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Biomedical subjects

K S Choi

Publications and source records attributed to K S Choi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Role of Hck in the pathogenesis of encephalomyocarditis virus-induced diabetes in mice.

Soluble mediators such as interleukin-1beta, tumor necrosis factor alpha (TNF-alpha), and inducible nitric oxide synthase (iNOS) produced from activated macrophages play an important role in the destruction of pancreatic beta cells in mice infected with a low dose of the D variant of encephalomyocarditis (EMC-D) virus. The tyrosine kinase signaling pathway was shown to be involved in EMC-D virus-induced activation of macrophages. This investigation was initiated to determine whether the Src family of kinases plays a role in the activation of macrophages, subsequently resulting in the destruction of beta cells, in mice infected with a low dose of EMC-D virus. We examined the activation of p59/p56(Hck), p55(Fgr), and p56/p53(Lyn) in macrophages from DBA/2 mice infected with the virus. We found that p59/p56(Hck) showed a marked increase in both autophosphorylation and kinase activity at 48 h after infection, whereas p55(Fgr) and p56/p53(Lyn) did not. The p59/p56(Hck) activity was closely correlated with the tyrosine phosphorylation level of Vav. Treatment of EMC-D virus-infected mice with the Src kinase inhibitor, PP2, resulted in the inhibition of p59/p56(Hck) activity and almost complete inhibition of the production of TNF-alpha and iNOS in macrophages and the subsequent prevention of diabetes in mice. On the basis of these observations, we conclude that the Src kinase, p59/p56(Hck), plays an important role in the activation of macrophages and the subsequent production of TNF-alpha and nitric oxide, leading to the destruction of pancreatic beta cells, which results in the development of diabetes in mice infected with a low dose of EMC-D virus.

Animals↗
PubMed2001

Evaluation of pH inhibition effect on activated sludge by the pseudo toxic concentration (CPT) concept model.

It is generally accepted that the inhibition effect of pH on activated sludge follows the non-competitive inhibition kinetics. But the non-competitive inhibition kinetic equation cannot be directly applied to pH inhibition, due to the difficulty in quantification of pH as a term of inhibitor concentration. So, many empirical equations were developed especially for acidic condition to describe pH inhibition effect. In this research, the pseudo toxic concentration (CPT) concept model to quantify pH inhibition effect on activated sludge was proposed and compared with other existed models. Prediction of performance, presented by Prediction Accuracy and Prediction Accuracy Index, showed that the CPT concept model can explain the reduction of the maximum specific growth rate (mu max) more accurately than any other models do at a wide range of pH. The CPT concept model was applicable not only to activated sludge but also to specific microorganism groups, such as nitrifier, less acidophilic species and nitrifying biofilm.

Bacteria↗
PubMed2001

Differential diagnosis of Salmonella gallinarum and S. pullorum using PCR-RELP.

Salmonellosis in poultry of Korea is a significant health problem, which causes substantial economic losses. The most common causative agents of chicken salmonellosis ar S. gallinarum and S. pullorum. Traditional methods used to detect Salmoenella spp. In chicken are tedious, time consuming and confer little guarantee of sensitivity and species specificity. Therefore, a rapid and sensitive method for the differentiation of Salmonella serogroup D was assessed. We first amplified the rfbS genes by PCR and characterized the amplified product by nucleotide sequence analysis. The homology of nucleotide sequence was 99.7% between S. gallinarum and S. pullorum rfbS genes. Further comparisons of the sequences of S. gallinarum, S. gallinarum fied strain, S. pullorum and S. typhi(GenBank Accession No.M29682) showed a homology of 98.3%. The predicted amino acid sequence homology was 97.1%, 97.1% and 97.5%, respectively. Based on this comparison of these nucleotide sequences, we found unique restriction enzyme sites within the rfbS genes of S. gallinarum and S. pullorum. Thus, the PCR products could be further digested with restriction enzymes TfiI and PleI for use in a restriction fragment length polymorphism (RELP) technique. This method can be applied in the differential diagnosis between S. gallinarum and S. pullorum.

