Biological dosimetry of chernobyl cleanup workers: inclusion of data on age and smoking provides improved radiation dose estimates

We report the results of a study of chromosome translocations in 126 Russian subjects who participated in the cleanup activities at Chernobyl and another 53 subjects, from other places in Russia, who were not exposed at Chernobyl. In agreement with our earlier study, we find increased translocation frequencies among the exposed compared to Russian controls. We describe statistical methods for estimating the dose of ionizing radiation determined by scoring chromosome translocations found in circulating lymphocytes sampled several years after exposure. Two statistical models were fitted to the data. One model assumed that translocation frequencies followed an overdispersed Poisson distribution. The second model assumed that translocation frequencies followed a negative binomial distribution. In addition, the effects of radiation exposure were modeled as additive or as multiplicative to the effects of age and smoking history. We found that the negative binomial model fit the data better than the overdispersed Poisson model. We could not distinguish between the additive and the multiplicative model with our data. Individual dose estimates ranged from 0 (for 43 subjects) to 0.56 Gy (mean 0.14 Gy) under the multiplicative model and from 0 to 0.95 Gy (mean 0.15 Gy) under the additive model. Dose estimates were similar under the two models when the number of translocations was less than 4 per 100 cells. The additive model tended to estimate larger doses when the number of translocations was greater than 4 per 100 cells. We also describe a method for estimating upper 95% tolerance bounds for numbers of translocations in unexposed individuals. We found that inclusion of data on age and smoking history was important for dose estimation. Ignoring these factors could result in gross overestimation of exposures, particularly in older subjects who smoke.     

Comparative investigation of structural and gene somatic mutations in workers of nuclear chemical plants. I. A study of stable and unstable chromosome aberrations

A study of frequency of unstable chromosome aberrations in 50 workers of nuclear chemical plants in remote period after beginning or finishing professional contact with ionizing radiation was carried out. 14 persons from this cohort were mainly whole-body exposed to external gamma-rays and 36 were exposed to combined external and internal radiation from incorporated Pu nuclides. In results of this irradiating practically every subject had a chronical radiation sickness. In the 1-st group the frequency of unstable aberrations varied from 0.2 to 3.6 per 100 cells and exceeded reliably control level in 5 persons. In the 2-nd group the frequency of unstable aberrations varied from 0 to 11.6 per 100 cells and exceeded reliably control level in 20 examined workers. The FISH study of frequency of stable aberrations was performed in 13 subjects who were exposed to combined external and internal radiation. Total frequency of complete and incomplete translocations varied from 0.6 to 18.5 aberrations per genome per 100 cells and reliable exceeded control level in 9 subjects. Non-random participation in exchange rearrangements (translocations) was revealed for used set of chromosomes (2, 3 and 8).     

Local gene density predicts the spatial position of genetic loci in the interphase nucleus

Specific chromosomal translocations are hallmarks of many human leukemias. The basis for these translocation events is poorly understood, but it has been assumed that spatial positioning of genes in the nucleus of hematopoietic cells is a contributing factor. Analysis of the nuclear 3D position of the gene MLL, frequently involved in chromosomal translocations and five of its translocation partners (AF4, AF6, AF9, ENL and ELL), and two control loci revealed a characteristic radial distribution pattern in all hematopoietic cells studied. Genes in areas of high local gene density were found positioned towards the nuclear center, whereas genes in regions of low gene density were detected closer to the nuclear periphery. The gene density within a 2 Mbp window was found to be a better predictor for the relative positioning of a genomic locus within the cell nucleus than the gene density of entire chromosomes. Analysis of the position of MLL, AF4, AF6 and AF9 in cell lines carrying chromosomal translocations involving these genes revealed that the position of the normal genes was different from that of the fusion genes, and this was again consistent with the changes in local gene density within a 2 Mbp window. Thus, alterations in gene density directly at translocation junctions could explain the change in the position of affected genes in leukemia cells.     

Frequency, dynamics, and structure of congenital malformations in populations under long-term exposure to ionizing radiation]

Information on the dynamics, frequency, and structure of congenital malformations (CMs) and chromosomal diseases in two generations of rural populations from the Semipalatinsk region was obtained for the first time. The tests performed in the Semipalatinsk nuclear test site (STS) for many years were demonstrated to deteriorate the genetic health of the populations of the zones of extreme and maximum radiation risks. Mutagenic and teratogenic effects of long-term ionizing irradiation were detected. These were mainly expressed as an increase in the frequencies of strictly registered CMs (SR CMs), including the Down syndrome, multiple malformations (MMs) and microcephaly (1.45 +/- 0.11, 1.39 +/- 0.01, and 0.77 +/- 0.05 per 1000 births, respectively). SR CMs exhibited linear trends toward higher frequencies in two generations of exposed persons after surface nuclear tests in 1949-1963. Their frequency was strongly correlated with the effective population dose of radiation; the main population genetic parameters (inbreeding coefficient, endogamy index, etc.) had less pronounced effects on Cms.     

