bluuebunny/crossref_metadata_2025 huggingface dataset:
Norepinephrine release in isolated arteries induced by K-free solution
Authors: Bonaccorsi A. , Hermsmeyer K. , Smith C. B. , Bohr D. F.
Published: December 2017

Helical strips from arteries with a rich sympathetic innervation (rat tail and femoral, and dog mesenteric arteries) develop a sustained contracture when exposed to a K-free physiological salt solution (PSS). The contracture can be blocked by phentolamine and does not occur in arteries whose nerve terminals have been destroyed with 6-hydroxydopamine. The temporal relationship between force development and efflux of NE was determined. Helical strips of rat tail arteries or dog mesenteric arteries were incubated in PSS containing 1-norepinephrine-7-3H([3H]NE). They were then transferred to a superfusion system which allowed isometric recordings and collection of the superfusate for the estimation of [3H]NE content. Following exposure to a K-free PSS force development paralleled NE release and both parameters were potentiated by ouabain. These data demonstrate that this neurogenic mechanism plays a most important role in the K-free contracture of the vascular smooth muscle studied. It is in accord with the observation that NE is released by adrenergic nerves following inhibition of Na+-K+-ATPase.
Arotic Evans blue dye accumulation: its measurement and interpretation
Authors: Fry D. L.
Published: December 2017

Parenteral Evans blue dye (EBD) binds to albumin and thus can indicate transvascular protein flux. A model was developed to relate the arterial surface accumulation of EBD to the light refected from the opened vessel surface. The accumulation, M (nmol cm-2), was related to the optical "absorbance" (rho) of the surface by the equation, M = 3.92 rho + 0.80 rho3, where rho = -ln(I/I0) and I and I0 are the intensities of light reflected from the surface in the stained and unstained state, respectively. The validity of the model was examined in two ways, 1) by comparing the value of the optical absorption coefficient for EBD predicted by the model to the measured value: the predicted value was 0.128 +/- SD 0.015 cm2 nmol-1, the measured value was 0.125 +/- SD 0.005 cm2 nmol-1; and 2) by comparing predicted changes in vessel wall stretch to measured values: the percentage changes (Y) in area predicted by the model from changes in M were linearly related to the directly measured percentage area changes (X) by Y = 0.09 + 1.01X, +/- SD 2.54, with a correlation coefficient of 0.994.
Capillary filtration measurement by strain gauge. I. Analysis of methods
Authors: Katz M. A.
Published: December 2017

The strain-gauge method for measuring changes in limb size, introduced by Whitney in 1953 has not received wide usage for measurement of capillary filtration coefficient (CFC). This method was compared for the dog hindlimb to simultaneous measurements by the classic gfavimetric technique and was found to give comparable results. The larger question of whether either method gives useful information about the true CFC of the limb was addressed by a mathematical analysis of the technique combined with analysis of data concerning methodologically induced alterations in the Starling forces in and around the capillaries. It was concluded that systematic error due to the method is probably less than -1% with an outside error of -14.6%. These findings demonstrate the strain gauge to be a useful tool in determining CFC.
Increased dynamic stiffness of trabeculae carneae from senescent rats
Authors: Spurgeon H. A. , Thorne P. R. , Yin F. C. , Shock N. W. , Weisfeldt M. L.
Published: December 2017

Dynamic stiffness was measured in both adult and senescent Wistar rats using sinusoidal length perturbations from 17 to 40 Hz, superimposed on isometric contractions at low and below Lmax. The slope of the stiffness-tension relationship was found to be increased in senescent muscles of both sexes and at two different temperatures. The age dependence of the slope was independent of resting muscle length. The slope also exhibited frequency dependence and hysteresis that indicates the presence of viscoelasticity during activation. No age dependence was seen in peak active tension, peak dT/dt, or resting stiffness. The findings of this study, taken together with other studies that have shown a decreased shortening ability in the senescent muscle, explain in part the maintenance of active tension development in the face of decreased shortening ability associated with the senescent muscle.
Reactive hyperemia in capillaries of red and white skeletal muscle
Authors: Klabunde R. E. , Johnson P. C.
Published: December 2017

Reactive hyperemia was examined in individual capillaries of the red anterior (ALD) and white posterior (PLD) latissimus dorsi muscles of the anesthetized chicken following total blood flow occlusion of 3.5-180 s in length. Capillary red cell velocities were measured by the dual-slit photometric technique. The control capillary velocities in the ALD and PLD were 0.56 +/- .03 (SE) and 0.34 +/- .03 mm/s, respectively. With increasing occlusion lengths, the reactive hyperemia peak velocity, hyperemia duration, and excess flow were found to increase progressively in both muscles suggesting a metabolic origin for the response. The ALD showed a greater peak reactive hyperemia flow than the PLD following occlusion lengths of 7-60 s and a greater excess flow following occlusion lengths of 15 s and longer. However, when these data were normalized to control velocities by calculating the peak-to-control velocity ratio and percent flow debt repayment, no significant differences were found between the two muscles. Furthermore, the reactive hyperemia durations were similar in the two muscles at each occlusion length. These data demonstrate that reactive hyperemia is similar in two muscle types which are known to differ considerably in resting metabolism and anaerobic capacity.
Circuit for automatically zeroing aortic flow base line from electromagnetic flowmeter
Authors: Wantzelius D. G. , Goetz K. L.
Published: December 2017

