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S K Han

Publications and source records attributed to S K Han.

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

Bacterial expression and characterization of human pancreatic phospholipase A2.

Mammalian pancreatic phospholipases A2 (PLA2) have recently been implicated in cell surface receptor-mediated inflammation. As a first step toward understanding how human pancreatic PLA2 (hp-PLA2) interacts with membranes and other biological targets including cell-surface receptors, we constructed its bacterial expression vector which can be used for the mutagenesis and protein over-expression. The expression vector (pSH-hp) was constructed using a synthetic hp-PLA2 gene whose transcription is controlled by T7 promoter. hp-PLA2 was expressed as a mature protein in high concentration in Escherichia coli cells and formed inclusion body. The solubilization of inclusion body protein followed by the refolding and purification produced ca. 5 mg of pure protein from one liter of growth medium. Kinetic studies of recombinant human, bovine and porcine pancreatic PLA2s using polymerized mixed liposomes and micelles as substrates showed that despite their highly homologous structures these mammalian pancreatic PLA2s have distinct phospholipid head group specificity and different activity toward various lipid substrates.

Amino Acid Sequence↗
PubMed1997

Structural aspects of interfacial adsorption. A crystallographic and site-directed mutagenesis study of the phospholipase A2 from the venom of Agkistrodon piscivorus piscivorus.

Recent genetic and structural studies have shed considerable light on the mechanism by which secretory phospholipases A2 interact with substrate aggregates. Electrostatic forces play an essential role in optimizing interfacial catalysis. Efficient and productive adsorption of the Class I bovine pancreatic phospholipase A2 to anionic interfaces is dependent upon the presence of two nonconserved lysine residues at sequence positions 56 and 116, implying that critical components of the adsorption surface differ among enzyme species (Dua, R., Wu, S.-K., and Cho, W. (1995) J. Biol. Chem. 270, 263-268). In an effort to further characterize the protein residues involved in interfacial catalysis, we have determined the high resolution (1.7 A) x-ray structure of the Class II Asp-49 phospholipase A2 from the venom of Agkistrodon piscivorus piscivorus. Correlation of the three-dimensional coordinates with kinetic data derived from site-directed mutations near the amino terminus (E6R, K7E, K10E, K11E, and K16E) and the active site (K54E and K69Y) defines much of the interface topography. Lysine residues at sequence positions 7 and 10 mediate the adsorption of A. p. piscivorus phospholipase A2 to anionic interfaces but play little role in the enzyme's interaction with electrically neutral surfaces or in substrate binding. Compared to the native enzyme, the mutant proteins K7E and K10E demonstrate comparable (20-fold) decreases in affinity and catalysis on polymerized mixed liposomes of 1-hexadecanoyl-2-(1-pyrenedecanoyl)-sn-glycero-3-phosphocholine and 1,2-bis[12-(lipoyloxy)dodecanoyl]-sn-glycero-3-phosphoglycerol, while the double mutant, K7E/K10E, shows a more dramatic 500-fold decrease in catalysis and interfacial adsorption. The calculated contributions of Lys-7 and Lys-10 to the free energy of binding of A. p. piscivorus phospholipase A2 to anionic liposomes (-1.8 kcal/mol at 25 degrees C per lysine) are additive (i.e. -3.7 kcal/mol) and together represent nearly half of the total binding energy. Although both lysine side chains lie exposed at the edge of the proposed interfacial adsorption surface, they are geographically remote from the corresponding interfacial determinants for the bovine enzyme. Our results confirm that interfacial adsorption is largely driven by electrostatic forces and demonstrate that the arrangement of the critical charges (e.g. lysines) is species-specific. This variability in the topography of the adsorption surface suggests a corresponding flexibility in the orientation of the active enzyme at the substrate interface.

Adsorption↗
PubMed1997

Oleanolic acid and ursolic acid stabilize liposomal membranes.

