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Biomedical subjects

N Kim

Publications and source records attributed to N Kim.

At least 91 records · Page 5Linked to original sources
PubMed1998

Identification of differentially expressed genes in human hepatoblastoma cell line (HepG2) and HBV-X transfected hepatoblastoma cell line (HepG2-4x).

Hepatitis B virus-X protein (HBV-X) is known to be an important factor in the formation of hepatocellular carcinoma by acting as a transcriptional activator on viral or cellular genes. To identify differentially expressed genes between the human hepatoblastoma cell line HepG2 and HBV-X gene transfected hepatoblastoma cell line HepG2-4X, we used a differential display polymerase chain reaction technique. The technique produced numerous up-regulated and down-regulated bands, each representing a partial cDNA fragment. We isolated 23 different kinds of cDNA fragments that showed marked differences in two cell lines. The fragments were used as templates for DNA sequencing analysis and as probes for Northern blot analysis. This analysis revealed that eight cDNA clones were differentially expressed in each cell line but fifteen cDNA clones were not. Among the 8 clones, 3 clones showed sequence similarities with human mitochondrial ATPase subunit 6 (mtATPase 6) and the human amidophosphoribosyl transferase (ATase) precursor, whereas 5 other clones were human novel protein encoding genes. Two genes having similarity with known genes were repressed by HBV-X. These results reflect that complex alterations of the expression of enzymes concerning the energy-generating system in mitochondria and metabolite synthesis are closely associated with the HBV-X function during the formation of hepatocellular carcinoma. These newly obtained genes will be useful for analyzing HBV-X functions. We are in the process of further characterizing these genes.

Blotting, Northern↗
PubMed1998

Establishment and characterization of cell lines constitutively expressing hepatitis B virus X-protein.

We prepared human hepatoma cell lines, which expressed the human hepatitis B virus-X gene product. The plasmid pMAMneo-X, containing an HBV-X gene promoter, an enhancer and a structural gene was constructed. Transfected HBV-X gene integration and expression were detected by Southern and Northern blotting, as well as by chloramphenicol acetylase transferase (CAT) assay using various kinds of promoter-CAT reporter systems. HBV-X protein expression in stable transfectants was confirmed by immunofluorescence microscopy. Transfected cell lines showed permanent expression of HBV-X proteins. The HBV-X transfectant activated its target promoters in promoter-CAT constructs as reporters. The HBV-X transfectant enhanced AP-1 transcription factor binding to its target DNA. Therefore, X-transfectants are not only stable, but also have specific biological functions. Cell cycle analysis by flow cytometry showed that the majority of the transfectant cells are arrested in the G1 or G2 phase of the cell cycle. These cell lines may be useful in analyzing the biological functions of HBV-X and its functional role in the formation of hepatocellular carcinomas.

Carcinoma, Hepatocellular↗
PubMed1998

Trabecular myocytes of the embryonic heart require N-cadherin for migratory unit identity.

The myocardial wall of the vertebrate heart changes from a simple epithelium to a trabeculated structure during embryogenesis. This process occurs when epithelioid cardiomyocytes migrate toward the endocardium, which we show is coincident with up-regulation of the cell adhesion molecule, N-cadherin. To study the role of N-cadherin expressed at the trabeculation stage, a replication-defective retrovirus expressing a dominant negative mutant of N-cadherin (delta N-cadherin) was engineered. Control viruses were designed to express beta-galactosidase or a full-length N-cadherin. Viruses were introduced into epithelioid presumptive myocytes at the time they initiate the epithelial-mesenchymal transformation. Individual cells infected with control viruses generated daughter myocytes which migrated toward endocardium as a tight cluster, thereby generating a clone that forms a single or at most two trabeculae. In contrast, myocytes expressing delta N-cadherin were sparsely distributed within the myocardium and failed to form the ridge-shaped clone. Thus, in addition to its known roles in myocyte epithelialization and intercalated disc formation, N-cadherin appears to play a role in homotypic interactions between nonepithelial migratory myocytes during trabecular formation of the embryonic heart.

