bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoelectric method for estimating hemodynamic changes in regional cerebral tissue
Authors: Tomita M. , Gotoh F. , Sato T. , Amano T. , Tanahashi N. , Tanaka K. , Yamamoto M.
Published: December 2017

A new photoelectric method for measuring hemodynamic changes in a thin layer of cerebral tissue in situ is described. The apparatus consists of a miniature lamp of 0.7 mm OD and a photodiode with a color filter having maximum light transmission at 548 nm. The lamp was chronically or acutely implanted into the brain tissue of animals as a light source, and the intensity of the light transmitted through the cerebral tissue was monitored with the photodiode from the brain surface. The intensity of the transmitted light was quantified for cerebral blood volume (CBV). The mean transit time of blood (t) was obtained from tissue hemodilution curves produced by saline injection into the carotid artery. The regional blood flow was calculated from the values of CBV and t according to the Stewart-Hamilton equation. The apparatus was shown to be stable, rapid in response, easy to operate, and to give reproducible results. Possible sources of error are discussed.
Hemodynamic functions and blood viscosity in surface hypothermia
Authors: Chen R. Y. , Chien S.
Published: December 2017

Hemodynamic functions and blood viscosity changes in hypothermia (core approximately 25 degrees C) were studied in 14 pentobarbital-anesthetized dogs subjected to surface cooling. The viscosity of blood (eta B) increased progressively to 173% of that at 37 degrees C when body temperature was lowered to 25 degrees C. The increase in blood viscosity was caused by: a) the direct effect of low temperature on plasma viscosity, b) hemoconcentration as a result of plasma loss, and c) the low-flow (low-shear) state induced by hypothermia. A larger portion of the increased viscosity was caused by the low-flow state in hypothermia. The systemic flow resistance (SFR) increased to 271% of control, and this was attributable about equally to the increases in blood viscosity and systemic vascular hindrance (SFR/eta B). Similarly, the viscosity of blood contributed significantly to raising the pulmonary flow resistance. The relative constancy of mixed venous O2 saturation suggests that the cardiac output at low body temperature is generally adequate to meet the metabolic needs
Influence of tris on contracile responses of isolated rat aorta and portal vein
Authors: Turlapaty P. D. , Altura B. T. , Altura B. M.
Published: December 2017

The influence of tris(hydroxymethyl)-aminomethane (Tris) on the spontaneous mechanical activity (SMA) and agonist-induced contractile responses of rat portal vein and aorta was investigated. Tris, in a concentration-dependent manner (5, 10, and 30 mM), significantly increased frequency and attenuated amplitude of SMA in portal vein. Tris, in all concentrations, abolished spontaneous activity of aorta. Tris (5 mM) attenuated epinephrine-, angiotensin-, and potassium-induced contractile responses in portal vein and in aorta: the vein responses exhibited the greater sensitivity to Tris inhibition. In the presence of Tris, agonist dose-response curves were shifted to the right, concomitant with a reduction in maximum tension in portal vein. In contrast, in aorta, only a rightward shift of the dose-response curves was observed, withour any change in maximum tensions in the presence of Tri. Tris (5 mM) depressed contractions induced by calcium in potassium-depolarized aortic and venous smooth muscle. These results suggest that Tris may interfere with the binding, translocation, and utilization of calcium ions at or beyond the membrane in venous smooth muscle and at the membrane in aortic smooth muscle.
Autonomic control of pacemaker activity in the atrioventricular junction of the dog
Authors: Wallick D. W. , Felder D. , Levy M. N.
Published: December 2017

A stable atrioventricular (AV) junctional rhythm was induced in open-chest, anesthetized dogs by injecting pentobarbital into the sinus node artery. A factorial experimental design was used to quantify the changes in AV junctional rate as a function of the frequency of cardiac sympathetic and parasympathetic stimulation. The AV junctional pacemaker cells were more responsive to autonomic neural stimulation, but the vagal-sympathetic interactions were less pronounced than had previously been observed for the SA nodal pacemaker cells. In a group of seven animals, sympathetic stimulation at a frequency of 1.4 Hz increased the AV junctional rate by 102% from a control rate of 54 beats/min. In the same animals, vagal stimulation at a frequency of 8.4 Hz reduced the AV junctional rate by 56%. In three other animals, the AV junction was even more responsive; equivalent chronotropic effects were achieved with stimulation frequencies that were only about one-third of those cited above. There was a moderate, but significant, autonomic interaction: in the group of seven animals, the positive chronotropic effect of sympathetic stimulation at 1.4 Hz was 72% greater at the low level (0 Hz) than at the high level (8.4 Hz) of vagal activity.
Procoagulant activity of peritoneal leukocytes: effects of cortisone and endotoxin
Authors: Robinson A. J. , Rapaport S. I. , Brown S. F.
Published: December 2017

Procoagulant activity of peritoneal leukocytes from rabbits given cortisone acetate, endotoxin, and both materials was measured in studies designed to test the hypothesis that cortisone acetate prepares rabbits for the generalized Shwartzman reaction by enhancing leukocyte procoagulant activity. Two types of peritoneal leukocyte suspensions were examined: mixed granulocyte-macrophage suspensions and macrophage suspensions. In both types, procoagulant activity could be accounted for by the number of macrophages in the suspensions. Cortisone alone did not affect the procoagulant activity, whereas endotoxin increased the procoagulant activity. Suspensions from animals given both cortisone and endotoxin varied in activity depending upon cell composition. Granulocyte-macrophage suspensions had less apparent procoagulant activity than suspensions with endotoxin alone. In contrast, macrophage suspensions--particularly sonicated suspensions--had greater procoagulant activity than those with endotoxin alone. The ability of cortisone acetate to increase macrophage procoagulant activity after endotoxin could represent one mechanism whereby cortisone acetate prepares rabbits for the generalized Shwartzman reaction after endotoxin.
Effects of coronary ligation of the chromically sympathectomized dog ventricle
Authors: Jones C. E. , Beck L. Y. , DuPont E. , Barnes G. E.
Published: December 2017

