bluuebunny/crossref_metadata_2025 huggingface dataset:
HCO 3 − -dependent alkalinizing transporter in adult rat ventricular myocytes: characterization and modulation
Authors: Le Prigent Karine , Lagadic-Gossmann Dominique , Mongodin Emmanuel , Feuvray Danielle
Published: December 2017

The present work was designed to identify the [Formula: see text]-dependent alkalinizing carrier in ventricular myocytes of normal and diabetic adult rats and to determine to what extent this system contributes to acid-equivalent extrusion after an intracellular acidification. We also examined the possible influence of intracellular Ca2+([Formula: see text]) and glycolytic inhibition on the carrier activation. Intracellular pH (pHi) was recorded using seminaphthorhodafluor-1. The [Formula: see text] method was used to induce an intracellular acid load. Evidence is provided for the existence of a Cl−-independent Na+-[Formula: see text]cotransport contributing to pHirecovery from an intracellular acid load in ventricular cells of adult rats. Na+-[Formula: see text]cotransport accounts for 33% of the total acid-equivalent efflux ([Formula: see text]) from normal adult myocytes after intracellular acidification at pHi6.75 in CO2/[Formula: see text]-buffered solution. In addition, the activity of this carrier, which is not affected either by decreasing [Formula: see text] or by inhibiting Ca2+/calmodulin protein kinase II, is downregulated by inhibition of glycolysis. Under pathophysiological conditions such as diabetes, although total[Formula: see text] was significantly decreased compared with normal myocytes,[Formula: see text] carried by Na+-[Formula: see text]cotransport remained unchanged. However, because of a decrease in Na+/H+exchange, the contribution of this carrier to total[Formula: see text] increased with decreasing pHi(i.e., under conditions that may be associated with an ischemic episode), reaching ∼58% of total[Formula: see text] at pHi6.75 (vs. ∼33% in normal myocytes).
Ventricular-vascular uncoupling by acute conotruncal occlusion in the stage 21 chick embryo
Authors: Keller Bradley B. , Yoshigi Masaaki , Tinney Joseph P.
Published: December 2017

Embryonic ventricular diastolic and systolic function was evaluated during normal ejection (coupled) and during acute ventricular outflow tract occlusion (uncoupled) in the stage 21 chick embryo. We simultaneously measured ventricular pressure with a servo-null system and ventricular dimensions using video microscopy. Experimental protocols included 1) baseline recording followed by acute conotruncal (CT) ligation ( n = 15) and 2) baseline recording, preload increase using Krebs-Henseleit buffer (3 μl), preload reduction via venous hemorrhage, and then CT occlusion ( n = 20). Ventricular epicardial cross-sectional area was converted to internal volume using wall volume measures and assuming an ellipsoid geometry to produce pressure-volume loops. We calculated the time constant of ventricular pressure decline using a monoexponential decay function with a pressure asymptote. As previously noted, heart rate was unaffected by acutely altered preload or afterload. CT ligation increased end-systolic pressure, maximal +dP/d t, and the time constant of ventricular pressure decline and decreased stroke volume indexed for end-diastolic volume. Thus the embryonic ventricle has significant contractile reserve masked in vivo by the dynamic coupling between the ventricle and arterial circulation.
Modulation of the transient outward current in adult rat ventricular myocytes by polyunsaturated fatty acids
Authors: Bogdanov K. Y. , Spurgeon H. A. , Vinogradova T. M. , Lakatta E. G.
Published: December 2017

With the whole cell patch-clamp technique, we studied the effects of the n-3 and n-6 polyunsaturated fatty acids (PUFAs), linoleic (C18:2n-6), eicosapentaenoic (C20:4n-3), docosahexaenoic (C22:5n-3), and arachidonic (AA; C20:4n-6) acids, on K+currents in rat ventricular myocytes. At low concentrations (5–10 μM) all PUFAs except AA inhibited, by ∼40%, the transient outward current ( Ito) without affecting other K+currents and markedly prolonged the action potential (AP). AA inhibited Itobut also augmented a sustained depolarization-induced outward K+current ( Isus); the latter effect did not occur in the presence of 4-aminopyridine or with eicosatetraynoic acid, a nonmetabolizable analog of AA. Higher concentrations of PUFAs (20–50 μM) further inhibited Itoand also inhibited Isus. Thus, at high concentrations, PUFAs have a nonspecific effect on several K+channels; at low concentrations, PUFAs preferentially inhibit Itoand prolong the AP.
Effects of aminooxyacetate on glutamate compartmentation and TCA cycle kinetics in rat hearts
Authors: Sherry A. D. , Zhao P. , Wiethoff A. J. , Jeffrey F. M. H. , Malloy C. R.
Published: December 2017

The nonspecific transaminase inhibitor aminooxyacetate (AOA) has multiple influences on the dynamics of13C appearance in glutamate in rat hearts as measured by13C nuclear magnetic resonance (NMR) without altering O2consumption or tricarboxylic acid (TCA) cycle flux. These include the following: 1) a reduced rate of13C enrichment at glutamate C3 and C4; 2) a near coalescence of the C3 and C4 fractional enrichment curves; 3) a dramatic alteration in the time-dependent evolution of the glutamate C4 multiplets, C4S and C4D34; and 4) a decrease in the NMR visibility of glutamate. A fit of the13C fractional enrichment curves of glutamate C4 and C3 in the absence of inhibitor to a kinetic model of the TCA cycle gave values for transaminase flux of 7.5 μmol ⋅ min−1⋅ g dry wt−1and TCA cycle flux of 7.5 μmol ⋅ min−1⋅ g dry wt−1, thereby confirming reports by others that the kinetics of13C enrichment of glutamate C3 and C4 in heart tissue is significantly affected by flux through reactions other than TCA cycle. The13C fractional enrichment data collected in the presence of 0.5 mM AOA could not be fitted using this same kinetic model. However, kinetic simulations demonstrated that the time-dependent changes in C4S and C4D34 are only consistent with a 10-fold reduction in the size of intermediate pools undergoing rapid turnover in the TCA cycle. We conclude that inhibition of glutamic-oxalacetic transaminase by AOA effectively reduces the size of the α-ketoglutarate pool in rapid exchange with the TCA cycle. Our data indicate that changes in glutamate multiplet areas in the13C NMR spectra of heart (as demonstrated by glutamate C4S and C4D34) are more sensitive to alterations in metabolic pool sizes in exchange with the TCA cycle than are measurements of13C fractional enrichment at glutamate C3 and C4.
VEGF upregulates ecNOS message, protein, and NO production in human endothelial cells
Authors: Hood John D. , Meininger Cynthia J. , Ziche Marina , Granger Harris J.
Published: December 2017