The effects of oleanolic acid (OA) and ursolic acid (UA) on the fluidity and stability of dipalmitoyl phosphatidylcholine (DPPC) liposomal membrane were monitored by measuring the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene labeled in the liposomal membrane and the leakage of calcein from the probe-encapsulated liposomes. The experiments with the liposomes made of DPPC and OA or UA showed that OA and UA exhibited a moderate fluidity-modulating effect for the liquid-crystalline liposomal membrane, and a strong condensing effect for both crystalline and liquid-crystalline liposomal membranes. Their effects were comparable to those of cholesterol. These results suggest that their fluidity-modulating and condensing effects might have some implications in their biological functions.

Diphenylhexatriene↗
PubMed1997

Summer-type hypersensitivity pneumonitis outside Japan: a case report and the state of the art.

A 61-year-old Korean housewife developed dyspnoea, cough and weight loss in the summer of 1994. The case was diagnosed as definite summer-type hypersensitivity pneumonitis (SHP) according to the criteria proposed for hypersensitivity pneumonitis and for SHP. Her serum antibodies to Trichosporon were positive. Her symptoms were exacerbated after she returned home and Trichosporon was isolated from the patient's home, indicating Trichosporon as the causative antigen. This is the first confirmed case of SHP outside Japan. On the basis of our research in SHP to date, we propose that SHP occurs in other Asian countries and that the assay of anti-Trichosporon antibodies is useful for the diagnosis of the disease.

Alveolitis, Extrinsic Allergic↗
PubMed1997

Isoniazid resistance and the point mutation of codon 463 of katG gene of Mycobacterium tuberculosis.

It has long been known that almost all isoniazid (INH) resistant mycobacteria lose the catalase and peroxidase activities along with reduced or no virulence for guinea pigs. Recently resistance to INH has become known to be associated with mutations of katG gene encoding the HPI (Hydroperoxidase I) type catalase and peroxidase. Among these mutations, the point mutation of codon 463 of katG gene is found frequently, and is suggested as being associated with INH resistance. Therefore we performed this study in order to confirm the correlation between the point mutation of codon 463 of the katG gene and INH resistance of M. tuberculosis in Korea. Fifty isolates, 32 of which were resistant to INH, and 18 of which were sensitive to INH, were selected for this study. We used PCR-SSCP and RFLP analysis to detect the point mutation of the codon 463 of katG gene and confirmed the CGG (arginine) to CTG (leucine) mutation by direct sequencing analysis. Among 32 resistant isolates, 7 isolates (22%) had the same restriction pattern compared with that of the reference strain (H37Rv), and 25 isolates (78%) showed a different restriction pattern. Among 18 sensitive isolates, 7 isolates (39%) had the same restriction pattern compared with that of H37Rv, and 11 isolates (61%) showed a different restriction pattern. These results suggest that the CGG to CTG change of codon 463 of katG gene of M. tuberculosis may be a polymorphism not related with INH resistance.

Antitubercular Agents↗
PubMed1996

Inhibition of catalase in mesencephalic cultures by L-DOPA and dopamine.

Catalase activity in cell cultures of fetal rat mesencephalon was decreased by 42 and 50%, respectively, after exposure to L-3,4-dihydroxyphenylalanine (L-DOPA, 100 microM) or dopamine (100 microM) for 48 h. Catalase activity was also decreased 21% by 10 microM hydroquinone. Ascorbic acid (200 microM), an agent that suppresses the autoxidation of L-DOPA and dopamine, blocked the anti-catalase effect of L-DOPA, but not that of dopamine. Inhibitors of the A and B forms of monoamine oxidase (20 microM clorgyline plus 20 microM pargyline) had no effect on the anti-catalase action of either L-DOPA or dopamine. The latter results suggest that products of the oxidative deamination of dopamine by monoamine oxidase are not involved in the suppression of catalase activity. However, autoxidation reactions of L-DOPA may play a role since ascorbate suppressed the anti-catalase effect of L-DOPA. On the contrary, the basis for the failure of ascorbate to similarly block the anti-catalase effect of dopamine is uncertain. L-DOPA and dopamine (25 microM) also inhibited crystalline catalase in solution after incubation for 1 h at neutral pH (40-50% inhibition). Inhibition was blocked by 0.45 M ethanol, indicating a need for autoxidation and the formation of compound II, which is an enzymatically inactive form of catalase. The ability to model the enzyme inhibition in purely chemical experiments indicates a probable mechanism for loss of enzymatic activity in cell cultures. Inhibition of catalase may contribute to cell damage during incubation of cultures with L-DOPA, dopamine, or other autoxidizable compounds.

