bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitric oxide modulates endotoxin-induced platelet-endothelial cell adhesion in intestinal venules
Authors: Cerwinka Wolfgang H. , Cooper Dianne , Krieglstein Christian F. , Feelisch Martin , Granger D. Neil
Published: March 2015

Although platelets have been implicated in the pathogenesis of vascular diseases, little is known about factors that regulate interactions between platelets and the vessel wall under physiological conditions. The objectives of this study were to 1) define the contribution of nitric oxide (NO) to endotoxin (lipopolysaccharide, LPS)-induced platelet-endothelial cell (P/E) adhesion in murine intestinal venules and 2) determine whether the antiadhesive action of NO is mediated by soluble guanylate cyclase (sGC). Adhesive interactions between platelets and endothelial cells were monitored by intravital microscopy. LPS administration into control wild-type mice (WT) resulted in a >15-fold increase in P/E adhesion. Similar responses were observed using endothelial NO synthase (eNOS)-deficient platelets. However, treatment with the NO donor diethylenetriamine-nitric oxide (DETA-NO) attenuated the P/E adhesion response to LPS, whereas the NO synthase inhibitor NG-nitro-l-arginine methyl ester or eNOS deficiency resulted in an exacerbation. P/E adhesion response did not differ between LPS-treated WT and inducible NOS-deficient mice. Inhibition of sGC abolished the attenuating effects of DETA-NO, whereas the sGC activator 3-(5′-hydroxymethyl-2′-furyl)-1-benzyl indazole (YC-1) reduced LPS-induced P/E adhesion. These findings indicate that 1) eNOS-derived NO attenuates endotoxin-induced P/E adhesion and 2) sGC is responsible for the antiadhesive action of NO.
IκB overexpression in cardiomyocytes prevents NF-κB translocation and provides cardioprotection in trauma
Authors: Carlson Deborah L. , White D. Jean , Maass David L. , Nguyen Robin C. , Giroir Brett , Horton Jureta W.
Published: March 2015

This study examined the effects of either IκBα overexpression (transgenic mice) or N-acetyl-leucinyl-leucinyl-norleucinal (ALLN) administration (proteosome inhibitor in wild-type mice) on cardiomyocyte secretion of tumor necrosis factor-α (TNF-α) and on cardiac performance after burn trauma. Transgenic mice were divided into four experimental groups. IκBα overexpressing mice were given a third-degree scald burn over 40% of the total body surface area or wild-type littermates were given either a scald or sham burn to provide appropriate controls. Pharmacological studies included ALLN (20 mg/kg) administration in either burned wild-type mice or wild-type shams. Burn trauma in wild-type mice promoted nuclear factor-κB (NF-κB) nuclear translocation, cardiomyocyte secretion of TNF-α, and impaired cardiac performance. IκBα overexpression or ALLN treatment of burn trauma prevented NF-κB activation in cardiac tissue, prevented cardiomyocyte secretion of TNF-α, and ablated burn-mediated cardiac contractile dysfunction. These data suggest that NF-κB activation and inflammatory cytokine secretion play a significant role in postburn myocardial abnormalities.
Does whole body autoregulation mediate the hemodynamic responses to increased dietary salt in rats with clamped ANG II?
Authors: Fine Deborah M. , Ariza-Nieto Pilar , Osborn John W.
Published: March 2015

The present study was conducted to test the hypothesis that salt-dependent hypertension, in rats with an unresponsive renin-angiotensin system, is characterized by a “whole body autoregulation” hemodynamic profile. To test this hypothesis, rats were chronically instrumented to continuously measure cardiac output (CO) and arterial pressure (AP). A venous catheter was implanted for infusion of saline vehicle (Veh; n = 8) or treatment [enalapril (2 mg · kg–1 · day–1) plus ANG II: ANG-NORM (5 ng · kg–1 · min–1 ANG II, n = 8) or ANG-HI (10 ng · kg–1 · min–1 ANG II, n = 9)] to pharmacologically clamp plasma ANG II. After a 10-day recovery period on a 0.1% NaCl diet, AP and CO were measured continuously for 5 days of control (0.1% NaCl), 7 days of high salt (4.0% NaCl), and 5 days of recovery (0.1% NaCl). Hemodynamics did not change in the Veh group at any time. AP increased by ∼20 mmHg in the ANG-NORM and ANG-HI groups when NaCl was increased. Hypertension was mediated by an increase in CO of ∼12% at steady state, with no change in total peripheral resistance (TPR) during the high salt period. AP returned to control levels when dietary sodium was decreased, mediated by a ∼10% decrease in TPR, with CO remaining elevated. There was no difference in the hemodynamic responses to increased salt between the ANG-HI and ANG-NORM groups. We conclude that the whole body autoregulation hypothesis does not explain the hemodynamic profile of salt-dependent hypertension in rats with an unresponsive renin-angiotensin system.
Nitric oxide modulates right ventricular flow and oxygen consumption during norepinephrine infusion
Authors: Setty Srinath , Tune Johnathan D. , Downey H. Fred
Published: March 2015

This study was designed to test if nitric oxide (NO) contributes to norepinephrine-induced right coronary vasodilation and if NO blunts the norepinephrine-induced increase in myocardial oxygen consumption (MV˙o2) in the right ventricle. In five anesthetized, open-chest dogs, mean aortic pressure, heart rate, right ventricular rate of pressure development over time (dP/d t), right coronary blood flow, and right ventricular MV˙o2were measured before and during graded intracoronary infusions of norepinephrine in the absence and presence of a NO synthase blocker, Nω-nitro-l-arginine methyl ester (l-NAME; 150 μg/min ic). During both conditions, right coronary blood flow and right ventricular MV˙o2significantly increased with graded infusions of norepinephrine. l-NAME significantly blunted the coronary hyperemic response to norepinephrine, althoughl-NAME did not alter the relationship between right ventricular MV˙o2and norepinephrine dose. However, when right ventricular function was indexed by heart rate × right ventricular maximum dP/d t × peak right ventricular systolic pressure, l-NAME significantly increased the oxygen cost of right ventricular function. These results indicate that NO contributes to norepinephrine-induced right coronary vasodilation and improves right ventricular oxygen utilization efficiency.
Moderate alcohol consumption induces sustained cardiac protection by activating PKC-ε and Akt
Authors: Zhou Hui-Zhong , Karliner Joel S. , Gray Mary O.
Published: March 2015

