背根神经节分节格式的形成和体节再分节

把分散的鹌鹑体节板细胞移植到鸡的体节板区。移植后１７ｈ，在移植区形成大小不等、排列杂乱的ＤＣ体节。有些体节靠近神经管，有些较靠外侧。移植后２９～３２ｈ，靠近神经管的ＤＣ体节向中壁破裂，外迁的间充质细胞在生肌节与神经管和脊索之间，形成生骨节（即原位生骨节）。每个生骨节再分为前后两半，位于外侧的ＤＣ体节，在移植后３３～３８ｈ，其侧壁或外侧壁破裂。外迁的间充质细胞在生肌节的外侧或生肌节之间，数量、大小和

THE FORMATION OF SEGMENTAL PATTERN OF DORSAL ROOT GANGLIA AND RESEGMENTATION OF SOMITE

The relationship between the resegmentation of somite and the segmental pattern of dorsal root ganglia was investigated by grafting the dissociated segmental plate cells (DC) of quail embryo to replace the right segmental plate to reconstruct an artificial disordered somite pattern. Seventeen hours after grafting, the DC somites were formed in the area of grafting. The DC somites were disordered in number, size and arrangement, some were near neural tube and some were further away from neural tube. After 29-32 h of grafting, the medial wall of DC somite was broken down and migrating mesenchymal cells moved toward notochord and formed sclerotome (the sclerotome in situ) between myotomes and neural tube as well as notochord. Each sclerotome was divided into two parts, the rostral and caudal sclerotome, as the somites on control side. The DC somites located further away from neural tube resegmented after 33-38 h, and the outside or lateral wall, not the medial wall, was distrupted and allosclerotome were formed outside to or among myotomes. So that the sclerotome could came from any side of the somitic epithelia as long as they disorganized and became mesenchymal cells in time. Corresponding to the sclerotome on control side, there were two kinds of dorsal root ganglia, the dorsal root ganglia in situ and alloganglia at the experimental side. The number, size and arrangment of sclerotomes formed in situ were independent on the somite from which they created, but corresponded to those of the sclerotome on the control side. So did the dorsal root ganglia in situ as the sclerotome in situ. The number of allosclerotoms was also independent on the somites from which they were derived, but matched the number of the sclerotome in situ, and the number of alloganglia was the same as the allosclerotomes.