bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytochemically assayable Na+,K+-ATPase inhibition by Milan hypertensive rat plasma.
Authors: Holland S , Millett J , Alaghband-Zadeh J , de Wardener H , Ferrari P , Bianchi G
Published: June 2012

The ability of plasma from 3- and 9-week-old Milan hypertensive rats and their normotensive controls to inhibit Na+,K+-adenosine triphosphatase (ATPase) was studied using cytochemical bioassay techniques in fresh tissue. With a validated cytochemical bioassay that measures the capacity of biological samples to stimulate glucose-6-phosphate dehydrogenase activity in guinea pig proximal tubules as an indication of their capacity to inhibit Na+,K+-ATPase, the mean glucose-6-phosphate dehydrogenase-stimulating ability of the plasma of the 9-week-old Milan hypertensive rats and their normotensive controls was 586.0 +/- 88 and 23.4 +/- 8.3 U/ml (n = 7; p less than 0.001), while that of the 3-week-old Milan hypertensive rats (before the main rise in arterial pressure) and their normotensive controls was 99.9 +/- 27.4 and 7.8 +/- 1.8 U/ml (n = 7; p less than 0.001). With the use of a semiquantitative cytochemical assay that measures Na+,K+-ATPase activity directly, plasma from the adult hypertensive rats had a much greater capacity to inhibit Na+,K+-ATPase than the plasma of the control rats. The significantly raised levels found in the young hypertensive rats before the main rise in arterial pressure are consistent with the hypothesis that the rise in the ability of plasma to inhibit Na+,K+-ATPase is due to an inherited renal difficulty in excreting sodium.
Decreased density of vascular receptors for atrial natriuretic peptide in DOCA-salt hypertensive rats.
Authors: Schiffrin E L , St-Louis J
Published: June 2012

We have previously found that vascular receptors for atrial natriuretic peptide (ANP) in the rat are down-regulated by volume expansion. For this reason vascular ANP receptor density and affinity were examined in a model of volume-expanded hypertension, the deoxycorticosterone acetate (DOCA)-salt hypertensive rat. The density of mesenteric vascular ANP binding sites was decreased in DOCA-salt hypertensive rats from a control value in uninephrectomized rats of 203 +/- 25 fmol/mg protein to 60 +/- 13 fmol/mg protein (p less than 0.01). The sensitivity of norepinephrine-precontracted aorta to ANP was significantly reduced in DOCA-salt hypertensive rats (p less than 0.001). DOCA-salt hypertensive rats infused intravenously for 4 days with ANP, 100 to 300 ng/hr, did not experience a lowering of blood pressure, in contrast to the significant reduction in blood pressure seen in two-kidney, one clip Goldblatt hypertensive rats similarly infused. In the latter there was no natriuretic response to ANP, while in the DOCA-salt hypertensive rats natriuresis occurred without lowering of blood pressure. In the DOCA-salt hypertensive rats plasma ANP concentration was increased to 68 +/- 8 fmol/ml from 10 +/- 1 fmol/ml in uninephrectomized rats. In conclusion, raised ANP concentration in plasma of volume-expanded hypertensive rats (DOCA-salt hypertension) may result in decreased density of ANP vascular receptors. These results suggest that a decrement in the number of ANP receptors may be a cause of decreased sensitivity of vascular responses to ANP in vitro and resistance to the blood pressure-lowering action of ANP in vivo.
Central alpha 2-adrenergic stimulation increases neurointermediate lobe immunoreactive beta-endorphin in spontaneously hypertensive rats.
Authors: Yasunari K , Kanayama Y , Kohno M , Murakawa K , Kawarabayashi T , Takeda T
Published: June 2012

A possible influence of the central alpha 2-adrenergic system on beta-endorphin was examined in rat anterior pituitary, neurointermediate lobe, and plasma. The concentration of beta-endorphin in anterior pituitary, neurointermediate lobe, and plasma was determined by radioimmunoassay 15 minutes after subcutaneous injection of clonidine in 14-week-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Clonidine reduced the concentration of the plasma beta-endorphinlike immunoreactivity in SHR and to a lesser extent in WKY. No significant changes in the concentration of beta-endorphinlike immunoreactivity were observed in anterior pituitary. Clonidine increased the concentration of neurointermediate lobe beta-endorphinlike immunoreactivity in SHR in a dose-related manner but did not affect the concentration in WKY. Administration of yohimbine (1 mg/kg) completely blocked the clonidine-induced increase of neurointermediate lobe beta-endorphinlike immunoreactivity in SHR, while prazosin (1 mg/kg) had no effect. These data suggest that the central alpha 2-adrenergic activation increases the neurointermediate lobe concentration of beta-endorphinlike immunoreactivity in SHR by suppressing beta-endorphin release from the neurointermediate lobe into the circulation.
Partial characterization of a renin-releasing factor from plasma and hypothalamus.
Authors: Van de Kar L D , Urban J H , Brownfield M S , Simmons W H
Published: June 2012

