Bartnik E, Weber K
Max Planck Institute for Biophysical Chemistry, Göttingen, Federal Republic of Germany.
Eur J Cell Biol. 1988 Feb;45(2):291-301.
The body muscle cells of the nematode Ascaris lumbricoides are characterized by massive amounts of intermediate filaments (IF). These occur in all three regions of this giant cell type. They traverse the cytoplasm of the balloon-like belly, which houses the nucleus, and occur as bundles in the arm-like extensions to the nerve. The organization of IF in the third region, the contractile fiber, was analyzed further by serial sections and three-dimensional reconstruction. IF bundles traverse the glycogen-rich lumina of the fiber and reach as baskets around the sarcomeres. Together with numerous dense bodies they form the Z-band-like arrangements. IF bundles reach the plasma membrane at hemidesmosome-like specializations often situated at deep membrane invaginations filled with a fibrillar component of the extracellular matrix. The ultrastructural appearance of IF bundles is connected to the contractional state of the sarcomeres. They appear straight in extended muscle but coil up upon contraction. In the pharynx massive IF bundles are oriented longitudinally. A second type of IF bundles follows the radially oriented sarcomeres. These reveal pronounced Z-band type structures with massive disks. IF surround the sarcomeres and seem to terminate at these disks. We discuss possible functions of the complex IF organization in body muscle and pharynx.
蛔虫（Ascaris lumbricoides）的体肌细胞以大量中间丝（IF）为特征。这些中间丝存在于这种巨型细胞类型的所有三个区域。它们穿过容纳细胞核的气球状腹部的细胞质，并以束状形式存在于伸向神经的臂状延伸部分。通过连续切片和三维重建进一步分析了中间丝在第三个区域（收缩纤维）的组织情况。中间丝束穿过纤维中富含糖原的腔，并像篮子一样围绕着肌节。它们与众多致密体一起形成类似Z带的排列。中间丝束在通常位于充满细胞外基质纤维成分的深膜内陷处的半桥粒样特化结构处到达质膜。中间丝束的超微结构外观与肌节的收缩状态相关。它们在伸展的肌肉中看起来是直的，但在收缩时会盘绕起来。在咽中，大量中间丝束纵向排列。第二种中间丝束沿着径向排列的肌节分布。这些显示出带有大量盘状结构的明显的Z带型结构。中间丝围绕着肌节，似乎在这些盘状结构处终止。我们讨论了身体肌肉和咽中复杂的中间丝组织的可能功能。
