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Biomedical subjects

Y K Shin

Publications and source records attributed to Y K Shin.

At least 55 records · Page 3Linked to original sources
PubMed1999

Cardioprotective effects of a novel proteasome inhibitor following ischemia and reperfusion in the isolated perfused rat heart.

Ischemia followed by reperfusion in the presence of polymorphonuclear leukocytes (PMNs) results in cardiac contractile dysfunction as well as myocardial injury. These effects are due in large part to endothelial dysfunction leading to an upregulation of cell adhesion molecules and subsequent neutrophil induced cardiac injury. The proteasome inhibitor, PS-519, has been shown to attenuate leukocyte-endothelial cell interactions. We tested the effects of PS-519 on neutrophil mediated cardiac dysfunction in ischemia/reperfusion. This study examines the effects of PS-519 in a neutrophil dependent isolated perfused rat heart model of ischemia (I) (20 min) and reperfusion (R) (45 min). Administration of PS-519 (0.01, 0.1, 0.3, 1.0 mg/kg) to I/R hearts perfused with PMNs improved coronary flow, and preserved left ventricular developed pressure (LVDP) and + dP/dt max as indices of cardiac contractile function. At 1.0 mg/kg, PS-519 treated hearts exhibited a final LVDP of 98 +/- 3% of initial compared to 52 +/- 8% in I/R hearts receiving only vehicle (P < 0.001). In addition, PS-519 significantly reduced PMN accumulation in the ischemic myocardium from 25.1 +/- 2.1 PMNs/mm2 in untreated hearts to 7.3 PMNs/mm2, and attenuated P-selectin surface expression on coronary vascular endothelium from 7.1 +/- 0.3% to 1.4 +/- 0.2% (P < 0.01). These results provide evidence that PS-519 is a potent and effective cardioprotective agent that inhibits P-selectin leukocyte-endothelial cell interactions and preserves cardiac contractile function and coronary perfusion following myocardial ischemia and reperfusion.

Animals↗
PubMed1999

Reduced expression of CD99 and functional disturbance in anencephalic cortical thymocytes.

In a significant proportion of cases, anencephaly is associated with thymic enlargement, suggesting a possibility that anencephalic fetuses have a functional disturbance in thymocyte differentiation and development. In this report, we demonstrated that CD99 expression was consistently reduced in cortical thymocytes of all anencephalic fetuses. In addition, the CD99-dependent aggregation of immature cortical thymocytes was almost completely impaired and apoptosis of thymocytes was markedly reduced in several cases. These results are in agreement with previous findings that CD99 regulates the aggregation and apoptosis of various types of cells. These data strongly suggest that functional disturbance of thymocytes and thymic hyperplasia are related to the reduced expression of CD99 molecule in anencephalic fetuses.

12E7 Antigen↗
PubMed1999

Recombinant soluble P-selectin glycoprotein ligand-1 protects against myocardial ischemic reperfusion injury in cats.

OBJECTIVE: Neutrophils (PMNs) contribute importantly to the tissue injury associated with ischemia and subsequent reperfusion of a vascular bed. The effects of a recombinant soluble human form of P-selectin glycoprotein ligand-1 (rsPSGL.Ig) on PMN-endothelial cell interactions were investigated in a well established model of feline myocardial-ischemia reperfusion injury. METHODS: Cats were subjected to 90 min of myocardial ischemia followed by 270 min of reperfusion. RESULTS: Administration of rsPSGL.Ig (1 mg/kg) just prior to reperfusion resulted in a significant reduction in myocardial necrosis compared to that in cats administered a low affinity mutant form of rsPSGL.Ig (1 mg/kg) (16 +/- 3 vs. 42 +/- 7% of area-at-risk, P < 0.01). Cardioprotective effects were confirmed by significant (P < 0.05) reductions in plasma creatine kinase activity in cats treated with rsPSGL.Ig. Inhibition of PMN-endothelial cell interactions was evidenced by a significant attenuation in cardiac myeloperoxidase activity (P < 0.01) and reduced PMN adherence to ischemic-reperfused coronary endothelium (P < 0.001). In addition, rsPSGL.Ig treatment significantly (P < 0.01) preserved endothelium-dependent vasorelaxation in ischemic-reperfused coronary arteries. CONCLUSION: These results demonstrate that the administration of a recombinant soluble PSGL-1 reduces myocardial reperfusion injury and preserves vascular endothelial function, which is largely the result of reduced PMN-endothelial cell interactions.

