bluuebunny/crossref_metadata_2025 huggingface dataset:
Difference between human red blood cell Na+-Li+ countertransport and renal Na+-H+ exchange.
Authors: Kahn A M
Published: June 2012

Several laboratories have reported that the activities of sodium-lithium countertransport are increased in red blood cells from patients with essential hypertension. Based on the many similarities between this transport system and the renal sodium-proton exchanger, a hypothesis has been put forth in the literature that increased red blood cell sodium-lithium countertransport activity may be a marker for increased sodium-proton exchange activity in the renal proximal tubule. The present studies were designed to test the hypothesis that sodium-lithium countertransport in red blood cells from humans or rabbits is mediated by the same transport mechanism that mediates sodium-proton exchange in the renal brush border from those species. Similar to what has been reported for the rabbit, the present studies show that an amiloride-sensitive sodium-proton exchanger is present in human renal brush border vesicles. However, Na+-Li+ countertransport in human and rabbit red blood cells, assayed under several different conditions, was not inhibited by amiloride. In agreement with what has been reported for humans, the present studies show that extracellular proton-stimulated sodium efflux is inhibited by amiloride in rabbit red blood cells. These data demonstrate a difference (amiloride sensitivity) between the red blood cell sodium-lithium countertransporter and the renal brush border sodium-proton exchanger in humans and rabbits. These experiments detract from the hypothesis that increased red blood cell sodium-lithium countertransport activity in patients with essential hypertension is a marker for increased sodium-proton exchange activity in the renal brush border.
Opposite central cardiovascular effects of nifedipine and BAY k 8644 in anesthetized rats.
Authors: Laurent S , Girerd X , Tsoukaris-Kupfer D , Legrand M , Huchet-Brisac A M , Schmitt H
Published: June 2012

The central cardiovascular effects of the calcium channel blocker nifedipine and the calcium channel activator BAY k 8644 were studied in anesthetized and ventilated normotensive Wistar-Kyoto (WKY) or spontaneously hypertensive rats (SHR). Both drugs were administered in a 1.5-microliter volume into the lateral ventricle of the brain (i.c.v.) or into the cisterna magna (i.c.). The injection of vehicle alone (i.c. or i.c.v.) did not significantly change mean arterial pressure (MAP) or heart rate. Nifedipine (5 and 50 micrograms/kg) and BAY k 8644 (5 and 50 micrograms/kg) induced opposite effects on MAP when centrally injected. Nifedipine decreased MAP and induced a bradycardia (i.c.v.) or no change in heart rate (i.c.), and BAY k 8644 increased MAP without any significant change in heart rate (i.c. or i.c.v.). These effects were more marked with the highest dose of either drug. These effects seemed to be of central origin, since they were suppressed by ganglionic blockade by hexamethonium (100 mg/kg i.v.), whereas after hexamethonium the hypotensive and the hypertensive responses to intravenously injected nifedipine and BAY k 8644, respectively, were preserved. Bilateral vagotomy suppressed the bradycardia induced by i.c.v. administered nifedipine. Previously i.c.v. administered nifedipine (5 micrograms/kg) antagonized the pressor response to BAY k 8644 (5 micrograms/kg i.c.v.). Changes in MAP and heart rate were significantly more marked in SHR than in WKY. These results indicate that a calcium channel inhibitor and a calcium channel activator can modulate in opposite fashion central mechanisms involved in blood pressure control.
Influence of blood pressure on development of aortic medial smooth muscle hypertrophy in spontaneously hypertensive rats.
Authors: Owens G K
Published: June 2012

The hypothesis that a primary stimulus for aortic medial hypertrophy in spontaneously hypertensive rats (SHR) is increased blood pressure was tested by determining whether development of smooth muscle cell hypertrophy and hyperploidy in SHR could be dissociated from blood pressure levels in rats treated with various antihypertensive drugs with different mechanisms of action. Wistar-Kyoto rats (WKY) and SHR were treated between 2 and 5 months of age with captopril (375 mg/L), hydralazine (40 mg/L), or propranolol (1.5 mg/L) administered in their drinking water. Smooth muscle hypertrophy and hyperploidy were analyzed by morphometric evaluation of medial smooth muscle content, flow cytometric analysis of the frequency of polyploid smooth muscle cells, and biochemical estimates of smooth muscle cell number. All drugs significantly lowered blood pressure in SHR compared with untreated controls (order of efficacy: captopril greater than hydralazine greater than propranolol). Captopril also was most effective at changing blood pressure in WKY, while propranolol and hydralazine had similar blood pressure-lowering effects. The efficacy of drugs in preventing the development of smooth muscle cell polyploidism and medial hypertrophy in SHR was the same as their efficacy in lowering blood pressure, although propranolol had no effect on medial smooth muscle hypertrophy despite lowering blood pressure by 26 mm Hg. Regression analyses showed a high degree of correlation between blood pressure and the frequency of polyploid smooth muscle cells and medial smooth muscle content. These results are consistent with the hypothesis that aortic medial hypertrophy may be, in part, a response to increased blood pressure or wall stress. However, analysis of covariance and two-stage multiple regression analyses indicated that captopril had an effect over and above that predicted by its blood pressure-lowering effect. Furthermore, propranolol lowered blood pressure but did not affect medial hypertrophy. These results suggest that smooth muscle hypertrophy is not simply a response to increased blood pressure, but that other factors, such as angiotensin II, may be important in modulating aortic medial hypertrophy in SHR.
The prognosis of hypertension according to age at onset.
Authors: Buck C , Baker P , Bass M , Donner A
Published: June 2012

