Yaginuma H, Shiga T, Homma S, Ishihara R, Oppenheim R W
Department of Neurobiology and Anatomy, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27103.
Development. 1990 Apr;108(4):705-16. doi: 10.1242/dev.108.4.705.
The early development of interneurons in the chick embryo spinal cord was studied using a monoclonal antibody against a neuron-specific beta-tubulin isoform. Early developing interneurons were divided into two cell groups on the basis of their location and the pattern of growth of their axons. One group is composed of cells that establish a primitive longitudinal pathway (PL-cells), whereas the other group contains cells constituting a circumferential pathway (C-cells). The onset of axonal development in both cell groups occurs at stage (st.) 15 (embryonic day, (E), 2) in the branchial segments, which is prior to axonogenesis of motoneurons. PL-cells develop in the region between the floor plate and the motoneuron nucleus. Their axons are the first neuronal processes ('pioneer axons') to arrive in the ventrolateral marginal zone and they project both rostrally and caudally to establish a primitive longitudinal association pathway at the ventrolateral surface of the neural tube. This pathway is formed before axons of C-cells arrive in the ventrolateral region. The first C-cells are initially located in the most dorsal portion of the neural tube, whereas later appearing C-cells are also located in both intermediate and ventral regions of the neural tube. The axons of C-cells project ventrally, without fasciculating, along the lateral border of the neural tube. Some of their axons enter the ipsilateral ventrolateral longitudinal pathway at st. 17. We often observed apparent contacts and interactions between preexisting axons of PL-cells and newly arriving axons of C-cells. The axons of commissural C-cells first enter the floor plate at st. 17 and cross the midline at st. 18. Axons of C cells begin to join the contralateral ventrolateral longitudinal pathway at st. 18+ to st. 19. In the floor plate region, contacts between growth cones and axons were often observed. However, axons in the floor plate at these stages were not fasciculated. These observations establish the timing and pattern of growth of axons from two specific populations of early developing interneurons in the chick spinal cord. Additionally, we have identified an early and apparently previously undescribed 'pioneer' pathway that constitutes the first longitudinal pathway in the chick spinal cord.
利用一种针对神经元特异性β-微管蛋白异构体的单克隆抗体，对鸡胚脊髓中中间神经元的早期发育进行了研究。根据早期发育的中间神经元的位置及其轴突的生长模式，将其分为两个细胞群。一组由建立原始纵向通路的细胞（PL细胞）组成，而另一组包含构成圆周通路的细胞（C细胞）。两个细胞群轴突发育的起始发生在鳃节的第15阶段（胚胎日，（E），2），这早于运动神经元的轴突发生。PL细胞在底板和运动神经元核之间的区域发育。它们的轴突是最早到达腹外侧边缘区的神经元突起（“先驱轴突”），并且它们向头侧和尾侧投射，在神经管的腹外侧表面建立一条原始纵向联合通路。这条通路在C细胞的轴突到达腹外侧区域之前就已形成。第一批C细胞最初位于神经管的最背侧部分，而后来出现的C细胞也位于神经管的中间和腹侧区域。C细胞的轴突沿着神经管的外侧边缘向腹侧投射，不形成束状。它们的一些轴突在第17阶段进入同侧腹外侧纵向通路。我们经常观察到PL细胞先前存在的轴突与新到达的C细胞轴突之间明显的接触和相互作用。连合C细胞的轴突在第17阶段首先进入底板，并在第18阶段穿过中线。C细胞的轴突在第18 +阶段至第19阶段开始加入对侧腹外侧纵向通路。在底板区域，经常观察到生长锥与轴突之间的接触。然而，这些阶段底板中的轴突没有形成束状。这些观察结果确定了鸡脊髓中早期发育的两个特定中间神经元群体轴突生长的时间和模式。此外，我们还确定了一条早期的、显然以前未描述过的“先驱”通路，它构成了鸡脊髓中的第一条纵向通路。
