Publication Date


Document Type


First Advisor

Prahlad, K. V.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


Embryology--Amphibians; Xenopus laevis; Frogs


It has been long thought that Xencrus laevis embryos (stage 25-25) have low permeability to labelled direct precursors of macromolecules. To study synthetic activities in early amphibian embryos, several indirect methods have been used by other workers: incubation of intact embryos in ¹⁴CO₂ environment; uptake of nucleic acid and protein precursors by dissociated Xenopus cells; and micro-injection of embryos. We have shown that radioactive labelled precursors are taken up in amounts sufficient to study cellular biochemical events in intact normally developing embryos kept in modified Holtfretter's media maintained at a pH of 7.2. ¹⁴C-leucine is taken up by the embryo with Kₘ, of C.73 x 10⁻⁵M and a V[sub max] of 5.4 x 10⁻⁸ uM/min. The level of uptake is 0.05 ug leucine per embryo which is a significant percentage of the free leucine pool. Also using this method it can be demonstrated that amino acids and nucleic acid precursors are taken up by embryos and the jelly coat has a selective influence on such uptake. This study clearly demonstrates that unmodified, intact, normally developing Xenopus laevis embryos will take up and incorporate protein and nucleic acid precursors.


Includes bibliographical references.||Includes illustrations.


vi, 61 pages




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