Showing papers on "Hydrogen peroxide published in 1982"

Serum triglycerides determined colorimetrically with an enzyme that produces hydrogen peroxide.

Abstract: In this direct colorimetric procedure, serum triglycerides are hydrolyzed by lipase, and the released glycerol is assayed in a reaction catalyzed by glycerol kinase and L-alpha-glycerol-phosphate oxidase in a system that generates hydrogen peroxide. The hydrogen peroxide is monitored in the presence of horseradish peroxidase with 3,5-dichloro-2-hydroxybenzenesulfonic acid/4-aminophenazone as the chromogenic system. The high absorbance of this chromogen system at 510 nm affords useful results with a sample/reagent volume ratio as low as 1:150, and a blank sample measurement is not needed. A single, stable working reagent is used; the reaction is complete in 15 min at room temperature. The standard curve is linear for triglyceride concentrations as great as 13.6 mmol/L. Average analytical recovery of triglycerides in human sera is 100.1%, and within-run and between-run precision studies showed CVs of less than or equal to 1.6 and less than or equal to 3.0%, respectively. The method is suitable for automation.

A comprehensive system of leaf analyses and its use for diagnosing crop nutrient status

Abstract: A comprehensive system for the determination of N,‐ P, K, Ca, Mg, Na, B, Cu, Fe, Zn, S, and F in plant tissue is presented. A wet ash procedure using sulfuric acid and hydrogen peroxide permits determination of N, P, K, Ca, Mg, Na, B, Cu, Fe, Zn in one digest. S and F are determined in solutions of separate dry ashings. The use of leaf analyses and its limitations are discussed.

Chlorination of taurine by human neutrophils. Evidence for hypochlorous acid generation.

Abstract: The model hydrogen peroxide-myeloperoxidase-chloride system is capable of generating the powerful oxidant hypochlorous acid, which can be quantitated by trapping the generated species with the beta-amino acid, taurine. The resultant stable product, taurine chloramine, can be quantitated by its ability to oxidize the sulfhydryl compound, 5-thio-2-nitro-benzoic acid to the disulfide, 5,5'-dithiobis(2-nitroben-zoic acid) or to oxidize iodide to iodine. Using this system, purified myeloperoxidase in the presence of chloride and taurine converted stoichiometric quantities of hydrogen peroxide to taurine chloramine. Chloramine generation was absolutely dependent on hydrogen peroxide, myeloperoxidase, and chloride and could be inhibited by catalase, myeloperoxidase inhibitors, or chloride-free conditions. In the presence of taurine, intact human neutrophils stimulated with either phorbol myristate acetate or opsonized zymosan particles generated a stable species capable of oxidizing 5-thio-2-nitrobenzoic acid or iodide. Resting cells did not form this species. The oxidant formed by the stimulated neutrophils was identified as taurine chloramine by both ultraviolet spectrophotometry and electrophoresis. Taurine chloramine formation by the neutrophil was dependent on the taurine concentration, time, and cell number. Neutrophil-dependent chloramine generation was inhibited by catalase, the myeloperoxidase inhibitors, azide, cyanide, or aminotriazole and by chloride-free conditions, but not by superoxide dismutase or hydroxyl radical scavengers. Thus, it appears that stimulated human neutrophils can utilize the hydrogen peroxide-myeloperoxidase-chloride system to generate taurine chloramine. Based on the demonstrated ability of the myeloperoxidase system to generate free hypochlorous acid we conclude that neutrophils chlorinate taurine by producing this powerful oxidant. The biologic reactivity and cytotoxic potential of hypochlorous acid and its chloramine derivatives suggest that these oxidants play an important role in the inflammatory response and host defense.

Spontaneous oxygen radical generation by sickle erythrocytes.

