Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.5.3 (complex I)
 8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The oxidative and phosphorylative properties of mitochondria isolated from Neurospora crassa were investigated as a function of growth stage. The rates of oxidation of exogenous NADH and NADPH varied independently of each other, thus ruling out the existence of only one unspecific dehydrogenase. Two different pathways were involved in the oxidation of NAD-linked substrates, as indicated by changes in the rate of oxygen uptake, the sensitivity to rotenone, and the efficiency of phosphorylation. One pathway was sensitive to rotenone and involved three energy-coupling sites, whereas the other was resistant to rotenone and bypassed complex I. Our results indicated that the activity of complex I of the respiratory chain increased markedly in the late exponential phase of growth, remained high in the stationary phase, and then decreased when conidiae were formed. In contrast, the activity of the rotenone-resistant bypass was maximal in the early exponential phase. With malate (plus glutamate) as a substrate, the sensitivity to rotenone and the ADP/O ratios were always lower than those observed with other NAD-linked substrates, suggesting a possible cooperation between malate dehydrogenase and the rotenone-resistant pathway. The rate of oxygen uptake measured in the presence of rotenone was significantly increased by the addition of exogenous NAD+, suggesting that added NAD+ could interact with the rotenone-resistant bypass.
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PMID:Properties of mitochondria as a function of the growth stages of Neurospora crassa. 646 22

(CBA X C57B1) X F1 mice were sensitized intraperitoneally with sheep erythrocytes and infected with influenza A viruses: nonpathogenic Leningrad-77 (H1N1) or pathogenic PR8 (HON1), before or five days after administration into the oesophagus of sodium succinate, levamisole, complexes I (panangin, sodium succinate, sodium glutamate) and 2 (lipoic acid, phosphothyamine, riboflavin, sodium pantothenate). The number of rosette-forming cells (RFC) in the spleen at 7 and 14 days postinfection, antibody titres, interferon level in the blood, the amount of virus in the lungs, spleen and lung morphology were studied. All the preparations used were found to increase the number of RFC in the spleen. Most effective were levamisole before infection, sodium succinate after infection, combination thereof, complex I after infection.
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PMID:[Effect of a number of preparations on the function of the immune system in experimental influenza in mice]. 651 25

A new peroxide compound (ML-X) was isolated from an autoxidation product of methyl linoleate and was determined as methyl 9-hydroperoxy-12, 13-epoxy-10-octadecenoate. This compound inhibited state 3 respiration of rat heart- and liver mitochondria when glutamate and malate were used as substrates, but not when the substrate was succinate. State 4 respiration of mitochondria was not affected when glutamate-malate was used as the substrate, but it was stimulated when the substrate was succinate. ML-X inhibited oxidative phosphorylation of the mitochondria and abolished the membrane potential formed by respiration or by added ATP. NADH oxidase activity of submitochondrial particles was inhibited by ML-X but succinate oxidase activity was not inhibited. NADH-acceptor reductase activities of submitochondrial particles were inhibited by ML-X to the same extents as by rotenone. These findings show that ML-X has dual effects on mitochondrial respiration as (1) an inhibitor of NADH dehydrogenase complex and (2) an uncoupler. Neither methyl linoleate monohydroperoxide nor methyl epoxy stearate has such effects. ML-X is a new type of inhibitor-uncoupler of mitochondrial respiration in which hydroperoxy- and epoxy groups co-operate.
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PMID:Methyl hydroperoxy-epoxy-octadecenoate as an autoxidation product of methyl linoleate: a new inhibitor-uncoupler of mitochondrial respiration. 717 40

