Environmental and Molecular Mutagenesis - Legacy Tobacco ...

84 1989 EMS Abstracts
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
Notes the SV-40 T antigen gene leads to nontumorigenic cell lines that have a nearly normal
pathway of terminal squamous differentiation and can be readily transformed to
malignant cells by transfected Ha-ras . N-ras or K1-ras . The combination of
transfected c-myc c and c-raf-1 will aTso cause neoplastic transformation of human
bronchial epitheTial cetls that exhibit some phenotypic traits found in small cell
carcinomas . These and other results indicate that proto-oncogenes dysregulate
pathways of growth and differentiation of human bronchial epithelial cells and play
an important role in human lung carcinogenesis . Allelic deletion and somatic cell
genetic analyses suggest that tumor suppressor genes may be present on chromosomes
3p, llp, 13q and 17p . These studies also indicate that tumor suppressor genes may
play a dominant role in lung carcinogenesis and provide in vitro model systems for
isolating these genes by subtraction library and insertlonaT-mu-Tagenesis approaches .
INVESTIGATION OF SPONTANEOUS TRANSFORMATION OF BALB/c-3T3 CELLS . S .B . Harris and
E .J . Matthews, Hazleton Laboratories America, Inc ., Kensington, Maryland .
239
Spontaneous transformation (ST) was investigated using the A31, I-13 clone of chemical
transformable BALB/c-3T9 cells . All experiments were performed with one lot of
fetal bovine serum, and one cryopreserved pool of cells . ST was shown to include a
continuum of Type I, 11, and III foci of diffarent sizes and morphologies, and the
appearance of foci in individual dishes in an experiment was not normally distributed
. A log, mathematical transformation of the ST data was shown to convert it to
a normal distr1bution . Detection of ST was determined to be influeneed by several
different experimental parameters . First, ST was expressed in proportion to the
tog „ of the surface area of the culture vessels over the range of 36 to 160 mm in
diameter . Second, ST was significantly different for cells derived from different
ampules of cells . Third, pre-existing spontaneous transformants were occasionally
observed in experiments, and these foci were detected in cultures seeded at cell densities
> 3 .2 x 10• ce11s/60 mm dish . In contrast, two experimental parameters did
not effect ST . First, the level of ST was shown to be expressed independently of the
initial seeding density of the cell cultures . Seeond, ST was relatively constant for
10 passages and up to 60 population doublings . Taken together, these data permitted
an estimation of the frequency of spontaneous transformants of 0 .64 x 10-6 for a
contact-inhibited monolayer of cells in a 60 mm dish . Investigations were supported
by NIEHS Contract NO1-ES-66160 .
240
NATURALLY OCCURRING . IMIDAZOLE-CONTAINING ANTIMUTAGENS : ERGOTHIONEINE AND CARNOSINE .
Philip E . Hartman, Department of Biology, The Johns Hopkins University, Baltimore,
MD .
Ergothioneine (2-thiol-L-histidine betaine) has properties both of a thlol and
of a thione ; it is present in millimolar ooncentrations in fungi synthesizing it and
in particular tissues of animals ingesting it . Ergothioneine !s oxidized and
catalyzes the oxidation of reduoed glutathione to the disulfide in the presence of
H=0, (reviewed in Hartman PE 1989 Meth Enzymols in press) . Ergothioneine protects
baeteriophages from Y-irradiation (Hartman et al 1988 Radiat Rea 114 :319) and
decreases mutagenicity of t-butylhydroperoxide and products of nltrosated spermidine
for Salmonella (Hartman Z and Hartman PE 1987 Environ Moleo Mutagen 10 :3) .
Ergo one ne lessens lipid peroxidation in animal systems (Kawano at al 1983 Chem
Pharm Bull 31 :1676, 1682) -- Carnosine (6-alanyl-L-histidine) is present in
millimolar amounts in striated musolea of humans and other animals (Crush 1970 Comp
Biochem Physiol 34 :3 ; Parkhouse at ai 1985 J Appl Physiol 58s14) . Carnoaine quenches
singlet oxygen and traps lipid peroxyl radicals more effeotively than does free
L-histidine (Dahl at al 1988 Photochem Photobiol 47 :357 ; Kohen at al 1988 Proo Natl
Aead Sei USA 85 :3175 ; Hartman Z at al these prooeedings), proteots baoteriophages
from Y-irradiation (Hartman at al 198~ op oit), and prevents induction of lipid
peroxidation in muscle sarcoplasmio retioultso (Dupin at al 1987 Biochemistry
52 :672) . Honocarnosine (Y-aminobutyryl-L-hiatldine) exhibite similar prQteotive
actiona (Kricheskaya et al 1985 Vopr Med Khim 31(4) :75 : Kohen at al 1985 0 oit) .
--These prevalent and naturally occurring imidazole compounds warrant furtRer
investigation as to their possible protective actions against a range of chemioal
mutagens .
241
C-TERMINAL HISTIDINE DIPEPTIDES AS EFFECTIVE SCAVENGERS OF SINGLET MOLECULAR OXYGEN .
Zlata Hartman, Philip E . Hartman and Katherine T . Ault, Department of Biology, The
Johns Hopkins University, Baltimore, MD 21218 USA .
Exogenous singlet oxygen ('0,) ia highly oytotoxic for Salmonella (Dahl at al 1988
Photochem Photobiol 47 :357) but non-mutagenio (Dahl at al-T986'Mdt Res 201 :127) .
Free deoxyguanosine is degraded by ainglet oxygen but ia about 40-fold less sensitive
when in single-stranded DNA and 1000-fold less sensitive when in duplex DNA (E
Hildebrand 1989 PhD Thesis, Johns Hopkins University) . The imidazole, L-histidine, a
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