A MELAS syndrome family harboring two mutations in mitochondrial genome

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a genetically heterogeneous mitochondrial disorder with variable clinical symptoms. Here, from the sequencing of the entire mitochondrial genome, we report a Korean MELAS family harboring two homoplasmic missense mutations, which were reported 9957T>C (Phe251Leu) transition mutation in the cytochrome c oxidase subunit 3 (COX3) gene and a novel 13849A>C (Asn505His) transversion mutation in the NADH dehydrogenase subunit 5 (ND5) gene. Neither of these mutations was found in 205 normal controls. Both mutations were identified from the proband and his mother, but not his father. The patients showed cataract symptom in addition to MELAS phenotype. We believe that the 9957T>C mutation is pathogenic, however, the 13849A>C mutation is of unclear significance. It is likely that the 13849A>C mutation might function as the secondary mutation which increase the expressivity of overlapping phenotypes of MELAS and cataract. This study also demonstrates the importance of full sequencing of mtDNA for the molecular genetic understanding of mitochondrial disorders.     

A review of current activities of analytical separation in Korea in 2004

This review gives a quick overview of the current Korean research activities and trends in the field of analytical science with specific focus on the use of analytical separation techniques. In this review, the current standing and central trends, emerging techniques in the Korean community of analytical separation researchers are emphasized.     

Reaction of organic sulfur compounds with superoxide anion—III : Oxidation of organic sulfur compounds to sulf1nic and sulfonic acids

Organic sulfur compounds such as disulfide, thiolsulfinate, thiolsulfonate, thiol, sodium thiolate, and sodium sultinale were readily oxidized to both sulfinic and sulfonic acids with superoxide anion generated from potassium superoxide and 18-crown-6-ether under mild conditions. However, both sulfide and sulfoxide did not react with superoxide anion, O₂^-. Although thiol was easily oxidized to disulfide with O₂^? at room temperature, it was oxidized further with O₂^? at 60° to the corresponding sulfinic and sulfonic acids. Symmetrical disulfide was obtained in the reaction of unsymmetrical thiolsulfinate or thiolsulfonate along with both sulfinic and sulfonic acids. Most reactive was thiolsulfinate which reacted at lower temperature ranging between ?40 and 0° to afford the products within 30 min. Relative reactivities fall in the following order: thiolsulfinate > thiolsulfonate > disulfide ? sodium thiolate ? sodium sulfinate. Polar solvents such as pyridine and acetonitrile were more effective than such a less polar solvent as benzene in the oxidation of the substrate, and increased amount of the crown ether shortened the reaction time. Nucleophilic attack of O₂^? and electron transfer processes are believed to be involved in these oxidations.     

Covariational reasoning among U.S. and South Korean secondary mathematics teachers

We investigated covariational reasoning among 487 secondary mathematics teachers in the United States and South Korea. We presented an animation showing values of two varying magnitudes (v and u) on axes in a Cartesian plane along with a request that they sketch a graph of the value of u in relation to the value of v. We classified teachers’ sketches on two independent criteria: (1) where they placed their initial point, and (2) their graph’s overall shape irrespective of initial point. There are distinct differences on both criteria between U.S. and South Korean teachers, suggesting that covariational reasoning is more prominent among South Korean secondary teachers than among U.S. secondary teachers. The results also suggest strongly that forming a multiplicative object that unites quantities’ values is necessary to express covariation graphically.     

Mixed-mode stress intensity factors and critical angles of cracks in bolted joints by weight function method

Summary   Mechanical joints, such as bolted or riveted joints, are widely used in structural components. Reliable determination of stress intensity factors for cracks in bolted joints is required to evaluate their safety and fatigue life. The weight function method is an efficient technique to calculate stress intensity factors for various loading conditions by the stress analysis of an uncracked model. In this paper, the mixed-mode stress intensity factors for cracks in bolted joints are analyzed by the weight function method, and coefficients included in the weight function are determined by finite element analysis for reference loadings. The critical angle at which mode I stress intensity factor becomes maximum is determined, and the effects of the amount of clearance and crack length on the critical angle are investigated. Received 28 February 2001; accepted for publication 22 June 2001 RID=" ID=" The authors are grateful for the support provided by a grant from the Korea Science & Engineering Foundation (KOSEF) and Safety and Structural Integrity Research Center at the Sungkyunkwan University.     

Association of ADIPOR1 polymorphisms with bone mineral density in postmenopausal Korean women

Adiponectin may affect bone through interactions with two known receptors, adiponectin receptors (ADIPOR) 1 and 2. We examined the association between polymorphisms of ADIPOR1 and ADIPOR2 and bone mineral density (BMD) in postmenopausal Korean women. Six polymorphisms in ADIPOR1 and four polymorphisms in ADIPOR2 were selected and genotyped in all study participants (n = 1,329). BMD at the lumbar spine and femur neck were measured using dual-energy X-ray absorptiometry. Lateral thoracolumbar (T4-L4) radiographs were obtained for vertebral fracture assessment and the occurrence of non-vertebral fractures examined using self-reported data. P values were adjusted for multiple testing using Bonferroni correction (P(corr)). ADIPOR1 rs16850799 and rs34010966 polymorphisms were significantly associated with femur neck BMD (P(corr) = 0.036 in the dominant model; P(corr) = 0.024 and P(corr) = 0.006 in the additive and dominant models, respectively). Subjects with the rare allele of each polymorphism had lower BMD, and association of rs34010966 with BMD showed a gene dosage effect. However, ADIPOR2 single nucleotide polymorphisms and haplotypes were not associated with BMD at any site. Our results suggest that ADIPOR1 polymorphisms present a useful genetic marker for BMD in postmenopausal Korean women.     

Facile,single-pot preparation of nanoporous SiO2 particles (carrier) with AgNPs at core and crust for controlled disinfectant release

This study demonstrates a novel, facile and one-pot approach to synthesize silica nanoparticles with silver at core and crust (SiNP-AgCC). A modified Stöber method was used to make SiNP-AgCC. A significant reduction in the size of SiO₂ nanoparticles was seen, with 2–5 nm AgNPs being uniformly distributed on the surface and 10–20 nm AgNPs in the center. A typical mesoporous SiO₂ particle (SiNP) produced using the Stöber method was transformed to nanoporous SiO₂ by this modified Stöber method. Nanoporous SiO₂ particles with silver in the center are advantageous for slow and consistent Ag⁺ release, which was confirmed by Ag⁺ ion release test. Antibacterial activities of the samples were tested to evaluate the disinfection performance of the samples on gram-negative bacteria (Escherichia coli) using disk diffusion and the LB-agar method. SiNP-AgCC showed prolonged silver release for more than 20 days and improved antibacterial properties even after five days of incubation.