Frequency of micronuclei in peripheral blood lymphocytes from subjects occupationally exposed to low levels of ionizing radiation

Genotoxicity of Gamma Radiation Against Lymphocytes of Radiation Workers: The Cytokinesis-Block Micronucleus Assay

<b>Background and Objective:</b> Gamma irradiation induces genotoxicity, characterized by the formation of extra-nuclear bodies and left behind during the anaphase stage of cell division, often referred to as a micronucleus (MN). The present work aims to monitor exposure to ionizing radiation as a genotoxic agent in the lymphocytes of workers at radiation energy centers. <b>Materials and Methods:</b> The lymphocyte cytokinesis block micronucleus assay used and analyzed the correlation between the Nuclear Division Index (NDI), age, blood type and the number of micronuclei (MN). Blood samples were collected from 20 volunteers in heparin tubes, exposed to 2 Gy gamma rays and cultured <i>in vitro</i>. <b>Results:</b> A significant difference in the number of micronuclei between blood group A and blood groups A, B and AB. The Nuclear Division Index (NDI) value for lymphocytes of radiation energy center workers after gamma radiation was significant (1.74±0.1) but still within the normal range. Neither MN frequency nor NDI values correlated with age, but MN frequency showed a correlation with blood type. <b>Conclusion:</b> The gamma irradiation did not induce a cytostatic effect but proved genotoxic to the lymphocytes of radiation energy center workers. Notably, blood type A demonstrated higher sensitivity to gamma radiation.

Biological response to the continuous occupational exposure to antineoplastic drugs and radionuclides

PURPOSE

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.

MATERIALS AND METHODS

Blood samples from 314 healthy donors divided into 3 groups (control, exposed to antineoplastic drugs and exposed to radioiodine) were collected and cytogenetically analyzed.

RESULTS

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.

CONCLUSION

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.

Re-evaluation of CBMN test reference values of persons continuously occupationally exposed to low doses of ionizing radiation in Serbia

When established, cytokinesis-block micronucleus (CBMN) test reference values should be periodically evaluated according to the recommendations of reference documents. The biodosimetry cytogenetic laboratory of the Serbian Institute of Occupational Health established the CBMN test reference range for people occupationally exposed to ionizing radiation in 2016. Since then, new occupationally exposed persons have been subjected to micronucleus testing, resulting in the need for re-evaluation of existing CBMN test values. The examined population comprised 608 occupationally exposed subjects - 201 from the previous laboratory database and 407 newly examined. Comparison of groups based on gender, age and cigarette consumption did not show significant differences, although certain CBMN values differed significantly between the old and new groups. Duration of occupational exposure, gender, age and smoking habit influenced micronuclei frequency in all three analyzed groups, while no relation was found between type of work and micronucleus test parameters. Since the mean values of all tested parameters in the new group of examinees are within previously established reference ranges, existing values can be used in further research.

Factors associated with genetic damage - an analysis integrating human populations from Southern Brazil

Socioeconomic and demographic factors, lifestyle and cultural characteristics may play an important role in the development of genetic damage. This damage represents a potential health risk to an individual and increases the risk of developing negative outcomes. The aim of this study was to investigate the association of a set of factors and genetic damage by gathering data from previously studied populations in southern Brazil. This study analyzed data related to genetic damage and socioeconomic, demographic, and lifestyle variables of 514 individuals aged 18 to 64 years, residing in 8 cities located in the extreme south of the Brazil. A total of twelve factors were considered in the analysis, and of these seven had some association with the frequency of micronucleus or some parameter of the comet assay. Interestingly, age was a factor weakly associated with genetic damage, while skin color, occupational exposure, drug use, exposure to radiation, and the cultural habit of consuming chimarrão were shown to be associated with genetic damage when analyzed using multivariate regression. Therefore, we suggest that yerba mate consumption is a confounding factor and should be considered in cytogenetic studies in the southern region of South America. These results reinforce the need for human biomonitoring studies to include consideration of a broad range of population and cultural characteristics when seeking to identify relevant associations.

Biomarkers of Genotoxicity in Medical Workers Exposed to Low-Dose Ionizing Radiation: Systematic Review and Meta-Analyses

Medical staff represent the largest group of workers occupationally exposed to ionizing radiation (IR). Chronic exposure to low-dose IR may result in DNA damage and genotoxicity associated with increased risk of cancer. This review aims to identify the genotoxicity biomarkers that are the most elevated in IR-exposed vs. unexposed health workers. A systematic review of the literature was performed to retrieve relevant studies with various biomarkers of genotoxicity. Subsequent meta-analyses produced a pooled effect size for several endpoints. The search procedure yielded 65 studies. Chromosome aberrations (CA) and micronuclei (MN) frequencies were significantly different between IR-exposed and unexposed workers (θ_pooled = 3.19, 95% CI 1.46–4.93; and θ_pooled = 1.41, 95% CI 0.97–1.86, for total aberrant cells and MN frequencies, respectively), which was not the case for ring chromosomes and nucleoplasmic bridges. Although less frequently used, stable translocations, sister chromatid exchanges (SCE) and comet assay endpoints were also statistically different between IR-exposed and unexposed workers. This review confirms the relevance of CA and MN as genotoxicity biomarkers that are consistently elevated in IR-exposed vs. unexposed workers. Other endpoints are strong candidates but require further studies to validate their usefulness. The integration of the identified biomarkers in future prospective epidemiological studies is encouraged.

