Role of the processes of repair of DNA damage in the repair of cytogenetic disorders. Participation of the repair of DNA single-strand breaks in the repair of cytogenetic disorders

A comparison was made between the results of the effect of poly(ADP-ribosylation) inhibitors (e.g. nicotinamide and 3-aminobenzamide) and a chromatin proteinase inhibitor, phenylmethylsulfonylfluoride, on the cytogenetic damages repair, by a micronucleus test and DNA repair in Chinese hamster fibroblasts. The values of the repair half-periods (5-7 min for the cytogenetic damages and 5 min for the rapidly repaired DNA damages) and a similar modifying effect with regard to radiation cytogenetic damages and kinetics of DNA damages repair were found to be close. This confirms the contribution of repair of DNA single-strand breaks in the initiation of structural damages to chromosomes.     

Dynamics of the cytogenetic effect in re-examined individuals who have participated in eliminating the emergency at the Chernobyl Atomic Power Plant in various periods after irradiation]

The repeat cytogenetic examination of 22 persons who were exposed to acute radiation while eliminating emergency at the Chernobyl Atomic Power Plant has revealed interindividual variability in the rate of elimination of radiation-induced chromosome mutations. The data obtained have confirmed complexity to reconstruct individual radiation doses by the results of cytogenetic analysis carried out 1-3 years after the ionizing radiation effect.     

Therapy-related myeloid neoplasms - what have we learned so far?

Therapy-related myeloid neoplasms are neoplastic processes arising as a result of chemotherapy, radiation therapy, or a combination of these modalities given for a primary condition. The disease biology varies based on the etiology and treatment modalities patients receive for their primary condition. Topoisomerase Ⅱ inhibitor therapy results in balanced translocations. Alkylating agents, characteristically, give rise to more complex karyotypes and mutations in p53. Other etiologies include radiation therapy, high-dose chemotherapy with autologous stem cell transplantation and telomere dysfunction. Poor-risk cytogenetic abnormalities are more prevalent than they are in de novo leukemias and the prognosis of these patients is uniformly dismal. Outcome varies according to cytogenetic risk group. Treatment recommendations should be based on performance status and karyotype. An in-depth understanding of risk factors that lead to the development of therapyrelated myeloid neoplasms would help developing riskadapted treatment protocols and monitoring patients after treatment for the primary condition, translating into reduced incidence, early detection and timely treatment.     

Evaluation of developmental stability and cytogenetic homeostasis in populations of European green frogs (Rana esculenta-complex) under natural and anthropogenic conditions]

The status of amphibians in populations subjected to anthropogenic influence of various natures has been evaluated. We studied the effect of complex anthropogenic influences as well as chemical and radiation pollution. The status of the specimens in populations was evaluated by morphological (developmental stability as the level of fluctuating asymmetry) and cytogenetic (micronucleus test) methods. Disturbed developmental stability and cytogenetic homeostasis have been observed in populations affected by anthropogenic factors, which indicates the changed status of the organism.     

Cytogenetic effect of gamma quanta and secondary radiation generated by 70 GeV protons on Chinese hamster fibroblasts

The study of the cytogenetic effects (for instance, the chromosome aberration frequency in G2 cells and micronucleus formation) after exposure of Chinese hamster cells to gamma-rays and secondary radiation generated by 70 GeV protons showed that the relative biological effectiveness (RBE) of secondary radiation was approximately 3. The contribution of isochromatid deletions and exchanges into the total spectrum of rearrangements induced by the secondary radiation was different from that observed on gamma-irradiation. The absence of the modifying effect of caffeine on the cells exposed to the secondary radiation indicated that RBE of the secondary radiation from 70 GeV protons was mainly associated with its inhibitory action on the cytogenetic damages repair.     

