Rossant J
J Embryol Exp Morphol. 1975 Jul;33(4):979-90.
Inner cell masses (ICMs) were dissected from 3 1/2- and 4 1/2-day blastocysts and cultured in contact with 2 1/2-day morulae. Blastocysts and morulae were homozygous for different electrophoretic variants of the enzyme glucose phosphate isomerase (GPI). Aggregation of ICMs and morulae was observed, and such aggregates were able to form blastocysts in vitro and morphologically normal foetuses in utero. GPI analysis of these conceptuses revealed that most were chimaeric. However, donor ICM-type isozyme was only detected in the embryonic and extra-embryonic fractions of the chimaeras and never in the trophoblastic fraction. Thus, ICM cells appear unable to form trophoblast derivatives even when exposed to 'outside' conditions as experienced by developing trophoblast cells. This is evidence that ICM cells, although not overtly differentiated, are determined by 3 1/2 days.
从3.5天和4.5天的囊胚中分离出内细胞团（ICM），并与2.5天的桑椹胚接触培养。囊胚和桑椹胚对于磷酸葡萄糖异构酶（GPI）的不同电泳变体是纯合的。观察到ICM和桑椹胚的聚集，并且这种聚集体能够在体外形成囊胚，并在子宫内形成形态正常的胎儿。对这些概念体的GPI分析表明，大多数是嵌合体。然而，供体ICM型同工酶仅在嵌合体的胚胎和胚外部分中检测到，而从未在滋养层部分中检测到。因此，即使暴露于发育中的滋养层细胞所经历的“外部”条件下，ICM细胞似乎也无法形成滋养层衍生物。这证明ICM细胞虽然没有明显分化，但在3.5天时就已确定。
