Role of alpha- and beta-adrenoreceptors in rat monocyte/macrophage function at rest and acute exercise

Previous studies from our laboratory have demonstrated that a single bout of moderate exercise stimulates macrophage function, increasing phagocytic capacity, and production of hydrogen peroxide and nitric oxide (NO˙) through nuclear factor kappa B activation. In this work, we investigated the role of α- and β-adrenoreceptors on the function of monocyte/macrophages during rest and exercise. Adult male Wistar rats were i.p. administered (100 μL/100 g) with specific adrenergic antagonists before an acute moderate exercise bout: prazosin (α₁-specific antagonist 2 mg/kg), propranolol (unspecific β_1/β₂ antagonist 10 mg/kg), double blockade (α₁ and β_1/β₂), or phosphate-buffered saline (control). Acute exercise consisted in a single swimming session of moderate intensity (5 % body weight overload on the chest) for 60 min. Control groups (rest) received the same antagonists and were killed 60 min after drug administration. Exercise increased phagocytic capacity (1.7-fold, p?<?0.05), NO˙ production (5.24 fold, p?<?0.001), and inducible nitric oxide synthase (NOS2) expression (by 58.1 %), thus suggesting macrophage activation. The β-adrenoreceptor blockade did not change this behavior. In resting animals, α₁ antagonist, as well as the double (α₁/β) blockade, however, further increased phagocytic capacity (by up to 261 %, p?<?0.001), NO˙ production (by up to 328 %, p?<?0.001), and the expressions of NOS2 (by 182 %, p?<?0.001) and HSP70 (by 42.5 %, p?<?0.01) suggesting a tonic inhibitory effect of α₁ stimulation on macrophage activation. In exercised animals, α₁-blockade showed similar enhancing effect on phagocytic indices and expressions of NOS and HSP70, particularly in double-blocked groups, although NO˙ production was found to be reduced in exercised animals submitted to both α- and β-blockade. Redox (glutathione) status and lipoperoxidation were evaluated in all test groups and approximately paralleled macrophage NO˙ production. We suggest the prevalence of a peripheral α₁-adrenoreceptor inhibitory tonus that limits macrophage responsiveness but operates differently after physical exercise.     

Theoretical description of the magnetic properties of μ3-hydroxo bridged trinuclear copper(II) complexes

A theoretical study of the magnetic properties, using density functional theory, of a family of trinuclear μ₃-OH copper(II) complexes reported in the literature is presented. The reported X-ray crystal structures of [Cu₃(μ₃-OH)(aat)₃(H₂O)₃](NO₃)₂·H₂O (HUKDUM), where aat: 3-acetylamine-1,2,4-triazole; [Cu₃(μ₃-OH)(aaat)₃(H₂SO₄)(HSO₄)(H₂O)] (HUKDOG), where aaat: 3-acetylamine-5-amine-1,2,4-triazole; [Cu₃(μ₃-OH)(PhPyCNO)₃(tchlphac)₂] (HOHQUR), where PhPyCNO: phenyl 2-pyridyl-ketoxime and tchlphac: acid 2,4,5-trichlorophenoxyacetic; [Cu₃(μ₃-OH)(PhPyCNO)₃(NO₃)₂(CH₃OH)] (ILEGEM); [Cu₃(μ₃-OH)(pz)₃(Hpz)₃(ClO₄)₂] (QOPJIP), where Hpz?=?pyrazole; [Cu₃(μ₃-OH)(pz)₃(Hpz)(Me₃CCOO)₂]?2Me₃CCOOH (DEFSEN) and [Cu₃(μ₃-OH)(8-amino-4-methyl-5-azaoct-3-en-2-one)₃][CuI₃] (RITXUO), were used in the calculations. The magnetic exchange constants were calculated using the broken-symmetry approach. The calculated J values are for HUKDUM J₁?=??68.6 cm^?1, J₂?=??69.9 cm^?1, J₃?=??70.4 cm^?1; for HUKDOG, J₁?=??73.5 cm^?1, J₂?=??58.9 cm^?1, J₃?=??62.1 cm^?1; for HOHQUR J₁?=??128.3 cm^?1, J₂?=??134.1 cm^?1, J₃?=??120.4 cm^?1; for ILEGEM J₁?=??151.6 cm^?1, J₂?=??173.9 cm^?1, J₃?=??186.9 cm^?1; for QOPJIP J₁?=??118.3 cm^?1, J₂?=??106.0 cm^?1, J₃?=??120.6 cm^?1; for DEFSEN J₁?=??74.9 cm^?1, J₂?=??64.0 cm^?1, J₃?=??57.7 cm^?1 and for RITXUO J₁?=??10.9 cm^?1, J₂?=?+14.3 cm^?1, J₃?=??35.4 cm^?1. The Kahn-Briat model was used to correlate the calculated magnetic properties with the overlap of the magnetic orbitals. Spin density surfaces show that the delocalization mechanism is predominant in all the studied compounds.

