Don W. Fawcett, F. D. Warner, D. R. Mitchell, P. Satir (2011) CIL:11627, Tetrahymena sp. SPE01, Elliptio crassidens, ciliated cell, ciliated epithelial cell. CIL. Dataset

Figure 320 & 321 from Chapter 13 (Cilia and Flagella) of 'The Cell' by Don W. Fawcett M.D. The disposition of the dynein arms along the length of the doublets is studied to best advantage in dissociated cilia examined with negative staining. The upper figures show parts of three overlapping doublets from a demembranated cilium disintegrated in the presence of ATP. The second figure is a reinforced image of the same micrograph produced by a two-step linear translation. Free dynein arms can be seen projecting from the lowermost doublet at intervals of 24 nm along its length. Somewhat less clearly shown are arms bridging the interspaces between the three doublets. During active sliding, the space between doublets is considerably less than that usually seen in electron micrographs of thin cross sections. The microtubule sliding responsible for ciliary bending is believed to be due to attachment of arms on subunit A of one doublet to subunit B of the adjacent doublet followed by a conformational change resulting in arm deflection.
The second set of figures are a thin longitudinal section of a cilium showing the radial spokes joining subunit A of a doublet to a row of projections along one of the central pair of microtubules. The spokes occur in groups of three with a repeat of 86 nm. The second figure is a reinforced image of the same micrograph resulting from linear translation in steps corresponding to 86nm between successive exposures. A copy of the chapter is available on the ASCB's BioEDUCATE website.

图320与321分别来自《细胞》一书中第13章（纤毛和鞭毛）的内容，由Don W. Fawcett M.D.所著。本研究旨在探究双微管沿其长度方向上的动力臂分布，最佳观察方式为通过负染色技术对解离后的纤毛进行观察。上图中展示了由ATP存在下解离的脱膜纤毛的三重叠双微管的部分。第二图是对同一显微照片通过两步线性转换加强后的图像。可以观察到自由的动力臂从最底部的双微管底部以24纳米的间隔向外延伸。在三个双微管之间的间隔中，连接这些间隔的动力臂也显示得相对模糊。在活跃滑动过程中，双微管之间的空间相较于在电子显微镜下观察到的薄横切面的空间要小得多。负责纤毛弯曲的微管滑动被认为是由一个双微管的亚基A与相邻双微管的亚基B的附着，随后通过构象变化导致动力臂偏转的结果。第二组图像为纤毛的纵向薄切片，展示了连接双微管的亚基A至中央一对微管上的投影行的辐射辐条。辐条以86纳米的重复率以三组的形式出现。第二图是对同一显微照片通过线性转换加强后的图像，转换步骤与连续曝光之间的86纳米间隔相对应。该章节的副本可在ASCB的BioEDUCATE网站上找到。