Lewis N E, Rossant J
J Embryol Exp Morphol. 1982 Dec;72:169-81.
A detailed comparison of the postimplantation development of normal and double-sized mouse embryos, produced by aggregating two 8-cell stage eggs, revealed that size regulation occurred in the double embryos between 5 days, 16 h post coitum (p.c.) and 6 days, 16 h p.c. Size regulation occurred simultaneously in all tissues, suggesting that a single regulatory mechanism may control size in the early embryo. Size regulation appeared to be brought about by alteration in cell cycle length. There was no obvious increase in cell death in the double embryos nor an increase in the non-dividing cell population. However, colcemid treatment revealed a significant difference in mitotic index between double and control embryos over the period of size regulation. Control embryos showed a proliferative burst around 6 days, 8 h p.c. which did not occur in the double embryos. It is not yet clear whether this control of proliferative activity in double embryos is exerted by the embryo itself or by the uterine environment. Histological analysis also suggested that proamniotic cavity formation, which occurs before size regulation, was dependent on total cell number and not on the number of cell cycles undergone since fertilization. Proamniotic cavity formation was observed to occur at different times but at similar cell numbers in double, control and half embryos.
对通过聚合两个8细胞期卵子产生的正常大小和双倍大小小鼠胚胎植入后发育的详细比较显示，在交配后5天16小时（p.c.）至6天16小时p.c.期间，双倍胚胎中发生了大小调节。所有组织同时发生大小调节，这表明单一调节机制可能控制早期胚胎的大小。大小调节似乎是由细胞周期长度的改变引起的。双倍胚胎中细胞死亡没有明显增加，非分裂细胞群体也没有增加。然而，秋水仙酰胺处理显示，在大小调节期间，双倍胚胎和对照胚胎的有丝分裂指数存在显著差异。对照胚胎在交配后6天8小时左右出现增殖爆发，而双倍胚胎中未出现。目前尚不清楚双倍胚胎中这种增殖活性的控制是由胚胎自身还是子宫环境施加的。组织学分析还表明，在大小调节之前发生的羊膜腔形成取决于总细胞数，而不取决于受精后经历的细胞周期数。在双倍、对照和半胚胎中，观察到羊膜腔形成发生在不同时间但细胞数相似的时候。
