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1.
Abstract: We studied the action of H2 O2 on the exocytosis of glutamate by cerebrocortical synaptosomes. The treatment of synaptosomes with H2 O2 (50–150 µ M ) for a few minutes results in a long-lasting depression of the Ca2+ -dependent exocytosis of glutamate, induced by KCl or by the K+ -channel inhibitor 4-aminopyridine. The energy state of synaptosomes, as judged by the level of phosphocreatine and the ATP/ADP ratio, was not affected by H2 O2 , although a transient decrease was observed after the treatment. H2 O2 did not promote peroxidation, as judged by the formation of malondialdehyde. In indo-1-loaded synaptosomes, the treatment with H2 O2 did not modify significantly the KCl-induced increase of [Ca2+ ]i . H2 O2 inhibited exocytosis also when the latter was induced by increasing [Ca2+ ]i with the Ca2+ ionophore ionomycin. The effects of H2 O2 were unchanged in the presence of superoxide dismutase and the presence of the Fe3+ chelator deferoxamine. These results appear to indicate that H2 O2 , apparently without damaging the synaptosomes, induces a long-lasting inhibition of the exocytosis of glutamate by acting directly on the exocytotic process. 相似文献
2.
In embryos of the sea urchin, Hemicentrotus pulcherrimus , as well as in cultured cells derived from isolated micromeres, spicule formation was inhibited by allylisothiocyanate, an inhibitor of H+ , K+ -ATPase, at above 0.5 μM and was almost completely blocked at above 10 μM. Amiloride, an inhibitor of Na+ , H+ antiporter, at above 100 μM exerted only slight inhibitory effect, if any, on spicule formation. Intravesicular acidification, determined using [ dimethylamine -14 C]-aminopyrine as a pH probe, was observed in the presence of ATP and 200 mM KCl in microsome fraction obtained from embryos at the post gastrula stage, at which embryos underwent spicule calcification. Intravesicular acidification and K+ -dependent ATPase activity were almost completely inhibited by allylisothiocyanate at 10 μM. Allylisothiocyanate-sensitive ATPase activity was found mainly in the mesenchyme cells with spicules isolated from prisms. H+ , K+ -ATPase, an H+ pump, probably mediates H+ release to accelerate CaCO3 deposition from Ca2+ , CO2 and H2 O in the primary mesenchyme cells. Intravesicular acidification was stimulated by valinomycin at the late gastrula and the prism stages but not at the pluteus stage. K+ permeability probably increases after the prism stage to activate H+ release. 相似文献
3.
The hydrogen peroxide (H2 O2 ) stress response in Enterococcus faecalis ATCC19433 was investigated. A 2·4 mmol l−1 H2 O2 pretreatment conferred protection against a lethal concentration (45 mmol l−1 ) of this agent. The relatively high concentrations of H2 O2 used for adaptation and challenge treatments in Ent. faecalis emphasised the strong resistance towards oxidative stress in this species. Various stresses (NaCl, heat, ethanol, acidity and alkalinity) induced weak or strong H2 O2 cross-protection. This paper describes the involvement of protein synthesis in the active response to lethal dose of H2 O2 , in addition to the impressive enhancement of synthesis of five H2 O2 stress proteins. Combined results suggest that these proteins might play an important role in the H2 O2 tolerance response. 相似文献
4.
Suspension-cultured rose ( Rosa damascena Mill. cv. Gloire de Guilan) cells irradiated with UV-C (254 nm. 558 J m−2 ) showed a transient production of H2 O2 as measured by chemiluminescence of luminol in the presence of peroxidase (EC 1.1 1.1.7). The peak concentration of H2 O2 , which occurred at about 60–90 min after irradiation, was 8–9 μ M . The time course for the appearance of H2 O2 matched that for UV–induced K+ efflux. Treatments that inhibited the UV-induced efflux of K+ , including heat and overnight incubation with cycloheximide and diethylmaleate, also inhibited the appearance of H2 O2 . The converse was not always true, since catalase (EC 1.11.1.6. and salicylhydroxamic acid, which inhibited luminescence, did not stop K+ efflux. We conclude that H2 O2 synthesis depends on K+ efflux. Because H2 .O2 in the extracellular space is required for lignin synthesis in many plant tissues, we suggest that the UV–stimulated production of H2 O2 is an integral part of a defensive lignin synthesis. 相似文献
5.
