Induction of micronuclei by five pyrethroid insecticides in whole-blood and isolated human lymphocyte cultures

Genotoxicity analysis of two hydroxyfuranones, byproducts of water disinfection, in human cells treated in vitro

In general, water for human consumption is chemically disinfected, usually by adding chlorine. As well as producing safe drinking water however, the chlorine treatment, also results in a number of disinfection byproducts (DBPs). One important class of these DBPs is made up of hydroxyfuranones (HFs). In this article, we report the results of a recent investigation to assess the genotoxicity of two HFs, namely mucobromic acid (MBA) and mucochloric acid (MCA), in cultured human cells. The comet assay is used to measure the induction of primary DNA damage and to determine the DNA repair kinetics and the ability of the tested compounds to cause oxidative damage. In addition, the micronucleus (MN) assay is applied to evaluate chromosome damage. The results of the comet assay reveal that both HFs are clearly genotoxic leading to high levels of DNA breaks, and that MBA is more effective than MCA. According to the comet results, the DNA damage induced by MBA repairs well over time, but not the one induced by MCA. Furthermore, HFs produce high levels of oxidized bases. In contrast, the results from the MN assay, which measures the induction of clastogenic and/or aneugenic effects, are mainly negative for the two HFs tested, although MCA is able to increase significantly the frequency of micronuclei in binucleated TK cells, at the concentration of 10 microM.

Evaluation of the cytotoxicity and genotoxicity of curcumin in PC12 cells

Neurotoxicity induced by reactive oxygen species can appear as an adverse effect of chemotherapy treatment with platinum compounds, such as cisplatin. The use of this drug in clinical practice is limited due to its adverse effects, including nephrotoxicity, ototoxicity, neurotoxicity and genotoxicity. Functional foods or nutraceuticals have demonstrated potential neuroprotective activity in several experiments and models. This study aimed to investigate the possible cytotoxicity and genotoxicity/antigenotoxic effects of curcumin in PC12 cells exposed to cisplatin. Cell viability and genotoxicity/antigenotoxicity were evaluated by the MTT assay and micronucleus test, respectively. PC12 cells were treated with different concentrations of cisplatin and curcumin (0.5 -- 128 microg/mL). Analysis of the results showed that high concentrations of curcumin were cytotoxic and increased micronuclei frequency compared to the control group. In the associated treatments, at all three concentrations evaluated, curcumin significantly reduced the total frequency of micronuclei induced by cisplatin. Determining the cytotoxic and genotoxic/antigenotoxic effects of this frequently used antioxidant in a neuronal model is important to assess possible hazards when combined with other chemical agents, including chemotherapy drugs used in cancer therapy.

Genotoxicity analysis of two halonitromethanes, a novel group of disinfection by-products (DBPs), in human cells treated in vitro

Halonitromethanes (HNMs) constitute an emerging class of disinfection by-products (DBPs) produced when chlorine and/or ozone are used for water treatment. The HNMs are structurally similar to halomethanes, but have a nitro-group in place of hydrogen bonded to the central carbon atom. Since little information exists on the genotoxic potential of HNMs, a study has been carried out with two HNM compounds, namely trichloronitromethane (TCNM) and bromonitromethane (BNM) by using human cells. Primary damage induction has been measured with the Comet assay, which is used to determine both the repair kinetics of the induced damage and the proportion of induced oxidative damage. In addition, the fixed DNA damage has been evaluated by using the micronucleus (MN) assay. The results obtained indicate that both compounds are genotoxic, inducing high levels of DNA breaks in the Comet assay, and that this DNA damage repairs well over time. In addition, oxidized bases constitute a high proportion of DNA-induced damage (50-75%). Contrarily, no positive effects were observed in the frequency of micronucleus, which measures both clastogenic and aneugenic effects, neither using TK6 cells nor peripheral blood lymphocytes. This lack of fixed genetic damage would minimize the potential mutagenic risk associated with HNMs exposure.

Genotoxicity of heptachlor and heptachlor epoxide in human TK6 lymphoblastoid cells

The genotoxic potential of the organochlorine insecticides heptachlor (HC) and its metabolite heptachlor epoxide (HCE) has been evaluated in TK6 cells, a well-established human lymphoblastoid cell line. Genotoxicity has been determined by scoring the induction of DNA breaks in the comet assay and by measuring the frequency of micronuclei (MN) in binucleated cells. The results indicate that both compounds are able to induce significant increases in the percentage of DNA in the tail, the parameter used in the comet assay, with a direct dose-response relationship. Nevertheless, both compounds were unable to induce an increase in the frequency of MN. The comet assay measures primary DNA damage, while the induction of MN measures fixed damage. Thus, our results would suggest that the DNA damage induced by the two insecticides is not fixed as chromosome damage, which would be detectable by means of the MN assay (chromosome breaks and aneuploidy).

Evaluation of the cytogenetic damage induced by the organophosphorous insecticide acephate

The organophosphorous insecticide acephate was tested for its ability to induce in vitro cytogenetic effect in human peripheral lymphocytes by using the chromosomal aberrations (CAs), sister chromatid exchange (SCE) and micronuclei (MN) assay. The level of nuclear DNA damage of acephate was evaluated by using the comet assay. Concentrations of 12.5, 25, 50, 100 and 200 mug mL(-1) of acephate were used. All concentrations of acephate induced significant increase in the frequency of CAs and in the formation of MN dose dependently (r = 0.92 at 24 h, r = 0.95 at 48 h for CAs, r = 0.87 for MN). A significant increase was observed in induction of SCE at 50, 100 and 200 mug mL(-1) concentrations during 24 h treatment and at all concentrations (except 12.5 mug mL(-1)) during 48 h treatment period in a dose-dependent manner (r = 0.84 at 24 h, r = 0.88 at 48 h). Acephate did not affect the replicative index and cytokinesis-block proliferation index (CBPI). However, it significantly decreased the mitotic index at all three highest concentrations (50, 100, 200 mug mL(-1)) for 24 h treatment and at all concentrations (except 12.5 mug mL(-1)) for 48 h treatment, dose-dependently (r = 0.94 at 24 h, r = 0.92 at 48 h). A significant increase in mean comet tail length was observed at 100 and 200 mug mL(-1) concentrations compared with negative control in a concentration-dependent manner (r = 0.94). The mean comet tail intensity was significantly increased at only 200 mug mL(-1) concentration. The present results indicate that acephate is a clastogenic, cytotoxic agent and it causes DNA damage at high concentrations in human lymphocytes in culture.

