bluuebunny/crossref_metadata_2025 huggingface dataset:
Potentiation of Vascular Myotropic Responses by Metanephrine and other Noncatecholamines
Authors: KHAIRALLAH PHILIP A. , PAGE IRVINE H. , TURKER KAZIM R.
Published: June 2012

Contractile responses of vascular smooth muscle strips (rabbit aorta) to angiotensin, vasopressin and serotonin are potentiated by amounts of metanephrine, ephedrine or tyramine that produce no contractions by themselves. Epinephrine and norepinephrine contractions of aortic strips are not potentiated. Phentolamine and bretylium prevent this potentiating effect of meta-nephrine and ephedrine; the effect of tyramine is blocked by bretylium but only partially by high doses of phentolamine. Contractions of strips pretreated with reserpine are not potentiated except when repleted with norepinephrine. It is suggested as a working hypothesis that low doses of metanephrine release storage norepinephrine which acts on the contractile machinery to potentiate its response to other stimulating agents.
Coronary Blood Flow Measurements in the Presence of Arterial Obstruction
Authors: HARMAN MAUREEN A. , MARKOV ANGEL , LEHAN PATRICK H. , OLDEWURTEL HENRY A. , REGAN TIMOTHY J.
Published: June 2012

As an approach to delivery of inert gas to the myocardium in the presence of coronary artery obstruction, Kr
85
in saline was injected into a catheter in the coronary venous system of intact anesthetized dogs. Isotope delivered at the level of the great cardiac vein was selectively localized in the region of myocardium subserved by the vein and the left anterior descending artery. Similarly, injection at the coronary sinus level was attended by localization of isotope to the area perfused by the circumflex branch of the left coronary artery. Precordial counting of isotope delivered in this retrograde manner yielded coronary blood flow values that closely corresponded to those derived from coronary arterial injection.

Coronary thrombus formation in either of the major left coronary branches was reflected in substantial flow reductions when isotope was delivered via the artery distal to the thrombus. A similar flow decrement was observed when the gas was delivered via the corresponding venous site, while normal blood flow levels were derived from the nonischemic area. Application of the method to detection of coronary arterial obstruction in man is discussed.
Human Cerebral Blood Flow Measured by Two Inert Gas Techniques
Authors: LASSEN N. A. , HØEDT-RASMUSSEN K.
Published: June 2012

Two inert gas methods for measurement of tissue blood flow were compared. The two methods are (1) Kety and Schmidt's inert gas saturation method, in which the tissue saturation is followed by detecting the concentration of the tracer in the venous blood leaving the organ and (2) the intraarterial radioactive inert gas injection method where the tissue washout is measured by detecting the residue inside the tissue by an external scintillation detector.

Theoretical considerations show a close relation between the two methods when carried to the time of full saturation or desaturation of the tissue or when stopped before full saturation.

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

The Kety-Schmidt outflow detection method is the method of choice for studying over-all tissue perfusion and metabolism. The residue detection method is best suited for measuring flow through circumscribed regions
inside
an organ and for resolving the flow curve to yield estimates of flow and relative weight of various tissue components.
Interstitial Fluid Pressure
Authors: GUYTON ARTHUR C. , PRATHER JOHN , SCHEEL KONRAD , MCGEHEE JAMES
Published: June 2012

Fluid movement through the capillary membrane has been measured in the lower legs of dogs by using implanted, perforated capsules as internal plethysmographs. Utilizing this procedure it was possible to compare the effects of changes in interstitial fluid pressure with the effects of changes in venous pressure and arterial pressure on movement of fluid through the capillary membrane. A decrease in interstitial fluid pressure of 1 mm Hg increased the filtration of fluid out of the capillaries 1.20 as much as did 1 mm Hg increase in venous pressure. The filtration coefficient for fluid movement through the capillary wall per unit change in
interstitial fluid pressure
was 0.058 µliter/min per mm Hg per g of tissue. This value is in the same range as filtration coefficients that others have determined following changes in
capillary pressure
.
The Zero of Potential of the Electrical Field Produced by the Heart Beat
Authors: BAYLEY ROBERT H. , KINARD CONRAD L.
Published: June 2012

The zero of potential of the electrical field produced by the heart beat is defined and measured as the average value over the surface of a large spherical, integrating electrode which contains the subject and a homogeneous conducting medium. The Zero of potential thus defined is apparently free of assumptions of any kind and is used to evaluate the error on the three-branch and the four-branch central terminal with equal resistances. The latter may, in certain instances, be brought to zero by using unequal resistances. The potential function at its electrodes is that of an unweighted resultant vector or a point dipole. The electrodes which contribute to its potential are remote.
Electrocardiographic Effects of Cortisone and Related Compounds on the Dog
Authors: LUBSCHEZ ROSE , MAGIDA MELVILLE G. , PlKE NORMA
Published: June 2012

Infusion of cortisone and related compounds in the normal dog under standardized conditions resulted in increased voltage and peaking of the T wave of the electrocardiogram. These alterations were not associated with significant changes in the plasma electrolytes. Plasma inorganic phosphate decreased and urinary phosphate excretion increased. Cortisone appears to alter ventricular repolarization, but the mechanism of the effect is unknown.
General Theory of Heart-Vector Projection
Authors: FRANK ERNEST
Published: June 2012

