Biomedical subjects

H Park

Publications and source records attributed to H Park.

At least 145 records · Page 8Linked to original sources

PubMed2000

In vivo antioxidant effect of green tea.

OBJECTIVE: The object of this study was to investigate the in vivo antioxidant effect of green tea and dosage effect of green tea on antioxidant effect. DESIGN: We tested 10 healthy subjects (aged 23-25 y, five women and five men) with overnight fasting. The total antioxidant capacity of plasma was measured at baseline and 60 min and 120 min after ingestion of 150 ml green tea. Green tea was prepared by infusing 2.5 g of dried green tea leaves for 2 min at 80 degrees C in 150 ml of water. In the second week, they took 300 ml of tea (5.0 g of green tea leaves) and, in the third week, 450 ml of tea (7.5 g of green tea leaves). The total antioxidant capacities of plasma were determined with a Total Antioxidant Kit (Randox Laboratories Ltd, UK) using a Cobas Mira analyser (Roche Diagnostic Systems Inc., Switzerland). The mean intra-assay coefficient of variation was 1.2%. RESULTS: The total antioxidant capacity of plasma increased by 1.1% at 60 min and 2.1% at 120 min over baseline value in subjects consuming 150 ml of green tea, which was statistically not significant. However, total antioxidant capacity of plasma after consuming 300 ml of green tea showed a significant increase of 7.0% after 60 min and 6.2% after 120 min (P<0.0001), and after consuming 450 ml 12.0% after 60 min and 12.7% after 120 min over baseline value (P<0.0001). CONCLUSIONS: Total antioxidant capacity of plasma was significantly increased after taking green tea in amounts of 300 and 450 ml. A positive increment according to green tea dosage was also observed. SPONSORSHIP: This work was funded by the Pacific Corporation (Korea).

Adult↗

PubMed2000

Interleukin-18 and the costimulatory molecule B7-1 have a synergistic anti-tumor effect on murine melanoma; implication of combined immunotherapy for poorly immunogenic malignancy.

Interleukin-18 has been described recently as a cytokine secreted primarily by Kupffer cells. Furthermore, it has been shown that it has significant anti-tumor effects, which are mediated by T cells and natural killer cells, in a manner similar to interleukin-12. Here, we report the evaluation of the effects of the systemic administration of interleukin-18 in combination with B7-1 (CD80) expressed on tumor cells [interleukin-18 + B7-1] on the growth of murine B16 melanoma in vivo. After the subcutaneous inoculation of B16 melanoma, B16 tumors grew progressively in immunocompetent syngeneic C57BL/6 mice. Mice treated with either interleukin-18 or immunized with B7-1-transduced B16 did not demonstrate significant anti-tumor effect. The combination of the two treatments, however, resulted in dramatic suppression of melanoma formation, tumor growth, and a significant improvement in survival. Inhibitory effects of [interleukin-18 + B7-1] on lung metastasis in mice were also detected. Additionally, mice treated with [interleukin-18 + B7-1] showed an increase of natural killer cytotoxicity and interferon-gamma production in vivo. Unlike [interleukin-18 + B7-1], [interleukin-12 + B7-1] did not have a strong anti-tumor effect against B16 melanoma. Histologic characterization after the [interleukin-18 + B7-1] treatment confirmed the infiltration of natural killer cells into the tumor, suggesting that natural killer cells may be involved in the [interleukin-18 + B7-1]-induced anti-tumor effect. This finding was confirmed by showing that depletion of NK1.1+ cells before immunization inhibits the [interleukin-18 + B7-1]-induced anti-tumor effect. Depletion of CD3+ cells in vivo also decreased the anti-tumor effect of [interleukin-18 + B7-1], suggesting the importance of CD3+ T cells. Collectively, combination with interleukin-18 and B7-1 expression has synergistic anti-tumor effects against B16 murine melanoma.

Animals↗

PubMed2000

Effect of endotoxin on opossum oesophageal motor function.

