Showing papers by "Chung-Ang University published in 2008"

Twenty-Eight-Day Oral Toxicity, Genotoxicity, and Gender-Related Tissue Distribution of Silver Nanoparticles in Sprague-Dawley Rats

Abstract: The antibacterial effect of silver nanoparticles has resulted in their extensive application in health, electronic, and home products. However, while the population exposed to silver nanoparticles continues to increase with ever new applications, silver nanoparticles remain a controversial research area as regards their toxicity to biological systems. In particular, the oral toxicity of silver nanoparticles is of particular concern to ensure public and consumer health. Accordingly, this study tested the oral toxicity of silver nanoparticles (60 nm) over a period of 28 days in Sprague-Dawley rats following Organization for Economic Cooperation and Development (OECD) test guideline 407 with Good Laboratory Practice (GLP) application. Eight-week-old rats, weighing about 283 g for the males and 192 g for the females, were divided into four 4 groups (10 rats in each group): vehicle control, low-dose group (30 mg/kg), middle-dose group (300 mg/kg), and high-dose group (1000 mg/kg). After 28 days of exposure, the blood biochemistry and hematology were investigated, along with a histopathological examination and silver distribution study. The male and female rats did not show any significant changes in body weight relative to the doses of silver nanoparticles during the 28-day experiment. However, some significant dose-dependent changes were found in the alkaline phsophatase and cholesterol values in either the male or female rats, seeming to indicate that exposure to over more than 300 mg of silver nanoparticles may result in slight liver damage. There were no statistically significant differences in the micronucleated polychromatic erythrocytes (MN PCEs) or ratio of polychromatic erythrocytes among the total erythrocytes after silver nanoparticle exposure when compared with the control. Therefore, the present results suggest that silver nanoparticles do not induce genetic toxicity in male and female rat bone marrow in vivo. Nonetheless, the tissue distribution of silver nanopaticles did show a dose-dependent accumulation of silver content in all the tissues examined. In particular, a gender-related difference in the accumulation of silver was noted in the kidneys, with a twofold increase in the female kidneys when compared with the male kidneys.

A DNA-gold nanoparticle-based colorimetric competition assay for the detection of cysteine.

Abstract: We report the development of a highly sensitive and selective colorimetric detection method for cysteine based upon oligonucleotide-functionalized gold nanoparticle probes that contain strategically placed thymidine-thymidine (T-T) mismatches complexed with Hg2+. This assay relies upon the distance-dependent optical properties of gold nanoparticles, the sharp melting transition of oligonucleotide-linked nanoparticle aggregates, and the very selective coordination of Hg2+ with cysteine. The concentration of cysteine can be determined by monitoring with the naked eye or a UV-vis spectrometer the temperature at which the purple-to-red color change associated with aggregate dissociation takes place. This assay does not utilize organic cosolvents, enzymatic reactions, light-sensitive dye molecules, lengthy protocols, or sophisticated instrumentation thereby overcoming some of the limitations of more conventional methods.

Asia-Pacific consensus guidelines on gastric cancer prevention.

Abstract: Background and Aim: Gastric cancer is a major health burden in the Asia–Pacific region but consensus on prevention strategies has been lacking. We aimed to critically evaluate strategies for preventing gastric cancer. Methods: A multidisciplinary group developed consensus statements using a Delphi approach. Relevant data were presented, and the quality of evidence, strength of recommendation, and level of consensus were graded. Results: Helicobacter pylori infection is a necessary but not sufficient causal factor for non-cardia gastric adenocarcinoma. A high intake of salt is strongly associated with gastric cancer. Fresh fruits and vegetables are protective but the use of vitamins and other dietary supplements does not prevent gastric cancer. Host–bacterial interaction in H. pylori infection results in different patterns of gastritis and differences in gastric acid secretion which determine disease outcome. A positive family history of gastric cancer is an important risk factor. Low serum pepsinogens reflect gastric atrophy and may be useful as a marker to identify populations at high risk for gastric cancer. H. pylori screening and treatment is a recommended gastric cancer risk reduction strategy in high-risk populations. H. pylori screening and treatment is most effective before atrophic gastritis has developed. It does not exclude the existing practice of gastric cancer surveillance in high-risk populations. In populations at low risk for gastric cancer, H. pylori screening is not recommended. First-line treatment of H. pylori infection should be in accordance with national treatment guidelines. Conclusion: A strategy of H. pylori screening and eradication in high-risk populations will probably reduce gastric cancer incidence, and based on current evidence is recommended by consensus.

