bluuebunny/crossref_metadata_2025 huggingface dataset:
Endothelial function in well-developed canine coronary collateral vessels
Authors: Altman J. , Dulas D. , Pavek T. , Laxson D. D. , Homans D. C. , Bache R. J.
Published: December 2017

This study examined responses of coronary collateral blood flow to endothelial-dependent vasodilators. Studies were performed in 13 dogs 4-6 mo after embolic occlusion of the left anterior descending coronary artery (LAD). Collateral flow was determined as the sum of retrograde flow from the cannulated LAD, and continuing tissue flow was measured with microspheres administered during the retrograde flow collection. Agonists were introduced into the left main coronary artery to reach collaterals arising from the left coronary arterial system. The endothelial-dependent vasodilators acetylcholine and bradykinin caused 21 +/- 7 and 25 +/- 8% increases of collateral flow, respectively (each P < 0.05). This was not different from the 28 +/- 8% increase in collateral flow produced by nitroglycerin. To determine whether vasodilator prostaglandins contributed to the increased collateral flow, studies were performed after cyclooxygenase blockade with indomethacin (5 mg/kg iv). Indomethacin caused a 30 +/- 9% decrease of retrograde flow during basal conditions but did not blunt the maximum collateral flow rates produced by acetylcholine, bradykinin, or nitroglycerin. These data demonstrate intact endothelial-dependent vasodilator mechanisms in the well-developed coronary collateral circulation.
Floating axis does not reduce motion artifacts in a model of left ventricular wall motion in dogs
Authors: Nguyen T. N. , Glantz S. A.
Published: December 2017

Methods of measuring regional wall motion of the left ventricle superimpose end-diastolic and end-systolic images. Differences in dimensions between images are assumed to be due to contraction, but they are also due to motion artifacts. To determine whether the errors caused by motion artifacts are reduced when measured with floating-axis referencing, and whether the measurement method affects these errors, we simulated end-systolic angiograms of a pure contraction (control) and contractions affected by motion artifacts and then measured differences in wall motion between angiograms with hemichord, radial, and trapezoid methods, using floating-axis and fixed-axis referencing. We chose these three methods because they form the basis for other methods, e.g., the center line method. For the simulations, we applied deformation patterns of the left ventricle, computed from the motion of tantalum markers implanted in the endocardiums of six dogs, to end-diastolic angiograms. This marker method measured the myocardial wall motion directly, independent of the angiogram. We found that differences caused by motion artifacts were not significantly reduced when measured with floating-axis referencing in our model. Normalized differences measured by radial and trapezoid methods were not significantly different, but they were significantly smaller than those measured by the hemichord method. We conclude that the axis referencing system has no significant effect on errors caused by motion artifacts in regional wall motion in our model. The measurement method, however, does affect these errors, with the radial and trapezoid methods being superior to the hemichord method.
Isolation and characterization of human and rat cardiac microvascular endothelial cells
Authors: Nishida M. , Carley W. W. , Gerritsen M. E. , Ellingsen O. , Kelly R. A. , Smith T. W.
Published: December 2017

Although reciprocal intercellular signaling may occur between endocardial or microvascular endothelium and cardiac myocytes, suitable in vitro models have not been well characterized. In this report, we describe the isolation and primary culture of cardiac microvascular endothelial cells (CMEC) from both adult rat and human ventricular tissue. Differential uptake of fluorescently labeled acetylated low-density lipoprotein (Ac-LDL) indicated that primary isolates of rat CMEC were quite homogeneous, unlike primary isolates of human ventricular tissue, which required cell sorting based on Ac-LDL uptake to create endothelial cell-enriched primary cultures. The endothelial phenotype of both primary isolates and postsort subcultured CMEC and their microvascular origin were determined by characteristic histochemical staining for a number of endothelial cell-specific markers, by the absence of cells with fibroblast or pericyte-specific cell surface antigens, and by rapid tube formation on purified basement membrane preparations. Importantly, [3H]-thymidine uptake was increased 2.3-fold in subconfluent rat microvascular endothelial cells 3 days after coculture with adult rat ventricular myocytes because of release of an endothelial cell mitogen(s) into the extracellular matrix, resulting in a 68% increase in cell number compared with CMEC in monoculture. Thus biologically relevant cell-to-cell interactions can be modeled with this in vitro system.
Determination of left atrial volume using sonomicrometry: a cast validation study
Authors: Hoit B. D. , Shao Y. , McMannis K. , Gabel M. , Walsh R. A.
Published: December 2017

We developed a technique for left atrial (LA) volume estimation using two pairs of sonomicrometers sewn to the anteroposterior (LAX) and mediolateral (SAX) LA diameters and validated the method against water displacement of LA casts in 15 dogs. LA pressure was adjusted to a preselected level (5, 10, or 15 mmHg) by dextran infusion and was matched by postmortem infusion of casting resin (Conthane DPEN-18402). LA volume was modeled empirically as an ellipsoid of revolution without regression constants [(SAX)2(LAX)]. There was a strong correlation between the calculated LA volume and water displacement of the LA body [r = 0.87, standard error of estimate (SEE) = 3.3 ml, P = 0.0001] but a weaker correlation against water displacement of the entire LA (body+appendage, r = 0.81, SEE = 3.9 ml, P = 0.0003). The appendage volume fraction (appendage volume/total LA volume), as determined by water displacement of the casts, increased with increasing LA size (r = 0.78, P = 0.001). These data indicate that, in the normal canine heart, LA volume can be estimated accurately with high temporal and spatial resolution sonomicrometry using two atrial dimensions, and the contribution of appendage to total LA volume may become significant as the atrium enlarges.
Effects of chronic heart failure on skeletal muscle vascular transport capacity of rats
Authors: McAllister Richard M. , Laughlin M. Harold , Musch Timothy I.
Published: December 2017

