Cytogenetic monitoring of hospital workers occupationally exposed to ionizing radiation using the micronucleus centromere assay

A cytogenetic study was performed in lymphocytes of hospital workers occupationally exposed to X- and gamma-rays using the micronucleus centromere assay. A comparison of the data for the exposed group and an age-matched group of non-exposed hospital workers showed a significant (P < 0.05) increase in centromere-positive micronuclei for the radiation workers, while no effect on centromere-negative micronuclei was present. The observed systematic increase in micronucleus frequency with age was mainly due to increased chromosome loss, reflected in the centromere-positivity of the micronuclei. The micronucleus frequencies were 40% higher in females than in males, which can again be attributed to higher chromosome loss. Two exposed individuals showed exceptionally high micronucleus yields, 90% of which were centromere-positive. In situ hybridization with a centromeric probe for chromosome X shows that X chromosome loss is responsible for these high micronucleus yields. In the studied population, smoking had no significant effect on the micronucleus yields. The results obtained indicate that in contrast to the predominantly clastogenic action of acute exposure to ionizing radiation, the aneugenic properties of radiation may be important after long-term chronic low dose exposure.     

Health status of persons occupationally exposed to chromium, nickel, manganese and polycyclic aromatic hydrocarbons

Occupational environment monitoring and biological-medical monitoring of persons professionally exposed to welding fumes have been performed. Chromium, manganese and polycyclic aromatic hydrocarbons in welding fumes represents an important health risk. Pollutant concentrations found in metal welding fumes represented only fractions of those acceptable ones. Polycyclic aromatic hydrocarbons have been reached the concentration found in a busy road crossing in Hradec Králové (compared with these as in Czech Republic no maximum acceptable levels for PAHs having been declared). Family, personal and occupational history have been taken. Health state including total haematological count, biochemical and cytogenetical changes of 19 stainless steel welders were checked-up. The level of mercapturates in urine were examined as well. The data were statistically compared with those of non exposed (control group). No changes witnessing the above mentioned risk factors influence on the haematological, biochemical and cytogenetical findings were ever proved. In conclusion, our results did not confirm an increased professional risk in this group of welders.     

Chromosomal aberrations and micronucleus frequency in nurses occupationally exposed to cytotoxic drugs

In this study, we evaluated the effect of low level occupationalexposure of nurses in a medical oncology unit in Cairo, Egypt,to anticancer drugs. Twenty nurses who constantly handled thesedrugs and 20 controls, matched according to age and sex, wereexamined. Metaphase chromosomes were studied. Percentages ofmetaphases with chromosomal aberrations were significantly higher(P < 0.001) in the exposed group (6.1 ± 2.7) versusthe controls (2.6 ± 1.6). The detected chromosomal aberrationswere in the form of chromatid gaps, chromatid breaks and acentricfragments. Micronucleated peripheral blood lymphocytes werealso analyzed in cytochalasin B treated binucleated lymphocytes.There was significant increase in cells with micronuclei (P< 0.001) in nurses (10.05 ± 4.71) in comparison tothe matched control (5.42 ± 2.22) (P < 0.001). Nursesexposed to the cytotoxic drugs for     

Genotoxic effects of oestrogens in breast cells detected by the micronucleus assay and the Comet assay

