Level Of Cytogenetic Damage Research Articles

Hypothermia differentially modulates the formation and decay of NBS1, \u03b3H2AX and 53BP1 foci in U2OS cells exposed to gamma radiation

In studies on the mechanism of DNA damage response where ionizing radiation is used as the DNA damaging agent, cells are often exposed to ionizing radiation on melting ice (corresponding to 0.8 °C). The purpose of this procedure is to inhibit cellular processes i.e. DNA repair. Low temperature at exposure has been shown to act in a radioprotective manner at the level of cytogenetic damage, but its mechanisms of action are poorly understood. The aim of the study was to analyze the effect of hypothermia at the level of formation and decay of NBS1, γH2AX, and 53BP1 foci, micronuclei, survival, cell cycle progression and oxidative stress in U2OS cells. The results show that hypothermia alone induced oxidative stress and foci. When applied in combination with radiation but only during the exposure time, it potentiated the formation of γH2AX and 53BP1 but not of NBS1 foci. When applied during irradiation and subsequent repair time, 53BP1 and NBS1 foci formed and decayed, but the levels were markedly lower than when repair was carried out at 37 °C. The frequency of micronuclei was elevated in cells irradiated at 0.8 °C, but only when analysed 20 h after irradiation which is likely due to a reduced G2 cell cycle block. Hypothermia reduced cell survival, both with and without radiation exposure. The temperature effect should be considered when cooling cells on melting ice to inhibit DNA repair in the induction of DNA damage.

АНАЛИЗ ПОЯВЛЕНИЯ МИКРОЯДЕР В ЭРИТРОЦИТАХ И АКТИВНОСТИ ПРОЛИФЕРАЦИИ КЛЕТОК КОСТНОГО МОЗГА ПОСЛЕ ПРОЛОНГИРОВАННОГО ОБЛУЧЕНИЯ МЫШЕЙ БЫСТРЫМИ НЕЙТРОНАМИ В НИЗКИХ ДОЗАХ

Purpose: To analyze the level of cytogenetic damage and the activity of bone marrow cells proliferation in C57BL/6 mice after prolonged fast neutrons low dose irradiation at 10–500 mGy. 
 Material and methods: Male C57BL/6 mice at the age of 7–8 and 16 weeks were used in the experiments. Irradiation was carried out on an OR-M installation in the field of fast neutrons and gamma quanta using five Pu(α,n)Be radionuclide sources with a high fast neutron yield at a dose rate of 2.13 mGy/h. The frequency of polychromatophilic (PCE) and normochromic (NCE) erythrocytes with micronuclei (MN) and the ratio of PCE and NCE were analyzed using light microscopy after cytochemical staining of the bone marrow cells of control and irradiated mice. The proliferation activity of bone marrow cells was determined by the number of Ki-67+-cells. The parameters of the cell cycle and the level of apoptosis were studied after DNA staining with DAPI using flow cytometry. Statistical processing of the results was carried out according to the Student’s method using the computer program Origin.
 Results: It was found that prolonged irradiation of mice with fast neutrons at a low dose rate (2.13 mGy/h) at doses from 10 to 500 mGy after 24 h led to statistically significant increase in the frequency of PCE with MN at all studied doses. No dose dependence of this parameter was observed in the studied range. The increase in the frequency of PCE with MN at a dose of 500 mGy was prolonged and persisted for at least 72 h. A significant increase in the frequency of NCE with MN 24 h after irradiation was found only at a dose of 500 mGy, which persisted up to 48 h. At this dose, there was also a decrease in the number of nucleated cells in the bone marrow 24 – 72 h after exposure, a decrease in the number of Ki-67+-cells 24 h after irradiation of mice, a block of the cell cycle in the G2/M phase, and a decrease of cells in the G0/G1 phase, but after 48 h, there were no disturbances in the cell cycle. 
 Conclusion: It has been shown that after a single total prolonged irradiation of mice at low doses (10–500 mGy), when analyzing the frequency of PCE with MN, cytogenetic damage is recorded in the bone marrow, which indicates the genetic danger of exposure to even such low levels of fast neutron irradiation. A decrease in Ki67+ cells and cell cycle arrest at the G2/M phase were found only after irradiation of mice at a dose of 500 mGy and only 24 h after exposure, while the number of nucleated cells in the bone marrow at this dose was reduced, at least to 72 h.