The cardiac response to acute coronary occlusion was studied after chronic ventricular sympathectomy. Infarct size was measured using nitro blue tetrazolium. In 11 control dogs, 8 dogs with ventricles sympathectomized 2 wk earlier, and 5 sham-operated dogs, mean infarct size was 20.0%, 8.9%, and 20.4% of the left ventricular weight, respectively. Infarct size in sympathectomized ventricles was significantly less than in control or sham-operated hearts (P less than 0.05). Left ventricular perfusion before and after coronary occlusion was measured in 10 controls and 7 sympathectomized ventricles using tracer microspheres. Preocclusion flow values in chronically sympathectomized ventricles were approximately 30–40% less than in controls even though arterial pressure and heart rate were no different, suggesting an increased efficiency. Furthermore, after coromanary occlusion, collateral perfusions in the central and peripheral ischemic zones of the sympathectomized ventricles were 200–400% of those in nonsympathectomized ventricles. When collateral perfusion was related to the respective preocclusion flows, the difference between control and sympathectomized ventricles was even greater. Thus, chronic ventricular sympathectomy results in reduced infarct size, and this effect may be due to a reduced flow demand as well as to an increased collateral perfusion.
Role of oxygen in arteriolar functional vasodilation in hamster striated muscle
Authors: Gorczynski R. J. , Duling B. R.
Published: December 2017

Small isolated groups of striated muscle cells were stimulated in the hamster cremaster muscle. During and after stimulation, oxygen microelectrodes were employed to determine the relationships among arteriolar vasodilation, tissue Po2, and periarteriolar Po2. Localized contraction produced a biphasic arteriolar vasodilation without associated alteration of Po2 on the surface of the arterioles (vascular smooth muscle Po2). In contrast, muscle contraction produced a decline in muscle tissue Po2 that was proportional to the contraction frequency over the range of 1--4 contractions per second. An increase in contraction frequency also produced a graded increase in arteriolar diameter, the magnitude of which was statistically correlated with the steady-state change in tissue Po2. However, arteriolar diameter changes preceded tissue Po2 changes, both with the initiation of functional dilation and during the recovery period. Tissue Po2 was manipulated at rest and during contraction by increasing the Po2 of the superfusion solution. Increasing the tissue Po2 caused a decrease in vascular diameter under both conditions and a reduction in the magnitude of the arteriolar vasodilation during contraction. Restoration of tissue Po2 to resting levels during muscle contraction produced only partial restoration of vascular diameters. The results are consistent with the hypothesis that at least three components are involved in the vascular control process during muscular activity: an early component independent of tissue oxygen levels, a late component independent of oxygen, and a late component associated with a decrease in muscle Po2, without an effect on vascular smooth muscle Po2. The evidence indicated that Po2 of the smooth muscle of the arterioles had no role in the dilation observed.
Effects of sympathetic nerves on cerebral vessels in dog, cat, and monkey
Authors: Heistad D. D. , Marcus M. L. , Gross P. M.
Published: December 2017

Cerebral vascular responses to sympathetic stimulation and denervation were examined in three species during acute severe hypertension as well as normal conditions. Cerebral blood flow (CBF) was measured with microspheres after the superior cervical sympathetic trunk was cut and during electrical stimulation of the superior cervical sympathetic ganglion. Sympathetic denervation did not increase CBF in anesthetized cats or monkeys. Under normal conditions, sympathetic stimulation decreased CBF significantly in monkeys (-26 +/- 3%) (mean +/- SE) but not in cats. During acute severe hypertension, decreases in CBF due to sympathetic stimulation were greatly augmented in cats (-29 +/- 7%, compared to -3 +/- 3%), only modestly augmented in dogs (-9 +/- 3%, compared to -1 +/- 2%), and not augmented in monkeys (-17 +/- 3%, compared to -23 +/- 4%). Disruption of the blood-brain barrier during hypertension was reduced by sympathetic stimulation. We conclude that 1) sympathetic tone to cerebral vessels is minimal because denervation does not increase CBF; 2) sympathetic stimulation decreases CBF under normal conditions in monkeys and during severe hypertension in cats, dogs, and monkeys, and it reduces disruption of the blood-brain barrier; and 3) there is an important species difference in responses to sympathetic stimulation under normal conditions and during acute hypertension.
Constituents of chyme responsible for postprandial intestinal hyperemia
Authors: Chou C. C. , Kvietys P. , Post J. , Sit S. P.
Published: December 2017

While local venous outflow was measured in anesthetized dogs, various constituents of intestinal chyme were placed in the jejunal lumen to identify those responsible for postprandial intestinal hyperemia. Digested food and its supernatant increased local blood flow, whereas its precipitate, undigested food, and pancreatic enzymes did not. In the jejunum bile alone had no effect, but it markedly enhanced the hyperemic effect of digested food. Bile in the ileal lumen, however, increased local blood flow. At physiological postprandial concentrations in the jejunum, glucose, and micellar solutions of oleic acid and monoolein increased flow, but taurocholate and 16 common dietary amino acids did not. The hyperemic effect of lipids required the presence of taurocholate. Of the 16 amino acids, only Glu and Asp increased flow at 10 times the physiological concentrations (28 and 20 mM, respectively). The study indicates that the constituents of chyme responsible for postprandial intestinal hyperemia are the hydrolytic products of food, especially those of carbohydrates and fats and that bile plays an important role in the hyperemia.
Analysis of myocardial and total body integral extraction ratios of rubidium-86
Authors: McDonagh P. F. , Salel A. F. , Krohn K. A. , Rhode E. A. , Mason D. T.
Published: December 2017