Analysis of Variance↗
PubMed1999

Prevention of ultraviolet radiation-induced suppression of contact hypersensitivity by Aloe vera gel components.

We have recently reported that Aloe vera gel contains small molecular weight immunomodulators, G1C2F1, that restore ultraviolet B (UVB)-suppressed accessory cell function of epidermal Langerhans cells (LC) in vitro. In the present study we evaluated the UVB-protective activity of G1C2F1 in vivo. Exposure of the shaved abdominal skin of mice to 2.4 KJ/m2 of UVB radiation resulted in suppression of contact sensitization through the skin to 41.1%, compared to normal unirradiated skin. Topical application of G1C2F1 immediately after irradiation reduced this suppression significantly. The percentage recovery of UVB-suppressed contact hypersensitivity (CHS) response was 52.3, 77.3, and 86.6% when the irradiated skin was treated once with 0.1, 0.5, and 2.5 mg/ml of G1C2F1-containing cream, respectively. G1C2F1 did not show nonspecific stimulatory activity on CHS response. The present study, together with the previous observation, show that Aloe vera gel contains small molecular weight immunomodulators that prevent UVB-induced immune suppression in the skin by restoration of UVB-induced damages on epidermal LC.

Adjuvants, Immunologic↗
PubMed1999

A novel 5 displacement spin-labeling technique for electron paramagnetic resonance spectroscopy of RNA.

An RNA spin-labeling technique was developed using the well-characterized interaction between the HIV Rev peptide and the Rev response element (RRE) RNA as a model system. Spin-labeled RNA molecules were prepared by incorporating guanosine monophosphorothioate (GMPS) at the 5' end using T7 RNA polymerase and then covalently attaching a thiol-specific nitroxide spin label. Three different constructs of the RRE RNA were made by strategically displacing the 5' end within the native three-dimensional structure. Nitroxide-to-nitroxide distance measurements were made between the specifically bound RNA and peptide using electron paramagnetic resonance (EPR) spectroscopy. The dipolar EPR method can reliably measure distances up to 25 A, the calculation of which is derived from the 1/r3 dependence of the broadening of EPR lines in motionally frozen samples. This RNA-labeling technique, dubbed 5' displacement spin labeling, extends the usefulness of the dipolar EPR method developed for analysis of protein structure. The advantage of this technique is that it is applicable to large RNA systems such as the ribosome, which are difficult to study by other structural methods.

Electron Spin Resonance Spectroscopy↗
PubMed1999

Classification of 'Nocardioides fulvus' IFO 14399 and Nocardioides sp. ATCC 39419 in Kribbella gen. nov., as Kribbella flavida sp. nov. and Kribbella sandramycini sp. nov.

By 16S rDNA sequence analysis, two strains identified previously as members of the genus Nocardioides, namely 'Nocardioides fulvus' IFO 14399 and Nocardioides sp. ATCC 39419, were found to form lines of descent distinct from the genus Nocardioides. Therefore, the two strains were studied taxonomically in detail by phenotypic, particularly chemotaxonomic, characterization, and by phylogenetic analysis including other related taxa. The genomic DNA G + C contents of 'N. fulvus' IFO 14399 and Nocardioides sp. ATCC 39419 are 70 and 68 mol%, respectively. The two strains contain LL-diaminopimelic acid as the diamino acid in their peptidoglycan, together with L-alanine at position 1 of the peptide subunit. The predominant menaquinone found in the two strains is MK-9(H4). The major cellular fatty acid found in the two strains is anteiso-C15:0' which is a minor component of members of the genus Nocardioides. The diagnostic polar lipid of the two strains is phosphatidylcholine. A phylogenetic tree was constructed which showed that the two strains from evolutionary lineages distinct from other LL-diaminopimelic-acid-containing taxa such as, for example, the genus Nocardioides. On the basis of our data, a new genus, Kribbella gen. nov., and two new species, Kribbella flavida gen. nov., sp. nov. and Kribbellla sandramycini gen. nov., sp. nov., are proposed. It is also proposed that the new genus be included in the family Nocardioidaceae.