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.     

Fine mapping of the distal short arm of the human X chromosome using X/Y translocations.

The loci for steroid sulfatase (STS), the deficiency of which causes X-linked ichthyosis, the cell surface antigen 12E7 (MIC2X), and the blood group antigen Xg (Xg) have been mapped to Xp22.3. These loci are of particular interest since they do not appear to undergo X-chromosome inactivation. In an attempt to establish the relative order of STS and MIC2X, fibroblasts from carriers of four different X/Y translocations and an X/10 translocation were obtained and fused with mouse cell lines deficient in hypoxanthine phosphoribosyltransferase. The breakpoints on the X chromosome in these five translocations are in Xp22. Several independent clones from each fusion were isolated in HAT medium. The clones were examined cytogenetically, and in each case at least two independent clones were identified that have an active X/Y or X/10 translocation chromosome in the absence of other X or Y material. These clones were then tested for STS and 12E7 expression. In two of the X/Y translocations, the markers, STS and 12E7, were both absent. In the X/10 and a third X/Y translocation, both markers were retained. In each of three clones containing the fourth X/Y translocation, STS activity was retained but 12E7 antigenicity was lost. Assuming that this is a simple translocation and does not represent a more complex rearrangement, these results suggest that MIC2X is distal to STS.     

Some immunophysiological features of sports activity under climatic and geographical conditions of the middle Ob region

This paper analyzes the cellular and humoral components of the immune system in athletes who were born, lived, and trained under the conditions of the middle Ob region (Khanty-Mansi Autonomous Okrug—Yugra, KhMAO–Yugra). The main group included young men and women, who were engaged in cross-country skiing (12 men and 10 women) and volleyball (11 men and 10 women). The control group (regional norm) included ten men and ten women, who were born and currently lived in KhMAO–Yugra and did not do any sports on a regular basis. The age of the subjects ranged from 19 to 22 years. It was found that the parameters of cellular and humoral immunity differed slightly with respect to the control group. A significant decrease in the total count of leukocytes, neutrophils, and lymphocytes was observed in men and women, who were born, lived, and trained under the conditions of the middle Ob region; in addition, a decrease in the parameters of humoral immunity (B cells and IgA) was also observed in male skiers. It was found that the total leukocyte count, the level of B cells, and the IgG concentration in men who live in the middle Ob region and do not do any sports is higher than that in women of the same group.     

Mechanism of staurosporine-induced apoptosis in murine hepatocytes

Staurosporine (STS) induces apoptosis in various cell lines. We report in this study that primary cultured mouse hepatocytes are less sensitive to STS compared with Jurkat cells and Huh-7 cells. In contrast to the cell lines, no apparent release of cytochrome c or loss of mitochondrial transmembrane potential was detected in primary hepatocytes undergoing STS-induced apoptosis. Caspase-3 was activated in primary hepatocytes by STS treatment, but caspase-9 and -12 were not activated, and caspase-3 activation is not dependent on caspase-8. These findings point to a novel pathway for caspase-3 activation by STS in primary hepatocytes. Pretreatment with caspase inhibitor converted STS-induced apoptosis of hepatocytes to necrotic cell death without significantly changing total cell death. Thus STS causes hepatocytes to commit to death upstream of the activation of caspases. We also demonstrated that STS dramatically sensitized primary hepatocytes to tumor necrosis factor-alpha-induced apoptosis. STS activated I kappa B kinase and nuclear factor-kappa B (NF-kappa B) nuclear translocation and DNA binding but inhibited transactivation of I kappa B-alpha, inducible nitric oxide synthase, and inhibitor of apoptosis protein-1 in hepatocytes and NF-kappa B reporter in transfected Huh-7 cells.     