Coronary blood flow (QM) measurement with radiorubidium (Rb) assumes that Rb distributes to the myocardium in proportion to flow. This assumption is correct if the integral myocardial Rb extraction ratio (ERM) equals total body extraction (ERTB). A right-heart-bypass preparation was employed to test the hypothesis that ERM = ERTB and to examine the determinants of Rb extraction. Dogs were anesthetized with pentobarbital, and arterial, coronary venous, and total body venous Rb concentrations were continuously measured for 4 min after injection. We found that ERM (0.56 +/- 0.01) was significantly less than ERTB (0.70 +/- 0.01), P less than 0.01 (n = 29) and concluded that Rb did not distribute in proportion to flow. We do not recommend this method for clinical use. ERM is flow dependent and ERRB is a function of the total cardiac output and the distribution of cardiac output. Before employing Rb in animal experiments, it is recommended that a preliminary study be performed comparing flow measured with Rb to an independent measure of blood flow.
Autoregulation of superior mesenteric flow in fasted and fed dogs
Authors: Norris C. P. , Barnes G. E. , Smith E. E. , Granger H. J.
Published: December 2017

Pressure-flow relations in the intestinal vasculature were obtained by producing stepwise reductions of intestinal perfusion pressure with an adjustable metal clamp placed upon the descending thoracic aorta. To eliminate intervention of the baroreceptor reflex, systemic arterial pressure was maintained constant by a pressure compensation system connected to the two carotid arteries. In the fed dogs, autoregulatory vasodilatory responses to reduced perfusion pressure maintained flow within 5% of control in the 85-125 mmHg range. In 30% of the fed dogs, superior mesenteric flow actually increased as perfusion pressure was reduced in the pressure range 85-125 mmHg, indicating superregulation of flow in the intestinal vasculature. The degree of flow autoregulation in the fasted dog was less than in the fed dog. Moreover, superregulation of intestinal flow was not observed in any of the fasted animals. These data suggest an intimate link between parenchymal activity and local flow control in the small intestine.
Cardiac lymph flow in conscious dogs
Authors: Michael L. H. , Lewis R. M. , Brandon T. A. , Entman M. L.
Published: December 2017

The cardiac lymphatic duct was cannulated in dogs and the exteriorized cannula allowed chronic collection of lymph during the awake state for as long as 3 wk. The surgical methodology and inherent difficulties in the technique are describ:d. Cardiac lymph flow ranged from 0.45--5.6 ml/h in the control state in 14 dogs. An occluding device and flow probe were placed on the circumflex coronary artery (CFX); ultrasonic segment length crystals were placed in the left ventricular free wall in 4 dogs. Occlusion of the CFX in these conscious dogs caused lymph flow to fall as great as 46% below control during the 1st half-hour. Reperfusion of the occluded vessel caused an increase in lymph flow as great as 67% above control. The effect on cardiac lymph flow was demonstrated for a few select drugs that have known effects on the cardiovascular system. Cardiac lymph flow was altered from control as follows: isoproterenol, 42 +/- 11% increase; RO 2-2985, 118 +/- 8% increase; verapamil, 101 +/- 10% increase; propranolol caused no significant change. The conscious dog with cardiac lymph vessel cannulated should provide a model to further study the complexities of cardiac metabolism and physiology without interference of anesthesia and surgical stress.
Uncoupling cation effects on cardiac contractility and sarcolemmal Ca2+ binding
Authors: Bers D. M. , Langer G. A.
Published: December 2017

Studies have been performed correlating the effects of cationic uncouplers on intact cardiac muscle and on Ca2+ bound to isolated cardiac plasma membranes. Sarcolemmal vesicles were isolated from neonatal rat hearts. Ca2+ binding experiments were performed and Scatchard plot analysis indicated two classes of Ca2+ binding sites. The ability of certain cations to displace Ca2+ bound to these vesicles was measured. The effects of these same cations on the tension developed by neonatal rat papillary muscles and on the Ca2+ content of tissue culture cells (from neonatal rat heart) were measured. The results show that a) the selectivity sequence (Y3+ greater than Nd3+ greater than La3+, Cd2+ greater than Co2+ greater than Mg2+) of sarcolemmal Ca2+ binding sites is the same as the effective uncoupling sequence; b) the amount of Ca2+ bound at these sites (approximately 700 micromol/kg wet wt) is more than adequate to support tension development; c) the dependence of sarcolemmal Ca2+ binding at low-affinity sites and tension development on [Ca2+]o is essentially the same. It is then reasonable to propose that the Ca2+ bound to these sarcolemmal sites plays an important role in controlling the amount of Ca2+ available to the myofilaments and thus myocardial contractility.
Vasodilation of cat cerebral arterioles by prostaglandins D2, E2, G2, and I2
Authors: Ellis E. F. , Wei E. P. , Kontos H. A.
Published: December 2017

