[Correlation between cholesterol and various indicators of oxidation-reduction in atherosclerosis].
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Adult↗
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[Disorder of oxidation-reduction processes in various forms of coronary insufficiency and their dynamics as a function of the therapy applied].
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Adult↗
[Use of biochemical tests and oxidative-reductive enzymatic activity indices in the dynamic evaluation of the state of patients with severe forms of peritonitis].
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Acid-Base Equilibrium↗
[Cytochemical method of simultaneous determination of oxidation-reduction enzymes and acid phosphatase in blood lymphocytes].
The results of cytochemical tests for simultaneous measurements of dehydrogenases and acid phosphatase in blood leukocytes do not differ from the results of the original methods developed by R. P. Nartsissov (1969) and A. Goldberg and T. Bark (1962). Use of this method permits the physician to have simultaneous information about two aspects of metabolism in the cells and cuts down the time needed for measuring the activities of two enzymes in the leukocytes.
Acid Phosphatase↗
[Oxidation-reduction potentials of chlorophyll pigments in photosynthesizing organisms on different levels of evolutionary development].
According to polarographically measured EOred of bacteriochlorophyll "a", chlorobium chlorophyll "660", "b" and "a" chlorophylls (-0.67 V, -0.73 V, -0.79 V, -0.86 V-n.h.e.) and literature data about Eoox of these pigments (+/-0.62 V, + 0.62 V, + 0.78 V, +0.77 V correspondingly) it has been shown that chemical energy stored in the singular photochemical set is increased in the evolution of the photosynthetic apparatus. It has apparently resulted in the possibility of evolutionary approach to utilization of more inert and more accessible (water) electron donors and favoured further development of photosynthesizing organisms.
Bacteria↗
[Effect of therapy on indices of oxidation-reduction processes in pregnancy complicated by rheumatic heart disease].
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Carbon Dioxide↗
Cytochrome c oxidase catalysis of the reduction of nitric oxide to nitrous oxide.
Reduction of nitric oxide (NO) to nitrous oxide (N2O) is catalyzed by bovine heart cytochrome c oxidase (CcO) in anaerobic solutions at pH 7.2 and 20 degrees C. Cyanide inhibits and forms Fea3(3+)CN. The mononitrosyl (Fea3(2+)NO), but not the dinitrosyl (Fea3(2+)NO; CuB+NO), is a likely intermediate in N2O formation. One-electron reduction of NO at Fea3(2+) could yield N2O via HNO. However, a two-electron reduction of the NO ligand to give an intermediate that reacts with a second NO to give N2O and H2O appears more likely. Conversion of NO to N2O is favored by low levels of both NO and O2, higher NO levels can inhibit both cytochrome c oxidase and NO reductase activities. Raising the O2 level will favor catalysis of NO oxidation to NO2 by CcO. The reactions of NO and the specific CcO activity that occur in tissue will be critically dependent on NO, O2, and CcO levels.
Animals↗
Alcohol-induced oxidative stress and reduction in oxidation by ascorbate/L-cys/ L-met in the testis, ovary, kidney, and lung of rat.
Chronic exposure to high doses of alcohol results in many pathophysiologic changes in cellular function caused by the alcohol itself and the effects of its metabolism (ie, generation of acetaldehyde, nicotinamide adenine dinucleotide [NADH], free radicals, and oxidative stress). However, the role of each of these effects on the testis, ovary, kidney, and lung in chronic alcoholism must be investigated. It is hypothesized that cysteine-methionine and vitamin C might neutralize harmful compounds and potentiate the antioxidant capacity of the cell or tissue. In this study, rats were fed regular diets and were maintained in the following groups for 90 days: control group; alcoholic group (2.5 g of 50% ethanol/kg body wt administered intragastrically every other day); and alcoholic with antioxidant supplement group (2.5 g of 50% ethanol plus a solution containing 200 mg vitamin C, 100 mg cysteine, and 100 mg methionine/kg body wt administered intragastrically every other day). After treatment had been completed, rat blood, testis, ovary, kidney, and lung were taken for biochemical analysis. Mean alcohol level in the alcoholic group was raised (by 40%) compared with that in the control group, but it was lower (by 30%) in the antioxidant-supplemented group than in the alcoholic group. In accordance with the levels of alcohol, oxidized protein and lipid content in the testis, ovary, kidney, and lung were low in the control group, higher in the antioxidant-supplemented group, and highest in the alcoholic group. It is interesting to note that levels of glutathione in the testis and lung of the alcoholic group were lower than those in both the control and antioxidant-supplemented groups. In conclusion, chronic alcohol administration led to a significant increase in the level of protein oxidation in the ovary and kidney of rats. Simultaneous intake of ascorbate/L-cys/L-met, along with ethanol, partly attenuated the amount of lipid and protein oxidation that occurred in tissues with oxidative stress caused by alcohol consumption.
