Biomedical subjects

S Y Choi

Publications and source records attributed to S Y Choi.

At least 109 records · Page 6Linked to original sources

PubMed1997

Moloney murine leukemia virus long terminal repeat activates monocyte chemotactic protein-1 protein expression and chemotactic activity.

Moloney murine leukemia virus (Mo-MuLV) is a thymotropic and leukemogenic retrovirus which causes T lymphomas. Recently, Mo-MuLV has been shown to trans-activate cellular genes. Monocyte chemoattractant protein-1 (MCP-1) is a chemokine which can promote the migration and diapedesis of monocytes and lymphocytes, as well as inducing metastasis of lymphomas. Here we demonstrate that introduction of Mo-MuLV or the MuLV LTR alone, transiently or stably, into Balb/c-3T3 cells or HeLa cells resulted in 9-11 fold increases in MCP-1 transcripts. This trans-activation of the MCP-1 gene by the Mo-MuLV LTR is independent of the physical location of the MCP-1 gene or of the LTR, occurring whether the LTR or the MCP-1 gene is integrated in the genome or transiently expressed. Immunoblot analysis using an anti-MCP-1 polyclonal antibody showed that the expression of the MuLV LTR in HeLa cells also induced the appearance of the MCP-1 protein. Boyden Chamber analysis demonstrated that the MCP-1 chemotactic activity produced by HeLa cells with an integrated MuLV LTR was elevated by 11 fold and that neutralizing antibody to human MCP-1 abrogated monocyte migration in response to MuLV LTR expression. Promoter deletional analysis showed the LTR responsive cis-acting element in the MCP-1 promoter is located between -141 and -88. Deletion of this region abolished the trans-activation of MCP-1 by the LTR. These LTR-mediated activations of a chemotactic and inflammatory cytokine may be relevant as mechanisms whereby retroviruses which do not contain oncogenes can induce neoplasia.

Animals↗

PubMed1997

Evidence of Hop Japanese pollinosis in Korea: IgE sensitization and identification of allergenic components.

BACKGROUND: Hop Japanese (Hop J) pollens are abundant in the air of Korea during the autumn season. Their significance as a source of allergic sensitization is still unclear. OBJECTIVES: We sought to detect the sensitization rate to Hop J pollen as an inhalant allergen and to identify its allergenic components. METHOD: We carried out skin prick tests with Hop J pollen extract in 1287 patients with respiratory allergy who visited our hospital over the course of 1 year. The serum-specific IgE antibody to Hop J pollen antigen was detected by ELISA, and its binding specificity was confirmed by the ELISA inhibition test. To confirm the respiratory sensitization, bronchoprovocation tests were performed in 16 asthmatic patients sensitive to this pollen. To characterize allergenic components, Hop J pollen extract was analyzed by means of sodium dodecylsulfate-polyacrylamide gel electrophoresis followed by IgE immunoblotting. RESULTS: A positive result on the skin prick test (> or = 2+ of the antigen to histamine ratio) was noted in 79 (6.1%) patients. The serum-specific IgE antibody was detected in 18 (41.9%) patients among 43 positive reactors tested. The ELISA inhibition test with the addition of Hop J pollen extract showed a dose-dependent response. Minimal inhibitions were noted with addition of ragweed and mugwort pollen extracts. Nine asthmatic patients showed significant bronchoconstriction after inhalation of the Hop J pollen extract (five early and four dual asthmatic responders), and all of them had high specific IgE binding. Immunoblot analysis revealed 12 IgE-binding components ranging from 13 to 89 kd. Three bands (13 kd, 74 kd, and 80 kd) were bound to the IgE among the sera tested from more than 50% of the patients. CONCLUSION: We believe that the Hop J pollen should be considered as a relevant allergen during the autumn season and thus included in skin test batteries in Korea. Some patients diagnosed as having "intrinsic" asthma or rhinitis might be sensitized to this pollen and other previously unknown allergens.

Adult↗

PubMed1997

Short-term effects of flurbiprofen and diclofenac on refractive outcome and corneal haze after photorefractive keratectomy.

