Salviati G, Betto R, Ceoldo S, Pierobon-Bormioli S
Consiglio Nazionale delle Ricerche Centro di Studio per la Biologia e la Fisiopatologia Muscolare, Università di Padova, Italy.
Am J Physiol. 1990 Jul;259(1 Pt 1):C144-9. doi: 10.1152/ajpcell.1990.259.1.C144.
The elastic filament was studied in chemically skinned fibers from rabbit psoas muscle by electron microscopy and resting tension measurements. Extraction of skinned fibers with 40 mM sodium pyrophosphate caused a selective removal of about two-thirds of the thick filaments and formed a gap between the remaining portion of the A band and the I band. Very thin filaments were seen in the gap and were decorated by anti-titin antibody. The resting tension of these fibers was comparable to that of unextracted control fibers. When the M band was completely extracted by a solution containing 0.6 M NaCl, the resting tension completely disappeared at sarcomere lengths from 2.8 to approximately 3.4 microns. These results suggest that the elastic force of short sarcomeres is endowed in the titin filaments and that these filaments are anchored to some structures of the Z and M lines. Other filaments were found in the gap between the two I bands of NaCl-extracted sarcomeres. These filaments differed from titin filaments by a larger diameter and the anchoring points. They may represent the sarcomeric structures responsible for the resting tension of extracted fibers stretched at sarcomere lengths longer than 3.4 microns.
通过电子显微镜和静息张力测量，对来自兔腰大肌的化学去膜纤维中的弹性丝进行了研究。用40 mM焦磷酸钠提取去膜纤维导致约三分之二的粗丝被选择性去除，并在A带的剩余部分和I带之间形成间隙。在间隙中可见非常细的丝，并用抗肌联蛋白抗体进行标记。这些纤维的静息张力与未提取的对照纤维相当。当用含有0.6 M NaCl的溶液完全提取M带时，在肌节长度从2.8到约3.4微米时静息张力完全消失。这些结果表明，短肌节的弹力赋予肌联蛋白丝，并且这些丝锚定在Z线和M线的某些结构上。在NaCl提取的肌节的两个I带之间的间隙中发现了其他丝。这些丝与肌联蛋白丝的不同之处在于直径更大和锚定点不同。它们可能代表了在肌节长度大于3.4微米时被拉伸的提取纤维的静息张力所涉及的肌节结构。
