Showing papers by "Chonbuk National University published in 2009"

Overexpression of SIRT1 Protects Pancreatic β-Cells Against Cytokine Toxicity by Suppressing the Nuclear Factor-κB Signaling Pathway

Abstract: OBJECTIVE—SIRT1, a class III histone/protein deacetylase, is known to interfere with the nuclear factor-κB (NF-κB) signaling pathway and thereby has an anti-inflammatory function. Because of the central role of NF-κB in cytokine-mediated pancreatic β-cell damage, we postulated that SIRT1 might work in pancreatic β-cell damage models. RESEARCH DESIGN AND METHODS—RINm5F (RIN) cells or isolated rat islets were treated with interleukin-1β and interferon-γ. SIRT1 was activated by resveratrol, a pharmacological activator, or ectopic overexpression. The underlying mechanisms of SIRT1 against cytokine toxicity were further explored. RESULTS—Treatment of RIN cells with cytokines induced cell damage, and this damage was well correlated with the expression of the inducible form of nitric oxide (NO) synthase (iNOS) and NO production. However, SIRT1 overexpression completely prevented cytokine-mediated cytotoxicity, NO production, and iNOS expression. The molecular mechanism by which SIRT1 inhibits iNOS expression appeared to involve the inhibition of the NF-κB signaling pathway through deacetylation of p65. In addition, SIRT1 activation by either resveratrol or adenoviral-directed overexpression of SIRT1 could prevent cytokine toxicity and maintain normal insulin-secreting responses to glucose in isolated rat islets. CONCLUSIONS—This study will provide valuable information not only into the mechanisms underlying β-cell destruction but also into the regulation of SIRT1 as a possible target to attenuate cytokine-induced β-cell damage.

Preparation and Enhanced Hydrostability and Hydrogen Storage Capacity of CNT@MOF-5 Hybrid Composite

Abstract: Metal−organic frameworks (MOFs) are a rapidly growing class of microporous materials. Various MOFs with tailored nanoporosities have recently been developed as potential storage media for natural gases and hydrogen. However, wider applications have been limited because even atmospheric moisture levels cause MOF instability, and unexpectedly low H2 storage capacity, at 298 K. To overcome these problems, we synthesized a hybrid composite of acid-treated multiwalled carbon nanotubes (MWCNTs) and MOF-5 [Zn4O(bdc)3; bdc = 1,4-benzenedicarbocylate] (denoted MOFMC). In a successful synthesis, well-dispersed MWCNTs in dimethylformamide (DMF) were mixed with a DMF solution of zinc nitrate tetrahydrate and terephthalic acid. The MOFMCs obtained had the same crystal structure and morphology as those of virgin MOF-5, but exhibited a much greater Langmuir specific surface area (increased from 2160 to 3550 m2/g), about a 50% increase in hydrogen storage capacity (from 1.2 to 1.52 wt % at 77 K and 1 bar and from 0.3 to ...

Impact of oxidative stress on lung diseases

Abstract: Reactive oxygen species (ROS) are products of normal cellular metabolism and are known to act as second messengers. Under physiological conditions, ROS participate in maintenance of cellular ‘redox homeostasis’ in order to protect cells against oxidative stress through various redox-regulatory mechanisms. Overproduction of ROS, most frequently due to excessive stimulation of either reduced nicotinamide adenine dinucleotide phosphate by cytokines or the mitochondrial electron transport chain and xanthine oxidase, results in oxidative stress. Oxidative stress is a deleterious process that leads to lung damage and consequently to various disease states. Knowledge of the mechanisms of ROS regulation could lead to the pharmacological manipulation of antioxidants in lung inflammation and injury.

Ethnic return migration and hierarchical nationhood

Abstract: Though nationhood is typically understood to be an equalizing or horizontal concept, the phenomenon of ethnic return migration has shown that states as well as societies can draw hierarchical distinctions between persons of the same ancestry. We demonstrate two dimensions - legal and social - of this 'hierar- chical nationhood' by analysing the South Korean policy and citizen attitudes regarding Joseonjok, or ethnic Korean Chinese citizens moving to South Korea. On the legal dimension, the Korean state defines Joseonjok as foreigners, allowing them entry mainly for low-wage jobs and excluding them from social benefits, while preferring them over other foreigners. The legal dimension of hierarchy is also institutionalized in a more favourable visa for Korean Americans that excludes Joseonjok. The social dimension of hierarchical nationhood is shown by public opinion data of Korean citizens towards Joseonjok foreign workers and data on reported experiences of discrimination. Finally, the authors show how Korea's hierarchical nationhood is shaped by economic and geopolitical goals, and describe analogous cases in Asia and Europe.

The efficacy of plate construct augmentation versus cage alone in anterior cervical fusion.

Abstract: STUDY DESIGN.: Retrospective study. OBJECTIVE.: To compare the efficacy of anterior cervical discectomy and fusion with cage alone (ACDF-CA) with cage and plate construct (ACDF-CPC) in regards to fusion rate, radiologic and clinical outcomes. SUMMARY OF BACKGROUND DATA.: ACDF-CA has shown good results; however, debate exists regarding the high rate of complications such as pseudarthrosis, subsidence, and local kyphosis. In an attempt to avoid these complications, the authors have performed ACDF with cage and plate construct (ACDF-CPC). METHODS.: A total of 78 consecutive patients who underwent 1- or 2-level ACDF-CA or ACDF-CPC suffering from cervical radiculopathy were divided into 2 groups; Group A (n = 38) underwent ACDF-CA; Group B (n = 40) underwent ACDF-CPC. Fusion rate, segmental kyphosis, disc height, and subsidence rate were assessed by radiographs. Clinical outcomes were assessed using Robinson criteria. RESULTS.: Solid fusion was achieved in 78.9% (30/38) of subjects in group A compared to 97.5% (39/40) of subjects in group B (P = 0.01). Segmental kyphosis was noted in 42.1% (16/38) in group A compared with 10% (4/40) in group B (P < 0.01). There was a significant decrease in disc height in group A compared to group B (P < 0.05). Subsidence occurred in 32.3% (19/59 levels) of group A compared with 9.7% (6/62 levels) of group B (P < 0.01). Clinical outcomes were similar for both treatment groups. The pseudarthrosis rate in group A was higher than that in group B (P = 0.01). Revision surgery was required in 10.5% (4/38) of group A, whereas none of group B required reoperation (P < 0.01). CONCLUSION.: The use of cage and plate construct in 1- or 2-level ACDF results in a more lordotic alignment, an increased disc height, a higher fusion rate, a lower subsidence rate, and a lower complication rate than that of cage alone; however, there is no significant difference in clinical outcome between groups.

Expression of DBC1 and SIRT1 is associated with poor prognosis of gastric carcinoma.

Abstract: Purpose: SIRT1 (silent mating-type information regulation 2 homologue 1) expression has been reported to predict poor survival in some cancers. We therefore investigated the expression levels of SIRT1 and its negative regulator, DBC1 (deleted in breast cancer 1), in gastric cancer patients. Experimental Design: We evaluated immunohistochemical expression of DBC1, SIRT1, and p53 using 3-mm tumor cores from 177 gastric cancer patients for tissue microarray. Results: Positive expressions of DBC1 and SIRT1 were seen in 62% (109 of 177) and in 73% (130 of 177) of patients, respectively. Expression of DBC1 was significantly correlated with tumor stage ( P = 0.007), lymph node metastasis ( P < 0.001), tumor invasion ( P = 0.001), venous invasion ( P = 0.001), histologic types ( P < 0.001), p53 expression ( P < 0.001), and SIRT1 expression ( P < 0.001). SIRT1 expression was also significantly correlated with tumor stage ( P < 0.001), lymph node metastasis ( P < 0.001), tumor invasion ( P < 0.001), histologic types ( P < 0.001), and p53 expression ( P = 0.001). In addition, expression of DBC1 was significantly associated with shorter overall survival and relapse-free survival by univariate analysis ( P < 0.001 and P < 0.001, respectively). SIRT1 expression was also significantly associated with shorter overall survival and relapse-free survival by univariate analysis ( P = 0.001 and P = 0.001, respectively). Multivariate analysis showed that tumor stage and expression of DBC1 were independent prognostic factors significantly associated with overall survival and relapse-free survival. Conclusion: This study shows that expression of DBC1 and SIRT1 is a significant prognostic indicator for gastric carcinoma patients.

