Search Results
Results 551 - 600 of 1560
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Barton Cyril H - - 2003
BACKGROUND: Chronic exposure to hypobaric hypoxia has been shown to increase arterial pressure in genetically normal rats. The associated increase in blood pressure is unrelated to the hypoxia-induced erythrocytosis and persists indefinitely after restoration of normoxia. It is accompanied by a marked reduction in urinary excretion of nitric oxide metabolites ...
Mateika Jason H - - 2004
We hypothesized that the acute ventilatory response to hypoxia is enhanced after exposure to episodic hypoxia in awake humans. Eleven subjects completed a series of rebreathing trials before and after exposure to eight 4-min episodes of hypoxia. During the rebreathing trials, subjects initially hyperventilated to reduce the partial pressure of ...
Hui Anna S - - 2003
Chronic intermittent hypoxia, a characteristic feature of sleep-disordered breathing, induces hypertension through augmented sympathetic nerve activity and requires the presence of functional carotid body arterial chemoreceptors. In contrast, chronic sustained hypoxia does not alter blood pressure. We therefore analyzed the biosynthetic pathways of catecholamines in peripheral nervous system structures involved ...
Oh HyunSoo - - 2003
The purpose of this study was to clarify the effects of interventions that were applied to prevent endotracheal suction-induced hypoxia by meta-analysis. To obtain a sample for this meta-analysis, a computerized search was performed through MEDLINE in addition to tracking down additional references cited in bibliographies of past reports. Finally ...
O'Driscoll Denise M - - 2004
The cardiovascular response to an arousal occurring at the termination of an obstructive apnea is almost double that to a spontaneous arousal. We investigated the hypothesis that central plus peripheral chemoreceptor stimulation, induced by hypercapnic hypoxia (HH), augments the cardiovascular response to arousal from sleep. Auditory-induced arousals during normoxia and ...
Sakai Akio - - 2003
The blue-sheep, pika, and yak live in the Tibetan highlands at an altitude of 6,100 m and are typical mammals adapted to high-altitudes. These animals have a long history of habitation at high-altitudes and are considered to be "animals completely adapted to high-altitudes" because of their physiological and morphological traits ...
Springer J - - 2003
Substance P (SP) levels have been reported to be elevated in animal models of pulmonary hypertension (PH) and chronic administration of SP has been shown to induce PH. In the present study, the role of reactive oxygen species (ROS) as mediators of SP-induced vascular remodelling and PH was analysed. Vascular ...
Phillips Shane A - - 2004
The goal of the present study was to evaluate the effects of relatively short-term chronic intermittent hypoxia (CIH) on endothelial function of resistance vessels in the skeletal muscle and cerebral circulations. Sprague-Dawley rats were exposed to 14 days of CIH (10% fraction of inspired oxygen for 1 min at 4-min ...
Mortazavi Amir - - 2003
BACKGROUND: Individuals with pulmonary and cardiac disorders are particularly at risk of developing hypoxemia at altitude. Our objective is to describe the normal and maladaptive physiological responses to altitude-related hypoxia, to review existing methods and guidelines for preflight assessment of air travelers, and to provide recommendations for treatment of hypoxia ...
Menna Tara M - - 2003
In the externally pipped chicken embryo, oxygen consumption through the chorioallantoic membrane (VO2CAM) ranged between 2 and 55% (mean approximately 24%) of that through the lungs (VO2lung). Hypercapnia (5'-10' of 2, 5, or 8% CO2) or mild hypoxia (15% O2) had minor effects on VO2, whereas moderate or severe hypoxia ...
Hanada Akiko - - 2003
Acute systemic hypoxia causes significant increases in human skeletal muscle sympathetic nerve activity (MSNA), heart rate and ventilation. This phenomenon is thought to be primarily mediated by excitation of peripheral chemoreceptors sensing a fall in arterial free oxygen partial pressure (Pa,O2). We directly tested the role of Pa,O2 on MSNA ...
Halliwill John R - - 2003
We tested the hypothesis that activation of peripheral chemoreceptors with acute isocapnic hypoxia resets arterial baroreflex control of both heart rate and sympathetic vasoconstrictor outflow to higher pressures, resulting in increased heart rate and muscle sympathetic nerve activity without changes in baroreflex sensitivity. We further hypothesized that this resetting would ...
Calbet Jose A L - - 2003
Chronic hypoxia is associated with elevated sympathetic activity and hypertension in patients with chronic pulmonary obstructive disease. However, the effect of chronic hypoxia on systemic and regional sympathetic activity in healthy humans remains unknown. To determine if chronic hypoxia in healthy humans is associated with hyperactivity of the sympathetic system, ...
