Biomedical subjects

S P Hong

Publications and source records attributed to S P Hong.

At least 19 recordsLinked to original sources

PubMed2006

Resistance to adefovir dipivoxil in lamivudine resistant chronic hepatitis B patients treated with adefovir dipivoxil.

BACKGROUND: Adefovir dipivoxil (ADV) is a potent nucleotide analogue against both the wild-type and lamivudine (LMV) resistant hepatitis B virus (HBV). The cumulative incidence of ADV resistant mutations in the nucleoside/-tide treatment naive chronic hepatitis B patient (CHB) at weeks 48, 96, and 144 was 0, 0.8-3%, and approximately 5.9%, respectively. AIMS: The aim of this study was to characterise the genotypic and phenotypic mutation profiles to ADV in 67 LMV resistant CHB patients who were treated with ADV. METHODS: Serum HBV DNA was quantified by real time polymerase chain reaction. The ADV mutant was detected using matrix assisted laser desorption/ionisation time of flight mass spectrometry based genotyping assays, termed restriction fragment mass polymorphism (RFMP). RESULTS: RFMP analysis revealed that a total of 11 amino acid substitutions developed in the rt domain of the HBV polymerase in nine patients. The cumulative incidence of genotypic ADV resistance at months 12 and 24 was 6.4% and 25.4%, respectively. The rtA181V, rtN236T, and rtA181T mutations were detected in five, four, and two of the 67 patients at treatment months 12-17, 3-19, and 7-20, respectively. Serial quantification of serum HBV DNA revealed that two patients with the rtA181V mutation, with or without the rtN236T mutation, and one patient with the rtA181T mutation displayed HBV DNA rebound. CONCLUSION: Emergence of the ADV mutation in LMV resistant patients who are treated with ADV appeared to present earlier and more frequently than was reported in previous studies on nucleoside/-tide treatment naive patients.

Adenine↗

PubMed2003

The small bovine amelogenin LRAP fails to rescue the amelogenin null phenotype.

Amelogenins are the most abundant secreted proteins in developing dental enamel. These evolutionarily-conserved proteins have important roles in enamel mineral formation, as mutations within the amelogenin gene coding region lead to defects in enamel thickness or mineral structure. Because of extensive alternative splicing of the primary RNA transcript and proteolytic processing of the secreted proteins, it has been difficult to assign functions to individual amelogenins. To address the function of one of the amelogenins, we have created a transgenic mouse that expresses bovine leucine-rich amelogenin peptide (LRAP) in the enamel-secreting ameloblast cells of the dental organ. Our strategy was to breed this transgenic mouse with the recently generated amelogenin knockout mouse, which makes none of the amelogenin proteins and has a severe hypoplastic and disorganized enamel phenotype. It was found that LRAP does not rescue the enamel defect in amelogenin null mice, and enamel remains hypoplastic and disorganized in the presence of this small amelogenin. In addition, LRAP overexpression in the transgenic mouse (wildtype background) leads to pitting in the enamel surface, which may result from excess protein production or altered protein processing due to minor differences between the amino acid compositions of murine and bovine LRAP. Since introduction of bovine LRAP into the amelogenin null mouse does not restore normal enamel structure, it is concluded that other amelogenin proteins are essential for normal appearance and function.

Amelogenesis↗

PubMed2003

Relationship of phenotype and genotype in X-linked amelogenesis imperfecta.

X-linked amelogenesis imperfectas (AI) resulting from mutations in the amelogenin gene (AMELX) are phenotypically and genetically diverse. Amelogenin is the predominant matrix protein in developing enamel and is essential for normal enamel formation. To date, 12 allelic AMELX mutations have been described that purportedly result in markedly different expressed amelogenin protein products. We hypothesize that these AMELX gene mutations result in unique and functionally altered amelogenin proteins that are associated with distinct amelogenesis imperfecta phenotypes. The AMELX mutations and associated phenotypes fall generally into three categories. (1) Mutations (e.g., signal peptide mutations) causing a total of loss of amelogenin protein are associated with a primarily hypoplastic phenotype (though mineralization defects also can occur). (2) Missense mutations affecting the N-terminal region, especially those causing changes in the putative lectin-binding domain and TRAP (tyrosine rich amelogenin protein) region of the amelogenin molecule, result in a predominantly hypomineralization/hypomaturation AI phenotype with enamel that is discolored and has retained amelogenin. (3) Mutations causing loss of the amelogenin C terminus result in a phenotype characterized by hypoplasia. The consistent association of similar hypoplastic or hypomineralization/hypomaturation AI phenotypes with specific AMELX mutations may help identify distinct functional domains of the amelogenin molecule. The phenotype-genotype correlations in this study suggest there are important functional domains of the amelogenin molecule that are critical for the development of normal enamel structure, composition, and thickness.

Amelogenesis Imperfecta↗

PubMed2003

Small sewage treatment system with an anaerobic-anoxic-aerobic combined biofilter.

The objective of this study was to investigate a small sewage treatment system that could improve nitrogen and BOD5 removal efficiency as well as generate less solid using an anaerobic-anoxic-aerobic biofiltration system. Wastewater temperature was in the range of 14-25 degrees C, and hydraulic residual times were 12 h for each reactor. The upflow anaerobic digester equipped with anoxic filter was fed with both raw sewage and recycled effluent from the aerobic filter to induce denitrification and solid reduction simultaneously. In the subsequent aerobic filter, residual organic carbon and ammonia might be oxidized and finally nitrate formed. In the anaerobic reactor, about 71% of influent TCOD was removed by sedimentation of the un-filterable COD at the recycle ratio of 300%. Another 20% of influent TCOD was removed in the anoxic filter by denitrification of the recycled nitrate. After 100 days operation, solid reduction and nitrification efficiency were about 30% and 95%, respectively. Overall removal efficiencies of COD and total nitrogen (T-N) were above 94% and 70% at the recycle ratio of 300%, respectively. Total wasted solid from the system after 100 days operation was about 316 g, which was only 44% of the solid generated from a controlled activated sludge system operated at sludge retention time of 8 days.

Bacteria, Anaerobic↗

PubMed2002

Geobacillus toebii sp. nov., a novel thermophilic bacterium isolated from hay compost.

A thermophilic, spore-forming rod isolated from hay compost in Korea was subjected to a taxonomic study. The micro-organism, designated strain SK-1(T), was identified as being aerobic, Gram-positive, motile and rod-shaped. Growth of the isolate was observed at 45-70 degrees C (optimum 60 degrees C) and pH 6.0-9.0 (optimum pH 7.5). The G+C content of the genomic DNA was 43.9 mol%. Chemotaxonomic characteristics of the isolate included the presence of mesodiaminopimelic acid in the cell wall and iso-C15:0 and iso-C17:0 as the major cellular fatty acids. The predominant isoprenoid quinone was MK-7. The chemotaxonomic characteristics of strain SK-1(T) were the same as those of the genus Geobacillus. Phylogenetic analysis based on 16S rDNA sequences showed that strain SK-1(T) is most closely related to Geobacillus thermoglucosidasius. However, the phenotypic properties of strain SK-1(T) were clearly different from those of G. thermoglucosidasius. The level of DNA-DNA relatedness between strain SK-1(T) and the type strain of G. thermoglucosidasius was 27%. On the basis of the phenotypic traits and molecular systematic data, strain SK-1(T) represents a novel species within the genus Geobacillus, for which the name Geobacillus toebii sp. nov. is proposed. The type strain is strain SK-1(T) (= KCTC 0306BP(T) - DSM 14590(T)).

Base Composition↗

PubMed2001

A purified inactivated Japanese encephalitis virus vaccine made in Vero cells.

A second generation, purified, inactivated vaccine (PIV) against Japanese encephalitis (JE) virus was produced and tested in mice where it was found to be highly immunogenic and protective. The JE-PIV was made from an attenuated strain of JE virus propagated in certified Vero cells, purified, and inactivated with formalin. Its manufacture followed current GMP guidelines for the production of biologicals. The manufacturing process was efficient in generating a high yield of virus, essentially free of contaminating host cell proteins and nucleic acids. The PIV was formulated with aluminum hydroxide and administered to mice by subcutaneous inoculation. Vaccinated animals developed high-titered JE virus neutralizing antibodies in a dose dependent fashion after two injections. The vaccine protected mice against morbidity and mortality after challenge with live, virulent, JE virus. Compared with the existing licensed mouse brain-derived vaccine, JE-Vax, the Vero cell-derived JE-PIV was more immunogenic and as effective as preventing encephalitis in mice. The JE-PIV is currently being tested for safety and immunogenicity in volunteers.

Animals↗

PubMed2001

Evaluation of the anti-tumor and anti-angiogenic effect of paclitaxel and thalidomide on the xenotransplanted oral squamous cell carcinoma.

