bluuebunny/crossref_metadata_2025 huggingface dataset:
Extracorporeal Circulation: A Device for the Quantitative Study of Thrombus Formation in Flowing Blood
Authors: DOWNIE H. G. , MURPHY E. A. , ROWSELL H. C. , MUSTARD J. F.
Published: June 2012

A standardized extracorporeal shunt system has been described. It allows examination of the sequence of events in thrombus formation and it provides a means of quantitating it in flowing blood. It further allows assessment to be made of the usefulness of classical in vitro clotting tests in thrombogenesis. The platelet adhesive index and clotting time in silicone showed the best correlation with the amount of thrombus formed.

Pig serum presumably rich in serum thrombotic accelerator (STA) has been shown to enhance thrombus formation from flowing blood.

Within the limits of these experiments, the rate of blood flow has been found to be of little importance.
Comparison of the Action of Ouabain on the Heart in Hypothyroid, Euthyroid and Hyperthyroid Dogs
Authors: ROSEN ANDERS , MORAN NEIL C.
Published: June 2012

Ouabain-induced changes in cardiac contractile force and differences in the amount of ouabain required to induce arrhythmias and to produce death were evaluated in normal, thyroidectomized and thyroxine-treated dogs. It was found, that ouabain, following alterations in thyroid function, still substantially augmented cardiac contractile force in anesthetized open-chest dogs. In both the hypothyroid and the hyperthyroid animals a moderate dose of ouabain produced an increase in contractile force of approximately the same extent as in the euthyroid animals, although of slower onset in the hypothyroid dogs. Larger doses of ouabain caused a smaller positive inotropic response. in hyperthyroid dogs than in euthyroid and hypothyroid animals. Changes in thyroid function increased the arrhythmia-producing and the lethal dose of ouabain, which in the hyperthyroid dogs may have been due to the markedly elevated heart rate.
Neurogenic Control of Peripheral Resistance in Renal Hypertension
Authors: TAQUINI ALBERTO C.
Published: June 2012

The increased peripheral resistance responsible for hypertension associated with unilateral renal ischemia and contralateral nephrectomy, is abolished after destruction by pithing of the central nervous system of dogs and rats, or after inactivation of the inhibitory carotid sinus reflex in dogs. The tissue catecholamine content of renal hypertensive rats was in the same range as in the normotensive animals. These results suggest that the increased peripheral resistance in hypertension is neurogenically mediated and that the increased resistance is due to an increased response of the resistance vessels to normal neurogenic stimulation.
Vasoactive Peptides and Substrates and Their Relation to Protein Handling by the Kidney
Authors: M.D. RAMON B.
Published: June 2012

The properties of anephrotensin, a polypeptide liberated by acid incubation of serum, are reviewed. Experiments with antirenin rule out the possibility that renin is the enzyme that liberates anephrotensin.

Serum anephrotensinogen increases after bilateral nephrectomy or after several weeks of treatment with desoxycorticosterone (DCA). There are perallel changes under these conditions in the amounts of anephrotensinogen and angiotensinogen in the serum, suggesting that a common substrate may be involved. The increase in substrate is in accord with the possibility that DCA treatment results in some deficiency in the handling of proteins by the kidney.

There is an increase in urine vasoactive peptides and total proteins in DCA-treated rats. These increases are probably related to deficiency in tubular reabsorption. The increase in the albumin/globulin ratio of the urine proteins under these circumstances supports this idea.

The changes described above are not necessarily related to the onset of hypertension. Whether the changes in protein handling by the kidney are related to the hypertension produced by DCA treatment is an unsettled question.
Influence of Ouabain on Contractile Force, Resting Tension, Ca
45
Entry and Tissue Ca Content in Rat Atria
Authors: GERSMEYER GUDRUN , HOLLAND WILLIAM C.
Published: June 2012

As was the case with guinea pig atria, ouabain induced a small but significant increment in Ca
45
uptake and a drop of tissue Ca content in rat atria during the positive inotropic effect. In ouabain contractures, the uptake rate increased 87% to 170% and there was little increase in tissue Ca. Concentrations of the glycosides required to produce a positive inotropic effect and contracture in rat atria were 100- to 200-fold greater than those required in guinea pig atria.
Pulsatile Pressure and Flow Through Distensible Vessels
Authors: STREETER VICTOR L. , KEITZER W. FORD , BOHR DAVID F.
Published: June 2012

The basic differential equations for elastic wall material and for continuity and momentum are derived, including fluid frictional resistance of the wall of the tubes, based on one-dimensional flow. These partial differential equations are transformed into four ordinary differential equations using the theory of characteristics. Then difference equations are developed and by an interpolation method (method of specified time intervals) equations are obtained for computation of velocity and pressure at equally-spaced sections along the vessel at specified equal time intervals. The equations are first applied to a flexible tube of initial constant diameter, with a pulse flow taken from in vivo experiments.

