bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of isolated rat heart cells to hypoxia, re-oxygenation, and acidosis.
Authors: Altschuld R A , Hostetler J R , Brierley G P
Published: June 2012

Responses of isolated adult rat heart cells to conditions that emphasize various aspects of ischemia have been evaluated. Cells maintained in hypoxic media with limited substrate deteriorate more rapidly than aerobic controls supplemented with glucose. Two distinct irreversible pathways for cell alteration can be distinguished as follows: (1) continued anaerobic aging in the absence of glucose results in the production of large numbers of cells which retain the rod-shaped morphology of heart cells in situ, but which have lost sarcolemmal integrity, and (2) after a period of anaerobic aging, reaeration of the cells produces large numbers of rounded cells in irreversible contracture. These cells maintain an intact sarcolemma and are indistinguishable from those produced by addition of 1 mM Ca2+ to Na+-loaded, aerobic cells. Contracture of isolated cells on re-aeration is at least superficially analogous to the oxygen paradox in situ, but since the isolated cells maintain an intact sarcolemma, there is no loss of creatine phosphokinase or other components of the cytosol. Incubation of isolated heart cells at acid pH (pH 6.8 to 6.2) largely prevents both Ca2+-dependent contracture and a Ca2+- dependent loss of respiratory capacity. The acidic conditions virtually eliminate the net influx of 45Ca2+ into isolated cells that occurs at neutral pH, and the inhibition appears to be localized at the sarcolemma.
Prejunctional inhibition of norepinephrine release caused by acetylcholine in the human saphenous vein.
Authors: Rorie D K , Rusch N J , Shepherd J T , Vanhoutte P M , Tyce G M
Published: June 2012

We performed experiments to determine whether or not acetylcholine exerts a prejunctional inhibitory effect on adrenergic neurotransmission in the human blood vessel wall. Rings of human greater saphenous veins were prepared 2 to 15 hours after death and mounted for isometric tension recording in organ chambers filled with Krebs-Ringer solution. Acetylcholine depressed contractile responses to electric activation of the sympathetic nerve endings significantly more than those to exogenous norepinephrine; the relaxations caused by the cholinergic transmitter were antagonized by atropine. Helical strips were incubated with [3H]norepinephrine and mounted for superfusion. Electric stimulation augmented the fractional release of labeled norepinephrine. Acetylcholine caused a depression of the evoked 3H release which was antagonized by atropine but not by hexamethonium. These experiments demonstrate that, as in animal cutaneous veins, there are prejunctional inhibitory muscarinic receptors on the adrenergic nerve endings in the human saphenous vein. By contrast, the human vein also contains postjunctional inhibitory muscarinic receptors.
The effect of right ventricular filling on the pressure-volume relationship of ejecting canine left ventricle.
Authors: Maughan W L , Kallman C H , Shoukas A
Published: June 2012

Acute shifts in the pressure-volume relationship of the left ventricle occur under several conditions. One potential mechanism for this phenomenon is ventricular interdependence, that is, the influence of right ventricular filling on the left ventricle. This mechanism was studied in an isolated cross-circulated ejecting canine heart preparation with balloons sewn into both right and left ventricles and connected to volumetric chambers allowing continuous and accurate simultaneous measurement of right and left ventricular pressures and volume. Sets of left ventricular pressure-volume loops were obtained under a variety of right ventricular volumes. Experiments were repeated with and without the pericardium. Both diastole and systole were studied. We show that in the pericardium-free heart working over a normal range of volumes, the right ventricle exerts little influence on left ventricular pressure. With the pericardium present, there is a small but significant effect of right ventricular volume on left ventricular pressure during systole and diastole. Over a wider range of volumes imposed in the arrested heart, the right ventricle does influence left ventricular pressure even without the pericardium. Thus we have demonstrated that ventricular interdependence is not likely to lead to large acute pressure-volume shifts, either during diastole or systole, except in the presence of considerably above normal right ventricular volumes.
Ontogeny of blood pressure and the renin-angiotensin-aldosterone system. Sequential studies in the newborn lamb.
Authors: Wilson T A , Kaiser D L , Wright E M , Peach M J , Carey R M
Published: June 2012

To test the hypothesis that the rise in arterial pressure occurring with maturation is due to an increase in the vascular responsiveness to angiotensin II, sequential cumulative doses of angiotensin II were infused intravenously into chronically catheterized newborn lambs maintained on a constant, weight-adjusted sodium intake from birth to 8 weeks of age. Basal mean arterial pressure correlated with both age and weight, but age was a stronger determinant of mean arterial pressure than was weight. No change in the mean arterial pressure response to angiotensin II occurred with maturation. Basal plasma renin activity and plasma aldosterone concentrations were low and did not change significantly with age. Therefore, in the newborn lamb in the sodium replete state, age is a better determinant of arterial pressure than is weight. However, an age-related change in vasoconstrictor responsiveness to angiotensin II does not occur and, therefore, cannot account for the rise in arterial pressure that is observed with maturation.
Blood pressure response to central and/or peripheral inhibition of phenylethanolamine N-methyltransferase in normotensive and hypertensive rats.
Authors: Black J , Waeber B , Bresnahan M R , Gavras I , Gavras H
Published: June 2012

