30
i
J
RADIATION-INDUCED CLEAVAGE
DELAY IN MINUTES
[
60/-
I
|
T
|
CONTROL
DIVISION
TIMES
8,
{
\.
*
\
+
29-—___|
N
@
Z
a
\
\
\
\
_
e
|
10
0
|
20
|
|
|
|
|
30
40
50
60
7O
880
MINUTES AFTER FERTILIZATION
|
30
i
=6100
Fig. 26.—The sensitivity to radiation-induced cleavage delay as a function of the postfertilization time Arbacia zygotes ar
radiated. The dashed curve showsthe effect of treatment with 0.1 M beta mercaptoethanol for 30 min right after fertilization
normal temperatures were restored. The reactions
sponsible for the shape of the radiation curves, th
fore, are inhibited by reduced temperature, intel
ence
with
oxidative
metabolism,
treatment
\
ribonuclease, DO, and beta mercaptoethanol. T
do not appear responsive, however, to the actio1
RADIATION- INDUCED CLEAVAGE DELAY IN MINUTES
EDTAor colchicine. EDTA treatment, and to a le
degree colchicine treatment, nevertheless, slow d:
later reactions, protect while present and alter sul
quent responses to radiation. Hopefully, similar
periments with other agents will help to shed n
light on the mechanisms associated with the ra
tion response of developing sea urchin egg systems.
DISCUSSION AND SUMMARY
CONTROL
DIVISION
TIMES
{ 2|'——» Y
Reeovery from radiation-induced division delay
sea urchin eggs has been shown to occur when
normal cell division time is extended by tempor:
treatment with a number of agents, except the lov
ing of temperature. The recovery mechanism, the
fore, is felt to have approximately the same tempe
ture coefficient as the general processes leading to +
division. Considering the interpretations of the
0
lO
20
30
49
50
60
70
80
MINUTES AFTER FERTILIZATION
Fic. 27——The sensitivity to radiation-induced cleavage delay as a function of the postfertilization time Arbacia zygotes
are irradiated, The dashed curve showsthe effect of treatment
with 10 mg/ml EDTA for 25 min right after fertilization.
tions of the actions of the agents so far used, it «
be inferred that mterference with aerobic metaboliprotein synthesis or mitotic apparatus developm:
does not block this recovery process. The actions
ribonuclease and EDTA are not so well defined. }
bonuclease is reported to bind to the cell surface a
perhaps inhibit cleavage nonenzymatically by int
pve hd