Kouchi K, Takahashi H, Shimada Y
Department of Anatomy/Cell Biology, School of Medicine, Chiba University, Japan.
J Muscle Res Cell Motil. 1993 Jun;14(3):292-301. doi: 10.1007/BF00123094.
Incorporation of microinjected biotin-labelled actin into nascent myofibrils of cultured cardiac muscle cells was investigated by immunogold electron microscopy. At the proximal parts of myofibrils, gold labelling was first found (at about 4 min after injection) around the A-band level. This observation suggests that polymerization of actin or the addition of newly-formed actin filaments occurs preferentially in association with myosin filaments to increase the myofibrillar girth. The distal terminals of developing myofibrils were also labelled at about 4 min after injection. This rapid incorporation of actin subunits at the myofibrillar ends suggests the continued reorganization and/or de novo formation of myofibrils at these positions. Along the extending direction of the myofibrillar terminals, gold particles were arranged in rows on the inner surface of the sarcolemma. These rows of particles continued to become longer with incubation. It appears that actin subunits are added at the membrane-associated ends of pre-existing actin filaments to increase the length of myofibrils.
通过免疫金电子显微镜研究了微注射生物素标记的肌动蛋白掺入培养心肌细胞新生肌原纤维的情况。在肌原纤维的近端部分，首先在A带水平周围发现金标记（注射后约4分钟）。这一观察结果表明，肌动蛋白的聚合或新形成的肌动蛋白丝的添加优先与肌球蛋白丝相关联，以增加肌原纤维的周长。发育中肌原纤维的远端末端在注射后约4分钟也被标记。肌动蛋白亚基在肌原纤维末端的这种快速掺入表明这些位置的肌原纤维持续重组和/或从头形成。沿着肌原纤维末端的延伸方向，金颗粒排列在肌膜内表面的行中。随着孵育，这些颗粒行持续变长。似乎肌动蛋白亚基在预先存在的肌动蛋白丝的膜相关末端添加，以增加肌原纤维的长度。
