bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of pH on Blood Flow and Peripheral Resistance in Muscular and Cutaneous Vascular Beds in the Hind Limb of the Pentobarbitalized Dog
Authors: DEAL C. P. , GREEN HAROLD D.
Published: June 2012

The responses of the vascular beds in skeletal muscle and skin to changes in blood pH on the acid and alkaline sides of the physiologic range were compared. Dilatation occurred in both cutaneous and muscular beds when the blood pH was shifted to the acid range. Dilatation also occurred in the muscle beds when the blood pH was shifted to the alkaline range but such change in blood pH caused vasoconstriction in skin.
Comparison of the Bromsulphalein Method with Simultaneous Direct Hepatic Blood Flow
Authors: SELKURT EWALD E.
Published: June 2012

A method has been devised for directly measuring hepatic outflow in dogs so as to permit simultaneous comparison with the indirect method, employing the hepatic removal of Bromsulphalein (BSP). The results show that the indirect method averages 7.3 per cent higher than the direct. This difference is attributed to a small Degrees of extrahepatic removal of the dye.
The Effect of Soybean Sterols on the Absorption of Cholesterol by the Rat
Authors: ROSENMAN RAY H. , BYERS SANFORD O. , FRIEDMAN MEYER
Published: June 2012

Mixed soybean sterols (80 per cent sitosterols) were fed to rats simultaneously with cholesterol in acute and chronic experiments. In acute experiments, concurrent feeding of a test dose of soybean sterols and cholesterol did not diminish the usual fraction of cholesterol absorption into the thoracic duct lymph. In chronic experiments the addition of 2 or 10 per cent soybean sterols to a diet which induces chronic hypercholesteremia in rats failed to inhibit the development or magnitude of chronic hypercholesteremia.
Electron Microscopy of Human Plasma Lipoprotein Separated by Ultracentrifugation
Authors: BEISCHER D. E.
Published: June 2012

The particle size distribution of the S
f
30 "class" of serum lipoprotein was determined by the electron microscope. Most of the lipoprotein molecules are not spherical but have the shape of ellipsoids of rotation with an axis ratio of 1.5. The molecules of a homogeneous flotation "class" show differences in the reactivity of their lipid moiety demonstrated by their staining properties with osmium tetroxide.
The Permeability of Excised Arteries and Other Tissues to Serum Lipid
Authors: WILENS SIGMUND L. , McCLUSKEY ROBERT T.
Published: June 2012

Excised arterial tissue is shown to differ from other excised tissues by its property of retaining fractions of serum lipids that are transfiltered under pressure in the form of zonal deposits at the elastic tissue membranes. The mode of deposition of artificially produced lipid accumulations and spontaneously formed ones is probably very similar. Various factors that influence the deposition of lipid in excised arteries are examined in detail. The most important of these prove to be the structural peculiarities of arterial tissue and the concentration of lipid in the serum.
Chronic Pressor Effect of Kidney Extracts Containing Renin in Experimental Hypertensions
Authors: WAKERLIN G. E. , KREMEN S. , FRANK M. H. , SCHMID H. E. , GRAHAM L. , KEITH B
Published: June 2012

A course of daily intramuscular injections of dog renin produced a maintained chronic pressor effect persisting for months during and following the renin injections in a majority of renal hypertensive dogs. Semipurified hog renin produced a temporary chronic pressor effect persisting for several weeks or somewhat longer but not throughout the renin injections in a minority of renal hypertensive dogs. The maintained chronic pressor effect was obtained only in the absence of antirenin; the temporary chronic pressor effect was lost when antirenin appeared in the plasma. Normotensive dogs were significantly less responsive to the chronic pressor effect of dog and hog renins than were renal hypertensive dogs. The mechanism of the chronic pressor effects is unknown.
Studies on the Mechanism of Ventricular Activity
Authors: SMITH L. ALLEN , KENNAMER REXFORD , PRINZMETAL MYRON
Published: June 2012

Controlled studies of ventricular excitation were performed in dogs exhibiting various Degreess of right and left bundle-branch block. Increases in the intraventricular conduction time during complete bundle-branch block are attributed to free wall as well as septal factors. Incomplete bundle-branch block may be either segmental or diffuse. In the segmental type, delayed excitation is present in only a portion of the involved ventricle. In the diffuse type, delayed excitation of the entire homolateral ventricle occurs, but some portions of the ventricle tend to be delayed to a greater extent than others. Certain segements of the ventricular myocardium appear to be supplied by fixed portions of the conducting system, without cross connections operating physiologically. The clinical implications of these observations are briefly discussed.
Intestinal Absorption of Cholesterol by the Nephrotic Rat
Authors: ROSENMAN RAY H. , FRIEDMAN MEYER , BYERS SANFORD O.
Published: June 2012

Exogenous cholesterol, absorbed from the intestinal tract, is transported into the blood by the lymph of the thoracic duct. By means of thoracic duct cannulation and subsequent lymph collection following stomach feeding of 100 mg. of cholesterol dissolved in olive oil, it was found that the nephrotic rat has a diminished rate of cholesterol absorption. This could not be ascribed to a deficiency of lymph flow or of bile in the intestinal tract.
Assay of Renin and Hypertensin with the Isolated Guinea-Pig Ileum
Authors: PICARELLI ZULEIKA P. , KUPPER REGINA , PRADO ELINE S. , PRADO J. L. , VALLE J. R.
Published: June 2012

Renin and hypertensin may be easily assayed with the isolated guinea-pig ileum, which is as sensitive as the vascular toad preparation. Hypertensin itself is the substance which acts on the smooth muscle of the ileum.
Pathogenesis of Polyarteritis Nodosa in Hypertensive Rats
Authors: RACE GEORGE J. , PESCHEL ERNST
Published: June 2012

The pathogenesis of the vascular lesions of polyarteritis nodosa found in young rats with experimental renal hypertension is described. The panarteritic lesion was a product of the combination of renal injury and feeding sodium chloride. It began with a fibrinoid necrosis of the intima and media which was followed by an extensive inflammatory reaction with subsequent fibrosis of all layers of the vessel wall.
Congenital Cardiovascular Anomalies Induced by Pteroylglutamic Acid Deficiency during Gestation in the Rat
Authors: BAIRD CATHERINE D. C. , NELSON MARJORIE M. , MONIE IAN W. , EVANS HERBERT M.
Published: June 2012

Congenital cardiovascular anomalies were observed in the offspring when rats were placed on a dietary regimen deficient in pteroylglutamic ("folic") acid during gestation. These cardiovascular malformations occurred only when the mothers were given this diet for specific periods, as short as two or three days, in early pregnancy, at a time when the heart and aortic arches were in the initial stages of development.
Effect of Blood and Saline Infusion on Cardiac Performance in Normal Dogs and Dogs with Arteriovenous Fistulas
Authors: FERGUSON THOMAS B. , GREGG DONALD E. , SHADLE OSCAR W.
Published: June 2012

Maximum left ventricular work response (and other hemodynamic changes) to infusion of saline and whole blood was compared in normal dogs and in dogs with aorta-caval and multiple peripheral fistulas. In the dogs with fistulas the augmented preinfusion levels of cardiac work and left ventricular end-diastolic pressure approximated those in normal dogs after maximum response to infusion. Following infusion in the dogs with fistulas, end-diastolic pressure characteristically increased but cardiac work did not. Thus maximum cardiac work was of the same order of magnitude in the normal dogs and in the dogs with fistulas. In all groups maximum left ventricular work was effected mainly through an increased cardiac output.
Series Elasticity in Heart Muscle
Authors: PARMLEY WILLIAM W. , SONNENBLICK EDMUND H.
Published: June 2012

The series elasticity (SE) of cat papillary muscle was measured in 6 muscles by the isotonic quick-release method, with careful correction for the compliance of the equipment. The resultant SE curve was exponential in form with an extension of 4% to 5% of initial muscle length for a preload of 0.5 g and a developed tension of 10 g; this demonstrates a stiffer SE for cardiac muscle than has previously been reported. The quick-release SE extension curve was unaffected by inotropic interventions or changing the time of quick release, and was less compliant than the SE curves calculated by two different isotonic methods. These differences arise from the fact that contractile element velocity has a secondary rise during the transition from the isometric to isotonic phase of any afterloaded contraction. With increasing preload (and initial muscle length) the SE became stiffer, suggesting that a substantial part of it is in series with both the contractile and parallel elastic elements.
Disturbances in the A-V Conduction System in Chagas' Myocarditis in the Dog
Authors: ANSELMI ALFONSO , GURDIEL ORLANDO , SUAREZ JOSé ANGEL , ANSELMI GERARDO
Published: June 2012

Atrioventricular (A-V) conduction and the functional refractory period (FRP) of the A-V system were studied in 13 dogs chronically infected by T. cruzi that had ECG disturbances indicative of myocarditis. Histopathologic findings at the A-V node and the bundle of His were correlated with the FRP and with conduction times of the A-V propagation system. Retarded conduction was related to inflammatory and fibrotic processes localized at the bundle of His. At relatively slow rates of stimulation, conduction time was prolonged, but the ventricle was capable of following high atrial rates. With augmented FRP, mononuclear cell infiltrates were observed in the A-V node or in the septal muscle around the node. This suggests that the node was included in the inflammatory process. No correlation was found between inflammatory infiltrates of the bundle of His and changes in the FRP. At relatively slow rates of stimulation, normal A-V conduction time corresponded to prolonged FRP. A-V conduction became slow as the atrial rate increased. A point was reached when the ventricle could not follow the moderately increased atrial rates.

Excitability of cardiac tissues was so markedly altered in 5 dogs with severe inflammatory infiltrates that a similar study of the A-V system could not be made.
Korotkoff Sounds
Authors: MCCUTCHEON ERNEST P. , RUSHMER ROBERT F. , Jacobson O. , Sandier Harold
Published: June 2012

The Korotkoff sounds which serve as criteria for sphygmomanometry are composed of at least two components, (1) an initial transient (K
i
), and (2) a more prolonged "compression murmur" (K
c
). In this experimental survey, the Doppler flow detection device was used to acquire evidence indicating that K
i
occurs at the very onset of flow under the cuff and probably represents an acceleration transient producing abrupt displacement of the arterial wall and surrounding tissues distal to the point of compression. It is nonspecific in nature and can be simulated by tapping the skin of the hand. K
c
follows the initial transient and appears to represent audible sounds from turbulence or eddies in the blood flowing from the constricted artery under the cuff. Muffling seems attributable to the attenuation of frequencies between 60 and 180 cycle/sec, as the initial transient sound disappears, leaving the "compression murmur" as the muffled sound. Studies of cineangiograms and casts of arteries demonstrated that the arterial lumen under the cuff is primarily tapered and that the circumference of the artery shrinks considerably as the wall is unloaded by decreased transmural pressure. In contrast, rubber tubes become unstable and flatten into a binodal configuration when externally compressed. It seems doubtful that rubber tubes constitute adequate models for arteries in situ in the study of the genesis of Korotkoff sounds.
Sequence of Atrial Depolarization at Different Stages of Development of the Chick Embryo
Authors: HAIT GERSHON , LICATA RICHARD H.
Published: June 2012

