• Environmental Mutagens and Carcinogens
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• v.15 no.2
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• pp.88-93
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• 1995

Effects of hyperthermia on the induction of DNA single strand breaks and replication inhibition were studied in bleomycin-treated CHO-K$_1$ cells by alkaline elution and alkaline sucrose gradient sedimentation. Bleomycin-induced DNA single strand breaks of DNA were dose-and time-dependently increased, and these strand breaks of DNA were gradually rejoined as post-incubation time passed. Treatment with hyperthermia alone did not affect the induction of DNA single strand breaks. However, pre-exposure of cells to hyperthermia followed by bleomycin treatment greatly increased the single strand breaks, and also reduced the rejoining processes of bleomycin-induced DNA single strand breaks. Bleomycin selectively inhibited the replicon initiation. The combined treatment with hyperthermia and bleomycin markedly potentiated the nonspecific inhibition of replication.

• Journal of the Korean Chemical Society
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• v.65 no.2
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• pp.121-124
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• 2021

RNA molecules which bind to the G-rich sequence in the 5'-UTR RNA which plays an important role in expression of N-ras, were selected. The secondary structures of five selected RNA aptamers including primer sequence were found by the CLC RNA workbench ver. 4.2 program (www.clcbio.com) and investigated with RNA structural probes such as RNase T1 which has specificity for a G in single-stranded region, RNase V1 specific for double strand and nuclease S1 specific for single strand. The generalized secondary structure model was proposed and characterized. It was composed of a central long double strand region flanked by single strand region at both end sides. The double strand region had an internal single-strand region and bulges. The single strand loop in the right side was composed of four or five nucleotides.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.4
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• pp.346-351
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• 2003

Single-cell gel electrophoresis (comet assay) was used to detect DNA single strand break in blood cells from several marine fish species. Three fish species were collected from Georgia coastal area. Mummichog, Fundulus heteroclitus showed higher DNA damage than sea bass, Lateolabrax japonicus and trout, Oncorhynchus masou masou under the same experimental conditions. Mummichogs had more alkaline-labile sites on their DNA than other fish species. The comet assay with mummichog blood cells at pH 12.5 showed a dose-response curve with the increasing concentrations of hydrogen peroxide. While the isolated leucocytes showed no increase of DNA damage after in vitro exposure to 2-methyl-1,4-naphthoquinone (MNQ), erythrocytes showed dose-dependent DNA damage. These results indicate that the comet assay can be applied successfully as a bioassay using erythrocyte for environmental monitoring.

• Toxicological Research
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• v.2 no.1
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• pp.1-7
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• 1986

Procarcinogen induced DNA single-strand breaks and unschduled DNA synthesis were measured in primary rat hepatocytes culture. For DNA single-strand breaks assay, rat liver DNA was prelabeled by injection 3H-thymidine during the peak of DNA synthesis following partial hepatectomy. Hepatocytes were isolated from the rat 2 weeks after surgery by a collagenase perfusion techinique and maintained as monolayers in serum free medium on collagen-coated culture dishes. DNA sigle-strand breaks were measured by the alkaline elution techinique.

• Radiation Oncology Journal
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• v.8 no.2
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• pp.137-144
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• 1990

The filter elution technique was used to assay Co-60 $\gamma$ ray-induced DNA single-strand breaks(SSB) in EL 4 mouse leukemia cell and mouse spleen lymphocyte. The lymphocytes were stimulated with lipopolysaccharide (LPS, 20 $\mug/ml$) to label [${^3}H$] thymidine. EL 4 cells and lymphocytes in suspension were exposed at $0^{\circ}C$ to 0 Gy, 1 Gy, 5 Gy,10 Gy of Co-60 radiation and elution procedure was performed at PH 12.1. The number of DNA single-strand breaks increased with increasing doses of $\gamma$ rays. The strand scission factor (SSF) was estimated in each experiment (eluted volume 21 ml). The slope for EL 4 cells was $0.01301\pm0.00096\;Gy^{-1}(n=5)$ and the slope for lymphocytes was $0.01097\pm0.00091\;Gy^{-1}(n=5)$. The slopes were significantly different (P<0.005). Thus EL 4 cells were more sensitive to induction of DNA SSB by ionizing radiation than lymphocytes.

• Journal of Microbiology and Biotechnology
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• v.16 no.12
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• pp.2004-2007
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• 2006

An efficient method for the in vitro reassembly of homologous DNA sequences is presented. The proposed method involves obtaining single strands of homologous genes and hybridizing them to obtain partially hybridized heteroduplex DNA; cleaving the single-stranded regions of the heteroduplex DNA using S1 nuclease to generate double-strand DNA fragments; denaturing the double-strand DNA fragments to generate single-strand DNA fragments; conducting a series of polymerase chain reactions (PCR) using the single-strand DNA fragments as internal primers and a mixture of homologous DNA as templates to obtain elongated reassembled DNA; and finally, amplifying the reassembled DNA by a PCR using terminal primers. As a result, DNA reassembly could be achieved between homologous genes with a sequence similarity as low as 78%.

