Radiation-induced Division Delay inDictyostelium Discoideum:Relation to Survival in Resistant and Sensitive Strains

Abstract

Vegetative amoeboid cells of the cellular slime mould, Dictyostelium discoideum NC-4, are very resistant to gamma-radiation . Mutant strains have been isolated which are significantly more radiosensitive . Studies were conducted to measure division delays and other growth responses after irradiation of strain NC-4 and two mutant strains . Some division of non-surviving (non-colonyforming) cells was observed in all strains . Total cell populations (surviving plus non-surviving cells) in all three strains showed essentially equivalent division-delay responses . However, surviving cells of the mutant strains revealed division delays that were much longer than those of the total cell populations . A model is proposed to interpret these results . A basic premise of the model is that, if more time is allowed for repair of potentially lethal damage incurred by the sensitive strains, cellular survival will be greater . Support for this model was obtained by producing artificially long delays in populations consisting of irradiated mutant cells . Increases in survival were observed for the sensitive strains but not for strain NC-4 .

Annual Report for Period Ending April 30, 1970.

“…Support for the idea that longer delay may, in·general, result in more repair and, therefore, greater survival, apparently was obtained from experiments with vegetative amoeboid cells of Dictyostelium discoideum (Cleveland and Deering 1972). Cleveland and Deering found that the survivors of irradiated cells of radiosensitive strains suffered unusually long division delays compared to the total cells in the population.…”