bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of Ventricular Volumes by a Constant Infusion Indicator Dilution Technique
Authors: SHAFFER AARON B.
Published: June 2012

A constant infusion indicator dilution method for estimating ventricular volumes is introduced and its feasibility demonstrated. Using this method, volumes can be calculated by two different approaches, one of which does not assume effective distribution of indicator throughout end diastolic volume (
EDV
). This offers a means of assessing the effects of nonmixing on the form of the stepwise rise in concentration of the constant infusion curve, which has relevance to the basically related stepwise decline in concentration following sudden injection of indicator. It is suggested that the degree of mixing of diastolic venous return in the previous end systolic volume (
ESV
) is basic to the distribution of indicator introduced into the ventricle. If mixing is incomplete, the site of origin of stroke volume (
SV
) from
EDV
is an important factor in determining the form of an indicator dilution curve and the
EDV
as calculated from ratios of successive concentrations. The possible range of effects of nonmixing on the form of the constant infusion curve for ventricular volume, as derived from a mathematical model, is outlined. End diastolic volumes, as estimated from ratios of successive concentrations in a series of constant infusion indicator dilution curves obtained experimentally, are tabulated, and as a group do not differ materially from those obtained by the sudden injection method.
Transthoracic Ventricular Defibrillation with Square-wave Stimuli: One-Half Cycle, One Cycle, and Multicycle Waveforms
Authors: SCHUDER JOHN C. , STOECKLE HARRY , DOLAN ALFRED M.
Published: June 2012

A very high powered amplifier for experimental transthoracic ventricular defibrillation has been described. The effectiveness of both one-half-cycle unidirectional and one-cycle bidirectional square waves in terminating ventricular fibrillation first increases, then reaches a maximum and finally decreases as the duration of the shock is increased. With 10- and 20-ampere unidirectional shocks and 10-ampere bidirectional shocks, a maximal effectiveness of substantially 100% was found under the chosen experimental conditions. Five-ampere unidirectional and bidirectional shocks yielded maximal effectiveness of 70%. The effectiveness of a 128-millisecond, 5-ampere, multicycle square-wave shock is a strong function of frequency and has a maximal value of approximately 70%.
Comparison of Dilution Technics Using Aortic Injection with Upstream Sampling for Assessment of Aortic Regurgitation
Authors: ARMELIN EGAS , DONALD DAVID E. , WOOD EARL H.
Published: June 2012

The distances between the aortic valve and sites in the aorta from which no retrograde flow of injected indicator could be detected in the left ventricle were determined, without thoracotomy, in two normal dogs and in ten dogs with chronic experimental aortic regurgitation. It was found that these distances attained maximal values when the aortic injections were timed to occur just at the end of systole or onset of diastole.

Distances downstream from the origin of the left subclavian artery from which no retrograde flow occurred to this vessel were determined similarly in these same animals and, in confirmation of Warner and Toronto, similar relationships to the timing of the injections were obtained. These distances down the aorta, designated as "disappearance distances", were converted to "disappearance volumes" by measuring the diameters of the silhouette of successive aortic segments from aortograms made after contrast medium was injected into the left ventricle of these animals.

The regurgitant flow through the aortic valve per heartbeat was estimated on the basis of the amount of immediately appearing indicator detected in the left ventricle following injection of indicator approximately 1 cm downstream from the aortic valve. Correlation coefficients of 0.88 and 0.77 were obtained between these stroke-regurgitation values and the disappearance volumes from the aortic valve and subclavian artery, respectively. The standard errors of the estimate of the regurgitant flow per beat from these regression equations were ± 2.7 and ± 2.9 ml/beat, respectively. The correlation coefficients between stroke-regurgitation values and the disappearance distances from the valve and subclavian artery were 0.83 and 0.81, respectively, and the respective standard errors of the estimate of stroke regurgitation from these regression equations were ± 3.2 and ± 3.3 ml/beat.

It is concluded that determination of the maximal distances downstream in the aorta of sites from which retrograde flow of injected indicator can be detected in the left ventricle or subclavian artery is a valid method for estimating the severity of experimental aortic regurgitation in dogs. Since determinations of the disappearance distance from the aortic valve can be carried out readily in conjunction with measurement of the left ventricular regurgitation fraction, it is suggested that advantage be taken of the increase in reliability which accrues from the combined use of these two independent methods for the estimation of the degree of aortic regurgitation.
Abnormal Indicator Dilution Patterns in Dogs Produced by Flowmeter Probes on the Pulmonary Artery
Authors: FOX IRWIN J. , CASTANEDA ALDO R. , WEBER KENNETH C.
Published: June 2012

In acute experiments on open chested dogs, indicator dilution curves were recorded before and after placing electromagnetic flow probes on the pulmonary artery. The flow probes caused severe abnormalities in the dilution curves. The abnormalities resembled those seen in cases with left-to-right shunts.