We describe an inexpensive circuit designed to correct base-line drift of electromagnetic flowmeters automatically when cardiac output is being measured. The circuit measures the flowmeter output voltage during a portion of each diastole when blood flow in the aorta is assumed to be zero. Any deviation of the flowmeter output voltage from zero during this time represents either base-line offset or drift. The output voltage obtained during zero flow conditions is stored throughout the next cardiac cycle and subtracted continuously from the flowmeter output during each beat, thus giving a beat-by-beat correction of any base-line drift.
Arteriolar reactive hyperemia: modification by inhibitors of prostaglandin synthesis
Authors: Messina E. J. , Weiner R. , Kaley G.
Published: December 2017

Several studies implicate endogenously synthesized prostaglandins in the mediation of reactive hyperemic responses in the coronary, renal, and skeletal muscle circulations. We sought additional evidence to involve locally released prostaglandins in the mediation of reactive hyperemia in skeletal muscle at the level of the microcirculation. The cremaster muscle of pentobarbital-anesthetized Wistar-strain rats was prepared for direct in vivo observation and measurement of postocclusive responses of single arterioles. Responses of individual arterioles were reproducible over a 3-h test period. The postocclusion increase in diameter and the duration of response were dependent upon the duration of the occlusion. Repetitive occlusions did not influence arteriolar responsiveness to vasoactive substances. Indomethacin and 5-8-11-14-eicosatetraynoic acid, inhibitors of prostaglandin synthesis, did not affect resting arteriolar diameters; however, both drugs decreased the maximum increase in diameter and duration of the vasodilator response following release of the arteriolar occlusion. These findings suggest that in this microcirculatory bed, prostaglandins contribute little to resting vascular tone; in contrast, temporary arteriolar occlusion elicits the local release of dilator prostaglandins which contribute to the reactive hyperemic response.
Spinal interneurons in the baroreceptor reflex arc
Authors: McCall R. B. , Gebber G. L. , Barman S. M.
Published: December 2017

The zona intermedia of the cat thoracic spinal cord was explored with metal microelectrodes in an attempt to locate interneurons within the pathway that mediates the spinal component of baroreceptor-induced sympathoinhibition. Twenty-nine neurons whose discharges were interrupted during occlusion of the common carotid arteries were found in the vicinity of the intermediomedial nucleus (IMM). The spontaneous discharges of 10 of these units were correlated in time with the R wave of the ECG. The pattern of R-wave locking of spinal unitary discharge was similar to that for some neurons in the nucleus of the tractus solitarius (NTS; primary site of baroreceptor fiber termination). In addition, spinal units, whose discharges were interrupted during carotid artery occlusion, were activated by stimulation of depressor sites in NTS. These observations suggest that bulbospinal fibers of the baroreceptor reflex arc terminate on and excite interneurons in the vicinity of IMM. It is postulated that these neurons directly inhibit components of sympathoexcitatory pathways located in the intermediolateral spinal nucleus. Furthermore, it was demonstrated that the inhibitory interneurons receive auxiliary input from sympathetic afferents in the inferior cardiac nerve.
Perfusion rates and the transfer of water across isolated guinea pig placenta
Authors: Schroder H. , Leichtweiss H. P.
Published: December 2017

The transfer of tritiated water across the isolated, artificially perfused guinea pig placenta was the subject of 21 experiments. The observed relationship between the flow rates and the relative transfer of water cannot be explained by a concurrent or pool-flow system. If the direction of the fetal flow is reversed, the rate of transfer is lowered. It may be concluded, that the decrease is a result of a change from a nonideal countercurrent flow system to a nonideal concurrent system. This conclusion, however, holds only if all other parameters that determine the exchange as well remain unaffected. In the range of flows investigated, the transfer of water is flow limited.
Effect of prostaglandins on macromolecular transport from blood to lymph in the dog
Authors: Joyner W. L.
Published: December 2017

The effect of various prostaglandins on hindlimb lymph flow and macromolecular transport was studied in dogs anesthetized with pentobarbital sodium. Lymph obtained by cannulating the popliteal lymphatics was collected at 30-min intervals and analyzed for protein and exogenously administered dextran (Dextran 110). Arterial blood was obtained at the midpoint of each collection period and similarly analyzed. Prostaglandins (E1, E2, F2alpha, and A2), the vehicle and histamine were injected subcutaneously into the paw of the dog. Prostaglandins slightly increased lymph flow (L') but the lymph-to-plasma concentration ratios (R) for total protein (T) and Dextran 110 (D) decreased. Permeability surface area products (PS) were not altered. The sieving ratios (RD/RT) were substantially less than 1 and were not altered by prostaglandins. These results indicate that selective permeability of the capillary is not impaired by prostaglandins. Timing sequences and dose-response relations were also completed for prostaglandins by subcutaneous testing in dogs injected with Evans blue (T-1824). Leakage of the T-1824-albumin complex occurred when large amounts (migrogram) of prostaglandins were administered, and the response appeared to be short lived (less than 30 min). While the prostaglandins possess vasoactive properties, as demonstrated by an increased lymph flow, they do not alter the restrictive transport of large molecules.
Interaction of aortic pressure and left ventricular end-diastolic pressure in the dog
Authors: Foster J. R. , Powers E. R. , Powell W. J.
Published: December 2017

