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Biomedical subjects

B C Park

Publications and source records attributed to B C Park.

At least 37 records · Page 2Linked to original sources
PubMed1997

Cloning and expression of the gene for xylose isomerase from Thermus flavus AT62 in Escherichia coli.

The gene encoding xylose isomerase (xylA) was cloned from Thermus flavus AT62 and the DNA sequence was determined. The xylA gene encodes the enzyme xylose isomerase (XI or xylA) consisting of 387 amino acids (calculated Mr of 44,941). Also, there was a partial xylulose kinase gene that was 4 bp overlapped in the end of XI gene. The XI gene was stably expressed in E. coli under the control of tac promoter. XI produced in E. coli was simply purified by heat treatment at 90 degrees C for 10 min and column chromatography of DEAE-Sephacel. The Mr of the purified enzyme was estimated to be 45 kDa on SDS-polyacrylamide gel electrophoresis. However, Mr of the cloned XI was 185 kDa on native condition, indicating that the XI consists of homomeric tetramer. The enzyme has an optimum temperature at 90 degrees C. Thermostability tests revealed that half life at 85 degrees C was 2 mo and 2 h at 95 degrees C. The optimum pH is around 7.0, close to where by-product formation is minimal. The isomerization yield of the cloned XI was about 55% from glucose, indicating that the yield is higher than those of reported enzymes. The K(m) values for various sugar substrates were calculated as 106 mM for glucose. Divalent cations such as Mn2+, Co2+, and Mg2+ are required for the enzyme activity and 100 mM EDTA completely inhibited the enzyme activity.

Aldose-Ketose Isomerases↗
PubMed1997

Lack of colocalization of HBxAg and insulin like growth factor II in the livers of patients with chronic hepatitis B, cirrhosis and hepatocellular carcinoma.

To evaluate the possibility that HBxAg is related to an enhanced expression of IGF-II, immunohistochemical staining was performed for distribution and colocalization of HBxAg and IGF-II in liver tissues from 40 chronic active hepatitis (CAH-B), 51 cirrhosis and 46 hepatocellular carcinoma (HCC) patients using polyclonal rabbit anti HBxAg raised against full length-recombinant HBxAg and monoclonal mouse anti IGF-II. HBxAg in CAH-B, cirrhosis and HCC tissues was detected in 95%, 39% and 17%, whereas IGF-II in the same tissues was seen in 0%, 92% and 100%, respectively. There was a gradual decrease in the prevalence of HBxAg expression in cirrhosis and HCC, as compared to CAH-B tissues. All of the cirrhosis and HCC samples with positive staining for HBxAg expressed IGF-II. However, 55% of cirrhosis and 100% of HCC samples without HBxAg staining also expressed IGF-II. Moreover, colocalization at neighboring sections, even in both HBxAg and IGF-II positive samples, was not regularly observed. It is concluded that HBxAg expression in CAH-B may play a role in the pathogenesis of CAH-B. Although HBxAg may be related to the expression of IGF-II in some cirrhotic and HCC tissues, IGF-II expression in a large majority of these cases may be related to other factor(s) than HBxAg.

Adult↗
PubMed1996

Cloning and characterization of chitin synthase gene fragments from Penicillium chrysogenum.

DNA fragments homologous to chitin synthase were amplified from the genomic DNA of Penicillium chrysogenum by PCR. Cloning and sequencing of the PCR-amplified fragments led to the identification of four different genes, designated PcCHS1, PcCHS2, PcCHS3, and PcCHS4. By comparison of the deduced amino acid sequences, PcCHS1 was identified as a gene for class I chitin synthase, PcCHS2 and PcCHS3 were for class II, and PcCHS4 was for class III. Among these only PcCHS4 includes an intervening sequence of 56 bp. The analysis of the deduced amino acid sequences revealed a close evolutionary relationship between Penicillium and ascomycetous fungi.

Amino Acid Sequence↗
PubMed1996

Anti-invasive activity of ursolic acid correlates with the reduced expression of matrix metalloproteinase-9 (MMP-9) in HT1080 human fibrosarcoma cells.

