Spectroscopic evaluation of human tear lipids.

Infrared and fluorescence spectroscopies were applied to characterize the molecular conformational/structure and dynamics of human meibum (ML) and tear lipids (SSL). ML lipids contained more CC and CH3 moieties than SSL. SSL contained OH groups that were not apparent in the spectra of ML.

Oxidation-induced changes in human lens epithelial cells 2. Mitochondria and the generation of reactive oxygen species.

The relationships among reactive oxygen species (ROS) generation, lipid compositional changes, antioxidant power, and mitochondrial membrane potential were determined in a human lens epithelial cell line, HLE-B3. Cells grown in a hyperoxic atmosphere grew linearly for about 3 days, and then progressively died. Total antioxidant power and ROS generation increased by 50 and 43%, respectively, in cells grown in a hyperoxic atmosphere compared to those cultured in a normoxic atmosphere.

Regulation of sarco/endoplasmic and plasma membrane calcium ATPase gene expression by calcium in cultured human lens epithelial cells.

Since Ca(2+)-ATPase is a major determinant of calcium homeostasis in the lens, we examined the expression of Ca(2+)-ATPase by calcium. An immortalized human lens epithelial cell line, HLE B-3, was treated with thapsigargin to inhibit sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) releasing calcium from intracellular stores. Isoforms of the plasma membrane Ca(2+)-ATPase (PMCA) and SERCA were quantified by Western blot and quantitative real time reverse transcription polymerase chain reaction.

The influence of membrane lipid structure on plasma membrane Ca2+ -ATPase activity.

Lipid composition and Ca(2+)-ATPase activity both change with age and disease in many tissues. We explored relationships between lipid composition/structure and plasma membrane Ca(2+)-ATPase (PMCA) activity. PMCA was purified from human erythrocytes and was reconstituted into liposomes prepared from human ocular lens membrane lipids and synthetic lipids.

alpha-Crystallin binding in vitro to lipids from clear human lenses.

The association of alpha-crystallin to lens membranes increases with age and cataract. Lipid compositional changes also occur with age, cataract, and diabetes. In this study we determined the influence of lipid compositional differences on the binding capacity of alpha-crystallin to lipid vesicles in vitro.

Human lens phospholipid changes with age and cataract.

Purpose: To determine the phospholipid changes responsible for the increase in membrane lipid hydrocarbon chain order, or stiffness, with age and cataract in the human lens.

Methods: Clear human lenses were pooled into four groups, with donors ranging in age from 15 to 29, 30 to 49, 50 to 64, and 65 to 74 years. Whole human cataractous lenses were obtained from donors after extracapsular cataract extraction.

Direct perturbation of lens membrane structure may contribute to cataracts caused by U18666A, an oxidosqualene cyclase inhibitor.

Induction of cataracts in experimental animals is a common toxic feature of oxidosqualene cyclase (OSC) inhibitors. U18666A has been shown to produce irreversible lens damage within a few weeks of treatment. Drug actions, besides reducing the availability of cholesterol, could contribute to cataract formation.

Influence of age, diabetes, and cataract on calcium, lipid-calcium, and protein-calcium relationships in human lenses.

Purpose: Calcium is elevated in most cataractous human lenses and may contribute to cataractogenesis. In this study, age-related changes were examined in the total calcium content of clear human lenses and the binding of calcium to lens lipids and proteins.

Methods: Total lens calcium was determined by atomic absorption spectroscopy.

Light scattering of human lens vesicles in vitro.

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).

Isolation and lipid characterization of cholesterol-enriched fractions in cortical and nuclear human lens fibers.

Purpose: Human lens membranes contain unusually high levels of cholesterol and sphingolipids, lipids known to segregate into liquid-ordered domains. The current study was conducted to pursue the determination and characterization of these domains in membranes of clear and cataractous human lenses.

Methods: Cortical and nuclear regions of aged clear and cataractous lenses were obtained.

31P NMR quantification and monophasic solvent purification of human and bovine lens phospholipids.

Most lipid extraction procedures [Folch, J., Lees, M., and Sloane-Stanley, G.