Equations are then developed for tapering tubes with distributed outflow along their lengths (to simulate branches). Pressure-time data from femoral artery measurements are then used to compute flow through the artery, and the results are compared with electromagnetic flowmeter data. Computed flow is greater than measured flow if a friction factor for laminar flow is used. Frictional losses of energy in the normal pulsatile flow in the femoral artery are similar to those of turbulent flow.
Gaseous Diffusion from Alveoli to Pulmonary Vessels of Considerable Size
Authors: SOBOL BRUCE J. , BOTTEX GEORGES , EMIRGIL CEMIL , GISSEN HAROLD
Published: June 2012

Thirty patients have been presented in whom the appearance of inhaled hydrogen gas at an electrode in the wedge position of a pulmonary artery was seen to occur within two seconds. In 13 of these patients the appearance of hydrogen occurred with equal or nearly equal rapidity in a pulmonary artery at least 3 mm in diameter. In 11 patients increasing alveolar oxygen tension by the inhalation of a single breath of 100% oxygen or by voluntary hyperventilation produced a rapid response at the wedge position as well. It is concluded that the rapid appearance of hydrogen and oxygen is due to direct diffusion of the inhaled gas from the alveoli to the pulmonary arterial blood.
Induced Changes in the Pattern of Pulmonary Blood Flow in the Rabbit
Authors: Lehr David E. , Tuller Martin A. , Fisher Lloyd C. , Ellis Kent , Fishman Alfred P.
Published: June 2012

1. In the normal, unanesthetized rabbit, resting quietly in its normal position, catheterization of the right ventricle (and central veins) altered the distribution of blood throughout the lung in a characteristic manner.

2. Regional pulmonary vasoconstriction, rather than passive changes in vascular caliber or in the flow properties of blood, seemed to be involved.

3. The mechanism for the regional pulmonary vasoconstriction is considered in terms of a neurohumoral pathway, involving afferent pathways from the right heart, connecting channels in the upper cervical segments of the spinal cord, and release of a histamine-like substance at the neuro-vascular junctions.
Actin from Heart Muscle: Isolation, Purification, and Physicochemical Properties
Authors: KATZ ARNOLD M. , HALL ELIZABETH J.
Published: June 2012

A systematic study of the preparation of actin from cardiac muscle has led to the use of a modification of Straub's original technique which gave good yields of an F-actin with very high polymerizing activity. The G-actin obtained by this method was found to be homogneous in starch gel electrophoresis; the sedimentation behavior suggested that small amounts of oligomers of G-actin may have been present in addition to monomeric G-actin, but there was no evidence of impurity.

The partial specific volume of dog cardiac actin was approximately 0.715 ml/g, the sedimentation coefficient extrapolated to infinite dilution of the protein was 3.44 S, and the intrinsic viscosity was 0.16 dl/g. Precise measurement of the diffusion coefficient was not feasible due to the instability of the G-actin monomers in solutions of high ionic strength. The sedimentation behavior of rabbit cardiac actin was similar to that of dog cardiac actin.

The molecular weight of dog cardiac actin, estimated from sedimentation and viscosity data, was 62, 300. Since this estimate of molecular weight is similar to published values for rabbit skeletal actin, the different properties of cardiac and skeletal muscle cannot be attributed to a major physicochemical difference between the actins of these two tissues.
Effect of Experimental Congestive Heart Failure and Acetyl Strophanthidin on Myocardial Electrolyte and Water Content
Authors: BLISS HARRY A. , ADOLPH ROBERT J.
Published: June 2012

The syndrome of chronic congestive heart failure was produced in female dogs by progressive pulmonary artery constriction. A factorial experimental design, containing seven experiments of four dogs each, was employed. Each experiment was completed in one day and consisted of two groups of two dogs each, one group containing dogs with heart failure and the other, normal dogs. One animal from each group received intravenous acetyl strophanthidin, 0.015 mg/kg ascites-free weight, while the other was given an injection of inert material. The heart was quickly removed from the chest nine minutes after the injection and the right ventricle was taken for analysis. Previous work indicated that this dose of the drug produced and inotropic effect both in normal animals and in dogs with heart failure without producing digitalis toxicity.

The myocardium from animals with congestive heart failure contained significantly less potassium but more sodium, chloride, and water per kilogram of dry fat-free blood-free myocardium than the myocardium from normal dogs. The concentration of sodium plus potassium in tissue water was subnormal in failing hearts. The sodium and chloride composition of the fluid gained by failing hearts differed significantly from that of interstitial fluid.

Acetyl strophanthidin increased myocardial chloride and water. Although potassium in the myocardium was unchanged in treated control dogs, it increased significantly after acetyl strophanthidin in animals with heart failure.

The findings are consistent with myocardial cellular swelling in congestive heart failure. The quantity of blood in each kilogram of failing myocardial tissue was severely reduced, probably because of muscle fiber hypertrophy. The possibility is considered that this alteration, together with the increased tissue water, may lead to lowered oxygen tension in failing heart muscle.

It is suggested that digitalis exerts two opposing effects on ion transport through the myocardial cell membrane and that neither of these is fundamental to its inotropic action.
Group Isolation and Atherosclerosis in Cholesterol-Fed Cockerels
Authors: PICK RUTH , KATZ LOUIS N. , CENTURY DOLORES , Johnson Philip J.
Published: June 2012

Group isolation, a highly unnatural environmental situation in cockerels, increases atherogenesis and decreases regression of previously induced atherosclerosis. This alteration occurs despite the absence of change in the hypercholesterolemic response to the diet in the induction experiments. It is accompanied by a reduction in weight gain despite food intake similar to the controls.