Data from a program for hypertension screening and follow-up were used to study the relationship between age at onset of hypertension and the risk of cardiovascular complications. The risk for hypertensive subjects, compared with normotensive subjects of similar age, declined significantly as age of onset increased from 40 to 69 years. This pattern was not explained by differences in initial severity of hypertension, control of hypertension, obesity, smoking, or alcohol consumption. A sex-specific analysis showed that the pattern was confined to male subjects, but it is argued that it might be seen in female subjects if data for women of more advanced age were available. Further lines of investigation of this interesting phenomenon are proposed.
Area postrema is critical for angiotensin-induced hypertension in rats.
Authors: Fink G D , Bruner C A , Mangiapane M L
Published: June 2012

The effect of surgical ablation of the area postrema on acute (5-10 minutes) and chronic (5-10 days) increases in mean arterial pressure produced by intravenous infusion of angiotensin II in conscious, instrumented rats was studied. In agreement with previous studies, pressor responses of area postrema-ablated rats (n = 11) to acute angiotensin II infusion were identical to those of control sham-lesioned rats (n = 13). In these same rats, however, a 5-day infusion of angiotensin II produced a sustained hypertension in the sham-lesioned group whereas mean arterial pressure was increased only transiently (1-3 days) in the area postrema-ablated rats. No differences before infusion of arterial pressure, heart rate, water intake, urinary sodium excretion, and urinary potassium excretion were observed between sham-lesioned and area postrema-ablated rats; only arterial pressure was changed significantly during angiotensin II infusion in either group. Twenty-four hours after terminating angiotensin II infusion, mean arterial pressure was within the normotensive range in both sham-lesioned and area postrema-ablated rats. In a separate group of sham-lesioned (n = 13) and area postrema-ablated (n = 12) rats, angiotensin II was infused intravenously for a 10-day period; mean arterial pressure was increased significantly over the entire 10-day infusion in sham-lesioned rats, but for only 1 day in area postrema-ablated rats. An intact area postrema appears necessary for the development of chronic, but not acute, hypertension during intravenous infusion of angiotensin II in the rat.
Hemodynamic characteristics of sodium-sensitive human subjects.
Authors: Sullivan J M , Prewitt R L , Ratts T E , Josephs J A , Connor M J
Published: June 2012

Fifty-eight normal subjects and 51 subjects with borderline hypertension underwent microvascular and hemodynamic studies while on an ad libitum diet and during periods of sodium depletion (10 mEq/day) and repletion (200 mEq/day). Hemodynamic measurements included arterial blood pressure, cardiac index, total peripheral resistance, forearm blood flow, vascular resistance, venous compliance, and capillary filtration fraction. Studies of the microcirculation consisted of macrophotography of the bulbar conjunctiva with measurement of anteriolar, venular, and capillary density and diameter. During sodium repletion, cardiac index increased significantly in the normal subjects (2.35 +/- 0.7 vs 2.44 +/- 0.7 L/min/m2; p less than 0.01) and in the borderline hypertensive subjects (2.50 +/- 0.7 vs 2.70 +/- 0.8 L/min/m2; p less than 0.01). However, mean blood pressure rose by more than 5% in only 33 subjects, 13 with normal and 20 with borderline hypertension. When these sodium-sensitive subjects were compared with those whose blood pressure did not rise, the former were found to have significantly higher forearm vascular resistance (32.2 +/- 21 vs 17.9 +/- 12 mm Hg/ml/min/100 g; p less than 0.01), lower forearm blood flow (4.42 +/- 2.7 vs 7.47 +/- 5.0 ml/min/100 g) and lower conjunctival capillary density (3.72 +/- 1.7 vs 5.18 +/- 2.1 [SD] mm/mm2; p less than 0.05). These results indicate that sodium sensitivity in humans is accompanied by elevation of forearm vascular resistance and attenuation of the microcirculation.
Water loading and restriction in essential hypertension.
Authors: Velasquez M T , Skelton M M , Cowley A W
Published: June 2012

Blood pressure, plasma arginine vasopressin (AVP), and renal excretory responses to short-term water loading (oral load of 20 ml/kg body weight over 30-45 minutes) were compared in 10 normotensive and 13 mild to moderately essential hypertensive subjects. In addition, we examined the renal concentrating ability of an additional group of 10 normotensive subjects and 12 hypertensive subjects in response to a 24-hour water restriction and intranasal administration of 10 micrograms of [1-deamino,8-D-arginine]vasopression. The hypertensive subjects exhibited both an exaggerated diuresis and natriuresis to the water load. At 20- and 60-minutes after water loading, hypertensive subjects had excreted 34 and 55% of the load, respectively, compared with 15 and 35% in normotensive subjects. Mean blood pressure rose significantly in both groups and hypertensive subjects exhibited a greater rise of systolic blood pressure (16 mm Hg) than normotensive subjects (8 mm Hg) 20 minutes after water loading. The maximum diuresis and natriuresis corresponded to the period in which the rise of blood pressure was greatest. The hypertensive subjects diluted and concentrated their urine as well as normotensive subjects did, indicating normal renal responsiveness to AVP. Plasma Na, osmolality, and AVP decreased similarly in both groups after water loading and rose similarly in the two groups after water restriction. This finding suggests that osmotic responsiveness of AVP is not altered in hypertensive subjects. In conclusion, the data suggest that the exaggerated renal response to water loading could be explained by the greater rise of blood pressure in hypertensive subjects rather than by altered AVP responses.
Hormonal responses and blood pressure maintenance in normal and hypertensive subjects during acute blood loss.
Authors: Velasquez M T , Menitove J E , Skelton M M , Cowley A W
Published: June 2012

