bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of High-Energy Phosphate Depletion and Repletion on the Dynamics and Electrocardiogram of Isolated Rat Hearts
Authors: SCHEUER JAMES , STEZOSKI S. WILLIAM 
Published: June 2012

To explore the sequence of metabolic, mechanical, and electrocardiographic (ECG) events during myocardial anoxia, isolated rat hearts were paced from the atrium. Anoxic and recovery periods were studied. Adenosine triphosphate (ATP) and creatine phosphate (CP) declined to 50% of control during the first minute and remained at that level for the 5-minute anoxic period. ATP and CP returned to control values after 10 and 20 seconds of recovery. Lactate and potassium efflux from the myocardium closely followed the highenergy phosphate changes. During anoxia, left ventricular systolic pressure increased initially, then fell below the control level after 2 minutes, and recovered within 20 seconds of reoxygenation. In catecholamine-depleted hearts, it fell immediately with anoxia, and recovery was incomplete. The conduction time for the pacing stimulus to reach the ventricle increased with anoxia and decreased with reoxygenation. S-T alterations in the ECG also lagged behind high-energy phosphate reduction and recovery.
The study demonstrates that in the isolated heart, ECG evidence of myocardial hypoxia may be absent when high-energy phosphate levels in the myocardium are very low. Mechanical changes are more closely related temporally to high-energy phosphate alterations than are ECG changes. The release of endogenous catecholamines is important to maintain mechanical function in the hypoxic heart.
Binding Characteristics of Myosin and F-Actin from Dog Hearts
Authors: CONWOY GENE , HEAZLITT ROBERT , ROBERTS JOE L. , STEWART LEROY 
Published: June 2012

We used light scattering and ultracentrifugation to study the binding ratio of myosin and actin from normal and failing dog hearts and to determine the effect of temperature and adenosine triphosphate (ATP) on the binding. For comparison, similar studies were done on myosin and actin from rabbit skeletal muscle.
We found a higher combining ratio, by weight, for cardiac myosin and actin (4.8 : 1) than for skeletal myosin and actin (4.4 : 1). The dissociation constants were similar at 24°C for cardiac and skeletal proteins. But at 10°C, the dissociation constant was greater for cardiac proteins, and the difference appeared more pronounced when phosphate was used to buffer the solutions.
The dissociation constant at 10°C was greater for myosin and actin from failing dog hearts.
ATP caused dissociation of cardiac and skeletal F-acto-heavy meromyosin and F-actomyosin. There was evidence that the binding of cardiac proteins may not be as tight as that of skeletal muscle proteins.
Relationship between Fatty-Acid Composition of Platelets and Platelet Aggregation in Rat and Man
Authors: RENAUD S. , KUBA K. , GOULET C. , LEMIRE Y. , ALLARD C. 
Published: June 2012

Male rats fed a diet rich in butter or stearic acid presented a marked predisposition to endotoxin-initiated thrombosis. This was preceded by hypercholesterolemia, hypercoagulability, and an increased susceptibility of platelets to thrombin-induced aggregation. In contrast to this, feeding of corn oil or linoleic or oleic acids did not result in such marked changes in the blood or in severe thrombosis.
Gas-liquid chromatographic analysis of total lipids of platelet and plasma indicated that the thrombogenic fat or fatty acid resulted in a highly significant increase, mostly in the platelets, of the ratio of saturated + monounsaturated to polyunsaturated fatty acids (S+M)/P.
In patients who had suffered a myocardial infarction as compared with men without risk factors for coronary heart disease, an increase in the (S+M)/P in plasma and platelets was also observed.
Among 17 active middle-aged businessmen, the five who presented signs of coronary heart disease also showed the highest susceptibility to thrombin-induced aggregation, but not to ADP or collagen. In these 17 subjects, the results of the thrombin aggregation could be correlated with the platelet (S+M)/P, but not with the plasma or platelet cholesterol.
In both the rat and man, a high thrombotic tendency may be associated with a platelet hypersusceptibility to thrombin which, in turn, is related to changes in fatty-acid composition.
Morphology and Metabolism of Intact Muscle Cells Isolated from Adult Rat Heart
Authors: BERRY MICHAEL N. , FRIEND DANIEL S. , SCHEUER JAMES 
Published: June 2012

