bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alterations with Age in the Viscoelastic Properties of Human Arterial Walls
Authors: Learoyd Brian M. , Taylor Michael G. 
Published: June 2012

The circumferential incremental Young's modulus was measured in 59 major arteries of both "young" (less than 35 years of age) and "old" (greater than 35 years of age) subjects.
Dynamic measurements of wall elasticity and viscosity were made which indicated a high viscosity in the femoral arteries. This was attributed to their high content of muscle.
Although the "young" group showed, at any given pressure, an increasing wall stiffness towards the periphery, in "old" arteries, an opposite trend was found. When dimensional changes (radius and wall thickness) in the "old" group were considered it was apparent that at all sites the arterial wall tissue became weaker with age. Nevertheless, as a consequence of these dimensional changes the impedance characteristics of the old arterial tree still retained the nonuniformity (an increase towards the periphery) of the "young" which has considerable haemodynamic advantage.
Cardiovascular Effects of Sustained Norepinephrine Infusions. III. Lactic Dehydrogenase Isoenzyme Release
Authors: Schenk Eric A. , Galbreath Robert , Moss Arthur J. 
Published: June 2012

Infusion of norepinephrine (NE) in dogs in doses of 1 to 4 µg/kg/min resulted in a rapid and dose related increase in serum lactic dehydrogenase (LDH) and those isoenzymes of LDH present in the heart. Histochemically definable lesions in the heart were correlated with the isoenzyme release produced by 2 and 4 µg/kg/min NE infusion.
Evidence of LDH isoenzyme release from organs other than the heart was found only in dogs in the highest dose group that, in addition, had evidence of low cardiac output.
Nonlinear Analysis of the Baroreceptor Reflex System
Authors: Levison William H. , Barnett G. Octo , Jackson William D. 
Published: June 2012

The regulation of blood pressure by the baroreceptor reflex was examined in anesthetized dogs. The receptor feedback path was broken by surgical intervention, the input (carotid sinus pressure) was controlled by an external servo system, and simultaneous records of input and output (systemic arterial pressure) were obtained. A variety of pressure waveforms were applied to the carotid sinus so that the nonlinear behavior could be explored thoroughly. Most of the input waveforms consisted of relatively small signals about an operating point in the normal blood pressure range.
The nonlinear behavior of the reflex was illustrated in a number of ways. Square waves, sinusoids, and short pulses produced asymmetric arterial pressure waveforms. An overshoot in the arterial pressure always followed the rising edge of the input square wave, but was generally absent following the negative-going part of the square wave. Either positive or negative pulses caused a transient drop in arterial pressure. The sinusoidal response was often distorted, with the falling portion of the output waveform steeper than the rising portion. The system behaved as a rectifier, or envelope-detector, as illustrated by 1) the decrease in mean arterial pressure when either the amplitude or the frequency of a sinusoidal input was increased and 2) the appearance in the arterial pressure waveform of a component correlated with the envelope of a modulated carrier. Another nonlinear phenomenon was the decrease in low-frequency sinusoidal gain caused by the addition of a high-frequency sinusoid to the sinus pressure waveform. This behavior indicates that if closed loop behavior in the intact animal is to be predicted from the open loop sinewave response, the effects of the cardiac pressure pulse must be considered.
A model was constructed from standard electronic components to simulate the input-output behavior of the baroreceptor reflex. The model was able to simulate the response to high- and low-frequency sinusoids and to reproduce the essential features of the square-wave and pulse responses. On this basis the model was considered adequate for simulating the performance of the baroreceptor reflex in certain open loop and closed loop situations.
Human Cerebral Blood Flow Measured by Two Inert Gas Techniques
Authors: LASSEN N. A. , HØEDT-RASMUSSEN K. 
Published: June 2012

Two inert gas methods for measurement of tissue blood flow were compared. The two methods are (1) Kety and Schmidt's inert gas saturation method, in which the tissue saturation is followed by detecting the concentration of the tracer in the venous blood leaving the organ and (2) the intraarterial radioactive inert gas injection method where the tissue washout is measured by detecting the residue inside the tissue by an external scintillation detector.
Theoretical considerations show a close relation between the two methods when carried to the time of full saturation or desaturation of the tissue or when stopped before full saturation.