Blood pressure (BP) and plasma indices of three major pressure control systems--plasma norepinephrine and epinephrine, plasma renin activity (PRA), and plasma arginine vasopressin--were measured simultaneously in 12 normal and 15 mildly essential hypertensive subjects before and after removal of 480 ml of blood by phlebotomy, to determine if there were differences in the compensatory response to acute blood loss. Responses to postural stress (change from supine to sitting position) following phlebotomy were also compared in a second group of subjects. Before phlebotomy, supine plasma hormone levels did not differ in the two groups. After phlebotomy, both groups exhibited only slight decreases (5 mm Hg) in systolic BP and a transient rise in heart rate. Only plasma norepinephrine increased significantly in both groups (35% above control in normal and 43% in hypertensive subjects). Similar results were obtained in a second group of normal and hypertensive subjects, who were also subjected to a 10-minute postural challenge after phlebotomy. After 10 minutes in a sitting position, BP in these subjects remained unchanged but heart rate and plasma norepinephrine increased further to levels almost twice that produced by phlebotomy alone. Plasma epinephrine levels and PRA also increased with this additional stress, but plasma vasopressin remained unchanged. Changes in BP, heart rate, plasma norepinephrine and epinephrine, and PRA did not differ significantly between the two groups. These data indicate that hypertensive subjects are as capable as normal subjects of maintaining BP when subjected to standard phlebotomy, the sympathetic nervous system appears to be the predominant pressor mechanism activated following an acute, nonhypotensive blood loss in both groups of subjects,(ABSTRACT TRUNCATED AT 250 WORDS)
Impaired responses of sympathetic nerves to cardiac receptor stimulation in hypertension.
Authors: Thames M D
Published: June 2012

We recently reported that the vagal cardiopulmonary baroreceptor reflex inhibition of renal nerve traffic is impaired in rabbits with renal hypertension. The purpose of this study was to determine if the locus of the abnormality is mainly in the brain or in the afferent limb of the reflex. Experiments were done in alpha-chloralose-anesthetized rabbits with (n = 10) or without (n = 10) hypertension induced 6 to 8 weeks before study by wrapping the left kidney in cellophane followed by removal of the right kidney. The left side of the chest was opened, and a pericardial cradle was made. Nicotine was applied to the epicardial surface of the heart in concentrations of 10 to 500 micrograms/ml, and changes in arterial pressure and renal nerve traffic were measured. Dose-dependent decreases in traffic and arterial pressure resulted that were significantly smaller in hypertensive than in normotensive rabbits. After sinoaortic baroreceptor denervation, a similar impairment in the responses of hypertensive rabbits was observed. Vagotomy nearly abolished the responses of the renal nerves to epicardial nicotine. The responses of the lumbar sympathetic nerves to epicardial nicotine also were impaired in renal hypertensive (n = 8) compared with normotensive rabbits (n = 8). If the behavior and number of chemically sensitive endings are assumed to be unaltered in hypertension, then these findings are explained best by an abnormality in the central nervous system. These results support the view that the previously reported impairment in the vagal cardiopulmonary baroreceptor reflex control of renal nerve traffic is due mainly to a central abnormality, although they do not exclude an abnormality in the afferent limb of the reflex.
Effects of high potassium or low sodium diet on vascular Na+,K+-ATPase activity and blood pressure in young spontaneously hypertensive rats.
Authors: Sugden A L , Bean B L , Straw J A
Published: June 2012

These studies were designed to investigate whether the antihypertensive effects of high potassium or low sodium diets are related to changes in vascular Na+,K+-adenosine triphosphatase (ATPase) activity. Vascular Na+,K+-ATPase was measured as ouabain-sensitive rubidium uptake in aorta incubated in buffer or plasma from spontaneously hypertensive rats (SHR) fed either a high potassium, a low sodium, or a normal diet for 2 weeks. The high potassium diet significantly increased Na+,K+-ATPase activity, whereas the low sodium diet significantly decreased activity. There was no evidence of a ouabainlike factor in plasma. The increased pump activity on the high potassium diet appeared to be due to an increase in maximum activity (Vmax) of the enzyme, rather than to an increased affinity for potassium. Potentially, an increase in Na+,K+-ATPase activity could contribute to the antihypertensive effect of potassium by hyperpolarizing the cell membrane. The decrease in vascular Na+,K+-ATPase activity on a low sodium diet probably is unrelated to its depressor effect, but it may be a homeostatic mechanism for maintaining sodium balance in the animal.
Absence of hypertension despite chronic marked elevations in plasma norepinephrine in conscious dogs.
Authors: King B D , Sack D , Kichuk M R , Hintze T H
Published: June 2012

