Pseudo-exfoliation fibrils examined by negative staining.

Pseudo-exfoliation (PE) material, collected from lenses extracted because of cataract, has been examined by negative staining. The material was fragmented by ultrasound into single fibrils and small collections of fibrils. The fibrils were composed of a small number of filamentous subunits associated with or surrounded by a fuzzy material which had side excrescences at regular intervals of 50--55 nm or 25--30 nm. The side excrescences correspond to the cross-bands of the PE fibrils. It is proposed that the PE fibrils are composed of a few subunits of a fibrillar protein, which form a core to which glycosaminoglycan side chains are attached. The visible periodicity of the PE fibrils, appearing as cross-bands, is thought to be caused by clusters of glycosaminoglycan distributed at regular intervals along the fibrils.