Search Results
Results 401 - 450 of 1063
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Brusselmans K - - 2001
Deprivation of oxygen (hypoxia) and/or glucose (hypoglycemia) represents a serious stress that affects cellular survival. The hypoxia-inducible transcription factor-1alpha (HIF-1alpha), which has been implicated in the cellular response to hypoxia (Semenza, G. L. (1999) Annu. Rev. Cell Dev. Biol. 15, 551-578), mediates apoptosis during hypoxia (Halterman, M. W., Miller, C. ...
Kuwahira I - - 2001
Pulmonary blood flow (PBF) distribution was studied at rest and during exercise in rats acclimatized to chronic hypoxia (barometric pressure [PB] 370 Torr for 3 weeks, A rats) and non-acclimatized (NA) littermates. Both A and NA rats exercised in hypoxia (inspired O2 pressure [PIO2] approximately 70 Torr) or in normoxia ...
Schurr A - - 2001
Ischemic preconditioning (PC) of heart and brain is a well-documented phenomenon. However, the mechanism underlying the increased resistance to severe ischemia by a preceding mild ischemic exposure remains unclear. Over a decade ago, we demonstrated the existence of hypoxic PC in the hippocampal slice preparation. Here we report the ability ...
Gargaglioni L H - - 2001
Nucleus isthmi (NI) is a mesencephalic structure of the amphibian brain that has been reported to participate in CO(2) chemoreception and in the ventilatory response to hypoxia. However, no information exists about the modulators and/or mediators involved. In the present study, we assessed the participation of nitric oxide (NO) in ...
Masuda A - - 2001
To compare the effect of hypoxia on ventilatory responses and respiratory sensation to carbon dioxide, 29 young adults were examined using a modified Read's rebreathing method with four experimental conditions. We used varying gas mixtures and kept PET(O2) constant at >300, 100, 80 and 60 mmHg for each four rebreathing ...
Peltonen J E - - 2001
There is a prevailing hypothesis that an acute change in the fraction of oxygen in inspired air (F(I)O2) has no effect on maximal cardiac output (Qcmax), although maximal oxygen uptake (VO2max) and exercise performance do vary along with F(I)O2. We tested this hypothesis in six endurance athletes during progressive cycle ...
Sausen K P - - 2001
The current training program for hypoxia familiarization requires a low-pressure chamber that places aviator trainees at risk for decompression sickness. A cost-effective reduced oxygen-breathing (ROB) paradigm that decreases oxygen (O2) concentration leading to normobaric hypoxia was assessed as an alternative to the hypobaric chamber. PURPOSE: To help establish the validity ...
Andersen J B - - 2001
The release of catecholamines during hypoxia has received limited attention in amphibians and the adrenergic regulation of cardio-pulmonary functions is, therefore, not well understood at the organismic level. To describe the changes in plasma catecholamine concentrations, we exposed toads (Bufo marinus) to different levels of hypoxia at two temperatures (15 ...
Clanton T L - - 2001
Intermittent hypoxia (IH) describes conditions of repeated, transient reductions in O2 that may trigger unique adaptations. Rest periods during IH may avoid potentially detrimental effects of long-term O2 deprivation. For skeletal muscle, IH can occur in conditions of obstructive sleep apnea, transient altitude exposures (with or without exercise), intermittent claudication, ...
Currie S - - 2001
Using ventricular cardiomyocytes of the common frog, Rana temporaria, we investigated the metabolic strategies employed by the heart to tolerate 4 mo of hypoxic submergence (overwintering) as well as acute bouts of anoxia. In contrast to what is observed for the whole animal, there was no change in oxygen consumption ...
Cerami A - - 2001
Erythropoietin (EPO) is a glycoprotein that has been shown to mediate response to hypoxia, and is most notably recognized for its central role in erythropoiesis. In a series of experiments using rodent models, the ability of systemically administered recombinant human erythropoietin (r-HuEPO, epoetin alfa) to cross the blood-brain barrier and ...
Katayama K - - 2001
The purpose of this study was 1) to test the hypothesis that ventilation and arterial oxygen saturation (Sa(O2)) during acute hypoxia may increase during intermittent hypoxia and remain elevated for a week without hypoxic exposure and 2) to clarify whether the changes in ventilation and Sa(O2) during hypoxic exercise are ...
