Search Results
Results 701 - 750 of 1508
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Bak M I - - 1998
To test the hypotheses that aged myocardium has lower ATP concentration and that a greater ATP hydrolysis during hypoxia exaggerates diastolic dysfunction in aged myocardium, we used 31P NMR spectroscopy to measure ATP and phosphocreatine (PCr) contents combined with heart function at baseline and during hypoxia and reoxygenation in perfused ...
Hogan Q H - - 1998
BACKGROUND: Although pulmonary function is minimally changed by neuraxial blockade in most cases, ventilatory arrest may ensue in rare cases. The authors examined the mechanism of apnea in a rabbit model of sudden ventilatory arrest during the combination of epidural anesthesia and hypoxia. METHODS: Rabbits were studied during alpha-chloralose sedation ...
McCormick A - - 1998
To evaluate whether changes in extracellular glutamate (Glu) levels in the central nervous system could explain the depressed hypoxic ventilatory response in hypothermic neonates, 12 anesthetized, paralyzed, and mechanically ventilated piglets <7 days old were studied. The Glu levels in the nucleus tractus solitarius obtained by microdialysis, minute phrenic output ...
Maggiorini M - - 1998
The pig has been reported to present with a stronger hypoxic pulmonary vasoconstriction than many other species, including the dog, but it is not known whether this is associated with a different longitudinal partitioning of pulmonary vascular resistance (PVR). We investigated the relationships between cardiac output (Q) and mean pulmonary ...
Wassmann H - - 1998
An in vitro human neocortical and rodent hippocampus brain slice technique was used under repeated hypoxia to investigate the cerebroprotective effect of hypothermia. As a hallmark of the neuronal hypoxic reaction anoxic terminal negativity (ATN) was registered to test whether hypothermia delays the onset of ATN. The experiments clearly confirm ...
Cao W - - 1998
Our study was designed to elucidate the effects of tetramethylpyrazine (TMP), a Chinese medicine, on plasma endothelin-1 (ET-1) levels in dogs with acute pulmonary alveolar hypoxia. Anesthetized dogs were used under artificial ventilation with room air or a hypoxic gas mixture (10% O2 and 90% N2) (n = 10) for ...
Amess P N - - 1998
The aim of this study was to assess the possible adverse effects of hypothermia, used as neural rescue therapy in a newborn piglet model. Sixteen newborn piglets were subjected to transient cerebral hypoxia-ischaemia by temporary occlusion of the carotid arteries and reduction of the fractional inspired oxygen to 0.12. On ...
Palhares D B - - 1998
This study examined the response of 10 newborns admitted to the Neonatal Intensive Care Unit of Hospital Universitário, UFMS, Campo Grande, MS, Brazil, submitted to mechanical ventilation under the following ventilator parameters: FiO2 = 100%, PIP (24 mmHg, rate > 30 mpm. All had severe hypoxia and were treated with ...
Serebrovskaya T - - 1998
Ventilatory responses to isocapnic, progressive hypoxic rebreathing (HVR), in supine and sitting positions, lung ventilation and gas exchange while breathing air and during 5 min of breathing 11% O2 in N2 were studied in 12 healthy young (20-28 years), 5 old (57-73 years) male subjects, and in 7 male patients ...
Lesske J - - 1997
BACKGROUND: The sleep apnea syndrome (SAS) is a common health problem with a 30% prevalence among patients with so-called essential hypertension. OBJECTIVE: Prompted by this epidemiologic link we tried to find out whether there is a cause-effect relationship between SAS and systemic hypertension. DESIGN: We developed an animal model to ...
Toporsian M - - 1997
The effect of prior in vivo hypoxia on the in vitro responses to changes in transmural pressure, alpha-adrenoceptor activation, and depolarization with KCl were evaluated in first-order diaphragmatic arterioles. Rats (n = 14 per group) were exposed to normoxia (controls) or to hypoxia (inspired O2 concentration = 10%) for 12 ...
Tamayo L - - 1997
Hypoxia activates erythropoietin-producing cells, chemoreceptor cells of the carotid body and pulmonary artery smooth muscle cells (PSMC) with a comparable arterial PO2 threshold of some 70 mmHg. The inhibition by CO of the hypoxic responses in the two former cell types has led to the proposal that a haemoprotein is ...
McKean T - - 1997
Previous studies on the effects of ischaemia or hypoxia in ectothermic vertebrate hearts have generally used preparations that were not performing at physiological levels of pressure and flow. The conclusions that ischaemia or hypoxia are not stressful to these organisms were examined in another species, Bufo marinus, in which a ...
