bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations on the Extrinsic Neural Control of Cerebral Blood Flow in the Baboon
Authors: JAMES I. M. , Millar R. A. , PURVES M. J.
Published: June 2012

Cerebral blood flow was measured using
133
xenon in forty-five baboons lightly anesthetized with pentobarbital. Blood flow varied between 62 and 82 ml/100g/min in gray matter and between 15 and 21 ml/100g/min in white matter. Hypercapnia and hypoxia caused a rise in blood flow and a fall in vascular resistance. Blood flow was independent of mean arterial blood pressure over the range 60 to 130 mm Hg. Section of the cervical sympathetic nerve enhanced the vascular response to CO
2
. Stimulation of the sympathetic nerve caused a reduction in blood flow in proportion to the initial blood flow. Similarly, after sympathectomy, blood flow was uniformly higher than control over the range of Pa
o
2
tested (35 to 450 mm Hg). After sympathectomy, blood flow was little different from control at low blood pressure but was higher within the physiological range and blood flow then fell steadily as pressure was reduced. When the carotid, vagus, and aortic nerves were cut in the neck, the blood flow response to hypoxia and hypercapnia was reduced, and when the aortic or vagus nerves were stimulated centrally, blood flow increased independently of Pa
CO
2
. Section of the seventh cranial nerve caused small and variable changes in blood flow, but if the vagus nerves had previously been sectioned, stimulation of the seventh cranial nerve caused an increase in blood flow in some of the tests. These results indicate that cerebral blood vessels are under reflex control. Possible receptors and pathways involved are discussed.
Experimental Myocardial Infarction in the Dog
Authors: REES J. RUSSELL , REDDING V. J.
Published: June 2012

Control measurements of myocardial blood flow were made in intact dogs by a method of
133
Xe clearance, using a catheter positioned radiographically in the circumflex artery. Acute myocardial infarction was then caused by tying the anterior descending artery. A small catheter was inserted distally beyond the obstructed artery into the infarct, and another proximally toward the anterior ventricular artery supplying adjacent left ventricular muscle. Their ends were brought out as the chest was closed.
133
Xe in solution was injected serially over 4 hours to determine myocardial blood flow within the infarct, in adjacent muscle, and in more distant muscle supplied by the circumflex artery. Myocardial blood flow in the circumflex artery usually fell as a result of infarction. A constant finding was that adjacent flow exceeded the more distant flow by 6% up to 43% (mean 20%) regardless of either spontaneous or induced changes in blood pressure. The difference was not related to the collateral flow rate and was abolished by dipyridamole. Perfusion of muscle adjacent to the infarct was less homogenous than that of more distant muscle.

In the normal dog rates of myocardial blood flow in the distribution of the circumflex and anterior descending branches of the left coronary artery were the same, contrasting with lower rates for the right.
Glucagon
Authors: LUCCHESI BENEDICT R. , STUTZ DAVID R. , WINFIELD ROBERT A. , BROWN JEANNE L. , NOBEL NANCY L.
Published: June 2012

The effects of glucagon on atrioventricular nodal automaticity and ventricular automaticity were studied in anesthetized open-chest dogs. After the sinoatrial node was crushed, glucagon, 4 µg/kg, produced a marked and sustained increase in the rate of A-V nodal discharge (27.6 ± 10.1 vs. 117.4 ± 6.5 beats/min) that persisted for an average of 20 minutes. The effect of glucagon was not modified by previous administration of propranolol, 2 mg/kg. Repeated administrations of glucagon, 1 µg/kg every 15 min, for a period of 2 hours, sustained A-V nodal rhythm. The effects of glucagon on ventricular automaticity were studied in unanesthetized dogs 48 and 72 hours after surgical ligation of the anterior descending coronary artery and were compared to the effects of epinephrine. Unlike the catecholamine, glucagon did not enhance ventricular automaticity in the infarcted myocardium. The results suggest that glucagon might be of therapeutic value in the management of heart block and in cardiogenic shock after acute myocardial infarction. The inability to augment ventricular ectopic activity suggests that glucagon possesses an advantage over the catecholamines as an inotropic agent.
Capacitance Responses and Fluid Exchange in the Cat Liver during Stimulation of the Hepatic Nerves
Authors: Greenway Clive V. , Stark Ronald D. , Lautt W. Wayne
Published: June 2012

