bluuebunny/crossref_metadata_2025 huggingface dataset:
Hemodynamic Changes in Fetal Lamb in Utero in Response to Asphyxia, Hypoxia, and Hypercapnia
Authors: Assali N. S. , Holm L. W. , Sehgal N.
Published: June 2012

The effects of hypoxia (administration of 10 per cent O
2
in N
2
and constriction of the uterine arteries), of hypercapnia (administration of 8 per cent CO
2
in air), and of asphyxia (obstruction of the umbilical circulation) were studied on the fetus in utero in near-term pregnant ewes under spinal anesthesia.

Hypoxia and hypercapnia produced increases in the maternal arterial pressure, maternal heart rate, and uterine blood flow. Fetal arterial pressure and carotid and umbilical blood flows increased, while the fetal heart rate decreased. Fetal femoral flow decreased during hypoxia and increased during hypercapnia. There was a delay of five to six minutes between the initiation of hypoxia or hypercapnia and the appearance of fetal circulatory changes.

Transient reduction of uterine blood flow evoked insignificant hemodynamic alterations in the mother and fetus. A reduction of flow greater than 50 per cent of control values produced a fetal bradycardia along with increases in fetal arterial pressure, carotid and umbilical flows.

Constriction of the umbilical veins with the umbilical arteries intact produced a prompt bradycardia together with a decrease in fetal arterial pressure and regional blood flows. Constriction of the umbilical arteries alone also produced a bradycardia with an initial rise in arterial pressure and carotid flow. Similar changes were observed after cutting the umbilical cord. Elimination of the low resistance of the placenta played a major role in these changes.

Placing the lamb in the head-down position caused a marked increase in carotid blood flow without greatly modifying arterial pressure.
Relation Between Mural Force and Pressure in the Left Ventricle of the Dog
Authors: Hefner Lloyd L. , Sheffield L. Thomas , Cobbs Glenn C. , Klip Willem
Published: June 2012

An investigation of the relationship in the dog between left ventricular pressure, left ventricular size, and total longitudinal force developed by the wall of the left ventricle is reported. This study required the development of a method for recording the force needed to keep together the two edges of a slit in the ventricle. Such a method is described, and samples of the force curves are shown, the general features of which are consistent with predictions from the physiology of muscle strips. The net force which the muscle fibers develop perpendicular to a given plane through the ventricle is almost identical to the product of the intracavitary pressure and the area of the cavity included in the plane. This relationship holds true regardless of the thickness of the wall or the shape of the ventricle.
Anaerobic Metabolism of Heart
Authors: Ballinger Walter F. , Vollenweider Heinz
Published: June 2012

Calculation of excess lactate removal and production, together with the arteriovenous difference of oxygen and carbon dioxide content of the coronary circulation, was performed during normal ventilation, induced hypoxia, and apnea in dogs. During ventilation with 100 per cent oxygen or room air, excess lactate was removed by the canine heart and continued to be removed until the arterial oxygen content fell to an average level of 9 ml./100 ml. of arterial blood. Below this level, excess lactate was produced by the heart, indicating a shift to anaerobic metabolism. The heart continued to work anaerobically, and its efficiency was increased since little, if any, oxygen was utilized. During severe hypoxia, the oxygen equivalent of the excess lactate produced was equal to the carbon dioxide produced. The heart, still performing work, was functioning completely anaerobically.
Partition of Coronary Flow and Cardiac Oxygen Extraction Between Coronary Sinus and Other Coronary Drainage Channels
Authors: Lafontant Robert R. , Feinberg Harold , Katz Louis N.
Published: June 2012

The open-chest anesthetized dog was prepared to permit the partition of coronary outflow into the coronary sinus and the extracoronary sinus venous channels. The effects of increased resistance-load of the left ventricle, of augmented effort of the right ventricle, and of induced acceleration of the heart rate were analyzed. In several animals, the effect of
l
-epinephrine exhibition was also determined. The effect of spontaneous tachycardia which developed in two dogs was also analyzed. A balloon inserted into the right ventricular cavity was used to augment its effort under isovolumic conditions.

Overall, the coronary sinus was found to drain approximately 60 per cent of the total coronary flow. Notable deviations from this mean were encountered in all experiments. The most marked occurred during spontaneous tachycardia and
l
-epinephrine exhibition, Significant changes also were observed when heart rate changes were induced. Increasing right ventricular effort had no apparent effect on the amount of blood drained via the coronary sinus. Augmenting left ventricular effort increased both coronary sinus and extra-coronary- sinus drainage more or less proportionately on the whole.

Myocardial oxygen consumption was measured as the sum of the oxygen consumption calculated from the coronary sinus and from the extra-coronary-sinus channels. In each case, this measurement was the product of flow in the drainage system and the arteriovenous oxygen difference found in that system. The venous oxygen content in the two drainage systems differed significantly and altered to varying degrees when conditions changed. Augmentation of left ventricular effort primarily increased the oxygen usage measured from the coronary sinus, while increased effort of the right ventricle primarily augmented that measured from the extra-coronary-sinus channels.

