Bishop Derron L, Milton Richard L
E. F. Ball Medical Education Center, 221 North Celia Avenue, Muncie, Indiana 47303, USA.
Muscle Nerve. 2002 Dec;26(6):791-7. doi: 10.1002/mus.10270.
To investigate the processes by which motoneurons control protein synthesis, and thus the ultrastructure of the muscle fibers they innervate, ectopic endplates were induced to form on adult mouse skeletal muscle fibers by transplantation of a foreign nerve onto the muscle. In the dually innervated muscle fibers thus created, we examined two ultrastructural parameters that correlate with the expression of distinct isoforms of the myofibrillar proteins alpha-actinin and titin, specifically, Z-line width and sarcomere length. It was found that Z-lines were significantly thinner (98 vs. 128 nm) and sarcomeres were significantly shorter (1.69 vs. 2.06 microm) near the ectopic than near the original endplates. Thus, ectopic endplate formation on adult skeletal muscle fibers induces a localized alteration in myofibrillar morphology. These results may help to elucidate the role played by motoneurons in the determination and maintenance of muscle fiber properties and the processes that occur following muscle reinnervation after nerve injury.
为了研究运动神经元控制蛋白质合成的过程，进而研究其支配的肌纤维的超微结构，通过将一条异体神经移植到成年小鼠骨骼肌纤维上，诱导异位终板在其上形成。在由此产生的双重支配的肌纤维中，我们检测了两个与肌原纤维蛋白α -辅肌动蛋白和肌联蛋白不同亚型表达相关的超微结构参数，即Z线宽度和肌节长度。结果发现，与原始终板附近相比，异位终板附近的Z线显著更窄（98纳米对128纳米），肌节显著更短（1.69微米对2.06微米）。因此，成年骨骼肌纤维上异位终板的形成会引起肌原纤维形态的局部改变。这些结果可能有助于阐明运动神经元在决定和维持肌纤维特性以及神经损伤后肌肉重新支配后发生的过程中所起的作用。