Disturbing the social order by altering the pecking order in flocks of cockerels on a cholesterol-oil containing diet does not alter hypercholesterolemia and atherogenesis. However, it leads to increase in sex characteristics. Physical activity, with or without alterations in pecking order, causes a reduced weight gain even when food intakes are not altered.

It is concluded that environmental factors can and do influence atherosclerosis. The types of environmental change which can produce this effect and the exact mechanisms involved require further study.
Vasopressor Material in Experimental Renal Hypertension
Authors: Koletsky Simon , Pritchard Walter H.
Published: June 2012

Transfer of blood from rats with acute renal hypertension to normal recipient rats demonstrated that a vasopressor substance was present in the circulation of the hypertensive animals. This is consistent with the view that a humoral mechanism plays a role in the origin of the hypertension. In contrast to the acute stage, no vasoactive material could be demonstrated in the blood after the second week of hypertension. Either the amount of pressor substance was too small to detect or none was being produced. In the latter case, chronic renal hypertension cannot be attributed to a humoral mechanism.
Congenital Heart Disease and Other Malformations Produced by Influenza A Virus and Allantoic Fluid in the Chick Embryo
Authors: de la Cruz Maria V. , Campillo-Sainz Carlos , Munoz-Armas Simón , Pascual-Chávez Asunción , Zamudio-Bandera Rafaela
Published: June 2012

The effect of both active and heat-inactivated influenza A virus, chick allantoic fluid, and of buffered saline solution on the mortality and appearance of congenital malformations in the white Leghorn chick embryo, especially in the heart, was studied. Active influenza A virus produced a high mortality rate during the initial stages of development, when formation of the cardiac septa had barely begun and the primordia of the valves were yet to appear. Consequently, no congenital heart disease was found in the group inoculated with active virus, though profound alterations of the nervous system, sensorial organs and general body shape were observed. The effects of allantoic fluid with and without heat-inactivated virus were the same high incidence of congenital valvular disease (pulmonary stenosis, thickening of the mitral valve), and interventricular septal defect. Inoculation of buffered saline solution produced an increased mortality rate and structural malformations outside the heart, but had no effect on the development of the heart. Possible mechanisms of action of these terato-genic agents are discussed.
Changes of Boundary Layer Flow in Model Systems
Authors: Scharfstein Heinz , Gutstein William H. , Lewis Leon
Published: June 2012

A model system using fluid driven through glass and plastic tubes coated with resin, demonstrated augmentation of the viscous shearing stresses at the inner surface of the wall when variations in shape were introduced into the tube and at branch points. The hydrodynamic basis of these increased stresses is presented from the point of view of boundary layer theory, and the relevance for initiation of arterio-atherosclerosis is discussed.
Pressure Transients Occurring in Diastole in the Central Aorta
Authors: Piemme Thomas E. , Dexter Lewis
Published: June 2012

From the observations noted and from physical considerations, the following may be concluded:

Cardiac events of sufficient energy content to cause sudden displacement of the heart and great vessels give rise to pressure transients that may be seen in all chambers if carefully looked for. These are, in reality, "acceleration" waves superimposed upon otherwise smooth pressure functions.

Such an oscillation occurs normally at the time of isometric ventricular contraction. The energy content of isometric ventricular contraction results in an induced pressure wave in all chambers, but is most prominently seen in the low pressure atria as the "c wave, " and in the aorta and pulmonary artery as small, relatively high frequency, presystolic impulses. The event is obscured in the ventricles by the rapidly rising intraventricular pressure but may be identified when the ventricular pressure is differentiated.

Under pathological circumstances, atrial contraction and early ventricular filling may result in peripherally recordable pressure deflections.
Production of Hypertension and Vascular Disease by Kidney Extracts
Authors: MASSON GEORGES M. C. , KASHII CHUJIRO , PANISSET JEAN-CLAUDE , YOGI SHIGERU , PAGE IRVINE H.
Published: June 2012

Hypertension was induced in rats by constricting the aorta between the origins of the renal arteries. The left kidney, which became ischemic and atrophic ("endocrine kidney"), caused a malignant type of hypertension associated with weight loss, cardiac hypertrophy, hypertension, cardiac necrosis, nephrosclerosis of the right kidney, and arteritis. Amounts of pressor substances were increased in the left kidney and decreased in the right as compared with those in kidneys of normal rats.

Aqueous extracts of ischemic kidneys, of kidneys contralateral to ischemic kidneys and of normal kidneys were prepared and the supernatant solutions were injected subcutaneously into test rats which had been uninephrectomized a few hours previously. Extracts of ischemic kidneys caused hypertension, cardiac hypertrophy, weight loss, and renal and vascular lesions mimicking the signs which result from renal ischemia. The extracts from the other kidneys were inactive. Administration of renin in doses roughly equivalent in pressor activity to the extracts of ischemic kidneys caused a rise in pressure, diuresis, and proteinuria but no lesions when given subcutaneously.