To better define the mechanisms of blood pressure control in states of catecholamine excess, we infused norepinephrine for 28 days using subcutaneously implanted osmotic pumps in dogs previously instrumented for monitoring left ventricular dynamics and cardiac output. Plasma norepinephrine rose from 238 +/- 27 to 4346 +/- 952 pg/ml at 21 days, while epinephrine and dopamine levels did not change. Heart rate fell from 85 +/- 4 to 63 +/- 6 beats/min, while arterial pressure was unchanged from baseline. Total peripheral resistance rose 0.011 +/- 0.003 mm Hg/ml/min from a control value of 0.029 +/- 0.002 mm Hg/ml/min, and cardiac output decreased 1093 +/- 292 ml/min from a baseline level of 3575 +/- 156 ml/min. Since stroke volume did not change, the maintenance of arterial pressure is related to decreases in cardiac output secondary to bradycardia. Buffering mechanisms are responsible for maintenance of systemic arterial pressure because hexamethonium and atropine caused hypertension. Although left ventricular end-diastolic pressure, end-diastolic diameter, shortening, rate of change of pressure, velocity of myocardial shortening, cardiac work, stroke work, and the double product did not change significantly during the study, postmortem examination demonstrated biventricular hypertrophy. Thus, despite markedly elevated catecholamine levels and no elevation of systemic arterial pressure, myocardial hypertrophy developed. These studies lend support to the hypothesis that norepinephrine may be a direct myocardial tropic hormone and suggest that intense activation of reflex buffering mechanisms maintains blood pressure in the normal range during chronic catecholamine infusion.
Overall hemodynamic pattern in coarctation of the abdominal aorta in conscious rats.
Authors: Stanek K A , Coleman T G , Murphy W R
Published: June 2012

This study was designed to examine the total body hemodynamics of abdominal aortic coarctation hypertension. The study quantitates both regional and organ blood flow and resistance in conscious rats both above and below an experimentally produced coarctation. The experimental group consisted of 10 male Sprague-Dawley rats with a mean pressure gradient of 68 mm Hg across the coarctation. This experimental group was compared with a group of eight control rats with no pressure gradient. Flow measurements were made with radioactively labeled microspheres 4 weeks after aortic constriction. This aortic coarctation produced an increase in cardiac index (22%) and total peripheral resistance (19%). Blood flow through tissues proximal to the coarctation was not different from control; vascular resistance was increased (31%). Flow through the tissues distal to the coarctation was increased (16%); vascular resistance was decreased (-22%). The upper carcass, diaphragm, and brain were the tissues most representative of flow above the coarctation, and the lower carcass and large intestine were the tissues most representative of flow below the coarctation. Coarctation of the aorta produced cardiac hypertrophy and increased microsphere shunting to the lungs.
Demonstration of neuronal and extraneuronal uptake of circulating norepinephrine in the forearm.
Authors: Chang P C , van der Krogt J A , van Brummelen P
Published: June 2012

Disturbances in peripheral norepinephrine release or removal by neuronal and extraneuronal uptake may have pathogenetic significance in cardiovascular disease states. We investigated the mechanisms of removal of norepinephrine in the forearm of healthy subjects under basal conditions, using measurements of arterial and venous plasma norepinephrine concentrations, blood pressure, heart rate, and forearm blood flow. The specific inhibitor of neuronal uptake, desipramine, was infused intra-arterially into the brachial artery of five subjects. Net norepinephrine overflow from the forearm increased markedly, revealing considerable local release of norepinephrine. Six other subjects received four intra-arterial infusions of norepinephrine, 1.18 pmol/kg/min, with various doses of desipramine and the extraneuronal uptake-inhibiting drug hydrocortisone. The forearm extraction rate for circulating norepinephrine decreased with increasing doses of desipramine (from 69.4 +/- 3.0 [SEM] to 35.3 +/- 8.4%; p less than 0.001). Increasing doses of hydrocortisone during continued inhibition of neuronal uptake resulted in decreased forearm extraction of norepinephrine (from 63.3 +/- 4.9 to 40.6 +/- 4.4%; p less than 0.01). In six other subjects who received the highest dose of hydrocortisone without concomitant inhibition of neuronal uptake, forearm extraction of norepinephrine decreased from 57.1 +/- 4.9 to 51.5 +/- 4.7% (p less than 0.05). These results suggest that neuronal uptake contributes markedly to the removal of circulating and endogenously released norepinephrine in the forearm. For circulating norepinephrine, a corticosteroid-sensitive mechanism of extraneuronal uptake was also demonstrated. These results indicate that neuronal and extraneuronal uptake can be estimated separately in this vascular bed. Similar organ-specific studies in patients may reveal disturbances in mechanisms of norepinephrine removal.
Nucleotide Metabolism in Cardiac Activity
Authors: KHAIRALLAH PHILIP A. , MOMMAERTS W. F. H. M.
Published: June 2012

Relaxed mammalian hearts contain ATP as the predominant nucleotide, sometimes accompanied by smaller amounts of ADP, presumably formed during manipulation. In systole, one-tenth of the nucleotide is changed into a new compound, nucleotide H.
Tension and Distensibility of Carotid Sinus Wall, Pressoceptors and Blood Pressure Regulation
Authors: HEYMANS C. , DELAUNOIS A. L. , VAN DEN HEUVEL-HEYMANS G.
Published: June 2012

