Fig. 4.

Transmission electron microscopy of primary stroma in E4 (A–C), E6 (D–F) and E10 (G–I) chick cornea after contrast enhanced fixation of proteoglycans with cupromeronic blue. Whole thickness stroma is seen in A; sub-epithelial stroma in B, D, G and H, and mid-depth stroma in C, E, F and I. Epithelium (e) and lens (l) are separated by undulating primary stromal collagen at E4 (A). Epithelial basement membrane (arrow) exhibits a complex array of proteoglycans as dense filaments at all stages. Proteoglycan filaments, regularly distributed along collagen fibrils are evident at E4 and E6, including many elongate elements traversing fibril bundles and running axially along fibrils (C, F). At E10, proteoglycan filament-collagen periodic alignment and linkages between fibrils in longitudinal and transverse section are evident (G–I).