bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction of neutrophils and endothelium in isolated coronary venules and arterioles
Authors: Yuan Y. , Mier R. A. , Chilian W. M. , Zawieja D. C. , Granger H. J.
Published: December 2017

This study reports measurements of porcine neutrophil dynamics in isolated microvessels. Porcine coronary venules and arterioles were isolated, cannulated, and perfused with fluorescently labeled neutrophils at a series of flow velocities. In venules (62.50 +/- 5.41 microns diam) under control conditions, rolling neutrophils were often observed at intraluminal flow velocities ranging from 600 to 6,000 microns/s, and the rolling fraction varied inversely as a function of flow velocity. There was no significant adherence under the control conditions at any of the various flow velocities. Pretreatment of the neutrophils with human recombinant complement 5a (C5a, 10(-8) M) increased adherence at low flow velocities but did not alter the rolling fraction. In contrast to venules, rolling neutrophils were not observed in arterioles (58.80 +/- 5.6 microns diam). Furthermore, neutrophils that were pretreated with C5a did not adhere to the arteriolar endothelium even at low flow velocities. We suggest that 1) isolated microvessels perfused with fluorescently labeled neutrophils are suitable models for the study of the interaction between neutrophils and the microvascular endothelium, 2) shear force plays an important role in neutrophil rolling in coronary venules but is not the major factor that prevents neutrophil rolling and adherence in arterioles, and 3) C5a causes neutrophil adherence in venules but not in arterioles, indicating that different mechanisms underlie the interaction between neutrophils and endothelium in venules and arterioles.
Protein synthesis and rapid recovery of endothelium-dependent dilation after endothelial injury of pial arterioles
Authors: Rosenblum W. I. , Nelson G. H. , Murata S.
Published: December 2017

A laser-dye technique is known to injure selectively microvascular endothelium in situ. With the use of the arterioles on the surface of the mouse brain (pial arterioles), the endothelial injury is manifest by loss of several endothelium-dependent responses, including the dilation produced by topical application of acetylcholine (ACh), bradykinin (BK), and calcium ionophore A-23187. The responses normally recover by 60 min following injury. The present study shows that inhibitors of protein synthesis prevent the recovery. Either actinomycin D (Act-D; 1 mg/kg) or cycloheximide (CX; 10 mg/kg) was injected intraperitoneally 35 min before the light-dye injury. The CX was used in separate studies with ACh, BK, and ionophore. In each study, recovery of the endothelium-dependent dilation failed to occur 60 min after injury, while recovery occurred in contemporary vehicle-treated controls. Act-D was used in separate studies of ACh and BK. Again, recovery of endothelium-dependent dilation was prevented. Neither CX nor Act-D inhibited the response to ACh in uninjured vessels. Thus response to ACh was intact in such arterioles 90 min after the injection of CX or Act-D. CX was also given to uninjured mice and was found to have no inhibitory action on the response to ionophore 90 min later. CX and Act-D inhibit protein synthesis by very different mechanisms, inhibition of translation and of transcription, respectively. Because both prevented recovery of the endothelium-dependent responses, we conclude that one or more rapidly synthesized proteins are required for the recovery.
Aging and vasoreactivity: in vivo responses in the beagle hindlimb
Authors: Haidet G. C. , Wennberg P. W. , Rector T. S.
Published: December 2017

The purpose of this investigation was to determine whether vasodilator responses are attenuated and whether vasoconstriction is augmented with age in resistance vessels in the hindlimb of the dog. We examined blood flow (FAF) and pressure (FAP) responses in the femoral arterial system in older (109 +/- 8-mo-old) and younger mature (31 +/- 3-mo-old) female beagles during pentobarbital anesthesia. Vasodilator responses were evaluated during the intra-arterial administration of acetylcholine (ACh), which produces endothelium-dependent vasodilation, and albuterol, which mediates relaxation in vascular smooth muscle via beta-adrenoceptors. The vasoconstrictor response to phenylephrine (PE), an alpha-adrenergic agonist, was also examined. ACh and albuterol each induced dose-dependent vasodilation in the older and in the younger dogs. Resultant changes in neither FAF nor FAP were affected by age in response to either of these vasodilator substances. Likewise, reductions in femoral vascular resistance (FVR) in response to ACh or to albuterol were not age dependent. Vasodilation following induced hindlimb ischemia resulted in similar increases in FAF in both groups, but produced a greater reduction in FAP in older vs. younger dogs (P = 0.05). Similarly, FVR decreased more in the older beagles (P = 0.02). Vasoconstriction mediated by PE resulted in similar reductions in FAF in both age groups, but the increase in FAP was less at several PE doses in older vs. younger dogs (P < 0.05). However, increases in FVR in response to PE were not statistically different in the younger and older beagles.(ABSTRACT TRUNCATED AT 250 WORDS)
Pressure wave propagation and input impedance in thoracic aorta of conscious newborn sheep
Authors: Adamson S. L. , Whiteley K. J. , Langille B. L.
Published: December 2017

Aortic hemodynamics were examined in eight conscious newborn sheep. Flow and pressure in the thoracic aorta and pressure in the distal abdominal aorta were measured under control conditions and during pressure changes caused by bottle feeding or during intravenous infusions of nitroprusside, norepinephrine, or angiotensin II. Vasoconstriction affected aortic impedance, pressure wave amplification, and wave velocity similarly whether induced by feeding or by drugs. Central hemodynamics in the lamb were surprisingly similar to hemodynamics in the sheep fetus despite major changes in cardiovascular function at birth, largely because pressure-related increases in pulse wave velocity postpartum compensated for increased arterial lengths and increased heart rate. Wave reflection effects on pressure-flow relations were more prominent during vasoconstriction and less prominent during nitroprusside. Wave reflections in both lambs and fetal sheep return to the heart in early diastole; therefore, they do not add to ventricular afterload. Early diastolic return of reflected waves characterizes adults of many species, and demonstration of the phenomenon throughout the perinatal period reinforces arguments for its adaptive value.
Increased thromboxane-mediated contractions of retinal vessels of newborn pigs to peroxides
Authors: Abran D. , Varma D. R. , Chemtob S.
Published: December 2017

