bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium Exchange in a Single Layer of Rat Cardiac Cells Studied by Direct Counting of Cellular Activity of Labeled Calcium
Authors: LANGER G. A. , SATO E. , SERAYDARIAN M.
Published: June 2012

Calcium exchange was studied in rat cardiac cells grown in tissue culture. A new technique was employed which depended on the growth of a single layer of cells on the surface of a slide composed of glass scintillator material. The cells remained actively contractile on the glass surface. The pattern of
45
Ca uptake and washout from the preparation was defined and found to be reproducible. Low Na
+
perfusion rapidly augmented
45
Ca uptake in the cultured cells. An increment in
45
Ca uptake (65 µmoles Ca
2+
/kg cells) occurred within 6 seconds of the start of low Na
+
perfusion.
Increased Myocardial Oxygen Consumption and Contractile State Associated with Increased Heart Rate in Dogs
Authors: BOERTH ROBERT C. , COVELL JAMES W. , POOL PETER E. , ROSS JOHN
Published: June 2012

The effects of increasing the frequency of contraction on myocardial oxygen consumption per minute (MV
·
o
2
) were examined in eight dogs using an isovolumic left ventricular preparation. MV
·
o
2
was determined at two to four levels of heart rate in each animal. Peak wall stress was maintained constant in each animal so that changes in it would not influence the effects of heart rate on oxygen consumption per beat. As heart rate was increased, there was a highly significant linear increase in MV
·
o
2
. Oxygen consumption per beat was shown to be a negative linear function of the reciprocal of heart rate. Thus, as heart rate increased there was a significant increase in oxygen consumption per beat; when basal oxygen consumption was subtracted from total oxygen consumption, there was a much larger increase in oxygen consumption per beat. Myocardial contractile state, defined as the maximum observed contractile element velocity at the lowest common level of wall stress, was significantly increased by increasing heart rate. The data suggest that the increased M
·
Vo
2
associated with augmented heart rate is secondary to augmentation of contractile state, as well as to the increase in stress development per minute.
Erythrocyte Velocity and a Velocity Pulse in Minute Blood Vessels on the Surface of the Mouse Brain
Authors: ROSENBLUM WILLIAM I.
Published: June 2012

High-speed microcinematography of vessels in the subarachnoid space of the anesthetized mouse was used to measure the velocity of erythrocytes in arterioles and venules less than 30µ in diameter. Within arterioles the velocity averaged 3.5 mm/sec, while in venules an average value of 1.9 mm/sec was obtained. A rhythmic alteration in velocity was often observed in the arterioles and was seen occasionally in venules. This cyclical change in velocity was termed the "velocity pulse." The frequency of the velocity pulse was virtually identical to that of the peripheral pulse and is believed to result from a propagation of that pulse into the microcirculation. The velocity pulse was not recognizable in vessels 5µ to 10µ wide. In vessels 10µ, to 30µ, in diameter, the velocity pulse was not accompanied by changes in the width of the vessels.
Myocardial Connective Tissue Metabolism in Response to Injury: HISTOLOGICAL AND CHEMICAL STUDIES OF MUCOPOLYSACCHARIDE AND COLLAGEN IN RAT HEARTS AFTER ISOPROTERENOL-INDUCED INFARCTION
Authors: JUDD JOSEPH T. , WEXLER BERNARD C. , WILLIAMSON GEORGE , BICKERS MARY , SPRINGS MYRA
Published: June 2012

Arteriosclerotic and nonarteriosclerotic rats were given isoproterenol sufficient to cause massive myocardial injury. Hearts, livers, and kidneys were taken for analysis of the connective tissues at various intervals. Mucopolysaccharide was identified as Hale-positive material digestible with testicular hyaluronidase. Hexosamine and hydroxyproline were determined by chemical means. The changes in the connective tissue following infarction were divided into two phases. The first, occurring 1 to 2 days after the induction of necrosis, was characterized by extensive edema, accumulation of hexosamine, and by histologically demonstrable mucopolysaccharide. The second phase, 3 to 7 days after infarction, was characterized by changes typical of wound healing in general, involving both mucopolysaccharide and collagen deposition in foci of myocardial scar tissue formation. The increase in hexosamine was the same in arteriosclerotic breeder animals, which required one-half the dose of isoproterenol, as in virgin animals receiving the full dose of isoproterenol. Since the dose was selected to produce relatively the same degree of necrosis in each type of animal, it was thought that the increase in hexosamine was directly related to the injury and not to the isoproterenol
per se
. No comparable increase in hexosamine was observed in either the liver or kidney.
Blood Flow in Cutaneous Tissue in Man Studied by Washout of Radioactive Xenon
Authors: SEJRSEN PER
Published: June 2012

Washout of
133
xenon from a local depot in cutaneous tissue has been investigated in man to develop a method for blood flow measurement in that tissue. The tissue was labeled both by injecting
133
xenon in saline solution intracutaneously and by a nontraumatic epicutaneous application technique. The initial selectivity of the labeling and the subsequent accumulation of
133
xenon in subcutaneous tissue were examined by radioautography and by a special tissue separation technique. From the observations a two-compartment clearance model is suggested by which the cutaneous blood flow can be obtained separately from that of the subcutaneous tissue. Blood flow in the cutaneous tissue in the lateral region of the leg was 5.7 (SD 1.3) ml/100 g
·
min at an ambient temperature of 19° to 22°C. There were variations between different skin sites.
Pressure-Flow Relationships in the Coronary Circulation
Authors: Fam Wadie M. , McGregor Maurice
Published: June 2012

