bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Dicumarol on Blood Vascular Integrity in the Rabbit
Authors: NELSON THOMAS E. 
Published: June 2012

Results of experiments in rabbits in which the disappearance of Evans Blue labeled plasma proteins was used as a measure of vascular integrity, indicate that Dicumarol does increase the rate of loss of plasma proteins from the blood stream. This action does not occur immediately after the introduction of Dicumarol into the blood stream but requires a latent period of between 90 and 180 minutes. During this time there may actually be a decreased rate of loss from the blood.
The degree of increase in the dye disappearance rate, although not directly correlated with the degree of hypoprothrombinemia, can be roughly correlated with the extent and severity of internal hemorrhage. These results tend to confirm the idea that vascular fragility, usually considered independent of vascular permeability, may in this instance be the preliminary manifestation of Dicumarol hemorrhagic diathesis.

In experiments where the effect of Dicumarol on exchange of protein between plasma and the peritoneal cavity was measured, it has been found that the presence of vitamin K
1
in the blood in sufficient amount to completely block the hypoprothrombinemic action will also block the tendency toward increased protein exchange. Also, if Dicumarol is introduced into the peritoneal cavity rather than directly into the blood stream, the increase in transperitoneal protein exchange rate appears to be fairly proportional to the degree of hypoprothrombinemia.

It is concluded that although the possibility of several independent actions of Dicumarol exists, one effecting vascular permeability and another inhibiting the elaboration of coagulation factors, it is more likely that the changes seen in vascular integrity are related to the effects of the drug on the coagulation mechanism by way of vitamin K inhibition.
Quantitative Analysis of the Development of Experimental Atherosclerosis in the Dog
Authors: DUNCAN LEROY E. , BUCK KATHERIN , Lynch Almorris 
Published: June 2012

Atherosclerosis was produced in dogs by feeding them thiouracil and cholesterol. The increments in cholesterol concentration at sites along the length of the aortas of these dogs Avere determined by subtracting from the value for each site the corresponding value obtained from normal dogs. After about 1 month on the experimental regimen the cholesterol increments along the length of the aorta formed a gradient. The increment was greatest in the proximal aorta and progressively less down the length of the aorta. After about 5 months on the regimen, the gradient no longer existed. Instead, the cholesterol increment in the abdominal aorta exceeded that in the thoracic aorta. Albumin is known to enter aortic wall with a gradient of rates that is similar to the gradient of cholesterol increments early in the course of experimental atherosclerosis.
The foregoing facts are consistent with the following theory: In the development of atherosclerosis, intact low-density lipoproteins containing cholesterol enter the aortic wall with a gradient of rates. They enter fastest in the proximal aorta and progressively less rapidly down the length of the aorta. However, cholesterol is removed from the abdominal aorta much more slowly than from the thoracic aorta. Thus, the increment in cholesterol concentration in the abdominal aorta eventually exceeds that in the thoracic aorta.
Levels of Phosphate Compounds in Experimental Cardiac Hypertrophy
Authors: MINTON PAUL R. , ZOLL PAUL M. , NORMAN LEONA R. 
Published: June 2012

Arterial hypertension was produced in 66 rats by means of constricting latex capsules about the kidneys, by the intramuscular implantation of desoxycorticosterone pellets, and by the subcutaneous injection of desoxycorticosterone. The most satisfactory method was the intramuscular implantation of desoxycorticosterone pellets. Myocardial hypertrophy was produced in 43 rats.
Biochemical analysis of the ventricles of 80 control and 45 hypertrophied rats were performed for creatine phosphate, adenosine triphosphate, and free inorganic phosphate. Cardiac hypertrophy in rats was accompanied by a statistically significant decrease in the ventricular concentration of creatine phosphate, while levels of adenosine triphosphate and free inorganic phosphate were not significantly altered.
It is suggested that congestive heart failure in hypertrophied hearts is related to a defect in the utilization of phosphate-bond energy by the hypertrophied myocardial fiber.
Effects of Cholesterol-Fat Diets on Pigeons Susceptible and Resistant to Atherosclerosis
Authors: CLARKSON THOMAS B. , LOFLAND HUGH B. 
Published: June 2012

