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Biomedical subjects

C Y Kim

Publications and source records attributed to C Y Kim.

At least 73 records · Page 4Linked to original sources
PubMed1999

Competitive binding of calmodulin isoforms to calmodulin-binding proteins: implication for the function of calmodulin isoforms in plants.

In plants, multiple calmodulin (CaM) isoforms exist in an organism which vary in their primary structures in as much as 32 residues out of their 148 amino acids. These CaM isoforms show differences in their expression patterns and/or target enzyme activation ability. To further understand the biological significance of CaM isoforms, we examined whether CaM isoforms act on specific regulatory targets. In gel overlay assays on various soybean tissue extracts, surprisingly, two soybean CaM isoforms (SCaM-1 and SCaM-4) did not show significant differences in their target binding protein profiles, although they exhibited minor differences in their relative target binding affinities. In addition, both SCaM isoforms not only effectively bound five known plant CaMBPs, but also showed competitive binding to these proteins. Finally, immunolocalization experiments with the SCaM proteins in sections of various tissues using specific antibodies revealed similar distribution patterns for the SCaM isoforms except for root tissues, which indicates that the SCaM isoforms are concomitantly expressed in most plant tissues. These results suggest that CaM isoforms may compete for binding to CaMBPs in vivo. This competitive nature of CaM isoforms may allow modulation of Ca(2+)/CaM signaling pathways by virtue of relative abundance and differential target activation potency.

Binding, Competitive↗
PubMed1999

Identification of a nucleic acid binding domain in eukaryotic initiation factor eIFiso4G from wheat.

Higher plants have two complexes that bind the m7G-cap structure of mRNA and mediate interactions between mRNA and ribosomal subunits, designated eIF4F and eIFiso4F. Both complexes contain a small subunit that binds the 5'-cap structure of mRNA, and a large subunit, eIF4G or eIFiso4G, that binds other translation factors and RNA. Sequence-specific proteases were used to cleave native cap-binding complexes into structural domains, which were purified by affinity chromatography. We show here that eIFiso4G contains a central protease-resistant domain that binds specifically to nucleic acids. This domain spans Gln170 to Glu443 and includes four of the six homology blocks shared by eIFiso4G and eIF4G. A slightly shorter overlapping sequence, from Gly202 to Lys445, had no nucleic acid binding activity, indicating that the N-terminal end of the nucleic acid binding site lies within Gln170 to Arg201. The binding of the central domain and native eIFiso4F to RNA homopolymers and double- and single-stranded DNAs was studied. Both molecules had highest affinity for poly(G) and recognized single- and double-stranded sequences.

Amino Acid Sequence↗
PubMed1999

A novel parvovirus isolated from Manchurian chipmunks.

A novel parvovirus was identified in Manchurian chipmunks inhabiting Korea. Hepatitis B surface antigen (HBsAg) was detected in sera from 4 animals among 62 apparently healthy chipmunks. Electron microscopic examination of the HBsAg-positive sera revealed virus-like spherical particles 20-22 nm in diameter. Extraction of nucleic acid under annealing conditions from the serum samples containing virus-like particles yielded a single species of DNA molecule with the electrophoretic mobility of 5.6-kb double-stranded DNA. Four overlapping clones that encompassed almost the full-length viral genome, except both ends, were obtained. By sequencing these clones, we determined the sequence of 5097 nucleotides of the viral DNA. Two open reading frames were identified, with the left side open reading frame encoding a putative nonstructural protein and the right side open reading frame encoding a putative capsid protein. The nucleotide and amino acid sequences showed significant homology to parvovirus B19 and simian parvovirus, but showed little homology to other mammalian autonomous parvoviruses or adeno-associated viruses. These observations indicate that the virus isolated from Manchurian chipmunks is a novel parvovirus and may be a potentially useful animal model of human B19 infection as a new member of the Erythrovirus genus of the Parvoviridae.

Amino Acid Sequence↗
PubMed1999

Structural changes measured by X-ray scattering from human flap endonuclease-1 complexed with Mg2+ and flap DNA substrate.