The vasomotor effects of three peroxides (H2O2, cumene hydroperoxide, and t-butyl hydroperoxide) on the retinal vasculature, as well as the role of thromboxane in these effects, were studied using time-frame photography of isolated eyecup preparations from newborn and adult pigs. All three peroxides caused constriction of retinal arteries and veins, and these effects were greater in the newborn than in the adult. The cyclooxygenase inhibitor indomethacin, the thromboxane synthase blocker CGS-13080, and the thromboxane receptor blockers GR-32191B and L-670,596 inhibited the peroxide-induced vasoconstriction. The peroxides also increased thromboxane levels in the retina, and this increase was greater in newborn than in adult tissues. Both indomethacin and CGS-13080 prevented the peroxide-induced increase in retinal thromboxane. The thromboxane analogue U-46619 also produced constriction of newborn and adult retinal vessels, but its effects on the retinal veins of newborn pigs were less than those on adult veins. Data indicate an important role for increased production of thromboxane in the relative increase in the vasoconstrictor effects of peroxides on the newborn retinal vasculature. These findings suggest that the vasoconstriction and occlusion after oxidative stresses, which precede retinal neovascularization, are mediated by thromboxane.
CaMKII is responsible for activity-dependent acceleration of relaxation in rat ventricular myocytes
Authors: Bassani R. A. , Mattiazzi A. , Bers D. M.
Published: December 2017

We investigated the role of Ca/calmodulin-dependent protein kinase (CaMKII) in relaxation and cytosolic free [Ca] ([Ca]i) decline during steady-state (SS) and postrest (PR) twitches in intact rat ventricular myocytes. Half-time of mechanical relaxation and time constant of [Ca]i decline (tau) were twofold greater during PR than with SS at 1 Hz. This difference was 1) abolished by inhibition of sarcoplasmic reticulum (SR) Ca accumulation by thapsigargin or caffeine; 2) greater at higher stimulation frequency and extracellular [Ca], which affected only SS tau; 3) abolished by the protein phosphatase inhibitor okadaic acid (10 microM, which selectively accelerated [Ca]i decline during PR); 4) still present during stimulation or inhibition of adenosine 3',5'-cyclic monophosphate-dependent protein kinase (PKA) by 10 microM forskolin or 1 microM H-89, respectively (SS and PR tau values were abbreviated and prolonged, respectively); and 5) suppressed by 10 microM KN-62, a selective inhibitor of CaMKII, which selectively prolonged [Ca]i decline during SS twitches. Both protein kinase inhibitors were also shown to decrease the SR Ca-uptake rate in digitonin-permeabilized rat myocytes. We conclude that CaMKII plays a major role in modulation of relaxation in rat ventricular myocytes, enhancing SR Ca uptake in a activity-dependent fashion. Our results are also compatible with a background, activity-independent stimulation of SR Ca uptake by PKA in intact rat myocytes.
Cholinergic and alpha-adrenergic coronary vasomotion [corrected] with increasing ischemia-reperfusion injury
Authors: Ehring T. , Krajcar M. , Baumgart D. , Kompa S. , Hummelgen M. , Heusch G.
Published: December 2017

Ischemia-reperfusion-induced injury of the coronary vasculature could result in an attenuated vasodilator or increased vasoconstrictor tone that might impact on myocardial recovery and viability. In 30 open-chest dogs the left circumflex coronary artery was occluded for 15 or 60 min and then reperfused, and responses to intracoronary acetylcholine, the alpha 1-adrenergic agonist methoxamine, and the alpha 2-adrenergic agonist BHT-933 (n = 10 each) were measured. In the experiments with 60 min of occlusion, triphenyltetrazolium chloride (TTC) staining was used to distinguish reversibly (TTC+) and irreversibly (TTC-) injured myocardium. After 15 min of occlusion, the vasodilator response to acetylcholine was not altered but was significantly reduced in TTC+ subendocardium and midmyocardium after 60 min of occlusion and was further reduced in TTC- subendocardium, midmyocardium, and also in subepicardium. The vasoconstrictor responses to methoxamine and BHT-933 were not altered after 15 or 60 min of occlusion in both TTC+ and TTC- myocardium. Posterior wall thickening was not affected by acetylcholine, methoxamine, or BHT-933. Thus, in reversibly injured myocardium after 15 min of occlusion, cholinergic and alpha-adrenergic coronary vasomotor responses are unchanged. With increasing duration of ischemia, reversibly and even more so irreversibly injured reperfused myocardium are characterized by an impaired cholinergic coronary vasodilation but not an enhanced alpha-adrenergic coronary vaso-constriction.
Angiotensin II inhibition of L-type Ca2+ current in sinoatrial node cells of rabbits
Authors: Habuchi Y. , Lu L. L. , Morikawa J. , Yoshimura M.
Published: December 2017

