Model P G
Brain Res. 1982 Jan;255(1):109-21. doi: 10.1016/0165-3806(82)90078-5.
In premetamorphic amphibians, the Mauthner cells (M-cells), a single pair of large neurons, are present in the medulla at ear level. M-cells are easily identified morphologically. Lability of the major axes of the CNS in the axolotl (Ambystoma mexicanum) through midneural plate stages suggests that regionalization of the CNS does not occur prior to that time. Thus, prospective forebrain-midbrain from early midneurulae was unilaterally substituted for prospective hindbrain in hosts of the same stages. Light microscopic examination of feeding larvae showed that the implanted tissue developed as hindbrain and, in addition, produced an M-cell. Proof that the graft itself differentiated as medulla was obtained through implantation of [3H]-thymidine labeled tissue into unlabeled host embryos and through implantation of pigmented tissue into albinos. The competence of prospective forebrain-midbrain taken from early midneurulae to produce medullae as well as M-cells indicates that specification of spatial pattern in the developing CNS has not yet occurred and that very precise regulating factors from the surrounding host tissues can override the original fate of the graft to bring it into accord with the system as a whole. The data also provide the first unequivocal demonstration of the generation of an identified central neuron from foreign tissue in a vertebrate.
在变态前的两栖动物中，Mauthner细胞（M细胞）是一对位于延髓耳部水平的大型神经元。M细胞在形态上易于识别。蝾螈（美西钝口螈）在神经板中期之前，中枢神经系统主轴的不稳定性表明中枢神经系统在那时之前尚未发生区域化。因此，将早期神经中胚层的预期前脑 - 中脑单侧替换同一阶段宿主的预期后脑。对摄食幼虫的光学显微镜检查表明，植入的组织发育为后脑，并且还产生了一个M细胞。通过将[3H] - 胸腺嘧啶标记的组织植入未标记的宿主胚胎以及将有色组织植入白化病宿主中，获得了移植物本身分化为延髓的证据。从早期神经中胚层获取的预期前脑 - 中脑产生延髓和M细胞的能力表明，发育中的中枢神经系统中空间模式的特化尚未发生，并且来自周围宿主组织的非常精确的调节因子可以覆盖移植物的原始命运，使其与整个系统一致。这些数据还首次明确证明了脊椎动物中从外来组织产生已识别的中枢神经元。