These observations lend support to the hypothesis that the coronary sinus represents blood draining primarily from the left ventricle and the extra-coronary-sinus channels primarily that from the right ventricle. However, the extra-coronary-sinus channels also drain the left ventricle, and the percentage distribution between them and the coronary sinus can vary significantly as far as cardiac oxygen consumption is concerned, especially when
l
-epinephrine is exhibited or when the heart changes its rate spontaneously or with an artificial pacemaker.

It is concluded that while the coronary sinus catheterization method is the best available to compute the oxygen usage of the left ventricle in the closed-chest animal or in man, it has limits of accuracy as a completely reliable method for assessing the oxygen consumed by the whole heart or the left ventricle. This limitation applies especially (1) during stress when the heart speeds up, (2) in hearts that are abnormal or diseased, and (3) when the effects of inotropic agents are being examined.
Pressure-Volume Relationships in Right Ventricle
Authors: Lafontant Robert R. , Feinberg Harold , Katz Louis N.
Published: June 2012

Contour changes of the pressure curve of the isovolumic right ventricle were analyzed as its volume increased and during spontaneous tachycardia and
l
-epinephrine exhibition. Evidence of an early diastolic dip going below ambient pressure was observed when spontaneous tachycardia developed. Evidence was clear that the impedance to filling during the phase of active relaxation lessened in the right ventricle when spontaneous tachycardia occurred and
l
-epinephrine was exhibited, and to a lesser extent when the ventricle became more dynamic. However, there was no evidence of any shift in the right ventricular pressure/volume relationship at the end of diastole during spontaneous tachycardia or
l
-epinephrine action. On the other hand, the pressure/volume relationship at the end of systole was altered under these two conditions, in that the pressure for any volume was increased. The curves of the pressure/volume relationship of the right ventricle at the end of systole and at the end of diastole were found to be similar in contour to those of the left ventricle except for the magnitude of change.
Effect of Acute Experimental Aortic Stenosis on Coronary Circulation
Authors: Blumenthal Marvin R. , Wang Hsueh-Hwa , Wang S. C.
Published: June 2012

Acute experimental aortic stenosis was produced by a special instrument in dogs anesthetized with morphine and chloralose. The effect of aortic stenosis was compared to aortic constriction distal to the coronary ostia in 45 matched runs in 12 dogs. In 10 pairs of matched runs in eight dogs, coronary oxygen A-V difference was measured. The runs were matched as to duration, heart rate, and rise in left intraventricular systolic pressure. With the increase in left intraventricular systolic pressure, the mean arterial blood pressure did not change significantly, and the left ventricular output either remained the same or decreased only slightly. The coronary sinus outflow increased in all runs of aortic stenosis as well as in aortic constriction. The coronary oxygen A-V difference tended to increase in aortic stenosis and to decrease in aortic constriction. The rise in coronary blood flow in aortic stenosis was due to vasodilatation alone, since the perfusion pressure remained the same and there was an increase in extravascular compression; in aortic constriction, the increased coronary blood flow was best explained by increased coronary perfusion pressure.
Relationship Between Adrenergic Activity and Cardiac Actions of Quinidine
Authors: Roberts Jay , Stadter Richard P. , Cairoli Vincent , Madell Walter
Published: June 2012

Unanesthetized dogs with complete heart block were used to explore the relationship between adrenergic activity and quinidine action on the heart. After vagolysis, quinidine still increased both the atrial and ventricular rates. Following reduction in adrenergic activity by reserpine, hexamethonium, or surgical sympathectomy, the atrial and ventricular pacemakers were depressed. After sympathetic activity had been reduced by a combination of hexamethonium and reserpine, quinidine caused profound pacemaker depression and sometimes ventricular asystole. Quinidine produced coupling and occasionally runs of ventricular tachycardia independent of the level of sympathetic activity. There was no significant prolongation of the QRS time by quinidine in doses of 5 and 10 mg./Kg. Both the development of ectopic pacemakers and the depression of pacemaker activity of quinidine were dose dependent.
Effect of Acute Sympathectomy on Responses to Angiotensin and Norepinephrine
Authors: Zimmerman B. G.
Published: June 2012

The vasopressor response to angiotensin administered intra-arterially to the perfused hindquarters of the dog was reduced significantly after acute sympathectomy. Responses to norepinephrine and tyramine remained unchanged. Similar results were obtained following gangliouic blockade with hexamethonium and cervical spinal transection. After the response to augiotensin was reduced following sympathectomy, the cut lumbar sympathetic nerves were stimulated electrically. During the period of stimulation, an increase in the vasoconstrictor effect to angiotensin was obtained, but complete restoration to the control magnitude was not seen consistently. Possible mechanisms for the reduction in the response to angiotensin following sympathectomy are discussed. The present evidence suggests that the tonic discharge of normally functioning sympathetic nerves is capable of facilitating the response to angiotensin and that sympathectomy results in an abolition of this effect.
Alteration of Coronary Blood Flow in the Dog by Inhalation of 100 Per Cent Oxygen
Authors: Sobol Bruce J. , Wanlass Stanley A. , Joseph Edward B. , Azarshahy Ismail
Published: June 2012