The following facts suggest that the abnormalities are caused by turbulence and eddy formation near the flowmeter probe: (a) Direct measurements with a fiberoptic densitometer showed that clearance of dye just proximal to the probe was delayed. (b) The abnormalities disappeared immediately after removal of the probe or when the dye was injected just downstream to the probe. (c) The areas under curves recorded from the pulmonary artery upstream from the probe were greater than the areas under curves recorded at this same site without the probe.

Cardiac output and systemic arterial pressure were lower in animals with abnormal dilution curves than in those with normal femoral curves.
Carotid Sinus Baroreceptor Reflex Effects upon Myocardial Contractility
Authors: DE GEEST HILAIRE , LEVY MATTHEW N. , ZIESKE HARRISON
Published: June 2012

The reflex effects of stimulation of the carotid sinus baroreceptors on left atrial and ventricular performance have been studied in an auxotonic and an isovolumetric left heart preparation, which was innervated, though completely isolated hydraulically. Reflex changes of heart rate, arterial impedance, venous return, and level of circulating catecholamines were prevented from influencing cardiac performance. In the auxotonic preparation, stimulation of the carotid sinus baroreceptors decreased aortic pressure, cardiac output, and external left ventricular work. Simultaneously, mean left atrial pressure rose definitely. In the isovolumetric preparation, a decrease of the left ventricular peak systolic pressure was observed. These changes in atrial and ventricular dynamics were attributed primarily to a reflex negative inotropic effect directly upon the atrial and ventricular mycardium, mediated by the sympathetic nervous system. No definite changes in distensibility of the isovolumetric left ventricle were observed, although this could not be excluded in the auxotonic preparation. Primary changes in the coronary vascular bed were not considered to be responsible for the observed changes in atrial and ventricular dynamics.
Effect of Coronary Vasodilator Drugs on Retrograde Flow in Areas of Chronic Myocardial Ischemia
Authors: FAM WADIE M. , MCGREGOR MAURICE
Published: June 2012

The effects of two coronary vasodilator drugs, nitroglycerin and dipyridamole, on the coronary collateral flow were studied in twelve dogs with chronic myocardial ischemia and in five normal dogs, by means of the retrograde flow technique.

In the ischemic dogs with well developed collateral circulation, both drugs caused a reduction in systemic blood pressure. Dipyridamole caused a significant reduction in both the retrograde flow and peripheral coronary pressure as well. Nitroglycerin, by contrast, did not cause a significant reduction in either retrograde flow or peripheral coronary pressure in spite of a greater fall in mean arterial pressure. When arterial pressure was held constant artificially, nitroglycerin caused a large increase of retrograde flow in chronic "ischemic" dogs while dipyridamole did not.

In normal dogs these differences between the two drugs were not observed. Both drugs caused a reduction of retrograde flow and peripheral coronary pressure which paralleled the reduction in systemic pressure.

In both ischemic and normal dogs, dipyridamole caused a reduction in the coronary arteriovenous oxygen difference. Nitroglycerin did not change this value.

Reported differences between these two drugs, together with these observations, suggest that nitroglycerin may have an action which is to be seen only in the presence of well developed collateral circulation; this is to increase flow through collateral channels without significantly altering total coronary artery flow. Dipyridamole does not seem to alter collateral flow but does increase total coronary flow. The site of action of these two drugs in the coronary vascular tree must thus be different.
Protection and Reactivation of Cardioglobulin-A by High Energy Phosphate Compounds
Authors: LEONARD EDWARD J. , HAJDU STEPHEN
Published: June 2012

The biological activity of cardioglobulin-A can be destroyed enzymatically by a short equilibration with homogenates prepared from a wide variety of tissues. Blood plasma alone also contains a cardioglobulin-A inactivating system which is stimulated by the removal or dilution of an unidentified small molecule normally present in the plasma.

Inactivation of cardioglobulin-A can be prevented by the addition of certain high energy phosphate compounds, notably
ATP, ADP
or
CP
. Furthermore, the biological activity of inactivated cardioglobulin-A can frequently be restored by addition of
CP.

When the whole cardioglobulin system acts on the frog heart, cardioglobulin-A activity is gradually depleted. This is associated with a loss of protein-bound phosphorus from a component of the mixture. Activity can be restored by addition of
CP
.

It has been proposed that the action of the cardioglobulin system involves the release of bound cardioglobulin-C calcium. A possible role of cardioglobulin-A may be to provide, through a ∼ P linkage, the energy for the release of this calcium.
Effect of Ischemia on Adenine Nucleotides in Cardiac and Skeletal Muscle
Authors: IMAI SHOICHI , RILEY ARTHUR L. , BERNE ROBERT M.
Published: June 2012

Rabbit skeletal muscle contains 56% more
ATP
and 225% more creatine phosphate than rabbit cardiac muscle. With ischemia the per cent reduction in
ATP
and creatine phosphate is less in skeletal than cardiac muscle and
ADP
and
AMP
decrease in skeletal and increase in cardiac muscle,
IMP
is present in skeletal muscle and increases with ischemia, whereas it is absent in cardiac muscle but appears with ischemia. Adenosine, inosine, and hypoxanthine are absent in skeletal and cardiac muscle. Ischemia results in the appearance of adenosine, inosine, and hypoxanthine in cardiac muscle but only the latter two compounds appear in ischemic skeletal muscle. Although complete ischemia is required to demonstrate the presence of adenosine in cardiac muscle, the appearance of this nucleoside is nevertheless consistent with the hypothesis that under physiological conditions quantities of adenosine, undetectable by present methods, may play a role in the regulation of coronary blood flow.
Incorporation of Sulfate-S
35
and Glucosamine-1-C
14
into Heparin During Perfusion of Isolated Rat Liver
Authors: FERRANTE NICOLA Di , MEYERS ANN L. , MILLER LEON L.
Published: June 2012

Sulfate-S
35
and glucosamine-1-C
14
are incorporated into heparin which has been added to the blood perfusing an isolated, surviving rat liver. Although both labels are firmly bound to heparin, such uptake does not necessarily indicate synthesis of the polymer.

Despite the fact that the perfused heparin has undergone some moderate depolymerization, its biological activity remains unchanged.

The presence in the bile of material containing hexuronic acid and hexosamine but deprived of anticoagulant activity suggests that products derived from heparin breakdown may be eliminated in the bile.
Influence of Cooling the Heart on Reactive Hyperemia of the Coronary Bed in the Heart-Lung Preparation
Authors: BADEER HENRY S.
Published: June 2012

Left coronary artery inflow was recorded in the dog heart-lung preparation by means of a Gregg cannula and a Shipley-Wilson recording rotameter. Reactive hyperemia (RH) was induced by 10-second occlusions. The excess blood flow after release was quantified by planimetry and related to the "blood flow debt" incurred during the period of occlusion. In the normothermic heart, the excess coronary flow was 431% of the flow debt. At heart temperatures of 30 and 25.6° C, it dropped to 228% and 143% respectively. There was shortening of the duration of reactive hyperemia and reduction of peak flow at lower temperatures. These results were discussed in the light of chemical theories of the mechanism of reactive hyperemia and the effect of hypothermia thereon.
Regional Distribution of Catecholamines in the Dog Heart
Authors: ANGELAKOS EVANGELOS T. , Millard Ronald W.
Published: June 2012

The concentrations of norepinephrine (NE), epinephrine (E) and dopamine (DA) were determined in dog hearts, each divided into a total of 18 parts. The concentration of NE was found to be significantly (three times) higher in the atria than in the ventricles while smaller differences existed within various subdivisions. In particular, the left atrial body had a lower concentration than other atrial tissue. The same was true of the left ventricular apex as compared to the base. No significant differences in NE were observed between the average concentrations in epicardial vs. endocardial layers of left ventricle, nor in the S-A or A-V node areas vs. surrounding tissues.

The concentration of DA was also higher in atria than in ventricles. However there was no consistent correlation between NE and DA concentrations in the various atrial and ventricular parts. In the ventricles, DA was higher in left than in right ventricle and still higher in the A-V node region. In the atria DA was highest in the S-A node region and least in the atrial body. Both right and left atrial appendages contained high DA concentrations especially in their upper parts. In these parts and in the S-A node region the DA concentration was nearly equal to or slightly higher than that of NE. In most other areas DA was one-fifth to one-tenth the NE concentration.

By contrast E was present in very low concentrations amounting on the average to less than 5% the amount of NE in the same tissue. No distinct pattern of E distribution in various parts of the heart could be established.

It is concluded that no sample of the heart can be considered as representative of the entire organ, and that the catecholamine content of the entire heart cannot be taken as reflecting the concentrations in various specific areas.
Vasodilator Therapy in Acute Hemorrhagic Shock
Authors: VICK JAMES A. , CIUCHTA HENRY P. , MERICKEL JOSEPH H. , LINDSETH ESTEN O.
Published: June 2012

Results of this study show that 18 of 20 dogs survived prolonged periods of arterial hypotension when phenoxybenzamine was given to maintain adequate flow to the vital tissues of the body. This drug was used in order to block the catecholamine-induced arteriolar vasoconstriction and the histamine-induced venospasm. Reduction of peripheral resistance results in an increased perfusion of the capillary beds and a correction of O
2
and CO
2
tensions at the tissue level. One must emphasize the need for adequate fluid replacement, with this form of therapy; otherwise the marked vasodilation which occurs with phenoxybenzamine might result in an inadequate circulation, even as the resistance to flow in hypoxic tissues is eliminated.
Cardiac Action of Vasoactive Polypeptides in the Rat
Authors: GROSS MICHAEL , MONTAGUE DROGO , ROSAS RAMON , BOHR DAVID F.
Published: June 2012

Intravenous injection of bradykinin in ganglionically blocked rats has a predominantly pressor effect, instead of the depressor effect it is known to have in unblocked rats. Intra-arterial injection of bradykinin (0.01 to 0.02 µg) either before or after blockade produced a decrease of pressure in the hind limb perfused at a constant rate with autogenous blood. The response of the vascular bed was directly proportional to the perfusion pressure, but at a given pressure no difference was seen between blocked and unblocked animals. At the
IV
infusion rates used (12.5 and 25 µg/kg/min), bradykinin produced a large increase of CO. Because this action remains after autonomic blockade, it seems probable that its mechanism of action is largely independent of the carotid baroreceptor system. Bradykinin caused a slight increase in heart rate and a marked increase in stroke volume, apparently by a direct effect on the heart. In the blocked animal the vasodilator effect of bradykinin is less than its cardiac stimulating action and the resulting effect is an elevation of arterial pressure.

