Copp A J
J Embryol Exp Morphol. 1981 Feb;61:277-87.
The number of trophoblast giant cells in outgrowths of mouse blastocysts was determined before, during and after egg-cylinder formation in vitro. Giant-cell numbers rose initially but reached a plateau 12 h before the egg cylinder appeared. A secondary increase began 24 h after egg-cylinder formation. Blastocysts whose mural trophectoderm cells were removed before or shortly after attachment in vitro formed egg cylinders at the same time as intact blastocysts but their trophoblast outgrowths contained fewer giant cells at this time. The results support the idea that egg-cylinder formation in vitro is accompanied by a redirection of the polar to mural trophectoderm cell movement which characterizes blastocysts before implantation. The resumption of giant-cell number increase in trophoblast outgrowths after egg-cylinder formation may correspond to secondary giant-cell formation in vivo. It is suggested that a time dependent change in the strength of trophoblast cell adhesion to the substratum occurs after blastocyst attachment in vitro which restricts the further entry of polar cells into the outgrowth and therefore results in egg-cylinder formation.
在体外，于小鼠囊胚形成卵柱之前、期间及之后，测定了滋养层巨细胞在囊胚外植体中的数量。巨细胞数量最初上升，但在卵柱出现前12小时达到稳定水平。在卵柱形成后24小时开始了第二次增加。在体外附着前或附着后不久移除壁滋养外胚层细胞的囊胚与完整囊胚同时形成卵柱，但此时它们的滋养层外植体中巨细胞较少。这些结果支持这样一种观点，即体外卵柱的形成伴随着从极滋养外胚层细胞向壁滋养外胚层细胞运动的重新定向，这是植入前囊胚的特征。卵柱形成后滋养层外植体中巨细胞数量的再次增加可能与体内次级巨细胞的形成相对应。有人提出，体外囊胚附着后，滋养层细胞与基质的黏附强度会发生时间依赖性变化，这限制了极细胞进一步进入外植体，从而导致卵柱的形成。
