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S Ohya

Publications and source records attributed to S Ohya.

At least 55 records · Page 3Linked to original sources
PubMed1997

Apamin-sensitive Ca2+-dependent K+ current and hyperpolarization in human endothelial cells.

Vascular endothelial cells have several types of Ca2+-dependent K+ current (I(K-Ca)). Here, we describe apamin-sensitive I(K-Ca) which is activated by treatment with histamine (His) in human umbilical vein endothelial cells (HUVECs). In 65 % of HUVECs examined, 100 nM apamin potently inhibited I(K-Ca) and hyperpolarization induced by His (19 and 7 % of control, respectively). In contrast, application of 5 mM tetraethylammonium, a non-selective K channel blocker, or 100 nM iberiotoxin, a selective K channel blocker for a large conductance Ca2+-dependent K+ channel, had small (78 % of control) or no effects (102 % of control) on I(K-Ca), respectively. These findings suggest that apamin-sensitive Ca2+-dependent K+ channels are expressed in HUVECs and activated by receptor stimulation.

Apamin↗
PubMed1997

Molecular cloning of a novel gene involved in serotonin receptor-mediated signal transduction in rat stomach.

In Xenopus oocytes injected with small size mRNAs (500-700 b), obtained from rat stomach by fractionation, application of 10 microM 5-HT induced a substantial Ca2+-activated Cl- current (I(Cl-Ca)). I(Cl-Ca) was not elicited by 5-HT in native oocytes. Consistent results from this assay in the oocyte expression system motivated cDNA cloning experiments. A novel cDNA (named rat stomach serotonin receptor-related cDNA: RSS cDNA) which encodes a small protein involved in specific 5-HT receptor-mediated I(Cl-Ca) activation was identified. The molecular weight of RSS protein in the reticulocyte lysate translation system (approximately 10 kDa) is identical to that calculated from the amino acid sequence. Computer-aided analysis of the predicted protein does not show any obvious sequence homologies (< 18%) to any other proteins including G protein-coupled receptors. Northern analysis revealed that RSS mRNA is ubiquitously expressed at varying levels in a number of different tissues. Furthermore, the binding of [3H]spiperone, a 5-HT2 receptor antagonist, was examined in CHO cells, which highly expressed RSS transcripts (named CHO-RSS). Specific binding of [3H]spiperone was not clearly observed in native CHO but was detected in CHO-RSS. The dissociation constant was 10.3 nM in CHO-RSS. These results suggest that RSS protein may be a factor which facilitates 5-HT receptor expression or, alternatively, an enhancer of the affinity of native 5-HT receptor to 5-HT.

Amino Acid Sequence↗
PubMed1997

Persistent production of interferon-gamma (IFN-gamma) and IL-12 is essential for the generation of protective immunity against Listeria monocytogenes.

IFN-gamma and IL-12 are believed to be important in the host defence against Listeria infection in mice. However, the relationship between these two cytokines and generation of protective immunity remains poorly understood. In the present study, it was found that at least 4 days of immunizing infection were required for the generation of protective immunity against L. monocytogenes. Protective immunity was generated only by immunizing infection with virulent strain. Even repeated injections of avirulent strain failed to induce protective immunity. When the immunizing infection was terminated with antibiotics, generation of protective immunity and IFN-gamma-producing ability was impaired, while expression of IFN-gamma and IL-12 was also impaired. The mutual relationship between IFN-gamma and IL-12 in L. monocytogenes infection was analysed in vitro. After neutralization of IL-12, IFN-gamma production was completely blocked and IFN-gamma expression was also inhibited. In contrast, there was no change of IL-12 expression after neutralization of IFN-gamma. Taking all facts into consideration, it may be concluded that persistent production of IFN-gamma induced by persistent production of IL-12 during immunizing infection is essential for the generation of protective immunity against L. monocytogenes.

Animals↗
PubMed1997

In vitro and in vivo antibacterial activities of CS-834, a novel oral carbapenem.

