Date of Award
Master of Science
It has long been known that hormones of the thyroid gland participate in the development and function of the central nervous system (Kollros, 1943). Manifestations of the intimate relation between brain activity and hormones of the gland are seen in the mental retardation of the patient suffering from hypothyroidism and in the hyperexcitability and psychosis often accompanying hyperthyroidism (Eayrs, 1964).
It is generally agreed that thyroid hormone accelerates the maturation of many components of the central nervous system, while conversely in the absence of thyroid hormone maturation is considerably delayed.
Metamorphosis in the amphibian is apparently accomplished by specific cell responses to thyroid hormone (reviews by Allen, 1938; Lynn and Wachowski, 1951; Etkin, 1955; Kollros, 1961). Individual cells are capable of reacting in diverse ways to thyroxine, such as by growth in size or regression, and by differentiation or cell division. In Rana pipiens larvae, presumptive neurons of the lateral motor column in the lumbosacral spinal cord have been found to respond to an implanted thyroxine pellet by a rapid increase in size (Beaudoin, 1956). Conversely later in the larval period, certain of these same neurons respond to thyroxine by becoming pycnotic and disappearing (Kollros and Race, 1960; Race, 1961). Early in the larval period, exposure to high thyroxine levels results in precocious cytodifferentiation of the motor neurons, including the appearance of a single nucleolus, cytoplasmic processes, and finely granulated nucleoplasm (Reynolds, 1963).
E. W. Martin
Prairie View A&M College
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Date of Digitization
John B Coleman Library
City of Publication
Walker, A. S. (1971). The Effects of Triiodothyronine on Deoxyribonucleic Acid and Ribonucleic Acid Content in the Brain of Rana Clamitans Tadpoles. Retrieved from https://digitalcommons.pvamu.edu/pvamu-theses/1298