The purpose of this study was to determine the effects of chronic heart failure (HF) on the vascular transport capacity of rat skeletal muscle. A large myocardial infarction (MI) was surgically produced in rats by ligating the left main coronary artery (n = 10). Sham operations were performed in control animals (Sham, n = 4). The vascular transport capacity of each animal's hindquarters was determined 8–9 mo post-MI to ensure that each rat was in a chronic state of left ventricular (LV) dysfunction and HF. With the use of an isolated, maximally vasodilated hindquarters preparation, we found that perfusion pressures, capillary pressures, capillary filtration coefficients, and precapillary vascular resistances were similar for the two groups under isogravimetric conditions. In contrast, postcapillary resistance was elevated (Sham, 0.9 ± 0.2; MI, 1.5 ± 0.2 mmHg·m−1·min·100 g; P = 0.03), and flow to the hindquarters was reduced for rats in chronic HF compared with controls (Sham, 16.1 ± 2.3; MI, 12.1 ± 0.9 ml·min−1·100 g−1; ,P = 0.07). Vascular flow capacity (VFC) for the hindquarters was similar for control rats and rats with chronic HF across a wide range of perfusion pressures (20–60 mmHg). However, regional flow capacities were reduced in soleus and red gastrocnemius but not in white gastrocnemius muscles of rats in chronic HF compared with controls. These results suggest that the VFC of muscle comprised primarily of high oxidative fibers is selectively reduced in rats with chronic HF. Given the obligatory role for high oxidative muscle fibers in locomotion, these decrements in VFC may contribute to the decreased exercise tolerance commonly found with this disease.

blood flow; vascular resistance; radiolabeled microspheres

Submitted on May 8, 1992

Accepted on October 16, 1992
ANG II receptors, c-myc, and c-jun in myocytes after myocardial infarction and ventricular failure
Authors: Reiss K. , Capasso J. M. , Huang H. E. , Meggs L. G. , Li P. , Anversa P.
Published: December 2017

To determine the relationship between reactive cardiac hypertrophy and the expression of angiotensin II (ANG II) receptors in surviving myocytes after infarction, large infarcts were produced in rats that were killed 2–3 days later. Measurements of global ventricular dynamics indicated that left ventricular failure and right ventricular dysfunction occurred in experimental animals. These alterations in ventricular pump function were associated with increases in ventricular weight-to-body weight ratio, indicative of developing cardiac hypertrophy. Such a response was coupled with a 6.6-fold increase in ANG II receptor mRNA in myocytes from the left ventricle. A 2.3-fold increase in the expression of ANG II receptor in myocytes from the right ventricle was also found. Radioligand binding assay documented a 44% increase in the density of ANG II receptors on left ventricular myocytes of infarcted hearts. To establish whether the induction of genes commonly associated with myocyte hypertrophy was present, the message for c-myc and c-jun was biventricularly assessed. Myocardial infarction was accompanied by overexpressions of c-myc and c-jun that were more prominent in left than in right ventricular myocytes. In conclusion, the enhanced expression of ANG II receptor and its receptor protein and c-myc and c-jun in myocytes may participate in the reactive growth processes of these cells after infarction.
Cardiopulmonary and carotid baroreflex control of splanchnic and forearm circulations
Authors: Escourrou P. , Raffestin B. , Papelier Y. , Pussard E. , Rowell L. B.
Published: December 2017

The objective was to determine whether a rise in carotid sinus transmural pressure by neck suction (NS) would counteract vasoconstriction secondary to inhibition of discharge of arterial and cardiopulmonary baroreceptors by simultaneous lower body negative pressure (LBNP). NS alone was applied to seven normal human subjects at -40 mmHg for 400–600 ms at each heartbeat during a 6-min period. NS reduced mean arterial pressure (MAP) from 94 +/- 6 to 86 +/- 9 mmHg and heart rate (HR) from 64 +/- 5 to 60 +/- 4.7 beats/min but did not affect vascular resistance in the splanchnic region (flow by constant infusion of indocyanine green; assumed constant extraction) or in the forearm (venous occlusion plethysmography). The same NS stimulus was applied during 23 min of continuous LBNP at -40 mmHg. LBNP alone before NS significantly reduced central venous pressure (CVP) from 5 +/- 0.3 to 1 +/- 0.5 mmHg and raised splanchnic (+34%) and forearm (+70%) vascular resistances and HR (from 64 to 74 beats/min) without reducing MAP. NS plus LBNP reduced MAP from 103 +/- 8 to 95 +/- 6 mmHg and HR from 74 +/- 6 to 67 +/- 5 beats/min without changing CVP but did not alter vascular resistances, which remained elevated and constant throughout LBNP before and after NS. Increments in plasma concentrations of renin (240%), aldosterone (70%), epinephrine (112%), and norepinephrine (46%) accompanied LBNP and NS; a separate influence of NS was not discernible. We conclude that vasoconstriction in response to combined cardiopulmonary and aortic inhibition is not overpowered by carotid sinus stimulation.
Transvascular albumin flux in rabbit hindlimb after tourniquet ischemia
Authors: Kupinski A. M. , Shah D. M. , Bell D. R.
Published: December 2017

