bluuebunny/crossref_metadata_2025 huggingface dataset:
IL-10 deficiency increases superoxide and endothelial dysfunction during inflammation
Authors: Gunnett Carol A. , Heistad Donald D. , Berg Daniel J. , Faraci Frank M.
Published: December 2017

Little is known about the role of interleukin-10 (IL-10), an anti-inflammatory cytokine, in blood vessels. We used IL-10-deficient mice (IL-10 −/−) to examine the hypothesis that IL-10 protects endothelial function after lipopolysaccharide (LPS) treatment. The responses of carotid arteries were studied in vitro 6 h after injection of a relatively low dose of LPS (10 μg ip). In IL-10 −/− mice, the maximum relaxation to ACh (3 μM) was 56 ± 6% (means ± SE) after LPS injection and 84 ± 4% after vehicle injection ( P < 0.05). Thus endothelium-dependent relaxation was impaired in carotid arteries from IL-10 −/− mice after LPS injection. In contrast, this dose of LPS did not alter relaxation to ACh in vessels from wild-type (IL-10 +/+) mice. Relaxation to nitroprusside and papaverine was similar in arteries from both IL-10 −/− and IL-10 +/+ mice after vehicle or LPS injection. Because inflammation is associated with increased levels of reactive oxygen species, we also tested the hypothesis that superoxide contributes to the impairment of endothelial function by LPS in the absence of IL-10. Results using confocal microscopy and hydroethidine indicated that levels of superoxide are elevated in carotid arteries from IL-10 −/− mice compared with IL-10 +/+ mice after LPS injection. The impaired relaxation of arteries from IL-10 −/− mice after LPS injection was restored to normal by polyethylene glycol-suspended superoxide dismutase (50 U/ml) or allopurinol (1 mM), an inhibitor of xanthine oxidase. These data provide direct evidence that IL-10 protects endothelial function after an acute inflammatory stimulus by limiting local increases in superoxide. The source of superoxide in this model may be xanthine oxidase.
Nonlinear dynamics of heart rate variability during experimental hemorrhage in ketamine-anesthetized rats
Authors: Skinner James E. , Nester Brian A. , Dalsey William C.
Published: December 2017

Indexes of heart rate variability (HRV) based on linear stochastic models are independent risk factors for arrhythmic death (AD). An index based on a nonlinear deterministic model, a reduction in the point correlation dimension (PD2 i), has been shown in both animal and human studies to have a higher sensitivity and specificity for predicting AD. Dimensional reduction subsequent to transient ischemia was examined previously in a simple model system, the intrinsic nervous system of the isolated rabbit heart. The present study presents a new model system in which the higher cerebral centers are blocked chemically (ketamine inhibition of N-methyl-d-aspartate receptors) and the system is perturbed over a longer 15-min interval by continuous hemorrhage. The hypothesis tested was that dimensional reduction would again be evoked, but in association with a more complex relationship between the system variables. The hypothesis was supported, and we interpret the greater response complexity to result from the larger autonomic superstructure attached to the heart. The complexities observed in the nonlinear heartbeat dynamics constitute a new genre of autonomic response, one clearly distinct from a hardwired reflex or a cerebrally determined defensive reaction.
PKCε modulates NF-κB and AP-1 via mitogen-activated protein kinases in adult rabbit cardiomyocytes
Authors: Li Richard C. X. , Ping Peipei , Zhang Jun , Wead William B. , Cao Xinan , Gao Jiuming , Zheng Yuting , Huang Shuang , Han Jiahuai , Bolli Roberto
Published: December 2017

We have previously shown that protein kinase C (PKC)-ε, nuclear factor (NF)-κB, and mitogen-activated protein kinases (MAPKs) are essential signaling elements in ischemic preconditioning. In the present study, we examined whether activation of PKCε affects the activation of NF-κB in cardiac myocytes and whether MAPKs are mediators of this signaling event. Activation of PKCε (+108% above control) in adult rabbit cardiomyocytes to a degree that has been previously shown to protect myocytes against hypoxic injury increased the DNA-binding activity of NF-κB (+164%) and activator protein (AP)-1 (+127%) but not that of Elk-1. Activation of PKCη did not have an effect on these transcription factors. Activation of PKCε also enhanced the phosphorylation activities of the p44/p42 MAPKs and the p54/p46 c-Jun NH2-terminal kinases (JNKs). PKCε-induced activation of NF-κB and AP-1 was completely abolished by inhibition of the p44/p42 MAPK pathway with PD98059 and by inhibition of the p54/p46 JNK pathway with a dominant negative mutant of MAPK kinase-4, indicating that both signaling pathways are necessary. Taken together, these data identify NF-κB and AP-1 as downstream targets of PKCε, thereby establishing a molecular link between activation of PKCε and activation of NF-κB and AP-1 in cardiomyocytes. The results further demonstrate that both the p44/p42 MAPK and the p54/p46 JNK signaling pathways are essential mediators of this event.
Starling forces that oppose filtration after tissue oncotic pressure is increased
Authors: Hu X. , Adamson R. H. , Liu B. , Curry F. E. , Weinbaum S.
Published: December 2017

We tested the hypothesis that the effective oncotic force that opposes fluid filtration across the microvessel wall is the local oncotic pressure difference across the endothelial surface glycocalyx and not the global difference between the plasma and tissue. In single frog mesenteric microvessels perfused and superfused with solutions containing 50 mg/ml albumin, the effective oncotic pressure exerted across the microvessel wall was not significantly different from that measured when the perfusate alone contained albumin at 50 mg/ml. Measurements were made during transient and steady-state filtration at capillary pressures between 10 and 35 cmH2O. A cellular-level model of coupled water and solute flows in the interendothelial cleft showed water flux through small breaks in the junctional strand limited back diffusion of albumin into the protected space on the tissue side of the glycocalyx. Thus oncotic forces opposing filtration are larger than those estimated from blood-to-tissue protein concentration differences, and transcapillary fluid flux is smaller than estimated from global differences in oncotic and hydrostatic pressures.
Novel characteristics of a misprocessed mutant HERG channel linked to hereditary long QT syndrome
Authors: Ficker Eckhard , Thomas Dierk , Viswanathan Prakash C. , Dennis Adrienne T. , Priori Silvia G. , Napolitano Carlo , Memmi Mirella , Wible Barbara A. , Kaufman Elizabeth S. , Iyengar Sudha , Schwartz Peter J. , Rudy Yoram , Brown Arthur M.
Published: December 2017