A mathematical and physical basis for heart-vector projection concepts is presented and its significance for current practices in frontal-plane and spatial electrocardiography is discussed. Assumptions underlying the theory are stated and utilized to derive a general relationship between the heart dipole and the potentials it produces in the body. Specific equations are given for unipolar and bipolar leads and the Wilson central-terminal voltage. Coefficients determined experimentally for human torso models differ markedly from those that stem from Einthoven's hypothesis. Einthoven's equilateral triangle represents a special case of the general theory. Geometric interpretations are applied to a quantitative frontal-plane example, to the Wilson central-terminal voltage and extended to the concept of an image surface corresponding to the human body surface.
The Interplay of Coronary Vascular Resistance and Myocardial Compression in Regulating Coronary Flow
Authors: WIGGERS CARL J.
Published: June 2012

By integrating phasic coronary sinus flow curves in such a way that volume flow during systole plus isometric contraction and that during the remainder of diastole can be compared, the relative contribution of ventricular compression and coronary resistance to mean coronary flow can be assessed. It was found that anoxia, adenylic acid, compression of the aorta or pulmonary artery reduces coronary vascular resistance while epinephrine increases it. The augmentation in coronary mean flow following epinephrine is due solely to the greater force of ventricular contractions. On the basis of such evidence a revival of the "massaging theory" in modified form is suggested. Evidence was incidentally obtained which supports a former conclusion that the coronary sinus drains territories supplied by the right as well as the left coronary artery.
Measurement of Pressures in Man by Cardiac Catheters
Authors: WOOD EARL H. , LEUSEN ISIDOOR R. , WARNER HOMER R. , WRIGHT J. LEO
Published: June 2012

Relationships between artefacts in recorded intracardiac pulses and the dynamic response and susceptibility of catheter-manometer systems to artefacts caused by motion of the catheter were investigated. Sine-wave motions of the catheter, resembling motion frequently seen when the catheter is in the pulmonary artery, produce sine-wave pressure variations with peak-to-peak amplitudes of 10 mm. Hg. Square-wave motions (impacts) produce high-frequency pressure variations, greatest (10 to 200 mm. Hg) when directed along the axis and much less when perpendicular to the axis of the catheter. High-fidelity records of pressure by conventional cardiac catheter-manometer systems are most unlikely when such catheters are threaded through the beating heart.
Squalene Feeding in Experimental Atherosclerosis
Authors: KRITCHEVSKY DAVID , MOYER ARDEN W. , TESAR WALTER C. , LOGAN JOHN B. , BROWN RAYMOND A. , RICHMOND GILBERT
Published: June 2012

The hydrocarbon squalene, which has been suggested as a precursor in the biosynthesis of cholesterol, was fed to rabbits to see whether cholesterol thus synthesized would be efficacious in producing atheromatous lesions. Rabbits on a 3 per cent squalene diet for seven weeks showed an increase in liver weight and liver nonsaponifiable material but no more atheroma than did controls. Animals on the same diet for 14 weeks showed an increase in the cholesterol-rich lipoproteins as determined in the ultracentrifuge. Addition of squalene in no way altered the atherogenic propensities of the cholesterol diet.
A Lamellar Unit of Aortic Medial Structure and Function in Mammals
Authors: WOLINSKY HARVEY , GLAGOV SEYMOUR
Published: June 2012

The close association of elastin, collagen, and smooth muscle in the mammalian aortic media results in viscoelastic properties that account for many of its static and dynamic mechanical features. The structural components of the media are precisely oriented in concentric layers, or lamellar units, of fairly uniform composition. A comparative study of the adult thoracic aorta in 10 mammalian species, including 15 canine breeds, showed that the number of lamellar units in the media of adult mammalian aortas is very nearly proportional to aortic radius regardless of species or variations in measured wall thickness. Estimated wall tensions ranged from 7,820 dynes/cm in a 28-g mouse to 203,000 dynes/cm in a 200,000-g sow, but the average tension per lamellar unit of an aortic media was remarkably constant regardless of species, ranging from 1,090 to 3,010 dynes/cm. The findings suggest that the elastin lamella and the contents of its adjacent interlamellar zone represent the unit of structure and function of the mammalian aortic wall.
Comparison of the Reflexes Elicited from Combined or Separate Stimulation of the Aortic and Carotid Chemoreceptors on Myocardial Contractility, Cardiac Output and Systemic Resistance
Authors: STERN SHLOMO , RAPAPORT ELLIOT
Published: June 2012

Changes in left ventricular performance, stroke volume, and peripheral vascular resistance were studied in dogs after combined and separate stimulation of the aortic and carotid chemoreceptors. Selective stimulation of the aortic chemoreceptors produced an immediate increase in myocardial contractility as judged by the force developed by a strain gauge arch sewn into the left ventricular myocardium and by changes in the first derivative of the left ventricular pressure. Similar results were seen when heart rate changes were prevented by prior administration of atropine, when changes in outflow impedance were prevented by previous blockade of the alpha-adrenergic receptors, and when there was combined chemoreceptor stimulation. Beta-adrenergic blockade prevented the increase in myocardial contractility observed after chemoreceptor stimulation. With selective carotid chemoreceptor stimulation there was no significant change in contractility. Aortic chemoreceptor stimulation increased the heart rate and peripheral vascular resistance, while stroke volume decreased; carotid chemoreceptor stimulation slowed the heart rate and increased the stroke volume, but not change peripheral vascular resistance.
Sympathetic Control of Coronary Circulation
Authors: FEIGL ERIC O.
Published: June 2012

