Hexabromocyclododecane-induced developmental toxicity and apoptosis in zebrafish embryos

Hexabromocyclododecane (HBCD) is widely used as a brominated flame retardant, and has been detected in the aquatic environment, wild animals, and humans. However, details of the environmental health risk of HBCD are not well known. In this study, zebrafish embryos were used to assess the developmental toxicity of the chemical. Four-hour post-fertilization (hpf) zebrafish embryos were exposed to various concentrations of HBCD (0, 0.05, 0.1, 0.5, and 1.0 mg L-1) until 96 h. Exposure to 0.1, 0.5, and 1.0 mg L-1 HBCD significantly increased the malformation rate and reduced survival in the 0.5 and 1.0 mg L-1 HBCD exposure groups. Acridine orange (AO) staining showed that HBCD exposure resulted in cell apoptosis. Reactive oxygen species (ROS) was significantly induced at exposures of 0.1, 0.5, and 1.0 mg L-1 HBCD. To test the apoptotic pathway, several genes related to cell apoptosis, such as p53, Puma, Apaf-1, caspase-9, and caspase-3, were examined using real-time PCR. The expression patterns of these genes were up-regulated to some extent. Two anti-apoptotic genes, Mdm2 (antagonist of p53) and Bcl-2 (inhibitor of Bax), were down-regulated, and the activity of capspase-9 and caspase-3 was significantly increased. The overall results demonstrate that waterborne HBCD is able to produce oxidative stress and induce apoptosis through the involvement of caspases in zebrafish embryos. The results also indicate that zebrafish embryos can serve as a reliable model for the developmental toxicity of HBCD. (C) 2009 Elsevier B.V. All rights reserved.

Cytotoxicity evaluation of three pairs of hexabromocyclododecane (HBCD) enantiomers on Hep G2 cell

Hexabromocyclododecanes (HBCDs) are additive brominated flame retardants mainly used in plastics and textiles. At the present time, these compounds are found in almost all environmental and human samples. In order to evaluate the environmental safety and health risk of HBCDs, the enantiomerically pure alpha-, beta-, and gamma-HBCD were prepared using high performance liquid chromatography (HPLC) on a PM-P-CD column and the cytotoxicities of their enantiomers were evaluated in Hep G2 cells. Results from the 3-(4,5-dimethylthioazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), resazurin reduction and lactate dehydrogenase (LDH) release assays showed a good agreement that the order of cytotoxicity was gamma-HBCD >= beta-HBCD > alpha-HBCD, and that significantly lower cell viability and higher LDH release were observed in all (+)-enantiomers ((+) alpha-, (+) beta- and (+) gamma-HBCD) than the corresponding (-)-forms ((-) alpha-, (-) beta- and (-) gamma-HBCD). Additionally, the formation of reactive oxygen species (ROS) induced by these HBCD enantiomers were detected. The positive correlation between the LDH release and ROS formation demonstrated that the toxic mechanism might be mediated by oxidative damage. These results suggest that environmental and human health risks of HBCDs must be evaluated at the level of individual enantiomers. (C) 2008 Published by Elsevier Ltd.

DE-71-induced apoptosis involving intracellular calcium and the Bax-mitochondria-caspase protease pathway in human neuroblastoma cells In vitro

Polybrominated diphenyl ethers (PBDEs) are used extensively as flame-retardants and are ubiquitous in the environment and in wildlife and human tissue. Recent studies have shown that PBDEs induce neurotoxic effects in vivo and apoptosis in vitro. However, the signaling mechanisms responsible for these events are still unclear. In this study, we investigated the action of a commercial mixture of PBDEs (pentabrominated diphenyl ether, DE-71) on a human neuroblastoma cell line, SK-N-SH. A cell viability test showed a dose-dependent increase in lactate dehydrogenase leakage and 3-(4,5-dimethylthia-zol-2-yl)-2,5-diphenyl-tetrazolium bromide reduction. Cell apoptosis was observed through morphological examination, and DNA degradation in the cell cycle and cell apoptosis were demonstrated using flow cytometry and DNA laddering. The formation of reactive oxygen species was not observed, but DE-71 was found to significantly induce caspase-3, -8, and -9 activity, which suggests that apoptosis is not induced by oxidative stress but via a caspase-dependent pathway. We further investigated the intracellular calcium ([Ca2+](i)) levels using flow cytometry and observed an increase in the intracellular Ca2+ concentration with a time-dependent trend. We also found that the N-methyl d-aspartate (NMDA) receptor antagonist MK801 (3 mu M) significantly reduced DE-71-induced cell apoptosis. The results of a Western blotting test demonstrated that DE-71 treatment increases the level of Bax translocation to the mitochondria in a dose-dependent fashion and stimulates the release of cytochrome c (Cyt c) from the mitochondria into the cytoplasm. Overall, our results indicate that DE-71 induces the apoptosis of ([Ca2+](i)) in SK-N-SH cells via Bax insertion, Cyt c release in the mitochondria, and the caspase activation pathway.

