bluuebunny/crossref_metadata_2025 huggingface dataset:
Cross-linking of actin and fibrin by fibrin-stabilizing factor
Authors: Mui P. T. , Ganguly P.
Published: December 2017

Fibrin-stabilizing factor is known to cross-link fibrin monomers. This study was undertaken to explore whether a similar interaction might occur between actin and fibrin. Purified actin and fibrinogen were labeled with 131I and 125I, respectively. The interaction of actin and fibrin, under different conditions, was evaluated by gel electrophoresis. The data show that actin and fibrin are cross-linked in the presence of fibrin-stabilizing factor.
Loss of regional ventricular postextrasystolic potentiation after coronary occlusion in dogs
Authors: Crozatier B. , Franklin D. , Theroux P. , Tomoike H. , Sasayama S. , Ross J.
Published: December 2017

Postextrasystolic potentiation following coronary artery occlusion was studied serially using pairs of ultrasonic crystals to measure regional myocardial function in control, marginally ischemic, and ischemic segments of the left ventricle in dogs. Prior to coronary occlusion (CO), percent shortening in control (normal) segments increased by an average of 51.4 +/- 4.6% in the beat after a premature ventricular contraction (post-PVC beat), and this response changed little after coronary occlusion. During the 1st min after CO, in ischemic segments, systolic expansion developed but was replaced by active shortening in post-PVC beats; however, after 3 min of CO (average) and thereafter, there was no net positive shortening in post-PVC beats. In marginally ischemic segments early after CO, hypokinesia developed, but there was marked augmentation of percent shortening (208.6 +/- 32.6%) which persisted in post-PVC beats even after 2 h. It is concluded that loss of postextrasystolic potentiation occurs rapidly in ischemic regions after CO and is not indicative of irreversible damage; partially ischemic regions retain this mechanism for prolonged periods.
Vascular prostaglandin synthesis in the spontaneously hypertensive rat
Authors: Limas C. J. , Limas C.
Published: December 2017

Vascular prostaglandin synthesis was studied in tissues (aorta and inferior vena cava) obtained from spontaneously hypertensive rats (SHRs) of the Aoki-Okamoto strain and age-matched Wistar-Kyoto (WKYs) controls. PGE2 synthesis in aortas from SHRs was significantly enhanced at 10 wk of age (5.3 +/- 0.7 nmol PGE2/mg protein per 10 min vs. 1.9 +/- 0.03 nmol PGE2/mg protein per min in the WKYs, P less than 0.001) and increased progressively until 22 wk of age; PGE2alpha synthesis in SHRs was not significantly different from WKYs. In the venous walls from SHRs, PGF2alpha was the prostaglandin predominantly synthesized (7.1 +/- 0.6 vs. 1.9 +/- 0.05 nmol PGE2alpha/mg protein per 10 min in the WKY controls, P less than 0.01). The activities of 15-hydroxy prostaglandin dehydrogenase and PGE 9-ketoreductase were also compared in the two groups of animals. The only difference detected was a significant increase in venous PGE 9-ketoreductase of SHR's (7.3 +/- 0.06 vs. 4.8 +/- 0.04 nmol PGF2alpha/mg per min, P less than 0.01). The results suggest that increased vascular synthesis of prostaglandins accompanies the development of spontaneous hypertension and may serve to attenuate the effects of blood pressure elevation.
Influence of the burn wound on peripheral circulation in thermally injured patients
Authors: Aulick L. H. , Wilmore D. W. , Mason A. D. , Pruitt B. A.
Published: December 2017

Simultaneous measurements of resting leg blood flow and surface and rectal temperatures were made in 45 studies of 9 normal subjects and 28 burn patients. The patients had burns from 3-86% of the total body surface with leg injury ranging from 0-87.5% of the leg surface. In the patient group, blood flow was essentially normal in the uninjured legs, increased in a curvilinear manner with the size of the leg burn, and approached a plateau of 8.0 ml/100 ml-min as the percent of leg burn exceeded 60%. Increasing the leg surface temperature by 5 degrees C increased blood flow in patients with burned and unburned extremities to the same extent as in normal subjects. Increased peripheral blood flow following thermal injury is directed primarily to the burn wound. Variations in surface temperature modify this peripheral vascular response to injury.
Physiologic determinants of left ventricular strength-interval curve of the dog
Authors: Goodyer A. V. , Wong B. Y.
Published: December 2017

Strength-interval curves, relating an index of the contractile vigor of premature beats to their coupling intervals, were elicited in anesthetized, open-chest dogs prepared for atrial or ventricular pacing and the high-fidelity measurement of left ventricular pressure. During inotropic interventions, changes of the curves were evaluated in terms of the parameters (slopes and intercepts) of their straight lines of best fit. These parameters were altered by isoproterenol, propranolol, and heart rate, and were correlated closely with paired values of isovolumic Vmax (of driven beats). The strength-interval curves were reproducible and were not affected by large changes of venous return or arterial blood pressure. These results provide a basis for the use of strength-interval curves for the evaluation of ventricular contractile state, using fluid-filled catheters for the measurement of left ventricular pressure.
Reflex effects of thoracic sympathetic afferent nerve stimulation on the kidney
Authors: Purtock R. V. , von Colditz J. H. , Seagard J. L. , Igler F. O. , Zuperku E. J. , Kampine J. P.
Published: December 2017