Morphologically intact muscle cells were prepared by perfusing adult rat hearts with a balanced salt medium containing 0.1% collagenase and 0.2% hyaluronidase. Yields of intact cells representing up to 25% of the weight of the heart were obtained. The cells separated along the line of the intercalated discs, with cleavage of desmosomes but with tearing of the plasma membrane in the region of the gap junction, so that when two contiguous cells were parted, the gap junction was retained intact attached to one of the cells. The fine structure of undamaged cells was indistinguishable from that of normal myocardial cells in situ, whereas damaged cells characteristically revealed numerous cytoplasmic vacuoles, clumping of myofilaments, and blebbing of the cell membrane, but morphologically normal mitochondria. The earliest lesion detected was a dilatation of the T (transverse tubular) system.
Respiration in the intact cells was linear for 30 to 60 minutes and approximately two to three times the rate observed with heart muscle slices or the arrested isolated perfused heart. Oxygen uptake was stimulated by pyruvate but not by lactate. These observations demonstrate the feasibility of preparing intact isolated cells from adult rat heart and their potential value in histologic, pharmacologic, and metabolic studies.
Current Trends in Atherosclerosis Research
Authors: KATZ LOUIS N. 
Published: June 2012

Obviously, crystallization of information concerning atherosclerosis will come only by the proper free interplay and adequate fusion of the three major approaches to the problem, epidemiologic, clinical and experimental. We are getting to our goal--but we have not reached it yet. We have a motif, the life span unbalanced luxus diet, rich in calories, fats and cholesterol. We must look into other aspects, as for example: (1) the causes for localization of lesions in particular sites, (2) the causes for intimal ulceration, (3) the influence of hemorrhage and thrombosis, (4) the influence of physical and psychic stresses. These are, as it were, decorations to beautify the motif, they must not be mistaken for the motif itself.
We have come a long way along the road to the solution of the problem of atherosclerosis in the last two decades. The goal is dimly glimpsed through the haze ahead. But we are not there yet, considerable labor on the part of many, carried out in a truly scientific atmosphere still lies ahead. But the reward will more than repay the effort still to be employed.
An Analysis of Coronary Flow and Related Factors Following Vagotomy, Atropine, and Sympathectomy
Authors: SCOTT J. C. , BALOURDAS T. A. 
Published: June 2012

Coronary blood flow in the dog has been measured by the nitrous oxide desaturation method before and after acute bilateral cervical vagotomy, intravenous injection of atropine, and chronie sympathectomy. Vagotomy and atropine markedly increased coronary flow, myocardial oxygen consumption, and heart rate, but decreased left ventricular efficiency. Chronic sympathectomy resulted in the following smaller but statistically significant changes: a decrease in coronary flow, myocardial oxygen consumption, and heart rate, but an increase in left ventricular efficiency.
Increasing the oxygen content of the arterial blood decreased the coronary flow. A comparison of diallylbarbiturate acid and urethane with morphine and chloralose anesthesia gave similar flow values, but cardiac efficiency was increased in the latter case.
An analysis of the relationships between coronary flow, left ventricular oxygen consumption, and the arteriovenous oxygen difference is presented.
Mineralocorticoid Hypertensive Cardiovascular Disease Induced in Hypophysectomized Rats
Authors: HALL C. E. , HALL O. , RENNELS E. G. 
Published: June 2012

Reports in the literature to the contrary, hypertensive cardiovascular disease proved to be readily induced by desoxycorticosterone in hypophysectomized rats sensitized to steroid action by partial nephreetomy and high NaCl intake. In the absence of the pituitary, however, hypertension was somewhat slower in onset and progress. Although hypophysectomized animals were able to develop hypertension as severely as did intact animals, they were not, as judged by their better survival and less evident cardiorenal vascular lesions, as severely injured thereby.
Contrasted with their exuberant development in hypertensive intact animals, renal lesions in hypertensive hypophysectomized animals were rare. Necrotizing arteritis in the heart was seen in about half of the hypox animals, and periarteritis nodosa of pancreatic and mesenteric arteries was more widespread and severe than in similarly treated intact animals which had, however, died earlier.
Steroid treated animals bearing pituitary autotransplants beneath the renal capsule, developed more severe and widespread cardio-renal lesions than did similarly treated hypophysectomized animals, but incidence and severity of periarteritis nodosa in splanchnic arteries was about the same in each.
The ingestion of sodium chloride caused "salt hypertension" in some of the pituitary-bearing controls, but not in either hypophysectomized or autotransplant-bearing controls.
Early Stages in the Development of Collateral Circulation to the Lung in the Rat
Authors: WEIBEL EWALD R. 
Published: June 2012

