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Biomedical subjects

S Shin

Publications and source records attributed to S Shin.

At least 37 records · Page 2Linked to original sources
PubMed2004

Psychiatric issues in the management of patients with multidrug-resistant tuberculosis.

INTRODUCTION: Psychiatric issues present a challenge in the treatment of patients with multidrug-resistant tuberculosis (MDR-TB). Both baseline psychiatric disorders and development of psychiatric complications related to anti-tuberculosis drugs and psychosocial factors require aggressive management. SETTING: A community-based non-governmental health organization in Lima, Peru. OBJECTIVE: To review the literature for psychiatric complications associated with anti-tuberculosis medications, to describe the incidence and prevalence of depression, anxiety and psychosis among individuals receiving MDR-TB therapy, and to detail the management approach used in this cohort. METHODS: A retrospective case series was performed among the first 75 patients to receive individualized MDR-TB therapy in Lima, Peru, between 1996 and 1999. RESULTS: Baseline depression and baseline anxiety were observed in respectively 52.2% and 8.7% of this cohort. Most individuals with baseline depression experienced improvement of depressive symptoms during the course of TB therapy. The incidence of depression, anxiety and psychosis during MDR-TB treatment was 13.3%, 12.0% and 12.0%, respectively. While the majority of individuals with depression, anxiety and psychosis required psychiatric pharmacotherapy, cycloserine was successfully continued in all but one case. CONCLUSION: Psychiatric comorbidities are not a contra-indication to MDR-TB therapy. Management of psychiatric complications is possible without compromising anti-tuberculosis treatment.

Adult↗
PubMed2003

Definitive experimental evidence for two-band superconductivity in MgB2.

The superconducting-gap of MgB2 has been studied by high-resolution angle-resolved photoemission spectroscopy. The results show that superconducting gaps with values of 5.5 and 2.2 meV open on the sigma band and the pi band, respectively, but both the gaps close at the bulk transition temperature, providing a definitive experimental evidence for the two-band superconductivity with strong interband pairing interaction in MgB2. The experiments validate the role of k-dependent electron-phonon coupling as the origin of multiple-gap superconductivity as well as the high transition temperature of MgB2.

Journal Article↗
PubMed2003

Resonant double excitation observed in the near-threshold evolution of the photoexcited F K alpha satellite intensity in NaF.

We present a precise measurement of the photoexcited F K alpha satellite intensity's evolution for NaF from [1s2p] double excitation threshold to saturation. A direct comparison between the observed evolution and the x-ray absorption spectrum was successfully made, and the contribution of multielectron transitions to the absorption spectrum was clearly resolved for the first time. A resonance-like feature observed in the near-threshold evolution is attributed to the [1s2p]3p(2) resonant double excitation as confirmed by calculations.

Journal Article↗
PubMed2003

Inhibitory effects of the stem bark of Catalpa ovata G. Don. (Bignoniaceae) on the productions of tumor necrosis factor-alpha and nitric oxide by the lipopolisaccharide-stimulated RAW 264.7 macrophages.

In order to validate the use of the stem bark of Catalpa ovata G. Don. (Bignoniaceae) as an anti-inflammatory drug in the traditional Korean medicine, we have investigated the effects of the methanol extract of this folk medicine on the productions of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) on RAW 264.7 macrophages activated with the endotoxin lipopolysaccharide. The extract inhibited the productions of TNF-alpha and NO with significant decreases in mRNA levels of TNF-alpha and inducible NO synthase, suggesting that the stem bark of Catalpa ovata may have therapeutic potential in the control of inflammatory disorders.

Animals↗
PubMed2003

Antifungal activity of the essential oil of Agastache rugosa Kuntze and its synergism with ketoconazole.

