Updated on 2021/10/21

写真a

 
OKAMOTO Takashi
 
Organization
Natural Science and Technology Assistant Professor
Position
Assistant Professor
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Degree

  • 学士(理学) ( 東京理科大学 )

  • 修士(教育学) ( 神戸大学 )

  • 博士(理学) ( 神戸大学 )

Research Interests

  • 植物生理学

  • ケミカルバイオロジー

Research Areas

  • Life Science / Plant molecular biology and physiology

Education

  • Kobe University    

    1996.4 - 2000.3

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    Country: Japan

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  • Kobe University   大学院教育学研究科   理科教育専攻

    1994.4 - 1996.3

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  • Tokyo University of Science   Faculty of Science, Division 1   Department of Applied Chemistry

    1990.4 - 1994.3

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    Country: Japan

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Research History

  • - 岡山大学自然科学研究科 助教

    2011

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  • 北海道大学理学研究院 博士研究員

    2009 - 2011

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  • Kobe University   Radio Isotope Division, Center for Supports to Research and Education Activities

    2004 - 2009

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  • Kobe University   Faculty of Human Development

    2000 - 2004

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Professional Memberships

 

Papers

  • The root growth reduction in response to mechanical stress involves ethylene-mediated microtubule reorganization and transmembrane receptor-mediated signal transduction in Arabidopsis Reviewed

    Takashi Okamoto, Shogo Takatani, Hiroyasu Motose, Hidetoshi Iida, Taku Takahashi

    Plant Cell Reports   40   575 - 582   2021.1

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1007/s00299-020-0

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  • Microtubule Response to Tensile Stress Is Curbed by NEK6 to Buffer Growth Variation in the Arabidopsis Hypocotyl. Reviewed International journal

    Shogo Takatani, Stéphane Verger, Takashi Okamoto, Taku Takahashi, Olivier Hamant, Hiroyasu Motose

    Current biology : CB   2020.3

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    Language:English  

    Growth variability generates mechanical conflicts in tissues. In plants, cortical microtubules usually align with maximal tensile stress direction, thereby mechanically reinforcing cell walls, and channeling growth rate and direction. How this is achieved remains largely unknown and likely involves microtubule regulators. The NIMA-related microtubule-associated kinase NEK6 phosphorylates tubulin, leading to the depolymerization of a subset of microtubules. We found that cortical microtubules exhibit a hyper-response to mechanical stress in the nek6 mutant. This response contributes to local cell protrusions in slow-growing regions of the nek6 mutant hypocotyl. When growth amplitude is higher, the hyper-alignment of microtubules leads to variable, stop-and-go, phenotypes, resulting in wavy hypocotyl shapes. After gravistimulation or touch, the nek6 mutant also exhibits a hyperbent hypocotyl phenotype, consistent with an enhanced perception of its own deformation. Strikingly, we find that NEK6 exhibits a novel form of polarity, being recruited at the ends of a subset of microtubules at cell edges. This pattern can be modified after local ablation, matching the new maximal tensile stress directions. We propose that NEK6 depolymerizes cortical microtubules that best align with maximal tensile stress to generate a noisier network of microtubules. This prevents an overreaction of microtubules to growth fluctuations and, instead, promotes the buffering of growth variations.

    DOI: 10.1016/j.cub.2020.02.024

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  • Omeprazole Enhances Mechanical Stress-Induced Root Growth Reduction in Arabidopsis thaliana. Reviewed

    Takashi Okamoto, Shogo Takatani, Yoshiteru Noutoshi, Hiroyasu Motose, Taku Takahashi

    Plant & cell physiology   59 ( 8 )   1581 - 1591   2018.8

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    Language:English   Publishing type:Research paper (scientific journal)  

    Mechanical sensing is one of the most fundamental processes for sessile plants to survive and grow. The response is known to involve calcium elevation in the cell. Arabidopsis seedlings grown horizontally on agar plates covered with a dialysis membrane show a 2-fold reduction in root growth compared with those grown vertically, a response to mechanical stress generated due to gravitropism of the root. To understand the molecular mechanism of how plant roots sense and respond to mechanical stimuli, we screened chemical libraries for compounds that affect the horizontal root growth in this experimental system and found that, while having no effect on root gravitropism, omeprazole known as a proton pump inhibitor significantly enhanced the mechanical stress-induced root growth reduction especially in lower pH media. In contrast, omeprazole reversed neither the alleviation of the mechanical stress-induced growth reduction caused by calcium depletion nor the insensitivity to the mechanical stress in the ethylene signaling mutant ein2. Together with the finding that omeprazole increased expression of touch-induced genes and ETHYLENE RESPONSE FACTOR1, our results suggest that the target of omeprazole mediates ethylene signaling in the root growth response to mechanical stress.

