Date of Award

1994

Degree Name

Ph.D. in Biology

Advisor/Chair

Dr. Panagiotis A. Tsonis

Abstract

The newt, Notophthalmus viridescens, and the Mexican axolotl, Amblystoma mexicanum, are examples of urodeles which have the unique ability to regenerate appendages as adults. Vitamin A metabolites (retinoids) have been shown to have an adverse effect upon the regeneration process by inducing abnormalities, inhibitions or proximalizations of the regenerate. Vitamin D is related to the retinoids via the molecular mechanism by which it elicits effects (the nuclear receptor). The results of the first study suggest that there is an effect by vitamin D metabolites on axolotl limb regeneration and chick limb development. The data also reports that synergistic effects exist between the vitamin D metabolites and retinoid hormones tested to elicit proximalization of the axolotl limb. These data implicate interactions at the molecular level between the nuclear receptors. Molecular cloning and expression analysis of the chicken vitamin D receptor was also performed. The last two studies deal with the culturing of newt regeneration blastema and newt limb ceUs. An in vitro culturing system for amphibian cells was established. The blastema cell population has been shown to be composed of four different cell types, all of which may play a role in the regeneration process. The data indicate that two of the cell types are not produced from dedifferentiation but are of hematopoietic origin. The ability to readily obtain newt limb cells facilitated the establishment of two transformed cell lines via introduction of an oncogene, the SV40 large T-antigen. Oncogenetransfected cell lines express the large T-antigen and display the characteristic transformed phenotype. The cell lines were tested for the ability to participate in the regeneration process by implanting the cells back into a regenerating newt limb. Reimplantation resulted in the participation by the cells in the regeneration process.

Keywords

Salamanders, Extremities (Anatomy) Regeneration

Comments

Illustrative matter includes mounted photographs. Reprint of the author's "Variable manifestations in the short toes (s) mutation of the axolotl inserted in appendix after leaf 112

Rights Statement

Copyright © 1994, author

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