Search PubMed⌕ Search

Biomedical subjects

H K Kim

Publications and source records attributed to H K Kim.

At least 19 recordsLinked to original sources
PubMed2000

Characterization of glk, a gene coding for glucose kinase of Corynebacterium glutamicum.

The glk gene from Corynebacterium glutamicum was isolated by complementation using Escherichia coli ZSC113 (ptsG ptsM glk). We sequenced a total of 3072 bp containing the 969-bp open reading frame encoding glucose kinase (Glk). The glk gene has a deduced molecular mass of 34.2 kDa and contains a typical ATP binding site. Comparison with protein sequences revealed homologies to Glk from Streptomyces coelicolor (43%) and Bacillus megaterium (35%). The glk gene in C. glutamicum was inactivated on the chromosome via single crossover homologous recombination and the resulting glk mutant was characterized. Interestingly, the C. glutamicum glk mutant showed poor growth on rich medium such as LB medium or brain heart infusion medium in the presence or absence of glucose, fructose, maltose or sucrose as the sole carbon source. Growth yield was reduced significantly when maltose was used as the sole carbon source using minimal medium. The growth defect of glk mutant on rich medium was complemented by a plasmid-encoded glk gene. A chromosomal glk-lacZ fusion was constructed and used to monitor glk expression, and it was found that glk was expressed constitutively under all tested conditions with different carbon sources.

Amino Acid Sequence↗
PubMed2000

Natural and synthetic analogues of actinomycin D as Grb2-SH2 domain blockers.

Natural analogues (D, C2, and VII) of actinomycin inhibit Grb2 SH2 domain binding with phosphopeptide-derived from Shc in vitro and in intracellular system. To study structure-activity relationships, 13 actinomycin analogues were synthesized and we found that the inhibition activity depended on the substituents of cyclic peptide groups in actinomycin and two analogues with Tyr residue are the most potent inhibitors with IC50 value of 0.5 and 0.8 microM, respectively.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Inhibitory effect of Artemisia asiatica alkaloids on acetylcholinesterase activity from rat PC12 cells.

We screened 42 Korean traditional tea plants to determine the inhibitory effect of acetylcholinesterase and attenuation of toxicity induced by amyloid-beta peptide, which were related to the treatment of Alzheimer's disease (AD). The methanolic extract from Artemisia asiatica among tested 42 tea plants, showed the highest inhibitory effect (48%) on acetylcholinesterase in vitro. The methanolic extract was further separated with n-hexane, chloroform, and ethyl acetate of water, in order. The chloroform solubles, which were high in inhibitory effect of acetylcholinesterase, were repeatedly subjected to open column chromatography on silica gel. From the highest inhibitory fraction (78%) on acetylcholinesterase, the single compound was obtained by the Sep-Pak Cartridge (C18: reverse phase column). This compound was found to react positively on Dragendorff's reagent (potassium bismuth iodide), which typically reacted with the alkaloid. This compound was purified by HPLC (mu-bondapack C18 reverse phase column: 3.9 x 150 mm). The IC50 (the concentration of 50% enzyme inhibition) value of this compound was 23 micrograms/ml and the inhibitory pattern on acetylcholinesterase was mixed with competitive/non-competitive type. We examined the effects of this compound on toxicity induced by A beta (25-35) in rat pheochromocytoma PC12 cells. Pretreatment of the PC12 cells for 2 h with an alkaloid of Artemisia asiatica (1200 microg/ml) reduced the toxicity induced by A beta. This study demonstrated that an alkaloid of Artemisia asiatica, which was metabolized to small molecule in digestive tract and then could pass through the blood-brain barrier, appeared to be an acetylcholinesterase inhibitor with a blocker of neurotoxicity induced by A beta in human brain causing Alzheimer's disease.

Acetylcholinesterase↗
PubMed2000

Disruption of interkringle disulfide bond of plasminogen kringle 1-3 changes the lysine binding capability of kringle 2, but not its antiangiogenic activity.

