Biography:

In the past Koichi Yamaguchi has collaborated on articles with Katsuhiro Yamaguchi and Tsukasa Yoshida. One of their most recent publications is Asymmetric addition of thiol to diene polymer in the presence of optically active amines as catalyst. Which was published in journal Polymer.

More information about Koichi Yamaguchi research including statistics on their citations can be found on their Copernicus Academic profile page.

Koichi Yamaguchi's Articles: (12)

Asymmetric addition of thiol to diene polymer in the presence of optically active amines as catalyst

AbstractThe asymmetric addition reaction of thiolacetic acid or benzylmercaptan to diene polymer (natural rubber, cis- and trans-1,4-polyisoprene, cis-1,4-polybutadiene, various styrenebutadiene copolymers and alternating acrylonitrile-butadiene copolymer) by optically active catalysts such as d-bornylamine ([α]d−45.2°), l-aspartic diethyl ester (−11.2°), l-aspartic dibutyl ester (−5.3°) were carried out in benzene at room temperature to 90°C. The optically active polymers were obtained from natural rubber and cis-1,4- and trans-1,4-polyisoprene, but were not obtained from cis-1,4-polybutadiene, styrene-butadiene copolymers, and butadiene-acrylonitrile copolymer. The [α]25D value of optically active derivatives was −0.1° ∼ −1.0° (in benzene), and the optical rotatory dispersion curves were found to fit the simple Drude equation.

Reaction of thiol to diene polymer in the presence of various catalysts

AbstractThe addition reaction of benzylmercaptan to diene polymer (natural rubber, and cis-1,4-polyisoprene) by various optically active catalysts such as d-camphorsulphonic acid, d-percamphoric acid, and active-amylalcoholate (sodium and barium) were carried out in benzene or anisole at room temperature to 100°C. The optically active adduct polymer was only obtained from the reaction of benzylmercaptan to natural rubber and cis-1,4-polyisoprene by active-amylalcoholate (barium), but was not obtained by the other catalysts. The [α]25 value of optically active adduct polymer was −0·1°C∼−0·6°C (in benzene), and the optical rotatory dispersion curves were found to fit the simple Drude equation. The reaction of benzylmercaptan to cis-1,4-polybutadiene, various styrene-butadiene copolymers, and alternating butadiene-acrylonitrile copolymer were carried out, but the optically active adduct polymers were not obtained by these catalysts.

Laboratory investigationAbducens neuropathy detected by three-dimensional magnetic resonance imaging using a multiplanar reconstruction technique with gadolinium-DTPA enhancement

AbstractThree-dimensional magnetic resonance imaging (3D MRI) using a multiplanar reconstruction technique with gadolinium diethylenetriamine pentaacetic acid (DTPA) enhancement was used for assessment of a 20-year-old woman who had sudden complete restriction of abduction in the right eye. The 3D MRI revealed abducens nerve enhancement in the cisternal portion. An enhanced lesion was also observed in the right lower pons at the pontomedullary junction. These clinical and 3D-MRI findings were diagnosed as right abducens palsy due to abducens neuropathy. Observation of the entire pathway of the cisternal portion of the cranial nerves can be extremely useful in patients with ophthalmoplegia.

Atom-by-atom growth of cadmium sulfide thin films by electroreduction of aqueous Cd2+–SCN− complex☆

AbstractElectrodeposition of cadmium sulfide thin films was realized by the electroreduction of the aqueous thiocyanato complex of Cd2+. Formation of CdS is supposed to proceed via metal-catalyzed ligand reduction. The film thickness increased linearly with the electricity consumed, confirming the electrochemical growth of CdS. The deposition bath was fairly stable and could be used repeatedly to prepare many CdS films. While all the previously reported techniques for the chemical or electrochemical growth of CdS thin films in aqueous systems are accompanied by homogeneous chemical reactions to generate solid particles of CdS or S in the bulk of the solutions, the present technique seems to be the only example to achieve purely electrochemical growth of CdS from a single solution. The resultant CdS thin film had a uniform structure in which each grain was made up with single phase crystalline hexagonal CdS. When the deposition was carried out on poly-crystalline Ni, the deposited CdS thin film showed a strong preferential orientation with the c-axis perpendicular to the substrate surface, suggesting an epitaxial growth of 6-fold planes of CdS onto Ni(111) planes in a (√3×√3)R30° structure, owing to their small lattice mismatch of 4.17%.

