bluuebunny/crossref_metadata_2025_split huggingface dataset:
Duration of the Phases of Left Ventricular Systole
Authors: WALLACE ANDREW G. , MITCHELL JERE H. , SKINNER N. SHELDON , SARNOFF STANLEY J. 
Published: June 2012

The effects of altering stroke volume, aortic pressure and heart rate on the duration of each phase of left ventricular systole were investigated in a denervated dog heart.
Augmenting stroke volume was found to prolong ejection, shorten the isovolumic period and had little or no effect on the duration of total systole. Elevating mean aortic blood pressure shortened ejection time, prolonged the isovolumic phase and either had no effect or decreased slightly the duration of total systole. Increasing heart rate at constant aortic pressure and stroke volume reduced the duration of all phases of systole. Digitalis and norepinephrine shortened all phases of systole.
These findings demonstrate that the duration of each phase of left ventricular systole is dependent upon existing hemodynamic conditions as well as on the contractile state of the myocardium. By means of intrinsic mechanisms the ventricle exhibits the remarkable capability of being able to adjust the duration of each phase of systole in a manner appropriate to changing hemodynamic conditions.
Pressure Transmission in Pulmonary Arteries Related to Frequency and Geometry
Authors: ATTINGER ERNST O. 
Published: June 2012

The propagation of the pulse wave through the canine pulmonary arterial tree has been evaluated by means of harmonic analysis. The apparent phase velocity varied both with frequency and distance as one would expect in the presence of reflected waves. The phase velocity was about 230 cm/sec for the inflated and 325 cm/sec for the deflated lung. Theoretical considerations as well as experimental results indicate that the major branches represent the primary reflection site for the pulse wave. The pulse pressure is transmitted across the pulmonary capillary bed, although at a high attenuation, and the transmission varies markedly with lung volume.
The dimensions of the pulmonary arterial tree were evaluated from casts. Data for the length and cross sections of the various branches are given. The volume of the arterial tree as represented by the casts was 24 ml. The cross section of the various branches represents an ellipse rather than a circle, and the cross section ratios of the major branch points is considerably less than those postulated for optimal energy transfer. The implications of the geometrical findings for the relation between pressure gradient and flow are briefly discussed.
Magnesium Deficiency in the Cebus Monkey
Authors: VITALE JOSEPH J. , VELEZ HERNAN , GUZMAN CARLOS , CORREA PELAYO 
Published: June 2012

Purified diets containing cholesterol and deficient or adequate in magnesium were fed to young growing Cebus (fatuella) monkeys.
Diet-induced magnesium deficiency resulted in weight loss, hyperirritability, and in several monkeys, convulsions.
In addition to the expected hypomagnesemia, deficient animals also had decreased serum potassium levels. However, after several weeks on diet, the electrocardiogram of deficient animals showed significant changes consisting primarily of S-T segment depression and peaking of the T wave; changes usually seen in hyperkalemic states.
Prior to sacrificing the animals, the tolerance to K-strophanthidin, a cardiac glycoside, was ascertained in both deficient and control animals. The cardiac glycoside was administered slowly by the intravenous route to anesthetized monkeys and the appearance of four consecutive ventricular premature contractions in the electrocardiogram was taken as the end-point. Deficient animals required approximately one-half the dose administered to control monkeys to develop extrasystoles.
The histopathology consisted of marked vascular sudanophilic deposits and dense fibrous connective tissue plaques in the ascending and descending aorta of deficient monkeys. Control animals showed little, if any, vascular sudanophilia.
The serum cholesterol concentration increased significantly in the deficient group while the rise seen in control monkeys lacked statistical significance.
Alteration of Blood During Acute Hypotension: Effect of Continuous Glass Wool Filtration
Authors: SWANK ROY L. , ISSELHARD WOLF H. , HISSEN WOLFGANG , MERGUET HANS 
Published: June 2012

Acute hypotension was produced in heparinized and nonheparinized dogs by hemorrhage and by injections of histamine, and adhesiveness and aggregation of blood elements determined periodically by the screen filtration pressure method. This method measures the pressure required to force blood at a constant rate through a standardized screen with multiple square holes each 20 x 20 micra. In some cases the arterial blood was perfused through a glass wool filter in an extracorporeal system both before and during periods of hypotension. The results of these studies justify the following conclusions:
1. Increased adhesiveness and aggregation of platelets and other blood elements which occur during hypotension produced by hemorrhage or intravenous injections of histamine were indicated by an increase in the screen filtration pressure of blood. These changes were not prevented from developing, or significantly altered by heparinization of the animal.
2. The amount of blood which could be obtained during arterial hemorrhage was significantly increased by heparinization of the animal.
3. The adhesive and aggregated platelets and leucocytes, which formed during hypotension, were removed from the blood when it was perfused through a column of glass wool. This treatment was attended by a decrease in the screen filtration pressure of the blood to or below normal.
4. The increase in screen filtration pressure which occurred during hypotension was much less marked if the animals' blood had first been circulated through pyrex glass wool.
5. Filtration of blood through pyrex glass wool was also attended by a progressive decrease in the mean arterial blood pressure of the animal.
Control of Coronary Blood Flow by an Autoregulatory Mechanism
Authors: MOSHER PAUL , ROSS JOHN , MCFATE PATRICIA ANN , SHAW ROBERT F. 
Published: June 2012