It is proposed as a working hypothesis that renal hypertensive disease results not only from increased secretion of renin and formation of angiotensin but from simultaneous release from kidneys with reduced perfusion pressure of a substance which augments the enzymatic formation of angiotensin. This substance is presumably absent from normal kidneys and from semipurified renin preparations.
Innervation of the Systemic Heart of the California Hagfish
Authors: HIRSCH EDWIN F. , JELLINEK MAX , COOPER THEODORE
Published: June 2012

Large nerves with myelinated fibers and ganglion cells were demonstrated in proximate relationship to the systemic heart of the California hagfish (
Eptatretus stouti
). A system of ganglion cells with fibers is distributed along the aorta, the epicardium, and the endocardium. The myocardium has a plexus of coarse and fine argyrophilic fibers and fibril branches similar to, if not as extensive as, that which occurs in the hearts of fish and amphibians.

These details of anatomical structure contradict the original statement by Greene that the heart of the hagfish is aneural, a conclusion which he derived from his inability to obtain a change in the rate and force of cardiac contraction by electric stimulation of the vagus nerve.

The high catecholamine content of the cardiac tissues of the California hagfish (
Eptatretus stouti
) is verified. Over 99% was determined to be epinephrine.
Coronary Circulation and the Tail of First-Pass Indicator Dilution Curves
Authors: CROWDER BENNETT L. , GREER WILLIAM C. , SHEPPARD CHARLES W.
Published: June 2012

In a series of canine heart-lung preparations, single-pass indicator dilution curves were obtained with and without cannulation of the coronary sinus. Further evidence was obtained that the tails of the curves are significantly elevated above the tails predicted from the simple one-dimensional random-walk relation.

To provide estimates of the contributions which dye circulating through the coronaries might make to the tails, curves were obtained in the same preparation with and without cannulation, and at high and low mean arterial pressure. A method was developed for cannulation which permitted sampling through an exterior low-resistance cannula system which was secured in the coronary sinus without producing serious obstruction of the coronary sinus tributaries or interference with the conduction system.

Although the classical exponential down-slope gave better agreement than the random-walk relation, the experimental curves were frequently elevated and prolonged when compared to the exponential curve. The difference in area amounted to approximately 4.5%. In experiments at high mean arterial pressure without bypass of coronary dye the tail was significantly higher on the average by 3% compared to the tail in the same preparation with bypass at low pressure. Estimating that 60 to 70% of coronary dye would be successfully bypassed, the total coronary contribution to the tail of 4 to 5% of dye on the average is not sufficient to account for the excess of experimental tails over random-walk curves.
Functional Cardiac Deterioration During Development of Hemorrhagic Circulatory Deficiency
Authors: GOMEZ OSCAR A. , HAMILTON WILLIAM F.
Published: June 2012

A massive infusion test has been devised to evaluate the functional capacity of the heart.

In five dogs extensive surgical procedures followed by episodes of arterial hypotension at 30 mm Hg and lasting 90 minutes caused severe cardiac incapacity, which was demonstrated by failure of rate of cardiac work to increase throughout the infusion together with a large rise in left atrial pressure. This incapacity was not evident in tests made immediately after the hypotensive episode. The damage became more and more severe in tests performed 90 and 150 minutes after the end of the hypotension even though mean arterial pressure was maintained at 100 mm Hg. Operated control dogs did not show cardiac deterioration in tests timed as above. The rate of cardiac work continued to increase throughout the infusion with a relatively small rise of left atrial pressure.

In a series of five dogs, flow to the coronary arteries and to those supplying the head and forelimbs was maintained by normal blood pressure while the rest of the animal was made hypotensive for 90 minutes. The arterial pressure in the whole animal was then returned to an average level of 100 mm Hg. Tests made at intervals after the hypotension showed equivocal evidence of cardiac deterioration.

In another series of four dogs, prepared as above, the partial hypotension lasted 150 minutes before the arterial pressure was returned to normal. Tests at intervals after hypotension showed cardiac damage in all the animals and severe damage in three. Evidence is presented indicating that the peripheral vascular bed had deteriorated functionally as a result of 150 minutes of partial hypotension.
Cyclic Changes in the Oxygen Consumption of the Aorta in Female Rats
Authors: MALINOW M. R. , MOGUILEVSKY J. A. , GERSCHENSON L.
Published: June 2012

The endogenous oxygen consumption of aorta and of diaphragmatic muscle have been studied in female rats and correlated with different phases of estrus. Cyclic changes of oxygen consumption were demonstrated in the aorta but not in the diaphragm. Estradiol in vitro depressed the endogenous Qo
2
of the aorta from diestrous animals. Possible implications of this work are discussed.
Direct Detection and Timing of Aortic Valve Closure
Authors: MACCANON D. M. , AREVALO F. , MEYER E. C.
Published: June 2012

A special electrical contacting device was developed and used to time the relationship between aortic valve closure and the aortic incisura in closed chest anesthetized dogs. High speed tracings showed that the aortic valve is closed at least 5 to 13 msec before the incisura. It is concluded that the aortic pressure incisura results from rebound of the aortic blood column and walls
after
valve closure and that the second heart sound is
not
caused by collision of the valve leaflets but by the same mechanical factors which are responsible for the incisura.
Effect of Posthemorrhagic Anemia on the Renal Circulation of the Unanesthetized Rabbit
Authors: STOKES GORDON S. , KORNER PAUL I.
Published: June 2012

