Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ascorbic acid (AsA), after being oxidized in 0.1 M phosphate (pH 7.0) buffer under the catalytic influence of adventitious iron, reacted with glutamine (Gln) derivatives with the formation of stable fluorophores showing lipofuscin-like blue (350/430 nm) fluorescence. The fluorescence was reversibly quenched by acidity and enhanced by alkaline conditions, and the fluorescence intensity was directly proportional to the Gln and AsA concentrations. Addition of H2O2 considerably increased the velocity of the fluorescence formation. Incubation of AsA/Gln in 0.1 M phosphate buffer at pH 5.0 gave a slower fluorophore formation as compared with incubation at pH 7.0. The iron chelators DTPA and desferrioxamine inhibited the fluorophore development by preventing the iron catalyzed AsA oxidation. This was in contrast to the effects of the chelators ADP and EDTA which did not show such preventive activity. The fluorophores produced by the AsA/Gln reaction are thought to be Schiff bases formed secondary to Maillard reactions involving oxidized AsA. Considering that ascorbic and dehydroascorbic acid are active and common reductones, the oxidation-enhanced carbonyl-protein cross-linking is suggested to be an important chemical reaction which may take place during ageing and be involved in lipofuscinogenesis.
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PMID:Lipofuscin-like fluorophores can result from reactions between oxidized ascorbic acid and glutamine. Carbonyl-protein cross-linking may represent a common reaction in oxygen radical and glycosylation-related ageing processes. 156 Jun 82

Several strains of Escherichia coli were markedly sensitised to killing at pH 2.5 or 3.5 when the ColV,I-K94 virulence plasmid was introduced into them. For strain 1829, the effect on acid sensitivity was due to the presence of plasmid in the previously resistant strain rather than to its introduction into an acid-sensitive variant already in the population. Acid sensitivity was also conferred by the ColV-K30 and ColB-K98 plasmids and the resistance plasmid R124-F2; other plasmids tested had no marked effect. Studies of ColV+ strains carrying mutant plasmids indicated that it was the presence of ColV-encoded transfer components that made ColV,I-K94+ strains acid-sensitive. Organisms in the exponential phase of growth were more sensitive to acid than were those from stationary phase cultures and this difference was more marked for ColV,I-K94+ strains than for Col- ones. Moreover, ColV+ strains exposed to conditions of low pH for short periods subsequently grew less well than the Col- parent and appeared to be sensitised by the damage to the effects of H2O2. These results indicate that some ColV+ strains may be more sensitive to gastric acid and to phagocytic acidity than are Col- strains. ColV,I-K94+ strains grew as well as Col- ones in broth or urine at pH 4.5-6.0 which suggests that the presence of the plasmid would not be detrimental to bacterial growth in the urinary tract. The presence of transfer components in the outer membrane of ColV,I-K94+ bacteria may destabilize the lipopolysaccharide layer allowing increased penetration of hydrogen ions.
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PMID:Virulence plasmid-associated sensitivity to acid in Escherichia coli and its possible significance in human infections. 353 74

Bacterial vaginosis (BV) is a common cause of abnormal malodorous vaginal discharge and can be frustrating to manage in its recurrent form. Metronidazole is the standard treatment, but is unacceptable to many women when given repeatedly. Results of treating recurrent BV using a single vaginal washout with 3% hydrogen peroxide are analysed. A total of 30 symptomatic women with clinically confirmed recurrent BV in the absence of other genital infections were recruited after informed consent. Hydrogen peroxide (3%) was instilled into the vagina, left for 3 minutes and drained. Reassessment was at 3 weeks after treatment. A total of 23 women completed the study. Symptoms cleared completely in 78% (18/23), improved in 13% (3/23) and remained unchanged in 9% (2/23). All the 3 women with improved symptoms had a mild vaginal discharge, but only one of them was still able to perceive the malodour. The amine test was negative in all 23 women including the 2 (9%) who felt no change in their symptoms following treatment. Mixed anaerobes isolated in all women before treatment were not re-isolated, and microscopy did not show 'clue cells' in the vaginal discharge following treatment. Vaginal acidity was restored to normal in all but one (96%). No side-effects were observed in the treated women. Hydrogen peroxide (3%) used as a single vaginal wash was as effective as any other agent in current use in clearing the vaginal malodour of bacterial vaginosis at 3 weeks after treatment.
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PMID:Recurrent bacterial vaginosis--an old approach to a new problem. 908 37

