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

Cells cultivated in 80% O2 were shown, by cytophotometric and histoautoradiographic methods, to undergo alterations concerning DNA, RNA and total proteins synthesis. These changes appear almost at the same time for all the above-named biological metabolites. Proliferative cell cycle undergoes changes before the blocking of the cells first in post-synthetic (G2) and then in pre-synthetic period (G1). It was also seen that protein synthetic rate of the cells is proportional to their DNA content, in other words tetraploid cells synthesize a double protein amount in comparison to diploid cells. Nucleolus labelling after Uridine-3H incorporation disappear the last under the effect of hyperoxia. Finally it was observed that DNA values (measured with scanning microscope) of prometaphase are higher than the mean values of other mitotic phases.
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PMID:[Histochemical study of nucleic acids and proteins by cytophotometry and histoautoradiography in fibroblasts cultivated in hyperoxia (author's transl)]. 40 24

For studying the mechanism of hyperoxia toxic effect on metabolism in the rat brain localization of lysosomes enzymes - acid phosphatase, DNase II and acid peptid-hydrolases were investigated in the brain subcellular fractions under different phases of oxygen poisoning and in the in vitro experiments. Under hyperoxia redistribution of the lysosome enzymes is found between the fraction enriched with lysosomes and the soluble one. The character of redistribution evidences for disturbance of permeability in the brain lysosome membranes under hyperoxia. Urea possessing a protective effect under these conditions prevents from labilization of lysosome enzymes which is evoked by the effect of oxygen hyperoxia. When studying manifestation of the effect of lysosome hydrolases release on the substrate level there were found constancy of DNA content in the brain under hyperoxia and a decrease in polymeric property of the brain DNA an hour after the beginning of the terminal phase of oxygen poisoning.
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PMID:[Lysosome enzymes of brain in hyperoxia and under the effect of urea]. 120 6

Pulmonary superoxide dismutase (SOD) acitivity was determined for various groups of human fetuses, infants, and adults. Enzyme activity was found to increase with age from a low of 17 +/- 1 units/mg DNA in fetal lung to 49 +/- 6 units/mg DNA in infant lung and finally to 110.2 +/- 14.8 units/mg DNA in adult lung (P less than 0.05). No difference in lung SOD activity was demonstrated between normal infants and those with idiopathic respiratory distress/hyaline membrane disease (IRDS/HMD). No significant differences in SOD activity were found among all the samples of infant blood. Adult blood samples, however, contained significantly greater SOD activity both in terms of heme concentration and volume of whole blood (P less than 0.05). SOD activity in lung tissue from both rats and rabbits were also found to increase with age from a low value in fetal animals to a maximum activity in adults (P less than 0.05). Exposure of New Zealand White rabbits, prematurely delivered by caesarian section, to 80% oxygen for 24 hr resulted in a 42% increase in lung SOD activity. Similarly, 7-day-old Sprague-Dawley rats exposed to 85% oxygen for 24 hr showed a 43% increase in pulmonary SOD activity. No increase in pulmonary SOD was observed when adult rats were exposed to 85% oxygen for 24 hr. The effect of hyperoxia on SOD activity in excised lung was investigated. Rat lung, incubated in either heparinized whole blood or in plasma and exposed to 100% oxygen, showed a 30% increase in SOD activity after 2 hr. This capacity of lung tissue to respond to hyperoxia in vitro with increased SOD activity was age dependent. The maximum increase in SOD activity was seen with lungs from 10-12-day-old rats. The oxygen-stimulated increase in lung SOD activity disappeared at about 19-20 days of age.
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PMID:Developmental characteristics of pulmonary superoxide dismutase: relationship to idiopathic respiratory distress syndrome. 125 Jun 44

The effects of hyperoxia on endothelial cells from human umbilical veins were studied in vitro by flow cytometric DNA analysis, cell proliferation, and morphology. Exposure of the cells to PO2 of approximately 400 and 500 mmHg (corresponding to O2 concentrations of 65 and 95%, respectively) caused, after 24 h, an increase in the proportion of S-phase cells from 18 to 33%. This was followed by a dramatic decrease of S-phase cells to about 4% after 48 h of O2 exposure. This decrease was also sustained after 72 h of O2 treatment. Concomitant with the depletion of S-phase cells was an increase from 13 to 21% in the proportion of cells in the G2M phase, indicating that cells were unable to undergo cell division after a 48-h exposure to 65 and 95% O2. Cells exposed to various PO2 levels (124, 248, 400, and 500 mmHg) showed a dose-dependent reduction in cell proliferation leading to a total inhibition of cell growth after exposure to PO2 of 400 and 500 mmHg. Cells exposed to 248 mmHg PO2 exhibited similar growth rates as the control cells during the first 3 days. Thereafter there was a 50% reduction in cell density as compared to the control cells. Light and scanning electron microscopy showed that the hyperoxic cells underwent morphologic changes characterized by cell contraction and swelling. Thus it is shown that exposure to very high PO2 tensions first stimulates the cells to enter the S phase of the cell cycle. Thereafter changes take place leading to a nearly complete reduction of cell proliferation.
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PMID:Effects of hyperoxia on human endothelial cell proliferation and morphology in vitro. 130 69