Control of the coronary circulation has been investigated in an experimental preparation in which coronary flow was suddenly increased or decreased by the imposition of sudden changes in coronary perfusion pressure during periods of constant cardiac performance.
The transient response to these changes in coronary perfusion pressure was an initial abrupt change in flow in the same direction, followed by a prompt return of flow toward the previous level. The response was completed in 10 to 15 sec, and was followed by a few cycles of damped oscillation having a period of 10 to 12 sec.
Steady-state pressure-flow curves demonstrated a range of perfusion pressures over which coronary blood flow was relatively independent of pressure. Below this pressure range the coronary bed appeared to be fully dilated, and the blood flow was directly dependent upon perfusion pressure.
Elevation of the level of cardiac function resulted in autoregulation of coronary flow at a higher level of flow, and decreasing the level of cardiac function resulted in regulation of coronary flow at a lower flow rate.
Instantaneous pressure-flow characteristics of the coronary bed, exclusive of compensatory influences, were also determined.
The experiments demonstrated an intrinsic mechanism that regulated blood flow to the myocardium. In the physiologic range of arterial pressure, coronary perfusion pressure did not appear to be a major determinant of coronary blood flow. Coronary flow appeared to be autoregulated at a level related to myocardial effort.
Control of Renin Secretion
Authors: SKINNER SANDFORD L. , MCCUBBIN JAMES W. , PAGE IRVINE H. 
Published: June 2012

Renin secretion was found to be controlled by a renal baroreceptor rather than by ischemia. Development of a sensitive assay technique that detects renin in small quantities of renal venous and peripheral arterial plasma has permitted the demonstration that the rate of renin secretion varies inversely with the level of arterial pressure independently of renal blood flow.
When mean renal perfusion pressure was reduced 5 to 40 mm Hg by a constricting band around the aorta above the level of the renal arteries, increased renin secretion commenced within 60 seeonds. Reductions of this magnitude did not necessarily cause mean perfusion pressure to fall below control levels of diastolic perfusion pressure. Rises in perfusion pressure had the reverse effect, reducing the rate of renin secretion again without measurable change in renal blood flow. Compression of the kidney within an oncometer by an applied forece of from 15 to 40 mm Hg also caused increases in the rate of renin secretion in the absence of change in total renal blood flow. Reduction of pulse pressure alone did not provoke secretion of renin, nor did reduced oxygen tension, or renal ischemia. Rise in perfusion pressure due to occlusion of the common carotid arteries was associated with reduction in the rate of renin secretion.
A small amount of renin was secreted continuously under the conditions of these experiments; physiologic changes in mean perfusion pressure served to alter the rate. This suggests that a renal baroreceptor mechanism regulates renin secretion under normal circumstances and that arterial pressure tends to stabilize at a level at which renin secretion is minimal.
Circulatory Changes Following Birth of the Calf and the Effect of Hypoxia
Authors: REEVES JOHN T. , LEATHERS JAMES E. 
Published: June 2012

Circulatory and ventilatory measurements were made during the course of 66 cardiac catheterizations in 20 unanesthetized Jersey calves, age two hours to eight weeks. The salient findings were:
1. The pulmonary arterial pressure was high during the first two to three hours of extra-uterine life (up to 80 mm Hg) and it decreased rapidly (30 to 40 mm Hg) during the next nine to ten hours.
2. The pulmonary ventilation appeared good, judging by the active appearance of the calves, the volumes of respired air, the arterial blood gases, and the ventilatory response to hypoxia.
3. The pulmonary blood flows in these calves were not higher in the first hours of life than on subsequent days, and there was little contribution to the pulmonary blood flow by a left to right shunt through the ductus arteriosus.
4. Hypoxia, if severe, could increase the pulmonary arterial pressure to systemic levels on the day of birth, but not in older calves.
5. Pulmonary vasoconstriction sometimes followed puncture of the aorta or other procedures in calves less than twelve hours old. The lability of the pulmonary blood vessels during the first hours of extra-uterine life suggested that large changes in pulmonary vascular tone also occur in utero.
Instantaneous Pressure Distribution Along the Human Aorta
Authors: LUCHSINGER PETER C. , SNELL ROBERT E. , PATEL DALI J. , FRY DONALD L. 
Published: June 2012

