bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of cardiac output response to hypertonic sodium chloride infusion in dogs
Authors: Liang C. S. , Hood W. B.
Published: December 2017

Hypertonic sodium chloride and tris(hydroxymethyl)amino-methane (Tris) hydrochloride (0.3 mmol/kg.min) were infused intravenously into chloralose-anesthetized dogs over a 20-min period. Cardiac output, maximum left ventricular dP/dt, and (dP/dt)/P increased by 55, 33, and 23%, respectively, during NaCl infusion, but Tris HCl infusion had no effects. NaCl infusion did not change heart rate or left ventricular end-diastolic pressure. Mean systemic and pulmonry arterial blood pressures increased, whereas total peripheral and pulmonary vascular resistances decreased. Responsiveness of cardiac beta-adrenergic receptors, as determined by serial intravenous injections of epinephrine, was not affected by NaCl infusion. Plasma catecholamine concentration, however, increased during NaCl infusion. In addition, the increases in cardiac output, maximum left ventricular dP/dt and (dP/dt)/P were abolished by prior treatment with practolol, a cardioselective beta-adrenergic receptor blocking agent. These results suggest that the hemodynamic effects of NaCl infusion were caused, at least in part, by the inotropic action of catecholamines.
Role of autoregulation in spatial and temporal perfusion heterogeneity of canine myocardium
Authors: Sestier F. J. , Mildenberger R. R. , Klassen G. A.
Published: December 2017

Spatial heterogeneity, the region-to-region variation in flow at an instant, and temporal heterogeneity, the time variation of flow in a small region of myocardium, were investigated with radioactive labeled microspheres in 111 regions of left ventricular myocardium. The error of the method was measured by simultaneously injecting four differently labeled microspheres (15 +/- 5 (SD) micron). The coefficient of variation (CV) was 6.5 +/- 1.0%. Spatial variation with autoregulation intact was 21.7 +/- 1.4% (CV); with autoregulation abolished and low perfusion pressure, it was 34.3 +/- 3.7%; and with normal perfusion pressure, 30.8 +/- 6.4% (differences not significantly). This degree of variation was similar in the entire left ventricle and its layers. Forces which tended to cause vessel closure (low perfusion pressure, ventricular systolic pressure, and ventricular diastolic pressure) tended to increase CV. Temporal heterogeneity as measured by 20-s intervals between microsphere injections was 11.1 +/- 1.0% (CV) with autoregulation, 9.8 +/- 1.3% (P less than 0.05) with autoregulation abolished, and 8.4 +/- 0.8% (P less than 0.05) when perfusion pressure was restored. A periodicity of flow cycles of 30-90 s was suggested by the data. These results suggest that spatial heterogeneity is less influenced by autoregulation than by hydraulic considerations, whereas temporal heterogeneity is a component of autoregulation.
Adrenergic vasoconstriction of the goat middle cerebral artery
Authors: Conde M. V. , Marin J. , Salaices M. , Marco E. J. , Gomez B. , Lluch S.
Published: December 2017

The effects of field electrical stimulation on the contractile response of the isolated middle cerebral artery of the goat were evaluated before and after the use of experimental procedures designed to test the adrenergic component involved. Supramaximal stimuli produced frequency-dependent increases in tension. This response was significantly reduced by phentolamine (10(-6) M), tetrodotoxin (3 X 10(-6) M), and bretylium (5 X 10(-5) M), but not by cocaine (10(-6) M). Arterial segments from goats pretreated with reserpine and from goats in which both superior cervical sympathetic ganglia had been removed 12 days prior to the experiment also showed a significant decrease in the contraction elicited by electrical stimulation. The norepinephrine concentration of the arteries of the circle of Willis from control goats was 2.10 microgram per gram of tissue. Reserpine or gangliectomy reduced the catecholamine content to undetectable levels. It is likely that a major part of the contractile response of cerebral arteries to electrical stimulation is due to release of endogenous norepinephrine which in turn activates the alpha-adrenergic receptors.
Effect of ventricular end-diastolic volume on vectorcardiographic potentials of the pig
Authors: Millard R. W. , Hodgkin B. C. , Nelson C. V.
Published: December 2017

The Brody hypothesis proposes that alterations in end-diastolic blood volume will produce changes in the magnitude of cardiac electrical potentials recorded at the body surface. To test this hypothesis, several procedures that affect end-diastolic volume were applied in 28 anesthetized domestic piglets. The pig dipole moment magnitude curve is typified by two peaks, designated M2 and M3, which responded to these procedures. Doubling heart rate by electrical pacing or hemorrhage of 20 ml/kg produced reduction in M2 by 30% and 29%, respectively. M3 rose by 27% and 29%, respectively, under these two conditions. Reduction of end-diastolic volume by partial occlusion of the vena cava produced similar effects. Maneuvers increasing end-diastolic volume produced directionally opposite effects. Temporary aortic coarctation of phenylephrine injection caused an increase in M2 with no change in M3, accompanied an acute elevation of arterial pressure. Thus, the pig electrocardiogram shows changes, attributable to adjustments in end-diastolic volume, consistent with the Brody hypothesis, suggesting potentials for this technique in monitoring changes in end-diastolic volume.
Left and right ventricular dimensions during ventricular fibrillation in the dog
Authors: Mashiro I. , Cohn J. N. , Heckel R. , Nelson R. R. , Franciosa J. A.
Published: December 2017