The early stages of the development of collateral circulation to the lung following experimental ligation of the pulmonary artery were studied in adult rats. Five different types of vessels were found to be involved:
1. The bronchial arteries enlarge. Quantitative gross and microscopic studies indicated that this is first due to hemodynamic factors leading to dilatation of the vessels. After 5 days, true growth of the vessels occurs, associated with proliferative changes in the vessel wall, including mitoses in endothelial and smooth muscle cells.
2. Pre-existing nutrient arteries of the heart muscle coat of the pulmonary veins enlarge by the same processes.
3. New vessels form in the granulation tissue at the ligature. They can grow through the thick vessel wall into the lumen of the main pulmonary artery to form a considerable portal of entry for blood into this vessel.
4. Vessels form in pleural adhesions and can supply blood to the lung from intercostal arteries.
5. New bronchial arteries form in regions where no granulation tissue formation could stimulate their development. The primary anlage consists of a solid cell cord, soon surrounded by an envelope of spindle-shaped cells, representing the anlage of the media. The cell cord differentiates secondarily to an endothelial tube by forming a lumen.
The enlarged systemic arteries are directly connected to the lung capillaries by means of multiple small branches, which are also newly formed arteries or arterioles. Arterial bronchopulmouary anastomoses are not as commonly found early in the development of collateral circulation in the rat, as late in this process in dogs. It may be concluded that the enlargement of collateral arteries to the lung following ligation of the pulmonary artery may be initiated by hemodynamic conditions, such as changed pressure gradients. After 5 days, however, other, probably humoral, factors must be responsible for further stimulation of the growth of pre-existing vessels and for the initiation and guidance of new vessel formation.
Comparison of Two Types of Mechanical Assistance in Experimental Heart Failure
Authors: SALISBURY PETER F. , CROSS CECIL E. , RIEBEN P. ANDRE , LEWIN RICHARD J. 
Published: June 2012

In open-chest dog experiments, 7 different types of cardiac failure were produced. In each type of failure, the effect of veno-arterial pumping and of left ventricular bypass (blood pumped from the left atrium to femoral artery) was investigated. Pressures were recorded in the left ventricle, the left atrium, the right ventricle, and the femoral artery.
Veno-arterial pumping reversed failure of the right ventricle. It also was beneficial when overtransfusion had aggravated failure of the right or left ventricles, except in pre-existing aortic insufficiency. Veno-arterial pumping markedly increased decompensation of the left heart in the majority of observations, even though it occasionally reduced pressures in the left atrium and the right ventricle. The experiments suggest the use of veno-arterial pumping or of partial bypass with a heart-lung machine in acute cor pulmonale and in pulmonary congestion caused by abnormalities of the mitral valve where the left ventricle remains compensated. Veno-arterial pumping appears contraindicated in true failure of the left ventricle.
Left ventricular bypass always restored compensation in all types of heart failure except cor pumonale. The experiments suggest the clinical use of left ventricular bypass in left heart failure.
Pressure Variations in Small Veins in the Hindleg of the Dog
Authors: WIEDEMAN MARY P. 
Published: June 2012

Rhythmical changes in small vein pressure were shown to follow the direction of changes in intra-abdominal pressure. Pressure waves in small veins could be diminished considerably during femoral artery occlusion when the venous cannula was directed away from the vena cava. They were only slightly affected when the venous cannula was directed toward the vena cava. Small vein pressure waves were markedly decreased by opening the abdomen and reducing intra-abdominal pressure.
It is concluded that intra-abdominal pressure change is a major factor in varying small vein pressure in the hindleg of an anesthetized dog in a supine position.
Influence of Sex Difference and Hormones on Elastine and Collagen in the Aorta of Chickens
Authors: CEMBRANO JOSÉ , LILLO MANUEL , VAL JOSÉ , MARDONES JORGE 
Published: June 2012

