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

The influence of regional alveolar oxygen and carbon dioxide tensions on the distribution of lung blood flow and gas exchange was studied in unanaesthetised sheep. Right apical lobe (RAL) hypoxia, induced by administering nitrogen or nitrogen/oxygen mixtures to the lobe, stimulated a prompt, graded and well sustained reduction in lobar blood flow. Maximum hypoxia was accompanied by an approximate 65% reduction in perfusion, a significant fall in RAL carbon dioxide tension and output, a reversal of lobar oxygen flux and an average 13 Torr fall in arterial oxygen tension. The reduction in perfusion and gas exchange persisted in the face of elevated systemic oxygen tensions produced by giving pure oxygen instead of air to the remainder of the lung (RL). Mild RAL hypercapnia potentiated the hypoxia-induced change in perfusion and gas exchange. During lobar hypoxia RL blood flow and gas exchange increased to maintain total pulmonary gas exchange at an essentially constant level. RAL hyperoxia did not significantly alter the distribution of perfusion or gas exchange.
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PMID:Regional alveolar gas composition and lung function in sheep. 49 47

Using the technique of artificial ponto-medullary perfusion, the steady state ventilation during hyperoxia was measured in 15 anaesthetized cats as a function of the central PaCO2 (PaCO2) and peripheral PaCO2 (PapCO2). To a first approximation the ventilatory response was linearly related to both the central and peripheral arterial carbon dioxide pressures, viz. VE=SC . PacCO2 + Sp . PapCO2 - K where Sc and Sp represent the overall central and peripheral sensitivity to carbon dioxide. The mean ratio Sp/Sc was 0.48 (range 0.21 to 1.08). In carotid sinus denervated cats Sp was zero, while the values of Sc in these cats were in the range of Sc of cats with intact carotid sinus nerves. It is concluded that the peripse to CO2 under steady-state conditions. Chemodenervation experiments revealed that the carotid bodies play an essential role in this contribution.
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PMID:Relative contribution of central and peripheral chemoreceptors to the ventilatory response to CO2 during hyperoxia. 49 56

A five month old boy suffered from primary alveolar hypoventilation, with attacks of apnea during sleep (Ondine's curse syndrome). The ventilation did not increase when PACO2 was increased. However, it decreased during hyperoxia. This indicates a strong peripheral chemoreceptor drive and a dysfunction of the central chemoreception. The infant died from circulatory failure following an aspiration pneumonia. Autopsy revealed the absence of the external arcuate nucleus, which may be involved in the central chemocreception.
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PMID:Primary alveolar hypoventilation (Ondine's curse syndrome) in an infant without external arcuate nucleus. Case report. 49 94

The homocarnosine content and homocarnosine synthetase activity were studied in the brain of rats in normal state and under hyperoxia. The homocarnosine content is higher in phylogenetically old brain areas as compared with that in the cerebral hemispheres. Its nonuniform distribution in the brain is associated with different activity of homocarnosine-carnosine synthetase in the corresponding brain areas. At the preconvulsive stage of oxygen poisoning the homocarnosine content in all the brain areas does not change, the homocarnosine-carnosine synthetase activity is 32% lower. At the convulsive stage of hyperoxia the homocarnosine amount in the cerebral hemisphere decreases by 33%, in the midbrain and diencephalon -- by 70, in the medulla oblongata -- by 60, in the cerebellum -- by 58%. The decrease in the homocarnosine content correlates with that in the activity of homocarnosine-carnosine synthetase in the corresponding brain areas; in the cerebral hemispheres -- by 33%, in the midbrain and diencephalon -- by 50, in the medulla oblongata -- by 49, in the cerebellum -- by 40%.
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PMID:[Homocarnosine content and homocarnosine-carnosine synthetase activity in brain areas of hyperoxic rats]. 51 82

During sleep, of ventilated newborns and young infants, spontaneous respiratory movements may occur, unrelated to the ventilation impulsions. The respiratory pattern is then classified as "active". On the contrary, the respiratory pattern is classified as "passive", when all respiratory movements are related to the ventilation insufflation. The factors which influence the dependence on the ventilator are studied in a group of 20 newborn and young infants. Prematurity, some biological data such as hyperoxia, hypocapnia, seem to favor this dependence. A rapid rate of ventilation (superior to 30/minute) is rarely related to an active respiration; a slow rate of ventilation seems favor this respiratory pattern. It is clear that adaptation to artificial ventilation is better during quiet sleep than during active sleep. Some physiopathological considerations are developed.
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PMID:[Assisted ventilation of newborn infants during sleep. Study of factors modifying adaptation to ventilation]. 52 40

