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

Water-insoluble proteins of rat brain were studied as affected by hyperbaric oxygenation (oxygen pressure 6 at.ga. convulsion state). Solubilization of proteins under effect of hyperoxia and triton X-100 increases by 32-81%. Changes in the amino acidic composition of proteins extracted by 0.5% triton X-100 are characterized by an increase in the amount of aspartic acid, cystin, leucine and isoleucine and by a decrease in the amount of histidine, arginine and methionine. Electrophoresis in 7.5% polyacrylamide gel of proteins in the 0.5% triton X-100 extract showed changes in the number and mobility of protein bands.
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PMID:[Effect of hyperoxia on water-insoluble proteins of the brain]. 68 68

The transport activity for cystine in cultured human fibroblasts decreased after incubation of the cells under a low oxygen concentration. After the incubation for 48 h under 3% oxygen, the Vmax of the transport was decreased to less than one-third of that of the control cells, with little change in Km. The similar transport activity was observed in the cells cultured under 3% oxygen for 10-40 days with several times of passages. When these low oxygen-cultured cells were incubated under room air, the activity was enhanced with a lag of about 4 h and was almost completely restored within 24 h. This restoration required protein synthesis. The cystine transport activity increased by 50% after exposure of the cells to hyperoxia (40% oxygen). From these results it is concluded that the transport activity for cystine is induced by oxygen. In contrast, little change in the transport activities for alanine and leucine occurred in the cells exposed to the corresponding hypoxia or hyperoxia. Since the cystine transported into the cells is reduced to cysteine and the cysteine readily exits to the culture medium where it autoxidizes to cystine, a cystine-cysteine cycle across the plasma membrane has been postulated. Since the autoxidation of cysteine in the culture medium was markedly slowed down under the low oxygen concentration, the change in the cystine transport activity in response to the oxygen concentration was regarded as pertinent. Induction of the cystine transport activity may constitute a protective mechanism against the oxidative stress, to which the culture cells are exposed, by providing the cells with cysteine which is mainly incorporated into glutathione.
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PMID:Induction of cystine transport activity in human fibroblasts by oxygen. 280 85

We studied the influence of prolonged exposure to hyperoxia (O(2) > 98%) on protein synthesis and on the ultrastructure of the granular pneumocyte. To study protein synthesis, as indicated by l-[U-(14)C]-leucine incorporation into protein, lung slices were incubated with radioactive leucine and a surface-active fraction was obtained by ultracentrifugation of lung homogenates. We found that, following an initial depression in protein synthesis after 48 h of hyperoxia, protein synthesis in rats exposed to oxygen for 96 h rose to greater than control levels. This increase in protein synthesis was noted in whole lung protein and in protein present in the surface-active fraction. Stereologic ultrastructural analysis of granular pneumocytes revealed that the lamellar bodies occupy the same percentage of cytoplasmic volume in oxygen-exposed and control rats after 96 h; a previous study had shown lamellar bodies of oxygen-exposed rats to occupy less volume than those of control rats after 48 h of exposure at which time protein synthesis was also depressed. After 96 h of exposure there is a greater amount of rough endoplasmic reticulum in the granular pneumocytes of oxygen-exposed rats. These studies show that after 96 h of hyperoxia the lung has recovered its ability to synthesize protein including protein in the surface-active fraction and that these biochemical changes are associated with consistent ultrastructural alterations in the granular pneumocyte.
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PMID:Adaption to hyperoxia. Influence on protein synthesis by lung and on granular pneumocyte ultrastructure. 440 5