Animals↗
Anoxic function for the Escherichia coli flavohaemoglobin (Hmp): reversible binding of nitric oxide and reduction to nitrous oxide.
The flavohaemoglobin Hmp of Escherichia coli is inducible by nitric oxide (NO) and provides protection both aerobically and anaerobically from inhibition of growth by NO and agents that cause nitrosative stress. Here we report rapid kinetic studies of NO binding to Fe(III) Hmp with a second order rate constant of 7.5 x 10(5) M(-1) s(-1) to generate a nitrosyl adduct that was stable anoxically but decayed in the presence of air to reform the Fe(III) protein. NO displaced CO bound to dithionite-reduced Hmp but, remarkably, CO recombined after only 2 s at room temperature indicative of NO reduction and dissociation from the haem. Addition of NO to anoxic NADH-reduced Hmp also generated a nitrosyl species which persisted while NADH was oxidised. These results are consistent with direct demonstration by membrane-inlet mass spectrometry of NO consumption and nitrous oxide production during anoxic incubation of NADH-reduced Hmp. The results demonstrate a new mechanism by which Hmp may eliminate NO under anoxic growth conditions.
Anaerobiosis↗
Reduction of hexavalent chromium collected on PVC filters.
Chromium exists at various valences, including elemental, trivalent, and hexavalent chromium, and undergoes reduction-oxidation reactions in the environment. Since hexavalent chromium is known as a human carcinogen, it is most important to evaluate the oxidation-reduction characteristics of the hexavalent chromium species. Although hexavalent chromium can be reduced to trivalent state, the detailed information on this in workplace environments is limited. The purpose of this study was to investigate hexavalent chromium reduction in time in various conditions. A pilot chrome plating operation was prepared and operated in a laboratory for this study. There was evidence that the hexavalent chromium was reduced by time after mist generation. The percentage ratio (with 95% confidence intervals in parentheses) of hexavalent chromium to total chromium was almost 100% (99.1 approximately 102.3) immediately after mist generation, and was reduced to 87.4% (84.8 approximately 89.9) at 1 hour and 81.0% (78.3 approximately 83.5) at 2 hours, respectively. Another test indicated that hexavalent chromium collected on PVC filters was also reduced by time after sampling. Hexavalent chromium was reduced to 90.8% (88.2 approximately 93.3) at 2 hours after sampling. It also was found that hexavalent chromium was reduced during storage in air. It is recommended that air samples of hexavalent chromium be protected against reduction during storage.
Aerosols↗
Reductive and oxidative DNA damage by photoactive platinum(II) intercalators.
Several photoactive platinum alpha-diimine intercalators have been prepared to develop new probes of DNA oxidation and reduction chemistry. Five water-soluble bis(mes')Pt(II) complexes (mes' = N,N,N,3,5-pentamethylaniline) with various aromatic alpha-diimine ligands (dppz = dipyridophenazine, np = naphtha[2,3-f][1,omega]phenanthroline, CN-np = naphtho[2,3-f][1,10]phenanthroline-9-carbonitrile, CN(2)-np = naphtho[2,3-f][1,10]phenanthroline-9,14-dicarbonitrile, and bp = benzo-[f][1,10]phenanthroline) were synthesized. The complex [(np)Pt(mes')(2)]Cl(2) was also characterized by X-ray crystallography, and the crystal structure shows that the ortho-methyl groups of the mes' ligands conveniently block substitution at the vacant sites of platinum without overlapping with the intercalating alpha-diimine ligand. The Pt(II) complexes were found to have excited-state oxidation and reduction potentials of -0.6 to -1.0 and 1.0 to 1.5 V versus NHE, respectively, making them potent photoreductants as well as photooxidants. Many of the complexes are found to promote the photooxidation of N(2)-cyclopropyldeoxyguanosine (d(Cp)G). Photoexcited [(dppz)Pt(mes')(2)](2+) is found to be most efficient in this photooxidation, as well as in the photoreduction of N(4)-cyclopropylcytidine ((Cp)C); these modified nucleosides rapidly decompose in a ring-opening reaction upon oxidation or reduction. Photoexcited [(dppz)Pt(mes')(2)]Cl(2), upon intercalation into the DNA pi stack, is found, in addition, to promote reductive and oxidative damage within the DNA duplex, as is also probed using the kinetically fast electron and hole traps, (Cp)C and (Cp)G. These Pt complexes may therefore offer useful reactive tools to compare and contrast directly reductive and oxidative chemistry in double helical DNA.
Cations, Divalent↗
Selective modulation of NMDA responses by reduction and oxidation.
