Long-term morphofunctional changes in the skin of Chernobyl clean-up workers

Musculocutaneous samples taken from 19 Chernobyl clean-up workers were morphofunctionally examined to trace the changes, which had happened in them under the lasting exposure to low doses of ionizing radiation. The analysis showed that the greatest changes had taken place in the epidermis in the form of thickening of corneal and cellular layers and inflammatory infiltration of lymphocytes provided with the productive panvasculitis in the majority of arterioles. It is supposed that after the long low-doce irradiation two forms of reactions developed in the skin: a defense reaction in the form of proliferative hyperkeratosis and an immunopathological reaction. The latter is a consequence of activation in the cellular layer of epidermis combined with the appearance of effector component of immune response, which stimulates the interaction of epidermal T-lymphocytes with the endothelial cells of derma vessels and systemic involving of blood vessels of microcircular blood stream.     

The distribution of chromosome damage, non-reciprocal translocations and clonal aberrations in lymphocytes from Chernobyl clean-up workers

In this paper we determined whether the frequencies of translocations and insertions are proportional to chromosome size in peripheral blood lymphocytes from Chernobyl nuclear accident clean-up workers and healthy unexposed control subjects. The frequency of aberrations among chromosomes 1, 2 and 4 in both groups was found to be significantly different from the distribution expected on the basis of chromosome size, although the difference was only marginally significant in controls. We also determined whether differences exist in aberration frequencies measured by two scoring systems: the classical method, where reciprocal exchanges are scored as one event, and PAINT, where each break junction is scored as a single event. The two scoring systems gave highly correlated results which yielded an interpretable arithmetic relationship between frequency measurements using the two systems. Approximately 34% of all translocations were observed to be non-reciprocal, and cells bearing clones of abnormal cells were observed in 6 of 198 subjects (3.0%). Our results demonstrate that clones of abnormal cells and the presence of non-reciprocal translocations contribute to the non-proportional distribution of radiation-induced and spontaneous cytogenetic damage.     

Chromosome aberrations and rogue cells in lymphocytes of Chernobyl clean-up workers

A cytogenetic analysis was performed on peripheral blood lymphocytes from 183 Chernobyl clean-up workers and 27 control individuals. Increased frequencies of chromosome aberrations were associated with exposure to radiation at Chernobyl, alcohol abuse and a history of recent influenza infection. However, only approximately 20% of Chernobyl clean-up workers had an increased frequency of dicentric and ring chromosomes. At the same time, an increased frequency of acentric fragments in lymphocytes of clean-up workers was characteristic. The use of multivitamins as dietary supplement significantly decreased the frequency of chromosome aberrations, especially of chromatid breaks. Rogue cells were found in lymphocytes of 28 clean-up workers and 3 control individuals. The appearance of rogue cells was associated with a recent history of acute respiratory disease (presumably caused by adenoviral infection) and, probably, alcohol abuse. Dicentric chromosomes in rogue cells were distributed according to a negative binomial distribution. Occurrence of rogue cells due to a perturbation of cell cycle control and abnormal apoptosis is suggested.     

Genetic instability in peripheral blood lymphocytes of Chernobyl clean-up workers.

The group of clean-up workers involved in the liquidation of the consequences of the major accident at the Chemobyl nuclear power plant (CNPP) was exposed to high doses of radiation. In this review, we summarize the results of a long-term study of the cytogenetic status of CNPP clean-up workers. The data revealed different trends of the parameters of the cytogenetic status in the course of the study. The results of biological dose reconstruction, based on the frequency of mutant T-helper cells, are discussed.     