Welling K L - - 1997
In a biventricular bypass preparation with constant-flow perfusion, pulmonary arterial pressure (Ppa), average pulmonary capillary pressure (Ppc), venous pressure (Pv), extravascular lung water volume (EVWd) and capillary permeability-surface area product for urea (PS) were determined in control animals and in animals subjected to alveolar hypoxia. During hypoxia, Ppa increased in ...
Miyamae M - - 1997
During mild graded ischemia in perfused rat hearts, we (V.M. Figueredo, R. Brandes, M. W. Weiner, B. M. Massie, and S. A. Camacho. J. Clin. Invest 90: 1794-1802, 1992) previously found a relationship between decreased left ventricular developed pressure (LVDP) and increased Pi, in which intracellular pH, cytosolic Ca2+ concentration ...
Simon B A - - 1997
The effects of hypoxia on lung and airway mechanics remain controversial, possibly because of the confounding effects of competing reflexes caused by systemic hypoxemia. We compared the effects of systemic hypoxemia with those of unilateral alveolar hypoxia (with systemic normoxemia) on unilateral respiratory system impedance (Z) in intact, anesthetized dogs. ...
Waters K A - - 1997
In early development, respiratory disorders can produce recurring hypoxic episodes during sleep. To examine possible effects of daily repeated vs. isolated hypoxic hypoxia, cardiorespiratory functions and central, respiratory-related neuromodulator levels in 21- to 32-day-old, chronically instrumented, unsedated piglets were compared between a fifth sequential daily hypoxia and an isolated hypoxia ...
Gaudet E A - - 1997
This study examined the possible contribution of the brain renin-angiotensin system on the sympathetic activation induced by hypoxia in conscious rabbits. Blood pressure (BP), heart rate (HR) and renal sympathetic nerve activity (RSNA) were recorded under conditions of normoxia and hypoxia (10% O2 + 3% CO2) before and after fourth ...
Bari F - - 1997
We examined the effects of hypoxic/ischemic stress on cerebral arteriolar responses to oxytocin in anesthetized piglets. Pial arteriolar diameters were measured using a cranial window and intravital microscopy. First, we evaluated arteriolar responses to topical application of oxytocin during normoxic conditions. We then determined whether 5-10 min of arterial hypoxia, ...
Portman M A - - 1997
Regulation of intracellular pH (pHi) may contribute to maintenance of cardiac contractile function during graded hypoxia in vivo. To test this hypothesis, we disturbed pHi regulation in vivo using two approaches: alpha-adrenoreceptor antagonism with phentolamine (1 mg/kg) (Phen; n = 9); and Na+/H+ exchange inhibition with HOE-642 (2 mg/kg; n ...
Kantrow S P - - 1997
Nitric oxide (NO.) has been proposed to modulate hypoxic vasoconstriction in the lung. The activity of nitric oxide synthase (NOS) can be inhibited by hypoxia because molecular oxygen is a necessary substrate for the enzyme. On the basis of this mechanism, we hypothesized that NOS activity has a key role ...
Bolling K S - - 1997
OBJECTIVES: Recent studies have shown that an injury occurs when the hypoxic heart is suddenly reoxygenated (as occurs with cardiopulmonary bypass), resulting in myocardial depression, impaired oxygenation, and increased pulmonary vascular resistance. We hypothesize that this injury is, in part, due to oxygen-derived radicals produced by activated white cells and ...
Pfeifer M - - 1997
It is unclear whether the increase in plasma atrial natriuretic peptide (ANP) concentration during hypoxia is due to direct, hypoxia-induced upregulation of ANP secretion in the heart, or to pressure overload of the right ventricle (RV) following hypoxia-induced pulmonary hypertension. To test the hypothesis that hypoxia leads to an early ...
Liu S Q - - 1997
The elastic laminae of the pulmonary arteries (PAs) undergo a progressive structural change in hypoxic hypertension. This study focused on the reversibility of altered PA elastic laminae of the rat due to hypoxic hypertension. The structure and cross-sectional area of the PA medial elastic laminae were examined by using electron-microscopic ...
Dwinell M R - - 1997
Episodic hypoxia has been shown to induce augmented normoxic ventilatory drive or long-term facilitation (LTF, continued hyperventilation after termination of hypoxic stimulation) in awake dogs and awake goats. The main objective of these experiments was to examine whether continuous isocapnic hypoxia in awake goats elicits LTF and additionally, to determine ...
