bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cardiac Arrhythmias Following Condenser Discharges and Their Dependence Upon Strength of Current and Phases of Cardiac Cycle
Authors: PELEŠKA BOHUMIL , Blažek, Z. , PRábl, M. , Sládková E. , Roth Z. 
Published: June 2012

To improve technics for electrical defibrillation of the heart, an apparatus was constructed for the application of a condenser discharge at any selected phase of the cardiac cycle. With this apparatus 2160 discharges were applied through the intact chests of 240 dogs under thiopental anesthesia. The voltage ranged from 0.5 to 6 kv, the condenser capacity from 0.5 to 100 µF, the total energy from 0.06 to 1800 watts. The associated changes in cardiac rhythm were graded from one (no abnormalities) through two (mild, brief extrasystoles), three (more protracted but fully reversible periods of bigeminy, extrasystoles, block, etc.), four (severe but reversible changes lasting several minutes, usually with fall in blood pressure), to five (severe arrhythmias changing into ventricular fibrillation).
The severity of the arrhythmias increased progressively as the voltage was increased, and to a much smaller extent with increases in the total amount of electrical energy. Arrhythmias also were significantly more severe when the shock was delivered during the refractory period (S-T interval) than during the excitable (P interval) stage of the cardiac cycle. Two types of ventricular fibrillation of very different prognosis were revealed. One came on suddenly after low voltage shocks and could easily be terminated by a single adequate defibrillation impulse. The other came on more gradually after high voltages and energies and tended to be irreversible.
Observations thus far made indicate that the severity of the arrhythmia following condenser shocks gives an approximate indication of the severity of pathological changes in the heart. Excessive currents could damage the heart to such an extent that myocardial contractions were weak or absent although electrical activity persisted. Therefore the parameters of condenser discharges used for clinical defibrillation should be such that they will produce only the mildest and briefest arrhythmias.
Thebesian Drainage in the Left Heart of the Dog
Authors: MOIR THOMAS W. , DRISCOL THOMAS E. , ECKSTEIN RICHARD W. 
Published: June 2012

Direct left heart drainage from the common left coronary artery has been demonstrated in the normally beating dog heart by an isotope dilution technique. The major portion of this drainage has been shown to be through the left circumflex branch of the common left coronary artery. The left anterior atrial artery, a branch of the left circumflex, has in turn been shown to be the major pathway of drainage from the latter. Left heart drainage could not be demonstrated from isotope injections into the left anterior descendens artery, and in only one preparation could such drainage be documented from the septal branch of the common left artery.
The magnitude of left heart Thebesian drainage has been estimated by analysis of time-concentration curves recorded from the aorta. An average of 2% of total common left coronary artery inflow drains directly into the left heart. Although the major drainage is probably into the left atrium, left ventricular drainage has not been excluded.
Indirect Action of Epinephrine on Intraventricular Conduction Time
Authors: MENDEZ CARLOS , ERLIJ DAVID , MOE GORDON K. 
Published: June 2012

In dogs with denervated hearts intravenous infusions of epinephrine (1.0 to 3.0 µg/kg/min) caused marked acceleration of the heart rate and a significant reduction of intraventricular conduction time. Equal doses infused into the descending thoracic aorta increased the heart rate only slightly, but exerted undiminished effects upon conduction time.
Evisceration did not modify the intraventricular dromotropic effect of epinephrine so long as the hepatic arterial supply was preserved. Occlusion of the hepatic artery abolished the dromotropic effect of epinephrine without modifying its chronotropic action.
The time course of the dromotropic effect and of the kalemic action of epinephrine was approximately the same.
Intravenous infusions of KCl matching the hyperkalemic effect of epinephrine caused similar dromotropic actions.
Isoproterenol even in high doses (up to 2.0 µg/kg/min) did not decrease intraventricular conduction time and had only a slight hyperkalemic effect.
After the administration of SY28 (1.0 mg/kg) epinephrine caused neither hyperkalemia nor decreased intraventricular conduction time.

