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

To investigate the effect of resting blood oxygen concentration on the hemodynamic response to functional brain activation, we compared activation-induced changes in hemoglobin oxygenation during normoxia with systemic hyperoxia or mild hypoxia. Hemoglobin oxygenation changes were measured by microfiber optical spectroscopy (500-590 nm) in response to physiological whisker barrel cortex activation by whole whisker pad deflection (4 s, 4 Hz) in alpha-chloralose/urethane anesthetised male Wistar rats. During systemic hyperoxia (n=6), the stimulation-induced hyperoxygenation response was decreased and prolonged, whereas during mild systemic hypoxia (n=7) the peak response was significantly increased followed by a faster return to baseline. During normoxia, a poststimulation under- (oxy-hemoglobin) and overshoot (deoxy-hemoglobin) was observed, which disappeared during systemic hyperoxia and was pronounced during systemic hypoxia. Although averaging out below statistical significance when combining all animals, during mild systemic hypoxia a very small early increase of deoxy-Hb at the beginning of the stimulation period was conspicuous more often than during normoxic or even hyperoxic conditions. This small early increase of deoxy-Hb never preceded the onset of the oxy-Hb response, and was not accompanied by a concomitant decrease in oxy-Hb. Hyperoxia or hypoxia did not affect the induced neuronal responses. Our findings support the concept that the hemodynamic response is regulated according to the metabolic demand of oxygen within the activated tissue.
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PMID:Neuronal activity-induced changes of local cerebral microvascular blood oxygenation in the rat: effect of systemic hyperoxia or hypoxia. 1276 1

The purpose of this study was to test whether chronically enhanced O2 delivery to tissues, without arterial hyperoxia, can change acute ventilatory responses to hypercapnia and hypoxia. The effects of decreased hemoglobin (Hb)-O2 affinity on ventilatory responses during hypercapnia (0, 5, 7, and 9% CO2 in O2) and hypoxia (10 and 15% O2 in N2) were assessed in mutant mice expressing Hb Presbyterian (mutation in the beta-globin gene, beta108 Asn --> Lys). O2 consumption during normoxia, measured via open-circuit methods, was significantly higher in the mutant mice than in wild-type mice. Respiratory measurements were conducted with a whole body, unrestrained, single-chamber plethysmograph under conscious conditions. During hypercapnia, there was no difference between the slopes of the hypercapnic ventilatory responses, whereas minute ventilation at the same levels of arterial PCO2 was lower in the Presbyterian mice than in the wild-type mice. During both hypoxic exposures, ventilatory responses were blunted in the mutant mice compared with responses in the wild-type mice. The effects of brief hyperoxia exposure (100% O2) after 10% hypoxia on ventilation were examined in anesthetized, spontaneously breathing mice with a double-chamber plethysmograph. No significant difference was found in ventilatory responses to brief hypoxia between both groups of mice, indicating possible involvement of central mechanisms in blunted ventilatory responses to hypoxia in Presbyterian mice. We conclude that chronically enhanced O2 delivery to peripheral tissues can reduce ventilation during acute hypercapnic and hypoxic exposures.
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PMID:The affinity of hemoglobin for oxygen affects ventilatory responses in mutant mice with Presbyterian hemoglobinopathy. 1295 18

With altitude acclimatization, blood hemoglobin concentration increases while plasma volume (PV) and maximal cardiac output (Qmax) decrease. This investigation aimed to determine whether reduction of Qmax at altitude is due to low circulating blood volume (BV). Eight Danish lowlanders (3 females, 5 males: age 24.0 +/- 0.6 yr; mean +/- SE) performed submaximal and maximal exercise on a cycle ergometer after 9 wk at 5,260 m altitude (Mt. Chacaltaya, Bolivia). This was done first with BV resulting from acclimatization (BV = 5.40 +/- 0.39 liters) and again 2-4 days later, 1 h after PV expansion with 1 liter of 6% dextran 70 (BV = 6.32 +/- 0.34 liters). PV expansion had no effect on Qmax, maximal O2 consumption (VO2), and exercise capacity. Despite maximal systemic O2 transport being reduced 19% due to hemodilution after PV expansion, whole body VO2 was maintained by greater systemic O2 extraction (P < 0.05). Leg blood flow was elevated (P < 0.05) in hypervolemic conditions, which compensated for hemodilution resulting in similar leg O2 delivery and leg VO2 during exercise regardless of PV. Pulmonary ventilation, gas exchange, and acid-base balance were essentially unaffected by PV expansion. Sea level Qmax and exercise capacity were restored with hyperoxia at altitude independently of BV. Low BV is not a primary cause for reduction of Qmax at altitude when acclimatized. Furthermore, hemodilution caused by PV expansion at altitude is compensated for by increased systemic O2 extraction with similar peak muscular O2 delivery, such that maximal exercise capacity is unaffected.
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PMID:Plasma volume expansion does not increase maximal cardiac output or VO2 max in lowlanders acclimatized to altitude. 1514 51