Animals↗
PubMed1998

Leukotriene D4-induced contraction of cat esophageal and lower esophageal sphincter circular smooth muscle.

BACKGROUND & AIMS: In esophageal circular muscle, acetylcholine activates phosphatidylcholine-specific phospholipases C and D and phospholipase A2, producing diacylglycerol and arachidonic acid, which cause contraction by interacting synergistically to activate protein kinase C. In a model of acute esophagitis, leukotriene D4 (LTD4) contributes to acetylcholine-induced contraction. We examined intracellular signaling in LTD4-induced contraction. METHODS: Esophageal and lower esophageal sphincter (LES) cells, isolated by enzymatic digestion, were contracted by LTD4 in the absence or presence of inhibitors. Permeabilization by saponin allowed use of G-protein antibodies and heparin. RESULTS: Esophageal contraction was inhibited by pertussis toxin, Gi3 antibodies, D609 (phosphatidylcholine-specific phospholipase C inhibitor), propranolol (phospholipase D pathway inhibitor), and chelerythrine (protein kinase C antagonist) but not W7 (calmodulin antagonist). LES contraction was unaffected by pertussis toxin. It was inhibited by Gq antibodies, U-73122 (phosphatidylinositol-specific phospholipase C inhibitor), heparin (inositol 1,4,5-trisphosphate inhibitor), and W7 and reduced by D609. CONCLUSIONS: In the esophagus, LTD4 activates a protein kinase C-dependent pathway through pertussis toxin-sensitive Gi3 proteins and phosphatidylcholine-specific phospholipase. In the LES, LTD4 activates a calmodulin-dependent pathway through pertussis toxin-insensitive Gq proteins and phosphatidylinositol-specific phospholipase C. The intracellular pathways activated by LTD4 in the esophagus and the LES are similar to those activated by acetylcholine and other agonists.

Animals↗
PubMed1998

Relative bradycardia and lymphopenia in patients with babesiosis.

The medical records of 17 patients with babesiosis were reviewed. Nine of 17 patients (52.9%) presented with fever (temperature, > 101 degrees F), and 8 of the 9 patients (88.9%) had relative bradycardia. Four of the nine patients (44.4%) had morning temperature spikes during initial hospitalization. As revealed by laboratory analysis, 13 of 17 patients (76.5%) with babesiosis had lymphopenia, and 5 of 17 patients (29.4%) had rouleaux formation in their peripheral blood smears. These newly described clinical and laboratory findings represent additional clinical and laboratory features that may be used as diagnostic clues in the differential diagnosis of babesiosis.

Adult↗
PubMed1998

Long-term effect of Helicobacter pylori eradication on gastric metaplasia in patients with duodenal ulcer.

There have been conflicting reports on the effect of Helicobacter pylori eradication on gastric metaplasia in the duodenal bulb (DGM). In the present study, we have investigated the relationships between DGM and H. pylori by examining whether or not H. pylori-positive patients had more DGM than H. pylori-negative patients with nonulcer dyspepsia (NUD) or duodenal ulcer (DU), and by examining the effect of eradication of H. pylori on the prevalence and the extent of DGM during the long-term up to 4 years. Fifty H. pylori-positive and seven H. pylori-negative patients with DU and 23 H. pylori-positive and 23 H. pylori-negative NUD subjects were studied. Two duodenal bulb biopsy specimens were taken for histologic evaluation and the presence and the extent of DGM were evaluated. The extent of DGM was classified as none (grade 0), focal (grade 1), multifocal (grade 2), and diffuse type (grade 4). In H. pylori-positive patients with DU, follow-up gastroscopy was conducted 4 weeks, 1 year, and 4 years after H. pylori eradication. DGM was significantly (p < 0.001) more common (DU: 93%, NUD: 22%) and significantly (p < 0.001) greater in extent for patients with DU than for NUD subjects (DU: 1.89, NUD: 0.28). Neither the prevalence nor the extent of DGM was affected by H. pylori status in patients with DU or NUD; the prevalence (extent) of DGM of H. pylori-positive and -negative patients with DU were 96% (1.94) and 71% (1.57), respectively. In the 43 "H. pylori-eradicated" group, initial prevalence of DGM was 95% and those of 4 weeks, 1 year, and 4 years after eradication were 91%, 96%, and 79%, respectively. The initial extent of DGM was 1.93, and those of 4 weeks, 1 year, and 4 years after eradication were 1.90, 1.88, and 1.57, respectively. In conclusion, the prevalence and the extent of DGM were not related to H. pylori in patients with DU or NUD. In addition, the prevalence and the extent of DGM did not change until 1 year after H. pylori eradication in patients with DU, and decreased to the initial level of the H. pylori-negative DU group but without statistical significance after 4-year follow-up.