Ventricular dimensions by surface echocardiography and intraventricular pressures were monitored in 27 dogs before and during ventricular fibrillation (VF) induced by coronary embolization (nine dogs), potassium infusion (nine dogs) and calcium infusion (nine dogs). Left ventricular diameter (LVD) fell by an average of 10.3 mm during the first 30 s after the onset of VF induced by ischemia or potassium and remained smaller than the prefibrillation end-diastolic LVD during the ensuing 10 min. LVD fell during calcium infusion, and after the onset of VF it remained only slightly larger than the preinfusion end-systolic LVD. Right ventricular (RV) diameter increased progressively for the first 2 min during VF an average of 15.9 mm. The failure of LV size to increase during VF was explained by a pressure gradient inhibiting LV filling during the early phase of VF. Despite progressive RV filling, pressure in the more compliant RV remained lower than in the LV, which exhibited reduced compliance during VF. Therefore, cardiac dilation during VF appears to be confined to the RV, and inhibition to LV filling is an important feature of the syndrome.
Species differences in responses to hyperosmolality and D600 in cat and rat heart
Authors: Willerson J. T. , Wheelan S. , Adcock R. C. , Templeton G. H. , Wildenthal K.
Published: December 2017

The direct inotropic effect of hypertonic mannitol was compared in isolated rat and cat papillary muscles. The inotropic effects of paired electrical stimulation and D600 were also evaluated in the same species. At extracellular calcium concentrations of 2.5 mM, hypertonic mannitol (25--100 mosmol/kg H2O above normal) depressed contractility in isolated rat myocardium; hyperosmolality exerted a positive effect only when extracellular Ca2+ was low (e.g., 0.3 mM). Paired pacing exerted a small but significant inotropic effect in rat heart when extracellular Ca2+ was 2.5 mM, and a larger effect at lower Ca2+. As previously noted, hypertonic mannitol and paired pacing both produced significant positive effects in isolated cat heart at an extracellular Ca2+ concentration of 2.5 mM. D600 exerted less of a depressant effect on contractility in rat than in cat heart at concentrations of 10(-6)--10(-7) M. The data suggest that 1) in contrast to results in cat heart, the positive inotropic effect of hyperosmolality in isolated rat cardiac muscle is apparent only when extracellular calcium concentration is reduced; 2) the inotropic effect of paired pacing in rat heart is greatest at low Ca2+ levels, but persists to a lesser degree at extracellular calcium concentrations of 2.5 mM; and 3) D600-inhibitable calcium channels appear to be relatively less important in the maintenance of cardiac contractility in rat than in cat cardiac muscle.
Transmural myocardial deformation in the canine left ventricular wall
Authors: Fenton T. R. , Cherry J. M. , Klassen G. A.
Published: December 2017

A biplane cineradiographic technique was used to measure deformation of the myocardium as indicated by small lead spheres implanted into the anterior left ventricular wall of anesthetized dogs. Deformation was resolved into nine separate components for each of the epicardial, middle, and endocardial layers. The data illustrate the mechanical effect of myocardial fiber orientation and the ability of muscle layers to deform differentially. In order to present an overview of all the results, the implications of the deformation components are discussed first separately and then in a coordinated fashion.
Accentuation of heart sounds in anemia: an effect of blood viscosity
Authors: Stein P. D. , Sabbah H. N.
Published: December 2017

The effect of blood viscosity on the intensity of heart sounds was investigated in 25 anemic patients and 41 control subjects. Calibrated phonocardiograms showed that in anemic patients, the aortic component of the second sound was of greater amplitude (54 +/- 3 vs. 33 +/- 3 dyn/cm2) (P less than 0.001). The pulmonary component of the second sound and the first sound were also of higher amplitude in anemic patients (both P less than 0.001). The viscosity of blood of anemic patients was lower (0.029 +/- 0.001 vs. 0.045 +/- 0.001 poise) (P less than 0.001). Blood pressure was comparable among the two groups. Sound produced by closure of a normal porcine valve in an in vitro flow system also showed an accentuated sound with liquids of lower viscosity. Augmented diastolic vibrations of the closed valve, shown by high-speed motion pictures, accompanied the accentuated sound. These observations suggest that the accentuated second sound in anemic patients results from the lower blood viscosity, which reduces the damping forces that act upon the semilunar valve as it vibrates after closure. The reduced damping would allow augmented vibrations that result in an accentuated sound.
Cardiac output, GFR, and renal excretion rates during maintained volume load in rats
Authors: Ackermann U.
Published: December 2017

The correlation among cardiac output (CO), glomerular filtration rate (GFR), fractional tubular sodium rejection (TFRNa), and renal excretion rates of water and salt was investigated during ischemic blood volume expansion in rats. Initially circulating blood volume was equilibrated isovolemically with a reservoir volume of 6% albumin solution equal to one-third the estimated blood volume. Later the equilibrated reservoir contents were infused intravenously. CO was measured by thermodilution, GFR by inulin clearance. Significant linear correlations existed between GFR and the rates of urine flow (r = 0.90), sodium excretion (r = 0.75) and potassium excretion (r = 0.76) that prevailed 5--10 min after a given GFR change. The increased GFR was highly correlated with CO (r = 0.94), probably correlated with mean central venous pressure (r = 0.45), but not correlated with mean abdominal aortic blood pressure. The correlation between CO and time-delayed (5--10 min) TRFNa was also highly significant (r = 0.98). The saluresis appears to have been caused initially by increased tubular load and subsequently by decreased absolute tubular reabsorption.
Contribution of myocardial contractility to myocardial perfusion
Authors: Trimble J. , Downey J.
Published: December 2017