Vascular endothelial growth factor (VEGF) is an endothelium-specific secreted protein that potently stimulates vasodilation, microvascular hyperpermeability, and angiogenesis. Nitric oxide (NO) is also reported to modulate vascular tone, permeability, and capillary growth. Therefore, we hypothesized that VEGF might regulate endothelial production of NO. The production of nitrogen oxides by human umbilical vein endothelial cells (HUVECs) was measured after 1, 12, 24, and 48 h of incubation with VEGF. VEGF treatment resulted in both an acute (1 h) and chronic (>24 h) stimulation of NO production. Furthermore, Western and Northern blotting revealed a VEGF-elicited, dose-dependent increase in the cellular content of endothelial cell nitric oxide synthase (ecNOS) message and protein that may account for the chronic upregulation of NO production elicited by VEGF. Finally, endothelial cells pretreated with VEGF for 24 h and subsequently exposed to A-23187 for 1 h produced NO at approximately twice the rate of cells that were not pretreated with VEGF. We conclude that VEGF upregulates ecNOS enzyme and elicits a biphasic stimulation of endothelial NO production.
Hepatic venular resistance responses to norepinephrine, isoproterenol, adenosine, histamine, and ACh in rabbits
Authors: Rothe Carl F. , Maass-Moreno Roberto
Published: December 2017

Changes in hepatic venous resistance were estimated in rabbits from the hepatic venular-inferior vena caval pressure gradient [servo-null micropipettes in 49 ± 15 (SD) μm vessels] and the total hepatic blood flow (ultrasound probe encircling the hepatic artery and the portal vein). Changes in liver volume, and thus vascular capacitance, were estimated from measures of the liver lobe thickness. Norepinephrine (NE), isoproterenol (Iso), adenosine (Ado), histamine (Hist), or acetylcholine (ACh) was infused into the portal vein at a constant rate for 5 min. NE, Hist, and Ado increased hepatic venular pressure, but only NE and Hist significantly increased hepatic venular resistance. NE reduced the liver thickness, but Hist and Ado caused engorgement. Hepatic blood flow was increased by NE and Ado and decreased by ACh. The influence of intraportal vein infusion of Iso on the liver vasculature, at doses similar to that of NE, was insignificant. We conclude that NE acted on all the hepatic microvasculature, increasing resistance and actively decreasing vascular volume. Hist passively induced engorgement by increasing outflow resistance, whereas the liver engorgement seen with Ado was passively related to the increased blood flow. ACh constricted the portal venules but did not change the liver volume.
Optical mapping of atrioventricular node reveals a conduction barrier between atrial and nodal cells
Authors: Choi Bum-Rak , Salama Guy
Published: December 2017

The mechanisms responsible for atrioventricular (AV) delay remain unclear, in part due to the inability to map electrical activity by conventional microelectrode techniques. In this study, voltage-sensitive dyes and imaging techniques were refined to detect action potentials (APs) from the small cells comprising the AV node and to map activation from the “compact” node. Optical APs (124) were recorded from 5 × 5 mm (∼0.5-mm depth) AV zones of perfused rabbit hearts stained with a voltage-sensitive dye. Signals from the node exhibited a set of three spikes; the first and third ( peaks I and III) were coincident with atrial (A) and ventricular (V) electrograms, respectively. The second spike ( peak II) represented the firing of midnodal (N) and/or lower nodal (NH) cell APs as indicated by their small amplitude, propagation pattern, location determined from superimposition of activation maps and histological sections of the node region, dependence on depth of focus, and insensitivity to tetrodotoxin (TTX). AV delays consisted of τ1 (49.5 ± 6.59 ms, 300-ms cycle length), the interval between peaks I and II (perhaps AN to N cells), and τ2 (57.57 ± 5.15 ms), the interval between peaks II and III (N to V cells). The conductance time across the node was 10.33 ± 3.21 ms, indicating an apparent conduction velocity (ΘN) of 0.162 ± 0.02 m/s ( n = 9) that was insensitive to TTX. In contrast, τ1 correlated with changes in AV node delays (measured with surface electrodes) caused by changes in heart rate or perfusion with acetylcholine. The data provide the first maps of activation across the AV node and demonstrate that ΘN is faster than previously presumed. These findings are inconsistent with theories of decremental conduction and prove the existence of a conduction barrier between the atrium and the AV node that is an important determinant of AV node delay.
Effect of ventricular stretch on contractile strength, calcium transient, and cAMP in intact canine hearts
Authors: Todaka Koji , Ogino Kazuhide , Gu Anguo , Burkhoff Daniel
Published: December 2017

