P 152 The role of xanthine oxidase in the anterior eye segment irradiated with UVB rays

HIRSCH M. PRENANT G. and POULIQUEN Y. INSERM lJ.86, H&e1 Dieu. Pari.v (France) Puroose. The objective was to determine the supramolecular organization of the cornea1 stroma extracellular matrix (ECM) and the changes which occured during the acquisition of transparency. Methods. Mature corneas and chicken embryo corneas were used. Samples were frozen against a metal block cooled at -18O”C, transferred on a cold stage of a freeze-etch unit, cleaved, etched and rotary replicated in vacuum. Results. Mature corneas displayed type I collagen Bbrils with high and low molecular density regions and microfibrillar subunits of 8nm in diameter. Interfibrillar bridges with globular entities linked adjacent fibrils. Filaments with globules were found running along the tibtils. Networks of beaded microfilaments with 100-I IOnm periodicity were often encountered. These macromolecular assemblies were suggestive of proteoglycans, type IX and type VI collagens, respectively. The secondary developing stroma showed disordered arrays of collagen fibrils and interfibrillar bonds which organized during the maturation. Sheets of closely associated tine, long filaments, ressembling type IV collagen were encountered. The beaded microfilaments were also present. Conclusion2 Used in conjonction with other approaches, this method should offer a very useful aid in the understanding of the interactions of ECM macromolecules in the comeal stroma.