Quantitative analysis of tight junctions during ciliary epithelium development.

The tight junctions of the ciliary epithelium constitute the main morphological counterpart of the blood-aqueous barrier. Although well-known in the adult, they have only been poorly studied during the morphogenesis of the ciliary processes. We thus analysed them during this period in order to detect whether any changes appear in their general pattern. In the rat, results show that during ciliary body development, the junctional depth and the number of superimposed junctional fibrils decrease, the P-face intramembranous particle density within and outside the junctional domains increase, and particular structures, namely the 'complex strands', are numerous at the early stages and become rare in the adult. Thus, the tight junctions appear as non-stable structures during ciliary-body development and these modifications in their morphology may correspond to changes in barrier properties during the development of this tissue.