Neubauer J A - - 2001
This mini-review summarizes the physiological adaptations to and pathophysiological consequences of intermittent hypoxia with special emphasis given to the pathophysiology associated with obstructive sleep apnea. Intermittent hypoxia is an effective stimulus for evoking the respiratory, cardiovascular, and metabolic adaptations normally associated with continuous chronic hypoxia. These adaptations are thought by ...
Fatemian M - - 2001
Ventilatory acclimatization to altitude is associated with a progressive increase in ventilation, a progressive decrease in end-tidal PCO2 and a progressive increase in the acute ventilatory sensitivity to hypoxia. Ventilatory acclimatization has been observed with mild exposure to hypoxia when the duration of exposure has been of some length (e.g. ...
Waters K A - - 2001
Ventilatory responses (VRs) were measured via a sealed face mask and pneumotachograph in 30 unsedated, mixed-breed miniature piglets at 12.6 +/- 2.3 days of age (day 1) and then repeated after seven daily 24-min exposures to 10% O(2)-6% CO(2) [hypercapnic hypoxia (HH)]. Arterial blood was sampled at baseline, after 10 ...
Ai K - - 2001
BACKGROUND: Because it is postulated that gut is important via bacterial translocation in the development of the systemic inflammatory response and multiple organ dysfunction, the preservation of gut integrity is a therapeutic goal for physicians who care for critically ill patients. The aim of the current study was to evaluate ...
Kamel K S - - 2001
OBJECTIVE: To examine the impact of administration of NaHCO3 on contractility and energy metabolism of the myocardium during hypoxemia. METHODS: Regional myocardial hypoxia was induced in the left anterior descending (LAD) artery myocardium in anesthetized, open-chest dogs, using a perfusion circuit between the right atrium and the LAD artery, and ...
Hoppeler H - - 2001
It is widely accepted that prolonged exposure to extreme altitude is detrimental for exercise performance and muscle structure. Moreover, highly trained subjects seem to suffer more under hypoxic conditions than untrained people. When using hypoxia as an ergogenic stimulus in athletes, it has thus become customary to limit hypoxia exposure ...
Tieman J G - - 2001
The acoustic startle eyeblink response (ASER) is a useful probe for investigating central nervous system activity associated with emotional responses to aversive and appetitive stimuli. Though the ASER is sensitive to change in emotional arousal, the effect of acute physical exertion on ASER has not been reported. We examined changes ...
Garcia N - - 2001
We used two protocols to determine if hypoxic ventilatory decline (HVD) involves changes in slope and/or intercept of the isocapnic HVR (hypoxic ventilatory response, expressed as the increase in VI per percentage decrease in SaO2). Isocapnia was defined as 1.5 mmHg above hyperoxic PET(CO2). HVD was recorded in protocol I ...
Dolbier W R WR - - 2001
There is a great deal of clinical and experimental interest in determining tissue hypoxia using non-invasive imaging methods. We have developed EF5, 2-(2-nitro-1[H]-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)-acetamide, with both invasive and non-invasive hypoxia detection in mind. EF5 and other 2-nitroimidazoles are used to detect hypoxia, because the rate of their bioreductive metabolism is inversely ...
Bernardi L - - 2001
Interval hypoxic training (IHT) is a technique developed in the former Soviet Union, that consists of repeated exposures to 5-7 minutes of steady or progressive hypoxia, interrupted by equal periods of recovery. It has been proposed for training in sports, to acclimatize to high altitude, and to treat a variety ...
Dagg K D - - 2001
These studies examine the effect of acute hypoxia on airway smooth muscle relaxation in response to salbutamol in vitro in human isolated bronchi from non-asthmatics and in vivo in-patients with asthma. Isometric responses were measured from rings of human bronchi pre-constricted with methacholine under oxygen tensions of 95% (hyperoxia), 20% ...
Gamboa A - - 2001
This study was designed to determine in subjects born at high altitude who move to sea level (HA-SL: born at 3500 m or above; n = 25) whether their cardiorespiratory responses to hypoxia and exercise are similar to those of sea level natives (SL,n = 25). The average age (39 ...
Verin E - - 2001
Ventilatory motor output is known to influence the upper airway. Although inspiratory upper airway resistance decreases during progressive hypoxia or hypercapnia, the effects of hypoxia and hypercapnia on expiratory upper airway resistance remain unknown. In the present study, we attempted to examine whether the expiratory and the inspiratory upper airway ...