Isovolumic contractions were imposed by intraventricular balloon in 39 isolated, blood-perfused canine hearts to investigate the effects of myocardial stretch on contractile force. After stabilization at 37°C, left ventricular volume was increased so that end-diastolic pressure increased from 0 to 5 mmHg. After the immediate increase in developed pressure [DP; from 37 ± 14 to 82 ± 22 mmHg (means ± SD)], there was a slow secondary rise in DP (97 ± 27 mmHg) that peaked at 3 min. However, DP subsequently decreased over the next 7 min back to the initial value (84 ± 25 mmHg). Light emission from macroinjected aequorin ( n = 10 hearts) showed that changes in intracellular calcium [3 min: 124 ± 15% ( P < 0.01); 10 min: 99 ± 18% of baseline] paralleled DP changes. Increases in myocardial adenosine 3′,5′-cyclic monophosphate (cAMP) content ( n = 12) accompanied the secondary rise in DP. In contrast, the gradual elevation of DP after the stretch was not exerted during continuous β-adrenergic stimulation by isoproterenol. Thus, in contrast to isolated muscle, stretch only transiently increases intracellular calcium and contractile strength in intact hearts. The findings of changes in cAMP and abolition of the phenomena by β-stimulation suggest that a primary stretch-mediated influence on cAMP metabolism may underlie these phenomena.
Molecular characterization of rabbit CPP32 and its function in vascular smooth muscle cell apoptosis
Authors: Wang He , Keiser Joan A.
Published: December 2017

Vascular remodeling in atherogenesis is marked not only by cellular proliferation and migration but is also impacted by apoptotic cell death. Extensive studies have focused on the signal transduction events leading to apoptosis. CPP32, a member of the caspase/interleukin-1β-converting enzyme (ICE) protease family, has emerged as a central player in several reports of apoptosis pathways. Vascular smooth muscle cells (SMC) undergo apoptosis after treatment with various stimuli, including nitric oxide (NO) donors, such as sodium nitroprusside (SNP, 0.1–1 mM). The aim of the present study was to evaluate the role of CPP32 in SNP-induced apoptosis of SMC. We isolated a rabbit CPP32 cDNA by using degenerate primers and polymerase chain reaction technique. The predicted protein encoded by this cDNA contains the conserved sequence (QACRG) necessary for covalent linkage to poly(ADP-ribose) polymerase (PARP) as well as the three amino acids responsible for substrate recognition and catalysis reported in other caspase members. Using a segment of this cDNA as a probe, we found no change of CPP32 mRNA in cultured arterial SMC before and after SNP treatment. We also measured the protease activity of CPP32 against a chromophore p-nitroaniline (pNA)-labeled substrate, DEVD-pNA. Our results showed a dose-dependent increase of CPP32 activity in SMC, with a maximal 10-fold increase after SNP treatment. Addition of a competitive CPP32 inhibitor, DEVD-CHO, produced a 50% reduction in maximal stimulation. Immunoblot analysis illustrated that SNP treatment induced proteolytic cleavage of CPP32 into its enzymatically active subunit p17 as well as the degradation of PARP into a 85-kDa fragment. We further demonstrated that incubation of cultured SMC with DEVD-CHO significantly reduced SNP-induced DNA fragmentation. DNA fragmentation analysis was carried out using several methods including a cell death detection enzyme-linked immunosorbent assay kit, in situ end labeling, and DNA electrophoresis in agarose gel. Our data indicate that CPP32 mRNA is constitutively expressed in rabbit SMC and activation of CPP32 protein has a pivotal role in SNP-induced SMC apoptosis.
Temporally localized contributions to measures of large-scale heart rate variability
Authors: Roach Daniel , Sheldon Aaron , Wilson Wendy , Sheldon Robert
Published: December 2017

The purpose of this work was to determine the temporal origins of the standard deviation of successive 5-min mean heart period sequences (SDANN) and the power of the ultralow-frequency (ULF) spectral band (<0.0033 Hz). We hypothesized that SDANN and ULF might have their origins in changes in human activity rather than slow oscillatory rhythms. Heart period sequences were obtained from 24-h Holter electrocardiograms of 10 healthy ambulatory subjects. There was no evidence of any persistent oscillation within the ULF band. Using moving 4-h windows in short-time Fourier transforms, we showed that the amplitude of ULF fluctuated markedly, particularly during times bordering sleep. The local ULF amplitude correlated ( r = 0.59 ± 0.09) with large-scale changes in heart period quantified with 2- and 4-h wavelet transforms. Local SDANN also fluctuated, mainly around times of sleep. Although the 24-h SDANN and ULF values correlated highly, there was little correlation between their temporal distributions ( r = 0.10 ± 0.25). The temporal distributions of measures of long-range heart period variability suggest that they reflect changes in human activity levels.
Flow-generating capability of the isolated skeletal muscle pump
Authors: Sheriff Don D. , Van Bibber Richard
Published: December 2017

We sought to test directly whether the mechanical forces produced during rhythmic muscle contraction and relaxation act on the muscle vasculature in a manner sufficient to initiate and sustain blood flow. To accomplish this goal, we evaluated the mechanical performance of the isolated skeletal muscle pump. The hindlimb skeletal muscle pump was isolated by reversibly connecting the inferior vena cava and terminal aorta with extracorporeal tubing in 15- to 20-kg anesthetized pigs ( n = 5). During electrically evoked contractions (1/s), hindlimb muscles were made to perfuse themselves by diverting the venous blood propelled out of the muscles into the shunt tubing, which had been prefilled with fresh arterial blood. This caused arterial blood to be pushed into the distal aorta and then through the muscles (shunt open, proximal aorta and vena cava clamped). In essence, the muscles perfused themselves for brief periods by driving blood around a “short-circuit” that isolates muscle from the remainder of the circulation, analogous to isolated heart-lung preparations. Because the large, short shunt offers a negligible resistance to flow, the arterial-venous pressure difference across the limbs was continuously zero, and thus the energy to drive flow through muscle could come only from the muscle pump. The increase in blood flow during normal heart-perfused contractions (with only the shunt tubing clamped) was compared with shunt-perfused contractions in which the large veins were preloaded with extra blood volume. Muscle blood flow increased by 87 ± 11 and 110 ± 21 (SE) ml/min in the first few seconds after the onset of shunt-perfused and heart-perfused contractions, respectively ( P > 0.4). We conclude that the mechanical forces produced by muscle contraction and relaxation act on the muscle vasculature in a manner sufficient to generate a significant flow of blood.
Degranulation enhances release of a stable contractile factor from rabbit polymorphonuclear leukocytes
Authors: Hamilton Justin R. , Hart Joanne L. , Woodman Owen L.
Published: December 2017