Pressures at various points of the human aorta were recorded and resolved into their sinusoidal components by Fourier analysis. A progressively decreasing phase angle with distance along the aorta was found. This was considered compatible with a traveling wave system. The pressure moduli generally increased with distance along the aorta. This was attributed to the progressively increasing stiffness of the aorta peripherally. Minor undulations in moduli could be explained on the basis of superimposed reflections.
The apparent phase velocities were calculated for various points along the aorta. They tended to converge at higher frequencies to a value of 5 m/sec.
Systemic and Coronary Energetics in the Resting Unanesthetized Dog
Authors: GREGG DONALD E. , KHOURI EDWARD M. , RAYFORD CLAUDIA R. 
Published: June 2012

This report is an initial attempt to study the coronary circulation in the chronic unanesthetized dog. A standardized preparation has been developed in which phasic aortic pressure and flow, phasic left coronary inflow, and myocardial metabolism have been studied for many weeks in the unanesthetized dog under resting conditions.
The flow patterns in the main left coronary artery and in its major branches are very similar. In the resting dog, the left coronary inflow during systole is 7 to 45% of that during diastole. We believe that much of this flow into the epicardial arteries penetrates into the myocardium. Stroke coronary flow can change considerably without significant alterations of blood pressure and heart rate. Despite this, the coronary flow values (37 to 58 cc) and oxygen usage values (4.4 cc to 8.6 cc) per 100 grams left ventricle per minute are low. Since, however, these measurements can vary considerably not only in different dogs but also in the same dog on the same day, and from day to day, it is suggested that these animals were in a semiresting state and probably not in a basal state.
Oscillatory Flow Impedance in Electrical Analog of Arterial System:
Authors: JAGER GERARD N. , WESTERHOF NICO , NOORDERGRAAF ABRAHAM 
Published: June 2012

In the analog computer for the human systemic circulatory system, the electrical equivalents of a segment of artery as designed up till now are not satisfactory, because they lack representation of the sleeve effect, which results from the interaction between viscous and inertial forces during pulsatile blood flow. First, a network which accounts for this effect was derived, starting out from entirely different equations. It was surprising to find that this does not alter the circuit completely, but only requires adding to the former circuit a corrective network which, however, may have considerable influence.
Second, the effect of the anomalous viscosity of blood was taken into account. Its influence on oscillatory flow has been investigated by Taylor, who derived an expression for the relation between pressure-gradient and flow under the assumption that there exists a small boundary layer of lower viscosity at the wall, and found a similar formula for the case in which the blood is assumed to slip at the wall. The modifications of the electrical circuit, necessary to represent these conditions, are given in this paper and turn out to be remarkably simple.
Steroids Produced in Vitro by Adrenal Glands of Normal and Arteriosclerotic Rats During and After Drug-Induced Myocardial Necrosis
Authors: WEXLER BERNARD C. , KITTINGER GEORGE W. , Schreiber Joan E. 
Published: June 2012

The subcutaneous injection of the potent catecholamine, isoproterenol, on two consecutive days causes active and massive myocardial necrosis in rats. Infarctoid myocardial necrosis was produced in male and female virgin rats free of arterial disease, in male breeder rats which have microscopic arteriosclerosis only, and in female breeder rats having early or advanced gross arteriosclerosis. During the active development of myocardial necrosis and heart failure, an apparent shift in distribution of body fluid produced systemic dehydration, pulmonary edema, and hydrothorax. Animals which survived the myocardial destruction showed gradual reduction of the congestive heart failure and beginning myocardial repair. Virgin animals with no pre-existing arterial disease developed more severe signs of shock and congestive heart failure than breeder rats with pre-existing arteriosclerosis.
In vitro estimation of the adrenal steroids produced by the animals with myocardial necrosis indicated intense in vivo stimulation of adrenocorticoid production coincident with the increasing severity of the myocardial necrosis. Steroid production returned to normal during progressive myocardial repair. Virgin rats showed a very prompt adrenal response to the stress of myocardial destruction but breeder rats, which also have pre-existing reduced adrenal function, showed a lag in the response of their adrenal glands. Chemical and histological analyses of the adrenal glands indicated a pronounced increase of aldoster-one production during the experiment, this increase being associated with loss of fluid and electrolytes from the vascular space. The production of aldosterone appears to be vital to the physiological adjustments needed by these animals during heart failure because the production of aldosterone seems to occur at the expense of the other adrenal steroids, e.g., corticosterone, 18-hydroxy-deoxycorticoster-one and total steroid. These comparative studies suggest that adrenal responsiveness during the stress of myocardial infarctoid necrosis is quantitatively different in animals free of previous arterial disease from that found in animals with pre-existing microscopic or grossly visible arteriosclerosis. The specific kind and the amount of adrenal steroid produced during myocardial destruction may be of vital importance for survival.
Direct Renal Vasodilatation Produced by Dopamine in the Dog
Authors: McNAY JOHN L. , McDONALD ROBERT H. , GOLDBERG LEON I. , Davis Carolyn 
Published: June 2012

