COMPARATIVE DYNAMICS OF RELEASE FROM POTE NTIAL CHROMOSOME-DAMAGE OBSERVED IN MOUSE BONE-MARROW CELLS UNDER EXPOSURE TO LOW AND MODERATE RADIATION-DOSES

Possible dynamics of the incidence, repair, and realization of potenti al chromosome aberrations (PAs) was examined by indirect methods based on cytogenetic analysis of radiation effects. PAs were characterized as chemical modifications of DNA responsible for the incidence of stru ctural aberrations of chromosomes. We interpreted our data as providin g evidence that two types of radiation-induced PAs, differing in repai r rates, could occur in the exposed cells: quick- (short-term) and slo w (long-term) repairing PAs. We showed that the PA spectrum gradually changed with an increase in radiation dose within the interval from 24 to 150 cGy, phis process was paralleled by changes in the cell respon se and chromosome resistance to radiation. Short-term PAs were induced mainly by low radiation doses ranging from 24 to 75 cGy. Their incide nce was associated with activation of the corresponding repair process , Further increase in radiation dose resulted in changes in the PA spe ctrum, and doses of 150 cGy induced predominantly long-term PAs with c oncomitant activation of the appropriate repair process, Induction of repair occurred in the dose intervals limited by lower and upper thres hold doses, D-1 and D-u. In our experiments, short-term PAs were repai red when D-1 < 24 cGy and 126 cGy < D-u << 150 cGy, Long-term PAs were repaired when 75 cGy < D-1 < 99 cGy and D-u > 150 cGy.