Search Results
Results 301 - 350 of 796
< 2 3 4 5 6 7 8 9 10 11 12 >
Tschakovsky M E - - 1999
Considerable debate surrounds the issue of whether the rate of adaptation of skeletal muscle O2 consumption (QO2) at the onset of exercise is limited by 1) the inertia of intrinsic cellular metabolic signals and enzyme activation or 2) the availability of O2 to the mitochondria, as determined by an extrinsic ...
McCanse W - - 1999
Systemic O2 transport during maximal exercise at different inspired PO2 (PIO2) values was studied in sodium cyanate-treated (CY) and nontreated (NT) rats. CY rats exhibited increased O2 affinity of Hb (exercise O2 half-saturation pressure of Hb = 27.5 vs. 42.5 Torr), elevated blood Hb concentration, pulmonary hypertension, blunted hypoxic pulmonary ...
Rice A J - - 1999
A group of 15 competitive male cyclists [mean peak oxygen uptake, VO2peak 68.5 (SEM 1.5 ml x kg(-1) x min(-1))] exercised on a cycle ergometer in a protocol which began at an intensity of 150 W and was increased by 25 W every 2 min until the subject was exhausted. ...
Richardson R S - - 1999
Maximal O2 delivery and O2 uptake (VO2) per 100 g of active muscle mass are far greater during knee extensor (KE) than during cycle exercise: 73 and 60 ml. min-1. 100 g-1 (2.4 kg of muscle) (R. S. Richardson, D. R. Knight, D. C. Poole, S. S. Kurdak, M. C. ...
Roach R C - - 1999
A universal O2 sensor presumes that compensation for impaired O2 delivery is triggered by low O2 tension, but in humans, comparisons of compensatory responses to altered arterial O2 content (CaO2) or tension (PaO2) have not been reported. To directly compare cardiac output (QTOT) and leg blood flow (LBF) responses to ...
MacDonald M J - - 1999
We hypothesized that near-infrared spectroscopy (NIRS) measures of hemoglobin and/or myoglobin O2 saturation (IR-SO2) in the vascular bed of exercising muscle would parallel changes in femoral venous O2 saturation (SfvO2) at the onset of leg-kicking exercise in humans. Six healthy subjects performed transitions from rest to 48 +/- 3 (SE)-W ...
Buck D - - 1999
The aim of this present study was to evaluate the effect of the number of submaximal exercise bouts used to construct the power-VO2 regression, on calculations of MAOD through the sequential and systematic removal of the highest and lowest submaximal VO2 values from the standard ten point regression line. Eight ...
Jung F - - 1999
The oxygen partial pressure (pO2) in the anterior tibial muscle was measured in n=12 (6 physically active and 6 sedentary) apparently healthy subjects. This was the first time a flexible micro catheter with an outer diameter of 0.45 mm was used during skeletal muscular activity in men. A two level ...
Bergman B C - - 1999
To evaluate the hypothesis that endurance training increases intramuscular triglyceride (IMTG) oxidation, we studied leg net free fatty acid (FFA) and glycerol exchange during 1 h of cycle ergometry at two intensities before training [45 and 65% of peak rate of oxygen consumption (V(O2) peak)] and after training [65% pretraining ...
Wasserman K - - 1999
During exercise, O2 transport from capillary to myocyte is not diffusion-limited until end-capillary PO2 reaches its lowest value (critical capillary PO2). Critical capillary PO2 is reached at the mid-level of the subject's work capacity, not at Vo2 max. Femoral vein lactate does not increase until the critical capillary PO2 is ...
Hopkins S R - - 1999
Increased ventilation-perfusion (VA/Q) inequality is observed in approximately 50% of humans during heavy exercise and contributes to the widening of the alveolar-arterial O2 difference (A-aDO2). Despite extensive investigation, the cause remains unknown. As a first step to more direct examination of this problem, we developed an animal model. Eight Yucatan ...
Billat V L - - 1998
The purpose of this study was to examine the influence of the type of exercise (running vs. cycling) on the O2 uptake V(O2) slow component. Ten triathletes performed exhaustive exercise on a treadmill and on a cycloergometer at a work rate corresponding to 90% of maximal VO2 (90% work rate ...
