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

We studied the effects of oxygen-derived free radicals on the ultrastructure of brain cortical slices and the release of fatty acids from phospholipids of crude synaptosomes. Xanthine oxidase, hypoxanthine, and ADP-Fe3+, a free-radical-generating system, caused swelling of cellular processes and mitochondria. The oxygen-derived free radicals also caused the rapid release and accumulation of endogenous polyunsaturated fatty acids (PUFA) from membrane phospholipids as determined by high-performance liquid chromatography (HPLC). Furthermore, [3H]-arachidonic acid was also rapidly released from prelabeled phospholipids concomitant with a decrease in radioactivity in various phospholipid fractions. The radioactivities of neutral lipids including diacylglycerols were unchanged by free radicals. These data indicate that the activation of phospholipase A2 and the release of PUFA may have overt effect on membrane integrity and the subsequent development of cellular injury and brain edema.
 ...
PMID:Release of polyunsaturated fatty acids from phospholipids and alteration of brain membrane integrity by oxygen-derived free radicals. 651 90

Evidence is presented for a sensitive method useful for the detection of hydroxyl free radical generation in various systems. The methodology employs high pressure liquid chromatography with electrochemical detection (LCED) for the quantification and identification of the hydroxylation products from the reaction of OH with both phenol and salicylate. A detection limit of less than 1 pmol for the hydroxylation products has been achieved with electrochemical detector responses linear over at least three orders of magnitude. Detection and quantitation of the hydroxylation products obtained and formed during OH generation from biologically meaningful systems have been demonstrated. The three systems utilized were ADP/FE(II)/H2O/, hypoxanthine/xanthine oxidase plus chelated iron, and UV photolysis of H2O2.
 ...
PMID:Sensitive assay of hydroxyl free radical formation utilizing high pressure liquid chromatography with electrochemical detection of phenol and salicylate hydroxylation products. 653 May 10

We studied the cerebral effects of oxygen-derived free radicals generated from the xanthine oxidase/hypoxanthine/ADP-Fe3+ system. Xanthine oxidase/hypoxanthine/ADP-Fe3+ solution (0.1 ml) was infused into caudate putamen, and brain was frozen rapidly in situ. Brain water and sodium content increased concomitant with decreased potassium content at 24 hours and 48 hours after the infusion. The degree of brain edema and injury depended on the dose of xanthine oxidase. Spongy neuropil and neuronal cytoplasmic vacuoles were seen at 2 hours, with an infiltration by polymorphonuclear leukocytes at 24 hours, followed by lipid-laden macrophages and reactive astrocytes. Leakage of fluorescent dye into neuropil was seen at 2 hours, but not later. These data suggest that oxygen-derived free radicals damage endothelial cells of the blood-brain barrier; the brain injury is characterized by edema and by structural damage of neurons and glia.
 ...
PMID:Brain injury, edema, and vascular permeability changes induced by oxygen-derived free radicals. 654 10

The synthesis of thromboxane B2 is increased in platelets from rabbits with experimental hypercholesterolemia, but the increase is not due to increased phospholipids hydrolysis. We have clarified the mechanism for the increased thromboxane synthesis. The biosyntheses of prostaglandin H2 and thromboxane B2 were unaffected by superoxide dismutase, xanthine oxidase, mannitol, or benzoate in other experiments designed to study the possible involvement of reactive oxygen species. These results suggest that O2.- and OH were not likely to be involved as intermediates in the synthesis of prostaglandin H2 and thromboxane B2 in platelets. The rate of prostaglandin H2 biosynthesis was promoted in deuterium oxide, and this deuterium oxide enhancement effect was reversed by 2,5-diphenylfuran, suggesting that singlet oxygen may be involved in prostaglandin H2 biosynthesis. The biosynthesis of prostaglandin H2 was promoted by ADP-Fe3+ but inhibited by EDTA and EDTA-Fe3+. The effect of ADP-Fe3+ could not be replaced by EDTA-Fe3+. The effects of glutathione, glutathione peroxidase and H2O2 on cyclooxygenase and thromboxane synthetase were studied by using partially purified enzymes and platelet microsomes. Glutathione and glutathione peroxidase inhibited the activity of cyclooxygenase but did not inhibit that of thromboxane synthetase. H2O2 caused the inactivation of cyclooxygenase, but the addition of H2O2 did not inhibit the formation of thromboxane B2 from prostaglandin H2. An examination of glutathione concentration and glutathione peroxidase activity in platelets from normal and experimentally hypercholesterolemic rabbits demonstrated that both were decreased in platelets from later group. The observed alterations in glutathione levels and glutathione peroxidase activity are large enough to cause increased thromboxane B2 synthesis in platelets but the possibility that other unidentified factors may also contribute cannot be excluded.
 ...
PMID:Increased thromboxane B2 biosynthesis in platelets. 681 1

