Effects of X-Irradiation on the Mitotic Cycle of Ehrlich Ascites Tumor Cells

Abstract

Effects of X-irradiation (300r, 500r, and l000r) on mitosis and DNA synthesis in Ehrlich ascites tumor cells have been studied. Dose-effect relations and time sequence of effects on the 2 processes have been compared. The technique of H3-thymidine labeling of DNA with autoradiography was utilized in conjunction with the mitotic index, to study alterations in the mitotic cycle. It was concluded that X-irradiation affected cells in the G2 and S periods so that the rate of exit from G2 was reduced. Evidence, based on mean grain count/labeled cell and %age of cells labeled, was found for a slight reduction in rate of DNA synthesis after irradiation. The delay in rate exit from G2, however, was apparently a block at the end of the period.