The role of glutathione metabolism in tolerance of tobacco BY-2 suspension cells to microcystin-RR

This study was undertaken to investigate the role of the glutathione-involved detoxifying mechanism in defending the tobacco BY-2 suspension cells against microcystin-RR (MC-RR). Analysis showed that exposure of the cells to different concentrations of MC-RR (0.1, 1 and 10 mu g/mL) for 0-6 days resulted in a time and concentration-dependent decrease in cell viability and increase in reactive oxygen species (ROS) content. Reduced glutathione (GSH) and total glutathione (tGSH) content as well as glutathione reductase (GR), glutathione peroxidase (GPX) and glutathione-S-transferase (GST) activities significantly increased after 3-4 days exposure in the highest two concentration treated groups, while decreased until reaching the control values except for GPX at day 6. Oxidized glutathione (GSSG) content markedly increased compared with control in high concentration MC-RR treated group after 6 days exposure. The GSH/GSSG ratio was much higher than control in 10 mu g/mL MC-RR treated group at day 4, but after 6 days exposure, the ratios in all treated groups were lower than that of the control group.

Induction of hepatic enzymes and oxidative stress in Chinese rare minnow (Gobiocypris rarus) exposed to waterborne hexabromocyclododecane (HBCDD)

The objective of this study was to evaluate the sub-lethal toxicity of hexabromocyclododecane (HBCDD) in fish. Adult Chinese rare minnows as in vivo models were exposed to waterborne HBCDD from 1 to 500 mu g/l for 14, 28 and 42 days. Hepatic CYP1A1 (ethoxyresorufin-O-deethylase, EROD) and CYP2B1 (pentaoxyresorufin-O-depentylase, PROD) activities were measured. At the same time, molecular biomarkers of oxidative stress were also assayed in the brain, including reactive oxygen species (ROS), lipid peroxidation products (thiobarbituric acid-reactive substances, TBARS), DNA damage and protein carbonyl, as well as superoxide dismutase (SOD) activity and glutathione (GSH) content. DNA damage was evaluated using the Comet assay on erythrocytes. Besides, the content of HBCDD in whole fish was determined after 42 days exposure. The results show that HBCDD could induce EROD and PROD at 500 mu g/l after 28 days exposure, and at 100 to 500 mu g/l after 42 days exposure (P < 0.05), respectively. ROS formation in fish brain was observed to be increased in both time- and dose-dependent manner due to HBCDD exposure. The significant increases in TBARS and protein carbonyl contents occurred in fish brain after 28 and 42 days exposure (P < 0.05). Significant DNA damage in erythrocytes by Comet assay was also found in the 100-500 mu g/l exposure groups (P < 0.05) after 42 days exposure. Moreover, significant depletion in brain GSH content occurred in all treated groups (P < 0.05) and apparent inhibition in SOD activity in brain was observed in the groups of 10-500 mu g/l concentrations during 42 days exposure. The results demonstrate that increasing duration of HBCDD exposure induced EROD and PROD activities, caused excess ROS formation, finally resulted in oxidative damage to lipids, proteins and DNA and decreased antioxidant capacities in fish. Chemical analysis of HBCDD in whole fish showed accumulation up to 654 mu g/g wet weight. (c) 2007 Elsevier B.V. All rights reserved.