The actions of angiotensin II (ANG II) were examined in the spontaneously active cells isolated from the rabbit sinoatrial node, using the nystatin-permeabilized, whole cell, patch-clamp method. At 30 nM, ANG II significantly lowered the spontaneous firing rate of the action potentials from 212 +/- 21 to 172 +/- 32 beats/min, with a concomitant reduction in the action potential amplitude. The voltage-clamp experiments showed that ANG II inhibited the L-type Ca2+ current (ICa) with a dissociation constant (Kd) of approximately 4 nM and a maximal inhibition of 30%. The inhibition was blocked by an AT1-receptor antagonist CV11974. Acetylcholine (ACh) at 10 microM reduced the ICa by 42 +/- 12%, and ANG II did not cause any further inhibition in the presence of ACh. At 100 nM, ANG II reduced the ICa by only 12% in the presence of 2 microM isoproterenol, and a similar inhibition was observed with 0.1 microM ACh. ANG II did not affect the dibutyryl adenosine 3',5'-cyclic monophosphate-stimulated ICa. Protein kinase C activator 12-O-tetra-decanoylphorbol-13-acetate did not mimic ANG II in the effects on ICa, and preincubation of the cells with calphostin C, a protein kinase C inhibitor, did not attenuate the ANG II effect. ANG II exerts a negative chronotropic effect in the pacemaker cells as its direct action through a pathway involving adenosine 3',5'-cyclic monophosphate-dependent protein kinase.
Alternations in liver hemodynamics in an intact porcine model of endotoxin shock
Authors: Ayuse T. , Brienza N. , Revelly J. P. , O'Donnell C. P. , Boitnott J. K. , Robotham J. L.
Published: December 2017

Septic shock decreases preload, increases splanchnic blood pooling and edema formation, and induces hepatic dysfunction. We hypothesized that the hemodynamic effects of endotoxemic shock on the portal venous (PV) and hepatic arterial (HA) vascular beds contribute to this picture. Multipoint pressure-flow relationships were generated to evaluate the slope (resistance or conductance) and effective back pressure (Pback) in each bed in an intact porcine model of endotoxemia. Slope and Pback were determined during endotoxemia over 300 min (n = 8) and compared with sham-treated control studies (n = 5). At time (t) = 60 min, HA slope significantly decreased (P < 0.05) without a change in Pback. The HA buffer response (HABR), defined as a decrease in HA resistance produced by reduction in PV flow (Qpv), was abolished at t = 90 min. The PV Pback significantly increased without a change in PV slope. At t = 300 min, HA slope returned to baseline, and the HABR was present while PV slope and Pback increased (P < 0.05). Fractional flow (flow relative to cardiac output) was constant except for a transient increase in HA fractional flow at t = 60 min. Histological studies showed focal necrosis and hemorrhage without evidence of vasoconstriction or thrombosis. In conclusion, endotoxic shock leads to time-dependent impairment of Qpv with increased PV resistance, causing an increase in splanchnic blood pooling and subsequent decrease in venous return. The HA bed is dilated early with an absent HABR. Later an HABR is present but defined by increased HA resistance for a given Qpv.(ABSTRACT TRUNCATED AT 250 WORDS)
Transient adenosine infusion before ischemia and reperfusion protects against metabolic damage in pig hearts
Authors: Yokota R. , Fujiwara H. , Miyamae M. , Tanaka M. , Yamasaki K. , Itoh S. , Koga K. , Yabuuchi Y. , Sasayama S.
Published: December 2017

We investigated whether transient adenosine (Ado) infusion before ischemia had the same effect on myocardial metabolism and function as ischemic preconditioning (IP). The control (C) group underwent 15 min of coronary artery occlusion followed by 120 min of reperfusion. The Ado group received a 15-min infusion of Ado (200 micrograms.kg-1.min-1) into the left atrium starting 20 min before ischemia. IP was elicited by two cycles of 5-min ischemia and 5-min reperfusion. In the area at risk, tissue levels of ATP, creatine phosphate (CP), and intracellular pH (pHi) were serially measured by 31P-nuclear magnetic resonance spectroscopy in 10 pigs from each group, and percent segment shortening (%SS) was measured in 7 pigs from each group. ATP and pHi were preserved after 15 min of ischemia in both Ado and IP groups [ATP = 64 +/- 7, 76 +/- 6, and 74 +/- 9% of baseline; pHi = 6.35 +/- 0.19, 6.54 +/- 0.11, and 6.64 +/- 0.11 in C, Ado, and IP groups, respectively (P < 0.05, Ado and IP vs. C)]. During reperfusion, ATP was restored progressively in both groups [71 +/- 7, 90 +/- 8, and 91 +/- 9% of baseline at 120 min of reperfusion in C, Ado, and IP groups, respectively (P < 0.05, Ado and IP vs. C)]. However, in contrast to the IP group, CP was not preserved during 15-min ischemia nor did it show persistent overshoot during reperfusion in the Ado group. There were no significant differences in %SS during ischemia and reperfusion among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Functional capillary organization in striated muscle
Authors: Berg B. R. , Sarelius I. H.
Published: December 2017

In striated muscle, capillaries occur as independent network groups. Network architecture was quantitated in cremaster muscle of pentobarbital sodium-anesthetized hamsters in three age groups [51 +/- 1 (SE), 65 +/- 1, and 79 +/- 1 days old]. We observed that networks consist of independent subgroups of capillaries, called modules. Module architecture did not vary significantly with age during maximal dilation (Max, 10(-4) M adenosine): tissue area (A) = 1.87 +/- 0.16, 1.19 +/- 0.13, and 1.81 +/- 0.3 x 10(5) microns 2; total segment length (sigma L) = 3.07 +/- 0.23, 2.15 +/- 0.21, and 3.02 +/- 0.45 x 10(3) microns; and segment number (N) = 14.5 +/- 1.1, 9.9 +/- 1.1, and 12.6 +/- 1.6, at ages 51, 65, and 79 days, respectively. Max module architecture was not different at 65 days of age at a second site of known higher O2 inflow: A = 2.03 +/- 0.32 x 10(5) microns 2; sigma L = 3.07 +/- 0.47 x 10(3) microns; and N = 13.1 +/- 2.1. During control conditions (Rest) there was also no significant difference with age: A = 1.68 +/- 0.18, 1.15 +/- 0.19, and 1.64 +/- 0.24 x 10(5) microns 2; sigma L = 2.31 +/- 0.23, 1.91 +/- 0.33, and 2.82 +/- 0.37 x 10(3) microns; N = 10.2 +/- 1.0, 7.8 +/- 1.3, and 11.0 +/- 1.4, at ages 51, 65, and 79 days, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Comparison of myocardial ischemia induced by endothelin vs. mechanical stenosis in pigs
Authors: Watanabe S. , Buffington C. W. , Moresea G.
Published: December 2017

