288
JOHN RUNNSTRÖM
synthesis in the egg is directly connected with the early cortical changes
irrespective of whether these have been initiated by fertilization or by
chemical activation. By means of electron microscopy the present writer
found that a polysome formation appears in the region below the
site of sperm entrance (unpublished results, 1964). This region moves
with the sperm head and centrosome toward the center of the egg. The
stimulus for polysome formation may start from the point of fusion of
the plasma membranes of the gametes, where an intense enzyme activity
is likely to arise. Even after the release of the protein synthesis, at least
one more step is necessary to achieve a complete activation, as shown by
the failure of the butyric acid-treated eggs to undergo a regular cleavage
and subsequent development. Here again an impulse that stems from the
cortex is necessary. This is demonstrated in the experiments carried out
by Allen and Hagström (1955) and of Runnström (1959a,b), which were
discussed in Section II,C. As a consequence of the temporary warming,
many eggs undergo only a partial activation. Nevertheless, a fusion of
the pronuclei usually occurs. The zygote nucleus often enters the egg
region in which no cortical changes have occurred (Fig. 23B). In this
environment, the zygote nucleus does not divide or undergoes, at the
most, some few irregular divisions. It was inferred that, under the conditions described, the replication of the centrosome was inhibited. A factor
emanating from the activated cortex was necessary to remove the
inhibition. It seems reasonable to assume that, in the butyric acidactivated eggs, the missing step is that involving the release of the
mentioned factor. The well-known elimination of the female centrosome
after the maturation division may be due to a similar inhibition as that
conferred upon the centrosome introduced with the spermatozoon, when
this centrosome is surrounded by cytoplasm with a nonactivated cortex.
This inhibition is in keeping with the general inhibitory state in the mature virgin egg.
Loeb (1913) showed that the activation of sea urchin eggs may be
completed when the butyric acid treated eggs are exposed to hypertonic
sea water for a suitable time. This treatment could release a factor bound
to an inhibitor, analogous to the splitting of the dextran sulfate-fibrinogen complex in the experiments of Sasaki and Nogucki (1959). It is of
interest that the hypertonic treatment may be applied before or after
the cortical changes induced by butyric acid treatment. This shows that
in Loeb's experimenal procedure the events occurring upon treatment
are rather independent of each other. In the normal activation process
the events are connected, both being brought about by the propagating
impulse. On consideration of Fig. 23B, it is rather clear that the factor
of the centrosomes is not diffusing from the site of sperm entry.
JOHN RUNNSTRÖM
synthesis in the egg is directly connected with the early cortical changes
irrespective of whether these have been initiated by fertilization or by
chemical activation. By means of electron microscopy the present writer
found that a polysome formation appears in the region below the
site of sperm entrance (unpublished results, 1964). This region moves
with the sperm head and centrosome toward the center of the egg. The
stimulus for polysome formation may start from the point of fusion of
the plasma membranes of the gametes, where an intense enzyme activity
is likely to arise. Even after the release of the protein synthesis, at least
one more step is necessary to achieve a complete activation, as shown by
the failure of the butyric acid-treated eggs to undergo a regular cleavage
and subsequent development. Here again an impulse that stems from the
cortex is necessary. This is demonstrated in the experiments carried out
by Allen and Hagström (1955) and of Runnström (1959a,b), which were
discussed in Section II,C. As a consequence of the temporary warming,
many eggs undergo only a partial activation. Nevertheless, a fusion of
the pronuclei usually occurs. The zygote nucleus often enters the egg
region in which no cortical changes have occurred (Fig. 23B). In this
environment, the zygote nucleus does not divide or undergoes, at the
most, some few irregular divisions. It was inferred that, under the conditions described, the replication of the centrosome was inhibited. A factor
emanating from the activated cortex was necessary to remove the
inhibition. It seems reasonable to assume that, in the butyric acidactivated eggs, the missing step is that involving the release of the
mentioned factor. The well-known elimination of the female centrosome
after the maturation division may be due to a similar inhibition as that
conferred upon the centrosome introduced with the spermatozoon, when
this centrosome is surrounded by cytoplasm with a nonactivated cortex.
This inhibition is in keeping with the general inhibitory state in the mature virgin egg.
Loeb (1913) showed that the activation of sea urchin eggs may be
completed when the butyric acid treated eggs are exposed to hypertonic
sea water for a suitable time. This treatment could release a factor bound
to an inhibitor, analogous to the splitting of the dextran sulfate-fibrinogen complex in the experiments of Sasaki and Nogucki (1959). It is of
interest that the hypertonic treatment may be applied before or after
the cortical changes induced by butyric acid treatment. This shows that
in Loeb's experimenal procedure the events occurring upon treatment
are rather independent of each other. In the normal activation process
the events are connected, both being brought about by the propagating
impulse. On consideration of Fig. 23B, it is rather clear that the factor
of the centrosomes is not diffusing from the site of sperm entry.