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)

Ethanolic extracts of Propolis are used as antiinflammatory and wound healing drugs since ancient times. In order to facilitate a comparison of different extracts, the standardization on the basis of quantitative determination of prominent components of these extracts has been substituted for simple biochemical "activity" tests. One of these activity tests bases on the inhibition of peroxidase-catalyzed oxidation of indole acetic acid indicating the presence of a defined mixture of monophenolic and diphenolic compounds. Other tests (diaphorase-catalyzed reductions and xanthine oxidase-catalyzed oxidations) demonstrate significant radical scavenging properties. Water-soluble extracts of propolis exhibit higher antioxidative and inhibitory activities as compared to the ethanolic extract.
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PMID:Biochemical activities of propolis extracts. I. Standardization and antioxidative properties of ethanolic and aqueous derivatives. 829 22

Xanthine oxidoreductase exists in two functionally distinct forms. Under normal conditions, the larger part of the enzyme occurs as an NAD(+)-dependent dehydrogenase form which produces NADH and urate. The dehydrogenase can be transformed under various (patho)physiological conditions to an oxygen-dependent oxidase form which produces oxygen radicals and/or hydrogen peroxide and urate. Tetrazolium salts are used to demonstrate the total activity of both the dehydrogenase and the oxidase form of the enzyme. We have developed a procedure to detect the oxidase form only in unfixed cryostat sections with the use of cerium on the basis of the semipermeable membrane technique. The incubation medium contained hypoxanthine as substrate, cerium ions, and sodium azide to inhibit catalase and peroxidase activity. In a second-step reaction, diaminobenzidine was polymerized in the presence of cobalt ions by decomposition of cerium perhydroxide. Large amounts of final reaction product were found in milk droplets in the acini of lactating bovine mammary gland, whereas milk-secreting epithelial cells contained hardly any final reaction product. In rat duodenum, enzyme activity was found in the cytoplasm of enterocytes and goblet cells but not in the mucus. Control reactions performed in the absence of substrate or in the presence of substrate and allopurinol, a specific inhibitor of xanthine oxidase, were completely negative in both tissues, with the exception of polymorphonuclear leukocytes in the lamina propria of duodenum. The positive nonspecific reaction in these cells was caused by myeloperoxidase activity. We conclude that the present method is specific for the detection of xanthine oxidase activity. Moreover, conversion of the dehydrogenase form into the oxidase form can be prevented by omission of chemical fixation of the tissue in the present procedure.
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PMID:A histochemical procedure for light microscopic demonstration of xanthine oxidase activity in unfixed cryostat sections using cerium ions and a semipermeable membrane technique. 846 47

Effects of 60 and 120 minutes of in-vitro ischaemia on the localization of xanthine oxidase activity were studied in rat intestine and liver. A histochemical method was applied on unfixed cryostat sections using a semipermeable membrane. The incubation medium contained hypoxanthine as substrate, cerium ions which capture the enzyme product, hydrogen peroxide, and sodium azide to inhibit catalase and peroxidase activities. In a second step reaction diaminobenzidine was polymerized in the presence of cobalt ions and hydrogen peroxide by decomposition of cerium perhydroxide. Large amounts of final reaction product were found in the cytoplasm of enterocytes and goblet cells of control small intestine. When the incubation was performed in the absence of substrate or in the presence of substrate and allopurinol, a specific inhibitor of xanthine oxidase activity, no reaction product was found. After 60 and 120 minutes of storage of tissue blocks at 37 degrees C enzyme activity was significantly reduced in the apical region of epithelial cells, whereas a high activity was present in the basal region of these cells. A very low xanthine oxidase activity was found in rat liver. Highest activity was present in endothelial cells, whereas in liver parenchymal cells, a more pronounced activity was found in pericentral than in periportal hepatocytes. Ischaemia up to 120 minutes did not affect the enzyme activity in livers. It was concluded that increased xanthine oxidase activity during ischaemia may not be responsible for cell damage during reperfusion in contrast with assumptions in the literature.
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PMID:The effect of ischaemia on xanthine oxidase activity in rat intestine and liver. 847 32