The sympathetic control of left circumflex coronary blood flow was studied by stellate ganglion and hypothalamic stimulation. Flow was measured acutely in dogs under chloralose or pentobarbital anesthesia by an electromagnetic flowmeter. Coronary vasoconstriction was observed when the left stellate ganglion was stimulated after blocking beta receptors with propranolol or INPEA. The possibility of coronary sympathetic cholinergic vasodilation of the type found in skeletal muscle was examined in three types of experiments in which vasodilation occurred in skeletal muscle: (1) peripheral sympathetic nerve stimulation after chronic catecholamine depletion with reserpine, (2) peripheral sympathetic nerve stimulation after acute block of alpha and beta receptors, (3) hypothalamic stimulation to give a defense reaction after acute block of alpha and beta receptors. Within the limits of these experiments, skeletal muscle cholinergic vasodilation was demonstrated but coronary sympathetic cholinergic vasodilation was not, even as part of the defense reaction elicited by hypothalamic stimulation.
Volumes and Compliances Measured Simultaneously in the Right and Left Ventricles of the Dog
Authors: LAKS MICHAEL M. , GARNER DANIEL , SWAN H. J. C.
Published: June 2012

In 10 normal dogs, the right and left ventricular volumes and compliances were determined in the fresh post-mortem heart. With the use of a SigmaMotor pump, Ringer's solution at 23°C was simultaneously infused into both ventricles within an hour after death. When the ventricles were full but open to atmospheric pressure, the mean volumes were 35.8 ml/m
2
for the right and 23.1 ml/m
2
for the left ventricle; when the transmural pressure was increased by 10 mm Hg, the mean volumes were 56.9 ml/m
2
for the right and 41.9 ml/m
2
for the left ventricle; at 20 mm Hg, the values were 60.8 and 48.5 ml/m
2
, respectively. The initial volumes and the increases in volume produced by increase in transmural pressure were affected by the position of the ventricular septum and by the presence of rigor mortis. With infusions into only one ventricle, right and left ventricular volumes were 20 to 74% greater at 10 mm Hg than the values when both ventricles were filled simultaneously. Compliance began to decrease 40 to 60 min after death; at 130 min after death (23°C), the change in volume when the transmural pressure was increased to 10 mm Hg was only about 1/5 of that immediately after death.
The Circulation of the Fetus in Utero
Authors: RUDOLPH ABRAHAM M. , HEYMANN MICHAEL A.
Published: June 2012

Techniques are described for insertion of vinyl catheters into the umbilical and limb vessels of the fetus of the sheep or the goat through small uterine incisions, with the ewes under spinal analgesia. The catheters are exteriorized and the fetus can be studied in its normal intrauterine environment. During constant infusion of antipyrine into a fetal limb vein, placental arteriovenous difference of antipyrine was measured, and fetal umbilical blood flow was calculated by the Fick method. "Carbonized" microspheres (50-µ diameter) labeled with various nuclides were injected into different venous sites in the fetus. The distribution pattern of the microspheres was used to determine the relative distribution of blood flow. Experimental evidence is provided that (1) there is no significant recirculation of microspheres, (2) the distribution of spheres is proportional to flow, and (3) circulatory physiology is not altered by injection of spheres. Quantitative data on the distribution of umbilical venous and superior and inferior vena caval return were obtained. It was possible to determine the actual blood flow to each of the fetal organs by relating the proportions of nuclide in each organ to that in the placenta. Total cardiac output was then calculable, taking into consideration the hemodynamic arrangement of the fetal circulation.
Decreased Ca
2+
Uptake by Sarcoplasmic Reticulum after Coronary Artery Occlusion for 60 and 90 Minutes
Authors: LEE KWANG S. , LADINSKY HERBERT , STUCKEY JACKSON H.
Published: June 2012

Dogs were placed on total cardiopulmonary bypass and the anterior descending branch of the left coronary artery was occluded for the duration of 15 min, 60 min or 90 min. In some experiments the coronary perfusion was restored after the occlusion. Fragments of sarcoplasmic reticulum were isolated from ischemic and nonischemic cardiac tissue and the Ca
2+
transport mechanism of the reticulum was studied. The Ca
2+
uptake of reticulum fragments obtained from cardiac tissue ischemic for 15 min was not impaired compared to the nonischemic control hearts. However, ischemia for 60 or 90 min caused impairment of Ca
2+
uptake by the sarcoplasmic reticulum isolated from the ischemic tissue. The functional damage brought by coronary occlusion for 60 min could be reversed by the restoration of coronary circulation after the occlusion, but after occlusion for 90 min it was irreversible.
Chemical Assay of Phospholipid Renin Preinhibitor in Canine and Human Blood
Authors: OSTROVSKY D. , SEN S. , SMEBY R. R. , BUMPUS F. M.
Published: June 2012

