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Articles by M Usui
Total Records ( 3 ) for M Usui
  Y Abe , H Wada , E Yamada , M Noda , M Ikejiri , J Nishioka , T Kobayashi , T Matsumoto , M Masuya , S Isaji , M Usui , S Uemoto , N Katayama and T. Nobori

Thrombotic microangiopathy (TMA) or thrombotic thrombocytopenic purpura (TTP) is a life-threatening syndrome characterized by increased number of fragmented red cells (FRCs) and thrombocytopenia. FRCs can be measured using the recently developed automated hematology analyzer XE-2100. The normal range for FRCs is 0% to 0.205%, as determined by the automated hematology analyzer XE-2100. The FRC count is significantly elevated in patients with TMA associated with liver transplantation, bone marrow transplantation, or TTP. In patients with TMA after liver transplantation, the FRC count is significantly higher than in those without TMA. In receiver operating characteristic analysis for the diagnosis of TMA, the area under the curve is 0.986, suggesting that FRC is a useful marker for the diagnosis of TMA. When the cutoff value of FRC for TMA is 1.2%, the sensitivity is 90% and the specificity is 96%, indicating that FRC is the most useful screening test for the diagnosis of TMA.

  H Nomura , H Wada , T Mizuno , Y Yamashita , K Saito , S Kitano , N Katayama , N Yamada , T Sugiyama , A Sudo , M Usui , S Isaji and T. Nobori

Background: Most patients with malignant diseases are frequently complicated with some type of thrombosis, such as disseminated intravascular coagulation (DIC) or deep vein thrombosis (DVT)/pulmonary embolism (PE). Objective: The cohort and retrospective study was designed to examine the frequency of thrombosis in patients with malignant diseases and to evaluate the efficacy of D-dimer and soluble fibrin (SF) for the diagnosis of thrombosis. Patients/Methods: The plasma concentrations of D-dimer and SF were measured in patients with malignant diseases suspected of having thrombosis. D-dimer and SF were measured using a latex aggregation assay. Results: Thrombosis was observed in 23.3% of the patients with malignant diseases. Disseminated intravascular coagulation was frequently observed in patients with hepatoma, and DVT/PE was frequently observed in patients with colon cancer, lung cancer, and uterine cancer. The plasma levels of D-dimer and SF were increased in malignant diseases, especially hepatoma. Plasma levels of D-dimer and SF were significantly higher in patients with thrombosis in comparison to patients without thrombosis. A receiver operating characteristic (ROC) analysis showed the D-dimer and SF levels to be useful in the diagnosis of thrombosis. Conclusion: Elevated D-dimer and SF levels might indicate a high risk of thrombosis in patients with malignant disease; however, these assays still need to be standardized.

  R.M.C Deshapriya , S Yuhashi , M Usui , T Kageyama and Y. Yamamoto

To identify functionally essential sequences and residues of CTLA-2, in vitro mutagenesis was carried out. The coefficient of inhibition (Ki) was determined towards rabbit cathepsin L using Z-Phe-Arg-MCA as the substrate. Recombinant CTLA-2 inhibited the enzyme potently (Ki = 15 nM). A truncated mutant, lacking the N- and C-terminal Ala1–Asp9 and Leu80–Glu109 regions, was also a potent inhibitor (Ki = 10 nM). Subsequent short deletions in the central region (Asn10–Ser79) showed three functionally essential distinct regions: Asn10–Phe19, His30–Ala44 and Ser55–Ser79. These regions cover sequences corresponding to three helices (1, 2 and 3) and sequences that interact with the cognate enzyme. Alanine scanning showed that replacement of one of three conserved Trp residues increased the Ki by 15–20-fold; whereas, replacement of two/three Trp residues at once caused complete loss of potency, as did replacing Cys75 with Ala or Ser. The proteins from wild-type (WT) CTLA-2 and mutant C75A were stable overnight when incubated with cathepsin L; whereas, proteins from mutants W12A, W15A and W35A were quickly digested. Incubation of cathepsin L/WT CTLA-2 formed a complex; whereas, C75S did not form a complex. Our overall results point to a critical role of W12, W15, W35 and Cys75 residues in CTLA-2.

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