Thoracic sympathetic afferents may play a role in the reflex control of renal vascular resistance during hypotension. Mongrel dogs were anesthetized with ketamine hydrochloride and maintained on a 50-50, O2-N2O mixture supplemented with 0.5%-1.0% halothane. Systemic arterial blood pressure was lowered to 50 mmHg with use of a constant pressure hemorrhage technique. The renal circulation was perfused with a constant-flow perfusion system. Low-frequency (3 Hz) stimulation of thoracic sympathetic afferents produced renal vasodilation. A reduction of renal vascular resistance was measured as a decrease in constant-flow perfusion pressure. Vagotomy accentuated the dilator response to stimulation. High-frequency (30 Hz) afferent
Ionic basis of electrical activity in cardiac tissues
Authors: Coraboeuf E.
Published: December 2017

Cardiac electrical events are described in terms of membrane physiology. The concept that cardiac membranes possess specific ionic channels controlled by gates bearing electrical charges is discussed. When open, these channels permit ions to cross the membrane, giving rise to passive inward (depolarizing) and outward (repolarizing) currents. Two different inward and four or five different outward currents appear to be responsible for the development of cardiac electrical activity; both inward currents appear to be controlled by activation and inactivation variables, whereas outward currents are essentially controlled by activation variables and/or inward-going rectifiers. The potential range in which the different currents activate and inactivate (or are limited by inward-going rectification), and the kinetics of activation and inactivation processes explain the development of electrical activity in normal cardiac tissues and in partially depolarized fibers. In addition to passive ionic currents, electrogenic active transport participates in the development of electrical phenomena. The conductance of the membrane for potassium ions and the electrical coupling between cardiac cells depend on the intracellular concentration of calcium ions.
Direct effect of physiological doses of arginine vasopressin on the arterial wall in vivo
Authors: Monos E. , Cox R. H. , Peterson L. H.
Published: December 2017

Effects of topically applied arginine vasopressin (VPA), in 100-150 muU/ml blood concentration, on external diameter (D) and on dynamic elastic modulus (E*) of surgically denervated common carotid (CC) and femoral (FA) arteries have been studied before and after hypophysectomy in anesthetized dogs. Changes in D, E*, and flow resistance (R) of the CC and FA vascular beds before and after removal of the pituitary were also determined. It was found that VPA elicited a substantial (max 21-26%) decrease in E* and a smaller (max 5.9-6.9%) reduction in D of FA independent of the presence of absence of the pituitary gland. The VPA effect developed more rapidly after hypophysectomy than before. In the CC, VPA did not significantly affect values of E*. During the 1-h period after hypophysectomy, statistically significant decreases in E*-CC, E*-FA, and D-CC were observed, but D-FA did not change, although arterial pressure as well as R-FA and R-CC were diminished. These results give further support to physiological vascular actions of VPA and a possible role in short-term circulatory control. In large arteries, the effects of VPA also seem to be regionally differentiated.
Interaction of descending spinal sympathetic pathways and afferent nerves
Authors: Barman S. M. , Wurster R. D.
Published: December 2017

With the use of computer-aided techniques, the interaction of descending spinal sympathetic pathways and afferent nerve fibers (cervical dorsal roots and tibial nerve) in regulation of thoracic (T2) preganglionic nerve activity was investigated in anesthetized, vagotomized, and paralyzed cats. High-frequency activation of a sympathoinhibitory pathway (ventrolateral funiculus) depressed the evoked discharges in the T2 preganglionic nerve elicited by stimulation of a sympathoexcitatory pathway (dorsolateral funiculus) and the spinal component of the somatosympathetic reflex. Submaximal evoked responses were also inhibited through baroreceptor reflex activation (blood pressure elevations up to 225 mmHg). Facilitation of the spinal component of the somatosympathetic reflex occurred during stimulation of the excitatory pathway. Carotid occlusion (baroreceptor inactivation) facilitated the submaximal evoked discharges from stimulation of the descending excitatory pathway. These data support the contention that sympathetic nerve activity can be modified by the integration of excitatory and inhibitory impulses at the spinal level.
Cardiovascular-respiratory reflex interactions between carotid bodies and upper-airways receptors in the monkey
Authors: Daly M. B. , Korner P. I. , Angell-James J. E. , Oliver J. R.
Published: December 2017

The carotid bodies were stimulated in the anesthetized pig-tailed macaque monkey (Macaca nemestrina) using i) brief injections of cyanide or CO2-equilibrated bicarbonate solution into a common carotid artery, and ii) longer perfusion with hypoxic hypercapnic blood in vascularly isolated chemoreceptor preparations. In spontaneously breathing animals, brief stimulations of the chemoreceptors consistently caused an increase in pulmonary ventilation, bradycardia, and an increase in femoral vascular resistance. When the same chemoreceptor stimulus was superimposed during the apneic period, reflexly evoked by stimulating either the central ends of the superior laryngeal nerves or the nasopharynx, the respiratory stimulation was absent or minimal, but the bradycardia and vasconstriction were greatly enhanced and exceeded the summed responses of separate stimulation of the chemoreceptors and one or the other of the upper-airways inputs. With sustained stimulation of the carotid bodies, hyperventilation, tachycardia, and femoral vasodilatation occurred due to overriding respiratory mechanisms. When superior laryngeal nerve stimulation was superimposed on this response, apnea occurred and tachycardia was reversed to bradycardia, and femoral vascular resistance increased above resting level. The interaction of autonomic responses resulting from chemoreceptor stimulation and from increases in the upper-airways inputs are qualitatively similar in the monkey and in subprimate species. Those involving specifically cardioinhibitory vagal responses are, in part at least, dependent on mechanisms related to the concomitant changes in respiration.
Intestinal muscle and mucosal blood flow during direct sympathetic stimulation
Authors: Bohlen H. G. , Henrich H. , Gore R. W. , Johnson P. C.
Published: December 2017