Simultaneous left and right atrial surface electrograms were obtained from the right and left atria of 30 chick embryos. These were divided into 3 equal groups that were studied at 15 to 16, 10 to 11, and 5 to 7 days of incubation. The embryos were removed from the shell with their circulation intact and temperature maintained constant. In an early stage of development (5 to 6 days), the left atrium and its appendage were larger than the right, and left preceded right atrial depolarization. At and after 7 days of incubation, the right atrium and its appendage were larger than the left, and right preceded left atrial depolarization. The intervals for interatrial conduction and for atrio-ventricular conduction were about the same at all stages of development. Since the length and width of the heart at 15 to 16 days of incubation were about 3 times those of a heart at 5 to 7 days of incubation, it is proposed that the higher the stage of development of the chick embryo the greater must be the conduction velocity between the two atria and from atrium to ventricle. This was assumed to be related to the degree of development of the specialized conduction pathways that are probably absent or underdeveloped in early stages of development.
Cardiac Failure in the Dog as a Consequence of Exogenous Hyperthyroidism
Authors: PIATNEK-LEUNISSEN DOROTHY , OLSON ROBERT E.
Published: June 2012

Thirty dogs were made hyperthyroid by feeding them 1 g/kg USP thyroid powder or injecting 1.2 mg/kg of 1-thyroxine/day. Seven of the 30 dogs used had surgically induced mild valvular lesions of the right heart to determine whether preexistent organic disease was a requisite to the induction of failure in hyperthyroidism.

At 2 to 27 months the animals were subjected to cardiac catheterization for measurement of cardiac work and metabolism in vivo. The animals were then killed and the levels of the high energy phosphate compounds creatine phosphate (CP) and the adenine nucleotides (ATP+ADP) in the heart were measured as an index of the net efficiency of the processes of oxidative phosphorylation.

By hemodynamic or histopathologic criteria, 13 dogs showed signs of failure, only 3 of which had preexistent valvular lesions. The failure was not accompanied by a decreased efficiency of oxidative phosphorylation. Net levels of CP and ATP + ADP in the myocardium were normal. Preliminary studies with sarcosomes isolated from 5 animals also revealed normal P/O ratios in 3 dogs with and in 2 without signs of cardiac failure. Liver mitochondria isolated from these same 5 animals all demonstrated decreased P/O ratios. Decreased myocardial extractions of both glucose and pyruvate occurred with failure, suggesting some degree of myocardial hypoxia with increased intracellular glycolysis. Areas of relative hypoxia may exist in a hypertrophied myocardium of the hyperthyroid animal.
Histochemical and Chemical Studies of the Localization of Adrenergic and Cholinergic Nerves in Normal and Denervated Cat Hearts
Authors: JACOBOWITZ DAVID , COOPER THEODORE , BARNER HENDRICK B.
Published: June 2012

The localization of adrenergic and cholinergic nerves in normal and denervated cat hearts was studied histochemically. The norepinephrine content of atria and ventricles was chemically determined by a spectrofluorometric method. In hearts denervated 9 to 42 days, little or no norepinephrine was detected. Histochemically, many catecholamine-containing fibers were present in the atria and ventricles of normal cats, whereas in denervated cats there were none in one and very few in four. There were many cholinergic nerves in the atria and a small to moderate number in the ventricles. The left atria of denervated hearts showed a marked reduction in cholinergic nerve fibers. It is concluded that cardiac denervation by mediastinal neural ablation is often incomplete. When norepinephrine is not detectable by chemical analysis, individual nerve fibers not sectioned can still be histochemically identified.
A Mathematical Model for the Estimation of Heart Volumes from Indicator Dilution Curves
Authors: HOMER LOUIS D. , KRAYENBUEHL HANS P.
Published: June 2012

The estimation of ventricular volumes by indicator dilution methods is subject to errors resulting from incomplete mixing and nonuniform sampling. A mathematical model is proposed which theoretically permits calculation of these errors. The model allows for nonuniform distribution of indicator in the ventricle and for nonuniform representation of the end-diastolic volume (EDV) in the systolic ejectate. It is assumed that the concentration of indicator and the flow at a given cross section of the aorta are uniform but not necessarily the same at a different cross section, or at different times during the cardiac cycle. In respect to the validity of the popular formula,
EDV
=
SV/l-K
(
K
= average residual fraction), it was shown that the conditions traditionally believed to be satisfying for accurate measurements of EDV are neither sufficient nor necessary. Less restrictive alternative conditions sufficient for accurate measurements are proposed.
Reduction of Cardiac Tyrosine Hydroxylase Activity in Experimental Congestive Heart Failure
Authors: POOL PETER E. , COVELL JAMES W. , LEVITT MORTON , GIBB JAMES , BRAUNWALD EUGENE
Published: June 2012

