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Now showing items 17 - 32 of 40

  • Development of an experimentally useful model of acute myocardial infarction: 2/3 nephrectomized triple nitric oxide synthases-deficient mouse

    Uchida, Taro   Furuno, Yumi   Tanimoto, Akihide   Toyohira, Yumiko   Arakaki, Kumiko   Kina-Tanada, Mika   Kubota, Haruaki   Sakanashi, Mayuko   Matsuzaki, Toshihiro   Noguchi, Katsuhiko   Nakasone, Junko   Igarashi, Tomonori   Ueno, Susumu   Matsushita, Masayuki   Ishiuchi, Shogo   Masuzaki, Hiroaki   Ohya, Yusuke   Yanagihara, Nobuyuki   Shimokawa, Hiroaki   Otsuji, Yutaka   Tamura, Masahito   Tsutsui, Masato  

    We investigated the effect of subtotal nephrectomy on the incidence of acute myocardial infarction (AMI) in mice deficient in all three nitric oxide synthases (NOSs). Two-thirds nephrectomy (NX) was performed on male triple NOSs(-/-) mice. The 2/3NX caused sudden cardiac death due to AMI in the triple NOSs(-/-) mice as early as 4 months after the surgery. The 2/3NX triple NOSs(-/-) mice exhibited electrocardiographic ST-segment elevation, reduced heart rate variability, echocardiographic regional wall motion abnormality, and accelerated coronary arteriosclerotic lesion formation. Cardiovascular risk factors (hypertension, hypercholesterolemia, and hyperglycemia), an increased number of circulating bone marrow-derived vascular smooth muscle cell (VSMC) progenitor cells (a pro-arteriosclerotic factor), and cardiac up-regulation of stromal cell-derived factor (SDF)-1 alpha (a chemotactic factor of the progenitor cells) were noted in the 2/3NX triple NOSs(-/-) mice and were associated with significant increases in plasma angiotensin II levels (a marker of renin-angiotensin system activation) and urinary 8-isoprostane levels (a marker of oxidative stress). Importantly, combined treatment with a clinical dosage of an angiotensin II type 1 receptor blocker, irbesartan, and a calcium channel antagonist, amlodipine, markedly prevented coronary arteriosclerotic lesion formation and the incidence of AMI and improved the prognosis of those mice, along with ameliorating all those pro-arteriosclerotic parameters. The 2/3NX triple NOSs(-/-) mouse is a new experimentally useful model of AMI. Renin-angiotensin system activation, oxidative stress, cardiovascular risk factors, and SDF-1 alpha-induced recruitment of bone marrow-derived VSMC progenitor cells appear to be involved in the pathogenesis of AMI in this model. (C) 2014 Elsevier Ltd. All rights reserved.
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  • Curing and degradation reactions of oil paints exposed to environmental pollutants (NO2 and SO2) as studied by NIR-excited Raman spectrometry

    UCHIDA, Taro   YOSHIDA, Ayumi   TAKAHASHI, Kanako   HIGUCHI, Seiichiro  

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  • Initial insights from a global database of rainfall-induced landslide inventories: the weak influence of slope and strong influence of total storm rainfall

    Marc, Odin   Stumpf, André   Malet, Jean-Philippe   Gosset, Marielle   Uchida, Taro   Chiang, Shou-Hao  

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  • Changes in depression and anxiety through mindfulness group therapy in Japan: the role of mindfulness and self-compassion as possible mediators

    Takahashi, Toru   Sugiyama, Fukiko   Kikai, Tomoki   Kawashima, Issaku   Guan, Siqing   Oguchi, Mana   Uchida, Taro   Kumano, Hiroaki  

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  • Increasing dihydrobiopterin causes dysfunction of endothelial nitric oxide synthase in rats in vivo

    Hamadate, Naobumi   Matsuzaki, Toshihiro   Sakanashi, Mayuko   Nakasone, Junko   Uchida, Taro   Arakaki, Kumiko   Kubota, Haruaki   Ishiuchi, Shogo   Masuzaki, Hiroaki   Sugahara, Kazuhiro   Ohya, Yusuke   Sakanashi, Matao   Tsutsui, Masato  