Actinomycetales↗
PubMed1999

MgATP binding and hydrolysis determinants of NtrC, a bacterial enhancer-binding protein.

When phosphorylated, the dimeric form of nitrogen regulatory protein C (NtrC) of Salmonella typhimurium forms a larger oligomer(s) that can hydrolyze ATP and hence activate transcription by the sigma(54)-holoenzyme form of RNA polymerase. Studies of Mg-nucleoside triphosphate binding using a filter-binding assay indicated that phosphorylation is not required for nucleotide binding but probably controls nucleotide hydrolysis per se. Studies of binding by isothermal titration calorimetry indicated that the apparent K(d) of unphosphorylated NtrC for MgATPgammaS is 100 microM at 25 degrees C, and studies by filter binding indicated that the concentration of MgATP required for half-maximal binding is 130 microM at 37 degrees C. Filter-binding studies with mutant forms of NtrC defective in ATP hydrolysis implicated two regions of its central domain directly in nucleotide binding and three additional regions in hydrolysis. All five are highly conserved among activators of sigma(54)-holoenzyme. Regions implicated in binding are the Walker A motif and the region around residues G355 to R358, which may interact with the nucleotide base. Regions implicated in nucleotide hydrolysis are residues S207 and E208, which have been proposed to lie in a region analogous to the switch I effector region of p21(ras) and other purine nucleotide-binding proteins; residue R294, which may be a catalytic residue; and residue D239, which is the conserved aspartate in the putative Walker B motif. D239 appears to play a role in binding the divalent cation essential for nucleotide hydrolysis. Electron paramagnetic resonance analysis of Mn(2+) binding indicated that the central domain of NtrC does not bind divalent cation strongly in the absence of nucleotide.

Adenosine Triphosphate↗
PubMed1999

High CD99 expression in memory T and B cells in reactive lymph nodes.

We investigated the expression of CD99 in 35 hyperplastic perigastric lymph nodes, which were resected for gastric carcinoma or chronic peptic ulcer. Essentially, all lymphocytes in lymph nodes expressed CD99, but there were two populations with respect to the intensity of CD99 expression--CD99high and CD99low cells. We showed CD99high cells were distributed in paracortical and medullary cords by immunohistochemical study while germinal center cells were CD99low. Using three-color flow cytometric analysis with CD3, CD4, CD8, CD19, CD23, CD45RA, CD45RO, CD69, CD138, IgM, IgD, and IgG, most of CD99high cells were shown to be activated/memory T cells. CD4+CD45RO+ T cells were the subset revealing the highest intensity of CD99 expression while CD4+CD45RA+ T cells were CD99low. Among B cells, IgG+ B cells revealed a higher level of CD99 molecules than IgM+ B cells. These results suggest that CD99 is one of activation-related molecules which are upregulated in recently activated lymphocytes.

12E7 Antigen↗
PubMed1998

Generation of cells with Hodgkin's and Reed-Sternberg phenotype through downregulation of CD99 (Mic2).

Despite the fact that Hodgkin's and Reed-Sternberg (H-RS) cells are morphological hallmarks of Hodgkin's disease (HD), the nature of H-RS cells still remains to be resolved. Here we report that downregulation of CD99 (Mic2) leads to the generation of cells with an H-RS phenotype. IM9 and BJAB B-cell lines that were transfected with an antisense CD99 expression construct showed the morphological and immunological characteristics of H-RS cells such as multinuclearity, expression of CD15, decreased expression of major histocompatibility complex (MHC) class I and CD45RB, and deregulated secretion of cytokines. The reduced expression of CD99 was also confirmed in H-RS cells of patient's lymph nodes and three HD-derived cell lines, L428, KM-H2, and HDLM-2. Moreover, features characteristic of H-RS cells were completely abolished by forced expression of CD99 and by a constitutively active form of Rac, which functions downstream of CD99. We suggest that CD99 molecules play a crucial role in regulating functions and morphology of cells through a Rac-Rho signaling pathway and that the loss of CD99 expression is a significant molecular event to generate H-RS cells.