The reactivity of subpleural strips of lung parenchyma reflects primarily the tone of the smooth muscle in the peripheral airways. Lung strips taken from ten dogs relaxed when the oxygen level in the gas bubbling through the bath was reduced from 95% to 18%. Subsequent hypocapnia (carbon dioxide reduced from 5% to 0%) induced contraction of all strips. These changes were reversed when the oxygen or carbon dioxide tensions were restored to control levels. Addition of either indomethacin or meclofenamate, two chemically dissimilar inhibitors of prostaglandin synthetase, reduced the resting tone in each of six strips and prevented the hyperoxic constriction which was observed in paired, control strips (oxygen increased from 18% to 95%). Blockers of histamine and catecholamines had no effect. The reactivity of the distal airways to changes in gas tension provides a mechanism by which ventilation and perfusion can be matched. The action of indomethacin and meclofenamate indicates that a prostaglandin-like substance may be involved in the maintenance of distal airway tone and in the constriction produced by hyperoxia. The addition of prostaglandin F2 alpha or E1, after meclofenamate, in a further nine pairs of strips did not restore the hyperoxic constriction. This suggests that prostaglandins may mediate, rather than merely facilitate, the response.
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PMID:Distal airway responses to changes in oxygen and carbon dioxide tensions. 52 47

Hyperoxia has been shown to enhance the toxicity of the herbicide paraquat. Experiments were conducted to learn more about the effects of oxygen following acute poisoning with paraquat as well as the structurally related herbicide, diquat. Rats were injected intravenously with various doses of diquat or paraquat and placed into an atmosphere of either 100% oxygen or room air. The time required for 50% lethality (LT50) of both diquat and paraquat was greatly diminished by hyperoxia and was dependent upon the herbicide dosage. Rats treated with 40 or 80 mg/kg diquat and exposed to 100% oxygen had a shorter LT50 than those treated similarly with paraquat. A dose of 20 mg/kg was equitoxic in 100% oxygen while rats treated with 5 or 10 mg/kg diquat had a longer LT50 than rats treated with the same dose of paraquat. All animals exhibited severe respiratory distress terminally. The plasma concentrations and tissue distribution of either herbicide at 20 mg/kg were the same in oxygen and air exposed animals. When oxygen concentrations were varied between 100% and 60% rats treated with 20 mg/kg diquat or paraquat exhibited increasing but equal LT50's. In 40% oxygen diquat treated rats died more rapidly than paraquat treated rats. These data demonstrate a toxic interaction between hyperoxia and diquat as well as paraquat.
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PMID:The influence of hyperoxia on the acute toxicity of paraquat and diquat. 54 May 39

To study transvascular filtration of fluid and microvascular permeability to protein in the lung during prolonged hyperoxia, we measured lung lymph flow, protein transport, and simultaneous pulmonary vascular pressures of six lambs breathing 100 percent O2 for five days. Lymph flow doubled, protein flow increased by 131 percent, and radioactive tracer studies demonstrated a clearcut increase in pulmonary microvascular permeability to protein after five days of continuous O2 breathing.
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PMID:Pulmonary oxygen toxicity: increased microvascular permeability to protein in unanesthetized lambs. 54 18

The content of glutamic, asparaginic and gamma-aminobutyric (GABA) acids in norm and under hyperoxia was determined in different cerebral areas of susliks living in places at different heights above sea level. In susliks at a height of 1700-2000 m above sea level the content of glutamate aspartate and GABA lowers significantly as compared to that in susliks at a height of 500-600 m above sea level. Under the effect of oxygen 6 at. ga at the 22nd minute on the average there occur convulsions in susliks living both in high mountains and middle mountains. Acute oxygen poisoning is not accompanied by noticeable shifts in the content of free dicarboxylic amino acids in the studied cerebral areas of middle-mountain susliks and is characterized only by an increase of the GABA content in the cerebellum. In high-mountain susliks the content of glutamate under these conditions increases in great cerebral hemispheres, while the asparate content lowers in cerebral hemispheres and cerebellum. In the latter the drop in the content of GABA is statistically significant.
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PMID:[Content of dicarboxylic acids and GABA in normal suslik brain and under the effect of oxygen at higher pressure]. 55 58

Cidal activities of 24-h exposures to 100% O2 and 95% O2 + 5% CO2 were assayed at 1 and 3 ATA. Studied were 21 yeasts isolated from humans: Candida albicans (8 strains), C. tropicalis (3 strains), C. krusei (3 strains), C. parapsilosis (2 strains), C. guilliermondii (2 strains), and one strain each of C. pseudotropicalis, C. stellatoidea, and Torulopsis sp. Generally, these were extremely sensitive to hyperbaric oxygen, although species and strain differences were observed. Indices of kill from 80-100 (total kill) characterized 17 of the 21 yeasts (81%). Hyperoxia (O2 +/- CO2 at 1 ATA) was not lethal. Deprivation of CO2 as a consequence of hyperbaric exposure to 100% O2 enhanced cidal activity for only 2 of 21 yeasts, whereas hyperbaric exposure to the mixture enhanced activity against four yeasts. Cidal activities were not significantly different for the remaining 15 yeasts. This response to deprivation of CO2 is different from that of bacteria, and manifests fundamental differences between procaryotic and eucaryotic cells.
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PMID:Quantitative cidal activity of hyperbaric oxygen for opportunistic yeast pathogens. 56 66


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