We investigated the release of a stable contractile factor(s) from rabbit isolated polymorphonuclear leukocytes (PMNs; 108cells/ml) incubated in Tyrode buffer at 37°C. PMNs were untreated, stimulated with N-formylmethionyl-leucyl-phenylalanine (FMLP; 0.1 μM), or degranulated with cytochalasin B (1 μM) in combination with FMLP (0.1 μM). Products from unstimulated PMNs incubated for 60 min caused significantly greater contraction of rabbit isolated aorta (0.56 ± 0.12 g, n = 8) than did products released from PMNs during a 5-min incubation (0.32 ± 0.07 g, n = 11, P < 0.05). Stimulation alone did not affect contractile factor release; however, products released from degranulated PMNs caused significantly greater aortic contraction (0.48 ± 0.08 g, n = 5) than products from nondegranulated PMNs (0.24 ± 0.04 g, n = 5, P < 0.05) after a 5-min incubation. The contractile activity of PMN-derived products was virtually abolished by heat (90°C, 10 min) or protease (trypsin; 166 U/ml, 5 h) treatment. These findings suggest a PMN-derived protein vasoconstrictor(s) is spontaneously released at a slow rate in vitro and that degranulation can enhance this rate of release. Because PMN degranulation in vivo is associated with inflammation, these results support suggestions that PMN-derived contractile factors may contribute to the impaired blood flow observed during postischemic reperfusion.
ATP-dependent K+ channel activation reduces loss of opioid dilation after brain injury
Authors: Armstead William M.
Published: December 2017

ATP-dependent K+(KATP) channel function is impaired after fluid percussion brain injury (FPI). Additionally, the nitric oxide (NO) releaser sodium nitroprusside and a cGMP analog elicit pial dilation via KATP channel activation, whereas opioids such as methionine enkephalin (Met) elicit pial dilation via NO and KATP channel activation. Decremented Met dilation contributes to reductions in pial artery diameter and altered cerebral hemodynamics after FPI. This study was designed to investigate the role of KATP channel activation before FPI in the loss of opioid dilation subsequent to FPI in newborn pigs equipped with a closed cranial window. FPI was produced by allowing a pendulum to strike a piston on a saline-filled cylinder that was fluid coupled to the brain via a hollow screw in the cranium. FPI blunted dilation to Met (7 ± 1, 11 ± 1, and 17 ± 1% before FPI vs. 1 ± 1, 4 ± 1, and 6 ± 1% after FPI for 10−10, 10−8, and 10−6 M Met, respectively). Met-associated elevation in cerebrospinal fluid (CSF) cGMP was similarly blunted (350 ± 12 and 636 ± 12 fmol/ml before FPI vs. 265 ± 5 and 312 ± 17 fmol/ml after FPI for control and 10−6 M Met, respectively). In piglets pretreated with cromakalim (10−10 M) 20 min before FPI, Met dilation was partially restored (7 ± 1, 10 ± 1, and 15 ± 1% before FPI vs. 4 ± 1, 7 ± 1, and 11 ± 1% after FPI for 10−10, 10−8, and 10−6 M Met, respectively). Met cGMP release was similarly partially restored (400 ± 9 and 665 ± 25 fmol/ml before FPI vs. 327 ± 11 and 564 ± 23 fmol/ml after FPI for control and 10−6 Met, respectively). Cromakalim (10−10 M) had no effect on pial diameter itself but prevented pial artery constriction by FPI (148 ± 5 to 124 ± 5 μm vs. 139 ± 4 to 141 ± 4 μm in the absence vs. presence of cromakalim pretreatment, respectively). In contrast, pretreatment with a subthreshold concentration of NS-1619, a calcium-dependent K+ channel agonist, did not restore vascular and biochemical parameters after FPI. These data indicate that prior KATP channel activation reduces the loss of opioid dilation after FPI.
PDGF-BB-induced DNA synthesis is delayed by angiotensin II in vascular smooth muscle cells
Authors: Dahlfors Gunilla , Chen Yun , Wasteson Maria , Arnqvist Hans J.
Published: December 2017

The interaction of ANG II with platelet-derived growth factor (PDGF)-BB-induced DNA synthesis was studied in cultured rat aortic smooth muscle cells. PDGF-BB-induced DNA synthesis was delayed (∼6–8 h) by ANG II as shown by a time-course experiment. Losartan, an AT1-receptor antagonist, blocked the transient inhibitory effect of ANG II, whereas the AT2-receptor antagonist PD-123319 had no effect. Autocrine- or paracrine-acting transforming growth factor-β1 (TGF-β1), believed to be a mediator of ANG II-induced inhibitory effects, was not responsible for the delay of PDGF-BB-induced DNA synthesis, because a potent TGF-β1 neutralizing antibody could not reverse this effect of ANG II, nor was the delay of the PDGF-BB effect caused by inhibition of PDGF-β-receptor phosphorylation as shown by Western blot analysis of immunoprecipitated PDGF-β receptor. In conclusion, our results show that ANG II can exert a transient inhibitory effect on PDGF-BB-induced proliferation via the AT1receptor.
cGMP modulates basal and activated microvessel permeability independently of [Ca2+]i
Authors: He P. , Zeng M. , Curry F. E.
Published: December 2017

