McKay S E, Oppenheim R W
Department of Neurobiology and Anatomy, Wake Forest University Bowman Gray School of Medicine, Winston-Salem, North Carolina 27157.
J Neurobiol. 1991 Oct;22(7):721-33. doi: 10.1002/neu.480220707.
Chick embryos and posthatched chicks were examined at several ages for the presence of pyknotic interneurons in the lumbar spinal cord. Because no pyknotic interneurons were found, direct cell counts of healthy interneurons were carried out and a comparison made between early- and late-stage embryos and hatchlings. There was no decrease in the number of interneurons in the ventral intermediate gray matter of the spinal cord between embryonic day (E) 8 and 2 weeks posthatching (PH) or in the dorsal horn between E10 and 2 weeks PH. To study whether interneuron survival is regulated by targets or afferents, a situation known to exist in other developing neural populations, early embryos were subjected to (1) removal of one limb, resulting in the loss of lateral motor column motoneurons and dorsal root ganglion sensory afferents; (2) transection of the thoracic spinal cord, thereby removing both descending afferents and rostral targets of spinal interneurons, or (3) a combination of the two operations. No reductions in interneuron numbers were found as a result of these operations. Furthermore, morphometric analysis also revealed no change in neuronal size following these experimental manipulations. By contrast, there was a slight decrease in the total area of spinal gray matter that was most prominent in the dorsal region following limb bud removal. Our results indicate (1) that spinal interneurons fail to exhibit the massive naturally occurring death of postmitotic neurons that has been observed for several other populations of spinal neurons, and (2) spinal interneurons appear to be relatively resistant to induced cell death following the removal of substantial numbers of afferent inputs and targets.
在几个不同的年龄段对鸡胚和刚孵出的雏鸡进行检查，以确定腰脊髓中是否存在固缩的中间神经元。由于未发现固缩的中间神经元，因此对健康的中间神经元进行了直接细胞计数，并对早期和晚期胚胎及雏鸡进行了比较。在胚胎期（E）8至孵化后2周（PH）期间，脊髓腹侧中间灰质中的中间神经元数量没有减少；在E10至2周PH期间，背角中的中间神经元数量也没有减少。为了研究中间神经元的存活是否受靶标或传入神经的调节（这是已知在其他发育中的神经群体中存在的情况），对早期胚胎进行了以下操作：（1）切除一条肢体，导致外侧运动柱运动神经元和背根神经节感觉传入神经缺失；（2）横断胸段脊髓，从而去除脊髓中间神经元的下行传入神经和头端靶标，或（3）两种操作相结合。这些操作均未导致中间神经元数量减少。此外，形态计量分析也显示，这些实验操作后神经元大小没有变化。相比之下，在去除肢体芽后，脊髓灰质的总面积略有减少，这在背侧区域最为明显。我们的结果表明：（1）脊髓中间神经元并未表现出有丝分裂后神经元大量自然发生的死亡现象，而这种现象在其他几种脊髓神经元群体中已被观察到；（2）在去除大量传入输入和靶标后，脊髓中间神经元似乎对诱导性细胞死亡具有相对抗性。
