Roy R R, Talmadge R J, Hodgson J A, Oishi Y, Baldwin K M, Edgerton V R
Brain Research Institute, UCLA School of Medicine, Center for the Health Sciences, Los Angeles, California 90095-1761, USA.
Muscle Nerve. 1999 Feb;22(2):230-41. doi: 10.1002/(sici)1097-4598(199902)22:2<230::aid-mus11>3.0.co;2-r.
Adult cats were spinal transected (T12-13) and maintained for approximately 6 months. Spinal cats were either not trained (N-T) or trained for 30 min/day to either step on a treadmill (Stp-T) or stand (Std-T). Spinalization resulted in a decrease in the mass and maximum tension potential of the medial gastrocnemius (MG), a fast ankle extensor. These adaptations were ameliorated in Std-T but not Stp-T cats. The maximum rate of shortening was elevated by 18 (ns), 34, and 19 (ns)% in the N-T, Std-T, and Stp-T cats, respectively, a finding consistent with a shift in the percentage of fast fibers, a decrease in the percentage of fibers expressing only type I myosin heavy chain, and an increase in myofibrillar adenosine triphosphatase activity. The shift toward a faster fiber type profile in the tibialis anterior (TA), a fast ankle flexor, was of a lesser magnitude than in the MG. There were no significant effects on the contractile properties of the TA in any group of spinal cats. The greater preservation of muscle mass, shift toward faster physiological and biochemical properties, and fatigability in the MG of Std-T than Stp-T cats suggest that factors other than the level of activation and force generation must play a role in muscle homeostasis. From a clinical perspective, the results indicate that muscles innervated by motor neurons below the level of a complete spinal cord lesion are affected differentially by specific neuromuscular activity patterns.
成年猫进行T12 - 13节段脊髓横断，并维持约6个月。脊髓损伤的猫要么不接受训练（N - T），要么每天训练30分钟，分别在跑步机上行走（Stp - T）或站立（Std - T）。脊髓横断导致快速踝关节伸肌内侧腓肠肌（MG）的质量和最大张力潜能下降。这些适应性变化在Std - T组猫中得到改善，但在Stp - T组猫中未得到改善。N - T、Std - T和Stp - T组猫的最大缩短速率分别提高了18（无显著性差异）、34和19（无显著性差异）%，这一结果与快肌纤维百分比的变化、仅表达I型肌球蛋白重链的纤维百分比的降低以及肌原纤维三磷酸腺苷酶活性的增加一致。快速踝关节屈肌胫骨前肌（TA）向更快纤维类型特征的转变幅度小于MG。在任何一组脊髓损伤的猫中，对TA的收缩特性均无显著影响。与Stp - T组猫相比，Std - T组猫的MG肌肉质量保存更好、向更快的生理和生化特性转变以及疲劳性更高，这表明除了激活水平和力量产生之外，其他因素也必须在肌肉稳态中发挥作用。从临床角度来看，结果表明，在完全性脊髓损伤水平以下由运动神经元支配的肌肉，会受到特定神经肌肉活动模式的不同影响。