Local carotid sinus application of noradrenaline induces a stimulation of the pressoceptors at different constant physiologic and nonphysiologic intrasinusal pressure ranges. Tension and resistance to stretch of the arterial wall where the pressoceptors are located, are the fundamental factors affecting, at different pressure ranges, those receptors which regulate and moderate reflexly the systemic arterial pressure.
Hemodynamic Studies in Tricuspid Stenosis of Rheumatic Origin
Authors: FERRER M. IRENÉ , HARVEY RÉJANE M. , KUSCHNER MARVIN , RICHARDS DICKINSON W. , COURNAND ANDRÉ
Published: June 2012

Clinical data and hemodynamic measurements made by cardiac catheterization are presented in two patients with tricuspid stenosis of rheumatic origin. In one, pure tricuspid stenosis was proved by autopsy, and in the second the development of tricuspid stenosis and insufficiency was demonstrated by means of cardiocirculatory studies made 27 months apart. A detailed analysis of the pressure pattern characteristic of this type of valvular stenosis is given. The measurement of the stenosed tricuspid valve area by three methods is described and discussed.
Amines in Experimental Hypertensions
Authors: OHLER E. A. , WAKERLIN G. E.
Published: June 2012

A sympathomimetic amine, Paredrine, was shown to be a good antihypertensive agent in experimental renal, experimental neurogenic and spontaneous hypertensions in the dog. Other closely related amines failed to possess antihypertensive activity. Paredrine did not prevent the development of experimental renal hypertension. This amine was also without chronic effect on the blood pressure of normotensive dogs.
Some Properties of Contractile Proteins of the Heart as Studied on the Extracted Heart Muscle Preparation
Authors: TAESCHLER MAX , BING R. J.
Published: June 2012

The physiologic properties of the contractile elements (actomyosin) have been studied on the extracted heart muscle of the dog. It was found that many properties of fresh heart muscle are due to inherent qualities of the contractile proteins. For example, the speed of contraction decreased with increasing loads, the work increased with rising tension up to an optimal value, and increased fiber length resulted in greater muscle work.
The T Deflection of Isolated Mammalian Heart Muscle Electrogram
Authors: GARB SOLOMON , CHENOWETH MAYNARD B.
Published: June 2012

Both bipolar and unipolar electrograms recorded from well-oxygenated isolated papillary muscle preparations consist of R and T deflections in the same direction. The T is inverted by anoxia, rapid late, and injury. When cut linear strips of ventricular muscle are observed for many hours, during which time they presumably recover from the initial injury, the T deflection becomes upright in most cases, and then can be depressed and inverted by anoxia or rapid rates of stimulation. Since, in the absence of modifying factors, the T is in the same direction as the R deflection in a simple linear strip, it probably cannot be adequately explained on the basis of membrane repolarization. Since the nerve after-potentials are believed to represent processes involving oxidative metabolism, the T deflection may also be produced by metabolic processes, although the possibility cannot be excluded that it represents a combination of membrane repolarization and other processes.
Cardiac Function in Experimental Mitral Stenosis
Authors: HADDY F. J. , FERRIN A. L. , HANNON D. W. , ALDEN J. F. , ADAMS W. L. , BARONOFSKY I. D.
Published: June 2012

The results of 85 combined right and left heart catheterizations in normal dogs and dogs with experimental mitral stenosis are presented. Animals lived as long as 10 months with elevated pulmonary vein pressures. Pulmonary vein pressures in excess of 15 mm. Hg were associated with mitral orifice areas which were smaller than those found in normal animals. Elevation of pulmonary vein pressure was associated with a decrease in the pulmonary vascular pressure gradient, with no change in cardiac index as measured and with a decrease in calculated pulmonary vascular resistance.
Metabolic Studies on Cardiac Tissue Obtained by Needle Biopsy in the Intact Unanesthetized Dog
Authors: CASTEN GUS G. , MARSH JULIAN B.
Published: June 2012

This paper describes the use of needle biopsy of the heart as a method of obtaining specimens of cardiac muscle for biochemical study in the intact Unanesthetized dog. The procedure is simple and may be repeated many times. Studies indicate that tissue obtained by this method resembles conventional heart slices in its behavior in vitro. Included are data on respiration and the effect of digitalis on cardiac glycogen stores.
Effects of Anoxia on Postarteriolar Pulmonary Vascular Resistance
Authors: HALL PHILIP W.
Published: June 2012

Studies on an isolated pulmonary lobe, perfused in situ from a carotid artery under regulated arterial pressure, showed that changes in its ventilation from room air to nitrogen promptly causes a slight but definite increase in pulmonary vascular resistance which, from the nature of the experimental arrangements, must lie beyond the pulmonary arterioles.
The Influence of Erythrocyte Concentration upon the Pressure-Flow Relationships in the Dog's Hind Limb
Authors: LEVY MATTHEW N. , SHARE LEONARD
Published: June 2012