We examined the anti-invasive activity of ursolic acid (UA) on the highly metastatic HT1080 human fibrosarcoma cell line. UA reduced tumor cell invasion through a reconstituted basement membrane in a transwell chamber. A significant down-regulation of matrix metalloproteinase-9 [MMP-9; Mr 92,000 gelatinase/type IV collagenase (gelatinase B)] by UA was detected by Northern blot analysis. However, MMP-2 [Mr 72,000 gelatinase/type IV collagenase (gelatinase A)] and membrane-type MMP were constantly expressed, and the expression of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 also was not changed after 3 and 6 days of treatment with UA. Quantitative gelatin-based zymography confirmed a markedly reduced expression of MMP-9 but not MMP-2 after treatment with UA. To confirm the UA-induced down-regulation of MMP-9 expression, we constructed a secreted alkaline phosphatase (SEAP) reporter vector including MMP-9 promoter. After transfection of MMP-9/SEAP reporter vector into HT1080 cells, reduced SEAP activity was detected after treatment with UA. These results suggest that down-regulation of MMP-9 contributes to the anti-invasive activity of UA in HT1080 cells.

Basement Membrane↗
PubMed1996

In vitro induction of differentiation by ginsenoides in F9 teratocarcinoma cells.

The aim of this study was to determine the ability of the ginsenosides, extracts of Panax ginseng C.A. Meyer, to cause differentiation of F9 teratocarcinoma stem cells as a model system. F9 stem cells cultured in the presence of the ginsenosides together with dibutyryl cyclic AMP (dbcAMP) became parietal endoderm-like cells. Moreover, the expression of differentiation marker genes, such as laminin B1 and type IV collagen, was increased after treatment with the ginsenosides. Among the various purified ginsenosides, Rh1 and Rh2 were the most effective at causing differentiation of F9 cells. Since ginsenosides and glucocorticoid hormone have similar chemical structures, we examined the possibility of the involvement of a glucocorticoid receptor (GR) in the differentiation process induced by the ginsenosides. According to Southwestern blot analysis, a 94 kDa protein regarded as a GR was detected in F9 cells cultured in the medium containing the ginsenosides Rh1 or Rh2. In addition, F9 stem cells treated with the ginsenosides Rh1 or Rh2 and with RU486, a glucocorticoid antagonist with a high affinity for the GR, did not differentiate into endoderm cells morphologically, and the expression of laminin B1 gene was not induced in these cells. In a gel mobility shift assay, protein factors capable of binding to the glucocorticoid responsive element (GRE) specifically were detected in nuclear extracts of the ginsenoside-treated F9 cells. Moreover, overexpression of GR by cotransfection of GR expression vector and GRE-luciferase vector enhanced the transactivation activity of GRE promoter in the presence of ginsenosides Rh1 or Rh2 and was further augmented by dbcAMP. In addition, ginsenosides Rh1 and Rh2 bound to a GR assessed by whole-cell binding assay, even though the specific binding affinity was weaker compared to dexamethasone. Based on these data, we suggest that the ginsenosides Rh1 and Rh2 cause the differentiation of F9 cells and the effects of ginsenosides might be exerted via binding with a GR or its analogous nuclear receptor.

Animals↗
PubMed1996

Combined cis-platinum and alpha interferon therapy of advanced hepatocellular carcinoma.