It is concluded that in the heart in situ the effect of epinephrine on intraventricular conduction is the result of an indirect action mediated through the liberation of K
+
ions from the liver.
Production of Chronic Elevation of Left Ventricular End Diastolic Pressure in Dogs: Hemodynamic and Renal Studies
Authors: FRIEDBERG CHARLES K. , LASSER RICHARD P. , ALLEN DOUGLAS F. , FURST STEPHEN E. , GABOR GEORGE E. 
Published: June 2012

In an effort to produce a preparation for the study of sodium excretion in chronic left heart failure a graft anastomosis was created between the left subclavian artery and the left atrium in five dogs. This resulted in chronic progressive elevation of left ventricular end diastolic and left atrial pressures. Maximal left ventricular end diastolic pressures ranged between 18 and 30 mm Hg, 10 to 20 weeks postoperatively. There was only a slight rise in right ventricular diastolic pressure and no clinical evidence of right heart failure.
Cardiac outputs remained within normal limits in all animals. Serial electrocardiograms disclosed the development of left ventricular hypertrophy and left ventricular hypertrophy and dilatation were observed at postmortem examination. One dog which survived with a patent shunt for more than a year had right as well as left ventricular hypertrophy but no right heart failure. Glomerular filtration rates, renal plasma flow and excretion of rapidly infused isotonic saline remained unaltered even at the highest levels of left ventricular end diastolic pressure. Although the development of left and eventually right ventricular hypertrophy, the chronic and progressive elevation of left ventricular end diastolic, mean left atrial and pulmonary arterial pressure, with only slight elevation of right ventricular end diastolic pressure, were regarded as characteristic features of isolated left ventricular failure, the propriety of this term may be questioned in view of the unaltered cardiac output and renal hemodynamics. But the observations do indicate that marked elevation of left ventricular end diastolic and presumably pulmonary venocapillary pressure, such as occur in left heart failure, do not impair renal excretion of sodium.
Renal Baroreceptor Control of Acute Renin Release in Normotensive, Nephrogenic and Neurogenic Hypertensive Dogs
Authors: SKINNER SANDFORD L. , MCCUBBIN JAMES W. , PAGE IRVINE H. 
Published: June 2012

Graded reductions in mean renal perfusion pressure cause kidneys of normotensive, renal, and neurogenic hypertensive dogs to release renin. In anesthetized normal dogs with mean resting pressures of 110 to 150 mm Hg, increased renin secretion occurred at renal perfusion pressures of 90 to 120 mm Hg. In dogs hypertensive from constriction of a renal artery, pressure beyond the constriction was within the normal range, and lowering of renal perfusion pressure caused release in the same range as in normal dogs. In dogs with neurogenic hypertension due to section of the carotid sinus and aortic depressor nerves, return was released at perfusion pressures within, or only slightly above, the normal range.
In sharp contrast with these three groups, renin was released in dogs with hypertension due to perinephritis at mean pressures of 140 to 165 mm Hg when lowered from resting levels of 180 to 220 mm Hg. This different range could depend either upon reduced intrarenal pressure which mimicks the effects of a renal artery clamp or upon a change in range of response of the renal baroreceptor due to some more direct effect of the perinephritic hull. No evidence was found that the renal baroreceptor control of renin secretion is nonfunctional in dogs with renal hypertension.
Use of Radioiodinated Fatty Acid for Photoscans of the Heart
Authors: EVANS JOHN R. , GUNTON RAMSAY W. , BAKER ROBERT G. , BEANLANDS DONALD S. , SPEARS JOHN C. 
Published: June 2012

Radioiodinated fatty acid bound to albumin (RIFA) was given by intravenous injection to dogs and moribund human subjects in order to label heart muscle.
Photoscans of the thorax of dogs given RIFA revealed concentration of radioactivity in the ventricular region of the heart due to incorporation of the labeled fatty acid into myocardial triglyceride and phospholipid.

Photoscans of the thorax following intravenous injection of radioiodinated serum albumin or NaI
131
showed a different density pattern in the region of the heart due to radioactivity in blood within the cardiac chambers.