To determine the possible role that endogenously produced prostaglandins may play in the regulation of cerebral blood flow, the responses of cerebral precapillary vessels to prostaglandins (PG) D2, E2, G2, and I2 (8.1 X 10(-8) to 2.7 X 10(-5) M) were studied in cats equipped with cranial windows for direct observation of the microvasculature. Local application of PGs induced a dose-dependent dilation of large (greater than or equal to 100 microns) and small (less than 100 microns) arterioles with no effect on arterial blood pressure. The relative vasodilator potency was PGG2 greater than PGE2 greater than PGI2 greater than PGD2. With all PGs, except D2, the percent dilation of small arterioles was greater than the dilation of large arterioles. After application of prostaglandins in a concentration of 2.7 X 10(-5) M, the mean +/- standard error of the percent dilation of large and small arterioles was, respectively, 47.6 +/- 2.7 and 65.3 +/- 6.1 for G2, 34.1 +/- 2.0, and 53.6 +/- 5.5 for E2, 25.4 +/- 1.8, and 40.2 +/- 4.6 for I2, and 20.3 +/- 2.5 and 11.0 +/- 2.2 for D2. Because brain arterioles are strongly responsive to prostaglandins and the brain can synthesize prostaglandins from its large endogenous pool of prostaglandin precursor, prostaglandins may be important mediators of changes in cerebral blood flow under normal and abnormal conditions.
Prostaglandin E2-induced hypertension in conscious dogs
Authors: Hockel G. M. , Cowley A. W.
Published: December 2017

The effects of continuous intrarenal prostaglandin E2 (PGE2) infusion (7 days) on sodium and water balance, plasma renin activity (PRA), and sodium and water balance, plasma renin activity (PRA), and mean arterial pressure (MAP) were examined in conscious, unilaterally nephrectomized dogs maintained on a fixed sodium intake of 55 meq/day. PGE2 infusion (2 microgram/min) resulted in a sustained threefold increase in both urine output and water intake without a measurable change in glomerular filtration rate. PRA increased from 0.4 +/- 0.1 during the control period to 2.2 +/- 0.9 ng AI.ml-1.h-1 on day 1 and averaged 3.6 +/- 0.5 for the remaining 6 days of PGE2 infusion. Concurrently, MAP increased from 102 +/- 3 to a maximum of 117 +/- 4 mmHg on day 5; changes in PRA and MAP were significantly correlated (r = 0.96, P less than 0.001). Sodium excretion increased from 54.5 +/- 3 to 88.0 +/- 19 meq/day on day 1, and then declined to an average of 64.8 +/- 1 meq/day for the remaining 6 days of infusion. All variables returned to the control level during the recovery period. Intravenous infusion of PGE2 (2 microgram/min) yielded directionally similar but statistically insignificant effects. It is concluded that chronic intrarenal PGE2 infusion results in marked diuresis, polydipsia, a moderate loss of sodium, enhanced PRA, and mild hypertension.
Cardiac function and morphology with aging in the spontaneously hypertensive rat
Authors: Pfeffer J. M. , Pfeffer M. A. , Fishbein M. C. , Frohlich E. D.
Published: December 2017

To determine the effects of a chronic pressure load on cardiac function and morphology, spontaneously hypertensive rats (SHR) and two normotensive strains of Wistar rats (WKY and NWR) were studied under ether anesthesia at 13, 25, 52, and 90 wk of age. Although resting cardiac index of the SHR was comparable to that of WKY and NWR at all ages, the peak cardiac output and peak stroke volume per gram of left ventricle determined during a rapid intravenous infusion of Tyrode solution was markedly reduced in the SHR only at 90 wk of age. Autonomic inhibition did not alter the peak stroke volume attained, but reduced peak cardiac output at all ages in each of the strains. Absolute left ventricular dimensions in the SHR increased out of proportion to body growth, consistent with concentric hypertrophy. As peak pumping ability markedly declined from 52 to 90 wk of age in the SHR, the free wall of the left ventricle greatly thickened whereas the septum remained unchanged. At this time the right ventricle also hypertrophied. This disproportionate thickening of the walls of the left ventricle and the hypertrophy of the right ventricle were reflected in measurements of their fiber diameters. These alterations in ventricular architecture may contribute to the decrease in pumping ability observed in long-standing hypertension.
Increased passive stiffness of short-term pressure-overload hypertrophied myocardium in cat
Authors: Natarajan G. , Bove A. A. , Coulson R. L. , Carey R. A. , Spann J. F.
Published: December 2017

The passive stress-strain relationship of right ventricular papillary muscles from 10 normal and 9 experimental cats with short-term pressure-overload right ventricular hypertrophy-failure was examined by plotting the logarithm of instantaneous stress (ln sigma) against the natural strain calculated as ln(l/l0) where l = instantaneous length and l0 = length at zero force. Such a stress-strain relationship was well approximated by a linear relationship. The slope K obtained from this linear relationship was higher in the hypertrophy-failure muscles (normal, 15.01 +/- 0.87 (SEM); hypertrophy-failure, 31.79 +/- 4.09; P less than 0.005). The value of the intercept, ln C was similar in the two groups (normal, -4.33 +/- 0.20; hypertrophy-failure, -4.71 +/- 0.10). This analysis indicates the the ln sigma-natural strain relationship is linear in the papillary muscle and the slope of this relationship, an index of stiffness, is increased in hypertrophy-failure muscles. Using a three-element muscle model, it is shown that increased diastolic stiffness may contribute to the decreased systolic performance.
Postnatal regulation of canine oxygen delivery: erythrocyte components affecting Hb function
Authors: Mueggler P. A. , Jones G. , Peterson J. S. , Bissonnette J. M. , Koler R. D. , Metcalfe J. , Jones R. T. , Black J. A.
Published: December 2017