To evaluate the clinical efficacy of alpha-interferon(IFN-alpha) plus cis-platinum in hepatocellular carcinoma(HCC). 56 inoperable patients with HCC were divided into IFN-alpha plus cis-platinum treated group (n = 30) and no antitumor therapy group (n = 26). The survival of IFN-alpha plus cis-platinum treated patients was significantly better than that of patients who received no antitumor therapy (p = 0.001). Median survival time was 33 weeks and 14.0 weeks, respectively. The cumulative estimated survival rates of our IFN-alpha plus cis-platinum treated group (93.5% at 3mo, 75.0% at 6mo) were for longer than that of the no antitumor therapy group (84.6% at 3mo, 57.7% at 6mo). Objective tumor regression, greater than 50% was observed in 13.3% (4 of 30) of patients receiving IFN-alpha plus cis-platinum. By the univariate analysis, the absence of portal vein thrombus (p < 0.05), alkaline phosphatase lesser than 280 U/L (p = 0.001), total bilirubin less than 2.0 mg% (p < 0.05), serum triglyceride less than 155 mg/dl (p < 0.05) were shown to be the factors most significantly favoring a better survival. By the multivariate analysis, using Cox proportional hazards model, IFN-alpha plus cis-platinum treated group (p = 0.0001), alkaline phosphatase less than 280 mg/dl (p = 0.005), the absence of portal vein thrombus (p = 0.020) were independent favorable prognostic factors. We conclude that IFN-alpha plus cis-platinum is useful in patients with inoperable HCC and the above favorable prognostic factors may also be useful in the design and analysis of future clinical trials of systemic chemotherapy for HCC.

Adult↗
PubMed1995

Differential expression of transforming growth factor alpha and insulin-like growth factor II in chronic active hepatitis B, cirrhosis and hepatocellular carcinoma.

In the present study we investigated the expression of transforming growth factor alpha and insulin-like growth factor II to explain the role of these growth factors in the development of hepatocellular carcinoma from chronic active hepatitis B and cirrhosis. The expression of transforming growth factor alpha and insulin-like growth factor II was tested in 38 tissue samples from patients with chronic active hepatitis B, 32 cirrhosis and 31 hepatocellular carcinoma, by immunohistochemical staining using monoclonal anti-transforming growth factor alpha and anti-insulin-like growth factor II. All patients were seropositive for HBsAg. Transforming growth factor alpha was expressed in 26 (68.4%) of 38 chronic active hepatitis B, 18 (56.3%) of 32 cirrhosis and 16 (51.6%) of 31 hepatocellular carcinoma tissue samples. Transforming growth factor alpha was found in the periportal hepatocytes of chronic active hepatitis B and in regenerating hepatocytes of cirrhotic nodules. In hepatocellular carcinoma tissues, transforming growth factor alpha-containing tumor cells were evenly distributed within the tumor tissues but focal distribution limited to a part of tumor tissues was also observed. The expression of insulin-like growth factor II was observed in 30 (93.8%) of 32 cirrhosis and all the 31 hepatocellular carcinoma tissue samples tested, but not in chronic active hepatitis B samples. Insulin-like growth factor II was expressed in most hepatocytes of regenerating nodules and in tumorous as well as non-tumorous hepatocytes of hepatocellular carcinoma tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Prevalence of hepatitis C antibody in patients with chronic liver disease and hepatocellular carcinoma in Korea.

To investigate the contribution of hepatitis C virus (HCV) to chronic liver disease and hepatocellular carcinoma (HCC) in Korea, antibodies to HCV (anti-HCV) were tested by enzyme immunoassay in 1759 patients with chronic liver disease and HCC, and in 808 healthy adults. The prevalence of anti-HCV was 1.6% in 808 controls. Anti-HCV was present in 32 (7.7%) of 418 hepatitis B surface antigen (HBsAg)-positive and 128 (53.1%) of 241 HBsAg-negative patients with chronic hepatitis, 16 (6.0%) of 265 HBsAg-positive and 90 (30.5%) of 295 HBsAg-negative patients with liver cirrhosis, and 16 (4.8%) of 330 HBsAg-positive and 61 (29.0%) of 210 HBsAg-negative patients with HCC. Antibodies to hepatitis B core antigen (anti-HBc) were present in 80-88% of patients who were seropositive for anti-HCV and seronegative for HBsAg. Among the sera from 114 patients with HBsAg-negative and anti-HCV-positive chronic liver diseases, HBV DNA and HCV RNA were detected by polymerase chain reaction (PCR) in 54 (47.4%) and 61 (53.3%), respectively. Both HBV DNA and HCV RNA were detected in 4 (4.4%) samples. The mean age of the patients with both HBsAg and anti-HCV was not different from that of patients who were seropositive for HBsAg alone. These findings indicate that current and/or past HBV infection is still the main cause of chronic liver disease in Korea.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Cytochemical localization of the acetone-inducible cytochrome P-450 isoform, CYP2E1, in murine colonic epithelium.

