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Results 301 - 350 of 915
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Vinereanu D - - 2002
Adenosine stress echocardiography was performed in nine patients (58 (+/-3) years, eight women) with documented microvascular angina. Global ventricular function was assessed by Tc(99m) blood pool imaging and Doppler, whereas longitudinal ventricular function was assessed by simultaneous tissue Doppler echocardiography of the lateral mitral annulus. Adenosine was infused incrementally to ...
Ren Yilin - - 2002
BACKGROUND: The macula densa (MD), a plaque of specialized tubular epithelial cells, senses changes in tubular NaCl concentration and sends a signal(s) that controls the resistance of the glomerular afferent arteriole (Af-Art). This mechanism, called tubuloglomerular feedback (TGF), is thought to be important in the homeostasis of body fluids and ...
Buus N H - - 2001
BACKGROUND: Myocardial perfusion during adenosine-induced hyperemia is used both in clinical diagnosis of coronary heart disease and for scientific investigations of the myocardial microcirculation. The objective of this study was to clarify whether adenosine-induced hyperemia is dependent on endothelial NO production or is influenced by adrenergic mechanisms. METHODS AND RESULTS: ...
Peart J - - 2001
OBJECTIVES: To characterize the 'anti-ischemic' effects of adenosine metabolism inhibition in ischemic-reperfused myocardium. METHODS: Perfused C57/B16 mouse hearts were subjected to 20 min ischemia 40 min reperfusion in the absence or presence of adenosine deaminase inhibition (50 microM erythro-2-(2-hydroxy-3-nonyl)adenine; EHNA) adenosine kinase inhibition (10 microM iodotubercidin; IODO), or 10 microM ...
Tofovic S P - - 2001
The purpose of this study was to investigate in vivo the effects of modulating the adenosine system on endotoxin-induced release of cytokines and changes in heart performance and neurohumoral status in early, profound endotoxemia in rats. Time/pressure variables of heart performance and blood pressure were recorded continuously, and plasma levels ...
Xia Z - - 2001
Cutaneous burn trauma causes functional inhibition of the heart, but the mechanism is unclear. Using a high dissociation constant (K(D)) calcium indicator TF-BAPTA and 19F MR spectroscopy, the relationship between the changes of cytosolic free calcium and cardiac function after burn trauma was examined. Sprague-Dawley rats received scald (43% TBSA) ...
Sinkovec M - - 2001
Adenosine may be a potential mediator in the pathogenesis of vasovagal syncope. Intravenous adenosine increases sympathetic discharge and provokes vasovagal syncope in sensitive subjects. No data are available for endogenous adenosine. The authors compared the results of head-up tilt-table testing (HUT) (45 minutes at 60 degrees) of three arbitrary groups ...
Meyer T E - - 2001
In the present study, we sought to evaluate whether the antiadrenergic action of adenosine in the heart is altered in pressure overload hypertrophy produced in rats by suprarenal aortic banding. Epicardial and coronary effluent adenosine and inosine concentrations and release were significantly elevated in compensated pressure overload hypertrophy but not ...
Stegen E - - 2001
The effects of adenosine and adenine nucleotides on haemolymph velocity and on heart rate and scaphognathite frequency were investigated in the American lobster Homarus americanus. The infusion of 0.25-2.4 nmol g(-1) min(-1) adenosine produced steady-state concentrations of 2-3 micromol l(-1) adenosine and approximately 80 micromol l(-1) inosine in the haemolymph. ...
Saupe K W - - 2001
In situations such as severe low-flow ischemia, where myocardial work output is low and dependence on anaerobic glycolysis is high, increasing the myocardial supply of glucose and insulin is cardioprotective. Our goal was to determine whether this strategy of "metabolic support" would also be cardioprotective in the moderately hypoperfused heart ...
Alavi-Harati A - - 2001
We have performed studies of the K(0)(L)-->pi(+)pi(-)gamma direct emission ( DE) and inner Bremsstrahlung ( IB) vertices, based on data collected by KTeV during the 1996 Fermilab fixed target run. We find a(1)/a(2) = -0.737+/-0.034 GeV2 for the DE form-factor parameter in the rho-propagator parametrization, and report on fits of ...
Miltényi G - - 2001
Hemodialysis (HD) causes rapid volume shifts and circulatory changes. In chronic renal failure (CRF) Na+/K+ATP-ase is depressed, whereas endogenous digoxin-like factor (EDLF) is elevated. Our aim was to characterize HD-induced cardiovascular adaptation and its possible links to Na+/K+ATP-ase and EDLF. Eleven children with CRF on HD (aged 14.7 +/- 3.7 ...
