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Biomedical subjects

S H Kang

Publications and source records attributed to S H Kang.

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

Up-regulation of human telomerase catalytic subunit during gastric carcinogenesis.

BACKGROUND: Telomerase activation is thought to be essential for the stabilization of telomere length, through which immortalization and oncogenesis are achieved, but little is known about the regulation of telomerase in human gastric carcinoma cells. METHODS: A total of 27 primary gastric tumors, 29 cases of intestinal metaplasia, and 30 cases of normal mucosa, as well as 8 gastric carcinoma cell lines, were examined for the relation between telomerase activation and gastric carcinogenesis. Telomerase activity was detected by telomeric repeat amplification protocol, and the expression of each telomerase subunit was evaluated by Northern blot analysis or reverse transcriptase--polymerase chain reaction. RESULTS: Telomerase activity was found in all 8 gastric carcinoma cell lines and in 25 of 27 gastric carcinoma tissue samples (93%), and weakly observed in 11 of 29 gastric intestinal metaplasia samples (38%). None of 30 normal gastric tissue samples displayed telomerase activity. The mRNA expression of human telomerase catalytic subunit (hTERT) was up-regulated in 26 of 26 tumor tissue samples (100%) and in 19 of 24 intestinal metaplasia (79%) in which telomerase activity was weak or negative. Normal gastric mucosa expressed the telomerase gene, albeit at low levels. In contrast to hTERT, human telomerase RNA component and human telomerase-associated protein expression did not parallel telomerase activity, which was independent of tumor stage and histology. CONCLUSIONS: hTERT expression is up-regulated during an early stage in the carcinogenic process, and telomerase activation may be a critical step in gastric carcinogenesis.

Adult↗
PubMed1999

The effect of external electron beam on neointima in rat carotid artery injury model.

PURPOSE: Endovascular irradiation with either a gamma or a beta source has shown to reduce neointimal proliferation. However, the effect of external-beam radiation on neointimal hyperplasia is controversial. The objective of this study was to determine the effect of external-beam irradiation with different doses on neointimal hyperplasia in the rat carotid artery injury model. METHODS AND MATERIALS: Twenty-seven Sprague-Dawley rats underwent endothelial denudation injury by 2F Fogarty balloons on carotid artery. Immediately after the injury, rats were irradiated externally using 6-MeV electrons. Rats were grouped according to the radiation doses, 0 Gy as controls (n = 5), 5 Gy (n = 5), 10 Gy (n = 5), 15 Gy (n = 6), and 20 Gy (n = 6). Then, rats were sacrificed after 2 weeks and the carotid arteries were perfusion-fixed in paraformaldehyde. External elastic lamina (EEL) area, lumen area, maximal intimal thickness (MIT), and intimal area (IA) of the injured segments were measured on the basis of histomorphometry. RESULTS: In EEL and lumen area, there was no statistically significant difference between the irradiated groups and the controls. In MIT and IA, low-dose radiation (5 Gy and 10 Gy) did not induce any significant reduction. High-dose radiation (15 Gy and 20 Gy), however, reduced MIT and IA significantly. CONCLUSION: External electron beam reduced the intimal area, and the inhibition of neointimal proliferation was dependent upon radiation doses. This study suggests that the minimal effective dose for the inhibition of neointimal hyperplasia following denudation injury in the rat carotid model is between 10 Gy and 15 Gy.

Animals↗
PubMed1999

Truncation of the TGF-beta type II receptor gene results in insensitivity to TGF-beta in human gastric cancer cells.

