Search Results
Results 551 - 600 of 1063
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Peltonen J E - - 1997
Six male rowers rowed maximally for 2500 m in ergometer tests during normoxia (fractional concentration of oxygen in inspired air, F(I)O2 0.209), in hyperoxia (F(I)O2 0.622) and in hypoxia (F(I)O2 0.158) in a randomized single-blind fashion. Oxygen consumption (VO2), force production of strokes as well as integrated electromyographs (iEMG) and ...
Almaas R - - 1997
Previously, high postmortem concentrations of hypoxanthine have been found in vitreous humor of children dying from sudden infant death syndrome (SIDS). We wanted to investigate further the accumulation of hypoxanthine in vitreous humor during hypoxia. Twenty-four piglets aged 9-15 days were exposed to continuous hypoxemia (180 min 11% O2, n ...
Schellart N A - - 1997
The effect of acute air-hyperbarism (maximal 520 kPa), normobaric low and high FIO2 levels (minimal 0.1, maximal 1.0) and hyperbaric oxygen (HBO2) on the red-green sensitivity ratio (rgSR) and on color discrimination for foveal vision were studied. Effects were quantified by measuring the red-green flicker (16 Hz) fusion point for ...
Pandit J J - - 1997
The purpose of this study was to examine whether sustained hypoxia during exercise attenuates the degree of decline in hypoxic ventilatory sensitivity which occurs during sustained hypoxia at rest. The acute ventilatory response to hypoxia (AHVR) was used as a measure of the hypoxic ventilatory chemoreflex sensitivity. Seven subjects undertook ...
Benoit H - - 1997
There is a growing need to measure arterial oxygen saturation with a non-invasive method during heavy exercise under severe hypoxic conditions. Although the accuracy of pulse oximetry has been challenged by several authors, it has not been done under extreme conditions. The purpose of this study was to evaluate the ...
Ferretti G - - 1997
1. Endurance athletes (E) undergo a marked reduction of arterial O2 saturation (Sa,O2) at maximal exercise in normoxia, which disappears when they breathe hyperoxic mixtures. In addition, at a given level of hypoxia, the drop in maximal O2 consumption (VO2,max) is positively related to the individual normoxic VO2,max. 2. These ...
Carmichael L - - 1997
OBJECTIVE: The purpose of this study was to determine whether activation of the hypothalamic-pituitary-adrenal (HPA) axis and uteroplacental prostaglandin (PG) response occur before metabolic deterioration with a progressive decrease in fetal oxygenation. METHODS: Twenty-one chronically catheterized fetal sheep were studied between 126 and 135 days' gestation during a 24-hour normoxic ...
van Ginneken V - - 1996
We used 31P nuclear magnetic resonance (31P-NMR) spectroscopy to measure intracellular pH (pHi) and high-energy phosphate levels of white muscle of the fish tilapia (Oreochromis mossambicus) during exposure to the stressors hypoxia and water acidification separately and simultaneously. The protocol for the graded hypoxia load was 100, 40, 30, 20, ...
Engelen M - - 1996
It is unclear whether hypoxia alters the kinetics of O2 uptake (VO2) during heavy exercise [above the lactic acidosis threshold (LAT)] and how these alterations might be linked to the rise in blood lactate. Eight healthy volunteers performed transitions from unloaded cycling to the same absolute heavy work rate for ...
Moore P J - - 1996
In nineteen alpha-chloralose-anaesthetized 3- to 8-day-old lambs, the effect of cooling focally in the region of the locus coeruleus on respiratory output, as measured from phrenic nerve activity, was examined during normoxia and isocapnic hypoxia, and during infusion of adenosine or saline. Eleven lambs showed a 'biphasic' respiratory response to ...
al-Haboubi H A - - 1996
The aim of this study was to investigate the effect of a moderate degree of hypoxia on coronary vascular permeability to various lipophobic solutes. Using the multiple indicator dilution method the permeability-surface area (PS) products were determined for 125I-albumin, 125I-insulin and 57Co-cyanocobalamin in perfused rat hearts (flow approximately 10 ml.min-1.g-1) ...
Bari F - - 1996
BACKGROUND AND PURPOSE: Recent studies in piglets show that either asphyxia or global cerebral ischemia, which combines effects of hypoxia and hypercapnia, transiently attenuates N-methyl-D-aspartate (NMDA)-induced pial arteriolar dilation. The purpose of this study was to determine individually the effects of hypoxic hypoxia and normoxic hypercapnia on NMDA-dependent cerebrovascular reactivity. ...
