[Kinetics of bone marrow cells under conditions of fractional x-irradiation].

A study was made of the damaging effect of fractionating X-irradiation (12 rad a day, up to the sum total doses of 250, 500, 750, 1000 and 1500 rad) on the hemopoiesis in guinea pigs. A phasic character of the changes in the erythro- and myelopoiesis during the damage was revealed. The first phase was attented by the activation of the proliferation processes expressed in the increase of mitotic index, reduced duration of the mitotic cycle of the cells belonging to the erythroid and the myeloid series and their accelerated differentiation, this stipulating for a sufficient entrance of the cells into the blood flow and maintaining the erythrocyte and leukocyte content in the peripheral blood approaching the normal level. A reduction of the proliferative processes in the bone marrow was observed during the second phase; these were also a reduction of the mitotic index, prolongation of the mitotic cycle and of the rate cell diferentiation of the erythroid and myeloid series, this being accompanied by anemia and leukopenia in the peripheral blood.