Cholesterol-fat diets are markedly more atherogenic when fed to a strain of pigeons susceptible to spontaneous atherosclerosis, as compared to a strain resistant to the disease. A breed of pigeons intermediate in susceptibility was found to be intermediate in their response to a high cholesterol-high fat diet. Serum cholesterol levels were similar among the three breeds.
The White Carneau pigeons developed lesions complicated by connective tissue proliferation while the Autosexing Kings and Racing Homers developed merely "pure atheroma" or "fatty streaks."
Cardiovascular Dynamics of Vasovagal Reactions in Man
Authors: GREENE MURRAY A. , BOLTAX ADOLPH J. , ULBERG ROBERT J. 
Published: June 2012

The dynamics of vasovagal reactions which occurred in 2 patients during right heart catheterization were studied. Both subjects initially had systemic hypertension with corresponding increases in peripheral resistances. Subject B had considerably decreased blood flow, moderately elevated pulmonary artery and right ventricular end-diastolic pressures, and elevated central blood volume. These parameters were normal in subject A.
The characteristic features of the reactions were appreciable declines in cardiac outputs coincident with decreased systemic arterial systolic, diastolic, and pulse pressures, decreased heart rates, and slight increases in calculated peripheral resistances. Stroke volumes were moderately reduced. A slight decrease in pulmonary artery systolic pressure occurred in subject A. In subject B, pulmonary artery and right ventricular enddiastolic pressures declined to normal and central blood volume decreased moderately. The return of heart rate to control values had no significant effects on the other physiologic parameters.
The data demonstrate that reductions in cardiac output, due primarily to decreased stroke outputs, were predominantly responsible for the arterial hypotensions during the vasovagal reactions in these 2 subjects. The ineffectiveness of atropine in restoring hemodynamics in one subject suggested the importance of inhibition of efferent sympathetic activity in the etiology of this reaction. The failure of peripheral resistance to compensate for decreased blood flow suggested inhibition of arteriolar tone.
Concealed Conduction
Authors: HOFFMAN BRIAN F. , CRANEFIELD PAUL F. , STUCKEY JACKSON H. 
Published: June 2012

The existence of concealed conduction of atrial beats has been demonstrated. Concealed conduction within the atrioventricular node has been studied by recording the transmembrane potential of single nodal fibers. Conduction block in this part of the specialized conducting system depends more upon decremental conduction within certain nodal fibers than upon differences in action-potential duration. Also, the extreme delay of activation that results from such decremental conduction explains certain changes in atrioventricular delay associated with premature atrial beats as well as a prolonged refractoriness of atrioventricular transmission after concealed nodal conduction of an atrial extrasystole.
In the in situ dog heart, local bipolar electrograms recorded from various parts of the bundle of His, bundle branches, and peripheral Purkinje fibers have shown that con cealed conduction may extend through the atrioventricular node and the bundle of His and that block may occur between common bundle and bundle branches or between the latter and the peripheral Purkinje fiber. Block in these locations, which results from local differences in the action-potential duration, has been compared to decremental conduction within the atrioventricular node.
Influence of Airway Pressures on Edema in the Isolated Dog's Lung
Authors: WAGNER ERICH , RIEBEN P. ANDRE , KATSUHARA KIMIKO , SALISBURY PETER F. 
Published: June 2012

