Oka, Kotaro



Faculty of Science and Technology, Department of Biosciences and Informatics (Yagami)



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Career 【 Display / hide

  • 1988.04

    (株)富士通研究所入社 機能有機材料研究部 ,技師補研究員

  • 1991.10

    米国国立衛生研究所(NIH)国立精神障害・卒中研究所(NINDS) ,客員研究員

  • 1992.06

    米国マサチューセッツ州ウッズホール海洋生物学研究所 ,research associate

  • 1995.04

    慶應義塾大学理工学部機械工学科 ,専任講師

  • 1996.04

    慶應義塾大学理工学部システムデザイン工学科 ,専任講師

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Academic Background 【 Display / hide

  • 1983.03

    Keio University, Faculty of Engineering, 計測工学科

    University, Graduated

  • 1985.03

    Keio University, Graduate School, Division of Engineering, 計測工学専攻

    Graduate School, Completed, Master's course

  • 1988.03

    Keio University, Graduate School, Division of Science and Engineeri, 計測工学専攻

    Graduate School, Completed, Doctoral course

Academic Degrees 【 Display / hide

  • 工学 , Keio University, 1988.03

  • 工学 , Keio University, 1988.03


Research Areas 【 Display / hide

  • Life / Health / Medical informatics (Biological/Living Body Informatics)

  • Neurophysiology / General neuroscience (General Neuroscience)

  • Biophysics

Research Keywords 【 Display / hide

  • Biophysics, Neuroscience, Systems Biology


Books 【 Display / hide

  • Development of Near-Infrared Fluorescent Mg<sup>2+</sup> Probe and Application to Multicolor Imaging of Intracellular Signals

    Shindo Y., Ikeda Y., Hiruta Y., Citterio D., Oka K., Methods in Molecular Biology, 2021

     View Summary

    Recent extensive studies revealed that the intracellular concentration of magnesium ions (Mg2+) is one of the important factors to regulate cellular functions. To evaluate the impact of Mg2+ concentration changes on intracellular signals or events, simultaneous imaging of Mg2+ with those phenomena is a powerful technique. The present protocol describes the synthesis and evaluation of near-infrared (NIR) fluorescent Mg2+-selective probes, named KMG-500 series, and the application to simultaneous imaging of the corresponding intracellular signal transductions and molecular events. The present protocol for multicolor imaging using fluorescent probes in the NIR and visible ranges is highly useful to reveal how multiple molecular events are correlated each other in each single cell.

  • 生体の科学

    岡 浩太郎, 医学書院, 2017.10

    Scope: 446-447

  • 社会適応 発現機構と機能障害

    岡 浩太郎, オーム社, 2010

    Scope: 121-160

  • 身近な動物を使った実験2

    北村美一郎、岡浩太郎, 三共出版, 2009

    Scope: 65-82

  • 昆虫ミメティックス

    小川宏人、岡 浩太郎, エヌ・ティー・エス, 2008

    Scope: 650-656

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Papers 【 Display / hide

  • Mechanical stimulus-evoked signal transduction between keratinocytes and sensory neurons via extracellular ATP

    Shindo Y., Fujita K., Tanaka M., Fujio H., Hotta K., Oka K.

    Biochemical and Biophysical Research Communications (Biochemical and Biophysical Research Communications)  582   131 - 136 2021.12

    ISSN  0006291X

     View Summary

    The skin is exposed to various external stimuli. Keratinocytes, which are the main cell type in the epidermis, interact with peripheral sensory neurons and modulate neuronal activity. Recent studies have revealed that keratinocytes play crucial roles in nociception, and that ATP is one of the main mediators of signal transduction from keratinocytes to sensory neurons. However, no quantitative cellular level analyses of ATP-mediated information flow from keratinocytes to sensory dorsal root ganglion (DRG) neurons have been conducted. In this study, we performed simultaneous imaging of cell surface ATP and intracellular Ca2+ signals using both iATPSnFR, a genetically encoded ATP probe localized to the outside of the cell membrane, and the Ca2+ probe, Fura-red. Upon mechanical stimulation of the keratinocyte with a glass needle, an increase in Ca2+ and ATP release were observed around the stimulated area, and these phenomena were positively correlated. In cultured DRG neurons and keratinocytes neighboring the stimulated keratinocyte, increased intracellular Ca2+ concentration and levels of cell surface ATP on the side closer to the stimulated cell were detected. The ratio of Ca2+ response to input ATP signal was significantly larger in DRG neurons than in keratinocytes. We found that DRG neurons were more sensitive to ATP than keratinocytes, and therefore, only DRG neurons responded to ATP at 1 μM or lower concentrations when in co-culture with keratinocytes. Moreover, signals caused by moderate mechanical stimulation of keratinocytes were transmitted predominantly to DRG neurons. These findings would be important in the further determination of the detailed mechanism of nociception in the epidermis.