The involvement of the antioxidant system in protection of desert cyanobacterium Nostoc sp against UV-B radiation and the effects of exogenous antioxidants

In this study, we found that UV-B radiation decreased photosynthetic activity and boosted lipid peroxidation of desert Nostoc sp., and exogenous chemicals (ascorbate acid (ASC), N-acetylcysteine (NAC), and sodium nitroprusside (SNP)) had obvious protective effects on photosynthesis and membranes under UV-B radiation. High-concentration SNP boosted the activities of antioxidant enzymes, but low-concentration SNP reduced the activities of antioxidant enzymes. Both NAC and ASC treatments of cells decreased activities of antioxidant enzymes. The results suggested that those chemicals possibly had different mechanisms of protection of algae cells against UV-B radiation. SNP might play double roles as a signal molecule in the formation of algae cell protection of Photosystem 11 under UV-B radiation and as a (reactive oxygen species) scavenger, while NAC and ASC might function as antioxidant reagents or precursors of other antioxidant molecules, which could protect cells directly against ROS initiated by UV-B radiation. (c) 2006 Elsevier Inc. All rights reserved.

Oxidative damage in unfertilized eggs of Chinese rare minnow (Gobiocypris rarus) exposed to nonylphenol

In the present study, female Chinese rare minnows (Gobiocypris rarus) were used as in vivo models and exposed to nonylphenol (NP) at concentrations of 1 to 200 mu g/L for 21 d under semistatic conditions. Molecular biomarkers of oxidative stress were measured in unfertilized eggs and included reactive oxygen species (ROS), lipid peroxidation products (thiobarbituric acid-reactive substances [TBARS] and protein carbonyl), superoxide dismutase activity, and glutathione. Cathepsin D activity as an indicator of egg viability also was assayed. Nonylphenol induced ROS formation in unfertilized eggs in all exposed groups compared to the controls. The levels of protein carbonyl and TBARS in unfertilized eggs were significantly increased (p < 0.05) at 10 to 200 and 100 to 200 mu g/L, respectively. Good positive correlations were shown between ROS induction and levels of TBARS and protein carbonyl in eggs (R = 0.918, p < 0.05 and R = 0.784, p < 0.05, respectively). Superoxide dismutase activity in eggs was significantly inhibited (p < 0.05) in the 50 to 200 mu g/L exposure groups. Glutathione levels in eggs were significantly depleted (p < 0.05) at 100 to 200 mu g/L concentrations. In addition, ROS induction resulted in oxidative damage to lipid and protein in chorions. Significant reductions (p < 0.05) of the protein and lipid contents in chorions were both found in the 50 to 200 mu g/L exposure groups. A previous study found that NP exposure could lead to chorion thinning in zebra fish. Thus, the reductions in protein and lipid contents in chorion could be the reason for chorion thinning by NP exposure. Meanwhile, cathepsin D activity was significantly inhibited (p < 0.05) in all exposure groups. The results demonstrated that NP-induced oxidative stress could damage the chorion of unfertilized eggs and lead to a decline in gamete quality in female Chinese rare minnow.

Apoptosis induction on human hepatoma cells Hep G2 of decabrominated diphenyl ether (PBDE-209)

Polybrominated diphenyl ethers (PBDEs) are an important class of halogenated organic brominated flame retardants. Because of their presence in abiotic and biotic environments widely and their structural similarity to polychlorinated biphenyls (PCBs), concern has been raised on their possible adverse health effects to humans. This study was designed to determine the anti-proliferative, apoptotic properties of decabrominated diphenyl ether (PBDE-209), using a human hepatoma Hep G2 line as a model system. Hep G2 cells were cultured in the presence of PBDE-209 at various concentrations (1.0-100.0 mu mol/L) for 72 h and the percentage of cell viability was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The results showed that PBDE-209 inhibited the cells viability in time and concentration-dependent characteristics at concentrations (10.0-100.0 mu mol/L). We found that anti-proliferative effect of PBDE-209 was associated with apoptosis on Hep G2 cells by determinations of morphological changes, cell cycle and apoptosis. Mechanism study showed that PBDE-209 could increase the generation of intracellular reactive oxygen species (ROS) concentration-dependently. Antioxidant N-acetylcyteine partially inhibited the increase of ROS. The mechanism for its hepatoma-inhibitory effects was the induction of cellular apoptosis through ROS generation. In addition, activity of lactate dehydrogenase (LDH) release increased when the cells incubated with PBDE-209 at various concentrations and times. These results suggested that PBDE-209 had the toxicity activity of anti-proliferation and induction of apoptosis in tumor cells in vitro. (c) 2007 Elsevier Ireland Ltd. All rights reserved.

