Environmental and Molecular Mutagenesis - Legacy Tobacco ...

scavenger of singlet oxygen (Bellus 1979 Adv Photoohem 11 :105), reacts with singlet
oxygen about 8-fold more rapidly than does free deoxyguanosine (Hildebrand, op cit) .
Comparative studies were carried out on over 30 imidazole-containing compounds using a
modification of the RNO bleaching assay for ainglet oxygen of Krali6 (of Verlhac et al
1984 Nouv J Chim 8 :401) . L-Carnosine (B-alanyl-L-hiatidine), the imidazole compound
prevalent in human striated muscle (Parkhouse et al 1985 J Appl Physiol 58 :14),
scavenges singlet oxygen 2- to 3-fold faster than does L-histidine (also see Dahl et
al, op cit) . We find similar high efficiencies for other dipeptidea with oarboxyterminal
histidyls . These dipeptides are roughly twice as effective as analogous
dipeptides with histidine at the amino terminus . A number of other imidazole
containing compounds either have low solubility, do not exhibit increasing efficiencies
with increasing concentrations over the range tested (1 .5 - 15 mM), or lose their
measured capacity for quenching of singlet oxyaen uDon Grolonged ex ofure to oxidants .
L-Carnosine may be a near-optimal molecule that doubly serves as a gu fer and as a
defense against oxidative damage .
242
ENHANCEMENT OF GENOTOXICITY BY LEAD .
A . Hartwig, R . Schlepegrell, and D . Beyersmann, University of Bremen, Bremen (F .R .G .)
Inorganic lead compounds are considered as suspected carcinogens ; however, the mode
of action is not well understood . Part of the contradictory results in short-term
assays might be due to differences in bioavailability, since we found a'marked dependency
of lead cytotoxicity and uptake on cell type and medium composition . Because
mutagenicity and transforming ability are not accompanied by direct DNA damage (1), we
investigated whether the genotoxic action of lead is due to rather indirect effects by
interfering with genetic control and repair mechanisms, using UV as a standard mutagen .
Pb(II) is comutagenic with UV in the V79 HGPRT-assay . Even though there is only a weak
induction of SCE's in the same cell line by lead alone, we find a pronounced enhancement
of UV-induced SCE's . Pb(II) did not produce DNA strand breaks itself but increased
the number of breaks generated during repair of UV damage, indicating an inhibition of
the polymerisation or the ligation step of excision repair . We conclude that the genotoxicity
of lead compounds is in part due to interference with repair processes .
Reference : .
1 . Zelikoff, J .T ., Li, J .H ., Hartwig, A . Wang, X .W ., Costa, M . and Rosaman, T .G . (1988)
Carcinogenesis 9, 1727 - 1732 .
243
FLOW CYTOMETRIC MICRONUCLEUS TEST WITH MOUSE BONE MARROW AND PERIPHERAL
BLOOD ERYTHROCYTFS
Makoto Hayashil .2, Hannu Norppa2, Toshio Sofunil and Motoi Ishidate. Irl
1Divisioo of Mutagenesis, Biological Safety Research Center, National Institute of Hygienic Sciences,
1-18-1 Kamiyoga, Setagaya-ku, Tokyo, 158 Japan
2Mutagen Laboratory, Department of Industry Hygiene and Toxicology, Institute of Occupational Healtb,
Topeliuksenkatu 41 aA, SF-00250 Helsinki, Finland
Flow cytometry was applied to the micronucleus test with mouse bone marrow (BM) and peripheral
blood (PB) erythrocytes. BM cells were fixed with 1% glutaraldehyde in 1/20 M phosphate buffer at pH
6 .8 and stored in 70% ethanol . PB erythrocytes were sphered and fixed with 1% glutaraldehyde containing
0 .03 mg/ml of sodium dodecyl sulfate in 1/20 M phosphate buffer at pH 6 .8. PB cells were also treated
with RNase to reduce noise from RNA-eoataining erythrocytes . The cells were stained with DAPI, and
50000 erythrocytes were analyzed in an EPICS V flow cytometer using a UV laser operating at 150-200
mW. Data from the flow cytometer were further analyzed by a computer program Including model fitting
to estimate the frequency of micronueleated erythrocytea . For each sample 1000-2000 srythrocytea were
also analyzed from Giemsa-stained smears microscopically . There was a good correlation between the
flow cytometric and microscopical measurements after treatment with mitomycia C (BM,PB), benzene
(BM,PB), 6-mercaptopurine (PB), benzo[aJpyrene (PB), N-ethyl-N-nitrosourea (PB), bromodichloromethane
(PB), and potassium chromate (PB) . A repeated experiment with mitomycin C also showed good
reproducibility for the flow cytometric measumeat of mieronuelai In BM . Generally, standard deviations
were smaller by the flow cytometric method than by the manual method probably because of the different
sample sizes (50000 erythrocytes for flow cytometry and 1000-2000 erythrocytes for manual analysis) .
244
MONITORING OF FOOD MUTAGENS
Hikoya Hayatsu
Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700, Japan
Monitoring of food for mutagenicity requires a simple, practical way of preparing
testable samples . We have been using the blue cotton method for this purpose . Blue
cotton is absorbent cotton bearing covalently linked copper phthalocyaaine trisulfonate .
Since this ligand has a selective affinity to polycyclic compounds, adsorption of mutagens
having polycyclic structures takes place when food extracts in aqueous media are
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1989 EMS Abstracts 85
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