Satoshi Ameyama

TOYAMA Chemical, Edo, Tōkyō, Japan

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Publications (5)12.9 Total impact

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    ABSTRACT: Using an intestinal methicillin-resistant Staphylococcus aureus (MRSA)-carrying rat model, we compared the influence of piperacillin (PIPC) on the intestinal flora to those of cefazolin (CEZ), cefmetazole (CMZ), and flomoxef (FMOX). The number of MRSA did not increase after PIPC and CEZ administrations compared with the nontreated group. However, it significantly increased in the cases of FMOX and CMZ administration (P < 0.01). In the FMOX- and CMZ-treated groups, the intestinal flora was severely disrupted and the recovery of the number of Escherichia coli and Bacteroides spp. cells was delayed. On the other hand, in the PIPC- and CEZ-treated groups, the rapid recovery of bacteria that composed the intestinal flora was observed. The C(max)/MIC(50) and C(trough)/MIC(50) ratios in E. coli and Bacteroides spp. in the case of FMOX and CMZ were relatively higher than those in the case of the PIPC- and CEZ-treated groups.
    Journal of Infection and Chemotherapy 01/2005; 10(6):338-42. · 1.38 Impact Factor
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    Satoshi Ameyama, Yuko Shinmura, Masahiro Takahata
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    ABSTRACT: The gyrA and gyrB genes of Chlamydia pneumoniae TW-183 were cloned, and their proteins were purified by use of a fusion system with a maltose-binding protein. The 50% inhibitory concentrations of garenoxacin, sparfloxacin, moxifloxacin, gatifloxacin, and levofloxacin were 10.1, 47.5, 39.6, 64.2, and 156.9 microg/ml, respectively, and the MICs against C. pneumoniae TW-183 were 0.008, 0.016, 0.063, 0.125, and 0.25 microg/ml, respectively.
    Antimicrobial Agents and Chemotherapy 08/2003; 47(7):2327-9. · 4.45 Impact Factor
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    ABSTRACT: We investigated behaviors of the rabies virus matrix (M) protein using a monoclonal antibody (mAb), #3-9-16, that recognized a linear epitope located at the N-terminus of the protein. Based on the reactivity with this mAb, M proteins could be divided into at least two isoforms; an ordinary major form (Malpha) whose 3-9-16 epitope is hidden, and an N-terminal-exposed epitope-positive form (Mbeta). The Mbeta protein accounted for about 25-30% of the total M proteins in the virion, while its content in the cell ranged from 10 to 15% of total M protein. Fluorescent antibody (FA) staining showed that the Mbeta antigen distributed in the Golgi area where the colocalized viral glycoprotein antigen was also detected. Mbeta antigen was shown to be exposed on the surface of infected cells by both immunoprecipitation and FA staining with the mAb, whereby the cells might have become sensitive to the mAb-dependent complement-mediated cytolysis. Similarly, the Mbeta antigen was shown to be exposed on the virion surface, and the infectivity of the virus was destroyed by the mAb in the presence of a complement. Together with these results, we think that the M protein molecule takes either of two conformations, one (Mbeta) of which exposes the 3-9-16 epitope located in the N-terminal region of the M protein, that are also exposed on the surface of the virion and infected cells, whereby it might play a certain important role(s) in the virus replication process differently from the other form (Malpha), probably through its intimate association with the Golgi area and/or the cell membrane.
    Microbiology and Immunology 02/2003; 47(9):639-51. · 1.31 Impact Factor
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    ABSTRACT: We investigated multiple forms of rabies virus matrix (M) protein. Under non-reducing electrophoretic conditions, we detected, in addition to major bands of monomer forms (23- and 24-kDa) of M protein, an M antigen-positive slow-migrating minor band (about 54 kDa) in both the virion and infected cells. Relative contents of the 54-kDa and monomer components in the virion were about 20-30% and 70-80% of the whole M protein, respectively, while the content of the 54-kDa component was smaller (about 10-20% of the total M protein) in the cell than in the virion. The 54-kDa components could be extracted from the infected cells with sodium deoxycholate, but they were quite resistant to extraction with 1% nonionic detergents by which most monomer components were solubilized. The 54-kDa component was precipitated more efficiently than the monomer by a monoclonal antibody (mAb; #3-9-16), which recognized a linear epitope located at the N-terminal of the M protein. The mAb #3-9-16 coprecipitated the viral glycoprotein (G), which was demonstrated to be due to strong association between the G and 54-kDa component of the M protein. Monomers and the 54-kDa polypeptide migrated to the same isoelectric point (pI) in twodimensional (2-D) gel electrophoresis, implicating that the 54-kDa component was composed of component(s) of the same pI as that of the M protein monomers. From these results, we conclude that the M antigen-positive 54-kDa polypeptide is a homodimer of M protein, taking an N-terminal-exposed conformation, and is strongly associated with the viral glycoprotein. Possible association with a membrane microdomain of the cell will be discussed.
    Microbiology and Immunology 02/2003; 47(12):977-88. · 1.31 Impact Factor
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    ABSTRACT: Neisseria gonorrhoeae strains with reduced susceptibility to cefixime (MICs, 0.25 to 0.5 micro g/ml) were isolated from male urethritis patients in Tokyo, Japan, in 2000 and 2001. The resistance to cephems including cefixime and penicillin was transferred to a susceptible recipient, N. gonorrhoeae ATCC 19424, by transformation of the penicillin-binding protein 2 gene (penA) that had been amplified by PCR from a strain with reduced susceptibility to cefixime (MIC, 0.5 micro g/ml). The sequences of penA in the strains with reduced susceptibilities to cefixime were different from those of other susceptible isolates and did not correspond to the reported N. gonorrhoeae penA gene sequences. Some regions in the transpeptidase-encoding domain in this penA gene were similar to those in the penA genes of Neisseria perflava (N. sicca), Neisseria cinerea, Neisseria flavescens, and Neisseria meningitidis. These results showed that a mosaic-like structure in the penA gene conferred reductions in the levels of susceptibility of N. gonorrhoeae to cephems and penicillin in a manner similar to that found for N. meningitidis and Streptococcus pneumoniae.
    Antimicrobial Agents and Chemotherapy 01/2003; 46(12):3744-9. · 4.45 Impact Factor

Publication Stats

106 Citations
12.90 Total Impact Points


  • 2003
    • TOYAMA Chemical
      Edo, Tōkyō, Japan
    • Kyoto University
      • Graduate School of Pharmaceutical Sciences / Faculty of Pharmaceutical Sciences
      Kioto, Kyōto, Japan