Induction of micronuclei and nuclear lesions in Channa punctatus following exposure to carbosulfan,glyphosate and atrazine

Abstract

The genotoxic effects of commonly used agricultural pesticides viz., carbosulfan, glyphosate, and atrazine, were evaluated in Channa punctatus (Pisces, Perciformes) using micronucleus (MN) test and induction of nuclear lesions (NL). The 96?h LC₅₀ value were estimated by probit analysis as 0.27, 32.0 and 42.0?mg?L^?1, respectively, for carbosulfan, glyphosate, and atrazine using semi-static bioassays. Based on these values, three sublethal test concentrations of carbosulfan (0.07, 0.13, 0.20?mg?L^?1), glyphosate (8.1, 16.3, 24.4?mg?L^?1) and atrazine (10.6, 21.2, 31.8?mg?L^?1) corresponding to ¼, ½ and ¾ of the LC₅₀ of the pesticides respectively, were selected for exposure for 96?h. Peripheral blood samplings were taken at intervals of 24?h for assessment of MN and NL frequencies. Considerably higher genotoxic damage was induced by carbosulfan as compared to glyphosate and atrazine. There were significant effects (p?<?0.01) of concentrations in all the treated groups. The induction of MN and NL was highest at 96?h pesticide exposure at all test concentrations. The nuclear abnormalities recorded in this study, such as blebbed-, lobed-, notched- and bi-nuclei, other than micronuclei, are indicators of genotoxic damage.     

Genotoxicity assessment of carp (Cyprinus carpio L.) fingerlings by tissue DNA damage and micronucleus test,after environmental exposure to fenitrothion

The purpose of this study was to evaluate the adverse effects of sublethal doses of fenitrothion, an organophosphothionate insecticide on brain, gill, liver, and muscle tissues as a ratio of 8-OHdG to dG to indicate the DNA damage and erythrocyte micronucleus frequency for genotoxicity of carp (Cyprinus carpio L.) fingerlings. In our study, the mean weights and lengths of the fish (n?=?4–12) were 31.13?±?14.24?g and 12.53?±?1.41, respectively. Before the experiment, fish were maintained in aerated dechlorinated tap water at 21.8?±?1°C and fed daily with commercial feed at a rate of 2% of their body weights. Experiments were conducted under static conditions in the aquaria. Technical grade (95%) fenitrothion was diluted in acetone to give a dosing solution of 10?mg/L. The increased lesions/10⁶ DNA bases (p?<?0.05) of liver tissue of exposure group (0.49?±?0.18) was observed when compared to control group (0.28?±?0.30). There was not any significant differences between brain tissues, no damage were detectable in gill and muscle tissues of control groups, and in exposure groups altered levels of damage were detected for gill (0.06?±?0.05) and muscle (0.16?±?0.21) tissues. The increased micronucleus frequencies (%) in erythrocytes of carp following the exposure to 48?h fenitrothion (6.43?±?3.89; p<0.05) was observed when compared to control group (1.29?±?1.03). The available data indicate that there is still lack of well-established dose–response relationships between occupational or environmental exposures and the induction of 8-OHdG. Such biomarkers may be used in assessing adverse/toxic effects of pesticides as environmental stressors.     

Assessment of DNA damage in lymphocytes of workers exposed to X-radiation using the micronucleus test and the comet assay.

The mutagenic and carcinogenic effects of genotoxic agents on exposed people have constituted an increasing concern. Therefore, the objective of this work was to assess DNA damage in lymphocytes of workers exposed to X-radiation using the cytokinesis-blocked micronucleus test and the comet assay (single-cell gel electrophoresis), and to compare these two techniques in the monitoring of exposed populations. The cytokinesis-blocked micronucleus test and the comet assay were employed in the monitoring of 22 workers occupationally exposed to X-radiation in a hospital in southern Brazil. The frequency of dicentric bridges was also measured. The results of both assays and the frequency of dicentric bridges revealed a significant increase in genetic effects on the cells of exposed individuals. Age was significantly correlated with micronucleus frequency and damage index in the comet assay. The concomitant analysis of dicentric bridges when determining micronucleus frequency does not require much extra work, and may serve as a reference to the type of mutagenic effect (clastogenic or aneugenic). The combination of the alkaline comet assay with the cytokinesis-blocked micronucleus test appears to be very informative for the monitoring of populations chronically exposed to genotoxic agents.     