We studied the effects on blood pressure and heart rate of two different phenylethanolamine N-methyltransferase (PNMT) inhibitors in normotensive, in two-kidney renal hypertensive, and in deoxycorticosterone-salt (DOC-salt) hypertensive rats. One compound (SK&F 64139) blocks the conversion of norepinephrine to epinephrine in both the central and the peripheral nervous system, whereas the other (SK&F 29661) does not cross the blood-brain barrier and therefore is active mostly in the adrenal glands. In the rats given SK&F 29661, practically no acute blood pressure changes were in the adrenal glands. In the rats given SK&F 64139 induced only a minor blood pressure and heart rate response in normotensive and two-kidney renal hypertensive rats. However, in DOC-salt hypertensive rats, it reduced arterial pressure to approximately normal levels and concomitantly slowed pulse rate. There was a close correlation between the magnitude of the blood pressure response observed in all SK&F 64139-treated animals and the control plasma norepinephrine (4 = -0.795, P less than 0.001) and epinephrine (r = -0.789, P less than 0.001) levels. These results suggest an important role for central epinephrine in regulating the peripheral sympathoadrenomedullary and the baroreceptor reflex activity, particularly when the maintenance of the high blood pressure is not renin-dependent.
Regulation of large coronary arteries by increases in myocardial metabolic demands in conscious dogs.
Authors: Macho P , Hintze T H , Vatner S F
Published: June 2012

In order to assess the effects of increasing myocardial metabolic demand on the large epicardial coronary arteries, we measured left circumflex coronary artery diameter (ultrasonic transit time technique) and blood flow in conscious dogs with chronically implanted transducers. Myocardial oxygen consumption was increased by pacing-induced tachycardia and aortic constriction, and monitored by multiplying left circumflex coronary arterial blood flow by coronary arterio-venous oxygen content difference. Increase of heart rate by 90 beats/min caused myocardial oxygen consumption to increase by 34 +/- 4.3% (1 SEM); coronary blood flow at constant arterial pressure to increase by 32 +/- 6.8%; and coronary diameter to increase by 0.07 +/- 0.01 mm, P less than 0.01. Aortic constriction, producing a 53 +/- 5.1% increase of left ventricular systolic pressure, caused myocardial oxygen consumption to increase by 49 +/- 7.2%, coronary blood flow to increase by 50 +/- 6.0%, and coronary diameter to increase 0.03 mm, P less than 0.01. The increases in coronary artery diameter were gradual, not immediate, in onset and not altered by beta-adrenergic blockade. Thus, increased myocardial metabolic demand dilates large epicardial coronary arteries, but with a slower response time than the rapid dilation of the smaller resistance vessels.
Myocardial relaxation. III. Reoxygenation mechanics in the intact dog heart.
Authors: Blaustein A S , Gaasch W H
Published: June 2012

Reoxygenation of hypoxic isolated cardiac muscle results in prolonged duration of contraction-relaxation. To determine whether similar mechanical changes occur in the intact left ventricle (LV), and especially to assess the influence of prolonged relaxation on LV diastolic stiffness, we examined LV pressure transients (micromanometer) and changes in myocardial segment length (ultrasonic transit time) during reoxygenation in 22 anesthetized dogs following 15 minutes of hypoxia (PaO2 = 21 +/- 2 mm Hg). The time constant (T) of LV isovolumic exponential pressure decline was used as an index of myocardial relaxation; LV end-diastolic stiffness was assessed from stiffness constants derived from multiple coordinates of end-diastolic pressure and segment length (volume loading). During reoxygenation, after LV systolic pressure and segment length measurements had returned to control levels, relaxation was prolonged; T increased from a control of 32 +/- 2 to 44 +/- 3 msec at 5 minutes of reoxygenation (P less than 0.01). Prolonged relaxation resulted in a consistent increase in LV early-diastolic pressures. Furthermore, calculated values for LV end-diastolic stiffness increased during reoxygenation when the next beat began less than 3.5 T after maximum negative dP/dt; this condition was present more frequently at a heart rate of 150 beats/min than at 120 beats/min. Thus, rapid correction of acute hypoxia in the dog results in prolonged LV relaxation; prolonged relaxation can influence LV end-diastolic stiffness when relaxation is sufficiently slow and/or when diastole is sufficiently short.
The effect of streptozotocin-induced diabetes in rats on cardiac contractile proteins.
Authors: Malhotra A , Penpargkul S , Fein F S , Sonnenblick E H , Scheuer J
Published: June 2012

In order to determine whether diabetic cardiomyopathy in rats is associated with altered contractile proteins, male and female rats were made diabetic with intravenous streptozotocin (STZ). Calcium ATPase activity of cardiac actomyosin was significantly decreased after 1 week of diabetes and was depressed by 60% by 2 weeks. Rats pretreated with 3-O-methyl glucose to prevent the hyperglycemia caused by STZ had normal Ca2+-actomyosin ATPase activities, and non-diabetic rats whose food was restricted to keep their body and heart weights similar to those found in diabetic animals had only a slight fall in actomyosin ATPase activity. Ca2+-ATPase and actin-activated ATPase activities of pure myosin were similarly depressed in preparations from hearts of diabetic animals. Sodium dodecylsulfate gel electrophoresis and isoelectric focusing failed to reveal differences in the patterns of contractile proteins or light subunits between diabetics and controls, but pyrophosphate gels showed a shift in the myosin pattern. Because of depressed circulating thyroid hormone levels in diabetic animals, cardiac contractile proteins were also studied in preparations from thyroidectomized rats. Calcium activities of actomyosin and myosin ATPase were lower than values found in hearts of diabetic rats. When diabetic animals were kept euthyroid with thyroid replacement, actomyosin ATPase activity was still depressed. Thus STZ diabetes causes a significant decrease in cardiac contractile protein ATPase activity. This may be related to altered proportions of myosin isoenzymes.
Correlation of alterations in cation exchange and sarcolemmal ultrastructure produced by neuraminidase and phospholipases in cardiac cell tissue culture.
Authors: Langer G A , Frank J S , Philipson K D
Published: June 2012