• Journal of Species Research
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• v.9 no.4
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• pp.448-454
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• 2020

Nine free-living heterotrophic flagellates were cultured from marine intertidal sediments and freshwater sediments from Korea. These species are described with uninterpreted records based on light microscopy of living cells and reported taxonomically for the first time from Korea. Diagnostics of these species are as follows; Notosolenus hemicircularis: 9-11.8 ㎛ long with flagellar reservoir, ventrally flattened and dorsally convex with hyaline semicircular collar around short anterior neck, and 8 ridges on cell surface. Thecamonas tranhens: 4.5-7.1 ㎛ long, plastic with proboscis comprising an anterior flagellum surrounded by membranous sleeve. Bodomorpha minima: 4.5-7.0 ㎛ long, rigid with small rostrum in anterior end and active anterior flagellum. Cercomonas hiberna: 5.6-10.9 ㎛ long, very plastic with pseudopodia, cytoplasmic strand and 1 or 2 contractile vacuoles. Cercomonas pellucida: 7.5-13 ㎛ long, plastic with pseudopodia, cytoplasmic strand and single contractile vacuole. With nucleus closely connected to basal bodies. Eocercomonas echina: 4.7-6.5 ㎛ long, plastic with pseudopodia, cytoplasmic strand and 1 or 2 contractile vacuoles. Paracercomonas astra: 5.7-7.3 ㎛ long, moderately metabolic with pseudopodia, cytoplasmic strand and 1 or 2 contractile vacuoles. Paracercomonas minima: 5-9 ㎛ long, metabolic with pseudopodia, cytoplasmic strand and single contractile vacuole. Paracercomonas producta: 6.1-9.9 ㎛ long, very metabolic with pseudopodia, long cytoplasmic strand and single contractile vacuole.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.2011-2014
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• 2010

The fluorescence intensity of a single-stranded oligonucleotide containing a fluorene-labeled deoxyuridine $(U^{Fl})$ unit increases by only 1.5-fold upon formation of its perfectly matched duplex. To increase the fluorescence signal during hybridization, we positioned a quencher strand containing a deoxyguanine (dG) nucleobase, functioning as an internal quencher, opposite to the $U^{Fl}$ unit to reduce the intrinsic fluorescence upon hybridization with a probe. From an investigation of the optimal length of the quencher strand and the effect of the neighboring base sequence, we found that a short strand (five-nucleotide) containing all natural nucleotides and dG as an internal quencher was effective at reducing the intrinsic fluorescence of a linear beacon; it also exhibited high total discrimination factors for the formation of perfectly matched and single base-mismatched duplexes. Such assays that function based on clear changes in fluorescence in response to single-base nucleotide mutations would be useful tools for accelerating diagnoses related to various diseases.

• Molecular & Cellular Toxicology
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• v.1 no.2
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• pp.99-105
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• 2005

Perchloroethylene (tetrachloroethylene, PCE), a dry cleaning and degreasing solvent, can enter ground-water through accidental leak or spills. PCE can be degraded to trichloroethylene (TCE), 1, 1-dichloroethylene (DCE) and vinyl chloride (VC) as potential bio-product. These compounds have been reported that they can cause clinical diseases and cytotoxicity. However, only a little genotoxic information of these compounds has been known. In this study, we investigated DNA single strand breaks of PCE, TCE, DCE and VC by single cell gel electrophoresis assay, (comet assay) which is a sensitive, reliable and rapid method for DNA single strand breaks with mouse lymphoma L5178Y cells. From these results, $37.5\;{\mu}g/ml$ of PCE, $189\;{\mu}g/ml$ of TCE and $56.4\;{\mu}g/ml$ of DCE were revealed significant DNA damages in the absence of S-9 metabolic activation system meaning direct-acting mutagen. And in the presence of S-9 metabolic activation system, $41.5\;{\mu}g/ml$ of PCE, $328.7\;{\mu}g/ml$ of TCE and $949\;{\mu}g/ml$ of DCE were induced significant DNA damage. In the case of VC, it was revealed a significant DNA damage in the presence of S-9 metabolic activation system. Therefore, we suggest that chloroethylene compounds (PCE, TCE, DCE and VC) may be induced the DNA damage in a mammalian cell.

• Journal of Radiation Industry
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• v.5 no.3
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• pp.243-247
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• 2011

In this study, a convenient method for the selective immobilization of single strand DNA (ssDNA) on a polymer surface was described. A positively charged polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA), was spin-coated on a tissue culture petridish and the micropatterns of the PDDA were formed by selective ion implantation through a pattern mask. The surface property of the implanted PDDA was investigated by using a surface profiler and FT-IR spectrometer. Cy3-labeled ssDNA was selectively immobilized on the PDDA patterns through ionic interaction and thus, well-defined ssDNA patterns were obtained.