Transvascular clearance of labeled rabbit albumin was measured in gastrocnemius muscle and heel skin from anesthetized rabbits after 1 or 2 h of tourniquet ischemia. Albumin clearance, calculated as a 1-h extravascular uptake, was 4.7 +/- 0.4 and 29 +/- 1 microliter.h-1 x g dry wt-1 for control gastrocnemius muscle and heel skin, respectively. During the first hour of reperfusion, the clearance was 101 +/- 23 and 56 +/- 6 microliters.h-1 x g dry wt-1 in the muscle and skin, respectively. The clearance in skin during the second and third hour of reperfusion was not different from control. The increased clearance in muscle persisted during 2 h of reperfusion but returned to control levels during the third hour of reperfusion. The solvent drag reflection coefficient was measured by increasing venous pressure during reperfusion in one leg after bilateral ischemia. In skin, the reflection coefficient, calculated as 1 minus the change in clearance divided by the change in water weight, was 0.94 +/- 0.05 and did not change with tourniquet ischemia. The reflection coefficient in muscle was 0.98 +/- 0.01 for control animals and decreased to 0.66 +/- 0.11 during the first hour of reperfusion. The reflection coefficient was not different from control during the third hour of reperfusion. The transitory increase in microvascular permeability to albumin in skeletal muscle is more indicative of an acute inflammatory response than of endothelial injury.
Effects of leukocyte activation on capillary hemodynamics in skeletal muscle
Authors: Harris A. G. , Skalak T. C.
Published: December 2017

Leukocytes may be an important determinant of microvascular resistance, particularly during pathological states that cause cell activation and cytoplasmic stiffening. Significant mechanisms include capillary plugging and venular adhesion. Previous quantitative studies on leukocyte-capillary plugging focused solely on arteriolar-capillary branchpoints. There are no quantitative data on plugging throughout the capillary network either under normal conditions or after leukocyte activation. Plugging measurements were made throughout capillary networks at both arteriolar-capillary and capillary-capillary branchpoints in spinotrapezius muscle of anesthetized rats under normal physiological conditions and after leukocyte activation by superfusion with 1 x 10(-7) M N-formyl-methionyl-leucylphenylalanine (FMLP). These data were used to estimate the increase in microvascular flow resistance due to leukocyte plugging. The increase was 1.1% in control and 15.9% in the activated state. On an individual network basis, this represents an average 23-fold increase (P < 0.002) in network resistance, suggesting that leukocyte activation has a significant impact on microvascular blood flow.
Abnormal responses to pulmonary vasodilators in conscious dogs after left lung autotransplantation
Authors: Nishiwaki K. , Nyhan D. P. , Stuart R. S. , Rock P. , Desai P. M. , Peterson W. P. , Murray P. A.
Published: December 2017

We investigated the extent to which left lung autotransplantation (LLA) alters endothelium-dependent (bradykinin and acetylcholine) and endothelium-independent (sodium nitroprusside) vasodilation in the pulmonary circulation of conscious dogs. Continuous left pulmonary vascular pressure-flow (LPQ) plots were generated in conscious dogs 3–4 wk post-LLA and in sham-operated controls. LLA resulted in a marked upward shift in the baseline LPQ relationship compared with the control group (P < 0.01), i.e., LLA caused a chronic increase in pulmonary vascular resistance. The thromboxane analogue, U-46619, was used to acutely preconstrict the pulmonary circulation in control dogs, which shifted the control LPQ relationship to the same position measured post-LLA. Under these circumstances, bradykinin, acetylcholine, and nitroprusside caused pulmonary vasodilation in the control group, whereas these responses were either attenuated or reversed to vasoconstriction post-LLA. After acute preconstriction with U-46619 post-LLA, the pulmonary vasodilator responses to bradykinin and acetylcholine were again attenuated, but the response to nitroprusside was unaltered compared with control. These results indicate that a significant component of the chronic increase in pulmonary vascular resistance post-LLA is passively mediated and does not reflect an active increase in baseline vasomotor tone. Moreover, LLA results in an impairment in endothelium-dependent, but not endothelium-independent, pulmonary vasodilation in conscious dogs.
Effect of residual stress on transmural sarcomere length distributions in rat left ventricle
Authors: Rodriguez E. K. , Omens J. H. , Waldman L. K. , McCulloch A. D.
Published: December 2017

It has been previously shown that the myocardium in the walls of the unloaded passive left ventricle (LV) is not stress free. To assess the functional significance of residual stress in the ventricular wall, we compared the transmural distributions of sarcomere length (SL) in specimens of rat LV myocardium fixed in the unloaded (residually stressed) and stress-free states. When a cross-sectional ring cut from the equatorial region of the freshly arrested rat hearts was cut radially to relieve residual stress, it sprang open into an arc with a mean opening angle of 45 +/- 15 degrees (SD) (n = 8). During immersion fixation in glutaraldehyde, the opening angle increased 9.3 +/- 7.1 degrees (SD) overall. SLs were measured at 16 equally spaced transmural locations from the free wall in the stress-free tissue sections and were compared with control measurements from adjacent cross-sectional rings in which residual stress had not been relieved. Average SL for the stress-free tissue (n = 11) was 1.84 +/- 0.05 (SD) microns and for the unloaded tissue was 1.83 +/- 0.06 (SD) microns. However, analysis of covariance on the pooled data showed that the transmural distributions were significantly different (P < 0.0001). Whereas SL was uniform across the wall in the stress-free state with a mean gradient of -0.014 +/- 0.044 (SD) microns/total wall thickness, there was a significant decrease (P = 0.001) in SL from epicardium to endocardium in the intact unloaded tissue [slope = -0.114 +/- 0.054 (SD) microns/total wall thickness].(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of epoxyeicosatrienoic acids on isolated hearts and ventricular myocytes
Authors: Moffat M. P. , Ward C. A. , Bend J. R. , Mock T. , Farhangkhoee P. , Karmazyn M.
Published: December 2017

