Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aims of this study were to investigate the interaction between oxygen radicals and mucus secretion from cultured rat gastric mucous cells, and to assess the role of prostaglandin production in the modulation of mucus secretion in vitro. Xanthine oxidase in the presence of hypoxanthine caused a dose-dependent increase in the presence of hypoxanthine caused a dose-dependent increase of mucus secretion, as assessed by release of [3H]glucosamine from prelabeled cells, whereas xanthine oxidase or hypoxanthine alone did not. Xanthine oxidase (10 mU/ml) increased release of [3H]glucosamine by 57 +/- 6% compared with control values (P less than 0.001). Catalase (3,000 U/ml) inhibited xanthine oxidase-induced mucus secretion by 69 +/- 9% (P less than 0.01), whereas superoxide dismutase did not. Pretreatment with deferoxamine, an inhibitor of hydroxyl radical generation through chelating ferric ion, diminished oxygen radical-induced mucus release to control values. Xanthine oxidase dose dependently stimulated prostaglandin E2 (PGE2) production, which was blocked by catalase but not by superoxide dismutase. However, oxygen radical stimulation of mucus secretion was not inhibited by the addition of indomethacin. Moreover, PGE2, exogenously administered, did not significantly accelerate mucus secretion. Stimulation of mucus secretion by oxygen radicals was not accompanied by increased 51Cr release or by leakage of intracellular lactate dehydrogenase. These results suggest that oxygen species, particularly hydroxyl radical, stimulate mucous glycoprotein secretion from cultured rat gastric mucous cells. However, it seems unlikely that prostaglandin production mediates the oxygen species-induced stimulation of mucus secretion.
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PMID:Oxygen metabolites stimulate mucous glycoprotein secretion from cultured rat gastric mucous cells. 192 52

We investigated the interaction between activated cat polymorphonuclear neutrophils (PMNs) and coronary vascular endothelial cells in vitro. It was shown that 1) 90 minutes of low-flow perfusion without reperfusion had no deleterious effects on endothelium-dependent vasodilation, whereas 90 minutes of low-flow perfusion and 20 minutes of reperfusion with a blood cell-free solution induced a 20-25% endothelial dysfunction; 2) activated PMNs produced endothelium-dependent vasoconstriction in coronary artery rings isolated from cat hearts undergoing 90 minutes of low-flow perfusion and 20 minutes of reperfusion with a blood cell-free Krebs-Henseleit solution; 3) addition of the superoxide free radical scavenger, superoxide dismutase (150 micrograms/ml), or an antibody directed against CD18 of PMN adherence glycoprotein complex (MAbR15.7, 20 micrograms/ml) attenuated PMN-induced vasoconstriction significantly, but addition of a hydroxyl radical scavenger [N-(2-mercaptopropionyl)-glycine, 150 micrograms/ml], a cyclooxygenase inhibitor, or a lipoxygenase inhibitor had no protective effect; 4) exposure of rings to a superoxide radical-generating system (i.e., xanthine and xanthine oxidase) produced significant vasoconstriction that was similar to that observed with activated PMNs and was inhibited by superoxide dismutase; and 5) activated PMNs produced a marked coronary endothelial dysfunction characterized by a decreased response to the endothelium-dependent vasodilators acetylcholine and A23187. Addition of either superoxide dismutase or MAbR15.7 protected against endothelial dysfunction. These results indicate that activated PMNs produce significant vasoconstriction and endothelial dysfunction in coronary arteries isolated from low-flow perfusion-reperfused hearts. These effects appear to be mediated primarily by superoxide radicals generated by activated PMNs that either inactivate or inhibit the synthesis and release of endothelium-derived relaxing factor. We conclude that activated PMNs are able to induce endothelial dysfunction by releasing free radicals and possibly other substances.
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PMID:Neutrophil-mediated vasoconstriction and endothelial dysfunction in low-flow perfusion-reperfused cat coronary artery. 205 45

A blotting method is described to detect enzymes that do not normally yield a colored product. The method can be used for dot blotting as well as blotting after gel electrophoresis of many enzymes if the reactions they catalyze can be coupled to an oxidase or a dehydrogenase. The latter, designated "auxiliary enzymes," are preimmobilized on membranes of nitrocellulose or positively charged nylon and the reaction they catalyze is coupled with reduction of tetrazolium salt to yield colored formazan on areas of the transfer membrane occupied by the blotted enzymes. In the examples reported here, preimmobilized glucose oxidase, L-amino acid oxidase, xanthine oxidase, malate dehydrogenase, and a mixture of hexokinase and glucose-6-phosphate dehydrogenase were used as auxiliary enzymes to detect blotted invertase, leucine aminopeptidase, purine nucleoside phosphorylase, fumarase, and adenylate kinase, respectively. Detection limits varied, but never exceeded 100 ng for these enzymes. After blotting from polyacrylamide gels, the fumarase assay was the most sensitive of those investigated, detecting 10 ng of enzyme used for electrophoresis. Invertase, a glycoprotein, was detected with higher sensitivity on nitrocellulose membranes when concanavalin A was present on the membrane in addition to the auxiliary enzyme, glucose oxidase. On blots from isoelectric focusing gels, the assay detected two isozymes of purine nucleoside phosphorylase in a sample from calf spleen and at least five isozymes of this enzyme in lysates from human red cells.
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PMID:Activity staining of blotted enzymes by reaction coupling with transfer membrane-immobilized auxiliary enzymes. 245 38

Thrombolytic therapy has gained widespread acceptance as a means of treating coronary artery thrombosis in patients with acute myocardial infarction. Although experimental data have demonstrated that timely reperfusion limits the extent of infarction caused by regional ischemia, there is growing evidence that reperfusion is associated with an inflammatory response to ischemia that exacerbates the tissue injury. Ischemic myocardium releases archidonate and complement-derived chemotactic factors, e.g., leukotriene B4 and C5a, which attract and activate neutrophils. Reperfusion of ischemic myocardium accelerates the influx of neutrophils, which release reactive oxygen products, such as superoxide anion and hydrogen peroxide, resulting in the formation of a hydroxyl radical and hypochlorous acid. The latter two species may damage viable endothelial cells and myocytes via the peroxidation of lipids and oxidation of protein sulfhydryl groups, leading to perturbations of membrane permeability and enzyme function. Neutrophil depletion by antiserum and inhibition of neutrophil function by drugs, e.g., ibuprofen, prostaglandins (prostacyclin and PGE1), or a monoclonal antibody, to the adherence-promoting glycoprotein Mo-1 receptor, have been shown to limit the extent of canine myocardial injury due to coronary artery occlusion/reperfusion. Recent studies have challenged the hypothesis that xanthine-oxidase-derived oxygen radicals are a cause of reperfusion injury. Treatment with allopurinol or oxypurinol may exert beneficial effects on ischemic myocardium that are unrelated to the inhibition of xanthine oxidase. Furthermore, the human heart may lack xanthine oxidase activity. Further basic research is needed, therefore, to clarify the importance of xanthine oxidase in the pathophysiology of reperfusion injury.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Myocardial ischemia and reperfusion: the role of oxygen radicals in tissue injury. 248 90

1. N-glycanase, but not O-glycanase, released carbohydrates from butyrophilin of rat and cow milk lipid globule membranes. 2. 1-Deoxynojirimycin, and inhibitor of glucosidases I and II of the glycoprotein processing pathway, increased the amount or extent of glycosylation of butyrophilin in rat milk lipid globules. 3. Butyrophilin and xanthine oxidase of milk lipid globule membrane had a nearest neighbor relationship, as demonstrated through specific crosslinking of these proteins. 4. From these results it is suggested that butyrophilin has asparagine-linked oligosaccharides which bypass the processing apparatus of endoplasmic reticulum and Golgi apparatus. Butyrophilin may be responsible for anchoring xanthine oxidase to the inner (cytoplasmic) face of milk lipid globule membrane.
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PMID:Butyrophilin of milk lipid globule membrane contains N-linked carbohydrates and cross-links with xanthine oxidase. 252 60

The milk-fat-globule membrane (MFGM) was isolated from guinea-pig milk and the membrane-associated proteins and glycoproteins characterized by electrophoretic techniques. Major components of the membrane included PAS-I, a sialoglycoprotein of Mr greater than or equal to 200000, the redox enzyme xanthine oxidase and the glycoprotein, butyrophilin. Membrane preparations also contained two other glycoproteins, GP-80 and GP-55, of Mr 80000 and 55000, respectively. Comparison of guinea-pig xanthine oxidase and butyrophilin with proteins from bovine MFGM by peptide mapping procedures, showed that the two proteins in both species were similar, but not identical. GP-55 may also be related to glycoproteins of Mr 45000 and 48000 in the bovine membrane. The integral and peripheral components of guinea-pig MFGM were identified by treating membrane preparations with sodium carbonate solutions at high pH and by partitioning the membrane proteins in solutions of Triton X-114. By these criteria xanthine oxidase and GP-55 appeared to be peripheral components and GP-80 an integral protein of the membrane. PAS-I and butyrophilin displayed hydrophilic properties in Triton X-114 solutions, but could not be removed from membrane preparations with sodium carbonate. Possible reasons for these ambiguous data are discussed. The observed similarity between several of the proteins of guinea-pig and bovine MFGM implies that these proteins may have specific functions related to milk secretion in mammary tissue, e.g. in the budding of milk-fat globules or the exocytosis of milk protein and lactose at the apical surface.
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PMID:Identification and characterization of the principal proteins of the fat-globule membrane from guinea-pig milk. 402 34

Guinea-pig mammary tissue was perfused in vitro, radiolabelled with [35S]methionine and intracellular protein precursors of the milk-fat-globule membrane (FGM) recovered by immunoabsorption techniques. Labelled xanthine oxidase was solely detected in post-microsomal supernatants and butyrophilin in carbonate-washed membranes. A major glycoprotein (Gp 55), was initially present in a membrane-bound form, but after longer perfusion times a fraction of this protein was recovered in the post-microsomal supernatant. These results are discussed with reference to formation of the apically-derived FGM.
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PMID:Protein synthesis in lactating guinea-pig mammary tissue perfused in vitro. II. Biogenesis of milk-fat-globule membrane proteins. 653 41

