Localization of glycine‐2‐C 14 injected into adult female frogs

Radioactive amino acids labeled with C14 or Sa5 have proved to be extremely valuable tools for the biochemist investigating the metabolism of proteins in a variety of biological systems, both ipz vivo and in vitro (Borsook, '50; Lee, Anderson, Miller and Williams, '51 ; Borsook, Deasy, Haagen-Smit, Keighley and Lowy, '52 ; Christensen, Riggs and Ray, '52 ; Mueller, '53 ; Ficq, Gavosto and Errera, '54a, '54b; Zamecnik and IESlcller, '54)The discoveries that fetal and malignant tissues incorporate amino acids to a greater extent than normal tissues in the adult (Friedberg, Shulman and Greenberg, '48 ; Christensen and Streicher, '48; Zamecnik, Frantz, Jr., Loftfield and Stephenson, '48 ; Christensen, Riggs, Fischer and Palatine, '52) are provocative to the embryologist, and have stimulated a series of investigations on protein synthesis and its relation to development in the amphibian embryo (Friedberg and Eakin, '49 ; Eakin, Berg and Kutsky, '50 ; Eakin, Kutsky and Berg, '51; Kutsky, Eakin, Berg and Kavanau, ' 5 3 ) . The present study stemmed from the author's interest in the synthesis of yolk in the developing oocytes of the frog, since the yolk platelets of Amphibia are rich in protcins, including phosphoproteins and probably nucleoproteins