bluuebunny/crossref_metadata_2025 huggingface dataset:
Left ventricular parallel conductance during cardiac cycle in children with congenital heart disease
Authors: White P. A. , Chaturvedi R. R. , Shore D. , Lincoln C. , Szwarc R. S. , Bishop A. J. , Oldershaw P. J. , Redington A. N.
Published: December 2017

This study examines the accuracy of the conductance catheter technique and, in particular, parallel conductance [expressed as offset volume (Vc)] changes during the cardiac cycle in the human left ventricle. Two groups of patients were assessed: group 1, with an open atrial septal defect, and group 2, with an interventricular communication. In a subgroup, pre- and postoperative data were compared to assess the possible impact of shunting or anatomic considerations on our measurements. Vc is normally obtained by a saline-dilution technique previously described by Baan et al. [Vc(Baan); J. Baan, E. T. Van der velde, H. G. Debruin, G. J. Smeenk, J. Koops, A. D. Van Dijk, D. Temmerman, P. J. Senden, and B. Buis. Circulation 70: 812-823, 1984]. This does not take into account potential changes during the cardiac cycle. Four cardiac cycles were taken from the hypertonic saline washin and were divided into six equal isochrones between the maximum and minimum first derivatives of left ventricular pressure (dP/dtmax and dP/dtmin, respectively). The apparent ventricular volume was regressed against stroke volume for the corresponding cardiac cycle. The volume at the gamma-intercept corresponds to the Vc at each time interval [Vc(t)]. In group 1, there was a variation in Vc(t) during systole, but the temporal changes were quite small, on the order of 4.28% (SD = 5.18%) of total corrected end-diastolic volume (mean maximal variation of 2.60 ml). Furthermore, the value of Vc obtained at dP/dtmax was not significantly different from that obtained at dP/dtmin. For group 2 as a whole, mean Vc(Baan) did not change significantly with ventricular septal defect closure (preoperative, 8.85 +/- 11.1 ml; postoperative, 9.82 +/- 11.84 ml). Group 2 children also exhibited a systolic cyclical variation in Vc(t) similar to group 1. Finally, Vc(t) as a percentage of end-diastolic volume was no different when group 1 and group 2 were compared. We conclude that in the left ventricle, even in the presence of a left-to-right shunt, there is a small but insignificant difference in parallel conductance during ventricular ejection. The magnitude of this cyclical change does not preclude ventricular volume measurement in congenital heart disease by the conductance catheter technique.
Skeletal muscle ischemia-reperfusion causes transitory increase in microvascular protein permeability
Authors: Kupinski A. M. , Bock D. E. , Bell D. R.
Published: December 2017

The aim of this study was to determine whether the length of ischemia in skeletal muscle influences the return of normal microvascular permeability during reperfusion in addition to influencing the size of the initial changes. In anesthetized rabbits, the transvascular clearance of labeled albumin was measured in the gastrocnemius and soleus muscles during the first, second, third, or fourth hour of reperfusion after 1, 2, 3, or 4 h of ischemia. The size of the increases in albumin clearance, tissue water, and myeloperoxidase activity during the first hour of reperfusion was dependent on the length of ischemia. The return of the albumin clearance to control values during the fourth hour of reperfusion was independent of the length of ischemia. Tissue water, extravascular mass of native albumin, and myeloperoxidase activity remained elevated during the 4 h of reperfusion. After 4 h of ischemia, the solvent-drag reflection coefficient for albumin was significantly less than control during the first hour of reperfusion. The value during the fourth hour of reperfusion was not significantly different from control. These results suggest that the inflammatory mediators producing a change in permeability are washed out of the microvasculature during the first few hours of reperfusion.
Inhibition of NO synthesis does not potentiate dynamic cardiovascular response to sympathetic nerve activity
Authors: Miyano H. , Kawada T. , Sugimachi M. , Shishido T. , Sato T. , Alexander J. , Sunagawa K.
Published: December 2017

We examined whether the inhibition of nitric oxide (NO) synthesis potentiates the dynamic sympathetic regulation of the cardiovascular system through the baroreflex. In anesthetized rabbits, we imposed random pressure perturbations on the isolated carotid sinuses to evoke random changes in sympathetic nerve activity (SNA). We estimated the transfer functions from SNA to both aortic pressure (AoP) and heart rate (HR). The inhibition of NO synthesis by NG-monomethyl-L-arginine (L-NMMA, 40 mg/ kg) altered neither the transfer function from SNA to AoP nor that from SNA to HR. In contrast, sodium nitroprusside (3-6 micrograms.kg-1.min-1) significantly decreased the steady-state gain (40.3 +/- 11.7% of the control, P < 0.05) of the transfer function from SNA to AoP without affecting the HR responses. We conclude that the basal release of NO may have a role in the tonic blood pressure regulation, whereas it may not be involved in the dynamic sympathetic regulation of AoP or HR through the baroreflex.
Role of leukocytes in cerebral autoregulation and hyperemia in bacterial meningitis in rabbits
Authors: Slater A. J. , Berkowitz I. D. , Wilson D. A. , Traystman R. J.
Published: December 2017