Endotoxin induces nitric oxide (NO*) synthase and alters gastrointestinal functions. We explored the effect of lipopolysaccharide (LPS) on oesophageal motor function at 6, 12, 24, and 48 h. The effects of inhibiting inducible NO* synthase (iNOS) were studied 12 h after administration of LPS with/without aminoguanidine (AG). Oesophageal manometry was performed and tissue bath studies were performed with muscle strips from the oesophagus and lower oesophageal sphincter (LOS). Plasma nitrite/nitrate concentrations were determined. The amplitudes of peristaltic pressure waves, resting LOS pressure and the percentage LOS relaxations were diminished by LPS. AG attenuated the decrease in amplitude of oesophageal pressure waves, LOS pressure, and percentage relaxation of LOS brought about by LPS. LPS decreased electrical field stimulation (EFS)-induced relaxation of LOS muscle. AG attenuated this decrease in LOS relaxation. The off-response of transverse oesophageal muscle strips was decreased, and AG antagonized this effect. Plasma concentrations of nitrite/nitrate were increased. The increase in plasma nitrite/nitrate was attenuated by AG. These studies support the hypothesis that endotoxin modulates oesophageal motor function by increasing NO production and suggest that this results from the induction of iNOS.

Animals↗

PubMed2000

Serum total bile acid level as a sensitive indicator of hepatic histological improvement in chronic hepatitis C patients responding to interferon treatment.

BACKGROUND AND METHODS: Serum total bile acid (TBA) levels are used clinically as a sensitive and reliable index of hepatobiliary diseases. In the present study, to assess the clinical usefulness of determining TBA in interferon (IFN)-treated patients, changes in liver function test values, including TBA and liver histology, were examined in 36 chronic hepatitis C patients for 3 years after a sustained response to IFN treatment. RESULTS: Alanine aminotransferase and gamma-glutamyl transpeptidase values significantly decreased during the period of IFN treatment compared to the same measures before IFN treatment. Albumin, cholinesterase, total cholesterol and platelet count values temporarily decreased during IFN treatment, then increased significantly and reached a plateau 6-12 months after the end of IFN treatment. The zinc sulphate turbidity test and TBA values began to decrease during IFN treatment and continued to decrease during the 3-year follow-up period. The histological activity index of the liver (Knodell's score) significantly decreased, whereas the staging score was unchanged 1 year after the end of IFN treatment. In patients who had a TBA value > 10 micromol/L before IFN treatment, a significant correlation was observed between the decrease of TBA and liver histology grading score. CONCLUSIONS: A decrease in serum TBA level reflected histological improvement in the liver more precisely than did changes in the other liver function test values following IFN therapy.

Adult↗

PubMed2000

Evidence for interaction of yeast protein kinase C with several subunits of oligosaccharyl transferase.

Oligosaccharyltransferase (OT) in Saccharomyces cerevisiae is an enzyme complex consisting of 8 transmembrane proteins located in the endoplasmic reticulum (ER). Studies on potential protein-protein interactions in OT using a two-hybrid library screen revealed that protein kinase C (Pkc1p) interacted with the lumenal domains of several OT subunits. Additional genetic experiments revealed that overexpression of two OT subunits rescued the growth defect caused by overexpression of a Pkc1 active site mutant, implying that there are specific genetic interactions between PKC1 and OT. These in vivo findings were complemented by in vitro studies that showed that several of the OT subunits bound to a fusion protein consisting of glutathione S-transferase linked via its C-terminus to Pkc1p. Assays of OT activity, in which glycosylation of a simple acceptor peptide was assayed in microsomes from wild-type and a pkc1 null revealed a 50% reduction in activity in the microsomes from the null strain. In contrast, strains containing null mutations of two other genes known to be downstream of Pkc1p in the PKC1-MAP kinase pathway had a level of OT activity comparable to that of wild-type cells. These in vivo and in vitro experiments suggest that in yeast cells Pkc1p may be involved in regulation of the N-glycosylation of proteins.

Asparagine↗

PubMed2000

A new orthoborate, Sr3Ga3(BO3)4O(OH)

The crystal structure of tristrontium trigallium tetraborate oxide hydroxide has been determined by X-ray diffraction using a crystal grown by hydrothermal crystallization of a strontium gallo-borate glass. It represents a new orthoborate structure type built of complex layers formed by BO(3) triangles sharing corners with Ga(2)O(7) tetrahedral dimers and GaO(4)OH square pyramids. The Sr atoms occupy both inter- and intralayer sites.

