Fraher J P
J Anat. 1978 Sep;127(Pt 1):1-15.
The lengths of internodes on peripheral and central stretches of the same ventral motoneuron axons were measured in 6 day rats. The former were more than twice as long as the latter. The distribution of peripheral internodal lengths was broader, and was shifted to the right, relative to that of central internodes. Short internodes were present centrally and peripherally throughout the early period of rapid myelination occurring immediately after birth. All such internodes appeared normal centrally, as did a proportion found peripherally. Some peripheral examples appeared to be degenerating. Evidence is presented suggesting that some short internodes, both peripherally and centrally, increase in length to achieve a normal appearance. Many central stretches of central motoneuron axons which were myelinated at some levels, at other levels possessed unmyelinated segments covered by numberous short glial processes. Such bare stretches commonly occurred immediately deep to the cord surface. The lengths of the unmyelinated stretches decreased as age advanced, perhpas due to the extension of adjacent myelinated segments along them.
在6日龄大鼠中测量了同一腹侧运动神经元轴突外周段和中枢段的节间长度。外周段的长度是中枢段的两倍多。外周节间长度的分布更宽，相对于中枢节间的分布向右偏移。在出生后立即发生的快速髓鞘形成的早期，中枢和外周都存在短节间。所有这些节间在中枢看起来正常，外周的一部分也是如此。一些外周的节间似乎正在退化。有证据表明，一些外周和中枢的短节间会延长以达到正常外观。在某些水平有髓鞘形成的中枢运动神经元轴突的许多中枢段，在其他水平则具有被许多短神经胶质突起覆盖的无髓鞘段。这种裸露段通常紧邻脊髓表面深处出现。随着年龄的增长，无髓鞘段的长度会缩短，这可能是由于相邻有髓鞘段沿着它们延伸所致。
