摘要:

The effects of coronary artery ligation on regional arterial and venous O2 saturation, oxygen extraction, blood flow, and oxygen consumption were studied in occluded and unoccluded areas of the hearts of fourteen anesthetized open-chest dogs. In seven animals, a coronary artery was occluded for 10 minutes and in seven others a vessel was ligated for 2 hours. Microspectrophotometric observations of small regional arteries and veins in quick-frozen hearts to determine regional O2extraction were combined with regional blood flow measurements with radioactive microspheres to determine regional myocardial O2 consumption by the Fick principle. Flow was significantly lower in the occluded compared to the control area at both times. The subendocardial: subepicardial flow ratio was reversed at 2 hours in the occluded area. Oxygen extraction was greater in the occluded areas. Oxygen consumption was lower in the occluded area. At 2 hours, the subendocardial: subepicardial consumption ratio was reversed in the occluded area, indicating a greater decrement in consumption in the subendocardium. Measurements of arterial saturation indicate an increasing number of blood vessels with O2 saturations below 80% with coronary artery occlusion. These vessels were found in all occluded areas. This would indicate a marked heterogeneity of blood flow within the area of occlusion. Some vessels may have normal flow and others low or no flow. There was heterogeneity of flow and oxygen extraction which led to areas with relatively normal oxygen consumption in the core of the infarct.CircRes 47: 400-407, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

In 21 dogs on cardiopulmonary bypass with ventricles kept empty, the mean beating but nonworking myocardial oxygen consumption (mVO2) was 3.8 ml/min per 100 g at a heart rate of 158 beats/min. After subsequent potassium chloride arrest, the basal mVOs was 1.74 ml/min per 100 g. To compare these values with the working situation, we measured mVOj in these hearts before instituting bypass when the heart rate averaged 179 beats/min and arterial pressure averaged 108 mm Hg; mVOj was 9.2 ml/min per 100 g. Atrioventricular dissociation was induced in five beating, nonworking hearts; electrical pacing at increasing heart rates produced a linear increase in mVO2. Extrapolation to zero heart rate yielded a value of 1.24 ml/min per 100 g, which was not significantly different from the KC1 arrest value of 1.25 ml/min per 100 g in these same hearts. These measurements permitted calculation of an energy expenditure per beat of 10.4 mj/g. Subtraction of the basal value of 2.0 mJ/g yielded a value for energy of contraction of 8.4 mJ/g. The stress-independent component was estimated to be 2.7 mJ/g. The basal rnVO2at normal perfusion pressure remained constant for arrest periods of at least 1 hour. Perfusion with modified Krebs-Henseleit buffer caused a 30% reduction in the basal mVOj in spite of maintained perfusion pressure, O2 supply in excess of consumption, coronary venous Po2values above 60 mm Hg, and the addition of amino acids. It is possible that this finding indi-cates deficient oxygenation of myocardial cells in hearts perfused with solutions lacking red cells. Circ Res 47: 408-417, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Tissue, cellular, and subcellular morphometry of the thoracic aorta in 1-, 5-and 11-day-old rats was used to quantify the cellular hypertrophy and proliferation of smooth muscle cells and the absolute increases in volume of elastic laminae and collagen during the early postnatal period. In the 1-to 5-day interval, total wall volume increased 2.9-fold, wall thickness and the number of smooth muscle cells doubled, mean cell volume increased by 40%, and the volumes of elastic laminae and collagen increased 3.7-and 3.3-fold, respectively. From 5 to 11 days, circumferential growth of the aortic wall, without further thickening, produced smaller and unequal growth increments of each of its component structures, with increases in collagen (3.2-fold) > elastic laminae (2.3-fold) > muscle cells (1.6-fold). In the overall growth of smooth muscle cells (4.6-fold) from 1 to 11 days, only the cytoplasmic volume fractions of glycogen aggregates and rough endoplasmic reticulum were altered significantly (−78%, +32%). Certain aspects of normal postnatal aortic growth paralleled the response of adult aorta to experimentally induced hypertension.Circ Res 47: 417−424, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Subclavian-to-femoral artery pulse wave velocity, as a measure of aortic stiffness, was determined in 31 rhesus monkeys(Macaca mulatto)which were divided into three groups on athero-genic progression or regression diets: nine monkeys (IIA) were fed a high cholesterol diet for 38 months, resulting in an average plasma cholesterol concentration of 638 mg/dl; and 10 (IIBi) and 12 (IIC1) monkeys were fed the same progression diet followed by 24-month regression diets which were manipulated to maintain plasma cholesterol concentrations as close as possible to 300 and 200 mg/dl, respectively. Average pulse wave velocity at a diastolic blood pressure of 70 mm Hg was significantly greater (9.4 ± 1.0 (mean ± SEM) m/sec) in the IIA group than in the IIBi (6.3 ± 0.3) or IIC, (6.6 ± 0.3) groups, although four of the IIA monkeys had pulse wave velocities that were not significantly higher than the regression monkeys. Total thoracic plus abdominal aortic cholesterol concentration was significantly reduced from 10.2 ± 1.4 mg/g wet weight in the IIA group to 5.7 ± 0.6 (IIBi) and 4.6 ± 0.6m g/S wet weight (IIC2). The total percentage of thoracic plus abdominal aortic intimal surface covered with fibrous plus fatty plaque averaged 56.9 ± 9.2% (IIA) vs. 33.5 ± 6.7 (IIBi) and 35.0 ± 7.4% (IIC1). Collagen content beneath a given intimal square surface significantly increased from 4.59 ± 0.31 mg/ cm2(IIA) to 6.46 ± 0.33 (HB,) and 6.49 ± 0.48 mg/cm2(IIC1), whereas elastin content decreased from 9.47 ± 1.56 (IIA) to 6.58 ± 0.73 (IIBi) and 6.01 ± 0.39 mg/cm2(IIC,). There was no significant difference in any parameter between the two regression groups. These studies suggest a functional improvement of aortic elastic properties with regression of atherosclerosis. When comparing groups, the improve-ment appears to follow the reductions in total aortic cholesterol concentrations and in the extent of total atherosclerotic plaque rather than alterations in the collagen: elastin ratio which, in fact, increased when arterial stiffness decreased with regression.Circ Res 47: 425-432, 1980.

