Comparison of bovine corneal and scleral mucopolysaccharides

Design, synthesis, and biomedical applications of synthetic sulphated polysaccharides

This review summarizes the synthetic methods to sulphated polysaccharides, describes their compositional and structural diversity in regards to activity, and showcases their biomedical applications.

Lead concentration in different compartments of the bovine eye

It is known that lead is a metabolic substitute of calcium and recently, in vitro results showed that glycosaminoglycans and proteins are capable of binding lead. Therefore, in this work, the level of lead in aqueous humor, vitreous humor, lens and sclera of bovine eyes was analyzed in order to establish a relationship between lead concentration and the contents of glycosaminoglycans, proteins, water and calcium in those structures. Lead was determined by means of atomic absorption spectrometry after acid digestion. Our results suggest a direct relationship between the contents of proteins and glycosaminoglycans, and the ability of the different eye structures to retain lead. Nevertheless, an inverse relationship between water content and lead concentration was found. No association between calcium and lead concentrations was observed.

Age-related changes of scleral hydration and sulfated glycosaminoglycans

Human scleras were analyzed to determine if tissue hydration changed in an age-related fashion, and whether this change could be related to decreased levels of glycosaminoglycans. The anterior half of normal human scleras were examined with donor ages ranging from newborn to 99 years (n = 40). Tissue hydration was found to decrease by 1.06% per decade (P = 0.0012). Glycosaminoglycans were extracted from scleras with guanidine hydrochloride, purified by anion exchange chromatography and quantitated using dimethylene blue and selective enzymatic digestion. The glycosaminoglycans of the sclera were primarily dermatan sulfate and chondroitin sulfate with small quantities of hyaluronic acid. While no loss of chondroitin sulfate with age was detected, a significant age-related loss of dermatan sulfate was found (P = 0.0006, n = 14). An examination of the relationship between glycosaminoglycan concentration and scleral hydration showed that increased levels of sulfated glycosaminoglycans were associated with increased levels of scleral hydration (P < 0.02, n = 14). No improvement in the correlation could be achieved by considering either dermatan sulfate or chondroitin sulfate individually. Our results suggest that, as in other connective tissues, aging is associated with a loss of glycosaminoglycans, and their loss is coincident with decreased tissue hydration.

Visualization of hyaluronic acid in the anterior segment of rabbit and monkey eyes

Hyaluronic acid was visualized using a new histochemical technique: the hyaluronic acid-binding region of the cartilage proteoglycan was isolated, linked with biotin and used in histological sections as a ligand for hyaluronic acid. Staining was performed using the avidin-biotin-peroxidase technique. The presence of hyaluronic acid in the anterior segments of rabbit and monkey eyes was studied in fresh-frozen, as well as in fixed paraffin sections; addition of cetyl-pyridinium chloride to the fixative was essential. In both species intense staining was seen in the stroma of the conjunctiva, the connective tissue of the ciliary processes, and on the apical membranes of the corneal endothelium. Species differences were observed in both conventional and unconventional outflow pathways. In rabbits, the tissue located directly adjacent to the aqueous plexus and the connective tissue surrounding the poorly developed ciliary muscle were stained. In monkeys, only the anterior, non-filtering part of the trabecular meshwork and the outer wall of Schlemm's canal showed intense staining in paraffin sections. In frozen sections, the inner wall (cribriform region of the trabecular meshwork) was also stained. The spaces between the anterior part of the ciliary muscle bundles remained almost unstained.