Search Results
Results 501 - 550 of 1063
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Rodríguez F A - - 1999
PURPOSE: The purpose of the study was to examine the effect of a very short intermittent exposure to moderate hypoxia in a hypobaric chamber on aerobic performance capacity at sea level and the erythropoietic response. The effects of hypobaric hypoxia alone and combined with low-intensity exercise were also compared. METHODS: ...
Malisza K L - - 1999
Cerebral metabolite concentrations were measured in infant rats using proton magnetic resonance spectroscopic imaging. Measurements were made prior to, during and after exposure of rats (6- and 7-day-old) to unilateral cerebral hypoxia-ischemia (right carotid artery occlusion +2h 8% oxygen). Data clustered according to age and outcome-6-day-old animals with no infarct ...
Serebrovskaya T V - - 1999
Intermittent hypoxic training (IHT) shows promise for prevention and treatment of some diseases and efficiently produces great advancement in athletic training. We studied (1) hypoxic ventilatory responses (HVR) in supine and sitting positions during normobaric, isocapnic, progressive hypoxia (rebreathing technique) and (2) lung ventilation and gas exchange while breathing ambient ...
Horváth I - - 1999
Oxidative stress and hypoxia, which may occur in cystic fibrosis patients (CF) at rest and may be worsened by exercise, induce the expression of heme oxygenase (HO)-1, resulting in increased carbon monoxide (CO) formation. We tested that exhaled CO level (eCO) was higher in CF patients than in healthy subjects, ...
Trittenwein G - - 1999
Initiation of extracorporeal membrane oxygenation (ECMO) in septic children with severe respiratory failure often improves oxygenation but not pulmonary function. The factors affecting pulmonary function following onset of ECMO are not completely understood, but are thought to involve injury mediated, in part, by reactive oxygen species. We hypothesized that induction ...
Honess D J - - 1998
PURPOSE: The 99mTc-labelled amine oxime 99mTc-HL91 (Prognox) is under investigation as a potential noninvasive clinical marker of tumour hypoxia whose uptake can be monitored by gamma camera imaging. The aim was to assess its retention in 3 tumours under control and enhanced oxygenation conditions. MATERIALS AND METHODS: The SaF murine ...
Fatemian M - - 1998
During ventilatory acclimatization to hypoxia (VAH), the relationship between ventilation (VE) and end-tidal PCO2 (PETCO2) changes. This study was designed to determine 1) whether these changes can be seen early in VAH and 2) if these changes are present, whether the responses differ between isocapnic and poikilocapnic exposures. Ten healthy ...
Arnulf I - - 1998
Pontine cat is an ectothermic preparation, whose central temperature can artificially be lowered from 36 degrees C to 26 degrees C; this gradual hypothermia is accompanied by a dramatic increase in paradoxical sleep (PS). Two main hypotheses might explain this result: executive systems of PS might be switched on gradually ...
Hu Y - - 1998
The purpose of this study was to compare the effects of continuous and intermittent exercise training on serum testosterone [T] and corticosterone concentrations [Cort] during normoxia and hypobaric hypoxia. Male rats swam with loads of 3% (normoxia) or 2.25% (462 mmHg) body mass for 60 min in the continuous training ...
Cartwright C R - - 1998
BACKGROUND: The ventilatory response to acute hypoxia is biphasic, with an initial rapid increase followed by a slower decline. In humans, there is evidence that the magnitude of the decline in ventilation is proportional to the size of the initial increase. This study was done to define the role of ...
Stonestreet B S - - 1998
We tested the hypotheses that, in hypoxic young pigs, reductions in cardiac output restrict systemic oxygen transport to a greater extent than does hypoxia alone and that compensatory responses to this restriction are more effective in higher than in lower priority vasculatures. To study this, 10- to 14-day-old instrumented awake ...
Lenz T - - 1998
Chronic hypoxia has been shown to increase plasma endothelin levels. The current study was undertaken to examine the effect of exercise-induced tissue hypoxia on plasma levels of endothelin-1 (ET-1) and its precursor big endothelin-1 (Big-ET-1). After approval by the local ethical committee an incremental dynamic exercise test was performed in ...
Katayama K - - 1998
The present study was performed to investigate the effects of a combination of intermittent exposure to hypoxia during exercise training for short periods on ventilatory responses to hypoxia and hypercapnia (HVR and HCVR respectively) in humans. In a hypobaric chamber at a simulated altitude of 4,500 m (barometric pressure 432 ...