The transforming growth factor-beta (TGF-beta receptor system has been implicated in the development of resistance to the growth-inhibitory effects of TGF-beta. It has been reported that resistance to TGF-beta correlates with inactivation of the TGF-beta type II receptor (RII). In the present report, we examine the genetic changes in the TGF-beta RII gene of human gastric cancer cell lines, SNU-5 and SNU-668, which we had previously reported to express truncated TGF-beta RII transcripts. By independent PCR and Southern hybridization analysis of genomic DNA, we found that the genomic sequence of TGF-beta RII is truncated after exon 2 in SNU-5 and after exon 3 in SNU-668. This was confirmed by sequencing the TGF-beta RII cDNA cloned from a SNU-5 cDNA library. Predicted TGF-beta RII protein of SNU-5 cells based on sequencing data contains only a part of extracellular domain of TGF-beta RII. We demonstrate that cotransfection of 3TP-Lux and wild type TGF-beta RII restores the TGF-beta responsiveness in SNU-5 cells, suggesting that genetic changes in the TGF-beta RII gene of SNU-5 cells are responsible for the loss of sensitivity to TGF-beta. This is the first report demonstrating that truncation of the TGF-beta RII gene is an alternative mechanism to inactivate the TGF-beta signal transduction pathways.

Amino Acid Sequence↗
PubMed1999

Rapid induction of p21WAF1 but delayed down-regulation of Cdc25A in the TGF-beta-induced cell cycle arrest of gastric carcinoma cells.

Transforming growth factor-beta (TGF-beta) is a multifunctional polypeptide that inhibits cellular proliferation in most epithelial cells. cdk4 and several cyclin-dependent kinase (cdk) inhibitors (p15INK4B, p21WAF1/Cip1 and p27Kip1) have been implicated in the TGF-beta-induced cell cycle arrest. More recently, down-regulation of Cdc25A, a cdk activator, was additionally suggested as a mechanism underlying growth inhibition by TGF-beta. The existence of diverse cellular mediators of TGF-beta, however, raises the question of whether their involvement might occur in a redundant manner or coordinately in a certain cell type. Using two TGF-beta-sensitive gastric carcinoma cell lines (SNU-16 and -620), we addressed the contributory roles of several cdk inhibitors, and of cdk4 and Cdc25A, in TGF-beta-induced cell cycle arrest by comparing their temporal expression pattern in response to TGF-beta. Among the cdk inhibitors examined, p21 mRNA was most rapidly (in less than 1 h) and prominently induced by TGF-beta. In contrast, p15 mRNA was more slowly induced than p21 in SNU-620 cells, and not expressed in SNU-16 cells harbouring homozygous deletion of p15. Western blotting results confirmed the rapid increase of p21, while opposite patterns of p27 expression were observed in the two cell lines. The down-regulation of Cdc25A mRNA occurred, but was more delayed than that of p15 or p21. Until G1 arrest was established, changes in the protein levels of both Cdc25A and cdk4 were marginal. Co-immunoprecipitation with anti-cdk4 antibody showed that induced p21 associates with cdk4 and that its kinase activity is reduced by TGF-beta, which kinetically correlates closely with G1 arrest following TGF-beta treatment of both cell lines. These results suggest that in certain human epithelial cells, p21 may play an early role in TGF-beta-induced cell cycle arrest, and its cooperation with other cdk inhibitors is different depending on cell type. Delayed down-regulation of Cdc25A and cdk4 may contribute to cell adaptation to the quiescent state in the two gastric carcinoma cell lines studied.

Cell Cycle↗
PubMed1999

(-)-Epiafzelechin: cyclooxygenase-1 inhibitor and anti-inflammatory agent from aerial parts of Celastrus orbiculatus.

An inhibitor of cyclooxygenase (COX)-1 activity of prostaglandin H2 synthase was isolated from aerial parts of Celastrus orbiculatus Thunb. (Celastraceae), an oriental folk medicine for rheumatoid arthritis by activity-guided column chromatographic methods. The COX inhibitor was identified as (-)-epiafzelechin, a member of flavan-3-ols by the structural analysis with HR-EI-mass, 1H-NMR and 13C-NMR spectral data. The compound exhibited a dose-dependent inhibition on the COX activity with an IC50 value of 15 microM. (-)-Epiafzelechin exhibited about 3-fold weaker inhibitory potency on the enzyme activity than indomethacin as a positive control. (-)-Epiafzelechin exhibited significant anti-inflammatory activity on carrageenin-induced mouse paw edema when the compound (100 mg/kg) was orally administrated at 1 h before carrageenin treatment.