Cumulative exposure to oestrogen has been linked to increased risk of breast cancer. Whilst oestrogens induce cancers in rodent bioassays it is unclear whether the mechanisms involved are genotoxic and/or epigenetic. The cytokinesis block micronucleus (CBMN) and the alkaline single cell-gel electrophoresis 'Comet' assays were used to examine MCF-7 cells for chromosomal damage and DNA single-strand breaks (SSBs), respectively. The comet-forming activities of oestrogens were also tested in a 72 h primary culture of cells isolated from freshly expressed breast milk. Micronuclei (MN) were scored in 500 binucleate cells per treatment and SSBs were quantified by comet tail length (CTL) (microm). Effects on mitotic rate (per cent binucleate cells) and cell viability (per cent plating efficiency) were also assessed. beta-Oestradiol, oestrone and oestriol were tested for genotoxicity in the 10(-10)-10(-4) M and 10(-10)-10(-2) M concentration ranges in the CBMN and Comet assays, respectively. Beta-Oestradiol, following 24 h treatment but not 120 h treatment, induced increases (up to 3-fold) in MN at a concentration of 10(-9) M. Oestrone induced dose-related increases in MN (up to 5-fold) following both 24 and 120 h treatment, whereas oestriol appeared not to induce MN. All three oestrogens induced dose-related increases in per cent binucleate cells suggesting that they enhance mitotic rate. In the Comet assay both beta-oestradiol and oestrone induced dose-related increases in SSBs (up to 7-fold over control CTL) and were significantly comet-forming (P < 0.0001) at concentrations as low as 10(-9) and 10(-8) M, respectively, whereas oestriol was less genotoxic. All three oestrogens were significantly comet-forming (P < 0.0001) in a primary culture of breast milk cells, suggesting that they can damage the target cells from which breast cancers may eventually arise.     

A cytokinesis-blocked micronucleus study of the radioadaptive response of lymphocytes of individuals occupationally exposed to chronic doses of radiation

Human lymphocytes pre-exposed to very low doses of ionizingradiation show an adaptive response, which make these cellsless sensitive to subsequent higher exposures. To verify thehypothesis that a similar phenomenon can be induced by occupationally(in vivo) received doses of ionizing radiation, the cytogeneticresponses of 24 medical radiation workers to 1 and 2 Gy     

Chromosomal aberration,micronucleus and Comet assays on peripheral blood lymphocytes of leprosy patients undergoing multidrug treatment

To evaluate the genetic damage in leprosy patients, we carried out the alkaline Comet assay and chromosomal aberration (CA) and micronucleus (MN) tests in peripheral blood lymphocytes of 50 leprosy patients receiving multidrug treatment (MDT) and 50 healthy individuals. The Comet assay showed statistically higher mean values for length to width ratios of DNA mass (P < 0.01) and for mean frequencies of tailed cells (P < 0.001) in cells of leprosy patients than in those of controls. Similarly, the mean frequencies of micronucleated cells (per 1000 cytochalasin B-induced binucleated cells) were significantly greater (P < 0.001) in leprosy patients (19.92 +/- 2.564) than in controls (1.6 +/- 0.231). A statistically significant 10-fold increase in the frequency of CAs (11.16 +/- 0.411) was observed in leprosy patients compared with controls (1.28 +/- 0.242). In multiple regression analyses, when patients and controls were considered together, disease factor alone significantly influenced the genotoxicity markers. In the control group, age and alcohol consumption significantly influenced MN and length to width ratios and CA frequency, respectively. However, in MDT-treated leprosy patients none of the other confounding factors (sex, age, smoking and alcohol drinking) significantly affected the extent of genetic damage.     

The alkaline Comet assay as biomarker in assessment of DNA damage in medical personnel occupationally exposed to ionizing radiation

The alkaline Comet assay was selected as a biomarker of exposure to evaluate the ongoing exposure to ionizing radiation of 50 medical workers occupationally exposed to ionizing radiation and 50 corresponding unexposed control subjects. The primary DNA damage was evaluated by measuring the extent of DNA migration in peripheral blood leukocytes. The inter-individual differences in DNA damage between exposed subjects were compared with their dosimeter readings and occupation. It was found that medical workers who were occupationally exposed to ionizing radiation for different periods of time showed highly significant increases in levels of DNA damage compared with controls. However, influences of the different occupational settings and doses absorbed on the levels of DNA damage, assessed by use of the Comet assay, might be excluded in the majority of subjects. Differences in comet parameters measured due to smoking and gender were not statistically significant in either exposed or control subjects. The results obtained have confirmed the usefulness of the alkaline Comet assay as an additional complement to standard biodosimetric methods. By detection of momentary DNA damage and/or repair activity, it reflects the concurrent exposure and the actual levels of DNA damage present in peripheral blood leukocytes of the radiological workers at the moment of blood sampling.     