Cytogenetic effect of caffeine in the micronucleus test

Relevance. The consumption of caffeine-containing food in the modern world must necessarily be safe for humans, including should not affect the hereditary material of the body. Objective: to determine the possible effect of caffeine at the cytogenetic level by the micronucleus method on erythrocytes. Materials and Methods. The objects for the study were non-linear mice, which were divided into 6 groups - one control group and 5 experimental groups. The first experimental group and the second in the experiment received caffeine in doses of 40 mg/kg and 100 mg/kg.The control group received saline. Caffeine was administered orally. The mutagen (dioxidine) was injected intraperitoneally. On the 5th day of the experimental study, we performed blood sampling for cytogenetic analysis. Results and Discussion. Our study of the caffeine preparation made it possible to determine the following patterns. Firstly, when administered within 5 days, caffeine at a dose of 40 and 100 mg/kg did not cause an increase in the number of micronuclei in erythrocytes in mice. Secondly, the combined use of caffeine (both at a dose of 40mg/kgand at a dose of 100 mg / kg) and dioxidine significantly increased the level of micronuclei in comparison with the control group. Thirdly, caffeine at a dose of 40mg/kgdid not increase the mutagenic activity of dioxidine, but a dose of caffeine of 100mg/kgwhen combined with a mutagen led to a significant increase in the level of cytogenetic damage. Conclusion. According to our data, caffeine in the experimental study was not a mutagen, but at a dose of 100 mg/kg it represented a comutagenic effect.

Mitomycin C induced genotoxic stress in endothelial cells is associated with differential expression of proinflammatory cytokines

Mitomycin C (MMC) is an alkylating chemotherapy drug that causes DNA crosslinking resulting in transcription arrest and apoptosis. DNA crosslinking is a critical damage to DNA that can be caused not only by MMC and other antitumor drugs, but also by various environmental and anthropogenic endo- and exogenous agents. Mammalian cells exposed to alkylating mutagens are characterized by severe genotoxic stress. Somatic mutations and genotoxic stress may lead to endothelial dysfunction, which is the initial stage of atherosclerosis, a leading cause of morbidity and mortality worldwide. Here we studied DNA damage, protein secretion and gene expression of IL6 and IL8 in primary human coronary artery endothelial cells (HCAEC) and human internal thoracic artery endothelial cells (HITAEC) in vitro exposed to 500 ng/mL MMC. We observed an increase in levels of cytogenetic damage (micronuclei, nucleoplasmic bridges and nuclear buds) in MMC-treated cells compared to control cells. After 6 h incubation with MMC, both HCAEC and HITAEC displayed a decrease in IL8 concentration and the mRNA level of IL6 and IL8 compared to control cells. Removal of MMC from cultures after 6 h followed by 24 h incubation of cells in complete growth media led to a sharp increase in secretion and gene expression of the studied cytokines in both HCAEC and HITAEC. Moreover, HCAEC were more susceptible to mutagenic exposure compared to HITAEC. These findings suggest that the MMC-induced genotoxic stress in endothelial cells derived from different arteries is associated with differential secretion and gene expression of proinflammatory cytokines IL6 and IL8.

Complex Approach to Evaluating Genotoxicity from Occupational Factors in Coal Mining Industry