    Noguchi K, Hamadate N, Matsuzaki T, Sakanashi M, Nakasone J, Uchida T, Arakaki K, Kubota H, Ishiuchi S, Masuzaki H, Sugahara K, Ohya Y, Sakanashi M, Tsutsui M. Increasing dihydrobiopterin causes dysfunction of endothelial nitric oxide synthase in rats in vivo. Am J Physiol Heart Circ Physiol 301: H721-H729, 2011. First published May 28, 2011; doi:10.1152/ajpheart.01089.2010.-An elevation of oxidized forms of tetrahydrobiopterin (BH4), especially dihydrobiopterin (BH2), has been reported in the setting of oxidative stress, such as arteriosclerotic/atherosclerotic disorders, where endothelial nitric oxide synthase (eNOS) is dysfunctional, but the role of BH2 in the regulation of eNOS activity in vivo remains to be evaluated. This study was designed to clarify whether increasing BH2 concentration causes endothelial dysfunction in rats. To increase vascular BH2 levels, the BH2 precursor sepiapterin (SEP) was intravenously given after the administration of the specific dihydrofolate reductase inhibitor methotrexate (MTX) to block intracellular conversion of BH2 to BH4. MTX/SEP treatment did not significantly affect aortic BH4 levels compared with control treatment. However, MTX/SEP treatment markedly augmented aortic BH2 levels (291.1 +/- 29.2 vs. 33.4 +/- 6.4 pmol/g, P < 0.01) in association with moderate hypertension. Treatment with MTX alone did not significantly alter blood pressure or BH4 levels but decreased the BH4-to-BH2 ratio. Treatment with MTX/SEP, but not with MTX alone, impaired ACh-induced vasodilator and depressor responses compared with the control treatment (both P < 0.05) and also aggravated ACh-induced endothelium-dependent relaxations (P < 0.05) of isolated aortas without affecting sodium nitroprusside-induced endothelium-independent relaxations. Importantly, MTX/SEP treatment significantly enhanced aortic superoxide production, which was diminished by NOS inhibitor treatment, and the impaired ACh-induced relaxations were reversed with SOD (P < 0.05), suggesting the involvement of eNOS uncoupling. These results indicate, for the first time, that increasing BH2 causes eNOS dysfunction in vivo even in the absence of BH4 deficiency, demonstrating a novel insight into the regulation of endothelial function.
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  • Unusually Stable Plastic Crystal Phase of CCl4 Confined in Graphitic Slit-shaped Micropores from Neutron Diffraction

    Yoshimoto, Masatsugu   Futamura, Ryusuke   Hoshikawa, Akinori   Ishigaki, Toru   Uchida, Taro   Iiyama, Taku  

    Structural changes with temperature of CCl4 confined in a 1.1 nm slit-shaped carbon nanospace were investigated by neutron diffraction (ND) measurements and radial distribution function f(drdf) analyses. Bulk CCl4 exhibits a plastic crystal (PC) phase between 225.5 and 250 K. In the confined space, although clear phase transition points cannot be determined, f(drdf) suggests that the PC phase extends to temperatures as low as 160 K. The smooth surface of the activated carbon assists the rotational motion of CCl4.
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  • A Novel Method of Quantifying Catchment鈥怶ide Average Peak Propagation Speed in Hillslopes: Fast Hillslope Responses are Detected During Annual Floods in a Steep Humid Catchment

    Asano, Yuko   Uchida, Taro   Tomomura, Mitsuhide  

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  • Flow path depth is the main controller of mean base flow transit times in a mountainous catchment

    Asano, Yuko   Uchida, Taro  

    Transit time of discharge is a hydrological characteristic used in water resource management. Previous studies have demonstrated large spatial variation in the mean transit time (MTT) of stream base flow in meso-scale catchments. Various relationships between topography and MTT have been reported. Although it is generally assumed that base flow MTT is controlled by the depth of the hydrologically active layer that recharges a stream, this hypothesis has not been tested in field studies. This study confirmed that the depth of hydrologically active soil and bedrock controls spatial variation in MTT. The study used isotopic and geochemical tracer data gathered in the 4.27 km(2) Fudoji catchment, central Japan. The results, together with previously documented relationships between topography and MTT, indicate that the depth of the hydrologically active layer is sometimes, but not always, related to topography. A comprehensive understanding of the factors that control base flow production in mountainous catchments will require further study of the water flow path depths that recharge streams.
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  • Effect of caffeine contained in a cup of coffee on microvascular function in healthy subjects.