    DOI: 10.1093/pcp/pcy131

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  • Genetic dissection of hormonal responses in the roots of Arabidopsis grown under continuous mechanical impedance. Reviewed International journal

    Takashi Okamoto, Seiji Tsurumi, Kyohei Shibasaki, Yoshimi Obana, Hironori Takaji, Yutaka Oono, Abidur Rahman

    Plant physiology   146 ( 4 )   1651 - 62   2008.4

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    Language:English   Publishing type:Research paper (scientific journal)  

    We investigated the role of ethylene and auxin in regulating the growth and morphology of roots during mechanical impedance by developing a new growing system and using the model plant Arabidopsis (Arabidopsis thaliana). The Arabidopsis seedlings grown horizontally on a dialysis membrane-covered agar plate encountered adequate mechanical impedance as the roots showed characteristic ethylene phenotypes: 2-fold reduction in root growth, increase in root diameter, decrease in cell elongation, and ectopic root hair formation. The root phenotype characterization of various mutants having altered response to ethylene biosynthesis or signaling, the effect of ethylene inhibitors on mechanically impeded roots, and transcription profiling of the ethylene-responsive genes led us to conclude that enhanced ethylene response plays a primary role in changing root morphology and development during mechanical impedance. Further, the differential sensitivity of horizontally and vertically grown roots toward exogenous ethylene suggested that ethylene signaling plays a critical role in enhancing the ethylene response. We subsequently demonstrated that the enhanced ethylene response also affects the auxin response in roots. Taken together, our results provide a new insight into the role of ethylene in changing root morphology during mechanical impedance.

    DOI: 10.1104/pp.107.115519

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  • Ethylene signaling plays a pivotal role in mechanical stress-induced root growth cessation in Arabidopsis thaliana. Reviewed

    Takashi Okamoto, Taku Takahashi

    2019.9

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1080/15592324.2019.1669417

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  • Salt hypersensitivity is associated with excessive xylem development in a thermospermine-deficient mutant of Arabidopsis thaliana Reviewed

    Shiori Shinohara, Takashi Okamoto, Hiroyasu Motose, Taku Takahashi

    Plant Journal   2019.7

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1111/tpj.14448

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  • Saturated humidity accelerates lateral root development in rice (Oryza sativa L.) seedlings by increasing phloem-based auxin transport Reviewed

    Tory Chhun, Yuichi Uno, Shin Taketa, Tetsushi Azuma, Masahiko Ichii, Takashi Okamoto, Seiji Tsurumi

    JOURNAL OF EXPERIMENTAL BOTANY   58 ( 7 )   1695 - 1704   2007

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:OXFORD UNIV PRESS  

    Auxin transport plays a significant role modifying plant growth and development in response to environmental signals such as light and gravity. However, the effect of humidity on auxin transport is rarely documented. It is shown here that the transport of labelled indole-3-acetic acid (IAA) from the shoot to the root is accelerated in rice (Oryza sativa L. ssp. indica cv. IR8) seedlings grown under saturated humidity (SH-seedlings) compared with plants grown under normal humidity (NH-seedlings). The development of lateral roots in SH-seedlings was greatly enhanced compared with NH-seedlings. Removal of the shoot from SH-seedlings reduced the density of lateral roots, and the application of IAA to the cut stem restored the lateral root density, while the decapitation of NH-seedlings did not alter lateral root development. Phloem-based auxin transport appeared responsible for enhanced lateral root formation in SH-seedlings since (i) the rate of IAA transport from the shoot to the root tip was greater than 3.5 cm h(-1) and (ii) naphthylphthalamic acid (NPA)-induced reduction of polar auxin transport in the shoot did not influence the number of lateral roots in SH-seedlings. It is proposed that high humidity conditions accelerate the phloem-based transport of IAA from the leaf to the root, resulting in an increase in the number of lateral roots.

    DOI: 10.1093/jxb/erm026

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  • Metal ions dramatically enhance the enantioselectivity for lipase-catalysed reactions in organic solvents Reviewed

    T Okamoto, E Yasuhito, S Ueji

    ORGANIC & BIOMOLECULAR CHEMISTRY   4 ( 6 )   1147 - 1153   2006

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ROYAL SOC CHEMISTRY  

    We propose a simple and a powerful method to enhance the enantioselectivity for lipase-catalysed transformations in organic solvents by an addition of metal ion-containing water to the reaction mixture. In this paper, various metal ions such as LiCl or MgCl2 are tested to improve the enantioselectivity for the model reactions. The enantioselectivities obtained are dramatically enhanced, the E values of which are about 100-fold as compared with the ordinary conditions without a metal ion, for example, E = 200 by addition of LiCl. Furthermore, lowering the reaction temperature led to an almost perfect enantioselectivity of lipase in the presence of a metal ion, for example, E = 1300 by addition of LiCl. Also, a mechanism for the drastic enhancement by metal ions is discussed briefly on the basis of the EPR spectroscopic study and the initial rate for each enantiomer of the substrate.