The level of cytogenetic damage was analyzed in coal miners (N = 116) and the control sample (N = 169) using an assay for scoring of chromosomal aberrations (CAs) and the DNA comet assay in lymphocytes, as well as the micronucleus test in buccal epithelial cells (MN in BEC). The group of coal miners was characterized by a statistically significantly increase in the main index values of the used test system, compared to the control group. Specifically, the level of chromosomal aberrations in the miner and control groups was 4.69 ± 0.28 and 2.13 ± 0.10%; the proportion of DNA in the comet tail was 4.33 ± 0.38 and 2.16 ± 0.24%; and the micronucleus level was 1.44 ± 0.21 and 0.23 ± 0.12‰, respectively (Р < 0.05). Moreover, in the sample of coal miners, a considerable increase in the levels of additional test indices was observed. For CAs, these parameters included the frequency of single fragments, chromatid-type aberrations, paired fragments, dicentrics without fragments, chromosome exchanges, and chromosome-type aberrations; for the DNA comet assay, these were the comet tail moment and Olive tail moment; for the MN in BEC, the frequencies of binucleated cells, cells with notched nuclei, geminate nuclei, karyorhexis, and apoptotic bodies. Ranking of the results according to major cytogenetic abnormalities made it possible to establish that, in the group of miners, the proportion of individuals with the index values above the background was 68.97% for CAs, 52.13% for the DNA comet assay, and 36.08% for the MN in BEC. The proportion of individuals with cytogenetic damage higher than the background simultaneously in three test systems was 20% of the total sample of miners. To assess the mutagenic effects from occupational factors of coal mining enterprises, it seems reasonable to use a complex of test systems (CA test, DNA comet assay, and MN in BEC).

Cytogenetic alterations in rheumatoid arthritis patients treated with methotrexate and dry olive leaf extract

Oxidative stress and inflammation are DNA instability factors for rheumatoid arthritis (RA) patients. The aims of this study were to evaluate cytogenetic alterations in Peripheral Blood Lymphocytes (PBL) in two groups of RA patients: the early and the long-term RA group; and to examine potential of concomitant treatment with Methotrexate (MTX) and Dry olive leaf extract (DOLE) against cytogenetic damage in RA patients after a 3-weeks treatment. A total of 32 RA patients and 10healthy individuals were included. RA patients were equally divided into four groups: two groups with early phase RA (one treated with MTX alone, the other in combination with DOLE); and two long-term phase RA groups (group with active disease and group with low disease activity)-both treated with MTX and DOLE combination. PBL cultures were screened for chromosome aberrations and micronuclei frequencies. Significantly increased frequencies of micronuclei were shown in active phase RA disease (both early and long-term) but not in the group with low disease activity, as compared to controls. Chromosome aberrations were detected for all 4 RA groups. The highest frequencies of micronuclei and chromosome aberrations were found in the long-termactive RA group. After 3 weeks-treatment, there were no significant decrease of the micronuclei frequencies compared to baseline, although they were reduced in all RA groups, except for the group with the long-term active disease. High level of cytogenetic damage in RA patients was concordant with duration and activity of the RA disease. At 3 weeks of therapy, neither the combined treatment (MTX+DOLE), nor MTX alone did not affect the frequency of micronuclei formation.

Ascorbic acid and retinol palmitate modulatory effect on omeprazole-induced oxidative damage, and the cytogenetic changes in S. cerevisiae and S180 cells

Omeprazole (OM), a prototype proton pump inhibitor, oxidizes thiol groups and induces DNA damage. The aim of this study was to evaluate the oxidative effects of omeprazole and its interactions with ascorbic acid (AA, 50 μM) and retinol palmitate (RP) in proficient and deficient Saccharomyces cerevisiae strains, as well as levels of cytogenetic damage in Sarcoma 180 (S180) cells. Omeprazole was tested at concentrations of 10, 20 and 40 μg/mL, whereas H2O2 (10 mM), cyclophosphamide (20 mg/mL), and saline (0.9% NaCl solution) were employed as stressor, positive control, and negative control, respectively. Results revealed that omeprazole concentration-dependently induces oxidative effects in S. cerevisiae strains. However, omeprazole co-treated with ascorbic acid (50 μM) and retinol palmitate (100 IU) significantly modulated the oxidative damage inflected on the S. cerevisiae strains. Furthermore, omeprazole did not produce micronucleus formation and chromosomal bridges in S180 cells, but induced shoots. Significant increase in karyolysis and karyorrhexis were also observed with the omeprazole treated groups, which was modulated by co-treatment with ascorbic acid and retinol palmitate. Taken all together, it is suggested that ascorbic acid and retinol palmitate can substantially modulate the oxidative damage caused by omeprazole on the S. cerevisiae strains, however, much precaution is recommended with omeprazole and antioxidant co-treatment.