Effects of cytochrome P-450 metabolites of arachidonic acid, epoxyeicosatrienoic acids (EETS; 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET), were examined in isolated guinea pig hearts and ventricular myocytes. Addition of 1-16 ng/ml EETs to normal isolated hearts produced no effects on contractility or coronary pressure. In hearts subjected to 60 min of low-flow ischemia, impairment of contractility and declines in heart rate and coronary perfusion pressure were similar in the presence or absence of 1 ng/ml EETs. However, in the presence of either 5,6- or 11,12-EET, recovery was delayed for the first 10 min only. No significant differences were found in any group regarding heart rate, coronary perfusion pressure, or energy metabolite content after 30 min of reperfusion. In myocytes, both 5,6- and 11,12-EET (100 pg/ml, 1.0 ng/ml, and 20 ng/ml) significantly increased cell shortening as well as intracellular calcium concentrations, whereas 8,9- or 14,15-EET was without effect on these parameters. These results describe for the first time the direct effects of various EETs on cardiac cell function as well as their ability to modulate some of the myocardial responses to postischemic reperfusion. The results suggest a potential role for these substances in the response of the heart to pathological insult.
Trauma-hemorrhage and resuscitation in the mouse: effects on cardiac output and organ blood flow
Authors: Wang P. , Ba Z. F. , Burkhardt J. , Chaudry I. H.
Published: December 2017

Although mice are widely used for the study of immune consequences of hemorrhage, the changes of cardiac output (CO) and blood flow (BF) in response to trauma and hemorrhage in this species have not been well defined. To study this, nonheparinized C3H/HeN mice (n = 6 per group) underwent laparotomy (i.e., trauma induced), were bled to a mean arterial pressure of 35 mmHg, and maintained for 90 min by withdrawing more blood or returning Ringer lactate. The animals were then resuscitated with four times the volume of maximal bleedout in the form of Ringer lactate over 60 min. Sham-operated mice underwent the same procedure but were neither bled nor resuscitated. At the end of hemorrhage, 60 min postresuscitation, or corresponding time after sham operation, CO and BF were determined by radioactive microspheres. Results indicate that CO and BF decreased significantly at the end of hemorrhage. Resuscitation, however, restored CO and BF in various organs except the brain and skeletal muscle. Despite this, 9 of 16 mice died within 6 days postresuscitation, whereas none of sham mice died (n = 16 per group in this additional study). Therefore, we have developed a nonheparinized model of trauma-hemorrhage and resuscitation in mice that is associated with late mortality. Furthermore, the microsphere technique provides a reliable method for assessing CO and BF in mice. Thus it may be possible to study the correlation between cardiovascular and immunologic alterations under such conditions.
Near-wall excess of platelets induced by lateral migration of erythrocytes in flowing blood
Authors: Uijttewaal W. S. , Nijhof E. J. , Bronkhorst P. J. , Den Hartog E. , Heethaar R. M.
Published: December 2017

In this study we present experimental data on the inhomogeneous distribution of platelets in polyethylene tubes (200 microns diam) based on the inverse Fahraeus effect for platelets. It is shown that platelets are expelled toward the red blood cell-depleted marginal layer near the tube wall by mutual interaction with erythrocytes. By means of a straightforward model, the near-wall concentration of platelets could be estimated from measurements on the average tubular platelet concentration. The marginal layer originates from the hydrodynamic interaction of the deformable erythrocytes with the tube wall. If the tube diameter is large compared with the size of the erythrocytes, the lateral migration effects can effectively be scaled on the absolute distance between the erythrocytes and the tube wall. This results in the main conclusion that the near-wall concentration of platelets is significantly enhanced up to about seven times the average concentration, practically irrespective of the tube diameter in the range of 100-500 microns. Where comparable, the results of this study are in accordance with experimental data of other authors.
Amino acids modify activity of canine intrinsic cardiac neurons involved in cardiac regulation
Authors: Huang M. H. , Smith F. M. , Armour J. A.
Published: December 2017

The effects of amino acids on intrinsic cardiac neuronal activity identified in 10 anesthetized dogs were investigated. Local injection of small volumes (1-10 microliters) of the excitatory amino acids, glutamate (100 mM) and aspartate (10 mM), and the inhibitory amino acids, gamma-aminobutyric acid (GABA; 10 mM) and glycine (10 mM), modified the activity of 39 of 50 identified neurons. Spontaneous activity of eight neurons was modified by both excitatory and inhibitory amino acids. Cardiodynamic responses accompanied neuronal activity modification in 15 instances. After acute decentralization, repeat doses of amino acids altered the activity of 21 neurons and elicited cardiovascular responses in 7 instances. Neuronal and cardiovascular responses were elicited after atropine administration. Neuronal but not cardiac responses were elicited after subsequent timolol administration. In other animals, GABA but not other amino acids elicited neuronal and cardiodynamic responses after hexamethonium administration in decentralized preparations, indicating that non-nicotinic synapses were involved in some GABA-induced responses. These results demonstrate that excitatory and inhibitory amino acids can modify intrinsic cardiac neuronal activity such that, as a consequence, cardiac variables can be modified.
Distribution, propagation, and coordination of contractile activity in lymphatics
Authors: Zawieja D. C. , Davis K. L. , Schuster R. , Hinds W. M. , Granger H. J.
Published: December 2017