Previous studies have indicated that administration of the serotonin releaser p-chloroamphetamine HCl produces a dose-dependent increase in renin secretion through a blood-borne renin-releasing factor. The present studies were designed to partially characterize this renin-releasing factor using an in vitro kidney slice method for the bioassay of renin-releasing activity. Plasma from p-chloroamphetamine-treated, nephrectomized rats was used to obtain the renin-releasing factor, which was fractionated by ultrafiltration into fractions of molecular weight ranges of 1000 to 5000, 5000 to 10,000, and 10,000 to 20,000. The molecular weight ranges of the renin-releasing factor was determined to be between 5000 and 10,000. Since previous studies have shown that lesions in the hypothalamus prevent the effect of p-chloroamphetamine on renin secretion, we tested whether a hypothalamic extract can release renin from kidney slices. Addition of extracts of boiled rat hypothalamic tissue to the kidney slices caused an increase in renin release. Addition of cerebellar extracts produced a smaller increase in renin release, whereas addition of pituitary extracts had no effect. Fractionation by ultrafiltration of bovine hypothalamic extract revealed that the fraction with a molecular weight range of 5000 to 10,000 possessed the highest renin-releasing ability. The 1000 to 5000 (molecular weight) fraction possessed a sizeable renin-releasing activity, but the 10,000 to 20,000 fraction had no renin-releasing activity. Both bovine hypothalamus fractions (molecular weights between 1000-5000 and 5000-10,000) and plasma fraction lost their renin-releasing activity after digestion with pronase, suggesting that the renin-releasing factor or factors are peptides. These results suggest that a renin-releasing factor originate in the hypothalamus.
Inhibition of renin release by analogues of adenosine in rabbit renal cortical slices.
Authors: Barchowsky A , Data J L , Whorton A R
Published: June 2012

Renal cortical slices obtained from male New Zealand rabbits were used to investigate the role of adenosine in the regulation of renin release. Isoproterenol produced a significant (p less than 0.01), twofold to threefold increase in renin release, that was both dose-dependent and time-dependent. Addition of either the l-phenylisopropyl or the N6-ethylcarboxamido derivative of adenosine attenuated this stimulation at concentrations as low as 10(-9) M or 10(-8) M, respectively. Higher doses of d-phenylisopropyladenosine (10(-6) M) or adenosine (10(-5) M) were necessary to significantly reduce the beta-adrenergic response (p less than 0.01). Inhibition was absent in slices preincubated with 10(-5) M 8-phenyltheophylline, a concentration that had no effect on either basal or stimulated renin release. The site of inhibition appeared to be distal to beta-adrenergic and prostaglandin receptors since l-phenylisopropyladenosine (10(-8) M) blocked stimulation by selective beta-adrenergic receptor agonists, prenalterol (10(-6) M) or salbutamol (10(-5) M), and by prostaglandin E1. These data suggest that adenosine and its analogues inhibit renin release and that this inhibition may be mediated by a receptor-dependent action on a common point in the pathway leading to release.
Intrathoracic Volume Changes in Relation to the Cardiopneumogram
Authors: HAMILTON W. F. , LOMBARD E. A.
Published: June 2012

The outflow of blood from the chest during the phases of the cardiac cycle is found to be nearly equaled by a phasic inflow. The net volume change exerts very small pressure changes in the intrathoracic (intrapulmonary) air. This is not due to the distensibility of the chest wall because when allowance is made for this factor and the intrathoracic blood volume change is calculated, it is found to be a very small fraction of the stroke volume.
Oxygen Administration upon Ventricular Tachycardia and Blood Pressure in Animals with Acute Myocardial Infarction
Authors: HARRIS A. SIDNEY , OLSEN ROY W. , ESTANDÍA ANTONIO , FORD TEDROE J.
Published: June 2012

The administration of oxygen, 60 to 70 per cent in inspired air, to dogs with ectopic ventricular tachycardia resulting from myocardial infarction produced no consistent changes in ectopic frequency, but the blood pressure was elevated during oxygen administration in every trial.
The Lipoprotein Composition of Dog Lymph
Authors: PAGE IRVINE H. , LEWIS LENA A. , PLAHL GEORGE
Published: June 2012

Deposition of lipids during development of atherosclerosis may come from extracellular fluid rather than directly from plasma. The lipoprotein composition of lymph thus assumes importance in the genesis of atherosclerosis. The predominant component found in thoracic duct lymph was the -S
1.21
4 and 7, with lesser amounts of the 23. It was similar qualitatively but not quantitatively to dog's serum. The bulk of lymph lipoproteins derive from blood plasma. After fat feeding the absorbed lipid is delivered by the lymph to the blood in large aggregates containing large quantities of -S > 70 component. The > 70 component seemed to reflect changes in lipid transport in dogs more actively than the relatively more stable -S, 4, 7 and 23 components.
A Photoelectric Ear Densitometer for Continuously Recording the Arterial Concentration of T-1824 in the Dye-Dilution Method
Authors: MILNOR WILLIAM R. , TALBOT SAMUEL A. , McKEEVER WILLIAM P. , MARYE ROBERT B. , NEWMAN ELLIOT V.
Published: June 2012

To eliminate the collection of serial samples of arterial blood an instrument has been developed which records dye-dilution curves by measuring changes in optical density of a segment of a heatflushed car. Comparison with curves from arterial samples shows close similarity in the shape of the curves, and good agreement between the cardiac outputs calculated from them. Other advantages of the technic are the relatively small close of dye needed, the linear relation between deflection of the recording galvanometer and changes in dye concentration in the blood, and the fact that determinations can be repeated several times at intervals of three or four minutes.
An Evaluation of Wedge Pressures in Dogs under Conditions of Normal and Elevated Pulmonary Vascular Pressures
Authors: HADDY F. J. , ALDEN J. F. , FERRIN A. L. , HANNON D. W. , ADAMS W. L. , BARONOFSKY I. D.
Published: June 2012

