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Results 451 - 500 of 817
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Ince C - - 1993
Heterogeneity in the hypoxic state of Tyrode-perfused rat hearts was studied using NADH and Pd-porphine videofluorometry. Ischemic as well as high-flow anoxia resulted in a homogeneous rise of tissue NADH fluorescence, whereas normoxic recovery from both types of anoxia caused transiently persisting patchy fluorescent areas. Patterns were always the same ...
Koos B J - - 1993
The mechanism by which adenosine increases heart rate was investigated in 21 chronically catheterized fetal sheep (> 0.8 term). Intra-arterial infusion of adenosine (0.16 mg.min-1.kg fetal wt-1) for 1 h significantly increased fetal heart rate within 5 min with maximum values of approximately 68 beats/min above the control mean of ...
Hashimoto K - - 1993
Administration of exogenous adenosine triphosphate (ATP) as a vasodilator during cardiopulmonary bypass was assessed in consecutive adult patients (n = 24) who demonstrated a high arterial perfusion pressure (mean, > 90 mm Hg). The action of ATP was characterized by rapid induction and stabilization of the blood pressure level. The ...
Wesley R C RC - - 1993
OBJECTIVE: The aim was to examine the effect of a selective A1 adenosine receptor antagonist (N-0861) on postdefibrillation cardiovascular depression to determine whether antagonist mediated enhanced postdefibrillation haemodynamic recovery is due to reversal of the antiadrenergic action of adenosine, an A1 receptor mediated effect. METHODS: Halothane-nitrous oxide anaesthetised Duroc pigs ...
Wainwright C L - - 1993
OBJECTIVES: Adenosine has previously been shown to protect against ischaemia induced ventricular arrhythmias. The aim of this study was to determine whether stimulation of A1 adenosine receptors with a selective agonist also protects against arrhythmias, and to attempt to elucidate the underlying mechanisms. METHODS: Large White/Welsh Landrace cross breed domestic ...
Janier M F - - 1993
To evaluate the role of adenosine receptors in the mediation of adenosine-induced protection of the heart during ischemia and reperfusion, isolated rabbit hearts were perfused at constant flow with 1 microM adenosine started before low-flow ischemia followed by reperfusion. Adenosine delayed the time of onset of ischemic contracture [to 28 ...
Garlick P B - - 1993
NMR spectroscopy, possibly, does not detect 100% of large molecules such as glycogen (mol.wt = 10(7)-10(9)). Using both NMR and chemical quantification methods, we have, therefore, determined the NMR visibility of cardiac glycogen (defined as the ratio of the NMR value to the chemical value, expressed as a percentage) in ...
Blum H - - 1993
A number of cardiac metabolic intermediates, namely, adenosine triphosphate (ATP), H+, phosphocreatine (PCr), inorganic phosphate (Pi), adenosine diphosphate (ADP), and related functions of these intermediates, Gibbs' free energy of ATP hydrolysis (delta G) and phosphorylation ratio [ATP/(ADP.Pi)], are thought to adjust mitochondrial oxidative phosphorylation rates to conform to mechanical demand. ...
Aussedat J - - 1992
We report studies on the isolated hearts of rats treated with triiodothyronine (0.2 mg/kg daily) for 14 days, on spontaneously hypertensive rats (12 and 21 weeks old, Lyon strain) and on their respective controls. A 30% increase in cardiac weight was developed with triiodothyronine and a 40% increase in heart ...
Tanaka K - - 1992
A new gating NMR technique triggered by pulses for the cardiac pacing of isolated, perfused rat heart is described. This technique is suitable for obtaining spectra at the same positions over the cardiac cycle with the same RF pulse repetition time and with constant heart rate. Accordingly, each recovered magnetization ...
Ely S W - - 1992
We employed an isolated guinea-pig heart model perfused at constant pressure (70 cmH2O) to test the hypothesis that inhibition of adenosine metabolism increases interstitial adenosine concentrations (as measured with epicardial discs) and coronary flow. Iodotubercidin (ITU, 1 microM) and EHNA (erythro-9-[2-hydroxy-3-nonyl] adenine, 5 microM) were used to inhibit adenosine kinase ...
Orito K - - 1992
Vasodepressor mechanisms of adenosine were investigated in spinally-anesthetized dogs. An i.v.-infusion of adenosine (0.1-10 mumol/kg/min) caused a slowly developing and sustained decrease in blood pressure (BP). This vasodepression was antagonized by glibenclamide, a blocker of ATP-sensitive K+ (KATP) channels. On the other hand, a transient decrease in BP caused by ...
