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Results 351 - 400 of 1552
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Sasaki Clarence T - - 2009
OBJECTIVES: Aspiration has been identified as one of the independent risk factors for development of respiratory tract infections, the incidence of which varies from 10% to 65% in patients in intensive care units. The primary defense mechanism for protection of the lower airway is the glottic closure reflex (GCR), elicited ...
Heman-Ackah Yolanda D - - 2009
OBJECTIVES: The laryngeal chemoreflex is a reflexive central apnea, bradycardia, and cardiovascular collapse that occurs in young, maturing mammals in response to exposure of the laryngeal mucosa to acidic and/or organic stimuli. The severity of the laryngeal chemoreflex varies within a species from one animal to another, and in some ...
Wilson Mark H - - 2009
Cellular hypoxia is the common final pathway of brain injury that occurs not just after asphyxia, but also when cerebral perfusion is impaired directly (eg, embolic stroke) or indirectly (eg, raised intracranial pressure after head injury). We Review recent advances in the understanding of neurological clinical syndromes that occur on ...
Sandblom Erik - - 2009
Hypoxia and increased temperature alter venous blood pressures in teleosts through active changes in venous tone. Elasmobranchs possess a capacious venous system but have limited adrenergic vascular innervation and subambient central venous pressure (P(cv)). In this study, we explored venous hemodynamic responses to acute temperature increase and moderate (6.9 kPa) ...
Jin Chunhong - - 2009
It is unclear whether nitrous oxide (N(2)O) has a protective effect on cardiac function in vitro. In addition, little is known about the cardioprotective effect of anesthesia administered during hypoxia or ischemia. We therefore studied the cardioprotective effects of N(2)O and sevoflurane administered before or during hypoxia in isolated rat ...
González-Martín M C - - 2009
Obstructive sleep apnoea syndrome (OSAS) is a disorder characterized by repetitive episodes of complete (apnoea) or partial (hypopnoea) obstruction of airflow during sleep. The severity of OSAS is defined by the apnoea hypopnoea index (AHI) or number of obstructive episodes. An AHI greater than 30 is considered severe, but it ...
Iturriaga R - - 2009
It has been proposed that chronic intermittent hypoxia (CIH) contributes to generate hypertension in patients with obstructive sleep apnea syndrome and animal models, due to an enhanced sympathetic outflow. A possible contributing mechanism to the CIH-induced hypertension is a potentiation of carotid body (CB) chemosensory responses to hypoxia, but early ...
Davies Andrew J - - 2009
OBJECTIVE: To determine the incidence of acute mountain sickness (AMS), the frequency of summiting success, and the factors that affect these in trekkers on Kilimanjaro, one of the world's most summitted high-altitude peaks. METHODS: The study group comprised 312 trekkers attempting Mt Kilimanjaro summit by the Marango Route. Trekkers ascended ...
Moore G W K - - 2009
Global warming impacts a wide range of human activities and ecosystems. One unanticipated consequence of the warming is an increase in barometric pressure throughout the troposphere. Mount Everest's extreme height and resulting low barometric pressure places humans near its summit in an extreme state of hypoxia. Here we quantify the ...
Hauton David - - 2009
Chronic hypoxia in utero (CHU) is one of the most common insults to fetal development and may be associated with poor cardiac recovery from ischaemia-reperfusion injury, yet the effects on normal cardiac mechanical performance are poorly understood. Pregnant female wistar rats were exposed to hypoxia (12% oxygen, balance nitrogen) for ...
Millonig Gunda - - 2009
HIF1 (hypoxia-inducible factor 1 alpha) is considered a central oxygen-threshold sensor in mammalian cells. In the presence of oxygen, HIF1 is marked by prolyl hydroxylases (PHDs) at the oxygen-dependent degradation (ODD) domain for ubiquitination followed by rapid proteasomal degradation. However, the actual mechanisms of oxygen sensing by HIF1 are still ...
Marcus Noah J - - 2009
In rats, acute exposure to hypoxia causes a decrease in mean arterial pressure (MAP) caused by a predominance of hypoxic vasodilation over chemoreflex-induced vasoconstriction. We previously demonstrated that exposure to chronic intermittent hypoxia (CIH) impairs hypoxic vasodilation in isolated resistance arteries; therefore, we hypothesized that the acute systemic hemodynamic responses ...
Richardson Matt X - - 2009
Increased hemoglobin concentration (Hb) and hematocrit (Hct), attributable to spleen contraction, raise blood gas storage capacity during apnea, but the mechanisms that trigger this response have not been clarified. We focused on the role of hypoxia in triggering these Hb and Hct elevations. After horizontal rest for 20 min, 10 ...
