Biomedical subjects

C S Hwang

Publications and source records attributed to C S Hwang.

At least 19 recordsLinked to original sources

PubMed2006

Chronic myelomonocytic leukaemia after platinum-based therapy for non-small cell lung cancer: case report and review of the literature.

Chronic myelomonocytic leukaemia (CMML) is a preleukaemic condition with myeloproliferative features, and classified as a part of myelodysplastic syndrome (MDS). Other than alkylating agents and topoisomerase II inhibitors, there is less evidence that chemotherapeutic drugs are associated with therapy-related CMML, acute leukaemia or MDS. We present a patient who developed CMML within 2 years of platinum-based chemotherapy for a metastatic non-small cell lung cancer. He received a cumulative dose of 240 mg/m(2) of cisplatin, and 1123 mg/m(2) of carboplatin before developing CMML. The cytogenetic study revealed trisomy 8. This is the first reported case that links platinum-based therapy with development of CMML with trisomy 8. Although the relationship between platinum therapy and the development of CMML is difficult to assess due to combinational nature of therapy in most cases, physicians should consider the possibility of CMML in patients with symptoms or signs suggestive of haematologic malignancy after platinum therapy.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2001

Mitochondrial NADH-cytochrome b(5) reductase plays a crucial role in the reduction of D-erythroascorbyl free radical in Saccharomyces cerevisiae.

The relevance of NADH-cytochrome b(5) reductase to the NADH-dependent reduction of D-erythroascorbyl free radical was investigated in Saccharomyces cerevisiae. MCR1, which is known to encode NADH-cytochrome b(5) reductase in S. cerevisiae, was disrupted by the insertion of URA3 gene into the gene of MCR1. In the mcr1 disruptant cells, the activity of NADH-D-erythroascorbyl free radical reductase almost disappeared and the intracellular level of D-erythroascorbic acid was about 11% of that of the congenic wild-type strain. In the transformant cells carrying MCR1 in multicopy plasmid, the intracellular level of D-erythroascorbic acid and the activity of NADH-D-erythroascorbyl free radical reductase increased up to 1.7-fold and 2.1-fold, respectively. Therefore, it indicated that the MCR1 product, mitochondrial NADH-cytochrome b(5) reductase, plays a key role in the NADH-dependent reduction of D-erythroascorbyl free radical in S. cerevisiae. On the other hand, the mcr1 disruptant cells were hypersensitive to hydrogen peroxide and menadione, and overexpression of MCR1 made the cells more resistant against oxidative stress. These results suggested that the mitochondrial NADH-cytochrome b(5) reductase functions as NADH-D-erythroascorbyl free radical reductase and plays an important role in the response to oxidative damage in S. cerevisiae.

Ascorbic Acid↗

PubMed2001

Duodenojejunal intussusception secondary to hamartomatous polyps of duodenum surrounding the ampulla of Vater.

Duodenojejunal intussusception is a rare pediatric emergency. A case of duodenojejunal intussusception secondary to hamartomatous polyps of the second portion of duodenum in a 10-month-old boy is reported. Surgical excision of the polyps and reduction of the intussusception were performed. Pathologic examination found hamartomatous polyps. This is the third case report of children in literature, but this is the first case of a child with intussusception surrounding the ampulla of Vater and a successful excision performed without damaging the ampulla of Vater.

Ampulla of Vater↗

PubMed2001

Outcomes of cardiopulmonary arrest in an acute rehabilitation setting.

OBJECTIVE: Fifty consecutive cases of cardiopulmonary arrest with administration of cardiopulmonary resuscitation (CPR) during a 6-yr period at a freestanding academic acute rehabilitation hospital were identified. DESIGN: Medical records of 49 patients were available for review. Outcomes of survival of arrest, survival to 24 hr postarrest, survival to discharge from the hospital were determined, and chi2 or Fisher's exact tests were performed to investigate relationships between survival and admission functional status, age, gender, and medical comorbidities. RESULTS: Forty-three percent of patients survived the initial arrest, 37% survived to 24 hr post-CPR, and 18% survived to hospital discharge. We were unable to identify any statistically significant predictors of survival post-CPR. Six of the nine survivors returned to the acute rehabilitation setting after cardiopulmonary arrest, and five of these patients made significant functional gains. CONCLUSIONS: Outcomes after CPR in patients undergoing acute rehabilitation in one setting were not significantly different from those reported for patients in other healthcare settings. These data may be used by healthcare professionals to enhance discussions concerning advance healthcare planning (including resuscitation plans) with patients and families. Larger studies are needed to clarify the prognostic role of prior functional status in predicting CPR outcomes, particularly in the context of various diagnostic categories and age groups.

