重金属诱导拟南芥原生质体DNA损伤的单细胞凝胶电泳检测

以拟南芥原生质体为实验体系,研究不同浓度的3种重金属离子对拟南芥原生质体的毒性和DNA损伤的差异。结果表明,用1-5mmol·L^-1的Zn^2＋、Cd^2＋和Cu^2＋分别处理的拟南芥原生质体,2小时内活力逐渐下降,并表现出明显的浓度依赖性：与相同浓度的Cd^2＋和Cu^2＋相比,Zn^2＋对拟南芥原生质体活力的影响程度较小,表现出较低的毒性。单细胞凝胶电泳检测发现,用0．1-0．8mmol·L^-1的Zn^2＋、Cd^2＋和Cu^2＋分别处理拟南芥原生质体30分钟,以OTM值表示的原生质体DNA损伤量随重金属离子浓度的增加而递增：相同浓度（0．5mmol·L^-1）的3种重金属离子相比,Zn^2＋对原生质体的遗传毒性明显低于Cu^2＋和Cd^2＋。综合原生质体活力和DNA损伤的单细胞凝胶电泳检测结果,发现ZnO^2＋对拟南芥原生质体的遗传毒性较低,而CdO^2＋和Cu^2＋的遗传毒性较高。本研究建立的拟南芥原生质体实验体系,结合运用单细胞凝胶电泳技术,能够快速、灵敏地检测重金属对植物细胞的遗传毒性。     

重金属Cd2+、Pb2+ 和Zn2+ 对泥鳅 DNA损伤的研究

采用单细胞凝胶电泳技术(SCGE),研究重金属Cd2 、Pb2 、Zn2 在不同暴露时间(1—35d)、单一重金属离子不同暴露浓度(0.05mg/L、0.5mg/L、5.0mg/L)或混合重金属离子(Cd2 Pb2 、Cd2 Zn2 、Pb2 Zn2 、Cd2 Pb2 Zn2 )相同浓度(0.5mg/L)条件下对泥鳅肝胰脏细胞核DNA的损伤作用。以带彗尾核DNA百分率和彗尾长度(TL)与核直径(D)比值为指标,探讨DNA损伤级别与处理浓度间的相关性。结果显示,随着处理时间的延长,带彗尾核DNA百分率和TL/D值均呈上升趋势,5.0mg/L Zn2 组28d时带彗尾核DNA百分率最高(84.85%),35d的TL/D值亦为所有组中最高(2.50);对DNA损伤作用,初期以1级损伤为主,7d后以3级损伤为主,且损伤率超过80%;Cd2 、Pb2 和Zn2 之间的联合毒性表现复杂,但总体表现为Cd2 存在时能增强Pb2 或Zn2 对DNA的损伤作用。总之,重金属Cd2 、Pb2 和Zn2 对泥鳅肝胰脏细胞核DNA损伤具有明显的浓度和时间效应,利用SCGE技术可对水环境污染导致的生物基因毒性作用进行监测。     

过量表达拟南芥AtGCS可以提高E.coli的重金属耐受性及富集能力(英文)北大核心CSCD

谷胱甘肽(GSH)是一类在生物体内广泛存在,并且是十分重要的重金属毒害保护剂之一。本研究将编码拟南芥γ-谷氨酰半胱氨酸合成酶基因AtGCS(GSH合成的关键酶之一)转化到大肠杆菌(BL21)中,通过IPTG诱导过量表达TrxA-AtGCS融合蛋白来分析AtGCS在提高大肠杆菌重金属耐受性方面的作用。过量表达TrxA的大肠杆菌被用作对照。研究结果表明,在1 mmol.L-1Cd2+、Zn2+或Cu2+重金属胁迫下,过量表达TrxA-AtGCS的大肠杆菌细胞的生长状态要明显优于表达TrxA的对照细胞。同时,过量表达TrxA-AtGCS的大肠杆菌表现出超出对照细胞5倍以上的Cd2+、Zn2+和Cu2+累积量和4倍以上的GSH含量,其中,高于对照10倍的Cd2+富集量尤为明显。因而可以得出结论,拟南芥AtGCS的大量表达大大提升了大肠杆菌的谷胱甘肽含量,从而使GSH可以直接或间接地富集更多的重金属离子,进而提高了大肠杆菌对重金属逆境的抗性。     