Adolescent↗
PubMed1998

Helicobacter pylori reinfection rate and duodenal ulcer recurrence in Korea.

In the short term, the eradication of Helicobacter pylori in patients with duodenal ulcer (DU) is deemed to be clearly effective; the long-term effectiveness apparently depends on the H. pylori reinfection rate. We conducted the present study to investigate the rates of H. pylori reinfection and DU recurrence in 45 patients previously cured of DU in whom H. pylori had been eradicated. These patients underwent gastroscopy and tests for H. pylori at least 1 year after eradication. In a control group comprising 31 patients with DU who were not treated with H. pylori eradication regimen, the DU recurrence rate was checked annually for 4 years. Twenty of 45 patients (44.4%) in whom the mean follow-up period was 3.5 years were again found to be H. pylori positive, and the reinfection rate was 12.8% per year. DU recurred in 8 of these 20 (40%) but not in any nonreinfected patients. In the control group, the DU recurrence rate was 61% within 1 year, 81% within 2 years, 84% within 3 years, and 90% within 4 years. The respective recurrence rates in the 45 patients in whom the bacteria had been eradicated were 0%, 4%, 13%, and 18%. The H. pylori reinfection rate was as high as 12.8% per year in Korea, but in that the DU recurrence rate is significantly lower (p < 0.01; odds ratio, 129.5) in the H. pylori-eradicated group than in the control group, the eradication of H. pylori in DU patients is effective over the long term (at least 4 years).

Adolescent↗
PubMed1998

Cis-acting sequences that affect somatic hypermutation of Ig genes.

We review our studies on the mechanism of somatic hypermutation of immunoglobulin genes. Most experiments were carried out using Ig transgenes. We showed in these experiments that all required cis-acting elements are present within the 10-16 kb of a transgene. Only the Ig variable region and its proximate flanks are mutated, not the constant region. Several Ig gene enhancers are permissive for somatic mutation. Association of the enhancer with its natural Ig promoter is not necessary. However, the mutation process seems specific for Ig genes. No mutations were found in housekeeping genes from cells with high levels of somatic hypermutation of their Ig genes. The Ig enhancers may provide the Ig gene specificity. An exception may be the BCL6 gene, which was mutated in human but not in mouse B cells. Transcription of a region is required for its mutability. When the transcriptional promoter located upstream of the variable region is duplicated upstream of the constant region, this region also becomes mutable. This suggests a model in which a mutator factor associates with the RNA polymerase at the promoter, travels with the polymerase during elongation, and causes mutations during polymerase pausing. The DNA repair systems, nucleotide excision repair and DNA mismatch repair, are not required. Our recent data with an artificial substrate of somatic mutation suggest that pausing may be due to secondary structure of the DNA or nascent RNA, and the specific mutations to preferences of the mutator factor.

Animals↗
PubMed1998

Ultrasound image texture analysis for characterizing intramuscular fat content of live beef cattle.