Kringle 1-3 of human plasminogen is a potent inhibitor of endothelial cell proliferation. To understand a possible role for the unique cystine bridge between kringle 2 and kringle 3, we disrupted the interkringle disulfide bond by mutating Cys(169) and Cys(297) to serine residues. The yield of the mutant during the refolding process was decreased significantly. Anti-endothelial cell proliferative activity of the mutant was similar to that of the wild type. There was no significant difference in in vivo antiangiogenic activity between the wild type and the mutant in chorioallantoic membrane assay. However, in the mutant, the weak lysine binding capability of kringle 2 was not detected and its mobility in nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis is different from that of the wild type. These results support the notion that the overall antiangiogenic function of angiostatin is mediated by individual kringles, and suggest that the lysine binding capability of kringle 2 is likely not important for the antiangiogenic activity of kringle 1-3.

Amino Acid Substitution↗
PubMed2000

Crystal structure of NAD(+)-dependent DNA ligase: modular architecture and functional implications.

DNA ligases catalyze the crucial step of joining the breaks in duplex DNA during DNA replication, repair and recombination, utilizing either ATP or NAD(+) as a cofactor. Despite the difference in cofactor specificity and limited overall sequence similarity, the two classes of DNA ligase share basically the same catalytic mechanism. In this study, the crystal structure of an NAD(+)-dependent DNA ligase from Thermus filiformis, a 667 residue multidomain protein, has been determined by the multiwavelength anomalous diffraction (MAD) method. It reveals highly modular architecture and a unique circular arrangement of its four distinct domains. It also provides clues for protein flexibility and DNA-binding sites. A model for the multidomain ligase action involving large conformational changes is proposed.

Amino Acid Sequence↗
PubMed2000

Activation of a heterologously expressed octopamine receptor coupled only to adenylyl cyclase produces all the features of presynaptic facilitation in aplysia sensory neurons.

Short-term behavioral sensitization of the gill-withdrawal reflex after tail stimuli in Aplysia leads to an enhancement of the connections between sensory and motor neurons of this reflex. Both behavioral sensitization and enhancement of the connection between sensory and motor neurons are importantly mediated by serotonin. Serotonin activates two types of receptors in the sensory neurons, one of which is coupled to the cAMP/protein kinase A (PKA) pathway and the other to the inositol triphosphate/protein kinase C (PKC) pathway. Here we describe a genetic approach to assessing the isolated contribution of the PKA pathway to short-term facilitation. We have cloned from Aplysia an octopamine receptor gene, Ap oa(1), that couples selectively to the cAMP/PKA pathway. We have ectopically expressed this receptor in Aplysia sensory neurons of the pleural ganglia, where it is not normally expressed. Activation of this receptor by octopamine stimulates all four presynaptic events involved in short-term synaptic facilitation that are normally produced by serotonin: (i) membrane depolarization; (ii) increased membrane excitability; (iii) increased spike duration; and (iv) presynaptic facilitation. These results indicate that the cAMP/PKA pathway alone is sufficient to produce all the features of presynaptic facilitation.

Action Potentials↗
PubMed2000

Analysis of the yeast arginine methyltransferase Hmt1p/Rmt1p and its in vivo function. Cofactor binding and substrate interactions.

Many eukaryotic RNA-binding proteins are modified by methylation of arginine residues. The yeast Saccharomyces cerevisiae contains one major arginine methyltransferase, Hmt1p/Rmt1p, which is not essential for normal cell growth. However, cells missing HMT1 and also bearing mutations in the mRNA-binding proteins Npl3p or Cbp80p can no longer survive, providing genetic backgrounds in which to study Hmt1p function. We now demonstrate that the catalytically active form of Hmt1p is required for its activity in vivo. Amino acid changes in the putative Hmt1p S-adenosyl-L-methionine-binding site were generated and shown to be unable to catalyze methylation of Npl3p in vitro and in vivo or to restore growth to strains that require HMT1. In addition these mutations affect nucleocytoplasmic transport of Npl3p. A cold-sensitive mutant of Hmt1p was generated and showed reduced methylation of Npl3p, but not of other substrates, at 14 degrees C. These results define new aspects of Hmt1 and reveal the importance of its activity in vivo.

Binding Sites↗
PubMed2000

Prevalence of anti-protein S antibodies in patients with systemic lupus erythematosus.

