SUGAWARA Michiko Department of Mechanical Engineering, Tohoku University, Research Associate, 大学院・工学研究科, 助手 (30323041)
IKEDA Katsuhisa Tohoku University, School of Medicine, Assistant Professor, 大学院・医学系研究科, 助教授 (70159614)
TAKASAKA Tomonori Tohoku University, School of Medicine, Professor, 大学院・医学系研究科, 教授 (80004646)
|Budget Amount *help
¥38,800,000 (Direct Cost: ¥38,800,000)
Fiscal Year 2000: ¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 1999: ¥35,300,000 (Direct Cost: ¥35,300,000)
Although the amplitude of the tympanic membrane vibrations is only a few nanometers when we speak in a low voice, we can understand clearly what is being said. This is speculated to be due to the cochlear amplification which is based on the outer hair cell (OHC) motility, and the motility is estimated to be due to the conformational change of motor proteins within the plasma membrane of the cell. However, the function of the motor protein is unclear, and the effect of the cytoskeleton, which underlies the plasma membrane, on the motility of the cell has not been clarified yet.
Therefore, in this study, in order to understand the function of the cell, the deformations of the cell in response to the hypotonic stimulation and the motility of the cell in response to the electrical stimulation are analyzed. Moreover, the ultrastructure of the cell lateral wall is investigated by atomic force microscopy (AFM), and the mechanism of the outer hair cell motility is studied. When the position along the cell axis is represented by the normalized distance from the basal end and the positions of the basal and apical ends are expressed by 0.0 and 1.0, respectively, the following conclusions can be drawn.
(1) The longitudinal stiffness of the cell is constant in the region between 0.0 and 0.881 from the basal end, and the stiffness of the cell in the region between 0.881 and 1.0 from the basal end is higher than that in other regions.
(2) The distribution of the protein motor along the cell axis is constant in the region between 0.142 and 0.893, and in the other regions at the apical and basal parts of the cell, the protein motor does not exist.
(3) The circumferential filaments, which would be actins in the cortical lattice, are observed by AFM, and the density of the circumferential filaments at the apical part, where the stiffness is high, is higher than that at the basal part.