Maccabe J A, Parker B W
J Embryol Exp Morphol. 1979 Oct;53:67-73.
When polarizing mesoderm from the posterior border of the 4-day chick limb bud is placed adjacent to anterior limb mesoderm and ectodermal ridge, the anterior ridge thickens and mesodermal outgrowth ensues, resulting in supernumerary limb structures. This apposition of anterior and posterior limb tissues can be accomplished by cutting off the apical one third of the limb bud and reimplanting it on the stump with its anteroposterior axis reversed. The preaxial response to polarizing activity can be obtained after only 12--18 h in the reoriented position. Reversed apical mesoderm develops supernumerary digits when combined with untreated ectoderm. The reciprocal combination, reversed ectoderm and untreated mesoderm, fails to develop supernumerary structures. We have interpreted this as evidence that, in inducing supernumerary limb structures, polarizing activity acts only on the mesoderm.
当将来自4日龄鸡胚肢体芽后缘的极化中胚层置于前肢中胚层和外胚层嵴附近时，前嵴增厚，随后中胚层长出，从而产生多余的肢体结构。前后肢组织的这种并置可以通过切除肢体芽的顶端三分之一并将其前后轴反转后重新植入残端来实现。在重新定向的位置仅12 - 18小时后，即可获得对极化活性的前轴反应。当与未处理的外胚层结合时，反转的顶端中胚层会发育出多余的指。相反的组合，即反转的外胚层和未处理的中胚层，则无法发育出多余的结构。我们将此解释为极化活性在诱导多余肢体结构时仅作用于中胚层的证据。