Techniques are described to study the hepatic vascular bed in the anesthetized cat without interference with the hepatic artery or portal vein. Liver volume was recorded with a plethysmograph while simultaneous recordings were made of arterial and portal pressures and total hepatic blood flow. Hepatic venous pressure could be raised to any desired level, and capillary filtration coefficients could therefore be determined. The hepatic blood volume was 27 ± 3.3 ml/100 g liver (14% of the total blood volume of the cat). Stimulation of the hepatic nerves decreased liver volume. Maximal responses were reached at frequencies of about 6/sec, and 50% of the blood in the liver was expelled. The hepatic vascular bed is thus an important blood reservoir. The capillary filtration coefficient was 0.30 ± 0.03 ml/mm/mm Hg/100 g, and this value was not significantly changed during stimulation of the hepatic nerves.
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.
Observations on the Control of Cerebral Blood Flow in the Sheep Fetus and Newborn Lamb
Authors: Purves M. J. , James I. M.
Published: June 2012

Cerebral blood flow was measured with xenon
133
in 21 fetal sheep and 14 newborn lambs under 48 hours old. When the ewe breathed air, the average gray matter blood flow in the fetuses was 70.6 ml/100 g/min, the average white matter blood flow 15.4 ml/100 g/min and average gray matter oxygen consumption 2.06 ml/100 g/min. The corresponding values in the newborn lambs were 87.2, 17.8, and 2.98 ml/100 g/min. A reduction of fetal Pao
2
by 7 to 11 mm Hg at a constant Paco
2
or an increase of Paco
2
at constant Pao
2
caused a rise in blood flow and arterial pressure and a fall in vascular resistance. Intravenous catecholamines caused variable changes in blood flow but no significant change in gray matter oxygen consumption. Occlusion of the umbilical cord caused an average increase in gray matter blood flow of 50% of control, in white matter blood flow of 30%, and in gray matter oxygen consumption of 90%. By the end of the first hour, these values had fallen and were then similar to those seen in the newborn lamb. These changes were not seen in fetuses in which both vagi had been cut nor in two fetuses with a failing circulation.
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.
Left Ventricular Wall Stress Calculated from One-Plane Cineangiography
Authors: FALSETTI HERMAN L. , MATES ROBERT E. , GRANT COLIN , GREENE DAVID G. , BUNNELL IVAN L.
Published: June 2012

Left ventricular dimensions from routine clinical one-plane cineangiograms were combined with left ventricular pressure measurements to permit calculation of left ventricular wall stresses. The 25 patients included 12 with normal left ventricular dynamics, 6 with volume overload, 3 with outflow obstruction, and 4 with cardiomyopathy. Average stresses calculated on the basis of an ellipsoid model agreed with average values obtained from the exact solution of a thick-walled elastic ellipsoidal shell. Peak values were 150 to 625 g/cm
2
in the circular direction and 75 to 365 g/cm
2
in the longitudinal direction. A fiber-corrected stress was defined which represents a force per muscle fiber. The variation in fiber-corrected stress during the cardiac cycle may be considerably different from the variation in simple stress.

The force-velocity characteristics of circular fibers for the 25 patients are presented. The data on peak wall stress overlap in the four groups of patients. Peak velocity of circumferential fiber shortening varied from 0.44 to 0.63 lengths/sec in patients with myocardial weakness and varied from 0.74 to 2.56 lengths/sec in the other patients. Contractile element velocity was determined during ventricular ejection when the rate of force change equaled zero. Contractile element velocity of shortening was 0.22 to 0.32 lengths/sec in the cardiomyopathy group and 0.50 to 1.32 lengths/sec in the other patients.
Thoracic Chemoreceptors in the Dog
Authors: COLERIDGE HAZEL M. , COLERIDGE JOHN C. G. , HOWE ALAN
Published: June 2012

Anatomical and electrophysiological techniques were employed to investigate the aortic bodies in anesthetized puppies and dogs. The microscopic appearance, location, innervation, and vasculature of the aortic bodies were investigated by microdissection and histological examination of gelatine-injected preparations. Thoracic chemoreceptor impulses were recorded from the cervical vagus nerves, the nervous pathways in the thorax identified by cold blockade, and the blood supply to the receptors investigated by injection of drugs. Large, circumscribed aortic bodies were few, the majority of glomus cells being scattered in small groups along the vagal branches coursing on the walls of the pulmonary artery and aorta. Very few bodies were found in groups 1 and 2 at the right and left subclavian angles. The majority were in group 3, ventral to the aortic arch and pulmonary bifurcation and supplied by the ventromedial cervical cardiac branch of the left vagus, and in group 4, between the aorta and pulmonary artery, supplied by the recurrent cardiac branch of the right vagus. The arterial supply to the aortic chemoreceptors stemmed from the aorta and the brachiocephalic and left coronary arteries. In neither puppies nor adult dogs was there evidence of a supply from the pulmonary artery.
Electrophysiological Properties of the Canine Peripheral A-V Conducting System
Authors: MYERBURG ROBERT J. , STEWART JOHN W. , HOFFMAN BRIAN F.
Published: June 2012

Action potential durations and local refractory periods were mapped along the course of canine conducting tissue from bundle branches to the termination of false tendons in ventricular muscle. Standard microelectrode techniques were used. Areas of maximum action potential duration, which coincided with areas of maximum local refractory periods, were consistently found 2 to 3 mm proximal to the termination of conducting fibers in muscle. The refractory periods at the areas of maximum action potential duration were quantitatively identical in the multiple false tendons of a segment of the conducting system, providing a uniform functional limit for the propagation of premature impulses across the distal end of the conducting system of the segments studied. It was demonstrated that appropriately timed premature impulses could be confined within conducting tissue either proximal or distal to the area of maximum action potential duration. This occurred when the area of maximum duration was still refractory, after other areas of the conducting system had recovered excitability. In most preparations, maximum action potential durations and functional refractory periods across distal false tendons were longer in tissue from the right side than from the left side of the conducting system.
Response of the Limb Vascular Bed in Man to Intrabrachial Arterial Infusions of Hypertonic Dextrose or Hypertonic Sodium Chloride Solutions
Authors: OVERBECK HENRY W. , GREGA GEORGE J.
Published: June 2012

Infusions of hypertonic dextrose or NaCl solutions reduce resistance in several vascular beds of experimental animals. To study the response in man, 60 intrabrachial arterial jet infusions of hypertonic dextrose solution or hypertonic NaCl solution, each at 3 dose levels (1, 2, and 4 milliosmols/min), were made in 19 male student volunteers aged 21 to 29 years. Limb blood flow was measured by continuous infusion indicator-dilution, and vascular resistance calculated as mm Hg/ml flow/100 cm
3
limb vol/min. Measured increases in ipsilateral cephalic venous plasma osmolarity and serum dextrose and sodium concentrations during hypertonic infusions ranged from 7 to 30 milliosmols/liter, 153 to 481 mg/100 ml and 4 to 19 mEq/liter, respectively. Measured limb venous blood hematocrit during hypertonic infusions was similar to that during control isotonic infusions. All 60 hypertonic infusions evoked an increase in limb blood flow and decrease in limb vascular resistance as compared to "resting" values during paired control isotonic NaCl infusions. There was a significant (P<.01) positive linear correlation between level of initial vascular resistance and magnitude of response to all hypertonic infusions. At each dose level, neither regression coefficient nor regression adjusted mean response to dextrose was significantly different from that to hypertonic NaCl (P>.05).

The results of these studies indicate that the local vascular response to hypertonicity in the limb of man is a decrease in resistance, the magnitude of which is a function of the level of plasma osmolarity and the level of initial limb resistance. The steady-state responses to hypertonic dextrose are quantitatively similar to those to hypertonic NaCl.
Blood Flow, Oxygen Consumption, and Free Fatty Acid Release in Subcutaneous Adipose Tissue during Hemorrhagic Shock in Control and Phenoxybenzamine-Treated Dogs
Authors: KOVÁCH A. G. B. , ROSELL SUNE , SÁNDOR PÉTER , KOLTAY EDITH , KOVÁCH EMMA , TOMKA NATÁLIA
Published: June 2012

