Accession Number : AD0645104

Title :   THE EFFECT OF FUDR ON SEGMENTATION AND INCORPORATION OF URACIL-H3 IN AMPHIBIAN EMBRYOS,

Corporate Author : NAVAL RADIOLOGICAL DEFENSE LAB SAN FRANCISCO CALIF

Personal Author(s) : Bielavsky,Nicolas ; Leong,George F.

Report Date : 18 OCT 1966

Pagination or Media Count : 31

Abstract : Previous investigations of the effect of FUDR, a fluoro-inhibitor of DNA synthesis, on the segmentation of amphibian embryos have demonstrated that cleavage and development proceed normally through 8-10 mitotic cycles before further development is blocked by the inhibitor. It has been implied that this ability of the embryo, in the presence of FUDR, to continue normal development through several segmentation stages may be due to an alternate biochemical pathway for DNA synthesis which is insensitive to the inhibitor. In the present experiments, by micro-injecting embryos (to assure the presence of FUDR in the cytoplasm) at specific stages of segmentation we have demonstrated that cleavage and development of embryos are sensitive to and blocked by FUDR only at the young blastula stages. Mitoses and the incorporation of labelled uracil into DNA are similarly affected as to time sequences. Prior to the young blastula-mid blastula stages labelled uracil is incorporated into the DNA of embryos primarily as methyl cytosine. The data suggest that during early segmentation, the reaction desoxyuridine to thymidine (FUDR sensitive) does not occur in the cytoplasm of embryos and that probably uracil is incorporated preferentially into methyl cytosine to thymidine, an alternate pathway which is not sensitive to FUDR. The transformation desoxyuridine to thymidine would occur then at the young blastula stage thus resulting in blockage of further embryonic development. (Author)

Descriptors :   (*MITOSIS, INHIBITION), (*DEOXYRIBONUCLEIC ACIDS, BIOSYNTHESIS), PYRIMIDINES, METABOLISM, AUTORADIOGRAPHY, EMBRYOS, AMPHIBIANS, GROWTH(PHYSIOLOGY), LABELED SUBSTANCES, THYMIDINES

Subject Categories : Biochemistry
      Anatomy and Physiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE