Cytogenetic effects of radiation and genetic polymorphisms of the XRCC1 and XRCC3 repair genes in industrial radiographers.

Different types of DNA damages caused by ionizing radiation may enhance the cancer risk in exposed individuals. Inherited variations in DNA repair genes cause the inter-individual variability in response to ionizing radiation. The purpose of this study was to determine the association between single nucleotide polymorphism (SNP) of two important DNA repair genes (XRCC1 R399Q and XRCC3 T241M) and the level of DNA damage investigated by micronucleus (MN) frequency in peripheral blood lymphocytes of 120 industrial radiographers (IR) and 120 non-exposed control individuals. The frequencies of MN and nucleoplasmic bridges were significantly higher in the IR group than in the control group (33.83 ± 11.96 vs. 7.47 ± 2.96, p < 0.0001 and 1.69 ± 1.86 vs. 0.12 ± 0.33, p < 0.0001). MN frequencies in the IR group were associated with the cumulative radiation doses (p < 0.0001, r = 0.58 for last 1 year of exposure and p < 0.0001, r = 0.67 for last 5 years of exposure). Polymorphism of XRCC3 T241M was associated with higher MN frequencies in the IR group. However, the same result was not observed between XRCC3 SNP and MN frequency in the control group. Consequently, XRCC3 241Met alleles may cause the increased DNA damage in the industrial radiographers.

226Ra, 238U and Cd adsorption kinetics and binding capacity of two cyanobacterial strains isolated from highly radioactive springs and optimal conditions for maximal removal effects in contaminated water.

Biomass-based decontamination methods are among the most interesting water treatment techniques. In this study, 2 cyanobacterial strains, Nostoc punctiforme A.S/S4 and Chroococcidiopsis thermalis S.M/S9, isolated from hot springs containing high concentrations of radium (226Ra), were studied to be associated with removal of radionuclides (238U and 226Ra) and heavy metal cadmium (Cd) from aqueous solutions. The adsorption equilibrium data was described by Langmuir and Freundlich isotherm models. Kinetic studies indicated that the sorption of 3 metals followed pseudo-second-order kinetics. Effects of biomass concentration, pH, contact time, and initial metal concentration on adsorption were also investigated. Fourier-transform infrared spectroscopy revealed active binding sites on the cyanobacterial biomass. The obtained maximum biosorption capacities were 630 mg g-1 and 37 kBq g-1 for 238U and 226Ra for N. punctiforme and 730 mg g-1 and 55 kBq g-1 for C. thermalis. These 2 strains showed maximum binding capacity 160 and 225 mg g-1, respectively for Cd adsorption. These results suggest that radioactivity resistant cyanobacteria could be employed as an efficient adsorbent for decontamination of multi-component, radioactive and industrial wastewater.

CONSTRUCTION AND VALIDATION OF IN VITRO DOSE-RESPONSE CALIBRATION CURVE USING DICENTRIC CHROMOSOME ABERRATION.

Cytogenetic biodosimetry is a well-known method for quantifying the absorbed dose based on measuring biological radiation effects. To correlate the induced chromosomal abberrations with the absorbed dose of the individuals, a reliable dose-response calibration curve should be established. This study aimed to use frequencies and distributions of radiation-induced dicentric chromosome aberrations to develop a standard dose-response calibration curve. Peripheral blood samples taken from six male donors irradiated by an X-ray generator up to 4 Gy were studied. Three different blood samples were irradiated by known doses, then scored blindly for verification of the proposed calibration curve. Dose estimation was also carried out for three real overexposed cases. The results showed good accordance with the other published curves. The constructed dose-response curve provides a reliable tool for biological dosimetry in accidental or occupational radiation exposures.

A COMPARISON OF OCCUPATIONAL DOSES IN CONVENTIONAL AND INTERVENTIONAL RADIOLOGY IN IRAN.

Occupational exposures in conventional and interventional radiology were investigated over a period of 10 years for all radiation workers. The statistical analysis carried out on the refined data showed that the average annual effective doses in conventional and interventional radiology were 0.28 and 0.59 mSv for measurably exposed workers and 0.18 and 0.52 mSv for all monitored workers in 2014. More than 99.9 and 82.8% of radiation workers in conventional and interventional radiology received annual doses less than the public dose limit (1 mSv) in 2014. Comparing the occupational dose levels of different countries (including Iran) in conventional as well as interventional radiology showed a poor comparability among them. Regarding the doses above the investigation level, the analysis showed that majority of them were due to improper use of personal dosimeters (false doses) and only 0.01 and 0.12% of the dose records actually crossed the level in conventional and interventional radiology in 2014.

A cytogenetic biomonitoring of industrial radiographers occupationally exposed to low levels of ionizing radiation by using cbmn assay.