Chronic exposure to low doses of ionizing radiation impacts the processing of glycoprotein N-linked glycans in Medaka (Oryzias latipes)

PURPOSE

Ionizing radiation is found naturally in the environment. Low doses of IR may have beneficial applications, yet there is also potential for detrimental long-term health effects. Impacts following exposure to low levels of IR have been refractory to identification and quantification. Glycoprotein glycosylation is vital to cell-cell communication and organismal function, and sensitive to changes in an organism's macro- and cellular environment. We investigated whether accumulated low doses of IR (LoDIR) affect the N-linked glycoprotein glycans using Medaka fish (Oryzias latipes).

MATERIALS AND METHODS

State-of-the-art methods in radiation exposure and glycan analysis were applied to study N-glycan changes after 190 day exposure at three different rates of gamma irradiation (2.25, 21.01, and 204.3 mGy/day) in wild-type adult Medaka. Tissue N-glycans were analyzed following enzymatic release from extracted proteins.

RESULTS

N-linked glycan profiles are dominated by complex type N-glycans modified with terminal sialic acid and core fucose. Fucosylation and sialylation of N-linked glycoprotein glycans are affected by LoDIR and a subset of N-glycans are involved in the organismal radio-response.

CONCLUSION

This is the first indication that the glycome can be interrogated for biomarkers that report the impact of chronic exposure to environmental stressors, such as low-level IR.

Genotoxic risk in health-care professionals occupationally exposed to low doses of ionizing radiation

The purpose of this study was to evaluate the potential influence of occupational ionizing radiation (IR) exposure on health professionals, assessing DNA damage using the comet and micronucleus (MN) assays and analyzing relative risks, correlations, and associated factors between outcomes and socioeconomic and lifestyle factors. Blood and buccal samples were collected from 36 workers, who actively participated in an imaging sector of a hospital, who were either exposed to IR directly or indirectly (9 internal control and 27 exposed), and 27 individuals living in the same city but with no occupational exposure (external control, unexposed/healthy). All radiation dosages performed on the 36 workers were less than 20 mSv/y, not exceeding the effective dose limit for occupational exposure. A questionnaire identified socioeconomic and lifestyle factors associated with the outcomes. The results of the MN assay showed a significant difference between both internal control and the exposed group when compared to the external control. For the comet assay, there were significant differences between the percent of tail DNA of the exposed group and external controls, but no difference was found between the exposed group and internal controls. Relative risk associations were found in time of exposure, hours worked per week, and perceived stress. Correlations were found between the outcomes and age, consumption of alcohol, and frequencies of X-rays during life. Variables that showed to be significant in the adjusted analysis were skin color and recent exposure to radiation. Albeit limited, the findings of this study suggest genotoxicity in both blood and buccal mucosa cells of workers exposed directly or indirectly to IR and that lifestyle and socioeconomic factors are associated and correlated with the risk of developing these outcomes.

Genotoxic risk in health-care professionals occupationally exposed to low doses of ionizing radiation

The purpose of this study was to evaluate the potential influence of occupational ionizing radiation (IR) exposure on health professionals, assessing DNA damage using the comet and micronucleus (MN) assays and analyzing relative risks, correlations, and associated factors between outcomes and socioeconomic and lifestyle factors. Blood and buccal samples were collected from 36 workers, who actively participated in an imaging sector of a hospital, who were either exposed to IR directly or indirectly (9 internal control and 27 exposed), and 27 individuals living in the same city but with no occupational exposure (external control, unexposed/healthy). All radiation dosages performed on the 36 workers were less than 20 mSv/y, not exceeding the effective dose limit for occupational exposure. A questionnaire identified socioeconomic and lifestyle factors associated with the outcomes. The results of the MN assay showed a significant difference between both internal control and the exposed group when compared to the external control. For the comet assay, there were significant differences between the percent of tail DNA of the exposed group and external controls, but no difference was found between the exposed group and internal controls. Relative risk associations were found in time of exposure, hours worked per week, and perceived stress. Correlations were found between the outcomes and age, consumption of alcohol, and frequencies of X-rays during life. Variables that showed to be significant in the adjusted analysis were skin color and recent exposure to radiation. Albeit limited, the findings of this study suggest genotoxicity in both blood and buccal mucosa cells of workers exposed directly or indirectly to IR and that lifestyle and socioeconomic factors are associated and correlated with the risk of developing these outcomes.

Chromosomal aberrations in C-arm fluoroscopy, CT-scan, lithotripsy, and digital radiology staff

We have assessed chromosome-type aberrations and micronuclei in the peripheral lymphocytes of personnel working with C-arm fluoroscopy, multi-slice CT-scan, lithotripsy, and digital radiology medical procedures. The study population comprised of 46 exposed workers and 35 controls matched for age, gender, and other confounding factors. Chromosome-type aberrations and micronuclei were analyzed and compared with occupational dosimetry data. The highest frequency of both chromosome aberrations (1.62 CA/100 cells) and MN (MN = 7.47 ± 2.55) was observed in the operating room group. According to occupational dosimetry, surgeons and medical staff received 0-2.99 mSv over the previous year, well below the limit established by the International Committee on Radiation Protection. An increased level of chromosomal aberrations was observed among workers exposed in the operating rooms. We recommend that operating room radiation safety programs be improved and better supervised, in particular for orthopedic surgeons and personnel performing fluoroscopically guided procedures.