Fiber length (preload) is an important determinant of left ventricular performance. Mean aortic blood pressure also influences ventricular performance. The present study was undertaken to examine the influence of mean aortic pressure on the fiber length-ventricular performance relationship. Fifteen anesthetized, adrenergically blocked dogs were studied on right-heart bypass at constant heart rate and coronary blood flow. An increase in mean aortic pressure permitted a greater improvement in performance as evaluated by stroke work for a given increase in left ventricular end-diastolic pressure. A given increase in mean aortic pressure at a constant stroke volume produced a greater rise in stroke work over intermediate ranges of left ventricular end-diastolic pressure than occurred with higher or lower left ventricular end-diastolic pressure. Thus, the degree of afterload-induced performance improvement depended on the magnitude of the preload. External circumference-left ventricular end-diastolic pressure data suggested a possible relationship between isovolumic systolic circumferential expansion and the improvement of ventricular performance at higher mean aortic pressures.
Effects of systemically infused histamine on transvascular fluid and protein transfer
Authors: Marciniak D. L. , Dobbins D. E. , Maciejko J. J. , Scott J. B. , Haddy F. J. , Grega G. J.
Published: December 2017

Histamine (4-64 microgram base/min) infused into the brachial artery clearly promotes edema formation in forelimbs perfused at natural flow. In contrast, intravenously administered histamine, even in blood concentrations exceeding those achieved by local infusion, not only fails to promote edema formation, but rather causes net extravascular fluid reabsorption. In this study, high concentrations of histamine were infused into the left ventricular chamber to bypass the pulmonary circuit. Histamine (400-800 microgram base/min) infused into the left ventricle of the heart for 90 min produced marked hypotension and only very slight increases in forelimb skin lymph flow and lymph protein concentration and failed to produce visible signs of edema. Thus the differential actions of local and intravenous histamine on lymph flow, protein efflux, and fluid fluxes cannot be explained by uptake or destruction of histamine in the lung during intravenous infusions of this agent. It seems more likely that they result from different actions on microvascular pressure, surface area, and/or permeability to plasma proteins. Prior hypotension produced either by acetylcholine, systemically infused histamine, or arterial hemorrhage almost completely prevents the increase in skin lymph flow and lymph protein concentration by histamine infused locally into the brachial artery, even in forelimbs perfused at constant flow.
Effect of anomalous pathway location on rate of canine experimental A-V reentrant tachycardia
Authors: Teague S. , Denes P. , Amat-y-Leon F. , Rosen K. M.
Published: December 2017

The effect of anomalous pathway (AP) location and conduction time on the cycle length (CL) and sustainability of paroxysmal A-V reentrant tachycardia was studied in 15 dogs, using an anomalous pathway simulator (APS). The APS was a programmable digital electronic circuit with ability for unidirectional conduction, ventricular sensing, adjustable delay, and atrial stimulation. Contiguous pairs of ventricular sensing electrodes were placed along the A-V ring in each dog at the following sites: anterior, posterior, and lateral right (AR, PR, and LR) and anterior, posterior, and lateral left (AL, PL, and LL) and septal (S). There were significant differences in the CL of tachycardias among the tested sites (P less than 0.01). The CL of tachycardias from the LL site was significantly longer and from the PR site significantly shorter than that from the other sites (P less than 0.05). These differences in CL of tachycardias in relation to the AP location were explicable in terms of corresponding variation in conduction times of the various components of the tachycardia circuit (e.g., intra-atrial, A-V nodal, intraventricular conduction times). The differences in magnitude of the CL of tachycardias, although significant, were small. It was also found that all sites allowed maintenance of tachycardias up to an AP conduction time of 10 ms. In 27% of experiments, atrial refractoriness prevented sustained tachycardias at pathway delays of 1 ms. The relationship between AP conduction time and CL of tachycardias was exponential.
Simultaneous accumulation of Evans blue dye and albumin in the canine aortic wall
Authors: Fry D. L. , Mahley R. W. , Weisgraber K. H. , Oh S. Y.
Published: December 2017

The simultaneous transport of Evans blue dye (EBD) and 125I-labeled canine albumin (IALB) across normal and injured endothelial surface was measured by determining the intimal accumulation of EBD (ME) by a reflectometric method and accumulation of equimolar concentrations of EBD and IALB, ME was related to MI by ME = 0.092 + 5.04 MI - 0.508 MI2 for injured and ME = 0.002 + 0.435 MI (nmol-cm-2) for normal surfaces. Both ME and MI varied nonlinearly with exposure time for injured and linearly with time for normal surfaces, giving apparent permeability coefficients of 0.92 X 10(-8) cm-sec-1 for EBD and 2.00 X 10(-8) cm-sec-1 for albumin. These results show that the transvascular flux of EBD can be related to that of albumin by empirical equations, which is of practical importance but also implies unique underlying physical laws. Study of these physical laws will provide deeper insight into transvascular macromolecular transport processes.
Reflex suppression of renin release by ventricular receptors with vagal afferents
Authors: Thames M. D.
Published: December 2017

