Oxidation, antioxidants and cataract formation: a literature review

PURPOSE: This review aims to provide a literature survey of the association between photo-oxidation of lens proteins and lipid peroxidation with the genesis of age-related cataract in laboratory studies using rodent models, in epidemiological and interventional studies in humans. MATERIALS AND METHODS: A Medline search using initial search terms lens, oxidation, antioxidant, and diet was employed to search for research papers covering the areas noted above from 1995 to 2005. Literature cited in those papers was also reviewed to provide as comprehensive a coverage of research work as possible. RESULTS: Lens protein photo-oxidation and lipid peroxidation are widely acknowledged as important steps in age-related cataractogenesis. Dietary antioxidants are central in retarding cataractogenesis, although most evidence for this is gained from laboratory-based work on relatively unphysiologic rodent cataract models, using antioxidant regimes that could not be sustained in clinical practice. Most research in humans is retrospective epidemiology although some interventional research has been undertaken, with mixed results. CONCLUSIONS: Dietary antioxidants are likely to be important in retarding cataractogenesis in older animals and in humans. Work on companion animals could provide a valuable stepping stone between rodent-based laboratory work and human interventional studies.     

Photosynthesis and growth responses of grapevine to acetochlor and fluoroglycofen

Acetochlor and fluoroglycofen are herbicides used in vineyards to eradicate weeds. This present study characterized the effects of these chemicals on photosynthetic characteristics and the antioxidant enzyme system in non-target grape leaves. The results showed that acetochlor and fluoroglycofen reduced net photosynthetic rate in a dose-dependent manner, but also reduced or increased pigment contents, respectively. According to chlorophyll fluorescence measurements, acetochlor and fluoroglycofen decreased the photochemical efficiency of photosystem II in the light and increased non-photochemical quenching. These herbicides enhanced malondialdehyde contents and accelerated the superoxide anion production rate in dose-dependent manners, which might be associated with lower antioxidant enzyme activities, especially at higher concentrations of the herbicides. Acetochlor and fluoroglycofen inhibited grapevine growth in the growth season one-year after herbicide treatment, and stem height was inhibited by up to 55.4% and 88.0%, respectively. Taken together, these results suggest that both herbicides are detrimental for grape photosynthesis and this might be associated with increased oxidative stress in the first year, while growth inhibition in the second year might be due to after effects of herbicide treatment.     

猕猴桃果实发育过程中AsA代谢产物积累及相关酶活性的变化

 以美味猕猴桃品种‘秦美’果实为材料, 研究了其生长发育过程中与AsA代谢循环系统相关的物质抗坏血酸(AsA) 、谷胱甘肽(GSH) 、草酸(OA) 、酒石酸( TA) 和过氧化氢(H₂O₂ ) 的含量及相关酶活性的变化及其相互关系。结果表明: 在果实生长发育过程中, 花后AsA含量明显增加, 花后30 d达到最高后开始下降, 花后75 d后基本保持不变。就整个果实中总的AsA积累量而言, 花后开始显著增加, 到45 d达到最大值后至成熟基本保持不变。这表明猕猴桃果实的AsA积累主要发生在幼果期。GSH随着果实发育在花后120 d前其含量及积累量均有增加, 但积累也主要发生在幼果期。OA含量的变化与H₂O₂含量和抗坏血酸过氧化物酶(APX) 活性相似, 均在花后开始显著下降, 到花后30 d后变化不大; 而TA含量的变化趋势与AsA一致。抗坏血酸氧化酶(AO) 、单脱氢抗坏血酸还原酶(MDHAR) 和脱氢抗坏血酸还原酶(DHAR) 的活性变化基本一致, 均在花后开始显著升高, 60 d达到最大后迅速下降, 在90 d后至成熟基本保持不变。     

