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Biomedical subjects

S U Kim

Publications and source records attributed to S U Kim.

At least 91 records · Page 5Linked to original sources
PubMed1997

Differences in resistance to herpes simplex virus type 1 (HSV-1) among oligodendroglia derived from different strains of mice are determined after viral adsorption but prior to the expression of immediate early (IE) genes.

The nature of an innate cellular resistance to HSV-1 of cultured murine oligodendrocytes (OLs) in three strains of mice (C57BL/6J, Balb/cByJ and A/J) was investigated. The expression of immediate early (ICP4), early (ICP8) and late (gC) antigens in primary OL cultures was studied using an indirect immunofluorescence (IF) technique. HSV-1 infected OLs from C57BL/6J mice showed no viral antigens at 24 h post infection (p.i.) but rather a marked delay in antigen expression beginning at 60 h p.i. In contrast all three proteins were expressed in A/J OLs at 24 h p.i. while Balb/cByJ OLs showed an intermediate protein expression pattern. These results suggest that the innate cellular resistance to HSV-1 is determined prior to the expression of immediate early viral antigens. To further study these differences, the adsorption capacity between the three mouse strains was compared using dextran purified, [3H]thymidine labelled virus. No differences in HSV-1 adsorption were identified. Results from viral penetration studies approached statistical significance suggesting that penetration may be impaired in C57BL/6J and Balb/cByJ OLs when compared to A/J OLs and is likely fusion independent. The selective differences in HSV-1 resistance mediated by OLs, reflect differences in virus host cell interactions, that likely contribute to differences in mortality, viral spread, and the ability of virus to induce central nervous system (CNS) demyelination.

Adsorption↗
PubMed1997

Induction of micronucleus in NSC19 motoneuron cell line by genotoxic chemicals.

Micronucleus is formed when chromosomal fragments behave independently of remaining chromosomes during the division of cells damaged by genotoxic agents, and the frequency of micronucleus is considered to reflect genotoxic damage to cells. In order to obtain a simple, fas and low-cost assay system to evaluate genotoxicity in the nervous system, we utilize the micronucleus test in a NSC19 mouse neuroblastoma x spinal motoneuron hybrid cell line which was exposed to 4-nitroquinoline-N-oxide (4NQO). There was a significant increase in number of micronuclei in NSC19 cells following 24 hr exposure to 4NQO. Two other genotoxic chemicals, cytosine beta-D-arabinofuranoside (AraC) and ethylmethanesulfate (EMS), similarly increased the frequency of micronucleated cells in a dose-dependent manner. The micronucleus test described in the present study is useful as a short-term genotoxicity evaluation system for cells of nervous system origin.

4-Nitroquinoline-1-oxide↗
PubMed1996

Effects of phorbol ester on intracellular Ca2+ and membrane currents in cultured human microglia.

The effects of protein kinase C (PKC) activation by phorbol ester on intracellular Ca2+ concentration ([Ca2+]i) and membrane currents in human microglia grown in culture were investigated. Treatment of microglia with phorbol myristate acetate (PMA) resulted in a large increase in [Ca2+]i in cells loaded with fura-2. The increased levels of [Ca2+]i were not altered following removal of the phorbol ester. In Ca(2+)-free medium, application of PMA did not increase [Ca2+]i. In addition, PMA application in standard Ca(2+)-solution containing lanthanum (1.8 mM) had no effect on the microglial response to PMA, suggesting that the phorbol ester actions were due to transmembrane influx of Ca2+ but not through voltage-gated Ca2+ channels. Whole-cell patch clamp measurements demonstrated that PMA potentiated an outward K+ current and inhibited an inward rectifier K+ current. This study is the first demonstration that PKC activation by phorbol ester leads to increased intracellular [Ca2+] and changes in membrane currents in human microglia.

Brain↗
PubMed1996

Differential expression of gangliosides and galactolipids in fetal human oligodendrocytes and astrocytes in culture.