Exogenous salicylic acid regulates reactive oxygen species metabolism and ascorbate–glutathione cycle in <Emphasis Type="Italic">Nitraria tangutorum</Emphasis> Bobr. under salinity stress

The effect of 0.5–1.5 mM salicylic acid (SA) on modulating reactive oxygen species metabolism and ascorbate–glutathione cycle in NaCl-stressed Nitraria tangutorum seedlings was investigated. The individual plant fresh weight (PFW) and plant dry weight (PDW) significantly increased under 100 mM NaCl while remained unchanged or decreased under 200–400 mM NaCl compared to the control. Superoxide anion (O ₂ ^·? ), hydrogen peroxide (H₂O₂), thiobarbituric acid reactive substances (TBARS), reduced ascorbate (AsA), dehydroascorbate (DHA), reduced glutathione (GSH) and oxidized glutathione (GSSG) increased whereas the ratios of AsA/DHA and GSH/GSSG decreased under varied NaCl treatments. Ascorbate peroxidase (APX) and glutathione reductase (GR) activities were enhanced while dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) activities remained unvaried under 100–400 mM NaCl stresses. In addition, exogenous SA further increased PFW, PDW and root/shoot ratio. SA effectively diminished O ₂ ^·? accumulation. H₂O₂ and TBARS decreased under 0.5 and 1.0 mM SA treatments compared to those without SA. 0.5 mM of SA increased while 1.0 and 1.5 mM SA decreased APX activities. DHAR activities were elevated by 0.5 and 1.0 mM SA but not by 1.5 mM SA. MDHAR and GR activities kept constant or significantly increased at varying SA concentrations. Under SA treatments, AsA and GSH contents further increased, DHA and GSSG levels remained unaltered, while the decreases in AsA/DHA and GSH/GSSG ratios were inhibited. The above results demonstrated that the enhanced tolerance of N. tangutorum seedlings conferred by SA could be attributed mainly to the elevated GR and DHAR activities as well as the increased AsA/DHA and GSH/GSSG ratios.     

Oxidative stress in rheumatoid arthritis patients: relationship to diseases activity

The aim of this study was to assess the oxidative stress status in rheumatoid arthritis (RA) by measuring markers of free radical production, systemic activity of disease, and levels of antioxidant. 52 RA patients and 30 healthy controls were included in the study, and clinical examination and investigations were performed and disease activity was assessed. Peripheral blood samples were used for all the assays. We assessed the markers of oxidative stress, including plasma levels of index of lipid peroxidation-thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H₂O₂), superoxide anion radical (O₂ ^?), nitric oxide (NO), and superoxide dismutase activity (SOD), catalase activity (CAT) and glutathione levels in erythrocytes. In the RA group, levels of H₂O₂, O₂ ^?, and TBARS were significantly higher than in controls (4.08 ± 0.31 vs. 2.39 ± 0.13 nmol/l, p < 0.01; 8.90 ± 1.28 vs. 3.04 ± 0.38 nmol/l, p < 0.01, 3.65 ± 0.55 vs. 1.06 ± 0.17 μmol/l, p < 0.01). RA patients had significantly increased SOD activity compared with healthy controls (2,918.24 ± 477.14 vs. 643.46 ± 200.63UgHbx103, p < 0.001). Patients had significantly higher levels of pro-oxidants (O₂ ^?, H₂O₂, and TBARS) compared to controls, despite significantly higher levels of SOD. Significant differences were also observed in serum levels of NO in patients with high-diseases activity. Our findings support an association between oxidative/nitrosative stress and RA. Stronger response in samples with higher diseases activity suggests that oxidative/nitrosative stress markers may be useful in evaluating the progression of RA as well as in elucidating the mechanisms of disease pathogenesis.     