The effect of leukocytes on regional cerebral blood flow (rCBF) and cerebrovascular autoregulation in experimental meningitis was determined in rabbits. Four groups of animals were studied. Cerebrospinal fluid (CSF) leukocyte migration was prevented in two groups by pretreatment with 1.5 mg/kg of IB4, a monoclonal antibody directed against CD11/18 leukocyte adhesion receptors. Intracisternal inoculation was performed with saline (control and control-IB4 groups) or Haemophilus influenzae type b (Hib and Hib-IB4 groups). Eighteen hours later, rCBF was determined with radiolabeled microspheres. Autoregulation was assessed by graded hemorrhagic hypotension. Compared with untreated meningitis (Hib group), IB4-pretreated meningitis (Hib-IB4 group) was associated with a reduced CSF leukocyte count (1,980 +/- 880 vs. 200 +/- 110 cells/microliter; P < 0.05) and an elevated CSF colony count (2.87 +/- 0.08 vs. 5.63 +/- 0.72 log10colony-forming units/ml; P < 0.05). Compared with control, baseline CBF was elevated in both untreated and IB4-pretreated meningitis (51 +/- 2, 54 +/- 2, 66 +/- 5, and 102 +/- 17 ml.100 g-1.min-1 in control, control-IB4, Hib, and Hib-IB4 groups, respectively). The degree of hyperemia in meningitis was related to the CSF colony count, with a high CBF occurring in animals with high colony counts. During hypotension, CBF remained at or above baseline in the Hib group and both control groups, indicating preservation of cerebrovascular autoregulation in untreated Hib meningitis. In the Hib-IB4 group, the elevated baseline CBF was not maintained during hypotension, falling to 51% of baseline at a cerebral perfusion pressure of 30 mmHg and indicating impairment of cerebrovascular autoregulation. These results suggest that CSF leukocytes are not primarily responsible for the hyperemic response in Hib meningitis. Cerebral hyperemia may be induced either directly by bacterial components or indirectly by components of the inflammatory cascade that precede CSF leukocyte migration.
CRE-like response element regulates expression of rat alpha 2D-adrenergic receptor gene in vascular smooth muscle
Authors: Yang N. , Eckhart A. D. , Xin X. , Faber J. E.
Published: December 2017

Contractile and binding studies indicate that alpha 2-adrenergic receptors (ARs) are differentially expressed by vascular smooth muscle cells (SMCs) according to vascular segment (artery, arteriole, vein). In the present study, alpha 2D-AR mRNA was two- to threefold higher in vena cava than in aorta. To understand vascular regulation of alpha 2D-AR expression in these cells, we sequenced 2.8 kb of the 5' flanking region of the alpha 2D-AR gene. Notable features include two potential TATA boxes, an adenosine 3',5'-cyclic monophosphate response element (CRE)-like binding element, and an Sp1 element. Comparison of the rat and human genes revealed an overall homology of 74% over the 1.87-kb sequence 5' to the translation initiator methionine, including complete homology at the distal TATA, CRE-like, and Sp1 sites, alpha 2D-AR transcription starts from the guanine nucleotide 18 base pair downstream from the distal TATA box. Reporter gene constructs demonstrated strong alpha 2D-AR promoter activity, but with several differences in construct activity, in both rat aorta and vena cava SMCs. Analysis of an essential promoter fragment revealed two regions protected by aorta and vena cava SMC nuclear proteins. The core sequences of these protected regions are TGACGCTA and TATAA. The former CRE-like element conferred specific binding of both aorta and vena cava nuclear proteins. In addition, promoter activity was increased 300% by forskolin or 8-bromoadenosine 3',5'-cyclic monophosphate, indicating that the CRE-like element may regulate alpha 2D-AR expression in vascular tissue.
In vivo adaptive responses of the aorta to hypertension and aging
Authors: Sumitani M. , Cabral A. M. , Michelini L. C. , Krieger E. M.
Published: December 2017

To investigate the dynamic behavior of the aorta of freely moving rats during the maintenance of hypertension, a longitudinal study was performed in renal hypertensive (Goldblatt 1 kidney, 1 clip) rats aged 3, 6, and 9 mo in which hypertension was maintained for 1, 3, and 6 mo, respectively. The pulsatile caliber of the thoracic aorta was measured (electrolytic strain gauge chronically implanted) simultaneously with aortic pressure under basal conditions and during transient changes of blood pressure. Aortic thickness was determined postmortem by morphometry. Establishment of hypertension (179 +/- 5 mmHg) by increasing the stress developed by the aorta caused increases in the resting values of caliber (20%), thickness (21%), and strain (95%); the maintenance of hypertension for a 6-mo period caused a further increase in thickness (58% vs. age-matched normotensive aortas) but not in aortic caliber and strain, the subsequent alterations of which were due only to growth/aging. Although different calibers, thicknesses, and dynamic strains were presented, the stress-strain relationship during transient blood pressure changes was similar for all hypertensive and normotensive groups with the exception of renal hypertensive rats aged 6 mo, which presented a steeper relationship (a large transitory increase in aortic distensibility was observed at that age). Dynamic adaptive responses of the aorta to hypertension compensate for geometric changes in such a way as to maintain a near-constant distensibility. It was concluded that, in contrast to the extrathoracic vessels, the adaptive responses of the aorta to hypertension were directed to maintain its compliance without changing the distensibility and stress-strain relationship, contributing to partially counterbalance the increased pressure and the decreased compliance of the more peripheral components of the arterial tree.
Effects of ionic channel antagonists barium, cesium, and UL-FS-49 on vagal slowing of atrial rate in dogs
Authors: Wallick Don W. , Kuguoglu Akin , Yang Tianen , Stuesse Sherry L. , Levy Matthew N.
Published: December 2017

In response to a brief vagal stimulus, the atrial rate initially slows, then transiently accelerates, and slows a second time. We determined the effects of three antagonists to two ionic channels on this characteristic triphasic pacemaker response. Brief bursts of vagal stimulation were delivered to anesthetized dogs, and atrial cycle lengths were recorded. Either barium, cesium, or UL-FS-49 was administered. Barium, which primarily blocks the acetylcholine-sensitive potassium current ( I K,ACh), attenuated the initial vagally induced bradycardia by >50% without affecting the subsequent acceleration or the secondary slowing. Cesium and UL-FS-49 [both of which primarily block the pacemaker current ( I f)] did not affect the initial vagal slowing of atrial rate but abolished the acceleratory portion of the response. The secondary slowing was abolished by cesium but not by UL-FS-49. We conclude that the initial rapid atrial response to acetylcholine is mediated mainly by the I K,ACh, with little contribution from the I f. The subsequent acceleration is mediated by activation of the I f.
Reduced L-type calcium current in ventricular myocytes from endotoxemic guinea pigs
Authors: Zhong Juming , Hwang Tzyh-Chang , Adams H. Richard , Rubin Leona J.
Published: December 2017