The effects on directly measured renal blood flow, mean blood pressure, and calculated renal vascular resistance of intravenous infusions of dopamine, isoproterenol, and norepinephrine were compared. Dopamine, at doses not affecting mean blood pressure, decreased renal vascular resistance and increased renal blood flow. In contrast, isoproterenol decreased both blood pressure and renal vascular resistance but did not consistently increase renal blood flow. Renal artery injection of dopamine produced vasodilatation at doses ranging from 0.75 to 12 µg and biphasic flow responses including transient vasoconstriction at higher doses. It is concluded that the probable basis for the effect of intravenous dopamine infusion on renal blood flow is its direct renal vasodilating action.
The direct effect of dopamine on the femoral vascular bed is vasoconstriction. The combination of renal vasodilating, and femoral vasoconstricting, effects is unique and is interpreted as evidence for a renal vasodilating effect of dopamine distinct from the conventional beta-adrenergic mechanism. A possible physiological role for dopamine other than as a precursor to norepinephrine may be related to this property. It is also suggested that the ability of dopamine to alter the distribution of cardiac output in favor of visceral organs may find useful clinical applications.
Polycythemia and Right Ventricular Hypertrophy
Authors: SWIGART RICHARD H. 
Published: June 2012

Polycythemia was induced in rats by injecting 10 mg CoCl
2
/kg body wt/day intraperitoneally or by placing them in a low pressure chamber at a reduced barometric pressure equivalent to 18,000 feet of altitude for approximately 23 hours/day. After 63 days of treatment a significant hypertrophy of the right ventricular wall was found in both groups of animals. The increase in weight of the right ventricle in the CoCl
2
-injected rats was approximately 45% of that found in rats exposed to chronic hypoxia.

Polycythemia was induced in mice by injecting 0.5 ml of packed, whole erythrocytes per day, intraperitoneally, for four consecutive days. A high hematocrit was maintained by additional periodic intraperitoneal injections of erythrocytes. After twenty-two days a significant right ventricular hypertrophy was observed.
It is concluded that polycythemia and hypervolemia are important factors in producing right ventricular hypertrophy in rats and mice without airway hypoxia and also may be significant factors in the cardiac hypertrophy induced by high altitude.
Action of Driving Stimuli from Intrinsic and Extrinsic Sources on in Situ Cardiac Pacemaker Tissues
Authors: LANGE GERTRUDE 
Published: June 2012

The interactions between pacemakers, and the effects on pacemakers, of terminating imposed driving were studied in the
in situ
heart 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.
Overestimation of Left Ventricular Volume by the Indicator Dilution Technique
Authors: Carleton Richard A. , Bowyer Allen F. , Graettinger John S. 
Published: June 2012

The applicability of the indicator dilution method to the measurement of left ventricular volume has been studied. When compared with angiocardiographic measurements, the dilution technique overestimates volume by an average of 52 and 91% in end diastole and end systole respectively. Studies which demonstrated more rapid indicator washout from the outflow than from the apical portion of human and canine left ventricles suggest that faulty intraventricular indicator dispersion is the major cause of the volume over-estimates yielded by the dilution method. Procedures designed to alter ventricular size by altering venous return produced parallel changes in ventricular circumference and in ventricular indicator washout volume.
The indicator dilution method does not provide a measure of left ventricular volume, but may, in carefully designed studies, yield an index of changes in ventricular size.
The Rabbit Placenta as an Organ of Diffusional Exchange
Authors: FABER J. JOB , HART FREDERICK M. 
Published: June 2012

The umbilical arteries of intact, in-situ placentas of one series of anesthetized rabbits were perfused with deoxygenated blood equilibrated with 10% or 20% acetylene and in another series with oxygenated blood without acetylene. The transfer of acetylene, and probably also of oxygen, were shown not to be limited by diffusion. Above the normal physiological rates of fetal placental flow, oxygen uptake in the fetal placental circulation did not increase appreciably with an increase in the rates of perfusion; below it, it decreased almost proportionally with a decrease in the rate of perfusion.
To explore the applicability of these results to the human placenta, the experimental data were reduced to dimensionless form. It was shown that three dimensionless variables suffice to describe the characteristics of diffusional exchange in the placenta. The dimensionless diagrams were very similar for the ideal countercurrent exchanger and for the rabbit placenta but these differed from diagrams made from data published on human, sheep, cow, and monkey placentas. The authors propose the dimensionless diagram as a concise description of the passive transfer characteristics of a placenta, at least until measurements of vascular geometry, regional permeabilities and flow patterns allow the calculation of mean diffusion gradients.