The proteinaceous coat associated with the cytoplasmic side of milk lipid globule membranes (MLGM) was prepared from bovine and caprine milk by removal of membrane material with non-ionic detergent. These coat preparations, which were enriched in two major proteins, a glycoprotein of polypeptide M, 67 000 (butyrophilin) and a non-glycosylated protein of polypeptide Mr 155 000 (xanthine oxidase), contained small amounts of fatty acids which could not be removed by exhaustive extractions with organic solvents. Both butyrophilin and xanthine oxidase of bovine MLGM were excised and eluted from SDS-polyacrylamide gels and were shown to contain 1 to 2 moles of bound fatty acids per mole of protein. Palmitic, stearic and oleic acids were the predominant protein-bound fatty acids, but no specificity for binding of individual fatty acids was observed. The fatty acids were not rendered soluble in organic solvents when the protein preparations were incubated with phospholipases A or C or with trypsin. Treatment with 0.25 M NaOH at 100 degrees C for 1 h or with 1 M hydroxylamine at 4 degrees C for 16 h, however, released virtually all of the fatty acids associated with these proteins. Similar results were obtained with two major proteins, bands 3 and 4.1, or rat erythrocyte plasma membrane. By contrast, skeletal muscle actin and serum albumin had no bound fatty acids that could be released by alkali treatment. These results show that fatty acids are bound to a number of membrane-associated proteins, both glycosylated and unglycosylated, via linkages that resist purification of the proteins on SDS-polyacrylamide gel electrophoresis and are suggestive of covalent attachment of fatty acids to these proteins. The possible involvement of this acylation in processes characterized by local changes of membrane shape and plasticity is discussed.
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PMID:Tight attachment of fatty acids to proteins associated with milk lipid globule membrane. 706 4

Exocytosis from Weibel-Palade bodies, the secretory granules of vascular endothelial cells, causes the rapid release of von Willebrand factor (vWF), an adhesive glycoprotein involved in primary hemostasis, and cell surface expression of P-selectin, a membrane protein involved in neutrophil binding. Thus, exocytosis may represent a link between hemostasis and inflammation. We investigated the effect of reactive oxygen intermediates (ROIs) on vWF secretion. Incubation of cultured endothelial cells with xanthine oxidase (XO), which generates superoxide anions (O2-), induces a potent, rapid secretory response. However, vWF release was not observed in response to H2O2. Extracellular, subendothelial vWF deposits typically seen after exocytosis from Weibel-Palade bodies were observed after exposure to XO. XO caused a rapid, sustained increase in intracellular free calcium concentration ([Ca2+]i). vWF secretion was markedly inhibited by BAPTA-AM, a cell-permeant calcium chelator. Removal of extracellular calcium did not inhibit vWF release, although the sustained phase of the [Ca2+]i increase was suppressed. These results suggest that XO-induced vWF release is mediated by the initial increase in [Ca2+]i which is caused by calcium mobilization from intracellular stores rather than by calcium influx. Exocytosis from Weibel-Palade bodies may contribute to the pathogenic effect of ROIs in atherosclerosis and inflammation.
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PMID:Reactive oxygen intermediates induce regulated secretion of von Willebrand factor from cultured human vascular endothelial cells. 775 49

The gastric epithelium is exposed to oxygen radicals that are generated within the lumen. Much interest has been focused on the role of mucus in maintaining integrity of the gastric mucosa against oxidants, because gastric mucus may act as a scavenger of oxygen radicals. The aim of this study was to assess the role of mucous glycoprotein in protecting cultured gastric epithelial cells against oxygen radicals. Monolayer cultures of rat gastric mucus-producing cells were studied. Oxygen radicals were generated by hypoxanthine and xanthine oxidase. Cytotoxicity was quantified by measuring chromium 51 release form prelabeled cells. Rate of mucous synthesis was estimated by incorporation of tritiated glucosamine into the cells. The effects of tetraprenyl acetone (a stimulant of mucus production) and N-acetyl-L-cysteine (a mucolytic agent) on oxygen radical-induced damage were determined. Preincubation with tetrapenyl acetone, while stimulating mucous glycoprotein by the cultured cells, caused a dose-dependent reduction of hypoxanthine-xanthine oxidase-induced 51Cr release, reaching maximum protection of the damage by 31% to 50%. In contrast, pretreatment with N-acetyl-L-cysteine potentiated oxygen radical-induced 51Cr release dose dependently. The protective effect of tetraprenyl acetone was significantly abolished by N-acetyl-L-cysteine. Neither tetraprenyl acetone nor N-acetyl-L-cysteine alone under the conditions of this study affected the cellular content of glutathione, which modulates oxygen radical injury to these cells. These results suggest that mucous glycoprotein partially but significantly protects cultured gastric epithelial cells against extracellularly generated oxygen radicals. It seems likely, therefore, that gastric mucus is involved in antioxidant defenses in these cells.
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PMID:Role for mucous glycoprotein in protecting cultured rat gastric mucosal cells against toxic oxygen metabolites. 845 39


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