Dogs were anesthetized with α-D (+)-glucochloralose. After bleeding to a mean arterial pressure of 55 mm Hg, blood flow in subcutaneous adipose tissue decreased from 6 ± 0.9 (mean ± SE) to 0.6 ± 0.21 ml/min/100 g (P < 0.001), and remained at that low level during bleeding to 35 mm Hg for an additional 90-minute period. In five out of nine experiments the blood flow ceased completely. Sixty minutes after reinfusion, the blood flow was significantly lower than control, and in two there was no blood flow after reinfusion. In animals previously treated with phenoxybenzamine (5 mg/kg), the decrease in blood flow was significant only at 35 mm Hg arterial pressure (2.6 ± 0.67 ml/min/100 g). After reinfusion blood flow increased to a mean above 10 ml/min/100 g, significantly higher than resting blood flow (P < 0.05). There was no significant change in arterial FFA concentration or FFA release in subcutaneous adipose tissue during bleeding and after reinfusion. In phenoxybenzamine-treated animals there was a tendency to have higher arterial FFA concentration and FFA release. The oxygen uptake fell from 0.47 ± 0.07 to 0.13 ± 0.05 ml/min/100 g (P<0.01) during 55 mm Hg arterial pressure and remained significantly lower also during 35 mm Hg arterial pressure. Previous treatment with phenoxybenzamine prevented a fall in O
2
uptake in subcutaneous adipose tissue. The decrease in blood flow in subcutaneous adipose tissue during bleeding was more pronounced than found in other organs with same hemorrhagic shock procedure. After reinfusion, flow in subcutaneous adipose tissue could not be restored, indicating irreversible vascular damage, α-receptor activity seems to play a significant part in the development of vascular and metabolic changes in subcutaneous adipose tissue during bleeding.
Measurement of the Interstitial Pressure in Subcutaneous Tissue in Dogs
Authors: LADEGAARD-PEDERSEN HANS JØRGEN
Published: June 2012

A probe consisting of a cotton thread fitted inside a 15-cm Teflon tube with an inner diameter of 0.8 mm and connected to a transducer was used to measure the interstitial pressure in the subcutaneous tissue in six anesthetized dogs. The measurements were reproducible with a standard deviation of ±0.64 mm Hg. In six dogs the mean pressure in the subcutaneous tissue of the thorax was --2.74 mm Hg (range --3.25 to --1.99 mm Hg). After hemorrhage and dextran (10%) infusion, the mean pressure decreased by 1.70 mm Hg. After infusion of lactated Ringer's solution, the pressure increased to the control values.
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.
Static Elastic Properties of the Left Coronary Circumflex Artery and the Common Carotid Artery in Dogs
Authors: PATEL DALI J. , JANICKI JOSEPH S.
Published: June 2012

Static elastic properties were studied in isolated segments of the left coronary circumflex artery (LCCA) and the right common carotid artery (CA) from 14 dogs at in-vivo values of pressure and length. A microscope with a Filar micrometer was used to measure radius and length. From these data it was possible to study the pressure-radius relationship and compute various anisotropic elastic moduli as well as the strain energy density (SED). Results indicate: (1) Both arteries exhibited hysteresis which could be minimized within two inflation-deflation cycles. (2) The pressure-radius relationship at constant length was essentially linear over a pressure range corresponding to the in-vivo pulse pressure. (3) The value of volume distensibility was 3.4 x 10
-6
cm
2
/dyne for LCCA and 1.5 x 10
-6
cm
2
/dyne for CA. (4) LCCA was more distensible than CA in the circumferential direction. (5) LCCA was stiffer in the longitudinal direction than in the circumferential direction; the reverse was true of CA. (6) SED values at physiologic dimensions were 314 x 10
3
dyne/cm
2
for LCCA and 226 x 10
3
dyne/cm
2
for CA. These values could be reproduced within 6% when the loading procedure was altered.
Blood Fibrinolytic Activity in Man
Authors: ROSING DOUGLAS R. , BRAKMAN PIETER , REDWOOD DAVID R. , GOLDSTEIN ROBERT E. , BEISER G. DAVID , ASTRUP TAGE , EPSTEIN STEPHEN E.
Published: June 2012

This investigation was undertaken in normal subjects to define the relationship between the intensity of exercise and magnitude of fibrinolytic response and to examine the effect of diurnal variations on the exercise response. Fibrinolytic activity was measured on fibrin plates and expressed as mm
2
. Diurnal variations occurred with lowest activity at 8:00
AM
(mean, 66 mm
2
), and peak activity between 5:00 and 8:00
PM
(mean, 266 mm
2
,
P
<0.001). Five minutes of maximal treadmill exercise caused a marked increase in mean activity from 90 to 658 mm
2
(
P
<0.001). Five minutes of 70% maximal exercise produced no significant increase, but 30 minutes increased activity to 626 mm
2
(
P
<0.005). In contrast, 30 minutes of 40% maximal exercise produced a small elevation from 80 to 173 mm
2
(
P
<0.005). Maximal and 40% maximal exercise evoked greater responses at 4:00
PM
than 8:00
AM
. Exercise produces increases in fibrinolytic activity which are related to the relative intensity of exercise, its duration, and the time of day it is performed. Short bursts of intense exercise cause marked increases, but more prolonged bouts of moderate exercise are required to produce similar increases. The increases with prolonged mild exercise are small and comparable to those observed during resting diurnal variations.
Intracellular Calcium and Myocardial Contractility
Authors: SUKO JOSEF , VOGEL JOHN H.K. , CHIDSEY CHARLES A.
Published: June 2012

