bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased vasodilator responses to acetylcholine in psychosocial hypertensive mice.
Authors: Webb R C , Vander A J , Henry J P
Published: June 2012

Responsiveness to endothelium-dependent (acetylcholine and A23187) and endothelium-independent (nitroprusside and 8-bromo cyclic guanosine 3',5'-monophosphate [cGMP]) vasodilators was examined in two vascular preparations from hypertensive and normotensive mice. CBA Agouti mice were made hypertensive by exposure to social stress in a complex population cage. After 2 months, the hindquarter vascular bed was pump-perfused at a constant flow with plasma substitute to evaluate changes in perfusion pressure, and helical strips of aorta were suspended in muscle baths for measurement of isometric force generation. Tissues were treated with methoxamine to induce contractile tone. Threshold dilator responses to acetylcholine were elicited at a significantly lower dose in the hindquarters of hypertensive mice than in those from normotensive mice, indicating increased vasodilator sensitivity. In contrast, vasodilator responsiveness to nitroprusside in hindquarters of hypertensive mice did not differ from that in hindquarters of normotensive mice. Aortas from hypertensive mice were more sensitive (lower ED50) to the relaxant effects of acetylcholine and A23187 than those from normotensive mice. The relaxant effects of nitroprusside and 8-bromo cGMP on aortas from hypertensive mice were not significantly different from those in normotensive aortas. Aortic strips that had been rubbed on the lumen surface with a wooden stick did not relax to acetylcholine or A23187. In aortas that were not initially contracted with methoxamine, acetylcholine and A23187 caused small contractions from baseline. The magnitude of these contractile responses were potentiated after removal of the endothelium, and the potentiation was greater in aortas from hypertensive mice. These results demonstrate an increased responsiveness to endothelium-dependent vasodilators in this psychosocial model of hypertension.
Evidence against a pressor role for vasopressin in spontaneous hypertension.
Authors: Sladek C D , Blair M L , Mangiapane M
Published: June 2012

The hypothesis that the vasoconstrictor action of vasopressin may contribute to the development of hypertension in spontaneously hypertensive rats (SHR) was tested by chronic infusion of a specific antagonist of the vascular effects of vasopressin. From 4 to 13 weeks of age, SHR and Wistar-Kyoto rats (WKY) received subcutaneously either isotonic saline or the vasopressin pressor antagonist, d(CH2)5Tyr(Me)arginine vasopressin by osmopump. Systolic blood pressure was measured by tail cuff from 5 to 11 weeks of age. In SHR, the vasopressin analogue did not alter the rate or magnitude of increase in systolic blood pressure. In WKY, systolic blood pressure in the vasopressin analogue group was slightly reduced compared with the saline infusion values until 10 weeks of age (F1, 10 = 10.18, p = 0.008). At 12 to 14 weeks of age, all animals were prepared with indwelling arterial and venous catheters. Resting mean arterial pressure was not altered significantly by the vasopressin analogue infusion in either strain, but the response to an acute vasopressin infusion of 5, 15, or 50 ng/kg body weight was markedly attenuated by the analogue treatment, indicating that plasma levels of the vasopressin analogue were sufficient to block pressor effects of endogenous vasopressin. A bolus injection of the angiotensin II converting enzyme inhibitor teprotide (SQ 20881) resulted in a decrease in mean arterial pressure (p less than 0.05) that was comparable in all groups, and serum renin concentration was not elevated in the vasopressin analogue-treated rat.(ABSTRACT TRUNCATED AT 250 WORDS)
Analysis of the cardiovascular effects of arginine vasopressin in conscious dogs.
Authors: Tipayamontri U , Young D B , Nuwayhid B S , Scott R E
Published: June 2012

The effects of physiological elevations in arginine vasopressin on the cardiovascular system were studied in a group of nine conscious, chronically instrumented dogs. The animals were studied under normal conditions (plasma vasopressin, 4.1 +/- 0.4 pg/ml), after 24 hours of dehydration (plasma vasopressin, 7.3 +/- 1.5 pg/ml), after a 30-minute vasopressin infusion at 2.6 ng/kg/min (plasma vasopressin, 96.6 +/- 8.1 pg/ml). These increases in vasopressin concentration resulted in no change in arterial pressure and significant changes in the following: a 13 and 29% decrease in resting cardiac output during dehydration and acute infusion, respectively; a 26% reduction in heart rate during acute infusion; a 12 and 54% increase in total peripheral resistance during dehydration and acute infusion; a 16 and 22% reduction in mean circulatory filling pressure during dehydration and chronic vasopressin infusion. In addition, maximum pumping ability of the heart was reduced 16 and 31% during dehydration and acute infusion, respectively. These data suggest that elevations of vasopressin such as those occurring during dehydration or volume depletion potentially may affect cardiovascular performance by three mechanisms: greatly increasing resistance to flow, reducing heart rate, suppressing the pumping ability of the heart.
Vascular reactivity in the spontaneously hypertensive stroke-prone rat. Effect of antihypertensive treatment.
Authors: Soltis E E , Bohr D F
Published: June 2012