The effect of direct sympathetic stimulation on intestinal muscle and submucosal-mucosal vasculatures was studied in the anesthetized rat. Blood flow was calculated from direct measurements of vessel diameter and red cell velocity. Stimulation at 4 Hz caused a slight reduction (4%) in muscle flow, but had no measurable effect on submucosal-mucosal flow; stimulation at 8 and 16 Hz caused muscle flow to decrease to 58.3 +/- 8.7% (SE) and 31 +/- 5.1%, respectively, of control flow, and mucosal flow, to 73 +/- 3.4% and 54.1 +/- 1.2%, respectively, of control flow. Calculations of muscle and mucosal vascular resistances from flows and microvascular pressures indicate that muscle resistance increased proportionately more than mucosal resistance at 4 and 8 Hz. However, during stimulation at 16 Hz, the mucosal resistance is only 55% of control, and muscle resistance is not significantly (P less than 0.05) different from control. Therefore, reduction of muscle and mucosal flows during 16-Hz stimulation must be caused by the intestinal arterioles and venules in series with these vasculatures.
Cardiac muscle mechanics from Doca- and aging spontaneously hypertensive rats
Authors: Heller L. J.
Published: December 2017

Contractile properties of isolated papillary muscles from three age groups of spontaeously hypertensive rats (SHRs) were compared to those from age-matched Wistar-Kyoto rats (WKYs) to assess whether there were differences between the strains preceding and during the course of the hypertension. In all three age groups (7, 12, and 50 wk), the mechanical refractory periods (MRP) were longer and aftercontractions more prominent after paired pulse stimulation in preparations from SHRs than from age-matched WKYs. Other isometric twitch properties of SHR papillary muscles at Lmax were not different from WKYs, with the exception of a shorter half-relaxation time in the youngest SHR group. Although hypertension and cardiac hypertrophy increased in SHRs with age, aging had similar influences on most cardiac contractile properties in both strains. None of the isometric properties of papillary muscles from rats made hypertensive by Doca treatment were different from those in normotensive control preparations. This suggests that differences seen between SHRs and WKYs probably represent genetic differences between these strains and are not directly caused by the hypertension.
The pacemaker cell of the sinoatrial node of the rabbit
Authors: Taylor J. J. , D'Agrosa L. S. , Burns E. M.
Published: December 2017

Rabbit sinoatrial nodes were isolated and studied in an attempt to determine the cell of origin of the true pacemaker potential. Cells of the sinoatrial node of the rabbit giving rise to the characteristic true pacemaker potential were iontophoretically tagged with lanthanum. The lanthanum appeared within the cytoplasm of cells, which morpholigically are (P) cells. The lanthanum appeared as small, amorphous, electron-dense globules. It is concluded from this study that the P or pale cell is the source of the true pacemaker action potential of the sinoatrial node.
Characteristics of coronary blood flow and transmural distribution in miniature pigs
Authors: Sanders M. , White F. C. , Peterson T. M. , Bloor C. M.
Published: December 2017

The relationship between phasic systolic and diastolic coronary blood flow and its transmural distribution has been studied in 29 Yucatan miniature pigs at rest and during heavy exercise, with and without adenosine infusion (1.5 mg . kg-1 . min-1) and with and without a subtotal coronary artery occlusion. Altered factors that affected coronary flow included vascular resistance, perfusion pressure, myocardial oxygen demand, and extra-vascular pressure. The data indicate that, at rest, endomural perfusion is significantly dependent on diastolic blood flow. However, the ability of the myocardial vessels to autoregulate during systole as well as during diastole was clearly shown with the use of adenosine infusion. This ability to regulate flow intrinsically appeared to transcend the endocardial dependency on diastolic perfusion under certain stressful conditions, e.g., during heavy exercise, when the diastolic duration was significantly reduced. Systolic transmural perfusion may then become a significant factor in meeting the blood flow demands of the myocardium. However, due to gradients in vascular resistance, perfusion pressure, and oxygen demand, the coronary reserve of the epicardium appears to be greater than that of the endocardium under any condition.
Inhibitory effect of hypertonic mannitol on vasoconstrictor and vasodilator responses of isolated coronary arteries
Authors: Krishnamurty V. S. , Adams H. R. , Templeton G. H. , Willerson J. T.
Published: December 2017

The effect of hypertonic mannitol on pressor responses to vasoactive agents was studied in isolated canine coronary arteries perfused with physiologic salt solution at a constant flow. When perfusion pressure was increased with 60 mM KCl, mannitol (50 mosM) consistently caused a decrease in perfusion pressure that lasted for at least 1 h. Withdrawal of mannitol from the perfusion media was associated with a vasoconstrictor response that was not prevented by alpha- or beta-adrenoceptor blockade or by the presence of either nitroglycerin or norepinephrine. Hypertonic mannitol also reduced the responsiveness of the isolated smooth muscle preparations to several different mechanistically unrelated vasodilator agents. The mechanism(s) responsible for the paradoxical ability of hypertonic mannitol to reduce vascular responsiveness to both vasoconstrictor and vasodilator interventions in isolated canine coronary arteries is not known, but future studies should be directed at elucidating it as well as determining whether similar phenomena occur in vivo.
Ovine placental vascular responses to indomethacin
Authors: Rankin J. H. , Berssenbrugge A. , Anderson D. , Phernetton T.
Published: December 2017