Kahaly G J - - 1998
Dyspnea on exertion is a common complaint in hyperthyroidism, and this thyroid dysfunction has been implicated as a primary cause of impaired effort tolerance. Using spirometry and spiroergometry, 42 patients with untreated hyperthyroidism were examined, and the condition was controlled 7 days later under propranolol monotherapy, as well as after ...
Ferretti G - - 1998
The hypothesis was tested that prolonged bed rest impairs O2 transport during exercise, which implies a lowering of cardiac output Qc and O2 delivery (QaO2). The following parameters were determined in five males at rest and at the steady-state of the 100-W exercise before (B) and after (A) 42-day bed ...
Scheuermann B W - - 1998
Inhibition of carbonic anhydrase (CA) is associated with a lower plasma lactate concentration ([La-]pl) during fatiguing exercise. We hypothesized that a lower [La-]pl may be associated with faster O2 uptake (V(O2)) kinetics during constant-load exercise. Seven men performed cycle ergometer exercise during control (Con) and acute CA inhibition with acetazolamide ...
Haseler L J - - 1998
There is evidence that the concentration of the high-energy phosphate metabolites may be altered during steady-state submaximal exercise by the breathing of different fractions of inspired O2 (FIO2). Whereas it has been suggested that these changes may be the result of differences in time taken to achieve steady-state O2 uptake ...
St Croix C M - - 1998
Twenty-eight healthy women (ages 27.2 +/- 6.4 yr) with widely varying fitness levels [maximal O2 consumption (VO2 max), 31-70 ml . kg-1 . min-1] first completed a progressive incremental treadmill test to VO2 max (total duration, 13.3 +/- 1.4 min; 97 +/- 37 s at maximal workload), rested for 20 ...
Heil D P - - 1998
This study examined the scaling relationships of net O2 uptake [V(O2)(net) = V(O2) - resting V(O2)] to body mass (MB) and combined mass (MC = MB + bicycle) during uphill treadmill bicycling. It was hypothesized that V(O2)(net) (l/min) would scale proportionally with MC [i.e., VO2(net) approximately M1.0C] and less than ...
Hopkins S R - - 1998
During maximal exercise, ventilation-perfusion inequality increases, especially in athletes. The mechanism remains speculative. We hypothesized that, if interstitial pulmonary edema is involved, prolonged exercise would result in increasing ventilation-perfusion inequality over time by exposing the pulmonary vascular bed to high pressures for a long duration. The response to short-term exercise ...
Wolfel E E - - 1998
Whole body O2 uptake (VO2) during maximal and submaximal exercise has been shown to be preserved in the setting of beta-adrenergic blockade at high altitude, despite marked reductions in heart rate during exercise. An increase in stroke volume at high altitude has been suggested as the mechanism that preserves systemic ...
Stubenitsky R - - 1998
OBJECTIVE: The present study determined the role of the autonomic nervous system (ANS) in the regulation of systemic and pulmonary circulation and of O2 delivery and utilization in swine at rest and during graded treadmill exercise. METHODS: Instrumented swine (n = 12) were subjected to treadmill exercise (1-5 km/h) under ...
Feet B A - - 1998
We tested the hypothesis that early brain recovery in hypoxic newborn piglets is improved by resuscitating with an O2 supply close to the minimum level required by the newborn piglet brain. Severely hypoxic 2-5-d-old anaesthetized piglets were randomly divided into three resuscitation groups: hypoxaemic (n = 8), 21% O2 (n ...
van Beek J H - - 1998
Although usually steady-state fluxes and metabolite levels are assessed for the study of metabolic regulation, much can be learned from studying the transient response during quick changes of an input to the system. To this end we study the transient response of O2 consumption in the heart during steps in ...
Grant S M - - 1998
Scuba diving is becoming more and more popular and dentists are increasingly likely to encounter patients with diving-related problems. Protruded mandibular positions and the biting forces exercised on the anterior occlusion during diving can cause pain and dysfunction, particularly where a predisposing factor such as bruxism exists. In this article, ...
García García J J - - 1998
It is not clear how macrophages respond to exercise when the immune system is previously activated. The aim of the present work was to determine the response of macrophages to exercise in already immunostimulated animals with polar glycopeptidolipids extracted from Mycobacterium chelonae (GPLp-Mc). Results showed an increased phagocytosis and O2- ...
