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Fahlman Andreas - - 2002
We report the development and testing of a simple breathing circuit that maintains isocapnia in human subjects during hypoxic hyperpnea. In addition, the circuit permits rapid switching between two gas mixtures with different partial pressures of oxygen. Eleven volunteers breathed repeated cycles of exposure to air (2 min of 21% ...
Zhu Xiaoping - - 2003
Hypoxia disturbs Ca(2+) regulation and increases the intracellular Ca(2+) concentration ([Ca(2+)](i)), which may in turn activate the nitric oxide synthase (NOS) regulated by [Ca(2+)](i). Since nitric oxide (NO) reduces the isometric contractility of rat diaphragm in vitro, we hypothesized that NO contributes to the impaired force generation of an hypoxic ...
Overstreet Edward H EH 3rd Advanced Bionics Corporation, 12740 San Fernando Road, Sylmar, CA 91342, - - 2002
Using a laser velocimeter, basilar membrane (BM) responses to tones were measured in neonatal gerbils at a site near the round window of the cochlea. In adult gerbils, "active" BM responses at this site are most sensitive at 34-37 kHz and exhibit a compressive non-linearity. Postmortem, BM responses in adults ...
Moraes G - - 2002
Oxygen of tropical freshwater environments fluctuates drastically. Eutrophic lakes and ponds of warm waters frequently reach very low oxygen concentrations. This is the most common habitat of the banded knife fish "tuvira" Gymnotus carapo. This electric fish is reported to present bimodal breathing to cope with low environmental oxygen. Biochemical ...
Chapman Lauren J - - 2002
In Lake Nabugabo, Uganda, a satellite of Lake Victoria, approximately 50% of the indigenous fishes disappeared from the open waters subsequent to the establishment of the introduced predatory Nile perch, Lates niloticus. This pattern is similar to the faunal loss experienced in the much larger Lake Victoria. Several of these ...
Grover Robert F - - 2002
In Andean natives (NAT), the ventilatory response to hypoxia is blunted at rest but potential interaction with exercise has been little studied. Therefore, during three levels of submaximal exercise, 13 NAT were compared with 6 sojourners (SOJ) acclimatized at 4,360 m for an average of 7 months. Exercise ventilation was ...
Zimmer M Beth - - 2002
The present study examined the effects of severe hypothermia in the absence of anesthesia on breathing pattern, ventilatory control and chemosensitivity in a cold tolerant species capable of seasonal hibernation. Hypothermia was induced in ground squirrels and ventilation and heart rate were recorded in animals breathing air at a body ...
Domenici Paolo - - 2002
The effect of progressive hypoxia on the structure and dynamics of herring (Clupea harengus) schools in laboratory conditions was investigated. The length, width and depth of schools of about 20 individuals were measured from video recordings to test the hypothesis that during hypoxia fish schools change their shape and volume. ...
Calbet J A L - - 2003
The aim of this study was to evaluate the effects of severe acute hypoxia on exercise performance and metabolism during 30-s Wingate tests. Five endurance- (E) and five sprint- (S) trained track cyclists from the Spanish National Team performed 30-s Wingate tests in normoxia and hypoxia (inspired O(2) fraction = ...
Garske Luke A - - 2003
Acetazolamide (Acz) is used at altitude to prevent acute mountain sickness, but its effect on exercise capacity under hypoxic conditions is uncertain. Nine healthy men completed this double-blind, randomized, crossover study. All subjects underwent incremental exercise to exhaustion with an inspired O(2) fraction of 0.13, hypoxic ventilatory responses, and hypercapnic ...
Calbet J A L - - 2003
To unravel the mechanisms by which maximal oxygen uptake (VO2 max) is reduced with severe acute hypoxia in humans, nine Danish lowlanders performed incremental cycle ergometer exercise to exhaustion, while breathing room air (normoxia) or 10.5% O2 in N2 (hypoxia, approximately 5,300 m above sea level). With hypoxia, exercise PaO2 ...
Matei Gina - - 2002
Sevoflurane is a volatile anesthetic agent that reduces cerebral metabolism and thereby may reduce neuronal damage during energy deprivation. We have examined the effect of sevoflurane on hypoxic neuronal damage in rat hippocampal slices. Slices were subjected to 0%, 2%, or 4% sevoflurane 10 minutes before, during, and 10 minutes ...