The function of the sarcoplasmic reticulum of the failing myocardiums was studied in vitro by comparing calcium uptake and calcium-activated ATPase in microsomes prepared from hearts of control calves and calves in which right ventricular failure developed during experimentally induced pulmonary hypertension. The rate of calcium uptake averaged .147 µmole·mg
-1
·min
-1
at 25°C in the presence of oxalate in control preparations and was significantly reduced in preparations from failing right ventricles (avg .086 µmoles·mg
-1
·min
-1
). Calcium-activated ATPase was also diminished significantly in failure (avg .184 compared to .073 µmoles·mg
-1
·min
-1
). Although two preparations also showed diminished calcium activities in the nonfailing left ventricle, group these activities were not significantly depressed in preparations from ventricle in calves with failure. A similar reduction in calcium activities observed at 37°C with preparations further purified by sucrose gradient centrifugation. The uptake capacity of microsomes, measured as calcium uptake in the absence of oxalate, was not diminished in the preparations from failing hearts. Mitochondrial contamination did not appear to be a factor since azide inhibited calcium activity almost completely in mitochondria, whereas inhibition was less than 10% in microsomes of both control and failing hearts. Ouabain had no effect on the microsomes from failing hearts. These studies indicate that there is a defect in calcium transport in microsomes and a functional abnormality of the sarcoplasmic reticulum in the intact myocardial cell in heart failure which could lead to changes in the excitation-contraction coupling mechanisms of clinical importance.
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.
Intraluminal Pressure and Ionic Distribution in the Tail Artery of Rats
Authors: GUIGNARD JEAN-PIERRE , FRIEDMAN SYDNEY M.
Published: June 2012

The relationship between changes in perfusion pressure and ionic transfers in the vascular wall has been studied using the rat tail vascular bed perfused at constant flow rate. Perfusion pressure was increased by elevating venous pressure, or by infusing norepinephrine. The ensuing ionic shifts were monitored by means of Na
+
and K
+
electrodes. In both instances, the rise in pressure was associated with ionic redistribution measured as a gain in K
+
and a loss in Na
+
in the perfusing medium. The increase in pressure showed a close correlation with K
+
efflux from the vascular wall, and a somewhat more variable correlation with Na
+
influx. While the qualitative aspect of the ionic transfers was similar in the two conditions, their size differed. It was much larger during a rise in pressure induced by venous back pressure, in which condition the wall tension was also proportionately larger. The occurrence of ionic transfers in response to changes in transmural distending pressure was confirmed in the isolated artery, perfused in situ. It is suggested that vascular tension is directly related to step levels of transmembrane ionic distribution, and that this distribution is regulated by passive stretch.
Effects of Various Inotropic Interventions on the Dynamic Properties of the Contractile Elements in Heart Muscle of the Cat
Authors: Brutsaert Dirk L. , Parmley William W. , Sonnenblick Edmund H.
Published: June 2012

Force-velocity-length (FVL) relations were obtained by determining the phase-plane tracings of velocity of shortening vs. length during isotonic contractions. These measurements were then replotted in a three-dimensional graph after correction for the series elastic extension during the isometric phase of the contractions as derived from a quick release contraction. On examining the influence of temperature (29° and 37°), preload, frequency of stimulation (12/min and 24-30/min), paired stimulation (PS), calcium (2.5 mM and 7.5 mM), and iso-proterenol (10
-5
M), it was shown that the surface created by the three-dimensional FVL relations of the contractile element (CE) is unique for a given state of contractility. Furthermore, the course of velocity vs. length is determined only by the instantaneous CE length, regardless of the contractile state of the CE, and is independent of the time after stimulation over a large portion of the shortening. From the intersection of the linear load-shortening relation observed for the CE with the load axis the maximum force (P
o
) development of the CE was derived. The highest values of this corrected P
o
(1.80 ± 0.13 kg/cm
2
) were seen following inotropic interventions such as PS, calcium, or isoproterenol. Using the corrected P
o
, truly hyperbolic force-velocity curves were constructed from which V
max
and the Hill equation constants
a
and
b
were derived for the various inotropic interventions.
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.
Longitudinal Gradients in Periarteriolar Oxygen Tension
Authors: DULING BRIAN R. , BERNE ROBERT M.
Published: June 2012

