Mitrani E, Eyal-Giladi H
Nature. 1981 Feb 26;289(5800):800-2. doi: 10.1038/289800a0.
The primitive streak of the chick embryo develops from one of the two layers of cells of the stage XIII blastoderm, the epiblast. The other layer of cells, the hypoblast, seems to be necessary for the induction of the primitive streak and also determines its orientation--rotation of the hypoblast by 90 degrees is followed by a similar rotation of the embryonic axis. After stage XIII, the hypoblast is replaced by the invaginating endoderm and plays no further part in the development of the embryo. By means of a technique for disaggregation and reconstituting cells of stage XIII hypoblasts, we have been able to show that the two functions, induction and orientation are independent and that with reconstituted hypoblasts, the orientation of the primitive streak is determined by the epiblast.
鸡胚的原条由第 XIII 期胚盘两层细胞之一的上胚层发育而来。另一层细胞，即下胚层，似乎对于原条的诱导是必需的，并且还决定其方向——下胚层旋转 90 度后，胚胎轴也会随之发生类似的旋转。在第 XIII 期之后，下胚层被内陷的内胚层所取代，在胚胎发育中不再起进一步作用。通过一种用于分解和重组第 XIII 期下胚层细胞的技术，我们已经能够表明诱导和方向这两种功能是独立的，并且对于重组的下胚层而言，原条的方向由上胚层决定。
