Chromosome damage and micronucleus formation in human blood lymphocytes exposed in vitro to radiofrequency radiation at a cellular telephone frequency (847.74 MHz, CDMA)

Peripheral blood samples collected from four healthy nonsmoking human volunteers were diluted with tissue culture medium and exposed in vitro for 24 h to 847.74 MHz radiofrequency (RF) radiation (continuous wave), a frequency employed for cellular telephone communications. A code division multiple access (CDMA) technology was used with a nominal net forward power of 75 W and a nominal power density of 950 W/m(2) (95 mW/cm(2)). The mean specific absorption rate (SAR) was 4.9 or 5.5 W/kg. Blood aliquots that were sham-exposed or exposed in vitro to an acute dose of 1.5 Gy of gamma radiation were included in the study as controls. The temperatures of the medium during RF-radiation and sham exposures in the Radial Transmission Line facility were controlled at 37 +/- 0.3 degrees C. Immediately after the exposures, lymphocytes were cultured at 37 +/- 1 degrees C for 48 or 72 h. The extent of genetic damage was assessed from the incidence of chromosome aberrations and micronuclei. The kinetics of cell proliferation was determined from the mitotic indices in 48-h cultures and from the incidence of binucleate cells in 72-h cultures. The data indicated no significant differences between RF-radiation-exposed and sham-exposed lymphocytes with respect to mitotic indices, frequencies of exchange aberrations, excess fragments, binucleate cells, and micronuclei. The response of gamma-irradiated lymphocytes was significantly different from that of both RF-radiation-exposed and sham-exposed cells for all of these indices. Thus there was no evidence for induction of chromosome aberrations and micronuclei in human blood lymphocytes exposed in vitro for 24 h to 847.74 MHz RF radiation (CDMA) at SARs of 4.9 or 5.5 W/kg.     

Resveratrol mitigates genotoxicity induced by iodine-131 in primary human lymphocytes

The purpose of this study was to investigate the radioprotective effects of resveratrol as a natural product that protects against genotoxic actions of ¹³¹I in cultured human lymphocytes. Whole-blood samples from human volunteers were treated with resveratrol at doses of 0.5, 1, 5, and 50 μg/mL for 1 h, after which the lymphocytes were incubated with ¹³¹I (100 μCi/1.5 mL) for 2 h. The lymphocyte cultures were then mitogenically stimulated to enable evaluation of the number of micronuclei in cytokinesis-blocked binucleated cells. Incubation of lymphocytes with ¹³¹I induced genotoxicity, which was reflected by an increase in micronuclei frequency. At the doses tested, resveratrol significantly reduced micronuclei frequency. Maximal protective effects occurred at a dose of 1 μg/mL, with total micronuclei values being reduced by 65 % compared to controls. In conclusion, our results indicate protective effects of resveratrol at low doses against genetic damage and adverse effects induced by ¹³¹I administration.     

Ratio of γ-H2AX level in lymphocytes to that in granulocytes detected using flow cytometry as a potential biodosimeter for radiation exposure

This study aims to assess utilisation of the ratio of γ-H2AX in lymphocytes to that in granulocytes (RL/G of γ-H2AX) in blood as a rapid method for population triage and dose estimation during large-scale radiation emergencies. Blood samples from healthy volunteers exposed to 0–10 Gy of ⁶⁰Co irradiation were collected. The samples were cultured for 0–24 h and then analysed using flow cytometry to measure the levels of γ-H2AX in lymphocytes and granulocytes. The basal RL/G levels of γ-H2AX in healthy human blood, the response of RL/G of γ-H2AX to ionising radiation and its relationship with doses, time intervals after exposure and individual differences were also analysed. The level of γ-H2AX in lymphocytes increased in a dose-dependent manner after irradiation, whereas the level in granulocytes was not affected. A linear dose–effect relationship with low inter-experimental and inter-individual variations was observed. The RL/G of γ-H2AX may be used as a biomarker for population triage and dose estimation during large-scale radiation emergencies if blood samples can be collected within 24 h.     

