Environmental and Molecular Mutagenesis - Legacy Tobacco ...

347
CLASTOGENICITY OF HEPTACRLOR ON ERYTHROBLASTS OF THE MOUSE, T. $z l,in, J . J . Temenak,
$ . C . Oh, E . Zhou and T . D . Chen, Institute for Environmental Management and
Department of Biological Sciences, Western Illinois IIniveraity, Macomb, IL 61455
(USA)
Neptachlor, an agent commonly found in the uncontrolled industrial waste site, was
tested for its clastogenicity using Mouse Peripheral Erythrooyte-MSoronucleus
bioassay . The chemical was first dissolve in ethanol and diluted with tapwater to the
final concentrations of 0 .5 and 5 .0 uM to feed the mice . Fifteen Balb white mioe were
divided into 3 groups and two groups were fed with the heptachlor solution and one
group with tapwater as the control . Animals were treated with these chronic low doses
of heptachlor for 3 weeks, with a weekly change of fresh aolutions . Two mice were
died during the second week in the 0 .5 uM treated group, and 1 died during the third
week in the 5 .0 uM treated group . Peripheral blood was collected from their tails 7
days after the end of treatment . Two blood smear slides were made from each the the
mice and stained with hematoxylin and Giemea to reveal mioronuolei in both
polychromatic and normochromatio erythrocytes . Mioronuclei (MCN) frequencies were
scored from 10,000 cells in each elide . Preliminary results show that the means and
the standard errors of the control group , 0 .5 aM and 5 .0 uld treated groups were around
0 .7 (+0 .3) ; 1 .7 (+0 .4) ; and 1 .4 (+0 .1) MCM/1000 cells respectively. This indicates
that heptachlor is toxic and also exhibits clastogenicity to the ohromoeomes of
erythroblasts of the mouse .
348
MICRONUCLEATED ERYTHROCYTES AS A MARKER OF CYTOGENETIC DAMAGE IN MAN . J .T . MacGreaor,
Department of Biochemistry, University of California, Berkeley, CA (USA)
Splenectomized individuals constitute a unique population for studies of chromosomal
damage in man . Because micronucleated erythrocytes derived from damaged erythroblasts
remain in peripheral blood with a lifespan approximately equal to that of normal
erythrocytes, the incidence of micronucleated cells in peripheral blood can be used as an
index of chromosomal damage in nucleated precursor cells . The target cell population is
rapidly dividing in vivo, and therefore is sensitive to agents and conditiohs which act
during cell division . This is a significant advantage for studies of conditions such as
transient nutritional imbalances, to which nondividing cells (e .g .,lymphocytes) are
relatively insensitive . Two distinct age populations of erythrocytes can be monitored : 1)
newly-formed erythrocytes, identified by their RNA-positive staining characteristic, which
reflect damage occurring 4-6 days prior to sampling, and 2) RNA-negative erythrocytes,
which reflect the average damage over the 4-month period prior to sampling (corresponding
to the turnover time of the mature erythrocyte pool) . Studies to date have established that
micronucleated cell frequencies increase dramatically following treatment with clastogenic
drugs, and that the kinetics of the observed increases in erythrocyte subclasses parallel
the kinetics of erythrocyte formation and turnover . Studies of environmental factors
associated with modification of the spontaneous frequency of micronucleated cells have
established significant associations between observed frequencies and caffeinated beverage
consumption, folate status, calcium supplement consumption in women, and consumption of
antioxidant vitamin supplements . Age was strongly associated with the micronucleated cell
frequency when other factors were not considered, but not when adjusted for the above
factors .
349
AMPLIFICATION OF mRNA OF THE HPRT GENE FROM LYSATES OF MUTANT HUMAN CELLS AND DIRECT
DNA SEQUENCING TO DETERMINE THE SPECTRA OF MUTATIONS INDUCED BY CARCINOGENS . V .M.
Maher, J .-L . Yang, and J .J . McCormick, Carcinogenesis Laboratory, Michigan State
University, East Lansing, MI 48824 (USA)
Strong evidence points to mutation induction as one mechanism by which changes
are introduced into normal cells to convert them into cancer cells . To understand
the mechanisms by which mutations are induced in human cells by carcinogens, we
are determining the kinds and spectra of mutations induced in the coding region
of the hypoxanthine(guanine)phosphoribosyltransferase (HPRT) gene . This region,
composed of 654 bp, represents nine exons from a 44 kbp gene . To be able to analyze
a large number of independent mutants rapidly and economically, we have optimized
the conditions for copying mRNA directly from lysates of a small number of cells
(e .g ., 200) from a thioguanine resistant clone using reverse transcriptase and
oligo(dT)1P_18 primers . Then two 20-mer primers, specific for the cDNA of the
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1989 EMS Abstracts 121
Notes