Angiotensin in the rat has twofold action: a constrictor effect on the arterioles, and a stimulating effect on the heart. The vasoconstrictor effect is direct, unmodified by denervation or by sympathetic blockade. In the intact rat the cardiac action is masked by the activation of the baroreceptor mechanism which overrides the direct cardiac action and causes a decrease in CO. After autonomic blockade the cardiac action of angiotensin becomes apparent and an increase of CO is seen, while changes in TPR remain similar to those of unblocked animals. Since the CO effect cannot be explained by changes in HR and CVP, it appears that angiotensin has a positive isotropic action. In blocked, reserpinized animals angiotensin infusion causes no significant change in CO. These results suggest that catecholamines account for at least part of the cardiac activity of angiotensin.
Electrocardiographic Studies in Homologous Canine Heart Transplantations
Authors: DEPASQUALE NICHOLAS P. , BURCH GEORGE E. , PENA EDGAR , REEMTSMA KEITH
Published: June 2012

1) In a series of ten dogs subjected to heart transplantation, serial electrocardiograms were recorded from the transplanted and the recipient hearts.

2) Approximately one week following transplantation, changes appeared in the S-T segment and the T wave of the electrocardiogram of the recipient heart without significant alteration of the QRS complexes. These findings resembled those associated with myocarditis and/or pericarditis.

3) Electrocardiographic changes did not appear in animals treated with drugs alone or in animals subjected to kidney transplantation. These findings suggest the possibility of release from transplanted hearts of an organ-specific substance or substances which affected the hearts of the recipients.
Effects of Acetylstrophanthidin on Coronary Vascular Resistance and Myocardial Oxygen Consumption
Authors: WALDHAUSEN JOHN A. , KILMAN JAMES W. , HERENDEEN THOMAS L. , ABEL FRANCIS L.
Published: June 2012

The effects of acetylstrophanthidin on coronary circulation were studied in 31 dogs. Coronary blood flow was measured in empty beating hearts or in fibrillating hearts by collecting coronary venous return during perfusion of the systemic circulation (cardiopul-monary bypass). In 14 animals with ventricular fibrillation, acetylstrophanthidin caused an initial coronary constriction and fall in coronary blood flow. This was followed, after approximately 10 minutes, by a significant drop in resistance and a rise in coronary blood flow which persisted for the remainder of the experiment. Associated with the increase of blood flow was an increase of myocardial oxygen consumption. This effect was not abolished by ganglionic blockade, cardiac denervation or bilateral adrenalectomy.

In nine dogs with beating but empty hearts, after the initial constriction of the coronary vessels, there was only a small change in coronary blood flow and resistance, although myocardial oxygen consumption was increased. The lack of coronary vasodilatation was attributed to increased mechanical resistance due to the augmented force of contraction produced by the drug.
Spontaneous Bundle Branch Block in Rhesus Monkeys
Authors: BRISTOW J. DAVID , MALINOW MANUEL RENE
Published: June 2012

Naturally occurring ventricular conduction abnormalities are described in 23 rhesus monkeys and compared with findings in 15 control animals. Electrocardiograms and Frank vectorcardiograms were recorded and ventricular endocardial leads were obtained in four of the animals. Three examples of left bundle branch block and five of right bundle branch block were found. Less marked degrees of abnormal intraventricular conduction are described in 15 others.
Lipolytic Activity of Post-Heparin Plasma in Hyperlipemia and Hypolipemia
Authors: KUO PETER T. , BASSETT DAVID R. , DIGEORGE ANGELO M. , CARPENTER GARY G.
Published: June 2012

(1) The role of post-heparin plasma lipolytic activity (PPLA) in the production of hyperglyceridemia was investigated in patients with high concentrations of plasma triglycerides produced in two ways, viz. fat-induced and "mixed" (both fat and carbohydrate-induced). While on a self-chosen diet, the PPLA levels of patients with "mixed" type of hyperglyceridemia differed little from those of young healthy subjects. PPLA levels of these patients were promptly lowered by rice diet, despite the persistence of hyperglyceridemia. Normal serum lipid concentrations and low PPLA levels were induced and maintained in these patients by reducing moderately their intake of both dietary fat and calories.

(2) PPLA levels were reduced in the fat-induced hyperglyceridemic patients both before and after the use of low fat diet to reduce their plasma triglyceride concentrations.

