EARLY DEVELOPMENT OF THE SEA URCHIN
107
which
14
C-glucose was used as a precursor (Monroy and Vittorelli, 1962),
the rate of uptake in the fraction soluble in TCA also followed the
respiratory curve (Fig. 7) whereas, as already mentioned, the curve of
the incorporation into proteins is identical to the curve obtained when
amino-acids were administered to the eggs. That the observed incorporation is due, at least in part, to net synthesis rather than to a turnover
is suggested by some experiments in which the cell-fluid proteins of eggs
1200
Ε
CL
Ο
4000
2000
1600
1200
2
800
D
Ο
Σ> 400
Ε
CL
Ο
3000
2000
1000
0
-
TC A- insoluble
- ο
- à
/ο
-Ι
Ο
ί
Total
I
00 I
J
ο *
S
*·
e> ό
S
ζ ώ J
(a)
(b)
FIG. 6. Rate of uptake by the eggs (Total) and incorporation in the TCA-insoluble
fraction of
36
S-methionine (a) and
14
C-leucine (b) in the developmental stages of Paracentrotus lividus. Eggs and embryos were exposed to the isotope for 30 minutes and processed immediately afterwards. The first set of points close to the ordinate indicates the
data from experiments carried out immediately after fertilization. The other vertical
lines correspond to the 4- to 8-cell stage (4-8 BL.); 64-cell stage (64 BL.); mesenchyme
blastula (M.B.); early gastrula (E.G.); late gastrula (L.G.) and prisma (PR.)» (From
Giudice etal., 1962.)
and embryos raised in the presence of
35
S-methionine during the first
few cleavages were fractionated by starch gelelectrophoresis. Thus, a
small component was identified that, between fertilization and the 64-cell
stage, showed a significant increase of its area and exhibited at the same
time the highest specific activity of all the components present (Monroy
and Vittorelli, 1960; Monroy et al., 1961b). It must, however, be noted
that this protein component is already present in the unfertilized egg,
i.e., it is not a new protein species that is being synthesized. Some results
obtained with different methods by Ranzi (1957) and by Ishida and
Yasumasu (1957) are interesting in connection with this point. By the
107
which
14
C-glucose was used as a precursor (Monroy and Vittorelli, 1962),
the rate of uptake in the fraction soluble in TCA also followed the
respiratory curve (Fig. 7) whereas, as already mentioned, the curve of
the incorporation into proteins is identical to the curve obtained when
amino-acids were administered to the eggs. That the observed incorporation is due, at least in part, to net synthesis rather than to a turnover
is suggested by some experiments in which the cell-fluid proteins of eggs
1200
Ε
CL
Ο
4000
2000
1600
1200
2
800
D
Ο
Σ> 400
Ε
CL
Ο
3000
2000
1000
0
-
TC A- insoluble
- ο
- à
/ο
-Ι
Ο
ί
Total
I
00 I
J
ο *
S
*·
e> ό
S
ζ ώ J
(a)
(b)
FIG. 6. Rate of uptake by the eggs (Total) and incorporation in the TCA-insoluble
fraction of
36
S-methionine (a) and
14
C-leucine (b) in the developmental stages of Paracentrotus lividus. Eggs and embryos were exposed to the isotope for 30 minutes and processed immediately afterwards. The first set of points close to the ordinate indicates the
data from experiments carried out immediately after fertilization. The other vertical
lines correspond to the 4- to 8-cell stage (4-8 BL.); 64-cell stage (64 BL.); mesenchyme
blastula (M.B.); early gastrula (E.G.); late gastrula (L.G.) and prisma (PR.)» (From
Giudice etal., 1962.)
and embryos raised in the presence of
35
S-methionine during the first
few cleavages were fractionated by starch gelelectrophoresis. Thus, a
small component was identified that, between fertilization and the 64-cell
stage, showed a significant increase of its area and exhibited at the same
time the highest specific activity of all the components present (Monroy
and Vittorelli, 1960; Monroy et al., 1961b). It must, however, be noted
that this protein component is already present in the unfertilized egg,
i.e., it is not a new protein species that is being synthesized. Some results
obtained with different methods by Ranzi (1957) and by Ishida and
Yasumasu (1957) are interesting in connection with this point. By the