Cytogenetic and Molecular Genetic Indexes in Populations of Anura (Rana arvalis Nilsson) under Conditions of Radioactive and Chemical Pollution of an Aquatic Environment

Amphibians are one of the most poorly studied groups of vertebrates in ecotoxicology and radioecology. The level of cytogenetic damage in the blood cells of tadpoles Rana arvalis Nilsson living on the territory of the Ukhta district of the village of Vodnyi in the Komi Republic, which is contaminated with technogenic radionuclides and heavy metals, is evaluated by “Comet assay”. It is shown that, in animals that develop in water bodies with high concentrations of radionuclides and heavy metals, the frequency of alkalilabile sites and single-strand break of DNA is higher than in the control area. No significant differences have been found when estimating the level of double-strand break of DNA. AFLP analysis indicates a weak genetic differentiation of the studied populations of amphibians.

Hypothermia modulates the DNA damage response to ionizing radiation in human peripheral blood lymphocytes

Purpose: Low temperature at exposure has been shown to act in a radioprotective manner at the level of cytogenetic damage. It was suggested to be due to an effective transformation of DNA damage to chromosomal damage at low temperature. The purpose of the study was to analyze the kinetics of aberration formation during the first hours after exposing human peripheral blood lymphocytes to ionizing radiation at 0.8 °C and 37 °C.Materials and methods: To this end, we applied the technique of premature chromosome condensation. In addition, DNA damage response was analyzed by measuring the levels of phosphorylated DNA damage responsive proteins ATM, DNA-PK and p53 and mRNA levels of the radiation-responsive genes BBC3, FDXR, GADD45A, XPC, MDM2 and CDKN1A.Results: A consistently lower frequency of chromosomal breaks was observed in cells exposed at 0.8 °C as compared to 37 °C already after 30 minutes postexposure. This effect was accompanied by elevated levels of phosphorylated ATM and DNA-PK proteins and a reduced immediate level of phosphorylated p53 and of the responsive genes.Conclusions: Low temperature at exposure appears to promote DNA repair leading to reduced transformation of DNA damage to chromosomal aberrations.

Evaluation of ecological and genetic condition of Rivne city for Micronucleus Test

Bioindication evaluation of air condition in the city of Rivne has been carried out using the micronucleus (MN) test on the oral mucous in under-school-age children. The highest maximum values of MN indices were determined for children who live in the studied test ranges, where the content of CO (carbon oxide) exceeds the maximum permissible concentration. Cytogenetic indicators vary in a wide range of numerical values; moreover, the level of cytogenetic damage is an informative bioindicational feature. With the monitoring purpose, the researched urban area of Rivne was divided into 12 test ranges with different anthropogenic load; a number of large and small manufacturing firms are situated there. The analysis of statistical and analytical data on the traffic intensity in the city was conducted. The study was also based on the analysis of personal researches, obtained through a comprehensive survey carried out on 167 children in 12 test ranges in 12 preschools, the average age of children was 6-7 years. A total of 64,950 mucosal epithelial cells were explored. It has been shown that the deterioration of ecological and genetic conditions of the urban environment in test ranges I, II, VI, VII, VIII, XI based on the cell damage level was below average, the condition of the children's organism was alarming but the state of the environment has changed from “excellent” to “satisfactory”. This kind of research can enable observations of the mutagenic background of regions, genetic health, and genetic threats to humans due to harmful factors.

RADIOPROTECTIVE PROPERTIES OF SODIUM HUMATE IN RADIATION-INDUCED MUTAGENESIS IN CULTURED LYMPHOCYTES OF THYROID CANCER PATIENTS

To investigate the effect of sodium humate on the level of cytogenetic damage in culture of lymphocytes of patients with thyroid cancer after γ-irradiation. Metaphase analysis of chromosome aberrations in cultured peripheral blood lymphocytes of 10 individuals with thyroid cancer was performed after irradiation of lymphocytes in vitro at a dose of 1 Gy from (137)Cs source at the early G0 phase of cell cycle. Sodium humate was added to cell culture for 30 ± 15 min after phytohemagglutinin stimulation at concentrations of 10 and 100 μg/ml. Sodium humate exhibited antimutagenic properties. The preparation at a concentration of 10 μg/ml was more effective than at a concentration of 100 μg/ml, reducing the average incidence of radiation-induced chromosome aberrations by 51.88 and 38.77%, respectively. The most pronounced antimutagenic effect of sodium humate was the reduction of the frequency of chromosomal type aberrations, however, such efficiency varied between individual patients with thyroid cancer. Sodium humate could be considered as a potential therapeutic modifier of radiation damage.