Gas Chromatography Residue Analysis of Bifenthrin in Pears Treated with 2% Wettable Powder

This study was conducted to monitor the level of bifenthrin residues in pear sprayed with 2% bifenthrin wettable powder (WP) at the recommended rate at four different schedules prior to harvest. The target analyte was extracted with acetone, partitioned into dichloromethane, and then purified by florisil chromatographic column. The residue determination was performed on a DB-5 capillary column using GC with electron capture detector (ECD). Linearity of this method was quite good (r² = 0.9951) in the concentration ranged from 0.2 mg/kg to 10 mg/kg. Recovery test was carried out at two concentration levels, 0.2 mg/kg and 1.0 mg/kg, in three replicates, and their rates were from 82.9% to 107.2%. No quantitative bifenthrin was detected in pear of all kinds of treatments including the treatment sprayed 4 times until 7 days before harvest. This sensitive and selective method can be used to monitor the trace residual amounts of bifenthrin in pear in a quite low concentration level.

Pyrethroids as promising marine antifoulants: laboratory and field studies

Due to the regulations and bans regarding the use of traditional toxic chemicals against marine fouling organisms and the practical impediments to the commercialization of natural product antifoulants, there is an urgent need for compounds that are antifouling-active, environmentally friendly, and have a potential for commercial application. In this study, a series of common, commercially available pyrethroid products, which are generally used as environmentally safe insecticides, was evaluated for antifouling activity in the laboratory using an anti-settlement test with cyprids of the barnacle Balanus albicostatus and also in a field experiment. Laboratory assay showed that all eleven pyrethroids (namely, rich d-trans-allethrin, Es-biothrin, rich d-prallethrin, S-prallethrin, tetramethrin, rich d-tetramethrin, phenothrin, cyphenothrin, permethrin, cypermethrin, and high active cypermethrin) were able to inhibit barnacle settlement (EC(50) range of 0.0316 to 87.00 microg/ml) without significant toxicity. Analysis of structure-activity relationships suggested that the cyano group at the alpha-carbon position had a significant influence on the expression of antifouling activity in pyrethroids. In the field, the antifouling activity of pyrethroids was further confirmed, with the most potent pyrethroids being cypermethrin and high active cypermethrin, which displayed efficiency comparable with that of tributyltin. In summary, our investigation indicated that these pyrethroids have a great and practical commercial potential as antifouling agents.

The in vitro genotoxic effects of a commercial formulation of alpha-cypermethrin in human peripheral blood lymphocytes

alpha-Cypermethrin, a highly active pyrethroid insecticide, is effective against a wide range of insects encountered in agriculture and animal husbandry. The potential genotoxicity of a commercial formulation of alpha-cypermethrin (Fastac 100 EC, containing 10% alpha-cypermethrin as the active ingredient) on human peripheral lymphocytes was examined in vitro by sister chromatid exchange (SCE), chromosomal aberrations (CAs), and micronucleus (MN) tests. The human lymphocytes were treated with 5, 10, 15, and 20 microg/ml of alpha-cypermethrin for 24- and 48-hr. alpha-Cypermethrin induced SCEs and CAs significantly at all concentrations and treatment times and MN formation was significantly induced at 5 and 10 microg/ml of alpha-cypermethrin when compared with both the control and solvent control. Binuclear cells could not be detected sufficiently in the highest two concentration of alpha-cypermethrin (15 and 20 microg/ml) for both the 24- and 48-hr treatment times. alpha-Cypermethrin decreased the proliferation index (PI) at three high concentrations (10, 15, and 20 microg/ml) for both treatment periods as compared with the control groups. In addition, alpha-cypermethrin reduced both the mitotic index (MI) and nuclear division index (NDI) significantly at all concentrations for two treatment periods. The PI and MI were reduced by alpha-cypermethrin in a concentration-dependent manner during both treatment times. In general, alpha-cypermethrin showed higher cytotoxic and cytostatic effects than positive control (MMC) at the two highest concentrations for the 24- and 48-hr treatment periods. The present study is the first to report the genotoxic and cytotoxic effects of commercial formulation of alpha-cypermethrin in peripheral blood lymphocytes.

Chronic toxicity and cytotoxicity of synthetic pyrethroid insecticide cis-bifenthrin

With the increasing use of synthetic pyrethroids (SPs), the significance of ecological safety and health risk is an emerging concern. In this study, we evaluated the chronic aquatic toxicity of cis-bifenthrin (cis-BF) in Daphnia magna and its cytotoxicity in Chinese hamster ovary (CHO) cells as well as human cervical carcinoma (Hela) cells. Chronic aquatic toxicity tests showed that cis-BF could significantly affect the reproduction of D. magna. The lowest observed effective concentration and the non-observed effective concentration of cis-BF to D. magna were 0.02 and 0.01 microg/L, respectively, and the chronic value was 0.014 microg/L. The intrinsic rate of natural increase was significantly decreased (p < 0.05) to 0.02 microg/L. The cytotoxicity assay demonstrated that cis-BF decreased cell viability in CHO and Hela cells in a concentration- and time-dependent manner. The IC50 values for Hela and CHO cells were 4.0 x 10(-5) and 3.2 x 10(-5) mol/L, respectively. Together, these results indicated that cis-BF induced chronic toxicity in both aquatic invertebrate animals and mammalian cells. These findings assist in understanding the impact of SPs on health and environmental safety. Considering the wide spectrum of SPs, a more comprehensive understanding of the negative effects is indispensible for planning future application and regulation of these pesticides.

The antibiotic erythromycin did not affect micronucleus frequency in human PHA-stimulated lymphocytes

The aim of the present study was to investigate the ability of the antibiotic erythromycin to induce micro?nucleus (MN) frequency and the cytokinesis block proliferation index (CBPI) in human peripheral blood lymphocytes in vitro using the cytokinesis-block micronucleus test (CBMN). Cell cultures were treated with five different concentrations of erythromycin ranging from 0.68 x 10-4 to 5.45 x 10-4 M. The positive control cells were treated with a known mutagen, mitomycin C (MMC), in a concentration of 1.6 x 10-6 M. None of the tested concentrations of erythromycin significantly changed the average MN frequency or CBPI in PHA-stimulated lymphocytes (p > 0.05).

The Assesment 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.