The phenotypic expression of gangliosides and galactolipids was investigated using primary cultures of fetal human oligodendrocytes and astrocytes. These glial cells were isolated from fetal human brains of 12-18 weeks' gestation. Expression of gangliosides and galactolipids in oligodendrocytes and astrocytes was investigated by double labeling immunocytochemistry using rabbit antibodies specific for galactocerebroside (GalC, a cell type-specific marker for oligodendrocyte) and glial fibrillary acidic protein (GFAP, a cell type-specific marker for astrocyte) in combination with a panel of mouse monoclonal antibodies which react with specific gangliosides or galactolipids. A considerable number of GalC+ oligodendrocytes expressed intense immunoreactivities specific for GM3 (19%) and GM2 (45%) gangliosides. Approximately 11% of GalC+ oligodendrocytes expressed GM4 immunoreactivity, and smaller numbers of GalC+ oligodendrocytes expressed GD3 (4%), GD2 (1%), GT1b (5%) and A2B5 (3%) immunoreactivities. However, GalC+ oligodendrocytes did not express GM1, GD1a, GT1b or GQ1c. Major populations of GalC+ oligodendrocytes immunolabeled by rabbit anti-GalC antibody reacted with anti-GalC mAb (Ranscht mAb, 81%) or by anti-sulfatide mAb (O4 mAb, 91%). A considerable number of GFAP+ astrocytes expressed intense GM2 (26%) and GD2 (15%) immunoreactivities, while a smaller population expressed intense GM3 (3%), GD3 (6%) and GM4 (4%) immunoreactivities. Weak immunoreactions specific for GD1b, A2B5 and sulfatide were found in less than 1% each of GFAP+ astrocytes, while GFAP+ astrocytes did not express GM1, GD1a, GT1a, GT1b or GQ1b. These results indicate that GM3, GM2 and sulfatide are expressed in a major population of GalC+ oligodendrocytes, while GM3, GM2, GD3, GD2, and GM4 are expressed in a small but distinctive population of GFAP+ astrocytes. Our results suggest that GM4, GM1 and GD3, which are utilized as markers for adult human oligodendrocytes and myelin, are not the major ganglioside constituents in cultured fetal human oligodendrocytes.

Antibodies, Monoclonal↗
PubMed1996

Interleukin-15 gene expression in human astrocytes and microglia in culture.

Interleukin-15 (IL-15) is a novel cytokine that has recently been cloned and expressed. IL-15 interacts with components of the IL-2 receptor and exhibits T-cell stimulating activity similar to that of IL-2. In the present study, we investigated the expression of IL-15 in enriched cultures of human fetal astrocytes and microglia using reverse transcription-polymerase chain reaction (RT-PCR) and immunodetection analysis. Low levels of IL-15 were expressed by unstimulated human fetal astrocytes and microglia, and treatment of astrocytes with interleukin-1 beta (IL-1 beta), interferon-gamma (IFN-gamma), or tumor necrosis factor-alpha (TNF-alpha) increased the expression of IL-15 at both the mRNA and protein level. Treatment of microglia with IFN-gamma and lipopolysaccharide (LPS) similarly increased IL-15 expression in microglia. These findings suggest that IL-15 produced by human fetal astrocytes and microglia may have a role in T cell-mediated immune responses in the human CNS.

Astrocytes↗
PubMed1996

Midkine-like immunoreactivity in extracellular neurofibrillary tangles in brains of patients with parkinsonism-dementia complex of Guam.

Midkine (MK) has been shown to be present in amyloid deposits in Alzheimer's disease (AD). In the present study, expression of midkine was examined immunohistochemically in brains of patients with the parkinsonism-dementia complex of Guam, lytico bodig disease (LB), using an affinity purified antibody to midkine. Positive staining was identified on some extracellular neurofibrillary tangles. The relative prevalence was somewhat less than for beta-amyloid protein (Abeta)-positive extracellular tangles. The results demonstrate that expression of MK and Abeta is not an exclusive feature of amyloid deposits in Alzheimer brain, but is also found in LB brain.

Antibody Specificity↗
PubMed1996

Complement expression on astrocytes and astrocytoma cell lines: failure of complement regulation at the C3 level correlates with very low CD55 expression.

Primary fetal human astrocytes and an astrocytoma cell line, U373-MG, expressed membrane cofactor protein (CD46), CD59, and low levels of decay-accelerating factor (CD55). Astrocyte CD55 was capable of regulating C3 deposition on the cell surface; albeit at a lower level than primary human fibroblasts. Negligible complement-mediated lysis of primary astrocytes and the U373-MG cell line was observed, even when large amount of astrocyte-specific, complement-activating antibodies were bound to the cells. Blocking the function of CD59 on astrocytes resulted in a > 90% cell lysis, while equivalent lysis of fibroblasts could only be achieved with additional blocking of CD55.

Antigens, CD↗
PubMed1996

Production of methyl 3-oxoartemisinate from methyl artemisinate by suspension cell culture of Mentha piperita.

Methyl artemisinate was fed to the suspension cell culture of Mentha piperita. The biotransformation product was isolated and identified as a novel compound, methyl 3-oxoartemisinate. The Mentha cells were apparently capable of extensively oxidizing at the allylic C-3 position, to give rise to an oxo group. The conversion of the fed methyl ester of the acid reached a maximum in 48 h with 5.5% conversion. The physicochemical data of the oxo compound are presented.

Acrylates↗
PubMed1996

The Streptomyces peucetius drrC gene encodes a UvrA-like protein involved in daunorubicin resistance and production.