Human flap endonuclease-1 (FEN-1) is a member of the structure-specific endonuclease family and is essential in DNA replication and repair. FEN-1 has specific endonuclease activity for repairing nicked double-stranded DNA substrates that have the 5'-end of the nick expanded into a single-stranded tail, and it is involved in processing Okazaki fragments during DNA replication. Magnesium is a cofactor required for nuclease activity. We used small-angle x-ray scattering to obtain global structural information pertinent to nuclease activity from FEN-1, the D181A mutant, the wild-type FEN-1. 34-mer DNA flap complex, and the D181A.34-mer DNA flap complex. The D181A mutant, which has Asp-181 replaced by Ala, selectively binds to the flap structure, but has lost its cleaving activity. Asp-181 is thought to be involved in Mg2+ binding at the active site (Shen, B., Nolan, J. P., Sklar, L. A., and Park, M. S. (1996) J. Biol. Chem. 271, 9173-9176). Our data indicate that FEN-1 and the D181A mutant each have a radius of gyration of approximately 26 A, and the effect of Mg2+ on the scattering from the proteins alone is insignificant. The 34-mer DNA fragment was constructed such that it readily forms a 5'-flap structure. The formation of the flap conformation of the DNA substrate was evident by both the extrapolated Io scattering and radius of gyration and was supported by NMR spectrum and nuclease assays. In the absence of magnesium, the FEN-1.34-mer DNA flap complex has an Rg value of approximately 34 A, whereas the D181A.34-mer DNA flap complex self-associates, suggesting that a significant protein conformational change occurs by addition of the flap DNA substrate and that Asp-181 is crucial for proper binding of the protein to the DNA substrate. A time course change in the scattering profiles arising from magnesium activation of the FEN-1.34-mer DNA flap complex is consistent with the protein completely releasing the DNA substrate after cleavage.

DNA↗
PubMed1999

Effect of DA-6034, a derivative of flavonoid, on experimental animal models of inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a multifactorial disorder with unknown etiology and pathogenesis. DA-6034, 7-carboxymethyloxy-3', 4', 5-trimethoxy flavone, is a synthetic flavonoid known to possess anti-inflammatory activity. This study was performed to evaluate the oral therapeutic effect of DA-6034 in three experimental animal models of IBD: two chemical-induced IBD models of rats and the human leukocyte antigen (HLA)-B27 transgenic rat model known to develop spontaneous colitis without the use of exogenous agents. Acute chemical colitis was induced by intracolonic instillation of 1.2 ml of 4% acetic acid solution. Prednisolone (1 mg/kg), sulfasalazine (100 mg/kg) and DA-6034 (0.3 to approximately 3 mg/kg) were orally administered twice daily for 6 days in these rats. In addition, chronic chemical colitis was induced by intracolonic administration of trinitrobenzene sulfonic acid (TNBS) 30 mg in 50% ethanol and agents were orally administered for 6 or 20 days. In chemical-induced IBD models, all of these agents reduced the severity of colitis and specially, DA-6034 (3 mg/kg) showed more potent effect than other drugs in macroscopic lesion score. In HLA-B27 transgenic rats, DA-6034 (3 mg/kg) and prednisolone (0.5 mg/kg) were treated orally twice daily for 6 weeks. The HLA-B27 transgenic rats showed only mild colitis, compared with the chemical-induced colitis models. DA-6034 ameliorated the loose stool and decreased microscopic damage, which is the important indicator of this model. In conclusion, oral therapy of DA-6034 attenuated the macroscopic and histologic damages of the colon in all three experimental models of IBD, which suggest that DA-6034 could be a promising drug in the treatment of IBD.

Acetic Acid↗
PubMed1999

Neurenteric cyst: its various presentations.

