Search Results
Results 251 - 300 of 802
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Sakai K - - 1998
The vasodilator effects of adenosine injected into the femoral artery (i.a.) of rabbits were analyzed. Single bolus i.a. doses of adenosine (0.3-10 microg) and 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA) (0.03-1 microg), an adenosine A2-receptor agonist, produced dose-dependent increases in femoral blood flow and decreases in resistance, almost without affecting blood pressure, heart rate, ...
Mehta A B - - 1998
This study was designed to study the role of adenosine in ischaemic preconditioning. The clinical, electrocardiographic and metabolic parameters of ischaemia were compared before and after intracoronary adenosine during percutaneous transluminal coronary angioplasty in 15 patients with significant stenosis of the left anterior descending artery. Baseline ischaemia was demonstrated by ...
Nomura F - - 1998
OBJECTIVE: Leukocytes have been shown to have an important role in ischemia/reperfusion injury. Adenosine also reduced this ischemia/reperfusion injury. There is an interaction between adenosine and leukocyte via receptor mediated function. To determine whether beneficial effects of adenosine on reperfusion injury is mediated by changes in leukocyte function, we studied ...
Leone R J RJ - - 1998
This study was designed to test whether increased inotropy caused by raising intracellular cAMP would add to the positive inotropy caused by reducing cGMP and whether this relationship was affected by experimental hypertrophy. We used open chest anesthetized dogs with left ventricular hypertrophy (LVH) induced by valvular aortic stenosis and ...
Takahashi K - - 1998
The effects of ketamine and isoflurane on the phosphoenergetic state of the liver during haemorrhage were investigated using 31P nuclear magnetic resonance (NMR) spectroscopy. Male Wistar rats were anaesthetized with ketamine (1.0 mg kg-1 min-1 i.v., Ket 1.0 group, or 1.5 mg kg-1 min-1 i.v., Ket 1.5 group), or isoflurane ...
Rongen G A - - 1998
Blood pressure and heart rate responses to adenosine infusion (35, 70, and 140 microg/kg/min, intravenously) were studied in 7 healthy men after 6, 30, 78, 150, and 318 hours of abstinence from regular caffeine use. The finding that caffeine abstinence augmented the systolic pressor response (from -1 +/- 2 mm ...
Spindler M - - 1998
An arginine to glutamine missense mutation at position 403 of the beta-cardiac myosin heavy chain causes familial hypertrophic cardiomyopathy. Here we study mice which have this same missense mutation (alphaMHC403/+) using an isolated, isovolumic heart preparation where cardiac performance is measured simultaneously with cardiac energetics using 31P nuclear magnetic resonance ...
Tofovic S P - - 1998
Adenosine is an ubiquitously occurring endogenous nucleoside that via cell surface receptors exerts multiple antihypertensive actions, and mediates a number of biological responses that may reduce cardiovascular disease risk. Therefore modulation of endogenous levels of adenosine may offer beneficial effects in hypertension. The objective of this study was to determine ...
Deem S - - 1998
Red blood cells (RBCs) are known to augment hypoxic pulmonary vasoconstriction (HPV). To determine whether this phenomenon is hematocrit (Hct) dependent and related to alterations of either nitric oxide (NO) or adenosine metabolism, we studied mechanically ventilated, pump-perfused lungs from euthanized New Zealand White rabbits. Lungs were perfused in situ ...
Rongen G A - - 1998
We tested the hypothesis that endogenous angiotensin II participates in the direct and reflex effects of adenosine on the sympathetic nervous system. Nine healthy men were studied after 1 wk of the angiotensin II type I receptor antagonist losartan (100 mg daily) or placebo, according to a double-blind randomized crossover ...
Holtzman D - - 1998
The creatine kinase (CK) reaction is thought to be important in coupling ATP metabolism and regulating ADP concentration in tissues with high and variable ATP turnover, including cerebral gray matter (GM). There is low phosphocreatine (PCr), low CK reaction rates, and high mitochondrial CK (MiCK) isoenzyme activity in GM compared ...
Horn M - - 1998
Little is known about the regulation of total creatine concentration in heart, skeletal muscle, brain, liver and kidney in response to increased dietary creatine intake. The phosphorylated fraction of intracellular creatine (phosphocreatine) remain relatively constant, and therefore, higher intracellular creatine levels may increase the energy reserve of the heart [phosphocreatine ...
Thiel M - - 1998
OBJECTIVES: To determine the effects of a prophylactic intravenous infusion of adenosine on cardiopulmonary functions and oxygen-derived variables in a porcine model of endotoxemia. DESIGN: Prospective, randomized, placebo-controlled, unblinded study. SETTING: University research laboratory. SUBJECTS: Thirty country bred pigs, aged 6 to 7 wks, weighing 24.9 +/- 0.65 (SEM) kg ...
Katagiri N - - 1998
The deamination of cyclaradine corresponding to a carbocyclic analogue of ara-A having anti-HSV activity by adenosine deaminase was examined under various pressure. The deamination of (+)- and (+/-)-cyclaradine was remarkably facilitated by high pressure, and the rate was increased with increasing of pressure. However, (-)-cyclaradine was not deaminated even under ...
Manthei S A - - 1998
OBJECTIVE: The purpose of this study was: 1) to evaluate a dual microdialysis technique coupled with local drug administration in the regionally ischemic rabbit heart, and; 2) to assess the ischemia-induced changes in interstitial fluid (ISF) adenosine during inhibition of adenosine deaminase or adenosine kinase. METHODS: Two microdialysis probes were ...
Neubauer S - - 1998
This review describes the effects of changes in left ventricular pressures and heart rate on myocardial high-energy phosphate metabolism. When cardiac workload is substantially increased, creatine kinase flux will increase markedly, phosphocreatine will show a small but detectable decrease, and ATP will not change. In this context, heart rate is ...
Wasser J S - - 1997
Although freshwater turtles as a group are highly anoxia tolerant, dramatic interspecific differences in the degree of anoxia tolerance have been demonstrated in vivo. Painted turtles (Chrysemys picta bellii) appear to be the most hypoxia-tolerant species thus far studied, while softshelled turtles (Trionyx spinifer) are the most hypoxia-sensitive. We have ...
Friehs I - - 1997
BACKGROUND: The cardioprotective properties of exogenous and endogenously produced adenosine during ischemia have been shown previously. The models used to demonstrate the efficacy and mechanism of effect have been primarily of normothermic ischemia where adenosine was given pre-ischemia in an effort to mimic the preconditioning phenomena. The proposed mechanisms responsible ...
Balschi J A - - 1997
This study has two objectives; first, to develop perfusion conditions that decrease the free energy of ATP hydrolysis, Delta GATP, in isolated hearts; and, second, to modulate the Delta GATP in these perfused hear models. To accomplish the first goal, a series of inhibitors was employed to restrict acetyl-CoA oxidation. ...
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 ...
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