85 results on '"Sekiya F"'
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2. IOFI recommended practice for the use of predicted relative‐response factors for the rapid quantification of volatile flavouring compounds by GC‐FID
- Author
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Cachet, T., primary, Brevard, H., additional, Chaintreau, A., additional, Demyttenaere, J., additional, French, L., additional, Gassenmeier, K., additional, Joulain, D., additional, Koenig, T., additional, Leijs, H., additional, Liddle, P., additional, Loesing, G., additional, Marchant, M., additional, Merle, Ph., additional, Saito, K., additional, Schippa, C., additional, Sekiya, F., additional, and Smith, T., additional
- Published
- 2016
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3. IOFI guidelines for the isolation of flavouring substances by simultaneous distillation-extraction
- Author
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Cachet, T., primary, Brevard, H., additional, Cantergiani, E., additional, Chaintreau, A., additional, Demyttenaere, J., additional, French, L., additional, Gassenmeier, K., additional, Joulain, D., additional, Koenig, T., additional, Leijs, H., additional, Liddle, P., additional, Loesing, G., additional, Marchant, M., additional, Saito, K., additional, Scanlan, F., additional, Schippa, C., additional, Scotti, A., additional, Sekiya, F., additional, Sherlock, A., additional, and Smith, T., additional
- Published
- 2014
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4. Determination of volatile ‘restricted substances’ in flavourings and their volatile raw materials by GC-MS
- Author
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Cachet, T., primary, Brevard, H., additional, Cantergiani, E., additional, Chaintreau, A., additional, Demyttenaere, J., additional, French, L., additional, Gassenmeier, K., additional, Joulain, D., additional, Koenig, T., additional, Leijs, H., additional, Liddle, P., additional, Loesing, G., additional, Marchant, M., additional, Saito, K., additional, Scanlan, F., additional, Schippa, C., additional, Scotti, A., additional, Sekiya, F., additional, Sherlock, A., additional, and Smith, T., additional
- Published
- 2014
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5. Determination of volatile 'restricted substances' in flavourings and their volatile raw materials by GC-MS.
- Author
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Cachet, T., Brevard, H., Cantergiani, E., Chaintreau, A., Demyttenaere, J., French, L., Gassenmeier, K., Joulain, D., Koenig, T., Leijs, H., Liddle, P., Loesing, G., Marchant, M., Saito, K., Scanlan, F., Schippa, C., Scotti, A., Sekiya, F., Sherlock, A., and Smith, T.
- Subjects
VOLATILE organic compounds ,RAW materials ,ESSENTIAL oils ,GAS chromatography ,STANDARD deviations ,FLAVORING essences - Abstract
Many flavour regulations around the world contain a list of so-called 'restricted substances' (RS), i.e. substances that occur naturally in source materials for flavourings and food ingredients with flavouring properties, but whose presence in certain foods is restricted and/or for which maximum levels are set, for example, the European regulation 1334/2008. Only a few publications refer to the determination of RS in compound flavourings or their raw materials, and the latter only concern the analysis of one or two individual RS in single essential oils. The Working Group on Methods of Analysis of the International Organization of the Flavor Industry (IOFI) has developed a method for the rapid routine determination of β-asarone, coumarin, menthofuran, methylchavicol, methyleugenol, pulegone, safrole and α- and β-thujones in flavourings and their raw materials by gas chromatography-mass spectrometry (GC-MS), using selected-ion monitoring and internal standards. The method has been evaluated by nine flavour-industry laboratories using a complex surrogate flavouring containing all of the above analytes, at concentrations that would be likely to produce levels in finished foods of around typical maximum limits for these RS. Results were obtained from a total of 15 columns and sets of analytical conditions, using 11 GC/MS instruments, with in each case a determination of the analyte in two versions of the flavouring. With reproducibility relative standard deviations (RSD
R ) of less than about 20%, and recoveries of 80-120%, the method performance can be considered as satisfactory for rapid routine checks on the levels of restricted substances in compound flavourings. The method is intended for flavour-industry laboratories in order for them to fulfil their obligation to inform food-industry clients of the amounts of these substances in commercial flavourings, but is not intended for their analysis in finished foods. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]- Published
- 2015
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6. Comparative Biochemistry of Disintegrins Isolated from Snake Venom: Consideration of the Taxonomy and Geographical Distribution of Snakes in the Genus Echis
- Author
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Okuda, D., primary, Nozaki, C., additional, Sekiya, F., additional, and Morita, T., additional
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- 2001
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7. Blood Coagulation Factor IX-Binding Protein from the Venom of Trimeresurus flavoviridis: Purification and Characterization
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Atoda, H., primary, Ishikawa, M., additional, Yoshihara, E., additional, Sekiya, F., additional, and Morita, T., additional
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- 1995
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8. Activation of prothrombin by a novel membrane-associated protease. An alternative pathway for thrombin generation independent of the coagulation cascade.
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Sekiya, F, primary, Usui, H, additional, Inoue, K, additional, Fukudome, K, additional, and Morita, T, additional
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- 1994
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9. Collagen-binding domain within bovine propolypeptide of von Willebrand factor.
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Takagi, J, primary, Fujisawa, T, additional, Sekiya, F, additional, and Saito, Y, additional
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- 1991
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10. IOFI guidelines for the isolation of flavouring substances by simultaneous distillation-extraction.
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Cachet, T., Brevard, H., Cantergiani, E., Chaintreau, A., Demyttenaere, J., French, L., Gassenmeier, K., Joulain, D., Koenig, T., Leijs, H., Liddle, P., Loesing, G., Marchant, M., Saito, K., Scanlan, F., Schippa, C., Scotti, A., Sekiya, F., Sherlock, A., and Smith, T.
- Subjects
DISTILLATION ,EXTRACTIVE distillation ,SOLVENTS ,EVAPORATION (Chemistry) ,AQUEOUS solutions ,METHANETHIOL - Abstract
ABSTRACT Simultaneous distillation-extraction (SDE) combines, in a single step, hydro-distillation of volatiles from a sample with continuous solvent extraction of the solutes dissolved in the aqueous distillate. The solvent extract containing the isolated flavour volatiles can be subsequently analysed by gas chromatography. The technique is applicable to compounds possessing a wide range of volatility, but it is suitable neither for compounds of low volatility (e.g. vanillin), nor for highly volatile materials (e.g. methanethiol). The present guidelines concern the isolation of flavouring substances by simultaneous distillation-extraction (SDE), based on the experience of the authors in laboratories of the flavour industry. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
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- 2015
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11. Differential roles of the Src homology 2 domains of phospholipase C-gamma1 (PLC-gamma1) in platelet-derived growth factor-induced activation of PLC-gamma1 in intact cells.
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Poulin, B, Sekiya, F, and Rhee, S G
- Abstract
Upon stimulation of cells with platelet-derived growth factor (PDGF), phospholipase C-gamma1 (PLC-gamma1) binds to the tyrosine-phosphorylated PDGF receptor through one or both of its Src homology 2 (SH2) domains, is phosphorylated by the receptor kinase, and is thereby activated to hydrolyze phosphatidylinositol 4, 5-bisphosphate. Association of PLC-gamma1 with the insoluble subcellular fraction is also enhanced in PDGF-stimulated cells. The individual roles of the two SH2 domains of PLC-gamma1 in mediating the interaction between the enzyme and the PDGF receptor have now been investigated by functionally disabling each domain. A critical Arg residue in each SH2 domain was mutated to Ala. Both wild-type and mutant PLC-gamma1 proteins were transiently expressed in a PLC-gamma1-deficient fibroblast cell line, and these transfected cells were stimulated with PDGF. The mutant protein in which the COOH-terminal SH2 domain was disabled bound to the PDGF receptor. Accordingly, it was phosphorylated by the receptor, catalyzed the production of inositol phosphates, and mobilized intracellular calcium to extents similar to (but slightly less than) those observed with the wild-type enzyme. In contrast, the mutant in which the NH(2)-terminal SH2 domain was impaired did not bind to the PDGF receptor and consequently was neither phosphorylated nor activated. These results suggest that the NH(2)-terminal SH2 domain, but not the COOH-terminal SH2 domain, of PLC-gamma1 is required for PDGF-induced activation of PLC-gamma1. Functional impairment of the SH2 domains did not affect the PDGF-induced redistribution of PLC-gamma1, suggesting that recruitment of PLC-gamma1 to the particulate fraction does not involve the SH2 domains.
- Published
- 2000
12. AHNAK, a protein that binds and activates phospholipase C-gamma1 in the presence of arachidonic acid.
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Sekiya, F, Bae, Y S, Jhon, D Y, Hwang, S C, and Rhee, S G
- Abstract
We have recently shown that phospholipase C-gamma (PLC-gamma) is activated by tau, a neuronal cell-specific microtubule-associated protein, in the presence of arachidonic acid. We now report that non-neuronal tissues also contain a protein that can activate PLC-gamma in the presence of arachidonic acid. Purification of this activator from bovine lung cytosol yielded several proteins with apparent molecular sizes of 70-130 kDa. They were identified as fragments derived from an unusually large protein (approximately 700 kDa) named AHNAK, which comprises about 30 repeated motifs each 128 amino acids in length. Two AHNAK fragments containing one and four of the repeated motifs, respectively, were expressed as glutathione S-transferase fusion proteins. Both recombinant proteins activated PLC-gamma1 at nanomolar concentrations in the presence of arachidonic acid, suggesting that an intact AHNAK molecule contains multiple sites for PLC-gamma activation. The role of arachidonic acid was to promote a physical interaction between AHNAK and PLC-gamma1, and the activation by AHNAK and arachidonic acid was mainly attributable to reduction in the enzyme's apparent Km toward the substrate phosphatidylinositol 4,5-bisphosphate. Our results suggest that arachidonic acid liberated by phospholipase A2 can act as an additional trigger for PLC-gamma activation, constituting an alternative mechanism that is independent of tyrosine phosphorylation.
