Chick limb buds from 4- to 7-day-old embryos and sterna from 14-day-old embryos were labeled with [35S]sulfate, and the sulfated proteoglycans (PGS) were extracted either with associative (0.5 M guanidine . HCl) or dissociative (4.0 M guanidine . HCl) solvents. The existence of several populations of PGS is revealed in each age group when the limb extracts are analyzed on sucrose density gradie...