Pelouch V - - 1997
Chronic hypoxia induces pulmonary hypertension and right ventricular hypertrophy. These changes are completely reversible, except for persistent myocardial fibrosis. The aim of the present study was to determine whether treatment with the angiotensin-converting enzyme (ACE) inhibitor enalapril can reduce the ventricular collagen content in animals recovering from chronic hypoxia. Adult ...
Eichinger M R - - 1997
Acute hypoxia attenuates agonist-induced constrictor and pressor responses in conscious rats, and a recent report suggests that hypoxia may also diminish myogenic reactivity in isolated, perfused rat kidneys. Thus we hypothesized that the diminished responsiveness to pressor agents during hypoxia is caused by an impairment of myogenic reactivity. Male Sprague-Dawley ...
Draper N J - - 1997
Brief myocardial hypoxia causes both systolic and diastolic dysfunction, the latter often persisting during re-oxygenation. The underlying mechanisms may involve cytosolic Ca2+ overload as well as altered myofilament properties. Recent studies show that nitric oxide enhances myocardial relaxation via a cGMP-induced reduction in myofilament response to Ca2+. We studied the ...
Haaland K - - 1997
The purpose of this study was to determine whether mild hypothermia after a moderate hypoxic-ischemic insult reduces the extent of brain damage. Hypoxia was achieved in newborn piglets (n = 24; age, 14-72 h) by abrupt reduction of the inspired oxygen concentration (FiO2) to the maximum concentration (approximately 6%) giving ...
Loeppky J A - - 1997
To investigate the possible effect of hypobaria on ventilation (VE) at high altitude, we exposed nine men to three conditions for 10 h in a chamber on separate occasions at least 1 week apart. These three conditions were: altitude (PB = 432, FIO2 = 0.207), normobaric hypoxia (PB = 614, ...
Groom A S - - 1997
1. It has been proposed that hypertension alters the respiratory and cardiovascular responses to chemoreceptor stimulation. However, in studies of human hypertension or in genetic animal models of hypertension it has been difficult to unequivocally attribute the changes to hypertension per se, rather than to a genetic predisposition towards an ...
Ziegler M G - - 1997
Patients with obstructive sleep apnea (OSA) are often hypertensive, and both apneics and hypertensives are reported to have increased sympathetic nerve activity. We measured plasma norepinephrine (NE) levels, clearance, and release rate among 65 subjects who breathed room air, a hypoxic gas mixture, and the hypoxic mixture combined with intermittent ...
Lindeis A E - - 1997
Positive pressure breathing (PPB) is a survival system that delivers high-pressure oxygen and body counterpressure in the event of cockpit depressurization at high altitude, but the ability of aircrew to perform an emergency "get-me-down" maneuver with this system is unknown. To address this question, a serial choice reaction time (RT) ...
Smith C A - - 1997
Specific carotid body (CB) hypocapnia in the-10-Torr (less than eupneic) range reduced ventilation in the awake and sleeping dog to the same degree as did CB hyperoxia [CB PO2 (PCBO2); > 500 Torr; C.A. Smith, K.W. Saupe, K. S. Henderson, and J. A. Dempsey. J. Appl. Physiol. 79:689-699, 1995], suggesting ...
Suzuki S - - 1997
BACKGROUND: It has previously been shown that fenoterol, a beta 2 adrenergic agonist, increases the ventilatory response to hypoxia (HVR) and hypercapnia (HCVR) in normal subjects. The effects of beta 2 adrenergic agonists on chemoreceptors in patients with chronic obstructive pulmonary disease (COPD) remain controversial. This study was designed to ...
Asano K - - 1997
BACKGROUND: The sympathetic nervous activity increases at high altitude but is not maximal initially when hypoxemia is most severe. HYPOTHESIS: The sympathetic activation would correlate better to the ventilatory response to chronic hypoxia than to the severity of hypoxia per se. METHODS: Eleven healthy male volunteers (27 +/- 1 yr) ...
Takeda S - - 1997
BACKGROUND: The mechanisms by which acute alveolar hypoxia induces pulmonary vasoconstriction remain unclear. We investigated whether endothelin-1 (ET-1) could be detected in plasma during pulmonary alveolar hypoxia without systemic hypoxemia (one-lung hypoxia) and whether the levels could be related to hemodynamic status in humans. METHODS: Thirteen adult patients with primary ...
