The assessment of genotoxicity of carbamazepine using cytokinesis-block (CB) micronucleus assay in cultured human blood lymphocytes

The genotoxic effect of CBZ has been investigated in few studies. There is little evidence linking carbamazepine (CBZ) with any genotoxic effects, particularly in vitro micronucleus test using cytogenesis-block technique. In this study, the genotoxicity of the antiepileptic drug, carbamazepine, was tested using cytokinesis-block (CB) micronucleus assay. In vitro analysis was performed in human blood lymphocytes from four healthy persons at five different concentrations of carbamazepine (6, 8, 10, 12, 14 microg/mL). Genotoxic potential and cytotoxic effects of carbamazepine were evaluated by using micronucleus assay and cytokinesis-block proliferation index (CBPI), called the parameter of cytotoxicity in human peripheral blood lymphocyte cultures, respectively. The results of this study indicate that CBZ caused the genotoxic effect under in vitro conditions, except at the dose of 6 microg/mL, and cytotoxic effects of carbamazepine were revealed by a decrease in the cytokinesis-block proliferation index at all the concentrations.     

A research on the genotoxicity of stevia in human lymphocytes

Stevia extracts are obtained from Stevia rebaudiana commonly used as natural sweeteners. It is ～250–300 times sweeter than sucrose. Common use of stevia prompted us to investigate its genotoxicity in human peripheral blood lymphocytes. Stevia (active ingredient steviol glycoside) was dissolved in pure water. Dose selection was done using ADI (acceptable daily intake) value. Negative control (pure water), 1, 2, 4, 8 and 16?μg/ml concentrations which were equivalent to ADI/4, ADI/2, ADI, ADI?×?2 and ADI?×?4 of Stevia were added to whole-blood culture. Two repetitive experiments were conducted. Our results showed that there was no significant difference in the induction of chromosomal aberrations and micronuclei between the groups treated with the concentrations of Stevia and the negative control at 24 and 48?h treatment periods. The data showed that stevia (active ingredient steviol glycosides) has no genotoxic activity in both test systems. Our results clearly supports previous findings.     

Marine toxin okadaic acid induces aneuploidy in CHO-K1 cells in presence of rat liver postmitochondrial fraction, revealed by cytokinesis-block micronucleus assay coupled to FISH

Okadaic acid (OA), a major polyether toxin involved in diarrhetic shellfish poisoning (DSP), is a potent tumor promoter in rodent skin and glandular stomach and a specific inhibitor of the serine/threonine protein phosphatases PP1 and PP2A. A previous study, which used the cytokinesis-block micronucleus (CBMN) assay in CHO-K1 cells, showed that OA induced chromosome damage in the presence of a rat liver metabolic activation system (S9). To support OA biotransformation by S9, the same test system was performed, and DNA damage induced by OA was measured with and without metabolic activation as well as in the presence of heat-inactivated S9 fraction. The results showed that only in the presence of active S9 did OA significantly increased the frequency of micronucleated binucleated (MNBN) cells. After a 4-h treatment a 2- to 5-fold increase of MNBN cells was observed at 30 nM and at 50 nM of OA. However, without S9 or in the presence of heat-inactivated S9, OA did not induce any chromosome damage. We concluded that OA can be metabolically activated in vitro into metabolites that are more genotoxic. The CBMN assay coupled with fluorescence in situ hybridization (FISH) using a DNA probe for centromere detection was performed to discriminate between clastogenic (chromosome breakage) and aneugenic (chromosome loss) effects. FISH analysis showed that OA metabolites increased in a dose-dependent manner in centromere positive micronuclei (CEN+): 60% of CEN+ at 30 nM and 75% of CEN+ at 50 nM of OA. The uptake of OA into CHO-K1 cells and the biotransformation of the toxin are discussed.     

The in vitro genotoxic and cytotoxic effects of remeron on human peripheral blood lymphocytes

Remeron (Mirtazapine) is an antidepressant drug which exerts its action by blocking presynaptic α-2-adrenergic receptors and postsynaptic serotonin types 2 and 3 receptors. In this in vitro analysis, human peripheral blood lymphocytes was treated by remeron (10, 25, 40 and 55 μg/mL) for 24 hours and 48 hours periods, then it was attempted to study of genotoxic and cytotoxic effects of the substance on human peripheral blood lymphocytes by some tests such as sister chromatid exchange (SCE), chromosomal abnormalities (CA) and micronucleus (MN) tests. Also proliferating effect of the substance was investigated. Remeron didn’t significantly cause chromosomal abnormalities and sister chromatid exchange while caused micronucleus at 40 μg/mL concentration and 24?h periodic time and increased proliferation index of the both 24 and 48 hours treated cells was decreased in a concentration manner. Also, exposing to the remeron for 24 and 48 hours leaded to a decrease in mitotic index and nucleus division index in the cells by concentration dependent manner. These findings showed that remeron did not have significantly genotoxic effects on human peripheral blood lymphocytes while it showed cytotoxic effects on the cells, which is the first report on genotoxic and cytotoxic properties of remeron.     