Metabolic control analysis was applied to describe the control of mitochondrial oxidative phosphorylation in calcium (approximately 2 microM free calcium) activated saponin-skinned rat musculus soleus fibers oxidizing glutamate and malate. Under these circumstances approximately 80% of mitochondrial active-state respiration was reached due to the activation of ATP turnover by actomyosin ATPase. The flux control coefficients of H(+)-ATPase, adenine-nucleotide translocase, phosphate transporter, NADH:ubiquinone oxidoreductase and cytochrome-c oxidase were determined to be equal to 0.16 +/- 0.08 (n = 6), 0.34 +/- 0.12 (n = 5), 0.08 +/- 0.03 (n = 5), 0.01 +/- 0.006 (n = 4) and 0.09 +/- 0.03 (n = 3) using inhibitor titrations with the specific inhibitors oligomycin, carboxyatractyloside, mersalyl, rotenone and cyanide, respectively, and applying non-linear regression of the entire titration curve. The flux control coefficient of actomyosin ATPase was determined with vanadate to be equal to 0.50 +/- 0.09 (n = 6), measuring independently the vanadate-caused inhibition of fiber respiration and ATP-splitting activity. In contrast to results with isolated rat skeletal muscle mitochondria reconstituted with soluble F1-ATPase the decrease in phosphate concentration from 10 mM to 1 mM only slightly affected the distribution of flux control coefficients. This difference is caused by different kinetic properties of soluble F1-ATPase and actomyosin ATPase. Therefore, phosphate seems to be in skeletal muscle in vivo only a modest modulator of control of oxidative phosphorylation.
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PMID:Distribution of flux control among the enzymes of mitochondrial oxidative phosphorylation in calcium-activated saponin-skinned rat musculus soleus fibers. 760 28

Trimetazidine (TMZ) is an anti-ischemic compound whose precise mode of action is unknown, although several studies have suggested a metabolic effect, and there have been reports of protection of mitochondria against oxidative stress damage. Using a Langendorff rat heart model, we examined the effects of TMZ on the mitochondrial damage following 30 minutes of ischemia and 5 minutes of reperfusion. Mitochondrial respiration with succinate, glutamate-malate and ascorbate-N,N,N',N'-tetramethylphenylenediamine (TMPD) as substrates was significantly decreased following ischemia-reperfusion. Preperfusion with 10(-5) M TMZ had no effect on these rates in normoxic or ischemic hearts. However, 10(-3) M TMZ significantly decreased the glutamate-malate rate in mitochondria from normoxic hearts, and this rate was not further decreased following ischemia-reperfusion, and 10(-3) M TMZ also partially protected ascorbate-TMPD activity. The effect on glutamate-malate was probably due to an inhibition of complex I by TMZ, which specifically inhibited reduced nicotinamide-adenine-dinucleotide-cytochrome c reductase and complex I in lysed mitochondria. We also studied the effects of TMZ on the activity of pyruvate dehydrogenase (PDH) in normoxic and ischemic hearts perfused with 0.5 mM palmitate, which caused the enzyme to be almost completely inactivated. After short periods of ischemia (10-20 minutes) the PDH inactivation by palmitate was progressively lost. Preperfusion with 10(-5) M TMZ had a tendency to decrease lactate dehydrogenase release, accompanied by a maintenance of the inhibition of PDH by palmitate. This may allow the heart to oxidize fatty acids preferentially during reperfusion, hence removing possible toxic acyl esters.
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PMID:Trimetazidine effects on the damage to mitochondrial functions caused by ischemia and reperfusion. 764 24

Numerous observations strongly support the hypothesis that dopaminergic neurons could be particularly vulnerable to an impairment of their energetic metabolism. In order to demonstrate the existence of such a selective vulnerability, the toxic effects of rotenone, an inhibitor of complex I of the respiratory chain, and of glutamate, which is very likely involved in the neurotoxicity induced by an energetic stress, were analyzed on cultured mouse mesencephalic neurons. Toxicity toward dopaminergic and GABAergic neurons was compared by measuring the residual uptakes of dopamine and GABA. Exposure to 5 nM rotenone for 6 hr or to a low concentration of glutamate (100 microM) for 1 hr did not lead to a high selective toxic effect on dopaminergic neurons. In contrast, dopaminergic neurons were three times less resistant to the sequential exposure to rotenone and glutamate than GABAergic neurons. A particular resistance of mesencephalic GABAergic neurons to the synergistic toxic effects of rotenone and glutamate was ruled out since two other neuronal types, the striatal cholinergic and GABAergic neurons, displayed the same weak vulnerability as the mesencephalic GABAergic neurons. This selective toxic effect of glutamate on rotenone-pretreated dopaminergic neurons was blocked by either AMPA or NMDA receptor antagonists and mimicked by combined treatment with AMPA and NMDA, or by NMDA alone when the medium was deprived of Mg2+ ions. Moreover, this NMDA-selective neurotoxicity was critically dependent on the presence of a physiological extracellular sodium concentration, since the use of choline chloride instead of sodium chloride had a protective effect on dopaminergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A selective toxicity toward cultured mesencephalic dopaminergic neurons is induced by the synergistic effects of energetic metabolism impairment and NMDA receptor activation. 766 76