The administration of 10 mg/kg indomethacin to chronically catheterized near-term sheep resulted in a change in cotyledonary vascular resistance from 0.133 +/- 0.016 to 0.180 +/- 0.022 (mmHg . min)/ml (P less than 0.001). The noncotyledonary uterine vascular resistance increased to 191% of the original value (P less than 0.001) and the renal vascular resistance increased to 147% of the control value (P less than 0.001). The maternal blood pressure increased from 96 +/- 3.4 to 108 +/- 3.4 mmHg (P less than 0.001). Indomethacin (12 mg/kg) was given to nine fetuses, and observations were made in the control condition and at 15, 120, and 240 min. Cotyledonary vascular resistances were 144%, 152%, and 213% of the control values at those times. All changes were significant (P less than 0.03). The umbilical vascular resistance rose slowly throughout the study even though the concentration of indomethacin was falling during that time. These data suggest that this response may be an indirect effect. In the maternal circulation the rapid increase in the cotyledonary vascular resistance seen after indomethacin was probably due to a decreased level of endogenous prostaglandin synthesis.
Plasma volumes and hematocrits in rats with chronic sinoaortic denervation hypertension
Authors: Alexander N.
Published: December 2017

Plasma volume changes were assessed in female Wistar rats with neurogenic hypertension induced by sinoaortic denervation, SAD. Tail veins of conscious, restrained rats were used for injection of Evans blue dye and for sampling into microhematocrit tubes. Only at 3 days did total plasma volume of SAD rats show a modest reduction of about 16% (P less than 0.05 vs. sham-operated plus unoperated controls). At 3, 6, and 13 wk, SAD mean body weight, plasma volume, and sodium concentration were similar to sham values. SAD hematocrits, however, like arterial pressures, were elevated at all postoperative times studied. In anesthetized SAD and sham rats, red blood cell (51Cr method) and plasma volumes were the same and so were hematocrits. The latter was unlike the finding in unanesthetized groups. Hematocrits from the same SAD rats were lower after induction of anesthesia than before (P less than 0.025). Thus, elevated hematocrits apparently resulted from the release of sequestered red blood cells into the circulation by unanesthetized SAD rats. In conclusion, plasma volume is within the normal range in SAD rats except for the first few postoperative days. Factors affecting volume regulation at that time are discussed.
Characteristics of active Na transport in intact cardiac cells
Authors: Glitsch H. G.
Published: December 2017

An active Na transport maintains the Na and K concentration gradients across the cell membrane of many cells and restores them following excitation. Heart muscle cells display frequent electrical discharges and thus the cardiac Na pump is of fundamental functional significance. Some methods for studying active Na transport are described. The active Na efflux from heart muscle cells is activated by an increase in the intracellular Na and the extracellular K concentration. The linkage between active Na efflux and active K influx varies widely according to the experimental conditions. The cardiac Na pump is electrogenic and can contribute directly to the membrane potential of the cells. The effects of active Na transport on contraction and intercellular coupling in myocardium are discussed.
Inferior cardiac nerve activity in the cat during occlusion of the mesenteric artery
Authors: Tuttle R. S. , McCleary M.
Published: December 2017

A number of studies in this and other laboratories using hemodynamic and pharmacologic evidence have suggested that occlusion of the mesenteric artery evokes a pressor reflex initiated by mesenteric baroreceptors. To provide additional evidence in support of this hypothesis, neurophysiological recordings were made of inferior cardiac nerve activity during mesenteric artery occlusion (MAO). The results indicate that MAO enhances inferior cardiac nerve activity in the cat, providing that the carotid sinus nerves have been cut. Cutting of the mesenteric nerves further facilitates cardiac nerve activity and abolishes the response to mesenteric artery occlusion. The evidence suggests that MAO evokes a reflex sympathetic discharge which is subject to override by the carotid sinus depressor reflex. The afferent limb of the reflex is characterized by a tonic depressor outflow from the mesenteric pressure receptors.
Indices of myocardial oxygen consumption for isotonic contraction
Authors: Lambert C. R. , Posner P.
Published: December 2017

To investigate the model-independent mechanical determinants of energy expenditure, a respirometer was constructed to study isolated feline papillary muscles. Mechanical parameters recorded were the distance of shortening (deltaL), peak velocity of shortening (Vp), mean velocity of shortening (V), tension-time index (TTI), afterload (P), and the integral of the contraction portion of the phase plane trajectory of velocity and length (integral of VdL). Oxygen consumption (Vo2) during 15-min isotonic contraction periods was monitored with a polarographic electrode. Vp, V, and delta L were inversely related to Vo2 in a curvilinear manner. P and TTI were directly related to Vo2 in a curvilinear fashion. Integral of VdL was inversely related to Vo2 in a linear manner. In several experiments the contractile state of the muscles was augmented by addition of norepinephrine (7 X 10(-8) M). The relationship between integral of VdL and Vo2 was shifted above and parallel to that for the control muscles. These experiments indicate that the index integral of VdL is linearly related to the oxygen consumed in isotonic contraction of isolated mammalian ventricular myocardium at a given level of contractile state.
Changes in ultrasonic attenuation indicative of early myocardial ischemic injury
Authors: Mimbs J. W. , O'Donnell M. , Miller J. G. , Sobel B. E.
Published: December 2017

