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Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Content and catalytic activity of cytochrome P-450 were studied using amidopyrine as a substrate of the I type and aniline as a substrate of the II type. In hypoxia content of cytochrome P-450 and metabolism of amidopyrine were increased, while the enzyme content and the substrate metabolism were decreased in hyperoxia.
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PMID:[A system of liver microsomal oxidation in hypoxia and hyperoxia]. 342 Aug 13

Hyperbaric oxygen (HPO) was administered to rats (100% O2 at 2.8 atm for 90 min) immediately or 1 hr after severe carbon tetrachloride (CCl4) intoxication in order to study the mechanisms of protection against hepatocellular injury by hyperoxia. Slight to moderate hepatocellular injury was observed, particularly by morphologic criteria, 4 hr after CCl4 intoxication. Little cell death was observed; 24 hr after CCl4, 20% of the untreated animals died. In the survivors, the following typical changes occurred in the liver: extensive hepatocellular swelling, vacuolization and necrosis; severe ultrastructural alterations; binding of CCl4 to microsomal lipids; elevation of lipid peroxidation products (conjugated dienes); little decrease in cytochrome b5 and severe decrease in cytochrome P-450 levels. Serum transaminase (alanine aminotransferase and aspartate aminotransferase) levels were elevated. Immediate treatment with HPO prevented the mortality and markedly decreased the hepatocellular necrosis 24 hr after intoxication. Immediate HPO treatment did not lower the levels of free CCl4 in the liver. However, the rise in lipid peroxidation products caused by CCl4 intoxication at 4 hr was reduced. Delayed treatment with HPO (1 hr after CCl4) prevented the mortality but was less effective in preventing necrosis. Some hepatocellular protection was still demonstrable. In particular, the rise in lipid peroxidation products was reduced. Hyperoxia protects hepatocytes against CCl4 toxicity. The rapid decline in protective effect within 60 min of intoxication suggests that hyperoxia inhibits CCl4 activation and/or damage from molecular intermediates. Hyperoxia has little effect on the progression of sublethal injury to cell death in the livers of CCl4-intoxicated rats.
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PMID:Protection of hepatocytes with hyperoxia against carbon tetrachloride-induced injury. 653 53

Interferon inducers, poly I:poly C, endotoxin, hepatic RNA, and Tilorone, were administered to rats at different time points in relation to the onset of hyperoxic exposure (O2 greater than 97%). All interferon inducers tested significantly reduced the mortality of rats when compared with the control groups. In hyperoxia alone, malondialdehyde, a product of lipid peroxidation, was significantly increased and the microsomal enzyme NADPH cytochrome c reductase decreased as measured in the whole lung. With the administration of either endotoxin or poly I:poly C these two parameters remained within the range of control values. These data suggest that the administration of interferon inducers protects against hyperoxic microsomal damage. After the administration of these interferon inducers with or without hyperoxia the increased activity of heme oxygenase and marked reduction of the heme content of microsomes were demonstrated. Since cytochrome P-450 and b5 are the major hemoproteins of microsomes and the known source of oxygen-free radical generation, the results obtained in this study appear to indicate that the depression of the hemoprotein of microsomes by the administration of interferon inducers may be largely responsible for the protective effects of these agents against hyperoxia.
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PMID:Protective effect of interferon inducers against hyperoxic pulmonary damage. 654 2

Cells that are exposed to free radicals have increased levels of DNA strand breaks with accumulation of the tumor suppressor protein p53, which induces cell cycle arrest and/or apoptosis. Because oxidants injure pulmonary epithelial cells, it was hypothesized that exposure to hyperoxia promotes DNA strand breaks in lung epithelium, resulting in increased expression of p53 and loss of epithelial cell function. Adult male C57Bl/6J mice were exposed to > 95% oxygen for 72 h and DNA integrity was determined in their lungs by terminal transferase immunoreactivity. Both nonimmunoreactive and lightly stained nuclei were observed in cells comprising the airway and parenchyma. Exposure to hyperoxia resulted in a marked increase in the intensity of nuclear staining in distal bronchiolar epithelium and alveolar epithelial and endothelial cells. Airway epithelial cells from control lungs contained detectable levels of p53 protein, which markedly increased in both nuclei and cytoplasm of distal bronchiolar epithelial cells and to a lesser extent in alveolar epithelial cells that were morphologically consistent with type II cells. Western and Northern blot analyses revealed that hyperoxia increased total lung p53 protein expression but not levels of mRNA. Changes in terminal transferase immunoreactivity and p53 expression were not observed in large airway cells, fibroblasts underlying distal airway, or smooth muscle cells. Expression of SP-B mRNA modestly increased and Clara cell secretory protein and cytochrome P-450 2F2 mRNAs decreased, providing additional evidence that hyperoxia injured pulmonary epithelial cells. These findings support the concept that hyperoxia damages DNA of pulmonary epithelial cells, which respond by accumulating p53 and changes in epithelial cell-specific gene expression.
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PMID:Exposure to hyperoxia induces p53 expression in mouse lung epithelium. 944 44

