Classification and Protein Distribution in a Series of Intracapsular Cataracts

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The crystallin profiles of the cortices and nuclei of intracapsular cataractous lenses were studied by high pressure liquid chromatography (HPLC), polyacryl-amide gel electrophoresis (PAGE), and dot blotting. The complete personal and medical history of 381 patients and the Cooperative Cataract Research Group (CCRG) classification of each were obtained. Few statistically significant associations between patient personal history and cataract types were found. Protein profiles of selected cataracts which had specifically located opacities (i.e., nuclear only, cortical only, etc.) were studied in detail. Sodium dodecyl sulphate-PAGE revealed few differences in lens-soluble proteins between cataractous and normal cortices or nuclei. By HPLC, the proteins of cataractous cortices and their nuclei differed very little from age-matched controls. The cortical proteins of nuclear cataracts appeared normal. However, two major alterations of proteins were observed in the nuclei of dense nuclear cataracts. Increased high molecular weight protein and increased components with molecular weights <20,000 Da were found in cataractous nuclei as compared with normal age-matched control lens nuclei. Dot blot (immunological) analyses identified the crystallins of normal lenses that eluted from the HPLC column more efficiently than those of cataractous lenses. Cortical protein HPLC samples had the most specificity. Nuclear protein HPLC samples of older normal and cataractous lenses had little if any alpha crystallin specificity in the void volume peak. A relation between the presence of opacities and changes in molecular weight distribution of crystallins was found in the opaque nuclei but not in the opaque cortices. Cortical opacities seem more related to structural changes in the fiber cells, whereas nuclear opacities may be related to altered states of the crystallins, such as aggregation and breakdown.

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