Contractility and ultrastructure in glycerol--extracted muscle fibers. I. The relationship of contractility to sarcomere length.
Contractility and ultrastructure in glycerol--extracted muscle fibers. I. The relationship of contractility to sarcomere length.
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DOI：
10.1083/jcb.27.1.25
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发表时间：
1965-10
期刊：
影响因子：
--
通讯作者：
Knappeis GG
中科院分区：
文献类型：
--
作者：
Carlsen F;Fuchs F;Knappeis GG
这项研究的目的是确定甘油提取的兔腰肌纤维在被拉伸到初级和次级肌丝不再重叠的长度后是否会产生张力和缩短。设计了一种方法来测量预拉伸的分离纤维中初始肌节长度和 ATP 诱导的等张缩短，该纤维受到小预载荷（0.02 至 0.15 P 0）。在所有拉伸程度下，纤维都能缩短（60％至75％）：当初始长度为3.7μ或更小时，肌节长度缩短至0.7μ，随着初始肌节长度的增加（3.8μ至4.4μ），长度增加至0.9μ至1.8μ。通过电子显微镜证实，在肌节长度为 3.8 至 4.5 µ 时，肌丝的重叠消失。通过光学和电子显微镜测量来评估单根纤维内肌节长度的变化。在长度达 10 毫米的纤维中，拉伸沿纤维均匀分布，并且当肌节间距大于 4 µ 时，只有很小的机会发现肌节与细丝重叠。这些观察结果显然与 A 丝和 I 丝重叠对于张力产生和缩短是必要的假设相矛盾。
This study was undertaken to determine whether glycerol-extracted rabbit psoas muscle fibers can develop tension and shorten after being stretched to such a length that the primary and secondary filaments no longer overlap. A method was devised to measure the initial sarcomere length and the ATP-induced isotonic shortening in prestretched isolated fibers subjected to a small preload (0.02 to 0.15 P 0). At all degrees of stretch, the fiber was able to shorten (60 to 75 per cent): to a sarcomere length of 0.7 µ when the initial length was 3.7 µ or less, and to an increasing length of 0.9 to 1.8 µ with increasing initial sarcomere length (3.8 to 4.4 µ). At sarcomere lengths of 3.8 to 4.5 µ, overlap of filaments was lost, as verified by electron microscopy. The variation in sarcomere length within individual fibers has been assessed by both light and electron microscopic measurements. In fibers up to 10 mm in length the stretch was evenly distributed along the fiber, and with sarcomere spacings greater than 4 µ there was only a slight chance of finding sarcomeres with filament overlap. These observations are in apparent contradiction to the assumption that an overlap of A and I filaments is necessary for tension generation and shortening.