The oxygen tension (Po
2
) on the external surface of arterioles between 8 and 100µ in diameter was measured with oxygen microcathodes (2 to 6µ diameter) in the suffused cheek pouch of hamsters and in the cremaster muscle of hamsters and rats anesthetized with pentobarbital and urethane. Intravascular Po
2
was measured in 10 vessels and compared with extravascular Po
2
. Good agreement was found, with a mean difference of 1.4 ± 0.8 (
SE
) mm Hg. Significant longitudinal gradients were observed in periarteriolar Po
2
. Oxygen tension fell from 35 ± 4 mm Hg on the small arteries (ca. 80µ diameter) to 20 ± 3 mm Hg at the end of the terminal arterioles. These measurements were obtained with a suffusion solution Po
2
of 39 ± 8 mm Hg, a tissue Po
2
of 8 ± 2 mm Hg and femoral arterial blood Po
2
of 69 mm Hg. When the suffusion solution Po
2
was raised to 79 mm Hg, the resultant measurements were 42 ± 3 on the small arteries and 21 ± 3 mm Hg at the end of the terminal arterioles. Similar experiments were carried out while animals were breathing 95% oxygen and the Po
2
of the cheek pouch suffusion solution was 39 mm Hg. Under these conditions, small artery Po
2
was 152 ± 13 mm Hg and terminal arteriolar Po
2
was 37 ± 9 mm Hg. Femoral artery blood Po
2
was 427 ± 12 mm Hg. These data are consistent with the hypothesis that oxygen diffuses from the precapillary vessels and that intravascular Po
2
falls progressively along the resistance vessels. This finding suggests a possible mechanism for the involvement of O
2
in local regulation of blood flow.
Plasma Renin Activity and the Effects of Deoxycorticosterone Acetate in Dogs with Chronic Left Ventricular Overload
Authors: BAUMBER JOHN S. , DAVIS JAMES O. , SCHNEIDER EDWARD G. , JOHNSON J. Alan
Published: June 2012

Chronic left ventricular overload and left heart failure were produced by an aortic-left atrial shunt and superimposed aortic constriction. With the shunt alone, plasma renin activity and sodium balance were normal. Superimposed aortic constriction produced a further elevation in left ventricular end diastolic pressure (LVEDP), increased plasma renin activity and sodium retention occurred. Seven dogs died in pulmonary edema within a week, but nine others recovered with a return in plasma renin activity and sodium excretion to normal. Five of these nine dogs that survived the acute effects of aortic stenosis developed pulmonary edema at least 7 days after aortic constriction; LVEDP was markedly elevated, plasma renin activity was high and sodium retention occurred. Six other dogs with chronic left ventricular overload, but not retaining sodium, were given deoxycorticosterone acetate (DOCA), 15 mg/day, to study the response in renal sodium excretion. In two of the dogs, LVEDP was below 35 mm Hg and the normal "escape" pattern, characterized by return of sodium excretion to the normal control level, was observed. However, in the other four animals, LVEDP was above 35 mm Hg, escape failed to occur and marked sodium retention resulted; a further elevation of LVEDP was observed and pulmonary edema occurred on four occasions. The failure of dogs with marked elevation of LVEDP to escape from DOCA indicates that other factors in addition to the renin-angiotensin-aldosterone system are involved in the sodium retention of left ventricular failure.
Local Regulation of Vascular Cross Section during Changes in Femoral Arterial Blood Flow in Dogs
Authors: LIE MONS , SEJERSTED OLE M. , KIIL FREDRIK
Published: June 2012

Diameters of the exposed femoral artery of anesthetized dogs were continuously measured with ultrasonic elements of lead zirconate titanate. In 13 of 16 dogs vascular diameters increased following a sudden increment in arterial blood flow induced by the injection of vasodilating agents (acetylcholine, histamine) peripheral to the recording level, by opening an arteriovenous shunt, or after tetanic stimulation of the sciatic nerve. The dilatation response occurred despite slight reductions in femoral blood pressure, and was present after ganglionic blockade, blockade of alpha and beta receptors with phenoxybenzamine and propranolol, atropinization and injection of an antihistamine. The dilatation response was also observed after transsection of the femoral artery distal to the recording level and is therefore not dependent on the retrograde propagation of nervous or myogenous impulses along the vascular wall.
Capillary Exchange Modeling
Authors: GORESKY CARL A. , ZIEGLER WILFRED H. , BACH GLEN G. , wangel Brita
Published: June 2012

In the well-perfused visceral organs, active flow occurs in most capillaries, and they are packed closely. In this situation, lateral diffusion equilibration is relatively rapid and the distribution of exchanging materials is governed chiefly by the permeability of the capillary walls. We modeled extravascular distribution of exchanging substances from this kind of capillary and illustrated the changes expected in the outflow profile with increasing permeability, the evolution from the barrier-limited to the flow-limited case. We then examined the two extremes of the assemblies of such capillaries in an organ. In one, the large-vessel transit times are constant and the capillary transit times account for the outflow distribution of the vascular reference substance; in the other, the capillary transit times are constant but the large-vessel transit times vary. The barrier-limited and flow-limited cases corresponding to these are very different. In the case intermediate between these two extremes, the transit times in both the large vessels and the capillaries in the organs vary. If the organ is functionally homogeneous, the distribution of capillaries supplied by each large vessel is the same, and the situation may be described by a product distribution. The formulation for this intermediate case may then be used both to quantify capillary permeability and to describe the distributions of large-vessel and capillary transit times.
Longitudinal Distribution of Blood in the Rabbit in Relation to the Heart, with Observations on the Contribution of Different Organs
Authors: DICKINSON C. John , SECKER Walker ROGER H.
Published: June 2012

The distribution of blood along the length of an animal is relevant to the stability of cardiac filling pressure during tilting. We investigated the longitudinal distribution of blood in conscious, anesthetized, and dead, rabbits by a scanning technique, after labeling red blood cells with
51
Cr. The mean longitudinal distributions of blood were computed after standardization for body size and radioactivity. The longitudinal distribution of blood showed a large main peak near the level of the tricuspid valve. General anesthesia produced very little change in blood distribution, but after death blood left the lower abdomen and accumulated in the upper abdomen, probably in the liver. The liver made much the greatest contribution (25 to 30%) to the total pool of blood, but the blood contained within it was labile and could be largely removed by bleeding the animal, or transferred to the lungs during pulmonary congestion.
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.
Mechanism of Action of Tris (Hydroxymethyl) Aminomethane on the Negative Inotropic Effect of Carbon Dioxide
Authors: GONZALEZ NORBERTO C. , CINGOLANI HORACIO E. , MATTIAZZI ALICIA R. , MARSIGLIA JUAN C. , SERUR JUAN R.
Published: June 2012

Administration of isotonic THAM to the blood of the heart-lung preparation induced a decrease in the negative inotropic effect of CO
2
, suggested by the fact that, at constant stroke work, an increase in P
co
2
of 26 ± 1.9 mm Hg was followed by an increase in left ventricular end-diastolic pressure (LVEDP) of 3.8 ± 0.2 mm Hg before the infusion of THAM; after THAM was given, a similar increase in P
co
2
induced an increase in LVEDP of 1.8 ± 0.2 mm Hg (P<0.01). When pH was increased by 0.15
M
NaHCO
3
, no changes in myocardial contractility or in the tolerance of the heart to CO
2
were found. On the other hand, hemodilution with isotonic sucrose reproduced the effect of THAM. Either sucrose or THAM produced a decrease in plasma Na. Myocardial contractility, previously increased by THAM or sucrose, returned to control after plasma Na was restored. When cat papillary muscles were immersed in Ringer's solution with normal (142 m
M
) and low (112 m
M
) Na concentration, it was observed that a similar increase in P
co
2
originated a smaller decrease in contractility when the muscles were in the low Na solution. It is concluded that the effect of THAM in the present experiments is due, at least to an important extent, to changes in extracellular Na.
Total Systemic Vascular Compliance Measured as Incremental Volume-Pressure Ratio
Authors: SHOUKAS ARTIN A. , SAGAWA KIICHI
Published: June 2012

