252
SILVIO RANZI
down. Does this agree with the findings of experimental embryology?
All the authors who speak of development inhibition induced by
LiCl in vertebrates, have encountered the resistance to breakdown of
protein ultrastructures at a microscopic level. The delay in synthesis due
to Li is in agreement with the lower enzymic activity of LiCl-treated
embryos, compared with normal embryos, as reported by many scientists of the Wenner Gren group, by Lallier (1955) and by others. Thomason (1957) observed that radioactive phosphate incorporation is less
active in Li-treated Xenopus embryos than in controls.
On the other hand, animalization seems in fact to correspond to the
breakdown of pre-existing protein structures. Proteolytic enzymes
(chymotrypsin, ficin, trypsin) are animalizing agents (Hörstadius 1949,
1953 and Moore, 1952). The observation made by Lindahl, Swedmark
and Lundin (1951) in this field is highly significant: that from a population of more easily animalizable sea urchin eggs it is possible to extract
in 0-54 M-Nal a greater amount of soluble N (that is to say they contain
a lower proportion of insoluble N).
Animalization can sometimes be induced under the same conditions
as protein denaturation. Hörstadius (1949) found that animalization
occurs more easily at low temperature, while Jacobsen and Christensen
(1948) found that denaturation, induced by urea, is also easier to obtain
at low temperature. Animalization induced by NaSCN occurs more
easily in calcium-free sea water; Ca prevents many proteins from undergoing denaturation (Gorini, 1950).
The regions hyperdeveloped by the action of animalizing agents, and
inhibited by vegetalizing agents, show a comparatively high oxidationreduction potential (see the work of Child, 1936a, b ; Ranzi, 1939;
Hörstadius, 1955; and Lallier, 1956). I think that this may be interpreted as an indication of a much more active protein breakdown. It is
possible to follow the formation of the ciliary tuft and of mitochondria
in the cells of the animal pole of the sea urchin embryo (Gustafson, 1954;
Shaver, 1955) which shows a higher oxidation-reduction potential. Direct
analyses can also be used to demonstrate protein breakdown. In the
frog blastoporal dorsal lip, that is the notochord rudiment, at the time
when it is sensitive to animalizing and vegetalizing agents, Deuchar
(1956) found a higher content of free amino acids than in other areas of
the embryo. D'Amelio and Ceas (1957) showed that in the same region
of the young gastrula there is stronger proteolytic activity. The findings
of Kavanau (1954) also seem important. He found that the content of
free amino acids was highest in sea urchin embryos exactly at the stage
which Bäckström and Gustafson (1953) found to be most sensitive to
the action of LiCl.
SILVIO RANZI
down. Does this agree with the findings of experimental embryology?
All the authors who speak of development inhibition induced by
LiCl in vertebrates, have encountered the resistance to breakdown of
protein ultrastructures at a microscopic level. The delay in synthesis due
to Li is in agreement with the lower enzymic activity of LiCl-treated
embryos, compared with normal embryos, as reported by many scientists of the Wenner Gren group, by Lallier (1955) and by others. Thomason (1957) observed that radioactive phosphate incorporation is less
active in Li-treated Xenopus embryos than in controls.
On the other hand, animalization seems in fact to correspond to the
breakdown of pre-existing protein structures. Proteolytic enzymes
(chymotrypsin, ficin, trypsin) are animalizing agents (Hörstadius 1949,
1953 and Moore, 1952). The observation made by Lindahl, Swedmark
and Lundin (1951) in this field is highly significant: that from a population of more easily animalizable sea urchin eggs it is possible to extract
in 0-54 M-Nal a greater amount of soluble N (that is to say they contain
a lower proportion of insoluble N).
Animalization can sometimes be induced under the same conditions
as protein denaturation. Hörstadius (1949) found that animalization
occurs more easily at low temperature, while Jacobsen and Christensen
(1948) found that denaturation, induced by urea, is also easier to obtain
at low temperature. Animalization induced by NaSCN occurs more
easily in calcium-free sea water; Ca prevents many proteins from undergoing denaturation (Gorini, 1950).
The regions hyperdeveloped by the action of animalizing agents, and
inhibited by vegetalizing agents, show a comparatively high oxidationreduction potential (see the work of Child, 1936a, b ; Ranzi, 1939;
Hörstadius, 1955; and Lallier, 1956). I think that this may be interpreted as an indication of a much more active protein breakdown. It is
possible to follow the formation of the ciliary tuft and of mitochondria
in the cells of the animal pole of the sea urchin embryo (Gustafson, 1954;
Shaver, 1955) which shows a higher oxidation-reduction potential. Direct
analyses can also be used to demonstrate protein breakdown. In the
frog blastoporal dorsal lip, that is the notochord rudiment, at the time
when it is sensitive to animalizing and vegetalizing agents, Deuchar
(1956) found a higher content of free amino acids than in other areas of
the embryo. D'Amelio and Ceas (1957) showed that in the same region
of the young gastrula there is stronger proteolytic activity. The findings
of Kavanau (1954) also seem important. He found that the content of
free amino acids was highest in sea urchin embryos exactly at the stage
which Bäckström and Gustafson (1953) found to be most sensitive to
the action of LiCl.