Intracoronary injection of veratrum alkaloids is known to stimulate ventricular receptors with vagal afferents resulting in bradycardia and hypotension. This study examined the role of veratrum-sensitive ventricular receptors in the control of renin secretion in eight chloralose-anesthetized dogs. Hemorrhage of 10% caused renin release to increase significantly from a control of 778 to 1,971 ng/min. Arterial pressure and renal blood flow did not change significantly. The augmented release of renin during volume depletion was virtually abolished by injection of cryptenamine (2 microgram/kg) into the main left coronary artery, falling from 1,971 to 269 ng/min by 4 min after the cryptenamine injection. Blood pressure decreased significantly from 130 mmHg before to 111 mmHg after injection. Renal blood flow did not change significantly. This reflex suppression of renin release by excitation of ventricular receptors was abolished by vagotomy. These data indicate that ventricular receptors with vagal afferents participate in the reflex control of renin release.
Effects of Ca2+ and catecholamines on the guinea pig atrium action potential plateau
Authors: Robinson R. B. , Sleator W. W.
Published: December 2017

The activation process in isolated electrically driven guinea pig atria was studied by means of simultaneous microelectrode and tension recording. Reducing external calcium from 2.5 to 1.25 mM prolonged the plateau but further reduction of calcium shortened it. Progressively increasing doses of the calcium antagonist D600 (up to 1.4 micrometer), however, monotonically decreased plateau duration. Either protocol monotonically decreased steady-state tension, but with markedly different effects on the restitution relation. Epinephrine, and to a lesser extent isoproterenol, restored plateau duration after exposure to either a calcium-free or D600-containing solution, but only the isoproterenol effect was propranolol sensitive. Addition of calcium chelators enhanced rather than prevented the effect of epinephrine on plateau duration in a calcium-free solution, extending the plateau duration to more than 3 times normal in some cases. These results are explained in terms of two opposing effects of a change in calcium concentration on plateau formation, one action being through the slow inward current and the second through a shift in a calcium dependence of the inward-rectifying, potassium conductance system.
Effect of methylcellulose injection on murine hematopoiesis
Authors: Stang H. D. , Boggs D. R.
Published: December 2017

This study was designed to determine the effect of methylcellulose (MC)-induced reticuloendothelial (RE) hypertrophy on neutrophils and hematopoietic stem cells and to contrast its overall hematologic effect in the mouse to the more frequently studied rat model. Mice were given MC 3 times/wk and studies were done at 2, 3, and 4 wk, with maximal hematologic change by 2 wk. A stable, but incompletely compensated hemolytic anemia developed which was accompanied by a significant shift of erythropoiesis from marrow to spleen. Thrombocytopenia developed as did neutrophilia, accompanied by an increased number of marrow neutrophil precursors. Extramedullary hematopoiesis was observed in the liver. The number of cells forming spleen colonies in irradiated recipients increased in the spleen but not in marrow. The number of cells producing granulocyte and macrophage colonies in semisolid media increased in spleen and marrow. Splenectomized mice, treated with MC, developed changes very similar to intact mice. Thus, it appears that all three major hematopoietic lines may be destroyed by the MC-hypertrophied RE system. The mouse differs from the rat in its hematologic response to MC by destroying cells in organs other than the spleen, by increasing neutrophil production, by developing hepatic hematopoiesis, and by developing all changes more rapidly.
Role of sympathetics in the response to acute venous occlusion
Authors: Curd L. H. , Conrad M. C.
Published: December 2017

The effect of venous ligation and subsequent blockade of alpha receptors on hindlimb venous pressure, vascular resistance, oxygen extraction and carbon dioxide removal was evaluated in mongrel dogs with use of constant-flow perfusion of the extremity bed. Perfusion, metatarsal vein, femoral vein, and central vein pressures, and changes in paw and thigh circumference were recorded in mongrel dogs in which the hindlimb was perfused at a constant flow. Arterial, metatarsal venous, and femoral venous blood gases were drawn and analyzed for arteriovenous oxygen and carbon dioxide differences. Measurements were repeated following extensive ligation of veins and after subsequent alpha-receptor blockade with Dibenzyline. Findings indicated that ligation of extremity veins resulted in an active increase in total limb resistance upstream from the ligation, and an increase in volume of the limb. Following alpha-adrenergic blockade with Dibenzyline, limb volume increased and oxygen extraction decreased below control levels. The reflex constriction following ligation of veins protected against the detrimental effect of excessive accumulation of fluid in tissue spaces.
Reflex effects on circulation and respiration from contracting skeletal muscle
Authors: Mitchell J. H. , Reardon W. C. , McCloskey D. I.
Published: December 2017

Isometric exercise induced by ventral root stimulation in the anesthetized cat caused heat rate (HR) to increase from 199 +/- 6 beats/min to 206 +/- 6 (P less than 0.001); mean arterial pressure (MAP) from 99 +/- 5.3 mmHg to 112 +/- 5.8 (P less than 0.001); and left ventricular dp/dt at developed pressure of 25 mmHg from 3,960 +/- 204 mmHg/s to 4,380 +/- 220 (P less than 0.001), while end-diastolic pressure remained unchanged. Respiratory volume (RV) increased from 755 +/- 71 ml/min to 1,160 +/- 123 (P less than 0.001). These changes were abolished by cutting the dorsal roots receiving afferents from the exercising muscle. Beta-adrenergic blockade with propranolol (1 mg/kg) abolished the changes in heart rate and contractile state; however, changes in MAP and RV still occurred. Induced isometric exercise causes a small rise in HR with a more marked increase in MAP, the contractile state of the left ventricle and RV. In this preparation the cardiovascular and respiratory changes reflexly originate from contracting skeletal muscle as proven by section of the corresponding dorsal roots, and the cardiovascular changes are mediated in part by activation of beta-adrenergic receptors in the heart.
In situ measurement of papillary muscle dynamics in the dog left ventricle
Authors: Hirakawa S. , Sasayama S. , Tomoike H. , Crozatier B. , Franklin D. , McKown D. , Ross J.
Published: December 2017

