Search Results
Results 351 - 400 of 802
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Decking U K - - 1995
The decreased contraction amplitude of isolated cardiac myocytes from guinea pigs exposed to lipopolysaccharide (LPS) was reported to be partially reversed by nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase (NOS) [Brady, et al., Am. J. Physiol. 263 (Heart Circ. Physiol. 32): H1963-H1966, 1992]. We have tested the ...
Gao Z P - - 1995
OBJECTIVE: The aim was to test the role of interstitial adenosine in protective downregulation of myocardial energy demand during myocardial hibernation. METHODS: Isolated working guinea pig hearts, perfused with glucose fortified Krebs-Henseleit, were subjected to 60 min global low flow ischaemia followed by 30 min reperfusion. Left ventricular performance was ...
Silva P H - - 1995
OBJECTIVE: The objectives were to determine the effects of the adenosine deaminase inhibitor pentostatin (deoxycoformycin) on interstitial fluid (ISF) adenosine before, during, and after myocardial ischaemia and to ascertain whether augmented endogenous ISF adenosine reduces myocardial infarction. METHODS: Untreated anaesthetised dogs (n = 11) were compared to dogs treated with ...
Ponce-Hornos J E - - 1995
Heat production and isovolumetric pressure development (P) were measured simultaneously in the arterially perfused rat ventricle. The time course of the calorimetric signal that follows a contraction could be decomposed into four components of energy released. Three of these components (H1, H2, and H4) were pressure independent, only H3 correlated ...
Laghi Pasini F - - 1995
1. The hypothesis that endogenous adenosine could play a role in the haemodynamic response to L-arginine is investigated. 2. The study has been divided into two parts. The first part was a single blind, randomized, placebo-controlled study in which L-arginine i.v. infusion (0.07 mmol/kg per min) in five healthy volunteers ...
Raschke P - - 1995
OBJECTIVE: The aim was to establish whether polymorphonuclear neutrophils can, by themselves, elicit depression of postischaemic heart function immediately after short periods of ischaemia, and to examine the involvement of endogenous adenosine and platelet activating factor (PAF) in the observed phenomena. METHODS: Isolated buffer perfused guinea pig hearts performing pressure-volume ...
Holmes G - - 1995
This study was designed to investigate effects of perfusate oxygenation and maturation on coronary flow (CF), interstitial transudate adenosine (ITA) and coronary effluent adenosine (CEA) in isolated rabbit hearts. Hearts were paced at a fixed rate and were perfused under constant pressure at two different levels of perfusate oxygenation: baseline ...
Johnston D L DL Division of Cardiovascular Diseases, Mayo Clinic Rochester, MN - - 1995
To compare the hemodynamic responses and the adverse effects associated with two coronary vasodilators used for pharmacologic stress testing. We retrospectively studied the results of adenosine and dipyridamole perfusion imaging in a large group of patients who underwent pharmacologic stress radionuclide perfusion imaging. One thousand patients given dipyridamole between April ...
Nascimben L - - 1995
BACKGROUND: Converting enzyme inhibitor treatment of congestive heart failure slows progression to failure and reduces mortality rate. It is known whether these benefits are due solely to improved hemodynamics or also to improved myocyte energetics. This study examines the effect of enalapril treatment on both isovolumic contractile performance and its ...
Conti J B - - 1995
BACKGROUND: Adenosine administered intravenously terminates supraventricular tachycardias (SVT) involving the AV node as part of the reentrant circuit. Dipyridamole increases interstitial myocardial levels of this nucleoside. This study was designed to determine whether intravenous dipyridamole increases coronary sinus plasma adenosine concentrations ([Ado]cs) in humans to levels sufficient to alter electrophysiological ...
Jackson D C - - 1995
In vitro working hearts of the turtle, Chrysemys picta bellii, paced at 30 beats/min, were studied over a range of input pressures in the following sequence of perfusion conditions: control normoxia, control anoxia, lactacidotic normoxia, and lactacidotic anoxia. Two such series of experiments were performed. In series 1 (n = ...
Pagliaro P - - 1995
In 5 anaesthetized vagotomized dogs the administration of an inhibitor of the synthesis of nitric oxide (NO) was seen to reduce the heart rate, although the arterial pressure was prevented from increasing. Such a finding suggests that the inhibition of nitric oxide release can produce bradycardia without the involvement of ...
Cano C - - 1995
Adenosine produced a negative inotropic effect in hearts isolated from calm rabbits but not from those exhibiting alarm behavior during handling. This study was conducted to determine whether protein kinase C (PKC) activation is responsible for the loss of adenosine-induced negative inotropism in the hearts of hyperexcited rabbits. Adenosine (10 ...