A rightward shift in the blood oxygen dissociation curve occurs during the 1st mo of canine life. A detailed peptide analysis indicated that dogs do not have a separate fetal hemoglobin. Other erythrocyte components such as ATP, K+, Na+, and H+ were excluded as significant mediators of the postnatal oxygen affinity change. Erythrocyte 2,3-DPG levels essentially zero in fetal dogs, increased rapidly during the 1st mo of canine life. There was a significant correlation between this postnatal 2,3-DPG increase and the postnatal decrease in blood oxygen affinity. Dialyzed hemolysates of fetal or adult canine blood have the same intrinsic oxygen affinity and the same response to normal adult levels of 2,3-DPG. Furthermore, the magnitude and direction of this 2,3-DPG-induced decrease in oxygen affinity in vitro are comparable to the in vivo postnatal change in oxygen affinity.
Control of fetal cardiac output during changes in blood volume
Authors: Gilbert R. D.
Published: December 2017

Changes in cardiac output (Qco), heart rate, right atrial pressure, (Pra), and mean systemic pressure (Pms) in response to blood volume changes were measured in chronically prepared fetal sheep. With a 10% decrease in blood volume, fetal cardiac output, measured with the microsphere technique, decreased significantly from 592 +/- 28 to 471 +/- 32 ml . min-1 . kg-1. Heart rate changed little from control animals (163 +/- 5) to those with decreased volume (161 +/- 10 beats/min). Right atrial pressure decreased significantly from 5.4 +/- 0.4 to 4.2 +/- 0.6 mmHg. Mean systemic pressure decreased from 13.8 +/- 0.3 to 10.5 +/- 0.6 mmHg. With a 10% increase in fetal blood volume, cardiac output rose insignificantly to 632 +/- 38 ml . min-1 . kg-1. However, right atrial pressure increased significantly to 8.9 +/- 0.6 mmHg and mean systemic pressure increased significantly to 16.5 +/- 0.8 mmHg with the increased volume. Heart rate again changed little (153 +/- 9 beats/min). The fact that cardiac output rose only a small amount, whereas right atrial pressure rose sharply with an increased blood volume, suggests that the fetal heart is operating near the upper limit of its Starling function curve. As a result, there is very limited cardiac reserve for increases in fetal cardiac output.
Adaptation of left ventricle to chronic pressure overload: response to inotropic drugs
Authors: Newman W. H. , Webb J. G.
Published: December 2017

Left ventricular (LV) force-generating capacity was determined in eight anesthetized dogs with pressure-overload hypertrophy. Length-contractile force (CF) curves recorded from the LV with a modified Walton-Brodie arch were displaced upward from control. However, when CF was normalized for LV wall thickness changes accompanying hypertrophy and expressed as g/cm2, the length-CF curve was depressed compared to normal. The CF response to isoproterenol and calcium was depressed in dogs with hypertrophy; however, the CF response to ouabain was not different from control. Taken collectively these findings suggest that pressure-overload hypertrophy is associated with a depressed force-generating capacity per unit cross section of myocardium at any given muscle length, i.e., a depressed inotropic state, but that the hypertrophied LV has a greater than normal force-generating capacity due to an increased number of weaker cross-sectional units. Further, the depressed inotropic state is not associated with augmented plasma norepinephrine levels. Therefore, adaptation of the LV to pressure overload is by cardiac hypertrophy alone.
Effect of hyperoxia on regional blood flow after coronary occlusion in awake dogs
Authors: Rivas F. , Rembert J. C. , Bache R. J. , Cobb F. R. , Greenfield J. C.
Published: December 2017

The effect of 100% oxygen inhalation on regional transmural myocardial blood flow following 45 s of actue total left circumflex coronary artery occlusion was studied in six awake dogs chronically instrumented with a coronary occluder and catheters in the aorta and left atrium. After inhalation of either room air or 100% oxygen for at least 30 min and following the 45-s occlusion, transmural myocardial blood flow was determined with radioactive microspheres (7--10 micrometers). Each dog underwent two occlusions of the left circumflex coronary artery; one during inhalation of rrom air and the other during 100% oxygen. During room air inhalation, mean regional myocardial blood flow to nonischemic, intermediate, and ischemic regions was 0.92 +/- 0.05, 0.51 +/- 0.08, and 0.10 +/- 0.02 ml . min-1 . g-1, respectively. During 100% oxygen administration, flow was significantly diminished in each region to 0.75 +/- 0.04, 0.41 +/- 0.07, and 0.06 +/- 0.01 ml . min-1 . g-1, respectively. Transmural blood flow to each layer was uniformly reduced in all regions. These data indicate that 100% oxygen further reduces myocardial blood flow to ischemic regions.
A servo-controlled roller pump for cardiovascular research
Authors: Mohrman D. E.
Published: December 2017

This paper describes a servo-controlled roller pump system that can be applied to a variety of experimental situations that require either flow or pressure control. The roller pump employs a special race design that nearly eliminates the outflow pulsations inherent in conventional roller pumps. This pump simplifies servo-system design because the outflow rate is related to rotor speed by a fixed constant throughout a pump cycle. The system can control either speed or, with an appropriate feedback signal from an external transducer and preamplifier, the pressure on the output side of the pump. The time constant of the step response under speed control is less than 0.01 s, whereas that for pressure control is less than 0.2 s. System operation in the speed mode is independent of pump loading. In the pressure control mode, system operation is optimized for particular loading conditions by a single gain control. The pump can control pressure in loads ranging from a blind-ended tube through loads accepting up to 1 l/min.
Norepinephrine release by ventricular stimulation: effect on fibrillation thresholds
Authors: Euler D. E.
Published: December 2017

