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Query: UMLS:C0392674 (exhaustion)
 13,658 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ubiquinone-9, an ubiquinone with a side-chain containing 9 prenyl residues, was purified from Hyphomicrobium spec. strain ZV 580, and identified by thin-layer chromatography, UV spectroscopy, and mass spectrometry. The participation of the quinone in the reactions of the respiratory chain was established by observing its increasing reduction in a membrane fraction upon the addition of NADH, the exhaustion of oxygen, and in the presence of NADH plus cyanide. The degrees of reduction in these states matched those of the cytochromes b and c.
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PMID:Respiratory ubiquinone-9 from Hyphomicrobium spec. Strain ZV 580. 626 32

Tetrahymena microsomes contain cytochrome b5 and an NADH-dependent cytochrome b5 reductase, but these proteins are present at only one-tenth the levels observed in rat liver microsomes. We show that both proteins can be partially purified by techniques developed for the rat liver proteins. We can show that cyanide inhibits the rate of exhaustion of NADH, and therefore reoxidation of cytochrome b5 by microsomes, and that stearoyl CoA enhances the rate of reoxidation of the cytochrome. Also, we find that a fragment of rat liver NADH-cytochrome b5 reductase can restore NADH-dependent cytochrome b5 reduction to Tetrahymena microsomes which have been treated with N-ethylmaleimide to eliminate endogenous reductase activity. These results indicate that there is considerable resemblance between the rat and Tetrahymena systems, and that desaturation of stearoyl and oleoyl groups may occur in Tetrahymena via pathways similar to those known in liver.
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PMID:A cytochrome b5 electron transport chain in Tetrahymena. 683 Aug 27

It has been shown that in bovine heart submitochondrial particles, antimycin and 2-heptyl-4-hydroxyquinoline N-oxide (HQNO) inhibit the oxidation of NADH, succinate, and reduced ubiquinone incompletely, the uninhibited rate being about 20-40 nmol of substrate oxidized min-1 (mg of protein)-1. By contrast, rotenone, cyanide, BAL (2,3-dimercaptopropanol), and 5-n-undecyl-6-hydroxy-4,7-dioxobenzothiazole [Trumpower, B. L., & Haggerty, J. G. (1980) J. Bioenerg. Biomembr. 12, 151-164] caused essentially complete inhibition when added alone or after maximal inhibition by antimycin or HQNO. Having thus ascertained that the electron leak through the antimycin block appeared to follow the normal path through complex III (ubiquinol: cytochrome c oxidoreductase) and cytochrome oxidase, the reduction of the b cytochromes by substrates and their oxidation through the leak in the antimycin block by molecular oxygen were studied. It was shown that at normal electron flux from NADH and succinate, both cytochromes b562 and b566 were reduced in antimycin-treated submitochondrial particles. Their oxidation after substrate exhaustion was biphasic, however. At 565 minus 575 nm, 56% of the total reduced cytochrome b was oxidized through the leak in the antimycin block at a more rapid rate, while the remaining 44% was oxidized about 10 times slower. When electron flux from substrates to complex III was slowed down by the use of inhibitors or substrates at less than or equal to 0.1 Km concentration, then only reduced b562 accumulated in antimycin-treated particles. The oxidation of b562 after substrate exhaustion or inhibition of substrate oxidation by an appropriate inhibitor occurred at a rate comparable to that of the slower reoxidation phase described above. These results indicated, therefore, that cytochromes b566 and b562 are oxidized through the leak in the antimycin block at two different rates, the reoxidation rate of b566 being about 10 times faster than that of b562. The implications of these findings on the kinetic relationship of these two cytochromes in the respiratory chain have been discussed.
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PMID:Kinetics of cytochrome b oxidation in antimycin-treated submitochondrial particles. 715 May 80

Changes in the activity of the cell respiration of the yeast Candida lipolytica and its ATP, ADP, NADH, NAD+ pools during the development of the cyanide-resistant respiration were studied. A change-over of the yeast culture to the stationary growth phase conditioned by glucose exhaustion or aerobic incubation of the resting cells in the exponential growth phase without the exogenous carbon source were shown to be accompanied by: 1) decrease of the rate of oxygen consumption; 2) appearance of the cyanide-resistant respiration; 3) appearance of the benzhydroxamic acid-sensitive respiration; 4) appearance of stimulating dinitrophenol action on the rate of oxygen consumption; 5) increase in the ATP content and decrease of the ADP content in the cells. It was concluded that the appearance of the cyanide-resistant respiration is induced by the decrease of the activity of the respiratory chain due to the increase of the ATP concentration and the decrease of the ADP concentration in yeast cells. The functioning of the cyanide-resistant pathway of the electron transfer is one of the ways of NAD+ pool regulation in yeast cells.
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PMID:[Cause of the appearance of cyanide-resistant respiration in the yeast Candida lipolytica]. 723 95