Brurok H - - 1995
RATIONALE AND OBJECTIVES: Manganese dipyridoxyl diphosphate (MnDPDP) is a promising contrast agent for magnetic resonance imaging of the liver. The authors explored the possibility that high concentrations of MnDPDP may cause manganese ion (Mn++)-induced side effects on cardiac function. METHODS: Potential cardiodepression by MnDPDP, DPDP--, and manganese chloride (MnCl2) (100-3,000 ...
Wikström G - - 1995
A diagonal branch of the left anterior descending artery was occluded for 80 min. One microdialysis probe was inserted in the ischaemic area and two in the non-ischaemic areas. In six animals radiolabelled microspheres were injected before and during ischaemia and after reperfusion to monitor flow. Arterial and pulmonary artery ...
Itoh S - - 1995
1. The effects of OPC-18790, a novel positive inotropic agent, on cardiac function and myocardial energy metabolism in the guinea-pig isolated heart with ischaemia were studied by 31P-magnetic resonance spectroscopy (MRS) and compared with those of amrinone and dobutamine. 2. Cardiac ischaemia was induced by intracoronary infusion of 15 microns ...
Mathôt R A - - 1995
1. The aim of the present investigation was to determine the relationship between the blood concentration and haemodynamic effects of the adenosine A2a receptor agonist, CGS 21680C (the sodium salt of 2-p-(2-carboxyethyl)phenylethylamino-5'-N-ethylcarboxamidoadeno sin e) in conscious normotensive rats. 2. Chronically cannulated rats were randomly assigned to three groups which received ...
Rath D P - - 1995
BACKGROUND: Transmural analyses of the creatine phosphate (CP)/ATP ratio in various lamina of the canine myocardium have previously revealed significant variations in the CP/ATP ratio, with the subendocardial layer displaying a decreased ratio relative to the subepicardial layer. Without exception, these results were obtained under sodium pentobarbital anesthesia. These findings ...
Goossens A - - 1995
RATIONALE AND OBJECTIVES: Bolus injection of iodinated contrast media has been observed to alter myocardial mechanical function, but the consequences on cellular metabolism are poorly documented. Modifications of metabolic parameters (intracellular pH as well as adenosine triphosphate [ATP], phosphocreatine, and inorganic phosphate contents) and of mechanical function (coronary flow, heart ...
Houltz E - - 1995
The effects of adenosine on central hemodynamics, ST-segment changes, and left ventricular (LV) systolic and diastolic function, determined by transesophageal 2-D and Doppler echocardiography, were investigated in 20 patients shortly after coronary surgery. After control measurements, adenosine was infused at incremental infusion rates (30, 60, and 120 micrograms.kg-1.min-1). Adenosine caused ...
Pettersen M D - - 1995
We sought to determine the role of adenosine in the sustained but reversible decrease in cardiac neurotransmission that occurs after brief ischemia. Adult mongrel dogs were anesthetized and instrumented for measurements of heart rate, arterial pressure, and left anterior descending coronary artery (LAD) and left circumflex coronary artery (LCX) flow ...
Rath D P - - 1995
In this work, an x-irradiation/high fat/high cholesterol diet-induced atherogenic model was invoked to examine the effects of severe diffuse atherosclerosis on myocardial metabolism in the in vivo porcine heart. This model was studied using spatially localized 31P-nuclear magnetic resonance (NMR) to monitor pH and the levels of inorganic phosphate, phosphomonoesters, ...
Nootens M - - 1995
Vasodilators have been a main focus of therapy for primary pulmonary hypertension. Adenosine and prostacyclin have been shown to reduce pulmonary vascular resistance acutely in these patients. In order to compare the acute hemodynamic effects of adenosine and prostacyclin, ten patients with severe primary pulmonary hypertension, unresponsive to medical therapy, ...
Lorek A - - 1994
Phosphorous (31P) spectra from the brains of severely birth-asphyxiated human infants are commonly normal on the first day of life. Later, cerebral energy failure develops, which carries a serious prognosis. The main purpose of this study was to test the hypothesis that this delayed ("secondary") energy failure could be reproduced ...
Kobayashi S - - 1994
A 21-yr-old man with multiple pulmonary AV fistulae presented with moderate hypoxemia with chronic hyperventilation, which continued even after sufficient oxygenation by 100% O2 inhalation. The infusion of aminophylline, an adenosine receptor blocker, not only increased PaCO2 from 35 to 39 mm Hg but also depressed the magnitude of hypoxic ...