Dahan A - - 1996
To evaluate whether the intact hypoxic drive from the carotid bodies during sustained hypoxia is required for the generation of hypoxic depression of ventilation (VE), 16 volunteers were exposed to two consecutive periods of isocapnic hypoxia (first period 20 min; second period 5 min; end-tidal PO2 45 Torr) separated by ...
McEvoy R D - - 1996
We compared the effects of sustained isocapnic hypoxia (SIH; 20 min) and repetitive isocapnic hypoxia (RIH; 10 2-min episodes) on ventilation (VI), genioglossal (EMGgg) and diaphragmatic electromyographic (EMGdi) activities, and supraglottic airway resistance in 11 normal supine male subjects (36.6 +/- 2.2 yr) during wakefulness. Seven of the subjects had ...
Gautier H - - 1996
This review attempts to emphasize the fact that the interpretation of the ventilatory response to hypoxia may be complicated by the reduction in metabolic rate that is often associated with hypoxia. The hypoxic hypometabolism is more apparent when oxygen consumption is relatively high, either in small or young mammals at ...
Lammerich A - - 1996
Hypoxia, ischemia and reoxygenation cause contractile dysfunction which will be characterized by the time course of isometric contraction of human atrial trabeculae. Post-rest potentiation (PRP) and postextrastimulatory potentiation (PEP) were elicited to obtain indirect information about the the role of the sarcoplasmic reticulum (SR) in excitation-contraction coupling. As lipid peroxidation ...
Melton J E - - 1996
In peripherally chemodenervated, vagotomized, chloralose-anesthetized cats, hypoxia can produce central cardiorespiratory depression or excitation depending on severity. We monitored phrenic and cervical sympathetic neurograms during either hypoxic depression or gasping and 30 min of subsequent isocapnic reoxygenation to determine whether the response of these outputs during hypoxia predicts their activity ...
Eriksson L I - - 1996
BACKGROUND: It was hypothesized that non-depolarizing neuromuscular blocking agents impair hypoxic chemosensitivity in man. METHODS: In thirty randomly allocated male volunteers the hypoxic and hypercarbic ventilatory responses were measured during partial paralysis (TOF ratio 0.70) due to either atracurium (n = 10), pancuronium (n = 10) or vecuronium (n = ...
Costes F - - 1996
Near-infrared spectroscopy (NIRS) is a noninvasive way of measuring muscular oxygenation. We evaluated the relationship between NIRS signal [infrared muscle oxygen saturation (IR-SO2mus)] and the femoral venous oxygen saturation (SfvO2) during cycling exercise. Six healthy subjects performed a 30-min steady-state exercise at 80% maximal oxygen uptake in normoxia and hypoxia ...
Groenendaal F - - 1996
To determine the role of nitric oxide production during hypoxia, the presence of two forms of neuronal nitric oxide synthase, cytosolic (cNOS) and membrane-bound (memNOS), in cortical tissue of newborn piglets and the effects of hypoxia on the activity of these enzymes were studied. Experiments were performed in 12 anesthetized ...
Dahan A - - 1996
Short-term potentiation (STP) of breathing refers to respiratory activity that persists at termination of a primary stimulus and is not related just to the dynamics of chemoreceptors. In humans, STP is activated by brief episodes of hypoxia and voluntary hyperventilation (VHV). STP exerts a stabilizing influence on breathing pattern. To ...
Wilderman M J - - 1996
It has previously been observed that nitric oxide (NO) and the opioids Met- and Leu-enkephalin contribute to hypoxia-induced pial artery dilation in the newborn pig. The present study was designed to investigate the relationship between NO and opioids in hypoxic pial dilation. Piglets equipped with closed cranial windows were used ...
Suguihara C - - 1996
OBJECTIVE: Infants exposed to cocaine in utero have been reported to have a higher incidence of apnea and altered ventilatory response to carbon dioxide and hypoxia. We investigated whether in utero cocaine exposure results in greater ventilatory depression during hypoxia in piglets. METHODS: Cocaine hydrochloride, 1.0 or 2.0 mg/kg given ...
Corbett R J - - 1996
Newborn and 1-mo-old swine were exposed to identical durations (18 min) and degrees of hypoxia (O2 content = 4 mL/dL), to examine the effects of hypoxia on cerebral energy metabolism and intracellular pH (pHi) in vivo, using 31P and 1H nuclear magnetic resonance spectroscopy. Hypoxia produced the same extent of ...
