Redenbach D M, Ovalle W K, Bressler B H
Department of Anatomy, University of British Columbia, Vancouver, Canada.
Histochemistry. 1988;89(4):333-42. doi: 10.1007/BF00500634.
This study was designed to assess the changes in fiber-type distribution of the extensor digitorum longus (EDL) muscle of the mouse during the first 21 days of age following neonatal sciatic neurectomy. Denervated and normal muscles were compared at 7, 14, and 21 days of age and the normal EDL was also studied at 1 day of age. Frozen sections of the EDL were treated histochemically to detect NADH-tetrazolium reductase and myosin ATPase reactions. Quantitative assessment included measurements of cross-sectional areas and fiber counting. Denervation resulted in muscle atrophy which was due primarily to a decrease in individual fiber area as opposed to fiber loss. Histochemical maturation of the EDL was severely affected by neonatal denervation during the first three postnatal weeks. By 21 days, two extrafusal fiber types which were both oxidative could be distinguished. One type was highly atrophied and resembled an immature fiber exhibiting myosin ATPase staining at both acid and alkaline preincubation conditions, whereas another type was less atrophied and showed myosin ATPase staining resembling fast-twitch (type IIA) fibers. These findings emphasize the importance of an intact nerve supply in determining the phenotypic expression of skeletal muscle, and point to the early postnatal period as a critical stage in fiber type differentiation.
本研究旨在评估新生小鼠坐骨神经切断术后21天内，其趾长伸肌（EDL）纤维类型分布的变化。在7日龄、14日龄和21日龄时，对去神经支配的肌肉和正常肌肉进行比较，并在1日龄时对正常EDL进行研究。对EDL的冰冻切片进行组织化学处理，以检测NADH-四唑还原酶和肌球蛋白ATP酶反应。定量评估包括横截面积测量和纤维计数。去神经支配导致肌肉萎缩，这主要是由于单个纤维面积减小，而非纤维丢失。在出生后的前三周，新生去神经支配严重影响了EDL的组织化学成熟。到21日龄时，可以区分出两种均为氧化型的梭外纤维类型。一种类型高度萎缩，类似于在酸性和碱性预孵育条件下均显示肌球蛋白ATP酶染色的未成熟纤维，而另一种类型萎缩程度较轻，显示出类似于快肌（IIA型）纤维的肌球蛋白ATP酶染色。这些发现强调了完整神经供应在决定骨骼肌表型表达中的重要性，并指出出生后早期是纤维类型分化的关键阶段。