Genotoxicity of the organochlorine pesticides 1,1-dichloro-2,2- bis(p-chlorophenyl)ethylene (DDE) and hexachlorobenzene (HCB) in cultured human lymphocytes

The possible genotoxic potential of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), which is a metabolite of dichlorobiphenyltrichloroetane (DDT), and hexachlorobenzene (HCB), which are organochlorine pesticides have been evaluated in vitro by using human lymphocytes as test system. Genetic damage was determined by scoring the frequency of micronuclei (MN) in primary lymphocyte cultures obtained from different donors. The results indicated that, under the experimental conditions used, the DDT metabolite DDE was able to induce significant increases in the frequency of micronucleated cells, which indicate a certain clastogenic and/or aneugenic potential. DDE was tested in the range of 10-80 mM, but the only concentration producing a significant genotoxic effect was 80 mM. On the other hand, HCB was unable to induce a significant increase in the MN frequency in the range of concentrations assayed, from 0.005 to 0.1mM. The selected concentrations of DDE and HCB were chosen according to their toxicity in cell blood cultures; higher concentrations reduced significantly cell proliferation and produced a low frequency of binucleated cells. In conclusion, the results indicate that a genotoxic risk is associated with the exposure to DDE at concentrations 80 mM and above.

Clastogenic effects of food additive citric acid in human peripheral lymphocytes

Clastogenic properties of the food additive citric acid, commonly used as an antioxidant, were analysed in human peripheral blood lymphocytes. Citric acid induced a significant increase of chromosomal aberrations (CAs) at all the concentrations and treatment periods tested. Citric acid significantly decreased mitotic index (MI) at 100 and 200 mug ml(-1) concentrations at 24 h, and in all concentrations at 48 h. However, it did not decrease the replication index (RI) significantly. Citric acid also significantly increased sister chromatid exchanges (SCEs) at 100 and 200 mug ml(-1) concentrations at 24 h, and in all concentrations at 48 h. This chemical significantly increased the micronuclei frequency (MN) compared to the negative control. It also decreased the cytokinesis-block proliferation index (CBPI), but this result was not statistically significant.

In vitro safety evaluation and anticlastogenic effect of BacoMind on human lymphocytes

OBJECTIVE

BacoMind (BM) is a standardized extract of Bacopa monnieri, which belongs to the family Scrophulariaceae and is a creeping annual plant found throughout the Indian subcontinent. It has been used by Ayurvedic medicinal practitioners in India for almost 3000 years and is classified as a medharasayana, a substance which improves memory and intellect. With the widespread traditional use as well as scientific validation of Bacopa monnieri for nootropic activity, a bioactive-rich unique phytochemical composition-BacoMind was developed from B. monnieri for use as a cognition and memory enhancing agent. The present study aimed to investigate the in vitro toxicity of this formulation of BacoMind on human lymphocytes and to rule out its possible contribution to mutagenicity.

METHODS

In the present investigation the active ingredients present in BM were identified and quantified by high performance liquid chromatography (HPLC) and high performance thin-layer chromatography (HPTLC). Antioxidant and anticlastogenic properties of BM were studied in vitro with and without metabolic activation. Doses of BM were chosen on the basis of mitotic index (MI) and cytokinesis-block proliferation index (CBPI). Clastogenicity assays were performed at 31.2 microg/mL, 62.5 microg/mL, and 125 microg/mL, while the Salmonella reverse mutation assay (Ames test) was performed at doses of 61.72, 185.18, 555.55, 1666.67, and 5000.00 microg/plate.

RESULTS

HPLC and HPTLC analysis of BM revealed the presence of bacoside A3, bacopaside I, bacopaside II, jujubogenin isomer of bacopasaponin C, bacosine, luteolin, apigenin, bacosine, and beta-sitosterol D glucoside. BM demonstrated significant antioxidant activity. The number of chromosomal aberrations and the frequency of micronuclei induced by BM were not statistically significant up to a dose of 62.5 microg/mL. A subsequent dose of 125 microg/mL prior to metabolic activation induced mild clastogenicity, but it was found to be biologically insignificant as this effect was not seen post metabolic activation. BM also demonstrated a dose-dependent protection against the clastogens used in this study using the above tests for clastogenicity. Maximum protection was observed in presence of metabolic activation. Moreover, BM demonstrated no mutagenic effect on the tested strains, as observed in the Ames test.

CONCLUSION

BM protected human lymphocytes against various clastogens. BM also exhibited high antioxidant activity which might be responsible for the observed protective effects against the clastogens since the used clastogens are known to induce their clastogenic effects via production of oxidative radicals.

Assessment of the genotoxicity of imidacloprid and metalaxyl in cultured human lymphocytes and rat bone-marrow

Imidacloprid and metalaxyl are two pesticides that are widely used in agriculture, either separately, or in combination. These agents were studied for their possible genotoxic effects with respect to the following cytogenetic end-points: (1) in vitro micronucleus (MN) formation and sister-chromatid exchange (SCE) induction in human lymphocytes and (2) in vivo micronucleus induction in polychromatic erythrocytes (PCEs) of the rat bone-marrow. The results of the MN analysis indicate that MN frequencies after treatment with both pesticides, separately or as a mixture, do not significantly differ from those in the controls except after treatment with metalaxyl alone at 50 microg/ml (p<0.05). The results of the SCE analysis show that SCE frequencies after treatment with imidacloprid do not differ significantly from those in the controls. A statistically significant increase (p<0.05) in SCE frequency resulted from treatments with metalaxyl at 5, 10 and 100 microg/ml and with the combination of imidacloprid and metalaxyl at 100 and 200 microg/ml. Finally, the in vivo micronucleus assay with rat bone-marrow polychromatic erythrocytes showed a statistically significant effect upon separate treatments with imidacloprid and metalaxyl at doses of 300 mg/kg body weight (b.w.) (p<0.01) or upon combined treatment with 200 mg/Kg b.w. (p<0.001) and 400 mg/kg b.w. (p<0.05).

In vitro induction of cytotoxicity and DNA strand breaks in CHO cells exposed to cypermethrin, pendimethalin and dichlorvos

The indiscriminate use of pesticides and herbicides to increase crop productivity has aroused a great concern among the environmental and health scientists due to their adverse effects in both target as well as non-target species. Although substantial information is available regarding their environmental and ecological impact, not much is known in regard to its toxicity in the mammalian system. Therefore a study was conducted for the assessment of cytotoxic and genotoxic effects of cypermethrin (Type II pyrethroid) dichlorvos (organophosphate) and pendimethalin (dinitroaniline herbicide) in Chinese hamster ovary (CHO) cells. CHO cells were exposed to 1 microM, 10 microM, 100 microM, 1000 microM, and 10,000 microM, cypermethrin, pendimethalin and dichlorvos for 3h and cytotoxicity was assessed by MTT assay. Their genotoxic potential was also evaluated by Comet assay. The results demonstrate that dichlorvos and pendimethalin exhibited higher extent of cytotoxicity as compared to cypermethrin. A significant (p<0.05) concentration dependent increase in DNA damage was observed with dichlorvos (0.01 microM and above) and pendimethalin (0.1 microM and above) as evident by Comet assay parameters viz., Olive tail moment (arbitrary units), tail DNA (%) and tail length (muM). Cypermethrin induced a significant (p<0.05) DNA damage only at higher concentrations (1000 and 5000 microM). Our data indicates that these chemicals produce cytotoxicity and DNA damage in mammalian cells and should be used with caution.

