Clone-size Analysis in the Study of Cell Growth Following Single or during Continuous Irradiation

Abstract

SummaryAnalysis of the clone sizes of HeLa cells plated out by the Puck technique showed that the distribution broadened when the cell population included damaged cells with a slower net growth rate. This broadening of the clone-size distribution was found after repeated trypsinization of control cells as well as following single radiation doses and continuous irradiation. The development of these broad clone-size distributions has been studied over a number of days. The resultant families of distribution curves reveal additional data about the population kinetics of irradiated cells, which can be related to the growth curves and survival fractions obtained under the same experimental conditions.The more slowly growing clones, which develop after irradiation, have been shown to maintain proliferative capacity. The implications of this non-lethal radiation damage are discussed. It is emphasized that the usual parameter of a certain minimum clone size (usually 50 cells) is an arbitrary definition of the reproductive integrity of surviving cells, and that under certain conditions it is more meaningful to study the full clone-size distribution.