Animals↗
PubMed2001

Effect of ethylene glycol monoethyl ether on the spermatogenesis in pubertal and adult rats.

The effects of ethylene glycol monoethyl ether (EGEE) on testicular cell populations in pubertal (5 weeks old) and adult (9 weeks old) male rats were investigated by a flow cytometric method. A total of 50 rats (in number, 25 pubertal and 25 adult rats) was divided into 5 experimental groups including 0 (control), 50, 100, 200, and 400 mg EGEE/kg of body weight. The animals were administered by gavage for 4 weeks. In adult rats, the treatment of EGEE at the dose of 400 mg/kg of body weight decreased significantly the populations of haploid, while it increased those of diploid and tetraploid cells. In pubertal rats, the treatment of EGEE at the dose of 400 mg/kg of body weight caused only minimal changes in the relative percent of testicular cell types. These results suggest that the effects of EGEE on testicular function in pubertal rats appear to be less pronounced than in adult rats.

Animals↗
PubMed2000

Sulfosalts with alkaline earth metals. Centrosymmetric vs acentric interplay in Ba3Sb4.66S10 and Ba2.62Pb1.38Sb4S10 based on the Ba/Pb/Sb ratio. Phases related to arsenosulfide minerals of the rathite group and the novel polysulfide Sr6Sb6S17.

The new compounds, Sr6Sb6S17, Ba2.62Pb1.38Sb4S10, and Ba3Sb4.66S10 were prepared by the molten polychalcogenide salt method. Sr6Sb6S17 crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 8.2871(9) A, b = 15.352(2) A, c = 22.873(3) A, and Z = 4. This compound presents a new structure type composed of [Sb3S7]5- units and trisulfide groups, (S3)2-, held together by Sr2+ ions. The [Sb3S7]5- fragment is formed from three corner-sharing SbS3 trigonal pyramids. The trisulfide groups are separated from the [Sb3S7]5- unit and embedded between the Sr2+ ions. Ba3Sb4.66S10 and Ba2.62Pb1.38Sb4S10 are not isostructural but are closely related to the known mineral sulfosalts of the rathite group. Ba3Sb4.67S10 is monoclinic P2(1)/c with a = 8.955(2) A, b = 8.225(2) A, c = 26.756(5) A, beta = 100.29(3) degrees, and Z = 4. Ba2.62Pb1.38Sb4S10 is monoclinic P2(1) with a = 8.8402(2) A, b = 8.2038(2) A, c = 26.7623(6) A, beta = 99.488(1) degrees, and Z = 4. The Sb atoms are stabilized in SbS3 trigonal pyramids that share corners to build ribbonlike slabs, which are stitched by Ba/Pb atoms to form layers perpendicular to the c-axis. These materials are semiconductors and show optical band gaps of 2.10, 2.14, and 1.64 eV for Sr6Sb6S17, Ba3Sb4.66S10, and Ba2.62Pb1.38Sb4S10, respectively. Raman spectroscopic characterization is reported. Sr6Sb6S17, Ba3Sb4.66S10, and Ba2.62Pb1.38Sb4S10 melt congruently at 729, 770, and 749 degrees C, respectively.

Journal Article↗
PubMed2000

Identification of differentially expressed genes in normal and tumor human gastric tissue.

The search for differentially expressed genes in gastric cancer may help define molecular alterations and molecular diagnosis of gastric cancer. Using the differential display PCR technique, we identified 18 genes that are differentially expressed between normal and tumor human gastric tissues. Their expressions were verified with reverse Northern blot analysis and Northern blot analysis. Oxidative phosphorylation-related genes, antizyme inhibitor of ornithine decarboxylase, protein phosphatase-1beta, 35-kDa peroxisomal membrane protein, and cystic fibrosis transmembrane conductance receptor were highly expressed in tumor tissue, whereas pepsinogen A, Na-K ATPase alpha subunit, nerve growth factor receptor, and alpha-tropomyosin were highly expressed in normal tissue. In addition, 3 unknown genes were found to be differentially expressed in paired gastric tissues. These differentially expressed genes may provide significant opportunities for further understanding of gastric carcinogenesis and the molecular diagnosis of gastric cancer.

DNA, Complementary↗
PubMed2000

Cytokines secreted by lymphokine-activated killer cells induce endogenous nitric oxide synthesis and apoptosis in DLD-1 colon cancer cells.

IL-2-activated killer lymphocytes (LAK cells) secrete inflammatory cytokines such as interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNFalpha) that can induce nitric oxide (NO) synthesis. We evaluated whether LAK cells could activate NO synthesis in human cancer cells. LAK cells and their culture supernatants induced NO synthesis in DLD-1 colon cancer cells in a dose-dependent manner. NO synthesis was inhibited completely by blocking antibodies to IFN-gamma, demonstrating a key role for this LAK cell cytokine in regulating NO synthesis. The addition of TNFalpha antibodies resulted in partial inhibition. Induction of iNOS mRNA and protein expression in DLD-1 cells was detected. Endogenous NO production inhibited DLD-1 cell proliferation and induced apoptosis, processes that were inhibitable by the NO synthase inhibitor N(G)-monomethyl-l-arginine. Our study has identified a novel, non-contact-dependent LAK cell cytotoxic mechanism: induction of growth inhibition and programmed cell death due to endogenous NO synthesis in susceptible human cancer cells.

Antigens, CD↗
PubMed2000

Regulation of plasmin activity by annexin II tetramer.

Annexin II tetramer (AIIt) is a major Ca(2+)-binding protein of the endothelial cell surface which has been shown to stimulate the tissue plasminogen activator (t-PA)-dependent conversion of plasminogen to plasmin. In the present report, we have examined the regulation of plasmin activity by AIIt. The incubation of plasmin with AIIt resulted in a 95% loss in plasmin activity. SDS-PAGE analysis established that AIIt stimulated the autoproteolytic digestion of plasmin heavy and light chains. The kinetics of AIIt-stimulated plasmin autoproteolysis were first-order, suggesting that binding of plasmin to AIIt resulted in the spontaneous autoproteolysis of the bound plasmin. AIIt did not affect the activity of other serine proteases such as t-PA or urokinase-type plasminogen activator. Furthermore, other annexins such as annexin I, II, V, or VI did not stimulate plasmin autoproteolysis. Increasing the concentration of AIIt on the surface of human 293 epithelial cells increased cell-mediated plasmin autoproteolysis. Thus, in addition to stimulating the formation of plasmin, AIIt also promotes plasmin inactivation. These results therefore suggest that AIIt may function to provide the cell surface with a transient pulse of plasmin activity.

Animals↗
PubMed2000

Differential expression of four sweet potato peroxidase genes in response to abscisic acid and ethephon.

Expression of four peroxidase (POD) genes, three anionic PODs (swpa1, swpa2 and swpa3), and one neutral POD (swpn1) isolated from suspension cultures of sweet potato (Ipomoea batatas) were analyzed by measuring the accumulation of transcripts in suspension cultured cells and leaves of sweet potato in response to the stress-related plant hormones abscisic acid (ABA) and ethephon (an ethylene generating chemical). The four genes responded differently to ABA (0.1 mM) and ethephon (0.1 mM) in cultured cells and leaves. In suspension cultures, ABA reduced the expression levels of swpa1, swpa2, and swpn1, but did not affect the level of swpa3. Ethephon strongly increased expression levels of swpa3 and swpn1, and slightly increased the level of swpa1. The expression level of swpa2 was reduced. Expression levels in intact leaves, however, were significantly changed by this treatment. Expression of the swpa1 and swpa2 genes was induced 15 min after ABA treatment, followed by a decrease to a basal level after 3 h. A strong re-expression occurred after 12 h. Expression of the swpa3 and swpn1 genes occurred from 3 to 24 h after treatment. All four genes were differentially expressed 12 h after ethephon treatment. The swpa2 gene was strongly expressed immediately after ethephon treatment. The results indicate that each POD gene is differentially regulated by ABA and ethylene in whole plants and in cultured cells in vitro.

