Holder N, Clarke J D, Stephens N, Wilson S W, Orsi C, Bloomer T, Tonge D A
Anatomy and Human Biology, King's College, London, England.
J Comp Neurol. 1991 Jan 22;303(4):534-50. doi: 10.1002/cne.903030403.
During growth of the axolotl, motor neurons, and muscle fibres are added to the motor system. By double labelling neurons with tritiated thymidine and retrogradely transported HRP, we show that some motor neurons are born at postembryonic stages. Further analysis of motor neurons with the aid of HRP reveals this population of newly born cells relatively frequently in small (5-7 cm long) axolotls, but only rarely in large (7-13 cm long) axolotls. Evidence is presented that suggests that these immature cells are in the process of migrating from close to the ependyma out to the ventral horn. HRP transport also reveals growth cones of advancing axons within spinal nerves in animals up to 6 cm in length. Cell counts by light and electron microscopic methods show that muscle fibres are generated throughout larval life in the iliotibialis, a typical limb muscle. This analysis provides data consistent with the notion that new muscle fibres are added from a localised growth zone situated at the superficial edge of the muscle. These results are discussed in terms of the correlation between continuous growth of the motor system and the ability of the axolotl to functionally repair lesions to the peripheral nervous system.
在美西螈生长过程中，运动神经元和肌纤维会添加到运动系统中。通过用氚标记胸腺嘧啶核苷对神经元进行双重标记，并逆行运输辣根过氧化物酶（HRP），我们发现一些运动神经元在胚胎后期阶段产生。借助HRP对运动神经元进行的进一步分析表明，在小（5 - 7厘米长）美西螈中相对频繁地发现这群新生细胞，而在大（7 - 13厘米长）美西螈中则很少见。有证据表明，这些未成熟细胞正处于从靠近室管膜向腹角迁移的过程中。HRP运输还揭示了在长达6厘米的动物的脊神经中前进轴突的生长锥。通过光学和电子显微镜方法进行的细胞计数表明，在典型的肢体肌肉——髂胫肌中，肌纤维在整个幼虫期都在产生。该分析提供的数据与新肌纤维从位于肌肉表面边缘的局部生长区添加的观点一致。根据运动系统的持续生长与美西螈对外周神经系统损伤进行功能修复的能力之间的相关性，对这些结果进行了讨论。