The circulatory response to gram-negative sepsis and its experimental counterpart, endotoxemia, includes a profound dysfunction in myocardial contractility that is resident to the myocyte and associated with reduced systolic free intracellular Ca2+concentration ([Ca2+]i). We explored the possibility that decreased systolic [Ca2+]iin endotoxemic myocytes is correlated with reduced L-type Ca2+current ( ICa,L). Ventricular myocytes were isolated from guinea pigs 4 h after an intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS; 4 mg/kg). Membrane potentials and Ca2+currents were measured using whole cell patch-clamp methods. The action potential duration of endotoxemic myocytes was significantly shorter than control values (time to 50% repolarization: LPS, 314 ± 23 ms; control, 519 ± 36 ms, P < 0.05). Correspondingly, endotoxemic myocytes demonstrated significantly reduced peak ICa,Ldensity (3.5 ± 0.2 pA/pF) and Ba2+current ( IBa) density (7.3 ± 0.5 pA/pF) compared with respective values of control myocytes ( ICa,Ldensity 6.1 ± 0.3 pA/pF, IBadensity 11.3 ± 0.8 pA/pF; P < 0.05). Endotoxemia-induced reduction in peak ICa,Lcould not be attributed to alterations in current-voltage relationships, steady-state activation and inactivation, or recovery from inactivation. The β-adrenoceptor agonist isoproterenol, but not the Ca2+channel activator BAY K 8644, reversed the LPS-induced reduction in peak ICa,L, cell contraction, and systolic [Ca2+]i. These data demonstrate that part of the host response to endotoxemia involves diminished sarcolemmal ICa,Lof ventricular myocytes.
Role of nitric oxide in poly(I-C)-induced endothelial cell expression of leukocyte adhesion molecules
Authors: Faruqi Tatjana R. , Erzurum Serpil C. , Kaneko F. Takao , Dicorleto Paul E.
Published: December 2017

Polyinosinic-polycytidylic acid [poly(I-C)] is a synthetic double-stranded RNA (dsRNA) that simulates a viral-infected state in cells. It has been shown that viral infection, as well as poly(I-C), stimulates leukocyte adhesion to endothelial cell (EC) monolayers and that this is mediated through the surface expression of the adhesion molecules E-selectin, vascular cell adhesion molecule 1 (VCAM-1), and intercellular adhesion molecule 1. We have tested the involvement of nitric oxide (NO) in poly(I-C)-induced monocytic cell adhesion to human vascular EC. Using primary cultured EC for these studies, we confirmed the results from previous reports that these cells have higher basal levels of NO production than passaged cells. Poly(I-C)-induced monocytic cell adhesion to primary EC was concentration-dependently inhibited by 40–74% by the nitric oxide synthase (NOS) inhibitor NG-methyl-l-arginine (l-NMA), as well as three other NOS inhibitors, without significantly affecting interleukin-1β-induced adhesion.l-NMA inhibited poly(I-C)-induced surface expression of E-selectin and VCAM-1 by 25 and 45%, respectively, and mRNA levels of E-selectin and VCAM-1 by 62 and 74%, respectively. Primary EC transiently transfected with a plasmid containing an E-selectin promoter-driven luciferase reporter gene showed that l-NMA treatment reduced poly(I-C)-induced E-selectin promoter activity to basal levels. Electrophoretic mobility shift analysis indicated that poly(I-C)-induced nuclear factor-κB (NF-κB) binding to a radiolabeled oligonucleotide corresponding to the consensus NF-κB binding domain of the E-selectin promoter was decreased byl-NMA pretreatment. Hence, NO appears to augment E-selectin gene expression in response to poly(I-C) at the transcriptional level in vascular EC. Collectively, these data support the hypothesis that NO augments poly(I-C)-induced EC activation. These data suggest a novel role for NO as a response mediator in dsRNA-induced leukocyte adhesion to EC.
Erythrocyte aggregation tendency and cellular properties in horse, human, and rat: a comparative study
Authors: Baskurt Oguz K. , Farley Robert A. , Meiselman Herbert J.
Published: December 2017

Horse blood has a higher tendency to form red blood cell (RBC) aggregates compared with human blood, with this enhanced aggregation previously attributed to differences in plasma factors. Our results confirm this observation and further indicate that washed horse RBC also have a significantly higher aggregation tendency in dextran 70 solutions (i.e., horse RBC have a higher “aggregability”). In contrast, the aggregation tendency of rat RBC, both in autologous plasma and in dextran 70, is significantly less compared with human and horse RBC. Other rheological findings for horse and rat RBC include smaller changes in RBC deformation indexes over the same shear stress range and a lower RBC shape recovery time constant. Rat RBC also had higher two-phase aqueous polymer partition coefficients, suggesting a higher surface charge. Membrane protein analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed marked differences: 1) band 4.2 protein was lacking in horse RBC membranes, and 2) carbohydrate groups have different distributions in human, rat, and horse RBC, as indicated by different patterns in periodic acid-Schiff-stained protein bands. Our results clearly indicate significant differences in RBC aggregability among the three species and indicate that cellular factors contribute importantly to these differences. Furthermore, they suggest that systematic studies of blood and RBC from different species should provide insight into the mechanism(s) of RBC aggregation.
BNP gene expression is specifically modulated by stretch and ET-1 in a new model of isolated rat atria
Authors: Bruneau Benoit G. , Piazza Leonardo A. , De Bold Adolfo J.
Published: December 2017