This study investigated vascular responsiveness in stroke-prone spontaneously hypertensive rats (SHRSP) and the effect of antihypertensive treatment on this responsiveness. Weanling (4-week-old) male and female SHRSP and Wistar-Kyoto rats (WKY) received either the antihypertensive combination treatment of hydralazine plus hydrochlorothiazide in drinking water or tap water alone (controls) for 15 weeks. Whereas the antihypertensive combination prevented the development of hypertension in treated SHRSP (SHRSP-T), blood pressure remained unchanged in treated WKY (WKY-T). Femoral arterial smooth muscle responsiveness to KCl, norepinephrine, and calcium (in the presence of either 40 mM KCl or 1 microM norepinephrine) was not altered in SHRSP when compared with WKY. A significant increase in the sensitivity of femoral arteries to KCl and calcium (in the presence of 40 mM KCl) was seen, however, in SHRSP-T and WKY-T. An increased sensitivity to norepinephrine and calcium (in the presence of 1 microM norepinephrine) was seen only in SHRSP-T. Isoproterenol-induced relaxation was significantly attenuated in both SHRSP and SHRSP-T. Relaxation induced by sodium nitroprusside and calcium (membrane stabilization) was not different between the four groups. These results show that femoral arterial smooth muscle responsiveness to vasoconstrictor stimuli is not altered in SHRSP but that beta-adrenergic-mediated relaxation is attenuated. Antihypertensive treatment resulted in an enhanced responsiveness to these vasoconstrictor stimuli but had no effect on the relaxation properties of femoral arterial smooth muscle.
Cryoblockade of the ventromedial frontal cortex reverses hypertension in the rat.
Authors: Szilagyi J E , Taylor A A , Skinner J E
Published: June 2012

The anteroventral part of the hypothalamus adjacent to the third ventricle (AV3V) has been implicated in electrolytic lesion studies as a site crucial to the development and maintenance of hypertension. Cryoblockade is known to alter synaptic and axonal transmission differently at different temperatures. In this study, cooling of the hypothalamus, including the AV3V area, to the temperature known to block only synaptic function did not alter blood pressure in two different models of experimental hypertension in the rat. Cooling sufficient to block both synaptic and axonal transmission, however, reduced blood pressure elevations to near normotensive levels. Synaptic cryoblockade in the ventromedial portion of the frontal cortex lowered experimental hypertension by 21 +/- 3 mm Hg (p less than 0.05). In normotensive controls, blood pressure was not altered by cryoblockade in either the frontal cortex or hypothalamus. Anatomical evidence provided by others shows that cells in the ventromedial frontal cortex project, in part, through the AV3V region to the brainstem cardioregulatory structures. These results indicate that neural activity arising in frontal cortex is axonally projected through the hypothalamus to maintain elevated blood pressure in experimental hypertension.
Heparin interferes with the biological effectiveness of atriopeptin.
Authors: Wei Y F , Holmberg S W , Leahy K M , Olins P O , Devine C S , Needleman P
Published: June 2012

The chromatographic mobility of atriopeptin-28 or of the prohormone is markedly altered by preincubation of the peptides with heparin before separation on reverse-phase high performance liquid chromatography. Protamine prevented the heparin effect and reestablished the original migration pattern of the atrial peptides. The addition of heparin to either rat or human plasma samples did not interfere with the atriopeptin immunoreactivity. The influence of heparin on the biological activity of the atriopeptin-28 in anesthetized rats was also investigated. Infusion of heparin (30 U/min) significantly reduced the dose-dependent fall of blood pressure produced by atriopeptin-28, but did not interfere with the hypotensive effect of nitroglycerin. Similarly, infusion of heparin in volume-expanded rats markedly decreased the diuresis produced by atriopeptin-28 without altering the urine volume excreted in response to furosemide. These data suggest that the highly charged molecule heparin can modify the physical and biological properties of atriopeptins, perhaps by binding to the numerous arginine residues (i.e., 5 arginine residues in atriopeptin-28) in the atriopeptin molecules.
Effect of Blood and Saline Infusion on Ventricular End Diastolic Pressure, Stroke Work, Stroke Volume and Cardiac Output in the Open and Closed Chest Dog
Authors: FERGUSON THOMAS B. , SHADLE OSCAR W. , GREGG DONALD E.
Published: June 2012

Left and right ventricular end diastolic pressure, stroke work, stroke volume, and cardiac output were measured in open and closed chest dogs infused with blood and/or saline. The methods employed permitted repeated determinations of these factors during short time intervals. For nonfatigued hearts in the open chest preparation point to point correlation of end diastolic pressure with the other three variables was very good, but in closed chest animals a number of non-correlations occurred. Sufficient variation was seen to indicate that factors other than those measured in this study will have to be known before cardiac performance in the intact animal can be fully assessed.
Extent of Agreement between Two Methods for Estimating Acute Directional Changes of Cardiac Stroke Index
Authors: OPDYKE DAVID F. , ZANETTI MARY E.
Published: June 2012

Cardiovascular physiologists frequently infer directional changes in cardiac stroke volume and cardiac output from changes in aortic pulse pressure and atrial pressure. Errors are probably not infrequent. The Hamilton and Remington pressure pulse contour method can also indicate directional fluctuations in cardiac stroke volume. Comparison of the results of the two methods of analysis in situations where cardiac stroke index was changed acutely revealed good correspondence of indicated changes under conditions of simple alterations in venous return, but poor correspondence under more complex conditions such as after injections of pressor amines.
Application of "Thorium B" Labeled Red Corpuscles in Blood Volume Studies
Authors: HEVESY GEORGE , NYLIN GUSTAV
Published: June 2012

