大气污染物致突变研究中的Breakpoint回归

本文在用Ames试验和SOS显色法两个细菌短期测试系统研究广州地区1991年的大气总悬浮颗粒（TSP）二氯化烷（DCM）提取物遗传毒性的基础上,建立了气温（T）,气压（P）,风速（W）,降雨量（R）,相对湿度（RH）5种主要气象因素与诱变力和诱导力之间的Breakpoint回归模型,回归效果显著。     

Sensitivity of different endpoints for in vitro measurement of genotoxicity of extractable organic matter associated with ambient airborne particles (PM10)

Sensitivity and correlations among three endpoints were evaluated to assess the genotoxic potential of organic complex mixtures in vitro. This study was focused on DNA adduct formation, DNA single strand break induction and tumour suppressor p53 protein up-regulation produced by extractable organic matter (EOM) absorbed on respirable particulate matter PM₁₀ (particulate matter < 10 μm) collected in three European cities (Prague, Sofia, Košice) during winter and summer period. To compare the sensitivity of particular endpoints for in vitro measurement of complex mixture genotoxicity, the metabolically competent human hepatoma cell line Hep G2 was treated with equivalent EOM concentration of 50 μg/ml. Cell exposure to EOMs resulted in significant DNA adduct formation and DNA strand break induction, however, a lack of protein p53 up-regulation over the steady-state level was found. While the maximum of DNA strand breaks was determined after 2 h cell exposure to EOMs, 24 h treatment interval was optimal for DNA adduct determination.No substantial location- and season-related differences in EOM genotoxicity were detected using DNA strand break assessment. In agreement with these results no significant variation in DNA adduct levels were found in relation to the locality and season except for the monitoring site in Prague. The Prague EOM sample collected during summer period produced nearly three-fold lower DNA adduct level in comparison to the winter EOM sample.Comparable results were obtained when the ambient air genotoxicity, based on the concentration of carcinogenic PAHs in cubic meter of air (ng c-PAHs/m³), was elicited using either DNA adduct or strand break determination. In general, at least six-fold higher genotoxicity of the winter air in comparison to the summer air was estimated by each particular endpoint. Moreover, the genotoxic potential of winter air revealed by DNA adduct assessment and DNA strand break measurement increased in the same order: Košice  Prague < Sofia.Based on these data we suppose that two endpoints DNA breakage and DNA adduction are sensitive in vitro biomarkers for estimation of genotoxic activity of organic complex mixture associated with airborne particles. On the other hand, the measurement of protein p53 up-regulation manifested some limitations; therefore it cannot be used as a reliable endpoint for in vitro genotoxicity assessment.     

急性臭氧暴露对大鼠肺部细胞遗传毒性的影响*

目的: 探讨不同浓度臭氧急性暴露对大鼠肺部细胞的遗传毒性的影响。方法: 36只wistar大鼠随机分为对照组(过滤空气暴露)、臭氧暴露组(0.12 ppm、0.5 ppm、1.0 ppm、2.0 ppm、4.0 ppm)共6组,每组6只。以不同浓度的臭氧对大鼠进行动态染毒4 h后,取肺组织并分离单细胞,采用酶联免疫吸附法检测8-羟基脱氧鸟苷(8-OHdG),利用彗星实验、微核试验和DNA-蛋白质交联实验进行DNA和染色体损伤分析。结果: 与对照组相比,肺组织中8-OHdG含量从臭氧暴露浓度为0.12 ppm起即显著增加,在0.5 ppm时达到最高值。随着臭氧暴露浓度升高,彗星拖尾率逐渐上升,且存在明显的剂量-效应关系;DNA-蛋白质交联率有先升高后下降的趋势,且在2.0 ppm时达到最大值;而肺部细胞微核率尽管呈现出上升趋势,但与对照组相比无显著性差异。结论: 急性臭氧暴露在较低浓度(0.12 ppm)时即可导致大鼠肺部细胞的DNA损伤;而在较高浓度(4 ppm)时却未见显著的染色体损伤。     

Structure/activity investigations in eight arylalkyltriazenes comparison of chemical stability,mode of decomposition,and SCE induction in Chinese hamster V79-E cells