Effect of chemical functionalization of multi-walled carbon nanotubes with 3-aminopropyltriethoxysilane on mechanical and morphological properties of epoxy nanocomposites

Abstract: Nanocomposites based on epoxy resin and different weight percentages of unmodified, oxidized, and silanized multi-walled carbon nanotubes (MWCNTs) were prepared by cast molding method. Effects of MWCNTs content on the flexural properties were examined. The results showed that as the loading of the MWCNTs increased, improved flexural strength and flexural modulus were observed. The mechanical properties decreased when the MWCNTs content exceeded 0.2 wt.% due to agglomeration of MWCNTs. These results prove the effect of functionalization on the interfacial adhesion between epoxy and MWCNTs. This was further confirmed by morphology study of fractured surfaces of nanocomposites by SEM and TEM.

Arthroscopic Pullout Suture Repair of Posterior Root Tear of the Medial Meniscus: Radiographic and Clinical Results With a 2-Year Follow-up

Abstract: Purpose This study was undertaken to document the short-term clinical efficacy of arthroscopic pullout suture repair in treating posterior root tears of the medial meniscus. Methods From March 2004 to August 2006, 26 patients (27 knees) with posterior root tears of the medial meniscus were treated with arthroscopic pullout suture repair surgery by the senior author. Of these, 20 consecutive patients (21 knees) with a minimum of 2 years' follow-up treated by arthroscopic pullout suture repair were analyzed. Clinical results by use of the Lysholm knee and Hospital for Special Surgery scores and radiographic grade were evaluated, both preoperatively and at final follow-up. In addition, the second-look arthroscopic findings for 10 knees were analyzed. Results A radiographic evaluation using the criteria of Kellgren and Lawrence at final follow-up showed an increase in radiographic grade by 1 grade in only 1 knee. On the second-look arthroscopies performed in 10 knees (47.6%), all repaired menisci had healed completely without additional chondral lesions in the knee. The mean Hospital for Special Surgery scores improved from 61.1 preoperatively to 93.8 at final follow-up ( P P Conclusions Arthroscopic pullout suture repair is an effective treatment for alleviating meniscal symptoms in patients with a symptomatic posterior root tear of the medial meniscus with degenerated articular cartilage of less than grade III. In addition, no discernable degenerative arthritic changes were found in terms of radiographic features with our limited short-term follow-up. Level of Evidence Level IV, therapeutic case series.

SERS imaging of HER2-overexpressed MCF7 cells using antibody-conjugated gold nanorods

Abstract: Antibody-conjugated gold nanorods (GNRs) have been used for the targeting and imaging of specific cancer markers expressed on the surface membrane of cancer cells. GNRs with various aspect ratios were fabricated, and their surface-enhanced Raman scattering enhancement effects were evaluated. To attach the GNRs selectively onto the targets in cancer cells, specific antibodies were immobilized on the surface of GNRs using the layer-by-layer deposition method. First, Raman reporter molecules, mercaptopyridine, were attached to the surface of GNRs, and their surface charge was modified using poly(sodium 4-styrene-sulfonate) to make the surface charge negative. Then, anti-rabbit IgGs were immobilized onto the surface of the GNRs by electrostatic interactions. HER2 markers, expressed on the cell surface, were treated with anti-HER2 primary antibodies. Finally, the functionalized nanoprobes, conjugated with secondary antibodies, were attached to the markers on cancer cells by antibody–antibody interactions. In the present study, MCF7 cells overexpressing breast cancer marker HER2 were used as the optical imaging targets. Our experimental results demonstrate the potential feasibility of antibody-conjugated GNRs for the highly sensitive targeting and imaging of biomarkers expressed on the surface membrane of cancer cells.

Production of Smooth and Pure Nickel Metal Nanofibers by the Electrospinning Technique: Nanofibers Possess Splendid Magnetic Properties

Abstract: In the present study, smooth, unceasing, hydrogen-free, and pure nickel metal nanofibers have been synthesized using the electrospinning technique. A sol−gel consisting of nickel acetate tetrahydrate and poly(vinyl alcohol) has been electrospun, and the obtained nanofiber mats were vacuously dried and then calcined in argon atmosphere at 700 °C. The invoked physiochemical characterization instruments assured formation of pure nickel nanofibers with an average diameter of 120 nm after the calcination process. The electrospun nickel nanofibers have revealed unique magnetic properties, with much enhanced coercivities relative to bulk materials. The outstanding features of this approach to get one-dimensional magnetic nanostructure are its simplicity, effectiveness, safety, and ease of assembly.