Hereditary long QT syndrome (hLQTS) is a heterogeneous genetic disease characterized by prolonged QT interval in the electrocardiogram, recurrent syncope, and sudden cardiac death. Mutations in the cardiac potassium channel HERG ( KCNH2) are the second most common form of hLQTS and reduce the delayed rectifier K+currents, thereby prolonging repolarization. We studied a novel COOH-terminal missense mutation, HERG R752W, which segregated with the disease in a family of 101 genotyped individuals. When the mutant cRNA was expressed in Xenopus oocytes it produced enhanced rather than reduced currents. Simulations using the Luo-Rudy model predicted minimal shortening rather than prolongation of the cardiac action potential. Consequently, a normal or shortened QT interval would be expected in contrast to the long QT observed clinically. This anomaly was resolved by our observation that the mutant protein was not delivered to the plasma membrane of mammalian cells but was retained intracellularly. We found that this trafficking defect was corrected at lower incubation temperatures and that functional channels were now delivered to the plasma membrane. However, trafficking could not be restored by chemical chaperones or E-4031, a specific blocker of HERG channels. Therefore, HERG R752W represents a new class of trafficking mutants in hLQTS. The occurrence of different classes of misprocessed channels suggests that a unified therapeutic approach for altering HERG trafficking will not be possible and that different treatment modalities will have to be matched to the different classes of trafficking mutants.
Mitochondrial NAD(P)H, ADP, oxidative phosphorylation, and contraction in isolated heart cells
Authors: White Roy L. , Wittenberg Beatrice A.
Published: December 2017

To examine the relationship between mitochondrial NADH (NADHm) and cardiac work output, NADHmand the amplitude and frequency of the contractile response of electrically paced rat heart cells were measured at 25°C. With 5.4 mM glucose plus 2 mM β-hydroxybutyrate, NADHmwas reversibly decreased by 23%, and the amplitude of contraction was reversibly decreased by 27% during 4-Hz pacing. With glucose plus 2 mM pyruvate or with 10 mM 2-deoxy-d-glucose, NADHmwas maintained during rapid pacing, and the contractile amplitude remained high. Phosphocreatine levels decreased with 2-deoxy-d-glucose administration but not with rapid pacing. Respiration increased to meet the increased ATP demand at 30°C. The data suggest that 1) when NADHmis decreased during rapid pacing with defined substrates, the amplitude of contraction is decreased; 2) the amplitude of contraction during electrical pacing does not change with rate of pacing when both the ATP and NADHmlevels are continuously replenished; and 3) the replenishment of NADHmduring pacing with physiological substrates may be rate-limited by substrate supply to mitochondrial dehydrogenases. During activation of mitochondrial dehydrogenases, or a significant increase in free ADP induced by 2-deoxy-d-glucose, this rate limitation is bypassed or overcome.
cGMP-independent inotropic effects of nitric oxide and peroxynitrite donors: potential role for nitrosylation
Authors: Paolocci Nazareno , Ekelund Ulf E. G. , Isoda Takayoshi , Ozaki Michitaka , Vandegaer Koenraad , Georgakopoulos Dimitrios , Harrison Robert W. , Kass David A. , Hare Joshua M.
Published: December 2017

Nitric oxide (NO) has concentration-dependent biphasic myocardial contractile effects. We tested the hypothesis, in isolated rat hearts, that NO cardiostimulation is primarily non-cGMP dependent. Infusion of 3-morpholinosydnonimine (SIN-1, 10−5M), which may participate in S-nitrosylation (S-NO) via peroxynitrite formation, increased the rate of left ventricular pressure rise (+dP/d t; 19 ± 4%, P < 0.001, n = 11) without increasing effluent cGMP or cAMP. Superoxide dismutase (SOD; 150 U/ml) blocked SIN-1 cardiostimulation and led to cGMP elaboration. Sodium nitroprusside (10−10–10−7M), an iron nitrosyl compound, did not augment +dP/d t but increased cGMP approximately eightfold ( P < 0.001), whereas diethylamine/NO (DEA/NO; 10−7M), a spontaneous NO· donor, increased +dP/d t (5 ± 2%, P < 0.05, n = 6) without augmenting cGMP. SIN-1 and DEA/NO +dP/d t increase persisted despite guanylyl cyclase inhibition with 1 H-(1,2,4)oxadiazolo-(4,3,- a)quinoxalin-1-one (10−5M, P < 0.05 for both donors), suggesting a cGMP-independent mechanism. Glutathione (5 × 10−4M, n = 15) prevented SIN-1 cardiostimulation, suggesting S-NO formation. SIN-1 also produced SOD-inhibitable cardiostimulation in vivo in mice. Thus peroxynitrite and NO donors can stimulate myocardial contractility independently of guanylyl cyclase activation, suggesting a role for S-NO reactions in NO/peroxynitrite-positive inotropic effects in intact hearts.
Evidence for nitroxidergic innervation in monkey ophthalmic arteries in vivo and in vitro
Authors: Ayajiki Kazuhide , Tanaka Toshiki , Okamura Tomio , Toda Noboru
Published: December 2017