The hydrogen peroxide (H2O2) stress response in Enterococcus faecalis ATCC19433 was investigated. A 2.4 mmol l-1 H2O2 pretreatment conferred protection against a lethal concentration (45 mmol l-1) of this agent. The relatively high concentrations of H2O2 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 H2O2 cross-protection. This paper describes the involvement of protein synthesis in the active response to lethal dose of H2O2, in addition to the impressive enhancement of synthesis of five H2O2 stress proteins. Combined results suggest that these proteins might play an important role in the H2O2 tolerance response.
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PMID:The oxidative stress response in Enterococcus faecalis: relationship between H2O2 tolerance and H2O2 stress proteins. 963 90

The aim of this investigation was to compare an improved fluorometric method with an UV absorbance assay for their ability to monitor low density lipoprotein (LDL) modification by myeloperoxidase (MPO) and to evaluate determining factors influencing the modification of LDL. Using absorbance at 234 nm to study the kinetics of LDL aggregation, and a native fluorescence assay for protein oxidation, we found that all components of the MPO/H2O2/Cl- system may have rate determining effects on LDL modification. While the lipoprotein modification rate correlated positively with enzyme concentration, variation of the concentration of H2O2 had a biphasic effect on the maximal rate of LDL modification with both methods. Furthermore, a positive association was found between the maximal rate of LDL modification and the acidity of the medium, with a pathophysiologically relevant optimal rate at a slightly acidic pH of 5-6, but hardly any modification above pH 6.8. In summary, both methods provide simple and useful tools for the continuous monitoring of LDL modification by the MPO/H2O2/Cl- system, but the more sensitive fluorometric method is preferable, since it allows the application of experimental conditions which are much closer to the situation in vivo.
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PMID:An improved method for the sensitive monitoring of low density lipoprotein modification by myeloperoxidase. 1164 17

The oxidative cleavage of alkenes to carboxylic acids with 40% w/v aqueous hydrogen peroxide catalyzed by methyltrioctylammonium tetrakis(oxodiperoxotungsto)phosphate(3-) (Ia) is reported to occur in high yields and selectivities under two-phase conditions in the absence of organic solvents. On the basis of a study of the reaction, two main reaction pathways leading to acids have been recognized, the first one involving the perhydrolysis and the second one the hydrolysis of the epoxide initially formed. The "perhydrolytic" reaction pathway appears to play a primary role in the oxidation of medium- and long-chain alkenes to acids, while it intervenes to a rather limited extent in the oxidation of arylalkenes and C(5)-C(7) cycloalkenes. The occurrence of this pathway has been proved by the isolation of the intermediate beta-hydroperoxy alcohols and their transformation into acids with H(2)O(2) and Ia. The course of this transformation, involving an initial oxidation (to alpha-oxo hydroperoxide) or decomposition (to carbonyl compounds) of the beta-hydroperoxy alcohol intermediate, is described. The primary oxidation products, alpha-hydroperoxy ketones, have been isolated in the case of internal beta-hydroperoxy alcohols, whereas their presence has been evidenced with terminal beta-hydroperoxy alcohols bearing a secondary hydroxy group. Hydrogen peroxide concentration appears to exert a remarkable influence on medium acidity, and its effects on the reaction efficiency are shown.
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PMID:Efficient Oxidative Cleavage of Olefins to Carboxylic Acids with Hydrogen Peroxide Catalyzed by Methyltrioctylammonium Tetrakis(oxodiperoxotungsto)phosphate(3-) under Two-Phase Conditions. Synthetic Aspects and Investigation of the Reaction Course. 1167 60