In five open-chest dogs, pairs of ultrasonic dimension gauges were implanted in the anterior papillary muscle and in a circumferential subendocardial segment of the anterior left ventricular free wall, and simultaneous recordings were made with intracardiac pressure. The average shortening of the anterior segment in isovolumetric systole was 6% of end-diastolic length (EDL), with a total shortening of 19%. In the papillary muscles, isovolumetric shortening averaged 2%, total shortening was 10%, and shortening velocity was only 0.60 length/s. With acute pressure and volume overload, or inotropic interventions, changes in EDL were relatively less in papillary muscles than in the free wall. During acute occlusion of the anterior descending coronary artery, shortening of anterior segments and papillary muscles was replaced by holosystolic lengthening, and occlussion of the circumflex artery produced augmentation of shortening in both these regions, with lengthening of the posterior papillary muscle. The present study documents shortening of the anterior left ventricular papillary muscle throughout systole that is substantially less than that of the circumferential free wall, and demonstrates severe papillary muscle dysfunction with systolic elongation during regional ischemia.
Effect of isoproterenol on relation between maximal rate of contraction and maximal rate of relaxation
Authors: de Gende A. O. , Alzueta D. P. , Cingolani H. E.
Published: December 2017

The relaxing effect of two positive inotropic interventions was studied in the isolated rat heart beating at constant rate and perfused at constant coronary flow. Experiments were performed under isotonic or isometric conditions during heart perfusions with Ca2+, 3.5 X 10(-3) M, and with isoproterenol, 10(-7) to 10(-8) M. Changes induced in maximal velocity of contraction (+L or +T) and maximal velocity of relaxation (-L or -T) were analyzed as the ratio between both maximal velocities (+L/-L or +T/-T). For similar increments in the amount of the apex-to-base shortening or in developed tension during Ca2+ or isoproterenol perfusions, the effect on the maximal velocity of relaxation differed for each intervention. High Ca2+ perfusion increased velocities of contraction and relaxation proportionally without significant changes in their ratio. Isoproterenol increased -L or -T more than +L or +T and the ratio showed a significant fall both in isotonic and isometric experiments (+L/-L, -0.33 +/- 0.11 and +T/-T, -0.38 +/- 0.09; P less than 0.01). The relaxing effect of the beta agonist seems to be related to the activation of the protein kinase system since perfusions with dibutyryl 3',5'-cAMP had a greater effect on the relaxation of the hearts.
Right ventricular performance during ischemia: an anatomic and hemodynamic analysis
Authors: Brooks H. , Holland R. , Al-Sadir J.
Published: December 2017

This study in the pig was designed to characterize right ventricular (RV) contractile responses during infarction involving three areas of the heart--anteroseptal, anterolateral, and inferoseptal. Porcine coronary architecture was studied from multicolor vinyl casts. Distribution of blood supply to ventricular myocardium and papillary muscles was defined by intra-arterial dye injection. High-fidelity pressure and flow data were measured simultaneously in both ventricles following ligation of approximately equal lengths of the anterior descending, left circumflex, or posterior descending arteries. In the three groups, weight of myocardium involved by the occluded artery was comparable and there was significant depression of left ventricular performance, more pronounced in the two anterior infarcts. However, in anterolateral infarction, despite the obligatory drop in RV flow, there was no significant alteration in RV end-diastolic pressure (EDP), peak rate of rise of RV pressure (dP/dt), or time-to-peak developed dP/dt. In contrast, with both anteroseptal and inferoseptal infarctions there were significant alterations in all RV contractile parameters, at increased levels of RVEDP, signifying a primary depression in RV contractile state. With inferoseptal infarction, further occlusion of the right coronary near its origin produced a more exaggerated and selective RV contractile abnormality and, in half of the animals, varying degrees of acute tricuspid insufficiency.
Cardiac arrhythmias of sympathetic origin in the dog
Authors: D'Agrosa L. S.
Published: December 2017

The effects of ventrolateral and ventromedial cardiac nerve (left sympathetics) stimulation on cardiac force, on rate, and on arrhythmogenic responses were characterized and quantitated. The stimulation of left sympathetic nerves produced augmentation in cardiac contraction in 45% of the experiments, an augmentation of both a cardiac rate and force in 47%, and in cardioacceleration alone in 8%. Two characteristic patterns of arrhythmogenic responses were elicited from stimulations of 100 sympathetic nerves. The two types of neurally induced arrhythmias were atrioventricular junctional or ventricular in origin. The onset and duration of the arrhythmias were quantitated. Both types of neurally induced arrhythmias were prevented either by blocking the beta receptors with propranolol or by preventing the neural release of norepinephrine with bretylium tosylate. The neurally induced arrhythmias were probably the result of enhanced automaticity in the atrioventricular junction area and in the ventricles produced by stimulating the sympathetic nerve fibers. This report thus implicates the ventromedial cardiac nerve in the genesis of cardiac arrhythmias.
Inhibitory effect of cardiac contraction on coronary collateral blood flow
Authors: Russell R. E. , Chagrasulis R. W. , Downey J. M.
Published: December 2017