C57BL/6 mice were fed 18% ethanol (vol/vol) in drinking water for 12 wk. Isovolumic hearts were subjected to 20 min of ischemia and 30 min of reperfusion on a Langendorff apparatus. There were no differences in baseline hemodynamic function between hearts from ethanol (EtOH)-fed mice and controls. However, prior alcohol consumption doubled recovery of left ventricular developed pressure (68 ± 8 vs. 33 ± 8 mmHg for controls; n = 10, P < 0.05) and reduced creatine kinase release by half (0.26 ± 0.04 vs. 0.51 ± 0.08 U · min−1 · g wet wt−1 for controls; n = 10, P < 0.05). EtOH feeding doubled expression of activated protein kinase C epsilon (PKC)ε ( n = 6, P < 0.05); whereas PKC inhibition blocked protection during ischemia-reperfusion. EtOH feeding also increased expression of Akt three- to fivefold ( n = 6, P < 0.05), whereas PKC inhibition prevented increases in Akt kinase activity. We conclude that signaling pathways involving PKC-ε are critical for sustained EtOH-mediated cardioprotection and that Akt may be a downstream effector of resistance to myocardial reperfusion injury.
Evidence for association of coronary sinus levels of hepatocyte growth factor and collateralization in human coronary disease
Authors: Lenihan Daniel J. , Osman Abdulfatah , Sriram Vissa , Aitsebaomo Julius , Patterson Cam
Published: March 2015

The therapeutic use of angiogenic factors to protect ischemic myocardium is limited by our incomplete understanding of their endogenous production. We determined the association between angiogenic factors and collateral formation in patients with coronary artery disease (CAD). A total of 71 patients underwent catheterization with sampling of the pulmonary artery, aorta, and coronary sinus (CS) to determine the levels of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). VEGF and HGF levels were not different in the three vascular sites, suggesting that the heart is not a major source of these cytokines in the circulation. CS VEGF and HGF levels were similar in patients with and without CAD. Elevated CS HGF levels were associated with collateral formation, whereas VEGF levels were not. Additionally, CS HGF was significantly elevated in patients with left ventricular dysfunction. These data map for the first time the concentration of endogenous angiogenic factors in the coronary circulation and support further studies to determine whether HGF may be an endogenous cardioprotective angiogenic factor.
Pattern formation of vascular smooth muscle cells subject to nonuniform fluid shear stress: role of PDGF-β receptor and Src
Authors: Liu Shu Q. , Tieche Christopher , Tang Dalin , Alkema Paul
Published: March 2015

Blood vessels are subject to fluid shear stress, a hemodynamic factor that inhibits the mitogenic activities of vascular cells. The presence of nonuniform shear stress has been shown to exert graded suppression of cell proliferation and induces the formation of cell density gradients, which in turn regulate the direction of smooth muscle cell (SMC) migration and alignment. Here, we investigated the role of platelet-derived growth factor (PDGF)-β receptor and Src in the regulation of such processes. In experimental models with vascular polymer implants, SMCs migrated from the vessel media into the neointima of the implant under defined fluid shear stress. In a nonuniform shear model, blood shear stress suppressed the expression of PDGF-β receptor and the phosphorylation of Src in a shear level-dependent manner, resulting in the formation of mitogen gradients, which were consistent with the gradient of cell density as well as the alignment of SMCs. In contrast, uniform shear stress in a control model elicited an even influence on the activity of mitogenic molecules without modulating the uniformity of cell density and did not significantly influence the direction of SMC alignment. The suppression of the PDGF-β receptor tyrosine kinase and Src with pharmacological substances diminished the gradients of mitogens and cell density and reduced the influence of nonuniform shear stress on SMC alignment. These observations suggest that PDGF-β receptor and Src possibly serve as mediating factors in nonuniform shear-induced formation of cell density gradients and alignment of SMCs in the neointima of vascular polymer implants.
α1-Adrenergic receptor responses in α1AB-AR knockout mouse hearts suggest the presence of α1D-AR
Authors: Turnbull Lynne , McCloskey Diana T. , O'Connell Timothy D. , Simpson Paul C. , Baker Anthony J.
Published: March 2015

Two functional α1-adrenergic receptor (AR) subtypes (α1Aand α1B) have been identified in the mouse heart. However, it is unclear whether the third known subtype, α1D-AR, is also present. To investigate this, we determined whether there were α1-AR responses in hearts from a novel mouse model lacking α1A- and α1B-ARs (double knockout) (ABKO). In Langendorff-perfused hearts, α1-ARs were stimulated with phenylephrine. For ABKO hearts, phenylephrine reduced left ventricular pressure and coronary flow (to 87 ± 2% and 86 ± 4% of initial, respectively, n = 11, P < 0.01). These effects were blocked by prazosin and 8-{2-[4-(2-methoxyphenyl)-1-piperazinyl]-8-azaspirol[4,5]decane-7,9-dione} dihydrochloride, suggesting that α1D-AR-mediated responses were present. In contrast, right ventricular trabeculae from ABKO hearts did not respond to phenylephrine, suggesting that in ABKO perfused hearts, the effects of phenylephrine were not mediated by direct actions on cardiomyocytes. A novel finding was that α1-AR stimulation caused positive inotropy in the wild-type mouse heart, in contrast to negative inotropy observed in mouse cardiac muscle strips. We conclude that mouse hearts lacking α1A- and α1B-ARs retain functional α1-AR responses involving decreases of coronary flow and ventricular pressure that reflect α1D-AR-mediated vasoconstriction. Furthermore, α1-AR inotropic responses depend critically on the experimental conditions.
Mechanism of dilation to reactive oxygen species in human coronary arterioles
Authors: Sato Atsushi , Sakuma Ichiro , Gutterman David D.
Published: March 2015

We tested whether reactive oxygen species (ROS) generated from treatment with xanthine (XA) and xanthine oxidase (XO) alter vascular tone of human coronary arterioles (HCA). Fresh human coronary arterioles (HCA) from right atrial appendages were cannulated for video microscopy. ROS generated by XA (10–4M) + XO (10 mU/ml) dilated HCA (99 ± 1%, 20 min after application of XA/XO). This dilation was not affected by denudation or superoxide dismutase (150 U/ml). Catalase (500 U/ml or 5,000 U/ml) attenuated the dilation early on, but a significant latent vasodilation appeared after 5 min peaking at 20 min (51 ± 1%, 20 min after application of XA/XO + 500 U/ml catalase, P < 0.01 vs. control). KCl (40 mM) reduced the early and sustained vasodilation to XA/XO in the absence of catalase but 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 5 × 10–5M), diethyldithiocarbamate trihydrate (DDC, 10–2M), and deferoxamine (DFX, 10–3M) had no effect. In contrast, the catalase-resistant vasodilation was significantly attenuated by DDC, ODQ, and DFX as well as polyethylene-glycolated catalase (5,000 U/ml), but KCl had no effect. Confocal microscopy revealed that even in the presence of catalase, 2′,7′-dichlorodihydrofluoresein diacetate fluorescence was observed in the vascular smooth muscle, but this was abolished by DDC. These data indicate that the exogenously generated superoxide anion ([Formula: see text]) by XA/XO is spontaneously converted to H2O2, which dilates HCA through vascular smooth muscle hyperpolarization. [Formula: see text] is also converted to H2O2likely by superoxide dismustase within vascular cells and dilates HCA through a different pathway involving the activation of guanylate cyclase. These findings suggest that exogenously and endogenously produced H2O2may elicit vasodilation by different mechanisms.
Mechanism of thrombin-induced vasodilation in human coronary arterioles
Authors: Bosnjak John J. , Terata Ken , Miura Hiroto , Sato Atsushi , Nicolosi Alfred C. , McDonald Monica , Manthei Sara A. , Saito Takashi , Hatoum Ossama A. , Gutterman David D.
Published: March 2015

Thrombin (Thromb), activated as part of the clotting cascade, dilates conduit arteries through an endothelial pertussis toxin (PTX)-sensitive G-protein receptor and releases nitric oxide (NO). Thromb also acts on downstream microvessels. Therefore, we examined whether Thromb dilates human coronary arterioles (HCA). HCA from right atrial appendages were constricted by 30–50% with endothelin-1. Dilation to Thromb (10−4–1 U/ml) was assessed before and after inhibitors with videomicroscopy. There was no tachyphylaxis to Thromb dilation (maximum dilation = 87.0%, ED50 = 1.49 × 10−2). Dilation to Thromb was abolished with either hirudin or denudation but was not affected by PTX. Neither N ω-nitro-l-arginine methyl ester ( n = 7), indomethacin ( n = 9),1H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one ( n = 6), tetraethylammonium chloride ( n = 5), nor iberiotoxin ( n = 4) reduced dilation to Thromb. However, KCl (maximum dilation = 89 ± 5 vs. 20 ± 10%; P < 0.05; n = 7), tetrabutylammonium chloride (maximum dilation = 79 ± 7 vs. 21 ± 4%; P < 0.05; n = 5), and charybdotoxin (maximum dilation = 89 ± 4 vs. 10 ± 2%; P < 0.05; n = 4) attenuated dilation to Thromb. In contrast to animal models, Thromb-induced dilation in human arterioles is independent of Gi-protein activation and NO release. However, Thromb dilation is endothelium dependent, is maintained on consecutive applications, and involves activation of K+ channels. We speculate that an endothelium-derived hyperpolarizing factor contributes to Thromb-induced dilation in HCA.
Natriuretic peptide gene expression in DOCA-salt hypertension after blockade of type B endothelin receptor
Authors: Bianciotti Liliana G. , de Bold Adolfo J.
Published: March 2015

We investigated the effect of long-term in vivo blockade of the ET-1 receptor subtype B (ETB) with A-192621, a selective ETBantagonist, on atrial and ventricular natriuretic peptide (NP) gene expression in deoxycorticosterone acetate (DOCA)-salt hypertension. In this model, stimulation of the cardiac natriuretic peptide (NP) and the endothelin system and suppression of the renin-angiotensin system is observed. DOCA-salt induced significant hypertension, cardiac hypertrophy and increased NP plasma and left atrial and right and left ventricular NP gene expression. ETBblockade per se produced hypertension and left ventricular hypertrophy but induced little change on the levels of ventricular NP and only increased left atrial natriuretic factor (ANF) mRNA levels. Combined ETBblockade/DOCA-salt treatment worsened hypertension, increased left ventricular hypertrophy and induced right ventricular hypertrophy. All animals so treated had increased ventricular NP gene expression. Collagen III and β-myosin heavy chain gene expression were enhanced in both the right and the left ventricle of DOCA-salt hypertensive rats. The results of this study suggest that the ETBreceptor does not participate directly in the modulation of atrial or ventricular NP gene expression and that this receptor mediates a protective cardiovascular function. ETBblockade can induce significant ventricular hypertrophy without an increase in ANF or brain NP gene expression.
Constitutive properties of hypertrophied myocardium: cellular contribution to changes in myocardial stiffness
Authors: Harris Todd S. , Baicu Catalin F. , Conrad Chester H. , Koide Masaaki , Buckley J. Michael , Barnes Mary , Cooper George , Zile Michael R.
Published: March 2015