The administration of 100 per cent oxygen to the open-chest anesthetized dog results in a decrease in coronary blood flow. This occurs whether the animal is fully saturated on ambient air or not. It occurs as well whether or not the animal is in vascular collapse requiring pressor agents for the maintenance of its blood pressure.
Effects of Reserpine and Guanethidine on Venous Reflexes
Authors: Gaffney Thomas E. , Bryant W. Michael , Braunwald Eugene
Published: June 2012

The effects of reserpine and guanethidine on reflex venoconstriction were studied in a group of open-chest anesthetized dogs by the major vessel occlusion technique described by Bartelstone. Guanethidine (10 mg./Kg. intravenously) blocked reflex venous constriction following carotid occlusion and central vagal stimulation within, five minutes after injection in five dogs. Reserpine (0.5 mg./Kg. intravenously) required 50 to 110 minutes to abolish these venopressor reflexes in five animals. Pretreatment with either reserpine (0.5 mg./Kg. intraperitoneally on two consecutive days in four dogs) or guanethidine (10 mg./Kg. intravenously on two days in four dogs) also abolished reflex venoconstriction. These results indicate that reserpine and guanethidine are capable of blocking reflex venoconstriction, and it is suggested that this action may contribute to their effects in the treatment of hypertension.
Comparison of Adrenergic Activation by Anticholinesterases and by Hypoxia
Authors: Varagić Vladislav M. , Beleslin Duŝan B.
Published: June 2012

The hypertensive response to eserine in the rat is accompanied by an increase in lung resistance to inflation. Usually, these two effects do not occur simultaneously. The effects of acute hypoxemia on the blood pressure of the rat were found to be variable, ranging from a biphasic effect to a pure hypertension or hypotension. Inhalation of 11 per cent oxygen in nitrogen produced only a fall of blood pressure.

Bretylium was found to block the hypertensive response to eserine, while leaving intact the effect of eserine on the bronchi. On the other hand, bilateral vagotomy was found to block the effect of small doses of eserine on the bronchi and not to affect the blood pressure response to eserine.

Neostigmine caused a small rise of blood pressure and a very significant bronchoconstriction. It is concluded that bronchoconstriction and subsequent hypoxia might contribute to the hypertensive response to eserine in the curarized rat, but this mechanism does not seem to be of primary importance for a hypertensive action of eserine.
Hypocholesteremic Effect of Phenoxybenzamine (Dibenzyline), An Adrenergic Blocking Agent
Authors: Jagannathan S. N. , Srikantia S. G. , Gopalan C.
Published: June 2012

The effect of an orally effective adrenergic blocking agent, Dibenzyline, on serum cholesterol levels was studied in human subjects and in monkeys on high-fat diets. In addition, the effect of the phenoxyethyl analogue of Dibenzyline, G-D 131, was also investigated in monkeys.

The studies showed that the increase in serum cholesterol level brought about by a high-fat diet in monkeys could be considerably reduced by supplementation with Dibenzyline. This hypocholesteremic action was also observed with the analogue of Dibenzyline, G-D 131, which does not possess the adrenergic blocking property. It appears, therefore, that the hypocholesteremic action of Dibenzyline is independent of its adrenergic blocking activity. When a high-fat diet which also contained a high amount of cholesterol was used, Dibenzyline retarded the increase in serum cholesterol of monkeys for a considerable length of time.

Administration of Dibenzyline, 10 mg. daily for 11 days, brought about a fall in serum cholesterol in two of the three human subjects and arrested the further increase in serum cholesterol in the third subject on a high-butterfat diet. All the subjects showed increased fecal elimination of cholic and dihydroxycholanic acids during the Dibenzyline-supplemented period, suggesting that the hypocholesteremic effect of the drug is at least partly mediated through increased elimination of cholesterol as bile acids.
Effect of Angiotensin on Juxtaglomerular Cells and Vessels of the Kidney
Authors: Katz Yale J. , Patek Paul R. , Bernick Sol
Published: June 2012

Angiotensin II, given subcutaneously in pressor doses to rats three times a day, causes a prompt increase in the size and granulation of the juxtaglomerular cells. After one week of angiotensin injections, there is some loss of granules from these cells. Concurrently, degenerative changes develop in the intrarenal arteries. These changes may result from vasoconstriction in the vessels proximal to the afferent arterioles.

Epinephrine given in an amount similar in pressor effect to angiotensin II did not produce these changes. Vascular lesions were not seen in the heart, lung, brain, aorta, liver, and spleen of animals given angiotensin over the two-week injection period. This study provides additional evidence that the vessels of the kidney are uniquely sensitive to angiotensin.
Removal of Distortion from Indicator Dilution Curves with Analog Computer
Authors: COOPER JAMES K. , SCHWEIKERT J. ROBERT , ARNOLD THOMAS G. , LACY WILLIAM W.
Published: June 2012

A method has been developed for characterizing quantitatively, and for removing from indicator dilution curves, the distortion introduced by catheter sampling systems.

The method involves a specially constructed cuvette and analog computer analysis of the curves recorded by densitometers placed at the entrance of the catheter and at points downstream.

This method of correction of distortion is based on a general theory of function transformation which is applicable to all situations and not upon empirically established constants which are only valid in special situations.

The geometry (coiling, bending) of the catheter has been found to affect the distortion. Disruption of the flow pattern by insertion of a braided wire in the lumen causes less variation of the distortion caused by bending and coiling.