We have determined the transmural distribution of myocardial flow and ischemia during endothelin (ET-1) infusion and compared these results with the effects of mechanical stenosis. In anesthetized pigs, coronary flow was reduced 15, 30, and 50% from baseline values with a mechanical stenosis (n = 7) or increasing doses of intracoronary ET-1 (n = 8). The inner-to-outer flow ratio decreased with decreasing total flow during mechanical stenosis, and S-T segment elevation occurred predominantly in the subendocardium. In contrast, the inner-to-outer flow ratio exceeded 1.0 and actually increased during ET-1 infusion. ET-1 limited the electrocardiographic evidence of subendocardial ischemia and attenuated contractile dysfunction compared with mechanical stenosis at the same coronary flows, even though lactate flux was similar. Reactive hyperemia was retained with ET-1, even when coronary flow was reduced enough to cause lactate production. These results demonstrate a more uniform transmural distribution of flow caused by microvascular constriction than by a large-vessel stenosis.
Validation of 1- and 2-mm transit-time ultrasound flow probes on mesenteric artery and aorta of rats
Authors: D'Almeida M. S. , Gaudin C. , Lebrec D.
Published: December 2017

The aim of this investigation was to validate and calibrate the 1- and 2-mm transit-time ultrasound, perivascular flow probes on the superior mesenteric artery and aorta of the rat by using an in vivo and in situ calibration system. The baseline blood flows measured by the flowmeter zero-flow function and the true-zero flow measurement, after complete occlusion of the vessels, were not different. The probes were then calibrated, in situ, by timed-volume measurements with a blood/saline pump-perfused circuit. The relationship between measured flow and true flow was linear for both probes. The slope of the 1-mm probe data was not significantly different from the line of identity, whereas the 2-mm probe data slightly overestimated the true flow (slope = 1.2, y-intercept = -3.2 ml/min). The slope of the middle region of the 2-mm probe data, however, was not significantly different from the line of identity, suggesting that the 2-mm probe has a window of accuracy over this range of flows. Progressive elimination of the low and high data points varying the most from the line of identity and reanalysis of the data revealed that the window of accuracy for the 2-mm probe, under our experimental conditions, was between 10.4 and 45.1 ml/min.
Effect of perfusion pressure on diastolic stress-strain relations of isolated rat papillary muscle
Authors: Allaart C. P. , Sipkema P. , Westerhof N.
Published: December 2017

The effect of perfusion on diastolic muscle properties was investigated in six isolated right ventricular papillary muscles from rat hearts perfused with a crystalloid solution via the septal artery. Stress-strain relations were obtained at different perfusion pressures. Increased perfusion pressure caused an increase of stress at large strains but a decrease of stress at low strains. Thus stress-free strain increased with increasing perfusion pressure. Stress-strain relations of a given muscle at different perfusion pressures (range 12–122 cmH2O) intersected at a single “crossover” strain. Muscle stiffness, defined as the slope of the stress-strain relation, increased at all strains. Muscle diameter measurements indicated that the observed changes of the stress-strain relation occurred in association with vascular filling rather than with formation of edema. To explain the findings, the papillary muscle was modeled by two parallel compartments: muscle cells (together with the extracellular matrix) and vasculature. Perfusion was assumed to have an effect on the axial vascular properties but not on muscle cells. Combination of the stress-strain data of the muscle compartment and the vascular compartment (taken from literature) predicted stress-strain relations similar to those obtained in our perfused papillary muscles. We conclude that increased muscle stiffness at increased perfusion pressure is mainly caused by pressure-dependent changes in mechanical behavior of the vascular compartment.
ATP-MgCl2 restores depressed endothelial cell function after hemorrhagic shock and resuscitation
Authors: Wang P. , Ba Z. F. , Chaudry I. H.
Published: December 2017

Although ATP-MgCl2 produces beneficial effects following various adverse circulatory conditions, it remains unknown whether this agent restores the depressed endothelial cell function [i.e., the reduced release of endothelium-derived nitric oxide (EDNO) and endothelium-derived contracting factors (EDCF)] in a model of trauma-hemorrhage and resuscitation. To determine this, rats underwent laparotomy (i.e., trauma induced), were bled to and maintained at a mean arterial pressure of 40 mmHg until 40% of shed blood volume was returned in the form of Ringer lactate (RL). The animals were then resuscitated with four times the volume of maximal bleedout with RL, following which ATP-MgCl2 (50 mumol/kg body wt) or saline was administered. At 1.5 h postresuscitation, the aorta and superior mesenteric artery (SMA) were isolated, and dose-responses for acetylcholine (ACh, an endothelium-dependent vasodilator, via EDNO) and nitroglycerin (an endothelium-independent vasodilator) were determined. In addition, hypoxia-induced contraction, a process mediated by EDCF, was assessed. The results indicate that the decreased endothelium-dependent relaxation after hemorrhage (sham 94 +/- 3 and 97 +/- 3% vs. hemorrhage 64 +/- 5 and 57 +/- 11% at 10-5 M ACh in aorta and SMA, respectively, P < 0.05) was restored with ATP-MgCl2 treatment. In contrast, there was no significant difference in nitroglycerin-induced relaxation. Moreover, the decreased hypoxia-induced aortic contraction after hemorrhage (sham 221 +/- 26 mg/ring vs. hemorrhage 124 +/- 22 mg/ring, P < 0.05) was attenuated by administration of ATP-MgCl2.(ABSTRACT TRUNCATED AT 250 WORDS)
Technical aspects of evaluating brachial artery vasodilatation using high-frequency ultrasound
Authors: Corretti M. C. , Plotnick G. D. , Vogel R. A.
Published: December 2017

