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Paterson D J - - 1991
Raising arterial potassium ([K+]a) from ca. 3.5 to 6.5 mM, as occurs in heavy exercise, excites the arterial chemoreceptors and ventilation (VE) in anaesthetised cats. We have previously shown that the excitation of chemoreceptors by potassium is enhanced by hypoxia and abolished by hyperoxia, and here we show, in decerebrate ...
Naqvi S S - - 1991
We studied the effects of removing cyclic pulmonary afferent neural information on respiratory pattern generation in anesthetized dogs. Phrenic neural output during spontaneous breathing (SB) was compared with that occurring during constant-flow ventilation (CFV) at several levels of eucapnic hypoxemia. Hypoxia caused an increase in both the frequency and the ...
Lawrence D L - - 1991
To evaluate the possible physiologic role of atrial natriuretic factor (ANF) in the observed dissociation of aldosterone secretion from the renin-angiotensin system during hypoxic exercise, 12 untrained men, ages 18 to 24, were studied on two separate days for 30 min during hypoxic (16% O2) and normoxic (room air) exercise ...
Rivera R K - - 1991
In this study we explored the relationship between hypoxic exposure level and corneal response by assuming that the partial pressure of oxygen (PO2) under a contact lens during eye closure is directly related to oxygen transmissibility (Dk/L). To study this relationship, we monitored a group of subjects who wore RGP ...
Dahan A - - 1991
The ventilatory response to isocapnic, sustained hypoxia is characterized by initial hyperventilation followed by ventilatory decline. The ventilatory response to isocapnic sustained hypoxia during i.v. administration of midazolam was assessed in five healthy subjects. Compared with control experiments, the hyperventilatory effect of hypoxia was not decreased following administration of midazolam. ...
Story D A - - 1991
The effect of hypoxia on plasma atrial natriuretic factor (ANF), plasma renin activity (PRA), and plasma aldosterone concentration (PAC) was evaluated during 2 h of treadmill exercise at 2 km/h, 0 grade at sea level. Six male subjects exercised on 2 separate days during normoxia (21% O2) and hypoxia (13.3 ...
Kinkead R - - 1991
This study assessed the effects of experimentally elevated plasma catecholamine levels on gill ventilation in rainbow trout (Oncorhyncus mykiss) exposed to various external ventilatory stimulants. Trout were exposed to hypoxia (water PO2 (PwO2) = 90 Torr) or hypercapnia (water PCO2 (PwCO2) = 4.5 Torr) for 30 min. These conditions caused ...
Cartee G D - - 1991
Hypoxia caused a progressive cytochalasin B-inhibitable increase in the rate of 3-O-methylglucose transport in rat epitrochlearis muscles to a level approximately six-fold above basal. Muscle ATP concentration was well maintained during hypoxia, and increased glucose transport activity was still present after 15 min of reoxygenation despite repletion of phosphocreatine. However, ...
Hochachka P W - - 1991
Maximum O2 and CO2 fluxes during exercise were less perturbed by hypoxia in Quechua natives from the Andes than in lowlanders. In exploring how this was achieved, we found that, for a given work rate, Quechua highlanders at 4,200 m accumulated substantially less lactate than lowlanders at sea level normoxia ...
Giesbrecht G G - - 1991
We studied whether exercise endurance under normobaric hypoxia can be enhanced by increasing hypoxic ventilatory sensitivity with almitrine bismesylate (ALM). On both ALM and placebo (PL) days, resting subjects breathed a hypoxic gas mixture (an inspired O2 fraction of 10.4-13.2%), which lowered resting arterial O2 saturation (SaO2) to 80%. After ...
Denjean A - - 1991
Hypoxia enhances bronchial responsiveness in sheep and dogs and we recently reported a similar effect in asthmatic subjects. Activation of a reflex arc due to stimulation of peripheral chemoreceptors has been suggested to explain this finding. We evaluated the contribution of carotid body chemoreceptors to hypoxia-induced bronchial responsiveness in conscious ...
Myrmel T - - 1991
The mechanism involved in ischemia-induced myocardial lipolysis is still a matter of controversy. To elucidate the regulation of lipolysis at the cellular level, we incubated isolated rat myocytes in normoxic or hypoxic medium containing 11.1 mM glucose. Rates of lipolysis (glycerol output) were significantly (P less than 0.05, n = ...