    Noguchi, Katsuhiko   Matsuzaki, Toshihiro   Sakanashi, Mayuko   Hamadate, Naobumi   Uchida, Taro   Kina-Tanada, Mika   Kubota, Haruaki   Nakasone, Junko   Sakanashi, Matao   Ueda, Shinichiro   Masuzaki, Hiroaki   Ishiuchi, Shogo   Ohya, Yusuke   Tsutsui, Masato  

    Recent epidemiological studies have demonstrated that coffee drinking is associated with reduced mortality of cardiovascular disease. However, its precise mechanisms remain to be clarified. In this study, we examined whether single ingestion of caffeine contained in a cup of coffee improves microvascular function in healthy subjects. A double-blind, placebo-controlled, crossover study was performed in 27 healthy volunteers. A cup of either caffeinated or decaffeinated coffee was drunk by the subjects, and reactive hyperemia of finger blood flow was assessed by laser Doppler flowmetry. In an interval of more than 2 days, the same experimental protocol was repeated with another coffee in a crossover manner. Caffeinated coffee intake slightly but significantly elevated blood pressure and decreased finger blood flow as compared with decaffeinated coffee intake. There was no significant difference in heart rate between caffeinated and decaffeinated coffee intake. Importantly, caffeinated coffee intake significantly enhanced post-occlusive reactive hyperemia of finger blood flow, an index of microvascular endothelial function, compared with decaffeinated coffee intake. These results provide the first evidence that caffeine contained in a cup of coffee enhances microvascular function in healthy individuals. Copyright =C2=A9 2015 Japanese Pharmacological Society. Production and hosting by Elsevier B.V. All rights reserved.
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  • Speciation of Adsorbed Phosphate at Gold Electrodes:A Combined Surface-Enhanced Infrared Absorption Spectroscopy and DFT Study

    Yaguchi, Momo   Uchida, Taro   Motobayashi, Kenta   Osawa, Masatoshi  

    Despite the significance of phosphate buffer solutions in (bio)-electrochemistry, detailed adsorption properties of phosphate anions at metal surfaces remain poorly understood. Herein, phosphate adsorption at quasi-Au(111) surfaces prepared by a chemical deposition technique has been systematically investigated over a wide range of pH by surface-enhanced infrared absorption spectroscopy in the ATR configuration (ATR-SEIRAS). Two different pH-dependent states of adsorbed phosphate are spectroscopically detected. Together with DFT calculations, the present study reveals that pK(a) for adsorbed phosphate species at the interface is much lower than that for phosphate species in the bulk solution; the dominant phosphate anion, H2PO4- at 2 < pH < 7 or HPO42- at 7 < pH < 12, undergoes deprotonation upon adsorption and transforms into the adsorbed HPO4 or PO4, respectively. This study leads to a conclusion different than earlier spectroscopic studies have reached, highlighting the capability of the ATR-SEIRAS technique at electrified metal-solution interfaces.
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  • Simple monitoring method for precaution of landslides watching tilting and water contents on slopes surface

    Uchimura, Taro   Towhata, Ikuo   Anh, Trinh Thi Lan   Fukuda, Jou   Bautista, Carlos J. B.   Wang, Lin   Seko, Ichiro   Uchida, Taro   Matsuoka, Akira   Ito, Yosuke   Onda, Yuichi   Iwagami, Sho   Kim, Min-Seok   Sakai, Naoki  

    A low-cost and simple monitoring method for early warning of landslides is proposed. To detect abnormal deformation of a slope, this method employs a tilt sensor in place of an extensometer on the slope surface. In order to examine the relevance of measuring rotation angle on a slope surface by tilt sensor, model tests were conducted, and rotation on the slope surface was observed together with slide displacement along the surface. The rotation data responded 30 min before failure in a model test, which could be useful as a signal for early warning. However, the behavior of rotation before failure varies from case to case, and thus, criteria to issue warning should be defined more carefully. For a model slope made of uniform loose sand, measurement of slide displacement along the slope surface is sensitive to failure at the toe, while the measurement of rotation on the slope surface is useful to detect the development of progressive failure upward along the slope. Wireless sensor units with microelectromechanical systems (MEMS) tilt sensor and volumetric water content sensor were also examined on a real slope in Kobe City, and a long-term monitoring was attempted. A simple but possible way to define the criteria of judgment to issue warning can be proposed based on combination of data obtained by the tilt sensors and volumetric water content sensors.
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  • Hydrogen evolution reaction catalyzed by proton-coupled redox cycle of 4,4 '-bipyridine monolayer adsorbed on silver electrodes RID A-5294-2012

