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Results 801 - 850 of 1063
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Miyamura M - - 1990
In order to investigate the effects of acute hypoxia and accompanying hypocapnia on the ventilatory response at the onset of dynamic exercise, four healthy adult men performed 50W rectangular loads on a cycle-ergometer in normoxic (FIO2 = 0.21) and hypoxic (FIO2 = 0.11) conditions. No statistically significant differences in the ...
Griffiths T L - - 1990
1. We have studied the carotid body contribution to hypoxic respiratory drive, using a hypoxic/hyperoxic switching technique, and the ventilatory response to intravenous infusion of adenosine, a recently described respiratory stimulant, in five patients with bilateral carotid endarterectomy. 2. The contribution made by the carotid bodies to total ventilatory drive ...
Barnas G M - - 1990
To study the inhibitory effect of hypoxia on the cold defense mechanism, pigeons were exposed at low ambient temperature (5 degrees C) to various inhaled gas mixtures: normoxia [0.21 fractional concentration of O2 (FIO2)], hypoxia (0.07 FIO2), and normocapnic hypoxia (0.07 FIO2 + 0.045 FICO2). Electromyographic (EMG) activity indicative of ...
Ohyabu Y - - 1989
Ventilatory and heart rate responses to hypoxia at rest and during light exercise (30W) were compared in 21 high school judo athletes. The results of ventilatory and heart rate responses to hypoxia were analyzed by the hyperbolic equations, VE = VO + AVE/(PETO2-CVE) and HR = HRO + AHR/(PETO2-CHR), respectively, ...
Schaefer S L - - 1989
Hypoxia potentiates the ventilatory response to exercise, eliciting a greater decrease in arterial PCO2 (PaCO2) from rest to exercise than in normoxia. The mechanism of this hypoxia-exercise interaction requires intact carotid chemoreceptors. To determine whether carotid chemoreceptor stimulation alone is sufficient to elicit the mechanism without whole body hypoxia, ventilatory ...
van Lunteren E - - 1989
Both isocapnic and poikilocapnic hypoxia may elicit a biphasic respiratory response, during which an initial ventilatory stimulation is followed by a reduction in breathing and diaphragm (DIA) electrical activity. To ascertain whether during adulthood other respiratory muscles have biphasic hypoxic responses similar to the DIA, in nine anesthetized cats electromyograms ...
Woods S D - - 1989
Oxygen saturation and pulse rate were recorded using pulse oximetry during 50 consecutive endoscopic retrograde cholangiopancreatography (ERCP) examinations. Oxygen saturation dropped to below 90% in 22 patients at some point during the procedure. Multiple regression analysis revealed that increasing age and weight were the most significant variables in predicting tachycardia ...
Neubauer S - - 1989
To test whether verapamil protects myocardial high-energy phosphate content during hypoxia by reducing pre-hypoxic cardiac work or secondary to metabolic events that occur during hypoxia, we compared the relation between myocardial performance and high-energy phosphate content during normoxia, hypoxia and reoxygenation using 31P NMR spectroscopy in isolated, isovolumic buffer-perfused rat ...
Takasaki Y - - 1989
We studied the electromyographic activity of the diaphragm (EMGdi) and abdominal external oblique (EMGeo) muscles in response to progressive hypercapnia (HCVR) and hypoxia (HVR) in five normal males. The slopes of the regression lines relating log EMGdi activity to minute volume of ventilation (VE) were steeper during HVR runs than ...
Somers V K - - 1989
We compared the effects of isocapnic hypoxia (IHO) and hyperoxic hypercapnia (HC) on sympathetic nerve activity (SNA) recorded from a peroneal nerve in 13 normal subjects. HC caused greater increases in blood pressure (BP), minute ventilation (VE), and SNA [53 +/- 14% (SE) during HC vs. 21 +/- 7% during ...
Airlie M A - - 1989
1. In a double-blind placebo-controlled study, we have investigated the effect of the peripheral chemoreceptor stimulant drug almitrine bismesylate on hypoxic ventilatory drive (expressed as the slope of the minute ventilation/arterial oxygen saturation relationship in litres min-1+-1) as measured by both progressive isocapnic hypoxia at rest and transient hypoxia (three ...
Paloheimo M P - - 1989
Spontaneous cerebral biopotentials were monitored during and after hypoxic insults in 30 ketamine-anesthetized rats. Upper facial electromyographic (EMG, mean integrated amplitude) and electroencephalographic (mean zero cross frequency (ZXF) and mean integrated amplitude (MIA] data were recorded within 30 min after reoxygenation and cardiopulmonary resuscitation. The animals were separated into 2 ...