In anesthetized monkeys, electrical stimulation (ES) of the pterygopalatine or geniculate ganglion dilated the ipsilateral ophthalmic artery (OA). The induced vasodilatation was unaffected by phentolamine but potentiated by atropine. Intravenous N G-nitro-l-arginine (l-NNA) abolished the response, which was restored byl-arginine. Hexamethonium-abolished vasodilator responses induced solely by geniculate ganglionic stimulation. Thel-NNA constricted OA; l-arginine reversed the effect. Destruction of the pterygopalatine ganglion constricted the ipsilateral artery. Helical strips of OA isolated under deep anesthesia from monkeys, denuded of endothelium, responded to transmural ES with relaxations, which were abolished by tetrodotoxin and l-NNA but were potentiated by atropine. It is concluded that neurogenic vasodilatation of monkey OA is mediated by nerve-derived nitric oxide (NO), and the nerve is originated from the ipsilateral pterygopalatine ganglion that is innervated by cholinergic neurons from the brain stem via the geniculate ganglion. The OA appears to be dilated by mediation of NO continuously liberated from nerves that receive tonic discharges from the vasomotor center. Acetylcholine liberated from postganglionic cholinergic nerves would impair the release of neurogenic NO.
Voltage-independent changes in L-type Ca2+current uncoupled from SR Ca2+ release in cardiac myocytes
Authors: Janczewski Andrzej M. , Lakatta Edward G. , Stern Michael D.
Published: December 2017

To determine the effect of voltage-independent alterations of L-type Ca2+ current ( I Ca) on the sarcoplasmic reticular (SR) Ca2+ release in cardiac myocytes, we measured I Ca and cytosolic Ca2+ transients (Cai 2+; intracellular Ca2+ concentration) in voltage-clamped rat ventricular myocytes during 1) an abrupt increase of extracellular [Ca2+] (Cao 2+) or 2) application of 1 μM FPL-64176, a Ca2+channel agonist, to selectively alter I Ca in the absence of changes in SR Ca2+ loading. On the first depolarization in higher Cao 2+, peak I Ca was increased by 46 ± 6% ( P < 0.001), but the increases in the maximal rate of rise of Cai 2+(dCai 2+/d t max, where t is time; an index of SR Ca2+ release flux) and the Cai 2+ transient amplitude were not significant. Rapid exposure to FPL-64176 greatly slowed inactivation of I Ca, increasing its time integral by 117 ± 8% ( P < 0.001) without significantly increasing peak I Ca, dCai 2+/d t max, or amplitude of the corresponding Cai 2+ transient. Prolongation of exposure to higher Cao 2+ or FPL-64176 did not further increase peak I Ca but greatly increased dCai 2+/d t max, Cai 2+ transient amplitude, and the gain of Ca2+ release (dCai 2+/d t max/ I Ca), evidently due to augmentation of the SR Ca2+ loading. Also, the time to peak dCai 2+/d t maxwas significantly increased in the continuous presence of higher Cao 2+ (by 37 ± 5%, P < 0.001) or FPL-64176 (by 63 ± 5%, P < 0.002). Our experiments provide the first evidence of a marked disparity between an increased peak I Ca and the corresponding SR Ca2+ release. We attribute this to saturation of the SR Ca2+ release flux as predicted by local control theory. Prolongation of the SR Ca2+ release flux, caused by combined actions of a larger I Ca and maximally augmented SR Ca2+ loading, might reflect additional Ca2+ release from corbular SR.
Vascular endothelial growth factor is modulated in vascular muscle cells by estradiol, tamoxifen, and hypoxia
Authors: Bausero P. , Ben-Mahdi M.-H. , Mazucatelli J.-P. , Bloy C. , Perrot-Applanat M.
Published: December 2017

Vascular endothelial growth factor (VEGF) promotes neovascularization, microvascular permeability, and endothelial proliferation. We described previously VEGF mRNA and protein induction by estradiol (E2) in human endometrial fibroblasts. We report here E2 induction of VEGF expression in human venous muscle cells [smooth muscle cells (SMC) from human saphenous veins; HSVSMC] expressing both ER-α and ER-β estrogen receptors. E2 at 10−9to 10−8M increases VEGF mRNA in HSVSMC in a time-dependent manner (3-fold at 24 h), as analyzed by semiquantitative RT-PCR. This level of induction is comparable with E2 endometrial induction of VEGF mRNA. Tamoxifen and hypoxia also increase HSVSMC VEGF mRNA expression over control values. Immunocytochemistry of saphenous veins and isolated SMC confirms translation of VEGF mRNA into protein. Immunoblot analysis of HSVSMC-conditioned medium detects three bands of 18, 23, and 28 kDa, corresponding to VEGF isoforms of 121, 165, and 189 amino acids. Radioreceptor assay of the conditioned medium produced by E2-stimulated HSVSMC reveals an increased VEGF secretion. Our data indicate that VEGF is E2, tamoxifen, and hypoxia inducible in cultured HSVSMC and E2 inducible in aortic SMC, suggesting E2 modulation of VEGF effects in angiogenesis, vascular permeability, and integrity.
Phenotypical features of long Q-T syndrome in transgenic mice expressing human Na-K-ATPase α3-isoform in hearts
Authors: O'Brien Sharon E. , Apkon Michael , Berul Charles I. , Patel H. T. , Saupe Kurt , Spindler Mathias , Ingwall Joanne S. , Zahler Raphael
Published: December 2017