Nomura Norikazu - - 2003
BACKGROUND: Cardiotrophin-1 (CT-1) reduces arterial blood pressure by activating nitric oxide synthesis. This study attempted to elucidate the effect of CT-1 on pulmonary arteries of pulmonary hypertensive rats. METHODS: Pulmonary hypertension was induced in rats in a hypoxic chamber containing 10% to 11% oxygen. Rats kept in the hypoxic environment ...
Crosby Alexi - - 2003
The risk of venous thrombosis may be increased during aeroplane flights, which may, partly, relate to activation of coagulation by hypoxia that is caused by the reduction of pressure in the aircraft cabin. To find out whether hypoxia activates coagulation, we exposed eight healthy human participants to 8 h of ...
Glaus T M - - 2003
Pulmonary hypertension is a well-recognised condition in dogs, and, among other mechanisms, is caused by hypoxia. In order to evaluate the effect of chronic hypobaric hypoxia on pulmonary arterial pressure in dogs, a colony of 19 clinically and biochemically healthy Greenland sled dogs living permanently at at least 2300 m ...
Nelin Leif D - - 2003
Inhaled nitric oxide (iNO) is used as a selective pulmonary vasodilator, and often under conditions when a high fraction of inspired oxygen is indicated. However, little is known about the potential toxicity of iNO therapy with or without concomitant oxygen therapy. NO can combine with superoxide (O2-) to form peroxynitrite ...
Perreault Thérèse - - 2003
During the fetal period, blood is oxygenated through the placenta, and most of the cardiac output bypasses the lung through the ductus arteriosus. At birth, pulmonary vascular resistance falls with the initiation of ventilation. Coincidentally, the ductus arteriosus constricts. Endothelin-1 (ET-1) appears to play an important role during that transition ...
Broberg Craig S - - 2003
In response to chronic fetal anemia, coronary blood flow, maximal coronary conductance, and coronary reserve increase. We sought to determine whether chronic fetal anemia alters left ventricular (LV) function in adulthood. We studied adult sheep that had been made anemic for 20 days in utero by phlebotomy. They were transfused ...
McKenzie D J - - 2003
European eels were exposed for 6 weeks to water CO(2) partial pressures (P(CO)(2)) from ambient (approx. 0.8 mmHg), through 15+/-1 mmHg and 30+/-1 mmHg to 45+/-1 mmHg in water with a total hardness of 240 mg l(-1) as CaCO(3), pH 8.2, at 23+/-1 degrees C. Arterial plasma P(CO)(2) equilibrated at ...
Wangsa-Wirawan Norbert D - - 2003
We reviewed research on retinal oxygen (O2) distribution and use, focusing on O2 microelectrode studies in animals with circulatory patterns similar to those of humans. The inner and outer halves of the retina are different domains in terms of O2. Understanding their properties can suggest mechanisms of and therapies for ...
Nishioka Nobuko - - 2003
AIM: To investigate the effect of hypoxia on the auditory system in fetuses, we attempted to analyze the auditory brainstem response, the middle latency response, and changes of several physiological parameters of goat fetuses during extrauterine incubation. METHODS: We conducted extrauterine incubation of five goat fetuses at around 127days of ...
Yelmen Nermin Karaturan - - 2003
The purpose of this study was to investigate the stimulatory effect of hypoxia on the secretion of serotonin by neuroepithelial bodies (NEB) as well as to determine the relation between its level and changes in pulmonary arterial pressure (PAP) and also to determinate the effect of serotonin antagonists (pizotifen and ...
Ning Xue-Han - - 2003
Hypothermia before and/or during no-flow ischemia promotes cardiac functional recovery and maintains mRNA expression for stress proteins and mitochondrial membrane proteins (MMP) during reperfusion. Adaptation and protection may occur through cold-induced change in anaerobic metabolism. Accordingly, the principal objective of this study was to test the hypothesis that hypothermia preserves ...
Emery C J - - 2003
We aimed to explain diverse pulmonary vascular responses to hypoxia in different preparations and their modulation by NO. In rats we compared isolated perfused lungs (IPL), small vessels in vitro (PRVs) and in vivo preparations. In IPL and in vivo, acute and chronic nitric oxide synthase (NOS) blockade with L-NAME ...