  • Spatiotemporal dynamics of single cell stiffness in the early developing ascidian chordate embryo

    Fujii Y., Koizumi W.C., Imai T., Yokobori M., Matsuo T., Oka K., Hotta K., Okajima T.

    Communications Biology (Communications Biology)  4 ( 1 )  2021.12

     View Summary

    During the developmental processes of embryos, cells undergo massive deformation and division that are regulated by mechanical cues. However, little is known about how embryonic cells change their mechanical properties during different cleavage stages. Here, using atomic force microscopy, we investigated the stiffness of cells in ascidian embryos from the fertilised egg to the stage before gastrulation. In both animal and vegetal hemispheres, we observed a Rho kinase (ROCK)-independent cell stiffening that the cell stiffness exhibited a remarkable increase at the timing of cell division where cortical actin filaments were organized. Furthermore, in the vegetal hemisphere, we observed another mechanical behaviour, i.e., a ROCK-associated cell stiffening, which was retained even after cell division or occurred without division and propagated sequentially toward adjacent cells, displaying a characteristic cell-to-cell mechanical variation. The results indicate that the mechanical properties of embryonic cells are regulated at the single cell level in different germ layers.

  • Small molecule-based alkaline-earth metal ion fluorescent probes for imaging intracellular and intercellular multiple signals

    Hiruta Y., Shindo Y., Oka K., Citterio D.

    Chemistry Letters (Chemistry Letters)  50 ( 5 ) 870 - 887 2021.05

    ISSN  03667022

     View Summary

    This highlight review overviews recent progress in fluorescence imaging technology for the alkaline-earth metal ions calcium, and magnesium, by small molecule-based fluorescent probes. Fluorescent probes for Ca2+ using 1,2-bis-(o-aminophenoxy)- ethane-N,N,N′,N′-tetraacetic acid (BAPTA) as a recognition unit are introduced. Focus is set on the fluorescence characteristics and intracellular dynamics of Ca2+ fluorescent probes depending on the differences in fluorophore units. In addition, this review comprehensively covers Mg2+ fluorescent probes from Mg2+ selective ligands and fluorophore units to their application. In particular, the influence of the molecular structure of the fluorescent probes on organelle localization and fluorescence wavelength for imaging intracellular signals in organelles and intercellular multiple signal interactions are summarized, providing a strategy for probe design for chemists, and for selecting the appropriate imaging technique for biologists.

  • Peripheral-neuron-like properties of differentiated human dental pulp stem cells (hDPSCs)

    Arimura Y., Shindo Y., Yamanaka R., Mochizuki M., Hotta K., Nakahara T., Ito E., Yoshioka T., Oka K.

    PLoS ONE (PLoS ONE)  16 ( 5 May )  2021.05

     View Summary

    Elucidating the mechanisms underlying human pain sensation requires the establishment of an in vitro model of pain reception comprising human cells expressing pain-sensing receptors and function properly as neurons. Human dental pulp stem cells (hDPSCs) are mesenchymal stem cells and a promising candidate for producing human neuronal cells, however, the functional properties of differentiated hDPSCs have not yet been fully characterized. In this study, we demonstrated neuronal differentiation of hDPSCs via both their expression of neuronal marker proteins and their neuronal function examined using Ca2+ imaging. Moreover, to confirm the ability of nociception, Ca2+ responses in differentiated hDPSCs were compared to those of rat dorsal root ganglion (DRG) neurons. Those cells showed similar responses to glutamate, ATP and agonists of transient receptor potential (TRP) channels. Since TRP channels are implicated in nociception, differentiated hDPSCs provide a useful in vitro model of human peripheral neuron response to stimuli interpreted as pain.

  • High responsiveness of auditory neurons to specific combination of acoustic features in female songbirds

    Inda M., Hotta K., Oka K.