To understand why the adult human heart expresses three isoforms of the sodium pump, we generated transgenic mice (TGM) with 2.3- to 5.5-fold overexpression of the human α3-isoform of Na-K-ATPase in the heart. Hearts from the TGM had increased maximal Na-K-ATPase activity and ouabain affinity compared with control hearts, even though the density of Na-K-ATPase pump sites (of all isoforms) was similar to that of control mice. In perfused hearts, contractility both at baseline and in the presence of ouabain tended to be greater in TGM than in controls. Surface electrocardiograms in anesthetized TGM had a steeper dependence of Q-T on sinus cycle length, and Q-T intervals measured during atrial pacing were significantly longer in TGM. Q-T dispersion during sinus rhythm also tended to be longer in TGM. Thus TGM overexpressing human α3-isoform have several of the phenotypical features of human long Q-T syndrome, despite the absence of previously described mutations in Na+or K+channels.
Molecular distribution of volume-regulated chloride channels (ClC-2 and ClC-3) in cardiac tissues
Authors: Britton Fiona C. , Hatton William J. , Rossow Charles F. , Duan Dayue , Hume Joseph R. , Horowitz Burton
Published: December 2017

The molecular identification of cardiac chloride channels has provided probes to investigate their distribution and abundance in heart. In this study, the molecular expression and distribution of volume-regulated chloride channels ClC-2 and ClC-3 in cardiac tissues were analyzed and quantified. Total RNA was isolated from atria and ventricles of several species (dog, guinea pig, and rat) and subjected to a quantitative RT-PCR strategy. ClC-2 and ClC-3 mRNA expression were calculated relative to β-actin expression within these same tissues. The transcriptional levels of ClC-3 mRNA were between 1.8 and 10.2% of β-actin expression in atria and between 3.4 and 8.6% of β-actin in ventricles ( n= 3 for each tissue). The levels of ClC-2 in both atria and ventricles were significantly less than those measured for ClC-3 ( n = 3; P < 0.05). ClC-2 mRNA levels were between 0.04–0.08% and 0.03–0.18% of β-actin expression in atria and ventricles, respectively ( n = 3 for each tissue). Immunoblots of atrial and ventricular wall protein extracts demonstrated ClC-2- and ClC-3-specific immunoreactivity at 97 and 85 kDa, respectively. Immunohistochemical localization in guinea pig cardiac muscle demonstrates a ubiquitous distribution of ClC-2 and ClC-3 channels in the atrial and ventricular wall. Confocal analysis detected colocalization of ClC-2 and ClC-3 in sarcolemmal membranes and distinct ClC-3 immunoreactivity in cytoplasmic regions. The molecular expression of ClC-2 and ClC-3 in cardiac tissue is consistent with the proposed role of these chloride channels in the regulation of cardiac cell volume and the modulation of cardiac electrical activity.
Upregulation of p67phoxand gp91phoxin aortas from angiotensin II-infused mice
Authors: Cifuentes M. Eugenia , Rey Federico E. , Carretero Oscar A. , Pagano Patrick J.
Published: December 2017

Although NAD(P)H oxidase-derived superoxide (O2−) is increased during the development of angiotensin II (ANG II)-dependent hypertension, vascular regulation at the protein level has not been reported. We have shown that four major components of NAD(P)H oxidase are located primarily in the vascular adventitia as a primary source of vascular O2−. Here we compare vascular levels of O2−and NAD(P)H oxidase in normotensive and ANG II-infused hypertensive mice and show that, after 7 days of ANG II infusion (750 μg · kg−1· day−1ip) in C57B1/6 mice, systolic blood pressure was increased compared with that after sham infusion, concomitant with increased O2−in the thoracic aorta as measured using lucigenin (25 μM)-enhanced chemiluminescence. Both p67phoxand gp91phoxwere detectable by Western blotting in aortic homogenates, and we observed increased protein levels of NAD(P)H oxidase subunits. These ANG II-induced increases were normalized by simultaneous treatment with the AT1receptor antagonist losartan. Moreover, the primary location of these subunits was the adventitia as detected immunohistochemically. Our results suggest that ANG II-induced increases in O2−are due to increased adventitial NAD(P)H oxidase activity, brought about by the heightened expression and interaction of its components.
Effects of microtubule disruption on force, velocity, stiffness and [Ca2+]iin porcine coronary arteries
Authors: Paul Richard J. , Bowman Peggy Sue , Kolodney Michael S.
Published: December 2017

Force generated by smooth muscle cells is believed to result from the interaction of actin and myosin filaments and is regulated through phosphorylation of the myosin regulatory light chain (LC20). The role of other cytoskeleton filaments, such as microtubules and intermediate filaments, in determining the mechanical output of smooth muscle is unclear. In cultured fibroblasts, microtubule disruption results in large increases in force similar to contractions associated with LC20phosphorylation (15). One hypothesis, the “tensegrity” or “push-pull” model, attributes this increase in force to the disruption of microtubules functioning as rigid struts to resist force generated by actin-myosin interaction (9). In porcine coronary arteries, the disruption of microtubules by nocodazole (11 μM) also elicited moderate but significant increases in isometric force (10–40% of a KCl contracture), which could be blocked or reversed by taxol (a microtubule stabilizer). We tested whether this nocodazole-induced force was accompanied by changes in coronary artery stiffness or unloaded shortening velocity, parameters likely to be highly sensitive to microtubule resistance elements. Few changes were seen, ruling out push-pull mechanisms for the increase in force by nocodazole. In contrast, the intracellular calcium concentration, measured by fura 2 in the intact artery, was increased by nocodazole in parallel with force, and this was inhibited and/or reversed by taxol. Our results indicate that microtubules do not significantly contribute to vascular smooth muscle mechanical characteristics but, importantly, may play a role in modulation of Ca2+signal transduction.
NO is involved in MCh-induced accentuated antagonism via type II PDE in the canine blood-perfused SA node
Authors: Sasaki Shingo , Daitoku Kazuyuki , Iwasa Atsushi , Motomura Shigeru
Published: December 2017