αB-crystallin regulates oxidative stress-induced apoptosis in cardiac H9c2 cells via the PI3K/AKT pathway

The present study was carried out to observe the protective effects of αB-crystallin protein on hydrogen peroxide (H₂O₂)-induced injury in rat myocardial cells (H9c2) and to investigate the mechanisms of these protective effects at the cellular level, which could provide the experimental basis for future applications of αB-crystallin in the treatment of cardiovascular disease. Western blotting was used to measure the expression of αB-crystallin in cultured H9c2 cells in vitro. A αB-crystallin recombinant expression vector, pcDNA3.1-Cryab, was constructed to transfect H9c2 cells for the establishment of cells that stably expressed αB-crystallin. A tetrazolium-based colorimetric assay (MTT test) was used to measure changes in the viability of the H9c2 cells at 1, 2, 3 and 4 h after induced by 150 μM H₂O₂ to establish a model of H₂O₂ injury to cells. H₂O₂ was applied to H9c2 cells that were stably transfected with αB-crystallin, and the effect of αB-crystallin overexpression on the viability of myocardial cells subjected to H₂O₂-induced injury was measured by the MTT assay. The effect of αB-crystallin overexpression on the H₂O₂-induced injury of H9c2 cells was also analyzed by flow cytometry. The mitochondrial components and cytoplasmic components of H9c2 cells were separated, and western blotting was used to measure the effect of αB-crystallin overexpression on the release of cytochrome c from the mitochondria. Western blotting was also used to measure the effect of αB-crystallin overexpression on the expression of the anti-apoptosis protein Bcl-2 and components of the phosphatidylinositol 3-OH kinase (PI3K)/AKT pathway. The αB-crystallin recombinant expression vector pcDNA3.1-Cryab successfully transfected H9c2 cells, and H9c2 cells that were stably transfected with αB-crystallin were established after G418 selection. The measurements carried out by western blotting showed that αB-crystallin proteins are expressed in normal H9c2 cells, but the proteins’ expression was much higher in pcDNA3.1-Cryab transfected cells (P < 0.01). The MTT assays showed that 4 h of H₂O₂ treatment induced significant injury in H9c2 cells (P < 0.01), but αB-crystallin overexpression can effectively antagonize the H₂O₂-induced injury to H9c2 cells (P < 0.05). The results of flow cytometry analysis showed that αB-crystallin overexpression can significantly reduce apoptosis in H₂O₂-injured H9c2 cells (P < 0.05). The results of western blotting showed that αB-crystallin overexpression in myocardial cells can reduce the H₂O₂-induced release of cytochrome c from the mitochondria (P < 0.05), antagonize the H₂O₂-induced downregulation of Bcl-2 (P < 0.05) and magnify the decrease in phosphorylated AKT levels induced by H₂O₂ injury (P < 0.05). The overexpression of αB-crystallin has a protective effect on H₂O₂-injured H9c2 cells, and αB-crystallin can play a protective role by reducing apoptosis, reducing the release of cytochrome c from the mitochondria and antagonizing the downregulation of Bcl-2 expression. The protective effects of αB-crystallin may be related to the PI3K/AKT pathway.     

