Complex cytogenetic characteristic of people suffered from Chernobyl accident

A cytogenetic study was performed on Chernobyl cleanup workers, on their children, on persons evacuated from contaminated aeria (adult and children), on so named "veterans of particular risk" irradiated due to the accidents on the nuclear plant, testing of nuclear weapons etc. and on control donors. The yield of stable (FISH analysis) and of unstable chromosome aberrations, micronuclei in both lymphocytes and erythrocytes, HPRT mutations was found to be increased in exposed groups as compared to control ones. In children of liquidators and in evacuated children we observed genomic instability and increased in vitro chromosomal radiosensitivity. Acceleration of age accumulation of translocations characterized the exposed population in comparison with control group. People with the highest level of routine chromosome aberrations had cardiovascular and digestive diseases more often likely than those with the lowest level. In frame of International Project ECP-6--"Biological dosimetry" the dose-responses for dicentrics and translocations were constructed in dose range 0-100 cGy of gamma-irradiation on the base of data of 8 laboratories. On cancer patients undergone whole-body gamma-irradiation (every day at the dose 11.5 cGy to a total of dose 57.5 cGy) we constructed the dose-responses for the dicentrics and translocations and compared them with the dose-responses for these aberrations after the in vitro irradiation of lymphocytes of the same patients. For the dicentrics the effectiveness of the in vivo irradiation was less than of the in vitro one. No differences were found for translocations.     

Results of cytogenetic studies of the consequences of the Chernobyl accident

The selected results of the cytogenetic studies of the Chernobyl accident consequences were summarised. The chromosomal aberrations were used as a method of biodosimetry for a dose assessment for victims during the initial period after the Chernobyl accident. A good correlation between doses calculated based on chromosomal aberrations (dicentrics) and severity of acute radiation syndrome observed in clinic was found. The biodosimetry based on conventional cytogenetic technique (dicentrics) has been unsuccessful for various groups (rehabilitation workers, evacuees, inhabitants of contaminated areas) sampled long time after the Chernobyl accident. The possible reasons of the failure are analysed. The original results of multiaberration cell yield observed in different cohorts of the Chernobyl victims are presented. The problems related to the phenomena are discussed.     

Results of experimental radiobiological studies made within the 10-kilometer zone of the Chernobyl AES accident]

A study was made of the effect of high radioactive contamination on the animal organism (C57BL/6 mice) and HeLa cell culture within the ten-kilometer zone of the Chernobyl A.P.S. accident. The total radiation dose, as calculated by a gamma-component, was 0.09 to 2 Gy. A long-term exposure of mice within the zone (cumulative dose of 1.8 to 2 Gy) caused a significant decrease in bone marrow stem potencies and changes in the brain vascular system; subsequent acute exposure of animals increased interferon titres in the serum to a much greater extent than a single acute exposure did. As to HeLa cells, irradiation there of with doses of 0.09 to 0.4 Gy during 15-20 postirradiation generations caused a decrease in the proliferative activity, an emergence of cells with micronuclei and of giant cells, and remote cell death.     

The possibility of using the preparation MIGI-K in districts exposed to radioactive contamination following the accident at the Chernobyl AES]

A preparation from mussels, MIGI-K, used as an additive to the diet of people working at the Chernobyl power plant has proved to be efficient in increasing the total resistance of the body, including the resistance to ionizing radiation. In experiments with animals, MIGI-K has been shown to accelerate excretion of 45Ca and 86Rb from the body. The combination of these properties of MIGI-K permits us to consider it an efficient drug to be used within the regions affected by the Chernobyl disaster.     