The effect of 835.62 MHz FDMA or 847.74 MHz CDMA modulated radiofrequency radiation on the induction of micronuclei in C3H 10T(1/2) cells

To determine if radiofrequency (RF) radiation induces the formation of micronuclei, C3H 10T(1/2) cells were exposed to 835.62 MHz frequency division multiple access (FDMA) or 847.74 MHz code division multiple access (CDMA) modulated RF radiation. After the exposure to RF radiation, the micronucleus assay was performed by the cytokinesis block method using cytochalasin B treatment. The micronuclei appearing after mitosis were scored in binucleated cells using acridine orange staining. The frequency of micronuclei was scored both as the percentage of binucleated cells with micronuclei and as the number of micronuclei per 100 binucleated cells. Treatment of cells with cytochalasin B at a concentration of 2 microg/ml for 22 h was found to yield the maximum number of binucleated cells in C3H 10T(1/2) cells. The method used for the micronucleus assay in the present study detected a highly significant dose response for both indices of micronucleus production in the dose range of 0.1-1.2 Gy and it was sensitive enough to detect a significant (P > 0.05) increase in micronuclei after doses of 0.3 Gy in exponentially growing cells and after 0.9 Gy in plateau-phase cells. Exponentially growing cells or plateau-phase cells were exposed to CDMA (3.2 or 4.8 W/kg) or FDMA (3.2 or 5.1 W/kg) RF radiation for 3, 8, 16 or 24 h. In three repeat experiments, no exposure condition was found by analysis of variance to result in a significant increase relative to sham-exposed cells either in the percentage of binucleated cells with micronuclei or in the number of micronuclei per 100 binucleated cells. In this study, data from cells exposed to different RF signals at two SARs were compared to a common sham-exposed sample. We used the Dunnett's test, which is specifically designed for this purpose, and found no significant exposure-related differences for either plateau-phase cells or exponentially growing cells. Thus the results of this study are not consistent with the possibility that these RF radiations induce micronuclei.     

Induction of micronuclei by 153Sm-EDTMP in peripheral blood lymphocytes of patients with bone metastases.

The purpose of this study was to evaluate the degree of cytological radiation damage to peripheral blood lymphocytes induced by 153Sm-EDTMP applied for palliation of metastatic bone pain. Blood samples from 16 patients (46-82 years old), 10 without previous radiotherapy and 6 with previous radiotherapy, were collected before and one hour after the administration of a mean activity of 41.7+/-5.8 MBq/kg of 153Sm-EDTMP. Then the lymphocytes were cultured for cytokinesis block micronucleus (MN) assay. The number of MNper binucleated cells (BC) in patients without previous radiotherapy before the treatment was of 0.030 (+/- 0.016) and after one hour 0.035 (+/- 0.013), although we could find inter individual differences. The basal MN/BC of the patients with no previous radiotherapy was similar to the controls. The increment in the percentage of BC with MN was similar in patients with and without previous radiotherapy. The observed mean of MN/BC is equivalent to a dose range of 0.05 to 0.10 Gy of 153Sm-EDTMP in vitro. The relatively low frequency of lymphocyte with micronuclei after the exposure to 153Sm-EDTMP supported the contention that radiation damage in lymphocytes of patients with painful bone metastases is minimal.     

Cytogenetic studies in human blood lymphocytes exposed in vitro to 2.45 GHz or 8.2 GHz radiofrequency radiation

Peripheral blood samples collected from healthy human volunteers were exposed in vitro to 2.45 GHz or 8.2 GHz pulsed-wave radiofrequency (RF) radiation. The net forward power, average power density, mean specific absorption rate, and the temperature maintained during the 2-h exposure of the cells to 2.45 GHz or 8.2 GHz were, respectively, 21 W or 60 W, 5 mW/cm(2) or 10 mW/cm(2), 2.13 W/kg or 20.71 W/kg, and 36.9 +/- 0.1 degrees C or 37.5 +/- 0.2 degrees C. Aliquots of the same blood samples that were either sham-exposed or exposed in vitro to an acute dose of 1.5 Gy gamma radiation were used as unexposed and positive controls, respectively. Cultured lymphocytes were examined to determine the extent of cytogenetic damage assessed from the incidence of chromosomal aberrations and micronuclei. Under the conditions used to perform the experiments, the levels of damage in RF-radiation-exposed and sham-exposed lymphocytes were not significantly different. Also, there were no significant differences in the response of unstimulated lymphocytes and lymphocytes stimulated with phytohemagglutinin when exposed to 8.2 GHz RF radiation. In contrast, the positive control cells that had been subjected to gamma irradiation exhibited significantly more damage than RF-radiation- and sham-exposed lymphocytes.     