In this investigation, we tested the hypothesis that the cytochrome P-450 (CYP) inhibitor 1-aminobenzotriazole (ABT) alters the susceptibility of rats to hyperoxic lung injury. Male Sprague-Dawley rats were treated i.p. with ABT (66 mg/kg), i.v. with N-benzyl-1-aminobenzotriazole (1 micromol/kg), or the respective vehicles, followed by exposure to >95% oxygen for 24, 48, or 60 h. Pleural effusion volumes were measured as estimates of hyperoxic lung injury, and lung microsomal ethoxyresorufin O-deethylation (EROD) (CYP1A1) activities and CYP1A1 apoprotein levels were determined by Western blotting. ABT-pretreated animals exposed to hyperoxia died between 48 and 60 h, whereas no deaths were observed with up to 60 h of hyperoxia in vehicle-treated animals. In addition, three of four ABT-treated rats exposed to hyperoxia for 48 h showed marked pleural effusions. Exposure of vehicle-treated rats to hyperoxia led to 6.3-fold greater lung EROD activities and greater CYP1A1 apoprotein levels than in air-breathing controls after 48 h, but both declined to control levels by 60 h. Liver CYP1A1/1A2 enzymes displayed responses to hyperoxia and ABT similar to the effects on lung CYP1A1. N-Benzyl-1-aminobenzotriazole markedly inhibited lung microsomal pentoxyresorufin O-depentylation (principally CYP2B1) activities in air-breathing and hyperoxic animals but did not affect lung EROD or liver CYP activities. In conclusion, the results suggest that induction of CYP1A enzymes may serve as an adaptive response to hyperoxia, and that CYP2B1, the major pulmonary CYP isoform, does not contribute significantly to hyperoxic lung injury.
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PMID:Potentiation of oxygen-induced lung injury in rats by the mechanism-based cytochrome P-450 inhibitor, 1-aminobenzotriazole. 1064 Feb 92

Analyzing his own findings and the data available in the literature, the author has found that free radicals are a connecting link in the development of early and prolonged adaptation. With rapid adaptation, they make a weighty contribution to the body's bactericidal protection and antimicrobial constitutional immunity. This role is mainly played by the oxygen-dependent phagocytic bactericidal system that generates active oxygen forms and by the inducible arginine-dependent connective tissue cell system that synthesizes nitrogen oxide. While performing, the above enzymatic systems spend their cell energy resources on two concurrent processes: the formation of free radical products and the work of ionic pumps that restore an intracellular ionic and osmotic balance. This causes the accelerated expenditure of the body's energy "currency" ATP and the development of energy deficiency in the cells and tissues. Energy shortage serves as a signal for triggering the cellular genetic apparatus to primarily induce the increased development of the cell energy system, namely that of mitochondria, and the activation of the key systems responsible for steady-state long-term individual adaptation of the immune system, antioxidative protection, etc. It has been now ascertained that there is a common pathogenetic link (excessive production of free radicals) in the mechanism responsible for the influence of not only infections on the body, but other environmental factors (fibrogenic dust, ionizing or ultraviolet radiation, cooling, toxic agents oxidized on cytochrome P-450, hypoxia, hyperoxia, etc.) and vital functions (physical overstrain, emotional stress, informational overload, etc.). The above factors all cause the same metabolic change in different ways: the production of higher quantities of active oxygen forms, nitrogen oxide, and other radical products. So the generation of free radicals is an universal connecting link of early and prolonged adaptation. The fact that there is a common link (the excessive production of radicals) in the mechanism of influence of environmental factors and vital activities makes the most important biological reserve (cross adaptation that lies in higher resistance to the whole complex of active influences at adaptation to one of them) serve as a preventive means. The most rapid increase in the production of free radicals and the development of energy-rich products are achieved by hypoxia. So the adaptive and preventive effect of dosage hypoxia are the most pronounced.
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PMID:[Free radical oxidation as a link of early and prolonged adaptation to environmental factors]. 1151 77


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