Collagen and elastine of the aorta were estimated in normal chickens of both sexes in cockerels, gonadectomized or treated with estradiol, and in hens treated with testosterone.
The results showed that collagen and elastine were significantly higher in males than in females. Gonadectomy in males decreased significantly the content of collagen and elastine, so that the values became similar to those observed in females. The treatment of males with estradiol lowered the collagen and elastine content to values similar to those observed in females and in gonadectomized males. The treatment of females with testosterone increased significantly the collagen and elastine content of the aorta to levels similar to those observed in males.
Cause of Genuine Autoregulation of the Renal Circulation
Authors: WAUGH WILLIAM H. , SHANKS ROBERT G. 
Published: June 2012

The mechanism causing renal vascular flow to vary less than proportional to changes in arterial-venous pressure gradient, was studied in isolated dog kidneys perfused with whole blood and with cell-free colloidal solutions. This autoregulation of renal flow rapidly deteriorated along with vascular reactivity to drugs when oxygenated polyvinyl-pyrrolidone-Locke solution was used for perfusion. This deterioration was prevented by the addition of plasma to the colloidal perfusate.
During the first 2 seconds of suddenly raised arterial pressure, renal flow normally increased proportionately or slightly more than proportionately to the increase in arterial pressure; intrarenal venous pressure, needle tissue pressure and kidney weight rose simultaneously. During the next 4 seconds, increasing vascular resistance upstream from the intrarenal veins caused parallel reductions in renal flow, intrarenal venous pressure, needle tissue pressure and at times kidney weight. After brief rhythmical changes in prevenous segmental resistance, flow became steady to show intense autoregulation, while intrarenal venous pressure and needle tissue pressure remained relatively low.
This genuine autoregulation of renal flow was abolished by cooling kidneys to 3 to 10 C, and by treatment with chloral hydrate and with procaine in concentrations rendering the smooth muscle of the renal blood vessels relatively inert to direct drug stimulants. On the other hand, at temperatures of 3 to 10 C., and usually with chloral hydrate treatment, a factitious and passive type of flow autoregulation was observed, caused by the effects of abnormally high tissue pressures.
Renal flow autoregulation was not appreciably impaired by anesthetization of the intrarenal nerves by procaine in concentrations which did not simultaneously depress vascular smooth muscle reactivity. Yohimbine induced sympatholysis did not impair autoregulation, and Dibenzyline treatment to intrarenal sympatholysis depressed only slightly autoregulation of renal flow. It was not inhibited by γ-aminobutyric acid.
Anoxic perfusion which did not appreciably depress the reactivity of intrarenal autonomic ganglia, impaired autoregulation moderately. The loss of autoregulation of renal flow, accompanied by vasoconstriction following severe hemorrhage in the kidney donor dog, was slowly reversible upon perfusion of the subsequently isolated kidney and was related to smooth muscle contracture within the arterial-arteriolar vasculature.
It is concluded, that myogenic vasomotion in the renal arterial-arteriolar tree in response to the level of transmural vascular pressure is the fundamental cause of genuine renal circulatory autoregulation. It is furthermore suggested that the myocytes of the juxtaglomerular apparatus may act as myogenic pacemakers in the vasomotion responsible for the essentially perfect autoregulation of the normal kidney.
Circulation of the Giraffe
Authors: GOETZ ROBERT H. , WARREN JAMES V. , GAUER OTTO H. , PATTERSON JOHN L. , DOYLE JOSEPH T. , KEEN E. N. , McGREGOR MAURICE , TILLER L. M. , SMITH M. , Mance E. 
Published: June 2012

