共查询到20条相似文献,搜索用时 46 毫秒
1.
Kroll Sandra L.; Czyzyk-Krzeska Maria F. 《American journal of physiology. Cell physiology》1998,274(1):C167
In the currentstudy, we investigated links betweenO2-regulatedH2O2formation and the hypoxic induction of mRNA for tyrosine hydroxylase(TH), the rate-limiting enzyme in catecholamine synthesis, inO2-sensitive PC-12 cells. Duringexposure of PC-12 cells to 5% O2,H2O2concentration decreased by 40% as measured with2',7'-dichlorofluorescein (DCF). Treatment withH2O2reduced TH mRNA during normoxia and prevented the induction of TH mRNAduring hypoxia. Treatment with catalase orN-(2-mercaptopropionyl)-glycine, areducing antioxidant agent that decreasesH2O2concentration, also induced TH mRNA. Deferoxamine (DF), an ironchelator, failed to affectH2O2formation but induced TH mRNA in normoxia and hypoxia.CoCl2 led to a decrease inH2O2at 20 h of treatment but induced TH mRNA during normoxia and hypoxiabefore it affectedH2O2.In conclusion, TH gene expression correlates inversely withH2O2formation. DF and Co2+ seem toaffect TH gene expression in themechanism downstream from theH2O2formation rather than by interfering with theH2O2-generating activity of the O2 sensor. 相似文献
2.
Illuminated intact spinach chloroplasts decomposed one moleculeof H218O2 which resulted in the evolution of a half moleculeof 16O2, but little 18O2. The chloroplasts showed the same rateof photoreduction of 18C2 as that of the evolution of 16O2 withoutaccumulation of H218O2. These reactions were suppressed by DCMU,and also by several inhibitors of ascorbate peroxidase and dehydroascorbateand monodehydroascorbate reductases in chloroplasts. These observationsindicate that the hydrogen peroxide produced in chloroplastsis reduced to water by a peroxidase using a photoreductant asthe electron donor. The hydrogen peroxide scavenging systemof chloroplasts was inactivated if hydrogen peroxide was addedin the dark, but not if added during the light. (Received May 4, 1984; Accepted July 10, 1984) 相似文献
3.
Elevated CO2 reduces O3 flux and O3-induced yield losses in soybeans: possible implications for elevated CO2 studies 总被引:2,自引:0,他引:2
Soybeans were grown for three seasons in open-top field chambersto determine (1) whether elevated CO2 (360 versus 700 µmolmol1) alleviates some of the yield loss due to pollutantO3, (2) whether the partial stomatal closure resulting fromchronic O3 exposure (charcoal-filtered air versus 1.5 ambientconcentrations) is a cause or result of decreased photosynthesis,and (3) possible implications of CO2/O3 interactions to climatechange studies using elevated CO2. Leaf conductance was reducedby elevated CO2, regardless of O3 level, or by exposure to O3alone. As.a result of these effects on conductance, high CO2reduced estimated midday O3 flux into the leaf by an averageof 50% in charcoal-filtered air and 35% in the high O3 treatment.However, while exposure to O3 reduced seed yields by 41% atambient CO2 levels, the yield reduction was completely amelioratedby elevated CO2. The threshold midday O3 flux for yield lossappears to be 2030 nmol m2 s1 in this study.Although elevated CO2 increased total biomass production, itdid not increase seed yields. A/Ci curves show a large reductionin the stomatal limitation to photosynthesis due to elevatedCO2 but no effect of O3. These data demonstrate that (1) reducedconductance due to O3 is the result, and not the cause, of reducedphotosynthesis, (2) 700 µmol mol1 CO2 can completelyameliorate yield losses due to O3 within the limits of theseexperiments, and (3) some reports of increased yields underelevated CO2 treatments may, at least in part, reflect the ameliorationof unrecognized suppression of yield by O3 or other stresses. Key words: Stomatal limitation, elevated CO2, O3 flux, Glycine max, yield suppression 相似文献
4.