Modulation of redox regulatory molecules and electron transport chain activity in muscle of air breathing fish Heteropneustes fossilis under air exposure stress

Responses of redox regulatory system to long-term survival (>18 h) of the catfish Heteropneustes fossilis in air are not yet understood. Lipid and protein oxidation level, oxidant (H₂O₂) generation, antioxidative status (levels of superoxide dismutase, catalase, glutathione peroxidase and reductase, ascorbic acid and non-protein sulfhydryl) and activities of respiratory complexes (I, II, III and IV) in mitochondria were investigated in muscle of H. fossilis under air exposure condition (0, 3, 6, 12 and 18 h at 25 °C). The increased levels of both H₂O₂ and tissue oxidation were observed due to the decreased activities of antioxidant enzymes in muscle under water deprivation condition. However, ascorbic acid and non-protein thiol groups were the highest at 18 h air exposure time. A linear increase in complex II activity with air exposure time and an increase up to 12 h followed by a decrease in activity of complex I at 18 h were observed. Negative correlation was observed for complex III and V activity with exposure time. Critical time to modulate the above parameters was found to be 3 h air exposure. Dehydration induced oxidative stress due to modulation of electron transport chain and redox metabolizing enzymes in muscle of H. fossilis was clearly observed. Possible contribution of redox regulatory system in muscle tissue of the fish for long-term survival in air is elucidated. Results of the present study may be useful to understand the redox metabolism in muscle of fishes those are exposed to air in general and air breathing fishes in particular.     

Effects of hydrogen peroxide on relaxation through the NO/sGC/cGMP pathway in isolated rat iliac arteries

Abstract

The production of reactive oxygen species, including hydrogen peroxide (H₂O₂), is increased in diseased blood vessels. Although H₂O₂ leads to impairment of the nitric oxide (NO)/soluble guanylate cyclase (sGC)/cGMP signaling pathway, it is not clear whether this reactive molecule affects the redox state of sGC, a key determinant of NO bioavailability. To clarify this issue, mechanical responses of endothelium-denuded rat external iliac arteries to BAY 41-2272 (sGC stimulator), BAY 60-2770 (sGC activator), nitroglycerin (NO donor), acidified NaNO₂ (exogenous NO) and 8-Br-cGMP (cGMP analog) were studied under exposure to H₂O₂. The relaxant response to BAY 41-2272 (pD₂: 6.79?±?0.10 and 6.62?±?0.17), BAY 60-2770 (pD₂: 9.57?±?0.06 and 9.34?±?0.15) or 8-Br-cGMP (pD₂: 5.19?±?0.06 and 5.24?±?0.08) was not apparently affected by exposure to H₂O₂. In addition, vascular cGMP production stimulated with BAY 41-2272 or BAY 60-2770 in the presence of H₂O₂ was identical to that in its absence. On the other hand, nitroglycerin-induced relaxation was markedly attenuated by exposing the arteries to H₂O₂ (pD₂: 8.73?±?0.05 and 8.30?±?0.05), which was normalized in the presence of catalase (pD₂: 8.59?±?0.05). Likewise, H₂O₂ exposure impaired the relaxant response to acidified NaNO₂ (pD₂: 6.52?±?0.17 and 6.09?±?0.16). These findings suggest that H₂O₂ interferes with the NO-mediated action, but the sGC redox equilibrium and the downstream target(s) of cGMP are unlikely to be affected in the vasculature.     

Identification and <Emphasis Type="Italic">In Silico</Emphasis> Analysis of Major Redox Modulated Proteins from <Emphasis Type="Italic">Brassica juncea</Emphasis> Seedlings Using 2D Redox SDS PAGE (2-Dimensional Diagonal Redox Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis)

