| 1. |
- Matsuoka, Atsuko, et al.
(författare)
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Correlation of sister chromatid exchange formation through homologous recombination with ribonucleotide reductase inhibition.
- 2004
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Ingår i: Mutat Res. - 0027-5107. ; 547:1-2, s. 101-7
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We conducted the recombination and sister chromatid exchange (SCE) assays with five chemicals (hydroxyurea (HU), resveratrol, 4-hydroxy-trans-stilbene, 3-hydroxy-trans-stilbene, and mitomycin C) in Chinese hamster cell line SPD8/V79 to confirm directly that SCE is a result of homologous recombination (HR). SPD8 has a partial duplication in exon 7 of the endogenous hprt gene and can revert to wild type by homologous recombination. All chemicals were positive in both assays except for 3-hydroxy-trans-stilbene, which was negative in both. HU, resveratrol, and 4-hydroxy-trans-stilbene were scavengers of the tyrosyl free radical of the R2 subunit of mammalian ribonucleotide reductase. Tyrosyl free radical scavengers disturb normal DNA replication, causing replication fork arrest. Mitomycin C is a DNA cross-linking agent that also causes replication fork arrest. The present study suggests that replication fork arrest, which is similar to the early phases of HR, leads to a high frequency of recombination, resulting in SCEs. The findings show that SCE may be mediated by HR.
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| 2. |
- Matsuoka, Atsuko, et al.
(författare)
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Development of an in vitro screening method for safety evaluation of nanomaterials
- 2009
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Ingår i: Bio-medical materials and engineering. - 0959-2989 .- 1878-3619. ; 19:1, s. 19-27
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the role of particle size in cytotoxicity tests of nanomaterials (NMs), we exposed Chinese hamster cells to polystyrene (PS) spheres with defined diameters ranging from 0.1 to 9.2 mu m. We found that the 4.45-mu m PS particles were most cytotoxic while sizes 0.1 and 0.2 mu m showed no cytotoxicity up to 1000 mu g/ml. In the chromosome aberration test, the 4.45-mu m PS particles induced polyploidy in amass concentration-dependent manner in 24- and 48-h treatments. The 5.26-mu m PS particles induced polyploidy only at 1000 mu g/ml for 48 h. Next, we performed the cytotoxicity test with as-grown single walled carbon nanohorns (NHas). These were suspended in DMSO and then transferred into the culture medium followed by sonication. Six suspensions differently sonicated showed the same apparent toxicity, although the total particle size distributions differed. However, the sizes of NHas particles predicted to be most toxic from the experiments with PS particles, i.e. 1.01-4.47 mu m constituted 40-60% of all particles in all six suspensions. The results suggest that the cytotoxicity of NMs in suspension depends on specific sizes of aggregates and therefore suspensions should be checked with regard to particle size distributions in assays of toxic effects. The uptake of particles into cells was confirmed by confocal microscopy.
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