The significance of cytogenetic investigation for the estimation of Chernobyl accident consequences

The results of the cytogenetic investigation of people, which were exposed to radiation in the result of the Chernobyl NPP accident, were presented. Also the possibilities of the application of cytogenetic findings for dose estimations and for the prediction of the radiation influence consequences were examined. During the period of time since 1986 till 2004 the cytogenetic investigations of 1724 liquidators participating in the liquidation works after the Chernobyl accident were carried out. The radiation dose estimated by the frequency of dicentrics in 1986 was about 0.16 Gy. The doses for liquidators were determined by the frequency of translocations (FISH method) during the period from 1992 till 1995. For liquidators who worked in Chernobyl only in 1986 the average dose of radiation was about 0.19 Gy and for liquidators who worked repeatedly during the period from 1986 till 1995 - 0.39 Gy. There was shown that during the whole period of investigation (1986-2004) the frequency of dicentrics in peripheral blood lymphocytes was significantly higher than the control level. The cytogenetic investigation of Bryansk region inhabitants which was carried out in 1992-1994 discovered heightened value in 5 times than the control one. Findings are of great importance for the prediction of ill effects of radiation and for the development of sensitive criterions for early exposure disturbances in state of health.     

Evaluation of Developmental Stability and Cytogenetic Homeostasis in Populations of European Green Frogs (Rana esculenta-Complex) under Natural and Anthropogenic Conditions

The status of amphibians in populations subjected to anthropogenic influence of various natures has been evaluated. We studied the effect of complex anthropogenic influences as well as chemical and radiation pollution. The status of the specimens in populations was evaluated by morphological (developmental stability as the level of fluctuating asymmetry) and cytogenetic (micronucleus test) methods. Disturbed developmental stability and cytogenetic homeostasis have been observed in populations affected by anthropogenic factors, which indicates the changed status of the organism.     

The role of irreparable DNA damage in initiating chromosomal mutagenesis in Chinese hamster cells irradiated with gamma and secondary proton radiation with an energy of 70 GeV

The study on the kinetics of DNA injury repair in Chinese hamster cells exposed to gamma and secondary proton radiation (70 GeV) has demonstrated the absence of distinctions in the kinetics of repair of rapidly repaired damages, a decreased rate of repair of slowly repaired lesions, and an increased residual irreparable damage induced by secondary radiation that reliably correlates with the RBE value estimated by the cytogenetic effect.     

Biological indication and dosimetry of unstable chromosome aberration frequencies in human lymphocytes

Review is devoted to the problems of biological (cytogenetic) dosimetry and indication of degree of radiation lesions based on analysis of unstable chromosome aberrations in lymphocytes of human peripheral blood. Effects of radiation in low doses on human chromosomes and methodology of interpretation of the character of dose cytogenetic curves are discussed. Traditional cytogenetic analysis remains the basic one for monitoring in groups of people with accidental irradiation.     

Cytogenetic and radiation hybrid mapping of human arachidonate 5-lipoxygenase-activating protein (ALOX5AP) to chromosome 13q12

Arachidonate 5-lipoxygenase-activating protein (ALOX5AP) is an arachidonic acid binding protein that has been shown to be critical in the biosynthesis of leukotrienes. We mapped the ALOX5AP gene to the chromosome 13q12 region by cytogenetic mapping, yeast artificial chromosome (YAC) pool screening, and radiation hybrid mapping. It was mapped to YAC contig WC13.2 by YAC pool screening with an unambiguous hit to WI-4874, which is at 78 cR on the radiation hybrid map, 3.36 cR, by radiation hybrid mapping, from WI-4874.     

The experience of FISH technique application for reconstruction of individual radiation doses in Chernobyl liquidators in the framework of Ukrainian-American project "Leukemia"

The results of proper investigations received under the cytogenetic examination of 225 persons (control groups, Chernobyl liquidators exposed to different radiation doses, oncogematology patients) had been summarized and analyzed. The conclusion concerning possibilities and limitations of FISH technique usage for retrospective biodosimetry of human radiation exposure has been presented.     