Experimental studies of cerebral blood flow in nine human subjects using Kr
85
revealed a close correlation between the two methods without any systematic difference between the two sets of data.

The Kety-Schmidt outflow detection method is the method of choice for studying over-all tissue perfusion and metabolism. The residue detection method is best suited for measuring flow through circumscribed regions
inside
an organ and for resolving the flow curve to yield estimates of flow and relative weight of various tissue components.
Distribution of Size and Shape in Populations of Normal Human Red Cells
Authors: CANHAM P. B. , BURTON ALAN C. 
Published: June 2012

The diameter, area, and volume of individual human erythrocytes (of 8 subjects, newborn to age 71) were determined by photographing the cells hanging on edge. Measurements from high magnification prints were processed by computer. The distributions of diameter, area, and volume are described statistically, with the unexpectedly linear regression equations for their interrelations. The plot of area vs. volume for the 1016 normal cells from seven subjects (newborn excluded) was remarkably linear with a "straight-line" boundary restricting the distribution. Shape was characterized by a dimensionless "sphericity index" (4.84.volume
2/3
/area). Cells of larger volume tended to be thinner than the smaller cells.

The red cell can easily be deformed at constant volume, but an increase in membrane area results in hemolysis. A theoretical geometric parameter, the "minimum cylindrical diameter" (MCDiam), in microns, the thinnest cylindrical channel through which each individual cell could pass, predicts the linear boundary of the plot of area vs. volume. The MCDiam value of 3.66 µ ± 0.04 SEM accurately represents the thinnest channel through which 95% of the cells can pass.
In two splenectomized patients with hereditary spherocytosis the MCDiam was increased to approximately 4.0 µ, suggesting that the severest restriction is located in the spleen.
Reversal of Pulmonary Hypertension by Prolonged Oxygen Administration to Patients with Chronic Bronchitis
Authors: ABRAHAM ABRAHAM S. , COLE RICHARD B. , BISHOP JOHN M. 
Published: June 2012

Established pulmonary hypertension associated with hypoxemia in patients with chronic bronchitis is probably secondary to hyperplasia of the smooth muscle of pulmonary arterioles. To investigate the possibility that this increase in pulmonary arterial pressure was reversible, the floating catheter technique was used to study the effects of continuous administration of oxygen for 4 to 8 weeks on the pulmonary circulation.
In six patients, there was a gradual fall in pulmonary arterial pressure, the mean pressure for the group being 42.5 mm Hg before, and 32.3 mm Hg after, the period of oxygen administration. All measurements were made when the patients breathed air. There was no change in cardiac output. Hematocrit decreased from 51.4% to 42.5%, but total blood volume remained unchanged.
It has been shown previously that brief inhalation of oxygen can cause a slight temporary reduction in the pulmonary hypertension associated with chronic bronchitis and anoxemia. The present findings show that the residual, established hypertension is also reversible if oxygen therapy is continued for weeks. It is suggested that this reversal may be brought about by regression of the muscular hyperplasia of the small pulmonary vessels consequent to longterm relief of hypoxia.
Observations on the Origin of Renin in Human Urine
Authors: LUMBERS EUGENIE R. , SKINNER S. L. 
Published: June 2012

Excretion of renin into urine was studied using specific assay methods in normal subjects and hospital patients. Urinary renin output and renal clearance of renin varied widely among normal subjects but remained similar over months in any one subject. Renin clearance was significantly less in normal males (range 12 to 893 ml/24 hours) than females (79 to 3,149 ml/24 hours), but no reason for this was established.
In normal subjects renin excretion did not show a diurnal variation and was not directly dependent upon creatinine clearance, protein clearance, plasma renin levels, or sodium or water output.
Fivefold elevations in plasma renin level induced by natriuretic therapy increased renin excretion twofold and caused renin clearance to fall to 43% of control without a change in creatinine clearance. Total protein excretion did not change with this elevation in plasma renin level.
Excess renin excretion did not occur in patients with proteinuria unless plasma levels were grossly elevated. The findings suggest that renin is filtered and selectively reabsorbed. No diagnostic application is apparent.
In-Vitro Studies of Myocardial Asynchrony and Regional Hypoxia
Authors: TYBERG JOHN V. , PARMLEY WILLIAM W. , SONNENBLICK EDMUND H. 
Published: June 2012

