Yeungnam University

About: Yeungnam University is a education organization based out in Daegu, South Korea. It is known for research contribution in the topics: Thin film & Catalysis. The organization has 9885 authors who have published 22075 publications receiving 372798 citations.

Involvement of NADPH oxidase-mediated generation of reactive oxygen species in the apototic cell death by capsaicin in HepG2 human hepatoma cells.

Abstract: Although capsaicin (8-methyl-N-vanillyl-6-nonenamide), a pungent ingredient in a variety of red peppers of the genus Capsicum, has been shown to induce apoptotic cell death in many cancer cells, the exact mechanism of this action of capsaicin is not completely understood. In this study, we investigated the possible mediation of the NADPH oxidase-modulated production of reactive oxygen species (ROS) in the apoptotic mechanism of capsaicin in HepG2 human hepatoblastoma cells. Capsaicin induced apoptotic cell death in a time- and dose-dependent manner. Capsaicin at the concentration of inducing apoptosis also markedly increased the level of ROS. The capsaicin-induced generation of ROS and apoptosis was significantly suppressed by treatment with antioxidants, DPPD and tocopherol. In addition, inhibitors of NADPH oxidase, diphenylene iodonium, apocynin and neopterine, profoundly blocked the capsaicin-induced ROS generation and apoptosis. The expression of Rac1N17, a dominant negative mutant of Rac1, also signi...

Regulating DNA translocation through functionalized soft nanopores

Abstract: Nanopores have emerged as promising next-generation devices for DNA sequencing technology The two major challenges in such devices are: (i) find an efficient way to raise the DNA capture rate prior to funnelling a nanopore, and (ii) reduce the translocation velocity inside it so that single base resolution can be attained efficiently To achieve these, a novel soft nanopore comprising a solid-state nanopore and a functionalized soft layer is proposed to regulate the DNA electrokinetic translocation We show that, in addition to the presence of an electroosmotic flow (EOF), which reduces the DNA translocation velocity, counterion concentration polarization (CP) occurs near the entrance of the nanopore The latter establishes an enrichment of the counterion concentration field, thereby electrostatically enhancing the capture rate The dependence of the ionic current on the bulk salt concentration, the soft layer properties, and the length of the nanopore are investigated We show that if the salt concentration is low, the ionic current depends largely upon the length of the nanopore, and the density of the fixed charge of the soft layer, but not upon its degree of softness On the other hand, if it is high, ionic current blockade always occurs, regardless of the levels of the other parameters The proposed soft nanopore is capable of enhancing the performance of DNA translocation while maintaining its basic signature of the ionic current at high salt concentration The results gathered provide the necessary information for designing devices used in DNA sequencing

Quantized Sampled-Data Control for Synchronization of Inertial Neural Networks With Heterogeneous Time-Varying Delays

Abstract: This paper is concerned with the problem of synchronization for inertial neural networks (INNs) with heterogeneous time-varying delays (HTVDs) through quantized sampled-data control. The control scheme, which takes the communication limitations of quantization and variable sampling into account, is first employed for tackling the synchronization of INNs. A novel Lyapunov–Krasovskii functional (LKF) is constructed for synchronizing an error system. Compared with existing LKFs by the largest upper bound of all HTVDs, the proposed LKF is superior, since it can make full use of the information on the lower and upper bounds of each HTVD. Based on the LKF and a new integral inequality technique, less conservative synchronization criteria are derived. The desired quantized sampled-data controller is designed by solving a set of linear matrix inequalities. Finally, a numerical example is given to illustrate the effectiveness and conservatism reduction of the proposed results.

Inhibitory effect of piperlonguminine on melanin production in melanoma B16 cell line by downregulation of tyrosinase expression

Abstract: Tyrosinase is a key enzyme for melanin biosynthesis, and hyperpigmentation disorders are associated with abnormal accumulation of melanin pigments, which can be improved by treatment with depigmenting agents In the present study, piperlonguminine from Piper longum was discovered to inhibit melanin production in melanoma B16 cells stimulated with alpha-melanocyte stimulating hormone (alpha-MSH), 3-isobutyl-1-methylxanthine or protoporphyrin IX, where the compound exhibited stronger depigmenting efficacy than kojic acid However, piperlonguminine did not affect 1-oleoyl-2-acetyl-sn-glycerol-induced melanogenesis and did not affect protein kinase C-mediated melanin production Surprisingly, piperlonguminine did not inhibit the catalytic activity of cell-free tyrosinase from melanoma B16 cells but rather suppressed tyrosinase mRNA expression This effect was attributed to the inhibitory action of piperlonguminine on alpha-MSH-induced signaling through cAMP to the cAMP responsive element binding protein that in turn regulates the expression of the microphthalmia-associated transcription factor, a key activator of the tyrosinase promoter This study demonstrates that piperlonguminine is an efficient depigmenting agent with a novel mechanism of action