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The incident of Chernobyl Nuclear Power Plant (CNPP) explosion has pioneered a plethora of studies unfolding various biological effects of radiation stress on several living systems. Determining radiation dose rates at which both acute and chronic biological effects occur in different biological systems will aid in the ex-situ generation of radiation-tolerant organisms. So far, the accumulation of data on different radiation doses from Chernobyl area demonstrating various biological impacts has not been documented altogether vastly. Therefore, this review aims to document the recorded doses in CNPP over the years at which different biological changes have been observed in plants, soil, aquatic organisms, birds, and animals. A total of 72 peer-reviewed papers obtained from PubMed, Google Scholar, Scopus, and Research4life were included in this review. A few factors have come under attention in this review. Firstly, plant and soil systems combinedly showed the most published studies after the catastrophe where plants showed a higher frequency of DNA methylation in their genome to resist radiation stress. Secondly, reduced species abundance, chromosomal aberrations, increased sterility, and mortality were mostly observed in the aftermath of Chernobyl catastrophe among plants, soil, aquatic organisms, birds, and small mammals. Furthermore, major scares of data after 2018 were prominently observed. Very few studies on radiation dose levels after 2018 are available. Hence, a major research area has emerged for radiation biologists to study present radiation levels and any genetic changes in the recent generation of the original victim species. This will help provide a standard dataset that can act as a reference resource for radiation biologists and future research on the impact of both acute and chronic radiation on the different biological systems. [ABSTRACT FROM AUTHOR]

Purpose: Nowadays people are exposed to radiation due to various reasons, including natural, diagnostic, occupational or accidental exposure. High level of exposure to ionizing radiation can be fatal to human body. Synthetic drugs used to prevent radiation-induced damage are toxic in nature. Recently, Herbal drugs are being screened as an alternative due to their mechanism of action. Garcinia indica (G. indica) is one of the traditional medicinal plant which contains phytochemicals having several medicinal properties. Materials and methods: In this study, G. indica extract was observed for its modulatory effect against 3 Gray (Gy) gamma radiation-induced damages in human peripheral blood lymphocytes. Various concentrations of G. indica extract ranging from 1 to 25 µg/mL was added to the blood post irradiation at 0 hr. Chromosomal aberration (CA) and Cytochalasin B blocked Micronuclei Cytome (CBMN) Assay were performed as per standard procedure. Results: Radiomodulatory effect of Garcinia indica fruit rind extract (GIFRE) on CA and MN formation was observed in this study. Treatment of GIFRE did not affect the mitotic index. Positive inhibition percentages for dicentrics, total chromosomal aberrations and micronuclei were observed except for one instance. Conclusion: Owing to the various properties of Garcinia extracts, it makes it a potential candidate to be tested for its radiomodulatory effect. Based on the results observed in this preliminary study, it could act as a radiomodulatory agent. Radiomodulatory effect of GIFRE could possibly serve it as a potential herbal medicinal alternative to current drugs. However, results of this study need to be validated on larger sample size. [ABSTRACT FROM AUTHOR]

AbstractTo quantitatively investigate the effects of chronic low-dose internal exposure to Cesium-137 on DNA damage, carcinogenicity, and offspring over multiple generations. The potential genetic risk in humans was predicted based on next-generation murine mutation rates to confirm the reasonableness of the current Cesium-137 dose limits for food. Cesium-137 (100 Bq/mL) was provided in drinking water to A/J mice, facilitating chronic, low-dose, low-dose-rate internal exposure through sibling mating over 25 generations (G25). The A/J mice were compared with a control strain with the same origin ancestry (no Cesium-137 water) for DNA double-strand breaks (DSBs), oxidative stress, chromosome aberrations, micronucleus test results, whole genome analysis, carcinogenicity, tumor growth rate, and immune competence. Compared to the control group, DNA DSBs and oxidative stress were significantly increased in the Cesium-137 group. However, no significant differences were observed between the groups regarding chromosome aberration, micronuclei, or the whole genome sequence mutation analysis. Although the carcinogenic rate did not differ between the groups, the rate of tumor growth was significantly suppressed in the Cesium-137 group. The anti-tumor cytokine trend in the Cesium-137 group likely contributed to this effect. No pathological or genetic effects were observed in the offspring of mice drinking water containing 100 Bq/mL Cesium-137 after G25. The contribution of low dose-rate radiation to carcinogenicity was not additive but growth-inhibitory. Although the negative data are not conclusive, these findings are deemed highly reliable. [ABSTRACT FROM AUTHOR]

Lymphopenia is now generally recognized as a negative prognostic factor in radiotherapy. Already at the beginning of the century we demonstrated that high-energy carbon ions induce less damage to the lymphocytes of radiotherapy patients than X-rays, even if heavy ions are more effective per unit dose in the induction of chromosomal aberrations in blood cells irradiated ex-vivo. The explanation was based on the volume effect, i.e. the sparing of larger volumes of normal tissue in Bragg peak therapy. Here we will review the current knowledge about the difference in lymphopenia between particle and photon therapy and the consequences. There is nowadays an overwhelming evidence that particle therapy reduces significantly the radiotherapy-induced lymphopenia in several tumor sites. Because lymphopenia turns down the immune response to checkpoint inhibitors, it can be predicted that particle therapy may be the ideal partner for combined radiation and immunotherapy treatment and should be selected for patients where severe lymphopenia is expected after X-rays. [ABSTRACT FROM AUTHOR]

Antineoplastic drugs and radioiodine are recognized occupational risk factors affecting the genetic material of exposed persons. To assess cytogenetic damage and evaluate the presence of chromosomal instability during occupational exposure, a biomonitoring study was performed using a chromosomal aberration assay and a cytokinesis-block micronucleus (CBMN) test. Blood samples from 314 healthy donors divided into 3 groups (control, exposed to antineoplastic drugs and exposed to radioiodine) were collected and cytogenetically analyzed. There was an increase in almost all analyzed parameters registered in the exposed persons. Chromatid breaks were higher in the subjects exposed to antineoplastic drugs, while dicentrics and premature centromere division (PCD) parameters were higher in nuclear medicine workers. The total number of micronuclei was higher in both groups of the exposed. The correlation analysis indicated the association of dicentrics, acentrics, chromosome and chromatid break with PCDs in both groups of the exposed, and micronuclei and nucleoplasmic bridges with PCDs in the subjects exposed to radioiodine. The discriminant analysis marked off PCD1-5 as the best predictor of exposure. Age, sex, sampling season and duration of exposure significantly influenced the analyzed parameters, while smoking habits did not show any influence. Based on the observed results, premature centromere division can be considered a valuable parameter of genotoxic risk for individuals occupationally exposed to low doses of ionizing radiation. [ABSTRACT FROM AUTHOR]

To deepen our knowledge on the effects of high levels of indoor radon exposure, we assessed the frequencies of unstable and stable chromosome aberrations and micronucleus (MN), as well as the concentration of an endogenous antioxidant (catalase, CAT), in blood samples of individuals chronically exposed to high indoor radon concentrations in Indonesia (Tande-Tande sub-village, Mamuju, West Sulawesi). Moreover, we also investigated the occurrence of a radio-adaptive response (RAR) in Tande-Tande sub-village inhabitants using the G2 MN assay. The frequencies of dicentric (DC), acentric (AF), ring (R), and translocation (Tr) chromosomes in Tande-Tande inhabitants were compared to those in people living in a reference area with low levels of indoor radon levels (Topoyo village, Indonesia). The number of MN per 1000 binucleated cells (BNC) and CAT concentration per total protein was quantified and compared between groups. Lastly, we irradiated (2 Gy) phytohemagglutinin-stimulated samples in vitro and measured the frequency of MN to verify the occurrence of a RAR in Tande-Tande sub-village inhabitants. The frequencies of DC, AF, and Tr did not differ between Tande-Tande inhabitants and control subjects (p = 0.350, 0.521, 0.597). The frequency of MN in Tande-Tande inhabitants was significantly lower than that in the control group (p = 0.006). Similarly, CAT concentration in Tande-Tande inhabitants was also significantly lower than that in the control population (p < 0.001). Significant negative correlations were identified for MN number and CAT concentration versus indoor radon concentration, annual effective dose, or cumulative dose both within groups and when all data were analyzed together. Our findings indicate that, despite the high indoor radon levels, Tande-Tande inhabitants are not under oxidative stress, since this group had lower CAT concentration and MN frequency than those in the control group. The negative correlation between MN frequency and indoor radon concentration, annual effective dose, and cumulative dose suggests the occurrence of an RAR phenomenon in Tande-Tande sub-village inhabitants. This interpretation is also supported by the results of the G2 MN assay, which revealed lower MN frequencies after in vitro irradiation of samples from Tande-Tande sub-village inhabitants than those in samples from the control group (p = 0.0069, for cumulative MN frequency; p = 0.0146, for radiation-induced MN only). [ABSTRACT FROM AUTHOR]

