摘要:

Left ventricular volumes were measured at rest and during electrically stimulated muscular exercise in 28 anesthetized dogs. Volumes were calculated from images obtained during biplane cineangiofluorography. Under control resting conditions from 30 to 55% of the diastolic volume of the left ventricle remained after ejection. This residual volume of blood became an immediate source of the increased ventricular output during the beginning of exercise. Following vagectomy, sympathectomy, and total cardiac denervation, the ability to increase cardiac output during exercise persisted, but was accomplished by increased ventricular filling rather than by diminution of the residual volume.

ISSN:0009-7330    

出版商:OVID    

年代:1965

数据来源: OVID

摘要:

The secretion rate of aldosterone was increased by infusion of valine-5-angiotensin II into the adrenal arterial blood supply of sheep. The dimensions of the increase in aldosterone output were inversely related to the control plasma concentration. This high aldosterone secretion was reduced substantially by concurrent adrenal infusion of concentrated NaCl solution which increased plasma sodium concentration by approximately 10 meq/liter. The reduction of aldosterone secretion occurred within 20 minutes. Angiotensin II infusion did not increase the secretion rates of cortisol or corticosterone.The significance of the finding that environmental sodium concentration has different effects on the aldosterone-stimulating action and the pressor action of angiotensin II is discussed.

ISSN:0009-7330    

出版商:OVID    

年代:1965

数据来源: OVID

摘要:

That the radiorubidium distribution method provides good estimates of blood flow to the gastrointestinal organs was demonstrated by comparing the arterial concentration course of the isotope with the simultaneous venous concentration for the individual organs. Blood flow to stomach, intestine and colon are accurately assessed by this method. Estimates for pancreas, gall bladder, esophagus and duodenum are probably correct. Average perfusion rates in the pentobarbital anesthetized dog are, in cc/min.g of tissue: —esophagus, 0.21; stomach, 0.51; duodenum, 0.70; small intestine, 0.72; colon, 0.82; pancreas, 0.60; and gall bladder, 0.39.

ISSN:0009-7330    

出版商:OVID    

年代:1965

数据来源: OVID

摘要:

Single-comb, Hy-line white leghorns were hatched in one lot, brooded in one flock through 7 weeks, then assigned randomly to cages in one large room with 15 hours of light per day. The birds were studied in the following situations: a) separately caged cocks and hens, b) paired cocks and hens, and c) 3 cock-3 hen groups and 6 cock-6 hen groups. Basic space allowance was 2 square ft per bird which was increased to 8 square ft for some of the larger groups. Commercial rations and water were supplied ad libitum. Stenosing lesions of the intramural coronary arteries began development in cocks and hens before age 7 weeks (10 to 12 weeks before sexual maturity) and progressed with age. Progress, as measured by heart scores, was not influenced by space allowance but was related to social situation. The rate for separately caged cocks was significantly higher than for other birds. Cocks of the larger groups and cocks of the pairs were next in order, while heart scores for cocks of the smaller groups were third but not significantly higher than for grouped hens. Heart scores of grouped hens sometimes exceeded heart scores for cocks of corresponding groups.High mean heart scores for grouped cocks correlated with high mean heart scores for hens of their groups, and low heart scores for grouped cocks with low scores for hens of their groups.

ISSN:0009-7330    

出版商:OVID    

年代:1965

数据来源: OVID

摘要:

The present study has attempted to establish a reliable method for distinguishing quantitatively between pulmonary engorgement and engorgement plus edema. Pulmonary engorgement was produced in intact, anesthetized dogs by inflating a balloon in the left atrium followed by saline hemodilution. Hemodynamic events monitored included left atrial and pulmonary arterial pressures, and the colloid osmotic pressure. Clinical criteria, such as the rate and frequency of breathing, the chest roentgenogram, and the presence of audible rales, failed to distinguish reliably between engorgement and edema. The mechanics of breathing were more severely altered by engorgement and edema than by engorgement alone, but considerable overlap was present. Determination of the pulmonary blood volume and the extravascular water space of the lungs, by means of simultaneous T-1824 and tritiated water dilution curves, as described by Chinard and Enns, was a reliable method of detecting and quantifying pulmonary edema. The water space measured by this technique averaged 3.5 ml/kg body wt in normal, anesthetized dogs. It correlated well with the total lung water content determined at autopsy, measuring a constant fraction (approximately 50%) of the total lung water content, even in the presence of severe pulmonary edema. According to the results of the present study, pulmonary edema could be predicted reliably at autopsy when the extra-vascular water space was 6.0 ml/kg of body wt or greater.