Journal Article↗

PubMed2000

Does interview date affect match list position in the emergency medicine national residency matching program match?

OBJECTIVE: Some residency applicants believe that the date on which they interview with a residency program influences how the program ranks them in the National Residency Matching Program (NRMP). Therefore, the authors studied whether interview date affects match list position in the emergency medicine (EM) residency match. METHODS: Forty-four Accreditation Council for Graduate Medical Education (ACGME)-accredited EM residency programs participated in this multicenter study. The interview date and match list position were collected for each interviewee for the 1997-98 season. Programs were also asked about factors that might potentially bias interview date assignment. Statistical analyses were performed both with and without these programs included. Interview dates and match list positions were standardized into percentile date and percentile rank for each program and were compared using linear regression analysis. Scatterplots graphed interview date vs match list position. Two-sample t-tests compared interview dates for ranked and nonranked interviewees. RESULTS: Data were collected for 3,800 individual interviews; 14% of these resulted in unranked applicants. Twenty-three programs, representing 1,997 interviews, reported potential bias in their interview date assignment. Regression analysis revealed an R(2) of 0.018268 (correlation coefficient = 0. 1352, 95% CI = 0.0992 to 0.1617) for all programs, R(2) of 0.010626 (correlation coefficient = 0.1031, 95% CI = 0.0571 to 0.1485) for programs without reported potential bias, and R(2) of 0.02444 (correlation coefficient = 0.1563, 95% CI = 0.10887 to 0.20309) for programs with reported bias. Scatterplots revealed no linear correlation. Two-sample t-tests for all programs, and programs with and without reported bias showed no significant difference in average interview date for ranked and unranked interviewees (both with p > 0.2). CONCLUSION: In this study, interview date for EM residency positions in the 1997-98 season did not affect match list position among ranked applicants. Moreover, interview date had nno effect on the decision to leave candidates unranked.

Emergency Medicine↗

PubMed2000

Detection and identification of mycobacteria by amplification of the internal transcribed spacer regions with genus- and species-specific PCR primers.

We evaluated the usefulness of PCR assays that target the internal transcribed spacer (ITS) region for identifying mycobacteria at the species level. The conservative and species-specific ITS sequences of 33 species of mycobacteria were analyzed in a multialignment analysis. One pair of panmycobacterial primers and seven pairs of mycobacterial species-specific primers were designed. All PCRs were performed under the same conditions. The specificities of the primers were tested with type strains of 20 mycobacterial species from the American Type Culture Collection; 205 clinical isolates of mycobacteria, including 118 Mycobacterium tuberculosis isolates and 87 isolates of nontuberculous mycobacteria from 10 species; and 76 clinical isolates of 28 nonmycobacterial pathogenic bacterial species. PCR with the panmycobacterial primers amplified fragments of approximately 270 to 400 bp in all mycobacteria. PCR with the M. tuberculosis complex-specific primers amplified an approximately 120-bp fragment only for the M. tuberculosis complex. Multiplex PCR with the panmycobacterial primers and the M. tuberculosis complex-specific primers amplified two fragments that were specific for all mycobacteria and the M. tuberculosis complex, respectively. PCR with M. avium complex-, M. fortuitum-, M. chelonae-, M. gordonae-, M. scrofulaceum-, and M. szulgai-specific primers amplified specific fragments only for the respective target organisms. These novel primers can be used to detect and identify mycobacteria simultaneously under the same PCR conditions. Furthermore, this protocol facilitates early and accurate diagnosis of mycobacteriosis.

Base Sequence↗

PubMed2000

Caveolin-1 regulates shear stress-dependent activation of extracellular signal-regulated kinase.