Nuclear weapons testing in the northern Marshall Islands between 1946 and 1958 resulted in ionizing radiation (IR) exposure of the thousands of Marshallese. Furthermore, numerous islands were contaminated by radioactive fallout. Significant increases in cancer and metabolic syndrome incidences have been reported among Marshallese, and potential for further increases looms due to the latency of radiation-induced health effects. The purpose of this study was to investigate the genetic and epigenetic effects of exposure to IR that could be associated with radiation-induced disease among the Northwest Arkansas (NWA) Marshallese. We performed analysis of chromosomal aberrations and DNA methylation based on residential and exposure history of NWA Marshallese. Analysis of chromosomal aberrations demonstrated higher incidence of genetic rearrangements in women with self-reported history of radiation exposure (95% CI: 0.10, 1.22; p=.022). Further clustering of study participants based on their residential history demonstrated that participants who spent substantial amounts of time (≥6 months) in the northern atolls (thus, in the proximity of nuclear tests) before 1980 had more chromosomal aberrations than their peers who lived only in the southern atolls (95% CI: 0.08, −0.95; p=.021), and that this difference was driven by women. A relationship between the time spent in the northern atolls and increase in chromosomal aberrations was observed: 0.31 increase in chromosomal aberrations for every 10 years spent at northern atolls (95% CI: 0.06, 0.57; p=.020). Finally, significant inverse correlations between the chromosomal aberrations and the extent of DNA methylation of four LINE-1 elements L1PA2, L1PA16, L1PREC1, and L1P4B were identified. The results of this study provide first evidence of the presence of stable genetic and epigenetic rearrangements in peripheral lymphocytes of NWA Marshallese and warrant further studies to analyze the role of radiation exposure in health disparities experienced by this Pacific Island nation. [ABSTRACT FROM AUTHOR]

To investigate the effects of chronic exposure to low-dose radiation on bone marrow (BM) hematopoiesis of bank voles inhabiting the radioactively contaminated territory of the Chornobyl exclusion zone. Animals were collected within the highly radioactive area of the so-called Red Forest located close to the destroyed 4th reactor of the Chornobyl Nuclear Power Plant. Radioecological investigations included evaluation of radiocontamination of soil samples by 90Sr and 137Cs, levels of incorporated radionuclides in animals' bodies and organs, as well as the absorbed dose rates. The study of peripheral blood and BM parameters combined with cytogenetic analysis of BM micronucleated polychromatic erythrocytes (MNPCEs) and standard metaphase test was carried out. The blood system of the exposed animals manifested significant changes in peripheral blood parameters (anemia and leucocyte formula left shift), ineffective differentiation, and maturation of BM cells, particularly relevant to the erythroid and granulocyte pools. Increased yields of BM MNPCEs and chromosomal aberrations, including dicentrics (dics) and Robertsonian fusion-like configurations (Rbts), were revealed. Observed disturbances in the BM and peripheral blood suggest functional instability and inefficient compensatory and recovery reactions of the blood system of the bank voles from the contaminated areas of the Chornobyl exclusion zone. We assume that they are the consequences both of direct radiation exposure and hereditary pathological changes that have formed in a number of generations inhabiting radioactively contaminated areas. [ABSTRACT FROM AUTHOR]

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan on March 11 2011, the surroundings became contaminated with radionuclides. To understand the possible biological effects after chronic low dose-rate radiation in contaminated areas of Fukushima, we assessed the effects in large Japanese field mice (Apodemus speciosus) by means of chromosome aberration analysis. We collected A. speciosus in five sites around Namie Town, Fukushima (contaminated areas) and in two sites in Hirosaki City, Aomori (control areas, 350 km north of FDNPP) from autumn 2011 to 2013. The number of mice captured and ambient dose-rates were as follows: high (n = 11, 10.1–30.0 µGy h−1), moderate (n = 10, 5.7–15.6 µGy h−1), low (n = 12, 0.23–1.14 µGy h−1) and control (n = 20, 0.04–0.07 µGy h−1). After spleen extraction from rodents, spleen cell culture was performed to obtain metaphase spreads. Chromosome aberrations were assessed on Giemsa-stained metaphase spreads. Although the mice in the contaminated areas were chronically exposed, there was no radiation-specific chromosome aberrations observed, such as dicentric chromosomes and rings. Some structural aberrations such as gaps and breaks were observed, and these frequencies decreased annually in mice from Namie Town. These findings suggest that chromosome aberration analysis is useful to evaluate and monitor radiation effects in wild animals. [ABSTRACT FROM AUTHOR]

The development of an exposure apparatus for in situ α-irradiation studies of cells. The construction of the apparatus is simple and the apparatus is maintenance free, easy to use and of low cost. This small device can be placed in an incubator, where the exposure environment is controlled. Moreover the vapor saturated incubator protects the cells from drying out, allowing long irradiation intervals. The system includes a 234U alpha (α)-source of total activity 0.77 ± 0.03 MBq in the form of a thin disk deposited on an aluminum substrate. The α-particles emitted in the air have a mean energy of 4.9 MeV at the disk surface. Source homogeneity has been studied via Rutherford Backscattering Spectrometry. Using SRIM 2013 and Monte Carlo (MC) simulations via the MCNP6.1 code, LET and energy deposition values have been calculated for various filling gasses. Furthermore, based on these simulations, the assembly's dimensions and equivalent irradiation rate have been determined. With respect to the aforementioned dimensions, the experimental setup is constructed in a way to provide uniform irradiation of the sample. Using Sacalc3v1.4 irradiation radial homogeneity has been studied. In order to evaluate biologically our apparatus, a well-established chromosomal aberration assay has been utilized, applied in exponentially growing hamster (CHO) cells. Furthermore, immunofluorescence gamma-H2AX/53BP1 foci assay has been performed as a 'biological detector', in order to validate α-particles surface density. Source surface homogeneity: emission deviations do not exceed 10–15%. The optimal distance between the source and the cells for irradiation is determined to be 14.8 mm. Irradiation radial homogeneity: a deviation of 5% occurs at the first 8 mm from the center of the irradiation area, and a 10% deviation occurs after 12 mm. Chromosomal aberrations were found in good agreement with the corresponding in bibliography. The current technical report describes analytically the development and evaluation stages of this experimental housing; from MC simulations to the irradiation of mammalian cells and data analysis. Moreover, guidance is provided as well as a report of the variables on which critical parameters are depended, so as to make this work useful to anyone who wants to construct a similar in-house α-irradiation apparatus for radiobiological studies using mammalian cells. [ABSTRACT FROM AUTHOR]

Ionizing radiation is a well-known carcinogen, and epidemiologic efforts have been made to evaluate cancer risks following a radiation exposure. The basic approach has been to estimate increased levels of cancer mortality resulting from exposures to radiation, which is consistent with the somatic mutation theory of cancer. However, the possibility that an irradiation might cause an earlier onset of cancer has also been raised since the earliest days of animal studies. Recently, the mutation induction model has been challenged because it is unable to explain the observed dose-related parallel shift of entire mouse survival curves toward younger ages following an irradiation. This is because if it is assumed that only a fraction of the irradiated individuals are affected, the irradiated population would consist of two subpopulations with different mean lifespans, which makes the overall distribution of individual lifespans broader, and hence the slope of the survival curves shallower. To explain this parallel shift, it is necessary to assume that all individuals of a population are affected. As a result of these observations, possible mechanisms which could account for the parallel shift of mouse survival curves were sought by examining the radiation induction of various types of tissue damage which could facilitate an earlier onset of spontaneously arising cancers. A proposed mechanism postulates that a radiation exposure leads to tissue inflammation which subsequently stimulates spontaneously arising cancers and allows them to appear earlier than usual. This notion is not unprecedented, and because the background incidence of cancer increases exponentially with an increase in age, a slight shift of the onset age toward younger ages may make it appear as if the risk is increased. In this scenario, a radiation exposure induces DNA damage, cell death, chromosome aberrations etc., which leads to the multi-pathway responses including activation of stromal fibroblasts, macrophages and various inflammatory factors. Such an inflamed microenvironment favors the growth of spontaneously arising tumor cells although currently, the sequential order or relative importance of the individual factors remains to be known. [ABSTRACT FROM AUTHOR]

Mutual cooperation of biodosimetry laboratories is required for dose assessments of large numbers of people with potential radiation exposure, as in mass casualty accidents. We launched an intercomparison exercise to validate the performance of biodosimetry laboratories in South Korea. Participating laboratories shared metaphase images from dicentric chromosome assays (DCAs) and fluorescence in situ hybridization (FISH)-based translocation assays, which were evaluated based on their own scoring protocols. Overall, the coefficient of variation among three laboratories was less than 10% for counting scorable metaphases and chromosomal aberrations. However, there was variation in the interpretation of the International Atomic Energy Agency guidelines for selecting scorable metaphases and identifying chromosomal aberrations. In a technical workshop, scoring discrepancies were extensively discussed in order to harmonize biodosimetry protocols in Korea. In addition, metaphase images with agreement among all participating laboratories were compiled into an image databank, which can be used for education and training of scorers. These findings and exercises may improve the accuracy of dose assessment, as well as increase the capacity for biodosimetry in South Korea. [ABSTRACT FROM AUTHOR]