The possible role of type II (cGMP-stimulated cAMP hydrolysis) phosphodiesterase (PDE) in the accentuated antagonism of muscarinic effects on heart rate during β-stimulation via endogenous nitric oxide (NO) was evaluated. The canine isolated sinoatrial node preparation was cross circulated with arterial blood of a support dog. The sinoatrial rate of the preparation was 96 ± 5 beats/min ( n = 16) at control. Methacholine (MCh; 0.01–1 μg) injected into the right coronary artery in a bolus fashion caused dose-dependent decreases in sinoatrial rate. Under an intra-arterial infusion of isoproterenol (1 μM), resulting in ∼50% increase in sinoatrial rate, MCh-induced decreases were markedly augmented from −18 ± 3% to −44 ± 4% at 0.3 mg of MCh. When NG-nitro-l-arginine methyl ester (100 μM) or NG-monomethyl-l-arginine (100 μM) were continuously infused, the augmented MCh-induced decreases in sinoatrial rate were significantly suppressed (−29 ± 3% or −25 ± 3%, respectively, P < 0.01). Pretreatment with either 3-isobutyl-1-methylxanthine (IBMX; 20 μM), a non-selective PDE inhibitor, or amrinone (20 μM), a selective type III (cGMP inhibited cAMP hydrolysis) PDE inhibitor, doubled the isoproterenol-induced increase in the sinoatrial rate. However, the augmented MCh-induced decreases in sinoatrial rate were significantly depressed by IBMX (from −23 ± 5% to −14 ± 1%, P < 0.01) but not by amrinone (to −20 ± 3%). These results suggest that MCh-induced accentuated antagonism in the sinoatrial node pacemaker activity can be modulated by endogenous NO via an activation of the type II cyclic GMP-stimulated cAMP PDE.
Responses of neurons in rostral ventrolateral medulla to activation of cardiac receptors in rats
Authors: Li De-Pei , Pan Hui-Lin
Published: December 2017

Ischemic stimulation of cardiac receptors reflexly excites the cardiovascular system. However, the supraspinal mechanisms involved in this reflex are not well defined. This study examined the responses of barosensitive neurons in the rostral ventrolateral medulla (RVLM) to stimulation of cardiac receptors and the afferent pathways involved in these responses. Single-unit activity of RVLM neurons was recorded in α-chloralose-anesthetized rats. Cardiac receptors were stimulated by epicardial application of 10 μg/ml of bradykinin (BK). Barosensitive neurons were silenced by stimulation of baroreceptors. Application of BK increased the mean arterial pressure from 65.2 ± 1.9 to 89.3 ± 2.9 mmHg and excited RVLM barosensitive neurons from 6.2 ± 0.7 to 10.7 ± 0.9 impulses/s ( P < 0.05, n = 40). BK had no effect on 21 nonbarosensitive neurons. Blockade of stellate ganglia abolished the response of barosensitive neurons to BK. Cervical vagotomy significantly increased the baseline discharges of RVLM barosensitive neurons but had no effect on their responses to BK. Thus this study indicates that stimulation of cardiac receptors selectively activates RVLM barosensitive neurons through sympathetic afferent pathways. This information suggests that the RVLM barosensitive neurons are likely involved in the sympathetic control of circulation during myocardial ischemia.
Adenosine preconditions against endothelin-induced constriction of coronary arterioles
Authors: Merkus Daphne , Stepp David W. , Jones Deron W. , Nishikawa Yasuhiro , Chilian William M.
Published: December 2017

Myocardial hypoperfusion is accompanied by concomitant increases in adenosine and endothelin-1 (ET-1) production, but the vasodilatory effect of adenosine prevails over that of ET-1. Therefore, we hypothesized that adenosine-induced or ischemic preconditioning reduces the vasoconstrictive effect of ET-1. Coronary arteriolar diameter in vivo was measured using fluorescence microangiography in anesthetized open-thorax dogs. ET-1 (5 ng · kg−1 · min−1administered intracoronary, n = 10) induced progressive constriction over 45 min [25 ± 6% (SE)]. The constriction was blocked by preconditioning with adenosine (25 μg · kg−1 · min−1administered intracoronary) for 20 min and 10 min of washout ( n = 10) or attenuated by ischemic preconditioning (four 5-min periods of ischemia, 9 ± 5% at 45 min). To investigate the receptor involved in this process, coronary arterioles (50–150 μm) were isolated and pressurized at 60 mmHg in vitro. The ET-1 dose-response curve (1 pM–5 nM) was rightward shifted after preconditioning with adenosine (1 μM) for 20 min and 10 min of washout ( n = 11). Blockade of A2 receptors [8-(3-chlorostyryl)caffeine, 1 μM, n = 9] but not A1 receptors (8-cyclopentyl-1,3-dipropylxanthine, 100 nM, n = 7) prevented this shift. These results suggest that adenosine confers a vascular preconditioning effect, mediated via the A2 receptor, against endothelin-induced constriction. This effect may offer a new protective function of adenosine in preventing excessive coronary constriction.
Myocardial ischemia-reperfusion damage after pacing-induced tachycardia in patients with cardiac syndrome X
Authors: Buffon Antonino , Rigattieri Stefano , Santini Stefano A. , Ramazzotti Vito , Crea Filippo , Giardina Bruno , Maseri Attilio
Published: December 2017

The presence of myocardial ischemia in syndrome X (chest pain, “ischemia-like” electrocardiogram changes, and normal coronary angiograms) is uncertain possibly because, when focally distributed, it may not cause contractile dysfunction or lactate production. We measured lipid hydroperoxides (ROOHs) and conjugated dienes (CDs), two sensitive, independent markers of ischemia-reperfusion oxidative stress, in paired aortic and great cardiac vein blood samples before and after pacing-induced tachycardia in nine patients with syndrome X. Diagnostic ischemic S-T segment changes during pacing were followed by a consistent increase in ROOH and CD levels in the great cardiac vein (from 4.83 ± 1.18 μmol/l at baseline to 7.88 ± 1.12 μmol/l and from 0.038 ± 0.002 to 0.051 ± 0.003 arbitrary units, respectively, P < 0.01). In controls, ROOH and CD levels did not change after pacing. The large postpacing cardiac release of lipid peroxidation products, consistently observed in all patients and similar to that previously observed after ischemia caused by percutaneous transluminal coronary angioplasty, is consistent with an ischemic origin of syndrome X.
Interstitial hydraulic conductivity in a fibrosarcoma
Authors: Zhang Xiao-Yu , Luck Jason , Dewhirst Mark W. , Yuan Fan
Published: December 2017