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- 1999
13. Regulation of phospholipase C isozymes: activation of phospholipase C-@c in the absence of tyrosine-phosphorylation
- Author
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Sekiya, F., Bae, Y.S., and Rhee, S.G.
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- 1999
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14. Inhibition of phospholipase D by clathrin assembly protein 3 (AP3).
- Author
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Lee, C, Kang, H S, Chung, J K, Sekiya, F, Kim, J R, Han, J S, Kim, S R, Bae, Y S, Morris, A J, and Rhee, S G
- Abstract
In the accompanying paper (Chung, J.-K., Sekiya, F., Kang, H.-S., Lee, C., Han, J.-S., Kim, S. R., Bae, Y. S., Morris, A. J., and Rhee, S. G. (1997) J. Biol. Chem. 272, 15980-15985), synaptojanin is identified as a protein that inhibits phospholipase D (PLD) activity stimulated by ADP-ribosylation factor and phosphatidylinositol 4, 5-bisphosphate (PI(4,5)P2). Here, the purification from rat brain cytosol of another PLD-inhibitory protein that is immunologically distinct from synaptojanin is described, and this protein is identified as clathrin assembly protein 3 (AP3) by peptide sequencing and immunoblot analysis. AP3 binds both inositol hexakisphosphate and preassembled clathrin cages with high affinity. However, neither inositol hexakisphosphate binding nor clathrin cage binding affected the ability of AP3 to inhibit PLD. AP3 also binds to PI(4,5)P2 with low affinity. But the PI(4,5)P2 binding was not responsible for PLD inhibition, because the potency and efficacy of AP3 as an inhibitor of PLD were similar in the absence and presence of PI(4,5)P2. A bacterially expressed fusion protein, glutathione S-transferase-AP3 (GST-AP3), also inhibited PLD with a potency equal to that of brain AP3. The inhibitory effect of AP3 appeared to be the result of direct interaction between AP3 and PLD because PLD bound GST-AP3 in an in vitro binding assay. Using GST fusion proteins containing various AP3 sequences, we found that the sequence extending from residues Pro-290 to Lys-320 of AP3 is critical for both inhibition of and binding to PLD. The fact that AP3 is a synapse-specific protein indicates that the AP3-dependent inhibition of PLD might play a regulatory role that is restricted to the rapid cycling of synaptic vesicles.
- Published
- 1997
15. Synaptojanin inhibition of phospholipase D activity by hydrolysis of phosphatidylinositol 4,5-bisphosphate.
- Author
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Chung, J K, Sekiya, F, Kang, H S, Lee, C, Han, J S, Kim, S R, Bae, Y S, Morris, A J, and Rhee, S G
- Abstract
A 150-kDa protein that inhibits phospholipase D (PLD) activity stimulated by ADP-ribosylation factor and phosphatidylinositol 4, 5-bisphosphate (PI(4,5)P2) was previously purified from rat brain. The sequences of peptides derived from the purified PLD inhibitor now identify it as synaptojanin, a nerve terminal protein that has been implicated in the endocytosis of fused synaptic vesicles and shown to be a member of the inositol polyphosphate 5-phosphatase family. Further characterization of the enzymatic properties of synaptojanin now shows that it hydrolyzes only the 5-phosphate from inositol 1,4,5-trisphosphate (I(1,4,5)P3) and that it does not catalyze the dephosphorylation of either I(1,3,4)P3 or inositol 1, 4-bisphosphate. However, synaptojanin hydrolyzes both the 4- and 5-phosphates of PI(4,5)P2 and the 4-phosphate of phosphatidylinositol 4-phosphate, converting both compounds to phosphatidylinositol. Magnesium is required for the hydrolysis of I(1,4,5)P3, but not for that of phosphoinositides, by synaptojanin. The inhibition of PLD by synaptojanin is attributable to its ability to hydrolyze PI(4,5)P2. Synaptojanin did not inhibit PLD in the absence of PI(4,5)P2, and the extent of PLD inhibition was related to the extent of PI(4,5)P2 hydrolysis in substrate vesicles. It has been proposed that the biosynthesis of PI(4,5)P2 and the activation of PLD by ADP-ribosylation factor constitute a positive loop to increase rapidly the concentrations of PI(4,5)P2 and phosphatidic acid (PA) during membrane vesiculation. The PA thus produced, probably together with PI(4,5)P2, facilitates vesicle coat assembly. The hydrolysis of PI(4,5)P2, and consequent inhibition of PLD, by synaptojanin might therefore constitute a mechanism to halt the positive loop connecting PI(4,5)P2 and PA during the endocytotic cycle of synaptic vesicles and serve as a signal for uncoating.
- Published
- 1997
16. Magnesium(II) is a crucial constituent of the blood coagulation cascade. Potentiation of coagulant activities of factor IX by Mg2+ ions.
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Sekiya, F, Yoshida, M, Yamashita, T, and Morita, T
- Abstract
We recently showed that not only Ca2+ ions but also Mg2+ ions play a crucial role in stabilizing the native conformation of coagulation factor IX. We here report that Mg2+ ions at physiological concentrations greatly augment the biological activities of factor IX. In clotting assays with dialyzed plasma, addition of Mg2+ ions enhanced the apparent coagulant activity of factor IXa, while that of factor Xa was scarcely affected. Activation of factor X by factor IXa in the presence of factor VIIIa, phospholipids, and Ca2+ ions was accelerated by Mg2+ ions. It appeared that the cation increased the affinity between factor IXa and factor VIIIa, thereby increasing the apparent catalytic efficacy of the enzyme. We also evaluated the effect of Mg2+ ions in the coagulation pathway initiated by tissue factor and found that activation of factor IX by factor VIIa*tissue factor was accelerated by the cation. Consequently, clotting of normal plasma induced by factor VIIa*tissue factor was shortened by the cation, while no such effect was observed in plasma deficient in factor IX or VIII. These results indicate that the previously unrecognized plasma component, Mg2+ ions, plays crucial roles in blood coagulation and, moreover, that contributions of factors IX and VIII in the coagulation cascade have been seriously underestimated in previous investigations.
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- 1996
17. Inhibition of Platelet-Collagen Interaction by Propolypeptide of von Willebrand Factor
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Takagi, J, Sekiya, F, Kasahara, K, Inada, Y, and Saito, Y
- Abstract
A collagen-binding glycoprotein was isolated from human platelets using affinity chromatography of immobilized collagen. Based upon characterizations of this protein we confirmed that it was identical to the propolypeptide of von Willebrand factor (pp-vWF), which is also called von Willebrand antigen II. The characteristics we have investigated are molecular weight, existence of carbohydrate chains, and the NH2-terminal amino acid sequence. pp-vWF has strong affinity to collagen and inhibits collagen-induced aggregation of human platelets at a concentration as low as 2 µg/ml even in the presence of plasma. This inhibitory effect is specific for collagen-induced aggregation since it does not inhibit aggregation of platelets induced by other agonists such as ADP, arachidonic acid, platelet-activating factor, ionophore A23187, and ristocetin. As pp-vWF is quickly released from platelets upon activation by various agonists, it is possible that pp-vWF functions as a repressor for excess platelet aggregation induced by collagen and constitutes a negative feed-back mechanism. Considering the fact that mature vWF supports platelet adhesion to subendothelium, present observations suggest that the propeptide portion and the mature protein could have opposing effects on hemostasis.
- Published
- 1989
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18. Isolation and characterization of carinactivase, a novel prothrombin activator in Echis carinatus venom with a unique catalytic mechanism.
- Author
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Yamada, D, Sekiya, F, and Morita, T
- Abstract
The venom of the viper Echis carinatus contains a metalloprotease, ecarin, that is a potent prothrombin activator. We here show that the venom is also rich in another prothrombin activator, which does not belong to any known category of prothrombin activators. The novel enzyme, designated carinactivase-1 (CA-1), consists of two subunits held together non-covalently but very tightly. One subunit is a 62-kDa polypeptide that has metalloprotease activity and is homologous to the single-chain enzyme ecarin; the other subunit of 25 kDa consists of two disulfide-linked polypeptides of 17 and 14 kDa, and this subunit resembles the anticoagulant in the habu snake venom, IX/X-bp, that specifically binds the Gla domains of coagulation factors IX and X in a Ca2+-dependent fashion. The activation of prothrombin by CA-1 requires Ca2+ ions at millimolar concentrations and in the absence of Ca2+ ions this enzyme is virtually inactive. By contrast, activation by ecarin is completely independent of Ca2+ ions. CA-1, unlike ecarin, does not activate prothrombin derivatives, in which binding of Ca2+ ions has been perturbed, namely prethrombin-1 and acarboxyprothrombin. Furthermore, the isolated catalytic subunit, although its activity is greatly reduced as compared to that of the holoenzyme, no longer requires Ca2+ ions for the activation of prothrombin. Reconstitution with the non-catalytic 25-kDa subunit restores high level activity and the dependence on Ca2+ ions. Finally, prothrombin activation by CA-1 is inhibited by prothrombin fragment 1, and the isolated non-catalytic subunit is capable of binding fragment 1 in the presence of Ca2+ ions. From these observations, we postulate the following unique mechanism for the activation of prothrombin by CA-1. The enzyme primarily recognizes the Ca2+-bound conformation of the Gla domain in prothrombin via the 25-kDa regulatory subunit, and the subsequent conversion of prothrombin to active thrombin is catalyzed by the 62-kDa catalytic subunit.
