Fig. 4. Chemically modified heparin derivatives show differential bypass-inducing activities. (A) The structure of the disaccharide units in heparin and heparan sulfate. (B) Various concentrations of heparin derivatives were exogenously applied to exposed brains. Results are plotted as a percentage of embryos showing the bypass phenotype. The curves correspond to unmodified bovine lung heparin (filled circles), completely de-N-sulfated/re-N-acetylated heparin (open circles), completely de-6-O-sulfated heparin (filled squares), completely de-2-O-sulfated heparin (open squares), and per-sulfated heparin (filled triangles). (C) Partially de-2-O-sulfated heparin (open squares) and de-6-O-sulfated heparin (filled squares) were applied to exposed brains at 10 µg/ml. The percentage of the bypass phenotype induction is plotted against the degree of desulfation. Numbers in parentheses indicate total number of embryos.