Molecular-cellular characteristic of blood lymphocytes in Hodgkin lymphoma

The molecular-cellular parameters complex has been studied on the blood lymphocytes of malignant Hodgkin's lymphoma (HL) patients: the frequency of cells with micronuclei (MN) and chromosome aberrations; the level of DNA single and double strand breaks - OR and DR DNA (DNA comet assay), oxidative status--the content of reactive oxygen species (ROS) by using nonfluorescent dye that is oxygenated in the cells to fluorescent reagent and detection of fluorescence intensity after there. It was shown that the patients with LH had the increased level of DR and OR DNA, the increased frequency of cells with chromosome aberrations and the number of aberrations per cell was increased too. The concentration of ROS is increased too for the most individuals with intoxication. In the process of the chemical and radiation therapy the increase of OR DNA level, the frequency of the cell with MN has been registered. The ROS concentration correlates with the level of DNA-strand breaks. So the blood lymphocytes of HL patients before treatment differ from the lymphocytes of healthy donors. The damage of genome and the change of oxidative status have been observed that can be additive markers for the HL diagnosis, their sensitivity to the treatment and the characteristic of lymphocytes changes by this disease.     

Molecular and cellular consequences of the Chernobyl accident

In this paper the results of the Chernobyl accident investigation 5-10 and 24 years after are summarized. The genomic instability, adaptive response formation, genome damage and oxidative status have been investigated. The studies were performed on cells in culture, mice, children and adults living in contaminated areas and liquidators. On cells in culture after exposition in the accident zone and culturing thereafter in laboratory conditions the cell proliferative activity decrease; the late cell death, the frequency of cells with micronuclei and giant cells increasing have been observed. In the progeny of exposed cells the enhancement of radiosensitivity has been noticed. So we can suppose that in cultured cells exposition in the zone of the accident the genomic instability is induced which results in many disturbances. At the organism level in mice exposed in the Chernobyl zone the radiosensitivity increase and the decrease of endotheliocytes density in brain tissue has been observed. On the stimulated by PHA blood lymphocytes of children the increase of the frequency of cells with micronuclei more than 2 time have been noticed. In all groups investigated, the decrease of individuals with significant adaptive response was observed. In children and adults inhabitants the increase of radiosensitivity after low dose of irradiation has been noticed. 24-year after the accident it was discovered that in liquidators lymphocytes the frequency of cells with micronuclei, with chromosome type aberrations, with DNA double strand breaks have been increased; the reactive oxygen species (ROS) were decreased in comparison with the control population. We can suppose that genomic instability induced in residents of contaminated regions and liquidators long after the accident results in the genetic apparatus damage, radiosensitivity enhancement, hypoxia that represent risk factors and increase the probability of tumour and non-tumour diseases. The development of these pathological processes may happen in much more remote periods.     

Allelic variants of polymorphic genes associated with a higher frequency of chromosome aberrations

Genotypic associations were studied for the frequency of chromosome aberrations in human peripheral blood lymphocytes. Cytogenetic analysis (1000 metaphase plate per individual) and genotyping at 19 sites of genes involved in detoxification and DNA repair were performed in a sample of 83 Chernobyl liquidators and a matched control sample of 96 volunteers. In either sample, the frequency of chromosome aberrations was higher in carriers of the minor alleles of the XPD gene (sites 2251T > G and 862G > A) and the positive genotypes of the GSTM1-GSTT1 genes. The highest frequency of chromosome aberrations was observed in carriers of a combined genotype including at least one minor allele of the XPD sites + at least one insertion in the GSTM1-GSTT1 genes. The high-risk genotype, which had a prevalence of 64%, was strongly associated with a higher frequency of chromosome aberrations in both volunteers (OR = 6.9, P = 0.008) and Chernobyl liquidators (OR = 5.6, P = 0.002).     

