Morphogenesis of conjunctival papillae from normal and scaleless chick embryos

摘要

AbstractMorphogenesis of avian conjunctival papillae follows a predictable temporal and spatial pattern and is in some manner directly related to the induction of the underlying scleral ossicles. We have been able, using Scanning Electron Microscopy (SEM), to correlate all of Murray's ('43) histological stages (1–6) of papillae development, with changes in elevation and morphology of the surface of the conjunctiva. The first indication of morphogenesis is the formation of “papillae primordia”. The centers of these primordia exhibit decreased intercellular contact, and become elevated as radially symmetrical humps whose surfaces are composed of rounded cells with numerous microvillar projections. As the papillae become asymmetrical and elongate, cells near the tip of the papillae enlarge and develop microridges. During regression of the papillae, single clusters of cells appear to become lost from the surfaces of the papillae into the surrounding fluid. In contrast to normal chick embryos, those homozygous for the “scaleless” gene (Abbott and Asmundson, '57) display reduction in the number of papillae and underlying scleral ossicles (Palmoski and Goetinck, '70). SEM of the mutant conjunctival surface indicates that these papillae do not exhibit all of Murray's ('43) histological stages and are morphologically abnormal. Data from the present SEM study of the normal and scaleless conjunctiva are discussed in relation to those data of other investigators, and we suggest that Stage 4 in papillae development is critical to scleral ossicle