168
R. LALLIER
metabolism of different fractions of amino-acids: free amino-acids,
amino-acids of peptides, and proteins either soluble or insoluble. In each
fraction the amino-acids studied show fluctuations according to a
characteristic pattern. The pattern of change is different in each fraction.
The fluctuations would result from the degradation of reserve yolk
proteins and from the synthesis of new proteins. Kavanau has observed
several successive periods of protein synthesis and yolk-protein breakdown. In early cleavage, during the determination period, protein
synthesis is gradual. It is intensive in the mid-blastula and after hatching.
The breakdown of the yolk-proteins is very intensive during early
cleavage and in the late blastula. The periods of synthesis correspond
with the sharp increase in respiration while the periods of breakdown
take place when respiration remains more or less constant.
The use of labelled amino-acids allows us to follow their incorporation
into protein and cellular inclusions. Hultin (1950b, 1952, 1953b, c) has
observed that the rate of incorporation of
15
iV-glycine,
15
iV-DL-alanine
and
16
iV-H 4 Cl into microsomes increases rapidly during the early stages
of development, i.e., during the primary determination phase, whereas
incorporation into the soluble protein fraction markedly increases from
the mesenchyme blastula stage.
35
Ä-methionine is incorporated into
microsomes, mitochondria and soluble proteins from early development
(Nakano and Monroy, 1958; Monroy, 1960). Their incorporation into
mitochondria follows an S-shaped curve analogous to that for respiration
(Monroy etal, 1959).
According to Hultin and Bergstrand (1960) the incorporation of
14
C-L-leucine quickly increases during the early stages of development
with a culmination in the late blastula stage. This increase would be in
accordance with the augmentation of the content of active ribonucleoprotein particles. From the results of Markman (1961a) this incorporation follows an S-shaped curve analogous to that for respiration. The
autoradiographic method reveals regional differences in the incorporation of
14
C-L-leucine. In the early blastula stage, incorporation is stronger
in the animal region ; after the mesenchyme blastula stage, it predominates in the vegetal region. Different results have been obtained by
Bosco and Monroy (1962) who studied the incorporation of
35
£-DLmethionine,
14
C-DL-leucine and
14
C-DL-alanine by autoradiography. In
the blastula, incorporation appears strongest in the ectoderm. No
significant differences have been observed between the various regions
of the gastrula. Measurements of activity of isolated animal and vegetal
halves with a Geiger tube reveal that the incorporation of
14
0-leucine is
greater in animal halves (Markman, 1961c). More information is
necessary, using different labelled precursors, before a definite conclusion about the regional differences in incorporating activity of
R. LALLIER
metabolism of different fractions of amino-acids: free amino-acids,
amino-acids of peptides, and proteins either soluble or insoluble. In each
fraction the amino-acids studied show fluctuations according to a
characteristic pattern. The pattern of change is different in each fraction.
The fluctuations would result from the degradation of reserve yolk
proteins and from the synthesis of new proteins. Kavanau has observed
several successive periods of protein synthesis and yolk-protein breakdown. In early cleavage, during the determination period, protein
synthesis is gradual. It is intensive in the mid-blastula and after hatching.
The breakdown of the yolk-proteins is very intensive during early
cleavage and in the late blastula. The periods of synthesis correspond
with the sharp increase in respiration while the periods of breakdown
take place when respiration remains more or less constant.
The use of labelled amino-acids allows us to follow their incorporation
into protein and cellular inclusions. Hultin (1950b, 1952, 1953b, c) has
observed that the rate of incorporation of
15
iV-glycine,
15
iV-DL-alanine
and
16
iV-H 4 Cl into microsomes increases rapidly during the early stages
of development, i.e., during the primary determination phase, whereas
incorporation into the soluble protein fraction markedly increases from
the mesenchyme blastula stage.
35
Ä-methionine is incorporated into
microsomes, mitochondria and soluble proteins from early development
(Nakano and Monroy, 1958; Monroy, 1960). Their incorporation into
mitochondria follows an S-shaped curve analogous to that for respiration
(Monroy etal, 1959).
According to Hultin and Bergstrand (1960) the incorporation of
14
C-L-leucine quickly increases during the early stages of development
with a culmination in the late blastula stage. This increase would be in
accordance with the augmentation of the content of active ribonucleoprotein particles. From the results of Markman (1961a) this incorporation follows an S-shaped curve analogous to that for respiration. The
autoradiographic method reveals regional differences in the incorporation of
14
C-L-leucine. In the early blastula stage, incorporation is stronger
in the animal region ; after the mesenchyme blastula stage, it predominates in the vegetal region. Different results have been obtained by
Bosco and Monroy (1962) who studied the incorporation of
35
£-DLmethionine,
14
C-DL-leucine and
14
C-DL-alanine by autoradiography. In
the blastula, incorporation appears strongest in the ectoderm. No
significant differences have been observed between the various regions
of the gastrula. Measurements of activity of isolated animal and vegetal
halves with a Geiger tube reveal that the incorporation of
14
0-leucine is
greater in animal halves (Markman, 1961c). More information is
necessary, using different labelled precursors, before a definite conclusion about the regional differences in incorporating activity of