Davidowitz J, Rubinson K, Onejeme A
Department of Ophthalmology, New York University Medical Center, NY 10016, USA.
Tissue Cell. 2000 Aug;32(4):336-50. doi: 10.1054/tice.2000.0114.
In a previous study of myofibril size in 'Pale' (fast-twitch-glycolytic) fibers of rabbit extraocular muscle (EOM), it was found that individual long Pale fibers demonstrate a substantial increase in the size of myofibril profiles from their proximal to their distal halves (Davidowitz et al., 1996b). That finding raised the question of whether such proximal-to-distal increase of myofibril size in the Pale fibers is determined by: (1) longitudinal position within the individual muscle fibers themselves or (2) location along the length of the muscle as a whole? This question was tested in the present study by comparing the original group of long Pale fibers, which extend the full length of the muscle, with two groups of short Pale fibers, which are respectively confined to the proximal and distal halves of the muscle. It was found that (a) in the proximal half of the muscle, the short fibers and the adjacent portions of the long fibers have the same smaller size of myofibrils, and (b) in the distal half of the muscle, the short fibers and the adjacent portions of the long fibers have the same larger size of myofibrils. This finding indicates that the proximal-to-distal increase of myofibril-profile size in these EOM Pale fibers is determined by location along the length of the muscle as a whole, and is not related to longitudinal position within the individual fibers themselves.
在之前一项关于兔眼外肌（EOM）“苍白”（快肌糖酵解型）纤维肌原纤维大小的研究中，发现单个长的苍白纤维从其近端到远端，肌原纤维轮廓大小显著增加（Davidowitz等人，1996b）。这一发现引发了一个问题，即苍白纤维中肌原纤维大小的这种近端到远端的增加是由以下哪种因素决定的：（1）单个肌纤维自身内部的纵向位置，还是（2）整个肌肉长度上的位置？在本研究中，通过将一组贯穿肌肉全长的原始长苍白纤维与两组分别局限于肌肉近端和远端的短苍白纤维进行比较，对这个问题进行了验证。结果发现：（a）在肌肉的近端，短纤维和长纤维的相邻部分具有相同的较小肌原纤维大小；（b）在肌肉的远端，短纤维和长纤维的相邻部分具有相同的较大肌原纤维大小。这一发现表明，这些眼外肌苍白纤维中肌原纤维轮廓大小从近端到远端的增加是由整个肌肉长度上的位置决定的，与单个纤维自身内部的纵向位置无关。