CS-834 is a novel oral carbapenem antibiotic. This compound is an ester-type prodrug of the active metabolite R-95867. The antibacterial activity of R-95867 was tested against 1,323 clinical isolates of 35 species and was compared with those of oral cephems, i.e., cefteram, cefpodoxime, cefdinir, and cefditoren, and that of a parenteral carbapenem, imipenem. R-95867 exhibited a broad spectrum of activity covering both gram-positive and -negative aerobes and anaerobes. Its activity was superior to those of the other compounds tested against most of the bacterial species tested. R-95867 showed potent antibacterial activity against clinically significant pathogens: methicillin-susceptible Staphylococcus aureus including ofloxacin-resistant strains, Streptococcus pneumoniae including penicillin-resistant strains, Clostridium perfringens, Neisseria spp., Moraxella catarrhalis, most members of the family Enterobacteriaceae, and Haemophilus influenzae (MIC at which 90% of strains are inhibited, < or =0.006 to 0.78 microg/ml). R-95867 was quite stable to hydrolysis by most of the beta-lactamases tested except the metallo-beta-lactamases from Stenotrophomonas maltophilia and Bacteroides fragilis. R-95867 showed potent bactericidal activity against S. aureus and Escherichia coli. Penicillin-binding proteins 1 and 4 of S. aureus and 1Bs, 2, 3, and 4 of E. coli had high affinities for R-95867. The in vivo efficacy of CS-834 was evaluated in murine systemic infections caused by 16 strains of gram-positive and -negative pathogens. The efficacy of CS-834 was in many cases superior to those of cefteram pivoxil, cefpodoxime proxetil, cefdinir, and cefditoren pivoxil, especially against infections caused by S. aureus, penicillin-resistant S. pneumoniae, E. coli, Citrobacter freundii, and Proteus vulgaris. Among the drugs tested, CS-834 showed the highest efficacy against experimental pneumonia in mice caused by penicillin-resistant S. pneumoniae.

Administration, Oral↗
PubMed1997

[Combination effect between panipenem and vancomycin on highly methicillin-resistant Staphylococcus aureus].

We investigated the in vitro and in vivo combination effects between panipenem (PAPM) and vancomycin (VCM) on highly methicillin-resistant strains of Staphylococcus aureus (MRSA) isolated from various clinical specimens. Examination of combination between panipenem and vancomycin using checkerboard titration showed a good effect with mean fractional inhibitory index of 0.32 +/- 0.12 on 40 MRSA strains, and the effects were judged as synergistic against 33 strains (83%) and additive against 7 strains (17%). In the combination of PAPM and VCM at 1/4 MIC each against exponentially growing MRSA, bactericidal activity was found when PAPM was added at 1 hour or 2 hours prior to VCM-addition, and PAPM with VCM was added simultaneously, although bactericidal activity was scarcely demonstrated when VCM was added at 1 hour or 2 hours prior to PAPM-addition. Bactericidal activity was enhanced against MRSA in the combination of PAPM and VCM at 1/4 MIC each for MRSA than the bactericidal activity of VCM at 1 MIC alone, and the combination showed a strong bactericidal activity against P. aeruginosa. VCM alone, however, had no bactericidal activity in the in vitro mixed cultures of the two bacteria. Furthermore, the combination of PAPM and VCM induced a marked damage to cell surface and bacteriolysis against MRSA and P. aeruginosa in the mixed cultures, although VCM alone induced only slight morphological alterations. Penicillin-binding proteins (PBPs) including MRSA-specific PBP 2' were decreased greatly in the amounts in MRSA-cells with the increase of VCM-treated concentration. The combination therapy of PAPM and VCM showed a greater efficacy than the therapeutic efficacy of each antibiotic alone against mixed infection in burned mice caused by MRSA and P. aeruginosa, and the activity was judged as synergistic based on the FED index smaller than 0.34.

Animals↗
PubMed1997

[Remission induction after pentoxifylline treatment in a patient with rheumatoid arthritis].

Pentoxifylline (POF) has been shown to have anti-inflammatory and immunomodulatory effects. including suppression of TNF-alpha production by activated macrophages, Th-1 response of T cells, and fibroblasts' proliferation and metalloproteinase production. Pentoxifylline was also reported to possess therapeutic properties in 50% of severe refractory RA in an open study. We experienced a 64 year-old man with seronegative RA, stage 2, class 3. He showed 23 swollen joints, 32 painful joints, ADL score 37/40, and ESR 135 mm/h. All these parameters were dramatically improved 3 weeks after administration of POF 300 mg/d and prednisolone 5 mg/d. Discontinuation of POF resulted in rapid exacerbation of RA. POF was restarted and the patient showed complete recovery from arthritis with normalization of ESR within 3 months and was maintained a complete remission for another 1 year. This case further supports a potential antirheumatic effect of POF on some patients with RA.

Anti-Inflammatory Agents↗
PubMed1996

Involvement of various combinations of endogenous inflammatory cytokines in Listeria monocytogenes-induced expression of inducible nitric oxide synthase in mice.

