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Biomedical subjects

C Kim

Publications and source records attributed to C Kim.

At least 127 records · Page 7Linked to original sources
PubMed2000

K562 cells implicate increased chromatin accessibility in Alu transcriptional activation.

Alu repeats in K562 cells are unusually hypomethylated and far more actively transcribed than those in other human cell lines and somatic tissues. Also, the level of Alu RNA in K562 cells is relatively insensitive to cell stresses, namely heat shock, adenovirus infection and treatment with cycloheximide, which increase the abundance of Alu RNA in HeLa and 293 cells. Recent advances in understanding the interactions between DNA methylation, transcriptional activation and chromatin conformation reveal reasons for the constitutively high level of Alu expression in K562 cells. Methylation represses transcription of transiently transfected Alu templates in all cell lines tested but cell stresses do not relieve this repression suggesting that they activate Alu transcription through another pathway. A relatively large fraction of the Alus within K562 chromatin is accessible to restriction enzyme cleavage and cell stresses increase the chromatin accessibility of Alus in HeLa and 293 cells. Cell stress evidently activates Alu transcription by rapidly remodeling chromatin to recruit additional templates.

Adenoviridae↗
PubMed2000

Mass Balance of the Greenland Ice Sheet at High Elevations.

Comparison of ice discharge from higher elevation areas of the entire Greenland Ice Sheet with total snow accumulation gives estimates of ice thickening rates over the past few decades. On average, the region has been in balance, but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast. The north of the ice sheet shows less variability, with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest. These results agree well with those from repeated altimeter surveys, except in the extreme south, where we find substantially higher rates of both thickening and thinning.

Journal Article↗
PubMed2000

Signature of superfluid density in the single-particle excitation spectrum of Bi(2)Sr(2)CaCu(2)O(8+delta)

We report that the doping and temperature dependence of photoemission spectra near the Brillouin zone boundary of Bi(2)Sr(2)CaCu(2)O(8+delta)exhibit unexpected sensitivity to the superfluid density. In the superconducting state, the photoemission peak intensity as a function of doping scales with the superfluid density and the condensation energy. As a function of temperature, the peak intensity shows an abrupt behavior near the superconducting phase transition temperature where phase coherence sets in, rather than near the temperature where the gap opens. This anomalous manifestation of collective effects in single-particle spectroscopy raises important questions concerning the mechanism of high-temperature superconductivity.

Journal Article↗
PubMed2000

First success of catalytic epoxidation of olefins by an electron-rich iron(III) porphyrin complex and H2O2: imidazole effect on the activation of H2O2 by iron porphyrin complexes in aprotic solvent.

An electron-rich iron(III) porphyrin complex (meso-tetramesitylporphinato)iron(III) chloride [Fe(TMP)Cl], was found to catalyze the epoxidation of olefins by aqueous 30% H2O2 when the reaction was carried out in the presence of 5-chloro-1-methylimidazole (5-Cl-1-Melm) in aprotic solvent. Epoxides were the predominant products with trace amounts of allylic oxidation products, indicating that Fenton-type oxidation reactions were not involved in the olefin epoxidation reactions. cis-Stilbene was stereospecifically oxidized to cis-stilbene oxide without giving isomerized trans-stilbene oxide product, demonstrating that neither hydroperoxy radical (HOO*) nor oxoiron(IV) porphyrin [(TMP)FeIV=O] was responsible for the olefin epoxidations. We also found that the reactivities of other iron(III) porphyrin complexes such as (meso-tetrakis(2,6-dichlorophenyl)porphinato)iron(III) chloride [Fe(TDCPP)Cl], (meso-tetrakis(2,6-difluorophenyl)porphinato)iron(III) chloride [Fe(TDFPP)Cl], and (meso-tetrakis(pentafluorophenyl)porphinato)iron(III) chloride [Fe(TPFPP)CI] were significantly affected by the presence of the imidazole in the epoxidation of olefins by H2O2. These iron porphyrin complexes did not yield cyclohexene oxide in the epoxidation of cyclohexene by H2O2 in the absence of 5-Cl-1-MeIm in aprotic solvent; however, addition of 5-Cl-1-MeIm to the reaction solutions gave high yields of cyclohexene oxide with the formation of trace amounts of allylic oxidation products. We proposed, on the basis of the results of mechanistic studies, that the role of the imidazole is to decelerate the O-O bond cleavage of an iron(III) hydroperoxide porphyrin (or H2O2-iron(II) porphyrin adduct) and that the intermediate transfers its oxygen to olefins prior to the O-O bond cleavage.

Alkenes↗
PubMed2000

Instrumentation for photocrystallographic experiments of transient species.