Animals↗
PubMed1996

L-DOPA up-regulates glutathione and protects mesencephalic cultures against oxidative stress.

Incubation with L-DOPA induced a rise in GSH level in cultures of fetal rat mesencephalon, mouse neuroblastoma (Neuro-2A), human neuroblastoma (SK-N-MC), pig kidney epithelial cells (LLC-PK1), and glia from newborn rat brain, but not C6 glioma cells or neuronal cultures (no glia) from the mesencephalon. The pure neuronal cultures were destroyed by incubation with L-DOPA; added ascorbic acid or superoxide dismutase protected the cells. Washout of L-DOPA after 48 h amplified the rise in GSH content in mixed cultures (neurons plus glia). Examination of structure-activity relationships for elevating GSH levels in responsive cell types revealed that autooxidizable compounds (alpha-methyl-DOPA, dopamine, apomorphine, catechol, and hydroquinone) behaved similarly to L-DOPA, whereas structural analogues that cannot undergo autooxidation (3-O-methyl-DOPA, tyrosine, 2,4-dihydroxyphenylalanine, and resorcinol) failed to elevate GSH levels. Therefore, up-regulation of GSH appears to be a response to a mild oxidative stress. When mixed mesencephalic cultures were exposed to a strong oxidant stress by incubation with tert-butyl hydroperoxide, a loss in viability was seen. Cultures pretreated with L-DOPA or hydroquinone were protected from loss of viability. However, when cultures were pretreated with both L-DOPA and ascorbate, which prevents the rise in GSH level, protection was lost, in accord with the failure to up-regulate GSH. These results show that the up-regulation of cellular GSH evoked by autooxidizable agents is associated with significant protection of cells. Glia play an essential role in the response of mesencephalic cell cultures. An ability to up-regulate GSH may serve a protective role in vivo.

Animals↗
PubMed1996

Fingertip replantations: clinical evaluation of 135 digits.

From July 1985 to February 1993, 135 digits in 119 patients with complete amputations at or distal to the distal interphalangeal joint (zone I for amputations distal to the nail base of zone II for amputations between the distal interphalangeal joint and the nail base) were replanted using a microsurgical technique at Korea University Guro Hospital. Because of the high social value placed on body form and function, the indication for replantation was extended to cases with severe soft-tissue injuries and attempted replantation as a routine procedure in nearly all distal amputation cases. The overall survival rate was 78 percent, with the survival rate for zone I being 70 percent and that for zone II reaching 86 percent. Even in cases with severe soft-tissue injury, the survival rate was high, with viability in avulsion injuries and crush injuries reaching 75 percent each. The most common type of vascular repair in zone I cases was revascularization of one artery only and no vein repair (87 percent). Of these cases, interpositional vein grafts were used in 65 percent. In zone II cases, the most common combination repair was one artery and one vein anastomosis (70 percent), with interpositional vein grafts for arterial anastomosis in 49 percent; most of the venous repair was feasible by the direct method (78 percent). The follow-up period ranged from 1 month to 5 years with a mean of 14.8 months; 52 patients were followed-up for more than 6 months. In 52 long-term follow-up patients, the average two-point discrimination was 8 mm. Patient satisfaction, aesthetically and functionally, was high (91 percent).

Adult↗
PubMed1996

Prognostic factors of patients with thymoma.