Animals↗
PubMed1999

Delivery of antisense oligonucleotides and plasmid DNA with various carrier agents.

A series of cationic nucleic acid carriers was evaluated for their ability to deliver pLuc plasmid DNA or a 2'-O-methyl-oligoribonucleoside phosphorothioate, ON-705. Oligonucleotide delivery and its antisense function were assayed by a recently developed assay based on alternative splicing of modified luciferase pre-mRNA (Kang et al., 1998). This assay scores only the nuclear and sequence-specific antisense activity of the oligonucleotides. The results show that the efficiencies of delivery of plasmid DNA and oligonucleotides by the tested carriers, with the exception of Exgene and Lipofectamine, differed markedly. The efficiency of the delivery of ON-705 oligonucleotide was reduced by 70%-90% for all carriers, except Effectene, in culture media containing 8% fetal bovine serum. Interestingly, the efficiency of delivery of the ON-705-Effectene complex increased with serum concentrations of up to 30%.

Alternative Splicing↗
PubMed1999

von Willebrand disease with G4022A mutation (vWd Sungnam): a case report.

A 10-year-old male patient affected by type 2 von Willebrand disease (vWD) and his family members were investigated by hemostatic and molecular genetic studies. The propositus, who experienced frequent bleeding episodes, was characterized by a normal level of von Willebrand factor (vWF) antigen (54%), reduced vWF ristocetin cofactor activity (5%), decreased factor VIII clotting activity (25%) and absent high molecular weight multimers in the plasma. An exon 28 fragment coding for the A1 and A2 domains was amplified by polymerase chain reaction and sequenced. We found a heterozygous mutation (G4022A), producing an additional PstI restriction site, which resulted in the substitution of Arg578Gln. Family studies, including the parents and a brother, were negative for this mutation and vWF abnormalities were not observed. We confirmed that G to A mutation in the region of the platelet glycoprotein Ib binding domain of vWF causes the qualitative type 2 defect in von Willebrand disease.

Alanine↗
PubMed1998

Increased MAPK activity and MKP-1 overexpression in human gastric adenocarcinoma.

Mitogen-activated protein kinase (MAPK) has been known to play a critical role in the regulation of the carcinogenesis in human cancers. In an effort to understand the functional role of the MAPK in the carcinogenesis of human gastric tissues, we examined the changes of MAPK levels in human gastric adenocarcinoma. We found that increased MAPK activity was accompanied by overexpression of mitogen-activated protein kinase phosphatase-1 (MKP-1), suggesting that signaling pathways leading to the activation of MAPK and the induction of MKP-1 expression are associated with carcinogenesis of human gastric adenocarcinoma.

Adenocarcinoma↗
PubMed1998

Genetic integrity of transforming growth factor beta (TGF-beta) receptors in cervical carcinoma cell lines: loss of growth sensitivity but conserved transcriptional response to TGF-beta.

Transforming growth factor beta (TGF-beta) exerts an inhibitory effect on the growth of most epithelial cell types, and the loss of responsiveness to this growth inhibition has been implicated in the development of a variety of human cancers. The genetic alteration of TGF-beta receptors is known to play a critical role in this escape from growth regulation. We asked whether there is a correlation between TGF-beta sensitivity and the genetic status of TGF-beta type I and type II receptors (RI and RII, respectively) in human cervical carcinoma cell lines. Among 8 cell lines examined, 3 (ME-180, C-33A and HeLaS3) showed resistance to TGF-beta and 3 (SiHa, CaSki and HeLa229) showed minimal response to the growth inhibitory effect of TGF-beta; the other cell lines (HeLa and HT-3) were sensitive. Northern blot analysis revealed that the RII mRNA was not expressed in 2 TGF-beta-resistant cell lines (ME-180 and C-33A) but was expressed in the other cell lines. Southern blot analysis of RI and RII revealed a homozygous deletion of the entire TGF-beta RII gene in the cell line ME-180. We then asked whether the other TGF-beta-resistant or refractory cell lines had microsatellite instability and/or poly-adenine tract mutations of RII. We also checked for point mutations in the individual exons of the entire RII using polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP). Although C-33A exhibited poly-adenine microsatellite instability, its RII gene showed no signs of mutation. The molecular integrity of the TGF-beta, receptors in all cell lines, except ME-180 and C-33A, could be confirmed by examining the distinct transcriptional induction of plasminogen activator inhibitor-1 (PAI-1), p21(WAF1/CIP1) and, in some cases, the accompanying downregulation of c-myc in response to TGF-beta. Our observations, taken together, indicate that inactivation of the RII contributes to the resistance to TGF-beta of some cervical carcinoma cell lines. Loss of or attenuated sensitivity to TGF-beta growth inhibition in other cells may be attributed to the disruption of distal components in the TGF-beta signal pathway, but not to the receptor system.