Instrumentation for stroboscopic time-resolved diffraction studies at low temperatures is described. Exciting laser light is delivered to the crystal through an optical fiber. During the diffraction experiment, fluorescence from the sample is focused onto a fiber optic bundle surrounding the laser-light fiber, and monitored by a photodiode. A rotating slotted disk produces a pulsed X-ray beam with pulse frequencies suitable for the study of molecular excited states with lifetimes of 10 micros or longer. Synchronization of the laser-pump/X-ray-probe pulses is achieved through a trigger signal from a photosensor mounted on the rotating disk, or from an X-ray sensitive photodiode inserted in the beamstop. For the study of shorter-lived species the time structure of the synchrotron beam is to be used. Equations are derived for the maximum and average fractional excited-state populations as a function of lifetime, pulse frequency and the fraction of molecules being excited by the laser pulse.

Journal Article↗
PubMed2000

The Arabidopsis thaliana salt tolerance gene SOS1 encodes a putative Na+/H+ antiporter.

In Arabidopsis thaliana, the SOS1 (Salt Overly Sensitive 1) locus is essential for Na(+) and K(+) homeostasis, and sos1 mutations render plants more sensitive to growth inhibition by high Na(+) and low K(+) environments. SOS1 is cloned and predicted to encode a 127-kDa protein with 12 transmembrane domains in the N-terminal part and a long hydrophilic cytoplasmic tail in the C-terminal part. The transmembrane region of SOS1 has significant sequence similarities to plasma membrane Na(+)/H(+) antiporters from bacteria and fungi. Sequence analysis of various sos1 mutant alleles reveals several residues and regions in the transmembrane as well as the tail parts that are critical for SOS1 function in plant salt tolerance. SOS1 gene expression in plants is up-regulated in response to NaCl stress. This up-regulation is abated in sos3 or sos2 mutant plants, suggesting that it is controlled by the SOS3/SOS2 regulatory pathway.

Alleles↗
PubMed2000

Micropatterning of organic electronic devices by cold-welding

A simple and general postdeposition electrode patterning technique for active organic electronic devices is demonstrated and is applied to patterning the metal cathodes of organic light-emitting devices. Selective lift-off of the metal cathode layer is achieved by pressing a prepatterned, metal-coated silicon stamp on the unpatterned device layers. Under pressure, the metal coating on the stamp cold-welds to the metal cathode coating the underlying organic films. Subsequent separation of the stamp from the substrate results in removal of the cathode metal in the regions contacted by the stamp, resulting in submicrometer feature definition. A 17x17 passive matrix display, with a pixel size of 440 micrometers by 320 micrometers, was fabricated with this process. Cold-welding followed by lift-off of the cathode metal allows simple, cost-effective, and high-throughput large-area fabrication of organic electronic devices.

Journal Article↗
PubMed2000

Phylogenetic and phenotypic diversity of 4-chlorobenzoate-degrading bacteria isolated from soils.

Twenty numerically dominant 4-chlorobenzoate (4-CBA)-degrading bacteria were isolated from agricultural soils. The isolates were able to utilize 4-CBA as a sole source of carbon and energy. A total of 65% of the isolates was identified to the species level by fatty acid methyl ester (FAME) analysis, and the isolates were strains of Micrococcus, Pseudomonas, Oerskovia, Cellulomonas, and Arthrobacter species. The chromosomal DNA patterns of the isolates obtained by polymerase chain reaction (PCR) amplification of repetitive extragenic palindromic (REP) sequences were distinct from each other. Most of the isolates grew rapidly in 4-CBA medium, but their substrate utilization capabilities were generally restricted. Plasmid DNAs were detected from 55% of the isolates, and one strain, HR7, was shown to have self-transmissible, 4-CBA degradative plasmids. 4-CBA degradative enzymes were inducible by the presence of 4-CBA and most of the isolates appeared to mineralize it through 4-hydroxybenzoate rather than 4-chlorocatechol.

Journal Article↗
PubMed2000

Identification of the calcium binding sites in translationally controlled tumor protein.

Translationally controlled tumor protein (TCTP), also known as IgE-dependent histamine-releasing factor, is a growth-related tumor protein. Although the primary sequence of rat TCTP does not reveal any recognizable Ca2+ -binding motif, previous studies have demonstrated that rat TCTP consisting of 172 amino acids is a Ca2+ -binding protein. However, the region of TCTP required for Ca2+ interaction has not been mapped to the molecule. Here, we reported that the Ca2+ binding region of TCTP, which was mapped by using a combination of deletion constructs of rat TCTP and 45Ca2+ -overlay assay, was confined to amino acid residues 81-112. This binding domain did not show any peculiar loop of calcium-binding motif such as CaLB domain and EF hand motif and it seems to be constituted of random coil regions neighboring the a helix. Thus, our data confirm that TCTP is a novel family of Ca2+ -binding protein.