This study was designed to determine whether quantitative alterations in ultrasonic attenuation are associated with myocardial changes occurring after acute ischemic injury. Five hundred seventeen regions of myocardium from 41 dogs were studied in vitro at five intervals after coronary occlusion: 15 min, 1 h, 6 h, 24 h, 3 days, and 6 wk. Quantitative indices of ultrasonic attenuation were determined from the measured frequency dependence of the ultrasonic attenuation coefficient characterizing each myocardial region over the range 2-10 MHz. Independent definition of regions of ischemic injury was provided by either creatine kinase depletion or colloidal carbon dye distribution. Results of this study indicate that ischemic myocardial regions investigated 15 min to 24 h after coronary occlusion demonstrated ultrasonic attenuation significantly decreased from nonischemic regions (P less than 0.05). In contrast, ultrasonic attenuation was significantly increased in zones of ischemia or infarction investigated at 3 days and 6 wk after coronary occlusion (P less than 0.05 and P less than 0.01, respectively). These results indicate that altered attenuation of transmitted ultrasound by myocardium in vitro is an early manifestation of ischemia.
Thermal quantification of region myocardial perfusion and heat generation
Authors: Hernandez E. J. , Hoffman J. K. , Fabian M. , Siegel J. H. , Eberhart R. C.
Published: December 2017

A technique for experimental determination of regional myocardial blood flow and heat generation has been developed, based on a heat-clearance method. This method allows repetitive and frequent measurements of regional blood flow without necessity for biopsy or microspheres. Testing was performed on a pedicle preparation, an intact segment of left ventricular myocardium dependent on a single diagonal coronary artery and situated in situ in the left ventricular free wall. Total blood flow to the pedicle was measured by an electromagnetic flow probe. A specially designed 3-thermistor microprobe was positioned in the pedicle to continuously sense temperature changes in the subepicardium, midmyocardium, and subendocardium. The theory underlying this method is based on a heat balance that includes local myocardial heating, conduction, and convection. Comparison of the predicted time- and position-dependent temperature with that measured experimentally allows extraction of the local myocardial blood flow and heating rates. This method allows resolution of differential flows in subendocardial, midmyocardial, and subepicardial myocardium and provides quantification of dynamic flow changes in each layer in response to various stimuli such as ischemia or pressor agents, without in itself causing damage to the myocardial microvasculature. Our data show total flow, based on summation of thermally calculated regional flows, to have correlation coefficients of 0.88 with both the flowmeter and microsphere results. Resting flow values for Nembutal-anaesthetized, open-chest dogs of 0.66 ml/(g . min) compare favorably with values obtained by microsphere studies. Infusion of norepinephrine increased total flow and all layer flows, but the increase in subendocardial flow with norepinephrine was less than the increase of the other layers, perhaps accounting for the vulnerability of this region during catecholamine stress. Local myocardial heating rates in subepicardial, midendocardial, and subendocardial layers are shown to follow the same dependence on local myocardial blood flow in response to anoxic stress or norepinephrine-induced vasodilation. Specifically, local heating rate increases to a factor of 10 at flow below resting level.
A perfused canine right bundle branch-septal model for electrophysiological studies
Authors: Arbel E. R. , Prabhu R. , Ramesh V. , Pick R. , Glick G.
Published: December 2017

As documented in the literature, isolated ventricular muscle preparations perfused with protein-free media become edematous and deteriorate. We hypothesized that the addition of colloid oncotic pressure to the perfusion medium might affect favorably the electrical characteristics and survival of an isolated right bundle branch-septal muscle preparation perfused via the anterior septal artery. Perfusion with protein-free Tyrode solution produced edema formation and a loss of transmembrane potential of Purkinje and muscle cells within 5.9 +/- 0.40 h. Addition of bovine albumin, 4 g/100 ml, to the Tyrode solution or perfusion with horse serum greatly reduced the formation of edema. Furthermore, intact electrical activity continued for more than 9 +/- 0.31 h (P less than 0.001). The preparations showed a greater diastolic potential and action potential amplitude during perfusion than during superfusion with Tyrode solution. In conclusion: 1) a viable, perfused septal muscle preparation was developed for electrophysiological studies, and 2) colloid oncotic pressure in the perfusion medium is essential to preserve the integrity of the capillary circulation and to eliminate edema formation and tissue death.
Minute-to-minute covariations in cardiovascular activity of conscious dogs
Authors: Anderson D. E. , Yingling J. E. , Sagawa K.
Published: December 2017

Cardiovascular activity of chronically instrumented conscious dogs was monitored continuously during daily sessions of rest or of intermittent aversive stimulation. Data analysis of minute-to-minute averages revealed that cardiovascular variables changed in patterns, rather than as isolated independent events. Variations in cardiac output were highly positively correlated with concurrent variations in heart rate in all subjects under both conditions (mean r = +0.93). Variations in heart rate were two to five times as great as stroke volume, which was remarkably constant (coefficient of variation averaged only 4.6%). Variations in mean arterial pressure were consistently correlated with the variations in cardiac output (mean r = + 0.66) and heart rate (mean r = +0.68), but were poorly correlated with the small changes in stroke volume (mean r = -0.17) and total peripheral resistance (mean r = -0.16).
Total mechanical energy of a ventricle model and cardiac oxygen consumption
Authors: Suga H.
Published: December 2017