In adult dogs anesthetized with pentobarbital sodium, ventricular fibrillation thresholds determined by scanning the vulnerable period with a train of 14 pulses (4 ms, 100 Hz) were significantly less (P less than 0.01) than fibrillation thresholds determined by scanning the vulnerable period with a single 10-ms stimulus. Following beta-adrenergic blockade with propranolol, the relative increase in the fibrillation thresholds measured with trains was about seven times greater than the relative increase in the single-stimulus threshold (P less than 0.01). In a group of animals subjected to chronic cardiac denervation, fibrillation thresholds measured with trains were about three times greater than in a group of shamthoracotomized animals (P less than 0.01). Furthermore, the train fibrillation thresholds of the catecholamine-depleted hearts were not significantly different from the train thresholds of beta-blocked innervated hearts. These data, coupled with the finding that trains of stimuli produced a marked augmentation in local myocardial contractile force, suggest that locally released norepinephrine during a fibrillation-threshold determination may exert a profound influence on the level of current necessary to evoke fibrillation.
Permeability of intestinal capillaries to endogenous macromolecules
Authors: Granger D. N. , Taylor A. E.
Published: December 2017

Steady-state lymphatic and plasma protein concentration (CL and CP) and lymph flows were analyzed in an autoperfused cat ileum preparation at venous outflow pressures of 0, 10, 20, and 30 mmHg. Albumin and nine endogenous protein fractions were analyzed in lymph and plasma by polyacrylamide gradient gel electrophoresis. The osmotic reflection coefficient (sigma d = 1--CL/CP when CL/CP is no longer influenced by capillary filtration rate. The sigma d values acquired increased as the molecular radius of the protein fraction increased. Permeability-surface area products were estimated for the various protein fractions by applying the acquired data to the Kedem-Katchalsky protein flux equation. A comparison of the permeability-surface area products at various venous pressures suggests a reduction in capillary surface area as venous pressure is increased to 20 and 30 mmHg. The results suggest that intestinal capillaries selectively restrict macromolecules to a greater degree than the continuous type of capillaries of many other organs.
Anesthetic effects on hemodynamics of spontaneously hypertensive and Wistar-Kyoto rats
Authors: Smith T. L. , Hutchins P. M.
Published: December 2017

We studied the effects of three anesthetic agents on the central hemodynamics of spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats instrumented with chronic electromagnetic flow probes and arterial pressure catheters. Cardiovascular alterations due to ether, pentobarbital sodium (PBS; 50 mg/kg), and a 2% chloralose-7.5% urethan mixture (CU; 6 ml/kg) were determined. Ether produced significant elevations in heart rate (HR), cardiac index (CI), stroke volume (SV), and peak aortic flow velocity (PAFV) in SHRs (P less than 0.01) and elevations of HR and CI in WKYs (P less than 0.05). Ether reduced total peripheral resistance (TPR) and mean arterial pressure (MAP) in WKYs and SHRs (P less than 0.01). PBS decreased HR, CI, SV, MAP, PAFV, and minute work (MW) in both WKYs and SHRs (P less than 0.05--P less than 0.001). PBS also lowered TPR in WKYs (P less than 0.05). CU produced effects similar to those of PBS, but did not alter HR or TPR. Central hemodynamics are therefore significantly altered by these anesthetics when compared to those of conscious rats. These agents also have differential effects on the hemodynamics of SHRs and WKYs.
Reflexes from isolated carotid sinuses of intact and vagotomized conscious dogs
Authors: Stephenson R. B. , Donald D. E.
Published: December 2017

Exposure of the vascularly isolated carotid sinuses of 8 conscious dogs to static pressures between 50 and 240 mmHg caused significantly smaller increases [23 +/- 5(SE) mmHg] than decreases (37 +/- 4 mmHg) in arterial pressure frossure and heart rate and shifted the stimulus-response curve upward. Bilateral cervical vagotomy in conscious dogs caused sustained (3 h) increases in arterial pressure (40 +/- 5 mmHg), significantly larger than after atropinization (7 +/- 2 mmHg). In anesthetized, but not in conscious dogs, high sinus pressure reversed the hypertension caused by vagotomy. After vagotomy, low sinus pressure resulted in arterial pressures greater than 200 -mHg. In conscious dogs the carotid baroreflex can widely vary arterial pressure and heart rate despite buffering by extracarotid baroreceptors with vagal afferents, but cannot fully compensate for the acute loss of the latter. Extracarotid baroreceptors actively participate with carotid baroreceptors in the regulation of arterial pressure and better buffer carotid baroreflex-induced increases than decreases in arterial pressure.
Development of autonomic heart rate control in the kitten during sleep
Authors: Egbert J. R. , Katona P. G.
Published: December 2017

Development of cardiac rate control was studied in 34 kittens aged 4 days to 6 wk during quiet and active sleep, using atropine and propranolol to quantitatively assess the degree of tonic parasympathetic and sympathetic control, with the analysis based on the Rosenblueth and Simeone model. The order of blocking agent administration did not significantly affect the results if a correction was made for the baroreceptor-mediated heart rate change after the blockade of a single autonomic branch. During the first 4 wk, the heart rate in quiet sleep was lower than in active sleep due to a significantly higher parasympathetic tone. The heart rate decreased with age in both sleep states: the decrease in quiet sleep was accompanied by a transition from sympathetic to parasympathetic dominance. The intrinsic rate of the pharmacologically denervated heart was maximum at about 2 wk and decreased steadily thereafter. The observed changes may help explain some features of the development in heart rate previously reported for sleeping human infants.
Response of systemic arterial input impedance to volume expansion and hemorrhage
Authors: Dujardin J. P. , Stone D. N. , Paul L. T. , Pieper H. P.
Published: December 2017

