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Biomedical subjects

C C Winterbourn

Publications and source records attributed to C C Winterbourn.

At least 163 records · Page 9Linked to original sources
PubMed1983

Changes in ascorbate levels on stimulation of human neutrophils.

Changes in ascorbate levels have been measured in human neutrophils stimulated with opsonized zymosan, phorbol myristate acetate and formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe), in the presence and absence of cytochalasin B. After stimulation with opsonized zymosan or phorbol myristate acetate, there was no loss of total ascorbate, but 30-40% of the reduced ascorbate was oxidized to dehydroascorbate. Superoxide dismutase and catalase added to the cell suspension did not inhibit this oxidation. fMet-Leu-Phe, however, gave no net oxidation but about 20% of the total ascorbate was lost during 2 h incubation. These results imply that there is not a simple relationship between superoxide and hydrogen peroxide production and ascorbate oxidation, and that release of ascorbate into the phagolysosomes does not occur.

Ascorbic Acid↗
PubMed1983

Lactoferrin-catalysed hydroxyl radical production. Additional requirement for a chelating agent.

The ability of lactoferrin to catalyse hydroxyl radical production was determined by measuring ethylene production from methional (2-amino-4-methylthiobutyraldehyde) or 4-methylthio-2-oxobutyrate. Lactoferrin, isolated from human milk and saturated by adding the exact equivalents of Fe3+-nitrilotriacetic acid and dialysing, give little if any catalysis of the reaction between H2O2 and either O2-. or ascorbic acid at either pH 7.4 or pH 5.0. However, in the presence of chelating agents such as EDTA or nitrilotriacetic acid that can complex with lactoferrin, hydroxyl radical production by both mechanisms was observed.

Aldehydes↗
PubMed1983

Rapid proteolysis of unstable globins in human bone marrow.

To determine whether human red cells contain a proteolytic system capable of rapidly degrading unstable proteins, the fate of pulse-labelled puromycyl polypeptides was investigated. In erythroid bone marrow cells these unstable polypeptides were degraded to TCA-soluble fragments with a mean half-life of 4 . 5 min. However, in peripheral blood reticulocytes no proteolysis was observed, indicating that this activity declines as the red cell matures.

Bone Marrow↗
PubMed1983

Haemoglobin oxidation and free radical production in the red cell.

The production and fate of superoxide and other free radicals, and the role of superoxide dismutase in the red cell is considered. Superoxide reacts slowly and at a comparable rate with oxyhaemoglobin and methaemoglobin, but superoxide dismutase markedly accelerates oxidation of oxyhaemoglobin by oxidizing drugs or xenobiotics such as quinones or paraquat. The mechanism involves inhibition by the enzyme (via its reaction with superoxide) of methaemoglobin reduction by the drug radicals. The possibility that such inhibition of organic radical reactions by superoxide dismutase is one of its protective functions is discussed.

Catalase↗
PubMed1983

The reaction of hemoglobin with paraquat radicals in the presence and absence of O2.

Paraquat radicals generated with xanthine oxidase in N2 reduced methemoglobin to deoxyhemoglobin. In air, reduction to oxyhemoglobin occurred but at one third the rate. In air the reaction was 10 times faster and gave greater overall reduction to oxyhemoglobin than with O2 generated at a similar rate. Aerobic methemoglobin reduction in the presence of paraquat was inhibited by superoxide dismutase. It is concluded that paraquat radicals reduce methemoglobin directly in air and that this reaction must be very fast with a rate constant of the order of 10(9) M-1 s-1. This is an example where paraquat radicals in air do not all react with O2. It cannot therefore be assumed that the radical reactions of paraquat in air are due solely to O2 and its products.

Aerobiosis↗
PubMed1982

Superoxide dismutase-inhibitible reduction of cytochrome c by the alloxan radical. Implications for alloxan cytotoxicity.

Cytochrome c was reduced when superoxide was generated from xanthine oxidase in the presence of alloxan, and by the reaction of alloxan and with reduced glutathione. In each case, most of the reduction was inhibited by superoxide dismutase, but considerably more enzyme was required than with superoxide alone. This indicates that the superoxide dismutase-inhibitible cytochrome c reduction was mainly due to a direct reaction with the alloxan radical, and implies that other reactions that are inhibited by superoxide dismutase could be due to either alloxan radicals or superoxide.

Alloxan↗
PubMed1982

Deoxyribose breakdown by the adriamycin semiquinone and H2O2: evidence for hydroxyl radical participation.

We report our finding that the reaction between the adriamycin semiquinone (produced by reduction of the drug by xanthine oxidase) and H2O2 in N2 causes deoxyribose degradation to a thiobarbituric acid-reactive chromogen. Deoxyribose breakdown was inhibited by scavengers of hydroxyl radicals, providing evidence for the participation of hydroxyl radicals. The reaction was detected in air, but was less efficient in air than in N2. Deoxyribose degradation did not require a metal catalyst, and was inhibited by superoxide dismutase in air, but not N2. A similar reaction with deoxyribose in DNA may be of major importance in the antitumour action of adriamycin.

Air↗
PubMed1982

Reactions of Adriamycin with haemoglobin. Superoxide dismutase indirectly inhibits reactions of the Adriamycin semiquinone.