Chonan T - - 1998
We assessed the effect of sustained isocapnic hypoxia (PCO2 = 40 Torr, SaO2 = 80%) on the sensation of dyspnea in 16 normal healthy males. Subjects rated the sensation of dyspnea (c) on 15 cm visual analog scales during 20 min of sustained hypoxia. Following this hypoxic period, 8 subjects ...
Richardson R S - - 1998
It remains controversial whether lactate formation during progressive dynamic exercise from submaximal to maximal effort is due to muscle hypoxia. To study this question, we used direct measures of arterial and femoral venous lactate concentration, a thermodilution blood flow technique, phosphorus magnetic resonance spectroscopy (MRS), and myoglobin (Mb) saturation measured ...
Kimura H - - 1998
Ventilatory response to eucapnic sustained mild hypoxia was measured in one patient with unilateral and three patients with bilateral carotid body (CB) resection (defined UR and BR, respectively). The profile of ventilatory response in UR patient was initially augmented then gradually declined (biphasic pattern) as generally seen in normal subjects ...
Piehl Aulin K - - 1998
Effects on erythropoiesis and blood pressure as well as physical performance and mental effects were studied in 15 healthy subjects during intermittent exposure to normobaric hypoxia corresponding to either 2000 m (6 persons) or 2700 m (9 persons) above sea level; another group (5 persons) also served as controls at ...
Mohanraj P - - 1998
In hypoxia, mitochondrial respiration is decreased, thereby leading to a buildup of reducing equivalents that cannot be transferred to O2 at the cytochrome oxidase. This condition, called reductive stress, can paradoxically lead to enhanced formation of reactive O2 species, or a decrease in the ability of the cell to defend ...
Shapiro J I - - 1998
We examined the effects of acute and/or chronic hypokalemia on responses to 30 min of hypoxia and recovery in the isolated, perfused heart model. We found that both acute hypokalemia and chronic hypokalemia impaired contractility [expressed as maximum slope of pressure increase over time (dP/dt): 501 +/- 49 and 529 ...
Powell F L - - 1998
The ventilatory response to hypoxia depends on the pattern and intensity of hypoxic exposure and involves several physiological mechanisms. These mechanisms differ in their effect (facilitation or depression) on different components of ventilation (tidal volume and frequency) and in their time course (seconds to years). Some mechanisms last long enough ...
Greiner C - - 1998
To estimate whether mild hypothermia during repetitive hypoxia provides a neuroprotective effect on brain tissue, hippocampal slice preparations were subjected to repetitive hypoxic episodes under different temperature conditions. Slices of guinea pig hippocampus (n=40) were placed at the interface of artificial cerebrospinal fluid (aCSF) and gas (normoxia: 95% O2, 5% ...
Hanson M A - - 1998
Effects of chronic hypoxia on chemoreceptors and chemoreflexes in the fetus and neonate are reviewed. The effects are discussed in relation to those in the adult, in which there is an apparent paradox between the increase in chemoreflex gain during acclimatisation to the hypoxia of altitude vs the 'blunting' reported ...
Frappell P - - 1998
1. Ventilation (VE) in unanaesthetized hypothermic animals remains tightly coupled to oxygen consumption (VO2) such that VE/VO2 remains constant despite changes in body temperature. 2. Ventilatory responses to hypoxia would suggest that, relative to metabolic rate, the gain of the respiratory system is unaltered in hypothermic animals. 3. Future studies ...
Gavin T P - - 1998
The role of ventilation in the response in aerobic capacity and arterial oxygen saturation (SaO2) to acute hypoxic exercise was studied in 13 healthy active men divided into two groups based on their normoxic maximal exercise VE/VO2 (LOW < or =27.7; HIGH > or = 30.2) and PAO2 estimates (LOW ...
Janssen P L - - 1998
Ventilatory acclimatization to hypoxia (VAH) is the time-dependent increase in ventilation that occurs during sustained exposure to hypoxia. The mechanism for VAH remains elusive. We sought to determine whether a deficiency in the availability of carotid body dopamine is the mechanism of increased ventilatory responsiveness to hypoxia during VAH in ...