Adolescent↗

PubMed2001

Identification of a mutation in the human raloxifene response element of the transforming growth factor-beta 3 gene.

The human transforming growth factor-beta 3 (TGF-beta 3) is an important cytokine to maintain bone mass by inhibiting osteoclast differentiation. Recently raloxifene response element (RRE), a new enhancer with a polypurine sequence for estrogen receptor (ER)-mediated gene activation, was identified on the TGF-beta 3 gene. Functional analysis of the RRE-mediated pathway has shown that this would be an important pathway for bone preserving effect. We found a novel mutation in the RRE sequence by single-strand conformational polymorphism analysis in one of 200 Korean women. Cloning and sequencing revealed a heterozygote in which one allele had an insertion of 20 nucleotides (AGAGAGGGAGAGGGAGA GGG) between nucleotide +71 and +72 and a point mutation at nucleotide +75 (G-A transition), and the other allele had normal sequence. The insertion was a nearly perfect tandem duplication of the wild type DNA sequence. The bone mineral density of the affected woman was not much lower than that of age-matched controls. Transient transfection of the mutant allele showed no significantly different activity compared with that of the wild type allele. These observations suggest that the heterozygote variation of the RRE sequence seems not to be operative in determination of bone mass.

Estrogen Antagonists↗

PubMed2001

Deflazacort increases osteoclast formation in mouse bone marrow culture and the ratio of RANKL/OPG mRNA expression in marrow stromal cells.

Information on precise effects of deflazacort on bone cell function, especially osteoclasts, is quite limited. Therefore, the present study was undertaken to test effects of deflazacort on osteoclast-like cell formation in mouse bone marrow cultures and on the regulation of osteoprotegerin (OPG) and its ligand (RANKL) mRNA expressions by RT-PCR in the ST2 marrow stromal cells. TRAP-positive mononuclear cells increased after the treatment of deflazacort at 10(-9) to 10(-7) M alone for 6 days in a dose-dependent manner. Number of TRAP-positive multi-nucleated cells (MNCs) increased significantly with combined treatment of deflazacort at 10(-7) M and 1,25-(OH)2D3 at 10(-9) M compared to that of cultures treated with 1,25-(OH)2D3 alone (p<0.05). Exposure to deflazacort at 10(-7) M in the presence of 1,25-(OH)2D3 at 10(-9) M in the last 3-day culture had greater stimulatory effect on osteoclast-like cell formation than that of the first 3-day culture did. Deflazacort at 10(-10) -10(-6) M downregulated OPG and upregulated RANKL in mRNA levels in a dose-dependent manner. These observations suggest that deflazacort stimulate osteoclast precursor in the absence of 1,25-(OH)2D3 and enhance differentiation of osteoclasts in the presence of 1,25-(OH)2D3. These effects are, in part, thought to be mediated by the regulation of the expression of OPG and RANKL mRNA in marrow stromal cells.

Animals↗

PubMed2000

Mitomycin C induces apoptosis in a caspases-dependent and Fas/CD95-independent manner in human gastric adenocarcinoma cells.

We investigated the mechanism of mitomycin C (MMC)-induced apoptosis in SNU-16 human gastric adenocarcinoma cells. Caspase-8 and caspase-3 were activated in MMC-treated cells whereas caspase-1 was not activated, and cytochrome c was released from mitochondrial membrane to cytosol suggesting that caspase-9 was activated during the MMC-induced apoptotic process. Protein kinase C (PKC) delta was cleaved to its characteristic 40 kDa fragment in a caspase-3-dependent manner; on the other hand PKC zeta was cleaved to approximately 40 kDa independently of caspase-3 in the drug-induced apoptosis of the cells. Incubation with z-DEVD-fmk and benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (z-VAD-fmk) almost completely abrogated MMC-induced DNA fragmentation, indicating that activation of these caspases was crucially involved in MMC-induced apoptosis. Activation of caspase-8 in response to Fas triggering by recruitment of caspase-8 to the Fas has also been found, however, MMC did not induce FasL and Fas expression, as evidenced by reverse transcriptase-polymerase chain reaction and Western blotting. Taken together, these findings indicate that MMC-induced apoptosis in SNU-16 cells was mediated by caspase-8, caspase-9, and caspase-3 activation independently of FasL/Fas interactions.

