[An analysis of the cytogenetic effects of gamma and neutron irradiation in a human lymphocyte culture at the G0 and G1 stages of the mitotic cycle (a structural-functional approach)].

A study was made of the dose dependence of the chromosome aberration frequency in human lymphocytes exposed to 60Co-gamma radiation and neutrons (mean energy of 0.85 MeV) at the G0 stage and in different periods of the G1 and G1/S stages of the cycle. With gamma irradiation the dose dependence for cells at the G1 and G1/S stages was at a higher level than that for cells at the G0 stage, whereas the opposite picture was observed for cells exposed to neutron radiation. The difference was also noted in the time-response curves where gamma radiation increased and neutrons, on the contrary, decreased the aberration yield in the cells that passed from G0 to G1 stage. The experimental data obtained are attributed to activation of repair system at the G1 stage which is mainly conditioned by chromatin decondensation; the activating, that is, the functional factor influences the aberration induction with gamma irradiation, while the decondensation, that is, the structural factor, with neutron irradiation.