The effects of K+ concentration, light intensity and CO2 levels on the volume of Commelina communis L. guard cell protoplasts were studied. Two degrees of swelling response were observed, both dependent on an external supply of K+ , but not necessarily on the supply of a permeant anion. The presence of K+ itself, independent of light or CO2 level, stimulated swelling at a relatively slow rate. When K+ , light and low CO2 conditions were supplied together, the swelling was relatively rapid and of high magnitude. The rapid swelling was specific for K+ and Rb+ giving a half maximal effect after 2 h at a KCl concentration of about 18 mmol m−3 . The addition of CaCl2 at 1 mol m−3 inhibited K+ -dependent swelling under all conditions tested. The response to light and low CO2 levels by Commelina guard cell protoplasts is thought to reflect a high degree of physiological integrity. 相似文献
6.
Abstract In cell suspensions of the methanogenic bacterium strain Gö1 or Methanosarcina barkeri H2 formation from methanol in the presence of 2-bromoethanesulfonic acid (BES) was strictly dependent on sodium ions; apparent K S for Na+ , 1.3±0.3 mM.H2 formation was inhibited by the uncoupler tetrachlorosalicylanilide (TCS), but this inhibition could be temporarily overcome, when a sodium pulse (100 mM) was given to the cell suspension. On the other hand, H2 formation from formaldehyde in the presence of BES (rate: 300 nmol H2 /h·mg protein as compared to 25 nmol H2 /h·mg protein from methanol) was not sodium-dependent, not TCS-sensitive and not inhibited by addition of monensin. H2 formation was accompanied by CO2 formation in stoichiometric amounts, 3 H2 :1 CO2 for methanol and 2 H2 :1 CO2 for formaldehyde oxidation. 相似文献
7.
YUKIO FUJINO KEIKO MITSUNAGA IKUO YASUMASU 《Development, growth & differentiation》1987,29(6):591-597
Embryos kept with omeprazole, a specific H+ , K+ -ATPase inhibitor, in a period of development between the mesenchyme blastula and the pluteus corresponding stage became abnormal plutei having quite small spicules, somewhat poor pluteus arms and apparently normal archenterons. In micro-mere-derived cells, kept with omeprazole at pH 8.2 in a period between 15 and 40 hr of culture at 20°C, omeprazole strongly inhibited spicule formation but did not block the outgrowth of pseudopodial cables, in which spicule rods were to be formed. These indicate that omeprazole probably exerts no obvious inhibitory effects other than spicule rods formation. Omeprazole-sensitive H+ , K+ -ATPase, an H+ pump, seems to be indispensable for CaCO3 deposition (formation of spicule rod) in these spicule forming cells. H+ , produced in overall reaction for CaCO3 formation: Ca2+ + CO2 +H2 O°CaCO3 +2H+ , is probably released from the cells by this H+ pump and hence, this reaction tends to go to CaCO3 production to form spicule rods. Omeprazole, known to become effective following its conversion to a specific inhibitor of H+ , K+ -ATPase at acidic pH, is able to inhibit formation of spicule rod at alkaline pH in sea water. This is probably due to an acidification of sea water near the cell surface by H+ ejection in H+ , K+ -ATPase reaction. 相似文献
8.
