ABSTRACT
Elaine R. Bermany Hadassah-Hebrew University Medical School, Jerusalem, Israel
n INTRODUCTION 393
n FIBER CELL PLASMA MEMBRANES AND CYTOSKELETON 393 n Main Intrinsic Protein 393 n Other Membrane Proteins 394 n Cytoskeletal Components 394
n CRYSTALLINS AND ENZYME ACTIVITIES 394 n Overview 394 n High-Molecular-Weight
Aggregates 396
n LENS METABOLISM 396 n Overview 396 n Glycolytic and Oxidative
Enzymes 397 n Glycation Reactions 397 n Photochemical Changes 398
n REFERENCES 399
Aging is intimately associated with lens opacification (cataract), and the latter is often perceived as an accelerated form of aging. A broad spectrum of biochemical and structural changes occur in the lens during normal development, maturation, and aging. Among the most prominent in the aging lens are increases inweight, thickness, coloration,nontryptophan fluorescence, and light absorbance (18,19).Absorbanceof light at <400nm is more than double at 76 years of age than at 42 years of age (Fig. 1). Other important agerelated changes include increased glycation of crystallins and cleavage of fiber cellmembraneproteinMP26. There arealso significantdecreases inenzymeactivities.A large body of information has accumulated during the past two decades on these changes, and for clarity of presentation, this discussion is limited to age-related changes found in clear noncataractous lenses.