Given equal doses, it is well-known that densely ionizing radiations are more potent in causing a number of biological effects compared to sparsely ionizing radiations, such as x- or gamma rays. According to classical models of radiation action, this results from differences in the spatial distribution of lesions along charged particle tracks. In recent years investigators have been barraged with the alternative narrative that this is instead due to 'qualitative' differences in the types of molecular lesions that each type of radiation produces. The present review discusses, mainly from a cytogenetic perspective, the merits and shortcomings of these seemingly contradictory viewpoints. There may be a kernel of truth to the idea that qualitative differences in the types of molecular lesions produced at the nanometer level affect RBE/LET relationships, but to ignore the fact that such differences result from longer-range spatial distributions of lesions produced along charged particle tracks is an unjustifiably narrow stance tantamount to employing Occam's Broom. Not only are such spatial considerations indispensable in explaining the impact of ionization density upon higher-order biological endpoints, particularly chromosome aberrations, the explanations they provide render arguments based principally on the quality of IR damage largely superfluous. [ABSTRACT FROM AUTHOR]

In case of a mass-casualty radiological event, there would be a need for networking to overcome surge limitations and to quickly obtain homogeneous results (reported aberration frequencies or estimated doses) among biodosimetry laboratories. These results must be consistent within such network. Inter-laboratory comparisons (ILCs) are widely accepted to achieve this homogeneity. At the European level, a great effort has been made to harmonize biological dosimetry laboratories, notably during the MULTIBIODOSE and RENEB projects. In order to continue the harmonization efforts, the RENEB consortium launched this intercomparison which is larger than the RENEB network, as it involves 38 laboratories from 21 countries. In this ILC all steps of the process were monitored, from blood shipment to dose estimation. This exercise also aimed to evaluate the statistical tools used to compare laboratory performance. Blood samples were irradiated at three different doses, 1.8, 0.4 and 0 Gy (samples A, C and B) with 4-MV X-rays at 0.5 Gy min−1, and sent to the participant laboratories. Each laboratory was requested to blindly analyze 500 cells per sample and to report the observed frequency of dicentric chromosomes per metaphase and the corresponding estimated dose. This ILC demonstrates that blood samples can be successfully distributed among laboratories worldwide to perform biological dosimetry in case of a mass casualty event. Having achieved a substantial harmonization in multiple areas among the RENEB laboratories issues were identified with the available statistical tools, which are not capable to advantageously exploit the richness of results of a large ILCs. Even though Z- and U-tests are accepted methods for biodosimetry ILCs, setting the number of analyzed metaphases to 500 and establishing a tests' common threshold for all studied doses is inappropriate for evaluating laboratory performance. Another problem highlighted by this ILC is the issue of the dose-effect curve diversity. It clearly appears that, despite the initial advantage of including the scoring specificities of each laboratory, the lack of defined criteria for assessing the robustness of each laboratory's curve is a disadvantage for the 'one curve per laboratory' model. Based on our study, it seems relevant to develop tools better adapted to the collection and processing of results produced by the participant laboratories. We are confident that, after an initial harmonization phase reached by the RENEB laboratories, a new step toward a better optimization of the laboratory networks in biological dosimetry and associated ILC is on the way. [ABSTRACT FROM AUTHOR]

The objective of this research was to explore the dose-effect relationships of dicentric plus ring (dic + r), micronucleus (MN) and nucleoplasmic bridges (NPB) induced by carbon ions in human lymphocytes. Venous blood samples were collected from three healthy donors. 12C6+ ions beam was used to irradiate the blood samples at the energy of 330 MeV and linear energy transfer (LET) of 50 keV/μm with a dose rate of 1 Gy/min in the spread-out Bragg peak. The irradiated doses were 0 (sham irradiation), 1, 2, 3, 4, 5 and 6 Gy. Dic + r chromosomes aberrations were scored in metaphases. The cytokinesis-block micronucleus cytome (CBMN) was conducted to analyze MN and NPB. The maximum low-dose relative biological effectiveness (RBEM) values of the induction of dic + r, MN and NPB in human lymphocytes for 12C6+ ions irradiation was calculated relative to 60Co γ-rays. The frequencies of dic + r, MN and NPB showed significantly increases in a dose-depended manner after exposure to 12C6+ ions. The distributions of dic + r and MN exhibited overdispersion, while the distribution of NPB agreed with Poisson distribution at all doses. Linear-quadratic equations were established based on the frequencies of dic + r and MN. The dose-response curves of NPB frequencies followed a linear model. The derived RBEM values for dic + r, MN and NPB in human lymphocytes irradiated with 12C6+ ions were 8.07 ± 2.73, 2.69 ± 0.20 and 4.00 ± 2.69 in comparison with 60Co γ-rays. The dose-response curves of carbon ions-induced dic + r, MN and NPB were constructed. These results could be helpful to improve radiation risk assessment and dose estimation after exposed to carbon ions irradiation. [ABSTRACT FROM AUTHOR]

Biodosimetry with persistent cytogenetic indicators in peripheral blood lymphocytes (PBLs) plays crucial role in regulatory/medical management of individuals overexposed to radiation. Conventional methods require ∼48 h culture and have limited dose range (0.1–5Gy) applications due to checkpoint arrest/poor stimulation. G0-Phase Premature chromosome condensation (G0-PCC) allows chromosome aberration analysis within hours after blood collection. Due to high skill demand, applications of G0-PCC were not very well explored and being re-visited worldwide. Among all aberrations, analysis of excess chromosomal fragments is quickest. Radiation dose response curve for the fragments has been reported. In present study, excess fragment analysis has been addressed in detail, in addition to validation of radiation dose response curve, gender variation in the response, dose dependent repair kinetics, minimum detection limit (MDL), duration and accuracy of final dose estimation with 5blindfolded, ex vivo irradiated samples have been studied. In extension, feasibility of multiparametric dosimetry with Fluorescent in situ hybridization (FISH) based endpoints were qualitatively explored. PBLs were exposed to Gamma-Radiation and G0-PCC was performed at different time points. Decay kinetics and dose response curve were established. Gender Variation of the frequency of the fragments was assessed at 0, 2 and 4 Gy. FISH was performed with G0-PCC applying centromere probe, whole chromosome paints, multi-color FISH and multi-color banding probes. Radiation response curve for fragments was found to be linear (Slope 1.09 ± 0.031 Gy-1). Background frequency as well as dose response did not show significant gender bias. Based on variation in background frequency of fragments MDL was calculated to be ∼0.3 Gy. Kinetics of fragment tested at 0, 4, 8, 16 and 24 h showed exponential decay pattern from 0 to 8 h and without further decay. Final dose estimation of five samples was completed within 13 man-hours. Dicentric chromosomes, translocations, insertions and breaks were identifiable in combination with centromere FISH and WCP. Advanced methods employing multicolor FISH and multi-color banding were also demonstrated with PCC spreads. G0-PCC, can be useful tool for high dose biodosimetry with quick assessment of fragment frequency. Further, it holds potential for multi-parametric dosimetry in combination with FISH. [ABSTRACT FROM AUTHOR]

Purpose: Studying the relationship between epigenetic variability with different individual radiosensitivity and adaptive capacity. Material and method: Using a simple and convenient experimental model – maize seedlings with different germination terms and epigenetic patterns – the hypothesis was tested that homogeneous genetically but epigenetic different organisms have different radiosensitivity and radioadaptive capacity. Differences in the DNA methylation profiles of individual subpopulations of seedlings were used as a marker of epigenetic differences and the yield of chromosomal aberration was used as an indicator of DNA vulnerability and its changes under different UV-C irradiation modes. In two series of experiments involving а UV-C acute single and exposure according to the scheme 'adaptive – challenging', the investigation of possible biological importance of epigenetic polymorphism has been performed. The study used a cytogenetic analysis of the yield of chromosomal aberrations and restriction analysis followed by ITS-ISSR- PCR. Results: Significant differences have been established in chromosome aberration yield and DNA methylation profile in control and under UV-C exposure for seedlings of subpopulations differing in time of germination. The differences in the DNA methylation profiles and the yield of chromosomal aberrations in the control subpopulations of seedlings of different germination term indicate the influence of the DNA methylation profile on DNA damage by regular metabolic factors, such as thermal vibrations or reactive oxygen species (ROS). This phenomenon can be explained with different chromatin conformation determining structural or 'passive' resistance, which provides different DNA availability to damage. Methylation switching into de novo under different mode radiation exposure could become a marker of gene expression changes due to induced repair and protecting. Conclusions: The obtained data indicate the importance of epigenetic factors in determining the radio-resistance and adaptive capacity of organisms. It points out that the epigenetic mechanisms that determine the choice of the metabolic pattern also contribute to the individual radiosensitivity and adaptive capacity of the organisms. This contribution is determined by two ways. First, the DNA methylation profile affects the initial damage processes and secondly, the type of methylation switching into de novo is associated with the further development of protection and repair processes. [ABSTRACT FROM AUTHOR]