Myoblasts and fibroblasts in cultured derived from neonatal rat hearts were exposed to neuraminidase and phospholipases C (PLC) and A2 (PLA2). Calcium (Ca) and potassium (K) exchange of the cells was measured before and after enzymatic exposure. The exchange characteristics of control and treated cells were correlated with cellular ultrastructure including assessment of intramembrane particle (IMP) density and aggregation by freeze-fracture. Neuraminidase exposure (removal of sialic acid) known to produce marked increase in calcium permeability without change in potassium permeability in myoblasts produced no change in IMP configuration of these cells. PLC, however, produced marked increase in both Ca and K permeabilities, permitted entry of La, and was associated with IMP aggregation in myoblastic cells. PLA2 produced no change in ionic permeability and no alteration in intramembrane particle configuration in myoblasts. Exposure of fibroblasts to PLC caused no change in either Ca or K permeability and no change in IMP distribution. These results, coupled with those of previous studies of permeability changes induced by sialic acid removal, indicate that control of cellular Ca permeability resides in at least two separate sites at the cellular surface: (1) the glycocalyx and (2) the lipid bilayer. By contrast, K permeability control is based within the bilayer. Ultrastructural correlations suggest that IMP aggregation may be associated with changes in bilayer permeability.
Birefringent Property of Hypercholesterolemic Rabbit Serum
Authors: EVANS SILAS M. , BROWN KENNETH D. , IHRIG HARRY K.
Published: June 2012

Serum of hypercholesterolemic rabbits, when pulsated for 72 hours at pressures of 300 mm. Hg/0 mm. Hg with a pulse rate of 80 produced a birefringent deposit in excised pieces of rabbit aortae. Serum from normal rabbits did not produce this deposit. The active component or components responsible for this deposit are in the β-lipoprotein fraction of serum. The birefringent material is detectable in serum by this method before lipoid degeneration of the arterial intima becomes apparent in the sacrificed animal.
Cardiac and Cerebral Hemodynamics in Drug Induced Postural Collapse
Authors: FINNERTY FRANK A. , GUILLAUDEU ROBERT L. , FAZEKAS JOSEPH F.
Published: June 2012

When signs of cerebral ischemia were induced by the administration of hexamethonium or head-up tilting, the cardiac output was reduced in all patients. Although the level of arterial pressure during cerebral ischemia varied between 34 and 100 mm. Hg, cerebral blood flow at this time was reduced to 30.8 ± 4.6 ml./100 Gm. brain/min. Despite a reduction in cardiac output averaging 47 per cent, approximately the same percentage was diverted to the brain during cerebral ischemia.
An Evaluation of Modern Pressure Recording Systems
Authors: FRY DONALD L. , NOBLE FRANK W. , MALLOS ALEXANDER J.
Published: June 2012

An evaluation of the stability and accuracy of modern physiologic pressure measuring systems is reported with a brief review of some of the problems of catheter pressure recording. Evaluation of stability consisted of measuring the drift of the baseline and of the calibration factors of the gage and amplifier combination with time and temperature change. Evaluation of the accuracy of these pressure measuring systems consisted of determining their static accuracy, their dynamic accuracy, and the pressure errors introduced by catheter accelerations and bending.
A Study of the Mechanism of Pressure Wave Distortion by Arterial Walls Using an Electrical Analog
Authors: WARNER HOMER R.
Published: June 2012

The large arteries may be expected to respond to a central pulse wave as a resonant system and the pressure pulse can be resolved into a series of pure sinusoidal waves. Therefore, a frequency filter network was designed which could duplicate the resonant frequency and damping coefficient of a segment of artery by proper adjustment of the circuit constants. Data are presented which support the concept that much of the distortion of a pressure wave in its transmission down an artery can be explained in terms of a resonant frequency and damping coefficient, and that these variables in turn arc dependent upon physical properties of the segment of artery transmitting the wave.
Ventricular Fibrillation and Ion Transport
Authors: ARMITAGE A. K. , BURN J. H. , GUNNING A. J.
Published: June 2012

Ventricular fibrillation has been studied by driving the ventricles of the isolated rabbit heart electrically and observing whether fibrillation persisted after stimulation was stopped. The hearts were perfused by solutions of different ionic composition and the proportion of hearts in which persistent fibrillation was seen was determined for each solution. The proportion was controlled from 0 to 100 per cent according to the amount of K
+
, hearts fibrillating spontaneously in .25 N K
+
. A similar study was made by varying Ca
++
. Fibrillation was arrested by ATP and prolonged by dinitrophenol. Fibrillating hearts lost more K
+
than when they were not fibrillating. Fibrillation appeared to depend on disturbances of the metabolic processes concerned with ion movements.
Distribution Volumes of T-1824 and Chromium
51
Labelled Red Cells Immediately Following Intravenous Injection
Authors: VIDT DONALD GARDNER , SAPIRSTEIN LEO A.
Published: June 2012