We have assessed the effects of stretch or endothelin-1 (ET-1) on atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP) secretion and gene expression using a new model of isolated right atria from the rat. This model allows for comparatively long-term in vitro study of adult tissue while retaining the anatomic conformation of the atrium. Stretch and ET-1 resulted in a transient stimulation of ANF and BNP secretion, with an initially larger proportional increase in ANF release. Stretch and ET-1 induced a marked increase in BNP gene expression after 1.5 and 4 h, respectively; the increase in BNP mRNA levels was maintained throughout the 8-h experimental period. Stretch and ET-1 also stimulated c- myc and Egr-1 mRNA levels, two markers of mechanical and receptor-mediated transcriptional activation. The selective response of the BNP gene to stretch and ET-1 and the distinct responses of ANF and BNP secretion indicate that the atrial cardiocytes have the capability to individually regulate the synthesis of its endocrine products. This suggests that each hormone plays a specific role in the response of the heart to hemodynamic or neuroendocrine imbalances.
α-Adrenergic vasoconstriction reduces systolic retrograde coronary blood flow
Authors: Morita Koichi , Mori Hidezo , Tsujioka Katsuhiko , Kimura Akihiro , Ogasawara Yasuo , Goto Masami , Hiramatsu Osamu , Kajiya Fumihiko , Feigl Eric O.
Published: December 2017

There is a paradoxical α-adrenoceptor-mediated coronary vasoconstriction whenever there is adrenergic activation of the heart, as during cardiovascular reflexes or exercise. A previous study demonstrated that this paradoxical vasoconstriction helps maintain blood flow to the vulnerable inner layer of the left ventricular wall during exercise, but the mechanism for this effect was not elucidated. The purpose of the present investigation was to test the hypothesis that α-adrenoceptor-mediated vasoconstriction lessens the to-and-fro oscillation of blood flow that occurs in the coronary arterial tree during systole and diastole. Septal coronary artery blood velocity was measured in anesthetized open-chest dogs with a 20-MHz pulsed Doppler velocimeter. Systolic retrograde velocity and diastolic forward velocity were compared during norepinephrine infusion before and after α-adrenoceptor blockade with phenoxybenzamine. Systolic aortic pressure was held constant by aortic banding; heart rate was controlled by pacing at 80, 140, and 200 beats/min; and maximum left ventricular dP/d t was unchanged by α-blockade. At each pacing rate, systolic retrograde velocity was significantly greater after α-blockade, indicating that α-vasoconstriction reduced systolic retrograde flow by changing coronary vascular impedance. Transmural blood flow was measured with microspheres in a second group of dogs during the same experimental conditions, and flow to the inner layer of the left ventricle was diminished by α-adrenoceptor blockade at a heart rate of 250 beats/min, demonstrating a beneficial effect of α-vasoconstriction. In conclusion, adrenergic α-adrenoceptor-mediated coronary vasoconstriction reduces systolic retrograde coronary flow during norepinephrine infusion. This lessens to-and-fro flow oscillation in the coronary circulation and probably is the mechanism whereby α-vasoconstriction helps maintain blood flow to the inner layer of the left ventricle during exercise.
Forebrain parasympathetic control of heart activity: retrograde transneuronal viral labeling in rats
Authors: Ter Horst Gert J. , Postema Folkert
Published: December 2017

Dysfunction of parasympathetic command neurons may be a cause of cardiac autonomic imbalance, which has been implicated as a pathogenic mechanism of lethal arrhythmias. The locations in the brain of these command neurons are not known. The aim of this investigation is to identify selectively the parasympathetic command neurons in the forebrain. Male Wistar rats were inoculated in the left ventricular myocardium with 2 ml of a 3 × 106 plaque-forming units/ml of a pseudorabies virus (PRV)-Bartha solution. Eighteen hours after the infection the spinal cord was transected at T1. Six of fourteen rats showed PRV-immunoreactive cells in the forebrain after 6 postoperative survival days. Bilaterally, the infections were located in the prelimbic, anterior cingulate, frontal, and insular cortexes, various hypothalamic and midbrain nuclei, the nucleus of the solitary tract, the dorsal motor vagus, and periambiguus nuclei. Control animals receiving intravenous PRV-Bartha injections were not infected. Using transneuronal retrograde viral labeling and spinal cord transection, we were able to localize the forebrain parasympathetic command neurons that maintain cardiac autonomic balance. The virus-infected cells were localized in regions that previously showed susceptibility for immune activation-mediated selective cerebral endothelial leakage. We hypothesize that such selective endothelial leakage could induce autonomic imbalance after myocardial infarction.
Dehydrogenase regulation of metabolite oxidation and efflux from mitochondria in intact hearts
Authors: O’Donnell J. Michael , Doumen Chris , Lanoue Kathryn F. , White Lawrence T. , Yu Xin , Alpert Nathaniel M. , Lewandowski E. Douglas
Published: December 2017

To test how α-ketoglutarate dehydrogenase (α-KGDH) activity influences the balance between oxidative flux and transmitochondrial metabolite exchange, we monitored these rates in isolated mitochondria and in perfused rabbit hearts at an altered kinetics ( Km) of α-KGDH for α-ketoglutarate (α-KG). In isolated mitochondria, relative Kmdropped from 0.23 mM at pH = 7.2 to 0.10 mM at pH 6.8 ( P < 0.05), and α-KG efflux decreased from 126 to 95 nmol ⋅ min−1⋅ mg−1. In intact hearts, Kmwas reduced with low intracellular pH, while matching control workload and respiratory rate with increased Ca2+(pHi= 7.20, perfusate CaCl2= 1.5 mM; pHi= 6.89, perfusate CaCl2= 3 ± 1 mM). Sequential13C nuclear magnetic resonance spectra from hearts oxidizing [2-13C]acetate provided tricarboxylic acid cycle flux and the exchange rate between α-KG and cytosolic glutamate ( F1). Tricarboxylic acid cycle flux was 10 μmol ⋅ min−1⋅ g−1in both groups, but F1fell from a control of 9.3 ± 0.6 to 2.8 ± 0.4 μmol ⋅ min−1⋅ g−1at low Km. The results indicate that increased activity of α-KGDH occurs at the expense of α-KG efflux during support of normal workloads.
Sympathetic innervation modulates repolarizing K+ currents in rat epicardial myocytes
Authors: Liu Qin-Yue , Rosen Michael R. , McKinnon David , Robinson Richard B.
Published: December 2017

