Search

Your search keyword '"Miura, Shin-ichi"' showing total 29 results
Start Over Author "Miura, Shin-ichi"
29 results on '"Miura, Shin-ichi"'

3. Fabrication of sustainable Au mono-atomic wire showing conductance quantization in solution

Author

Kiguchi, Manabu, Konishi, Tatsuya, Miura, Shin-ichi, and Murakoshi, Kei

Subjects
Anion, Mono atomic wire, Conductance quantization, Ion adsorption, Electrochemical potential
Abstract

Electric conductance of the Au nano constrictions was investigated in 0.1M Na2SO4 solution under electrochemical potential control. Point contact of Au showing the unit of the quantum conductance, G0 (2e^2/h), can be stretched as long as 1 nm when the electrochemical potential of the contact was kept at 0.5 V vs. Ag/AgCl. The result proves superior stability of Au mono atomic wire fabricated in solution. As the electrochemical potential changed to negative, the stretch length of the mono atomic wire decreased. The change of the stability was recovered as the potential became positive, indicating that the stability of the wire can be fully controlled by the electrochemical potential. In the time cause of the conductance trace, fluctuation was observed. The change in the value in the conductance was less than -15%. This fluctuation was attributed to the change in the number of atoms in the mono atomic wire. Observed changes in the conductance reflect the characteristics of the dynamical formation/deformation processes of the mono atomic wire showing conductance quantization in solution at room temperature.

Published
2005

4. Summary Report of Questionnaire Survey on Current Situation and Issues of Human Mass Balance Study Using Radioisotopes in Japan

Author

HASEGAWA, Hiroshi, primary, FURUTA, Shigeru, additional, KURIBAYASHI, Shunji, additional, TSUDA, Minoru, additional, SATSUKAWA, Masahiro, additional, SUZUKI, Motohiro, additional, ISHII, Satoru, additional, KONDO, Hiroshi, additional, MINATO, Kouichi, additional, SATO, Takashi, additional, TSUTSUI, Masaru, additional, KURAHASHI, Yoshikazu, additional, MIURA, Shin-ichi, additional, and NAKAMURA, Kazuichi, additional

Published
2015
Full Text
View/download PDF

10. Renal and hepatic microsomal enzymes responsible for bioactivation of 3-methoxy-4-aminoazobenzene in the rodent

Author

Degawa Masakuni, Miura Shin-Ichi, and Hashimoto Yoshiyuki

Subjects
Male, medicine.medical_specialty, Guinea Pigs, Hamster, Hydroxylation, Kidney, Biochemistry, Mice, Cytochrome P-450 Enzyme System, Internal medicine, Cricetinae, medicine, Animals, Enzyme inducer, Carcinogen, Biotransformation, Pharmacology, chemistry.chemical_classification, Mice, Inbred BALB C, biology, Mesocricetus, Mutagenicity Tests, Cytochrome P450, Rats, Inbred F344, Rats, Enzyme, Endocrinology, medicine.anatomical_structure, chemistry, p-Aminoazobenzene, Enzyme Induction, Phenobarbital, biology.protein, Microsome, Microsomes, Liver, medicine.drug, Methylcholanthrene
Abstract

Activities of the renal and hepatic microsomal enzymes responsible for the N-hydroxylation and mutagenic activation of 3-methoxy-4-aminoazobenzene (3-MeO-AAB) were examined in male mice, rats, hamsters and guinea pigs. In all these rodent species, hepatic microsomes showed definite N-hydroxylation of 3-MeO-AAB, whereas the renal activity was detected only in mice. The hepatic enzyme responsible for N-hydroxylation of 3-MeO-AAB (3-MeO-AAB N-hydroxylase) was induced in all species except mice by phenobarbital and selectively in mice and hamsters by 3-methylcholanthrene, whereas these cytochrome P450 inducers did not affect the renal enzyme in mice, rats or hamsters. In individual microsome samples, activities for N-hydroxylation and mutagenic activation of 3-MeO-AAB correlated well. These results indicate that the renal and hepatic enzymes responsible for the metabolic activation of 3-MeO-AAB differed among different species of rodent animals in terms of their activity and inducibility with cytochrome P450 inducers.

