Environmental and Molecular Mutagenesis - Legacy Tobacco ...

454 © 1989 EMS Abstracts
CYTOGENETICS IN ENVIRONMENTAL MUTAGENESIS . R. Julian Preston . Biology Division, Oak
Ridge National Laboratory, Qak Ridge, TN 37831
It is 50 years since Karl Sax demonstrated that x rays could induce chromosome aberrations, and that the
rc~pcrose was dose-dependent. In the period since•we have learned that a whole range of chemical agents
c: n also induce similar alterations. It is also apparent that specific chromosome alterations arc as .cociated
with many birth defects and with tumor initiation and/or progression . Important corollaries of these
observations are can we determine which agents are mutagenic (or carcinogenic) and can we estimate the
risk (genetic and somatic) from exposure to such agents? The answers are still equivocal . This stems from
the fact that the mechanism of induction of chrotnDrame aberrations has not been determined, and the role
of specific aberrations in the induction of birth defects and cancer are not generally known . Many new
techniques have become available in the past few years to help in this endeavor . It is possible for example.
to characterize chromosomes by using specific DNA probes, to identify and sequence chromosome breakpc
ints, and to identify chromosomal regions by sophisticated banding techniques and in situ hybridization .
These methods can be used to determine if agents present in the environment can induce specilic
chromosome aberrations, not just aberrations in general . It is also of importance to determine if there is
a range of sensitivities to aberration induction within the population and the bases for this, (e .g ., replication
fidelity, repair competence, and chromosome fragility) . The incorporation of molecular techniques into shortterm
assays (in vitro and in vivo) and population monitoring studies will enhance their utility, and hopefully
allow truly predictive information to be obtained . Operated by Martin Marietta Energy Systems, Inc . under
contract DE-ACA5-840R21400 with the U . S. Dept. of Energy .
455
RESTRICTION ENDONUCLEASE INDUCED CHROMOSOME DAMAGE : A MODEL FOR IONIZING
RADIATION AND A PROBE OF INTERCHANGE HOTSPOTS . R.J . Preston, G .J. Hook, and G.J. Horesovsky,
University of Tennessee Biomedical Graduate School, and Biology Division, Oak Ridge National Laboratory, Oak
Ridge, TN 37831 .
Type II restriction endonucleases (REs) are capable of recognizing specific DNA sequences and indbcing blunt
or cohesive ended double strand cuts at these sites . Since only one type of DNA damage is induced by REs they
represent a good model system for studying the importance of double strand breaks in the formation of CAs (CAs) .
In addition since the cuts are persumabley at a specific location it should be possible to produce very specific types
of CAs. Using cell electroporation we have designed experimental protocols by which the validity of RE induce
damage as a model system, specifically for radiation damage, as well as the feasibility of looking at specific
chromosome interactions can be tested. Cell electroporation has the advantage over other techniques used to
introduce RE into cells in that very low doses of RE can be used, and .a greater percentage of the cells exhibit
damage. Experiments have been carried out in CHO cells using the blunt end cutter Rsa I and the four base
cohesive end cutter Sau 3A1 . The CHO cells were harvested 6 and 22 hrs after treatment so that cells treated in
G= and G, would be sampled . The induction of chromosome abemations by concentrations of 1-g0 units for Rsa
I and 5-30 units for Sau 3AI have been analyzed . As reported by others, REs induce a much higher percentage of
exchange type aberrations than is found for X irradiation at similar levels of deletions . Both Rsa I and Sau 3AI are
capable of inducing CAs In 01 and G= at all the concentrations tested. The shape of dose response curves are
different from those reported elsewhere in that they are non-linear . For both Rsa I and Sau 3AI the dose response
curves are biphasic ending in a plateau . No straightforward correlation can be made between double strand cuts
induced by REs and double strand breaks induced by X irradiation . (Research sponsored by the Office of Health
and Environmental Research, U . S. Department of Energy under contract DE-AO0S-840R21400 with the Martin
Marietta Energy Systems, Inc. GJ Horesovsky is supported by NIH-CA 09104-13)
456
COMPARATIVE ANTIMUTAGENICITY OF Cff1 .OROPHYLLIN AND FIVE COMRtON ANTIMUTAGENS AGAINST
FOUR LABORATORY I4UTAGENS IN Salmonella typhimurium STRAINS TA98 AND TA100 .
K . Pupatwibul and N . E . Brockman, Illinois State University, Normal, IL (USA)
Chlorophyllin (C1Q.) is a potent inhibitor of the mutagenlcity of 10 complex
mixtures in Salmonella typhimurium strain TA98 (Ong, Whong, Stewart and Brockausn,
1986) . Furthermore, CNL is more effective than 4 common antimutagens (B-carotene
and vitamins A, C, and E) against the mutagenicity of 5 of these complex mixtures
in TA98 (Ong, Whong, Stewart and Brockman, 1989) . Based on these results, we have
initiated in S . typhimurium strains TA98 and TA100 a comparative study of the
antimutagenic activity of CHL and commonly used antimutagens against the
mutagenicity of laboratory mutagens with different mutagenic mechanisms ; we will
extend this comparative study to other short-term tests for genetic toxicity . We
report here our results on the antimutagenic activities of CHL . B-carotene,
retinoic acid, and vitamins A, C, and E against the mutagenicity of N-methyl-N'nitro-N-nitrosoguanidine
(MOING) and 6-N-hydroxylaminopurine in TA100 and of
aflatoxin BI and the acridine mustard ICR-170 in TA98 . Vitamin A inhibited the
mutagenicity of all 4 mutagens, and CHL inhibited the mutagenicity of all of the
mutagens except PINNG : Retinoic acid and 8-caroteae inhibited the mutagenicity only
of aflatoxin B . Dose-response curves of antimutagenic activity will be presented .
(H .E .B . acknowledges the support of the U .S . EPA Distinguished Visiting Scientist
Program .)
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
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