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RADIATION- INDUCED CLEAVAGE DELAY IN MINUTES
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20
30
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40
50
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MINUTES AFTER FERTILIZATION
3 are irOnl.
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30
40
50
60
70
MINUTES AFTER FERTILIZATION
J
Fic. 29-—The sensitivity to radiation-induced cleavage delay as a function of the postfertilization time Arbacta zygotes
are irradiated. The dashed curve shows the effect of treatment
with nitrogen for 30 min right after fertilization.
80
terfer- |
i neil UE: EN
tte
Tic, 28.—The sensitivity to radiation-induced cleavage dewith : lay as a function of the postfertilization time Arbacta zygotes
They, are irradiated. The open circles and squares represent experi-~
ments on the same control gametes in the morning and afterion of ° noon, respectively. The solid curve is drawn through these
. lesser svmbols. The dashed curve shows the effect of treatment with
down ° 75 * 10°M colchicine for 30 min right after fertilization,
subse- ; while the dotted curve shows the effect of 125 x 10*M
colchicine treatment for 30 min right after fertilization.
Ta
ir exmore
acting as a basic protein with the cell surface.“ The
radia- *
chelating activity of EDTA is presumed responsible
in some way for its action. As discussed in last year’s
report,‘®) comparisons of recovery rates under the action of these various agents tends to implicate some
mctabolic activity in the recovery process. One indi-
Eee
. cation is that more recovery generally occurs during
extensions of the cell division period induced by physico-chemical agents like D2O, colchicine, and EDTA
» than during comparable time periods induced by met-
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IMES
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200—~CO«B—Ci4—C
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MINUTES AFTER FERTILIZATION
From analysis of the variations in radiation re-
Fic. 30.—The sensitivity to radiation-induced cleavage delay as a function of the postfertilization time Arbacia zygotes
are irradiated. The dashed curve shows the effect of incubation at 6.5° C for 30 min right after fertilization.
covered. Thus, the radiation response of zygotes that
tion afforded, for example, by hypoxia. Therefore, the
‘bolie inhibitors.
| §ponse curves as a function of the time during the
cell eyele that fertilized eggs are exposed, a “modifi: cation” effect of certain of the agents has been un-
ing exposure, it cannot be the usual type of protec-
have been treated with sodium azide, beta mercapto-
phenomenon has been termed modification. In a sim-
‘reated counter-parts. Since this reduced response is
observed at times when the agent is not present dur-
sensitize fertilized Arbacia eggs to subsequent radia-
‘thanol, nitrogen, and EDTA is less than their un-
ilar experiment, puromycin treatment, on the other
hand, has been shown by Rustad and Burchill*® to