The primary factors in determining beef quality grades are the amount and distribution of intramuscular fat percentage (IMFAT). Texture analysis was applied to ultrasound B-mode images from ribeye muscle of live beef cattle to predict its IMFAT. We used wavelet transform (WT) for multiresolutional texture analysis and second-order statistics using a gray-level co-occurrence matrix (GLCM) technique. Sets of WT- and GLCM-based texture features were calculated from ultrasonic images from 207 animals and linear regression methods were used for IMFAT prediction. WT-based features included energy ratios, central moments of wavelet-decomposed subimages and wavelet edge density. The regression model using WT features provided a root mean square error (RMSE) of 1.44 for prediction of IMFAT using validation images, while that of GLCM features provided an RMSE of 1.90. The prediction models using the WT features showed potential for objective quality evaluation in the live animals.

Adipose Tissue↗
PubMed1998

Purification and characterization of a recombinant human cripto-1 protein.

Cripto-1 (CR-1) is a novel protein that contains a modified EGF-like motif and that does not directly bind to any of the known erb B type-1 receptor tyrosine kinase receptors. To more clearly define the biological effects of CR-1 and to more adequately compare the structure-function relationships of CR-1 with other members of the EGF family of growth factors, we have expressed a modified, full-length recombinant human CR-1 protein (rhCR-1) in E. coli and have devised a procedure for the solubilization, refolding and purification of a biologically active form of this protein. We have generated the mature form of hCR-1 from computer assisted predictions of potential signal peptide cleavage sites. Expression of the modified rhCR-1 protein in E. coli was limited to the inclusion bodies. The rhCR-1 protein was found to be expressed at high levels in bacterial cells when fused to a histidine-tag sequence. Refolding of rhCR-1 was found to be difficult because of the large number of cysteine residues in the protein which results in protein aggregation. By chemically modifying the cysteine residues in the rhCR-1 protein with 3-trimethylammoniopropyl methanethiosulfonate, additional positive charges have been introduced into the protein by this disulfiding reagent. This modification facilitates solubilization of the protein when rhCR-1 is denatured. The solubilized, denatured protein was then purified by CM cation exchange and C4 reverse phase HPLC chromatography and refolded in a redox buffer. The refolded, modified rhCR-1 protein was found to be biologically active by its ability to inhibit beta-casein expression, to stimulate the tyrosine phosphorylation of Shc and the activation of MAPK and by its capacity to facilitate branching growth of mouse mammary epithelial cells in type I collagen gels.

Animals↗
PubMed1998

Web based 3-D medical image visualization on the PC.

With the recent advance of Web and its associated technologies, information sharing on distribute computing environments has gained a great amount of attention from many researchers in many application areas, such as medicine, engineering, and business. One basic requirement of distributed medical consultation systems is that geographically dispersed, disparate participants are allowed to exchange information readily with each other. Such software also needs to be supported on a broad range of computer platforms to increase the softwares accessibility. In this paper, the development of world-wide-web based medical consultation system for radiology imaging is addressed to provide platform independence and greater accessibility. The system supports sharing of 3-dimensional objects. We use VRML (Virtual Reality Modeling Language), which is the defacto standard in 3-D modeling on the Web. 3-D objects are reconstructed from CT or MRI volume data using a VRML format, which can be viewed and manipulated easily in Web-browsers with a VRML plug-in. A Marching cubes method is used in the transformation of scanned volume data sets to polygonal surfaces of VRML. A decimation algorithm is adopted to reduce the number of meshes in the resulting VRML file. 3-D volume data are often very large in size, hence loading the data on PC level computers requires a significant reduction of the size of the data, while minimizing the loss of the original shape information. This is also important to decrease network delays. A prototype system has been implemented (http://cybernet5.snu.ac.kr/-cyber/mrivrml .html), and several sessions of experiments are carried out.

Algorithms↗
PubMed1998

Toluene distribution of glue sniffers' biological fluid samples in Korea.

We have studied the distribution of toluene in glue sniffers' biological fluid samples by gas chromatography or gas chromatography/mass spectrometry. The determined toluene concentrations ranged from 0.1 to 40.3 mg/L in urine samples and from 0.1 to 74.7 mg/L in blood samples, respectively. Among the 120 urine samples, 61% of all cases ranged between 0.1 and 1.0 mg/L and 27% was between 1.0 and 5.0 mg/L, respectively. On the other hand, 39% and 46% of all 99 blood samples ranged between 0.1 and 1.0 mg/L, or 1.0 and 5.0 mg/L, respectively. In the fatal cases (36 cases), the distribution of toluene ranged from 0.3 to 40.5 mg/L in the blood samples.

Adhesives↗
PubMed1998

Immunoglobulin transgenes as targets for somatic hypermutation.

This review describes studies on somatic hypermutation of immunoglobulin genes that were started in the mid-80s in collaboration with Ralph Brinster. Almost all of the experiments were carried out using Ig transgenes as targets for the somatic mutation mechanism. Ig transgenes can be very good targets of somatic mutation, despite many different transgene integration sites. Thus, the required cis-acting elements must be present within the approximately 10 kb of the transgene. Only the Ig variable region and its proximate flanks are mutated, not the constant region in unmanipulated sequences. Several Ig gene enhancers are permissive for somatic mutation and they do not have to be associated with the Ig promoter they normally interact with. However, the mutation process does seem to be specific for Ig genes. No mutations were found in several housekeeping genes isolated from cells that had very high levels of somatic hypermutation of their Ig genes. This suggests that the Ig enhancers provide the lg gene specificity. An exception is the Bcl-6 gene, encoding a transcription factor, which was found to be mutated in normal human memory B cells. When the transcriptional promoter that is located upstream of the variable region is duplicated upstream of the constant region, this region is mutated as well. This suggests a transcription coupled model in which a mutator factor associates with the RNA polymerase at the initiation of transcription, travels with the polymerase during elongation, and causes mutations during polymerase pausing. Our recent data with an artificial substrate for somatic mutation suggest that the mutations are increased by increased stability of the secondary structures in the nascent RNA, and the specific nucleotides that are mutated are due to preferences of a mutator factor.

Animals↗
PubMed1997

Molecular characterization of a nonsuppressible allele (prC4) of the Drosophila purple gene.

Purple gene encodes 6-pyruvoyl tetrahydropterin synthase (PTP synthase) in Drosophila. The enzyme PTP synthase catalyzes the conversion of dihydroneopterin triphosphate (H2-NTP) to 6-pyruvoyl tetrahydropterin (PTP), an important intermediate for pterin compounds. The extreme purple mutant, prC4, shows a very low activity of PTP synthase. The mutant purple gene has been cloned by screening with the subgenomic library of prC4. The size and expression level of PTP synthase gene transcripts in prC4 were almost the same as those of the wild type. The genomic DNA was also examined in the purple region by Southern blot analysis, but no changes in restriction pattern could be detected. Compared with the wild type PTP synthase sequence, the mutant PTP synthase of prC4 showed three missense mutations: the replacement of alanine 7 by serine (A7S), leucine 9 by phenylalanine (L9P), and aspartic acid 168 by glycine (D168G). Significance of these mutations was discussed in relation to the formation of the oligomeric structure of PTP synthase.

Alleles↗
PubMed1997

B lymphocytes of xeroderma pigmentosum or Cockayne syndrome patients with inherited defects in nucleotide excision repair are fully capable of somatic hypermutation of immunoglobulin genes.