During postnatal development, sympathetic innervation of the heart evolves, and repolarization accelerates. Our goal in this study was to test whether sympathetic innervation modulates the ion channels that regulate repolarization. We studied action potentials and repolarizing K+ currents in epicardial myocytes from rats in which sympathetic innervation was accelerated or delayed, respectively, by subcutaneous injection of nerve growth factor (NGF) or NGF antibody (Ab) for the first 15 days of life. A placebo group was included as well. Action potential duration (APD) to 90% repolarization was greater in the Ab (158 ± 18 ms)-treated than the NGF (106 ± 10 ms)-treated animals ( P < 0.05); the APD at 90% repolarization for the placebo group was intermediate (125 ± 30 ms). The transient outward ( I to) and inward rectifier ( I K1) K+ currents were recorded in freshly dissociated cells using the whole cell patch-clamp technique. I to was decreased in density at potentials positive to +40 mV in Ab-treated rats when compared with rats treated with NGF ( P< 0.05). In addition, the inactivation curve of I to in Ab-treated rats was shifted 13 mV positive to that of NGF-treated rats. I K1 also decreased in the Ab-treated group compared with the NGF group in the potential ranges of −100 to −90 mV ( P < 0.05). However, the channel transcript abundance (RNA) in NGF-, Ab-, or placebo-treated rat hearts did not differ. Our results suggest that sympathetic innervation contributes to the developmental differences in K+ currents and APD postnatally in the rat.
Angiogenic potential of perivascularly delivered aFGF in a porcine model of chronic myocardial ischemia
Authors: Lopez John J. , Edelman Elazer R. , Stamler Alon , Hibberd Mark G. , Prasad Pottumarthi , Thomas Kenneth A. , Disalvo Jerry , Caputo Ronald P. , Carrozza Joseph P. , Douglas Pamela S. , Sellke Frank W. , Simons Michael
Published: December 2017

A number of heparin-binding growth factors, including basic (bFGF) and acidic (aFGF) fibroblast growth factors have been shown to promote angiogenesis in vivo. In this study, we employed a sustained-release polymer extravascular delivery system to evaluate the angiogenic efficacy of a novel form of genetically modified aFGF in the setting of chronic myocardial ischemia. Fifteen Yorkshire pigs subjected to Ameroid occluder placement on the left circumflex (LCX) artery were treated with perivascularly administered aFGF in ethylene vinyl acetate (EVAc) polymer (10 μg, n = 7) or EVAc alone (controls, n = 8). Seven to nine weeks later, after coronary angiography to document Ameroid-induced coronary occlusion, all animals underwent studies of coronary flow and global and regional left ventricular function. Microsphere-determined coronary flow in the Ameroid-compromised territory was significantly increased in aFGF-treated compared with control animals, and this improvement in perfusion was maintained during ventricular pacing. Left ventricular function studies demonstrated improved global and regional function in aFGF-treated animals. We conclude that local perivascular delivery of genetically modified aFGF results in significant improvement in myocardial flow and regional and global left ventricular function.
Metabolic inhibition in the perfused rat heart: evidence for glycolytic requirement for normal sodium homeostasis
Authors: Dizon José , Burkhoff Daniel , Tauskela Joseph , Whang John , Cannon Paul , Katz José
Published: December 2017

Subcellular compartmentalization of energy stores to support different myocardial processes has been exemplified by the glycolytic control of the ATP-sensitive K+channel. Recent data suggest that the control of intracellular sodium (Nai) may also rely on glycolytically derived ATP; however, the degree of this dependence is unclear. To examine this question, isolated, perfused rat hearts were exposed to hypoxia, to selectively inhibit oxidative metabolism, or iodoacetate (IAA, 100 μmol/l), to selectively inhibit glycolysis. Naiand myocardial high-energy phosphate levels were monitored using triple-quantum-filtered (TQF)23Na and31P magnetic resonance spectroscopy, respectively. The effects of ion exchange mechanisms (Na+/Ca2+, Na+/H+) on Naiwere examined by pharmacological manipulation of these channels. Nai, as monitored by shift reagent-aided TQF23Na spectral amplitudes, increased by ∼220% relative to baseline after 45 min of perfusion with IAA, with or without rapid pacing. During hypoxia, Naiincreased by ∼200% during rapid pacing but did not increase in unpaced hearts or when the Na+/H+exchange blocker ethylisopropylamiloride (EIPA, 10 μmol/l) was used. Neither EIPA nor a low-Ca2+perfusate (50 μmol/l) could prevent the rise in Naiduring perfusion with IAA. Myocardial function and high-energy phosphate stores were preserved during inhibition of glycolysis with IAA and continued oxidative metabolism. These results suggest that glycolysis is required for normal Na+homeostasis in the perfused rat heart, possibly because of preferential fueling of Na-K-adenosinetriphosphatase by glycolytically derived ATP.
Continuous release of vasodilator prostanoids contributes to regulation of resting forearm blood flow in humans
Authors: Duffy Stephen J. , Tran Binh T. , New Gishel , Tudball Ronald N. , Esler Murray D. , Harper Richard W. , Meredith Ian T.
Published: December 2017