Flow-mediated brachial artery vasoactivity has been recently proposed as a noninvasive means for assessing endothelial function. To better characterize this technique, we measured brachial artery diameter and flow using 7.5-MHz ultrasound following 1, 3, and 5 min of upper arm blood pressure cuff occlusion in 19 normal volunteers and 13 patients with coronary artery disease (CAD). Although similar flow increases were observed with each protocol, statistically significant vasodilatation (12.6 +/- 5.7%) was observed in the normals only after 5 min of occlusion. With the use of this protocol, postocclusion blood flow increased 528 +/- 271 and 481 +/- 247% in the normals and CAD patients, respectively (P = NS). More vasodilatation was observed in the normals compared with the CAD patients (11.3 +/- 5.4 vs. 1.6 +/- 5.2%, P < 0.001). Interestingly, vasodilatation persisted for 20 min despite return of blood flow to baseline in 2 min. With the use of lower arm occlusion, arterial diameter was found to decrease 4.4 +/- 3.9% in response to a 85 +/- 7% decrease in flow. We conclude that 1) longer brachial artery occlusion results in more vasodilatation despite similar hyperemic responses, 2) vasodilatation persists substantially beyond hyperemia, and 3) CAD patients have impaired flow-mediated vasodilatation using this noninvasive technique.
Exposure of energy-depleted rat trabeculae to low pH improves contractile recovery: role of calcium
Authors: van Hardeveld C. , Schouten V. J. , Muller A. , van der Meulen E. T. , Elzinga G.
Published: December 2017

The beneficial effect of low pH during cardiac ischemia on reperfusion injury has often been attributed to its energy-saving effect due to inhibition of contraction. The role of low pH on Ca2+ accumulation and muscle tension was assessed in energy-depleted tissue by changing the pH of the medium from 7.4 to 6.2 at onset of rigor development during metabolic inhibition (MI), i.e., in the energy-depleted phase. Cytosolic free Ca2+ ([Ca2+]i) and intracellular H+ (pHi) were measured in rat trabeculae at 20 degrees C with fura 2 and 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, respectively, and tension was recorded. The preparations were energy depleted by stimulation at 1 Hz in glucose-free Tyrode solution with 2 mM NaCN. Rigor developed within 20 min, indicating energy depletion. Resting [Ca2+]i was followed during 50 min (group I) or 100 min (group II) of rigor, and recovery was followed for 60 min in glucose-containing Tyrode solution at 0.2-Hz stimulation. Resting [Ca2+]i rose within 50 min (group I) but stabilized in the 50- to 100-min period (group II). All preparations from group I (n = 5) resumed contraction in the recovery period but in group II (n = 10) 70% failed to recover, and [Ca2+]i remained elevated compared with those that recovered. An extracellular pH of 6.2, resulting in similar pHi, from onset of rigor development (group III) led to only a modest rise in [Ca2+]i during the 100-min rigor period, and all preparations resumed contraction after approximately 3 min in normal medium. ATP was very low in all groups at the end of MI but was still significantly lower in group II than in groups I and III. A beneficial energy-sparing effect of low pH during the rigor phase can therefore not be excluded. We conclude that 1) the capacity of trabeculae to recover from MI depends on the time period and magnitude of the [Ca2+]i rise in the energy-depleted phase and 2) low pH in energy-depleted trabeculae protects against Ca overload, improving recovery after normalization of perfusion conditions.
New insights into the physiology of retrograde cardioplegia delivery
Authors: Villanueva F. S. , Spotnitz W. D. , Glasheen W. P. , Watson D. D. , Jayaweera A. R. , Kaul S.
Published: December 2017

Although retrograde cardioplegia (RC) is being increasingly used in clinical practice, its physiology is unclear. Because the microvascular architecture of the coronary venous system is different from that of the arterial system, we hypothesized that myocardial perfusion would be different during RC compared with anterograde cardioplegia (AC) delivery. To better understand these differences, three groups of dogs were studied during similar RC and AC flow rates. Radiolabeled microsphere-derived microvascular flow underestimated total cardioplegia flow by 66% during RC. For the same flows, the first-pass extraction fractions of 201Tl and 99mTc were significantly less during RC compared with AC despite adjusting for microsphere loss. Myocardial contrast echocardiography (MCE), however, provided an accurate estimation of AC and RC flow rates. In addition, the rate of myocardial cooling for most of the left ventricular myocardium was similar for AC and RC at the same flow rates, as long as the flow rates were brisk. It is concluded that microvascular and nutrient flows are significantly lower at the same flow rates during RC compared with AC due to loss of RC at different microvascular sites. Unlike microspheres and diffusible radioisotopes, MCE can provide a reliable measure of myocardial flow during RC delivery. Furthermore, myocardial cooling is similar in most of the myocardium during high-flow RC and AC, which suggests that the clinical benefits of RC are probably related to myocardial cooling and that substrate replenishment may be better achieved at the same flow rates and myocardial temperatures with AC rather than RC.
Viscoelastic behavior of "in situ" aortic wall during hemorrhagic hypotension
Authors: Xavier-Neto J. , Krieger E. M.
Published: December 2017