This study was designed to define more accurately the respective influences of perfusion pressure and flow on coronary resistance. Resistance in a coronary branch, perfused at constant flow, was reduced immediately following temporary perfusion arrest. Large epicardial arteries did not appear to take part in this reaction. In the first 10 to 15 seconds after flow was restored, resistance for that flow was uninfluenced by the duration of the preceding perfusion arrest. That mechanism which caused coronary resistance to fall as a result of metabolic factors, such as reduced availability of oxygen, was thus maximally activated. By observing the relationship of coronary resistance to perfusion pressure at this time, it could be shown that resistance vessels and their surrounding structures showed little evidence of distensibility (resistance constant from 20 to 60 mm Hg). The difference between resistance at steady state and resistance at maximal vasodilatation defines the extent of vasomotion attributable at any flow rate to metabolic factors. Perfusion with venous blood caused a fall of resistance which was greater at any flow rate than could be accounted for by the differences in oxygen delivery rate.
Changes in the Pulmonary Circulation after Bronchial Occlusion in Anesthetized Dogs and Cats
Authors: Barer Gwenda R. , Howard Peter , McCurrie Janice R. , Shaw John W.
Published: June 2012

The effects of bronchial occlusion on the pulmonary circulation were studied in anesthetized cats and dogs. Immediately after occlusion, blood flow fell rapidly at normal pulmonary arterial pressure (–71% cats, –54% dogs), and in constant flow perfusion experiments, perfusion pressure rose (+50% cats, +28% dogs). These resistance changes were reversed by vasodilator drugs, alkali, or perfusion of the lung with arterial blood. We concluded that an active mechanism, probably an increase in vasomotor tone, was involved; a mechanical process would not be reversed in this way. Pulmonary venous Po
2
was the factor most closely related to the increase in resistance. In collapsing "oxygen-filled" lobes, compared with "air-filled" lobes the resistance change was delayed until the pulmonary venous Po
2
fell. Hypoventilation and ventilation with hypoxic mixtures causing a fall in pulmonary venous Po
2
similar to that due to collapse caused equivalent changes in blood flow. Changes in pH, Pco
2
and lung volume played a relatively minor role in resistance changes following collapse. The increase in resistance may be caused by a mechanism regulating ventilation-perfusion ratios in both normal and diseased lung.
Static Anisotropic Elastic Properties of the Aorta in Living Dogs
Authors: Patel Doli J. , Janicki Joseph S. , Carew Thomas E.
Published: June 2012

Static anisotropic elasticity was studied in the middle descending thoracic aorta of 14 living dogs. Special transducers were used to measure radius and longitudinal stress at several pressures in situ in an isolated vessel segment. From these data, moduli describing elastic properties of the vessel wall were calculated. Results indicate that (1) at a physiologic pressure of 154 cm H
2
O (extension ratio of 1.52 circumferentially) the mean values for the incremental elastic moduli in the radial, circumferential, and longitudinal directions were 5480, 7510, and 10,100 g/cm
2
, respectively; (2) these moduli increased with an increase in intravascular pressure; and (3) the longitudinal modulus decreased when the vessel was studied in vitro (from the removal of longitudinal tethering).
Myocardial Connective Tissue Metabolism in Response to Injury
Authors: JUDD JOSEPH T. , WEXLER BERNARD C. , Williamson George , Boyer Jacob
Published: June 2012

Myocardial necrosis was produced in rats by administering isoproterenol, and the increase in hexosamine-containing materials in the injured myocardium was investigated. Total hexosamine, galactosamine, neutral sugars, and uronic acids were determined on various fractions isolated from the hearts. Mucopolysaccharides were precipitated as the cetyl pyridinium chloride complex and fractionated according to their solubility in NaCl solutions. Of the hexosamine in the heart, approximately 50% was retained after proteolytic digestion and dialysis. Approximately one-fourth to one-third of the nondialyzable hexosamine was in mucopolysaccharides. The hyaluronic acid fraction of the mucopolysaccharides increased during the early edematous reaction observed in the hearts. The chondroitin sulfate fraction increased in conjunction with the beginning fibrinogenic processes and remained elevated during repair. There was evidence that the glycoproteins may be involved in the myocardial necrosis and repair.
Coronary Vascular Effects of Glucagon in the Isolated Dog Heart
Authors: MOIR THOMAS W. , NAYLER WINIFRED G.
Published: June 2012

Glucagon decreases peripheral vascular resistance by direct action on the arterioles. The present experiments were performed to study the effect of glucagon on the coronary resistance vessels. In isolated hearts from eight dogs the coronary arteries were perfused at a constant rate and the change in coronary pressure was used as an index of change in resistance after the intracoronary injections of glucagon (50 µg/kg). In the beating heart, glucagon caused a 22% decrease in the average coronary pressure (from 102 to 80 mm Hg); however, with this decrease in coronary resistance, myocardial contractility rose an average of 45% (from 11 to 16 units), the average heart rate increased 38% (from 156 to 213 beats/min), and the average coronary venous oxygen saturation decreased from 79.7% to 63.7%. However, when similar intracoronary injections of glucagon were made after cardiac arrest by potassium there was no change in coronary venous oxygen saturation and no significant decrease in coronary pressure. We conclude that the decrease in coronary resistance in the beating heart after glucagon injection is secondary to the metabolic effects of the increased myocardial contractility and heart rate, and that there is no significant direct vasodilating effect on the coronary resistance vessels.
A Sensitive Double-Isotope Derivative Assay for Norepinephrine and Epinephrine
Authors: ENGELMAN KARL , PORTNOY BARRY , HURLEY NANCY
Published: June 2012