Abstract: Involvement of reactive oxygen species has been implicated in plant defence against pathogens. We report here a novel pathway of H2 O2 generation induced by the addition of phosphate in soybean ( Glycine max L.) cell suspension cultures. This H2 O2 generation was initiated shortly after the addition of phosphate, and lasted only approximately one hour, as opposed to several hours observed during an attack by an avirulent strain of the bacterial pathogen Pseudomonas syringae pv. glycinea (Psg). In addition, when cell cultures were treated with both phosphate and the avirulent pathogen, two distinct oxidative burst events were observed. In contrast to DPI-sensitive Psg -induced H2 O2 generation, phosphate-induced H2 O2 generation was insensitive to this NADPH oxidase inhibitor. This suggests that an NADPH oxidase-independent pathway may be involved in the phosphate-induced H2 O2 accumulation, which could be involved in sensing of phosphate availability in the environment. 相似文献
9.
Tae-Ju Park Sungkwon Chung †Myung Kwan Han †Uh-Hyun Kim Kyong-Tai Kim 《Journal of neurochemistry》1998,71(3):1251-1260
Abstract: The role of the A2A adenosine receptor in regulating voltage-sensitive calcium channels (VSCCs) was investigated in PC12 cells. Ca2+ influx induced by membrane depolarization with 70 m M K+ could be inhibited with CGS21680, an A2A receptor-specific agonist. Both L- and N-type VSCCs were inhibited by CGS21680 treatment. Effects of adenosine receptor agonists and antagonists indicate that the typical A2A receptor mediates inhibition of VSCCs. Cholera toxin (CTX) treatment for 24 h completely eliminated the CGS21680 potency. Similar inhibitory effects on VSCCs were obtained by membrane-permeable activators of protein kinase A (PKA). These effects were blocked by Rp -adenosine-3',5'-cyclic monophosphothioate, a PKA inhibitor. The data suggest that activation of the A2A receptor leads to inhibition of VSCCs via a CTX-sensitive G protein and PKA. ATP pretreatment caused a reduction in subsequent rise in cytosolic free Ca2+ concentration induced by 70 m M K+ , presumably by inactivation of VSCCs. Simultaneous treatment with ATP and CGS21680 produced significantly greater inhibition of VSCCs than treatment with CGS21680 or ATP alone. Furthermore, the CGS21680-induced inhibition of VSCCs was not affected by the presence of reactive blue 2. CGS21680 still significantly inhibited ATP-evoked Ca2+ influx without VSCC activity after cobalt or 70 m M K+ pretreatment. These data suggest that the A2A receptor-sensitive VSCCs differ from those activated by ATP treatment. Although A2A receptors induce inhibition of VSCCs as well as ATP-induced Ca2+ influx, the two inhibitory effects are clearly distinct from each other. 相似文献
10.
Catherine Van Renterghem Paul Vigne Christian Frelin 《Journal of neurochemistry》1995,65(3):1274-1281
Abstract: A charybdotoxin-sensitive, Ca2+ -activated K+ channel was identified in cultured rat brain capillary endothelial cells by using conventional single-channel recording techniques and 86 Rb+ -influx and efflux experiments. Channel activity was dependent on the presence of Ca2+ on the cytosolic face of the membrane with a threshold concentration of 100 n M . It was inhibited by charybdotoxin (IC50 30 n M ) and quinine (IC50 0.1 m M ) but not by apamin. K(Ca) channels showed unusual inward rectifying properties under asymmetrical ionic conditions. They were activated by endothelin-1 (EC50 0.7 n M ) and endothelin-3 (EC50 7–10 n M ). The actions of endothelins were prevented by BQ-123 ( K i = 8 n M ) in a competitive fashion, hence suggesting the involvement of an ETA -receptor subtype. The channel activity was unaffected by cyclic AMP- or cyclic GMP-elevating agents. The possible role of the intermediate conductance, Ca2+ -activated K+ channels for mediating K+ movements across the blood-brain barrier is discussed. 相似文献
11.
