Chromosome alterations in cleanup workers sampled years after the Chernobyl accident

Cytogenetic Effects in Patients after Computed Tomography Examination

Millions of people around the world are exposed to low doses of ionizing radiation from diagnostic computed tomography (CT) scans. Currently available data on the potential cancer risk after CT scans are contradictory and therefore demand further investigations. The aim of the current study was to obtain estimations of genome damage after CT scans in 42 non-cancer patients and to conduct a comparison of the results with 22 control subjects. The frequency of dicentric ring chromosomes and chromosome breaks was significantly increased in irradiated patients compared to the controls. The distribution of dicentrics among the cells demonstrated non-Poisson distribution that reflected non-uniform and partial-body radiation exposure. A fraction of patients followed Poisson distribution, which is typical for uniform whole-body exposures. Some patients demonstrated a level of dicentrics similar to the control subjects. The individual variations in the frequency and dicentric distribution suggested complex mechanisms of chromosome aberration induction and elimination that could be associated with individual radiosensitivity, as well as previous diagnostics that used ionizing radiation or the redistribution of small fractions of irradiated lymphocytes within the circulatory pull. In conclusion, CT scans may cause genome damage and possible increases in cancer risk. The introduction of a specific follow-up of such patients, especially in the case of repeated CT scans, is suggested.

LONG/TERM GENETIC AND EPIGENETIC DISORDERS IN PERSONS EXPOSED TO IONIZING RADIATION AND THEIR DESCENDANTS (review)

The review is devoted to long-term genetic and epigenetic disorders in exposed individuals and their descendants,namely to cytogenetic effects in the Chornobyl NPP accident clean-up workers and their children, DNA methylation as an epigenetic modification of human genome. Data presented in review expand the understanding of risk of the prolonged exposure for the present and future generations, which is one of key problems posed by fundamental radiation genetics and human radiobiology.

CYTOGENETIC BIODOSIMETRY OF ACCIDENTAL EXPOSURES IN THE LONG TERMS AFTER IRRADIATION

The group of radiation victims who had received radiation injures similar to those of Chernobyl accident victims was evaluated in terms of retrospective cytogenetic biodosimetry in the long term period of from 17 y up to 50 y after irradiation. Based on the existing results of the long-term cytogenetic examination of the victims injured after the Chernobyl accident, an original method was developed. This method of retrospective dose recovery was based on the use of a special computer program, the time elapsed after irradiation and the frequency of atypical chromosomes. Both patient groups were examined using conventional cytogenetic analysis. The new method of a retrospective biodosimetry was tested on the non-Chernobyl group. As a result the multiple regression equations which included frequency atypical chromosomes produced better results because the majority of the estimates of the retrospective doses fell into the 95%-prediction intervals for the reference group of the Chernobyl victims.

Radioactively contaminated areas: Bioindicator species and biomarkers of effect in an early warning scheme for a preliminary risk assessment

Concerns about the impacts on public health and on the natural environment have been raised regarding the full range of operational activities related to uranium mining and the rest of the nuclear fuel cycle (including nuclear accidents), nuclear tests and depleted uranium from military ammunitions. However, the environmental impacts of such activities, as well as their ecotoxicological/toxicological profile, are still poorly studied. Herein, it is discussed if organisms can be used as bioindicators of human health effects, posed by lifetime exposure to radioactively contaminated areas. To do so, information was gathered from several studies performed on vertebrates, invertebrate species and humans, living in these contaminated areas. The retrieved information was compared, to determine which are the most used bioindicators and biomarkers and also the similarities between human and non-human biota responses. The data evaluated are used to support the proposal for an early warning scheme, based on bioindicator species and on the most sensitive and commonly shared biomarkers, to perform a screening evaluation of radioactively contaminated sites. This scheme could be used to support decision-making for a deeper evaluation of risks to human health, making it possible to screen a large number of areas, without disturbing and alarming local populations.

Capabilities for Clinical Management of Radiation Injuries of the Nikiforov Russian Center of Emergency and Radiation Medicine (EMERCOM of Russia)

This article presents an overview of the capabilities for clinical management of radiation injuries available at the Nikiforov Russian Center of Emergency and Radiation Medicine (NRCERM) of the Ministry of the Russian Federation for Civil Defense, Emergencies and Elimination of Consequences of Natural Disasters (EMERCOM). NRCERM is a federal state budgetary institution and the Russian Federation's head organization for providing medical assistance for persons overexposed to ionizing radiation, responders to radiation emergencies and people evacuated from radiation contaminated areas. As the WHO Collaborating Center for Treatment and Rehabilitation of Accident Recovery Workers of Nuclear and Other Disasters and a member of the WHO Radiation Emergency Medical Preparedness and Assistance Network (REMPAN), NRCERM is prepared to provide assistance and technical support in case of a radiation accident. For this purpose, NRCERM hospitals are equipped with technologically advanced facilities and possess well-trained specialist staff.