The epidemiological analysis of monitoring of the immune status in liquidators of consequences of the Chernobyl accident for early identification of risk groups and diagnostics of oncological diseases. Report 1

Ionizing radiation is one of major factors of risk of oncological diseases. A question about the frequency of malignant neoplasms (MN) and their early identification in the liquidators of consequences of the Chernobyl accident remains opened. In the present work, the results of long-term immunological monitoring of the liquidators of consequences of the failure at the Chernobyl Nuclear Power Plant (ChN PP) living in the Northwest region of Russia are analyzed; we also heve made an attempt to reveal the predictors of oncological diseases in this group of individuals. The frequency of the newly revealed MN cases in a cohort of the persons who took part in liquidation of consequences of the ChNPP failure and were followed-up in 1999-2009, has made up 89 cases per 1005 persons (8.856%), which somewhat exceeds general population indicators. Regarding the frequency of separate MN localizations, lung cancer, cancer of stomach and cancer of prostate gland predominated, which corresponds to the world's tendency of MN prevalence. It has been established that as early as 1-3 years before diagnosis of MN is confirmed in liquidators, a number of changes in the immune status comes to light: drop in percentage of CD3+ and CD4(+)-T-lymphocytes, B-lymphocytes to a lesser extent, decrease in the CD4+/CD8+ index, increase of the relative and absolute content of CD16(+)-lymphocytes, increase of absolute content of CD8(+)-T-lymphocytes, prevalence of CD3+16/56+(NK-T) cell over CD3-16/56+(NK) cells, rise of the activity of phagocytes. Patients with the presence of one or several of the above-mentioned signs should be attributed to the MN risk group for determination of tumor markers, thorough examination and dynamic observation.     

The molecular and cellular consequences of the chernobyl accident

In this paper the results of research at 5–10 and 24 years after the Chernobyl accident are summarized. These results include the investigation of genomic instability, formation of the adaptive response, genome damage, and oxidative status. The studies were performed on cells in culture, mice, children and adults who lived in the contaminated areas, and liquidators of the consequences of the Chernobyl accident. Inhibition of cell proliferative activity, late cell death, and the increase in micronucleus and giant cell frequency were observed after the exposure of cells in culture in the accident zone followed by their culturing in laboratory conditions. In the progeny of the exposed cells, the effect of enhanced radiosensitivity was detected. Thus, it can be assumed that exposure of parental cells in culture in the area of the accident induced genomic instability that resulted in the development of various abnormalities in progeny cells. At the organism level, the Chernobyl zone exposure of mice caused an increase in radiosensitivity; as well, a decrease in the endotheliocyte density in the cerebral cortex and other brain tissues was observed. In the blood lymphocytes of children stimulated by PHA, a more than two times increase in micronucleus cell frequency was detected. A reduced number of individuals with significant adaptive response was found in both the juvenile and adult groups. In all investigated populations, an increased number of individuals with enhanced radiosensitivity were observed in response to low-dose radiation exposure. At 24 years after the accident liquidators were subjected to examinations, which revealed an increased frequency of cells with micronuclei and chromosome-type aberrations in blood lymphocytes, an elevated level of DNA double strand breaks, and a reduced level of reactive oxygen species compared to those of the control group. This means that the genomic instability that was accumulated by the residents of the contaminated regions and liquidators as a result of the accident leads to damage of the genetic apparatus, an increase in radiosensitivity, and hypoxia as late consequences that all are risk factors and increase the probability of the development of tumor and non-tumor diseases. The development of the above-mentioned pathological processes may occur in the distant future.

     

The role of cytogenetic examination for prognosis of remote consequences of irradiation

Correlation between the level of somatic pathology and cytogenetic characteristics of blood was analyzed in a group of liquidators of the accident at the Chernobyl Nuclear Power Plant (ChNPP). A statistically significant correlation was found between the occurrence of cardiovascular diseases and the level of chromosome aberrations (total frequency of chromosome aberrations, frequency of dicentrics and centric rings, frequency of chromatid aberrations). The results obtained are of great importance for the substantiated prediction of the development of postradiation pathologies.     

An epidemiological analysis of monitoring of the immune status of chernobyl nuclear accident liquidators for early detection of risk groups and diagnosis of cancer diseases. Communication 1

