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Biomedical subjects

S Y Choi

Publications and source records attributed to S Y Choi.

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

Cloning, characterization, and expression of the CIP2 gene induced under cadmium stress in Candida sp.

We isolated, sequenced, and expressed a cadmium-induced gene, CIP2, that specifically hybridizes to a mRNA of approximately 950 nucleotides. The CIP2 mRNA was barely present in normal Candida cells, but accumulated at higher levels in cadmium-treated cells. Other heavy metals such as copper, mercury, lead, and manganese had no effect on the expression of the CIP2 gene. CIP2 contains an open reading frame encoding a protein of 203 amino acids. This gene was also activated by an oxidant, diamide. Our results suggest that CIP2 may play a crucial role in the specific cellular response to oxidative stress evolved by the cadmium treatment.

Amino Acid Sequence↗
PubMed1998

Activation of two types of brain glutamate dehydrogenase isoproteins by gabapentin.

The stimulatory effects of gabapentin on the activities of two types of glutamate dehydrogenase (GDH) isoproteins homogeneously purified from bovine brain have been studied at various conditions. When the effects of different gabapentin concentrations on GDH activities were studied in the direction of reductive amination of 2-oxoglutarate with NADPH as a coenzyme, a marked activation was observed for both isoproteins, whereas both isoproteins showed activation to a lesser extent with NADH as a coenzyme. Stimulatory effects of gabapentin on GDH activities in the direction of the oxidative deamination of glutamate were also observed, but to a much lesser extent than reductive amination. There were big differences between the two GDH isoproteins in their sensitivity to the action of gabapentin. The largest activation was observed with GDH II when NADPH was used as a coenzyme. Half-maximal stimulation was reached at around 1.5 mM. Gabapentin relieved the inhibition of GDH isoproteins by GTP and this resulted in an increase in the apparent activation by gabapentin in the presence of GTP. 2-Oxoglutarate was found to give rise to high substrate inhibition and gabapentin reduced the substrate inhibition in the presence of 0.2 mM NADH. Since there are neurodegenerative disorders in which GDH activity is decreased, the therapeutic modulation of the activity of this enzyme may be clinically useful.

Acetates↗
PubMed1998

A glycosidase antibody elicited against a chair-like transition state analog by in vitro immunization.

Antibodies were generated against the positively charged chair-like glycosidase inhibitor nojirimycin by in vitro immunization. A number of catalytic antibodies were isolated, one of which catalyzes the hydrolysis of p-nitrophenyl beta-D-glucopyranoside 3 with a rate enhancement (kcat/kuncat) of 10(5) M over the HOAC-catalyzed reaction. The antibody discriminates modifications in the pyranoside ring of substrate 3 at the C2, C4, and the anomeric positions. The pH dependence of the reaction and chemical modification studies suggest the presence of an active-site Asp or Glu residue that may function as a general acid. This study further defines those requirements necessary to generate antibodies that efficiently cleave glycosidic bonds.

1-Deoxynojirimycin↗
PubMed1998

Expression of the CIP1 gene induced under cadmium stress in Candida sp.

Cadmium is a toxic heavy metal with no known biological activity. Differential display of mRNA was employed to isolate cDNA corresponding to the transcript that is induced in cadmium-treated Candida sp. In this report we describe the molecular characterization of the CIP1 gene, which was shown to be rapidly induced after cadmium treatment. Northern blot analysis showed that the CIP1 transcript was not present in normal cells, but accumulated at higher levels in cadmium-treated cells. Treatment of other heavy metals such as copper, mercury, lead, zinc, or heat-shock had no effect on the expression of the CIP1 gene. Sequence analysis of CIP1 revealed that it encodes a 32 kDa hydrophobic protein that contains a putative transmembrane domain. The deduced amino acid sequence of CIP1 showed a little homology with isoflavone reductase of plants. From the promoter sequence analysis, we also identified a sequence similar to pas, a cadmium-responsive element of the ParA gene in tobacco. Our results suggest that Candida CIP1 may play a crucial role in the establishment of specific cellular response to stress evolved by the cadmium treatment.

