Seoul National University

About: Seoul National University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Catalysis. The organization has 65879 authors who have published 138759 publications receiving 3715170 citations. The organization is also known as: SNU & Seoul-dae.

Subchronic oral toxicity of silver nanoparticles

Abstract: The antibacterial effect of silver nanoparticles has resulted in their extensive application in health, electronic, consumer, medicinal, pesticide, and home products; however, silver nanoparticles remain a controversial area of research with respect to their toxicity in biological and ecological systems. This study tested the oral toxicity of silver nanoparticles (56 nm) over a period of 13 weeks (90 days) in F344 rats following Organization for Economic Cooperation and Development (OECD) test guideline 408 and Good Laboratory Practices (GLP). Five-week-old rats, weighing about 99 g for the males and 92 g for the females, were divided into four 4 groups (10 rats in each group): vehicle control, low-dose (30 mg/kg), middle-dose (125 mg/kg), and high-dose (500 mg/kg). After 90 days of exposure, clinical chemistry, hematology, histopathology, and silver distribution were studied. There was a significant decrease (P < 0.05) in the body weight of male rats after 4 weeks of exposure, although there were no significant changes in food or water consumption during the study period. Significant dose-dependent changes were found in alkaline phosphatase and cholesterol for the male and female rats, indicating that exposure to more than 125 mg/kg of silver nanoparticles may result in slight liver damage. Histopathologic examination revealed a higher incidence of bile-duct hyperplasia, with or without necrosis, fibrosis, and/or pigmentation, in treated animals. There was also a dose-dependent accumulation of silver in all tissues examined. A gender-related difference in the accumulation of silver was noted in the kidneys, with a twofold increase in female kidneys compared to male kidneys. The target organ for the silver nanoparticles was found to be the liver in both the male and female rats. A NOAEL (no observable adverse effect level) of 30 mg/kg and LOAEL (lowest observable adverse effect level) of 125 mg/kg are suggested from the present study.

What Factors Drive Global Stock Returns

Abstract: Using monthly returns for over 27,000 stocks from 49 countries over a three-decade period, we show that a multifactor model that includes factor-mimicking portfolios based on momentum and cash flow-to-price captures significant time series variation in global stock returns, and has lower pricing errors and fewer model rejections than the global CAPM or a popular model that uses size and book-to-market factors. We find reliable evidence that the global cash flow-to-price factor is related to a covariance risk model. In contrast, we reject the covariance risk model in favor of a characteristic model for size and book-to-market factors.

Designed fabrication of multifunctional magnetic gold nanoshells and their application to magnetic resonance imaging and photothermal therapy.

Abstract: T.H. acknowledges financial support by the Korean Ministry of Science and Technology through the National Creative Research Initiative Program of the Korea Science and Engineering Foundation (KOSEF). M.H.C. is supported by the NSI-NCRC program of KOSEF. S.K.K. is supported by a National Research Laboratory Grant and a Chemical Genomics Grant. J.H.L. is supported by the Centre for Biological Modulators of the 21st Century Frontier R&D Program. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z602471_s.pdf or from the author.

Safety of intravenous infusion of human adipose tissue-derived mesenchymal stem cells in animals and humans.

Abstract: Adipose tissue-derived mesenchymal stem cells (AdMSCs) represent an attractive and ethical cell source for stem cell therapy. With the recent demonstration of MSC homing properties, intravenous applications of MSCs to cell-damaged diseases have increased. In the present study, the toxicity and tumorigenicity of human AdMSCs (hAdMSCs) were investigated for clinical application. Culture-expanded hAdMSCs showed the typical appearance, immunophenotype, and differentiation capacity of MSCs, and were genetically stable at least 12 passages in culture. Cells suspended in physiological saline maintained their MSC properties in a cold storage condition for at least 3 days. To test the toxicity of hAdMSCs, different doses of hAdMSCs were injected intravenously into immunodeficient mice, and the mice were observed for 13 weeks. Even at the highest cell dose (2.5×10(8) cells/kg body weight), the SCID mice were viable and had no side effects. A tumorigenicity test was performed in Balb/c-nu nude mice for 26 weeks. Even at the highest cell dose (2×10(8) MSCs/kg), no evidence of tumor development was found. In a human clinical trial, 8 male patients who had suffered a spinal cord injury >12 months previous were intravenously administered autologous hAdMSCs (4×10(8) cells) one time. None of the patients developed any serious adverse events related to hAdMSC transplantation during the 3-month follow-up. In conclusion, the systemic transplantation of hAdMSCs appears to be safe and does not induce tumor development.