In the unanesthetized rabbit made acutely anemic by bleeding with plasma replacement, there was no change in renal blood flow (RBF), a reduction in glomerular filtration rate (GFR), and a reduction in renal vascular resistance with a fall in the filtration fraction. There was evidence of renal tissue hypoxia and reduction in renal PAH extraction ratio. The extraction ratio was 97% at a hematocrit ratio of 34.5%, 91% at a hematocrit of 11.5%, and 84% with hematocrits between 6 and 10%. The effects of carboxyhemoglobinemia at normal blood viscosity were compared with the effects of anemia; a smaller reduction in renal PAH extraction ratio was found and there was no reduction in filtration fraction. The reductions in renal vascular resistance and filtration fraction in anemia were partly reversed by breathing 100% O
2
, viscosity changes again being minimized. It was concluded that renal tissue hypoxia and reduction in red cell concentration contribute in varying degrees to the changes in the renal vascular bed and the PAH extraction ratio.
Thrombin Generation in Normal Subjects and Cardiac Patients
Authors: VON KAULLA KURT N. , VON KAULLA EDITH
Published: June 2012

A refined, reliable thrombin generation test with good sensitivity for both hypo- and hypercoagulability is described. When serial thrombin generation curves were obtained in cardiac patients subjected to standardized treadmill stress, fluctuations of the clotting system were observed in some and a marked tendency to hypercoagulability in others. The relationship of in vitro hypercoagulability as reflected by thrombin generation to an increased tendency to thrombosis remains to be determined.
Systemic Blood Pressure Response to Changes in Right Ventricular Function
Authors: PINKERSON ALAN L. , KOT PETER A.
Published: June 2012

The relationship between right ventricular and aortic pressure was studied in open-chest anesthetized dogs. A simultaneous increase in both pressures was observed in animals with an intact circulation and animals with the systemic circulation perfused at a constant rate and stroke volume by an extracorporeal pump. With gradual partial constriction of the main pulmonary artery, the increase in right ventricular systolic and aortic pressures occurred without consistent change in other measured parameters. Bilateral cervical vagotomy abolished the systemic vascular response.

These observations are consistent with a pressor reflex which is mediated over vagal afferent fibers from the right ventricle. It is suggested that in animals under varying physiologic stimuli an increase in right ventricular pressure is associated with a reflex increase in systemic vascular resistance. In abnormal circumstances with increased resistance to right ventricular emptying, the increased total peripheral vascular resistance would be important in maintaining systemic blood pressure and blood flow.
Stasis Thrombi Induced by Bacterial Endotoxin
Authors: THOMAS DUNCAN P. , WESSLER STANFORD
Published: June 2012

1. In normal rabbits, single intravenous doses of
E. coli
and
Salmonella
endotoxin produce an immediate, transient, hypercoagulable state. Venous stasis occurring during such a state allows the formation of massive red thrombi at sites of obstructed blood flow. The duration of stasis required to produce thrombi following endotoxin administration depends in part on the preinfusion silicone clotting time of the rabbit.

2.
E. coli
endotoxin shortens the recalcification time of platelet-poor plasma obtained from normal subjects and from patients with heredofamilial coagulation defects of Factor XII (Hageman) and Factor IX (plasma thromboplastin component). In contrast, the recalcification time of platelet-poor plasma obtained from patients with Factor XI (plasma thromboplastin antecedent) deficiency is lengthened by endotoxin. It is suggested that the heat-labile plasma factor known to be required for the platelet-endotoxin interaction may be related to Factor XI.
Vascular Reactivity in Experimental Diabetes Mellitus
Authors: BRODY MICHAEL J. , DIXON ROBERT L. , A. Shaffer Richard
Published: June 2012

Vascular reactivity was examined in vessels of the perfused hindquarters of alloxan diabetic and control rats. A significant increase was noted in responsiveness of the diabetic animals to intra-arterial injection of epinephrine, norepinephrine, and synthetic angiotensin. No difference was observed in the vasoconstrictor effects of lumbar sympathetic nerve stimulation or intra-arterial administration of tyramine. Results obtained in diabetic animals were compared with those in animals treated with reserpine. It was found that the reserpinized animals exhibited increased vascular responsiveness only to the catecholamines, and not to angiotensin, vasopressin, tyramine, or barium chloride. Whereas the vascular smooth muscle of diabetic rats was sensitized to epinephrine and norepinephrine, isolated atria from these animals responded normally to the catecholamines. The 24-hour urinary excretion of the catecholamines was significantly elevated in diabetic animals. The data suggest that enhanced vascular reactivity seen in diabetic rats does not result from neuropathy of the sympathetic nervous system. The possible contributions of factors including alloxan per se and body weight to development of increased vascular reactivity in diabetes were considered, but the mechanism for the increase in vascular responsiveness remains unidentified.
A Complex Manifestation of Concealed A-V Conduction in the Dog Heart
Authors: MOE GORDON K. , MENDEZ CARLOS , ABILDSKOV J. A.
Published: June 2012

Conditions under which an apparently non-propagated atrial (concealed) response facilitated the passage of a subsequent response to the ventricle are described. Analysis of the time relations of atrial and ventricular events suggest that the apparent facilitation results from a dissociation of two pathways through the A-V node.
Microcirculatory Effects of Emulsified Fat Infusions
Authors: BRåNEMARK P.-I. , LINDSTRöM J.
Published: June 2012