Experiments on 12 anesthetized dogs were performed to study the effects of changes in blood volume on the pulsatile hemodynamics of the arterial system as seen from its input. Pressure and flow were measured in the ascending aorta under control conditions, after volume expansion with dextran 70 (+30% of estimated blood volume), and after hemorrhage (-15% of estimated blood volume). The input inpedance of the arterial system was calculated for each condition. It was found that after volume expansion the characteristic impedance of the proximal aorta, Zc, was decreased by 26.6 +/- 5.1% (SE) (P less than 0.01). After hemorrhage Zc was increased by 30.4 +/- 3.4% (P less than 0.01). Since it is well known that Zc is a very weak function of the mean arterial pressure, it is concluded that the changes in Zc seen with volume expansion or hemorrhage are caused mainly by changes in aortic smooth muscle activity. This conclusion is also supported by direct measurements of aortic pressure diameter relationships in earlier work from our lab.
Effects of Ca2+ antagonism on energy metabolism: Ca2+ and heart function after ischemia
Authors: Watts J. A. , Koch C. D. , LaNoue K. F.
Published: December 2017

Isolated rat hearts reperfused after 25 min of ischemia have 23% of control mechanical function, 65% of control nucleotides, 52% of control ATP, and 75% of control creatine phosphate, whereas cellular calcium is increased 2.3-fold. Initiating reperfusion with verapamil or low Ca2+-containing buffer did not alter these tissue parameters or improve function over hearts reperfused with control buffer only. Also, when verapamil was present before and during ischemia, improvement in cardiac function resulted, and the adenine nucleotides, tissue ATP, and creatine phosphate concentrations were increased while cellular Ca2+ was reduced compared with the other reperfused ischemic hearts. Verapamil apparently improves recovery of function by decreasing energy demand during ischemia rather than by blocking Ca2+ influx during reprefusion. The respiration of isolated mitochondria and homogenates from reperfused ischemic hearts and homogenates of ischemic hearts was decreased by 20-30%, possibly due to sarcolemmal damage, although the respiration of isolated cells from ischemic hearts was normal. Cells isolated from ischemic hearts may represent a selected population lacking sarcolemmal damage.
Interaction between the rigt heart ventricle and its arterial load: a quantitative solution
Authors: Piene H.
Published: December 2017

Piene and Sund (Cardiovasc. Res., 1980) have recently demonstrated that the performance of the ventricle can be expressed by relating the principal variables pressure (P), volume (V), and time after onset of contraction (t): P = function (V,t). The function can be mapped experimentally as a three-dimensional surface, denoted the PVt surface, and can thereafter be approximated by an empirical equation. The vascular load of the ventricle is defined by the arterial input impedance vs. frequency graph, Z(f), which can be converted to the time domain by inverse Fourier transformation. This report describes how flow and pressure generated by the ventricle can be calculated when the independent expressions for the ventricle and for the load are given. The method is applied on right ventricular contractions of isolated cat hearts, and excellent fit between calculated and observed flow and pressure curves was obtained.
Cardiac physiologic-metabolic changes after chronic low-level heavy metal feeding
Authors: Kopp S. J. , Perry M. , Glonek T. , Erlanger M. , Perry E. F. , Barany M. , D'Agrosa L. S.
Published: December 2017

Female Long-Evans hooded rats received 0 or 5 parts per million Cd, Pb, or Cd + Pb in the drinking water from weaning to 20 mo. Growth, measured as body weight, and organ weights were comparable among heavy metal and control animals. Indirect blood pressure responses measured trimonthly are discussed. Analysis of His bundle electrograms (HBE) and electrocardiograms recorded in sodium pentobarbital-anesthetized animals at 20 mo demonstrated that Cd selectively depressed conduction system excitability proximal to the common His bundle (atrioventricular node region), whereas Pb and Pb + Cd impaired conductivity distal to the common His bundle (His-Purkinje system). Perchloric acid extracts of liquid N2-freeze-clamped isolated perfused hearts, derived from a subpopulation of control and Cd-fed rats in which HBE analyses were not performed, were analyzed by phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopic techniques to quantitate [31P]phosphate metabolite profiles. Cardiac active tension and atrioventricular node excitability were depressed in the Cd group. High-energy phosphate and glycerol 3-phosphorylcholine concentrations were depressed. Results demonstrate potentially significant pathophysiological changes within cardiovascular tissues that develop in the absence of overt heavy metal toxicity manifestations.
Sodium permeability and myocardial resistance to cell swelling during metabolic blockade
Authors: Pine M. B. , Kahne D. , Jaski B. , Apstein C. S. , Thorp K. , Abelmann W. H.
Published: December 2017