De Scheerder I K - - 1992
The effect of repeated short anoxic or ischemic periods on ATP breakdown and cardiac function remains controversial. To analyze this issue further and to study the regulation of adenine nucleotide breakdown during recurrent cardiac anoxia, we compared two different protocols of intermittent anoxia. Four rat hearts, perfused according to Langendorff, ...
Haywood G A - - 1992
BACKGROUND: Elevation of pulmonary vascular resistance is an important determinant of right ventricular function in patients with end-stage biventricular heart failure. Vasodilator drug therapy directed at the pulmonary vasculature is used in the hemodynamic assessment of patients for orthotopic heart transplantation, and therapy aimed at decreasing pulmonary vascular resistance and ...
Yanagi S - - 1992
OBJECTIVE: The excessive release of adenosine has been reported to cause hyperaemia and to attenuate ischaemic injury in microembolised hearts. The direct effects of exogenous adenosine on cardiac performance were investigated in microembolised guinea pig hearts with the simultaneous measurement of phosphate compounds. METHODS: 21 male guinea pig hearts were ...
Ogilby J D - - 1992
BACKGROUND: Myocardial perfusion imaging during adenosine-induced hyperemia with dipyridamole or adenosine is an accepted method to diagnose coronary artery disease (CAD) and risk assessment. The mechanism of perfusion abnormality may be caused by disparate flow responses or coronary steal. This study examined the relation between 201Tl perfusion pattern and hemodynamic/angiographic ...
Sidi A - - 1992
We hypothesized that either through local myocardial or systemic effects, adenosine could be used to control hypotension during ischemia. Therefore, we compared the effects of systemic with intracoronary infusion of adenosine on myocardial hemodynamics and metabolism during ischemia in 27 dogs. Left anterior descending artery (LADa) flow was measured and ...
Yamamoto R - - 1992
In the isolated mesenteric vasculature of rats, moderate cooling significantly augments the perfusion pressure responses to transmural field stimulation (TFS), whereas it depresses markedly TFS-induced endogenous norepinephrine (NE) release. Moderate cooling also reduces the perfusion pressure responses to exogenous NE. The present experiments, therefore, were performed to analyze further the ...
Sommers K E - - 1992
BACKGROUND: The biochemical basis for postischemic myocardial stunning is not fully elucidated. Magnesium is an important regulator of cellular energetic processes and excitation-contraction coupling. We hypothesized that the decrease in function in the postischemic period may be the result of an alteration in magnesium regulation. METHODS: In a Langendorf perfused ...
Elliott A C - - 1992
1. The effects of global ischaemia on phosphorus metabolites, intracellular pH (pHi) and developed pressure were measured in isolated whole ferret hearts using 31P nuclear magnetic resonance (NMR) spectroscopy. 2. Brief (10 min) periods of global ischaemia reduced left ventricular developed pressure (LVDP) to undetectable levels. This fall in LVDP ...
Jolin A - - 1992
Unlike other vascular beds, lung vessels constrict when exposed to hypoxia. However, a marked difference has been noticed as regards the elicitability of hypoxic pulmonary vasoconstriction (HPV) in vivo as compared to in vitro models, like a preparation of isolated rat lungs; in the latter, HPV cannot be evoked from ...
Shinzato T - - 1992
Two types of dialysis induced hypotension apparently exist. One type presents as gradually decreasing blood pressure with eventual symptoms (gradual hypotension), whereas the other presents as abruptly and sharply decreasing blood pressure, along with symptoms (abrupt hypotension). In the current study, the authors found that the plasma hypoxanthine concentration during ...
Schaefer S - - 1992
In order to determine if an increase in myocardial oxygen consumption is accompanied by changes in high energy phosphates in normal subjects and patients with dilated cardiomyopathy, phosphorus-31 spectra were acquired under resting conditions and during dobutamine infusion. In seven normal subjects, dobutamine raised the rate-pressure product to 226% of ...
Bak M I - - 1992
31P-nuclear magnetic resonance (31P-NMR) spectroscopy is widely used to monitor sequential changes in the nucleoside triphosphate (NTP) pool in intact tissues. Recently, the validity of this technique to quantitate incremental changes in ATP in heart has been challenged. Accordingly, we compared NTP measured by 31P-NMR and by chemical techniques in ...
Gorman M W - - 1992
Cardiac adenosine release is thought to depend on the oxygen supply/demand ratio, and this effect may be mediated by changes in high energy phosphate concentrations. Previous studies supporting this hypothesis have been done primarily in isolated hearts. We tested this hypothesis in intact dog hearts. Anesthetized, open-chest dogs were placed ...
