[Effect of a fractionated dose of fast electrons on mitotic activity and the number of DNA-synthesizing cells of tumor NK/Ly].

The mitotic activity and DNA synthesis in cells of NK/LY tumors in mice were studied after irradiation with fast electrons in fractionation of the dosage in 3 regimens having similar total dosage (1000 rad) and the total time of irradiation (5 days) but different single doses, the number of fractions and an interval between them. A marked decrease in mitotic indices values (MI) was observed with all three regimens during the first hours after irradiation. 3--6 hours after irradiation the period of their restoration started, which was mostly intensive in daily irradiation with 200 rad. A dependence between the time of MI restoration and the dosage per fraction and number of fractions is described as an exponential function with an index 1.47. The kinetics of variations in the number of labelled cells showed a similar character, but it was less pronounced, whereas peaks of rising of the label index in all regimens did not exceed the control level.