The present study was undertaken to determine the effect of contraction on overall flow in an area supplied by collateral vessels. Changes in the distribution of blood flow across the wall of ischemic and normally perfused regions of the left ventricle were observed during normal beating and during vagal arrest. The main left coronary artery was cannulated and perfused at constant pressure (125 mmHg) using a servo pump apparatus. An ischemic area supplied by collaterals was created by ligating the left anterior descending artery. Radiomicrospheres (15 micrometer) were injected into the perfusion apparatus during beating. Then spheres with a different label were administered to the same heart during arrest. The results revealed that beating caused a gradient of blood flow inhibition from near zero at the epicardium to about 50% at the endocardium in both zones. Inhibition to flow at the mid wall of the ischemic zone, 71%, was significantly greater than that seen at the corresponding depth in the normally perfused region, 33%. These results indicate that contraction not only inhibits collateral blood flow to an ischemic region, but also that the inhibition is actually magnified at the mid wall.
Effect of prophylactic digitalization on the development of myocardial hypertrophy
Authors: Cutilletta A. F. , Rudnik M. , Arcilla R. A. , Straube R.
Published: December 2017

The effect of prophylactic digitalization on the development of left ventricular hypertrophy was studied in adult rats. Digitoxin, 0.1 mg/100 g body wt or solvent was given daily for 1 wk prior to either aortic constriction or sham operation and was continued until the animals were killed, either 1 or 4 wk after surgery. A hemodynamic study was done in those animals killed 1 wk after surgery; hearts of all animals were examined for evidence of myocardial hypertrophy. Constriction of the ascending aorta had no significant effect on cardiac output but did reduce peak flow velocity and flow acceleration. An increase in left ventricular mass, RNA, and hydroxyproline was found in the animals with aortic constriction. Digitoxin treatment did not alter peak flow velocity or flow acceleration, but did significantly increase isovolumic (dP/dt)P-1. Digitoxin had no effect on body weight, heart weight, RNA, or hydroxyproline in either the sham-operated animals or in the animals with aortic constriction. Therefore, despite plasma digitoxin levels sufficient to affect myocardial contractility, left ventricular hypertrophy still developed after aortic constriction.
Plasma volume, red cell volume, and thoracic duct lymph flow in hypothermia
Authors: Chen R. Y. , Chien S.
Published: December 2017

The effects of hypothermia on plasma volume (125I-albumin), red blood cell volume (51 Cr-RBC), and capillary permeability (thoracic duct lymph flow and protein concentration) were determined on dogs anesthetized with pentobarbital, paralyzed with succinylcholine, and mechanically ventilated. Red blood cell volume and plasma protein concentration did not change significantly after cooling. Reductions in plasma volume and total plasma proteins indicate that whole plasma was excluded from the effective circulating blood volume. Except for a lesser increase in hematocrit, chronically splenectomized dogs showed essentially the same changes as normal dogs in response to hypothermia. Following application of ice bags, there was a biphasic response in lymph flow. The early increase in lymph flow accompanying a slight decrease in plasma volume was attributable to transcapillary fluid loss into interstitial space, probably due to cold-induced sympathetic activity. The later decrease in lymph flow in hypothermia resulted from a decrease of lymph production secondary to a decrease in available capillary diffusion area. This decrease in lymph flows and the continued reduction in plasma volume suggest an intravascular sequestration of whole plasma.
Transient postocclusive renal vasospasm in conscious rhesus monkeys
Authors: Olsson R. A.
Published: December 2017

Transient postocclusive renal vasospasm occurred in nine conscious postoperative monkeys with electromagnetic flowmeters implanted on the left renal artery. During an interval of 5–7 days, beginning approximately 1 wk after the implantation of an electromagnetic flowmeter and pneumatic occlusive cuff on the renal artery, occlusions produced by 2- to 15-s inflations of the cuff were invariably followed by flow reduction of 40%–90%, which began 30–60 s after occlusion and lasted from 3 to 60 min. These flow reductions were not related to changes in heart rate, cardiac output, blood pressure, nor to flow in other branches of the aorta; nor were they affected by papaverine (5 mg/kg), propranolol (1 mg/kg), phentolamine (3–5 mg/kg per min), or dipyridamole (1 mg/kg). This response to renal artery occlusion disappeared after 5-7 days and did not recur. This phenomenon should be kept in mind when planning experiments involving long-term implantation of flowmeters on the renal arteries of monkeys.
Myocardial contracture and accumulation of mitochondrial calcium in ischemic rabbit heart
Authors: Henry P. D. , Schuchleib R. , Davis J. , Weiss E. S. , Sobel B. E.
Published: December 2017