Use of C-banding for identifying radiation induced micronuclei

Differentiation of micronuclei (MN) caused by ionizing radiation from those caused by chemicals is a crucial step for managing treatment of individuals exposed to radiation. MN in binucleated lymphocytes in peripheral blood are widely used as biomarkers for estimating dose of radiation, but they are not specific for ionizing radiation. MN induced by ionizing radiation originate predominantly as a result of chromosome breaks (clastogenic action), whereas MN caused by chemical agents are derived from the loss of entire chromosomes (aneugenic action). C-banding highlights centromeres, which might make it possible to distinguish radiation induced MN, i.e., as a byproduct of acentric fragments, from those caused by the loss of entire chromosomes. To test the use of C-banding for identifying radiation induced MN, a blood sample from a healthy donor was irradiated with 3 Gy of Co-60 gamma rays and cultured. Cells were harvested and dropped onto slides, divided into a group stained directly with Giemsa and another processed for C banding, then stained with Giemsa. The frequency of MN in 500 binucleated cells was scored for each method. In preparations stained with Giemsa directly, the MN appeared as uniformly stained structures, whereas after C banding, some MN exhibited darker regions corresponding to centromeres that indicated that they were not derived from acentric fragments. The C-banding technique enables differentiation of MN from acentric chromosomal material. This distinction is useful for improving the specificity of the MN assay as a biomarker for ionizing radiation.     

Investigating micronucleus assay applicability for prediction of normal tissue intrinsic radiosensitivity in gynecological cancer patients

BackgroundPelvic organs morbidity after irradiation of cancer patients remains a major problem although new technologies have been developed and implemented. A relatively simple and suitable method for routine clinical practice is needed for preliminary assessment of normal tissue intrinsic radiosensitivity. The micronucleus test (MNT) determines the frequency of the radiation induced micronuclei (MN) in peripheral blood lymphocytes, which could serve as an indicator of intrinsic cell radiosensitivity.AimTo investigate a possible use of the micronucleus test (MNT) for acute radiation morbidity prediction in gynecological cancer patients.Materials and methodsForty gynecological cancer patients received 50 Gy conventional external pelvic irradiation after radical surgery. A four-field “box” technique was applied with 2D planning. The control group included 10 healthy females.Acute normal tissue reactions were graded according to NCI CTCAE v.3.0. From all reaction scores, the highest score named “summarized clinical radiosensitivity” was selected for a statistical analysis.MNT was performed before and after in vitro irradiation with 1.5 Gy. The mean radiation induced frequency of micronuclei per 1000 binucleated cells (MN/1000) and lymphocytes containing micronuclei per 1000 binucleated cells (cells with MN/1000) were evaluated for both patients and controls.An arbitrary cut off value was created to pick up a radiosensitive individual: the mean value of spontaneous frequency of cells with MN/1000 ± 2SD, found in the control group.ResultsBoth mean spontaneous frequency of cells with MN/1000 and MN/1000 were registered to be significantly higher in cancer patients compared to the control group (t = 2.46, p = 0.02 and t = 2.51, p = 0.02). No statistical difference was registered when comparing radiation induced MN frequencies between those groups.Eighty percent (32) of patients developed grade 2 summarized clinical radiosensitivity, with great variations in MNT parameters. Only three patients with grade 2 “summarized clinical radiosensitivity” had values of cells with MN/1000 above the chosen radiosensitivity threshold.ConclusionThe present study was not able to confirm in vitro MNT applicability for radiosensitivity prediction in pelvic irradiation.     

DNA damage and micronucleus induction in human leukocytes after acute in vitro exposure to a 1.9 GHz continuous-wave radiofrequency field

