摘要:

Some statistical techniques for analyzing the kinds of studies typically reported inCirculation Researchare described. Particular emphasis is given to the comparison of means from more than two populations, the joint effect of several experimentally controlled variables, and the analysis of studies with repeated measurements on the same experimental units.Circ Res 47: 1-9, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

We analyzed the isotope dilution residue function from a single cardiac chamber for an arbitrary inlet distribution of tracer and arbitrary mixing within the chamber, and established a general relationship between cardiac output and the chamber residue function. In our experiments, we made simultaneous temperature measurements in three left ventricular chamber subregions of the dog subjected to left and right atrial injections of chilled saline. Flow-proportional tracer labeling always occurred at the left ventricular inlet when injection was into the right atrium. This state almost never obtained, however, with direct left atrial injection, although it was approximated most closely when multiple side hole cathers were used. We also demonstrated that imperfect tracer mixing in the normal ventricle can lead to significant regional temperature inequalities during tracer passage. These ine-qualities are more pronounced in the ventricle with compromised function, but in both normal and compromised ventricles they are minimal several beats after tracer concentration peaks if injection is into the right atrium.Circ Res 47: 10-20, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

Physiological loads were imposed on contracting isolated cat papillary muscles. The interaction of a hypothetical cylindrical ventricle with a three-element vascular impedance model dictated these physiological loads. The length-tension relation of the physiologically loaded muscle and the pressure-volume relation of the hypothetical ventricle were simultaneously analyzed while the resistive and capacitive components of the vascular impedance were varied widely. Both the end-systolic muscle length-tension relation and the end-systolic ventricular pressure-volume relation were constructed using stepwise increments in either peripheral vascular capacitance or peripheral vascular resistance. The slope of the relation line connecting the end-systolic pressure-volume points under stepwise increases in resistive load was smaller (p< 0.0005) than the slope of this line under stepwise increases in capacitive load. Therefore, the end-systolic pressure-volume relation behaves differently with respect to capacitive and resistive loads. The different loading pattern within the same beat under these varying loading conditions and the coincidence of end-systole with end-ejection in these naturally ejecting contractions are responsible for the shifts in slope of the end-systolic pressure-volume relation. Neither the slope nor the volume intercept of the end-systolic pressure-volume relation was changed when initial muscle length was decreased from 1.0 to 0.95 ImaxWhen the Ca2+concentration in the bathing solution was increased from 2.5 to 7.5 mM, the slope of the end-systolic pressure-volume relation increased (P< 0.0005), and the volume intercept of the curve decreased (P< 0.025). These results are similar to data reported for conscious animals and to data obtained from catheterization of the human left ventricle.Circ Res 46: 20-26, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

The significance of the intact pericardium for cardiac performance was examined in 18 open-chest dogs. Myocardial chord lengths (MCL) in the right and left ventricle were measured simultaneously by ultrasonic crystals implanted in the myocardium of the anterior walls. In 14 dogs, the ultrasonic elements were inserted into the myocardium through needle openings in the pericardium (intact pericardium). In four other dogs, the elements were inserted through 6-to 7-cm-long incisions in the pericardium which were sutured afterward (sutured pericardium). Stroke volume was calculated in each of seven dogs with an intact pericardium from electromagnetic measurement of flow in the superior and inferior venae cavae. After blood volume expansion to about 13 mm Hg, the pericardium was opened and the end-diastolic pressure-MCL relationships and stroke volumes before and after pericardiotomy were compared. By opening the intact pericardium, the right and left ventricular end-diastolic MCL rose by 2.7 ± 0.7± and by 3.7 ± 1.1±, respectively, and stroke volume increased by 13 ± 4±. However, by reopening the sutured pericardium, the increases in both right and left ventricular end-diastolic MCL were clearly greater (12.2 ± 5.6± and 9.9 ± 2.9±, respectively), and the restrictive effect of the pericardium was therefore overestimated when the pericardium was not left intact. Thus, after a moderate blood volume expansion, the intact pericardium exerts a certain, although moderate restrictive effect on cardiac performance.Circ Res 47: 27-32, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