Changes of flow through minute vessels during hyperlipemia after intravenous infusion of fat emulsion have been analyzed by high resolution vital microscopy of connective tissue in ear chambers and of mesentery in rabbits. The shape of erythrocytes was characteristically changed. Granulocytes often stuck to the endothelium. The velocity of capillary blood flow diminished at first and then reverted fairly quickly to normal. Some chylomicra passed through the capillary walls. No intercorpuscular aggregation, no adhesion of erythrocytes and no adhesion of platelets were observed.
Cardiovascular Responses Following Immunological Sympathectomy
Authors: BRODY MICHAEL J. , Shaffer Richard A.
Published: June 2012

Sympathetic function and cardiovascular responses were measured in rats treated at birth with an antiserum developed to the sympathetic nerve growth factor. The intact animals exhibited ptosis, miosis, and decreased excretion of norepinephrine in the urine. Electrical stimulation of the sympathetic innervation to the vessels of the perfused hindquarters failed to produce vasoconstriction or vasodilatation in any of the treated rats over a wide range of stimulus parameters. Alterations in vascular reactivity characteristic of sympathetic denervation were noted; responsiveness was increased to norepinephrine but not to other constrictor agents. Chemical stimulation of the sympathetic ganglia with 1,1-dimethyl-4-phenyl-piperazinium iodide (DMPP) did not activate the postganglionic fibers but did promote the release of catecholamines from the adrenal medulla. The treated rats showed elevated resistance to flow in the hindquarters. The results of this investigation thus demonstrate that treatment with the antinerve growth factor effectively abolishes vasomotor function of the fibers of the sympathetic nervous system.
Pacemaker Activity During Vagal Escape Rhythms
Authors: WALLACE ANDREW G. , DAGGETT WILLARD M.
Published: June 2012

In dogs, bipolar electrograms were recorded from the SA node and His bundle to localize pacemaker sites during vagal escape and to study the effects of isoproterenol on escape mechanisms. Vagal escape can result from the development of pacemaker activity above the A-V node, within the region of the A-V node, and below the common bundle of His. Isoproterenol shortened the period of asystole prior to the onset of vagal escape, increased the rate of escape rhythms at all pacemaker sites, and occasionally changed the pacemaker to a higher focus in the conduction system.
Peripheral Vasodilator Action of Eledoisin, Bradykinin, and Nitroglycerin in Anesthetized Dogs
Authors: BERGAMASCHI MARIO , GLÄSSER ALFREDO H.
Published: June 2012

The peripheral vasodilator action of the endecapeptide eledoisin in the anesthetized dog has been described in this paper.

Blood flow through the vascular beds supplied by the femoral artery increased following doses of eledoisin as low as 0.5 nanogram/kg (4.25·10
-13
mole/kg) injected intravenously, and 0.001 ng/kg (8.5·10
-16
mole/kg) injected intra-arterially. The blood vessels of the skin were less reactive than blood vessels in muscle.

Eledoisin exerted a powerful vasodilator effect on vascular beds supplied by the common carotid, the external and internal carotid, the occipital and the vertebral arteries.

Renal and mesenteric vascular beds did not respond significantly to eledoisin.

Comparison with some other vasodilator drugs was made. Following intra-arterial doses which do not affect systemic blood pressure, eledoisin was 5 to 50 times more active than bradykinin on total femoral and muscle flows; both showed the same activity on skin flow. Nitroglycerin, carbaminoylcholine, and papaverine were even less active than bradykinin.
Effect of Tension on Induction of Automaticity by Epinephrine in Papillary Muscle
Authors: INNES I. R. , SANDERS H. D.
Published: June 2012

Sudden increase in tension on the quiescent isolated cat papillary muscle from 1 to 5 or 10 g lowered the threshold concentration of epinephrine needed to induce automaticity. The threshold was lowered for no longer than 30 seconds. Slow changes in tension did not lower the threshold. Sustained tension of 5 or 10 g did not change the threshold, nor prolong the lowering of threshold resulting from sudden increase in tension. Contractions of muscles after a sudden rise to 10 g tension or sustained at this level were irregular in rhythm and strength, in contrast to the contractions of muscles under 1 g tension. Sensitization of cardiac muscle to epinephrine by tension changes progressively increasing with each successive beat may account for the effects of elevation of arterial blood pressure in cyclopropane-epinephrine and other arrhythmias.
Water and Electrolyte Content of Normal and Hypertensive Arteries in Dogs
Authors: JONES ALLAN W. , FEIGL ERIC O. , PETERSON LYSLE H.
Published: June 2012

This study was designed to establish values for the water and electrolyte content along the arterial tree in the dog under normal conditions and to determine how the normal electrolyte pattern was altered in renal hypertension.

Determinations of vessel wall water, potassium, sodium, and chloride contents have shown that the water and electrolyte contents from the various sites along the arterial tree differ significantly from each other. Total water and potassium contents decrease progressively from the ascending aorta to the femoral and carotid sites, while the sodium and chloride contents showed the opposite trend. These differences were significant statistically. These trends may not persist along the entire vascular tree to very small arteries, as indicated by analysis of mesenteric arterial samples. Studies of vessel wall inulin space supported the view that these differences result from the relative distribution of cellular and noncellular material; thus the proximal aorta contains a relatively greater proportion of cellular (smooth muscle) material than more distal sites such as the femoral and carotid arteries. A review of the literature further supports these findings.