All-optical dynamic grating generation based on Brillouin scattering in polarization-maintaining fiber.

Abstract: We report a novel kind of all-optical dynamic grating based on Brillouin scattering in a polarization maintaining fiber (PMF). A moving acoustic grating is generated by stimulated Brillouin scattering between writing beams in one polarization and used to reflect an orthogonally polarized reading beam at different wavelengths. The center wavelength of the grating is controllable by detuning the writing beams, and the 3 dB bandwidth of approximately 80 MHz is observed with the tunable reflectance of up to 4% in a 30 m PMF.

Toward the Model of University Image: The Influence of Brand Personality, External Prestige, and Reputation

Abstract: Although the concepts of image and reputation have been increasingly emphasized in the fields of public relations and marketing, the association of these 2 concepts has not been empirically studied within the public relations domain. Furthermore, although significant research into corporate image has been established, relatively less image research has been conducted on service-oriented organizations such as universities. The purpose of this study is to assess the impact of institutional image and image-related constructs on students' supportive attitude, which represents the student's commitment to and identification with the organization. After identifying the components that construct corporate image, the study examines the relationships among these constructs under the concept of corporate image. It also attempts to analyze the impact of this image in order to understand its influence on student recruitment, and to describe the strategic implications for university communication management. Structural...

Cultural Orientation and Attitudes Toward Different Forms of Whistleblowing: A Comparison of South Korea, Turkey, and the U.K.

Abstract: This article reports the findings of a cross-cultural study that explored the relationship between nationality, cultural orientation, and attitudes toward different ways in which an employee might blow the whistle. The study investigated two questions – are there any significant differences in the attitudes of university students from South Korea, Turkey and the U.K. toward various ways by which an employee blows the whistle in an organization?, and what effect, if any, does cultural orientation have on these attitudes? In order to answer these questions, the study identified six dimensions of whistleblowing and four types of cultural orientation. The survey was conducted among 759 university students, who voluntarily participated; 284 South Korean, 230 Turkish, and 245 U.K. Although all three samples showed a preference for formal, anonymous and internal modes of whistleblowing, there were significant variations related to nationality and cultural orientation. The findings have some key implications for organizational practice and offer directions for future research.

Adaptive contrast enhancement using gain-controllable clipped histogram equalization

Abstract: Histogram equalization is a simple and effective method for contrast enhancement as it can automatically define the intensity transformation function based on statistical characteristics of the image. However, it tends to alter the brightness of the entire image, which it is not suitable for consumer electronic products, where preservation of the original brightness is essential to avoid annoying artifacts. This paper presents a new contrast enhancement method for generalization of the existing bihistogram equalization (BHE) and recursive mean-separate histogram equalization (RMSHE) methods. The proposed method is referred to gain-controllable clipped histogram equalization (GC-CHE) to provide both histogram equalization and brightness preservation. More specifically adaptive contrast enhancement is realized by using clipped histogram equalization with controllable gain. The clipping rate is determined based on the mean brightness, and the clipping threshold is determined based on the clipping rate. The clipping rate is adaptively controlled to enhance the contrast with preserving the mean brightness. It is mathematically proven that the mean brightness of the output image converges to that of the input image with adaptive controlled. Simulation results show that the proposed GC-CHE method outperforms existing histogram-based methods, such as HE, BHE, and RMSHE, in various situations.

Amplification of uncultured single-stranded DNA viruses from rice paddy soil.

