Nornes H O, Hart H, Carry M
J Comp Neurol. 1980 Jul 1;192(1):119-32. doi: 10.1002/cne.901920108.
Previous studies on the rigid time and position pattern of embryonic spinal cord development are extended to include the pattern of growth of axonal processes. This study was designed to analyze the position of axons in the marginal zone as they course (fasciculate) in the ascending and descending direction from a single spinal segment. Injections of 3H-proline were made into L1 or T6 of chick embryos of stages 21--29 (3.5--6 days of incubation). The location of radioactive label in the marginal zone was analyzed autoradiographically to show the location of labeled axons originating from the injected segment. In the early stages of development (stage 21), the labeled descending axons were located in the most ventromedial aspect of the marginal zone. The labeled ascending axons were located more laterally and to the perimeter of this zone. In stages 27--29, the labeled axons near the site of injection were located in the inner two-thirds of the marginal zone, and in the progressively more rostral levels the label shifted laterally and to the perimeter in a laminar pattern. It was concluded that the labeled ascending axons from an individual spinal segment layer upon the axons which originate from the more rostral segments. How this rigid time and position pattern of axonal growth can impart a topographic order into fiber tracts of the spinal cord was discussed.
以往关于胚胎脊髓发育的严格时间和位置模式的研究得到扩展，将轴突生长模式也纳入其中。本研究旨在分析轴突在边缘区的位置，这些轴突从单个脊髓节段向上升和下降方向走行（成束）。将³H-脯氨酸注射到处于21-29期（孵化3.5-6天）的鸡胚的L1或T6节段。通过放射自显影分析边缘区放射性标记的位置，以显示源自注射节段的标记轴突的位置。在发育早期（21期），标记的下行轴突位于边缘区最腹内侧。标记的上行轴突位于更外侧且靠近该区域的周边。在27-29期，注射部位附近的标记轴突位于边缘区内三分之二处，在逐渐更靠头端的层面，标记呈层状模式向外侧和周边移动。得出的结论是，来自单个脊髓节段的标记上行轴突叠加在源自更靠头端节段的轴突之上，并讨论了这种严格的轴突生长时间和位置模式如何能将拓扑顺序赋予脊髓纤维束。
