Unscheduled DNA synthesis in plant populations exposed to chronic irradiation.

The intensity of gamma-ray-induced unscheduled DNA synthesis (UDS) was measured in a number of natural populations of Vicia cracca which have been growing for some decades under conditions of chronic alpha- or beta-irradiation. It was shown that the level of UDS increased in more radioresistant beta-irradiated populations as compared to control populations and this increase was dose rate-dependent. In alpha-irradiated populations, the intensity of UDS was decreased, but only at the highest dose of gamma-radiation (500 Gy) and was not changed at the lower doses. The sensitivity of UDS to inhibitors of DNA and protein synthesis was studied in control and radioresistant populations. In control plants UDS was resistant to cycloheximide (Cyc) and aphidicolin (Aph), but totally inhibited by dideoxythymidine (ddT). In radioresistant population UDS was inhibited by both Aph and ddT as well as by Cyc. I assume that in controls, UDS is mediated by beta-like DNA polymerase; however, in a radioresistant population, both DNA polymerases alpha and beta take part in this process. In the radioresistant population UDS is partially inducible.

Human cytogenetic consequences of the Chernobyl accident.

The frequency of chromosomal aberrations was evaluated in more than 500 liquidators of the Chernobyl accident. The 'sarcophagus' builders and the dosimetrists showed the highest frequency of aberrations per 100 cells: 3.24 +/- 0.25 and 3.11 +/- 0.43. For Chernobyl Atomic Power Station staff members the mean frequencies of aberrations per 100 cells was 2.37 +/- 0.20. The mean yields of aberrations in the other groups was between 1.31 and 1.47 per 100 cells. If the mean frequencies of aberrations are converted into equivalent whole body doses, values between 136 and 414 mGy are obtained. Especially in the group of 'sarcophagus' builders, the yields of aberrations varied interindividually and corresponded to equivalent whole body doses of up to about 2 Gy.

Analysis of DNA strand break induction and repair in plants from the vicinity of Chernobyl.

For 3 years following the Chernobyl accident, DNA repair efficiency was studied in irradiated and control populations of various plant species. Compared with the control populations, some irradiated populations exhibited increases in the yield of DNA single-strand breaks per unit dose of challenge radiation. The effect was registered in low-dose-rate alpha-irradiated populations, but was absent in plant populations growing in conditions of low-dose-rate beta-irradiation. The efficiency of single-strand DNA repair was identical in control and irradiated populations and approximated 100%.