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

Influence of Body Mass Index and Duration of Disease on Chromosome Damage in Lymphocytes of Patients with Diabetes

It is well-established that patients with diabetes mellitus (DM) have a higher incidence of several types of cancer. The precise mechanisms of this association are still unknown, but obesity and chronic inflammation-induced reactive oxygen species (ROS) are thought to be the main risk factors. ROS may produce different DNA damage, which could eventually lead to cancer. The main objective of this study was to evaluate the relation of chromosome aberrations (CA) with disease status, demographics, and clinical parameters in 33 subjects with type 1 DM (T1DM), 22 subjects with type 2 DM (T2DM), and 21 controls. CAs were analyzed in cultured peripheral blood lymphocytes and subdivided into chromatid (CTA)- and chromosome (CSA)-type aberrations. Compared with controls, higher levels of CTAs and CSAs were observed in T1DM (p = 0.0053 and p = 0.0203, respectively) and T2DM (p = 0.0133 and p = 0.00002, respectively). While there was no difference in CTAs between T1DM and T2DM, CSAs were higher in T2DM (p = 0.0173). A significant positive association between CTAs and disease duration (rs = 0.2938, p = 0.0099) and between CSAs and disease duration (rs = 0.4306, p = 0.0001), age (rs = 0.3932, p = 0.0004), and body mass index (BMI) (rs = 0.3502, p = 0.0019) was revealed. After multiple regression analysis, duration of disease remained significant for CTA, CSA, and CAs (p = 0.0042, p = 0.00003, and p = 0.00002, respectively). For CSA, BMI and the use of statins were the other important confounding variables (p = 0.0105 and p = 0.0763). Thus, this study demonstrated that both T1DM and T2DM patients had a higher number of all types of aberrations than controls, which increases with the prolonged disease duration. Higher BMI was associated with a higher frequency of CSA. The use of statins might be beneficial for reducing chromosome damage, but further investigations are needed to confirm this association.

Identifying Genomic Signatures of Positive Selection to Predict Protective Genomic Loci in the Cohort of Lithuanian Clean-Up Workers of the Chornobyl Nuclear Disaster

Some people resist or recover from health challenges better than others. We studied Lithuanian clean-up workers of the Chornobyl nuclear disaster (LCWC) who worked in the harshest conditions and, despite high ionising radiation doses as well as other factors, continue ageing relatively healthily. Thus, we hypothesised that there might be individual features encoded by the genome which act protectively for better adaptiveness and health that depend on unique positive selection signatures. Whole-genome sequencing was performed for 40 LCWC and a control group composed of 25 men from the general Lithuanian population (LTU). Selective sweep analysis was performed to identify genomic regions which may be under recent positive selection and determine better adaptiveness. Twenty-two autosomal loci with the highest positive selection signature values were identified. Most important, unique loci under positive selection have been identified in the genomes of the LCWC, which may influence the survival and adaptive qualities to extreme conditions, and the disaster itself. Characterising these loci provide a better understanding of the interaction between ongoing microevolutionary processes, multifactorial traits, and diseases. Studying unique groups of disease-resistant individuals could help create new insights for better, more individualised, disease diagnostics and prevention strategies.

Possible Protective Effect of LOXL1 Variant in the Cohort of Chernobyl Catastrophe Clean-Up Workers

Ionising radiation (IR) is an environmental factor known to alter genomes and therefore challenge organisms to adapt. Lithuanian clean-up workers of the Chernobyl nuclear disaster (LCWC) experienced high doses of IR, leading to different consequences. This study aims to characterise a unique protective genomic variation in a relatively healthy LCWC group. This variation influenced their individual reaction to IR and potentially protects against certain diseases such as exfoliation syndrome and glaucoma. Clinical and IR dosage data were collected using a questionnaire to characterise the cohort of 93 LCWC. Genome-wide genotyping using Illumina beadchip technology was performed. The control group included 466 unrelated, self-reported healthy individuals of Lithuanian descent. Genotypes were filtered out from the microarray dataset using a catalogue of SNPs. The data were used to perform association, linkage disequilibrium, and epistasis analysis. Phenotype data analysis showed the distribution of the most common disease groups among the LCWC. A genomic variant of statistical significance (Fishers' exact test, p = 0.019), rs3825942, was identified in LOXL1 (NM_005576.4:c.458G>A). Linkage disequilibrium and epistasis analysis for this variant identified the genes LHFPL3, GALNT6, PIH1D1, ANKS1B, and METRNL as potentially involved in the etiopathogenesis of exfoliation syndrome and glaucoma, which were not previously associated with the disease. The LOXL1 variant is mostly considered a risk factor in the development of exfoliation syndrome and glaucoma. The influence of recent positive selection, the phenomenon of allele-flipping, and the fact that only individuals with the homozygous reference allele have glaucoma in the cohort of the LCWC suggest otherwise. The identification of rs3825942 and other potentially protective genomic variants may be useful for further analysis of the genetic architecture and etiopathogenetic mechanisms of other multifactorial diseases.