Amino Acid Sequence↗
PubMed1998

Identification of three novel mutations and a high frequency of the Arg778Leu mutation in Korean patients with Wilson disease.

Four mutations--R778L, A874V, L1083F, and 2304delC--in the copper-transporting enzyme, P-type ATPase (ATP7B), were identified in Korean Patients with Wilson disease. Arg778Leu, the most frequently reported mutation of this enzyme, was found in six of eight unrelated patients studied, an allele frequency of 37.5%, which is considerably higher than those in other Asian populations. The novel single nucleotide deletion, 2304delC, was found in one patient. Since a mutation at cDNA nucleotide 2302 (2302insC) had been previously described, this region of the ATP7B gene may be susceptible to gene rearrangements causing Wilson disease.

Adenosine Triphosphatases↗
PubMed1998

Expression of GABA transaminase immunoreactivity in interneurons of the rat neostriatum.

Immunoreactivity for gamma-aminobutyric acid transaminase (GABA-T), a degradation enzyme for GABA, was localized by immunocytochemistry in the rat neostriatum and the globus pallidus using a monoclonal antibody. Immunoreactivity for GABA-T was found primarily in interneurons and in the neuropilar elements in the neostriatum. Many of GABA-T-immunoreactive neurons were found to display parvalbumin immunoreactivity. This indicates many of the GABA-T-immunoreactive neurons are striatal GABAergic interneurons. Occasionally, GABA-T-immunoreactive glial cells were found. In the globus pallidus, many pallidal neurons also displayed GABA-T immunoreactivity and many of the immunoreactive neurons were seen to express parvalbumin immunoreactivity. Immunoreactivity for GABA-T was also detected in the neuropil of the globus pallidus. The present results indicate the GABAergic interneurons in the neostriatum and a subpopulation of pallidal neurons play an important role in metabolic degradation of GABA in the basal ganglia.

4-Aminobutyrate Transaminase↗
PubMed1998

Porcine pyridoxal kinase c-DNA cloning, expression and confirmation of its primary sequence.

Porcine brain pyridoxal kinase has been cloned. A 1.2 kilo-based cDNA with a 966-base pair open reading frame was determined from a porcine brain cortex cDNA library using PCR technique. The DNA sequence was shown to encode a protein of 322 amino acid residues with a molecular mass of 35.4 kDa. The amino acid sequence deduced from the nucleotide sequence of the cDNA was shown to match the partial primary sequence of pyridoxal kinase. Expression of the cloned cDNA in E. coli has produced a protein which displays both pyridoxal kinase activity and immunoreactivity with monoclonal antibodies raised against natural enzyme from porcine brain. With respect to the physical properties, it is shown that the recombinant protein exhibits identical kinetic parameters with the pure enzyme from porcine brain. Although the primary sequence of porcine pyridoxal kinase has been shown to share 87% homology with the human enzyme, we have shown that the porcine enzyme carries an extra peptide of ten amino acid residues at the N-terminal domain.

Amino Acid Sequence↗
PubMed1998

A competence regulon in Streptococcus pneumoniae revealed by genomic analysis.

Transformation in bacteria is the uptake and incorporation of exogenous DNA into a cell's genome. Several species transform naturally during a regulated state defined as competence. Genetic elements in Streptococcus pneumoniae induced during transformation were identified by combining a genetic screen with genomic analysis. Six loci were discovered that composed a competence-induced regulon. These loci shared a consensus promoter sequence and encoded proteins, some of which were similar to proteins involved in DNA processing during transformation in other bacteria. Each locus was induced during competence and essential for genetic transformation.

Consensus Sequence↗
PubMed1998

Non-organ specific cancer prevention of ginseng: a prospective study in Korea.