H(2)O(2)-mediated permeability: role of MAPK and occludin 总被引:4,自引:0,他引:4
Kevil CG Oshima T Alexander B Coe LL Alexander JS 《American journal of physiology. Cell physiology》2000,279(1):C21-C30
H2O2-mediated elevation inendothelial solute permeability is associated with pathological eventssuch as ischemia-reperfusion and inflammation. To understand howH2O2 mediates increased permeability, weinvestigated the effects of H2O2 administrationon vascular endothelial barrier properties and tight junctionorganization and function. We report that H2O2exposure caused an increase in endothelial solute permeability in atime-dependent manner through extracellularly regulated kinase 1 and 2 (ERK1/ERK2) signal pathways. H2O2 exposurecaused the tight junctional protein occludin to be rearranged fromendothelial cell-cell junctions. Occludin rearrangement involvedredistribution of occludin on the cell surface and dissociation ofoccludin from ZO-1. Occludin also was heavily phosphorylated onserine residues upon H2O2 administration. H2O2 mediates changes in ERK1/ERK2phosphorylation, increases endothelial solute permeability, and altersoccludin localization and phosphorylation were all blocked by PD-98059,a specific mitogen-activated protein (MAP) or ERK kinase 1 inhibitor. These data strongly suggest thatH2O2-mediated increased endothelial solutepermeability involves the loss of endothelial tight junction integritythrough increased ERK1/ERK2 activation. 相似文献
5.
Takamiya Ken-ichiro; Kimura Keiko; Doi Michio; Nishimura Mitsuo 《Plant & cell physiology》1980,21(3):405-411
The O2 uptake linked to NADH2 and succinate oxidation was observedin chromatophores from photosynthetically grown Chromatium vinosum. The maximal rate was 60120 nmoles of O2 uptake per minper {diaeresis}mole of bacterio-chlorophyll. The rate of O2uptake linked to NADH2 oxidation was higher in the neutral-to-acidicpH range than in the alkaline range, whereas that linked tosuccinate oxidation was higher in the alkaline range. The O2 uptake linked to NADH2 oxidation was inhibited by rotenone,amytal, antimycin A, KCN and NaN3, while that linked to succinateoxidation was inhibited by antimycin A, KCN and NaN3. Malate,citrate, pyruvate, acetate, -ketoglutarate, NADPH2 and thiosulfatedid not serve as substrates for the O2 uptake of isolated chromatophores. The rates of the O2 uptake linked to both NADH2 and succinateoxidation were not stimulated by adding uncouplers or underphosphorylating conditions. Little or no ATP was synthesizedin the dark, coupled to either NADH2 or succinate oxidation,in spite of a high activity of photophosphorylation in Chromatiumchromatophores. (Received February 26, 1980; ) 相似文献
6.
Wolfel Eugene E.; Selland Mark A.; Cymerman A.; Brooks George A.; Butterfield Gail E.; Mazzeo Robert S.; Grover Robert F.; Reeves John T. 《Journal of applied physiology》1998,85(3):1092-1102
Wholebody O2 uptake (O2)during maximal and submaximal exercise has been shown to be preservedin the setting of -adrenergic blockade at high altitude, despitemarked reductions in heart rate during exercise. An increase in strokevolume at high altitude has been suggested as the mechanism thatpreserves systemic O2 delivery (blood flow × arterialO2 content) and thereby maintains O2 at sea-level values. To test thishypothesis, we studied the effects of nonselective -adrenergicblockade on submaximal exercise performance in 11 normal men(26 ± 1 yr) at sea level and on arrival and after 21 days at 4,300 m. Six subjects received propranolol (240 mg/day), and five subjectsreceived placebo. At sea level, during submaximal exercise, cardiacoutput and O2 delivery were significantly lower inpropranolol- than in placebo-treated subjects. Increases instroke volume and O2 extraction were responsible for themaintenance of O2. At 4,300 m,-adrenergic blockade had no significant effect onO2, ventilation, alveolarPO2, and arterial blood gases duringsubmaximal exercise. Despite increases in stroke volume, cardiac outputand thereby O2 delivery were still reduced inpropranolol-treated subjects compared with subjects treated withplacebo. Further reductions in already low levels of mixed venousO2 saturation were responsible for the maintenance ofO2 on arrival and after 21 days at4,300 m in propranolol-treated subjects. Despite similarworkloads and O2,propranolol-treated subjects exercised at greater perceived intensitythan subjects given placebo at 4,300 m. The values for mixed venousO2 saturation during submaximal exercise inpropranolol-treated subjects at 4,300 m approached thosereported at simulated altitudes >8,000 m. Thus -adrenergicblockade at 4,300 m results in significant reduction in O2delivery during submaximal exercise due to incomplete compensation bystroke volume for the reduction in exercise heart rate. Total bodyO2 is maintained at a constant levelby an interaction between mixed venous O2 saturation, thearterial O2-carrying capacity, and hemodynamics duringexercise with acute and chronic hypoxia. 相似文献
7.