Industrial radiography is the process of using either gamma-emitting radionuclide sources or X-ray machines to examine the safety of industrial materials. The average annual effective dose in industrial radiography is one of the highest among radiation workers. The aim of this study was to investigate the cytogenetic effects of ionizing radiation in the peripheral blood lymphocytes of 60 industrial radiographers and 40 non-exposed individuals as the control group by using cytokinesis-block micronucleus (CBMN) assay. Totally, the frequencies of micronuclei (MN), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) were significantly higher in the industrial radiographers than in the controls (p = 0.000). The mean MN frequency per 1000 binucleated cells in the industrial radiographers with last 5-y radiation dose of >100 mSv was significantly higher than those with ≤100 mSv (34.81 ± 12.7‰ vs. 26.33 ± 7.94‰, p = 0.024). The effect of age was observed in the control group and subjects with the age of >30 y showed significantly higher MN frequency compared with the subjects with the age of ≤30 y (9.45 ± 3.71‰ vs. 6.81 ± 3.05‰, p = 0.02). No obvious trend of increased MN as a function of either duration of employment or age or smoking status was observed in the industrial radiographers. The results show the increased levels of cytogenetic damages in the industrial radiographers. Even the workers exposed to the permissible doses are subjected to elevated frequencies of DNA damages. These findings confirm the importance of cytogenetic biomonitoring program beside physical dosimetry, surveying radiation safety of equipment and periodic training of workers for improvement of safety and radiation protection.

PHYSICIANS' KNOWLEDGE ABOUT RADIATION DOSE AND POSSIBLE RISKS OF COMMON MEDICAL TESTS: A SURVEY IN IRAN.

Recent data suggest that knowledge of radiation exposures among physicians is inadequate. This study, therefore, aimed to evaluate their knowledge of the radiation doses their patients received and awareness of associated biological risks of radiation exposure. A questionnaire in multiple-choice format consisted of four sections with a total of 10 questions based on the literature review. A total of 136 questionnaires were returned from 69 general practitioners and 67 physicians in various specialties from 10 different hospitals in the capital city of Tehran, Iran. Fifty-four percent of general practitioners and twenty-five percent of specialties declared that they are not aware of biological risks of radiation exposure. Fifty-six percent of physicians did not know the correct definition of absorbed dose. Only 33% of physicians knew the dose exposure of a chest X-ray and only 31% knew the approximate doses of various procedures relative to a chest X-ray. Forty-seven percent of physicians incorrectly distinguished the stochastic effects of radiation from the deterministic effects, and thirty-eight of physicians did not know the organs of the body that are most sensitive to ionizing radiation. Only 23.5% of physicians were aware of the one in 2000 risk of induction of fatal carcinoma from computed tomography of the abdomen. Seventy-nine percent of physicians incorrectly underestimated the contribution of nuclear and radiological tests in exposure of an average person. The mean score of the specialties trended toward being more accurate than general practitioners (4.18 ± 1.28 vs. 3.89 ± 1.46, respectively, from a potential accurate total score of 9), but these differences were not statistically significant. Among specialists, orthopedics had the highest scores. The present study demonstrated the limited knowledge of radiation exposures among general practitioners and specialists and a need to improve their knowledge by means of targeted training and re-education.

Cytogenetic monitoring of personnel working in angiocardiography laboratories in Iran hospitals.

Angiocardiography is an X-ray examination of the blood vessels or chambers of the heart for evaluation of the number and severity of blockages in arteries that supply blood to the heart. Cardiologists and staff members applying these procedures are exposed to high levels of scattered radiation. In the present study we analyzed and followed-up on the cytogenetic effects of X-ray angiography in personnel of laboratories for treatment of cardiovascular disease. According to film dosimeter analysis, personnel received 0.25-15 mSv during the previous year (average of 3 mSv/y), which indicated an exposure below the limit established by the International Commission on Radiological Protection (ICRP). Samples of peripheral blood were collected from cardiologists, nurses and technicians and from a matched control group. The incidence of unstable chromosomal aberrations (dicentrics, acentric fragments, ring chromosomes) and cytokinesis-blocked micronuclei were analyzed. Results show a high frequency of acentric fragments in cardiologists, nurses and technicians compared to controls (P < 0.001). When the exposed groups were compared, a higher percentage of acentric fragments was observed in the nurses and technicians compared to cardiologists (P = 0.004). Six individuals presented with dicentric chromosomes and their equivalent whole-body doses ranged from 0.05 to 0.10 Gy. No correlation was observed between chromosome aberrations and annual effective dose or age of the exposed groups. Although the mean frequency of chromosome aberrations in the male workers was slightly higher than in the females, no significant difference was observed between male and female workers in each group (P = 0.86). The mean number of micronuclei per 1000 binucleated cells was significantly higher in the exposed groups compared with the matched control group (P < 0.001). In a follow-up study, chromosome aberrations in lymphocytes of 23 exposed personnel were analyzed five times during 3 years. Results show that the mean number of acentric fragments decreased gradually during 36 months in those workers who followed the radiation protection guides. The results of this study emphasize the importance of individual biomonitoring, limiting exposure and radiation safety programs.