The left lower lobe of anesthetized, heparinized dogs was excised, weighed, and cannulated. Another lobe of the same dog was excised for control purposes. The cannulated lobe was perfused by a system of adjustable reservoirs which was fed with fresh blood from a donor dog. The perfused lobe was mounted on an electronic balance so that weight changes could be recorded together with the pressures in the inflow and outflow conduits and in the bronchus. When the per fusion pressures were varied within normal limits, the weight of the lobes reached stable plateaus. Abnormally high perfusion pressures caused a continuous, steady increase in lobe weight, which was evident from the slope of the weight registration. Blood holdup in the lobe was measured by comparing the hemoglobin content of the control lobe with that of the experimental specimen taken at the end of an experiment. Blood holdup accounted for only about 10 per cent of the weight increase of edematous lobes. Initial observations were made in collapsed lobes; in the course of some experiments these lobes were inflated and the static airway pressures were then kept at varying levels.
Irrespective of the perfusion pressures, transudate did not issue from the airway as long as the lobe was collapsed. Abnormal perfusion pressures caused the accumulation of fluid, which continued as long as the perfusion pressures were constant. The rate of transudation was determined by the perfusion pressures and was not influenced by inflation of the collapsed lobe nor by variations of the static airway pressure. When a collapsed lobe had become edematous anti was then inflated, transudate issued from the airway. Increases of the static airway pressure did not decrease the rate of fluid accumulation, but only confined the transudate to the lung and prevented its discharge from the airway.
Release of Pressor Substances from Renal Grafts Originating from Rats with Renal Hypertension
Authors: OMAE TERUO , MASSON GEORGE M. C. , PAGE IRVINE H. 
Published: June 2012

A method is described for grafting kidneys on bilaterally nephrectomized rats without interrupting renal blood flow. Under these conditions, normal kidneys caused a pressor response characterized by a gradual rise in pressure suggesting a continuous endocrine secretion. Kidneys from rats made hypertensive by unilateral clipping of the renal artery, renal encapsulation, or partial infarction were tested during the acute and chronic stages of the experimental disease. Wrapped and infarcted kidneys, as well as the untouched contralateral organs, released little or no pressor substances. On the other hand, clipped kidneys released normal or slightly greater amounts of pressor substances; the eontralateral untouched kidney did not elicit any pressor effect. Morphological examination showed a relationship between presence of nephroselerotic lesions and absence of, or decrease of, reninlike pressor substance released. Both changes are believed to be due to high renal vascular pressure against which the partly clipped kidney is protected.
These observations suggest that, if renin is a primary factor in the pathogenesis of renal hypertension, hypertension due to renal artery constriction has a mechanism different from that caused by renal manipulation or infarction.
Electrocardiographic Effects of Changing the Nature of the Contact Between the Exposed Heart and the Body
Authors: SAYEN JOHN J. , KATCHER AARON H. , PEIRCE GEORGE 
Published: June 2012

In dog studies designed to improve the accuracy of direct extracellular heart-body leads, the electrocardiographic representation of the heart when maximally insulated (connected to the body only by its vascular pedicdc) was compared with common open-chest experimental situations in which portions of the normally behaving ventricular surface are allowed to remain in contact with the body. The addition of any ventricular surface to the heart-body contact area (by removal of insulation) lowered the R-wave amplitude in all. direct heart-body leads from the ventricular surface or wall.
The effects of locally altering the physiological behavior of portions of the left ventricle were also studied. Any portion of the ventricular surfaces of maximally insulated hearts could be altered by locally applied agents to show heart-body lead changes entirely confined to the area of demonstrably local physiological disturbance. Small- or medium-sized areas of transmural regional is chemia likewise produced electrocardiographic changes only in the vicinity of the ischeniic muscle. In the case of less completely in Sn lated hearts, direct heart-body lead changes consequent to localized physiological change
Effects of Catecholamines and Atropine on Cardiovascular Response to Exercise in the Dog
Authors: KECK ERNST W. O. , ALLWOOD MICHAEL J. , MARSHALL ROBERT J. , SHEPHERD JOHN T. 
Published: June 2012

