Sanders E J
J Cell Sci. 1980 Aug;44:225-42. doi: 10.1242/jcs.44.1.225.
Endoblast and hypoblast tissue, dissected from early chick embryos, was explanted and cultured on glass or plastic substrata. These tissues grew rapidly to form epithelial sheets. Under the same conditions, mesoderm, dissected without the aid of dissociating agents, grew poorly. After 24 h in culture, the mesoderm explants consisted of a sparse outgrowth of fibroblast-like cells. When pieces of mesoderm were seeded onto the dorsal surface of the epithelia, however, the cells penetrated the sheet and rapidly spread on the substratum within 4 h. If the epithelial sheet was detached from the substratum and the mesoderm then seeded onto areas of substratum previously occupied by epithelium, similar rapid spreading occurred. This effect could be produced in the absence of serum. The method used to remove the epithelium (EDTA, detergent or manual dissection) did not influence the result. When the substratum-attached material (SAM) was examined by scanning electron microscopy, 2 types of material were seen. One type appeared to be the remains of detached filopodia and cytoplasmic lamellae, while the other appeared to be of extracellular origin. Both these types reacted positively by immunofluorescence using anti-fibronectin serum. SAM derived from mesoderm reacted negatively. When mesoderm was cultured in the presence of plasma fibronectin on unmodified plastic or glass, spreading was complete in 4-5 h and thus was similar to mesoderm seeded onto SAM. The morphology of mesoderm explants on SAM or in the presence of plasma fibronectin was more epithelial than on untreated substratum in normal medium. Hypoblast and endoblast cultured in the presence of anti-fibronectin serum failed to spread normally, apparently being unable to attach to the substratum. Mesoderm did not spread rapidly on SAM in the presence of this antiserum. Cycloheximide reversibly inhibited the spreading of hypoblast and endoblast, and this effect could be eliminated, at least for hypoblast, by the addition of plasma fibronectin. Covering attachment sites on the substratum with bovine serum albumin, thereby preventing the attachment of SAM or fibronectin, also inhibited spreading. It is proposed that mesoderm cells have low levels of surface fibronectin in comparison with endoblast and hypoblast, and that this results in a comparatively low adhesiveness, which is important for its morphogenetic activity within the embryo.
从早期鸡胚中分离出内胚层和下胚层组织，将其接种并培养在玻璃或塑料基质上。这些组织迅速生长形成上皮片层。在相同条件下，未经解离剂辅助分离的中胚层生长不佳。培养24小时后，中胚层外植体由稀疏生长的成纤维细胞样细胞组成。然而，当中胚层碎片接种到上皮片层的背表面时，细胞在4小时内穿透该片层并迅速在基质上扩散。如果将上皮片层从基质上分离，然后将中胚层接种到先前被上皮占据的基质区域，也会发生类似的快速扩散。在无血清条件下也能产生这种效应。用于去除上皮的方法（乙二胺四乙酸、去污剂或手动解剖）不影响结果。当通过扫描电子显微镜检查基质附着材料（SAM）时，观察到两种类型的材料。一种类型似乎是脱离的丝状伪足和细胞质薄片的残余物，而另一种似乎是细胞外来源的。使用抗纤连蛋白血清通过免疫荧光检测，这两种类型均呈阳性反应。源自中胚层的SAM呈阴性反应。当中胚层在血浆纤连蛋白存在下于未修饰的塑料或玻璃上培养时，4 - 5小时内扩散完成，因此与接种到SAM上的中胚层相似。与在正常培养基中未处理的基质上相比，中胚层外植体在SAM上或在血浆纤连蛋白存在下的形态更具上皮性。在抗纤连蛋白血清存在下培养的下胚层和内胚层无法正常扩散，显然无法附着于基质。在这种抗血清存在下，中胚层在SAM上也不会迅速扩散。放线菌酮可逆地抑制下胚层和内胚层扩散，并且至少对于下胚层而言，通过添加血浆纤连蛋白可以消除这种效应。用牛血清白蛋白覆盖基质上的附着位点，从而阻止SAM或纤连蛋白的附着，也会抑制扩散。有人提出，与内胚层和下胚层相比，中胚层细胞表面纤连蛋白水平较低，这导致其黏附性相对较低，这对其在胚胎内的形态发生活动很重要。