Electron transport and production of O2-/H2O2 by the NADH dehydrogenase flavin-semiquinone (FMNH.) and ubisemiquinone (UQH.) were studied in a model of in vivo ischemia-reperfusion in rat kidney. H2O2 production rates were assessed in isolated mitochondria using either succinate, with and without antimycin, or malate-glutamate, with and without rotenone. Respiratory activities of isolated mitochondria and activity of NADH- and succinate-cytochrome c reductase and of NADH- and succinate-dehydrogenase in submitochondrial particles were measured to evaluate the electron flux throughout respiratory carriers. The mitochondrial H2O2 production rate was approximately 1.5- and 4-times increased in ischemic and ischemic-reperfused kidneys, respectively. Ischemia caused a marked decrease in the electron transport throughout the NADH-UQ segment with no significant changes either in the NADH dehydrogenase activity or in the electron flux trough the succinate-cytochrome oxidase segment. Reperfusion did not further affect the NADH-ubiquinone segment but markedly inhibited the succinate-supported oxygen consumption, succinate-cytochrome c reductase and succinate dehydrogenase activity. Our results show a redistribution of the electron flux with an increased rate of superoxide anion/hydrogen peroxide production at NADH dehydrogenase in mitochondria subjected to ischemia only. After 10 min reperfusion an impairment of the electron flow at succinate-cytochrome c segment is established and hydrogen peroxide production by UQH. increases up to maximal values becoming the major source of superoxide anion/hydrogen peroxide.
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PMID:Mitochondrial sites of hydrogen peroxide production in reperfused rat kidney cortex. 772 10

Changes in the concentrations of intracellular free calcium ([Ca2+]i) and adenine nucleotides were determined in response to metabolic inhibitors in the motoneuron cell line NSC-19. The NADH dehydrogenase inhibitor amobarbital (Amytal) and the mitochondrial uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) were used to alter energy metabolism. Exposure of cells to 5 mM Amytal did not significantly change ATP concentrations but produced transient elevations of [Ca2+]i of approximately 80 nM, which were reduced by 32% when cells were studied in Ca(2+)-free solutions. CCCP (10 microM) caused a transient reduction in ATP concentration of 33%. CCCP also produced sustained elevations of [Ca2+]i of about 280 nM, which were reduced by 47% when in Ca(2+)-free solutions. In spite of the sustained elevation of [Ca2+]i induced by CCCP, NSC-19 showed no reduction in cell viability after 48 h compared with controls. Ruthenium red, a blocker of Ca2+ uptake by mitochondria, had little effect on the CCCP-induced [Ca2+]i increment. KCl or glutamate did not produce significant changes in [Ca2+]i, indicating that these cells do not possess significant numbers of voltage-dependent Ca2+ channels or excitatory amino acid receptor-gated channels. [Ca2+]i values in these cells were modified by changes in extracellular Ca2+ concentrations. In Ca(2+)-containing solutions, inhibition of Na+/Ca2+ exchange by amiloride and bepridil led to increased [Ca2+]i, as did blockade of Ca2+ ATPase by vanadate, suggesting that membrane transporters are important in Ca2+ efflux in NSC-19. The present studies indicate that exposure of NSC-19 cells to Amytal and CCCP produces Ca2+ increments by release from internal stores, as well as by transmembrane influx. These results demonstrate that small increments in [Ca2+]i can be produced by metabolic inhibitors or other compounds and that such changes are not associated with immediate cell death. Changes in [Ca2+]i could potentially result in abnormal cell function secondary to altered action of Ca(2+)-dependent enzymes.
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PMID:Intracellular calcium concentrations during metabolic inhibition in the motoneuron cell line NSC-19. 782 81