Klaus Stephan - - 2003
Oxygen deficiency during critical illness may cause profound changes in cellular metabolism and subsequent tissue and organ dysfunction. Clinical treatment in these cases targets rapid reoxygenation to avoid a prolonged impaired synthesis of cellular high-energy phosphates (ATP). However, the effect of this therapeutic intervention on tissue metabolism has not been ...
Kemming G I - - 2003
OBJECTIVE: During normovolaemic haemodilution arterial O(2)-content decreases exponentially. Nevertheless, tissue oxygenation is first maintained initially by increased organ perfusion and O(2)-extraction. As soon as these compensatory mechanisms are exhausted, myocardial ischaemia and tissue hypoxia occur at an individual 'critical' haematocrit (Hct) value. This study was conducted in order to assess ...
Andersen Johnnie B - - 2003
Amphibians exhibit cardiorespiratory responses to hypoxia and, although several oxygen-sensitive chemoreceptor sites have been identified, the specific oxygen stimulus that triggers these responses remains controversial. This study investigates whether the cardiovascular response to oxygen shortage correlates with decreased oxygen partial pressure of arterial blood (Pa(O(2))) or reduced oxygen concentration ([O(2)]) ...
Savourey Gustave - - 2003
Since Bert (1878) and Barcroft (1925), studies on hypoxia are realized by lowering ambient O(2) partial pressure (PO(2)) either by barometric pressure reduction (hypobaric hypoxia HH) or by lowering the O(2) fraction (normobaric hypoxia NH). Today, a question is still debated: "are there any physiological differences between HH and NH ...
Miyamura Miharu - - 2003
In order to clarify whether or not ventilatory and circulatory responses to hypoxia and hypercapnia at rest in male vocalists (n = 11) are identical to those of untrained subjects (n = 11), ventilatory responses to hypoxia (HVR) and hypercapnia (HCVR) were estimated as the slope of regression relating .VI ...
Hansen Jim - - 2003
Acute exposure to hypoxia causes chemoreflex activation of the sympathetic nervous system. During acclimatization to high altitude hypoxia, arterial oxygen content recovers, but it is unknown to what degree sympathetic activation is maintained or normalized during prolonged exposure to hypoxia. We therefore measured sympathetic nerve activity directly by peroneal microneurography ...
Peng Ying-Jie - - 2003
Long-term facilitation (LTF) of breathing elicited by episodic hypoxia (EH) is an extensively studied example of plasticity of respiratory motor behavior. Previous studies employed the paradigm of EH wherein each episode of hypoxia was 5 min. This paradigm is rarely encountered in nature. Brief episodes of hypoxia are encountered frequently ...
Taylor Barbara E - - 2003
Lymnaea stagnalis were exposed to hypoxic and chemical challenges while ventilation, heart rate and metabolism were monitored. Hypoxia increased ventilatory behavior, but this response was eliminated by immersion in 0.75 mM nitric oxide synthase (NOS) inhibitor, 7-nitroindazole (7 NI). 7 NI also suppressed ventilatory behavior under normoxia. 10.0 mM L-arginine ...
McGaw Iain J - - 2003
Decapod crustaceans inhabit aquatic environments that are frequently subjected to changes in salinity and oxygen content. The physiological responses of decapod crustaceans to either salinity or hypoxia are well documented; however, there are many fewer reports on the physiological responses during exposure to these parameters in combination. We investigated the ...
Bosco Gerardo - - 2003
We tested the hypothesis that acute hypoxia may alter the circadian pattern of body temperature in adult humans. Six healthy subjects were studied in normoxia, hypoxia (approximately 13% inspired O(2)), and again normoxia, each session lasting >24 h and spaced a few days apart, with a constant routine protocol of ...
Sundell Hakan W - - 2003
The hypothesis that postnatal nicotine exposure weakens cardiorespiratory recovery from reflex apnea and bradycardia was tested in eight lambs continuously infused with nicotine from the day of birth at a dose of 1 to 2 mg.kg(-1).d(-1). Eight age-matched lambs infused with saline served as controls. Apnea and bradycardia were elicited ...
Sarybaev Akpay S - - 2003
Chronic alveolar hypoxia due to disease or low atmospheric pressure at high altitude results in the development of hypoxic pulmonary hypertension. The effects of intermittent hypoxia on pulmonary hemodynamics in healthy men have not been studied. We aimed to investigate, prospectively, pulmonary hemodynamics in workers commuting between an elevation of ...
Kleinsasser Axel - - 2003
High altitude pulmonary edema (HAPE) affects unacclimatized individuals ascending rapidly to high altitude. The pathogenesis of HAPE is not fully elucidated, and many investigative techniques that could provide valuable information are not suitable for use in humans; thus, an animal model is desirable. Rabbits, sheep, dogs, and ferrets have been ...