Van Wylen D G - - 1992
Cardiac microdialysis is a recently developed technique that allows intramyocardial interstitial fluid (ISF) to be sampled via the implantation and perfusion of a small, hollow dialysis fiber within the myocardium. The purpose of this paper is to describe initial studies using cardiac microdialysis in the isolated perfused heart. Microdialysis probes, ...
Glick M R - - 1992
To determine the effect of adenosine on the venous system, mean circulatory filling pressure (MCFP) was determined during infusion of intravenous (i.v.) adenosine (66.5 to a maximum of 532 microgram.kg-1.min-1) in 9 awake instrumented rats before and during ganglionic blockade with i.v. hexamethonium, 0.6 mg.kg-1.min-1. MCFP, the equilibrated pressure (mm ...
Angelini G D - - 1992
We investigated the effect of a novel surgical preparative technique for human saphenous vein by using the concentration of adenosine triphosphate and the adenosine triphosphate/diphosphate ratio to quantify medial integrity and by using stimulated rates of prostacyclin production to quantify endothelial function. Freshly isolated vein had an adenosine triphosphate concentration ...
Masuda M - - 1992
Purine nucleotide catabolism was examined during 24 hours of cold (0.5 degree C) storage of human transplant recipient hearts, baboon hearts, and dog hearts. The hearts were excised either after cold hyperkalemic cardioplegic arrest or after simple hypothermic arrest (25 degrees C). In human myocardium, hypothermia alone preserved the adenosine ...
von Planta M - - 1992
BACKGROUND AND HYPOTHESIS TESTED: The effects of adenosine (100 micrograms/kg/min; n = 7) were examined during rodent cardiopulmonary resuscitation (CPR). Change in coronary artery perfusion pressure, end-tidal PCO2, and arterial acid-base status of anesthetized, male, Sprague-Dawley rats were compared with CPR controls (0.9% sodium chloride; n = 7) and with ...
Sato H - - 1992
BACKGROUND: Adenosine attenuates beta-adrenoceptor-mediated inotropic responses through GTP-binding protein in vitro. The goal of the present study was to test the hypothesis that endogenous adenosine released from the ischemic myocardium blunts the inotropic response to beta-adrenergic stimulation. METHODS AND RESULTS: In 45 open-chest dogs, the left anterior descending coronary artery ...
Zhang Y - - 1992
A haemorrhage model was used to impose severe metabolic stress in anaesthetized cats by removing blood (15.3 ml min-1) to attain an arterial pressure of ca. 50 mmHg for a 2 h period. Adenosine levels in central venous blood rose by 5 min, reached a peak of about 3.5 times ...
Dev B R - - 1992
Neurochemical changes in the extracellular fluid of the rostral ventrolateral medulla (RVLM) were produced by changes in arterial blood pressure. Blood pressure was raised or lowered with systemic infusions of phenylephrine or nitroprusside and neurochemicals were recovered from RVLM by in vivo microdialysis. A dialysis probe 300 microns in diameter ...
Ning X H - - 1992
The purpose of this study was to examine adenosine release and high-energy phosphate concentrations during norepinephrine (NE) infusion in isolated guinea pig hearts perfused with a physiological salt solution (PSS) containing erythrocytes (RBC). Phosphate concentrations were monitored using 31P-nuclear magnetic resonance spectroscopy while NE was infused at 6 x 10(-10) ...
Honma M - - 1992
Using Langendorff isolated perfused rat hearts, we demonstrated direct effects of cyanide on the heart. A heart from a sacrificed male rat was placed on a Langendorff apparatus and perfused with Tyrode solution containing 2.0 mM NaCN (CN-TS), following with normal Tyrode solution (TS) at 37 degrees C. During perfusion ...
Downing S E - - 1992
We have recently shown that low-flow (10%) ischemia in the isolated piglet heart causes an abrupt fall in mechanical function and metabolic activity (acute hibernation), with nearly complete preservation of high-energy phosphates and glycogen after 2 hours of ischemia. We attempted to determine if norepinephrine, as occurs in vivo, would ...
Haneda T - - 1992
The effects of bunazosin on the ischemic myocardium were investigated in isolated, perfused working rat hearts. Ischemia decreased the pressure-rate product and tissue adenosine triphosphate and creatine phosphate levels. Reperfusion did not restore the pressure-rate product nor the adenosine triphosphate levels completely. Bunazosin (5 x 10(-7) and 5 x 10(-6) ...