Murphy P C - - 1989
The ability of the cardiorespiratory system to adapt to the demands of increased exercise intensity was studied under the effects of hypoxia with two different submaximal cycling exercise protocols. A step transition in work rate from 25 W to 105 W and a ramp increase in work rate from a ...
Mortola J P - - 1989
We asked whether the lack of sustained hyperventilation during acute hypoxia, often reported to occur in the infant, is a common characteristic among newborn mammalian species, and to which extent inter-species differences may be accounted for by differences in metabolic responses. Ventilation (VE) and breathing pattern have been measured by ...
Kumazawa T - - 1989
Effects of opioids on the activity of visceral nociceptors were tested using the in vitro testis-spermatic nerve preparations excised from deeply anesthetized dogs. Morphine, DADLE and dynorphin (10 microM) elicited discharges of polymodal receptors in approximately 1/3 of the tested cases. The incidence of the excitatory response of morphine increased ...
Seguchi M - - 1989
We studied the effect of respiratory acidosis (pH = 6.8) on mechanical function, tissue adenosine triphosphate (ATP), and effluent creatine kinase (CK) in isolated arterially perfused hypoxic newborn and adult rabbit hearts. In the oxygenated muscle, acidosis reduced tension (T) and maximal tension first derivative [+ dT/dt (max)] in the ...
Hopkins S R - - 1989
Arterial desaturation in athletes during intense exercise has been reported by several authors, yet the etiology of this phenomenon remains obscure. Inadequate pulmonary ventilation, due to a blunted respiratory drive, has been implicated as a factor. To investigate the relationship between the ventilatory response to hypoxia, exercise ventilation, and arterial ...
Georgopoulos D - - 1989
In adult humans the ventilatory response to sustained hypoxia (VRSH) is biphasic, characterized by an initial brisk increase, due to peripheral chemoreceptor (PC) stimulation, followed by a decline attributed to central depressant action of hypoxia. To study the effects of selective stimulation of PC on the ventilatory response pattern to ...
Canet E - - 1989
This study was designed to elucidate the effect of hypoxia on the breathing rhythmicity and the effect of hypoxia on periodic breathing (PB) in two groups of newborn lambs (less than 2 days and 10 days of age). Lambs undergoing a hypoxic ventilatory test [0.08 inspired O2 fraction (FIo2) for ...
Georgopoulos D - - 1989
In 10 normal young adults, ventilation was evaluated with and without pretreatment with aminophylline, an adenosine blocker, while they breathed pure O2 1) after breathing room air and 2) after 25 min of isocapnic hypoxia (arterial O2 saturation 80%). With and without aminophylline, 5 min of hyperoxia significantly increased inspiratory ...
Moffat M P - - 1989
This study examined the effects of quinacrine on the functional and electrophysiological responses of isolated guinea pig hearts and isolated canine papillary muscle and Purkinje fibre preparations. A dose-response relationship for quinacrine (0.01-10.0 micrograms/mL) was studied in isolated guinea pig hearts perfused for 40 min. Quinacrine was found to exert ...
Bonora M - - 1989
The effects of the level of oxygenation on the respiratory response to heat exposure have been studied in conscious cats during normoxia, severe or mild hypocapnic hypoxia [inspired O2 fraction (FIO2) = 0.11 or 0.13], or hyperoxia. Several cats were also studied during severe normocapnic hypoxia. Experiments were repeated while ...
Hannhart B - - 1989
Pregnancy increases ventilation and ventilatory sensitivity to hypoxia and hypercapnia. To determine the role of the carotid body in the increased hypoxic ventilatory response, we measured ventilation and carotid body neural output (CBNO) during progressive isocapnic hypoxia in 15 anesthetized near-term pregnant cats and 15 nonpregnant females. The pregnant compared ...
Edoute Y - - 1989
We determined the effect of high-flow hypoxia and reoxygenation on myocardial function and O2 uptake. Isolated working rat hearts were subjected to a 30-min period of hypoxia (pO2 = 384, 296, 207 and 131 torr), followed by 30 min of reoxygenation (pO2 = 500 torr). Another group of normoxic hearts ...
Tanonaka K - - 1989
The present study was designed to determine whether the 1-form of YM-12617, which was developed recently as an alpha 1-adrenoceptor blocker, is capable of protecting the myocardium from hypoxia-induced disturbances of cardiac function and metabolism. Isolated rabbit hearts were perfused for 25 min under hypoxic conditions in the absence or ...