Fifty-six combined right and left heart catheterizations in normal dogs and dogs with experimental mitral stenosis failed to show a significant positive correlation between pulmonary artery wedge pressure and pulmonary vein pressure when the latter was below approximately 17 mm. Hg. Evidence is presented which suggests that the wedged catheter outlets are totally occluded in many instances in the dog. Pulmonary vein wedge pressure reflected a pressure nearer the pulmonary artery pressure than the expected capillary pressure. One instance of mitral regurgitation revealed large pulmonary vein and pulmonary artery wedge pulse pressures.
Electrocardiographic Alterations Produced by an Increase in Plasma pH, Bicarbonate and Sodium as Compared with Those Seen with a Decrease in Potassium
Authors: MAGIDA MELVILLE G. , ROBERTS KATHLEEN E.
Published: June 2012

The effects of an increase in plasma pH, bicarbonate and sodium on the electrocardiogram of the normal dog have been compared with those produced by a decrease in plasma potassium. The electrocardiographic alterations in these experimentally induced situations were found to be similar in form and progression.
Theoretic Analysis of the Influence of Heart-Dipole Eccentricity on Limb Leads, Wilson Central-Terminal Voltage and the Frontal-Plane Vectorcardiogram
Authors: FRANK ERNEST
Published: June 2012

This is a theoretic investigation of the influence of the position of a current dipole on the electric potential produced at the boundary of a homogeneous conducting sphere. Thirty different eccentric dipole positions are selected within the sphere to bear analogy to locations of the equivalent dipole of the human heart within the chest, and boundary-potential calculations are made from points selected to bear analogy with body-surface points utilized in limb leads, Wilson centralterminal and frontal-plane electrocardiography. The point of view taken differs completely from the scalene-triangle geometric representation of eccentricity; instead, an equilateral triangle is used in conjunction with assigned strength and orientation time-variations for the eccentric dipole.

It is concluded that if electrocardiography were subject to no other limitation of the application of field analysis, eccentricity of dipole position alone can produce very significant deviations between the manifest heart vector and the true heart vector in both direction and magnitude. The dependence of the Wilson central-terminal voltage on dipole eccentricity is likewise appreciable and of the same order of magnitude as reported by several experimenters; however, the effects of eccentricity on the Wilson central-terminal voltage are generally less pronounced than on the manifest heart vector.
Relationship between Cerebrospinal Fluid Pressure Changes and Cerebral Blood Flow
Authors: RICH M. , SCHEINBERG P. , BELLE M. S.
Published: June 2012

This study of the effects of certain drugs, gas mixtures, and other stimuli on the cerebrospinal fluid pressure corroborates previous conclusions that alterations in cerebral blood flow are reflected by similar changes in the cerebrospinal fluid pressure in the same direction. The hypothesis is advanced that the elevations and depressions in cerebrospinal fluid pressure resulting from these agents are due to the respective increased and decreased volume of the vascular structures of the brain, expanding within its rigid container.
Local and Long Distance Transmission and Storage of Electrocardiograms and other Low Frequency Signals
Authors: RAHM W. E. , BARMORE J. L. , ELLESTAD I. M. , DUNN F. LOWELL
Published: June 2012

A procedure using frequency modulation is described for transmission of electrocardiograms and electroencephalograms over available local and long distance telephone facilities.
Chronic Effect on Blood Pressure of Bilateral Carotid and Vertebral Ligation in the Rabbit
Authors: Lowe R. D.
Published: June 2012

A method is described of performing bilateral carotid ligation in the rabbit preserving the carotid sinus and the central artery of the ear. Of 26 animals prepared in this way, and 14 with bilateral vertebral ligation, none developed chronic hypertension. The development of a collateral circulation is shown by serial retinal artery pressure readings and by resin casts of cerebral vessels; neither carotid nor vertebral ligations produce any permanent ischemia in their area of supply. In 25 animals subjected to combined vertebral and carotid ligation, a marked lowering of arterial pressure in the head was obtained, but no animal developed hypertension until the carotid sinuses were subsequently denervated. It is concluded that previous workers who have reported chronic hypertension following ligation of cerebral arteries have been studying the effects of interference with buffer-nerve function.
Analysis of the Acute Circulatory Effects of Guanethidine and Bretylium
Authors: Gaffney Thomas E. , Braunwald Eugene , Cooper Theodore
Published: June 2012

The acute effects of guanethidine and bretylium on myocardial contractile force, heart rate, mean arterial pressure, and cardiac out put were studied in normal dogs and cardiac denervated, myocardial catecholamine-depleted dogs. Right ventricular contractile force was measured by means of a Walton-Brodie strain-gauge arch. Cardiac output was measured by the dye-dilution technique.

In normal dogs, guanethidine produced marked increases of myocardial contractile force, heart rate, cardiac output, and arterial pressure. In the cardiac-denervated dogs. guanethidine produced a small decrease in myocardial contractile force and a small increase in heart rate ; the cardiac output and pressor responses were also markedly reduced. Thus, it appears that sudden release of myocardial eateeholamines is largely responsible for the acute circulatory effects of guanethidine.