The drrC gene, cloned from the daunorubicin (DNR)- and doxorubicin-producing strain of Streptomyces peucetius ATCC 29050, encodes a 764-amino-acid protein with a strong sequence similarity to the Escherichia coli and Micrococcus luteus UvrA proteins involved in excision repair of DNA. Expression of drrC was correlated with the timing of DNR production in the growth medium tested and was not dependent on the presence of DNR. Since introduction of drrC into Streptomyces lividans imparted a DNR resistance phenotype, this gene is believed to be a DNR resistance gene. The drrC gene could be disrupted in the non-DNR-producing S. peucetius dnrJ mutant but not in the wild-type strain, and the resulting dnrJ drrC double mutant was significantly more sensitive to DNR in efficiency-of-plating experiments. Expression of drrC in an E. coli uvrA strain conferred significant DNR resistance to this highly DNR-sensitive mutant. However, the DrrC protein did not complement the uvrA mutation to protect the mutant from the lethal effects of UV or mitomycin even though it enhanced the UV resistance of a uvrA+ strain. We speculate that the DrrC protein mediates a novel type of DNR resistance, possibly different from the mechanism of DNR resistance governed by the S. peucetius drrAB genes, which are believed to encode a DNR antiporter.

Adenosine Triphosphatases↗
PubMed1996

Counteracting effect of IFN-beta on IFN-gamma-induced proliferation of human astrocytes in culture.

Recent clinical trials have shown that interferon beta (IFN-beta) is effective in reducing exacerbations in relapsing-remitting MS, while interferon gamma (IFN-gamma) precipitates the relapses. To investigate mechanisms underlying the beneficial effects of IFN-beta and the detrimental effects of IFN-gamma in MS, cell growth-regulatory effects of IFNs were examined in astrocyte-enriched cultures isolated from fetal brains of 12-20 weeks' gestation. Treatment with IFN-gamma (50 or 500 IU ml-1) stimulated significantly the proliferation of astrocytes in 6 out of 9 culture series examined, while IFN-beta (50 or 500 IU ml-1) inhibited the astrocytic proliferation in 3 out of 9 cultures, and IFN-alpha (50 or 500 IU ml-1) did not affect the proliferation IFN-beta and to a lesser degree IFN-alpha reduced the astrocytic proliferation induced by IFN-gamma-treatment in 8 out of 9 culture series. The counteracting effect of IFN-alpha/IFN-beta against IFN-gamma-induced astrocytic proliferation was verified by the DNA content distribution analysis of propidium iodide-labeled cells. The antagonistic effect of IFN-alpha/IFN-beta on the growth-promoting activity of IFN-gamma in cultured human astrocytes suggests that interferons serve as growth regulators of astrocytes at sites of reactive gliosis lesions of MS.

Astrocytes↗
PubMed1996

GERI-BP002-A, novel inhibitor of acyl-CoA: cholesterol acyltransferase produced by Aspergillus fumigatus F93.

A new inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), designated GERI-BP002-A, was isolated from the culture broth of Aspergillus fumigatus F93 by acetone extraction, EtOAc extraction, SiO2 column chromatography and reverse phase HPLC. Spectroscopic analyses of the compound identified bis (2-hydroxy-3-tert-butyl-5-methylphenyl) methane as the structure and its molecular weight and formula to be 340 and C23H32O2, respectively. GERI-BP002-A inhibited ACAT activity by 50% at the concentration of 50 microM in an enzyme assay system using rat liver microsomes.

Aspergillus fumigatus↗
PubMed1996

Methylmercury-induced neurotoxicity in cerebral neuron culture is blocked by antioxidants and NMDA receptor antagonists.

The neurotoxic effects of methylmercury on cerebral neuron cultures derived from neonatal mouse were studied. Exposure of cerebral neurons to methylmercury chloride resulted in significant cell damage and death in a time-dependent manner in cerebral neuron cultures. The methylmercury neurotoxicity was blocked by oxygen radical scavengers such as glutathione, catalase, selenium, and cysteine. Antagonists of the N-methyl-D-aspartate (NMDA) receptor, including MK-801 (a non-competitive NMDA antagonist), D-2-amino-5-phosphonovaleric acid (APV) (a competitive NMDA antagonist), and 7-chlorokynurenic acid (an antagonist at the glycine site associated with the NMDA receptor), similarly blocked methylmercury-induced neurotoxicity in cerebral neuron cultures. These results indicate that both oxygen radicals and excitotixic amino acids are involved in the methylmercury-induced neurotoxicity of cerebral neuron cultures.

Animals↗
PubMed1995

T-cell costimulatory molecules B7-1 (CD80) and B7-2 (CD86) are expressed in human microglia but not in astrocytes in culture.