Areas of myocardial infarction were detected in photoscans of the thorax in 11 of 14 dogs in which one coronary artery was ligated. At necropsy the concentration of radioactivity was much higher in healthy myocardium than in infarcted muscle. The same distribution of radioactivity was observed in hearts from three human subjects with myocardial infarction given RIFA shortly before death. It is proposed that areas of myocardial infarction might be demonstrated during life by photoscans of the thorax following intravenous injection of RIFA.
Induced Pressure Gradients Across Infundibular Zone of Right Ventricle in Normal Dogs
Authors: TOBIN JOHN R. , BLUNDELL PETER E. , GOODRICH RALPH G. , SWAN H. J. C. 
Published: June 2012

In these experiments we have demonstrated that:
1. Right ventricular outflow-tract pressure gradients of significance can be induced in normal dogs by a sympathomimetic amine which increases the rate and force of ventricular contraction.
2. Such outflow-tract pressure gradients are magnified by the addition of other inotropic drugs, such as acetyl strophanthidin and calcium chloride.
3. These outflow-tract pressure gradients are not the result of an increase in the volume and rate of blood flow but are due to forceful contraction of the infundibulum.
Circulatory Response to Release of Chronic Pulmonary Artery Constriction
Authors: TOBIN JOHN R. , RASTELLI G. C. , BLUNDELL PETER E. , SWAN H. J. C. 
Published: June 2012

The imposition of a chronic work load (pulmonary artery constriction) on the right ventricle increases ventricular muscle mass. This is associated with increased ventricular stroke work when the animal is standing awake, during infusions of norepinephrine, and under conditions of exercise (running on a horizontal treadmill). Studies two weeks after release of chronic pulmonary artery constriction reveal stroke volume and cardiac output are increased during standing at rest, during norepinephrine infusion, and during exercise. Studies eight weeks after removal of pulmonary artery bands show that stroke volume and cardiac output are approaching the normal range. Right ventricular hypertrophy and right ventricular stroke work decline progressively and apparently in parallel in the weeks following release of chronic pulmonary artery constriction.
The stroke work capacity of the ventricle seems related to the presence of right ventricular hypertrophy. With a reduction in outflow tract resistance, the stroke volume for a given set of circumstances is markedly increased. From this standpoint, the work capacity of the right ventricle may be taken as a determinant of stroke volume and cardiac output.
Decrease of systemic vascular resistance and relative insensitivity of systemic vasoreceptors to norepinephrine were observed after the release of chronic pulmonary artery constriction. These phenomena have roles in the production of the observed hyperdynamic circulatory state, but their contributions to its genesis are secondary to the major role of the hypertrophied right ventricle.
Effect of Variations of Plasma Sodium Concentration on the Adrenal Response to Angiotensin II
Authors: BLAIR-WEST JOHN R. , COGHLAN JOHN P. , DENTON DEREK A. , GODING JAMES R. , WINTOUR MARELYN , WRIGHT R. DOUGLAS 
Published: June 2012

The secretion rate of aldosterone was increased by infusion of valine-5-angiotensin II into the adrenal arterial blood supply of sheep. The dimensions of the increase in aldosterone output were inversely related to the control plasma concentration. This high aldosterone secretion was reduced substantially by concurrent adrenal infusion of concentrated NaCl solution which increased plasma sodium concentration by approximately 10 meq/liter. The reduction of aldosterone secretion occurred within 20 minutes. Angiotensin II infusion did not increase the secretion rates of cortisol or corticosterone.
The significance of the finding that environmental sodium concentration has different effects on the aldosterone-stimulating action and the pressor action of angiotensin II is discussed.
Effects of Respiratory Center Activity on the Heart
Authors: Levy Matthew N. , DeGeest Hilaire , Zieske Harrison , Levy Donald 
Published: June 2012

Rhythmic fluctuations in heart rate and ventricular contractility at the frequency of the respiratory movements were observed in innervated, isovolumetric, canine, left ventricle preparations. The heart rate and contractility waves probably represent the radiation of activity from the respiratory centers to the cardiac autonomic centers within the central nervous system. In spontaneously beating hearts, the respiratory cardiac arrhythmia is mediated via the vagi predominantly, although a slight arrhythmia is still evident after bilateral vagotomy. The greater the vagal tone, the greater is the amplitude of the arrhythmia.
In paced hearts, the contractility waves exhibit significantly greater phase lags than do the heart rate waves in unpaced beats. The magnitude of the contractility waves varies inversely with the respiratory frequency. These waves are more prominent after bilateral vagotomy. Therefore, sympathetic influences appear to predominate in the mediation of the contractility waves, although the change in wave amplitude after vagotomy must be ascribed partly to the deceleration of respiratory frequency which occurs after vagotomy. The contractility waves represent rhythmic augmentations of contractility above a base line level after vagal section.
Cardiovascular Effects of Sustained Norepinephrine Infusions. II. Morphology
Authors: Schenk Eric A. , Moss Arthur J. 
Published: June 2012