PURPOSE: To evaluate the short-term effects of topical nonsteroidal anti-inflammatory drugs (NSAIDs) on refractive outcome and corneal haze after excimer laser photorefractive keratectomy (PRK) according to the degree of myopia and to compare the results with those of topical steroids. SETTING: Seoul National University Hospital, Seoul, Korea. METHODS: Patients were divided into two groups: low to moderate myopia (-6.00 diopters [D] or less) and high myopia (greater than 6.00 D). Then, each patient was randomly assigned to one of three drug subgroups for initial management (4 months post-PRK): corticosteroids (fluorometholone 0.1%); flurbiprofen sodium 0.03% (Ocufen); diclofenac sodium 0.1% (Decrol). Follow-up was 6 months. RESULTS: In eyes with low to moderate myopia, the steroid and diclofenac subgroups had significantly different refractions 2 and 4 months postoperatively but no difference at 6 months; subjective haze grading was consistently lower in the steroid subgroup than in the NSAID subgroups (flurbiprofen, diclofenac) after 2 months. In eyes with high myopia, the steroid subgroup had significantly less myopic regression after 3 weeks and lower subjective haze after 2 months than the NSAID subgroups. The steroid subgroup had severe myopic regression or corneal haze less frequently than the NSAID subgroups. CONCLUSION: Topical NSAIDs were less effective than topical steroids in reducing myopic regression and haze after PRK, especially in highly myopic eyes.

Adult↗

PubMed1997

Essential active-site lysine of brain glutamate dehydrogenase isoproteins.

Two soluble forms of bovine brain glutamate dehydrogenase (GDH) isoproteins were inactivated by pyridoxal 5'-phosphate. Spectral evidence is presented to indicate that the inactivation proceeds through Schiff's base formation with amino groups of the enzyme. Sodium borohydride reduction of the pyridoxal 5'-phosphate-inactivated GDH isoproteins produced a stable pyridoxyl enzyme derivative that could not be reactivated by dialysis. The pyridoxyl enzyme was studied through fluorescence spectroscopy. No substrates or coenzymes separately gave complete protection against pyridoxal 5'-phosphate. A combination of 10 mM 2-oxoglutarate with 2 mM NADH, however, gave complete protection against the inactivation. Tryptic peptides of the isoproteins, modified with and without protection, resulted in a selective modification of one lysine. In both GDH isoproteins, the sequences of the peptide containing the phosphopyridoxyllysine were clearly identical to sequences of other GDH species.

Animals↗

PubMed1997

Effects of brazilin on the altered immune functions in the early phase of halothane intoxication of C57BL/6 mice.

To investigate the effects of brazilin on the altered immune functions in the early phase of halothane intoxication in mice, several immune functions were investigated. Halothane was found to alter the immune functions which lead to hepatitis by autoimmune-mediated process. Based on the fact that immunomodulation at an initial step of autoimmune diseases is effective to prevent or control the diseases, in the present study the effects of brazilin on the altered immune functions in the early phase of halothane intoxication of C57BL/6 mice were investigated. By the treatment of halothane, delayed type hypersensitivity (DTH) and mitogen (ConA, LPS) induced proliferation of splenocytes were significantly increased and suppressor cell activity and mixed lymphocyte reaction (MLR) were decreased in C57BL/6 mice. But IgM plaque forming cells (PFCs) were not significantly changed. All the parameters tested were changed in homing patterns by the treatment with brazilin. But brazilin significantly increased IgM PFCs to higher than the normal level.

Animals↗

PubMed1997

Brazilin modulates immune function mainly by augmenting T cell activity in halothane administered mice.

Previously we reported that brazilin, the main principle of Caesalpinia sappan, was able to improve the altered immune functions caused by halothane administration in mice. To elucidate the mechanisms of its immunomodulating activities, the effects of brazilin on the functions of T cells and splenic cellularity were investigated. Brazilin decreased splenic cellularity and IL-2 production which had been augmented in mice treated with halothane (21.5% in olive oil, 10 mmol/kg) for 4 consecutive days whereas the reduced expression of IL-2 receptors by ConA or standard IL-2 was increased by brazilin treatment. These data indicate that halothane induced a dysfunction of T cells resulting in abnormal immune responses and these altered immune functions might be improved mainly by affecting the function of T cells.