Evaluation of the effect of the radioactive contamination of hydrobionts in the 30-kilometer control zone of the accident at the Chernobyl AES]

A study was made of hydrobionts, particularly fishes, living within the thirty-kilometer control zone of Chernobyl NPP and northern part of the Kiev basin, after the disaster. Out of 31 fish species living in the NPP cooling pond some were identified which were mostly affected by radioactive contamination. They were predators belonging, with respect to reproduction and development, to a lithophilous group. Peculiarities of reproduction of Hypophthalmichthys molitrix kept in stews of the cooling pond before the accident were studied. After a three-year exposure to ionizing radiation (cumulative dose of 8-9 Gy) no reduction in the reproductive capacity of mature fishes was observed.     

Content of free amino acids in blood plasma of the clean-up personnel at the Chernobyl nuclear power plant accident

In two groups of the persons participating in liquidation of the Chornobyl Power Plant Catastrophe (individuals which suffered from acute radiation sickness and those ones who were exposed to irradiation at doses 0.25-1.0 Gy) in a year after medical treatment the free amino acids, their derivatives, glucose, sodium lactate and pyruvate homeostasis changed in comparison with the control. The causes and possible mechanisms of these substances exchange regulation disorders in the key biochemical reactions ensuring the body organs and systems functioning were estimated. The experimental findings received can be used at planning the further examination and treatment-and-prophylactic measures for the persons which have been affected by ionizing radiation consequently the accident at the Chornobyl Nuclear Power Plant.     

The retrospective cytogenetic dosimetry using the results of conventional chromosomal analysis in Chernobyl clean-up workers

The paper presents the results of the cohortal biodosimetry carried out in 435 Chernobyl clean-up workers, who were surveyed with the conventional cytogenetic technique in terms from several days to 10 years after the end of their duties in the Chernobyl accident exclusive zone. An empirical model of the aberrant cell dynamics was utilized for the calculation of mean initial yields of dicentrics and centric rings in groups with different terms and duration of staying in the Chernobyl zone. Corresponding protracted irradiation doses estimated from aberration levels ranged from 79 to 670 mGy. The probabilistic distribution of the radiation doses was constructed by the applying the Bayesian analysis to initial individual chromosome exchange yields extrapolated to the exposure termination moment. This distribution was characterized by the mean dose about 460 mGy and maximum of probability density in the interval of 50-300 mGy. For the late somatic risk assessment in clean-up workers the probabilistic distribution of equivalentally-acute radiation doses was proposed; that had the mean value about 270 mGy, modal classes of 250-350 mGy and 99.8% of the probability density concentrated within the dose range from 0 to 1000 mGy.     

The cytogenetic indication of irradiation in persons exposed to the action of the factors in the Chernobyl accident]

363 men who have been working under conditions of additional irradiation in terms from few hours to some months were cytogenetically examined to define individual irradiation. In 111 men with the known dose of irradiation (5-140 cGy), the results of cytogenetic evaluation indicated, as a rule, a less intensive irradiation than physical dosimetry. This could be caused by elimination of chromosome aberrations, individual sensitivity, peculiar irradiation situation, or in some cases by incorrect evaluation of dose. In 252 men with the unknown dose of irradiation a tentative level was determined as based on frequency of metaphases with chromosome type aberrations. According to the study the absorbed dose was below 25 cGy in 209 cases, 26-50 cGy in 39 cases, and reached 51-90 cGy in 4 cases.     

The significance of cytogenetic investigation for the estimation of Chernobyl accident consequences

The results of the cytogenetic investigation of people, which were exposed to radiation in the result of the Chernobyl NPP accident, were presented. Also the possibilities of the application of cytogenetic findings for dose estimations and for the prediction of the radiation influence consequences were examined. During the period of time since 1986 till 2004 the cytogenetic investigations of 1724 liquidators participating in the liquidation works after the Chernobyl accident were carried out. The radiation dose estimated by the frequency of dicentrics in 1986 was about 0.16 Gy. The doses for liquidators were determined by the frequency of translocations (FISH method) during the period from 1992 till 1995. For liquidators who worked in Chernobyl only in 1986 the average dose of radiation was about 0.19 Gy and for liquidators who worked repeatedly during the period from 1986 till 1995 - 0.39 Gy. There was shown that during the whole period of investigation (1986-2004) the frequency of dicentrics in peripheral blood lymphocytes was significantly higher than the control level. The cytogenetic investigation of Bryansk region inhabitants which was carried out in 1992-1994 discovered heightened value in 5 times than the control one. Findings are of great importance for the prediction of ill effects of radiation and for the development of sensitive criterions for early exposure disturbances in state of health.     