Delacourt C - - 1996
Apneas are very common and normal in newborns but may become life threatening if they are not terminated appropriately. The aim of this study in newborn lambs was to investigate the influence on apnea termination of postnatal maturation, peripheral chemoreceptor function, and hypoxia. Apneas were induced by passive hyperventilation at ...
Hoffman W E - - 1996
In this case we evaluated brain tissue pO2, pCO2 and pH during ischemia and arterial oxygen desaturation (hypoxia). In both situations brain pO2 decreased. During ischemia, tissue pCO2 increased while pH decreased; but both pCO2 and pH were stable during hypoxia. These results suggest that brain tissue pO2, pCO2 and ...
Johnston C E - - 1996
Hypoxia lowers the basic thermoregulatory responses of animals and humans. In cold-exposed animals, hypoxia increases core temperature (Tco) cooling rate and suppresses shivering thermogenesis. In humans, the experimental effects of hypoxia on thermoregulation are equivocal. Also, the effect of hypoxia has not been separated from that of hypocapnia consequent to ...
Favier R - - 1996
In sea-level natives, exposure to hypoxia for a few weeks is characterized by an increased dependence on blood glucose and a decreased reliance on lactate for energy metabolism during exercise. These metabolic adjustments have been attributed to behavioral changes in the sympathoadrenergic and pancreatic systems. The aim of this study ...
Cowin G J - - 1996
Glycine-serine interconversion is important to numerous metabolic processes and serine release by the kidney. Incubation of freshly isolated rat renal proximal tubules with 5 mM glycine 75% 13C-labelled in the 2-position resulted in 13C-labelled incorporation into serine of 69 micromol.g protein(-1) (+/- 14, n = 16) at 20 min. Addition ...
Iturriaga R - - 1996
To determine if intracellular acidosis enhances hypoxic chemoreception in the absence of CO2-HCO3- at pH 7.4, the effects of sodium acetate (30 mM) were studied on the chemosensory responses of the cat carotid body to hypoxic, stagnant and cytotoxic hypoxia. Carotid bodies were perfused and superfused in vitro with Tyrode's ...
Sugimori K - - 1996
The ventilatory response to progressive hypoxia was studied in 15 healthy adult males by employing two different rates of desaturation. In a slow hypoxic ramp, peripheral oxygen saturation was gradually reduced to 70% over 10-13 min, while in a fast ramp the saturation was reduced over 3-5 min. The ventilatory ...
Schmidt H - - 1996
Anaerobic metabolism in the limnic annelid Hirudo medicinalis L. was investigated by direct and indirect calorimetry. During long-term severe hypoxia, the rate of heat dissipation was reduced up to 13% of the aerobic rate. At the same time, the rate of ATP turnover was reduced to about 30% of the ...
Portman M A - - 1996
Myocardial ATP utilization and resynthesis during hypoxia and reoxygenation were studied in vivo as a function of maturation. Graded hypoxia was performed in newborn (NB; 4-10 days old, n = 6) and mature sheep (MAT; 30-60 days old, n = 6). Time-resolved 31P-nuclear magnetic resonance was used to monitor myocardial ...
Saraví F D - - 1996
Electrogenic epithelial transport depends on oxidative metabolism. Acute hypoxia and subsequent reoxygenation effects on short-circuit current (Isc), transepithelial potential difference (PD) and tissue resistivity (TR) of rat distal colon were assessed. The tissue was mounted in an Ussing chamber filled with Ringer-HCO3-solution at 37 degrees C and bubbled with 95% ...
Maggi C A - - 1996
1. In the guinea pig isolated ureter, a maximally effective concentration of calcitonin gene-related peptide (CGRP, 0.1 microM) produced a prompt and transient suppression of myogenic phasic contractions (twitches) evoked by direct excitation (electrical field stimulation, EFS) of the smooth muscle. This suppressant effect is prevented by glibenclamide (1 and ...
Yu X Q - - 1996
To assess the effects of chloral hydrate (CH) on the cardiorespiratory response to hypoxia in the neonate, 17 newborn piglets were chronically instrumented 48-72 h before study and randomly assigned to a CH group (100 mg/kg, i.p.) or saline group. The animals were intubated and studied under quiet sleep which ...
Aaron E A - - 1996
To gain insight into the role of cerebral lactic acidosis in the hypoxic ventilatory response, we administered dichloroacetate (DCA) intravenously to inhibit lactic acid production in 7 awake goats (40-70 kg) during 0.5 h of normoxia (inspired O2 fraction = 0.209) and 5 h of poikilocapnic hypoxia (inspired O2 fraction ...