Convective transport of therapeutic agents in solid tumors can be improved through intratumoral infusion. To optimize the convection, we investigated the dependence of the hydraulic conductivity on tissue deformation induced by interstitial fluid pressure gradient during the infusion. Two experimental systems were used in the investigation: 1) one-dimensional perfusion through tumor slices and 2) intratumoral infusion using a needle. With these systems, we found that the apparent hydraulic conductivity ( K app) could be altered by several orders of magnitude in fibrosarcomas through changes in perfusion conditions. When the perfusion pressure was less than a threshold level, fluid flow in tissues could not be detected. When the perfusion pressure was increased above the threshold level, K appdepended on perfusion system and pressure. The maximum variation in K app in fibrosarcomas reached 80,260-fold in our experiments. The large variation in K app could be explained by perfusion pressure-induced tissue deformation. These experimental data suggest that the hydraulic conductivity is very sensitive to tissue deformation and imply that it is possible to improve intratumoral infusion of therapeutic agents through optimization of infusion conditions.
Nitric oxide: a trigger for classic preconditioning?
Authors: Lochner Amanda , Marais Erna , Genade Sonia , Moolman Johan A.
Published: December 2017

To determine whether nitric oxide (NO) is involved in classic preconditioning (PC), the effect of NO donors as well as inhibition of the l-arginine-NO-cGMP pathway were evaluated on 1) the functional recovery during reperfusion of ischemic rat hearts and 2) cyclic nucleotides during both the PC protocol and sustained ischemia. Tissue cyclic nucleotides were manipulated with NO donors [ S-nitroso- N-penicillamine (SNAP), sodium nitroprusside (SNP), or l-arginine] and inhibitors of nitric oxide synthase ( N ω-nitro-l-arginine methyl ester or N-nitro-l-arginine) or guanylyl cyclase (1 H-[1,2,4]oxadiazolol-[4,3- a]quinoxaline-1-one). Pharmacological elevation in tissue cGMP levels by SNAP or SNP before sustained ischemia elicited functional improvement during reperfusion comparable to that by PC. Administration of inhibitors before and during the PC protocol partially attenuated functional recovery, whereas they had no effect when given after the ischemic PC protocol and before sustained ischemia only, indicating a role for NO as a trigger but not as a mediator. Ischemic PC, SNAP, or SNP caused a significant increase in cGMP and a reduction in cAMP levels after 25 min of sustained ischemia that may contribute to the protection obtained. The results obtained suggest a role for NO (and cGMP) as a trigger in classic PC.
Distension of urinary bladder induces exaggerated coronary constriction in smokers with early atherosclerosis
Authors: Lee Tsung-Ming , Su Sheng-Fang , Suo Wen-Yi , Lee Chen-Yueh , Chen Ming-Fong , Lee Yuan-Teh , Tsai Chang-Her
Published: December 2017

Distension of the urinary bladder causes an increase in efferent sympathetic activity, which can precipitate myocardial ischemia. Smoking has been shown to modulate activities of afferent nerves from the distended urinary bladder and to impair endothelial function in response to sympathetic activation. To assess the effect of bladder distension on coronary dynamics in smokers, we measured epicardial and microvascular responses in 24 patients with early atherosclerosis (< 50% diameter stenosis). Patients were classified into habitual smokers ( group 1, n = 14) and nonsmokers ( group 2, n = 10). Habitual smokers were randomized into two subgroups on the basis of the use of doxazosin, as follows: subgroup 1A ( n = 7), without administration of doxazosin before catheterization; subgroup 1B( n = 7), with dosing doxazosin. In response to bladder distension (mean intravesical pressure 21.5 mmHg), bladder distension significantly decreased coronary diameter at the stenotic segments, coronary blood flow, and increased coronary resistance compared with baseline values, in subgroup 1A patients. In subgroup 1B patients during bladder distension, coronary diameter, coronary blood flow, and coronary resistance did not show significant changes compared with baseline values. There were significant differences of coronary diameter at the stenotic segments, coronary blood flow, and of changes of coronary vascular resistance between subgroup 1Aand group 2 during bladder distension, despite similar changes in rate-pressure product. The present study showed that urinary bladder distension caused an abnormal vasomotor response of epicardial vasoconstriction and a concomitant increased coronary resistance, which leads to reduction in coronary blood flow in patients with early atherosclerosis. Smoking may further impair the response, implying that smoking has exaggerated response to sympathetic stimulation of conduit and resistance vessels. The abnormal response was abolished by pretreated administration of doxazosin, suggesting that the involved mechanisms are related to α1-adrenoceptors.
Negative inotropism of hyperthermia increases oxygen cost of contractility in canine hearts
Authors: Saeki Akio , Goto Yoichi , Hata Katsuya , Takasago Toshiyuki , Nishioka Takehiko , Suga Hiroyuki
Published: December 2017