Kupriyanov V V - - 1992
The effect of severe reduction of cytosolic adenine nucleotide (AdN) pool and [ATP]/[ADP] ratio (by 2-deoxyglucose treatment) on functional and metabolic responses of isovolumic rat heart to increased energy demand induced by coronary flow (CF) rise and isoproterenol (Iso) addition has been investigated. AdN-depleted hearts had reduced phosphocreatine (PCr, by ...
Shryock J C - - 1992
Activation of cardiac A1 adenosine receptors slows atrioventricular conduction and attenuates the effects of catecholamines, whereas activation of A2 adenosine receptors causes coronary dilation. This study investigates the antagonism of the action of adenosine on A1 and A2 adenosine receptor subtypes by (+-)-N6-endonorbornan-2-yl-9-methyladenine (N-0861) in guinea pig isolated perfused hearts. ...
Weiss R G - - 1992
Although the tricarboxylic acid (TCA) cycle is the prime means of carbon metabolism for energy generation in normal myocardium, the noninvasive quantification of TCA cycle flux in intact cardiac tissues is difficult. A novel approach for estimating citric acid cycle flux using 13C nuclear magnetic resonance (NMR) is presented and ...
Conzen P F - - 1992
We investigated the effects of clinically administered volatile anesthetics and of adenosine on the microvasculature of the in situ beating canine heart. Thirteen dogs were studied during general anesthesia with an opioid (piritramide), which was infused throughout the experiments. Measurements were obtained in each animal at control (piritramide only) and ...
Hoka S - - 1992
To examine the cardiovascular response to prostaglandin E1 infusion, we observed hemodynamic changes including left ventricular diameter (an ultrasonic crystal pair) during PGE(1)-induced hypotension in anesthetized open-chest dogs. Left ventricular contractility was assessed primarily by measuring the slope of the left ventricular endsystolic pressure-diameter relation (ESPDR) determined by combining end-systolic ...
Osbakken M - - 1992
To determine whether cardiac hypertrophy secondary to chronic renovascular hypertension is associated with altered in vivo myocardial metabolism, phosphorus-31 nuclear magnetic resonance saturation transfer techniques were used to study creatine kinase (CK) kinetics in six chronically hypertensive dogs with moderate cardiac hypertrophy and eight control dogs. The forward rate constant ...
Ohhira A - - 1992
1. We have developed a new preparation for continuously measuring changes in vascular resistance of the vasa vasorum of the canine isolated thoracic aorta perfused at a constant flow rate with Krebs-bicarbonate solution. 2. An increase of more than 150 mmHg in aortic pressure caused a significant increase in the ...
Yamanaga K - - 1992
Repeated oral administration of the novel loop diuretic torasemide (3 mg kg-1) and frusemide (30 mg kg-1) for 7 days, elicited a significant fall in the systolic blood pressure in the one-kidney, one-clip Goldblatt renal hypertensive rat (RHR). The hypotensive action was greater in the torasemide group than in the ...
Koos B J - - 1992
Breathing responses to adenosine were determined in 12 chronically catheterized fetal sheep (greater than 0.8 term) in which hypoxic inhibition of breathing had been eliminated by brain stem section. The caudal extent of transection varied from the rostral midbrain to the pontomedullary junction. Isocapnic hypoxia [delta arterial PO2 (PaO2) of ...
Cuevas P - - 1991
Acidic and basic fibroblast growth factors (FGFs) are members of a family of proteins that are broad-spectrum mitogens, have diverse hormone-like activities, and function in tumorigenesis. FGF's ability to raise the concentration of intracellular calcium ion suggests that FGF could induce the synthesis of endothelium-derived relaxing factor (EDRF) and consequently ...
Demmy T L - - 1991
Recovery of energy metabolism and contractility in stunned myocardium requires several days, even when mechanical circulatory support is employed. This double-blind study was undertaken to determine if myocardial recovery could be accelerated by intracoronary infusion of adenosine during reperfusion. Ten mongrel dogs were subjected to 45 minutes of global normothermic ...
McKillop D F - - 1991
Increased hydrostatic pressure has previously been shown to reduce the tension of isometrically contracting skinned muscle fibres. An isomerization of the actomyosin complex is known to be pressure sensitive, but the pressure sensitivity of other steps in the ATPase pathway has not been characterised. We report here the effect of ...
Zweier J L - - 1991
To further evaluate the bioenergetic role of phosphocreatine, we assessed several parameters in normal and depleted rat hearts. Rats were fed (8 weeks) a diet containing either 1% beta-guanidinoproprionic acid or 2% beta-guanidinobutyric acid (beta-GBA), resulting in an 80% phosphocreatine depletion compared to controls. Left ventricular pressure-volume curves were obtained ...
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