A new method for determining blood volume utilizing thorium B, which has advantages over the use of P
32
, is described in detail. The problems of protecting the patient and operator from radiation activity are discussed in an appendix.
The Derivation of Coronary Sinus Flow During Elevation of Right Ventricular Pressure
Authors: GELLER HERMAN M. , BRANDFONBRENER MARTIN , WIGGERS CARL J.
Published: June 2012

The derivation of coronary sinus flow during increased pulmonary and right ventricular pressures was resubmitted to experimental study. The primary reduction and subsequent augmentation in coronary flow following pulmonary artery constriction and the persistence of a greater flow after release preclude the concept of a variable contribution via thebesian channels from the right ventricular cavity. When the magnitude of the increase is also considered, it is difficult to escape the conclusion that drainage from the right ventricle is also involved. The use of coronary sinus blood in studies of metabolism of the left ventricle under various dynamic conditions seems precarious.
Mechanisms of Fluid and Electrolyte Retention in Experimental Preparations in Dogs
Authors: DAVIS JAMES O. , HOWELL DAVID S.
Published: June 2012

Cardiovascular and renal hemodynamic function, nitrogen, electrolyte, and water balances, and circulating eosinophils have been studied before and during the formation of ascites produced by thoracic inferior caval constriction. The data show a striking decrease in the renal and fecal excretion of sodium (Na) and an elevation in fecal potassium (K) output. An analysis of possible factors which might effect the reduction in renal Na excretion demonstrates that neither a low cardiac output nor a depressed glomerular filtration rate is the primary factor.
Electrocardiographic Alterations Produced by a Decrease in Plasma pH, Bicarbonate and Sodium as Compared with those Produced by an Increase in Potassium
Authors: ROBERTS KATHLEEN E. , MAGIDA MELVILLE G.
Published: June 2012

The effects of a decrease in plasma pH, bicarbonate and sodium on the electrocardiographic pattern are compared with those produced by elevation of serum potassium and lithium in the dog. The electrocardiographic alterations were found to be similar in form and progression. The alterations can be correlated with those found in isolated nerve and muscle preparations.
Dynamic and Neurogenic Factors Determining the Hepatic Arterial Flow after Portal Occlusion
Authors: SANCETTA SALVATORE M.
Published: June 2012

Acute ligation of the portal vein in the barbital-anesthetized dog produces a significant increase in the hepatic arterial flow when the perfusion pressure remains elevated in the artery. Evidence is presented which supports the concept that the immediate readjustment is solely dependent on dynamic changes. The late readjustments are probably conditioned by the interplay of neurogenic and humoral factors.
Further Evidence for a Critical Vessel Caliber in Experimental Coronary Shock
Authors: JACOBS HOWARD I. , ROSEN VICTOR , AGRESS CLARENCE M.
Published: June 2012

New experiments confirm previous observations that production of protracted coronary shock in the closed-chest dog following microsphere embolization is a critical function of the embolus size. The vessels occluded by the critical emboli have been located by a plastic coronary injection-tissue corrosion technic, and a definite relationship has been demonstrated between vessel caliber and anatomic type, in a dog heart, for the gradient from epicardium through endocardium.
Acute Hemodynamic Effects of Hexamethonium in Normotensive Man
Authors: RAKITA LOUIS , SANCETTA SALVATORE M. , GLADYS HECKMAN R.N. , HANNA JANOUSKOVEC, R.Y.
Published: June 2012

The effect of intravenous hexamethonium bromide was studied in 10 normotensive human subjects in the steady state. In the absence of over-all change in cardiac output, the variable decrease in arterial pressure is accounted for by decrease in calculated total peripheral resistance.
Measurement of Coronary Blood Flow in Dogs and Man from Rate of Myocardial Nitrous Oxide Desaturation
Authors: GOODALE WALTER T. , HACKEL DONALD B.
Published: June 2012

A technic of measuring left ventricular coronary blood flow in dogs and man from the rate of desaturation of nitrous oxide from the myocardium is presented. The desaturation technic appears valid in comparison with the previously described saturation technic, and affords definite technical advantages. By combining the two technics, flows may be measured within much less timethan by repeating either method alone.
Spread of Electrical Activity Through the Wall of the Ventricle
Authors: SCHER ALLEN M. , YOUNG ALLAN C. , MALMGHEN ARTHUR L. , PATON RICHARD R.
Published: June 2012

Multipolar recording technics have been employed to record the spread of excitation through the wall of the ventricle. The construction of isochronous planes in a block of tissue aids in visualizing the direction of spread. The results give direct support to the idea of fast endocardial spread followed by syncytial spread through the wall at a slower rate. No evidence is found that the impulse spreads through the individual cardiac muscle bundles.
Dynamics of T-1824 Distribution in Patients with Traumatic Arteriovenous Fistulas
Authors: SCHREINER GEORGE E. , FREINKEL NORBERT , ATHENS JOHN W. , STONE WILLIAM
Published: June 2012