In normal dogs, bretylium increased myoeardial contractile force, heart rate, cardiac output, and arterial pressure. In cardiac denervated dogs, the increase in contractile force produced by bretylium was essentially unchanged from the normal, but the heart rate was decreased, and the cardiac output response appeared slightly reduced. These data suggest that myocard ial catecholamine release plays a limited but definite role in the acute circulatory effects of bretylium.

The negative inotropic effect of guanethidine and the negative chronotropic effect of bretylium in the denervated. amine-depleted heart suggest that these responses are direct effects of these drugs which are manifest only in the amine-depleted heart.
Evaluation of Procedures Designed to Enhance Coronary Collateral Blood Flow
Authors: Berne Robert M. , Jones Richard D. , Cross Frederick S.
Published: June 2012

Three procedures reported to improve the coronary collateral circulation were carried out in dogs: (1) placement of 0.25 to 0.5 Gm. of sterile shredded asbestos over the surface of the heart; (2) suturing of the mediastinal fat pad to the abraded left lateral surface of the heart in conjunction with the application of asbestos; (3) implantation of the internal mammary artery into the left ventricular wall in conjunction with application of Ivalon sponge to the denuded surface of the left ventricle.

The effectiveness of these measures was determined in dogs with previously narrowed left circumflex coronary arteries. As judged by retrograde flows and peripheral coronary pressures, the collateral vessel development was not increased over and above that produced by narrowing alone. Coronary artery injection studies revealed that only internal mammary artery implantation produced vascular connections between cardiac and extra-cardiac vessels.
On the Mechanism of Thrombolysis by Plasmin
Authors: Ambrus Clara M. , Back Nathan , Ambrus Julian L.
Published: June 2012

I
131
-labeled purified human fibrin clots were introduced into the circulation of dogs at various time intervals after an infusion of human plasmin. One hour later, the clots were removed and incubated in saline at 37 C. In most cases, at the time when these clots were in the circulation, there was no significant "free" plasmin activity demonstrable in the blood. Nevertheless, the clots removed from these animals exhibited in vitro lysis upon incubation. Plasmin-antiplasmin complexes were formed in vitro with no demonstrable caseinolytic activity. These complexes were as effective in dissolving fibrin clots in vivo as the same amounts of plasmin were alone. The activator (streptokinase) alone used to activate plasminogen to plasmin was significantly less effective than streptokinase-activated-plasmin, alone or in complex form with antiplasmin. These experiments were interpreted as pointing toward the ability of fibrin to compete effectively with antiplasmin for plasmin. Thus, antiplasmin may serve as a transport form or reservoir of plasmin, releasing it when fibrin clots are available, but protecting other plasma proteins from its proteolytic effect. Other phenomena apparently confirming this hypothesis have been mentioned.
Hemodynamics in Normal Cattle
Authors: Reeves John T. , Grover Robert F. , Will Donald H. , Alexander Archibald F.
Published: June 2012

A satisfactory method has been described for conducting hemodynamic studies in cattle. With the animals in normal standing position, and without sedation or tranquilization, cardiac catheterization can be readily performed. With a muzzle mask, ventilatory studies are also feasible. Using this method, each of 10 normal steers was studied four times during a six-month period. This permitted the establishment of normal values for a number of circulatory measurements. In addition, an evaluation of chlorpromazine administration in normal cattle demonstrated some of the numerous complex effects of this drug on the cardiovascular and respiratory systems. These included hemodilution, hypoventilation, and a marked reduction of the arteriovenous oxygen difference.
Acute Effects of Cardiac Glycosides on Aldosterone Secretion in Dogs with Hyperaldosteronism Secondary to Chronic Right Heart Failure
Authors: Carpenter Charles C. J. , Davis James O. , Wallace Charles R. , Hamilton William F.
Published: June 2012

A marked elevation in the rate of aldosterone secretion was observed in eight dogs with experimental congestive heart failure secondary either to controlled progressive pulmonic stenosis or to combined tricuspid insufficiency and pulmonic stenosis, and in one dog with spontaneously occurring congestive heart failure. In the dogs with pulmonic stenosis, digitalization with digoxin resulted in improvement in cardiovascular function, and subsequent further constriction of the pulmonary artery again led to right ventricular failure; in each animal aldosterone output decreased within 90 minutes after digitalization, and increased markedly within one hour after further constriction of the pulmonary artery. In the dog with naturally occurring congestive heart failure, ouabain administration caused a similar striking hemodynamic improvement, and a marked reduction in aldosterone secretion was observed within 55 minutes after the glycoside was given. In the dogs with combined tricuspid insufficiency and pulmonic stenosis, no hemodynamic improvement occurred after digitalization; in these animals, the aldosterone secretion rate did not change significantly during the two-hour period following the digoxin injection. These data demonstrate that changes in the rate of aldosterone secretion in dogs with right heart failure were closely correlated with alterations in cardiovascular function; in these animals, hemodynamic improvement consistently led to decreased aldosterone production, and subsequent worsening of cardiovascular function resulted in increased aldosterone output.
Circulatory Dynamics and the Effects of Respiration During Ventricular Asystole in Dogs with Complete Heart Block
Authors: Spach Madison S. , Scarpelli Emile M.
Published: June 2012