Ficus racemosa Stem Bark Extract: A Potent Antioxidant and a Probable Natural Radioprotector

Ethanol extract (FRE) and water extract (FRW) of Ficus racemosa (family: Moraceae) were subjected to free radical scavenging both by steady state and time resolved methods such as nanosecond pulse radiolysis and stopped-flow spectrophotometric analyses. FRE exhibited significantly higher steady state antioxidant activity than FRW. FRE exhibited concentration dependent DPPH, ABTS^•−, hydroxyl radical and superoxide radical scavenging and inhibition of lipid peroxidation with IC₅₀ comparable with tested standard compounds. In vitro radioprotective potential of FRE was studied using micronucleus assay in irradiated Chinese hamster lung fibroblast cells (V79). Pretreatment with different doses of FRE 1h prior to 2 Gy γ-radiation resulted in a significant (P < 0.001) decrease in the percentage of micronucleated binuclear V79 cells. Maximum radioprotection was observed at 20 μg/ml of FRE. The radioprotection was found to be significant (P < 0.01) when cells were treated with optimum dose of FRE (20 μg/ml) 1 h prior to 0.5, 1, 2, 3 and 4 Gy γ-irradiation compared to the respective radiation controls. The cytokinesis-block proliferative index indicated that FRE does not alter radiation induced cell cycle delay. Based on all these results we conclude that the ethanol extract of F. racemosa acts as a potent antioxidant and a probable radioprotector.

Cytogenetic effects of commercial formulations of deltamethrin and/or isoproturon on human peripheral lymphocytes and mouse bone marrow cells

The cytogenetic effects of deltamethrin (DEL) and/or isoproturon (ISO) were examined in human lymphocytes and mouse bone marrow cells. Peripheral lymphocytes were exposed to DEL (2.5, 5, 10, or 20 microM), ISO (25, 50, 100, or 200 microM), or DEL + ISO (2.5 + 25, 5 + 50, 10 + 100, or 20 + 200 microM) and cytogenic effects were evaluated via chromosomal aberrations (CA) and the cytokinesis-block micronucleus assay (CBMN). Mice were orally gavaged to single dose of DEL (6.6 mg/kg), ISO (670 mg/kg), or DEL+ISO (6.6 + 670 mg/kg) for 24 hr or to DEL (3.3 mg/kg/day), ISO (330 mg/kg/day), or DEL + ISO (3.3 + 330 mg/kg/day) for 30 days and analyzed for CA. DEL induced a significant frequency of CA at 10 microM whereas ISO (25-100 microM) alone, or in combination with DEL, did not show any significant effect. Micronucleus (MN) induction was observed to be concentration-dependent though significant frequencies were observed at 5 microM DEL, 100 microM ISO, or 5 + 50 microM DEL + ISO. In mice, DEL inhibited the mitotic index (MI) significantly (P < 0.001) at 24 hr while ISO alone, or in combination with DEL, did not cause any statistically significant effect. Following a 24 hr exposure, DEL and ISO alone induced significant (P < 0.01) frequencies of CA, whereas DEL + ISO in combination did not. Furthermore, 30 days exposure of ISO significantly inhibited the MI (P < 0.02 or < 0.01) and induced CA while DEL alone, or in combination with ISO, resulted in no significant effect on CA or the MI. The present findings indicate that the in vitro and in vivo exposure of a commercial formulation of DEL can cause genotoxic effects in mammals. However, the coexposure of DEL and ISO did not show additive effects, but instead demonstrated somewhat reduced genotoxicity.

In vitro evaluation of the genotoxicity of acetamiprid in human peripheral blood lymphocytes

Acetamiprid, a neonicotinoid insecticide, is commonly used both in agriculture and domestic areas against a wide range of insects. The potential genotoxicity of a commercial formulation of acetamiprid (Mosetam 20 SP, containing 20% acetamiprid as the active ingredient) on human peripheral blood lymphocytes was examined in vitro by sister chromatid exchange (SCE), chromosomal aberrations (CAs), and micronucleus tests. Cells were treated with 25, 30, 35, and 40 mug/ml of acetamiprid for 24 and 48 hr. Acetamiprid induced SCEs and CAs significantly at all concentrations and treatment times and micronucleus formation was significantly induced at 30, 35, and 40 mug/ml of acetamiprid as compared with both the control and solvent control. Acetamiprid decreased the proliferation index (PI) at the two highest concentrations (35 and 40 mug/ml) for the 24-hr treatment period and only at the highest concentration (40 mug/ml) for the 48-hr treatment period when compared with the control and solvent control. Peripheral lymphocytes exposed to all concentrations of acetamiprid showed significant decreases in mitotic index (MI) and nuclear division index (NDI) for both treatment periods when compared with both the control and solvent control. Furthermore, acetamiprid decreased the MI in both treatment periods, and the NDI only in the 24-hr treatment period to the same extent as the positive control, mitomycin C (MMC). This study presents the first in vitro evidence for the genotoxicity of a commercial formulation of acetamiprid in human peripheral lymphocytes.

Telomere length modulates human radiation sensitivity in vitro

The molecular basis of the interindividual differences of normal individuals to ionizing radiation is poorly understood. Several studies in telomerase KO mice with short telomeres have uncovered an inverse relationship between telomere length and radiation sensitivity. The present work aims to determine if chromosome radiosensitivity is correlated with telomere length in healthy individuals. With this purpose, individual radiosensitivity was determined by the micronucleus assay in peripheral blood lymphocytes from two groups of individuals of the same age but with highly heterogeneous telomere length, selected from a population of 181 individuals where we previously measured telomere length. Our study demonstrates that telomere length modulates chromosome in vitro radiosensitivity in healthy individuals as the group with short telomeres presented higher frequencies of ionizing radiation-induced micronuclei when compared to the long telomeres group. This result supports the conclusion that individual telomere length acts as biomarker of individual chromosome instability upon exposure to ionizing radiation.

