ABSTRACT
An experimental model for the study of hyperthyroidism in embryonic development was achieved in the local anuran larvae, Bufo melanostictus, by treatment with potassium perchlorate at a critical dose and time of embryogenesis.
Phocomely-hemimely and digital deformities of foreand hind limbs in high percentages of the population were found associated with such critically stimulated tadpoles. Similar deformities were reproduced by exogenous treatment with L-thyroxine sodium. The deformities were severely aggravated if the tadpoles had anti-thyroid treatment before critical stimulation with thyroxine in the sensitive phase of development.
Incoordinate cellular differentiation in the malformed limbs was indicated histologically by undifferentiated mesenchyme in the distal extremities although the overlying ectoderm had already formed mature epidermis with specialized skin glands. The differentiated mesodermal components (muscles, cartilages and connective tissues) more proximally were afflicted with degenerative changes. Lytic spinal motor neurones and involuted Mauthner’s neurones with precipitate metamorphosis were accompanying features. Embryonic thyrotoxicosis is discussed in relation to congenital deformities of limbs.