Using a in vitro infection of spleen cells with Listeria monocytogenes, the relationship between endogenous cytokines and the expression of inducible nitric oxide synthase (iNOS) was examined. When all interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 alpha, or the combination of IFN-gamma with either TNF-alpha or IL-1 alpha were neutralized by antibodies, there was a significant reduction of iNOS expression and nitrite production in culture. However, there was no reduction of iNOS expression and nitrite production when these cytokines were individually neutralized. After the depletion of natural killer cells, there was no change in the expression of Listeria-induced iNOS and nitrite production although the IFN-gamma production was abrogated. Neutralization of TNF-alpha and IL-1 alpha in natural killer cell-depleted culture resulted in the reduction of iNOS expression. Thus, various combinations of cytokines to play an important role in iNOS induction by L. monocytogenes.

Animals↗
PubMed1996

Quantitative correlation between susceptibility and OprJ production in NfxB mutants of Pseudomonas aeruginosa.

Various Pseudomonas aeruginosa PAO1 NfxB mutants were isolated on agar plates containing cefpirome and ofloxacin. They were classified into type A and type B, based on the degrees of changes in their susceptibilities. Type A mutants were four to eight times more resistant to ofloxacin, erythromycin, and new zwitterionic cephems, i.e., cefpirome, cefclidin, cefozopran, and cefoselis, than was the parent strain, PAO1. In contrast, type B mutants were more resistant to tetracycline and chloramphenicol, as well as ofloxacin, erythromycin, and the new zwitterionic cephems, than was PAO1, and they were four to eight times more susceptible to carbenicillin, sulbenicillin, imipenem, panipenem, biapenem, moxalactam, aztreonam, gentamicin, and kanamycin that was PAO1. The changes in susceptibilities of type B mutants were greater than those of type A mutants. The susceptibilities of both type A and type B mutants were restored to the level of PAO1 by transformation with plasmid pNF111, which contained the wild-type nfxB gene, demonstrating that they are NfxB mutants. Immunoblot analysis with a monoclonal antibody to OprJ revealed that type B mutants produced larger amounts of outer membrane protein OprJ than did type A mutants and that PAO1 produced an undetectable amount of it. Moreover, transconjugants obtained with the different types of NfxB mutants as the donor strains showed almost the same phenotypes as the corresponding donor strains. These results suggest that there are at least two nfxB mutations that show different phenotypes and that production of OprJ is associated with changes in susceptibilities of NfxB mutants.

Anti-Bacterial Agents↗
PubMed1996

Hydrophilicity of quinolones is not an exclusive factor for decreased activity in efflux-mediated resistant mutants of Staphylococcus aureus.

The elevated expression of the norA gene is responsible for efflux-mediated resistance to quinolones in Staphylococcus aureus (E.Y.W. Ng, M. Trucksis, and D.C. Hooper, Antimicrob. Agents Chemother. 38:1345-1355, 1994). For S. aureus transformed with a plasmid containing the cloned norA gene, SA113(pTUS20) (H. Yoshida, M. Bogaki, S. Nakamura, K. Ubukata, and M. Konno, J. Bacteriol. 172:6942-6949, 1990), and an overexpressed mutant, SA-1199B (G.W. Kaatz, S.M. Seo, and C.A. Ruble, J. Infect. Dis. 163:1080-1086, 1991), the MICs of norfloxacin increased 16 and 64 times compared with its MICs for the recipient and wild-type strains, SA113 and SA-1199, respectively. MICs of CS-940, however, increased only two and eight times, even though these two fluoroquinolones are similarly hydrophilic (apparent logPs of approximately -1). No good correlation was found, among 15 developed and developing quinolones, between the increment ratio in MICs and hydrophobicity (r = 0.61). Analysis of the quantitative structure-activity relationship among 40 fluoroquinolones revealed that the MIC increment ratio was significantly correlated with the bulkiness of the C-7 substituent and bulkiness and hydrophobicity of the C-8 substituent of fluoroquinolones (r = 0.87) and not with its molecular hydrophobicity (r = 0.47). Cellular accumulation of norfloxacin in SA-1199B was significantly lower than that in SA-1199, and it was increased by addition of carbonyl cyanide m-chlorophenyl hydrazone. On the other hand, accumulations of CS-940 in these strains were nearly identical, and they were not affected by addition of the protonophore.

Anti-Infective Agents↗
PubMed1996

A novel phospholipase C inhibitor, S-PLI produced by Streptomyces sp. strain no. A-6288.