The difference in distribution volumes of T-1824 and Cr
51
labelled red cells is fully realized within 30 sec. after their simultaneous intravenous injection in the dog. This indicates the existence of a rapidly circulating extravascular protein pool.
Pathogenesis of Spontaneous and Pyelonephritic Hypertension in the Dog
Authors: KATZ J. I. , SKOM J. H. , WAKERLIN G. E. , Graham L. , Keith B. , Speer R.
Published: June 2012

The upper limit of normotension in the trained, unanesthetized dog appears to be 145 (135-155) ± 7.5 mm. Hg mean femoral arterial pressure. The incidence of naturally occurring hypertension on the basis of this criterion was 0.9 per cent in 1000 dogs, 1 to 4 years of age. Six of the dogs had so-called spontaneous hypertension which may be similar to or the counterpart of essential hypertension in man. The other three had hypertension associated with chronic pyelonephritis. A renal, renin pathogenesis is indicated for both of these hypertensions by the antihypertensive effect produced by injections of hog renin with resulting antirenin and by passive transfer of high titre homologous antiserum containing antirenin to hog renin which also neutralizes dog renin.
Mechanism of Pressor Response to l-Norepinephrine During Hemorrhagic Shock
Authors: FOWLER NOBLE O. , FRANCH ROBERT
Published: June 2012

Dogs were bled 50 ml./min. until mean systemic pressure approximated 35 mm. Hg. Blood pressure was maintained at this level for 30 min. l-Norepinephrine was then infused in amounts sufficient to increase systemic blood pressure to twice the shock level or more. Measurements of systemic blood pressure, right atrial and pulmonary arterial pressures and of direct Fick cardiac output were made in the control period, during shock, during norepinephrine infusion, and following discontinuation of norepinephrine. Both cardiac output and peripheral resistance increased during the infusion of norepinephrine.
Transmembranal Potentials from the Human Heart
Authors: WOODBURY J. WALTER , LEE JOHN , BRADY ALLAN J. , MERENDINO K. ALVIN
Published: June 2012

Intracellular action potentials from human ventricular muscle have been recorded with the flexibly mounted ultramicroelectrode. The complete record, correlated with the lead I electrocardiogram, is presented. The size, duration and shape of the human potentials closely resemble those previously recorded from lower animals.
Pathogenesis of Pulmonary Edema by Alloxan
Authors: AVIADO DOMINGO M. , SCHMIDT CARL F.
Published: June 2012

Alloxan causes pulmonary edema in anesthetized dogs by a local action in the lungs. Measurements of blood pressures, flow, vascular resistance and blood volume of intact and perfused lungs suggest that the initiation of edema is due to capillary congestion brought about by constriction of Pulmonary veins.
Persistent Right Umbilical Vein as a Result of Vitamin Deficiency During Gestation
Authors: MONIE I. W. , NELSON M. M. , EVANS H. M.
Published: June 2012

Of the two umbilical veins formed in young rat embryos, the right regresses early while the left persists until birth. In a number of rat fetuses from mothers subjected to a transitory deficiency of pteroylglutamic ("folic") acid during pregnancy, this pattern was reversed and the right, instead of the left, umbilical vein persisted until birth. In such cases, the ductus venosus was always absent. No record of persistent right umbilical vein has been found in the literature.
Effect of Hypophysectomy on Cardiovascular Actions of ACTH and STH
Authors: SALGADO ERNESTO D.
Published: June 2012

These experiments indicate that the pituitary adrenocorticotropic hormone (ACTH) and somato trophic hormone (STH) share the ability to produce hypertension, nephroselerosis, myocarditis and periarteritis nodosa in the intact rat. In the absence of the hypophysis rise in arterial pressure was less and no vascular lesions were observed.
Sensitivity of the Hypothermic Myocardium to Calcium
Authors: ANGELAKOS E. T. , DEUTSCH S. , WILLIAMS L.
Published: June 2012

The susceptibility of the dog heart to ventricular fibrillation (VF) induced by CaCl
2
infusions is several fold greater in hypothermia than in normothermia, i.e., both the amount of CaCl
2
infused and the terminal plasma levels are found to be less in hypothermia. Dogs rendered hypercalcemic prior to hypothermia induction also succumb to ventricular fibrillation, and at relatively high heart temperatures (22-27 C.), whereas those rendered hypocalcemic by Na-EDTA infusions succumb to asystole at much lower temperatures (14-18 C.). The calcium sensitivity is not pH dependent either at normal or low temperatures.
Effect of Small Degrees of Venous Distension on the Apparent Inflow Rate of Blood to the Human Calf
Authors: COLES D. R. , KIDD B. S. L.
Published: June 2012

The apparent blood flow through the human calf has been measured by venous occlusion plethysmography in the horizontal subject both at rest, and while the volume of the calf was increased by up to 3 per cent by venous congestion. When this degree of venous distension was continued for 5 min., the apparent blood flow through the calf was not altered significantly. Since the perfusion pressure is presumably reduced, this suggests that the vessels of the calf offering resistance to flow are slightly dilated.
Volume-Pressure Curves of the Human Arm
Authors: LANARI A. , BROMBERGER-BARNEA B. , LAMBERTINI A.
Published: June 2012