Vedam Hima - - 2009
This study examined the effects of hypoxia (80% arterial oxyhaemoglobin saturation for 20 min) and the accompanying changes in heart rate and blood pressure on two components of arterial stiffness in healthy men. Augmentation index (AIx) and time to reflection (Tr) representing measures of muscular artery and aortic stiffness, respectively, ...
Copeland Jennifer - - 2009
Development in chronic hypoxia has been shown to have a significant negative impact on the developing cardiovascular system. The developing chicken embryo has two ductus arteriosi (DA) that shunt blood away from the lungs to the systemic circuit and constrict during hatching in response to an increase in arterial partial ...
Xia Hong-Ping - - 2008
BACKGROUND: Birth asphyxia may result in multiple organ dysfunction such as lung injury. Inhalation of nebulized nitric oxide precursor can selectively reduce pulmonary hypertension. However, it is unknown whether such precursors can alleviate lung injury induced by hypoxia. We evaluated the effect of inhalation of nebulized nitroglycerine and sodium nitroprusside ...
Kourtidou-Papadeli C - - 2008
Thousands of people work and perform everyday in high altitude environment, either as pilots, or shift workers, or mountaineers.The problem is that most of the accidents in this environment have been attributed to human error. The objective of this study was to assess complex cognitive performance as it interacts with ...
Talbot N P - - 2008
BACKGROUND: Hypoxic pulmonary vasoconstriction (HPV) helps match pulmonary perfusion to ventilation. The peptide endothelin-1 (ET-1) may be involved in the cellular mechanisms of this response. We hypothesized that increasing plasma ET-1 concentration during hypoxia would enhance HPV in humans and might represent a strategy for improving gas exchange during single-lung ...
Ream Margie A - - 2008
The catecholamine norepinephrine is required for fetal survival, but its essential function is unknown. When catecholamine-deficient [tyrosine hydroxylase (Th) null] mouse fetuses die at embryonic day (E)13.5-14.5, they resemble wild-type (wt) fetuses exposed to hypoxia. They exhibit bradycardia (28% reduction in heart rate), thin ventricular myocardium (20% reduction in tissue), ...
Guner Ibrahim - - 2008
Hypoxia causes changes in the rate of synthesis or release of neurotransmitters in the brain. The accumulation of serotonin (5-HT) in the central nervous system might cause hypoxic respiratory depression. In the present study, we aimed to examine the role of central 5-HT on normoxic and acute hypoxic ventilatory depression ...
Rivera-Ch Maria - - 2008
Although the effects of acetazolamide (ACZ) on ventilation during acute mountain sickness are well known, there are no studies assessing its effect on ventilatory response in chronic hypoxia. We studied this effect in patients with chronic mountain sickness (CMS). Subjects with CMS, living permanently at 4300 m, were assigned in ...
Gilmartin Geoffrey S - - 2008
Recurrent and intermittent nocturnal hypoxia is characteristic of several diseases including chronic obstructive pulmonary disease, congestive heart failure, obesity-hypoventilation syndrome, and obstructive sleep apnea. The contribution of hypoxia to cardiovascular morbidity and mortality in these disease states is unclear, however. To investigate the impact of recurrent nocturnal hypoxia on hemodynamics, ...
Wasserfuhr Daniela - - 2008
We have previously shown that 2 weeks of hypoxia protect the right ventricle of the rat heart from subsequent ischemia and reperfusion (I/R). In the present study, we examined the following: (1) Do shorter periods of hypoxia protect from subsequent I/R? (2) Does intermittent normoxia increase the cardioprotective effect? (3) ...
Rey Sergio - - 2008
Chronic intermittent hypoxia (CIH) contributes to the development of hypertension in patients with obstructive sleep apnea and animal models. However, the early cardiovascular changes that precede CIH-induced hypertension are not completely understood. Nevertheless, it has been proposed that one of the possible contributing mechanisms to CIH-induced hypertension is a potentiation ...
Wang Qianwen - - 2008
During ischemia and heart failure, there is an increase in cardiac glycolysis. To understand if this is beneficial or detrimental to the heart, we chronically elevated glycolysis by cardiac-specific overexpression of phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2) in transgenic mice. PFK-2 controls the level of fructose-2,6-bisphosphate (Fru-2,6-P2), an important regulator of phosphofructokinase and ...
Zhou Zhao-Nian - - 2008
Could the intrinsic characteristics of tolerance to hypoxia be retained in Tibetan high-altitude natives after they had migrated to a low altitude? To answer this question, we undertook a study of 33 healthy male adolescent Tibetans born and raised in a high plateau (3,700 m [12,140 ft] above sea level) ...