A phospholipid previously shown to be converted to a lysophospholipid renin inhibitor has been demonstrated in the plasma and red cells of man and the dog. This inhibitor precursor, designated preinhibitor, is chromatographically identical to the compound previously isolated from kidneys of dogs and hogs. A method for its quantitative measurement in plasma and red cells is presented. Normal dogs tested so far have an average of 119.6 µg of preinhibitor phospholipid/ml of blood; 16.3 µg of this is in the plasma. These concentrations are constant (in red cells even increased) 48 hr after bilateral nephrectomy. To assess the physiological importance of preinhibitor, it may be necessary to measure its active lyso derivative as well as the lipase(s) most directly involved in maintaining blood levels of these two phospholipids.
Effects of Mild Chronic Hypoxia on the Pulmonary Circulation in Calves with Reactive Pulmonary Hypertension
Authors: VOGEL JOHN H. K. , McNAMARA DAN G. , HALLMAN GRADY , ROSENBERG HARVEY , JAMIESON GAIL , McCRADY J. D.
Published: June 2012

The effects of the mild hypoxia at an altitude of 5280 ft on the pulmonary circulation were examined in normal calves and calves with a preexisting stimulus to maintain a reactive pulmonary vascular bed. In a serial study, 9 calves born at 5280 ft and 9 calves born at sea level underwent left pulmonary artery (LPA) ligation; 3 calves born at 5280 ft and 8 calves born at sea level underwent right pulmonary artery (RPA) ligation within 24 to 48 hours after birth. Progressive pulmonary hypertension and right ventricular heart failure developed in all calves operated on at 5280 ft but not in those with LPA ligation performed at sea level until they were transferred to 5280 ft. In contrast, in some animals with RPA ligation at sea level, progressive pulmonary hypertension was noted. The increased pulmonary blood flow consequent to LPA ligation does not result in progressive pulmonary hypertension at sea level but the addition of the mild hypoxia at 5280 ft appears to provide additional sufficient stimulus to result in progressive pulmonary hypertension. However, the slightly higher pulmonary blood flow subsequent to RPA ligation is capable of producing progressive pulmonary hypertension at sea level. Correlation was found between these results and human patients with congenital unilateral absence of a pulmonary artery, indicating that, in subjects with some stimulus to maintain a reactive pulmonary vascular bed, the mild hypoxia of 5280 ft may exert a significant effect on the pulmonary circulation.
Association of Depressed Myofibrillar Adenosine Triphosphatase and Reduced Contractility in Experimental Heart Failure
Authors: CHANDLER BRIAN M. , SONNENBLICK EDMUND H. , SPANN JAMES F. , POOL PETER E.
Published: June 2012

Although previous studies have suggested a depression of myofibrillar ATPase in the presence of heart failure, their interpretation has been limited by failure to exclude mitochondrial contamination and lack of information regarding the contractility of the tissue studied. To explore this fundamental question, myofibrils were prepared from the right and left ventricles of 15 normal cats, 10 cats with right ventricular hypertrophy and 19 with right ventricular hypertrophy and right ventricular failure, the latter groups following graded pulmonary artery stenosis. The contractility of these hearts was assessed using their right ventricular papillary muscles isolated in a myograph. Myofibrillar ATPase in all groups was maximally activated by 5 mM ATP, 5 mM MgCl
2
at pH 7.0 and 37°C, while mitochondrial contamination was eliminated by sodium azide. In right ventricular failure, right ventricular myofibrillar ATPase was depressed by 39% from an average of 0.18±0.01 in normal cats to 0.11±0.01 µmole inorganic phosphate/mg protein per min (P<.001). In right ventricular hypertrophy, right ventricular myofibrillar ATPase was not significantly depressed (0.16±0.01 µmole/mg per min). Of note, left ventricular myofibrillar ATPase was also significantly (P<.05) depressed in right ventricular failure from 0.16±0.01 to 0.13±0.01 µmole/mg per min. Contractility of the associated right ventricular papillary muscles, expressed as maximum rate of force development at the apex of the length-active tension curve, was correlated with myofibrillar ATPase activity.
Electron Microscopic Alterations at the Alveolar Level in Pulmonary Edema
Authors: COTTRELL THOMAS S. , LEVINE O. ROBERT , SENIOR ROBERT M. , WIENER JOSEPH , SPIRO DAVID , FISHMAN ALFRED P.
Published: June 2012

The electron microscopic alterations of the alveolar septum in advanced hemodynamin and alloxan-induced pulmonary edema were compared. Pulmonary edema was produced in anesthetized dogs by means of increased lefy atrial pressure and hemodilution and by allocan administration. Sections of pulmonary tissue from these dogs and similarly anesthetized controls were processed for and examined by light and electron microscopy. In the hemodynamic form of edema the interstitial fluid collects only in the collagen-containing portions of the septum. The endothelium, epithelium, their respective basement membranes and large portions of the air-blood barrier are unaffected. Alloxaninduced edema, in contrast, is characterized by degeneration of both endothelium and epithelium and by the appearance of fibrin within the alveoli. The hemodynamic type of pulmonary edema appears to result from an accentuation of the normal process of fluid exchange within the lung. Allocan-induced edema, on the other hand, is a pathologic process. The functional implications of these results are discussed.
Left Anterior Arborization Block Combined with Right Bundle Branch Block in Canine and Primate Hearts
Authors: WATT THOMAS B. , FREUD GERRIT E. , DURRER DIRK , PRUITT RAYMAND D.
Published: June 2012

