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Results 351 - 400 of 793
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Butler P J - - 1997
This review concentrates on the physiological responses, and their control, in freely diving birds and mammals that enable them to remain submerged and sometimes quite active for extended periods of time. Recent developments in technology have provided much detailed information on the behavior of these fascinating animals. Unfortunately, the advances ...
Heller H - - 1997
Each of the pathways within respiration has been suspected of limiting maximal performance, suggesting that O2 transport may be affected by each single pathway. The use of the stable, isotopic O2 molecules 16O2 and 16O18O is presented as a novel method for assessing respiration. Because of their different molecular weights, ...
Koskolou M D - - 1997
Hypoxia affects O2 transport and aerobic exercise capacity. In two previous studies, conflicting results have been reported regarding whether O2 delivery to the muscle is increased with hypoxia or whether there is a more efficient O2 extraction to allow for compensation of the decreased O2 availability at submaximal and maximal ...
Jacobsen G - - 1997
A comprehensive computerized database of diving activity for a Norwegian offshore diving contractor [Stolt-Nielsen Seaway (SNS)] covering the years 1983-1990 has been established. The database contains detailed dive information about 12,087 surface-oriented and 2,622 saturation dives. During this period a majority of the divers were permanently employed. Preliminary analysis had ...
Cabanac A - - 1997
Volume changes in the spleens of hooded seals (Cystophora cristata) and harp seals (Phoca groenlandica) were measured plethysmographically in vitro in response to epinephrine, norepinephrine, isoprenaline, phentolamine, and acetylcholine. Dilated spleens contracted forcefully within 1-3 min of alpha-adrenoceptor activation with 1.0-5.0 micrograms epinephrine/kg body mass, whereas stimulation of beta-adrenoceptors and ...
Ben-Dov I - - 1997
The effect of venous obstruction on effort tolerance is not well appreciated. We studied a patient with severe lower body venous obstruction (with near normal heart and lung function) who had marked exercise intolerance. Peak O2 uptake for leg exercise was reduced, but peak O2 uptake for upper extremities was ...
Basson H - - 1997
Dopamine (DA) is thought to modulate the transduction of the hypoxic stimulus by the glomus cell in the carotid body (CB). The hypothesis tested here is that presynaptic DA D2 receptors (D2's) located on the type 1 cell function as autoreceptors to control DA release and/or synthesis. The aim of ...
Mootha V K - - 1997
It is difficult to estimate the maximum in vivo aerobic ATP production rate of the intact heart independent of limitations imposed by blood flow, oxygen delivery, and maximum mechanical power. This value is critical for establishing the kinetic parameters that control oxidative phosphorylation, as well as for providing insights into ...
O'Donnell D E - - 1997
The mechanisms of exertional dyspnea relief in response to supplemental oxygen (O2) in chronic airflow limitation (CAL) are not precisely known and are likely multifactorial. To explore factors contributing to the relief of dyspnea after oxygen administration, 11 patients with severe CAL (FEV1.0 = 39 +/- 3% predicted, mean +/- ...
Johnson D - - 1997
This study assessed the long-term (5-year) outcome of pediatric low-dose anthracycline therapy on the circulatory response to moderate exercise. Thirteen patients (13 +/- 4 years old) and 15 age-matched control subjects completed a maximal cycle ergometer protocol as well as two 5-minute cycling tests at 33% and 66% maximal oxygen ...
Kasemsri T - - 1997
BACKGROUND AND PURPOSE: Traumatic brain injury conveys significant morbidity and mortality to infants and children. In the newborn pig, opioids contribute to pial artery vasconstriction after fluid percussion injury (FPI). FPI attenuates vasodilation and cGMP production by methionine enkephalin (Met) and leucine enkephalin (Leu) and reverse dynorphin (Dyn) from a ...
Forte V A VA - - 1997
Some anesthetic gases interfere with the determination of blood O2 values. We evaluated, for its potential for such interference, a gas mixture containing (v/v) approximately 70% ethane, 20% sulfur hexafluoride, and 10% cyclopropane, as is currently used in trace amounts to determine ventilation-perfusion (v/Q) ratios. Normal human blood samples were ...
Lehnigk B - - 1997
We studied the effects of an experimental saturation dive to 360 and 450 m in a simulation chamber on spirometric lung function, diffusing capacity, pulmonary compliance, and exercise performance in eight professional divers (age 22-40 years). To assess intraindividual variability, all parameters were measured on 2 days before and on ...