A sensitive and specific double-isotope dilution method for assaying norepinephrine and epinephrine separately is described. The method is based on enzymatic conversion of these two catecholamines to their respective metanephrines and was applied successfully to measurement of resting plasma concentrations of norepinephrine and epinephrine in normal subjects with the finding that norepinephrine (0.20 ± 0.08 µg/liter) normally constitutes approximately 80% of the plasma catecholamine content and epinephrine (0.05 ± 0.03 µg/liter) 20%.
Propagated Vasodilation in the Microcirculation of the Hamster Cheek Pouch
Authors: DULING BRIAN R. , BERNE ROBERT M.
Published: June 2012

Propagated vasodilation has been observed in the peripheral vasculature and may be significant in integrating the behavior of terminal arterioles and larger vessels. We have studied the characteristics of propagated vasodilation induced by acetylcholine in the microcirculation of the cheek pouch of the golden hamster. The technique of microionophoresis was used as a means of achieving relatively precise temporal and spatial application of drugs to single arterioles. Application of acetylcholine to an arteriole usually resulted in vasodilation which spread rapidly upstream and downstream from the point of application at a rate much greater than could be accounted for by diffusion or by other means of movement of the agent. Longitudinal propagation velocities for a series of arterioles 20 to 40µ in diameter averaged 0.02 cm/sec. The propagated response was relatively specific, being induced by acetylcholine but not by histamine, K
+
, H
+
, or eledoisin. The response was graded in both extent and magnitude, was propagated bidirectionally from the point of origin, was observed in vessels as small as 15µ o.d., and could be blocked by lidocaine.
Contractility in Isolated Mammalian Heart Muscle after Acid-Base Changes
Authors: CINGOLANI HORACIO E. , MATTIAZZI ALICIA R. , BLESA ENRIQUE S. , GONZALEZ NORBERTO C.
Published: June 2012

In-vitro experiments performed in cat papillary muscles and strips of rat right ventricle suggest that the changes in myocardial contractility that follow acid-base disturbances are not a function of extracellular pH. Simultaneous changes in Pco
2
and NaHCO
3
concentration, with extracellular pH constant, decreased developed tension and maximal rate of rise of the tension (dT/dt) without significant changes in the time to peak tension when the muscle was exposed to the solution with higher Pco
2
and NaHCO
3
concentration. At an extracellular pH of 7.40, developed tension decreased 0.51 ± 0.13 g/mm
2
(
P
< 0.02) and dT/dt decreased 1.29 ± 0.50 g/sec (
P
< 0.05) with no significant change in time to peak tension (0.038 ± 0.022 sec). Changes in pH produced by increasing Pco
2
at constant NaHCO
3
concentration were followed by a significant decrease in contractility. A change of Pco
2
from 20 to 90 mm Hg that produced a change in extracellular pH from 7.60 to 7.00 was accompanied by a decrease in developed tension of 0.67 ± 0.14 g/mm
2
(
P
< 0.01), in dT/dt of 2.63 ± 0.54 g/sec (
P
< 0.01) with no changes in time to peak tension (0.0017 ± 0.10 seconds). We were unable to show significant variations in contractility when extracellular pH was changed at a constant Pco
2
of approximately 21 mm Hg (NaHCO
3
7.5, 15, and 30 m
M
) or at a Pco
2
of approximately 95 mm Hg (NaHCO
3
15, 30, 60, 80 and 120 m
M
). Only when extracellular pH reached a value as high as 8.0 (Pco
2
21 mm Hg, NaHCO
3
80 m
M
) a small but significant increase in contractility was evidenced. Either Pco
2
or intracellular pH could be the major determinants of the changes in myocardial contractility that follow acid-base alterations.
Effects of Adenosine Compounds on Renal Function and Renin Secretion in Dogs
Authors: TAGAWA HITOSHI , VANDER ARTHUR J.
Published: June 2012

In anesthetized salt-depleted dogs, infusion of adenosine (20 to 500 µg/min) directly into a renal artery induced an initial decrease of renal blood flow for 1 to 2 minutes but did not change or slightly increased this flow during the steady state. Statistically significant decreases occurred in glomerular filtration rate, filtration fraction, sodium excretion, and renal venous renin activity. Calculated afferent arteriolar resistance increased and efferent resistance decreased. 5'-AMP (50 to 200 µg/min) induced changes which were smaller but qualitatively similar to those of adenosine. ATP (50 to 500 µg/min) induced no initial reduction in blood flow, and, during the steady state, caused a significant increase in blood flow and decreases in glomerular filtration rate, filtration fraction, sodium excretion, and renal venous renin. Efferent resistance decreased but afferent resistance did not change. Cyclic AMP (1 to 5 mg/min) caused a very small initial transient reduction in blood flow but induced changes similar to those of ATP during the steady state. Inosine (200 µg/min) and inosine-5'-monophosphate (50 to 200 µg/min) produced no detectable effects. It is suggested that adenosine or 5'-AMP may be normal mediators of both autoregulation and renin secretion.
Frequency Function of Transit Times through Dog Pulmonary Circulation
Authors: MASERI ATTILIO , CALDINI PAOLO , PERMUTT SOLBERT , ZIERLER KENNETH L.
Published: June 2012

