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Results 351 - 400 of 884
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Van Schaick E A - - 1997
Partial adenosine A1 receptor agonists with reduced intrinsic activity at the cardiovascular system would be promising for therapeutic application (e.g., as antilipolytic agents). In the present study a series of 8-alkylamino [methyl (M)-, ethyl (E)-, propyl (P)-, butyl (B)- and cyclopentyl (CP)-] derivatives of N6-cyclopentyladenosine (CPA) were investigated in conscious ...
Zimmer K M - - 1997
The aim of this study was to examine and compare the potential influence of cyclooxygenase or lipoxygenase derived metabolites of arachidonic acid on myocardial injury produced either by a free radical generating system consisting of purine plus xanthine oxidase or that produced by hydrogen peroxide. A free radical generating system ...
Vander Elst L - - 1997
RATIONALE AND OBJECTIVES: Several works have shown that the hepatobiliary magnetic resonance imaging contrast agent manganese dipyridoxyl diphosphate (MnDPDP) partly releases its metallic ion and exhibits cardiovascular effects that are supposed to arise from the free manganese ions (Mn++). In the current study, the cellular internalization of Mn by the ...
Neubauer S - - 1997
BACKGROUND: The purpose of this work was to determine the clinical and hemodynamic correlates of alterations in cardiac high-energy phosphate metabolism in patients with aortic stenosis and with aortic incompetence. METHODS: Fourteen volunteers, 13 patients with aortic stenosis, and 9 patients with aortic incompetence were included. Patients underwent echocardiography and ...
Maclean D A - - 1997
The purpose of the present study was to examine the effects of femoral arterial injections of adenosine on muscle sympathetic nerve activity (MSNA) under three different conditions. These conditions were adenosine injection alone, adenosine injection after phenylephrine infusion, and adenosine injection distal to a thigh cuff inflated to arrest the ...
Stepp D W - - 1997
Autoregulation is defined as the intrinsic ability of an organ to maintain constant flow in the face of changing perfusion pressure. The present study evaluated the role of several potential mediators of coronary autoregulation: interstitial adenosine, ATP-sensitive K+ (K+ATP) channels, and myocardial oxygen and carbon dioxide tensions as reflected by ...
Phillis J W - - 1997
1. The roles of adenosine and adenosine 5'-triphosphate in cardiorespiratory regulation by the nucleus tractus solitarius (NTS) have been evaluated in a range of experiments, using micro-injections of selective agonists and antagonists of purinoceptors. 2. Adenosine injected into the caudal NTS decreases heart rate (HR), arterial blood pressure (BP) and ...
Redzić Z B - - 1997
The single pass paired dilution technique was used to measure the uptake of nucleosides across the basolateral face of the isolated in situ perfused sheep choroid plexus (CP). The uptake of labelled adenosine and guanosine into the CP was large (approximately 35%) whereas that of thymidine was less (approximately 15%). ...
Tian R - - 1997
BACKGROUND: Mechanisms in addition to diastolic calcium overload may contribute to diastolic dysfunction in hypertrophied hearts. In this study, we tested the hypothesis that failure to maintain a low ADP concentration in hypertrophied hearts contributes to diastolic dysfunction by inhibiting the rate of cross-bridge cycling. METHODS AND RESULTS: By perfusing ...
Mottet I - - 1997
The hypothesis of magnesium deficiency in isoproterenol (ISO) induced myocardial injury has been investigated by 31P nuclear magnetic resonance spectroscopy. High energy phosphate concentrations, pHi, and intracellular free magnesium concentration ([Mg2+]i) were measured in isolated rabbit hearts perfused at constant flow and subjected to 10(-6)M isoproterenol during 30 min. Recent ...
Stumpe T - - 1997
This study investigated the relationship between O2 consumption (VO2) and energy status in isolated rat cardiomyocytes using a system in which O2 supply (PO2) was maintained constant. For this purpose, VO2, phosphocreatine, ATP, intracellular pH, and adenosine of quiescent and stimulated cardiomyocytes were measured while the ambient PO2 was clamped ...
Bombardier H - - 1997
We have utilized DSC and high pressure FTIR spectroscopy to study the specificity and mechanism by which ATP protects actin against heat and pressure denaturation. Analysis of the thermograms shows that ATP raises the transition temperature Tm for actin from 69.6 to 75.8 degrees C, and the calorimetric enthalpy, deltaH, ...
Do E - - 1997
Using an isolated ferret heart preparation (Langendorff perfusion, perfusion pressure 90 mmHg), energy metabolism has been characterized in right and left ventricles from control and hypertrophied hearts. Hypertrophy was induced by pulmonary artery clipping for 30-45 days (right ventricle wall weight/body weight ratio increased by 70%). Myocardial contents of high ...