Human blood cultures were exposed to a 1.9 GHz continuous-wave (CW) radiofrequency (RF) field for 2 h using a series of six circularly polarized, cylindrical waveguides. Mean specific absorption rates (SARs) of 0.0, 0.1, 0.26, 0.92, 2.4 and 10 W/kg were achieved, and the temperature within the cultures during a 2-h exposure was maintained at 37.0 +/- 0.5 degrees C. Concurrent negative (incubator) and positive (1.5 Gy (137)Cs gamma radiation) control cultures were run for each experiment. DNA damage was quantified immediately after RF-field exposure using the alkaline comet assay, and four parameters (tail ratio, tail moment, comet length and tail length) were used to assess DNA damage for each comet. No evidence of increased primary DNA damage was detected by any parameter for RF-field-exposed cultures at any SAR tested. The formation of micronuclei in the RF-field-exposed blood cell cultures was assessed using the cytokinesis-block micronucleus assay. There was no significant difference in the binucleated cell frequency, incidence of micronucleated binucleated cells, or total incidence of micronuclei between any of the RF-field-exposed cultures and the sham-exposed controls at any SAR tested. These results do not support the hypothesis that acute, nonthermalizing 1.9 GHz CW RF-field exposure causes DNA damage in cultured human leukocytes.     

Micronuclei in human lymphocytes irradiated in vitro or in vivo

Venous blood from healthy donors or from patients with various lympho- and myeloproliferative diseases was incubated in vitro in the presence of cytochalasin B for the induction of binucleated lymphocytes. The time at which cytochalasin B was added depended on the proliferation rate of the lymphocytes. Proliferation was monitored using a semiautomatic microscope photometer/computer system. The background level of micronuclei in binucleated lymphocytes of the patients before radiotherapy was statistically indistinguishable from that of healthy persons. Blood from both groups was irradiated in vitro for the study of the dose-response relationship. The dose-response curves were very similar up to 3.75 Gy, and a somewhat lower micronucleus frequency was found in lymphocytes of patients after a 5-Gy exposure. These in vitro results were compared with in vivo exposure after total-body irradiation of leukemic patients. Due to heavy medication that accompanied radiation therapy, only two doses (1.25 and 2.5 Gy) could be checked after in vivo exposure. There was no statistically significant difference between in vitro and in vivo results after 1.25 Gy, but a slightly lower number of micronuclei was observed after in vivo exposure to 2.5 Gy.     

Primary DNA damage in human blood lymphocytes exposed in vitro to 2450 MHz radiofrequency radiation

Human peripheral blood samples collected from three healthy human volunteers were exposed in vitro to pulsed-wave 2450 MHz radiofrequency (RF) radiation for 2 h. The RF radiation was generated with a net forward power of 21 W and transmitted from a standard gain rectangular antenna horn in a vertically downward direction. The average power density at the position of the cells in the flask was 5 mW/cm(2). The mean specific absorption rate, calculated by finite difference time domain analysis, was 2.135 (+/-0.005 SE) W/kg. Aliquots of whole blood that were sham-exposed or exposed in vitro to 50 cGy of ionizing radiation from a (137)Cs gamma-ray source were used as controls. The lymphocytes were examined to determine the extent of primary DNA damage (single-strand breaks and alkali-labile lesions) using the alkaline comet assay with three different slide-processing schedules. The assay was performed on the cells immediately after the exposures and at 4 h after incubation of the exposed blood at 37 +/- 1 degrees C to allow time for rejoining of any strand breaks present immediately after exposure, i.e. to assess the capacity of the lymphocytes to repair this type of DNA damage. At either time, the data indicated no significant differences between RF-radiation- and sham-exposed lymphocytes with respect to the comet tail length, fluorescence intensity of the migrated DNA in the tail, and tail moment. The conclusions were similar for each of the three different comet assay slide-processing schedules examined. In contrast, the response of lymphocytes exposed to ionizing radiation was significantly different from RF-radiation- and sham-exposed cells. Thus, under the experimental conditions tested, there is no evidence for induction of DNA single-strand breaks and alkali-labile lesions in human blood lymphocytes exposed in vitro to pulsed-wave 2450 MHz radiofrequency radiation, either immediately or at 4 h after exposure.     

Effect of hawthorn (Crataegus oxycantha) crude extract and chromatographic fractions on multiple activities in a cultured cardiomyocyte assay

Extracts of hawthorn (Crataegus oxycantha) have become popular herbal supplements for their well-recognized cardiotonic effects. Many commercial preparations have been used successfully in the treatment of congestive heart failure, although the active principles within these extracts have yet to be conclusively identified. Several hawthorn preparations were studied and found to have negative chronotropic effects in a cultured neonatal murine cardiomyocyte assay using unpaced cells. As compared to conventional cardiac drugs (i.e., epinephrine, milrinone, ouabain, or propranolol), hawthorn extract has a unique activity profile. Hawthorn extract appears to be anti-arrhythmic and capable of inducing rhythmicity in quiescent cardiomyocytes. Hawthorn extract does not cause β-adrenergic receptor blockade at concentrations which cause negative chronotropic effects. Commercial hawthorn preparations, extracts prepared from dried leaves and those made from dried berries have similar chronotropic activities. When crude extracts are separated using size-exclusion chromatography, several fractions retain multiple cardiac activities. Assays with chromatographic fractions reveal that multiple dissimilar cardioactive components may exist within the extract, making the identification of individual active constituents more challenging.     