Assessment of the nuclear medicine personnel occupational exposure to radioiodine

PURPOSE

To physically and cytogenetically screen medical personnel of Department of Endocrinology and Nuclear Medicine, Holy Cross Cancer Center, Kielce, Poland (DENM) who are occupationally exposed to ¹³¹I.

MATERIALS AND METHODS

The exposure was monitored by whole-body and finger ring dosimeters. The thyroid iodine intake was measured by a whole-body spectrometer equipped with two semiconductor gamma radiation detectors. A cytokinesis-block micronucleus assay and the premature chromosome condensation technique were used to assess the aberration score. Cytogenetic analyses were carried out on a group of 29 workers and were compared to 32 controls (healthy donors), matched for gender and age.

RESULTS

On average, the exposed group showed a significantly higher frequency of genetic damage and a higher proliferation index compared to the control group. Smoking status, age and duration of exposure influenced the observed effects in both groups. No differences in measured biomarkers were observed after stratification of the exposed group into two subgroups based on the measured ¹³¹I activity below and above 6 Bq.

CONCLUSION

The findings suggest that radiation protection principles based on whole-body and finger ring dosimetry, supported by activity measurements with a whole-body spectrometer, may be insufficient to monitor the absorbed dose estimation of the nuclear medicine staff who are occupationally exposed to ¹³¹I. Furthermore, their future health risks are influenced by confounders. Direct assessments comparing physical and biological dose estimations on the larger group are needed to accurately monitor occupational radiation exposure.

THE INVESTIGATION OF MICRONUCLEI FREQUENCY DISTRIBUTION FOR EXPOSED AND UNEXPOSED PERSONNEL TO IONIZING RADIATION

To establish at which extent the micronuclei (MN) frequency is influenced by occupational exposure to ionizing radiation, peripheral blood samples collected from 2151 subjects of both genders, smokers and non-smokers were analyzed. Among them, 378 (17.6%) were unexposed while the other 1773 (82.4%) were exposed to ionizing radiation for periods between 1 year and more than 30 years, at levels never overpassing legally regulated limits. The final results showed that for all investigated categories, MN frequency monotonously increases with the age by 1.75 ± 0.17 times in the case of exposed subjects, but independent on gender and smoking habit.

Chronic low dose exposure of hospital workers to ionizing radiation leads to increased micronuclei frequency and reduced antioxidants in their peripheral blood lymphocytes

Purpose: The regular low dose occupational exposure to ionizing radiation may induce deleterious health effects, which may be of particular interest to medical radiation workers who daily handle X-ray machines. Human peripheral blood lymphocytes are able to retain the signature of radiation-induced DNA damage, therefore, the present study was undertaken to investigate the DNA damage and antioxidants status in hospital workers occupationally exposed to low doses of X-rays. Materials and methods: The peripheral blood lymphocytes of the occupationally exposed and control groups matched for age, gender, tobacco usage, and alcohol consumption were cultured and micronuclei frequency was determined. Activities of antioxidant enzymes and lipid peroxidation were also estimated in their plasma. Results: The micronuclei frequency in the occupationally exposed group (n = 33), increased significantly (p < .0001) followed by reduced glutathione-s-transferase (p < .01) and catalase (p < .001) activities, and increased lipid peroxidation (p < .05) when compared to the control group (n = 33). Occupational exposure resulted in an effective dose ranging between 3.14 to 144.5 mSv (40.88 ± 39.86mSv) depending on the employment duration of 3-29 years (10.33 ± 7.05 years). A correlation between the micronuclei frequency (p < .05) and catalase activity (p < .05) existed in the occupationally exposed individuals depending on the smoking habit, age, duration of employment, cumulative exposure dose and number of patients handled per day. Conclusions: We have observed that protracted low dose exposure to ionizing radiation is an inevitable occupational hazard leading to persistence of oxidative stress and increased genomic instability in the radiological technicians depending on the time spent with X-rays, cumulative dose received and the number of patients handled daily raising the risk of cancer development.

The Frequency of Lymphocytes Containing Dumbbell-Shaped Nuclei Depends on Ionizing Radiation Dose and Correlates with Appearance of Chromosomal Aberrations

Nuclear anomalies of different types appear in cells in response to the action of ionizing radiation after the passage of the first mitotic division. In this article, we present the results of the study of the frequency of occurrence of three types of nuclear anomalies ("tailed" nuclei, nucleoplasmic bridges, and dumbbell-shaped nuclei) in vitro in human lymphocytes cultured with cytochalasin B when exposed to X-rays at doses of 0.0, 0.1, 0.2, 0.4, 0.5, 0.7, 1.0, 1.5, and 2.0 Gy. To stop the cell cycle of cultured lymphocytes after the first mitotic division, a cytokinesis block was performed using cytochalasin B. Dose-dependent curves of the occurrence of lymphocytes containing "tailed" nuclei, nucleoplasmic bridges, or dumbbell-shaped nuclei after irradiation have been constructed. At the same time, frequencies of occurrence of chromosomal aberrations (dicentric and ring chromosomes) in the culture of lymphocytes exposed to the same radiation doses were studied. Comparison of the frequencies of occurrence of dicentric and ring chromosomes with frequencies of occurrence of nuclear anomalies allows us to conclude that these nuclear anomalies are formed as a result of chromosomal aberrations arising in lymphocytes under the action of ionizing radiation. More than that, most of the chromosomal aberrations are converted into dumbbell-shaped nuclei in vitro in the culture of lymphocytes in the cytochalasin block.

