PubMed Health⌕ Search

Biomedical subjects

Y Hahn

Publications and source records attributed to Y Hahn.

At least 19 recordsLinked to original sources
PubMed2003

Discovery of genes for ginsenoside biosynthesis by analysis of ginseng expressed sequence tags.

Expressed sequence tags (ESTs) provide a valuable tool that can be used to identify genes in secondary metabolite biosynthesis. Ginseng (Panax ginseng C.A Meyer) is a medicinal plant that accumulates ginsenosides in roots. We sequenced 11,636 ESTs from five ginseng libraries in order to create a gene resource for biosynthesis of ginsenosides, which are thought to be the major active component in roots. Only 59% of the ginseng ESTs exhibited significant homology to previously known polypeptide sequences. Stress- and pathogen-response proteins were most abundant in 4-year-old ginseng roots. ESTs involved in ginsenoside biosynthesis were identified by a keyword search of BLASTX results and a domain search of ginseng ESTs. We identified 4 oxidosqualene cyclase candidates involved in the cyclization reaction of 2,3-oxidosqualene, 9 nine cytochrome P450 and 12 glycosyltransferse candidates, which may be involved in modification of the triterpene backbone.

DNA, Plant↗
PubMed2001

Relaxation of cold plasmas and threshold lowering effect.

Low temperature plasmas are produced by photoionization of cold trapped atoms. Due to the threshold energy shift caused by overlapping ion fields, the effective kinetic energy of the free electrons is increased by delta(P)=2C(P)/a, where a is the Wigner-Seitz radius and C(P) approximately 11 is a universal constant. Detailed discussion is given on the self-consistent determination of C(P), using a Debye shielded, fluctuating lattice model. The attainable minimum electron temperature is given by the plasma density alone, as T(e) approximately delta(P)/3 approximately 7/a. No Wigner crystallization is possible in such plasmas, unless a strong confining external field is present. The shift imposes a stringent cutoff on the high Rydberg state contributions to the three-body recombination probabilities, and a new estimate of the rates is presented. For a freely expanding cold plasma, an additional mode of adiabatic motional recombination is found to dominate plasma relaxation.

Journal Article↗
PubMed2001

Dielectronic recombination in plasmas. II. Initial excited states.

Ions in a plasma recombine with electrons by both direct and resonant modes. The latter, the dielectronic recombination, can be a dominant process at temperature near T approximately equal to Z2 Ry, for ions with charge Z. The rates are usually given for target ions in their ground states, and contributions from all doubly excited intermediate states and final singly excited states of the recombined ions are summed over. To facilitate applications of the rates in plasma modelling in terms of rate equations, simple rate formulas are often devised. However, at finite temperature, a sizable fraction of ions is initially in an excited state, and after recombination, ions are usually left in singly excited final states. Thus new empirical rate formulas are needed that exhibit an explicit dependence on final as well as initial states of the ions before and after the recombination. We have calculated properly adjusted rates where (a) the target ions are allowed to be in their ground and excited states, and (b) contributions to the individual final states are explicitly separated. Multiple cascades are important in such calculations. For Al3+ ions we show that rates for the initial excited states are much larger than that for the ground state.

Journal Article↗
PubMed2001

Electrochemical behavior and differential pulse polarographic determination of rifampicin in the pharmaceutical preparations.

Differential pulse polarographic (DPP) analytical procedure for the rifampicin antibiotic, which can be applied to monitor its synthetic process from the starting antibiotic of rifamycin B or rifamycin SV, has been developed based on the electrochemical reduction of an azomethine group. Rifampicin exhibited a cathodic peak due to the azomethine group in the side chain of 3-[(4-methyl-1-piperazinyl)imino]methyl moiety and another cathodic peak due to the carbonyl group in rifamycin SV by DPP The experimental peak potential shift of an azomethine reduction was -73 mV/pH in the pH range between 3.0 and 7.5, agreeing with involvement of 4 e- and 5 H+ in its reduction. By the cyclic voltammetric(CV) studies, the azomethine and the carbonyl reductions in rifampicin were processed irreversibly on the mercury electrode. The plot of peak currents vs. concentrations of rifampicin ranging 1.0 x 10(-7) M tp approximately 1.0 x 10(-5) M yielded a straight line with a correlation coefficient of 0.9996. The detection limit was 1.0 x 10(-8) M with a modulation amplitude of 50 mV. DPP has been successfully applied for the determination of rifampicin in the pharmaceutical preparations.

Antibiotics, Antitubercular↗
PubMed2001

Phenotypic variation of a Thr704Met mutation in skeletal sodium channel gene in a family with paralysis periodica paramyotonica.

