Simulated microgravity-induced vascular hyporesponsiveness: role of signal transduction.
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Animals↗
Biomedical subjects
Y Kim
Publications and source records attributed to Y Kim.
Transcriptional activation of transforming growth factor beta1 and its receptors by the Kruppel-like factor Zf9/core promoter-binding protein and Sp1. Potential mechanisms for autocrine fibrogenesis in response to injury.
We have explored the regulation of transforming growth factor beta (TGF-beta) activity in tissue repair by examining the interactions of Zf9/core promoter-binding protein, a Kruppel-like zinc finger transcription factor induced early in hepatic stellate cell (HSC) activation, with promoters for TGF-beta1 and TGF-beta receptors, types I and II. Nuclear extracts from culture-activated HSCs bound avidly by electrophoretic mobility shift assay to two tandem GC boxes within the TGF-beta1 promoter but minimally to a single GC box; these results correlated with transactivation by Zf9 of TGF-beta1 promoter-reporters. Zf9 transactivated the full-length TGF-beta1 promoter in either primary HSCs, HSC-T6 cells (an SV40-immortalized rat HSC line), Hep G2 cells, or Drosophila Schneider (S2) cells. Recombinant Zf9-GST also bound to GC box sequences within the promoters for the types I and II TGF-beta receptors. Both type I and type II TGF-beta receptor promoters were also transactivated by Zf9 in mammalian cells but not in S2 cells. In contrast, Sp1 significantly transactivated both receptor promoters in S2 cells. These results suggest that (a) Zf9/core promoter-binding protein may enhance TGF-beta activity through transactivation of both the TGF-beta1 gene and its key signaling receptors, and (b) transactivating potential of Zf9 and Sp1 toward promoters for TGF-beta1 and its receptors are not identical and depend on the cellular context.
Animals↗
Dodecanethiol-Derivatized Au/Ag Bimetallic Nanoparticles: TEM, UV/VIS, XPS, and FTIR Analysis.
Dodecanethiol-derivatized Au/Ag bimetallic nanoparticles that can be dissolved in nonpolar solvents were prepared via a two-phase synthetic route in water/toluene mixtures. The position of the surface plasmon band was found to vary linearly between 419 and 522 nm as a function of mole fraction of Au (or Ag) content, implying ready formation of Au-Ag alloy clusters. Transmission electron microscopy images revealed that the bimetallic clusters were monodisperse with an average size of approximately 4 nm. Infrared spectral features indicate that the alkyl chains of the dodecanethiolate species take fully extended trans zigzag conformations on all alloy clusters. The most interesting finding deduced from X-ray photoelectron spectroscopy and FTIR spectroscopic measurements was that Ag atoms are enriched at the outer part of the alloy clusters when compared with the Au atoms. Copyright 1998 Academic Press.
Journal Article↗
Transcriptional regulation of cyclooxygenase-2 in mouse skin carcinoma cells. Regulatory role of CCAAT/enhancer-binding proteins in the differential expression of cyclooxygenase-2 in normal and neoplastic tissues.
Many studies have suggested that overexpression of cyclooxygenase-2 (COX-2) contributes to the development of tumors in several tissues. COX-2 expression tends to be up-regulated in various types of tumors and transformed cell lines, and the overexpression of COX-2 is caused by enhanced transcription of the gene. In an attempt to characterize the signaling pathway leading to the overexpression of COX-2 in the mouse skin carcinoma cell line JWF2, we investigated cis- and trans-acting factors required for COX-2 expression and demonstrated a molecular mechanism by which COX-2 is expressed differentially in normal and neoplastic tissues. Two regions of the COX-2 promoter containing an E-box and nuclear factor IL6 site were identified as the positive regulatory elements through transient transfections with luciferase reporter vectors containing the various 5'-flanking regions of the promoter. Moreover, electrophoretic mobility shift assays and cotransfection experiments showed that upstream stimulatory factors and CCAAT/enhancer-binding proteins (C/EBPs) bind to the E-box and nuclear factor IL6 site, respectively, and functionally transactivate the COX-2 promoter. We also found that C/EBP isoforms are expressed differentially during mouse skin carcinogenesis, suggesting that overexpression of COX-2 in tumors may be caused by a change in C/EBP expression levels.
Activating Transcription Factors↗
Homeodomain-interacting protein kinases, a novel family of co-repressors for homeodomain transcription factors.