重金属复合污染对小麦种子根活力的影响

应用二次回归旋转设计法,以小麦种子为材料,研究了水培条件下重金属复合污染对其根生长及活力的影响;借助回归分析建立了相应的数学模型,分析了Cu、Zn、Cd和Pb4种重金属对根活力的毒性、两两重金属问的联合作用以及各重金属的边际毒性效应．结果表明重金属对根活力的影响顺序为Pb＞Cu＞Cd＞Zn;Cu与Cd、Cu与Zn、Zn与Cd以及Cd与Pb元素间的互作效应显著;在0-20mg.L^-1浓度范围内,Cu和zn两元素在最小浓度时的边际效应值最大,Cd和Pb两元素的边际效应最大值却出现在最高浓度处．     

镉、锌、铜胁迫对向日葵早期幼苗生长的影响

分析了3种重金属离子(Cd2+、Cu2+、Zn2+)对向日葵种子胚根伸长和早期幼苗生长的影响.结果表明,3种重金属离子对向日葵胚根伸长的抑制作用依次为:Cd2+>Cu2+>Zn2+.3种重金属胁迫明显降低了幼苗生长和叶绿素含量,并显著提高了H2O2水平.其中Cd2+胁迫引起幼苗H2O2爆发高于Cu2+和Zn2+胁迫.进一步分析植株抗氧化系统的变化发现,随着重金属离子浓度的增加,向日葵幼苗酶类抗氧化物质SOD和CAT的活性表现为先增加后降低的趋势;重金属胁迫提高了非酶类的抗氧化物质脯氨酸和GSH的含量.其中Cd2+和Zn2+胁迫对脯氨酸含量变化的影响大于Cu2+胁迫;而Cu2+胁迫对GSH含量变化的影响大于Cd2+和Zn2+胁迫.     

重金属胁迫引起的水稻和小麦幼苗DNA损伤

供试浓度的重金属Cu2 、Cd2 和Hg2 能在不同程度上导致水稻和小麦DNA损伤。 (1)Hg2 ≥ 0 .0 2 5mmol L、Cu2 和Cd2 ≥ 0 .1mmol L处理使水稻幼苗期外DNA合成速率显著高于对照 ,且当Cu2 、Cd2 和Hg2 浓度进一步增高时 ,水稻幼苗期外DNA合成速率呈现先上升而后较最大值有所下降的规律。 (2 ) 0 .1～1.0mmol L的Cu2 及 0 .1mmol L的Cd2 、Hg2 能引起水稻、小麦叶内DNA和蛋白质交联 ,并且这种和DNA交联的蛋白质易被胰蛋白酶水解。 (3) 0 .1～ 1.0mmol L的Hg2 及 1.0mmol L的Cd2 还能使水稻、小麦叶片内DNA链间发生交联     

Ca~(2+)和K~+对拟南芥幼苗镉毒害的缓解作用

该文探讨了外源钙(Ca)或钾(K)处理对不同程度的镉(Cd)胁迫(0–80μmol·L–1)下拟南芥(Arabidopsis thaliana)幼苗的生长和生理特性的影响。综合Ca和K对不同浓度Cd胁迫下拟南芥幼苗生长、根长以及生物量的影响情况,表明各浓度Cd胁迫下外源Ca2+的最适缓解浓度均为10 mmol·L–1;而K+的最适缓解浓度在低浓度(20和40μmol·L–1)和高浓度(60和80μmol·L–1)Cd胁迫下分别为10 mmol·L–1和20 mmol·L–1。在低浓度Cd胁迫下,添加适宜浓度的Ca2+或K+后幼苗可溶性蛋白和丙二醛(MDA)含量以及超氧化物歧化酶(SOD)活性相比未添加Ca和K的对照组无显著变化,而过氧化物酶(POD)活性和总酚、类黄酮、花色素苷,酸溶性硫醇化合物、谷胱甘肽(GSH)、植物螯合肽(PCs)的含量均下降;高浓度Cd处理下,添加适宜浓度的Ca2+或K+后幼苗的SOD活性升高,POD活性降低,可溶性蛋白、MDA、总酚、类黄酮、花色素苷、酸溶性硫醇化合物、GSH以及PCs的含量也均低于对照组。在各浓度Cd胁迫下,添加外源Ca或K均使拟南芥幼苗根部细胞DNA损伤减弱,表现为TT嘧啶二聚体的累积量显著减少(P0.05)。以上结果表明,在Cd胁迫(尤其是高浓度Cd胁迫)下,外源Ca或K通过调节酚类、金属螯合物质的代谢水平以及提高拟南芥的抗氧化能力来缓解Cd对拟南芥幼苗的毒害效应,缓解细胞DNA损伤。该研究结果不仅能够为深入探讨Ca和K对缓解重金属毒害的分子机理提供实验依据,而且为Ca和K应用于重金属污染的防治提供参考。     

