Chromosomal mutagenesis in human somatic cells: 30-year cytogenetic monitoring after Chornobyl accident.

In the lecture we have generalized and analyzed the data of cytogenetic laboratory of National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine on 30-year selective cytogenetic monitoring among the priority contingents of different ages exposed to radiation after Chornobyl accident in Ukraine. It is highlighted that not only targeted but also untargeted radiation-induced cytogenetic effects should be explored, especially in delayed terms following radiation exposure. The new methodical approaches for studying "bystander effect", individual radiosensitivity, and various forms of radiation-induced chromosomal instability (delayed, hidden, transmissible) have been proposed. These approaches proved to be advantageous for analyzing cytogenetic patterns of induction and persistence of chromosomal instability in human somatic cells because of "bystander effect" and "bystander type effect". The phenomenon of positive "reverse" bystander effect has been found. The possibility of modifying the inherited individual human susceptibility to mutagenic exposure by ionizing radiation has been estimated. Finally, the association between hypersensitivity to radiation exposure and realization of oncopathology in exposed individuals has been revealed. The increased intensity of human somatic chromosomal mutagenesis was confirmed not only in the nearest but in the delayed terms following Chornobyl accident as a result of radiation-induced both targeted and untargeted cytogenetic effects. Such effects can be considered as risk factors for malignant transformation of cells, hereditary diseases, birth defects, and multifactorial somatic pathology. This article is a part of a Special Issue entitled "The Chornobyl Nuclear Accident: Thirty Years After".

Peculiarities of induction and persistence of hidden chromosome instability in peripheral blood lymphocytes of persons occupationally exposed to ionizing radiation. / Osoblyvosti indukcii' ta persystencii' pryhovanoi' hromosomnoi' nestabil''nosti v limfocytah peryferychnoi' krovi osib, jaki profesijno kontaktuvaly z ionizujuchoju radiacijeju.

Objective - to investigate the induction of hidden chromosome instability in persons occupationally exposed to ionizing radiation and its persistence in vitro in successive mitoses. Materials and methods. Using two tests ("G2-bleomycin sensitivity assay" and two-term cultivation of human peripheral blood lymphocytes) voluntary cytogenetic examination of 15 individuals participated in the conversion of the "Shelter" ("Chornobyl NPP") into ecologically safe system had been carried out. Total 24 034 metaphase had been analyzed, of which 12 243 - without additional mutagenic exposure, 11 791 - exposed to bleomycin in vitro at concentration of 0.05 µg/ml. Results. The magnitude and dynamics of background as well as bleomycin-induced cytogenetic effects in both terms of lymphocytes' cultivation in occupational group differed significantly from the group of comparison towards increasing of chromosome instability indices with significant interindividual fluctuations. Conclusion. Interindividual differences in persistence of radiation-induced hidden chromosome instability in successive generations of human somatic cells had been found.

The Ukrainian-American study of leukemia and related disorders among Chornobyl cleanup workers from Ukraine: I. Study methods.

There are relatively few data on the risk of leukemia among those exposed to external radiation during cleanup operations after the Chornobyl nuclear accident, and results have not been consistent. To investigate this further, we assembled a cohort of 110,645 male cleanup workers from Ukraine and identified cases of leukemia occurring during the period 1986 to 2000. Detailed interviews were conducted and individual bone marrow doses estimated using a new time-and-motion method known as RADRUE described in companion paper II. For the initial analyses we used a nested case-control approach with a minimum of five controls per case, matched for year of birth, oblast (region) of registration, and residence. All identified cases were reviewed by an international panel of experts; 87 of 111 were confirmed. The dose-response analysis and results are given in companion paper III. As background, we describe herein the design, procedures, outcome of case finding and confirmation, control selection, dose estimation and interviewing of subjects.