Animals↗

PubMed1997

Identification of a cis-acting element in the class I major histocompatibility complex gene promoter responsive to activation by retroviral sequences.

The infection of cells with Moloney murine leukemia virus (M-MuLV) causes an increase in specific cellular gene products, including the major histocompatibility complex (MHC) class I antigens. This upregulation occurs through a transactivation process mediated by the long terminal repeat (LTR) of M-MuLV, and we show here that the gene activation response to the LTR requires at least one specific cis element within the MHC proximal promoter region. Nested deletions of MHC class I H-2Kb gene promoter sequence were subcloned into a chloramphenicol acetyltransferase (CAT) reporter vector and then transiently introduced into BALB/c-3T3 cells expressing M-MuLV or cotransfected into BALB/c-3T3 cells with a vector containing subgenomic portions of the virus, including the LTR. CAT activity assays demonstrated that a minimal H-2Kb gene promoter (-64 to +12) contained elements sufficient for this transactivation. DNase I footprinting assays located a protein-binding site in the region of -64 to -34 bp from the transcriptional start site, and point mutation analysis confirmed the location of this cis-acting element, designated the let response element (LRE), and defined a binding motif. This LRE is distinct from binding sites for currently known transcription factors in the class I MHC gene promoter and is conserved in the promoters of human and murine MHC class I genes. Mutation of the LRE resulted in dramatic reduction in both DNA-protein binding activity in electrophoretic mobility shift assay and in the ability of the mutated promoter to respond to retroviral transactivation. Addition of the LRE to a heterologous promoter conferred the ability to respond to retroviral transactivation.

3T3 Cells↗

PubMed1997

Optic neuropathy associated with ethambutol in Koreans.

Ethambutol is a useful first line antituberculous drug, but can cause significant visual impairment. In order to determine the clinical manifestations of optic neuropathy associated with ethambutol, and the margin of drug safety in Koreans, we investigated ten men and four women, diagnosed between 1995 and 1997 at Seoul Municipal Boramae Hospital as suffering from ethambutol toxicity. After determining their history, including the period during which ethambutol had been administered, and its dose, a complete eye examination was performed, including measurement of best-corrected visual acuity, pupillary examination, color vision, fundus examination and a test of visual field. Ocular ethambutol toxicity was observed at a dose as low as 12.3 mg/kg. Abnormal ophthalmic findings include decreased visual acuity and abnormal visual field, especially in the central scotoma, and abnormal color perception. In conclusion, ethambutol at a low dose can cause optic neuropathy, and for the early detection of this, a color vision test is important.

Antitubercular Agents↗

PubMed1997

Dissociation of LPL and LDL: effects of lipoproteins and anti-apoB antibodies.

We have shown previously that the activity of lipoprotein lipase (LPL), the major enzyme responsible for hydrolysis of triglyceride contained in circulating lipoproteins, is associated with lipoproteins in postheparin plasma. In other studies, microtiter plate assays showed that LPL interaction with low density lipoprotein (LDL) and very low density lipoprotein (VLDL) was decreased by antibodies to apolipoprotein (apo)B. To test whether antibodies to apoB affected LPL-LDL association in solution, two types of assays were performed, gel filtration and coprecipitation. First we showed that LPL activity and immunoreactive mass co-eluted during gel filtration of normal postheparin plasma, approximately with the peak of low density lipoproteins. Then LPL was used for gel filtration studies in the presence and absence of LDL and anti-apoB monoclonal antibodies. LPL association with LDL was diminished by antibodies to the amino-terminal region of apoB; antibodies to the carboxyl-terminal LDL receptor binding region of apoB were less effective. LDL binding to LPL containing heparin-agarose was also disrupted by the amino-terminal antibodies to apoB. To determine the LPL-lipoprotein association in situations in which the distribution of plasma lipoproteins was altered, we studied plasma from two types of subjects with dyslipidemias. The addition of 125I-labeled LPL to type 1 postheparin plasma produced two peaks of radioactivity, one peak eluted in the void volume of the column (with the chylomicrons) and a second peak eluted just prior to the normal elution of low density lipoproteins. In postheparin plasma from an abetalipoproteinemic subject, LPL eluted with HDL. We conclude that LPL associates primarily with apoB-containing lipoproteins. The reason for this appears to be that LPL interacts with the apoB.

