Association of an ultraviolet irradiation sensitive cytoplasmic localization with the future dorsal side of the amphibian egg.

Drastic alterations in neural morphogenesis can be induced by ultraviolet irradiation of the amphibian egg. The target area of U.V. was determined either by direct irradiation of various regions of the egg or by comparing the area of the U.V. hit with the location of the dorsal lip. Axolotl eggs which displayed easily recognizable gray crescents were employed for the direct irradiation experiments and albino axolotl eggs were used for a comparison of the U.V. sensitivity of the animal and vegetal halves of the egg. Marked frog eggs were employed to determine the relationship between the sensitive area and the site of formation of the dorsal lip. It was concluded that the dorsal marginal zone of the fertilized, uncleaved egg was the most sensitive area of the egg. Ovarian homogenates provide a source of material for correcting, by microinjection, the effects of U.V.