We studied the effects of regional epicardial application of phenol on autonomic neural control of electrophysiological characteristics of the anterior left ventricle. In eight open-chest dogs, we applied a thin line of 88± phenol on the perimeter encircling a multipolar electrode and measured the effective refractory period (ERP) and recorded electrograms in phenol-encircled and untreated areas. Before phenol was applied, sympathetic nerve stimulation shortened ERP in all areas: percent change (Δ) ⩾ 12. Phenol application to an area with a radius of 1-2 cm prevented ERP shortening in encircled epicardium during sympathetic stimulation, ±Δ = 0.9 ± 0.8 (SEM), and attenuated ERP shortening in underlying endocardium, ±Δ = 2.5 ± 1.6, compared to ERP shortening in untreated areas, ±Δ = 10 ± 1. A subsequent phenol application to an area with a radius of 2-3 cm prevented ERP shortening during sympathetic stimulation in both encircled epicardium and underlying endocardium. Phenol did not alter electrograms, activation times, or ERP shortening produced by norepinephrine infusion; these data suggest that electrophysiological characteristics of ventricular muscle encircled by phenol were unchanged apart from effects of withdrawal of sympathetic neural influence. To support these functional data, norepinephrine content measured in phenol-treated epicardium and endocardium of three dogs was 7 and 21±, respectively, of the norepinephrine content of untreated areas. In eight additional dogs, vagus nerve stimulation during norepinephrine infusion prolonged ERP by 3-5 msec both before and after phenol encircling an area with a radius of 2-3 cm. In these dogs, phenol did prevent ERP shortening during sympathetic nerve stimulation. We conclude that epicardial phenol interrupts sympathetic neural influences to both epicardial and endocardial sites without impairing responses either to intravenous norepinephrine or to vagus nerve stimulation.Circ Res 47: 33-40, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

β-Adrenergic receptors in primary cultures of neonatal rat cardiac cells were identified with the radioligand [l25I]iodohydroxybenzylpindolol ([125I]IHYP). At the time of cell plating, a differ-ential attachment procedure was employed to separate myocardial (M) cells from fibroblast-like (F) cells. After 3-4 days, the cultures enriched in M cells were still more than 80% pure and the cultures enriched in F cells were more than 95% pure. For binding studies, confluent cell layers were nonenzy-matically detached as single cell suspensions. Both M and F cells contained a limited number of β-adrenergic receptors (M, 7600 % 2100 sites/cell; F, 9000 ± 2400 sites/cell) which had very high affinity (M, Kd= 88 % 33 PM; F, Kd= 71 % 23 pM) for [125I]IHYP. For each cell type, the binding sites were stereoselective for theI-isomers of agonists and antagonists. Further binding studies on the relative potency of β-agonists showed that the β-receptors in M cells could be subclassified as β1(isoproterenol > epinephrine = norepinephrine), whereas the β-receptors in F cells were more typical of β2(isoproterenol > epinephrine > norepinephrine). The order of potency of these catecholamines in stimulating the adenylate cyclase activity in M and F cells was consistent with the order of potency observed in binding studies. Practolol, a β1inhibitor, was 30 times more effective as a competitor of [125I]IHYP binding in M cells than in F cells. It thus appears that, whereas M and F cells share a similar number of receptors per cell and similar affinities for [125I]IHYP, the receptors in the two cell types nevertheless can be distinguished on the basis of their subclassification. These results also emphasize the importance of obtaining a homogeneous cell population for studies of the β-adrenergic receptor in cultured cardiac tissue.Circ Res 47: 41-48, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

To determine whether collagen content may be a determinant of the ultrasonic attenua-tion and backscatter in myocardium and to identify factors in the measurement of the backscatter coefficient needed for ultrasonic characterization of myocardium in vivo, two series of experiments were conducted. In the first series, the ultrasonic attenuation was measured from 110 regions in 18 dogs studied 2, 4, and 6 weeks after coronary occlusion. The increased slope of the attenuation of regions within zones of infarction correlated closely with regional content of collagen as determined from concentration of hydroxyproline in canine hearts (0.90 in hearts studied at 6 weeks and 0.77 and 0.73 in those studied 4 and 2 weeks after occlusion). In a second series of experiments in which hearts from 21 rabbits were studied from 5 to 7 weeks after coronary occlusion, ultrasonic attenuation, ultrasonic backscatter, and content of collagen within zones of regions of infarction were increased significantly compared to nonischemic regions from the same rabbits (P< 0.001 in each case). To determine whether the increased ultrasonic backscatter depended on the content of intact collagen in regions of infarction, isolated rabbit hearts were perfused with modified Krebs-Henseleit solution and collagenase resulting in a significant reduction of the backscatter coefficient (P< 0.05). Since regional ultrasonic backscatter in the heart appears to be influenced markedly by the regional content of intact collagen, characterization of tissue with reflected ultrasound may permit noninvasive estimation of replacement of myocardium by collagen in vivo facilitating diagnosis and evaluation of the evolution of conditions such as ischemic heart disease and cardiomyopathy.Circ Res 47: 49-58, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