Electrophysiological responses to the glutamate analog N-methyl-D-aspartate (NMDA) measured in three different central neuronal preparations are subject to a novel modulatory mechanism: they are substantially potentiated after exposure to the disulfide reducing agent dithiothreitol, while oxidation with 5-5-dithiobis-2-nitrobenzoic acid decreases the magnitude of the response. Modification of the NMDA response by either oxidation or reduction does not appear to affect the pharmacological properties of the receptor-channel complex. Since we observe that the redox state of the native receptor-channel complex varies widely among neurons, an in vivo mechanism that can strongly regulate NMDA-activated functions by either reduction or oxidation may exist. In addition, these results suggest that it may be possible to design specific redox agents for characterizing the NMDA receptor-channel complex.
Animals↗
Increase in oxidized NO products and reduction in oxidized glutathione in cerebrospinal fluid from patients with sporadic form of amyotrophic lateral sclerosis.
To determine the role of free radical mechanisms in the pathogenesis of amyotrophic lateral sclerosis (ALS), cerebrospinal fluid concentrations of oxidized nitric oxide (NO) products (nitrite and nitrate) and reduced and oxidized forms of glutathione (GSH and GSSG, respectively) were compared between patients with the sporadic form of ALS (SALS) and controls. In the SALS patients, the nitrate levels were significantly higher (by 73%) in contrast to remarkably lower GSSG/GSH ratio, approximately 3-fold, compared to controls. These results suggest that NO production or oxidation is activated in SALS patients, leading to a decrease in superoxide radicals to oxidize GSH. The subsequent generation of a highly reactive anion, peroxynitrite, may play a causal role in the pathogenesis of SALS.
Aged↗
Microbial reduction and oxidation of mercury in freshwater lakes.
The evasion of elemental mercury represents a significant pathway for reducing the level of this potentially toxic material in aquatic ecosystems. The evasion rate is controlled by the concentration of dissolved gaseous mercury (DGM) across the air-water interface, water, and air temperature as well as wind speed. Here we investigate the role of microbial mercury oxidation and reduction in regulating DGM diel patterns in two freshwater lakes, Jack's Lake and Lake Ontario. Three replicate diurnal cycles of DGM in Brookes Bay, Jack's Lake peaked at 313 fM between 9:00 to 10:30 and decreased to 79.6 fM by 16:00. Microbial mercury reductase activity (converts Hg2+ to Hg0) increased with DGM concentrations and mercury oxidase activity (converts Hg0 to Hg2+) increased as DGM concentrations decreased in the mid-afternoon. This illustrates that mercury oxidase activity was linked to hydrogen peroxide (H2O2) diurnal patterns. Thirty minutes after spiking Lake Ontario water with H2O2, mercury oxidase activity increased by 250% and by 60 min, DGM decreased to 28% of its initial value. Two hours after the H2O2 spike, mercury oxidase activity had declined, but mercury reductase activity and DGM both increased. Four hours after the spike, mercury reductase and DGM levels had returned to original levels. Our results are consistent with the following sequence of events. In the morning, microbial activity produces DGM (in addition to any DGM formed through photoreduction of Hg2+). As photochemically produced H2O2 increases in concentration it induces the biologically mediated decrease in DGM concentrations throughout the afternoon. To predict concentration of DGM in surface waters and flux rates to the atmosphere, the contribution of photoreduction and photooxidation must be placed in context with reduction and oxidation rates due to microbial activity.
Environmental Monitoring↗
Only the glutathione dependent antioxidant enzymes are inhibited by haematotoxic hydroxylamines.
Hydroxylamine and some of its derivatives are known to cause oxidative effects both in vitro and in vivo. In the current study we investigated the effects of hydroxylamines on the enzymatic antioxidant defense system in human erythrocytes. The activity of catalase and superoxide dismutase was not significantly influenced by any of the hydroxylamines tested. However, the activity of glutathione peroxidase (GPX) and glutathione S-transferase (GST) was strongly inhibited by hydroxylamine and its O-derivatives (O-methyl and O-ethyl hydroxylamine). GPX was also inhibited by two N-derivatives of hydroxylamine (i.e. N-dimethyl and N,O-dimethyl hydroxylamine). This indicates that exposure to hydroxylamines not only changes the cellular oxidation-reduction status but also leads to inhibition of the glutathione dependent antioxidant enzymes. GST as well as GPX have cysteine residues at the active site of the enzymes. Such an accessible thiol group is generally susceptible to formation of protein-mixed disulphides or intramolecular disulphides. If these thiol groups are essential for activity this would be accompanied by an increase or decrease in the enzyme activity. In principle this is also true for glutathione reductase (GR), which in this study was only inhibited by N,O-dimethyl and N-methyl hydroxylamines. However, GR is capable to reduce these disulphides by taking up two electrons, either from its substrate NAPDH or from another reductant. Oxidation of these thiol groups in GR would thus not lead to impairment of GR activity. The fact that NODMH and NMH do decrease the GR activity can therefore only be explained by other modifications. The activity loss of GST and GPX on the other hand, is likely to involve oxidation of critical cysteine residues. The practical consequence of these findings is that the cellular prooxidant state that may arise in erythrocytes exposed to hydroxylamines can be further increased by activity loss of protective enzymes, which may decrease the average life span of the red blood cell.
