Hiraoka, Yoshiki



School of Medicine, Department of Anatomy (Shinanomachi)


Assistant Professor/Senior Assistant Professor

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Career 【 Display / hide

  • 1983.04

    慶應義塾大学, 医学部解剖学教室, 助手

  • 1985.04


  • 1989.06

    慶應義塾大学, 医学部微生物学教室, 助手

  • 1994.10

    慶應義塾大学, 医学部解剖学教室, 専任講師

Academic Background 【 Display / hide

  • 1976.04

    Hokkaido University, 理学部高分子学科

    University, Graduated

  • 1980.04

    Hokkaido University, 理学研究科, 高分子学専攻

    Graduate School, Completed, Master's course

  • 1982.04

    Hokkaido University, 理学研究科, 高分子学専攻

    Graduate School, Withdrawal after completion of doctoral course requirements, Doctoral course

Academic Degrees 【 Display / hide

  • 理学博士, Hokkaido University, Coursework, 1985.09


Papers 【 Display / hide

  • Rapid induction of the growth hormone gene transcription by glucocorticoids in vitro

    Nogami H., Yamamoto N., Hiraoka Y., Aiso S., Sugimoto K., Yoshida S., Shutoh F., Hisano S.

    Journal of Neuroendocrinology 26 ( 3 ) 195 - 204 2014

    ISSN  0953-8194

     View Summary

    <p>The regulation of transcription of the growth hormone (GH) gene by glucocorticoids was studied in MtT/S cells, a cell line derived from an oestrogen-induced mammotrophic tumour in the rat, and in the primary culture of the anterior pituitary gland of adult mice. The levels of the GH heteronuclear RNA (GH hnRNA), which are mainly determined by the transcription rate, increased by 25-fold during 24 h in response to dexamethasone (DEX; 1 μm) in MtT/S cells that were cultured in the medium containing charcoal-stripped serum for 7 days. The stimulatory effect of DEX on the GH hnRNA levels was detectable as early as 30 min. This rapid effect of DEX did not require on-going protein synthesis, whereas it was considered that DEX requires the presence of unknown cellular proteins produced independently of DEX stimulation. By contrast, on-going protein synthesis was required for DEX action when incubated for 6 h, as has been observed in the previous studies. The specific inhibitor of glucocorticoid receptor, RU486, inhibited both rapid (30 min) and delayed (6 h) the effects of glucocorticoids on GH hnRNA levels. Membrane impermeable glucocorticoid, corticosterone-bovine serum albumin conjugate (CSBSA), was found to have effects similar to those of DEX and free corticosterone (CS), suggesting that glucocorticoids regulate GH gene transcription at least in part through the membrane bound receptors. From pharmacological studies, it was suggested that phosphatidylinositol 3-kinase (PI3K) activation is involved in the rapid effects but not in the delayed effects of glucocorticoids. This also suggests that the delayed effects of glucocorticoids depend on mechanisms other than the activation of PI3-kinase. Finally, both rapid and delayed effects of CS and CSBSA were observed not only in MtT/S cells, but also in the mouse pituitary cells in primary culture. Therefore, it is possible that the membrane initiated action of glucocorticoids is involved in the regulation of GH transcription in normal pituitary cells, as well as in pituitary tumour cells. © 2014 British Society for Neuroendocrinology.</p>

  • Epidermal Growth Factor-Activated Extracellular Signal-Regulated Kinase Suppresses Growth Hormone Expression and Stimulates Proliferation in MtT/E Cells

    Nogami H., Soya H., Hiraoka Y., Aiso S., Hisano S.