Wide acceptance has been given to the expansion of "blood volume" in the presence of an arteriovenous fistula. Most clinical measurements have been made with abbreviated technics of T-1824 dilution. In the present study, carried out on casualties of the Korean War, significant expansion of the "rapidly distributing T-1824 and effective circulating albumin" were found in 31 patients with traumatic arteriovenous fistulas. Analyses of dye disappearance slopes, prolonged studies with labeled albumin and dye infusion have been used to investigate the dynamics of these measured expansions.
Nervous Mechanisms in Ventricular Arrhythmias Induced by Calcium Chloride in Rats
Authors: MALINOW MANUEL RENÉ , BATLLE FERNANDO F. , MALAMUD BERNARDO
Published: June 2012

The ventricular arrhythmias induced in rats by standardized doses of calcium chloride are largely prevented by sympatholytic and autonomic blocking drugs, by encephalic and/or upper spinal destruction and by medullospinal section. They are not prevented by bilateral vagotomy, bilateral adrenalectomy, or by lower spinal destruction.
Cardiac Performance of Hypertensive Aorta-Constricted Rabbits
Authors: Alexander Natalie , Goldfarb Taki , Drury Douglas R.
Published: June 2012

A heart-lung preparation with flow limited to the coronary vessels was used to study cardiac performance 4 to 120 days after severe constriction of the abdominal aorta in rabbits. Cardiac performance was evaluated by finding the maximum mean arterial pressure against which the heart could pump. Cardiac performance began to exceed the normal, range by the second or third post operative week and was well above normal after the first month. A high cardiac performance was not necessarily associated with marked ventricular hypertrophy. Animals died of heart failure within the first month, and all had developed a much more rapid rate of blood pressure increase than those that survived without signs of decompensation. We conclude that the basic cause of heart failure after severe aorta constriction is a rapid rise in arterial pressure which exceeds the rate at which the heart develops an improved performance.
Direct Cardiac Effects of Dopamine
Authors: Holmes John C. , Fowler Nobel O.
Published: June 2012

The cardiac effects of dopaminie, an epinephrine precursor, were studied in 20 dog heart-lung preparations. In 8 uncontrolled rate preparations. dopamine, 0.5 to 1 mg., increased the heart rate an average of 18 pet cent. In controlled rate preparations. dopamine, 100 to 500
µg
., consistently increased ventricular contractile force, cardiac output and blood pressure; there was a consistent decrease of right and left atrial pressure. Comparable hemodynamic effects were produced by 1 to 5
µg
. of levarterenol, except that the effects of dopamine tended to be of longer duration and were less likely to be followed by cardiac depression. It is concluded that doparnine has significant positive inotropic and chronotropic effects in the dog heart-lung preparation.
Inhibition of the Vasomotor System of the Anesthetized Dog by Epinephrine and Norepinephrine
Authors: Jones James J.
Published: June 2012

The actions of epinephrine and norepinephrine on the vasomotor system of 55 dogs anesthetized with sodium pentobarbital were investigated with the innervated, perfused leg preparation attached to the body by the sciatic nerve alone. Injections of these catecholamines into the body of the dog produced a dilatation of the vessels in the skeletal muscle of the perfused limb which was unaltered by cholinergic blockade with atropine and no longer occurred after adrenergic blockade with phenoxybenzamine. Vasomotor inhibition by norepinephrine was greatly reduced after baroreceptor inactivation, whereas a much greater proportion of epinephrine's activity remained and is attributed to sympathetic ganglion blockade.
Respiratory Mechanics During Ventricular Asystole in Dogs with Complete Heart Block
Authors: Scarpelli Emile M. , Spach Madison S.
Published: June 2012

Eleven mongrel dogs were studied in which complete heart block had been produced surgically. Ventricular rate was maintained by artificial stimulation until the time of study. Each experiment involved abrupt cessation of stimulation and the monitoring of pulmonary mechanical behavior during the ensuing period of ventricular asystole. These studies have shown that all aspects of the mechanical behavior of the lungs are altered during ventricular asystole in complete heart block. The changes which occur during this short interval of time are basically attributable to the systemic, stagnant hypoxia and the central vascular congestion. The pulmonary changes produced include augmentation of the rate and depth of breathing, reduction of the functional residual capacity, decreased pulmonary compliance, and increased pulmonary airway resistance. The result is that both the inspiratory and expiratory work of breathing are increased, while the efficiency of breathing is decreased. All of these alterations occur within the 20-second period of ventricular asystole and are restored to control levels soon after the re-establishment of a normal ventricular rate. The possible mechanisms involved are discussed.
Influence of Catheter Tip Position on Pulmonary Wedge Pressures
Authors: Bell A. L. Loomis , Haynes William F. , Shimomura Seiichi , Dallas Donald P.
Published: June 2012