The propagation and coordination of lymphatic contractions were studied in the mesentery of the rat small intestine using in situ microscopic observation. Indexes of lymphatic diameter were simultaneously measured at two adjacent lymphangions in spontaneously contracting lymphatics (n = 51). Diameter index, contraction frequency, and the percentage of the intersegmental contractions that were propagated and coordinated (PP) were determined at both sites. The conduction velocity of the contractile activity and the percentage of the coordinated contractions that were propagated both antegrade to the direction of lymph flow and retrograde to the flow stream were determined. The results indicate that 1) 80-90% of the lymphatic contractions in the vessels we evaluated were propagated, 2) the wave of contractile activity propagated both centrally and peripherally, and 3) the conduction velocity of the contractile activity was approximately 4-8 mm/s. We tested the hypothesis that gap junctional communication is responsible for the coordination of the contractile event. To accomplish this, we used the gap junction blockers n-heptanol and oleic acid. PP was 90 +/- 4% under normal conditions and fell to a minimum value of 55 +/- 7% during the gap junction blockade. These results indicate that gap junctional communication played an important role in the propagation and coordination of contractions that occurred in spontaneously active lymphatics.
Adenosine A1 receptors, KATP channels, and ischemic preconditioning in dogs
Authors: Auchampach J. A. , Gross G. J.
Published: December 2017

The objective of the present study was to characterize the role of adenosine in myocardial ischemic preconditioning in the canine heart. Preconditioning with 5 min of ischemia resulted in a marked reduction in infarct size after 60 min of left circumflex coronary artery occlusion and 5 h of reperfusion in barbital-anesthetized dogs compared with dogs that were not preconditioned (4.8 +/- 1.9 vs. 27.9 +/- 4.5%; P < 0.05). Pretreatment with either the nonselective adenosine receptor antagonist PD 115199 or the selective adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine blocked this protective effect, although in the absence of preconditioning neither of the antagonists affected infarct size. Intracoronary infusion of two different doses of adenosine or dipyridamole over a 5-min period before a prolonged 60-min occlusion period did not mimic preconditioning; however, intracoronary infusion of a combination of adenosine and dipyridamole produced a significant reduction in infarct size (13.6 +/- 4.1%), which was abolished by pretreatment with the ATP-dependent potassium (KATP) channel antagonist glibenclamide. These results suggest that activation of adenosine A1 receptors produces myocardial preconditioning in the canine heart by opening KATP channels.
Role of cardiac mast cells in complement C5a-induced myocardial ischemia
Authors: Ito B. R. , Engler R. L. , del Balzo U.
Published: December 2017

Activated complement component C5a causes myocardial ischemia mediated by thromboxane (Tx) A2 and leukotrienes C4/D4. Blood cells are not involved in either the mediator release or the myocardial effects of C5a, suggesting that a C5a-sensitive, cardiac resident inflammatory cell is responsible. The goals of this study were to determine whether 1) cardiac mast cell activation accompanies the C5a response, 2) inhibition of mast cell degranulation inhibits the response, and 3) histamine release plays a role in the C5a-induced myocardial ischemia. The left anterior descending coronary artery (LAD) of open-chest pigs (n = 13) was perfused with arterial blood at constant pressure (95 mmHg). Coronary blood flow (CBF) was measured (in-line flowmeter) and regional function [percent segment shortening (%SS)] determined with sonomicrometry. A coronary vein was cannulated for measurement of plasma TxB2 and histamine (a marker of mast cell degranulation). Intracoronary C5a (500 ng) decreased coronary blood flow (45% of preinfusion levels) and LAD %SS (65% of preinfusion) and was accompanied by increases in coronary venous TxB2 (delta 63.3 ng/ml) and histamine (delta 200 nM). Mast cell inhibition with lodoxamide (2 mg/kg iv, n = 8) attenuated the C5a-induced fall in CBF (14 vs. 53% decrease, P < 0.01) and %SS (10 vs. 38% decrease, P < 0.01) and also reduced the C5a-induced increase in both coronary venous histamine (delta 26 vs. 278 nM, P < 0.05) and TxB2 (delta 0.34 vs. 63.3 ng/ml, P < 0.01). However, histamine H1 (pyrilamine) and H2 (ranitidine) receptor blockade had no effect on the C5a-induced fall in CBF or LAD %SS.(ABSTRACT TRUNCATED AT 250 WORDS)
Protective effects of histidine during ischemia-reperfusion in isolated perfused rat hearts
Authors: Kukreja R. C. , Loesser K. E. , Kearns A. A. , Naseem S. A. , Hess M. L.
Published: December 2017

We investigated the efficacy of histidine in reducing ischemia-reperfusion (I/R)-induced myocardial injury in isolated perfused rat hearts. In I/R hearts, the contractile function and coronary flow were 59 +/- 10 and 78 +/- 6% of control. Perfusion with histidine resulted in significant increase in contractility (94 +/- 4%) and coronary flow (92 +/- 4%). The incidence of arrhythmias during reperfusion was 100% (10 out of 10) in the I/R hearts with an average duration of 12.22 +/- 1.55 (SE) min. The duration of arrhythmias was shortened to 8.24 +/- 1.46, 2.15 +/- 0.9, and 2.49 +/- 1.50 min with 10, 25, and 50 mM histidine, respectively. The duration of sinus rhythm increased from 6.26 +/- 1.56 min in I/R hearts to 10.66 +/- 1.55, 14.99 +/- 1.61, and 17.18 +/- 0.95, and 11.73 +/- 0.93 min after perfusion with 10, 25, and 50 mM histidine, and superoxide dismutase (SOD)-catalase-mannitol, respectively. Electron microscopy revealed significant ultrastructural damage of myocytes in I/R hearts, which included swelling of the mitochondria and disruption of both the sarcolemma and the myofibrils. Histidine reduced the ultrastructural damage in a dose-dependent fashion. In general, the protective effect of histidine was superior than SOD-catalase-mannitol. We conclude that histidine protects myocardium against I/R damage most likely by a singlet oxygen scavenging mechanism.
Cardiac effects of acetylcholine in rat hearts: role of endothelium-derived relaxing factor and prostaglandins
Authors: Yang B. C. , Nichols W. W. , Mehta J. L.
Published: December 2017