Ten pairs of cat papillary muscles were arranged in tandem to study their individual and combined length-tension and force-velocity relationships. Physiologic asynchronous contraction (up to 60 msec) of the pair of muscles produced a change in the individual force-velocity relations of each muscle which was characteristic of a change in muscle length; i.e., there was an alteration of tension developed without a change in the maximum measured velocity of shortening. On the ascending limb of the length-active tension curve, asynchronous stimulation (average time interval 32 msec) increased the force developed (5.3 ± 1.4%) by the tandem pair, as compared to synchronous stimulation.
When one muscle was made hypoxic for 20 minutes, its force development was reduced by 64 ± 3%, and paradoxical motion occurred. After 2 minutes of reoxygenation, the time to peak tension was slightly prolonged, while the time for isometric tension to relax to one-half its peak value was increased to 234±27% of control. During this period the contraction pattern of the tandem pair was out of phase (asynergic), even though they were stimulated synchronously. Thus transient asynergy associated with regional myocardial ischemia may be explained in part by these observed alterations in the time course of contraction and relaxation.
Measurement of Cerebral Hemispheric Blood Flow by Intracarotid Injection of Hydrogen Gas: VALIDATION OF THE METHOD IN THE MONKEY
Authors: Shinohara Yukito , Meyer John S. , Kitamura Akira , Toyoda Masanaru , Ryu Tisuke 
Published: June 2012

To develop a reliable method for measuring hemispheric blood flow and metabolism in man, the clearance of hydrogen was measured in the cerebral lateral sinus blood of macaque monkeys after intracarotid injection. Hydrogen is an inert gas and its clearance from cerebral venous blood depends solely on arterial inflow, and since it is highly diffusible, rapid equilibrium is maintained between brain tissue and its capillary-venous blood. Cerebral venous clearance curves for hydrogen appeared to provide accurate and reproducible measures of cerebral blood flow.
A bolus of 0.2 to 0.3 ml of saline saturated with hydrogen was injected rapidly into the internal carotid artery. Electrodes placed on the cortex showed that the bolus was almost exclusively distributed to the ipsilateral cerebral hemisphere. Blood flow of each hemisphere was calculated by Meier and Zierler's formula based on the Stewart-Hamilton principle, as well as by compartmental analysis. The values obtained for hemispheric blood flow were in good agreement with average cerebral blood flow measured by inhalation of hydrogen using the Fick principle. Values for hemispheric blood flow were the same whether the intracarotid injection of hydrogen was rapid or slow.
Effect of Ganglion-Blocking Agents on Renin Release in Hypertensive Patients
Authors: KANEKO YOSHIHIRO , TAKEDA TADANAO , IKEDA TAKAO , TAGAWA HITOSHI , ISHII MASAO , TAKABATAKE YUTAKA , UEDA HIDEO 
Published: June 2012

In 18 patients with benign essential hypertension, renin release during reduction of arterial pressure due to sodium nitroprusside infusion was measured before and after administration of ganglion-blocking agents (pentolinium or trimethaphan). In 12 patients, renin release induced by reduction in pressure was significantly reduced but not abolished by ganglion blockade. Simultaneously, ganglion blockade significantly reduced renal vascular resistance (RVR) and almost abolished a decrease in renal blood flow (RBF) due to hypotension. In 6 other patients in whom no significant renin release resulted from hypotension, ganglion blockade caused little changes in renin release, RVR or RBF. The results support the hypothesis that renal sympathetic nerve activity is a factor in variations in renin release in patients with essential hypertension.
Following ganglion blockade in the responsive patients, the significant reciprocal correlation between renal venous renin activity and sodium excretion rate shifted but still persisted, suggesting that the renin-releasing mechanism related to sodium excretion may be independent of innervation. On the other hand, the correlation between renin activity and the degree of reduction in pressure was insignificant after ganglion blockade. It is concluded that two intrarenal mechanisms, nerve-dependent and nerve-independent, are involved in renin release due to reduction in pressure.
Ganglion blockade also exerted an inhibitory effect on renin release due to hypotension in 4 normotensive subjects and 5 patients with renovascular hypertension.
Redistribution of Cardiac Output during Hemorrhage in the Unanesthetized Monkey
Authors: FORSYTH RALPH P. , HOFFBRAND BARRY I. , MELMON KENNETH L. 
Published: June 2012