Continuous release of nitric oxide contributes to the maintenance of resting tone in the human forearm and coronary circulations; however, evidence for a similar role of vasodilator prostanoids such as prostacyclin is lacking. We examined whether continuous release of prostacyclin contributes to basal forearm blood flow. Flow was measured using venous occlusion plethysmography in 38 healthy volunteers [mean age 21.3 ± 2.5 yr (±SD); 13 female, 25 male] at rest, after administration of three incremental intra-arterial infusions of either the cyclooxygenase inhibitor aspirin or placebo, and before and after administration of the endothelium-dependent and -independent dilators acetylcholine (30 μg/min) and nitroprusside (1 μg/min). To assess the effect of aspirin on the production of prostacyclin, plasma 6-keto prostaglandin F1α(6-keto-PGF1α; the stable metabolite of prostacyclin) was measured by simultaneous arterial and venous sampling. Aspirin produced a time- and dose-dependent reduction in forearm blood flow, resulting in a 32% decrease at the highest dose. The effect was maximal after 10 min. Flow at rest and after aspirin doses of 1, 3, and 10 mg/min was 2.6 ± 0.2, 2.3 ± 0.2, 2.1 ± 0.2, and 1.8 ± 0.2 ml ⋅ 100 ml forearm tissue−1 ⋅ min−1, respectively (means ± SE, P< 0.001). Commensurate with these data, the net forearm production of 6-keto-PGF1α was 52.9 ± 16.4, 11.7 ± 8.6, 18.7 ± 8.5, and 12.0 ± 12.5 pg ⋅ 100 ml forearm tissue−1 ⋅ min−1 for the respective doses ( P = 0.04). No time-dependent reduction in flow was seen in subjects with vehicle infusion. Aspirin did not affect the responses to acetylcholine or nitroprusside. These data suggest that continuous release of prostacyclin plays a role in the maintenance of resting forearm blood flow. There appears to be a direct link between the reduction in flow with aspirin and inhibition of prostacyclin production.
Cardiovascular responses attenuate with repeated NO synthesis inhibition in conscious fetal sheep
Authors: Chlorakos A. , Langille B. L. , Adamson S. L.
Published: December 2017

The cardiovascular effects of repeated administration of the nitric oxide (NO) synthesis inhibitor N ω-nitro-l-arginine methyl ester (l-NAME) were assessed daily for 3 days in fetal sheep near term (124–126 days gestation) beginning 4 days after surgery ( n = 7). In the first hour on day 1, fetal infusion ofl-NAME (30 mg bolus, 6 mg/min infusion iv for 3 h) significantly increased fetal arterial pressure from 41 ± 2 to 58 ± 3 mmHg, decreased heart rate from 173 ± 5 to 134 ± 3 beats/min, increased umbilicoplacental resistance from 0.16 ± 0.02 to 0.28 ± 0.07 mmHg ⋅ ml−1 ⋅ min, and inhibited the hypotensive response to acetylcholine (ACh; 2 μg iv bolus). All changes were sustained except for arterial pressure, which decreased significantly to 50 ± 3 mmHg in the third hour. Within 17 h, all cardiovascular variables returned to control.l-NAME readministered on days 2 and 3 had no effect on cardiovascular variables. l-NAME did not potentiate the pressor response to angiotensin II on day 2 and caused a surprising attenuation of the pressor response to endothelin-1 on day 3. We conclude that, whereas NO normally contributes to low arterial pressure, high heart rate, and low umbilicoplacental vascular resistance in fetal sheep near term, the role of NO in these functions is replaced by an alternate mechanism within 17 h after NO synthesis inhibition withl-NAME.
Myocardial matrix metalloproteinase activity and abundance with congestive heart failure
Authors: Coker Mytsi L. , Thomas Chadwick V. , Clair Mark J. , Hendrick Jennifer W. , Krombach R. Stephen , Galis Zorina S. , Spinale Francis G.
Published: December 2017

The left ventricular (LV) myocardial collagen matrix has been proposed to participate in the maintenance of LV geometry. Thus alterations in the composition of the LV myocardial collagen matrix may influence LV function. The matrix metalloproteinases (MMPs) are a family of enzymes that contribute to extracellular remodeling in several disease states. However, the types of MMPs expressed in the normal and congestive heart failure (CHF) state and the relation to MMP activity remained unclear. Accordingly, after 3 wk of pacing (240 beats/min), changes in LV function, substrate-specific MMP activity, and MMP subclass abundance were measured in comparison with control pigs ( n = 6). Changes in LV function and geometry were measured by echocardiography; LV end-diastolic dimension increased (3.6 ± 0.1 vs. 6.0 ± 0.1 cm, P < 0.05) and LV fractional shortening decreased (47 ± 1 vs. 15 ± 1%, P < 0.05) compared with controls. Degradation of fibrillar collagen is achieved through the combined action of interstitial collagenase (MMP-1), gelatinase A (MMP-2), and stromelysin (MMP-3) (He, C., S. Wilheilm, A. Pentland, B. Marmer, G. Grant, A. Eisen, and G. Goldberg. Proc. Natl. Acad. Sci. USA 86: 2632–2636, 1989; Woessner, J. FASEB J. 5: 2145–2154, 1991). Accordingly, the relative abundance of specific MMPs (MMP-1, MMP-2, and MMP-3) was examined by immunoblotting. With pacing CHF, the relative abundance for MMP-1 increased to 319 ± 94%, MMP-2 increased to 194 ± 31%, and MMP-3 increased to 493 ± 159% (all P < 0.05). With pacing CHF, LV myocardial zymographic activity for the substrate gelatin increased by 119% ( P < 0.05) and for the substrate collagen III by 153% ( P < 0.05) over controls. Caseinolytic activity also increased with pacing CHF by 139% ( P < 0.05) over controls. In conclusion, LV myocardial MMP activity and abundance increased with pacing-induced CHF. These findings demonstrate that pacing-induced CHF leads to changes in myocardial MMP activity and expression that may be responsible for LV remodeling in CHF.
Effect of BAY y 5959 on myocardial function and metabolism in normal and failing hearts
Authors: Todaka Koji , Wang Jie , Yi Geng-Hua , Gu Anguo , Zhu Shu-Ming , Zhang Hui , Burkhoff Daniel
Published: December 2017