    DOI: 10.1039/b514885e

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  • How does lipase flexibility affect its enantioselectivity in organic solvents? A possible role of CH center dot center dot center dot pi association in stabilization of enzyme-substrate complex Reviewed

    K Watanabe, T Uno, T Koshiba, T Okamoto, Y Ebara, S Ueji

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   77 ( 3 )   543 - 548   2004.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:CHEMICAL SOC JAPAN  

    For lipase-catalyzed reactions of 2-(4-substitued phenoxy)propionic acids with alcohols in organic solvents containing a small amount of water, the increase of the lipase flexibility brought about by addition of water is found to be favorable for the induced-fit motion of the lipase for the correctly binding enantiomer of the substrate used, thus resulting in the improvement of the lipase enantioselectivity. In particular, for the reaction of the substrate with rich pi electron density on its aromatic ring, the enantioselectivity was much more sensitive to the change of the lipase flexibility. Thus, in the induced fit motion, the CH...pi association between amino acids side chains around the lipase's active site and the aromatic ring of the correctly binding enantiomer is assumed to accelerate the accommodation Of the Substrate into the lipase's active site and the stabilization of the complex between the enzyme and the substrate. This assumption is also Supported by a discussion based on the value of the Michaelis constant obtained. Furthermore, on the basis of a model concerning the acyl-enzyme structure for the incorrectly binding enantiomer, the long alkyl chain alcohols as a nucleophile are found to improve the lipase enantioselectivity markedly.

    DOI: 10.1246/bcsj.77.543

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  • How does lipase flexibility affect its enantioselectivity in organic solvents? A possible role in CH・・・π association in stabilization of enzyme-substrate complex Reviewed

    Keiichi Watanabe, Tetsuya Uno, Takashi Okamoto, Yasuhito Ebara, Shin-ichi Ueji

    Bulletin of Chemical Society of Japan   76   399 - 403   2004

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    Language:English   Publishing type:Research paper (scientific journal)  

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  • Flexibility of lipase brought about by solvent effects controls its enantioselectivity in organic media Reviewed

    S Ueji, T Taniguchi, T Okamoto, K Watanabe, Y Ebara, H Ohta

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   76 ( 2 )   399 - 403   2003.2

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:CHEMICAL SOC JAPAN  

    The behavior of the enantioselectivity of Candida rugosa lipase was investigated in the esterification of 2-(4-substituted phenoxy)propionic acids with 1-butanol in aliphatic, aromatic, and ethereal solvents. The observed enantioselectivity (E value) was greatly affected by the solvent nature. Two key solvent characteristics, dielectric constant (E) and hydrophobicity (log P), failed to explain the solvent effects on the E value. On the other hand, the variation of the E value was found to be successfully correlated with the lipase flexibility brought about by the solvent effects, the flexibility of which was estimated by the ESR measurements of the spin-labeled lipase. Although organic chemists should often undertake a solvent screening step in the biocatalytic asymmetric resolutions, the obtained correlation will provide a useful guide in the solvent optimization step.

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  • Chemical modification of lipases with various hydrophobic groups improves their enantioselectivity in hydrolytic reactions Reviewed

    S Ueji, A Ueda, H Tanaka, K Watanabe, T Okamoto, Y Ebara

    BIOTECHNOLOGY LETTERS   25 ( 1 )   83 - 87   2003.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:KLUWER ACADEMIC PUBL  

    Semi-purified lipases from Candida rugosa, Pseudomonas cepacia and Alcaligenes sp. were chemically modified with a wide range of hydrophobic groups such as benzyloxycarbonyl, p-nitrobenzyloxycarbonyl, p-methoxybenzyloxycarbonyl, t-butoxycarbonyl, lauroyl and acetyl moieties. The Candida rugosa lipase MY modified with the benzyloxycarbonyl group (modification ratio = 84%) brought about a 15-fold increase in enantioselectivity (E value) towards the hydrolysis of racemic butyl 2-(4-ethylphenoxy) propionate in an aqueous buffer solution, although the enzymatic activity was decreased. The origin of the enantioselectivity enhancement by chemical modification of the lipase is attributed to a significant deceleration in the initial reaction rate for the incorrectly binding enantiomer.

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  • Effects of chiral additives on enantioselectivity for lipase-catalyzed esterifications in an organic solvent. A remarkable enhancement of its enantioselectivity due to cooperative effects of two kinds of additives Reviewed

    S Ueji, H Sakamoto, K Watanabe, T Okamoto, S Mori

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   75 ( 10 )   2239 - 2240   2002.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:CHEMICAL SOC JAPAN  

    The enantioselectivity for the lipase-catalyzed esterifications in an organic solvent was found to be enhanced by addition of (+)- or (-)-camphor as a chiral additive. A more remarkable enhancement of its enantioselectivity was brought about by the cooperative effects of two kinds of additives: (-)-camphor and water.