Since alterations in cell-plasma ratios are of paramount importance in the assessment of peripheral resistance, a study of pressure-flow relations was made in which blood having wide hematocrit values was perfused through a dog's hind limb in which collateral circulation has been excluded. When vessels were moderately dilated by denervation, the relative apparent viscosity was not affected by the perfusion pressure. When, however, the vessels were maximally dilated after a preceding period of anoxia, the relative apparent viscosity was found to become greater as perfusion pressure was progressively reduced. The in vivo relative apparent viscosity did not significantly exceed that of plasma until the erythrocyte concentration reached 30 per cent.
Mechanisms of Fluid and Electrolyte Retention in Experimental Preparations in Dogs
Authors: DAVIS JAMES O. , HOWELL DAVID S. , SOUTHWORTH JAMES L.
Published: June 2012

The role of the adrenal cortex in the pathogenesis of ascites has been studied in adrenalectomized dogs with thoracic inferior caval constriction. Discontinuation of hormone therapy resulted in a diuresis which demonstrates that adequate adrenocortical function or replacement therapy is essential for ascites formation during normal sodium (Na) intake. Evidence is presented in support of the thesis that sodium retention results from an excess of circulating adrenocortical salt-retaining hormones.
The Disappearance of K
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from the Nonuniformly Mixed Circulation Pool in Dogs
Authors: SHEPPARD C. W. , OVERMAN R. R. , WILDE W. S. , SANGREN W. C.
Published: June 2012

The disappearance of injected labeled substances which disappear rapidly from the circulation is discussed theoretically and tested in experiments with injected K
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in the dog. Comparing the inflow and outflow from a capillary bed, using semilogarithmic plots of label concentrations, events upstream are repeated downstream but displaced in time by the amount of the mean circulation time between the points of observation. Downward displacement occurs owing to the intervening loss of material, and smearing of the time relations is produced by the dispersing action of variable path lengths in the capillary labyrinth. For the circulation as a whole, the time relations consist of the sum of a periodic component and an aperiodic component. The periodic component is governed by the mixing relations in a virtual circulation whose architecture approximates that of the real circulation. Extrapolating the aperiodic component to zero time yields the volume of dilution of the injected material in the virtual circulation, providing that injection and sampling points are close together. When the points are separated, correction must be made for time delay and loss of label between. The initial slope is governed not only by the mean rate of exchange of injected substance with the tissues but also by the mean circulation time.
Energy Metabolism of the Completely Isolated Mammalian Heart in Failure
Authors: LORBEK VICTOR
Published: June 2012

Experimental cardiac failure was reinvestigated in the completely isolated mammalian heart using a simplified system in which only the left ventricle performs work and exhibits volume changes. An effort was made to assess the importance of such experimental artefacts as acapnia, altered or depleted substrate, and controlled (constant) diastolic volume. None of these factors appeared to play a determining role in the mechanism of experimental failure, which was characterized by a decline in mechanical efficiency, with little or no impairment of total energy liberation.
The Potter Electroturbinometer
Authors: SARNOFF STANLEY J. , BERGLUND ERIK
Published: June 2012

The flowmeter described is a turbine which can be driven by the bloodstream. In the turbine is a magnet which induces a recordable signal in an adjacent coil. The flowmeter records pulsating flow as well as steady flow; it is insensitive to temperature and wide variations of blood viscosity. The pressure drop is rather high. The baseline and calibration are steady over long periods of time. The flowmeter has been successfully used for continuously recording the systemic output in the dog.
Interrelated Hormonal Factors in Cardiac Hypertrophy
Authors: DE GRANDPRÉ R. , RAAB W.
Published: June 2012

Evidence is presented that cardiac hypertrophy may ultimately be due to metabolic influences of hormones among which the pituitary growth hormone (somatotrophic hormone, STH) is the most important. In hypophysectomized rats, marked cardiac hypertrophy was elicited by administration of STH in the presence of subnormal blood pressure levels. Other hormones, especially the thyroid hormone and the adrenal mineralocorticoids--the latter through their action on myocardial electrolyte balance--seem to play subsidiary roles. Cortisone inhibited the cardiotrophic effect of STH and by itself decreased cardiac mass.
Glomerular Filtration Rate, Renal Blood Flow and Blood Viscosity during and after Diabetic Coma
Authors: REUBI FRANÇOIS C.
Published: June 2012

The azotemia of patients in diabetic coma is the result of impaired blood supply, unless tubular impairment antedates or supervenes. Clearance and blood pressure data are presented which strongly suggest that increased blood viscosity is the dominant reason for the reduced renal blood flow.
The Effect of Diet on the Blood Pressure and Heart Rate of Normal Dogs
Authors: WILHELMJ C. M. , MEYERS V. W. , MILANI D. P. , McDONOUGH J. R. , RACHER E. M. , MCGUIRE T. F. , WALDMANN E. B. , McCARTHY H. H.
Published: June 2012

Trained standardized dogs were fasted until the blood pressure declined to the stable fasting level and were realimented with isocaloric diets high in protein (horse meat) or in carbohydrate (rice or cracker meal). Realimentation was at low maintenance or luxus consumption levels of caloric intake. At the former level, there was no difference between the diets, but at the latter level, the systolic blood pressure and pulse rate were higher on the carbohydrate diet, while the diastolic pressure was normal or low. Preliminary fasting was necessary to obtain a prolonged effect of the carbohydrate diet. Meat appears to antagonize carbohydrate.
Protection Against Hypertension, Arteriolonecrosis and Death by Hog Renal Extracts in Experimental Malignant Hypertension
Authors: BURNS R. O. , WAKERLIN G. E.
Published: June 2012