We asked whether lung innervation was essential for the normal postnatal development of the lung in conditions of normoxia, hypoxia, or hyperoxia. Litters of newborn rats were assigned to a normoxic [inspired oxygen partial pressure (PIO2) = 150 Torr, eight litters], hypoxic (PIO2 = 100 Torr, nine litters), or hyperoxic (PIO2 = 360 Torr, nine litters) group. Each litter consisted of 12 pups. Two days after birth, one-third of the litter had the vagus and sympathetic trunk cut in the neck on the left side [left denervated (L)], one-third was denervated on the right side (R), and one-third was sham-operated (S). From day 3, all pups were exposed to the designed PIO2, until day 8 or days 21-22. Almost all rats, whether S, R, or L, survived in normoxia and hyperoxia, whereas in hypoxia survival at day 22 of R and L was approximately 60-65%. Body growth was the same in S, R, and L and less in hypoxia than in normoxia or hyperoxia. At days 8 and 22, hematocrit and hemoglobin concentration, heart and lung dry and wet weights, and lung DNA content did not differ among S, R, and L, whether the pups were raised in normoxia, hypoxia, or hyperoxia. At days 21-22, aerobic metabolism and breathing pattern, both measured during air breathing, as well as compliance of isolated lungs, were also similar among S, R, and L for each of the conditions in which the pups were raised.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Postnatal development of the denervated lung in normoxia, hypoxia, or hyperoxia. 144 92

Oxygen tensions play an important role in the outcome of infections. Oxygen is cidal or static for microorganisms that lack defenses against oxidants. Hyperoxia and hyperbaric oxygen exert antimicrobial effects by increasing the intracellular flux of reactive oxygen species. In bacteria, such species cause DNA strand breaks, degradation of RNA, inhibition of amino acid biosynthesis, and inactivation of membrane transport proteins. Oxygen tensions also affect the activity of antimicrobial agents. In general, hyperoxia potentiates while anaerobiosis decreases the activity of many antimicrobial drugs. With regard to host defenses, hyperoxia elevates oxygen tensions in infected tissues to levels that facilitate oxygen-dependent killing by leukocytes. Prolonged hyperoxia inhibits DNA synthesis in lymphocytes and impairs chemotactic activity, adherence, phagocytic capacity, and generation of the oxidative burst in polymorphonuclear leukocytes and macrophages.
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PMID:Oxygen tensions and infections: modulation of microbial growth, activity of antimicrobial agents, and immunologic responses. 152 Jul 72

The conversion of xanthine dehydrogenase (XDH) to xanthine oxidase (XO) and the reaction of XO-derived partially reduced oxygen species (PROS) have been suggested to be important in diverse mechanisms of tissue pathophysiology, including oxygen toxicity. Bovine aortic endothelial cells expressed variable amounts of XDH and XO activity in culture. Xanthine dehydrogenase plus xanthine oxidase specific activity increased in dividing cells, peaked after achieving confluency, and decreased in postconfluent cells. Exposure of BAEC to hyperoxia (95% O2; 5% CO2) for 0-48 h caused no change in cell protein or DNA when compared to normoxic controls. Cell XDH+XO activity decreased 98% after 48 h of 95% O2 exposure and decreased 68% after 48 h normoxia. During hyperoxia, the percentage of cell XDH+XO in the XO form increased to 100%, but was unchanged in air controls. Cell catalase activity was unaffected by hyperoxia and lactate dehydrogenase activity was minimally elevated. Hyperoxia resulted in enhanced cell detachment from monolayers, which increased 112% compared to controls. Release of DNA and preincorporated [8-14C]adenine was also used to assess hyperoxic cell injury and did not significantly change in exposed cells. Pretreatment of cells with allopurinol for 1 h inhibited XDH+XO activity 100%, which could be reversed after oxidation of cell lysates with potassium ferricyanide (K3Fe(CN)6). After 48 h of culture in air with allopurinol, cell XDH+XO activity was enhanced when assayed after reversal of inhibition with K3Fe(CN)6, and cell detachment was decreased. In contrast, allopurinol treatment of cells 1 h prior to and during 48 h of hyperoxic exposure did not reduce cell damage. After K3Fe(CN)6 oxidation, XDH+XO activity was undetectable in hyperoxic cell lysates. Thus, XO-derived PROS did not contribute to cell injury or inactivation of XDH+XO during hyperoxia. It is concluded that endogenous cell XO was not a significant source of reactive oxygen species during hyperoxia and contributes only minimally to net cell production of O2- and H2O2 during normoxia.
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PMID:The contribution of vascular endothelial xanthine dehydrogenase/oxidase to oxygen-mediated cell injury. 156 25