To investigate the mechanisms whereby guanosine 3′,5′-cyclic monophosphate (cGMP) modulates microvessel permeability in vivo, we measured changes in microvessel hydraulic conductivity ( L p) and endothelial cytoplasmic Ca2+concentration ([Ca2+]i) in response to the cGMP analogs 8-bromo-cGMP (8-BrcGMP) and 8-( p-chlorophenylthio)cGMP (8-pCPT-cGMP) in the presence and absence of inflammatory stimuli in intact individually perfused microvessels in frog and rat mesenteries. The cGMP analog caused a transient increase in L p and potentiated ATP or bradykinin-induced increases in L p in frog and rat mesenteric microvessels, respectively. The mean peak value of the test L p/control L p after exposure to 8-BrcGMP was 5.3 ± 0.5 in frog microvessels and 2.8 ± 0.4 in rat microvessels. The ATP-induced increase in L p in frog microvessels was further raised by 8-BrcGMP from 7.0 ± 0.9 to 12.4 ± 1.9 times the control. In rat mesenteric microvessels, the bradykinin-induced increase in L p was potentiated by 8-BrcGMP from 4.8 ± 0.4 to 8.3 ± 1.3 times the control and was suppressed by the guanylate cyclase inhibitor LY-83583 to 2.6 ± 0.5 times the control. A similar but larger effect was found when using 8-pCPT-cGMP. In contrast to the actions of increased cGMP on microvessel permeability, cGMP analogs had no effect on basal endothelial [Ca2+]iand did not alter the magnitude and time course of ATP or bradykinin-induced increases in endothelial [Ca2+]i. These results suggested that an elevation of cGMP levels in endothelial cells is a necessary step to increase microvessel permeability in intact microvessels, and this regulatory process occurs downstream from Ca2+ influx, which differs from that reported in large-vessel endothelium in culture and in vascular smooth muscle cells. Experiments carried on microvessels in both frog and rat mesenteries provided a direct comparison of the endothelial cell regulatory mechanisms between species.
Treatment with dimethylthiourea prevents impaired dilatation of the basilar artery during diabetes mellitus
Authors: Mayhan William G. , Patel Kaushik P.
Published: December 2017

The goal of this study was to test the hypothesis that the synthesis/release of hydroxyl radical accounts for impaired nitric oxide synthase-dependent dilatation of the basilar artery during diabetes mellitus. We measured the diameter of the basilar artery in vivo in nondiabetic and diabetic rats (streptozotocin, 50–60 mg/kg ip) in response to nitric oxide synthase-dependent agonists (acetylcholine and substance P) and a nitric oxide synthase-independent agonist (nitroglycerin). Reactivity of the basilar artery was measured in untreated nondiabetic and diabetic rats and in nondiabetic and diabetic rats treated with a daily intraperitoneal injection of dimethylthiourea (DMTU; 50 mg/kg). Injection of DMTU was started 48 h after injection of streptozotocin and was continued throughout the diabetic period (3–4 wk). Topical application of acetylcholine (0.1, 1.0, and 10 μM) and substance P (0.1 and 1.0 μM) produced similar dilatation of the basilar artery in untreated and DMTU-treated nondiabetic rats. In untreated diabetic rats, the magnitude of vasodilation produced by acetylcholine and substance P was significantly less than in untreated nondiabetic rats. However, in DMTU-treated diabetic rats, dilatation of the basilar artery in response to acetylcholine and substance P was similar to that observed in nondiabetic rats. Dilatation of the basilar artery in response to nitroglycerin was similar in untreated and DMTU-treated nondiabetic and diabetic rats. These findings suggest that impaired nitric oxide synthase-dependent dilatation of the basilar artery during diabetes mellitus may be related to the synthesis/release of hydroxyl radical.
Exercise training enhances basic fibroblast growth factor-induced collateral blood flow
Authors: Yang H. T. , Ogilvie Robert W. , Terjung Ronald L.
Published: December 2017

This study evaluated whether daily exercise would enhance the peripheral collateral vessel development found in response to exogenous basic fibroblast growth factor (bFGF) infusion. After bilateral femoral occlusion, male Sprague-Dawley rats (∼325 g) received intra-arterial infusions of either bFGF (1 μg/day; n = 15) or carrier solution ( n = 13) via osmotic pumps for 2 wk. Subgroups of each treatment were kept sedentary (cage activity) or trained by walking at 20 m/min at 15% grade, two times a day, 5 days/wk for 4 wk. Training markedly increased citrate synthase activity in the active muscle ( P < 0.001). Muscle function and blood flows (85Sr microsphere) were evaluated using an isolated hindquarter perfused at 100 mmHg via the abdominal aorta. The significant increase in blood flow to the entire hindlimb in the sedentary animals, caused by bFGF infusion ( P < 0.05), was further increased ( P < 0.01) in the bFGF-trained group. The quantitatively largest increases in blood flows were observed in the collateral-dependent tissues of the distal hindlimb. Blood flows to the entire calf muscle group increased ∼140% in carrier-trained ( P < 0.001), ∼180% in bFGF sedentary ( P< 0.001), and ∼240% in the bFGF-trained ( P < 0.001) groups compared with the carrier sedentary group. The increases in collateral blood flow were functionally important, as improvements in calf muscle performance correlated with measured blood flows. Our results demonstrate that exogenous bFGF administration in combination with a moderate-intensity exercise program greatly increases collateral-dependent blood flow and improves muscle performance. That physical activity enriched the bFGF response is consistent with the hypothesis that hemodynamic factors are important contributors to collateral vessel enlargement.
Three noncontiguous peptides comprise binding sites on high-molecular-weight kininogen to neutrophils
Authors: Khan Mohammad M. H. , Kunapuli Satya P. , Lin Yingzhang , Majluf-Cruz Abraham , Cadena Raul A. Dela , Cooper Stuart L. , Colman Robert W.
Published: December 2017

