Biomedical subjects

S B Lee

Publications and source records attributed to S B Lee.

At least 19 recordsLinked to original sources

PubMed2006

Depression in vascular dementia is quantitatively and qualitatively different from depression in Alzheimer's disease.

BACKGROUND/AIMS: To compare the prevalence and characteristics of depression in vascular dementia (VaD) and Alzheimer's disease (AD) after adjusting for dementia severity and gender. METHODS: One hundred and eight pairs of VaD and AD patients matched for dementia severity and gender were assessed. RESULTS: Major depressive disorder (MDD) was more prevalent in the VaD group than in the AD group (20.4% in VaD, 10.2% in AD, p = 0.04, Cochran-Mantel-Haenszel, CMH, test) regardless of the dementia severity and gender. The odds ratio for developing MDD in the VaD group versus the AD group was estimated to be 2.20 (95% confidence interval = 1.02-4.74). Neurovegetative symptoms such as 'felt tired and weak all the time' (30.6% in VaD, 13.9% in AD, p = 0.003, CMH test) and 'changed weight without trying' (16.7% in VaD, 6.5% in AD, p = 0.02, CMH test) were more prevalent in the VaD group than in the AD group. CONCLUSION: Depression in VaD was quantitatively and qualitatively different from that in AD regardless of the severity of dementia and gender; depression was more prevalent, severer and more retarded and vegetative in VaD than in AD.

Aged↗

PubMed2006

Simultaneous measurement of bending and temperature based on a single sampled chirped fiber Bragg grating embedded on a flexible cantilever beam.

We propose and experimentally demonstrate a simple and practical scheme for simultaneous measurement of bending and temperature based on a single sampled chirped fiber Bragg grating with multiple resonant peaks, which is embedded on a flexible cantilever beam. The wavelength spacing of the grating can be changed by adjusting the bending curvature change, since the compressive strain gradient induced by the bending of the cantilever beam changes the chirp ratio of the fiber grating. However, the wavelength spacing of the fiber grating is not changed by the temperature variation; the multiple resonant wavelengths are only shifted into the longer wavelength because of the positive thermal-expansion and thermo-optic coefficients of the fiber grating. Consequently, the proposed scheme allows for discrimination between two effects of bending and temperature.

Journal Article↗

PubMed2006

Detection of donor-specific anti-HLA class I and II antibodies using antibody monitoring system.

The antibody monitoring system (AMS, GTI Inc) is a solid enzyme-linked immunosorbent assay (ELISA) crossmatch test for the detection of immunoglobulin G (IgG) antibody to donor-specific solubilized HLA class I and class II antigens. The objective of this study was to compare the results of the AMS assay with donor-specific anti-HLA IgG antibodies (DS-HLA Abs), as determined by ELISA panel reactive antibody (PRA) and the flow cytometric crossmatch test (FCXM). A total of 107 sera were screened for the presence of HLA Abs by ELISA PRA (LAT-M, One-Lambda Inc), the DS-HLA Abs were determined in 34 serum samples (31.8%) by an ELISA panel (LAT class I and class II, One-Lambda Inc) and FCXM. The FCXM and AMS assays were performed with matched lymphocytes from 56 donors. There was a significant degree of concordance (89.7%) between the two tests (P < .001). The sensitivity, specificity, positive predictive value, and negative predictive value of AMS assay to detect DS-HLA Abs was 88.2%, 94.5%, 88.2%, and 94.5%, respectively. The AMS is a simple, objective test, which has several advantages over the cell-based crossmatch test, such as elimination of non-HLA antibody reactivity, elimination of non-donor-specific antibody reactivity, no need for viable cells, and preparation of the donor's HLA antigens in advance. In summary, this study suggested that AMS may be useful as a supportive crossmatch test or as a monitoring test after transplantation to detect class I or class II DS-HLA Abs.

Enzyme-Linked Immunosorbent Assay↗

PubMed2006

Evaluation of subchronic inhalation toxicity of dimethyl disulfide in rats.