(3) PPLA was also low in patients with low and absent beta-lipoproteins, and in those with disturbance of intestinal fat digestion and absorption.
Differences in Cardiac Hypertrophy in Exercise and in Hypoxia
Authors: VAN LIERE EDWARD J. , KRAMES BARBARA BAUGH , NORTHUP DAVID W.
Published: June 2012

A group of rats, including both sexes, was exercised on an electrically-driven treadmill at the rate of one mile per hour for two hours daily to a total of 60 hours. Another group, also including both sexes, was exposed to intermittent hypoxia for eight hours daily, six days per week, for four weeks at a barometric pressure of 303 mm Hg corresponding to a simulated altitude of approximately 24,000 feet (7,315 m). All these animals showed significant hypertrophy of both ventricles.

Exercise produced about the same percentage of weight increase in the right and also in the left ventricular walls. The per cent increase of the right ventricular wall relative to that of the left ventricular wall was greater after intermittent hypoxia than after exercise. The ratio of left ventricular weight/right ventricular weight was significantly less in the hypoxic group than in the exercised group. This indicates a relative right ventricular hypertrophy produced by the intermittent hypoxia. Reasons are given to indicate that the pulmonary hypertension associated with hypoxia is the cause of this right ventricular predominance.
Analysis of Ventricular Dimension in the Unanesthetized Dog
Authors: NINOMIYA ISHIO , WILSON MICHAEL F. , Gibson John M. , Segnitz Richard H.
Published: June 2012

Left ventricular dynamics was studied in the unanesthetized dog by an analysis of simultaneous recordings of left ventricular transverse dimension, pressure, and ascending aortic flow in 16 experiments while the dogs were reclining, standing, and during graded treadmill exercise. Statistical analysis of the dimension data revealed typical patterns of isovolumetric changes which suggest asynchronous contraction and relaxation. The fact that maximum and minimum dimension levels did not coincide with levels at onset and end of ejection led to the concept of the "effective" stroke shortening in the left ventricular transverse dimension.

An ellipsoid of revolution was the best approximation of left ventricular shape while reclining and standing, but during exercise the shape constant decreased toward a paraboloid of revolution. Analysis of the data from correlation coefficients and by using the principle of the compression ratio, which is independent of shape, indicated that stroke shortening and stroke volume may be a function of initial length or volume for the resting states but that during exercise their increase was due primarily to extrinsic influences which acted to change the magnitude of the contractile response.
Oxidative Phosphorylation in the Failing Dog Heart-Lung Preparation
Authors: PROCITA LEONARD , SCHWARTZ ARNOLD , LEE KWANG SOO
Published: June 2012

Utilizing dog heart-lung preparations mitochondria were obtained from control preparations and from hearts failing spontaneously, or as a result of pressure-loading or venous inflow-loading. The mitochondria were compared with respect to their oxidative phosphorylating capacity. The data on the P:O ratios indicate that there is an uncoupling of oxidative phosphorylation in the mitochondria from hearts in spontaneous failure, and in the mitochondria of hearts failing as a result of pressure-loading. In the case of failure due to venous inflow-loading of the heart the mitochondrial P:O ratios are within the control range. The data definitely support the conclusion that in certain types of failure in the dog heart-lung preparation the energy generating or liberating mechanisms may be impaired. This conclusion is contrary to that in the literature based on measurements of high-energy compounds and oxygen consumption, namely, that energy liberation, including transfer of oxidative energy in the form useful for contraction, is not impaired in the failing heart.
Spread of Excitation from the Sinus Node
Authors: SANO TOYOMI , YAMAGISHI SHUNICHI
Published: June 2012

Microelectrodes were employed to determine the mode of propagation of excitation from the sinus node in the rabbit heart. The excitation starts from the sinus node radially, at first, but then proceeds to the crista terminalis, often obliquely. This is because some special tissue having a slow conduction velocity lies behind the sinus node, and also because there is a zone of relatively faster conduction at the basal wall of the superior vena cava. Once the excitation wave enters the crista terminalis, it travels rapidly in two opposite directions through two branches of the ring-like structure which is formed by the crista terminalis and its extension. The excitation wave traveling through the branch encircling the inferior vena cava reached the atrioventricular node earlier in most instances.

In the caval region inside the ring-like structure there is a zone of relatively faster conduction. The conduction to the atrioventricular node through this route is latent in the normal state, because conduction through the ring-like structure takes place beforehand.

In the caval region near the sinus node, the conduction velocity of the excitation wave from the spontaneously beating sinus node was greater than that from the electrically driven atrium. The spontaneous action potential showed also a steeper rise than that produced by electrical stimulation. The mechanism responsible for this is discussed.
Mechanism of Slow Conduction at the Bulbo-ventricular Junction
Authors: IRISAWA HIROSHI , HAMA KIYOSHI , IRISAWA AYA
Published: June 2012

Delay of conduction of excitation from the ventricle to the bulbus cordis in the frog heart occurred mainly in the narrow junctional area on the ventricular side of the bulbus cordis tissue. The action potential of this tissue was different from that seen in the bulbus cordis and the ventricle, showing a low rate of depolarization and low resting potential. Several physiological phenomena which have been observed in this junctional tissue can also be seen in the A-V nodal tissue. Histological studies revealed a difference in the direction of fibers and the presence of special cells in the junctional tissue. The mechanism responsible for the low conduction velocity in this area can be attributed, in part, to the histological arrangement found in the junctional tissue.
Effects of Bradykinin on Forearm Venous Tone and Vascular Resistance in Man
Authors: MASON DEAN T. , MELMON KENNETH L.
Published: June 2012