煤矿区耐镉青霉菌的分离鉴定

[目的]分离鉴定煤矸石中耐Cd2+菌株.[方法]用菌落形态和18S rRNA序列分析鉴定菌株,研究菌株的重金属耐性和在酸性煤矸石浸出液的生长能力,分析其抗氧化酶活性对重金属复合污染的响应.[结果]BJKD4菌株为青霉属(Penicillium sp.)菌,能耐29 mmol/L的Cd2+,不同重金属对BJKD4的毒性大小依次为:Cu2+＞Ni2+＞Cd2+＞pb2+或Zn2+＞Mn2+.正交试验表明BJKD4菌株能在不同浓度重金属Cd、Zn、Ni和Mn等复合污染条件下生长,SOD活性在重金属复合污染时升高,CAT活性变化依重金属的种类和浓度不同而不同;此外,BJKD4能在含有煤矸石酸性浸出液的培养基中生长,并提高其pH.[结论]BJKD4菌株能耐多种重金属,具有阻止煤矸石山淋溶液酸化的应用潜力.抗氧化酶在减缓重金属诱导的氧化胁迫中起重要作用.     

除草剂乐草隆对红鲫的遗传毒性研究

目的　探讨除草剂乐草隆对红鲫的遗传毒性。方法　用单细胞凝胶电泳检测不同浓度的乐草隆对红鲫外周血淋巴细胞DNA的损伤作用。结果　乐草隆致毒红鲫的淋巴细胞DNA的迁移度均较阴性对照组高 (P<0 0 5 ) ,在一定浓度范围内 (0～ 7 0 0mg L)DNA损伤程度与浓度呈正相关 (r=0 982 ,P <0 0 1)。在 12h、2 4h、4 8h、96h、10d实验组DNA损伤程度均有增强的趋势。结论　乐草隆对红鲫具有一定的遗传毒性     

四种重金属对中国鲎(Tachypleus tridentatus)胚胎发育的影响

分析了不同离子浓度的Zn、Pb、Cu、Cd对中国鲎胚胎发育的影响.结果表明①4种金属离子浓度≤渔业水域水质标准浓度4倍时,对中国鲎胚胎发育无明显毒性效应;≥渔业水域水质标准浓度8倍时,Cd离子和Cu离子对中国鲎胚胎发育无明显影响,而Zn离子组Pb离子组胚体发育随离子浓度提高而卵径变小,发育速度下降;②浓度为1.6mg/L时,Zn和Pb离子组胚胎致畸率分别为44%和58%,Pb离子组胚体孵化率仅2.67%;③4种重金属对中国鲎胚胎发育的毒性效应表现为Pb＞Zn＞Cu=Cd;④中国鲎胚胎对重金属有蓄积作用,蓄积效应随金属种类不同而异.     