油菜种子发芽过程中依赖于抗坏血酸的H_2O_2清除酶活性的变化

用在黑暗中培养７２ｈ的油菜种子，研究其吸胀和发芽过程中依赖于抗坏血酸Ｈ２Ｏ２清除途径的酶和过氧化氢酶的活性变化．实验表明，油菜干种子抗坏血酸过氧化物酶活性很低，种子在吸胀过程中，活性缓慢增加，萌发后活性很快增加．单脱氢抗坏血酸还原酶活性在种子萌发以后增加很快，而脱氢抗坏血酸还原酶除了在种子萌发后短时间内增加以外，活性变化不大．谷胱甘肽还原酶活性在种子萌发以后明显增加．过氧化氢酶的活性在种子萌发前开始增加，萌发后增加较快．每粒种子的抗坏血酸含量萌发后增加明显，而单位鲜重的抗坏血酸含量变化不大．单位鲜重脱氢抗坏血酸含量减少     

Growth, Oxidative Damage and Antioxidant Responses in Greengram (Vigna radiata L.) under Short-term Salinity Stress and its Recovery

Spatio-temporal differences under short-term NaCl-salinity (0, 50, 100, 150 m m l⁻¹) stress for 24 h and post-NaCl recovery after 24 h on the growth, water relations, ionic composition, proline and antioxidants of 12-day-old roots, stem and leaves of Vigna radiata were observed. Fresh and dry weight, relative water content and K⁺ ion decreased, whereas, Na⁺ ion and Na⁺/K⁺ ratio increased significantly in roots, stem and leaves. Post-NaCl recovered roots, stem and leaves showed similar results with lower values. Chlorophyll and carotenoid pigments decreased significantly in the leaves. Peroxide and lipid peroxidation level increased significantly with higher ratio in stressed compared to recovered leaves. Ascorbate and proline content increased significantly with no significant change in glutathione content in stressed roots, stem and leaves. Significant decrease in protein content, SOD, CAT, POX, APX and GR activities was observed in roots with no significant change in stem and leaves. The recovered parts showed similar results except increased POX and GR activities showing a tissue-specific response to NaCl-salinity stress. Improved tolerance to salt stress may be accomplished by increased capacity of antioxidative defence system and by lower level of lipid peroxidation and improvement in the plant water status, activities of some of the antioxidants in the recovered parts suggest that significant tissue differences in response to salt stress in V. radiata is closely related to differences in the activities of antioxidants, ion and proline content.     

Exogenous paraquat changes antioxidant enzyme activities and lipid peroxidation in drought-stressed cucumber leaves

In order to examine whether paraquat modifies the functioning of antioxidants and oxidative stress levels in drought-stressed plants, a cucumber cultivar (Cucumis sativus cv. Yuexiu no. 3) was grown hydroponically for 2 days. Drought stress, which was induced by polyethylene glycol (PEG), increased the contents of malonaldehyde (MDA), superoxide radical (O₂⁻) and hydrogen peroxide (H₂O₂) in cucumber leaves, while pretreatment of paraquat decreased them. Under drought stress induced by PEG, we observed the decreased contents of MDA, H₂O₂ and O₂⁻ in paraquat-pretreated plants in comparison to unpretreated stressed plants. Drought stress and paraquat both increased the activities of antioxidants such as superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), guaiacol peroxidase (GPX, EC 1.11.1.7), ascorbate peroxidase (APX, EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), monodehydroascorbate reducatase (MDHAR, EC 1.6.5.4), glutathione reductase (GR, EC 1.6.4.2), reduced glutathione (GSH) and reduced ascorbate (AsA). But the combined effect of paraquat application and drought stress resulted in the highest activities of antioxidants. So paraquat is able to moderate the activities of scavenging system enzymes and to influence oxidative stress intensity under drought stress induced by PEG.     