Structural and compositional analyses on indium sulfide thin films deposited in aqueous chemical bath containing indium chloride and thioacetamide

AbstractChemical bath deposition of indium sulfide thin films from aqueous mixtures containing indium chloride and thioacetamide under the two extreme reaction conditions, namely, at 30 and 70 °C, has been examined in order to obtain further insights for understanding the reaction mechanism. The S/In ratio of both the films and the precipitates was low at the early stage of the reaction and it gradually increases to 1.5, which corresponds to the stoichiometric composition of In2S3. X-ray analyses of the films have indicated the formation of amorphous indium hydroxysulfide in the early stage, followed by the formation of nanocrystalline indium sulfide in the late stage of the film growth. The films deposited at 30 °C had a cauliflower-like morphology, whereas the fibrous structure was observed at 70 °C. It is inferred that the rate-determining step for the film growth at the higher temperature is not identical to that at the lower temperature.

Regular ArticleFluoranthene-Induced Apoptosis in Murine T Cell Hybridomas Is Independent of the Aromatic Hydrocarbon Receptor☆

AbstractRecent studies suggest that environmental chemicals such as polycyclic aromatic hydrocarbons (PAH) compromise the immune system in part through the induction of programmed cell death (apoptosis). Nevertheless, mechanisms through which PAH induce apoptosis remain elusive. In particular, the role of the 8S AhR remains controversial and the nature of intracellular signal transduction in PAH-induced apoptosis remains largely undefined. To extend previous studies to the T cell compartment and to develop a clonal system in which intracellular signals leading to PAH-induced apoptosis can be dissected, the ability of fluoranthene, a ubiquitous, but less well-studied PAH, to induce apoptosis in murine T cell hybridomas was evaluated. Particular emphasis was placed on the role of the 8S AhR. The data indicate that (1) three of four hybridomas studied undergo apoptosis within 8 hr of fluoranthene exposure; (2) fluoranthene induces growth arrest concurrent with apoptosis; (3) at doses sufficient to induce lymphocyte apoptosis, fluoranthene does not induce AhR nuclear translocation in cells expressing high AhR levels; (4) fluoranthene-responsive hybridomas do not express AhR mRNA or protein; (5) the Ca2+chelating agent EGTA partially inhibits fluoranthene-induced apoptosis. These results (1) indicate the immunosuppressive potential of fluoranthene; (2) support a role for apoptosis in PAH immunotoxicity; (3) demonstrate that fluoranthene-mediated T cell death and growth arrest are AhR independent; and (4) illustrate similarities between PAH- and antigen-specific receptor-mediated apoptosis. These findings encourage consideration of AhR-independent events in PAH risk assessment.

Regular ArticleInduction of PreB Cell Apoptosis by 7,12-Dimethylbenz[a]anthracene in Long-Term Primary Murine Bone Marrow Cultures☆

AbstractNumerous studies demonstrate that polycyclic aromatic hydrocarbons (PAH) suppress immunity by modifying the function of both B and T cells. Relatively few studies have assessed the effects of these common environmental chemicals on immature lymphocytes. In the present study, long-term primary bone marrow cultures were employed to investigate the effects of a prototypic PAH and aryl hydrocarbon receptor (AhR) agonist, 7,12-dimethylbenz[a]anthracene (DMBA), on immature B lymphocytes. In this system, immature preB cells are maintained in a supportive microenvironment provided by bone marrow stromal cells. Results presented here demonstrate that (1) exposure of primary bone marrow cultures to DMBA results in preB cell death by apoptosis; (2) notably low doses of DMBA (≥10−8m) induce preB cell apoptosis; (3) in long-term cultures, bone marrow stromal cells, but not preB cells, express AhR mRNA and protein as determined byin situhybridization, RT-PCR, and immunoblotting; (4) freshly isolated unfractionated bone marrow cells, but not purified bone marrow B cells, express AhR protein as assessed by immunohistochemistry; (5) α-naphthoflavone, a competitive AhR inhibitor and cytochrome P450 antagonist, completely blocks DMBA-induced preB cell apoptosis in primary bone marrow cultures; and (6) DMBA or benzo[a]pyrene injectionin vivoresults in bone marrow cell apoptosis consistent with the death of hematopoietic cells clustered around stromal elements. The results implicate programmed cell death as a mechanism underlying DMBA-mediated immunosuppression and suggest that preB cell death is influenced by local interactions with AhR+bone marrow stromal cells.

Virtual MR microscopy for unruptured aneurysm

AbstractPurpose: This study was performed to evaluate the usefulness of virtual magnetic resonance microscopy (VMRM) for the diagnosis of cerebral aneurysms. Materials and methods: We reviewed 11 patients with unruptured aneurysms confirmed by angiography or surgical therapy. We evaluated the ability of VMRM to represent aneurysms and the findings of the form and neck of the aneurysms. Results: VMRM revealed 17 aneurysms, one of which was not detected by MR angiography (MRA). One suspected aneurysm by MRA was denied by VMRM. Although VMRM did not clearly demonstrate either one giant aneurysm or distal middle cerebral artery, two aneurysms in the cavernous sinus were clearly visualized by VMRM. VMRM seems to be almost equivalent to computed tomography angiography when detecting aneurysms without additional radiation exposure. Conclusion: VMRM is found valuable not only to plan the microscopic surgical therapy, but to visualize aneurysms.

