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Articles by M Okamoto
Total Records ( 7 ) for M Okamoto
  M Muraoka , A Fukushima , S Viengchareun , M Lombes , F Kishi , A Miyauchi , M Kanematsu , J Doi , J Kajimura , R Nakai , T Uebi , M Okamoto and H. Takemori

Salt-inducible kinase 2 (SIK2) is expressed abundantly in adipose tissues and represses cAMP-response element-binding protein (CREB)-mediated gene expression by phosphorylating the coactivator transducer of regulated CREB activity (TORC2). Phosphorylation at Ser587 of SIK2 diminishes its TORC2 phosphorylation activity. In 3T3-L1 white adipocytes, SIK2 downregulates lipogenic gene in response to nutritional stresses. To investigate the impact of SIK2 on the function of brown adipose tissue (BAT), we used T37i brown adipocytes, mice with diet-induced obesity, and SIK2 mutant (S587A) transgenic mice. When T37i adipocytes were treated with insulin, the levels of peroxisome proliferator-activated receptor-coactivator-1 (PGC-1) and uncoupling protein-1 (UCP-1) mRNA were increased, and the induction was inhibited by overexpression of SIK2 (S587A) mutant or dominant-negative CREB. Insulin enhanced SIK2 phosphorylation at Ser587, which was accompanied by decrease in phospho-TORC2. Similarly, the decrease in the level of SIK2 phosphorylation at Ser587 was observed in the BAT of mice with diet-induced obesity, which was negatively correlated with TORC2 phosphorylation. To confirm the negative correlation between SIK2 phosphorylation at Ser587 and TORC2 phosphorylation in BAT, SIK2 mutant (S587A) was overexpressed in adipose tissues by using the adipocyte fatty acid-binding protein 2 promoter. The expression of recombinant SIK2 (S587A) was restricted to BAT, and the levels of phospho-TORC2 were elevated in BAT of transgenic mice. Male transgenic mice developed high-fat diet-induced obesity, and their BAT expressed low levels of PGC-1 and UCP-1 mRNA, suggesting that SIK2-TORC2 cascade may be important for the regulation of PGC-1 and UCP-1 gene expression in insulin signaling in BAT.

  S Hoshi , N Hoshi , M Okamoto , J Paiz , T Kusakabe , J. M Ward and S. Kimura

NKX2-1 is a homeodomain transcription factor that is critical for genesis of the thyroid and transcription of the thyroid-specific genes. Nkx2-1-thyroid-conditional hypomorphic mice were previously developed in which Nkx2-1 gene expression is lost in 50% of the thyroid cells. Using this mouse line as compared with wild-type and Nkx2-1 heterozygous mice, a thyroid carcinogenesis study was carried out using the genotoxic carcinogen N-bis(2-hydroxypropyl)-nitrosamine (DHPN), followed by sulfadimethoxine (SDM) or the non-genotoxic carcinogen amitrole (3-amino-1,2,4-triazole). A significantly higher incidence of adenomas was obtained in Nkx2-1-thyroid-conditional hypomorphic mice as compared with the other two groups of mice only when they were treated with DHPN + SDM, but not amitrole. A bromodeoxyuridine incorporation study revealed that thyroids of the Nkx2-1-thyroid-conditional hypomorphic mice had >2-fold higher constitutive cell proliferation rate than the other two groups of mice, suggesting that this may be at least partially responsible for the increased incidence of adenoma in this mouse line after genotoxic carcinogen exposure. Thus, NKX2-1 may function to control the proliferation of thyroid follicular cells following damage by a genotoxic carcinogen.

  M Nakayama , K Hayakawa , M Okamoto , Y Niibe , H Ishiyama and S. Kotani

A Phase I/II study of S-1 combined radiation therapy was conducted in patients with Stage II (T2N0) glottic cancer. The purpose of the Phase I study was to identify the maximum tolerated dose, the recommended dose and the dose limiting toxicity. The objectives in the phase II study were to estimate the local control and the overall survival, and the incidence of adverse events.


In Phase I, S-1 was administered orally in a split-course fashion as two doses of 40 mg/m2, for a total daily dose of 80 mg/m2. The course involved a 2-week rest after a 2-week administration (Level 1) and a 1-week rest after a 3-week administration (Level 2). Radiation therapy was administered in 2-Gy daily (total 60-Gy) standard fractionation.


Seven patients were enrolled in the Phase I, and 19 in the Phase II study. Mucositis was the most common toxicity encountered. All 26 patients completed radiation therapy without delay. The overall response rate was 100% (26/26) with all patients showing a complete response. One patient developed a local recurrence 28 months after the treatment. The 3-year local control and overall survival rates were 94.7 and 85.4%, respectively (limited to 22 patients from Level 2).


The use of S-1 at 80 mg/m2 per day in a split-course with 1-week rest during the course of radiation therapy was safe and effective for Stage II glottic cancer. The treatment strategy employing orally available S-1 proved to be beneficial over the conventional injection of antitumor agents for maintaining the patients' quality of life.

  M Okamoto , T Suzuki , S Nobori , H Ushigome and N. Yoshimura

We describe herein a case of kidney transplantation after extremely long-term haemodialysis. A 66-year-old male received a kidney transplant from a deceased donor after maintenance haemodialysis for 38 years and 2 months. In spite of long-term haemodialysis, he showed minimal calcification of the iliac vessels, and transplantation was carried out successfully. Other than some difficulties in vesical rehabilitation, his postoperative course was favourable and he was finally discharged from the hospital on the 84th postoperative day. On a review of the literature, this case might represent the longest period of haemodialysis ever prior to kidney transplantation in the world.

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