Pressure-flow changes during ventricular asystole (but with atrial activity present) were studied in 11 dogs with complete heart block. The influence of respiration on these parameters was evaluated during spontaneous breathing, intermittent positive pressure respiration, and apnea. During spontaneous breathing, the pulmonary artery pressure initially fell below the right atrial pressure following the onset of ventricular asystole. Both pressures then showed a gradual rise which was accompanied by flow of blood into the pulmonary artery (estimated to be 121 to 139 ml./min.). The mean pressure in the left atrium became greater than that in the pulmonary artery, concomitant with a gradual rise in the end-expiratory intrathoracic pressure. Despite this mean pressure change, flow from the pulmonary artery to the left atrium was demonstrated. Analysis of the instantaneous pressures during the atrial cycle showed that flow could occur during early atrial diastole in both phases of respiration and throughout atrial diastole during inspiration. Following each atrial beat, the left atrium received blood from the pulmonary veins and left ventricle (mitral regurgitation). There was a continued fall in the aortic pressure and, when it was exceeded by the left atrial systolic pressure, blood was propelled into the aorta. These pressure-flow changes were affected by positive pressure respiration and apnea. All pressures were significantly lower during these respiratory conditions and flow from the pulmonary artery to left atrium could not be demonstrated. The marked effects of respiration on the circulatory dynamics in animals during ventricular asystole must be considered in the interpretation of the results of studies, particularly in thoracotomized or apneic dogs, whenever there are conditions of low flow or pressure in the central circulation.
Dynamics of Ventricular Ejection
Authors: SPENCER MERRILL P. , GREISS FRANK C.
Published: June 2012

Left ventricular ejection in open-chest, anesthetized dogs begins with an abrupt acceleration of blood into the ascending aorta, reaching an average maximum of 4,650 cm./sec./sec. Velocity reaches a sharp peak of 88 cm./sec. (average) within the first one-third to one-half of the ejection period. Deceleration is more gradual and continues to the closure of the aortic valve. The general pattern of the time-course recording is that of a triangle with its peak skewed into early systole and separated from a flat diastolic period of zero flow by a deep notch of backflow attending closure of the aortic valve. Ventricular pressure exceeds aortic pressure only during the brief period between the opening of the valve and peak systolic velocity, a period of approximately 45 per cent of the ejection period. This "positive" (headward) gradient represents the acceleration transient and explains the sharp rise in flow to a maximum in early systole. During the deceleration (terminal) phase of ventricular ejection, the pressure gradient is against the direction of flow. This reversal in pressure gradient brings about a gradual deceleration of flow to zero. These findings are considered experimental proof that the major phenomenon relating pressure and flow in the ascending aorta is that governing mass acceleration.
Cardiodynamic Effects of Experimental Bundle-Branch Block in the Dog
Authors: WENNEMARK JAMES R. , BLAKE DAVID F. , KEZDI PAUL
Published: June 2012

Electrical-mechanical relationships of the canine heart were studied using simultaneous right and left intraveutricular pressures. In the control tracings, there was usually some asynchrony in the onset of ventricular isometric contraction with the right ventricle following the left ventricle. Right bundle-branch block and left bundle-branch block produced a delay in the onset of isometric contraction of the homolateral ventricle. A change in contour of the right intraventricular curve was frequently seen with right, bundle-branch block.
Reducation of the Utilization of the Heart by Left Heart Bypass
Authors: DENNIS CLARENCE , HALL DAVID P. , MORENO JUAN R. , SENNING ÅKE
Published: June 2012

Full left heart bypass reduces the oxygen utilization of the heart to about half the control levels, as measured by coronary sinus flow and arteriovenous oxygen differences. All measured lesser degrees of bypass reduce the oxygen utilization less markedly, but with high statistical significance of the reductions below controls. The reduction in oxygen utilization upon institution of partial or complete left bypass is usually the result more of a decrease in arteriovenous oxygen difference than of a decrease in coronary sinus blood flow. These results support the thesis that left heart bypass should be beneficial in reducing the internal work of the left ventricle in acute left heart failure with competent aortic valve.
Mechanism of the Myocardial Effects of Bretylium
Authors: GILMORE J. P. , SIEGEL J. H.
Published: June 2012

The increased myocardial contractility resulting from the injection of bretylium has been shown to be accompanied by a myocardial release of catecholamines. Cardiac sympathetic nerve stimulation following bretylium is associated with neither an increased contractility nor a release of myocardial catecholamines. The failure to release catecholamines under these conditions does not result from depletion, but rather from a block of the nerve release mechanism.
Anemia-induced Changes in Cardiac Output in Dogs Treated with Dichloroisoproterenol
Authors: GOWDEY CHARLES W.
Published: June 2012

The cardiac output of anesthetized dogs was markedly elevated by the production of severe acute anemia by exchanging dextran for blood. Dichloroisoproterenol, in a dose which completely blocked the positive chronotropic effect of epinephrine and several reflexes, usually had minimal effects on the cardiac output. The cardiac responses to acute anemia were not different in the DCI-treated and the control groups. It is concluded that the effect of acute anemia on cardiac output is probably not mediated by the action of adrenergic substances on the heart.
Electrocardiogram of Bundle-Branch Block in the Bovine Heart
Authors: Pruitt Raymond D.
Published: June 2012