After interruption of the circulation, pressure changes in the brachial artery and a forearm vein were recorded and plotted against volume of blood injected intra-arterially expressed in ml./100 cc. of arm tissue. The resulting volume-pressure curves showed a steep rise with the first injection, a linear rise in the center section and a rapid increase during the last injection. These curves were not influenced by either sex, age or moderate systemic hypertension.
Effect of Plethora and Hemorrhage on Left Ventricular Volume and Pressure
Authors: HOLT J. P. , Allensworth J. , Diana J. , Collins David , Kines Helga
Published: June 2012

By combining conventional methods for recording pressures from the left ventricle and pleural cavity with a new procedure for estimating end-diastolic volume (EDV) and end-systolic volume (ESV) of the left ventricle it was found in the closed-chest dog that plethora increased EDV, ESV and stroke volume while hemorrhage had the opposite effect. There were linear relationships between EDV and ESV, and between EDV and stroke volume. There was little change in left ventricular "effective" end-diastolic pressure when the EDV changed over a wide range, beginning with the smallest EDV consistent with life; but after a certain large EDV had been reached, large increases in effective end-diastolic pressure were associated with little or no further increase in EDV.
Regulation of the Degree of Emptying of the Left Ventricle by the Force of Ventricular Contraction
Authors: HOLT J. P. , Allensworth J. , Diana J. , Collins David , Kines Helga
Published: June 2012

Results are presented which indicate that left ventricular end-systolic volume is determined by the force-length relationship of the ventricular muscle at the end of systole. In other words the muscle continues to shorten until it meets a certain force the magnitude of which depends on the length of the musclc fibers at that time; when it meets this force it shortens no further. Since the end-systolic volume is an important determinant of stroke volume the suggestion is made that future studies should be directed toward measuring the effect of various influences on the force-length relationship and the modulus of elasticity of the end of systole in addition to studying the effects on the end-diastolic volume.
Action of Human Plasma on the Isolated Frog Heart
Authors: HAJDU STEPHEN , LEONARD EDWARD , AKERS ROBERT P.
Published: June 2012

Plasma samples from certain patients affect the staircase phenomenon of the frog heart. Comparison of 3 groups of subjects, normal controls, patients without essential hypertension, and patients with severe essential hypertension shows that plasmas from the last group generally abolish the staircase, whereas plasmas of the other 2 groups exhibit little or no such activity.
Rationale of Venous Occlusion Plethysmography
Authors: FORMEL PAUL F. , DOYLE JOSEPH T.
Published: June 2012

The experimental evidence reported here supports the validity of venous occlusion plethysmography.
Mechanism of Congestive Heart Failure Following Aorta Constriction in Rabbits
Authors: ALEXANDER NATALIE , HINSHAW LERNER B. , DRURY DOUGLAS R. , DeCuir Marjorie
Published: June 2012

Severe constriction of the abdominal aorta in rabbits caused congestive heart failure and death in 4 to 7 days. Expansion of total plasma volume suggested that aortic narrowing increases the vascular bed distal to the stricture. Reduction of total body fluids did not prevent total plasma volume expansion, unless it caused severe dehydration. A large percentage of dietary sodium was retained. Expansion of extraccilular volume occurred even when sodium intake was reduced. The early, gradual post-operative rise in arterial pressure probably depends, in part, on development of an effective circulating plasma volume. A tentative answer is given to the question of what factors determine the exact time that heart failure will occur.
Functional Changes During High Output Failure Produced by Daily Hemorrhage in Dogs with Pulnionic Stenosis
Authors: DAVIS JAMES O. , GOODKIND M. Jay , BALL WILMOT C. , Casper Alfred
Published: June 2012

The relationship of changes in cardiovascular and renal hemodynamic function to sodium excretion has been studied following daily hemorrhage in dogs with pulmonic stenosis and in normal dogs. The animals with pulmonic stenosis developed signs of right heart failure, but the normal dogs failed to show evidence of cardiac decompensation during the course of the anemia. The two most striking differences in the responses of the 2 groups of dogs were the increase in mean right atrial pressure and the occurrence of sodium retention, both of which were observed only in the dogs with pulmonic stenosis. The increase in cardiac output and the renal functional changes were similar in the 2 groups of animals; glomerular filtration rate was unchanged or increased in the majority of dogs with pulmonic stenosis and heart failure.
Comparison of the Intravascular Mixing and Disappearance of Radiosodium, Radiopotassiuin and T-1824
Authors: BARLOW GEORGE , AGERSBORG HELMER P. K. , OVERMAN RICHARD R.
Published: June 2012

A method is presented utilizing the rapid intravenous injection of a dye-isotope mixture and rapid, serial arterial sampling which permits the determination of rates of disappearance of these materials from the vascular system. Since K
+
traverses capillary endothelial walls at about twice the rate of Na
+
it appears that these two ions, while being about the same size and having the same charge, are handled in different manners by the capillaries. Other variables obtainable from the T-1824 isotope time-concentration curves such as plasma volume, circulation time, cardiac output and isotope distribution volumes are also presented.
Effects of Hypothyroidism on Estrogen-Induced Inhibition of Coronary Atherogenesis in Cholesterol-Fed Cockerels
Authors: PICK RUTH , STAMLER JEREMIAH , KATZ LOUIS N. , Johnson Philip , Friedman Dolores
Published: June 2012