Pokorski M - - 1991
The effects of the opiate antagonist naloxone (0.4 mg.kg-1, i.v.) on carotid chemoreceptor and ventilatory responses to graded steady-state levels of hypoxia and hypercapnia were investigated in two groups of cats: chronically normoxic and chronically hypoxic. The cats of the latter group were exposed to PIO2 of about 70 mm ...
Velazquez M - - 1991
We compared the effects of left caudal lobe (LCL) alveolar hypoxia on regional pulmonary blood flow (PBF) with the effects due to alveolar edema induced by plasma instilled directly into the LCL airways of 16 dogs. Regional measurements were made with positron emission tomography. After hypoxic ventilation of the LCL ...
Trendelenburg U - - 1991
The combination of hypoxia plus glucose deprivation or of hypoxia plus lactate induces carrier-mediated outward transport of 3H-noradrenaline in the rat vas deferens. Lactate efflux is higher from atria than from vas deferens. Hence, the much lower contribution by outward transport to the spontaneous efflux of 3H-noradrenaline in vas deferens ...
Springer C - - 1991
Control of ventilation and heart rate during exercise appears to undergo maturation, while aerobic metabolism (VO2) may not. Since we had previously found that hypoxia during exercise produced different ventilatory responses in children (C) compared to adults (A), we hypothesized that VO2 and heart rate kinetics during exercise would show ...
Freisleben H J - - 1991
Hypoxia and reoxygenation in working rat hearts were investigated in this study. Cardiac hemodynamic parameters which decline immediately under hypoxic conditions, recover during reoxygenation. Biochemical and ultrastructural alterations exhibit a more complicated pattern. There is a primary phase in hypoxic perfusion up to 15 min with a steep increase of ...
Eyer C L - - 1991
The isolated, electrically-driven, guinea pig left atrium was used to study the ability of two perfluorocarbon emulsions to prevent anaerobic hypofunction in the myocardium. A 20% perfluorodecalin (PFD) emulsion maintained peak tension at 80% of aerated levels for more than 20 minutes. Emulsions of perfluorooctylbromide (PFOB) ranging from 25 to ...
Reid P G - - 1991
Intravenous infusion of the nucleoside adenosine stimulates respiration, probably at least partly by an action in the carotid bodies, and also potentiates the ventilatory response to hypoxia, suggesting that it might be involved in the control of breathing. Whether the effects of adenosine occur at concentrations likely to be achieved ...
Felzen B - - 1991
We tested the hypothesis that the decrease in the thyroid state, with age, contributes to the age-related increase in myocardial responsiveness to cardiac glycosides. Thyroid hormone levels (reflecting the thyroid state): total T4 (microgram/dl) and total T3 (ng/dl) in the 3 groups of guinea pigs were (mean +/- SEM): adults ...
Laudignon N - - 1991
The effect of hypoxia on the levels of adenosine, inosine and hypoxanthine in the cerebrospinal fluid (CSF) was determined by HPLC in newborn (1- to 3-day-old, n = 6) and 1-month-old (n = 5) piglets. Serial CSF samples (q 60 s) were obtained from the cisterna magna during normoxia and ...
Hasegawa K - - 1991
To elucidate the role of free radicals in the pathogenesis of neonatal hypoxic encephalopathy, we determined the content of thiobarbituric acid reactants (TBARs), as an index of lipid peroxidation related with a free radical reaction, in the brains of newborn mice during hypoxia and recovery from hypoxia. Hypoxic stress was ...
Hampl V - - 1991
Oxygen tension is known to control the pulmonary vascular tone. We reviewed three hypotheses that try to explain the mechanism whereby hypoxia is sensed in the lung tissue. The first hypothesis concerns the role of the oxygen binding hemoprotein cytochrome P-450. Studies using various inhibitors and activators of cytochrome P-450 ...
Inscore S C - - 1991
Neonates and infants presenting with pulmonary hypertension and chronic hypoxia often exhibit airway obstruction. To investigate this association, we utilized a system in which neonatal calves are exposed to chronic hypobaric hypoxia and develop severe pulmonary hypertension. For the present study, one of each pair of six age-matched pairs of ...
Li K Y - - 1990
1. The discharge of single afferent chemoreceptor fibres was recorded from the cut sinus nerve over periods of 60 or 90 min of constant, isocapnic hypoxia (arterial O2 pressure, Pa,O2, 3.13-5.25 kPa), in twenty anaesthetized rabbits, after dividing the sympathetic supply to the carotid body. 2. Under control conditions, discharge ...
