Synthesis of nuclear and cytoplasmic proteins in the early development of fishes and echinoderms.

Synthesis of nuclear and cytoplasmic proteins was studied biochemically and autoradiographically in early loach (Misgurnus fossilis) and sea-urchin (Strongylocentrotus nudus) embryos. After incubation with [C]amino acids for 5-120 min the ratio of the specific activities of nuclear, mitochondrial and 12000g supernatant proteins was shown to be equal approximately to 6:1:2 in loach embryos and to 8:4:3 in sea-urchin embryos independently of the duration of labelling. After incubation with [H]amino acids the number of silver grains per unit section was on the average 2-4 times higher for nuclei than it was for cytoplasm at mid-blastula and midgastrula stages. At the mid-gastrula the vegeto-animal gradient of protein synthesis was found. A higher level of the synthesis of nuclear proteins as compared with that of cytoplasmic proteins appears to be related to an increase in the nuclear volume and the nucleocytoplasmic ratio during the early development of the loach and sea-urchin embryos.