Specific spatial and temporal expression of native CS/DS sulphation motif epitopes recognized by mAbs 3B3(−) and 6C3 in developing embryonic chick tissues at stages E12 and E14. Joint tissues from stage E12 [A–F] and E14 [G–L] embryonic chicks stained with Alcian Blue [A,B,G,H] and immunostaining with mAbs 3B3(−) [C,D,I,J] and 6C3 [E,F,K,L]. Circles indicate regions shown at higher magnifications in adjacent frames. The asterisks (*) highlight unstained fibrocartilagenous articular cartilage; that is, at E12 mAb 6C3 is broadly labelling the epiphyses and not the overlaying fibrous articular cartilage, whereas 3B3(−) immunostaining is different and identifies a specific subset of cells and matrix in the developing articular cartilage.