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

We studied the relationships among levels of acid cholesteryl esterase (ACE) activity in kidney, liver, and aorta and clearance of125I-labeled human low density lipoprotein (LDL) from the circulation. The premise was that levels of ACE (which is involved in the hydrolysis of the cholesteryl esters of LDL) might correspond to the rate at which LDL was removed from the circulation, or fractional catabolic rate (FCR). The models used were rats with streptozotocin diabetes and^ exercised (swimming) rats. In the diabetic rat, ACE specific activity was increased by 46% in kidney and 30% in liver anddecreasedby 25% in aorta when compared to controls. The FCR of LDL increased by 25% in the diabetic animal over control values. Insulin treatment restored all these alterations to normal. Swimming rats showed no change in ACE-specific activity of kidney or liver, but aortic ACE increased by approximately 25% over levels in sedentary rats. The FCR of radioiodinated LDL in swimmers was unchanged from normal. Return of swimmers to a sedentary existence resulted in persistence of normal ACE activity in kidney and liver and in FCR of LDL; however, previously elevated aortic ACE activity returned to normal. Thus, dynamic, irreversible removal of LDL from the circulation (FCR) is changed in the same direction as, and may be linked to, ACE activity in non-vascular tissues. Aortic ACE activity, on the other hand, is not so related to either ACE in those tissues or to FCR of LDL. One implication of this finding is that the general pattern of LDL catabolism by the rat is distinct from the local problem of LDL catabolism by the blood vessel wall.Circ Res 47: 433-442, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