Observations on the circulatory functions of 4 giraffes are recorded. Both the right and the left heart were catheterized under local anesthesia with a miniature manometer.
Cardiac output was determined by employing both indicator dilution method and the Fick principle. Other parameters, such as the circulation time, blood volume, velocity, right and left ventricular pressure ascent as well as the changes in blood pressure occurring with changes in the Posture of the head were recorded. The difficulties of the experiments created certain limitations in their interpretation. The arterial blood pressure is high by human standards and adequate to maintain cerebral perfusion without other means of support. The arterial pressure pulse contour suggests a relatively lax vascular bed with considerable reserve distensibility. Values for cardiac output and blood volume were roughly comparable to those recorded in domestic cattle of the same approximate weight.
Influence of Cardiac Sympathetic and Vagal Nerve Stimulation on the Relation Between Left Ventricular Diastolic Pressure and Myocardial Segment Length
Authors: MITCHELL J. H. , LINDEN R. J. , SARNOFF S. J. 
Published: June 2012

During the continuous and simultaneous recording of left ventricular diastolic pressures and changes in the length of a segment of left ventricular myocardium it was demonstrated that neither cardiac sympathetic nor vagal efferent nerve stimulation produces a change in ventricular myocardial extensibility. It was further shown that, at the heart rates studied, autonomic nerve stimulation does not modify the end-diastolic pressurelength curve. These data indicate that, during cardiac sympathetic stimulation, the augmented ventricular stroke work from any given end-diastolic Pressure is accomplished without a change in end-diastolic fiber length.
Evidence was obtained, however, which suggests that the abbreviation of diastole at high imposed heart rates or large stroke volumes may leave an inadequate time for ventricular relaxation to take place and for inertial and viscous factors to be dissipated. Under these circumstances, sympathetic stimulation, by shortening systole and thereby lengthening diastole, permits the ventricle to remain on its "normal" pressure-length curve. This component of cardiac sympathetic efferent activity is peculiarly appropriate to the tachycardia that occurs with increased sympathetic outflow to the heart.
Condensing Enzyme Levels in the Serum After Experimental Myocardial Infarction
Authors: KOSICKI GEORGE W. , SWAIN HENRY H. , SRERE PAUL A. 
Published: June 2012

Increased levels of condensing enzyme are shown to occur in the sera of dogs after experimental myocardial infarction. The animals with the elevated levels also showed characteristic changes of the electrical activity of the heart and associated increases in the glutamate-oxal acetate transaminase activity of serum.
Condensing enzyme has been detected in the sera of patients who suffered myocardial infarctions.
Dicumarol Therapy
Authors: MURPHY E. A. , MUSTARD J. F. 
Published: June 2012

One of the problems of Dicumarol administration has been determination of the adequacy of therapy. A fundamental stage in thrombus formation in the circulation is platelet clumping. Since platelets are involved in both hemostasis and thrombosis, a study of changes in platelet function may prove useful. The effects of Dicumarol on platelet clumping and adhesiveness have, therefore, been studied and related to changes in other clotting mechanisms.
Comparison of platelet function in control periods and during Dicumarol administration shows that this drug lowers the adhesive index and prolongs the platelet clumping time to a highly significant degree. The accuracy of estimates of these 2 platelet functions given by 3 other tests, prothrombin time, whole blood clotting time and plasma activity in the thromboplastin generation tests have been compared. By any criterion, degree of correlation, consistency of regression slopes, intercepts or scatter about regression lines, clotting time was the most efficient of the 3 tests for evaluting platelet function. The prothrombin time was the least efficient. Furthermore, hemorrhage from excessive dosage was closely related to the platelet clumping time and clotting time. It should be pointed out, however, that in about one-third of the patients the prothrombin time was as good an index of platelet clumping time as clotting time. While prothrombin times done with 2 different sources of thromboplastin may give congruous results in untreated patients, considerable discrepancies may appear during Dicumarol therapy.
If prothrombin time is to be used as a guide to Dicumarol therapy, it is important to establish in each patient separately its reliability as a measure of the behavior of the clotting mechanism as a whole. For those in whom it seems reliable, an individual "therapeutic range" should be determined. For other cases, some other suitable test should be employed. It is emphasized that regulation of Dicumarol dosage is an individual problem and that only those tests shown to be reliable indices of safe effective modifications of clotting mechanism in the individual patient should be used.