266
JOHN RUNNSTRÖM
the rate of acid formation increases, but the maximum rate is attained
only after 80-90 sec when the cortical particles have opened widely. At
about 140 sec after insemination, acid formation comes to a standstill.
According to Runnström's manometric studies, acid formation in Paracentrotus lividus amounted to 6.5 χ 10~
3 mEq per milliliter of eggs. The
ensuing pH changes within the egg would depend on the thickness of
the layer within which the acid is released. Presumably it is formed in a
rather limited peripheral surface layer.
Runnström and Immers (1956) regarded acid formation as the consequence of a release and splitting of sulfated mucopolysaccharides.
Aketa (1963), on the other hand, inferred that acid formation corresponds to a splitting of sulfuric acid from sulfated polysaccharides.
Acid formation evidently requires enzyme activation. According to
Aketa (1961b), acid formation takes place in the cortical particles. Accordingly the acid formation would start with the opening of the cortical
particles surrounding the site of sperm entry. The acid formation may
participate in breaking weak bonds in the way proposed by Isaka and
Aikawa (1963a,b). There will be opportunities to come back to these
problems in Section II,F.
C. The Opening of the Cortical Particles
According to Wolpert and Mercer (1961), the vitelline membrane
would act as a restraint preventing the opening of the cortical particles.
This should mean that the separation of the vitelline membrane would
be sufficient to cause the opening of the cortical particles. However, a
pretreatment with crystalline trypsin at a concentration that breaks
down the vitelline membrane more or less completely does not cause the
opening of the cortical particles. At the most, fenestrated fertilization
membranes (see Runnström, 1961a) were formed upon fertilization of
eggs pretreated with 2 χ 10~
4
% trypsin for 20 min. In numerous experiments, it was observed in phase contrast that the cortical lamellae were
extruded directly into the surrounding medium without any trace of
membrane fragment (Wicklund, 1949, and unpublished observations by
Wicklund, 1964). In these cases the vitelline membrane must have been
completely removed, but no opening of the cortical particles ensued before fertilization of the egg. Runnström (1948) and Endo (1952) observed
a delayed opening of cortical particles after a previous formation of a fertilization membrane. The delayed opening of the cortical particles had
nothing to do with the elevation of the vitelline membrane. The delayed
opening shows that many of the cortical particles are not attached to
the plasma membrane. The explanation cannot be that the delayed cortical particles are unripe and have not yet established the contact with
JOHN RUNNSTRÖM
the rate of acid formation increases, but the maximum rate is attained
only after 80-90 sec when the cortical particles have opened widely. At
about 140 sec after insemination, acid formation comes to a standstill.
According to Runnström's manometric studies, acid formation in Paracentrotus lividus amounted to 6.5 χ 10~
3 mEq per milliliter of eggs. The
ensuing pH changes within the egg would depend on the thickness of
the layer within which the acid is released. Presumably it is formed in a
rather limited peripheral surface layer.
Runnström and Immers (1956) regarded acid formation as the consequence of a release and splitting of sulfated mucopolysaccharides.
Aketa (1963), on the other hand, inferred that acid formation corresponds to a splitting of sulfuric acid from sulfated polysaccharides.
Acid formation evidently requires enzyme activation. According to
Aketa (1961b), acid formation takes place in the cortical particles. Accordingly the acid formation would start with the opening of the cortical
particles surrounding the site of sperm entry. The acid formation may
participate in breaking weak bonds in the way proposed by Isaka and
Aikawa (1963a,b). There will be opportunities to come back to these
problems in Section II,F.
C. The Opening of the Cortical Particles
According to Wolpert and Mercer (1961), the vitelline membrane
would act as a restraint preventing the opening of the cortical particles.
This should mean that the separation of the vitelline membrane would
be sufficient to cause the opening of the cortical particles. However, a
pretreatment with crystalline trypsin at a concentration that breaks
down the vitelline membrane more or less completely does not cause the
opening of the cortical particles. At the most, fenestrated fertilization
membranes (see Runnström, 1961a) were formed upon fertilization of
eggs pretreated with 2 χ 10~
4
% trypsin for 20 min. In numerous experiments, it was observed in phase contrast that the cortical lamellae were
extruded directly into the surrounding medium without any trace of
membrane fragment (Wicklund, 1949, and unpublished observations by
Wicklund, 1964). In these cases the vitelline membrane must have been
completely removed, but no opening of the cortical particles ensued before fertilization of the egg. Runnström (1948) and Endo (1952) observed
a delayed opening of cortical particles after a previous formation of a fertilization membrane. The delayed opening of the cortical particles had
nothing to do with the elevation of the vitelline membrane. The delayed
opening shows that many of the cortical particles are not attached to
the plasma membrane. The explanation cannot be that the delayed cortical particles are unripe and have not yet established the contact with