Denaturing gradient gel electrophoresis (DGGE) and constant denaturant gel electrophoresis (CDGE) are methods based on sequence-determined melting characteristics of DNA and thus detect different ...types of single base changes in the amplified fragments. We have studied detection of 19 mutations in the human N-
ras oncogene and 10 mutations in exon 3 of the Chinese hamster hypoxanthine-guanine phosphoribosyltransferase (
hprt) gene using GC-clamped DGGE and CDGE. After allowing formation of heteroduplexes with the corresponding wild type sequence, all the mutations separated from the wild type in at least one concentration of the denaturants used in CDGE but two of the mutations in
hprt exon 3 did not show separation in any of the DGGE runs. Melting behavior of the mutant fragments was dependent, as expected, on both the type and the location of a mutation. We describe conditions allowing separation of the mutations in the fewest possible DGGE and CDGE runs.
Tobacco smoke is highly genotoxic and produces chromosomal damage in several experimental systems. Active smokers have been shown to have an increased prevalence of somatic chromosome damage in their ...peripheral blood lymphocytes: this is seen in most cases as an increased sister-chromatid exchange (SCE) frequency and often also as increased structural chromosome aberrations (CAs). Among passive smokers, in association with exposure to environmental tobacco smoke, no such induction of chromosomal damage has been documented. In the present paper we report negative results on induction of chromosomal damage in 2 separate groups of intensive involuntary exposure to tobacco smoke, non-smoking restaurant personnel and newborn children of smoking mothers. While significant exposure in these groups is clearly seen in biochemical intake markers, e.g. cotinine and thiocyanate values in plasma, the conventional cytogenetic parameters, structural chromosome aberrations and sister-chromatid exchanges, are unable to detect the low exposures of involuntary smokers.
The frequency of sister-chromatid exchanges (SCEs) was studied in peripheral blood lymphocytes of 26 young male smokers and 10 non-smokers who had recently entered military service. The levels of ...SCEs were examined in 4 consecutive blood samples taken after short experimental periods of smoking only low-tar (LT) or medium-tar (MT) cigarettes. The incidence of SCEs was significantly higher in the the group of smokers than in the group of non-smokers. The SCE levels of the smokers were found to be associated with the personal smoking history; the observed increase in the SCE frequency correlated with the years of smoking measured as cumulative pack years. The difference in type of cigarette did not influence the SCE frequencies.
In vivo inhalation exposure to styrene oxide (25, 50, 75 and 100 ppm) for 2, 4 or 20 days (25 ppm only) had no effects on chromosomal aberration rates or sister chromatid exchange (SCE) frequencies ...(BrdU/labelling performed in vitro) in the bone marrow cells of Chinese hamsters. The only positive response in aberration frequency was obtained when styrene oxide was injected in lethal concentration (500 mg/kg body weight, i.p.) into the animal. One animal out of six showed slightly elevated SCE values after this high dose. The response of the hepatic drug metabolizing enzymes to styrene oxide exposure was found to be rather weak, which may be due to rather high activity of epoxide hydratase in Chinese hamsters as compared to e.g. mouse.