The goal of this study was to test the hypothesis that endotoxin-induced bacterial translocation is the result of a selective decrease in intestinal blood flow that causes an oxidant-mediated intestinal mucosal injury. To accomplish this goal, 116 instrumented rats receiving a nonlethal dose of endotoxin (5 mg/kg IP) or saline were studied. Organ blood flow and cardiac output were measured using the microsphere technique and intestinal permeability was measured both by the blood to luminal clearance of 51Cr-EDTA and by horseradish peroxidase. Cardiac output was higher in the endotoxin-treated group than in the saline group (76 +/- 12 versus 95 +/- 17 mL/min; p < 0.05). Although endotoxin induced a hyperdynamic state, blood flow to the distal ileum and cecum was selectively decreased by 35%-50% (p < 0.01), whereas blood flow to the rest of the intestine, spleen, pancreas, and liver was normal. Furthermore, blood flow to the ileal mucosa was decreased to a greater extent than to the remainder of the gut wall (p < 0.05). Small bowel permeability to 51Cr-EDTA was increased at sites of decreased blood flow (ileum) but not at sites of normal (jejunum) blood flow. Allopurinol, a competitive inhibitor of xanthine oxidase, ameliorated the endotoxin-induced decrease in ileal blood flow as well as the increase in ileal permeability. Thus these studies support the hypothesis that endotoxin-induced mucosal injury is the result of an ischemia reperfusion-mediated injury of the distal small intestine and cecum.
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PMID:Mechanisms of endotoxin-induced intestinal injury in a hyperdynamic model of sepsis. 849 2

Bio- and chemiluminescence have proved sensitive enough to compete with chromogenic and radioisotopic tracers for in situ detection. However, they must also provide a discriminant morphological analysis of the specific signal. We have tested seven bio- or chemiluminescent reagents for tissue antigen and nucleic acid detection by immunocytochemistry (ICC) or in situ hybridization (ISH). They were based on luminescent detection of peroxidase, alkaline phosphatase, beta-galactosidase or xanthine oxidase. We also explored whether high molecular weight polymers could increase the spatial definition of the photon emission. An ICCD camera was used to collect the light signal provided by immunolabelling of endothelial cells and by ISH of human papilloma virus on cell smears. Among the enzyme-luminescent substrate combinations tested, the enhanced luminol chemiluminescence (ECL) gave the best resolution of the specific signal. The other systems were mainly hampered by a high diffusion of the reaction product over the tissue section. Unfortunately, in this case, the high molecular weight polymers tested were inefficient. However, the addition of polyvinylalcohol (PVA) or polyvinylpyrrolidone (PVP) significantly improved respectively the definition and intensity of ECL photon emission. We demonstrate that chemiluminescence gives a morphological resolution allowing histological examination. The extension of this new application, now depends on physicochemical adaptation of chemiluminescent reagents to the constraints of tissue detection.
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PMID:Comparison of seven bio- and chemiluminescent reagents for in situ detection of antigens and nucleic acids. 853 6

Myeloperoxidase (MPO) is a lysosomal enzyme found in the primary granules of mammalian neutrophils. Together with MPO, peroxide and halide form a system of defense against bacteria. The present investigation was undertaken to study the bactericidal effects of the bovine-MPO/peroxide/halide system on pathogenic bacteria associated with bovine mastitis. We demonstrated that MPO together with oxidizing agents generated by xanthine oxidase, hypoxanthine and chloride form a potent antibacterial system against the common udder pathogens Staphylococcus aureus, Streptococcus uberis, Streptococcus agalactiae, Streptococcus dysgalactiae and Escherichia coli in a synthetic medium. However, when milk was added to the reaction mixture, the bactericidal properties of this enzyme system were completely inhibited. Loss of bactericidal activity in the milk-containing cultures was unable to be restored by increasing the concentration of MPO. Nor did an increase in concentrations of hypoxanthine and xanthine oxidase, or the replacement of the above-mentioned peroxidase generating system with a high concentration of hydrogen peroxide, significantly elevated the bactericidal activity that was inhibited by milk. The addition of bovine serum albumin to the synthetic medium reduced the bactericidal activity of the MPO/peroxide/chloride system in a dose-dependent manner. Therefore, milk proteins probably form adducts with strong bactericidal agents that are generated by the MPO system and thereby reduce the bactericidal potential of this system.
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PMID:Bactericidal activity of the bovine myeloperoxidase system against bacteria associated with mastitis. 856 Jul 39