Amino Acid Sequence↗
PubMed2000

Acid and base catalyzed intramolecular cyclizations of N-benzoylthiocarbamoyl-acetals.

Acid and base catalyzed intramolecular cyclizations of N-benzoylthioureidoacetal, containing four functional groups adjacent to thiourea such as benzocarbamoyl, acetal, thioure and amide, were investigated. The condensation reaction of N-benzoyl thiocarbamoylglycine amide in the presence of 10% aqueous NaOH provided 1-(2,2-dimethoxy)ethyl-imidazolidine-2-thione exclusively. In the presence of pyridine, it was transformed to 2-thiohydantoin. N-Benzoyl thiocarbamoyl glycine amide was completely transformed to an iminothiazolidine exclusively in the presence of Lewis acid such as borontrifluoride etherate or trimethylsilyl iodide. 1-(2,2-Dimethoxy)ethyl-imidazolidine-2-thione was transformed to imidazole[2,1-b]thiazole and pyrazino[5,1-a]imidazole in the presence of BF3.Et2O and formic acid, respectively.

Acids↗
PubMed2000

Generation of nuclear hybrids overcoming the natural barrier of incompatibility: transfer of nuclei from Lentinula edodes into protoplasts of Coriolus versicolor.

Heterokaryotic nuclear hybrids overcoming the natural barriers of incompatibility have been studied in basidiomycetes. To produce these nuclear hybrids between incompatible mushrooms, which have several potent pharmacological effects, nuclear transfer was performed between Lentinula edodes and Coriolus versicolor. Nuclei from serine auxotrophs of Lentinula edodes, LE207 (Ser-) were transferred into the protoplasts of arginine auxotrophs of Coriolus versicolor, CV17 (Arg-), using 30% polyethylene glycol 4000 in 10 mM CaCl2-glycine solution (pH 8.0). Nuclear transfer progenies were selected by nutritional complementation on minimal media supplemented with 0.6 M sucrose. The progenies were classified based on colony morphology to L. edodes-like, C. versicolor-like and non-parental type. Most of the progenies grew slower than either parent. The number of nuclei per cell was similar but the DNA content varied between progenies. The isozyme patterns of nuclear hybrids resembled either of the parent profiles or showed a mixed profile.

Cell Nucleus↗
PubMed2000

Association between birth weight and insulin sensitivity in healthy young men in Korea: role of visceral adiposity.

Recent studies have demonstrated decreased insulin sensitivity in individuals with low birth weight. This study was performed to examine whether abdominal obesity is a link between insulin resistance and low birth weight. We studied the relationships between birth weight and insulin secretion, insulin sensitivity, and various anthropometric indices including visceral fat area in 22 healthy young Korean adults. Birth weight correlated significantly with diastolic blood pressure (r=-0.47, P<0.05) and insulin sensitivity index (S(I)) measured by a frequently sampled intravenous glucose tolerance test (FSIGT) (r=0.54, P<0.05), but not with insulin secretory indices such as acute insulin responses during FSIGT (r=-0.35, NS) or hyperglycemic clamp (r=0.17, NS) and submaximum insulin response during hyperglycemic clamp (r=0.10, NS). S(I) correlated significantly with abdominal obesity measurements such as waist circumference (r=-0.48, P<0.05), waist-to-hip ratio (r=-0.53, P<0.05) and visceral fat area (r=-0.58, P<0.01). However, we could not find significant correlation between birth weight and any of the abdominal obesity measurements (r=-0.35 for waist-to-hip ratio, r=-0.22 for visceral fat area, and r=-0.24 for visceral-to-subcutaneous fat ratio; NS for all). The present data confirm that low birth weight is associated with insulin resistance in adult life. However, our data suggest that the association between low birth weight and insulin resistance is not mediated by abdominal obesity.

Adipose Tissue↗
PubMed2000

Rac2 stimulates Akt activation affecting BAD/Bcl-XL expression while mediating survival and actin function in primary mast cells.

Mast cells generated from Rac2-deficient (-/-) mice demonstrated defective actin-based functions, including adhesion, migration, and degranulation. Rac2(-/-) mast cells generated lower numbers and less mast cell colonies in response to growth factors and were deficient in vivo. Rac2(-/-) mast cells demonstrated a significant reduction in growth factor-induced survival, which correlated with the lack of activation of Akt and significant changes in the expression of the Bcl-2 family members BAD and Bcl-XL, in spite of a 3-fold induction of Rac1 protein. These results suggest that Rac2 plays a unique role in multiple cellular functions and describe an essential role for Rac2 in growth factor-dependent survival and expression of BAD/Bcl-XL.

