Proteoglycan-fibrillar collagen interactions

A quantitative chemical study of glycosaminoglycans in the articular disc of the bovine temporomandibular joint

Glycosaminoglycans were prepared from the disc by digestion with papain. The disc contained 5% of its dry weight as glycosaminoglycan. Fractionation by ion-exchange chromatography, followed by precipitation at varying concentrations of ethanol, together with chemical and enzymatic analyses, showed this glycosaminoglycan to consist of approx. 5% hyaluronic acid, 14% dermatan sulphate, 79% chondroitin sulphate and 2% keratan sulphate. Disaccharides obtained from the chondroitin sulphate were 75% 6-sulphated, 21% 4-sulphated and 4% non-sulphated. Chemical analysis showed a low average degree of sulphation of chondroitin sulphate. Immunohistochemical staining of sagittal sections of the disc showed chondroitin sulphate to be distributed throughout, whereas dermatan sulphate (as proteodermatan sulphate) appeared to be concentrated in the periphery.

Vitreous humor of chicken contains two fibrillar systems: an analysis of their structure

An analysis of the structure of chicken vitreous humor after brief homogenization of the tissue was performed. Electron micrographs prepared after rotary shadowing with platinum showed the presence of two distinct fibrils. The collagen fibril was coated by glycosaminoglycan which could be removed by chondroitinase ABC digestion. In addition, individual molecules of tenascin were observed wrapped around some of the collagen fibrils. A second beaded fibril was present and several fine filaments were observed to extend from each bead. The beaded fibril is formed by the overlap of these filaments, and beaded fibrils were observed in either a "closed" or an "open" form dependent on whether all of the filaments are brought together to form the overlap. A schematic diagram is presented for the structure of the beaded fibril. The potential relationship of the beaded fibril to the zonular fibrils and the elastin microfibrils is briefly discussed.

Identification of specific binding sites for keratan sulphate proteoglycans and chondroitin-dermatan sulphate proteoglycans on collagen fibrils in cornea by the use of cupromeronic blue in 'critical-electrolyte-concentration' techniques

Proteoglycans (PGs) in bovine corneal stroma were stained with Cupromeronic Blue in 'critical-electrolyte-concentration' (CEC) methods for electron microscopy, and were located vis-à-vis collagen fibril a-e banding patterns. Keratanase and chondroitin ABC lyase digestion showed that a + c-band- and d + e-band-associated PGs were keratan sulphate-rich and chondroitin (dermatan) sulphate-rich respectively. The CEC pattern proved that the keratan sulphate PGs at the a and c bands differed. Comparison of their CECs with their behaviour on anion-exchange chromatography confirmed previous (indirect) attempts at identification [Scott & Haigh (1985) Biosci. Rep. 5, 765-774]. Similar arguments were applied to the dermatan sulphate PGs at the d and e bands. These results strongly support the one-PG-one-binding-site hypothesis [e.g. Scott (1988) Biochem. J. 252, 313-323]. Remarkable inter-species variations in the keratan sulphate PG patterns contrast with the relatively constant picture of dermatan sulphate PG-collagen fibril interactions.