Exposure of spermatozoa to duroquinone may impair reproduction of the common carp (Cyprinus carpio) through oxidative stress

Toxicity of many waterborne organic contaminants to aquatic organisms is mediated through oxidative damages resulting from the production of reactive oxygen species (ROS). Using duroquinone as a model ROS inducer, we carried out in vitro and in vivo experiments to test the hypothesis that reproduction in common carp (Cyprinus carpio) can be impaired through oxidative damage of their spermatozoa. In vitro exposure of fish spermatozoa to 0, 12.5, 25, 50, 100 and 200 mu M duroquinone for 2 h showed a significant increase in the level of ROS in a dose-dependant manner. Sperm motility was significantly reduced in all exposure groups, but lipid peroxidation (LPO) and DNA strand break (measured by comet assay) were only enhanced at 50 mu M and above. A significant decrease in subsequent hatching rate was recorded in all the exposure groups, despite fertilization rate was not affected. In the in vivo experiment, spermatozoa were collected 24 and 72 h after fish received intra-peritoneal injections of 1.0 and 10 mg kg(-1) body weight duroquinone. DNA damage was clearly evident in spermatozoa of all treatment groups after 72 h exposure, and ROS was significantly enhanced in the high concentration group. LPO however, remained unchanged in both treatment groups. The overall results of both our in vitro and in vivo experiments demonstrated that duroquinone can induce ROS production in spermatozoa, which may impair sperm quality and subsequently reproductive success through oxidative stress. (c) 2006 Elsevier B.V. All rights reserved.

Growth and antioxidant system of the cyanobacterium Synechococcus elongatus in response to microcystin-RR

Microcystins, one type of the cyanobacterial toxins, show a broad range of hazardous effects on other organisms. Most of the researches on the toxic effects of microcystins have involved in animals and higher plants. Little work, however, has been done on evaluating the mechanisms of microcystin toxicity on algae. In this study, the toxicological effects of microcystin-RR (MC-RR) on the cyanobacterium Synechococcus elongatus were investigated. For this purpose, six physio-biochemical parameters (cell optical density, reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GSH-Px) and glutathione S-transferase (GST)) were tested in algal cells when exposed to 100 mug(-1) microcystin-RR. The results showed that the growth of Synechococcus elongatus ( expressed as optical density) was significantly inhibited compared with the control. At the same time, the treated algae exhibited a pronounced increase in production of ROS and MDA after 6 days exposure to microcystin-RR. Signi. cant changes in GSH levels and GSH-Px, GSH activities were also detected in algal cells, with higher values being observed in the toxin treated algae after 6 days exposure. GST activities in the treated algae exhibited a decline after exposure and rapid augmentation on day 3, thereafter, they kept at a high level when compared to the control group. GSH contents and GSH-Px activities were also significantly raised in the toxin-treated algae cells from day 3, but they showed a sharp decrease on day 4, which was the onward of cell proliferation. These results suggested that oxidative stress manifested by elevated ROS levels and MDA contents might be responsible for the toxicity of microcystin to Synechococcus elongatus and the algal cells could improve their antioxidant ability through the enhancement of enzymatic and non-enzymatic preventive substances.

