170
R. LALLIER
chyme in the embryos. Longer treatments give rise to radial larvae.
Bosco and Monroy conclude that the protein synthesis requiring
methionine is of importance for the differentiation of the primary
mesenchyme.
Barbieri et al. (1960) have shown in Escherichia coli that D-cycloserine
behaves like a D-alanine analogue and inhibits the incorporation of
DL-alanine14
C in bacterial proteins. In sea urchin eggs, D-cycloserine
induces exogastrulation, but no enlargement of the endoderm is obtained.
DL-alanine protects the embryos against the effects of D-cycloserine
(Lallier, 1962b). An analogue of phenylalanine, the p-fluorophenylalanine, exerts inhibitory effects on the development of sea urchin eggs
but embryonic determination is not changed (Lallier, 1962c). With an
analogue of tryptophane, 7-azatryptophane, a few vegetalized larvae
were obtained (Lallier 1962c). Thus, the effects of analogues of aminoacids on embryonic determination appears weak and restricted to
general retardation of development and unspecific disturbances of
morphogenesis. Inconsistencies in the effects of amino-acids analogues
are frequently observed. For instance, ethionine may cause radialization
in whole eggs but, on the other hand, favours the vegetalizing action of
lithium. DL-/?-phenyllactic acid presents another example of inconsistent
action. Used alone, DL-ß-phenyllactic acid induces the radialization of
whole eggs ; in combination with lithium, it acts in the vegetal direction.
These inconsistencies raise doubts about the idea that the analogues of
amino-acids act by virtue of their antimetabolic properties. Though the
activity of the amino-acids and of their analogues may be linked to their
action on protein metabolism in their quality as metabolites or antimetabolites, but it may also result from particular physico-chemical
effects. The study of the effects of treatments combining an amino-acid
and its antimetabolite appears necessary to make a definitive distinction
between the various possible types of activity.
In contrast to the weak effects of amino-acid analogues, an inhibitor
of protein synthesis, chloramphenicol, has been shown to be able to
induce strong vegetalization in whole eggs (Lallier, 1961c). Further,
chloramphenicol enhances the vegetalizing effects of lithium ions and
depresses the animalizing effects of zinc ions or Evans blue. These
results suggest that protein synthesis connected with the determination
of ectodermal structures is more sensitive to the inhibitory action of
chloramphenicol than the protein synthesis connected with the determination of entomesodermal structures. New research is necessary to
analyse the effects of chloramphenicol on protein synthesis in the sea
urchin egg. A study of the effects of various inhibitors of protein
synthesis may prove useful in analysing the process of embryonic
differentiation.
R. LALLIER
chyme in the embryos. Longer treatments give rise to radial larvae.
Bosco and Monroy conclude that the protein synthesis requiring
methionine is of importance for the differentiation of the primary
mesenchyme.
Barbieri et al. (1960) have shown in Escherichia coli that D-cycloserine
behaves like a D-alanine analogue and inhibits the incorporation of
DL-alanine14
C in bacterial proteins. In sea urchin eggs, D-cycloserine
induces exogastrulation, but no enlargement of the endoderm is obtained.
DL-alanine protects the embryos against the effects of D-cycloserine
(Lallier, 1962b). An analogue of phenylalanine, the p-fluorophenylalanine, exerts inhibitory effects on the development of sea urchin eggs
but embryonic determination is not changed (Lallier, 1962c). With an
analogue of tryptophane, 7-azatryptophane, a few vegetalized larvae
were obtained (Lallier 1962c). Thus, the effects of analogues of aminoacids on embryonic determination appears weak and restricted to
general retardation of development and unspecific disturbances of
morphogenesis. Inconsistencies in the effects of amino-acids analogues
are frequently observed. For instance, ethionine may cause radialization
in whole eggs but, on the other hand, favours the vegetalizing action of
lithium. DL-/?-phenyllactic acid presents another example of inconsistent
action. Used alone, DL-ß-phenyllactic acid induces the radialization of
whole eggs ; in combination with lithium, it acts in the vegetal direction.
These inconsistencies raise doubts about the idea that the analogues of
amino-acids act by virtue of their antimetabolic properties. Though the
activity of the amino-acids and of their analogues may be linked to their
action on protein metabolism in their quality as metabolites or antimetabolites, but it may also result from particular physico-chemical
effects. The study of the effects of treatments combining an amino-acid
and its antimetabolite appears necessary to make a definitive distinction
between the various possible types of activity.
In contrast to the weak effects of amino-acid analogues, an inhibitor
of protein synthesis, chloramphenicol, has been shown to be able to
induce strong vegetalization in whole eggs (Lallier, 1961c). Further,
chloramphenicol enhances the vegetalizing effects of lithium ions and
depresses the animalizing effects of zinc ions or Evans blue. These
results suggest that protein synthesis connected with the determination
of ectodermal structures is more sensitive to the inhibitory action of
chloramphenicol than the protein synthesis connected with the determination of entomesodermal structures. New research is necessary to
analyse the effects of chloramphenicol on protein synthesis in the sea
urchin egg. A study of the effects of various inhibitors of protein
synthesis may prove useful in analysing the process of embryonic
differentiation.