The electron transport chain (ETC) of Pseudomonas thermophila K-2 was examined by the amperometric determination of O2 uptake by the preparations of membranes isolated by ultracentrifugation at 14,000 g. Amytal and cyanide were found to inhibit endogenous respiration of membranes from freshly grown cells. The membrane preparations, after exhaustion of endogenous substrates in them, oxidized NADH and succinate at rates of 4.00 and 0.83 mumole/min per 1 mg of membrane protein, respectively. The oxidation of NADH was inhibited by rotenone and cyanide, while the oxidation of succinate, only by cyanide. Maxima corresponding to NADH and iron-containing proteins were found in the fluorescence spectra of membrane preparations from Ps. thermophila K-2. Endogenous NADH was not susceptible either to incubation of the preparations in the air, or to hydrogen being bubbled through. These results and the data reported in literature make it possible to conclude that the membrane preparations from Ps. thermophila K-2 contain all the ETC components similar to the mitochondrial ones.
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PMID:[Functional characteristics of the membrane preparations from the cells of the thermophilic hydrogen bacterium. Pseudomonas thermophila]. 740 27

Oxygen release accompanying oxidation of vanadyl by diperoxovanadate was suppressed on addition of NADH. The added NADH was rapidly oxidized, oxygen in the medium was consumed, and the reaction terminated on exhaustion of either NADH or vanadyl. The consumption of oxygen and disappearance of NADH needed small concentrations of diperoxovanadate to initiate and increased with increase in the concentration of vanadyl and NADH or decrease of pH. The products of the reaction were found to be NAD+ from NADH and vanadate oligomers from vanadyl and oxygen. The reaction was insensitive to catalase and was not dependent on H2O2. The reaction was inhibited by superoxide dismutase, cytochrome c, EDTA, Mn2+, histidine, and DMPO, but not by hydroxyl radical scavengers such as ethanol and benzoate. The ESR spectrum of the reaction mixture showed the presence of the 1:2:2:1 quartet signal typical of a DMPO-OH adduct, but this was not modified by ethanol. This oxygen radical species, possibly of .OV type derived from diperoxovanadate, is proposed to have a role in the reactions of oxygen release and NADH oxidation.
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PMID:Requirement of a diperoxovanadate-derived intermediate for the interdependent oxidation of vanadyl and NADH. 784 Jun 32

Addition of NADH decreased the oxygen release that accompanied oxidation of vanadyl by H2O2. The added NADH was oxidized rapidly and oxygen was consumed with a stoichiometry of 1:1 for NADH/O2. Small concentrations of H2O2 were sufficient to trigger this oxygen-consuming NADH oxidation which terminated on exhaustion of either NADH or vanadyl. The oxidation of NADH increased proportionately with concentration of NADH and vanadyl. The oxidation products of vanadyl were found to be a mixture of vanadate oligomers and peroxovanadates. The reaction was sensitive to catalase, SOD, histidine and EDTA. Using ESR spectroscopy with DMPO as the spin trap, an adduct corresponding to DMPO-OH was detected in these phosphate-buffered reaction mixtures. Participation of hydroxyl radicals in NADH oxidation, however, seems doubtful because even high concentrations of ethanol, methanol, mannitol, formate and benzoate, known to scavenge these radicals, did not block the reaction. The results indicate that peroxovanadate intermediates formed during vanadyl oxidation by H2O2 play a key role in the oxidation of NADH.
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PMID:NADH oxidation is stimulated by an intermediate formed during vanadyl-H2O2 interaction. 794 44