Cataracts among Chernobyl clean-up workers: implications regarding permissible eye exposures

The eyes of a prospective cohort of 8,607 Chernobyl clean-up workers (liquidators) were assessed for cataract at 12 and 14 years after exposure. The prevalence of strictly age-related cataracts was low, as expected (only 3.9% had nuclear cataracts at either examination), since 90% of the cohort was younger than 55 years of age at first examination. However, posterior subcapsular or cortical cataracts characteristic of radiation exposure were present in 25% of the subjects. The data for Stage 1 cataracts, and specifically for posterior subcapsular cataracts, revealed a significant dose response. When various cataract end points were analyzed for dose thresholds, the confidence intervals all excluded values greater than 700 mGy. Linear-quadratic dose-response models yielded mostly linear associations, with weak evidence of upward curvature. The findings do not support the ICRP 60 risk guideline assumption of a 5-Gy threshold for "detectable opacities" from protracted exposures but rather point to a dose-effect threshold of under 1 Gy. Thus, given that cataract is the dose-limiting ocular pathology in current eye risk guidelines, revision of the allowable exposure of the human visual system to ionizing radiation should be considered.     

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.     

Time-effect relationship of chromosome aberrations in peripheral lymphocytes after radiation therapy for seminoma

The time-effect relationship of dicentrics and cells containing unstable chromosome abnormalities (Cu cells) was studied in peripheral lymphocytes of 40 blood samples from 23 patients suffering from seminoma during a time period of 0-1720 days after radiation therapy. Nine patients were studied before treatment. Since the half-time for the disappearance of damaged cells from circulating blood is an increasing function of post-exposure time it can only be expressed as a differential value. The present model discriminates between the mean lifetime m for lymphocytes and a parameter q which is the differential half-time for the decline of damaged cells immediately after exposure (t = 0). If the time t is short compared with m the decline is asymptotically time-hyperbolic rather than exponential and can be described by q only. According to recalculations of previous data, comprising 30 years post exposure, m approximates 10 years. Differential half-times can be derived for any time post treatment within the analysed time period for the decline of the incidence of dicentrics. For example at the end of therapy (t = 0) the differential half-time was calculated to be 0.4 years and at 1720 days post exposure 3.6 years resulted. The corresponding values for the percentage of Cu cells cannot be derived for t = 0; at 1720 days 3.9 years resulted.     

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.     

Chromosomal aberrations and parameters of oxidative stress in Chernobyl clean-up workers in a remote period after ionizing radiation

This investigation was performed to test a supposition about the influence of disturbances in antioxidative system on cytogenetical parameters in Chernobyl' clean-up workers. It was shown that some cytogenetical parameters straightly correlated with the parameters of oxidative stress, while other cytogenetical parameters show just reverse correlations. Apparently, these relationships are not of cause-and-effect type, but they reflect a complex processes occurring in humans for a long period after radiation exposure.     

Leukemia incidence in the Russian cohort of Chernobyl emergency workers

Of all potentially radiogenic cancers, leukemia, a type of cancer of the blood, has the highest risk attributable to ionizing radiation. Despite this, the quantitative estimation of radiation risk of a leukemia demands studying very large exposed cohorts, because of the very low level of this disease in unexposed populations and because of the tendency for its radiation risk to decrease with time. At present, the Japanese cohort of atomic bomb survivors is still the primary source of data that allows analysis of radiation-induced leukemia and the underlying dose–response relationship. The second large cohort that would allow to study radiation-induced leukemia is comprised of individuals who were exposed due to the accident of the Chernobyl nuclear power plant in 1986. The objective of the present study was to estimate radiation risks of leukemia incidence among the Russian cohort of Chernobyl emergency workers, for different time periods after the accident. Twenty-five years after the Chernobyl accident and based on the results of the present study, one can conclude that the radiation risk of leukemia incidence derived from the Russian cohort of Chernobyl emergency workers is similar to that derived from the cohort of atomic bomb survivors: The time-averaged excess relative risk per Gray (ERR Gy⁻¹) equals 4.98 for the Russian cohort and 3.9 for the life span study (LSS) cohort; excess absolute risk decreases with time after exposure at an annual rate of 9% for the Russian cohort, and of 6.5% for the LSS cohort. Thus, the excess in risk of leukemia incidence in a population due to a single exposure is restricted in time after exposure by the period of about 15 years.     