Cytogenetic observations in human peripheral blood leukocytes following in vitro exposure to THz radiation: a pilot study

Emerging technologies are considering the possible use of Terahertz radiation in different fields ranging from telecommunications to biology and biomedicine. The study of the potential effects of Terahertz radiation on biological systems is therefore an important issue in order to safely develop a variety of applications. This paper describes a pilot study devoted to determine if Terahertz radiation could induce genotoxic effects in human peripheral blood leukocytes. For this purpose, human whole blood samples from healthy donors were exposed for 20 min to Terahertz radiation. Since, to our knowledge, this is the first study devoted to the evaluation of possible genotoxic effects of such radiation, different electromagnetic conditions were considered. In particular, the frequencies of 120 and 130 GHz were chosen: the first one was tested at a specific absorption rate (SAR) of 0.4 mW g-1, while the second one was tested at SAR levels of 0.24, 1.4, and 2 mW g-1. Chromosomal damage was evaluated by means of the cytokinesis block micronucleus technique, which also gives information on cell cycle kinetics. Moreover, human whole blood samples exposed to 130 GHz at SAR levels of 1.4 and 2 mW g-1 were also tested for primary DNA damage by applying the alkaline comet assay immediately after exposure. The results obtained indicate that THz exposure, in the explored electromagnetic conditions, is not able to induce either genotoxicity or alteration of cell cycle kinetics in human blood cells from healthy subjects.

Cytotoxicity and genotoxicity of ultrafine crystalline SiO2 particulate in cultured human lymphoblastoid cells

Respirable crystalline silica has been classified as a human lung carcinogen. Ultrafine (diameter < 100 nm) silica particles may be important in carcinogenesis, although the mechanisms remain unclear. In the present study, WIL2-NS cells were incubated for 6, 24, and 48 hr with 0, 30, 60, and 120 microg/ml ultrafine crystalline SiO(2) (UF-SiO(2)). The cytotoxic and genotoxic effects caused by UF-SiO(2) in cultured human cells were investigated via a set of bioassays. Significant dose- dependent decreases in percent cell viability were seen with increasing dose of UF-SiO(2) in the methyl tetrazolium assay. Significant decreases were seen at 120 microg/ml (58, 38, and 57% for 6, 24, and 48-hr exposure, respectively). During 4 days growth in the flasks, there was a slight recovery observed after washing off UF-SiO(2) as measured by the population growth assay. Significant dose-dependent reduction in the cytokinesis block proliferation index was observed by the cytokinesis block micronucleus assay. Treatment with 120 microg/ml UF-SiO(2) for 24 hr produced a fourfold increase in the frequency of micronucleated binucleated cells (MNBNC). The increase in MNBNC was dose-dependent. The lowest dose that gave a statistically significant increase in MNBNC was 30 microg/ml (24-hr treatment), which had cytotoxicity of less than 10%. There was no significant difference in DNA strand breakage as measured by the Comet assay. A significant increase in induced mutant frequency was found at 120 microg/ml as detected by the hypoxanthine guanine phosphoribosyltransferase mutation assay. The results indicate that UF-SiO(2) is cytotoxic and genotoxic in cultured human cells.

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.

Aneugenic potential of the nitrogen mustard analogues melphalan, chlorambucil and p-N,N-bis(2-chloroethyl)aminophenylacetic acid in cell cultures in vitro

Melphalan (MEL), chlorambucil (CAB) and p-N,N-bis(2-chloroethyl)aminophenylacetic acid (PHE) are nitrogen mustard analogues, which are clinically used as chemotherapeutic agents. They also exert carcinogenic activity. The aim of this study was to investigate the aneugenic potential of the above drugs and the possible mechanism responsible for this activity. The Cytokinesis Block Micronucleus (CBMN) assay in combination with fluorescence in situ hybridization (FISH) was used in human lymphocyte cultures to evaluate micronucleus (MN) frequency. Pancentromeric probe (alpha-satellite) was applied to identify chromosomes in micronuclei and an X-chromosome specific centromeric probe was used to asses micronucleation and non-disjunction of this chromosome in binucleated cells. The effect of the above compounds on the organization of mitotic apparatus, as a possible target of chemicals with aneugenic potential, was investigated in C(2)C(12) mouse cell line by double immunofluorescence of alpha- and gamma-tubulin. We found that the studied drugs increased MN frequency in a linear dose-dependent manner primarily by chromosome breakage and in a lesser extent by an aneugenic mechanism. Non-disjunction and micronucleation of X-chromosome were also induced. Abnormal metaphase cells were linearly increased with concentration and characterized by abnormal centrosome number. Interphase cells with micronuclei and abnormal centrosome number were also observed. Since nitrogen mustards are highly reactive agents, with low selectivity and form covalent bonds with different nucleophilic sites in proteins and nucleic acids, it is reasonable to consider that one possible pathway for nitrogen mustard analogues to exert their aneugenic activity is through reaction with nucleophilic moieties of proteins or genes that are involved in the duplication and/or separation of centrosomes, resulting in abnormal centrosome number. Based on our results the carcinogenicity of nitrogen mustard analogues studied may be attributed not only to their activity to trigger gene mutation and chromosome breakage, but also to their aneugenic potential. Further studies are warranted to clarify the above two hypotheses.

The frequency of sister chromatid exchange and micronuclei in evaluation of cytogenetic activity of Kombucha on human peripheral blood lymphocytes

Kombucha is a refreshing beverage obtained by the fermentation of sweetened black tea with a ?tea fungus? (symbiotic culture of acetic acid bacteria and yeasts). It is consumed due to its potential beneficial effects on human health. The aim of this study was to investigate activity of Kombucha on human peripheral blood lymphocytes in vitro. We analyzed Kombucha made from different substrates: Camellia sinensis and Satureja montana, and effects of substrates alone. The frequencies of sister chromatid exchange (SCE) and micronuclei (MN) were scored as genetic endpoints and mitomycin C was used as model mutagen. Kombucha from Camellia sinensis and Camellia sinensis substrate increased frequency of MN and SCE on mitomycin C-treated and -untreated peripheral blood lymphocytes. However, Kombucha from Satureja montana reduced incidence of MN on mitomycin C-treated and -untreated peripheral blood lymphocytes, while SCE frequency was higher than control value. In our pilot study we showed for the first time that Kombucha from different substrates induced different effects on mitomycin C-treated and -untreated peripheral blood lymphocytes.

Increased frequency of micronuclei in peripheral blood lymphocytes of subjects infected with Helicobacter pylori

Epidemiological studies have demonstrated a close association between infection with Helicobacter pylori and the development of gastric carcinoma and mucosa-associated lymphoid tissue lymphomas in humans. The cytokinesis-block micronucleus assay was performed on peripheral blood lymphocytes of H. pylori-infected patients in order to investigate the possible induction of genotoxic damage. The study group consisted of 70 infected subjects including 33 women and 37 men, and 66 healthy controls (37 females and 29 males). Our results indicate that in the infected group the overall frequency of binucleated micronucleated cells (BNMN) per 1000 cells was higher (17.65+/-1.55) than in the controls (7.39+/-0.66), this difference being statistically significant. No differences were found between the infected and control groups regarding the cytokinesis-block proliferation index (CBPI). When the effect of different counfounding factors was evaluated, mutivariate statistical analysis revealed that age and alcohol consumption modulated the frequency of BNMN in infected people, and the interaction between alcohol use-smoking-infection also affected the BNMN frequency in H. pylori patients. Our results indicate that infection by H. pylori is associated with an increased level of cytogenetic damage in the cells of the host.

