bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretic Analysis of the Influence of Heart-Dipole Eccentricity on Limb Leads, Wilson Central-Terminal Voltage and the Frontal-Plane Vectorcardiogram
Authors: FRANK ERNEST 
Published: June 2012

This is a theoretic investigation of the influence of the position of a current dipole on the electric potential produced at the boundary of a homogeneous conducting sphere. Thirty different eccentric dipole positions are selected within the sphere to bear analogy to locations of the equivalent dipole of the human heart within the chest, and boundary-potential calculations are made from points selected to bear analogy with body-surface points utilized in limb leads, Wilson centralterminal and frontal-plane electrocardiography. The point of view taken differs completely from the scalene-triangle geometric representation of eccentricity; instead, an equilateral triangle is used in conjunction with assigned strength and orientation time-variations for the eccentric dipole.
It is concluded that if electrocardiography were subject to no other limitation of the application of field analysis, eccentricity of dipole position alone can produce very significant deviations between the manifest heart vector and the true heart vector in both direction and magnitude. The dependence of the Wilson central-terminal voltage on dipole eccentricity is likewise appreciable and of the same order of magnitude as reported by several experimenters; however, the effects of eccentricity on the Wilson central-terminal voltage are generally less pronounced than on the manifest heart vector.
Analysis of the Acute Circulatory Effects of Guanethidine and Bretylium
Authors: Gaffney Thomas E. , Braunwald Eugene , Cooper Theodore 
Published: June 2012

The acute effects of guanethidine and bretylium on myocardial contractile force, heart rate, mean arterial pressure, and cardiac out put were studied in normal dogs and cardiac denervated, myocardial catecholamine-depleted dogs. Right ventricular contractile force was measured by means of a Walton-Brodie strain-gauge arch. Cardiac output was measured by the dye-dilution technique.
In normal dogs, guanethidine produced marked increases of myocardial contractile force, heart rate, cardiac output, and arterial pressure. In the cardiac-denervated dogs. guanethidine produced a small decrease in myocardial contractile force and a small increase in heart rate ; the cardiac output and pressor responses were also markedly reduced. Thus, it appears that sudden release of myocardial eateeholamines is largely responsible for the acute circulatory effects of guanethidine.
In normal dogs, bretylium increased myoeardial contractile force, heart rate, cardiac output, and arterial pressure. In cardiac denervated dogs, the increase in contractile force produced by bretylium was essentially unchanged from the normal, but the heart rate was decreased, and the cardiac output response appeared slightly reduced. These data suggest that myocard ial catecholamine release plays a limited but definite role in the acute circulatory effects of bretylium.
The negative inotropic effect of guanethidine and the negative chronotropic effect of bretylium in the denervated. amine-depleted heart suggest that these responses are direct effects of these drugs which are manifest only in the amine-depleted heart.
Evaluation of Procedures Designed to Enhance Coronary Collateral Blood Flow
Authors: Berne Robert M. , Jones Richard D. , Cross Frederick S. 
Published: June 2012

Three procedures reported to improve the coronary collateral circulation were carried out in dogs: (1) placement of 0.25 to 0.5 Gm. of sterile shredded asbestos over the surface of the heart; (2) suturing of the mediastinal fat pad to the abraded left lateral surface of the heart in conjunction with the application of asbestos; (3) implantation of the internal mammary artery into the left ventricular wall in conjunction with application of Ivalon sponge to the denuded surface of the left ventricle.
The effectiveness of these measures was determined in dogs with previously narrowed left circumflex coronary arteries. As judged by retrograde flows and peripheral coronary pressures, the collateral vessel development was not increased over and above that produced by narrowing alone. Coronary artery injection studies revealed that only internal mammary artery implantation produced vascular connections between cardiac and extra-cardiac vessels.
Relation of Renin and Angiotensin II to the Control of Aldosterone Secretion
Authors: Davis James O. , Carpenter Charles C. J. , Ayers Carlos R. 
Published: June 2012

1. Evidence is presented to show that the renin-angiotensin system leads to increased aldosterone secretion following acute blood loss, during experimental heart failure, during thoracic inferior vena cava constriction, during chronic sodium depletion and in malignant experimental renal hypertension. Since alterations in sodium intake constitute one of the most important factors in the daily regulation of aldosterone secretion, studies of sodium-depleted animals suggest that the renin-angiotensin system is important in the physiological regulation of aldosterone secretion.
2. Renin appears to be secreted by the juxtaglomerular cells of the kidney. Some hemodynamic alteration secondary to a decrease in pressure and flow through the kidney leads to release of renin by the juxtaglomerular cells. Available data indicate that angiotensin II acts on the zona glomerulosa of the adrenal cortex to promote aldosterone production.
Renal Medulla and Renoprival Hypertension
Authors: Muirhead E. E. , Kosinski Mary 
Published: June 2012

A crude extract of renal medulla (medullorenal extract) has been studied in relation to a crude extract of renal cortex which possessed potent renin pressor activity. The medullorenal extract either effected no immediate change in the arterial pressure or caused a mild to moderate pressor effect. The latter was thought to be due to contamination with renin, since precise separation of cortex and medulla may not have been consistent. The medullorenal extract did not display a sustained, acute depressor effect. The extract was not pyrogenic in rabbits.
The production of renin pressor effect in nephrectomized dogs did not alter the evolution of renoprival hypertension. The mixture of renin and nonrenal extracts did not alter the evolution of renoprival hypertension in the dog. The medullorenal extract, on the other hand, prevented renoprival hypertension in the presence of daily renin pressor responses. The latter results were similar to those obtained when renin was infused in normal dogs.
The results suggest that the medullorenal extract protected against renoprival hypertension by a route other than one directly related to the renin-angiotensin system. Such a route could be due to an effect on small arteries and arterioles. The results also are consistent with an active principle in the medullorenal extract which reproduces the function of intact renal tissue.
Left Ventricular Function Described in Physical Terms
Authors: Franklin Dean L. , van Citters Robert L. , Rushmer Robert F. 
Published: June 2012

A description in standard physical terminology of the variations of the left ventricle in its role as a pump was derived. Left ventricular pressure, left ventricular outflow, and an external dimension of the left ventricle were measured in unanesthetized, active dogs during spontaneous activities and infusions of autonomic drugs. Secondary variables pertinent to a functional description of a pump were derived continuously from the primary variables by analogue computers. The derived variables included stroke volume, cardiac output, effective power, stroke work, average power, volume acceleration, rate of change of pressure, duration of systole, and heart rate.
These techniques allowed a detailed description in meaningful terminology of the integrated effects on the left ventricle of such stimuli as sleep, startle, exercise, postural variations, and infusions of autonomic drugs.
The descriptions of the variations in the characteristics of the left ventricle allow tests to be made of hypothetical cardiovascular control mechanisms. The use of standard, well-accepted, physical terminology allows the descriptions to be evaluated in different laboratories by totally different measuring techniques. The terminology used was contrasted with operationally denned or ambiguous terms such as "contractility" or "vigor of contraction."
Production of Ulcerated Atherosclerotic Lesions in Cockerels
Authors: Pick Ruth , Katz Louis N. , Century Dolores , Johnson Philip J. 
Published: June 2012

1. Ulcerated abdominal aorta and coronary lesions have been produced in cockerels.
2. The prerequisite for ulceration is a lesion previously induced by a high-cholesterol, high-fat, low-protein diet, followed by the administration of large doses of estrogens.
3. The possible mechanisms leading to ulceration have been discussed.
Determination of Infused Epinephrine and Norepinephrine in Plasma Using Isolated Guinea Pig Heart Technique
Authors: Booker Walter M. , Walton Tracy , Linares Rafael , De Schaepdryver Andre F. 
Published: June 2012

Experiments have been described which show the very high sensitivity of the isolated perfused guinea pig heart preparation in the estimation of plasma levels of catecholamines after intravenous infusion in dogs. It was observed that crude plasma samples show the same pattern of positive inotropic response as extracts of these samples. By means of the isolated guinea pig heart method, the presence of circulating catecholamines could still be detected 30 minutes after the end of infusion.
The observation that dichloroisoproterenol may block the positive inotropic effect of epinephrine, while only slightly reducing the positive inotropic effect of norepinephrine, may be used to differentiate between these two catecholamines.
Distribution of Heart Potentials on Dog's Thoracic Surface
Authors: Taccardi Bruno 
Published: June 2012

The distribution of equipotential lines on the surface of the trunk has been determined experimentally in the dog at 8 to 15 instants of time during ventricular depolarization. Multiple potential maxima and minima are simultaneously present on the explored area during a large part of the activation time: their number, shape, and location vary continuously during ventricular excitation, following the same general scheme in all the animals studied.
The single dipole theory does not account for the experimental data, reported in this paper. As far as surface potentials are concerned, the dog heart behaves as a multipolar generator.
Complete exploration of the chest surface yields much more information about the electrical activity of the heart than is obtainable from routine limb and chest electrocardiograms.
The relationships between the location of the potential maxima and minima on the body surface and the probable situation of the excitation waves in the heart are tentatively discussed.
Resistivity of Body Tissues at Low Frequencies
Authors: RUSH STANLEY , ABILDSKOV J. A. , MCFEE RICHARD 
Published: June 2012

The resistivity of tissues of the thorax of dogs has been measured in situ under nearly normal conditions. Additional data have been obtained from humans.
Approximate values of tissue resistivity found are 160 ohm-cm for blood, 2,000 ohm-cm for lung, 2,500 ohm-cm for fat, 700 ohm-cm for liver, 250 and 550 ohm-cm (anisotropic) for heart muscle and 150 and 2,500 ohm-cm (anisotropic) for skeletal muscle. Reasons for the differences between these and previously reported values have been found, and in some cases, verified experimentally. Predictions of whole trunk resistivity based on anatomical data and these measurements are within 8% of actual trunk measurements.
Production of Arterial Lesions by a Humoral Factor in Parabiotic Rats
Authors: PATEK PAUL R. , BERNICK SOL , MACCALLUM DONALD K. 
Published: June 2012

The experimental production of arteriosclerosis and atherosclerosis by RES blocking agents such as colloidal carbon and thorium dioxide has implicated the RES as a factor in the etiology of these diseases. Holtzman strain male rats each received a single intravenous injection of colloidal carbon (5 mg/100 g animal body wt). Three days later the injected animals were united by parabiosis to non-injected animals of the same sex, weight and genetic strain.
Carbon granules were found in the RES of injected rats, but few or no granules were found in Kupffer cells of their non-injected parabiotic partners. Coronary arteries of both injected and non-injected animals showed thickening and fragmentation of the internal elastic membrane after two months. After four to six months the lesions included degenerative changes of muscle cells just external to the internal elastic membrane and thickening of the intima. Hyperplasia of the thyroid was found in both parabionts.
Addition of 1% cholesterol-5% fat to the diet caused deposition of lipid in endothelial cells and intimal macrophages of the damaged arteries of both parabionts. Distribution of lipid within the hepatic parenchymal cells was also altered in the experimental animals but not in controls.
It is suggested that uptake of particulate matter by cells of the RES causes them to release a substance capable of producing arterial lesions.
Cardiovascular Effects of Infusions of Epinephrine and Angiotensin Singly and in Combination
Authors: BINNION PETER F. , HATCHER J. DONALD 
Published: June 2012

Angiotensin infused at 0.05 mcg/kg per min for 30 minutes into anesthetized dogs reduces cardiac output, raises arterial blood pressure, increases total peripheral resistance, but does not raise right ventricular pressure nor change left ventricular stroke work. It is suggested that this infusion rate may be comparable to the rate of production under certain conditions.
The cardiovascular action of epinephrine given at rates similar to those occurring under stress, namely 0.1 mcg/kg per min and 0.2 mcg/kg per min for 30 minutes, are discussed. In the former dose no cardiovascular effects are seen, but with the latter dose the usual cardiovascular effects were observed.
A transient augmentation of effect on cardiac output and stroke work is noted with a combination of epinephrine 0.1 mcg/kg per min and angiotensin 0.05 mcg/kg per min, and of stroke work alone when the dose of each is doubled. It is suggested that the physiological importance of this interaction may be limited to the initial phases of certain stresses in which both these substances are released. The mechanism of this effect is not clear, but may be the result of the interaction of epinephrine, angiotensin and aldosterone.
Influence of Respiratory Acidosis on Circulatory Effect of Epinephrine in Dogs
Authors: BENDIXEN HENRIK H. , LAVER MYRON B. , FLACKE WERNER E. 
Published: June 2012

The circulatory depressant effects of respiratory acidosis and the relation between acidosis and the circulatory effects of epinephrine were studied in anesthetized intact dogs after sympathetic and parasympathetic block. Respiratory acidosis invariably depressed myocardial contractile force, cardiac rate, and mean arterial pressure, but only the fall, in contractile force showed a relation with the degree of acidosis.
The effect of epinephrine on myocardial contractile force decreased with decreasing arterial pH, but no correlation was found between pH and the effect of epinephrine on arterial blood pressure and on cardiac rate. During continuous infusion of epinephrine, arterial pressure continued to rise after the contractile force had reached its maximum. With repeated periods of epinephrine infusion in the same animal, the response of the myocardial contractile force declined, while the response of the arterial blood pressure was unchanged. Such "differential tachyphylaxis" may occur under clinical conditions with prolonged infusions of vasopressor agents.
An Analysis of Arrhythmias Induced by Ouabain in Intact Dogs
Authors: Vassalle Mario , Greenspan Kalman , Hoffman Brian F. 
Published: June 2012

The results of this study show that ouabain administration quite often causes idioventricular automaticity to undergo an initial depression and a subsequent enhancement. When the electrocardiogram shows normal sinus rhythm these changes in ventricular automaticity can be unmasked by vagal stimulation which causes either sinus arrest or atrioventricular block. On occasion, the depression of idioventricular automaticity is permanent; if ouabain produces complete atrioventricular block at this time, ventricular arrest ensues. When, on the contrary, the automaticity of Purkinje fibers is progressively enhanced, a stage is reached in which the idioventricular rhythm becomes faster than the sinus rhythm. Eventually the basic ventricular rhythm exhibits pauses during which electrocardio-graphic complexes of different form become apparent.
The second class of arrhythmias comprises extrasystoles which may or may not show a constant coupling to sinus beats but which are characterized by a dependence on an initiating beat. It was demonstrated in this investigation that these extra beats appear during slow intravenous administration of ouabain and that they disappear not only on suppression but also on slowing of the sinus rhythm. Furthermore, it was shown that bigeminal rhythm may be transformed into extrasystoles occurring after every second sinus beat by means of vagal stimulation which slows the sinus rate. If, however, the heart was driven at faster rate, several extrasystoles followed one atrial beat. At a more advanced stage of ouabain intoxication these extrasystoles lose their fixed relationship with the sinus beat and runs of self-sustaining tachycardia appear. Such runs of ventricular tachycardia are unaffected by vagal stimulation but have a tendency to subside, spontaneously, and start anew after another initiating sinus beat. If vagal stimulation inhibits the initiating beat, the run of tachycardia also is suppressed. At an advanced stage of intoxication, however, when polymorphic ventricular complexes are present, vagal stimulation no longer produces any apparent effects.
Finally, this investigation has shown that, during vagal stimulation which produces sinus arrest or A-V block, atrial fibrillation can be initiated by retrograde transmission of ventricular escape beats even though atrial escape beats are ineffective in eliciting the same phenomenon.
Effect of Epinephrine on the Mechanical and Phosphorylase Activity of Normo-and Hypothermic Hearts
Authors: NAYLER WINIFRED G. , WRIGHT JULIET E. , HOWELLS JANET 
Published: June 2012

The effect of temperature on the action of epinephrine and on the percentage of the enzyme phosphorylase present in the a form in isolated rat (homeothermic) and toad (poi-kilothermic) hearts was investigated.
Rat hearts responded to cold per se with reduced amplitude of contraction and bradycardia. The percentage of the phosphorylase enzyme which was in the a form declined as the perfusion temperature fell. Mechanical activity ceased when rat hearts were perfused at temperatures below 10°C. Epinephrine failed to exert a positive inotropic effect when added to rat hearts perfused at 12°C; at this temperature epinephrine increased the phosphorylase a activity to only 42% compared with 66% at 35°C.
The response of toad hearts to cold per se differed from that of rat hearts. At 2°C the contractile amplitude of toad hearts was maximal and the phosphorylase a activity was well maintained. Stimulation enhanced, DCI and preliminary reserpinisation reduced the proportion of the enzyme which was in the a form in 2°C toad hearts.
It is suggested that poikilothermic hearts may respond to cold by releasing their endogenous catecholamines and that this may be indirectly responsible for the ability of poikilothermic cardiac tissue to withstand low temperatures.
Renal Effects of Angiotensin II Infusions in Normotensive Pregnant and Nonpregnant Women
Authors: CHESLEY LEON C. , WYNN RALPH M. , SILVERMAN NEIL I. 
Published: June 2012

Normotensive pregnant women are relatively resistant to angiotensin II in that they give smaller pressor responses and show smaller reductions in urine flow and sodium and chloride excretions than do normotensive nonpregnant women.
Women early in the third trimester of pregnancy are more resistant to angiotensin II than are women at term, with respect to the effect upon sodium and chloride excretions.
The less pronounced renal effects of angiotensin II in pregnant women cannot be attributed merely to error caused by increase in the dead space of the urinary tract.
Functional Properties of the Atrioventricular Conduction System
Authors: HOFFMAN BRIAN F. , MOORE E. NEIL , STUCKEY JACKSON H. , CRANEFIELD PAUL F. 
Published: June 2012

Experiments were designed to study A-V transmission of premature atrial responses by recording electrical activity directly from selected parts of the conducting system. This experimental design permits a more exact interpretation of results than is the case when records are obtained only from the atria and ventricles.
Two types of experiments have been conducted in studies of the response of the specialized conducting system of the mammalian heart to premature activation. Records of transmembrane potentials from single fibers of the A-V node and Purkinje system show that premature responses may show a reduced rate of rise and amplitude and thus may be conducted slowly or may decrement completely. Under other conditions, premature responses may show local delay or block because they arise from a local response of considerable duration.
Records obtained directly from different parts of the in situ specialized conducting system show that the same phenomena probably occur in the intact, normal heart. These properties of the various fibers of the conducting system, in conjunction with the normal local differences in action potential duration, conduction velocity, and excitability, seem to account quite adequately for the variations which have been noted during A-V propagation of premature responses. On the basis of these results, it seems unnecessary to postulate a dual A-V conducting system in the mammalian heart.
Angiotensin in Blood and Lymph Following Reduction in Renal Arterial Perfusion Pressure in Dogs
Authors: SKINNER SANDFORD L. , MCCUBBIN JAMES W. , PAGE IRVINE H. 
Published: June 2012

Systemic pressor responses occurred consistently 5 to 15 minutes following reduction of renal perfusion pressure and were accompanied by the appearance of pressor material in renal vein blood. The pressor material is probably angiotensin formed from renin released by the kidney, since its activity was not affected by protein precipitation, was eliminated by incubation with chymotrypsin, and since it caused enhanced pressor responses to tyramine, all of which are characteristic of angiotensin. Activity was unaffected by pharmacologic blockade of response to norepinephrine and serotonin. Its renal origin is indicated by the greater amount of pressor activity in renal venous than in arterial blood throughout the systemic pressor responses.
Smaller amounts of pressor material, also with properties of angiotensin, were found in thoracic duct lymph. They did not contribute materially to the systemic pressor response since external drainage of all lymph did not modify the response, and since the time course of the response correlated with an increase in pressor activity in renal vein blood but not in lymph. The late appearance of angiotensin in thoracic duct lymph is probably due to renin secretion by the kidney into renal lymph rather than transfer from circulating blood; activity did not appear in lymph when renin was infused intravenously in amounts that caused rises in systemic pressure comparable to those produced by reduction of renal perfusion pressure.
The results indicate that during short periods of reduced renal perfusion pressure, renin is released in larger amounts in blood than in lymph.