Proteoglycans in the notochord sheath of lampreys

The distribution of proteoglycans in the sheath and epithelial cells of the lamprey notochord had been studied using electron microscopy on material stained with the dye cupromeronic blue (CMB). CMB-precipitates, which indicate the presence of sulphated proteoglycans, were found in the inner collagenous but not the outer "elastica externa" regions of the notochord sheath. Precipitates were also found in the zone of the basement membrane of the notochord epithelial cells, in intercellular spaces within the notochord epithelium, and in intracellular spherical bodies of the epithelial cells. These results indicate that the proteoglycans in the notochord sheath are produced by the notochord cells. The combined presence of sulphated proteoglycans and collagen type II in the notochord sheath parallels the situation found in the cartilage of higher vertebrates.