Actins↗
PubMed2000

Effects of mixing on fed-batch fermentation of L-ornithine.

The effects of mixing on L-ornithine fermentation were studied using an L-arginine auxotrophic mutant of Brevibacterium ketoglutamicum ATCC 21092. Three different modes of fed-batch culture using two different impeller types were studied in a 7 l fermentor. The first two modes of fed-batch culture were carried out in a fermentor equipped with six-flat-blade disk-turbine impellers with top and bottom feeding. The third mode of fed batch culture was carried out using pitched-six-flat-blade disk-turbine impellers with top feeding. The titre of L-ornithine increased up to 1.8 fold with bottom-feeding or when the pitched-six-flat-blade disk-turbine impellers were used compared to when the six-flat-blade disk-turbine impellers with top-feeding were used. It was observed that the mixing time of the limiting nutrients varied significantly depending on both the direction of feeding and the impeller type. Since the profiles of the specific rates of CO2 evolution, oxygen and glucose uptakes were very similar for the three culture modes, it could be reasonably assumed that the microorganism exhibited similar growth rates for each mode used. However, different amino acid producing activities were observed in the three culture modes. From these results it is concluded that the productivity of L-ornithine fermentation is significantly improved by shortening the mixing time of the limiting nutrient in the fermentor.

Journal Article↗
PubMed2000

P-glycoprotein (encoded by multidrug resistance genes) is not required for interleukin-2 secretion in mice and humans.

P-glycoprotein (encoded by multidrug resistance genes), a member of the ATP-binding cassette transporter protein superfamily, has been shown to play a role in the secretion of cytokines. This conclusion was based upon the inhibition of cytokine secretion by anti-P-gp monoclonal antibodies. In this study, we show that anti-CD3-stimulated lymphocytes from wild-type, mdr1a knock out and mdr1ab double knock out mice produce similar amounts of IL-2, IFN-gamma, IL-4, and IL-10. In addition, Jurkat T cells that lack P-gp and MDR1-transfected Jurkat T cells (JurkatP-gp) as well as purified human peripheral blood CD4+ P-gp+ and CD4+ P-gp- and CD8+ P-gp+ and CD8+ P-gp- T cell subsets produced comparable amounts of IL-2. These data show that P-gp is not required for secretion of IL-2, IFN-gamma, IL-4, and IL-10 secretion in mice and IL-2 secretion in humans.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Efficiency of promoter and cell line in high-level expression of erythropoietin.

Efficiency of viral promoters and various cell lines in directing high-level expression of human erythropoietin (Epo) was investigated. To investigate the effects of various viral promoters and cell lines on the Epo expression level, genomic Epo with the 5' and 3' untranslated regions (UTRs) deleted was cloned next to the simian virus 40 early promoter, cytomegalovirus early promoter or SRalpha promoter. These expression vectors were transfected into COS-7, BHK-21 and Chinese hamster ovary (CHO)/dhfr(-) cells, respectively. The COS-7 cells transfected with the vector containing the SRalpha promoter showed the highest expression level ( approximately 103 IU/ml) at 72 h post-transfection. For the development of Epo-producing stable cell lines, BHK-21 and CHO/dhfr(-) cells transfected with the 5',3'-UTR-deleted genomic Epo under the control of the SRalpha promoter were cultured with media containing zeocin. Several clones of zeocin-resistant BHK-21 and CHO/dhfr(-) cells were cultured in the presence of methotrexate (MTX). A BHK-21 clone selected in the presence of 500 nM MTX expressed and secreted approximately 490 IU/ml Epo into the medium. A CHO/dhfr(-) clone selected in the presence of 20 nM MTX expressed and secreted approximately 45 IU/ml Epo into the medium. Southern-blot analysis indicated that enhancement of Epo expression in the MTX-resistant stable cells might be related to the amplification of gene copy number.

Animals↗
PubMed2000

Combined pituitary hormone deficiency and pituitary hypoplasia due to a mutation of the Pit-1 gene.

Several mutations of the pituitary-specific transcription factor Pit-1 have been identified. We describe a girl with a mutation of the Pit-1 gene leading to a complete lack of GH, TSH and prolactin and a marked hypoplasia of the anterior pituitary gland. The patient had a homozygous nonsense-mutation at position 172 (CGA to TGA), converting arginine into a stop codon, leading to an early termination of protein translation. During the infancy period the girl had very conspicuous symptoms of hypothyroidism and the diagnosis of thyroid insufficiency preceded the diagnosis of GH-deficiency by 1.5 years. Treatment with thyroxine and GH resulted in excellent catch-up growth.

Body Height↗