Ponganis P J - - 1997
California sea lions, Zalophus californianus, were trained to elicit maximum voluntary breath holds during stationary underwater targeting, submerged swimming, and trained diving. Lowest heart rate during rest periods was 57 bpm. The heart rate profiles in all three protocols were dominated by a bradycardia of 20-50 bpm, and demonstrated that ...
Pedersen P K - - 1996
Performance of intense dynamic exercise in highly trained athletes is associated with a reduced arterial haemoglobin saturation for O2 (SaO2) and lower arterial PO2 (PaO2). We hypothesized that compared with upright exercise, supine exercise would be accompanied by a smaller reduction in SaO2 because of a lower maximal O2 uptake ...
Whipp B J - - 1996
Noninvasive techniques have been devised to estimate cardiac output (Q) during exercise to obviate vascular cannulation. However, although these techniques are noninvasive, they are commonly not nonintrusive to subjects' spontaneous ventilation and gas-exchange responses. We hypothesized that the exercise stroke volume (SV) and, hence, Q might be accurately estimated simply ...
Stinkens D - - 1996
Oxygenation performance was tested in 15 membrane oxygenators by calculating the resistance for oxygenation (R) and the calculation of oxygen transferred versus FiO2. The clinical data reveal that the SARNS Turbo 440 (36.7-51.9%), the AFFINITY (37.2-50.1%) and the HF 5400 (37.5-52.3%) are the oxygenators with the lowest FiO2 settings for ...
Julian D - - 1996
The modified hindgut of the echiuran marine worm Urechis caupo functions as a water lung and has been assumed to be a much more important respiratory surface than its thick, muscular body wall. We tested this assumption by measuring whole animal O2 consumption, hindgut O2 uptake, and hindgut ventilation activity ...
Honda Y - - 1996
Sixteen healthy volunteers breathed 100% O2 or room air for 10 min in random order, then their ventilatory response to sustained normocapnic hypoxia (80% arterial O2 saturation, as measured with a pulse oximeter) was studied for 20 min. In addition, to detect agents possibly responsible for the respiratory changes, blood ...
Becker H F - - 1996
We have recently shown that breathing 50% O2 markedly stimulates ventilation in healthy subjects if end-tidal PCO2 (PETCO2) is maintained. The aim of this study was to investigate a possible dose-dependent stimulation of ventilation by O2 and to examine possible mechanisms of hyperoxic hyperventilation. In eight normal subjects ventilation was ...
Lawrence C H - - 1996
An experienced diver drowned after a generalised seizure caused by oxygen toxicity during a 19-minute "technical" dive to a depth of 47 m. He had used a 50% oxygen/nitrogen gas mixture inappropriately during the dive. This case attests the risk of oxygen toxicity from oxygen-enriched air during deep dives, the ...
Wagner P D - - 1996
Although the horse is considered an elite athlete with a specific VO2max some 2-4 times higher than man, maximal O2 transport is compromised both by moderately severe arterial desaturation and by failure to extract all O2 from blood perfusing exercising muscle. This prompted the present study to ascertain whether correction ...
Chung Y - - 1996
Perfused rat heart experiments focused on determining the critical O2 level in postischemic myocardium. After a 20-min global ischemia, reperfusion began with O2-saturated saline buffer reflowing at different rates (0.5-12 ml/min). The 1H nuclear magnetic resonance (NMR) signal of the Val E11 myoglobin (Mb) gave an index of the intracellular ...
Berendes E - - 1996
OBJECTIVES: To examine the influence of positive end-expiratory pressure (PEEP) ventilation on splanchnic oxygenation and lactate production in humans without pulmonary disorders. DESIGN: Prospective study. SETTING: Single-institutional surgical intensive care unit in a university hospital. PARTICIPANTS: Twenty patients who underwent major abdominal surgery. INTERVENTIONS: Radial artery, pulmonary artery, and right ...
Weibel E R - - 1996
This paper integrates the results of a series of studies on the supply of O2 and substrates for oxidative muscle metabolism and draws conclusions on the role of structural design in partitioning and limiting substrate supply. The studies compared dogs and goats exercising at different intensities and combined physiological, biochemical ...