The relationship between myocardial contracture and cell calcium was studied in electrically paced, isolated perfused rabbit hearts. Isovolumic left ventricular dP/dt and end-diastolic pressure were utilized as indexes of contractility and ventricular stiffness. After 60 min of low flow (ischemia) without or with reperfusion at high flow for 10 min, calcium was measured in the mitochondrial fraction and used as an indicator of intracellular calcium. Low flow led to ventricular standstill and contracture, and reperfusion produced partial mechanical recovery with end-diastolic pressure remaining markedly elevated. Nifedipine (10(-7) M), an antagonist of myocardial calcium uptake, prevented contracture and permitted nearly complete mechanical recovery without elevation in diastolic pressure. Increases in mitochondrial calcium paralleled the severity of contracture and the lack of diastolic relaxation after reperfusion. Mitochondrial calcium did not increase in hearts protected by nifedipine. Results demonstrate a close relationship between mechanical changes induced by ischemia and accumulation of intracellular calcium.
End-systolic force-length relationship of nonexcised canine papillary muscle
Authors: Suga H. , Saeki Y. , Sagawa K.
Published: December 2017

End-systolic force-length (F-L) relationships were studied in blood-perfused papillary muscles remining in the canine right ventricle. The muscles contracted spontaneously at a regular rate of 114 +/- 4 (SE, N = 31) beats/min at 37 degrees C. In each muscle, end-systolic F-L curves were obtained in different modes of contraction at different diastolic lengths between the unstressed length (9.4 +/- 0.7 mm) and 143 +/- 4% of it. At the latter length, muscles developed a peak isometric force of 46 +/- 4 g (5.1 +/- 0.5 g/mm2). The isotonic F-L curve was lower than the isometric F-L curves to various extents. An auxotonic F-L curve fell between the two curves. At identical end-systolic lengths peak isometric forces were greater than isotonic forces by 14.4 +/- 1.4% in the first transient beats after switching the contraction mode from isometric to isotonic. The difference increased to 28.5 +/- 3.5% in the steady-state beats. The reduced force in the first isotonic beat was suspected to be due to the uncoupling effect of shortening. The further reduction of isotonic force in the steady-state beats was caused by viscous properties (creep and stress relaxation) and by a gradual decrease in contractility.
Cardiac output and renal excretion rates during acute blood volume expansion in rats
Authors: Ackermann U.
Published: December 2017

Selected central vascular parameters and renal excretion rates were monitored in anesthetized rats after acute, isohemic blood volume expansion by 33 percent. The infusate was an equilibrated mixture of animals' own blood and isotonic, isoncotic (6 percent) bovine albumin. Expansion increased mean arterial pressure by 35 percent, mean central venous pressure (CVP) by 850 percent, cardiac output (CO) by 56 percent, hematocrit (Hct) by 25 percent, plasma protein concentration (Ppr) by 25 percent, renal excretion rates of volume by 4,400 percent, of sodium by 2,800 percent, and of potassium by 360 percent of the respective preinfusion value. Hct and Ppr measurements suggested that 15 min after the end of the infusion, only 33 percent of infused volume remained within the circulation and that there was little further change in this during the remainder of the experiment. At the end of the elevated renal response, CVP and CO alone had returned to control values. Renal excretion rates were highly correlated with CO, but they were delayed by 2-5 min with respect to it. The results suggest that the renal response to acute volume expansion does not primarily control blood volume. Cardiac output may be the controlled variable in the response.
Relation of mitral valve opening and closure to left atrial and ventricular pressures in the intact dog
Authors: Tsakiris A. G. , Gordon D. A. , Padiyar R. , Frechette D.
Published: December 2017

The exact times of mitral valve opening and closure were determined in dogs under varying hemodynamic conditions in 143 cardiac cycles (five experiments). Radiopaque markers had been sutured to the cusps and the valve annulus 7-124 wk before the studies. Valve opening and closure times were correlated with simultaneously obtained high-fidelity intracardiac pressures. Closure of the mitral valve was completed 5-105 ms after the atrial-ventricular pressure crossover; the time interval between the onset of ventricular systole and the instance of complete valve closure varied less (10-40 ms). These observations suggest that in the intact heart alpha, rapid mitral cusp closure at the end of diastole is initiated and completed by ventricular systole alone, and beta, the ventricular isovolumic contraction period might be shorter than assumed. Opening of the valve during ventricular relaxation was characterized by 1) initial separation of the markers placed on the free edges of the cusps, of variable duration, apparently due to alterations in ventricular geometry, and 2) a rapid opening motion which clearly preceded the diastolic pressure crossover by 5-60 ms. This finding would suggest that ventricular isovolumic relaxation might be shorter than generally accepted, although the mechanism of early opening is not adequately explained by the data.
Role of the descending pressor pathway in the conscious and pentobarbital-anesthetized dog
Authors: Geis G. S. , Barratt G. , Wurster R. D.
Published: December 2017

Resting cardiovascular parameters and the responses to bilateral carotid occlusions (BCO) were monitored in pentobarbital-anesthetized and conscious dogs before and after placing lesions in the dorsolateral funiculi at C7-C8 and after spinal transections at C7. Pre- and postlesion blood pressure (BP) and heart rate (HR) responses to exercise were also monitored. The lesions significantly attenuated the responses to BCO and decreased resting BP in anesthetized dogs. Yet neither resting HR in anesthetized or conscious dogs nor the resting BP in conscious dogs was affected by the lesions. Subsequent spinal transections significantly decreased resting HR and BP and the responses to BCO but did not affect the BP response to BCO in anesthetized dogs as compared with corresponding postlesion parameters. BP responses to exercise were significantly attenuated by the lesions, but HR responses were not affected. Since stimulation and BP studies indicated that the descending pressor pathway had been ablated, the data suggest that the pathway mediates BP and HR responses to BCO in pentobarbital-anesthetized and conscious dogs. It does not maintain resting HR in anesthetized or conscious animals, and the resting BP in conscious dogs. This pathway is important for BP responses to exercise but is not necessary for HR responses. Finally, other spinal pathways are involved in cardiovascular control.
Norepinephrine metabolism in canine saphenous vein: prevalence of glycol metabolites
Authors: Muldoon S. M. , Vanhoutte P. M. , Tyce G. M.
Published: December 2017