Angiogenesis is an essential process for the growth and invasion of cancer. However, it is uncertain that anti-angiogenic effects can be a major treatment strategy of oral cancer. The aim of this study was to investigate whether thalidomide and paclitaxel, which are known to be potent inhibitors of angiogenesis, have inhibitory effects on the growth of oral squamous cell carcinoma (OSCC) xenotransplanted into nude mice and whether anti-angiogenesis can be included as a major treatment strategy of oral cancer. After human OSCC cell line, KB, was subcutaneously inoculated into 32 nude mice, the volume of tumor was measured every 3 days. When the tumor mass reached 300-500 mm3, thalidomide (200 mg/kg) and paclitaxel (13 mg/kg) were administered into the animals and tumor volume change was checked. The excised tumor masses on the 30th day after administration were frozen and processed for immunohistochemistry using vascular endothelial growth factor (VEGF) and CD31, and for real-time reverse transcription-polymerase chain reaction (RT-PCR). We evaluated VEGF expression and the expression of its mRNA and CD31 for vessel density. Paclitaxel showed an inhibitory effect on the growth of transplanted human OSCC and reduced the immunohistochemical expression of VEGF and CD31 and VEGF mRNA (P<0.01). Thalidomide also lowered remarkably VEGF expression (P<0.01) and CD31 (P<0.01) as well as VEGF mRNA (P<0.05), but it did not show statistically significant inhibitory effect on the tumor growth. These results suggest that the growth of human OSCC is not simply dependent on VEGF-induced angiogenesis and that anti-angiogenic therapy alone is not likely to be effective for the treatment of OSCC, but might be regarded as adjuvant chemotherapeutic strategy.

Angiogenesis Inhibitors↗

PubMed2001

Chiral separation of beta2-agonists by capillary electrophoresis using hydroxypropyl-alpha-cyclodextrin as a chiral selector.

Enantiomers of five racemic beta2-agonists were investigated by capillary electrophoresis employing a hydroxypropyl-beta-cyclodextrin (HP-beta-CD). The effects of the concentration of HP-beta-CD added to the background electrolyte and of the pH of the buffer on the effective mobility and resolution of the studied compounds were examined. Very good resolution was achieved for terbutaline and clenbuterol; salbutamol and bambuterol was able to be partially resolved. Enantioselectivity and resolution were influenced by the concentration of the HP-beta-CD, buffer composition and pH.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed2001

Chiral separation of beta-blockers after derivatization with (-)-alphamethoxy-alpha-(trifluoromethyl)phenylacetyl chloride by gas chromatography.

Gas chromatographic method was investigated for the chiral separation of several beta-blockers(atenolol, betaxolol, bisoprolol, metoprolol and pindolol) using (-)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride as a chiral derivatizing agent for amino group. Prior to N-acylation, hydroxyl group was converted into O-silyl ethers by react with N-methyl-N-(trimethylsilyl)trifluoroacetamide. The reaction was selective and rapid and the diastereomeric derivatives were well separated by capillary gas chromatography. (R)-isomers were eluted faster than (S)-isomers when (-)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride was used as the chiral derivatizing agent. But in the opposite sequence when (+)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride was used. No racemization was found during the reaction.

Adrenergic beta-Antagonists↗

PubMed2001

Physiological and biochemical characteristics of poly gamma-glutamate synthetase complex of Bacillus subtilis.

An enzymatic system for poly gamma-glutamate (PGA) synthesis in Bacillus subtilis, the PgsBCA system, was investigated. The gene-disruption experiment showed that the enzymatic system was the sole machinery of PGA synthesis in B. subtilis. We succeeded in achieving the enzymatic synthesis of elongated PGAs with the cell membrane of the Escherichia coli clone producing PgsBCA in the presence of ATP and D-glutamate. The enzyme preparation solubilized from the membrane with 8 mM Chaps catalyzed ADP-forming ATP hydrolysis only in the presence of glutamate; the D-enantiomer was the best cosubstrate, followed by the L-enantiomer. Each component of the system, PgsB, PgsC, and PgsA, was translated in vitro and the glutamate-dependent ATPase reaction was kinetically analyzed. The PGA synthetase complex, PgsBCA, was suggested to be an atypical amide ligase.

Adenosine Triphosphatases↗

PubMed2001

Odontogenic keratocyst: Review of 256 cases for recurrence and clinicopathologic parameters.