Immunolocalization of a toxicologically important cytochrome P-450 isoform, the alcohol-inducible CYP2E1, was examined in mouse colon. Male CD-1 mice (30-40 g) were exposed to acetone (1% v/v), a potent inducer of hepatic CYP2E1, in drinking water for 14 days. Tissue sections were fixed in 1% paraformaldehyde and incubated with anti-rat CYP2E1 polyclonal antibody. Immunohistochemical staining on tissue sections was performed using the indirect peroxidase-antiperoxidase method. In acetone-exposed mice, immunoreactivity was localized exclusively within the cytoplasm of surface epithelial cells of the proximal colon. Infrequently, only very faint staining was evident in colons of untreated control mice. Using the same monospecific antibody, the presence of CYP2E1 was confirmed by Western blot analysis. A 2-to 3-fold elevation in immunoreactivity corresponding to cytochrome P-4502E1 was found in colon microsomes isolated from acetone-exposed form acetone-exposed mice. Further evidence for colonic CYP2E1 is provided by elevation (up to 2.5-fold) in levels of chlorzoxazone 6-hydroxylase, a CYP2E1 substrate, after acetone treatment. The significance of these finding is discussed in terms of the potential for proximal colonic epithelial cells to participate directly in bioactivation of dietary promutagenic substances.

Acetone↗
PubMed1995

Expression of insulin-like growth factor II in chronic hepatitis B, liver cirrhosis, and hepatocellular carcinoma.

In this study we investigated the expression of insulin-like growth factor II (IGf-II) to explain a role for this growth factor in concert with hepatitis B virus (HBV) involvement in the development of hepatocellular carcinoma (HCC) from chronic hepatitis type B (CAH-B) and liver cirrhosis (LC). The expressions of IGF-II and HBsAg were tested in tissue samples from 38 patients with CAH-B, 32 with LC, and 31 with HCC, by immunohistochemical staining using monoclonal anti IGF-II and anti HBs. All patients were seropositive for the presence of HBsAg. The expression of IGF-II was observed in 30 out of 32 (93.8%) LC and all 31 (100%) HCC tissue samples tested. IGF-II was expressed in most hepatocytes of regenerating nodules and in tumorous as well as nontumorous cells of HCC tissues. Neither normal liver tissues nor CAH-B tissue samples expressed IGF-II. HBsAg was expressed in 34 out of 38 (89.5%) CAH-B, 24 out of 32 (75%) LC and 13 out of 31 (41.9%) HCC tissue samples. The expression sites of HBsAg were not correlated with those of IGF-II in any tissue samples tested. The present study indicates that IGF-II plays a role in cell proliferation of regenerating nodules as well as in the development of hepatocellular carcinomas. In addition, there was no direct evidence of HBV involvement in the overexpression of this growth factor.

Adolescent↗
PubMed1994

Metal affinity engineering of proinsulin carrying genetically attached (His)10-X-Met affinity tail and removal of the tag by cyanogen bromide.

An E. coli expression clone coding for human proinsulin, which was fused to NH2-terminal beta-galactosidase, was engineered for the separation from host proteins by introducing peptide devices, and for the sequential removal of the fused polypeptide by cyanogen bromide in front of the NH2 terminal residue (methionine) of the human proinsulin gene. Short synthetic genes encoding oligopeptide residues including (Glu)n, (His)n, (Trp)n, and (Ser)n (n = 10 or 11), which have certain characteristic physical properties such as metal-affinity, polarity, hydrophobicity, and hydrophilicity, respectively, were inserted at the junction region of the gene fusion. Interestingly, it was found that among the oligopeptides, the oligohistidine residue as an affinity-tag has greatly facilitated the procedures for FPI purification, particularly in the manner of selective metal-affinity precipitation. The chelating peptide covering the NH2-terminal beta-galactosidase portion could then be removed simply after purification to generate a protein with the natural amino acid sequence of proinsulin by cyanogen bromide.