Pulmonary artery wedge pressures and wedge pulmonary arteriograms were obtained in 68 patients with either mitral stenosis, congenital heart disease, or no demonstrable heart disease. The arteriogram defines five catheter tip positions in the wedged artery. Tip positions unfavorable for left atrial pressure transmission occurred in 20 of the 68 trials and accounted for 19 of the 31 unsatisfactory tracings. Favorable tip positions were found in 48 instances and resulted in 36 phasic tracings. Unsatisfactory tracings in patients with pulmonary hypertension and congenital heart disease are shown to result primarily from unfavorable catheter tip positions. In these patients structural changes in the larger pulmonary arteries may prevent proper wedging. Increased left atrial pressure assures transmission of a cyclic left atrial pulse to a properly impacted catheter regardless of the degree of associated pulmonary hypertension. It is concluded that the fortuitous position assumed by the catheter tip in the wedged artery and the level of the left atrial pressure are factors of major importance in the satisfactory recording of the left atrial pulse curve by the wedged catheter.
Work of the Heart Under the Effect of Induced Arterial Pressure Oscillations Studied in Intact Anesthetized Dogs
Authors: PIEPER HEINZ P.
Published: June 2012

The arterial system of intact anesthetized dogs and a physical model, which consisted of a "heart," an elastic "arterial" reservoir, and a "peripheral resistance," have both been studied in comparison. In both systems, the volume contained in the arterial reservoir was rhythmically altered by means of a slow sinusoidal piston pump which resulted in slow oscillations of the mean arterial pressure with the arterial pressure pulsations superimposed.

It was found that in the physical model, the systolic pressure pulse was larger during the phase of rising pressure (increasing volume) than during the phase of falling pressure (decreasing volume), while in the animal the systolic pressure pulses were equal in either phase. The aortic pressure pulse of the animal was a linear function of the presystolic aortic pressure during pressure oscillation and independent of the induced volume alteration.

Recordings of the stroke output of the heart revealed that the heart of the animal adjusted its output in such a manner that the induced systolic changes of the arterial contents were quantitatively compensated. The mechanism by which this is accomplished is of particular interest, since it would also enable the heart to compensate instantaneously for physiological alterations of the volume in the arterial system as caused by changes in peripheral runoff. This mechanism of instantaneous adjustment of the stroke output can be explained on the basis of Starling's Law of the Heart if the procedure of the calculation of the external work is modified.
Diagnostic Applications of Indicator-Dilution Technics In Congenital Heart Disease
Authors: Wood Earl H.
Published: June 2012

In summarizing the diagnostic value of the indicator-dilution technics in the study and investigation of congenital heart disease, perhaps a simple listing of the advantages and disadvantages of the technics will suffice.

The advantages are as follows: 1. The technics have a high degree of safety. In the more than 3000 cardiac patients in whom they have been utilized there have been no deaths and little or no morbidity. 2. The sensitivity of the technics for the detection and localization of right-to-left and left-to-right shunts is much superior to that of the conventional blood-gas methods. 3. Quantitative determinations of systemic and pulmonary blood flow and intrathoracic shunts by indicator-dilution methods can be made simultaneously over periods of less than 1 minute; when indicator dyes are used, these technics do not require manometrie analyses, accessory respiratory exchange studies, or active cooperation of the patient; and they are independent of foreign (anesthetic) gases in the blood. 4. The technics are versatile and can be extremely useful either for the detection and diagnosis of minimal, relatively simple defects or for the elucidation of the extremely complex types of congenital malformations. 5. The information obtained is of both a qualitative and a quantitative nature; that is, the nature and location of defects can be determined and, in addition, the magnitude and direction of flow through the defects in question as well as the levels of systemic and pulmonary blood flows can be estimated.

The disadvantages of the technics are as follows: 1. Rather complicated and sensitive recording equipment is essential. 2. Considerable technical skill is required of the persons carrying out the procedure in the placement of the necessary needles and catheters and in the proper selection of the multiple possible injection and sampling sites reached by these instruments in order to obtain the information needed to establish the diagnosis in question. 3. Correct interpretation of the diagnostic significance of the dilution curves obtained requires careful study and considerable experience by the person responsible for this phase of the investigation.

In other words, these technics entail relatively little discomfort and little danger for the patient, but require good equipment and, more important, considerable time, effort and skill on the part of the investigator and his assistants in order to obtain highly successful results.
Effects of Adenosinetriphosphate and Potassium Chloride on Ventricular Fibrillation Induced by Lack of Substrates
Authors: Penna Mario , Illanes Alejandro , Pupkin Marcos
Published: June 2012

The perfusion of the isolated guinea pig or cat heart with a substrate-free Tyrode solution induces a decrease in rate, a lengthening of the P-R interval, a decreased amplitude of the R wave, ventricular premature contractions, A-V dissociation, insignificant changes of the Q-T interval, and, finally, ventricular fibrillation with a regular atrial rhythm. In isolated hearts of both species, the reversal of ventricular fibrillation induced by lack of metabolites was attempted as follows: in guinea pig hearts, increasing the potassium chloride concentration of the Tyrode solution without glucose to 5.4 mM/L. reversed ventricular fibrillation in all cases. Adenosinetriphosphate (ATP) reversed this arrhythmia in only two of seven cases. However, in the isolated cat heart, potassium chloride in the same concentration (5.4 mM/L.) reversed ventricular fibrillation only in three out of seven cases. ATP did not reverse ventricular fibrillation in any cases, but potassium given with ATP reversed this arrhythmia in two out of four cases. In the cat heart, the reversal of ventricular fibrillation in all cases was accomplished only by increasing potassium chloride concentration to 5.4 mM/L. and adding glucose (1 Gm./L.).
Reflex Changes on the Pulmonary and Systemic Pressures Elicited by Stimulation of Baroreceptors in the Pulmonary Artery
Authors: Osorio Jose , Russek Mauricio
Published: June 2012