OBJECTIVES: Patients with paralysis periodica paramyotonica exhibit a clinical syndrome with characteristics of both hyperkalaemic periodic paralysis and paramyotonia congenita. In several types of periodic paralysis associated with hyperkalaemia, mutations in the skeletal muscle sodium channel (SCN4A) gene have been previously reported. Phenotypic variations of mutations in SCN4A, however, have not been described yet. The present study aimed to evaluate genetic variations in a family with clinical and electrophysiological characteristics of paralysis periodica paramyotonia. METHODS: Seven members of a family affected with symptoms of paralysis periodica paramyotonia were studied by electrophysiological and genetic analyses. There were increased serum potassium concentrations in four members during paralytic attacks induced by hyperkalaemic periodic paralysis provocation tests. Short exercise tests before and after cold immersion were carried out in four patients to distinguish electrophysiological characteristics of hyperkalaemic periodic paralysis and paramyotonia. Sequencing analyses of SCN4A were performed on one patient and a normal control to identify polymorphisms. Restriction fragment length polymorphism (RFLP) analysis was then performed at the identified polymorphic sites. RESULTS: Electrophysiological studies showed both exercise sensitivity and temperature sensitivity. Compound motor action potential (CMAP) amplitudes were decreased (7.3%-28.6%) after short exercise tests. The CMAP amplitudes were even more severely decreased (21.7%-56.5%) in short exercise tests after cold exposure. Three polymorphic sites, Gln371Glu, Thr704Met, and Aspl376Asn were identified in SCN4A. RFLP analyses showed that all affected patients carried the Thr704Met mutation, whereas unaffected family members and a normal control did not. CONCLUSION: Phenotypic variation of the Thr704Met mutation, which was previously reported in patients with hyperkalaemic periodic paralysis, is described in a family affected with paralysis periodica paramyotonia.

Adult↗
PubMed2000

Duplication of genes encoding non-clathrin coat protein gamma-COP in vertebrate, insect and plant evolution.

Coatomer is a major component of COPI vesicles and consists of seven subunits. The gamma-COP subunit of the coatomer is believed to mediate the binding to the cytoplasmic dilysine motifs of membrane proteins. We characterized cDNAs for Copg genes encoding gamma-COP from mouse, zebrafish, Drosophila melanogaster and Bombyx mori. Two copies of Copg genes are present in vertebrates and in B. mori. Phylogenetic analysis revealed that two paralogous genes had been derived from a single ancestral gene by duplication independently in vertebrates and in B. mori. Mouse Copg1 showed ubiquitous expression with the highest level in testis. Zebrafish copg2 was biallelically expressed in hybrid larvae in contrast to its mammalian ortholog expressed in a parent-of-origin-specific manner. A phylogenetic analysis with partial plant cDNA sequences suggested that copg gene was also duplicated in the grass family (Poaceae).

Amino Acid Sequence↗
PubMed2000

Mit1/Lb9 and Copg2, new members of mouse imprinted genes closely linked to Peg1/Mest(1).

Two mouse genes, Mit1/Lb9 and Copg2, linked to Peg1/Mest on mouse chromosome 6, were identified to be imprinted maternally and paternally, respectively. Mit1/Lb9 encoding untranslated transcripts resides within the intron 20 of Copg2. The gene is maternally imprinted in adult mouse brain, partially imprinted in other tissues. Copg240 kb genomic region, being expressed ubiquitously in mouse tissues with a partial imprinting pattern in embryos, neonates, and adult brain in contrast to maternally imprinted human COPG2. In addition, we identified an antisense transcript of Copg2, Copg2AS, which overlaps 3'-UTRs of Copg2 and Peg1/Mest. The Copg2AS transcript is maternally imprinted in embryos, neonates, and adult tissues.

Amino Acid Sequence↗
PubMed2000

Characterization of JDP genes, an evolutionarily conserved J domain-only protein family, from human and moths.

We characterized evolutionarily conserved J domain containing protein (JDP) genes from human, Bombyx mori, and Manduca sexta. Each of the JDP proteins contains a J domain at its N-terminus and a highly conserved C-terminal domain. Southern blot analysis revealed that the human JDP1 gene is present as a single copy in the human genome. Expression was higher in brain, heart, and testis than in kidney or stomach. Human JDP1 was mapped in silico to chromosome 10q21.1, which exhibits a conserved synteny with the central region of mouse chromosome 10. Drosophila jdp is located at 99F4-99F11 on the right arm of the third chromosome.

Amino Acid Sequence↗
PubMed2000

The use of insulin and glucose during resuscitation from hemorrhagic shock increases hepatic ATP.