A. Eshel 《Physiologia plantarum》1985,64(3):308-315
The response of Suaeda aegyptiaca (Hasselq.) Zoh. to various salinity treatments was tested in sand culture. Growth was promoted by NaCl and by Na2 SO4 at all tested concentrations, but not by KCl. The effect of NaCl on growth was stronger than that of Na2 SO4 and it increased gradually up to a 125 eq. m−3 optimum. Ion uptake was also affected by the different salts. Cl− was taken up in similar quantities from KCl and from NaCl solutions and the content of the respective cations was also similar to one another. The presence of Na+ in the medium lowered the content of K+ in the plants and at the same time increased growth by as much as 900%. Transpiration was reduced and water use efficiency increased by Na+ -salts. Highest water use efficiency was exhibited by plants which were treated with 125 eq. m−3 NaCl. It is concluded that Na+ at the macronutrient level has a specific promotive effect on the physiological processes of S. aegyptiaca. This effect is not due to replacement of K+ by Na+ ; neither can it be achieved by increasing the K+ concentration. Cl− has an additional positive effect on growth of S. aegyptiaca. This effect is only expressed in the presence of Na+ . 相似文献
12.
13.
The carboxanilide systemic fungicide 2-iodobenzanilide (2-IB) after 2 h pretreatment at 0.25 m M inhibited K+ and SO4 2- uptake by excised corn roots ( Zea mays L., cv. Dekalb 342) up to ca 70 and 40%, respectively. Proton extrusion from corn roots was also reduced by ca 50% after 1 h contact, and the microsomal K+ -stimulated ATPase activity from corn roots and pea stems ( Pisum sativum L., cv. Alaska) inhibited by 50 and 72%, respectively. In contrast, the Mg2+ -ATPase activities of microsomes and mitochondria at pH 6.0 and 8.7, respectively, were unaffected. After 2 h of preincubation with 0.25 m M 2-IB, O2 consumption by corn roots and pea stems was inhibited by 12 and 18%, respectively. ATP content of corn roots was not altered by 2-IB treatment. Therefore, energy availability "in vivo" was unaffected and the primary effect on corn roots is suggested to be at the plasmalemma ATPase which forms the proton gradient.
With isolated pea stem mitochondria, 0.25 m M 2-IB inhibited O2 consumption by ca 60% when NADH or malate plus pyruvate were added as substrates; when succinate was used O2 consumption was unaffected. The mode of action on isolated mitochondria was different from that shown for carboxin and also formerly attributed to the whole class of carboxanilide fungicides. 相似文献
With isolated pea stem mitochondria, 0.25 m M 2-IB inhibited O
14.
Massimo Malerba Paolo Crosti Raffaella Cerana Renato Bianchetti 《Physiologia plantarum》2003,119(4):480-488
Fusicoccin (FC) is a well known toxin acting as a 14-3-3 protein-mediated activator of the plasma membrane H+ -ATPase and it has been widely used to study the regulatory mechanism and the physiological role of this enzyme's activity. Recently, FC has been shown to induce other responses similar to those occurring under a stress condition, perhaps not strictly dependent on the activation of proton extrusion. In this paper we report that in cultured sycamore ( Acer pseudoplatanus L.) cells FC induces H2 O2 overproduction as well as other novel, presumably related responses, such as the activation of the alternative oxidase and the leakage of cytochrome c from the mitochondria, accompanied by a decrease of the cytochrome pathway capacity. The relationship between H2 O2 production and other phenomena has also been studied by means of exogenously added H2 O2 . 相似文献
15.