This study was carried out to investigate the potential subchronic inhalation toxicity of dimethyl disulfide (DMDS) via whole-body exposure in F344 rats. Groups of 10 rats of each sex were exposed to DMDS vapor by whole-body exposure at concentrations of 0, 5, 25, or 125 ppm for 6 h/day, 5 days/wk for 13 wk. All the rats were sacrificed at the end of treatment period. During the test period, clinical signs, mortality, body weights, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, organ weights, and histopathology were examined. At 25 ppm, a decrease in the body weight gain, food intake, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and blood urea nitrogen (BUN) was observed in the males, but not in the females. However, at 125 ppm, a decrease in the body weight gain, food intake, and thymus weight and an increase in the weights of adrenal glands were observed in both genders. Serum biochemical investigations revealed a decrease in the AST, ALT, BUN, creatine phosphokinase (CPK), and triglyceride levels and an increase in the glucose level. In contrast, no treatment-related effects were observed in the 5 ppm group. The toxic potency of DMDS was slightly higher in males than that in females. In these experimental conditions, the target organ was not determined in rats. The no-observed-adverse-effect concentration (NOAEC) was found to be 5 ppm, 6 h/day for male rats and 25 ppm, 6 h/day for female rats.

Alanine Transaminase↗

PubMed2005

Bandwidth control in a hybrid fiber acousto-optic filter.

We report a bandwidth variation technique in an acousto-optic filter. Utilizing the adiabatic conversion in both optical and acoustic modes, we obtain a novel hybrid waveguide composed of serial concatenation of single-mode fiber (SMF) and two-mode hollow optical fiber (HOF). On the basis of dissimilarity in the phase-matching conditions and beat-length dispersion in SMF and HOF, the FWHM of the resonant bands is varied from 3.8 to 190 nm near the 1.5-microm region in a single device. Furthermore, we theoretically analyze the acousto-optic coupling among the guided modes in HOF, which shows good agreement with experimental observations.

Journal Article↗

PubMed2003

Direct observation of localized defect States in semiconductor nanotube junctions.

We report scanning tunneling microscopy of semiconductor-semiconductor carbon nanotube junctions with different band gaps. Characteristic features of the wave functions at different energy levels, such as a localized defect state, are clearly exhibited in the atomically resolved scanning tunneling spectroscopy. The peaks of the Van Hove singularity on each side penetrate and decay into the opposite side across the junction over a distance of approximately 2 nm. These experimental features are accounted for, with the help of tight-binding calculation, by the presence of pentagon-heptagon pair defects at the junction.

Journal Article↗

PubMed2003

Carbon onions: carriers of the 217.5 nm interstellar absorption feature.

Ultraviolet-visible absorption measurements of high purity and well separated carbon onion samples are reported. The results show that, after purification, absorption features from carbon onions match well with the interstellar UV spectrum. The measurements show that the absorption peak position remains constant at 4.55+/-0.1 microm(-1), and the width varies from 1.2-1.6 microm(-1), a key feature of the interstellar spectrum. The similarities between the experimental and observed absorption spectra indicate that carbon onions are very strong candidates for the origin of the UV interstellar absorption peak at 4.6 microm(-1).

Journal Article↗

PubMed2003

Suspended multiwalled carbon nanotubes as self-aligned evaporation masks.

We describe the nanofabrication study of self-aligned electrodes on suspended multiwalled carbon nanotube structures. When metal is deposited on a suspended multiwalled carbon nanotube structure, the nanotube acts as an evaporation mask, resulting in the formation of discontinuous electrodes. The metal deposits on the nanotubes are removed with lift-off. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gapped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems.

Chromium↗

PubMed2002

Typing of clinical isolates of Mycobacterium leprae and their distribution in Korea.

Although there is no genetic diversity in isolates of Mycobacterium leprae, the variance of tandem repeats in the rpoT gene was recently demonstrated. We have typed clinical isolates of M. leprae in Korea using difference of the tandem repeats in the rpoT gene. Among 69 patients, 65 Korean isolates (94.2%) demonstrated four copies of the 6 bp tandem repeat (GACATC) in the rpoT gene, and incidences of three copies were found in only two Koreans and two foreigners (2.9%, respectively).

Base Sequence↗

PubMed2001

Modulation of the multisubstrate specificity of Thermus maltogenic amylase by truncation of the N-terminal domain and by a salt-induced shift of the monomer/dimer equilibrium.