The frequency function of transit times through the pulmonary vascular system in dogs was obtained by deconvolution of a pair of simultaneous tracer dilution curves. One tracer dilution curve represented transit times from pulmonary artery to aorta; the other represented transit times from left atrium to aorta. Theory of and requirements for deconvolution are presented. Two preparations were used: closed chest with recirculation, open chest with only myocardial recirculation. The frequency function of pulmonary vascular transit times was skewed markedly to the right. At constant cardiac output and left atrial pressure it was unaffected by change in heart rate or by respiratory movements. Frequency functions of transit time obtained by deconvolution of observed tracer concentration curves, including recirculation, were compared with those obtained by monoexponential extrapolation of the same tracer concentration curves to "eliminate" recirculation. If recirculation seemed to appear before the observed concentration curve (aortic sampling following pulmonary arterial injection) fell to 20% of peak, monoexponential extrapolation led to a 10% overestimate of mean transit time and to greater errors in estimate of higher moments. If recirculation did not seem to occur until the concentration fell to 10% or less of peak, there was no difference between the frequency functions of transit times calculated by the two methods. Increased coefficients of variance and skewness were associated with large mean transit times produced by hypovolemia and reduced cardiac output secondary to withdrawal of blood.
Arterial Wall Vibration Distal to Stenoses in Isolated Arteries of Dog and Man
Authors: FOREMAN JOHN E. K. , HUTCHISON KENNETH J.
Published: June 2012

It has been suggested that poststenotic weakening of arterial walls is caused by arterial wall vibration and structural fatigue initiated by pressure disturbances in turbulent blood flow. We examined the frequency spectra of wall vibration downstream from experimental arterial stenoses and compared them with the natural resonant vibration characteristics of the artery walls.

Spectra of arterial wall displacement of isolated perfused dog and human arteries were measured with a noncontacting capacitance transducer during conditions of fluid flow through the artery; resonant vibration characteristics were determined during pure sine and random sound stimulation of the artery walls in the absence of flow.

It is concluded that fluid flow through isolated arteries with an experimental stenosis excites the artery wall to vibrate over a wide range of frequencies within which are discrete frequencies that coincide with the resonant frequencies of the artery wall.
Dual Adrenergic and Cholinergic Innervation of the Cerebral Arteries of the Rat
Authors: IWAYAMA T. , FURNESS J. B. , BURNSTOCK G.
Published: June 2012

The innervation of the anterior cerebral artery of the rat was examined by electron microscopy and by the fluorescence method for localizing adrenergic nerves. Two groups of axon bundles were associated with the artery; one at the outer margin of the adventitia (
periadventitial
bundles) and the other within the adventitia or at the adventitia-media border (
adventitial
bundles). Periadventitial bundles consisted of nonmyelinated axons (0.1-2µ diam), some of which contained synaptic vesicles; in some bundles, myelinated axons were seen. Adventitial axons often contained many synaptic vesicles and were free of Schwann cell sheath in areas apposed to smooth muscle cells. The closest observed approach of axon to muscle cell was 800 A. No nerve fibers penetrated the medial muscle. After fixation with glutaraldehyde plus osmium, large (1000 A) granular and small (500 A) agranular vesicles were seen within many axon profiles. Small granular vesicles were rare. After permanganate fixation, terminal axons contained (besides large granular vesicles) either predominantly small granular vesicles or exclusively small agranular vesicles. Two days after sympathetic denervation, no axons containing small granular vesicles and no fluorescent fibers were seen. Adrenergic fibers were readily identified after injection of rats with 6-hydroxydopamine; small vesicles of adrenergic axons contained highly opaque granular cores, even in osmium-fixed material. Axons containing small agranular vesicles after 6-hydroxydopamine were considered cholinergic. The density of granulation of the large vesicles of adrenergic, but not cholinergic, axons was considerably enhanced following 6-hydroxydopamine. Both adrenergic and cholinergic axons come into close relationship with smooth muscle cells.
Effects of Intra-Aortic Balloon Counterpulsation on Cardiac Performance, Oxygen Consumption, and Coronary Blood Flow in Dogs
Authors: POWELL WM. JOHN , DAGGETT WILLARD M. , MAGRO ALFRED E. , BIANCO JESUS A. , BUCKLEY MORTIMER J. , SANDERS CHARLES A. , KANTROWITZ ARTHUR R. , AUSTEN W. GERALD
Published: June 2012

The effect of intra-aortic Counterpulsation (IACP) with a balloon upon myocardial oxygen consumption (MV
·
o
2
), coronary blood flow (TCF), and left ventricular performance was studied in 23 anesthetized canine right heart bypass preparations at constant heart rate and cardiac output. In nonhypotensive, nonTCF-limited preparations, IACP produced a fall in left ventricular peak systolic pressure (LVP) and a decrease in MV
·
o
2
(-1.1 ± 0.2 (SE) ml/min/100 g LV). In these animals there was little steady state change in TCF (-5.6±5.9 ml/min), secondary to autoregulation by the coronary vascular bed. Left ventricular end-diastolic pressure (LVEDP) fell if elevated but exhibited little change if initially normal.

However, in hypotensive preparations, in which left ventricular performance was substantially limited by a decreased TCF, IACP produced a striking increase in TCF (+40.9 ± 8.6 ml/min) accompanied by an increase in MV
·
o
2
(+1.2±0.3 ml/min/100 g LV). Elevated LVEDPs fell substantially toward normal. Directionally similar changes in LVEDP could be produced by increasing TCF alone in the absence of balloon pumping. When TCF was maintained constant in the hypotensive, TCF-limited preparation, IACP produced a fall in peak LVP and LVEDP.