BACKGROUND: Hemorrhagic shock produces a marked decrease in hepatic ATP, adenylate energy charge, and total adenosine nucleotides. This is followed by slow recovery to normal levels after resuscitation. Nucleotide metabolites are increased following shock and resuscitation. Previous experimental work has shown that supraphysiologic doses of insulin have salutary effects in animals with hemorrhagic shock and in cardiac patients. It appears that insulin causes increased availability of glucose and energy-producing substrates. This study examined whether resuscitation with glucose and insulin after hemorrhagic shock would alter the changes previously seen to occur in hepatic ATP levels, adenylate energy charge, or nucleotide metabolites. METHODS: Male Sprague-Dawley rats were bled to a mean arterial blood pressure of 40 mm Hg for 30 min. They were then resuscitated with the shed blood and one of three fluids: (1) lactated Ringer's, (2) lactated Ringer's with 10% glucose, (3) lactated Ringer's with 10% glucose + 6 units/kg regular insulin. Liver biopsies were obtained prior to shock (baseline), after 30 min of shock (shock), and 90 min after resuscitation (90 min). Tissue levels of ATP, ADP, AMP, adenosine, inosine, hypoxanthine, and xanthine were measured. Serum at 90 min was evaluated for potassium, glucose, and tumor necrosis factor alpha (TNF-alpha). RESULTS: The insulin-treated group had significantly increased hepatic ATP and energy charge following resuscitation compared with the other two groups. The insulin group also exhibited significant hypoglycemia. Total adenine nucleotides (ATP, ADP, and AMP) were significantly elevated 90 min postresuscitation in the insulin group. Mean blood pressures throughout the experiment were not significantly different among groups. TNF-alpha was highest in the insulin-treated group, but this was not significant. CONCLUSIONS: Resuscitation with insulin and dextrose significantly increased hepatic ATP and adenylate energy charge after hemorrhagic shock in rats. Total nucleotide pool levels were not different between groups, indicating that there was a shift of the equilibrium away from the metabolites toward ATP and ADP in the insulin-treated group. Insulin treatment had no significant effect on blood pressure or TNF-alpha. However, it caused significant hypoglycemia and hypokalemia.

Adenosine Diphosphate↗
PubMed2000

Electrochemical behavior and differential pulse polarographic determination of piperacillin sodium.

In an aqueous piperacillin sodium solution, a well-defined single wave or single peak was observed by direct current (DC) polarography or differential pulse polarography (DPP). The peak potential change per pH unit was -54 mV in the phosphate buffer at 18 degrees C, which indicated that protons were involved in the electrochemical reduction of the 2,3-dioxopiperazine moiety of piperacillin sodium with a H+/e- ratio of one. Using a phosphate buffer of pH 4.3, the 1.0 x 10(-7) M piperacillin sodium single peak could be determined by DPP with relative standard deviation of 1.6% (n=3). Piperacillin sodium could be analyzed without interference from penicillin G-potassium, which enabled the employment of DPP as a fast and simple technique for monitoring the synthetic process of the antibiotic.

Calibration↗
PubMed2000

Dielectronic recombination in plasmas: the final state distribution

The dielectronic recombination rate is one of the important input parameters to rate equations for modeling plasmas, where the excited state population of the plasma ions is determined by taking into account the radiative and collisional effects of plasma particles. The rates are often conveniently summarized in the form of empirical formulas to facilitate their use; in particular, properly designed rate formulas are needed that describe the electron capture to the individual singly excited final recombined states. However, the currently available rate formulas fail to meet this requirement, although they are obtained from more detailed benchmark calculations that explicitly include all the important transitions. The modified rate formulas may be obtained by keeping separate the rates to the individual singly excited final states, but still summing the contributions from different intermediate resonance states, with proper account of the cascades. Ne-like Al3+ ions in their ground state are used as examples to show that the rates to the final ground state are reduced by as much as a factor of 5 from the total rates.

Journal Article↗
PubMed2000

Reduced frequencies of peripheral interferon-gamma-producing CD4+ and CD4- cells during acute Kawasaki disease.