DNA damage and oxidative stress induced by CeO2 nanoparticles in human dermal fibroblasts: Evidence of a clastogenic effect as a mechanism of genotoxicity

Abstract

The broad range of applications of cerium oxide (CeO₂) nanoparticles (nano-CeO₂) has attracted industrial interest, resulting in greater exposures to humans and environmental systems in the coming years. Their health effects and potential biological impacts need to be determined for risk assessment. The aims of this study were to gain insights into the molecular mechanisms underlying the genotoxic effects of nano-CeO₂ in relation with their physicochemical properties. Primary human dermal fibroblasts were exposed to environmentally relevant doses of nano-CeO₂ (mean diameter, 7?nm; dose range, 6?×?10^?5–6?×?10^?3?g/l corresponding to a concentration range of 0.22–22?µM) and DNA damages at the chromosome level were evaluated by genetic toxicology tests and compared to that induced in cells exposed to micro-CeO₂ particles (mean diameter, 320?nm) under the same conditions. For this purpose, cytokinesis-blocked micronucleus assay in association with immunofluorescence staining of centromere protein A in micronuclei were used to distinguish between induction of structural or numerical chromosome changes (i.e. clastogenicity or aneuploidy). The results provide the first evidence of a genotoxic effect of nano-CeO₂, (while not significant with micro-CeO₂) by a clastogenic mechanism. The implication of oxidative mechanisms in this genotoxic effect was investigated by (i) assessing the impact of catalase, a hydrogen peroxide inhibitor, and (ii) by measuring lipid peroxidation and glutathione status and their reversal by application of N-acetylcysteine, a precusor of glutathione synthesis in cells. The data are consistent with the implication of free radical-related mechanisms in the nano-CeO₂-induced clastogenic effect, that can be modulated by inhibition of cellular hydrogen peroxide release.     

Antioxidant and Anticlastogenic Capacity of Prickly Pear Juice

Plants belonging to the genus Opuntia spp. are the most abundant of the Cactaceae family, grown throughout America and the Mediterranean central area. Its fruit, known as cactus pear or prickly pear, is an oval berry grouped in different colors. Some studies have shown its antioxidant activities which may help in preventing chronic pathologies such as diabetes. The purpose of the study was to evaluate the antioxidant capacity of three varieties of prickly pear juice (red-purple, white-green and yellow-orange) in five different concentrations (100, 250, 500, 750, and 1000 mg/mL) by DPPH (1,1-diphenyl-2-picrylhydrazyl radical) colorimetric method, selecting the best variety to determine its anticlastogenic potential against methyl methanesulfonate (MMS). The results indicate that the highest antioxidant was found in the juice of the prickly pear red-purple variety (PPRP), in all concentrations. Its anticlastogenic potential was therefore evaluated with a micronucleus assay. The experiment was run over two weeks. A negative control was included along with a positive control with MMS (40 mg/kg), a group of mice treated with PPRP (25 mL/kg), and three groups with PPRP (in doses of 25, 16.5 and 8.3 mL/kg) plus the mutagen. The PPRP was administered daily by oral gavage and the MMS was injected intraperitoneally five days prior to the end of the experiment. Blood samples were obtained at 0, 24, 48, 72 and 96 h in order to determine the frequency of micronucleated polychromatic erythrocytes (MNPE). The results indicated that PPRP is not a genotoxic agent, on the contrary, it may reduce the number of MNPE. In this regard, the PPRP showed an anticlastogenic effect directly proportional to its concentrations. Thus, the highest protection was obtained with a concentration of 25 mL/kg after 48 h of treatment.     

无花果提取物致突变及抗突变研究

目的: 研究无花果提取液(fig extract,FE)致突变及抗突变效应.方法:用体外人淋巴细胞微核测试法,研究了FE对丝裂霉素C(MMC)和-射线诱变作用的影响.结果:FE 0.05～0.45 (g/ml)剂量范围内,对人淋巴细胞无致突变性,但可拮抗MMC和-射线诱发突变和老年人、肿瘤患者自发微核形成.结论:FE具抗突变作用.     

Cytogenetic effects of vincristine sulfate and ethylene dibromide in human peripheral lymphocytes: micronucleus analysis.