Shigeru Hishinuma Akie Naiki Hirofumi Tsuga J. Michael Young 《Journal of neurochemistry》1998,71(6):2626-2633
Abstract: We investigated the regulation by intracellular Ca2+ of agonist-induced sequestration of Gq protein-coupled histamine H1 receptors in human U373 MG astrocytoma cells. Histamine-induced sequestration of H1 receptors from the cell surface membrane was detected as the loss of [3 H]mepyramine binding sites on intact cells accessible to the hydrophilic H1 -receptor antagonist pirdonium. The changes in the pirdonium-sensitive binding of [3 H]mepyramine were mirrored by changes in the subcellular distribution of H1 receptors detected by sucrose density gradient centrifugation. The histamine-induced sequestration of H1 receptors did not occur in hypertonic medium, in which clathrin-mediated endocytosis is known to be inhibited, but was significantly accelerated in the absence of extracellular Ca2+ or in the presence of the calmodulin antagonists W-7 and calmidazolium. Inhibitors of protein kinase C (H-7 and GF109203X), Ca2+ /calmodulin-dependent protein kinase II (KN-62), or protein phosphatase 2B (FK506) did not alter the time course of H1 -receptor sequestration. These results provide the first evidence that agonist-induced, clathrin-mediated sequestration of Gq protein-coupled receptors is transiently inhibited by Ca2+ /calmodulin, with the result that receptors remain on the cell surface membrane during the early stage of agonist stimulation. 相似文献
16.
Effects of 1-Methyl-4-Phenylpyridinium on Isolated Rat Brain Mitochondria: Evidence for a Primary Involvement of Energy Depletion 总被引:7,自引:1,他引:6
T. E. Bates S. J. R. Heales S. E. C. Davies P. Boakye J. B. Clark 《Journal of neurochemistry》1994,63(2):640-648
Abstract: The effects of 1-methyl-4-phenylpyridinium (MPP+ ) on the oxygen consumption, ATP production, H2 O2 production, and mitochondrial NADH-CoQ1 reductase (complex I) activity of isolated rat brain mitochondria were investigated. Using glutamate and malate as substrates, concentrations of 10–100 µ M MPP+ had no effect on state 4 (−ADP) respiration but decreased state 3 (+ADP) respiration and ATP production. Incubating mitochondria with ADP for 30 min after loading with varying concentrations of MPP+ produced a concentration-dependent decrease in H2 O2 production. Incubation of mitochondria with ADP for 60 min after loading with 100 µ M MPP+ caused no loss of complex I activity after washing of MPP+ from the mitochondrial membranes. These data are consistent with MPP+ initially binding specifically to complex I and inhibiting both the flow of reducing equivalents and the production of H2 O2 by the mitochondrial respiratory chain, without irreversibly damaging complex I. However, mitochondria incubated with H2 O2 in the presence of Cu2+ ions showed decreased complex I activity. This study provides additional evidence that cellular damage initiated by MPP+ is due primarily to energy depletion caused by specific binding to complex I, any increased damage due to free radical production by mitochondria being a secondary effect. 相似文献
17.
Abstract: Rat brain microsomes were preincubated with S -adenosylmethionine (SAM), MgCl2 , and CaCl2 , then re-isolated, and the activity of Na+ ,K+ -ATPase determined. SAM inhibited the Na+ ,K+ -ATPase activity compared with microsomes subjected to similar treatment in the absence of SAM. A biphasic inhibitory effect was observed with a 50% decrease at a SAM concentration range of 0.4 μ M -3.2 μ M and a 70% reduction at a concentration range above 100 μ M . Inclusion of either S- adenosylhomocysteine or 3-deazaadenosine in the preincubations prevented the SAM inhibition of Na+ ,K+ -ATPase activity. The inhibition by SAM appeared to be Mg2+ - or Ca2+ -dependent. 相似文献
18.