Influence of zinc levels on the toxic manifestations of lead exposure among the occupationally exposed workers

Lead and zinc are usually found at the same occupational places and occur as co-contaminants. Effects of lead toxicity are detrimental on human health as it is probable carcinogen and impairs normal growth and development. On the other hand, zinc is an important nutritional element, the deficiency of which causes debilitating effects on growth and development. The purpose of this study was to examine the possible association of blood lead and zinc levels and any influence of zinc over DNA damage, blood cell membrane aberration and oxidative stress among lead and zinc co-exposed workers. Atomic absorption spectroscopy was used for lead and zinc measurement and comet assay for DNA damage assessment. Haematological aberrations were studied using light and electron microscopy (LM and EM) followed by electron density X-ray spectroscopy (EDS) and elemental mapping. Occupational exposure was observed to cause significant elevation in blood lead levels among workers. This elevation in lead levels and associated DNA damage among workers was significantly high in comparison to controls. Further light and electron micrographs of red blood cells revealed significant morphological alterations associated with increased lead ions in workers. It was clear from SEM-based elemental maps and EDS graphs that elevated lead levels were associated with low levels of zinc. The results suggest that lead absorption is highly influenced due to zinc levels in body which has an impact over DNA damage, blood cell aberration and oxidative stress caused by lead exposure. Efforts are going on to understand the role of other trace metals on lead toxicity in order to develop a sustainably nutrition-based therapeutic intervention. Graphical abstract.

Comparison of dicentric dose response curves of 6MV LINAC X-rays and 60Co γ-rays for biodosimetry application

In vitro Dicentric (DC) dose response curves of 6MV X-rays (3Gy/min) and ⁶⁰Co γ-rays (0.63Gy/min) were generated and compared (intra-laboratory) to understand their similarities and differences. Human peripheral blood samples exposed to ten different doses (0, 0.05, 0.1, 0.25, 0.5, 1, 2, 3, 4 and 5Gy) of 6MV X-rays and ⁶⁰Co γ-rays were subjected to Dicentric Chromosome Assay (DCA) and dicentrics, excess acentric fragments (AF) and chromatid breaks (CB) were scored. Totally about 31,553 metaphase spreads were scored for the purpose. Dose response curves of both radiation qualities were almost same except for a 13.8% higher β value for 6MV X-rays. However, blind tests results revealed that both these curves are biologically equivalent and exhibited good dose prediction accuracy for the entire dose range. This demonstrated the feasibility of interchangeable use of these curves in biodosimetry. Consequently it has been suggested that LINAC facilities worldwide can be roped in for biodosimetry capacity augmentation towards managing nuclear emergency situations involving γ-radiation exposures.

Possible role of zinc in diminishing lead-related occupational stress-a zinc nutrition concern

Lead and zinc are mostly present at the same occupational source and usually found as co-contaminants. Lead is known to associate with detrimental effects to humans. Zinc however is an essential nutrient and its deficiency causes debilitating effects on growth and development. Besides, it acts as core ion of important enzymes and proteins. The purpose of this study was to examine if zinc concentrations are associated with blood lead levels and if zinc may prevent lead-induced DNA damage. Blood samples were collected from 92 workers as participants occupationally exposed to lead or lead and zinc and 38 comparison participants having no history of such exposure. Lead and zinc levels were determined from blood by atomic absorption spectrophotometry and genetic damage was assessed by comet assay. Correlation was calculated by Spearman's rho. Lead concentrations were observed to increase among workers with increase in years of exposure. There was a significant difference (p < 0.001) in blood lead levels between workers and controls. In addition, significant difference (p < 0.001) in the genetic damage was observed among workers and controls. A clear effect of increased occupational exposure was visible among workers. Multiple regression analysis further reveals the positive effect of lead, while as the inverse effect of zinc on DNA damage. The results suggest that zinc may influence body lead absorption and may have a role in preventing the genetic damage caused by lead.

