Cellularly Generated Active Oxygen Species and Hela Cell Proliferation

In HeLa cells evidence is provided that active oxygen species such as hydrogen peroxide and superoxide at low levels are important growth regulatory signals. They may constitute a novel regulatory redox system of control superimposed upon the established cell growth signal transduction pathways. Whilst for example hydrogen peroxide can be added exogenously to elicit growth responses in these cells, it is clear that cellularly generated superoxide and hydrogen peroxide are important. Experiments with superoxide dismutase, superoxide dismutase mimics and inhibitors of both superoxide dismutase and xanthine oxidase suggest that superoxide generated intracellularly and superoxide released extracellularly are both relevant to growth control in HeLa cells.     

Cellularly Generated Active Oxygen Species and Hela Cell Proliferation

In HeLa cells evidence is provided that active oxygen species such as hydrogen peroxide and superoxide at low levels are important growth regulatory signals. They may constitute a novel regulatory redox system of control superimposed upon the established cell growth signal transduction pathways. Whilst for example hydrogen peroxide can be added exogenously to elicit growth responses in these cells, it is clear that cellularly generated superoxide and hydrogen peroxide are important. Experiments with superoxide dismutase, superoxide dismutase mimics and inhibitors of both superoxide dismutase and xanthine oxidase suggest that superoxide generated intracellularly and superoxide released extracellularly are both relevant to growth control in HeLa cells.     

Possible accumulation of non-active molecules of catalase and superoxide dismutase in S. cerevisiae cells under hydrogen peroxide induced stress

The effect of hydrogen peroxide on the activities of catalase and superoxide dismutase (SOD) in S. cerevisiae has been studied under different experimental conditions: various H₂O₂ concentrations, time exposures, yeast cell densities and media for stress induction. The yeast treatment with 0.25–0.50 mM H₂O₂ led to an increase in catalase activity by 2–3-fold. At the same time, hydrogen peroxide caused an elevation by 1.6-fold or no increase in SOD activity dependently on conditions used. This effect was cancelled by cycloheximide, an inhibitor of protein synthesis in eukaryotes. Weak elevation of catalase and SOD activities in cells treated with 0.25–0.50 mM H₂O₂ found in this study does not correspond to high level of synthesis of the respective enzyme molecules observed earlier by others. It is well known that exposure of microorganisms to low sublethal concentrations of hydrogen peroxide leads to the acquisition of cellular resistance to a subsequent lethal oxidative stress. Hence, it makes possible to suggest that S. cerevisiae cells treated with low sublethal doses of hydrogen peroxide accumulate non-active stress-protectant molecules of catalase and SOD to survive further lethal oxidant concentrations.     

Evidence for Superoxide Dismutase and Catalase in Mollicutes and Release of Reactive Oxygen Species

The presence of superoxide dismutase was demonstrated in 21 strains of mollicutes, including achuloplas-mas, mycoplasmas and ureaplasmas. Additionally, catalase activities were demonstrated in nearly 50% of the cell lysates. whereas no peroxide activities were detectable. The production of O₂-and H₂O₂ with glucose as substrate was demonstrated for 8 strains of 10 strains tested. Anaerobic mycoplasmas showed the highest amount of radical production, whereas superoxide dismutase and catalase activities were in the range of activities estimated for aerobic mollicutes. Some pathogenic strains additionally released compounds into the culture medium, which stimulated O₂-production by PMNs.     

Commentary: Oxygen Radicals, A Failure Or A Success of Evolution?

Oxygen radicals are no doubt involved in the development of many pathological states. Nevertheless, the possibility that oxygen radical production was selected for during biological evolution in order to perform useful roles in relation to cellular metabolism is contemplated; previous data on this subject are briefly reviewed. The concept of an “oxygen radical cycle” is proposed as a useful theoretical model.     

Peroxide metabolism in the cestodes Hymenolepis diminuta and Moniezia expansa

The enzymes of hydrogen peroxide metabolism have been investigated in the cestodes H. diminuta and M. expansa. Neither catalase, lipoxygenase, glutathione peroxidase, NADH peroxidase nor NADPH peroxidase could be detected in homogenates of either species. However, both H. diminuta and M. expansa possessed a peroxidase which had a high affinity for reduced cytochrome c. The peroxidase was characterized by substrate and inhibitor studies and cell fractionation showed the enzyme to be located in the mitochondrial membrane fraction. The peroxidase could act as a substitute for catalase, by destroying metabolic hydrogen peroxide. Appreciable superoxide dismutase activity was found in M. expansa and H. diminuta and it is possible that this enzyme is the source of helminth hydrogen peroxide.     

The Effect of Xanthine/Xanthine Oxidase Generated Reactive Oxygen Species on Synaptic Transmission

The effect of reactive oxygen species generated by the interaction of xanthine and xanthine oxidase on synaptic transmission was examined at the squid giant synapse and the lobster neuromuscular junction. Exposure of these synaptic regions to xanthine/xanthine oxidase produced a significant depression in evoked release, with no change in either resting membrane properties or in the action potential. Addition of catalase to the xanthine/xanthine oxidase-containing media partially blocked the synaptic depression, indicating that H₂ O ₂ contributes to the synaptic changes induced by exposure to xanthine/xanthine oxidase. H₂ O ₂ applied directly to the perfusing media also produced a decrease in synaptic efficacy. The results demonstrate that reactive oxygen species, in general, depress evoked synaptic transmission.     

