Effects of Oxidative Stress Caused by Oxygen and Hydrogen Peroxide on Energy Metabolism and Senescence in Oat Leaves

In attached oat leaves the levels of adenine nucleotides decreasedduring leaf development and senescence. However, the energycharge (EC) only decreased from 0.90 in 4-cm leaves to 0.80in senescent leaves. In detached leaves the levels of adeninenucleotides increased for 48 h, in association with an increasein RNase activity and a decrease in levels of RNA. The EC remainedhigh until late senescence when levels of adenine nucleotidesfell to about 30% of initial values. A decrease in energy parametersinduced by transfer from light to darkness and from high (21%)to low (0.5% and anoxia) concentrations of oxygen resulted inan increase in membrane permeability. Oxidative stress (above 0.5% O₂ induced an increase in levelsof malondialdehyde (MDA) and then in permeability, associatedwith a decrease in levels of adenine nucleotides. Oxidativestress provoked by 0.05 and 0.10 M H₂O₂ caused a more rapiddecrease in energy parameters than O₂. Under oxidative stress(above 0.5% O₂) there is, first of all, an increase in membranepermeability and then a decrease in energy parameters, whichin turn are involved with senescence via increases in oxidationof membranes and degradation of energy-producing systems. (Received October 6, 1987; Accepted October 19, 1988)     

邻啡罗啉-Cu诱发小麦离体叶片的氧化损伤

邻啡罗啉-Cu处理小麦叶片,加快O2^-的产生,提高SOD和POD活性,加速叶绿体色素和蛋白质降解,因而MDA积累增加。暗示邻啡罗啉-Cu有诱导植物组织产生活性氧、促进过氧化的作用。     

Structural and Functional Damage Caused by Boron Deficiency in Sunflower Leaves

Photosynthetica - Boron deficiency induced a dramatic inhibition in sunflower plant growth, shown by a reduction in dry mass of roots and shoots of plants grown for 10 d in nutrient solution...     

Structural and Functional Damage Caused by Boron Deficiency in Sunflower Leaves

Boron deficiency induced a dramatic inhibition in sunflower plant growth, shown by a reduction in dry mass of roots and shoots of plants grown for 10 d in nutrient solution supplied with 0.02 μM B. This low B supply facilitated the appearance of brown purple pigmentation on the plant leaves over the entire growth period. Compared to B-sufficient (BS) leaves, leakage from B-deficient (BD) leaves was 20 fold higher for potassium, 38 fold for sucrose, and 6 fold for phenolic compounds. High level of membrane peroxidation was detected by measuring peroxidase activities as well as peroxidative products in BD sunflower plants. Soluble and bound peroxidase activities measured in BD thylakoid membranes were accelerated two fold compared to those detected in BS-membranes. No detectable change in soluble peroxidase activity in roots whereas a 4 fold stimulation in bound peroxidase activity was detected. Thylakoid membranes subjected to low B supply showed enhancement in lipoxygenase activity and malondialdehyde (MDA) content in parallel with 40 and 30 % decrease of linoleic and linolenic acid contents (related to total unsaturated fatty acids). A slower rate of Hill reaction activity (40 %) and a suppressed flow of electron transfer of the whole chain (30 %) were detected in BD thylakoid membranes. This reduction was accompanied with a decline in the activity of photosystem 2 shown by a diminished rate of oxygen evolution (42 %) coupled with a quenching (27.5 %) in chlorophyll a fluorescence emission spectra at 685 nm (F₆₈₅). Thus B is an important element for membrane maintenance, protection, and function by minimizing or limiting production of free oxygen radicals in thylakoid membranes of sunflower leaves. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Oxidative Damage in Lung of Mice Caused By Lanthanoide

This study was performed with the objective of assessing the antioxidant response of the lung of mice to different rare earths. LaCl₃, CeCl₃, and NdCl₃ at a higher dose of 20 mg/kg body weight were injected into the nasal cavity of ICR mice for consecutive 14 days, respectively. The increase of pulmonary lipids peroxide produced by Ln suggested an oxidative attack that was activated by a reduction of antioxidative defense mechanisms as measured by analyzing the activities of superoxide dismutase, catalase, ascorbate peroxidase, and total antioxidant capacity, as well as antioxidant levels such as glutathione and ascorbic acid, which were greatest in Ce³⁺ treatment, medium in Nd³⁺, and least in La³⁺. It implied that the antioxidative responses of lung may be involved in 4f shell and alternable valence properties of Ln-induced lung toxicity.     