Radio-adaptive response in peripheral blood lymphocytes of individuals residing in high-level natural radiation areas of Kerala in the southwest coast of India

The present study investigates whether the chronic low-dose radiation exposure induces an in vivo radio-adaptive response in individuals from high-level natural radiation areas (HLNRA) of the Kerala coast. Peripheral blood samples from 54 adult male individuals aged between 26 and 65 years were collected for the study with written informed consent. Each of the whole blood sample was divided into three, one was sham irradiated, second and third was exposed to challenging doses of 1.0 and 2.0 Gy gamma radiation, respectively. Cytokinesis-block micronucleus (CBMN) assay was employed to study the radio-adaptive response. Seventeen individuals were from normal-level natural radiation area (NLNRA ≤1.5 mGy/year) and 37 from HLNRA (> 1.5 mGy/year). Based on the annual dose received, individuals from HLNRA were further classified into low-dose group (LDG, 1.51-5.0 mGy/year, N = 19) and high-dose group (HDG >5.0 mGy/year, N = 18). Basal frequency of micronucleus (MN) was comparable across the three dose groups (NLNRA, LDG and HDG, P = 0.64). Age of the individuals showed a significant effect on the frequency of MN after challenging dose exposures. The mean frequency of MN was significantly lower in elder (>40 years) individuals from HDG of HLNRA as compared to the young (≤40 years) individuals after 1.0 Gy (P < 0.001) and 2.0 Gy (P = 0.002) of challenging doses. However, young and elder individuals within NLNRA and LDG of HLNRA showed similar frequency of MN after the challenging dose exposures. Thus, increased level of chronic low-dose radiation (>5.0 mGy/year) seems to act as a priming dose resulting in the induction of an in vivo radio-adaptive response in elder individuals of the Kerala coast.

Micronuclei as a marker for medical screening of subjects continuously occupationally exposed to low doses of ionizing radiation

CONTEXT

Genotoxicity assays are widely employed in human biomonitoring studies to assess genetic damage inflicted by genotoxic agents.

OBJECTIVE

Evaluation of micronuclei (MN) as a screening marker of occupational ionizing radiation (IR) exposure.

MATERIALS AND METHODS

Using micronucleus test, peripheral blood lymphocytes (PBL) of 402 control and exposed subjects were screened for genetic damage.

RESULTS

The mean frequencies of micronucleus test parameters were significantly higher in exposed persons. Increase of micronucleus yield with duration of exposure (DOE) by 0.303MN/year was revealed.

DISCUSSION AND CONCLUSION

The obtained data encourage us to consider MN as valuable markers for preventive medical screening of occupationally exposed groups.

Effects of age on the frequency of micronuclei and degenerative nuclear abnormalities

Abstract The effects of aging, gender and lifestyle factors on inducing chromosomal damage (micronuclei) and nuclear degenerative changes were assessed using the micronucleus test on exfoliated cells of the oral mucosa. The sample included 80 healthy subjects divided into four groups according to age and gender: men and women aged 19-29 years (M19, W19) and men and women aged over sixty years (M60, W60). An interview questionnaire was used to characterize the sample and to determine an index reflecting lifestyle (HLI). The frequency of micronuclei and nuclear degenerative changes was significantly higher among the elderly (p<0.001) and did not differ by gender among young people (p>0.05). The occurrence of micronuclei was similar among elderly men and women (p>0.10), but karyorrhexis and karyolysis were more frequent among men (p<0.005 and p<0.025, respectively), who also had a lower HLI than the other groups (p<0.0004). The results of the study indicate that age is the main factor associated with the induction of genetic material damage.

Apoptosis and morphological alterations after UVA irradiation in red blood cells of p53 deficient Japanese medaka (Oryzias latipes)

Morphological alterations in red blood cells were described as hematological bioindicators of UVA exposure to investigate the sensitivity to UVA in wild type Japanese medaka (Oryzias latipes) and a p53 deficient mutant. The fewer abnormal red blood cells were observed in the p53 mutant fish under the control conditions. After exposure to different doses of UVA radiation (15min, 30min and 60min/day for 3days), cellular and nuclear alterations in red blood cells were analyzed in the UVA exposed fish compared with non-exposed controls and those alterations included acanthocytes, cell membrane lysis, swollen cells, teardrop-like cell, hemolyzed cells and sickle cells. Those alterations were increased after the UVA exposure both in wild type and the p53 deficient fish. Moreover, apoptosis analyzed by acridine orange assay showed increased number of apoptosis in red blood cells at the higher UVA exposure dose. No micronuclei but nuclear abnormalities as eccentric nucleus, nuclear budding, deformed nucleus, and bilobed nucleus were observed in each group. These results suggested that UVA exposure induced both p53 dependent and independent apoptosis and morphological alterations in red blood cells but less sensitive to UVA than Wild type in medaka fish.

