The dependence of the synergetic action of ultrasound and hyperthermia on ultrasound intensity

The inactivation of wild-type yeast Saccharomyces cerevisiae was studied af ter simultaneous treatment with ultrasound and hyperthermia. A temperature range was established within which ultrasound and hyperthermia exert a syne rgistic action. The effect was shown to depend on ultrasound intensity and the temperature at which the treatment takes place. The temperature range e nhancing the ultrasound effect shifted forward higher temperature with Incr easing ultrasound intensity. For every intensity value, an optimal temperat ure exists at which the synergetic effect is maximum. The biophysical inter pretation of the results obtained is based on the assumption that synergism is due to an additional lethal damage, which arises from the interaction o f some sub-lesions induced by both agents. These sublesions are considered non-lethal if the agents are applied separately.