Monopoli A - - 1994
The pharmacological profile of 2-hexynyl-5'-N-ethylcarboxamidoadenosine (2HE-NECA, CAS 141018-30-6), a new selective A2a adenosine receptor agonist, was characterized. In binding studies on both rat and bovine brain, 2HE-NECA was more potent on A2a receptors (Ki = 2.2 and 1.5 nmol/l, respectively) than the reference A2a agonist, 2-[4-(2-carboxyethyl)-phenethylamino]-5'-N-ethylcarboxamidoaden osi ne (CPEC) or ...
Gorman M W - - 1994
Adrenergic receptor blockade has been reported to decrease cardiac adenosine formation and release during hypoxia. We wished to determine whether this occurs by an improvement in the energy supply/demand ratio. Isolated guinea pig hearts were perfused at a constant pressure of 50 mm Hg. Hypoxia (30% O2) was maintained for ...
Engelstein E D - - 1994
BACKGROUND: Exogenous adenosine has been shown to increase muscle sympathetic nerve activity (MSNA), blood pressure, heart rate, and ventilation in conscious humans, effects attributed to peripheral chemoreceptor activation. METHODS AND RESULTS: To determine whether endogenous adenosine has similar effects and whether they are mediated through chemoreceptor activation, we examined the ...
Kollias-Baker C - - 1994
The 2-amino-3-benzoylthiophene derivative PD 81,723 potentiates the A1 receptor-mediated negative dromotropic effect of exogenous adenosine and adenosine receptor agonists in guinea pig isolated perfused and in situ hearts. The objective of this study was to determine whether PD 81,723 could amplify the cardiac actions of endogenous adenosine. Two approaches known ...
Munger K A - - 1994
We examined the renal effects of a specific adenosine A1-receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 10 micrograms.kg-1.min-1 iv). Since adenosine is a potent inhibitor of renin release, additional experiments were performed with an angiotensin AT1-receptor antagonist (losartan, 10 mg/kg i.v.). DP CPX alone induced a significant (P < 0.05) decrease in afferent ...
Bolling S F - - 1994
During induced ischemia for cardiac surgery, nucleotides are degraded while being used to maintain myocyte integrity. The resulting nucleosides washout upon reperfusion, limiting nucleotide resynthesis resulting in poor postischemic cardiac function. We studied if the mechanism of the beneficial effect of adenosine, a nucleotide precursor, which is known to improve ...
Portman M A - - 1994
The purpose of this study was to measure myocardial buffering capacity and adenosine triphosphate utilization rates in the newborn animal in vivo during hypothermic circulatory arrest and recovery. METHODS: These studies were performed with 31P magnetic resonance spectroscopic techniques, which supplied a 12- to 16-second time resolution, to monitor intracellular ...
Wannenburg T - - 1994
We studied the effects of adenosine on oxygen consumption and contractile state in 17 isolated, crystalloid-perfused, isovolumically contracting rat heart preparations at constant coronary flow. In 10 experiments we determined adenosine-contractile state dose-response relationships in three groups of hearts using two different perfusates and in the presence and absence of ...
Cabell F - - 1994
The aim of the present study was to investigate the contribution of large-conductance calcium-activated potassium (large-conductance KCa) channels to adenosine (Ado)- and nitroprusside-mediated relaxation in small coronary arteries. Canine subepicardial arteries (170 +/- 23 microns at 120 mmHg) were studied as in vitro pressurized vessels. Pressure-diameter experiments showed myogenic tone ...
Dawid-Milner M S - - 1994
In pentobarbitone anaesthetized and paralysed cats the effects of the A1 adenosine antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) have been observed on the pressor response to stimulation of the hypothalamic defence area (HDA) and on the effects of baroreceptor and chemoreceptor reflex activation on arterial blood pressure. The administration of DPCPX decreased the ...
Komaru T - - 1994
Previous studies in which an isolated heart or in situ constant pressure preparation was used suggested a minimal role for adenosine in autoregulatory control of coronary circulation. These results, however, are controversial, and the role of adenosine in autoregulation of flow in heart is uncertain. To test the hypothesis that ...
Schjøtt J - - 1994
We examined whether pretreatment with lidocaine could influence the cardiac kinetics of adenosine and thereby strengthen the physiologic responses of the nucleoside, either exogenously administered or endogenously produced. Isolated rat hearts perfused with lidocaine, 0.05 microM to 500 microM, were subjected to 6 min. of adenosine infusion followed by 30 ...
Thomas T - - 1994
In two groups of Saffan-anaesthetized, spontaneously breathing rats we have attempted to identify the peripheral influences of adenosine in mediating the responses evoked by hypoxia by using an adenosine receptor antagonist, 8-sulphophenyltheophylline (8-SPT, 20 mg kg-1 i.v., Group 1) and adenosine deaminase (ADA, 500 units in 0.04 ml infused into ...
