Sister chromatid exchange analysis in patients exposed to low dose of iodine-131 for thyroid scintigraphy

Retrospective Biological Dosimetry at Low and High Doses of Radiation and Radioiodine Impact on Individual Susceptibility to Ionizing Radiation

Iodine-131 (I-131) is often used in thyroid diagnostics and therapy. External and internal exposure to radioiodine can lead to molecular and cellular damage in peripheral blood lymphocytes. The aim of this study was to explore the influence of low and high doses of I-131 on susceptibility to ionizing radiation. Study groups consisted of 30 individuals free of thyroid diseases, 41 patients exposed diagnostically to low doses of I-131, and 37 hyperthyroidism patients exposed therapeutically to high doses. The standardized DNA repair competence assay was used to test the efficacy of the fast DNA repair process in G0 cells. Cytogenetic preparations were made in fresh blood samples before and after challenging cells in vitro with X-ray dose. The frequency of sister chromatid exchanges (SCE) and percentage of cells with significantly elevated numbers of SCE were used as cytogenetic biomarkers associated to homologous recombination and compared to reported earlier cytogenetic biomarkers of cancer risk. Strong individual variation in the biomarkers is observed in all investigated groups before and after challenging. Nevertheless, the efficiency of post challenging fast repair is significantly high in the patients exposed to diagnostic I-131 doses than in unexposed control group and linked to decreased cytogenetic damage. However, 5 weeks after administration of therapeutic doses, significant increases of unrepaired post challenging DNA and cytogenetic damages were observed indicating a health risk. Results also suggest that the appearance of cancers in immediate families might influence DNA repair differently in patients exposed to low than to high doses.

Increased frequency of chromosomal aberrations and sister chromatid exchanges in peripheral lymphocytes of radiology technicians chronically exposed to low levels of ionizing radiations

Chromosome aberrations (CAs) and sister chromatid exchanges (SCEs) frequencies were estimated in peripheral lymphocytes from 21 radiology technicians, and from 21 non-exposed control subjects. We exclusively considered individuals who neither smoke nor consume drugs or alcohol for a period of at least two years prior to the analysis. Significant differences were found between exposed and controls in terms of SCEs and CAs frequencies. Technicians showed a significant higher number of high-frequency individuals (HFIs) with respect to the control group. Nevertheless, the mean frequency of SCEs observed among technician HFIs did not significantly differ with respect to that observed among control HFIs. Vice versa, the non-HFIs belonging to technicians group showed a statistically higher difference in the SCEs/NSM value with respect to the non-HFIs belonging to control group. Since the differences in the SCEs frequencies between the two groups are due to non-HFIs, our results seem to indicate a general genotoxic effect of the IR, not affected by HFIs. Among technicians, the level of chromosome damage correlated neither with years of radiation exposure nor with the age of the subjects. Vice versa, in the control group, a positive correlation was found between the number of SCEs and age. In both samples the gender status did not influence the frequencies of CAs and SCEs. Our results suggest that chronic long-term exposure to low doses of ionizing radiation could increase the CAs and SCEs frequencies. This study reinforces the relevance of the biomonitoring of hospital workers chronically exposed to ionizing radiation.

Evaluation of the genotoxic effects of chronic low-dose ionizing radiation exposure on nuclear medicine workers

INTRODUCTION

Nuclear medicine workers are occupationally exposed to chronic ionizing radiation. It is known that ionizing radiation may have damaging effects on chromosomes. In the present study, we investigated the genotoxic effects of ionizing radiation on nuclear medicine workers. We used two different indicators of genotoxicity methods: sister chromatid exchange (SCE) and micronucleus (MN).

METHODS

The present research was carried out using 21 nuclear medicine workers (11 females and 10 males) during two periods: during normal working conditions and after a 1-month vacation. The radiation dose varied from 1.20 to 48.56 mSv, which accumulated during the occupational exposure time between two vacations. Peripheral blood samples were taken from each subject for two distinct lymphocyte cultures (SCE and MN) in each period.

RESULTS

In nearly all subjects, SCE values increased significantly during radiation exposure compared to the postvacation period (P<.05). Similarly, MN frequencies in most of the subjects increased significantly during radiation exposure compared to the postvacation period (P<.05).

CONCLUSIONS

This study revealed that both SCE and MN frequencies in most of the subjects were significantly higher during exposure to ionizing radiation than after a 1-month vacation period. However, this genotoxic effect was reversible in most of the subjects.

Genotoxic effect of albendazole in pediatric patients with hepatic hydatid disease

OBJECTIVE

Hydatid disease occurs throughout the world and is treated with both surgery and medical administration of albendazole. Some adverse effects of albendazole are known. However, its genotoxic effect on humans has not been reported yet. In this study, we aimed to investigate the genotoxic effect of albendazole on human lymphocytes in vivo.

METHODS

The study involved 14 children (eight males and six females) who had undergone operations for hepatic hydatid disease. The ages of the patients ranged from 6 to 13 years. Genotoxicity of albendazole was evaluated as the frequency of sister chromatid exchange (SCE) and micronucleated cells in the patient's lymphocytes. Prior to and after albendazole treatment, blood samples were obtained from these patients for SCE and micronucleus (MN) studies. SCE and MN frequencies of the patients were measured separately before and after albendazole treatment.

