Environmental and Molecular Mutagenesis - Legacy Tobacco ...

56 1989 EMS Abstracts
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
Notes ALTERATIONS IN l41NG-INDUCED MUTATIONS AT SPECIFIC LOCI IN E• COLI i1U3610 UNDER
CONDITIONS OF THE "ADAPTIVE RESPONSE" . R .K . Elespuru and L .L . Stupar . Basic
Research Program, NCI-Frederick Cancer Research Facillty, Frederick, MD 21701 .
156
Treatment of EU coli with low concentrations of alkylating agents results in the
induction of the "adaptive response", an alkylation damage-specific DNA repair
response . Increased levels of two enzyses, an 0s-alkylguanine alkyltransferase, and
a 3-aethyladenlne glycosylase, are associated with this response . Among guanine
lesions, the transferase is specific for, and removes stoichiometrically, alkyl
groups at the 0s position . We have exmined the spectrum of mutations lnduced by
N-methyl-N'-nitro-N-nitrosoguanidine (NNNG) at 8 monitorable sites in E . coli IJU3610
under normal and adaptive conditions . The level of mutations at three monitorabie
GC-AT transition sites was reduced by 90-95% under adaptive conditions, implicating
the 0s-methylguanlne lesion as the causative agent in the generation of these
mutations . A substantial loss of mutants was also observed at two putative AT•GC
transition sites, consistent with the existence of 04-aethylthyaine as a premutatlonal
lesion at these sites (0'-aethylthyaine has been reported to be a
substrate of the transferase) . Little or no change was observed in mutation
frequency at two TA+AT transversion sites . Increases at these sites might have been
expected via glycosylase removal of 3-aethyladenine lesions and generation of
apurinic sites . However, unlike the transferasa, th.re is a high constitutive level
of 3-MA glycosylase in normal E . coli . Action of the induced enzyme could have been
masked by the constitutive activity . Research sponsored by National Cancer
Institute, DHHS, under contract No . NO1-CO-74101 with Bionetics Research, Inc .
157
SOLl181LQATION OF PARTICULATE CHROMIUM COMPOIlnIDS AND tTS RELEVANCE TO CYTOTOXICITY
AND MORPHOLOGICAL TRANSFORMATION OF SYRIAN FNMSTER EMBRYO (SHE) CELLS.
Z . Elias, O . Poirot, M .C . DaniBre, F. Terzetp, O . Schneider and F . Baruthio, I .N .R .S .,
54501 Vandoeuvre (France)
From previous experiments concerning water-Insoluble or poorly soluble Cr(VI) compounds,
we have found differences In cytotoxiclty and transforming potency among some of them . In the
present study we examine the possible relevance of the extracellular solubilization and
intracellular level of Cr accumulation to cytotoxicity end morphological transformation of SHE
cells Induced by particulate Cr compounds . Ca, Sr, Zn and Pb chromatea, of inedium, slight and
scarcely water solubilities, were tested . In two parallel experiments, the cells were treated with
supernatants or with suspensions of the Cr compounds . The cloning efficiency and the
transformation frequency for each compound were determined after 7 days of exposure .
Measurements of Cr In complete medium alone . In cell culture conditions and In counted cells were
made by electrothermal atomic absorption spectrometry . The results showed that : (1) Incubation
In cell culture conditions significantly increased the solubilization process ; (2) Intracellular Cr
concentration was directly related to Cr treatment concentration ; (3) oytotoxidty was dependent
on the extracellular solubillzed Cr ; (4) transformation frequency induced by Ca, Sr and Zn
chromates correlated to the intracetlular soluble Cr concentration ; (5) Pb=• lons could play a
role In transforming activity of Pb chromate . The results suggest that the oytotoxicity and
transformation are distinct processes and depend, among other factors, on the stte and the kinetics
of particle dissolution .
158
EVALUATION OF THE BIOLUMINESCENCE ASSAYS AS SCREENS FOR GENOTOXIC CHEMICALS .
Eugene Elmore, NSI Technology Services Corporation, P .O . Box 12313, Research Triangle
Park, North Carolina 27709
The need for rapid and cost efficient screens for muteyens and other toxicants has
increased dramatically over the past few years . This increase is due In part chemical
manufacturing and the need for monitoring of effluents and clean up activities at hazardous
waste sites . The bioluminescence test was first proposed for screening
genotoxic agents by Ulitzur et al . (Mutat . Res . 74, 113-124, 1980) . Bioluminsscence
tests measure the ability of the test chemicals to restore luminescence to dark
mutants of various Photobacterium species, probably by derepression of the luminescence
operon . A variety of chemicals with known mutagenic or carcinogenic activity
have been evaluated and the bioluminescence assay has been shown to be responsive to
direct mutagens lncluding point and frameshift mutayens, DNA-damsplny agents, DNAintercalating
agents, and DNA synthesis Inhibitors . The results correlate very well
with the published data obtained with the Ames assay . The results of a coded validation
study using chemicals provided by the National Toxicology Program In the
Microbics Mutatox11 Assay, which uses dark mutants of the luminous bacteria, P . phosphoraeum,
will be reviewed .