At the time of appearane of neurala plata,condensed heterochro- matin become sufficiently decondensed euchromatin,they are found in the nuclei of ectoderm cells of dorsoanterior embryos induced by lithium treatment.

• 神经板形成后,神经外胚层细胞核内染色质多呈分散状态,到较晚阶段,细胞核内有一部分染色质又由分散状态转变为凝聚状态,利用LiCl在囊胚中期前处理,可产生明显的胚胎背前部化发育,这样的胚胎其外胚层细胞核内染色质的超微变化与未处理胚胎的一致。