The Effect of Xanthine/Xanthine Oxidase Generated Reactive Oxygen Species on Synaptic Transmission

The effect of reactive oxygen species generated by the interaction of xanthine and xanthine oxidase on synaptic transmission was examined at the squid giant synapse and the lobster neuromuscular junction. Exposure of these synaptic regions to xanthine/xanthine oxidase produced a significant depression in evoked release, with no change in either resting membrane properties or in the action potential. Addition of catalase to the xanthine/xanthine oxidase-containing media partially blocked the synaptic depression, indicating that H₂ O ₂ contributes to the synaptic changes induced by exposure to xanthine/xanthine oxidase. H₂ O ₂ applied directly to the perfusing media also produced a decrease in synaptic efficacy. The results demonstrate that reactive oxygen species, in general, depress evoked synaptic transmission.     

Reactive oxygen species are involved in pollen tube initiation in kiwifruit

The role of reactive oxygen species (ROS) during pollen tube growth has been well established, but its involvement in the early germination stage is poorly understood. ROS production has been reported in germinating tobacco pollen, but evidence for a clear correlation between ROS and germination success remains elusive. Here, we show that ROS are involved in germination and pollen tube formation in kiwifruit. Using labelling with dihydrofluorescein diacetate (H(2) FDA) and nitroblue tetrazolium (NBT), endogenous ROS were detected immediately following pollen rehydration and during the lag phase preceding pollen tube emergence. Furthermore, extracellular H(2) O(2) was found to accumulate, beginning a few minutes after pollen suspension in liquid medium. ROS production was essential for kiwifruit pollen performance, since in the presence of compounds acting as superoxide dismutase/catalase mimic (Mn-5,10,15,20-tetrakis(1-methyl-4-pyridyl)21H,23H-porphin, Mn-TMPP) or as NADPH oxidase inhibitor (diphenyleneiodonium chloride, DPI), ROS levels were reduced and pollen tube emergence was severely or completely inhibited. Moreover, ROS production was substantially decreased in the absence of calcium, and by chromium and bisphenol A, which inhibit germination in kiwifruit. Peroxidase activity was cytochemically revealed after rehydration and during germination. In parallel, superoxide dismutase enzymes, particularly the Cu/Zn-dependent subtype - which function as superoxide radical scavengers - were detected by immunoblotting and by an in-gel activity assay in kiwifruit pollen, suggesting that ROS levels may be tightly regulated. Timing of ROS appearance, early localisation at the germination aperture and strict requirement for germination clearly suggest an important role for ROS in pollen grain activation and pollen tube initiation.     

Functional Quality,Antioxidant Capacity and Essential Oil Percentage in Different Mint Species Affected by Salinity Stress

Saline stress is responsible for significant reductions in the growth of plants, and it globally leads to limitations in the performance of crops, especially in drought-affected areas. However, a better understanding of the mechanisms involved in the resistance of plants to environmental stress can lead to a better plant breeding and selection of cultivars. Mint is one of the most important medicinal plants, and it has important properties for industry, and for the medicinal and pharmacy fields. The effects of salinity on the biochemical and enzymatic properties of 18 ecotypes of mint from six different species, that is, Mentha piperita, Mentha mozafariani, Mentha rotundifolia, Mentha spicata, Mentha pulegium and Mentha longifolia, have been examined in this study. The experimental results showed that salinity increased with increasing in stress integrity influenced the enzymatic properties, proline content, electrolyte leakage, and the hydrogen peroxide, malondialdehyde, and essential oil contents. Cluster analysis and principal component analysis were conducted, and they grouped the studied species on the basis of their biochemical characteristics. According to the obtained biplot results, M. piperita and M. rotundifolia showed better stress tolerance than the other varieties, and M. longifolia was identified as being salt sensitive. Generally, the results showed that H₂O₂ and malondialdehyde had a positive connection with each other and showed a reverse relationship with all the enzymatic and non-enzymatic antioxidants. Finally, it was found that the M. spicata, M. rotundifolia and M. piperita ecotypes could be used for future breeding projects to improve the salinity tolerance of other ecotypes.     

Paclobutrazol delayed dark-induced senescence of mung bean leaves

Sixty days old mung beans Vigna radiata (L.) Wilczek were treated with soil applied paclobutrazol, at the rate of 500 μg per 10 inch pot. After seven days of application, the plants along with untreated controls were transferred to the dark for induction of senescence. The treated plants exhibited higher chlorophyll content and activity of catalase (CAT) compared to controls. In contrast, control leaves had higher activity of peroxidase (POX) and a higher content of malondialdehyde (MDA), while superoxide dismutase (SOD) activity remained unchanged. Upon transfer to dark, chlorophyll content declined in both control and treated plants but the decline was much faster in control. The activity of CAT decreased significantly in controls while POX activity and MDA content remained higher in control than in treated plants. Paclobutrazol delayed the dark-induced senescence in attached mung bean leaves in association with the maintenance of higher activity of CAT, low activity of POX, and low MDA contents. The variation in SOD activity was not discernible with senescence levels.     

