The periphery of the developing collagen fibril. Quantitative relationships with dermatan sulphate and other surface-associated species

Dermatan sulphate, hydroxyproline and collagen fibril diameters were measured in flexor tendons from chick and calf limbs, from early in embryonic development to maturity. The collagen fibril is viewed as a long thin cylinder. A species X present at the periphery of the cylinder, regularly and specifically arrayed along the fibril, should then satisfy the relationship [X]/[collagen]r = k where [X] and [collagen] are tissue concentrations of X and collagen, and r is the fibril radius. Throughout the developmental period studied, dermatan sulphate (i.e.X) in chick, calf and rat tendons fits the relationship, implying that it is specifically, regularly and entirely associated with collagen fibrils, thus confirming and extended previous electron histochemistry [Scott & Orford (1981) Biochem. J. 197, 213-216]. This approach explains the pattern of change of dermatan sulphate content during development of the tendon. The findings imply that the dermatan sulphate proteoglycan-collagen interaction is evolutionarily highly conserved. The relationship [X]/[collagen]r = k is used to show that surface concentrations of covalently bound species, such as extension propeptides, can be easily assessed, given the data base described in paragraph 1 above.

Electron histochemistry and ultrastructural localization of carbohydrate-containing substances in the sheath of Volvox.

The location and characteristics of carbohydrate-containing structures within the intact sheath of Volvox were studied by 3,3'-diaminobenzidine tetrahydrochloride-osmium, colloidal iron, colloidal thorium, ruthenium red and periodic acid-silver methenamine staining. The sheath consists of external and internal fibrillar layers separated by a tripartite structure. The external layer reacts positively with 3,3'-diaminobenzidine tetrahydrochloride, colloidal iron, colloidal thorium and ruthenium red, indicating that it contains acid mucosaccharides. Staining in the external layer is abolished by Ba(OH)2 treatment. The tripartite structure and internal fibrillar layer contain periodic acid reactive groups which do not occur in the external layer. Under certain conditions, reactions between the cationic dyes and the internal material were also observed. It is postulated that the internal matrix of the sheath contains glycoproteins or a mixture of acid mucosaccharides and glycoproteins. Possible functions of the sheath material are discussed.