In their paper on opossum cartilage, Archer et al. (1996)
contend that their ‘data pose questions [ctdot ] to the idea that
global patterns of matrix components exist in mammalian
articular cartilages’. We believe that this statement is not
supported by their data. The points at issue concern the
distributions of chondroitin sulphate (CS) and keratan
sulphate (KS) in adult cartilage. Earlier work showed that:
(1) the highest concentrations of CS are in the midzone of
the noncalcified layer of the cartilage (Stockwell & Scott,
1967; Maroudas et al. 1969; Lemperg et al. 1974), while the
authors' opossum data apparently show that the intensity of
staining with Safranin O (and various antibodies specific for
CS) ‘is greatest in the upper third of the tissue depth’; (2)
in the noncalcified cartilage, the concentration of KS
increases with distance from the articular surface (Stockwell
& Scott, 1967; Maroudas et al. 1969; Venn, 1978). By
contrast in the opossum, the authors state that there was
‘intense labelling throughout the upper half of the articular
cartilage depth’. They considered that this finding, in
particular, questions ‘the notions which link KS substitution
with conditions of low oxygen tension’, since articular
cartilage generally obtains its nutrient and O2 through the
articular surface and thence by diffusion through the tissue depth.