Several studies suggest that during early larval development of lower vertebrates convective blood flow is not essential to supply oxygen to the tissues, but information about the oxygenation status of larvae during the time of cutaneous respiration is still missing. If convective oxygen transport contributes to the oxygen supply to tissues, venous blood in the central circulatory system should be partly deoxygenated, and hyperoxia should increase the oxygen saturation of the hemoglobin. To analyze the changes in hemoglobin oxygen saturation induced by hyperoxic incubation, zebrafish larvae were incubated in a tiny chamber between polytetrafluoroethylene membranes (Teflon), so that the oxygen supply could be rapidly modified. Hemoglobin oxygen saturation was measured in vivo by combining video imaging techniques with a spectrophotometrical analysis of hemoglobin light absorption at specific wavelengths for maximal absorption of oxygenated and deoxygenated blood (413 nm and 431 nm, respectively) under normoxic conditions and after a 10 min period of hyperoxia (P(O(2))=100 kPa), assuming that at a P(O(2)) of 100 kPa the hemoglobin is fully saturated. The results demonstrated that red blood cell oxygenation of zebrafish larvae at 4 days post fertilization (d.p.f.), 5 d.p.f. and 12 d.p.f. could be increased by hyperoxia. The data suggest that at the time of yolk sac degradation (i.e. 4 d.p.f. and 5 d.p.f.), when the total surface area of the animal is reduced, bulk diffusion of oxygen may not be sufficient to prevent a partial deoxygenation of the hemoglobin. The decrease in hemoglobin oxygenation observed at 12 d.p.f. confirms earlier studies indicating that at 12-14 d.p.f., convective oxygen transport becomes necessary to ensure oxygen supply to the growing tissues.
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PMID:The influence of environmental P(O(2)) on hemoglobin oxygen saturation in developing zebrafish Danio rerio. 1563 50

A total of 44 donor/recipient perioperative and intraoperative variables were prospectively analyzed in 89 deceased-donor liver transplantations classified as initial good graft function (IGGF) or initial poor graft function (IPGF) according to a scoring system based on values obtained during the 1st 72 postoperative hours from the serum alanine aminotransferase (ALT) concentration, bile output, and prothrombin activity. The IGGF compared with the IPGF group showed: 1) longer graft (P = .002) and patient (P = .0004) survival; 2) at univariate analysis, a higher (mean [95% confidence interval]) preharvest donor arterial partial pressure of oxygen (PaO(2)) (152 [136-168] and 104 [91-118] mmHg, respectively; P = .0008) and arterial hemoglobin oxygen saturation (97.9 [97.2-98.7] and 96.7 [95.4-98.0]%, respectively; P = .0096), a lower percentage of donors older than 65 years (13 and 33%, respectively; P = .024), a lower percentage of donors treated with noradrenaline (16 and 41%, respectively; P = .012). At multivariate analysis, IGGF was associated positively with donor PaO(2) and negatively with donor age greater than 65 years and with donor treatment with noradrenaline. Independently from the grouping according to initial graft function, graft survival was longer when donor PaO(2) was >150 mmHg than when donor PaO(2) was < or =150 mmHg (P = .045). In conclusion, preharvest donor hyperoxia predicts IGGF and longer graft survival.
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PMID:Preharvest donor hyperoxia predicts good early graft function and longer graft survival after liver transplantation. 1566 81

The expected cost-explosion in transfusion medicine (increasing imbalance between donors and recipients, treatment of transfusion-associated complications) increases the socio-economic significance of the development of safe and effective synthetic oxygen carriers as an alternative to the transfusion of allogeneic red blood cells. Currently two types of artificial oxygen carriers have been tested for safety and efficacy in cases of severe anemia otherwise requiring transfusion. Solutions based on human or bovine hemoglobin (HBOC) possess vasoconstrictor properties in addition to their oxygen transport capacity. The impact of vasoconstriction on tissue perfusion and organ function is however not yet fully understood. Nevertheless, in 2001 the bovine HBOC Hemopure was approved in South Africa for treatment of acutely anemic surgical patients. The purely synthetic perfluorocarbon (PFC) emulsions increase the physically dissolved portion of arterial oxygen content. Due to their particulate nature (emulsion droplets) PFCs may only be infused in low doses to avoid overload and malfunction of phagocytic cells of the reticulo-endothelial system. As part of a multimodal blood conservation program (including normovolemic hemodilution and hyperoxia) the low-dose administration of Oxygent effectively increases intraoperative anemia tolerance. Although reduction of perioperative allogeneic blood transfusion has already been demonstrated for HBOC and PFC, the global clinical establishment of artificial oxygen carriers is not to be expected in the near future.
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PMID:[Artificial oxygen carriers as an alternative to red blood cell transfusion]. 1602 90