Mechanical energy (ENG) required by a time-varying elastance model of the ventricle was compared with oxygen consumption per beat (VO2) of the canine left ventricle contracting under a variety of loading conditions. ENG needed for this model to increase its elastance during systole is shown to be equal to the sum of the potential energy built in the elastance during systole plus the external mechanical stroke work. This ENG is equivalent to the area (PVA) bounded by the end-systolic and end-diastolic P-V curves and the systolic limb of the P-V loop trajectory in the P-V plane. There was a high correlation (r = 0.89) between VO2s documented in the literature and PVAs assessed by the author from the accompanying P-V data from both isovolumic and ejecting contractions in 11 hearts. A linear regression analysis yielded an empirical equation: VO2 (ml O2/beat) = a . PVA (mmHg . ml/beat) + b, where a = 1.37 X 10(-5) and b = 0.027, which can be used to predict VO2 from PVA. A preliminary experimental study in my laboratory confirmed the validity of this empirical equation.
Accuracy of ventricular lumen volume measurement by intraventricular balloon method
Authors: Suga H. , Sagawa K.
Published: December 2017

To assess the accuracy of left ventricular volume measured by the intraventricular balloon method, we measured the space between the endocardium and the gradually inflated balloon in six Formalin-fixed canine left ventricles. The space was as small as 1-1.5 ml for intraballoon pressure of 100-200 mmHg and tended to increase to 2 ml with decreases in pressure to 50 mmHg.
Effect of tetrodotoxin on action potentials of the conducting system in the dog heart
Authors: Coraboeuf E. , Deroubaix E. , Coulombe A.
Published: December 2017

Tetrodotoxin (TTX) shortens Purkinje fiber action potential duration (APD) at concentrations (greater than or equal to 3.3 x 10(-8) M) lower than that at which the maximum rate of rise decreases (approximately 10(-6) M). The shortening effect of TTX occurs either at low or high driving rate and is much greater in Purkinje fibers than in bundle branch and muscle fibers. As a result, at a TTX concentration of 1.3 x 10(-6) M, the APD is no longer statistically different all along the conducting system, i.e., the gating mechanism described by Myerburg et al. (Circ. Res. 26: 361-378, 1970) is suppressed. It is concluded that this gating mechanism is attributable, at least in part, to the existence of a TTX-sensitive inward sodium current lengthening the plateau of the Purkinje fiber action potential. Our experimental results and reconstruction of Purkinje fiber action potentials suggest that this current, which is more sensitive to TTX than the normal rapid sodium current, flows through a background sodium conductance or/and a small proportion of sodium channels with no inactivation mechanism (or inactivation mechanism different from normal). The importance of this finding for the mechanism of action of antiarrhythmic drugs is pointed out.
Effect of pentobarbital anesthesia on hypotension after 10% hemorrhage in the dog
Authors: Hosomi H. , Sagawa K.
Published: December 2017

The effect of pentobarbital anesthesia, 30 mg.kg body wt-1, on the rapidly acting arterial pressure control system was studied on splenectomized dogs chronically instrumented with catheters for pressure measurement and hemorrhage and with a flow probe for measurement of aortic flow. The dogs were subjected to 10% hemorrhage in 30 s under conscious and anesthetized states before and after denervation of the carotid sinus nerves (CS) and/or the vagi (V). In the intact nerve condition, arterial pressure fall (delta AP) at 1-2 min after hemorrhage was 8.0 +/- 1.3 (mean +/- SE) mmHg in conscious dogs and 9.4 +/- 2.0 mmHg in dogs under anesthesia. There was no significant difference between these delta APs or other pairs of delta APs in conscious and anesthetized states at any stage of denervation. As long as the CS reflex was intact, heart rate and total peripheral resistance increased in response to hemorrhage as in the intact condition. In conclusion, the pentobarbital anesthesia had little effect on the rapidly acting arterial pressure control system as far as its capacity to restore mean arterial pressure after the brief 10% hemorrhage is concerned.
Choline acetyltransferase activity in rat and guinea pig heart following vagotomy
Authors: Lund D. D. , Schmid P. G. , Roskoski R.
Published: December 2017

Choline acetyltransferase (CAT), which serves as a marker for the preganglionic and postganglionic parasympathetic cholinergic neurons in heart, was measured in heart regions in rats and guinea pigs after either a right or a left unilateral cervical vagotomy or a sham operation. One day after a left vagotomy in rat, CAT activity was decreased in the region of the SA and AV nodes. In rats killed on the 2nd, 4th, and 8th day after left vagotomy, the activity of CAT in these regions increased to the control level. CAT activity in the remainder of the heart did not decrease. In guinea pig 1 wk after a left vagotomy, CAT activity was decreased in the anterior interventricular septum but not in other regions. Selective increases in enzyme activity were noted in the right atrial appendage following left vagotomy and in the superior interventricular septum following right vagotomy. These results suggest that compensatory increases in CAT activity occur that may be related to collateral sprouting similar to that observed in the frog heart.
Development and use of a new high-frequency, low mechanical impedance strain gauge
Authors: Nellis S. H. , Liedtke A. J.
Published: December 2017

