VITELLINE MEMBRANE AND CORTICAL PARTICLES 275
showed definite differences in activity according to their provenience
from fertilized or unfertilized eggs. Both Connors and Scheer, and Mullins
found that the ATPase was activated by addition of Ca
2+ to their extracts. Monroy (1957a), however, found a Mg
2 +
-activated ATPase in
the mitochondria of Paracentrotus,
and this also showed increased
activity upon fertilization. The Ca
2 +
-activated ATPase may be present
in the cortical layer of the egg but inside the permeability barrier, as
seems to follow from observations of Mullins (1949), according to which
neither fertilized nor unfertilized jelly-free living eggs showed ATPase
activity. According to Connors and Scheer (1947) the ATPase activity
is inhibited by Mg
2 +
. This may also be of interest in connection with the
effect of Ca
2+ and Mg
2+ on the shrinkage of unfertilized eggs in a hypertonic medium (see Section I). A Ca
2 +
-ATPase system may also be
of importance for the movements and contractions that occur in the
egg surface. Eggs of Psammechinus
miliaris were activated by exposure
to 6 χ 10~
5 M sodium periodate (NaI0 4 ) in sea water. A smooth fertilization membrane was formed, and the usual movements occurred in the
egg surface with formation of a concavity (Kuhl and Kuhl, 1949) which
did not reverse as early as in normal fertilization. A fertilization (activation) membrane of normal character was elevated. In calcium-free sea
water, on the other hand, no concavity formation was observed, and a
slightly elevated membrane which formed was thin and soon disappeared.
It seems likely that the inhibited state of an ATPase may have contributed to the differences found between Ca
2 +
-containing and Ca
2 +
-free
sea water. More work is needed, and it must be kept in mind that Ca
2+
has an effect on systems other than ATPase. Evidence to be presented
in Section IV,A indicates, however, that ATPase activity is involved
in the cortical changes.
Lipids are probably involved in the cortical changes. Treatment with
30-40 μg per milliliter bee venom led to an instantaneous formation of
a membrane that is similar to a fertilization membrane (Öhman, 1944).
It was well elevated, but its birefringence was not as pronounced as in
the fertilized control. The elevation of the membrane subsequent to bee
venom treatment took place also in the absence of Ca
2+ in the sea
water, but cytolysis of the cytoplasmic surface began much sooner in
Ca
2+
-free than in Ca
2 +
-containing sea water (observations on Strongylocentrotus droebachiensis).
Maggio and Monroy (1955) found that the
spermatozoa of sea urchin cause a breakdown of phosphatides of the
yolk from hens' eggs (see also Monroy, 1956).
Warming of the eggs of sea urchins to temperatures above 38°C leads
to formation of hyaline blisters that have a lipoid or lipoprotein character. The readiness of formation of the blisters may be different in un-
showed definite differences in activity according to their provenience
from fertilized or unfertilized eggs. Both Connors and Scheer, and Mullins
found that the ATPase was activated by addition of Ca
2+ to their extracts. Monroy (1957a), however, found a Mg
2 +
-activated ATPase in
the mitochondria of Paracentrotus,
and this also showed increased
activity upon fertilization. The Ca
2 +
-activated ATPase may be present
in the cortical layer of the egg but inside the permeability barrier, as
seems to follow from observations of Mullins (1949), according to which
neither fertilized nor unfertilized jelly-free living eggs showed ATPase
activity. According to Connors and Scheer (1947) the ATPase activity
is inhibited by Mg
2 +
. This may also be of interest in connection with the
effect of Ca
2+ and Mg
2+ on the shrinkage of unfertilized eggs in a hypertonic medium (see Section I). A Ca
2 +
-ATPase system may also be
of importance for the movements and contractions that occur in the
egg surface. Eggs of Psammechinus
miliaris were activated by exposure
to 6 χ 10~
5 M sodium periodate (NaI0 4 ) in sea water. A smooth fertilization membrane was formed, and the usual movements occurred in the
egg surface with formation of a concavity (Kuhl and Kuhl, 1949) which
did not reverse as early as in normal fertilization. A fertilization (activation) membrane of normal character was elevated. In calcium-free sea
water, on the other hand, no concavity formation was observed, and a
slightly elevated membrane which formed was thin and soon disappeared.
It seems likely that the inhibited state of an ATPase may have contributed to the differences found between Ca
2 +
-containing and Ca
2 +
-free
sea water. More work is needed, and it must be kept in mind that Ca
2+
has an effect on systems other than ATPase. Evidence to be presented
in Section IV,A indicates, however, that ATPase activity is involved
in the cortical changes.
Lipids are probably involved in the cortical changes. Treatment with
30-40 μg per milliliter bee venom led to an instantaneous formation of
a membrane that is similar to a fertilization membrane (Öhman, 1944).
It was well elevated, but its birefringence was not as pronounced as in
the fertilized control. The elevation of the membrane subsequent to bee
venom treatment took place also in the absence of Ca
2+ in the sea
water, but cytolysis of the cytoplasmic surface began much sooner in
Ca
2+
-free than in Ca
2 +
-containing sea water (observations on Strongylocentrotus droebachiensis).
Maggio and Monroy (1955) found that the
spermatozoa of sea urchin cause a breakdown of phosphatides of the
yolk from hens' eggs (see also Monroy, 1956).
Warming of the eggs of sea urchins to temperatures above 38°C leads
to formation of hyaline blisters that have a lipoid or lipoprotein character. The readiness of formation of the blisters may be different in un-