The Adriamycin semiquinone produced by the reaction of xanthine oxidase and xanthine with Adriamycin has been shown to reduce both methaemoglobin and cytochrome c. In air, but not N2, both reactions were inhibited by superoxide dismutase. With cytochrome c, superoxide formed by the rapid reaction of the semiquinone with O2, was responsible for the reduction. However, even in air, methaemoglobin was reduced directly by the Adriamycin semiquinone. Superoxide dismutase inhibited this reaction by removing superoxide and hence the semiquinone by displacing the equilibrium: Semiquinone + O2 in equilibrium or formed from quinone + O2-. to the right. This ability to inhibit indirectly reactions of the semiquinone could have wider implications for the protection given by superoxide dismutase against the cytotoxicity of Adriamycin. Oxidation of haemoglobin by Adriamycin has been shown to be initiated by a reversible reaction between the drug and oxyhaemoglobin, producing methaemoglobin and the Adriamycin semiquinone. Reaction of the semiquinone with O2 gives superoxide and H2O2, which can also react with haemoglobin. Catalase, by preventing this reaction of H2O2, inhibits oxidation of oxyhaemoglobin. Superoxide dismutase, however, accelerates oxidation, by inhibiting the reaction of the semiquinone with methaemoglobin by the mechanism described above. Although superoxide dismutase has a detrimental effect on haemoglobin oxidation, it may protect the red cell against more damaging reactions of the Adriamycin semiquinone.

Catalase↗
PubMed1981

Hydroxyl radical production in body fluids. Roles of metal ions, ascorbate and superoxide.

Hydroxyl radical production, detected by ethylene formation from methional, has been investigated in plasma, lymph and synovial fluid. In the presence of added iron--EDTA, addition of either H2O2 or xanthine and xanthine oxidase gave rise to hydroxyl radical formation that in most cases was not superoxide-dependent. The ascorbate already present in the fluid appeared to participate in the reaction. In the absence of added catalyst, the reaction was hardly detectable, the rate being less than 5% of that observed with 1 microM-iron--EDTA added. This implies that the fluids had little if any capacity to catalyse hydroxyl radical production via this mechanism.

Aldehydes↗
PubMed1981

Unstable haemoglobin haemolytic crises: contributions of pyrexia and neutrophil oxidants.

Pyrexia and the production of oxidants by phagocytic cells have been examined as two possible causes of haemolytic crises associated with infections in carriers of unstable haemoglobins. Three unstable haemoglobins were examined, both in red cells and after purification. Incubation at 40 degrees C rather than 37 degrees C resulted in only a slight increase in autoxidation rate, but a considerable increase in the rate of precipitation of the haemoglobins as Heinz bodies. Oxidants produced by activated neutrophils were capable of oxidizing haemoglobin both in solution and red cells, though there was no preferential effect on the unstable as opposed to the normal haemoglobin. It is concluded that haemolytic crises associated with infections in carriers of unstable haemoglobins can be explained by increased intracellular precipitation of the haemoglobin as Heinz bodies caused by the accompanying pyrexia.

Heinz Bodies↗
PubMed1981

Oxidative hemoglobin breakdown induced by a rubber additive.

An antioxidant commonly present in black rubber, N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD) caused very rapid oxidation and denaturation of purified hemoglobin. In the red cells, the reaction resulted in the formation of Heinz bodies, a decrease in reduced glutathione concentration, and stimulation of the hexose monophosphate shunt. IPPD appears therefore to have the potential to induce hemolysis in glucose-6-phosphate dehydrogenase deficiency. It would be expected to be more potent than most redox reagents of this type. It does not require further metabolism to be reactive, and its reactivity is similar to that of phenylhydrazine. But in particular since both IPPD and its oxidized form can oxidize hemoglobin it can act catalytically, and at low concentrations is much more effective than phenylhydrazine. Oxidation of blood stored in contact with rubber seals containing IPPD has been observed. It is also possible that prolonged contact of susceptible individuals either with rubber containing IPPD or to IPPD itself during rubber manufacture could result in hemolysis.

Anemia, Hemolytic↗
PubMed1979

The reaction of menadione with haemoglobin. Mechanism and effect of superoxide dismutase.

1. Menadione was found to react with both the haem groups and the beta-93 thiol groups of haemoglobin. 2. It oxidized the haem groups of oxyhaemoglobin, giving mainly methaemoglobin and a smaller amount of haemichrome. The reaction rate was decrease in the presence of catalase and markedly accelerated in the presence of superoxide dismutase. It is proposed that the overall reaction involves the initial reversible formation of methaemoglobin and the semiquinone, and that the effect of superoxide dismutase is to prevent the reverse reaction, by removing superoxide and hene O2-. E.s.r. evidence for the information of the semi-quinone and its reactions is presented. 3. The reaction of menadione with the beta-93 thiol groups of haemoglobin appeared to be similar to that with other thiols, forming the 3-thioether derivative of menadione, but it was also accompanied by reduction of methaemoglobin. This reduction was prevented by superoxide dismutase, but appeared to be caused by the semiquinone radical, which was produced as an intermediate. 4. Reduced glutathione functioned only to a limited extent as a scavenger of the menadione semiquinone. Its main reaction was directly with menadione to form the thioether. Ascorbate was a more efficient scavenger, and accelerated the oxidation of oxyhaemoglobin by menadione. 5. The significance of these findings in relation to menadione-induced erythrocyte haemolysis is discussed.

Catalase↗
PubMed1979

Protection by ascorbate against acetylphenylhydrazine-induced Heinz body formation in glucose-6-phosphate dehydrogenase deficient erythrocytes.

Ascorbate was found to inhibit oxidation of oxyhaemoglobin and Heinz body formation in glucose-6-phosphate dehydrogenase deficient red cells incubated with acetylphenylhydrazine. It is proposed that ascorbate can substitute for the glutathione which is depleted and act as a scavenger for drug free radicals generated during the reaction. Ascorbate was protective at concentrations only a little higher than that in normal blood, and the possibility that administration of ascorbate could protect GSH deficient cells against the action of oxidative drugs such as APH is considered. A simple method of quantitatively assessing Heinz body formation by measuring the turbidity of the lysed cells is described.

Ascorbic Acid↗