A selective and sensitive method for the determination of the total amount of vanadium in nutritional and biological substrates is proposed. The method is based on the reaction of vanadium with 2-alpha-pyridylthioquinaldinamide (PTQA) in the presence of H2O2. The product of this reaction emits constant fluorescence, in a sulfuric acid environment, at 490 nm, with the exciting radiation set at 340 nm. Various parameters such as acidity, flow rate, solvents, and temperature were studied. The presence of a surface-active agent was also considered in order to increase sensitivity. At the optimal conditions, a calibration curve was constructed, revealing a linear range of 2-100 microg L(-1) and a detection limit as low as 0.5 microg L(-1) while the RSD ranged in the area of 0.1-1.8%, depending on vanadium concentration. The method was successfully applied to the analysis of a wide variety of food samples, which are known to contribute to the dietary required amount of vanadium and to relevant biological matrixes. Reversing the conditions of the above reaction, the effect of the peroxy group on the vanadium-PTQA system was examined. The formation of a vanadyl complex was revealed which was suitable for the determination of hydrogen peroxide and peroxy acids. Linear calibration curves in the range of 0.2-50 microM for H2O2 and 0.1-2 microM for a respective peroxy acid were obtained, yielding detection limits of 0.05 and 0.03 microM, respectively.
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PMID:Spectrofluorometric determination of vanadium based on the formation of a ternary complex between vanadium, peroxides, and 2-alpha-pyridylthioquinaldinamide. Application to the determination of hydrogen peroxide and peroxy acids. 1179 76

Anionic phospholipids are largely absent from the external leaflet of the plasma membrane of mammalian cells under normal conditions. Exposure of phosphatidylserine on the cell surface occurs during apoptosis, necrosis, cell injury, cell activation, and malignant transformation. In the present study, we determined whether anionic phospholipids become exposed on tumor vasculature. A monoclonal antibody, 9D2, which specifically recognizes anionic phospholipids, was injected into mice bearing a variety of orthotopic or ectopic tumors. Other mice received annexin V, a natural ligand that binds to anionic phospholipids. Both 9D2 and annexin V specifically localized to vascular endothelium in all of the tumors, and also to tumor cells in and around regions of necrosis. Between 15 and 40% of endothelial cells in tumor vessels were stained. No localization was detected on normal endothelium. Various factors and tumor-associated conditions known to be present in the tumor microenvironment were examined for their ability to cause exposure of anionic phospholipids in cultured endothelial cells, as judged by 9D2 and annexin V binding. Hypoxia/reoxygenation, acidity, thrombin, and inflammatory cytokines all induced exposure of anionic phospholipids. Hydrogen peroxide was also a strong inducer. Combined treatment with inflammatory cytokines and hypoxia/reoxygenation had greater than additive effects. Possibly, injury and activation of tumor endothelium by cytokines and reactive oxygen species induce exposure of anionic phospholipids, most likely phosphatidylserine. Anionic phospholipids on tumor vessels could potentially provide markers for tumor vessel targeting and imaging.
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PMID:Increased exposure of anionic phospholipids on the surface of tumor blood vessels. 1241 38

The sorption of a triazol derivative, 1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)penten-3-ol with a common name of S3307D, on fifteen soils and three H2O2-treated soils was investigated. The sorption isotherm for each untreated and treated soil was non-linear, and was best fitted to Freundlich sorption equation. Soils containing high amount of clay content or organic matter or both sorbed much higher amounts of the chemical than soils that had low contents of these soil constituents. H2O2-treated soils showed considerable sorptive affinity for S3307D. It was concluded that both organic matter and mineral fraction in natural soils contributed to the sorption of the basic compound. Sorption by the H2O2 treated soils increased as suspension pH decreased, but all suspension pHs exceeded the pKa of the compound by more than two units. This implies that organic base protonation can occur on surfaces of soil components, and surface acidity (exchangeable acidity) is important in sorption process of the organic base rather than suspension pH.
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PMID:Sorption of a triazol derivative by soils: importance of surface acidity. 1293 91

A study on the destruction of 1,3-dinitrobenzene (1,3-DNB) in aqueous solution was carried out under ultraviolet (UV) irradiation alone and UV irradiation in the presence of hydrogen peroxide (H2O2). The combination of UV and H2O2 is significantly effective in degrading 1,3-DNB in terms of initial reaction rate and the mineralization of organic carbons. The photodegradation process can be influenced in certain extent by increasing the content of H2O2 and the acidity of reaction matrices. It was found that a variety of phenolic intermediates and inorganic acid were formed via hydroxyl radicals attacking the parent compound. The UV/H2O2 oxidation of 1,3-DNB was characterized by pseudo-zero order reaction for the degradation of 1,3-DNB with a 20 times enhanced rate constant of 1.36 x 10(-7) Ms(-1) and the initial rate constant was dependent on the initial concentration of 1,3-DNB.
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PMID:Photochemical degradation of 1,3-dinitrobenzene in aqueous solution in the presence of hydrogen peroxide. 1498 32


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