Viscoelastic and electrophysiological mechanisms have been implicated in resetting of baroreceptors in hypertension, but resetting in response to hypotension has been less exhaustively studied. To assess the importance of viscoelastic mechanisms in hypotension, we examined the behavior of the "in situ" aorta during hemorrhage. Fifteen minutes of hemorrhage in anesthetized Wistar rats produced stable hypotension (30 mmHg) and a progressive contraction of the mean aortic caliber (-93.8 +/- 18.0 microns, P < 0.05) compared with control measurements. Contraction was not altered by sinoaortic denervation, vagotomy, nephrectomy, adrenalectomy, hexamethonium (30 mg/kg), losartan (10 mg/kg), V1 antagonist (10 micrograms/kg), arterial pH and blood gas control, or indomethacin (3.0 mg/kg). Aortic contraction was greater in rats treated with N omega-nitro-L-arginine (-164.0 +/- 43.0 microns, P < 0.05) than in those treated with sodium nitroprusside (-54.1 +/- 7.5 microns, P < 0.05). The results indicate that aortic contraction is compatible with viscoelastic contraction and suggest that shortening of viscoelastic elements in series with baroreceptor endings increases stress at the baroreceptor membrane and contributes to the development of baroreceptor resetting to hypotension.
Unaltered size of right ventricular infarct in dogs with right ventricular hypertrophy induced by pressure overload
Authors: Tsumoto S. , Kawashima S. , Iwasaki T.
Published: December 2017

We investigated whether right ventricular infarct size is increased in the hypertrophied right ventricle. In dogs, we produced chronic pressure overload-induced right ventricular hypertrophy (RVH) and acute pulmonary stenosis (APS) with a similar right ventricular systolic pressure to RVH. Then, in an open-chest model, right coronary artery occlusion for 4 h followed by 1 h of reperfusion was performed in animals with RVH or APS or in controls. Regional myocardial blood flow was measured with nonradioactive colored microspheres. Compared with the control group, regional myocardial oxygen consumption in the right ventricle was increased in the APS but not in the RVH group. The risk area and collateral blood flow were comparable in the three groups. However, the infarct size relative to risk area was increased in the APS group (42.3 +/- 4.9%), but that in the RVH group (21.1 +/- 4.4%) was not different from controls (26.1 +/- 4.2%). Thus right ventricular infarction in the heart with RVH was not increased compared with the normal heart.
Thyroid status and Na(+)-K+ pump current, intracellular sodium, and action potential duration in rabbit heart
Authors: Doohan M. M. , Hool L. C. , Rasmussen H. H.
Published: December 2017

Thyroid status influences the abundance of Na(+)-K+ pumps in the heart. To evaluate whether this phenomenon may contribute to a dependence of the action potential duration (APD) on thyroid status, we induced hypothyroidism in a group of New Zealand White rabbits. Another group was treated similarly but also received triiodothyronine (T3). Right ventricular myocytes were isolated and voltage clamped at -40 mV. We identified Na(+)-K+ pump current (Ipump) as a ouabain-induced shift in holding current. Mean Ipump, measured using patch pipettes containing 10 mM Na+, was 0.24 +/- 0.02 pA/pF in 9 cells from 4 hypothyroid rabbits and 0.48 +/- 0.05 in 10 cells from 4 rabbits treated with T3 (P < 0.001). Because thyroid status influences Na+ influx, we measured intracellular Na+ activity (aiNa) in right ventricular papillary muscles. We found that aiNa was 5.20 +/- 0.42 mM in nine papillary muscles from seven hypothyroid rabbits and 7.62 +/- 0.69 mM in nine papillary muscles from six rabbits treated with T3 (P < 0.01). The effect of thyroid-induced changes in Ipump and aiNa on APD was stimulated with a computer model. The simulations predicted that thyroid-induced changes in Ipump can influence APD. The predicted changes were similar to changes in APD measured in isolated papillary muscles.
Tirilazad mesylate (U-74006F) inhibits effects of endotoxin in dogs
Authors: Zhang H. , Spapen H. , Manikis P. , Rogiers P. , Metz G. , Buurman W. A. , Vincent J. L.
Published: December 2017

The present study explored the effects of a potent antioxidant, the 21-aminosteroid U-74006F, on the systemic and regional hemodynamics and the oxygen extraction capabilities during endotoxic shock. Twenty-four anesthetized dogs were randomized into three groups. Group 1 (n = 8) served as control. Group 2 (n = 8) and group 3 (n = 8) received 2 mg/kg iv of Escherichia coli endotoxin, followed 30 min later by saline infusion. Group 3 was given U-74006F as an intravenous bolus of 80 micrograms/kg followed by an infusion of 10 micrograms.kg-1.min-1, and group 2 received an equivalent volume of vehicle. Tamponade was induced 30 min later to study the oxygen extraction capabilities of the animals. Compared with the endotoxin-alone group, the U-74006F-treated dogs maintained higher mean arterial pressure, cardiac index, stroke volume index, and left ventricular stroke work index and lower pulmonary vascular resistance. They also showed a higher fractional blood flow to mesenteric and renal beds. Endotoxin administration increased whole body critical oxygen delivery (DO2crit) from 7.7 +/- 2.4 to 12.0 +/- 1.9 ml.kg-1.min-1 (P < 0.05), but U-74006F decreased DO2crit to 7.8 +/- 2.0 ml.kg-1.min-1 (P < 0.05 vs. endotoxin alone). Endotoxin decreased critical oxygen extraction ratio (O2ERcrit) from 75.0 +/- 12.7 to 44.3 +/- 8.7% (P < 0.05), but U-74006F increased O2ERcrit to 64.1 +/- 11.2% (P < 0.05 vs. endotoxin alone). U-74006F also decreased endotoxin-induced elevation of mesenteric and renal DO2crit and markedly increased regional O2ERcrit. Systemic and regional blood lactate concentrations were lower in the U-74006F-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of L-arginine analogues on vasomotion of isolated porcine coronary arteries
Authors: Nakaike R. , Shimokawa H. , Yasutake H. , Sumimoto H. , Ito A. , Numaguchi K. , Egashira K. , Takeshige K. , Takeshita A.
Published: December 2017

