Cytological and microfluorometrical study of irradiation effects on the cell cycle of tumor cells

Irradiation effects on the progression into the mitosis of cells in each period of mitotic cycle were examined by cytological and microfluorometrical analysis using Ehrlich ascites tumor (EAT-Cl-4) cells. The results were obtained as follows. 1. The entrance of pre DNA synthetic (G1) cells into mitosis delayed several hours by irradiation with 500 rad. The delay time of G1 cells corresponded to that of post DNA synthetic (G2) cells. 2. A cause of the division delay of G1 cells was the temporary inhibition of the entry into DNA synthetic (S) phase for a few hours after the irradiation. 3. On the basis of DNA content per cell, the accumulation of G2 cells was not found during mitotic inhibition following the irradiation. (author)