摘要:

Static elastic properties were studied in isolated segments of the left coronary circumflex artery (LCCA) and the right common carotid artery (CA) from 14 dogs at in-vivo values of pressure and length. A microscope with a Filar micrometer was used to measure radius and length. From these data it was possible to study the pressure-radius relationship and compute various anisotropic elastic moduli as well as the strain energy density (SED). Results indicate: (1) Both arteries exhibited hysteresis which could be minimized within two inflation-deflation cycles. (2) The pressure-radius relationship at constant length was essentially linear over a pressure range corresponding to the in-vivo pulse pressure. (3) The value of volume distensibility was 3.4 × 10−6cm2/dyne for LCCA and 1.5 × 10−6cm2/dyne for CA. (4) LCCA was more distensible than CA in the circumferential direction. (5) LCCA was stiffer in the longitudinal direction than in the circumferential direction; the reverse was true of CA. (6) SED values at physiologic dimensions were 314 × 103dyne/cm2for LCCA and 226 × 103dyne/cm2for CA. These values could be reproduced within 6% when the loading procedure was altered.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Cellular resting and action potentials and total tissue concentrations of K+, Na+, and Cl−were measured in canine myocardial and Purkinje tissues. The results with myocardium were consistent with those of others: the total tissue concentration of K+was greater than that of Na+of Cl−In Purkinje tissue, the total tissue concentration of K+was relatively low, while that of Na+and of Cl−was high. Extracellular space was calculated on the basis of four different assumptions about the intracellular concentration of one of the ions: (1) the intracellular concentrations of Cl−is zero; (2) the electrochemical equilibrium potential of Cl−equals the cellular resting potential; (3) the electrochemical equilibrium potential of K+equals the cellular maximum diastolic potential; (4) the electrochemical equilibrium potential of Na+equals the reversal of the cellular action potential. In the myocardium, the lowest estimate of extracellular space was 14±2%, and the highest was 18±2%. In the Purkinje tissue, the minimum extracellular space: (1) permitting adequate intracellular K+to account for the maximum diastolic potential was 45±3%; (2) consistent with passive distribution of Cl−was 61±4%; (3) yielding low enough intracellular concentration of Na+to account for the reversal of the action potential was 63±10%. These results suggest that in cardiac Purkinje tissue: (1) the extracellular space is unusually large with respect to that of myocardium and skeletal muscle; (2) intracellular activities of ions do not necessarily equal concentrations; or (3) intracellular space is not necessarily a single compartment.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

This investigation was undertaken in normal subjects to define the relationship between the intensity of exercise and magnitude of fibrinolytic response and to examine the effect of diurnal variations on the exercise response. Fibrinolytic activity was measured on fibrin plates and expressed as mm2. Diurnal variations occurred with lowest activity at 8:00 AM (mean, 66 mm2), and peak activity between 5:00 and 8:00 PM (mean, 266 mm2,P<0.001). Five minutes of maximal treadmill exercise caused a marked increase in mean activity from 90 to 658 mm2(P<0.001). Five minutes of 70% maximal exercise produced no significant increase, but 30 minutes increased activity to 626 mm2(P<0.005). In contrast, 30 minutes of 40% maximal exercise produced a small elevation from 80 to 173 mm2(P<0.005). Maximal and 40% maximal exercise evoked greater responses at 4:00 PM than 8:00 AM. Exercise produces increases in fibrinolytic activity which are related to the relative intensity of exercise, its duration, and the time of day it is performed. Short bursts of intense exercise cause marked increases, but more prolonged bouts of moderate exercise are required to produce similar increases. The increases with prolonged mild exercise are small and comparable to those observed during resting diurnal variations.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Using a constant infusion of two indicators, T-1824 bound to albumin and tritiated water, flow and transit time were measured in the left coronary system of intact man. Indicators were infused for 6 minutes into the left coronary artery with sampling from the coronary sinus in a region that drained exclusively the inflow of the left coronary artery and from the brachial artery for recirculation. The degree of heterogeneity of myocardial perfusion could be defined by the time required for the curve to reach a plateau. A correlation coefficient of 0.966 was found between the two indicator-measured blood flows. The average myocardial hematocrit was calculated and found to be similar to the arterial. In the presence of myocardial disease, total flow of the left coronary artery was increased. When this was divided by tissue volume, the blood flow per unit volume of tissue was decreased in the presence of the idiopathic cardiomyopathy.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The rabbit immunized against angiotensin II was shown to be a valid model for the study of renal-clip hypertension. In particular, there was a specific and complete blockade of the pressor effect of high doses of intravenous renin and angiotensin in vivo, even at angiotensin II production rates which far exceeded those associated with renal-clip hypertension. Despite this, four immunized rabbits developed hypertension after renal-artery clipping with contralateral nephrectomy, and in three of these the hypertension was severe. In four other rabbits, there was no evidence of modification of an established hypertension after immunization against angiotensin II. In both groups, the specific absence of pressor response to high doses of renin and angiotensin II after immunization was confirmed. These studies provide strong evidence that angiotensin is not the sole or even the major factor in either the initiation or maintenance of this form of hypertension.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Influence of duration of cholesterol feeding on esterification of fatty acids and hydrolysis of cholesteryl esters was studied in cell-free preparations of aorta from White Carneau pigeons. Esterification of fatty acids required ATP and CoA; greater than 80% of the esterifying activity was located in the particulate fraction obtained by centrifugation at 105,000×g(after a preliminary centrifugation at 1000×g). Fatty acids were incorporated most efficiently into phospholipid, primarily (82%) lecithin. Greater than 87% of the fatty acid was esterified at the 2-position. During 8 months of cholesterol feeding, incorporation of oleic acid into phospholipids and triglycerides increased relatively little (less than double that of controls); no changes were seen before 1 month. Esterification of oleic acid to cholesterol was increased after 2 weeks of cholesterol feeding (before gross lesions were seen), eventually reaching a maximum increase of 30- to 50-fold. Cholesterol was esterified by transfer of fatty acyl-CoA to cholesterol, a mechanism similar to that described for liver and adrenal cortex. Little if any cholesterol esterification occurred when lecithin labeled at the 2-position with oleic acid-l-14C was used as substrate. The relationship between duration of cholesterol feeding and hydrolysis of cholesteryl oleate could not be evaluated since results depend directly on an unknown extent of equilibration of substrate with pre-existing cholesteryl ester pools.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID