Pierotti D J, Roy R R, Hodgson J A, Edgerton V R
Brain Research Institute, University of California, Los Angeles 90024-1761.
Muscle Nerve. 1994 Nov;17(11):1324-35. doi: 10.1002/mus.880171112.
Neuromuscular activity was eliminated in the tibialis anterior muscle of adult cats for 6 months by spinal isolation (SI), i.e., complete spinal cord transections at T-12-13 and at L-7-S-1, plus bilateral dorsal rhizotomy between the two transection sites. One motor unit from each muscle was isolated using ventral root teasing procedures and physiologically tested. The fibers belonging to each motor unit were visualized in PAS-stained sections by the loss of glycogen following prolonged repetitive stimulation. Qualitatively, the normal enzymatic interrelationships among fibers identified by myosin heavy chain composition were unchanged by SI. Generally, each motor unit from SI cats were of a single myosin immunohistochemical type. The same physiological motor unit types that typify control muscles were found in SI cats. In SI compared to control cats, there was approximately a 10% increase in the number of muscle fibers expressing fast myosin. Mean fiber activity levels of ATPase and SDH for a given fiber type (based on MHC antibody reactions) decreased by approximately 10% and 25%, whereas GPD activity increased approximately 35%. It is concluded that differential levels or patterns of activity are not essential to maintain the range of histochemical and physiological motor unit types found in the tibialis anterior of normal adult cats.
通过脊髓隔离（SI），即分别在T-12-13和L-7-S-1水平完全横断脊髓，并在两个横断部位之间进行双侧背根切断术，消除成年猫胫前肌的神经肌肉活动6个月。采用腹根分离法从每块肌肉中分离出一个运动单位并进行生理测试。通过长时间重复刺激后糖原的消失，在PAS染色切片中观察属于每个运动单位的纤维。定性地说，由肌球蛋白重链组成确定的纤维之间正常的酶学相互关系未因脊髓隔离而改变。一般来说，脊髓隔离猫的每个运动单位都属于单一的肌球蛋白免疫组织化学类型。在脊髓隔离猫中发现了与对照肌肉相同的典型生理运动单位类型。与对照猫相比，脊髓隔离猫中表达快肌球蛋白的肌纤维数量增加了约10%。给定纤维类型（基于MHC抗体反应）的ATPase和SDH平均纤维活性水平分别下降了约10%和25%，而GPD活性增加了约35%。得出的结论是，不同水平或模式的活动对于维持正常成年猫胫前肌中发现的组织化学和生理运动单位类型范围并非必不可少。