OBJECTIVES: To analyze the prognostic factors influencing the survival of patients with thymoma, clinical characteristics, treatment modalities and survival of patients were evaluated. The efficacy of chemotherapy was also determined. METHODS: Retrospective study was done on one hundred patients whose diagnosis was confirmed pathologically at Seoul National University Hospital from 1981 to 1994. The staging was carried out according to the Masaoka system. Survival rate was calculated by the Kaplan-Meier method and prognostic factors were analyzed by a multivariate analysis (Weibull model). RESULTS: The stage of 100 patients was as follows: Stage I-50, II-6, III-27, IV A-10, IV B-7. The overall survival rates at 5 and 10 years after diagnosis were 73.1% and 58.7%, respectively. The 5-year survival differences, according to various prognostic factors, were as follows: 1) Stage: I-92.8%, II-100%, III-71.6%, IVA-25.9% and IVB-32.9% (p = 0.0029). 2) Age: < 60 years-79.5% and > or = 60 years-41.5% (p = 0.0489). 3) Extent of resection: Total patients: complete resection-87.6% and incomplete resection-50.5% (p > 0.05) Stage III: complete resection-66.7% and incomplete resection-75.5% (p > 0.05) 4) Myasthenia gravis: present-71.6% and absent-74.9% (p > 0.05) Seventeen patients were treated with a combination chemotherapy of Cyclophosphamide, Adriamycin and cisplatin(CAP). Two complete responses and seven partial responses (overall response rate of 53%) were observed with a median response duration of fourteen months. Combination chemotherapy with CAP was effective. CONCLUSIONS: Stage and age were the independent prognostic factors in patients with thymoma. However, the presence of myasthenia gravis or the extent of resection in stage III patients was not associated with the survival time.

Adolescent↗
PubMed1996

An adult case of pulmonary sling with complete tracheal ring.

Pulmonary sling is a rare congenital condition in which the left pulmonary artery arises from the right pulmonary artery forming a sling around the trachea causing tracheal compression. Many cases are associated with cardiovascular and tracheo-bronchial anomalies. When combined with complete tracheal ring, it is called "ring-sling complex". The average onset of symptoms is 2 months and about half have symptoms from birth. The anomaly, if not corrected, can be fatal within the first year of life. In an adult, it is most often asymptomatic and usually found incidentally. We report an adult case who was diagnosed as pulmonary sling with complete tracheal ring by CT and bronchoscopy along with a literature review.

Adult↗
PubMed1995

Giant lymph node hyperplasia (Castleman's disease) in the chest.

We have experienced 7 cases of giant lymph node hyperplasia in the chest from 1981 to 1992. The ages of the 1 male and 6 female patients ranged from 9.9 to 40.4 years (mean age, 29.2 +/- 10.4 years). In 4 patients, a mass was discovered in routine radiographs. Focal calcification suggesting continual enlargement over a long time was noted in 1 patient. The sites of lesions were unusual in 2 patients (intercostal space and intrapulmonary fissure). All patients underwent surgical removal of the mass. Five cases had typical features of the hyaline-vascular type, and 2 cases revealed a mixture of the hyaline-vascular type and the plasma-cell type. Follow-up was available in all patients (mean follow-up, 31.9 months). In 1 patient, recurrence was observed 9 years after surgical removal. In general, giant lymph node hyperplasia can occur anywhere in the chest, grow without symptoms, and recur in spite of complete resection. Surgical resection and close follow-up are advised.

Adult↗
PubMed1995

Erythema induratum with pulmonary tuberculosis: report of three cases.

Three cases of erythema induratum which occurred in the patients with pulmonary tuberculosis are described. The cutaneous lesions were violaceous, indurated nodules on both lower legs above the malleoli. Histologically, tuberculoid granuloma with caseation necrosis was found in one case; necrotizing vasculitis was the prominent finding in other two cases. The erythema induratum promptly responded to antituberculous therapy. We believe that, in light of these cases, the association between erythema induratum and infection with tubercle bacilli should be re-emphasized.

Adult↗
PubMed1994

Human papillomavirus detection in cervical carcinoma tissues and paraaortic lymph nodes by the polymerase chain reaction.