Glycolytic inhibitor, 2-deoxy-D-glucose, does not enhance radiation-induced apoptosis in mouse thymocytes and splenocytes in vitro

Earlier studies have shown that 2-deoxy-D-glucose (2-DG), a glucose analogue and inhibitor of glycolytic ATP production selectively enhances radiation-induced damage in cancer cells by inhibiting the energy (ATP) dependent postirradiation DNA and cellular repair processes. A reduction in radiation induced cytogenetic damage has been reported in normal cells viz., peripheral blood lymphocytes and bone marrow cells. Since induction of apoptosis plays a major role in determining the radiosensitivity of some most sensitive normal cells including splenocytes and thymocytes, we investigated the effects of 2-DG on radiation induced apo tosis in these cells in vitro. Thymocytes and splenocytes isolated from normal Swiss albino mouse were irradiated with Co60 gamma-rays and analyzed for apoptosis at various post-irradiation times. 2-DG added at the time of irradiation was present till the termination of cultures. A time dependent, spontaneous apoptosis was evident in both the cell systems, with nearly 40% of the cells undergoing apoptosis at 12 hr of incubation. The dose response of radiation-induced apoptosis was essentially similar in both the cell systems and was dependent on the incubation time. More than 70% of the splenocytes and 60% of the thymocytes were apoptotic by 12 hr following an absorbed dose of 2 Gy. Presence of 2-DG marginally reduced the fraction of splenocytes undergoing apoptosis at all absorbed doses, while no change was observed in thymocytes. Presence of 2-DG did not significantly alter either the level or the rate of induction of spontaneous apoptosis in both these cell systems. These results are consistent with the earlier findings on radiation-induced cytogenetic damage in human PBL in vitro and mouse bone marrow cells and lend further support to the proposition that 2-DG does not enhance radiation damage in normal cells, while radiosensitizing the tumors and hence is an ideal adjuvant in the radiotherapy of tumors.     

Proteinase participation in chromosome radiation damage. Research on the action of phenylmethylsulfonyl fluoride

Phenylmethylsulfonyl fluoride, a chromatin proteinase inhibitor, caused a nearly twofold diminution of the cytogenetic injury and a twofold increase in the rate of DNA repair in gamma-irradiated (3-15 Gy) Chinese hamster fibroblasts. The effect of the inhibitor was mainly exhibited by a rapidly repaired (for 15-20 min) component of the cytogenetic damage. A simultaneous treatment with phenylmethylsulfonyl fluoride and nicotinamide did not influence the effect of the proteinase inhibitor under study. The results obtained are indicative of poly (ADP-ribosylation)-independent contribution of chromatin proteinases to radiation-induced chromosome mutagenesis.     

The characteristics of the realization of cytogenetic damage in mammalian and plant cells exposed to low doses of radiation]

A complicated character of the cytogenetic injury dependence upon radiation dose was revealed after low-level gamma irradiation of Vicia faba seedlings and Chinese hamster fibroblasts. The dependence was linear with low-level secondary exposure to 70 GeV protons. The authors discuss a threshold nature of induction of the cytogenetic damage repair responsible for a high outcome of damages under the effect of low-level gamma radiation.     

Cell cycle-dependent potentiation of X-ray-induced chromosomal aberrations by 3-aminobenzamide

The poly(ADP-ribose) polymerase inhibitor 3-aminobenzamide had dramatically different effects on X-ray-induced cytogenetic damage in human lymphocytes depending on the stage of the cell cycle in which cells were irradiated. 3-Aminobenzamide (0.08-3.00 mM) potentiated the frequency of chromosomal aberrations when lymphocytes were irradiated in G1, S, or late G2. No effect was observed, however, when lymphocytes were irradiated in G0 or at the S/G2 boundary 6 h before termination of culture. These results indicate that poly(ADP-ribose) polymerase may be involved in chromosomal repair of radiation damage only during specific stages of the cell cycle.     

