Ultrastructure of traumatic cataractogenesis in the frog: A comparison with mouse and human lens

Abstract

Normal and needle-punctured lenses of Rana pipiens were examined with the electron microscope in order to characterize the sequence of ultrastructural changes that follow the injury over a 5-month period. Results were compared with those obtained previously in experimentally injured mouse and accidentally injured human lenses. The normal adult frog lens was found to have a morphology similar to that of mammalian lenses. As in the human, frog lens epithelial cells contained scattered microfilaments and were connected by desmosomes and gap junctions. They differed from mouse cells, which had been shown to lack desmosomes and to have microfilaments organized into dense bundles. These differences are postulated to be related to the degree of accommodative deformation of the lens displayed by these species. After injury, cellular debris and fibrin, accumulated in the wound, were phagocytized by extrinsic cells derived from the blood and ocular tissues. Leucocytes, pigmented cells and fibroblasts remained in the wound for eight weeks, along with epithelial cells which proliferated and migrated from the wound margins.Epithelial cells showed an increase in those organelles associated with protein synthesis and transport, and in microfilaments. In cataractous lenses, epithelial cells showed changes in matrix, and lens fibers became organized into smaller, denser compressed units. At five months, considerable healing had taken place, but localized opacities persisted in many frog lenses.