Warner M M - - 1990
The ventilatory response to moderate exercise is potentiated during hypoxia in goats, causing PaCO2 to decrease more from rest to exercise than in normoxia. We investigated the hypothesis that this response is due to the ventilatory stimulus provided by an interaction between exercise induced hyperkalemia and hypoxia. Plasma potassium concentration ...
Bascom D A - - 1990
One hypothesis concerning the origin of hypoxic ventilatory decline is that hypoxia acts centrally to depress peripheral chemoreflex loop activity. To investigate possible changes in peripheral chemoreflex loop activity during sustained, isocapnic hypoxia, the ventilatory responses to four one minute pulses of either extra hypoxia (45 Torr) or carbon dioxide ...
Georgopoulos D - - 1990
In adult humans, the ventilatory response to acute sustained hypoxia is biphasic, characterized by an initial brisk increase followed by a decline to an intermediate plateau. Recently, it has been shown that hypoxic lactate formation in the brain depresses ventilation in peripherally chemodenervated animals, and postulated that this formation might ...
Lookinland S - - 1990
The aim of this study was to compare the hemodynamic and oxygen transport responses to sudden, acute progressive hypoxia in normal control conditions (six healthy dogs) and in subacute respiratory failure (six dogs with naturally occurring distemper). The latter were used to simulate respiratory failure from viral pneumonitis in man. ...
Lane R - - 1990
1. The sensation of breathlessness increases when ventilation is reflexly stimulated but it is not clear whether different stimuli have specific effects in the genesis of this sensation. 2. Our aim was to compare subjective assessments of the intensity of breathlessness at the same levels of ventilation induced by different ...
Baur T S - - 1990
STUDY OBJECTIVE: The aim was to determine if prostaglandin like activity might be involved in changes due to exercise training in the coronary flow responses to hypoxia. DESIGN: The coronary flow response to hypoxia was measured under constant perfusion pressure in isolated perfused hearts from 12 endurance exercise trained rats ...
Georgopoulos D - - 1990
After voluntary hyperventilation, normal humans do not develop a significant ventilatory depression despite low arterial CO2 tension, a phenomenon attributed to activation of a brain stem mechanism referred to as the "afterdischarge." Afterdischarge is one of the factors that promote ventilatory stability. It is not known whether physiological stimuli, such ...
Bissonnette J M - - 1990
The respiratory responses to theophylline during normoxia and hypoxia were determined in 13 unanesthetized fetal sheep. Theophylline (plasma levels approximately 111 mumol/L) increased the incidence of fetal breathing movements measured over 120 min from 37.7 +/- 4.8% to 61.1 +/- 5.7% (SEM) in normoxic fetuses. In isocapnic hypoxia (arterial O2 ...
Fantini E - - 1990
The effects of hypoxia and reoxygenation on action potentials (AP), contractions, and certain biochemical parameters were studied in isolated rat ventricular myocytes in monolayer culture in the presence and absence of glucose. Substrate deprivation alone had no influence on the basal properties. In the presence of glucose, a 4-h hypoxic ...
Harman A W - - 1990
Cytosolic free Mg2+ concentration was determined in 1-day cultured rat hepatocytes using Multiparameter Digitized Video Microscopy (MDVM) of the fluorescent probe, mag-fura-2. Chemical hypoxia with KCN (5 mM) and iodoacetate (1 mM), a model which mimics the ATP depletion and reductive stress of hypoxia, caused a rapid increase of free ...
Ruegg C E - - 1990
Innate biochemical responses of rabbit renal proximal convoluted (PCT) and straight (PST) segments following in vitro exposure to anoxia or hypoxia were investigated to delineate the mechanisms responsible for segment-selective injury in vivo. After bulk isolation, suspensions (1 mg/ml) enriched in either PCT or PST were preincubated in Dulbecco's modified ...
Hoop B - - 1990
Glutamate stimulates resting ventilation by altering neural excitability centrally. Hypoxia increases central ventilatory drive through peripheral chemoreceptor stimulation and may also alter cerebral perfusion and glutamate metabolism locally. Therefore the effect of hypoxia and peripheral chemodenervation on cerebrospinal fluid (CSF) transfer rate of in vivo tracer amidated central nervous system ...
Martin G V GV Division of Cardiology, Seattle Veterans Administration Medical Center, WA - - 1990
Fluoromisonidazole is metabolically trapped in viable hypoxic cells in vitro. This property is the basis for the hypothesis that [18F]fluoromisonidazole can be used to detect hypoxic tissues noninvasively using positron emission tomography. To assess the potential usefulness of this compound as a marker for hypoxic myocardium, we measured the accumulation ...
