Edds K T
J Cell Biol. 1975 Jul;66(1):156-64. doi: 10.1083/jcb.66.1.156.
Echinosphaerium nucleofilum exhibits at least three kinds of movement: locomotion by the bending and shortening of its many axopodia, feeding by means of food-cup pseudopodia formed from its cortical cytoplasm, and saltatory motion of cytoplasmic particles, especially in the cortex and axopodia. Since previously presented evidence indicated that the microtubular axoneme is not essential for particle motion, the cytoplasm was investigated for the possible existence of contractile behavior and for the possible presence of linear elements other than microtubules. Cytoplasm can be isolated in physiological media in which rigor, relaxation, and contraction can be induced, as in muscle, by manipulating the concentrations of calcium ions and magnesium-adenosine triphosphate. Contraction is initiated by calcium ions at concentrations above 2.4 times 10-minus 7 M. The rigor-to-relaxation transition occurs at subthreshold calcium concentrations on the addition of 10-minus 3 M ATP. Negatively stained preparations of isolated cytoplasm show two types of filaments: thin filaments identified as cytoplasmic actin by virtue of their binding heavy meromyosin from striated muscle in characteristic arrowhead arrays, and thicker filaments which do not strictly resemble myosin aggregates from muscle or amoeba but could conceivably by myosin aggregated in an unfamiliar form.
通过其许多轴伪足的弯曲和缩短进行移动，借助由其皮质细胞质形成的食物杯伪足进行摄食，以及细胞质颗粒的跳跃运动，尤其是在皮质和轴伪足中。由于先前提出的证据表明微管轴丝对于颗粒运动并非必不可少，因此对细胞质进行了研究，以寻找收缩行为的可能存在以及除微管之外的线性元件的可能存在。细胞质可以在生理介质中分离出来，在这种介质中，通过操纵钙离子和镁 - 三磷酸腺苷的浓度，可以像在肌肉中一样诱导僵直、松弛和收缩。当钙离子浓度高于2.4×10⁻⁷ M时引发收缩。在添加10⁻³ M三磷酸腺苷时，在亚阈值钙浓度下发生从僵直到松弛的转变。分离出的细胞质的负染制剂显示出两种类型的细丝：细的细丝通过其与横纹肌中的重酶解肌球蛋白以特征性箭头状排列结合而被鉴定为细胞质肌动蛋白，以及较粗的细丝，它们与肌肉或变形虫中的肌球蛋白聚集体并不严格相似，但可以想象是肌球蛋白以一种不常见的形式聚集而成。