Results of dynamic cytogenetic study of children and teenagers living in areas, radioactive by contaminated after the Chernobyl accident

Results of multiyear cytogenetic study of children and teenagers living in areas, radioactive by contaminated after Chernobyl accident, were adduced. Mean density of 137Cs contamination in two compared living areas were 111 and 200 kBq/m2 and mean external doses accumulated for 1986-2001 were 6.7 and 11.4 mGy correspondingly. Averaged thyroid doses receives by subjects of all age groups in the second area were approximately 1.5 times higher than in the first area; in the youngest group (0-1 year) the doses were 114.3 and 174.3 mGy. During 17 years cytogenetic investigation approximately from 30% to 60% of examined persons were observed the increased level of chromosome aberrations in lymphocytes of peripheral blood. Average frequency of unstable aberrations (acentrics, dicentrics and centric rings) constituted about 0.4 per 100 cells (0.22 per 100 cells in controls) during all period of observation. Level of marker aberrations (dicentrics and centric rings) was increased almost all times of study and varied within 0.04-0.19 per 100 cell (0.03 in control group). The parallel investigation of frequency of stable aberrations by FISH method showed up their level about 3 times exceeding observed dicentrics level. Comparably higher indexes of cytogenetic disturbances were revealed in group exposed in utero during period of accident.     

Comparative analysis of the effectiveness of countermeasures in rural settlements in the long-term period after the accident at the Chernobyl AES

A comparative analysis of the strategy of countermeasures aimed at reducing exposure doses to the rural population is presented. The effectiveness of the proposed system of countermeasures assessed by criteria such as reduction factor of exposure doses and cost of averted doses. Costs of countermeasures in the rural settlements located in the affected zone are calculated for a long term after the Chernobyl NPP accident.     

Long-term cytogenetic effects in children prenatally-exposed to radiation as a result of the accident at the Chernobyl Atomic Energy Station

Forty-two children exposed to ionizing radiation in prenatal period and 15 children of control group were examined in the remote terms after the accident using the method of differential G-staining of chromosomes in lymphocytes of peripheral blood. It was found that the average group rate of aberrant cells and chromosome aberrations was reliably higher in the children exposed in utero compared to control. Long-term cytogenetic consequences of the pre-natal exposure were characterized by prevalence of aberrations of a chromosome type, mainly stable chromosome lesions. At chronic exposure to low doses of ionizing radiation the increase in the rate both stable and unstable chromosome aberrations.     

Chernobyl clean-up workers erythrocyte membrane lipid content at the remote period

Chernobyl Nuclear Power Plant accident clean-up workers were exposed to different radiation doses. Realization of remote effects depends on cellular membrane structure and function. We studied lipid composition of erythrocyte ghost and blood plasma in clean-up workers on the 12-th year after the accident. Groups of Chernobyl accident clean-up workers, non-irradiated patients with the same diseases and healthy controls were studied. Phospholipids were analyzed by two dimentional thin layer chromatography on silica gel. To analyse fatty acids and cholesterol gas chromatography was used. Total cholesterol and total phospholipids amounts in clean-up workers erythrocyte ghost were increased. The level of sphingomyelin and phosphatidylethanolamine raised. In some of the studied irradiated patients lysophosphatidylethanolamine appeared. The distribution of (diacyl)- and plasmalogen forms of phosphatidylcholine and phosphatidylethanolamine was not affected. The fatty acid composition changed slightly except 22:5 n-3, which level significantly increased and 22:5 n-6, which quantity lowered. The unsaturation index remains unchanged. No change in lipid composition of blood plasma was detected. All the changes in lipid composition of erythrocyte ghost of irradiated and unexposed patients were very similar. The obtained results confirm the suggestion about non-specific remote effects after exposure to low doses of ionizing irradiation.     