Marshall J M - - 1989
1. In cats anaesthetized with Saffan, which does not block afferent activation of the brain stem defence areas, we have analysed the cardiovascular changes induced by 3 min periods of graded systemic hypoxia (fraction of O2 in inspirate, Fi,O2, 0.15, 0.12, 0.08, 0.06). 2. At light levels of Saffan anaesthesia, ...
Ward S A - - 1989
1. Respiratory sensation during exercise is generally considered to be related to respiratory mechanical factors which may be manifest as an abnormal relationship between the force applied to the lungs and chest wall and the resulting motion (if any); that is, a 'length-tension' inappropriateness (Campbell & Howell, 1963). This suggests ...
Dusseau J W - - 1989
Numerous studies have demonstrated an increased capillarity in response to hypoxia in a variety of tissues. We studied the effects of hypoxia on the number and morphology of pre- and postcapillary vessels in the chick chorioallantoic membrane (CAM). Measurements of CAM microvessels were made from in vivo photographs after incubation ...
Reed P N - - 1989
Arterial oxyhaemoglobin saturation (SaO2) was monitored continuously during normal labour in 33 healthy parturients receiving pethidine and nitrous oxide for analgesia. Sixteen (49%) had episodes exceeding 10 s duration when SaO2 was less than 90% (mean 83.7%, range 89-60%). Two women had multiple episodes of profound hypoxia with SaO2 less ...
Wei J Y - - 1989
To test the hypothesis that chronic exercise may improve tolerance to hypoxia in aged hearts, we compared cardiac function of exercised rats to that of their age-matched, nonexercised controls. Right ventricular papillary muscles were removed from young adult (9 mo) and old (24-26 mo) male Fischer 344 rats that were ...
Blake D R - - 1989
A series of experiments showed that, on exercise of the inflamed human knee, intra-articular pressure rises above synovial capillary perfusion pressure, causing intra-articular hypoxia; and that, on cessation of exercise, there is oxidative damage to lipids and IgG within the joint. These findings are consistent with the hypothesis that persistence ...
Long G R - - 1989
The biphasic nature of the ventilatory response to sustained (30 min) hypoxia may be explained by the central accumulation of a neurochemical with net inhibitory effect or, alternatively, peripheral chemoreceptor adaptation. To determine the role of serotonin (a putative central neuroinhibitor) and calcium ions (a putative peripheral neurotransmitter) in this ...
Sarkany I - - 1989
Posture has long been recognized to be a crucial factor in the etiology of venous leg ulcers. Activation of the stretch receptors in the veins by venous distention induces reflex vasoconstriction and hypoxia. In patients with defective venous return, exercise fails to reduce venous pressure when the legs are dependent; ...
Barstow T J - - 1989
Because the natural enrichment of carbohydrate with 13C is greater than that of lipid, we hypothesized that the natural enrichment of exhaled CO2 with 13C (EN) could be used to gauge endogenous substrate utilization in exercising human subjects. To test this, EN and the respiratory exchange ratio (R) which equals ...
Mélot C - - 1989
The effect of almitrine bismesylate on hypoxic pulmonary vasoconstriction (HPV) remains controversial. We therefore investigated in a double-blind, placebo-controlled, randomized design the effects of low dose of almitrine bismesylate (4 micrograms/kg/min given intravenously) on blood gases, pulmonary hemodynamics, and ventilation-perfusion (VA/Q) distributions in normal subjects breathing a hypoxic mixture (FIO2, ...
Watchko J F - - 1989
We examined genioglossal and diaphragmatic EMG activities in one- and two-month-old anesthetized kittens during acute exposures to hypoxic (13% or 10% O2) and hyperoxic hypercapnic (8% CO2/50% O2/balanced N2) gas mixtures. Phasic genioglossal EMG activity, frequently characterized by a combined inspiratory-expiratory discharge pattern, was observed in 3 of 8 one-month-old ...
Yoshida T - - 1989
The purpose of the present study was to investigate whether, in humans, hypoxia results in an elevated lactate production from exercising skeletal muscle. Under conditions of both hypoxia [inspired oxygen fraction (F1O2): 11.10%] and normoxia (F1O2: 20.94%), incremental exercise of a forearm was performed. The exercise intensity was increased every ...
