Environmental and Molecular Mutagenesis - Legacy Tobacco ...

76 1989 EMS Abstracts
Notes
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
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THE CARCINOGENICITY PREDICTOR : AN ONLINE ANALYSIS BASED UPON THE RESULTS OF SHORT-TERM
GENOTOXICITY TESTS . Mildred R . Green, Technical Database Services Inc ., 10 Colusobus
Circle, New York, NY 10019
The Carcinogenicity Predictor is a computerized package based upon the CPBSTM research
model developed at Case Western Reserve University(CWRU) by H . S . Rosenkranz and
others . The program calculates the probability that a chemical is carcinogenic from
results of short-term genotoxic assays . The user identifies one or more tests in a
battery, indicates the results (positive or negative) for each one, and specifies the
prior probability of carcinogenicity for the chemical in question . The prediction of
probability results from a Bayeslan analysis of the information input and of data quantifying
the sensitivity and specificity of each assay which is stored in the package .
The sensitivity and specificity values reflect the performance of each genotoxic test
in distinguishing between known carcinogens and noncarcinogens . Currently, the Carcinogenicity
Predictor contains a database of sensitivities and specificities for 32 different
assays ; updated values will be added as a result of further research at CSiRU .
However, users have the opportunity to create their own databases if they want to use
other values for a particular test . Calculations may be obtained at a single value of
prior probability (the default of 0 .5 or some other value chosen by the user) or as a
graph and a table of predicted probabilities of carcinogenicity at 11 values of the
prior probability from 0 .0 to 1 .0 . Recent enhancements to the package include the development
of a user interface which permits the evaluation of genetic toxicity via remote
accew The new version of the Carcinogenicity Predictor is available on the
Numerica online service of Technical Database Services .
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COMPLEMENTATION ANALYSIS OF X RAY SENSITIVElARA-C RESISTANT HAMSTER CELL
(AraC 213) - HUMAN ATAXIA TELANGIECTASIA HYBRIDS . Gloria Greer and R. Julian Preston,
Univ. of Tennessee Biomed. Grad. Sch . and Biology Division, ORNL, Oak Ridge, TN 37831 .
We have recently isolated an ara-C resistant X ray sensitive cell line, AraCa 213. Initial studies had been
performed with the cell line Ara 2 .1 (derived from a CHO-KI cell line) which was screened for X ray
sensitivity after selection for ara-C resistance at a concentration of S x 10' M . This mutant cell line was
mutagenized a second time with EMS and selected at a concentration of 10° M ara-C in an effort to isolate
a mutant which would exhibit an increase in X ray sensitivity . Thiss was found to be the case . This hamster
mutant cell line (AraC 213) shows an increased sensitivity to X ray-induced chromatid-type aberrations for
G, exposures, as is also the case with ata :aa telangiectasia (AT) cells. Other characteristics of AraC" 213
are similar also to those of AT. Therefore, cell fusion etperiments were performed using K1-CHO hgprt'
or AraC` 213 with a wild type human lymphoblastoid cell line (GM606), or an AT lymphoblastoid cell line
(GM717). Complementation analysis of the hamster-human hybrids was assessed by colony forming ability
after exposure to X rays. Preliminary experiments show that the CHO-AT hybrid has the same sensitivity
as the normal hamster cells, while the AraC` 213-AT hybrid showed no complementation ; it was still X ray
sensitive . These results suggest that there might be a common repair deficiency in the ara-C resistant mutant
and the AT cells. Additional experiments will further characterize the defects such that AraCR 213 can be
used to isolate the human repair gene that reverts the ara-C resistance phenotype and also the AT X ray
sensitivity . (Operated by Martin Marietta Energy Systems, Inc . under contract DE-ACOS-840R21400 with the
U. S. Dept. of Energy. GG is supported by NIH-CA08104-13) .
SITE-SPECIFIC MUTAGENESIS . Arthur P. Grollman, SUNY at Stony Brook . Stony Brook. NY
11794.
Chemical methods have been developed by which nucleoside adducts and related lesions
may be incorporated at defined positions in DNA. Biological systems have been devised which
allow mutagenic spectra to be determined, site-specifically, in bacteria and mammalian cells as
follows : A duplex oligodeoxynucleotide containing an adduct or other lesion is ligated into an
SV40-based shuttle plasmid vector, then used to transform bacteria or transfect simian kidney
(COS) cells. Mutations are fixed during plasmid replication . Progeny DNA. recovered from a
COS cell lysate, is amplified in F. coG, then digested by a restriction enzyme known to cleave within
a unique nucleotide sequence that includes the site of adduct modification. Circular DNA, obtained
from mutant plasmids, is amplified preferentially by transforming competent strains of E coJl .
Specific mutations are identified by oligonucleotide hybridization techniques. The advantages of
this experimental system include the homogeneity of input DNA, lack of bias in the procedure used
for detection of mutations and the potential for systematically altering base sequence in the vicinity
of the adduct . This approach has been used to establish the mutagenic specificity of abasic sites,
selected bulky and exocyclic DNA adducts and to explore molecular mechanisms Involved in
chemical mutagenesis .
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