Electrospun Antimicrobial Polyurethane Nanofibers Containing Silver Nanoparticles for Biotechnological Applications

Abstract: In this study, a new class of polyurethane (PU) nanofibers containing silver (Ag) nanoparticles (NPs) was synthesized by electrospinning. A simple method that did not depending on additional foreign chemicals was used to self synthesize the silver NPs in/on PU nanofibers. The synthesis of silver NPs was carried out by exploiting the reduction ability of N,N-dimethylformamide (DMF), which is used mainly to decompose silver nitrate to silver NPs. Typically, a sol-gel consisting of AgNO3/PU was electrospun and aged for one week. Silver NPs were created in/on PU nanofibers. SEM confirmed the well oriented nanofibers and good dispersion of pure silver NPs. TEM indicated that the Ag NPs were 5 to 20 nm in diameter. XRD demonstrated the good crystalline features of silver metal. The mechanical properties of the nanofiber mats showed improvement with increasing silver NPs content. The fixedness of the silver NPs obtained on PU nanofibers was examined by harsh successive washing of the as-prepared mats using a large amount of water. The results confirmed the good stability of the synthesized nanofiber mats. Two model organisms,E. coli andS. typhimurium, were used to check the antimicrobial influence of these nanofiber mats. Subsequently, antimicrobial tests indicated that the prepared nanofibers have a high bactericidal effect. Accordingly, these results highlight the potential use of these nanofiber mats as antimicrobial agents.

The effect of MG132, a proteasome inhibitor on HeLa cells in relation to cell growth, reactive oxygen species and GSH.

Abstract: MG132 (carbobenzoxy-Leu-Leu-leucinal) is a peptide aldehyde, which effectively blocks the proteolytic activity of the 26S proteasome complex. We evaluated the effects of MG132 on the growth of human cervix cancer HeLa cells in relation to the cell growth, reactive oxygen species (ROS) and glutathione (GSH) levels. Dose-dependent inhibition of cell growth was observed in HeLa cells with an IC50 of approximately 5 microM MG132 for 24 h. DNA flow cytometric analysis indicated that treatment with MG132 induced S, G2-M or non-specific phase arrests of the cell cycle dose-dependently. Treatment with MG132 induced apoptosis in a dose-dependent manner, as evidenced by sub-G1 cells and annexin V staining cells. Treatment with MG132 also induced the loss of mitochondrial membrane potential in HeLa cells. The intracellular ROS levels including O2*- were significantly increased in MG132-treated cells. Furthermore, the depletion of intracellular GSH content was observed in cells treated with MG132. In conclusion, MG132 inhibited the growth of HeLa cells via inducing the cell cycle arrest as well as triggering apoptosis. The changes of ROS and GSH by MG132 were closely related to apoptosis in HeLa cells.

Fourier Transform-Based Modified Phasor Estimation Method Immune to the Effect of the DC Offsets

Abstract: This paper proposes a Fourier transform-based modified phasor estimation method to eliminate the adverse influence of the exponentially decaying dc offsets when discrete Fourier transform (DFT) is used to calculate the phasor of the fundamental frequency component in a relaying signal. By subtracting the result of odd-sample-set DFT from the result of even-sample-set DFT, the information of dc offsets can be obtained. Two dc offsets in a secondary relaying signal are treated as one dc offset which is piecewise approximated in one cycle data window. The effect of the dc offsets can be eliminated by the approximated dc offset. The performance of the proposed algorithm is evaluated by using computer-simulated signals and Electromagnetic Transients Program-generated signals. The algorithm is also tested on a hardware board with TMS320C32 microprocessor. The evaluation results indicate that the proposed algorithm can estimate the accurate phasor of the fundamental frequency component regardless of not only the primary decaying dc offset but also the secondary decaying dc offset caused by CT circuit itself including its burden.

Sobolev inequalities with symmetry

Abstract: In this paper, we derive some Sobolev inequalities for radially symmetric functions in Ḣs with 1/2 < s < n/2. We show the end point case s = 1/2 on the homogeneous Besov space . These results are extensions of the well-known Strauss' inequality [13]. Also non-radial extensions are given, which show that compact embeddings are possible in some Lp spaces if a suitable angular regularity is imposed.