Regional flow measurements were made, using the Rudolph and Heymann microsphere technique, before and after 10, 30, and 50% of the previously measured blood volume was withdrawn from five unanesthetized rhesus monkeys restrained in horizontally tilted primate chairs. Measurements at similar time intervals were also made in seven control monkeys. Systemic arterial and central venous pressures, cardiac output, stroke volume, and hematocrit decreased progressively at each level of bleeding. Heart rate (until severe hemorrhage), respiratory rate, and blood levels of α-glucosidase rose; bradykinin levels in arterial blood were unchanged. The fraction of cardiac output was found to be progressively increased to brain, heart, adrenal gland, and hepatic artery vascular bed at the expense of skin, spleen, and pancreas. The hepatic artery vascular bed was the only one that showed significant vasodilatation at either 30 or 50% hemorrhage.
During acute endotoxin shock in monkeys, we have previously found a similar fall in systemic arterial pressure due to a decrease in total peripheral resistance and a different pattern of regional blood flow changes. The lack of bradykinin production, the integrity of cardioregulatory mechanisms, and the fall of hematocrit levels found during hemorrhage may help account for some of the hemodynamic differences between these two types of shock.
Effect of Timing of Vagal Stimulation on Heart Rate in the Dog
Authors: DONG EUGENE , REITZ BRUCE A. 
Published: June 2012

The effects of right vagus nerve stimulation on heart rate were examined in 16 dogs anesthetized with chloralose (60 mg/kg, iv) and urethane (600 mg/kg, iv) after a bilateral cervical vagotomy.
Two protocols were followed. In the first, trains of 1, 3, or 5 stimuli, 2 msec each in duration, 10 to 15 v in magnitude, and separated by 10 msec were delivered at predetermined times after "P" wave onset as a single stimulation. In the second, the stimulation was carried out repetitively for 2 minutes at a predetermined frequency. Typically, in the first, the later in the cycle the stimulation occurred, the greater was the prolongation of the included cycle. With one stimulus in the stimulation, a typical P-P interval was 574 msec with a "P" to stimulation delay of 4 msec, and 620 msec when the "P" to stimulation delay was 200 msec. With five stimuli moving the stimulation through a range of 200 msec, the change in P-P interval was 150 msec. There was a functional dependence of the P-P cycle length on the time of arrival of the inhibitory pulse. The slope of this relationship is a function of the number of stimuli in the stimulation.
With repetitive stimulation in the second protocol, there were zones wherein the heart rate synchronized to the vagal stimulation rate not only at the fundamental frequency but also at harmonics and subharmonics. This range of entrainment was also dependent upon the number of stimuli in the stimulation. The data suggest the possibility of phase shift as a mechanism for vagal regulation of heart rate.
Renin Excretion in Patients with Renal Disease
Authors: PESSINA ACHILLE C. , HULME BARRY , RAPPELLI ALESSANDRO , STANLEY PEART W. 
Published: June 2012

The renal handling of renin was studied in normal subjects and in patients with predominant tubular and glomerular damage.
The renin in plasma and urine was assayed in the blood pressure preparation of the rat.
Excessive renin excretion occurred only in patients with proximal tubular dysfunction and was not related to creatinine clearance, proteinuria or plasma renin levels. However, a significant correlation was found between renin clearance and clearances of other low molecular weight proteins which pass freely through the glomerular membrane and are normally reabsorbed by the tubules. All the evidence points to the important role played by tubular reabsorption in the control of renin urinary excretion.
Renin and Aldosterone Secretion in Man as Influenced by Changes in Electrolyte Balance and Blood Volume
Authors: BULL MARCIA B. , HILLMAN ROBERT S. , CANNON PAUL J. , LARAGH JOHN H. 
Published: June 2012