Distortion was not significantly affected by change in blood temperature in our system.
Uptake and Metabolism of Tritiated Norepinephrine in the Isolated Canine Heart
Authors: CHIDSEY CHARLES A. , KAHLER RICHARD L. , KELMINSON LESLIE L. , BRAUNWALD EUGENE
Published: June 2012

Using an isolated canine heart preparation, the myocardial norepinephrine pool was labeled by injecting tritiated norepinephrine into the blood perfusing the heart. The extraction of the norepinephrine during a single circulation through the coronary bed was shown to be large (74%). As the isotopic material, which was extracted, was released spontaneously from the norepinephrine pool 75% to 88% of it was metabolized before appearing in the coronary venous blood. The chief metabolite has been demonstrated to be normetanephrine which accounts for 39.0% to 61.7% of the spontaneously released norepinephrine. Because of this it is concluded that catechol-O-methyl transferase is the enzyme primarily responsible for the metabolic inactivation of norepinephrine in the canine heart. When release was increased by the injection of tyramine, more of the released norepinephrine appeared unmetabolized in coronary venous blood, suggesting that the enzymatic process by which norepinephrine is inactivated may be limited. Therefore, the extent to which enzymatic processes contribute to the termination of augmented adrenergic activity in the heart may be questioned.
Conduction of Cardiovascular Sound Along Arteries
Authors: FARBER J. JOB , PURVIS JAMES H.
Published: June 2012

The velocity of the transmission of the second heart sound in the thoracic aorta of dogs was measured. The average velocity was found to be 5.7 meters per second. The figure agrees well with the published figures for the pulse wave velocity in the thoracic aorta of dogs.

It was shown in humans that the velocity with which the second heart sound is conducted along the carotid artery does not change appreciably with frequency between 25 and 100 cycles per second. The average increase in velocity of 2.7% per half octave increase in frequency is, with 30% probability, due to random errors.

The fraction of the energy of a murmur transmitted in the form of a transverse vibration along the abdominal aorta of dogs was estimated from recordings made before and after the transverse motion of the arterial wall was impeded with a clamp. Most of the energy of the murmur was found to be transmitted in the form of a transverse vibration in the aortic wall.

It was concluded that most of the energy of cardiovascular sound in arteries is transmitted in a mode which is exactly analogous to the transmission of the pulse wave.

Some puzzling features of intravascular sound conduction, such as the apparent transmission of murmurs mainly in the direction of flow, could be explained on this basis.
Intraventricular Pressure and the Distribution of Coronary Blood Flow
Authors: CUTARELLI RENATO , LEVY MATTHEW N. , Zieske Harrison , Nelson Geroldine
Published: June 2012

The subepicardial: subsendocardial ratio of Rb
86
contents was measured and used as an index of the distribution of coronary blood flow to the more superficial and deeper layers of the canine myocardium. In the normally beating heart, the level of intraventricular pressure did not exert any detectable influence upon this ratio of Rb
86
contents. In the fibrillating heart, or in an ischemic (and presumably non-beating) region of the beating heart, on the other hand, this ratio increased as intraventricular pressure was progressively raised. It is concluded, therefore, that the intraventricular pressure exerts a significant influence upon the distribution of blood flow to the deeper and more superficial layers of myocardium only in regions which are not beating normally.
Cardiovascular Effects of Thyroxine Treatment in Hypophysectomized Rats
Authors: BEZNAK MARGARET , Marcsan A. , Fournie T.
Published: June 2012

Oxygen consumption, weight and rate of the heart, blood pressure, cardiac output and work are restored to normal if rats hypophysectomized two to three months previously are treated with thyroxine over a period of three to five weeks. Although under basal conditions the above parameters in these rats are the same as those in normal rats, the maximum output and work during loading by infusion of polyvinylpyrrolidone into the right side of the heart are less in hypophysectomized rats treated with thyroxine than they are in normal rats. Similarly, if a load is imposed on the heart by constriction of the aorta, cardiac output and work are well below the values measured in normal rats with aortic constriction. It is concluded that thyroxine treatment of hypophysectomized rats can restore to normal the performance of the cardiovascular system under basal conditions but that during loading (polyvinylpyrrolidone infusion, aortic constriction) the performance of the cardiovascular system is less than in normal rats.
Distribution of Heart Potentials on the Thoracic Surface of Normal Human Subjects
Authors: TACCARDI BRUNO
Published: June 2012

The distribution of isopotential lines on the thoracic surface of 15 normal subjects aged 15 to 43 was determined at 10 to 20 instants of time during ventricular activation. At the beginning of the QRS interval a precordial maximum and a dorsal minimum of potential can be observed. Thereafter, the minimum migrates toward the right shoulder and appears then anteriorly in the right subclavicular fossa, while another minimum appears near the mid-sternal line. The two minima finally merge together, and the potential distribution becomes dipolar once again. During the last third of the QRS interval the maximum of potential moves toward the left axillary and dorsal region, while a new maximum appears near the upper end of the sternum. A tentative correlation between surface and intracardiac electrical events can be established on the basis of the most generally accepted descriptions of ventricular activation processes. During some phases of ventricular activation, the potential distribution on the surface of the body is of the dipolar type, and there are no measurable local components; during other phases of ventricular depolarization, however, proximity potentials do appear on the thoracic surface, yielding information about local activation waves. When the ventricular activation is altered, the location and time course of local and dipolar potentials show important modifications.
Renal Blood Flow, Glomerular Filtration Rate, Renal PAH Extraction Ratio, and the Role of the Renal Vasomotor Nerves in the Unanesthetized Rabbit
Authors: Pascoe PAUL I. , KORNER Yvonne
Published: June 2012