Odontogenic keratocyst (OKC) is of particular interest because of its high recurrence rate and aggressive behavior. Two hundred fifty-six cases of OKC were reviewed for the age of the patient at diagnosis, sex of the patient, OKC location, and radiographic findings, and 132 patients with OKC were observed to estimate recurrence, which was analyzed for age, sex, location, and several histopathologic findings. OKCs occurred more frequently in men (58.6%) than in women (41.4%), and they occurred in patients within a wide age range, most commonly in patients in the third decade of life (28.9%), followed by those in the second decade (25.0%); the mean age of patients with OKC was 30.8 years. One hundred ninety-six of the 256 cases (76.5%) occurred in the mandible, and the other 60 cases (23.5%) occurred in the maxilla. The mandibular molar and the premolar areas (51.2%) were the most common sites, and the most frequent clinical manifestations at first admission were swelling, pain, or both (82.4% of total cases). Radiographic impressions included dentigerous cyst (27.3%), OKC (25.4%), primordial cyst (14.8%), ameloblastoma (11.7%), residual cyst (9.8%), and radicular cyst (3.1%). The frequency of recurrence at the follow-up examination was 58.3%. There was no significant difference in the recurrence rate on the basis of the sex of the patient. However, OKCs had a significantly higher recurrence rate in patients in the fifth decade of life than in patients in the other age groups (P = .005).Recurrence rates were significantly dependent on the sites of involvement, and OKCs in the mandibular molar region had significantly higher recurrence rates than those in other sites (P = .001). The histopathologic presence of one or more daughter cysts was significantly related to recurrence (P = .03).

Adolescent↗

PubMed2001

Interaction of the Srb10 kinase with Sip4, a transcriptional activator of gluconeogenic genes in Saccharomyces cerevisiae.

Sip4 is a Zn(2)Cys(6) transcriptional activator that binds to the carbon source-responsive elements of gluconeogenic genes in Saccharomyces cerevisiae. The Snf1 protein kinase interacts with Sip4 and regulates its phosphorylation and activator function in response to glucose limitation; however, evidence suggested that another kinase also regulates Sip4. Here we examine the role of the Srb10 kinase, a component of the RNA polymerase II holoenzyme that has been primarily implicated in transcriptional repression but also positively regulates Gal4. We show that Srb10 is required for phosphorylation of Sip4 during growth in nonfermentable carbon sources and that the catalytic activity of Srb10 stimulates the ability of LexA-Sip4 to activate transcription of a reporter. Srb10 and Sip4 coimmunoprecipitate from cell extracts and interact in two-hybrid assays, suggesting that Srb10 regulates Sip4 directly. We also present evidence that the Srb10 and Snf1 kinases interact with different regions of Sip4. These findings support the view that the Srb10 kinase not only plays negative roles in transcriptional control but also has broad positive roles during growth in carbon sources other than glucose.

Bacterial Proteins↗

PubMed2001

Nucleotide sequence of envelope protein of Japanese encephalitis virus SA14-14-2 adapted to vero cells.

Live attenuated Japanese encephalitis (JE) virus SA(14)-14-2 produced in primary dog kidney cells (PDK) was adapted to Vero cells. In an effort to gain insight into the molecular basis of the biological characteristics of the SA14-14-2(Vero) strain, the 1500 nucleotide sequence encoding the envelope (E) gene which possesses major neutralizing epitopes was determined and compared with the sequences of two other attenuated JE virus strains, SA14-14-2(PHK) and SA14-14-2(PDK). The amino acid sequence of the C-terminal region (a.a. 280-500) was found to be identical for all three strains, while the N-terminal region (a.a. 1-279) shows sequence variation. The distribution of mutations in the N-terminal region was nearly the same among the three attenuated strains, suggesting that the N-terminal sequences might be related with virus-host cell specificity. However, it was found that Lys and Val (a.a. 138 and 176, respectively), known to be responsible for attenuation, are still conserved in SA(14)-14-2(Vero). Animal testing showed that SA(14)-14-2(Vero) has an attenuation phenotype similar to that of the parent SA(14)-14-2(PDK) strain in mice.

Amino Acid Sequence↗

PubMed2000

Regulation of the balance of one-carbon metabolism in Saccharomyces cerevisiae.

One-carbon metabolism in yeast is an essential process that relies on at least one of three one-carbon donor molecules: serine, glycine, or formate. By a combination of genetics and biochemistry we have shown how cells regulate the balance of one-carbon flow between the donors by regulating cytoplasmic serine hydroxymethyltransferase activity in a side reaction occurring in the presence of excess glycine. This control governs the level of 5,10-methylene tetrahydrofolate (5,10-CH(2)-H(4)folate) in the cytoplasm, which has a direct role in signaling transcriptional control of the expression of key genes, particularly those encoding the unique components of the glycine decarboxylase complex (GCV1, GCV2, and GCV3). Based on these and other observations, we propose a model for how cells balance the need to supplement their one-carbon pools when charged folates are limiting or when glycine is in excess. We also propose that under normal conditions, cytoplasmic 5,10-CH(2)-H(4)folate is mainly directed to generating methyl groups via methionine, whereas one-carbon units generated from glycine in mitochondria are more directed to purine biosynthesis. When glycine is in excess, 5, 10-CH(2)-H(4)folate is decreased, and the regulation loop shifts the balance of generation of one-carbon units into the mitochondrion.