高浓度O3和CO2对银杏、油松活性氧代谢的影响

采用开顶箱法模拟大气O3和CO2浓度升高（80 nmol•mol-1，700 μmol•mol-1），对银杏（Ginkgo biloba）和油松（Pinus tabulaeformis）幼树进行了连续两个生长季的熏蒸试验，研究了银杏叶片和油松针叶活性氧产生清除系统的生理变化过程，从活性氧代谢生理机制上揭示其抗性变化规律，为研究城市森林对全球变化的响应与反馈机制提供重要的理论基础。 得出如下结论： 1. 高浓度O3显著增加了银杏叶片ASA含量和抗氧化酶（SOD、APX）活性，增强了活性氧清除能力；但这种抗氧化能力的提高不足以消除高O3带来的氧化逆境，H2O2和MDA含量显著高于对照处理。与银杏相比，高浓度O3在试验初期诱导油松针叶SOD和APX酶活性升高，增强了活性氧清除能力；随着处理时间的延长ASA被耗竭，H2O2过量积累显著地抑制了抗氧化酶活性，加剧了氧化伤害。银杏和油松结果的差异表明，银杏对80 nmol•mol-1浓度的O3具有更高的抗性，而油松针叶活性氧代谢等生理过程受其影响更大。 2. 高浓度CO2对银杏叶片活性氧代谢无显著性影响。然而，高浓度CO2减缓了油松针叶活性氧的产生，抗氧化酶活性呈降低的趋势；但针叶内ASA含量显著高于对照处理，这说明高浓度CO2促进了油松针叶ASA合成，或者是减少了ASA的消耗。在试验处理后期，针叶内H2O2含量和MDA含量显著低于对照处理。 3. 高浓度O3和高浓度CO2复合处理中，高浓度CO2缓解了高浓度O3对银杏叶片和油松针叶造成的氧化胁迫，但其生理机制不同：银杏叶片ASA含量以及抗氧化酶活性普遍低于高浓度O3单因素处理而高于对照处理，并且叶片H2O2含量和膜质过氧化产物MDA含量显著低于高浓度O3单因素处理，这说明高浓度CO2通过减少活性氧的产生来缓解高浓度O3所致的活性氧积累以及膜质过氧化伤害。与银杏不同的是，高浓度CO2使油松针叶内ASA含量显著高于高浓度O3处理，增强了活性氧清除能力，减轻了活性氧对抗氧化酶活性的抑制作用，有效的控制了ROS的产生与清除之间的平衡，缓解了高O3带来的氧化伤害。