The effects of intravenous injections of synthetic bradykinin on the vascular dynamics of the forearm were studied in nine normal subjects. A plethysmographic technique was used to measure forearm blood flow and to estimate forearm venous tone. Bradykinin decreased mean systemic arterial pressure, elevated forearm blood flow, and reduced calculated forearm vascular resistance and also venous tone. The venodilatation was preceded by brief venoconstriction which was prevented in five subjects pretreated with the antiadrenergic agent, guanethidine. It is postulated (a) that this venoconstriction is one of the compensatory reflex actions that accompany reduction of systemic arterial pressure, and (b) that the prime effect of bradykinin on both the arterial and the venous beds of the forearm is a direct vasodilatation.
Effects of Adenine Nucleotides and Microsomes on Glucose Utilization in Rat Heart Homogenates
Authors: HAUGAARD NIELS , HAUGAARD ELLA S. , ANTONIO ABILIO
Published: June 2012

The utilization of glucose by rat heart homogenate may proceed rapidly at low concentrations of
ATP
when conditions are such that this nucleotide is rapidly regenerated.

When high concentrations of
ATP
are present, glucose utilization is depressed markedly. The inhibition of glucose metabolism is abolished completely by magnesium ions.

Glucose is utilized at a rapid rate by a system consisting of heart mitochondria and the soluble components of a heart homogenate. The addition of microsomes to such a system produces a large increase in the rate of glucose disappearance and a decrease in the concentration of
ATP
. The stimulatory effect of microsomes appears to be mainly a result of an increase in
ATP
ase activity.

A possible role for
ATP
and magnesium in the regulation of glucose phosphorylation in the intact heart has been discussed.
Pulmonary Vascular Changes with Chronic Unilateral Pulmonary Hypoxia
Authors: NAEYE RICHARD L.
Published: June 2012

One main bronchus was ligated in each of twelve dogs and three calves. In eight of the animals, the bronchus reopened spontaneously with a 2 to 4 mm aperture permitting re-expansion of the associated lung. Both smooth muscle hyperplasia and hypertrophy developed in small arteries of the poorly ventilated dog lungs. In the calves, muscular hyperplasia and hypertrophy developed in small pulmonary veins of the hypoxic lungs. Since arterial pressures and pulmonary arterial oxygen saturation were presumably identical in hypoxic and control lungs, changes in vascular muscle are postulated to be the result of altered oxygen tension of the surrounding alveolar gas.
Dipole Moments of Dog, Monkey, and Lamb Hearts
Authors: NELSON CLIFFORD V. , ANGELAKOS E. T. , GASTONGUAY PAUL R.
Published: June 2012

The magnitude and direction of the spatial dipole moments of hearts of a dog, monkey and lamb were obtained in vivo from, multiple potentials on the body surface. A comparison between peak dipole moment and body weight in mammals showed a definite relationship. A comparison with spatial vectors calculated from the equilateral tetrahedron system showed significant differences. Graphs of instantaneous potential distributions around the chest showed that bidipolar conditions existed at certain times and locations, but the distributions were mostly unidipolar. Frontal plane angles calculated from the Einthoven triangle were about 30° too high, on the average.
Observations on the Relation Between Ventricular Activation Sequence and the Hemodynamic State
Authors: ABILDSKOV J. A. , EICH ROBERT H. , HARUMI KENICHI , SMULYAN HAROLD
Published: June 2012

Hemodynamic parameters including records of left and right ventricular pressure, aortic pressure, the first derivative of the left ventricular pressure curve, and carotid flow were recorded with different patterns of ventricular activation. Special measures were used to achieve a comparable role of the atrium in ventricular filling with the different ventricular activation patterns.

With an intact cardiac conduction system, definite but small differences in the hemodynamic parameters named were associated with different activation patterns. Normal ventricular activation produced slightly higher peak pressures in both ventricles and higher carotid flow than did abnormal activation. Each different activation pattern was associated with differences in the detailed shape of the ventricular pressure curves and with differences in the relative time of onset of pressure rise in right and left ventricles. When the specialized conduction system was blocked with large doses of ouabain, various patterns of ventricular activation were associated with marked differences of the hemodynamic parameters named. These findings may explain previously published conflicting results. They also suggest that disease of the conduction system may have a significant functional role in cardiac disease.
Pacemaker Periodicity in Atrial Fibrillation
Authors: BATTERSBY EDWARD J.
Published: June 2012

The presence of a periodic component in the atrial waveform of patients with chronic atrial fibrillation can be demonstrated by the use of autocorrelation techniques, and is interpreted as evidence for the presence of a periodic or almost periodic pacemaking mechanism. In twelve patients the average rate of this periodic element was 421 per minute with a range of 346 to 528. No correlation is present between increasing rate and disorder of the waveform.