BAY y 5959 is a dihydropyridine derivative with positive inotropic actions mediated by a direct increase in intracellular calcium. We characterized the direct myocardial actions of this new agent in hearts isolated from seven normal dogs and from five dogs with repeated coronary microembolization-induced heart failure. Inotropic actions of BAY y 5959 were accompanied by little effect on duration of contraction and by prolongation of the monophasic action potential (MAP); in contrast, isoproterenol decreased contraction and MAP durations. Whereas inotropic responsiveness to isoproterenol was blunted in embolized hearts, these actions of BAY y 5959 were relatively preserved in the heart failure state. Isoproterenol increased heart rate, whereas BAY y 5959 had little effect. Changes in coronary vascular resistance also decreased similarly for isoproterenol and BAY y 5959. Finally, for comparable inotropy, increases in myocardial oxygen consumption were similar for isoproterenol and for BAY y 5959. In summary, preserved inotropic responsiveness and lack of positive chronotropic actions are two clinically favorable features of this type of inotropic agents compared with a typical β-adrenergic agonist.
Interaction between carotid baroreflex and exercise pressor reflex depends on baroreceptor afferent input
Authors: Potts Jeffrey T. , Li Jianhua
Published: December 2017

Because arterial baroreceptor and skeletal muscle receptor afferents project to cardiovascular regions in the lower brain stem such as the nucleus tractus solitarii (NTS), it is likely that the level of baroreceptor afferent input will modify the excitatory cardiovascular responses evoked by contraction-sensitive skeletal muscle afferents. The purpose of this study was to determine the effect of carotid sinus baroreceptor afferent input (CSA) on reflex heart rate (HR) and mean arterial pressure (MAP) responses evoked by activation of skeletal muscle receptor afferents (SMA). CSA input was servo controlled at three levels of carotid sinus pressure using the isolated carotid sinus preparation, and SMA input was varied by induced muscle contraction (L7-S1ventral root stimulation) or passive muscle stretch. Experiments were performed in α-chloralose-anesthetized and vagotomized dogs ( n = 9). When CSA input was low (106 ± 35 mmHg), electrically induced muscle contraction increased HR and MAP (30 ± 8 beats/min and 42 ± 12 mmHg, respectively, P < 0.05). However, when CSA input was high (221 ± 9 mmHg), the reflex changes in HR and MAP during muscle contraction were attenuated (6 ± 4 beats/min and 18 ± 4 mmHg, respectively, P< 0.05). Similarly, the sympathoexcitatory responses evoked by passive muscle stretch were attenuated in a baroreceptor-dependent manner. These results suggest that changing CSA input from low (106 mmHg) to high (221 mmHg) shifts the interaction from facilitation to inhibition. Therefore, it is concluded that the nature of the interaction (i.e., facilitation or inhibition) between the baroreflex and the exercise pressor reflex is dependent on the level of baroreceptor input. Moreover, our findings substantiate early studies showing that the level of afferent input from arterial baroreceptors is a powerful modulator of sympathoexcitation evoked by mechanically and metabolically sensitive skeletal muscle receptors.
Cerebral blood flow during hypoxic hypoxia with plasma-based hemoglobin at reduced hematocrit
Authors: Ulatowski John A. , Bucci Enrico , Razynska Anna , Traystman Richard J. , Koehler Raymond C.
Published: December 2017

We determined whether cerebral blood flow (CBF) remained related to arterial O2 content ([Formula: see text]) during hypoxic hypoxia when hematocrit and hemoglobin concentration were independently varied with cell-free, tetramerically stabilized hemoglobin transfusion. Three groups of pentobarbital sodium-anesthetized cats were studied with graded reductions in arterial O2saturation to 50%: 1) a control group with a hematocrit of 31 ± 1% (mean ± SE; n = 7); 2) an anemia group with a hematocrit of 21 ± 1% that underwent an isovolumic exchange transfusion with an albumin solution ( n = 8); and 3) a group transfused with an intramolecularly cross-linked hemoglobin solution to decrease hematocrit to 21 ± 1% ( n = 10). Total arterial hemoglobin concentration (g/dl) after hemoglobin transfusion (8.8 ± 0.2) was intermediate between that of the control (10.3 ± 0.3) and albumin (7.2 ± 0.4) groups. Forebrain CBF increased after albumin and hemoglobin transfusion at normoxic O2 tensions to levels attained at equivalent reductions in [Formula: see text] in the control group during graded hypoxia. Over a wide range of arterial O2 saturation and sagittal sinus[Formula: see text], CBF remained greater in the albumin group. When CBF was plotted against[Formula: see text] for all three groups, a single relationship was formed. Cerebral O2 transport, O2 consumption, and fractional O2 extraction were constant during hypoxia and equivalent among groups. We conclude that CBF remains related to [Formula: see text] during hypoxemia when hematocrit is reduced with and without proportional reductions in O2-carrying capacity. Thus O2 transport to the brain is well regulated at a constant level independently of alterations in hematocrit, hemoglobin concentration, and O2 saturation.
Perivascular nerves contribute to cortical spreading depression-associated hyperemia in rats
Authors: Reuter Uwe , Weber Joerg R. , Gold Lorenz , Arnold Guy , Wolf Tilo , Dreier Jens , Lindauer Ute , Dirnagl Ulrich
Published: December 2017