Ionizing radiation is one of the major risk factors for cancer diseases. The question on the rate of malignant neoplasms (MNs) and their early detection in Chernobyl nuclear accident (ChNA) liquidators is still open. In this work, the results of a long-term immunological monitoring of the ChNA liquidators who live in the northwestern region of Russia have been analyzed with an attempt to detect the predictors of cancer in this population cohort. The rate of newly detected MN cases in the cohort of followup ChNA liquidators monitored in 1990–2009 was 8.856% (89 cases per 1005 persons), which is somewhat higher as compared with the average rate for the total population. As for the rate of individual MN types, lung, gastric, and prostate cancers were prevalent, which matches the worldwide trend in MN abundance. It was shown that 1-3 years before the MN diagnosis, liquidators displayed detectable changes in their immune status, including a decrease in the percentages of CD3⁺ and CD4⁺ T lymphocytes, and, to a lesser degree, B lymphocytes; a decrease in the CD4⁺/CD8⁺ ratio; increase in the relative and absolute contents of CD16⁺ lymphocytes; increase in the absolute CD8⁺ T lymphocyte counts; prevalence of CD3⁺16/56⁺ (NK-T) cells over CD3-16/56⁺ (NK) cells; and increase in the activity of phagocytes. The patients who displayed one or several of the listed characteristics should be ascribed to the MN risk group to be assessed for cancer markers, be more comprehensively examined, and be the subjects of dynamic observation.     

Molecular-biological properties of blood lymphocytes of Hodgkin's lymphoma patients. Plausible possibility of treatment effect prognosis

Hodgkin's lymphoma (HL) patients were investigated before and during chemical and radiation therapy. The properties of peripheral blood lymphocytes of the HL patients before treatment have been compared with healthy donors and the patients during the treatment. The genetic damage--frequency of cells with micronuclei (MN), the level of DNA single- and double-strand breaks (SSB and DSB), DNA-protein cross-links (DPC) have been studied. Biochemical and physiological parameters have been compared as well: the concentration of reactive oxygen species (ROS), the ability to the adaptive response induction. The radiosensitivity of lymphocytes in vitro exposed to the 1 Gy irradiation has also been determined (by MN test). It was shown that in Hodgkin's lymphoma patients' lymphocytes (in comparison with healthy donors) the frequency of cells with MN does not change, the level of SSBs and DSBs increases, the amount of DPC does not change, and ROS concentration (on average) significantly increases because of the part of the population that have high ROS content. The ROS concentration decreases to control level, the frequency of cells with MN increases, the level of DSBs does not change but the level of DPCs (which prevents the determination of DSB) increases in the patients during treatment. It was also discovered that lymphocyte radiosensitivity correlates with the MN cells frequency before treatment and the ROS concentration. These results make it possible to suppose that the high MN frequency and high ROS concentration in Hodgkin's lymphoma patient lymphocytes (before treatment) can serve as prognostic factors for the effectiveness of radio and chemical therapy.     

The epidemiological analysis of monitoring of the immune status in liquidators of consequences of the Chernobyl accident for early identification of risk groups and diagnostics of oncological diseases. Report 2. Dependence of frequency and changes in the immune status on risk factors of radiation accident

Malignant neoplasms (MN) have been found to develop most frequently in the liquidators of entry into the ChNPP zones in 1986 (43.75%), as well as among the liquidators who worked for long, one quarter of whom participated in liquidation of the consequences of failure (LCF) in 1986. Specific features of the immune status depending on the timing of participation in LCF and the year of entry into the ChN PP zone have been established. Changes in the immune system in the persons with a confirmed diagnosis of MN who took both a non-permanent and permanent part in liquidating the consequences of the ChNPP failure in 1986 had the same character of deviations and differed in the magnitudes of deviations of immunological parameters. Continuous participation in the period of extreme conditions and a greater exposure to the radiation factor led to the increased content of CD8(+)-T-cells, CD16(+)-lymphocytes and activated T-lymphocytes, as well as to the reduced index of immune regulation, decreased content ofCD3-16/56+(NK)-cells (%) and the total IgE and to a greater deficiency of B-lymphocytes. Distinctions in the groups of liquidators who participated in LCF in 1986 and 1987 have been revealed. The greatest deviations in the IS indicators were found in liquidators-87. A similar effect came to light in case of a continuance in the ChNPP zones in 1986 and 1987; however, the degree of deviation of the content of CD4(+)-T-lymphocytes (41), CD8(+)-T-lymphocytes (1) and the immune regulation index (41) were remarkably higher in liquidators-87. A continuous stay in the ChNPP zones in 1987 led to the deficiency of CD4(+)-T-lymphocytes, increased values of CD8(+)-T-lymphocytes, a decreased index of CD4+/CD8+, as well as to the change in the ratio between NK-T and NK cells, increased numbers of CD95+, HLA-DR+ and activated T-lymphocytes, and a lower level of the total IgE. Long-term participation in LCF didn't cause any enhanced expression of cellular activation markers in liquidators-86. Specific features of changes in IS depending on a dose of external gamma-irradiation have been established. Increase in the frequency of MN among liquidators, in relation to the number of examinees in each age group, with age has been revealed. Distinctions in the age dynamics of IS in liquidators in the presence and in the absence of MN manifested themselves in a stable level of values of CD3+, CD4+, CD8(+)-T-lymphocytes, immune regulation index, CD95+, serum IgA at the age between 40 and 70 years old with a subsequent reduction in indicators and increase in the content of CD8(+)-T-lymphocytes with age in the absence of MN; continuous increase of CD3-16/56(+)-NK-cells in the presence of MN and decrease in the values after 70 in the absence of MN. Also revealed in IS of the both age groups of liquidators over 70 with and without MN was the deficiency of the T-cell component (CD3+, CD4(+)-T-lymphocytes, CD4+/CD8+ index) and the increase in absolute values of CD8(+)-T-lymphocytes. The growing deficiency of CD4(+)-T-lymphocytes during monitoring against the background of ever rising values of CD8(+)-T-lymphocytes leading to the weakening of the immune regulation due to progressing disorders of the T-lymphocyte regulatory subpopulation distribution can serve an indicator for the adverse prognosis of the life expectancy in the presence of MN.     