mFISH analysis of chromosome aberrations in workers occupationally exposed to mixed radiation

We performed a study on the presence of chromosome aberrations in a cohort of plutonium workers of the Mayak production association (PA) with a mean age of 73.3 ± 7.2 years to see whether by multi-color fluorescence in situ hybridization (mFISH) translocation analysis can discriminate individuals who underwent occupational exposure with internal and/or external exposure to ionizing radiation 40 years ago. All Mayak PA workers were occupationally exposed to chronic internal alpha-radiation due to incorporated plutonium-239 and/or to external gamma-rays. First, we obtained the translocation yield in control individuals by mFISH to chromosome spreads of age-matched individuals and obtained background values that are similar to previously published values of an international study (Sigurdson et al. in Mutat Res 652:112-121, 2008). Workers who had absorbed a total dose of >0.5 Gy external gamma-rays to the red bone marrow (RBM) displayed a significantly higher frequency of stable chromosome aberrations relative to a group of workers exposed to <0.5 Gy gamma-rays total absorbed RBM dose. Thus, the translocation frequency may be considered to be a biological marker of external radiation exposure even years after the exposure. In a group of workers who were internally exposed and had incorporated plutonium-239 at a body burden >1.48 kBq, mFISH revealed a considerable number of cells with complex chromosomal rearrangements. Linear associations were observed for translocation yield with the absorbed RBM dose from external gamma-rays as well as for complex chromosomal rearrangements with the plutonium-239 body burden.

Long-term exposure to depleted uranium in Gulf-War veterans does not induce chromosome aberrations in peripheral blood lymphocytes

Depleted uranium (DU) is a high-density heavy metal that has been used in munitions since the 1991 Gulf War. DU is weakly radioactive and chemically toxic, and long-term exposure may cause adverse health effects. This study evaluates genotoxic effects of exposure to DU by measuring chromosome damage in peripheral blood lymphocytes with fluorescence in situ hybridization whole-chromosome painting. Study participants are Gulf War-I Veterans with embedded DU fragments and/or inhalation exposure due to involvement in friendly-fire incidents; they are enrolled in a long-term health surveillance program at the Baltimore Veterans Administration Medical Center. Blood was drawn from 35 exposed male veterans aged 39 to 62 years. Chromosomes 1, 2, and 4 were painted red and chromosomes 3, 5, and 6 were simultaneously labeled green. At least 1800 metaphase cells per subject were scored. Univariate regression analyses were performed to evaluate the effects of log(urine uranium), age at time of blood draw, log(lifetime X-rays), pack-years smoked and alcohol use, against frequencies of cells with translocated chromosomes, dicentrics, acentric fragments, color junctions and abnormal cells. No significant relationships were observed between any cytogenetic endpoint and log(urine uranium) levels, smoking, or log(lifetime X-rays). Age at the time of blood draw showed significant relationships with all endpoints except for cells with acentric fragments. Translocation frequencies in these Veterans were all well within the normal range of published values for healthy control subjects from around the world. These results indicate that chronic exposure to DU does not induce significant levels of chromosome damage in these Veterans.

Aberrant and multiaberrant (rogue) cells in peripheral lymphocytes of Hodgkin's lymphoma patients after chemotherapy

