被动收缩所致家兔肌肉早期僵硬及其超微结构的变化

动物实验表明,肌肉工作引起早期肌僵硬的过程中有突变与持续性。僵硬后即刻与24小时该肌肌节长度与对照肌相比明显缩短,肌原纤维排列规则,说明处于放松不全(痉挛)状态;48、72小时肌原纤维排列紊乱,出现“Z线流”,肌核见明显切迹,染色质弥散,出现中位核。0—72小时均见肌纤维间隙增宽,显示水肿。

THE STUDY OF EARLY MUSCLE STIFFNESS AND THE CHANGES OF ITS ULTRASTRUCTURE INDUCED BY ELECTRICAL STIMULATION IN RABBITS

Early muscle stiffness and the changes of its ultrastructure induced by passive contraction, were investigated in 21 adult rabbits,1) Muscles and nerves of posterior thigh were stimulated by a train of square impulses with the duration of 0.1-0.3 ms at 66 Hz for 0.5 sec. Muscles contracted isometrically and tetanically-3h/trial continued 4 or 5 times until muscle stiffness appeared. The force-displacement meter was applied to record force-displacement curve, and its integral value was obtained as an indicator of muscle stiffness. 2) Muscle needle biopsy for EM was examined both in the intervals of 0h, 24h, 48h, 72h after appearance of stiffness.The results of the integral value of force-displacement curve showed that the early muscle stiffness could be induced in all animals by electrical stimulation usually during the 4th or 5th trial. The average stiffness index (H) by our designation was greater than 1.96 S. D., and remained for lh after the stimulation was stopped (H>2.58 S. D.). The progress of early muscle stiffness was characterized by a sudden change and was maintainable. With EM, the sarcomere of stiffened muscles was significantly shorter than that of non-stimulated legs at 0h (P<0.05) and 24h (P<0.005) after stiffness appeared, indicating that myofibers were in "spasm". Moreover, edema of interfibers was seen from 0h-72h after stiffness.From these findings, it is in our opinion that spasm of myofibers may be one of the main reasons causing muscle stiffness.