Heart temperature affects left ventricular (LV) function and myocardial metabolism. However, how and whether increasing heart temperature affects LV mechanoenergetics remain unclear. We designed the present study to investigate effects of increased temperature by 5°C from 36°C on LV contractility and energetics. We analyzed the LV contractility index ( Emax) and the relation between the myocardial oxygen consumption (MV˙o2) and the pressure-volume area (PVA; a measure of LV total mechanical energy) in isovolumically contracting isolated canine hearts during normothermia (NT) and hyperthermia (HT). HT reduced Emaxby 38% ( P < 0.01) and shortened time to Emaxby 20% ( P < 0.05). HT, however, altered neither the slope nor the unloaded MV˙o2of the MV˙o2-PVA relation. HT increased the oxygen cost of contractility (the incremental ratio of unloaded MV˙o2to Emax) by 49%. When Ca2+infusion restored the reduced LV contractility during HT to the NT baseline level, the unloaded MV˙o2in HT exceeded the NT value by 36%. We conclude that HT-induced negative inotropism accompanies an increase in the oxygen cost of contractility.
Mechanisms of I Ks suppression in LQT1 mutants
Authors: Bianchi Laura , Priori Silvia G. , Napolitano Carlo , Surewicz Krystyna A. , Dennis Adrienne T. , Memmi Mirella , Schwartz Peter J. , Brown Arthur M.
Published: December 2017

Mutations in the cardiac potassium ion channel gene KCNQ1 (voltage-gated K+ channel subtype KvLQT1) cause LQT1, the most common type of hereditary long Q-T syndrome. KvLQT1 mutations prolong Q-T by reducing the repolarizing cardiac current [slow delayed rectifier K+ current ( I Ks )], but, for reasons that are not well understood, the clinical phenotypes may vary considerably even for carriers of the same mutation, perhaps explaining the mode of inheritance. At present, only currents expressed by LQT1 mutants have been studied, and it is unknown whether abnormal subunits are transported to the cell surface. Here, we have examined for the first time trafficking of KvLQT1 mutations and correlated the results with the I Ks currents that were expressed. Two missense mutations, S225L and A300T, produced abnormal currents, and two others, Y281C and Y315C, produced no currents. However, all four KvLQT1 mutations were detected at the cell surface. S225L, Y281C, and Y315C produced dominant negative effects on wild-type I Ks current, whereas the mutant with the mildest dysfunction, A300T, did not. We examined trafficking of a severe insertion deletion mutant Δ544 and detected this protein at the cell surface as well. We compared the cellular and clinical phenotypes and found a poor correlation for the severely dysfunctional mutations.
Urocortin, a member of the corticotropin-releasing factor family, in normal and diseased heart
Authors: Nishikimi Toshio , Miyata Atsuro , Horio Takeshi , Yoshihara Fumiki , Nagaya Noritoshi , Takishita Shuichi , Yutani Chikao , Matsuo Hisayuki , Matsuoka Hiroaki , Kangawa Kenji
Published: December 2017

In the present study we investigated the form of expression, action, second messenger, and the cellular location of urocortin, a member of the corticotropin-releasing factor (CRF) family, in the heart. Urocortin mRNA, as shown by quantitative RT-PCR analysis, is expressed in the cultured rat cardiac nonmyocytes (NMC) as well as myocytes (MC) in the heart, whereas CRF receptor type 2β (CRF-R2β), presumed urocortin receptor mRNA, is predominantly expressed in MC compared with NMC. Urocortin mRNA expression is higher in left ventricular (LV) hypertrophy than in normal LV, whereas CRF-R2β mRNA expression is markedly depressed in LV hypertrophy compared with normal LV. Urocortin more potently increased the cAMP levels in both MC and NMC than did CRF, and its effect was more potent in MC than in NMC. Urocortin significantly increased protein synthesis by [14C]Phe incorporations and atrial natriuretic peptide secretion in MC and collagen and increased DNA synthesis by [3H]prolin and [3H]Thy incorporations in NMC. An immunohistochemical study revealed that urocortin immunoreactivity was observed in MC in the normal human heart and that it was more intense in the MC of the human failing heart than in MC of the normal heart. These results, together with the recent evidence of urocortin for positive inotropic action, suggest that increased urocortin in the diseased heart may modulate the pathophysiology of cardiac hypertrophy or failing heart, at least in part, via cAMP signaling pathway.
Detection and sources of nonlinearity in the variability of cardiac R-R intervals and blood pressure in rats
Authors: González Julián J. , Cordero Juan J. , Feria Manuel , Pereda Ernesto
Published: December 2017

Beat-to-beat R-R interval (RRV) and systolic blood pressure (SPV) variability signals were obtained from unrestrained rats in baseline and under different pharmacological treatments. The origin and extent of the nonlinearity in both signals, as well as their degree of mutual coupling, was estimated using measurements from the correlation integral (CI) and recurrence quantification analysis (RQA). After the respiratory component of baseline signals was removed, the nonlinearity was lower in the RRV and disappeared in the SPV. This also decreased the RRV-SPV coupling. The nonlinearity of RRV was also reduced after atropine, and the nonlinearity of SPV was strengthened after prazosin and N ω-monomethyl-l-arginine (l-NMMA). Atropine and prazosin decreased CI measures of both signals, whereas propranolol, phenylephrine, andl-NMMA decreased only those of SPV. RQA indexes of RRV increased after atropine and decreased after propranolol, whereas the reverse occurred for the RRV-SPV coupling. These results suggest that: 1) the nonlinearity of RRV appears to be very dependent on the parasympathetic activity, whereas that of SPV seems to come from its respiratory component through a nonneural pathway; 2) respiratory component appears to be involved, through the parasympathetic system, in the RRV-SPV coupling; and 3) CI and RQA measures seems to be useful in assessing autonomic mediation of RRV and RRV-SPV coupling.
Form and function of fetal and neonatal pulmonary arterial bifurcations
Authors: Bennett Stephen H. , Eldridge Marlowe W. , Zaghi Daniel , Zaghi Shaaron E. , Milstein Jay M. , Goetzman Boyd W.
Published: December 2017

