Homma S, Yaginuma H, Oppenheim R W
Department of Neurobiology and Anatomy, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157-1010.
J Comp Neurol. 1994 Jul 15;345(3):377-95. doi: 10.1002/cne.903450305.
The spatiotemporal distribution of cell death in the chick embryo neural tube and spinal cord (brachial region) was examined between stage (St.) 12 and 22, in plastic semithin sections. Between St. 12 and 16, the total number of pycnotic cells per segment was low, whereas after St. 16 the number of pycnotic cells was substantially increased. Between St. 17 and 19 three cell death foci or regions could be recognized. One region, the dorsal pycnotic zone, was located in the most dorsal part of the spinal cord, including the neural crest, with the highest number of pycnotic cells observed at St. 18. The second region, or ventral pycnotic zone, was located between motoneurons and the floor plate and had the highest number of dying cells at St. 17. The third region, the floor plate pycnotic zone, was located in the midportion of the floor plate and had the greatest amount of cell death at St. 19. Although low numbers of pycnotic cells were also observed in other regions between St. 17 and 19, no pycnotic cells were found in the ventrolateral region that gives rise to motoneurons. Ultrastructural observations as well as data from in situ nick end labeling indicate that the pycnotic cells observed in the neural tube die by apoptosis and that the debris from the dead cells is phagocytized primarily by adjacent healthy neuroepithelial cells. Although the spatiotemporal distribution of pycnotic cells suggests that cell death at these early stages could play a role in establishing the pioneer axonal pathway for spinal commissural neurons, preliminary observations following perturbations of cell death do not support this notion. Alternatively, early cell death may be involved in the regulation of cellular patterning along the dorsoventral axis of the neural tube by a kind of negative selection of specific progenitor cells.
在第12至22期之间，利用塑料半薄切片检查了鸡胚神经管和脊髓（臂部区域）中细胞死亡的时空分布。在第12至16期之间，每节段的固缩细胞总数较低，而在第16期之后，固缩细胞的数量大幅增加。在第17至19期之间，可以识别出三个细胞死亡焦点或区域。一个区域，即背侧固缩区，位于脊髓最背侧部分，包括神经嵴，在第18期观察到的固缩细胞数量最多。第二个区域，即腹侧固缩区，位于运动神经元和底板之间，在第17期有最多的死亡细胞。第三个区域，即底板固缩区，位于底板中部，在第19期有最大量的细胞死亡。尽管在第17至19期之间在其他区域也观察到少量固缩细胞，但在产生运动神经元的腹外侧区域未发现固缩细胞。超微结构观察以及原位缺口末端标记数据表明，神经管中观察到的固缩细胞通过凋亡死亡，并且死细胞的碎片主要被相邻的健康神经上皮细胞吞噬。尽管固缩细胞的时空分布表明这些早期阶段的细胞死亡可能在为脊髓连合神经元建立先驱轴突途径中起作用，但细胞死亡受干扰后的初步观察结果并不支持这一观点。另外，早期细胞死亡可能通过对特定祖细胞的一种负选择参与神经管背腹轴细胞模式的调节。