Woodcock E A - - 1997
The pathways of release and metabolism of inositol phosphates in intact heart tissue are different from those observed in isolated cardiomyocytes in culture. Thus, it is essential that methods are available for the quantitation of inositol phosphates in intact tissue preparations. This manuscript describes methods which allow the quantitation of ...
Tabrizchi R - - 1997
The effects of adenosine and adenosine analogues, 2-[p-(2-[carboxyethyl) phenethylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680) and N6-2-(4-aminophenyl)-ethyladenosine (APNEA), on mean arterial pressure, cardiac output, mean circulatory filling pressure, arterial resistance, venous resistance and heart rate in untreated or treated (with ganglion-blockers mecamylamine and atropine) pentobarbital-anesthetized rats were examined. Infusion of adenosine (100, 300 and ...
Tian B - - 1997
The effects of single or multiple topical doses of the relatively selective A1 adenosine receptor agonists (R)-phenylisopropyladenosine (R-PIA) and N6-cyclohexyladenosine (CHA) on intraocular pressure (IOP), aqueous humor flow (AHF) and outflow facility were investigated in ocular normotensive cynomolgus monkeys. IOP and AHF were determined, under ketamine anesthesia, by Goldmann applanation ...
Amanullah A M - - 1997
Whether adenosine myocardial perfusion single-photon emission computed tomography (SPECT) remains accurate for detecting coronary artery disease (CAD) in the absence of peripheral hemodynamic changes is unknown. To assess the hemodynamic correlates of perfusion defects, we studied 222 consecutive patients (age 71 +/- 11 years) without prior myocardial infarction or revascularization ...
Otomo J - - 1997
Nitric oxide (NO) and adenosine are important mediators in the regulation of coronary vascular tone and are released into the interstitium from the vascular endothelium and myocardium, respectively. The roles of these autacoids in the regulation of coronary flow in the basal and reactive hyperemic states were examined in Langendorff ...
Xia Z F - - 1997
To test the hypothesis that energy deficits and intracellular ion derangements may be the cellular basis for intrinsic myocardial dysfunction in rats after burn trauma, we examined ATP metabolism, intracellular pH, sodium, and mechanical performance simultaneously in perfused beating hearts from sham burn or burned rats (43% TBSA, 3 degrees ...
Vanelli G - - 1997
The effects of blockading the ATP-sensitive potassium channel (K+ATP channels) on endotoxin-induced vascular derangements was studied. Escherichia coli endotoxin was infused (20 micrograms/kg per h) intravenously for 180 min into anaesthetized, mechanically ventilated, indomethacin-treated pigs. After 150 min of endotoxaemia, glibenclamide (a K+ ATP channel blocker) was infused intravenously at ...
Tomera J F - - 1997
This study examined the effect of N-ethylmaleimide (NEM, 10(-7) M) on agonist-induced contraction and the relaxation following drug-washout, of vascular smooth muscle (VSM) segments derived from hypertensive rabbits. Mean blood pressure increase was produced either by renal constriction plus contralateral nephrectomy, or by cadmium acetate ingestion. Freely-ionized calcium (45Ca)flux, cyclic ...
Macedo M P - - 1997
Our objective was to determine the vasodilator effect of adenosine and isoproterenol on the hepatic artery (HA) and superior mesenteric artery (SMA) before and after blockade of nitric oxide (NO) production to evaluate the possibility of organ specificity. Vascular circuits supplied blood flow to the liver or intestine in cats ...
Elias A N - - 1997
1. The effect of high-dose adenosine administration on atrial natriuretic peptide (ANP) and antidiuretic hormone (ADH) release is not completely understood, and data concerning the effect of adenosine on renal and systemic hemodynamics in the pig are lacking. Measurements of central hemodynamics, renal blood flow and urine production were made ...
Tian R - - 1997
Sarcomere relaxation depends on dissociation of actin and myosin, which is regulated by a number of factors, including intracellular [MgATP] as well as MgATP hydrolysis products [MgADP] and inorganic phosphate [Pi], pHi, and cytosolic calcium concentration ([Ca2+]c). To distinguish the contribution of MgADP from the other regulators in the development ...
Sabates B L - - 1997
The following experiments were conducted to determine whether, and the mechanisms through which, endogenous peptides alter coronary artery blood flow. Ultrasonic transit time probes were placed around the ascending aorta and left anterior descending coronary artery in groups of anesthetized, open-chest dogs. A Millar pressure catheter monitored left ventricular developed ...
