E A R L Y D E V E L O P M E N T O F T H E S E A U R C H I N
103
meres (Berg, 1958). As already mentioned, in the blastula the rate of
uptake of labelled amino-acids has been found to be considerably lower
in the vegetal than in the animal region thus suggesting a lower protein
metabolism in the former at the time of formation of the primary
mesenchyme (Bosco and Monroy, 1962).
B. Protein Synthesis During the Early Post-Fertilization Stages
There seems to be good evidence that a metabolic block is established
in the egg at some time during maturation (Lindahl and Holter, 1940;
Maggio and Monroy, 1959) resulting, among other things, in the arrest
of protein synthesis. The histo-autoradiography of gonads of animals
which had been injected with radioactive amino-acids shows, in fact,
lively incorporation in the oocytes but no incorporation whatever in the
mature eggs (Fig. 2). This is not due to an impermeability of the eggs as
FIG. 2. Histo-autoradiogram of an ovary of Paracentrotus lividus labelled with 1 4
C-DLalanine. Heavy labelling of the oocytes (note accumulation of tracks on and around the
nucleolus) while in the mature eggs radioactivity is at background level.
it can be shown that they do take up and metabolize amino-acids and
amino-acid precursors. Thus 3 5S -glutathione is formed in the mature
eggs following administration of 3 5S -methionine (Nakano and Monroy,
1958b) and 14C-glucose is utilized for the synthesis of 14C-alanine, serine,
103
meres (Berg, 1958). As already mentioned, in the blastula the rate of
uptake of labelled amino-acids has been found to be considerably lower
in the vegetal than in the animal region thus suggesting a lower protein
metabolism in the former at the time of formation of the primary
mesenchyme (Bosco and Monroy, 1962).
B. Protein Synthesis During the Early Post-Fertilization Stages
There seems to be good evidence that a metabolic block is established
in the egg at some time during maturation (Lindahl and Holter, 1940;
Maggio and Monroy, 1959) resulting, among other things, in the arrest
of protein synthesis. The histo-autoradiography of gonads of animals
which had been injected with radioactive amino-acids shows, in fact,
lively incorporation in the oocytes but no incorporation whatever in the
mature eggs (Fig. 2). This is not due to an impermeability of the eggs as
FIG. 2. Histo-autoradiogram of an ovary of Paracentrotus lividus labelled with 1 4
C-DLalanine. Heavy labelling of the oocytes (note accumulation of tracks on and around the
nucleolus) while in the mature eggs radioactivity is at background level.
it can be shown that they do take up and metabolize amino-acids and
amino-acid precursors. Thus 3 5S -glutathione is formed in the mature
eggs following administration of 3 5S -methionine (Nakano and Monroy,
1958b) and 14C-glucose is utilized for the synthesis of 14C-alanine, serine,