RESULTS

All patient SCE values increased significantly after albendazole administration (p<0.001). Similarly, MN frequencies in all the patients increased significantly following albendazole treatment (p<0.001).

CONCLUSION

This study revealed that both SCE and MN frequencies are higher after albendazole treatment. The results suggest that albendazole may be genotoxic to human lymphocytes in vivo.

Chromosome and sister chromatid exchange studies in Behcet's patients

Behcet's disease is a chronic multisystemic disease of unknown pathogenesis characterized by four major symptoms: oral aphthous ulcers, skin lesions, ocular symptoms and genital ulcerations. The disease is spread throughout the world, but it is most frequent in Turkey, Japan, Korea and China. Although HLA-Bw51 has been found to predominate in Behcet's cases, the genetic etiology has not yet been clarified. In this study, we investigated the chromosomal abnormalities and sister chromatid exchange rates in patients with Behcet's diseases. Thirty-eight patients with Behcet's disease (diagnosed for the first time) and 30 healthy subjects (as controls) were included in this study. Although numerical and structural chromosomal abnormalities were not detected in our patients, we found an increased rate of sister chromatid exchange in patients over the control groups (P < 0.01). On the basis of these results, we discuss the genetic etiology of Behcet's disease.

Ability of 13 chemical agents used in dental practice to induce sister-chromatid exchanges in Syrian hamster embryo cells

To evaluate the genotoxic potential of 13 chemical agents used in dental practice, the abilities of these agents to induce sister-chromatid exchanges (SCEs) were examined using Syrian hamster embryo (SHE) cells. Statistically significant increases in the frequencies of SCEs were observed in SHE cells treated with all seven of the chemical agents used as endodontic medicaments: p-chlorophenol, m-cresol, formaldehyde, guaiacol, hydrogen peroxide, p-phenolsulfonic acid, and sodium hypochlorite (P < 0.01; Student t test). Assessment of two chemical agents that are applied to the oral mucosa as antiseptics showed that SCEs were induced by iodine (P < 0.01), but not by chlorhexidine. Of three chemical agents that are used as dyes for disclosing dental plaque, erythrosine B had no effect on SCE induction, while acid fuchsin and basic fuchsin increased the SCE frequencies in SHE cells (P < 0.01). Glutaraldehyde, which is used as a disinfectant for dental instruments and impressions, also induced SCEs (P < 0.01). Because SCE assays are used as a sensitive indicator for evaluating genetic toxicity of chemicals, the chemical agents that had a positive response in the present study are potentially genotoxic to mammalian cells.

Sister chromatid exchanges in lymphocytes of nuclear medicine physicians

OBJECTIVE

The aim of this study was to assess whether occupational exposure to chronic, low doses of Iodine 131 (I-131) and Technetium 99m (Tc-99m) may lead to genotoxicity. Medical personnel occupied in nuclear medicine departments are occupationally exposed to low doses of I-131 and Tc-99m. The determination of the frequency of sister chromatid exchanges (SCEs) and of cells with a high frequency of SCEs (HFC) is considered to be a sensitive indicator for detecting genotoxic potential of mutagenic and carcinogenic agents. Therefore, we examined peripheral lymphocytes from nuclear medicine physicians for the presence of both SCE and HFC.

METHODS

Sixteen exposed nuclear medicine physicians (non-smokers) were compared to 16 physicians (non-smokers) who had not been exposed to chemical or physical mutagens in their usual working environment at the same hospital.

RESULTS

A statistically significant difference was found between SCE frequencies and HFC percentages measured in lymphocytes from the exposed and control groups.

CONCLUSIONS

The present observation on the effect of chronic low doses of I-131 and Tc-99m indicates the possibility of genotoxic implications of this type of occupational exposure. Hence, the personnel who work in nuclear medicine departments should carefully apply the radiation protection procedures and should minimize, as low as possible, radiation exposure to avoid possible genotoxic effects.

Sister chromatid exchange analysis and chromosoma aberration studies in interventional cardiology laboratory workers: one war follow up study

Invasive cardiology laboratory workers are occupationally exposed to chronic ionizing radiation. It is known that ionizing radiation has a damaging effect on chromosomes. In present study. we investigated the frequency of sister chromatid exchange (SCE) and chromosomal aberrations in 11 invasive cardiology laboratory workers and 11 healthy controls. After a vacation period, we took blood samples for chromosome analysis in months 0, 4, 8 and 12 (last two month period was the nonradiation time). The SCE frequencies did not change significantly after exposure to ionizing radiation in any worker. Our study has revealed that non-specific structural chromosome aberrations such as gaps, isogaps, acentric chromosomes, chromatids and chromosome breakage could be in the 4th and 8th months after ionizing radiation exposure in the metaphase plaques. All abnormal chromosomal effects had disappeared by the end of the two month non-exposure period in each worker. In conclusion, the results suggest that SCE frequencies are not significantly affected in invasive cardiology laboratory workers who are exposed occupationally to ionizing radiation, although some degree of reversible chromosomal aberrations did appear.