Interruption of anterior fibers of the left bundle branch system together with right bundle branch block was accomplished experimentally in canine and primate hearts. In both species the electrocardiographic effects included a major alteration of the mean electrical axis to a superior and anterior direction. Epicardial excitation was markedly delayed anteriorly, causing widening of the QRS complex in standard electrocardiographic leads. Normal outward intramural spread of excitation in anterior regions of the left ventricle was reversed after left anterior arborization block alone. After addition of right bundle branch block, intramural spread of excitation was again directed outwardly but was markedly delayed in endocardial onset. Electrical effects of these blocks could be "corrected" individually or in combination by introducing synchronized electrical stimuli distal to each lesion. A scheme is proposed by which various forms of intraventricular conduction disturbance can be defined in terms of block of one or more divisions of a three-pronged system of rapid ventricular excitation.
Sympathetic Innervation of the Juxtaglomerular Cells of the Kidney
Authors: WÅGERMARK JAN , UNGERSTEDT URBAN , LJUNGQVIST ARNE
Published: June 2012

Combination of a histochemical fluorescence method for biogenic monoamines and staining of juxtaglomerular cell granules demonstrated sympathetic nerve terminals in the rat kidney in the walls of the parts of the juxtaglomerular arterioles that contain granulated cells. This forms a morphological basis for a direct influence of sympathetic nervous activity on the liberation of renin. The juxtaglomerular granules were nonfluorescent, an indication that, in the rat, the granulated juxtaglomerular cells are not equivalent to mast cells.
Capillary Filtration Coefficient in the Extremities of Man in High Environmental Temperatures
Authors: HYMAN CHESTER , WONG W. H.
Published: June 2012

The capillary filtration coefficient was measured in human extremities by a simplified technique using the capacitance plethysmograph. The method was validated in terms of consistency of values obtained on the same individual at various times, the correspondence between values obtained on a group of normal persons, and the agreement between values reported here and those of earlier workers made under corresponding environmental conditions and duration of measurement after venous occlusion. The technique was used to evaluate the change in capillary filtration coefficient in the calves of subjects when ambient temperature was increased from 20° to 35°C. Corresponding measurements of total blood flow in this segment and determinations of the clearance of iodide ion from pretibial intradermal depots were made in both environments. Cutaneous blood flow increased by almost 170% and the capillary filtration coefficient by about 40%, whereas the clearance did not change. It is concluded that neither the capillary filtration coefficient nor the clearance of isotopes from tissue depots has been established as a valid measure of capillary surface area. The possibility that during venous occlusion, fluid accumulated primarily in the subcutaneous tissues of the extremity is suggested and discussed.
Effect of Respiration on Pulmonary Capillary Blood Flow in Man
Authors: VERMEIRE PAUL , BUTLER JOHN
Published: June 2012

Pulmonary capillary blood flow was measured in man during slow breathing by a modification of the body plethysmograph technique for measuring N
2
O uptake. In seated subjects breathing slowly, flow was significantly higher during inhalation. In supine subjects whose legs were raised, the difference between inhalation and exhalation was not significant. Flow was usually greater during tidal inhalation than exhalation, but there was considerable variation. The changes in flow were not directly related to intrathoracic pressures or lung volumes. The results suggest that it is the amount and pressure of the venous blood available for aspiration into the thorax that influences pulmonary capillary blood flow during the course of a respiratory cycle.
Evidence for a Dilator Action of Carbon Dioxide on the Pulmonary Vessels of the Cat
Authors: VILES PETER H. , SHEPHERD JOHN T.
Published: June 2012

Isolated cat lungs perfused at constant flow (75 ml/min per kg total body weight) were ventilated with gases of varying CO
2
content (0 to 10%), 20% O
2
, and the balance N
2
. Tidal volume was constant, and airway pressure did not change. Left atrial pressure was held constant, and changes in pulmonary artery pressure (PPA) were taken to reflect changes in pulmonary vascular resistance. Progressive hypercapnia (Pco
2
= 0 to 60 mm Hg) resulted in an increase in PPA as pH decreased. Equivalent degrees of acidosis, produced by the infusion of 0.3 N lactic acid, resulted in a higher PPA. Changes in PPA produced by lactic acid were reversible with 0.89 M sodium bicarbonate. With Pco
2
constant, and pH changed by lactic acid or sodium bicarbonate infusion, PPA was higher in lungs ventilated with room air (Pco
2
= 0) than in those ventilated with 5 or 10% CO
2
(Pco
2
= 30 or 60 mm Hg) at the same hydrogen ion concentration of the perfusate. These findings can be explained by two opposing actions of CO
2
on pulmonary vessels: a dilator action due to the direct effect of CO
2
and a constrictor action caused by the increase in hydrogen ion concentration.
Distribution of Size and Shape in Populations of Normal Human Red Cells
Authors: CANHAM P. B. , BURTON ALAN C.
Published: June 2012

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

The red cell can easily be deformed at constant volume, but an increase in membrane area results in hemolysis. A theoretical geometric parameter, the "minimum cylindrical diameter" (MCDiam), in microns, the thinnest cylindrical channel through which each individual cell could pass, predicts the linear boundary of the plot of area vs. volume. The MCDiam value of 3.66 µ ± 0.04 SEM accurately represents the thinnest channel through which 95% of the cells can pass.

