Acceleration of amphibian embryonic melanophore development by melanophore-stimulating hormone, N6,O2-dibutyryl adenosine 3',5'-monophosphate and theophylline.

Stage 14 (Gallien and Durocher, 1957)Pleurodeles waltlii embryos were treated with α- or β-melanophore-stimulating hormone (MSH), ACTH, dbc-AMP, c-AMP plus theophylline, theophylline, 5′-AMP, or 2′,3′-AMP. The development of melanophores was accelerated (appearing two stages earlier than in control embryos) by α- or β-MSH, ACTH, dbc-AMP, c-AMP plus theophylline, or theophylline alone. By the time embryos developed to stage 28, the control and treated embryos were indistinguishable in the number, distribution, and general morphology of their melanophores, suggesting these agents do not induce melanophore formation or mitosis. Cyclic AMP alone, 5′-AMP or 2′,3′-AMP were ineffective. Accelerated cytodifferentiation apparently requires preinduction by the invaginating chordo-mesoderm during stages 13 and 14 as presumptive neural plate explants cultured before chordo-mesoderm induction (stage 8) failed to produce melanophores with or without α-MSH or dbc-AMP. Explants from stage 14 embryos treated with α-MSH or dbc-AMP developed the same number of melanophores at the approximate time that treated whole embryos developed melanophores. Whole embryo experiments involving the faster developing embryos of Xenopus laevis were similar to those described for P. waltlii.