Serebrovskaya Tatiana V - - 2008
During acute episodes of hypoxia, chemoreceptor-mediated sympathetic activity increases heart rate, cardiac output, peripheral resistance and systemic arterial pressure. However, different intermittent hypoxia paradigms produce remarkably divergent effects on systemic arterial pressure in the post-hypoxic steady state. The hypertensive effects of obstructive sleep apnea (OSA) vs. the depressor effects of ...
Dine C Jessica - - 2008
A large number of patients with underlying pulmonary disease travel by air each year and are therefore at risk for significant cardiopulmonary effects of induced hypoxia at higher altitudes. The hypoxia altitude simulation test provides a simple way to identify those patients at risk by simulating conditions encountered at high ...
Cathcart Mary-Clare - - 2008
Exogenous prostacyclin is effective in reducing pulmonary vascular resistance in some forms of human pulmonary hypertension (PH). To explore whether endogenous prostaglandins played a similar role in pulmonary hypertension, we examined the effect of deleting cyclooxygenase (COX)-gene isoforms in a chronic hypoxia model of PH. Pulmonary hypertension, examined by direct ...
Joynt Chloë - - 2008
OBJECTIVE: Neonatal asphyxia causes cardiogenic shock and pulmonary hypertension with decreased brain perfusion. We examined the dose-response of milrinone on systemic, pulmonary, and carotid circulations in a model of neonatal hypoxia-reoxygenation. DESIGN AND SETTING: Controlled, block-randomized study in a university research laboratory. SUBJECTS: Mixed breed piglets (1-3 days, 1.5-2.3 kg). ...
Kaufmann B A - - 2008
An exaggerated increase in pulmonary arterial pressure is the hallmark of high-altitude pulmonary edema (HAPE) and is associated with endothelial dysfunction of the pulmonary vasculature. Whether the myocardial circulation is affected as well is not known. The aim of this study was, therefore, to investigate whether myocardial blood flow reserve ...
Jakoubek Vít - - 2008
An increase in fetoplacental vascular resistance caused by hypoxia is considered one of the key factors of placental hypoperfusion and fetal undernutrition leading to intrauterine growth restriction (IUGR), one of the serious problems in current neonatology. However, although acute hypoxia has been shown to cause fetoplacental vasoconstriction, the effects of ...
Ainslie Philip N - - 2008
We examined the cardiorespiratory and cerebrovascular responses to hyperoxic and hypoxic rebreathing at low attitude and high altitude. We measured ventilation, middle cerebral artery blood flow velocity (MCAv) and arterial blood pressure in conditions of eucapnia, hypocapnia (voluntary hyperventilation) and during hyperoxic and hypoxic rebreathing firstly at low altitude (1400 ...
Uenoyama M - - 2008
AIM: Experimental pulmonary hypertension induced in a hypobaric hypoxic environment (HHE) is characterized by structural remodelling of the heart and pulmonary arteries. Osteopontin (OPN) has emerged as a key factor in cardiovascular remodelling in response to pressure or volume overload. We studied the possible effects of HHE on the OPN ...
Jones J Gareth - - 2008
BACKGROUND: Airliners at cruise altitudes have cabin pressures of 84.3-75.2 kPa, equivalent to 5000-8000 ft. Supplementary oxygen in flight is generally advised for patients whose ground-level arterial oxygen saturation by pulse oximetry (SpO2) is < 92%. However, some pulmonary patients with values above that threshold nevertheless develop profound in-flight hypoxemia ...
Argacha Jean-François - - 2008
BACKGROUND: The peripheral chemoreflex contributes to cardiovascular regulation and represents the first line of defence against hypoxia. The effects of nicotine on chemoreflex regulation in non-smoking humans are unknown. METHOD: We conducted a prospective, randomized, crossover, and placebo-controlled study in 20 male non-smokers to test the hypothesis that nicotine increases ...
Sergueeva Adelina I - - 2008
In Chuvash polycythemia, homozygous von Hippel-Lindau (VHL) 598C>T leads to increased hypoxia inducible factor-1alpha and 2alpha, thromboses and lower systemic blood pressures. Circulating homocysteine, glutathione, gamma-glutamyltransferase and cysteinylglycine concentrations were higher in 34 VHL598C>T homozygotes than in 37 normal controls and cysteine was lower. Multivariate analysis showed elevated homocysteine independently ...