Alleviation of NaCl Stress by Pretreatment with Phytohormones in Vigna radiata

Efficiency of pretreatment as foliar spray of indole-3-acetic acid, gibberellic acid and kinetin, each ranging from 0.1 to 10.0 μM concentration, in restoring the metabolic alterations imposed by NaCl salinity was investigated in Vigna radiata (L.) Wilczek. Glycolate oxidase, superoxide dismutase, catalase and peroxidase activities increased under stress in leaves and roots also. Malondialdehyde content and total peroxide content also increased under stress. All the three hormones used were able to overcome to variable extents the adverse effects of stress imposed by NaCl to these parameters. This revised version was published online in July 2006 with corrections to the Cover Date.     

活性氧参与-氧化氮诱导的神经细胞凋亡

采用激光共聚焦成像技术,用氧化还原敏感的特异性荧光探针(DCFH-DA和DHR123)直接研究了一氧 化氮供体S-亚硝基-N-乙酰基青霉胺(SNAP)诱导未成熟大鼠小脑颗粒神经元凋亡过程中的细胞胞浆、线粒体 中活性氧水平的变化,发现神经细胞经0.5mmol/LSNAP处理1h后,细胞胞浆及线粒体中活性氧水平大大增 加.一氧化氮清除剂血红蛋白能够有效抑制细胞胞浆、线粒体中活性氧的产生,防止细胞凋亡.外源性谷胱甘 肽对细胞也具有良好的保护作用,而当细胞中谷胱甘肽的合成被抑制后,一氧化氮的神经毒性大大增强.实验 结果表明一氧化氮通过促进神经细胞产生内源性活性氧而启动细胞凋亡程序,而谷胱甘肽可能是重要的防止一 氧化氮引发神经损伤的内源性抗氧化剂     

活性氧所致超氧化物歧化酶肽链断裂的观察

探究活性氧所致铜锌超氧化物歧化酶（ＳＯＤ）肽链断裂的情况。将过氧化氢或抗坏血酸－Ｆｅ（Ⅲ）分别作用于马来酰亚胺标记的ＳＯＤ,然后用高效液相反相色谱（ＲＰＨＰＬＣ）分析,经１ｍｍｏｌ／ＬＨ２Ｏ２处理后ＳＯＤ用ＲＰ－ＨＰＬＣ分离出二个肽段,用顺磁共振检测显示只有一个肽段具有马来酰亚胺信号,经５ｍｍｏｌ／ＬＨ２Ｏ２处理后ＳＯＤ有四个肽段生成,其中有一个肽段具有马来酰亚胺信号,用５ｍｍｏｌ／Ｌ抗坏血酸和０．０１ｍｍｏｌ／ＬＦｅＣｌ３处理后ＳＯＤ有三个肽段生成,用５０ｍｍｏｌ／Ｌ抗坏血酸及１．０ｍｍｏｌ／ＬＦｅＣｌ３处理后ＳＯＤ也产生相同的三个肽段,只是肽段的量多．结果提示Ｈ２Ｏ２所致ＳＯＤ肽链断裂无“定点”现象,而抗坏血酸－Ｆｅ（Ⅲ）所致ＳＯＤ肽链断裂呈“定点”断裂。     

活性氧所致超氧化物歧化酶疏水性的变化

用抗坏血酸-Fe(Ⅲ)和过氧化氢分别作用于铜锌超氧化物歧化酶(SOD),经疏水层析分离得到亲水型和疏水型SOD.用胰蛋白酶和胃蛋白酶分别作用于天然SOD,亲水型SOD及疏水型SOD,结果表明疏水型SOD较亲水型SOD及天然SOD易被降解,提示活性氧氧化修饰后的SOD对蛋白水解酶敏感性提高与其疏水性增高有关.     

Salicylic acid induced changes on antioxidant capacity,pigments and grain yield of soybean genotypes in water deficit condition

Salicylic acid (SA) plays an important role in the regulation of plant growth and development in response to water deficit. The effect of SA (0, 0.4 and 0.8?mM) on some physiological parameters of three soybean genotypes was investigated in three irrigation schedules included (85%, 65% and 45% of field capacity) during 2014–2015. Results showed that water deficit decreased stomatal conductance, leaf area index, relative water content, membrane stability index, yield components and grain yield particularly in L17 genotype. Activities of superoxide dismutase, ascorbate peroxidase and concentration of hydrogen peroxide, proline and total protein were increased in response to water deficit as well as SA applications. SA inhibited catalase activity resulting in increased hydrogen peroxide accumulation in soybean genotypes. Application of 0.4?mM SA decreased the adverse effects of water deficit in soybean genotypes by elevation of antioxidant enzymes activity and reducing malondialdehyde formation especially in Williams genotype.