Michele Glinn Binhui Ni Robert P. Irwin S. W. Kelley Sui-Zhen Lin Steven M. Paul 《Journal of neurochemistry》1998,70(5):1850-1858
Abstract: Inorganic phosphate (Pi ) plays a vital role in intracellular energy metabolism. Its many effects include stimulation of glucose use, enhancement of high-energy phosphate concentrations, and modulation of cytosolic free [Ca2+ ]. Cultured fetal rat cortical neurons constitutively import Pi , and cytosolic levels positively correlate with [ATP], [NADPH], and energy charge. In the present study, we demonstrate that the concentration of intracellular Pi is an important determinant of acute neuronal survival after an excitotoxic or oxidative insult to cultured fetal rat cortical neurons. Extracellular Pi dose-dependently enhanced survival of cortical neurons after exposure to NMDA at early (≤6 h) time points after termination of the insult. Pi similarly increased neuronal survival after exposure to kainic acid or H2 O2 . Pi -exposed neurons had higher basal intracellular [Pi ], [ATP], and [GSH], and slightly lower cytosolic free [Ca2+ ], compared with Pi -deprived neurons. Pi -exposed neurons maintained increased [ATP] after exposure to NMDA and displayed reduced formation of reactive oxygen species after exposure to kainic acid or H2 O2 , compared with Pi -deprived neurons. These findings demonstrate that changes in extracellular and intracellular Pi can affect neuronal survival after excitotoxic or oxidative insults. 相似文献
19.
Hans Thordal-Christensen Ziguo Zhang Yangdou Wei David B. Collinge 《The Plant journal : for cell and molecular biology》1997,11(6):1187-1194
Active oxygen species (AOS) are believed to have important roles in plants in general and in plant—pathogen interactions in particular. They are believed to be involved in signal transduction, cell wall reinforcement, hypersensitive response (HR) and phytoalexin production, and to have direct antimicrobial effects. Since current methods are inadequate for localizing AOS in intact plant tissue, most studies have been conducted using cell suspension culture/elicitors systems. 3,3-diaminobenzidine (DAB) polymerizes instantly and locally as soon as it comes into contact with H2 O2 in the presence of peroxidase, and it was found that, by allowing the leaf to take up this substrate, in-vivo and in-situ detection of H2 O2 can be made at subcellular levels. This method was successfully used to detect H2 O2 in developing papillae and surrounding haloes (cell wall appositions) and whole cells of barley leaves interacting with the powdery mildew fungus. Thus, H2 O2 can be detected in the epidermal cell wall subjacent to the primary germ tube from 6 h after inoculation, and subjacent to the appressorium from 15 h. The earliest time point for observation of H2 O2 in relation to epidermal cells undergoing HR is 15 h after inoculation, first appearing in the zones of attachment to the mesophyll cells underneath, and eventually in the entire epidermal cell. Furthermore, it was observed that proteins in papillae and HR cells are cross-linked, a process believed to be fuelled by H2 O2 . This cross-linking reinforces the apposition, presumably assisting the arrest of the pathogen. 相似文献
20.
Zhiyuan Zhang Russell E. Rydel Gary J. Drzewiecki Kimberly Fuson Sarah Wright Mark Wogulis James E. Audia Patrick C. May Paul A. Hyslop 《Journal of neurochemistry》1996,67(4):1595-1606
Abstract: H2 O2 and free radical-mediated oxidative stresses have been implicated in mediating amyloid β(1–40) [Aβ(1–40)] neurotoxicity to cultured neurons. In this study, we confirm that addition of the H2 O2 -scavenging enzyme catalase protects neurons in culture against Aβ-mediated toxicity; however, it does so by a mechanism that does not involve its ability to scavenge H2 O2 . Aβ-mediated elevation in intracellular H2 O2 production is suppressed by addition of a potent H2 O2 scavenger without any significant neuroprotection. Three intracellular biochemical markers of H2 O2 -mediated oxidative stress were unchanged by Aβ treatment: (a) glyceraldehyde-3-phosphate dehydrogenase activity, (b) hexose monophosphate shunt activity, and (c) glucose oxidation via the tricarboxylic acid cycle. Ionspray mass spectra of Aβ in the incubation medium indicated that Aβ itself is an unlikely source of reactive oxygen species. In this study we demonstrate that intracellular ATP concentration is compromised during the first 24-h exposure of neurons to Aβ. Our results challenge a pivotal role for H2 O2 generation in mediating Aβ toxicity, and we suggest that impairment of energy homeostasis may be a more significant early factor in the neurodegenerative process. 相似文献