Ginseng reduces the micronuclei yield in lymphocytes after irradiation

To assess the effect of Chinese ginseng in modifying the radiation-induced micronuclei (MN) yield in human G(o) peripheral blood lymphocytes (PBL), we conducted the cytokinesis-blocked (CB) MN assay in blood samples obtained from healthy volunteers (n=4). Before (137)Cs ex vivo irradiation, mononuclear cell cultures from each sample were incubated 24 h with different concentrations (0-2000 microg ml(-1)) of crude water extract of ginseng dry root. We found that (1) at 0 Gy and without the presence of ginseng, MN yield (mean+/-S.E.M.) was 11.7+/-2.7 per 1000 binucleated (BN) cells. Different concentrations of ginseng crude water extract did not affect the MN yields and the proliferative activity of PBL; (2) after 1 and 2 Gy exposure, radiation alone sharply increased the MN yields, respectively, to 119.6+/-17.4 and 340.5+/-20.9 per 1000 BN cells. However, treatment with ginseng for 24 h before radiation exposure, resulted in a significant linear decline of MN yields as ginseng concentration increases. Compared to radiation alone, the extent to which ginseng water extract reduced the MN yields induced by 1 Gy exposure was 46.0% at 1500 microg ml(-1) and 61.5% at 2000 microg ml(-1), and with 2 Gy exposure, it was 38.6% at 1500 microg ml(-1) and 46.5% at 2000 microg ml(-1); (3) MN data suggested a tendency for overdispersion relative to the Poisson model; and (4) over the different levels of ginseng concentrations, the trend in micronucleated BN index was as similar as that of the MN yields. These results indicated that (1) ginseng crude water extract exerts no apparent cytogentic effect on human PBL at concentrations up to 2000 microg ml(-1) as evaluated by the CBMN assay; and (2) the protection of ginseng water extract against (137)Cs-induced MN in human PBL is concentration-dependence. Therefore, our findings indicated that ginseng may have therapeutic value as a possible radioprotector for normal tissue during radiotherapy of cancer patients.     

Protection of cellular DNA from γ-radiation-induced damages and enhancement in DNA repair by troxerutin

The effect of troxerutin on γ-radiation-induced DNA strand breaks in different tissues of mice in vivo and formations of the micronuclei were studied in human peripheral blood lymphocytes ex vivo and mice blood reticulocytes in vivo. Treatments with 1 mM troxerutin significantly inhibited the micronuclei induction in the human lymphocytes. Troxerutin protected the human peripheral blood leucocytes from radiation-induced DNA strand breaks in a concentration dependent manner under ex vivo condition of irradiation (2 Gy). Intraperitoneal administration of troxerutin (175 mg/kg body weight) to mice before and after whole body radiation exposure inhibited micronuclei formation in blood reticulocytes significantly. The administration of different doses (75, 125 and 175 mg/kg body weight) of troxerutin 1 h prior to 4 Gy γ-radiation exposure showed dose-dependent decrease in the yield of DNA strand breaks in murine blood leucocytes and bone marrow cells. The dose-dependent protection was more pronounced in bone marrow cells than in blood leucocytes. Administration of 175 mg/kg body weight of the drug (i.p.) 1 h prior or immediately after whole body irradiation of mice showed that the decrease in strand breaks depended on the post-irradiation interval at which the analysis was done. The observed time-dependent decrease in the DNA strand breaks could be attributed to enhanced DNA repair in troxerutin administered animals. Thus in addition to anti-erythrocytic, anti-thrombic, fibrinolytic and oedema-protective rheological activity, troxerutin offers protection against γ-radiation-induced micronuclei formation and DNA strand breaks and enhances repair of radiation-induced DNA strand breaks. (Mol Cell Biochem xxx: 57–68, 2005)     

Bystander effects induced by direct and scattered radiation generated during penetration of medium inside a water phantom

Background

The biological effects of ionizing radiation have long been thought to results from direct targeting of the nucleus leading to DNA damage. Over the years, a number of non-targeted or epigenetic effects of radiation exposure have been reported where genetic damage occurs in cells that are not directly irradiated but respond to signals transmitted from irradiated cells, a phenomenon termed the “bystander effects”.