Purpose: To analyze the effects of DNA repair polymorphism and other factors on the frequency chromosome aberrations in an irradiated cohort of subjects living around the Semipalatinsk nuclear test site and non-exposed group of subjects from ecologically favorable zones of Kazakhstan. Materials and methods: Blood samples were collected in the rural areas of the East Kazakhstan district around the Semipalatinsk nuclear test site and ecologically favorable zones of Almaty region of Kazakhstan. Chromosome aberrations in the fresh and cryopreserved peripheral blood lymphocyte cultures were analyzed by Giemsa staining. Single nucleotide polymorphisms at eight DNA repair genes (XRCC1 rs1799782, XRCC1 rs25487, XRCC3 rs861539, ATM rs1801516, XPD rs1799793, XPD rs13181, APEX1 rs1130409, and hOGG1 rs1052133) were determined by PCR-RFLP method. Results: The age of donors and smoking significantly affected the frequency of chromosome aberrations among the irradiated and control subjects. In the irradiated and control cohorts, the frequency of chromosome aberrations was significantly increased in the heterozygous ATM rs1801516 (1853 Asp/Asn) individuals; for the rest of the loci no significant associations between polymorphism and the frequency of chromosome aberrations were detected. Conclusions: The age of donors, smoking, and the ATM rs1801516 polymorphism significantly affect the frequency of chromosome aberrations among individuals inhabiting contaminated area around the Semipalatinsk nuclear weapon test site, as well as among those inhabiting ecologically favorable zones of Kazakhstan. [ABSTRACT FROM AUTHOR]

Purpose: Non-Targeted effects (NTE), such as bystander effect (BE) and genomic instability (GI) challenge central dogma of radiation biology. Moreover, there is a need to understand its universality in different type of cells and radiation quality. Materials and method: To study BE (primary and secondary) and GI Human adult dermal fibroblast (HADF) and peripheral blood lymphocytes (PBL) were exposed to low fluence of 241Am alpha (α) particle and 6 MV X-ray. The BE was carried out by means of co-culture methodology after exposing the cells to both types of radiation and damage was measured using micronucleus assay (MN) and chromosomal aberration assay (CA) in the p1 cells while the GI was followed up in their progeny. Results: A dose-dependent increase in DNA damages (MN and CA) was observed in directly irradiated and bystander cells. The magnitude of BE was higher (6 fold) in cells co-cultured with the α-irradiated cells than that of with X-irradiated cells. Cross exposure of both cell types confirms that radiation induced BE is cell type dependent. In addition, induced DNA damage persisted for a longer population doubling in α-particle irradiated cells. Conclusion: This work adds evidence to secondary bystander response generated from primary bystander normal cells and its dependence to radiation quality. [ABSTRACT FROM AUTHOR]

Purpose: Radon is of health concern because they can cause lung cancer when inhaled over many years. Cytogenetic biomarkers proved to be excellent methods to detect and estimate radiation induced DNA damage. Two well established cytogenetic assays are available to detect the DNA damage caused by ionizing radiation namely Dicentric (DC) assay and Cytokinesis-Blocked Micro Nucleus (CBMN) assay. Chromosomal aberrations such as dicentric and acentric fragments can be analyzed in DC assay. Micronuclei and Nucleoplasmic bridges can be analyzed in CBMN assay. The present study focuses on correlation between the aberrations observed in DC and CBMN assay caused by low doses of radon in smokers. Material and methods: Blood samples were collected, after prior consent, from smokers as well as healthy non-smoking individuals and exposed in vitro to radon ranging between 0–5.2 mGy using a simple, portable irradiation assembly designed and tested at authors' laboratory. Results: A significant increase in frequencies of dicentrics and excess acentric fragments were observed with increasing dose. Interestingly in CBMN assay also, the frequencies of micronuclei and nucleoplasmic bridges were increased with dose. There was a significant correlation between nucleoplasmic bridges and dicentrics for both smokers and non-smokers. Significant correlation between acentric fragments and micronucleus was observed only for non-smokers. Conclusions: By considering the correlation between the two cytogenetic assays, the CBMN assay can be used as an alternative to DC assay for non-smokers. In case of smokers, nucleoplasmic bridges can be used to measure the radiation exposure. This study is first of its kind to correlate the cytogenetic biomarkers obtained from DC and CBMN assay for smokers with very low doses of radon. [ABSTRACT FROM AUTHOR]

Purpose: Dose assessment plays an important role in case of radiological accidents and can be performed by scoring structural changes of chromosome morphology induced in cells by ionizing radiation. The results of such a test are biased by scorer experience, therefore, simple to learn assays are recommended to be used when fast analysis of a large amount of data is needed. The aim of this study was to compare the performance of two radiobiological assays – chromosomal aberrations and micronuclei – by unexperienced scorers with the reference values generated by an expert. Materials and methods: Each participant of an EU-funded two-week radiobiology course was asked to score Chinese hamster ovary cells exposed to gamma radiation up to 4 Gy. The congruence of students' and expert's scores at each dose and the coherence of the dose-response curve parameters between the students were investigated. Results: Micronucleus test tended to be faster and easier to learn than scoring chromosomal aberrations. However, both assays carried out by inexperienced students showed reasonable dose-response curves. Conclusions: In the case of a large radiological accident involving many casualties, the unexperienced scorers would support the process of biodosimetric triage by cytogenetic biological dosimetry. [ABSTRACT FROM AUTHOR]

Purpose: It is important to understand the significance of alpha (α) radiation-induced bystander effects (RIBE) and its relative biological effectiveness (RBE); this is because the phenomenon is not universal and the mechanism is unclear and because the RBE is widely varying and projected to be very high. Materials and methods: Isolated lymphocytes from healthy volunteers (n = 10) were exposed to either low fluence α-particles (241Am), γ-rays (60Co), or X-rays (225 kVp and 6 MV). Co-culture methodology was employed to investigate bystander effects (BEs). Chromosomal aberrations (CA) and micronucleus (MN) formation were used to study the BE and calculated RBE. Results: Lymphocytes directly exposed to the types of radiation used showed a dose-dependent increase in the frequency of CA and MN; dose independent increases in the frequency of these chromosomal damages in co-cultured bystander cells, implies that all three types of radiation-induced a BE. The calculated RBE at the level of 5% induced aberrations varied between 9 and 20. Conclusion: The magnitude of low fluence α-particle induced RIBE is higher than in low LET (linear energy transfer) radiation. The RBE also varies depending upon the endpoints used and adds up to targeted effects. Since the endpoint of CA is considered as an important and early marker of risk prediction, the RIBE and RBE using CA as a marker are relevant for radiation protection purposes. [ABSTRACT FROM AUTHOR]

Lipopolysaccharide-responsive, beige-like anchor protein (LRBA) deficiency is an autosomal recessive primary immunodeficiency disease characterized by a CVID-like phenotype, particularly severe autoimmunity and inflammatory bowel disease. This study was undertaken to evaluate radiation sensitivity in 11 LRBA-deficient patients. Therefore, stimulated lymphocytes of the studied subjects were exposed to a low dose γ-radiation (100 cGy) in the G2 phase of the cell cycle and chromosomal aberrations were scored. Lymphocytes of age-sex matched healthy individuals used in the same way as controls. Based on the G2-assay, six (54.5%) of the patients had higher radiosensitivity score comparing to the healthy control group, forming the radiosensitive LRBA-deficient patients. This chromosomal radiosensitivity showed that these patients are predisposed to autoimmunity and/or malignancy, and should be protected from unnecessary diagnostic and therapeutic procedures using ionizing radiation and exposure to other DNA damaging agents. [ABSTRACT FROM AUTHOR]

Purpose: The purposes of this study are to investigate spontaneous dicentric frequencies and dose–response curves of dicentrics induced by gamma 60Co for replenishing the data sets used for biodosimetry in Vietnam. Materials and methods: One hundred and four healthy donor blood samples were collected for chromosome aberrations background study, 03 healthy donor blood samples were used for generating the dose–response curves at 1.96 mGy/min and 275 mGy/min. Blood collection, in vitro irradiation, cell culture and harvest, slide preparation and metaphase scoring were performed according to IAEA standard protocol (2011). Blind exposed samples were scored for verifying each curve. Results: The dicentric, fragment and chromatid break frequencies in 106,310 metaphases of 104 donors were 0.023% ± 0.005%, 0.045% ± 0.007% and 0.101% ± 0.011%, respectively. The dose–response curve for low-dose rate was y = C + (0.0137 ± 0.0055)D + (0.0912 ± 0.0142)D2 and for high-dose rate was y = C + (0.0337 ± 0.0046)D + (0.0539 ± 0.0031)D2, where both of them were verified. Conclusion: The data of this study were established for biological dose assessment in cases with low LET of accidental or occupational radiation exposures in the dose range of 0.1–5.0 Gy. [ABSTRACT FROM AUTHOR]

