Differences in the profile of unfused tetani of fast motor units with respect to their resistance to fatigue in the rat medial gastrocnemius muscle
Differences in the profile of unfused tetani of fast motor units with respect to their resistance to fatigue in the rat medial gastrocnemius muscle
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DOI：
10.1023/a:1005541013209
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发表时间：
1999-10-01
影响因子：
2.7
通讯作者：
Bichler, E
中科院分区：
文献类型：
--
作者：
Celichowski, J;Grottel, K;Bichler, E
在大多数对哺乳动物肌肉运动单位进行的研究中，将这些单位分为快型和慢型是基于未融合破伤风轮廓中可见的“下垂”。本研究分析了快速运动单位未融合强直的松弛时间过程。根据标准疲劳试验期间计算的疲劳指数，将大鼠内侧腓肠肌的快速单位分为快速疲劳（FF）或快速抗疲劳（FR）。在中度融合破伤风（融合指数0.25-0.75）中，观察到FF运动单位的下垂比FR单位更短且发生更早。此外，在FF单位，下垂后，增强张力，而FR单位，这种增强是较弱的，甚至没有。引入了强直形状指数，该指数表示强直记录的第一部分（张力记录和基线之间，从强直开始到张力记录中的下垂期间的最低点）的面积与强直记录的第二部分（从该最低点到记录结束）下的面积的比率。对于FF装置，该指数范围为0.13至0.47，而对于FR装置，该指数范围为0.54至17.8（有一个例外）。这些结果表明，在破伤风形状指数中表达的未融合破伤风的差异可用作将快速单元分为FF和FR组的准确替代方法。此外，FF和FR组的下垂时间过程的差异。此外，在FF和FR单位下垂的时间过程的差异表明，负责这种收缩现象的代谢是显着不同的时间过程中的IIa和IIb肌纤维，分别构成FF和FR单位。
In most studies performed on motor units in mammalian muscles the division of these units into fast and slow types has been based on the 'sag' visible in the profile of unfused tetanus. The time course of the sag in unfused tetani of fast motor units was analysed in the present study. Fast units of rat medial gastrocnemius muscle were classified as fast fatigable (FF) or fast resistant to fatigue (FR) on the basis of a fatigue index calculated during the standard fatigue test. In middle-fused tetani (fusion index 0.25-0.75), it was observed that for FF motor units the sag was shorter and occurred earlier than for FR units. Moreover, in FF units, the sag was followed by potentiating tension, whereas for FR units this potentiation was weaker or even absent. A tetanus shape index, which expressed the ratio of the area of the first part of the tetanus record (between the tension record and the baseline, from the beginning of tetanus up to the lowest point during the sag in the tension record) to the area under the second part of tetanus (from this lowest point up to the end of the record) was introduced. For FF units, this index ranged from 0.13 to 0.47, whereas for FR units it ranged from 0.54 to 17.8 (with one exception). These results showed that the difference in unfused tetanus expressed in this tetanus shape index could be used as an accurate alternative method of dividing fast units into FF and FR groups. Moreover, the difference in sag time course in FF and FR groups. Moreover, the difference in sag time course in FF and FR units suggests that the metabolism responsible for this contractile phenomenon is significantly different time courses in IIa and IIb muscle fibres, constituting FF and FR units, respectively.