Maruyama R - - 1989
To estimate the sensitivity to hypoxic inhibition of various regulatory processes for respiration, changes in breathing pattern during hypoxic ventilatory depression (HVD) were analyzed in the halothane-anesthetized spontaneously breathing rat using a "progressive isocapnic hypoxia test." In the carotid sinus nerve (CSN) intact rats, ventilatory augmentation was followed by depression ...
Kwarecki K - - 1989
Groups of 20-45-day-old rats maintained on a light (0600-1800)/dark (1800-0600) regimen with food and water available ad libitum were studied for the effect of hypoxic hypoxia on the circadian rhythm of corneal epithelial mitosis and thymidine incorporation. In experiments conducted during the months of September and November, hypoxic hypoxia was ...
Nishino T - - 1988
We investigated changes in activities of phrenic nerve (PN) and the recurrent laryngeal nerve (RLN) during progressive hypoxia produced by administration of a mixture of 5% O2 in N2 and a mixture of 5% O2 in N2O in 8 vagotomized, paralyzed, and artificially ventilated cats anesthetized with halothane. During progressive ...
Martin-Body R L - - 1988
1. The characteristics of hypoxic ventilation were studied in awake adult rats after brain transections about the intercollicular level. The results were compared with studies made before transection, 17-24 h after bilateral carotid body denervation effected by carotid sinus nerve section. 2. Transection at or below the intercollicular level converted ...
Marshall J M - - 1988
1. In rats anaesthetized with Saffan, we have further analysed the respiratory, cardiac and regional vascular responses induced by 3 min periods of graded hypoxia (breathing 15, 12, 8 or 6% O2 in N2). 2. Frequently, hypoxia evoked an episode, lasting 1-1.5 min, of tachycardia, renal and mesenteric vasoconstriction and ...
Thordstein M - - 1988
To elucidate if there is a reduced perinatal tolerance of hypoxia in growth retardation and approach its pathophysiologic background, newborn guinea pigs of different weights were subjected to standardized hypoxia. Intrauterine growth retardation was induced through uterine artery ligation. After spontaneous delivery experiments were performed within 2 days. After stabilization, ...
Rowell L B - - 1988
Venomotor responses, measured as the pressure rise in occluded forearm veins, were used in a two-part experiment to test presence or absence of sympathetic neuroeffector mechanisms in 10 men made moderately to severely hypoxemic. In part I, forearm venoconstriction was induced by ice water on the contralateral forearm (a spinal ...
Filuk R B - - 1988
In nine normal subjects we measured the ventilatory response to isocapnic hypoxia with and without an intravenous infusion of 1 mg of somatostatin. Arterial O2 saturation was rapidly lowered to 80 +/- 2% in 2 min and maintained for 30 min. During control experiments, ventilation increased immediately (3-5 min) and ...
Jones D R - - 1988
The effect of denervation of the carotid labyrinths on breathing responses to simultaneously applied aerial and aquatic normoxia, hypoxia, or hypercapnia has been studied in unrestrained Xenopus laevis. Denervation significantly reduced VI of normoxic toads compared with VI in intact and sham-operated toads, due to a significant reduction in the ...
Burger R E - - 1988
1. We have studied the effects of intravenous infusions of 0.1 mmol/min KCl (raising arterial potassium from ca. 3.2 to 6.0 mM) on the steady-state responses of carotid body chemoreceptors to end-tidal PCO2 and PO2 in the pentobarbitone-anaesthetized cat. 2. The excitatory effect of these KCl infusions was enhanced by ...
Mortola J P - - 1988
Newborns respond to acute hypoxia with a brief increase in ventilation (VE) followed by a decline toward the normoxic value. We asked to what extent this biphasic pattern is determined by changes in metabolic rate. In newborn awake kittens within the first week after birth we measured VE by the ...
Fisher M J - - 1988
31P-NMR spectroscopy was performed on vascular smooth muscle (VSM; porcine carotid artery) superfused with a substrate-free high K(+)-PSS. Scans were collected before (control), during (hypoxia), and after (post-control) hypoxia, and chemical measurements of ATP (0.070 +/- 0.13 mumoles/g wet wt.) and creatine (2.04 +/- 0.14 mumol/g wet wt.) were made. ...
Burnier M - - 1988
Recent in vitro studies have suggested that the presence of extracellular acidosis is protective against the development of oxygen-deprivation injury in several tissues. Because cellular Ca accumulation after renal ischemia may represent a major pathogenic event leading to cellular damage, the purpose of the present study was to examine the ...
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