Oba Toshiharu; Ishikawa Tatsuya; Yamaguchi Mamoru 《American journal of physiology. Cell physiology》1998,274(4):C914
The mechanism underlying H2O2-inducedactivation of frog skeletal muscle ryanodine receptors was studiedusing skinned fibers and by measuring single Ca2+-releasechannel current. Exposure of skinned fibers to 3-10 mM H2O2 elicited spontaneous contractures.H2O2 at 1 mM potentiated caffeine contracture.When the Ca2+-release channels were incorporated into lipidbilayers, open probability (Po) and open timeconstants were increased on intraluminal addition ofH2O2 in the presence of cis catalase,but unitary conductance and reversal potential were not affected.Exposure to cis H2O2 at 1.5 mM failedto activate the channel in the presence of trans catalase.Application of 1.5 mM H2O2 to the transside of a channel that had been oxidized by cisp-chloromercuriphenylsulfonic acid (pCMPS; 50 µM) still led to anincrease in Po, comparable to that elicited bytrans 1.5 mM H2O2 without pCMPS.Addition of cis pCMPS to channels that had been treated with orwithout trans H2O2 rapidly resulted inhigh Po followed by closure of the channel. Theseresults suggest that oxidation of luminal sulfhydryls in theCa2+-release channel may contribute toH2O2-induced channel activation and musclecontracture. 相似文献
8.
Oba T Ishikawa T Murayama T Ogawa Y Yamaguchi M 《American journal of physiology. Cell physiology》2000,279(5):C1366-C1374
We examined theeffect of low concentrations of H2O2 on theCa2+-release channel/ryanodine receptor (RyR) to determineif H2O2 plays a physiological role in skeletalmuscle function. Sarcoplasmic reticulum vesicles from frog skeletalmuscle and type 1 RyRs (RyR1) purified from rabbit skeletal muscle wereincorporated into lipid bilayers. Channel activity of the frog RyR wasnot affected by application of 4.4 mM (0.02%) ethanol. Openprobability (Po) of such ethanol-treated RyRchannels was markedly increased on subsequent addition of 10 µMH2O2. Increase of H2O2to 100 µM caused a further increase in channel activity. Applicationof 4.4 mM ethanol to 10 µM H2O2-treated RyRsactivated channel activity. Exposure to 10 or 100 µMH2O2 alone, however, failed to increasePo. Synergistic action of ethanol andH2O2 was also observed on the purified RyR1 channel, which was free from FK506 binding protein (FKBP12).H2O2 at 100-500 µM had no effect onpurified channel activity. Application of FKBP12 to the purified RyR1drastically decreased channel activity but did not alter the effects ofethanol and H2O2. These results suggest thatH2O2 may play a pathophysiological, butprobably not a physiological, role by directly acting on skeletalmuscle RyRs in the presence of ethanol. 相似文献
9.
H2O2-mediated permeability II: importance of tyrosine phosphatase and kinase activity 总被引:1,自引:0,他引:1
Kevil Christopher G.; Okayama Naotsuka; Alexander J. Steven 《American journal of physiology. Cell physiology》2001,281(6):C1940
We previously reportedthat exposure of endothelial cells to H2O2results in a loss of cell-cell apposition and increased endothelialsolute permeability. The purpose of this study was to determine howtyrosine phosphorylation and tyrosine phosphatases contribute tooxidant-mediated disorganization of endothelial cell junctions. Wefound that H2O2 caused a rapid decrease in total cellular phosphatase activity that facilitates a compensatory increase in cellular phosphotyrosine residues.H2O2 exposure also results in increasedendothelial monolayer permeability, which was attenuated by pp60, aninhibitor of src kinase. Inhibition of protein tyrosinephosphatase activity by phenylarsine oxide (PAO) demonstrated a similarpermeability profile compared with H2O2,suggesting that tyrosine phosphatase activity is important inmaintaining a normal endothelial solute barrier. Immunofluorescence shows that H2O2 exposure caused a loss ofpan-reactive cadherin and -catenin from cell junctions that was notblocked by the src kinase inhibitor PP1.H2O2 also caused -catenin to dissociate fromthe endothelial cytoskeleton, which was not prevented by PP1. Finally,we determined that PP1 did not prevent cadherin internalization. Thesedata suggest that oxidants like H2O2 produce biological effects through protein phosphotyrosine modifications bydecreasing total cellular phosphatase activity combined with increasedsrc kinase activity, resulting in increased endothelial solute permeability. 相似文献
10.
