Proliferation Kinetics of X-irradiated Mouse L Cells Studied with Time-lapse Photography. II

Abstract

SummaryProliferation kinetics of x-irradiated mouse L-P59 fibroblasts were studied by constructing cell pedigrees from photographic records. Parameters of proliferation showed marked age dependence; early G1 cells were most resistant and late S-G2 cells were most sensitive in terms of reduction in probability of division, increase in generation time, and induction of abnormal mitotic figures (multipolar and incomplete mitoses). Division probabilities were higher at first division than at subsequent divisions, and cell death in some pedigrees was absent until the fourth generation or later. Prolongation in generation time occurred during several post-irradiation divisions, most noticeably in abortive clones. The idea that chromosome damage may not be the major cause of cell killing is suggested by the observations that (1) frequency of first division lethal sectoring showed no age dependence; (2) multipolar mitosis appeared to account for a significant proportion of non-surviving clones at low doses.