Antibodies, Monoclonal↗

PubMed1997

Possibility of chemoprevention by the eradication of Helicobacter pylori: oxidative DNA damage and apoptosis in H. pylori infection.

OBJECTIVES: The purpose of this study was to study the changes of 8-hydroxydeoxyguanosine (8-OH-dG) contents of DNA from human gastric mucosa with or without Helicobacter pylori and the changes of two biomarkers, iNOS and apoptosis, in gastric biopsies obtained before and after the eradication of H. pylori. METHODS: DNA isolated from the biopsied human gastric mucosa was digested to deoxynucleotides by nuclease P1, then with Escherichia coli alkaline phosphatase, and analyzed by HPLC-ECD system. 8-OH-dG content was expressed as the number of residues per 10(5) deoxyguanosine. iNOS immunohistochemical staining was performed with antihuman iNOS antiserum generated in mice at a dilution of 1:500, and in situ apoptosis was detected by in situ terminal deoxyribonucleotide transferase (TdT)-mediated dUTP nick end labeling. Both the density of H. pylori and the degree of inflammation were scored. RESULTS: The 8-OH-dG contents of healthy normal controls with negative H. pylori were 4.31 +/- 2.33 (8-OH-dG/10(5) dG), whereas those of patients with positive H. pylori were 10.40 +/- 7.25. The difference between these two values was statistically significant (p < 0.01). The 8-OH-dG contents were significantly decreased after the eradication of H. pylori (12.22 +/- 2.09 vs. 2.42 +/- 1.22, p < 0.001). After the eradication of H. pylori, both the apoptotic index and the iNOS scores were significantly decreased, compared with those before eradication (3.72 +/- 1.74 vs. 1.17 +/- 1.06 for apoptosis and 10.34 +/- 6.79 vs. 1.43 +/- 1.14 for iNOS, p < 0.001). Statistically significant correlations were observed among apoptotic index, iNOS score, degree of inflammation, and density of H. pylori (p < 0.05). CONCLUSIONS: The increased levels of oxidative DNA damage, increased occurrences of apoptosis, and increased expressions of iNOS suggest mechanistic links between H. pylori infection and gastric carcinogenesis.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1996

Identification of a peptide of the guanosine triphosphate binding site within brain glutamate dehydrogenase isoproteins using 8-azidoguanosine triphosphate.

Photoaffinity labeling with [gamma-32P]8N3GTP (8-azidoguanosine triphosphate) was used to identify the guanine binding peptides of the GTT binding site within two types of glutamate dehydrogenase isoproteins (GDH I and GDH II) isolated from bovine brain. 8N3GTP, without photolysis, mimicked the inhibitory properties of GTP on GDH I and GDH II activities. Saturation of photoinsertion of GDH isoproteins revealed an apparent Kd of 8 microM (GDH I) and 24 microM (GDH II) for [gamma-32P]8N3GTP. Ion exchange and reversed-phase high-performance liquid chromatography (HPLC) were used to isolate photolabel-containing peptides generated with trypsin. This identified a portion of the guanine binding domain within the GTP binding site is the region containing the sequence I-S-G-A-S-E-X-D-I-V-H-S-A-L-A-Y-T-M E-R (GDH I) and I-S-G-A-S-E-X-D-I-V-H-S-G-L-A-Y-T-M-E-R (GDH II). The symbol X indicates a position for which no phenylthiohydantoin-amino acid could be assigned. The missing residue, however, can be designated as a photolabeled lysine since the sequences including the lysine residue in question have a complete identity with those of the other GDH species known. Also, trypsin was unable to cleave the photolabeled peptide at this site. Photolabeling of these peptides was prevented by the presence of GTP during photolysis, while other nucleotides could not reduce the amount of photoinsertion as effectively as GTP. These results demonstrate selectivity of the photoprobe for the GTP binding site and suggest that the peptide identified using the photoprobe is located in the GTP binding domain of the brain GDH isoproteins.

Affinity Labels↗

PubMed1996

The ATP synthase of Trypanosoma brucei is developmentally regulated by an inhibitor peptide.