Effects of tartrazine on proliferation and genetic damage in human lymphocytes

The color additive, tartrazine (TRZ), is widely used in food products, drugs and cosmetics. Genotoxicity of TRZ and its metabolites has not been investigated in detail in the presence and absence of a metabolic activator (S9 mix) in human. Therefore, the aim of this study is to investigate the cytotoxic and genotoxic effects of TRZ and its metabolites on cultured human lymphocytes by using chromosome aberration (CA) and micronucleus (MN) tests. Cultures were treated with 625, 1250 and 2500?μg/ml of TRZ in the presence and absence of S9 mix. TRZ showed cytotoxic activity at the highest concentration due to significant decrease in mitotic index (MI) in the absence of S9 mix when compared with solvent control. TRZ and metabolites significantly increased the CAs and aberrant cells in the presence and absence of S9 mix at the higher concentrations. Increased MN values in cultures with and without S9 mix were found to significantly at the highest concentration when tested. Our results indicated that while both TRZ and its metabolites have genotoxic potential on human lymphocyte cultures with and without S9 mix, TRZ can induce cytotoxicity at the highest concentration in culture without S9 mix under the experimental conditions.     

Comparative genotoxicity of nanosilver in human liver HepG2 and colon Caco2 cells evaluated by a flow cytometric in vitro micronucleus assay

Two widely used in vitro cell culture models, human liver HepG2 cells and human colon Caco2 cells, and flow cytometry techniques were evaluated as tools for rapid screening of potential genotoxicity of food‐related nanosilver. Comparative genotoxic potential of 20 nm silver was evaluated in HepG2 and Caco2 cell cultures by a flow cytometric‐based in vitro micronucleus assay. The nanosilver, characterized by the dynamic light scattering, transmission electron microscopy and inductively coupled plasma–mass spectrometry analysis, showed no agglomeration of the silver nanoparticles. The inductively coupled plasma–mass spectrometry and transmission electron microscopy analysis demonstrated the uptake of 20 nm silver by both cell types. The 20 nm silver exposure of HepG2 cells increased the concentration‐dependent micronucleus formation sevenfold at 10 µg ml^–1 concentration in attached cell conditions and 1.3‐fold in cell suspension conditions compared to the vehicle controls. However, compared to the vehicle controls, the 20 nm silver exposure of Caco2 cells increased the micronucleus formation 1.2‐fold at a concentration of 10 µg ml^–1 both in the attached cell conditions as well as in the cell suspension conditions. Our results of flow cytometric in vitro micronucleus assay appear to suggest that the HepG2 cells are more susceptible to the nanosilver‐induced micronucleus formation than the Caco2 cells compared to the vehicle controls. However, our results also suggest that the widely used in vitro models, HepG2 and Caco2 cells and the flow cytometric in vitro micronucleus assay are valuable tools for the rapid screening of genotoxic potential of nanosilver and deserve more careful evaluation. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

Investigation of cytotoxic and genotoxic effects of the antihistaminic drug,loratadine, on human lymphocytes

Context: Loratadine (LOR) is a new generation antihistamine used in the treatment of allergic disorders. Objective: The aim of this study was to evaluate the cytogenotoxic effect of LOR on human peripheral blood lymphocytes. Materials and methods: We investigated the genotoxic effect of this drug in cultured human peripheral blood lymphocytes using sister chromatid exchange (SCE), chromosomal aberrations (CA) and micronucleus (MN) assay in culture conditions. Proliferation index (PI), mitotic index (MI) and nuclear division index (NDI) were also calculated to determine the cytotoxic/cytostatic effect. Cultures were treated with LOR at three concentrations (5, 15 and 25?µg/ml) for 48?h. Results: Although the MI significantly decreased at the higher concentrations (15 and 25?µg/ml) compared with negative (solvent) control, LOR indicated weaker cytotoxic potential in PI and NDI values at all the tested concentrations. LOR increased the frequencies of SCE, CA and MN in all lymphocyte cultures. However, significant increase was observed in MN at the medium and highest doses (15 and 25?µg/ml) and in CA at the medium dose (15?µg/ml) compared with negative (solvent) control culture. Our results indicate that LOR has cytotoxic and genotoxic effects on human peripheral blood lymphocyte cultures. Discussion: Although most of previously findings have shown that LOR does not reflect genotoxicity, our results indicated that it may be a genotoxic drug. Conclusion: More studies are necessary to elucidate the relationship between cytotoxic, genotoxic and apoptotic effects, and to make a possible risk assessment in patients receiving therapy with this drug.     