Relationships between cytokine (IL-6 and TGF-β1) gene polymorphisms and chromosomal damage in hospital workers

Cytokine gene polymorphisms have been found to be associated with a pre-disposition to a variety of diseases, including inflammatory and cancer diseases. The present study evaluated the influence of six cytokine gene polymorphisms on the level of genomic damage observed in peripheral blood lymphocytes from hospital pathologists chronically exposed to low doses of different xenobiotics. Lymphocytes from 50 pathologists and 50 control subjects were recruited and analyzed in Sister Chromatid Exchange (SCE) and Chromosomal Aberrations (CA) assays. The frequencies of six cytokine gene polymorphisms and their relationships with the cytogenetic damage levels were also evaluated. The results indicated that significant differences were found between pathologists and controls in terms of SCE frequency (p < 0.001) and RI values (p < 0.001), as well as in terms of CA and cells with aberrations (p < 0.001). No associations were found between all analyzed cytokine gene polymorphisms and CA frequency in both pathologists and control groups. Vice versa, among pathologists, homozygote individuals for the IL-6 G allele showed a significantly (p = 0.017) lower frequency of SCE with respect to heterozygote subjects. Similarly, for TGFβ1 codon 10 locus, homozygote for T allele and heterozygote TC subjects showed a significantly (p = 0.021) lower frequency of SCE with respect to homozygote CC individuals. Among controls, no significant differences were found in the frequency of SCE between genotypes at all loci. Based on these results, we speculate that high circulating levels of a pro-inflammatory cytokine like IL-6 and lower levels of the immunosuppressant cytokine TGFβ1 could be associated directly with a longer duration and/or greater intensity of inflammatory processes, and indirectly with significantly higher levels of genomic damage.

Modulation of radiation-induced cytogenetic damage in human peripheral blood lymphocytes by hypothermia

PurposeRecent studies have shown that low temperature (hypothermia) at exposure can act in a radio-protective manner at the level of cytogenetic damage. The mechanisms of this phenomenon are not understood, but it was suggested to be due to hypothermia-induced perturbations of the cell cycle. The purpose of the present study was to detect whether a reduced frequency of micronuclei is observed in peripheral blood lymphocytes (PBL) irradiated at low temperature and harvested sequentially at 3 time points. Additionally, the level of apoptosis was estimated by microscopic analysis of the MN slides. Materials and methodsExperiments were carried out with blood drawn from three donors at the Stockholm University and from three donors at the Jan Kochanowski University. Prior to irradiation, blood samples were incubated for 20min and irradiated at the respective temperature (0°C and 37°C) with gamma rays. Whole blood cultures were set up, cytochalasin B was added after 44h of irradiation and the samples were harvested after 72, 96 and 120h of incubation time. Results and conclusionsThe frequency of micronuclei was markedly lower in PBL harvested at 72h, 96h and 120h following irradiation at 0°C as compared to 37°C. This indicates that the temperature effect observed in peripheral blood lymphocytes after irradiation is not related to a temporary perturbation of the cell cycle. Also, it is not due to selective elimination of damaged cells by apoptosis.