The Trypanosoma brucei ATP synthase, like those of other organisms, is composed of two moieties, the membrane bound F0 and the catalytic F1 with each of these parts comprised of multiple subunits. In addition, an endogenous inhibitor peptide of the ATP synthase has been identified from a variety of sources. Previous reports have suggested that the Trypanosoma brucei ATPase may not possess such an inhibitor. Recently, we have isolated an inhibitor peptide fraction from the procyclic form of Trypanosoma brucei by modification of a previously published procedure. This fraction is composed of two dominant polypeptides with estimated molecular weights of 14,000 and 12,000 and an additional polypeptide of 15,000 that may or may not be functionally required. Antibodies raised to the smallest polypeptide showed strong cross reactivity with the other two polypeptides, suggesting that they are related. Antibodies to rat liver inhibitor peptide show cross reactivity with the same polypeptides in crude fractions. The inhibitor peptide fraction strongly suppresses the ATPase activity of membrane bound ATPase in a Mg(2+)-dependent manner and is cold and heat stable. Using antibodies to the smallest polypeptide and rat liver inhibitor peptide we have shown in crude extracts from the three experimental life cycle stages of T. brucei that the inhibitor peptide(s) is developmentally regulated to a modest extent. The pattern of regulation is opposite of the pattern seen for the ATP synthase complex. This suggests that the ATP synthase is stringently controlled in T. brucei in a unique way.

Animals↗

PubMed1996

Inactivation of an NADPH-dependent succinic semialdehyde reductase by o-phthalaldehyde.

Incubation of an NADPH-dependent succinic semi-aldehyde reductase from bovine brain with o-phthalaldehyde resulted in a time-dependent loss of enzyme activity. The inactivation followed pseudo first-order kinetics with the second-order rate constant of 28 M(-1) s(-1). The inactivation was prevented by preincubation of the enzymes with NADPH, but not by succinic semialdehyde. There was a linear relationship between isoindole formation and the loss of enzyme activity. Spectrophotometric studies indicated that complete inactivation of the enzyme resulted from the formation of one isoindole derivative per molecule of enzyme, which was formed from the reaction of cysteine and lysine residues with o-phthalaldehyde at or near the enzyme active site.

Animals↗

PubMed1996

Molecular cloning and expression of the hot pepper ERabp1 gene encoding auxin-binding protein.

The 22 kDa auxin-binding proteins in higher plants have received considerable attention as candidates for an auxin receptor. A cDNA clone Ca-ERabp1 of hot pepper (Capsicum annum) was isolated using the oligonucleotides as PCR primers. The cDNA codes for a polypeptide related to the major 22 kDa auxin-binding protein from maize and Arabidopsis ERabp1. The deduced amino acid sequence contains an endoplasmic reticulum retention signal, the KDEL sequence located at the C-terminal end, and has two possible auxin-binding sites, HRHSCE and YDDWSVPHTA conserved sequences. Northern hybridization analysis revealed that the Ca-ERabp1 gene is differentially expressed in total RNA isolated from different organs of a pepper plant, showing the highest level of expression in fruits but barely detectable in leaves and roots.

Amino Acid Sequence↗

PubMed1996

Transcriptional enhancement of tyrosine hydroxylase by prostaglandin E2 in SK-N-BE(2) C cells.

Transcriptional regulation of the rat tyrosine hydroxylase (TH) gene by prostaglandin E2 (PGE2) was investigated in human neuroblastoma SK-N-BE(2)C cells. Prostaglandins increased intracellular cAMP in the presence of 3-isobutyl-1-methylxanthine (IBMX), a cAMP phosphodiesterase inhibitor. Among the prostaglandins tested for their cAMP raising property PGE2 was the most effective. The results suggest that the cells express adenylyl cyclase-linked prostanoid receptors that have a higher affinity for PGE2 than for any other naturally occurring prostaglandin. The treatment of cells with PGE2 increased the TH gene expression approximately 2-fold, even though the cAMP accumulation induced by PGE2 alone was almost negligible. Simultaneous treatment with PGE2 and IBMX enhanced the gene expression concomitantly with a marked accumulation of cAMP. Transient transfection assays with 5' upstream serially deleted constructs of the rat TH gene promoter region fused to the chloramphenicol acetyltransferase (CAT) gene revealed that a cAMP response element (CRE) located at -45 to -38 from the start of the TH gene was essential for the enhancement of TH gene expression by PGE2. Site-directed mutagenesis and specific deletion within the sequence of the CRE motif abolished the transcriptional enhancement by PGE2. In addition, a protein kinase A (PKA) inhibitor, H89, specifically blocked the PGE2 effect on TH gene expression. Northern blot analysis revealed that the increase in TH gene transcription with PGE2 is associated with an elevated TH mRNA level. Gel retardation and competition assays confirmed that the binding of nuclear factors to the CRE site was sequence specific and was augmented by PGE2. Our data indicate that PGE2 enhances transcription of the TH gene mediated by the CRE motif through the activation of PKA. They also suggest that the signal flow from the adenylyl cyclase-linked prostanoid receptor to the nucleus is efficient although cAMP accumulation is not prominent.