Tissues of 45 cervical cancers and paraaortic lymph nodes from the same patients were evaluated by polymerase chain reaction with L1 consensus primers and hybridization with type-specific oligomer probes of HPV-6, -11, -16, -18, -31, -33, -35, and -45 for the detection and classification of subtypes of human papillomavirus (HPV). The clinicohistologic findings of surgical specimens from radical hysterectomy were compared with the results of HPV detection to use as a possible prognostic marker for the early detection of paraaortic nodes involvement. Metastasis to paraaortic nodes in cervical cancer, suggesting extrapelvic involvement of tumor, is clinically important to predict prognosis. The HPV-16 DNA was most prevalent in cervical cancers (76%; 34/45). Five tumors were positive for HPV-18, two tumors each were positive for HPV-31 or -33, one tumor was hybridized to HPV-45, and one woman had an unidentified type of HPV. No HPV was detected in three cases of cervical cancer. The histologic types of the cervical cancers were correlated with the HPV types. Of the 39 tissue specimens of squamous carcinomas analyzed, only 2 (5%) showed HPV-18, in contrast to 30 (77%) of 39 squamous carcinomas having HPV-16. Of the 5 cases of adenocarcinomas, 3 (50%) showed HPV-18, and 3 (50%) showed HPV-16. HPV DNAs were detected in histologically negative paraaortic lymph nodes (31%; 14/45): the HPV-positive PCR products from paraaortic nodes were only hybridized to HPV-16. The nature of the relationship between the presence of HPV DNA and node tumor involvement is still not known. HPV-16 DNA in paraaortic nodes may suggest subclinical early metastasis or tumor cells destroyed by immune cells and may provide important information in decisions regarding postoperative adjuvant treatment. The prognostic significance of HPV DNA in histologically negative paraaortic lymph nodes remains to be established after several years of follow-up.

Adult↗
PubMed1994

Direct in vivo gene transfer and expression in malignant cells using adenovirus vectors.

To evaluate the ability of replication-deficient, recombinant adenovirus vectors to transfer genes to human tumor cells in vivo, adenovirus vectors containing the Escherichia coli lacZ (Ad.RSV beta gal) gene (coding for beta-galactosidase; used as a cell marker for gene transfer) or the human alpha 1-antitrypsin (Ad-alpha 1AT) cDNA (used as an example of a secreted protein) were administered intraperitoneally to nude mice with human malignant mesothelioma cell (H-MESO-1) malignant ascites. Preliminary in vitro studies showed that both vectors effectively transferred genes to H-MESO-1 cells. Tumor cells recovered from ascites of animals intraperitoneally administered a control adenovirus revealed no evidence of beta-galactosidase (beta-gal) activity 3 or 14 days later. In contrast, beta-gal activity was detected at the same time points in tumor cells from animals receiving intraperitoneal Ad.RSV beta gal. Flow cytometric quantification of beta-gal activity in recovered cells showed < 3% beta-gal-positive cells in animals administered control virus, but in animals administered intraperitoneal Ad.RSV beta gal there was a mean of 71 +/- 18% positive cells at 3 days and 56 +/- 27% at 14 days. Human alpha 1AT was not detected by enzyme-linked immunosorbent assay (ELISA) in ascites of animals receiving a control virus; however, in ascites of animals administered Ad-alpha 1AT, 21,000 +/- 3,800 ng/ml of human alpha 1AT was detected at 3 days and 4,900 +/- 1,700 ng/ml at 14 days. These data demonstrate that replication-deficient recombinant adenovirus vectors can be used to transfer genes to malignant cells in vivo and suggest a new strategy for genetic modification for antitumor therapy.

Adenoviruses, Human↗
PubMed1994

Suppression of in vivo tumorigenicity of human lung cancer cells by retrovirus-mediated transfer of the human tumor necrosis factor-alpha cDNA.

The clinical use of tumor necrosis factor-alpha (TNF) is constrained by tumor cell resistance and systemic toxicity. Based on observations with murine tumors, we hypothesized that induction of local TNF production by the tumor may suppress growth of human cancer cells. To evaluate this, a human TNF cDNA was transferred to human lung cancer cell lines in vitro using a retrovirus vector to produce TNF cDNA-modified cell lines secreting TNF. In vitro cell growth was similar for parental and modified cells. All cells were resistant to TNF. The in vivo tumorigenicity of parental and modified cells was compared in nude mice. Animals injected subcutaneously with parental cells uniformly developed tumors. Tumor growth was markedly less for all modified cells, and this suppression of tumor development was reversed by anti-TNF antibody administration. Animals injected with a mixture of 50% modified and 50% parental cells or parental cell tumors injected with modified cells had decreased tumor growth, demonstrating that modified cells could suppress tumorigenicity. These data suggest that TNF can induce antitumor defenses to suppress in vivo human tumor cell growth and provide a rationale for transferring the human TNF cDNA directly to malignant cells for the therapy of human lung cancer.

Animals↗