Published
1991

23. Mechanism-Based Inhibition of Human Cytochrome P450 2B6 by Ticlopidine, Clopidogrel, and the Thiolactone Metabolite of Prasugrel

Author

Nishiya, Yumi, Hagihara, Katsunobu, Ito, Takashi, Tajima, Masami, Miura, Shin-ichi, Kurihara, Atsushi, Farid, Nagy A., and Ikeda, Toshihiko

Abstract

Mechanism-based inhibition of CYP2B6 in human liver microsomes by thienopyridine antiplatelet agents ticlopidine and clopidogrel and the thiolactone metabolites of those two agents plus that of prasugrel were investigated by determining the time- and concentration-dependent inhibition of the activity of bupropion hydroxylase as the typical CYP2B6 activity. By comparing the ratios of kinact(maximal inactivation rate constant)/KI(the inactivator concentration producing a half-maximal rate of inactivation), it was found that the thiolactone metabolite of prasugrel is 10- and 22-fold less potent, respectively, in the mechanism-based inhibition of CYP2B6 than ticlopidine and clopidogrel. The kinact/KIratio of the thiolactone metabolite of ticlopidine was comparable with that of the parent compound, whereas this ratio for the thiolactone metabolite of clopidogrel was significantly smaller than that of clopidogrel. In conclusion, ticlopidine, its thiolactone metabolite, and clopidogrel were more potent mechanism-based inhibitors of CYP2B6 than the thiolactone metabolite of prasugrel.

Published
2009

24. Mechanism for Covalent Binding of Rofecoxib to Elastin of Rat Aorta

Author

Oitate, Masataka, Hirota, Takashi, Takahashi, Makoto, Murai, Takahiro, Miura, Shin-ichi, Senoo, Akira, Hosokawa, Tsunemichi, Oonishi, Tadahiro, and Ikeda, Toshihiko

Abstract

We have previously reported that oral administration of [14C]rofecoxib to rats resulted in the long retention of radioactivity by the aorta as a consequence of covalent binding to elastin. Treatment of rats with α-phenyl-α-propylbenzeneacetic acid 2-[diethylamino]-ethyl ester hydrochloride (SKF-525A), a cytochrome P450 inhibitor, significantly decreased the systemic exposure of 5-hydroxyrofecoxib, one of the main metabolites of rofecoxib, whereas there was no statistically significant change in the retention of radioactivity from [14C]rofecoxib in the aorta. On the other hand, the aortic retention of radioactivity closely correlated to the systemic exposure of unchanged rofecoxib in the dose range between 2 and 10 mg/kg. A covalent binding study of [14C]rofecoxib in vitro using rat aorta homogenate in the presence of d-penicillamine, hydralazine, β-aminopropionitrile, and sodium borohydride suggested that the aldehyde group of allysine in elastin was relevant to the covalent binding. In a model reaction using benzaldehyde, rofecoxib but not 5-hydroxyrofecoxib reacted with the aldehyde group of benzaldehyde in a manner of condensation reaction under a physiological pH condition. A histopathological examination using an electron microscope demonstrated that multiple oral administration of rofecoxib to rats caused marked degradation of the elastic fiber system of the aorta. These results suggested that rofecoxib as such is reactive in vivo, undergoing a condensation reaction with allysine, thereby preventing the formation of cross-linkages in elastin, i.e., desmosine and isodesmosine, and causing the degradation of the elastic fibers.

Published
2007
Full Text
View/download PDF

29. [Network for the collection and distribution of Japanese liver tissues resected surgically for drug development and research use].

Author

Sunouchi M, Sakemi K, Kubota K, Kita J, Kamikawa Y, Uchida K, Miura S, Shigehara E, Fujioka H, and Ohno Y

Subjects
Aged, Cell Separation, Cells, Cultured, Cytochrome P-450 Enzyme System physiology, Female, Hepatectomy, Humans, Japan, Male, Medical Waste, Middle Aged, Testosterone metabolism, Drug Design, Hepatocytes metabolism, Liver, Research, Specimen Handling
Abstract

We focused on the establishment of a trial procedure for the collection and distribution of Japanese liver tissues obtained from waste surgical resections for drug development and research use. The following procedures were prepared for this project: the pretreatment of liver tissues before storage, their storage at 4 degrees C, the transport of liver samples, the setting up of a communication network among the participating hospitals and laboratories and the approval of each ethics committee. Thirteen liver samples (1.6-7.6 g) obtained from patients whose livers were excised due to cirrhosis, hepatocellular carcinoma, cholangiocarcinoma, or metastasis from colorectal carcinoma and were donated for research. Informed consent was obtained from every patient. Freshly isolated human hepatocytes were prepared from nine liver samples (viability 34.3-86.1%). Four samples were unsuitable to prepare hepatocytes. The profile of testosterone metabolism as 6beta-, 2beta-, 16beta-, 16alpha- and 2alpha-hydroxytestosterone and androstenedione in freshly isolated hepatocytes was shown to be specific for human liver. The 6beta-hydroxylation activity catalyzed by CYP3A4/5 indicated a high level of metabolism (139-996 pmol/min/million cells). Levels of 7-ethoxycoumarin O-deethylation and glucronidation activities were sufficient for analysis in freshly isolated human hepatocytes. We conclude that liver tissues from waste surgical resections supplied from a participating hospital can constitute a valuable source of freshly isolated human hepatocytes for drug development and safety evaluation.

Published
2005

Catalog

Books, media, physical & digital resources
See catalog results