We used the technique of lineal analysis to study the influence of 48 h of hyperoxia on cytoplasmic organelles of pulmonary granular pneumocytes with particular reference to their lamellar bodies. We undertook this study because lamellar bodies are considered to be storage granules for pulmonary surfactant and because we had found that hyperoxia decreased [(14)C]leucine incorporation into protein of a surface-active lung fraction. We found that for lamellar bodies the percent cytoplasmic volume was 12.8+/-1.5 (mean+/-SEM) and 8.4+/-2.2, the organelle area (mum(2)) per organelle was 0.98+/-0.13 and 0.62+/-0.10 and the organelle volume (mum(2)) was 0.35+/-0.04 and 0.18+/-0.01, for air- and oxygen-exposed rats, respectively, (P=<0.05). The surface density of the lamellar body membrane was 7.05+/-0.47 and 9.36+/-0.96 (P=<0.05) for air- and oxygen-exposed rats. There were no differences in lamellar body number per cytoplasmic area or per pneumocyte between air- and oxygen-exposed rats. There were no statistical differences in these parameters between mitochondria of air- or oxygen-exposed rats. The surface density of the rough endoplasmic reticulum was the same in both groups. This study indicates that granular pneumocytes of rats exposed to hyperoxia have the same number of lamellar bodies as control rats but the lamellar bodies are smaller. This findings in consistent with the hypothesis that the hyperoxia-induced decrease in protein synthesis by lung represents at least in part a decreased synthesis of the secretory lipoprotein-pulmonary surfactant.
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PMID:Hyperoxia: a stereologic ultrastructural examination of its influence on cytoplasmic components of the pulmonary granular pneumocyte. 468 81

We studied the time-course of the influence of in vivo hyperoxia on lung mechanics and on protein synthesis. After 24 h of exposure to greater than 98% O2 at 1 atm there were no alterations in descending pressure-volume curves (air or saline) of lungs excised from O2-exposed rats compared to control rats. After 48 h of hyperoxia there was a decrease in lung compliance. To study protein synthesis, as indicated by L-[U-(24)C] leucine incorporation into protein, lung slices were incubated with L-[U-(14)C]leucine and surface-active material then obtained by ultracentrifugation of lung homogenates. We measured radioactivity in total protein and in protein in the surface-active fraction. There were no alterations in incorporation after 12 h of hypertoxia. After 24 h of hyperoxia there were significant decreases (P<0.05) in L-[U-(14)C]leucine incorporation into total protein and into protein of the surface-active fraction. After 48 h of hyperoxia incorporation into protein of the surface-active fraction was decreased to a greater extent than incorporation into total protein, 63+/-4% and 75+/-5%, respectively, (P<0.025). These studies show that hyperoxia produces a major decrease in protein synthesis, including synthesis of protein in a surface-active fraction, before the onset of any detectable changes in the static compliance of excised lungs.
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PMID:Hyperoxia: influence on lung mechanics and protein synthesis. 473 91

Rats fed 3% casein diets for 6 days showed an increased susceptibility to greater than 98% oxygen [mean survival time 46.9 +/- 4.1 (SD) h] compared with animals fed 25% casein diets (mean survival time 60 +/- 5 h). The 3% casein diet did not reduce the responses to hyperoxia of lung glucose-6-phosphate dehydrogenase, glutathione peroxidase, and glutathione reductase (NAD(P)H), which maintain tissue levels of reduced glutathione or lung superoxide dismutase levels. While supplementation of the 3% casein diet with the sulfur-containing amino acids (cysteine, cystine, or methionine) prevented the increased oxygen toxicity, supplementation with leucine, a nonsulfur-containing amino acid, had no effect on potentiation of toxicity. Animals fed the unsupplemented 3% casein diet failed to show an elevation of lung glutathione in response to hyperoxia. When the 3% casein diet was supplemented with cysteine, total lung glutathione levels increased normally during oxygen exposure. Supplementation of the 25% protein diet with cysteine did not further protect these animals. We conclude that potentiation of oxygen toxicity by dietary protein deficiency in the rat is due to the low sulfur-containing amino acid content of the diet; the mechanism of increased toxicity by hyperoxia is probably related to an inability to increase glutathione levels due to a shortage of the cysteine component of the glutathione tripeptide.
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PMID:Potentiation of oxygen toxicity in rats by dietary protein or amino acid deficiency. 682 98