The unanesthetized rabbit has been found to be a satisfactory animal for studying the renal circulation. Techniques for measuring renal clearances and cardiac output, for carrying out renal vein catheterization, and for measuring renal clearances separately for each kidney are described. Normal values are presented from data obtained from 86 rabbits. Renal blood flow and glomerular filtration rate were found to be stable, judged by the reproducibility of these measurements over a period of three hours. Renal PAH extraction ratios averaged 95.5% in 16 unanesthetized animals. In 12 animals renal blood flow was 6% higher in one chronically denervated kidney than in the contralateral innervated kidney, indicating a low degree of sympathetic vasoconstriction in the normal resting circulation of the rabbit. All the results were obtained in the rabbit in the course of moderate water and mannitol diuresis.
Repair Processes in Arterial Tissue. Biochemical Alterations in Rabbit Aorta Induced by Norepinephrine
Authors: LORENZEN IB
Published: June 2012

Male albino rabbits were injected intravenously with large doses of l-norepinephrine daily for 15 days. Morphological alterations in the aortae were insignificant but significant increases in the aortic content of acid muco-polysaccharides and in the uptake of S
35
-labeled sulfate in acid mucopolysaccharides were observed in the experimental animals in comparison to saline-injected controls. Increase in the carbazole to orcinol ratio of the acid mucopolysaccharides indicated qualitative, as well as quantitative, alterations. The alterations were interpreted as reparative processes in the arterial wall following injury produced by the intense vasoconstrictor action of norepinephrine. This interpretation finds support in the similarity between the observed alterations and those which occur during wound-healing or which follow exposure to a variety of agents known to damage blood vessels.
Studies on the Origin of the Lipid Components of Xanthomata
Authors: WILSON JEAN D.
Published: June 2012

As the result of in vitro studies of lipid synthesis in slices of rabbit and human xanthomata and of studies on the origin of xanthoma cholesterol in the intact rabbit it has been concluded that although slight amounts of cholesterol may be synthesized in situ, the xanthoma cholesterol is derived predominantly from the blood stream. It has also been demonstrated that the xanthomata possesses the ability to synthesize actively two other lipid components in these lesions--phospholipids and fatty acids.
Juxtaglomerular Cells
Authors: HARTROFT PHYLLIS M.
Published: June 2012

Morphological and ultrastructural characteristics of JG cells are consistent with the concept of secretory or endocrine activity. At least in the chronic situation, evidence indicates that hypergranulation of JG cells--or elevated JGI--means hyperactivity. Factors that control cytological activity of JG cells are concerned with volume or pressure changes and with sodium. Despite the influence of potassium in the adrenal zona glomerulosa, potassium does not affect JG cells. The fluorescent antibody technique in the rabbit, dog, and domestic pig, demonstrates that renin is located in the JG cells, but not in the macula densa or other structures of the renal cortex. Inhibition of sodium retention by antirenin in sodium-deficient dogs provides further evidence that renin, secreted by JG cells, is concerned in the regulation of sodium excretion, whether by its influence on aldosterone or by an intrarenal mechanism.
Myocardial Necrosis in Rats: Serum Enzymes, Adrenal Steroid and Histopathological Alterations
Authors: Wexler Bernard C. , Kittinger George W. , Springs Myra E. , Conatser DHman
Published: June 2012

Acute infarctoid myocardial necrosis has been produced in virgin rats by injection of isoproterenol. The lesions are essentially identical, both grossly and microscopically, with naturally occurring acute infarcts which we have observed in arteriosclerotic breeder rats.

During the establishment of drug-induced necrosis the animals displayed signs of shock and congestive heart failure. Serum transaminases and lactic dehydrogenase levels underwent changes which coincided with the establishment and repair of the myocardial damage. The male rats had a higher mortality rate than the females. The male rats also developed more massive myocardial necrosis and showed a decreased capacity to repair myocardial damage. The adrenal glands became greatly hypertrophied and the thymus became severely involuted coincident with the acute establishment of the myocardial lesion. In vitro studies indicated that changes in adrenal function also accompanied the acute onset of myocardial destruction. The adrenal hypertrophy decreased during recovery from shock and during repair of the lesion.
Sodium, Potassium, and Peripheral Resistance in the Rat Tail
Authors: FRIEDMAN SYDNEY M. , NAKASHIMA MIYASHI , FRIEDMAN CONSTANCE L. , Vizsolyi Elizabeth
Published: June 2012