Improving the Performance of Wheat by Seed Priming Under Saline Conditions

Salinity is one of a major threat in harvesting good wheat stand on sustained basis. In this study, potential of seed priming techniques to improve the performance of wheat varieties (SARC‐1 and MH‐97) in a saline field was tested. For priming, wheat seeds were soaked in aerated solution of ascorbate (50 mg l^?1; ascorbate priming), salicylic acid (50 mg l^?1; salicylicate priming), kinetin (50 mg l^?1; kinetin priming) and CaCl₂ (50 mg l^?1; osmopriming) for 12 h. For comparison, seeds were also soaked in simple water (hydropriming); in addition, untreated seeds were also taken as control. Seed priming treatments substantially improved the stand establishment; osmopriming (with CaCl₂) was at the top however. Likewise maximum fertile tillers, grains per spike, 1000‐grain weight, grain yield and harvest index were observed in plants raised from seeds osmoprimed (with CaCl₂) followed by ascorbate priming in both the varieties tested. As an index of salinity tolerance, seed priming treatments also improved the leaf K⁺ contents with simultaneous decrease in Na⁺ concentration, osmopriming being the best treatment. Similarly, maximum total phenolic contents, total soluble proteins (TSP), α‐amylase and protease activities were observed in osmoprimed (with CaCl₂) seeds followed by ascorbate priming. Economic analysis also indicated that osmopriming is more viable with maximum net return and benefit‐to‐cost ratio. In conclusion, different seed priming treatments in wheat seeds improved the salinity tolerance nonetheless osmopriming (with CaCl₂) was the most effective treatments to get higher grain yield and net return in both wheat varieties whereas kinetin was the least effective.     

枣树ZjAPX基因的原核表达

为了解枣树抗氧化系统中抗坏血酸过氧化物酶基因的作用和功能,将从枣树结果枝cDNA文库中筛选获得的ZjAPX cDNA序列,连接到原核表达载体pGEX-4T-2,导入E.coli体内进行了表达产物鉴定。SDS-PAGE电泳检测表明,1.0 mmol/L的IPTG诱导4 h表达了蛋白产物;IPTG的浓度和诱导时间优化表明,1.2 mmol/LIPTG诱导5 h时,蛋白的表达量最大。研究为枣抗坏血酸过氧化物酶基因生物学功能的深入研究奠定了基础。     

Modelling ozone deposition fluxes: The relative roles of deposition and detoxification processes

A new Model of Ozone Deposition and Detoxification (MODD) is presented. This model describes stomatal ozone uptake and deposition on external plant surfaces and soil; it accounts for diurnal variability of detoxification processes and reactive ozone uptake on cuticular waxes and soil surface. The mechanistic modelling of plant defense reactions is based on the Plöchl et al. (2000) detoxification model in which the dynamics of apoplast chemistry are considered. To estimate ozone deposition fluxes on cuticular waxes and soil surface, we use a revised version of the Morrison and Nazaroff (2002) model developed to account for ozone uptake on material surfaces. This model which has been fully integrated with a soil-plant-atmosphere continuum model ensures a complete coupling between stomatal conductance and O₃ exchanges between leaves and the atmosphere. The observed diurnal variations in stomatal conductance which largely control the influx of O₃ into the leaf are well reproduced. Model simulations point out that the pool of ascorbate located in the mesophyll cell wall plays a significant role in the detoxification of O₃. Besides stomatal conductance, it is the key process involved in the control of ozone flux to the cell wall. A decrease in the pool of ascorbate lengthens the chemical lifetime of O₃ in the cell wall then the virtual apoplastic resistance is found to increase with decreasing ascorbate. Although the atmospheric ozone concentration increases as the weather becomes hot and dry, the virtual apoplastic resistance follows the same trend, indicating a decrease of the ascorbate pool in the mesophyll cell wall. Results also indicate that for the pre-senescence period 57% of the ozone is deposited onto the cuticular surfaces, 4% on soil and only 37% is absorbed by stomata. The comparison of modelled and measured data reported in this study indicates that the model is capable of predicting the major features of the patterns of total ozone flux.     

Effect of arbuscular mycorrhizal fungi on growth,mineral nutrition,antioxidant enzymes activity and fruit yield of tomato grown under salinity stress

The purpose of this study was to investigate the mechanisms underlying alleviation of salt stress by arbuscular mycorrhizal fungi Glomus mosseae. Tomato (Lycopersicon esculentum L. cv. Zhongzha105) plants were cultivated in soil with 0, 50 and 100 mM NaCl. Mycorrhization alleviated salt induced reduction of root colonization, growth, leaf area, chlorophyll content, fruit fresh weight and fruit yield. The concentrations of P and K were higher in AM compared with nonAM plants grown under nonsaline and saline conditions. Na concentration was lower in AM than nonAM plants grown under nonsaline and saline conditions. AMF colonization was accompanied by an enhancement of activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) in leaves of both salt-affected and control plants. In addition, inoculation with AMF caused reduction in MDA content in comparison to salinized plants, indicating lower oxidative damage in the colonized plants.