We examined the effects of acetylcholine (ACh) on coronary perfusion pressure (CPP) and force of cardiac contraction (FCC) in isolated rat hearts. Perfusion of hearts with ACh increased both CPP and the FCC, whereas cardiac contraction rate fell. These effects of ACh were abolished by atropine but were not affected by the beta 1-adrenergic antagonist metoprolol. The nonselective beta-adrenergic antagonist propranolol decreased ACh-mediated increase in FCC but did not affect the rise in CPP. Pretreatment of hearts with cyclooxygenase inhibitor indomethacin or thromboxane (Tx) A2-endoperoxide receptor antagonist SQ 29,548 decreased ACh-mediated increase in CPP and FCC, suggesting release of TxA2 in the microvasculature, which may partially account for the increase in CPP and FCC with ACh infusion. In contrast to the effect of indomethacin and SQ 29,548, pretreatment of hearts with endothelium-derived relaxing factor (EDRF) synthetase inhibitor NG-monomethyl-L-arginine (L-NMMA) or guanylate cyclase inhibitor methylene blue potentiated ACh-mediated increase in CPP and attenuated the increase in FCC, suggesting that ACh-mediated increase in CPP is modified by basal EDRF release. Thus the cardiac effects of ACh are related to muscarinic receptor activation, and the release of prostaglandins and EDRF modulates the effects of ACh in isolated rat heart.
Effects of E. coli sepsis and myocardial depressant factor on interval-force relations in dog ventricle
Authors: Jha P. , Jacobs H. , Bose D. , Wang R. , Yang J. , Light R. B. , Mink S.
Published: December 2017

We examined whether depressed left ventricular (LV) contractility during Escherichia coli sepsis in dogs was due to a decrease in the fractional release of calcium from the sarcoplasmic reticulum (SR) or a reduction in calcium content in this organelle. To indirectly assess SR calcium availability in a right ventricular (RV) trabecular muscle preparation, we utilized functional indexes of cellular myocardial calcium metabolism, which included rapid-cooling contracture (RCC), an indicator of SR calcium content, and postrest contraction (PRC), an index of calcium availability from the release compartment of the SR. Measurements were made during steady-state stimulation at 0.5 and 1.5 Hz, during which time rest intervals of 30-240 s were periodically imposed. SR calcium availability was measured in RV trabeculae of dogs subjected to 4 h of E. coli sepsis and was compared with calcium availability measured in nonseptic dogs. We further characterized a filterable cardiodepressant substance (FCS), which has been previously shown to be associated with LV depression in this model, to determine whether it produced changes in calcium metabolism similar to those found in sepsis. The results showed that calcium availability from the SR of septic dogs was not impaired. Furthermore, FCS was found in the 10,000- to 30,000-mol wt fraction of plasma and produced changes in PRC in canine trabeculae that were similar to those produced during sepsis. We conclude that, as assessed by PRC and RCC, SR calcium content and release are not impaired in sepsis.
Postischemic oxygen radical production varies with duration of ischemia
Authors: Henry T. D. , Archer S. L. , Nelson D. , Weir E. K. , From A. H.
Published: December 2017

Oxygen radicals have been implicated in the pathogenesis of myocardial injury. Enhanced chemiluminescence is a sensitive technique for continuous nondestructive measurement of oxygen radical generation. Using an isolated perfused rat heart model, we studied the effect of variable durations of ischemia on oxygen radical generation and postischemic myocardial function. Peak postischemic oxygen radical generation was higher with an intermediate period of ischemia (11.5 min; 528 +/- 53 counts/s) than with either a shorter period (5 min; 328 +/- 21 counts/s) or a prolonged period (40.8 min; 286 +/- 53 counts/s). The magnitude of oxygen radical generation did not correlate with postischemic mechanical function, although it was related to the duration of ischemia with regard to brief and intermediate periods of ischemia (both associated with limited mechanical damage). The increased reperfusion chemiluminescence seen with the intermediate versus the brief ischemic insults can be explained by time-dependent enhancement of the mechanisms present during ischemia that serve to increase oxygen radical generation during reperfusion. In contrast, the longer period of ischemia, resulting in severe mechanical dysfunction, was associated with lower levels of chemiluminescence than observed with an intermediate ischemic duration. This most likely results from the irreversible myocardial injury associated with prolonged ischemia and the consequent inability to generate oxygen radicals. We conclude that, although reperfusion-associated enhancement of myocardial free radical generation may be related to mild to moderate postischemic mechanical dysfunction (stunning), this mechanism may not be of importance in the generation of irreversible reperfusion myocardial injury.
Prostanoid synthesis in response to high CO2 in newborn pig brain microvascular endothelial cells
Authors: Hsu P. , Shibata M. , Leffler C. W.
Published: December 2017