Cyto- and genotoxicity of ultrafine TiO2 particles in cultured human lymphoblastoid cells

Titanium dioxide is frequently used in the production of paints, paper, plastics, welding rod-coating material, and cosmetics, because of its low toxicity. However, recent studies have shown that nano-sized or ultrafine TiO(2) (UF-TiO(2)) (<100 nm in diameter) can generate pulmonary fibrosis and lung tumor in rats. Cytotoxicity induced by UF-TiO(2) in rat lung alveolar macrophages was also observed. This generates great concern about the possible adverse effects of UF-TiO(2) for humans. The cytotoxicity and genotoxicity of UF-TiO(2) were investigated using the methyl tetrazolium cytotoxicity (MTT) assay, the population growth assay, the apoptosis assay by flow cytometry, the cytokinesis block micronucleus (CBMN) assay, the comet assay, and the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene mutation assay. WIL2-NS cells were incubated for 6, 24 and 48 h with 0, 26, 65 and 130 microg/ml UF-TiO(2). Significant decreases in viability were seen in the MTT assay at higher doses; for example, 61, 7 and 2% relative viability at 130 microg/ml for 6, 24 and 48-h exposure (P<0.01). A dose-dependent relationship was observed, while a time-dependent relationship was seen only at the highest dose (130 microg/ml) after exposure for 24 and 48 h. Treatment with 130 microg/ml UF-TiO(2) induced approximately 2.5-fold increases in the frequency of micronucleated binucleated cells (P<0.01). In addition, a significant reduction in the cytokinesis block proliferation index was observed by the CBMN assay (P<0.05). In the comet assay, treatment with 65 microg/ml UF-TiO(2) induced approximately 5-fold increases in olive tail moment (P<0.05). In the HPRT mutation assay, treatment with 130 microg/ml UF-TiO(2) induced approximately 2.5-fold increases in the mutation frequency (P<0.05). The results of this study indicate that UF-TiO(2) can cause genotoxicity and cytotoxicity in cultured human cells.

Methylglyoxal-bis(guanylhydrazone), a polyamine analogue, sensitized γ-radiation-induced cell death in HL-60 leukemia cells Sensitizing effect of MGBG on γ-radiation-induced cell death

Methylglyoxal-bis(guanylhydrazone) (MGBG), a polyamine analogue, has been known to inhibit the biosynthesis of polyamines, which are important in cell proliferation. We showed that MGBG treatment significantly affected γ-radiation-induced cell cycle transition (G(1)/G(0)→S→G(2)/M) and thus γ-radiation-induced cell death. As determined by micronuclei and comet assay, we showed that it sensitized the cytotoxic effect induced by γ-radiation. One of the reasons is that polyamine depletion by MGBG treatment did not effectively protect against the chemical (OH) or physical damage to DNA caused by γ-radiation. Through in vitro experiment, we confirmed that DNA strand breaks induced by γ-radiation was prevented more effectively in the presence of polyamines (spermine and spermidine) than in the absence of polyamines. MGBG also blocks the cell cycle transition caused by γ-radiation (G(2) arrest), which helps protect cells by allowing time for DNA repair before entry into mitosis or apoptosis, via the down regulation of cyclin D1, which mediates the transition from G(1) to S phase of cell cycle, and ataxia telangiectasia mutated, which is involved in the DNA sensing, repair and cell cycle check point. Therefore, the abrogation of G(2) arrest sensitizes cells to the effect of γ-radiation. As a result, γ-radiation-induced cell death increased by about 2.5-3.0-fold in cells treated with MGBG. However, exogenous spermidine supplement partially relieved this γ-radiation-induced cytotoxicity and cell death. These findings suggest a potentially therapeutic strategy for increasing the cytotoxic efficacy of γ-radiation.

SFTG international collaborative study on in vitro micronucleus test

This study on the in vitro micronucleus assay, comprising 11 laboratories using human lymphocytes, was coordinated by an organizing committee supported by the SFTG (the French branch of the European Environmental Mutagen Society). Nine coded substances were assessed for their ability to induce micronuclei in human lymphocytes in vitro, mitomycin C being used as a positive control. Cultures were exposed to the test substances for a short (early or late) time or for a long time, followed by a short or long recovery period, in the presence of cytochalasin B. Each chemical was evaluated, generally in two laboratories, using three treatment schedules at least twice. The data were assessed for acceptability, and then classified as negative, positive or equivocal. Two of seven genotoxic compounds, namely colchicine and bleomycin, clearly induced micronuclei. Reproducible results were difficult to obtain for some substances, which tended to be those acting at specific stages of the cell cycle. Cytosine arabinoside, diethylstilboestrol and 5-fluorouracil were classified as equivocal. Urethane and thiabendazole were classified as negative. The two presumed non-genotoxic compounds, mannitol and clofibrate, did not induce micronuclei. Repeat testing, exposing cells at both an early and late time after mitogenic stimulation, was needed to detect substances classified as equivocal. These results show the importance of achieving sufficient inhibition of nuclear division to avoid the possibility of missing an effect. The evaluation of micronuclei in mononucleated as well as binucleated cells was particularly useful to detect aneugens. There were no false positive results using lymphocytes, indicating a high specificity. It is concluded that the clastogenic or aneugenic potential in vitro of the substances tested was correctly identified in this study, but that refining the protocol to take into account factors such as the stages of the cell cycle exposed to the compound, or the duration of recovery would be likely to improve the sensitivity of detection using lymphocytes.

Exposure to Radiofrequency Radiation (900 MHz, GSM signal) does not Affect Micronucleus Frequency and Cell Proliferation in Human Peripheral Blood Lymphocytes: An Interlaboratory Study

The objective of this study was to investigate whether 24 h exposure to radiofrequency electromagnetic fields similar to those emitted by mobile phones induces genotoxic effects and/or effects on cell cycle kinetics in cultured human peripheral blood lymphocytes. The effect of 900 MHz exposure (GSM signal) was evaluated at four specific absorption rates (SARs, 0, 1, 5 and 10 W/kg peak values). The exposures were carried out in wire patch cells under strictly controlled conditions of both temperature and dosimetry, and the induction of genotoxic effects was evaluated in lymphocyte cultures from 10 healthy donors by applying the cytokinesis-block micronucleus assay. Positive controls were provided by using mitomycin C. Two research groups were involved in the study, one at ENEA, Rome, and the other at CNR-IREA, Naples. Each laboratory tested five donors, and the resulting slides were scored by both laboratories. Following this experimental scheme, it was also possible to compare the results obtained by cross-scoring of slides. The results obtained provided no evidence for the existence of genotoxic or cytotoxic effects in the range of SARs investigated. These findings were confirmed in the two groups of five donors examined in the two laboratories and when the same slides were scored by two operators.