We analyzed spontaneous chromosome lesions in peripheral lymphocytes cultured from Hodgkin's lymphoma (HL) patients before and after cytostatic chemotherapy. The mean aberration frequency was significantly higher in HL patients after chemotherapy (7.20+/-0.58 per 100 metaphases) than in non-treated HL patients (4.80+/-0.54), and in non-treated patients than in healthy subjects (2.12+/-0.13). In lymphocytes of HL patients, who received chemotherapy, we found, in addition to ordinary aberrant cells, a large number of multiaberrant (or rogue) cells, i.e. metaphases carrying multiple (at least four) chromosome-type exchange aberrations. Rogue cells were found in 15 out of 18 chemotherapeutically treated HL patients (in total, 60 rogue cells per 5,568 scored cells), whereas in 30 non-treated patients only 1 rogue cell was found (per 4,988 scored cells). No correlation was found between the yield of rogue cells and the aberration frequency in ordinary aberrant cells. Aberration spectra (ratios of chromatid- to chromosome-type aberrations and of breaks to exchanges) were essentially different in ordinary aberrant and multiaberrant cells. These data, as well as analysis of cellular distributions of aberrations, implied independent induction of chromosome damage in ordinary aberrant and rogue cells. Analysis of aberration patterns in diploid and polyploid rogue metaphases belonging to the first, second, and third in vitro division indicated that rogue cells could be formed both in vivo and in vitro, and could survive at least two rounds of in vitro replication, given blocked chromosome segregation. These results suggested that formation of rogue cells, unlike ordinary aberrant cells, was triggered by events other than direct DNA and/or chromosome lesions. A hypothesis regarding disrupted apoptosis as a candidate mechanism for rogue cell formation seems to be most suitable for interpretation of our data. Cultured lymphocytes of chemotherapeutically treated HL patients may represent a model system for further examination of the multiaberrancy phenomenon.

The evaluation of micronucleus frequency by acridine orange fluorescent staining in peripheral blood of rats treated with lead acetate

The data concerning the mutagenic, clastogenic and carcinogenic properties of inorganic lead compounds have been conflicting. Here, we evaluated the frequency of micronuclei in the peripheral blood of female rats treated with three different lead acetate doses. Outbred female Wistar rats were treated by gavage once per week for 10 weeks with cumulative doses of 140, 250 and 500 mg/kg body weight (body wt) of lead acetate. Mitomycin C (MMC) 2 mg/kg body wt was used as a positive control. The aim of the present study was to investigate the possible cytotoxic and genotoxic effects of lead acetate on peripheral blood reticulocytes using the micronucleus test following chronic exposure. The results show the effects of lead acetate in peripheral blood reticulocytes. These effects are both cytotoxic and genotoxic because of a decrease in the number of polychromatic erythrocytes in the peripheral blood and an increase in frequency of micronucleated reticulocytes, respectively.

Evaluation of chromosomal aberrations, micronuclei, and sister chromatid exchanges in hospital workers chronically exposed to ionizing radiation

Cytogenetic analysis was performed in peripheral blood lymphocytes from hospital workers chronically exposed to ionizing radiation in comparison to matched non-exposed individuals. The accumulated absorbed doses calculated for the radiation workers ranged from 9.5 to 209.4 mSv. The endpoints used were chromosomal aberrations (CA), micronuclei (MN), and sister chromatid exchanges (SCE). The frequencies of CA/100 cells observed for the exposed group were significantly (P=0.018) higher than in the control group: 3.2 and 2.6, respectively. Similarly, the mean numbers of SCE per cell were statistically higher (P=0.025) in the exposed group (6.2) in comparison with the control group (5.8). In the case of micronuclei analysis, no significant (P=0,06) difference between both groups was found, but these data should be cautiously interpreted since an increase in the frequencies of MN was found for radiation workers (3.0 MN/100 cells), compared to the control group (2.6 MN/100 cells) and this increase occur in parallel to CA and SCE frequencies. The difference between the results could be explained by the nature of CA and MN generation. The increased frequencies of CA and SCE in radiation workers indicate the cumulative effect of low-level chronic exposure to ionizing radiation, and the relevance of conducting cytogenetic analysis in parallel to physical dosimetry in the working place.

An investigation of the age-dependency of chromosome abnormalities in human populations exposed to low-dose ionising radiation

Among various cytogenetic changes stable chromosome aberrations (SCHA) seem to be the most significant for ageing and carcinogenesis. Being nonlethal they can persist through cell divisions and accumulate in time. We studied the age response of SCHA (translocations and insertions) in normal and radiation exposed human populations. Two cohorts of people at the age range of 3--72 years were studied: control (43 persons) and exposed to low doses of accidental irradiation due to Chernobyl accident and atomic bomb testing in Semipalatinsk (67 persons). FISH method was used for visualisation of chromosome aberrations. Metaphases from cultured lymphocytes were hybridised with biotinilated whole chromosome specific DNA probes for 1, 4 and 12 chromosomes, and with pancentromeric probe labelled with digoxigenin. The frequency of SCHA in lymphocytes increased as a quadratic function of donor age in both populations studied, being higher in exposed cohort as compared with control one. No age dependence for dicentrics was observed. The frequency of SCHA is a reliable biomarker of ageing in humans. Quadratic model of their age-response gives reasons to suggest that their increase is due to lower level of DNA repair or/and the genomic instability in older people. The exposure of people to low doses of ionising radiation accelerates the age-related increase of SCHA frequency.