To examine the disposition of [3H]norepinephrine ([3H]NE) in adrenergically innervated veins, helical strips of canine saphenous veins were incubated in Krebs-Ringer solution containing D,L[3H]NE (2 X 10(-7) M) for 2 h. [3H]NE and its metabolites were measured in extracts of veins and in superfusate (Krebs-Ringer) collected during basal conditions and during release of [3H]NE evoked by electrical stimulation (1-8 Hz), tyramine (5 X 10(-6) to 5 X 10(-4) M), or high concentrations of potassium (35-100 meq/liter). During basal conditions, the efflux from veins comprised mainly metabolits of [3H]NE, especially 3,4-dihydroxphenylglycol (DOPEG) and 3-methoxy-4-hydroxyphenylglycol (MOPEG); this pattern was unchanged by cocaine treatment, and monoamine oxidase inhibition reduced the formation of DOPEG. During evoked release of NE, the major metabolites in the perfusate were DOPEG, MOPEG, and normetanephrine, and their proportions differed with the stimulus used: O-methylated metabolites in the perfusate always increased more than did the deaminated catechol compounds; DOPEG and MOPEG were released in greater amounts than the corresponding acids; and cocaine treatment caused a higher content of all metabolites except DOPEG. 3-Methoxy-4-hydroxymandelic acid was also formed by the vein but was retained in the tissue.
Measurement of Vmax of the cardiac action potential with a sample/hold peak detector
Authors: Hondeghem L. M. , Cotner C. L.
Published: December 2017

A simple device for measuring the maximum upstroke velocity (Vmax) of the cardiac action potential is described. It consists of a differentiator, filter, and sample/hold peak detector. The sample/hold cycles are automatically set by the stimulus. The circuit can drive a standard pen recorder and digital voltmeter, resulting in rapid and accurate measurements. An example of the effect of quinidine on the upstroke of the cardiac action potential is shown. The circuit can easily be adapted to other applications.
Fluorescein dye-dilution technique and retinal circulation
Authors: Riva C. E. , Feke G. T. , Ben-Sira I.
Published: December 2017

Using theoretical models for the flow of fluourescein dye in retinal arteries and veins, we have determined the effects of optical absorption in blood of the incident excitation light and the emitted fluorescent light on the time course of measured fluorescence intensity, I(t). Our results indicate that I(t) curves recorded from arteries adequately represent the mean time course of the fluorescein concentration (C(t)), when either a circular or rectangular light-collecting aperture is used. I(t) curves recorded from veins adequately represent C(t), but only when a circular aperture of approximately the same diameter as that of the vessel is used. A two-point fluorophotometer, which provides simultaneous, on-line measurements of arterial and venous I(t) curves is described. Typical recordings obtained with the instrument are shown and the method employed to analyze the curves quantitatively is described in detail. This method, which consists of fitting the first passage of the fluorescence intensity curve with a log-normal function, provides results that are more accurate than those obtained using the standard exponential extrapolation method.
Effects of central and peripheral angiotensin blockade in hypertensive rats
Authors: Mann J. F. , Phillips M. I. , Dietz R. , Haebara H. , Ganten D.
Published: December 2017

The angiotensin II (AII) antagonist [Sar1-Ala8]AII (Saralasin) was injected into the brain ventricles (IVT) and intravenously (IV) in five different types of hypertensive unanesthetized rats. Renal hypertension was studied 16-22 days after kidney clipping. Intravenous infusions of cumulative doses (0.1-100 microgram/kg per min) and IVT injections (5-40 microgram) of Saralasin did not change mean arterial pressure (MAP) in controls and in one-clip, one-kidney Goldblatt hypertension, whereas MAP decreased in one-clip, two-kidney Goldblatt hypertension following IV and IVT Saralasin. In two-clip, two kidney hypertensive rats, IVT Saralasin decreased MAP but was ineffective when infused IV. Both IV and IVT Saralasin increased MAP in DOC hypertension. In spontaneously hypertensive (SH) rats, IV Saralasin increased MAP; IVT injection decreased MAP. The effect of IVT Saralasin in SH rats persisted 15-20 h after nephrectomy. We conclude that plasma AII may contribute to peripheral and central mechanisms of blood pressure regulation. The dissociation of the effects of IV and IVT Saralasin and the persistance of blood pressure decrease in nephrectomized SH rats following IVT Saralasin further support a role for locally formed brain angiotensin.
An accurate and rapid inflation device for pneumatic cuffs
Authors: Rubin S. A. , Quilter R. , Battagin R.
Published: December 2017

A simple and inexpensive semiautomatic device was constructed and calibrated for rapid and accurate inflation of limb pneumatic cuffs. An automatic timer was designed for use in cuff inflation requiring repetition or exact timing.