L-Arginine analogues have been widely used to examine the role of endothelium-derived nitric oxide (NO) in vascular responses; however, the effects of the agents on coronary vasomotion are not fully understood. In this study, we examined the effects of the analogues on vasomotion of isolated porcine coronary arteries. Strips of the porcine coronary artery were suspended for isometric tension recording in Krebs-Henseleit solution. L-Arginine analogues, N omega-nitro-L-arginine methyl ester (L-NAME, 10(-9)-10(-3) M), NG-monomethyl-L-arginine (L-NMMA, 10(-9)-10(-3) M), and NG-nitro-L-arginine (L-NNA, 10(-9)-10(-3) M), caused dose-dependent contractions, which were greater in strips with than in those without endothelium. Those endothelium-dependent contractions were almost abolished by indomethacin (10(-5) M) and FeCl2 (10(-3) M). The latter reduces prostaglandin H2 to 12-heptadecatrienoic acid, which has no vasoconstrictor effect. These results indicate that the L-arginine analogues cause endothelium-dependent contractions that are mediated by prostaglandin endoperoxides and suggest that they have properties other than simple inhibition of NO synthesis in porcine coronary arteries.
Solvent drag of LDL across mammalian endothelial barriers with increased permeability
Authors: Rutledge J. C. , Curry F. E. , Blanche P. , Krauss R. M.
Published: December 2017

We investigated the mechanisms of hamster low-density lipoprotein (LDL) transport across the endothelial barrier in individually perfused venular microvessels in hamster mesentery. These experiments are the first to use microperfusion techniques and quantitative fluorescence microscopy to investigate LDL transport across mammalian microvessel endothelium. The apparent permeability coefficient for hamster LDL, PsLDL, rose from 2.7 x 10(-7) cm/s at control to 23.2 x 10(-7) cm/s at the peak of the biphasic increase in microvessel permeability after exposure of the vessels to 100 microM histamine. Close to the peak, PsLDL rose 1.85 x 10(-7) cm/s for every centimeter of H2O increase in hydrostatic pressure. Thus, at a mean pressure of 11.3 cmH2O, 90% of the LDL flux was coupled to transendothelial water flow by a solvent drag mechanism. The corresponding solvent drag reflection coefficient for hamster LDL was estimated to be approximately 0.8. These results are consistent with sieving hamster LDL (effective radius 14.9 nm) through equivalent pores of approximately 22 nm radius. Similar results were found with human LDL (effective radius 13.2 nm) in hamster microvessels. The results provide a bridge between studies of LDL transport across cultured endothelial barriers, where high diffusive permeability coefficients to LDL may obscure the contributions of solvent drag, and studies in whole animals, where the consequences of sieving of LDL at the vessel wall, even in the high permeability state, have not received much attention.
Lysophosphatidic acid alters cerebrovascular reactivity in piglets
Authors: Tigyi G. , Hong L. , Yakubu M. , Parfenova H. , Shibata M. , Leffler C. W.
Published: December 2017

Effects of the lipid mediator lysophosphatidic acid (LPA) were studied on the cerebral circulation of newborn pigs using closed cranial windows. Topical application of synthetic LPA caused dose-dependent vasoconstriction and inhibited vasodilation to hypercapnia and isoproterenol. These vasodilators elicited a rise in the adenosine 3',5'-cyclic monophosphate (cAMP) content of the cerebrospinal fluid, which was inhibited dose dependently by LPA. Pertussis toxin (1 microgram/ml) completely abolished LPA-induced vasoconstriction and the altered vascular reactivity, and LPA no longer decreased cAMP. Electrophysiological recording of currents evoked by LPA-like lipids in Xenopus oocytes showed that cerebrospinal fluid is normally devoid of LPA-like factors. In contrast, the amount of LPA-like factors generated 4 days after intrathecal injection of autologous blood was in the range of 1-10 microM LPA equivalents. The data indicate that LPA-like bioactive mediators were generated in an intracranial hematoma model and that these phospholipids might play a role in the pathophysiology of altered vascular reactivity often found in posthemorrhagic conditions and could also contribute to the development of posthemorrhagic vasoconstriction.
Effects of chronic supraventricular pacing tachycardia on relaxation rate in isolated cardiac muscle cells
Authors: Zile M. R. , Mukherjee R. , Clayton C. , Kato S. , Spinale F. G.
Published: December 2017

Chronic supraventricular pacing tachycardia (SVT) causes abnormalities in both ventricular and cellular relaxation. The mechanisms causing these abnormalities have not been fully determined. To examine two of the possible mechanisms, a decrease in restoring force or an impairment of the intrinsic myocardial relaxation process, cardiocytes were enzymatically isolated from the left ventricle of pigs subjected to left atrial pacing at 240 beats/min for 3 wk and normal control pigs. SVT caused a decrease in the extent of cardiocyte shortening and the velocity of cardiocyte lengthening. To determine whether the changes in the relaxation velocity merely reflected a concomitant decrease in the extent of cardiocyte shortening (and a resultant decrease in restoring forces) or, in addition, reflected impairment in intrinsic relaxation properties, the relation between cardiocyte relaxation velocity and cardiocyte shortening extent was examined. There was a direct relation between relaxation velocity and shortening extent in both control and SVT cardiocytes. However, SVT decreased the relaxation velocity at any common extent of shortening and decreased the slope of the direct relation (slope 5.91 in control vs. 3.51 s-1 in SVT, P < 0.05). Therefore, these data suggested that SVT caused a primary impairment in the intrinsic myocardial relaxation process independently of a decrease in restoring force.
Evidence for involvement of opioid receptors in ischemic preconditioning in rat hearts
Authors: Schultz J. E. , Rose E. , Yao Z. , Gross G. J.
Published: December 2017