Elevated chromosome translocation frequencies in New Zealand nuclear test veterans

In 1957/58 the British Government conducted a series of nuclear tests in the mid-Pacific codenamed Operation Grapple, which involved several naval vessels from Britain and New Zealand. Two New Zealand frigates with 551 personnel onboard were stationed at various distances between 20 and 150 nautical miles from ground zero. In the present study we applied the cytomolecular technique mFISH (multicolour fluorescent in situ hybridisation) to investigate a potential link between chromosome abnormalities and possible past radiation exposure in New Zealand nuclear test veterans who participated in Operation Grapple. Compared to age matched controls, the veterans showed significantly higher (P < 0.0001) frequencies of chromosomal abnormalities (275 translocations and 12 dicentrics in 9,360 cells vs. 96 translocations and 1 dicentric in 9,548 cells in the controls), in addition to a significant excess of CCRs (complex chromosomal rearrangements) in the veterans. A Kolmogorov-Smirnoff test showed that the distributions of translocations for the two groups were significantly different.     

The Frequency, Dynamics, and Structure of Congenital Malformations in Populations under Long-Term Exposure to Ionizing Radiation

Information on the dynamics, frequency, and structure of congenital malformations (CMs) and chromosomal diseases in two generations of rural populations from the Semipalatinsk region was obtained for the first time. The tests performed in the Semipalatinsk nuclear test site (STS) for many years were demonstrated to deteriorate the genetic health of the populations of the zones of extreme and maximum radiation risks. Mutagenic and teratogenic effects of long-term ionizing irradiation were detected. These were mainly expressed as an increase in the frequencies of strictly registered CMs (SR CMs), including the Down syndrome, multiple malformations (MMs) and microcephaly (1.45 ± 0.11, 1.39 ± 0.01, and 0.77 ± 0.05 per 1000 births, respectively). SR CMs exhibited linear trends toward higher frequencies in two generations of exposed persons after surface nuclear tests in 1949–1963. Their frequency was strongly correlated with the effective population dose of radiation; the main population genetic parameters (inbreeding coefficient, endogamy index, etc.) had less pronounced effects on Cms.     

Radiobiological effects on plants and animals within Semipalatinsk Test Site (Kazakhstan)

The Semipalatinsk Test Site (STS) was the main place of nuclear devices tests in the former Soviet Union. From 1949 to 1989 about 460 nuclear explosions have been carried out at STS. Radioactive contamination of STS territory has the extremely non-uniform character. The main dose-forming radionuclides are 137Cs, 90Sr, 152Eu, as well as 154Eu, 60CO, 239,240Pu and 241Am. The greatest specific activity of 137Cs and 239,240Pu in ground are n x 10(3) kBk/kg, 152Eu - 96 kBk/kg, 154Eu - 10.4 kBk/kg, 60Co - 20.5 kBk/kg, 241Am - 15 kBk/kg. However, up to now, within STS sites exists where gamma-dose rate comes to 60 microGy/h, that is enough for induction reliable biological effects in animals and plants. Inhabiting territory of STS plants and animals are characterized by increased level of mutagenesis, changes of morpho-anatomic indices and parameters of peripheral blood, by the increase of asymmetry bilateral indices, change of composition and structure of communities.     

Glycophorin A somatic cell mutations in a population living in the proximity of the Semipalatinsk nuclear test site

The glycophorin A (GPA) somatic mutation assay was performed to evaluate the magnitude of exposure to ionizing radiation among the human population living in the vicinity of the Semipalatinsk nuclear test site in Kazakhstan. All together, 113 blood samples were analyzed from three generations of people living in villages that were under the trail of the radioactive cloud from the first Soviet surface nuclear test performed in August 1949 and from later tests. The oldest generation (P0) lived in the area at the time of testing, whereas the younger generations (F1, F2) were exposed to smaller doses from the residual fallout and later tests. The GPA assay did not reveal significant differences in the variant cell frequencies for all subjects selected from the Semipalatinsk area compared with 74 matched controls living in a noncontaminated area. However, a significant increase (P < 0.05) in the mean allele-loss ON variant frequency was observed among the exposed P0 generation (12 x 10(-6)) in comparison to controls (7 x 10(-6)). Considering the sensitivity of the GPA assay, the results suggest that the mean dose to the P0 generation of the affected villages was relatively low, a finding which is in accordance to the conclusions obtained from other biological assays performed on the same population.     