In six normal volunteers maintained on a constant dietary intake, serial studies were made of plasma renin activity, blood volume, aldosterone secretion and sodium balance, first following dietary and diuretic-induced depletion of sodium and blood volume, then following a period of sodium repletion during a maintained reduction in blood volume, and finally after blood volume repletion. In the first phase, during which depletion of blood volume paralleled sodium depletion, renin and aldosterone secretion were both increased. Under the circumstances of a subsequent study period, however, it was possible to separate the effects of sodium depletion from those of reduction in total blood volume. In this period, the administration of sodium chloride was associated with an increased urinary sodium excretion and a marked suppression of plasma renin and aldosterone secretion at a time when total blood volumes were maintained below control values by repeated plasmapheresis and phlebotomy.
This sodium-dependent suppression of renin and aldosterone secretion may have been mediated by an expansion in extravascular fluid volume(s). However, the observed effects are perhaps better explained in terms of an induced change in intrarenal tubular sodium transport. The parallelism observed between the changes in renin and aldosterone secretion suggests that under the conditions of these studies renin plays a major role in regulating aldosterone secretion.
The Effect of Moderate Changes in Blood Volume on Left and Right Atrial Pressures
Authors: HENRY JAMES P. , GAUER OTTO H. , SIEKER HERBERT O. 
Published: June 2012

The blood volume of 15 dogs was progressively increased an estimated 30 per cent by repeated blood infusions and decreased 30 per cent by stepwise hemorrhage. The pressures in the venous system, both atria and the pulmonary artery, rose and fell in unison with these moderate changes in blood volume and the new levels remained stable for at least 10 to 20 minutes.
Although the right ventricle anatomically separates the systemic venous bed from the pulmonary circulation, small hemorrhages and transfusions have so little effect on its activity that, from the point of view of pressure volume relationships, the systemic veins and the left atrium are parts of the same functional unit.
Interrelation Between Central and Peripheral Mechanisms Regulating Blood Pressure
Authors: WILSON MICHAEL F. , CLARKE NEVILLE P. , SMITH ORVILLE A. , RUSHMER ROBERT F. 
Published: June 2012

Electrical stimulation of selected discrete sites in the diencephalon induced a profound and coordinated response consisting of increased respiratory activity, limb movements, and cardiovascular adjustments. The effects on the cardiovascular system were similar to those of exercise, although the increases in aortic pressure, left ventricular pressure, and heart rate were greater. Massive splanchnicnerve discharge occurred immediately when the diencephalon was stimulated, but splanchilic activity abruptly fell below control levels with cessation of the stimulus. The increase in respiratory activity and the organized running movements seen during stimu lation apparently did miot contribute to the pressor and cardioaccelerator responses.
There appeared to be no marked difference between control and diencephalic-stimulation experiments in the ease with which in duced pressure pulsations in the partially isolated carotid sinus caused bradycardia and blood-pressure depression. It may be that the influences of the diencephalon and carotid- sinus reflex upon blood pressures are inde pendent and sum algebraically.
Experiments in which effects of epinephrine on splanchnic-nerve activity and systemic arterial pressure were measured before and during dieneephalic stimulation did not support the concept that catecholamines have an important role in normal pressor responses.
Effects of Exercise and Anemia on Coronary Arteries of Small Animals as Revealed by the Corrosion-Cast Technique
Authors: TEPPERMAN JAY , PEARLMAN DAVID 
Published: June 2012

Vinyl acetate corrosion casts were prepared of the coronary arterial trees of chronically exercised rats and of suitable control animals. In four experiments, there was a statistically significant increase in the mean coronary-cast weight of the exercised animals over that of controls. In two experiments, the coronary- cast/heart-weight ratios were significantly increased.
In three-week-old ducklings rendered anemic by an iron-deficient diet, corrosion casts of the coronary vessels showed marked increases in cast weight, increase in size of homologous vessels, and generally more luxuriant arborization of the tree. No differences were found when coronary casts of thyroxin-injected or of pentaerythritol tetranitrate-injected rats were compared with those of control animals. Right-to-left-side coronary anastomoses were demonstrated in 75 per cent of guinea-pig hearts studied by the corrosion-cast technique. In five experiments, retrograde filling of a ligated anterior descending branch of the left coronary artery was demonstrated when the vinyl acetate solution was injected into the aorta.