Neurenteric (NE) cyst is an uncommon developmental lesion lined with epithelium of endodermal origin. To investigate the clinical manifestation and response to surgery, we retrospectively analyzed eight cases of NE cyst that has been confirmed by surgery. Four were in children. The duration of follow-up ranged from 2 to 105 (mean 38) months. One cyst was in the ventral portion of the posterior cranial fossa and the other seven were on the spinal cord. The chief complaints were motor weakness (5), pain (2), and voiding difficulty (1). In one child and three adults, the duration of symptoms was more than 3 years. Children tended to show rapid progression and excellent recovery after surgery. Although total removal of cyst was possible only in two cases, there was no recurrence. The presentation of an NE cyst may be insidious. Clinical suspicion is important for an early diagnosis and better outcome. Because of the benign course after subtotal excision, too-aggressive removal of the lesion should be avoided.

Adult↗
PubMed1999

Characterization of two fungal-elicitor-induced rice cDNAs encoding functional homologues of the rab-specific GDP-dissociation inhibitor.

By using the mRNA differential display approach to isolate defense signaling genes active at the early stage of fungal infection two cDNA fragments with high sequence homology to rab-specific GDP-dissociation inhibitors (GDIs) were identified in rice (Oryza sativa L.) suspension cells. Using polymerase-chain-reaction products as probes, two full-length cDNA clones were isolated from a cDNA library of fungal-elicitor-treated rice, and designated as OsGDI1 and OsGDI2. The deduced amino acid sequences of the isolated cDNAs exhibited substantial homology to Arabidopsis rab-GDIs. Northern analysis revealed that transcripts detected with the 3'-gene-specific DNA probes accumulated to high levels within 30 min after treatment with a fungal elicitor derived from Magnaporthe grisea. The functionality of the OsGDIs was demonstrated by their ability to rescue the Sec19 mutant of Saccharomyces cerevisiae which is defective in vesicle transport. The proteins, expressed in Escherchia coli, cross-reacted with a polyclonal antibody prepared against bovine rab-GDI. Like bovine rab-GDI, the OsGDI proteins efficiently dissociated rab3A from bovine synaptic membranes. Using the two-hybrid system, it was shown that the OsGDIs specifically interact with the small GTP-binding proteins belonging to the rab subfamily. The specific interaction was also demonstrated in vitro by glutathione S-transferase resin pull-down assay.

Animals↗
PubMed1999

Ginsenosides that produce differential antinociception in mice.

Ginsenoside Rc, Rd, and Re induced antinociception in writhing and formalin tests among five representative ginsenosides: Rb1, Rc, Rd, Re, and Rg1. However, these ginsenosides had no effect in the tail-flick test. The antinociceptive effects induced by three ginsenosides were dose dependent. ED50 was 20.5 (7.3-57.4 mg/kg) for Rc, 17 (11.0-27.6 mg/kg) for Rd, and 3.5 (1-12 mg/ kg) for Re in the writhing test and 62 (42-90 mg/kg) for Rc, 45 (20.5-99.0 mg/kg) for Rd, and 82 (48-139 mg/kg) for Re in the second phase of the formalin test. The antinociceptive effects were not blocked by the opioid receptor antagonist naloxone in the writhing and formalin tests. These three ginsenosides did not affect motor function. Ginsenoside Rc and Rd induced hypothermia for 30 to 60 min, and ginsenoside Rc induced hyperthemia after 150 min of treatment at doses of 100 mg/kg. These results suggest that ginsenosides such as Rc, Rd, or Re inhibit mainly chemogenic pain rather than thermal pain by the nonopioid system in mice.

Acetic Acid↗
PubMed1999

Effect of Korean folk medicine 'Chung-Dae-San' on mast cell-dependent anaphylactic reaction.

We investigated the effect of the herbal formulation 'Chung-Dae-San' (CDS) on anaphylactic reactions. CDS inhibited compound 48/80-induced anaphylactic shock 100% with the dose of 10(0) g/kg body weight (BW). When CDS was given as pretreatment at concentrations ranging from 10(-4) to 10(0) g/kg BW, the serum histamine levels induced by compound 48/80 were reduced in a dose-dependent manner. We also investigated the effect of CDS on mast cell-dependent passive cutaneous anaphylaxis (PCA) activated by anti-dinitrophenyl (DNP) IgE antibody. CDS potently inhibited PCA when administered orally, topically, intraperitoneally or intradermally. However, it did not show inhibitory activity when administered intravenously. CDS dose-dependently inhibited the histamine release from the rat peritoneal mast cells (RPMC) by compound 48/80 and anti-DNP IgE. Moreover, the level of cAMP in RPMC, when CDS was added, significantly increased about 4-fold at 4 min compared with that of basal cells. These results indicate that CDS may possess strong antianaphylactic activity and also suggest the differential activity following administration routes may be caused by difference in bioavailability.