Recent experiments have strongly suggested that the process of somatic mutation is linked to transcription initiation. It was postulated that a mutator factor loads onto the RNA polymerase and, during elongation, causes transcriptional arrest that activates DNA repair, thus occasionally causing errors in the DNA sequence. We report the analysis of the role of one of the known DNA repair systems, nucleotide excision repair (NER), in somatic mutation. Epstein-Barrvirus-transformed B cells from patients with defects in NER (XP-B, XP-D, XP-V, and CS-A) were studied. Their heavy and light chain genes show a high frequency of point mutations in the variable (V), but not in the constant (C) regions. This suggests that these B cells can undergo somatic hypermutation despite significant defects in NER. Thus, it is doubtful that NER is an essential part of the mechanism of somatic hypermutation of Ig genes. As an aside, NER seems also not involved in Ig gene switch recombination.

Adolescent↗
PubMed1997

Leukotrienes in acetylcholine-induced contraction of esophageal circular smooth muscle in experimental esophagitis.

BACKGROUND & AIMS: Phospholipase A2 (PLA2) participates in acetylcholine (ACh)-induced contraction of esophageal circular smooth muscle. Because PLA2, arachidonic acid, and its metabolites are involved in inflammatory responses, their role after induction of experimental esophagitis was examined. METHODS: Experiments were performed in esophageal smooth muscle cells (ESO) isolated by enzymatic digestion from the circular layer of normal and esophagitis animals. Content of peptidoleukotrienes (leukotriene [LT] C4, LTD4, and LTE4) was measured in esophageal circular muscle tissue. RESULTS: The cytosolic PLA2 antagonist trifluoromethyl ketone analogue of arachidonic acid inhibited ACh-induced contraction of normal and esophagitis ESO. Inhibition by secreted PLA2 antagonists AM5 and MJ33 was significantly greater in esophagitis ESO. The lipoxygenase inhibitor nordihydro-guaiaretic acid and the LTD4 antagonist ICI 198,615 inhibited ACh-induced contraction of esophagitis but not of normal ESO. Secreted PLA2 and LTD4 contracted normal ESO more than esophagitis ESO. However, in esophagitis, ESO contraction was increased by threshold diacylglycerol concentration. Resting levels of LTs were greater in esophagitis than in normal circular esophageal muscle and increased in response to ACh in esophagitis but not in normal esophageal muscle. CONCLUSIONS: Esophagitis shifts the signal transduction pathway activated by ACh. Esophagitis increased the contribution of secreted PLA2 and of LTs to ACh-induced contraction.

Acetylcholine↗
PubMed1997

Effectiveness of the 40 adolescent AIDS-risk reduction interventions: a quantitative review.

OBJECTIVE: (1) To review evaluations of Acquired Immunodeficiency Syndrome (AIDS) prevention interventions targeting adolescents to determine whether these efforts have been effective in reducing risk behaviors. (2) To examine the relation between intervention design issues and outcomes measures. METHOD: A systematic review of five electronic databases and hand-searches of 11 journals, were undertaken for articles published from January 1983 through November 1995 that reported evaluations of adolescent AIDS risk-reduction interventions conducted in the United States. Outcomes examined include: improved attitudes about AIDS risk and protective behaviors, increased intention to abstain from sexual intercourse or to use condoms, and reduced sexual risk behaviors. RESULTS: Forty studies that met preestablished inclusion criteria were found. For each outcome assessed, a majority of studies found a positive intervention impact (88% of studies assessing changes in knowledge; 58% changes in attitude, 60% changes in intention to use condoms, 73% in condom use, and 64% in decreasing number of sexual partners). Interventions that demonstrated an increase in intention to use a condom were significantly more likely to be theory-based than those that did not show any significant changes in intention (100% vs. 0%, p = .048). Interventions that increased condom use and decreased the number of sexual partners were longer in duration than those that did not improve these outcomes. CONCLUSIONS: AIDS risk reduction interventions can be effective in improving knowledge, attitudes, and behavioral intentions and in reducing risk practices. The positive relationship between improved outcomes and several elements of intervention design underscores the need for increased focus on intervention design in future studies.

Acquired Immunodeficiency Syndrome↗