OBJECTIVE: To determine the prevalence of circulating anti-protein S (anti-PS) antibodies in association with PS deficiency in patients with systemic lupus erythematosus (SLE). METHODS: Plasma was obtained from blood samples collected from 27 patients with SLE (5 men, 22 women; mean +/- SD age 32 +/- 10 years). Anti-PS antibodies were detected by immunoblotting according to a previously described method. Levels of free and total PS antigen were measured by enzyme-linked immunosorbent assay. PS activity was assayed by a clotting method. Levels of C4b binding protein (C4bBP) were measured by latex immunoassay. RESULTS: Among 27 patients with SLE, 19 (70.4%) had PS activity, and 12 (44.4%) had PS free antigen below the lower limit established for a normal population (mean -2SD). There was good correlation between PS activity and levels of PS free antigen (r = 0.851, P < 0.001), PS total antigen (r = 0.743, P < 0.001), and C4bBP (r = 0.597, P = 0.001). Circulating anti-PS antibodies and antiphospholipid antibodies (aPL) (IgG type) were detected in 7 (25.9%) and 14 (51.9%) of the 27 patients with SLE, respectively. Only 1 patient (3.7%) had both anti-PS antibodies and aPL. PS activities in patients who were positive for anti-PS antibodies (mean 38.7%) tended to be lower than those in patients who were negative for anti-PS antibodies (mean 54.9%), but the difference was not statistically significant. CONCLUSION: Anti-PS antibodies, independently of aPL, may play a role in the occurrence of PS deficiency in some patients with SLE, with possible effects on the function of PS that do not change the levels of PS antigens.

Adult↗
PubMed2000

Aromatase inhibitors from Isodon excisus var. coreanus.

The diethyl ether extract of Isodon excisus var. coreanus exhibited significant inhibitory activity in aromatase assay. Bioactivity-guided fractionation of the extract led to the isolation of three active compounds: inflexin (ent-1alpha-hydroxy-3beta,6a-diacetoxykaur-16-en-11,15-dione ) (1), ursolic acid (2), and ursolic acid 3-O-acetate (3).

Anticarcinogenic Agents↗
PubMed2000

Needle thoracic sympathectomy for essential hyperhidrosis: intermediate-term follow-up.

BACKGROUND: Essential hyperhidrosis is a condition with excessive sweating localized to certain part of the body. A definitive cure can be obtained by upper thoracic sympathectomy. METHOD: Between June and October 1997, 117 patients with essential hyperhidrosis underwent needle thoracoscopic sympathectomy. Of the 94 patients, 42 were men and 52 women. Their ages ranged from 14 to 63 years, with a mean age of 23 years. RESULTS: There were no mortality or life-threatening complications. Symptomatic improvement was found in 95.7%. Compensatory hyperhidrosis was found in 71.2% of the patients, but in these compensatory hyperhidrosis were mostly tolerable. CONCLUSIONS: This therapeutic procedure is minimally invasive and very effective. Further development of the new device and surgical technique are expected to follow.

Adolescent↗
PubMed2000

Comparison of 1- and 2-incision posterior cruciate ligament reconstructions.

This study compared the results of the 1-incision technique and the conventional 2- incision technique for the arthroscopic treatment of the posterior cruciate ligament (PCL) injury. The 2-incision technique was performed in 10 patients (group I) and the 1-incision technique in 45 patients (group II). The average duration of follow-up was 45 months in group I and 36 months in group II. Bone-patellar tendon-bone (BTB) autografts were used for all patients in group I. In group II, 34 BTB autografts and 11 BTB allografts were used. Postoperative Lysholm mean values were 90.0 in group I and 90.6 in group II. HSS mean values were 87.7 in group I and 92.6 in group II (P = .037). The Tegner activity level scales were 6.4 in group I and 6.5 in group II. The average side-to-side difference of the corrected posterior translation measured by the KT-2000 arthrometer were 2.10 mm in group I and 2.38 mm in group II. There were no statistically significant differences between the 2 groups in postoperative mean values except HSS scores. The arthroscopic PCL reconstruction using the 1-incision technique showed good results comparable with the conventional 2-incision technique. This technique needs no another incision or dissection over the medial femoral condyle.