Allard M F - - 1994
The contribution of glycolysis and oxidative metabolism to ATP production was determined in isolated working hypertrophied hearts perfused with Krebs-Henseleit buffer containing 3% albumin, 0.4 mM palmitate, 0.5 mM lactate, and 11 mM glucose. Glycolysis and glucose oxidation were directly measured by perfusing hearts with [5-3H/U-14C]glucose and by measuring 3H2O ...
Clarke K - - 1994
To quantify metabolite and cation concentrations using NMR spectroscopy, the volumes of intracellular and extracellular spaces must be known. We describe a simple 31P NMR spectroscopic method that employs dimethyl methylphosphonate (DMMP) as a marker of total water space and phenylphosphonate (PPA) as a marker of extracellular space to determine ...
Sellke F W - - 1994
Crystalloid cardioplegia may cause coronary microvascular endothelial dysfunction during cardiopulmonary bypass. The perioperative administration of either adenosine or AICA-riboside (acadesine, 5-aminoimidazole-4-carboxamide-1-ribofuranoside) has been associated with improved myocardial functional preservation and improved coronary blood flow after ischemic arrest. To examine if this enhanced recovery of myocardial function and perfusion may be ...
Offstad J - - 1994
OBJECTIVE: ATP gated potassium (KATP) channels and adenosine are of crucial importance in coronary blood flow regulation and activation of KATP channels and adenosine receptor stimulation protect against infarction and development of stunning. The aim of this study was to test the hypothesis that opening of KATP channels and adenosine ...
Shinzato T - - 1994
First, this investigation showed that plasma levels of inosine, hypoxanthine, and xanthine, which are metabolites of adenosine, rose sharply when blood pressure dropped suddenly along with symptoms during a hemodialysis session (sudden hypotension), but not when it decreased gradually with eventual symptoms (gradual hypotension). Because adenosine has an action to ...
Vials A J - - 1994
The Langendorff heart preparation was used to investigate the mechanism of action of vasodilatation evoked by ATP and its analogues in guinea pig coronary vasculature. The relative order of potency of ATP and its analogues in causing a reduction in perfusion pressure was 2-methylthioATP (2-meSATP) > ATP > beta, gamma-methyleneATP ...
Bache R J - - 1994
Spatially localized nuclear magnetic resonance (NMR) spectroscopy was used to examine the effect of tachycardia and inotropic stimulation on myocardial ATP, creatine phosphate (CrP), and inorganic phosphate (Pi) in animals with left ventricular hypertrophy (LVH). Studies were performed in eight normal dogs and seven dogs with moderate LVH produced by ...
Yao Z - - 1994
BACKGROUND: Adenosine has been proposed to be an important mediator of ischemic preconditioning. Intracoronary administration of adenosine has recently been shown to mimic the effects of preconditioning in isolated rabbit hearts. However, it is not known whether this agent can duplicate the effects of preconditioning in vivo or in other ...
Wilson A N - - 1994
1. The role of adenosine in the control of coronary vessel tone was studied using two guinea-pig hearts in series. Vasodilatory mediator(s) released by the donor heart were assayed by the recipient heart. 2. Adenosine deaminase reduced the activity of vasodilatory mediator(s) released by histamine and isoprenaline by 58.0 +/- ...
Koglin J - - 1994
OBJECTIVES: The purpose of this study was to investigate the antiadrenergic effects of adenosine and carbachol on beta-adrenoceptor-stimulated human ventricular contractility in vivo. In addition, the antiadrenergic effects of adenosine and carbachol were compared in vitro. BACKGROUND: Adenosine is reported to exhibit an antiadrenergic negative inotropic response in the beta-adrenergic-stimulated ...
Vander Elst L - - 1994
The biochemical and mechanical effects of a new calcium ion channel antagonist, fantofarone ((2-isopropyl-1-((4-(3-(N-methyl-N-(3,4-dimethoxy-beta-phenethyl)-amino) propyloxy)benzenesulfonyl))-indolizine), on isovolumic perfused rat heart have been assessed by using 31P nuclear magnetic resonance (NMR) spectroscopy together with simultaneous monitoring of myocardial mechanical function. Cytosolic pH and phosphocreatine, adenosine triphosphate and inorganic phosphate contents were ...
Elliott A C - - 1994
1. The metabolic consequences of an increase in the frequency of stimulation were examined in isolated ferret hearts. Intracellular pH (pHi) and the intracellular concentrations of phosphocreatine ([PCr]i), inorganic phosphate ([Pi]i) and ATP were measured by 31P nuclear magnetic resonance (NMR) spectroscopy. 2. Increasing the stimulus rate from 0.1-0.7 to ...
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