Fraher J P, Rossiter J P
J Anat. 1983 Jan;136(Pt 1):111-28.
Clusters of cells are a prominent feature on the most proximal part of rat ventral rootlets between 15 and 21 days of fetal life and they increase to a maximum size at 17 days post conception. By means of extensive sheath-like processes the component cells of the clusters encapsulate one another in a very complex manner. Cells also give rise to processes which extend into the underlying axon bundles in the most proximal part of the ventral root and there form a highly complex matrix of interwoven fine cytoplasmic processes which separate individual axons from one another from a very early stage. With maturation, the clusters become smaller and the complex matrix disappears. Cells separate off from the clusters and enter the underlying ventral rootlets where they differentiate into Schwann cells and come to envelop the axons in the manner characteristic of the latter. However, the proximal part of the rootlet remains at a much less advanced state of maturation than more distal parts up to the end of fetal life. It is possible that cell clusters are in part produced by overgrowth of CNS tissue around the axon bundles in the ventral rootlets. This strips the cells distally and causes them to become piled up as collars around the most proximal part of the ventral rootlet.
在胎儿期15至21天之间，细胞簇是大鼠腹侧神经根最近端部分的一个显著特征，它们在受精后17天增大到最大尺寸。通过广泛的鞘样突起，细胞簇的组成细胞以非常复杂的方式相互包裹。细胞还产生延伸到腹侧神经根最近端部分下方轴突束中的突起，并在那里形成一个由交织的细细胞质突起组成的高度复杂的基质，从很早阶段就将单个轴突彼此分开。随着成熟，细胞簇变小，复杂的基质消失。细胞从细胞簇中分离出来，进入下方的腹侧神经根，在那里它们分化为施万细胞，并以后者特有的方式包裹轴突。然而，直到胎儿期结束，神经根的近端部分仍比更远端部分处于成熟程度低得多的状态。细胞簇部分可能是由腹侧神经根中轴突束周围的中枢神经系统组织过度生长产生的。这将细胞向远端剥离，导致它们像项圈一样堆积在腹侧神经根最近端部分周围。