Genotoxicity of hydrochlorothiazide in cultured human lymphocytes. I. Evaluation of chromosome delay and chromosome breakage

Hypertension is often treated with diuretics, like hydrochlorothiazide (HCTZ). Previous results on the in vitro genotoxicity of HCTZ are equivocal. In the present study, we have evaluated the genotoxicity of HCTZ in cultured human lymphocytes using the Cytokinesis Blocked Micronucleus (CBMN) assay. In addition, micronucleus (MN) induction was analyzed by Fluorescence In Situ Hybridization (FISH) with an alpha-satellite DNA centromeric probe to distinguish between clastogenic and aneugenic effects. Lymphocyte cultures from 32 healthy adults were exposed to 5 and 40 microg/ml HCTZ. Age, gender, and smoking were evaluated as factors affecting the MN analysis. We found that HCTZ increased MN frequencies. FISH analysis revealed that HCTZ exerts its genotoxicity more strongly at the 40 microg/ml concentration, and principally through chromosome delay (aneugenicity). Multiregression analysis of our results confirmed the known effect of age and gender on MN induction in human lymphocytes. Smoking was also a confounding factor for MN induction, especially for centromere-negative MN frequencies. Under the experimental conditions used, only age had a clear positive effect on the response of lymphocytes to HCTZ. These data indicate that HCTZ produces micronuclei in cultured human lymphocytes by a mechanism that involves chromosome delay and to a lesser extent through chromosome breakage.

Potential of chlorpyrifos and cypermethrin forming DNA adducts

DNA adducts consist of DNA monoadducts, DNA intrastrand crosslinks, DNA interstrand crosslinks, and DNA-protein crosslinks. If not repaired or mistakenly repaired, DNA adducts may lead to gene mutations and initiate carcinogenesis. Two insecticides, chlorpyrifos and cypermethrin, were studied for their potential of forming DNA monoadducts, DNA interstrand crosslinks, and DNA-protein crosslinks in primary mouse hepatocytes via the assays of bioluminescence, ethidium bromide fluorescence, and K+-SDS precipitation. DNA interstrand crosslinks were also measured on calf thymus DNA. It was shown that chlorpyrifos could not form DNA adducts. Cypermethrin formed DNA monoadducts and DNA interstrand crosslinks in hepatocytes. However, cypermethrin didn't form DNA interstrand crosslinks on calf thymus DNA and in hepatocytes treated with SKF-525A, a cytochrome P450 inhibitor, which suggests that active metabolites of cypermethrin instead of cypermethrin itself caused DNA interstrand crosslinks and that cytochrome P450 may be involved in the activation of cypermethrin.

Effects of Tiron, 4,5-dihydroxy-1,3-benzene disulfonic acid, on human promyelotic HL-60 leukemia cell differentiation and death

Tiron, 4,5-dihydroxy-1,3-benzene disulfonic acid, has been known to be a widely used antioxidant to rescue ROS-evoked cell death and a non-toxic chelator to alleviate an acute metal overload. In this study, we showed that Tiron is a potent inducer of cell differentiation and apoptotic cell death in human promyelotic HL-60 leukemia cell. At a low level of concentration (<0.5mM), Tiron caused HL-60 cells to induce differentiation-related alterations such as the increase of CD11b and CD14 expression or chromatin condensation. Hypoxia inducible factor-1alpha (HIF-1alpha) was also increased at mRNA and protein level, and thus the CCAAT/enhancer-binding protein alpha, which is a downstream target of HIF-1alpha and acts as a critical factor for granulocytic differentiation was increased. High dose of Tiron (>0.5mM) induced severe DNA damage in HL-60 cells, as measured by the cytokinesis-block micronucleus test and the comet assay. Consequently, high dose of Tiron led to apoptotic cell death, which showed the DNA fragmentation, the caspase activation and the unbalance between antiapoptotic (Bcl-2) and proapoptotic proteins (Bax). However, an exogenous supplement of iron (FeCl(3)) reversed all of these effects, the cell differentiation and the apoptotic cell death. Therefore, these results suggest that Tiron-mediated differentiation and cell death result from the disturbance of iron metabolism.

Cytogenetic analysis of Pakistani individuals occupationally exposed to pesticides in a pesticide production industry

Although several cytogenetic biomonitoring studies on workers exposed to pesticides have been reported, there is only limited information on this topic from developing countries where pesticides have been widely used over the years. People in developing countries are at higher risk from exposure, due to poor working conditions and a lack of awareness of the potential hazards during manufacturing and application of the pesticides. The present study has assessed the genotoxic effects of pesticides on workers involved in the pesticide manufacturing industry. Subjects in the exposed group (29) were drawn from workers at a pesticide production plant in district Multan (Pakistan). The control group (unexposed) composed of 35 individuals from the same area but was not involved in pesticide production. Liver enzymes, serum cholinesterase (SChE), micronucleus assay and some haematological parameters were used as biomarkers in this study. A statistically significant (P < 0.001) increase in levels of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase was detected in exposed workers with respect to the control group. There was a significant (P < 0.001) decrease in the level of SChE in the exposed group. Exposed individuals exhibited cytogenetic damage with increased frequencies (P < 0.001) of binucleated cells with micronuclei and total number of micronuclei in binucleated lymphocytes in comparison with subjects of the control group. A decrease (P < 0.001) in cytokinesis block proliferation index similarly demonstrates a genotoxic effect due to pesticide exposure. The results indicate that the pesticide industry workers have experienced significant genotoxic exposure. This study highlights the risk to workers in the pesticide manufacturing industries of developing countries such as Pakistan and the need for implementation of suitable safety measures to prevent/limit exposure to harmful toxins.

Clastogenicity of the fungicide afugan in cultured human lymphocytes

The genotoxic effects of the fungicide afugan were analysed by measuring chromosomal aberrations (CAs), sister chromatid exchange (SCE) and micronuclei (MN) in cultured human peripheral lymphocytes. Concentrations of 2.5, 5, 10 and 20 microg/ml of afugan were used during 24 and 48 h. Afugan significantly increased the frequency of CAs at 5, 10 and 20 microg/ml concentrations during a 48 h treatment period. A significant increase was observed for induction of SCE and MN at all treatments compared with the negative control. A significant dose-response correlation was found in all tests. Afugan did not affect the replicative index (RI), however it significantly decreased the mitotic index (MI) at all treatment concentrations except 2.5 microg/ml, and at both treatment times. The present results indicate that afugan is clastogenic and cytotoxic to cultured human lymphocytes.