Arisi A C - - 1998
Chloroplast-targeted overexpression of an Fe superoxide dismutase (SOD) from Arabidopsis thaliana resulted in substantially increased foliar SOD activities. Ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase activities were similar in the leaves from all of the lines, but dehydroascorbate reductase activity was increased in the leaves of the FeSOD transformants relative ...
Jammes Y - - 1998
Very few data are found in the literature on the adjustment of the motor drive to contracting muscles to their oxygen uptake (V(O2)). The present study examines in seven untrained and trained individuals, who performed a progressive 8 min and two 5 min constant-load cycling exercises, the changes in the ...
Heller H - - 1998
In this study we investigated the contribution of diffusion limitation to the exercise-induced hypoxaemia in interstitial lung disease (ILD). We applied isotopic analysis to the composition of the stable isotopic oxygen molecules 16O2 and 16O18O in expiratory gas mixtures obtained from six ILD patients and six healthy subjects at rest ...
Cardús J - - 1998
In a recent study of completely sedentary normal young subjects, leg VO2max was reduced by hypoxia in proportion to mean capillary PO2 as F(I)O2 was reduced from 0.15 to 0.12. However, the increase in VO2max from F(I)O2 = 0.15 to 0.21 was less than expected for the increase in mean ...
Feet B A - - 1998
We tested the hypothesis that hypoxic newborn piglets can be successfully resuscitated with lower O2 concentrations than 21%. Severely hypoxic, 2-4-d-old, anesthetized piglets were randomly divided into five resuscitation groups: 21% O2 (n = 10), 18% O2 (n = 9), 15% O2 (n = 9), 12% O2 (n = 8), ...
Hijazi O M - - 1998
Patients who have undergone pneumonectomy (PNX) show limited exercise capacity, partly attributable to an impaired stroke index (SI). To determine whether this limitation is due to deconditioning, we assessed exercise performance and cardiopulmonary function in seven patients after PNX (age: 59 +/- 2 yr, mean +/- SEM) and eight normal, ...
Yu X O - - 1998
OBJECTIVE: To study the relationship between oxygen (O2) delivery (DO2) and O2 consumption (VO2) in surfactant-depleted newborn piglets. DESIGN: Prospective animal study. SETTING: Hospital surgical research laboratory. SUBJECTS: Twenty-six anesthetized and ventilated newborn piglets. INTERVENTIONS: Twenty of the animals were subjected to repeated saline lung lavages, and then assigned to ...
Suarez R K - - 1998
Mass-specific rates of aerobic metabolism VO2/Mb) scale in inverse proportion to body mass (Mb). Thus, small hummingbirds display the highest VO2/Mb known among vertebrates. Among all animals, higher VO2/Mb values are known only in flying insects. The high body-mass-specific rates of metabolism seen in hummingbirds are made possible by high ...
Moore G E - - 1998
Exercise intolerance is a problem in renal failure. Stationary cycle training during hemodialysis treatment is recommended as safe, effective, and practical, but requires compensations for both exercise and acute changes in uremia. Eight patients pedalled for 5 minutes, at 60% of VO2peak, at 0, 1, 2, and 3 hours of ...
Arras T - - 1998
The growth rates of Pseudomonas putida KT2442 and mt-2 on benzoate, 4-hydroxybenzoate, or 4-methylbenzoate showed an exponential decrease with decreasing oxygen tensions (partial O2 tension [pO2] values). The oxygen tensions resulting in half-maximal growth rates were in the range of 7 to 8 mbar of O2 (corresponding to 7 to ...
Feet B A - - 1998
We tested the hypothesis that controlled hypoxemic resuscitation improves early cerebral metabolic and electrophysiological recovery in hypoxic newborn piglets. Severely hypoxic anesthetized piglets were randomly divided into three resuscitation groups: hypoxemic, 21% O2, and 100% O2 groups (8 in each group). The hypoxemic group was mechanically ventilated with 12-18% O2 ...
Legate N J - - 1998
The function of myoglobin at the cellular level was investigated by comparing O2 consumption in isolated myoglobin-rich cardiac myocytes from the sea raven (Hemitripterus americanus) and myoglobin-poor myocytes from the ocean pout (Macrozoarces americanus). O2 consumption by sea raven myocytes, 0.21 +/- 0.04 microM O2/10(6) cells.min-1, was significantly higher than ...