Oxygen therapy in preterm infants is associated with bronchopulmonary dysplasia, but the relative importance of oxygen toxicity as compared to adverse effects of intubation and mechanical ventilation, remains uncertain. In freely-breathing neonatal rats, exposure to 100% oxygen for as little as 2 hr produced a significant reduction in lung DNA synthesis, evaluated by [3H]thymidine incorporation, without a concomitant effect on [3H]leucine incorporation into protein. These results indicate that hyperoxia has a selective deleterious effect on mitosis in developing lung.
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PMID:Immediate decline in DNA synthesis in neonatal rat lung caused by exposure to 100% oxygen. 835 12

Oxidation of amino acid residues causes noticeable changes in gating of many ion channels. We found that P/C-type inactivation of Shaker potassium channels expressed in Xenopus oocytes is irreversibly accelerated by patch excision and that this effect was mimicked by application of the oxidant H(2)O(2), which is normally produced in cells by the dismutase action on the superoxide anion. The inactivation time course was also accelerated by high concentration of O(2). Substitution of a methionine residue located in the P-segment of the channel with a leucine largely eliminated the channel's sensitivity to patch excision, H(2)O(2), and high O(2). The results demonstrate that oxidation of methionine is an important regulator of P/C-type inactivation and that it may play a role in mediating the cellular responses to hypoxia/hyperoxia.
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PMID:Acceleration of P/C-type inactivation in voltage-gated K(+) channels by methionine oxidation. 1062 Feb 84

Hyperoxia is cytotoxic and depresses many cellular metabolic functions including protein synthesis. Translational control is exerted primarily during initiation by two mechanisms: 1) through inhibition of translation initiation complex formation via sequestration of the cap-binding protein, eukaryotic initiation factor (eIF) 4E, with inhibitory 4E-binding proteins (4E-BP); and 2) by prevention of eIF2-GTP-tRNA(i)(Met) formation and eIF2B activity by phosphorylated eIF2alpha. In this report, exposure of human lung fibroblasts to 95% O2 decreased the incorporation of thymidine into DNA at 6 h and the incorporation of leucine into protein beginning at 12 h. The reductions in DNA and protein synthesis were accompanied by increased phosphorylation of eIF4E protein and reduced phosphorylation of 4E-BP1. At 24 h, hyperoxia shifted 4E-BP1 phosphorylation to lesser-phosphorylated isoforms, increased eIF4E expression, and increased the association of eIF4E with 4E-BP1. Although hyperoxia did not change eIF2alpha expression, it increased its phosphorylation at Ser51, but not until 48 h. In addition, the activation of eIF2alpha was not accompanied by the formation of stress granules. These findings suggest that hyperoxia diminishes protein synthesis by increasing eIF4E phosphorylation and enhancing the affinity of 4E-BP1 for eIF4E.
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PMID:Hyperoxia alters the expression and phosphorylation of multiple factors regulating translation initiation. 1554 44

The focus of this work was to elucidate the mechanism for inhibition of neutrophil beta(2) integrin adhesion molecules by hyperoxia. Results demonstrate that exposure to high oxygen partial pressures increases synthesis of reactive species derived from type 2 nitric-oxide synthase and myeloperoxidase, leading to excessive S-nitrosylation of beta-actin and possibly profilin. Hyperoxia causes S-nitrosylation of the four cysteine moieties closest to the carboxyl-terminal end of actin, which results in formation of short actin filaments. This alters actin polymerization, network formation, and intracellular distribution, as well as inhibits beta(2) integrin clustering. If neutrophils are exposed to ultraviolet light to reverse S-nitrosylation, or are incubated with N-formyl-methionyl-leucine-phenylalanine to trigger "inside-out" activation, the effects of hyperoxia are reversed. We conclude that cytoskeletal changes triggered by hyperoxia inhibit beta(2) integrin-dependent neutrophil adhesion.
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PMID:Actin S-nitrosylation inhibits neutrophil beta2 integrin function. 1828 5


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