In vitro sensitivities to UVA of lymphocytes from patients with colon and melanoma cancers and precancerous states in the micronucleus and the Comet assays

To use lymphocytes as surrogate cells to investigate their in vitro sensitivities to ultraviolet (UV) treatment in different cancers and precancerous states by comparison with lymphocytes from healthy control individuals was the main aim of this research. UV light induces precise cellular and genomic mutations. In this study, the effect of ultraviolet A (UVA) (320-400 nm) was used as a generic mutagen to evaluate in vitro different sensitivities from lymphocytes of patients with suspected melanoma (SM), malignant melanoma (MM), polyposis coli (PC) and colorectal cancer (CRC). DNA damage was evaluated by two different methods: the micronucleus (MN) assay and the Comet assay. The baseline frequency of MNs was significantly increased in lymphocytes from all patients (SM, MM, PC and CRC) when compared to healthy individuals. After UV irradiation, MN frequencies were significantly increased in lymphocytes of all groups, both patients and healthy individuals. However, the MN frequency in all patient groups was significantly higher than in the healthy individual group. Similar results for the induction of genomic DNA damage were obtained for the Comet assay. Also for the Comet assay, UVA-induced DNA damage for all four patient groups was significantly increased when compared to healthy individuals (SM, MM, PC and CRC groups: P < 0.001). Conclusively, peripheral lymphocytes from patients with cancers MM and CRC or precancerous states SM and PC are more sensitive to a generic mutagen such as UVA than lymphocytes from healthy individuals. This feature may be used as an essential biomarker to screen and diagnose precancerous states and cancers in early stages.     

Risk assessment of welders using analysis of eight metals by ICP-MS in blood and urine and DNA damage evaluation by the comet and micronucleus assays; influence of XRCC1 and XRCC3 polymorphisms

The aims of the present study were to assess the occupational risk of welders using analysis of metals in biological fluids, DNA damage evaluation by complementary genotoxic endpoints and the incidence of polymorphisms in DNA repair genes. A biomonitoring study was conducted that included biometrology (blood and urinary concentrations of aluminium, cadmium, chromium, cobalt, lead, manganese, nickel, zinc by ICP-MS), comet and cytokinesis-block micronucleus assays in peripheral lymphocytes and genetic polymorphisms of XRCC1 (p.Arg399Gln) and XRCC3 (p.Thr241Met). This study included 60 male welders divided into two groups: group 1 working without any collective protection device and group 2 equipped with smoke extraction systems. A control group (n = 30) was also included in the study. Higher chromium, lead and nickel blood and urinary concentrations were detected in the two groups of welders compared to controls. Statistically differences between welders of group 1 and group 2 were found for blood concentration of cobalt and urinary concentrations of aluminium, chromium, lead and nickel. The alkaline comet assay revealed that welders had a significant increase of OTMchi2 distribution at the end of a work week compared to the beginning; a significant induction of DNA strand breaks at the end of the week was observed in 20 welders out of 30. The cytokinesis-block micronucleus assay showed that welders of group 1 had a higher frequency of chromosomal damage than controls. The XRCC1 variant allele coding Gln amino acid at position 399 was found to be associated with a higher number of DNA breaks as revealed by the comet assay. Increased metal concentrations in biological fluids, DNA breaks and chromosomal damage in lymphocytes emphasized the need to develop safety programmes for welders.     

