Graham S C, Roy R R, Navarro C, Jiang B, Pierotti D, Bodine-Fowler S, Edgerton V R
Department of Kinesiology, University of California, Los Angeles.
Muscle Nerve. 1992 Jan;15(1):27-36. doi: 10.1002/mus.880150106.
Spinal isolation (SI), i.e., the isolation of the lumbar spinal cord via a rostral and a caudal cord transection and bilateral dorsal rhizotomy, was used to determine the effects of chronic (6 months) inactivity on the size and metabolic properties of fibers in the cat soleus. Fibers were classified as dark or light, based on their staining reactions to myosin ATPase, alkaline preincubation, and immunohistochemically as expressing fast and/or slow myosin heavy chains (MHC). Succinate dehydrogenase (SDH) and alpha-glycerophosphate dehydrogenase (GPD) activities were assessed histochemically. Following SI, both the light and the dark ATPase fibers in the SI cats were significantly smaller than the light ATPase fibers in the controls. Normally 100% of the fibers were light ATPase and reacted exclusively with the slow antibody. After SI, approximately 45% of the fibers were dark ATPase fibers, many reacting with both fast and slow MHC antibodies. The total amount and concentration of GPD were higher in the light and dark ATPase fibers in SI compared with light ATPase fibers in controls. In contrast, although the total amount of SDH per fiber was decreased, reflecting the decrease in fiber size, the mean SDH concentration per fiber was unchanged following SI. These data indicate that there is a close coordination in the regulation of GPD activity and the type of myosin. SDH activity, on the other hand, appears to be resistant to decreased levels of activity and unloading, i.e., there seems to be a minimum level of oxidative potential in the soleus that is independent of activity level. Fiber sizes, however, are very sensitive to less-than-normal amounts of neuromuscular activity and/or loading.
脊髓隔离（SI），即通过脊髓头端和尾端横断以及双侧背根切断术来隔离腰段脊髓，用于确定长期（6个月）不活动对猫比目鱼肌纤维大小和代谢特性的影响。根据纤维对肌球蛋白ATP酶的染色反应、碱性预孵育以及免疫组织化学中表达快和/或慢肌球蛋白重链（MHC）的情况，将纤维分为深色或浅色。通过组织化学方法评估琥珀酸脱氢酶（SDH）和α-甘油磷酸脱氢酶（GPD）的活性。脊髓隔离后，接受脊髓隔离的猫的浅色和深色ATP酶纤维均明显小于对照组的浅色ATP酶纤维。正常情况下，100%的纤维为浅色ATP酶纤维，且仅与慢肌抗体发生反应。脊髓隔离后，约45%的纤维为深色ATP酶纤维，许多纤维同时与快肌和慢肌MHC抗体发生反应。与对照组的浅色ATP酶纤维相比，脊髓隔离组的浅色和深色ATP酶纤维中GPD的总量和浓度更高。相比之下，尽管每根纤维中SDH的总量有所下降，这反映了纤维大小的减小，但脊髓隔离后每根纤维的平均SDH浓度并未改变。这些数据表明，GPD活性调节与肌球蛋白类型之间存在密切协调。另一方面，SDH活性似乎对活性降低和卸载具有抗性，即比目鱼肌中似乎存在一个与活性水平无关的最低氧化电位水平。然而，纤维大小对低于正常水平的神经肌肉活动和/或负荷非常敏感。
