In Vitro Regression of Tadpole Tail by Thyroid Hormone

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Abstract
The tail of tadpole (Rana pipiens) was successfully maintained in vitro over a period of 2 wk in a physiological salt solution. When Derby''s methods of tissue culture was applied to tadpoles of bullfrog, Rana catesbeiana, the tissue regressed spontaneously without stimulation of thyroid hormone. Several different media were examined to select a better culture medium for the bullfrog tadpole tissues. RPMI-1640 medium supplemented with insulin and transferrin was satisfactory for this aim. With this improved medium, the interaction between the epidermis and the mesenchyme was investigated during the hormone-induced tadpole tail regression and the epidermal dependence of the mesenchyme regression was demonstrated by the following 3 experiments. Some of the surgically prepared mesenchymes regressed in response to thyroid hormone. In these cases the mesenchymes were contaminated with the remaining epidermal cells. Complete removal of the epidermis was accomplished by the chemical treatment. The mesenchyme thus obtained (nude tail fin) was insensible to thyroid hormone. Skin conditioned medium (SCM) was prepared by culturing the skin in the presence and absence of thyroid hormone. Nude tail fin regressed when cultured in the SCM containing thyroid hormone.