Assessment of cytotoxic and genotoxic potential of pyracarbolid by Allium test and micronucleus assay

The present study evaluates the cytotoxic and genotoxic potential of pyracarbolid using both micronuleus (MN) assay, in human lymphocytes, and Allium cepa assay, in the root meristem cells. In Allium test, EC₅₀ value was determined in order to selecting the test concentrations for the assay and the root tips were treated with 25?ppm (EC₅₀/2), 50?ppm (EC₅₀) and 100?ppm (EC₅₀?×?2) concentrations of pyracarbolid. One percent of dimethyl sulphoxide (DMSO) and methyl methane sulfonate (MMS) were used as negative and positive controls, respectively. In the micronucleus assay, the cultures were treated with four concentrations (250, 500, 750 and 1000?µg/ml) of pyracarbolid for 24 and 48?h, negative and positive controls were also used in the experiment parallely. The results showed that mitotic index (MI) significantly reduced with increasing the pyracarbolid concentration at each exposure time. It was also obtained that prophase and metaphase index decreased significantly in all concentration at each exposure time. Anaphase index decreased as well and results were found to be statistically significant, except 24?h. A significant increase was observed in MN frequency in all concentrations and both treatment periods when compared with the controls. Pyracarbolid also caused a significant reduction in the cytokinesis block proliferation index (CBPI) in all concentration and both exposure time.     

Ziprasidone induces cytotoxicity and genotoxicity in human peripheral lymphocytes

It has been stated that some antipsychotic drugs might cause genotoxic and carcinogenic effects. Ziprasidone (ZIP) is commonly used an antipsychotic drug. However, its genotoxicity and carcinogenicity data are very limited. The cytotoxicity and genotoxicity of ZIP on human peripheral blood lymphocytes were examined in vitro by sister chromatid exchange (SCE), chromosome aberration (CA) and micronucleus (MN) tests in this study. Lymphocyte cultures were treated with 50, 75 and 100?μg/ml of ZIP in the presence and absence of a metabolic activator (S9 mix). Dimethylsulfoxide was used as a solvent control. While the cells were treated with ZIP for 24?h and 48?h in cultures without S9 mix, the cultures with S9 mix were exposed to ZIP for 3?h. ZIP and its metabolites can exert cytotoxic activities due to significant decreases in mitotic index, proliferation index and nuclear division index in the presence and absence of S9 mix. Statistically significant increases in CAs, aberrant cells and MN values in the presence and absence of S9 mix were found in cultures treated with ZIP. While ZIP significantly increased the SCE values in the absence of S9 mix at all concentrations, increased SCE values in cultures with S9 mix were not found to significantly at all concentrations tested. Our results indicated that both ZIP and its metabolites have cytotoxic, cytostatic and genotoxic potential on lymphocyte cultures under the experimental conditions. Further studies are necessary to make a possible risk assessment in patients receiving therapy with this drug.     

Investigation of genotoxic effects of paraben in cultured human lymphocytes

Paraben is a phenolic derivative of benzoic acid extensively used as preservatives in food, pharmaceutical, and cosmetic industries due to its antimicrobial characteristics. The objective of this study was to evaluate the in vitro genotoxic effects of paraben in human lymphocyte cultures. Cells were analyzed by cytokinesis-block micronucleus (CBMN), chromosome aberration (CA), sister chromatid exchange (SCE), and comet tests. For CBMN, CA, and SCE assays, the human lymphocytes were isolated from healthy donors and incubated with 500, 250, 100, and 50?µg/mL of paraben for 24 and 48?h, and for comet assay, cells were exposed to 1000, 750, 500, and 250?µg/mL of paraben for an hour. Results showed that numbers of MN and SCEs were not significant in the cells exposed to paraben when compared to the solvent control. However, 500 and 250?µg/mL of paraben induced the CA after 24?h. Also, we observed a significant decrease in the cytokinesis-block proliferation index in cells exposed 250–500?µg/mL paraben for 24?h, and 100, 250, and 500?µg/mL for 48?h. The mitotic index was also decreased at all concentrations and periods. However, the proliferation index was statistically decreased at all concentrations after 48?h treatments. Only the highest concentration of paraben caused DNA migration (mean tail length) in human lymphocytes analyzed by Comet assay. Taken together, results indicated that paraben had cytotoxic effects and caused genotoxicity by affecting directly chromosomes and DNA in human lymphocyte cells in vitro, and may have genotoxic potential for human.     