The major toxic effect of norepinephrine (NE) infusion in dogs, cats, and rabbits in doses relatively comparable to those used clinically has been shown to be on the heart. Noncardiac lesions were those of congestion, and were seen in animals receiving the higher doses. The dogs in these dose groups showed evidence of progressive deterioration of cardiac function. All dogs which developed cardiac lesions also developed an acute adrenalitis.
The cardiac lesions in all animals consisted of focal degeneration and necrosis of myofibers, and subendocardial hemorrhage. These lesions healed within two weeks by fibrosis.
Distribution of Blood Flow within the Skin of the Rabbit with Particular Reference to Hair Growth
Authors: Thorburn Geoffrey D. , Casey Brian H. , Molyneux Geoffrey S. 
Published: June 2012

Previous work using a Kr
85
clearance technique demonstrated the existence in rabbit thigh skin of a bimodal distribution of blood flow which was consistent with the presence of two distinct vascular compartments with markedly different flow rates. These observations on the rabbit thigh have been extended to compare flow patterns during the inactive phase of the hair growth cycle and during active hair growth.

Resting areas and hair-growing areas of rabbit skin have been examined histologically and the vascular pattern has been demonstrated after perfusion of the vessels with India ink. The results provide an anatomical basis for the two-compartment model derived from analysis of the clearance curves.
The mean rate of blood flow for the fast compartment during the inactive phase was 29.7 ml/100 g tissue/min and 4.3 ml/100 g tissue/min for the slow compartment; these did not change significantly with active hair growth. However the relative size of the fast compartment altered markedly with active hair growth, the relative size of the fast compartment increasing from 21 to 67% of the tissue mass. The mean cutaneous blood flow was more than doubled during the active phase.
Histological studies demonstrated a marked increase in the size of the follicles during the active phase and a concomitant increase in the extent of the vascular bed around the follicles. This would indicate that the fast compartment represents the follicular tissue and its associated blood supply; its flow rate was a measure of nutrient blood flow to the hair follicle. The flow rate of the slow compartment was then a measure of nutrient blood flow in the rest of the skin. These conclusions were supported by observations in areas of skin with sparse hair growth. The effect of body heating and cooling on cutaneous blood flow distribution was also noted.
Spontaneous Aortic Lesions in Rabbits I. Morphologic Characteristics
Authors: SCHENK ERIC A. , GAMAN ELIZABETH , FEIGENBAUM A. S. 
Published: June 2012

A number of morphologically distinct, spontaneously occurring lesions are present in the rabbit aorta. Intimal atheromata occur in newborn rabbits, decrease in incidence as the rabbit becomes weaned, and are a rarity in the adult. Intimal mesenchymal thickening is first seen in weanling rabbits and is almost universally present in the adult. Medial sclerotic changes involving exclusively the inner one-half of the media and termed "type A" lesions are present in weanling and adult, but not in newborn rabbits.
Type A lesions have a variable gross appearance, but a fairly uniform microscopic appearance, which shows principally fragmentation and calcification of elastic lamina and accumulation of acid mucopolysaccharides.
"Type B" lesions, medial sclerosis involving exclusively the outer half of the media, usually occur throughout the entire aorta, and only in adult rabbits.
Cardiac Myosin Adenosinetriphosphatase Activity
Authors: LUCHI ROBERT J. , KRITCHER EVE Marie 
Published: June 2012