Expression and subcellular localization of thymosin beta15 following kainic acid treatment in rat brain

Thymosin β15 (Tβ15) is a pleiotropic factor which exerts multiple roles in the development of nervous system and brain diseases. In this study, we found that the expressions of Tβ15 mRNA and protein were substantially increased in several brain regions including hippocampal formation and cerebral cortex, following kainic acid (KA)-evoked seizures in rat. Interestingly, a subset of cortex neurons exhibited nuclear Tβ15 immunoreactivity upon KA treatment. Furthermore, translocation of Tβ15 from cytosol to nuclei was observed in cultured neurons or HeLa cells during staurosporine (STS)-induced apoptosis, which was also verified by time-lapse imaging of YFP-tagged Tβ15. It appeared that localization of Tβ15 is restricted to the cytosol in normal condition by its G-actin-interacting domain, because site-directed mutagenesis of this region resulted in the nuclear localization of Tβ15 in the absence of STS treatment. To explore the role of nuclear Tβ15, we enforced Tβ15 to localize in the nuclei by fusion of Tβ15 with nuclear localization signal (NLS-Tβ15). However, overexpression of NLS-Tβ15 did not alter the viability of cells in response to STS treatment. Collectively, these results suggest that nuclear localization of Tβ15 is a controlled process during KA or STS stimulation, although its functional significance is yet to be clarified.     

Array-CGH characterization of a de novo t(X;Y)(p22;q11) in a female with short stature and mental retardation

We report the clinical and molecular investigations in a girl with 46,X,-X,+der(X)t(X;Y)(p22;q11) de novo karyotype who presented an intricate phenotype characterized by mental retardation and facial dysmorphisms in combination with short stature. The structure of the derivative X chromosome was studied using BAC array-CGH which disclosed the Xp22 breakpoint between the STS and the VCX3A gene and the presence of the Yq11.1qter chromosome. It is common that females with Xp;Yq translocations present only short stature and are normal in every other aspect. Thus, this would be the first case in which a girl with Xp;Yq translocation presents an unusual phenotype with intermediate male clinical features with Xp;Yq translocations. The risk of developing gonadoblastoma in females with Y chromosome material is also discussed and, to this effect, different explanations related to this apparent variation are also presented.     

Cytogenetic abnormalities of the descendants of permanent residents of heavily contaminated East Kazakhstan

More than 400 nuclear explosion tests were conducted at the Semipalatinsk Nuclear Test Site (SNTS) and significant radioactive substances were released. The long-term consequences of the activities at the SNTS and the appearance of any hereditary effects remain insufficiently studied about 25 years after the test site was closed. The population living in villages near the SNTS are considered to have been heavily exposed to external and internal radiation. This study aims to perform an assessment and comprehensive cytogenetic analysis of the inhabitants living near the SNTS, and their first-(F1) and second-(F2) generation children. Residents of the East Kazakhstan region living in the area covered by the former SNTS were included in the study. To evaluate the hereditary effects of nuclear testing, comprehensive chromosome analyses were performed in lymphocytes using conventional Giemsa and fluorescent in situ hybridization methods in 115 F1 and F2 descendants in the villages of Dolon and Sarzhal, which were heavily contaminated. The parents of the subjects had permanently lived in the villages. A higher number of stable-type chromosome aberrations such as translocations was found in these residents than in 80 residents of the control area, Kokpecty, which indicates the possibility that radiation had biological effects on the exposed subjects.     

Dynamic balance control during sit-to-stand movement: an examination with the center of mass acceleration

The purpose of this study was to establish the region of stability of balance control using the center of mass (COM) acceleration and to characterize age-related differences during sit-to-stand (STS) movement. Whole body motion data were collected from 10 young and 10 elderly subjects while performing STS at their self-selected manners. In addition, young subjects were asked to perform another block of trials with their trunk purposely bent forward prior to seat-off. With the use of a single-link-plus-foot inverted pendulum model, boundaries for the region of stability were determined based on the COM position at seat-off and its instantaneous velocity or its peak acceleration (ROSv or ROSa, respectively). No significant group differences were detected in COM velocities at seat-off. However, peak COM accelerations differed significantly between groups and conditions. This suggested that even though a similar COM momentum was observed at seat-off, this momentum was controlled differently prior to seat-off. Young and elderly subjects utilized similar strategies but with different COM acceleration profiles to perform STS. Furthermore, data from an elderly subject who complained of difficulty in STS during the experiment were located outside the forward boundary of the ROSa, demonstrating a potential use of ROSa to differentiate individuals with declined balance control ability. The ROSa could provide insights into how the COM is controlled prior to seat-off, which may allow us to better identify elderly individuals who are most likely at a risk for imbalance or falls.     