Fluid shear stress activates a member of the mitogen-activated protein (MAP) kinase family, extracellular signal-regulated kinase (ERK), by mechanisms dependent on cholesterol in the plasma membrane in bovine aortic endothelial cells (BAEC). Caveolae are microdomains of the plasma membrane that are enriched with cholesterol, caveolin, and signaling molecules. We hypothesized that caveolin-1 regulates shear activation of ERK. Because caveolin-1 is not exposed to the outside, cells were minimally permeabilized by Triton X-100 (0.01%) to deliver a neutralizing, polyclonal caveolin-1 antibody (pCav-1) inside the cells. pCav-1 then bound to caveolin-1 and inhibited shear activation of ERK but not c-Jun NH(2)-terminal kinase. Epitope mapping studies showed that pCav-1 binds to caveolin-1 at two regions (residues 1-21 and 61-101). When the recombinant proteins containing the epitopes fused to glutathione-S-transferase (GST-Cav(1-21) or GST-Cav(61-101)) were preincubated with pCav-1, only GST-Cav(61-101) reversed the inhibitory effect of the antibody on shear activation of ERK. Other antibodies, including m2234, which binds to caveolin-1 residues 1-21, had no effect on shear activation of ERK. Caveolin-1 residues 61-101 contain the scaffolding and oligomerization domains, suggesting that binding of pCav-1 to these regions likely disrupts the clustering of caveolin-1 or its interaction with signaling molecules involved in the shear-sensitive ERK pathway. We suggest that caveolae-like domains play a critical role in the mechanosensing and/or mechanosignal transduction of the ERK pathway.

Animals↗

PubMed2000

Adaptive method of realizing natural gradient learning for multilayer perceptrons.

The natural gradient learning method is known to have ideal performances for on-line training of multilayer perceptrons. It avoids plateaus, which give rise to slow convergence of the backpropagation method. It is Fisher efficient, whereas the conventional method is not. However, for implementing the method, it is necessary to calculate the Fisher information matrix and its inverse, which is practically very difficult. This article proposes an adaptive method of directly obtaining the inverse of the Fisher information matrix. It generalizes the adaptive Gauss-Newton algorithms and provides a solid theoretical justification of them. Simulations show that the proposed adaptive method works very well for realizing natural gradient learning.

Algorithms↗

PubMed2000

Immunogenicity of antigens in boiled alginate microspheres.

Vaccine efficacy can be enhanced by delivery of antigens in synthetic microspheres. The process of antigen incorporation into microspheres can expose fragile antigens to damaging conditions, such as high temperatures, and to bacterial contamination. Maintenance of immunogenicity of several antigens and reduction of bacterial load in alginate microspheres following boiling was evaluated. Mice were immunized subcutaneously, initially and again 21 days later, with either non-boiled or boiled microspheres containing ovalbumin (OVA), a culture supernatant vaccine of Pasteurella haemolytica (PHV), or a potassium thiocyanate extract of P. multocida (PTE). Serum samples were obtained prior to immunization and at the time of euthanasia 28 days later. Culture of microspheres showed that boiling completely eliminated aerobic bacterial growth for OVA-containing microspheres, and reduced growth by a factor of 10(4) for PTE microspheres. More bacteria were cultured after boiling than before for PHV microspheres. ELISA performed on serum and intestinal lamina propria explant supernatants showed that immunogenicity of PHV microspheres was not altered by boiling. Boiled OVA microspheres were still able to stimulate a significant serum IgG anti-OVA titer in mice, but boiled PTE microspheres completely lacked immunogenicity. Elispot assays of spleens showed that only PHV microspheres were able to retain immunogenicity after boiling. Results indicate that boiling is not an effective means for reducing the bacterial load of alginate microspheres and that the process is associated with a diminution of vaccine immunogenicity.

Alginates↗

PubMed2000

pH-sensitivity of fast responsive superporous hydrogels.

Stimuli-sensitive hydrogels (or smart hydrogels) are hydrogels that swell or shrink in response to small changes in environmental conditions in which they are placed. While the extent of swelling or shrinking may be large, the kinetics of such changes is slow, since the diffusion of water into and out of the hydrogel is a slow process. To obtain fast responses, we have prepared superporous hydrogels (SPHs) that can swell or shrink extremely fast regardless of their dimensions. The swelling and shrinking are orders of magnitude faster than expected for a nonporous hydrogel of the same dimensions. Water molecules are taken up into the SPHs by capillary forces, and this makes water uptake much faster than diffusion. The swelling ratio of the poly(acrylamide-co-acrylic acid) (p(AM-co-AA)) SPHs was dependent on the pH and ionic strength of the medium. The effect of pH was most pronounced and the effect of ionic strength was observed at all pH values. SPHs made at pH around 5 showed transient maximum swelling when exposed to pH 1.2 medium due to the transient low hydrogen ion concentration inside the swelling SPHs. The p(AM-co-AA) SPHs showed repeated swelling and shrinking by alternating the medium pH between 1.2 and 7.5, and the changes in swelling ratio was quite fast occurring in a matter of a minute. This fast sensitivity may make the stimuli sensitive hydrogels useful in many applications not previously possible. These materials can be used for applications where a single-piece hydrogel is more advantageous than hydrogel microparticulates.