The distribution of individual radiation doses in liquidators of Chernobyl accident using cytogenetic analysis

The cytogenetic screening was carried out in 100 Chernobyl clean-up workers (liquidators) with registered doses during 1 year after exposure. The bayesian analysis has been applied for constructing the individual distribution of probability density for biological doses estimated from dicentric and centric ring yields in liquidators. The coincidence of the biological and registered dose has been found in 25% of cases; among the rest persons the documented doses exceeded the biological estimations in 25% of cases and the cytogenetic doses were higher than registered ones in 50% of cases. The total distribution of biological doses was constructed by pooling the individual data in 50 mGy dose intervals. The distribution obtained had the maximum at 300-350 mGy and contained 68% of probability density in the dose range 0-1000 mGy. The probabilistic approach in cohort biodosimetry showed the necessity of corrections in radiogenic risk assessment for Chernobyl liquidators. The advantages of bayesian technique for biodosimetrical treatment of cytogenetic data in conditions of small number of cells scored and low aberration yields induced by low dose irradiation were discussed.     

The cytogenetic effect in peripheral blood lymphocytes as an indicator of the effect on man of factors of the Chernobyl accident]

The data obtained confirm the possibility of both individual and population cytogenetic indication of the effect of low intensity radiation, exceeding the background level, and exhibit a positive correlation with the radio-ecological situation formed. The cytogenetic effect, that indicates the disturbance of the genome stability, might be considered as an indicator of a high probability of occurrence of pathologies, with a genetic component, in the subpopulations under study, compared to spontaneous level.     

Estimation of long-time effects of Chernobyl AES accident on behavior markers in a small rodent population

Differences in behaviour reactions in "open field" and glycemia under conditions of immobilisation stress of vole (Microtus oeconomus, Pallas) from two groups ("Yanov" and "Lelev") were investigated. Rodents were ensnared from two populations reproduced for a long time (11 years) in the areas of ChNPP Exclusion Zone with different level of radioactive contamination. The radiation absorbed dose for animals of "Yanov" group (external and internal irradiation) was 11-20 times higher than that of "Lelev" group. Males and females from the area with worse radioecological condition had higher vertical and horizontal locomotion. The level of emotional reactions of "Yanov" males was lower than the "Lelev" one. Statistically significant variation in female emotional reaction was found, but it had not the same directions. In both groups higher locomotion activity and lower emotionality were associated with male sex. The males of both groups showed similar fasting glucose level and glycemic response after 30-min. immobilisation. Our data provide the additional evidence of existence of long-time genetic effects in small rodent populations permanently reproduced on radiation contaminated areas.     

Individual immunological parameters in clean-up team members and patients with sequelae of acute radiation sickness 5 years after the effects of the Chernobyl accident]

A study was made of deviations, beyond 1 sigma and 1.5 sigma of a mean value (M) of a donor group, in individual immunological parameters (for instance, the number of CD5+, CD2+, CD4+, CD8+, CD25+ and B-cells; alpha 1-thymosin concentration; and autoantibody titers to antigens of epithelial reticulum cell cytoplasm) in patients suffered acute radiation sickness (ARS) and liquidators of Chernobyl NPP accident. The radiation damage to the immune system was reliably detected in the affected subjects examined: they exhibited a decrease in the alpha 1-thymosin level below M = -1.5 sigma and in absolute B cellularity below M = -1 sigma; and increase in the number of CD25+ cells and in the level of serum autoantibodies to antigens of thymus epithelial reticulum cell cytoplasm. When several parameters selected were examined simultaneously the frequency of recording the deviations in merely one of them markedly increased.