A low mechanical impedance strain gauge that imposed insignificant preload to the myocardial fibers was tested in vitro and in vivo. The dynamic response of the gauge to an abrupt change in length (step response) and to sinusoidal perturbation was determined. The electrical output reached 95% of maximum steady-state response within 3-5 ms after a step displacement. Frequency analysis indicated a flat response up to 80 oscillations/s. The in vivo testings of the gauges were performed on intact, working swine hearts during control and ischemic flows in a regionally perfused preparation. During control perfusion the gauges demonstrated epicardial shortening in systole and early-to-mid diastole. Relaxation was confined to late diastole. With ischemic perfusion there was a progressive loss of systolic shortening, but minimal disruption in global hemodynamics. Correlative measurements were also made with sonomicrometers positioned in subepicardial myocardium. Patterns of motion, shortening, and changes in strain were similar between the two types of gauges.
Cardiac changes during behavioral stress in dogs
Authors: Galosy R. A. , Clarke L. K. , Mitchell J. H.
Published: December 2017

Alterations in heart rate (HR), left ventricular systolic pressure (LVP), and maximum rate of left ventricular pressure development (LV dP/dtmax) during a Sidman avoidance task were studied in eight chronically prepared dogs. Four of these animals comprised a nonstressed control group. In the experimental group, in addition to phasic increases in HR, LVP, and LV dP/dtmax during the avoidance period of each day, tonic increases in these measures were also observed over the 13 days of the experiment. Left ventricular systolic pressure was found to be least sensitive to the stress procedure inasmuch as the phasic changes were no longer present after the 10th day and tonic levels were within base-line values by the 13th day. When alterations in cardiac activity were observed in the nonstressed animals, there were decreases in function. It was concluded that controlled behavioral stress produces increased cardiac performance without increased bodily activity. It was also hypothesized that preavoidance increases in heart rate in experimental animals were the result of vagal influences on the heart, whereas avoidance increases in HR, LV dP/dtmax, and LVP were functions of increased beta-sympathetic activity on the heart and adaptive peripheral vascular changes.
A tethering system for direct measurement of cardiovascular function in the caged baboon
Authors: Byrd L. D.
Published: December 2017

A device suitable for the continuous measurement of physiological activity in large, conscious monkeys has permitted the direct recording of systemic arterial blood pressure and heart rate in caged baboons. The device comprises a lightweight fiberglass backpack, retained in place on the baboon by a thoracic elastic band and shoulder straps, and a flexible stainless steel tether connecting the pack to an electrocannular slip-ring in the top center of the baboon's cage. A chronically indwelling arterial catheter inserted retrograde into the abdominal aorta via the internal iliac artery and connected to a small pressure transducer on the pack provides direct measurement of blood pressure and heart rate. Body fluids can be sampled or drugs administered via an indwelling catheter in the inferior vena cava. Electrical and fluid connections between the fiberglass pack and recording and infusion equipment located outside the cage pass through the flexible tether and remain protected from the subject. The reliability of the tethering system has been demonstrated in physiological, pharmacological, and behavioral experiments with baboons.
High-resolution determination of the R-R interval
Authors: Law H. F. , Epstein R. A. , Epstein M. A.
Published: December 2017

A preprocessor is described that determines the time interval between successive R waves of the electrocardiogram with an error of less than 0.2 ms. It accomplishes this by sepearting in hardware the function of determining the approximate location of the R wave from the function of localizing with great accuracy the peak of the wave form. With this device it is possible to detect abnormal heart rate patterns characterized by exceedingly small beat-to-beat variability. The approach may be useful for other bioelectric signals.
Comparison of plethysmographic methods with pulsed Doppler blood flowmetry
Authors: Levy B. I. , Valladares W. R. , Ghaem A. , Martineaud J. P.
Published: December 2017

Hand blood flow was measured at rest, with local warming, and with local cooling. Three methods were simultaneously used: water plethysmography (WP), mercury-in-rubber strain gauge plethysmography (SG), and pulsed Doppler flowmetry (D). Of these, water plethysmography is the most sensitive and accurate; strain gauge plethysmography is simpler but less accurate; and pulsed Doppler flowmetry precisely measures instantaneous arterial blood flow without venous occlusion.
Quantitative study of intramyocardial compression in the fibrillating heart
Authors: Downey J. M. , Chagrasulis R. W. , Hemphill V.
Published: December 2017

Extravascular compression inhibits coronary blood flow in fibrillating hearts. Pressure-flow curves from spontaneously fibrillating hearts whose coronary arteries were maximally dilated were examined to see whether this inhibition involves a vascular waterfall mechanism as has been found in the beating heart. Waterfall behavior is indicated when pressure-flow curves are linear and experience a zero-flow intercept at pressures greater than venous pressure. Regional pressure-flow curves revealed a zero flow intercept of 28.4 mmHg for the inner quarter of the left ventricle, indicating that compression is quite high in that region. A zero-pressure intercept of only 15.1 was found at the outer quarter, which was not significantly different from venous pressure. We conclude that the spontaneously fibrillating heart experiences a gradient of compression falling from 28 mmHg at the subendocardium to near zero at the subepicardium.
Measurement of cardiac output by impedance cardiography under various conditions
Authors: Boer P. , Roos J. C. , Geyskes G. G. , Mees E. J.
Published: December 2017