Abscisic Acid↗
PubMed2000

Cisplatin-induced apoptotic cell death in mouse hybrid neurons is blocked by antioxidants through suppression of cisplatin-mediated accumulation of p53 but not of Fas/Fas ligand.

Peripheral neuropathy following cisplatin treatment is a major limiting factor in cisplatin chemotherapy of cancer patients. We investigated the pathomechanism underlying cisplatin neuropathy using a mouse dorsal root ganglion neuron-neuroblastoma hybrid cell line (N18D3) developed in our laboratory. DNA fragmentation, a characteristic feature of apoptosis, was induced in hybrid neurons following treatment with cisplatin. Accumulation of p53, Fas, and Fas ligand (Fas-L) was also demonstrated in these neurons. Preincubation with N-acetylcysteine (NAC), a precursor of glutathione, blocked cisplatin-induced apoptosis completely, whereas Trolox, a vitamin E analogue, blocked it partially. Cisplatin-induced p53 accumulation was suppressed by NAC treatment, whereas p53 accumulation was retarded by Trolox treatment. In contrast, neither NAC nor Trolox showed any inhibitory effect on cisplatin-induced Fas/Fas-L accumulation. These results suggest that the neuroprotective effects of antioxidants against cisplatin-induced neurotoxicity in hybrid neurons are mediated mainly through the inhibition of p53 accumulation but not of Fas/Fas-L accumulation by these antioxidants.

Acetylcysteine↗
PubMed2000

Long-term outcome and growth rate of subtotally resected petroclival meningiomas: experience with 38 cases.

OBJECTIVE: To evaluate the long-term outcome of a subtotally resected residual tumor and to assess its growth rate, we analyzed the records of 38 patients with residual petroclival meningioma. METHODS: Clinical records and radiological findings of 38 cases of petroclival meningioma that were diagnosed and subtotally resected at Seoul National University Hospital between 1981 and 1997 were carefully reviewed. Follow-up imaging studies were reviewed, and Karnofsky performance scale scores at the last follow-up were recorded. The duration of follow-up ranged from 6 to 141 months (mean, 47.5 mo; median, 30 mo). Tumor progression and progression-free survival rates were assessed. The growth rate of a residual tumor was evaluated by measuring the equivalent diameter and the tumor volume serially; the tumor doubling time was calculated, and the predictive factors for determining the growth pattern in residual tumors and the prognosis were analyzed. RESULTS: In 33 (87%) of the 38 patients, Karnofsky performance scale scores at the last follow-up were 80 or above. The median progression-free survival time among patients with subtotally resected tumors was 66 months, and the 5-year progression-free survival rate was 60%. The growth rate of residual tumors was low (volume increase, 4.94 cc/yr; diameter increase, 0.37 cm/yr). The mean tumor doubling time was 8 years. Although there were no significant predictive factors, age and extent of tumor resection seemed to influence the progression-free survival rate. Significant factors affecting the growth rate were age and occurrence of menopause. CONCLUSION: Subtotal resection with or without radiation or radiosurgery should be considered as a suitable treatment option for patients with petroclival meningiomas, especially the elderly, because the growth rate of residual tumors is low.

Adolescent↗
PubMed1999

Cdc2 and Cdk2 kinase activated by transforming growth factor-beta1 trigger apoptosis through the phosphorylation of retinoblastoma protein in FaO hepatoma cells.