Persistence of dicentrics in Chernobyl clean-up workers who suffered from low doses of radiation

Blood samples from 243 clean-up workers who undertook duties at Chernobyl in 1986 were examined in order to study temporal changes of chromosomal aberrations over long periods (6-12 yr) following irradiation. From an analysis of the elapsed time between irradiation and cytogenetic examination, it was found that the frequency of dicentrics and rings did not decrease during the 6 yr period of observation.

Cytogenetic analysis of children under long-term antibacterial therapy with nitroheterocyclic compound furagin

Cytogenetic analysis of chromosome aberrations (CAs) and sister chromatid exchanges (SCEs) was performed in 109 blood samples from 95 pediatric patients with urinary tract infections (UTIs). Children were exposed to diagnostic levels of X-rays during voiding cystourethrography and subsequently treated for one to 12 months with low doses of furagin - N-(5-nitro-2-furyl)-allylidene-1-aminohydantoin. Furagin is 2-substituted 5-nitrofuran, chemically and structurally similar to well-known antibacterial compound nitrofurantoin. Increased frequencies of CAs were found in children undergoing voiding cystourethrography as compared with the unexposed, acentric fragments being the most frequent alteration (2.03 versus 0.88 per 100 cells, P=0.006). However, a significant decrease in the frequency of acentric fragments was determined with the time elapsed since X-ray examination was performed. A time-independent increase in SCE frequency was found in lymphocytes of children treated with furagin. Total CA frequency did not differ significantly between groups of children with various duration of furagin treatment. However, frequency of chromatid exchanges (triradials and quadriradials) increased significantly with duration of treatment.

Stable and unstable aberrations in lymphocytes of Chernobyl accident clearance workers carrying rogue cells

Cells with multiple chromosomal aberrations, the so-called rogue cells, were found in blood samples from more than 100 Chernobyl accident clearance workers. A comparative analysis of frequencies of stable and unstable chromosomal aberrations in two worker groups--those with or without rogue cells was made. A higher level of unstable aberrations in persons carrying rogue cells was observed. No difference in the level of stable aberrations between the groups was seen. The possibility of low dose alpha irradiation causing the chromosomal damage is raised.

Chromosomal aberrations and sister-chromatid exchanges in Lithuanian populations: effects of occupational and environmental exposures

Cytogenetic analysis of chromosomal aberrations (CA) in 175,229 cells from 1113 individuals, both unexposed and occupationally or environmentally exposed to heavy metals (mercury and lead), organic (styrene, formaldehyde, phenol and benzo(a)pyrene) and inorganic (sulfur and nitrogen oxides, hydrogen and ammonium fluorides) volatile substances and/or ionizing radiation was performed. In addition, 11,250 cells from 225 individuals were scored for the frequency of sister-chromatid exchanges (SCE). Increased frequencies of CA were found in all occupationally exposed groups. A principal difference between the exposure to heavy metals and organic substances was found: increase in the CA frequency was dependent on duration of exposure to mercury but not dependent on duration of exposure to styrene, formaldehyde and phenol. A higher CA incidence was found in lymphocytes of children living in the vicinity of a plant manufacturing phosphate fertilizers. This indicates that children are a sensitive study group for the assessment of environmental exposure. However, the results of SCE analysis in these children were inconclusive. Exposure to ionizing radiation was found to cause chromosome breaks and chromatid exchanges in Chernobyl clean-up workers and chromatid breaks, chromatid exchanges, dicentric chromosomes and chromosome translocations in workers from the Ignalina Nuclear Power Plant. The increased frequency of chromatid exchanges in individuals exposed to ionizing radiation was quite unexpected. This may be attributed to the action of some unrecognized life-style or occupational factors, or to be a result of radiation-induced genomic instability. Also an increased SCE frequency was found in lymphocytes of Chernobyl clean-up workers.