In two splenectomized patients with hereditary spherocytosis the MCDiam was increased to approximately 4.0 µ, suggesting that the severest restriction is located in the spleen.
Renal Adaptation to Anemia
Authors: APERIA ANITA C. , LIEBOW AVERILL A. , ROBERTS LATHROP E.
Published: June 2012

Renal adaptation to anemia was studied in dogs that had been bled repeatedly during a week to produce hematocrit values of between 12 and 21%. Total renal blood flow was unaltered despite a significant increase in cardiac output. Total renal oxygen consumption was within normal limits, but the Po
2
of cortical tissue was significantly reduced. Glomerular filtration rate and therefore filtered sodium load were reduced. These alterations were interpreted as resulting from preglomerular vasoconstriction together with a decrease in postglomerular vascular resistance, the latter perhaps a consequence chiefly of the diminished blood viscosity. Sodium reabsorption in relation to filtered sodium load was unimpaired in anemic animals; actually the sodium excretion factor was lower than in normal animals. It is concluded that the maintenance of normal renal function in the anemic animal is obtained by a decrease in work load (i.e. reduced glomerular filtration rate) and more efficient oxygen extraction related to increased blood tissue Po
2
gradient. Increased titers of erythropoiesis-stimulating substance could be demonstrated in these anemic animals. It is suggested that the low cortical tissue Po
2
is responsible for the release of this factor.
Measurement of Left Ventricular Diameter In the Dog by Cardiac Catheterization
Authors: CARLETON RICHARD A. , CLARK JAMES G.
Published: June 2012

A cylindrical ultrasonic transducer on a catheter tip lodged in the cleft between the free wall of the right ventricle and the interventricular septum provides an easily measured echo from the posteroinferior left ventricular epicardial surface. The sonic path represents a diameter of the left ventricle at approximately its largest cross-sectional area. Experiments in six dogs demonstrated that measurements by ultrasound agree within ±6% with simultaneous radiographic measurements of left ventricular diameter. Procedures designed to alter left ventricular volume were employed in 14 dogs to clarify the physiologic meaningfulness of the left ventricular diameter measured by ultrasound. Both end-diastolic and end-systolic diameter increased with anoxia, with sudden injections of saline into the left ventricle, after propranolol, and after inflation of a balloon in the thoracic aorta. These diameters decreased with isoproterenol, with increased heart rate, and after inflation of a balloon in the inferior vena cava. The present technique provides accurate and physiologically meaningful estimates of left ventricular diameter. Ventricular diameter measurements obtained during cardiac catheterization should permit assessment of ventricular distensibility and of ventricular function.
Effects of Propranolol on the Transmembrane Potentials of Ventricular Muscle and Purkinje Fibers of the Dog
Authors: DAVIS LARRY D. , TEMTE JOHN V.
Published: June 2012

Papillary muscle-false tendon tissue preparations isolated from dog hearts were perfused with Tyrode's solution containing propranolol in concentrations ranging from 0.1 to 20.0 mg/liter. Transmembrane action potentials of both ventricular muscle fibers and Purkinje fibers were recorded. With sufficient concentration of drug, the velocity of the upstroke and the overshoot of both fiber types decreased. The curve relating upstroke velocity to level of membrane potential for Purkinje fibers was displaced to the right and down. The ability of both ventricular muscle fibers and Purkinje fibers to respond to rapid frequencies of stimulation was decreased. Repolarization of Purkinje fibers was accelerated by propranolol, but repolarization of ventricular muscle fibers was unaffected. Duration of the effective refractory period of Purkinje fibers decreased; that of ventricular muscle fibers was unchanged. Graded responses and decremental impulse conduction in Purkinje fibers were abolished in the presence of propranolol. Low doses of propranolol which caused no change in the transmembrane potential completely blocked the increase in Purkinje diastolic depolarization normally induced by epinephrine. The possible mechanisms by which propranolol might exert its antiarrhythmic actions on ventricular arrhythmias were discussed.
Influence of Developed Tension on Myocardial Potassium Balance in the Dog Heart
Authors: GILMORE J. P. , GERLINGS E. D.
Published: June 2012

Experiments were carried out to determine the effect of changing preload on myocardial potassium balance. A blood-perfused dog heart was employed. Changes in the pressure recorded from a balloon in the left ventricle were assumed to reflect directional changes in myocardial wall tension. Developed tension was altered by changing the volume of the balloon. Net potassium balance was calculated as the product of the coronary A-V plasma potassium difference and coronary plasma flow. When the ventricle was developing little tension, it usually gained potassium. When diastolic volume and thus developed tension was increased, a net loss of myocardial potassium occurred. In some experiments the hemodynamic response of the ventricle to the increase in diastolic volume suggested that the contractility of the heart was increasing while the heart was losing potassium.
Reversal of Pulmonary Hypertension by Prolonged Oxygen Administration to Patients with Chronic Bronchitis
Authors: ABRAHAM ABRAHAM S. , COLE RICHARD B. , BISHOP JOHN M.
Published: June 2012

Established pulmonary hypertension associated with hypoxemia in patients with chronic bronchitis is probably secondary to hyperplasia of the smooth muscle of pulmonary arterioles. To investigate the possibility that this increase in pulmonary arterial pressure was reversible, the floating catheter technique was used to study the effects of continuous administration of oxygen for 4 to 8 weeks on the pulmonary circulation.

