Publication Date


Document Type


First Advisor

Prahlad, K. V.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


Xenopus laevis; Embryology--Amphibians


The purpose of this investigation was to determine whether or not larval tissues of the amphibian Xenopus laevis are capable of responding to a very short exposure of 3,5,3'-triiodo-L-thyronine (T3), very early in their ontogeny. Ten dejellied embryos were immersed in 15 ml of aged tap water containing 30 ug of T3 per ml of medium. Exactly at the end of 24 hours all of the embryos were removed, rinsed thoroughly in aged tap water and placed in aged tap water in a larger container. Both gross morphological and histological observations were carried out on embryos and larvae at 12 hour intervals for 11 days from the termination of hormone treatment. In addition, embryos were immersed in labeled T3 to study the nature of hormone uptake. The following changes were clearly observed in experimental animals in contrast to controls (numbers in parenthesis indicate days after fertilization): (a) degenerative changes in adhesive gland (3.5); (b) more extensive development of nasal sac (5.0); (c) a visible and ventrally protruding hyoid arch (6.5); (d) a larger hind limb bud (5.0). In addition to the above, other obvious changes which were seen in experimental animals were a protruding lower jaw due to an extensive and well developed Meckel's cartilage, and a less extensive gut. The head was cone shaped in T3-treated animals. There was no change in tail to body length ratios. A greater uptake of labeled T3 was noticed in dejellied embryos than in embryos with jelly intact. Thin layer chromatography studies on butanol extracts of variously treated larvae, along with observational studies on tapazole-treated larvae, were performed. These studies showed that T3-treatment did not induce endogenous thyroid hormone synthesis. The facts mentioned above indicate a differential ontogenetic competence of embryonic and larval tissues of Xenopus in their response to T3.


Bibliography: pages [79]-84.


84 pages




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