Acrylamides↗

PubMed2000

Distribution of haptoglobin phenotypes in a Korean population, using the semi-automated PhastSystem.

We have established a new phenotyping method for haptoglobin, based on sodium dodecyl sulphate-polyacrylamide gel electrophoresis using the PhastSystem (Pharmacia Biotech, Uppsala, Sweden), followed by immunoblotting for detection. We measured haptoglobin concentrations and determined the haptoglobin phenotypes of 316 healthy Koreans using this method: 31 (9.8%) were of Hp 1-1 type, 140 (44.3%) of Hp 2-1 type and 145 (45.9%) of Hp 2-2 type. The haptoglobin allele frequencies were calculated to be 0.32 for Hp1 and 0.68 for Hp2. We were able to visualize up to 12 bands from the human Hp 2-2 polymeric series, with molecular weights in the range 171.9 x 10(3) to 802.2 x 10(3). The reference range of serum haptoglobin concentrations obtained by the IFCC (International Federation of Clinical Chemistry) standard method was 0.27-2.14 g/L. The serum haptoglobin concentration in Koreans was similar to that of Caucasians, but the Hp1 allele frequency was lower in Koreans. Our method could be used in clinical laboratories as a simple and practical method of haptoglobin phenotyping. In addition, the Hp 2-2 polymeric series could be used as high molecular weight standards.

Alleles↗

PubMed2000

Purification and characterization of aspartic proteinase from sunflower seeds.

Aspartic proteinases were purified from sunflower seed extracts by affinity chromatography on a pepstatin A-EAH Sepharose column and by Mono Q column chromatography. The final preparation contained three purified fractions. SDS-PAGE showed that one of the fractions consisted of disulfide-bonded subunits (29 and 9 kDa), and the other two fractions contained noncovalently bound subunits (29 and 9 kDa). These purified enzymes showed optimum pH for hemoglobinolytic activity at pH 3.0 and were completely inhibited by pepstatin A like other typical aspartic proteinases. Sunflower enzymes showed more restricted specificity on oxidized insulin B chain and glucagon than other aspartic proteinases. The cDNA coding for an aspartic proteinase was cloned and sequenced. The deduced amino acid sequence showed that the mature enzyme consisted of 440 amino acid residues with a molecular mass of 47,559 Da. The difference between the molecular size of purified enzymes and of the mature enzyme was due to the fact that the purified enzymes were heterodimers formed by the proteolytic processing of the mature enzyme. The derived amino acid sequence of the enzyme showed 30-78% sequence identity with that of other aspartic proteinases.

Amino Acid Sequence↗

PubMed2000

Remnant-like particle cholesterol levels in Korean patients with coronary artery disease and non-insulin dependent diabetes mellitus.

Several studies have provided evidence that the remnants of lipoproteins may be the atherogenic components of triglyceride-rich lipoproteins. The purpose of this study was to investigate whether the remnant-like particle cholesterol (RLP-C) is an independent risk factor for coronary artery disease (CAD) and non-insulin dependent diabetes mellitus (NIDDM) in the Korean population and to explore the relationship between RLP-C and other biochemical markers as well as the apolipoprotein (apo) E genotypes. Lipid and lipoproteins including RLP-C and apo E genotypes were analyzed in 98 normal adults (control group), 68 patients with CAD (CAD group), 88 patients with NIDDM (DM group), and 19 patients with both CAD and NDDM (CAD + DM group). RLP-C levels were significantly higher in the DM (p < 0.0001), CAD (p = 0.0012) and the CAD + DM groups (p = 0.0184) than in the controls. To determine which variable could discriminate most effectively and independently among the different groups, stepwise linear discriminant analysis was performed for all the variables that showed p < 0.15 by univariate analysis. RLP-C was selected as an independent discriminator between the control and patient groups. RLP-C levels showed a strong positive correlation with trigylceride levels in the control, CAD and DM groups (r = 0.783, r = 0.610 and r = 0.746, respectively). In overall groups, apo epsilon4 and epsilon2 carrier genotypes showed a significant increase in RLP-C levels compared with epsilon3/3 wild-type (p = 0.0085). After adjusting for the effect of apo E genotypes, a significant increase of the RLP-C levels in the disease groups remained. In conclusion, RLP-C was determined to be an independent risk factor in Korean patients with CAD and NIDDM and showed a strong correlation with triglyceride levels. We suggest that the increased cardiovascular risk associated with the epsilon4 and epsilon2 allele may be mediated by more atherogenic RLP-C.