Woodin M - - 1998
Underwater feeding behavior was measured in 10 captive canvasback ducks (Aythya valisineria) for 12 days under a 12:12-h light-dark photoperiod. Feeding activity exhibited a daily rhythm, with 76% of dives occurring at night. In separate experiments on six of these ducks, a circadian rhythm was observed in the duration of ...
Chen L - - 1998
The effects of hypoxemia and hypercapnia in acute cardiovascular response to periodic non-obstructive apneas were explored in seven preinstrumented, sedated paralyzed and ventilated pigs under three conditions: room air breathing (RA), O2 supplementation (O2), and supplementation with O2 and CO2 (CO2). EEG monitoring showed no arousal under any conditions. RA ...
Harms C A - - 1998
1. We questioned whether exercise-induced arterial hypoxaemia (EIAH) occurs in healthy active women, who have smaller lungs, reduced lung diffusion, and lower maximal O2 consumption rate (VO2,max) than age- and height-matched men. 2. Twenty-nine healthy young women with widely varying fitness levels (VO2,max, 57 +/- 6 ml kg-1 min-1; range, ...
Rohlicek C V - - 1998
We questioned whether the decrease in O2 consumption (VO2) during hypoxia in newborns is a regulated response or reflects a limitation in O2 availability. Experiments were conducted on previously instrumented conscious newborn dogs. VO2 was measured at a warm ambient temperature (30 degrees C, n = 7) or in the ...
Richardson R S - - 1998
The series of drops in PO2 which comprise the oxygen cascade from the air to mammalian tissue can provide useful information about O2 transport during exercise in both health and disease, but the complete cascade has been challenging to study in vivo. This paper reviews a series of in vivo ...
Webb P M - - 1998
Many techniques have been employed to measure metabolic and cardiovascular changes in diving marine mammals. Each of these methods has its advantages, but the methods also have drawbacks when applied to phocid seals. The aim of this study was to investigate heart rate and metabolic responses to diving in juvenile ...
Hindell M A - - 1998
Heart rate, swimming speed, and diving behaviour were recorded simultaneously for an adult female southern elephant seal during her postbreeding period at sea with a Wildlife Computers heart-rate time depth recorder and a velocity time depth recorder. The errors associated with data storage versus real-time data collection of these data ...
Aguilaniu B - - 1998
We have previously reported a reduction in exercise-induced hypoxaemia following polyunsaturated fatty acid supplementation (PUFA). Although this might have been explained by increases in membrane fluidity, a clear explanation could not be provided due to potentially confounding influences of series-2 prosta- glandin mediated effects resulting from PUFA. In this investigation, ...
Mekjavić I B - - 1998
Tear film bubble formation and ultrasound reflectivity of the lens-vitreous humor compartments were monitored following simulated dives in a hyperbaric chamber. the sensitivity of these methods in determining decompression stress was compared with the results of precordial Doppler ultrasound. In addition, the utility of these diagnostic techniques in testing decompression ...
Gelfand R - - 1998
Potential adverse effects on the O2-sensing function of the carotid body when its cells are exposed to toxic O2 pressures were assessed during investigations of human organ tolerance to prolonged continuous and intermittent hyperoxia (Predictive Studies V and VI). Isocapnic hypoxic ventilatory responses (HVR) were determined at 1.0 ATA before ...
Shaffer S A - - 1997
The white whale Delphinapterus leucas is an exceptional diver, yet we know little about the physiology that enables this species to make prolonged dives. We studied trained white whales with the specific goal of assessing their diving and swimming performance. Two adult whales performed dives to a test platform suspended ...
Bengtsson J - - 1997
OBJECTIVE: Fast paramagnetic oxygen analyzers have made it possible to measure inspiratory to end-tidal oxygen concentration difference (P(I-ET)O2) breath-by-breath. It is now frequently displayed on monitors during routine anesthesia. We wanted to study the effects of major changes in metabolism, ventilation and circulation on P(I-ET)O2. METHODS: Ten healthy male volunteers ...
Tonkonogi M - - 1997
Muscle oxidative function has been investigated in subjects with various training status (VO2 max, 41-72 mL O2 kg-1 body wt min-1, n = 10). Mitochondria were isolated from biopsies taken from m. vastus lateralis. Maximal mitochondrial oxygen consumption (QO2) and ATP production (MAPR) were measured with polarographic and bioluminometric techniques, ...
< 2 3 4 5 6 7 8 9 10 11 12 >