Purpose: To study the rhenium-188 labeling of polyamidoamine (PAMAM) generation 4 (G4) dendrimer and its evaluation on biodistribution and chromosomal aberrations in melanoma cells induced by ionizing radiation as potential treatment agent. Materials and methods: Dendrimers were first conjugated with Suc-HYNIC (succinimidyl 6-hydrazinopyridine-3-carboxylic acid hydrochloride). Dendrimer-HYNIC was then incubated with 188ReO4−. Biodistribution was performed administrating 188Re-dendrimer to normal (NM) or melanoma-bearing mice (MBM). Chromosome aberration test was conducted in order to measure treatment capacity of 188Re-dendrimer in melanoma cells. Results: Radiolabeling yield of dendrimer was approx. 70%. Biodistribution studies in NM showed blood clearance with hepatic and renal depuration. MBM showed a similar pattern of biodistribution with tumor uptake of 6% of injected dose. Aberrant metaphases quantified in control cells were 7%, increasing to 29.5% in cells treated with 15μCi (0.555 MBq) of 188Re-dendrimer for 24 h. Conclusions: 188Re-dendrimer can produce double-stranded breaks in DNA induced by ionizing radiation in melanoma cells in vitro. [ABSTRACT FROM AUTHOR]

Purpose: To present Poisson exact goodness-of-fit tests as alternatives and complements to the asymptotic u-test, which is the most widely used in cytogenetic biodosimetry, to decide whether a sample of chromosomal aberrations in blood cells comes from an homogeneous or inhomogeneous exposure. Materials and methods: Three Poisson exact goodness-of-fit test from the literature are introduced and implemented in the R environment. A Shiny R Studio application, named GOF Poisson, has been updated for the purpose of giving support to this work. The three exact tests and the u-test are applied in chromosomal aberration data from clinical and accidental radiation exposure patients. Results: It is observed how the u-test is not an appropriate approximation in small samples with small yield of chromosomal aberrations. Tools are provided to compute the three exact tests, which is not as trivial as the implementation of the u-test. Conclusions: Poisson exact goodness-of-fit tests should be considered jointly to the u-test for detecting inhomogeneous exposures in the cytogenetic biodosimetry practice. [ABSTRACT FROM AUTHOR]

Purpose: Exposure to ionizing radiation causes damage to the genomic integrity and stability of the cell. Though a large number of molecules have been studied for their radioprotective capability, no single agent is available today that meets all the requirements of a good radiprotector. In this study, we have investigated a combination of Resveratrol (RSV) and 3,3′-Diindolyl methane (DIM) for its efficacy for radioprotection. It is our hypothesis that this combination that possesses less toxicity than synthetic compounds, free radical scavenging potential, and the capacity to interfere with the several of the signaling cascades that trigger damage to cell by ionizing radiation may possess good radioprotective capability. Materials and methods: Mice were pre-treated with a combination of RSV and DIM and the 30-day mortality assay, endogenous antioxidant levels in intestinal mucosa, metaphase chromosomal aberrations, and micronuclei formation were assessed after exposed to ionizing radiation. Results: The dose modifying factor (DRF) obtained for RSV, DIM, and the combination is 1.15, 1.17, and 1.3, respectively. Pre-treatment of mice with the combination results in significant (***p = .001) protection of the endogenous antioxidant levels, chromosomal aberrations, micronuclei formation, after exposure to ionizing radiation. Conclusions: Our findings suggest that pre-treatment with the combination of RSV and DIM protects effectively from the ionizing radiation-induced damage at the molecular, cellular, and tissue levels by counteracting both the direct and indirect effects. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This review summarizes the results of experiments conducted in the Institute for Environmental Sciences for the past 21 years, focusing on the biological effects of long-term low dose-rate radiation exposure on mice. Mice were chronically exposed to gamma rays at dose-rates of 0.05, 1 or 20mGy/ day for 400 days to total doses of 20, 400 or 8000mGy, respectively. The dose rate 0.05mGy/day is comparable to the dose limit for radiation workers. The parameters examined were lifespan, neoplasm incidence, antineoplasm immunity, body weight, chromosome aberration(s), gene mutation(s), alterations in mRNA and protein levels and trans-generational effects. At 20mGy/day, all biological endpoints were significantly altered except neoplasm incidence in the offspring of exposed males. Slight but statistically significant changes in lifespan, neoplasm incidences, chromosome abnormalities and gene expressions were observed at 1mGy/day. Except for transient alterations in the mRNA levels of some genes and increased liver neoplasm incidence attributed to radiation exposure, the remaining biological endpoints were not influenced after exposure to 0.05mGy/day. Results suggest that chronic low dose-rate exposure may induce small biological effects. [ABSTRACT FROM AUTHOR]

Purpose: This study was conducted to evaluate and compare the influence of gamma radiations on morphological and chromosomal abnormalities in twenty mutagenized faba bean populations, representing first and second generations (M1 and M2) of five faba bean genotypes. Materials and methods: Five faba bean genotypes were exposed at two doses of gamma radiations (25 and 50Gy). For determining the types of chromosomal aberrations caused by the gamma radiation, mitotic and meiotic cells were isolated from root tips and pollen mother cells, respectively. Results: The M1 generations of the five genotypes varied for sensitivity to gamma radiations, for seedling emergence. The genotype Skah 2 was more sensitive than other genotypes, the order of sensitivity of other genotypes was Misr 3 > ILB 4347 > Hassawi 2 > Hassawi 3. However, seedling emergence of the M2 generations was not as much reduced as that of the M1 generations. Ten different chlorophylldeficient mutants were identified among the M2 generations. Gamma radiations also caused the development of abnormal leaflets, flowers and pollen grains. The most common types of chromosome aberrations in the mitotic cells were stickiness, laggard and chromosome breaks, whereas the most common types in the meiotic cells were stickiness and disturbed polarity. Conclusion: The gamma radiation decreased the seedling emergence and induced a wide range of morphological and chromosomal abnormalities in faba bean. [ABSTRACT FROM AUTHOR]

Purpose: Our study aimed at evaluating: 1) whether well-established variability in radioadaptive response (AR) in various donor blood lymphocytes might be attributed to inter-individual differences in radiosensitivity to different low dose levels; 2) whether AR is reproducibly present over time in the lymphocytes of AR-positive individuals. Experimental procedure: Whole blood samples of three donors were exposed to low doses (2-30 cGy) of γ-radiation alone (G0 phase) or followed by a 1 Gy challenge dose (late S/early G2 phase), and chromosome aberration were scored to assess the dose-response relationship and adaptive response, correspondingly. Three experiments were performed on blood samples of the same donors at six month intervals. Results: Significant differences in dose response relationship for blood lymphocytes were found among individuals. In most cases, the donors exhibited initial low-dose hypersensitivity (HRS) followed by an increase in radioresistance (IRR). AR could be successfully induced by some particular priming doses in the lymphocytes of each donor; however, the doses resulting in a protective response were quite different for all three donors. These protective doses could equally belong to either HRS or IRR region on the individual dose-response curves. In most cases, no clear AR outcome dependence on the priming dose was found at all. Moreover, pre-exposure to the same low dose could result in opposite effects in the lymphocytes of the same donor in different experiments. Conclusions: AR variability in human lymphocytes is not attributed to variation in radiosensitivity among individuals and is more drastic than was believed. It seems doubtful that AR is a universal phenomenon which has a consistent impact on the effects of radiation exposure on humans. [ABSTRACT FROM AUTHOR]

Purpose: In the framework of RENEB, several biodosimetry exercises were conducted analyzing different endpoints. Among them, the analysis of translocations is considered the most useful method for retrospective biodosimetry due to the relative stability of their frequency with post irradiation time. The aim of this study was to harmonize the accuracy of translocation-based biodosimetry within the RENEB consortium. Materials and methods: An initial telescoring exercise analyzing FISH metaphase images was done to harmonize chromosome aberration descriptions. Then two blind intercomparison exercises (IE) were performed, by sending irradiated blood samples to each partner. Samples were cultured and stained by each partner using their standard protocol and translocation frequency was used to produce dose estimates. Results: The coefficient of variation in the 1st IE (CV = 0.34) was higher than in the 2nd IE (CV = 0.16 and 0.23 in the two samples analyzed), for the genomic frequency of total translocations. Z-score analysis revealed that eight out of 10 and 17 out of 20 dose estimates were satisfactory in the 1st and 2nd IE, respectively. Conclusions: The results obtained indicate that, despite the problems identified in few partners, which can be corrected, the RENEB consortium is able to carry out retrospective biodosimetry analyzing the frequency of translocations by FISH. [ABSTRACT FROM AUTHOR]