Although it is clear that cardiac norepinephrine stores are often markedly reduced in congestive heart failure, the mechanism responsible for this depletion has not been elucidated. The objective of this study was to investigate cardiac synthesis of norepinephrine in experimental right-sided heart failure by measuring the activity of tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of norepinephrine. In homogenates of the right ventricles of 6 dogs with congestive heart failure and 2 with chronic cardiac denervation, myocardial tyrosine hydroxylase activity was severely reduced, averaging 0.4 ± 0.1 (SE) and 0.2 mµmole/g per hour respectively as compared to a normal value of 3.3 ± 0.7 mµmole/g per hour. Tyrosine hydroxylase activity was normal in reserpine-treated, norepinephrine-depleted dogs. These data provide evidence for a mechanism severely limiting norepinephrine biosynthesis in congestive heart failure.
Effects of Stimulation Frequency on Myocardial Extensibility
Authors: FEIGL ERIC O.
Published: June 2012

Whether a change in myocardial contractility is accompanied by a change in diastolic extensibility was studied by altering stimulation frequency, including paired stimulation, as the inotropic intervention. Isometric and isotonic contractions of isolated cat papillary muscles were examined. Apparent changes in diastolic extensibility were observed with paired stimulation in isometric preparations. Rapid changes were seen only in muscles that had spontaneous aftercontractions between driven beats. These changes were believed not to reflect true extensibility changes but rather a change in timing between the relaxation of a beat driven by a paired stimulus and the onset of an aftercontraction. In continuous isotonic (not afterloaded) preparations, end-diastolic length depended on beat frequency. The muscle crept to a longer length when diastole was prolonged by decreasing the heart rate. In isotonic experiments without aftercontractions myocardial extensibility remained unchanged during paired electrical stimulation and changes in beat frequency.
Coronary Inflow and Outflow Responses to Coronary Artery Occlusion
Authors: DRISCOL THOMAS E. , ECKSTEIN RICHARD W.
Published: June 2012

Sudden complete occlusion of a major coronary artery (left circumflex or right coronary artery) was produced in anesthetized dogs. The effect on arterial inflow, venous outflow and O
2
saturation of coronary venous blood from the nonischemic left ventricle was studied. The usual response to occlusion of the left circumflex artery was an increase in flow in the left anterior descending artery and in outflow from the great cardiac vein. The O
2
saturation of venous blood from the nonischemic muscle decreased. These changes did not occur following occlusion of the right coronary artery. It was not possible to measure tissue pressure accurately to relate this measurement to flow changes. Observations on coronary sinus flow and O
2
saturation were also made following occlusion of the left circumflex artery and retrograde flow collection from it. These observations plus the changes in anterior descending inflow and great cardiac vein outflow with coronary occlusion suggest that these changes are more likely due to alterations in O
2
consumption of the nonischemic muscle rather than to changes in flow through interarterial or non-interarterial collateral vessels.
The Mechanism of Canine Atrial Flutter
Authors: HAYDEN WILLIAM G. , HURLEY EDWARD J. , RYTAND DAVID A.
Published: June 2012

In anesthetized dogs, electrograms were recorded simultaneously from six atrial epicardial sites and a limb or esophageal lead in order to study the mechanism of atrial flutter induced electrically after an intercaval crush in comparison with atrial tachysystole induced by aconitine. In the former, with limb lead records resembling classical human flutter in form and regularity, activation occupied most of the atrial cycle and progressed in sequence caudally in the right atrium and cranially in the left (counterclockwise flutter); flutter was usually terminated by another crush extending from the initial one to the right atrioventricular junction. The most prominent wave in limb and esophageal leads coincided with left atrial activity. Sometimes activation proceeded clockwise. The two atrial appendages may be activated simultaneously during counterclockwise flutter. These findings support the circus movement hypothesis as the mechanism of pure atrial flutter. In contrast, with aconitine tachysystole, activation proceeded over both atria at once and was so brief that it left most of the slightly irregular atrial cycle electrically silent. Although limb leads after aconitine sometimes resembled those of flutter, the contrast in direction and duration of excitation demonstrates profound physiological differences between the two arrhythmias.
Experimental Production of Pulmonary Hypertension and Pulmonary Atherosclerosis in the Rabbit
Authors: KOMURO KAZUNOBU , ROSENZWEIG DAVID Y.
Published: June 2012

The experimental production of pulmonary atherosclerosis was studied in 39 rabbits. Variables examined included age, pulmonary hypertension after pneumonectomy, and high-fat diet. Right ventricular pressures were measured and then stress-strain elasticity measurements and histologic examination were made of the pulmonary arteries. High-fat diet alone produced neither right ventricular hypertension nor pulmonary atherosclerosis. Right ventricular hypertension occurred after pneumonectomy alone, but there were no anatomic changes unless the rabbits had eaten a high-fat diet. Pneumonectomy plus a high-fat diet was followed by persistent hypertension with right ventricular systolic pressures more than twice control values and by progressive pulmonary atherosclerosis consisting of discrete atheromata in the larger vessels and intimal fibrosis in the smaller arteries. No pathologic or physiologic differences were observed between the changes in the older (24 months) rabbits and the younger (6 months) ones, except in the measurements of elasticity. The old rabbit's pulmonary artery strip is slightly less extensible than that of the young rabbit, but pneumonectomy and high-fat diet did not reduce extensibility further. These preparations may serve adequately for the experimental study of pulmonary atherosclerosis.
Inert Gas Diffusion Method for Measurement of Blood Flow
Authors: TØNNESEN KNUD H. , SEJRSEN PER
Published: June 2012