Peripheral blood lymphocyte micronucleus frequencies in men from areas of Kerala, India, with high vs normal levels of natural background ionizing radiation

We have measured the frequencies of micronuclei (MN) in adult male individuals living in areas of the Kerala coast, southwest India, with either high (HLNRA, >1.5mGy/year) or normal levels of natural ionizing radiation (NLNRA, ≤1.5mGy/year). Blood samples were obtained from 141 individuals, 94 from HLNRA and 47 from NLNRA, aged 18-72, and were subjected to the cytokinesis-block micronucleus (CBMN) assay. An average of 1835 binucleated (BN) cells per individual were scored. The overall frequency of MN (mean±SD) was 11.7±6.7 per 1000 BN cells. The frequencies of MN in the HLNRA (11.7±6.6) and NLNRA (11.6±6.7) were not statistically significantly different (P=0.59). However, a statistically significant (P<0.001) age-dependent increase in MN frequency was observed among individuals from both HLNRA and NLNRA. No natural background radiation dose-dependent increase in MN frequency was seen. MN frequency was not influenced by tobacco smoking or chewing but it was increased among individuals consuming alcohol. Chronic low-dose radiation in the Kerala coast did not have a significant effect on MN frequency among adult men.

Effect of l-Thyroxine on Micronuclei Frequency in Peripheral Blood Lymphocytes in Clinical and Experimental Conditions

The aim was to study the genotoxic effect of high concentration of thyroxine (T4) in vivo in peripheral blood lymphocytes (PBL) of the patients suffering from thyroid disorders. The effect was compared by performing in vitro experiments with addition of increasing concentration of T4 (0.125-1 µM) in whole blood samples from healthy donors. Cytokinesis-blocked micronuclei (CBMN) assay method was used to assess the DNA damage in the PBL. The study included 104 patients which were grouped as control (n = 49), hyperthyroid (n = 31) and hypothyroid (n = 24). A significant increase in micronuclei (MN) frequency was observed in hyperthyroid patients when compared with the hypothyroid and euthyroid group thereby suggesting increased genotoxicity in hyperthyroidism (p < 0.001). A significant increase in MN frequency was observed at T4 concentration of 0.5 µM and above when compared to lower T4 concentrations (0.125 and 0.25 µM) and basal in in vitro experiments (p = 0.000). The results indicate that the T4 in normal concentration does not exhibit the genotoxic effect, as observed in both the in vivo and in vitro experiments. The toxicity of T4 increases at and above 0.5 μM concentration in vitro. Therefore acute T4 overdose should be handled promptly and effectively so as to avoid the possible genotoxic effect of high concentration of T4 in vivo.

Assessment of the genotoxicity and cytotoxicity in environmentally exposed human populations to heavy metals using the cytokinesis-block micronucleus cytome assay

The cytokinesis-block micronucleus cytome (CBMN-Cyt) assay was developed as a system for evaluating DNA damage, cytostasis, and cytotoxicity. The aim of the present study was to estimate levels of micronuclei (MNi), nucleoplasmic bridges (NPBs), nuclear buds (NBUDs), cell death (apoptosis/necrosis), nuclear division index, and nuclear division cytotoxicity index values in the peripheral blood lymphocytes of environmentally exposed subjects to heavy metals from five Bosnian regions, characterized by different exposure to heavy metals. The study was performed using CBMN-Cyt assay, considering factors, such as age, gender and smoking habits and their possible effects on analyzed parameters. In total, 104 healthy subjects were selected (49.04% females and 50.96% males; average age, 35.41 years; 51.92% smokers and 48.08% nonsmokers). There was significant difference between the frequency of NBUDs in Tuzla as compared to the control group. Furthermore, there was observed a statistically significant difference for the frequency of NPBs between Zenica, Olovo, and Kakanj when compared with the controls. Males showed a significantly higher number of apoptotic cells than females in controls. There were significant differences between smokers and nonsmokers in the frequency of NPBs in controls (higher in nonsmokers) and necrotic cells in Olovo (higher in nonsmokers). The pack years of smoking significantly influenced the number of necrotic cells in controls and the frequency of NBUDs in the overall sample. The results of the present study provide evidence of significantly increased frequency of NPBs and NBUDs in exposed subjects, suggesting that these endpoints are highly sensitive markers for measuring genotoxicity.

Nuclear and cytoplasmic changes in erythrocytes of p53-deficient medaka fish (Oryzias latipes) after exposure to gamma-radiation

Previous studies have examined the effects of gamma-radiation on Japanese fish, in particular medaka (Oryzias latipes). In the present work, alterations in erythrocytes were recorded as haematological bio-indicators of exposure to gamma-radiation. After exposure of medaka fish to two different doses of radiation (2 Gy and 10 Gy), many malformations in red blood cells were observed in the irradiated fish compared with control fish. These malformations included acanthocytes, crenated cells, amoeboid cells, and sickle cells. More malformations were seen at the higher radiation dose. No micronuclei were seen in any group, but nuclear abnormalities were observed. We conclude that gamma-radiation causes morphological malformations of erythrocytes and is harmful to medaka fish.

Cytogenetic analysis of peripheral blood lymphocytes, many years after exposure of workers to low-dose ionizing radiation

The present study aims to measure chromosomal aberrations and micronuclei in peripheral blood lymphocytes from 25 subjects exposed to 0.10-0.33 Gy external or internal irradiation 32-41 years ago using conventional cytogenetic analysis methods. The frequencies of total chromosome-type aberrations and micronucleus significantly increased in the exposed group compared with that in age-matched control group (p<0.001); chromatid-type aberrations showed no difference between the two groups (p>0.05). When exposed subjects were divided into two groups based on exposure dose, higher levels of dicentric plus translocation frequencies were observed in the ≥0.15 Gy dose group compared with those in the <0.15 Gy dose group, though the difference was not significant. Borderline association between exposure dose and dicentric frequency was detected in the exposed group (r=0.358; p=0.079). These results suggest that the genotoxic effects of ionizing radiation remain in subjects exposed to low-dose radiation even decades after exposure.