Chromosome aberrations of clonal origin in irradiated and unexposed individuals: assessment and implications.

Chromosome painting has proven useful for the detection of chromosomal rearrangements, although the presence of cells containing clonal aberrations can have an effect on the outcome of cytogenetic analyses (e.g. aberration frequency and chromosomal distribution studies). Cells with clonal chromosomal changes have been found in studies of both radiation-exposed Chernobyl cleanup workers ("liquidators") and healthy unexposed human subjects. We have used a simple statistical method to aid in the identification of individuals from distinct Chernobyl radiation-exposed and unexposed control populations who may possess cells containing clonal rearrangements. A chi2 value determined from the observed number of aberrations and the expected number based on chromosome length that corresponds to a probability less than 0.005 appears to be an indicator of clonality. These selected individuals can be analyzed further for clonality, thereby sparing detailed examination of the entire population. Here we present an analysis of individuals possessing clonal aberrations to assess the influence of clonality on the results of cytogenetic studies. Our results show that the subtraction of clonal events from the chi2 calculation for the "outliers" results in nearly all of these values losing their statistically significant deviation from proportionality. These adjustments can also be made to prevent the overestimation of frequencies of chromosome aberrations for biodosimetry. The frequency of clonal aberrations appears to increase as a function of age in control subjects, whereas an age effect was not evident in Chernobyl liquidators. This suggests that spontaneous and radiation-induced clonal expansion are occurring in control subjects and liquidators, respectively.     

An epidemiological analysis of monitoring of the immune status of chernobyl nuclear accident liquidators for early detection of risk groups and diagnosis of cancer diseases. Communication 2. Dependence of the rate and changes in the immune status on radiation accident risk factors