Root growth of 7-d-old wheat (Triticum aestivum cv. Gamenya)seedlings was impaired at dissolved O2 concentrations of 0.01and 0.055 mol m3 O2, while growth at 0.115 mol m3O2 was the same as that in continuously aerated controls (0.26mol m3 O2). Oxygen uptake by apical (02 mm), expanding (24mm) and expanded (1012 mm) tissues of the roots decreasedbelow 0.16, 0.09 and 0.05 mol m3 O2, respectively. Thishierarchy is consistent with the metabolic rates of these tissues.There was a small (c. 9%) inhibition of O2 uptake and some netsynthesis of ethanol and alanine in root apices at 0.115 molm3 O2. Significant amounts of anaerobic end-productsaccumulated at 0.055 mol m3 O2 and even more so at 0.01mol m3 O2, indicating that oxidative phosphorylationwas strongly inhibited. Net alanine synthesis increased in fully expanded (1016mm) tissues exposed to <0.0030.01 mol m3 O2,and this increase was accompanied either by a proportionallysmaller increase in the concentration of other free amino acidsor by a net decrease in free amino acid levels excluding alanine.This suggests that alanine was synthesized as an end-productof anaerobic catabolism and did not accumulate simply becauseof decreased net protein synthesis. Comparing the carbon flow to CO2, ethanol, lactate and alaninein roots at 0.01 mol m3 O2 with carbon loss as CO2 inaerated roots suggests that carbon flow to products of metabolismwas not greatly enhanced due to O2 deficiency. This infers,but does not prove that, in wheat, generation of energy duringperiods of O2 deficiency is not enhanced due to a Pasteur effect. Key words: Anaerobic, fermentation, oxygen, wheat 相似文献
11.
High O2 tensions, CO4, C2H4 and high temperatures were effectivenot only in breaking the dormancy of cocklebur (Xanthium pennsylvanicumWallr.) seeds but also in increasing the germination potentialof the nondormant but small seeds. There were few qualitativedifferences in response to these factors between the dormantand impotent seeds. Unlike CO2, however, enriched O2 and C2H4were stimulative even at the low temperature of 13°C. Germination induced by CO2, C2H4 and high temperature treatmentswas lowered when endogenously evolved C2H4 or CO2 was removed,whereas the effect of O2 enrichment was not affected by theirremoval. CO2 and high temperatures remarkably stimulated C2H4production, whereas O2 enrichment had no such effect. C2H4 productivity was lower in the dormant than non-dormantseeds, suggesting that the after-ripening is characterized byincreasing C2H4 production. (Received August 20, 1974; ) 相似文献
12.
Radioactive starch, glucose and fructose have been preparedfrom tobacco leaves after assimilation of C14O2. The apparatusused for photosynthesis consisted of a shallow Perspex leafchamber connected to a closed gas system, in which C14O2 wasgenerated from BaC14O2. Six leaves, area 14 to 18 sq. dm. whenexposed to bright sunlight with an initial CO2 concentrationof 8 to 10 per cent., assimilated 3.35 g. of C14O2 in 8 to 10hours. At least 80 per cent. of the C14O2 supplied appearedin the leaves as starch and sugar and over 80 per cent. of theradioactivity was accounted for in these carbohydrates. Thespecific activity per m. atom of carbon of the isolated productswas 85 to 90 per cent. of that of the C14O2. Small amounts ofradioactive carbon were also incorporated in the leaf proteinand in the celluose, hemicellulose and polyuronides. 相似文献
13.