Gore C J - - 1996
This study utilized a hypobaric chamber to compare the effects of mild hypobaria (MH; 50 mmHg, approximately 580 m altitude) on blood O2 status and maximal O2 consumption (VO2max) in 9 untrained and 11 trained (T) cyclists with VO2max values of 51 +/- 3 and 77 +/- 1 ml.kg-1.min-1, respectively. ...
Quigley P M - - 1996
OBJECTIVE: To determine whether pectus excavatum (PE) results in cardiopulmonary abnormalities, and whether surgical repair results in improvement. METHODS: We performed pulmonary function testing and incremental exercise testing in 36 adolescents with PE (aged 16 +/- 3 (SD) years) and 10 age-matched, healthy control subjects. Fifteen PE subjects were reexamined ...
Marrades R M - - 1996
Erythropoietin (rHuEPO) has proven to be effective in the treatment of anemia of chronic renal failure (CRF). Despite improving the quality of life, peak oxygen uptake after rHuEPO therapy is not improved as much as the increase in hemoglobin concentration ([Hb)] would predict. We hypothesized that this discrepancy is due ...
Culik B M - - 1996
Dive duration in wild king penguins and the energetic cost of swimming in a 30m long swim channel were determined at Ile de la Possession, Crozet Archipelago, using external data loggers and respirometry, respectively. Calibrated electronic data loggers equipped with a pressure sensor were used to determine dive durations: 95% ...
Clayton R A - - 1996
This study examined the effect of acute changes in oxygen tension on responses evoked by the bronchoconstrictor methacholine and the dilators salbutamol, atrial natriuretic peptide and isosorbide dinitrate in isolated bovine bronchi. Cumulative concentration-response curves to methacholine (10(-9)-3 x 10(-4) M) were constructed in three oxygen tensions; hyperoxia (95%), normoxia ...
Homma S - - 1996
We estimated a blood flow index, O2 supply index, and O2 consumption index from near-infrared (NIR) signals during venous occlusion imposed at rest and immediately after handgrip exercise with loads equal to 5, 10, 15, 20, 25, and 30% of the maximum voluntary contraction. We also estimated forearm blood flow ...
Zhou X - - 1996
BACKGROUND: We tested the hypothesis that late preconditioning is associated with increased antioxidant enzyme activity induced by initial oxidative stress. METHODS AND RESULTS: Isolated rat myocytes were preconditioned either with two cycles of 5 minutes of anoxia and 5 minutes of reoxygenation or with exogenous superoxide anion (O2-) generated by ...
Green S - - 1996
The VO2-power regression and O2 demand predicted for a supra-VO2peak intensity (i.e., 432 W) were determined in seven well-trained male cyclists (mean +/- SD: VO2peak = 5.29 +/- 0.51 l.min-1), using five incremental exercise protocols. These protocols were either continuous (CON) or discontinuous (DISCON), and comprised five to eight work ...
Broome J R - - 1996
An established swine model of neurologic decompression illness (DCI) was adapted to investigate the influence of no-stop ascent profile shape on DCI risk after deep air and heliox dives. Pigs underwent a simulated air dive in a dry chamber to 200 fsw (613 kPa) for 24 min bottom time. They ...
Thorens J B - - 1996
OBJECTIVE: To measure the effects of rapid permissive hypercapnia on hemodynamics and gas exchange in patients with acute respiratory distress syndrome (ARDS). DESIGN: Prospective study. SETTING: 18-bed, medical intensive care unit, university hospital. PATIENTS: 11 mechanically ventilated ARDS patients. INTERVENTION: Patients were sedated and ventilated in the controlled mode. Hypercapnia ...
Hill D W - - 1996
Usually, an initial step in determining accumulated O2 deficit is the estimation of the O2 demand of high intensity exercise by extrapolation from VO2 measured during steadystate submaximal exercise. It was hypothesized that O2 deficit could be determined without the need to estimate O2 demand by extrapolation. Ten women performed ...
Katz S L - - 1996
Gas exchange in the gills of the air-breathing fish Amia calva was modelled to determine how the gills modify fluctuations in venous P O2. These fluctuations form the physiological signal for aerial ventilation in these fish. This study was performed to examine the signal conditioning role that the gills may ...