It was demonstrated that malignant neoplasms (MNs) most frequently develop in the liquidators involved in the cleanup activities after the Chernobyl nuclear accident (ChNA) in 1986 (43.75%) and the liquidators involved in long-term activities, one-quarter of whom also participated in the cleanup in 1986. The specific features of the immune status (IS) depending on the period and year of the cleanup activities in the ChNA area were determined. In the cohort with a confirmed MN diagnosis, the observed deviations in the people who participated in these activities only in 1986 and on a permanent basis, including 1986, coincided in their pattern but differed in the magnitude of changes in immunological characteristics. Long-term participation during the extreme period and, correspondingly, higher exposure caused an increase in the contents of CD8⁺ T cells, CD16⁺ lymphocytes, and activated T lymphocytes, as well as decreases in the total immunoregulatory index, percentage of CD3-16/56⁺ (NK), and total IgE and a more pronounced deficiency in B lymphocytes. Differences between the groups of liquidators who participated in the cleanup activities in 1986 and 1987 were detected. The liquidators-1987 display the most pronounced deviations in the IS characteristics. Permanent presence in the ChNA area in 1986 and 1987 caused a similar effect but the magnitude of changes in the content of CD4⁺ T lymphocytes (↓), content of CD8⁺ T lymphocytes (↑), and immunoregulatory index (↓) was considerably higher in liquidators-1987. The permanent cleanup activities in Chernobyl in 1987 caused a deficiency in CD4⁺ T lymphocytes; more pronounced increase in the content of CD8⁺ T lymphocytes; decrease in CD4⁺/CD8⁺ index; change in the ratio of NK-T to NK cells; elevation in the counts of CD95⁺, HLA-DR⁺, and activated T lymphocytes; and decrease in the level of total IgE. Any increase in the expression of cell activation markers was undetectable in the liquidators-1986 involved in the cleanup activities on a long-term basis. The specific features of the IS changes depending on the dose of external γ-irradiation were determined. It was shown that the MN rate in liquidators increases with age relative to the number of examined people in each age cohort. The differences in the IS age-related dynamics in liquidators with and without MNs were detectable in stable contents of CD3⁺, CD4⁺, and CD8⁺ T lymphocytes; immunoregulatory index; and contents of CD95⁺ cells and serum IgA at ages of 40 to 70 years old with a subsequent decrease in these parameters and elevation in the content of CD8⁺ T lymphocytes with age in the absence of MNs; continuous increase in CD3-16/56⁺ (NK) cells in the presence of MNs; and decreases in these values after 70 years in the absence of MNs. In both groups of liquidators older than 70 years (with and without MNs), a deficiency in the T-cell component (CD3⁺ and CD4⁺ T lymphocytes and CD4⁺/CD8⁺ ratio) and an increase in the counts of CD8⁺ T lymphocytes are characteristic of the IS. A growing deficiency in CD4⁺ T lymphocytes during the monitoring on the background of increasing content of CD8⁺ T lymphocytes, which additionally contributes to the weakening of immune regulation due to progressing abnormalities in the ratio of regulatory T-lymphocyte subpopulations, can be regarded as one of the characteristics that suggest an adverse life expectancy prognosis for people with MNs.     

Chromosome instability revealed in children of fathers irradiated during Chernobyl accident

Four children groups with and without thyroid pathology born to fathers exposed to ionizing irradiation in 1986 during Chernobyl accident as liquidators as well as residents of territory with radioactive contamination have been cytogenetically observed. The frequency and spectrum of chromosome aberrations in peripheral blood lymphocytes have been studied using two-termed cultivation (during 48 and 144 hours). Under the short-term incubation the observed groups did not significantly differ on the mean-group integral cytogenetic parameters which corresponded to age norm, but in progeny of parents from radionuclide contaminated territory the increased level of chromosome type exchanges has been revealed. In long-termed lymphocyte cultures of children with chronic thyroiditis the significantly increased cytogenetic effects of both chromatid (single fragments) and chromosome types (abnormal monocentrics, centric rings) have been established. The data received testified the reality of the transmissible chromosome instability phenomenon in progeny of irradiated parents and confirmed the possibility of its expression in consequent mitoses.     

Transgenerational genomic instability in children of liquidators of the accident at the ChNPP (cytogenetic and immunogenetic characteristics)

A complex of cytogenetic and of immunogenetic study of the state of the lymphocyte genomes in the liquidators of the ChNPP accident and their unirradiated children has been carried out for the first time. Increased frequencies of the chromosome aberrations, of gene mutations (TCR mutations) and of predictors of apoptosis (cells with CD95+ immunophenotype) have been revealed in both generations. The analysis of correlations between the parameters under study has demonstrated distinctive features characteristic of induction of genomic instability in the organism of unirradiated children as compared to their fathers--liquidators directly exposed to radiation. Individual variability of genome destabilization were observed by all criteria used and manifested themselves in the diverse spectrum of transgenerational mutational effects and in different levels of their expression. The results obtained demonstrate the necessity of integral evaluation of the state of the genome using several genetic criteria to reveal transgenerational genomic instability in children of a special category--the offsprings of irradiated parents.     

