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G W Winston

Publications and source records attributed to G W Winston.

70 records · Page 4Linked to original sources
PubMed1983

NADPH-dependent production of oxy radicals by purified components of the rat liver mixed function oxidase system. I. Oxidation of hydroxyl radical scavenging agents.

Isolated microsomes catalyze an NADPH-dependent oxidation of typical hydroxyl radical scavenging agents. To determine which microsomal components participate in the oxidation of the scavengers, experiments were carried out with purified NADPH-cytochrome P-450 reductase and cytochrome P-450 isolated from phenobarbital-treated rats. The production of ethylene from 4-ketothiomethylbutyrate or of formaldehyde from either dimethyl sulfoxide or tertiary butyl alcohol was measured in the presence of NADPH plus reductase or NADPH plus reductase plus cytochrome P-450. The reductase-dependent system itself catalyzed the oxidation of the three scavengers. Addition of cytochrome P-450 had no effect on the rates of oxidation of the scavengers. Relative rates of oxidation of the scavengers reflected the amount of the reductase in the assay system. Varying the amount of cytochrome P-450 at a fixed concentration of the reductase did not result in rates different from that observed in the absence of cytochrome P-450. Dilauroyl phosphatidylcholine appeared to have a stimulatory role in these oxidations, whereas cytochrome P-450 reductase and NADPH were obligatory components. The reductase-dependent oxidation of the scavengers was inhibited by superoxide dismutase, catalase, and competing hydroxyl radical scavenging agents suggesting that superoxide, hydrogen peroxide, and an oxygen radical with the oxidizing power of the hydroxyl radical played a role in these oxidations. Further, these oxidations were inhibited by the iron-chelator desferrioxamine but stimulated by either EDTA or by iron. These results suggest that an iron-catalyzed Haber-Weiss reaction might be involved in the mechanism by which purified cytochrome P-450 reductase mediates the oxidation of typical hydroxyl radical scavengers. The results demonstrated that NADPH-cytochrome P-450 reductase may represent an important locus of oxygen activation leading to the production of a highly oxidizing species characteristic of the hydroxyl radical.

Animals↗
PubMed1983

Evidence for two ethanol oxidizing pathways in reconstituted mixed-function oxidase systems.

The oxidation of ethanol and typical hydroxyl radical scavengers by NADPH-cytochrome P-450 reductase and cytochrome P-450 purified from phenobarbital-treated rats were studied. Ethanol and the scavengers could be oxidized by the reductase system itself. This system was inhibited by superoxide dismutase, competing hydroxyl radical scavengers and desferrioxamine, but stimulated by either EDTA or iron. These results suggest that an iron-catalyzed Haber-Weiss reaction might be involved in the mechanism by which the reductase mediates the oxidation of typical hydroxyl radical scavengers and ethanol. The addition of cytochrome P-450 had no effect on the oxidation of the scavengers, whereas the oxidation of ethanol was enhanced two-to three-fold over the reductase-dependent rate. The oxidation of ethanol was dependent on both the amount of reductase and P-450. There was no effect of competing scavengers, superoxide dismutase or desferrioxamine on the increased rate of ethanol oxidation produced upon addition of cytochrome P-450. Organic hydroperoxides supported the oxidation of ethanol, but not that of the scavengers when added directly to cytochrome P-450. These results suggest that two independent pathways are operative in supporting NADPH-dependent microsomal oxidation of ethanol. One pathway involves hydroxyl radicals which can be generated by the reductase, whereas the other pathway requires the combined presence of both the reductase and cytochrome P-450, and appears to be independent of oxygen radicals.

Animals↗
PubMed1982

Disodium tetrachloropalladate (Na2PdCl4), an inhibitor of rat liver mitochondrial electron transport.

The effects of Na2PdCl4 were studied on isolated rat liver mitochondrial electron transport and oxidative phosphorylation in vitro. Significant reductions in ADP-stimulated respiration were observed with increasing Na2PdCl4 concentrations with both succinate and NADH-linked substrate oxidations. Concentration necessary for half-maximal inhibition of oxygen uptake (EC50) for an NADH-linked substrate system was 18 muM while with succinate as substrate the EC50 was 15 muM. At 64 muM both systems were inhibited maximally at 60 and 80%, respectively. At concentrations of Na2PdCl4 sufficient to inhibit acceptor-stimulated oxygen uptake, there was a concomitant decrease in the rate of ADP phosphorylation as measured by proton absorption. Uncoupling agents had no effect on Na2PdCl4 inhibited mitochondria. Mg-ATPase activity and phosphate acceptor limited (State 4) respiratory activity were not stimulated by any Na2PdCl4 concentration used in these investigations. Data from these experiments indicate that Na2PdCl4 inhibits the mitochondrial respiratory chain in vitro.

Adenosine Diphosphate↗
PubMed1981

Effects of chronic ethanol ingestion on liver glycogen phosphorylase in male and female rats.

The effects of chronic ethanol ingestion on a preparation of liver glycogen phsophorylase have been studied. A coupled assay in the direction of glycogenolysis was used. In the absence of AMP, a significant decrease in specific activity was observed in both males (19%) and females (30%). AMP additions stimulated phosphorylase activity and completely obliterated the ethanol-induced decreases in both sexes of animal. Kinetic studies, done in the absence of AMP, showed that only the apparent Vmax had been altered by ethanol. These data suggest that decreases in liver glycogen after chronic ethanol ingestion may not be related to the specific activity of glycogen phosphorylase. Using both glucose and caffeine as negative effectors, addditional studies demonstrated that the inhibitory effects of caffeine had been altered by ethanol in both males and females and that the inhibitory effects of glucose had been altered only in females. Even though the specific activity for phosphorylase did not directly implicate this enzyme in the ethanol-induced decrease in liver glycogen stores, the latter data regarding glucose and caffeine suggest that chronic ethanol ingestion has altererd this enzyme and that differences exist between males and females.