Affinity Labels↗
PubMed1993

A case of agenesis of the right lobe of the liver.

Agenesis of the right lobe of the liver is a rare congenital anomaly and only 29 cases have been reported in the literature. We encountered a patient with this anomaly diagnosed by ultrasonography, Computed tomography (CT), hepatobiliary scintigraphy, endoscopic retrograde cholangiopancreatography (ERCP) and celiac angiography. The radiological findings, differential diagnosis, and clinical significance of this anomaly are reviewed.

Adult↗
PubMed1990

Effect of adenine arabinoside and alpha-interferon in patients with HBeAg-positive chronic active hepatitis.

To evaluate and compare the therapeutic efficacy of adenine arabinoside (Ara-A) and alpha-interferon (alpha-INF), 40 patients with biopsy proven chronic active hepatitis B were chosen at random to receive Ara-A (15 mg/Kg, iv, for 10 day) or alpha-INF (3 million unit, sc, every other day for 12 wks) and followed up to 12 months after completion of the therapy. All patients were HBeAg positive. The clinical effects of Ara-A and alpha-INF on seroconversion of HBeAg positive. The clinical effects of Ara-A AND alpha-INF on seroconversion of HBeAg and the levels of serum aminotransferase (ALT) were closely matched and compared with those of the untreated control group (20 cases). Eighteen out of 20 patients received Ara-A, 19 patients received alpha-INF, and 19 out of 20 control cases were evaluated at 12 months after completion of treatment. Seroconversion of HBeAg in the alpha-INF treated group (19 cases) was observed in seven cases (36.8%), showing a higher seroconversion rate as compared to Ara-A-treated (2/18 cases, 11.1%) and to the control patients (1/19 cases, 5.3%). There were no effects of Ara-A on serum ALT levels in the treated patients compared with the untreated control patients. However there was a remarkable drop in serum ALT levels in the INF-treated patients (p less than 0.005, ALT levels at 12 months after treatment; 87.4 +/- 98.8 IU/L) compared to the pretreatment levels (256.7 +/- 175.8 IU/L).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Relationship between T-lymphocyte subsets and suppressor cell activity in patients with chronic active hepatitis B.

Thirty-nine patients with chronic HBV infection and 38 normal persons were investigated by simultaneous assay of T suppressor cell function and enumeration of T-lymphocyte subsets by monoclonal antibodies. In patients with chronic active hepatitis B (CAH-B), T suppressor cell activity (17.8 +/- 8.8%) was significantly lower than in healthy HBsAg carriers (35.4 +/- 12.3%) and normal control persons (38.3 +/- 16.3%). The proportions of T-lymphocyte subsets in patients with CAH-B were not different from those of healthy HBsAg carriers and control persons. No correlation was observed in between percentage suppression and proportions of T-lymphocyte subsets. These findings suggest that in the absence of a simultaneous assay of function, enumeration of T-lymphocyte subsets by using monoclonal antibodies is an inadequate assessment of immune regulation.

Adult↗
PubMed1980

A comparative study of blood pressure and sodium intake in Belgium and in Korea.

A comparative blood pressure and sodium excretion were higher in Korea than in Belgium. By multiple regression and covariance analysis an independent positive association between sodium and blood pressure and a negative correlation between potassium and blood pressure were found in some population subgroups and in the total population studied in Korea. In Belgium a positive association between sodium and blood pressure was found when higher powers of age, height, weight and sodium were included in the analysis. The independent influence of sodium on blood pressure was relatively small, amounting to about 2 mm Hg of pressure rise for an increase in 24-h excretion of 100 mmol of sodium.

Analysis of Variance↗