We investigated the contribution of perivascular nerves and neurotransmitters to cortical spreading depression (CSD)-associated hyperperfusion in the rat. Chronic transection of the nasociliary nerve (NCN, 2 wk before) decreased ipsilateral CSD-associated hyperperfusion by 23 ± 13% (mean ± SD; n = 5, P < 0.05), whereas acute transection of the NCN or sham surgery had no effect ( n = 8). When the NCN and parasympathetic nerve fibers (PSN) were both chronically transected, CSD hyperperfusion was attenuated by 55 ± 19% ( n = 5, P < 0.05). Cerebrovascular reactivity to hypercapnia was not significantly affected. Brain topical superfusion of the muscarinic receptor antagonist atropine (10−4 M) caused a reduction of CSD hyperperfusion by 41 ± 13% ( n = 5, P < 0.05). The competitive blockade of calcitonin gene-related peptide (CGRP) receptors by CGRP-(8—37) (5 × 10−7 M) afforded a decrease by 49 ± 19% ( n = 5, P < 0.05), without affecting CO2 reactivity ( n = 4). The combined application of both CGRP-(8—37) and atropine further attenuated CSD hyperperfusion (by 69 ± 17%, n = 5, P < 0.05). After chronic NCN and PSN transection brain topical superfusion of CGRP-(8—37) (5 × 10−7 M) reduced CSD hyperperfusion slightly by 9.5 ± 5% ( n = 3). Atropine (10−4 M) afforded a decrease by 17 ± 6% ( n = 3). These reductions were not statistically significant. We conclude that CSD-associated hyperperfusion is mediated in part by a depolarization of trigeminal sensory and parasympathetic nerve fibers, resulting in a release of vasoactive trigeminal and parasympathetic neurotransmitters.
Water channel proteins in rat cardiac myocyte caveolae: osmolarity-dependent reversible internalization
Authors: Page Ernest , Winterfield Jeffrey , Goings Gwendolyn , Bastawrous Amir , Upshaw-Earley Judy , Doyle Donald
Published: December 2017

We show by confocal immunofluorescence microscopy that the water channel protein aquaporin-1, not previously identified within cardiomyocytes, localizes at 20 and 37°C to rat cardiomyocyte sarcolemmal caveolar membrane and subsarcolemmal cytoplasm of primary atrial myocyte cultures, dissociated atrial and ventricular myocytes, and in situ cardiomyocytes of atrial and ventricular frozen sections. Confocal immunofluorescence microscopy shows that the normal in situ colocalization of the quasi-muscle-specific caveolar coating protein caveolin-3 with aquaporin-1 is reversibly disrupted by exposing in situ atrial or ventricular myocytes to physiological saline made hypertonic by adding 150 mM sucrose or 75 mM NaCl to isotonic physiological saline. This causes caveolae to close off from the interstitium and swell, while aquaporin-1 is internalized reversibly. At 4°C aquaporin-1 does not colocalize with caveolin-3. We suggest that 1) in vivo, under near-isotonic conditions, caveolae may alternate frequently between brief open and closed-off states; 2) aquaporin-1-caveolin-3 colocalization may be energy dependent; and 3) while closed off from the interstitium, each caveola transiently functions as an osmometer that experiences, monitors, and reacts to net water flow from or into the subcaveolar cytosol of the myocyte.
Modification of ischemia-reperfusion-induced changes in cardiac sarcoplasmic reticulum by preconditioning
Authors: Osada Mitsuru , Netticadan Thomas , Tamura Kohji , Dhalla Naranjan S.
Published: December 2017

To examine the effects of ischemic preconditioning on ischemia-reperfusion-induced changes in the sarcoplasmic reticulum (SR) function, isolated rat hearts were either perfused with a control medium for 30 min or preconditioned with three episodes of 5-min ischemia and 5-min reperfusion before sustained ischemia for 30 min followed by reperfusion for 30 min was induced. Preconditioning itself depressed cardiac function (left ventricular developed pressure, peak rate of contraction, and peak rate of relaxation) and SR Ca2+-release and -uptake activities as well as protein content and Ca2+/calmodulin-dependent protein kinase (CaMK) phosphorylation of Ca2+-release channels by 25–60%. Global ischemia for 30 min produced marked depressions in SR Ca2+-release and -uptake activities as well as SR Ca2+-pump protein content in control hearts; these changes were significantly attenuated by preconditioning. Compared with the control preparations, preconditioning improved the recovery of cardiac function and SR Ca2+-release and -uptake activities as well as Ca2+-release channel and Ca2+-pump protein contents in the ischemic-reperfused hearts. Unlike the protein kinase A-mediated phosphorylation in SR membranes, the CaMK-mediated phosphorylations at Ca2+-release channels, Ca2+pump, and phospholamban were depressed in the ischemic hearts; these changes were prevented by preconditioning. These results indicate that ischemic preconditioning may exert beneficial effects on ischemia-reperfusion-induced alterations in SR function by preventing changes in Ca2+-release channel and Ca2+-pump protein contents in the SR membrane.
Mitochondrial Ca2+uptake, efflux, and sarcolemmal damage in Ca2+-overloaded cultured rat cardiomyocytes
Authors: Korge Paavo , Langer Glenn A.
Published: December 2017

The purpose of this study was to determine mitochondrial Ca2+accumulation and its possible role in initiation of mitochondrial permeability transition (MPT) and sarcolemmal damage in Ca2+-overloaded cardiomyocytes. Cellular Ca2+overload, generated secondary to ouabain or p-chloromercuribenzoate-stimulated cell Na+concentration increase, induced Ca2+accumulation in mitochondria (∼¾ of total net uptake) as identified by kinetic analysis and verified by use of mitochondrial inhibition. Mitochondrial Ca2+uptake was followed by a rapid Ca2+efflux (∼1 mmol ⋅ kg dry wt−1⋅ min−1) that can be best explained by efflux via Ca2+-dependent nonspecific pores. Cell ATP concentration was stable during mitochondrial Ca2+uptake and decreased in parallel with Ca2+efflux. In addition, sarcolemmal damage was not related to the increase in mitochondrial Ca2+concentration per se, but rather connected with the extent of Ca2+efflux from the mitochondria. A decrease in the rate of this Ca2+efflux, indicating also a decrease in a subpopulation of mitochondria with open pores, was followed by decreased sarcolemmal damage. Both dithiothreitol and cyclosporin A decreased rapid Ca2+efflux and inhibited sarcolemmal damage, implicating MPT as an important component in the mechanism of sarcolemmal damage.