Osmo Regulation Of Amphibian Embryos And The Effects Of Thyroid Inhibitors And Accelerators On Metamorphosis

Abstract

It was the original intent that this paper he written on the effects of such compounds as Thyroxin, Tri-iodothyronine, Thiouracil, thymus material and others (see chapter IV) on the rate of metamorphosis in the tadpole larva of Rana pipiens. The experimentation for this work would involve either subjecting the tadpoles to environmental solutions which contained non-lethal concentrations of the various compounds to be tested, or injecting the tadpoles with these same compounds, then observing and interpreting the effects upon the resulting metamorphic changes. To perform the above experiments with proper technique it is necessary to obtain approximately 300 tadpoles, all of the same age (about four weeks from fertilization) and all of which have experienced as uniform environmental conditions as possible. The best manner for obtaining these uniform specimens would be one of artificially inseminating a large group of ovulated frog eggs and carefully keeping the early environment uniform for all the organisms involved. The difficulties encountered in attaining this uniform group of tadpoles have shown themselves to be much more extensive than was expected. Because of these difficulties the first chapter of this thesis deals with the techniques and problems involved in acquiring and fertilizing the amphibian egg. The second chapter, then, will be to follow the fertilized egg in its early development. This will include the normal embryonic amphibian development. The third chapter deals with the many abnormalities encountered in varying osmotic conditions with both Rana pipiens and Rana petiosa, plus a conclusion of the attained results. It is the purpose of the fourth chapter to provide a brief resume' of the influence of various compounds which affect either the thyroid gland of the pituitary gland of the metamorphosing tadpole. This will include a historical view of the many experiments which have been performed in this field and more specifically recent investigations in which injections and environmental solutions of more limited compounds have been compared.It was the original intent that this paper he written on the effects of such compounds as Thyroxin, Tri-iodothyronine, Thiouracil, thymus material and others (see chapter IV) on the rate of metamorphosis in the tadpole larva of Rana pipiens. The experimentation for this work would involve either subjecting the tadpoles to environmental solutions which contained non-lethal concentrations of the various compounds to be tested, or injecting the tadpoles with these same compounds, then observing and interpreting the effects upon the resulting metamorphic changes. To perform the above experiments with proper technique it is necessary to obtain approximately 300 tadpoles, all of the same age (about four weeks from fertilization) and all of which have experienced as uniform environmental conditions as possible. The best manner for obtaining these uniform specimens would be one of artificially inseminating a large group of ovulated frog eggs and carefully keeping the early environment uniform for all the organisms involved. The difficulties encountered in attaining this uniform group of tadpoles have shown themselves to be much more extensive than was expected. Because of these difficulties the first chapter of this thesis deals with the techniques and problems involved in acquiring and fertilizing the amphibian egg. The second chapter, then, will be to follow the fertilized egg in its early development. This will include the normal embryonic amphibian development. The third chapter deals with the many abnormalities encountered in varying osmotic conditions with both Rana pipiens and Rana petiosa, plus a conclusion of the attained results. It is the purpose of the fourth chapter to provide a brief resume' of the influence of various compounds which affect either the thyroid gland of the pituitary gland of the metamorphosing tadpole. This will include a historical view of the many experiments which have been performed in this field and more specifically recent investigations in which injections and environmental solutions of more limited compounds have been compared.