Abstract
Ehrlich ascites tumor cells labeled with 2-14C-thymidine were irradiated in vitro with 60Co-γ-rays. The total number of cells and total radioactivity were measured daily after intraperitoneal inoculation into mice and the following results were obtained. (1) Number of cell division after irradiation is not reflected in the number of cells, but cell division and rate of cell disappearance determine the number of cells. (2) Delay of the first cell division (G2 block) increases with dose. (3) After dissolution of G2 block, irradiated cells divide in the same rate as that of the control for the first 3 to 4 cell cycles in the dose range examined. (4) The average number of divisions which non-surviving cells go through decreases with increasing radiation dose. (5) The distribution of post-irradiation cell divisions which non-surviving cells go through may be fitted by the Poisson distribution.