Moss I R - - 1995
To distinguish pure effects of prenatal cocaine exposure on respiratory control from confounding factors inherent to drug abuse, a porcine model was established. Cocaine was administered at 2 mg/kg 4 times daily during 0.66-1.0 gestation to 5 paired sows. At birth, cocaine-exposed piglets were fostered to the unexposed paired sows ...
Shirai M - - 1995
Changes in efferent sympathetic nerve activity to the pulmonary vessels during systemic hypoxia have yet to be elucidated. The purpose of this study was to determine the pulmonary sympathetic nerve activity (PSNA) changes in response to acute systemic hypoxia before and after sinoaortic denervation plus vagotomy in anesthetized cats. The ...
O'Neill M - - 1995
In order to examine the value of assuming constant pulmonary venous admixture with respect to changes in inspired oxygen fraction (FIO2) and time during sustained unilateral hypoxia, we studied venous admixture for 6 h in 27 anaesthetized rabbits in which the left lung was filled with liquid, isosmotic with plasma. ...
Rantin F T - - 1995
Electrocardiography was applied to analyze cardiac function of four teleost species (Piaractus mesopotamicus, Hoplias malabaricus, Hoplias lacerdae and Cyprinus carpio) during normoxia and graded hypoxia. In these species, hypoxic bradycardia consistently occurred during severe hypoxia (below the critical oxygen tension--PCO2) and was accompanied by alterations in the ECG recordings. Three ...
Dahan A - - 1995
1. Short term potentiation (STP) of breathing refers to respiratory activity at a higher level than expected just from the dynamics of the peripheral and central chemoreceptors. In humans STP is activated by hypoxic stimulation. 2. To investigate the effects of the duration of hypoxia and the posthypoxic inspired O2 ...
Georgopoulos D - - 1995
In normal humans when a brief hypoxic ventilatory stimulus is terminated abruptly by breathing 100% O2, ventilation during hyperoxia gradually declines to baseline prehypoxic levels without an undershoot. This has been interpreted as evidence of decay of short-term potentiation (STP), a mechanism located in the brainstem and not dependent upon ...
Pan L G - - 1995
It has been postulated that the so-called area S of the ventrolateral medulla (VLM) integrates peripheral chemoreceptor activity; thus cooling-induced dysfunction of neurons in this VLM area should functionally eliminate carotid chemoreceptor stimulation of breathing. Accordingly, carotid chemoreceptor denervation (CBD) should not alter the breathing effects of VLM neuronal dysfunction. ...
Xu F - - 1995
The general contribution of the cerebellum to hypoxic respiratory responses and the special role of the fastigial nucleus (FN) in the hypoxic respiratory reflex mediated via peripheral chemoreceptors were investigated in anesthetized and spontaneously breathing cats. Seven cats were exposed to isocapnic progressive hypoxia before and after cerebellectomy by decreasing ...
van den Elsen M - - 1995
BACKGROUND: The purpose of this study was to quantify in humans the effects of subanesthetic isoflurane on the ventilatory control system, in particular on the peripheral chemoreflex loop. Therefore we studied the dynamic ventilatory response to carbon dioxide, the effect of isoflurane wash-in upon sustained hypoxic steady-state ventilation, and the ...
Takashima S - - 1995
Using near-infrared spectroscopy the changes of intracranial oxyhemoglobin, deoxyhemoglobin, total hemoglobin and cytochrome aa3, which show the progression of intracranial oxygenation, hemodynamics and cell metabolism, were recorded during prolonged partial hypoxia induced by carbon dioxide (CO2) and nitrogen (N2), ischemia induced by hyperventilation, and hypoxia during hypoglycemia in neonatal and ...
Olano M - - 1995
The present study describes the relationships of extracellular striatal dopamine, cortical oxygen pressure, and striatal hydroxyl radicals in brain of newborn piglets during hypoxia and posthypoxic reoxygenation. Hypoxia was induced by reducing the fraction of inspired oxygen (FiO2) from 22% (control) to 7% for 1 h. The FiO2 was then ...
Praud J P - - 1995
It has long been claimed that the active expiratory glottic closure observed in newborns, especially during hyaline membrane disease, is related to hypoxia. However, we recently showed that hypoxia does not lead to active expiratory glottic closure in nonsedated lambs. In this study, we test the hypothesis that glottic closure ...
Mou X B - - 1995
The ventilatory response to isocapnic hypoxia is biphasic, which makes any experimental assessment of the relationship between the acute (peak) ventilatory response and the level of hypoxia difficult. This study explored whether one particular protocol could be useful for determining this relationship. The protocol consisted of exposing subjects to seven ...
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