AIMS: To evaluate the fungitoxic activity of the essential oil of Agastache rugosa alone and to determine its combination effect with ketoconazole against Blastoschizomyces capitatus. METHODS AND RESULTS: The antifungal activities of the essential oil of A. rugosa and its main constituent estragole were investigated using the broth microdilution, disk diffusion methods and checkerboard microtitre assay. Both estragole and the essential oil exhibited strong activities against the tested fungi and showed synergism with ketoconazole against B. capitatus. CONCLUSIONS: Both estragole and the essential oil of A. rugosa have significant growth-inhibiting activities against B. capitatus showing strong synergistic effect with ketoconazole. SIGNIFICANCE AND IMPACT OF THE STUDY: The essential oil of A. rugosa, combined with ketoconazole, may be particularly useful against B. capitatus, a rare pathogenic fungus documented to cause severe and fatal mycoses in immunocompromised patients.

Agastache↗
PubMed2002

Observation of fluorapatite formation under hydrolysis of tetracalcium phosphate in the presence of KF by means of soft X-ray emission and absorption spectroscopy.

The effect of fluoride on the hydrolysis of tetracalcium phosphate (TTCP; Ca4(PO4)2O) in 0.1 mol/l KH2PO4 containing 62-83 mmol/l KF was studied with the help of X-ray fluorescence measurements. Fluorine X-ray emission and absorption spectra of the final product of hydrolysis and reference samples (CaF2 and Ca5(PO4)3F) were measured at Beamline BL-2C of Photon Factory (PF, Tsukuba). Based on these measurements we concluded that hydrolysis of TTCP in the presence of KF converts it into fluorapatite. Formation of CaF2, which is often found in the hydrolysis of hydroxyapatite at high fluoride concentration, was not observed.

Journal Article↗
PubMed2001

Fermi surface sheet-dependent superconductivity in 2H-NbSe2.

High-resolution angle-resolved photoemission spectroscopy was used to study the superconducting energy gap and changes in the spectral function across the superconducting transition in the quasi-two-dimensional superconductor 2H-NbSe2. The momentum dependence of the superconducting gap was determined on different Fermi surface sheets. The results indicate Fermi surface sheet-dependent superconductivity in this low-transition temperature multiband system and provide a description consistent with thermodynamic measurements and the anomalous de Haas-van Alphen oscillations observed in the superconducting phase. The present data suggest the importance of Fermi surface sheet-dependent superconductivity in explaining exotic superconductivity in other multiband systems with complex Fermi surface topology, such as the borides and f-electron superconductors.

Journal Article↗
PubMed2001

Synthesis, characterization, and applicability of neutral polyhydroxy phospholane derivatives and their rhodium(I) complexes for reactions in organic and aqueous media.

Two different protocols for the preparation of water-soluble, enantiomerically pure polyhydroxybisphospholanes from acid-labile acetal and tert-butyldimethylsilyl-protected derivatives are reported. These procedures circumvent two of the commonly encountered limitations in the synthesis of these potentially important ligands: (a) formation of phosphonium salts from the highly basic phosphine under acidic conditions, and (b) the need to start with preformed, fully protected cationic metal complex. Thus, cationic Rh complexes of these ligands have been prepared in a separate step, and they have been found to be excellent catalysts for organic and aqueous phase hydrogenation of dehydroamino acids. The viability of catalyst recovery has been demonstrated in three different systems, including two cases where > 99% ee can be achieved under recycling conditions.

Journal Article↗
PubMed2001

Evidence for a multiple superconducting gap in MgB(2) from high-resolution photoemission spectroscopy.

We study the new binary intermetallic superconductor MgB(2) using high-resolution photoemission spectroscopy. The superconducting-state spectrum measured at 5.4 K shows a coherent peak with a shoulder structure, in sharp contrast to that expected from a simple isotropic-gap opening. The spectrum can be well reproduced using the weighted sum of two Dynes functions with the gap sizes of 1.7 and 5.6 meV. Temperature-dependent study shows that both gaps close at the bulk transition temperature. These results provide spectroscopic evidence for a multiple gap of MgB(2).

Journal Article↗
PubMed2001

An anti-apoptotic protein human survivin is a direct inhibitor of caspase-3 and -7.

