Further studies on the role of sulfhydryl groups in the morphogenesis of the chick embryo.

The teratogenic effects on chick embryos of chloroacetophenone, a specific sulfhydryl reagent, are known to be reversible by cysteine and glutathione. Dithiothreitol (Cleland's reagent) and thiomalic acid cannot ameliorate the -SH block syndrome. While cysteine and glutathione can elicit differentiation of axial structures in the post-nodal pieces of the chick blastoderm, dithiothreitol and thiomalic acid cannot do so. This finding seems to suggest that the naturally occurring thiols, cysteine and glutathione, play an important role in the primary organizer action.