Myocardial contractility in open-chest anesthetized (sodium pentobarbital) dogs was varied while ventricular pressure, coronary perfusion pressure, and coronary tone were held constant. Under those conditions, changes in regional blood flow should reflect changes only in intramyocardial compression related to the altered inotropic state. Increasing contractility with isoproterenol caused flow to decrease in the outer myocardial layers without change at the subendocardium. When contractility was decreased with pentobarbital, flow at the subendocardium was increased with little change in the outer layers. By manipulating perfusion pressure in the latter experiments it was demonstrated that subendocardial compression was falling from a starting value that was somewhat above peak ventricular pressure.
Oxygen consumption of pial arteries
Authors: Navari R. M. , Wei E. P. , Kontos H. A. , Patterson J. L.
Published: December 2017

Pial arterioles and arteries, normally responsive to alterations in PaCO2, were obtained by microdissection from the parietal cortex of 53 anesthetized cats. The oxygen consumption of these vessels, determined with the Cartesian diver microrespirometer, was found to be size dependent. It increased progressively from vessels 60 mum in diameter to vessels 250 mum in diameter. In vessels 250--375 mum in diameter there was a progressive decrease in oxygen consumption with increasing vessel size. The oxygen consumption was not altered by increasing the oxygen concentration in the diver from 20% to 95%, or that of glucose from 1.1 to 2.0 mM. Planimetry of histological sections showed that the percentage of endothelium and smooth muscle increased as vessel diameter increased from 60 to 200 mum, and thereafter decreased with increasing vessel size. When these differences in the composition of the vessel wall were taken into account, there was still residual dependence of the oxygen consumption on vessel diameter. This may represent intrinsic differences in the metabolic rate of vascular smooth muscle in vessels of different size.
Arteriolar closure mediated by hyperresponsiveness to norepinephrine in hypertensive rats
Authors: Bohlen H. G.
Published: December 2017

This study was designed to determine if a mechanism exists to cause abnormally large number of arterioles to be closed to blood flow in spontaneously hypertensive rats (SHR). The contributions to vessel closure by neural control and constrictor response to norepinephrine were investigated. Normal rats (WKY) and SHR were studied at age 18--20 wk. Their respective mean arterial blood pressures were 100 +/- 4 (SE) and 154 +/- 7 mmHg when anesthetized with 10% urethan and 2% alpha-chloralose (0.6 mg/100 g ip). The number of arterioles open to blood flow was counted in a large portion of the cremasteric muscle before and after denervation. The percent change in control diameter of denervated arterioles was measured during iontophoretic application (2 min) of norepinephrine at dose currents of 10--300 nA. Following denervation, a 22.2 +/- 6.3% (SE) and 61.8 +/- 12 increase in the number of third-order arterioles open to flow occurred in WKY and SHR. The diameters, wall thicknesses, and cross-sectional areas of vessel walls were not significantly (P less than 0.05) different for comparable types of denervated arterioles in WKY and SHR. The percent changes in diameters of arterioles in SHR were 3--5 times greater at all dose currents than for vessels of WKY. These data indicate arteriolar closure occurs with higher incidence in SHR than WKY and is mediated by hyperresponsiveness of arterioles to norepinephrine.
Neural mechanism underlying tachycardia induced by nonhypotensive a-v shunt
Authors: Gupta P. D. , Singh M.
Published: December 2017

The mechanism underlying tachycardia resulting from nonhypotensive arteriovenous shunt (shunt open plus infusion of blood to compensate for the fall in mean arterial pressure resulting from opening of a shunt) was investigated in anesthetized, artificially ventilated dogs. In dogs with intact autonomic innervation, dogs with beta-adrenergic blockade (BB), and dogs with BB plus spinal section at C7 (BBSS), opening of the shunt resulted in tachycardia ( P < 0.01 for all comparisons), which was, however, not significantly different on comparison among groups ( P > 0.40 for all comparisons). This shows that afferent and efferent sympathetic-mediated reflexes do not play a significant role in this tachycardia response. Additionally, the tachycardia response was significant in dogs with BBSS plus right or left vagotomy, but it was completely abolished in dogs with BBSS plus bilateral vagotomy. This suggests that in dogs with blockade of sympathetic afferent and efferent pathways, tachycardia resulting from nonhypotensive arteriovenous shunt may be due to a cardioacceleratory reflex with its ascending and its descending pathways in each vagus nerve.

dog; heart rate; cardiac sympathetic efferents; spinal dog; cardioacceleratory reflex; vagovagal reflex; vagosympathetic reflex; spinovagal reflex; spinal afferents; vagal afferents; vagal efferents; arterial baroreceptors; beta-adrenergic blockade; vagotomy; nervous control of heart rate; propranolol

Submitted on May 12, 1978

Accepted on August 29, 1978
Shunting of microspheres across the canine coronary circulation
Authors: Crystal G. J. , Boatwright R. B. , Downey H. F. , Bashour F. A.
Published: December 2017