Hoyt R H - - 1990
To delineate potential structural mechanisms of impaired cell coupling induced by hypoxia in canine myocardium, we characterized derangements in intercellular junctions and alterations in the space constant in strips of ventricular epimyocardium before and after selected intervals of hypoxia in vitro. Tissue samples were analyzed morphometrically with transmission and freeze-fracture ...
Bamford O S - - 1990
In order to investigate possible mechanisms for the effect of hypoxia on fetal electrocortical (ECoG) activity, the effects of 30 min of isocapnic hypoxia on ECoG were studied in three groups of unanaesthetized late-gestation fetal lambs in utero. One group was intact, in the second the brainstem was transected between ...
Kaijser L - - 1990
The myocardial release of neuropeptide Y-like immunoreactivity (NPY-LI) and noradrenaline (NA) during exercise with and without arterial hypoxia was measured in 18 healthy men by arterial (a) and coronary sinus (cs) catheterization. Exercise was performed in the supine position on a cycle ergometer at a load, selected to produce a ...
Hughson R L - - 1990
The dynamic response characteristics of the oxygen uptake (VO2) response were investigated during upright cycle ergometer exercise in six healthy male volunteers. The exercise test consisted of a pseudorandom binary sequence (PRBS) with 15 units per sequence, each unit 15 s long, for a total period of 225 s. Six ...
Brice A G - - 1990
We determined the effect of acute hypoxia on the ventilatory (VE) and electromyogram (EMG) responses of inspiratory (diaphragm) and expiratory (transversus abdominis) muscles in awake spontaneously breathing ponies. Eleven carotid body-intact (CBI) and six chronic carotid body-denervated (CBD) ponies were studied during normoxia (fractional inspired O2 concn [FIO2] = 0.21) ...
Gaudy J H - - 1990
The ventilatory effects of 1 mg.kg-1 i.v. almitrine were studied in five dogs anaesthetized with halothane 2% under conditions of normoxia, hyperoxia and hypoxia. Ventilation (minute ventilation, respiratory frequency, tidal volume, duration of inspiration and expiration, ratio TI/Ttot and VT/TI), Pao2, Paco2, pHa, systemic arterial pressure and heart rate were ...
Stainsby W N - - 1990
We measured O2 uptake (VO2), CO2 output (VCO2), and net lactic acid output (L) during a 30-min period of repetitive 1/s isotonic tetanic contractions of the dog gastrocnemius-plantaris muscle group. The conditions were modest ischemic hypoxia (ischemia), hypoxia hypoxia (hypoxia), and free-flow normoxia (control). The major goal was to assess ...
McLellan T M - - 1990
The purpose of this study was to evaluate the effect of hypoxia (10.8 +/- 0.6% oxygen) on performance of 30 s and 45 s of supramaximal dynamic exercise. Twelve males were randomly allocated to perform either a 30 s or 45 s Wingate test (WT) on two occasions (hypoxia and ...
Szczech J - - 1990
Hypoxic hypoxia is used as one of the models for examining the unfavourable effect of oxygen deficit on the nervous system. Since some morphological studies concerning the effect of hypoxia on the central nervous system have given consideration to perivascular lesion zones and glia alterations in the white matter, the ...
Wyss V - - 1990
Seven healthy young male adults were subjected to a total of 56 tests to ascertain the effects of L-carnitine (L-C) and a placebo (P) on ventilation, O2 intake (VO2), CO2 output, heart rate, blood pressure and serum lactic acid, non-esterified fatty acid, glycerol and glucose during strenuous and aerobic/anaerobic threshold-level ...
Pilardeau P - - 1990
The effects of acute hypoxia (2 days at 4350 m) on whole saliva flow and composition were studied on 12 sea-level natives, at rest and following a maximal exercise. Exercise, performed in normoxia and hypoxia, did not induce variations in saliva flow rate, saliva potassium or alpha-amylase concentrations. In contrast, ...
Raynaud J - - 1990
To answer the question whether PCO2 affects the muscular metabolism, PO2, PCO2, pH, lactic acid concentration and hemoglobin were measured in the efferent muscular venous blood from common flexor digitorum, during forearm rhythmic exercise corresponding to VO2max. Exercise was carried out either in hypocapnic hypoxia i.e. in permanent high altitude ...
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