Smith W D - - 2001
This study compared the ventilatory response to 20 min of acute isocapnic hypoxia (end-tidal P(O(2)), 50 mmHg) using the technique of dynamic end-tidal forcing in young (Y) and old (O) men. Two groups of non-smoking male subjects (mean +/- s.d. age: Y, 29.8 +/- 6.9 years; O, 73.4 +/- 2.8 ...
Hong L Z - - 2001
We investigated the responses of systemic arterial pressure and vertebral sympathetic nerve activity to glutamate microinjections (0. 1 M, 70 nl) in the dorsomedial (DM) and the rostral ventrolateral medulla (RVLM) before hypoxia and after reoxygenation (posthypoxia) after various degrees of hypoxia in anesthetized cats. Hypoxia was produced by ventilating ...
Bailey D M - - 2001
The purpose of the present investigation was to determine the independent effects of hypoxia and physical exercise on peripheral cholecystokinin (CCK) metabolism in humans. Thirty-two physically active men were randomly assigned in a double-blind manner to either a normoxic (N; n = 14) or hypoxic (H; n = 18) group. ...
Greiner C - - 2000
Nimodipine and dimethyl sulfoxide (DMSO) were tested (alone and in combination) regarding their ability to increase hypoxic tolerance of brain slices under 'hypoxic' (deprivation of oxygen) or 'ischemic' (hypoxia+withdrawal of glucose) conditions. Direct current (DC) and evoked potentials were recorded in the CA1 region of hippocampal slices of adult guinea ...
Baker T L - - 2000
1. Intermittent hypoxia elicits long-term facilitation (LTF) of phrenic motor output in anaesthetized rats. We tested the hypothesis that an equal cumulative duration of continuous hypoxia would not elicit phrenic LTF. 2. Integrated phrenic nerve activity was recorded in urethane-anaesthetized, vagotomized, paralysed and ventilated rats exposed to: (1) 3 X ...
Penn J S - - 2000
PURPOSE: Loss of retinal capillaries is an inherent component of late stage autosomal dominant retinitis pigmentosa (ADRP). This study examined the hypothetical role of tissue hyperoxia in this vascular attenuation process and tested the potential of ambient hypoxia to reverse it. METHODS: Transgenic mice expressing a mutant opsin gene with ...
Aguilar N M - - 2000
Periophthalmodon schlosseri is a mudskipper which uses the vascularized buccopharyngeal cavity as a respiratory organ. The fish construct mud burrows that contain hypoxic water, but store air inside the burrows. Because the burrow gas is frequently hypoxic and hypercapnic, the effects of altered respiratory gas concentrations on the aerial ventilation ...
Brosnan M J - - 2000
The effect of hypoxia on the response to interval exercise was determined in eight elite female cyclists during two interval sessions: a sustained 3 x 10-min endurance set (5-min recovery) and a repeat sprint session comprising three sets of 6 x 15-s sprints (work-to-relief ratios were 1:3, 1:2, and 1:1 ...
Bach K B - - 2000
To investigate models of plasticity in respiratory motor output, we determined the effects of chronic unilateral phrenicotomy and/or exercise on time-dependent responses to episodic hypoxia in the contralateral phrenic nerve. Anesthetized (urethane), ventilated, and vagotomized rats were presented with three, 5-min episodes of isocapnic hypoxia (11% O(2)), separated by 5 ...
Shi Y - - 2000
Nitric oxide synthase (NOS) is believed to play an important role in protecting the myocardium against ischemia. Chronic hypoxia from birth increases NOS activity in the myocardium resulting in enhanced nitric oxide production and increased resistance to ischemia. We examined the effects of chronic hypoxia on NOS gene and protein ...
Krause W L - - 2000
Hypoxia causes arousal. Therefore, we hypothesized that hypoxia activates the human somatomotor system and should augment tremor. We determined the effects of hypoxia, PET(O2) = 45+/-2.2 mm Hg, hypocapnia, and the hypocapnic-hypoxic interaction on finger tremor during elastic loading. A total of 12 healthy male volunteers were studied during five ...
Miller M J - - 2000
The effects of recurrent hypoxia on cardiorespiratory reflexes were characterized in anesthetized piglets at 2-10 d (n=15), 2-3 weeks (n=11) and 8-10 weeks (n=8). Responses of phrenic and hypoglossal electroneurograms (ENG(phr) and ENG (hyp)) to hypoxia (8% 0(2), bal N(2), 5 min), hypercapnia (7% CO(2) bal O(2), 5 min) and ...