We evaluated the functional capacity of the intercoronary collateral vasculature in response to graded exercise 2 weeks after acute circumflex coronary artery occlusion. Acute myocardial infarction was produced in 11 chronically instrumented awake dogs by abrupt occlusion of the left circumflex coronary artery. Two weeks later regional myocardial blood flow was measured at rest and during three levels of graded treadmill exercise by injection of radionuclide-labeled microspheres, 7-10 jim in diameter, into the left atrium. The region of collateral-dependent myocardium was determined by injection of Evans blue dye into the coronary artery distal to the occluder, and the extent of infarction by histological examination. At rest, blood flow to collateral-dependent regions was directly proportional to the amount of viable myocardium present. In regions containing <25% infarcted myocardium, blood flow increased progressively with exercise as in normally perfused control areas from the anterior left ventricular wall. In regions containing >75% infarcted myocardium, blood flow did not increase significantly during exercise, and in over one-half flow, during exercise, actually fell below the resting level. In areas containing 26-75% infarcted myocardium, blood flow demonstrated an intermediate ability to increase in response to exercise. Thus, the capacity of the coronary collateral circulation to deliver blood to its dependent myocardium was compromised progressively in proportion to the degree of infarcted myocardium. Collateral-dependent areas containing relatively small propor-tions of infarcted myocardium had normal blood flow response to exercise, whereas regions containing extensive infarction had little or no functional reserve so that increasing hypoperfusion commonly occurred during exercise.Circ Res 47: 59-68, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

The applicability of the waterfall model was tested using the Starling resistor and different viscosities of fluids to vary the Reynolds number. The waterfall model proved adequate to describe flow in the Starling resistor model only at very low Reynolds numbers (Reynolds number <1). Blood flow characterized by such low Reynolds numbers occurs only in the microvasculature. Thus, it is inappropriate to apply the waterfall model indiscriminately to flow through large collapsible veins.Circ Res 47: 68-73, 1980

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

The cardiac neural elements which survive surgical denervation of the heart have been called the “intrinsic” innervation (ICN). These include postganglionic parasympathetic neurons and chromaffin cells. Specific activation of the ICN with nicotine (NIC) has been shown to produce powerful negative inotropic and chronotropic effects on the heart. The present study was performed to assess the influence of the ICN on dromotropic activity. Seven mongrel dogs successfully underwent surgical denervation of the heart. They were placed on cardiopulmonary bypass and conduction through the atrioventricular (AV) node as well as the right atrium was measured by an acrylic electrode plaque. Conduction through the right bundle branch (RBB) was measured using a second recording electrode. Drugs administered were acetylcholine (ACh, 0.1-10.0 μg); NIC (1-100 μg); and tetrodotoxin (TTX, 30 μg). All agents were injected by the intracoronary route. Both ACh and NIC caused significant increases in AV nodal conduction time; i.e., 5-49% and 11-49%, respectively. Intra-atrial, bundle branch, and His-to-ventricular muscle conduction was affected inconsistently, and the changes were nonsignificant. Responses to NIC, but not to ACh, were completely blocked by 30 μg of TTX. The effects of the ICN on ventricular conduction appear to parallel those of the parasympathetic innervation, i.e., profound influence on AV nodal conduction with little or no effect below this structure. In contrast, however, the ICN does not appear to affect intra-atrial conduction, nor do there appear to be functionally important chromaffin cells that affect conduction time.Circ Res 47: 74-79, 1980.

ISSN:0009-7330    

出版商:OVID    

年代:1980

数据来源: OVID