The presence of persistent random wavelets modifying the beat-to-beat spread of excitation generated by a periodic focal pacemaker is proposed as a unifying hypothesis explaining the variability of the atrial waveform in atrial fibrillation in man.
Left Ventricular Residual Volume in the Intact and Denervated Dog Heart
Authors: BRUCE THOMAS A. , CHAPMAN CARLETON B.
Published: June 2012

Left ventricular volumes were measured at rest and during electrically stimulated muscular exercise in 28 anesthetized dogs. Volumes were calculated from images obtained during biplane cineangiofluorography. Under control resting conditions from 30 to 55% of the diastolic volume of the left ventricle remained after ejection. This residual volume of blood became an immediate source of the increased ventricular output during the beginning of exercise. Following vagectomy, sympathectomy, and total cardiac denervation, the ability to increase cardiac output during exercise persisted, but was accomplished by increased ventricular filling rather than by diminution of the residual volume.
Gastrointestinal Blood Flow in the Dog
Authors: DELANEY JOHN P. , CUSTER JAMES
Published: June 2012

That the radiorubidium distribution method provides good estimates of blood flow to the gastrointestinal organs was demonstrated by comparing the arterial concentration course of the isotope with the simultaneous venous concentration for the individual organs. Blood flow to stomach, intestine and colon are accurately assessed by this method. Estimates for pancreas, gall bladder, esophagus and duodenum are probably correct. Average perfusion rates in the pentobarbital anesthetized dog are, in cc/min.g of tissue: --esophagus, 0.21; stomach, 0.51; duodenum, 0.70; small intestine, 0.72; colon, 0.82; pancreas, 0.60; and gall bladder, 0.39.
Coronary Arterial Lesions in Chickens
Authors: RATCLIFFE HERBERT L. , SNYDER ROBERT L.
Published: June 2012

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

High mean heart scores for grouped cocks correlated with high mean heart scores for hens of their groups, and low heart scores for grouped cocks with low scores for hens of their groups.
Hemodynamic Consequences of Induced Changes in Blood Volume
Authors: Conway James , Gellai Miklos
Published: June 2012

The effects of transfusion or bleeding on cardiac output and blood pressure have been followed for periods of seven to ten hours in trained, conscious dogs.

When blood volume is increased by transfusion of blood, supplemented by dextran to minimize the expected change in hematocrit, cardiac output and blood pressure increase initially. After one and one-half hours the cardiac output returns to the initial level but blood pressure remains elevated and calculated peripheral resistance increases. This state has been maintained for a period of ten hours by repeated transfusion.

After bleeding, with replacement of packed cells, again to minimize the change in hematocrit, cardiac output decreases initially and peripheral resistance increases, but after three hours, output returns to its former level, and peripheral resistance falls below the control value. These changes become more prominent when a second hemorrhage is performed two hours after the first one. The reduction of resistance was then maintained for seven hours.

These findings demonstrate that the effects of changes in blood volume are not limited to the acute changes in cardiac output and filling pressure. After periods of one to three hours, changes in peripheral resistance also become evident.
Hypertensive Vascular Disease Induced by Heterologous Renin
Authors: Masson Georges M. C. , Kashii Chujiro , Matsunaga Masato , Page Irvine H.
Published: June 2012

Chronic treatment with crude hog, or rat, renin administered subcutaneously to uninephrectomized rats elicits hypertension, renal and vascular lesions, hypertrophy of the zona glomerulosa of the adrenals, and renin depletion in the remaining kidney. Semipurified hog renin given in equipressor doses also causes renin depletion and stimulation of the zona glomerulosa, but no hypertension nor vascular disease. However, semipurified hog renin becomes as effective as the crude preparation after addition of retarding substances such as gelatin, oil, or cholesterol. Thus, a prolonged and sustained resorption of renin seems to be a prerequisite for the development of hypertension. Since hypertension takes place only after a latent period during which arterial pressure remains within the normal range, it does not appear that hypertension can be attributed to the acute pressor effect of renin. It is proposed as a working hypothesis that renin, through angiotensin, initiates nervous mechanisms which are responsible for the development of benign hypertension and that the acute pressor effect of angiotensin is more specifically associated with the malignant phase of hypertension.
Congenital Heart Defects in Chick Embryos Subjected to Temperature Variations
Authors: de la Cruz María V. , Campillo-Sainz Carlos , Muñoz-Armas Simón , Pallares Guillermina , Zamudio Bandera Rafaela
Published: June 2012

The effect of incubator temperature on mortality rates and on appearance of congenital malformations in white leghorn chicks and embryos was studied. The elevation of incubation temperature to 39.44°C led to a high mortality and to malformations in the eyes and the nervous system, as well as to abnormal torsion of the body axis. It did not produce any cardiac abnormalities, which would have been detected easily because the mortality peak occurred after the development of the heart was complete. Decreasing temperature of incubation to 35.83°C produced a high mortality rate and, very frequently, interventricular septal defects. These results and the possible mechanisms by which changes of temperature exert teratogenic effects are discussed.
Oxygen Cost of Electrical Activation of the Heart
Authors: Klocke Francis J. , Braunwald Eugene , Ross. John
Published: June 2012