Adenocarcinoma↗

PubMed1999

Sepiapterin reductase producing L-threo-dihydrobiopterin from Chlorobium tepidum.

A novel type of NADPH-dependent sepiapterin reductase, which catalysed uniquely the reduction of sepiapterin to l-threo-dihydrobiopterin, was purified 533-fold from the cytosolic fraction of Chlorobium tepidum, with an overall yield of 3%. The native enzyme had a molecular mass of 55 kDa and SDS/PAGE revealed that the enzyme consists of two subunits with a molecular mass of 26 kDa. The enzyme was optimally active at pH8.8 and 50 degrees C. Apparent Km values for sepiapterin and NADPH were 21 and 6.2 microM, respectively, and the kcat value was 5.0 s-1. Diacetyl could also serve as a substrate, with a Km of 4.0 mM. The inhibitory effects of N-acetylserotonin, N-acetyldopamine and melatonin were very weak. The Ki value of N-acetyldopamine was measured as 400 microM. The N-terminal amino acid sequence was revealed as Met-Lys-His-Ile-Leu-Leu-Ile-Thr-Gly-Ala-Xaa-Lys - Lys - Ile - Xaa - Arg - Ala - Ile - Ala - Leu - Glu - Xaa - Ala - Arg - Xaa-Xaa-Xaa-His-His-His-, which shared relatively high sequence similarity with other sepiapterin reductases.

Alcohol Oxidoreductases↗

PubMed1999

Up-regulation of uncoupling protein-3 by fatty acid in C2C12 myotubes.

Uncoupling proteins (UCPs) are mitochondrial membrane proton transporters that uncouple oxidative phosphorylation by dissipating the proton gradient across the membrane. We have investigated regulation of the UCP3 gene in skeletal muscle and C2C12 muscle cells. UCP3 mRNA in mouse skeletal muscle is markedly increased by fasting and rapidly (within 4 h) decreased by re-feeding. Methyl palmoxirate, which inhibits fatty acid uptake by mitochondria and increases blood free fatty acids, prevents the fall in UCP3 message level induced by re-feeding. These findings suggest that fatty acid or a metabolite thereof, activates the UCP3 gene. Proof that fatty acid per se up-regulates UCP3 mRNA was obtained with C2C12 muscle cells in culture. Thus, oleic acid activated expression of UCP3 mRNA in differentiated C2C12 myotubes in a time and concentration-dependent manner. Moreover, BRL49653, a ligand for the nuclear hormone receptor PPARgamma induces expression of UCP3 mRNA suggesting that PPARgamma may regulate transcription of the UCP3 gene.

Animals↗

PubMed1999

Copper- and zinc-containing superoxide dismutase and its gene from Candida albicans.

Cytosolic copper- and zinc-containing superoxide dismutase was purified 136-fold with an overall yield of 2.5% to apparent electrophoretic homogeneity from the dimorphic pathogenic fungus, Candida albicans. The molecular mass of the native enzyme was 39.4 kDa and the enzyme was composed of two identical subunits with a molecular mass of 19.6 kDa. The enzyme was stable in the range of pH 4.0-9.0 and up to 55 degrees C. The ultraviolet-visible absorption spectrum of the enzyme showed the absorption band of copper- and zinc-containing superoxide dismutase at 660 nm. The atomic absorption analysis revealed that the enzyme contained 0.87 g-atom of copper and 0.79 g-atom of zinc per mole of subunit. The N-terminal amino acid sequence alignments up to the 40th residue showed that copper- and zinc-containing superoxide dismutase from C. albicans has high similarity to other eukaryotic copper- and zinc-containing superoxide dismutases. The sod1 encoding copper- and zinc-containing superoxide dismutase has been cloned using a polymerase chain reaction fragment as a probe. Sequence analysis of the sod1 predicted a copper- and zinc-containing superoxide dismutase that contains 154 amino acids with a molecular mass of 16143 Da and displayed 79%, 69%, and 57% sequence identity to the homologues of Neurospora crassa, Saccharomyces cerevisiae, and bovine, respectively. The cloned sod1 contained an intron of 245 nucleotides, which was verified by reverse transcription-polymerase chain reaction.