In the present study, we investigated the effects of high levels of dietary fish oil on the growth of MX-1 human mammary carcinoma and its response to mitomycin C (MC) treatment in athymic mice. We found that high levels of dietary fish oil (20% menhaden oil + 5% corn oil, w/w) compared to a control diet (5% corn oil, w/w) not only lowered the tumor growth rate, but also increased the tumor response to MC treatment. We also found that high levels of dietary fish oil significantly increased the activities of tumor xanthine oxidase and DT-diaphorase, which are proposed to be involved in the bioreductive activation of MC. Since menhaden oil is highly unsaturated, its intake caused a significant increase in the degree of fatty acid unsaturation in tumor membrane phospholipids. This alteration in tumor membrane phospholipids made the tumor more susceptible to oxidative stress, as indicated by the increased levels of both endogenous lipid peroxidation and protein oxidation after feeding the host animals the menhaden oil diet. In addition, the tumor antioxidant enzyme activities, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPOx), and glutathione S-transferase peroxidase (GSTPx), were all significantly enhanced by feeding a diet high in fish oil. MC treatment caused further increases in tumor lipid peroxidation and protein oxidation, as well as in the activities of CAT, SOD, GPOx, and GSTPx, suggesting that MC causes oxidative stress in this tumor model which is exacerbated by feeding a diet high in menhaden oil. Thus, feeding a diet rich in menhaden oil decreased the growth of human mammary carcinoma MX-1, increased its responsiveness to MC, and increased its susceptibility to endogenous and MC-induced oxidative stress, and increased the tumor activities of two enzymes proposed to be involved in the bioactivation of MC, that is, DT-diaphorase and xanthine oxidase. These findings support a role of these two enzymes in the bioactivating of MC and indicate that the type of dietary fat may be important in tumor response to therapy.
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PMID:Dietary menhaden oil enhances mitomycin C antitumor activity toward human mammary carcinoma MX-1. 856 32

4-Aminodiphenylamine (N-phenyl-1,4-phenylenediamine, CAS 101-54-2) and its water-soluble HCl salt (CAS 2198-59-6) were demonstrated to be efficient mediators for glucose oxidase, lactate oxidase, xanthine oxidase, and lysine oxidase. Using cyclic voltammetry, single oxidative peak potentials were observed for scans ranging from 0 to 0.5 V vs Ag/AgCl. The half-wave potential for both preparations was 0.11 V vs Ag/AgCl at pH 7 and decreased 59 mV per unit pH increase. Peak current data were analyzed to estimate diffusivities of 0.8 x 10(-5) cm2/s for soluble 4-ADPA HCl, and 2.36 x 10(-5) cm2/s for 4-ADPA solubilized in 2.5 mM 2-hydroxypropyl-beta-cyclodextrin. The overall second-order kinetic constants (k) for the reaction of reduced glucose oxidase with oxidized 4-ADPA HCl and 4-ADPA in cyclodextrin were estimated to be 1.8 x 10(5) and 1.7 x 10(-5) M-1 s-1, respectively, using cyclic voltammetry measurements at varied scan rates and enzyme concentrations. Both preparations proved to be suitable electron acceptors for horseradish peroxidase, as indicated by changes in absorbance spectra upon oxidation or reduction. The electrochemical and spectral behavior of the preparations were applied in conjunction with glucose oxidase to devise mediated amperometric and hydrogen peroxide-coupled spectrophotometric assays for glucose. The results of both assays compared favorably with the hexokinase reference method.
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PMID:Dual functionalities of 4-aminodiphenylamine in enzymatic assay and mediated biosensor construction. 859 91

Aromatic amines are mammary carcinogens in rodents and exposure to aromatic amines may be associated with increased risk of breast cancer in women. Peroxidases present in milk can oxidize aromatic amines to reactive electrophiles which bind to DNA and induce mutations. Hydrogen peroxide, required for peroxidase-dependent oxidations, is supplied by milk xanthine oxidase and by the respiratory burst of neutrophils, cells which are present in milk and activated by exposure to it. In this paper, I propose that lactoperoxidase and myeloperoxidase activate aromatic amines, within the breast ducts, and that these enzymes play a crucial role in the chemical induction of breast cancer.
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PMID:The role of peroxidase-catalyzed activation of aromatic amines in breast cancer. 867 8

Bio-normalizer, a natural Japanese health food prepared by the fermentation of Carica papaya, exhibits therapeutic properties against various pathologies including tumors and immunodeficiency. To understand the mechanism of bio-normalizer's therapeutic effects, we studied its action on the production of active oxygen species in cell-free systems (the Fenton reaction, the xanthine-xanthine oxidase system, and the hydrogen peroxide-hypochloride or hydrogen peroxide-horseradish peroxidase systems) and by human blood neutrophils and erythrocytes and rat peritoneal macrophages. Bio-normalizer efficiently inhibited the formation of oxygen radicals in cell-free systems and partly decreased spontaneous and menadione-stimulated superoxide production by erythrocytes, but manifested both stimulatory and inhibitory effects on oxygen radical release by dormant and activated phagocytes (neutrophils and macrophages). We suggest that bio-normalizer is able to enhance the intracellular production of innocuous superoxide ion and, at the same time, to diminish the formation of reactive hydroxyl radicals, perhaps by the inactivation of ferrous ions, the catalysts of the superoxide-driven Fenton reaction. We also propose that the normalization of an organism's superoxide level is one of the molecular mechanisms of bio-normalizer activity.
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PMID:Effects of bio-normalizer (a food supplementation) on free radical production by human blood neutrophils, erythrocytes, and rat peritoneal macrophages. 874 24


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