ISSN:0009-7330    

出版商:OVID    

年代:1965

数据来源: OVID

摘要:

Cardiac output, left coronary artery flow, central aortic blood pressure and myocardial metabolism have been studied in the intact unanesthetized dog during exercise. Cardiac output and left coronary artery flow increase 350 to 400% during moderately severe exercise. The primary mechanical determinant of this increase appears to be cardio-acceleration; the stroke volume and stroke coronary flow contribution is relatively mild. Myocardial oxygen usage increases 300% or more with only a small elevation of the percentage of extraction of oxygen. The large increase of coronary flow in the dog and the significant elevation in hematocrit supply the extra oxygen.

ISSN:0009-7330    

出版商:OVID    

年代:1965

数据来源: OVID

摘要:

A method is described for estimating plasma renin activity by using renin substrate present in plasma. This method differs from other indirect renin assay methods by (1) incubation in the absence of ions thus establishing conditions for zero order kinetics for the reaction between endogeneous renin and substrate and (2) the use of angiotensinase inhibitors di-sodium ethylenediamine tetraacetic acid (EDTA) and d-isopropylfluorophosphate (DFP). Recoveries of renin added to plasma in levels similar to those occurring in plasma are 85% SD±7%.The incubation was done at pH 5.5 which was shown to be the optimum for human renin reacting with human substrate.By incubating human plasma samples with known quantities of human renin, evidence was obtained suggesting that factors other than enzyme or total substrate concentrations affect the velocity of angiotensin formation. This variability of reaction rate may be explained by the existence of an inhibitor or activator in this system or by a variation in the type of substrate.

ISSN:0009-7330    

出版商:OVID    

年代:1965

数据来源: OVID

摘要:

The interactions between pacemakers, and the effects on pacemakers, of terminating imposed driving were studied in thein situheart of anesthetized dogs.Following atrial fibrillation or termination of a fast drive imposed through an artificial pacemaker, pacemaker action in intrinsic pacemakers is suppressed.Pacemakers tend to accelerate and compete with imposed drives which exceed control rates by only a small percentage (10 to 15%). Arrhythmias may result if imposed drive is slower than or identical with intrinsic pacemaker rate.Post-drive depression of pacemakers and the resulting deceleration of the heart is followed normally by an overshoot or supranormal acceleration.The magnitudes and durations of depression and late acceleration are proportional, within limits, to the rate and duration of drive.Atrioventricular and ectopic atrial pacemakers are much more readily depressed than is the sinoatrial pacemaker. Furthermore, beats of ectopic origin are much more likely to occur while subsidiary pacemakers are recovering from post-drive depression.Augmentation of depression by Prostigmin, its diminution by atropine, and the potentiation of late acceleration by cocaine and its absence after reserpine or guanethidine pretreatment, indicate that acetylcholine and catecholamines are liberated by driving stimuli.Placement of the pacemaker over the sinoatrial node, or near to regions where nerve terminals are concentrated, results in the greatest post-drive effects. The fact that propagated action potentials cause depressions and accelerations subject to drug block or potentiation indicates that mediators are also released in the course of propagated activity.Since atropine does not completely block post-drive depression, it is thought that a potassium ion shift may be involved.

ISSN:0009-7330    

出版商:OVID    

年代:1965

数据来源: OVID

摘要:

Rapid drive of isolated pacemaker tissues from cats resulted in a post-drive depression followed by a late acceleration to supernormal rates of pacemaker activity. These effects were similar to those occurring after drive of the pacemakerin situ. Lower SA nodal pacemakers discharged more slowly and irregularly than did upper SA nodal pacemaker cells. They were more readily depressed by rapid imposed drive. The balance between depression and acceleration varied in different preparations. Drive at only slightly above the intrinsic rate resulted frequently in acceleration not preceded by depression. Within limits, the greater the frequency and duration of drive, the greater the intensity and duration of both the depression and the late acceleration.Prostigmin augmented and atropine reduced post-drive depression. Cocaine potentiated the late acceleration. Excess potassium reduced post-drive depression and, in concentrations used, caused some acceleration.Pacemaker cells could be driven less rapidly than could other SA nodal cells. Drive generally shifted pacemaker action to a distant site; the first post-drive propagated responses originated from other pacemaker cells and dominance by the original unit was reestablished slowly. Rapid drive reduced amplitudes of action potentials and prepotentials. It also raised threshold potentials and during the post-drive period the durations of pacemaker cell action potentials were temporarily prolonged. In some preparations membrane potentials remained at a subnormal value after drive. Subthreshold potentials occurred at a somewhat subnormal rhythm but gradually developed an effective amplitude.Conduction block was observed in isolated SA nodal tissue. This was augmented during the post-drive period of depression.This work lends support to the hypothesis1that dominating action by pacemaker cells influences the pacemaker activity in other potential pacemaker tissues.

ISSN:0009-7330    

出版商:OVID    

年代:1965

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1965

数据来源: OVID