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mg BAIB
LOG
mg GREATININE
Figure 47. Urinary BAIB excretion (mg-f-amino-ise-butyric acid per mg
creatinine) versus body load of Cs'*’ (uC), Rongelap inhabitants, 1959.
0.06; unexposed, 2.10 0.04). A scatter plot of
BAIB in man **:*4 and excreted in urine, since no
rik people 83% were high excretors, whichis not
significantly different from the Rongelap group
appreciable tubular reabsorption of BAIB occurs.** It is unlikely that the high incidence of high
BAIB excretors found in Rongelapis due to radiation. The identical average BAIB valuesin the exposed and unexposed groups preclude the possibility that the elevation is due to the fallout exposure in 1954, and it appears that radiation exposure (at the levels received at Rongelap) has no
long-term effect on BAIB excretion. The lack of
correlation with the Cs'*? and Zn®* body burdens
cluded in the Rongelap sample (i.e., father,
retained internal radiation. The nearly identical
Cs**’ levels and BAIB levels shows nocorrelation
(Figure 47), and neither does a similar plot between Zn* levels and BAIB tevels. The mean
BAIB excretion level for 18 Micronesians, who
were on Utirik at the time of the atomic explosion
andtherefore not exposed to significant radiation,
was 2.21 +0.13, which is extremely close to the
mean value for the Rongelapese. Amongthe Uti-
percentage. A number of complete families are in-
mother and at least one child); of these the high-
excretor by high-excretor matings are the only
ones providing significant genetic information.
There were 11 such matings with a total of 31 offspring (29 high excretors and 2 low excretors). One
of the low excretor offspring wasillegitimate, as
determined by blood group data, but the other re-
mains as an unexplained exception to genetic
hypothesis.
Rubiniet al.** have recently demonstrated that
BAIB excretion can be a sensitive indicator of
radiation exposure. The mechanism involvedis
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Cit
probably the same as that underlyingtheeffect of
nitrogen mustard on BAIB excretion.** Such
agents markedly increase DNA breakdown; the
thymine thusreleased is effectively converted to
rules against the elevation being due to the present
values in the Utirik group who received a very
small dose of radiation, and who have muchlower _
body burdensof radionuclides, is also consistent
with the thesis that a high incidence of the gene
underlying 6-amino-iso-butyric aciduria is responsible for the observed BAIB excretion rate.
The expression of the normal genetic difference is
probably dueto differential metabolism of BAIB
by high and low excretors.**
The level of BAIB excretion among the Marshallese is the highest yet reported for any population. Blood group®® and other anthropological
data on these people suggest a Southeast Asiatic
origin; if this is true, a high BAIB level can be
predicted for the populations of that region.
Studies of some Asiatic populations have given