Recent studies have suggested that pressure overload hypertrophy (POH) alters the viscoelastic properties of individual cardiocytes when studied in isolation. However, whether these changes in cardiocyte properties contribute causally to changes in the material properties of the cardiac muscle as a whole is unknown. Accordingly, a selective, isolated, acute change in cardiocyte constitutive properties was imposed in an in vitro system capable of measuring the resultant effect on the material properties of the composite cardiac muscle. POH caused an increase in both myocardial elastic stiffness, from 20.5 ± 1.3 to 28.4 ± 1.8, and viscous damping, from 15.2 ± 1.1 to 19.8 ± 1.5 s (normal vs. POH, P < 0.05), respectively. Recent studies have shown that cardiocyte constitutive properties could be acutely altered by depolymerizing the microtubules with colchicine. Colchicine caused a significant decrease in the viscous damping in POH muscles (19.8 ± 1.5 s at baseline vs. 14.7 ± 1.3 s after colchicine, P < 0.05). Therefore, myocardial material properties can be altered by selectively changing the constitutive properties of one element within this muscle tissue, the cardiocyte. Changes in the constitutive properties of the cardiocytes themselves contribute to the abnormalities in myocardial stiffness and viscosity that develop during POH.
Quantitation of superoxide generation and substrate utilization by vascular NAD(P)H oxidase
Authors: Souza Heraldo P. , Liu Xiaoping , Samouilov Alexandre , Kuppusamy Periannan , Laurindo Francisco R. M. , Zweier Jay L.
Published: March 2015

In vascular tissues, an NAD(P)H oxidase is the main source of superoxide; however, there has been much uncertainty regarding its activity and the levels of superoxide it generates. This problem has limited overall progress in this field. Therefore, studies were performed and techniques developed to quantitatively assess the function of the vascular NAD(P)H oxidase, measuring its rate of superoxide production and substrate consumption in rat aortic homogenates and intact segments. NADPH/NADH oxidation was measured spectrophotometrically, and oxygen consumption was measured by electrochemical probe. Superoxide was detected and quantitated by electron paramagnetic resonance spin trapping. Under basal conditions, superoxide generation and oxygen consumption were negligible. After addition of NADPH or NADH (0.1 mM), superoxide was generated at rates of 0.41 ± 0.03 or 0.36 ± 0.04 nmol · mg protein−1· min−1, respectively. Oxygen was consumed with a similar time course at rates of 1.5 ± 0.2 or 1.3 ± 0.3 nmol · mg protein−1· min−1, and NADPH or NADH were oxidized at rates of 1.8 ± 0.4 and 1.5 ± 0.3 nmol · mg protein−1· min−1, respectively. In intact aortic rings, superoxide was generated with rates of 4.0 ± 0.7 or 3.7 ± 0.7 pmol · mg tissue−1· min−1, whereas oxygen was consumed at rates of 22.1 ± 5.0 or 14.5 ± 3.3 pmol · mg tissue−1· min−1, for NADPH or NADH, respectively. These values are lower than those previously measured using lucigenin, which uncouples flavoenzymes, triggering additional superoxide generation. This quantitative approach for characterization of the vascular NAD(P)H oxidase activity should facilitate the further identification and cellular characterization of this enzyme(s) and its functional and signaling roles.
Uniaxial strain upregulates matrix-degrading enzymes produced by human vascular smooth muscle cells
Authors: Asanuma Kazuhiko , Magid Richard , Johnson Chad , Nerem Robert M. , Galis Zorina S.
Published: March 2015

Arteries remodel in response to environmental changes. We investigated whether mechanical strain modulates production of matrix metalloproteinase (MMP)-2 and -9 by cultured vascular smooth muscle cells (SMC). MMP-2 and MMP-9 expression were tested using human saphenous vein SMC cultured on silicone membranes at rest or subjected to physiological levels (5%) of stationary or cyclical (1 Hz) uniaxial strain. Compared with control, stationary strain significantly increased MMP-2 mRNA levels at all time points, whereas cyclic strain decreased it after 48 h. Both secreted and cell-associated pro-MMP-2 levels were increased by stationary strain at all times ( P < 0.01), whereas cyclic strain decreased secreted levels after 48 h ( P < 0.02). MMP-9 mRNA levels and pro-MMP-9 protein were increased after 48 h of stationary stretch ( P< 0.01) compared with both no strain and cyclic strain. Our study indicates that vascular SMC show a selective response to different types of strain. We suggest that local increases in stationary mechanical strain resulting from stenting, hypertension, or atherosclerosis may lead to enhanced matrix degradation by SMC.
Deficiency of TIMP-1 exacerbates LV remodeling after myocardial infarction in mice
Authors: Creemers Esther E. J. M. , Davis Jeniffer N. , Parkhurst Andrea M. , Leenders Peter , Dowdy Kathryn B. , Hapke Elizabeth , Hauet Anne M. , Escobar Patricia G. , Cleutjens Jack P. M. , Smits Jos F. M. , Daemen Mat J. A. P. , Zile Michael R. , Spinale Francis G.
Published: March 2015