Mini-and microsatellite mutations in children from Chernobyl accident cleanup workers

Knowledge about possible genotoxic effects of low-dose radiation on the human germline is limited and relies primarily on extrapolations from high-dose exposures. To test whether ionizing radiation can cause paternal genetic mutations that are transmitted to offspring, we enrolled families of 88 Chernobyl cleanup workers exposed to ionizing radiation. We analyzed DNA isolated from lymphocytes for mutations via DNA blotting with the multi-locus minisatellite probes 33.6 and 33.15 and via PCR in a panel of six tetranucleotide repeats. Children conceived before and children conceived after their father's exposure showed no statistically significant differences in mutation frequencies. We saw an increase in germline microsatellite mutations after radiation exposure that was not statistically significant. We found no dependence of mutation rate on increasing exposure. A novel finding was that the tetranucleotide marker D7S1482 demonstrated germline hypermutability. In conclusion, our results do not support an increased level of germline minisatellite mutations but suggest a modest increase in germline mutations in tetranucleotide repeats. Small sample size, however, limited statistical power.     

Chromosome alterations in cleanup workers sampled years after the Chernobyl accident

Cytogenetic analysis performed 4-13 years after the Chernobyl accident showed an elevated frequency of acentrics, chromatid exchanges, dicentrics and rings in Chernobyl cleanup workers compared to the control group. Cytogenetic data were analyzed according to the information on exposure to radiation (the year when the cleanup workers worked at the Chernobyl station, doses rates, time elapsed since exposure to radiation, and cytogenetic examination) and some lifestyle factors. The data obtained suggested that some types of chromosome aberrations could be influenced by the action of different environmental factors or lifestyle factors. The frequency of acentrics was correlated with the age of the cleanup workers, and the increased chromatid exchange frequency was attributed to smoking. The numbers of dicentrics and rings suggested a genotoxic effect of ionizing radiation that is still present over 13 years after the exposure.     

Leukaemia and thyroid cancer in emergency workers of the Chernobyl accident:

This work focuses on the direct epidemiological assessment of the risks of radiation-induced leukaemia and thyroid cancer in emergency workers (EW) after the Chernobyl accident. The Russian National Medical Dosimetric Registry (RNMDR) contains data for 168 000 EW as of January 1, 1996. The analysis relates to 48 leukaemias and 47 thyroid cancers, diagnosed and verified. Radiation risks are estimated by comparing the EW data with national data for a male population of the same age distribution. For leukaemia, an excess relative risk per Gy (ERR/Gy) of 4.30 (95% CI: 0.83, 7.75) is obtained, while the excess absolute risk per 10⁴ person-years (PY) Gy (EAR/10⁴ PY Gy) is found to be 1.31 (95% CI: 0.23, 2.39); for thyroid cancer an ERR/Gy of 5.31 (95% CI: 0.04, 10.58) is obtained, and an EAR/10⁴ PY Gy of 1.15 (95% CI: 0.08, 2.22).     

Electron microscopy and ultracytochemistry of lymphocytes containing Gall bodies in the blood of patients with diabetes mellitus, Hodgkin disease and clean-up workers of the Chernobyl Atomic Electric Plant accident

Submicroscopic and ultracytochemical changes in lymphocytes containing Gall body complex in the cytoplasm, have been studied in the blood of patients with type 1 and 2 diabetes mellitus, Hodgkin disease, and clean-up workers of the Chernobyl accident. It has been shown that each pathological state was characterized by specific changes in the ultrastructure of Gall body complex, that pointed out its important role in the function of this type of lymphocytes and may be used as an additional cytological criterion in the estimation of T-immunity status.     

Modeling of unstable heat-mass air exchange in the lungs

A mathematical model of the unsteady-state heat and mass exchange of expired air in the bronchial tree is suggested. The model includes heat and mass exchange between air and bronchial walls, and heat exchange between blood circulation and bronchial tree. A problem has been numerically solved as a unidimensional one in the quasi-steady-state formulation. It is shown that air conditioning occurs through the whole length of a respiratory tract. During inspiration bronchial walls are cooled, that in its turn induces a decrease of air temperature and water vapour content in time. That process depends on the intensity of lung blood circulation and character of air velocity changes during inspiration.     

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.