Bifurcation is a basic form of vascular connection. It is composed of a parent vessel of diameter d 0, and two daughter vessels, d 1 and d 2, where d 0 > d 1 ≥ d 2. Optimal values for the bifurcation area ratio, β = ( d 1 2 + d 2 2)/ d 0 2, and the junction exponent, x, in d 0 x = d 1 x + d 2 x , are postulated to be universal in nature. However, we have hypothesized that the perinatal pulmonary arterial circulation is an exception. Arterial diameters were measured in pulmonary vascular casts of a fetal lamb (140 days gestation/145 days term) and a neonatal lamb (1 day old). The values for β and x were evaluated in 10,970 fetal and 846 neonatal bifurcations sampled from the proximal and intermediate arterial regions. Mean values and confidence intervals (CI) for the fetus were β = 0.890 (0.886–0.895 CI) and x= 1.75 (1.74–1.76 CI); and for the newborn were β = 0.913 (0.90–0.93 CI) and x = 1.79 (1.75–1.82 CI). These values are significantly different from Murray's law (β > 1, x = 3) or the West-Brown-Enquist law (β = 1, x = 2). Therefore, perinatal pulmonary bifurcation design appears to be distinctive and exceptional. The decreasing cross-sectional area with branching leads to the hemodynamic consequence of shear stress amplification. This structural organization may be important for facilitating vascular development at low flow rates; however, it may be the origin of unstable reactivity if elevated blood flow and pressure occurs.
Slow intercellular Ca2+signaling in wild-type and Cx43-null neonatal mouse cardiac myocytes
Authors: Suadicani Sylvia O. , Vink Monique J. , Spray David C.
Published: December 2017

Focal mechanical stimulation of single neonatal mouse cardiac myocytes in culture induced intercellular Ca2+waves that propagated with mean velocities of ∼14 μm/s, reaching ∼80% of the cells in the field. Deletion of connexin43 (Cx43), the main cardiac gap junction channel protein, did not prevent communication of mechanically induced Ca2+waves, although the velocity and number of cells communicated by the Ca2+signal were significantly reduced. Similar effects were observed in wild-type cardiac myocytes treated with heptanol, a gap junction channel blocker. Fewer cells were involved in intercellular Ca2+signaling in both wild-type and Cx43-null cultures in the presence of suramin, a P2-receptor blocker; blockage was more effective in Cx43-null than in wild-type cells. Thus gap junction channels provide the main pathway for communication of slow intercellular Ca2+signals in wild-type neonatal mouse cardiac myocytes. Activation of P2-receptors induced by ATP release contributes a secondary, extracellular pathway for transmission of Ca2+signals. The importance of such ATP-mediated Ca2+signaling would be expected to be enhanced under ischemic conditions, when release of ATP is increased and gap junction channels conductance is significantly reduced.
Measurement of the activation time of oxidative phosphorylation in isolated mouse hearts
Authors: Gustafson Lori A. , Van Beek Johannes H. G. M.
Published: December 2017

The purpose of this study was to develop a technique for determination of the dynamic regulation of oxidative myocardial metabolism in the mouse. The response time of myocardial oxygen consumption (MV˙o 2) to a step in heart rate was determined in Langendorff-perfused mouse hearts. We examined the effect of glucose-only perfusate and glucose combined with 1, 3, or 6 mM pyruvate. Left ventricular systolic pressure (LVSP) decreased, yet the rate-pressure product (RPP) and MV˙o 2 increased with upward steps in heart rate. Pyruvate increased LVSP, RPP, and MV˙o 2 at the lower concentrations; however, when 6 mM pyruvate was added, LVSP and RPP became depressed while MV˙o 2 remained elevated. The mean response time of oxygen consumption to a step in heart rate from 270 to 350 beats/min was 9.8 s ( n = 7) in the glucose-only perfused hearts. Perfusion with glucose plus 6 mM pyruvate decreased the response time to 5.3 s. These results are similar to those found in the rabbit heart and lay the groundwork for further examination of the dynamic regulation of oxidative myocardial metabolism in genetically altered mice. We concluded that the activation time of oxidative phosphorylation in the mouse is similar to that in larger species, despite the high mitochondrial content and natural heart rate of the mouse.
cADP-ribose activates reconstituted ryanodine receptors from coronary arterial smooth muscle
Authors: Li Pin-Lan , Tang Wang-Xian , Valdivia Hector H. , Zou Ai-Ping , Campbell William B.
Published: December 2017

The present study was designed to test the hypothesis that cADP-ribose (cADPR) increases Ca2+release through activation of ryanodine receptors (RYR) on the sarcoplasmic reticulum (SR) in coronary arterial smooth muscle cells (CASMCs). We reconstituted RYR from the SR of CASMCs into planar lipid bilayers and examined the effect of cADPR on the activity of these Ca2+release channels. In a symmetrical cesium methanesulfonate configuration, a 245 pS Cs+current was recorded. This current was characterized by the formation of a subconductance and increase in the open probability (NPo) of the channels in the presence of ryanodine (0.01–1 μM) and imperatoxin A (100 nM). A high concentration of ryanodine (50 μM) and ruthenium red (40–80 μM) substantially inhibited the activity of RYR/Ca2+release channels. Caffeine (0.5–5 mM) markedly increased the NPoof these Ca2+release channels of the SR, but d- myo-inositol 1,4,5-trisphospate and heparin were without effect. Cyclic ADPR significantly increased the NPoof these Ca2+release channels of SR in a concentration-dependent manner. Addition of cADPR (0.01 μM) into the cis bath solution produced a 2.9-fold increase in the NPoof these RYR/Ca2+release channels. An eightfold increase in the NPoof the RYR/Ca2+release channels (0.0056 ± 0.001 vs. 0.048 ± 0.017) was observed at a concentration of cADPR of 1 μM. The effect of cADPR was completely abolished by ryanodine (50 μM). In the presence of cADPR, Ca2+-induced activation of these channels was markedly enhanced. These results provide evidence that cADPR activates RYR/Ca2+release channels on the SR of CASMCs. It is concluded that cADPR stimulates Ca2+release through the activation of RYRs on the SR of these smooth mucle cells.