The isolated cat gastrocnemius preparation was used to study the relation between the washout of
133
Xenon measured by external monitoring and blood flow measured directly by a dropcounter. The experimental possibility was thereby tested of recording the total tracer bolus and its subsequent washout by external monitoring, using the height
H
and the corresponding area
A
of the washout curve. The partition coefficient λ, and the amount of recirculation were evaluated in separate experiments. According to Zierler, the blood flow per gram of tissue should equal λ •
H/A
. This relation was verified experimentally. Exponential analysis was carried out but the results of it were not considered to support the hypothesis of a two compartment inparallel model in skeletal muscle. The shape of the washout curve did not suggest the existence of A-V shunts.
Blood Flow and Oxygen Consumption in Muscles after Section of Ventral Roots
Authors: HUDLICKÁ OLGA
Published: June 2012

Muscles deprived of somatic motor innervation (sensory and sympathetic motor innervation intact) served as a model for studying the role of vasoconstrictor fibers and skeletal muscle tone in the regulation of skeletal muscle blood flow. Blood flow, vascular resistance and O
2
consumption of the gastrocnemius muscle of the cat were measured 5 to 7, 10 to 16, and 27 to 44 days after unilateral section of ventral roots L
5
to S
5
in cats and compared to similar measurements in the normal gastrocnemius muscle and in that with its sciatic nerve cut. After section of the peripheral nerve, total blood flow increased and then returned to normal; after section of the ventral roots, total blood flow did not change significantly. In both cases, blood flow per 100 g of muscle increased as atrophy developed. After section of the ventral roots, O
2
consumption and CO
2
production per 100 g of muscle increased earlier than blood flow. Peripheral resistance was calculated before and immediately after acute section of both tibial nerves to evaluate the participation of muscle tone in the regulation of peripheral resistance. At rest, muscle tone appears to be responsible for about 25% of the peripheral resistance.
Cardiac Sarcotubular Vesicles
Authors: CARSTEN MARY E.
Published: June 2012

The transport of calcium through the membranes of the sarcoplasmic reticulum plays an important role in the relaxation-contraction cycle of the heart. To study and characterize this system, fragmented sarcotubular vesicles from dog hearts were prepared by ultracentrifugation. The fraction between 15,000 and 40,000 g was partially purified by gradient centrifugation. Calcium accumulation by the vesicles in the presence of ATP, Mg,
45
Ca, and oxalate was studied. The rate of calcium uptake increased with the ATP concentration and was not affected by changes in K or Na concentration nor by substitution of isosmotic amounts of sucrose for 75% of the Na ions. Splitting of ATP was increased upon substitution of sucrose. In aged preparations of vesicles, ouabain or acetylstrophanthidin decreased the rate of their calcium accumulation and partially reversed the inhibition of myofibrillar ATPase by the vesicles. It is suggested that the partial inhibition of calcium uptake increases the concentraton of free calcium, and thus makes more calcium available for contraction of the myofibril.
Role of the Autonomic Nervous System in the Renal Vasoconstriction Response to Hemorrhage in the Rabbit
Authors: KORNER PAUL I. , STOKES GORDON S. , WHITE SAXON W. , CHALMERS JOHN P.
Published: June 2012

In normal unanesthetized rabbits with intact autonomic effectors, rapid removal of 26% of the blood volume resulted in prolonged renal vasoconstriction. This response was completely absent in rabbits without functioning autonomic effectors (after guanethidine treatment + adrenalectomy + atropine), despite the greater arterial hypotension in this group. The effects of removing 26% and 32% of the blood volume were compared in the normal innervated and chronically surgically denervated kidney of the same animal. After 26% hemorrhage, the vessels of both kidneys constricted, but the response was significantly greater on the innervated side; reduction in GFR was the same in both kidneys. After 32% hemorrhage the renal constrictor response was greater than after 26% hemorrhage, the difference largely resulting from additional humoral effects, as estimated by the greater vasoconstriction observed in the hypersensitive surgically denervated kidney at this level of hemorrhage; GFR also fell more on the denervated side. The results indicate that sympatho-adrenal activity is essential in the production of renal vasoconstriction after hemorrhage, and suggest that this response is normally produced by the synergistic action of increased sympathetic nerve activity and humoral effects, including those of the adrenal catecholamines.
Transient Ventricular Conduction Disturbances Produced by Intra-atrial Injection of Single Doses of KCI
Authors: HAN JAOK , MALOZZI ANNA MAE , MOE GORDON K.
Published: June 2012

In dogs under pentobarbital anesthesia, the administration of KCl in single intra-atrial doses of 1 mg/kg produced varying effects on intraventricular conduction depending upon the initial potassium concentration of systemic blood. At normal and moderately increased systemic K concentrations, single injections of KCl improved intraventricular conduction, but at higher systemic K concentrations a negative dromotropic effect appeared. Following injection into the right atrium, the effect appeared immediately in the right ventricle, followed after some delay by an appreciably lesser effect in the left ventricle. Injection of potassium into the left atrium altered conduction in the left ventricle without affecting the right ventricle. The results indicate that transient alterations of [K] in the blood of the ventricular cavity can act directly on the specialized conduction network to alter the rate of intraventricular conduction.
Control of Ventricular Fibrillation during Induced Hypothermia in Cats after Differential Depletion of Cardiac Catecholamine Stores with Prenylamine (Segontin)
Authors: NIELSEN KAI C. , OWMAN CHRISTER
Published: June 2012

The role of adrenergic mechanisms for the development of ventricular fibrillation during induced hypothermia was studied in cats. Prenylamine (60 mg/kg) caused a disappearance of the adrenergic transmitter in the muscular nerves; those to the vessels were only slightly affected. Thus pretreated, animals can be cooled to 17.8 to 17°C rectal temperature, and subsequently rewarmed, without developing ventricular fibrillation. Blood pressure was maintained with metaraminol. Without pretreatment the animals constantly develop ventricular fibrillation at 23 to 18.6°C. When prenylamine was given in a dose (20 mg/kg) that does not overtly affect the norepinephrine content of the cardiac adrenergic nerves, ventricular fibrillation was not prevented. In one group of animals receiving 60 mg/kg of prenylamine, norepinephrine instead of metaraminol was infused to maintain the blood pressure during cooling. These animals developed ventricular fibrillation (or cardiac standstill). Fluorescence microscopy showed that the infusion had restored the norepinephrine content in the cardiac nerves previously depleted of their endogenous transmitter by prenylamine. The incidence of ventricular fibrillation seems to be related to the number of intact adrenergic nerves present in relation to the cardiac muscles. Hypothermia caused a distinct release of transmitter from the cardiac adrenergic nerves.
Limitation of Myocardial Function by Reduced Coronary Blood Flow during Isoproterenol Action
Authors: DANIELL HERMAN B. , BAGWELL ERVIN E. , WALTON ROBERT P.
Published: June 2012

The interpolated decrease in heart force or isometric systolic tension that occurs during isoproterenol stimulation has been examined in terms of changes in coronary flow and myocardial metabolism. In 67 open-chest dogs under pentobarbital anesthesia, determinations were made of lactate, pyruvate, Po
2
and Pco
2
in arterial and coronary sinus blood; coronary flow was measured with an electromagnetic flow transducer and ventricular force with a strain gauge arch. Although the characteristic, uncomplicated effect of isoproterenol is a marked increase in coronary flow and contractile force, this is briefly interrupted by a sharp decrease in these functions, and the decrease is associated with evidence of anaerobic metabolism. This decrease is concomitant with decreased coronary perfusion pressure and is intensified by sustained infusion of isoproterenol or by lowered oxygen concentrations in the inspired air. The stage of depressed function is counteracted by mechanical maintenance of high aortic pressure or by slow, controlled heart rate. When uncontrolled, tachycardia due to isoproterenol continues without phasic interruption. The intermediate period of depressed function is interpreted in terms of sharply decreased oxygen delivery when both cardiac rate and force are increased. The hemodynamic and metabolic values for these acutely occurring, reversible extremes have been specified.
An Intrinsic Neuromuscular Basis for Mitral Valve Motion in the Dog
Authors: SONNENBLICK EDMUND H. , NAPOLITANO LEONARD M. , DAGGETT WILLARD M. , COOPER THEODORE
Published: June 2012

The anterior leaflet of the mitral valve of the dog contains blood vessels, nerve fibers, and cardiac muscle in addition to elastic fibers and collagen. When studied in a myograph, the electrically stimulated mitral valve actively developed tension and shortened. Active tension was found to be a function of initial length of the valve and was increased by norepinephrine and decreased by acetylcholine. The presence of neuronally releasable norepinephrine stores in the valve was indicated by responsiveness to tyramine. The negative inotropic response of the mitral valve to acetylcholine was consistent with an atrial origin of the tissue. Possible functional roles for mitral valve muscle and the potential significance of its neural control are discussed.
A Quantitative Analysis of Left Ventricular Myocardial Function in the Intact, Sedated Dog
Authors: TAYLOR ROGER R. , ROSS JOHN , COVELL JAMES W. , SONNENBLICK EDMUND H. , Lewis Robert
Published: June 2012

Instantaneous contractile element velocity was calculated from left ventricular pressure and its first derivative during isovolumic left ventricular contractions produced by sudden balloon occlusion of the ascending aorta during diastole in closed-chest, sedated dogs. Wall tension was derived from ventricular pressure and volume, the latter being obtained from the pressure-volume relation of the arrested ventricle. During isovolumic contractions, there was an inverse curvilinear relation between tension and velocity, except at the onset of contraction and near peak tension. Increasing diastolic ventricular volume shifted the tension-velocity relations to the right, with increase in mean total isovolumic tension from 188 to 471 g/cm
2
, but without an obvious change in extrapolation to maximum velocity, which averaged 3.0 circumferences/sec. End-diastolic pressure-tension and circumference-tension relations indicated that active tension development continued to increase up to the maximum measured enddiastolic pressures of approximately 20 mm Hg. The normalized data, pooled from 15 animals, showed little scatter in the data for tension and velocity. It is concluded that the contractile properties of left ventricular muscle in the intact, sedated dog may be meaningfully described by tension-velocity relations obtained from single isovolumic contractions. The responses of the intact ventricle to increased diastolic volume and digitalis glycosides are analogous to those of isolated cardiac muscle. The small variability in the normalized tension-velocity relations in the normal dog suggests that it will also be possible to characterize abnormal left ventricular function with this approach.
Venous Occlusion Pressure Plethysmography in the Human Upper Limb
Authors: LUDBROOK JOHN , COLLINS GEOFFREY M.
Published: June 2012

Two techniques of venous occlusion pressure plethysmography were examined experimentally in the human upper limb. The first was the classical method, in which external pressure is applied to the limb solely by way of the plethysmograph. In the second, the entire upper limb including the plethysmograph and venous occlusion cuff was enclosed in a box within which the air pressure could be raised. For each method the predictability of perfusion pressure was estimated by measuring local tissue pressure, venous pressure and arterial pressure. Artifacts in the recording of blood flow were also sought. In the first method there was a nonuniform increase in tissue pressure, venous pressure and probably arterial pressure. The changes were uniform and predictable in the second. Flow cessation pressure was 19 to 36 mm Hg in the warm hand and 13 to 30 mm Hg in the forearm using the first method. It was less than 10 mm Hg with the other method. It is suggested that the second technique offers a method for reexamining pressure-flow relations in the human upper limb under more precisely controlled conditions than hitherto.
Validation of the Antipyrine Method for Measuring Fetal Umbilical Blood Flow
Authors: RUDOLPH ABRAHAM M. , HEYMANN MICHAEL A.
Published: June 2012

Vinyl catheters were inserted into an umbilical vein, a hindlimb vein and either an umbilical or dorsalis pedis artery in 9 lamb fetuses with gestational ages of 110 to 147 days. The lambs were then delivered from the uterus, but placental flow was maintained. Cannulating electromagnetic flow transducers were inserted into both umbilical veins. Antipyrine solution was constantly infused into the hindlimb vein, and after equilibration, umbilical blood flow was calculated by the Fick method. The values for umbilical flow measured by the antipyrine technique were comparable with those recorded simultaneously with electromagnetic flowmeters. There was also no difference in antipyrine concentrations in the peripheral and main umbilical veins. The study thus validates the use of the Fick method with continuous antipyrine infusion for measuring fetal umbilical blood flow.
Development of Tachyphylaxis to Aspartyl
1
and Not to Asparginyl
1
Angiotensin II in the Rat
Authors: SAMBHI MOHINDER P. , BARRETT JACK D.
Published: June 2012

Pressor responses to single increasing doses (0.001 to 10 µg) and constant infusions (0.01 to 5 mg/kg per hr) of synthetic aspartyl
1
angiotensin II (Asp
1
) and asparginyl
1
angiotensin II (Aspg
1
, Hypertensin, CIBA) were measured in normal and nephrectomized rats. Mean blood pressure was recorded directly using strain gauges. Angiotensin tachyphylaxis (decline of maximal response to increasing doses, or return of blood pressure to control levels on constant infusion) was consistently seen with greater than minimal doses of Asp
1
while the phenomenon was not observed with Aspg
1
at any dose level. The results indicate that in the rat the two octapeptide analogues of angiotensin are not identical in biologic activity as has been previously held, and that the N-terminal amino acid plays an important part in determining the pressor responsiveness especially to higher doses of angiotensin peptides. The pattern of response and development of tachyphylaxis to Asp
1
closely resembles that of well known tachyphylaxis to renin. These results lend further support to our earlier findings that Asp
1
represents the natural form of angiotensin released in vivo. Renin tachyphylaxis may in its entirety be explained to depend upon the actions of Asp
1
released by renin in plasma. Tachyphylaxis to endogenous angiotensin in pathologic as well as certain physiologic conditions may be expected to occur at lower dose levels than is indicated by the available experimental work with Aspg
1
.
Abnormal Storage of Norepinephrine in Experimental Hypertension in the Rat
Authors: KRAKOFF LAWRENCE R. , DE CHAMPLAIN JACQUES , AXELROD JULIUS
Published: June 2012

The storage and release of
3
H-norepinephrine in the hearts of rats made hypertensive by desoxycorticosterone and NaCl is reported. The initial uptake of the labeled catecholamine was similar in hypertensive and normotensive groups. After an intravenous injection of
3
H-norepinephrine, there was a greater and more prolonged fall in specific activity of cardiac norepineph-rine in the first few hours in the hypertensive animals. Subcellular distribution studies showed that in the hearts from hypertensive rats a greater proportion of the labeled amine was present in the soluble-cytoplasmic fraction than in the granular-storage fraction. In control rats an equilibrium between soluble and granular fractions was reached by 1 hr, while in the hypertensives it was not achieved within 24 hr. In the first few hours there was a 45% fall in specific activity in the granular fraction of the hypertensive rats, but only a small re-deuction in the controls. There was an elevation in the fraction of deaminated metabolites in the hearts of the hypertensive animals, while in the kidneys all
3
H-metabolites were increased. These observations are consistent with the concept that there is a defect in the storage and retention of norepinephrine by granules in sympathetic nerves in this type of experimental hypertension. Such an abnormality might permit increased amounts of physiologically active cate-cholamine to be available to the receptor.
Effect of Decreasing the Force of Right Atrial Contraction on Right Ventricular Stroke Volume
Authors: BOYD DANIEL L. , WILLIAMS JOHN W.
Published: June 2012

The effect of reducing the force of right atrial contraction on right ventricular stroke volume was determined in anesthetized open-chest dogs. Atrial contractile force, measured directly with a strain-gauge arch, was decreased by electrical stimulation of the right vagus nerve; right ventricular stroke volume was measured with an electro-magnetic flowmeter. Heart rate was maintained constant by electrical stimulation of the right atrium.

Vagal stimulation decreased atrial contractile force by an average of 47±2.6 (SEM)% of the control, and stroke volume fell by 4.0±0.9%. During vagal stimulation, no change was observed in right ventricular contractile force. In addition, no consistent change was noted in mean right atrial or right ventricular pressures. The relation between the decrease in atrial force and stroke volume was not altered significantly by the rate of right atrial pacing. In 7 of 10 experiments, increasing the inhibition of atrial force produced a further decrease in stroke volume.

Since neural, mechanical, and humoral factors modify atrial contractile force in the intact animal, the present study provides more definitive evidence that the ability to alter atrial force represents another adaptive mechanism in the regulation of cardiac performance.
Localized Myocardial Responses to Stimulation of Cardiac Sympathetic Nerves
Authors: SZENTIVANYI M. , PACE J. B. , WECHSLER J. S. , RANDALL W. C.
Published: June 2012

Myocardial contractile force was recorded at three to five positions on the canine heart while progressively more distal portions of the cardiac sympathetic nerves were electrically stimulated. When the electrodes were applied directly to the stellate ganglion or to the ansa subclavia, positive inotropic responses were generally observed on all of the test regions of the heart. However, when more distal branches of the cardiac nerves were stimulated, individual test regions were successively deleted from the general response. By carefully removing narrow strips of epicardium (epicardial denervation) from different portions of the heart, similar deletions in response were observed. These observations indicate that the peripheral autonomic innervation of the heart is distributed to circumscribed regions of cardiac musculature. Contractile segments of a given region of the heart may be organized in series and each component of the chain influences the contraction of neighboring elements, normally innervated segments mechanically interacting with noninnervated regions. Individual units of cardiac muscle may be markedly influenced through local intervention by the sympathetic nerve supply.
Influence of Diphenylhydantoin on Electrophysiological Properties of the Canine Heart
Authors: ROSATI ROBERT A. , ALEXANDER JAMES A. , SCHOOL STEPHEN F. , WALLACE ANDREW G.
Published: June 2012

These studies were designed to examine the electrophysiological effects of diphenylhydantoin (Dilantin) on the heart of awake dogs. Recording electrodes were implanted over the sinoatrial node, bundle of His, and right bundle branch, and studies were performed 2 to 6 weeks following recovery. Diphenylhydantoin (10 mg/kg) increased heart rate, shortened A-V conduction time and had little or no effect on conduction velocity in Purkinje tissue or total ventricular activation time. Similar effects were noted when heart rate was controlled by pacing. Following cardiac denervation, diphenylhydantoin decreased heart and prolonged A-V conduction time. It raised the threshold of atrial and ventricular muscle with no change of refractory periods. In dogs with heart block, it decreased the maximal rate at which the atria would respond to stimulation. When ventricular tachycardia was induced in dogs with heart block, by toxic doses of deslanoside, diphenylhydantoin abolished the ectopic tachycardia and restored the control rhythm.
Measurement of Total Cerebral Blood Flow in the Monkey by External Monitoring of Cesium-131
Authors: WEINER DANIEL E.
Published: June 2012

A modification of the
42
K fractionation technique has been developed which permits rapid, repeated measurement of cerebral blood flow by external isotope monitoring without jugular or carotid puncture.
131
Cs, an isotope with distribution characteristics similar to those of
42
K, has been used in this study. Cerebral blood flow measurement involves determination of the peak cephalic activity of an intravenously injected bolus of
131
Cs by digital rate counting in a well-scintillation crystal that encloses the head. If the entire fraction of the isotopic bolus entering the head appears in the cerebral circulation before significant venous loss of
131
Cs begins, the ratio of peak cephalic activity to total injected activity will represent the cephalic portion of the cardiac output. Since cerebral capillaries are not very permeable to
131
Cs, activity remaining in the head after decay of peak cephalic activity will represent uptake by noncerebral cephalic tissue, and the peak activity can be corrected to yield only the cerebral cardiac output fraction. Total cerebral blood flow calculated from
131
Cs injection was compared with measured bilateral internal jugular flow obtained by cannulation of the jugular veins. In anesthetized rhesus monkeys, the average ratio (calculated flow/measured flow) was 1.05±0.06.
Barium-Induced Automaticity in Right Ventricular Muscle in the Dog
Authors: REID J. Alan , HECHT HANS H.
Published: June 2012

Pacemaker activity was induced in trabecular muscle fibers of canine hearts using oxygenated Tyrode solution with added barium chloride. Following exposure to barium (0.2 to 5mM) the resting potential decreased toward zero from 10 to 60%, depending on the concentration. Simultaneously, the duration of the action potential increased and early diastolic hyperpolarization appeared with diastolic depolarization characteristic of latent pacemaker activity. In concentrations above 0.75 mM, spontaneous activity appeared with presystolic upsweep at the threshold potential. The changes were reversible when normal Tyrode solution was readministered. Suppression of the induced pacemaker activity occurred on cooling or following imposed rapid stimulation. The changes produced by barium are consistent with a decrease in the conductance of the membrane for potassium.