The electrocardiographic consequences of blocking the right or left bundle branch have been recorded in experiments on calves. Block of either bundle was attended by lengthening of QRS interval by approximately 0.02 second and by changes in form of QRS paralleling closely those occurring in canine hearts under comparable circumstances. Significance of this parallelism to concepts of morphology and function of ventricular conduction systems in bovine and canine hearts is considered. Data reported here render problematic the concept of functional continuity of right and left divisions of the specialized ventricular conduction tissue in the bovine heart.
Intramyocardial Pressure and Strength of Left Ventricular Contraction
Authors: Salisbury Peter F. , Cross Cecil E. , Rieben P. Andre
Published: June 2012

Intramyocardial pressure was followed with the Johnson-DiPalma method in isolated hearts and in hearts in situ. Systolic intramyocardial pressure curves from hearts in situ exhibited two pressure peaks which were believed to coincide with peak contractile tension and with myocardial fiber shortening, respectively. The following factors influenced intramyocardial pressure: ventricular cavity volume, heart rate, coronary perfusion pressure, outflow resistance, and "epicardial" compression. The contractile strength of the left ventricle varied in proportion with the intramyocardial pressure; it did not appear to be regulated primarily by diastolic volume or by metabolic support. Intramyocardial pressure was believed to determine the contractile strength of the heart by controlling the release of a potentiating substance.
Modification of Aortic Oxidative Enzymes in Rats by Gonadectomy and Substitutive Therapy
Authors: Malinow Manuel Rene , Moguilevsky Jaime Alberto , Lacuara Jorge Luis
Published: June 2012

Activity of the following enzyme systems has been determined in homogenates of aortas from rats: "succinic dehydrogenase," cytochrome oxidase, oxidation of α-ketoglutaric acid and of fumaric acid, DPN- and TPN-linked dehydrogenases, as well as lactic dehydrogenase. The following groups of animals were studied: (1) intact males; (2) castrated males; (3) castrated males injected with testosterone; (4) intact females; (5) spayed females; (6) spayed females injected with estradiol. Results demonstrated that gonadectomy in males stimulated "succinic dehydrogenase" and depressed the oxidation of fumaric acid; these effects were reversed by the injection of testosterone. Castration did not modify the activity of cytochrome oxidase, oxidation of α-ketoglutaric acid, DPN- and TPN-linked dehydrogenases, nor lactic dehydrogenase. Gonadectomy in females resulted in stimulation of "succinic dehydrogenase," cytochrome oxidase, as well as oxidation of α-ketoglutaric acid; these effects were reversed by the injection of estradiol into spayed females. No clear results were obtained in connection with oxidation of fumaric acid and no modifications were observed in the activity of DNP- and TPN-linked dehydrogenases nor in lactic dehydrogenase. Experiments performed in vitro showed that sexual hormones were able to depress the activity of oxidative systems in aortic homogenates.
Effect of Ventricular Rate on the Cardiac Output in the Dog with Chronic Heart Block
Authors: Miller D. Edmond , Gleason William L. , Whalen Robert E. , Morris James J. , Mclntosh Henry D.
Published: June 2012

The effect of heart rate on cardiac output and associated rate induced hemodynamic changes in dogs with chronic heart block is presented and discussed. At heart rates below 60/min., the stroke volume was maximum and relatively constant, and the cardiac output was largely rate-dependent. These relationships did not exist at ventricular rates above 60/min. Cinefluorographic evidence of decreased diastolic ventricular filling with increasing ventricular rates is presented. At very slow and very fast ventricular rates, the cardiac output decreased despite an increase in right atrial and right ventricular end-diastolic pressure. At slow rates the decreased output was due to rate alone, while at rapid rates it was attributed to the decreased diastolic filling period and resistance to ventricular distention, resulting in decreased diastolic filling.
Mechanism of Cardiogenic Shock
Authors: Guzman Santiago V. , Swenson Edward , Mitchell Robert
Published: June 2012

The acute hemodynamic changes that result from coronary embolization were studied in the intact dog. Coronary embolization with lycopodium spore suspension resulted in an immediate and marked decrease in cardiac output, hypotension to shock level, elevation of pulmonary arterial and left atrial pressures, and marked increase in total peripheral resistance. These profound hemodynamic responses were partially blocked in dogs previously atropinized. The therapeutic implications of the results were discussed.
Study of the Murmur Produced by Acute Pulmonary Artery Constriction
Authors: Moedjono Pwr , Little Robert C. , Orlando Robert A. , Brundage Bruce H.
Published: June 2012

The murmur produced by acute graded constriction of the base of the pulmonary artery was studied in the anesthetized dog by means of intraluminal phonocardiograms recorded from the pulmonary artery. In addition, right ventricular and distal pulmonary artery pressures were recorded, and the cardiac output was determined for each degree of pulmonary artery stenosis utilized in the study. A small diamond-shaped midsystolic murmur is normally recorded from inside the pulmonary artery. This murmur increases in intensity and duration with constriction of the base of the artery. A constant relationship was not found between the degree of pulmonary stenosis or pulmonary flow and the intensity of the murmur. The intensity did correlate, in an essentially linear fashion, with the average velocity of flow through the constricted area. The timing of the peak intensity of the murmur did not change in any consistent fashion with increasing degrees of pulmonary artery stenosis. Cardiac output and the velocity of flow through the constricted area of the pulmonary artery tended to increase with moderate degrees of constriction. When the lumen of the pulmonary artery was reduced 40 to 45 per cent, cardiac output and pulmonary artery pressure fell below control levels. With further constriction, cardiac output and pulmonary flow decreased; however, the velocity of flow through the stenotic area remained relatively rapid.
Hypophyseal Influence on Function and Composition of Cardiac Muscle
Authors: Whitehorn William V. , Grimm Arthur F. , King Theodore M.
Published: June 2012

