Contractile proteins in ocular tissues. Their role in health and disease

Various cytoskeletal and contractile filamentous systems are located within non-muscular eukaryotic cells including microtubules, intermediate filaments, myosin filaments, and actin microfilaments. Microtubules are a major component of cilia, flagella, axons, and the mitotic spindles, but apart from these more specialized roles they are cytoskeletal structures and are involved in the directional movement of organelles within the cytoplasm. Intermediate filaments are structurally and biochemically similar to neurofilaments and although they are present in most cells they are particularly prominent in mesenchymal cells. Their function is not fully understood but they probably have a supportive role and constrain organelles including the nucleus in position within the cell. The contractile proteins, actin and myosin, in their most complex forms are found as a variety of filamentous structures which are involved in such diverse processes as motility, adhesion, phagocytosis, endocytosis, and cytokinesis. In this study the distribution of cytoskeletal an contractile elements in the non-muscular tissues of the human and the rabbit eye were investigated both in vivo and in vitro using electron microscopy and indirect immunofluorescence. Particular emphasis was placed on the role of cytoplasmic filaments in normal tissue function and their possible significance in various pathological conditions.