Abstract: Viruses are known to be the most numerous biological entities in soil; however, little is known about their diversity in this environment. In order to explore the genetic diversity of soil viruses, we isolated viruses by centrifugation and sequential filtration before performing a metagenomic investigation. We adopted multiple-displacement amplification (MDA), an isothermal whole-genome amplification method with φ29 polymerase and random hexamers, to amplify viral DNA and construct clone libraries for metagenome sequencing. By the MDA method, the diversity of both single-stranded DNA (ssDNA) viruses and double-stranded DNA viruses could be investigated at the same time. On the contrary, by eliminating the denaturing step in the MDA reaction, only ssDNA viral diversity could be explored selectively. Irrespective of the denaturing step, more than 60% of the soil metagenome sequences did not show significant hits (E-value criterion, 0.001) with previously reported viral sequences. Those hits that were considered to be significant were also distantly related to known ssDNA viruses (average amino acid similarity, approximately 34%). Phylogenetic analysis showed that replication-related proteins (which were the most frequently detected proteins) related to those of ssDNA viruses obtained from the metagenomic sequences were diverse and novel. Putative circular genome components of ssDNA viruses that are unrelated to known viruses were assembled from the metagenomic sequences. In conclusion, ssDNA viral diversity in soil is more complex than previously thought. Soil is therefore a rich pool of previously unknown ssDNA viruses.

OsLIC, a Novel CCCH-Type Zinc Finger Protein with Transcription Activation, Mediates Rice Architecture via Brassinosteroids Signaling.

Abstract: Rice architecture is an important agronomic trait and a major limiting factor for its high productivity. Here we describe a novel CCCH-type zinc finger gene, OsLIC (Oraza sativa leaf and tiller angle increased controller), which is involved in the regulation of rice plant architecture. OsLIC encoded an ancestral and unique CCCH type zinc finge protein. It has many orthologous in other organisms, ranging from yeast to humane. Suppression of endogenous OsLIC expression resulted in drastically increased leaf and tiller angles, shortened shoot height, and consequently reduced grain production in rice. OsLIC is predominantly expressed in rice collar and tiller bud. Genetic analysis suggested that OsLIC is epistatic to d2-1, whereas d61-1 is epistatic to OsLIC. Interestingly, sterols were significantly higher in level in transgenic shoots than in the wild type. Genome-wide expression analysis indicated that brassinosteroids (BRs) signal transduction was activated in transgenic lines. Moreover, transcription of OsLIC was induced by 24-epibrassinolide. OsLIC, with a single CCCH motif, displayed binding activity to double-stranded DNA and single-stranded polyrA, polyrU and polyrG but not polyrC. It contains a novel conserved EELR domain among eukaryotes and displays transcriptional activation activity in yeast. OsLIC may be a transcription activator to control rice plant architecture.

Influence of Soil Components on the Biodegradation of Benzene, Toluene, Ethylbenzene, and o-, m-, and p-Xylenes by the Newly Isolated Bacterium Pseudoxanthomonas spadix BD-a59

Abstract: A bacterium designated strain BD-a59, able to degrade all six benzene, toluene, ethylbenzene, and o-, m-, and p-xylene (BTEX) compounds, was isolated by plating gasoline-contaminated sediment from a gasoline station in Geoje, Republic of Korea, without enrichment, on minimal salts basal (MSB) agar containing 0.01% yeast extract, with BTEX as the sole carbon and energy source. Taxonomic analyses showed that the isolate belonged to Pseudoxanthomonas spadix, and until now, the genus Pseudoxanthomonas has not included any known BTEX degraders. The BTEX biodegradation rate was very low in MSB broth, but adding a small amount of yeast extract greatly enhanced the biodegradation. Interestingly, degradation occurred very quickly in slurry systems amended with sterile soil solids but not with aqueous soil extract. Moreover, if soil was combusted first to remove organic matter, the enhancement effect on BTEX biodegradation was lost, indicating that some components of insoluble organic compounds are nutritionally beneficial for BTEX degradation. Reverse transcriptase PCR-based analysis of field-fixed mRNA revealed expression of the tmoA gene, whose sequence was closely related to that carried by strain BD-a59. This study suggests that strain BD-a59 has the potential to assist in BTEX biodegradation at contaminated sites.