The effects of hypophysectomy and of growth hormone (GH) on the properties and composition of rat myocardium were studied. GH, in dosage sufficient to maintain a normal rate of growth, did not correct the microcardia of hypophysectomy. Tension production of surviving left ventricular muscle columns was not modified by hypophysectomy or GH administration. Ventricular actomyosin concentration was slightly but significantly elevated in hypophysectomized animals, with or without GH. However, "ATP sensitivity" of the extracted actomyosin was markedly depressed by hypophysectomy and partially restored by GH. Differential hormonal regulation of cardiac actin and myosin is suggested.
Ventricular Response to a Pressure Load
Authors: Goodyer Allan V. N. , Goodkind M. Jay , Landry Arthur B.
Published: June 2012

The response of the left ventricle of the anesthetized dog to graded proximal aortic obstruction was expressed as a ventricular "pressure-function" curve relating peak ventricular pressure to end-diastolic ventricular pressure. Indices were suggested for numerical representation of the pressure-function curve and the normal variations of such indices in the same animal were defined. Pressure-function curves were found to be reproducible in the same animal during changes of cardiac output induced by arteriovenous fistulae or hemorrhage, but not after prolonged ventricular distention by high pressure loads. Changes of the pressure-function curves in both open-chest and closed-chest dogs paralleled changes of ventricular contractility which were expected during anoxia or the action of metaraminol, and which were measured in some experiments by strain-gauge arch or "flow-function" (Starling) curves. A theoretical basis for this relation of the pressure-function curve to ventricular contractility was discussed.
Body Composition in Experimental Congestive Heart Failure
Authors: Adolph Robert J. , Bliss Harry A.
Published: June 2012

The bodies of four dogs with experimental congestive heart failure and of four normal dogs were homogenized. Analyses for water, fat, sodium, potassium, chloride, and nitrogen were carried out after discarding ascitic fluid in the animals with heart failure. Sodium and chloride concentrations were increased in dogs with heart failure. Otherwise the two groups did not differ significantly.
Relation of Renin and Angiotensin II to the Control of Aldosterone Secretion
Authors: Davis James O. , Carpenter Charles C. J. , Ayers Carlos R.
Published: June 2012

1. Evidence is presented to show that the renin-angiotensin system leads to increased aldosterone secretion following acute blood loss, during experimental heart failure, during thoracic inferior vena cava constriction, during chronic sodium depletion and in malignant experimental renal hypertension. Since alterations in sodium intake constitute one of the most important factors in the daily regulation of aldosterone secretion, studies of sodium-depleted animals suggest that the renin-angiotensin system is important in the physiological regulation of aldosterone secretion.

2. Renin appears to be secreted by the juxtaglomerular cells of the kidney. Some hemodynamic alteration secondary to a decrease in pressure and flow through the kidney leads to release of renin by the juxtaglomerular cells. Available data indicate that angiotensin II acts on the zona glomerulosa of the adrenal cortex to promote aldosterone production.
Distribution of 4-Iodoantipyrine After Intravenous Injection in the Rat
Authors: Flora John H. , Phillips Don F. , Arcidiacono Francesco , Sapirstein Leo A.
Published: June 2012

The distribution of 4-iodoantipyrine does not parallel that of body water, as evidenced by its overaccumulation in some organs and underaccumulation in others. These disparities occur largely because I
131
is lost from the iodoantipyrine molecule, is converted to iodide, and is distributed and excreted as such. Any similarity between the distribution volume of iodoantipyrine and total body water is, therefore, happenstance.
Circulatory Response to Intra-abdominal Manipulation During Ether Anesthesia in Man
Authors: Vandam Leroy D. , Schweizer Hans J. , Kubota Yukio
Published: June 2012

Of 38 patients studied during a steady state of ether anesthesia before performance of the definitive phase of operation, hypotensive episodes were produced in 8 by deliberate intra-abdominal stimulation of various types. The production of hypotension was therefore not only unpredictable in the group as a whole, but it was also possible that a positive response in each case could have been mediated by a different circulatory mechanism. The protocol of these experiments was not designed either by method employed or time interval chosen to detect rapid or early changes responsible for the final steady-state measurements that were made. Arterial systolic, diastolic, mean, and pulse pressures decreased with a decline in pulse rate in several cases. As a result of a decreased stroke volume or slowing of the pulse, the cardiac output declined and was responsible for the pressure alterations observed. There was no directional change in the calculated overall peripheral resistance. The remainder of the circulatory measurements, including central venous pressure and central blood volumes, suggest that the circulatory changes are by no means simply explained and that vasodilation in peripheral vascular beds cannot be ruled out.
Ventricular Performance Modified by Elastic Properties of Outflow System
Authors: Salisbury Peter F. , Cross Cecil E. , Rieben P. Andre
Published: June 2012