Widespread use of O2 microsensors to measure O2 partial pressure(pO2) in plant tissues has been limited in part because of difficultyof construction and other technical obstacles. By modifyingpublished techniques, an O2 microsensor was constructed thatcombined the advantages of Clark-type microsensors with lesscomplicated construction techniques. The specifications andsome performance characteristics of the microsensor are: tipdiameter 15 µm; sensitivity 7.525 pA kPa1;negligible stir-induced current; response time 540 ms. The microsensorcan be used in air or solution, and each sensor can be usedfor several experiments. The sensitivity of the microsensorwas unchanged during measurements over the physiological rangeof pO2 in intact, growing maize (Zea mays L.) primary roots,and was thus unaffected by cellular fluids and turgor pressure.Use of the microsensor to compare pO2 profiles in vermiculite-and solution-grown roots is described. The O2 microsensor couldfind application in studies in which information on tissue pO2is needed, but for which conventional O2 probes are too large. Key words: Oxygen microsensor, Zea mays L., roots, oxygen partial pressure 相似文献
14.
Robinson MA Baumgardner JE Good VP Otto CM 《American journal of physiology. Cell physiology》2008,294(4):C1079-C1087
Nitric oxide (NO) production by inducible NO synthase (iNOS) is dependent on O2 availability. The duration and degree of hypoxia that limit NO production are poorly defined in cultured cells. To investigate short-term O2-mediated regulation of NO production, we used a novel forced convection cell culture system to rapidly (response time of 1.6 s) and accurately (±1 Torr) deliver specific O2 tensions (from <1 to 157 Torr) directly to a monolayer of LPS- and IFN-stimulated RAW 264.7 cells while simultaneously measuring NO production via an electrochemical probe. Decreased O2 availability rapidly (30 s) and reversibly decreased NO production with an apparent KmO2 of 22 (SD 6) Torr (31 µM) and a Vmax of 4.9 (SD 0.4) nmol·min–1·10–6 cells. To explore potential mechanisms of decreased NO production during hypoxia, we investigated O2-dependent changes in iNOS protein concentration, iNOS dimerization, and cellular NO consumption. iNOS protein concentration was not affected (P = 0.895). iNOS dimerization appeared to be biphasic [6 Torr (P = 0.008) and 157 Torr (P = 0.258) >36 Torr], but it did not predict NO production. NO consumption was minimal at high O2 and NO tensions and negligible at low O2 and NO tensions. These results are consistent with O2 substrate limitation as a regulatory mechanism during brief hypoxic exposure. The rapid and reversible effects of physiological and pathophysiological O2 tensions suggest that O2 tension has the potential to regulate NO production in vivo. inducible nitric oxide synthase; substrate limitation; nitric oxide consumption 相似文献
15.
Indirect evidence suggests that legumes can adjust rapidly theresistance of their root nodules to O2 diffusion. Here we describeexperiments using O2 specific micro-electrodes and dark fieldmicroscopy to study directly the operation of this diffusionbarrier. The O2 concentration sensed by the electrode decreasedsharply in the region of the inner cortex and was less than1.0 mmol m3 throughout the infected tissue in nodulesof both pea (Pisum sativum) and french bean (Phaseolus vulgaris).In a number of experiments the ambient O2 concentration wasincreased to 40% while the electrode tip was just inside theinner cortex. In 13 out of 21 cases the O2 concentration atthis position either remained low and unchanged or increasedirreversibly to near ambient values. In the remaining casesthe O2 concentration increased after 1 to 2.5 min and then decreasedto its former value. These results are ascribed to an increasein resistance of the barrier in response to increased O2 fluxinto the nodule. It was shown microscopically that air spacesboth at the boundary between the infected zone and the innercortex, and within the infected zone started to disappear 3min after nodules were exposed to high ambient O2 concentrationsand had disappeared completely after 8 min. These spaces werenot changed by exposure of the nodule for 10 min to either N2or air. Key words: Oxygen, root nodules, air spaces 相似文献
16.