Follow-up studies on genome damage in children after Chernobyl nuclear power plant accident

As children are more susceptible to ionizing radiation than adults, each nuclear accident demands special attention and care of this vulnerable population. The Chernobyl nuclear disaster occurred in a region populated with a large number of children, but despite all efforts and expertise of nuclear specialists, it was not possible to avoid casualties. As vast regions of Ukraine, Belarus and Russia were exposed to doses of ionizing radiation, which are known to be related with different diseases, shortly after the accident medical surveillance was launched, which also included analysis of genome damage. Child population affected by internal and external radiation consisted of subjects exposed prenatally, postnatally (both evacuated and non-evacuated), born by irradiated fathers who worked as liquidators, and parents exposed environmentally. In all groups of children during the last 30 years who were exposed to doses which were significantly higher than that recommended for general population of 1 mSv per year, increased genome damage was detected. Increased genome damage includes statistically higher frequency of dicentric and ring chromosomes, chromated and chromosome breaks, acentric fragments, translocations, and micronuclei. The presence of rogue cells confirmed internal contamination. Genome instability and radiosensitivity in children was detected both in evacuated and continuously exposed children. Today the population exposed to ionizing radiation in 1986 is in reproductive period of life and follow-up of this population and their offspring is of great importance. This review aims to give insight in results of studies, which reported genome damage in children in journals without language restrictions.

Cytogenetic analysis of peripheral blood lymphocytes, many years after exposure of workers to low-dose ionizing radiation

The present study aims to measure chromosomal aberrations and micronuclei in peripheral blood lymphocytes from 25 subjects exposed to 0.10-0.33 Gy external or internal irradiation 32-41 years ago using conventional cytogenetic analysis methods. The frequencies of total chromosome-type aberrations and micronucleus significantly increased in the exposed group compared with that in age-matched control group (p<0.001); chromatid-type aberrations showed no difference between the two groups (p>0.05). When exposed subjects were divided into two groups based on exposure dose, higher levels of dicentric plus translocation frequencies were observed in the ≥0.15 Gy dose group compared with those in the <0.15 Gy dose group, though the difference was not significant. Borderline association between exposure dose and dicentric frequency was detected in the exposed group (r=0.358; p=0.079). These results suggest that the genotoxic effects of ionizing radiation remain in subjects exposed to low-dose radiation even decades after exposure.

Effects of parental radiation exposure on developmental instability in grasshoppers

Mutagenic and epigenetic effects of environmental stressors and their transgenerational consequences are of interest to evolutionary biologists because they can amplify natural genetic variation. We studied the effect of parental exposure to radioactive contamination on offspring development in lesser marsh grasshopper Chorthippus albomarginatus. We used a geometric morphometric approach to measure fluctuating asymmetry (FA), wing shape and wing size. We measured time to sexual maturity to check whether parental exposure to radiation influenced offspring developmental trajectory and tested effects of radiation on hatching success and parental fecundity. Wings were larger in early maturing individuals born to parents from high radiation sites compared to early maturing individuals from low radiation sites. As time to sexual maturity increased, wing size decreased but more sharply in individuals from high radiation sites. Radiation exposure did not significantly affect FA or shape in wings nor did it significantly affect hatching success and fecundity. Overall, parental radiation exposure can adversely affect offspring development and fitness depending on developmental trajectories although the cause of this effect remains unclear. We suggest more direct measures of fitness and the inclusion of replication in future studies to help further our understanding of the relationship between developmental instability, fitness and environmental stress.

Analysis of genomic instability in the offspring of fathers exposed to low doses of ionizing radiation

Transgenerational genomic instability was studied in nonirradiated children born from fathers who were irradiated with low doses of ionizing radiation while working as clean-up workers at the Chernobyl Nuclear Power Plant (liquidators) and nonirradiated mothers from nuclear families. Aberrant cell frequencies (ACFs), chromosomal type aberration frequencies, and chromatid break frequencies (CBFs) in the lymphocytes of fathers-liquidators, and their children were significantly higher when compared with the control group (P < 0.05). Individual ACFs, aberration frequencies, and CBFs were independent of the time between irradiation of the father and conception of the child (1 month to 18 years). Chromosomes were categorized into seven groups (A through G). Analysis of aberrant chromosomes within these groups showed no differences in the average frequency of aberrant chromosomes between children and fathers-liquidators. However, significant differences were observed in the average frequency of aberrant chromosomes in groups A, B, and C between children and mothers in the families of liquidators. These results suggest that low doses of radiation induce genomic instability in fathers. Moreover, low radiation doses might be responsible for individual peculiarities in transgenerational genomic instability in children (as a consequence of response to primary DNA damage). Thus, genomic instability may contribute to increased morbidity over the lifetime of these children.

Delayed chromosomal instability in lymphocytes of cancer patients after radiotherapy

PURPOSE

To assess possible delayed chromosomal instability (DCI) expressed as elevated chromatid breakage in cells containing previously formed chromosome type aberrations in cultured blood lymphocytes of cancer patients after radiotherapy (RT).

MATERIALS AND METHODS

Twenty patients treated for uterine cancer with external Co(60) RT, without chemotherapy, were selected. Blood was taken before, 1-2 days after RT and one year later. Lymphocytes were cultured for 50 and 100 h. Metaphases were stained with fluorescence-plus-Giemsa and analysed for chromosome and chromatid aberrations in 1st (M1) and 3rd plus later (M3+) mitoses.

