94
THE SHORTER-TERM BIOLOGICAL RAZARDS OF A FALLOUT FIELD
Tapstk I-—-RESIDUAL INJURY AT VARIOUS
TIMES AFTER RADIATION EXPOSURE AS
MEASURED BY DEPRESSION OF THE LDn30 DAYS
Ltye-30
days '{t)
Rostdual
from first
dose? (per-
520
562
516
548
597
79
37
83
53
6
200
200
200
200
446
ATT
491
524
a7
61
55
34
400
400
400
400
400
400
400
400
264 (11 days)_
1,920 (80 days)...
3,100 (125 days)......-.
236
261
315
318
366
562
565
509
91
85
71
70
58
9
7
3
None
None
4-264 hr control_...__..
504 hr control__.
Initial
dase (ry
100
100
100
100
100
None
None
Time to seroud dose (hrs)
144 (6 days).
504 (21 days)
1,820 (80 days)...
1,920 hr control_
3,100 hr control__.__
cont)
599 |.------601
591
519
the fast component. These points and the regression line are shownin Figure 3. The halftime for repair of this component was about
9-10 hours.
Tu summary, when 30-daylethality was used.
as a biological end-point, (here appeared to be
two exponential components to the repair proe-
ess, a slow componentrepairing with a half-
time of about 30 days and a fast component
repairing with a half-(ime of 9-10 hours. The
size of the initial dose did not appear Lo influence
the repair process. There was no evidence of a
nonrepairing residual injury.
Tante IZ—-RESIDUAL INJURY AT VARIOUS
TIMES AFTER RADIATION EXPOSURE AS
MEASURED BY DEPRESSION OF THE LD»100 HOURS
Initial dose
a)
400...--.--
were replotted as log percent residual vs. time.
(This resulted in a curved regression line that
could be adequately described by the sumof
These lines were tenta-
tively identified as representing a slow component and a fast componentof the repair process. The experimentally determined values at
each time interval were averaged and those for
600..-.--.
time intervals of 32 hours or more were plotted
as a function of time. These values represent
the slow component in repair. They are plotted
with their calculated regression line in Figure 2.
It can be seen from this figure that the half-time
for repair for the slow component was about 33
days. By subtracting the contribution of the
slow component from the total residual, it was
possible to determine the half-time for repair of
In the second series of studies, mice were
exposed to 400, 600 or 800 r and at time intervals of 2, 4, 8, 24, 72, 240, or 336 hours a
second dose was delivered to determine the
LD,-100 hours. In this case, we were dealing
primarily with injury to the gastrointestinal
tract, since it is injury to this system that
results in survival times of this magnitude.
Residual damage was calculated as hefore.
Table I[ summarizes the results of these studies.
As in the case of the LDy-80 day studies, the
800... ---.--
Time to
second
dose
dhrs)
LDse100
hes!
tr)
2
4
4
8
24
72
240
336
770
872
894
784
884
931
944
979
1025
1025
1038
1025
1025
1025
1021
1052
64
38
36
60
36
24
19
18
05
1
2
4
4
8
8
24
24
48
48
72
72
508
640
684
872
660
648
730
780
765
780
900
810
830
1038
1038
1038
1038
1065
1038
1065
1038
1065
1038
1065
1038
1065
88
66
69
61
68
65
56
43
50
43
28
38
39
2
4
4
24
336
304
483
534
1025
1025
1038
1038
86
79
72
63
1 LDs0-100 hours for the second dose.
Controt
LDye-100 hes
w
to be related to the size of the initial dose.
The higher the dose, the higher the percent
finding contrasts with the LDg-30 day results
which indicated no differences in percent resid-
ual with initial dose.
described as the sumof two exponentials, These
were again identified as a fast and a slow component to the repair process. The points
obtained at 24 or more hours after the initial
dose were plotted and regression lines of the
+ Percent of inittal dose remalningattime of delivery of second dose.
type
log R= a+ bt
t =time between doses.
These data are plotted in Figure 4.
T
my
UETey
F
T
were calculated. The slope constants for
various sized initial doses did not differ significantly. They were averaged by weighting
The
i
T
T
wep
Perry
T
T
TOT
eT
100}-
4
sor
4
x 60;
+
3
<
&
z
A
curved regression line resulted which could be
where R=percent residual and
T
The data were replotted
as before as log percent residual vs. time.
residual to time was of the type
120,
This
residual injury measured at any time.
best. empirical regression line relating percent
Residual from
first dose 3
(percent)
95
percent of residual injuryat all times appeared
K==a+6 log i
; Paeeeat of Sfarthesecanddase, bt time of delivery of second. dose.
two exponential lines.
RATE OF REPAIR OF RADIATION DAMAGE IN MICE
i.
Oo
wl
@o
=
3
40r-
4
a
$
a 20-g
w
_
e 100r INITIALL DOSE
Of
a
a
9200 INITIAL DOSE
a
4400r INITIAL DOSE
~20
i
i
plese
10
1
=
°
4
else
wial
100
i
4.
rhoeveh
TIME BETWEEN DOSES (HOURS)
1,000
i
Nessa
dt
10,000
Fievre 1.— Percent residual damage as measured by depression of the LDsy-30 days as a function of log time.