The distention of a large branch of the pulmonary artery, with or without occlusion of the circulation, produces pulmonary hypertension. The occlusion of an entire hilum, without adequate stimulation of the arterial baroreceptors produces only a negligible increase in pulmonary arterial pressure. Together with the pulmonary hypertension, variable changes in the systemic pressure were observed. The most frequent reaction was hypotension. The vagal fibers play no role in the pulmonary hypertensive response.
Effect of Exercise on Blood Coagulation
Authors: Keeney Clifford E. , Laramie David W.
Published: June 2012

Whole blood clotting time was measured before and after four different intensities and durations of exercise, using 12 male college students as subjects. The exercises consisted of a 15-minute walk on a motor-driven treadmill at 2.5 m.p.h., a 2-hour walk on the treadmill at 2.5 m.p.h., a run to near exhaustion on the treadmill at 6.25 m.p.h., and a stepping exercise on a 12-inch bench, 30 steps per minute for 15 minutes. Thromboplastin generation rate was measured before and after the stepping exercise on blood samples drawn from 14 subjects, and thrombin generation rate was similarly measured on samples drawn from 16 subjects.

No statistically significant variation was found in whole blood clotting time of samples drawn before the exercise, 1 minute after the exercise, or 15 and 30 minutes after. Neither was there any significant change in the thromboplastin generation rate of samples drawn before, 1 minute after, and 30 minutes after exercise. Ten of the 16 subjects showed no change in thrombin generation rate after exercise. However, six subjects experienced an acceleration of thrombin generation from a mean time of maximum thrombin concentration at 5.2 minutes before exercise to 4.0 minutes one minute after exercise. This difference was statistically significant.

From these data it was concluded that, in general, exercise was not followed by hypercoagulability. However, in some subjects, thrombin generation rate was increased due to undetermined factors.
Renin Concentration of Normotensive and Hypertensive Dog Kidney
Authors: Schmid Herman E. , Graham Leonard , Brennan Betsy B. , Wakerlin George E.
Published: June 2012

This report relates blood pressure, serum antirenin titer, and renal renin concentration in normotensive, acute and chronic experimental renal hypertensive, and spontaneous hypertensive dogs sacrificed at different levels of neutralizing antibody (antirenin) produced by injections of hog kidney extracts containing renin. Sufficient levels of antirenin can prevent or lower the blood pressure elevations secondary to partial constriction of the renal arteries in the dog. A highly significant relationship and correlation was found between increasing titer of antirenin and renal renin concentrations in both normotensive and hypertensive dogs. Two dogs not developing antirenin, although injected for many months with hog renins, did not have a renal renin concentration above control level. Goats treated with hog renin developed high antirenin titers but did not have an increase in renal renin. The goat differs from the dog, as does the monkey and man, in that antirenin produced from hog or dog renins does not neutralize the endogenous renin of the animal. It is concluded that the increase in renal renin found in these experiments is related directly to the presence of antirenin which is capable of neutralizing the endogenous renin of the experimental animal.
Comparative Study of Effects of Levarterenol and Methoxamine in Shock Associated with Acute Myocardial Ischemia in Dogs
Authors: West James W. , Faulk Arthur T. , Guzman Santiago V.
Published: June 2012

Coronary arterial injections of levarterenol in dogs in shock from acute experimental myocardial ischemia (by selective coronary embolization with lycopodium spores) directly increased myocardial contraction and resulted in a lowering of both atrial and pulmonary arterial pressures while at the same time raising systemic arterial pressure. Appropriate intravenous administration of the same drug had similar effects and produced a greater rise in systemic arterial pressure. Methoxamine, when administered intravenously, elevated the lowered systemic arterial pressure, but produced a further elevation in the already high atrial and pulmonary arterial pressures. These experiments demonstrate that during acute myocardial ischemia with arterial hypotension, and even in the presence of elevated atrial and pulmonary pressures, a more favorable effect, i.e., increased systemic pressure at lower atrial and pulmonary pressures, is achieved by employing a pressor amine with a direct cardiac stimulating action which increases myocardial contraction in addition to a peripheral vasoconstricting effect. By selective coronary arterial injections, levarterenol has been shown to have a direct cardiac stimulating effect, and therefore satisfies the above requirement, whereas methoxamine does not, since it fails to stimulate myocardial contraction, or actually depresses it, when given into the same site.
Effects of Selective Coronary Embolization on Coronary Blood Flow and Coronary Sinus Venous Blood Oxygen Saturation in Dogs
Authors: West James W. , Kobayashi Tachio , Anderson Fred S.
Published: June 2012

The cardiovascular effects of selective coronary embolization were studied with improved techniques in an attempt to obtain evidence for the existence of intercoronary reflexes and their role in potentiating myocardial ischemia.