The early effects of systematic changes of environmental Na
+
on vascular resistance and on cationic equilibration were studied using a closed circuit perfusion of the rat tail. The recirculating medium was monitored for Na
+
and K
+
with glass electrodes operating through a computer. The composition of a given medium perfusing the vascular bed is very rapidly altered as it comes into equilibrium with cells and interstitial tissue. Because exchanges begin quickly, only limited conclusions can be drawn from manipulation of a perfusing medium without close monitoring of the equilibration process. Reduction of sodium in the medium, using sucrose as osmotic replacement, is followed by a rapid efflux of Na
+
, some of which apparently comes from cells. This is associated with a fall of vascular resistance. Neither efflux nor fall in resistance occurs if choline or K
+
is used as replacement for Na
+
. Elevation of potassium in the medium is followed by a gradual fall during equilibration of the ion and, if K
+
is raised sufficiently, an increase in vascular resistance occurs. These findings support the view that the transcellular distribution of Na
+
and K
+
is causally involved in the maintenance of vascular tone.
Effect of Angiotensin II on the Intact Forearm Veins of Man
Authors: DE PASQUALE NICHOLAS P. , BURCH GEORGE E.
Published: June 2012

Angiotensin II was injected into an isolated venous segment in eighteen human subjects and administered intravenously into a systemic vein in five other subjects. Injections of angiotensin II into an intact isolated venous segment produced no constriction of the segment. Intravenous systemic infusion of angiotensin II produced a slight constriction of the isolated venous segment in three subjects (mean 44 mm H
2
O) and no constriction of the segment in two subjects. The constriction in the venous segment associated with the systemic intravenous administration of the drug could be interrupted by blocking the nerves supplying the venous segment. Thus, angiotensin II has no direct effect upon the forearm veins of man. The rise in segmental venous pressure following the intravenous infusion of angiotensin II appears to originate from reflexes located outside the venous system which influence tone of the superficial veins of the forearm of man.
Hemodynamic Variables Affecting the Relation Between Mean Left Atrial and Left Ventricular End-Diastolic Pressures
Authors: WALLACE ANDREW G. , MITCHELL JERE H. , SKINNER N. SHELDON , SARNOFF STANLEY J.
Published: June 2012

The observations reported in this paper support the view that a vigorous and properly timed atrial contraction, by transporting blood into the ventricle and by approximating the atrioventricular valve prior to ventricular systole, provides a mechanism by which mean atrial pressure is maintained at a substantially lower level for any ventricular end-diastolic pressure than would be the case if these functions of the atrium were not operative. The central nervous system, by way of efferent sympathetic pathways, can regulate appropriately the vigor and timing of atrial systole as well as the duration of the diastolic filling period. The net effect of such regulation is to decrease mean atrial pressure at any given heart rate and cardiac output, and to permit rapid heart rates which could not otherwise be tolerated without elevations of atrial pressure. The fact that MLAP-LVEDP is independent of aortic pressure and stroke volume, and of heart rate over certain ranges suggests that this hemodynamic measurement is uniquely dependent on, and therefore useful in the analysis of, atrial performance.
Damping of Sound on the Chest Surface
Authors: FABER J. Job
Published: June 2012

The damping of sound during its transmission over the chest wall was measured in humans in order to establish whether the heart sounds spread in two-dimensions over the chest wall from their auscultatory areas, or in three-dimensions directly from their origins deep in the body.

The damping of frequencies from 50 to 400 cycles/sec in soft tissues and ribs can be predicted by an equation which consists of a geometrical term and a term due to viscous damping.

The term which represents the viscous damping in the soft tissues and ribs of the chest wall is proportional to the square root of the frequency.

The value of the geometrical term suggested that the intensity of the sounds was inversely proportional to the distance travelled, rather than inversely proportional to the square of the distance travelled. The former relationship would apply if the sound travels in a two-dimensional plane of material rather than in a three-dimensional volume. This is consistent with our earlier finding that the heart sounds travel from the heart to their auscultatory areas on the chest and from there over the chest surface.

For frequencies under 100 cycles/sec, the chest wall appears to be homogenous. For frequencies above 100 cycles/sec, the damping is much less for transmission over the sternum than for transmission elsewhere on the precordium.
Sustained Depressor Effect of Renal Medullary Extract in the Normotensive Rat
Authors: LEE JAMES B. , HICKLER ROGER B. , SARAVIS CALVIN A. , THORN GEORGE W.
Published: June 2012

Crude homogenates of rabbit, medulla produced a sustained depression of blood pressure when injected intravenously into the normotensive, anesthetized, pentolinium-treated rat. Similar activity was present in rat medulla, but not in extracts of renin-free cortex or certain nonrenal tissues.

The sustained depressor activity of medulary extract possessed different physiological and chemical characteristics from the shortacting nucleotide depressor activity which is present in both cortical and medullary extracts. In addition, prolonged medullary depressor activity was separable from medullary nucleotide activity by column chromatography.