The binding of high-molecular-weight kininogen (HK) to neutrophils (polymorphonuclear leukocytes, PMN) is required for the stimulation of aggregation and degranulation by human plasma kallikrein as well as the displacement of fibrinogen from this cell surface. The putative receptor for HK is the leukocyte integrin αMβ2, and domains 3 (D3) and 5 (D5) of HK form its binding site. To further map the binding sites on HK for PMN, we used D3 recombinant exon products and designed peptides from D3 and D5. In D3, a heptapeptide, Leu271-Ala277, from exon 7 product, and a peptide, Cys333-Cys352, from exon 9 product can inhibit binding of kininogen to PMN. Two contiguous peptides from D5 in the histidine-glycine-rich region, Gly442-Lys458and Phe459-Lys478, each inhibit the binding of HK to PMN. This study has thus delineated three noncontiguous surface-oriented sequences on HK, which together comprise all or most of the binding site for human PMN.
Ionic mechanisms underlying human atrial action potential properties: insights from a mathematical model
Authors: Courtemanche Marc , Ramirez Rafael J. , Nattel Stanley
Published: December 2017

The mechanisms underlying many important properties of the human atrial action potential (AP) are poorly understood. Using specific formulations of the K+, Na+, and Ca2+ currents based on data recorded from human atrial myocytes, along with representations of pump, exchange, and background currents, we developed a mathematical model of the AP. The model AP resembles APs recorded from human atrial samples and responds to rate changes, L-type Ca2+ current blockade, Na+/Ca2+ exchanger inhibition, and variations in transient outward current amplitude in a fashion similar to experimental recordings. Rate-dependent adaptation of AP duration, an important determinant of susceptibility to atrial fibrillation, was attributable to incomplete L-type Ca2+ current recovery from inactivation and incomplete delayed rectifier current deactivation at rapid rates. Experimental observations of variable AP morphology could be accounted for by changes in transient outward current density, as suggested experimentally. We conclude that this mathematical model of the human atrial AP reproduces a variety of observed AP behaviors and provides insights into the mechanisms of clinically important AP properties.
Structural adaptation and stability of microvascular networks: theory and simulations
Authors: Pries A. R. , Secomb T. W. , Gaehtgens P.
Published: December 2017

A theoretical model was developed to simulate long-term changes of vessel diameters during structural adaptation of microvascular networks in response to tissue needs. The diameter of each vascular segment was assumed to change with time in response to four local stimuli: endothelial wall shear stress (τw), intravascular pressure (P), a flow-dependent metabolic stimulus (M), and a stimulus conducted from distal to proximal segments along vascular walls (C). Increases in τw, M, or C or decreases in P were assumed to stimulate diameter increases. Hemodynamic quantities were estimated using a mathematical model of network flow. Simulations were continued until equilibrium states were reached in which the stimuli were in balance. Predictions were compared with data from intravital microscopy of the rat mesentery, including topological position, diameter, length, and flow velocity for each segment of complete networks. Stable equilibrium states, with realistic distributions of velocities and diameters, were achieved only when all four stimuli were included. According to the model, responses to τwand P ensure that diameters are smaller in peripheral than in proximal segments and are larger in venules than in corresponding arterioles, whereas M prevents collapse of networks to single pathways and C suppresses generation of large proximal shunts.
Stretch-induced changes in arrhythmogenesis and excitability in experimentally based heart cell models
Authors: Riemer Tara L. , Sobie Eric A. , Tung Leslie
Published: December 2017

Mechanoelectric coupling in the heart is well documented and has been suggested as a cause of arrhythmia. One hypothesized mechanism for the stretch sensitivity of cardiac muscle is the presence of stretch-activated channels (SACs). This study uses modeling to explore the influence of SACs on cardiac resting potential, excitation threshold, and action potential in the context of arrhythmia. We added a putative SAC, modeled as a linear, time-independent conductance with reversal potential of −20 or −50 mV, to guinea pig and frog ventricular membrane models. Increased stretch conductance led to resting potential depolarization, a decreased excitation threshold, altered action potential duration, and, under certain conditions, early afterdepolarizations. We conclude that stretch increases cellular excitability, making the heart prone to ectopic activity. Regional effects of stretch on action potential duration can vary and are influenced by factors such as the SAC reversal potential, ionic conditions, and baseline currents, all of which may lead to an increased dispersion of refractoriness throughout the heart and therefore an increased risk of arrhythmia.
Effects of ACE inhibition on cardiomyocyte apoptosis in dogs with heart failure
Authors: Goussev Anastassia , Sharov Victor G. , Shimoyama Hisashi , Tanimura Mitsuhiro , Lesch Michael , Goldstein Sidney , Sabbah Hani N.
Published: December 2017