The relation between the quaternary structure and the substrate specificity of Thermus maltogenic amylase (ThMA) has been investigated. Sedimentation diffusion equilibrium ultracentrifugation and gel filtration analyses, in combination with the crystal structure determined recently, have demonstrated that ThMA existed in a monomer/dimer equilibrium. The truncation of ThMA by removing the N-terminal domain, which is composed of 124 amino acid residues, resulted in the complete monomerization of the enzyme (ThMADelta124) accompanied by a drastic decrease in the activity for beta-cyclodextrin (beta-CD) and a relatively smaller reduction of the activity for starch. Despite the overall low activity of ThMADelta124, the activity was higher toward starch than beta-CD, and the ratio of the specific activities toward these substrates was approximately 100 fold higher than that of wild-type ThMA. Furthermore, the addition of KCl to wild-type ThMA shifted the monomer/dimer equilibrium toward the monomer. In the presence of 1.0 M KCl, the relative activity of ThMA toward beta-CD decreased to 74%, while that for soluble starch increased to 194% compared to the activities in the absence of KCl. Thus, the ThMA monomer and dimer are both inferred to be enzymatically active but with a somewhat different substrate preference. Kinetic parameters of the wild-type and truncated enzymes also are in accordance with the changes in their specific activities. We thus provide evidence in support of a model, which shows that the relative multisubstrate specificity of ThMA is influenced by the monomer/dimer equilibrium of the enzyme.

Amino Acid Sequence↗

PubMed2001

Destabilization of CHK2 by a missense mutation associated with Li-Fraumeni Syndrome.

Li Fraumeni Syndrome (LFS) is a multicancer phenotype, most commonly associated with germ-line mutations in TP53. In a kindred with LFS without an inherited TP53 mutation, we have previously reported a truncating mutation (1100delC) in CHK2, encoding a kinase that phosphorylates p53 on Ser(20). Here, we describe a CHK2 missense mutation (R145W) in another LFS family. This mutation destabilizes the encoded protein, reducing its half-life from >120 min to 30 min. This effect is abrogated by treatment of cells with a proteosome inhibitor, suggesting that CHK2(R145W) is targeted through this degradation pathway. Both 1100delC and R145W germ-line mutations in CHK2 are associated with loss of the wild-type allele in the corresponding tumor specimens, and neither tumor harbors a somatic TP53 mutation. Our observations support the functional significance of CHK2 mutations in rare cases of LFS and suggest that such mutations may substitute for inactivation of TP53.

Adult↗

PubMed2001

Trapping of a covalent enzyme intermediate in the reaction of Bacillus macerans cyclomaltodextrin glucanyltransferase with cyclomaltohexaose.

The mechanism of catalysis of Bacillus macerans cyclomaltodextrin glucanyltransferase (CGTase, EC 2.4.1.19) was studied by trapping and isolating a covalent-enzyme intermediate. CGTase catalyzes an acceptor or coupling reaction between cyclomaltohexaose and a carbohydrate acceptor such as D-glucose. CGTase was incubated with 3H-labeled cyclomaltohexaose in the absence of any added acceptor. After 30 s of reaction, the enzyme was rapidly denatured and precipitated by the addition of 10% trifluoroacetic acid (TFA). Extensive washing of the precipitated protein showed retention of radioactivity with the protein. The precipitate was dissolved in 0.1 M TFA, containing 6 M urea and passed over a BioGel P-10 column. The protein fraction retained 95% of its original radioactivity. The reaction with [3H]cyclomaltohexaose was also stopped by the addition of TFA to give an inactive enzyme at pH 2.5. The enzyme was separated from unreacted cyclomaltohexaose on a BioGel P-10 column and was shown to be radioactive. When the radioactive protein fraction was rechromatographed on BioGel P-10, it retained 100% of the label. These results demonstrate the formation of a covalent carbohydrate-enzyme intermediate in the reactions catalyzed by CGTase.

Bacillus↗

PubMed2001

Expression of the native cholera toxin B subunit gene and assembly as functional oligomers in transgenic tobacco chloroplasts.