Physiological increases in matrix calcium are known to stimulate three mitochondrial dehydrogenases. In mitochondria isolated from rat heart, calcium stimulates rates of State 3 respiration during oxidation of succinate and of several NAD-linked substrates. In this study, we investigated the effects of calcium on NADH dehydrogenase and succinate dehydrogenase activities since the mechanism of these effects is unresolved. The respiratory activities of intact mitochondria and submitochondrial particles (SMP) were compared during incubation in media containing either ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) or a Ca2+/EGTA buffer (approximately 1 microM free Ca2+). In intact mitochondria oxidizing 20 mM glutamate plus 2 mM malate, the membrane potential (delta psi) and matrix NAD(P)H were maintained at higher levels, and the maximal rate of ADP-stimulated respiration (State 3) was increased twofold by the presence of calcium. With succinate as substrate, calcium stimulated State 3 respiration but it did not influence the pyridine nucleotides redox state or membrane potential. Stimulation of succinate-supported respiration by addition of 6-10 microM ADP in the presence of hexokinase caused a sudden decrease in NAD(P)H and collapse of delta psi. This effect was not caused by inhibition of succinate dehydrogenase or by opening of the nonspecific pore. Calcium did not influence the oxidation of succinate by SMP containing either activated or nonactivated succinate dehydrogenase. In addition, calcium did not alter the kinetics of succinate dehydrogenase activation. Calcium and magnesium, in the concentration range of 0.02 to 5 mM, did not influence the NADH dehydrogenase activity of SMP. Energization of SMP by oligomycin addition, however, dramatically influenced the kinetic properties of NADH dehydrogenase. It is proposed that in heart mitochondria, calcium does not affect directly the components of electron transport but it may influence the activity of NADH dehydrogenase indirectly by increasing delta psi.
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PMID:Influence of calcium on NADH and succinate oxidation by rat heart submitochondrial particles. 786 38

The toxicity of hydrophilic (cholate) and lipophilic (deoxycholate, chenodeoxycholate, and lithocholate) bile acids on the function of the electron transport chain was investigated in intact and disrupted rat liver mitochondria. In intact mitochondria, lipophilic bile acids used at a concentration of 100 mumol/L (0.1 mumol/mg protein) inhibited state 3 and state 3u (dinitrophenol-uncoupled) oxidation rates for L-glutamate, succinate, duroquinol or ascorbate/N,N,N',N'-tetramethyl-p-phenylenediamine as substrates. In contrast, state 4 oxidation rates and ADP/oxygen ratios were not significantly affected. At a bile acid concentration of 10 mumol/L (0.01 mumol/mg protein), the state 3 oxidation rate for L-glutamate was decreased in the presence of deoxycholate, chenodeoxycholate or lithocholate, whereas only lithocholate inhibited state 3 oxidation for succinate or duroquinol. In broken mitochondria, inhibition of oxidative metabolism was found for NADH or duroquinol as substrate in the presence of 100 mumol/L lithocholate (0.2 mumol/mg protein) and for duroquinol in the presence of 100 mumol/L chenodeoxycholate. Direct assessment of the activities of the enzyme complexes of the electron transport chain revealed decreased activities of complex I and complex III in the presence of 100 mumol/L deoxycholate or chenodeoxycholate or 10 mumol/L lithocholate. Inhibition of complex IV required higher bile acid concentrations (300 mumol/L for chenodeoxycholate or 30 mumol/L for lithocholate), and complex II was not affected. Both chenodeoxycholate and lithocholate were incorporated into mitochondrial membranes. The phospholipid content of mitochondrial membranes decreased in incubations containing 100 mumol/L (0.1 mumol/mg protein) chenodeoxycholate but was not affected in the presence of 100 mumol/L lithocholate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Toxicity of bile acids on the electron transport chain of isolated rat liver mitochondria. 790 81


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