The suitability of impedance cardiography as a method to follow changes in cardiac output (CO) was investigated by comparing it with thermodilution and by measurements in conditions with predictable effects on CO. The correlation between absolute CO values obtained by impedance and thermodilution techniques was moderate (r = 0.61), but the percentage changes showed a good correlation (r = 0.84). Head-up tilting decreased CO by 25% in 5 normal subjects. Bloodletting in three subjects caused a 20% decrease, reinfusion in one subject a 16% increase. Occlusion of artificial large flow arteriovenous shunts in 6 dialysis patients caused a 12% decrease in CO, whereas the effect was less with moderate and absent with small flow shunts. Ultrafiltration caused a 28% decrease in two dialysis patients. In 20 hypertensive patients CO dropped 25% after salt depletion; propranolol administered intravenously gave a 15% decrease (n = 13), diazoxide intravenously a 30% increase (n = 6). It is concluded that, provided conditions are strictly defined, impedance cardiography is a reproducible method and suitable for the measurement of intrapatient changes in cardiac output.
An evaluation of large arteries compliance in man
Authors: Simon A. C. , Safar M. E. , Levenson J. A. , London G. M. , Levy B. I. , Chau N. P.
Published: December 2017

Cardiac output, blood pressure, and the characteristics of diastolic pressure decay were studied in 12 normal subjects and 23 sustained hypertensive patients of the same age. In normal subjects and in hypertensives, analysis of the diastolic decay showed that i) the form of the decay approximated a simple monoexponential curve during the last two-thirds of the diastolic segment, and ii) the time constant (t) of the curve was positively correlated with the total peripheral resistance (TPR), with an intercept of nearly zero. The validity of the relationship t = K x TPR was demonstrated both in groups of patients and also in individuals. Using a simple model for the vascular system, the K value was identified as the large arteries compliance and could thus be calculated in each individual. The values of arterial compliance was 1.26 +/- 0.04 ml.mmHg-1.m-2 in normal subjects and was significantly reduced in hypertensive patients (0.88 +/- 0.02 ml.mmHg=1.m-2,. P less than 0.001).
Interaction of somatic and cardiopulmonary receptors in control of renal circulation
Authors: Thames M. D. , Abboud F. M.
Published: December 2017

The purpose of this study was to determine if there is an important interaction between somatic and cardipulmonary receptors in the control of vasomotor outflow to the kidney. This interaction was examined by determining the renal vasoconstrictor responses to afferent electrical stimulation (30 V, 1 ms, 20--40 Hz) of the sectioned sciatic nerve in 8 chloralose-anesthetized dogs with sinoaortic deafferentation. During isovolemia, sciatic stimulation resulted in significant increases in arterial pressure and heart rate, and in renal vasoconstriction. Volume expansion significantly attenuated and vagotomy significantly augmented the renal vasoconstrictor responses to sciatic stimulation. These interventions did not significantly influence the arterial pressure or heart rate responses to sciatic stimulation. In 4 dogs with aortic nerves sectioned and carotid sinuses isolated and perfused at constant pressure (135 mmHg), the renal vasoconstrictor responses to stimulation were attenuated by volume expansion and augmented by vagotomy. These data show that in the absence of the arterial baroreceptors or with intermediate levels of carotid baroreceptor activation, volume expansion and, thus, augementation of discharge of cardiopulmonary receptors (vagal afferents) markedly attenuated the renal vasoconstrictor responses to somatic afferent stimulation.
Oxygen delivery in lambs: cardiovascular and hematologic development
Authors: Lister G. , Walter T. K. , Versmold H. T. , Dallman P. R. , Rudolph A. M.
Published: December 2017

After birth a decrease in hemoglobin concentration occurs while high metabolic demands are imposed on the infant by the extrauterine environment. Using the resting lamb as a model, we studied the mechanisms that are called into play during this period to maintain oxygen delivery. Measurements were made of oxygen consumption, arterial and mixed venous blood oxygen contents, cardiac output, hemoglobin concentration, percent fetal hemoglobin, 2,3-diphosphoglycerate, and hemoglobin oxygen affinity during the first two postnatal months. There was a rapid decrease in hemoglobin concentration after birth and concomitant decrease in hemoglobin oxygen affinity, changes similar to those described in humans. Cardiac output and oxygen consumption were both very high immediately after birth and declined in parallel, so that arteriovenous oxygen content difference was constant. Thus at rest cardiac output varies as a result of the changing need for oxygen. This relationship is independent of hemoglobin concentration or oxygen affinity within the normal range. If, however, oxygen demands were increased, oxygen delivery might be compromised by a limited ability to increase oxygen extraction during the immediate newborn period or when hemoglobin concentration is lowest.
Changing negative inotropic effect of acetylcholine in maturing canine cardiac muscle
Authors: Urthaler F. , Walker A. A. , James T. N.
Published: December 2017

The effect of maturation on the contractile response to acetylcholine was studied in canine right atrial and right ventricular trabeculae. At any age the only inotropic response observed was negative. The decrease in contractile performance was always significantly greater in the atrial trabecula. Between 3 and 9 mo of age (12 dogs each group) there was a significant increase in the amount of negative inotropic action exerted by identical concentrations of acetylcholine. These data suggest that either the number of muscarinic receptors or the target cell response to acetylcholine increases during maturation.