Recent studies have been directed at modulating the heart failure process through inhibition of activated matrix metalloproteinases (MMPs). We hypothesized that a loss of MMP inhibitory control by tissue inhibitor of MMP (TIMP)-1 deficiency alters the course of postinfarction chamber remodeling and induced chronic myocardial infarction (MI) in wild-type (WT) and TIMP-1−/− mice. Left ventricular (LV) pressure-volume loops obtained from WT and TIMP-1−/− mice demonstrated that LV end-diastolic volume [52 ± 4 (WT) vs. 71 ± 6 (TIMP-1−/−) μl] and LV end-diastolic pressure [9.0 ± 1.2 (WT) vs. 12.7 ± 1.4 (TIMP-1−/−) mmHg] were significantly increased in the TIMP-1−/− mice 2 wk after MI. LV contractility was reduced to a similar degree in the WT and TIMP-1−/− groups after MI, as indicated by a significant fall in the LV end-systolic pressure-volume relationship. Ventricular weight and cross-sectional areas of LV myocytes were significantly increased in TIMP-1−/− mice, indicating that the hypertrophic response was more pronounced. The observed significant loss of fibrillar collagen in the TIMP-1−/−controls may have been an important contributory factor for the observed LV alterations in the TIMP-1−/− mice after MI. These findings demonstrate that TIMP-1 deficiency amplifies adverse LV remodeling after MI in mice and emphasizes the importance of local endogenous control of cardiac MMP activity by TIMP-1.
N-methyl-d-aspartate-induced vasodilation is mediated by endothelium-independent nitric oxide release in piglets
Authors: Domoki Ferenc , Perciaccante James V. , Shimizu Katsuyoshi , Puskar Michelle , Busija David W. , Bari Ferenc
Published: March 2015

N-methyl-d-aspartate (NMDA) elicits pial arteriolar dilation that has been associated with neuronal nitric oxide (NO) production. However, endothelial factors or glial P-450 epoxygenase products may play a role. We tested whether NMDA-induced pial vasodilation 1) primarily involves NO diffusion from the parenchyma to the surface arterioles, 2) involves intact endothelial function, and 3) involves a miconazole-sensitive component. Arteriolar diameters were determined using closed cranial window-intravital microscopy in anesthetized piglets. NMDA (10–100 μM) elicited virtually identical dose-dependent dilations in paired arterioles ( r = 0.94, n = 15). However, NMDA- but not bradykinin (BK)-induced dilations of arteriolar sections over large veins were reduced by 31 ± 1% (means ± SE, P < 0.05, n = 4) compared with adjacent sections on the cortical surface. Also, 100 μM NMDA increased cerebrospinal fluid levels of NO metabolites from 3.7 ± 1.0 to 5.3 ± 1.2 μM ( P < 0.05, n = 6). Endothelial stunning by intracarotid injection of phorbol 12,13-dibutyrate did not affect NMDA-induced vasodilation but attenuated vascular responses to hypercapnia and BK by ∼70% ( n = 7). Finally, miconazole ( n= 6, 20 μM) pretreatment and coapplication with NMDA did not alter vascular responses to NMDA. In conclusion, NMDA appears to dilate pial arterioles exclusively through release and diffusion of NO from neurons to the pial surface in piglets.
Noninvasive identification of the total peripheral resistance baroreflex
Authors: Mukkamala Ramakrishna , Toska Karin , Cohen Richard J.
Published: March 2015

We propose two identification algorithms for quantitating the total peripheral resistance (TPR) baroreflex, an important contributor to short-term arterial blood pressure (ABP) regulation. Each algorithm analyzes beat-to-beat fluctuations in ABP and cardiac output, which may both be obtained noninvasively in humans. For a theoretical evaluation, we applied both algorithms to a realistic cardiovascular model. The results contrasted with only one of the algorithms proving to be reliable. This algorithm was able to track changes in the static gains of both the arterial and cardiopulmonary TPR baroreflex. We then applied both algorithms to a preliminary set of human data and obtained contrasting results much like those obtained from the cardiovascular model, thereby making the theoretical evaluation results more meaningful. This study suggests that, with experimental testing, the reliable identification algorithm may provide a powerful, noninvasive means for quantitating the TPR baroreflex. This study also provides an example of the role that models can play in the development and initial evaluation of algorithms aimed at quantitating important physiological mechanisms.
Effects of PP1/PP2A inhibitor calyculin A on the E-C coupling cascade in murine ventricular myocytes
Authors: duBell William H. , Gigena Marisa S. , Guatimosim Silvia , Long Xilin , Lederer W. J. , Rogers Terry B.
Published: March 2015

Calyculin A was used to examine the importance of phosphatases in the modulation of cardiac contractile magnitude in the absence of any neural or humoral stimulation. Protein phosphatase (PP)1 and PP2A activity, twitch contractions, intracellular Ca2+concentration ([Ca2+]i) transients, action potentials, membrane currents, and myofilament Ca2+sensitivity were measured in isolated mouse ventricular myocytes. Calyculin A (125 nM) inhibited PP1 and PP2A by 50% and 85%, respectively, whereas it doubled the twitch magnitude and increased twitch duration by 50% in field-stimulated cells. Calyculin A-evoked increases in L-type Ca2+current (70%) and the resulting [Ca2+]itransient (83%) explain the positive inotropic response. However, increases in twitch and action potential durations did not result from increased myofilament Ca2+sensitivity or K+current inhibition, respectively. Comparison of the effects of calyculin A and isoproterenol on [Ca2+]itransients and twitch contractions revealed that calyculin A had a much smaller lusitropic effect than the β-agonist, indicating that calyculin A did not significantly increase sarcoplasmic reticulum Ca2+reuptake. Thus while cardiac contractile magnitude is controlled by a steady-state kinase/phosphatase balance, this regulation is not equally operative at all of the steps in the excitation-contraction coupling pathway and may in fact be most important to the regulation of the L-type Ca2+channel.
Rho kinase inhibition partly weakens myogenic reactivity in rat small arteries by changing calcium sensitivity
Authors: Schubert Rudolf , Kalentchuk Vjatscheslav U. , Krien Ulrike
Published: March 2015