Navarro H - - 1998
L-aspartate (L-ASP) acts as an excitatory amino acid neurotransmitter at the synapses of brain stem respiratory neurons. In order to determine the effect of L-ASP on the neonatal ventilatory response to hypoxia, 9 control piglets [age 4.3 +/- (SD) 0.9 days, weight 1.9 +/- 0.5 kg] and 9 L-ASP-treated animals ...
Lueders M - - 1998
BACKGROUND/PURPOSE: Partial liquid ventilation (PLV) with perfluorocarbons decreases pulmonary vascular resistance (PVR) in injured piglet lungs without supplemental oxygen. These PVR changes may result either from direct mechanical effects or improved arterial oxygenation. In an uninjured hypoxic model of elevated PVR the authors asked the following questions: (1) Does prophylactic ...
Borel C O - - 1998
The effect of hypobaria on the ventilatory response to short-term hypoxia was studied by comparing the respiratory mechanical and inspired CO2 ventilatory responses to hypobaric hypoxia (438 mmHg) with normobaric hypoxia (11.8% FIO2). Fifteen spontaneously breathing, anesthetized cats were divided into three groups of five: time control, normobaric hypoxia and ...
Gonzalez N C - - 1998
Maximal exercise heart rate (HRmax) is reduced after acclimatization to hypobaric hypoxia. The low HRmax contributes to reduce maximal cardiac output (Qmax) and may limit maximal O2 uptake (VO2max). The objective of these experiments was to test the hypothesis that the reduction in Qmax after acclimatization to hypoxia, due, in ...
Saraví F D - - 1997
Short-circuit current (Isc) and transepithelial potential difference (PD) of the rat distal colon mucosa are sensitive to acute hypoxia in vitro. The relative contribution of luminal and serosal oxygenation in sustaining Isc and PD was assessed. Rat distal colon Isc and PD responses to hypoxia and reoxygenation of preparations of ...
Iwashiro K - - 1997
AIMS: We aimed at investigating contractile changes after hypoxia-reoxygenation and dobutamine challenge in superfused human atrial pectinate muscle to see whether high versus low stimulation rate during hypoxia might account for outcome differences compatible with the definition of an in vitro model of myocardial stunning and whether pretreatment with the ...
Tatsumi K - - 1997
Effective alveolar ventilation and hypoxic ventilatory response (HVR) are higher in females than in males and after endogenous or exogenous elevation of progesterone and estrogen. The contribution of normal physiological levels of ovarian hormones to resting ventilation and ventilatory control and whether their site(s) of action is central and/or peripheral ...
Thoresen M - - 1997
Hypothermia applied after hypoxia offers neuroprotection in neonatal animals, but the mechanisms involved remain unknown. Hypoxia was induced in newborn piglets and changes in excitatory amino acids (EAAs) and the citrulline:arginine ratio (CAR) were followed by microdialysis for 5 h. After the 45 min hypoxic insult, the animals were randomized ...
Lingenfelser T - - 1997
This study has investigated the relative importance of central nervous and peripheral nitroxidergic mechanisms in the control of pyloric motility. In 10 urethane-anaesthetized ferrets, drugs were administered directly to the CNS via a 0.5-mm-diameter cannula inserted into the 4th ventricle, approximately at the obex. Drugs were also given directly to ...
Esposito F - - 1997
1. The hypothesis that the ventilatory resistance to O2 flow (RV) does limit maximal O2 consumption (VO2,max) in hypoxia, but not in normoxia, at least in non-athletic subjects, was tested. RV was reduced by using He-O2 mixtures. 2. VO2,max was measured during graded cyclo-ergometric exercise in eight men (aged 30 ...
Saiki C - - 1997
During acute hypoxia, a hypometabolic response is commonly observed in many newborn and adult mammalian species. We hypothesized that, if hypoxic hypometabolism were entirely a regulated response with no limitation in O2 availability, pharmacological uncoupling of the oxidative phosphorylation should raise O2 consumption (VO2) by similar amounts in hypoxia and ...
Clar C - - 1997
This study examines the effects of prolonged hypoxia, with and without control of end-tidal CO2 partial pressure (PET,CO2), on the intensity-weighted mean velocity of blood flow in the middle cerebral artery (VIWM) and on heart rate (HR). Specifically, the time course of the responses, their reversibility with brief periods of ...
Groner J I - - 1997
PURPOSE: Both hypoxia and gram-negative sepsis are thought to play a role in the development of necrotizing enterocolitis (NEC). Endotoxin, a lipopolysaccharide (LPS), is a potent mediator of gram-negative sepsis. The author investigated the effect of LPS and hypoxia on arterial and mesenteric venous blood gas values in a piglet ...