Jubran A - - 2000
In the presence of either hypocapnia or sleep, hypoxia has been shown to induce periodic breathing and increase the total variational activity of breath components. It is not known whether hypoxia induces alterations in breathing variability during wakefulness and in the absence of hypocapnia. To address this issue, we studied ...
Fabris G - - 2000
The locus coeruleus modulates the ventilatory and thermoregulatory response to hypoxia and contains nitric oxide synthase. Therefore, we examined the effects of L-NAME unilaterally microinjected into the locus coeruleus on hypoxic hyperventilation and hypothermia. Ventilation and body temperature were measured before and after microinjection of L-NAME (100 nmol/0.5 microl) into ...
Burton M D - - 2000
A diverse group of processes are involved in central control of ventilation. Both fast acting neurotransmitters and slower acting neuromodulators are involved in the central respiratory drive. This review deals with fast acting neurotransmitters that are essential centrally in the ventilatory response to H(+)/CO(2) and to acute hypoxia. Data are ...
Warren P M - - 2000
We studied the effect of tramadol on the ventilatory response to 7 min acute isocapnic hypoxia (SpO2 85.1 (SD 0.4)%) during steady mild hypercapnia (PE'CO2 0.7 kPa above normoxic baseline) in 14 healthy volunteers (seven male). The acute hypoxic response was measured before and 1 h after oral placebo or ...
Solomon I C - - 2000
Severe brain hypoxia results in respiratory excitation and an increase in sympathetic nerve activity. Respiratory excitation takes the form of gasping which is characterized by an abrupt onset, high amplitude, short duration burst of inspiratory activity. Recent evidence suggests that centrally-mediated hypoxic respiratory and sympathetic excitation may result from direct ...
Ohguro N - - 2000
PURPOSE: This study was undertaken to evaluate the endothelial pump function by monitoring both corneal swelling response under hypoxia and dehydration response following hypoxia in vivo. METHODS: Humidified nitrogen gas was used to obtain corneal swelling, and humidified gas mixed with oxygen and nitrogen was used for corneal dehydration. First, ...
Lee W W - - 2000
The objective of this retrospective study was to identify factors affecting the accuracy of pulse oximetry in the ED. Over a 3-year period, 664 consecutive emergency department (ED) patients had simultaneous arterial blood gas (ABG) and pulse oximeter readings taken. Pulse oximeter saturations (SpO2) were compared with ABG CO-oximeter saturations ...
Dick T E - - 2000
The respiratory response to hypoxia is dynamic in the adult anesthetized Sprague-Dawley rat. Hypoxia elicits acute increases in both tidal volume (VT) and respiratory frequency (fR) followed by short-term increases in VT and short-term decreases in fR. After brief hypoxia (<1 min), recovery of the breathing pattern is again dynamic, ...
Powell F L - - 2000
Ventilatory acclimatization to hypoxia is the time-dependent increase in ventilation that occurs with chronic exposure to hypoxia. Despite decades of research, the physiological mechanisms that increase the hypoxic ventilatory response during chronic hypoxia are not well understood. This review focuses on adaptations within the central nervous system (CNS) that increase ...
Bailey D M - - 2000
PURPOSE: This study was designed to determine changes in metabolic and cardiovascular risk factors following normobaric hypoxic exercise training in healthy men. METHODS: Following a randomized baseline maximal exercise test in hypoxia and/or normoxia, 34 physically active subjects were randomly assigned to either a normoxic (N = 14) or a ...
Boutilier R G - - 2000
Specimens of Nautilus pompilius were trapped at depths of 225-300 m off the sunken barrier reef southeast of Port Moresby, Papua New Guinea. Animals transported to the Motupore Island laboratory were acclimated to normal habitat temperatures of 18 degrees C and then cannulated for arterial and venous blood sampling. When ...
Olson K R - - 2000
Isolated vessels from four elasmobranchs, yellow stingray (Urolophus jamaicensis), clearnose skate (Raja eglanteria), ghost shark (Hydrolagus novaezelandiae), and spiny dogfish (Squalus acanthias), were examined for the presence of spontaneous contractions (SC). SC were observed in otherwise unstimulated dorsal aortas (DA) from stingray and ghost shark, but not in skate DA. ...
Adamczewska A M - - 2000
Red crabs, Gecarcoidea natalis, exhibit seasonal activity patterns: low activity during the dry season when they shelter in burrows to avoid dehydration, and high activity during the wet season. Red crabs were examined in situ in the rainforest of Christmas Island to determine if there were underlying seasonal differences in ...
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