Summary
Tail fin pieces (“discs”) of Rana pipiens tadpoles were treated with thyroxine (T4) solution (50 μg/liter) and the induced changes were studied with the light and electron microscopes. Definitive effects first appeared after 4 days of treatment. Thereafter various resorptive processes proceeded at an accelerating pace. By the 9th or 10th day the discs were reduced to tiny spherules.
The most conspicuous changes were those of the breakdown and disposal of the basement lamella. First there was a “loosening” of the collagen layers followed by massive infiltration by macrophages which engulfed the collagen fibrils. By the 8th day the phagocytosis of the basement lamella was completed for the most part and the macrophages were clumped into masses.
After 6 days of T4 treatment the epidermis was transformed from a 2- or 3-cell layered epithelium to a multilayered one. This was due to the detachment of the basal epithelial cells from the basement lamella followed by their movement towards the surface. Later, the epidermal cells showed atrophy by extensive autolytic processes.
Discs incubated in the control medium (devoid of T4) remained intact for the duration of the experiment. Their morphology was essentially the same as that described by others from studies in vivo.
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This study was supported by Grants NIH T1-GM-102, NSF GB-5913, NIH NB-00840 and NIH NB-07566, and an Institutional Grant from the New Jersey College of Medicine and Dentistry.
I am indebted to Drs. J. Osinchak and W. Etkin for their encouragement.
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Gona, A.G. Light and electron microscopic study on thyroxine-induced in vitro resorption of the tadpole tail fin. Z. Zellforsch. 95, 483–494 (1969). https://doi.org/10.1007/BF00335142
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DOI: https://doi.org/10.1007/BF00335142