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  • A new method for improving the enantioselectivity of lipase-catalyzed hydrolysis in organic solvent containing a small amount of water in the presence of metal ions Reviewed

    T Okamoto, S Ueji

    BIOTECHNOLOGY LETTERS   22 ( 14 )   1169 - 1171   2000.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:KLUWER ACADEMIC PUBL  

    The hydrolysis of racemic butyl 2-(4-substituted phenoxy)propionates having various substituents catalyzed by lipase MY from Candida rugosa was achieved in di-isopropyl ether containing 0.75% (v/v) of 2.4 M LiCl or 1.2 M MgCl2 aqueous solution. Water molecules hydrated to the metal ion in isopropyl ether acted as a nucleophile to cause the hydrolysis of these esters as with water alone. Metal ions used significantly enhanced their enantioselectivities by 100-fold or above, as compared with the ordinary reaction media.

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  • Search for asymmetric reaction of amino acids by circularly polarized radiation using a polarizing undulator at the electrotechnical labolatory Reviewed

    The role of radiation in the origin and evolution of life   353 - 362   2000

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    Language:English   Publishing type:Research paper (scientific journal)  

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  • Drastic enhancement of the enantioselectivity of lipase-catalysed esterification in organic solvents by the addition of metal ions Reviewed

    T Okamoto, S Ueji

    CHEMICAL COMMUNICATIONS   ( 10 )   939 - 940   1999.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ROYAL SOC CHEMISTRY  

    By the addition of metal ion-containing water, a marked enhancement of the enantioselectivity for the lipase-catalysed esterification of 2-(4-substituted-phenoxy)propionic acids in (Pr2O)-O-i was observed, the mechanism of which will be discussed briefly on the basis of the initial rate obtained for each enantiomer of the substrate.

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Books

  • 「ニュースの科学用語これでわかった! ~180字で理解する、今さら聞けない科学と技術の基礎知識(共著)」

    技術評論社  2011 

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MISC

Presentations

  • サーモスペルミンとザイレミンを用いたシロイヌナズナ子葉の木部分化制御の解析

    日本植物学会第82回大会  2018 

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  • ヒトのH<SUP>+</SUP>-ATPaseの特異的阻害剤Omeprazoleはシロイヌナズナの根の機械的刺激感受性を高める

    第59回日本植物生理学会年会  2018 

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  • NEK6による微小管の張力応答の抑制はまっすぐな器官伸長に必要である

    日本植物生理学会第59回年会  2018 

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  • Omeprazole: a gastric H<SUP>+</SUP>-ATPase inhibitor, enhances sensitivity to mechanical stimulation in #IArabidopsis#IR roots.

    2018 

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  • NEK6 coordinates organ growth by the regulation of microtuble sensitivity to mechanical stress

    2018 

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  • シロイヌナズナNEK6はメカニカルシグナ ルを介した器官成長統御に関与する

    第58回日本植物生理学会年会  2017 

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  • 植物に機械的刺激を与える実験系を用いた機械的刺激感受・伝達に関わる因子の探索

    植物細胞骨格研究会  2017 

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  • Chemical Biology Approach to Dissect Root Morphology during Mechanical Stimulation in Arabidopsis thaliana

    2016 

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  • ケミカルバイオロジーによる植物の根への機械的刺激伝達に関わる因子の探索

    第57回日本植物生理学会年会  2016 

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  • 核燃料物質使用施設としての学内共同利用施設 -原子力規制庁及び国際原子力機関による立入検査への対応-

    日本アイソトープ協会 放射線安全取扱部会 中国・四国支部主任者研修会  2015 

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  • Chemical Biology Approach to Understand Root Morphology during Mechanical Stimulation in Arabidopsis thaliana

    Symposium on Interdisciplinary Researches in Okayama  2012 

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Research Projects

  • 植物の根の機械的刺激への応答機構に関する研究

    2021.09 - 2022.08

    公益財団法人 岡山工学振興会  公益財団法人 岡山工学振興会 萌芽研究助成  萌芽研究助成

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\350000 ( Direct expense: \350000 )

  • シロイヌナズナの機械的刺激の感受・伝達機構の解明に関する研究

    2019.10 - 2020.09

    公益財団法人 両備檉(てい)園記念財団  公益財団法人 両備檉(てい)園記念財団  研究助成  

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\350000 ( Direct expense: \350000 )

 

Class subject in charge

  • Introduction of Safety and Health (2021academic year) Fourth semester  - 金5~6

  • Biology (Cell Biology) (2021academic year) Second semester  - 木1~2

  • Biology (Cell Biology) (2020academic year) Second semester  - 木1,木2