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T. Matsuo; Cyclic Tetrasaccharide Prevents Cataract Formation in the Lens in vitro . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3856.
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Purpose: Cyclic tetrasaccharide has a ring structure consisting of four glucose residues joined by alternate alpha–1,3 and alpha–1,6 linkages. The structure is rigid and resistant to enzymatic hydrolysis by glycosidases such as amylases and alpha–glucosidases. Cyclic tetrasaccharide is present naturally at least in yeast but its biological function remains unknown. Recently, Hayashibara Biochemical Laboratories (Okayama, Japan) succeeded in mass production of cyclic tetrasaccharide from starch by a successive reaction of two glycosyltransferases, 1,6–alpha–glucosyltransferase and 1,3–alpha–isomaltosyltransferase. In this study, I tested whether cyclic tetrasaccharide could prevent cataract formation in isolated porcine lenses in vitro. Methods: Porcine eyes were obtained from a local slaughterhouse and used within 6 hours. The eye globes were cut at the midperiphery with a razor blade and the pressure with fingers was applied to the globe to eject the lens without touching. The isolated lenses were then washed with saline and transferred with a spoon to wells of a 24–well multidish with a lid. The lenses were maintained in saline, 1, 10, and 100 mM trehalose in saline, or 1, 10, 20, 50, and 100 mM cyclic tetrasaccharide in saline for one month in room temperature and in room humidity. Solution change or aeration was not done during the period. Cyclic tetrasaccharide was provided by Hayashibara Biochemical Laboratories. The lenses were observed with a dissecting microscope with transmitting light source (Olympus, Tokyo, Japan) and the images of the lenses were captured through a CCD camera into a computer with a software (ViewFinder, Olympus). The lens opacity was measured as mean density in a circle area placed inside the lens by Scion Image program. Results: Cyclic tetrasaccharide at the concentrations of 50 mM and 100 mM significantly prevented the development of lens opacity compared with saline, trehalose, and 20 mM or lower concentrations of cyclic tetrasaccharide. During the first several days, the lenses with 100 mM cyclic tetrasaccharide became opacified due to a high osmolarity of the solution but became translucent again afterwards. The lenses maintained translucency even after one month with 50 or 100 mM cyclic tetrasaccharide. Conclusions: Cyclic tetrasaccharide prevented the lens from developing the opacity in vitro. Cyclic tetrasaccharide could be used as a cataract–preventing agent.
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