RESULTS

RT caused a significant increase of radiation-specific chromosome aberrations in patients' lymphocytes together with DCI, which was observed as an excessive yield of cells containing both chromosome and chromatid aberrations (defined as C(acs&act)). This DCI passed successfully through mitoses in vitro, and at the end of RT a mean yield of 'extra' C(acs&act) was 3 x 10(-3) x cell(-1) amongst either M1 or M3+ cells. At the end of RT and one year later DCI in M1 lymphocytes appeared at random amongst patients, but some inter-individual variation was found for DCI presence in M3+ cells at both post-irradiation samplings. As time passed, the mean yield of lymphocytes exhibiting DCI decreased in vivo and one year after RT reached the pre-treatment level of 1 x 10(-3) x cell(-1).

CONCLUSIONS

DCI was demonstrated in descendants of human lymphocytes after therapeutic irradiation. The effect diminished one year later, suggesting that the progeny of patients' irradiated stem cells did not produce new daughter lymphocytes exhibiting DCI during the studied post-irradiation period.

Chromosomal aberrations and sickness rates in Chernobyl clean-up workers in the years following the accident

The aim of this investigation was to reveal a possible correlation between chromosomal aberrations and the health status of Chernobyl clean-up workers who suffered from a low dose of ionizing radiation. Unstable chromosomal aberrations in peripheral blood lymphocytes were investigated in 491 Chernobyl clean-up workers. Information about lifestyle factors (all persons) and medical history (212 persons) was collected. Connections between the rate of chromosomal aberrations and some types of diseases were found. It was also found that Chernobyl clean-up workers with oncological diseases and hypertension had increased rates of chromosomal aberrations. Positive correlations between the grade of hypertension and the level of chromosomal aberrations (r = 0.20, p < 0.01) was revealed. Further investigations need to be carried out in order to understand the mechanisms of this connection.

Transgenerational genomic instability in children of irradiated parents as a result of the Chernobyl Nuclear Accident

The study of families irradiated as a result of the accident at the Chernobyl Nuclear Power Plant revealed significantly increased aberrant genomes frequencies (AGFs) not only in irradiated parents (n=106, p<0.01), but also in their children born after the accident (n=159, p<0.05). This is an indicative of the phenomenon of transgenerational genomic instability. To elucidate this phenomenon, experiments were undertaken to model genomic instability by using single and fractional in vitro gamma-irradiation ((137)Cs) of peripheral blood samples from the children and their parents at doses of 0.1, 0.2 and 0.3 Gy. The spectrum and frequency of chromosome aberrations were studied in the 1st and 2nd cell generations. The average AGF was significantly increased at all doses (except 0.1 Gy) in children of irradiated parents, as compared to children born from non-irradiated parents. Amplification of cells with single-break chromosome aberrations in mitosis 2, as compared to mitosis 1, suggests the replication mechanism of realization of potential damage in DNA and the occurrence of genomic instability in succeeding cell generations.

Complementarity of standard cytogenetic assays

Standard cytogenetic assays used in genotoxicology usually include chromosome aberrations analysis and micronucleus cytokinesis-block assay. Both tests originate on standard protocol for lymphocyte culture and can be used as complement or substitute to each other. Aim of this study was to evaluate complementarities between results of chromosome aberration analysis assay and results of micronucleus cytokinesis-block assay in representative sample of inhabitants from Bosnia and Herzegovina. The aim was achieved by calculating Pearson correlation coefficient and simple linear regression.

Chromosome aberrations as bioindicators of environmental genotoxicity

Due to the exposure to various potentially genotoxic xenobiotics, derived from recent war activities such as NATO air strikes with antitank ammunition containing depleted uranium, we have evaluated chromosome aberrations in 84 peripheral blood samples from three local populations. One population sample included 30 individuals who lived in the Sarajevo area during and after the war (exposed to potential genotoxins), second population was presented with 26 employees of the tank repair facility in Hadzići (target of NATO air strikes), and 28 inhabitants of Posusje (not exposed to war-related activities) were treated as sample of control population. The mean of chromosome aberration frequencies for the population from Hadzići was significantly higher than the frequencies for the two other populations. Point bi-serial coefficient analysis did not reveal any relationship between the frequencies of chromosome aberrations and smoking habits or gender. Results suggest that depleted uranium could be a risk factor for human health.

Effect of war and postwar genotoxins on micronuclei frequency in Sarajevo study group

During the 1992-1995 siege, as well as after the war activities, citizens of Sarajevo were most probably exposed to various potential genotoxic agents. The effects of those potential genotoxins were evaluated by micronucleus-cytokinesis blocked assay. The study included 30 individuals who resided in the area of Sarajevo during the war and the postwar period. Point bi-serial coefficient analysis did not reveal any relationship between the frequencies of binuclear cells with micronuclei as well as total number of micronuclei and smoking habits or gender. Simple linear regression revealed statistically significant positive correlation between the age and micronuclei formation. Due to the war related environmental contamination more extensive study is recommended.