Fujiwara J - - 1996
Moyamoya disease is a cerebrovascular obstructive disease of unknown etiology. The rebuild-up phenomenon, slowing of waves on electroencephalogram (EEG) seen after cessation of hyperventilation (HV), is one of the characteristic phenomena of the disease and is thought to be related to a development of its symptoms. Therefore, we investigated the ...
Perego G B - - 1996
Arteriovenous O2 content (a-vCO2) differences increase during exercise in normal subjects through several mechanisms including PO2, O2 pressure at which hemoglobin (Hb) is half saturated with O2 (P50), and Hb concentration changes. The present study was undertaken to evaluate how much these biochemical changes are relevant to a-vCO2 difference through ...
Favier R - - 1996
The effects of coca chewing on prolonged submaximal exercise responses were investigated in chronic coca chewers and compared with a group of nonchewers. At rest, coca chewing during a 1-h period was followed by a significant increase in blood glucose, free fatty acid, and norepinephrine concentrations and a significant reduction ...
Monteiro M G - - 1996
Nitrogen narcosis is often compared to alcohol intoxication, but no actual studies have been carried out in humans to test the comparability of these effects. If a common mechanism of action is responsible for the behavioral effects of these substances, biological variability of response to alcohol should correlate to that ...
Urbanek H - - 1996
Generation of superoxide anion (O2-.) and peroxidase activity were significantly increased in bean leaves infected with incompatible and compatible pathogens: Botrytis fabae and Botrytis cinerea, respectively, but the induction was greater on direct inoculation with B. fabae, than with B. cinerea. A slightly higher O2-. level was also detected in ...
Zhuang J - - 1996
Previous studies have indicated that native Tibetans have a larger lung capacity and better maintain arterial O2 saturation during exercise than Han ("Chinese") acclimatized lowlanders. To test if differences in ventilation or alveolar-arterial O2 gradient (A-aDO2) were responsible, we compared 10 lifelong Tibetan and 9 Han acclimatized newcomer residents of ...
Wagner P D - - 1996
Maximal VO2 (VO2max) has mostly been the province of exercise physiologists wishing to provide a measure of athletic potential or to characterize subjects in exercise-related research. It is also used clinically to determine a patient's exercise capacity. More recently, it has been recognized that the study of VO2max can provide ...
Stiris T A - - 1996
PURPOSE: The effect of the cyclooxygenase inhibitor ibuprofen (IB) on choroidal (ChBF) and retinal (RBF) blood flow during hyperoxia was examined in 21 spontaneously breathing newborn piglets. METHODS: ChBF and RBF were measured using radiolabelled microspheres before and 30 min after either saline or IB (30 mg/kg, i.v.) infusion in ...
Pollard G W - - 1995
The effects of ascent rate and post-dive exercise on the incidence of decompression sickness (DCS) were investigated in six groups of 20 rats exposed for 2 h at a pressure equivalent to 240 feet of sea water (fsw; 735 kPa). Ascent rates were 30, 45, and 60 fsw/min (92, 138, ...
Thorsen E - - 1995
Dynamic lung volumes and flows, slope of phase III of the single breath oxygen test (delta-N2), closing volume (CV), and transfer factor for carbon monoxide (TICO) were measured before and 1 h after an air dive in a hyperbaric chamber to a pressure of 0.49 MPa for 40 min. Six ...
Ferretti G - - 1995
The aim of this study was to test at maximal exercise the hypothesis of the temperature-dependence of the kinetics of O2 consumption (VO2), which predicts a greater O2 deficit as muscle temperature is decreased. Six male subjects underwent 3 min exercise bouts at the minimum power eliciting maximum O2 consumption ...
Gallaugher P - - 1995
The optimal hematocrit (Hctopt) hypothesis was tested by altering Hct (and arterial blood oxygen content, CaO2) between extreme states of anemia and polycythemia (Hct = 8-55%) in the rainbow trout. Since blood viscosity (eta) effects on cardiac output (Q) and O2 transport (TO2) are likely to be greatest when O2 ...
Signore P E - - 1995
Neural control of free and forced diving bradycardia and peripheral resistance was studied in the muskrat (Ondatra zibethicus) by means of acute pharmacological blockade with the muscarinic blocker atropine, the alpha-adrenergic blocker phentolamine and the beta-adrenergic blockers nadolol and propranolol. Saline injection was used as a control. Heart rate in ...
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