Influence of DNA repair genes polymorphism on the karyology of buccal epithelium cells in humans exposed to radon

DNA samples from 318 children and adolescents (174 males, 144 females), exposed to radon at home and 65 children (23 males, 42 females) in the control group have been studied. Using the micronucleus test on buccal epithelial cells we identified a significant increase in the number of cells with cytogenetic and proliferative abnormalities in the exposed group. Associations between NBS1 (rs1805794), ATM (rs1801516), and ADPRT (rs1136410) genes polymorphisms and karyological abnormalities in buccal epithelial cells were investigated. For the exposed group, an association of NBS1 Glu185Gln polymorphism with an increased frequency of “broken egg”-type protrusions and apoptotic bodies was established. The NBS1 185Glu/Gln and the ATM1 1853Asp/Asp genotypes were associated with elevated levels of cytogenetic damage, while the NBS1 185Glu/Glu and ATM 1853Asp/Asn genotypes demonstrated a protective role. No significant associations were found in the control group.

Effect of hypothermia on radiation-induced micronuclei and delay of cell cycle progression in TK6 cells

Purpose: Low temperature (hypothermia) during irradiation leads to a reduced frequency of micronuclei in TK6 cells and it has been suggested that perturbation of cell cycle progression is responsible for this effect. The aim of the study was to test this hypothesis.Materials and methods: Human lymphoblastoid TK6 cells were treated by a combination of hypothermia (0.8°C) and ionizing radiation in varying order (hypothermia before, during or after irradiation) and micronuclei were scored. Growth assay and two-dimensional flow cytometry was used to analyze cell cycle kinetics following irradiated of cells at 0.8°C or 37.0°C.Results: The temperature effect was observed at the level of micronuclei regardless of whether cells were cooled during or immediately before or after the radiation exposure. No indication of cell cycle perturbation by combined exposure to hypothermia and radiation could be detected.Conclusions: The protective effect of hypothermia observed at the level of cytogenetic damage was not due to a modulation of cell cycle progression. A possible alternative mechanism and experiments to test it are discussed.

The dose-response relationship for dicentric chromosomes and γ-H2AX foci in human peripheral blood lymphocytes: Influence of temperature during exposure and intra- and inter-individual variability of donors

Purpose: Hypothermia during in vitro irradiation of human peripheral blood lymphocytes (PBL) affects the level of chromosome aberrations. The molecular mechanisms of this phenomenon are not fully understood. The aim of our study was to examine the effect of hypothermia on the dose-response relationship for dicentric chromosomes and the level of γ-H2AX (phosphorylated histone H2AX) foci. In addition, the inter- and intra-individual variability was assessed in relation to temperature.Materials and methods: PBL were kept at 0.8, 20 and 37°C and then exposed to gamma-rays (from 0–3 Gy). Dicentric chromosomes were scored in first post-treatment mitoses. γ-H2AX foci were scored 15, 30, 60, 120 min and 24 h post irradiation.Results: Our results revealed that the frequency of dicentric chromosomes in cells exposed at 37°C to gamma-rays was higher than after exposure at 0.8 and 20°C. No effect of temperature was observed on the number of γ-H2AX foci as well as on the intra- and inter-individual variations of the dicentric yield and the number of γ-H2AX foci.Conclusions: Temperature at exposure to ionizing radiation has a pronounced effect on the level of cytogenetic damage but not γ-H2AX foci.

Delayed effects of chronic low-dose high linear energy transfer (LET) radiation on mice in vivo

In the present work, the delayed effects of chronic high linear energy transfer (LET) radiation in polychromatic erythrocytes (PCEs) of mice bone marrow were investigated in vivo. Irradiation of the two-month-old SHK white mongrel random-bred male mice was performed in the radiation field behind the concrete shield of the accelerator of 70 GeV protons to accumulate doses of 0.005-0.16 Gy. The dependence of the biological response on dose, adaptive response (AR) and genomic instability (GI) in F(1) and F(2) generations from males irradiated with doses of 0.005 and 0.16 Gy and from males exposed to combined action of immunomodulator-bendazol hydrochloride (BH) and of 0.16 Gy irradiation, were examined using the micronucleus formation test. The data demonstrated that irradiation of mice with these doses lead to an increase in the level of cytogenetic damage and induces no AR. With analysis of the bone marrow radiosensitivity to 1.5 Gy of X rays and the capacity to AR it was found that the chronic high-LET irradiation of parents induced the GI at least two generations. The combined exposure to BH and the dose of 0.16 Gy induces no AR in F(0) generation but induces AR in F(1) and F(2) offspring.