Curtis Scott E.; Walker Thomas A.; Bradley W. E.; Cain Stephen M. 《Journal of applied physiology》1997,83(5):1681-1689
Curtis, Scott E., Thomas A. Walker, W. E. Bradley, andStephen M. Cain. Raising P50increases tissue PO2 in canineskeletal muscle but does not affect criticalO2 extraction ratio.J. Appl. Physiol. 83(5):1681-1689, 1997.Affinity of hemoglobin (Hb) forO2 determines in part the rate ofO2 diffusion from capillaries tomyocytes by altering capillary PO2.We hypothesized that a decrease in HbO2 affinity (increasedP50) would increase capillary and tissue PO2(PtiO2) andimprove O2 consumption duringischemia. To test this hypothesis, blood flow to the pump-perfused lefthindlimb of 18 anesthetized and paralyzed dogs was progressively decreased over 90 min while hindlimb O2 consumption andO2 delivery (O2)and PtiO2 weremeasured at the muscle surface. Arterial PO2 was maintained at 150 ± 10 Torr in all dogs. We increased P50by 12.3 ± 0.9 (SE) Torr in nine dogs with RSR-13, an allosteric modifier of Hb. This decreased arterialO2 saturation to 90-92% butincreased meanPtiO2 from 35.5 ± 11.6 to 44.1 ± 15.2 (SD) Torr(P < 0.05) with no change incontrols (n = 9).O2 extraction ratio at criticalO2was 74 ± 2% in controls and 79 ± 1% in RSR-13-treated dogs(P = not significant).PtiO2 was30-40% higher in the RSR-13-treated group at anyO2above critical but did not differ between groups below criticalO2.Perfusion heterogeneity and convergence of the dissociation curvesnear criticalO2 may have mitigated any effect of increasedP50 onO2 diffusion. Still, increasingP50 by 12 Torr with RSR-13significantly increased PtiO2 atO2values above critical. 相似文献
17.
Pollutant particles enhanced H2O2 production from NAD(P)H oxidase and mitochondria in human pulmonary artery endothelial cells 总被引:1,自引:0,他引:1
Li Z Hyseni X Carter JD Soukup JM Dailey LA Huang YC 《American journal of physiology. Cell physiology》2006,291(2):C357-C365
Particulate matter (PM) induces oxidative stress and cardiovascular adverse health effects, but the mechanistic link between the two is unclear. We hypothesized that PM enhanced oxidative stress in vascular endothelial cells and investigated the enzymatic sources of reactive oxygen species and their effects on mitogen-activated protein kinase (MAPK) activation and vasoconstriction. We measured the production of extracellular H2O2, activation of extracellular signal-regulated kinases1/2 (ERK1/2) and p38 MAPKs in human pulmonary artery endothelial cells (HPAEC) treated with urban particles (UP; SRM1648), and assessed the effects of H2O2 on vasoconstriction in pulmonary artery ring and isolated perfused lung. Within minutes after UP treatment, HPAEC increased H2O2 production that could be inhibited by diphenyleneiodonium (DPI), apocynin (APO), and sodium azide (NaN3). The water-soluble fraction of UP as well as its two transition metal components, Cu and V, also stimulated H2O2 production. NaN3 inhibited H2O2 production stimulated by Cu and V, whereas DPI and APO inhibited only Cu-stimulated H2O2 production. Inhibitors of other H2O2-producing enzymes, including N-methyl-L-argnine, indomethacin, allopurinol, cimetidine, rotenone, and antimycin, had no effects. DPI but not NaN3 attenuated UP-induced pulmonary vasoconstriction and phosphorylation of ERK1/2 and p38 MAPKs. Knockdown of p47phox gene expression by small interfering RNA attenuated UP-induced H2O2 production and phosphorylation of ERK1/2 and p38 MAPKs. Intravascular administration of H2O2 generated by glucose oxidase increased pulmonary artery pressure. We conclude that UP induce oxidative stress in vascular endothelial cells by activating NAD(P)H oxidase and the mitochondria. The endothelial oxidative stress may be an important mechanism for PM-induced acute cardiovascular health effects. mitogen-activated protein kinase; extracellular signal-regulated kinase; p38; vasoconstriction 相似文献
18.
Synthesis of Isozymes of Superoxide Dismutase in Maize Leaves in Response to O3, SO2 and Elevated O2
Matters, G. L. and Scandalios, J. G. 1987. Synthesis of isozymesof superoxide dismutase in maize leaves in response to O3 SO2and elevated O2.J. exp. Bot 38: 842852. The activities of the enzymes superoxide dismutase (SOD) andcatalase were determined in maize leaves treated with O3or SO2for8 h, or with elevated levels of oxygen for up to 96 h. NeitherO3nor SO2significantly increased the levels of superoxide dismutaseor catalase activity. However, after 72 h in an atmosphere containing90% oxygen, superoxide dismutase activity was increased, butnot the activities of catalase, ascorbate pcroxidase, and malatedehydrogenase. Immunological analysis showed that amounts ofthe cytosolic superoxide dismutase isozymes, SOD-2 and SOD-4,were increased by the elevated oxygen but not the chroloplast(SOD-1) or mitochondrial (SOD-3) isozymes. Immunoprecipitationof translation products of leaf polysomes indicated that thehigher levels of SOD-2 and SOD-4 were due to increased amountsof polysome-bound mRNA coding for these proteins. The specificresponse of SOD-2 and SOD-4 to 90% oxygen treatments contrastswith the increase in all SOD isozymes in maize leaves treatedwith the herbicide paraquat. Key words: Air pollutants, maize, oxidative stress, oxygen, superoxide dismutase 相似文献
19.