Abstract: Since the various membrane abnormalities of sickle erythrocytes might result from excessive accumulation of oxidant damage, we have measured the generation of superoxide, peroxide, and hydroxyl radical by normal and sickle erythrocytes using assays involving reduction of cytochrome c, aminotriazole inhibition of catalase, and methane evolution from dimethyl sulfoxide, respectively. Compared with normal erythrocytes, sickle erythrocytes spontaneously generate approximately twice as much superoxide, peroxide, and hydroxyl radical. One possible source of hydroxyl radical generation was identified as hemichrome, excessive amounts of which are bound to sickle erythrocyte membranes. Hemichrome did not generate hydroxyl radical when exposed to superoxide alone or peroxide alone. However, in the presence of both superoxide and peroxide, hemichrome greatly facilitated hydroxyl radical generation. Supporting this, normal erythrocyte membranes induced to acquire sickle hemichrome concomitantly acquired an enhanced ability to mediate hydroxyl radical generation. Finally, sickle erythrocyte membranes greatly enhanced superoxide/peroxide-driven hydroxyl radical generation as compared with normal erythrocyte membranes. These data suggest that an excessive accumulation of oxidant damage in sickle erythrocyte membranes might contribute to the accelerated membrane senescence of these cells. They further indicate that accumulation of oxidant damage could be a determinant of normal erythrocyte membrane senescence.

Superoxide-dependent formation of hydroxyl radicals and lipid peroxidation in the presence of iron salts. Detection of ‘catalytic’ iron and anti-oxidant activity in extracellular fluids

Abstract: Synovial fluid from rheumatoid patients and normal cerebrospinal fluid contains micromolar concentrations of non-protein-bound iron salts that can promote lipid peroxidation and also the superoxide-dependent formation of hydroxyl radicals from hydrogen peroxide. These iron catalysts of oxygen radical reactions cannot be detected by conventional assays unless interfering high-molecular-weight substances, probably proteins, are removed by ultrafiltration or inactivated by exposure to low pH values. The bleomycin assay for `catalytic' iron [Gutteridge, Rowley & Halliwell (1981) Biochem. J. 199, 263–265] does not suffer from these artifacts.

Oxidase and oxygenase function of the microsomal cytochrome P450 monooxygenase system.

Abstract: The rates of the NADPH-dependent formation of superoxide radicals and hydrogen peroxide have been measured in liver microsomes from phenobarbital-pretreated rats. Correcting a quenching of O2(-) radicals by microsomes, a stoichiometry of O2(-) to H2O2 close to 2:1 was obtained. This, and the fact that pseudo-substrates of microsomal cytochrome P450 like perfluoro-n-hexane and perfluorinated cyclohexane did not increase H2O2 formation in a catalase-inhibited assay, rules out a two-electron reduced oxygen species as the source of H2O2. The rates of O2(-) as well as H2O2 generation in the presence of 7-ethoxycoumarin were equally inhibited by carbon monoxide (75%) and resulted in photochemical action spectra with a maximum reactivation at 450 nm. Using the same conditions the monooxygenation was inhibited to a high degree (83%) but without exogenous substrate the inhibition of H2O2 formation dropped to 55%. It was concluded that most of the O2(-) originated from the oxycomplex of cytochrome P450 and that substrates can modify the rates of its decomposition and sensitivity to carbon monoxide. No correlation of H2O2 formation or of substrate monooxygenation with the optical substrate binding spectra could be observed. From the pH dependence a proton-assisted decomposition of oxy-cytochrome P450 appears likely. H2O2 formation was only slightly decreased at 20 microM dioxygen suggesting that H2O2 formation via cytochrome P450 should also occur in vivo.

The chemistry of favism-inducing compounds. The properties of isouramil and divicine and their reaction with glutathione

Abstract: Isouramil and divicine are pyrimidine aglycones of two glucosides found in broad beans. They have been shown to be strong reducing agents. Their reaction with oxygen in a (gas) saturated solution, 26 degrees C, is characterized by tau 1/2 = 1 min and 3 min respectively. Hydrogen peroxide is formed in this reaction stoichiometrically (1:1). The pyrimidines lose two hydrogen and form an intermediate that is structurally analogues to alloxan. This intermediate is not stable, and in the absence of reducing agents it decomposes, possibly by ring-cleavage. In the presence of reduced glutathione the intermediate is reduced and can now react with oxygen once again. Thus, the pyrimidines cycle between the two states and the net reaction is the catalytic oxidation of glutathione by molecular oxygen; in each cycle 4 molecules of glutathione are dissipated. The possible involvement of these pyrimidines in the pathogenesis of favism may be in a similar mechanism. Red blood cells deficient in glucose-6-phosphate dehydrogenase cannot cope with such an oxidative challenge exerted by the pyrimidines. Consequently an irreversible cellular damage can take place leading to the enhanced sequestration of these red blood cells by the reticuloendothelial system.