These data document two effects of intra-aortic balloon Counterpulsation upon cardiac dynamics: (1) IACP can decrease left ventricular peak systolic pressure and LVEDP independent of changes in coronary flow; (2) a major effect of IACP in the hypotensive, failing, TCF-limited preparation is to improve cardiac performance by increasing TCF with an associated increase in MV
·
o
2
.
Hydrodynamic Forces in Dissecting Aneurysms
Authors: PROKOP EDWARD K. , PALMER ROGER F. , WHEAT MYRON W.
Published: June 2012

It has been argued that pulse wave characteristics are important factors in extension and rupture of acute dissecting aneurysms. To test this, a standard model of an aorta was constructed, consisting of an outer layer of Tygon tubing and an inner layer of rubber cement. An "intimal tear" was produced and the "aorta" was subjected to nonpulsatile and pulsatile flow with increasing increments of pressure.

With nonpulsatile flow alone (97 experiments) no dissection occurred at pressures up to 400 mm Hg. Pulsatile flow produced rapid and usually complete dissection with a maximum systolic pressure of 120 mm Hg.

The extent of dissection per pulse was related to dp/dt
max
in the fluid. No dissection occurred until a critical value of dp/dt
max
(790 mm Hg/sec) was reached. Dog aortas were then used in place of the Tygon tube "aorta" with similar results; i.e., dissection did not occur with nonpulsatile flow, but did occur with pulsatile flow (3800 mm Hg/sec). The dissecting dog aorta ruptured to the outside or reentered the vessel lumen.

It was concluded that pulse wave characteristics, particularly dp/dt
max
, are important in the propagation of dissection.
Evaluation of the Early Extraction Method of Determining Capillary Permeability by Theoretical Capillary and Organ Models
Authors: LEVITT DAVID G.
Published: June 2012

The early extraction method of measuring capillary permeability was evaluated with theoretical models of capillaries and organs. The organs consisted of feeder lines and a capillary bed that was either homogeneous or heterogeneous with respect to capillary length or flow. The capillary permeability of the model organ determined by the early extraction method was compared with the actual permeability of the capillaries from which the organ was constructed. The main results of this analysis are: (1) If all the capillaries are identical and if the extravascular volume of distribution of the diffusible indicator is at least three times as large as the capillary volume, then the early extraction method provides a satisfactory measure of the capillary permeability. (2) If the capillaries are identical but the extravascular volume is about the same size as the capillary volume, then the early extraction method can lead to a qualitative underestimate of the permeability, namely assigning a significant diffusion limitation to a substance which is actually flow limited. (3) If the capillaries are not identical, either through differences of flow or length, then the early extraction method can again lead to the assignment of a significant diffusion limitation to a substance which is actually flow limited.
Circulatory and Humoral Changes in the Reversal of Renovascular Hypertension in Sheep by Unclipping the Renal Artery
Authors: FUNDER J. W. , BLAIR-WEST J. R. , CAIN M. C. , CATT K. J. , COGHLAN J. P. , DENTON D. A. , NELSON J. F. , SCOGGINS B. A. , WRIGHT R. D.
Published: June 2012

The renal arterial clip was removed from 11 sheep with chronic experimental renovascular hypertension (previous unilateral nephrectomy, unilateral renal arterial constriction for 3 to 8 weeks, blood pressure elevated and stable). In five animals cardiac output, blood volume, plasma [Na
+
], and plasma renin concentration were measured the day before, 1 day after, and 4 days after unclipping. In the other six animals, plasma [Na
+
], plasma renin concentration, and blood angiotensin concentration were determined before and after unclipping. After unclipping, blood pressure returned to normal levels in 24 to 96 hours; cardiac output and blood volume were essentially unaltered during the period of observation. No natriuresis was seen, nor any change in plasma [Na
+
], plasma renin concentration, or blood angiotensin concentration, which remained within the appropriate normal ranges throughout. Nephrectomy of five similarly hypertensive animals, and six previously unilaterally nephrectomized normotensive sheep, was performed as a control. Variables similar to those measured before and after unclipping were determined at similar time intervals. The second nephrectomy of hypertensive animals was followed by maintained hypertension; and of normotensive animals by maintained normotension. The role of the kidney in the maintenance and reversal of chronic experimental renovascular hypertension is evaluated in the light of these results.
Effect of Heart Rate on Electrically Induced Repetitive Ventricular Responses in the Digitalized Dog
Authors: HAGEMEIJER FRANS , LOWN BERNARD
Published: June 2012

After recovery from acetylstrophanthidin-induced ventricular tachycardia, a repetitive ventricular response (RVR) following a single diastolic stimulus could be elicited for 22 minutes. With atrial pacing at the maximum ventricular follow rate, RVR was obtainable for 70 minutes. A pause in pacing also evoked a ventricular ectopic beat; however, this persisted for only 27 minutes. The minimum heart rate required for RVR was always less than the minimum rate required for pause-induced ectopic beats. Extrasystoles following a pause during pacing, RVR in sinus rhythm, and RVR during rapid heart rates represent decreasing levels of ventricular automaticity corresponding to progressive dissipation of digitalis intoxication. The underlying mechanism for RVR probably is due to net loss of intracellular potassium, which can be induced both by digitalization and by rate acceleration.
Potentiation by Anticholinesterases of the Response of Rat Mesenteric Arteries to Sympathetic Postganglionic Nerve Stimulation
Authors: MALIK KAFAIT U.
Published: June 2012