The thiol–disulphide exchange regulates the activity of proteins by redox modulation. Many studies to analyze reactive oxygen species (ROS), particularly, hydrogen peroxide (H₂O₂) induced changes in the gene expression have been reported, but efforts to detect H₂O₂ modified proteins are comparatively few. Two-dimensional diagonal redox sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) was used to detect polypeptides which undergo thiol–disulphide exchange in Brassica juncea seedlings following H₂O₂ (10 mM) treatment for 30 min. Eleven redox responsive polypeptides were identified which included cruciferin, NLI [Nuclear LIM (Lin11, Isl-1 & Mec-3 domains)] interacting protein phosphatase, RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) large subunit, and myrosinase. Redox modulation of RuBisCO large subunit was further confirmed by western blotting. However, the small subunit of RuBisCO was not affected by these redox changes. All redox modulated targets except NLI interacting protein (although it contains two cysteines) showed oxidation sensitive cysteines by in silico analysis. Interestingly, interactome of cruciferin and myrosinase indicated that they may have additional function(s) beside their well-known roles in the seedling development and abiotic stress respectively. Cruciferin showed interactions with stress associated proteins like defensing-like protein 192 and 2-cys peroxiredoxin. Similarly, myrosinase showed interactions with nitrilase and cytochrome p450 which are involved in nitrogen metabolism and/or hormone biosynthesis. This simple procedure can be used to detect major stress mediated redox changes in other plants.     

Exogenous hydrogen peroxide enhanced the thermotolerance of Festuca arundinacea and Lolium perenne by increasing the antioxidative capacity

Heat stress is one of the most detrimental environment stresses for plants. Hydrogen peroxide (H₂O₂) is produced quickly in response to various stresses and likely plays a positive role in transmitting stress signal in organisms. This investigation addressed whether an exogenous H₂O₂ application would affect the heat response of turfgrasses and induce acclimation. Tall fescue (Festuca arundinacea cv. Barlexas) and perennial ryegrass (Lolium perenne cv. Accent), two important cool-season turfgrasses and forages, were sprayed with 10 mM H₂O₂ before they were treated with heat stress (38/30 °C, day/night) and compared with plants maintained at control temperatures (26/15 °C, day/night). Prior to the initiation of heat stress, H₂O₂ pretreatment increased the activities of guaiacol peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and glutathione-dependent peroxidase (GPX) and the ascorbate and glutathione pool, and it decreased the GSH/GSSG ratio. During the heat stress process, pretreated plants from both grasses exhibited higher turfgrass quality and relative water content, and they experienced lower oxidative damage and H₂O₂ levels. Moreover, the activities of APX, GR, GPX and glutathione-S-transferase increased significantly in response to H₂O₂ pretreatment under heat stress. These results suggested that H₂O₂ most likely participated in the transduction of redox signaling and induced the antioxidative defense system, including various enzymatic and nonenzymatic H₂O₂ scavengers. The scavengers played important roles in improving the thermotolerance of tall fescue and perennial ryegrasses.     

Evaluation of a dithiocarbamate derivative as a model of thiol oxidative stress in H9c2 rat cardiomyocytes

Thiol redox state (TRS) refers to the balance between reduced thiols and their corresponding disulfides and is mainly reflected by the ratio of reduced and oxidized glutathione (GSH/GSSG). A decrease in GSH/GSSG, which reflects a state of thiol oxidative stress, as well as thiol modifications such as S-glutathionylation, has been shown to have important implications in a variety of cardiovascular diseases. Therefore, research models for inducing thiol oxidative stress are important tools for studying the pathophysiology of these disease states as well as examining the impact of pharmacological interventions on thiol pathways. The purpose of this study was to evaluate the use of a dithiocarbamate derivative, 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylthiocarbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (2-AAPA), as a pharmacological model of thiol oxidative stress by examining the extent of thiol modifications induced in H9c2 rat cardiomyocytes and its impact on cellular functions. The extent of thiol oxidative stress produced by 2-AAPA was also compared to other models of oxidative stress including hydrogen peroxide (H₂O₂), diamide, buthionine sulfoximine, and N,N׳-bis(2-chloroethyl)-N-nitroso-urea. Results indicated that 2-AAPA effectively inhibited glutathione reductase and thioredoxin reductase activities and decreased the GSH/GSSG ratio by causing a significant accumulation of GSSG. 2-AAPA also increased the formation of protein disulfides as well as S-glutathionylation. The alteration in TRS led to a loss of mitochondrial membrane potential, release of cytochrome c, and increase in reactive oxygen species production. Compared to other models, 2-AAPA is more potent at creating a state of thiol oxidative stress with lower cytotoxicity, higher specificity, and more pharmacological relevance, and could be utilized as a research tool to study TRS-related normal and abnormal biochemical processes in cardiovascular diseases.     