Adenosine Monophosphate↗
PubMed1980

Chronic ethanol ingestion and glycogen metabolism in male and female rats.

Chronic ethanol ingestion decreased liver glycogen levels in both male and female rats; however plasma glucose was decreased only in males. The decreased levels of liver glycogen were related to increases of 42% and 122% in glycogen phosphorylase in males and females, respectively. Both a and b forms of phosphorylase were increased, but the b form was increased more than the a form. Phosphorylase phosphatase was found to be increased 75% and 267% in males and females, respectively. Studies using positive and negative phosphorylase effector molecules indicated that ethanol ingestion may have altered the structure of phosphorylase a and that the degree of alteration was sex related.

Alcoholism↗
PubMedDate not supplied

Distribution of microsomal CO-binding chromophores and EROD activity in sea anemone tissues.

Our previous studies indicated that sea anemone microsomes contain cytochrome P450 (CYP) and have ethoxyresorufin O-dealkylation (EROD) activity. Other marine invertebrates have discrete organs which concentrate cytochromes P450, whereas cnidarians have evolved only to the tissue level of development. To examine the distribution of CYP in sea anemones, microsomes were prepared from the following tissue regions of two sea anemones, Anthopleura xanthogrammica: outer (heavy muscular wall), inner (imperfect and perfect mesentery, and retractor muscle), soft (digestive sac, gonads, and mesentery filaments), and tentacular (including algal/diatom symbiont). The cytochrome P450 content was distributed relatively evenly among the tissue regions. In contrast, the 418-nm CO-binding chromophore was approximately 10 times greater in the outer region than in any other region. Further, the 490-nm peak (which interferes with quantification of CYP in sea anemones) was greater in the outer region. In general, the EROD activity was comparable in the inner and soft regions and highest in the tentacles. However, the EROD results may have been complicated by the presence of the algal/diatom symbiont.

Animals↗
PubMedDate not supplied

Oxidative stress in ecotoxicology: from the analysis of individual antioxidants to a more integrated approach.

An integrate approach will be discussed for investigations on oxidative stress in xenobiotic toxicity. While the analysis of individual antioxidants is useful for their sensitivity and to understand the mode of action of a stressor, the integration with the analysis of the total antioxidant capacity provides a more holistic assessment of the overall biological significance of such variations. TOSC has a greater predictive value on the health condition of the organisms and allows to discriminate the different role of specific ROS in oxidative stress syndrome.

Animals↗
PubMedDate not supplied

Effects of chronic ethanol ingestion on male and female rat liver glycogen phosphorylase phosphatase.

The effects of chronic ethanol ingestion on the interconversion of the active to the inactive form of glycogen phosphorylase by phosphorylase phosphatase was studied. Male and female rats also were compared. Chronic ethanol feeding decreased phosphorylase a and total phosphorylase activity in male rats. In females, no change was observed in phosphorylase a, whereas total phosphorylase activity was increased 73%. This was found to correlate with the relative activities of phosphorylase phosphatase. The data show differences between the two sexes with regard to the AMP inhibition of phosphorylase phosphatase and the caffeine stimulation of the phosphatase. Ethanol markedly enhanced the AMP inhibition of the phosphatase in males but had no effect in females. Further studies in females showed that ethanol completely obliterated the well documented stimulation of the phosphatase by caffeine; however, it did not alter the caffeine effect in males. These data suggest possible alterations in the tertiary structure of phosphorylase a.

Adenosine Monophosphate↗
PubMedDate not supplied

Ethanol oxidation by hydroxyl radicals: role of iron chelates, superoxide, and hydrogen peroxide.

Oxygen-derived free radicals such as the hydroxyl radical (.OH) have been shown to mediate the oxidation of ethanol by a variety of oxy radical-generating systems. Among these are microsomal electron transport systems (both intact and purified, reconstituted systems), the coupled oxidation of hypoxanthine or xanthine by xanthine oxidase, and the model iron-ascorbate system. The sequence of reactions leading to the oxy radical-dependent oxidation of ethanol as well as other hydroxyl radical-scavenging agents by these various systems is believed to proceed through the formation of a common intermediate, namely, hydrogen peroxide (H2O2), after dismutation of the superoxide anion radical (O2-.). The presence of iron, especially chelated iron, greatly enhances the production of .OH by serving as an oxidant for O2-. or a reductant for H2O2. Experiments were carried out to evaluate the role of iron, the chelating agent, O2-., and H2O2 in the oxidation of ethanol by a variety of in vitro systems (chemical, enzymatic, and intact membrane bound) that can produce oxy radicals via different mechanisms. The generation of .OH by all the systems studied was sensitive to catalase, which indicates that H2O2 is the precursor of .OH. Superoxide radical appears to be the reducing agent in the hypoxanthine-xanthine oxidase system, indicating an iron-catalyzed Haber-Weiss reaction. In the ascorbate, reductase, and microsomal systems, superoxide radical does not appear to be the reducing agent. However, superoxide radical probably is the precursor of H2O2. While iron plays an important role in the production of .OH by the various systems, the effect of iron depends on the nature of the iron chelate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