The B7-1 and B7-2 expressed on the 'professional' antigen-presenting cells (APC) of the lymphoid system are counterreceptors for the T cell antigens CD28/CTLA-4. The B7/CD28 interaction provides a critical costimulatory signal in the decision between functional activation or clonal anergy of T cells. To investigate the biological role of B7 in the central nervous system, constitutive and cytokine-induced expression of B7 was investigated in fetal human astrocytes and microglia in culture. B7-1 expression was minimally detectable in unstimulated microglia but was increased markedly following exposure to IFN-gamma or GM-CSF. B7-2 was expressed at a high level in untreated microglia and upregulated to a small degree by exposure to IFN-gamma or GM-CSF. In contrast, B7-1 and B7-2 were undetectable in astrocytes under unstimulated or IFN-gamma/GM-CSF-treated conditions. These results indicate that both B7-1 and B7-2 are expressed in cultured human microglia but not in astrocytes.

Antigens, CD↗
PubMed1995

Cation and anion unitary ion channel currents in cultured bovine microglia.

The use of excised patches has led to the identification and characterization of two channels not previously reported in microglia. A calcium-dependent K+ channel K(Ca) was activated in inside-out patches obtained from cultured bovine microglia and had a unitary conductance of 240 pS with symmetrical 140 mM K+ across patches. Mean open times of K(Ca) were exponentially dependent on patch potential and were increased with patch depolarization. Channel open probability (Popen) was increased with patch depolarization with either 5 mM or 140 mM internal K+ and was attributable to potential dependent enhancement of both opening frequency and mean open time. Whole cell currents showed the presence of a slowly activating K+ conductance, blocked by external TEA (at 2 mM) and likely the macroscopic correlate of the unitary K(Ca); half-maximal activation of the current occurred at +25 mV. An anion channel (unitary conductance of 325 pS with symmetrical Cl- across patches) was activated in inside-out patches with depolarizing and hyperpolarizing potential steps from 0 mV. Channel activation was not dependent on internal Ca2+. The anion currents inactivated during maintained potential steps with the time constant for inactivation faster with increased patch depolarization. The properties of the K(Ca) and anion channels in microglia membrane may have relevance to cell function in response to neuronal damage in the CNS.

Animals↗
PubMed1995

Differential expression of heat shock protein HSP27 in human neurons and glial cells in culture.

HSP27 expression was investigated in cultured neurons and glial cells isolated from fetal human brains using immunoblotting and immunocytochemistry. Under unstressed conditions, HSP27 was identified at a high level in astrocytes (> 99%), at a low level in neurons (7%), and at a minimally detectable level in microglia (< 1%), whereas it was undetectable in oligodendrocytes. Under these conditions, HSP27 was located in the cytoplasm, fractionated into the Triton X-100-soluble phase, and composed chiefly of the basic isoform (HSP27a). After exposure to heat stress (43 degrees C/90 min), the level of HSP27 expression was not altered in astrocytes but was elevated significantly in neurons (11-21%) and microglia (4-7%) during 8-48 hr postrecovery periods, while it remained undetectable in oligodendrocytes. In addition, various human neural cell lines exhibited differential patterns of HSP27 expression under unstressed and heat-stressed conditions. Following heat shock treatment (45 degrees C/30 min), granular aggregates of HSP27 were identified in the cytoplasm of astrocytes. Under heat-stressed conditions, HSP27 was distributed within the Triton X-100-insoluble fraction associated with an increase in two more acidic isoforms (HSP27b and HSP27c). HSP27 and alpha B-crystallin were coexpressed in astrocytes under unstressed and heat-stressed conditions. When astrocytes were exposed to known HSP27 inducers, hydrogen peroxide and cysteamine reduced the synthesis of HSP27, while estradiol showed no effects. The differential patterns of constitutive and heat-induced expression of HSP27 in cultured human neurons and glial cells suggest that the cellular mechanisms by which HSP27 expression is regulated are different among various cell types in the human central nervous system.

Astrocytes↗
PubMed1995

Constitutive and inducible expression of heat shock protein HSP72 in oligodendrocytes in culture.

The stress-induced HSP72 expression in bovine oligodendrocytes (OL) in culture was investigated following exposure to heat stress, oxidative stress and cytokines by immunoblotting and immunocytochemistry. Under the unstressed condition, HSP72 was expressed in a small number (3%) of OL. After exposure to heat stress, the level of HSP72 expression in OL was elevated significantly and an intense HSP72 immunolabelling was identified in almost all OL, while HSP72 was not induced by exposure to hydrogen peroxide (10 microM) or glucose oxidase (20 mU ml-1). The level of HSP72 expression was not elevated by treatment with interleuken (IL)-1 alpha (10 ng ml-1), IL-1 beta (10 ng ml-1), tumour necrosis factor (TNF)-alpha (200 ng ml-1), or TNF-beta (200 ng ml-1). Our results indicate that HSP72 is upregulated in cultured bovine OL by heat stress but not by oxidative stress or cytokines such as IL-1 and TNF.

Animals↗