Environmental and Molecular Mutagenesis - Legacy Tobacco ...

178 1989 EMS Abstracts
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
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Notes tes -- . .-DOMINANT SKBLB/Mtff MUTATION METHODS ARE BEING USED TO DETERMINE WHETHER
DOMINANT MUTATIONS ACCOUNT FOR THE MANY ABNORMAL FETUSES FOUND
FOLLOWING EXPOOF ZYGOTES TO ETHYLNITROSOUREA (ENU) . P. B . Selby, W. M.
Generoso, G. D. Re , W. McKinley, Jr., and K. T. Cain, Biology Division, Oak Ridge National
Laboratory. P.O. Box 2009, M.S . 8077, Oak Ridge, TN (USA)
Generoso et al . (Mutat. Res. 176:269-274 and 199 :175-181) discovered that there are remarkable increases
in the incidence of developmental abnormalities in fetuses after early rygotic stages are exposed to any one of
several chemicals, including ENU . Russell et al . (PNAS 85 :9167-9170) found that a 50 mg/kg i .p.
injection of ENU induces approximately 8 times more specific-locus mutations when It is administered
2 .5-3 h after mating instead of 5-6 h after mating. We Injected female mice with 40 mi ;/hz; of ENU (i .p .) at
either 2 .5 or 5 h after mating . Offspring are being examined for externally visible altered phenotypes and for
skeletal damage. The frequencies of mice wtih significant external findtng;(e.g., a missing eye, shortened
tail, misshapen head), among mice living 3 weeks or longer, were 8/207 (3 .9%) and 0/156 in the 2 .5-h and
5-h groups, respectively . The frequency at 2 .5 h is statistically significantly higher, and this difference, in
view of the spectfc-locus results, suggests that dominant gene mutations may be responsible for the
externally visible altered phenotypes. Results of detailed skeletal analyses will be presented, as will
preliminary results from breeding tests . Since dominant skeletal mutations are much more common than
dominant visible mutations, it is expected that a high frequency of dominant skeletal mutations will be found
if induced dominant mutations are responsible for the high frequency of abnormal fetuses . [Research jointly
sponsored by NIEHS under Interagency Agreement Y01-ES-10067 and the Office of Health and
Environmental Research, U .S . Deparanent of Energy under contract DE-ACOS-84OR21400 with Martin
Marietta Energy Systems, Inc .]
517
SUGGESTIONS FOR IMPROVING THE DIRECT METHOD OF GENETIC RISK ESTIMATION. P. B .
Selby . Biology Division, Oak Ridge National Laboratory, P .O. Box 2009, M .S. 8077, Oak Ridge, TN
(USA)
One of the methods used by committees for quantitative genetic risk estimation for radiation is based upon
a measure of induced phenotypic damage (usually malformed skeletons or cataracts) in the offspring of
irradiated mice . This method, which has been called the direct method, has several distinct advanta*es over
the doubling-dose method of genetic risk estimation. Much of the emphasis to date has been on induced
mutations that were proved to be transmitted to later penerations . However, If these are the only mutations
that are included in mutation frequencies, as is sometimes recommended, the following important classes of
mutations causing dominant damage are overlooked : (1) mutations causing sterility, (2) mutations causing
death before breeding tests can be completed, and (3) mutations with such low penetrance that transmission is
not confirmed in the relatively small numbers of offs'pring that can easily be raised in a breeding test .
Accordingly, it seems that the ideal method for collecting data to be used for genetic risk estimation is to
identify all of the first-generation offspring that exhibit any phenotypes that would be clinically important if
they were to occur in people . The induced mutation frequency could be calculated by subtracting the
frequency of offspring with clinically important phenotypes in the control group from that in the experimental
group . Various other suggestions will also be presented for improving our ability to estimate genetic risk by
the direct method . [Research sponsored by the Office of Health and Environmental Research, U .S .
Department of Energy under contract DE-ACO5-84OR21400 with Martin Marietta Energy Systems, Inc .]
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INFLUENCE OF OXIDANT STATE ON UV AND FINNO INDUCED MUTATION IN V79 CELLS-
Sharmila Sengupta and 1 u a , Saha Institute of
Nuclear Physics, I/AF, alt ce, a outta- 00 064, India .
Present day idea that oxidant state could be involved in carcinogenesie
makes it relevant to study the influence of sueh condition on the
mutation induction by W light and Mt+110 (N-methyl-N'-nitro-N-nitroeoguanidine)
. In our experiments, H20p aae been used to create the oxidant
state in V79 cells . The dose of H2 02 was in the non-toxio region ; for
tnis particular cell-line, it was 0 .9µg/ml . The end-point selected for
our mutation analysis was resistance to the drug 6-thioguanine . Oxidant
state itself did not create any mutation above the background level of
0 .33±0 .08 per 105 viable cells . For UV-light, different fluences ranging
frotn 4J/ms to 20J/m were usp~d to get the mutations wnieh varied from
8 .0+12 to 25 .60+7 .40 per 10 viable cells . For MNNG, the doses used
were in the region 0 .2µg/ml to 0 .6µg/ml and the correponding mutation
frequencies varied between 5 .0+1 .0 to 32•5+4 .2 per 101 viable cells . The
creation of oxidant state altered the value ; in case of MNNO, these
raaged between 12 .8+2 .3 to 56 .5+3•6 per M1 viable cells and in case of
UV light between 8 .7+1 .4 to 22 .3f8 .2 per 105 viable cells at the dose
ranges mentioned . It-wae seen that such a condition enhanced mutation
induction by NNN6 but had no effect on mutation by UV-light . Clearly,
the oxidant state, if involved in oarcinogeneais does not produce any
extra effect for the 254 nm UV-light but the situation is different in
case of chemical agents like MNO .
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