Nagyova B - - 1997
To determine the influence of 0.2 minimum alveolar concentration (MAC) of enflurane on the time course of ventilation during sustained hypoxia, we studied 10 healthy adult volunteers with and without enflurane. The following design was used: end-tidal Po2 was maintained at 13.3 kPa for 8 min, at 6.7 kPa for ...
Bendle R D - - 1997
In the present study we sought to determine the contribution of endogenous brain stem angiotensin to renal sympathetic reflexes in conscious rabbits. Initial studies determined the subtype of receptor involved in the pressor response to angiotensin II (ANG II) administration into the fourth ventricle (4V). The AT1 antagonist losartan (0.001-10 ...
Westendorp R G - - 1997
INTRODUCTION: Syncope at altitude of otherwise healthy individuals is a well-known phenomenon (22). We report on the cardiovascular effects observed in subjects exposed to hypoxia to illustrate the role of the sympathetic-adrenergic system in hypoxic syncope. This study describes unexpected episodes of (near) syncope during two crossover trials at simulated ...
Bolekhan E A - - 1997
The responses of cats with different levels of taste sensitivity to phenylthiocarbamide (PTC) bitters to five-minute hypoxia were studied; PTC sensitivity is a genetic marker of the activity of the cAMP system. Animals able to perceive PTC showed a number of functional differences, with higher levels of resistance to anoxia, ...
Bielefeldt K - - 1997
Ischemia-reperfusion injury leads to profound functional and structural alterations of the gastrointestinal tract. We developed an in vitro model of reperfusion injury to study the changes in intestinal motility during hypoxia followed by reoxygenation. We recorded the spontaneous motor activity of intestinal rings from the proximal mouse jejunum, using force ...
Kozuma S - - 1997
OBJECTIVE: To investigate whether carotid sinus nerve reflexes are linked to the increase in heart rate variation in acute (one hour) hypoxia in late gestation fetal sheep DESIGN: Comparison of short term variation between intact and carotid sinus denervated fetuses in normoxia, hypoxia and post-hypoxia. SUBJECTS: Sixteen chronically catheterised pregnant ...
Rollin F - - 1997
The effects of an acute non-isocapnic hypoxia on ventilation and pulmonary mechanics were investigated in 6 healthy unsedated Holstein-Friesian (HF) calves and in 7 double-muscled calves of the Belgian White and Blue (BWB) breed known to develop more severe hypoxemia during exercise and respiratory diseases. Data were collected at 1 ...
Osanai S - - 1997
The hypothesis that H2O2 plays a critical role in hypoxic chemoreception in the cat carotid body (CB) was tested using a perfused-superfused preparation in vitro, measuring chemosensory discharge and CB tissue PO2 (PtiO2). According to the hypothesis NADPH mediated, PO2 dependent increase in H2O2 production would hyperpolarize the glomus cell, ...
Obmiñski Z - - 1997
INTRODUCTION: There has been limited characterization of the endocrine stress reactivity of aircraft pilots under the adverse environmental condition of hypobaric-hypoxia. This seems especially true with respect to using the non-invasive technique of salivary hormonal analysis. Thus, the purpose of this study was to characterize the salivary cortisol response to ...
Turner D L - - 1997
1. This study tested two hypotheses: (1) that episodic hypoxia elicits long-term facilitation (LTF) in respiratory neurons that is manifest as an increase in ventilation in awake goats; and (2) that LTF causes complex changes in respiratory pattern which are responsible for the increase in ventilation. 2. Each goat participated ...
Feng J - - 1997
We examined the effect on 6-Keto-PGF1a and TXB2 (the stable metabolites of PGI2 and TXA2) outflow of pretreatment with tetramethylpyrazine in the hypoxic isolated rat heart. In control hearts, 6-Keto-PGF1a was increased from 185 +/- 46 pg/ml of baseline value to 335 +/- 76 pg/ml after 2 min of hypoxia ...
Tansley J G - - 1997
During 8 h of either isocapnic or poikilocapnic hypoxia, there may be a rise in ventilation (VE) that cannot be rapidly reversed with a return to higher PO2 (L. S. G. E. Howard and P. A. Robbins. J. Appl. Physiol. 78:1098-1107, 1995). To investigate this further, three protocols were compared: ...
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