Abstract
Some 3000 tadpoles (Rana pipiens) were treated during 5 months with the oestrogenic hormone theelin obtained from the Biochemical Laboratory of Doctor Doisy. Several series of experiments were carried on simultaneously in which the tadpoles were exposed to different concentrations of theelin over varying periods of time. In other experiments 100 tadpoles were injected with the hormone.
In one series 250 tadpoles just emerged from the gelatin coating were placed in a 1000 cc. aqueous solution of theelin 0.0000003125 mg./cc. for 60 minutes. On successive days the exposure time was increased by 60 minutes for a period of 10 days. This time increment was kept constant during the rest of the experiment but the concentration of the hormone was doubled every 10 days until a concentration of 0.0000025 mg/cc. was attained. The experiment was completed on the 40th day. Higher concentrations of the hormone effected a marked change during the last 10 days of the experiment.
Microscopic examination of fresh epidermis mounts revealed a recession of pigment centrally toward the cell body in the epidermal melanophores and a pseudopodial expansion of the leucophores.
Some 65 tadpoles (total length 26 mm.) were injected intraperitoneally with 0.05 cc. theelin 0.00035 mg./cc. on. 3 successive days by means of a glass needle (0.1 mm. diameter) attached to a Chambers microinjection apparatus. Color change (silvering) was first observed on the 6th day after the first injection. Tadpoles A and C (Fig. 1) shou the color change following the injection. Tadpole B (Fig. 1) is a control. This is a photograph of the living animals quieted in iced water. Fig. 2 shows a mounted section of epidermis from the mid-tail region of tadpole B. The epidermal melanophores are multi-branched with frequent anastomosis
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