In experimentally induced renal hypertension the same trends persist along the aorta, but the total water and sodium contents are significantly elevated at all sites.
Characteristics of Reactive Hyperemia in the Canine Intestine
Authors: SELKURT EWALD E. , ROTHE CARL F. , RICHARDSON DANIEL
Published: June 2012

The isolated ileum of the dog shows a characteristic hyperemia following brief periods of arterial occlusion. The magnitude of this reactive hyperemia depends more upon prolongation of flow related to duration of ischemia, than upon increases of maximal or peak blood flow. Repayment of flow deficit, by the added flow of reactive hyperemia, averaged only 35% in the intestine, far below that found by others in skeletal muscle and in the coronary circulation. Nevertheless, estimates of oxygen debt indicated that this debt was overpaid, even after five minutes of ischemia.

A small but consistent increase in weight of the isolated segment was observed during the postocclusion phase. It was found that this weight increase was due largely to increase of the volume of blood in the ileum. The peak of the volume increment appeared slightly later than the peak of flow increase, and for this reason was ascribed to increase in volume of the capacity vessels.

In an attempt to assess the respective roles of myogenic vs. metabolic mechanisms in causation of reactive hyperemia, arterial pressure was restored during occlusion by injecting dextran solution into the arterial segment. Pressures in excess of control values did not abolish the hyperemic response. It was concluded that the reactive hyperemia observed in the ileum was chiefly metabolic in origin.
An Adenosine Triphosphatase Preparation from a Membrane-Sarcotubular Fraction of Guinea Pig Heart Muscle
Authors: KRESPI VIVIAN , FOZZARD HARRY A. , SLEATOR WILLIAM
Published: June 2012

An adenosine triphosphatase (
ATP
ase) was prepared from guinea pig heart muscle membranes. It was found to require magnesium for activity, and to be stimulated by the presence of sodium and potassium ions. The
ATP
ase was partially inhibited by strophanthin at concentrations of the order of 10
-6
M. The results confirm the observations of Auditore and Murray.
5
Oxidative Capacity of Atherosclerotic Tissue of Rabbit and Dog, With Special Reference to Succinic Dehydrogenase and Cytochrome Oxidase
Authors: MAIER NELICIA , HAIMOVICI HENRY
Published: June 2012

The oxidative capacity of the succinic oxidase and cytochrome oxidase systems, as measured by the oxidative response to succinate and
p
-phenylenediamine was studied in slices of aortas from rabbits and dogs subjected to an atherogenic regimen, and in the liver as reference tissue.

In both animals, at an early stage in the atherosclerotic process, the oxidative capacity of both systems was increased in the atherosclerotic intima-media layer, separated at the cleavage plane, while at a later stage it was decreased.

The intima-media of the uninvolved portions of the aorta showed a decrease in the oxidative capacity of the cytochrome oxidase system, whereas that of the succinic oxidase system remained unchanged.

The liver, although the site of massive deposition of lipids, in the rabbit particularly, showed no enzymatic changes at any time during the administration of the atherogenic regimen.

These findings indicate that metabolic alterations of the arterial wall are associated with the development of atherosclerosis.
Comparative Cardiovascular Effects of Tyramine, Ephedrine, and Norepinephrine in Man
Authors: COHN JAY N.
Published: June 2012

The systemic hemodynamic and forearm vascular effects of tyramine, ephedrine, and norepinephrine were studied in normal male subjects. The pressor effect of tyramine was associated usually with bradycardia, unchanged cardiac output, and moderate arteriolar constriction in the forearm. A similar pressor effect of ephedrine was characterized by an increase of heart rate and output, with a slight fall in forearm vascular resistance. Occasional subjects responded to tyramine with an increase of cardiac output and a fall in forearm vascular resistance, and to ephedrine, with a marked increase of vascular resistance. The pressor effect of norepinephrine was associated always with bradycardia and with marked arteriolar and venous constriction in the forearm.

Brachial arterial infusions of the drugs in nonpressor doses confirmed the vascular effects. Norepinephrine produced dose-dependent forearm constriction in all subjects, while vasodilatation was observed occasionally with tyramine and frequently with ephedrine.

The demonstrated differences in local vascular and systemic hemodynamic effects of these drugs suggest some inconsistency in the hypothesis that the effect of either ephedrine or tyramine is mediated exclusively by norepinephrine release.
Nature of the Inotropic Action of Angiotensin on Ventricular Myocardium
Authors: KOCH-WESER JAN
Published: June 2012

The effect of changes in various chemical and physical factors on the positive inotropic action of angiotensin was studied in isolated papillary muscles of kittens. Pretreatment of the animals with reserpine did not diminish the positive inotropic effect of angiotensin. Concentrations of nethalide which strongly antagonize the response of the papillary muscle to levarterenol or tyramine had no effect on the inotropic concentration-effect curve for angiotensin. It is concluded that angiotensin does not release significant amounts of cate-cholamines from the cardiac stores and that its inotropic action on ventricular myocardium does not result from stimulation of adrenergic β-receptors.