The soluble flavohaemoglobin (Hmp) of Escherichia coli contains haem B and FAD in a single 44 kDa polypeptide, and shows NADH oxidase activity. The oxidized protein reacted rapidly with NADH in the presence of O2 to form an oxygenated species while the flavin remained largely oxidized. Spectral and kinetic analyses revealed rapid biphasic reduction and oxygenation of high-spin haem with apparent relaxation times of 6 and 64 ms at pH 8 and 25 degrees c, suggestive of a significant physiological role for the protein. This was followed by a monophasic reduction of the flavin with a relaxation time of 92 ms. On exhaustion of oxygen, the oxygenated haem was converted into the deoxy form biphasically with relaxation times of 43 and 170 s, followed by extensive reduction of the flavin with corresponding relaxation times of 70 and 256 s. Based on these observations, we propose that Hmp could act as an oxygen sensor in E. coli by combining with intracellular oxygen, thus limiting flavin reduction in the aerobic steady state. Lowering of the oxygen concentration causes dissociation of the oxy species and sustained flavin reduction. Because Hmp can reduce Fe(III), such a mechanism might control, for example, flavin-mediated Fe(III) reduction required for activation of the anaerobic gene regulator, Fnr.
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PMID:Reactions of the Escherichia coli flavohaemoglobin (Hmp) with oxygen and reduced nicotinamide adenine dinucleotide: evidence for oxygen switching of flavin oxidoreduction and a mechanism for oxygen sensing. 802 41

The soluble flavohaemoglobin (Hmp) of Escherichia coli, product of the hmp gene, contains haem B and FAD in a single polypeptide of molecular mass 44 kDa. The function of this protein (and of the similar proteins identified in several bacteria and yeast) is unknown, but the observation that the binding of oxygen to haem modulates the reduction level of FAD has suggested that Hmp could act as an oxygen sensor. Here, stopped-flow, rapid-scan spectroscopy has shown that the oxidized protein reacts rapidly with NADH to form an oxygenated species, even when efforts are made to reduce oxygen concentrations to sub-micromolar levels, suggesting a high affinity for this ligand. As is the case at high oxygen concentrations (130 microM), oxygenated species formation was kinetically and spectrally heterogeneous. Between 12 ms and 1 s after mixing, following transient formation of the deoxy form and its reaction with dioxygen, a steady-state level of the oxygenated species was attained. During the oxygenated steady state, the flavin remained largely oxidized, as observed previously at 130 microM oxygen. Hmp is an NADH oxidase; on exhaustion of oxygen by reduction (in < 10 s under these conditions), the oxygenated species disappeared to generate the deoxy Fe(II) haem, whereupon the flavin was reduced. The affinity for oxygen during NADH oxidation was measured by continuous dual-wavelength monitoring of the deoxygenation of oxymyoglobin. The Km for oxygen was 2.6 microM, much higher than the Km values determined, using the same method, for the membrane-bound terminal oxidases cytochromes bo' and bd. These results show that the oxidase activity of Hmp, but not necessarily oxygen binding, would be minimal at oxygen concentrations that limit terminal oxidase function.
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PMID:Reactions of the Escherichia coli flavohaemoglobin (Hmp) with NADH and near-micromolar oxygen: oxygen affinity of NADH oxidase activity. 870 56

The study was designed to investigate the role of hyperthermia in the tolerance of exercise in rats and the possible mechanism was examined. The hyperthermic pretreatment was performed using an electric pad on the anesthesized rats 24 hours before exercise. Rats were exercised passively in a motor-controlled round treadmill in high temperature environment (36-37 degrees C) until exhaustion. The capacity of tolerance was calculated. Lymphocytes and gastrocnemius muscle were collected from both groups. The changes in muscular morphology, mitochondria oxidative enzyme activity and induction of Hsp72 were investigated. The results revealed that experimental rats were more tolerant to exercise at high temperature than the control group; the duration time were 89 +/- 17.8 min and 63.1 +/- 7.3 min, respectively. Hsp72 was induced markedly in the experimental group, both in muscle and lymphocytes, indicating a heat shock response. There was no significant change in morphology of the mitochondria, 24 hours after hyperthermic treatment, as shown by histopathological and electromicroscopic investigation. However, the activity of mitochondrial enzymes increased significantly in experimental group before exercise: 84.6 +/- 6.3 and 345 +/- 15.4 (nmole cytochrome c/min/mg total protein) respectively of NADH-cytochome c reductase and succinate-cytochome c reductase activity in experimental group compared to 58.9 +/- 4.7 and 269.0 +/- 24.0 in control group (p < 0.05, by student t-test). It is concluded that hyperthermic treatment enhances muscular mitochondrial oxidative enzyme activity in rats, and results in increasing tolerance to exercise at high temperature. The heat shock response, most probably the inducible Hsp72, is a crucial factor in this effect.
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PMID:Previous hyperthermic treatment increases mitochondria oxidative enzyme activity and exercise capacity in rats. 1060 4


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