Cornea, acid mucopolysaccharides

Chondroitin 4- and 6-sulfates were originally designated as chondroitin sulfate A and C, respectively, and the close similarity in structure between them is demonstrated by the fact that both mucopolysaccharides yield the same disaccharide (chondrosine) on controlled, acidic hydrolysis together with sulfuric and acetic acids. Chondroitin 4-sulfate or chondroitin 6-sulfate, or both, occur in cartilage and adult bone, and the former mucopolysaccharide is a minor constituent of ligamentum nuchae and cornea (M17). Chondroitin 6-sulfate is a minor constituent of umbilical cord and occurs with dermatan sulfate (chondroitin sulfate B) and hyaluronic acid in heart valves and adult connective tissue (M17). An acid mucopolysaccharide isolated from human plasma resembles chondroitin 4-sulfate in its properties (S4). 

Keratan sulfate constitutes approximately half the total mucopolysaccharide fraction of bovine cornea, where it was isolated originally by Meyer et al. (M16). It occurs fairly widely in animal connective tissues, and its presence has been reported in nucleus pulposus (G2), aorta (B17), and costal cartilage (M20). Unlike the acid mucopolysaccharides described previously, keratan sulfate contains no uronic acid residue but is comprised of V-acetyl-n-glucosamine, D-galactose, and sulfate, in equimolar ratio. The small amount of L-fucose detected in acidic... 

Keratan sulfate an acidic mucopolysaccharide composed of N-acetyl-o-glucosamine 6-sulfate and D-galactose, linked alternately by P-1,3 and P-1,4 glyco-sidic bonds. K.s. is found in the cornea of the eye, in cartilage, in the aorta and in intervertebral discs. For formula, see Lysosomal storage diseases (Mucopolysaccharidoses). 

The only body part that has transparent materials in the human body is the eyeball. The cornea, lens and vitreous humor consist mainly of collagen and acidic mucopolysaccharides, which makes them gels. The attempt to use natural polymer gels as a cataract cure has met with limited success due to biocompatibility problems and long-term stability. On the otiier hand, if vitreous humor substances are replaced by artificial materials made of PVA hydrogel, the properties (transparency and refiactive index) are very like those of the vitreous humor. Hence, it is ideal as a replacement material [12]. 

Hyaluronic Add Sulfate.—Meyer and Chaffee108 showed that this mucopolysaccharide of the cornea was a true derivative of hyaluronic acid, since it could be hydrolyzed enzymically by what is now known as hyaluronidase. ... 

This mucopolysaccharide, possessing a strueture similar to those of chondroitin 4- and 6-sulfates but with a small content of sulfate, was isolated from bovine cornea (M16). Chondroitin resembles hyaluronic acid in its rate of hydrolysis by testicular and bacterial hyaluronidases, but was differentiated from hyaluronic acid ([a]n —65° to — 78°) by its optical rotation ( [o]d — 21°). Its structural similarity to chondroitin 4- and 6-sulfates was indicated by the fact that chondrosine was released in high yield on controlled, acidic hydrolysis (D3). The isolation of this mucopolysaccharide is of particular interest since it may be a precursor in the biosynthesis of chondroitin 4- and 6-sulfates. 

In rheumatic disease, the main pathological manifestations appear in connective tissue, the chief constituents of which are collagen, elastin and mucopolysaccharides. The last, apart from hyaluronic acid and chondroitin of cornea, are all sulphate esters , the sulphate groups of which are in a dynamic state with a short biological half-life. The sulphate exchange is under enzymic control and can be decreased in vitro and in vivo by corticosteroids " . Bostrom and Mansson examined the effects of a number of salicylates on the incorporation of S into calf costal cartilage slices in vitro. 

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