Survivin, an apoptosis inhibitor/cell-cycle regulator, is critically required for suppression of apoptosis and ensuring normal cell division in the G2/M phase of the cell cycle. It is highly expressed in a cell cycle-regulated manner and localizes together with caspase-3 on microtubules within centrosomes. Whether survivin is a physiologically relevant caspase inhibitor has been unclear due to the difficulties with obtaining correctly folded survivin and finding the right conditions for inhibition assay. In this study, recombinant, active human survivin was expressed in Escherichia coli and purified to homogeneity. The protein, existing as a homodimer in solution, binds caspase-3 and -7 tightly with dissociation constants of 20.9 and 11.5 nM, respectively, when evaluated by surface plasmon resonance spectroscopy. Consistently, survivin potently inhibits the cleavage of a physiological substrate poly(ADP-ribose) polymerase and an artificial tetrapeptide by caspase-3 and -7 in vitro with apparent inhibition constants of 36.0 and 16.5 nM, respectively. The data suggest that sequestering caspase-3 and -7 in inhibited states on microtubules is at least one mechanism of survivin in the suppression of default apoptosis in the G2/M phase. The localization of survivin on microtubules, which is essential for its function, should increase the protective activity at the action site.

Apoptosis↗
PubMed2001

Apoptosis induced by progesterone in human ovarian cancer cell line SNU-840.

Progesterone has been used as an ingredient of anticancer drug for patients with ovarian carcinoma. However, the mechanism of anticancer effects by progesterone has not been understood. In this study, the effects of progesterone on ovarian cancer cells, SNU-840, were investigated. After the incubation with progesterone, the viability of the cells was evaluated by MTT assay. As a result, 45% of the cells were viable after 48 h of incubation with 100 microM progesterone. In addition, [(3)H]thymidine incorporation assay showed that the proliferation of the cells was completely inhibited by progesterone after 48 h of incubation at 100 microM concentration. Colorimetric TUNEL assay revealed the fragmentation of the chromosomal DNA, suggesting that the process of the cell death was apoptosis. The level of the p53 mRNA was determined by northern blotting assay, since many apoptosis processes are mediated by up-regulation of the p53 expression. The level of the p53 mRNA reached its maximum at 12 h and decreased after 24 h of incubation with progesterone. In conclusion, progesterone inhibits the proliferation and elicits apoptosis of SNU-840 cells. Also, it up-regulates the p53 mRNA transiently.

Apoptosis↗
PubMed2001

Electrochemical behavior and differential pulse polarographic determination of rifampicin in the pharmaceutical preparations.

Differential pulse polarographic (DPP) analytical procedure for the rifampicin antibiotic, which can be applied to monitor its synthetic process from the starting antibiotic of rifamycin B or rifamycin SV, has been developed based on the electrochemical reduction of an azomethine group. Rifampicin exhibited a cathodic peak due to the azomethine group in the side chain of 3-[(4-methyl-1-piperazinyl)imino]methyl moiety and another cathodic peak due to the carbonyl group in rifamycin SV by DPP The experimental peak potential shift of an azomethine reduction was -73 mV/pH in the pH range between 3.0 and 7.5, agreeing with involvement of 4 e- and 5 H+ in its reduction. By the cyclic voltammetric(CV) studies, the azomethine and the carbonyl reductions in rifampicin were processed irreversibly on the mercury electrode. The plot of peak currents vs. concentrations of rifampicin ranging 1.0 x 10(-7) M tp approximately 1.0 x 10(-5) M yielded a straight line with a correlation coefficient of 0.9996. The detection limit was 1.0 x 10(-8) M with a modulation amplitude of 50 mV. DPP has been successfully applied for the determination of rifampicin in the pharmaceutical preparations.

Antibiotics, Antitubercular↗
PubMed2001

Incidence of intrauterine complications in monoamniotic twin gestation.

We compared the incidence of intrauterine complications, such as twin-twin transfusion syndrome, between monochorionic-monoamniotic (MM) and monochorionic-diamniotic (MD) twin gestations. We retrospectively evaluated a series of 11 MM and 211 MD twin gestations managed after 22 weeks' gestation at our hospitals. One MM twin gestation was diagnosed with twin-twin transfusion syndrome based on clinical presentation of polyhydramnios and hydrops. The incidence of twin-twin transfusion syndrome in MM twin gestations (9.1%) was not measurable different from that in the MD twin gestations (7.6%, p=0.09). There were no measurable differences in the incidence of other complications, such as growth discordance >25% or intrauterine fetal demise between the two groups. MM twin gestations should be kept under close management while carefully monitoring for any circulatory imbalance between the twins.

