• Molecules and Cells
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• v.42 no.2
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• pp.175-182
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• 2019

microRNAs regulate a diverse spectrum of cancer biology, including tumorigenesis, metastasis, stemness, and drug resistance. To investigate miRNA-mediated regulation of drug resistance, we characterized the resistant cell lines to 5-fluorouracil by inducing stable expression of miRNAs using lenti-miRNA library. Here, we demonstrate miR-551a as a novel factor regulating cell survival after 5-FU treatment. miR-551a-expressing cells (Hep3B-lenti-miR-551a) were resistant to 5-FU-induced cell death, and after 5-FU treatment, and showed significant increases in cell viability, cell survival, and sphere formation. It was further shown that myocyte-specific factor 2C is the direct target of miR-551a. Our results suggest that miR-551a plays a novel function in regulating 5-FU-induced cell death, and targeting miR-551a might be helpful to sensitize cells to anti-cancer drugs.

• Korean Journal of Materials Research
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• v.25 no.9
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• pp.429-434
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• 2015

Resistance switching memory cells were fabricated using atomically dispersed Pt-$SiO_2$ thin film prepared via RF co-sputtering. The memory cell can switch between a low-resistance-state and a high-resistance-state reversibly and reproducibly through applying alternate voltage polarities. Percolated conducting paths are the origin of the low-resistance-state, while trapping electrons in the negative U-center in the Pt-$SiO_2$ interface cause the high-resistance-state. Intermediate resistance-states are obtained through controlling the compliance current, which can be applied to multi-level operation for high memory density. It is found that the resistance value is related to the capacitance of the memory cell: a 265-fold increase in resistance induces a 2.68-fold increase in capacitance. The exponential growth model of the conducting paths can explain the quantitative relationship of resistance-capacitance. The model states that the conducting path generated in the early stage requires a larger area than that generated in the last stage, which results in a larger decrease in the capacitance.

• The Korean Journal of Physiology and Pharmacology
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• v.16 no.1
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• pp.11-16
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• 2012

Cancer stem cells (CSCs) are often characterized by the elevated expression of drug-resistance related stem-cell surface markers, such as CD133 and ABCG2. Recently, we reported that CSCs have a high level of expression of the IL-6 receptor (IL-6R). The purpose of this study was to investigate the effect of anticancer drugs on the expression of the drug resistance-related cancer stem cell markers, ABCG2, IL-6R, and CD133 in non-small cell lung cancer (NSCLC) cell lines. A549, H460, and H23 NSCLC cell lines were treated with the anticancer drugs 5-fluorouracil (5-FU; $25{\mu}g/ml$) and methotrexate (MTX; $50{\mu}g/ml$), and the expression of putative CSC markers was analyzed by fluorescent activated cell sorter (FACS) and the gene expression level of abcg2, il-6r and cd133 by reverse transcriptase-polymerase chain reaction (RT-PCR). We found that the fraction of ABCG2-positive(+) cells was significantly increased by treatment with both 5-FU and MTX in NSCLC cells, and the elevation of abcg2, il-6r and cd133 expressions in response to these drugs was also confirmed using RT-PCR. Also, the number of IL-6R(+) cells was increased by MTX in the 3 cell lines mentioned and increased by 5-FU in the H460 cell line. The number of CD133(+) cells was also significantly increased by both 5-FU and MTX treatment in all of the cell lines tested. These results indicate that 5-FU and MTX considerably enhance the expression of drug-resistance related CSC markers in NSCLC cell lines. Thus, we suggest that antimetabolite cancer drugs, such as 5-FU and MTX, can lead to the propagation of CSCs through altering the expression of CSC markers.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.425-427
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• 2008

Active area of dye-sensitized solar cell (DSSC) has an effect on the efficiency of DSSC. As the active area increases, the efficiency goes down in a general way. This is caused by the increase of internal resistance in DSSC. The internal resistances are related to various resistant elements. The charge transfer processes at Pt counter electrode and the sheet resistance of TCO are two of these resistant elements. In this study, we try to divide the active area into several small sections in a large sized cell to reduce these two internal resistant elements. As a result, we find out that the fill factor is increased and then the conversion efficiency is improved as the number of dividing active area into several small sections is increased.

• Microbiology and Biotechnology Letters
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• v.21 no.2
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• pp.176-180
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• 1993

Survival and heat resistance of Listeria monocytogenes Scott A in various nutritional environments and cell type on stainless steel were determined. Viable cell of L. monocytogenes Scott A was most rapidly decreased in phosphate buffer among various media such as NSM (30 g TSB/1 l D.W.), LNM (2 g TSB/1 l D.W.) and phosphate buffer (pH=7) during incubation at 21 and 35C but survived for 15 days at 21C. Vegetative and starved L. monocytogenes Scott A were survived after heat treatment for 5 min at 65C while not detected at 72C.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.170-172
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• 2005

Internal battery ohmic measurements have been a hot topic amongst battery users and battery manufacturers. As a battery deteriorates and loses its capacity, the internal resistance of the battery increases. Everyone seems to agree that measuring the internal parameters of a cell can be very useful in determining a battery's state of health. In this paper experiences show that if a cell's resistance increases by more than25% above its baseline value(known good resistance of new 100% capacity cell), the cell will no loger be able to deliver 80% or more of the rated capacity.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.1
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• pp.255-260
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• 2012