We studied relations between maximal O2 consumption (VO2 max) during forced exercise and subordinate traits associated with blood O2 transport and cellular respiration in four lines of mice selectively bred for high voluntary wheel running (S lines) and their four nonselected control (C) lines. Previously, we reported VO2 max of 59 females at three Po2 (hypoxia = 14% O2, normoxia = 21%, hyperoxia = 30%). Here, we test the hypothesis that variation in VO2 max can be explained, in part, by hemoglobin concentration and Po2 necessary to obtain 50% O2 saturation of Hb (an estimate of Hb affinity for O2) of the blood as well as citrate synthase activity and myoglobin concentration of ventricles and gastrocnemius muscle. Statistical analyses controlled for body mass, compared S and C lines, and also considered effects of the mini-muscle phenotype (present only in S lines and resulting from a Mendelian recessive allele), which reduces hindlimb muscle mass while increasing muscle mass-specific aerobic capacity. Although S lines had higher VO2 max than C, subordinate traits showed no statistical differences when the presence of the mini-muscle phenotype was controlled. However, subordinate traits did account for some of the individual variation in VO2 max. Ventricle size was a positive predictor of VO2 max at all three Po2. Blood Hb concentration was a positive predictor of VO2 max in S lines but a negative predictor in C lines, indicating that the physiological underpinnings of VO2 max have been altered by selective breeding. Mice with the mini-muscle phenotype had enlarged ventricles, with higher mass-specific citrate synthase activity and myoglobin concentration, which may account for their higher VO2 max in hypoxia.
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PMID:Maximal oxygen consumption in relation to subordinate traits in lines of house mice selectively bred for high voluntary wheel running. 1660 9

Simultaneous transcranial imaging of two functional parameters, the total concentration of hemoglobin and the hemoglobin oxygen saturation, in the rat brain in vivo is realized noninvasively using laser-based photoacoustic tomography (PAT). As in optical diffusion spectroscopy, PAT can assess the optical absorption of endogenous chromophores, e.g., oxygenated and deoxygenated hemoglobins, at multiple optical wavelengths. However, PAT can provide high spatial resolution because its resolution is diffraction-limited by photoacoustic signals rather than by optical diffusion. Laser pulses at two wavelengths are used sequentially to acquire photoacoustic images of the vasculature in the cerebral cortex of a rat brain through the intact skin and skull. The distributions of blood volume and blood oxygenation in the cerebral cortical venous vessels, altered by systemic physiological modulations including hyperoxia, normoxia, and hypoxia, are visualized successfully with satisfactory spatial resolution. This technique, with its prominent sensitivity to endogenous contrast, can potentially contribute to the understanding of the interrelationship between neural, hemodynamic, and metabolic activities in the brain.
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PMID:Noninvasive imaging of hemoglobin concentration and oxygenation in the rat brain using high-resolution photoacoustic tomography. 1667 5

Newborns are exposed to mechanical and oxidative stress during labor and to relative hyperoxia thereafter during the course of adaptation to the extrauterine conditions. Part of the adaptation mechanism is the rapid degradation of fetal hemoglobin and the oxidation of its heme moiety by heme oxygenases (HOs). Heme oxygenase-1 enzyme (HO-1) is the inducible isoform, which is induced by and protective against oxidative stress. We hypothesized that HO-1 may play a role in the physiological adaptation of newborns. We therefore measured the HO-1 mRNA expression with cRT-PCR during the first week after birth in healthy mature and premature newborns. We found that HO-1 was induced until day 2 or 3 after birth, but its level had dropped below the birth HO-1 mRNA level by the end of the first week. HO-1 levels and inducibility were similar in mature newborns and premature newborns. The fact that HO-1 was inducible even in gestation week 26 suggests that HO-1 plays an important role in the early adaptation processes.
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PMID:Heme oxygenase-1 expression in premature and mature neonates during the first week of life. 1720 80

Optical contrast is sensitive to functional parameters, including the oxygen saturation and total concentration of hemoglobin, in biological tissues. However, due to the overwhelming scattering encountered by light in tissues, traditional optical modalities cannot provide satisfactory spatial resolution beyond the ballistic (a few hundred microns) and quasiballistic (1-2 mm) regimes. Photoacoustic tomography is based on the high optical contrast yet utilizing the high ultrasonic resolution. Our work in this emerging area of research will be summarized in this invited talk. In this technology, a diffraction-based inverse-source problem is solved in the image reconstruction, for which we developed the rigorous reconstruction theory. We implemented a prototype and accomplished noninvasive transdermal and transcranial functional imaging of small-animal brains in vivo. Change in the cerebral blood oxygenation of a rat, as a result of the alternation from hyperoxia to hypoxia, was imaged successfully.
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PMID:High-resolution ultrasound-aided biophotonic imaging. 1727 39


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