The present study was undertaken to define the O
2
requirements of electrical activation of the heart. Thirteen isolated canine hearts were perfused with whole blood from which calcium had been removed with an exchange resin and to which the disodium salt of ethylenediaminetetraacetic acid had been added. Spontaneous depolarizations were suppressed by raising the plasma potassium to an average concentration of 7.5 mEq/liter, and the right ventricle was stimulated electrically at controlled frequencies. Although the stimuli produced propagated depolarizations, neither high-sensitivity strain gauge arches sutured to both ventricles, nor careful visual observation, showed any evidence of associated contractile activity. Ten of the hearts were studied with repetitive single stimuli applied in the conventional fashion, while the remaining three hearts were subjected to paired electrical stimulation. Changes of myocardial O
2
consumption (MV
·
O
2
) were measured at a constant coronary blood flow and arterial O
2
content by determining changes of venous O
2
content from a continuous recording of venous PO
2
. Increases of the frequency of depolarization were uniformly accompanied by small increases of MV
·
O
2
, averaging 0.40 ± 0.04 (SEM) µliter/activation/100 g. The increases were of the same order of magnitude in the hearts subjected to paired electrical stimulation as in the hearts studied with single stimulation, suggesting that the altered frequency and rhythm of depolarization in paired electrical stimulation cannot account for the marked increase of MV
·
O
2
which this intervention produces in the intact heart. It is concluded that the amount of O
2
required for electrical activation of the heart is less than 1% of the total O
2
consumption of the normally working heart.
Blood Rheology: Effect of Fibrinogen Deduced by Addition
Authors: Merrill Edward W. , Gilliland Edwin R. , Lee T. S. , Salzman Edwin W.
Published: June 2012

Viscometric measurements near zero shear stress were made on human blood and on suspensions of red cells in saline solutions of dialysed and nondialysed fibrinogen at 37°C at an hematocrit of 40. The principal viscometric parameter studied was the yield shear stress. The higher the value of yield stress, the greater is the viscosity defined as the ratio of shear stress to shear rate, in the region near zero flow, and the greater is the variation of viscosity with shear rate. The yield stress, zero in suspensions containing no fibrinogen, was found to increase with the fibrinogen concentration. At a given concentration of clottable fibrinogen (up to 1.20 g/100 ml) the yield shear stress was substantially greater in suspensions of red cells in their original plasma than in saline solutions of fractionated fibrinogen. Dialysis of the fractionated fibrinogen had no significant effect on the viscosity characteristics. For a given concentration of fibrinogen added to saline solutions, a higher yield stress was produced in the presence of A
+
cells than in the presence of O
+
cells.
Left Ventricular Volume Studies in Tranquilized Dogs with Local Anesthesia
Authors: Bristow J. David , Farrehi Cyrus , Ueland Kent
Published: June 2012

Left ventricular volumes were estimated by thermodilution in unanesthetized dogs given the tranquilizer, perphenazine. During systole, the left ventricle emptied an average of 40% of its end-diastolic volume. This is a significantly greater proportion than observed previously during general anesthesia with several different agents.

Left ventricular mid-systolic wall force was calculated. Higher force values at a given end-diastolic volume occurred during intravenous infusion of norepinephrine. Methoxamine failed to change these relationships.
Effects of Barium on Mature and Embryonic Heart Cells
Authors: Kleinfeld Morris , Stein Edward , Tionaytis Clem
Published: June 2012

Barium chloride was administered to isolated preparations of dog heart and rat atrium and to trypsinized embryonic chick heart cells cultured in vitro. Transmembrane action potentials recorded from pacemaker, specialized conductive and contractile fibers of the dog heart, and atrial fibers of rat heart showed a slowing in the rising and falling phases of the action potential and a prominent negative after-potential. The action potential of the Purkinje fiber of the dog heart showed in addition a depolarization during diastole. A decrease in resting potential was observed later.

The isometric tension developed by the rat atrium showed a significant increase which was greater at the higher concentractions (greater than 3.5 x 10
-4
M) of barium chloride. The cultured embryonic heart cells were appreciably more sensitive to barium than the mature heart cells. An increase in rate of beat of the embryonic heart cells was observed at concentrations of 10
-6
M whereas a change in heart rate was first observed in the adult heart at concentrations above 10
-4
M. The induction of beating in cell communities previously quiescent is due to a local automatic activity rather than to a propagated activity from an adjacent cell community.

The slowing in rise time of the action potential can be attributed to a depression of the sodium-carrying system. The slowing of repolarization can be ascribed to a decrease in potassium conductance. The pronounced negative after-potential can be explained on the basis of sustained impermeability of the membrane to potassium. The mechanism by which barium produces a positive inotropic effect in the rat atrium is open to conjecture. It cannot be attributed solely to a prolongation of the duration of the action potential nor can a direct effect on the contractile proteins be excluded. The presence of extracellular calcium is essential in order to obtain a positive inotropic effect in the rat atrium when barium is added.