This report deals with the question of whether hypothyroidism induced in various ways can influence the ability of estrogens to prevent coronary atherosclerosis in cholesterol-fed chicks.
Effects of Vagus Stimulation and of Acetylcholine on Myocardial Contractility, O
2
Consumption and Coronary Flow in Dogs
Authors: SCHREINER GÜNTHER L. , BERGLUND ERIK , BORST HANS G. , MONROE ROBERT G.
Published: June 2012

During vagus nerve stimulation the heart rate was maintained at a constant level by an electric pacemaker. Under these conditions no changes were found in ventricular function curves, myocardial oxygen consumption and coronary blood flow. Acetylcholine infusion, with heart rate maintained constant, caused decreased myocardial contractility and coronary and peripheral vasodilation.
Evaluation of Derivation of Cardiac Output from Blood Pressure Measurements
Authors: BROTMACHER LEON
Published: June 2012

This communication deals with a comparison of cardiac output in human subjects determined by the Fick method and estimates of cardiac output from arterial pressures according to formulas recently proposed by Hamilton, Remington, Starr and their respective associates. The results indicate that the cardiac output cannot be calculated from the blood pressure with any degree of accuracy.
Effect of pH Change upon Renal Vascular Resistance and Urine Flow
Authors: EMANUEL D. A. , FLEISHMAN MALCOLM , HADDY F. J. , Scott Jerry
Published: June 2012

In the dog kidney, acute increase and decrease in hydrogen ion concentration results in decrease and increase in renal vascular resistance respectively. These changes occur predominantly on the alkaline side of pH 7.3 and result from some direct effect upon vascular smooth muscle. The re sistance changes are less apparent in nerve intact than nerve sectioned kidneys due to opposing effects mediated through extrinsic nerves.
Right Ventricular Hypertrophy in Guinea Pigs Exposed to Simulated High Altitude
Authors: VALDIVIA ENRIQUE
Published: June 2012

Guinea pigs exposed to simulated altitudes of 18,000 feet developed right heart dilatation followed by hypertrophy, more conspicuous in the infundibular area of the right ventricle. Under the described experimental conditions, pulmonary artery hypertension may be the etiologic factor.
Active Constriction of Small Pulmonary Arteries in Rabbit
Authors: PATEL DALI J. , BURTON ALAN C. , Elston Mrs. Dorothy
Published: June 2012

This communication deals with the demonstration of active pulmonary vasomotion by injecting plastic material (vinyl acetate) which forms casts of the small pulmonary arteries simultaneously on a control side and on the test side submitted to action of vasoconstrictor drugs. Comparisons were made by direct microscopic observations and by weighing the casts after the lung tissue had been digested. Other indices such as relative weight of the two lungs, relative denseness of vascularity and estimates of pulmonary resistance supplied supplementary evidence of pulmonary vasomotion.
Pathogenesis of Experimental Hypertension Produced by Carotid Sinus Area Constriction in Dogs
Authors: CRANDALL EARLE E. , MCCROREY H. L. , SUKOWSKI E. J. , WAKERLIN GEORGE E. , Graham L. , Keith B. , Speer R.
Published: June 2012

Bilateral constriction of the carotid sinus area, the immediate arterial branches of the sinus, or (perhaps) the vertebral arteries, and bilateral resection of the carotid sinus produces a significant, persistent hypertension in dogs, the highest levels occurring in the carotid sinus area constricted dogs. Pathogenesis is still unsettled.
The effect of pH on the transient-state kinetics of Ca2+-Mg2+-ATPase of cardiac sarcoplasmic reticulum. A comparison with skeletal sarcoplasmic reticulum.
Authors: Mandel F , Kranias E G , Grassi de Gende A , Sumida M , Schwartz A
Published: June 2012

The effect of pH on the Ca2+-Mg2+-dependent ATPase of sarcoplasmic reticulum (SR) was investigated with a rapid mixing quench-flow apparatus capable of measuring phosphorylation and dephosphorylation at times as rapid as 4 msec. The rates of formation and decomposition of the phosphorylated intermediate (E approximately P) of the Ca2+-Mg2+-ATPase were studied in the pH range between 7.6 and 6.0. At pH 6.8, the rates of formation of the phosphorylated intermediate of the Ca2+-Mg2+-ATPase of sarcoplasmic reticulum are the same (t1/2 = 10 msec) for cardiac and skeletal sarcoplasmic reticulum preloaded with calcium, but decrease as the pH is lowered. The effect of acid pH (6.0) is more pronounced for cardiac sarcoplasmic reticulum (t 1/2 = 47 msec) than for skeletal sarcoplasmic reticulum (t 1/2 = 17 msec), in agreement with studies showing that acidosis has a more pronounced effect on cardiac muscle than on skeletal muscle. In addition, a decrease in pH results in a decrease in the rate of the E approximately P decomposition step (the slowest step in the SR reaction sequence). The E approximately P decomposition half-lives were observed to be 97 and 77 msec, respectively for cardiac and skeletal SR at pH 6.8. At pH 6.0, the half-lives were increased to 136 and 178 msec for cardiac and skeletal SR, respectively.
The effects of diltiazem and reduced serum ionized calcium on ischemic ventricular fibrillation in the dog.
Authors: Clusin W T , Bristow M R , Baim D S , Schroeder J S , Jaillon P , Brett P , Harrison D C
Published: June 2012

