Leg dysfunctions in a chick model of spina bifida aperta

我们在Hamburger和Hamilton阶段18或19的胚胎的神经管顶板上切开小鸡，造成了小鸡的脊柱裂(SBA)。切开5个和7个体节长度的小鸡，100%的孵化出SBA样畸形。SBO雏鸡没有表现出任何症状，而SBA雏鸡则表现出腿部肌肉瘫痪以及激动剂和拮抗剂腿部肌肉之间的失衡。这些SBA雏鸡的损伤位于脊髓节段，这些节段产生了支配功能障碍肌肉的运动神经元。组织学分析表明，SBA雏鸡病变部位的小脊髓中间神经元较正常雏鸡少，而大的脊髓运动神经元的数量无明显差异。这种SBA模型的腿功能障碍可能是由于脊髓节段中含有支配功能障碍肌肉的运动神经元的中间神经元数量较少所致。该模型有助于研究导致SBA雏鸡腿部功能障碍的病理机制。用抗胰岛-1的单抗进行免疫组织化学染色，观察SBA神经管。在腰椎第3椎体的等位位置测定胰岛-1阳性运动神经元的数量和分布，并比较SBA组和对照组之间的差异。在E4和E4.5，SBA组运动神经元数量少于对照组。在E6，SBA组和对照组之间的胰岛-1阳性神经元数量差异无统计学意义。此外，在胚胎6天，SBA组胰岛-1阳性细胞的分布与对照组不同。这些结果表明，SBA雏鸡胚胎运动神经元发育迟缓。

We created chicks with spina bifida aperta (SBA) by incising the roof plate of the neural tube of embryos at Hamburger and Hamilton stage 18 or 19. Incision over the length of five and seven somites caused SBA-like malformation in 100% of the hatchlings. The SBO chicks exhibited no symptoms, whereas the SBA chicks exhibited paralysis of a leg muscle and imbalance between an agonist and an antagonist leg muscles. Lesions in these SBA chicks were located in the spinal segments that give rise to motor neurons that innervated the dysfunctional muscles. Histological analysis revealed that there were fewer small spinal interneurons at the site of the lesion in SBA chicks than in the normal chicks and that there was no such difference in the number of the large spinal motor neurons. Leg dysfunctions in this model of SBA may be attributable to the smaller number of interneurons in the spinal segments that contain motor neurons that innervate the dysfunctional muscle. This model may facilitate studies of the pathological mechanisms that lead to leg dysfunctions in SBA chicks. We examined the SBA neural tube in by immuno- histochemical staining with the monoclonal antibody against Islet-1. The number and distribution of the Islet-1 positive motoneurons were determined at the position equivalent in the Lumbar 3rd vertebra and compared between SBA groups and control groups. On E4 and E4.5, the motoneuron number in the SBA group was less than that in the control group. On E6, the difference in the numbers of Islet-1 positive neuron between SBA group and control group was not significant. Moreover, the distribution of the Islet-1 positive cells in SBA group was different from that of control group on E6. These results suggest that the development of motoneuron is delayed in the chick embryos with SBA.