Carbon Monoxide Alleviates Salt-Induced Oxidative Damage in Wheat Seedling Leaves

Carbon monoxide （CO）, a by-product released during the degradation of heme by heme oxygenases （EC 1.14.99.3） In animals, is regarded as an important physiological messenger or bioactive molecule involved in many biological events that has been recently reported as playing a major role in mediating the cytoprotectlon against oxidant-induced lung Injury. In the present study, we first determined the protective effect of exogenous CO against salt-induced oxidative damage in wheat seedling leaves. Wheat seedlings treated with 0.01μmol/L hematin as the CO donor demonstrated significant reversal of chlorophyll decay, dry weight, and water loss induced by 300 mmol/L NaCl stress. Interestingly, the increase in lipid peroxidation observed in salt-treated leaves was reversed by 0.01μmol/L hematin treatment. Time-couree analyses showed that application of 0.01μmol/L hematln enhanced gualacol peroxidase, superoxide dismutase, ascorbate peroxidase and catalase activities in wheat seedling leaves subjected to salt stress. These effects are specific for CO because the CO scavenger hemoglobin （1.2 mg/L） blocked the actions of the CO donor hematln. However, higher concentration of the CO donor （1.0μmol/L） did not alleviate dry weight and water loss of salt-stressed wheat seedlings. These results suggest that exogenous application of low levels of a CO donor may be advantageous against salinity toxicity.     

Copper Intoxication; Antioxidant Defenses and Oxidative Damage in Rat Brain

Copper (Cu) is an integral part of many important enzymes involved in a number of vital biological processes. Even though Cu is essential to life, it can become toxic to cells, at elevated tissue concentrations. Oxidative damage due to Cu has been reported in recent studies in various tissues. In this study, we aimed to determine the effect of excess Cu on oxidative and anti-oxidative substances in brain tissue in a rat model. Sixteen male Wistar albino rats were divided into two groups: the control group, which was given normal tap water, and the experimental group, which received water containing Cu in a dose of 1 g/l. All rats were sacrificed at the end of 4 wk, under ether anesthesia. Cu concentration in the liver and in plasma alanine aminotransferase (ALT) and aspartate transaminase (AST) activities were determined. There were multiparameter changes with significant ALT and AST activity elevation and increased liver Cu concentration. In brain tissue, Cu concentration, superoxide dismutase (SOD) activities, malondialdehyde (MDA) levels and glutathione (GSH) concentrations were determined. Brain Cu concentration was significantly higher in rats receiving excess Cu, compared with control rats (p < 0.05). Our results showed that SOD activities and GSH levels in brain tissue of the Cu-intoxicated animals were significantly lower than in the control group (p < 0.01 and p < 0,001, respectively). The brain MDA levels were found to be significantly higher in the experimental group than in the control group (p < 0.001). The present results indicate that excessive Cu accumulation in the brain depressed SOD activities and GSH levels and resulted in high MDA levels in brain homogenate due to the lipid peroxidation induced by the Cu overload.     

硝普钠缓解镧引起的黑麦草幼苗生长抑制和根系氧化损伤

采用水培方法,研究了外源一氧化氮（NO）供体硝普钠（SNP）对300 μmol·L^-1 LaCl₃胁迫下黑麦草幼苗生长和根系活性氧代谢的影响。结果表明：在LaCl₃胁迫下,喷施50 μmol·L^-1 SNP能够抑制镧（La）从黑麦草根系向地上部的转运,缓解La对幼苗生长的抑制作用;提高幼苗根系超氧化物歧化酶和抗坏血酸过氧化物酶活性,降低过氧化物酶活性及谷胱甘肽、脯氨酸、H₂O₂、丙二醛含量、超氧阴离子产生速率和质膜相对透性,对过氧化氢酶活性和抗坏血酸含量无显著影响。表明NO可通过活性氧代谢的调节,缓解高浓度La胁迫对黑麦草幼苗生长的抑制作用。     

