The distribution of glycosaminoglycans in the axial region of the developing chick embryo. I. Histochemical analysis

Histochemical analysis of the developing chick axial region indicated very little sulphated glycosaminoglycan present in early embryonic stages (stage 17) and this appeared to be confined extra‐cellularly to the region of the notochordal sheath. Strongly acidic material was observed in the cytoplasm of cells in all examined axial areas, viz., dermatome, myotome, sclerotome, neural tube and notochord. Weakly acidic anionic glycosaminoglycans were present in the extracellular portion of all axial areas and increased in concentration during development, particularly in the neural tube and the sclerotome. At the same time the concentration of sulphated anionic glycosaminoglycans also increased in the extracellular matrix of all axial areas. By stage 25 the extracellular matrix of the perichordal scleratome appeared to be mostly sulphated polyanions, but elsewhere in the axial tissues the staining for sulphated glycosaminoglycans never approached that intensity demonstrated by the weakly acidic anionic glycosaminoglycans. Testicular hyaluronidase digestion suggested that most of the stainable material was either hyaluronic acid or chondroitin‐4‐sulphate and/or chondroitin‐6‐sulphate (chondroitin sulphate A and C). There was a small amount of strongly acidic (polysulphated) glycosaminoglycan present in the scleratome, neural tube and notochord.