A novel family of cofactors that differentially interact with homeoproteins have been identified via a yeast two-hybrid screen. The proteins contain a conserved protein kinase domain that is separated from a domain that interacts with homeoproteins and hence are termed homeodomain-interacting protein kinases (HIPKs): HIPK1, HIPK2, and HIPK3. We show that HIPKs are nuclear kinases using GFP-HIPK fusion constructs. The DNA binding activity of the NK-3 homeoprotein is greatly enhanced by HIPK2, but this effect is independent of its phosphorylation by HIPK2. In cultured cells, HIPKs localize to nuclear speckles and potentiate the repressor activities of NK homeoproteins. The co-repressor activity of HIPKs depends on both its homeodomain interaction domain and a co-repressor domain that maps to the N terminus. Thus, HIPKs represent a heretofore undescribed family of co-repressors for homeodomain transcription factors.
Amino Acid Sequence↗
Bacterial Poly(3-hydroxyalkanoates) Bearing Carbon-Carbon Triple Bonds.
Production of poly(3-hydroxyalkanoates), PHAs, by Pseudomonas oleovorans (P. oleovorans) and Pseudomonas putida (P. putida) grown with mixtures of nonanoic acid, NA, and 10-undecynoic acid, 10-UND( identical with), were investigated. Both microorganisms produced PHAs containing carbon-carbon triple bonds in fractions from 0 to 100%, depending on the composition of the carbon substrate mixture. The amounts of unsaturated repeating units in PHAs produced by P. oleovorans were higher than those in PHAs produced by P. putida grown with the same carbon substrates. The repeating units containing carbon-carbon triple bonds were 3-hydroxy-8-nonynoate, 3HN(&tbd1;), and 3-hydroxy-10-undecynoate, 3HUD(&tbd1;). 3HN(&tbd1;) was the major repeating unit formed from 10-UND(&tbd1;). The relative amounts of 3HN(&tbd1;) and 3HUD(&tbd1;) in PHAs produced by P. putida were slightly different from those in PHAs produced by P. oleovorans. The number average molecular weights of PHAs produced in this study were approximately 50 000, and polydispersity indices were approximately 2.5 as determined by gel permeation chromatography. The molecular weight distribution and the relative amounts of 3HN(&tbd1;) and 3HUD(&tbd1;) were not affected by either growth time or the composition of the carbon substrate. PHAs bearing triple bonds were soft and differential scanning calorimetry thermograms of these polymers showed very small melting endotherms at approximately 60 degreesC. The glass transition temperatures were in the range of -33 to -21 degreesC.
Journal Article↗
Mucocele-like Tumor of the Breast: A Case Report and Assessment of Aspirated Cytological Specimens.
BACKGROUND: Mucocele-like tumor(MLT)is a rare benign condition, and ofter misdiagnosed as mucinous carcinoma. METHODS: We encountered a 31-year-old woman with MLT of the breast. The patient presented with an elastic hard mass, 0.5cm in diameter, located in the upper outer quadrant of the right breast. RESULTS: Physical examination as well as ultrasonography and mammography indicated a benign lesion. However, mucinous carcinoma was suspected based on aspiration biopsy cytology. MLT was finally diagnosed on excisional biopsy. CONCLUSION: Awareness of this breast disease helps to prevent misdiagnosis and unnecessary surgery.
Journal Article↗
The influence of delayed postischemic hyperthermia following transient focal ischemia: alterations of gene expression.
We have recently shown that moderate hyperthermia, even if delayed, markedly enlarges the volume of an acute ischemic infarct. In the current study, we used in situ hybridization autoradiography to assess the effects of delayed hyperthermia on the regional expression of messenger RNA (mRNA) for the immediate early genes c-fos and c-jun, the inducible heat-shock protein 70 (hsp70) and glial fibrillary acid protein (GFAP) following 1 h of transient middle cerebral artery occlusion (MCAo) produced in rats by the insertion of an intraluminal suture. Sham-occluded rats were also studied. One day after MCAo, rats were placed into a heating chamber, where cranial temperature was either maintained at 37-38 degrees C (normothermic group) or was elevated to 40 degrees C (hyperthermic group) for 3 h. At either 2 or 24 h thereafter, brains were studied by in situ hybridization. Low-level constitutive c-fos and c-jun expression in sham-occluded rats was unaffected by delayed temperature manipulation. Prior MCAo decreased c-fos and c-jun mRNA in the affected striatum and overlying cortex. In rats studied 2 h after delayed hyperthermia, however, c-fos mRNA was markedly increased in ipsilateral cingulate cortex. By contrast, the pattern of c-jun mRNA was similar in rats with prior MCAo irrespective of delayed normothermia or hyperthermia: increased expression involved ipsilateral cingulate and paramedian cortical areas. Bilateral increases in hsp70 expression were produced by hyperthermia alone, and hsp70 mRNA was densely increased throughout the ischemic cortex and striatum following MCAo, while delayed hyperthermia altered this pattern by extending the zone of increased hsp70 message to cingulate and paramedian cortical areas at 2 h. GFAP mRNA was decreased within the previously ischemic field but increased in surrounding regions. The induction of c-fos and hsp70 message in tissue regions abutting zones of enhanced injury in brains with delayed postischemic hyperthermia indicates that these zones have been additionally stressed: these gene responses may possibly contribute to the protection of these threatened regions.
