Motoneurone projection patterns in the chick hind limb following early partial reversals of the spinal cord.
Motoneurone projection patterns in the chick hind limb following early partial reversals of the spinal cord.
复制标题
脊髓早期部分逆转后小鸡后肢的运动神经元投射模式。
DOI：
10.1113/jphysiol.1980.sp013262
复制
发表时间：
1980
期刊：
影响因子：
--
通讯作者：
L. Landmesser
中科院分区：
文献类型：
--
作者：
C. Lance‐Jones;L. Landmesser
1.研究了从轴突生长开始（St. 24）到成熟连接模式建立（St. 36）的鸡后肢反向脊髓节段运动神经元投射模式的发育。在第15 - 16节，大约前三个腰骶脊髓节段沿前后轴沿着翻转。2.在St. 30 - 36胚胎中，通过直接脊髓和脊神经刺激进行电生理学评估，并通过运动神经元的逆行辣根过氧化物酶（HRP）标记进行解剖学评估。在年轻的胚胎，反向轴突的路径，其特征在于在特定的反向脊髓段运动神经元的orthograde HRP标记。3.腰骶部运动神经元与个体肢体肌肉形成适当的功能连接，尽管其脊髓位置前后移位，并且其脊神经进入肢体芽的入口点随之移位。反向运动神经元供应个别后肢肌肉形成离散核的横向平面的脊髓。与对照胚胎相比，每个核和横向运动柱作为一个整体显示出相反的地形特征。这些观察是在运动神经元细胞死亡的主要时期之前（第30节）和之后（第35 - 36节）进行的。4.正确的连接性是由靠近单个肌肉神经分支的丛或主要神经干内轴突通路的特定改变引起的。此外，这种定向生长存在于轴突可以追溯到肢体的最早时间，这是在运动神经元细胞死亡和肌肉分裂开始之前。5.它的结论是，运动神经元指定项目个别肌肉或遵循特定的路径运动神经元的生日和肢芽形成之前。特定运动神经元连接的建立不能仅用被动或机械引导模型来解释。相反，运动神经元也必须积极响应肢体内的线索，或在早期中枢规范的基础上相互作用。
1. The development of motoneurone projection patterns in the chick hind limb from reversed spinal cord segments was studied from the onset of axonal outgrowth (St. 24) to the establishment of mature connectivity patterns (St. 36). Approximately the first three lumbosacral cord segments were reversed along the anterior‐posterior axis at St. 15‐16. 2. Projection patterns from reversed cord segments were assessed electrophysiologically by direct spinal cord and spinal nerve stimulation and anatomically by retrograde horseradish peroxidase (HRP) labelling of motoneurones in St. 30‐36 embryos. In younger embryos, paths taken by reversed axons were characterized by orthograde HRP labelling of motoneurones in specific reversed cord segments. 3. Lumbosacral motoneurones formed appropriate functional connexions with individual limb muscles in spite of anterior‐posterior shifts in their spinal cord position aned consequent shifts in their spinal nerve entry point into the limb bud. Reversed motoneurones supplying individual hind limb muscles formed discrete nuclei in the transverse plane of the cord. Each nucleus and the lateral motor column as a whole showed reversed topographical characteristics when compared to control embryos. These observations were made before (St. 30) and after (St. 35‐36) the major period of motoneurone cell death. 4. Correct connectivity resulted from specific alterations in axonal pathways within the plexus or major nerve trunks proximal to the branching of individual muscle nerves. Further such directed outgrowth was present from the earliest times that axons could be traced into the limb which is before the onset of motoneurone cell death and muscle cleavage. 5. It is concluded that motoneurones are specified to project to individual muscles or to follow particular pathways prior to motoneurone birthdays and limb bud formation. The establishment of specific motoneurone connectivity can not be accounted for by passive or mechanical guidance models alone. Rather, motoneurones must also actively respond to cues within the limb or interact among themselves on the basis of an early central specification.