BACKGROUND: This study was performed to analyze the frequencies of peripheral interferon (IFN)-gamma-producing cells at the single-cell level and to determine concentrations of circulating IFN-gamma in the acute and subacute phases of Kawasaki disease (KD). METHODS: Ten patients with KD were studied and seven healthy children were selected as control subjects. Using immunofluorescent detection of intracellular IFN-gamma in CD4-positive and CD4-negative cells, the frequencies of IFN-gamma-producing cells in peripheral blood mononuclear cells were studied. Circulating IFN-gamma levels were measured by enzyme-linked immunosorbent assay. RESULTS: The frequencies of peripheral blood CD4+ and CD4- IFN-gamma-producing cells in acute-phase KD patients were significantly lower than in subacute-phase KD patients and control children (p < 0.05). CD4- cells, thought to be mainly composed of CD8+ cells, appeared to be more responsible for the reduced frequencies of total IFN-gamma-producing cells than CD4+ cells. There were, however, no differences in the frequencies of IFN-gamma-producing cells between KD patients in the subacute phase and control children. In contrast, serum IFN-gamma levels were higher in KD patients in the acute phase than in the subacute phase (p < 0.05). CONCLUSIONS: The above results show increased levels of circulating IFN-gamma and decreased emergence of peripheral IFN-gamma-producing cells in acute KD patients, suggesting transient infiltration of activated IFN-gamma-producing cells into the inflammatory sites during acute KD. These findings also support the hypothesis that IFN-gamma plays an important role in the pathogenesis of KD-related vasculitis.

CD4-Positive T-Lymphocytes↗
PubMed1999

Structural analysis of phylogenetically conserved J domain protein gene.

Novel cDNAs encoding evolutionarily conserved J Domain Proteins (JDPs) were investigated from Drosophila and mouse. Each of the full coding sequences potentially encodes a conserved J domain, but lacks additional characteristic structures present in DnaJ family proteins. The expression was restricted to head in Drosophila. However, ubiquitous expression was observed in mice with the highest level in kidney.

Amino Acid Sequence↗
PubMed1999

Identification of the genes encoding enzymes involved in the early biosynthetic pathway of pteridines in Synechocystis sp. PCC 6803.

The biosynthetic pathway for the pteridine moiety of cyanopterine, as well as tetrahydrobiopterine, has been investigated in Synechocystis sp. PCC 6803. Open reading frames slr0426, slr1626, slr0078 and sll0330 of the organism putatively encoding GTP cyclohydrolase I, dihydroneopterine aldolase, 6-pyruvoyltetrahydropterine synthase and sepiapterine reductase, respectively, have been cloned into T7-based vectors for expression in Escherichia coli. The recombinant proteins have been purified to homogeneity and demonstrated to possess expected genuine activities except that of sll0330. Our result is the first direct evidence for the functional assignment of the open reading frames in Synechocystis sp. PCC 6803. Furthermore, the 6-pyruvoyltetrahydropterine synthase gene is demonstrated for the first time in prokaryotes. Based on the result, biosynthesis of cyanopterine is discussed.

Alcohol Oxidoreductases↗
PubMed1999

Cloning of mouse sepiapterin reductase gene and characterization of its promoter region.

We have isolated and characterized approximately 5 kb mouse sepiapterin reductase gene (Spr) and a highly homologous pseudogene (Sprp). The authentic Spr gene is present as a single copy in the mouse genome and is composed of three exons containing the entire coding region. The primer extension experiment located the transcription initiation site in a putative pyrimidine-rich Inr element. The promoter region of the Spr gene is embedded within a CpG island. It was shown that the promoter region is devoid of distinctive TATA and CAAT boxes. Transient transfection of a series of 5' deletion derivatives of the Spr promoter showed the sequence between -83 and -51 to be essential for promoter activity. The pseudogene Sprp lacks promoter region and exon 3.

Alcohol Oxidoreductases↗
PubMed1998

Genomic structure and expression of murine poly(A) binding protein II gene.

The genomic structure and expression of the murine poly(A) binding protein II (mPABII) gene were analyzed by using genomic DNA and cDNA clones. The expression level of the mPABII gene varied among tissues. Besides two transcripts detected in all tissues, an additional transcript was detected in testis. The mPAB gene has pseudogenes or related genes in its genome.

Amino Acid Sequence↗
PubMed1996

Structure and expression of the tenecin 3 gene in Tenebrio molitor.

A genomic DNA fragment encoding tenecin 3, an antifungal protein was cloned from the genomic DNA library of Tenebrio molitor. The DNA sequence analysis showed that the coding region is divided into two exons by an intron of 49 bp in the middle of the putative leader peptide coding region. Southern blot analysis suggests that the gene is present as a single copy. The transcription initiation site was determined by primer extension analysis and S1 mapping. The TATA box and CCAAT box sequences were found at -30, and -121, respectively, from the transcription initiation site. Tenecin 3 mRNA is abundantly expressed in larvae and adults, while little was detected in RNAs from pupae, suggesting that the expression of the tenecin 3 gene is developmentally regulated.

Amino Acid Sequence↗