The B subunits of enterotoxigenic Escherichia coli (LTB) and cholera toxin of Vibrio cholerae (CTB) are candidate vaccine antigens. Integration of an unmodified CTB-coding sequence into chloroplast genomes (up to 10,000 copies per cell), resulted in the accumulation of up to 4.1 % of total soluble tobacco leaf protein as functional oligomers (410-fold higher expression levels than that of the unmodified LTB gene expressed via the nuclear genome). However, expression levels reported are an underestimation of actual accumulation of CTB in transgenic chloroplasts, due to aggregation of the oligomeric forms in unboiled samples similar to the aggregation observed for purified bacterial antigen. PCR and Southern blot analyses confirmed stable integration of the CTB gene into the chloroplast genome. Western blot analysis showed that the chloroplast- synthesized CTB assembled into oligomers and were antigenically identical with purified native CTB. Also, binding assays confirmed that chloroplast-synthesized CTB binds to the intestinal membrane GM1-ganglioside receptor, indicating correct folding and disulfide bond formation of CTB pentamers within transgenic chloroplasts. In contrast to stunted nuclear transgenic plants, chloroplast transgenic plants were morphologically indistinguishable from untransformed plants, when CTB was constitutively expressed in chloroplasts. Introduced genes were inherited stably in subsequent generations, as confirmed by PCR and Southern blot analyses. Increased production of an efficient transmucosal carrier molecule and delivery system, like CTB, in transgenic chloroplasts makes plant-based oral vaccines and fusion proteins with CTB needing oral administration commercially feasible. Successful expression of foreign genes in transgenic chromoplasts and availability of marker-free chloroplast transformation techniques augurs well for development of vaccines in edible parts of transgenic plants. Furthermore, since the quaternary structure of many proteins is essential for their function, this investigation demonstrates the potential for other foreign multimeric proteins to be properly expressed and assembled in transgenic chloroplasts.

Blotting, Southern↗

PubMed2001

Isolation of a novel gene from Schizosaccharomyces pombe: stm1+ encoding a seven-transmembrane loop protein that may couple with the heterotrimeric Galpha 2 protein, Gpa2.

A putative seven transmembrane protein gene, stm1(+), which is required for proper recognition of nitrogen starvation signals, was isolated as a multicopy suppressor of a ras1 synthetic lethal mutant in Schizosaccharomyces pombe. Under nitrogen-deficient conditions, transcription of the stm1 gene was induced; deletion of stm1 was associated with early entry into G(1) arrest. Under nutritionally sufficient conditions, overexpression of Stm1 inhibited vegetative cell growth, resulted in decreased intracellular cAMP levels, increased the expression of the meiosis-specific genes ste11, mei2, and mam2, and facilitated sexual development in homothallic cells. However inhibition of vegetative cell growth and reduction of cAMP levels were not observed in a deletion mutant of the heterotrimeric G protein Galpha2 gene, gpa2, that is responsible for regulating intracellular cAMP levels, a key factor in determining the sexual development in S. pombe. Stm1 protein was shown to interact with Gpa2 through its C-terminal transmembrane domains 5-7. Mutation at Lys(199) in the C-terminal domain (stm1(K199A)) abolished the Stm1 overexpression effect on lowering cAMP levels. Induction of ste11, a meiosis-specific gene transcription factor, by Stm1 overexpression was enhanced in gpa2-deleted cells but was absent in a deletion mutant of sty1, a key protein kinase that links mitotic control with environmental signals and induces stress-responsive genes. Moreover, deletion of both stm1 and ras1 caused delayed entry into G(1) arrest in S. pombe when the cells were grown in a nitrogen-deficient medium. Thus we consider that the stm1 gene can function through Gpa2-dependent and/or -independent pathways and may play a role in providing the prerequisite state for entering the pheromone-dependent differentiation cycle in which heterotrimeric Galpha1 protein, Gpa1, and Ras1 play major roles. Stm1 could function as a sentinel molecule sensing the nutritional state of the cells, stopping the proliferative cell cycle, and preparing the cell to enter meiosis under nutritionally deficient conditions.

Adaptation, Biological↗

PubMed2001

Regulator of G-protein signaling 3 (RGS3) inhibits Gbeta1gamma 2-induced inositol phosphate production, mitogen-activated protein kinase activation, and Akt activation.

Regulator of G-protein signaling 3 (RGS3) enhances the intrinsic rate at which Galpha(i) and Galpha(q) hydrolyze GTP to GDP, thereby limiting the duration in which GTP-Galpha(i) and GTP-Galpha(q) can activate effectors. Since GDP-Galpha subunits rapidly combine with free Gbetagamma subunits to reform inactive heterotrimeric G-proteins, RGS3 and other RGS proteins may also reduce the amount of Gbetagamma subunits available for effector interactions. Although RGS6, RGS7, and RGS11 bind Gbeta(5) in the absence of a Ggamma subunit, RGS proteins are not known to directly influence Gbetagamma signaling. Here we show that RGS3 binds Gbeta(1)gamma(2) subunits and limits their ability to trigger the production of inositol phosphates and the activation of Akt and mitogen-activated protein kinase. Co-expression of RGS3 with Gbeta(1)gamma(2) inhibits Gbeta(1)gamma(2)-induced inositol phosphate production and Akt activation in COS-7 cells and mitogen-activated protein kinase activation in HEK 293 cells. The inhibition of Gbeta(1)gamma(2) signaling does not require an intact RGS domain but depends upon two regions in RGS3 located between acids 313 and 390 and between 391 and 458. Several other RGS proteins do not affect Gbeta(1)gamma(2) signaling in these assays. Consistent with the in vivo results, RGS3 inhibits Gbetagamma-mediated activation of phospholipase Cbeta in vitro. Thus, RGS3 may limit Gbetagamma signaling not only by virtue of its GTPase-activating protein activity for Galpha subunits, but also by directly interfering with the activation of effectors.