Increases in external calcium concentration, decreases in sodium concentration, and shortening of the interval between contractions diminish both the absolute and the relative inotropic effect of angiotensin. All these maneuvers and angiotensin itself raise myocardial contractility by increasing the degree of activation of the contractile element. Cooling of papillary muscles does not decrease the absolute inotropic effect of the drug. Angiotensin and increases in external calcium concentration affect the mechanical properties of papillary muscles in a similar fashion. Angiotensin may raise contractility by augmenting the entry of Ca
++
into the myocardial fiber.
Effect of Thiamine Deficiency on Potential Myocardial Contractility
Authors: ALDINGER EARL E.
Published: June 2012

After rats had been on a thiamine free diet for five weeks their myocardium in vivo showed a marked decrease (69%) of developed isometric tension. During the first two weeks on a thiamine free diet developed tension was within the control range; but by three weeks the developed tension and myocardial response to epinephrine were much diminished. The susceptibility of these animals to arrhythmias was increased markedly. The incidence of arrhythmias increased as the length of time on the thiamine free diet increased. In many instances terminal ventricular fibrillation occurred. The decrease of myocardial tension or potential contractility occurring in thiamine deficiency may be attributed, at least in part, to interference with energy liberation due to a reduction in the level of cocarboxylase which limits the utilization of carbohydrate by the myocardium.
Aberrant A-V Impulse Propagation in the Dog Heart: A Study of Functional Bundle Branch Block
Authors: MOE GORDON K. , MENDEZ CARLOS , HAN JAOK
Published: June 2012

Excessive delay and configurational change of ventricular responses to atrial premature beats, previously attributed to dissociation within the A-V node, were shown to be due to functional block of the right bundle branch. It was found that the refractory period (RP) of the right bundle branch often exceeded the functional refractory period (FRP) of the A-V node at slow heart rates, permitting an early premature atrial response to reach the ventricles before recovery of the right bundle. Vagal stimulation and rapid driving frequencies, by delaying the intranodal transit of the premature response, prevented the exposure of bundle branch block. Epinephrine in low doses sometimes facilitated its occurrence.

Premature responses initiated in the His bundle in open heart preparations were commonly blocked in the right bundle under conditions in which atrial premature responses were normally propagated to the ventricles. Evidence was obtained in such preparations that the portion of the right bundle system beyond the site of the block was activated retrogradely from the left side. Under certain conditions the retrograde activation process returned to the His bundle and the atrium as an echo.
Reactive Hyperemia in Legs of Dogs:
Authors: BACHE ROBERT J. , EDERSTROM H. E.
Published: June 2012

1. In normal dogs 5- and 10-minute occlusions of the femoral artery were followed by periods of reactive hyperemia (RH) whose duration closely approximated the length of occlusion. The resulting vasodilatation repaid about 50% of the blood flow debt, which was calculated from the flow rate measured just prior to occlusion.

2. When the animal's body temperature was lowered to 32°C, the duration and percentage blood flow debt repaid decreased to about one-half and one-third, respectively, of that found at 40°C. Observations of RH during rewarming revealed progressive increases in debt repayment and duration of the hyperemic period. The temperature characteristics of RH suggested that thermolabile factors were responsible for the vasodilatation that resulted from arterial occlusion.

3. Venous occlusion was followed by RH that was considerably reduced, resulting in a debt repayment of about one-fourth of that attained after arterial occlusion. The possibility that high transmural pressure might be a factor in reducing the intensity of RH that followed venous blockage was investigated. However, when a pressure equivalent to that in the carotid artery was maintained in the vasculature by pumping venous blood into the leg with its artery and vein clamped, the RH following restoration of blood flow closely resembled that induced by arterial clamping only. When arterial blood was infused, RH was reduced to the level seen after simple venous occlusion. It was concluded from these results that during venous occlusion some arterial blood entered the vascular bed, and brought with it chemical factors that reduced the degree of vasodilatation. Since total absence of arterial blood inflow was required to cause maximal dilatation, it may be that oxygen lack was involved in relaxation of the vascular wall, as has been implied by the work of investigators using other techniques.
Extraction Ratio and Bone Clearance of Sr
85
as a Measure of Effective Bone Blood Flow
Authors: COPP DOUGLAS HAROLD , SHIM SUN SHIK
Published: June 2012

When a nondiffusible plasma dye (T-1824) and Sr
85
were injected into the nutrient artery of the tibia in 10 dogs, 90% of the T-1824 and 21% of the Sr
85
were recovered from the femoral vein in the next five minutes. From these data, the extraction ratio for removal of Sr
85
was calculated to be 0.764 ± 0.066 (SD). The difference from unity may be accounted for in part by blood flow through bone marrow. It was concluded that initial (0 to 5 minute) Sr
85
clearance should give a useful measure of effective bone blood flow. Values obtained for femur, tibia, humerus, and talus in 10 dogs and 80 rabbits were all remarkably similar. The effective bone blood flow in all cases was approximately 10 ml/100 g/min or, for the entire skeleton, approximately 5 to 7% of the resting cardiac output. The rate of blood flow far exceeds the metabolic needs of bone. This may be related to its important homeostatic function in mineral metabolism.