Micronucleus frequency in Gomel (Belarus) children affected and not affected by thyroid cancer

Cytogenetic monitoring was carried out on a group of children from Gomel (Belarus), one of the areas most severely affected by radioactive contamination following the accident at the Chernobyl nuclear power plant, in 1986. We performed the micronucleus test (MN) in binucleated lymphocytes of 42 children (mean age: 11+/-2.34 years), 16 of whom were affected by thyroid gland tumor. Thirty healthy children living in Pisa (mean age: 14.96+/-2.17 years) were enrolled in the study as controls. Thyroid tumor affected children living in Gomel showed a statistically significant increase in the frequency of micronucleated cells as compared with the healthy children from Pisa. Moreover, a significant correlation was found between MN frequency and both the presence of tumor and higher 137Cs contamination. In addition, higher 137Cs contamination was more frequently observed in tumor affected children. These results suggest that the increased MN frequency is attributable more to 137Cs contamination rather than to the presence of the tumor itself.

The JC and BK human polyoma viruses appear to be recent introductions to some South American Indian tribes: there is no serological evidence of cross-reactivity with the simian polyoma virus SV40

In an effort to understand the unusual cytogenetic damage earlier encountered in the Yanomama Indians, plasma samples from 425 Amerindians representing 14 tribes have been tested for hemagglutination inhibition antibodies to the human JC polyoma virus and from 369 Amerinds from 13 tribes for hemagglutination inhibition antibodies to the human BK polyoma virus. There is for both viruses highly significant heterogeneity between tribes for the prevalence of serum antibody titers >/=1/40, the pattern of infection suggesting that these two viruses only relatively recently have been introduced into some of these tribes. Some of these samples, from populations with no known exposure to the simian polyoma virus SV40, also were tested for antibodies to this virus by using an immunospot assay. In contrast to the findings of Brown et al. (Brown, P., Tsai, T. & Gajdusek, D. C. (1975) Am. J. Epidemiol. 102, 331-340), none of the samples was found to possess antibodies to SV40. In addition, no significant titers to SV40 were found in a sample of 97 Japanese adults, many of whom had been found to exhibit elevated titers to the JC and BK viruses. This study thus suggests that these human sera contain significant antibody titers to the human polyoma viruses JC and BK but do not appear to contain either cross-reactive antibodies to SV40 or primary antibodies resulting from SV40 infection.

The incidence of cytogenetically abnormal rogue cells in peripheral blood

PURPOSE

To compare the occurrence of cytogenetically abnormal rogue cells, characterized by a high frequency of chromosome-type aberrations, in people exposed to ionizing radiation and in non-exposed subjects.

MATERIALS AND METHODS

Data on rogue cells from a total of nine cytogenetic studies on radiation-exposed populations and controls were collected from three laboratories in the United Kingdom, France and Finland. The studies were conducted on first-division metaphases of peripheral blood lymphocytes. Solid Giemsa-stained, G- or R-banded and FISH chromosome-painted material was included.

RESULTS

Rogue cells were found both from controls and from exposed subjects. The highest incidence of these cells was observed in a control group of young trainees (1:400), whereas the lowest incidence of rogue cells (1:36 500) was demonstrated in a follow-up study of people accidentally exposed to high levels of ionizing radiation. Rogue cells were found to be distributed non-randomly among individuals; the highest individual frequency was 1 in 50 analysed metaphases.

CONCLUSIONS

The origin of rogue cells is still unclear. The incidence of rogue cells showed a large variability between studies and individuals. No correlation between long-term radiation exposure and the occurrence of rogue cells was demonstrated. Although the presence of rogue cells in astronauts after a 6 month space flight may be attributable to high-LET radiation, the frequencies were not remarkable when compared with those in the other studies in this review.

Biomonitoring of workers exposed to lead. Genotoxic effects, its modulation by polyvitamin treatment and evaluation of the induced radioresistance