青杨组(Section Tacamahaca Spach)杨树不同种群对土壤干旱和重金属锰污染的生态生理响应

土壤是人类赖以生存的自然环境和农业生产的重要资源，世界面临的粮食、资源和环境问题与土壤密切相关，目前危害土壤的主要因素是干旱和重金属污染。杨树具有适应性强、生长快和丰产等特性，本论文以青杨组杨树为模式植物，采用植物生态、生理及生物化学等方法，研究杨树对土壤干旱和锰胁迫的生态生理反应以及种群间差异，研究成果可为我国干旱半干旱地区营造人工林、防止沙漠化提供理论依据，也为恢复与重建重金属污染地区退化生态系统提供科学指导。主要研究结果如下： 1. 青海杨不同种群对干旱胁迫的响应差异 干旱胁迫显著降低了两个青海杨种群（干旱种群和湿润种群）生物量积累，包括株高、基径、干物质积累等，通过植物结构的调整，有更多的生物量向根部分配。干旱胁迫还显著降低了叶绿素和类胡萝卜素含量，增加了游离脯氨酸和总氨基酸含量。另一方面，干旱胁迫诱导了活性氧的积累，作为第二信使，激活了抗氧化系统，包括抗坏血酸（ASA）含量和酶系统如超氧化物歧化酶（SOD），愈创木酚过氧化物酶（GPX），抗坏血酸过氧化物酶（APX）和谷胱甘肽还原酶（GR）。这样，杨树既有避旱机制又有耐旱机制，使其在干旱胁迫下有相当程度的可塑性。与湿润种群相比，干旱种群杨树有更多的生物量分配到根部，积累了更多的游离脯氨酸和总氨基酸来进行渗透调节，并且有更有效的抗氧化系统，包括更高含量的ASA 和更高活性的APX 和GR，这些使得干旱种群杨树比湿润种群杨树对干旱有更好的耐性。 2. 喷施硝普钠（SNP）对青海杨阿坝种群干旱胁迫耐性的影响 干旱胁迫显著的降低了青海杨阿坝种群的生长和生物量积累以及叶片相对含水量，还诱导了脯氨酸的合成以进行渗透调节。干旱胁迫下过氧化氢（H2O2）显著累积从而造成对膜脂和蛋白的伤害，使得丙二醛和蛋白羰基含量升高。干旱胁迫下喷施SNP可以减轻干旱胁迫造成的伤害，包括增加叶片的相对含水量，增加脯氨酸和总氨基酸的积累，并激活抗氧化酶系统如SOD，GPX和APX，从而减少丙二醛（MDA）和蛋白羰基（C＝O）的积累，但是在水分良好情况下SNP的效果不显著。 3. 青杨不同种群对锰胁迫的生长与形态响应差异 在同一锰浓度下，干旱种群的耐性指数都要高于湿润种群，这表明青杨对干旱和高锰胁迫具有交叉耐性。两个种群的株高，生物量和叶绿素含量都随锰浓度的升高而逐渐下降。就累积浓度而言，0 和0.1 mM 锰胁迫下，干旱种群积累的锰浓度要高于湿润种群，而在高浓度锰胁迫下(0.5 和1 mM)，湿润种群要高于干旱种群。在0，0.1 和0.5 mM下，锰大多积累在根中，叶片次之，茎中最少。而在1 mM，锰更多的积累在叶片中。就累积总量而言，在各个锰浓度胁迫下，根，茎和叶相比，两个种群青杨都是叶片累积的锰总量要高于根和茎。两个种群间比较，对照中没有显著区别，0.1 mM 锰胁迫下，湿润种群根中累积的锰要高于干旱种群，而在地上部中，干旱种群要高于湿润种群。而0.5 和1 mM 锰胁迫下，根、叶、茎+叶、根+茎+叶中，锰累积总量都是湿润种群高于干旱种群。锰胁迫下，青杨叶片数和叶面积包括总叶面积和平均叶面积都显著降低。叶片横切面的光学显微观察结果表明未经锰胁迫的栅栏组织的细胞饱满，海绵组织发达、清晰；胁迫后杨树叶片栅栏组织细胞出现不同程度的皱缩，海绵组织几乎不可见，此外还发现输导组织在胁迫下密度变小和分生组织严重割裂等现象。 4. 青杨不同种群对锰胁迫的生理与生化响应差异 青杨两个种群脱落酸（ABA）含量在锰胁迫下都显著增加，干旱种群的增幅更大。三种多胺含量在锰胁迫下显示了不同的响应趋势：腐胺在两个种群的各个锰处理下都增加，亚精胺只在干旱种群中显著增加，而精胺除了干旱种群在1 mM 下有所增加外，在锰胁迫下变化很小。谷胱甘肽含量随锰浓度升高而增加，在0.5 mM 锰时达到最高值，1mM 时有所下降。植物络合素（PCs）含量与非蛋白巯基（NP-SH）趋势相似，随锰浓度的升高而增加，且干旱种群中含量要高于湿润种群。锰处理还引起氧化胁迫，表现为过氧化氢和丙二醛含量增加。SOD 活性在湿润种群中，在0 到0.5 mM 锰胁迫下活性升高，但在1 mM 锰胁迫时，其活性有所下降。而在干旱种群中，SOD 活性变化较小，并始终维持在一个较高的水平。APX 活性在两个种群中都随锰浓度的升高而增加，干旱种群活性要高于湿润种群。锰胁迫还显著增加了酚类物质的含量，同时GPX 和多酚氧化酶（PPO）活性也随锰浓度的升高而增加。干旱种群的酚类含量和GPX 与PPO 活性都要高于湿润种群。锰胁迫还改变了氨基酸的含量和构成，根据锰胁迫下浓度变化的不同，可以将游离氨基酸分为三组：第一组包括，谷氨酸，丙氨酸和天门冬氨酸，这一组氨基酸含量在锰胁迫下有所下降。第二组包括缬氨酸，亮氨酸和苏氨酸含量在锰胁迫下基本不变化或变化很小。剩下的氨基酸为第三组，这组氨基酸含量在锰胁迫下显著增加，而根据增加的幅度又可以将它们分为两个亚组，丝氨酸，酪氨酸，苯丙氨酸，组氨酸和脯氨酸，在1 mM 下的含量是对照的4 倍以上。异亮氨酸，赖氨酸，精氨酸和甘氨酸含量在1 mM 下是对照含量的2 倍以下。同时，同一锰浓度下，干旱种群比湿润种群积累的氨基酸含量要高。 Soil is the indispensable environment for human survival and important resource foragriculture development. Food and environmental problems facing the world are all closelyrelated to soil and nowadays it is threatened by many factors, among which drought stress andheavy metal pollution are the most serious ones. Poplars (Populus spp.) are importantcomponents of ecosystem and suitable as a source of fuel, fiber and lumber due to their fastgrowth. In this study, different populations of Section Tacamahaca spach were used as modelplants to investigate the adaptability to drought stress and manganese toxicity and differencesbetween populations from dry and wet climate regions. Our results can provide theoreticalevidence for the afforestation and prevention of desertification in the arid and semi-arid areas,and also can supply scientific direction for the reconstruction and rehalibitation of ecosystemscontaminated by heavy metals. The results are as follows: 1. Differences in ecophysiological responses to drought stress in two contrastingpopulations of Populus przewalskii Drought stress not only significantly affected dry mass accumulation and allocation, butalso significantly decreased chlorophyll pigment contents and accumulated free proline andtotal amino acids. On the other hand, drought also significantly increased the levels ofabscisic acid and reactive oxygen species, as secondary messengers, to induce the entire set ofantioxidative systems including the increase of reduced ascorbic acid content and the activities of superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase and glutathioneredutase. Thus the combination of drought avoidance and tolerance mechanisms conferredpoplar a high degree of plasticity in response to drought stress. Compared with the wetclimate population, the dry climate population showed lower dry matter accumulation andallocated more biomass to root systems, and accumulated more free proline and total aminoacids for osmotic adjustment. The dry climate population also showed more efficientantioxidant systems with higher content of ascorbic acid and higher activities of ascorbateperoxidase and glutathione redutase than the wet climate population. All these made the dryclimate population superior in adaptation to drought stress than the wet climate population. 