Cardiomyocyte apoptosis or programmed cell death has been shown to occur in end-stage explanted failed human hearts and in dogs with chronic heart failure (HF). We tested the hypothesis that early long-term monotherapy with an angiotensin-converting enzyme (ACE) inhibitor attenuates cardiomyocyte apoptosis in dogs with moderate HF. Left ventricular (LV) dysfunction (ejection fraction 30–40%) was produced in dogs by multiple sequential intracoronary microembolizations. Dogs were randomized to 3 mo of therapy with enalapril (Ena, 10 mg twice daily, n = 7) or to no therapy at all (control, n = 7). After 3 mo of therapy, dogs were euthanized and the hearts removed. Presence of nuclear DNA fragmentation (nDNAf), a marker of apoptosis, was assessed in frozen LV sections using the immunohistochemical deoxynucleotidal transferase-mediated dUTP-digoxigenin nick-end labeling (TUNEL) method. Sections were also stained with ventricular anti-myosin antibody to identify cells of cardiocyte origin. From each dog, 80 fields (×40) were selected at random, 40 from LV regions bordering old infarcts and 40 from LV regions remote from any infarcts, for quantifying the number of cardiomyocyte nDNAf events per 1,000 cardiomyocytes. The average number of cardiomyocyte nDNAf events per 1,000 cardiomyocytes was significantly lower in Ena-treated dogs compared with controls (0.81 ± 0.13 vs. 2.65 ± 0.81, P < 0.029). This difference was due to a significantly lower incidence of cardiomyocyte nDNAf events in LV regions bordering scarred tissue (infarcts) in Ena-treated dogs compared with controls. We conclude that early long-term Ena therapy attenuates cardiomyocyte apoptosis in dogs with moderate HF. Attenuation of cardiomyocyte apoptosis may be one mechanism by which ACE inhibitors preserve global LV function in HF.
Oncostatin M regulates endothelin-1 production in human endothelial cells
Authors: Saijonmaa Outi , Nyman Tuulikki , Pacek Päivi , Fyhrquist Frej
Published: December 2017

The effect of the macrophage- and T-lymphocyte-derived cytokine oncostatin M (OSM) on endothelin-1 (ET-1) production in cultured human umbilical cord vein endothelial cells (HUVEC) was studied. OSM (2.5–10 ng/ml) stimulated ET-1 production and the expression of preproendothelin-1 mRNA. The stimulatory effect of OSM was reversed by anti-interleukin (IL)-6 IgG (33 μg/ml). IL-6 (10 ng/ml) was shown to stimulate ET-1 production. The tyrosine kinase inhibitors herbimycin (250–500 ng/ml) and genistein (1–4 μg/ml) suppressed basal ET-1 production and reversed the stimulatory effect of OSM, whereas daidzein (1–8 μg/ml), a less active analog of genistein, had no effect on basal ET-1 production and only partly reversed the stimulatory effect of OSM. The phorbol ester phorbol 12-myristate 13-acetate (PMA) inhibited ET-1 production. Downregulation of protein kinase C (PKC) with PMA (1 μM) preincubation potentiated OSM-induced ET-1 production. In summary, OSM stimulated ET-1 production in cultured HUVEC. The stimulation was probably mediated by IL-6. Furthermore, the present data suggest that tyrosine kinase activation was involved in ET-1 stimulation and that PKC activation leads to suppression of basal and OSM-stimulated ET-1 production.
Regulation of Ca2+sensitization by PKC and rho proteins in ovine cerebral arteries: effects of artery size and age
Authors: Akopov Sergey E. , Zhang Lubo , Pearce William J.
Published: December 2017

G protein-regulated Ca2+sensitivity of vascular contractile proteins plays an important role in cerebrovascular reactivity. The present study examines the intracellular mechanisms that govern G protein-regulated Ca2+sensitivity in cerebral arteries of different size and age. We studied β-escin-permeabilized segments of common carotid, basilar, and middle cerebral arteries from nonpregnant adult and near-term fetal sheep. Activation of protein kinase C (PKC) by (−)-indolactam V or a phorbol ester produced receptor-independent increases in Ca2+sensitivity. Such increases were more marked in immature arteries and were inversely correlated with artery size in both mature and immature arteries. However, inhibitors of PKC did not significantly affect increases in Ca2+sensitivity in responses to either serotonin (5-hydroxytryptamine, 5-HT) or guanosine 5′- O-(3-thiotriphosphate) (GTPγS). Alternatively, deactivation of rho p21, a small G protein associated with Rho kinase, by exotoxin C3 fully prevented increases in Ca2+sensitivity in responses to 5-HT or GTPγS in both adult and fetal arteries of all types. Neither inhibitors of PKC nor exotoxin C3 altered baseline Ca2+sensitivity. We conclude that patterns of receptor- and/or G protein-mediated modulation of Ca2+sensitivity are dependent on an intracellular pathway that involves activation of small G proteins and Rho kinase. In contrast, PKC has little, if any, role in agonist-induced Ca2+sensitization under the present experimental conditions.
Effect of acidosis on Ca2+uptake and release by sarcoplasmic reticulum of intact rat ventricular myocytes
Authors: Hulme J. T. , Orchard C. H.
Published: December 2017

The effect of acidosis on Ca2+uptake and release by the sarcoplasmic reticulum (SR) of rat ventricular myocytes has been investigated. Intracellular Ca2+concentration ([Ca2+]i) was monitored using fura 2; the L-type Ca2+current ( ICa) was monitored using the perforated patch-clamp technique. Acidosis was produced either by superfusing the cells with an acid solution (intracellular and extracellular acidosis) or by NH4Cl withdrawal (intracellular acidosis). Both types of acidosis increased the amplitude, and slowed the declining phase, of the Ca2+transient. Application of caffeine produced a rise of [Ca2+]i, which declined in the continued presence of caffeine; the declining phase was slowed by the acid solution but was unaffected by NH4Cl withdrawal. Acidosis decreased the fraction of the caffeine-induced release that was released by electrical stimulation but had no effect on ICa. It is concluded that acidosis inhibits SR Ca2+uptake and Ca2+-induced Ca2+release in intact myocytes but that these effects are compensated by an increase in SR Ca2+content secondary to a rise in cytoplasmic [Ca2+].
Neutrophil-dependent augmentation of PAF-induced vasoconstriction and albumin flux in coronary arterioles
Authors: Huang Qiaobing , Wu Mac , Meininger Cynthia , Kelly Katherine , Yuan Yuan
Published: December 2017

