178
R. LALLIER
and in the pancreas the microsomes, ribonucleoprotein particles of the
ergastoplasm, are able to incorporate amino-acids actively and to
synthesize specific proteins (Campbell, 1960). In the sea urchin egg, the
experiments of Hultin and of Monroy also indicate that the microsomes
incorporate amino-acids in the nucleoproteins. In this respect the
activity of the microsomes is always higher than that of the mitochondria
during the phase of embryonic determination (Hultin, 1953e). Finally,
Lallier (1950) has shown that in the egg of the frog lithium depresses
respiration and inhibits the use of the substrates of the Krebs cycle.
Lithium also modifies the ribonucleic acid content of the particulate
system. These observations indicate a double action of lithium on the
mitochondria and on the microsomes (Lallier, 1954, 1955b). The activity
of the microsomes is dependent upon the presence of a continually
renewed source of ATP. As ATP is formed during glycolysis and
oxidative phosphorylation, the activity of the microsomes in the intact
cells is closely related to those systems providing the energy. These
remarks emphasize the importance of the microsomes and their
functional relationship with the mitochondria for embryonic determination and differentiation.
IX. Biochemical Background of the Gradients of Reduction
The reduction gradients may correspond to an unequal distribution of
enzymes catalysing oxidation-reduction reactions or may reveal
differences in the distribution of the reducing substances.
Oxidation-reduction processes are implied in carbohydrate catabolism.
The biocatalytic oxidation of some intermediate metabolites is indeed
carried out by dehydrogenases which transfer to a flavoprotein the
electrons of the metabolite through the medium of the coenzymes,
diphosphopyridine nucleotide (DPN) or triphosphopyridine nucleotide
(TPN). The reduced flavoproteins may then be oxidized by certain
oxidation-reduction indicators, such as Janus green B, and the changes
in the colour that are shown by this indicator when passing from the
oxidized to the reduced state gives information concerning the activity
of the oxidation-reduction system. Cooperstein et al. (1960) have shown
that different parts of the cells are capable of reducing the Janus green B.
Dye reduction rates are dependent upon a critical balance of oxygen
tension, substrate, coenzyme concentration and enzyme distribution.
Tetrazolium blue is another oxidation-reduction indicator. In sea
urchin eggs, mitochondria reduce tetrazolium blue (Gonse and
Yotsuyanagi, 1955). Bäckström (1959d) has studied the reduction in the
presence of diverse substrates by the DPN or TPN-dependent dehydrogenases. Reduction of tetrazolium blue appears in the same regions of
R. LALLIER
and in the pancreas the microsomes, ribonucleoprotein particles of the
ergastoplasm, are able to incorporate amino-acids actively and to
synthesize specific proteins (Campbell, 1960). In the sea urchin egg, the
experiments of Hultin and of Monroy also indicate that the microsomes
incorporate amino-acids in the nucleoproteins. In this respect the
activity of the microsomes is always higher than that of the mitochondria
during the phase of embryonic determination (Hultin, 1953e). Finally,
Lallier (1950) has shown that in the egg of the frog lithium depresses
respiration and inhibits the use of the substrates of the Krebs cycle.
Lithium also modifies the ribonucleic acid content of the particulate
system. These observations indicate a double action of lithium on the
mitochondria and on the microsomes (Lallier, 1954, 1955b). The activity
of the microsomes is dependent upon the presence of a continually
renewed source of ATP. As ATP is formed during glycolysis and
oxidative phosphorylation, the activity of the microsomes in the intact
cells is closely related to those systems providing the energy. These
remarks emphasize the importance of the microsomes and their
functional relationship with the mitochondria for embryonic determination and differentiation.
IX. Biochemical Background of the Gradients of Reduction
The reduction gradients may correspond to an unequal distribution of
enzymes catalysing oxidation-reduction reactions or may reveal
differences in the distribution of the reducing substances.
Oxidation-reduction processes are implied in carbohydrate catabolism.
The biocatalytic oxidation of some intermediate metabolites is indeed
carried out by dehydrogenases which transfer to a flavoprotein the
electrons of the metabolite through the medium of the coenzymes,
diphosphopyridine nucleotide (DPN) or triphosphopyridine nucleotide
(TPN). The reduced flavoproteins may then be oxidized by certain
oxidation-reduction indicators, such as Janus green B, and the changes
in the colour that are shown by this indicator when passing from the
oxidized to the reduced state gives information concerning the activity
of the oxidation-reduction system. Cooperstein et al. (1960) have shown
that different parts of the cells are capable of reducing the Janus green B.
Dye reduction rates are dependent upon a critical balance of oxygen
tension, substrate, coenzyme concentration and enzyme distribution.
Tetrazolium blue is another oxidation-reduction indicator. In sea
urchin eggs, mitochondria reduce tetrazolium blue (Gonse and
Yotsuyanagi, 1955). Bäckström (1959d) has studied the reduction in the
presence of diverse substrates by the DPN or TPN-dependent dehydrogenases. Reduction of tetrazolium blue appears in the same regions of