The activity responsible for sustained depressor activity was a dialyzable, ethanol soluble, low molecular weight(<4500 mol wt) substance(s) which was resistant to a mixture of peptide hydrolases and destroyed by heating for one hour at 100°C.
Blood Coagulation Changes in Rats Fed High Fat Diets
Authors: Fisher Lyman M. , Kagan Eugene , Kupfer Henry G.
Published: June 2012

High fat diets were given
ad libitum
or
force-fed
to rats. The incidence of thrombosis in animals fed a cow butter diet was higher than in those fed a cocoa butter diet. No thrombosis was found in rats fed a diet containing peanut oil. Coagulation studies performed at weekly intervals on blood samples obtained from a tail vein of rats fed the diets
ad libitum
showed that there was a gradual but marked increase in the levels of Factors II, VII, and X of animals fed a diet containing cow or cocoa butter, but not one containing peanut oil. Several weeks prior to death, however, the level of all coagulation factors, including Factors I and V, fell. A significant prolongation of the values for the partial thromboplastin time was found in animals killed at the time when levels of plasma coagulation factors decreased. The pattern of changes in concentration of plasma coagulation factors was similar in the groups of animals dying with proven thrombosis and in those in which thrombosis was not found. All rats force-fed the above two diets died within two weeks, showing a marked fall in all coagulation factors and no thrombosis. Weight loss was more pronounced in the groups of animals fed the diet containing cow butter and cocoa butter than in animals fed Purina chow. Autopsy findings were: intra-ventricular thrombi with myocardial infarction, lung hemorrhage, pneumonia, and rarely jaundice. No cause of death other than inanition was discernible in some of the animals. Marked fatty infiltration of the liver was a feature of all animals autopsied.
Lipid Pattern in Experimental Canine Atherosclerosis
Authors: GUIDRY MARION A. , GEER JACK C. , ROBERTSON WILLIAM B.
Published: June 2012

An experiment was conducted to compare the effects of feeding cholesterol alone, thiouracil alone, and cholesterol and thiouracil combined, on the serum lipids and arteries of dogs. These substances were added to a basal diet rich in linoleic acid. Serum cholesterol and total serum lipids were determined periodically during the four-month period of feeding, and serum and tissue lipids obtained at necropsy were fractionated and analyzed by silicic acid column and gas chromatography.

During the period of feeding the experimental diets, three levels of hypercholesterolemia and hyperlipemia were produced. The smallest increase over control levels occurred in the animals receiving cholesterol alone; an intermediate increase was produced in those receiving thiouracil alone; and the greatest increase occurred in the group receiving both cholesterol and thiouracil. The lipemia was proportional to the cholesterolemia in each of the experimental groups. Only those dogs receiving both cholesterol and thiouracil developed arterial lesions.
Effects of Cardiac Sympathetic Nerve Stimulation on Conduction in the Heart
Authors: WALLACE ANDREW G. , SARNOFF STANLEY J.
Published: June 2012

The influence of cardiac sympathetic nerve stimulation on certain aspects of ventricular excitation was examined in dogs at constant heart rate. Bipolar electrodes were used to record electrical activity from atrium, His bundle, right Purkinje papillary muscle junction, basal interventricular septum and the epicardial surface of the ventricles. Stimulation of the left stellate ganglion reduced markedly the A-V nodal delay, but produced little or no change of conduction velocity in the Purkinje system or in the pattern of epicardial depolarization. Conduction in muscle was enhanced slightly by stellate stimulation and appears to account for the observed decrease of 2 to 3 msec in ventricular activation time. These data indicate that cardiac sympathetic nerve stimulation does not result in major changes in the sequence of ventricular excitation.
Coronary and Myocardial Actions of Angiotensin
Authors: FOWLER NOBLE O. , HOLMES JOHN C.
Published: June 2012

In the dog heart-lung preparation, single injections of 40 µg angiotensin II produced consistently a biphasic response. Initial impairment of cardiac function was observed with decrease of cardiac output and of ventricular force, and with increase of atrial pressures. After 10 to 20 seconds, there was a positive inotropic effect, with an increase of cardiac output and of ventricular force, and a decrease in atrial pressures. Responses were comparable in reserpinized and nonreserpinized preparations. Tachyphylaxis to angiotensin was found consistently in the heart-lung preparation, with a regular decrease in response following second and third injections. A positive inotropic action of angiotensin II was demonstrated in the cat papillary muscle preparation. These studies demonstrated that angiotensin has a direct cardiac action, namely a positive inotropic effect. This action probably does not depend upon myocardial stores of catecholamines.

When the left anterior descending coronary artery of the dog was perfused with blood at a constant flow, single intracoronary injections of angiotensin (1.0 µg) consistently increased coronary resistance (6% to 92%). Continuous intracoronary infusion of angiotensin increased coronary vascular resistance when blood concentrations were as low as 0.42 µg/ liter. No evidence of initial cardiac depression or of increased coronary vascular resistance was found after norepinephrine.

It is concluded that the initial impairment of cardiac performance following angiotensin is caused at least in part by decreased coronary blood flow. Caution is suggested in the use of angiotensin in the treatment of human shock because of its action upon the coronary circulation.
Demonstration by Pressor and Steroidogenic Assays of Increased Renin in Lymph of Dogs with Secondary Hyperaldosteronism
Authors: HIGGINS JAMES T. , DAVIS JAMES O. , URQUHART JOHN
Published: June 2012