Enzyme electrode and method for dextran analysis

Abstract: A method for the potentiometric determination of a dextran solution is provided wherein the dextran is enzymatically hydrolyzed to glucose, the glucose is oxidized to form hydrogen peroxide and the hydrogen peroxide is measured utilizing a redox electrode. A novel electrode having a plurality of enzyme impregnated layers is provided for converting the dextran to glucose.

Chemical and biochemical aspects of superoxide radicals and related species of activated oxygen

Abstract: The spectrum of biological processes in which oxygen is used by living systems is quite large, and the products include some damaging species of activated oxygen, particularly the superoxide radical (O-.2) and hydrogen peroxide (H2O2). Superoxide radicals and hydrogen peroxide, in turn, can lead to the formation of other damaging species: hydroxyl radicals (.OH) and singlet oxygen (1O2). Hydroxyl radicals react with organic compounds to give secondary free radicals that, in the presence of oxygen, yield peroxy radicals, peroxides, and hydroperoxides. Formation, interconversion, and reactivity of O-.2 and related activated oxygen species, methods available for their detection, and the basis of their biological toxicity are briefly reviewed.

The role of glutathione metabolism in the detoxification of H2O2 in rabbit lens.

Abstract: Aqueous humor is known to contain a significant level of H2O2, but the mechanisms by which ocular tissues protect against oxidative damage are not well understood. With the use ofC-1 -, C-2-, and C-6-labeled glucose, the contribution of glutathione (GSH) metabolism and the hexose monophosphate shunt (HMS) to the detoxification of peroxide in the lens his been evaluated. It teas observed that H202in the culture medium disappeared rapidly (0.5 /xmol H20 2/lensIhr) upon incubation of a rabbit lens at 37° C. At 0° to 3° C, however, the rate of disappearance of H2O2 was only one fifth of that observed at the higher temperature. In the absence of a lens or after pretreatment of the lens with methyl mercuric hydroxide, the rate of disappearance of peroxide from the medium was reduced to nearly zero. When a nearly constant level of H2O2 (0.05 to 0.07 mM) was maintained in the medium by means of a peristaltic pump, the amount of C02 liberated by the HMS at 37° C was found to be three times that liberated from lenses cultured in the absence of peroxide. No change was noted in the level of GSH in the H20^-treated lenses at 37° C. A significant decrease in GSH was observed, however, at 0° to 3° C, suggesting nonenzymatic oxidation of the tripeptide at the lower temperature. The results indicate that GSH metabolism and the HMS pathway contribute significantly to the detoxification ofH2O2in the lens. (INVEST OPHTHALMOL VIS SCI 22:330-335, 1982.)

Effects of potassium iodide, colchicine and dapsone on the generation of polymorphonuclear leukocyte-derived oxygen intermediates

Abstract: The effects of potassium iodide, colchicine and dapsone on the in vitro generation of polymorphonuclear leukocyte (PMN)-derived oxygen intermediates were investigated. These three drugs have beneficial effects on those conditions in which PMNs play an important pathogenetic role. Three oxygen intermediates, superoxide anion (O2-), hydrogen peroxide (H2O2), hydroxyl radical (OH.) and chemiluminescence were included in assay studies. Dose response studies were performed with therapeutic doses of the drugs (10 microM--mM). We found that both potassium iodide and dapsone significantly suppressed the generation of oxygen intermediates, except for O2-. Colchicine decreased OH. production. Our results show tha these agents to some extent exert their anti-inflammatory effects by interfering with the PMN-dependent production of oxygen intermediates, thus conferring protection from auto-oxidative tissue injury. This may account for their clinical efficacy in many PMN-mediated dermatological diseases.