‘Living cantilever arrays’ for characterization of mass of single live cells in fluids

Abstract: The size of a cell is a fundamental physiological property and is closely regulated by various environmental and genetic factors. Optical or confocal microscopy can be used to measure the dimensions of adherent cells, and Coulter counter or flow cytometry (forward scattering light intensity) can be used to estimate the volume of single cells in a flow. Although these methods could be used to obtain the mass of single live cells, no method suitable for directly measuring the mass of single adherent cells without detaching them from the surface is currently available. We report the design, fabrication, and testing of ‘living cantilever arrays’, an approach to measure the mass of single adherent live cells in fluid using silicon cantilever mass sensor. HeLa cells were injected into microfluidic channels with a linear array of functionalized silicon cantilevers and the cells were subsequently captured on the cantilevers with positive dielectrophoresis. The captured cells were then cultured on the cantilevers in a microfluidic environment and the resonant frequencies of the cantilevers were measured. The mass of a single HeLa cell was extracted from the resonance frequency shift of the cantilever and was found to be close to the mass value calculated from the cell density from the literature and the cell volume obtained from confocal microscopy. This approach can provide a new method for mass measurement of a single adherent cell in its physiological condition in a non-invasive manner, as well as optical observations of the same cell. We believe this technology would be very valuable for single cell time-course studies of adherent live cells.

Pretreatment with Cisplatin Enhances E7-Specific CD8+ T-Cell–Mediated Antitumor Immunity Induced by DNA Vaccination

Abstract: Purpose: Because the combination of multiple modalities for cancer treatment is more likely to generate more potent therapeutic effects for the control of cancer, we have explored the combination of chemotherapy using cisplatin, which is routinely used in chemotherapy for advanced cervical cancer, with immunotherapy using DNA vaccines encoding calreticulin (CRT) linked to human papillomavirus type 16 E7 antigen (CRT/E7) in a preclinical model. Experimental Design: We characterized the combination of cisplatin with CRT/E7 DNA vaccine using different regimen for its potential ability to generate E7-specific CD8+ T-cell immune responses as well as antitumor effects against E7-expressing tumors. Results: Our results indicate that treatment of tumor-bearing mice with chemoimmunotherapy combining cisplatin followed by CRT/E7 DNA generated the highest E7-specific CD8+ T-cell immune response and produced the greatest antitumor effects and long-term survival as well as significant levels of E7-specific tumor-infiltrating lymphocytes compared with all the other treatment regimens. Furthermore, we found that treatment with cisplatin leads to the cell-mediated lysis of E7-expressing tumor cells in vitro and increased number of E7-specific CD8+ T-cell precursors in tumor-bearing mice. In addition, we observed that E7-specific CD8+ T cells migrate to and proliferate in the location of TC-1 tumors in mice treated with cisplatin. Conclusions: Thus, our data suggest that chemoimmunotherapy using cisplatin followed by CRT/E7 DNA vaccine is an effective treatment against E7-expressing tumors and may potentially be translated into the clinical arena.

Gearing up for mobile advertising: A cross‐cultural examination of key factors that drive mobile messages home to consumers

Abstract: Mobile advertising is gearing up for success, but researchers and practitioners need to understand how to measure the effectiveness of this advertising form—particularly the factors that drive mobile messages home in different cultures. This study identifies key measures of effectiveness as well as antecedent variables in the context of 629 Korean and American consumers. Entertainment and credibility were key factors predicting positive attitude and purchase intention among both Koreans and Americans. However, this study found multiple cross-cultural differences—particularly in informativeness, perceived interactivity, and the value of mobile advertising. Theoretical explanations and practical implications are suggested. © 2008 Wiley Periodicals, Inc.