Lund Amie K - - 2008
The aryl hydrocarbon receptor (AHR) is a basic helix-loop-helix Per-Arnt-Sim transcription factor that mediates induction of metabolic enzymes and toxicity of certain environmental pollutants. Although AHR knockout (KO) mice develop cardiac hypertrophy, conflicting reports associate this pathology with hypotension or endothelin (ET)-1-dependent hypertension. Because hypertension occurred at modest altitude, we ...
Lee Shin-Da - - 2008
nocturnal sustained hypoxia during sleeping time has been reported in severe obesity, but no information regarding the cardiac molecular mechanism in the coexistence of nocturnal sustained hypoxia and obesity is available. This study evaluates whether the coexistence of nocturnal sustained hypoxia and obesity will increase cardiac Fas death receptor and ...
Golja Petra - - 2008
It is generally accepted that an increase in blood CO(2) increases ventilation. We also know that during carbohydrate metabolism a larger amount of CO(2) is produced than during metabolism of lipids or proteins. The aim of the present study was therefore to assess whether carbohydrate ingestion can increase CO(2) production ...
Suner Selim - - 2008
OBJECTIVES: Carbon monoxide (CO) toxicity causes significant central nervous system and cardiac injury. Although the neurological damage caused by CO toxicity is extensively described, the mechanisms underlying myocardial insult are unclear. The authors used an externally perfused isolated rat heart model to examine the effects of a physiological saline solution ...
Sangkatumvong Suvimol - - 2008
Abnormalities in autonomic control in sickle cell anemia (SCA) patients have been reported by multiple researchers. However their potential causal association with sickle cell crisis remains unknown. We employed hypoxia, a known trigger to sickle cell crisis, to perturb the autonomic systems of the subjects. Cardiac autonomic control was non-invasively ...
Basnyat Buddha - - 2008
In this randomized, double-blind placebo controlled trial our objectives were to determine if acetazolamide is capable of preventing high altitude pulmonary edema (HAPE) in trekkers traveling between 4250 m (Pheriche)\4350 m (Dingboche) and 5000 m (Lobuje) in Nepal; to determine if acetazolamide decreases pulmonary artery systolic pressures (PASP) at high ...
Richalet Jean-Paul - - 2008
A 24-year-old adult with a Down syndrome was admitted in December 2006 at the Moutiers hospital in the French Alps for an acute inaugural episode of high altitude pulmonary edema (HAPE) that occurred in the early morning of day 3 after his arrival to La Plagne (2000 m). This patient ...
Wilson Mark H - - 2008
Gross pupil dynamics are used as an indirect measure of brain function. Changes in hypoxia and intracranial pressure are thought to alter pupil responses to light. This study assessed a portable handheld pupil measuring device (pupillometer) in the field investigating the changes in pupil size, speed of reaction, and rate ...
Petersen Bodil - - 2008
Endogenous endothelin (ET)-1 modulates hypoxic pulmonary vasoconstriction (HPV). Accordingly, intravenously applied ET(A) receptor antagonists reduce HPV, but this is accompanied by systemic vasodilation. We hypothesized that inhalation of an ET(A) receptor antagonist might act selectively on the pulmonary vasculature and investigated the effects of aerosolized LU-135252 in an experimental model ...
Steinback Craig D - - 2008
We examined the cardiovascular and cerebrovascular responses to acute isocapnic (IH) and poikilocapnic hypoxia (PH) in 10 men (25.7 +/- 4.2 yr, mean +/- SD). Heart rate (HR), mean arterial pressure (MAP), and mean peak middle cerebral artery blood flow velocity (Vp) were measured continuously during two randomized protocols of ...
Cheung Po-Yin - - 2008
OBJECTIVES: The increase in oxidative stress following neonatal hypoxia-reoxygenation can be related to subsequent cardiovascular deficits. We compared the acute systemic, pulmonary and regional hemodynamic recovery in hypoxic newborn pigs reoxygenated by low (18%) or high (100%) concentration of oxygen with that by 21% oxygen. STUDY DESIGN: Pigs (1-3 days, ...
Querido Jordan S - - 2008
The purpose of this study was to determine the changes in human cerebrovascular function associated with intermittent poikilocapnic hypoxia (IH). Healthy men (n=8; 24+/-1 years) were exposed to IH for 10 days (12% O(2) for 5min followed by 5min of normoxia for 1h). During the hypoxic exposures, oxyhemoglobin saturation (SaO(2)) ...
Burtscher Martin - - 2008
When hypoxia increases during ascending in the mountains, ventilatory control and the related oxygenation may be challenged. The pre-treatment by intermittent hypoxia will elevate ventilation and offset hypoxemia and acetazolamide may inhibit peripheral chemosensitivity and act through central mechanisms. To study these effects in the field, one well-trained male mountaineer ...
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