12E7 Antigen↗
PubMed1998

Direct measurement of small ligand-induced conformational changes in the aspartate chemoreceptor using EPR.

Ligand-binding-induced conformational changes in the Salmonella typhimurium aspartate receptor were studied using spin-labeling electron paramagnetic resonance. Cysteine residues, introduced by site-directed mutagenesis at several positions in the aspartate receptor periplasmic domain, were used to attach covalently a thiol-specific spin label. The electron paramagnetic resonance spectra of these labeled proteins were obtained in the presence and absence of the ligand aspartate, and used to calculate the distance change between spin labels. The results support a model in which transmembrane signaling is executed by a combined movement of alpha helix 4 (which leads into transmembrane domain 2) relative to alpha helix 1 (connected to transmembrane domain 1), as well as a coming together of the two subunits. Ligand binding causes spin labels at position 39 and 179 (within one subunit) to move further from each other and spin labels at position 39 and 39' (between two subunits) to move closer to each other. Both of these changes are very small-less than 2.5 A. No similar changes were detected in any aspartate receptor samples solubilized in detergent, suggesting that the membrane is required for these conformational changes. This is the first case of physically measured ligand-induced changes in a full-length 1-2 transmembrane domain receptor, and the results suggest that very small ligand-induced movements can result in large effects on the activity of downstream proteins.

Aspartic Acid↗
PubMed1998

The mechanism for low-pH-induced clustering of phospholipid vesicles carrying the HA2 ectodomain of influenza hemagglutinin.

Homotrimeric hemagglutinin (HA) is one of the major spike membrane glycoproteins of the influenza virus. Initial pH-triggered conformational changes in the target membrane-interacting HA2 domain are necessary for a preliminary step in membrane fusion. Using spin-labeling electron paramagnetic resonance (EPR) spectroscopy, we examined subsequent pH-dependent changes of a membrane-bound HA2 construct (FHA2, aa 1-127). Residues 91-94, 108-115, 122, and 125 were mutated to cysteine and spin-labeled. Low solvent accessibility and side chain mobility were observed by EPR at positions 91-94, 122, and 125. Spin-labels at residues 108-115 were solvent-exposed and highly mobile, revealing the presence of a flexible loop. These results are consistent with the low-pH crystal structure of a truncated HA2 domain, particularly the unusual kink loop at residues 108-115 [Bullough et al. (1994) Nature (London) 371, 37-43]. Most interestingly, at endosomal pH, spin-labels at 108-115 become immobile and no longer solvent-exposed, and this change is reversible upon reneutralization. However, little change in the EPR line shape and accessibility of spin-labels was observed in other regions. This observation implies that the FHA2 trimers interact reversibly via this specific loop, most likely in an intermolecular fashion. Furthermore, this interaction correlates well with a reversible pH-dependent clustering of FHA2-bearing vesicles evidenced by the reversible increase in turbidity and further confirmed in detail by electron microscopy. The implications of this reversible, pH-dependent interaction between FHA2 trimers are discussed in light of recent fusion models.

Cysteine↗
PubMed1998

Effects of a metalloproteinase that truncates P-selectin glycoprotein ligand on neutrophil-induced cardiac dysfunction in ischemia/reperfusion.