We investigated the electrophysiological effects of cardiac hypertrophy induced by renal hypertension in rats by comparing transmembrane action potentials (AP) recorded from the papillary muscles of hypertensive (HBP) and normal (SHAM) rats. No significant difference was found between HBP and SHAM AP with regard to resting membrane potential (RMP), action potential amplitude (AMP), overshoot (OS), or maximum rate of rise of the upstroke. In contrast, the duration of 50% (APD50) and 75% (APD75) of repolarization to the RMP was significantly and consistently longer for HBP AP than for SHAM AP. The mechanism for prolonged HBP AP was investigated by changing extracellular fluid composition and by use of ion channel blockers. The responses of HBP and SHAM AP to various treatments differed in a quantitative rather than qualitative fashion. Exposure to C2+-containing or low-Na+Tyrode's solution produced a differentially greater decrease in APD50and APD75 in HBP AP than in SHAM AP. Treatment with D600 also produced differential shortening of HBP AP, but its effect was limited to APD50. In contrast, exposure to Sr2+-containing and TEA-containing Tyrode's solution produced an increase in APD50and APD75, but the lengthening effect was not differentially greater in HBP than in SHAM AP. Treatment with Ca2+-free Tyrode's solution had little effect on APD in either HBP and SHAM rats. None of the treatments had a significant differential action on RMP or AMP in HBP AP as compared to SHAM AP. Our results show that AP prolongation is a specific and consistent feature of hypertrophied myocardium and that the changes responsible for prolonged HBP AP are quantitative rather than qualitative in nature. The specific differential effects of high Ca2+concentration ([Ca2+]o) and low Na+concentration ([Na*]o) on the duration of HBP AP indicate that the membrane sensitivity to these ions is altered in hypertrophied myocardium and that one possible explanation for prolonged HBP AP is slowed inactivation of a Ca2+-inactivated inward current.Circ Res 47: 443-454, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Arrhythmias were simulated in sheets or cables, consisting of coupled excitable elements, which were characterized by a simple regenerative mechanism. The geometry of the network, the amount of coupling among individual elements, and the properties of the elements relating to excita-bility, automaticity, and duration of the refractory period could be adjusted arbitrarily in an interactive computer program. When a critical amount of coupling was present between automatic and non-automatic cells, sustained repetitive activity could be initiated and stopped by stimulation of the elements. Using this mechanism, it also was possible to evoke reciprocal activity in a one-dimensional cable. In uniform sheets of coupled elements, circus movement of the activation front could be evoked. The presence of an obstacle or dispersion of the refractory periods of the elements was not a prerequisite for the initiation of circus movements. The vortex of circus movements in the homogeneous sheets consisted of elements which were inactivated by depolarizing currents from the circulating wavefront. In sheets of sufficient size, multiple vortices could be present.Circ Res 47: 454-466, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Continuous positive-pressure ventilation (CPPV) decreases cardiac output by decreasing right and left ventricular end-diastolic volumes. To investigate the mechanism(s), we measured cardio-vascular responses to CPPV before and after opening the chest and holding the lungs away from the heart. Expiratory pressure was adjusted to achieve similar lung volumes when the chest was open and closed (12 cm H2O). Increasing expiratory pressure, when the chest was closed and evacuated, decreased cardiac output, ventricular end-diastolic volumes, and transmural ventricular end-diastolic pressures measured relative to lateral and posterior epicardial surface pressure(P<0.05). Transmural ventricular end-diastolic pressures measured relative to lateral pleural surface pressure did not change signifi-cantly, indicating that the increase in thoracic pressure was greater at the lateral and posterior epicardial surfaces than at the lateral pleural surface. Opening the chest and holding the lungs away from the heart eliminated the decrease in cardiac output and ventricular end-diastolic volumes during increased expiratory pressure. Pericardectomy did not affect the cardiovascular responses to increased expiratory pressure. We, therefore, conclude that decreased cardiac output and ventricular end-diastolic volumes during CPPV result from the effects of increased thoracic pressure on cardiac filling.Circ Res 47: 467-472, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Superfusion of isolated canine cardiac Purkinje fibers with ethanol (100-300 mg/ 100 ml) resulted in a concentration-dependent shortening of action potential duration. The effect occurred within 5 minutes of exposure to ethanol and was reversed completely after removal of the drug from the medium. Action potential amplitude, transmembrane resting potential, dV/dt of phase 0, and conduction time were not altered by these concentrations of ethanol. Superfusion with methanol, ethanol, l-butanol,n-butanol, and pentanol in a concentration of 200 mg/100 ml revealed that the magnitude of the alcohol-associated shortening of action potential duration was related directly to the water-octanol partition coefficient (lipophilic property) of the alcohol. Acetal-dehyde (0.08-0.80 DIM) prolonged the action potential duration of Purkinje fibers, but this effect was blocked by addition of the α-adrenergic blocking drug, phentolamine (10∽6M). Acetate (1-5 mM) did not alter action potential configuration or conduction time of cardiac Purkinje fibers. Ethanol (100-300 mg/100 ml), acetaldehyde (0.08-0.80 mM), and acetate (1-5 mM) did not significantly change the rate of spontaneous depolarization of isolated guinea pig atria. These studies show that ethanol, in concentra-tions present in plasma during ethanol consumption, exerts direct reversible effects on cardiac Purkinje fibers. These effects probably result from a physical alteration of the sarcolemma secondary to interaction of ethanol with hydrophobic regions of the lipid bilayer. However, the metabolic by-products of ethanol do not exert direct electrophysiological effects on canine Purkinje fibers or guinea pig atria.Circ Res 47: 473-478, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID