bluuebunny/crossref_metadata_2025 huggingface dataset:
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."
Role of Calclum and Lanatoside C in Increasing Oxygen Consumption in Human Myocardial Tissue Slices
Authors: Crevasse Lamar , Wheat Myron W.
Published: June 2012

1 x 10
-6
M Lanatoside C has been demonstrated to produce a sustained increase in oxygen consumption in human myocardial tissue slices as previously demonstrated by Burdette. This acceleration of qO
2
is independent of the substrates employed with the exception of succinate. This qO
2
acceleration has been demonstrated to be calcium dependent in human heart tissue slices similar to the known interrelationship of calcium and digitalis on myocardial contractility. The observation that the greatest increase in qO
2
occurred with glucose and without exogenous substrate suggests that the increase in qO
2
induced by the glycoside is dependent upon a stimulatory effect on glycolysis.
Effect of Antiheparin Agents on Venous Thrombosis Following Vascular Injury
Authors: Mersereau William A.
Published: June 2012

The effect of the antiheparin agents hexadimethrine bromide and protamine sulfate on venous thrombosis have been studied in the rat, rabbit, and dog. Untreated traumatized veins were not thrombosed. Traumatized veins treated with these agents topically, or in some species intravenously, thrombosed. The thrombi so produced consisted of an occluding mass of platelet trabeculae at the site of vascular injury, a red and white proximal tail, and a distal stasis clot. The hexadimethrine bromide-induced thrombus in the rat is prevented by pretreatment with Dicumarol or heparin. It is suggested that the antiheparin agents bring about thrombosis of the injured veins by neutralizing an anticoagulant liberated locally.
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.
Stability of Fibrin Contiguous to Intima of Veins
Authors: Messer Dale L. , Celander D. Robert , Guest M. Mason
Published: June 2012

A technique is described which employs an everted segment of canine jugular vein to study the effect of the intima on contiguous fibrin. Following eversion of the vein on a stainless steel rod of suitable dimensions, the vein was coated with a layer of fibrin by winding it onto the endothelial surface. The rate at which soluble Folin-Ciocalteu reactive material appeared in the incubated media of clots so prepared was significantly higher than that developed in systems containing either everted vein alone or fibrin alone. EACA suppressed the liberation of soluble tyrosine from contiguous fibrin but was without effect on the liberation of soluble Folin-Ciocalteu reactive material from the vein alone.
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.
Extensive Intraventricular Conduction Defect
Authors: Wennemark James R. , Blake David F. , Kezdi Paul , Lev Maurice
Published: June 2012

Destruction of the entire canine right ventricular Purkinje-net system, by the introduction of dilute Lugol's solution into the right ventricular cavity, results in an intraventricular conduction defect which is 20 to 30 msec. greater in duration than that of right bundle-branch block. The mode of right ventricular surface activation is altered. A characteristic electrocardiographic and vectorcardiographic pattern is produced. Histological studies confirmed the absence of Purkinje-net cells in animals with chronic block.
Spontaneous and Stress-Induced Myocardial Infarction in Aged Atherosclerotic Dogs
Authors: Sobel Harry , Mondon Carl E. , Straus Reuben
Published: June 2012

Male, mongrel dogs, six to eight years of age, were placed on an atherogenic regimen which included I
131
administration and/or thiouracil with cholesterol feeding and, in some cases, the addition of 10 per cent lard to the diet. As is usually observed in such experiments, the degree of hypercholesterolemia and atheromatosis varied greatly. However, in nine out of ten dogs with blood cholesterol levels of 1,800 mg. per cent or above for over 16 weeks, myocardial infarction appeared (a) spontaneously, (b) after pitressin administration, and (c) after exposure to a stresser. Myocardial infarction has been noticed only rarely previously. Reasons are given for the belief that the advanced age of the animals which were used here played a role in the genesis of infarction.
Pulmonary Arterial Tree following Prolonged Experimental Reduction of Pulmonary Blood Flow
Authors: NAEYE RICHARD L. , KUSSEROW BERT K. , JACOBSON JULIUS H.
Published: June 2012

A Blalock anastomosis between the left subclavian artery and the left pulmonary artery was performed on six dogs soon after birth. As an unexpected complication of surgery, blood flow through the left lungs of two of the dogs was greatly reduced. Over a period of 22 months, widespread arterial thromboses developed in these two lungs. The thrombotic lesions were comparable to those which develop in human beings with severe pulmonic valvular stenosis or atresia. Hypoxemia and polycythemia have often been implicated in the development of these lesions. Our study demonstrates that such lesions can be induced in the dog by reduction in pulmonary blood flow alone since hypoxemia and polycythemia were absent in our experimental animals.
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.
Electrocardiogram in Rabbit Fetuses
Authors: SAEZ ANTHONY J. , BASMAJIAN JOHN V.
Published: June 2012

Electrocardiograms were recorded by needle electrodes in 137 of 166 rabbit fetuses at 10½ to 31 days. Invariably, electrocardiograms were obtainable from the 12th day on, which in the rabbit is an early stage of development. The earliest electrocardiogram was obtained at 10 days, 22 hours, corresponding to about five weeks in human development. Sinus rhythm was evident from the start. The wave form consists of a pair of complexes 50 to 200 msec apart. The first complex is quite variable but appears to be atrial in origin; the second is surprisingly constant and appears to be ventricular.
Effects of Hemodialysis and of Glucose-Insulin Administration on Plasma Potassium and on the Electrocardiogram
Authors: SURAWICZ BORYS , KUNIN ARTHUR S. , SIMS ETHAN A. H.
Published: June 2012

Hypopotassemia was produced in dogs by hemodialysis or by intravenous administration of glucose with insulin. Both methods resulted in a similar decrease in plasma K concentration and similar ECG changes although K was withdrawn from the cells during dialysis while it entered the cells during glucose-insulin infusion. The maximal plasma K decrease occurred after two hours of dialysis or glucose-insulin infusion; administration of glucose-insulin after dialysis resulted in no further plasma potassium decrease. However, dialysis after glucose-insulin infusion caused further lowering of plasma potassium. The ECG changes were evaluated in relation to changes in plasma K concentration. The most consistent effects of hypopotassemia were in decreasing order: increased duration of the QRS complex, increased duration of the QT
c
interval and increase in amplitude of the P wave. Correlation coefficients (R) between these ECG changes and the plasma K decreases were of the order -0.48 to -0.54. The ECG changes failed to show even a weak correlation with absolute plasma K concentrations or with calculated changes in intracellular K.
Left Ventricular Oxygen Utilization in Intact Dogs: Effect of Systemic Hemodynamic Factors
Authors: NEILL WILLIAM A. , LEVINE HERBERT J. , WAGMAN RICHARD J. , GORLIN RICHARD
Published: June 2012

The influence of acute changes in systemic hemodynamics on the rate of oxygen utilization by the left ventricle has been studied in intact anesthetized dogs. Certain types of hemodynamic changes caused reproducible alterations in the relationship between oxygen consumption of the left ventricle and its external mechanical work. The relationship of left ventricular minute oxygen consumption to the product of mean systolic aortic pressure and systolic ejection period per minute was constant over an extreme range of varied types of hemodynamic alterations. Changes in oxygen consumption were proportionately less than concomitant changes in heart rate. These findings are in accord with previous studies of isolated heart preparations.
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.
On-line Computation of Cardiac Output from Dye Dilution Curves
Authors: HARA HIROSHI H. , BELLVILLE J. Weldon
Published: June 2012

An analog computer circuit for calculating cardiac output and mean transit time has been described which receives as its input the output of a cuvette densitometer. The results obtained with the computer have been compared with those obtained by the usual method.
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.
Two Mechanisms of Cardiac Arrest Produced by Potassium
Authors: SURAWICZ BORYS , GETTES LEONARD S. , SHIVE JAMES C. , BROOKS HARRY O.
Published: June 2012

Ventricular arrest occurs in isolated heart perfused with potassium-deficient solution when the extracellular potassium concentration is suddenly raised to a physiological concentration. This is known as a paradoxical phenomenon of Zwaardemaker and Libbrecht. Records of electrocardiograms, and ventricular and atrial transmembrane potentials from perfused rabbit hearts before, during and after this type of arrest revealed that its mechanism differs from the mechanism of cardiac arrest produced by an increase of external [K] above physiological concentration. The Zwaardemaker-Libbrecht phenomenon is associated with a striking increase in the velocity of repolarization while the typical effects of high-K concentration on the resting membrane potential and amplitude and upstroke velocity of the action potential are either very slight or absent. Conduction in the atria, ventricles and between the atria and the ventricles apparently is not disturbed during the Zwaardemaker-Libbrecht phenomenon; therefore, we attribute the cardiac arrest to a selective inhibition of the pacemaker activity. This might be due to an inhibition of the diastolic depolarization of the pacemaker fibers. A speculation is made that the type of imbalance between the intra- and extracellular K concentration in the myocardium which causes the Zwaardemaker-Libbrecht effect in the isolated heart could occur in situ and cause sudden death.
Eddy Formation and Turbulence in Flowing Liquids
Authors: MEISNER J. E. , RUSHMER ROBERT F.
Published: June 2012

The birefringent properties of a colloidal solution of white Hector bentonite were used as a means of studying the development of flow patterns in transparent models. The liquid had approximately the same viscosity as blood; flow rates were within the physiological range; and some of the flow channels were shaped to resemble portions of the cardiovascular system. The light patterns produced by laminar flow were distinct from those of eddy formation and turbulence. Turbulent flow developed downstream from a constriction, where the velocities of the entering jet were much below the so-called critical Reynolds number. The same flow pattern was observed in a model of aortic stenosis. Also displayed was the flow pattern as it might develop in vivo during midsystole when the semilunar valves are widely opened. Eddies originating from the edges of the valves, the flow around the aortic arch and the effects of the openings of the branches all contributed to a complex turbulent pattern. Eddy formation and turbulence can be produced at low velocities when unsteady flow and sudden changes in diameter occur. This technique is useful in the study of changes in flow pattern under different physiological or pathological conditions. Observations from these models indicate that a more detailed analysis of flow conditions is both possible and worthwhile.
Production of Sounds in Distensible Tubes
Authors: MEISNER JOHANN E. , RUSHMER ROBERT F.
Published: June 2012

A photocell was used to record vibrations in a solution of white Hector bentonite passing through a constriction introduced into Tygon or cellophane tubing, or into a transparent flat flow section with distensible sides. These vibrations were compared with those simultaneously recorded from the walls of the model. Both vibration spectra were also subjected to frequency analysis. At low steady flow rates in either three-dimensional system, the jet lost its laminar characteristics downstream from the constriction, but this disturbance was not accompanied by wall vibrations. At somewhat higher flow rates, the eddies impinged upon the walls and set up local wall vibrations, below the audible range. At still higher velocities, the turbulence became greater and the wall vibrations spread along the walls and became audible. However, the frequencies of the fluid motion did not necessarily appear in the frequency spectrum of the walls. The amount of energy necessary to set the walls in motion was partly determined by their physical characteristics; vibrations were more easily produced in the thin, flexible cellophane than in the thicker Tygon. Thus, the absence of murmurs does not mean that flow is laminar nor does the presence of wall vibrations mean that they are audible.
Control of Total Vascular Resistance in Hemorrhagic Shock in the Dog
Authors: ROTHE CARL F. , LOVE JAMES R. , SELKURT EWALD E.
Published: June 2012

Cardiac output in the dog was measured by indocyanine green dilution in 24 hemorrhagic shock experiments. Total peripheral resistance (TPR) was calculated from the cardiac output and systemic arterial blood pressure. Early in the hypotensive phase resulting from hemorrhage to 50 mm Hg blood pressure, the cardiac output was 19.3±6.6 (SD) % of control and the total peripheral resistance was 199 ±73 (SD) % of control. During the hypotensive phase the peripheral resistance declined significantly. This decline in TPR was associated with a significant decrease in respiration and heart rates, indicating a partial failure of the neurogenic control of the cardiovascular system. Following transfusions of the shed blood, the TPR decreased to the control value, but during subsequent progressive decline in blood pressure, vascular resistance again increased. Occasionally, TPR again fell terminally as the blood pressure decreased below 60 mm Hg. Although there is evidence for partial failure of peripheral resistance vessel tone during severe hypotension and some evidence for this following reinfusion of the shed blood, this failure, when observed, is a minor component of the progressive cardiovascular failure and is not the cause of irreversibility.
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.
Left Ventricular Tension and Stress in Man
Authors: Sandler Harold , Dodge Harold T.
Published: June 2012

A method is described for calculating tension and stress acting within the wall of the left ventricle during the cardiac cycle. This method is based upon ventricular pressure observations and measurements of left ventricular dimensions and wall thickness made from biplane angiocardiograms. To calculate wall tension and stress, it is assumed that the left ventricle can be represented as an ellipsoid of revolution with a relatively thin wall. The relative importance of ventricular pressure, volume, shape and wall thickness in determining the magnitude of wall tension and stress is illustrated and discussed.
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.
Influence of Temperature on Development of Rigor Mortis in Dog Hearts
Authors: KOLDER HANSIOERG , HORRES ALAN D. , BRECHER GERHARD A.
Published: June 2012

The effect of temperature (1°C to 50°C) on the onset and maximal development of rigor mortis in dog hearts was studied systematically under static conditions. Excised hearts were submerged in Ringer's solution so that the ventricle could assume an elastic equilibrium state. This was characterized by zero transmural pressure and the presence of a certain volume in the ventricle. Pressure-volume curves were obtained in 29 experiments by removal as well as by addition of fluid. The pressure-volume relations were the same at all temperatures prior to the onset of rigor mortis. The criterion for the beginning of rigor mortis was the first change in pressure-volume relations and for maximum rigor the constancy of the attained relations. The shortest interval between cessation of the circulation and the beginning of rigor mortis was 25 minutes at 37°C, and three hours at 10°C. These measurements provide data defining the minimal period during which pressure-volume determinations can be made without post mortem alterations. The phenomenon of "primary dilatation" was observed irrespective of a withdrawal or an addition of fluid to the ventricle. The weight gain of the quiescent ventricle in Ringer's solution was determined until autolysis began and was found to be 5% during the first five hours at all temperatures ranging from 5°C to 45°C.
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.
Potassium Exchange in the Dog Heart in Situ
Authors: GRUPP GUNTER , Astrida Charles
Published: June 2012

Coronary perfusion with constant flow and constant specific activity permitted an estimate of the transmembrane fluxes of potassium in both directions in the dog heart in situ. The determination of efflux was based on the washout characteristics. Perfusion pressure and coronary flow within the limits studied have little influence on efflux. The estimate of influx involved correction of experimental data using the efflux from the same experiment and is therefore less accurate; it is subject to changes due to alterations in collateral blood supply of the perfusion area. The efflux varies by 50% from heart to heart, averaging 0.68 mEq K
+
/kg and min at an average heart rate of 130 beats/min. Changes in heart rate reveal that 1.65 µEq K
+
/kg are exchanged per beat above the resting flux of the nonbeating heart; the latter was estimated by extrapolation to be 0.55 mEq K
+
/kg and min.
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.
Experimental Pulmonary Arterial Hypertension in the Newborn Calf
Authors: Vogel John H. K. , Averill Keith H. , Pool Peter E. , Blount S. Gilbert
Published: June 2012

1. The left pulmonary artery was ligated in day-old calves. All animals developed pulmonary arterial hypertension with resting
mean
pressures as high as 114 mm Hg. This was associated with a reduction in the pulmonary arterial vascular bed of the right lung and right ventricular hypertrophy. The longest survival has been five months; death being associated with congestive heart failure.

2. Pulmonary hypertension developed without concomitant rise of pulmonary arterial wedge pressure.

3. Inhalation of 13% O
2
caused an average rise of 45 mm Hg in mean pulmonary arterial pressure, as compared with 21 mm Hg in normal calves and nine in yearling steers.

4. Inhalation of 41% or 100% O
2
caused an average decrease of 29 mm Hg in pulmonary arterial pressure, as compared with 14 mm Hg in normal calves.

5. Acetylcholine reduced the elevated pulmonary arterial pressure suggesting that vaso-constriction played an important role in the development of the pulmonary hypertension. Tolazoline was ineffective.

6. The spectrum of reactivity of the pulmonary vascular bed among species as well as within a given species is illustrated.
Localization of Tritiated Digoxin in Dog Myocardium by Electron Microscopic Autoradiography
Authors: TUBBS F. EUGENE , CREVASSE LAMAR , WHEAT MYRON W.
Published: June 2012

Five mongrel dogs were given 0.08 mg/kg of tritiated digoxin over a 24-hour period. Left ventricular myocardium was excised and subsequently fixed, dehydrated, and embedded in Epon 812 epoxy resin. Tissue was sectioned and coated with a monolayer of photographic nuclear emulsion and exposed for varying time intervals up to three months. After development these autoradiographs were viewed with the electron microscope. It was found that of the total number of nuclear tracks counted, 75% were found to overlie the sarcomere of the myofibril, 27% to overlie the mitochondria, and 8% to overlie other structures. Of those tracks associated with the sarcomere, 72% were found to overlie the A band. Evaluation of the data obtained and the techniques used are presented.
Effects of Alterations in Aortic Impedance on the Performance of the Ventricles
Authors: WILCKEN DAVID E. L. , CHARLIER ANDRÉ A. , HOFFMAN JULIEN I. E. , GUZ ABRAHAM
Published: June 2012

We have investigated the effects of sudden changes in the load against which the left ventricle contracts in healthy conscious dogs. During a steady state, initial responses were assessed by comparing the beat before with the beat after such a change. Flow was measured by electromagnetic flowmeters and pressure usually by a catheter-tip transducer.

Results show that under the conditions of these experiments the curves relating external work and power to load are consistent with the parabolic relationship shown for isolated hearts and muscle strips and that in each case the left ventricle normally functions near the peak of the curve.

When an increased load was maintained until a new steady state was reached the left ventricle still functioned on the descending limbs of what presumably were different work-load and power-load curves. It was concluded from this that either the increase in load was too great or the time too short for reflex humoral and intrinsic mechanisms to readjust and permit the ventricle to function again at the peak of each curve, or that the circulatory system does not make relatively rapid adaptations in this way to an increase in systemic load.

The immediate effects of changes in load on left ventricular stroke volume were similar to those seen in isolated preparations. Stroke volume varied inversely with the load. Stroke volume changes were accompanied by changes in the duration, rate, and velocity of ejection. The duration of the isovolumetric phase was affected little but the period from valve closure to the end of ventricular relaxation varied with the load so that the total duration of contraction and relaxation of the ventricle was relatively unchanged, though an increase in load did tend to prolong it.

Before the onset of the baroreceptor response the right ventricle was not affected, the two ventricles acting independently in relation to all these changes.
Actin from Heart Muscle: Sulfhydryl Groups
Authors: KATZ ARNOLD M. , MAXWELL JOYCE B.
Published: June 2012

The number and reactivity of the sulfhy-dryl groups of cardiac and skeletal actin preparations have been examined, using material from dogs and rabbits. The number of sulfhy-dryl groups of all actins was approximately six per mole, two of which could be characterized as fast-reacting and were not essential for polymerization. The time course of the reaction of the sulfhydryl groups of heart and skeletal actins with -
p
mercuribenzoate were identical, and the effects of Ca
++
Mg
++
and adenosinetriphosphate upon this reaction were similar for actins from the two tissues. In accord with previous structural comparisons, no difference between cardiac and skeletal actin has been detected.
Application of a Constant Indicator Dilution Method to the Measurement of Local Venous Flow
Authors: KOUNTZ SAMUEL L. , DEMPSTER WILLIAM J. , SHILLINGFORD JOHN P. , Kastell Brian
Published: June 2012

A method for measuring local venous flow by a constant indicator dilution technique is described. The optimal conditions have been outlined and the accuracy tested in vitro and found to be within ±3%. When compared with direct measurements of venous flow in dogs, its accuracy was within ±5%. The method is safe, easy to perform and, with the catheters described, flow can be measured over ranges of 20 to 5,700 ml/min in any vein greater than 4 mm inner diameter in which the catheter tips can be introduced.
Effect of Carotid Baroceptor Stimulation upon the Forelimb Vascular Bed of the Dog
Authors: ZINGHER DIANA , GRODINS FRED S.
Published: June 2012

The response of the musculocutaneous vascular bed of the dog's forelimb to carotid baroceptor stimulation was determined by measuring pressures at the level of the large artery, small artery, small vein, and large vein along with limb blood flow. In one series, limb blood flow was uncontrolled. In two other series, the limb was perfused at a constant flow rate and was also isolated from collateral flow in one of these.

Elevation of carotid sinus pressure in the constant flow isolated (CFI) series produced an average fall in total limb, small vessel, and venous segment resistance of 27%, 36%, and 22% respectively but no significant change in arterial segment resistance. Since transmural pressure fell significantly in all three segments, active vasodilatation must also have occurred in all, including the arterial. This is reflected in the significant increase in compliance calculated for both the lumped arterial and lumped venous segments. In any given animal, there was a positive correlation between the percentage reduction in systemic pressure and total limb resistance, but this correlation was not evident between animals.

In the series in which limb blood flow was uncontrolled, flow decreased consistently and significantly when carotid sinus pressure was elevated, the average decrease being 30%. Despite possible confusion introduced by the presence of an added fixed resistance in the limb circuit (rotameter), it is probable that this finding faithfully reflects the behavior of the intact limb.
Intramural Myocardial Shear During the Cardiac Cycle
Authors: FEIGL ERIC O. , FRY DONALD L.
Published: June 2012

Instantaneous and continuous shearing strains at various sites in the wall of the left ventricle were measured in 19 dogs with a specially designed transducer. Relatively large shearing strains occurred during the "isovolumic" and immediately prediastolic portions of systole. Shearing strain during diastole was small. Under control conditions the average shearing strain during the ejection period of systole was 0.0218 radians (1.25°) at a 6 mm depth into the myocardium. Intravenous infusion of norepinephrine (approximately 0.001 mg/kg per minute) increased myocardial shear from 0.0177 radians (1.01°) to 0.0274 radians (1.57°) during the ejection period.

It is concluded that shearing strain in the myocardium during the ejection period is relatively small.
Measurement of Myocardial Blood Flow in Animals and Man by Selective Injection of Radioactive Inert Gas into the Coronary Arteries
Authors: ROSS RICHARD S. , UEDA KEIJI , LICHTLEN PAUL R. , REES J. RUSSELL , Redden Redden , Kaelber Christa
Published: June 2012

1. Human myocardial blood flow has been measured by the determination of precordial radioactivity after the injection of solutions of radioactive gas directly into the coronary arteries following coronary arteriography.

2. The accuracy of radioactive gas measurements has been established in dog experiments by comparison with coronary blood flow simultaneously measured by rotameter.

3. This method has two major advantages over the existing methods of measuring human myocardial blood flow. Firstly, the right and left coronary circulations can be studied separately, this being the only method whereby the right circulation can be studied in man. Secondly, anatomical and physiological correlations are readily available as arteriography is an essential feature of the method.
Tooth Pulp Tissue Pressure and Hydraulic Permeability
Authors: BROWN ARTHUR C. , YANKOWITZ DAVID
Published: June 2012

The object of these experiments was to evaluate the hydrostatic pressure and hydraulic permeability of the tooth pulp in situ. A small hole was drilled through the enamel and dentin to the dentinal-pulpal junction in canines and third incisors of anesthetized dogs. A threaded cannula filled with mammalian Ringer's solution was screwed into the hole and connected to a microsyringe and a pressure transducer of very low compliance.

Pressure was recorded when the cannula was first inserted into the hole; then small amounts of fluid were injected into the system or withdrawn from the system using the micro-syringe. The equilibrium pressure (
P
eq
), measured after transients had disappeared, was fairly constant for a given tooth over long periods of time. Referred to tooth level (which was approximately heart level),
P
eq
averaged 57 mm Hg (range 38 to 78 mm Hg) in the ten teeth tested. Superimposed upon the steady value was a random deviation (± 3 mm Hg), a hysteresis effect resulting in a higher pressure if the measurement had been preceded by injection of fluid rather than withdrawal (± 3 mm Hg), and a continuous drift with time ( + 3 mm Hg/hr).

The hydrostatic permeability was calculated from the rate of fluid flow when the pressure was above or below its steady state value. When the pressure was high (fluid being forced into the pulp) flow averaged about 0.33 µl/hr-mm Hg over the range
P
eq
to
P
eq
+ 20 mm Hg. When the pressure was low (fluid being withdrawn from the tooth), flow averaged about 0.14 µl/hr-mm Hg over the range
P
eq
to
P
eq
- 20 mm Hg.

It is concluded that
P
eq
probably represents the true hydrostatic tissue pressure normally existing within the tooth pulp. This implies a high capillary pressure and thus a relatively high resistance in the venous side of the pulp circulation. The interpretation of hydraulic permeability is not certain, but this quantity probably is related to the ease with which fluid passes into or out of the pulp capillaries.
Chronotropic Effects of Norepinephrine and Tyramine: A System Response Analysis
Authors: BATTERSBY EDWARD J. , NEWMAN ELLIOT V.
Published: June 2012

An analog simulation of the chronotropic effects of norepinephrine and tyramine in the canine heart-lung preparation is presented. The temporal aspects of those responses are described in quantitative terms.

Reserpine produced deprivation suprasensitivity to norepinephrine may be considered as a corollary of the system response nonlinearity to that drug.

Discrepancies between tyramine rate responses and the relatively small amounts of norepinephrine released are resolved by the assumption that the receptor space for norepinephrine has a capacitative function and is not in free dilutional equilibrium with the perfusing blood. This mechanism would allow for a unitary explanation of tyramine action based upon competition with norepinephrine for available storage sites.