著者

最上 善広

出版者

一般社団法人 日本航空宇宙学会

雑誌

日本航空宇宙学会誌 (ISSN:00214663)

巻号頁・発行日

vol.47, no.551, pp.283-287, 1999-12-05 (Released:2019-04-09)

参考文献数

14

著者

宮本 泰則 石川 祐希 最上 善広 Miyamoto Yasunori Ishikawa Yuki Mogami Yoshihiro

出版者

宇宙航空研究開発機構宇宙科学研究本部

雑誌

宇宙利用シンポジウム 第24回 平成19年度 = Space Utilization Research: Proceedings of the Twenty-fourth Space Utilization Symposium

巻号頁・発行日

pp.236-237, 2008-03

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資料番号: AA0063706061

著者

最上 善広

出版者

お茶の水女子大学

雑誌

基盤研究(C)

巻号頁・発行日

2011

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運動活性と酸素消費の同時測定を応用し、単細胞生物繊毛虫での「基礎代謝」を特定し、単細胞生物での、アロメトリー理論の生物界全般への普遍性の検証を行った。ゾウリムシに対して,コンピューター・トモグラフィーによる細胞重量の推定方法を適用することによって,細胞咽頭による餌の取り込みに依存するアイソメトリー関係と,細胞表面からの酸素の流入に依存するアロメトリー関係のふたつの基礎理論が導入された。測定精度を向上し,より精密な理論予測の検証を行うことで、アロメトリー理論の普遍性が検証される方向性が確立された。

著者

最上 善広 石井 淳子 馬場 昭次

出版者

日本宇宙生物科学会

雑誌

Biological Sciences in Space (ISSN:09149201)

巻号頁・発行日

vol.9, no.1, pp.17-35, 1995 (Released:2006-02-01)

参考文献数

28

被引用文献数

4 3

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In order to get an insight into the cellular mechanisms for the integration of the effects of gravity,we investigated the gravitactic behaviour in Paramecium. There are two main categories for the model of the mechanism of gravitaxis; one is derived on the basis of the mechanistic properties of the cell (physical model) and the other of the physiological properties including cellular gravireception (physiological model). In this review article, we criticized the physical models and introduced a new physiological model. Physical models postulated so far can be divided into two; one explaining the negative gravitactic orientation of the cell in terms of the static torque generated by the structural properties of the cell (gravity-buoyancy model by Verworn, 1889 and drag-gravity model by Roberts, 1970), and the other explaining it in terms of the dynamic torque generated by the helical swimming of the cell (propulsion-gravity model by Winet and Jahn, 1974 and lifting-force model by Nowakowska and Grebecki, 1977). Among those we excluded the possibility of dynamic-torque models because of their incorrect the oretical assumptions. According to the passive orientation of Ni2+-immobilized cells, the physical effect of the static torque should be inevitable for the gravitactic orientation. Downward orientation of the immobilized cells in the course of floating up in the hyper-density medium demonstrated the gravitactic orientation is not resulted by the nonuniform distribution of cellular mass (gravity-buoyancy model) but by the for-aft asymmetry of the cell (drag-gravity model). A new model explaining the gravitactic behaviour is derived on the basis of the cellular gravity sensation through mechanoreceptor channels of the cell membrane. Paramecium is known to have depolarizing receptor channels in the anterior and hyperpolarizing receptors in the posterior of the cell. The uneven distribution of the receptor may lead to the bidirectional changes of the membrane potential by the selective deformation of the anterior and posterior cell membrane responding to the orientation of the cell in the gravity field; i.e. negative- and positive-going shift of the potential due to the upward and downward orientation, respectively. The orientation dependent changes in membrane potential with respect to gravity, in combination with the close coupling of the membrane potential and the ciliary locomotor activity, may allow the changes in swimming direction along with those in the helical nature of the swimming path; upward shift of axis of helix by decreasing the pitch angle due to hyperpolarization in the upward-orienting cell, and also the upward shift by increasing the pitch angle due to depolarization in the downward-orienting cell. Computer simulation of the model demonstrated that the cell can swim upward along the “super-helical” trajectory consisting of a small helix winding helically an axis parallel to the gravity vector, after which the model was named as “super-helix model”. Three-dimensional recording of the trajectories of the swimming cells demonstrated that about a quarter of the cell population drew super-helical trajectory under the unbounded, thermal convection-free conditions. In addition, quantitative analysis of the orientation rate of the swimming cell indicated that gravity-dependent orientation of the swimming trajectory could not be explained solely by the physical static torque but complementarily by the physiological mechanism as proposed in the super-helix model.