Teratogenic effects of retinoic acid and dimethylsulfoxide on embryonic chick wing and somite

In order to document the stage(s) at which the embryonic chick wing bud is sensitive to vitamin A teratogenesis and the kinds of defects produced by vitamin A insult to the embryonic chick wing, 1-microgram doses of retinoic acid (1 microliter RA in 90% DMSO at a concentration of 1 microgram/microliter) were locally applied to the right wing bud of chick embryos at stages 17-23 (Hamburger and Hamilton: J. Morphol., 88:49-92, '51), and the resulting limb skeleton anatomy was observed at 10 days of incubation. Local application of RA at stages 17-20 resulted in distal wing skeleton defects. There were significantly more wing skeleton defects among embryos treated at these stages with RA solution than among solvent (DMSO)-treated control embryos and than among untreated control embryos. Wings of embryos treated with RA at stages 21-23 were always normal. Scapular and vertebral defects were seen at 10 days of incubation among embryos which had been treated prior to stage 21 with both the RA solution and the solvent control. Statistical analysis and histological data suggest that scapular and vertebral defects were caused by DMSO-induced damage to somites.