Saiki Chikako - - 2003
Many anesthetics are known to decrease ventilation (V(E)) and metabolic rate (MR). Because MR is known to contribute to the V(E) level, one would expect some parallelism between the changes in V(E) and MR during anesthesia. We tested this hypothesis in normoxia and hypoxia (12% O2) on male Wistar rats ...
Nouette-Gaulain Karine - - 2002
BACKGROUND: Adaptation to chronic exposure to hypoxia alters energy metabolism in the heart, particularly in the left ventricle, which undergoes a loss in oxidative capacity. Highly lipophilic local anesthetics interfere with mitochondrial energy metabolism. The purpose of this study was to compare the effects of bupivacaine on mitochondrial energy metabolism ...
Tinjust David - - 2002
PURPOSE: Few studies have investigated the effect of systemic hypoxia on the vascular and neural function of the human retina. Such studies can help us understand physiological responses to environmental hypoxia, as well as the pathophysiological mechanisms underlying certain ocular diseases. The objective of this study was to investigate the ...
Weissmann Norbert - - 2003
Hypoxic pulmonary vasoconstriction (HPV) matches lung perfusion to ventilation for optimizing pulmonary gas exchange. Chronic alveolar hypoxia results in vascular remodeling and pulmonary hypertension. Previous studies have reported conflicting results of the effect of chronic alveolar hypoxia on pulmonary vasoreactivity and the contribution of nitric oxide (NO), which may be ...
Golej J - - 2002
There is evidence that haemodynamic fluctuations on extracorporeal membrane oxygenation (ECMO) increase the risk of cerebral damage. We hypothesized that initiation of venovenous (VV) or venoarterial (VA) ECMO itself causes haemodynamic fluctuations and, thus, established an infant animal ECMO model in order to discuss this hypothesis. Five piglets were cannulated ...
Ledderhos C - - 2002
BACKGROUND: Primary hypertensives who are acutely exposed to hypoxic hypoxia show an enhanced reactivity of arterial chemoreceptors as well as an exaggerated response of the sympathetic nervous system. Since these phenomena could influence their ability to tolerate sustained hypoxic hypoxia, this study was performed to determine whether persons predisposed to ...
Bernardi Luciano - - 2003
Although cardiorespiratory complications contribute to the high morbidity/mortality of familial dysautonomia (FD), the mechanisms remain unclear. We evaluated respiratory, cardiovascular, and cerebrovascular control by monitoring ventilation, end-tidal carbon dioxide (CO2-et), oxygen saturation, RR interval, blood pressure (BP), and midcerebral artery flow velocity (MCFV) during progressive isocapnic hypoxia, progressive hyperoxic hypercapnia, ...
Bellezza M - - 2002
Hypoxic pulmonary vasoconstriction (HPV) is a regulatory mechanism by which blood is diverted from poorly ventilated to better ventilated areas of the lung. The aim of the present study was to assess the extent to which hypertonic saline dextran and dextran solutions modify the magnitude of HPV during isovolumic haemodilution ...
Gargaglioni Luciane H - - 2002
The nucleus isthmi (NI) is a mesencephalic structure of the amphibian brain that has recently been reported to participate in the hypoxic and hypercarbic drive to breathing. However, previous studies used electrolytic and kainic lesions, which causes diffuse and nonspecific destruction. Thus, in the present study, we assessed the participation ...
Halliwill John R - - 2002
We tested the hypothesis that acute hypoxia would alter the sensitivity of arterial baroreflex control of both heart rate and sympathetic vasoconstrictor outflow. In 16 healthy, nonsmoking, normotensive subjects (8 women, 8 men, age 20-33 yr), we assessed baroreflex control of heart rate and muscle sympathetic nerve activity by using ...
Kind Peter K - - 2002
The effects of moderate and severe hypoxia on air breathing frequency and respiratory properties of the blood of the Queensland (Australian) lungfish Neoceratodus forsteri were measured in fish exposed to these conditions for 14-22 days at 20 degrees C. Haemoglobin oxygen affinity increased after exposure to moderate hypoxia (PW(O(2)) = ...
Chittenden, Thomas William
The purpose of the current study was to test the hypothesis that chronic hypoxia associated with sleep-disordered breathing relates to abnormal Nitric Oxide (NO) production and vascular endothelial growth factor (VEGF) expression patterns that contribute to aberrancy of specific determinates of cardiovascular and cardiopulmonary function before, during, and after graded ...
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