Genotoxic evaluation of Halfenprox using the human peripheral lymphocyte micronucleus assay and the Ames test

The genotoxicity and mutagenicity of Halfenprox, a synthetic pyrethroid insecticide and acaricide, was assessed using two standard genotoxicity assays of the Salmonella typhimurium mutagenicity assay (Ames test) and in vitro micronucleus (MN) assay in human peripheral lymphocytes. In the Ames test, Salmonella strains TA98 and TA100 were treated with or without S9 fraction. The doses of Halfenprox were 6.25, 12.5, 25, 50, and 100?μg/plate and test materials were dissolved in DMSO. The concentrations of Halfenprox did not show mutagenic activity on both strains with and without S9 fraction. The MN assay was used to investigate the genotoxic effects of Halfenprox in human peripheral lymphocytes treated with 250, 500, 750, and 1000?μg/ml concentrations of Halfenprox for 24 and 48?h, and at 1000?μg/ml the concentration was significantly increased and the MN formation was compared with the negative control for both treatment periods. In addition, a significant decrease of the nuclear devision index (NDI) values at the higher concentrations of Halfenprox and at both treatment periods was observed.     

In vitro investigation of the genotoxic and cytotoxic effects of thiacloprid in cultured human peripheral blood lymphocytes

Thiacloprid, a neonicotinoid insecticide, is widely used for controlling various species of pests on many crops. The potential genotoxic effects of thiacloprid on human peripheral blood lymphocytes (PBLs) were investigated in vitro by the chromosome aberrations (CAs), sister chromatid exchanges (SCEs), and cytokinesis‐block micronucleus (MN) assays. The human PBLs were treated with 75, 150, and 300 μg/mL thiacloprid in the absence and presence of an exogenous metabolic activator (S9 mix). Thiacloprid increased the CAs and SCEs significantly at all concentrations (75, 150, and 300 μg/mL) both in the absence and presence of the S9 mix and induced a significant increase in MN and nucleoplasmic bridge formations at all concentrations for 24 h and at 75 and 150 μg/mL for 48‐h treatment periods in the absence of the S9 mix; and at all concentrations in the presence of the S9 mix when compared with the control and solvent control. Thiacloprid was also found to significantly induce nuclear bud (NBUD) formation at 300 μg/mL for 24 h and at 150 μg/mL for 48‐h treatment times in the absence of the S9 mix and at the two highest concentrations (150 and 300 μg/mL) in the presence of the S9 mix. Thiacloprid significantly decreased the mitotic index, proliferation index, and nuclear division index for all concentrations both in the absence and presence of the S9 mix. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 631–641, 2014.     

An alkaline comet assay study on the antimalarial drug atovaquone in human peripheral blood lymphocytes: a study based on clinically relevant concentrations

Atovaquone, a hydroxynaphthoquinone, is an anti‐parasite drug, selectively targeting the mitochondrial respiratory chain of malaria parasite. It is used for both the treatment and prevention of malaria, usually in a fixed combination with proguanil. Although atovaquone has not often been associated with severe adverse reactions in the recommended dosages and has a relatively favorable side effect profile, the present study was undertaken to evaluate its cytogenotoxic potential towards human peripheral blood lymphocytes. Two different concentrations of atovaquone found in plasma when used in fixed‐dose combination with proguanile hydrochloride were used with and without S9 metabolic activation: 2950 ng ml^?1 used for prophylactic treatment and 11 800 ng ml^?1 used in treatment of malaria. The results showed that lymphocyte viability was not affected after the treatment, suggesting that atovaquone was not cytotoxic in the given concentrations. With the alkaline comet assay we demonstrated that in human peripheral blood lymphocytes no significant changes in comet parameters occurred after the treatment. There were no differences in tested parameters with the addition of S9 metabolic activation, indicating that atovaquone either has no metabolite or it is not toxic in the given concentrations. Since no effects were observed after the treatment, it is to be concluded that atovaquone is safe from the aspect of genototoxicity in the recommended dosages. Copyright © 2011 John Wiley & Sons, Ltd.     