BACKGROUND: A number of studies have reported that increased consumption of natural products reduced the risk of cancer. Our previous case-control studies have shown a significant reduction in the risk of cancer development among those who regularly consumed ginseng. We conducted a prospective cohort study to evaluate the preventive effect of ginseng against cancer on a population residing in a ginseng cultivation area on the basis of the result of case-control studies. METHODS: This study was conducted in Kangwha-eup from August 1987 to December 1992. We studied 4634 people over 40 years old who completed a questionnaire on ginseng intake. In an attempt to obtain detailed information about ginseng intake, we asked them to specify their age at initial intake, their frequency and duration of ginseng intake, the kind of ginseng, etc. Multiple logistic regression was used to estimate relative risks (RR) when controlling simultaneously for covariates. RESULTS: Ginseng consumers had a decreased risk (RR = 0.40, 95% confidence interval [CI] : 0.28-0.56) compared with non-consumers. On the type of ginseng, the RR was 0.31 (95% CI: 0.13-0.74) for fresh ginseng extract consumers and 0.34 (95% CI: 0.20-0.53) for consumers of multiple combinations. There was no cancer death among 24 red ginseng consumers. There was a decreased risk with a rise in the frequency of ginseng intake, showing a dose-response relationship. The RR of ginseng consumers were 0.33 (95% CI: 0.18-0.57) in gastric cancer and 0.30 (95% CI : 0.14-0.65) in lung cancer. Among ginseng preparations, fresh ginseng extract consumers were significantly associated with a decreased risk of gastric cancer (RR = 0.33, 95% CI: 0.12-0.88). CONCLUSIONS: These results strongly suggest that Panax ginseng C.A. Meyer has non-organ specific preventive effect against cancer, providing support for the previous case-control studies.

Adult↗
PubMed1998

Two-year follow-up of eyes without topical corticosteroid treatment after photorefractive keratectomy (PRK).

This study was performed to evaluate the result of photorefractive keratectomy (PRK) without topical corticosteroid treatment at postoperative two years. PRK was performed by Summit OmniMed excimer laser, using a 5.0 mm ablation zone in 51 eyes of 29 patients who were then followed up for more than 2 years. During this period, patients who showed myopic regression of less than 1.5 diopters(D) or corneal haze less than grade 2, were regarded as the favorable result group and those who showed myopic regression equal to or greater than 1.5 D or corneal haze greater than grade 1 were regarded as the unfavorable result group. Thirty-four of 51 eyes showed favorable results without any corticosteroid treatment, and 17 eyes showed unfavorable results. In this latter group preoperative mean refractive error (-7.94 +/- 1.58 D) was significantly higher than in the favorable result group (-5.14 +/- 1.30 D) (p < 0.01, t-test); there was, though no statistical difference in age, gender, or corneal thickness. The results were unfavorable in only two of 32 eyes suffering from moderate myopia (< or = -6.0 D), but in 15 of 19 showing high myopia (> -6.0 D). In eyes suffering from moderate myopia, routine topical corticosteroid treatment after PRK does not appear to be necessary.

Administration, Topical↗
PubMed1998

Prevalence of viral hepatitis markers in Korean patients with hepatocellular carcinoma.

The positive rates of hepatitis B surface antigen (HBsAg) and antibody to hepatitis C virus (anti-HCV) were analyzed according to year, sex, age, and serum ALT levels in 1,370 patients with hepatocellular carcinoma (HCC) who visited the Korea Cancer Center Hospital between January 1989 and December 1994. The positive rate of HBsAg was 68.8 to 76.0% per year in patients with HCC, while that of anti-HCV was 3.2 to 9.8% per year. No sex predominance was found in the positive rates of HBsAg and anti-HCV. HBsAg positivity was distributed mostly in the 41 to 50 age group, whereas anti-HCV positivity was distributed mostly in the over 50 age group. Higher positive rate of anti-HCV was observed in HCC patients with serum ALT levels above the normal range than in those with serum ALT levels within the normal range. However, elevated serum ALT levels above the normal range was not related to the positive rate of HBsAg. The relatively low prevalence of anti-HCV in patients with HCC suggests that the role of HCV infection in the development of HCC lower than that of HBV infection in Korea. However, our results suggest that HCV is another potent risk factor for HCC even in HBV endemic areas.

Adolescent↗
PubMed1998

Surface ultrastructure of Metagonimus miyatai metacercariae and adults.

