Effect of X-Radiation on the Survival of Yeast in Dry and Wet Conditions

Abstract

THERE is a great deal of uncertainty regarding the direct and indirect actions of ionizing radiation on cells^1,2. The indirect effect occurs when chemically active intermediates are formed by the action of ionizing radiation on water surrounding the sensitive zones. These intermediates are capable of diffusing through the cell and of inactivating the vital molecules. The effect of direct action may be measured by irradiating dry material, in which case the energy is released directly by the ionizing radiation within the molecule which is inactivated. Several studies have been made on the survival of yeast cells irradiated in the wet condition^3,4,5, but the results observed are the combined effect of both direct and indirect actions. In order to assess the relative contributions of the two types of action, yeast cells in the dry and the wet state, but otherwise in exactly identical condition, have been irradiated with X-rays, so that from the observed difference in the radiosensitivity the contributions of the direct and indirect actions could be estimated.