Schirlo C - - 1997
To investigate the role of fluid shifts during the short-term adjustment to acute hypobaric hypoxia (AHH), the changes in lower limb (LV) and forearm volumes (FV) were measured using a strain-gauge plethysmograph technique in ten healthy volunteers exposed to different altitudes (450 m, 2500 m, 3500 m, 4500 m) in ...
Cogo A - - 1997
For the evaluation of a respiratory test at high altitude, several factors must be taken into account: the decreased barometric pressure, the decreased density of air and the degree of acclimatization which is related to the altitude and to the length of exposure. Several studies have shown a reduction in ...
Spencer R G - - 1997
To evaluate the resistance of physiologically hypertrophied hearts to hypoxic insult, we quantified the development of functional deficits during hypoxia and reoxygenation in hypertrophied hearts from swim-trained female rats and we correlated this with assessment of high-energy phosphate (HEP) metabolites from simultaneous 31P nuclear magnetic resonance (NMR) measurements. Furthermore, in ...
Vejlstrup N G - - 1997
There is disagreement in the literature about the time required for hypoxic constriction of pulmonary vessels to reach its full intensity. Some studies suggest that only minutes are required, others that several hours are needed. We examined the time course over 6 h of changes in pulmonary shunt (as a ...
Li H - - 1997
The role of phospholipase A2 (PLA2) and related inflammatory mediators in the mechanism of hypoxic pulmonary arterial hypertension was studied. Thirty Sprague-Dawley rats were equally divided into three groups at random: group A was the normal control group; group B was given 10% oxygen ventilation; group C was given 10% ...
Habermann G - - 1997
The effects of systemic hypoxia upon cardiovascular and renal function in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) are controversial. We examined the effects of systemic normobaric hypoxia (12.5% O2 in N2 for 4 hours) on arterial blood gases (pO2, pCO2, pH), mean arterial pressure (MAP), heart rate (HR), ...
Laks L - - 1997
The pulmonary artery pressure (Ppa) responses to short runs of acute hypoxia at two different levels of end-tidal CO2 were measured in nine normal subjects and in 20 patients with moderate to severe obstructive sleep apnea (OSA). In normal subjects the mean increase in Ppa in response to eucapnic hypoxia ...
Savourey G - - 1997
To investigate the effects of a short-term high altitude residence (2 weeks between 4150 m and 6885 m in the Andes) on the general and local cold responses after descent, 11 subjects were submitted both to a whole body standard cold air test (SCAT, dry bulb temperature = 1 degree ...
Malagon I - - 1996
OBJECTIVES: To measure, with the use of suprasternal Doppler ultrasound, the hemodynamic changes in patients and volunteers during air ambulance repatriation. DESIGN: Unblinded prospective observational study. SETTING: Chartered air ambulances for the international repatriation of patients. PATIENTS AND PARTICIPANTS: Six medical crew members and seven patients transported back to hospitals ...
Fletcher E C - - 1996
The systemic arterial blood pressure response to obstructive sleep apnea (OSA) in humans is usually repetitive (with each apnea) acute elevation with return to near baseline following the apnea. In addition, it is believed by most investigators that chronic diurnal elevation of systemic blood pressure may result from repetitive nightly ...
McKenzie D J - - 1996
Ventilatory and cardiac responses to hypoxia, sodium cyanide (NaCN), and intra-arterial injection of atropine, noradrenaline and DL-propranolol were investigated in the neotenous axolotl (Ambystoma mexicanum). Hypoxia elicited increased gill and lung ventilation and a tachycardia. Gill ventilation and air-breathing were stimulated by NaCN infused either into the ventilatory water stream ...
Green L R - - 1996
1. In fetal sheep (123-129 days gestation) we investigated the effect of acute isocapnic hypoxia (Pa,O2, 12 +/- 0.6 mmHg) on the fetal heart rate (FHR), mean systemic arterial blood pressure (MAP), carotid blood flow (CBF), femoral blood flow (FBF), carotid vascular resistance (CVR) and femoral vascular resistance (FVR) with ...
Loeppky J A - - 1996
BACKGROUND: Some reports claim that ventilation (VE) is greater in human subjects in normobaric hypoxia than at altitude following an equivalent drop in inspired PO2 (PIO2). It has been suggested that reduced barometric pressure (PB) may decrease chemoreceptor sensitivity and account for these results. In this pilot study we tested ...
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