Pallone T L - - 2001
Pericytes are contractile smooth muscle-like cells that surround descending vasa recta (DVR) and provide their capability for vasomotion. The importance of the medullary pericyte derives from the role of DVR to distribute most or all of the blood flow from juxtamedullary cortex to the renal inner and outer medulla. Physiological ...
Zhang C - - 2000
Coronary blood flow in the subendocardium is preferentially increased by adenosine but is redistributed to the subepicardium during ischemia in association with coronary pressure reduction. The mechanism for this flow redistribution remains unclear. Since adenosine is released during ischemia, it is possible that the coronary microcirculation exhibits a transmural difference ...
Oriji G K - - 2000
Adenosine acts as a cardioprotective agent by producing coronary vasodilation, decreasing heart rate and by antagonizing the cardiostimulatory effect of catecholamines; adenosine also exerts a direct negative inotropic effect. Myocardial ischemia is known to be associated with enhanced levels of adenosine, increased protein kinase C (PKC) activity and prostacyclin (PGI2) ...
Peart J - - 2000
We assessed the role of A(1) adenosine receptor (A(1)AR) activation by endogenous adenosine in the modulation of ischemic contracture and postischemic recovery in Langendorff-perfused mouse hearts subjected to 20 min of total ischemia and 30 min of reperfusion. In control hearts, the rate-pressure product (RPP) and first derivative of pressure ...
Berry D A - - 2000
This study is concerned with the molecular basis of human idiopathic dilated cardiomyopathy (DCM). This disorder affects the entire heart including both atria and ventricles. It is characterized by a progressive dilatation of the ventricles and loss of contractile power that results in an impaired cardiac output. Changes in cellular ...
Kasahara M - - 2000
PURPOSE: To determine whether continuous infusion of adenosine triphosphate (ATP), nitroglycerin (NTG) or amrinone (AM) would ameliorate the reductions in coronary blood flow (CBF) and myocardial oxygen tension (PmO2) induced by felypressin. METHODS: Seven open-chest dogs were studied under urethane and alpha-chloralose anesthesia. Hemodynamic variables including heart rate (HR), systolic ...
Konduri G G - - 2000
We investigated the hypothesis that the purine nucleotide ATP and its nucleoside adenosine cause pulmonary vasodilation in fetal lambs by the release of nitric oxide (NO). We also investigated the potential role of K(+)(ATP) channels in mediating the effects of ATP and adenosine on NO. We surgically prepared 28 fetal ...
Ford W R - - 2000
This study investigated the role of beta-adrenoceptors in the cardioprotective and metabolic actions of adenosine A(1) receptor stimulation. Isolated paced (300 beats min(-1)) working rat hearts were perfused with Krebs-Henseleit solution containing 1.2 mM palmitate. Left ventricular minute work (LV work), O(2) consumption and rates of glycolysis and glucose oxidation ...
Steinmetz M - - 2000
Diadenosine polyphosphates (ApnA; n = 3-6) are potent vasoactive agents in isolated vessels. Information on effects of ApnA in vivo is still limited despite the fact that these compounds are starting to be used in humans. This study was designed to compare the effects of ApnA and their possible metabolites ...
Zhao T - - 2000
BACKGROUND: The mechanism of delayed preconditioning induced by activation of adenosine A(1) receptors (A(1)ARs) is not fully understood. We determined the role of inducible nitric oxide synthase (iNOS) in mediating adenosine-induced late cardioprotection using pharmacological inhibitors and iNOS gene-knockout mice. METHODS AND RESULTS: Adult male mice were treated with saline ...
Fukuma T - - 2000
Both free radicals (FRs) and adenosine receptor activation contribute to triggering a mechanism of preconditioning (PC) against infarction. This study examined the possibility that there is some interaction between FRs and adenosine generation during PC. In the first series of experiments, the effects of an FR scavenger, N-2-mercaptopropionyl glycine (MPG), ...
Finegan B A - - 2000
Adenosine inhibits glycolysis from exogenous glucose, reduces proton production and enhances post-ischemic left ventricular minute work (LV work) following ischemia in isolated working rat hearts perfused with glucose and fatty acids. In hearts partially depleted of glycogen by antecedent ischemic stress (AIS)--two cycles of ischemia (10 min) and reperfusion (5 ...
Kawabata H - - 2000
The effect of beta-blocker (propranolol) on the metabolism and contraction of doxorubicin-induced cardiomyopathy during pacing or ischemia was examined by the phosphorus 31-nuclear magnetic resonance (31 P-NMR) in Langendorff hearts of chronically treated rabbits after cumulative doses of 16 mg doxorubicin/kg. After 8 weeks of doxorubicin treatment, beta-blocker (propranolol) was ...