Adult↗
PubMed2001

Understanding beta-hairpin formation by molecular dynamics simulations of unfolding.

We have studied the mechanism of formation of a 16-residue beta-hairpin from the protein GB1 using molecular dynamics simulations in an aqueous environment. The analysis of unfolding trajectories at high temperatures suggests a refolding pathway consisting of several transient intermediates. The changes in the interaction energies of residues are related with the structural changes during the unfolding of the hairpin. The electrostatic energies of the residues in the turn region are found to be responsible for the transition between the folded state and the hydrophobic core state. The van der Waals interaction energies of the residues in the hydrophobic core reflect the behavior of the radius of gyration of the core region. We have examined the opposing influences of the protein-protein (PP) energy, which favors the native state, and the protein-solvent (PS) energy, which favors unfolding, in the formation of the beta-hairpin structure. It is found that the behavior of the electrostatic components of PP and PS energies reflects the structural changes associated with the loss of backbone hydrogen bonding. Relative changes in the PP and PS van der Waals interactions are related with the disruption of the hydrophobic core of a protein. The results of the simulations support the hydrophobic collapse mechanism of beta-hairpin folding.

Animals↗
PubMed2001

Mesenchymal stem villous hyperplasia of the placenta and fetal growth restriction.

BACKGROUND: Mesenchymal stem villous hyperplasia of the placenta is a rare placental anomaly characterized by placental vascular malformation and the appearance of a partial mole. CASE: A multiparous woman presented with fetal growth restriction (FGR) at 35 weeks' gestation. Ultrasonographic examination showed multiple anechoic lesions on the placental surface. Cesarean delivery was performed at 37 weeks' gestation, and a healthy 1536-g female was delivered. The placenta had aneurysmal dilatations of the chorionic vessels. Unlike other cases, it also showed subamniotic hemorrhage and had no features of a partial mole. Histologic examination established the diagnosis of mesenchymal stem villous hyperplasia of the placenta with severe thrombosis. CONCLUSION: Fetal growth restriction can be caused by severe thrombosis in this placental anomaly.

Chorionic Villi↗
PubMed2001

Enzyme mechanism and catalytic property of beta propeller phytase.

BACKGROUND: Phytases hydrolyze phytic acid (myo-inositol-hexakisphosphate) to less-phosphorylated myo-inositol derivatives and inorganic phosphate. Phytases are used in animal feed to reduce phosphate pollution in the environment. Recently, a thermostable, calcium-dependent Bacillus phytase was identified that represents the first example of the beta propeller fold exhibiting phosphatase activity. We sought to delineate the catalytic mechanism and property of this enzyme. RESULTS: The crystal structure of the enzyme in complex with inorganic phosphate reveals that two phosphates and four calcium ions are tightly bound at the active site. Mutation of the residues involved in the calcium chelation results in severe defects in the enzyme's activity. One phosphate ion, chelating all of the four calcium ions, is close to a water molecule bridging two of the bound calcium ions. Fluoride ion, which is expected to replace this water molecule, is an uncompetitive inhibitor of the enzyme. The enzyme is able to hydrolyze any of the six phosphate groups of phytate. CONCLUSIONS: The enzyme reaction is likely to proceed through a direct attack of the metal-bridging water molecule on the phosphorous atom of a substrate and the subsequent stabilization of the pentavalent transition state by the bound calcium ions. The enzyme has two phosphate binding sites, the "cleavage site", which is responsible for the hydrolysis of a substrate, and the "affinity site", which increases the binding affinity for substrates containing adjacent phosphate groups. The existence of the two nonequivalent phosphate binding sites explains the puzzling formation of the alternately dephosphorylated myo-inositol triphosphates from phytate and the hydrolysis of myo-inositol monophosphates.

6-Phytase↗