This study was designed to test the effects of polymorphonuclear leukocytes (PMNs) in the presence and absence of a P-selectin blocker, mocarhagin, in provoking cardiac dysfunction in isolated perfused rat hearts following ischemia and reperfusion. Control rat hearts not subjected to ischemia were perfused without blood cells for 80 min. Additional control rat hearts were perfused with 100 x 10(6) PMNs in the presence and absence of 0.2 microgram/ml mocarhagin over a 5-min perfusion followed by a 45-min observation period. No significant reduction in coronary flow (CF), left ventricular developed pressure (LVDP), or the first derivative of LVDP (dP/dt max) was observed at the end of the observation period in any non-ischemic group. Similarly, global ischemia (I) for 20 min followed by 45 min of reperfusion (R) produced no sustained effects on the final recovery of any of these parameters in any group of hearts perfused in the absence of PMNs. I/R hearts perfused with PMNs exhibited decreases of 50-60% in all measurements of cardiac function (P < 0.001). These PMN perfused I/R hearts also exhibited marked increases in cardiac myeloperoxidase (MPO) activity indicating a significant PMN infiltration, and enhanced P-selection expression on the coronary microvascular endothelium. All cardiodynamic effects as well as MPO accumulation and PMN infiltration were attenuated markedly by the metalloproteinase, mocarhagin, which inhibits P-selectin-mediated cell adhesion by cleaving its high-affinity receptor, PSGL-1, present on neutrophils. These results provide evidence that neutrophils provoke post-reperfusion cardiac dysfunction, and that this may be largely due to P-selectin-induced adherence of neutrophils to the endothelium.

Animals↗
PubMed1998

Beneficial effects of N,N,N-trimethylsphingosine following ischemia and reperfusion in the isolated perfused rat heart.

OBJECTIVE: Ischemia followed by reperfusion in the presence of polymorphonuclear leukocytes (PMNs) results in cardiac contractile dysfunction as well as myocardial injury. These deleterious effects are due in large part to endothelial dysfunction leading to an upregulation of cell adhesion molecules and subsequent neutrophil-induced cardiac injury. At physiologically relevant concentrations, N,N,N-trimethylsphingosine (TMS), a synthetic N-methylated sphingosine derivative, has been shown to attenuate leukocyte-endothelial cell interactions. We wanted to test the effects of TMS on neutrophil-mediated cardiac dysfunction in ischemia/reperfusion. METHODS: This study examines the effects of TMS in a neutrophil-dependent isolated perfused rat heart model of ischemia (I) (20 min) and reperfusion (R) (45 min) injury. RESULTS: Administration of TMS (20 micrograms/kg) to I/R hearts perfused with PMNs improved coronary flow and preserved left ventricular developed pressure as an index of cardiac contractile function (95 +/- 5%) in comparison to those I/R hearts receiving only vehicle (60 +/- 7%) (P < 0.001). In addition, TMS significantly reduced PMN accumulation in the ischemic myocardium, as evidenced by an attenuation in cardiac myeloperoxidase activity from 1.12 +/- 0.04 in untreated hearts to 0.01 +/- 0.02 in treated hearts (P < 0.001). However, TMS did not directly stimulate nitric oxide (NO) release from rat vascular endothelium. CONCLUSION: These results provide evidence that TMS is a potent and effective cardioprotective agent that inhibits leukocyte-endothelial cell interactions and preserves cardiac contractile function and coronary perfusion following myocardial ischemia and reperfusion.

Animals↗
PubMed1998

The synaptic SNARE complex is a parallel four-stranded helical bundle.

The heterotrimeric synaptic soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, consisting of the synaptic vesicle-associated membrane protein 2 (VAMP2) and presynaptic plasma membrane proteins SNAP-25 (synaptosome-associated protein of 25,000 Mr) and syntaxin 1A, is a critical component of the exocytotic machinery. We have used spin labeling electron paramagnetic resonance spectroscopy to investigate the structural organization of this complex, particularly the two predicted helical domains contributed by SNAP-25. Our results indicate that the N- and C-terminal domains of SNAP-25 are parallel to each other and to the C-terminal domain of syntaxin 1A. Based on these findings, we propose a parallel four-stranded coiled coil model for the structure of the synaptic SNARE complex.

Animals↗
PubMed1998

De novo design of a peptide which partitions between water and phospholipid bilayers as a monomeric alpha-helix.