Toy P - - 2000
BACKGROUND: Transfusion guidelines recommend that clinicians assess patients for signs and symptoms of anemia before the transfusion of RBCs. However, studies of signs and symptoms associated with acute isovolemic anemia are limited. The objective of this study was to determine whether acute reduction of Hb concentration to 5 g per ...
Bian X - - 2000
Myocardial adenosine formation varies with myocardial oxygen consumption (MVO(2)), but whether concurrent hypoxia is required for adenosine formation is uncertain. Changes in right coronary (RC) perfusion pressure (RCP) produce directionally similar alterations in right ventricular (RV) MVO(2)and in RC venous P O(2)(P(v)O(2)), an index of myocardial P O(2). RCP was ...
Zimmer G G Center of Internal Medicine, Medical Clinic II, Membrane Structure Group, University Clinics, Frankfurt, Germany. - - 2000
Different beta-agonists are compared with regard to their cardiodepressive side effects. The metaphenolic bronchodilators reproterol, salbutamol, fenoterol, and terbutaline were introduced at a dosage of 0.0005 micromol to a maximum of 10 micromol per gram of heart tissue into the isolated working rat heart under hypoxic conditions, and the response ...
Jeremias A - - 2000
BACKGROUND: Measurements of Doppler derived coronary flow reserve (CFR) and pressure derived fractional flow reserve (FFR) for coronary stenosis assessment depend on the induction of maximal hyperemia. Adenosine is the most widely used pharmacological agent but is expensive and poorly tolerated by some patients. METHODS AND RESULTS: The objective of ...
Matsumoto Y - - 2000
This study was undertaken to clarify the role of high-energy phosphate metabolism in hydrogen peroxide-induced cardiac dysfunction using phosphorus and fluorine nuclear magnetic resonance spectroscopy. The exposure of a Langendorff-perfused heart to hydrogen peroxide (200-400 micromol/L, 8 min) provoked biphasic contractile dysfunction characterized by a transient depression of left ventricular ...
Reid G - - 2000
Sudden infant death syndrome (SIDS) occurs silently usually during sleep and, though remaining unexplained after autopsy, leaves footprints creating a pattern analogous to that which follows a flood of nitric acid (NO). These footprints in SIDS are associated with serious pathological changes, viz. elevated hepatic iron, bone marrow hyperplasia, hypomyelinated ...
Wright C E - - 1999
BACKGROUND: Increases in vascular resistance (or the reciprocal, vascular conductance) in response to constrictor drugs are amplified (or attenuated) in the hindquarter vascular bed of hypertensive rats and rabbits. However, such changes have not been observed for the total peripheral circulation. OBJECTIVE: To assess whether the vascular amplifier applies to ...
Siebenaller JF - - 1999
The effects of hydrostatic pressure on the receptor-stimulated exchange of guanosine triphosphate (GTP) for guanosine diphosphate (GDP) on the a subunit of G proteins were studied in two congeneric marine teleost fishes that differ in their depths of distribution. The poorly hydrolyzable GTP analog [35S]guanosine 5'-[gamma-thio]triphosphate ([35S]GTP[S]) was used to ...
Zahedi A - - 1999
BACKGROUND: Stimuli such as inferoposterior myocardial infarction and right coronary injection with radiographic contrast media evoke a vasodepressor reflex characterized by bradycardia and hypotension (Bezold-Jarisch reflex). Dipyridamole acts by adenosine-mediated coronary vasodilation to disclose myocardial perfusion heterogeneity for thallium-201 scintigraphy. OBJECTIVE: To determine whether there is a relationship between the ...
Gardiner S M - - 1999
1. To determine the putative contribution of K(ATP)-channels to the haemodynamic sequelae of endotoxaemia, three experiments were carried out in different groups of conscious, chronically-instrumented, unrestrained, male Long Evans rats. 2. In the first experiment, pretreatment with the K(ATP)-channel antagonist, glibenclamide, abolished the initial hypotension, but not the renal vasodilatation ...
Phillis J W - - 1999
Experiments were performed on isolated, nonworking rat hearts perfused at constant pressure according to the Langendorff technique to evaluate the role of adenosine in hypercapnia-evoked coronary vasodilation. Hypercapnia/acidosis resulted in increases in heart rate and coronary flow rates in conjunction with a decrease in ventricular contractile tensions. The adenosine deaminase ...
Arakawa J - - 1999
The present study was carried out to determine the effect of 5-(N, N-dimethyl)-amiloride (DMA), a specific inhibitor of the Na(+)/H(+) exchanger, on the cardiac mechanical and metabolic derangements induced by palmitoyl-L-carnitine (PALCAR). Rat hearts were perfused aerobically at a constant flow according to the Langendorff technique, while being paced electrically. ...