Investigating genetic damage in workers occupationally exposed to methotrexate using three genetic end-points

Genetic damage in workers occupationally exposed to an antineoplastic drug was studied using the micronucleus (MN) test, the comet assay, the hprt gene mutation assay and the TCR gene mutation assay. The subjects were divided into two groups: (i) 21 workers from a plant producing methotrexate (MTX); (ii) 21 controls were matched according to age, gender and smoking. Fresh blood samples were collected from the workers and controls. The results of the MN test showed that the mean micronuclei rate (MNR) and mean micronucleated cell rate (MCR) in workers were 10.10 +/- 0.95 per thousand and 8.05 +/- 0.75 per thousand, respectively, which were significantly higher than those (5.48 +/- 0.82 per thousand and 4.38 +/- 0.58 per thousand) in controls (P < 0.01). It was found in the comet assay that the mean tail length (MTL) of workers and controls were 1.30 +/- 0.06 microm and 0.07 +/- 0.01 microm, respectively. There was a significant difference between workers and controls for MTL (P < 0.01), but the difference between the mean tail moment (MTM, 0.23 +/- 0.03) of workers and MTM (0.17 +/- 0.04) of controls was not significant (P > 0.05). The results of hprt gene mutation assay showed that the average mutation frequency (Mf-hprt) of hprt in workers was 1.00 +/- 0.02 per thousand, which was significantly higher than that (0.86 +/- 0.01 per thousand) in controls (P < 0.01). Meanwhile, the results of TCR gene mutation assay indicated that Mfs-TCR gene mutation frequencies of workers and controls were 6.87 +/- 0.52 x 10(-4) and 1.67 +/- 0.14 x 10(-4), respectively, which were significantly different (P < 0.01). The results of our experiment suggest that genetic damage is detectable in the 21 workers occupationally exposed to methotrexate.     

Medical examination of the workers occupationally exposed to ionizing radiation

The hazardous effects of ionizing radiation to man are well recognized, and they are divided into two groups, the stochastic effects (hereditary and carcinogenic effect) and non-stochastic effects (somatic effects such as depression of hematopoiesis, chronic dermatitis and cataracta). The basic framework of the International Commission on Radiological Protection (ICRP) is intended to prevent the occurrence of non-stochastic effects, by keeping doses below the relevant thresholds, and to ensure that all reasonable aspects are taken to reduce the incidence of stochastic effects. In Japan, the regulatory provisions of radiological protection of the workers occupationally exposed to ionizing radiation are based on the recommendation of ICRP adopted in 1977. According to these regulations, the dose equivalent limits of occupational exposure of man has been decided at 50 mSv/year. The monitoring of exposure to the individual and the procedure of medical examination of the workers are briefly described and discussed.     

Reflections on the development of micronucleus assays

These are personal reflections on the development of methods to use micronuclei as a measure of genetic damage and their use in research and in toxicology by four people who have been intimately involved with this work, a personal rather than a comprehensive history. About 6000 papers have been published using such methods in many tissues in vivo or in cultured cells of many organisms from plants to humans, but the majority of the work has been on mammalian erythrocytes and human lymphocytes, the areas in which we have worked primarily. Although this is by no means a complete history, those working in the field may be interested in some of the personal events that lie behind the development and acceptance of methods that are now standard.     

Fish as bioindicators to assess the effects of pollution in two southern Brazilian rivers using the Comet assay and micronucleus test

Industrial effluents, agricultural runoff, and municipal wastewaters contain unknown substances and complex mixtures that are released into the environment and can lead to contamination of surface and subsurface waters. In the present report, we have used the alkaline Comet assay and the micronucleus (MN) test to detect the genotoxicity due to multiple sources of pollution in the peripheral blood of two native estuarine fish (mullet and sea catfish) and evaluated possible interactive genotoxic effects from multiple contaminants and the seasonal variation of the genotoxicity. Mullet and sea catfish were captured in the Tramandai and Mampituba Rivers in the southern Brazilian state of Rio Grande do Sul. Reference animals were obtained from the Armazem lagoon. Fish captured in the two estuaries during the four seasons over a period of 2 years had increased levels of DNA damage and MN frequencies relative to the reference fish. In general, the alkaline Comet assay was more sensitive to the genotoxicity of the river contaminants than the MN test. The Comet assay demonstrated significant differences in fish captured at different seasons and at the two river sites, while the MN test showed significant differences only for the annual average for mullet from both sites and fish from the control site. The increases in DNA damage appear to be related to the increase in the number of people in the towns close to the study areas during the warm spring and summer seasons. Although no specific cause-effect relationships were established, comparison of the chemical contaminants and physical variations in the rivers with the genotoxicity data indicate that there may be some association between hydrocarbons, metals, pH, and water temperature and the level of damaged cells observed in mullet and sea catfish from the Tramandai and Mampituba estuaries.     