Assessment of chromosomal aberrations and micronuclei in peripheral lymphocytes from tunisian hospital workers exposed to ionizing radiation

Epidemiological studies suggest that cytogenetic biomarkers, such as micronuclei (MN) in peripheral blood lymphocytes may predict cancer risk because they indicate genomic instability. The objective of the present study was to evaluate the frequencies of MN and chromosome aberrations (CA) in peripheral blood lymphocytes of hospital workers exposed to ionizing radiation and healthy subjects. The study was conducted using peripheral blood lymphocytes from 30 workers from the radiology department and 30 from the cardiology department. This study included 27 healthy age- and sex-matched individuals as the control group. The assessment of chromosomal damage was carried out by the use of CA and micronucleus assays in peripheral lymphocytes. Our results show that CA and micronucleus frequencies were significantly higher among the exposed groups when compared to controls. Our finding of significant increase of CA and MN frequencies in peripheral lymphocytes in exposed workers indicates a potential cytogenetic hazard due to this exposure. The enhanced chromosomal damage of subjects exposed to genotoxic agents emphasizes the need to develop safety programs.

The micronucleus assay as a biological dosimeter in hospital workers exposed to low doses of ionizing radiation

The health risk associated with low levels of ionizing radiation is still a matter of debate. A number of factors, such as non-target effects, adaptive responses and low-dose hypersensitivity, affect the long-term outcome of low-dose exposures. Cytogenetic bio-dosimetry provides a measure of the absorbed dose, taking into account the individual radiation sensitivity. The aim of the present study is to evaluate the value of the micronucleus (MN) test as a bio-dosimeter in hospital workers exposed to low doses of ionizing radiation. Blood samples were obtained from 30 subjects selected among workers exposed to X- and gamma-radiation, and 30 controls matched for sex, age and smoking from the same hospital. Micronucleus frequencies were analyzed by use of the cytokinesis-block method. The MN frequency was compared among the groups considering the confounding factors and the length of employment. No increase in the number of bi-nucleated cells with MN (BNMN), but a significant increase in the number of mono-nucleated cells with micronuclei (MOMN) was observed in exposed subjects compared with the controls. The relationship between MN frequency and accumulated dose (mSv) was evaluated. The length of employment did not affect the extent of MN frequency, but an increase of BNMN and MOMN cells was observed based on the accumulated radiation dose. Our study shows the sensitivity of the MN test in the detection of cytogenetic effects of cumulative exposure levels, suggesting the potential usefulness of this assay in providing a biological index in medical surveillance programs.

Biodosimetry using radiation-induced micronuclei in skin fibroblasts

PURPOSE

We assessed micronuclei in dermal fibroblasts as a local biodosimeter for estimating accidental in vivo radiation exposure.

MATERIALS AND METHODS

Male and female C3H/HeJ and C57Bl6 mice of four age groups (∼11, 36, 60 and 99 weeks) received a single whole body dose of gamma radiation (0-10 Gy) and radiation-induced micronuclei per 1,000 binucleated cells were assessed in skin fibroblasts in their first division after isolation from biopsies taken on days 1 and 7 post irradiation. The method of generalized estimating equations was used for statistical analyses.

RESULTS

Total micronuclei were increased on day 1 in a dose-dependent manner in the range of 1-10 Gy, with no significant attenuation of response between day 1 and day 7 and no significant effect of gender. Between-strain differences were observed with C3H/HeJ mice showing lower background micronuclei and a slightly steeper dose response. Age affected only the background micronuclei (moderate increase with age). The model demonstrated that the assay yields 'unbiased' prediction of the dose between 0 and 7 Gy. Within this dose range, the predicted dose was found to be accurate within ±1.5-2 Gy. When the specificity is set to 95%, the assay can distinguish between unexposed and 2 Gy exposed mice with a sensitivity of around 60%. The sensitivity approached 100% when discriminating between unexposed mice and mice receiving doses equal to or greater than 4 Gy. The percentage of binucleated cells with micronuclei was shown to be useful as a simpler and slightly faster substitute for the total micronuclei count.

CONCLUSION

Micronuclei in dermal fibroblasts isolated up to 1 week after irradiation can be a useful biodosimeter for local dose after accidental radiation exposure.

Chromosomal damage and apoptosis in exfoliated buccal cells from individuals with oral cancer

This study aimed to investigate cytological abnormalities indicative of chromosome damage (micronuclei) and apoptosis (karyorrhexis, pyknosis, and condensed chromatin) in exfoliated cells from the buccal mucosa of patients with oral cancer and control subjects. The sample included twenty individuals with oral cancer and forty individuals with normal buccal mucosa. Material was collected from the cheek epithelium in areas with lesions and areas without abnormalities. A minimum of one thousand cells was analyzed. Micronuclei were found significantly more frequently in cells collected from lesions than in cells from normal areas, independent of the presence/absence of cancer (P < 0.0001). They were also significantly more frequent in smokers and in mouthwash users (P < 0.0001). Apoptosis occurred significantly less frequently in individuals with oral cancer (P < 0.0001). These results show that oral cancer is associated with higher frequency of chromosomal damage and suggest that apoptosis is compromised in the buccal cells of individuals with this kind of neoplasia.