Animals↗
Size characterization of liposomes by flow field-flow fractionation and photon correlation spectroscopy. Effect of ionic strength and pH of carrier solutions.
The effect of ionic strength and pH of carrier solutions on the separation of liposomes by flow field-flow fractionation (flow FFF) has been studied for the determination of accurate vesicle size distribution of liposomes. Retention behaviors of liposomes (PC/PG/cholesterol) are observed in typical buffer solutions (PBS and Tris-HCl) of various ionic strengths as carrier liquids in flow FFF. The average diameters of collected fractions at each flow FFF run are measured by photon correlation spectroscopy (PCS) for the comparison with FFF calculations at corresponding time interval of collected fractions. A reasonable separation of liposomes is observed at I = 0.016 M for both buffer solutions. Retention of liposomes is found to be elongated at ionic strengths higher than an optimum condition found experimentally, but it is shortened at a lower ionic strength due to the electrostatic interaction between the channel wall and the liposomes. Finally, size distributions of liposomes are provided comparing the liposome preparations by flow FFF.
Drug Carriers↗
Activation of phospholipase D1 by direct interaction with ADP-ribosylation factor 1 and RalA.
Phospholipase D1 (PLD1) is known to be activated by ADP-ribosylation factor 1 (ARF1). We report here that ARF1 co-immunoprecipitates with PLD1 and that the ARF1-dependent PLD activation is induced by the direct interaction between ARF1 and PLD1. We found that RalA, another member of the small GTP-binding proteins, synergistically enhances the ARF1-dependent PLD activity with an EC50 of about 30 nM. Using in vitro binding assay, we show that ARF1 and RalA directly interact with different sites of PLD1. The results suggest that the independent interactions of RalA and ARF1 with PLD1 are responsible for the synergistic activation.
ADP-Ribosylation Factor 1↗
Isolation and analysis of metA, a methionine biosynthetic gene encoding homoserine acetyltransferase in corynebacterium glutamicum.
The metA gene encoding homoserine acetyltransferase, the first enzyme of the methionine biosynthetic pathway, was isolated from a pMT1-based corynebacterium glutamicum gene library via complementation of an Escherichia coli metA mutant. A DNA-sequence analysis of the cloned DNA is identified an open-reading frame of 1,137 bp which encodes a protein with the molecular weight of 41,380 comprising 379 amino acids. The putative protein product showed good amino acid-sequence homology to its counterpart in other organisms. The internal fragment of the cloned DNA was successfully used to disrupt chromosomal metA, demonstrating the identity of the cloned gene. The C. glutamicum metA mutant lost the ability to grow on glucose minimal medium supplemented with homoserine. However, the mutant could grow on a minimal medium supplemented with cystathionine, demonstrating that C. glutamicum uses the cystathionine route to synthesize methionine. Introduction of a plasmid carrying cloned metA into C. glutamicum resulted in a 10-fold increase in enzyme activities and expression of a protein product of M(r) 41,000, which agrees with the sequence data and is similar in size to those of other homoserine acetyltransferases. Unlike E. coli whose metA product uses succinyl coenzyme A as a substrate, the cloned metA gene produced homoserine acetyltransferase which uses only acetyl coenzyme A as the acyl donor.
Acetyltransferases↗
A survey of human serum samples for antibody against Clostridium perfringens type A enterotoxin in humans in Korea.
Serum samples from humans in Chongju City, Korea, were tested for the presence of Clostridium perfringens enterotoxin antibody by enzyme linked immunosorbent assay (ELISA). About half of the 1054 samples tested had high ELISA readings, which could be the result of exposure to enterotoxin produced by C. perfringens. The high prevalence of the antibody among the Korean population suggests that foodborne illnesses caused by C. perfringens may be common in Korea even though the occurrence has not been monitored.
