Protein Studies on the Human Vitreous Body

Abstract

INVESTIGATIONS of the vitreous body are beset with numerous technical difficulties. Its large water content and the instability of its structure make it difficult to obtain unchanged vitreous body in large amounts. Through the slit lamp and in fixed histological preparations (Lauber, 1936; Baurmann, 1926; Comberg, 1924; Duke-Elder, 1930), the human vitreous body appears as a structured mass. In order to circumvent the criticism that such structures are caused artificially, new methods of investigation had to be evolved. Through the ordinary microscope fresh vitreous body demonstrates no structural elements. On the other hand, investigations with the ultramicroscope (Friedenwald and Stiehler, 1935), darkfield microscope, and phase-contrast microscope (Redslob, 1932; Matoltsy and others, 1951; Grignolo, 1952) have not led to any single conclusion, but have given rise to the present view of the vitreous body as a gel, permeated by a net of submicroscopic fibrils. As Morner (1893) has shown, this structural part can be split off by filtration. The chemical and physical analysis of the filter remains (Pirie and others, 1948) resulted in a collagen-type protein and a polysaccharide acid which could be identified as hyaluronic acid (Meyer and Palmer, 1936). The further structural analysis of these elements by means of the electron microscope and x-ray diagrams (Pirie and others, 1948; Schwarz and Schuchardt, 1950; Schwarz, 1951; Matoltsy and others, 1951) led to the discovery of three main types of fibrils: (i) long unbranched threads with an indication of fine axon periods; (ii) delicate, unbranched, entangled threads with a distinct axon period of 500-850A; (iii) broad, striated fibrils with an axon period of 500-800A, which demonstrated the typical relationship of collagen. This structural residual protein consists of various components which can be separated and demonstrated by electrophoresis. To Hesselvik (1939), we owe the thorough electrophoretic analysis of the proteins of the vitreous body. Since the introduction and development of paper-electrophoresis, it has become possible to investigate the protein composition of single