Genotoxic damage in hospital workers exposed to ionizing radiation and metabolic gene polymorphisms

Of all workers exposed globally to synthetic sources of radiation, medical personnel represent the largest group, but receive relatively low doses. Accidental or therapeutic acute radiation exposure of humans was observed to induce various forms of cytogenetic damage, including the possibility of increasing the incidence of micronuclei (MN) and chromosomal aberrations (CA). The aim of this study was to assess occupationally induced chromosomal damage in a large population of hospital workers exposed to low doses of ionizing radiation (IR). The cytokinesis-block MN and comet assays were used to examine peripheral blood lymphocytes (PBL) of 31 exposed workers to IR and 33 control subjects corresponding in gender, age, and smoking. Glutathione S-transferases (GSTM1, GSTT1, and GSTP1) are postulated to be involved in the detoxification of endogenous and exogenous genotoxicants. The association between these biomarkers and polymorphic genes of xenobiotic metabolizing enzymes was thus also assessed. MN frequency was significantly higher in the exposed subjects compared controls. Comet assay results showed a significant increase of tail length in workers exposed to IR. Data obtained suggest that GSTM1, GSTT1, and GSTP1 polymorphism do not modify significantly the genotoxic potential of IR. Therefore, the exposed medical personnel need to carefully apply radiation protection procedures and minimize, as low as possible, IR exposure to avoid possible genotoxic effects.

Cytogenetic analysis of peripheral blood lymphocytes of hospital staff occupationally exposed to low doses of ionizing radiation

Ionizing radiation is known to induce mutations and cell transformations, predominantly by causing single-strand and double-strand DNA breakage, thereby leading to chromosome instability and carcinogenesis. The aim of this study was to evaluate genotoxic effects in hospital staff exposed to low-dose ionizing radiation in comparison with a selected control group, by using the cytokinesis-blocked micronucleus (CBMN) and sister chromatid exchange (SCE) tests in peripheral blood lymphocytes. The study included 40 exposed radiology staff and 30 control subjects. The frequency of micronuclei (MN) was significantly increased in radiation-exposed groups compared with control persons (p < 0.05). The frequency of SCE did not show any significant difference in the exposed individuals in comparison to the controls. Our results showed that low-level chronic occupational exposure to ionizing radiation causes an increase of MN frequency in chromosomes, even though the absorbed doses were below the permissible limits. Our studies indicate that the CBMN assay is considered to be sensitive test in contrast to SCE analysis to evaluate chromosomal damage induced by ionizing radiation.

Sex-specific aspects of tumor therapy

There is increasing evidence that sex-specific differences in toxicity profiles and outcome after radiotherapy are accumulating in medical oncology, and that treatment strategies may require some modification. Furthermore, sex-specific differences in the sensitivity to genotoxic and therapeutical agents are also of general concern for risk estimation. This review is focussed on the specific influence of sex on these endpoints covering both a clinical and a biological point of view. In this paper, the literature was systematically reviewed with respect to sex-specific differences in tumor and normal tissue sensitivity after exposure to ionizing radiation, as well as to the relevant underlying molecular and cellular mechanisms. Although a number of data on sex-specific differences are available and remarkable differences on clinical, molecular, and cellular levels have been reported, a firm conclusion on any existing sex-specific differences is not yet possible. Future studies are required and should be focussed on this aspect of individual radiosensitivity.

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.

Complementarity of standard cytogenetic assays

Standard cytogenetic assays used in genotoxicology usually include chromosome aberrations analysis and micronucleus cytokinesis-block assay. Both tests originate on standard protocol for lymphocyte culture and can be used as complement or substitute to each other. Aim of this study was to evaluate complementarities between results of chromosome aberration analysis assay and results of micronucleus cytokinesis-block assay in representative sample of inhabitants from Bosnia and Herzegovina. The aim was achieved by calculating Pearson correlation coefficient and simple linear regression.

Impacts of low-dose gamma-radiation on genotoxic risk in aquatic ecosystems

Chinook salmon cells were exposed to gamma radiation and chromosome damage was assessed using the micronucleus assay. The salmon cells were resistant to radiation at all doses compared to human and mammalian cells. We used an indirect approach to determine if prior low dose exposures at environmental dose levels might alter the consequences of radiation exposures to high doses of radiation (adaptive response). The cells adapted but only at doses which were above levels that might be expected environmentally. The "adaptive response" endpoint was useful to show biological responses to exposure, however, under these conditions it might not help in risk assessment of aquatic organisms since the cells seem to be very resistant and environmental radiation levels are typically extremely low. Preliminary experiments were conducted on two other fish cell model systems (Rainbow Trout and Medaka) to optimize conditions for the micronucleus assay for future environmental radiation studies. Since fish cells appear to be more radiation resistant than mammalian cells, we postulate that radiation risk in the whole organism may also be lower. Therefore whole body studies designed to test effects with the specific aim of assessing relative risk between species are in process.

Monitoring the genotoxic effects of radiosynovectomy with Re-186 in paediatric age group undergoing therapy for haemophilic synovitis

PURPOSE

The aim of this study was to investigate the genotoxic effect on the peripheral blood lymphocytes potentially induced by Re-186 in paediatric age group undergoing radiosynovectomy for haemophilic synovitis, by using chromosomal aberration analysis (CA) and the micronuclei (MN) assay for detecting chromosomal aberrations, as well as the sister chromatid exchanges (SCE) technique for assessing DNA damage.