Pretreatment of rats with endotoxin (E), a potent inducer of tumor necrosis factor alpha (TNF), and interleukin 1 beta (IL 1), or a combination of TNF and IL1, has been shown to increase levels of lung antioxidant enzymes and protect against pulmonary toxicity associated with hyperoxia. Inhalation of ozone (O3) induces cell injury, followed by increased DNA synthesis, cell proliferation, and secretory cell metaplasia in rat nasal transitional epithelium (NTE). This study was designed to test the effects of E, TNF, and IL1 pretreatment on acute O3-induced NTE cell injury as measured by changes in NTE cell DNA synthesis. Rats were exposed to either 0.8 ppm O3 or air for 6 hr in whole-body inhalation chambers. Immediately before exposure, rats in each group were injected intraperitoneally (ip) with either saline alone or saline containing E (1 microgram/g body wt), TNF (10 micrograms), IL1 (10 micrograms), or both TNF and IL1 (TNF/IL1; 10 micrograms each). Eighteen hours postexposure, rats were injected ip with bromodeoxyuridine (BrdU; 50 micrograms/g body wt) to label cells undergoing DNA synthesis and were euthanized 2 hr later. NTE was processed for light microscopy and immunochemically stained to identify cells that had incorporated BrdU into nuclear DNA. The number of BrdU-labeled NTE nuclei per millimeter of basal lamina was quantitated. There were no significant differences in the number of BrdU-labeled NTE nuclei in air-exposed rats that were injected with E, TNF, IL1, or TNF/IL1 compared with those in saline-injected, air-exposed controls. Rats that were injected with saline and exposed to O3 had approximately 10 times the number of BrdU-labeled NTE nuclei than saline-injected, air-exposed control rats. O3 exposure also induced a significant increase in labeled nuclei in rats that were pretreated with TNF alone. In contrast, pretreatment with E, IL1, or TNF/IL1 attenuated the O3-induced increase in NTE DNA synthesis. These results indicate that both E and the cytokines TNF and IL1 have physiologic effects that can attenuate O3-induced injury or modify the response to NTE cells to O3 exposure.
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PMID:Endotoxin or cytokines attenuate ozone-induced DNA synthesis in rat nasal transitional epithelium. 160 9

Dexamethasone accelerates the late gestational rise in rat lung catalase activity; neonatal hyperoxia elevates rat lung catalase activity. We studied the regulation of catalase gene expression in these instances. Catalase mRNA/mg DNA increased to gestation day 22 and then fell to the concentration in adult lungs. The rate of transcription of catalase mRNA was higher on gestation day 22 than gestation day 19, whereas the half-life of catalase mRNA (approximately 7 h) was the same on both days. Dexamethasone given 48 and 24 h before expected birth (gestation 22 days) increased catalase mRNA concentration at days 20 and 22 without a change in catalase mRNA stability. Early postnatal hyperoxia (greater than 95% O2, 72 h) elevated catalase mRNA/mg DNA and doubled its half-life without changing its rate of transcription. We conclude the normal late gestational elevation of catalase activity and the increase of activity during prenatal dexamethasone treatment are regulated at the level of gene transcription. By contrast, the elevation of catalase activity during neonatal hyperoxia is mediated posttranscriptionally by increased catalase mRNA stability.
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PMID:Perinatal rat lung catalase gene expression: influence of corticosteroid and hyperoxia. 171 85

Prolonged exposure to hyperoxia markedly inhibits normal lung development (alveolarization and respiratory surface area expansion) in immature animals. Since (a) hyperoxia results in excess hydroxyl radical (OH.) formation, (b) (OH.) is implicated in O2-induced lipid peroxidation and DNA alterations, and (c) both OH. formation and its interaction with DNA are Fe++ dependent; chelation of Fe++ should act to protect against pulmonary O2 toxicity and hyperoxic inhibition of lung development. We therefore treated litters of newborn rats with the iron chelator Deferoxamine mesylate (DES) (150 mg/kg/day) during a 10-day exposure to greater than 95% O2. Morphometric analysis demonstrated that compared to the mean airspace size in air control rat pups (Lm = 44.5 microns), hyperoxic exposure resulted in a 34% larger mean air space diameter in O2-saline rat lungs (59.5 microns) versus only an 11% enlargement in O2-DES lungs (51.1 microns*). Lung internal surface area (cm2) per 100-g body weight were air control = 4480, O2-saline = 3570 (decreases 20.3%), and O2-DES = 4125* (decreases 7.9%) (*p less than 0.05 versus O2-saline group). DES-treated animals also had significantly decreased lung conjugated diene levels during hyperoxic exposure and increased lung elastin content (reflective of preserved lung alveolar formation) compared to O2-saline rats. These results indicate that DES treatment substantially ameliorated the inhibitory effects of neonatal hyperoxic exposure on normal lung development.
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PMID:Hyperoxic inhibition of newborn rat lung development: protection by deferoxamine. 179 22


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