    Journal of Neuroendocrinology 24 ( 2 ) 357 - 365 2012.02

    ISSN  0953-8194

     View Summary

    <p>The mechanism for the inhibition of growth hormone (GH) expression by the epidermal growth factor (EGF) was examined in two clonal cell lines, MtT/E and MtT/S. The former has a negligible basal level of GH, whereas the latter has a high basal GH. The treatment of MtT/E cells with retinoic acid resulted in a significant increase in GH mRNA and subsequently GH. This stimulatory response to retinoic acid was strongly suppressed by EGF. This suppression was associated with an increase in the phosphorylation of extracellular signal-regulated kinase 1 and 2 (Erk1/2). The MEK [mitogen-activated protein kinase (MAPK) kinases that activate ERK1 and ERK2] inhibitor, PD98059, clearly inhibited the phosphorylation of Erk1/2 and restored the stimulatory effects of retinoic acid. These results suggest that the inhibitory effects of EGF on GH expression are mediated by MAPK activation in these cells. By contrast to the GH-producing clones examined previously, EGF showed a marked stimulation of proliferation of the MtT/E cells through a mechanism dependent on MAPK activation. On the other hand, the inhibitory effect of EGF on GH expression was less pronounced and the stimulation of cellular proliferation was not seen in MtT/S cells, even though it induced Erk-phosphorylation similar to that seen in MtT/E. The distinct difference in the response to EGF between these two GH cell lines appears to be attributed to differences in the function of MAPK cascade in each cell line. This may reflect the developmental stage of the cells from which MtT/E and MtT/S are derived. © 2011 The Authors. Journal of Neuroendocrinology © 2011 Blackwell Publishing Ltd.</p>

  • Inhibitory action of Xenopus dicalcin on sperm-egg interaction during fertilization

    Miwa Naofumi, Ogawa Motoyuki, Hiraoka Yoshiki, Takamatsu Ken, Kawamura Satoru

    DEVELOPMENTAL BIOLOGY 344 ( 1 ) 511 - 512 2010.08

    Research paper (scientific journal),  ISSN  0012-1606

  • Dicalcin Inhibits Fertilization through Its Binding to a Glycoprotein in the Egg Envelope in Xenopus laevis

    Miwa Naofumi, Ogawa Motoyuki, Shinmyo Yukiko, Hiraoka Yoshiki, Takamatsu Ken, Kawamura Satoru

    JOURNAL OF BIOLOGICAL CHEMISTRY 285 ( 20 ) 15627 - 15636 2010.05

    Research paper (scientific journal),  ISSN  0021-9258

  • Molecular analysis of inhibitory effects of Xenopus dicalcin on the fertilization process

    Miwa Naofumi, Ogawa Motoyuki, Hiraoka Yoshiki, Takamatsu Ken, Kawamura Satoru


    Research paper (scientific journal),  ISSN  1880-6546

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Presentations 【 Display / hide

  • アフリカツメガエルPaxillin蛋白質の卵形成における役割


    第108回 日本解剖学会総会全国学術集会 (福岡) , 2003.04, Poster (general)

  • The role of Xenopus Paxillin in oogenesis

    Ogawa Motoyuki, Hiraoka Yoshiki, Aiso Sadakazu

    International Xenopus Confererence, 2002.08, Oral Presentation(general)

  • アフリカツメガエルEnx-α遺伝子の胚発生における役割解明

    Ogawa Motoyuki,Hiraoka Yoshiki,Hasegawa Masanori,Hagiuda Jun,Aiso Sadakazu

    第107回日本解剖学会総会・全国学術集会, 2002.03

  • アフリカツメガエルxSox18遺伝子のcDNAクローニング

    Hiraoka Yoshiki,Hasegawa Masanori,Hagiuda Jun,Ogawa Motoyuki,Aiso Sadakazu

    第107回日本解剖学会総会・全国学術集会, 2002.03

  • Cloning and characterization of Xenopus Enx-alpha,enhancer of zeste homologue

    Ogawa Motoyuki, Hiraoka Yoshiki, Sakai Yukinao, Shiozawa Masahide, Aiso Sadakazu

    International Congress on Developmental Biology (14th ; 2001 ; Kyoto), 2001.07

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Courses Taught 【 Display / hide