These studies demonstrated that embolization of the coronary arterial bed by lycopodium spores produced an initial marked decrease in coronary blood flow followed by a maintained (approximately 10 minutes) increase which was accompanied by an increase in coronary sinus venous oxygen saturation. Supporting evidence was obtained from selective coronary angiograms and from changes in coronary vascular resistance. Attempts at eliminating these responses by certain autonomic blocking agents (atropine, hydralazine, tetraethylammonium chloride, hexamethonium, and dibozane), surgical denervation of the heart, and adrenalectomy were all ineffective. Experimental evidence obtained by comparing the initial effect of embolization with pitressin vasoconstriction and coronary occlusion all led to the conclusion that reflex coronary spasm does not occur during coronary occlusion. The cause of the initial decrease in coronary blood flow during embolization (lycopodium spores) is, therefore, mechanical block within the distribution of the vessel by the emboli.
Role of Potassium in the Pathogenesis of the "Electrolyte-Steroid-Cardiopathy with Necrosis"
Authors: Prioreschi P.
Published: June 2012

During the development of the "electrolytesteroid-cardiopathy with necroses" (ESCN) in rats, there is a decrease of myocardial potassium in the group bound to develop the cardiac necroses. A similar variation was observed in the control animals treated with a noncardiotoxic association of steroid and electrolytes. Only after the necrosis had been established was an important increase of sodium and decrease of potassium observed. On the basis of these and other previously deseribed facts, the author concludes that, although it is conceivable that the diminution of potassium in the heart could favor the development of the necroses, the hypothesis of the ESCN as a result of a simple potassium depletion cannot be accepted.
Relationship Between the Anatomical Orientation of the Interventricular Septum and the Manifest Orientation of Ventricular Depolarization in Dogs
Authors: Horan Leo G. , Hansen Fred L. , Bousquet Renee M.
Published: June 2012

Exact anatomical orientation of the interventricular septum was compared with apparent direction of electrical activity during ventricular depolarization in 22 dogs. In 15 control animals, the mean orientation of a vector normal to the right septal surface was toward the front, to the right, and slightly headward. The mean orientation of the 10-msec. vector (QRS) was almost directly toward the front and slightly tailward. The mean orientation of the polar vector was to the left, slightly to the front, and slightly headward. The values for each of these means were obtained in spherical coordinates: anatomical vector--141.7 degrees azimuth, 20.2 degrees altitude; 10-msec. vector (QRS)--92.0 degrees azimuth, -9.4 degrees altitude; and polar vector--14.8 degrees azimuth, 20.0 degrees altitude. In 7 dogs, rotation of the heart to the right by means of previously implanted guy sutures consistently moved the 10-msec. vector to the right also, but there was simultaneous unpredictable deviation either headward or tailward of the electrical vector. Polar vector shift was not consistent. Rotational transformation of axes for each dog, bringing the vector of the right septal surface into coincidence with the negative X-axis, did not bring to a focus the scatter of orientations of either group of electrical vectors, indicating that variation in electrical position depends upon other factors in addition to variation in anatomical position.
Study of High Frequency Components in Electrocardiogram by Power Spectrum Analysis
Authors: Franke Ernst K. , Braunstein John R. , Zellner David C.
Published: June 2012

A method has been developed for recording the power spectrum of the heart's electromotive force for the time interval corresponding to the QRS complex of the conventional electrocardiogram. Standards for healthy, young normals have been established. No significant change was noted in a group of healthy, middle-aged normals without heart disease. Three different patterns, however, were found for patients with ischemic heart disease, with and without evidence of infarction.
Hemodynamic and Metabolic Effects of Hypothermia and Extracorporeal Circulation in Experimental Myocardial Infarction and Shock
Authors: Kuhn Leslie A. , Weiser Frank M. , D'Aria John , Apter Ronald
Published: June 2012

The hemodynamic and metabolic effects of combined extracorporeal circulation and hypothermia induced by veno-arterial shunting were determined in 32 dogs following the production of acute myocardial infarction with shock by plastic sphere coronary embolization. Cardiac output, central aortic pressure, left ventricular work, systemic vascular resistance, left ventricular contractile force, right atrial and left ventricular pressures, arterial pH, CO
2
, potassium, plasma hemoglobin, and hematocrit were determined in dogs brought to the level of ventricular fibrillation or arrest or to profoundly hypothermic levels of 5 to 10 C. esophageal temperature for four to six hours and then rewarmed; in those maintained at 28 to 30 C. esophageal temperature for four to six hours and then rewarmed; and in those remaining normothermic for four to six hours following coronary embolization. The average esophageal temperature at the time of ventricular fibrillation was 19.3 C., and at the time of complete asystole was 12.0 C., figures comparable to results in normal animals. It is concluded that an animal with acute myocardial infarction and shock is not more susceptible to fatal hypothermic arrhythmia than is a normal animal. It was also demonstrated that there was relatively little irreversible deleterious hemodynamic effect after five to six hours of profound or moderate hypothermia combined with low-flow extracorporeal circulation, although the more profoundly cooled animals did demonstrate a metabolic acidosis and less return to precooling levels of cardiac output and aortic pressure following rewarming than did those maintained at 28 to 30 C. Both the profoundly and moderately cooled animals demonstrated, following rewarming, more adequate recovery of cardiac output, aortic pressure, and systemic vascular resistance than did animals which remained normothermic for similar periods after coronary embolization, suggesting that hypothermia affords a "protective" effect in recent myocardial infarction.
Role of Vasoconstriction in Experimental Arteriosclerosis
Authors: Gutstein William H. , LaTaillade Jean N. , Lewis Leon
Published: June 2012

A method is given for the study of local neuroexcitation with subsequent vasoconstriction and its relationship to experimental arteriosclerosis in unanesthetized animals under normal laboratory conditions. Histological observations of vasoactive areas of stimulated blood vessels in the laboratory rat disclose some of the features observed elsewhere in experimental arteriosclerosis. Possible pathogenic mechanisms relating neurostimulation of autonomic arterial nerves with in situ arteriopathies are discussed.
Renin, A Physiologic Regulator of Renal Hemodynamics?
Authors: Schmid Herman E.
Published: June 2012

1. Injections of hog renin and formation of antirenin in the dog will prevent or reduce the elevation of blood pressure associated with constriction of the renal arteries, but will not affect the systemic blood pressure in the normal animal.