Genotoxicity biomonitoring in coal regions using wild rodent Ctenomys torquatus by Comet assay and micronucleus test

Coal is a mixture of a variety of chemicals, especially hydrocarbons, which may give rise to polycyclic aromatic hydrocarbons (PAH). Many PAH compounds produce mutagenic and carcinogenic effects. The quality of mineral coal in Rio Grande do Sul (RS) is low and it is typically obtained by stripping operations; it represents approximately 87% of the Brazil reserves. This report concerns the application of the Comet assay to Ctenomys torquatus to detect the effects of coal, comparing the results with a micronucleus (MN) assay, both using peripheral blood. This study was performed over a 2-year period in an attempt to evaluate seasonal patterns. The wild rodent is fossorial, and its geographic distribution in RS coincides with the distribution of coal reserves. Three localitions were studied: two coal fields, Butiá (in a strip coal mine region) and Candiota (near a strip coal mine), and one control region, Pelotas (no coal). At the end of 2 years, 240 rodents had been analyzed. Our results showed that coal and derivatives induced DNA and chromosomal lesions in rodent cells that were demonstrated by Comet and MN assays. These tests also demonstrated quantitative differences between field exposures (Candiota > Butiá). The Comet assay was more sensitive and also showed a direct relationship between age and damage, and an inverse relationship between temperature and damage index.     

Assessment of DNA damage in lymphocytes of workers exposed to X-radiation using the micronucleus test and the comet assay.

The mutagenic and carcinogenic effects of genotoxic agents on exposed people have constituted an increasing concern. Therefore, the objective of this work was to assess DNA damage in lymphocytes of workers exposed to X-radiation using the cytokinesis-blocked micronucleus test and the comet assay (single-cell gel electrophoresis), and to compare these two techniques in the monitoring of exposed populations. The cytokinesis-blocked micronucleus test and the comet assay were employed in the monitoring of 22 workers occupationally exposed to X-radiation in a hospital in southern Brazil. The frequency of dicentric bridges was also measured. The results of both assays and the frequency of dicentric bridges revealed a significant increase in genetic effects on the cells of exposed individuals. Age was significantly correlated with micronucleus frequency and damage index in the comet assay. The concomitant analysis of dicentric bridges when determining micronucleus frequency does not require much extra work, and may serve as a reference to the type of mutagenic effect (clastogenic or aneugenic). The combination of the alkaline comet assay with the cytokinesis-blocked micronucleus test appears to be very informative for the monitoring of populations chronically exposed to genotoxic agents.     

Genotoxic effects in the Eastern mudminnow (Umbra pygmaea) after prolonged exposure to River Rhine water,as assessed by use of the in vivo SCE and Comet assays

The production of drinking water from river water requires a certain minimal river water quality. The Association of River Rhine Water Works (RIWA), therefore, operates a monitoring network. In vitro mutagenicity studies have shown that the genotoxicity of the River Rhine water steadily decreased from 1981 until 2001. Compared to a study in 1978, a decrease in genotoxicity was also observed in an in vivo genotoxicity study in 2005, in which Eastern mudminnows (Umbra pygmaea) were exposed to River Rhine water, and gill cells were used for the Sister Chromatid Exchange (SCE) test and the Comet assay. In this 2005 study, the in vivo genotoxicity increased upon extending exposure of the fish from 3 to 11 days. Therefore, the objectives of this study were to investigate (i) whether new data corroborate that in vivo genotoxicity of River Rhine water is at present lower than in 1978, (ii) whether the Comet assay is a suitable alternative to the SCE assay, and (iii) whether further prolonged exposure results in a further increase in in vivo genotoxicity. The new data corroborate that in vivo genotoxicity of River Rhine water is at present lower than in 1978. The Comet assay is a useful addition but does not provide a substitute for the SCE endpoint in these in vivo genotoxicity studies. Prolonging the exposure time of Eastern mudminnows to River Rhine water from 11 to 42 days did not give a significant increase in SCEs and DNA damage (Comet assay) in gill cells. Mol. Mutagen. 2012. © 2012 Wiley Periodicals, Inc.     