Catalase↗
Reduction of nitric oxide in bacterial nitric oxide reductase--a theoretical model study.
The mechanism of the nitric oxide reduction in a bacterial nitric oxide reductase (NOR) has been investigated in two model systems of the heme-b(3)-Fe(B) active site using density functional theory (B3LYP). A model with an octahedral coordination of the non-heme Fe(B) consisting of three histidines, one glutamate and one water molecule gave an energetically feasible reaction mechanism. A tetrahedral coordination of the non-heme iron, corresponding to the one of Cu(B) in cytochrome oxidase, gave several very high barriers which makes this type of coordination unlikely. The first nitric oxide coordinates to heme b(3) and is partly reduced to a more nitroxyl anion character, which activates it toward an attack from the second NO. The product in this reaction step is a hyponitrite dianion coordinating in between the two irons. Cleaving an NO bond in this intermediate forms an Fe(B) (IV)O and nitrous oxide, and this is the rate determining step in the reaction mechanism. In the model with an octahedral coordination of Fe(B) the intrinsic barrier of this step is 16.3 kcal/mol, which is in good agreement with the experimental value of 15.9 kcal/mol. However, the total barrier is 21.3 kcal/mol, mainly due to the endergonic reduction of heme b(3) taken from experimental reduction potentials. After nitrous oxide has left the active site the ferrylic Fe(B) will form a mu-oxo bridge to heme b(3) in a reaction step exergonic by 45.3 kcal/mol. The formation of a quite stable mu-oxo bridge between heme b(3) and Fe(B) is in agreement with this intermediate being the experimentally observed resting state in oxidized NOR. The formation of a ferrylic non-heme Fe(B) in the proposed reaction mechanism could be one reason for having an iron as the non-heme metal ion in NOR instead of a Cu as in cytochrome oxidase.
Bacteria↗
Solid-state kinetics from time-resolved in situ XAFS investigations: reduction and oxidation of molybdenum oxides.
The reduction of MoO3 with hydrogen was studied by in situ X-ray absorption spectroscopy. The experiments performed focused on elucidating phase composition and evolution with time under isothermal reduction conditions. From temperature programmed experiments short-range structural details about the early stage of the reduction were obtained.
Journal Article↗
A new nos gene downstream from nosDFY is essential for dissimilatory reduction of nitrous oxide by Rhizobium (Sinorhizobium) meliloti.
Rhizobium (Sinorhizobium) meliloti strains capable of dissimilatory nitrous oxide reduction (Nos+) carry a nosRZDFY gene cluster on a 10.1 kb EcoRI fragment of the nod megaplasmid near the fixGHIS genes. These nos genes are arranged in three complementation groups and the 10.1 kb EcoRI fragment is sufficient to confer Nos activity to R. meliloti strains lacking such activity. An overlapping HindIII fragment containing the nosRZDFY genes but missing a 0-6 kb HindIII-EcoRI downstream segment was found incapable of imparting Nos activity to strains unable to reduce nitrous oxide, suggesting the presence of other nos gene(s) in this region. Tn5 introduced near the HindIII site resulted in mutants with a Nos- phenotype. Complete sequence analysis of nosY showed that it was well-conserved with respect to that of Pseudomonas stutzeri. Two previously unreported genes downstream of nosY in R. meliloti were also revealed. Contiguous with nosY was a sequence showing 63% identity with the ORFL protein of P. stutzeri. It appeared to be in the same operon as nosDFY and was predicted to encode a membrane lipoprotein similar to the putative NosL of P. stutzeri. Unlike the latter protein, however, amino acid sequences typical of metal-binding sites and cysteine residues indicative of the active site of protein disulphide isomerase were absent in the predicted NosL of R. mellioti. The Tn5 mutations resulting in a Nos- phenotype were localized within a 966 nucleotide gene 31 nucleotides downstream of nosDFYL with the same orientation. The new gene, nosX, was determined to be in a separate complementation group. It encoded a periplasmic protein with homology in the C-terminal domain with Rnff of Rhodobacter capsulatus and with a hypothetical Escherichia coli protein, YOJK. It was concluded that there are seven genes constituting the nos cluster in R. meliloti. They are organized in four complementation groups and in the same orientation, spanning a distance of about 9 kb on the nod megaplasmid.
Amino Acid Sequence↗