Fractional Photothermolysis for the Treatment of Striae Distensae in Asian Skin

Abstract: Background:Striae distensae (SD) are dermal scars characterized by linear atrophic depressions. Fractional photothermolysis (FP) is an effective modality for the treatment of cutaneous scars. Objective:To evaluate the safety and efficacy of FP for the treatment of SD in Asian skin. Methods:Six female volunteers aged between 20 and 35 years with chronic striae albae phase SD on both buttocks were enrolled. SD lesions on the right buttock were irradiated with a 1550-nm FP laser and patients were followed every 4 weeks for a total of 8 weeks. Outcome assessments included serial photographs, erythema index and melanin index tracking, skin elasticity, histologic examination, and the patients’ subjective satisfaction scores. Results:FP treatment was associated with a substantial improvement in the appearance of SD at 8 weeks post-treatment. The erythema index and melanin index of the treated SD lesions tended to converge with those of the control skin at 4-week follow-up. Skin elasticity was found to be partially normalized after FP. In addition, there was a significant increase in epidermal thickness, collagen, and elastic fiber deposition after FP as demonstrated by histologic examination. Adverse effects of FP included mild and transient pain and hyperpigmentation. Conclusion:FP can reduce SD by stimulating new collagen and elastic fiber synthesis. In addition, repetitive treatments might constitute an effective approach to improving the treatment of SD.

Polyhydroxyalkanoate (PHA) production using waste vegetable oil by Pseudomonas sp. strain DR2.

Abstract: To produce polyhydroxyalkanoate (PHA) from inexpensive substrates by bacteria, vegetable-oil-degrading bacteria were isolated from a rice field using enrichment cultivation. The isolated Pseudomonas sp. strain DR2 showed clear orange or red spots of accumulated PHA granules when grown on phosphate and nitrogen limited medium containing vegetable oil as the sole carbon source and stained with Nile blue A. Up to 37.34% (w/w) of intracellular PHA was produced from corn oil, which consisted of three major 3-hydroxyalkanoates; octanoic (C8:0, 37.75% of the total 3-hydroxyalkanoate content of PHA), decanoic (C10:0, 36.74%), and dodecanoic (C12:0, 11.36%). Pseudomonas sp. strain DR2 accumulated up to 23.52% (w/w) of PHAMCL from waste vegetable oil. The proportion of 3- hydroxyalkanoate of the waste vegetable-oil-derived PHA [hexanoic (5.86%), octanoic (45.67%), decanoic (34.88%), tetradecanoic (8.35%), and hexadecanoic (5.24%)] showed a composition ratio different from that of the corn-oil-derived PHA. Strain DR2 used three major fatty acids in the same ratio, and linoleic acid was the major source of PHA production. Interestingly, the production of PHA in Pseudomonas sp. strain DR2 could not occur in either acetate- or butyrate-amended media. Pseudomonas sp. strain DR2 accumulated a greater amount of PHA than other well-studied strains (Chromobacterium violaceum and Ralstonia eutropha H16) when grown on vegetable oil. The data showed that Pseudomonas sp. strain DR2 was capable of producing PHA from waste vegetable oil.

Force-dependent hopping rates of RNA hairpins can be estimated from accurate measurement of the folding landscapes

Abstract: The sequence-dependent folding landscapes of nucleic acid hairpins reflect much of the complexity of biomolecular folding. Folding trajectories, generated by using single-molecule force-clamp experiments by attaching semiflexible polymers to the ends of hairpins, have been used to infer their folding landscapes. Using simulations and theory, we study the effect of the dynamics of the attached handles on the handle-free RNA free-energy profile Foeq(zm), where zm is the molecular extension of the hairpin. Accurate measurements of Foeq(zm) requires stiff polymers with small L/lp, where L is the contour length of the handle, and lp is the persistence length. Paradoxically, reliable estimates of the hopping rates can only be made by using flexible handles. Nevertheless, we show that the equilibrium free-energy profile Foeq(zm) at an external tension fm, the force (f) at which the folded and unfolded states are equally populated, in conjunction with Kramers' theory, can provide accurate estimates of the force-dependent hopping rates in the absence of handles at arbitrary values of f. Our theoretical framework shows that zm is a good reaction coordinate for nucleic acid hairpins under tension.