Hypercapnia-induced cerebral vasodilation involves prostanoids in newborn pigs. However, the source of prostanoids has not been determined. The current study was designed to address the hypothesis that piglet cerebral microvascular endothelial cells increase their synthesis of prostanoids in response to high CO2. Microvascular endothelial cells, smooth muscle cells, and glia were isolated and grown in primary culture. They were identified morphologically and by indirect immunofluorescence staining. Cerebral microvascular endothelial cell cultures from newborn pigs produced equal amounts of 6-ketoprostaglandin (PG) F1 alpha (stable hydrolysis product of PGI2), PGE2 and a small amount of PGF2 alpha under basal conditions. Administration of calcium ionophore A23187 to the endothelial cells increased release of all three prostanoids in a dose- and time-dependent manner. Exposure of piglet cerebral microvascular endothelial cells to higher than normal CO2 increased the production of 6-keto-PGF1 alpha and PGE2 but not of PGF2 alpha. The enhanced prostanoid biosynthesis was concentration dependent, peaking at 14% CO2, and was detected during the first 10 min exposure to 14% CO2. Hypercapnia-induced increased synthesis of prostanoids was blocked dose dependently by the simultaneous addition of PGH synthase inhibitor indomethacin. High CO2 did not increase prostanoid production by cerebral microvascular smooth muscle cells or glia, although A23187 enhanced prostanoid formation by both cell types. These data show that high CO2 stimulates prostanoid synthesis by newborn pig cerebral microvascular endothelial cells, which is consistent with an involvement of cerebral vascular endothelium in hypercapnia-induced vasodilation.
Effect of angiotensin-converting-enzyme inhibition on bradykinin metabolism by vascular endothelial cells
Authors: Grafe M. , Bossaller C. , Graf K. , Auch-Schwelk W. , Baumgarten C. R. , Hildebrandt A. , Fleck E.
Published: December 2017

The degradation of bradykinin by angiotensin-converting-enzyme (ACE) activity in cultured human endothelial cells was studied by direct measurement of bradykinin and by its effect on the release of endothelium-derived relaxing factors. The half-life of exogenous bradykinin (10,000 pg/ml) was calculated from the decay of the bradykinin concentration as 46 +/- 2 min in cell monolayers, 133 +/- 15 min in conditioned medium, and 24 +/- 2 min in homogenates. Most of the bradykinin-degrading activity in cell monolayers could be inhibited in a concentration-dependent manner by the ACE inhibitors lisinopril, ramiprilat, and captopril. Bradykinin-degrading activity was released into the culture medium containing one-fourth of the bradykinin-degrading activity found in the presence of cell monolayers. In cell homogenates higher unspecific bradykinin-degrading activities were present. The functional consequence of bradykinin degradation was demonstrated by the potentiating effect of ramiprilat on the generation of endothelium-derived relaxing factors nitric oxide and prostacyclin from endothelial cells. The study supports the concept of increased vasodilatory effects of bradykinin during ACE inhibition.
Spontaneous pressure-flow relationships in renal circulation of conscious dogs
Authors: Skarlatos S. , DiPaola N. , Frankel R. A. , Pomerantz R. W. , Brand P. H. , Metting P. J. , Britton S. L.
Published: December 2017

Renal pressure-flow (P-F) relationships are usually evaluated by measuring effects of mechanically induced changes in renal arterial pressure (AP) on renal blood flow (RBF). We devised a method allowing evaluation of renal P-F relationships during normal changes in AP occurring spontaneously in a conscious animal rather than during artificially induced changes in AP. In 18 trials in 6 dogs standing at rest, we measured average AP and RBF for each cardiac cycle over periods of approximately 35 min (approximately 3,100 cardiac cycles/trial). AP and RBF values for each cardiac cycle were expressed as percent change (%delta) from the 35-min average (beat-to-beat changes). Slope and angle of each consecutive beat-to-beat P-F change were calculated and collated into one of eight zones representing the possible physiological mechanisms responsible for concurrent, spontaneous changes in RBF and AP. In a predominance of the cardiac cycles (approximately 43%), the spontaneous AP-RBF relationship was consistent with being mediated by arterial baroreflexes (i.e., increases in AP were accompanied by proportionately greater increases in RBF during 44.4% of cardiac cycles in which AP increased, and decreases in AP were accompanied by proportionately greater decreases in RBF during 41.4% of cardiac cycles in which AP decreased). Blockade of autonomic ganglionic transmission with hexamethonium markedly attenuated this pattern. Our results indicate that renal circulation participates in moment-to-moment control of AP via a predominant baroreflex-like pattern.
Mechanisms for altered endothelium-dependent vasorelaxation in isolated kidneys from experimental hypertensive rats
Authors: Hayakawa H. , Hirata Y. , Suzuki E. , Sugimoto T. , Matsuoka H. , Kikuchi K. , Nagano T. , Hirobe M. , Sugimoto T.
Published: December 2017