Nitric oxide retards xanthine oxidase-mediated superoxide anion generation in Phalaenopsis flower: an implication of NO in the senescence and oxidative stress regulation

Senescence is a developmentally regulated and highly ordered sequence of events. Senescence leads to abscission of plant organs and eventually leads to death of a plant or part of it. Present study revealed that Phalaenopsis flower undergo senescence due to over activation of O₂ ^·−generating xanthine oxidase (XO), which consequently increases the concentrations of O₂ ^·− leading to enhanced oxidative damage and disturbed cellular redox environment as indicated by increased lipid peroxidation and DHA/AsA + DHA ratio, respectively. While activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and non-specific peroxidase (POD) were enhanced in sepals and petals of old flower, activities of catalase (CAT) and glutathione reductase (GR) were decreased. Exogenous application of nitric oxide (NO) retarded H₂O₂-induced senescence of Phalaenopsis flower by downregulating activity of XO and concentrations of O₂ ^·−, H₂O₂ and malondialdehyde (MDA, an index of lipid peroxidation). Exogenous application of NO also downregulated SOD activity and upregulated antioxidant enzymes involved in the detoxification of H₂O₂ (CAT and APX), and in the regulation of redox couples viz, monodehydroascorbate reductase (MDHAR) and GR, together with the modulation in non-protein thiol status and DHA/AsA + DHA ratio.     

Effects of elevated atmospheric O3 concentrations on early and late leaf growth and elemental contents of Acer truncatum Bung under mild drought

To investigate the possible interactive effects of elevated atmospheric ozone (O₃) concentrations and periodic drought stress on physiology of Shantung maple (Acer truncatum Bung), an experiment was conducted from the growth season of 2012 to 2013 with open-top chambers (OTCs) in Changping district, a suburb of Beijing, China. Four treatments were administered with three replications in twelve OTCs which were NN (well watered + ambient air), NO (well watered + add 100 nl l^? 1 O₃ above ambient air), DN (drought stress + ambient air) and DO (drought stress + add 100 nl l^? 1 O₃ above ambient air). Leaf area (LA), leaf mass per area (LMA), individual leaf weight (ILW), carbon(C), nitrogen (N) and sulfur (S) contents in early and late leaves were measured at the end of the second year. The results showed: (1) Both elevated O₃ concentration and drought treatments significantly reduced early leaf LMA, LA, ILW, leaf N and S contents, with a reduction of 28.7, 45.7, 61.3, 39.6, 16.1% by O₃ stress and 12.5, 46.8, 53.5, 15.45 and 22% by drought stress, respectively, while only LMA of late leaf was reduced 12.1% by O₃ treatments and LA and ILW were significantly reduced 23.3% and 30% by drought treatments. (2) Significant interactions of elevated atmospheric O₃ concentration and mild drought were detected on LMA, LA, ILW, N and C contents in early leaves and LMA in late leaves. Except for LA, the decreases under interactive treatments were all less than independent O₃ effects. In conclusion, late leaf had less responses to elevated O₃ and drought stresses than early leaves which need to be considered separately. The interactive effects suggested drought had antagonistic effects with O₃ on growth indicators except for LA, indicating drought could mitigate the adverse efforts from O₃ effects.     