- Published
- 1996
19. Regulation of the tertiary structure and function of coagulation factor IX by magnesium (II) ions.
- Author
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Sekiya, F, Yamashita, T, Atoda, H, Komiyama, Y, and Morita, T
- Abstract
The indispensable role of Ca2+ ions in the maintenance of the functional tertiary structures of vitamin K-dependent coagulation factors has been definitively established but the participation of Mg2+ ions, another alkaline-earth metal that is present abundantly in blood plasma, in such a process is not yet understood. We show here that the Ca(2+)-stabilized conformation of coagulation factor IX undergoes a further conformational change upon binding of Mg2+ ions using three independent structural probes. The probes we used were (i) IX/X-bp, a snake venom anticoagulant that recognizes the Gla domains in coagulation factors IX and X, (ii) conformation-specific polyclonal antibodies against bovine factor IX, and (iii) monoclonal antibodies against the Gla domain of human factor IX. The binding of all these probes had an absolute requirement for Ca2+ ions, and Mg2+ ions alone were ineffective. However, when added together with Ca2+ ions, Mg2+ ions at physiological concentrations greatly augmented the binding of these probes to factor IX; the required concentration of Ca2+ ions was much reduced, and the affinity of each probe for factor IX was increased even in the presence of an excess of Ca2+ ions. These results suggest the presence of a Mg(2+)-specific binding site that does not interact with Ca2+ ions in factor IX. Furthermore, Mg2+ ions potentiated the susceptibility of factor IX to activation by factor XIa, concomitant with their effect on the conformation. Similarly, the required Ca2+ concentration was reduced by Mg2+ ions, and the rate of conversion to factor IXa was increased by Mg2+ ions in the presence of an excess of Ca2+ ions. At a saturating concentration of Ca2+ ions (5 mM), addition of 1 mM Mg2+ reduced the apparent Km value for factor IX from 0.31 to 0.18 microM, and in the presence of a physiological concentration of Ca2+ ions (1 mM), the reduction in Km by Mg2+ ions was far more striking (from 0.91 to 0.24 microM). The apparent Vmax values were hardly affected by Mg2+ ions. Our present data reveal a hitherto novel physiological role of the Mg2+ ions in plasma. Not only Ca2+ ions but also Mg2+ ions are important regulators of the stabilization of the native conformation of factor IX as well as of its efficient activation.
- Published
- 1995
20. A Collagen-binding Glycoprotein from Bovine Platelets Is Identical to Propolypeptide of von Willebrand Factor
- Author
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Takagi, J, Kasahara, K, Sekiya, F, Inada, Y, and Saito, Y
- Abstract
Several proteins from bovine platelet lysate bound to type I collagen immobilized to the beads of formyl derivatives of cellulose. Among these proteins, a protein of about 100,000 daltons was purified to homogeneity by two additional affinity chromatographies, an organomercurial-agarose and a lentil lectin-agarose. This protein consisted of a single polypeptide chain which contains carbohydrate moiety and many intrapolypeptide disulfide bridges. In addition to platelets, this protein was present in plasma and cultured endothelial cells but not in red blood cells, leukocytes, and smooth muscle cells. Furthermore, it was released from platelets upon stimulation by various agonists. The purified 100-kDa protein was labeled with 125I to quantitate its binding to fibrillar type I collagen. The protein specifically bound to fibrillar collagen with the apparent dissociation constant of 5.6 × 10−8Mfor the high affinity site and 5.5 × 10−7Mfor the low affinity site. Analyses of amino acid sequences of both intact and tryptic fragments of this protein revealed that it had strong homology to the propolypeptide of human von Willebrand factor, which is also known as von Willebrand antigen II. Various properties of this protein listed above also strongly suggest that it was indeed the propolypeptide of bovine von Willebrand factor.
- Published
- 1989
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21. Cooperativity between platelet-activating factor and collagen in platelet aggregation
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Kojima, S., primary, Hagiwara, H., additional, Soga, W., additional, Sekiya, F., additional, Saito, Y., additional, and Inada, Y., additional
- Published
- 1987
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22. Studies on the tillering primordium and tillering bud in rice seedlings. : (1) The influence of water depth on the development of tillering primordium and tillering bud,
- Author
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SEKIYA, F., primary
- Published
- 1951
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23. STUDIES ON THE TILLERING PREMORDIUM AND TILLERING BUD IN RICE SEEDLINGS. : (2) Th Effect of Light on the Development of Tillering Primordium and Tillering Bud. (Prelminary)
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SEKIYA, F., primary
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- 1952
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24. Japan Flavour and Fragrance Materials Association's (JFFMA) safety assessment of food-flavouring substances uniquely used in Japan that belong to the class of aliphatic primary alcohols, aldehydes, carboxylic acids, acetals and esters containing additional oxygenated functional groups.
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Saito K, Hasegawa-Baba Y, Sekiya F, Hayashi SM, Mirokuji Y, Okamura H, Maruyama S, Ono A, Nakajima M, Degawa M, Ozawa S, Shibutani M, and Maitani T
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- Acetals, Alcohols, Aldehydes, Carboxylic Acids, Esters, Hazard Analysis and Critical Control Points, Humans, Japan, Molecular Structure, Flavoring Agents adverse effects, Flavoring Agents chemistry, Food Additives adverse effects, Food Additives chemistry, Risk Assessment
- Abstract
We performed a safety evaluation using the procedure devised by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) of the following four flavouring substances that belong to the class of 'aliphatic primary alcohols, aldehydes, carboxylic acids, acetals, and esters containing additional oxygenated functional groups' and are uniquely used in Japan: butyl butyrylacetate, ethyl 2-hydroxy-4-methylpentanoate, 3-hydroxyhexanoic acid and methyl hydroxyacetate. Although no genotoxicity study data were found in the published literature, none of the four substances had chemical structural alerts predicting genotoxicity. All four substances were categorised as class I by using Cramer's classification. The estimated daily intake of each of the four substances was determined to be 0.007-2.9 μg/person/day by using the maximised survey-derived intake method and based on the annual production data in Japan in 2001, 2005 and 2010, and was determined to be 0.250-600.0 μg/person/day by using the single-portion exposure technique and based on average-use levels in standard portion sizes of flavoured foods. Both of these estimated daily intake ranges were below the threshold of toxicological concern for class I substances, which is 1800 μg/person/day. Although no information from in vitro and in vivo toxicity studies for the four substances was available, these substances were judged to raise no safety concerns at the current levels of intake.
- Published
- 2017
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25. Safety and efficacy of the leukocytapheresis procedure in eighty-five patients with rheumatoid arthritis.
- Author
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Kitagaichi M, Kusaoi M, Tsukahara T, Murayama G, Nemoto T, Sekiya F, Kon T, Ogasawara M, Kempe K, Yamaji K, Tamura N, Tsuda H, and Takasaki Y
- Subjects
- Arthritis, Rheumatoid blood, Arthritis, Rheumatoid pathology, Arthritis, Rheumatoid physiopathology, C-Reactive Protein metabolism, Humans, Male, Middle Aged, Antirheumatic Agents administration & dosage, Arthritis, Rheumatoid therapy, Leukapheresis methods
- Abstract
Rheumatoid arthritis (RA) is a systemic inflammatory disease in which the predominant symptom is polyarthritis that follows a chronic and progressive clinical course characterized by destructive synovitis and various immune disorders. Striking progress in RA treatment was achieved with the emergence of monoclonal antibodies to target cytokines. However, drug choices are limited for many patients due to resistance to multidrug antirheumatic therapy, concomitant disease, and infection. We evaluated the efficacy of treatment in 85 patients with RA for whom leukocytapheresis (LCAP) was initiated at our hospital between 2006 and 2015. All patients continued drug therapy and were treated with LCAP once a week for up to 5 weeks. The clinical response was evaluated at the completion of LCAP series and 4 weeks later using the American College of Rheumatology (ACR) criteria and the 28-joint disease activity score (DAS28) of European League Against Rheumatism (EULAR). The tender joint counts, swollen joint counts, and C-reactive protein (CRP) levels decreased remarkably. DAS28-CRP was significantly improved by LCAP. And furthermore, the efficacy lasted at least 4 weeks after the completion of LCAP. These results suggest that LCAP is a beneficial and are consistent with several trials' reported effect of LCAP. This treatment can contribute to improvements in activities of daily living (ADLs) and long-term outcome by improving swollen and tender joint counts and CRP levels even in refractory patients for whom the use of conventional disease-modifying antirheumatic drugs (DMARDs) and biopharmaceuticals is problematic. LCAP might be a promise therapy to refractory RA., (Copyright © 2016 Elsevier Ltd. All rights reserved.)
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- 2016
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26. Involvement of Mucosal-associated Invariant T cells in Ankylosing Spondylitis.