In six patients, there was a gradual fall in pulmonary arterial pressure, the mean pressure for the group being 42.5 mm Hg before, and 32.3 mm Hg after, the period of oxygen administration. All measurements were made when the patients breathed air. There was no change in cardiac output. Hematocrit decreased from 51.4% to 42.5%, but total blood volume remained unchanged.

It has been shown previously that brief inhalation of oxygen can cause a slight temporary reduction in the pulmonary hypertension associated with chronic bronchitis and anoxemia. The present findings show that the residual, established hypertension is also reversible if oxygen therapy is continued for weeks. It is suggested that this reversal may be brought about by regression of the muscular hyperplasia of the small pulmonary vessels consequent to longterm relief of hypoxia.
Cardiovascular Performance of Alaska Sled Dogs during Exercise
Authors: VAN CITTERS ROBERT L. , FRANKLIN DEAN L.
Published: June 2012

Radiotelemetry was used to study regional blood flow distribution in Alaska sled dogs during cross-country runs. Doppler ultrasonic flowmeter transducers were chronically implanted on the coronary, renal, and mesenteric arteries, terminal abdominal aorta, and ascending aorta or pulmonary artery, and a miniature blood pressure gauge was installed in the aorta or carotid artery. Flow and pressure data telemetered from dogs running on the trail were received and recorded remotely. The heart rate, 40 to 60/min in sleeping dogs, increased to 80 to 100/min when the dogs were ambulatory and to 100 to 150/min when the dogs were excited before a race. Heart rate accelerated to 300/min at the start of exercise and commonly remained at that level throughout prolonged runs. Aortic blood pressure averaged 130/90 mm Hg at rest, but the systolic pressure often exceeded 300 mm Hg when the dogs were running. A transient drop in mean pressure occurred at the onset of running, but mean pressure during sustained exercise was practically identical to that at rest. Flow in the terminal aorta increased 9 to 12 times and coronary flow 5 to 6 times, but mesenteric and renal flows were unchanged during violent, prolonged exercise. These findings contrast with diminished visceral flows recorded in exercising humans and suggest that compensatory redistribution of flow is not a significant reserve mechanism in these animals during exercise.
Application of the Theory of Heat Exchangers to a Physiological Study of the Goat Placenta
Authors: RANKIN JOHN H. , PETERSON EDWARD N.
Published: June 2012

The exchange characteristics of the goat placenta were compared to those of several simple models. A technique is described whereby the fetal side of the placenta of the goat near term can be perfused with blood. The ratio of fetal to maternal blood flow was controlled in the range 0.17 to 4.80. The fractions of the maternal and fetal blood flows that did not enter the area of exchange (shunts) were determined by perfusion of the uterine and umbilical circulations with Krebs solution containing dextran and saturated with carbon monoxide and were found to be 36% (SD 3.9%) and 23% (SD 2.2%), respectively. These values were compatible with the shunt values obtained by graphical extrapolation of the data obtained with nitrous oxide and acetylene during perfusion with blood. The N
2
O and C
2
H
2
data showed that the goat placenta has the exchange characteristics of a countercurrent exchanger with extremely unevenly distributed uterine and umbilical flows or those of a concurrent exchanger with moderately uneven distribution of flows. The only available information in the literature on the distribution of flow in this type of placenta indicates that the distribution is moderately uneven.
A Study on the Healing-over of Myocardial Cells of Toads
Authors: DE MELLO W. C. , MOTTA G. E. , CHAPEAU M.
Published: June 2012

The possible role of the intercellular junctions on the sealing process of toad myocardium was investigated in preparations immersed in hypertonic sucrose solutions and in solutions containing EDTA, both of which caused the separation of many intercalated disks and of a large number of cells. The rate of healing was determined by measuring the amplitude of the injury potentials as a function of time. The potential differences were recorded with the "roving" electrode technique immediately after injury and then at 2-minute intervals. Measurements made in preparations immersed in normal Ringer's solution showed that the depolarization caused by a lesion was totally reversed in 10 to 12 minutes. In muscles immersed in hypertonic sucrose solutions for 20 minutes, a marked reduction of the rate of healing was observed. Similar results were obtained with EDTA (2.5 mM) or with Ca
2+
-free solutions. The effect of hypertonic solutions was not counteracted by the addition of 10 mM Ca
2+
to the solution. The results suggest that the integrity of the intercellular junctions is essential for the healing process.
Evidence Suggesting a Multigenic Origin of Membranous Septal Defect in Rats
Authors: FOX MORJORIE HOPKINS
Published: June 2012

The study was designed to assess the relative importance of parity, parental age and the fetal genome in the etiology of congenital interventricular septal defects in a subline of Long-Evans rats with a high incidence of malformation (25%). Analysis of successive litters produced in 27 full sibships indicated that parity and parental aging had no consistently significant influence on the incidence of defects. Relatively consistent litter incidences within sibships but highly significant differences in the mean litter incidences of the different sibships support the hypothesis that the fetal genome is of primary etiologic importance. Analysis of the half-sibships produced by 12 males in sequential matings with different young virgin females indicated that neither paternal age nor a parental age differential significantly influenced the incidence of defects. Highly significant differences between the half-sibships in respect to mean litter incidences of malformation were attributable to highly significant differences between sires, significant differences between dams and considerable within litter variation. Analysis of the parental-offspring distribution of defects rules out the possibility of fully penetrant unifactorial inheritance but suggests that ventricular anomalies are transmitted in accordance with a polygenic, quasi-continuous inheritance pattern.
Observations on the Origin of Renin in Human Urine
Authors: LUMBERS EUGENIE R. , SKINNER S. L.
Published: June 2012

Excretion of renin into urine was studied using specific assay methods in normal subjects and hospital patients. Urinary renin output and renal clearance of renin varied widely among normal subjects but remained similar over months in any one subject. Renin clearance was significantly less in normal males (range 12 to 893 ml/24 hours) than females (79 to 3,149 ml/24 hours), but no reason for this was established.