Calcium influx blockers reportedly suppress ventricular arrhythmias during acute ischemia. We therefore studied the effects of diltiazem and reduced serum ionized calcium on ventricular fibrillation (VF) in a reversible ligation model. VF was produced at 15-minute intervals by simultaneous occlusion of the left anterior descending and circumflex arteries of 31 dogs. Time from coronary occlusion to onset of VF showed no significant variation during 15 consecutive trials in six dogs that received saline alone. Intravenous infusion of diltiazem (0.02 mg/kg per min) markedly delayed the onset of VF in each of 10 dogs (P less than 0.0001). Mean VF latency increased from 138 to 295 seconds during a 45-minute diltiazem infusion, declined exponentially when the infusion ceased, and was strongly correlated with serum diltiazem concentration (r = 0.96, P less than 10(-6)). In five dogs, hemodynamic measurements, including coronary venous blood flow, were performed during each occlusion. The increase in VF latency by diltiazem was not due to increased coronary flow during occlusion or to reduction of left ventricular (LV) mechanical work. In six dogs, mean serum ionized calcium, [Ca++], was reduced from 1.11 to 0.59 mM by infusion of sodium citrate. Citrate infusion increased mean VF latency from 155 to 243 seconds, and the increase observed in each dog was correlated (r = 0.84, P less than 10(-6)) with the reduction in [Ca++]. VF latency was unaffected by lidocaine in nine dogs. The antifibrillatory effect of diltiazem during global LV ischemia may be an electrophysiological phenomenon related to reduction of cellular calcium influx.
Electrophysiological response of vascularized hamster cardiac transplants to ischemia.
Authors: Gilmour R F , Zipes D P
Published: June 2012

To study transmembrane electrophysiological properties of blood-perfused mammalian heart cells during normal perfusion and during acute ischemia, 1- to 2-mm cubes of neonatal hamster atrial and ventricular myocardium were transplanted to the adult hamster cheek pouch and studied with microelectrodes 4--7 days later, when vascularization and spontaneous contractions occurred. Action potentials recorded from the transplants were similar to those recorded from neonatal and adult hamster myocardium studied in vitro. Interrupting blood flow to spontaneously beating transplants reduced diastolic depolarization and suppressed automaticity. After automaticity ceased, the transplants were paced with a bipolar electrode or intracellular microelectrode. Action potential amplitude, resting potential, and dV/dtmax decreased during ischemia. Action potential duration and the intracellular current threshold for excitation increased initially, subsequently decreased to values less than control, and increased again prior to the onset of inexcitability. Conduction delay and block occurred during the late stages of ischemia. Depressed action potentials recorded during ischemia were suppressed by tetrodotoxin (10(-5) M) but not by verapamil (2 x 10(-6) M). These data indicate that: (1) the electrophysiological properties of cheek pouch cardiac transplants are normal, (2) ischemia suppresses transplant automaticity, (3) cellular excitability increases during the early stages of ischemia and decreases at a time when conduction delay and block occur, and (4) action potentials generated during the later stages of ischemia appear to be depressed fast responses, rather than slow responses.
Force-velocity characteristics and active tension in relation to content and orientation of smooth muscle cells in aortas from normotensive and spontaneous hypertensive rats.
Authors: Arner A , Uvelius B
Published: June 2012

Segments of abdominal aorta from spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats (20-25 weeks) were compared with respect to force production and dynamic mechanical properties. The preparations were mounted in vitro for determination of optimal length (lo) for active force, and then maximally stimulated (high-K+ solution, 10 mm Ca2+, 10(-5) m noradrenaline), and fixed for electron microscopy. Muscle cellular volume per mm vessel wall was significantly (p less than 0.01) higher in SHR (0.14 +/- 0.009 mm3, n = 7) compared to WKY (0.11 +/- 0.004 mm3, n = 7). Unchanged cell length and unaltered cross-sectional area (17 micrometers2) of nucleus containing cell profiles in SHR suggest an increased number of cells in the media. No difference was found in maximum force per unit cell area between SHR (271 +/- 31, n = 7) and WKY (305 +/- 49 mN/mm2, n = 7). Cell orientation was almost circular in both groups, showing that force was measured in parallel to the cell long axis. Aortic segments were mounted in an apparatus for quick-release experiments. They were maximally stimulated and force steps were imposed at peak of contractions. The series elastic component, characterized by the initial elastic recoils at 0.75 lo, has similar stiffness values in SHR and WKY. Velocities were measured 100 msec after release. The results were fitted to Hill's equation and maximum shortening velocity (Vmax) computed. No difference in Vmax was found at 0.75 lo (WKY: 0.048 +/- 0.005; SHR: 0.042 +/- 0.006 lo/s, n = 6 for both). At 0.85 lo, the data were corrected for passive tension (40% to total). Vmax at 0.85 lo was 0.071 +/- 0.009 lo/s (n = 5) for WKY, and 0.069 +/- 0.007 lo/s (n = 5) for SHR. Similar Vmax and force per cell cross-sectional area suggest similar characteristics of actomyosin interaction in SHR and WKY aorta.
Transient depolarization and spontaneous voltage fluctuations in isolated single cells from guinea pig ventricles. Calcium-mediated membrane potential fluctuations.
Authors: Matsuda H , Noma A , Kurachi Y , Irisawa H
Published: June 2012