Adolescent↗
Interactions of type IV collagen and its domains with human mesangial cells.
Type IV collagen (COL-IV) interacts with a variety of cell types. We present evidence that human mesangial cells (HMC) bind directly to COL-IV, its major triple helical domain, and the main non-collagenous, NC1 domain. A synthetic peptide, HEP-III, and its triple helical counterpart (THP-III), previously reported to be a heparin-binding domain, also promoted approximately 15% adhesion of HMC. HMC bound to solid-phase-immobilized, intact COL-IV (approximately 75%), isolated NC1 domain (approximately 15%), and a pepsin-derived triple helical fragment,which lacks Hep-III (approximately 65%). We further examined inhibition of HMC adhesion to COL-IV and its domains by using anti-integrin antibodies. Blocking monoclonal antibodies against the alpha2 integrin resulted in 70% inhibition of adhesion to COL-IV and 80% inhibition to HEP-III. Moderate inhibition was observed on the NC1 and triple helical fragments. Anti-alpha1 antibodies inhibited the binding of HMC to COL-IV, the NC1, and triple helical domains, but not to peptide HEP-III. Anti-beta1 antibodies inhibited almost completely (>95%) the adhesion to COL-IV, the NC1, and triple helical fragments; inhibition on HEP-III was approximately 30%. Affinity chromatography studies with solid-phase HEP-III and mesangial cell lysate also demonstrated the presence of integrin alpha2 beta1 along with alpha3 beta1. We conclude that alpha2 beta1 and alpha1 beta1 integrins mediate HMC adhesion to COL-IV. Peptide HEP-III is a major, specific site for alpha2 integrin-mediated binding of mesangial cells to COL-IV. Both the alpha1 beta1 and alpha2 beta1 integrins interact with the NC1 and triple helical fragments of COL-IV. Therefore, we demonstrate that several sites for integrin-mediated interactions exist on several collagenous and non-collagenous domains of COL-IV.
Antibodies, Monoclonal↗
Activation of NF-kappaB via a Src-dependent Ras-MAPK-pp90rsk pathway is required for Pseudomonas aeruginosa-induced mucin overproduction in epithelial cells.
Cystic fibrosis (CF) is an autosomal recessive disorder, the most common lethal genetic disease in Caucasians. Respiratory disease is the major cause of morbidity and mortality. Indeed, 95% of CF patients die of respiratory failure. Pseudomonas aeruginosa, an opportunistic pathogen, chronically infects the lungs of over 85% of CF patients. It is ineradicable by antibiotics and responsible for airway mucus overproduction that contributes to airway obstruction and death. The molecular mechanisms underlying this pathology are unknown. Here we show that P. aeruginosa activates a c-Src-Ras-MEK1/2-MAPK-pp90rsk signaling pathway that leads to activation of nuclear factor NF-kappaB (p65/p50). Activated NF-kappaB binds to a kappaB site in the 5'-flanking region of the MUC2 gene and activates MUC2 mucin transcription. These studies bring new insight into bacterial-epithelial interactions and more specifically into the molecular pathogenesis of cystic fibrosis. Understanding these signaling and gene regulatory mechanisms opens up new therapeutic targets for cystic fibrosis.
Calcium-Calmodulin-Dependent Protein Kinases↗
Genetic structure of the bphG gene encoding 2-hydroxymuconic semialdehyde dehydrogenase of Achromobacter xylosoxidans KF701.
2-Hydroxymuconic semialdehyde dehydrogenase catalyzes the conversion of 2-hydroxymuconic semialdehyde (HMS) to an enol form of 4-oxalocrotonate which is a step in the catechol meta-cleavage pathway. A bphG gene encoding HMS dehydrogenase of A. xylosoxidans KF701, a soil bacterium degrading biphenyl, was identified at between catechol 2,3-dioxygenase gene and HMS hydrolase gene, and its sequence was analyzed. An open reading frame (ORF) corresponding to bphG gene was consisted of 1461 nucleotides with ATG initiation codon and TGA termination codon. The ORF exhibited 66% of G + C content, and a putative ribosome-binding sequence, AGAGA, was identified at about 10 nucleotides upstream initiation codon of the bphG gene. The bphG gene can encode a polypeptide of molecular weight 52 kDa containing 486 amino acid residues. A deduced amino acid sequence of HMS dehydrogenase encoded in bphG gene from A. xylosoxidans KF701 exhibited the highest 94% homology with that of corresponding enzyme encoded in xylG from P. putida mt-2, 63% to 90% homology with those of other reported HMS dehydrogenases, and 29% to 42% homology with those of betaine aldehyde dehydrogenase, 5-carboxy-HMS dehydrogenase, aldehyde dehydrogenase, indole-3-acetaldehyde dehydrogenase, succinic semialdehyde dehydrogenase, methylmalonate semialdehyde dehydrogenase, and succinylglutamate 5-semialdehyde dehydrogenase. From an alignment of amino acid sequence of HMS dehydrogenase from A xylosoxidans KF701 with other reported dehydrogenases, putative cofactor NAD(+)-binding regions and catalytic residues were identified.