Since hog renin is effective in the treatment and prophylaxis of chronic experimental renal hypertension in the dog, probably through antirenin, a study was made of the prophylactic effect of crude and semipurified hog renins from cortex and from whole kidney on the hypertension, arteriolonecrosis, and course of experimental renal malignant hypertension in the dog. In the absence of medullary protein, protection against the hypertension was found to be well correlated with the antirenin titer. More importantly, the nonrenin fraction of crude hog renin from cortex significantly protected against the arteriolonecrotic lesions and death.
Acetylcholinesterase in the Conductive Tissue of the Heart
Authors: MOMMAKRTS W. F. H. M. , KHAIRALLAH P. A. , DICKENS MARY FLEMING
Published: June 2012

It is shown that the Purkinje system of bovine hearts contains a specific acetylcholinesterase resembling that of nervous tissue, in an amount comparable to that of peripheral nerve. Its possible implication in the conduction of impulses in the heart is discussed.
"Sodium Space" and Body Sodium Content, Exchangeable with Sodium
21
, in Normal Individuals and Patients with Ascites
Authors: WARNER GEORGE F. , SWEET NORMAN J. , DOBSON ERNEST L.
Published: June 2012

Tlie sodium space and body sodium content, exchangeable with sodium
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, were determined in 20 patients with ascites resulting from hepatic cirrhosis. Values were markedly increased over normal and roughly proportional to the degree of ascites estimated clinically. It appears that the expansion of the sodium space in cirrhosis with ascites represents the actual increase of body fluid due to the ascitic volume. No relationship was found between the serum sodium concentration and body sodium content. In the presence of ascites and/or edema, a deficiency of body sodium content cannot be inferred from a lowered sodium concentration in the serum.
The Alteration of the Lipemia-Clearing Effect of Heparin Following the Intravenous Injection of Thorium Dioxide (Thorotrast)
Authors: LEQUIRE VIRGIL S. , GRAY MARY E. , COBB CULLY A.
Published: June 2012

The lipemia-clearing response to intravenous heparin in the normal dog has been compared with that in dogs injected intravenously with Thorotrast. In normal dogs, intravenous heparin caused clearance of the lipemia (optical density) of approximately 77 per cent of the total amount possible. Dogs receiving low total amounts of Thorotrast (50 to 100 ml.) responded to heparin with a reduced ability to clear an alimentary lipemia, while dogs receiving large total amounts of Thorotrast (150 ml. or more) responded to heparin by becoming even more lipemic. The lipemia inducing effect of protamine was similar in both normal and Thorotrast-injected animals.
The Effect of a Cholesterol-Free Brain Fraction against Diet-Induced Atherosclerosis
Authors: JONES R. J. , KRAFT S. C. , HUFFMAN S. , BALTER E. L. , GORDON R. B.
Published: June 2012

The feeding of a lipid-poor and virtually cholesterol-free residue of mammalian brain mitigates the hypercholesteremia and atherosclerosis ordinarily seen in cholesterol-fed chicks. The probable mechanism depends on the previously demonstrated capacity of oral cerebrosides to convert a large proportion of fecal sterols into unabsorbable coprosterol, thus rendering intestinal cholesterol, unavailable to the body economy.
Balance Between Right and Left Ventricular Output
Authors: Franklin Dean L. , Van Citters Robert L. , Rushmer Robert F.
Published: June 2012

The right ventricular ejection pattern is characterized by early onset, gradual rise to peak flow velocities in midsystole and gradual return to baseline. Left ventricular ejection begins very shortly after right ventricular systole, abruptly reaches peak flow, and diminishes during the remainder of the systolic interval, terminating with a brief, sharp, retrograde surge as the aortic valves close. The duration of ejection is shorter in the left ventricle than in the right. In healthy dogs, respiratory activity produces very slight fluctuations in right and left ventricular output that are almost in phase. In dogs with hydrothorax and pulmonary atelectasis, the right and left ventricular outputs fluctuate in greatly exaggerated fashion with each forced respiratory effort. Under such conditions, the changes in right and left ventricular stroke volume are nearly 180 Degrees out of phase. Pulmonary outflow resistance is increased and the right ventricular ejection pattern closely resembles those generally characteristic of the left ventricle. Assume that the erect posture causes cardio-acceleration and large changes in right and left ventricular stroke volume. which are essentially synchronous. Treadmill exercise with sudden and unexpected onset produces changes in the outputs of the right and left ventricles without obvious lead or lag of one ventricle over the other. These experiments do not support the concept that changes in "venous return" are dominant mechanisms inducing alterations in cardiac output.
Responses of the Bronchial Veins in a Heart-Lung-Bronchial Preparation
Authors: Aramendia Pedro , de Letona Juan Martinez L. , Aviado Domingo M.
Published: June 2012

Blood collected from the bronchial veins of a heart-lung-bronchial preparation consists of two components: (a) fraction from the bronchial arteries, and (b) pulmonary to bronchial shunt It is estimated that the latter is more than half of total bronchial venous flow. The pulmonary to bronchial shunt is reduced by procedures which increase pulmonary arterial pressure. An intrinsic nervous reflex mechanism is suggested to explain such a response, particularly because the bronchial veins are more sensitive than the bronchial arteries to the vasoconstrictor action of epinephrine and norepinephirine, and to the vasodilator action of isoproterenol. acetylchohine, histamine, and DMPP. Alterations in bronchial venous flow induced by such chemical agents are independent of bronchoconstriction or bronchodilatation.
Tissue Blood Flow to the Heart
Authors: MacLean Lloyd D. , Hedenstrom Paul H. , Rayner Ralph R.
Published: June 2012