We developed a method to measure the compliance, defined as ΔVΔP, of the total systemic vascular bed (C
t
) without stopping systemic flow. In 10 open-chest dogs, venous return (and cardiac output) was maintained at a constant level by inserting a perfusion pump (with no reservoir) between the caval veins and the right atrium. About 5% of the estimated total blood volume was withdrawn from the dog within 45 seconds. Resultant changes in central venous pressure were measured 10, 30, 60, 120, and 180 seconds after the volume change. The bled volume was then reinfused to repeat similar venous pressure measurements for another 180 seconds. The measurements were repeated after slightly increasing the blood volume or sectioning the vagi. The mean value of C
t
measured 10 seconds after hemorrhage or reinfusion was 1.96 ± 0.10 (
SE
) ml/mm Hg/kg body weight before vagotomy. Paired
t
-tests indicated no significant difference between measurements of bleeding and reinfusion, measurements with different initial venous pressures or blood volume, or measurements before and after vagotomy. However, C
t
increased with time during the 2-minute period by about 25% of the initial 10-second value (
P
<0.001) and remained constant thereafter.
Cardiac Arrhythmias Simulated by Concealed Bundle of His Extrasystoles in the Dog
Authors: DAMATO ANTHONY N. , LAU SUN H. , BOBB GUSTAVUS
Published: June 2012

In 10 open-chest intact dog hearts, multiple close bipolar electrograms were obtained from various regions of both atria and the bundle of His. The bundle of His was also prematurely stimulated at varying coupling intervals following a sinus beat. At short coupling intervals, the bundle of His stimulus failed to propagate antegradely (no ventricular response) but did propagate retrogradely. Coupled bundle of His stimuli retrogradely concealed within the A-V node caused the next sinus impulse to be delayed or blocked. Types I and II second degree A-V block, 2:1 A-V block, and alternation of the P-R interval were simulated. An atrial (nonconducted) bigeminal rhythm was simulated when the bundle of His stimuli completely traversed the A-V node and completely (inverted P waves) or partially (fusion P waves) depolarized the atria.
Effects of Hypoxia on Pulmonary Vascular Reactivity in Pneumonectomized Puppies and Minipigs
Authors: KATO H. , KIDD L. , OLLEY P. M.
Published: June 2012

Pneumonectomy was performed on 25 1-month old beagle puppies and 13 2-month old minipigs. Three weeks or more later, pulmonary blood flow and pulmonary artery pressure were measured in the survivors and total pulmonary vascular resistance was calculated in each animal. These measurements were made at normal arterial Po
2
and at an arterial Po
2
of 31 ± 5 mm Hg produced by ventilating the animals with 10% oxygen in nitrogen. Seven normal puppies and seven normal minipigs of ages comparable to the pneumonectomized animals were studied as controls. The mean pulmonary artery pressure in the pneumonectomized puppies was not significantly different from that of the normal puppies. There was no significant pulmonary vascular response to hypoxia in the pneumonectomized puppies. The pneumonectomized minipigs had a significantly higher resting mean pulmonary artery pressure than the normals (
P
< 0.005). They did not, however, show a greater reactivity to hypoxia than did their normal litter mates. Both pneumonectomized and normal minipigs were more reactive to hypoxia than puppies. The minipigs were restudied approximately 16 weeks after the initial study. Four out of five animals showed a further rise in resting pulmonary artery pressure. Histological studies showed arteriolar medial hypertrophy in the minipig lungs.
Cerebral Ischemia and Reactive Hyperemia
Authors: SUNDT THORALF M. , WALTZ ARTHUR G.
Published: June 2012

Correlative studies of cortical blood flow measured by the
85
Kr washout technique and observations of the cortical blood vessels of 10 squirrel monkeys subjected to temporary occlusion of the middle cerebral artery are described. During occlusion, cortical blood flow in core areas of ischemia decreased to 0.12 to 0.90 ml/g/min (20 to 50% of preocclusion values) and became pressure dependent with failure of autoregulation. After release of the occluding clip, cortical blood flow was restored. Correlation between degree of vascular reaction judged by observation of the cortex and degree of hyperemia as determined by cortical blood flow was poor. There was incomplete correlation between the degree of hyperemia and the degree of preceding ischemia. Hyperemia, or "luxury perfusion," manifested by red venous blood, appears to be related to failure of cerebral tissue to utilize available oxygen as well as to "reactive" hyperemia, or supernormal blood flow, in regions previously ischemic. There was no demonstrable gradual failure of collateral circulation during occlusion. Cerebral edema was progressive and even progressed after restoration of cortical blood flow; it was incompletely correlated with the degree of ischemia and degree of hyperemia.