Vitamin E Protects Against Oxidative Damage Caused by Formaldehyde in the Liver and Plasma of Rats

Abstract Background: During myocardial ischemia, accumulation of end products from anaerobic glycolysis (hydrogen ions (H⁺), lactate) can cause cellular injury, consequently affecting organ function. The cells' ability to buffer H⁺ (buffering capacity (BC)) plays an important role in ischemic tolerance. Age related differences in myocardial lactate and H⁺ accumulation (one hour of ischemia) as well as differences in BC, myoglobin (Mb) and histidine (His) contents in the left (LV) and right (RV) ventricles were assessed in neonatal compared to adult pigs. The BC of the septum was also compared. Methods and Results: Neonatal RV and LV had lactate accumulations of 43% and 63% and significantly greater H⁺ (p < 0.004) compared to the adult. In the neonate LV, BC was 17% significantly poorer (p = 0.0001), had 33% lower Mb (p = 0.0002) and 15% lower His content (p = 0.0004) when compared to the adult. In the RV, despite similar BC between the neonate and adult, myoglobin content was 36% (p = 0.0004) lower in the neonate. The neonate septum had a BC that was 11% lower than that of the adult. With maturation, the adult LV had a BC that was 10% greater (p < 0.01) than the RV while the septum mirrored that of the LV. Conclusions: During maturation to adulthood, the BC of the septum begins to closely resemble the LV. Neonatal hearts have a potentially greater vulnerability to acid-base disturbances during ischemia in both ventricles when compared to hearts of adults. This is due to lower levels of myoglobin and histidine in the young, which could render them more susceptible to injury during ischemia.Condensed Abstract During myocardial ischemia, H⁺ and lactate accumulation may pose deleterious effects on the heart. The ability to buffer H⁺ (buffering capacity, BC) affects ischemic tolerance. Although lactate accumulation during 1 h of global ischemia was similar between ventricles of neonatal and adult swine, H⁺ accumulation was greater and BC, Mb and His content were lower. With maturation, LV BC was higher than the RV while septum developmentally resembled the LV. Thus, hearts of neonates may be at a greater risk of ischemic injury compared to hearts of adults. (Mol Cell Biochem xxx: 1–7, 2005)     

Oxidative Damage of U937 Human Leukemic Cells Caused by Hydroxyl Radical Results in Singlet Oxygen Formation

The exposure of human cells to oxidative stress leads to the oxidation of biomolecules such as lipids, proteins and nuclei acids. In this study, the oxidation of lipids, proteins and DNA was studied after the addition of hydrogen peroxide and Fenton reagent to cell suspension containing human leukemic monocyte lymphoma cell line U937. EPR spin-trapping data showed that the addition of hydrogen peroxide to the cell suspension formed hydroxyl radical via Fenton reaction mediated by endogenous metals. The malondialdehyde HPLC analysis showed no lipid peroxidation after the addition of hydrogen peroxide, whereas the Fenton reagent caused significant lipid peroxidation. The formation of protein carbonyls monitored by dot blot immunoassay and the DNA fragmentation measured by comet assay occurred after the addition of both hydrogen peroxide and Fenton reagent. Oxidative damage of biomolecules leads to the formation of singlet oxygen as conformed by EPR spin-trapping spectroscopy and the green fluorescence of singlet oxygen sensor green detected by confocal laser scanning microscopy. It is proposed here that singlet oxygen is formed by the decomposition of high-energy intermediates such as dioxetane or tetroxide formed by oxidative damage of biomolecules.     