Spatio-temporal patterns of grassland evapotranspiration and water use efficiency in arid areas

Understanding spatio-temporal patterns of grassland evapotranspiration (ET) and water use efficiency (WUE) in arid areas is important for livestock production and ecological conservation. Xinjiang, China, was used as an example in the Biome-BGC model to explore spatio-temporal patterns of grassland ET and WUE from 1979 to 2012 in arid areas. The ET ranked from high to low as follows: among seasons, summer (142.4 mm), spring (49.7 mm), autumn (45.9 mm) and winter (7.7 mm); among regions, the Tianshan Mountains (357.9 mm), northern Xinjiang (221.3 mm) and southern Xinjiang (183.2 mm); among grassland types, mid-mountain meadow (387.7 mm), swamp meadow (358.3 mm), typical grassland (343.9 mm), desert grassland (236.2 mm), alpine meadow (229.7 mm), and saline meadow (154.7 mm). The WUE ranked from high to low as follows: among seasons, summer (0.60 g C kg H₂O^?1), autumn (0.48 g C kg H₂O^?1) and spring (0.43 g C kg H₂O^?1); among regions, northern Xinjiang (0.73 g C kg H₂O^?1), the Tianshan Mountains (0.69 g C kg H₂O^?1) and southern Xinjiang (0.26 g C kg H₂O^?1); among grassland types, mid-mountain meadow (0.86 g C kg H₂O^?1), typical grassland (0.84 g C kg H₂O^?1), swamp meadow (0.77 g C kg H₂O^?1), saline meadow (0.52 g C kg H₂O^?1), alpine grassland (0.37 g C kg H₂O^?1) and desert grassland (0.34 g C kg H₂O^?1). In Xinjiang grasslands, the spatio-temporal ET patterns were more strongly influenced by precipitation than by temperature, whereas most high WUE values occurred when precipitation and temperature were relatively conducive to grass growth.     

Differential correlations between changes to glutathione redox state,protein ubiquitination,and stress-inducible HSPA chaperone expression after different types of oxidative stress

In primary bovine fibroblasts with an hspa1b/luciferase transgene, we examined the intensity of heat-shock response (HSR) following four types of oxidative stress or heat stress (HS), and its putative relationship with changes to different cell parameters, including reactive oxygen species (ROS), the redox status of the key molecules glutathione (GSH), NADP(H) NAD(H), and the post-translational protein modifications carbonylation, S-glutathionylation, and ubiquitination. We determined the sub-lethal condition generating the maximal luciferase activity and inducible HSPA protein level for treatments with hydrogen peroxide (H₂O₂), UVA-induced oxygen photo-activation, the superoxide-generating agent menadione (MN), and diamide (DA), an electrophilic and sulfhydryl reagent. The level of HSR induced by oxidative stress was the highest after DA and MN, followed by UVA and H₂O₂ treatments, and was not correlated to the level of ROS production nor to the extent of protein S-glutathionylation or carbonylation observed immediately after stress. We found a correlation following oxidative treatments between HSR and the level of GSH/GSSG immediately after stress, and the increase in protein ubiquitination during the recovery period. Conversely, HS treatment, which led to the highest HSR level, did not generate ROS nor modified or depended on GSH redox state. Furthermore, the level of protein ubiquitination was maximum immediately after HS and lower than after MN and DA treatments thereafter. In these cells, heat-induced HSR was therefore clearly different from oxidative stress-induced HSR, in which conversely early redox changes of the major cellular thiol predicted the level of HSR and polyubiquinated proteins.     

ROS generation and proline metabolism in calli of halophyte Nitraria tangutorum Bobr. to sodium nitroprusside treatment

Nitric oxide (NO) is a stress factor or a signal molecule involved in various plant physiological and developmental processes. In the present study, the generation of reactive oxygen species and the metabolism of proline due to different sodium nitroprusside (SNP, an NO donor) concentrations were investigated in callus from halophyte Nitraria tangutorum Bobr. Treatment with SNP led to significant increases of hydrogen peroxide (H₂O₂) content and cell viability but notable reductions in hydrogen radical level and lipid peroxidation degree, and superoxide onion (O₂ ^?) content also enhanced in 100 μM SNP-treated calli. Using a chemical inhibitor for plasma membrane (PM) NADPH oxidase diphenylene iodonium (DPI), we found low O₂ ^? generation in untreated and 25 μM SNP-treated calli, whereas in those treated with 100 μM SNP O₂ ^? level exhibited a very little alteration, comparable to the absence of DPI. These suggest a high activity of PM NADPH oxidase in untreated calli. H₂O₂ scavenging enzymes (catalase, peroxidase [POD] and ascorbate peroxidase) and H₂O₂ forming enzymes (superoxide dismutase [SOD], cell wall-POD and diamine oxidase [DAO]) stimulated significantly in calli treated with different SNP concentrations while glutathione reductase activity decreased. In addition, a reduction in proline content was observed in SNP-treated calli. Moreover, different SNP concentrations stimulated proline dehydrogenase (PDH) and ornithine δ-aminotransferase but inhibited r-glutamyl kinase (GK). In conclusion, our results suggest that the increasing H₂O₂ generation was associated with the stimulation of SOD, cell wall-POD and DAO, and that the reduction of proline content might be the consequence of increased PDH activity and decreased GK activity in N. tangutorum Bobr. calli under SNP treatment.     