Humic acids reduce the genotoxicity of mitomycin C in the human lymphoblastoid cell line TK6

The antimutagenic/desmutagenic activity of a leonardite humic acid (LHA) and a soil humic acid (SHA) was studied in the cultured human lymphoblastoid cell line TK6 treated with mitomycin C (MMC) as reference mutagen by evaluating the induction of micronuclei (MN). Two different concentrations of HA were used, 2.5 and 10 microg/ml, in three different treatments: (1) HA alone (genotoxic test); (2) HA after 2-h pre-incubation with 0.3 microM of MMC (desmutagenic test) and (3) combinations of HA and MMC at 0.3 microM without pre-incubation (antimutagenic test). Neither of the HA used alone did produce genotoxic effects, but both HAs reduced significantly the frequencies of MN induced by MMC, especially in the desmutagenic test. A slight cell-protective effect against the cytotoxicity of MMC was also exhibited by the two HAs in the desmutagenic test. The LHA showed a desmutagenic/antimutagenic activity that was more pronounced than that of SHA, which is possibly related to the higher carboxylic group content and lower phenolic group content of LHA. These results confirm the antigenotoxic action exerted by HAs in human cells, similarly to what has been previously observed in various plant species.

Cytogenetic effects of commercial formulation of cypermethrin in root meristem cells of Allium sativum: Spectroscopic basis of chromosome damage

To validate the use of Allium sativum as a sensitive test model for genotoxicity, the cytogenetic effects of a commercial formulation of the pyrethroid insecticide, cypermethrin, were evaluated in the root meristem cells of A. sativum. Ultraviolet (UV) and Fourier transform infrared (FTIR) spectral measurements were also carried out to understand the interaction of cypermethrin with DNA. In a preliminary toxicity assay, the EC50 for Allium root growth was estimated to be 8 ppm. For the cytogenetic assay, root meristem cells were exposed to 1, 2, 4, 8 and 16 ppm of the test compound for 24 h, and either processed immediately for analysis or incubated in water for 24 h of recovery and then processed. Cells analyzed immediately after the exposure had a significant, dose-dependent inhibition of mitotic index (MI) and induction of mitotic and chromosomal aberrations (MAs and CAs). The 24 h recovery period reduced the effect of the test compound on the MI and percent aberrations; however, cells exposed to 8 and 16 ppm showed a significant frequency of aberrations despite the recovery period. One part per million cypermethrin was consistently negative in the assay. The data indicate that higher doses of cypermethrin produce toxicity, CAs and MAs in A. sativum. The present study indicates that A. sativum is a sensitive and reliable test system. A bathochromic shift observed in UV absorption spectra reveals that cypermethrin binds with DNA. Role of vibrational modes of the active site in the recognition and reaction of cypermethrin with DNA has been discussed. Based on spectroscopic data and structural properties, a possible mechanism has been proposed for the interaction of cypermethrin with DNA resulting in chromosomal aberrations.

Evaluation of cytogenetic and DNA damage induced by the antibacterial drug, trimethoprim

Trimethoprim, a widely used antimicrobial drug was tested for its effect on the level of nuclear DNA damage in cultured peripheral blood lymphocytes in terms of chromosome and DNA alterations. The extent of cytogenetic damage, expressed as chromosome breakage and chromosome loss, was evaluated employing the cytokinesis block micronucleus method (CBMN) in cultured peripheral blood lymphocytes coupled with fluorescence in situ hybridization (FISH) using a digoxigenin-labelled alphoid DNA probe specific for the centromere of all human chromosomes. The DNA breakage level was evaluated by the Comet assay. Cultures were set up by using blood samples from two healthy donors. A range of concentrations of the test agent (from 1 to 100 microg/ml) was used for the micronuclei (MN) frequency and cytogenetic origin of MN. For the Comet assay the range of doses used was from 0.5 to 150 microg/ml. From the results obtained it appears that this antifolic agent has a significant clastogenic potential, as detected by a dose-dependent increase of the incidence of C-MN and significantly greater than control levels at the highest concentrations tested (25,100 microg/ml). In addition, the results obtained in the Comet assay also show that trimethoprim induces a dose-dependent increase in the level of DNA breakage, this increase attaining statistical significance at the highest concentrations tested (25, 100, 150 microg/ml), which would confirm its genotoxicity.

In vivo cytogenetic effects of a commercially formulated mixture of cypermethrin and quinalphos in mice

In vivo cytogenetic effects of commercially formulated cypermethrin (CYP, synthetic pyrethroid insecticide) and/or quinalphos (QUI, organophosphate insecticide), generally used in combination, were examined through chromosomal aberrations (CA) and micronucleus test (MT) in mice. Male mice were orally gavaged to a single dose of CYP/QUI commercial mixture (22, 44 or 67 mg/kg b.wt.) for 24h (CA) or 48 h (MT). Based on the concentrations of active ingredients of CYP and QUI present in the test doses of CYP/QUI mixture, mice were orally exposed to 0.66, 1.32 and 2 mg/kg of CYP or 4.4, 8.8 and 13.4 mg/kg of QUI. For reference, a group of five mice was intraperitoneally administered to cyclophosphamide (20 or 50 mg/kg) or orally gavaged to peanut oil for vehicle control. Exposure of CYP/QUI mixture inhibited the mitotic index (MI) and induced CA in a dose-dependent manner at 24 h; however, significant (p<0.01 or 0.001) frequencies of CA were observed at 44 mg/kg onwards, whereas inhibition of MI at 67 mg/kg. Independent exposure of QUI at 8.8 mg/kg onwards also significantly (p<0.01 or 0.001) inhibited MI and induced CA, whereas CYP at 2 mg/kg (highest concentration in CYP/QUI mixture) inhibited MI significantly but failed to induce CA. Chromatid breaks and fragments found to be frequent aberrations in all the test groups. Treatment of CYP/QUI mixture also induced micronucleus formation dose-dependently at 48 h, yet statistically significant (p<0.001) frequencies of micronucleated polychromatic erythrocytes (MNPCE) were observed at 44 mg/kg onwards. QUI (8.8 and 13.4 mg/kg) alone also induced significant frequencies of MNPCE, whereas frequencies of MNPCE observed with the CYP even at 2 mg/kg were comparable to that of vehicle control. Present findings indicate the genotoxicity potential of CYP/QUI mixture and suggest that the simultaneous presence of the toxic doses of CYP and QUI can lead to synergistic genotoxicity in mice and may pose mutagenic risk in human beings.