Regional tissue blood flow to the heart was measured in the dog using deuterium oxide as a tracer substance. The method assumes that the rate of uptake of the tracer by a tissue is limited by the blood flow through the tissue and that the exchange of the tracer between blood and the extravascular space in the organ is instantaneous by comparison. This assumption has had Previous confirmation. Six groups of animals were studied and the results revealed: (1) a uniform distribution of blood flow per unit of weight of tissue between the right ventricle and various parts of the left ventricle; (2) a decrease in tissue blood flow to (0.1 ml./Gm./min., or less), ap proximately 7 per cent of normal in the area supplied by the left anterior descending coronary artery after acute occlusion of this vessel; (3) a failure of two operative procedures designed to increase intercoronary anastomoses to influence this greatly de creased flow, when these procedures were performed six weeks to six months prior to testing; (4) an increase in tissue blood flow to an ischemie area of myocardium to 50 per cent of normal four to six months after coronary occlusion; (5) a failure of olerative procedures to increase significantly the blood flow to the ischemic area over that which developed naturally, indicating no additional collateral vessel development due to the operations. The results of this investigation were discussed in relation to experiments which deal with myocardial function and vulner ability to ventricular fibrillation after coronary occlusion.
Local Temperature Regulation of Microtissue Clearance from Rat Skeletal Muscle
Authors: Hyman Chester , Paldino Rita L.
Published: June 2012

The influence of local temperature changes on the effective blood flow in the rat spinotrapezius muscle was investigated by the extension of the microtissue clearance technique originally used for frog mesentery. The clearance of water blue from microinjection sites in rat skeletal muscle at 37 C. agrees favorab1y with the clearance of other crystalloid labels from gross injection sites in skeletal muscle of mammalian forms. The data show a direct relationship between clearance rates and temperature over a range of 25 to 45 C. The µ value for clearance agrees with the µ value computed from forearm muscle blood flow measurements, at corresponding temperature ranges.
Pathophysiological Changes in the Lungs During Extracorporeal Circulation
Authors: Cartwright Robert S. , Lim Thomas P. K. , Luft Ulrich C. , Palich William E.
Published: June 2012

An attempt has been made to determine the optimal method of managing the lungs during cardiopulmonary bypass. The chemical behavior (oxygen saturation, acid-base balance) of the pulmonary venous blood indicates (a) that static inflation of the lungs with either a gas mixture of high oxygen content or ambient air is sufficient to maintain a proper internal milieu for the pulmonary vasculature when the bronchial collateral flow is the sole pulmonary perfusate, and (b) that in adult human beings artificial respiration up to 2 L./min. is necessary when the pulmonary perfusate consists of the coronary venous blood in addition to the bronchial collateral flow.

The effective application of the heart-lung bypass procedure in physiological investigation is depicted by the studies on metabolic rate of the lung tissues and the measurement of bronchial flow. It is estimated that the bronchial collateral flow amounts to 8.8 ml./ min. or 0.7 per cent of the total systemic flow, and that the oxygen consumption of the lungs averages 1.6 ml./min. or 1 to 2 per cent of the total metabolic rate in the open-chest dogs. The pulmonary compliance did not change following either passive deflation or static inflation, but is transiently reduced after artificial respiration.
High Altitude-Induced Pulmonary Hypertension in Normal Cattle
Authors: Will Donald H. , Alexander Archibald F. , Reeves John T. , Grover Robert F.
Published: June 2012

Six months residence at an altitude of 10,000 feet produced significant pulmonary hypertension and arterial oxygen desaturation (86 per cent) in 10 normal steers born at 3,600 feet. Six of these animals, during the course of the experiment, showed a rise in mean pulmonary arterial pressure from 27 to 45 mm. Hg. The remaining four animals developed more severe pulmonary hypertension, and two with mean pressures greater than 100 mm. Hg had right heart failure. All 10 showed right ventricular hypertrophy proportional to the degree of pulmonary hypertension. Ten steers of similar age and origin, maintained as controls at 5,000 feet, showed a mean pulmonary arterial pressure of 27 mm. Hg throughout the experiment. The pulmonary hypertension observed at high altitude is considered to be due to an increased pulmonary vascular resistance resulting from a reduction in the total cross-sectional area of the pulmonary vascular bed. Chronic hypoxia appeared to be the most important etilogical factor responsible for initiating the hypertension. The observed beneficial effects of 100 per cent oxygen inhalation and the prompt recovery of an affected animal when moved to lower altitude supported the concept of pulmonary hypertension induced by hypoxia.
First Derivative of the Electrocardiogram
Authors: Langner Paul H. , Geselowitz David B.
Published: June 2012

A method for obtaining the first derivative of the ECG electronically has been described and the curve of the first derivative displayed with the original ECG. It has been demonstrated that the first derivative emphasizes the high frequency components of the ECG and firmly establishes the fact that these are very real and significant components of the ECG. The ultimate usefulness of this method in electrocardiographic diagnosis remains to be determined.