Aim

We compared the direct and bystander responses of human A 549, BEAS-2-B and NHDF cell lines exposed to both photon (6 MV) and electron (22 MeV) radiation inside a water phantom. The cultures were directly irradiated or exposed to scattered radiation 4 cm outside the field. In parallel, non-irradiated cells (termed bystander cells) were incubated in ICM (irradiation conditioned medium) collected from another pool of irradiated cells (termed donor cells).

Materials and methods

In directly irradiated cells as well as ICM-treated cells, the frequency of micronuclei and condensation of chromatin characteristic for the apoptotic process were estimated using the cytokinesis-block micronucleus test.

Results

In all tested cell lines, radiation induced apoptosis and formation of micronuclei. A549 and BEAS-2B cells cultured in ICM showed increased levels of micronuclei and apoptosis, whereas normal human fibroblasts (NHDF line) were resistant to bystander response. In A549 and BEAS-2B cells placed outside the radiation field and exposed to scattered radiation the formation of micronuclei and induction of apoptosis were similar to that after ICM-treatment.

Conclusion

Results suggest that the genetic damage in cells exposed to scattered radiation is caused by factors released by irradiated cells into the medium rather than by DNA damage induced directly by X rays. It seems that bystander effects may have important clinical implications for health risk after low level radiation exposure of cells lying outside the radiation field during clinical treatment.     

Cytogenetic monitoring of industrial radiographers using the micronucleus assay

Industrial radiography is the process of using either gamma-emitting radionuclide sources or X-ray machines to examine the safety of industrial materials. Industrial radiographers are among the radiation workers who receive the highest individual occupational radiation doses. To assess occupationally induced chromosomal damage, we performed the cytokinesis-block micronucleus (CBMN) assay in peripheral lymphocytes of 29 male industrial radiographers, exposed to ionizing radiation for 12.8 years±11.2, in comparison with 24 gender-, age-, and smoking habits-matched controls. The CBMN assay was combined with fluorescent in situ hybridization with a pan-centromeric DNA probe in 17 exposed subjects and 17 controls randomized from the initial populations. The mean cumulative equivalent dose, recorded by film dosimeters, was 67.2 mSv±49.8 over the past 5 years. The mean micronucleated binucleated cell rate (MCR) was significantly higher in the industrial radiographers than in the controls (10.7‰±5.2 versus 6.6‰±3.1, P=0.009); this difference was due to a significantly higher frequency of centromere-negative micronuclei (C−MN) in exposed subjects than in controls (8.5‰±4.9 versus 2.2‰±1.6, P<0.001). The two populations did not significantly differ in centromere-positive micronuclei (C+MN) frequency. These findings demonstrate a clastogenic effect in lymphocytes of industrial radiographers. MCR significantly positively correlated with age in the two groups. After correction for the age effect, MCR did not correlate with duration of occupational exposure. No correlation between radiation doses and MCR, C−MN, and C+MN frequencies was observed. In addition to physical dosimetry records, the enhanced chromosomal damage in lymphocytes of industrial radiographers emphasizes the importance of radiation safety programs.     

Evaluation of DNA damage in a population of bats (Chiroptera) residing in an abandoned monazite mine