Chung Y - - 1999
1H/(31)P NMR has followed the metabolic response to increased work in the glucose- and pyruvate-perfused rat myocardium during a heart cycle and at the steady state. With electrical pacing and dobutamine, the heart O(2) consumption increases by 56%. The phosphocreatine (PCr) level initially declines, but recovers within 15 min to ...
Fukata Y - - 1999
Usefulness of the Doppler method under continuous infusion of adenosine triphosphate disodium (ATP) for improvement of accuracy in the diagnosis of the left internal thoracic arterial graft (LITA) patency was examined using transthoracic ultrasonic echocardiography. 1) Influence of ATP on the Doppler velocity in a graft was examined in 7 ...
Mateo P - - 1999
To study the relation among mitochondrial energy supply, cardiac performance, and energy transfer through creatine kinase (CK), two acute models of inhibition of ATP synthesis were compared in the isovolumic acetate-perfused rat heart. Similar impairments of mechanical performance (rate-pressure product, RPP) were achieved by various stepwise decreases in O(2) supply ...
Rongen G A - - 1999
By stimulating afferent nerve endings in skeletal muscle, heart, kidney and the carotid body, adenosine infusion evokes a receptor-specific sympatho-excitatory reflex in humans that overrides its direct negative chronotropic effect. We tested the hypothesis that adenosine increases heart rate by suppressing parasympathetic and augmenting sympathetic components of heart rate variability. ...
Taguchi T - - 1999
The effects of YM934 [2-(3,4-dihydro-2,2-dimethyl-6-nitro-2H-1,4-benzoxazin-4-yl) pyridine N-oxide], an adenosine triphosphate (ATP)-sensitive potassium channel opener, on stunned myocardium were examined. Forty eight anesthetized dogs were subjected to 15 min of left anterior descending (LAD) coronary artery occlusion followed by 3 hours of reperfusion. To elucidate the possible contribution of the cardioprotective ...
Kalsi K K - - 1999
BACKGROUND: Impaired energy metabolism in the failing human heart could be an important mechanism of functional deterioration. The purpose of this study was to assess the changes of myocardial energy metabolism in the human heart at end-stage heart failure. MATERIALS AND METHODS: The left ventricular myocardium of patients undergoing heart ...
Bache R J - - 1999
BACKGROUND: High cardiac workloads produced by catecholamine infusion result in loss of myocardial phosphocreatine (PCr) and accumulation of inorganic phosphate (Pi) which are more prominent in heart with left ventricular hypertrophy (LVH) than in normal hearts. Since ischemia can cause changes in phosphorylated compounds similar to those during catecholamine stimulation, ...
Saupe K W - - 1999
Decreasing coronary perfusion causes an immediate decrease in contractile function via unknown mechanisms. It has long been suspected that this contractile dysfunction is caused by ischemia-induced changes in cardiac energetics. Our goal was to determine whether changes in cardiac energetics necessarily precede the contractile dysfunction as one would expect if ...
Hermann H P - - 1999
BACKGROUND: Pyruvate, as an intermediate in the Krebs cycle, is an important source of energy for myocardium and improves contractility of normal, hypoxic, and postischaemic animal myocardium. We investigated the effect of intracoronary pyruvate in patients with congestive heart failure. METHODS: Haemodynamic measurements were done in eight patients with dilated ...
Wicks T C - - 1999
Magnesium is the second most abundant intracellular cation in the human body and serves as an obligate cofactor in approximately 300 essential enzymatic cellular reactions. Magnesium is crucial for the generation and use of adenosine triphosphate and is required for oxidative phosphorylation. A wide variety of internal and external stresses ...
Abdel-Zaher A O - - 1999
The effect of lithium chloride on the mean arterial blood pressure, heart rate and heart contractility was evaluated in rabbits. The intravenous administration of 50 mg kg-1 lithium chloride as a bolus injection into rabbits produced a progressive decrease in the mean arterial blood pressure, heart rate and heart contractility ...
Dumont F - - 1999
We report the in vivo evaluation (biodistribution, displacement and metabolization in blood, brain and heart) in mice and the metabolism in blood of human volunteers of iodine-123 labelled 1-(2-iodophenyl)-N-methyl-N-(1-methyl-propyl)-3-isoquinoline carboxamide ([123I]iodo-PK11195), a potential radioligand for visualization of inflammation in humans by single-photon emission tomography. In three series of 18 white ...
Lurie K G - - 1999
Previous studies have demonstrated that the extracellular space (ECS) component of the atrioventricular (AV) node and His bundle region is larger than the ECS in adjacent contractile myocardium. The potential physiological significance of this observation was examined in a canine blood-perfused AV nodal preparation. Mannitol, an ECS osmotic expander, was ...
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