Coronary shunting of 9 +/-1 micrometer and 25 +/- 5 micrometer radiolabeled microspheres was examined in anesthetized, open-chest dogs, whose left common coronary arteries were perfused at controlled pressures. Shunting was estimated from the difference in radioactivity between perfusion line and coronary sinus blood samples during selective elevations of coronary perfusion pressure (CPP), left ventricular afterload, and inspired oxygen. A linear relationship was found between coronary shunting of 9-micrometer microspheres and CPP over the range 100-200 mmHg. According to regression analysis, percent shunt flow was 4.0% at control CPP (100 mmHg) and 10.0% at CPP of 200 mmHg. No shunting of 25-micrometer microspheres occurred at any CPP. Raising afterload did not affect shunting at control CPP but attenuated the increase in shunting at elevated CPP. Changing inspired gas from room air to 100% oxygen did not influence shunting at control or elevated CPP. Raising CPP to 150 and 200 mmHg also released 2.5% and 5.9% of pretrapped 9-micrometer microspheres, respectively. This study demonstrates that vessels permitting passage of microspheres across coronary circulation are sensitive to elevated perfusion pressure.
Actively circulating blood volume in endotoxin shock measured by indicator dilution
Authors: Rothe C. F. , Murray R. H. , Bennett T. D.
Published: December 2017

To estimate the size of the actively circulating blood volume of splenectomized dogs during control conditions and after endotoxin infusion, the pattern of concentration changes of 51Cr-labeled erythrocytes and 125I-labeled albumin was monitored. A dual exponential equation was fitted to the data. The total red blood cell and albumin volumes of distribution were determined from the slow exponential disappearance curves. The active red blood cell and albumin volumes were 89.8 +/- 5.3% and 92.0 +/- 2.0% of the total volumes, respectively. After endotoxin shock (mean arterial blood pressure 49.1 +/- 17.8 mmHg) the active volumes fell to only 60.0 +/- 10.3% and 56.2 +/- 20.0% of the total volumes, respectively. The fast-mixing time constants were similar (3.1 +/- 1.4 min and 2.5 +/- 2.7 min, respectively) and did not change significantly during the endotoxin shock, indicating that the albumin tag mixed into its larger volume of distribution as rapidly as the cells mixed into their indicated volume. We conclude that 1) an active blood volume can be distinguished, 2) it decreases for both red blood cells and albumin in endotoxin shock, and 3) a major part of the "extravascular plasma volume," as estimated by albumin dilution, is in the actively circulating circulation.
Diminished contractile response of aortas from diabetic rabbits
Authors: Sullivan S. , Sparks H. V.
Published: December 2017

We investigated the responsiveness of isolated diabetic and normal rabbit aortic strips to norepinephrine. Alloxan, 160 mg/kg, was administered intravenously 1 mo before experiments were performed. Helically cut thoracic aortic strips from diabetic and control animals were suspended side by side in the same muscle bath. The maximum contractile response to norepinephrine of diabetic strips was 68 +/- 5% of control in eight pairs of animals (P less than 0.001). This differential response was not changed by propranolol or cocaine, indicating that it is not explained by either enhanced beta receptor activity or more avid uptake of norepinephrine by nerve endings. Tyramine responses displayed the same differential, suggesting that endogenous release of norepinephrine also results in a lower response of diabetic aortic strips. Maximum responses to KCl were also markedly depressed in strips from nine diabetic rabbits (P less than 0.005). This indicates that the diabetes-induced changes occur at a stage in contraction beyond alpha-receptor activation.
Biocompatibility of standard and silica-free silicone rubber membrane oxygenators
Authors: Fountain S. W. , Duffin J. , Ward C. A. , Osada H. , Martin B. A. , Cooper J. D.
Published: December 2017

Spiral coil membrane oxygenators made from either standard silicone rubber or silica-free silicone rubber were compared using three priming techniques. Standard priming, carbon dioxide priming, and denucleation priming were employed with each type of device. Four-hour venovenous membrane oxygenator perfusions were carried out on awake sheep anticoagulated with heparin. Virtually no differences were observed in any parameters measured between standard silicone rubber and filler-free silicone rubber membranes. Significantly greater platelet losses occurred during the first hour of perfusion with standard priming and with carbon dioxide priming than with denucleation priming, using either type of membrane. These experiments demonstrate that denucleation priming reduces platelet losses during extracorporeal membrane oxygenator perfusion, but that the use of filler-free silicone rubber does not improve the biocompatibility of the membrane.
Renal vascular and excretory responses to prostaglandin endoperoxides in the dog
Authors: Oliver J. A. , Sciacca R. R. , Cannon P. J.
Published: December 2017

To determine whether the prostaglandin endoperoxides PGG2 and PGH2 have direct effects in the kidney, PGG2 and PGH2 were administered into the renal artery of anesthetized dogs and their effects were compared to those of PGE2. Like PGE2, PGG2 and PGH2 induced a dose-related renal vasodilation. A 50% increase in the renal blood flow was observed with 0.05 microgram/kg body wt of PGE2 and with four- and sixfold higher doses of PGH2 and PGG2, respectively. Infusion of all three compounds at doses inducing a 50% increase in the renal blood flow resulted in 1) increases in blood flow to all cortical areas, with the greatest increase occurring in the juxtamedullary area, 2) diuresis with no change in the glomerular filtration rate, and 3) natriuresis and kaliuresis. In vitro incubation of PGH2, a maneuver known to result in its conversion to other prostaglandins, had no influence on its renal effects. The data indicate that PGH2 and PGG2 are biologically active when infused into the renal artery of the anesthetized dog and suggest that the endoperoxides exert their effects after bioconversion to other prostaglandins.
Fiber orientation in hypertrophied canine left ventricle
Authors: Carew T. E. , Covell J. W.
Published: December 2017

