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I.A. Butovich, M.A. Di Pascuale, E. Uchiyama, J.D. Aronowicz, J.P. McCulley; Mass Spectrometric Analysis of Polar and Nonpolar Lipid Species Found in Meibomian Gland Secretions . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5605.
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© ARVO (1962-2015); The Authors (2016-present)
To qualitatively characterize the major polar and nonpolar lipid species present in meibomian gland secretions (MGS) of individual human subjects by means of mass spectrometric (MSn) analysis.
The samples of MGS collected from normal subjects and dry eye patients were analyzed individually on an LCQ Deca XP Max MSn ion trap mass spectrometer (Thermo Electron Corp., USA). The lipid material dissolved in MeOH:CHCl3=2:1 (v/v) solvent mixture was directly infused into the mass spectrometer and analyzed in both the negative and the positive ion modes. To obtain more detailed information on the structures, the major detected parent ions were isolated and subjected to further sequential fragmentation.
In the negative ion mode, three major compounds with m/z values of 730, 758 and 786 (all M–1) were systematically detected in all the samples. MSn analysis of them revealed that they were apparently related to anionic lipids of phosphatidyl glycerol family. Multiple parent peaks were observed in the positive ion mode. Among those, previously identified cholesterol (m/z 369.5, M–H2O+1) and a compound believed to be oleamide (m/z 304.5, M+23) were found. The other major compounds were nonpolar lipids of general formula CnH2n–2O2 (n=38–48, m/z 563, 577, 591, 605, 619, 633, 647, 661, 673, and 701, all M+1) and/or CnH2n–1 NO. Compared to normal subjects, the MGS from dry eye patients showed a tendency toward increased cholesterol to the other nonpolar lipids ratio, as well as decreased production of the anionic lipids, especially the compound with m/z ratio of 786.
The observed differences in the lipid compositions between normal subjects and dry eye patients could contribute to the differences in the physicochemical properties of the TFLL between two the groups and health or lack thereof of the ocular surface epithelium.
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