[Changes in the capacity of CFU-S to form macrocolonies under long-term chronic irradiation].

Distribution of CFU-S upon daily chronic irradiation of mice with doses of 0.25 and 0.5 Gy during 3-4 months was close to normal: the percentage of individuals without CFU-S capable of forming macrocolonies being high in both cases. 60 day after the end of the exposure the macrocolony-forming ability after the second transplantation was nearly twice as low and independent of daily dose and duration of exposure.