiation dose was used to estimate the probability of recovery per unit time and the irreversible component of damage. Using the experimental data obtained and the mathematical model described, it was shwon that the irreversible component, i.e. the fraction of cells incapable of recovery, increased with the exposure temperature, whereas the recovery constant, i.e. the probability of recovery per unit time, was independent of the exposure temperature. The increase in the irreversible component was accompanied by an increase in cell death without postirradiation division. It is concluded based on this that the synergistic interaction of UV light radiation and hyperthermia in yeast cells is not related to the impairment of the recovery process itself and that it may be attributed to an increased yield of the irreversible damage.

Quantitative estimation of UV light dose concomitant to irradiation with ionizing radiation

“…But in these investigations only a constant intensity of UV light was employed. However, it has been recently demonstrated that the effectiveness of the synergistic interaction of a simultaneous action of heat and UV light is a function of exposure temperature (Kim et al, 2004) and fluence rate of UV light (Kim et al, 2006). Therefore, it would be desirable to undertake experiments for simultaneous action of low energy X-ray (below 263 keV, noČerenkov emission) and 254 nm UV light on UV-hypersensitive bacterial strains under a wide variation in the intensities of both agents.…”