胁迫时间与非毒性离子对重金属抑制拟南芥种子发芽及幼苗生长的影响

测定了Hg²⁺、Cd²⁺、Cu²⁺、Pb²⁺单一重金属胁迫对拟南芥种子发芽和幼苗生长的影响.结果表明,重金属对幼苗生长的毒性大于对种子发芽的毒性,以抑制种子发芽的IC₅₀为指标,4种重金属的毒性顺序为Hg²⁺＞Cd²⁺＞Pb²⁺/Cu²⁺,以幼苗生长为指标,则毒性顺序为:Cu²⁺＞Hg²⁺＞Cd²⁺/Pb²⁺,并随着胁迫时间延长,种子萌发率下降.此外,不同重金属在不同发芽时段对种子的毒性也不尽相同,Cd²⁺的毒性在种子吸水后的0～12 h大于12～24 h,而Hg²⁺毒性在12～24 h大于0～12 h,其中,种皮对减轻重金属毒性起着十分重要的作用.通过非毒性离子(Ca²⁺、Mg²⁺、K⁺、Na⁺)与重金属离子(Hg²⁺、Cd²⁺、Cu²⁺、Pb²⁺)交互作用对拟南芥种子发芽及幼苗生长效应的研究发现, mmol·L^-1的Ca²⁺、Mg²⁺、K⁺、Na⁺可以增强Hg²⁺对种子发芽的毒性,但对Cd²⁺的毒性却没有影响.对于幼苗来说,Ca²⁺、Mg²⁺、K⁺、Na⁺可以显著增强Hg²⁺的毒性,Ca²⁺可以缓解Cd²⁺的毒性,但却增加Cu²⁺的毒性,K⁺可以缓解Pb²⁺对幼苗的毒害作用.最后,本文对重金属的毒害机理进行了探讨.     

Hyperaccumulation of cadmium and zinc in Thlaspi caerulescens and Arabidopsis halleri at the leaf cellular level

Vacuolar compartmentalization or cell wall binding in leaves could play a major role in hyperaccumulation of heavy metals. However, little is known about the physiology of intracellular cadmium (Cd) sequestration in plants. We investigated the role of the leaf cells in allocating metal in hyperaccumulating plants by measuring short-term (109)Cd and (65)Zn uptake in mesophyll protoplasts of Thlaspi caerulescens "Ganges" and Arabidopsis halleri, both hyperaccumulators of zinc (Zn) and Cd, and T. caerulescens "Prayon," accumulating Cd at a lower degree. The effects of low temperature, several divalent cations, and pre-exposure of the plants to metals were investigated. There was no significant difference between the Michaelis-Menten kinetic constants of the three plants. It indicates that differences in metal uptake cannot be explained by different constitutive transport capacities at the leaf protoplast level and that plasma and vacuole membranes of mesophyll cells are not responsible for the differences observed in heavy metal allocation. This suggests the existence of regulation mechanisms before the plasma membrane of leaf mesophyll protoplasts. However, pre-exposure of the plants to Cd induced an increase in Cd accumulation in protoplasts of "Ganges," whereas it decreased Cd accumulation in A. halleri protoplasts, indicating that Cd-permeable transport proteins are differentially regulated. The experiment with competitors has shown that probably more than one single transport system is carrying Cd in parallel into the cell and that in T. caerulescens "Prayon," Cd could be transported by a Zn and Ca pathway, whereas in "Ganges," Cd could be transported mainly by other pathways.     

Effects of heavy metals Cd2+, Pb2+ and Zn2+ on DNA damage of loach Misgurnus anguillicaudatus

The effects of heavy metals Cd2+, Pb2+ and Zn2+ at 0.05, 0.5 and 5.0 mg/L level and their interactions at 0.5 mg/L level on DNA damage in hepatopancreas of loach Misgurnus anguillicaudatus for 1-35 days exposure were examined by single cell gel electrophoresis (SCGE). For each test group, 20 loaches with similar body size (5.17-7.99g; 11.79-13.21 cm) were selected and kept in aquaria with dechlori-nated water at (22±1)℃ and fed a commercial diet every 48 h. According to the percentage of damaged DNA with tail and its TL/D (tail length to diameter of nucleus) value, the relationship between DNA damage degree and heavy metal dose and exposure time was determined. Results showed that the percentage of damaged DNA and the TL/D value were increased with the prolonged exposure time. The highest percentage (84.85%) of damaged DNA was shown in 5.0 mg/L Zn2+ group after 28 days exposure and the biggest TL/D value (2.50) in all treated groups after 35 days exposure. During the first treated week, the damnification of DNA was mainly recognized as the first level, after that time, the third damaged level was mostly observed and the percentage of damaged DNA was beyond 80%. The joint toxic effects among Cd2+, Pb2+ or Zn2+ revealed much complexity, but it generally displayed that the presence of Cd2+ could enhance the genotoxicity of Pb2+ or Zn2+. In conclusion, the results suggested that there was a significant time-and dose-depended relationship between the heavy metal and DNA damage in hepatopancreas of loach, and SCGE could represent a useful means to evaluate the genotoxicity of environmental contamination on aquatic organisms.     

