314
JOHN RUNNSTRÖM
by activating a proteolytic enzyme. The results of Hultin point to the
conclusion that Ε 2, which is considered here as the endogenous gelating
enzyme in the egg, may directly or indirectly activate an enzyme which
oxidizes SH groups in proteins. The possibility could also be considered
that this enzyme is activated in parallel with Ε 2.
Gross and Pearl (1950) and Gross (1954, 1956) have made further
valuable contributions to the knowledge of the phenomena first studied
by Hultin.
Ε 2 is the enzyme that under different conditions is activated in the
unfertilized egg in the presence of Ca
2+ in the medium, particularly after
exposure to low doses of trypsin. Even the exposure of unfertilized eggs
to merely sea water for 16-20 hr brings about an activation (see Runnström, 1961a). This is manifested by the rather adherent fertilization
membrane and the poor cleavage of these eggs. These symptoms are,
however, changed after some further hours; the vitelline membrane is
now attacked so that either a fragmentary fertilization membrane or
none at all appears. The soft condition of the fertilization membrane
after fertilization in the presence of cysteine points also to an activation
of a proteolytic enzyme of the type Ε 1 and Ε 3 (Section II,D). It was
shown previously that the shift discussed here takes place very rapidly if
eggs, pretreated with low doses of trypsin, are fertilized in the same
medium. A pretreatment with low-trypsin-dose concentrations, interrupted before fertilization and combined with warming to 32°C after
fertilization, brings about the shift, although each one of these treatments alone brings about gelation (Runnström, unpublished results,
1962). Hultin failed to observe a process corresponding to the second
phase in the scheme presented above. This may have depended on the
poor stability of his homogenate, which had to be processed without
access to a cooling device.
The more hydrolytic enzymes Ε 1 and Ε 3, as mentioned above, are inhibited rather than activated by Ca
2 +
. As suggested previously in this
section, this ion may be removed during relaxation by a mechanism
analogous to the relaxation mechanism found in cross-striated muscle.
The endoplasmic vesicles follow the sperm nucleus and centrosome
in their inward migration. This may involve a transportation of Ca
2 +
,
which is accumulated in the vesicles, toward the interior of the egg where
a release of Ca
2+ may be an important factor in the formation of the
mitotic apparatus.
D. Phase Separation and Mixing as Driving Forces
According to Runnström (1963b), certain cytoplasmic changes (for
example, the layering of cytoplasm at the entrance site of the spermatozoon and the formation of the reception cone) are expressions of a
JOHN RUNNSTRÖM
by activating a proteolytic enzyme. The results of Hultin point to the
conclusion that Ε 2, which is considered here as the endogenous gelating
enzyme in the egg, may directly or indirectly activate an enzyme which
oxidizes SH groups in proteins. The possibility could also be considered
that this enzyme is activated in parallel with Ε 2.
Gross and Pearl (1950) and Gross (1954, 1956) have made further
valuable contributions to the knowledge of the phenomena first studied
by Hultin.
Ε 2 is the enzyme that under different conditions is activated in the
unfertilized egg in the presence of Ca
2+ in the medium, particularly after
exposure to low doses of trypsin. Even the exposure of unfertilized eggs
to merely sea water for 16-20 hr brings about an activation (see Runnström, 1961a). This is manifested by the rather adherent fertilization
membrane and the poor cleavage of these eggs. These symptoms are,
however, changed after some further hours; the vitelline membrane is
now attacked so that either a fragmentary fertilization membrane or
none at all appears. The soft condition of the fertilization membrane
after fertilization in the presence of cysteine points also to an activation
of a proteolytic enzyme of the type Ε 1 and Ε 3 (Section II,D). It was
shown previously that the shift discussed here takes place very rapidly if
eggs, pretreated with low doses of trypsin, are fertilized in the same
medium. A pretreatment with low-trypsin-dose concentrations, interrupted before fertilization and combined with warming to 32°C after
fertilization, brings about the shift, although each one of these treatments alone brings about gelation (Runnström, unpublished results,
1962). Hultin failed to observe a process corresponding to the second
phase in the scheme presented above. This may have depended on the
poor stability of his homogenate, which had to be processed without
access to a cooling device.
The more hydrolytic enzymes Ε 1 and Ε 3, as mentioned above, are inhibited rather than activated by Ca
2 +
. As suggested previously in this
section, this ion may be removed during relaxation by a mechanism
analogous to the relaxation mechanism found in cross-striated muscle.
The endoplasmic vesicles follow the sperm nucleus and centrosome
in their inward migration. This may involve a transportation of Ca
2 +
,
which is accumulated in the vesicles, toward the interior of the egg where
a release of Ca
2+ may be an important factor in the formation of the
mitotic apparatus.
D. Phase Separation and Mixing as Driving Forces
According to Runnström (1963b), certain cytoplasmic changes (for
example, the layering of cytoplasm at the entrance site of the spermatozoon and the formation of the reception cone) are expressions of a