The anticholinesterase agents, physostigmine, neostigmine, and diisopropylfluorophosphonate were studied for their effect on the vasoconstrictor responses of perfused mesenteric arteries of rat produced by stimulation of their sympathetic postganglionic nerves. The experiments were performed at 30°C. All three anticholinesterase drugs greatly potentiated the vasoconstrictor response to nerve stimulation at a frequency of 1/sec, increased it less at a frequency of 2/sec, and still less at a frequency of 3/sec. At a frequency of 6/sec, there was practically no increase. The infusion of physostigmine potentiated slightly the response to injected norepinephrine, whereas the infusion of neostigmine or diisopropylfluorophosphonate did not alter the response to injected norepinephrine. The increase in response to adrenergic nerve stimulation produced by anticholinesterase agents was interpreted to be due to the inactivation of cholinesterase, thereby causing an increased accumulation of acetylcholine which in turn liberated more norepinephrine from the sympathetic postganglionic fibers.
Role of Lysosomes in the Pathogenesis of Splanchnic Ischemia Shock in Cats
Authors: GLENN THOMAS M. , LEFER ALLAN M.
Published: June 2012

Splanchnic arterial occlusion (SAO) for 2 hours followed by release of the occlusion in cats produced a lethal shock state characterized by cardiovascular collapse. Release of the occlusion resulted in a 45% fall in mean arterial blood pressure within 15 minutes; postrelease survival of these animals was 46 minutes. The plasma of cats with SAO shock exhibited a 3- to 4-fold increase in activities of the lysosomal enzymes β-glucuronidase and cathepsin, accompanied by accumulation of a myocardial depressant factor. Plasma from cats treated with methylprednisolone (20 mg/kg) prior to occlusion did not have significant levels of myocardial depressant factor nor significant increases in plasma lysosomal enzyme activity. Furthermore, the fall in mean arterial blood pressure in steroid-treated animals was significantly smaller when the occlusion was released and postrelease survival time was significantly longer. Pancreatic lysosomes from cats with SAO exhibited a marked increase in fragility as indicated by a reduction in total lysosomal enzyme activity and an increase in the percent of free enzyme activity, compared to lysosomes from cats with sham SAO or steroid-treated cats. These data indicate that the biochemical and hemodynamic alterations present in SAO-induced shock may be related to the disruption of pancreatic lysosomes and that glucocorticoids can markedly alter the course of this shock, possibly by decreasing the sensitivity of pancreatic lysosomes to splanchnic ischemia.
Protective Role of Increased Myocardial Glycogen Stores in Cardiac Anoxia in the Rat
Authors: SCHEUER JAMES , STEZOSKI S. William
Published: June 2012

To determine whether increased glycogen stores might protect the heart against anoxia, experiments were performed in the isolated perfused rat heart. Marked differences in cardiac glycogen were produced by comparing hearts from rats previously treated with reserpine with hearts from control rats. Lesser differences in cardiac glycogen were produced in hearts by perfusing them for 15 minutes without glucose (0 mM glucose) or with 20 mM glucose. Both groups were then studied during a 5-minute anoxic cycle with 5 mM glucose as the exogenous substrate. Hearts from the reserpine-treated rats had higher left ventricular pressures, maximal rate of left ventricular pressure rise, and lactate output after 2 minutes of anoxia than the hearts from control rats. Similar but less marked mechanical differences were observed between 0 mM glucose and 20 mM glucose hearts. The mechanical differences during anoxia between the two groups were not abolished by simultaneous L-norepinephrine administration. Hearts with greater initial glycogen stores had higher glycogenolytic rates, and proportionately more lactate was produced from glycogen than from glucose. Thus, anaerobic ATP production per mole of hexose was greater in hearts with higher glycogen stores. Calculated ATP production was also greater in hearts from the reserpine-treated rats than in those from control animals.

These studies demonstrate that both marked and minor elevations in cardiac glycogen are associated with greater glycolytic reserve and improved mechanical resistance to anoxia. This appears to be mainly due to enhanced glycogenolysis and anaerobic ATP production.
Hypercoagulability Induced by Hyperlipemia in Rat, Rabbit and Man
Authors: Renoud S. , Lecompte S.
Published: June 2012

Feeding a butter-rich diet to rats induced a "hypercoagulable state," since multiple large thrombi were observed in response to injection of
S. typhosa
endotoxin but the same stimulus was ineffective in rats fed a corn oil-rich diet or laboratory chow. In vitro hypercoagulability was noted in blood from the butter-fed rats, the recalcification plasma clotting time (PCT) being reduced by 34 to 45% in comparison with the controls. When a phospholipid suspension replaced the platelets in the plasma clotting test, the reduction was only 5 to 15%, but it was 31 and 43% when the platelets of these rats were washed and resuspended in a given standard plasma. Since lipid extract of these platelets could largely reproduce their activity, the factor involved must have been factor 3.

A similar result was obtained in rabbits fed a butter or corn oil diet, or laboratory chow, indicating that, in this species also, the hypercoagulability in response to hyperlipemia was largely due to factor 3. In addition, in rats and rabbits fed butter, the platelets were more susceptible to thrombin-induced aggregation.

In 27 human subjects of either sex and various ages, the state of coagulability as determined by the PCT was also mostly related to the platelet factor 3 activity, which was negatively correlated with serum cholesterol.
Epicardial Coronary Artery Compliance in the Dog
Authors: DOUGLAS JOHN E. , GREENFIELD JOSEPH C.
Published: June 2012