Adult↗

PubMed2000

Apoptosis and cell cycle progression in an acidic environment after irradiation.

Apoptosis and cell cycle progression in HL60 cells irradiated in an acidic environment were investigated. Apoptosis was determined by TUNEL staining, PARP cleavage, DNA fragmentation, and flow cytometry. The majority of the apoptosis that occurred in HL60 cells after 4 Gy irradiation took place after G(2)/M-phase arrest. When irradiated with 12 Gy, a fraction of the cells underwent apoptosis in G(1) and S phases while the rest of the cells underwent apoptosis in G(2)/M phase. The apoptosis caused by 4 and 12 Gy irradiation was transiently suppressed in medium at pH 7.1 or lower. An acidic environment was found to perturb progression of irradiated cells through the cell cycle, including progression through G(2)/ M phase. Thus it was concluded that the suppression of apoptosis in the cells after 4-12 Gy irradiation in acidic medium was due at least in part to a delay in cell cycle progression, particularly the prolongation of G(2)/M-phase arrest. Irradiation with 20 Gy indiscriminately caused apoptosis in all cell cycle phases, i.e. G(1), S and G(2)/M phases, rapidly in neutral pH medium and relatively slowly in acidic pH medium. The delay in apoptosis in acidic medium after 20 Gy irradiation appeared to result from mechanisms other than prolonged G(2)/ M-phase arrest.

Acids↗

PubMed2000

Hb Madrid [beta115(G17)Ala-->Pro] in a Korean family with chronic hemolytic anemia.

Hb Madrid, in which the alanine residue at beta115 (G17) is replaced by proline, results in a moderately severe hemolytic anemia due to the disruption of an alpha helical region and the weakening of an alpha1 beta1 contact (1,2). It was first discovered in a single Spanish patient, by protein structural analysis, whose parents did not carry the abnormality (1). The second observation of Hb Madrid was in an American Black teenager by DNA analysis, who had the family history of chronic hemolytic anemia, but none of family members were available for evaluation (3).

Adolescent↗

PubMed2000

Plasminogen activator inhibitor-1 4G/5G promoter polymorphism and coagulation factor VII Arg353-->Gln polymorphism in Korean patients with coronary artery disease.

An increased risk for arterial thrombosis is associated with high plasma levels of coagulation and fibrinolytic factors such as PAI-1 and FVII. In this study, the 4G/5G polymorphism in the promoter of PAI-1 gene and Arg353-->Gln polymorphism in the FVII gene were analysed in 139 normal adults and 158 patients with coronary artery disease (CAD), and their association with plasma lipid traits was investigated. There were no significant differences in the allele frequencies of PAI-1 and FVII polymorphisms between control and patient groups. The allelic distributions of both polymorphisms in Koreans were similar to those in Japanese but significantly different from those in Caucasians. In the CAD group, the 4G homozygotes of PAI-1 polymorphism showed significantly higher levels of total (p=0.0250) and LDL cholesterol (p=0.0335) with individuals having other genotypes. However, FVII polymorphism showed no association with lipid levels. In conclusion, the 4G/5G PAI-1 promoter polymorphism and Arg353-->Gln FVII polymorphism are not major genetic risk factors for CAD in Koreans. However, 4G allele of PAI-1 polymorphism revealed to be associated with the levels of cholesterol, especially LDL cholesterol levels in CAD patients.

Aged↗