Anaphylaxis↗
PubMed1999

Effect of ammonia and methionine sulfoximine on myo-inositol transport in cultured astrocytes.

Ammonia causes astrocyte swelling which is abrogated by methionine sulfoximine (MSO). Since myo-inositol is an important osmolyte, we investigated the effects of ammonia and MSO on myoinositol flux in cultured astrocytes for periods up to 72 hours. Uptake of myo-inositol was significantly decreased by 26.7 (P < 0.05) and 39.3 (P < 0.006) percent after 48 hours of exposure to 5 or 10 mM ammonia, respectively. The maximum rate of uptake was 14.0+/-0.5 nmol/hour/mg protein which was reduced to 7.45+/-0.27 and 7.02+/-0.57 nmoles/hour/mg protein by 5 or 10 mM ammonia, respectively. The Kms by Michaelis-Menten equation for the control, and in the presence of 5, or 10 mM ammonia were 32.5+/-4.52, 44.4+/-5.82, and 39.3+/-7.0 microM, respectively. Kms by Hanes-Woolf plot for the control, 5, or 10 mM ammonia were 25, 45, and 40 microM, respectively. Treatment of astrocytes with either 5 or 10 mM NH4Cl for 6 hours caused a decrease in myo-inositol content by 66% and 58%, respectively. MSO (3 mM) partially diminished the ammonia-induced inhibition of myo-inositol uptake and decreased myo-inositol content by 31% after 24 hours. Additionally, ammonia increased myo-inositol efflux briefly through the fast efflux component but had little effect on myo-inositol efflux through the slow efflux component of astrocytes exposed to ammonia for up to 72 hours. Predominantly decreased myo-inositol influx coupled with brief efflux through the fast component may represent an adaptive response to diminish the extent of ammonia-induced astrocyte swelling.

Ammonia↗
PubMed1999

Effect of dibutyryl cyclic AMP on the kinetics of myo-inositol transport in cultured astrocytes.

Dibutyryl cyclic AMP (dBcAMP) is known to induce maturation and differentiation in astrocytes. As myo-inositol is an important osmoregulator in astrocytes, we examined the effects of maturation and biochemical differentiation on the kinetic properties of myo-inositol transport. Treatment of astrocytes with dBcAMP significantly decreased the Vmax of myo-inositol uptake, but the effect on Km was not significant. The myo-inositol content of astrocytes was significantly decreased in cells treated for 5 days with dBcAMP as compared with untreated controls. Maximum suppression of myo-inositol uptake occurred 7 days after exposure of astrocytes to dBcAMP; this was gradually reversible when dBcAMP was removed from the medium. After exposure to hypertonic medium for 6 h, mRNA expression of the myo-inositol co-transporter was diminished by approximately 36% in astrocytes treated with dBcAMP as compared with untreated cells. It appears that myo-inositol transporters in astrocytes treated with dBcAMP are either decreased in number or inactivated during maturation and differentiation, suggesting that the stage of differentiation and biochemical maturation of astrocytes is an important factor in osmoregulation.

Animals↗
PubMed1999

Eradication of Helicobacter pylori infection did not lead to cure of duodenal mucosa-associated lymphoid tissue lymphoma.

Duodenal mucosa-associated lymphoid tissue (MALT) lymphoma is very rare, and little is known about its clinical course or association with Helicobacter pylori infection. This report describes the case of a 76-year-old man with a polypoid mass in the duodenal bulb, diagnosed as low-grade MALT lymphoma. H. pylori infection in the duodenal mucosa was confirmed by histology with silver stain. Endoscopic examination showed that the gross lesion regressed after the eradication of H. pylori despite its histopathologic persistence. Ten months later, however, cervical and intraperitoneal lymphadenopathy and bone marrow involvement was observed, and the pathologic diagnosis of the cervical lymph node was identical with that of the duodenal lesion.