Ionising radiation has the ability to induce DNA damage. While the effects of high doses of radiation of short duration have been well documented, the biological effects of long-term exposure to low doses are poorly understood. This study evaluated the clastogenic effects of low dose ionising radiation on a population of bats (Chiroptera) residing in an abandoned monazite mine. Bats were sampled from two chambers in the mine, where external radiation levels measured around 20 microSv/h (low dose) and 100 microSv/h (higher dose), respectively. A control group of bats was sampled from a cave with no detectable radiation above normal background levels. The micronucleus assay was used to evaluate residual radiation damage in binucleated lymphocytes and showed that the micronucleus frequency per 500 binucleated lymphocytes was increased in the lower radiation-exposed group (17.7) and the higher radiation-exposed group (27.1) compared to the control group (5.3). This study also showed that bats exposed to radiation presented with an increased number of micronuclei per one thousand reticulocytes (2.88 and 10.75 in the lower and high radiation-exposed groups respectively) when compared to the control group (1.7). The single-cell gel electrophoresis (comet) assay was used as a means of evaluating clastogenecity of exposure to radiation at the level of individual cells. Bats exposed to radiation demonstrated increased DNA damage as shown by the length of the comet tails and showed an increase in cumulative damage. The results of the micronucleus and the comet assays indicated not only a statistically significant difference between test and control groups (P<0.001), but also a dose-dependent increase in DNA damage (P<0.001). These assays may thus be useful in evaluating the potential clastogenecity of exposure to continuous low doses of ionising radiation.     

A cytogenetic study of nuclear power plant workers using the micronucleus-centromere assay.

A cytogenetic study was performed in 215 nuclear power plant workers occupationally exposed to radiation using the micronucleus-centromere assay for peripheral blood lymphocytes. As control population served administrative staff with yearly doses below 1 mSv. The increase of the micronucleus frequency with age, observed in the non-smoking control population, is mainly due to an enhanced number of centromere-positive micronuclei, pointing to an increased chromosome loss. No differences in the number of micronuclei, centromere-positive and centromere-negative micronuclei between smokers and non-smokers are observed. An analysis of the micronucleus data vs. the dose accumulated over the 10 years preceding the venepuncture shows no significant clastogenic or aneuploidogenic effects of the exposure in the studied population which is representative for workers in the nuclear industry at present. According to the linear fits to our data an increase of the micronucleus frequency pro rata 0.5 per 1000 binucleated cells per year, related to the centromere-negative micronuclei, may be expected for workers with the maximal tolerable dose of 20 mSv/year.     

Cytotoxic and genotoxic effects of sodium hypochlorite on human peripheral lymphocytes in vitro

Chlorination is widely used method in the disinfection of drinking and utility water worldwide. In this study, cytotoxic and genotoxic effects of sodium hypochlorite were investigated by the cytokinesis-block micronucleus assay and chromosomal aberration analysis on human peripheral lymphocytes in vitro. A significant increase in chromosomal aberration frequency was observed in all treatments of NaOCl (0.030, 0.065, 0.100, 0.25, 0.5, 1, 2, 4 μg/mL) at 24 and 48 h compared with the negative control and mitomycin C (MMC, 0.3 μg/mL), which was used as a positive control. NaOCl significantly increased the frequency of micronuclei in a dose dependent manner. The results showed that there was a significant correlation between NaOCl concentration and chromosomal aberration, micronuclei frequency, necrotic cells, apoptotic cells and binucleated cells.     

Acentromeric micronuclei are increased in peripheral blood lymphocytes of untreated cancer patients

Increased micronucleated cell rates, dicentric chromosomes, and other chromosomal damages have been reported in lymphocytes of cancer patients prior to the initiation of chemotherapy, and/or radiotherapy. The cause of these chromosomal damages in these lymphocytes remains unclear. In the present work, we investigated whether these micronuclei mainly reflect structural or numerical chromosomal aberrations by applying the cytokinesis-blocked micronucleus (CBMN) assay in combination with fluorescent in situ hybridization (FISH) of a DNA centromeric probe on blood samples of 10 untreated cancer patients (UCPs), and 10 healthy subjects (HSs). Micronucleated binucleated lymphocyte rate was significantly increased in patients (mean±S.D.: 19.0‰±14.1 versus 9.2‰±4.6 in controls). Trinucleated cytokinesis-blocked cells were not significantly higher in patients than in controls. Acentromeric, centromeric, and multicentromeric micronucleus levels were two-fold higher in patients than in controls, but the difference was significant only with acentromeric micronuclei. The percentage of micronuclei containing one or more centromeres averaged 69.2, and 71.5% in patients, and controls, respectively. The percentage of micronuclei containing several centromeres was 44.7% in patients, and 54.6% in controls. Among centromere-positive micronuclei, the percentage of micronuclei containing several centromeres averaged 59.7% in patients, and 75.4% in controls. These results indicate that genetic instability in peripheral blood lymphocytes of UCPs occurs because of enhanced chromosome breakage. However, a substantial proportion of this genetic instability occurs because of defects in chromosome segregation.