Assessment of the genotoxic effects of organophosphorus insecticides phorate and trichlorfon in human lymphocytes

In vitro genotoxic effects of organophosphorus insecticides Phorate (PHR) and Trichlorfon (TCF) were investigated using four genotoxicity endpoints. Different concentration ranges between 0.25–2.00 μg mL^?1 of PHR and 2.34–37.50 μg mL^?1 of TCF were applied to lymphocytes. PHR and TCF significantly increased the frequency of chromosomal aberrations (except 2.34 μg mL^?1 for TCF) and sister chromatid exchanges at all treatment times and concentrations. Most of the used concentrations induced a significant increase in the frequency of micronuclei. Furthermore, PHR and TCF significantly decreased the mitotic index at the higher concentrations after 24‐ and 48‐h treatments. In the comet assay, PHR and TCF significantly increased the comet tail at all concentrations. However, the comet tail intensity was significantly increased at only the highest concentration of PHR and at all concentrations of TCF. According to these results, PHR and TCF possess clastogenic, mutagenic, and DNA damaging effects in human lymphocytes in vitro. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 577–587, 2014.     

Cytotoxic and genotoxic effects of paraquat in Hordeum vulgare and human lymphocytes in vitro

Two phylogenetically distant types of test‐systems—root tip meristems of barley (Hordeum vulgare) and human lymphocytes in vitro were used to detect genotoxicity and cytotoxicity induced by the herbicide paraquat (PQ) in the concentration range (10^?6 to 5 × 10^?4 mol/l). As an endpoint for cytotoxicity the mitotic index (MI) was evaluated. The frequency of chromosome aberrations (CA) and the frequency of micronuclei (MN) were used as endpoints for genotoxicity. A dose‐dependent increase of CA and MN was observed in both test systems, although the values for PQ‐induced MN were somewhat lower. The increase of the genotoxic effect corresponds to a decrease of mitotic activity. The structurally reconstructed barley karyotype MK14/2034 allowed the allocation of the PQ‐specific features of aberration distribution patterns and gave information about which chromosome segments in different chromosomal positions were involved in induced aberrations. Paraquat produced preferably isochromatid breaks and “aberration hot spots” in a restricted number of heterochromatin‐containing segments. The comparative analysis of susceptibility in the used test‐systems to PQ with respect to its cytotoxic and clastogenic effect showed that the human lymphocytes were more sensitive than Hordeum vulgare. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.     

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. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 1331–1342, 2015.     

Assessment of genome damage in a population of Croatian workers employed in pesticide production by chromosomal aberration analysis,micronucleus assay and Comet assay

The widespread use of pesticides suggests that the evaluation of their genotoxicity should be extended using the different assays available. In the present study we used two standard cytogenetic methods (chromosomal aberration analysis and micronucleus assay) and the Comet assay as a relatively new and powerful technique. The study included 10 workers occupationally exposed to a complex mixture of pesticides (atrazine, alachlor, cyanazine, 2,4-dichlorophenoxyacetic acid, malathion) during their production and 20 control subjects with no history of exposure to any physical or chemical agents. For the chromosomal aberration analysis, whole blood was cultivated for 48 h, whereas for the micronucleus assay, whole blood was cultivated for 72 h. For the comet assay whole blood was embedded in agarose on a microscope slide, lysed with detergent, denaturated and subjected to alkaline electrophoresis. Damage to DNA was evaluated by measuring tail length and calculating the tail moment. A significantly increased number of chromatid and chromosome breaks, as well as the presence of dicentric chromosomes and chromatid exchanges in exposed subjects compared with control subjects (P < 0.05), was found. There was also a statistically significant difference in frequency and distribution of micronuclei between the two groups examined. In the exposed subjects the Comet assay showed a statistically significant (P < 0.001) increase in DNA migration. Results suggest that long-term occupational exposure to pesticides could cause genome damage in somatic cells and therefore may represent a potential hazard to human health.     