Alcaligenes↗
Structure of catechol 2,3-dioxygenase gene from Alcaligenes eutrophus 335.
Catechol 2,3-dioxygenase (C23O), one of extradiol-type dioxygenases cleaving aromatic C-C bond at meta position of dihydroxylated aromatic substrates, catalyzes the conversion of catechol to 2-hydroxymuconic semialdehyde. As our ongoing study to characterize biochemical and genetic properties of the extradiol-type dioxygenases at molecular level, a C23O gene encoded in chromosomal DNA of Alcaligenes eutrophus 335, a strain degrading phenol and p-cresol, was cloned. The C23O gene was localized in an 1.4-kb PstI fragment from A. eutrophus 335, and was expressed in E. coli HB101. The C23O exhibited the highest aromatic ring-fission activity to catechol as a substrate, and its relative activity to other dihydroxylated aromatic substrates was in order of catechol >> 4-methylcatechol > 3-methylcatechol, protocatechuate, 4-chlorocatechol > 3,4-dihydroxy-phenylacetate > 2,3-dihydroxybiphenyl. Nucleotide sequence of the 1.4-kb fragment has revealed that an open reading frame (ORF) corresponding to the C23O gene was composed of 930 base pairs. A putative ribosome-binding sequence of AGGAG was found at about 10 nucleotides upstream the ORF which can encode a polypeptide of molecular weight 34 kDa consisting of 309 amino acid residues. The deduced amino acid sequence of C23O from A. eutrophus 335 exhibited the highest 59% identity with those of corresponding enzymes from Pseudomonas sp. CF600 (p VI150), P. putida HS1 (pDK1), and P. putida PpG7 (NAH7). An alignment of amino acid sequences of extradiol-type dioxygenases including C23O from A. eutrophus 335 has revealed that catalytically and structurally important amino acid residues of the enzymes were conserved during evolution.
Alcaligenes↗
Oxyresveratrol as the potent inhibitor on dopa oxidase activity of mushroom tyrosinase.
Oxyresveratrol (2,3',4,5'-tetrahydroxystilbene), a naturally occurring compound particularly found in Morus alba L., exhibited a potent inhibitory effect on dopa oxidase activity of tyrosinase which catalyzes rate-limiting steps of melanin biosynthesis. Oxyresveratrol with 0.3 to 5 microM exhibited potent and dose-dependent inhibitions (25 to 84%) on the enzyme activity, where 50% of inhibition was shown at the concentration of about 1 microM. Oxyresveratrol seemed to inhibit the dopa oxidase activity of tyrosinase via a noncompetitive manner (Ki = 9.1 x 10(-7) M) when L-dopa was used as a substrate. Oxyresveratrol exhibited about a 150-fold more potent inhibitory effect than resveratrol (3,4',5-trihydroxystilbene). The more hydroxy groups of the hydroxystilbenes are methylated to be methoxy groups, while the less inhibitory effects on the enzyme activity were exhibited. The results indicate that both the number and positions of hydroxy groups in oxyresveratrol seem to play a critical role in exerting the inhibitory effect on dopa oxidase activity of mushroom tyrosinase.
Basidiomycota↗
Thiophilic ring-opening and rearrangement reactions of epoxyketone natural products.
Thiol additions to the highly functionalized core structures of aranorosin- and manumycin-type antibiotics reveal the general reactivity patterns of epoxyketone natural products. Rapid hemiacetal and hydrate formations decrease the reactivity of the epoxyketone moiety in aqueous media toward the cellular scavenger glutathione, and secondary 1,2-shift, elimination, aromatization and intramolecular aldol reactions provide novel reaction pathways. In a hydrophobic environment, the thiol-capture function of the ketone moiety facilitates electrophilic attack.
Anti-Bacterial Agents↗