The signaling pathway leading to TGF-beta1-induced apoptosis was investigated using a TGF-beta1-sensitive hepatoma cell line, FaO. Cell cycle analysis demonstrated that the accumulation of apoptotic cells was preceded by a progressive decrease of the cell population in the G(1) phase concomitant with a slight increase of the cell population in the G(2)/M phase in response to TGF-beta1. TGF-beta1 induced a transient increase in the expression of Cdc2, cyclin A, cyclin B, and cyclin D1 at an early phase of apoptosis. During TGF-beta1-induced apoptosis, the transient increase in cyclin-dependent kinase (Cdk) activities coincides with a dramatic increase in the hyperphosphorylated forms of RB. Treatment with roscovitine or olomoucine, inhibitors of Cdc2 and Cdk2, blocked TGF-beta1-induced apoptosis by inhibiting RB phosphorylation. Overexpression of Bcl-2 or adenovirus E1B 19K suppressed TGF-beta1-induced apoptosis by blocking the induction of Cdc2 mRNA and the subsequent activation of Cdc2 kinase, whereas activation of Cdk2 was not affected, suggesting that Cdc2 plays a more critical role in TGF-beta1-induced apoptosis. In conclusion, we present the evidence that Cdc2 and Cdk2 kinase activity transiently induced by TGF-beta1 phosphorylates RB as a physiological target in FaO cells and that RB hyperphosphorylation may trigger abrupt cell cycle progression, leading to irreversible cell death.

Animals↗
PubMed1999

A new autoantigen reactive with prediabetic nonobese diabetic mice sera.

The identification and characterization of new autoantigens would widen the knowledge of the pathogenic mechanism of insulin dependent diabetes mellitus. Screening of lambda gt11 mouse insulinoma (MIN6N8a) cell cDNA library with prediabetic nonobese diabetic (NOD) mice sera resulted in the isolation of a strong positive clone, named the clone 3-5, of 1579 nucleotides without a poly A region. After 5'-rapid amplification of the cDNA end (RACE), complete nucleotide sequence of the clone 3-5 gene consisting of 2231 nucleotides showed that the 3-5 gene had the theoretical open reading frame of 634 amino acids. However, the real antigenic protein of the clone 3-5 was only 21 amino acids long encoded by only 63 nucleotides. The 21 amino acids were expressed as a fusion protein in E. coli and purified by affinity chromatography. The purified 3-5 recombinant protein was examined for its reactivity with prediabetic NOD mice sera by immunoblotting. The only non-denatured form of the 3-5 protein showed a binding reactivity with NOD mice sera, demonstrating that the conformational epitope of 3-5 protein was important for antibody recognition. The prevalence of autoantibody reactive to the 3-5 protein was about 78% (14/18) and 46% (11/24) in prediabetic and acute diabetic NOD mice sera, respectively. However, the sera from other mouse strains such as BALB/c, ICR, C57BL/6, SJL/J, and NOD/SCID did not show a positive reactivity to the 3-5 protein, which indicated that immune reactivity against the 3-5 protein was autoimmune diabetic mouse-specific.

Amino Acid Sequence↗
PubMed1999

Production and characterization of monoclonal antibodies to porcine brain pyridoxal kinase.

Six monoclonal antibodies that recognize porcine brain pyridoxal kinase have been selected and designated as PK67, PK86, PK91, PK144, PK252 and PK275. A total of six monoclonal antibodies recognizing different epitopes of the enzyme were obtained, of which four inhibited the enzyme activity. When total proteins of porcine brain homogenate separated by SDS-PAGE were subjected to monoclonal antibodies, a single reactive protein band of molecular weight 39 kDa which comigrated with purified porcine pyridoxal kinase was detected. Using the anti-pyridoxal kinase antibodies as probes, the cross reactivities of brain pyridoxal kinase from human and other mammalian tissues and from avian sources were also investigated. Among human and all animal tissues tested, immunoreactive bands on Western blots appeared to have the same molecular mass of 39 kDa. These results indicate that mammalian brains contain only one major type of immunologically similar pyridoxal kinase, although some properties of the enzymes reported previously differed from one another.

Animals↗
PubMed1999

Hepatitis B prevalence and infection control among dental health care workers in a community in South Korea.