In a similar way to high-dose exposures to low-LET radiations, cells show difficulties reaching mitosis after high-LET radiation exposure. For this reason, techniques have been proposed that are able to analyze chromosome aberrations in interphase by prematurely condensing the chromosomes (PCC-techniques). Few dose-effect curves for high-LET radiation types have been reported, and none for α-particles. The aim of this study was to evaluate, by chemically-induced PCC, the chromosome aberrations induced by several doses of α-particles. Monolayers of peripheral lymphocytes were exposed to an α-source of Americium-241 with a mean energy entering the cells of 2.7 MeV. Lymphocytes were exposed to 10 doses, from 0–2.5 Gy, and then cultured for 48 h. Colcemid and Calyculin-A were added at 24 and 1 h before harvesting, respectively. During microscope analysis, chromosome rings and extra chromosome pieces were scored in G2/M-PCC and M cells, while dicentric chromosomes were only scored in M cells. As the dose increased, fewer cells were able to reach mitosis and the proportion of G2/M-PCC cells increased. Chromosome rings were hardly observed in M cells when compared to G2/M-PCC cells. Extra fragments were more frequent than rings in both G2/M-PCC and M cells, but with lower frequencies than in G2/M-PCC cells. The distribution of dicentrics and extra fragments showed a clear overdispersion; this was not so evident for rings. The dose-effect curves obtained fitted very well to a linear model. Damaged cells after α-particle irradiation show more difficulties in reaching mitosis than cells exposed to γ-rays. After α-particle irradiation the frequency of all the chromosome aberrations considered increased linearly with the dose, and α-particles clearly produced more dicentrics and extra chromosome pieces with respect to γ-rays. After α-particle exposure, the existence of extra chromosome fragments in PCC cells seems to be a good candidate for use as a biomarker for dose assessment. However, the observed frequencies of different types of chromosomal aberrations could be influenced by some methodological aspects; for this reason, and in order to avoid possible methodological bias, standardization of the technique will be desirable. [ABSTRACT FROM PUBLISHER]

Purpose:To study polymorphic variants of repair genes in people affected by long-term exposure to radon. The chromosome aberration frequency in peripheral blood lymphocytes was used as the biological marker of genotoxicity. Materials and methods:Genotyping of 12 single nucleotide polymorphisms in DNA repair genes (APE,XRCC1,OGG1,ADPRT,XpC,XpD,XpG,Lig4andNBS1) was performed in children with long-term resident exposure to radon. Quantification of the aberrations was performed using light microscopy. Results:The total frequency of aberrations was increased in carriers of the G/G genotype for theXpDgene (rs13181) polymorphism in recessive model confirmed by the results of ROC-analysis (‘satisfactory predictor’, AUC = 0.609). Single chromosome fragments frequency was increased in carriers of the G/G genotype in comparison with the T/T genotype. In respect to the total frequency of aberrations, the G/G genotype for theXpGgene (rs17655) polymorphism was also identified as a ‘satisfactory predictor’ (AUC = 0.605). Carriers of the T/C genotype for theADPRTgene (rs1136410) polymorphism were characterized by an increased level of single fragments relative to the T/T genotype. Conclusion:The relationships with several types of cytogenetic damage suggest these three SNP (rs13181, rs17655 and rs1136410) may be considered radiosensitivity markers. [ABSTRACT FROM AUTHOR]

Purpose: To examine the influence of α-particle radiation exposure from internally deposited plutonium on chromosome aberration frequencies in peripheral blood lymphocytes of workers from the Sellafield nuclear facility, UK.Materials and methods: Chromosome aberration data from historical single colour fluorescencein situhybridization (sFISH) and Giemsa banding (G-banding) analyses, together with more recent sFISH results, were assessed using common aberration analysis criteria and revised radiation dosimetry. The combined sFISH group comprised 29 men with a mean internal red bone marrow dose of 21.0 mGy and a mean external γ-ray dose of 541 mGy. The G-banding group comprised 23 men with a mean internal red bone marrow dose of 23.0 mGy and a mean external γ-ray dose of 315 mGy.Results: Observed translocation frequencies corresponded to expectations based on age and external γ-ray dose with no need to postulate a contribution from α-particle irradiation of the red bone marrow by internally deposited plutonium. Frequencies of stable cells with complex aberrations, including insertions, were similar to those in a group of controls and a group of workers with external radiation exposure only, who were studied concurrently. In a similar comparison there is some suggestion of an increase in cells with unstable complex aberrations and this may reflect recent direct exposure to circulating lymphocytes.Conclusions: Reference toin vitrodose response data for the induction of stable aberrant cells by α-particle irradiation indicates that the low red bone marrow α-particle radiation doses received by the Sellafield workers would not result in a discernible increase in translocations, thus supporting thein vivofindings. Therefore, the greater risk from occupational radiation exposure of the bone marrow resulting in viable chromosomally aberrant cells comes from, in general, much larger γ-ray exposure in comparison to α-particle exposure from plutonium. [ABSTRACT FROM PUBLISHER]

Purpose: The need to determine a reliable relative biological effectiveness (RBE) value for alpha exposures has become important as reports remain controversial. Although a radiation-weighting factor of 20 has been designated for alpha particles, uncertainty exists on realistic value of the RBE of alpha radiation. The aim of this study was to estimate RBE values for radon using chromosome aberrations as the endpoint in respect to various dose rates of gamma radiation. Materials and methods: Human blood samples were exposed ex vivo to different doses of radon ranging from 0.0011–0.008 Gy. Blood samples were also exposed to gamma radiation with dose rates of 1, 0.1, 0.01 and 0.001 Gy/min. Chromosome aberrations in giemsa-stained first division metaphase preparations were scored. Results: Dose response curves for dicentric chromosomal aberration yields were generated for both radon and gamma rays. Radon dose rates were compared with gamma dose rates to deduce RBE values. The values obtained were 16, 25, 29 and 38 for reference gamma dose-rates of 1, 0.1, 0.01 and 0.001 Gy/min, respectively. Conclusions: The study indicates that an RBE value of radon can range between 16 and 38, if one were to consider chromosome aberrations as an effective biomarker of risk due to ionizing radiation. [ABSTRACT FROM PUBLISHER]

Purpose: To test the hypothesis that differences in DNA double-strand breaks (DSB) repair fidelity underlies differences in radiosensitivity. Materials and methods: A primary fibroblast culture (C42) derived from a pediatric cancer patient treated with reduced radiation doses consequent to a family history of radiosensitivity reminiscent of chromosomal fragility syndrome, was compared to a normal control (C29). DNA DSB rejoining and repair fidelity were studied by Southern blotting and hybridization to specific fragments: Alu repetitive sequence representing the overall DSB rejoining capacity in the genome and a 3.2 Mbp NotI restriction fragment on chromosome 21 for DSB repair fidelity. Results: Although both assays showed statistically significant difference ( p ≤ 0.05) between the two cell strains in residual misrepaired (un-or mis-rejoined) DSB (24 h after 30 or 80 Gy), the residual damage was lower in the Alu enriched genome assay compared to NotI assay (0.01-0.07 and 0.10-0.37, respectively). Conclusions: These results suggest that, in comparison to classic DSB repair experiment, an assay of measuring DNA DSB repair fidelity can provide better resolution and a more accurate estimate of misrepair of radiation-induced DNA damage, which underlies genomic instability and increased radiosensitivity. [ABSTRACT FROM AUTHOR]

Purpose: One of the most important issues regarding radiofrequency electromagnetic fields (RF-EMF) is their effect on genetic material. Therefore, we investigated the cytogenotoxic effects of 900 MHz radiofrequency electromagnetic fields (RF-EMF) and the effect of a recovery period after exposure to RF-EMF on bone marrow cells of immature and mature rats. Materials and methods: The immature and mature rats in treatment groups were exposed to RF-EMF for 2 h/day for 45 days. Average electrical field values for immature and mature rats were 28.1 ± 4.8 V/m and 20.0 ± 3.2 V/m, respectively. Whole-body specific absorption rate (SAR) values for immature and mature rats were in the range of 0.38-0.78 W/kg, and 0.31-0.52 W/kg during the 45 days, respectively. Two recovery groups were kept for 15 days after RF-EMF exposure. Results: Significant differences were observed in chromosome aberrations (CA), micronucleus (MN) frequency, mitotic index (MI) and ratio of polychromatic erythrocytes (PCE) in all treatment and recovery groups. The cytogenotoxic damage in immature rats was statistically higher than the mature rats. The recovery period did not reduce the damage to the same extent as the corresponding control groups. Conclusions: The exposure of RF-EMF leads to cytotoxic and genotoxic damage in immature and mature rats. More sensitive studies are required to elucidate the possible carcinogenic risk of EMF exposure in humans, especially children. [ABSTRACT FROM AUTHOR]