The role of cell membrane permeability to sodium in cell volume regulation during inhibition of the sodium-potassium exchange pump with ouabain and during total metabolic blockade was evaluated in sections of guinea pig renal cortex, ventricle, and atrium incubated in Krebs-Henseleit solution. In all tissues, 2 and 3 h of ouabain and metabolic blockade resulted in similar marked losses of potassium and parallel continuous reductions in resting membrane potentials. Only metabolic blockade of renal cortex increased cell water, chloride, and total monovalent cations (potassium plus sodium) significantly. Compared to ouabain, metabolic blockade markedly increased the rate of cellular washout of 24Na+ from renal cortex (t 1/2 reduced by 47%), which was significantly greater than reductions in t 1/2 from ventricle (16%) and atrium (15%). Thus, inhibition of sodium-potassium exchange pump activity was not sufficient to produce cell swelling unless associated with marked increases in cell membrane permeability to sodium, in which case sodium influx exceeded potassium loss and substantial increases in monovalent cations, chloride, and water occurred.
Cardiovascular effects of vanadate in the dog
Authors: Inciarte D. J. , Steffen R. P. , Dobbins D. E. , Swindall B. T. , Johnston J. , Haddy F. J.
Published: December 2017

We have investigated the cardiovascular actions of vanadate, a naturally occurring Na+-K+-ATPase inhibitor, in six series of pentobarbitalized dogs. In three of the series, isomotic sodium vanadate was infused intravenously at progressively faster rates while arterial pressure and other parameters were measured. In two other series, the solution was infused directly into the coronary artery with coronary flow held constant during measurement of perfusion pressure, left ventricular contractile force (LVCF), and dP/dt. In one series, the agent was infused into the brachial artery with brachial artery flow held constant, and small and large vessel resistances in skin and muscle were calculated. Intravenous infusion increased arterial pressure and reduced cardiac output, the latter resulting from both decreased heart rate and stroke volume. LVCF fell. Total peripheral, pulmonary, coronary, and renal resistances rose. Coronary and renal flows fell, and the latter was associated with reduced urine flow. Intracoronary infusion raised coronary resistance, but had little effect on heart rate, LVCF, and dP/dt. Intrabrachial infusion raisedthe resistance to flow through all components of the forelimb vascular bed. Thus, in the dog, vanadate activates vascular smooth muscle, but has little effect on cardiac muscle. In the latter respect, its action differs from that of ouabain.
Effect of histamine and alloxan on canine pulmonary vascular permeability
Authors: Drake R. E. , Gabel J. C.
Published: December 2017

We estimated the pulmonary capillary membrane filtration coefficient (Kf) and the maximum capillary pressure (PCcritical) at which the lung could maintain a constant weight in 1) 5 control experiments in anesthetized open-chested dogs, 2) 7 experiments in which the dogs were given 3.6-8.3 microgram . kg-1 . min-1 of histamine phosphate, and 3) in 6 experiments after 75-100 mg/kg of alloxan. In additional experiments, pulmonary lymph flow (QL) and protein concentration (CL) were measured during the infusion of histamine and alloxan. After histamine, Kf averaged 0.045 +/- 0,008 ml . min-1mmHg-1 (SE) and PCcritical was 22.1 +/- 1.1 mmHg. These values were not significantly different from the control Kf and PCcritical (0.036 +/- 0.006 and 22.5 +/- 2.3, respectively). After alloxan, Kf (1.43 +/- 0.69) was larger and PCcritical (12.4 +/- 1.3) was significantly less than control (P less than 0.05). Histamine caused no significant change in QL or CL; however, both were increased after alloxan. These results show that Kf, PCcritical, QL, and CL are all changed by an increase in capillary membrane permeability caused by alloxan. Because none of these factors as significantly affected by histamine, dog lung capillary membrane permeability may not be affected by histamine.
Central oscillators responsible for sympathetic nerve discharge
Authors: Gebber G. L.
Published: December 2017

The current state of knowledge concerning central mechanisms responsible for the generation of background discharges in sympathetic nerves is examined. It is apparent from recent investigations that the classic concept of a randomly discharging and diffusely organized central network onto which rhythms (cardiac- and respiratory-related) are imposed by extrinsic inputs has not passed the test of time. Rather, brain stem as well as spinal networks that govern the discharges of sympathetic nerves are inherently capable of rhythm generation. Sympathetic nerve rhythms inherent to the central nervous system imply the existence of neuronal circuits that are capable of oscillatory activity. Central oscillators provide a mechanism for synchronization of the activity of populations of sympathetic neurons in the absence of periodic input from sources extrinsic to the central nervous system. Indeed, the thesis is developed that, rather than creating rhythms in sympathetic nerve discharge, the function of periodic input from extrinsic sources such as the baroreceptors is to entrain rhythms of central origin. Finally, the problems associated with the identification of neuronal types that comprise central oscillators which govern the discharges of sympathetic nerves are discussed.
Afferent pathways of reflex hypotension and bradycardia during coronary occlusion
Authors: Iwamura N. , Bishop V. S.
Published: December 2017

Neural afferent pathways mediating reflex hypotension and bradycardia during coronary occlusion (CO) were determined mainly on the right side in anesthetized cats. Brief occlusion of the left anterior descending (LAD) or circumflex coronary artery (Cx) reuslted in significant hypotension and bradycardia, both of which could be attenuated by bilateral (BVB), unilateral right (RVB), or left vagal cold blockade (LVB) in the nec. The degree of attenuation in the responses was greater as follows: BVB greater than RVB greater than LVB for LAD occlusion, and BVB greater than RBV = LBV for Cx occlusion. Randomized section of cardiac nerves, i.e., the pericoronary nerve, vagal cardiac nerve trunk, and caudal vagal cardiac nerves on the right side produced significant attenuations in the circulatory responses to CO. These results indicate that vagal afferent activity transmitted via these cardiac nerves plays an important role in mediating the reflex responses to CO. This conclusion was further substantiated by electrical stimulation of afferent fibers in thee nerves or by recording increased afferent spontaneous activity form them during CO.