Rongen G A - - 1997
Adenosine increases heart rate and sympathetic nerve activity reflexively in conscious humans through several mechanisms. The purpose of this study was to assess the relative contributions of arterial baroreceptor unloading, carotid chemoreceptor stimulation, and other adenosine-sensitive afferent nerves to these responses. In 12 healthy men, the effect on blood pressure, ...
Buijs E J - - 1997
The authors present a case of severe electrolyte and acid-base disturbances after administration of sorbitol. The rate of sorbitol infusion was in excess of the stated maximum safe infusion rate in parenteral nutrition. Sorbitol was used for treating raised intracranial pressure. The mechanisms of sorbitol metabolism leading to hyperlactacemia, lactic ...
Chang H Y - - 1997
The effects of glibenclamide (GLB), a specific blocker of ATP-sensitive potassium (KATP) channels, and tetraethylammonium (TEA) on modulating the regulation of diaphragmatic microcirculation were assessed in anesthetized mechanically ventilated rats. With bicarbonate-buffered Ringer solution continuously suffusing the left hemidiaphragm, microcirculatory blood flow was recorded by laser-Doppler flowmetry (QLDF). Hemorrhagic hypotension ...
Forrest E H - - 1997
BACKGROUND: Adenosine is a potent vasoactive substance that may be responsible for mediating the altered haemodynamics found in patients with cirrhosis. AIM: The administration of oral theophylline was used to investigate the effect of adenosine receptor antagonism upon the circulation of patients with cirrhosis. METHODS: Twenty eight patients were given ...
Van Way C W - - 1996
Certain tissues are known to be susceptible to shock-induced damage: liver, small bowel mucosa, and small bowel wall. This study was done to assess the changes in adenine nucleotides induced by hemorrhagic shock. Male Sprague-Dawley rats (n = 21; 300-350 g) were anesthetized with sodium pentobarbital (50 mg/kg, ip) and ...
Schlüter H - - 1996
1. Diadenosine phosphates were isolated from platelets, adrenal gland and autonomic nerves. The presence of diadenosine phosphates in storage pools releasable into the circulation suggests an important role in the control of blood pressure, and potentially to a modulation of the actions of catecholamines. 2. Besides a role of the ...
Jasmin G - - 1996
Previous studies on the heart necrotizing process at early stages of the hamster polymyopathy have led us to believe that this hereditary disease derives from a defective transmembrane ion flux resulting in myocardial Ca2+ over-load. On the other hand, certain K+ ATP channel openers were shown to prevent cytosolic Ca2+ ...
Griffiths T L - - 1996
BACKGROUND: In normal subjects intravenous adenosine infusion has been shown to stimulate ventilation with a consequent fall in arterial partial pressure of carbon dioxide (Paco2), probably by an action on the carotid bodies. The objective of this study was to determine whether the increase in Paco2 seen when patients with ...
van der Voort P H - - 1996
For calculation of fractional flow reserve (FFR), simultaneous registration of both aortic pressure (Pa) and transstenotic distal coronary pressure (Pd) is necessary at steady-state maximum coronary hyperemia. The aim of the present study was to compare the maximum transstenotic gradient (delta Pmax) and pressure-derived myocardial fractional flow reserve (FFRmyo), observed ...
Hara A - - 1996
The effect of dilazep, a potentiator of the adenosine-mediated effects, on the palmitoyl-L-carnitine (PALCAR)-induced mechanical derangement was studied in the isolated rat heart and compared with that of K-7259, a dilazep derivative having less potentiating action on the adenosine-mediated effects. The heart was perfused aerobically by the Langendorff's technique at ...
Chung Y - - 1996
Nitrite oxidation of oxymyoglobin in perfused rat myocardium under nonlimiting oxygen produces a detectable 1H nuclear magnetic resonance metmyoglobin (metMb) signal at -3.9 ppm. When the myocardium is perfused with < 10 mM nitrite, the 1H nuclear magnetic resonance MbO2 gamma CH3 Val E11 signal does not change intensity and ...
Qiu Y - - 1996
We used metabolic, enzymatic, and functional end points to compare the protective properties of continuous warm and intermittent cold cardioplegic infusion in isolated, blood-perfused rat hearts. After excision, hearts (n = 12 per group) were preserved for 3 hours by one of the following cardioplegic procedures: (1) continuous infusion of ...
