302
JOHN RUNNSTRÖM
fine structure. In a more distal region the fertilization membrane was
still in contact with villi, and the compartmented fine structure could
be perceived.
After "darkening," the fertilization membrane becomes more highly
elevated. This is due to the leveling of the folded state that prevails
before the uptake of the filling substance. This substance corresponds
to the membrane elevating factor (MbElF) earlier distinguished by
Runnström et al. (1954). In eggs pretreated with 5 X 10
5 M 2,4-dinitrophenol for 2 hr and fertilized in this medium, the defective fertilization membrane had usually not taken up the filling substance. This may
be due to the fact that a rather large number of cortical particles had not
opened, and the existing stomata of the cortical hollows were narrow. The
diffusion of certain contents of the cortical hollows is thus delayed or
prevented.
Surprisingly, the addition of 0.02 M sodium arsenate to the dinitrophenol brought about the normal elevation and smooth appearance of
the fertilization membrane. The electron-microscopic examination showed
that the membrane had taken up the filling substance. Sodium arsenate
causes an "arsenolysis" of polymerized polysaccharides, as was shown
for the sea urchin egg in unpublished work (1964) of J. Immers. Sodium
arsenate may cause a partial breakdown and release of polysaccharides
from the cortical hollows that may be taken up by the lamellar part of
the fertilization membrane. When this membrane remains compartmentalized, a substance is able to permeate the membrane and make
the jelly sticky so as to entangle spermatozoa. Similar phenomena
were discussed in Runnström (1964). The incorporation of the filling
material interrupts the permeation of the substance that makes the jelly
sticky. Instead, the smoothening of the fertilization membrane is followed by a swelling of the jelly coat.
The question of the role of Ca
2+ in the cortical changes (for references
see Runnström, 1949, p. 295) was taken up by Runnström and E. Wicklund (unpublished data, 1964). The eggs were inseminated in a small
volume of sea water on the bottom of tubes fitting a hand centrifuge.
After 5, 15, 25, 35, and 60 sec the different tubes were filled with Ca
2 +
-free
sea water to which 4 χ 10~
4 M ethylenediaminetetraacetate (EDTA) had
been added. In a small region restricted to the site of sperm entry the
fertilization membrane may show normal conditions, but otherwise it was
of the compartmented type. In many cases the sliding was incomplete
so that the fertilization membrane appeared granular when observed
in the light microscope. Platelike lamellae provided with 4-5 curls were
also observed in the perivitelline space. It was evident that the vitelline
membrane had not undergone the transformation normally occurring
JOHN RUNNSTRÖM
fine structure. In a more distal region the fertilization membrane was
still in contact with villi, and the compartmented fine structure could
be perceived.
After "darkening," the fertilization membrane becomes more highly
elevated. This is due to the leveling of the folded state that prevails
before the uptake of the filling substance. This substance corresponds
to the membrane elevating factor (MbElF) earlier distinguished by
Runnström et al. (1954). In eggs pretreated with 5 X 10
5 M 2,4-dinitrophenol for 2 hr and fertilized in this medium, the defective fertilization membrane had usually not taken up the filling substance. This may
be due to the fact that a rather large number of cortical particles had not
opened, and the existing stomata of the cortical hollows were narrow. The
diffusion of certain contents of the cortical hollows is thus delayed or
prevented.
Surprisingly, the addition of 0.02 M sodium arsenate to the dinitrophenol brought about the normal elevation and smooth appearance of
the fertilization membrane. The electron-microscopic examination showed
that the membrane had taken up the filling substance. Sodium arsenate
causes an "arsenolysis" of polymerized polysaccharides, as was shown
for the sea urchin egg in unpublished work (1964) of J. Immers. Sodium
arsenate may cause a partial breakdown and release of polysaccharides
from the cortical hollows that may be taken up by the lamellar part of
the fertilization membrane. When this membrane remains compartmentalized, a substance is able to permeate the membrane and make
the jelly sticky so as to entangle spermatozoa. Similar phenomena
were discussed in Runnström (1964). The incorporation of the filling
material interrupts the permeation of the substance that makes the jelly
sticky. Instead, the smoothening of the fertilization membrane is followed by a swelling of the jelly coat.
The question of the role of Ca
2+ in the cortical changes (for references
see Runnström, 1949, p. 295) was taken up by Runnström and E. Wicklund (unpublished data, 1964). The eggs were inseminated in a small
volume of sea water on the bottom of tubes fitting a hand centrifuge.
After 5, 15, 25, 35, and 60 sec the different tubes were filled with Ca
2 +
-free
sea water to which 4 χ 10~
4 M ethylenediaminetetraacetate (EDTA) had
been added. In a small region restricted to the site of sperm entry the
fertilization membrane may show normal conditions, but otherwise it was
of the compartmented type. In many cases the sliding was incomplete
so that the fertilization membrane appeared granular when observed
in the light microscope. Platelike lamellae provided with 4-5 curls were
also observed in the perivitelline space. It was evident that the vitelline
membrane had not undergone the transformation normally occurring