Cytogenetic Damage in Cells Exposed to Ionizing Radiation under Conditions of a Changing Dose Rate

The current international paradigm on the biological effects of radiation is based mainly on the effects of dose with some consideration for the dose rate. No allowance has been made for the potential influence of a changing dose rate (second derivative of dose), and the biological effects of exposing cells to changing dose rates have never been analyzed. This paper provides evidence that radiation effects in cells may depend on temporal changes in the dose rate. In these experiments, cells were moved toward or away from an X-ray source. The speed of movement, the time of irradiation, and the temperature during exposure were controlled. Here we report the results of the first experiments with TK6 cells that were exposed at a constant dose rate, at an increasing dose rate, or at a decreasing dose rate. The average dose rate and the total dose were same for all samples. Micronuclei were scored as the end point. The results show that the level of cytogenetic damage was higher in cells exposed to a decreasing dose rate compared to both an increasing and a constant dose rate. This finding may suggest that the second derivative of dose may influence radiation risk estimates, and the results should trigger further studies on this issue.

Effect of temperature during irradiation on the level of micronuclei in human peripheral blood lymphocytes exposed to X-rays and neutrons

Objectives: It has been reported that the level of cytogenetic damage in human peripheral blood lymphocytes (PBL) is higher following irradiation at 37°C than at 0–4°C. The mechanisms of this cytogenetic temperature effect are not fully known. The aim of our study was to check whether the effect was related to the indirect or direct action of radiation.Materials and methods: PBL were kept at 37°C and 0°C for 20 min and exposed to 2 Gy of X-rays. In some experiments PBL were isolated and 0.5 M dimethyl sulfoxide (DMSO) was added for 5 min before exposure. PBL were also irradiated at 37°C and 0°C with 1 Gy of 6 MeV neutrons. Micronuclei were scored as the endpoint. Following exposure to X-rays the level of initial DNA damage was also measured by the alkaline and neutral comet assay.Results: The frequency of micronuclei in cells exposed at 37°C to X-rays or neutrons was higher than that after exposure at 0°C. No effect of temperature was seen when PBL were exposed to X-rays in the presence of DMSO. No effect of temperature was observed on the level of DNA damage measured with the alkaline or neutral comet assay.Conclusions: The results of experiments with DMSO indicate that the temperature effect is due to the indirect action of radiation, i.e., via reactive oxygen species. However, this is not supported by the results with neutrons and the comet assay. Possible reasons for the discrepancies are discussed.

Cytogenetic Effects in Pinus sylvestris L. Populations Experiencing Chronic Low Level Radioactive Exposure

Contamination of the environment has become a worldwide problem. A clear understanding of all the dangers posed by environmental pollutants to both human health and ecologic systems are needed. An important gap in our knowledge is long-term ecotoxical effects induced by chronic low dose-rate and multi-pollutant exposure at contaminated sites. Actually, few studies exist that are directly relevant to revealing the responses of plant and animal populations to radionuclides in their natural environments. The results of long-term field studies of cytogenetic effects in Scots pine (Pinus sylvestris L.) populations growing in the vicinity of the radioactive wastes processing and storage facility (Leningrad region, Russia) and in the Bryansk region, Russia affected by the ChNPP accident are presented. Cytogenetic damage levels in root meristem of seedlings are found to significantly exceed corresponding controls. Adaptation processes in the affected tree populations are studied by means of an additional acute exposure of seeds. An enlargement of variance of studied cytogenetic parameters is found in the populations experiencing radiation and technogenic influence. This indicates processes of cytogenetical adaptation in the populations over 30 years experiencing anthropogenic influence. An analysis of the structure of ecological-genetical variability is carried out with the purpose of separating two components in the interpopulational variability – the first is engaged to the genetically determined variability of biological characteristics intrinsic for this species, and the second is responsible for the variability originating from anthropogenic contamination of the habitat areal. Changes of these two types of variability in pine populations in the Leningrad region are studied in dependence on time and technogenic impact severity. Our results have provided evidence that genetic diversity is increased in Scots pine populations occupying the radionuclide-contaminated and/or technogenically affected sites.