Myocardial fiber orientation was examined in transmural specimens obtained at the maximum diameter of the left ventricle from five dogs with pressure-overload hypertrophy produced by aortic stenosis, six dogs with volume-overload hypertrophy due to an arteriovenous fistula, and six exercise-hypertrophied greyhounds trained for racing. Hearts arrested in diastole were fixed in situ while the operating end-diastolic pressure was maintained. Fiber orientation changed smoothly from about +60 degrees (with respect to the equator) at the endocardium to about -69 degrees at the epicardium. The majority of fibers near the midwall were oriented circumferentially. These findings are quite similar to those previously reported for normal dogs. In comparison to normals, the left ventricles from dogs with pressure-overload had an increase in longitudinally oriented fibers, i.e. fiber angles between -67.5 degrees and -90 degrees and between +67.5 degrees and +90 degrees; these fibers comprised 10.4 +/- 1.8% of the total fibers in dogs with aortic stenosis vs. 2.9 +/- 1.8% of total fibers in normal dogs (P less than 0.001). Neither the dogs with volume-overload hypertrophy nor exercise-trained animals were significantly different from normals.
A simple method for volumetric measurements in isolated cardiac muscle
Authors: Houser S. R. , Freeman A. R.
Published: December 2017

A new method for the study of extracellular space and cell volume of cardiac muscle is described. Canine cardiac Purkinje strands and cat papillary muscles were placed within a fluid-filled aperture connecting two sides of an experimental chamber. Direct electrical current was passed through the hole, and changes in the voltage drop across it were correlated with Purkinje strand extracellular space and cell volume. The results of experiments on 21 Purkinje strands and 4 papillary muscles yielded an extracellular space of 51 +/- 2.1% (SEM) and 23.3 +/- 2.1%, respectively. When strands were superfused with hyper- (600 mosM) and hyposmotic (150 mosM) solutions, the preparations were found to attain new steady-state volumes that were 75 +/- 3.1% and 121 +/- 9% of control, respectively. This method can be used for volumetric studies in numerous cardiac muscle preparations and should be applicable to the study of volume abnormalities associated with certain disease states.
Microvascular responses to norepinephrine in renovascular and spontaneously hypertensive rats
Authors: Wiegman D. L. , Joshua I. G. , Morff R. J. , Harris P. D. , Miller F. N.
Published: December 2017

Closed-circuit television microscopy was used to quantitate the responses of in vivo small arteries (50-140 micrometer diam) and veins (95-265 micrometer) to topically applied norepinephrine in the cremaster muscle of four groups of urethan-chloralose anesthetized rats. The rat groups were: Sprague-Dawley control (SDC), Sprague-Dawley renovascular hypertensive (RVH), Wistar-Kyoto control (WKY), and spontaneous hypertensive (SHR). The cremaster muscle with intact circulation and innervation was suspended by sutures in a 60-ml bath of bicarbonate-buffered Krebs solution. The vascular responses to the addition of progressively higher concentrations of norepinephrine to the bath were quantitated to obtain concentration-response curves. We found that the RVH (vs. SDC) had a decreased small-artery control diameter and decreased sensitivity to norepinephrine, whereas the SHR (vs. WKY) had tachycardia and decreased small-vein control diameter. Thus, the microvascular characteristics of these two types of hypertension appear to be quite different.
Renal effects of left atrial distension in dogs with chronic congestive heart failure
Authors: Zucker I. H. , Share L. , Gilmore J. P.
Published: December 2017

The renal response to left atrial balloon inflation in normal dogs was compared with that in dogs with chronic congestive heart failure (CHF). CHF was induced by the production of an aortocaval fistula below the level of the renal arteries. CHF dogs showed elevated left ventricular end-diastolic pressure, enlarged hearts, a depression of myocardial contractility, pulmonary edema, ascites, and peripheral edema. They also showed significant decreases in urine flow, creatinine clearance, para-aminohippurate clearance, sodium and potassium excretion, fractional sodium excretion, osmolar clearance, arterial blood pressure, and heart rate. Balloon distension of the left atrium evoked a significant increase in urine flow and free-water clearance in the normal group. The reflex nature of this response was indicated by its blockade after bilateral cervical vagotomy. In contrast, the CHF group did not exhibit significant changes in urine flow or free-water clearance during balloon inflation. Plasma antidiuretic hormone (ADH) was significantly elevated in the CHF group; however, balloon distension reduced plasma ADH in both groups of dogs. Plasma renin activity was significantly elevated in the CHF dogs and was not changed by balloon distension in either group of dogs. It is concluded that animals with high-output CHF do not exhibit the atrial-diuretic reflex in spite of their ability to reduce ADH levels by atrial distension.
Involvement of renal alpha- and beta-adrenoceptors in release of renin by carotid baroreflex
Authors: Powis D. A. , Donald D. E.
Published: December 2017

In anesthetized vagotomized dogs with renal arterial pressure constant, carotid sinus hypotension (BCO) caused a reflex rise in systemic arterial pressure, a fall in renal blood flow, and a similar increase in renin release from both kidneys. Unilateral alpha-adrenoceptor blockade with phenoxybenzamine resulted in an increase in basal renal blood flow, a depression of basal renin release, and an abolition of the responses to BCO in the treated kidney. The untreated kidney responsed to BCO as before. Nonblocked and alpha-blocked kidneys released similar amounts of renin when renal blood flow was mechanically reduced by aortic constriction. Administration of propranolol to the nonblocked kidney prevented the release of renin but not the hemodynamic changes resulting from BCO. The experiments demonstrated that under certain conditions carotid sinus hypotension produced alpha-adrenoceptor-mediated changes in the kidney sufficient to cause increased renin release. A step in the renin release mechanism subsequent to the alpha-adrenoceptor-mediated changes in sensitive to propranolol.
Nerve growth factor-enhanced reinnervation of surgically denervated canine heart
Authors: Kaye M. P. , Wells D. J. , Tyce G. M.
Published: December 2017