METHODS

Cytogenetic analyses were evaluated in 20 boys (mean age: 13.8 +/- 2.7 years) before, and 2 and 90 days after radiosynovectomy from the peripheral lymphocytes of the patients. Joint retention and extra-articular spread of the radionuclides were evaluated by using quantitative gamma camera imaging.

RESULTS

Imaging after radiosynovectomy revealed local lymph node visualization in 8 (40%) patients and hepatosplenic visualization in 3 (15%) patients due to extra-articular leakage of radioactive material. The mean frequency of chromosome aberrations (0.2 +/- 0.4/1000 cells) determined prior to the onset of therapy was not significantly increased in comparison with control values obtained 2 days (0.4 +/- 0.5/1000 cells) and 90 days (0.2 +/- 0.4/1000 cells) after therapy (P = 0.754 and P = 1.0). In the analysis of MN and SCE, when we compare the baseline levels, the mean MN and SCE frequencies were slightly higher in the control analyses performed 2 and 90 days after radiosynovectomy but there were no significant differences between baseline and control levels (chi(2) = 2.621, P = 0.270 and F = 0.573, P = 0.569, respectively).

CONCLUSION

The major finding of this study with relatively small sample is that, radiosynovectomy with Re-186 does not seem to induce early genotoxic effects on the peripheral blood lymphocytes in paediatric age group.

Cytogenetic analysis in lymphocytes from workers occupationally exposed to low levels of ionizing radiation

The aim of the present study was to perform a cytogenetic analysis in peripheral lymphocytes of 36 individuals occupationally exposed to low levels of ionizing radiation, and compare the results with 36 controls, using the chromosomal aberrations test (CA), sensitivity to bleomycin and cytokinesis-blocked micronucleus assay (MN). The frequencies of CA/100 cells observed for the exposed workers were not significantly higher than in controls (P>0.05). The mean break/cell (b/c) for the controls and exposed workers was 0.59±0.39 and 0.57±0.29, respectively (P>0.01). The MN frequencies were significantly increased (P<0.01) in exposed workers (6.13±3.18) in comparison with controls (5.11±3.85). The mean MN was also statistically higher in the non-smoker exposed when compared with non-smoker controls, 5.80±3.09 and 5.15±4.08, respectively (P<0.01). The cytogenetic analysis of MN proved to be the most sensitive biological marker to assess the cellular response to low levels of irradiation.

Cytogenetic monitoring by use of the micronucleus assay among hospital workers exposed to low doses of ionizing radiation

The aim of this study was to assess occupationally induced chromosomal damage in a large population of hospital workers exposed to low doses of ionizing radiation. We used the cytokinesis-block micronucleus (CBMN) assay in the peripheral lymphocytes of 132 exposed workers compared with 69 controls matched for gender, age and smoking habits. The CBMN assay was combined with fluorescence in situ hybridization with a human pan-centromeric DNA probe in 32 exposed subjects and 30 controls randomly chosen from the initial populations. Occupational dosimetry records were collected over the last 10-year period and revealed very low exposure levels. The average binucleated micronucleated cell rate (BMCR) was significantly higher in the exposed subjects than in the controls (14.9 per thousand+/-8.1 versus 11.8 per thousand+/-6.5; P=0.011). About one-third of the micronuclei were centromere-negative in the exposed and control groups. BMCR significantly positively correlated with donor age in the exposed population; this correlation was at the border of significance in the control group. In the two groups, BMCR was significantly greater in females than in males, and the significant correlation between age and BMCR was observed in the female population, but not in the male one. No effect of smoking habits emerged. Univariate analysis revealed a possible influence of familial cancer history and diagnostic medical radiation dose (estimated from examinations reported in the questionnaire) on BMCR. Multiple regression analysis, taking into account all the previous confounding factors, showed that only occupational exposure status, gender and age had a significant effect on BMCR. In conclusion, the present study shows that chromosomal damage leading to micronucleated lymphocytes is more frequent in hospital workers exposed to ionizing radiation than in controls, despite the very low levels of exposure.

Induction of chromatid-type aberrations in peripheral lymphocytes of hospital workers exposed to very low doses of radiation

Radiological personnel represent workers exposed to low cumulative doses of radiation. As their surveillance is generally based on physical dosimetry, there is little or inconclusive information on biological effects due to radiation exposure at these doses. We aimed to explore the extent of chromosomal damage in circulating lymphocytes of hospital workers (technicians, nurses and physicians) chronically exposed to a very low level of radiation using conventional and molecular cytogenetic analyses (chromosome painting with chromosomes #2, #3 and #10 as probe cocktail). Compared with controls, exposed workers displayed a significant increase in the frequency of aberrant lymphocytes (1.26+/-0.11/100 cells versus 1.63+/-0.17/100 cells). In particular, exposed technicians showed significantly higher mean values than nurses or physicians (3.68+/-1.17/100 cells versus 1.36+/-0.18/100 cells and 1.36+/-0.09/100 cells, respectively). Interestingly, we found that the chromosomal damage was prevalently expressed as chromatid-type aberrations. Chromosome painting indicated that the frequency of chromosome rearrangements (CR; translocations and dicentrics pooled together) was approximately comparable between radiological workers and the control group. Moreover, we did not detect any significant difference due to radiation exposure when CR rates were considered separately for each of the three chromosomes in the probe cocktail.