28-Homobrassinolide potential for oxidative interface in <Emphasis Type="Italic">Brassica juncea</Emphasis> under temperature stress

Exploration of scavenging potential of 28-homobrassinolide (28-homoBL) in mitigating the oxidative stress caused by free radicals (·O₂ ^?, H₂O₂, ·NO, OH^?) produced due to temperature stress (4, 44 °C) in Brassica juncea L. was made in the present research. Brassica juncea var. RLC-1 seeds were given pre-sowing soaking of different concentrations of 10^?9 M 28-homoBL for 8 h. Seeds were sown in bedded petri plates lined with 10 No. What’s man filter paper under controlled laboratory conditions. Temperature of 4 and 44 °C, taken as low- and high-temperature stress, suppressed membrane stability and overall growth of the seedlings, while cell death was triggered. Accumulation of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and nitric oxide (NO) was boosted which resulted in enhanced oxidative stress on the 10th day after sowing. Activity level of antioxidant enzymes viz. superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPOX), and ascorbate peroxidase (APOX) was enhanced which was ensued for up-regulation of total antioxidant potential in 10-day-old plants exposed to negative effect of temperature stress. Priming treatment of 28-homoBL at seed level helped in maintaining the growth of seedlings to higher level as compared to only stressed as well as from control double distilled water-raised seedlings. 10^?9 M 28-HBL found to be the best in enhancing the enzymatic activities of SOD, CAT, GPOX, and APOX and thus maintained antioxidant potential at higher level which accounted for alleviating oxidative stress caused due to extreme temperature stress. Dead cell formation reduced significantly in 28-homoBL-treated plants, membrane stability was upturned, while production of MDA, H₂O_2, and NO was under control. These results suggested and try to establish 28-homoBL as effective stress protector for B. juncea particularly from the oxidative damage induced by extreme temperatures.     

High diving metabolism results in a short aerobic dive limit for Steller sea lions (Eumetopias jubatus)

The diving capacity of marine mammals is typically defined by the aerobic dive limit (ADL) which, in lieu of direct measurements, can be calculated (cADL) from total body oxygen stores (TBO) and diving metabolic rate (DMR). To estimate cADL, we measured blood oxygen stores, and combined this with diving oxygen consumption rates (VO₂) recorded from 4 trained Steller sea lions diving in the open ocean to depths of 10 or 40 m. We also examined the effect of diving exercise on O₂ stores by comparing blood O₂ stores of our diving animals to non-diving individuals at an aquarium. Mass-specific blood volume of the non-diving individuals was higher in the winter than in summer, but there was no overall difference in blood O₂ stores between the diving and non-diving groups. Estimated TBO (35.9 ml O₂ kg^?1) was slightly lower than previously reported for Steller sea lions and other Otariids. Calculated ADL was 3.0 min (based on an average DMR of 2.24 L O₂ min^?1) and was significantly shorter than the average 4.4 min dives our study animals performed when making single long dives—but was similar to the times recorded during diving bouts (a series of 4 dives followed by a recovery period on the surface), as well as the dive times of wild animals. Our study is the first to estimate cADL based on direct measures of VO₂ and blood oxygen stores for an Otariid and indicates they have a much shorter ADL than previously thought.