Role of Peroxidase in Lignification of Tobacco Cells : I. Oxidation of Nicotinamide Adenine Dinucleotide and Formation of Hydrogen Peroxide by Cell Wall Peroxidases

Abstract: The two peroxidase isoenzyme groups (GI and GIII) localized in the cell walls of tobacco (Nicotiana tabacum L.) tissues were compared with respect to their capacity for NADH-dependent H2O2 formation. Peroxidases of the GIII group are slightly more active than those of the GI group when both are assayed under optimal conditions. This difference is probably not of major regulatory importance. NADH-dependent formation of H2O2 required the presence of Mn2+ and a phenol as cofactors. The addition of H2O2 to the reaction mixture accelerated subsequent NADH-dependent H2O2 formation. In the presence of both cofactors or Mn2+ alone, catalase oxidized NADH. However, if the cofactors were absent or if only dichlorophenol was present, catalase inhibited NADH oxidation. No H2O2 accumulation occurred in the presence of catalase. Superoxide dismutase inhibited NADH oxidation quite significantly indicating the involvement of the superoxide radical in the peroxidase reaction. These results are interpreted to mean that the reactions whereby tobacco cell wall peroxidases catalyze NADH-dependent H2O2 formation are similar to those proposed for horseradish peroxidase (Halliwell 1978 Planta 140: 81-88).

On the significance of the cytochrome P-450-dependent hydroxyl radical-mediated oxygenation mechanism.

Abstract: 1. Reconstituted membrane vesicles containing purified preparations of cytochrome P-450 LM2 and NADPH-cytochrome P-450 reductase effectively destroyed 2-deoxy-D-ribose in an NADPH-dependent process.2. The destruction was mediated by hydroxyl radicals formed in an iron-catalysed Haber-Weiss reaction between superoxide anions and hydrogen peroxide liberated from the haemoprotein.3. Administration of ethanol or benzene to rabbits, compounds known to be oxygenated by the hydroxyl radical-dependent mechanism, resulted in induction of a species of cytochrome P-450 effective in the radical-dependent metabolism of both chemicals.4. Benzene treatment of rabbits also resulted in an enhanced hydroxyl radicaldependent metabolism of ethanol and benzene in liver microsomes.5. It is suggested that, for certain substrates, hydroxyl radical-mediated cytochrome P-450-dependent oxygenation reactions are of importance for the microsomal metabolism of these compounds.6. It is speculated that radical-producing species of cytoc...

New water-soluble hydrogen donors for the enzymatic photometric determination of hydrogen peroxide. II. N-ethyl-N-(2-hydroxy-3-sulfopropyl)aniline derivatives.

Abstract: Five N-ethyl-N-(2-hydroxy-3-sulfopropyl) aniline derivatives have been synthesized and assessed as water-soluble hydrogen donors for the photometric determination of hydrogen peroxide in the presence of peroxidase. These compounds, sodium salts of N-ethyl-N-(2-hydroxy-3-sulfopropyl) aniline, N-ethyl-N-(2-hydroxy-3-sulfopropyl)-m-toluidine, N-ethyl-N-(2-hydroxy-3-sulfopropyl)-m-anisidine, 3, 5-dimethyl-N-ethyl-N-(2-hydroxy-3-sulfopropyl) aniline and 3, 5-dimethoxy-N-ethyl-N-(2-hydroxy-3-sulfopropyl)-aniline, gave high absorbances at visible wavelengths in media in the weakly alkaline to fairly acidic pH range. Further, the urea adduct of hydrogen peroxide could be conveniently used as a standard material.

Color indicator composition and film for detecting hydrogen peroxide

Abstract: In a multilayer analysis film for detecting hydrogen peroxide by dry process which comprises a support and a reagent layer having contained therein a color indicator composition comprising peroxidase and a substance capable of causing a optically detectable change in the presence of hydrogen peroxide and peroxidase, the color indicator composition is characterized by further containing specific pyrogallol derivatives. Such pyrogallol derivatives improve stability during storage of such a multilayer analysis film.