VITELLINE MEMBRANE AND CORTICAL PARTICLES 315
phase separation with ensuing partition of inclusions between the different phases in accordance with the systems described by Albertsson
(1960). These phenomena, earlier described for oocytes (Runnström,
loc. cit.), occur in a similar way in the fertilization of the mature eggs
(Runnström, unpublished data, 1964). In Section IV,C (see also Section
II,G) reference was made to the formation of a layer rich in endoplasmic
vesicles. This layer seems to surround the sperm during its inward
movement.
Phase separation and phase mixing may be driving forces in
certain protoplasmic changes. The partition of macromolecules or particles between phases is also a spontaneous process that may induce or
inhibit certain interactions of relevance for control of enzymatic or other
processes.
Such spontaneous processes may arise wherever there is a mixture of
macromolecules of different compatibilities or incompatibilities (Albertsson, loc. cit.). The energy of the system resides in the specific structures
of its different macromolecular components that have been built up in
gene-governed synthesis.
Such a state as that diagrammed in Fig. 22 may also be the result
of a phase separation, as was claimed in Section I,B,3. The process may
depend on an enzyme-enhanced aggregation of certain proteins (those
constituting the contractile threads of Sakai, 1962a,b). The aggregation
may also be local; an example is the formation of reception cones in
oocytes. In extreme cases, however, the aggregation causes the separation
of the whole cortex from the endoplasm which eventually is covered
only by the plasma membrane. The shift from gelated to a more relaxed
state is evident also in the treated oocytes. In cases of less pronounced
phase separation a regression to a more uniformly distributed cortical
layer occurs. In more severe cases, a cytolysis occurs that may lead to
a variable degree of breakdown of the cortex and accompanying interior
layers. In such cases even the vitelline membrane was broken down (see
Section I,A) ; this is a sensitive test of proteolysis. The proximal-distal
polarity of the unfertilized egg (see Runnström, 1962) may be based on
an asymmetric distribution of the cortex. The initial cytoplasmic accumulation toward the site of effective sperm attachment may be a
phenomenon related to the described phase separation occurring in
oocytes (Section I,B,3). The same phenomenon returns in cell division
when a concentration of the cortical layer against the cleavage furrow
occurs.
E. Concatenations in the Fertilization Process
By way of summary, some of the most characteristic partial changes
accompanying fertilization have been recorded in Table I. References
phase separation with ensuing partition of inclusions between the different phases in accordance with the systems described by Albertsson
(1960). These phenomena, earlier described for oocytes (Runnström,
loc. cit.), occur in a similar way in the fertilization of the mature eggs
(Runnström, unpublished data, 1964). In Section IV,C (see also Section
II,G) reference was made to the formation of a layer rich in endoplasmic
vesicles. This layer seems to surround the sperm during its inward
movement.
Phase separation and phase mixing may be driving forces in
certain protoplasmic changes. The partition of macromolecules or particles between phases is also a spontaneous process that may induce or
inhibit certain interactions of relevance for control of enzymatic or other
processes.
Such spontaneous processes may arise wherever there is a mixture of
macromolecules of different compatibilities or incompatibilities (Albertsson, loc. cit.). The energy of the system resides in the specific structures
of its different macromolecular components that have been built up in
gene-governed synthesis.
Such a state as that diagrammed in Fig. 22 may also be the result
of a phase separation, as was claimed in Section I,B,3. The process may
depend on an enzyme-enhanced aggregation of certain proteins (those
constituting the contractile threads of Sakai, 1962a,b). The aggregation
may also be local; an example is the formation of reception cones in
oocytes. In extreme cases, however, the aggregation causes the separation
of the whole cortex from the endoplasm which eventually is covered
only by the plasma membrane. The shift from gelated to a more relaxed
state is evident also in the treated oocytes. In cases of less pronounced
phase separation a regression to a more uniformly distributed cortical
layer occurs. In more severe cases, a cytolysis occurs that may lead to
a variable degree of breakdown of the cortex and accompanying interior
layers. In such cases even the vitelline membrane was broken down (see
Section I,A) ; this is a sensitive test of proteolysis. The proximal-distal
polarity of the unfertilized egg (see Runnström, 1962) may be based on
an asymmetric distribution of the cortex. The initial cytoplasmic accumulation toward the site of effective sperm attachment may be a
phenomenon related to the described phase separation occurring in
oocytes (Section I,B,3). The same phenomenon returns in cell division
when a concentration of the cortical layer against the cleavage furrow
occurs.
E. Concatenations in the Fertilization Process
By way of summary, some of the most characteristic partial changes
accompanying fertilization have been recorded in Table I. References