2. Effect of exogenous applied SNP on drought tolerance in Populus przewalskii Drought stress significantly increased hydrogen peroxide content and caused oxidativestress to lipids and proteins assessed by the increase in malondialdehyde and total carbonylcontents, respectively. The cuttings of P. przewalskii accumulated proline and other aminoacids for osmotic adjustment to lower water potential, and activated the antioxidant enzymes such as superoxide dismutase, guaiacol peroxidase and ascorbate peroxidase to maintain thebalance of generation and quenching of reactive oxygen species. Moreover, exogenous SNPapplication significantly heightened the growth performance of P. przewalskii cuttings underdrought treatment by promotion of proline accumulation and activation of antioxidant enzymeactivities, while under well-watered treatment the effect of SNP application was very little. 3. Morphological responses to manganese toxicity in the two contrasting populations ofPopulus cathayana High concentration of manganese caused significant decrease in shoot height andbiomass accumulation. The tolerance index of the dry climate population was significantlyhigher than that of the wet climate population, suggesting the superior Mn tolerance in theformer and the existence of cross-tolerance of drought stress and high Mn toxicity. Injuries tothe leaf anatomical features were also found as the reduced thickness in palisade and spongyparenchyma, the decreased density in the conducting tissue and the collapse and split in themeristematic tissue in the central vein. As for the Mn concentrations in the plant tissues, under0, 0.1 and 0.5 mM, most of the Mn accumulated in the roots, then leaves, and stem the least, while under 1 mM, most of the Mn accumulated in the leaves. As far as the total amounts ofMn extraction are concerned, the leaf extracted more Mn than the root and stem in the twopopulations under various Mn concentrations. There is no difference between the twopopulations under control. Under 0.1 mM, the wet climate population extracted higher Mn inthe root than the dry climate population, while in the shoot, the dry climate populationextracted much more Mn. Under 0.5 and 1 mM, the wet climate population translocated moreMn both in the root and the shoot than the dry climate population. 4. Physiological and biochemical responses to manganese toxicity in the two contrastingpopulations of Populus cathayana Mn treatment resulted in oxidative stress indicated by the oxidation to lipids, proteinsand DNA. A regulated network of defence strategies was employed for the chelation,detoxification and tolerance of Mn including the enhanced synthesis of ABA and polyamines,the accumulation of free amino acids, especially His and Pro, and the activation of theenzymes superoxide dismutase and guaiacol peroxidase. Contents of non-protein thiol,reduced glutathione, phytochelatins and phenolics compounds and activities of superoxide dismutase, guaiacol peroxidase and polyphenol oxidase also increased significantly forantioxidant or chelation functions. The wet climate population not only accumulated lessabscisic acid, free amino acids, phytochelatins and phenolics compounds, but also exhibitedlower activities of superoxide dismutase, guaiacol peroxidase and polyphenol oxidase thusresulting in more serious oxidative damage and more curtained growth.