S-PLI, an inhibitor of phospholipase C (PLC) produced by Streptomyces sp. strain No. 6288, was purified from the culture filtrate by salting-out with solid ammonium sulfate, column chromatography on CM-cellulose and gel filtration on Sephadex G-75. The molecular weight of S-PLI was estimated to be 65,000 by SDS-polyacrylamide gel electrophoresis. The inhibitor was found to be a glycoprotein with a composition of 609 amino acids and 19 glucose residues having an isoelectric point at 7.8. S-PLI was stable from pH 3 to 10 at 37 degrees C and up to 40 degrees at pH 6.0. The inhibitory activity showed pH- and temperature-dependence with a maximum around pH 7.0 at 50 degrees C. S-PLI inhibited phospholipase C in a competitive manner (Ki value; 9.5 x 10(-6) mM), but did not inhibit S-Hemolysin, phospholipase A2; phospholipase B, phospholipase D and phosphatases. S-PLI is the first reported example of a glycoproteinaceous inhibitor of microbial origin which is able to specifically inhibit phospholipase C.

Amino Acids↗
PubMed1996

Non-contact specular microscopic observation for early response of corneal endothelium after contact lens wear.

PURPOSE: Contact lenses induce short- and long-term corneal endothelial changes, including endothelial blebs. The endothelial bleb is a reversible, short-term response found on the corneal endothelium after lens wear. We used non-contact specular microscopy to observe endothelial blebs occurring with different types of contact lenses. METHODS: We observed the time course, frequency, and location of endothelial blebs in 11 eyes of 9 contact lens wearing patients. Eight types of contact lenses with various oxygen transmissibilities (Dk/L) were used in the study. RESULTS: Blebs were observed in the central cornea in patients with polymethylmethacrylate and rigid gas permeable contact lenses, while blebs in the central to mid-peripheral cornea were seen in patients wearing soft contact lenses. CONCLUSIONS: Although the number of blebs vary by individual patient, there appears to be an inverse correlation between the number of blebs and the Dk/L of the contact lens.

Adult↗
PubMed1995

Outer membrane proteins responsible for multiple drug resistance in Pseudomonas aeruginosa.

Three types of multiple-drug-resistant mutants which were phenotypically similar to previously described nalB, nfxB, and nfxC mutants were isolated from Pseudomonas aeruginosa PAO1 and two clinical isolates. Type 1 (nalB-type) mutants showed cross-resistance to meropenem, cephems, and quinolones. They overproduced an outer membrane protein with an apparent molecular mass of 50 kDa (OprM). Type 2 (nfxB-type) mutants showed cross-resistance to quinolones and new cephems, i.e., cefpirome and cefozopran, concomitant with overproduction of an outer membrane protein with an apparent molecular mass of 54 kDa (OprJ). Type 3 (nfxC-type) mutants showed cross-resistance to carbapenems and quinolones. They produced decreased amounts of OprD and increased amounts of a 50-kDa protein (OprN), which was almost the same molecular weight as that of OprM, but it was distinguishable from OprM by its heat modifiability on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the presence of salicylate, the parent strains showed an increased level of resistance to carbapenems and quinolones and produced decreased amounts of OprD and increased amounts of OprN. Salicylate caused the repression of OprJ production and the loss of resistance to cefpirome and cefozopran in two of the three OprJ-overproducing mutants, although salicylate slightly increased the level of resistance in the parent strains. The changes in susceptibilities were transient in the presence of salicylate. These data suggest that at least three different outer membrane proteins, OprM, OprJ, and OprN, are associated with multiple drug resistance in P. aeruginosa.

Anti-Bacterial Agents↗
PubMed1995

Incidence of various gyrA mutants in 451 Staphylococcus aureus strains isolated in Japan and their susceptibilities to 10 fluoroquinolones.

Point mutations in the gyrA genes of 451 clinical strains of Staphylococcus aureus isolated in Japan were detected by a combination of nonradioisotopic single-strand conformation polymorphism analysis and restriction fragment length polymorphism analysis and by direct sequencing. Six types of gyrA mutations were observed in 149 of the 451 strains (33%), and ofloxacin MICs were greater than 6.25 micrograms/ml for 147 of the 149 strains (98.7%). These mutations were localized between codons 84 and 88, and they were associated with fluoroquinolone resistance. Two types of silent mutations were also found. Among these eight types of mutations, three types are novel, i.e., the serine at position 84 (Ser-84)-->Val (TCA-->GTA), Ser-84-->Leu (TCA-->TTA) plus Ile-86 (ATT-->ATC, silent), and Phe-110 (TTT-->TTC, silent). Among GyrA mutants, strains with a Ser-84-->Leu alteration and strains with a Glu-88-->Lys alteration were dominant. In contrast, few strains had Ser-84-->Ala and Glu-88-->Gly alterations. All fluoroquinolones tested showed greater than a fourfold decrease in their activities in terms of their MICs that inhibited 50% of strains tested for each GyrA mutant, in comparison with their MICs that inhibited 50% of strains tested for susceptible strains. Most of the currently available fluoroquinolones, such as norfloxacin, enoxacin, ofloxacin, ciprofloxacin, tosufloxacin, lomefloxacin, sparfloxacin, and fleroxacin, were ineffective against each mutant. Mutants containing a Ser-84-->Leu or Val alteration showed high-level resistance to fluoroquinolones, and one containing a Ser-84-->Ala alteration showed relatively low-level resistance. Double mutations were associated with a higher level of resistance than single mutations.

