Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A study of the membranes of human lens fiber cells revealed a very high protein to lipid ratio, which tended to increase with aging and in brunescent cataract. Phospholipids were more abundant than cholesterol, cholesterol esters, and other neutral lipids. With aging and cataract formation, a marked decrease in membranes phospholipid content occurred. Sphingomyelin was present in highest amount. Phosphatidylethanolamine, phosphatidylcholine, lysophosphatidyl-ethanolamine, phosphatidylserine, and phosphatidylglycerol were also present. Cholesterol represented approximately 40% of the total lipids. Saturated and unsaturated fatty acids having 16 to 24 carbons were present. The lipid composition varied according to the portion of the lens examined and the state of the lens. The results do not support a conclusion that lipid peroxidation represents a major mechanism of membrane damage that contributes to cataract formation, since there is no decrease in unsaturated fatty acids with age or in cataractous lenses. We suggest that the aggregation of soluble proteins, and their association with lens membranes, and altered membrane function due to the loss of phospholipids are important processes leading to loss of transparency.
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PMID:Lipids of human lens fiber cell membranes. 646 65

The presence of toluidine blue-staining vesicles and leaky membranes in the Philly mouse lens as early as 10 days after birth led us to investigate the phospholipid metabolism of these lenses. On a dry weight, or per lens, basis, the Philly mouse lens had a slightly higher than normal concentration of phosphatidyl choline (PC), phosphatidyl ethanolamine (PE), sphingomyelin (S) and cholesterol (C) at 10 days. The levels of PC and PE dropped between 10 and 30 days in the Philly mouse, while in the control lenses the amounts of both phospholipids, on a per lens basis, was increasing. 32P incorporation indicated an increased rate of turnover in the Philly lenses. Cholesterol and sphingomyelin concentrations closely paralleled the dry weight per lens curves in the Philly and control, Swiss-Webster, lenses. Sphingomyelin specific activity dropped rapidly in the first 10 day period, possibly reflecting the lowered PC pool available for S biosynthesis. These results suggest a lower utilization of biosynthesized lipids for membrane assembly in the Philly lens. The observed higher turnover of metabolically-active phospholipid supports the presence of increased degradative activity which may, in turn, result in leaky membranes and, thus, contribute to cataract development.
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PMID:Membrane lipid biosynthesis in the Philly mouse lens. I. The major phospholipid classes. 670 54

In passing through the lens, light crosses thousands of cell membranes. To explore the possible contribution of lipids to the scattering properties of the lens, we have carried out in vitro studies with lipids extracted from human lenses 1-90 years of age. Sphingomyelin and human lens lipids were extruded into large unilamellar vesicles (LUVs). The intensity of light scattered by human lens LUVs increased with age and lipid hydrocarbon chain order. Hydrocarbon chain order also correlated with light scattering intensity by sphingomyelin LUVs. Light scattered by LUVs composed of sphingomyelin (1-30 mg ml(-1)) was 20 to 100 times more intense than that scattered by the same concentration of alpha-crystallin in aqueous media. Increased lipid hydrocarbon chain order as well as variations in the headgroup and interfacial region of bilayers resulting from lipid compositional changes can influence membrane light scattering properties. In vitro measurements suggest that the contribution to light scattering by lipids may be significant and should not be disregarded in the investigation of factors and components that lead to the increase in light scattering by human lenses with age and cataract.
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PMID:Light scattering of human lens vesicles in vitro. 1269 24