Left ventricular and atrial pressures, left ventricular circumference and longitudinal meridional segment length, coronary flow, and cardiac oxygen consumption were measured under conditions which permitted intentional variation of the elasticity of the left ventricular outflow system and comparison of cardiac performance during steady states in which heart rate, stroke work, and stroke volume were identical, but the outflow elastic storage capacity was varied. When ejecting through a rigid (as compared with a distensible) system, the left ventricle generated a larger fraction of the contractile tension under auxotonic conditions (i.e., during the ejection phase), and left ventricular systolic peak pressure was increased. Ejections through rigid tubes proceeded from higher diastolic ventricular pressures and larger external dimensions. The effort of hearts which ejected through rigid outflow conduits was associated with a reduced myocardial oxygen consumption. Studies of left ventricular performance in isolated hearts are physiologically significant only when the experimental arrangement comprises an outflow system with distensibility characteristics similar to that of the arterial tree.
Role of Hyperplasia in Vascular Lesions of Cholesterol-fed Rabbits Studied with Thymidine-H
3
Autoradiography
Authors: Spraragen Sanford C. , Bond Victor P. , Dahl Lewis K.
Published: June 2012

Rabbit aorta and coronary vessels were studied with thymidine-H
3
and autoradiography. They were found to comprise an extremely stable population of cells, the latter probably even more stable than the former. Compensatory repair by means of regeneration at sites of bifurcation seems inadequate. This in part may explain the susceptibility of these areas to the development of atherosclerotic lesions. Proliferation, although sequentially secondary to fatty infiltration, plays an active role in the pathogenesis of cellular atherosclerotic lesions as seen in the rabbit. Foam cells possess the ability to synthesize DNA even when incorporated within the atherosclerotic lesion. Arguments in support of and opposed to some of the current hypotheses for the pathogenesis of atherosclerosis have been presented.
Cardiac Effects of Tyramine
Authors: Holmes John C. , Fowler Noble O.
Published: June 2012

The cardiac effects of tyramine (
p
-hydroxyphenylethylamine) were studied in 22 dog heart-lung preparations. In six uncontrolled rate preparations, tyramine 250 to 500 µg. increased the heart rate an average of 21 per cent. In controlled rate preparations, tyramine 100 to 250 µg. consistently increased ventricular contractile force, cardiac output, and blood pressure; there was a consistent decrease of right and left atrial pressures. Comparable hemodynamic effects were produced by 1 to 2.5 µg. of levarterenol, except that the effects of tyramine tended to be of longer duration and were less likely to be followed by cardiac depression. It is concluded that tyramine has significant positive inotropic and chronotropic effects in the dog heart-lung preparation. In three animals pretreated with reserpine, tyramine had little effect. Its action appears to depend to a large extent upon the presence of myocardial catecholamines.
Glucose Oxidation and High Energy Phosphate Production in Heart Homogenates
Authors: Haugaard Niels , Inesi Giuseppe , Haugaard Ella S.
Published: June 2012

Experimental conditions have been established for the study of glucose oxidation and high energy phosphate formation in cell-free rat heart homogenates. On addition of AMP to an otherwise complete system, an immediate formation of ADP and ATP occurs. Glucose oxidation is rapid, and high levels of ADP and ATP are maintained for long periods of time. In the absence of added AMP, rapid glucose oxidation also occurs despite low levels of ATP. It can be concluded that the high concentration of ATP, which the heart tissue is capable of accumulating, is far in excess of that necessary for efficient glucose oxidation.
Thrombosis in Connection with Serum Lipidic Changes in the Rat
Authors: Renaud Serge , Allard Claude
Published: June 2012

Addition of either propylthiouracil or cholic acid to a natural diet (Purina Laboratory Chow) enriched in certain lipids resulted in hypercholesteremia and hyperlipemia of about the same amplitude. However, only cholic acid could induce a high incidence of thrombosis and cardiac infarct and a regular decrease in the percentage of serum alphalipoproteins with an electrophoretic pattern similar to that found in essential hyperlipemia or in certain nephrotic syndromes associated with thrombosis. In the rat, the thrombi, located in the arterioles and the capillaries of the heart and other organs, presented a histological picture that resembled thrombotic-thrombocytopenic-purpura rather than coronary disease. This thrombotic phenomenon was preceded by an acute increase in serum cholesterol and total lipids and was accompanied by the production of a large quantity of macrophages, with a foamy appearance, in the lung and the spleen. If propylthiouracil was added to this thrombogenic diet, the survival time of the animals was considerably shortened and the percentage of iufarcts reduced, but in this case, thrombosis was mainly located in the ventricles and the aorta. Under these experimental conditions, both of the hypercholesterolemic agents being used, lipidic infiltration of the vessels was detected but no tissular reaction that could result in atheromatous plaques.
Instantaneous Increase in Mean Circulatory Pressure and Cardiac Output at Onset of Muscular Activity
Authors: Guyton Arthur C. , Douglas Ben H. , Langston Jimmy B. , Richardson Travis Q. , Abernathy Barry
Published: June 2012

In dogs with their spinal cords cut, sudden maximal muscular contraction in the lower half of the body caused the mean circulatory pressure to rise instantaneously to three times normal and the cardiac output to rise to an average of 40 per cent above normal. This instantaneous effect was not blocked by sympathetic blockade with hexamethonium but was blocked by skeletal muscle blockade with decamethonium. Furthermore, because of the transected cord, no cardiac reflex effects were observed. Therefore, it was concluded that skeletal muscle activity compresses the intra-muscular and intra-abdominal vessels and thereby increases the mean circulatory pressure. Evidence is presented to show that this, in turn, translocates blood into the heart and that the heart then responds in conformity with Starling's principle of cardiac adaptation to increase the cardiac output.