In normal subjects renin excretion did not show a diurnal variation and was not directly dependent upon creatinine clearance, protein clearance, plasma renin levels, or sodium or water output.

Fivefold elevations in plasma renin level induced by natriuretic therapy increased renin excretion twofold and caused renin clearance to fall to 43% of control without a change in creatinine clearance. Total protein excretion did not change with this elevation in plasma renin level.

Excess renin excretion did not occur in patients with proteinuria unless plasma levels were grossly elevated. The findings suggest that renin is filtered and selectively reabsorbed. No diagnostic application is apparent.
Mechanism of Vasopressin-induced Bradycardia in Dogs
Authors: VARMA SARLA , JAJU BHUWANESHWAR P. , BHARGAVA KRISHNA P.
Published: June 2012

In dogs anesthetized with intravenous chloralose, vasopressin was injected either intravenously or into the cerebral ventricles, and the cardiovascular effects were studied before and after stabilizing the arterial blood pressure, bilateral vagotomy, and transection of the cervical cord at the level of C
2
. Intravenous vasopressin caused a rise in arterial blood pressure and pronounced bradycardia. The bradycardia appeared to be partly due to a peripheral depressant action on the heart, probably resulting from coronary constriction and partly from reflex vagal stimulation resulting from the rise in arterial blood pressure. A direct stimulating action of vasopressin on the central cardioinhibitory neurons played only a minor role in the production of the bradycardia. Injections of vasopressin, into either a lateral or the fourth ventricle, produced an insignificant rise in arterial blood pressure but marked bradycardia. A peripheral effect of the vasopressin after its absorption into the blood stream could be excluded as the cause of the bradycardia, since an injection of vasopressin into the cerebral ventricles produced diuresis, not antidiuresis. The bradycardia was more pronounced and occurred earlier when the vasopressin was injected into the fourth rather than into a lateral ventricle. The bradycardia produced by the injection of vasopressin into the cerebral ventricles could be almost fully accounted for by a central stimulating action on the cardioinhibitory neurons in the region of the vagal nuclei, which are closer to the fourth ventricle than to the lateral ventricles.
Hemodynamic Patterns during Desynchronized Sleep in Intact Cats and in Cats with Sinoaortic Deafferentation
Authors: KUMAZAWA TOKAO , BACCELLI GIORGIO , GUAZZI MAURIZIO , MANCIA GIUSEPPE , ZANCHETTI ALBERTO
Published: June 2012

In unanesthetized, unrestrained cats, placed in a sound-attenuated cage, stroke volume and cardiac output were continuously monitored by an electromagnetic flow transducer chronically implanted around the ascending aorta, arterial pressure was measured by means of a femoral catheter connected to a strain-gauge transducer, and heart rate by a cardiotachograph. Total resistance was computed by dividing arterial pressure by cardiac output. Electroencephalograms, cervical electromyogram, and ocular movements were also monitored to obtain evidence of naturally occurring sleep. In animals with intact sinoaortic reflexes the fall in arterial pressure occurring during desynchronized sleep was associated with a small decrease in cardiac output and a relatively greater reduction in total resistance. After sinoaortic deafferentation, the conspicuously exaggerated fall in arterial pressure occurring during the same type of sleep was almost entirely due to a parallel exaggeration of the reduction in total resistance; changes in cardiac output were only slightly greater than before deafferentation. Only in the few episodes of desynchronized sleep in which extreme hypotension was accompanied by signs of cerebral anoxia, did cardiac output greatly decrease; in these cases, calculated resistance was found to increase. Both small and large changes in cardiac output were independent of heart innervation.
Difference in Geometry of Young and Old Human Erythrocytes Explained by a Filtering Mechanism
Authors: CONHAM PETER B.
Published: June 2012

A mechanism for the geometric difference between young and old human red blood cells is proposed. It is assumed that the bone marrow produces a population of cells with a range of sizes and shapes, but only those cells which can pass through a theoretical 3.65µ, cylindrical channel survive in the circulation. The important geometric parameters of an erythrocyte are the area and the volume. We suggest that as cells age they have a constant area but swell in proportion to their original volume. This hypothesis of aging was tested on 1,016 normal cells using the IBM 7040 computer. When the cells were theoretically swelled by approximately 15%, the population of cells which could still pass through the filter had a smaller mean area and volume and were more osmotically fragile than the same cells before swelling. Young and old cells were separated by centrifugation. The heaviest 10% of the cells (old cells) had a lower diameter, area, and volume and higher sphericity index than the lightest 20% (young cells). The calculated minimum filter diameter was not significantly different. The good agreement between the predicted and observed changes in cellular geometry between young and old cells provides supporting evidence that a cylindrical filter exists in the circulation and may play a role in determining the life span of the erythrocyte.