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Hayashi E, Chiba A, Tada K, Haga K, Kitagaichi M, Nakajima S, Kusaoi M, Sekiya F, Ogasawara M, Yamaji K, Tamura N, Takasaki Y, and Miyake S
- Subjects
- Adult, Female, Humans, Inflammation immunology, Inflammation metabolism, Lymphocyte Count, Male, Middle Aged, Mucosal-Associated Invariant T Cells metabolism, Spondylitis, Ankylosing metabolism, Cytokines metabolism, Lymphocyte Activation immunology, Mucosal-Associated Invariant T Cells immunology, Spondylitis, Ankylosing immunology
- Abstract
Objective: Ankylosing spondylitis (AS) is characterized by chronic inflammation of the axial and peripheral joints and ligamentous attachments. Gut immunity is thought to be involved in AS, because a prominent coexistence of gut and joint inflammation has been observed in patients with AS. Mucosal-associated invariant T (MAIT) cells are preferentially located in the gut lamina propria and produce inflammatory cytokines such as interleukin 17 (IL-17) and tumor necrosis factor-α (TNF-α), which are therapeutic targets for AS. This study aimed to investigate the involvement of MAIT cells in AS., Methods: The frequency of MAIT cells and their cytokine production were determined in patients with AS and healthy controls (HC). The expression of a MAIT cell activation marker (CD69) was analyzed in patients with AS by using flow cytometry., Results: The frequency of MAIT cells in the peripheral blood was lower in patients with AS compared with HC. The levels of IL-17 produced by MAIT cells after activation were higher in patients with AS than in the HC. CD69 expression on MAIT cells correlated with the Ankylosing Spondylitis Disease Activity Score in patients with AS., Conclusion: These results suggest the involvement of MAIT cells in the pathogenesis of AS.
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- 2016
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27. Separation of Circulating MicroRNAs Using Apheresis in Patients With Systemic Lupus Erythematosus.
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Kusaoi M, Yamaji K, Ishibe Y, Murayama G, Nemoto T, Sekiya F, Kon T, Ogasawara M, Kempe K, Tamura N, and Takasaki Y
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- Adult, Female, Humans, Male, Middle Aged, Treatment Outcome, Blood Component Removal methods, Lupus Erythematosus, Systemic blood, Lupus Erythematosus, Systemic therapy, MicroRNAs blood
- Abstract
MicroRNAs (miRNAs), which are important inhibitors of mRNA translation, participate in differentiation, migration, cell proliferation, and cell death. The pathology of miRNAs results in alterations in protein expression. Recently, miRNAs circulating in peripheral blood have been shown to control the synthesis and translation of proteins at distal sites after intake into local cells. A number of studies are currently being conducted to investigate how to use miRNAs in disease treatment, but no studies have attempted to alleviate disease by directly eliminating miRNAs from blood. Therefore, we examined whether the removal or reduction of circulating miRNAs with apheresis improved pathologies caused by miRNAs. After approval of the study by our medical school's ethics committee, we collected blood and separated plasma samples from three patients with systemic lupus erythematosus who were undergoing plasmapheresis at our hospital. Peripheral blood was collected before and after it was passed through a primary membrane, centrifuged, and used to extract circulating miRNAs. A comprehensive expression analysis was then performed with a miRNA array chip. The levels of expression of a large number of circulating miRNAs were measured in the plasma samples separated by the primary membranes from all 3 patients with systemic lupus erythematosus. We present the first report that circulating miRNAs in peripheral blood can be separated and possibly directly removed using membrane separation apheresis., (© 2016 International Society for Apheresis, Japanese Society for Apheresis, and Japanese Society for Dialysis Therapy.)
- Published
- 2016
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28. The Japan Flavour and Fragrance Materials Association's (JFFMA) safety assessment of acetal food flavouring substances uniquely used in Japan.
- Author
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Okamura H, Abe H, Hasegawa-Baba Y, Saito K, Sekiya F, Hayashi SM, Mirokuji Y, Maruyama S, Ono A, Nakajima M, Degawa M, Ozawa S, Shibutani M, and Maitani T
- Subjects
- Flavoring Agents chemistry, Food Additives chemistry, Humans, Japan, Molecular Structure, Flavoring Agents adverse effects, Food Additives adverse effects, Hazard Analysis and Critical Control Points
- Abstract
Using the procedure devised by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), we performed safety evaluations on five acetal flavouring substances uniquely used in Japan: acetaldehyde 2,3-butanediol acetal, acetoin dimethyl acetal, hexanal dibutyl acetal, hexanal glyceryl acetal and 4-methyl-2-pentanone propyleneglycol acetal. As no genotoxicity study data were available in the literature, all five substances had no chemical structural alerts predicting genotoxicity. Using Cramer's classification, acetoin dimethyl acetal and hexanal dibutyl acetal were categorised as class I, and acetaldehyde 2,3-butanediol acetal, hexanal glyceryl acetal and 4-methyl-2-pentanone propyleneglycol acetal as class III. The estimated daily intakes for all five substances were within the range of 1.45-6.53 µg/person/day using the method of maximised survey-derived intake based on the annual production data in Japan from 2001, 2005, 2008 and 2010, and 156-720 µg/person/day using the single-portion exposure technique (SPET), based on the average use levels in standard portion sizes of flavoured foods. The daily intakes of the two class I substances were below the threshold of toxicological concern (TTC) - 1800 μg/person/day. The daily intakes of the three class III substances exceeded the TTC (90 μg/person/day). Two of these, acetaldehyde 2,3-butanediol acetal and hexanal glyceryl acetal, were expected to be metabolised into endogenous products after ingestion. For 4-methyl-2-pentanone propyleneglycol acetal, one of its metabolites was not expected to be metabolised into endogenous products. However, its daily intake level, based on the estimated intake calculated by the SPET method, was about 1/15 000th of the no observed effect level. It was thus concluded that all five substances raised no safety concerns when used for flavouring foods at the currently estimated intake levels. While no information on in vitro and in vivo toxicity for all five substances was available, their metabolites were judged as raising no safety concerns at the current levels of intake.
- Published
- 2015
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29. Reduction in bradykinin generation during leukocytapheresis using novel cellsorba(TM) CS-180S: Effects of changing the filling solution.
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Yamada R, Kusaoi M, Murayama G, Yasui M, Hishinuma R, Nemoto T, Hohtatsu K, Kageyama M, Kawamoto T, Sugimoto K, Sekiya F, Kon T, Ogasawara M, Kempe K, Yamaji K, Tsuda H, and Takasaki Y
- Subjects
- Blood Coagulation, Bradykinin adverse effects, Humans, Solutions, Bradykinin biosynthesis, Leukapheresis methods
- Abstract
We evaluated the bradykinin generation level during leukocytapheresis (LCAP) using novel Cellsorba(TM) CS-180S, which has sodium pyrosulfite and sodium carbonate as a filling solution. Subjects of this study were 14 rheumatoid arthritis patients. Regardless of the type of anticoagulant used, bradykinin levels were lower with the novel CS-180S than with the conventional CS-180S (28.7 ± 53.3 vs. 8.0 ± 2.7 as the mean ± standard deviation). When anticoagulants other than nafamostat mesilate were used with the conventional CS-180S, bradykinin levels increased at the column outlet compared with the column inlet, and adverse effects of bradykinin were seen in several cases. In contrast, bradykinin levels remained low and no bradykinin-associated adverse events were observed with the novel CS-180S. We recommend using the novel column instead of the conventional column in the treatment of LCAP., (Copyright © 2013 Wiley Periodicals, Inc.)
- Published
- 2014
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30. The JFFMA assessment of flavoring substances structurally related to menthol and uniquely used in Japan.
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Mirokuji Y, Abe H, Okamura H, Saito K, Sekiya F, Hayashi SM, Maruyama S, Ono A, Nakajima M, Degawa M, Ozawa S, Shibutani M, and Maitani T
- Subjects
- Flavoring Agents toxicity, Japan, Menthol toxicity, Molecular Structure, Flavoring Agents chemistry, Menthol chemistry
- Abstract
Using the procedure devised by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), we performed safety evaluations on four flavoring substances structurally related to menthol (L-menthyl 2-methylbutyrate, DL-menthyl octanoate, DL-menthyl palmitate, and DL-menthyl stearate) uniquely used in Japan. While no genotoxicity study data were available in the literature, all four substances had no chemical structural alerts predictive of genotoxicity. Moreover, they all four are esters consisting of menthol and simple carboxylic acids that were assumed to be immediately hydrolyzed after ingestion and metabolized into innocuous substances for excretion. As menthol and carboxylic acids have no known genotoxicity, it was judged that the JECFA procedure could be applied to these four substances. According to Cramer's classification, these substances were categorized as class I based on their chemical structures. The estimated daily intakes for all four substances were within the range of 1.54-4.71 μg/person/day and 60-1250 μg/person/day, using the methods of Maximized Survey-Derived Intake and Single Portion Exposure Technique, respectively, based on the annual usage data of 2001, 2005, and 2010 in Japan. As the daily intakes of these substances were below the threshold of concern applied to class I substances viz., 1800 μg/person/day, it was concluded that all four substances raise no safety concerns when used for flavoring foods under the currently estimated intake levels., (Copyright © 2013 Elsevier Ltd. All rights reserved.)
- Published
- 2014
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31. Recent trends in use of nonbiologic DMARDs and evaluation of their continuation rates in single and dual combination therapies in rheumatoid arthritis patients in Japan.
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Ogasawara M, Kageyama M, Kusaoi M, Onuma S, Kon T, Sekiya F, Sugimoto K, Matsudaira R, Matsushita M, Tada K, Kempe K, Yamaji K, Tamura N, and Takasaki Y
- Subjects
- Adult, Cysteine analogs & derivatives, Cysteine therapeutic use, Drug Therapy, Combination, Female, Humans, Japan, Male, Methotrexate therapeutic use, Severity of Illness Index, Sulfasalazine therapeutic use, Treatment Outcome, Antirheumatic Agents therapeutic use, Arthritis, Rheumatoid drug therapy, Practice Patterns, Physicians' trends
- Abstract
Objective: We aim to examine changes in usage of nonbiologic, disease-modifying antirheumatic drugs (DMARDs) and evaluate their continuation rates in Japan., Methods: We analyzed DMARD treatment data for 3,734 patients with rheumatoid arthritis (RA) from 1998 to 2009 at Juntendo Hospital in Tokyo, Japan. The DMARD usage rate per month was determined to evaluate RA treatment history in the last decade. We also evaluated continuation rates of nonbiologic DMARDs in single and combination therapies and number of nonbiologic DMARD combination therapies used in each patient., Results: We found that nonbiologic DMARD usage has dramatically changed in the last decade, with the most commonly used DMARD shifting from bucillamine to methotrexate (MTX). MTX showed the highest continuation rate; however, much lower continuation rate was observed when used alone rather than in combination treatments. Further, MTX was also used in the highest number of different combination therapies for a particular patient., Conclusions: These findings indicate that single MTX treatment may be unable to keep patients in clinical remission or lower disease activity compared with several combination therapies. Recent change in permitted maximum dosage of MTX from 8 to 16 mg/week may improve its efficacy and continuation rate in treating Japanese RA patients.
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- 2012
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32. Gene expression analysis using a high-resolution DNA microarray of peripheral whole blood immediately before and after leukocytapheresis for rheumatoid arthritis.
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Kusaoi M, Yamaji K, Murayama G, Yasui M, Yamada R, Hishinuma R, Nemoto T, Hohtatsu K, Kageyama M, Kawamoto T, Sugimoto K, Sekiya F, Kon T, Ogasawara M, Kempe K, Tsuda H, and Takasaki Y
- Subjects
- Female, Gene Expression Profiling, Humans, Oligonucleotide Array Sequence Analysis, Treatment Outcome, Arthritis, Rheumatoid therapy, Down-Regulation, Leukapheresis methods, Up-Regulation
- Abstract
Leukocytapheresis (LCAP) is a safe, unique therapy pertaining to intractable rheumatoid arthritis (RA) even in cases of drug allergy or infectious states. To investigate how to represent LCAP efficacy, we have conducted gene expression analyses from the peripheral blood of RA patients treated with non-woven polyethylene terephthalate filters. Peripheral blood samples were collected immediately before and after treatment from eight RA patients who received LCAP. Among these patients, all of them achieved 20% improvement in the core set of the American College of Rheumatology (ACR20), and thus, they were confirmed as LCAP responders. Gene expression analysis was done with a high-resolution DNA microarray. The results of each of the two groups' gene expression values (immediately before and after LCAP) were calculated using Welch's t-test. Calculations were performed with a statistical software R.basic package: if the P-value was less than 0.05, this was seen as a significant change. In a comparison of 25,370 gene expressions, the number of genes showing a P-value < 0.05 in the upregulating group was 2110, and in the downregulating group it was 1864. The results of pathway analysis using the MetaCore program indicate that gene groups work for cytoskeletal remodeling are upregulated, and genes related to immune responses, such as antigens presenting via major histocompatibility complex class I and II, are downregulated just after LCAP. These findings may relate to LCAP efficacy for RA patients, but this needs further investigation., (© 2012 The Authors. Therapeutic Apheresis and Dialysis © 2012 International Society for Apheresis.)
- Published
- 2012
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33. Autofeedback from ultrasound images provides rapid improvement in palpation skills for identifying joint swelling in rheumatoid arthritis.
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Ogasawara M, Murayama G, Yamada Y, Nemoto T, Kageyama M, Toyama S, Kusaoi M, Onuma S, Kon T, Sekiya F, Sugimoto K, Matsudaira R, Matsushita M, Tada K, Kempe K, Yamaji K, Tamura N, and Takasaki Y
- Subjects
- Adult, Aged, Arthritis, Rheumatoid complications, Arthritis, Rheumatoid diagnostic imaging, Edema diagnostic imaging, Edema etiology, Female, Humans, Joints diagnostic imaging, Joints physiopathology, Male, Middle Aged, Predictive Value of Tests, Synovitis diagnostic imaging, Synovitis etiology, Young Adult, Arthritis, Rheumatoid diagnosis, Edema diagnosis, Feedback, Sensory, Joints pathology, Palpation methods, Synovitis diagnosis, Ultrasonography methods
- Abstract
Objective: Joint swelling, an important factor in the classification criteria and disease activity assessment in rheumatoid arthritis (RA), renders joint palpation a necessary skill for physicians. Ultrasound (US) examination that visualizes soft tissue abnormalities is now used to assess musculoskeletal disease. We assessed the usefulness of US assessments in enhancing physical joint examination skills., Methods: We examined 1944 joints (bilateral shoulder, elbow, wrist, metacarpophalangeal joints 1-5, and knee joints) in 108 patients with RA during April-July 2011. We first physically examined and confirmed joint swelling; subsequently, the same rheumatologist conducted US examinations and multiple assessors graded the joint swelling. When the 2 results differed, we received autofeedback from the US results to improve the physical examination skills., Results: The sensitivities and specificities of physical examination for US-detected swollen joint, the correlation coefficient (CC) of the swollen joint counts, and the concordance rate in each patient for joint swelling sites and power Doppler (PD)-positive sites with the κ coefficients between the physical and US examinations were compared over time. We found that the sensitivity of physical examination increased by 42 percentage points (pp), while the specificity decreased by 18 pp. The average CC in June-July was greater than that in April-May. The percentage of κ coefficients > 0.8 increased from 8.8% to 17% for joint swelling and from 8.3% to 14% for PD-positive sites., Conclusion: Our results suggest that autofeedback from US assessment provides quick improvement in palpation skills for identifying joint swelling in patients with RA.
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- 2012
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34. Single-center, retrospective analysis of efficacy and safety of tacrolimus as a second-line DMARD in combination therapy and the risk factors contributing to adverse events in 115 patients with rheumatoid arthritis.
- Author
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Ogasawara M, Tamura N, Kageyama M, Onuma S, Kusaoi M, Toyama S, Sekiya F, Matsudaira R, Nawata M, Tada K, Matsushita M, Kempe K, Amano H, Morimoto S, Yamaji K, and Takasaki Y
- Subjects
- Adult, Aged, Antirheumatic Agents adverse effects, Cysteine adverse effects, Cysteine analogs & derivatives, Cysteine therapeutic use, Disease Progression, Drug Therapy, Combination, Female, Humans, Male, Methotrexate adverse effects, Methotrexate therapeutic use, Middle Aged, Retrospective Studies, Risk Factors, Severity of Illness Index, Sulfasalazine adverse effects, Sulfasalazine therapeutic use, Tacrolimus adverse effects, Treatment Outcome, Antirheumatic Agents therapeutic use, Arthritis, Rheumatoid drug therapy, Tacrolimus therapeutic use
- Abstract
To retrospectively evaluate the efficacy and safety of combination therapy with tacrolimus (TAC) and other disease-modifying antirheumatic drugs (DMARDs). One hundred fifteen rheumatoid arthritis (RA) patients treated with tacrolimus were enrolled in this retrospective analysis. We collected clinical information, including patient background, treatment efficacy (evaluated using the DAS score), and adverse events observed. Multiple logistic regression analysis was conducted to analyze factors contributing to clinical response and adverse effects. The disease activity score of 28 joints (DAS28) improved significantly at 24 weeks, and continuation rate at 1 year was 57.9%. There was no difference in continuation rate between different DMARD combinations, and not only methotrexate (MTX) but also bucillamine (BUC) and salazosulfapyridine (SSZ) were effective combination partners with TAC. No serious adverse events were observed, and no different inefficacy or safety was observed between non-elderly (<65 years old) and elderly (≥65 years old) RA patients. By conducting multiple logistic regression analysis, combination therapy with MTX and TAC, the number of baseline DMARDs (specifically, ≥3), and old age were identified as risk factors for adverse events. Our findings indicate that TAC is a valuable DMARD for second-line combination therapy in RA.
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- 2012
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35. Anti-Ro/SSA antibodies are an independent factor associated with an insufficient response to tumor necrosis factor inhibitors in patients with rheumatoid arthritis.
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Matsudaira R, Tamura N, Sekiya F, Ogasawara M, Yamanaka K, and Takasaki Y
- Subjects
- Adalimumab, Adult, Antibodies, Monoclonal therapeutic use, Antibodies, Monoclonal, Humanized therapeutic use, Biomarkers blood, Etanercept, Female, Follow-Up Studies, Humans, Immunoglobulin G therapeutic use, Infliximab, Logistic Models, Male, Middle Aged, Receptors, Tumor Necrosis Factor therapeutic use, Retrospective Studies, Treatment Outcome, Antibodies, Antinuclear blood, Antirheumatic Agents therapeutic use, Arthritis, Rheumatoid blood, Arthritis, Rheumatoid drug therapy, Tumor Necrosis Factor-alpha antagonists & inhibitors
- Abstract
Objective: To study the significance of anti-Ro/SSA antibodies (anti-Ro) in the clinical response to tumor necrosis factor (TNF) inhibitors in patients with rheumatoid arthritis (RA)., Methods: The clinical responses of a cohort of 190 patients with RA who were treated with infliximab, etanercept, or adalimumab (n = 112, 64, and 14, respectively) as the first biologics were examined using the Disease Activity Score in 28 joints (DAS28) at 24 weeks and the discontinuation rate at 56 weeks. The baseline characteristics of responders and the nonresponders were compared. The clinical response was compared between anti-Ro-negative and -positive patients. The factors associated with the inefficiency of TNF inhibitors were estimated with a multivariable logistic regression analysis., Results: The positive rate of anti-Ro was significantly higher in patients with no European League Against Rheumatism (EULAR) response at 24 weeks (OR 3.64, 95% CI 1.45-9.01, p = 0.003). In anti-Ro-positive patients, a moderate or good EULAR response rate was significantly lower with a sustaining higher median DAS28 (p = 0.006), and this difference was greater among infliximab-treated patients. The discontinuation rate for TNF inhibitors due to inefficacy at 56 weeks was also higher in anti-Ro-positive patients (OR 4.68, 95% CI 1.82-11.99, p = 0.0005), and 75% of these patients received infliximab. The presence of anti-Ro was strongly associated with no EULAR response at 24 weeks and a higher discontinuation rate of TNF inhibitors by 56 weeks (OR 5.22, 95% CI 1.75-15.57, p = 0.003 and OR 10.18, 95% CI 2.18-49.56, p = 0.003)., Conclusion: The presence of anti-Ro might be related to the lesser clinical response to infliximab compared to other TNF inhibitors, suggesting that the presence of anti-Ro should be considered when choosing the appropriate biologics for patients with RA.