Animals↗

PubMed1996

Protective effect of ginseng on radiation-induced DNA double strand breaks and repair in murine lymphocytes.

We have examined the effects of ginseng on the induction and repair of gamma-ray-induced DNA double strand breaks (dsb) using neutral filter elution technique at pH 9.6 in cultured murine spleen lymphocytes. Ginseng water extract 500 micrograms/ml was added to the culture medium either for 48 hours prior to irradiation. Ginseng extract showed protective effect against the formation of dsb when it was treated for 48 hours before 100 Gy gamma-ray-irradiation. While repair was almost completed until 220.2 minutes after irradiation, DNA repair of irradiated cells in the presence of ginseng extract was did not return to the corresponding control levels even after 621.8 minutes. From these data, it could be calculated that ginseng reduced the relative strand scission factor (RSSF) by about 2. Therefore, it could be concluded that ginseng has radioprotective effect against gamma-ray induced DNA dsb and repair in cultured mouse lymphocytes.

Animals↗

PubMed1996

Characterization of Na+ influx mediated by ATP(4-)-activated P2 purinoceptors in PC12 cells.

1. Micromolar levels of extracellular ATP increased cytosolic Na+ concentration ([Na+]i) as well as cytosolic Ca2+ concentration ([Ca2+]i) in PC12 cells. 2. Pretreatment of cells with tetrodotoxin, benzamil or thapsigargin did not alter the ATP-induced Na+ influx. 3. Increased extracellular Mg2+ concentration decreased the ATP effect. Furthermore, when the extracellular ATP pool was treated to contain corresponding calculated concentrations of ATP4-, the increase in [Na+]i stayed linked to the ATP4- concentration rather than to the total ATP concentrations in the stimulants. 4. Extracellular ATP does not create nonselective pores as shown by the fact that ethidium bromide does not enter the cells upon ATP stimulation. 5. Among the tested nucleotides, only adenosine 5'-O-(3-thiotriphosphate), 2-methylthio ATP and 2-chloro ATP also caused Na+ influx. 6. Reactive Blue 2 specifically decreased the ATP effect in a concentration-dependent manner. 7. The results suggest that extracellular ATP triggers Na+ influx through a P2 purinoceptor which is activated by ATP4- in PC12 cells.

Adenosine Triphosphate↗

PubMed1995

Two soluble forms of glutamate dehydrogenase isoproteins from bovine brain.

Two soluble forms of novel glutamate dehydrogenase isoproteins, designated GDH I and GDH II, have been purified from bovine brain. GDH I and GDH II were separated on a hydroxyapatite column and eluted by a step gradient at different phosphate concentrations (30 mM and 50 mM for GDH I and GDH II, respectively). The preparations were homogeneous on SDS/PAGE. GDH I and GDH II showed similarity in their molecular sizes and are composed of six identical subunits having a molecular size of 57,500 Da. Differences between the biochemical properties of GDH I and GDH II, such as N-terminal amino acid sequences of intact and tryptic-digested enzymes, kinetic parameters, optimum pH and heat stability, were extensively examined in both reductive amination of alpha-oxoglutarate and oxidative deamination of glutamate. The different effects of ADP on GDH isoproteins were also studied under various conditions. These results indicate that GDH I and GDH II, isolated from bovine brain, are novel and distinct polypeptides.

Adenosine Diphosphate↗