Aged↗
PubMed1999

A precipitation reaction found in patients with hepatitis C as a marker for the purification of virus-like particles.

Even after the molecular cloning of the hepatitis C virus (HCV), an HCV-specific precipitation reaction has not yet been identified. We attempted to develop a precipitation system exclusively for anti-HCV-positive sera as a first step in finding an HCV-specific antigen and HCV-associated particles. In some patients being in a final stage of different liver diseases, we found sera (179/132,761; designated 'a-CK') which specifically precipitated with anti-HCV- and HCV-RNA-positive sera (designated 'CK'). When CK-positive sera were searched for in patients with various liver diseases using standard a-CK-positive plasma, CK was detected in 420 (57.9%) of 726 anti-HCV-positive sera and in none of the 1,630 anti-HCV-negative ones. The nature of CK and a-CK has not been fully clarified yet; CK demonstrated inter-betagamma mobility, whereas a-CK showed beta-globulin mobility; CK was not detected in cryoprecipitate, but HCV RNA was present in precipitates of CK-positive plasma incubated with one that was a-CK positive. Transmission electron microscopy revealed two size ranges of particles in the precipitate of CK- and a-CK-positive plasmas, 23-38 nm and 48-65 nm. We have found a novel precipitation system which is exclusive to anti-HCV-positive sera and which specifically precipitates an HCV-RNA-containing serum fraction and particles. This system can be useful for the purification and characterization of the circulating particles. Furthermore, it may be a new approach to the nature of HCV-RNA-carrying material.

Centrifugation↗
PubMed1999

Establishment of BALB/c mice model infected with Helicobacter pylori.

OBJECTIVES: Considering the geographic differences in the prevalence of virulence factors such as CagA or VacA of H. pylori isolated from Korean adults compared with those from western countries, the establishment of a mouse model infected with H. pylori isolated from Korean adults is needed to investigate the pathogenesis and to develop vaccines against H. pylori infection in Korea. The aim of this study was to establish the BALB/c mouse model infected with H. pylori isolated from Korean. METHODS: Six-week-old BALB/c mice were inoculated intragastrically with 10(9) CFU of H. pylori. Loss of glandular architecture, erosions and infiltration of inflammatory cells within the lamina propria compared with normal gastric mucosa were scrutinized. Evidence for H. pylori infection was assessed by rapid urease test of gastric mucosa and by microscopic examination using the H & E stain and Warthin-Starry silver stain. RESULTS: Rapid urease test was positive in 55% of all inoculated mice. Definite histologic changes and the evidence of H. pylori colonization were observed in the H. pylori infected group. Significant infiltration of inflammatory cells was observed 6 weeks after the last inoculation and the level of serum IgG against H. pylori was increased from 2 weeks after the last inoculation. CONCLUSIONS: The H. pylori isolated freshly from Korean adults could colonize the stomach of BALB/c mice and induce pathologic alterations that mimics human gastric diseases. This model would facilitate the investigations for the pathogenetic mechanisms of H. pylori infection.

Adult↗
PubMed1999

Development of a non-transformed human liver cell line with differentiated-hepatocyte and urea-synthetic functions: applicable for bioartificial liver.

There is a need to develop human hepatocyte cell lines which retain both replicating capacity and highly differentiated functions to facilitate the development of an efficient bioartificial liver. The present study was undertaken to differentiate, using sodium butyrate, the actively replicating immortalized human liver cell line. The effects of butyrate on cell growth and cell cycle were analyzed, and the albumin synthesis, cytochrome P450 and ammonia-detoxifying activity of the butyrate-treated cells were measured. Butyrate treatment resulted in G2/M arrest of the cell cycle and polygonal changes in the cell morphology. Neither the control nor the butyrate-treated cells showed transformed characteristics. Butyrate treatment increased the amount of albumin secretion, cytochrome P450 activity, and the urea production rate of the cells. The present study provides non-transformed human hepatocytes, which can replicate unlimitedly and then restore differentiated hepatocyte-specific functions by butyrate, and therefore, have applications for the development of an efficient bioartificial liver.