Micronuclei kinetics and persistence in mononucleated and binucleated human peripheral lymphocytes following short-term (4 hr) and continuous (until harvest) in vitro exposure to vincristine sulfate (VS) and ethylene dibromide (EDB) were studied. Lymphocytes were exposed to chemicals for various doses and harvested at different culture times. Micronucleus frequencies were scored in both mononucleated and binucleated cells on the same slide. VS-treated cells showed a significantly higher incidence of micronucleus in both mononucleated and binucleated cells than controls (P less than 0.01). The cells treated continuously with VS produced comparatively higher frequencies of micronucleated cells than those treated for 4 hr. Highest micronuclei frequencies were observed 24 hr after chemical treatment in both mononucleated and binucleated cells and decreased later with time. However, the micronucleus frequencies remained significantly higher than the controls even in the cells harvested at 144 hr. VS induced a large number of micronucleated cells with multiple micronuclei. VS also caused a severe decrease in nuclear division due to cytotoxic effect. Lymphocytes treated with EDB for 4 hr and continuously showed a statistically higher incidence of micronuclei in binucleated cells compared to the controls (P less than 0.05), whereas in mononucleated cells higher micronucleus frequencies were observed only in cultures treated continuously. Continuous presence of EDB induced both dose- and time-dependent increase of micronuclei in both mono- and binucleated cells (P less than 0.05). EDB induced relatively few multiple micronucleated cells in comparison with VS. EDB did not affect nuclear divisions even with continuous treatment. High micronucleus frequencies observed at 144 hr harvest following 4 hr treatment of both EDB and VS suggest the persistence of DNA damage in cells. These studies suggest that micronuclei kinetics in human peripheral lymphocytes depends on the genotoxic potentially and cytotoxicity of a genotoxicant.     

Inhibitory effects of water extract of propolis on doxorubicin-induced somatic mutation and recombination in Drosophila melanogaster.

Propolis is a substance produced by honeybees (Apis mellifera L.). Its components are strong antioxidants and free radical scavengers. The aim of this study was to evaluate the protective effects of a water extract of Brazilian green propolis (WEP) combined with the antitumor agent doxorubicin (DXR) on Drosophila melanogaster wing cells through the somatic mutation and recombination test (SMART). Two different crosses were used: The standard (ST) cross and the high bioactivation (HB) cross. The HB cross is characterized by a constitutively enhanced level of cytochrome P450 which leads to an increased sensitivity to a number of promutagens and procarcinogens. Larvae obtained from these two crosses were chronically treated with different concentrations of WEP (12.5,25.0 and 50.0 mg/mL) alone or combined with DXR (0.125 mg/mL). The results obtained with the two different crosses were rather similar. Neither toxicity nor genotoxicity were observed in WEP treated series. Simultaneous treatment with different concentrations of WEP and DXR led to a reduction in the frequency of recombination compared to the treatment with DXR alone. This anti-recombinogenic effect was proportional to the concentrations applied, indicating a dose-response correlation and can be attributed to the powerful scavenger ability of WEP.     

Evaluation of the genetic toxicity of middle distillate fuels

Petroleum middle distillate (PMD) fuels are mixtures of hydrocarbons that distill between ～ 170-370°C. Commercial products that fall into this category include kerosine, diesel fuel, jet fuel, and home heating oil. These products contain both saturated (paraffins and cycloparaffins) and aromatic species, but because of the boiling range normally contain very small amounts of the 3-6 ring polycyclic aromatic hydrocarbon (PAH) constituents, which are considered to be carcinogenic. Nevertheless, there is evidence of weak tumorigenic activity when these materials are repeatedly applied to mouse skin. In the current studies representative products were tested in two commonly used, short-term assays for genetic toxicity, the Salmonella/mammalian microsome mutagenicity assay and the mouse bone marrow micronucleus test. All samples were inactive in the micronucleus assay, and three were clearly inactive in the Salmonella test. Of the remaining two, one was marginally active in the Salmonella assay, and one was equivocal. The marginally active sample contained detectable levels of PAH due to the use of catalytically cracked materials as blending stocks. The results indicated that PMDs that do not contain cracked material were not mutagenic. Thus they may produce tumors via nongenotoxic processes. Those products that do contain cracked stocks may have sufficient PAH to be mutagenic in the Salmonella assay, and in those cases the PAH might also contribute to tumor formation. © 1994 Wiley-Liss, Inc.     

祛痹痛注射液的致突变作用观察

用３种不同遗传终点的短期测试方法检测一类新药祛痹痛的致突变作用。Ａｍｅｓ试验是检测基因突变的微生物回复突变试验，微核试验和ＣＨＬ细胞染色体畸变试验分别检测体细胞哺乳动物培养细胞的染色体损伤。结果表明这３种诱变试验均为阴性，提示祛痹痛注射液无致突变性。