Sharma A - - 2002
The effect of a carbohydrate supplement, offered as a diet option, on feeding behaviour, body weight gain, and endurance exercise was studied in rats exposed to hypobaric hypoxia. Male albino rats (n = 35) were randomly divided into 5 groups; hypoxic supplemented and control groups; normoxic supplemented and control groups, ...
Steiner Dawn R S - - 2002
Systemic hypoxia results in oxidative stress due to a change in the reactive oxygen species (ROS)-nitric oxide (NO) balance. These experiments explored two mechanisms for the altered ROS-NO balance: 1) decreased NO synthesis by NO synthase due to limited O(2) substrate availability and 2) increased superoxide generation. ROS levels and ...
Valdés Viviana - - 2003
We tested the hypothesis that nitric oxide (NO) produced within the carotid body is a tonic inhibitor of chemoreception and determined the contribution of neuronal and endothelial nitric oxide synthase (eNOS) isoforms to the inhibitory NO effect. Accordingly, we studied the effect of NO generated from S-nitroso-N-acetylpenicillamide (SNAP) and compared ...
Moosavi S H - - 2003
Anecdotal observations suggest that hypoxia does not elicit dyspnea. An opposing view is that any stimulus to medullary respiratory centers generates dyspnea via "corollary discharge" to higher centers; absence of dyspnea during low inspired Po(2) may result from increased ventilation and hypocapnia. We hypothesized that, with fixed ventilation, hypoxia and ...
Schmitt P M - - 2002
Many avian species exhibit an extraordinary ability to exercise under hypoxic condition compared with mammals, and more efficient pulmonary O(2) transport has been hypothesized to contribute to this avian advantage. We studied six emus (Dromaius novaehollandaie, 4-6 mo old, 25-40 kg) at rest and during treadmill exercise in normoxia and ...
Burleson Mark L - - 2002
The mechanisms responsible for altering cardioventilatory control in vertebrates in response to chronic hypoxia are not well understood but appear to be mediated through the oxygen-sensitive chemoreceptor pathway. Little is known about the effects of chronic hypoxia on cardioventilatory control in vertebrates other than mammals. The purpose of this study ...
Monahan Kevin D - - 2002
We determined the interaction between the vestibulosympathetic reflex and the arterial chemoreflex in 12 healthy subjects. Subjects performed three trials in which continuous recordings of muscle sympathetic nerve activity (MSNA), mean arterial blood pressure (MAP), heart rate (HR), and arterial oxygen saturation were obtained. First, in prone subjects the otolith ...
Lindqvist Anders - - 2002
Chronic hypoxia is a clinically important condition known to cause vascular abnormalities. To investigate the cellular mechanisms involved, we kept rings of a rat tail artery for 4 days in hypoxic culture (HC) or normoxic culture (NC) (PO(2) = 14 vs. 110 mmHg) and then measured contractility, oxygen consumption (JO(2)), ...
Van Cappellen Van Walsum Anne-Marie - - 2002
The purpose of the study was to investigate the sequence of processes occurring during and after hypoxia-induced acidemia. We used proton nuclear magnetic resonance spectroscopy, which provides an overview of metabolites in cerebrospinal fluid (CSF), reflecting neuronal metabolism and damage. The pathophysiological condition of acute fetal asphyxia was mimicked by ...
Shkoukani Mahdi - - 2002
We hypothesized that long-term facilitation (LTF) is due to decreased upper airway resistance (Rua). We studied 11 normal subjects during stable non-rapid eye movement sleep. We induced brief isocapnic hypoxia (inspired O(2) fraction = 8%) (3 min) followed by 5 min of room air. This sequence was repeated 10 times. ...
Johns Lisa - - 2002
The aim of this study was to investigate the effects of bilobalide, the postulated active constituent of Ginkgo biloba, on the release of glutamate elicited by hypoxia/hypoglycemia. Cortical slices were prepared from rat brain and perfused with normal artificial cerebrospinal fluid (aCSF) or aCSF made hypoxic by gassing with nitrogen, ...
Varathan Sriranganathan - - 2002
Because there are many conflicting reports on cerebroprotective effects of hypothermia and barbiturates, we examined the degree of neuroprotection at defined temperatures (normothermia, 37 degrees C; mild hypothermia, 32 degrees C; deep hypothermia, 22 degrees C; and profound hypothermia, 17 degrees C) and various concentrations (low, 4 microM; moderate, 40 ...
Paro Flávia M - - 2002
Endogenously carbon monoxide (CO) arises from the catabolism of heme to biliverdin, free iron and CO, a process catalyzed by the enzyme heme oxygenase (HO). In the present study, we tested the hypothesis that the central HO-CO pathway plays a role in hypoxia-induced hyperventilation. To this end, we used intracerebroventricular ...