Respiratory activity of isolated rat brain mitochondria was measured following in vitro exposure to oxygen radicals. The radicals were generated by hypoxanthine and xanthine oxidase in the presence of a suitable iron chelate and caused a severe inhibition of respiration stimulated by phosphate plus ADP (with malate + glutamate as substrate). The damage could be prevented by catalase or high concentrations of mannitol, but not by superoxide dismutase. A similar effect was observed when hypoxanthine and xanthine oxidase were replaced by glucose and glucose oxidase or by hydrogen peroxide. Most of the findings indicate that the hydroxyl radical is the damaging agent. It is concluded that brain mitochondria exposed to oxygen radicals in vitro show an inhibition of respiratory activity similar to that reported by other investigators as occurring in mitochondria in vivo following transient cerebral ischemia. Therefore, oxygen radicals may contribute to this type of cell damage.
 ...
PMID:Respiratory activity of isolated rat brain mitochondria following in vitro exposure to oxygen radicals. 684 68

Generation of H2O2 by rat liver mitochondria with choline, glycerol 1-phosphate and proline as substrates has been shown by using high-concentration phosphate buffer. Rates obtained under these conditions were higher and more consistent as compared with the earlier reports with high-concentration mannitol/sucrose/Tris buffer. Sulphate ions could replace phosphate indicating a requirement for a high concentration of oxygen-containing anions. H2O2 generation was dependent on the presence of native mitochondria and substrate. Maximal rates with various substrates were found to be the same as with succinate. Values of Km and Vmax for H2O2 generation were considerably less than those obtained for respective dehydrogenase activities, measured by dye reduction. Scavengers of O2-. and OH. inhibited generation of H2O2. ATP, ADP, thyronine derivatives and a number of phenolic compounds also showed very potent inhibitory effects of H2O2 generation, whereas phenyl compound had no effect. Phenolic compounds did not have any effect on mitochondrial superoxide dismutase and choline dehydrogenase activities as well as on O2-. generation by the xanthine-xanthine oxidase system. Inhibition by phenolic compounds may have potential for regulation of the intracellular concentration of H2O2, that is not considered to have a "second messenger' function.
 ...
PMID:Inhibition of H2O2 generation in rat liver mitochondria by radical quenchers and phenolic compounds. 730 14

Lazaroids, 21-aminosteroids without gluco- and mineralocorticoid activity, protect against oxidative injury in nervous system cells and may therefore also have a potential for treatment of pancreatitis, where oxidative stress contributes to cell injury. The present study evaluates the protective potential of the lazaroids U-78518F, U-74500A, and U-74389F against damage to isolated pancreatic acinar cells exposed to two models of oxidative stress: (a) a XOD/HX model, consisting of xanthine oxidase, hypoxanthine, and chelated FeCl3; and (b) an ADP/Fe model, consisting of FeSO4 and the reducing agent ADP. Both models caused time-dependent cell injury as assessed by uptake of trypan blue and release of lactate dehydrogenase. Short-term peak production of free radicals in the XOD/HX model--as monitored by the deoxyribose assay--was more injurious to cells than continuous radical generation at lower levels in the ADP/Fe model. In general, lazaroids at 1-10 microM reduced oxidative damage and deoxyribose oxidation in both models. The degree of reduction of cell damage and deoxyribose oxidation depended on the type and concentration of the lazaroid and the model used. Lazaroid concentrations < 0.1 microM were ineffective, and concentrations > 50 microM even accelerated cell injury, although lazaroids still served as scavengers at high concentrations. At least part of the noxious effects of high lazaroid concentrations is due to nonspecific membrane damage because these concentrations caused cell injury also in the absence of oxidative stress. The limited range of protective concentrations has to be observed in further in vivo studies. Interestingly, acinar cells in the absence of lazaroids also reduced radical-induced deoxyribose degradation.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Lazaroids protect isolated rat pancreatic acinar cells against damage induced by free radicals. 747 66