A population monitoring study was performed, by using the micronucleus (MN) assay in human peripheral lymphocytes, to investigate whether occupational exposure to lead is genotoxic to workers. In addition to the exposed workers group, two more groups were studied, an external group from a factory without exposure to lead and an internal control group, from the same factory as the exposed workers, but that were not directly exposed to lead. Measures of lead levels at working place and in blood were calculated, and blood samples were collected to carry out a MN study. The results from these studies indicate that the blood from workers directly exposed contained high levels of lead, compared with the other groups, and a significant increase in the frequency of both the total number of MN and the number of binucleated cells carrying MN appeared. In addition, a study on the antimutagenic effects of a polyvitamin rich diet was conducted by measuring the frequency of MN after the workers had a four month daily intake of a polyvitamin-polymineral complex. These results clearly show a significant reduction of the MN frequency evaluated after this treatment, obtaining values that were even lower than those obtained in the internal control group. Finally, a challenge assay was carried out to determine response to gamma-radiation as indication of any kind of radiosensitivity or radioresistance. The results of this experiment did not show any significant variation in the increase of the frequency of MN after challenge irradiation in the lead exposed workers; nevertheless this increase was significantly reduced in the sample obtained after the polyvitamin treatment indicating a radioresistance response.

An association, in adult Japanese, between the occurrence of rogue cells among cultured lymphocytes (JC virus activity) and the frequency of "simple" chromosomal damage among the lymphocytes of persons exhibiting these rogue cells

Data from a previous study of the cytogenetic effects, in cultured lymphocytes, of exposure to the atomic bomb in Hiroshima have been reanalyzed to determine the relationship between the occurrence of "rogue" cells in an individual and the frequency of "simple" chromosomal damage in the nonrogue cells of the same individual. Rogue cells are cells with complex chromosomal damage, currently believed to be a manifestation of the activity of a human polyoma virus termed "JC." Among a total of 1,835 persons examined, there were 45 exhibiting rogue cells. A total of 179,599 cells were scored for simple chromosomal damage. In both the exposed and the control populations, there was an absolute increase of approximately 1.5% in the frequency of simple chromosomal damage in the nonrogue cells of those exhibiting rogue cells, when compared with the frequencies observed in those not exhibiting rogue cells, which is a statistically significant difference. It is argued that this phenomenon, occurring not only in lymphocytes but possibly also in other cells/tissues, may play a contributory role in the origin of malignancies characterized by clonal chromosome abnormalities. Unexpectedly, among those exhibiting rogue cells, there was a disproportionately greater representation of persons who had received relatively high radiation exposures from the bomb. The reason for this is unclear, but it is tempting to relate the finding to some lingering effect of the exposure (or the circumstances surrounding the exposure) on immunocompetence.

Chromosomal aberrations in blood lymphocytes of astronauts after long-term space flights

PURPOSE

To analyse lymphocyte chromosomes from astronauts of MIR and EUROMIR missions.

MATERIALS AND METHODS

Peripheral lymphocytes from seven astronauts before and after space flights were cultured and analysed for structural chromosomal aberrations.

RESULTS

Chromosome-type but not chromatid-type aberrations were significantly elevated after space flights when compared to pre-flight values. In one astronaut two rogue cells were found.

CONCLUSIONS

Overall the frequencies of aberrations were found to be correlated with estimated absorbed cosmic radiation doses.

Increased level of chromosomal aberrations in lymphocytes of Chernobyl liquidators 6-10 years after the accident

Chromosomal aberrations (CA) were used to investigate the level of cytogenetical damage in peripheral blood lymphocytes from the liquidators in a remote period (6-10 years) after the Chernobyl accident. There was a significantly higher frequency of chromosomal radiation markers (dicentrics and rings) in the peripheral lymphocytes of the liquidators than in the control subjects. No differences between these groups were demonstrated by the micronucleus (MN) test. Increased frequency of chromatid exchanges was associated with the smoking habits of the liquidators.

High titers of antibodies to two human polyomaviruses, JCV and BKV, correlate with increased frequency of chromosomal damage in human lymphocytes

Associations of antibody titers to the JC and BK human polyoma viruses and the frequency of chromosome aberrations (CA) in human peripheral blood lymphocytes were studied. Study group consisted of 33 workers occupationally exposed to low doses of ionizing radiation and 11 control persons. There were no statistically significant differences in the JC and BK virus titer values between two groups of donors. It was found that JC and BK virus titers explained approximately 6% of total inter-individual variation in CA frequency. Such factors as alcohol abuse, age and, in this special group, exposure to ionizing radiation explained an additional 53% of the total variation in CA frequency. In six clean-up workers and one control, rogue cell (cells with multiple chromosome-type aberrations) were found. The incidence of rogue cells correlated significantly with JC and BK virus titers as well as a history of recent acute respiratory disease.