The hypothesis that Rho kinase is involved in myogenic reactivity was investigated in pressurized rat tail small arteries using videomicroscopic diameter determination and calcium fluorimetry. The potent Rho kinase inhibitor Y-27632 reversibly increased vessel diameter at 80 mmHg without changing the intracellular calcium concentration ([Ca]i) shifting the relationship between diameter change and [Ca]i to higher calcium levels. Neither endothelium removal nor inhibition of neural transmission affected the Y-27632-induced effect. Y-27632 at 3 × 10−6 mol/l attenuated the myogenic response in the pressure range from 10 to 120 mmHg, shifting the relationship between vessel tone and [Ca]i to higher calcium levels. In addition, the Y-27632-induced shift of the relationship between vessel tone and [Ca]i was larger at 80 than at 10 mmHg. These results suggest that smooth muscle cell Rho kinase in rat tail small arteries 1) is in an active state partly determining the level of the myogenic tone, and 2) alters the strength of the myogenic response by changing calcium sensitivity, probably caused by the pressure-induced activation of the kinase.
Plasticity of KIR channels in human smooth muscle cells from internal thoracic artery
Authors: Karkanis Tom , Li Shaohua , Pickering J. Geoffrey , Sims Stephen M.
Published: March 2015

Inwardly rectifying K+ (KIR) currents are present in some, but not all, vascular smooth muscles. We used patch-clamp methods to examine plasticity of this current by comparing contractile and proliferative phenotypes of a clonal human vascular smooth muscle cell line. Hyperpolarization of cells under voltage clamp elicited a large inward current that was selective for K+ and blocked by Ba2+. Current density was greater in proliferative compared with contractile cells (−4.5 ± 0.9 and −1.4 ± 0.3 pA/pF, respectively; P < 0.001). RT-PCR of mRNA from proliferative cells identified transcripts for Kir2.1 and Kir2.2 but not Kir2.3 potassium channels. Western blot analysis demonstrated greater expression of Kir2.1 protein in proliferative cells, consistent with the higher current density. Proliferative cells displayed a more negative membrane potential than contractile cells (−71 ± 2 and −35 ± 4 mV, respectively; P < 0.001). Ba2+ depolarized all cells, whereas small increases in extracellular K+ concentration elicited hyperpolarization only in contractile cells. Ba2+ inhibited [3H]thymidine incorporation, indicating a possible role for KIR channels in the regulation of proliferation. The phenotype-dependent plasticity of KIR channels may have relevance to vascular remodeling.
Modulation of action potential by [Ca2+]i in modeled rat atrial and guinea pig ventricular myocytes
Authors: Han Chunlei , Tavi Pasi , Weckström Matti
Published: March 2015

We simulated mechanisms that increase Ca2+ transients with two models: the Luo-Rudy II model for guinea pig (GP) ventricle (GP model) representing long action potential (AP) myocytes and the rat atrial (RA) model exemplifying myocytes with short APs. The interventions were activation of stretch-gated cationic channels, increase of intracellular Na+ concentration ([Na+]i), simulated β-adrenoceptor stimulation, and Ca2+accumulation into the sarcoplasmic reticulum (SR). In the RA model, interventions caused an increase of AP duration. In the GP model, AP duration decreased except in the simulated β-stimulation where it lengthened APs as in the RA model. We conclude that the changes in the APs are significantly contributed by the increase of the Ca2+ transient itself. The AP duration is controlled differently in cardiac myocytes with short and long AP durations. With short APs, an increase of the Ca2+ transient promotes an inward current via Na+/Ca2+-exchanger lengthening the AP. This effect is similar regardless of the mechanism causing the increase of the Ca2+ transient. With long APs the Ca2+ transient increase decreases the AP duration via inactivation of the L-type Ca2+ current. However, L-type current increase (as with β-stimulation) increases the AP duration despite the simultaneous Ca2+ transient augmentation. The results explain the dispersion of AP changes in myocytes with short and long APs during interventions increasing the Ca2+transients.
Role of endothelial Ca2+ stores in the regulation of hydraulic conductivity of Rana microvessels in vivo
Authors: Glass C. A. , Bates D. O.
Published: March 2015

Vascular permeability is regulated by endothelial cytosolic Ca2+concentration ([Ca2+]i). To determine whether vascular permeability is dependent on extracellular Ca2+influx or release of Ca2+ from stores, hydraulic conductivity ( L p) was measured in single perfused frog mesenteric microvessels in the presence and absence of Ca2+ influx and store depletion. Prevention of Ca2+ reuptake into stores by sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) inhibition increased L p in the absence of extracellular Ca2+ influx. L p was further increased when Ca2+ influx was restored. Depletion of the Ca2+ stores with ionomycin and SERCA inhibition increased L p in the presence and the absence of extracellular Ca2+ influx. However, store depletion in itself did not significantly increase L p in the absence of active Ca2+ release from stores into the cytoplasm. There was a significant positive correlation between baseline permeability and the magnitude of the responses to both Ca2+ store release and Ca2+ influx, indicating that the Ca2+ regulating properties of the endothelial cells may regulate the baseline L p. To investigate the role of Ca2+ stores in regulation of L p, the relationship between SERCA inhibition and store release was studied. The magnitude of the L p increase during SERCA inhibition significantly and inversely correlated with that during store release by Ca2+ ionophore, implying that the degree of store depletion regulates the size of the increase on L p. These data show that microvascular permeability in vivo can be increased by agents that release Ca2+ from stores in the absence of Ca2+ influx. They also show that capacitative Ca2+ entry results in increased L p and that the size of the permeability increase can be regulated by the degree of Ca2+ release.
Catecholamines act via a β-adrenergic receptor to maintain fetal heart rate and survival
Authors: Portbury Andrea L. , Chandra Rashmi , Groelle Marybeth , McMillian Michael K. , Elias Alana , Herlong James R. , Rios Maribel , Roffler-Tarlov Suzanne , Chikaraishi Dona M.
Published: March 2015

