The effect of calcitonin on the prechordal mesoderm, neural plate and neural crest of Xenopus embryos.

Developing Xenopus embryos treated during gastrulation with 22 micrograms/l of salmar calcitonin in the ambient water develop into larvae exhibiting a decrease in interocular distance. In view of the hypocalcaemic properties of calcitonin and the importance of calcium ions in cell aggregation, this phenomenon has been attributed to an alteration in cell adhesion which results in faulty cell migration during gastrulation with consequent abnormalities of the prechordal region of the archenteron roof and the overlying neural plate. Histological examination of affected specimens shows that the principal defect arising from the prechordal mesoderm and prechordal plate is aglossia and a severely reduced oral cavity. This results in narrowing of the head and consequent decrease in interocular distance. Accompanying this effect is distortion of the diencephalon and third ventricle, which may indicate faulty induction of the neural plate by the perturbed subjacent prechordal region.