The state of immunity in the liquidators of consequences of the Chernobyl accident with cardio-vascular diseases

The purpose of the work was research and functional reserves immunity in participants in the Chernobyl with cardiovascular disease. A Clinical Lab 49 men aged 44 to 52 years with diseases of the cardiovascular system, participated in the Chernobyl nuclear power plant in 1986 to 1988. As control used data 33 patients with similar pathology, and 16 healthy men. Researched the total number of white blood cells, lymphocytes and transfusions, the absolute number and relative CD4+ and CD8+, CD 16, CD20+, CD95+ lymphocytes peripheral blood, number mononuclear, synthesizing IL-1beta, TNF-alpha, INF-alpha, IL-4, the content of lipids and proteins, the activity of alkaline phosphatase and mieloperoksidazy in neutrophils. To assess the functional reserve immune system blood samples studied people subjected to radiation doses 0.25, 50, 1.0 Gy of in vitro and studied the reaction cytochemical indicators neutrophils before and after the radiative forcing. The liquidators not detected significant changes in the absolute number of leucocytes, but compared with control groups noted significant reduction in the absolute number of CD8+ and CD20+ lymphocytes, increased the number of cells, expression of FAS-antigen, change the number of mononuclear spontaneously synthesizing and produce cytokines, decreased maintenance of cation proteins in neutrophils. Radiation samples peripheral blood liquidators caused the same reaction cytochemical indicators of neutrophils and control groups, the compensatory and adaptive nature of the changes in the immune system, developed in response to complex factors radiation accident.     

Role of non-radiation factors in forming cytogenetic effects in evacuees from a 30-km zone of the Chernobyl Nuclear Power Plant

The time-effect relationship for chromatid type aberrations, chromosome type fragments, hyperploidy and polyploidy levels in peripheral blood lymphocytes were investigated in inhabitants of t. Pripiat' and nearby villages, who were departured from the Chernobyl NPP 30-km exclusive zone during first days after the Chernobyl catastrophe. The time-course changes of the mentioned cytogenetic indices in evacuees were displayed as a gradual decline of chromosomal rearrangements and genome abnormality frequencies from the statistically elevated level in the first 1-2 years after the accident to the subcontrol meanings at the end of the 14-years observation period. In early terms after exposure the frequency of chromatid exchanges in adult men and the polyploidy level in women aged 23-35 years were sufficiently increased comparing with other evacuee subgroups. Some peculiarities of the fragment aberration frequency dynamics were shown for persons with different terms of the departure from the Chernobyl zone. The role of the combination of mutagenic factors acted in the accidental situation at Chernobyl for inducing the elevated level of cytogenetic damage in evacuees is discussed.     

Dynamics of immune status indices of liquidators in the remote period after the accident at the Chernobyl NPP

In the report there are present the results of monitoring of the state of immune status in the remote period after the accident at the Chernobyl Nuclear Power Plant among three groups of liquidators, which were from Moscow and the Moscow district, the Northwestern region of Leningrad district and from Krasnoyarsk territory. During the monitoring of the liquidators from different regions there was found phenotype of immune status with regional characteristics. In the Moscow district the clinical displays of immune insufficiency prevail and in the North western region the modifications of immune status prevail among liquidators. In all the groups we could see quantitative and immunoregulatory disbalance with the increase of parameters of cellular activity such as CD95+, HLA-DR+, T-activated lymphocytes, fluctuation cytotoxic cells (CD8+, CD16+), persevering disimmunoglobulinemia with differently directed modification serum of immunoglobulins at decrease B-lymphocytes. By the end of the twenty-year period after the accident we can see a similar phenotype of immune status in all the groups with increasing of the marker of late activation (HLA-DR+) and apoptotic activity (CD95+) and it is potentially dangerous regarding cancerogenesis. According to the basis of long-term monitoring there has been discovered the immune characteristic of proliferative syndrome for the first time. The monitoring of 2004 has revealed a huge similarity immune status at non-malignant growth at significant decrease CD25+ in the Northwestern region and some differences in common IgE.     