The dynamic compliance of 21 coronary arteries from 17 dogs was determined in situ. Intramyocardial portions were occluded with a mixture of 200µ glass beads and liquid silicone. To simulate in vivo pressure-volume conditions, 0.1 ml of saline was injected in 150 to 240 msec at a rate of 30 pulses/min. Silicone casts of the vessels, made at 100 mm Hg distending pressure, were used as a reference volume. The results indicate that the dynamic compliance decreases as the initial distending pressure rises. The change in volume for a 50 mm Hg pressure increment (initial distending pressure of 100 mm Hg) was 3.7 ± 0.6% (mean ± SE). In four dogs, phasic flow in the left circumflex coronary artery was measured. The volume of systolic flow per beat during the control state was of the same order of magnitude as the compliance of the vessels; however, during reactive hyperemia, systolic coronary flow markedly exceeded the dynamic compliance of the coronary vessels. In six dogs the static compliance of a segment of coronary artery was obtained radiographically. A 30.1 ± 1.4% change in volume occurred when the intravascular pressure was increased from 70 to 120 mm Hg.
Evaluation of Increased Norepinephrine Excretion in Hypertension Using L-Dopa-
3
H
Authors: DEQUATTRO VINCENT
Published: June 2012

Four hypertensive patients with features of sympathoadrenal hyperactivity similar to those of patients with pheochromocytoma had rates of excretion of norepinephrine plus epinephrine (µg/day) of 135 ± 13 (mean ±
SE
) compared with 441 ± 59 in five patients with pheochromocytoma and 53 ± 7 in six patients with primary hypertension. The specific activities of urinary norepinephrine and the half-life of the rate of their decline were determined for each patient for 24 hours after intraneuronal labeling of norepinephrine using
L
-dopa-
3
H. The initial specific activities of norepinephrine (dpm/mµmole) and the half-life of the rate of their decline (hours) for the three groups were 2,920 ± 670 and 3.8; 291 ± 89 and 4.2; and 6.782 ± 1,003 and 6.0, respectively. However, the observed differences in the half-life values were not significant. The findings indicated that the rate of release and excretion of newly synthesized norepinephrine was increased in patients with hypertension and sympathoadrenal hyperactivity. Less than 1% of the infused
L
-dopa-
3
H was converted to norepinephrine in the chromaffin tumors of patients with pheochromocytoma, resulting in low specific activities of urinary norepinephrine; this may be of diagnostic value in hypertensive patients who have equivocally increased rates of norepinephrine excretion. The autonomic hyperactivity, hypertension, and excessive norepinephrine excretion in the four patients without pheochromocytoma may have been related to unidentified forms of stress.
Conduction of the Cardiac Impulse
Authors: CRANEFIELD PAUL F. , KLEIN HERMAN O. , HOFFMAN BRIAN F.
Published: June 2012

Depressed excitability and responsiveness were created in excised bundles of canine Purkinje fibers. A segment 8 mm long was depressed by being encased in agar containing 47 m
M
K
+
, the ends of the bundle outside the agar remaining normal. Either normal end could be excited through extracellular electrodes. Action potentials were recorded by intracellular microelectrodes at each end and within the depressed segment. Conduction velocity within the depressed segment fell as low as 0.05 m/sec. Abnormalities of impulse transmission through the depressed segment included delay, 2:1 block, higher degrees of block, rate-dependent block, and block showing the Wenckebach phenomenon. Asymmetries of conduction seen included one-way block. Action potentials in the depressed segment were of low amplitude and showed slow upstrokes. Variations in action potential duration occurred in the depressed segment when conduction failed or was very slow and when impulses were dropped. Delay in conduction too great to result simply from a slow upstroke is attributed to summation of excitatory events across regions of block in a syncytium of cells. The results prove that conduction delays great enough to permit re-entry can occur in short segments of Purkinje fibers subjected to high K
+
.
Effect of Ischemia and Antianginal Drugs on the Distribution of Radioactive Microspheres in the Canine Left Ventricle
Authors: BECKER LEWIS C. , FORTUIN NICHOLAS J. , PITT BERTRAM
Published: June 2012

Radioactive microspheres were used to estimate the changes in regional myocardial blood flow occurring during acute myocardial ischemia. Carbonized 15-µ spheres were injected into the left atrium of 28 open-chest dogs and the radioactivity of selected areas determined after sacrifice. Acute occlusion of the left circumflex coronary artery produced a significant diminution in the proportion of microspheres reaching the circumflex area. In addition, there was a disproportionate decrease in endocardial radioactivity in the ischemic area (endocardial/epicardial radioactivity ratio falling from 1.17 to 0.76, P < 0.001) but not in the nonischemic area. Both nitroglycerin (0.4 mg) and propranolol (1 mg/kg) failed to cause a significant change in the ratio of circumflex to descendens radioactivity during ischemia. They did, however, cause a significant increase in the ratio of endocardial to epicardial radioactivity in both ischemic and nonischemic areas.
Effects of Immunosympathectomy on Development of High Blood Pressure in Genetically Hypertensive Rats
Authors: CLARK DAVID W. J.
Published: June 2012

Newborn male rats from the New Zealand colony with genetic hypertension (hypertensive rats) and from a normotensive colony (controls) were immunosympathectomized by injections of antiserum to nerve growth factor. Blood pressure of immunosympathectomized hypertensive rats aged 63 days (128±2 mm Hg) was significantly less (
P
<.001) than that of untreated hypertensive rats (176±3 mm Hg) of the same age. Pressure of immunosympathectomized controls aged 63 days (107±2 mm Hg) was significantly less (
P
<.001) than that of untreated controls (126±1 mm Hg) at the same age. Pressure thereafter remained near these levels. In immunosympathectomized rats, ganglion blockade with supramaximal doses of hexamethonium still induced a lar51ge fall in pressure which was significantly lower than in untreated rats. The combination of immunosympathectomy and hexamethonium brought the pressure of hypertensive rats and controls down to the same level (68 mm Hg). The pressor response to intravenous norepinephrine was greater in immunosympathectomized than in untreated rats. Resistance to flow in perfused mesenteric arteries from immunosympathectomized hypertensive rats was significantly less (
P
<.05) than in arteries from untreated hypertensive rats. Hearts of immunosympathectomized hypertensive rats were significantly lighter (
P
<.01) than those of untreated hypertensive rats. Heart rates of hypertensive or control rats were not altered by immunosympathectomy.
Etiology of Pulmonary Artery Dilatation and Hilar Dance in Atrial Septal Defect
Authors: BOUGHNER DEREK R. , ROACH MARGOT R.
Published: June 2012