Platelet-activating factor (PAF) has been implicated in the pathogenesis of ischemic heart disease, reperfusion injury, and inflammatory reactions. Although neutrophils have been shown to primarily mediate PAF-induced microvascular dysfunction, the vasoactive effect of PAF and its neutrophil-dependent mechanism have not been directly and systematically studied in coronary resistance vessels. Therefore, the aim of this study was to examine the effects of PAF on coronary arteriolar function and neutrophil dynamics using an isolated and perfused microvessel preparation. Topical application of PAF to the vessels induced a dose-dependent decrease in the diameter but an increase in the apparent permeability coefficient of albumin. Disruption of the endothelium abolished the vasomotor response to PAF, and perfusion of neutrophils significantly augmented PAF-induced changes in vasomotor tone and permeability. Furthermore, the interaction between neutrophils and the endothelium was studied in the intact perfused coronary arterioles. Under control conditions, there were no adherent neutrophils observed in the vessels at varied intraluminal flow velocities. However, administration of PAF caused neutrophil adhesion to the endothelium of coronary arterioles at low flow velocities. Western blot analysis indicated that PAF upregulated the expression of intercellular adhesion molecule-1 in cultured coronary microvascular endothelial cells. Taken together, the results suggest that 1) PAF induces vasoconstriction and hyperpermeability in coronary arterioles via an endothelium-dependent and neutrophil-mediated mechanism, and 2) PAF is able to stimulate neutrophil adhesion in coronary arterioles under a condition of low flow rate.
Restoration of transient outward current by norepinephrine in cultured canine cardiac myocytes
Authors: Pacioretty Linda M. , Gilmour Robert F.
Published: December 2017

The mechanism for the reduction of the transient outward K+current ( Ito) in diseased myocardium is unknown. To identify potential mechanisms, the reduction of Itoand its subsequent restoration by norepinephrine (NE) were studied in cultured canine epicardial myocytes. After myocytes were cultured for 9 days ( day 9), Itodensity was decreased compared with density on the day of isolation ( day 0) (3.2 ± 0.4 vs. 10.4 ± 0.4 pA/pF; mean ± SE). The time constant of current decay (τdecay) was increased, the time course of recovery from inactivation was prolonged, and the half-inactivation voltage ( V1/2) was shifted to less negative potentials. Exposure of myocytes on day 8 to 1 μM NE or isoproterenol (Iso) for 1 h had no acute effect on Itobut restored Itodensity to 7.6 ± 1.2 or 9.7 ± 2.3 pA/pF, respectively, on day 9. Recovery from inactivation and τdecayremained slowed, and V1/2remained shifted to less negative potentials. The effects of NE and Iso were blocked by actinomycin D and were not mimicked by phenylephrine or phorbol ester. A-23187 (1 μM) also restored Ito. Thus β-adrenergic agonists restored normal Itodensity, but not normal Itokinetics, in cultured epicardial myocytes, possibly via increased intracellular Ca2+concentration.
Time-frequency analysis of fetal heartbeat fluctuation using wavelet transform
Authors: Kimura Yoshitaka , Okamura Kunihiro , Watanabe Takanori , Yaegashi Nobuo , Uehara Shigeki , Yajima Akira
Published: December 2017

We examined whether the nonlinear control mechanism of the fetal autonomic nervous system would change in various fetal states. Eight thousand or more fetal heartbeats were detected from normal, hypoxemic, and acidemic fetuses. Fetal heart Doppler-signal intervals were determined in a high-precision autocorrelation method, and a time series of fetal heart rate fluctuation was obtained. The distribution of the amplitude of temporal fluctuation in the low-frequency component of fetal heart rate frequency was studied using a method of time-frequency analysis called wavelet transform. Spline 4 was used as the mother wavelet function. A gamma distribution was observed from 17 wk of gestation onward. The value of the parameter ν of this gamma distribution was ∼1.6 and remained constant regardless of the gestational age or the time of day. The value of ν decreased significantly to 0.77 when the fetus developed acidemia and was 1.51 in hypoxemia and 1.54 in a normal condition. This study elucidates a nonlinear structure of the time series of heart rate fluctuation of the gamma distribution in the human fetus. This technique may provide a new quantitative index of fetal monitoring to diagnose fetal acidemia.
Characterization of cardiac malonyl-CoA decarboxylase and its putative role in regulating fatty acid oxidation
Authors: Dyck Jason R. B. , Barr Amy J. , Barr Rick L. , Kolattukudy Pappachan E. , Lopaschuk Gary D.
Published: December 2017

Malonyl-CoA is a potent inhibitor of fatty acid uptake into the mitochondria. Although the synthesis of malonyl-CoA in the heart by acetyl-CoA carboxylase (ACC) has been well characterized, no information is available as to how malonyl-CoA is degraded. We demonstrate that malonyl-CoA decarboxylase (MCD) activity is present in the heart. Partial purification revealed a protein of ∼50 kDa. The role of MCD in regulating fatty acid oxidation was also studied using isolated, perfused hearts from newborn rabbits and adult rats. Fatty acid oxidation in rabbit hearts increased dramatically between 1 day and 7 days after birth, which was accompanied by a decrease in both ACC activity and malonyl-CoA levels and a parallel increase in MCD activity. When adult rat hearts were aerobically reperfused after a 30-min period of no-flow ischemia, levels of malonyl-CoA decreased dramatically, which was accompanied by a decrease in ACC activity, a maintained MCD activity, and an increase in fatty acid oxidation rates. Taken together, our data suggest that the heart has an active MCD that has an important role in regulating fatty acid oxidation rates.