- Published
- 2011
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36. Effect of various anticoagulant agents on large-volume leukocytapheresis using new Cellsorba CS-180S Filter.
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Hohtatsu K, Yamaji K, Yamada R, Oda K, Kageyama M, Kusaoi M, Onuma S, Kawamoto T, Sugimoto K, Sekiya F, Kon T, Ogasawara M, Kempe K, Tsuda H, and Takasaki Y
- Subjects
- Arthritis, Rheumatoid therapy, Benzamidines, Carbonates chemistry, Filtration instrumentation, Humans, Leukapheresis instrumentation, Neutrophils metabolism, Sodium Citrate, Sulfites chemistry, Anticoagulants administration & dosage, Citrates administration & dosage, Guanidines administration & dosage, Heparin, Low-Molecular-Weight administration & dosage, Leukapheresis methods
- Abstract
We conducted a study to evaluate the effect of various anticoagulant agents on large-volume leukocytapheresis using the new Cellsorba CS-180S Filter filled with a changed solution of sodium pyrosulfite and sodium carbonate. We conducted the study on a total of 12 cases of rheumatoid arthritis. As the anticoagulant agents we used sodium citrate, nafamostat mesilate and low molecular weight heparin. The new Cellsorba CS-180S was safely used with the various blood anticoagulant agents. Also, through adjustment of the sodium citrate percentage to the blood flow volume, it is hypothesized that it is possible to increase the neutrophil removal rate., (© 2011 The Authors. Therapeutic Apheresis and Dialysis © 2011 International Society for Apheresis.)
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- 2011
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37. Observational cross-sectional study revealing less aggressive treatment in Japanese elderly than nonelderly patients with rheumatoid arthritis.
- Author
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Ogasawara M, Tamura N, Onuma S, Kusaoi M, Sekiya F, Matsudaira R, Kempe K, Yamaji K, and Takasaki Y
- Subjects
- Age Factors, Aged, Antibodies, Anti-Idiotypic blood, Antibodies, Monoclonal therapeutic use, Arthritis, Rheumatoid blood, Cross-Sectional Studies, Dose-Response Relationship, Drug, Etanercept, Female, Humans, Immunoglobulin G therapeutic use, Infliximab, Male, Matrix Metalloproteinase 3 blood, Methotrexate therapeutic use, Middle Aged, Peptides, Cyclic immunology, Receptors, Tumor Necrosis Factor therapeutic use, Rheumatoid Factor blood, Adrenal Cortex Hormones therapeutic use, Antirheumatic Agents therapeutic use, Arthritis, Rheumatoid drug therapy
- Abstract
Background: Elderly patients with rheumatoid arthritis (RA) have more aging-related complications than nonelderly patients with RA., Objectives: The objective of the study was to investigate the treatment status of elderly patients with RA., Methods: Between January and March 2008, 969 patients with RA were enrolled in this observational cross-sectional study. Prescription of disease-modifying antirheumatic drugs (DMARDs) and corticosteroids and laboratory data related to RA, including matrix metalloproteinase 3, rheumatoid factor, and anti-cyclic citrullinated peptide antibody levels, were compared between the elderly and the nonelderly patients., Results: Fewer DMARDs were prescribed to the elderly patients (1.40 [SD, 0.57] vs. 1.51 [SD, 0.61]; P = 0.029). Furthermore, a lower percentage of patients received methotrexate (MTX) (47.2% vs. 56.9%; P = 0.0001), a lower average dosage of MTX was administered (5.46 [SD, 1.66] mg/wk vs. 5.96 [SD, 1.77] mg/wk; P = 0.0001), and fewer biologic DMARDs were used (1.46% vs. 5.59% for infliximab, P = 0.0008; 0.58% vs. 3.19% for etanercept, P = 0.0038) in the elderly group. The laboratory data suggested that the disease status was uncontrolled to a greater extent, and complications were more common in the elderly group., Conclusion: Elderly patients with RA receive less aggressive treatment than nonelderly patients with RA, despite laboratory evidence for poorly controlled disease status among the elderly. The use of a less aggressive regimen could be attributed to the higher prevalence of complications and problems. Therefore, the elderly with RA should be considered a different patient population from the viewpoint of treatment and be administered specialized medical care.
- Published
- 2010
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38. Investigation of occurrence of osteonecrosis of the femoral head after increasing corticosteroids in patients with recurring systemic lupus erythematosus.
- Author
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Sekiya F, Yamaji K, Yang K, Tsuda H, and Takasaki Y
- Subjects
- Adult, Dose-Response Relationship, Drug, Female, Femur Head Necrosis blood, Femur Head Necrosis pathology, Humans, Lipids blood, Lupus Erythematosus, Systemic blood, Lupus Erythematosus, Systemic pathology, Magnetic Resonance Imaging, Male, Middle Aged, Recurrence, Severity of Illness Index, Young Adult, Femur Head Necrosis chemically induced, Glucocorticoids adverse effects, Lupus Erythematosus, Systemic drug therapy, Prednisolone adverse effects
- Abstract
Osteonecrosis (ON) of the femoral head is known to occur commonly in cases with systemic lupus erythematosus (SLE) that received corticosteroid (CS) treatment. However, there have been no detailed reports about the onset of ON in cases with recurrence of SLE. Using MRI, we followed up 17 patients who experienced recurrence of SLE for at least 1 year at our hospital and in whom the CS dose was increased from a maintenance dose to middle to high dose to see if ON would occur. We then compared the group that developed ON and the group that did not with respect to patient characteristics, blood test results, changes in serum lipid levels, and CS dose. ON occurred in five subjects (29.4%), revealing that osteonecrosis occurs not only when CS are first administered but also in cases which the CS dose is increased for recurrence of SLE. Especially, serum cholesterol levels and its rate of increase soared rapidly soon after increasing the CS dose in the ON group as compared with the non-ON group (P < 0.05). This suggests that increased serum lipid levels might be a contributing factor to onset of ON. Moreover, SLE disease activity index 2000 (SLEDAI-2K) scores when the CS dose was increased were significantly (P < 0.05) higher in the ON group, suggesting that SLE disease activity itself is a risk factor for onset of ON.
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- 2010
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39. Intramolecular interaction between phosphorylated tyrosine-783 and the C-terminal Src homology 2 domain activates phospholipase C-gamma1.
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Poulin B, Sekiya F, and Rhee SG
- Subjects
- Animals, Binding Sites, Enzyme Activation, In Vitro Techniques, Models, Biological, Mutagenesis, Site-Directed, Phospholipase C gamma, Phosphorylation, Protein Conformation, Rats, Recombinant Proteins chemistry, Recombinant Proteins genetics, Recombinant Proteins metabolism, Type C Phospholipases genetics, Tyrosine chemistry, src Homology Domains, Type C Phospholipases chemistry, Type C Phospholipases metabolism
- Abstract
Phospholipase C-gamma1 (PLC-gamma1) contains two tandem Src homology 2 (SH2) domains. The NH(2)-terminal SH2 domain has been known to mediate the binding of PLC-gamma1 to receptor protein tyrosine kinases, which then activate PLC-gamma1 via phosphorylation at Y783. We now show that the phosphorylated Y783 residue (pY783) associates with the COOH-terminal SH2 domain [SH2(C)] within the same molecule of PLC-gamma1. The specificity of this intramolecular interaction is demonstrated in several ways. The mutation of SH2(C), but not of the NH(2)-terminal SH2 domain, exposes pY783 and makes it available for binding by anti-pY783 antibodies, for intermolecular association with a GST fusion protein containing the tandem SH2 domains of PLC-gamma1 and for dephosphorylation by phosphatases. The intramolecular interaction between pY783 and SH2(C) induces a rearrangement of surface charge such that PLC-gamma1 molecules phosphorylated at Y783 are retained more strongly by heparin resins than are unphosphorylated molecules. Finally, the intramolecular interaction of pY783 with SH2(C) results in activation of phospholipase activity. Our results thus clarify the molecular mechanism of PLC-gamma1 activation, revealing the specific function of pY783 and the distinct roles of the two SH2 domains in this process.
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- 2005
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40. Mechanism of B-cell receptor-induced phosphorylation and activation of phospholipase C-gamma2.