Thoracic duct lymph from normal dogs and from dogs with hyperaldosteronism secondary to thoracic inferior vena caval constriction was assayed for renin. After acidification, dialysis and incubation, lymph from animals with caval constriction showed more angiotensin-like material than lymph of normal dogs when assayed for both pressor and aldosterone-stimulating activities. Nephrectomy was followed by a marked decrease or disappearance of renin activity from lymph. Lymph from dogs with renal venous hypertension secondary to abdominal vena caval constriction did not show increased renin content. Dual assay makes detection of angiotensin II more specific and the findings indicate that increased amounts of renin are released from the kidney into lymph of dogs with experimental secondary hyperaldosteronism.
Myocardial Oxygen Consumption During Ventricular Contraction and Relaxation
Authors: MONROE R. Grier
Published: June 2012

Determinations of left ventricular oxygen consumption were made in the isolated heart of a dog while the ventricle performed work by compressing air. In the described preparation the air compressed by the ventricle could be rapidly released and the ventricular pressure pulse repeatedly interrupted at specific points during its cycle. Upon interrupting the pressure pulse at its peak there was a 10% increase in peak pressure that appeared in the subsequent four to five beats. When the intraventricular pressure was released at various points during its ascent to peak pressure, left ventricular oxygen consumption could be correlated with both the pressure, at which it was interrupted, and the area under the pressure pulse. When the oxygen consumed by a ventricle developing a full pressure pulse was compared to that of a ventricle in which the intraventricular pressure was released at its peak-land when the peak systolic pressure of the two compared pulses were equal-then the oxygen consumed by the ventricle when the pulse was interrupted averaged 91% of that when the pulse was full. These studies indicate that by the time the pressure pulse has reached its peak, myocardial oxygen consumption has been largely determined, and that the oxygen cost of the ventricular relaxation is small.
Humoral Transmission of Cardiorespiratory Changes in Experimental Lung Embolism
Authors: Halmagyi DENIS F. J. , STARZECKI BOLESLAV , HORNER GEORGE J.
Published: June 2012

Pairs of sheep were connected via a unilateral carotid-jugular anastomosis in fourteen experiments. With the cross circulation open, pulmonary embolism induced in the donor sheep produced a rise in pulmonary arterial pressure, a fall in lung compliance, and an increase in ventilation in the recipient animal. The transmitted effects were more pronounced with barium sulfate lung embolism than with blood clot lung embolism.

These observations are consistent with the assumption that in acute experimental lung embolism a humoral agent is being released causing constriction of the lung vessels and airways.
Cardiac Arrhythmias Produced by Catecholamines in Anesthetized Dogs
Authors: MOORE E. NEIL , MORSE HOWARD T. , PRICE HENRY L.
Published: June 2012

1. Electrograms have been recorded simultaneously from the right atrium, bundle of His, and both ventricles, together with the lead II electrocardiogram in dogs receiving cyclopropane and oxygen. Following the administration of norepinephrine, both bigeminal rhythms and monofocal ventricular tachycardias were observed.

2. In our studies both the coupled and the monofocal ventricular beats originated distal to the His electrode.

3. The mechanism of the coupled beats could not be analyzed using either gross or intracellular recording methods; the monofocal tachycardias appeared to result from increased pacemaker activity in the ventricular conducting system.

4. The present results emphasize the hazards of proposing mechanisms to explain arrhythmias solely on the basis of electrocardiographic evidence.
Comparison of Tropomyosins from Cardiac and Skeletal Muscle
Authors: KATZ ARNOLD M. , CONVERSE RONALD P.
Published: June 2012

No differences were found between the sedimentation coefficients, intrinsic viscosities, amino acid contents, and peptide patterns resulting from tryptic digestion of rabbit cardiac and skeletal tropomyosins. From sedimentation and viscosity data, the molecular weights of cardiac and skeletal tropomyosins were estimated to be 54,800 for both. This value is similar to previous estimates of the molecular weight of rabbit skeletal tropomyosin.

No evidence was obtained for the existence in heart muscle of tropomyosin
A
. Of the three more abundant contractile proteins of the heart, myosin, actin, and tropomyosin, only myosin appears to differ from its skeletal counterpart.
Electrocardiographic Patterns During Resuscitation After Experimentally Induced Ventricular Fibrillation
Authors: MILLER DAVID I. , NACHLAS MARVIN M.
Published: June 2012

Continuous closed-chest massage (mechanized and manual) and ventilation with pure oxygen were performed for 15 and 30-minute periods, to maintain viability in 43 dogs with electrically induced ventricular fibrillation. External countershocks were applied and 32 of the animals lived more than 48 hours. The return of electrical and hemodynamic functions of the heart, as well as the function of the central nervous system, were graded arbitrarily to characterize recovery from poor to excellent. Electrocardiographic changes (lead II) were studied in detail and compared with the gross result of survival or death, and also with more quantitative characterization of recovery.

When the initial electrocardiogram after defibrillation contained a P wave, the prognosis was most favorable. When the P wave was absent the amount of ST segment depression in the initial complex differentiated the better from the poorer results.

During the first hour following defibrillation, a variety of arrhythmias was noted, as well as varying degrees of change in the R, T, and ST portions of the electrocardiogram. The most serious arrhythmias, in decreasing severity, were idioventricular rhythm, atrio-ventricular block, and multiple premature ventricular contractions. Recovery was poorest when multiple arrhythmias occurred. Changes in the voltage of the R and T waves could not be correlated with prognosis. However, more favorable recoveries were noted in animals without significant changes in the ST segment than in animals having ST segment depression greater than 4 mm.