Animals↗

PubMed2001

Wilms tumor and the WT1 gene.

Wilms tumor or nephroblastoma is a pediatric kidney cancer arising from pluripotent embryonic renal precursors. Multiple genetic loci have been linked to Wilms tumorigenesis; positional cloning strategies have led to the identification of the WT1 tumor suppressor gene at chromosome 11p13. WT1 encodes a zinc finger transcription factor that is inactivated in the germline of children with genetic predisposition to Wilms tumor and in a subset of sporadic cancers. When present in the germline, specific heterozygous dominant-negative mutations are associated with severe abnormalities of renal and sexual differentiation, pointing to the essential role of WT1 for normal genitourinary development. The role of this tumor suppressor in normal organ-specific differentiation is also supported by the highly restricted temporal and spatial expression of WT1 in glomerular precursors of the developing kidney and by the failure of kidney development in wt1-null mice. Of two major alternative splicing products encoded by WT1, the (-KTS) isoform appears to mediate transcriptional activation of genes implicated in cellular differentiation, possibly also repressing proliferation-associated genes. The (+KTS) isoform, whose DNA-binding domain is disrupted by the insertion of three amino acids, may be involved in some aspect of mRNA processing. In addition to its function in genitourinary development, a role for WT1 in hematopoiesis is suggested by its aberrant expression and/or mutation in a subset of acute human leukemias. WT1 is also expressed in mesothelial cells; a specific oncogenic chromosomal translocation fusing the N-terminal domain of the Ewing sarcoma gene EWS to the three C-terminal zinc fingers of WT1 underlies desmoplastic small round cell tumor, an abdominal tumor thought to arise from the peritoneal lining. Understanding the distinct functional properties of WT1 isoforms and tumor-associated variants will provide unique insight into the link between normal organ-specific differentiation and malignancy.

Acute Disease↗

PubMed2001

Inhibition of beta-glycosidases by acarbose analogues containing cellobiose and lactose structures.

Acarbose analogues, containing cellobiose and lactose structures, were prepared by reaction of the two disaccharides with acarbose and Bacillus stearothermophilus maltogenic amylase. The kinetics for the inhibition by the two analogues was studied for beta-glucosidase, beta-galactosidase, cyclomaltodextrin glucanosyltransferase (CGTase), and alpha-glucosidase. Both analogues were potent competitive inhibitors for beta-glucosidase, with K(I) values in the range of 0.04-2.44 microM, and the lactose analogues were good uncompetitive inhibitors for beta-galactosidase, with K(I) values in the range of 159-415 microM, while acarbose was not an inhibitor for either enzyme at 10 and 5 mM, respectively. Both analogues were also potent mixed inhibitors for CGTase, with K(I) values in the range of 0.1-9.3 microM. The lactose analogue was a 6.4-fold better competitive inhibitor for alpha-glucosidase than was acarbose.

Acarbose↗

PubMed2001

pH-switchable, ion-permselective gold nanotubule membrane based on chemisorbed cysteine.

An electroless gold plating method was used to deposit Au nanotubules within the pores of a polycarbonate template membrane. pH-switchable ion-transport selectivity was introduced by chemisorbing L-cysteine to the inside tubule walls. At low pH, where both the amino and carboxyl groups of the cysteine are protonated, these membranes preferentially reject cations and transport anions. At high pH, where both the amino and carboxyl groups are deprotonated, these membranes preferentially reject anions and transport cations. At pH = 6.0, near the isoelectric point of the chemisorbed cysteine, these membranes show neither cation nor anion transport selectivity. In addition to this electrostatically based selectivity, because of the small inside diameter of the Au nanotubules (as small as 0.9 nm), these membranes show molecular-size-based selectivity.

Journal Article↗