Effects of heavy metals on nitrogen uptake by Paxillus involutus and mycorrhizal birch seedlings

The effects of the heavy metals Cu, Cd, Ni, Pb and Zn on [(14)C]methylamine and [(14)C]aminoisobutyric acid uptake were studied in the free-living fungus Paxillus involutus and in mycorrhizal and non-mycorrhizal birch roots. The uptake of both N sources by P. involutus was inhibited by the five metals tested. However, Cu(2+) and Pb(2+) had a greater inhibitory effect. Non-competitive inhibitions were determined between heavy metals and [(14)C]methylamine uptake. [(14)C]Methylamine uptake was reduced by one third by 2 μM Cd(2+) and Cu(2+) in non-mycorrhizal roots, whereas that of mycorrhizal roots was not affected. However, it was reduced by 30 to 80% by 200 μM Cd(2+) and Cu(2+) irrespective of the mycorrhizal status. [(14)C]Aminoisobutyric acid uptake in mycorrhizal roots was not significantly affected by Cd(2+) and Cu(2+), whereas that of non-mycorrhizal roots was decreased by 77% at 200 μM Cu(2+). [(14)C]Aminoisobutyric acid uptake was 4.5 to 6 fold higher in mycorrhizal roots, compared with non-mycorrhizal roots, even under metal exposure. The high efficiency of N acquisition by mycorrhizal birch seedlings under metal exposure might be regarded as a mechanism of stress avoidance.     

Oxidative Stress Induced by Cadmium in the C6 Cell Line: Role of Copper and Zinc

In this report, we have investigated the role of copper (Cu) and zinc (Zn) in oxidative stress induced by cadmium (Cd) in C6 cells. Cells were exposed to 20 μM Cd, 500 μM Cu, and 450 μM Zn for 24 h. Then, toxic effects, cellular metals levels, oxidative stress parameters, cell death, as well as DNA damage were evaluated. Cd induced an increase in cellular Cd, Cu, and Zn levels. This results not only in the inhibition of GSH-Px, GRase, CAT, and SOD activities but also in ROS overproduction, oxidative damage, and apoptotic cell death not related to Cu and Zn mechanisms. The thiol groups and GSH levels decreased, whereas the lipid peroxidation and DNA damage increased. The toxicity of Zn results from the imbalance between the inhibition of antioxidant activities and the induction of MT synthesis. The increase in Cu and Zn levels could be explained by the disruption of specific transporter activities, Cd interference with signaling pathways, and metal displacement. Our results suggest that the alteration of Cu and Zn homeostasis is involved in the oxidative stress induced by Cd.     

6种重金属对赤子爱胜蚓的急性毒性效应与风险评价

【背景】近年来,土壤重金属污染问题日益凸显,对生态环境、食品安全和人体健康构成了严重威胁,其急性毒性尚未明确。【方法】采用滤纸接触法和人工土壤法测定了铜(Cu2+)、锌(Zn2+)、镍(Ni+)、镉(Cd2+)、铅(Pb2+)和锰(Mn2+)等6种重金属对赤子爱胜蚓的急性毒性效应,并参照欧盟指令91/414/EEC标准评价了其环境风险。【结果】滤纸接触法48h测定结果表明,6种重金属对蚯蚓的LC50为3.17(2.53～3.81)～90.42(69.45～140.47)μg.cm-2,其毒性次序为Cu2+>Zn2+>Ni+>Cd2+>Pb2+>Mn2+。人工土壤法14d测定结果表明,6种重金属对蚯蚓的LC50为1347(1236～1453)～6936(6144～8930)mg.kg-1,其毒性次序为Cu2+>Cd2+>Ni+>Zn2+>Mn2+>Pb2+。风险评价结果显示,Cu2+、Zn2+、Ni+、Cd2+、Pb2+和Mn2+等6种重金属的暴露比(toxicity/exposureratio,TER)分别为3.37、4.46、8.68、1428、13.87和5.85。【结论与意义】6种重金属对土壤动物蚯蚓均具有潜在的毒性效应。Cu2+、Zn2+、Ni+、Mn2+等4种重金属对赤子爱胜蚓存在急性毒性风险,而Cd2+和Pb2+对赤子爱胜蚓的急性毒性风险水平是可接受的。该评价结果可为我国制定基于风险的土壤环境质量标准提供依据。