Size-shrinkage effect of InAs quantum dots during a GaAs capping growth

AbstractThe modification of the InAs quantum dots (QDs) by the GaAs capping growth was studied by using cross-sectional STEM and atomic force microscopy. In case of the GaAs capping growth at 450 °C, it was found that the lateral size of the InAs QDs significantly decreases rather than the height and that this size-shrinkage effect is enhanced for the large QDs. The shrinkage behavior is mainly attributed to the indium surface segregation, strongly depending on the surface strain of the QDs. The growth process of the GaAs capping layer plays an important role for achieving the size ordering of the embedded QDs.

Atomically-controlled GaSb-termination of GaAs surface and its properties

AbstractAn atomically-controlled GaSb layer was fabricated on GaAs(0 0 1) substrates by using the surface exchange reaction between arsenic and antimony atoms. The exchange reaction process was controlled by molecular-beam irradiation of Sb4 and was monitored by using reflection high-energy electron-beam diffraction (RHEED). One-cycle oscillation of RHEED specular-beam intensity during the Sb4 irradiation was explained by the change of surface structure from GaAs to GaSb. From transmission electron microscopy and photoluminescence (PL) measurements, it was found that fabricated GaAs/GaSb quantum well (QW) structures have an abrupt heterointerface and high crystal quality. In scanning tunneling microscopy measurements, tunneling spectra obtained from the GaSb-terminated GaAs sample revealed suppression of density of surface states.

Original articleLong-term safety, efficacy, pharmacokinetics and pharmacodynamics of omalizumab in children with severe uncontrolled asthma

AbstractBackgroundOmalizumab is effective and well-tolerated in children with moderate to severe allergic asthma. However, the effects of long-term treatment with omalizumab in this population haven't been well investigated. The objective of this study is to evaluate the long-term safety, efficacy, pharmacokinetics and pharmacodynamics of omalizumab in children with uncontrolled severe asthma.MethodsThirty-eight Japanese children (aged 7–16 years) who completed the 24-week treatment core study were included in an uncontrolled extension study, in which treatment with omalizumab continued until the pediatric indication was approved in Japan (ClinicalTrials.gov number: NCT01328886).ResultsThirty-five patients (92.1%) completed the extension study. The median exposure throughout the core and extension studies was 116.6 weeks (range, 46.9–151.1 weeks). The most common adverse events were nasopharyngitis, influenza, upper respiratory tract infection, and asthma. Serious adverse events developed in 10 patients (26.3%), but resolved completely with additional treatments. Incidence of adverse events didn't increase with extended exposure with omalizumab. Twenty-nine patients (76.3%) achieved completely- or well-controlled asthma compared with 9 patients (23.7%) at the start of the extension study. QOL scores, the rates (per year) of hospitalizations and ER visits were significantly improved compared with the baseline of the core study [39.0 vs 48.0 (median), p < 0.001 for QOL, 1.33 vs 0.16, p < 0.001 for hospitalization, 0.68 vs 0.15, p = 0.002 for ER visits]. Remarkably, the mean total IgE level showed a decreasing trend while exposure to omalizumab remained at steady-state.ConclusionsLong-term treatment with omalizumab is well-tolerated and effective in children with uncontrolled severe allergic asthma. No new safety findings were identified.

Case reportThe relationship between the clinical course and cytokine in a patient with cigarette smoking-induced acute eosinophilic pneumonia – A case report

AbstractA 19-year-old female was admitted to our hospital because of a sudden onset fever and cough, and she was diagnosed to have acute eosinophilic pneumonia (AEP). The cause was thought to be cigarette smoking, because she had started smoking just before the development of AEP and her condition improved after cigarette smoking cessation, without corticosteroid treatment. The cytokines which are thought to be involved in eosinophilic accumulation in the lungs were analyzed using bronchoalveolar lavage fluid (BALF) and serum. Of the analyzed cytokines, only regulated on activation, normal T cell expressed and secreted (RANTES) increased in the serum after the improvement. RANTES is a unique chemokine which attracts not only eosinophils, but also T cells. Interestingly, in this case, the eosinophil count in the blood increased in parallel with the lymphocyte count after the improvement. These findings are interesting because it may help to understand the pathogenesis of AEP and the role of RANTES.

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