Differential proteome analysis of a selected bacterial strain isolated from a high background radiation area in response to radium stress.

The present study describes the response of a bacterial strain, isolated from a hot spring in an area with the highest levels of natural radiation, under radium ((226)Ra) stress. The bacterium has been characterized as a novel and efficient radium biosorbent and identified as a variant of Serratia marcescens by biochemical tests and molecular recognition. In order to gain insights into key cellular events that allow this strain to survive and undergo (226)Ra adaptation and biosorption, the strain was tested under two experimental conditions of 1000 and 6000 Bq (226)Ra stress. A proteomic approach involving two-dimensional polyacrylamide gel electrophoresis and mass spectrometry was used to identify the differentially expressed proteins under (226)Ra stress. Functional assessment of identified proteins with significantly altered expression levels revealed several mechanisms thought to be involved in (226)Ra adaptation and conferring resistant phenotype to the isolate, including general stress adaptation, anti-oxidative stress, protein and nucleic acid synthesis, energy metabolism, efflux and transport proteins. It suggests that this strain through evolution is particularly well adapted to the high background radiation environment and could represent an alternative source to remove (226)Ra from such areas as well as industrial radionuclide polluted wastewaters.

A cytogenetic approach to the effects of low levels of ionizing radiations on occupationally exposed individuals.

The aim of the present study was to assess occupationally induced chromosomal damage in hospital workers exposed to low levels of ionizing radiation. Thirty-two interventional cardiologists, 36 nuclear medicine physicians and 33 conventional radiologists were included in this study, along with 35 healthy age- and sex-matched individuals as the control group. We used conventional metaphase chromosome aberration (CA) analysis, cytokinesis-block micronucleus (MN) assay as important biological indicators of ionizing radiation exposure. Occupational dosimetry records were collected over the last year (ranged from 0.25 to 48mSv) and their whole life exposure (ranged from 1.5 to 147mSv). The results showed significantly higher frequencies of dicentric and acentric CAs (p<0.001) and MN (p<0.01) in all exposed groups than in the controls. Taking all the confounding factors into account, no obvious trend of increased chromosomal damages as a function of either duration of employment, exposed dose, sex or age was observed. Interventional cardiologists had the highest rates of CA and MN frequencies between the worker groups, though the differences were not significant. These results indicate that long term exposure to low dose ionizing radiation could result in DNA damage. Hence, the personnel who work in the hospitals should carefully apply the radiation protection procedures.

Serratia sp. ZF03: an efficient radium biosorbent isolated from hot-spring waters in high background radiation areas.

The aim of this study is to isolate and characterize (226)Ra biosorbing indigenous bacterial strains from soils and hot-springs containing high concentrations of (226)Ra by using biochemical and molecular approaches. Fifteen bacteria were isolated and their phylogenetic affiliations were determined based on their 16S rRNA gene and the two most relevant hypervariable regions of this gene; V3 and V6 analysis. A pigmented Serratia sp. ZF03 strain isolated from the water with (226)Ra content of 50471 mBq l(-1), caused 70% removal of (226)Ra at a radioactivity level of 50 Bq ml(-1), after 5 min and 75-80% in equilibrium time of 1 h, depending on the particular biosorption system and experimental conditions studied. The biosorption equilibrium was described by Langmuir and Freundlich isotherm models. Kinetic studies indicated that the biosorption follows pseudo-second-order kinetics. Effect of different physico-chemical parameters on (226)Ra sorption, FTIR, SEM and TEM analysis were also investigated.

Alteration of peripheral blood T-reg cells and cytokines production in angiography personnel exposed to scattered X-rays.

Angiocardiography is an X-ray examination of the blood vessels or chambers of the heart. Cardiologists and staff members applying this procedure are exposed to high levels of scattered radiation. In our previous study the incidence of unstable chromosomal aberrations and cytokinesis-blocked micronuclei were found to be significantly higher in exposed individuals than the age and sex matched controls. In the present study we assessed cytokine production by peripheral blood mononuclear cells of the above cases and the percentage of Treg cells. According to film dosimeter analysis, personnels received 0.25-15 mSv during the previous year (average of 3 mSv/y). Isolated PBMCs from the test and control groups were stimulated with Phorbol Myristate Acetate/ Ionomycin (PMA/I). Cytokine production was measured in the supernatants of cultured lymphocytes. The percentage of Treg cells was studied by flow cytometry. The production of IL-10 and IL-5 was significantly down-regulated in the test group compared to the control group. In contrast, IL-12 was up-regulated. Yet, no statistically significant difference was found for IFN- gamma between two groups. In addition, we found higher percentage of CD4+CD25+(bright) Treg cells in the study group compared to the controls. Taken together, it was shown that low doses of scattered X-rays could skew cytokine profile of peripheral blood mononuclear cells in favour of inflammatory response causing the increase of Treg cells.