To gain insight into the gene regulation and signal transduction effects of active oxygen in tumour promotion and progression, we studied the effect of active oxygen generated extracellularly by xanthine/xanthine oxidase (X/XO) in promotion-insensitive (P-), promotion-sensitive (P+) and transformed (Tx) mouse epidermal JB6 cells. Active oxygen inhibited growth, particularly of P- cells and increased poly ADPR transferase activity and PKC activity more significantly in P- cells. No phenotypic differences in the distribution pattern of PKC isotypes alpha, beta and gamma were seen in JB6 cells. PKC alpha was expressed abundantly, whereas beta and gamma were not detected. Basal levels of the antioxidant enzymes catalase and CuZn. Superoxide dismutase were higher in P+ and Tx cells. X/XO resulted in an initial decrease in the activity of these enzymes, followed by recovery or transient induction in Tx and P+ cells. X/XO induced c-myc and c-fos expression in JB6 cells, with c-fos induction being more pronounced in P- cells, whereas a biphasic increase in c-jun was seen in P+ cells. These early genes may play a role in proliferation whereas post-translational poly ADP-ribosylation and, perhaps, phosphorylation suggest a genetic-epigenetic mechanism in oxidant tumour promotion and progression.
 ...
PMID:The effect of active oxygen generated by xanthine/xanthine oxidase on genes and signal transduction in mouse epidermal JB6 cells. 760 57

The present study investigated the effect of the administration of oxypurinol (40 mg/kg), an inhibitor of xanthine oxidase, on adenosine and adenine nucleotide levels in the rat brain during ischemia and reperfusion. The brains of the animals were microwaved before, at the end of a 20-min period of cerebral ischemia, and after 5, 10, 45, and 90 min of reperfusion. Cerebral ischemia was elicited by four-vessel occlusion with arterial hypotension to 45-50 mm Hg. Adenosine and adenine nucleotide levels in the oxypurinol-pretreated (administered intravenously 20 min before ischemia) rats were compared with those in nontreated animals exposed to the same periods of ischemia and reperfusion. Oxypurinol administration resulted in significantly elevated ATP levels at the end of ischemia and 5 min after ischemia, but not at 10 min after ischemia. ADP levels were also elevated, in comparison with those in the control rats, at the end of the ischemic period. Conversely, AMP levels were significantly reduced at the end of ischemia and during the initial (5 min) period of reperfusion. Adenosine levels were lower in oxypurinol-treated rats, during ischemia, and in the initial reperfusion phase. Oxypurinol administration resulted in a significant increase in the energy charge both during ischemia and after 5 min of reperfusion. Physiological indices, namely, time to recovery of mean arterial blood pressure and time to onset of respiration, were also shortened in the oxypurinol-treated animals. These beneficial effects of oxypurinol may have been a result of its purine-sparing (salvage) effects and of its ability to inhibit free radical formation by the enzyme xanthine oxidase. Preservation of high-energy phosphates during ischemia likely contributes to the cerebroprotective potency of oxypurinol.
 ...
PMID:Oxypurinol-enhanced postischemic recovery of the rat brain involves preservation of adenine nucleotides. 772 3

The synthesis of uric acid from purine bases, nucleosides and nucleotides has been measured in reaction mixtures containing rat liver supernatant and each one of the following compounds at 1 mM concentration (except xanthine, 0.5 mM and guanosine and guanine, 0.1 mM). The rates of the reaction, expressed as nanomoles of uric acid synthesized g-1 of wet liver min-1 were: ATP, 10; ADP, 37; AMP, 62; adenosine, 108; adenine 6; adenylosuccinate, 9; IMP 32; inosine, 112; hypoxanthine, 50; GTP, 19; GDP, 19; GMP, 27; guanosine, 34; guanine, 72; XMP, 10; xanthosine, 24; xanthine, 144. These figures divided by 55 correspond to nanomoles of uric acid synthesized min-1 per mg-1 of protein. The rate of synthesis of uric acid obtained with each one of those compounds at 0.1 and 0.05 mM concentrations was also determined. ATP (1 mM) strongly inhibited uric acid synthesis from 0.05 mM AMP (91 per cent) and from 0.05 mM ADP (88 per cent), but not from adenosine. CTP or UTP (1 mM) also inhibited (by more than 90 per cent) the synthesis of uric acid from 0.05 mM AMP. Xanthine oxidase was inhibited by concentrations of hypoxanthine higher than 0.012 mM. The results favour the view that the level of uric acid in plasma may be an index of the energetic state of the organism. Allopurinol, besides inhibiting uric acid synthesis, reduced the rate of degradation of AMP. The ability of crude extracts to catabolize purine nucleotides to uric acid is an important factor to be considered when some enzymes related to purine nucleotide metabolism, particularly CTP synthase, are measured in crude liver extracts.
 ...
PMID:Uric acid synthesis by rat liver supernatants from purine bases, nucleosides and nucleotides. Effect of allopurinol. 783 12


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>