OBJECTIVES: The objectives of this study were to investigate the prevalence of hepatitis B vaccine and use of infection control procedures by dental health care workers in Taegu, South Korea. METHODS: Information was obtained with a mailed questionnaire sent to 300 private dental practices. Surveys were received from 177 dentists, 104 dental hygienists, and 46 dental assistants. All dental health care workers were asked to donate a blood sample for analysis of hepatitis B surface antigen (HBsAg) and antibody (anti-HBs). RESULTS: Vaccination against hepatitis B virus was reported by 63 percent of the respondents. About 40 percent of all participants answered that they were anti-HBs positive, while another 43 percent did not know their status. About 89 percent of dentists reported that they wore a mask with all patients, while hygienists (13.6%) and assistants (13.0%) were less likely to do so. Reported use of gloves (4.5%) and protective eyewear (14%) with all patients was extremely low in every group. Among the 56 dentists who were tested for HBV markers, 23 did not receive the vaccine against hepatitis B, and 13 percent (3 of 23) were positive for HBsAg as carriers. CONCLUSIONS: About 37 percent (120 of 327) of dental health care workers surveyed in this study in Korea did not receive the vaccine against HBV infection. Basic barrier techniques to prevent cross-contamination were not being used consistently. Nationwide guidelines for barrier techniques and hepatitis vaccinations should be developed and disseminated to dental personnel.

Chi-Square Distribution↗
PubMed1998

The p11 subunit of the annexin II tetramer plays a key role in the stimulation of t-PA-dependent plasminogen activation.

Annexin II tetramer (AIIt) is an important endothelial cell surface protein receptor for plasminogen and t-PA. AIIt, a heterotetramer, is composed of two p36 subunits (called annexin II) and two p11 subunits. In this report, we have compared the ability of the isolated p36 and p11 subunits to stimulate t-PA-dependent [Glu]plasminogen activation. The fluid-phase recombinant p11 subunit stimulated the rate of t-PA-dependent activation of [Glu]plasminogen about 46-fold compared to an approximate stimulation of 2-fold by the recombinant p36 subunit and 77-fold by recombinant AIIt. The stimulation of t-PA-dependent activation of [Glu]plasminogen by the p11 subunit was Ca2+-independent and inhibited by epsilon-aminocaproic acid. [Glu]Plasminogen bound to a p11 subunit affinity column and could be eluted with epsilon-aminocaproic acid. Both AIIt and the p11 subunit protected t-PA and plasmin from inactivation by PAI-1 and alpha2-antiplasmin, respectively. A peptide to the C terminus of the p11 subunit (85-Y-F-V-V-H-M-K-Q-K-G-K-K-96) inhibited the p11-dependent stimulation of t-PA-dependent plasminogen activation. In addition, a deletion mutant of the p11 subunit, missing the last two C-terminal lysine residues, retained only about 15% of the activity of the wild-type p11 subunit. Similarly, a mutant AIIt composed of the wild-type p36 subunit and the p11 subunit deletion mutant possessed about 12% of the wild-type activity. These results, therefore, suggest that the C-terminal lysine residues of the p11 subunit bind plasminogen and participate in the stimulation of t-PA-dependent activation of plasminogen by AIIt.

Aminocaproic Acid↗
PubMed1998

Flow cytometric measurement of benzo[a]pyrene-diol-epoxide-DNA adducts in normal human peripheral lymphocytes and cultured human lung cancer cells.

DNA adducts are mainly detected by 32P-postlabeling and enzyme-linked immunosorbent assays. We have established a method for detection of benzo[a]pyrene-diol-epoxide (BPDE)-DNA adducts by flow cytometry, and have clarified the effects of the DNA adducts on cell-cycle progression and the relationship between cell-cycle phases and DNA adduct formation, using human peripheral lymphocytes and three human lung cancer cell lines. We measured the BPDE-DNA adduct levels in both lymphocytes and cancer cells by isolating nuclei, using a nuclear isolation buffer containing Triton X-100 and staining with a BPDE-DNA-specific monoclonal antibody and biotin-streptavidin fluorescein conjugates. BPDE did not affect cell-cycle progression in human peripheral lymphocytes. However, in human lung cancer cells exposed to > 1 microg/ml BPDE, accumulation of cells in the S phase was seen. Cells with DNA content greater than G2M (aneuploid cells) or cells with less than G1 DNA content (apoptotic cells) increased gradually with exposure to increasing BPDE concentrations, suggesting that BPDE may affect cell-cycle progression through binding to DNA. Thus, the measurement of DNA adducts by flow cytometry may provide new insights into carcinogenesis.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