Mice lacking catecholamines die before birth, some with cardiovascular abnormalities. To investigate the role of catecholamines in development, embryonic day 12.5 (E12.5) fetuses were cultured and heart rate monitored. Under optimal oxygenation, wild-type and catecholamine-deficient fetuses had the same initial heart rate (200–220 beats/min), which decreased by 15% in wild-type fetuses during 50 min of culture. During the same culture period, catecholamine-deficient fetuses dropped their heart rate by 35%. Hypoxia reduced heart rate of wild-type fetuses by 35–40% in culture and by 20% in utero, assessed by echocardiography. However, catecholamine-deficient fetuses exhibited greater hypoxia-induced bradycardia, reducing their heart rate by 70–75% in culture. Isoproterenol, a β-adrenergic receptor (β-AR) agonist, reversed this extreme bradycardia, restoring the rate of catecholamine-deficient fetuses to that of nonmutant siblings. Moreover, isoproterenol rescued 100% of catecholamine-deficient pups to birth in a dose-dependent, stereo-specific manner when administered in the dam's drinking water. An α-AR agonist was without effect. When wild-type fetuses were cultured with adrenoreceptor antagonists to create pharmacological nulls, blockade of α-ARs with 10 μM phentolamine or β-ARs with 10 μM bupranolol alone or in combination did not reduce heart rate under optimal oxygenation. However, when combined with hypoxia, β-AR blockade reduced heart rate by 35%. In contrast, the muscarinic blocker atropine and the α-AR antagonist phentolamine had no effect. These data suggest that β-ARs mediate survival in vivo and regulate heart rate in culture. We hypothesize that norepinephrine, acting through β-ARs, maintains fetal heart rate during periods of transient hypoxia that occur throughout gestation, and that catecholamine-deficient fetuses die because they cannot withstand hypoxia-induced bradycardia.
Gene transfer of Cu/Zn SOD to cerebral vessels prevents FPI-induced CBF autoregulatory dysfunction
Authors: Kim Chi Dae , Shin Hwa Kyoung , Lee Hyun Seung , Lee Jeong Hyun , Lee Tae Ho , Hong Ki Whan
Published: March 2015

The goal of this study was to determine whether gene transfer of human copper-zinc (Cu/Zn) superoxide dismutase (SOD) has preventive effects on cerebral blood flow (CBF) autoregulatory dysfunction after fluid percussion injury (FPI). Rats subjected to FPI (2–2.5 atm) exhibited enhanced activity of reduced NADP (NADPH) oxidase in the cerebral vasculature. In line with these findings, the rats showed not only reduced vasodilation of the pial artery in response to calcitonin gene-related peptide and levcromakalim but also impaired autoregulatory vasodilation in response to acute hypotension. The FPI-induced hemodynamic alterations were significantly prevented by pretreatment with diphenyleneiodonium (10 μmol/l), an NAD(P)H oxidase inhibitor. Intracisternal application of recombinant adenovirus (100 μl of 1 × 1010pfu/ml)-encoding human Cu/Zn SOD 3 days before FPI prevented the impairment of vasodilation to hypotension and vasorelaxants, resulting in the restoration of CBF autoregulation. Our findings demonstrate that FPI-induced impairment of CBF autoregulation is closely related with NAD(P)H oxidase-derived superoxide anion, and these alterations can be prevented by the recombinant adenovirus-mediated transfer of human Cu/Zn SOD gene to the cerebral vasculature.
Vascular adaptations to pregnancy in mice: effects on myogenic tone
Authors: Veerareddy Sukrutha , Cooke Christy-Lynn M. , Baker Philip N. , Davidge Sandra T.
Published: March 2015

The mechanisms underlying vascular adaptations in pregnancy remain to be fully elucidated. One of the contributory mechanisms for reduced vascular tone may be a reduction of myogenic tone. Myogenic tone was assessed as the difference between internal diameter in the presence and absence of external calcium at different intramural pressure steps (60–100 mmHg). Myogenic responses were reduced in resistance-sized mesenteric and main uterine arteries in late pregnant compared with nonpregnant C57BL/6J mice. In vessels from pregnant, but not nonpregnant mice, the myogenic response was enhanced by preincubation with nitric oxide (NO) synthase inhibitor N G-nitro-l-arginine methyl ester, was further elevated by the gap junction inhibitor 18-α glycyrrhetinic acid, but was unaltered by the prostaglandin H synthase inhibitor meclofenamate. Endothelium removal enhanced myogenic tone only in the vessels from pregnant animals, thus confirming the role of the endothelium in modulating myogenic tone in pregnancy. These results suggest that endothelium-derived NO as well as gap junction communications modulate myogenic tone in mouse pregnancy.
HSP70.1 and -70.3 are required for late-phase protection induced by ischemic preconditioning of mouse hearts
Authors: Hampton Craig R. , Shimamoto Akira , Rothnie Christine L. , Griscavage-Ennis Jeaneatte , Chong Albert , Dix David J. , Verrier Edward D. , Pohlman Timothy H.
Published: March 2015