Adolescent↗
PubMed2000

Alternating current aspects of antimicrobial molecular complexes.

A novel method was designed involving the titration of alternating current titration in a cell where one electrode was shielded by a capillary enclosure restricting access to it by charge carriers. With this cell, charge transfer complex titration of several thiazines all with some antimicrobial properties was effected in acetonitrile, against the electron accepting molecule iodine. The maxima of the Job plots generated by these titrations exhibited displacement of their positions for the forward and reverse titrations with respect to electron donor-acceptor complexation conductivity and apparent stoichiometry. A plot of inverse conductivity maxima differences against literature-cited dipole moments squared yielded a straight line passing through the origin. The titration plot profiles are discussed in terms of the type, number, and mobility of charge carriers produced in the complexation interaction. This novel method may be used to determine dipole moments of bioactive homologues empirically. There was correlation between thiazine drug dipole moments and minimal inhibitory concentrations of these drugs for some bacterial and yeast species. Several new avenues of investigation of possible relevance to microbiology are suggested.

Anti-Bacterial Agents↗
PubMed2000

Charge transfer complexes of K vitamins with several classes of antimicrobials.

The charge transfer donor (D)-acceptor (A) complexes formed between three classes of vitamin K (all electron acceptors in this study) with several thiazine psychotropes, used also as antimicrobials, antimalarials, antibiotics, and anticoagulants, were studied by means of alternating current titrations. The monochloride thiazines formed 2:1 (D:A) complexes, interacting from 26 to 47.5%; the dihydrochloride formed a 3:1 (D:A) complex. The antimalarials quinine and its isomer quinidine yielded 2:1 (D:A) complexes, interacting 51 and 60%, respectively. Quinacrine did not complex with vitamin K. The antibiotics sulfisoxasole and sulfamethisole gave 1:1 complexes, respectively interacting 6.2 and 11.7%. The anticoagulants warfarin, coumarin and dicumarol, rather than forming complexes proceeded rapidly to chemical reaction. When the above thiazine antimicrobials, antimalarials and antibiotics are present in patients receiving vitamin K post-operatively the dosage of administered vitamin K should be increased to counteract the donor-acceptor interaction effect.

Anti-Bacterial Agents↗
PubMed2000

Adenovirus-mediated suicide-gene therapy using the herpes simplex virus thymidine kinase gene in cell and animal models of human prostate cancer: changes in tumour cell proliferative activity.