Current status of the problem of quantitative estimation of cytogenetic effects of low doses of radiation

The results of the author's own experimental studies and the literature on the cytogenetic effects in human lymphocyte culture induced by low-level radiation are presented. The quantitative regularities of the occurrence of structural chromosome damages in the genome of human somatic cells under the effect of low doses differ from those induced by high doses of ionizing radiation. The adequacy of extrapolating the risk of harmful after-effects from high-to low-level radiation is discussed.     

Chromosomal instability parameters in the population affected by nuclear explosions at the Semipalatinsk nuclear test site

A population genetic survey of 149 persons who were born and have permanently lived in the contaminated zones of the Semipalatinsk region has been performed. A cytogenetic study has demonstrated that the frequency of aberrant cells is 1.7-3 times higher than control parameters. The total frequencies of chromosome aberrations are 3.43 +/- 0.48, 3.1 +/- 0.3, 1.8 +/- 0.2, and 1.15 +/- 0.17 aberrations per 100 cells in the populations of the extreme radiation risk (ERR), maximum radiation risk (MaxRR), minimum radiation risk (MinRR), and control zones, respectively. The high chromosome aberration rate in all three zones of radiation risk has been detected mainly due to radiation-induced chromosome markers, including paired fragments (1.2 +/- 0.2, 0.94 +/- 0.13, and 0.43 +/- 0.06 per 100 cells, respectively), dicentric and ring chromosomes (0.44 +/- 0.04, 0.45 +/- 0.07, and 0.11 +/- 0.02 per 100 cells, respectively), and stable chromosome aberrations (0.74 +/- 0.16, 0.8 +/- 0.1, and 0.63 +/- 0.13 per 100 cells, respectively). The qualitative spectra of the cytogenetic lesions observed in these groups indicate a mutagenic effect of ionizing radiation on chromosomes in the populations studied.     

Cytogenetic characteristics of seed progeny of common oak trees (Quercus robur L.) exposed to the irradiation after the accident at the Chernobyl Nuclear Power Station and growing at the territories with different levels of anthropogenic contamination

The examination of cytogenetic characteristics (the mitotic activity, the time of passing of the mitotic stages by cells, the level and the spectrum of mitosis disturbances, the nucleoli characteristics) of seed progeny of common oak trees, exposed to the radiation exposure after the accident at the Chernobyl Nuclear Power Station and growing at the territories with different levels of anthropogenic contamination was held. In spite of the normalization of the radioactive level at the examined territories the changes of the cytogenetic characteristics of common oak seed progeny in comparison with the control were noticed. Obtained results are explained from the position of the radiation induced genomic instable and of the wave kinetic of the mutation process. The questions of the advisability and of the validity of using of the seed progeny of the common oak trees, exposed to the radiation exposure, in forest restoration measures are discussed.     

Radiation-induced modification of human somatic cells’ chromosome sensitivity to the testing mutagenic exposure of bleomycin in vitro in lung cancer patients in delayed terms following chernobyl accident

The above-background level of cytogenetic effect has been studied using the modified G₂-bleomycin sensitivity assay, the value of which was a marker of hidden chromosome instability (HCI). The following three groups were examined: (1) Chernobyl disaster liquidators (CDLs) (occupational group I), (2) patients with lung cancer (LC) who denied voluntary contact with ionizing radiation (comparative group); and (3) patients with LC participating in the liquidation of the Chernobyl disaster (occupational group 2). Significant interindividual variations in the cytogenetic effects induced by bleomycin and the absence of a positive correlation with the background and above-background frequency of chromosome aberrations have been revealed for all the three groups. It was established that occupational group 2 experienced the highest level of above-background cytogenetic effect and therefore had the highest number of patients with HCI. The data allowed us to hypothesize the existence of an association between a radiation-induced increase in individual susceptibility to testing mutagenic exposure and the development of cancer pathologies in patients exposed to ionizing radiation. The results showed the feasibility of using the G₂-bleomycin sensitivity assay for the examination of irradiated contingents for the detection of HCI as an informative marker of predisposition to cancer.