Proteolytic Activity at Alkaline pH in Oat Leaves, Isolation of an Aminopeptidase

Proteolytic activity in oat leaf extracts was measured with both azocasein and ribulose bisphosphate carboxylase (Rubisco) as substrates over a wide range of pH (3.0-9.2). With either azocasein or Rubisco activity peaks appeared at pH 4.8, 6.6, and 8.4. An aminopeptidase (AP) which hydrolyzes leucine-nitroanilide was partially purified. Purification consisted of a series of six steps which included ammonium sulfate precipitation, gel filtration, and two ionic exchange chromatographies. The enzyme was purified more than 100-fold. The apparent K_m for leucine-nitroanilide is 0.08 millimolar at its pH optimum of 8.4. AP may be a cystein protease since it is inhibited by heavy metals and activated by 2-mercaptoethanol. Isolated chloroplasts were also able to hydrolyze leucine-nitroanilide at a pH optimum of 8.4, indicating that AP could be localized inside the photosynthetic organelles.     

Induction of Protection against Paraquat-induced Oxidative Damage by Abscisic Acid in Maize Leaves is Mediated through Mitogen-activated Protein Kinase

Mitogen-activated protein kinase (MAPK) cascade has been shown to be important components in stress signal transduction pathway. In the present study, protection of maize seedlings ( Zea mays L.) against paraquat-generated oxidative toxicity by abscisic acid (ABA), its association with MAPK and ZmMPK5, a candidate for MAPK were investigated. Treatment of maize leaves with exogenous ABA led to significant decreases in the content of malondialdehyde, the percentage of ion leakage and the level of protein oxidation (in terms of carbonyl groups) under paraquat (PQ) stress. However, such decreases were blocked by the pretreatment with two MAPK kinase inhibitors PD98059 and U0126. The damage caused by PQ was further aggravated by inhibitors. Two inhibitors also suppressed the total activities of the antioxidant enzymes superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), and glutathione reductase (GR, EC 1.6.4.2). Besides, treatment with PQ stimulated the activation of a 46 kDa MAPK, which was identified as ZmMPK5 by in-gel kinase assay with immunoprecipitation. These results reveal that ABA-induced protection against PQ-generated oxidative damage is mediated through MAPK cascade in maize leaves, in which ZmMPK5, a candidate for MAPK, is demonstrated to be involved.     

Induction of Protection against Paraquat-induced Oxidative Damage by Abscisic Acid in Maize Leaves is Mediated through Mitogen-activated Protein Kinase

Mitogen-activated protein kinase （MAPK） cascade has been shown to be important components in stress signal transduction pathway. In the present study, protection of maize seedlings （Zea mays L.） against paraquat-generated oxidative toxicity by abscisic acid （ABA）, its association with MAPK and ZmMPK5, a candidate for MAPK were investigated. Treatment of maize leaves with exogenous ABA led to significant decreases in the content of malondialdehyde, the percentage of ion leakage and the level of protein oxidation （in terms of carbonyl groups） under paraquat （PQ） stress. However, such decreases were blocked by the pretreatment with two MAPK kinase inhibitors PD98059 and U0126. The damage caused by PQ was further aggravated by inhibitors. Two inhibitors also suppressed the total activities of the antioxidant enzymes superoxide dismutase （SOD, EC 1.15.1.1）, catalase （CAT, EC 1.11.1.6）, ascorbate peroxidase （APX, EC 1.11.1.tl）, and glutathione reductase （GR, EC 1.6.4.2）. Besides, treatment with PQ stimulated the activation of a 46 kDa MAPK, which was identified as ZmMPK5 by in-gel kinase assay with immunoprecipitation. These results reveal that ABA-induced protection against PQ-generated oxidative damage is mediated through MAPK cascade in maize leaves, in which ZmMPK5, a candidate for MAPK, is demonstrated to be involved.     