Time-effect relationship for unstable chromosome exchange levels in Chernobyl clean-up workers

The post-irradiation changes of dicentric and centric ring levels were studied in Chernobyl liquidators using the data of 507 individual chromosomal surveys of persons sampled at different time after their activities at Chernobyl NPP accident zone. The time-effect relationship within 0-10.5 years after exposure was displayed as exponential decline of the mean chromosome exchange frequency with average decay half-time 2.2 y. During 10.5-13 years after exposure the increasing and stabilization of chromosome exchange yield on the level 2-3-times higher than control was observed. In the first few months after irradiation the dicentric and centric ring frequency in liquidators had the clear reverse correlation with the duration of person's duties at the Chernobyl zone. The parameters of unstable chromosome exchange elimination were independent on the initially induced aberration yield, that resulted in earlier reaching the subcontrol level in persons who had more protracted duration of duties at the Chernobyl accident zone.     

Genotype dependence of cytogenetic and epidemiological characteristics in the liquidators of the accident at the ChNPP

The dependence of the level of unstable chromosome aberrations and nononcological diseases on the genotype in 57 liquidators of the ChNPP accident was studied. Candidate genes presumably affecting radiosensitivity were highly polymorphic loci of xenobiotic detoxication genes (glutathione-S-transferases GSTM1, GSTT1, GSTP1) and the 5,10-methylenetetrahydrofolate reductase gene (MTHFR) involved in DNA methylation and synthesis. An increased frequency (0.014 +/- 0.001 per cell) of unstable chromosome aberrations, including radiation-specific dicentrics and centric rings (0.0015 +/- 0.0002 per cell), has been found to be preserved in the group of liquidators examined in 2006-2007. No associations of polymorphism for each of the studied genes with cytogenetic parameters were revealed. Increased frequencies of chromosome aberrations were recorded in homozygous carriers of a deletion at the GSTM1 locus in combination with homozygosity for minor alleles at the MTHFR and GSTP1 loci (p = 0.00002 and p = 0.0233, respectively). The number of homozygous carriers of the minor allele GSTP1 was increased among patients with chronic obstructive pulmonary disease and in liquidators with acute circulation disturbances (p = 0.014 and p = 0.04, respectively). Double homozygotes for GSTM1 and GSTT1 deletions were significantly more frequent among subjects with benign tumors (cysts, polyps, p = 0.015) and with benign thyroid tumors (p = 0.017). This genotype has proved to be protective for patients with severe cardiovascular diseases (acute circulation disturbances, p = 0.027).     

Clastogenic effects of bleomycin, cyclophosphamide, and ethyl methanesulfonate on resting and proliferating human B- and T-lymphocytes

The effects of bleomycin (BM), cyclophosphamide (CP), and ethyl methanesulfonate (EMS) on the frequencies of chromosomal aberrations were tested in mitogen-stimulated highly purified human B- and T-lymphocytes. In unstimulated G0/G1 B- and T-lymphocytes the clastogen induction of chromosome fragments was investigated in prematurely condensed chromosomes (PCC) induced by cell fusion with xenogenic mitotic cells. BM, CP (with metabolic activation), and EMS induced a significant increase in chromosome aberrations in proliferating human B- and T-lymphocytes. There were no significant differences in the BM-induced aberration rates between the cell populations. CP and EMS induced more aberrations in T- than in B-lymphocytes. In the PCC tests, BM-exposed G0/G1 lymphocytes showed dose-dependent high yields of chromosome fragments. No significant differences between B- and T-lymphocytes were observed. CP and EMS induced no clear increase in fragments in either cell population.     

The Chernobyl fallout in Salzburg/Austria and its effect on blood chromosomes

The radioactive fallout of the Chernobyl accident caused an increase in radiation dose of 20 to 110 per cent over the normal environmental burden to the inhabitans of Salzburg City in Austria (in a distance of about 1300 km from the accident). The structural chromosome aberration in the lymphocytes of the peripheral blood of 15 test-persons have been investigated one year after the accident. From two of these we know also the aberration frequencies before the accident which were significantly lower. The results from all test persons were pooled according to their Cs137 and Cs134 content, measured by whole body counter. Their mean additional blood doses from the incorporated caesium plus the external fallout radiation were 0.23, 0.36 and 0.55 mGy/yr. The aberration frequencies increased with dose. The slope of the best straight-line through the points was 2.0 +/- 0.7 total chromosome type aberrations in 100 metaphases per mGy/yr. This result fits in well with former investigations of persons with individually calculated radiation burden from the environment. The sharp increase with dose at this low level is not compatible with values extrapolated from high doses. The usual dose assessment based on chromosome aberrations extrapolated from high to low doses is therefore not possible in the range considered in this investigation.