Preliminary FISH-based assessment of external dose for residents exposed on the Techa River

This paper presents the results of a feasibility cytogenetic study using the fluorescence in situ hybridization (FISH) translocation assay for residents of villages located on the Techa River (Southern Urals, Russia) contaminated with liquid radioactive wastes from the Mayak plutonium facility in 1949-1956. The study was conducted with two groups of donors that differed in their main pathways of exposure. The first group comprised 18 residents of the middle Techa region who were exposed predominantly from ingestion of radionuclides (mostly (89,90)Sr) via the river water and local foodstuffs. The second group included 20 residents of Metlino, the closest village to the site of releases, who were exposed to external γ radiation from the contaminated river bank and exposed internally from dietary intake of radionuclides. A significant linear dependence between the radiation-induced translocation frequency and individual red bone marrow dose from incorporated (89,90)Sr, calculated with the Techa River Dosimetry System (TRDS), was found in the first group of donors. This allowed us to take the contribution of (89,90)Sr to the total radiation-induced translocation frequency into account for the second group of donors and to analyze translocations resulting from external γ-ray exposure. Individual doses from external exposure derived from the corrected translocation frequency for the second group of donors (Metlino residents), using a linear dose-response coefficient of 0.015 translocation/cell/Gy recommended by Edwards et al. in 2005, were shown to vary up to 2.1 Gy, with an average value of 0.48 Gy, which was in agreement with TRDS-based external dose estimates for Metlino residents.     

A panel of human chromosome 22-specific sequence tagged sites

A panel of 29 sequence tagged sites (STSs) covering the long arm of chromosome 22 has been assembled. STS primer pairs were synthesized using available chromosome 22 sequence derived from the GenBank and EMBL DNA sequence databases, as well as published cDNA and genomic sequence, or from previously published and communicated primer pairs. Each STS was optimized for the polymerase chain reaction using a chromosome 22-only hybrid and human genomic DNA. Further STS content analysis on a panel of somatic cell hybrids that incorporated two chromosome 22 translocations resulted in the mapping of the X-box binding protein (XBP), D22S156, and transcobalamin II (TCN2) genes to 22q11-q13.1. The panel of STSs was used for the rapid determination of the STS content and thus the chromosomal DNA content of a new irradiation hybrid.     

A study to verify a reported excess of chromosomal aberrations in blood lymphocytes of Namibian uranium miners

This report describes a study to verify an earlier report of excess chromosomal damage in the blood lymphocytes of uranium miners. Coded blood samples from 10 miners and 10 controls were analyzed conventionally for unstable aberrations and by FISH for translocations. Conventional analysis, scoring 1000 metaphases per subject, showed no significant difference between miners and controls in the frequencies of chromosome- and chromatid-type aberrations. Investigators at two laboratories undertook FISH analyses, each scoring 4000 metaphases per subject. When the data from each laboratory were examined separately, one found slightly more translocations in the miners while the other found fewer. In neither case was the difference significant at the 95% level of confidence. Combining the data likewise showed no significant excess of damage in the miners. This applied to simple one- and two-way translocations and to cells with complex exchanges. There was no correlation between levels of translocations and total lifetime doses from occupational and/or background irradiation. A borderline significant excess of rogue cells was found in the miners. This may be a chance observation, as these rare, highly abnormal cells are considered to be unrelated to radiation exposure and are probably due to a virus. The overall conclusion is that the frequency of chromosomal damage in the miners did not exceed that in the controls. Therefore, the result of the earlier study was not confirmed.     

Renal dysfunction of cadmium-exposed workers residing in a cadmium-polluted environment

Human exposure to cadmium may occur in both occupational and general environments. We were interested in determining whether a combination of occupational and environmental exposure to cadmium results in different levels of severity of renal dysfunction relative to that arising from environmental or occupational exposure alone. We selected 44 residents, who once were employed in a smelter and lived in a cadmium-polluted area, as group A. Another 88 subjects, who never worked in the plant, but lived in the same area, were selected as group B. Group C consisted of 88 subjects who had no history of occupational exposure to cadmium and lived in a non-cadmium-polluted area. Statistical analysis demonstrated that there was no significant difference in age or gender among the three groups, nor were there significant differences in smoking habits. The prevalence of renal dysfunction as indicated by increased excretion of beta2-microglobulin (B2M), N-acetyl-beta-D-glucosaminidase (NAG) and albumin (ALB), was higher in group A than in group B. This finding suggests that exposure to cadmium both occupationally and environmentally results in a higher prevalence of renal dysfunction, relative to those who are exposed to cadmium only in the general environment. Therefore, this specific population, who once were occupationally exposed to cadmium and lived in polluted areas, should be identified. Furthermore, health examinations of this population should be conducted in time to prevent further health damage induced by cadmium exposure.