A series of seven 1-aryl-3.3-dialkyltriazenes, including 1-phenyl-3.3-dimethyltriazene (DMPT), 1-phenyl-3.3-di-(trideuteromethyl)-triazene (DMPT-ds), 1-p-methylphenyl-3.3-dimethyltriazene (DMpMPT), 1-p-nitrophenyl-3.3-dimethyltriazene (DMpNPT), 1-phenyl-3.3-diethyltriazene (DEPT), 1-phenyl-3.3-di-n-propyltriazene (DnPrPT) and 1-phenyl-3.3-diisopropyltriazene (DiPrPT) and 1.3-diphenyl-3-methyltriazene (DPMT), was synthesized and characterized by UV/VIS, IR and ¹H-NMR spectroscopy. Chemical half-life was determined in phosphate buffer at 37° using UV/VIS spectroscopy. With the exception of DMpNPT, which was stable, the triazenes underwent pH-dependent hydrolytic decomposition (acid catalysis). By means of UV/VIS spectra, TLC and HPLC, phenol, aniline and secondary azocoupling products were identified after complete hydrolytic cleavage of the parent compounds. Pathways of spontaneous hydrolysis are proposed and discussed. Genotoxic activity of the triazenes was assayed by measurement of sister chromatid exchanges (SCE) in V79-E cells without and with rat liver S9 mix as an exogenous metabolizing system. In the direct SCE assay (without S9 mix), all triazenes except DMpNPT exerted a toxic action (cell cycle delay) in a narrow concentration range between no effect and overt cytotoxicity. This non-specific toxicity depended on the pH of the incubation system and was inversely proportional to chemical half-life. The toxicity of these agents is most likely due to the arenediazonium cation which is a relatively stable intermediate. In a sublethal concentration range most triazeness induced significant increases of SCE rates. These are interpreted as an indirect consequences of cytotoxicity. Upon metabolic activation, the compounds were genotoxic in a dose-dependent fashion. Their SCE-inducing capacity depended on the nature of the alkylating species generated, i.e., the alkyldiazonium cation, and on chemical stability. Surprisingly, no deuterium isotope effect was observed in DMPT-d₆. The order of genotoxic activity among the aryldialkyltriazenes was DMpNPT DMPT = DMPT- ds > DMpMPT DEPT > DnPrPT DiPrPT. DMPT was a marginal SCE inducer but very toxic upon metabolic activation. As monooxygenation of DPMT, like spontaneous hydrolysis, should generate a phenyldiazonium cation, the results suggest that arylation of DNA causes a very low SCE induction, if any.Abbreviations BUdR 5-bromodeoxyuridine - CP cyclophosphamide - DEPT 1-phenyl-3.3-diethyltriazene - DiPrPT 1-phenyl-3.3-diisopropyltriazene - DMPT 1-phenyl-3.3-dimethyltriazene - DMPT-d₆ 1-phenyl-3.3-di(trideuteromethyl)triazene - DMpMPT 1-p-methylphenyl-3.3-dimethyltriazene - DMpNPT 1-p-nitrophenyl-3.3-dimethyltriazene - DnPrPT 1-phenyl-3.3-di-n-propyltriazene - DPMT 1.3-diphenyl-3-methyltriazene - SCE sister chromatid exchange     

Transcriptome profiling reveals similarities and differences in plant responses to cadmium and lead

We analyzed the influence of salts of two heavy metals—lead and cadmium (Pb²⁺ and Cd²⁺) on plants, including plant and root size, plant genome stability as well as global genome expression. Measurement of the metal uptake showed that there was a significantly higher incorporation of Cd than of Pb, 0.6 and 0.15 uM per gram of dry weight, respectively. The analysis of the root length and plant size showed a dose dependent decrease in plants exposed to cadmium. In contrast there was little difference in the size of plants exposed to lead, although there was nearly four-fold increase of the root length. Analysis of the genome stability revealed that cadmium led to a dose dependent increase of homologous recombination whereas lead had no effect.

Analysis of the global genome expression of plants chronically exposed to 50 uM of Cd and Pb revealed 65 and 338 up- and down-regulated genes by Cd and 19 and 76 by Pb, respectively. Interestingly, half of the genes that changed their expression in Pb-treated plants also changed their expression in Cd-treated ones. The greater number of genes regulated by Cd reflects generally higher genome instability of plants as well as higher uptake as compared to Pb.     

Role of the Alkali Labile Sites,Reactive Oxygen Species and Antioxidants in DNA Damage Induced by Methylated Trivalent Metabolites of Inorganic Arsenic

