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M. Wyman, M. Wang, P.F. Kador; Structure of Asteroid Hyalosis in the Vitreous of Galactose–Fed Dogs . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4224.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Asteroid hyalosis is a common degenerative process in which fatty calcium globules collect within the vitreous humor. The condition rarely causes visual disturbances and surgical removal is only rarely required when the floaters are visually disabling. The presence of asteroid hyalosis has been associated with systemic diseases such as diabetes, hyperlipidemia or hypertension; however, research in this area has been hampered by the lack of an animal model that forms asteroid hyalosis. Recently, we have observed that asteroid hyalosis occurs in galactose–fed dogs and the purpose of this study was to identify the main structural component of asteroid hyalosis in the vitreous of the dog. Methods: Vitreous humor containing asteroid hyalosis (AH) was collected and frozen from long–term galactose–fed beagles along with vitreous samples from age matched normal controls where asteroid hyalosis was absent (VH). The vitreous samples were sonicated into HPLC grade water and extracted with chloroform and butanol. The organic layers were dried in vacuo and the residues were analyzed by electrospray mass spectroscopy (ESI). Commercial elemental analysis was also conducted on portions of the vitreous samples. Results: : Vitreous samples containing asteroid hyalosis (AH) contained increased amounts of calcium and phosphorous. Negative mode ESI indicated that a predominant m/z 538.4 peak was present in the n–butanol extracts from both AH and VH samples. However, in the chloroform extracts, 3 peaks with m/z values of 547.1, 690.5, 1430.6 were only present in vitreous samples containing AH. Subsequent subtraction analysis identified the m/z 690.5 ion as the main difference peak. This peak was identified and confirmed to be the quasimolecular ion of 1,2–dipalmitoyl–glycero–3–phosphoethanolamine (DPPE). Conclusions: The main component of asteroid hyalosis in the galactose–fed dog is a quasimolecular ion of DPPE in which 2 molecules of 1,2–dipalmitoyl–glycero–3–phosphoethanolamine are complexed through their phosphates groups with calcium.
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