Sensitization and lung function in workers occupationally exposed to natural thickening products

BACKGROUND: Three workers engaged in the manufacture of natural thickener products (Cassia spp., guar, and tamarind flour) were occupationally sensitized to Cassia spp. Therefore, a cross-sectional study on the prevalence of sensitization among and respiratory health of the employees of this plant was conducted. METHODS AND RESULTS: Sixty-two workers (36 with high, 26 with low exposure) participated in the survey. Skin prick tests and specific IgE tests with extracts of these components revealed that 11.3% were sensitized to Cassia spp. and 9.7% to at least one species of storage mites, with a significantly higher portion of atopic subjects in the sensitized group. Overall, 55% of the subjects reported work-related symptoms (upper and lower airways, eyes, or skin). FVC % pred. was significantly lower in highly exposed workers, while RV % pred. and RV%TLC % pred. were significantly higher in this group. In the multivariate model, sensitization was not a risk factor for impairment of lung function. CONCLUSIONS: Dust exposure to flours may not only cause allergic sensitization but also induce chronic changes in lung function.     

镍铬合金烤瓷冠对人体尿中镍、铬离子的影响

背景：镍铬合金烤瓷冠因其机械性能优良、低廉价格,在国内口腔修复领域广泛应用。 目的：观察镍铬合金烤瓷冠对患者尿中镍、铬离子的量的影响。 方法：选择2009-03/2010-03在新疆医科大学第一附属医院就诊戴用镍铬合金烤瓷冠患者55例为实验组,同期未做任何修复治疗者55例为对照组,比较2组患者尿中镍、铬的离子水平。 结果与结论：镍铬合金冠修复患者尿镍、铬离子水平与对照组接近(P > 0.05),且镍铬合金烤瓷冠数量<5个与≥5个的患者的镍、铬离子水平也接近(P > 0.05),但与使用镍铬合金烤瓷冠<5年的患者相比,使用年限≥5年者的尿镍、尿铬离子水平升高(P < 0.05,P < 0.01)。提示镍铬合金烤瓷冠修复不会影响患者尿中镍、铬离子水平,但镍铬合金烤瓷冠使用年限会影响患者尿中的镍、铬离子的水平。     

Genotoxic risk and oxidative DNA damage in workers exposed to antimony trioxide

The growing use of antimony (Sb) compounds in industry and the consequent increase in the number of exposed workers make it important to carry out a health risk assessment. The main goal of this study was to assess the genotoxicity of Sb(2)O(3) in occupationally exposed workers. Genotoxicity was evaluated by the sister chromatid exchange (SCE) and micronucleus tests, and the enzyme (Fpg)-modified comet assay. In addition, antimony exposure levels were established by environmental monitoring with personal air samplers. We studied 23 male workers assigned to different fire retardant treatment tasks in the car upholstery industry and a control group of 23 healthy nonexposed males. The exposed workers were divided into two groups on the basis of their tasks and the work cycle: Group A comprised finishing and intermediate inspection operators who directly handled a mixture containing Sb(2)O(3); Group B were jet operators, not directly exposed to the compound. Environmental monitoring detected low Sb exposure levels but significant differences between the two groups, with Group A having the higher exposure level. Cytogenetic analyses showed no difference between exposed workers and controls for micronuclei and SCE. The enzyme-modified comet assay showed a probable relation between moderate levels of oxidative DNA damage and exposure to antimony, with a significantly higher proportion of workers in Group A having oxidative DNA damage compared to controls. The results support the theory that oxidative DNA damage is involved in the genotoxicity of antimony and indicate the need for further research in this field.