Under the influence of cardiotonic steroids, single ventricular cells exhibit transient depolarization after a train of driven action potentials or, in voltage clamp experiments, transient inward current after a depolarizing clamp pulse. Transient depolarization or transient inward current was abolished by an intracellular injection of ethyleneglycol-bis (beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) or by superfusion of 5 mM caffeine. Transient depolarization was elicited even in the control Tyrode's solution by an intracellular injection of CaCl2 or augmented by an injection of adenosine 3',5'-cyclic monophosphoric acid (cAMP). Along with transient depolarization or transient inward current, digitalis intoxication promoted spontaneous oscillatory fluctuations in membrane potential or in membrane current. Their power spectra showed peaks at frequencies ranging from 2 to 7 Hz, which coincided well with the frequency of repetitive transient depolarization or transient inward current. The fluctuations were eliminated by intracellular injections of EGTA and decreased in amplitude by 5 mM caffeine with a shift toward higher frequencies. Depolarization of the membrane caused a shift of the spectrum peak toward higher frequencies. These results suggest that an oscillatory release of Ca from intracellular storage sites is the common basis underlying both the transient events (depolarization or inward current) and the spontaneous miniature fluctuations in membrane potential or current.
Pulse wave reflection: can it explain the differences between systemic and pulmonary pressure and flow waves? A study in dogs.
Authors: van den Bos G C , Westerhof N , Randall O S
Published: June 2012

We have studied the effect of changes in pulse wave reflection on the configurations of pressure and flow in systemic and pulmonary circulation. Electromagnetic flow transducers, atrial catheters, and pacing leads were implanted in 10 dogs. In four animals, the flow transducer was placed on the pulmonary artery, in another four on the ascending aorta, and in two additional dogs on both vessels. One week later, ascending aortic and/or pulmonary artery flow and pressure (catheter tip manometer) were measured under general anesthesia (Nembutal, 30 mg/kg, iv). When the pulmonary circulation was studied (six dogs), measurements were made before and during serotonin infusion (0.5-0.75 mg/min). When the systemic circulation was studied (six dogs), measurements were made before and during nitroprusside infusion (50-200 micrograms/min). To quantify the arterial load, we calculated pulmonary and systemic input impedances. To estimate the amount of reflection, we used a reflection index which we defined as the amplitude ratio of reflected and forward wave. Nitroprusside decreased total peripheral resistance, increased total arterial compliance, and decreased the reflection index; similarity between aortic pressure and flow wave shapes increased, and they looked more like their pulmonary counterparts. Serotonin increased pulmonary vascular resistance, decreased pulmonary arterial compliance, and increased the reflection index. Resemblance of pressure and flow waves decreased. The differences in wave shapes can thus be explained by the amount of reflection: the less reflection the more pressure and flow resemble each other.
Studies of the effects of essential fatty acid deficiency in the rat.
Authors: Cox J W , Rutecki G W , Francisco L L , Ferris T F
Published: June 2012

We report a model of prostaglandin depletion induced in rats by fasting for 11 days, followed by institution of an essential fatty acid-deficient diet. Urinary prostaglandin E, 2 weeks after this diet had been implemented, was 22 +/- 2 ng/24 hours compared to 113 +/- 8.5 ng/24 hours in controls (P less than 0.01). There was no difference in 24-hour urine volume or solute excretion in controls and essential fatty acid-deficient rats. Five hours after administration of NaCl, 10 mM/kg, essential fatty acid-deficient diet rats excreted 1.85 +/- 0.78 ml urine compared to 6.42 +/- 2.26 ml in control (p less than 0.01) with Na+ excretion 447 +/- 273 muEq in essential fatty acid-deficient rats vs 1483 +/- 366 muEq in control (P less than 0.01). Intravenous isotonic NaCl, 1.5% body weight, resulted in increased urine flow rate in control rats from 8.3 +/- 2 microliter/min to 28.7 +/- 8.8 microliter/min with sodium excretion increasing from 0.19 +/- 0.2 to 3.3 +/- 0.9 muEq/min. In the essential fatty acid-deficient diet animals, there was no significant change in flow rate, 6.07 +/- 2.43 to 9.85 +/- 4.29 microliter/min, or sodium excretion, 0.09 +/- 0.03 to 0.40 +/- 0.24 muEq, after saline infusion. There was no difference in the glomerular filtration rate of plasma aldosterone in the two groups after the salt load. When given a water load, 3 ml/100 g body weight, essential fatty acid-deficient diet rats excreted 2.5 +/- 0.7 ml in 5 hours compared to 6.3 +/- 1.4 ml in controls (P less than 0.01). The defect in water excretion was not due to increased sensitivity to antidiuretic hormone, since similar sensitivity to this hormone was demonstrated in the essential fatty acid-deficient diet and control rats during a water diuresis. When isotonic saline was substituted for drinking water, there was an increase in systolic blood pressure in essential fatty acid-deficient diet rats from 124 +/- 2 to 142 +/- 3 mm Hg over 9 days (P less than 0.01) compared to 122 +/- 2 before and 122 +/- 2 mm Hg after saline drinking in controls. The administration of linoleic acid for 4 days increased urinary prostaglandin E excretion to 114 +/- 15 ng/24 hours from 23 +/- 4 (P less than 0.01), and the alterations in the ability to excrete a sodium and water load were reversed. In essential fatty acid-deficient diet animals made hypertensive by 9 days of saline drinking, the institution of linoleic acid to the diet normalized the blood pressure despite the continued administration of saline. These studies demonstrate that essential fatty acid-deficient diet animals develop salt-sensitive hypertension with a combined defect in both sodium and water excretion which is reversed following correction of the essential fatty acid deficiency.