Cardiac myosin prepared by any one of a number of modifications of the basic Szent-Gyorgyi method and cardiac myosin prepared by the lithium chloride-ammonium sulfate technique differ in two important respects: 1) Szent-Gyorgyi-prepared myosin solutions are inhomogeneous by both chemical and immunologic criteria; 2) the ATPase activity of Szent-Gyorgyi-prepared myosin is low in comparison to lithium chloride-ammonium sulfate prepared cardiac myosin. Evidence is presented in this paper showing that the reduced ATPase activity of Szent-Gyorgyi-prepared cardiac myosin is the result of inhibition of the enzyme, possibly by a nucleotide contaminant, and a "diluting" effect of other nitrogen-containing contaminants of low specific activity.
Many earlier studies indicate that cardiac and skeletal muscle myosin prepared by the Szent-Gyorgyi method differed strikingly in their ATPase activities. Comparison of lithium chloride-ammonium sulfate prepared cardiac and skeletal muscle myosin shows that skeletal muscle myosin has a slightly but significantly higher ATPase activity than canine cardiac myosin. A methodologic error was not excluded as the cause of this discrepancy. In a number of other characteristics, canine cardiac and skeletal muscle myosin ATPase activity was virtually identical.
Measurement of Left Ventricular Volume by Biplane Angiocardiography and Indicator-Washout Techniques: A Comparison in the Canine Heart
Authors: BARTLE STUART H. , SANMARCO MIGUEL E. 
Published: June 2012

Left ventricular volumes were determined sequentially in 31 dogs and simultaneously in 12 by biplane angiocardiography and a dye-dilution, thermal washout technique.
The mean ejected fraction (SV/EDV; systolic volume/end diastolic volume) was significantly higher when measured by angiocardiography (.53 ± .03) than by the washout method (.27 ± .02). The end diastolic volume measured by angiocardiography was lower, 21.1 ± 1.5 ml/10 kg versus 34.4 ± 3.6, as was the end systolic volume, 11.3 ± 1.3 ml/10 kg versus 25.5 ± 3.2. Mean stroke volume by angiocardiography was 10.9 ml/10 kg, or 1.8 ml greater than by dye dilution (the average amount of contrast material injected per beat was 1.9 ml/10 kg).
No difference was found between the washout fractions calculated from early and from late beats. There was a significant inverse correlation between the observed heart rate and washout SV/EDV. There was no correlation between heart rates and the discrepancy in measuring the various volumes.
Technical difficulties and theoretical considerations are discussed and it is concluded that in dogs the angiographic method gives more accurate calculations of end diastolic and end systolic volumes than the washout technique. The latter method appears to underestimate SV/EDV systematically, probably because of incomplete mixing of indicator in the ventricle. This leads to falsely high values for EDV and ESV.
Demonstration of a Dual A-V Nodal Conduction System in the Isolated Rabbit Heart
Authors: MENDEZ CARLOS , MOE GORDON K. 
Published: June 2012

The intranodal propagation of atrial and ventricular echoes in in-vitro preparations of the rabbit heart was traced from microelectrode records at many puncture sites. Composite records indicate that the upper part of the node can be functionally and spatially dissociated into two pathways (α and β), which communicate with a final common pathway (FCP) about halfway between the atrium and the His bundle.
Atrial echoes, induced by premature atrial stimulation, traverse the α pathway and return to the atrium from the middle part of the node over the β route; echoes can occur without propagation of the premature response to the ventricle.
Ventricular echoes, induced by premature stimulation of the His bundle, pass from the FCP to the atrium over the α route, and back to the FCP over the β route.
Repetitive reciprocation, in the nature of an intranodal circus movement, was commonly observed.
The results completely substantiate previous conclusions based on indirect observations in the dog heart.
Inert Gas Diffusion Method for Measurement of Blood Flow Using Saturation Techniques
Authors: SEJRSEN PER , TØNNESEN KNUD H. 
Published: June 2012

The isolated gastrocnemius muscle of the cat was used to study the relation between the desaturation of
133
xenon measured by external monitoring, and blood flow measured directly by a dropcounter.

The metered blood flow agreed with that calculated from the initial slope of the desaturation curve from tissue equilibrated by prolonged intra-arterial infusion and also by atraumatic gas labelling of a local area of the muscle (approximately 0.15% of the muscle weight). In this sense the concept of uniform distribution of blood flow in skeletal muscle has received substantial support. The identity of the results obtained by local gas labelling and by intra-arterial equilibration of the whole muscle with gas implies that there is, at least initially, diffusion equilibrium between tissue and blood in both.
However, the clearance curves could in no instance be fitted by a single exponential function. This indicates that the diffusion equilibrium is not maintained after the initial phase. It is suggested that this is not due to the presence of anatomical arteriovenous shunts or other types of uneven perfusion, but to counter current exchange of inert gas through the walls of vessels, i.e. shunting by diffusion explains the shape of the desaturation curves.