Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ability of niacin to relieve the growth-inhibiting effect of hyperoxia on Escherichia coli can be attributed to the dioxygen sensitivity of quinolinate synthetase. The activity of this enzyme within E. coli was diminished by exposure of the cells to 4.2 atm O2, while the activity in extracts was rapidly decreased by 0.2 atm O2. Neither catalase nor superoxide dismutase afforded detectable protection against the inactivating effect of O2, indicating that H2O2 and O2- were not significant intermediates in this process. Nevertheless, H2O2 at 1.0 mM did inactivate quinolinate synthetase, even under anaerobic conditions and in the absence of catalatic activity which might have generated O2. Addition of paraquat to aerobic cultures of E. coli caused an inactivation of quinolinate synthetase, which may be explained in terms of an increase in the production of H2O2. The O2-dependent inactivation of quinolinate synthetase in extracts was gradually reversed during anaerobic incubation and this reactivation was blocked by alpha, alpha'-dipyridyl or by 1,10-phenanthroline. The sequence of the quinolinate synthetase "A" protein contains a--cys-w-x-cys-y-z-cys--sequence, which is characteristic of (Fe-S)4-containing proteins. This sequence, together with the effect of the Fe(II)-chelating agents, suggests that the O2-sensitive site of quinolinate synthetase is an iron-sulfur cluster which is essential for the dehydration reaction catalyzed by the A protein.
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PMID:Quinolinate synthetase: the oxygen-sensitive site of de novo NAD(P)+ biosynthesis. 184 9

Impaired lung development has been demonstrated in neonatal animals exposed to hyperoxia. High lung cys-leukotriene levels may be a contributing factor towards the increase in oxygen toxicity. We investigated the effect of cysteinyl-leukotriene inhibition using the receptor antagonist, montelukast (MK, Singulair), on hyperoxia-induced changes in lung parenchymal structure in neonatal rat pups. Rat pups were exposed to 21% O(2) (air) or 50% O(2) (moderate hyperoxia) from days 1-14 after birth, and were administered the cys-leukotriene receptor antagonist MK (1 mg/kg/day) or normal saline from days 4-14. Somatic growth and morphometric measurements were done on day 15. There was a significant increase in bronchoalveolar lavage fluid cysteinyl-leukotriene levels (+61.9%) when animals were exposed to hyperoxia. O(2) exposure significantly decreased the specific internal surface area by 13%. There was a nonsignificant 5.8% and 19.6% increase in mean chord length and mean alveolar diameter, respectively, as well as an 8.6% decrease in lung volume to body weight ratio. Inhibition of only one arm of the arachidonic-acid cascade by MK was not sufficient to prevent these oxygen-induced changes.
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PMID:Montelukast does not protect against hyperoxia-induced inhibition of alveolarization in newborn rats. 1274 41