CHANGES IN PROPERTIES OF THE MEDIAL GASTROCNEMIUS MOTOR UNITS IN AGING RATS
CHANGES IN PROPERTIES OF THE MEDIAL GASTROCNEMIUS MOTOR UNITS IN AGING RATS
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DOI：
10.1152/jn.1989.61.4.737
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发表时间：
1989-04-01
影响因子：
2.5
通讯作者：
HASHIZUME, K
中科院分区：
文献类型：
--
作者：
KANDA, K;HASHIZUME, K
1. 研究了老年大鼠内侧腓肠肌 (MG) 的运动单位特性 [27.5 +/- 1.6 (SD) 月龄，n = 18]。通过腹根纤维分裂和分级刺激强度在功能上隔离各个运动单位。运动单位的肌肉单位部分通过糖原消耗法进行鉴定。将 6 只动物的 77 个运动单位的生理特性和 7 个慢肌单位（S 型）的组织学结果与中年大鼠（12.8 +/- 1.6 月龄，n = 33）同一肌肉的运动单位的数据进行比较。 2.使用相同的标准将运动单位分为四种类别[FF（疲劳指数小于或等于0.5的快肌运动单位）、FI（疲劳指数大于0.5但小于0.75的快肌运动单位）、FR（疲劳指数大于或等于0.75的快肌运动单位）、S（疲劳指数大于0.75的慢肌运动单位）] （即是否存在“下垂”特性和疲劳性）用于中年大鼠。尽管老年大鼠的 MG 肌肉表现出相对较高比例的 S 型单位和较少的 FR 型单位，但未检测到这些单位类型的相对分布存在显着差异。 3.FF+FI型和FR型单位的平均强直张力显着小于中年组大鼠。另一方面，S型运动单位比中年大鼠产生更多的张力。 4.旧运动单元的任何单元类型中运动轴突的传导速度都显着变慢，并且在FR型单元中发现最显着的变化。 5.老年大鼠MG的一般形态特征为纤维型成群，纤维呈播散性萎缩或成角，肌纤维总数减少，I型肌纤维数量增多。不同类型纤维的主要分布模式与中年MG相同。 6.产生大强直张力的七个S型单元的肌肉单元部分中的糖原被耗尽。与中年大鼠相比，这些单位具有较大的神经支配比率，而肌纤维的平均横截面积和计算的比张力保持不变。（摘要截断为400字）
1. The properties of motor units were investigated in the medial gastrocnemius (MG) of old rats [27.5 +/- 1.6 (SD) mo old, n = 18]. Individual motor units were functionally isolated by ventral root fiber splitting and grading stimulus intensity. The muscle-unit portion of the motor unit was identified by the glycogen depletion method. The physiological properties of 77 motor units in 6 animals and the histological results of 7 slow-twitch (type S) muscle units were compared with data from motor units in the same muscle of middle-aged rats (12.8 +/- 1.6 mo old, n = 33). 2. The motor units were classified into four types of categories [FF (fast-twitch motor units with a fatigue index less than or equal to 0.5), FI (fast-twitch motor units with a fatigue index greater than 0.5 but less than 0.75), FR (fast-twitch motor units with a fatigue index greater than or equal to 0.75), S (slow-twitch motor units with a fatigue index greater than 0.75)] using the same criteria (i.e., presence or absence of the "sag" property and fatigability) used for middle-aged rats. No significant difference in the relative distributions of these unit types was detected, although the MG muscle in old rats exhibited a relatively high proportion of type S units and fewer type FR units. 3. The mean tetanic tensions for type FF + FI and FR units were significantly smaller than those in the middle-aged rats. On the other hand, type S motor units produced more tension than in the middle-aged rats. 4. The conduction velocity of motor axons was considerably slower in any unit type of old motor units, and the most marked change was found in type FR units. 5. The general morphological features of the old rat MG were fiber-type grouping, disseminated atrophic or angulated fibers, a decrease in the total number of muscle fibers, and an increase in the number of type I muscle fibers. The major distribution patterns of fibers of different types were the same as those in the middle-aged MG. 6. Seven type S units that produced large tetanic tension were depleted of glycogen in the muscle-unit portions. These units had a large innervation ratio compared with those in the middle-aged rats, whereas the mean cross-sectional area of muscle fibers and the calculated specific tension remained unaltered.(ABSTRACT TRUNCATED AT 400 WORDS)