Antioxidant N-acetylcysteine attenuates the acute liver injury caused by X-ray in mice

The aim of this study was to evaluate the protective effects of different doses and administration modes of N-acetylcysteine (NAC) against X-ray-induced liver damage in mice. Kun-Ming mice were divided into four groups, each composed of six animals: two control groups and two NAC-treated groups. An acute study was carried out to determine alterations in lipid peroxidation (determined by measuring malondiadehyde (MDA) level), glutathione (GSH) content and superoxide dismutase (SOD) activity (assayed by colorimetric method), and DNA damage (characterized by DNA-single strand break using with comet assay) as well as cell apoptosis (measured by flow cytometry) at 12 h after irradiation. The results showed that there were dose-related decreases in MDA level, DNA damage and cell apoptosis, and dose-dependent increases in GSH content and SOD activity in all NAC-treated groups compared to control groups, indicating that pre-treatment or post-treatment with NAC significantly attenuates the acute liver damage caused by X-ray. In addition, significant positive correlations were observed between MDA level and DNA damage or cell apoptosis, implying that lipid peroxidation plays a major role in X-ray-induced liver injury. The data suggest that NAC exerts its radioprotective effect by counteracting accumulated reactive oxygen species in the liver through its properties as a direct antioxidant and a GSH precursor, when administered before or after X-ray irradiation.

Biphasic regulation of H2O2 on angiogenesis implicated NADPH oxidase

ROS (reactive oxygen species) take an important signalling role in angiogenesis. Although there are several ways to produce ROS in cells, multicomponent non-phagocytic NADPH oxidase is an important source of ROS that contribute to angiogenesis. In the present work, we examined the effects of H2O2 on angiogenesis including proliferation and migration in HUVECs (human umbilical vein endothelial cells), new vessel formation in chicken embryo CAM (chorioallantoic membrane) and endothelial cell apoptosis, which is closely related to anti-angiogenesis. Our results showed that H2O2 dose-dependently increased the generation of O-2(-) (superoxide anion) in HUVECs, which was suppressed by DPI (diphenylene iodonium) and APO (apocynin), two inhibitors of NADPH oxidase. H2O2 at low concentrations (10 mu M) stimulated cell proliferation and migration, but at higher concentrations, inhibited both. Similarly, H2O2 at 4 nmol/cm(2) strongly induced new vessel formation in CAM, while it suppressed at high concentrations (higher than 4 nmol/cm(2)). Also, H2O2 (200 similar to 500 mu M) could stimulate apoptosis in HUVECs. All the effects of H2O2 on angiogenesis could be suppressed by NADPH oxidase inhibitors, which suggests that NADPH oxidase acts downstream of H2O2 to produce O-2(-) and then to regulate angiogenesis. In summary, our results suggest that H2O2 as well as O-2(-) mediated by NADPH oxidase have biphasic effects on angiogenesis in vitro and in vivo.

低温弱光下类囊体腔内质子由CF_0渗漏引起黄瓜类囊体耦联度降低

毫秒延迟发光测定结果表明低温弱光处理黄瓜叶片导致类囊体原位 (in situ)耦联度显著降低。DCCD可以恢复低温弱光处理的黄瓜叶片的毫秒延迟发光的慢相强度和反映类囊体膜质子吸收的 9- AA(9- Aminoacridine)荧光猝灭能力 ,说明类囊体耦联度降低的原因是质子由 CF0 大量快速渗漏。进一步研究结果表明 ,活性氧和 CF1的脱落不是低温弱光引起黄瓜类囊体耦联度降低的根本原因。