2. The kidneys of both the normal and renal artery constricted animal respond with an increase in renin content during hog-renin injections which correlates closely with the serum antirenin titer.

3. The juxtaglomerular cell appears to be the site of renin formation and in this location may affect postglomerular vascular resistance.

4. Dogs with high titers of antirenin apparently have a reduced capacity to respond to an alteration in postglomerular resistance.

5. It is proposed that renin formation is controlled normally by a pressure-sensitive feedback mechanism operating across the glomerulus between the juxtaglomerular cell and postglomerular resistance.
Effects of Blood Flow and Left Atrial Pressure on Pulmonary Venous Resistance
Authors: Kuramoto Kizuku , Rodbard Simon
Published: June 2012

Pulmonary venular pressure was measured in 11 thoracotomized dogs and in 8 isolated lung lobes by introducing a small catheter (O.D. 0.6 or 0.9 mm.) as far as possible retrograde into the pulmonary veins. In thoracotomized dogs, insufflated with a maximal air pressure of 6 mm. Hg, the mean pulmonary arterial, venular, and left atrial pressures averaged 18.4, 9.1, and 4.2 mm. Hg, respectively. An almost linear relationship was found between venular pressure and pulmonary blood flow, except in the low flow ranges; venular pressures exceeded left atrial pressure by one-fourth to one-half of the gradient from pulmonary artery to left atrium. The calculated pulmonary venous resistance decreased with increased blood flow. The fall in pulmonary vascular resistance resulting from elevation of the left atrial pressure was shown to reside primarily in the venous system, especially when left atrial pressure was low; arterial and capillary resistance also fell, but to a lesser extent. Pulmonary venular pressure is higher than left atrial pressure by a factor which varies with blood flow. The effect of such mechanical forces on the venous resistance is discussed.
Left Atrial Pressure Curve as an Index of Control of Fluid Volume
Authors: Dubel Stephen J. , Soloff Louis A.
Published: June 2012

The concept that the left atrial pressure or pulse pressure acts as a stimulus to receptors for control of fluid volume was tested by examining the data on 67 persons who underwent right and left heart catheterization. Although there is no direct relationship between left atrial pulse pressure and congestive heart failure, no patient in failure had a pulse pressure below normal. Furthermore, those with the more severe grade of failure had the highest left atrial pulse pressure and the more rapid ascent of the left atrial pressure curve. These findings are inconsistent with the concept that a diminished left atrial pressure or pulse pressure stimulates left atrial receptors to set in motion a train of events which provoke antidiuresis in congestive heart failure. On the other hand, if increased left atrial pressure or pulse pressure promotes diuresis, the mechanism is completely overridden by more potent factors in human congestive heart failure.
Metabolism of Differently Labeled Cholesterol in Normal and Hypercholesteremic Rabbit
Authors: Bartz Walter M. , Kojima Inouye , Connor Mary
Published: June 2012

C-4- and C-26-labeled cholesterols were fed via stomach tube to normal and several groups of hypercholesteremic rabbits. The serum, liver, and aortic cholesterol levels were measured, as were the liver and intestinal content and stool nonsaponifiable and saponifiable lipid fractions. The appearance of the isotopic cholesterol in these fractions and in the exhaled CO
2
was measured. The recovery rates of the cholesterol -26-C
14
was 20.0 to 38.3 per cent, and of the cholesterol -4-C
14
, 79.0 to 109.2 per cent. The cholesterol-fed animals showed distinctly higher radioactivity in the blood and in the aorta. The C-26, but not the C-4, activity was detected in the exhaled CO
2
. No activity was detected in the urine. Both tags were detected in the saponifiable fractions of the liver and intestinal contents. Arachidonic acid supplements to four rabbits resulted in increased excretion of activity in the saponifiable portion of the intestinal contents.
Functional Sympatholysis During Muscular Activity
Authors: Remensnyder John P. , Mitchell Jere H. , Sarnoff Stanley J.
Published: June 2012

The effects of both direct and reflexly induced increases in sympathetic activity on the blood flow to an extremity at rest and during muscular activity have been studied. When the O
2
uptake of an extremity is increased during muscular activity, its vascular resistance falls sharply with a small increase in O
2
uptake and thereafter declines only slightly. The responsiveness of a vascular bed to adrenergic stimulation diminishes sharply with a small increase in O
2
uptake and thereafter diminishes only slightly. The role of the carotid sinus as a sense organ which helps to regulate blood flow to the various tissues of the organism in accordance with their varying metabolic requirements rather than one which acts only as a receptor that helps to safeguard flow to the vital organs has been discussed.