Amino Acid Sequence↗

PubMed1999

Manganese-containing superoxide dismutase and its gene from Candida albicans.

Mitochondrial manganese-containing superoxide dismutase was purified around 112-fold with an overall yield of 1.1% to apparent electrophoretic homogeneity from the dimorphic pathogenic fungus, Candida albicans. The molecular mass of the native enzyme was 106 kDa and the enzyme was composed of four identical subunits with a molecular mass of 26 kDa. The enzyme was not sensitive to either cyanide or hydrogen peroxide. The N-terminal amino acid sequence alignments (up to the 18th residue) showed that the enzyme has high similarity to the other eukaryotic manganese-containing superoxide dismutases. The gene sod2 encoding manganese-containing superoxide dismutase has been cloned using a product obtained from polymerase chain reaction. Sequence analysis of the sod2 predicted a manganese-containing superoxide dismutase that contains 234 amino acid residues with a molecular mass of 26173 Da, and displayed 57% sequence identity to the homologue of Saccharomyces cerevisiae. The deduced N-terminal 34 amino acid residues may serve as a signal peptide for mitochondrial translocation. Several regulatory elements such as stress responsive element and haem activator protein 2/3/4/5 complex binding sites were identified in the promoter region of sod2. Northern analysis with a probe derived from the cloned sod2 revealed a 0.94-kb band, which corresponds approximately to the expected size of mRNA deduced from sod2.

Amino Acid Sequence↗

PubMed1999

Lack of an intronic Sp1 binding-site polymorphism at the collagen type I alpha1 gene in healthy Korean women.

Osteoporosis is a disease that is strongly genetically influenced. However, the genes responsible for the disease are poorly defined. Recent data show that a G-T transition polymorphism of the Sp1 binding site at the collagen type I alpha1 gene (Sp1 polymorphism) is associated significantly with bone mineral density (BMD) and osteoporotic fracture in British women. To establish the association between the Sp1 genotypes and BMD in Korean women, we examined 200 healthy postmenopausal women of Korean ethnicity, ranging in age from 44 to 66 years (mean+/-SD: 54.7+/-5.3 years). PCR amplification using the same primers as those used previously, with enzyme digestion, revealed no restriction site in our samples. We also performed a single-strand conformational polymorphism (SSCP) analysis in 100 of the 200 samples and could not find any polymorphic sites in the PCR amplification region. Based on our study, the Sp1 polymorphism at the type I collagen alpha1 gene was not found in Korean women. Therefore, we suggest that the Sp1 polymorphism at the type I collagen alpha1 gene is absent or rare in Korean women. Based on the present findings, this polymorphism does not seem to be responsible for the entire genetic contribution to BMD.

Adult↗

PubMed1998

Bacterial lipopolysaccharide induces uncoupling protein-2 expression in hepatocytes by a tumor necrosis factor-alpha-dependent mechanism.

The liver is a target for bacterial lipopolysaccharide (LPS) and participates in the metabolic response to endotoxemia. Recently published evidence indicates that LPS increases the expression of mitochondrial uncoupling protein-2 (UCP-2) mRNAs in several tissues, including the liver. Because hepatocytes in the healthy liver do not express UCP-2, LPS was thought to induce UCP-2 in liver macrophages, which express UCP-2 constitutively. However, the present studies of cultured peritoneal macrophages indicate that LPS reduces steady state levels of UCP-2 mRNAs in these cells. In contrast, UCP-2 mRNAs are induced in hepatocytes isolated from LPS treated rats and transfection of these hepatocytes with UCP-2 promoter-reporter constructs demonstrates substantial increases in UCP-2 promoter activity. LPS induction of hepatocyte UCP-2 expression is virtually abolished by prior treatment of rats with neutralizing antibodies to tumor necrosis factor alpha (TNF). Futhermore, TNFalpha treatment induces UCP-2 mRNA accumulation in primary cultures of hepatocytes from healthy rats. Thus, hepatocytes are likely to be important contributors to endotoxin-related increases in liver UCP-2 via a mechanism that involves the LPS-inducible cytokine, TNFalpha.