- Author
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Kim YJ, Sekiya F, Poulin B, Bae YS, and Rhee SG
- Subjects
- Agammaglobulinaemia Tyrosine Kinase, Amino Acid Sequence, Animals, Antibodies, Binding Sites genetics, Cell Line, Enzyme Activation, Humans, In Vitro Techniques, Jurkat Cells, Mice, Molecular Sequence Data, Phospholipase C gamma, Phosphorylation, Protein-Tyrosine Kinases genetics, Protein-Tyrosine Kinases metabolism, RNA Interference, Sequence Homology, Amino Acid, Type C Phospholipases chemistry, Type C Phospholipases genetics, B-Lymphocytes metabolism, Receptors, Antigen, B-Cell metabolism, Type C Phospholipases metabolism
- Abstract
Phospholipase C-gamma2 (PLC-gamma2) plays an important role in B-cell signaling. Phosphorylation of various tyrosine residues of PLC-gamma2 has been implicated in regulation of its lipase activity. With the use of antibodies specific for each of the putative phosphorylation sites, we have now shown that PLC-gamma2 is phosphorylated on Y753, Y759, and Y1217 in response to engagement of the B-cell receptor in Ramos cells, as well as in murine splenic B cells. In cells stimulated maximally via this receptor, the extent of phosphorylation of Y1217 was three times that of Y753 or of Y759. Stimulation of Jurkat T cells or platelets via their immunoreceptors also elicited phosphorylation of Y753 and Y759 but not that of Y1217. A basal level of phosphorylation of Y753 was apparent in unstimulated lymphocytes. The extent of phosphorylation of Y753 and Y759, but not that of Y1217, correlated with the lipase activity of PLC-gamma2. Examination of the effects of various pharmacological inhibitors and of RNA interference in Ramos cells suggested that Btk is largely, but not completely, responsible for phosphorylation of Y753 and Y759, whereas phosphorylation of Y1217 is independent of Btk. Finally, phosphorylation of Y1217 and that of Y753 and Y759 occurred on different PLC-gamma2 molecules.
- Published
- 2004
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41. Identification of phospholipase C-gamma1 as a mitogen-activated protein kinase substrate.
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Buckley CT, Sekiya F, Kim YJ, Rhee SG, and Caldwell KK
- Subjects
- Amino Acid Sequence, Animals, Binding Sites, Binding, Competitive, Consensus Sequence, Female, Mitogen-Activated Protein Kinase 1 physiology, Mitogen-Activated Protein Kinases metabolism, Mitogen-Activated Protein Kinases physiology, Peptide Fragments metabolism, Phospholipase C gamma, Phosphorylation, Rats, Rats, Sprague-Dawley, Signal Transduction, Type C Phospholipases physiology, Mitogen-Activated Protein Kinase 1 metabolism, Receptor Cross-Talk, Type C Phospholipases metabolism
- Abstract
The discovery of sequence motifs that mediate protein-protein interactions, coupled with the availability of protein amino acid sequence data, allows for the identification of putative protein binding pairs. The present studies were based on our identification of an amino acid sequence in phosphatidylinositol-specific phospholipase C-gamma1 (PLC-gamma1) that fits the consensus sequence for a mitogen-activated protein kinase (MAPK) binding site, termed the D-domain. Extracellular signal-regulated kinase 2 (ERK2), an MAPK, and phospho-ERK2 were bound by an immobilized peptide sequence containing the identified PLC-gamma1 D-domain. Furthermore, a peptide containing the PLC-gamma1 D-domain was able to competitively inhibit the in vitro phosphorylation of recombinant PLC-gamma1 by recombinant phospho-ERK2, whereas a control peptide derived from a distant region of PLC-gamma1 was ineffective. Similarly, the peptide containing the PLC-gamma1 D-domain, but not the control peptide, competitively inhibited the in vitro phosphorylation of Elk-1 and c-Jun catalyzed by recombinant phospho-ERK2 and phospho-c-Jun N-terminal kinase 3 (phospho-JNK3), another type of MAPK, respectively. Incubation of anti-PLC-gamma1 immunocomplexes isolated from rat brain with recombinant phospho-ERK2 opposed the increase in PLC-gamma1-catalyzed hydrolysis of phosphatidylinositol 4,5-P(2) (PtdIns(4,5)P(2)), which was produced by a tyrosine kinase associated with the immunocomplexes, whereas in vitro phosphorylation of recombinant PLC-gamma1 by recombinant phospho-ERK2 did not alter PLC-gamma1-catalyzed PtdIns(4,5)P(2) hydrolysis. These studies have uncovered a previously unidentified mechanism for the integration of PLC-gamma1- and ERK2-dependent signaling.
- Published
- 2004
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42. Mechanism of tyrosine phosphorylation and activation of phospholipase C-gamma 1. Tyrosine 783 phosphorylation is not sufficient for lipase activation.
- Author
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Sekiya F, Poulin B, Kim YJ, and Rhee SG
- Subjects
- Animals, Antibodies chemistry, B-Lymphocytes metabolism, Binding Sites, Cell Division, Cell Line, Enzyme Activation, Epidermal Growth Factor metabolism, Humans, Hydrolysis, Immunoblotting, Inositol Phosphates metabolism, Jurkat Cells, Kinetics, Mice, Models, Genetic, Mutation, NIH 3T3 Cells, Phospholipase C gamma, Phosphorylation, Platelet-Derived Growth Factor metabolism, Precipitin Tests, Rats, T-Lymphocytes metabolism, Time Factors, Type C Phospholipases metabolism, Tyrosine chemistry, Lipase metabolism, Type C Phospholipases chemistry, Tyrosine metabolism
- Abstract
Phospholipase C-gamma 1 (PLC-gamma 1) is phosphorylated on three tyrosine residues: Tyr-771, Tyr-783, and Tyr-1253. With the use of antibodies specific for each of these phosphorylation sites, we have now determined the kinetics and magnitude of phosphorylation at each site. Phosphorylation of Tyr-783, which is essential for lipase activation, was observed in all stimulated cell types examined. The extent of phosphorylation of Tyr-1253 was approximately 50 to 70% of that of Tyr-783 in cells stimulated with platelet-derived growth factor (PDGF) or epidermal growth factor (EGF), but Tyr-1253 phosphorylation was not detected in B or T cell lines stimulated through B- and T-cell antigen receptors, respectively. Tyr-771 was phosphorylated only at a low level in all cells studied. In cells stimulated with PDGF, phosphorylation and dephosphorylation of Tyr-783 and of Tyr-1253 occurred with similar kinetics; the receptor kinase appeared to phosphorylate both sites, albeit with Tyr-783 favored over Tyr-1253, before the bound PLC-gamma 1 was released, and phosphorylation at the two sites occurred independently. PDGF and EGF induced similar levels of phosphorylation of Tyr-783 and of Tyr-1253 in a cell line that expressed receptors for both growth factors. However, only PDGF, not EGF, elicited substantial PLC activity, suggesting that Tyr-783 phosphorylation was not sufficient for enzyme activation. Finally, concurrent production of phosphatidylinositol 3,4,5-trisphosphate was found to contribute to the activation of phosphorylated PLC-gamma 1.
- Published
- 2004
- Full Text
- View/download PDF
43. Glycoproteins VI and Ib-IX-V stimulate tyrosine phosphorylation of tyrosine kinase Syk and phospholipase Cgamma2 at distinct sites.
- Author
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Suzuki-Inoue K, Wilde JI, Andrews RK, Auger JM, Siraganian RP, Sekiya F, Rhee SG, and Watson SP
- Subjects
- Agammaglobulinaemia Tyrosine Kinase, Animals, COS Cells, Chlorocebus aethiops, Intracellular Signaling Peptides and Proteins, Mice, Phospholipase C gamma, Phosphorylation, Platelet Aggregation, Ristocetin pharmacology, Syk Kinase, Type C Phospholipases physiology, Tyrosine metabolism, von Willebrand Factor pharmacology, Enzyme Precursors chemistry, Enzyme Precursors metabolism, Platelet Glycoprotein GPIb-IX Complex metabolism, Platelet Membrane Glycoproteins metabolism, Protein-Tyrosine Kinases chemistry, Protein-Tyrosine Kinases metabolism, Type C Phospholipases chemistry, Type C Phospholipases metabolism
- Abstract
Glycoproteins GPVI and GPIb-IX-V stimulate robust tyrosine phosphorylation of Syk and PLCg2 (phospholipase Cg2) in washed platelets, but only the former stimulates pronounced activation of phospholipase. Using phospho-specific antibodies, we demonstrate that GPVI, but not GPIb-IX-V, stimulates significant tyrosine phosphorylation of Syk at the autophosphorylation site pY525/526, a marker of Syk activity. In addition, GPVI stimulates tyrosine phosphorylation of PLCg2 at Tyr753 and Tyr759, whereas GPIb-IX-V only induces significant phosphorylation at Tyr753. Both receptors stimulate tyrosine phosphorylation of Btk at the regulatory Tyr223 and Tyr551. Syk and Btk phosphorylate peptides from PLCg2 containing Tyr753 and Tyr759 respectively, suggesting that they may stimulate phosphorylation at these sites in phospholipase. Studies using PLCg2-deficient platelets demonstrated that phospholipase is not required for the activation of integrin aIIbb3 by GPIb-IX-V. Our results demonstrate fundamental differences between GPVI and GPIb-IX-V in the regulation of tyrosine phosphorylation of Syk and PLCg2 consistent with the functional impairment of phospholipase in signalling by GPIb-IX-V.
- Published
- 2004
- Full Text
- View/download PDF
44. Regulation of phospholipase C isozymes: activation of phospholipase C-gamma in the absence of tyrosine-phosphorylation.