The manner in which the administration of epinephrine, norepinephrine, isoproterenol, and atrophic modifies the cardiovascular response to exercise has been studied in 12 dogs.
In control observations, exercise increased the cardiac output by 116 per cent, the heart rate by 102 per cent, and the stroke volume by 8 per cent. When epinephrine was infused during identical exercise, the cardiac output was similar; however, the stroke volume was increased by 50 per cent. During infusion of norepinephrine, the cardiac output was reduced by 11 per cent compared with that during control exercise, and the stroke volume was increased by 25 per cent. With isoproterenol, the cardiac output exceeded that during control exercise, but the stroke volume was unchanged.
Prior to administration of atropine, the cardiac output at rest averaged 4.2 L. per minute. After injection of atropine, the cardiac output averaged 3.7 L. per minute, the heart rate increased from 121 to 249 beats per minute, and the stroke volume decreased from 35 to 15 ml. Before atropinization, the cardiac output, heart rate, and stroke volume during exercise were increased by 95, .90, and 2 per cent over the resting values; after atropinization, the corresponding increases were 110, 7, and 100 per cent.
Thus, while cardiac output during exercise normally is regulated mainly by changes in the heart rate, the stroke volume may make a major contribution under other circumstances.
Experimental Verification of Wilson's Derivation of the Principle of the Ventricular Gradient
Authors: GARDBERG MANUEL , ROSEN IRVING L. 
Published: June 2012

The concept of the ventricular gradient is based upon the theoretical representation of the electrogram of a myocardial fiber as the sum of two monophasic action potential (M.A.P.) curves, each of which represents the electrical activity of one-half of the fiber. Wilson showed that from this premise certain mathematical deductions are possible: (1) that the area of the electrogram is equal to the sum of the areas of the two MAP. curves; (2) that this area is independent of the rela tion of the two M.A.P. curves with respect to time and, therefore, that it is independent of the path of excitation; and (3) that as a corol lary of the latter, the measurement of the area of the electrogram may be used as a measure of the net electrical effect of local differences in repolarization.
The present paper reports the results of experiments in which the electrical effects of a segment of a strip of turtle heart muscle were recorded as biphasic complexes and as two M.A.P. curves. Accurate measurement of the areas by means of an electronic integrator supports Wilson's premise. These observations furnish experimental confirmation of the theo retical basis of the concept of the ventricular gradient.
Comparative Effects of d-and L-3,5,3'-Triiodothyronine in Chronic Treatment of Hypercholesteremic Dogs
Authors: ELLISON THEODORE , GREENBERG SAMUEL M. , LIN TIEN-HUI 
Published: June 2012

Twenty intact, naturally hypercholestere-mic dogs were divided into five groups and chronically administered D-3,5,3'-triiodothy-ronine (d-T3) and L-3,5,3'-triiodothyronine (l-T3) at two levels, respectively, for 31 weeks. The administration of the drugs was divided into two periods, the first for 21 weeks, after which the dosage level for each of the four test groups was doubled for an additional 10 weeks. Plasma total cholesterol, total lipids, and phospholipids were significantly lowered by the administration at both levels of d-T3 and the higher level of l-T3. At the end of 21 and 29 weeks of thyromimetic administration, no differences in percentage of free or esterified cholesterol were observed for any of the treated groups when compared with the control groups. A battery of physiological and functional tests was performed at suitable intervals throughout the experimental period with no evidence of abnormalities due to the administration of the thyromimetic agents. The only significant functional change measured was a reduction in protein-bound-iodine levels in the clogs receiving the higher level of l-T3.
Throughout the entire experiment, all dogs remained in good health as judged by gross appearances and actions. The dogs receiving d-T3 gained less weight than did either the controls or the L-T3-treated groups, even though all animals ate isocaloric balanced diets. At post mortem, after 31 weeks of chronic thyromimetic administration, gross pathology was negative; chemical analyses of cholesterol content of aortas, adrenals, and livers indicated no significant differences. Analyses of livers for total lipids showed no significant differences, and no evidence of aortic sudanophilia was apparent in any of the experimental dogs.
Effect of Unilateral Pulmonary Artery Obstruction on Circulatory Dynamics in Dogs with Chronic Atrial Septal Defects
Authors: AMORIM DALMO DES. , MARSHALL HIRAM W. , DONALD DAVID E. , WOOD EARL H. 
Published: June 2012