Patients with non-small cell lung cancer (NSCLC) who have activating epidermal growth factor receptor (EGFR) mutations derive clinical benefit from treatment with EGFR-tyrosine kinase inhibitors ((EGFR-TKIs)-namely gefitinib and erlotinib. However, these patients eventually develop resistance to EGFR-TKIs. Despite the fact that this acquired resistance may be the result of a secondary mutation in the EGFR gene, such as T790M or amplification of the MET proto-oncogene, there are other mechanisms which need to be explored. MicroRNAs (miRs) are a class of small non-coding RNAs that play pivotal roles in tumorigenesis, tumor progression and chemo-resistance. In this study, we firstly successfully established a gefitinib resistant cell line-HCC827/GR, by exposing normal HCC827 cells (an NSCLC cell line with a 746E-750A in-frame deletion of EGFR gene) to increasing concentrations of gefitinib. Then, we found that miR-214 was significantly up-regulated in HCC827/GR. We also showed that miR-214 and PTEN were inversely expressed in HCC827/GR. Knockdown of miR-214 altered the expression of PTEN and p-AKT and re-sensitized HCC827/GR to gefitinib. Taken together, miR-214 may regulate the acquired resistance to gefitinib in HCC827 via PTEN/AKT signaling pathway. Suppression of miR-214 may thus reverse the acquired resistance to EGFR-TKIs therapy.

• Preventive Nutrition and Food Science
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• v.9 no.4
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• pp.367-373
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• 2004

The prevalence of type-2 diabetes increases remarkably in post-menopausal women, possibly because insulin secretion fails to compensate for the insulin resistance induced in various tissues by estrogen insufficiency. However, this has not been fully defined. Therefore, the present study investigated whether an ovariectomy (OVX) would increase insulin resistance and decrease the $\beta$-cell function and mass in female rats with and without a $90\%$ pancreatectomy (Px). Female rats aged 15 weeks were divided into four groups: 1) OVX + Px, 2) SOVX (sham operation of OVX) + Px, 3) OVX + SPx (sham operation of Px), and 4) SOVX + SPx, and given a $30\%$ fat diet for 8 weeks. At the end of the experimental period, the islet function and insulin resistance were determined using a hyperglycemic clamp and a euglycemic hyperinsulinemic clamp, respectively. The OVX only increased the body weight in the SPx rats, which was partially related to the food intake. Yet, the OVX did increase the peripheral insulin resistance, while the Px increased this resistance further. The OVX and Px both exacerbated the islet function, as measured by the insulin secretion pattern, while delaying and decreasing the first-phase insulin secretion. The OVX only decreased the proliferation of $\beta$-cells in the Px rats, while increasing apoptosis in both the Px and SPx rats. As a result, the OVX decreased the $\beta$-cell mass in the Px rats, but increased the mass in the SPx rats. In conclusion, an OVX was found to accelerate the development and progression of diabetes by increasing the insulin resistance and decreasing the $\beta$-cell mass. Therefore, menopause can be a risk factor for type-2 diabetes, mainly due to a deceased proliferation of $\beta$-cells.

• Journal of the Korean institute of surface engineering
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• v.41 no.2
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• pp.69-75
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• 2008

Electrochemical behaviors of surface modified and MC3T3-E1 cell cultured Ti-30Ta alloys have been investigated using various electrochemical methods. The Ti alloys containing Ta were melted by using a vacuum furnace and then homogenized for 6 hrs at $1000^{\circ}C$. MC3T3-E1 cell culture was performed with MC3T3-E1 mouse osteoblasts for 2 days. The microstructures and corrosion resistance were measured using FE-SEM, XRD, EIS and potentiodynamic test in artificial saliva solution at $36.5{\pm}1^{\circ}C$. Ti-Ta alloy showed the martensite structure of ${\alpha}+{\beta}$ phase and micro-structure was changed from lamellar structure to needle-like structure as Ta content increased. Corrosion resistance increased as Ta content increased. Corrosion resistance of cell cultured Ti-Ta alloy increased predominantly in compared with non cell cultured Ti- Ta alloy due to inhibition of the dissolution of metal ion by covered cell. $R_p$ value of MC3T3-E1 cell cultured Ti-40 Ta alloy showed $1.60{\times}10^6{\Omega}cm^2$ which was higher than those of other Ti alloy. Polarization resistance of cell-cultured Ti-Ta alloy increased in compared with non-cell cultured Ti alloy.

• Microbiology and Biotechnology Letters
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• v.14 no.4
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• pp.299-304
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• 1986

The cell volume, cell surface, cell concentration, dry cell weight, frequence of respiratory deficient mutation, resistance against ultraviolet irradiation, fermentation power, DNA contents of haploid diploid, triploid and tetraploid of Saccharomyces cerevisiae strain were investigated. Respiratory deficient mutants by spontaneous mutation were absolved more frequently in the haploid than in the diploid, triploid and tetraploid. And cell volume, cell surface, cell concentration, dry cell weight, resistance against ultraviolet irradiation, fermentation power, and DNA contents were significantly increased as the ploidy increased.