Hendrix R W, Zwaan J
J Embryol Exp Morphol. 1975 Jul;33(4):1023-49.
The cell coats of the presumptive lens cells and the extracellular interface between the lens rudiment and optic vesicle were investigated in the chicken embryo throughout the period during which lens induction is presumed to take place. Histochemical methods showed that the cell coats contained both glycoproteins and glycosaminoglycans. Autoradiography after [3H]glucosamine injection indicated incorporation of the precursor with subsequent localization primarily at the cell surface. No obvious changes in the properties of the coat were noted with the progression of early lens morphogenesis. The extracellular matrix at the interface between ectoderm and optic vesicle also contained glycoprotein and glycosaminoglycan. There was a heavy concentration of [3H]glucosamine-containing macromolecules in the area. Electron microscopy revealed that the interface consisted of the basement membrane systems of lens and optic vesicle, fused with their external fibrillar layers. In contrast to the findings on cell coats the density of the interfacial matrix increases appreciably during the lens induction period. Evidence suggests that the cells of the two ocular epithelia are themselves the source of the matrix materials. It is proposed that the macromolecules excreted by the epithelial cells into the interface interact at different concentrations to form aggregates of various structure by a process of self-assembly. This may be reflected in the different ultrastructure of the layers of the interfacial matrix. Quantitative changes in the density of the matrix, leading to increased adhesion between lens rudiment and optic vesicle, may restrict the lateral spreading of the lens cells and so fix the basal area of the lens rudiment. This, together with continued cell replication, may produce the cell crowding, placode formation and invagination characteristic of lens morphogenesis.
在假定晶状体诱导发生的整个时期内，对鸡胚中假定晶状体细胞的细胞被膜以及晶状体原基与视泡之间的细胞外界面进行了研究。组织化学方法表明，细胞被膜含有糖蛋白和糖胺聚糖。注射[3H]葡糖胺后的放射自显影显示前体的掺入，随后主要定位于细胞表面。随着早期晶状体形态发生的进展，未观察到被膜性质有明显变化。外胚层与视泡之间界面处的细胞外基质也含有糖蛋白和糖胺聚糖。该区域有大量含[3H]葡糖胺的大分子。电子显微镜显示，界面由晶状体和视泡的基底膜系统组成，并与其外部纤维层融合。与细胞被膜的研究结果相反，在晶状体诱导期，界面基质的密度明显增加。有证据表明，两种眼上皮细胞本身就是基质材料的来源。有人提出，上皮细胞分泌到界面中的大分子在不同浓度下相互作用，通过自组装过程形成各种结构的聚集体。这可能反映在界面基质各层不同的超微结构中。基质密度的定量变化导致晶状体原基与视泡之间的粘附增加，可能会限制晶状体细胞的侧向扩散，从而固定晶状体原基的基底区域。这与持续的细胞复制一起，可能会产生晶状体形态发生特有的细胞拥挤、基板形成和内陷。