Induction of Protection against Paraquat-induced Oxidative Damage by Abscisic Acid in Maize Leaves is Mediated through Mitogen-activated Protein Kinase

Mitogen-activated protein kinase (MAPK) cascade has been shown to be important components In stress signal trans-duction pathway. In the present study, protection of maize seedlings (Zea mays L.) against paraquat-generated oxidative toxicity by abscisic acid (ABA), its association with MAPK and ZmMPK5, a candidate for MAPK were investigated. Treatment of maize leaves with exogenous ABA led to significant decreases in the content of malondialdehyde, the percentage of ion leakage and the level of protein oxidation (in terms of carbonyl groups) under paraquat (PQ) stress. However, such decreases were blocked by the pretreatment with two MAPK kinase inhibitors PD98059 and U0126. The damage caused by PQ was further aggravated by inhibitors. Two inhibitors also suppressed the total activities of the antioxidant enzymes superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), and glutathione reductase (GR, EC 1.6.4.2). Besides, treatment with PQ stimulated the activation of a 46 kDa MAPK, which was identified as ZmMPK5 by in-gel kinase assay with immunoprecipitation. These results reveal that ABA-induced protection against PQ-generated oxidative damage is mediated through MAPK cascade in maize leaves, in which ZmMPK5, a candidate for MAPK, is demonstrated to be involved.     

Hydrogen Sulfide Promotes Wheat Seed Germination and Alleviates Oxidative Damage against Copper Stress

With the enhancement of copper (Cu) stress, the germination percentage of wheat seeds decreased gradually. Pretreatment with sodium hydrosulfide (NaHS), hydrogen sulfide (H2S) donor alleviated the inhibitory effect of Cu stress in a dose-dependent manner; whereas little visible symptom was observed in germinating seeds and radicle tips cultured in NaHs solutions. It was verified that H2S or HS- rather than other sulfur-containing components derived from NaHs attribute to the potential role in promoting seed germination against Cu stress. Further studies showed that NaHS could promote amylase and esterase activities, reduce Cu-induced disturbance of plasma membrane integrity in the radicle tips, and sustain lower levels of malondialdehyde and H2O2 in germinating seeds. Furthermore, NaHs pretreatment increased activities of superoxide dismutase and catalase and decreased that of lipoxygenase, but showed no significant effect on ascorbate peroxidase. Alternatively, NaHs prevented uptake of Cu and promoted the accumulation of free amino acids in seeds exposed to Cu. In addition, a rapid accumulation of endogenous H2S in seeds was observed at the early stags of germination, and higher level of H2S in NaHS-pretreated seeds. These data indicated that H2S was involved in the mechanism of germinating seeds' responses to Cu stress.     

Cadmium-Induced Accumulation of Putrescine in Oat and Bean Leaves

The effects of Cd²⁺ on putrescine (Put), spermidine (Spd), and spermine (Spm) titers were studied in oat and bean leaves. Treatment with Cd²⁺ for up to 16 hours in the light or dark resulted in a large increase in Put titer, but had little or no effect on Spd or Spm. The activity of arginine decarboxylase (ADC) followed the pattern of Put accumulation, and experiments with α-difluoromethylarginine established that ADC was the enzyme responsible for Put increase. Concentrations of Cd²⁺ as low as 10 micromolar increased Put titer in oat segments. In bean leaves, there was a Cd²⁺-induced accumulation of Put in the free and soluble conjugated fractions, but not in the insoluble fraction. This suggests a rapid exchange between Put that exists in the free form and Put found in acid soluble conjugated forms. It is concluded that Cd²⁺ can act like certain other stresses (K⁺ and Mg²⁺ deficiency, excess NH₄⁺, low pH, salinity, osmotic stress, wilting) to induce substantial increases in Put in plant cells.     

Relation between Respiration and Senescence in Oat Leaves

The respiration of excised oat (Avena sativa cv Victory) leaves and their sensitivity to inhibitors was followed during senescence under varied conditions. The respiration rate, which in controls reaches its peak on the third day in darkness, is lowered at the time of fastest loss of chlorophyll (as reported earlier) by seven unrelated reagents that all delay dark senescence. When senescence is delayed by white light or by cytokinins, the respiratory rise is correspondingly delayed. Kinetin and l-serine, which act as antagonists on senescence, also act as antagonists on the respiratory rate. However, an exception to this close correspondence between senescence and the respiratory rise is offered by the lower aliphatic alcohols, which delay dark senescence and yet accelerate the onset of the respiratory rise.