Coles Sharon K - - 2002
The ventilatory response to brief, severe hypoxia is biphasic consisting of an initial facilitation followed by a slowing of breathing frequency (fR). After the hypoxic stimulus is removed, fR drops below baseline levels. This phenomenon is called the post-hypoxic frequency decline (phfd). These fR changes are due to reciprocal changes ...
Katayama Keisho - - 2002
The purpose of the present study was to test the hypothesis that the ventilatory response to exercise at sea level may increase after intermittent hypoxic exposure for 1 week, accompanied by an increase in hypoxic or hypercapnic ventilatory chemosensitivity. One group of eight subjects (hypoxic group) were decompressed in a ...
Hildebrandt Wulf - - 2002
Oxygen-sensing chemoreceptors contribute significantly to the regulation of the respiratory drive and arterial PO(2) levels. The hypoxic ventilatory response (HVR) decreases strongly with age and is modulated by prolonged hypoxia and physical exercise. Several earlier studies indicated that the regulation of the ventilatory response and erythropoietin (EPO) production by the ...
Besse Sophie - - 2002
To determine the effects of prolonged hypoxia and hypoxia-reoxygenation in senescent blood vessels, isolated aortic rings from 4- and 24-month-old (mo) Wistar rats were submitted to prolonged hypoxia (50 min) or hypoxia/reoxygenation (20 min/30 min) and contractile function recorded. Phenylephrine-induced contraction and sodium nitroprusside- and acetylcholine-induced relaxations were measured after ...
Routley Matthew H - - 2002
The majority of vertebrates are not tolerant to hypoxia but epaulette sharks (Hemiscyllium ocellatum) living on shallow reef platforms appear to tolerate hypoxic periods during tidal fluctuations. The effects of progressive hypoxia on the metabolic and ventilatory responses of these elasmobranchs were examined in a closed respirometer. In order to ...
Robinson Dean M - - 2002
We examined the effects of in utero nicotine exposure on postnatal development of breathing pattern and ventilatory responses to hypoxia (7.4 % O2) using whole-body plethysmography in mice at postnatal day 0 (P0), P3, P9, P19 and P42. Nicotine delayed early postnatal changes in breathing pattern. During normoxia, control and ...
Frappell P B - - 2002
Metabolic and ventilatory variables were measured in a large semifossorial marsupial, the hairy-nosed wombat (Lasiorhinus latifrons, 21.9 kg). In normoxia, the rate of oxygen consumption was 63% of that predicted for a similar-sized marsupial, and the level of ventilation (V(E)) was such that the convective requirement (V(E)/VO2) was similar to ...
Richalet Jean-Paul - - 2002
The development of mining activities in North Chile involves a great number of workers intermittently exposed to high altitude for a long period of time (chronic intermittent hypoxia, CIH). A 2(1/2)-year prospective study aimed to characterize this model of exposure to CIH and to know whether this condition may progressively ...
Serebrovskaya Tatiana V - - 2002
This review aims to summarize the basic research in the field of intermittent hypoxia in the Soviet Union and the Commonwealth of Independent States (CIS) that scientists in other Western countries may not be familiar with, since Soviet scientists were essentially cut off from the global scientific community for about ...
Wu R S S - - 2002
Aquatic hypoxia caused by eutrophication may lead to mass mortality of valuable living resources such as fish and shrimp. However, there is little information on the hypoxic tolerance of penaeid shrimp, and whether they are able to avoid hypoxia. In laboratory experiments, LC50, LT50 and heart beats per minute were ...
Agvald Per - - 2002
Nitroglycerin (GTN), often used in conditions of cardiovascular ischaemia, acts through the liberation of nitric oxide (NO) and the local concentration of NO in the tissue is responsible for any biological effect. However, little is known about the way in which the concentration of NO from GTN and other NO-donors ...
Yamaya Yoshiki - - 2002
During exercise, pulse oximetry is problematic due to motion artifact and altered digital perfusion. New pulse oximeter technology addresses these issues and may offer improved performance. We simultaneously compared Nellcor N-395 (Oxismart XLTM) pulse oximeters with an RS-10 forehead sensor (RS-10), a D-25 digit sensor (D-25), and the Ivy 2000 ...
Baker T L - - 2001
The objectives of this paper are: (1) to review advances in our understanding of the mechanisms of respiratory plasticity elicited by episodic versus continuous hypoxia in short to intermediate time domains (min to h); and (2) to present new data suggesting that different patterns of hypercapnia also elicit distinct forms ...
