TRANSFORMATION OF ULTRASTRUCTURAL TYPE OF FAST-TWITCH MUSCLE FIBRES AFTER CROSS-INNERVATION BY TETRODOTOXIN-BLOCKED SLOW MUSCLE NERVE

It is shown in rats that cross-innervation of the fast-twitch muscle extensor digitorumlongus (EDL) by the nerve of the slow-twitch muscle soleus (SOL) can cause a complete trans-formation of the Z-band width from the fast to the slow muscle fibre type within two weeksand that it can still induce such a transformation, though usually less completely, even whenimpulse activity is excluded by chronical tetrodotoxin (TTX) block of the nerve. Thisprovides a piece of clear-cut evidence for the presence of some activity-independent trophicfactor in the neural determination of skeletal muscle fibre type.     

在完全排除拉长和张力的情况下,鸡的慢肌纤维仍发生去神经后肥大

本文证实了在鸡的纯慢肌(即前背阔肌)和两个混合肌(即尺侧曲腕肌和缝匠肌)的慢纤维,在防止肌肉去神经后被拉长和在切断肌腱而使肌肉处于缩短状态的条件下,去神经后肥大现象仍然发生.前背阔肌的慢纤维和混合肌中的慢纤维,在组织化学性质上和去神经后发生肥大的程度上明显的不同.混合肌慢纤维表现的去神经后肥大现象比前背阔肌纤维要显著得多,在这个现象的进一步研究中应更多地加以利用.     

为河豚毒素阻断的慢肌神经交叉支配后快肌纤维的精细结构类型的改造

此文报道大白鼠快肌(伸趾长肌,EDL)为慢肌(比目鱼肌,SOL)神经交叉支配,在二周内能使其肌纤维的Z-带宽度由快肌纤维型完全改造为慢肌纤维型。这种改造在慢肌神经的冲动传导为河豚毒素(TTX)阻断后仍能发生,虽然在此情况下改造通常不那么完全。以上结果提供一个明确的证据,证明在神经决定骨骼肌纤维类型的方式中,有独立于肌肉活动的营养性因素存在。