Albumins↗
PubMed1998

Reduced COX-2 protein in colorectal cancer with defective mismatch repair.

Most colorectal adenomas and carcinomas arise in the setting of chromosomal instability characterized by progressive loss of heterozygosity. In contrast, approximately 15-20% of colorectal neoplasms arise through a distinct genetic pathway characterized by microsatellite instability (MSI) associated with frequent loss of expression of one of the DNA mismatch repair enzymes, most often hMLH1 or hMSH2. These distinct genetic pathways are reflected by differences in tumor histopathology, distribution in the colon, prognosis, and dwell time required for progression from adenoma to carcinoma. To determine whether these two groups of tumors differ in their expression of cyclooxygenase-2 (COX-2), a putative chemopreventative target, immunostaining for this protein was performed in colorectal cancers categorized by the presence (n = 41) and absence (n = 66) of defective mismatch repair. Defective mismatch repair was defined by the presence of tumor microsatellite instability (MSI-H, > or =40% of markers demonstrating instability) and by the absence of protein expression for either hMLH1 or hMSH2. Overall, our results showed that low or absent COX-2 staining was significantly more common among tumors with defective mismatch repair (P = 0.001). Other features predictive of low COX-2 staining included marked tumor infiltrating lymphocytosis, and solid/cribiform or signet ring histological patterns. These observations indicate that colorectal cancers with molecular and phenotypic characteristics of defective DNA mismatch repair express lower levels of COX-2. The clinical implications of this biological distinction remain unknown but should be considered when assessing the efficacy of COX-2 inhibitors for chemoprevention in patients whose tumors may arise in the setting of defective DNA mismatch repair.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Hypermethylation of the hMLH1 promoter in colon cancer with microsatellite instability.

Recent studies have demonstrated the presence of microsatellite instability (MSI) in tumors from patients with hereditary nonpolyposis colon cancer and in a subset of patients with sporadic colorectal cancer (CRC). In sporadic CRC, three tumor phenotypes have been defined: microsatellite stable (MSS), low-frequency MSI, and high-frequency MSI (MSI-H). Although defective mismatch repair, consisting primarily of alterations in hMSH2 and hMLH1, is believed to be responsible for the MSI phenotype in the majority of patients with hereditary nonpolyposis colon cancer, the genetic defect responsible for this phenotype in sporadic CRC has yet to be clearly delineated. Somatic or germ-line alterations in these two genes have been identified in only a minority of these cases. Analysis of the protein expression patterns of hMSH2 and hMLH1 in unselected CRC, however, suggests that alterations in hMLH1 may account for a majority of the MSI-H cases. In an effort to explore the underlying molecular basis for these findings, we have examined the methylation status of the presumptive hMLHI promoter region in 31 tumors that vary in regard to their MSI status (MSI-H or MSS), their hMLH1 protein expression (MLH- or MLH+), and their gene mutation (Mut+ or Mut-) status. Hypermethylation of the hMLH1 promoter occurred in all 13 MSI-H/ MLH- tumors that did not have a detectable mutation within the hMLH1 gene. Of those MSI-H tumors containing germ-line or somatic alterations in hMLH1 (n = 7, including 3 frameshift, 1 nonsense, 2 missense mutations, and 1 tumor containing multiple mutations: missense, splice-site alteration, and a frameshift), four had a normal methylation pattern, whereas three others demonstrated hypermethylation of the hMLH1 promoter region. Two of these cases had a missense alteration, the other a frameshift alteration. The single MSI-H/Mut+ tumor that had normal hMLH1 and hMSH2 expression, as well as 9 of the 10 MSS cases, lacked methylation of the hMLH1 promoter. Hypermethylation of the hMSH2 promoter was not observed for any of the cases. These results suggest that hypermethylation of the hMLH1 promoter may be the principal mechanism of gene inactivation in sporadic CRC characterized by widespread MSI.

Adaptor Proteins, Signal Transducing↗