To dissect the determinants of protein insertion into membranes, we designed a model peptide which partitions between water and phospholipid bilayers as an alpha-helical monomer. We used a simplex method to optimize the 'a, d hydrophobicity' and 'e, g charge' of a series of five peptides, where 'abcdefg' correspond to the positions in two turns of an alpha-helix. Circular dichroism and analytical ultra-centrifugation experiments showed that the final peptide (helix5) is monomeric and has an alpha-helix content of approximately 89% at 0 degrees C in aqueous solution. In the presence of large unilamellar vesicles (LUVs), helix5 partitions between the aqueous and membranous phases with a partition constant well suited for measurements by electron paramagnetic resonance (EPR) spectroscopy. EPR power saturation experiments with a cysteine-scanning strategy showed that the alpha-helicity of helix5 is conserved upon binding to LUVs and that the alpha-helix binds parallel to the membrane surface with the central axis approximately 5 A below the lipid phosphate groups. Helix5 should be a useful model peptide for studies aimed at dissecting the determinants of the membrane binding of alpha-helices. The simplex-based strategy may be useful in the rational design of proteins when desired structural or partitioning properties cannot be selected or screened from libraries.

Drug Design↗
PubMed1998

The effect of propofol on isolated human pregnant uterine muscle.

BACKGROUND: Propofol is an alternative to thiopental as an intravenous induction agent for cesarean section. Because it has relaxant effects on vascular and other smooth muscles, the authors set out to determine whether propofol has any effect on pregnant human uterine smooth muscle in an isolated preparation. METHODS: Myometrial specimens were excised from 10 parturients undergoing elective cesarean section. The muscle strips were suspended in tissue baths and isometric tension was recorded. After establishment of rhythmic contractions in the buffer solution as a control, propofol (0.5 to 10 microg/ml) in fat emulsion was applied cumulatively to the bath. The effect of the fat emulsion at equivalent concentrations was also examined. RESULTS: Propofol concentrations of 2.7 x 10(-6) M (0.5 microg/ml) and 1.1 x 10(-5) M (2 microg/ml) had no significant effect on the active tension developed by muscle contraction. However, propofol at concentration of 5.5 x 10(-5) M (10 microg/ml) reduced the active tension by 45% (P < 0.02) compared with the control value. The fat emulsion had no effects on the active tension. CONCLUSIONS: These results imply that the decline in the active tension of muscle contraction was most likely caused by propofol and not by the fat emulsion. However, the propofol concentrations needed to produce a significant reduction in the uterine muscle tension appear to be much greater than the free propofol concentrations reported by others during cesarean section.

Adult↗
PubMed1998

The causative organisms of bacterial meningitis in Korean children, 1986-1995.

Bacterial meningitis remains a serious cause of morbidity and mortality in childhood. Epidemiologic investigations have shown variability in disease risks among different populations and races. In Korea, however, basic epidemiologic information on bacterial meningitis in children is limited. The main purpose of this study was to analyze bacteriologically proven meningitis cases in terms of the relative frequency of causative organisms, mortality rate, and age distribution beyond the neonatal period. Data was obtained from the hospital records who had been diagnosed with bacterial meningitis at 13 general or university hospitals from 1986 through 1995. The patients had at least one positive CSF culture for bacteria. Of 140 cases of CSF culture-proven bacterial meningitis, 46.4% was < or =1 year, 62.1% was < or =2 years, 81.4% was < or =5 years cumulatively. Streptococcus pneumoniae was the most common bacteria responsible for 48 (35.0%) of all cases regardless of age, followed by Haemophilus influenzae for 48 (34.3%) and Neisseria meningitidis for 8 (6.4%) patients. The case fatality rate was 20.0%, 17.1%, and 16.7% for N. meningitidis, S. pneumoniae, and H. influenzae, respectively. In conclusion, the most common organisms of culture-proven bacterial meningitis in the last 10 years have been S. pneumoniae, H. influenzae, and N. meningitidis in order of frequency. Further study should be extended to nation-wide epidemiologic evaluation to show the incidence of bacterial meningitis caused by these three important organisms.

Adolescent↗