Determinations of pressure, blood flows, and calculated pulmonary vascular resistance were made prior to and during acute individual occlusion of the right and left main branches of the pulmonary artery in random sequence in eight anesthetized, closed-chest dogs witn chronic atrial septal defects. Similar observations were made with occlusion of only the left pulmonary artery in three additional dogs. Obstruction of the pulmonary artery to one lung was immediately followed by a rise in systolic pressure in the right ventricle and pulmonary artery proximal to the obstruction, from an average normal value of 33.1 mm. Hg to an average value of 40.9 mm. Hg (range 32 to 47). This change was not associated with demonstrable systematic effects on right atrial or systemic arterial pressure or on the systemic blood flow.
As would be expected, the average calculated ratio of pressure to flow (vascular resistance) across the unoccluded lung was elevated during the obstruction. The resistance value during the occlusion, however, was less than the estimated pressure/flow ratio for this same lung, based on the measurements made prior to the occlusion. This apparent effective decrease in vascular resistance of the unoccluded lung is probably related to dilation of the pulmonary vessels as a result of an increase in intravascular pressure caused by the sudden removal of approximately half of the pulmonary vasculature from the circulation.
In spite of the elevation in right ventricular systolic pressure, occlusion of the left pulmonary artery was associated with a slight increase in pulmonary blood flow and a definite increase in the magnitude of the left-to-right shunt across the atrial septal defect, whereas no systematic effects were obtained during obstruction of the right branch in association with the same approximate levels of right ventricular systolic pressure. These data are regarded as further evidence that the preferential shunting of blood from the right lung in the presence of an atrial septal defect of the secundum type is primarily due to the anatomical relation between the opening of these vessels into the left atrium and the position of the defect in the atrial septum. Furthermore, they emphasize the importance of dynamic factors, related to the manner, site, and direction in which the pulmonary venous blood drains into the left atrium, as important determinants of the left-to-right shunt via such defects.
Interday variation and effect of transportation on indirect blood pressure measurements, plasma endothelin-1 and serum cortisol in Standardbred and Icelandic horses
Authors: Söder Josefin , Bröjer Johan T , Nostell Katarina EA 
Published: June 2012

AbstractBackgroundSystemic hypertension is a prominent feature in humans with metabolic syndrome (MS) and this is partly caused by an enhanced endothelin-1 (ET-1) mediated vasoconstriction. There are indications that systemic hypertension might be a feature in equine metabolic syndrome (EMS) but if ET-1 is involved in the development of hypertension in horses is not known. Increased levels of cortisol have also been found in humans with MS but there are no reports of this in horses. Before blood pressure, plasma ET-1 and serum cortisol can be evaluated in horses with EMS, it is necessary to investigate the interday variation of these parameters on clinically healthy horses. The aims of the present study were therefore to evaluate the interday variation and influence of transportation on systemic blood pressure, plasma ET-1 and serum cortisol in healthy Standardbred and Icelandic horses, and to detect potential breed differences.MethodsNine horses of each breed were included in the study. Blood pressure was measured and blood samples were collected between 6 and 9 am on two separate days. Eight of the horses (four of each breed) were transported to a new stable were they stayed overnight. The next morning, the sampling procedure was repeated.ResultsThe interday variation was higher for plasma ET-1 (37%) than for indirect pressure measurements (8-21%) and serum cortisol (18%). There were no differences in systemic blood pressure between the two breeds. The Icelandic horses had significantly lower serum cortisol and significantly higher plasma ET-1 concentrations compared to the Standardbred horses. Plasma ET-1 was significantly elevated after transportation, but systemic blood pressure and serum cortisol did not differ from the values obtained in the home environment.ConclusionsIndirect blood pressure, plasma ET-1 and serum cortisol are of interest as markers for cardiovascular dysfunction in horses with EMS. The elevated plasma ET-1 concentrations recorded after transportation was likely caused by a stress response. This needs to be considered when evaluating plasma ET-1 in horses after transportation. The differences detected in plasma ET-1 and serum cortisol between the two breeds might be related to differences in genetic setup, training status as well as management conditions.