- Author
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Sekiya F, Bae YS, and Rhee SG
- Subjects
- Animals, Arachidonic Acid metabolism, Enzyme Activation, Humans, Phosphatidic Acids metabolism, Phosphatidylinositol 3-Kinases metabolism, Phosphatidylinositol Phosphates metabolism, Phospholipase C gamma, Phospholipase D metabolism, Phospholipases A metabolism, Phospholipases A2, Phosphorylation, Second Messenger Systems, Isoenzymes metabolism, Type C Phospholipases metabolism, Tyrosine metabolism
- Abstract
Activation of PLC-gamma isozymes in response to various agonists involves tyrosine phosphorylation of the effector enzymes. Recent evidence indicates that PLC-gamma isozymes are additionally activated by phosphatidic acid, phosphatidylinositol 3,4,5-trisphosphate and arachidonic acid in the absence of PLC-gamma tyrosine phosphorylation. These lipid-derived messengers are the immediate products of phospholipase D, phosphatidylinositol 3-kinase, and phospholipase A2, enzymes which are often stimulated along with PLC-gamma in response to an agonist. Furthermore, phosphatidylinositol 4,5-bisphosphate acts as a substrate for both PLC-gamma and phosphatidylinositol 3-kinase and as an activator for phospholipase D and phospholipase A2. These results reveal an elaborate mechanism of cross-talk and mutual regulation between four effector enzymes that participate in receptor signaling by acting on phospholipids.
- Published
- 1999
- Full Text
- View/download PDF
45. Prothrombin and factor X activator activities in the venoms of Viperidae snakes.
- Author
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Yamada D, Sekiya F, and Morita T
- Subjects
- Animals, Calcium pharmacology, Cattle, Cysteine Endopeptidases analysis, Endopeptidases analysis, Metalloendopeptidases analysis, Viperidae, Factor X agonists, Neoplasm Proteins, Prothrombin agonists, Viper Venoms chemistry
- Abstract
A Ca(2+)-dependent prothrombin activator, carinactivase-1 (CA-1), was previously found in the venom of Echis carinatus leucogaster. In the present study, the activities of CA-1-like enzymes were screened in the venoms of various Viperidae snakes. The addition of 1 mM Ca2+ ions to the venoms of only Echis snakes in Viperidae produced considerably high prothrombin activator activity, indicating that only the Echis snake venoms contain not only the Ca(2+)-independent prothrombin activator, ecarin, but also Ca(2+)-dependent activator(s). CA-1-like activators and ecarin in the venom of each Echis snake were efficiently separated by Blue Sepharose column chromatography. The venoms of the various Viperidae snakes were also examined for factor X activator activity. The venoms of genera Daboia, Vipera, Cerastes, Echis, Calloselasma and Bothrops contained factor X activator activity in the presence of Ca2+ ions. Cerastes cerastes and Calloselasma rhodostoma venoms also had Ca(2+)-independent factor X activator activity.
- Published
- 1997
- Full Text
- View/download PDF
46. Localization of the specific binding site for magnesium(II) ions in factor IX.
- Author
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Sekiya F, Yoshida M, Yamashita T, and Morita T
- Subjects
- Amino Acid Sequence, Animals, Antibodies, Monoclonal metabolism, Binding Sites, Calcium metabolism, Cations, Cattle, Factor IX chemistry, Factor IX immunology, Molecular Sequence Data, Peptide Fragments metabolism, Protein Conformation, Sequence Homology, Amino Acid, Spectrometry, Fluorescence, Factor IX metabolism, Magnesium metabolism
- Abstract
We demonstrated recently that coagulation factor IX has a specific binding site(s) for Mg2+ ions, independent of the (Ca2+)-binding sites, and that binding of Mg2+ ions is very important for expression of the functional conformation of this protein. We report here the localization of this Mg2+-specific binding site. We prepared three Gla-containing fragments of bovine factor IX, namely GlaEGF(NC) (residues 1-144+286-296), GlaEGF(N) (1-83) and the Gla domain peptide (1-46). Fragments GlaEGF(NC) and GlaEGF(N) retained the ability to undergo a conformational change upon binding of Mg2+ ions in the presence of excess Ca2+ ions. This change could be detected by a conformation-specific antibody. Furthermore, the Gla domain peptide was capable of binding Mg2+ ions, as determined by the metal ion-induced quenching of the intrinsic fluorescence. It appears that the (Mg2+)-specific binding site of factor IX is located in the N-terminal Gla domain.
- Published
- 1996
- Full Text
- View/download PDF
47. Structure and functions of coagulation factor IX/factor X-binding protein isolated from the venom of Trimeresurus flavoviridis.
- Author
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Morita T, Atoda H, and Sekiya F
- Subjects
- Amino Acid Sequence, Animals, Binding Sites, Crotalid Venoms metabolism, Factor IX isolation & purification, Factor IX metabolism, Molecular Sequence Data, Sequence Alignment, Crotalid Venoms chemistry, Factor IX chemistry, Trimeresurus
- Published
- 1996
- Full Text
- View/download PDF
48. Role of calcium(II) ions in the recognition of coagulation factors IX and X by IX/X-bp, an anticoagulant from snake venom.
- Author
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Sekiya F, Yamashita T, and Morita T
- Subjects
- Animals, Cattle, Factor IX metabolism, Factor X metabolism, Hydrogen-Ion Concentration, Protein Binding, Spectrometry, Fluorescence, Trimeresurus, Anticoagulants metabolism, Blood Coagulation Factors metabolism, Calcium metabolism, Carrier Proteins metabolism, Crotalid Venoms metabolism, Reptilian Proteins
- Abstract
IX/X-bp, an anticoagulant protein isolated from the venom of the habu snake Trimeresurus flavoviridis, has a structure homologous to the carbohydrate-recognition domains of C-type (Ca(2+)-dependent) animal lectins, and it binds to the gamma-carboxyglutamic acid (Gla) domains of coagulation factors IX and X in a Ca(2+)-dependent fashion. In the present study, we elucidated the role of Ca2+ ions in this binding. The binding of 125I-labeled IX/X-bp to both coagulation factors required about 1 mM Ca2+ ions in this at pH 7.5. A decrease in the pH to 6.5 had a striking negative effect on the binding, and the Ca(2+)-requirement curve was shifted rightward. We investigated the binding of Ca2+ ions to IX/X-bp directly by equilibrium dialysis and identified two independent binding sites with different affinities. At pH 7.5, the apparent Kd values for these sites were 25 and 200 microM, respectively. When the pH was decreased to 6.5, the affinity of the high-affinity binding site was reduced only slightly but that of the low-affinity site was reduced considerably. Moreover, it was evident from observations of Ca(2+)-induced changes in the intrinsic fluorescence that IX/X-bp underwent a conformational change upon binding of Ca2+ ions.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1995
- Full Text
- View/download PDF
49. Isolation and characterization of an anticoagulant protein homologous to botrocetin from the venom of Bothrops jararaca.
- Author
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Sekiya F, Atoda H, and Morita T
- Subjects
- Amino Acid Sequence, Anticoagulants chemistry, Anticoagulants metabolism, Blood Coagulation Factors metabolism, Carrier Proteins isolation & purification, Carrier Proteins metabolism, Molecular Sequence Data, Sequence Homology, Amino Acid, Anticoagulants isolation & purification, Carrier Proteins chemistry, Crotalid Venoms chemistry, Reptilian Proteins
- Abstract
We previously isolated a unique anticoagulant protein named IX/X-bp (factor IX/factor X-binding protein) from the venom of the habu snake Trimeresurus flavoviridis. We recently determined its primary structure and found that this protein had a structure homologous to the carbohydrate-recognition domains of C-type lectins. Most interestingly, a high homology was found between this protein and botrocetin, an inducer of platelet agglutination found in the venom of the jararaca snake Bothrops jararaca. To examine the possible identity of these proteins, we searched for IX/X-bp-like protein(s) in the venom of B. jararaca. When the venom was subjected to DEAE anion-exchange chromatography, such an activity was eluted separately from that of botrocetin. This activity was purified to homogeneity and designated jararaca IX/X-bp. Jararaca IX/X-bp was a disulfide-linked heterodimer consisting of 16- and 15-kDa subunits, being structurally similar to botrocetin. The respective NH2-terminal amino acid sequences were also very similar. Jararaca IX/X-bp had no botrocetin-like activity. However, this protein did have an activity to bind to factors IX and X and protein S in a Ca(2+)-dependent fashion, that resulted in interference with coagulation, while botrocetin did not. The binding to coagulation factors appeared not to be mediated by the lectin-like activity of jararaca IX/X-bp, because a derivative of factor X free of carbohydrates retained the ability to bind. It is concluded, therefore, that the two proteins isolated from the same venom have different biological activities despite the high degree of structural similarity between them.
- Published
- 1993
- Full Text
- View/download PDF
50. Activation of phospholipases in platelets by polyclonal antibodies against a surface membrane protein.
- Author
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Hashimoto K, Sekiya F, Takagi J, Tsukada T, Sato F, and Saito Y
- Subjects
- Arachidonic Acids metabolism, Cytochalasin B pharmacology, Enzyme Activation, Humans, Kinetics, Platelet Aggregation, Thromboxanes biosynthesis, Antibodies physiology, Blood Platelets enzymology, Phospholipases metabolism, Protein Precursors immunology, von Willebrand Factor immunology
- Abstract
In a previous paper we demonstrated using immunochemical techniques that propolypeptide of von Willebrand factor was present on the surface of resting platelets. In the present paper we show that polyclonal antibodies against propolypeptide of von Willebrand factor induce activation of phospholipase(s) in platelets and lead to platelet aggregation. The antibody-stimulation of platelets induced the synthesis of thromboxane A2 (TXA2). Furthermore, the aggregation was inhibited by aspirin and an antagonist of TXA2. Aspirin inhibited not only the aggregation but also the activation of arachidonic acid liberation from phospholipids, but the effect of aspirin on arachidonic acid liberation was cancelled by the combined effect of the antibodies and a TXA2 mimetic agonist, which itself did not activate arachidonic acid liberation. The antibody-induced activation of arachidonic acid liberation and the aggregation were blocked by cytochalasin B. All these results obtained with antibodies were quite similar to the results obtained with collagen.
- Published
- 1992
- Full Text
- View/download PDF
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