To study mechanisms for attenuated endothelium-dependent vasorelaxation in hypertension, we examined the effects of acetylcholine (ACh) on renal vascular resistance (RVR) and release rates of endothelium-derived relaxing factor (EDRF) in kidneys isolated from spontaneously hypertensive rats (SHR), deoxycorticosterone acetate (DOCA) salt-hypertensive (DOCA salt) rats, and Dahl salt-sensitive (Dahl S) rats. Decreases in RVR by ACh were smaller in hypertensive rats than in their normotensive controls. The release rate of nitric oxide into the perfusate, which was estimated using nitrite-nitrate as an index, did not differ between SHR and Wistar-Kyoto rats (WKY). However, the release rate of EDRF was markedly decreased in both DOCA salt rats and Dahl S rats compared with their normotensive controls (10(-7) M ACh: DOCA salt 45 +/- 6 vs. control 410 +/- 60 pmol.min-1.g-1 kidney wt, P < 0.001). In SHR, high-K+ perfusion or pretreatment with glibenclamide, inhibitors of endothelium-derived hyperpolarizing factor (EDHF), significantly reduced ACh-induced vasorelaxation only in WKY, resulting in no differences in the RVR reduction between SHR and WKY. Thus attenuated ACh-induced vasorelaxation in the SHR kidney may be attributed to a decrease in EDHF, but to a decrease in EDRF in DOCA salt rats and Dahl S rats.
Characterization and mechanisms of H2O2-induced contractions of pulmonary arteries
Authors: Sheehan D. W. , Giese E. C. , Gugino S. F. , Russell J. A.
Published: December 2017

We studied H2O2-induced contractions of isolated rabbit intrapulmonary arteries mounted in standard tissue baths. All vessels were pretreated with a thromboxane A2/prostaglandin H2 receptor antagonist, SQ 29,548, to block immediate transient contractions to H2O2 and to isolate slowly developing sustained contractions. When exposed to H2O2 (0.1, 0.2, 0.3, 0.6, and 1.0 mM) for 30 min, vessels contracted in (0.1, 0.2, 0.3, 0.6, and 1.0 mM) for 30 min, vessels contracted in a concentration-dependent fashion between 0.1 and 0.3 mM H2O2; contractions at 0.6 and 1.0 mM H2O2 were not significantly different from those at 0.3 mM H2O2. During recovery (90 min) from H2O2 exposures, baseline tension was significantly greater, but active tension (10 microM phenylephrine) was significantly less for vessels previously exposed to 0.6 and 1.0 mM H2O2. Contractions to 0.3 mM H2O2 were not blunted by the following interventions: 1) endothelium rubbing, 2) incubation in Ca(2+)-free 100 microM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) Krebs-Ringer solution, 3) incubation in the Ca(2+)-free solution and depletion of ryanodine (20 microM)-sensitive Ca(2+) stores, or 4) pretreatment with the protein kinase C inhibitor 1-(5-isoquinolinylsulfonyl)-3-methyl-piperazine (20 microM). However, contractions were depressed by approximately 50% when vessels were pretreated with the phospholipase C/serine esterase inhibitor 2-nitro-4-carboxy-phenyl-N,N-diphenylcarbamate (50 microM). These results suggest that slow-developing contractions to H2O2 are concentration dependent and may result, in part, from activation of a serine esterase(s) and/or phospholipase C.
Extracardiac to coronary anastomoses support regional left ventricular function in dogs
Authors: Unger E. F. , Shou M. , Sheffield C. D. , Hodge E. , Jaye M. , Epstein S. E.
Published: December 2017

Intramyocardial implantation of a systemic artery [the internal mammary artery (IMA)] causes angiogenesis, with formation of systemic to coronary anastomoses. In dogs, we assessed the magnitude of IMA-derived nutritive flow and determined its influence on regional contraction. We also sought to determine whether acidic fibroblast growth factor (FGF), an angiogenic peptide, could enhance myocardial neovascularization. Ameroid constrictors and hydraulic balloon occluders were placed on the left anterior descending coronary artery (LAD) of 23 dogs, and the left IMA was implanted in the LAD territory. Dogs were randomized to receive continuous infusions of acidic FGF with heparin, heparin alone, or placebo directly into the IMA for 8 wk. Regional myocardial blood flow was assessed in the conscious state 3 days and 8 wk after operation. Left ventricular function was determined in the anesthetized state at the 8-wk conclusion of treatment. In all dogs, IMA occlusion reduced mean maximal LAD zone perfusion by 28% (P < 0.001), without influencing regional contraction. When IMA occlusion was superimposed on left circumflex coronary artery (LCX) occlusion, LAD zone perfusion declined by 34% (relative to LCX occlusion alone), significantly impairing regional contraction. Treatment with either acidic FGF plus heparin or heparin alone improved IMA-derived collateral flow; however, addition of acidic FGF to heparin afforded no additional advantage over heparin by itself. We conclude that acidic FGF did not enhance myocardial angiogenesis in this model. IMA-derived collateral flow has significant functional importance; however, it is evident in the dog only when other sources of collateral flow are compromised.
Stopped-flow epicardial lymph pressure is affected by left ventricular pressure in anesthetized goats
Authors: Han Y. , Vergroesen I. , Spaan J. A.
Published: December 2017

We measured epicardial lymph pressure (Plymph) in the anesthetized goat (n = 5 goats). To study the transmission of systolic left ventricular pressure (PLV) to Plymph, the effect of an increase in PLV caused by clamping of the descending aorta on Plymph was evaluated. Peak systolic PLV was 131 +/- 4 (+/- SE) mmHg during control (43 beats) and 188 +/- 4 mmHg when elevated due to aortic clamping (157 beats). Peak systolic Plymph was 24.8 +/- 1.0 and 34.8 +/- 1.1 mmHg during control and elevated PLV, respectively. In the first beat of elevated PLV, peak Plymph did not change, although the pressure waveform did. In the subsequent beats, Plymph increased proportionally with increased PLV. When PLV was decreased back to control, Plymph also decreased but did not reach control level until after three beats. The relationship between normalized Plymph and normalized PLV is given by Plymph = 0.70 x PLV + 0.09. The results show that PLV does affect Plymph in a normal beating heart.