Casas H - - 2001
The effect of acute hypoxia on blood concentration of ammonia ([NH3]b) and lactate (la-]b) was studied during incremental exercise(IE), and two-step constant workload exercises (CE). Fourteen endurance-trained subjects performed incremental exercise on a cycle ergometer under normoxic (21% O2) and hypoxic (10.4% O2) conditions. Eight endurance-trained subjects performed two-step constant ...
Sanchez A - - 2001
Lungfishes (Dipnoi) occupy an evolutionary transition between water and air breathing and possess well-developed lungs and reduced gills. The South American species, Lepidosiren paradoxa, is an obligate air-breather and has the lowest aquatic respiration of the three extant genera. To study the relative importance, location and modality of reflexogenic sites ...
Bonora M - - 2001
We tested whether the enhancement of end-expiratory activity of the diaphragm (DE) induced by acute hypoxia persists during long-lasting hypoxia and participates in the enlargement of end-expiratory lung volume (EELV). We thus measured these two parameters together with ventilation (VE) in 30 rats, either awake or anesthetized, exposed to (1) ...
Renolleau S - - 2001
Breathing during the first postnatal hours has not been examined in mice, the preferred mammalian species for genetic studies. We used whole body plethysmography to measure ventilation (VE), breath duration (T(TOT)), and tidal volume (VT) in mice delivered vaginally (VD) or by cesarean section (CS). In experiment 1, 101 VD ...
Bailey D M - - 2001
Oxidant generation during regular physical exercise training may influence the adaptive responses that have been shown to confer protection against oxidative stress induced by subsequent acute exercise. To examine this, we randomly assigned 32 males to either a normoxic (n=14) or a hypoxic (n=18) group. During the acute phase, subjects ...
van Hall G - - 2001
1. One to five weeks of chronic exposure to hypoxia has been shown to reduce peak blood lactate concentration compared to acute exposure to hypoxia during exercise, the high altitude 'lactate paradox'. However, we hypothesize that a sufficiently long exposure to hypoxia would result in a blood lactate and net ...
Peltonen J E - - 2001
BACKGROUND: Oxygen uptake (VO2) on-kinetics is decelerated in acute hypoxia and accelerated in hyperoxia in comparison with normoxia during submaximal exercise. However, the effects of fraction of oxygen in inspired air (FIO2) on VO2 kinetics during maximal exercise are unknown. HYPOTHESIS: The effects of FIO2 on VO2 on-kinetics during maximal ...
Xie A - - 2001
The relative contributions of hypoxia and hypercapnia in causing persistent sympathoexcitation after exposure to the combined stimuli were assessed in nine healthy human subjects during wakefulness. Subjects were exposed to 20 min of isocapnic hypoxia (arterial O(2) saturation, 77-87%) and 20 min of normoxic hypercapnia (end-tidal P(CO)(2), +5.3-8.6 Torr above ...
Lipton A J - - 2001
Increased ventilation in response to hypoxia has been appreciated for over a century, but the biochemistry underlying this response remains poorly understood. Here we define a pathway in which increased minute ventilation (&Vdot;E ) is signalled by deoxyhaemoglobin-derived S-nitrosothiols (SNOs). Specifically, we demonstrate that S-nitrosocysteinyl glycine (CGSNO) and S-nitroso-l-cysteine (l-CSNO)-but ...
Boutilier R G - - 2001
Most animals experience some degree of hypoxia and hypothermia during the course of their natural life history either as a consequence of ambient 'exposure' per se or through metabolic, respiratory and/or circulatory insufficiency. A prevailing experimental approach has been to probe tissues from natural models of hypoxia-tolerant and cold-tolerant vertebrates ...
Noakes T D - - 2001
An enduring hypothesis in exercise physiology holds that a limiting cardiorespiratory function determines maximal exercise performance as a result of specific metabolic changes in the exercising skeletal muscle, so-called peripheral fatigue. The origins of this classical hypothesis can be traced to work undertaken by Nobel Laureate A. V. Hill and ...
Favret F - - 2001
Chronic hypoxic exposure results in elevated sympathetic activity leading to downregulation of myocardial alpha(1)- and beta-adrenoceptors (alpha(1)-AR, beta-AR). On the other hand, it has been shown that sympathetic activity is reduced by exercise training. The objective of this study was to determine whether exercise training could modify the changes in ...
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