ANIMALIZATION AND VEGETALIZATION
187
microscope. The fate of this fibrous component during development is
not known.
Following fertilization, some of the proteins of the eggs undergo farreaching change (Mirsky, 1936; Monroy, 1950, 1957; Ceas et al., 1955).
Sea urchin eggs contain proteins that are very sensitive to the precipitating effects of calcium ions. The viscosity of the egg homogenates is
increased by calcium ions (Hultin, 1950a). Gross (1957) distinguishes
'soluble phase' and 'microsomal' fraction which precipitate with calcium
ions. Kane and Hersch (1959) have shown that the soluble-protein
fraction contains two major components. Both components produce a
gel in the presence of calcium ions. Spiegel and Schufer Spiegel (1959)
have analysed by electrophoresis the extractable proteins of sea urchin
embryos. The results revealed four major components plus one, or
possibly two, minor components. Moreover, the extracts prepared from
blastula, gastrula and pluteus had essentially identical electrophoretic
patterns. Kane and Hersch have suggested that the main component of
the soluble-protein fraction may be of major importance in the structural
organization of the cell. The removal of one-half of the cellular proteins
of the eggs of the sea urchin Arbacia punctulata removed all of the
cytoplasmic matrix and liberated most of the contents of the cell
structures (Kane, 1960).
Changes in the physico-chemical properties of proteins are brought
about during experimental modifications of embryonic determination.
These phenomena have been extensively studied by Ranzi and his
collaborators. Animalizing agents diminish the viscosity of protein
extracts containing fibrillar proteins. Vegetalizing agents increase the
viscosity of these extracts (Arosio et al., 1949). The viscosity changes
occur in vivo and in vitro. They are proportional to the morphogenetic
effects and are observed only with fibrillar proteins. In contrast, the
viscosity of the globular proteins is increased by both vegetalizing and
animalizing agents. In centrifuged whole eggs the tendency to stratify is
higher in eggs treated with an animalizing agent and lower in eggs
treated by lithium. These observations are in accord with the changes in
viscosity of protein extracts (Abruzzese Sgarlata, 1947; Lallier, 1955b).
The changes in viscosity shown by fibrillar proteins from sea urchin
embryos have also been observed in the fibrillar proteins of frog embryos
(Citterio and Ranzi, 1947), nucleohistone (Rebuffat and Brächet, 1947)
and actomyosin (Ranzi, 1952). After treatment with animalizing agents
the flow birefringence of actomyosin is decreased and this protein
appears less anisodiametric when observed with the electron microscope
(Ranzi, 1947). The number of —OH groups and of phenolic groups is
increased in actomyosin treated with animalizing agents (Arosio and
Bossi, 1954). Denaturing agents such as urea or heat induce the same
187
microscope. The fate of this fibrous component during development is
not known.
Following fertilization, some of the proteins of the eggs undergo farreaching change (Mirsky, 1936; Monroy, 1950, 1957; Ceas et al., 1955).
Sea urchin eggs contain proteins that are very sensitive to the precipitating effects of calcium ions. The viscosity of the egg homogenates is
increased by calcium ions (Hultin, 1950a). Gross (1957) distinguishes
'soluble phase' and 'microsomal' fraction which precipitate with calcium
ions. Kane and Hersch (1959) have shown that the soluble-protein
fraction contains two major components. Both components produce a
gel in the presence of calcium ions. Spiegel and Schufer Spiegel (1959)
have analysed by electrophoresis the extractable proteins of sea urchin
embryos. The results revealed four major components plus one, or
possibly two, minor components. Moreover, the extracts prepared from
blastula, gastrula and pluteus had essentially identical electrophoretic
patterns. Kane and Hersch have suggested that the main component of
the soluble-protein fraction may be of major importance in the structural
organization of the cell. The removal of one-half of the cellular proteins
of the eggs of the sea urchin Arbacia punctulata removed all of the
cytoplasmic matrix and liberated most of the contents of the cell
structures (Kane, 1960).
Changes in the physico-chemical properties of proteins are brought
about during experimental modifications of embryonic determination.
These phenomena have been extensively studied by Ranzi and his
collaborators. Animalizing agents diminish the viscosity of protein
extracts containing fibrillar proteins. Vegetalizing agents increase the
viscosity of these extracts (Arosio et al., 1949). The viscosity changes
occur in vivo and in vitro. They are proportional to the morphogenetic
effects and are observed only with fibrillar proteins. In contrast, the
viscosity of the globular proteins is increased by both vegetalizing and
animalizing agents. In centrifuged whole eggs the tendency to stratify is
higher in eggs treated with an animalizing agent and lower in eggs
treated by lithium. These observations are in accord with the changes in
viscosity of protein extracts (Abruzzese Sgarlata, 1947; Lallier, 1955b).
The changes in viscosity shown by fibrillar proteins from sea urchin
embryos have also been observed in the fibrillar proteins of frog embryos
(Citterio and Ranzi, 1947), nucleohistone (Rebuffat and Brächet, 1947)
and actomyosin (Ranzi, 1952). After treatment with animalizing agents
the flow birefringence of actomyosin is decreased and this protein
appears less anisodiametric when observed with the electron microscope
(Ranzi, 1947). The number of —OH groups and of phenolic groups is
increased in actomyosin treated with animalizing agents (Arosio and
Bossi, 1954). Denaturing agents such as urea or heat induce the same