    Uchida, Taro   Mogami, Hirokazu   Yamakata, Akira   Sasaki, Yoichi   Osawa, Masatoshi  

    The proton-coupled redox cycle of 4,4'-bipyridine monolayer adsorbed on an Ag electrode catalytically enhances hydrogen evolution reactions in basic and neutral solutions. The specific adsorption via one Wend facilitates electrochemical formation of an unstable N,N-dihydro bipyridine and its decomposition yields H(2).
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  • Bench-Scale Experiments on Effects of Pipe Flow and Entrapped Air in Soil Layer on Hillslope Landslides

    Tanaka, Yasutaka   Uchida, Taro   Nagai, Hitoshi   Todate, Hikaru  

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  • Effect of Hydrogen on the Orientation of Cinchonidine Adsorbed on Platinum:An ATR-SEIRAS Study

    Motobayashi, Kenta   Tomioka, Ryota   Uchida, Taro   Osawa, Masatoshi  

    The orientation of cinchonidine (CD) adsorbed on a Pt surface, a model system of enantioselective catalysis for hydrogenation reactions, is studied in 1,2-dichloroethane by in situ surface-enhanced infrared absorption spectroscopy in attenuated total reflection configuration. The quinoline (QN) moiety of CD is shown to be reoriented from a pi-bonded nearly parallel orientation to an N-bonded upright one by bubbling the solution with H-2. The origin of the reorientation is ascribed to the repulsive interaction of a QN pi-orbital and the negative surface charge induced by dissociative adsorption of H-2 and hydrogenation of the vinyl moiety.
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  • 4,4 '-Bipyridine as a molecular catalyst for electrochemical hydrogen production

    Uchida, Taro   Sasaki, Yoichi   Ikeshoji, Tamio   Osawa, Masatoshi  

    Hydrogen evolution reaction (HER) on Cu and Ag electrodes in neutral and alkaline media (but not in acidic media) is significantly accelerated by the addition of 4,4'-bipyridine (BiPy). The mechanism of the HER acceleration is discussed at a molecular level by using surface-enhanced infrared absorption spectroscopy (SEIRAS) coupled with electrochemical techniques and density functional theory (DFT) calculations. Simultaneous SEIRAS and cyclic voltammetry measurements reveal that the onset potential of the accelerated HER coincides with the 1e + 1H(+) reduction potential of adsorbed BiPy to yield monohydro BiPy radical (BiPy-H-center dot). Tafel plot analysis and DFT calculations suggest that BiPy-H-center dot is further reduced to N,C(3)-dihydro BiPy via a subsequent 1e + 1H(+) step and finally H-2 is evolved by the combination of two H atoms on N and C(3) atoms (BiPy-H-2 -> BiPy + H-2). Since adsorbed BiPy is readily reduced again to BiPy-H-center dot in the potential range of HER, the reaction process is catalytically cycled. The enhanced HER is not observed on Au electrodes due to the desoption of BiPy from the surface. Also the enhanced HER is not observed on Pt electrodes despite strong adsorption on Pt because the redox potential of adsorbed BiPy, the first step of the HER, is more negative than the onset of HER on bare Pt surface. (C) 2017 Elsevier Ltd. All rights reserved.
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  • The Role of Bridge-Bonded Adsorbed Formate in the Electrocatalytic Oxidation of Formic Acid on Platinum RID A-5294-2012 RID B-9805-2011 RID C-7151-2008

    Osawa, Masatoshi   Komatsu, Kei-ichi   Samjeske, Gabor   Uchida, Taro   Ikeshoji, Tamio   Cuesta, Angel   Gutierrez, Claudio  

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