Adenine↗

PubMed2000

Enantiomeric purity test of bevantolol by reversed-phase high performance liquid chromatography after derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate.

A reversed-phase high-performance liquid chromatographic method was developed to determine the optical purity of bevantolol enantiomers. (S)-(-)-Menthyl chloroformate((-)-MCF), (S)-(-)-alpha-methylbenzyl isocyanate((-)-MBIC) and 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate(GITC), which can react with the secondary amine group of bevantolol were investigated as chiral derivatization reagents. Among them indirect chiral HPLC method using GITC gave the best result. The derivatization proceeded quantitatively within 20 min at room temperature. Separation of the enantiomers as diastereomers was achieved by reversed-phase HPLC within 20min using ODS column. Different ratios of (S)-(-)-bevantolol and (R)-(+)-bevantolol were prepared. Enantiomeric separation of these mixtures took place on a chiralcel OD column or, after derivatization with GITC, on a ODS column. No racemization was found during the experiment. This method allowed determination of 0.05% of either enantiomer in the presence of its stereoisomer and method validation showed adequete linearity over the required range.

Adrenergic beta-Antagonists↗

PubMed2000

Quantitative determination of salidroside and tyrosol from the underground part of Rhodiola rosea by high performance liquid chromatography.

A reversed-phase high performance liquid chromatographic method was developed to determine salidroside and tyrosol simultaneously in the Rhodiola rosea. The optimum condition was Nova-Pak C18 as stationary phase, 6.5% methanol in water as mobile phase and detection at UV 225 nm. The identification was carried out by comparing the retention time and IC/MS spectrum of the relevant peaks with those of isolated standards. The contents of salidroside and tyrosol in the samples gathered from various area in China were ranged over 1.3-11.1 mg/g and 0.3-2.2 mg/g, respectively.

Chromatography, High Pressure Liquid↗

PubMed2000

Chiral separation of the enantiomers of metoprolol and its metabolites by high performance liquid chromatography.

(1'R, 2R)-, (1'R, 2S)-, (1'S, 2R)- and (1'S, 2S)-alpha-hydroxymetoprolol; (2R)- and (2S)-O-desmethylmetoprolol; and (2R)- and (2S)-metoprolol acid are major metabolites of (2R)-and (2S)-metoprolol, beta-adrenergic antagonist. The focus of most chiral separation methods until now has been on determination of the enantiomeric parent drug. However, it is just as important to be able to follow the metabolism of the enantiomers and their possible chiral metabolites. Therefore, for the study of stereoselective metabolism and pharmacokinetics of metoprolol, the chiral separation of the enantiomers of metoprolol and its metabolites has been investigated using four chiral stationary phases, i.e., Chiralcel OD, Chiral-AGP, Cyclobond I and Sumichiral OA-4900 columns. Metoprolol acid was resolved only by Sumichiral OA-4900. Chiralcel OD provided the highest separation factor and resolution value for metoprolol and O-desmethylmetoprolol and partially resolved the four stereoisomers of alpha-hydroxymetoprolol. Diastereomeric alpha-hydroxymetoprolols were resolved using the coupled column chromatographic system of two chiral stationary phases, Sumichiral OA-4900 column and Chiralcel OD column.

Adrenergic beta-Antagonists↗

PubMed2000

Reversed-phase high performance liquid chromatographic separation of the enantiomers of terbutaline by derivatization with 2,3,4,6-tetra-o-acetyl-beta-D-glucopyranosyl isothiocyanate.

The enantiomers of the bronchodilator terbutaline were separated by reversed-phase high performance liquid chromatography after derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate(GITC) reagent. The derivatization proceeded quantitatively within 1 h at room temperature. The corresponding diastereomeric thiourea derivatives were well resolved on an ODS column with acetonitrile-acetate buffer as a mobile phase. Elution orders of the diastereomers were confirmed by derivatization of R-(-)-terbutaline and S-(+)-terbutaline which were collected by semi-preparative chiral HPLC using Sumichiral OA-4700 column. The native fluorescence of terbutaline was quenched by derivatization with GITC. The detection limit was 25 ng when monitored at UV 278 nm.

Adrenergic beta-Agonists↗