Pollard T D, Ito S
J Cell Biol. 1970 Aug;46(2):267-89. doi: 10.1083/jcb.46.2.267.
The role of filaments in consistency changes and movement in a motile cytoplasmic extract of Amoeba proteus was investigated by correlating light and electron microscopic observations with viscosity measurements. The extract is prepared by the method of Thompson and Wolpert (1963). At 0 degrees C, this extract is nonmotile and similar in structure to ameba cytoplasm, consisting of groundplasm, vesicles, mitochondria, and a few 160 A filaments. The extract undergoes striking ATP-stimulated streaming when warmed to 22 degrees C. Two phases of movement are distinguished. During the first phase, the apparent viscosity usually increases and numerous 50-70 A filaments appear in samples of the extract prepared for electron microscopy, suggesting that the increase in viscosity in caused, at least in part, by the formation of these thin filaments. During this initial phase of ATP-stimulated movement, these thin filaments are not detectable by phase-contrast or polarization microscopy, but later, in the second phase of movement, 70 A filaments aggregate to form birefringent microscopic fibrils. A preparation of pure groundplasm with no 160 A filaments or membranous organelles exhibits little or no ATP-stimulated movement, but 50-70 A filaments form and aggregate into birefringent fibrils. This observation and the structural relationship of the 70 A and the 160 A filaments in the motile extract suggest that both types of filaments may be required for movement. These two types of filaments, 50-70 A and 160 A, are also present in the cytoplasm of intact amebas. Fixed cells could not be used to study the distribution of these filaments during natural ameboid movement because of difficulties in preserving the normal structure of the ameba during preparation for electron microscopy.
通过将光学显微镜和电子显微镜观察结果与粘度测量结果相关联，研究了丝状结构在变形虫（Amoeba proteus）可运动细胞质提取物的稠度变化和运动中的作用。提取物采用汤普森（Thompson）和沃尔珀特（Wolpert，1963年）的方法制备。在0摄氏度时，这种提取物不具有运动性，其结构与变形虫细胞质相似，由基质、囊泡、线粒体和一些160埃的细丝组成。当加热到22摄氏度时，提取物会发生显著的ATP刺激的流动。运动分为两个阶段。在第一阶段，表观粘度通常会增加，并且在用于电子显微镜观察的提取物样品中会出现许多50 - 70埃的细丝，这表明粘度的增加至少部分是由这些细丝的形成引起的。在ATP刺激运动的初始阶段，通过相差显微镜或偏光显微镜无法检测到这些细丝，但在运动的第二阶段，70埃的细丝会聚集形成双折射的微观纤维。不含160埃细丝或膜性细胞器的纯基质制剂几乎没有或没有ATP刺激的运动，但50 - 70埃的细丝会形成并聚集成为双折射纤维。这一观察结果以及可运动提取物中70埃和160埃细丝的结构关系表明，两种类型的细丝可能都是运动所必需的。这两种类型的细丝，50 - 70埃和160埃，也存在于完整变形虫的细胞质中。由于在制备用于电子显微镜观察的样品时难以保持变形虫的正常结构，因此不能使用固定细胞来研究这些细丝在自然变形运动过程中的分布。
