Protein Changes in Senile Cataract Formation

Abstract

Introduction Cataract, the lens opacity, is well recognized as a major cause of visual disability and blindness throughout the world (Spector ‘1974) . contract is a disease of old age and three fifth of all people between ages of 65 and 74 show beginning sign of Cataract, 9 Langone,1984) .About 17 million people in both developed and developing countries suffer from countries suffer from cataract . In united states , about 650,000 operation are performed per year. IN countries located in tropical areas like Egypt , Tunisia , Nepal , Pakistan and India , cataract accounts for higher proportion of blindness as compared to the West . Especially in Pakistan and India, cataract formation is more commonly observed in younger patients. (CHATTER JEE, 19730 .many factor cause cataract , such as genetic and metabolic disorder , intraocular diseases , chemicals and radiations , dietary deficiencies , diabetes and old age . So far , senile cataract due to age is most common and its formation is attributed to various factors superimposed by adding process. For Understanding The lens opacity, it is important to study lens and its relevant fluids, i.e. ; plasma and aqueous humor . Most forms of cataracts are clearly due to change in the chemical environment of the lens (Bito, 1977). Since senile cataract develops over a period of years or decades, it can be expected to result from very subtle changes in intraocular composition. The normal human lenses a transparent , pale yellow tissue which becomes darker in case of cataract . Lens contains 65% and 35% structural proteins ( Lerman, 1980) . On the basis of their solubility in water , these proteins have been divided into two classes: water soluble protein’s and water insoluble protein’s 9Morner < 1894) . Water soluble protein’s are further classified into three main classes ; A,B, G crystalline (Harding and Dilley< 1976). Alpha and beta crystalline are multimeric proteins having different subunits (Spector etal, 1971 : Blomendal and Herbrink, 19744) while g- crystalline is a monomer. In senile cataractous lenses, a marked increase in water soluble protein content was observed (Mach,1963). Electrophoretic and chromatographic studies showed the the low molecular weight crystalline is decreased in cataract lenses (Mach, 1963; Kramps etal , 19760. Maisel and Goodman (1965) suggested that this low molecular weight protein is g-crystalline level of which are markedly decreased during aging and cataract genesis (Siezen etal , 1985) . These investigations resulted to increased interest in the structural elucidation of g-crystalline. Present work is directed towards exploring biochemical basis of lens degeneration, an understanding of which may lead to establish a relationship between lens transparency and opacity.