Nerve growth factor (NGF) was administered in doses of 25,000 U daily for the first 5 postoperative days to dogs subjected to cardiac denervation. These dogs and untreated cardiac-denervated dogs were killed at 1, 2, 3, and 6 mo postoperatively. Tritiated norepinephrine ([3H]NE) was administered prior to death, after which the hearts were removed and eight segments (right and left atria, right ventricular conus and sinus, left ventricular base and apex and high and low ventricular septum) analyzed to determine myocardial NE content and uptake of [3H]NE. Our data demonstrated enhanced cardiac reinnervation of the left ventricular base in NGF-treated dogs.
Increase in passive tension of spontaneously beating atria in hyperosmolar media
Authors: Roberts L. A. , Hughes M. J.
Published: December 2017

Spontaneously beating rabbit atria were used for study of increases in passive tension induced by hyperosmolar Tyrode bathing media. The time course and degree of passive tension change was dependent on the level of osmolality and the osmotic agent used. The effectiveness of various agents added to Tyrode solution in increasing resting tension was in the order sucrose greater than mannitol greater than or equal to NaCl greater than glucose greater than = no change. The hyperosmotically induced "contracture" was similar to contracture induced by high Ca2+ medium, but the maximum hyperosmotic effect was greater than that of high Ca2+. In contrast to active atria, inactive atria showed no increase in passive tension in hyperosmotic solutions or in Tyrode solution containing high Ca2+. After depolarization with Tyrode medium containing high K+ or zero K+, increased Ca2+ caused contracture in inactive left atria greater than that caused by hyperosmotic media (+200 mM sucrose) in active right atria or atrial pairs. Results of the study indicate that although other factors may be involved, increased Ca2+ flux inward could largely account for the passive tension response.
Simple analog circuitry for measuring time to peaks
Authors: Abel F. L.
Published: December 2017

Two simple analog circuits are presented for measurement of time to the peak of a wave form. The principle involves measuring the voltage of a triggered and reset analog integrator.
Cardiac performance of isolated perfused hearts from alloxan diabetic rats
Authors: Miller T. B.
Published: December 2017

Acute alloxan diabetes (3 days) in the rat resulted in a decreased ability of the isolated perfused working heart to respond to increased atrial filling pressure with normal systolic (aortic) pressure development, using a physiologic concentration of glucose (5 mM) as substrate. The diabetic heart also exhibited impaired cardiac output, which could be attributed entirely to decreased aortic output without any apparent effect on coronary flow. This decrease in ventricular performance was accompanied by a 40% reduction in glucose uptake and a 20% reduction in tissue ATP concentrations even though perfusate glucose levels remained at or near physiologic levels. Perfusion of hearts with 5 mM glucose plus 10(-8) M insulin, with 10 or 30 mM glucose, or 1 mM octanoate reversed the diabetes-related decrease in systolic pressure development, cardiac output, and tissue ATP content. These data demonstrate that the defect in cardiac performance with increased work loads associated with acute insulin deficiency is due to the relative inability of the heart to utilize physiologic concentrations of glucose as substrate for energy production.
Oxygen exchange in the mesenteric microcirculation of the dog
Authors: Farrell K. J. , Witte C. L. , Witte M. H. , Mobley W. P. , Kintner K.
Published: December 2017

The relationships of O2 tension in mesenteric lymph (PmlO2) and mesenteric venous blood (PmvO2) to intestinal O2 delivery/O2 consumption (DO2/VO2) were examined after graded hemorrhage (10 dogs), stepwise increments in FIO2 (4 dogs), and regional infusion of papaverine (2 mg/min or IV glucagon (25 microgram/kg) (4 dogs). Measurements included superior mesenteric arterial flow (SMA-Q), PaO2, PmlO2, and arterial and mesenteric venous blood O2 content (CaO2, CmvO2). Intestinal DO2 was calculated as the product of SMA-Q and CaO2, and VO2 was calculated from the Fick equation [SMA-Q X (CaO2 - CmvO2)]. Graded hemorrhage lowered SMA-Q, DO2 and DO2/VO2 and increased splanchnic O2 extraction (CaO2 - CmvO2). Elevation of FIO2 increased PaO2, PmvO2, and PmlO2. Both PmlO2 and PmvO2 varied directly with DO2/VO2 and PaO2, but PmlO2 showed greater sensitivity to PaO2. Papaverine and glucagon both increased SMA-Q, DO2, CmvO2, and PmvO2, BUT PmlO2 rose after papaverine, indicating greater capillary perfusion, and fell after glucagon, suggesting diversion of mesenteric blood flow through arteriovenous shunts. Thus, either PmvO2 or PmlO2 is ordinarily an accurate measure of intestinal tissue oxygenation, but the disparate response after glucagon suggests that PmlO2 is a more reliable indicator.
Blood pressure fluctuations in human nailfold capillaries
Authors: Mahler F. , Muheim M. H. , Intaglietta M. , Bollinger A. , Anliker M.
Published: December 2017