Anti-Infective Agents↗
PubMed1994

Role of beta-lactamase of methicillin-susceptible Staphylococcus aureus in resistance to first-generation oral cephems both in vitro and in vivo.

Cefaclor, among the oral cephalosporins tested, showed the largest inoculum effect with respect to MIC values for 61 clinical isolates of methicillin-susceptible Staphylococcus aureus, including 39 beta-lactamase producing strains. These 39 strains were divided into eight type A, 29 type B or C, and two type D producers, by comparisons of specific activities to three substrates. Two producers, one each of types A and C, were further studied to investigate the effect of beta-lactamase on staphylococcal resistance to several beta-lactams. Concentrations of cefaclor and cephalexin in cultures of these strains decreased rapidly, whereas hydrolysis of these drugs by the purified beta-lactamases was moderate to low as detected by spectrophotometric assay. Cefaclor showed high affinities for penicillin-binding proteins 1, 2, and 3 of both beta-lactamase producers and their respective penicillinase-non-producing mutants. In experimental intraperitoneal infections in mice, cefaclor was therapeutically effective against both mutants, showing 50% effective doses of less than 10 mg/kg/dose. In contrast, it was not satisfactory against the parent strains, requiring greater-than-10-fold increases in concentration for the same degree of survival. We concluded that resistance to first-generation oral cephems seen both in vitro and in vivo was due mainly to the beta-lactamase production.

Administration, Oral↗
PubMed1994

[Inhibition of biofilm formation by clarithromycin (CAM) in an experimental model of complicated bladder infection--in vitro study using automated simulation of urinary antimicrobial concentration].

The role of clarithromycin (CAM) in biofilm formation has recently been reported. Inhibition of the production or promotion of the dissolution of the glycocalyx, a major component of biofilm, has been implicated in its mechanism of action. However, the details remain unclear. We used an experimental model of complicated urinary bladder infection and automated simulation of the variations in urinary antimicrobial concentration to study the efficacy of CMA in inhibiting biofilm formation and obtained the following results. 1) Prior to biofilm formation, Pseudomonas aeruginosa (P. aeruginosa) was exposed to ciprofloxacin (CPFX, MIC: 8 micrograms/ml), which was active against the organism, at a dose of 200 mg t.i.d. for 7 days. The bacteria were apparently eradicated from the culture medium in the experimental model of bladder infection (model bladder) after 32 hours. However, when the medium was changed to eliminate the antimicrobial agent on Day 7, bacterial regrowth was initiated after 4 hours. Scanning electron microscopy demonstrated sequential biofilm formation on the surface of glass beads in the model bladder diverticulumn, suggesting inside the biofilm were a source of regrowth. 2) Prior to biofilm formation, P. aeruginosa was also exposed to CAM alone, which has no antimicrobial activity against the organism (MIC: > 128 micrograms/ml) at a dose of 200 mg t.i.d. for 7 days. In this situation, CAM was not active against P. aeruginosa and the bactericidal concentration in the model bladder did not decrease markedly, reaching the initial level (10(7) CFU/ml) within 48 hours. However, although numerous bacteria were attached to the glass beads in the diverticulum, no biofilm was formed. 3) Exposure to a combination of CPFX and CAM (each at 200 mg t.i.d. for 7 days) resulted in the eradication of bacteria from the model bladder at 32 hours, and no bacterial regrowth was demonstrated after the medium was exchanged on Day 7. In addition, no biofilm was formed and the bacteria did not become attached to the glass beads. 4) The content of alginate, a major component of P. aeruginosa biofilm, was measured per 5 glass beads on Day 3, 5, and 7 after starting drug administration. The alginate content increased with time when CPFX was given alone at a dose of 200 mg t.i.d..(ABSTRACT TRUNCATED AT 400 WORDS)

Biofilms↗