A scanning electron microscopic study was performed to observe surface ultrastructures of excysted metacercariae and adults of Metagonimus miyatai. Metacercariae were collected from the scale of the pale chub (Zacco platypus), and adult flukes were harvested 1-4 weeks after infection to rats. In excysted metacercariae, the oral sucker was devoid of tegumental spines and had type I and type II sensory papillae. Anteriorly to the ventral sucker, spines were dense and digitated into 5-7 points, whereas near the posterior end of the body spines were sparse and digitated into 2-3 points. In one-week adults, 7 type II sensory papillae were arranged around the lip of the oral sucker, and at inner side of the lip one pair of small and two pairs of large type 1 sensory papillae were seen on each side. The distribution of tegumental spines was similar to that of metacercariae, but they were more differentiated with 9-11 pointed tips. In two- to four-week old adults, the surface ultrastructure was nearly the same as in one-week old adults, however, sperms were frequently seen entering into the Laurer's canal. Conclusively, the surface ultrastructure of M. miyatai was generally similar to that of M. yokogawai, however, differentiation of tegumental spines and distribution of sensory papillae around the oral sucker were different between the two species, which may be of taxonomic significance.

Animals↗
PubMed1997

Modulation of the catalytic activity of brain succinic semialdehyde reductase by reaction with pyridoxal 5'-phosphate.

An NADPH-dependent succinic semialdehyde reductase from bovine brain was inactivated by pyridoxal 5'-phosphate. Spectral evidence is presented to indicate that the inactivation proceeds through formation of a Schiff's base with amino groups of the enzyme. After sodium borohydride reduction of the inactivated enzyme, it was observed that 1 mol phosphopyridoxyl residue was incorporated/mol enzyme monomer. The coenzyme, NADPH, protected the enzyme against inactivation by pyridoxal 5'-phosphate. After tryptic digestion of the enzyme modified with pyridoxal 5'-phosphate in the presence and absence of NADPH followed by [1H]NaBH4 reduction, a radioactive peptide absorbing at 310 nm was isolated by reverse-phase HPLC. The amino acid sequence of the peptide identified a portion of the pyridoxal-5'-phosphate-binding site as the region containing the sequence I-L-E-N-I-Q-V-F-X-K, where X indicates that the phenylthiohydantoin amino acid could not be assigned. The missing residue, however, can be designated as a phosphopyridoxyl lysine as interpreted from the result of amino acid composition of the peptide. It is suggested that the catalytic function of succinic semialdehyde reductase is modulated by binding of pyridoxal 5'-phosphate to a specific lysyl residue at or near the coenzyme-binding site of the protein.

Amino Acids↗
PubMed1997

Distribution of succinic semialdehyde reductase in rat brain.

Succinic semialdehyde reductase (SSR) that catalyzes the reduction of succinic semialdehyde (SSA) to gamma-hydroxybutyrate (GHB) has been identified as one of the NADPH-dependent aldehyde reductases. Reduction of SSA to GHB strongly supports the proposal that GHB biosynthesis may be an important step in the GABA shunt. It is pharmacologically significant in anesthesia, evoking the state of sleep, and an increase in brain dopamine level. Monoclonal antibodies against bovine brain succinic semialdehyde reductase were produced. Using the anti-succinic semialdehyde reductase antibodies, we investigated the distribution of brain succinic semialdehyde reductase in rat brain. The brain tissues were sectioned with a basis on the rat brain atlas of Paxinos and were stained by the immunoperoxidase staining method using monoclonal antibodies. In the section of the frontal lobe, immunoreactive cells were observed in the lateral septal area, the ventral pallidum, which belongs to the substantia innominata. We could observe immunoreactive cells in the reticular thalamic nucleus, which is closely related with 'sleeping', the basal nuclei of Meynert, which is associated with Alzheimer's disease, and hypothalamic nuclei. Immunoreactive cells were also shown in raphe nuclei or the reticular formation of the midbrain, cerebellum, and inferior olivary nuclei of the medulla oblongata. Succinic semialdehyde reductase-immunoreactive cells were distributed extensively in rat brain, especially immunoreactive cells were strongly observed in the areas associated with the limbic system and reticular formation.