In the last decade arsenic metabolism has become an important matter of discussion. Methylation of inorganic arsenic (iAs) to monomethylarsonic acid (MMA^V) and dimethylarsinic acid (DMA^V) is considered to decrease arsenic toxicity. However, in addition to these pentavalent metabolites, the trivalent metabolites monomethylarsonous (MMA^III) and dimethylarsinous acid (DMA^III) have been identified recently as intermediates in the metabolic pathway of arsenic in cultured human cells. To examine the role of oxidative damage in the generation of DNA strand breaks by methylated trivalent arsenic metabolites, we treated human lymphocytes with both metabolites at non-cytotoxic concentrations. We further tested whether these effects are sensitive to modulation by the antioxidants ascorbate (Vitamin C) and selenomethionine (Se-Met). Both trivalent metabolites produced oxidative stress related DNA damage, consisting of single strand breaks and alkali-labile sites, with MMA^III being more potent at low concentrations than DMA^III. Neither MMA^III nor DMA^III induced DNA-double strand breaks. The oxidative stress response profiles of the metabolites were parallel as determined by lipid peroxidation induction. MMA^III induced peroxidation from the lowest concentration tested, while effects of DMA^III were apparent only at concentrations above 10 μM. The antioxidant Se-Met exhibited a more pronounced inhibition of trivalent arsenic metabolite-induced oxidative-DNA damage than did vitamin C. The present findings suggest that DNA damage by methylated trivalent metabolites at non-cytotoxic concentrations may be mediated by a mix of reactive oxygen and nitrogen oxidized species.     

单细胞凝胶电泳技术及在土壤生态毒理学中的应用

单细胞凝胶电泳技术又称为彗星实验,是最近几年发展起来的一种快速、简单、灵敏、可靠的检测细胞核DNA损伤的技术。总结了近几年来单细胞凝胶电泳技术的发展、原理、方法及其应用,并指出其下一步的发展趋势。彗星实验中,镶嵌于琼脂糖中的细胞核在电场中向正极移动,因细胞核与DNA片段迁移速率不同,而形成类似“彗星”的图像。目前采用的彗星实验有多种,可以检测诸如DNA双链断裂、单链断裂、碱不稳定位点等多种类型的DNA损伤。碱性彗星实验因其高灵敏度而被广泛采用。彗星实验的主要步骤包括细胞核悬浮液的获得、彗星电泳胶板制备、细胞裂解、DNA变性解旋、电泳、中和、染色和观察等。目前彗星实验广泛应用于各个研究领域,近年来开始用于环境污染的基因毒性研究和生物监测,并取得了迅速发展。     

Different effects of newly isolated saponins on the mutagenicity and cytotoxicity of the anticancer drugs mitomycin C and bleomycin in human lymphocytes

Aim of the present paper was to assess by using the in vitro micronucleus (MN) test in human lymphocytes the effect of two plant extracts isolated from Bupleurum fruticosum (saponins) on the clastogenicity and cytotoxicity of the anticancer drugs mitomycin C (MMC) and bleomycin (BLM). One saponin showed a dose-dependent MMC-induced mutagenesis inhibition together with co-genotoxic effect on BLM-treated cultures. The remaining saponin did not significantly alter MN induction of both chemotherapeutic agents whereas it enhanced BLM cytotoxicity.     

There is no such a thing as a free cigarette; lining nests with discarded butts brings short‐term benefits,but causes toxic damage

Adaptation to human‐modified environments such as cities is poised to be a major component of natural history in the foreseeable future. Birds have been shown to adapt their vocalizations, use of nesting places and activity rhythms to the urban environments, and we have previously reported that some species, including the house finch (Carpodacus mexicanus), use cellulose from smoked cigarette butts as lining material and thus reduce the number of ectoparasites in their nests, probably because the nicotine repels arthropods. Nicotine is only one of hundreds of potentially harmful substances found in cigarette butts. Here, we investigated whether the presence of such chemicals is harmful for house finches adding cigarette butts to their nests. We found that hatching and fledging success and chick immune response were all positively correlated to the proportion of the nest that was made up of butts. However, the signs of genotoxicity in the blood cells also increased with the proportion of butt cellulose in the nests. Although we have not measured the effect of genotoxicity on post‐fledging survival and breeding success, it seems that bringing cigarette butts to the nest has negative consequences that may counterbalance the benefits of using them as ectoparasites repellents.     

Investigation of Cadmium-Induced Genotoxicity and Oxidative Stress Response in Indian Major Carp,Labeo rohita

We investigated genotoxicity and oxidative stress in the gills of Labeo rohita exposed to 33.6, 67.1, and 100.6 mg L^–1of cadmium chloride at 96 h. Genotoxicity was assessed using single cell gel electrophoresis whereas oxidative stress was monitored through lipid peroxidation induction and antioxidant response parameters, namely reduced glutathione (GSH), glutathione peroxidase, glutathione-S-transferase, superoxide dismutase, and catalase (CAT) activities. Significant (p < .05) effect of both concentration and time of exposure was observed on the extent of DNA damage in treated fish. Similarly, malondialdehyde content, level of GSH, and activities of antioxidant enzymes were significantly elevated in treated groups, except CAT. The increased DNA damage and lipid peroxidation (LPO) content along with fluctuation in antioxidant defense system in fish indicated the interaction of cadmium (Cd) with DNA repair processes and production of reactive oxygen species. Thus, Cd is liable for induction of LPO, alteration of antioxidant defenses, and DNA damage in gills of L. rohita.