Duchen L W, Scaravilli F
J Anat. 1977 Jul;123(Pt 3):763-75.
Peripheral nerves and lumbar nerve roots of Sprawling, a neurological mutant mouse, were examined with light and electron microscopy. The peripheral nerves and the dorsal roots were thin and grey and were composed predominantly of small myelinated and unmyelinated axons. No evidence of axonal or myelin degeneration was found. Quantitative studies showed a marked reduction in the total number of myelinated axons with preponderance of those of 2-5 micron in diameter or less, most marked in the dorsal roots in which there was also an increase in the proportion of axons which were unmyelinated. In the ventral roots there was a deficiency in the contribution formed by myelinated axons of small calibre, probably indicating a deficiency of gamma fibres. Examination of the myelinated axons in nerves and roots showed a normal relationship between fibre size and internodal lengths and number of myelin lamellae. The findings suggest that the genetic defect in Sprawling is responsible for a failure of myelination of sensory axons. The deficiency of large sensory axons and of small motor axons can be correlated with the deficiency of muscle spindles.
对神经学突变小鼠“伸展”（Sprawling）的外周神经和腰神经根进行了光镜和电镜检查。外周神经和背根纤细且呈灰色，主要由小的有髓鞘和无髓鞘轴突组成。未发现轴突或髓鞘变性的证据。定量研究表明，有髓鞘轴突总数显著减少，直径为2 - 5微米或更小的轴突占优势，在背根中最为明显，其中无髓鞘轴突的比例也有所增加。在腹根中，小口径有髓鞘轴突形成的贡献不足，这可能表明γ纤维缺乏。对神经和根中有髓鞘轴突的检查显示，纤维大小与节间长度以及髓鞘板层数之间存在正常关系。这些发现表明，“伸展”小鼠的基因缺陷导致感觉轴突髓鞘形成失败。大感觉轴突和小运动轴突的缺乏与肌梭的缺乏相关。
