IONENAUSTAUSCH-CHROMATOGRAPHISCHE UNTERSUCHUNGEN 897 



5. Chez Rana temporaria le poids sec et le contenu de l'azote total restent 

 presque constants pendant toute l'embryogenèse. En contraste, la quantité totale 

 des substances positives à la ninhydrine diminue sans doute jusqu'au stade de la 

 gastrulation, suivie d'une augmentation jusque à l'éclosion. Cette augmentation 

 coïncide avec l'utilisation du vitellus et avec les processus de la différenciation 

 pendant la neurulation et au cours du développement larvaire. Les divers acides 

 aminés et leurs dérivés présentent des modifications quantitatives, spécifiques de 

 chaque stade, dont une partie seulement sont en corrélation avec les modifications 

 du contenu total. 



6. La signification biochimique et morphogénétique des résultats pour 

 l'embryogenèse des amphibiens est discutée. 



SUMMARY 



1. More than 30 ninhydrin-positive fractions were separated by ion-exchange 

 chromatography in différent embryonic stages of Rana temporaria, Triturus 

 alpestris, Triturus helveticus and Xenopus laevis. Ail amino acids needed for 

 protein synthesis could be identified with the exception of cystine and cysteine. 

 Amino acids with no direct participation in protein synthesis, such as [3-alanine, 

 a- and y-aminobutyric acid, p-aminoisobutyric acid, a-aminoadipinic acid, orni- 

 thine and 3-methyl-histidine, were also found. 



2. Amino acid derivatives occuring regularly in the amphibian embryos 

 studied are mainly phosphate esters and peptides. Among the phosphate esters 

 phosphoethanolamine, glycerophosphoethanolamine and phosphoserine have been 

 identified; the concentration of phosphoethanolamine is especially high. The tri- 

 peptide glutathione, either in the oxidized or reduced form, was found in ail 

 species and at ail stages studied. In Rana temporaria a peptide rich in serine was 

 also found. The fact that the concentration of glycine is increased 20 to 30 times 

 after hydrolysis indicates the occurrence of bound glycine. 



3. The pattern of free ninhydrin-positive substances by ion-exchange chroma- 

 tography is remarkably similar between the species studied and the différent 

 developmental stages of a single species. The qualitative différences reported by 

 other authors seem to be due to the limited amount of samples used and the low 

 concentration of thèse components. 



4. Paper chromatographic analyses of embryos of Bombina variegata at the 

 yolk-plug stage revealed 15 ninhydrin-positive substances, including phospho- 

 ethanolamine, phosphoserine and glutathione. 



5. Both the dry weight and total nitrogen content of Rana temporaria remain 

 at an essentially constant level during the whole embryogenesis, whereas the total 



