Sanders E J, Bellairs R, Portch P A
J Embryol Exp Morphol. 1978 Aug;46:187-205.
An unusual example of the invasion of one tissue by another occurs during gastrulation in the chick embryo when the definitive endoblast becomes inserted into the hypoblast. The two tissues were examined morphologically by SEM and TEM. They resemble each other in being of an epithelial type, though neither possesses a basal lamina. The definitive endoblast cells are flatter than the hypoblast cells and more closely attached to one another. When they were explanted in hanging drop cultures, the two tissues were found to exhibit differences in their behaviour. In comparison with the definitive endoblast, the hypoblast cells attached more readily to the glass, produced larger ruffle membranes, moved more rapidly, showed poorer contact-inhibition of locomotion and showed a greater tendency to break away from the main explant. When a hypoblast explant was confronted with a definitive endoblast explant, the hypoblast cells became displaced by the definitive endoblast. The hypoblast explant tended to fragment into smaller groups of cells, many of which migrated around the definitive endoblast, thus mimicking the situation in vivo. Control experiments comprised confronting hypoblast with hypoblast, hypoblast with somites, definitive endoblast with definitive endoblast, and definitive endoblast with somites. The hypoblast explants behaved in a consistent manner, always fragmenting when coming into contact with cells from a confronting explant. The definitive endoblast explants showed more contact inhibition of locomotion when confronted with definitive endoblast or with somites than when confronted with hypoblast. It is suggested therefore that the ability of the hypoblast cells to separate from one another may play an important role in the penetration of the hypoblast by the definitive endoblast both in vitro and in vivo.
在鸡胚原肠胚形成过程中，一种组织侵入另一种组织的一个不同寻常的例子发生在确定内胚层插入下胚层时。通过扫描电子显微镜（SEM）和透射电子显微镜（TEM）对这两种组织进行了形态学检查。它们在上皮类型上彼此相似，尽管两者都不具有基膜。确定内胚层细胞比下胚层细胞更扁平，并且彼此附着更紧密。当将它们接种在悬滴培养物中时，发现这两种组织在行为上表现出差异。与确定内胚层相比，下胚层细胞更容易附着在玻璃上，产生更大的褶皱膜，移动更快，表现出较差的运动接触抑制，并且表现出更大的从主要外植体脱离的倾向。当下胚层外植体与确定内胚层外植体接触时，下胚层细胞被确定内胚层取代。下胚层外植体倾向于分裂成较小的细胞群，其中许多细胞围绕确定内胚层迁移，从而模拟体内的情况。对照实验包括下胚层与下胚层接触、下胚层与体节接触、确定内胚层与确定内胚层接触以及确定内胚层与体节接触。下胚层外植体表现出一致的行为，当与来自相对外植体的细胞接触时总是会分裂。确定内胚层外植体在与确定内胚层或体节接触时比与下胚层接触时表现出更强的运动接触抑制。因此，有人提出下胚层细胞彼此分离的能力可能在确定内胚层在体外和体内穿透下胚层的过程中起重要作用。