    European Journal of Neuroscience (European Journal of Neuroscience)  53 ( 5 ) 1412 - 1427 2021.03

    ISSN  0953816X

     View Summary

    Zebra finch (Taeniopygia guttata) is a songbird species in which males sing their unique songs to attract females who then select their preferred male. Acoustic features in the songs of individual males are important features for female auditory perception. While the male of this species is a classic model of vocal production, it has been little known about auditory processing in female. In the higher auditory brain regions, the caudomedial mesopallium (CMM) and nidopallium (NCM) contribute to female's sound recognition, we, therefore, extracted acoustic features that induce neural activities with high detection power on both regions in female finches. A multiple linear regression analysis revealed that neurons were sensitive to mean frequency and Wiener entropy. In addition, we performed an experiment with modified artificial songs and harmonic songs to directly investigate neural responsiveness for deriving further evidence for the contribution of these two acoustic features. Finally, we illustrated a specific ratio combining these two acoustic features that showed highest sensitivity to neural responsiveness, and we found that properties of sensitivity are different between CMM and NCM. Our results indicate that the mixture of the two acoustic features with the specific ratio is important in the higher auditory regions of female songbirds, and these two regions have differences in encoding for sensitivity to these acoustic features.

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Papers, etc., Registered in KOARA 【 Display / hide

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Reviews, Commentaries, etc. 【 Display / hide

Presentations 【 Display / hide

  • 培養神経回路網における機能的結合の形成と維持


    第43回日本神経科学大会, 2020.07, Poster (general)

  • The properties of neural activities by acoustic factors in higher auditory region to sound stimuli in awake and anesthetized finches.

    A. Yoshida, M. Inda, K. Hotta, K. Oka.

    Neuroscience 2019 (Chicago (USA)) , 2019.10, Poster (general)

  • Region specific timescale dependency of auditory neural activity to song stimulus in avian brain.

    M. Inda, A. Yoshida, K. Hotta, K. Oka.

    Neuroscience 2019 (Chicago (USA)) , 2019.10, Poster (general)

  • Whole ganglion mapping for various mechanosensation in the leech nervous system using voltage-sensitive dye imaging.

    Y. Tomita, K. Oka, D. A. Wagenaar

    Neuroscience 2019 (Chicago (USA)) , 2019.10, Poster (general)

  • Quantitative analysis of cell cycle progression within heterogeneous cell population using information theory.

    The 6th International Symposium on Bioimaging, 2019.09, Poster (general)

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Research Projects of Competitive Funds, etc. 【 Display / hide

  • ヒト末梢神経系のin vitro再構成系の構築による痛み緩和メカニズムの解明


    MEXT,JSPS, Grant-in-Aid for Scientific Research, 岡 浩太郎, Grant-in-Aid for Challenging Research (Exploratory), Principal Investigator

  • Detection of singularity neurons during neural network formation


    MEXT,JSPS, Grant-in-Aid for Scientific Research, 岡 浩太郎, Grant-in-Aid for Scientific Research on Innovative Areas, Principal Investigator

  • Bio-imaging without targets


    MEXT,JSPS, Grant-in-Aid for Scientific Research, 岡 浩太郎, Grant-in-Aid for Challenging Research (Exploratory) , Principal Investigator

  • Is Mg ion a novel second messenger for regulating energy metabolism?


    MEXT,JSPS, Grant-in-Aid for Scientific Research, 岡 浩太郎, Grant-in-Aid for Scientific Research (A) , Principal Investigator

  • Comprehensive neuroanatomy by using non-staining imaging and informatics


    MEXT,JSPS, Grant-in-Aid for Scientific Research, 岡 浩太郎, Grant-in-Aid for Challenging Exploratory Research, Principal Investigator

     View Summary

    We have developed a new method to classify brain regions rationally. We obtain Raman spectral information for each pixel on the brain slices of songbirds. Using this spectral information, regions with similar spectra were extracted and mapped. As a result, myelin wrapped nerve fibers and several neurons with neurotransmitters (serotonin, dopamine and glutamate) could be detected without staining. As a method to rationally determine the brain region boundary, we attempted Voronoi division using nuclear position. As a result, we succeeded to divide the entire coronal section of the bird's brain into Voronoi units. By using this division method together with unstained imaging, it is possible to construct a brain draft map at high speed.


Courses Taught 【 Display / hide











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Social Activities 【 Display / hide

  • 農林水産省食品総合研究所

  • 放射線医学研究所(第3研究グループ)

  • 新技術事業団 河内微小流動プロジェクト


Memberships in Academic Societies 【 Display / hide

  • 日本バイオイメージング学会, 

  • Society for Neuroscience

  • 日本生物物理学会

  • 日本神経科学学会

  • 応用物理学会


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Committee Experiences 【 Display / hide

  • 1997.12

    幹事, 日本機械学会 「生物に学ぶメカニカルテクノロジー」委託出版分科会

  • 1997.11

    実行委員, 日本機械学会 1999年年次大会

  • 1997.11

    実行委員, 第11回日本ME学会秋季大会(1997年)

  • 1996.09

    特別研究員, 農林水産省食品総合研究所

  • 1995.08

    共同利用研究員, 放射線医学研究所(第3研究グループ)

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