Huxley V H - - 1996
We have developed a new method to quantify solute flux per unit surface area and concentration gradient (JS/S delta C) from arterioles isolated from pig hearts. The apparent permeability (Ps) was assessed from measurements of JS/S delta C for two proteins, alpha-lactalbumin (alpha-lactalb) and porcine serum albumin (PSA), labeled with ...
Beyer M E - - 1996
Positive inotropy of endothelin-1 (ET-1), which has already been described in vitro, has not been detected in vivo. Combination with vasodilators has been shown to unmask a positive inotropic effect of ET-1. The ET-induced direct positive inotropy, which seems to be mediated by endothelinB (ETB) receptors, is antagonized in vivo ...
Karimi A - - 1996
To examine a possible metabolic regulatory role for adenosine, infusions of adenosine and adenosine deaminase were given to 11 near-term fetal sheep during the simulation of birth in utero. Fetal arterial blood gases, the concentration of a number of metabolites, insulin, and whole body O2 consumption (VO2) were measured. After ...
Van Raemdonck D E - - 1996
BACKGROUND: If lungs could be retrieved for transplantation from non-heart-beating cadavers, the shortage of donors might be significantly alleviated. METHODS: Adenosine triphosphate (ATP) and hypoxanthine levels were measured postmortem in rabbit lungs comparing deflation (group 1), ventilation with room air (group 2), inflation with room air (group 3), ventilation with ...
Headrick J P - - 1996
OBJECTIVE: Adenosine, derived from hydrolysis of 5'-AMP, may be involved in coupling coronary blood flow to cardiac function and metabolism. The purpose of this study was to measure interstitial fluid (ISF) adenosine and 5'-AMP levels, and cytosolic 5'-AMP in in situ rabbit heart during beta-adrenergic stimulation. METHODS: Isoproterenol was infused ...
Tang Y Y - - 1996
We test the hypothesis that the heart and arteries enlarge with increased cardiac output (CO) during development and volume overload. Transparent albino tadpoles of Xenopus laevis at stages 43-50 were anesthetized in 0.3-0.5 mM benzocaine. Areas and radii [maximum and minimum radius (Rmax and Rmin, respectively)] of the ventricle were ...
Taillefer R - - 1996
BACKGROUND: Both dipyridamole and adenosine are widely used as pharmacologic stressors with 201Tl imaging for detection of coronary artery disease. The purpose of this study was to compare dipyridamole and adenosine 201Tl imaging directly in patients with angiographically proved coronary artery disease. METHODS AND RESULTS: Fifty-four patients were submitted to ...
Mathoôt R A - - 1996
1. The purpose of the present study was to develop an experimental strategy for the quantification of the cardiovascular effects of non-selective adenosine receptor ligands at the adenosine A1 and A2a receptor in vivo. 2-Chloroadenosine (CADO) was used as a model compound. 2. Three groups of normotensive conscious rats received ...
Kaplan L J - - 1996
In postischemia hearts, cytoplasmic creatinine kinase (CK) inactivation resulting from toxic oxygen metabolite injury may lead to bioenergetic and mechanical dysfunction. This study determines the relationship between CK activity, mechanical function, and bioenergetics during reperfusion (RP) after a reversible ischemic injury. Rat hearts pretreated after 12 hr without (CTRL) or ...
Matherne G P - - 1996
We examined myocardial responses to reduced arterial PO2 and the role of endogenous adenosine in constant-pressure perfused hearts from immature (Imm) and mature (Mat) rabbits. During normoxia, coronary flow and myocardial O2 consumption were similar in both groups. With moderate hypoxia, coronary perfusate flow increased by 125 +/- 16% in ...
Rongen G A - - 1996
ATP is coreleased with norepinephrine from sympathetic nerve endings and subsequently broken down to adenosine. In animal preparations, adenosine can inhibit norepinephrine release by stimulation of presynaptic receptors. We tested this feedback mechanism in humans by using a specific nucleoside transport inhibitor (draflazine) as a pharmacological tool to allow accumulation ...
Godart H - - 1996
1. Pressure induced a 4- to 5-fold stimulation of the residual (i.e. oubain-bumetanide insensitive) 86Rb+ influx across the human red cell membrane. This enhancement showed a broad pHo dependence with a maximum stimulation around pHo 7. 2. At atmospheric pressure, the protein kinase inhibitors staurosporine and chelerythrine stimulated a normally ...
Harrison G J - - 1996
Exogenous adenosine causes a monophasic dilation of the coronary vessels in paced, perfused rat heart preparations. Because levels of endogenous adenosine in paced hearts may mask the presence of high potency adenosine receptors, we have developed a method to measure coronary vascular responses in a potassium-arrested heart. Hearts from adult ...
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