Blotting, Southern↗
PubMed1998

High-performance liquid chromatography with a column-switching system and capillary electrophoresis for the determination of ibuprofen in plasma.

Quantitative aspects of high-performance liquid chromatography with a column-switching system (CSS-HPLC) and capillary electrophoresis (CE) were investigated for the determination of ibuprofen in plasma. For CSS-HPLC, 100 microl of plasma was directly injected onto the column system for the three separation steps: (1) deproteinization and fractionation of plasma samples with a polymer-coated mixed-function phase column, (2) concentration with an intermediate column and (3) final separation with a main column. For CE, a mixture of 50 microl of plasma and 1 ml of acetonitrile was centrifuged and the supernatant was introduced onto the capillary (66 cmX50 microm I.D.; 62 cm to detector) at 20 degrees C. Run buffer was 250 mM sodium borate buffer (pH 8.5) and applied electric field was 379 V cm(-1). Linear dynamic ranges were 0.1-250 microg ml(-1) in CSS-HPLC and 1-1000 microg ml(-1) in CE. Intra-day and inter-day coefficients of variation were less than 5.6% and 6.5% for CSS-HPLC, 6.3% and 6.5% for CE, respectively. The limits of detection (S/N=3) for CSS-HPLC and CE were 25 ng ml(-1) and 300 ng ml(-1), respectively. CSS-HPLC was superior in simplicity and sensitivity, while CE was better in efficiency, rapidity, and cost.

Animals↗
PubMed1998

Up-regulation of luciferase gene expression with antisense oligonucleotides: implications and applications in functional assay development.

HeLa Tet-Off cells were transfected transiently as well as stably with a recombinant plasmid (pLuc/705) carrying the luciferase gene interrupted by a mutated human beta-globin intron 2 (IVS2-705). The mutation in the intron causes aberrant splicing of luciferase pre-mRNA, preventing translation of luciferase. However, treatment of the cells with a 2'-O-methyl-oligoribonucleotide targeted to the aberrant splice sites induces correct splicing, restoring luciferase activity. The effects are sequence-specific, depend on the concentration of the oligonucleotide, and can be modulated by the pretreatment of the cell line, Luc/705, with tetracycline. Thus, the cell line provides, among others, a novel functional assay system superior to other procedures that are based on protein down-regulation. In particular, the system would be ideal in assessing the cellular delivery efficiency of antisense oligonucleotides.

Alternative Splicing↗
PubMed1998

Oxyresveratrol as the potent inhibitor on dopa oxidase activity of mushroom tyrosinase.

Oxyresveratrol (2,3',4,5'-tetrahydroxystilbene), a naturally occurring compound particularly found in Morus alba L., exhibited a potent inhibitory effect on dopa oxidase activity of tyrosinase which catalyzes rate-limiting steps of melanin biosynthesis. Oxyresveratrol with 0.3 to 5 microM exhibited potent and dose-dependent inhibitions (25 to 84%) on the enzyme activity, where 50% of inhibition was shown at the concentration of about 1 microM. Oxyresveratrol seemed to inhibit the dopa oxidase activity of tyrosinase via a noncompetitive manner (Ki = 9.1 x 10(-7) M) when L-dopa was used as a substrate. Oxyresveratrol exhibited about a 150-fold more potent inhibitory effect than resveratrol (3,4',5-trihydroxystilbene). The more hydroxy groups of the hydroxystilbenes are methylated to be methoxy groups, while the less inhibitory effects on the enzyme activity were exhibited. The results indicate that both the number and positions of hydroxy groups in oxyresveratrol seem to play a critical role in exerting the inhibitory effect on dopa oxidase activity of mushroom tyrosinase.