Purpose: Cells of the lung are at risk from exposure to low and moderate doses of ionizing radiation from a range of environmental and medical sources. To help assess human health risks from such exposures, a better understanding of the frequency and types of chromosome aberration initially-induced in human lung cell types is required to link initial DNA damage and rearrangements with transmission potential and, to assess how this varies with radiation quality. Materials and methods: We exposed normal human bronchial lung epithelial (NHBE) cells in vitro to 0.5 and 1 Gy low-linear energy transfer (LET) γ-rays and a low fluence of high-LET α-particles and assayed for chromosome aberrations in premature chromosome condensation (PCC) spreads by 24-color multiplex-fluorescence in situ hybridization (M-FISH). Results: Both simple and complex aberrations were induced in a LET and dose-dependent manner; however, the frequency and complexity observed were reduced in comparison to that previously reported in spherical cell types after exposure to comparable doses or fluence of radiation. Approximately 1-2% of all exposed cells were categorized as being capable of transmitting radiation-induced chromosomal damage to future NHBE cell generations, irrespective of dose. Conclusion: One possible mechanistic explanation for this reduced complexity is the differing geometric organization of chromosome territories within ellipsoid nuclei compared to spherical nuclei. This study highlights the need to better understand the role of nuclear organization in the formation of exchange aberrations and, the influence three-dimensional (3D) tissue architecture may have on this in vivo. [ABSTRACT FROM AUTHOR]

Purpose: Testicular seminoma cancer incidence has significantly increased over the last few decades, and although it is successfully treated by radiotherapy, long-term health risks are still unclear. The aim of the study was to show long-term genome damage in patients with seminoma after radiotherapy. Materials and methods: Chromosome aberration (CA) and micronucleus (MN) assays seven years after radiotherapy with a total dose of 25 Gy were conducted in 10 testicular seminoma patients aged 23-49 years and results were compared with 10 healthy control subjects matched for age and smoking status. Results: Although mean CA frequency did not deviate from control values, significantly increased frequencies of dicentrics, double minutes, and ring chromosomes were detected in seminoma patients. MN frequency in binuclear lymphocytes of patients was similar to controls (4.60/1000 vs. 5.82/1000, respectively). Significantly higher MN frequency was detected in mononuclear lymphocytes of patients than in controls (2.55/1000 vs. 0.73/1000, respectively). Average percentage of centromere-positive MN was 62.6% in seminoma patients. Conclusion: This study shows the persistence of unstable CA in seminoma patients seven years after radiotherapy and the relevance of long-term follow up. MN frequency in mononuclear lymphocytes was shown to be relevant biomarker of long-term genome damage. [ABSTRACT FROM AUTHOR]

Purpose: Biological effects produced by low doses of ionizing radiations, though relevant for the risk assessment, have not been fully elucidated. The aim of the present work was to evaluate cytogenetic endpoints, as telomere dysfunctions and chromosome instability in the low-dose range as a function of radiation quality. In particular, we analyzed whether the telomere length was modulated, as well as the involvement of telomeres in chromosomal alterations at anaphase, and the yield of stable simple and complex chromosome aberrations. Materials and methods: AG01522 human primary fibroblasts were irradiated with 0.1-1 Gy of X-rays, protons (28.5 keV/μm), and 4He2+ ions (62 keV/μm). Frequency of chromosome bridges carrying or not telomeric signals and telomere length were measured in irradiated samples up to 72 h. Moreover, chromosome instability was measured using multicolor fluorescence in situ hybridization (mFISH). Results: The results evidenced a linear energy transfer (LET)- and dose-dependent response in the frequency of anaphase bridges induction and in their persistence as a function of time. However, neither variation in telomere length and telomere loss, nor in the proportion of bridges bearing telomeric signals, was detected, thus indicating a minor role of telomeres in the generation of the radiation-induced chromosome bridges. Chromosome instability followed a linear-dependence with dose and LET, showing a far higher extent of complex translocations in helium-ion-irradiated cells than in proton- or X-ray-irradiated samples. Conclusions: Altogether, the results indicated the lack of telomere involvement in cytogenetic effects induced by low-dose ionizing radiation. On the contrary, chromosome aberration yield and spectrum were LET- and dose-dependent. [ABSTRACT FROM AUTHOR]

Purpose: The impact of the damage distribution to cellular survival and chromosomal aberrations following high Linear Energy Transfer (LET) radiation was investigated. Materials and methods: High LET iron-ions (500 MeV/n, LET 200 keV/μm) were delivered to G1-phase synchronized Chinese Hamster Ovary (CHO) cells located at a vertical or horizontal angle relative to the ion beam in order to give same dose but different fluence and damage distribution. Results: Horizontal irradiation produced DNA double-strand break (DSB) along each ion track represented as clustered lines, and vertical irradiation produced a greater fluence. The initial damages measured by premature chromosome condensation were equal per dose in both irradiation types. Horizontal irradiation proved to be less effective in cell killing than vertical at doses of more than 3 Gy. Vertical irradiation produced a higher number of metaphase chromosomal aberrations compared to horizontally irradiated samples. In particular, formation of exchange-type aberrations was the same, but that of deletion-type aberrations were significantly higher after vertical irradiation than horizontal irradiation. Conclusions: Therefore, we concluded that high fluence per dose is more effective than low fluence per dose to produce radiation-induced chromosomal aberrations and to kill exposed cells following high LET heavy-ion exposure. [ABSTRACT FROM AUTHOR]

Purpose: To study, characterize and compare chromosome aberrations and karyotype anomalies among newborns from high (> 1.5 mGy/y) and normal (≤ 1.5 mGy/y) level natural radiation areas of monazite-sand bearing southwest coast of Kerala in India. Materials and methods: Cord blood samples from newborns were collected from selected Government hospitals in heparinized vials and cultures were set up employing standard microculture techniques, slides were prepared, coded and stained with giemsa. Well spread metaphases were analyzed for chromosome aberrations and karyotype anomalies. Results: A total of 1,267,788 metaphases from 27,295 newborns of mothers aged 17-45 years (17,298 from high and 9,997 from normal level radiation areas) were analyzed during 1986-2007. Frequencies of dicentrics in high and normal level radiation areas were 1.90 ± 0.14 and 2.01 ± 0.26 per 10,000 cells, respectively (Relative frequency [RF] = 0.94; 95% CI: 0.71-1.26). Karyotype anomalies had a frequency of 5.49‰ and 6.7‰, respectively (RF = 0.82; 95% CI: 0.60-1.12). No dose-related trend was observed in chromosome aberrations or karyotype anomalies. Conclusion: Frequencies of chromosomal aberration and karyotype anomalies between the newborns from the high level natural radiation area (HLNRA) and normal level natural radiation areas (NLNRA) were very similar. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to compare levels of apoptosis, necrosis, mitotic cell death and senescence after treatment with both direct radiation and irradiated cell conditioned medium. Materials and methods: Human keratinocytes (HaCaT cell line) were irradiated (0.005, 0.05 and 0.5 Gy) using a cobalt 60 teletherapy unit. For bystander experiments, the medium was harvested from donor HaCaT cells 1 hour after irradiation and transferred to recipient HaCaT cells. Clonogenic assay, apoptosis, necrosis, mitotic cell death, senescence and cell cycle analysis were measured in both directly irradiated cells and bystander cells Results: A reduction in cell survival was observed for both directly irradiated cells and irradiated cell conditioned medium (ICCM)-treated cells. Early apoptosis and necrosis was observed predominantly after direct irradiation. An increase in the number of cells in G2/M phase was observed at 6 and 12 h which led to mitotic cell death after 72 h following direct irradiation and ICCM treatment. No senescence was observed in the HaCaT cell line following either direct irradiation or treatment with ICCM. Conclusion: This study has shown that directly irradiated cells undergo apoptosis, necrosis and mitotic cell death whereas ICCM-treated cells predominantly undergo mitotic cell death. [ABSTRACT FROM AUTHOR]

Background: A high cellular radiosensitivity may be connected with a risk for development of severe side effects after radiotherapy and indicate cancer susceptibility. Hence, a fast and robust in vitro test is desirable to identify radiosensitive individuals. Materials and methods: The study included 25 prostate cancer patients with severe side effects (S) and 25 patients without severe side effects (0) after radiotherapy as well as 23 male healthy age-matched donors. Blood samples were exposed to 0.5 Gy or 1 Gy of γ-rays. The initial level of double-strand breaks (dsb) and repair kinetics measured by phosphorylation of histone H2A (γ-H2AX-assay), apoptosis (Annexin V-assay) and the induction of chromatid aberrations after irradiation in the G2-phase of the cell cycle (G2-assay) were analysed. Results: A significant higher chromatid aberration yield was found in lymphocytes from prostate cancer patients when compared to healthy donors. We found no significant differences between patients S and patients 0. Conclusions: There is no obvious correlation between clinical and cellular radiosensitivity in lymphocytes of prostate cancer patients when all chosen in vitro assays are considered. Although 25% of the patients showed both severe side effects and increased radiation-induced chromosomal sensitivity, predictive value of G2-assay is doubtful. [ABSTRACT FROM AUTHOR]

