Ultrastructural observations on some membranous cytoplasmic inclusion bodies in follicular cells of experimentally-induced goitres in tadpoles and toads of Xenopus laevis Daudin

Summary Tadpoles and young toads of Xenopus laevis were maintained in aqueous solutions of potassium perchlorate or thiourea (0.005% or 0.01% w/v) for up to 20 months. Metamorphosis of tadpoles was inhibited. Within a short time large well-vascularized goitres developed in both tadpoles and toads. An ultrastructural investigation of some of the follicular epithelial cells of these goitres revealed some unusual cytoplasmic membranous inclusions and a morphological account of these structures is presented. It is suggested that some of these complex membranous inclusions may give rise to cytosomes. The relationship between these complex cytoplasmic organelles is considered together with their possible significance and role in thyroid cell functioning.This work was carried out during the tenure by one of us (R.C.) of a Medical Research Council Scholarship and forms part of a programme of research in amphibian thyroid physiology supported by the Medical Research Council to whom we are indebted for their generous assistance.