We investigated the role of inducible heat shock proteins 70.1 and 70.3 (HSP70.1 and HSP70.3, respectively) in myocardial ischemic preconditioning (IP) in mice. Wild-type (WT) mice and HSP70.1- and HSP70.3-null [HSP70.1/3(–/–)] mice were subjected to IP and examined 24 h later during the late phase of protection. IP significantly increased steady-state levels of HSP70.1 and HSP70.3 mRNA and expression of inducible HSP70 protein in WT myocardium. To assess protection against tissue injury, mice were subjected to 30 min of regional ischemia and 3 h of reperfusion. In WT mice, IP reduced infarct size by 43% compared with sham IP-treated mice. In contrast, IP did not reduce infarct size in HSP70.1/3(–/–) mice. Absence of inducible HSP70.1 and HSP70.3 had no effect, however, on classical or early-phase protection produced by IP, which significantly reduced infarct size in HSP70.1/3(–/–) mice. We conclude that inducible HSP70.1 and HSP70.3 are required for late-phase protection against infarction following IP in mice.
Activity-dependent role of NMDA receptors in transmission of cardiac mechanoreceptor input to the NTS
Authors: Seagard J. L. , Dean C. , Hopp F. A.
Published: March 2015

Evidence suggests that transmission of barosensitive input from arterial baroreceptors and cardiac mechanoreceptors at nucleus tractus solitarius (NTS) neurons involves non- N-methyl-d-aspartate (NMDA) glutamate receptors, but there is a possibility that the contribution of NMDA receptors might increase during periods of increased afferent input, when enhanced neuronal depolarization could increase the activation of NMDA receptors by removal of a Mg2+ block. Thus the effects of NMDA on cardiac mechanoreceptor-modulated NTS neuronal discharges were examined at different levels of arterial pressure used to change cardiac mechanoreceptor afferent input. To determine whether the response was specific to NMDA, (±)-α-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid (AMPA) was also administered at different levels of neuronal discharge. In anesthetized dogs, neuronal activity was recorded from the NTS while NMDA or AMPA was picoejected at high versus low arterial stimulating pressures. NMDA, but not AMPA, produced a significantly greater discharge of mechanoreceptor-driven NTS neurons at higher versus lower levels of stimulating pressure. These data suggest that the role played by NMDA receptors is greater during periods of enhanced neuronal depolarization, which could be produced by increases in afferent barosensitive input.
Basis for the cardiac-related rhythm in muscle sympathetic nerve activity of humans
Authors: Barman Susan M. , Fadel Paul J. , Vongpatanasin Wanpen , Victor Ronald G. , Gebber Gerard L.
Published: March 2015

We tested the hypothesis that the cardiac-related rhythm in muscle sympathetic nerve activity (MSNA) of humans reflects entrainment of a central oscillator by pulse-synchronous baroreceptor nerve activity. Partial autospectral analysis was used to mathematically remove the portion of cardiac-related power in MSNA autospectra that was attributable to its linear relationship to the ECG. In 54 of 98 cases, ≥15% of cardiac-related power remained after partialization with the ECG; peak residual cardiac-related power was often at a frequency different than heart rate. When assessed on a cardiac-related burst-by-burst basis, there was a progressive and cyclic change in the ECG-MSNA interval (delay from R wave to peak of cardiac-related burst) on the time scale of respiration in four subjects. In these subjects, as well as in some in which the interval appeared to change randomly, there was an inverse relationship between the ECG-MSNA interval and cardiac-related burst amplitude. However, in 45% of the cases, these parameters were not related. These results support the view that the cardiac-related rhythm in MSNA reflects forcing of a nonlinear oscillator rather than periodic inhibition of unstructured, random activity.
Static filling pressure in patients during induced ventricular fibrillation
Authors: Schipke J. D. , Heusch G. , Sanii A. P. , Gams E. , Winter J.
Published: March 2015

The static pressure resulting after the cessation of flow is thought to reflect the filling of the cardiovascular system. In the past, static filling pressures or mean circulatory filling pressures have only been reported in experimental animals and in human corpses, respectively. We investigated arterial and central venous pressures in supine, anesthetized humans with longer fibrillation/defibrillation sequences (FDSs) during cardioverter/defibrillator implantation. In 82 patients, the average number of FDSs was 4 ± 2 (mean ± SD), and their duration was 13 ± 2 s. In a total of 323 FDSs, arterial blood pressure decreased with a time constant of 2.9 ± 1.0 s from 77.5 ± 34.4 to 24.2 ± 5.3 mmHg. Central venous pressure increased with a time constant of 3.6 ± 1.3 s from 7.5 ± 5.2 to 11.0 ± 5.4 mmHg (36 points, 141 FDS). The average arteriocentral venous blood pressure difference remained at 13.2 ± 6.2 mmHg. Although it slowly decreased, the pressure difference persisted even with FDSs lasting 20 s. Lack of true equilibrium pressure could possibly be due to a waterfall mechanism. However, waterfalls were identified neither between the left ventricle and large arteries nor at the level of the diaphragm in supine patients. We therefore suggest that static filling pressures/mean circulatory pressures can only be directly assessed if the time after termination of cardiac pumping is adequate, i.e., >20 s. For humans, such times are beyond ethical options.
Diacylglycerol and protein kinase C activate cation channels involved in myogenic tone
Authors: Slish Donald F. , Welsh Donald G. , Brayden Joseph E.
Published: March 2015

The smooth muscle cells of resistance arteries depolarize and contract when intravascular pressure is elevated. This is a central characteristic of myogenic tone, which plays an important role in regulation of blood flow in many vascular beds. Pressure-induced vascular smooth muscle depolarization depends in part on the activation of cation channels. Here, we show that activation of these smooth muscle cation channels and pressure-induced depolarization are mediated by protein kinase C in cerebral resistance arteries. Diacylglycerol, phorbol myristate acetate, and cell swelling activate a cation current that we have previously shown is mediated by transient receptor potential channels. These currents, as well as the smooth muscle cell depolarizations of intact arteries induced by diacylglycerol, phorbol ester, and elevation of intravascular pressure, are nearly eliminated by protein kinase C inhibitors. These results suggest a major mechanism of myogenic tone involves mechanotransduction through phospholipase C, diacylglycerol production, and protein kinase C activation, which increase cation channel activity. The associated depolarization activates L-type calcium channels, leading to increased intracellular calcium and vasoconstriction.