Atrial septal defect is associated with increased diameter and pulsation of the pulmonary arteries. The high pulmonary flow rate produces turbulence and a murmur. Intraluminal pressure is normal and vessel wall elastic properties may be altered as in poststenotic dilatation. Pulmonary artery angiograms in 6 normal patients, 9 with pulmonary stenosis and 10 with atrial septal defect were recorded on film, projected and traced. Arterial diameters at maximum systole and diastole were measured and, with intraluminal pressures, 2 points on the elastic diagram were calculated. These points lay on the initial linear portion of the graph so that a line through them to zero wall tension gave the resting radius (R
o
) Each radius value (R) was normalized by dividing by the corresponding R
0
. By plotting wall tension versus strain (R/R
0
), a regression line was obtained for normals significantly different from that for poststenotic dilatation (
P
<0.01) and atrial septal defect (
P
<0.01). The slope of each line approximated vessel elastance at normal pressures: normals, 2.15 x 10
4
dyne/cm; poststenotic dilatation, 1.00 x 10
4
dyne/cm; and atrial septal defect, 0.89 x 10
4
dyne/cm. Increased pulmonary artery distensibility extends more peripherally in atrial septal defect, thus producing "hilar dance." A case of Marfan's syndrome showed similar changes.
Effects of Intrahypothalamic and Intraventricular Norepinephrine and 5-Hydroxytryptamine on Hypothalamic Blood Flow in the Conscious Rabbit
Authors: ROSENDORFF CLIVE , CRANSTON WILLIAM I.
Published: June 2012

Hypothalamic blood flow (HBF) was measured in the conscious rabbit using a
133
xenon clearance technique. The effects of intrahypothalamic norepinephrine (NE) and 5-hydroxytryptamine (5-HT) were determined by adding these compounds to the
133
xenon-in-saline injectate, in varying concentrations. NE produced dose-dependent changes in flow; 1 µg/m injection caused a mean increase in HBF of 55%, while doses of 10, 20, 40 and 200 µg/injection reduced HBF by mean values of 26%, 17%, 20% and 29% respectively. The constrictor effect of NE 40 µg/injection was prevented by the addition of phenoxybenzamine 50 µg/injection. Intrahypothalamic injections of 5-HT (20, 40 and 80 µg/injection) caused increases in mean HBF of 24%, 54% and 69% respectively. Injections of NE into the lateral cerebral ventricles caused an increase in HBF; 5-HT produced a variable response, but mean values for HBF tended to be lower after the injection. There were no changes in mean arterial blood pressure or arterial Pco
2
. It is concluded that NE and 5- HT have an action on hypothalamic resistance vessels when applied from the adventitial side, and that, in the case of NE, the response is dose dependent, and the vasoconstrictor effects may be mediated by alpha receptors in hypothalamic vessels.
Mechanics of the Aorta in Vivo
Authors: ARNDT J. O. , STEGALL H. F. , WICKE H. J.
Published: June 2012

The hydraulic properties of the unexposed thoracic aorta were studied in five cats by angiography. Repeated measurements of pressure and diameter were obtained at various distances from the aortic root, and it became obvious that the unexposed aorta in cats was more than twice as distensible as the exposed aorta. Diameter of the aortic root, for example, varied by about 20% over a physiologic pulse pressure (40 mm Hg); even in the lower thoracic aorta variations exceeded 15%. When plotted as a function of distance from the root, aortic diameter and distensibility both decreased, and the calculated impedance increased. Despite these changes, however, the calculated reflection coefficients were quite small. It was concluded that geometric and elastic inhomogeneities in the thoracic aorta tend to balance one another, keeping the reflection coefficient quite low and helping to "decouple" the oscillatory left ventricular pump from the static peripheral vasculature. Since the aortic pulse contour is reflection-free during the first 50 msec following the onset of ventricular ejection, it may reliably indicate left ventricular properties and their changes with stress. In several animals, norepinephrine infusion was used to elevate the aortic pressure to hypertensive levels. When compared to hypertension induced by carotid reflex stimulation or mechanical occlusion of the aorta, however, aortic wall properties were essentially the same, suggesting that this agent has no important direct effect on the aortic wall.
Effects of Reduced Hematocrit on Erythrocyte Velocity and Fluorescein Transit Time in the Cerebral Microcirculation of the Mouse
Authors: Rosenblum William I.
Published: June 2012

The red blood cell velocity and the arteriole-to-venule transit time of sodium fluorescein were measured in the pial microcirculation of 15 mice immediately before and after phlebotomy and hemodilution. The acute anemic state produced by the phlebotomy and hemodilution was accompanied by an increase in the velocity of the red blood cells and of the fluorescent plasma. Such increments in velocity must be attributable to either an increased blood pressure or a fall in cerebrovascular resistance. Increases in pressure were generally absent, as was vasodilation, one cause of a decreased resistance. On the other hand, decreased blood viscosity accompanies a fall in hematocrit and could therefore account for a decreased vascular resistance in every animal. These data are consonant with earlier reports in animals and man of an increased cerebral blood flow accompanying anemia. Moreover, the data support those workers who attributed this increase in flow at least partly to a decrease in blood viscosity.