Recovery and repair in yeast cells after irradiation with highly ionizing particles

A cybernetic model was developed for radiation effects in living cells. This model includes quantitative changes in radiation sensitivity with absorbed dose, recovery (split-dose reactivation) and repair (liquid-holding reactivation). The model was tested extensively with sparsely ionizing radiations (x rays and electrons) using diploid and haploid yeast cells. Experiments are described in which the model is used for analyzing irradiation with alpha particles from an americium source. These particles are representative of densely ionizing particles with known LETdistribution of absorbed dose. It can be shown quantitatively how much the unrepairable fraction of the radiation damage is increased in comparison with sparsely ionizing radiations. The quantitative data can be used for a prediction of reactions of fast and slow neutrons of various energy distributions. Consequences of these results for radiation therapy with fast neutrons and for radiation protection are discussed. (GE)