A study of the role of sulfhydryl groups in morphogenesis of the chick embryo.

The teratogenic effects on chick embryos of chloroacetophenone (CAP), a specific sulfhydryl blocking agent, are known to be reversible by a subsequent treatment with cysteine. However, cysteamine, the decarboxylation product of cysteine has been found to be unable to ameliorate the syndrome caused by CAP. It is suggested that CAP may act by binding the sulfhydryl of free cysteine in the cells of the organizer, thus indicating that cysteine may act as an inducing stimulus in primary organizer action. Post-nodal pieces of chick blastoderm exposed to the action of cysteine for 6 hours show differentiation of axial embryonic structures. Cysteamine has no such stimulatory effects on post-nodal pieces. This finding seems to further support the conclusion that cysteine may act as an inducing stimulus in primary organizer action.