Mutation Research Letters最新文献

The micronulceus test and sister-chromatic exchange (SCE) test were used to research the antimutagenic effect of pine needle extract. The results showed that the mutagenic effect of cyclosphamide (CP) was inhibited by the pine needle extract. The micronucleus frequencies (MNF) of mouse bone marrow and human lymphocytes from peripheral blood were decreased with the effect of the extract (the dose was 2000 mg/kg or 5 mg/ml); the frequency of SCE in human lymphocytes was also reduced significantly, which indicated that the MNF and the SCE frequencies were negatively correlated with the dose of pine needle extract (r = −0.9782, −0.9587, −.09765, respectively). This suggested that the pine needle extract was an effective antimutagen and it is important to choose the proper doses of pine needle extract for antitumor effect.

Micronucleus induction was compared in human lymphoblastoid TK6 and mouse lymphoma L5178Y cell lines treated with model clastogens and spindle poisons, i.e., X-rays, methyl methanesulfonate, ethyl methanesulfonate, mitomycin C, colcemid, and vincristine. The spontaneous micronucleated cell (MNC) frequency was stable and reproducible in both cell lines. All clastogens and spindle poisons studied here induced micronuclei in both cell lines. They increased MNC frequency at lower concentrations or caused a greater increase at the same concentration in TK6 cells. These clastogens and spindle poisons, however, were also more toxic to TK6 than to L5178Y cells and when comparison was based on cytotoxicity, they showed more efficient MNC induction in L5178Y cells. In conclusion, neither cell line was superior to the other, and both of them can be used as target cells in the in vitro micronucleus assay.

A simple and short-term micronucleus (MN) test in pulmonary alveolar macrophages (PAMs) of rats has been developed to assess potential genotoxic effects of gaseous environmental agents. The protocol has been tested in model experiments with indoor air pollutants like mosquito coil smoke (MCS) and mosquito mat vapour (MMV). Smears of pulmonary lavage fluid collected in hypotonic (0.56%) KC1 solution were fixed in absolute methanol and stained in Giemsa (10%). Characteristically the large size of the PAMs facilitates easy scoring of MN. An interval of 32 h post exposure seems to be suitable for MN preparation. A comparison of the concentration-response data on CAs (at 24 h post exposure) and MN (at 32 h post exposure) clearly reveals the validity of the MN assay in PAMs

The first 26 families of complex chromosome-type exchanges (from three breaks in two chromosomes to five breaks in five chromosomes) have been evaluated, and the 15 060 exchanges resulting from unrestricted restitution or rejoining of the break ends yields 203 distinctive patterns, if a single participating chromosome is FISH-painted.

If we assume that any exchange that produces an acentric fragment of any sort (compound-terminal or interstitial) will be ultimately eliminated in a continuously dividing cell population, then, irrespective of family origin, only 17 of these patterns (≈8%) will be transmitted, long-term.

The 17 are illustrated, and the implications briefly discussed.

The purpose of this study was to investigate the cytotoxic and genotoxic potential of low intensity laser irradiation (660 nm, 12 mW, 5 kHz) on mammalian cells. Thymidine kinase (TK)-positive and TK-deficient Friend erythroleukaemia (FEL) cells, clone 707 and subclone 707BUF respectively, were used in this investigation. Following irradiation of exponentially growing cells in suspension at doses of 2 and 20 J/cm² a number of sensitive bioassays were used to facilitate the detection of laser-induced mutations, DNA damage and cell killing. Mutations were assessed by the examination of chromosome spreads, the determination of micronucleus frequency and by the determination of the mutant frequency at the hypoxanthine-guanine phosphoribosyltransferase (hgprt) locus. DNA damage was quantified using a sensitive ELISA. The cytotoxic effect of laser irradiation was assessed using a cloning assay. The results of this investigation did not show any significant increase in mutation frequency, DNA damage or cell survival in the laser-irradiated cells, compared to sham-irradiated controls. The lack of any demonstrable cytotoxic and genotoxic effects of low intensity laser irradiation on mammalian cells in culture would support it as being a safe modality for clinical use.

Biochemically active human DNA repair protein, xeroderma pigmentosum G (XPG), was overexpressed in insect cells by a recombinant baculovirus. The recombinant baculovirus produced XPG with a mobility of ∼ 185 kDa in a denaturing polyacrylamide gel. Indirect immunofluorescence studies demonstrated that the recombinant full-length XPG protein was expressed predominantly as a nuclear protein. The recombinant XPG protein was purified to apparent homogeneity using Q-sepharose, S-300 size exclusion, and Mono Q column chromatography. XPG protein showed a structure-specific DNA endonuclease activity, and a preferential affinity to single-stranded DNA and RNA compared to double-stranded DNA.

To examine the suitability of using rat peripheral blood from animals used in subchronic toxicity studies for micronucleus analysis, we orally administered phenacetin or 6-mercaptopurine for 14 days to groups of six rats and compared their micronucleus frequencies to the bone marrow micronucleus frequencies of rats similarly treated for only 2 days. In the 14-day test, phenacetin significantly increased the frequency of micronucleated reticulocytes in peripheral blood at 500 mg/kg starting from day 9, and at 750 and 1500 mg/kg starting from day 6; 6-mercaptopurine topurine gave a positive response at 20 mg/kg starting from day 6. Positive responses in the bone marrow assay were obtained at the same dose levels. In the 2-day test, micronucleated polychromatic erythrocyte frequencies increased significantly at 1000 and 2000 mg/kg for phenacetin, and at 50, 100, and 200 mg/kg for 6-mercaptopurine. These results suggest that micronucleus assays using peripheral blood from rats in subchronic animal studies of phenacetin and 6-mercaptopurine are feasible and at least as sensitive for the assessment of micronuclei as an acute bone marrow micronucleus test.

The genotoxic effects of the methylating agent streptozotocin (STZ) on Chinese hamster cells CHO-9 and V79 were evaluated. The induction of cell killing, chromosomal aberrations, sister-chromatid exchanges (SCEs) and mutations was analyzed. Comparisons were made with the the STZ aglyconic analogue N-methyl-N-nitrosourea (MNU). V79 cells were found to be more resistant than CHO-9 cells to STZ and MNU killing effects, as well as to the induction of chromosomal aberrations and SCEs; however, V79 and CHO-9 cells appeared to be equally sensitive to the induction of 6-thioguanine resistant mutants by STZ. These results suggest that an error-free mechanisms that tolerates DNA methylation damage confers a resistant phenotype to V79 cells to the genotoxic effects of methylation damage.

The mutagenic activity of the aliphatic epoxide isoamylene oxide (2-methyl-2,3-epoxybutane) is not readily detectable in the standard Ames test. In this study, the clastogenic potential of isoamylene oxide was evaluated using an in vitro mammalian cell culture system. Approximately 48 h after establishing primary cultures of rat lymphoocyte cultures, the cells were treated for 4 h with various concentrations of isoamylene oxide (50, 166.7, 500, 1666.7 and 5000 μg/ml in the initial assay and 500, 1000, 2000, 3000, 4000, and 5000 μg/ml in the confirmatory assay). The cultures were harvested 24 h after termination of the treatment. Based upon the mitotic indices, cultures treated with the three highest concentrations in both the initial and confirmatory assays were evaluated to estimate the chromosomal aberration frequencies. Isoamylene oxide demonstrated a strong clastogenic activity in this assay: up to 29% aberrant cells (without gaps) were observed at the highest concentration analyzed. The presence of an external metabolic activation system (S9) did not seem to influence the magnitude of the response at the dose levels analyzed.