Comparative genotoxicity of nanosilver in human liver HepG2 and colon Caco2 cells evaluated by fluorescent microscopy of cytochalasin B‐blocked micronucleus formation

As a consequence of the increased use of silver nanoparticles in food, food contact materials, dietary supplements and cosmetics to prevent fungal and bacterial growth, there is a need for validated rapid screening methods to assess the safety of nanoparticle exposure. This study evaluated two widely used in vitro cell culture models, human liver HepG2 cells and human colon Caco2 cells, as tools for assessing the potential genotoxicity of 20‐nm nanosilver. The average silver nanoparticle size as determined by transmission electron microscopy (TEM) was 20.4 nm. Dynamic light scattering (DLS) analysis showed no large agglomeration of the silver nanoparticles. The silver concentration in a 20‐nm nanosilver solution determined by the inductively coupled plasma–mass spectrometry (ICP‐MS) analysis was 0.962 mg ml^?1. Analysis by ICP‐MS and TEM demonstrated the uptake of 20‐nm silver by both HepG2 and Caco2 cells. Genotoxicity was determined by the cytochalasin B‐blocked micronucleus assay with acridine orange staining and fluorescence microscopy. Concentration‐ and time‐dependent increases in the frequency of binucleated cells with micronuclei induced by the nanosilver was observed in the concentration range of 0.5 to 15 µg ml^?1 in both HepG2 and Caco2 cells compared with the control. Our results indicated that HepG2 cells were more sensitive than Caco2 cells in terms of micronuclei formation induced by nanosilver exposure. In summary, the results of this study indicate that the widely used in vitro models, HepG2 and Caco2 cells in culture, represent potential screening models for prediction of genotoxicity of silver nanoparticles by in vitro micronucleus assay. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

Application of dosimetry systems and cytogenetic status of the child population exposed to diagnostic X-rays by use of the cytokinesis-block micronucleus cytome assay

Low‐dose ionizing radiation used for medical purposes is one of the definite risk factors for cancer development, and children exposed to ionizing radiation are at a relatively greater cancer risk as they have more rapidly dividing cells than adults and have longer life expectancy. Since cytokinesis‐block micronucleus cytome (CBMN Cyt) assay has become one of the standard endpoints for radiation biological dosimetry, we used that assay in the present work for the assessment of different types of chromosomal damage in children exposed to diagnostic X‐ray procedures. Twenty children all with pulmonary diseases between the ages of 4 and 14 years (11.30 ± 2.74) were evaluated. Absorbed dose measurements were conducted for posterior–anterior projection on the forehead, thyroid gland, gonads, chest and back. Doses were measured using thermoluminescence and radiophotoluminescent dosimetry systems. It was shown that, after diagnostic X‐rays, the mean total number of CBMN Cyt assay parameters (micronucleus, nucleoplasmic bridges and nuclear buds) was significantly higher than prior to diagnostic procedure and that interindividual differences existed for each monitored child. For the nuclear division index counted prior and after examination, no significant differences were noted among mean group values. These data suggest that even low‐dose diagnostic X‐ray exposure may induce damaging effect in the somatic DNA of exposed children, indicating that immense care should be given in both minimizing and optimizing radiation exposure to diminish the radiation burden, especially in the youngest population. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparative evaluation of genotoxicity of captan in amphibian larvae (Xenopus laevis and Pleurodeles waltl) using the comet assay and the micronucleus test

Captan (N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide) is a fungicide used to inhibit the growth of many types of fungi on plants used as foodstuffs. The toxic and genotoxic potentials of captan were evaluated with the micronucleus test (MNT; AFNOR,2000) and the comet assay (CA) using amphibian larvae (Xenopus laevis and Pleurodeles waltl). Acute toxicity results showed that captan was toxic (1) to Xenopus larvae exposed to from 2 mg/L to 125 or 62.5 microg/L, depending on the nature of the water [reconstituted water containing mineral salts or mineral water (MW; Volvic, Danone, France)] and (2) to Pleurodeles exposed to from 2 mg/L to 125 microg/L in both types of water. The MNT results obtained in MW showed that captan (62.5 microg/L) was genotoxic to Xenopus but not genotoxic to Pleurodeles at all concentrations tested. CA established that the genotoxicity of captan to Xenopus and Pleurodeles larvae depended on the concentration, the exposure times, and the comet parameters (tail DNA, TEM, OTM, and TL). The CA and MNT results were compared for their ability to detect DNA damage at the concentrations of captan and the exposure times applied. CA showed captan to be genotoxic from the first day of exposure. In amphibians, CA appears to be a sensitive and suitable method for detecting genotoxicity such as that caused by captan.