Purpose: Our aim was to define dose-dependent and genotype-dependent components of radiosensitivity by resolving patterns of radiation-induced clonal inactivation into specific responses. Methods: In a set of 10 tumour cells with varying expression of radiosensitivity and genotype, we identified doses at which all tumour cells change in their rate of clonogenic inactivation. We tested intervening dose-segments as to whether inactivation was constant, expressing inactivation as a log-linear function of dose. We compared these segments to components proposed in the Hit-target (HT) model and the Linear-quadratic (LQ) model. Temporal changes in redistribution in cell-cycle prevalence and apoptosis were examined as essential components of cellular radiosensitivity. Results: We identified four distinct responses induced sequentially in all cells independent of genotype. Rates of inactivation within each response varied with expression of genotype and identified: (i) A hypersensitive component H (0.0--0.10 Gy); (ii) a resistant component R (0.1--0.2 Gy); (iii) an induced repair response alpha** (0.2 Gy and higher); and (iv) a more sensitive component omega** (3.0 Gy and higher). The H, alpha** and omega** components were fitted well by log-linear patterns, the R response did not. Conclusions: Four distinct, sequentially-induced responses comprise cellular radiosensitivity. H and R responses are associated with low dose hyper-radiosensitivity and early apoptosis, while the alpha** and omega** responses share characteristics of the HT and LQ models and are associated with post-repair apoptosis. Radiation induces these four responses at the same doses in all cells, but the rate of inactivation over each response depends on genotype. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of ubiquitin-like with plant homeodomain (PHD) and ring finger domains 1 (UHRF1) overexpression on radiosensitivity to X-rays in human breast cancer MDA-MB-231 cells. Materials and methods: Cell survival was determined by colony formation assay; cell cycle distribution was measured by flow cytometry; apoptosis was evaluated by DNA fragmentation assay and Annexin V apoptosis detection kit; protein expression was analysed by Western blot assay; chromosome aberrations (centric rings and dicentrics) were assayed by conventional chromosome analysis. Results: A significant decrease of radiosensitivity to X-rays was observed in MDA-MB-231 cells transfected with a full-length of human UHRF1 cDNA (MDA-MB-231/UHRF1) compared to the control cells (MDA-MB-231/parental and MDA-MB-231/pcDNA3 [[mammalian expression vector]]), and the similar results were observed in MDA-MB-468 cells. In contrast, a decreased expression of UHRF1 by a specific UHRF1-small interfering RNA (siRNA) significantly enhanced cell radiosensitivity. The UHRF1-mediated radioresistance was correlated with a G2Ra/M arrest, a decreased induction of apoptosis, a down-regulation of the pro-apoptotic protein anti-B cell lymphoma/leukemia 2 (bcl-2) associated X protein (Bax) and a up-regulation of the DNA damage repair proteins Lupus Ku autoantigen protein p70 (Ku-70) and Lupus Ku autoantigen protein p80 (Ku-80). Furthermore, chromosomal aberrations (centric rings and dicentrics) by X-rays were less in MDA-MB-231/UHRF1 than in MDA-MB-231/parental and MDA-MB-231/pcDNA3 control cells. Conclusions: These results suggested that UHRF1 may be a new target in the radiotherapy of breast cancer via affecting apoptosis and DNA damage repair. [ABSTRACT FROM AUTHOR]

Purpose: To quantitatively and qualitatively investigate the changes in chromosomal aberrations during early cleavage in mouse embryos derived from γγ-irradiated spermatozoa. Materials and methods: Mature males were exposed to 2 Gy or 4 Gy of 137Cs γγ-rays, and their spermatozoa were used to produce embryos via in  vitro fertilisation ((IVF)). The metaphase chromosomes were prepared from one-cell, two-cell, and four-cell embryos. In the chromosome preparations from two-cell and four-cell embryos, the separation of the sister blastomeres was precluded by treatment of the embryos with concanavalin A. The incidence of embryos with structural chromosomal aberrations, aneuploidy, or mosaicism was estimated. The fates of the different types of γγ-ray-induced structural chromosomal aberrations were also investigated in those embryos. Results: The exposure of spermatozoa to 2 Gy or 4 Gy γγ-rays caused structural chromosomal aberrations in 25.9%% and 35.7%% of the resultant one-cell embryos, respectively. At two-cell embryonic stage, the incidence of structural chromosomal aberrations was 17.4%% in the 2 Gy group and 27.1%% in the 4 Gy group. At the four-cell embryonic stage, although the incidence of control embryos with structural chromosomal aberrations was considerably high, the net incidence of embryos with radiation-induced structural chromosomal aberrations was similar to that at the one-cell stage. The incidence of aneuploidy was high in two-cell and four-cell embryos after both doses of γγ-rays. The incidence of mosaicism increased significantly in dose- and embryonic-stage-dependent manners. Anaphase lag, and the degeneration and non-disjunction of the aberrant chromosomes were frequently observed in aneuploid and mosaic embryos. Conclusions: Mouse sperm DNA is highly vulnerable to γγ-rays. The structural chromosomal aberrations of sperm origin are unstable in their behaviour and structure during cleavage, and therefore cause secondary aneuploidy and mosaicism in the early cleavage embryos. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the role of nucleophosmin (NPM/B23) in radiation-induced chromosomal instability and apoptosis in human lymphoblastoid cells with different protein 53 (p53) status. Materials and methods: Wild type (wt) p53 TK6 and mutant type (mt) p53 WTK1 with or without short hairpin RNA (shRNA)-mediated silencing of NPM, TK6 with or without short interfering RNA (siRNA)-mediated silencing of p53 (p53i and NEGi) were irradiated with 4 Gy gamma-rays. Six to 48 h after irradiation, the index of apoptosis, chromosome aberration, cell cycle distribution and the levels of total NPM and phosphorylated-threonine 199 (pThr199) NPM proteins were measured. Cells in some dishes were treated with 10 μM Olomoucine (OLO) for 3 h before irradiation and remained in the medium after irradiation. Results: The rates of radiation-induced apoptosis in TK6 and TK6/NEGi were about 2-fold of those in WTK1 and TK6/p53i, while the frequencies of polyploidy in TK6 and TK6/NEGi were obviously lower than those in WTK1 and TK6/p53i. Moreover, after irradiation, pThr199 NPM levels increased significantly in WTK1 and TK6/p53i, and slightly increased in TK6 and TK6/NEGi, indicating that the increased level of pThr199 NPM was related to p53 status. When Thr199 hyperphosphorylation of NPM was inhibited by OLO or when NPM was knocked down, we found that radiation-induced apoptosis was more pronounced and polyploidy formation was reduced as compared with negative control while the magnitude of these changes in TK6 was obviously higher than that in WTK1, indicating that NPM has an antagonistic interaction with wt p53. Conclusions: NPM/B23 plays an important role in protecting cells from radiation-induced apoptosis and increasing polyploidy formation via either a p53 or non-p53 pathway. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the distribution of chromosomal aberrations in chromosomes 2, 8 and 14 induced by charged particles, using the fluorescence in situ hybridisation (FISH) technique. Methods: Irradiation of peripheral blood from six healthy volunteers (four male and two female) was performed at the accelerators of the Joint Institute for Nuclear Research (JINR) in Dubna (Russia). Whole blood samples were irradiated with 2 and 3 Gy of protons (170 MeV/nucleon (n), linear energy transfer (LET) ≈ 0.5 keV/μm), 3.5 Gy of 12C ions (480 MeV/n, LET = 10.6 keV/μm), 3 Gy of 12C ions 500 MeV/n, LET = 12 keV/μm), 4 Gy of 7Li ions (30 MeV/n, LET ≈ 20 keV/μm) and 3 Gy of 11B ions (32 MeV/n, LET ≈ 55 keV/μm). Chromosomal aberrations were analysed in metaphase and prematurely condensed chromosomes (PCC) induced in G2-cells using calyculin A. Chromosomes 2, 8 and 14 were painted in different colours and aberrations scored with the help of an image-analysis system. Results: Chromosome 2 was generally less sensitive than expected on the basis of its DNA content. A higher than expected frequency of exchanges was found in chromosomes 8 and 14. On average, the dicentric frequency in chromosome 2 was higher than the translocation frequency, whereas variable dicentric to translocation ratios were observed in chromosomes 8 and 14. When aberrations in all painted chromosomes were summed up the ratio was close to 1. The frequency of complex aberrations correlated with LET. Conclusion: In lymphocytes of donors studied in this work chromosome 2 appears to be consistently less sensitive to protons and heavy ions than chromosomes 8 and 14. Complex aberrations appear to be a potential marker of radiation quality. [ABSTRACT FROM AUTHOR]