Dynamic blood pressure was measured in 33 human finger nailfold capillaries after direct cannulation with glass micropipettes by means of a resistance servo-nulling pressure measuring method. ECG, finger pulsations, and respiratory thorax excursions were monitored simultaneously. All recordings exhibited pulsatile oscillations related to the cardiac rhythm. These oscillations resembled the wave forms of arterial pulsations with steep upstroke and dicrotic notch when the pressure amplitudes were above 10 mmHg. There was no apparent dependence on respiration. In 12 instances, pressure fluctuations with frequencies ranging from 0.2 down to 0.07 Hz were observed in both the arteriolar and venular limb. Blood pressure in human skin capillaries is pulsatile and subject to remarkable fluctuations in the arteriolar as well as in the venular limb, systolic pressure values ranging from 14 to 71 mmHg and from 11 to 52 mmHg, respectively.
Transmural myocardial deformation in the canine left ventricular wall
Authors: Fenton T. R. , Cherry J. M. , Klassen G. A.
Published: December 2017

Page H523: T. R. Fenton, J. M. Cherry, and G. A. Klassen. “Transmural myocardial deformation in the canine left ventricular wall.” Page H527: in Figure 8, orientations of epi and endo axes should be interchanged. Page H528: in discussion at top left of page, results do not contradict results of Ingels et al. (22); they are reasonably comparable. Page H528: in Figure 9, orientations of epi and endo axes should be interchanged.
Auxotonic contractions in cardiac muscle segments
Authors: Huntsman L. L. , Joseph D. S. , Oiye M. Y. , Nichols G. L.
Published: December 2017

The dynamics of segment shortening have been measured in the central regions of isolated papillary muscles during muscle isometric and after-loaded isotonic contractions. Segment lengths are inferred from muscle cross-sectional area using an assumption that the segments remain isovolumic. Area is assessed with a magnetic induction technique. Infused microspheres have been used as visual markers to corroborate the segment length measurement. The results confirm the existence of major segmental shortening during muscle isometric conditions. However, the time course of shortening is not the same as that of force development. Rather, the segments remain shortened until after force has fallen significantly from its peak value. This behavior appears in the force-segment length plane as counterclockwise loops. The relationship of peak force to segment length has been determined and found to depend on the mechanical conditions under which the muscle is equilibrated. These results demonstrate the utility of the new technique and indicate central segment behavior that is substantially different from that observed for the whole muscle.
Effect of hypoxia on mechanical properties of hyperthyroid cat papillary muscle
Authors: Palacios I. , Sagar K. , Powell W. J.
Published: December 2017

It has been previously established that hyperthyroid myocardium exhibits increased performance under well-oxygenated conditions. To date, it is not known whether hyperthyroid cardiac muscle can maintain this increased performance during hypoxia. The responses of isolated right ventricular papillary muscles from hyperthyroid and euthyroid kittens to hypoxia were compared under isometric conditions at 31 degrees C. Under well-oxygenated conditions, the hyperthyroid cardiac muscle exhibited both an increased contractility and an accelerated rate of relaxation. A similar degree of acute hypoxic stress for 15 min resulted in a greater decrease in contractility in the hyperthyroid compared with the euthyroid papillary muscle as indicated by a greater fall in both peak tension development (2.2 +/- 0.25 from 4.2 +/- 0.2 vs. 0.9 +/- 0.15 from 3.2 +/- 0.4 g/mm2, P less than 0.01) and +dT/dt (12.9 +/- 2.3 from 25 +/- 3 vs. 4.0 +/- 0.6 from 14 +/- 1 g-s-1-mm-2, P less than 0.01). In addition, compared with the euthyroid data, hypoxia resulted in impaired myocardial relaxation in the hyperthyroid cardiac muscle. Thus, the hyperthyroid compared with the euthyroid papillary muscle exhibits both a greater decrease in contractility and an impairment of myocardial relaxation during hypoxia, indicating a greater susceptibility to a given hypoxic stress.
Microvascular hematocrit and red cell flow in resting and contracting striated muscle
Authors: Klitzman B. , Duling B. R.
Published: December 2017

Microvascular hematocrit and its possible relation to oxygen supply were systematically examined. We studied the red cell volume fraction (hematocrit) in arterial blood and in capillaries under a variety of circumstances. Control capillary hematocrit averaged 10.4 +/- 2.0% (SE) and arteriolar (14.2 micrometer ID) hematocrit averaged 13.9 +/- 1.2% in cremaster muscles of pentobarbital-anesthetized hamsters. Carotid artery hematocrit was 53.2 +/- 0.6%. The low microvessel hematocrit could not be entirely explained by a high red cell flux through arteriovenous channels other than capillaries (shunting). Hematocrit was not only low at rest, but varied with physiological stimuli. A 1-Hz muscle contraction increased capillary hematocrit to 18.5 +/- 2.4%, and maximal vasodilation induced a rise to 39.3 +/- 9.5%. The quantitative relations between capillary red cell flux, arterial hematocrit, and total blood flow could be explained by a two-element model of microvascular blood flow that incorporated a relatively slow-moving plasma layer (1.2 micrometer). Such a model would generate a low microvessel hematocrit and might reduce the diffusion capacity of individual capillaries, but would not reduce time-averaged red cell flux or alter steady-state vascular oxygen supply.
Indirect measurement of instantaneous arterial blood pressure in the rat
Authors: Yamakoshi K. I. , Shimazu H. , Togawa T.
Published: December 2017

We devised a hydraulic servo-control system for indirect blood pressure measurement in the rat's tail, by which beat-to-beat systolic and diastolic blood pressure can be obtained. In this method the principle of "unloading vascular wall" proposed by Shirer (1962) is employed. The proposed system is composed of a transmittance photoelectric plethysmograph with an occluding cuff, a small diaphragm actuator for compressing and decompressing the segment by the hydraulic pressure, and an electromagnetic shaker driven by a volume servo circuit in accordance with the signal from the photoelectric plethysmograph. The plethysmographic signal is clamped at a proper value corresponding to the unload vascular volume by the instantaneous hydraulic servo control. The cuff pressure thus automatically controlled follows the intra-arterial pressure in the tail segment. The accuracy of this method was evaluated in comparison with direct measurement of blood pressure recorded simultaneously from 16 unanesthetized spontaneously hypertensive and normotensive rats. Close agreement between the simultaneous data from these two methods were observed.
Augmented aftercontractions in papillary muscles from rats with cardiac hypertrophy
Authors: Heller L. J.
Published: December 2017