Animals↗
PubMed1997

A peptide with unique receptor specificity: stimulation of phosphoinositide hydrolysis and induction of superoxide generation in human neutrophils.

Previously, we identified peptides that stimulate phosphoinositide hydrolysis in several leukocyte cell lines from mixtures of random hexapeptide sequences. Moreover, the peptides activate phospholipase C via a pertussis toxin-sensitive G protein-coupled receptor. We now investigate the structure-activity relationship of the peptides with the goal of improving the activity of the peptides, as well as the biologic function of the peptides. Substitution of the L-methionine at the C terminus of peptides with D-methionine markedly increased the effectiveness of the peptides. The half-maximal effective concentrations of MKYMPm-NH2 and WKYMVm-NH2 for stimulation of phosphoinositide hydrolysis in U266 cells were 30 and 0.5 nM, respectively. By BIAcore analysis we confirmed the existence of a receptor for WKYMVm-NH2. Furthermore, the intracellular calcium concentration increase induced by WKYMVm-NH2 was not inhibited by several chemoattractants (FMLP, IL-8, platelet-activating factor, C5a, granulocyte-macrophage CSF, and granulocyte CSF) suggests that WKYMVm-NH2 has a unique cell surface receptor on leukocytes. WKYMVm-NH2 stimulated the phosphoinositide hydrolysis in U937, HL60, and U266 cells, as well as in human neutrophils. Moreover, WKYMVm-NH2 is more effective than FMLP in the production of superoxide in human neutrophils. The data suggest that WKYMVm-NH2 may have the ability to activate the microbicidal functions of human neutrophils.

Amino Acids↗
PubMed1997

Extracellular ATP-stimulated increase of cytosolic cAMP in HL-60 cells.

Extracellular ATP increases intracellular Ca2+ concentration ([Ca2+]i) through activation of P2U purinoceptors in HL-60 cells. We found that extracellular ATP also increased the intracellular cAMP level in undifferentiated HL-60 cells. ATP and the hydrolysis-resistant ATP analogue adenosine 5'-O-(3-thiotriphosphate) triggered cAMP production in a concentration-dependent manner. The effects of ATP analogues on the [Ca2+]i elevation was distinguished from their effects on cAMP generation. Reactive Blue 2, the antagonist of P2 purinoceptors, inhibited ATP-induced cAMP generation in a concentration-dependent manner without inhibiting Ca2+ mobilization. The results suggest that a distinct P2 purinoceptor, one different from P2U, is linked to adenylyl cyclase in HL-60 cells.

Adenosine Triphosphate↗
PubMed1997

Activation of collagenase IV gene expression and enzymatic activity by the Moloney murine leukemia virus long terminal repeat.

Moloney murine leukemia virus (Mo-MuLV) is a thymotropic and leukemogenic retrovirus which causes T lymphomas and leukemias, yet does not contain a transforming gene product. Mo-MuLV has been shown to trans-activate cellular genes via a polymerase III-generated transcript, designated let, from the long terminal repeat (LTR). Here we demonstrate that introduction of the Mo-MuLV LTR stably, or transiently, into murine or human cultured cells resulted in an 8- to 15-fold increase in collagenase IV (92-kDa gelatinase, gelatinase B, matrix metalloproteinase-9) gene expression. Collagenase IV protein expression was induced 9-fold by stable integration of MuLV LTR, as measured by immunoblot analysis using an anti-collagenase IV polyclonal antibody. The MuLV LTR coordinately stimulated the proteolytic activity of collagenase IV by 14-fold. The AP-1-binding site in the collagenase IV promoter was required for transactivation by the LTR. Collagenase type IV degrades type IV collagen, a major component of basement membrane, which constitutes the first step of the metastatic cascade. The activation of proteolytic enzymes by the MuLV LTR may thus play a contributory role in the development or spread of virus-induced lymphomas or leukemias.

3T3 Cells↗