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Abstract
Cataracts were induced in rat lenses by irradiation with x-rays generated at 1S5 kv. A single exposure of 1,000 τ or 500 τ was directed toward one eye, the other being shielded and used as the control. Sections from control lenses and lenses in different stages of cataract xoere studied by quantitative microradiography. This method enables the distribution of protein to be determined down to a subcellular level within the lens. Compared to normal lenses, the concentration of protein was reduced in most parts of the cataractous lens, most prominently in mature cataracts. The salient features were sharp, steep gradients in the distribution of protein, usually situated in the peripheral cortex. A close correspondence was present between the position of these protein gradients and that of the opacities. In the microradiograms of cataractous lenses, morphological changes in the lens fibers were identified. The physical basis of the opacities in these cataractous lenses is discussed. It is concluded that the main loss of transparency is due to mechanisms of reflection in the steep protein gradients corresponding to interfaces between regions with different refractive indices.