Paired-pulse stimulation induced larger aftercontractions in papillary muscles from spontaneously hypertensive rats (SHR) than from normotensive Wistar-Kyoto rats (WKY). To determine whether aftercontraction exaggeration is a general characteristic of hypertrophied cardiac muscle, three models were examined: SHRs, deoxycorticosterone acetate (DOCA)-treated rats, and aorta-constricted rats. Responses of pipillary muscles from hypertrophied hearts tested under conditions conducive to aftercontraction generation were compared to pipillary muscles from WKY or sham-treated controls, respectively. Field-stimulated papillary muscles mounted in an oxygenated temperature-controlled physiologic salt solution were exposed to calcium concentrations of 2.5 and 5.0 mM, and temperatures of 27 degrees C and 17 degrees C. Although testing conditions influenced the contractile responses to single stimuli, there was no difference in active tension, time to peak tension, or one-half relaxation time between the three experimental groups and their respective controls. Paired-pulse stimulation induced aftercontractions that were enhanced in high-calcium and low-temperature solutions. Under these conditions, papillary muscles from hypertrophied hearts developed larger aftercontractions than did their respective controls.
Effects of active shortening on tension development of rabbit papillary muscle
Authors: Leach J. K. , Brady A. J. , Skipper B. J. , Millis D. L.
Published: December 2017

Duration and intensity of force development have been shown to be less during active muscle shortening than during isometric contraction. The purpose of this study was to compare force developed during controlled shortening with that predicted by the Frank-Starling relation. Paillary muscles from the right ventricles of rabbits were arranged for isometric tension recording, and isometric contractions were recorded at several lengths. The muscles were then permitted to shorten at velocities of 0.2--6 mm/s, shortening beginning 150--200 ms after the stimulus. Length-tension-time curves constructed from the isometric contractions were used to determine predicted shortening tension (Pp), which was compared with actual tension during shortening (Ps) at corresponding times and lengths. Ps was significantly less than Pp and the ratio Ps/Pp decreased with increasing velocity of shortening. The decrease in Ps/Pp was directly related to the duration of shortening (P less than 0.001), suggesting that the fall of shortening tension reflected both the Hill force-velocity relation and shortening deactivation.
Carotid sinus control of pulsatile hemodynamics in halothane-anesthetized dogs
Authors: Cox R. H. , Bagshaw R. J.
Published: December 2017

The open-loop characteristics of the carotid sinus baroreceptor reflex control of pulsatile arterial pressure-flow relations were studied in halothane-anesthetized dogs. Pressures and flows were measured in the ascending aorta, the celiac, mesenteric, renal, and iliac arteries and were used to compute values of regional vascular impedance and hydraulic power. The carotid sinuses were bilaterally isolated and perfused under conditions of controlled mean pressure with a constant sinusoidal component. Measurements were made with the vagi intact and after bilateral vagotomy. Maximum values of open-loop gain averaged -0.78 +/- 0.08 before and -1.42 +/- 0.20 after vagotomy. Vagotomy produced significant increases in the variation of all hemodynamic variables with carotid sinus pressure that were nonuniformly affected in the various regional vascular beds. Aortic and regional vascular impedance showed significant variations with carotid sinus pressure that were augmented by vagotomy. Aortic impedance exhibited a minimum at the normal set point. These results indicate that a) carotid sinus baroreflexes are well preserved with halothane anesthesia, b) thoracic baroreceptor-mediated reflexes exert significant hemodynamic effects on systemic hemodynamics around normal set point values of arterial pressure, c) systemic baroreceptors exert control over large as well as small vessel properties, and d) the baroreceptor-mediated reflexes produce significant influences on hydraulic power and its components.
Cerebral circulatory and metabolic effects of vasoactive intestinal polypeptide
Authors: McCulloch J. , Edvinsson L.
Published: December 2017

Two aspects of the action of vasoactive intestinal polypeptide (VIP) within the cerebral vascular bed have been examined. First, in anesthetized rats, the vasomotor responses of individual pial arterioles on the convexity of cerebral cortex to the perivascular microinjection of vasoactive intestinal polypeptide were examined and, second, in anesthetized baboons, the effects of VIP on cerebral blood flow, cerebral oxygen consumption, and the electroencephalogram (EEG) were investigated both prior to and following the osmotic opening of the blood-brain barrier. The perivascular microinjection of VIP resulted in statistically significant increase in arteriolar caliber in the concentration range 10(-9) to 10(-6) M. For example, arteriolar caliber was increased by 22 +/- 3% (mean +/- SE) following the injection of VIP (10(-8) M). In the second series, in baboons, the intracarotid infusion of vasoactive intestinal polypeptide (10(-11) mol/min) did not affect cerebral blood flow, cerebral oxygen consumption, or the EEG under normal circumstances. If the same concentration of vasoactive intestinal polypeptide was administered following hypertonic opening of the blood-brain barrier, cerebral blood flow and oxygen consumption were both elevated (by 37 +/- 7% and 28 +/- 10%, respectively), accompanied by increased EEG activity.