Combined action of ultrasound and ionizing radiation on yeast cells.

This communication reports the observation of synergistic relationships between ultrasound and gamma-irradiation of stationary phase cultures of Saccharomyces cerevisiae of different strains. The gamma-ray dose was applied before or after the sound. The extent of synergism depended upon the sequence of application; it was smaller for (US + gamma-ray)-exposure in comparison with gamma-ray +US)-treatment. The combined action of both modalities had smaller or no synergistic effect for mutant(rad51) yeast cells incapable of recovery. On this basis, it was concluded that possible mechanisms for ultrasound radiosensitization of yeast cells may involve the reduced capacity of cells to recover damages resulted from the combined action and/or the enhanced expression of lethal damage.