OBJECTIVES: To determine the feasibility and efficacy of suicide-gene therapy using adenovirus (Ad)-mediated herpes simplex virus thymidine kinase (HSV-TK) and the prodrug acyclovir, and to evaluate changes in the biological phenotype for tumour cell proliferative activity after suicide-gene therapy in animal models of human prostate cancer. MATERIALS AND METHODS: Using a replication-defective adenoviral vector (cytomegalovirus, CMV) containing the beta-galactosidase gene (Ad-CMV-beta-gal) as a control and Ad-CMV-TK as the therapeutic vector under the transcriptional control of the CMV promoter, transduction efficiency was assessed in vitro by infecting LNCaP and PC-3 androgen-dependent and independent human prostate cancer cells with Ad-CMV-beta-gal, and using X-gal staining. The TK activity in prostate cancer cells infected with Ad-CMV-TK was determined by measuring TK-mediated [3H]-gancyclovir phosphorylation. The sensitivity of LNCaP and PC-3 cells to Ad-CMV-TK in vitro was determined after infection with the therapeutic vector with or without acyclovir. The inhibition of PC-3 tumour growth in vivo induced by the Ad-CMV-TK/acyclovir suicide-gene system was assessed in separate and controlled experiments using human prostate cancer mouse models. Ki-67 proliferative antigen and proliferating cell nuclear antigen (PCNA), both useful proliferative indices, were evaluated using immunohistochemical staining (MIB-1 monoclonal antibody and monoclonal anti-PCNA antibody) in formalin-fixed, paraffin-embedded tissues from gene therapy-treated and control animals. RESULTS: The mean TK activity was significantly higher in LNCaP and PC-3 cells infected with Ad-CMV-TK than in cells infected with Ad-CMV-beta-gal, used as a control (P < 0.05). The growth of human prostate cancer cells with Ad-CMV-TK was significantly inhibited by adding acyclovir in vitro (P < 0.05). In the in vivo experiments using the PC-3 human prostate cancer mouse model, tumour volume and growth was lower in mice treated with Ad-CMV-TK/acyclovir than in those treated with Ad-CMV-TK only, acyclovir only or untreated (controls) (P < 0.05). Histochemical staining of tumour tissues showed that Ad-CMV-TK/acyclovir destroyed PC-3 tumours through tumour cell death and apoptosis, with local lymphatic infiltration. The mean PCNA labelling index in prostate cancer cells of mice treated with Ad-CMV-TK/acyclovir was significantly lower than that in untreated controls (P < 0.05, Mann-Whitney U-test). The Ki-67 labelling index in prostate cancer cells of mice treated with Ad-CMV-TK/acyclovir was also lower than that in untreated controls (P < 0.05, Student's t-test). Adenovirus-mediated suicide-gene therapy using the HSV-TK gene decreased the proliferative activity of PC-3 human prostatic cancer cells in vivo. CONCLUSIONS: Adenovirus-mediated suicide-gene therapy using an HSV-TK/acyclovir system provided effective therapy in an experimental human prostate cancer mouse model, by significantly inhibiting tumour growth and decreasing the proliferative activity of human prostate cancer cells. Such therapy could be developed as a novel method for treating patients with androgen-independent prostate cancer.

Animals↗
PubMed2000

Crystallization and preliminary x-ray crystallographic analysis of NAD+-dependent DNA ligase from Thermus filiformis.

A highly thermostable DNA ligase from Thermus filiformis has been crystallized at room temperature using methoxypolyethylene glycol 5000 as a precipitant. The crystal belongs to the monoclinic space group P2(1), with unit-cell parameters a = 90.63, b = 117.80, c = 98. 65 A, beta = 115.56 degrees. Two molecules of DNA ligase are present in the asymmetric unit, giving a crystal volume per protein mass (V(m)) of 3.1 A(3) Da(-1) and a solvent content of 61%. A native data set extending to 3.0 A resolution has been collected at 100 K using synchrotron X-rays.

Bacterial Proteins↗
PubMed2000

Changes of plasma tissue factor and tissue factor pathway inhibitor antigen levels and induction of tissue factor expression on the monocytes in coronary artery disease.

BACKGROUND: Several studies have shown that thrombosis and inflammation play an important role in the pathogenesis of coronary artery disease (CAD). Tissue factor (TF) is responsible for the thrombogenicity of the atherosclerotic plaque and plays a key in triggering thrombin generation. The aim of this study was to assess the levels of TF and tissue factor pathway inhibitor (TFPI) in patients with angiographically documented CAD and also to evaluate TF induction on monocytes in vitro in the presence of these plasmas from patients with CAD. METHODS: Plasma antigen levels of soluble TF and TFPI were measured in 65 CAD patients and 22 healthy controls. Surface TF expression on monocytes from a healthy donor treated with plasma samples was evaluated by flow cytometry with a direct double-color immunofluorescence technique. RESULTS: Significantly elevated levels of both TF and TFPI were found in CAD patients compared with healthy controls (303.6 +/- 134.1 vs. 187.3 +/- 108.7 pg/ml, p < 0.05; 85.2 +/- 48.6 vs. 65.0 +/- 29.0 ng/ml, p < 0.05). By flow cytometry, monocytes from a healthy donor displayed higher TF antigen expression when incubated in the presence of CAD plasmas than in control plasmas (34.6 +/- 10.7 vs. 23.2 +/- 10.2%, p < 0.05). CONCLUSIONS: The high levels of circulating TF are present in CAD, which were not sufficiently inhibited by the elevated TFPI plasma levels. Although the source of circulating TF is unclear, TF induction of monocytes by plasma from CAD patients may contribute to the hypercoagulable state.

Adult↗