Animals↗

PubMed1998

Advanced field-measurement method with three orthogonal Hall probes for an elliptically polarizing undulator.

A three-orthogonal-Hall-probe assembly with an 'on the fly' mapping method has been developed to characterize an elliptically polarizing undulator (EPU). The underlying design concept is that it can measure the three real field components without any field correction under a reliable and synchronization measurement method. Therefore, the relative central position shift, orthogonal angle and the planar Hall effect error between the three Hall probes should be calibrated and readjusted. Experimental results demonstrate that this method can yield an r.m.s. reproducibility of 10 G cm for the three field components and 2 G for the peak field strength. Under precision conditions this system can completely measure the three on-axis field components within 2 min for a 4 m-long EPU.

Journal Article↗

PubMed1998

Effects of magnets with non-unit magnetic permeability on an elliptically polarizing undulator.

This study employs the three-dimensional magnetostatic code TOSCA to assess numerically the effects of NdFeB magnets with non-unit magnetic permeability on an elliptically polarizing undulator. A reduction of a few percent of the on-axis magnetic field strength is predicted. In addition, a deviation of +/-100 G cm uncompensated dipole steering is predicted in a phase shift of 180 degrees for the elliptically polarizing undulator EPU5.6 (having a period length of 56 mm) at the minimum gap of 18 mm, which is related primarily to the configuration of the device end scheme. Results presented herein demonstrate that implementing an active compensation mechanism is a prerequisite for minimizing the orbit distortion during phase-shift adjustment, particularly for operating such a polarizing undulator in a third-generation machine having a median energy similar to that of the 1.5 GeV storage ring at SRRC.

Journal Article↗

PubMed1998

An SRRC elliptically polarizing undulator prototype to examine mechanical design feasibility and magnetic field performance.

In this work, a 1 m long Sasaki-type elliptically polarizing undulator (EPU) prototype with 5.6 cm period length is used to examine the mechanical design feasibility as well as magnetic field performance. The magnetic field characteristics of the EPU5.6 prototype at various phase shifts and gap motion are described. The field errors from mechanical tolerances, magnet block errors, end field effects and phase/gap motion effects are analysed. The procedures related to correcting the field with the block position tuning, iron shimming and the trim blocks at both ends are outlined.

Journal Article↗

PubMed1998

The commissioning of a flexible low-cost multipurpose X-ray beamline at SRRC.

A low-cost multipurpose X-ray beamline has been commissioned at the bending magnet B15 of the Synchrotron Radiation Research Center (SRRC). The beamline is constructed in such a way to accommodate the various needs of small research consortia, from universities or research institutes, whose requirements of a beamline facility are quite diverse while under limited funding support. Flexibility is the special feature of this beamline. It is capable of performing quick test measurements without a prolonged reviewing process. Switching between different techniques, such as white-beam irradiation, EXAFS and X-ray scattering, can be achieved within 1 h. Novel experiments, such as energy-dispersive small-angle scattering experiments and energy-dispersive reflectivity measurements, can also be performed.

Journal Article↗

PubMed1998

Tepidopterin, 1-O-(L-threo-biopterin-2'-yl)-beta-N-acetylglucosamine from Chlorobium tepidum.

A novel pterin compound, designated as tepidopterin, was detected from a thermophilic photosynthetic green sulphur bacterium, Chlorobium tepidum. The amount of tepidopterin inside the cell was estimated to be 2-5 micromol g(-1) dry weight of cell. This compound was purified through a high performance liquid chromatography using preparative DeltaPak C18 column. This compound was characterized by chromatographic behavior and by absorption and fluorescence properties. Its structure was determined to be 1-O-(L-threo-biopterin-2'-yl)-beta-N-acetylglucosamine by 1D- and 2D-NMR spectroscopy, mass spectrometry and CD. The relative amount of tetrahydrotepidopterin was estimated to be 96.7% inside the cell, that of dihydrotepidopterin 2.9%, and that of fully oxidized tepidopterin 0.4%. The amount of tepidopterin within the cell increased continuously until the beginning of the stationary phase of the cell growth.

Acetylglucosamine↗