Basidiomycota↗
PubMed1998

Purification and characterization of a male-specific protein in the hemolymph of the wax moth, Galleria mellonella L.

A male-specific protein (MSP) present only in males was identified from the hemolymph of the wax moth, Galleria mellonella L., by polyacrylamide gel electrophoresis (PAGE) and purified by anion-exchange chromatography. MSP has a native molecular mass of 55 kDa and consists of two 27-kDa subunits. An isoelectric point of MSP was measured to be approximately 5.8. MSP is a glycoprotein that contains 1.7% carbohydrate. The compositional analysis of carbohydrate component indicated a predominance of fructose and glucose. MSP also contains large amounts of asparagine, aspartic acid, glutamine, glutamic acid, and lysine but small amounts of tyrosine, methionine, and tryptophan. Western blot analysis of the hemolymph of each developmental stage indicated that MSP is present in the hemolymph of 8-day-old pupa and adult. Also, results from Western blotting indicated that MSP is not present in the tissues of larvae and of female adults but appears in the fat body of male pupae and adult and testis of adult. The fat body and testis of male pupae and adult were cultured in vitro to trace the place and time of MSP synthesis. The fat body began to synthesize MSP in late pupae and showed active synthesis during the adult stage. The distribution of MSP in the testis was observed by electron microscopic immunogold labeling, using the antibody against MSP. MSP is present between the germinal cysts and is taken up through the basal surface of the seminiferous tubular epithelium.

Amino Acids↗
PubMed1998

Subcutaneous phaeohyphomycosis caused by Exophiala jeanselmei in a patient with advanced tuberculosis.

We report a case of subcutaneous phaeohyphomycosis due to Exophiala jeanselmei in an 84-year-old Korean farmer suffering from pulmonary tuberculosis. He presented with six subcutaneous, fluctuant abscesses on the left distal forearm and wrist. Subcutaneous infections by E. jeanselmei mostly present as a solitary cyst or abscess on an extremity. The present case showed localized multiple abscesses suggesting metastatic tuberculous abscesses or other pyogenic bacterial infections.

Aged↗
PubMed1998

Alpha-viniferin: a prostaglandin H2 synthase inhibitor from root of Carex humilis.

An inhibitor on cyclooxygenase activity of prostaglandin H2 synthase was purified from the root of Carex humilis Leyss (Cyperaceae) by a variety of column chromatographic methods. As a result of the structure analysis by FAB-mass, 1H-NMR, and 13C-NMR spectral data, the active compound was identified as (+)-alpha-viniferin, an oligomeric stilbene characterized originally from Caragana chamlagu Lamarck (Leguminosae). (+)-alpha-Viniferin exhibited a dose-dependent inhibition on cyclooxygenase activity, where 50% of inhibition (IC50) was shown at a final concentration of about 7 microM. Resveratrol, a putative building block of oligomeric stilbenes, also inhibited the cyclooxygenase activity. The inhibitory potency of (+)-alpha-viniferin was about 3- to 4-fold stronger than that of resveratrol on cyclooxygenase activity of prostaglandin H2 synthase partially purified from sheep seminal vesicles.

Animals↗
PubMed1998

Biological activity and phosphorylation of 2'-azido-2'-deoxyuridine and 2'-azido-2'-deoxycytidine.

2'-Azido-2'-deoxyuridine and 2'-azido-2'-deoxycytidine were evaluated for their inhibitory activity against ribonucleotide reductase and for subsequent cell growth inhibition. Their mono- and di-phosphates were synthesized and their inhibitory activities against the reductase were also determined in a permeabilized cell system, along with the two nucleosides. The results of the present study identify the first phosphorylation step involved in the conversion of the two azidonucleosides to the corresponding diphosphates to be rate-limiting in the overall activation.

Animals↗