Bruce Douglas; Popovic Radovan; Vidaver William; Colbow Konrad 《Plant & cell physiology》1983,24(5):877-882
The kinetics of the flash induced 518 nm absorbance change (A518)in lettuce leaves were found to be dependent on O2 concentration.(1) Either a lower O2 partial pressure or the addition of weakred background illumination accelerated the decay of (A518)while far-red background light induced a transient acceleration.(2) In the presence of background red light the accelerateddecay could be restored to the original dark level by the additionof O2. A linear relationship was found between the intensityof red background light and the O2 pressure required for thisrestoration. (3) The O2 dependence of (A518) decay halftimewas biphasic, the sensitive phase saturating at 0.3 atmospheresO2 independent of input light energy while the O2 concentrationneeded to saturate the second phase increased with increasinginput light energy (increasing flash frequency). (4) Treatmentwith N, N'-dicyclohexylcarbodiimide (DCCD) or KCN eliminatedall O2 and background light effects and DCMU treatment inhibitedall but the sensitive phase of the O2 dependence on (A518) decayhalftime. (5) The extent of the lag phase in the dark recoveryof (A518) normally present after preillumination induced accelerationof decay was decreased with added O2 or KCN. (6) It was concludedthat O2 competes directly with background red light inducedelectron transport to PS I acceptors to influence the (A518)decay. A possible mechanism involving the O2 sensitive ferredoxin-thioredoxin-reductaseactivation of chloroplast coupling factor 1 ATP-hydrolase activitywas discussed. (Received December 17, 1982; Accepted April 28, 1983) 相似文献
20.
Grassi Bruno; Gladden L. Bruce; Stary Creed M.; Wagner Peter D.; Hogan Michael C. 《Journal of applied physiology》1998,85(4):1404-1412
To test thehypothesis that muscle O2 uptake(O2) on-kinetics islimited, at least in part, by peripheralO2 diffusion, we determined theO2 on-kinetics in1) normoxia (Control);2) hyperoxic gas breathing(Hyperoxia); and 3) hyperoxia andthe administration of a drug (RSR-13, Allos Therapeutics), whichright-shifts the Hb-O2dissociation curve (Hyperoxia+RSR-13). The study was conducted inisolated canine gastrocnemius muscles(n = 5) during transitions from restto 3 min of electrically stimulated isometric tetanic contractions(200-ms trains, 50 Hz; 1 contraction/2 s; 60-70% peakO2). In all conditions,before and during contractions, muscle was pump perfused withconstantly elevated blood flow (), at a levelmeasured at steady state during contractions in preliminary trials withspontaneous . Adenosine was infusedintra-arterially to prevent inordinate pressure increases with theelevated . was measuredcontinuously, arterial and popliteal venousO2 concentrations were determinedat rest and at 5- to 7-s intervals during contractions, andO2 was calculated as · arteriovenous O2 content difference.PO2 at 50%HbO2saturation (P50) was calculated.Mean capillary PO2(cO2)was estimated by numerical integration.P50 was higher in Hyperoxia+RSR-13[40 ± 1 (SE) Torr] than in Control and in Hyperoxia (31 ± 1 Torr). After 15 s of contractions,cO2was higher in Hyperoxia (97 ± 9 Torr) vs. Control (53 ± 3 Torr) and in Hyperoxia+RSR-13 (197 ± 39 Torr) vs. Hyperoxia. Thetime to reach 63% of the difference between baseline and steady-stateO2 during contractions was 24.7 ± 2.7 s in Control, 26.3 ± 0.8 s in Hyperoxia, and 24.7 ± 1.1 s in Hyperoxia+RSR-13 (not significant). Enhancement ofperipheral O2 diffusion (obtainedby increasedcO2at constant O2 delivery) duringthe rest-to-contraction (60-70% of peakO2) transition did notaffect muscle O2on-kinetics. 相似文献