The purpose of the present study was to investigate a possible role of opioid receptors in ischemic preconditioning (PC). To test this hypothesis, anesthetized, open-chest, male Wistar rats were subjected to five different protocols. In group I, the control group was subjected to 30 min of left coronary artery occlusion and 2 h of reperfusion. In group II, ischemic PC was elicited by three 5-min occlusion periods interspersed with 5 min of reperfusion. In group III, naloxone (NL, 3 mg/kg iv), a nonselective opioid antagonist, was given to nonpreconditioned rats 10 min before the 30-min occlusion period. Finally, NL was administered 10 min before preconditioning (NL + PC, group IV) or immediately after the last 5-min preconditioning period (PC + NL, group V). Infarct size (IS) as a percentage of the area at risk (AAR) (IS/AAR) was determined by 2,3,5-triphenyltetrazolium chloride staining. PC resulted in a marked reduction in myocardial IS from 45 +/- 5 to 8 +/- 1 (P < 0.05). NL treatment before or immediately after PC abolished this protective effect; however, NL had no effect on IS in non-PC rats. These results are the first to support the hypothesis that activation of opioid receptors may play an important role in ischemic PC in the rat myocardium.
Capillary perfusion pattern and microvascular geometry in heterogeneous hypoxic areas of hypoperfused rat myocardium
Authors: Vetterlein F. , Prange M. , Lubrich D. , Pedina J. , Neckel M. , Schmidt G.
Published: December 2017

The origin of heterogeneities in tissue oxygenation due to low-flow ischemia was studied in hypoperfused myocardium of anesthetized rats. In frozen sections of myocardial biopsies the localization of increases in NADH fluorescence, an indicator of tissue hypoxia, was compared with microvascular flow distribution and capillary geometry. The latter parameters were accomplished through capillary labeling with indicator dyes in vivo and enzyme-histochemical staining in vitro, respectively. Most NADH-fluorescent areas were found to have developed despite sustained capillary flow. When the fractions of arterial, venous, and intermediate capillary segments were analyzed within circumscribed hypoxic fields (< 200 microns diam), frequencies of 30.7 +/- 6.1, 35.3 +/- 5.3, and 30.8 +/- 5.0%, respectively, were found. In contrast, a significantly higher fraction of arterial segments (63.2 +/- 3.3%) and a lower percentage of venous segments (16.4 +/- 2.5%) were determined in nonhypoxic islands enclosed by hypoxic tissue. These results support the view that the latter zones are located near the arterial portion of the capillary bed where their oxygenation is favored during low-flow states. This effect appears to contribute to the supply heterogeneities in hypoperfused myocardium.
Myocardial electrophysiological effects of neuropeptide Y in dogs
Authors: Kralios F. A. , Anderson F. L. , Hanson G. R. , Kralios A. C.
Published: December 2017

Neuropeptide Y (NPY) exerts coronary vasomotor and inotropic effects on the canine heart. To test whether NPY also exerts regional myocardial electrophysiological effects, dose-response and time course changes resulting from intravenous and regional intracoronary infusions of NPY were obtained in 14 alpha-chloralose-anesthetized dogs. Under constant ventricular pacing, activation (A), recovery (R), and A-R interval (ARI) maps were constructed from multiplexed unipolar surface electrograms recorded simultaneously from 64 sites within a 1.6 x 1.6-cm left ventricular region. Effects were compared with those of vasoactive intestinal peptide (VIP) infusions and supramaximal left ansae subclaviae sympathetic nerve stimulation (SNS). The main finding was a uniform shortening of ARI, which reached a maximum of 8.7 +/- 1.2 ms, or 7% of control (P < 0.001), at about three times the baseline NPY plasma concentration (21.6 +/- 1.9 pg/ml). This effect decayed slowly (> 15 min) along with NPY plasma levels. The effect of similar VIP infusions and of SNS was 11%. Thus, compared with the previously identified maximal effect of adenylate cyclase activation (20%), exogenous NPY exerts a moderate but markedly sustained ventricular myocardial electrophysiological effect, which reaches maximum in relatively low plasma concentrations.
Increased production of tumor necrosis factor and interleukin-6 by arterial wall of aged rats
Authors: Belmin J. , Bernard C. , Corman B. , Merval R. , Esposito B. , Tedgui A.
Published: December 2017

Plasma cytokine levels are enhanced in aged animals and in elderly people. Vascular cells are known to be both targets and sources of cytokines. To investigate the effect of aging on vascular cytokine synthesis, we studied tumor necrosis factor (TNF), interleukin-6 (IL-6), and prostacyclin (PGI2) production by the arterial wall using organoid culture of aorta from 10- (n = 8) and 30-mo-old (n = 8) rats, after activation by lipopolysaccharide (LPS). Biological activity of TNF and IL-6 was measured in supernatant from incubated vessels. 6-Ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), a stable metabolite of PGI2, a secondary inflammatory mediator, was measured using enzyme immunoassay. In the absence of LPS, TNF production was undetectable in most animals and was not significantly increased in the aged group. By contrast IL-6 and 6-keto-PGF1 alpha productions, in the absence of LPS, were significantly greater in 30- (8,140 +/- 1,350 U/micrograms DNA and 23.2 +/- 6.4 ng/micrograms DNA, respectively) than in 10-mo animals (3,060 +/- 350 U/micrograms DNA and 8.4 +/- 1.6 ng/micrograms DNA, P < 0.01 and P < 0.05, respectively). LPS-induced production of TNF, IL-6, and 6-keto-PGF1 alpha was significantly increased in old rats, being increased respectively by 3.2-, 3.5-, and 2.4-fold at 1 ng/ml LPS, compared with the production in young rats. Because TNF and IL-6 are capable of regulating vascular cell function such as proliferation protein synthesis and contractility, these cytokines might play a major role in age-related remodeling of arteries and age-related vascular diseases.