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Biomedical subjects

Yong Chen

Publications and source records attributed to Yong Chen.

At least 55 records · Page 3Linked to original sources
PubMed2006

Synthesis of bridged and metallobridged bis(beta-cyclodextrin)s containing fluorescent oxamidobisbenzoyl linkers and their selective binding towards bile salts.

A series of beta-cyclodextrin (beta-CD) dimers containing fluorescent 2,2'-oxamidobisbenzoyl and 4,4'-oxamidobisbenzoyl linkers--that is, 6,6'-[2,2'-oxamidobis(benzoylamino)]ethyleneamino-6,6'-deoxy-bis(beta-CD) (2), 6,6'-[2,2'-oxamidobis(benzoylamino)]diethylenediamino-6,6'-deoxy-bis(beta-CD) (3), 6,6'-[4,4'-oxamidobis(benzoylamino)]ethyleneamino-6,6'-deoxy-bis(beta-CD) (4), and 6,6'-[4,4'-oxamidobis(benzoylamino)]diethylenediamino-6,6'-deoxy- bis(beta-CD) (5)--were synthesized from the corresponding oxamidobis(benzoic acid)s through treatment with mono[6-aminoethyleneamino-6-deoxy]-beta-CD or mono[6-diethylenetriamino-6-deoxy]-beta-CD. Further treatment of 2-5 with copper perchlorate gave their Cu(II) complexes 6-9 in satisfactory yields. The conformation and binding behavior of 2-9 towards two bile salt guests--sodium cholate (CA) and sodium deoxycholate (DCA)--was comprehensively investigated by circular dichroism, 2D NMR spectroscopy, and fluorescence spectroscopy in Tris-HCl buffer solution (pH 7.2) at 25 degrees C. Thanks to the cooperative host-linker-guest binding mode, the stoichiometric 1:1 complexes formed by bis(beta-CD)s 2-5 with bile salts gave high stability constants (KS values) of up to 10(3)-10(4) M(-1). Significantly, benefiting from the intramolecular 1:2 or 2:4 binding stoichiometry, the resulting complexes of metallobis(beta-CD)s 6-9 with bile salts gave much higher KS values of up to 10(6)-10(7) M(-2). The enhanced binding abilities of bis(beta-CD)s and metallobridged bis(beta-CD)s are discussed from the viewpoints of induced-fit interactions and multiple recognition between host and guest.

Benzoates↗
PubMed2006

Mucosal tolerance to E-selectin and response to systemic inflammation.

Mucosal tolerance to E-selectin has been shown to prevent stroke and reduce brain infarcts in experimental stroke models. However, the effective E-selectin dose range required to achieve mucosal tolerance and the precise mechanisms of neuroprotection remain unclear. We sought to examine the mechanisms of cytoprotection using gene expression profiling of tissues in the setting of mucosal tolerance and inflammatory challenge. Using spontaneously hypertensive rats (SHRs), we achieved immune tolerance with 0.1 to 5 microg E-selectin per nasal instillation and observed a dose-related anti-E-selectin immunoglobulin G antibody production. We also show the distinct patterns of gene expression changes in the brain and spleen with the different tolerizing doses and lipopolysaccharide (LPS) exposure. Prominent differences were seen with such genes as insulin-like growth factors in the brain and downregulation of those encoding the major histocompatibility complex class I molecules in the spleen. In all, mucosal tolerance to E-selectin and subsequent exposure to LPS resulted in significant tissue changes. These changes, while giving an insight to the underlying mechanisms, serve as possible targets for future studies to facilitate translation to human clinical trials.

Animals↗
PubMed2006

Linear polypseudorotaxanes possessing many metal centers constructed from inclusion complexes of alpha-, beta-, and gamma-cyclodextrins with 4,4'-dipyridine.

Three cyclodextrin-based complexes, 1-3, bearing external coordination sites for metal cations were prepared in satisfactory yields (over 50%) by reactions of alpha-, beta-, and gamma-cyclodextrins with 4,4'-dipyridine in aqueous solutions. Subsequently, these inclusion complexes were further assembled to form linear polypseudorotaxanes 4-6 through the coordination linkage of Ni(II) or Cu(II) ions, and their assembly behaviors were comprehensively investigated in both solutions and the solid state by means of 1H NMR, FT-IR, UV-vis spectroscopy, conductivity titration, powder X-ray diffraction patterning, thermogravimetric and differential thermal analysis, scanning electron microscopy, scanning tunneling microscopy, and transmission electron microscopy. The results showed that these polypseudorotaxanes existed as individual linear arrays at a low concentration but tended to form polymeric rodlike fibers at a relatively high concentration. Significantly, the volume of the cyclodextrin cavity used not only determined the inclusion complexation stoichiometry between cyclodextrin and 4,4'-dipyridine but also predominated the morphology of resulting polypseudorotaxanes.

Journal Article↗
PubMed2006

Multi[2]rotaxanes with gold nanoparticles as centers.

[structure: see text] The multi[2]rotaxanes with gold nanoparticles as centers are constructed by introducing chromophoric beta-cyclodextrin-based [2]rotaxanes on the surface of gold nanoparticles, which show good photophysical and electrochemical properties superior to the parent rotaxane.

Journal Article↗
PubMed2006

Prolonged survival of mice with acute liver failure with transplantation of monkey hepatocytes cultured with an antiapoptotic pentapeptide V5.

BACKGROUND: Because hepatocyte transplantation has been considered to be an attractive method to treat acute liver failure (ALF), efficient recovery of hepatocytes and maintenance of differentiated hepatocyte functions is of extreme importance. We here report the usefulness of an antiapoptotic pentapeptide V5, composed of Val-Pro-Met-Leu-Lys, in the monkey hepatocyte cultures. METHODS: We evaluated albumin production, metabolizing abilities of ammonia, lidocaine, and diazepam of monkey hepatocytes cultured with V5. The protein expression of apoptosis-associated molecules was analyzed using power blot analysis. An unwoven cloth inoculated with V5-treated monkey hepatocytes was transplanted on the surface of the spleen of both SCID mice and Balb/c mice suffering from ALF induced by 90% hepatectomy. RESULTS: When 100 microM V5 was utilized, ammonia-, lidocaine- and diazepam- metabolizing capacities and albumin production ability were significantly increased in V5-treated monkey hepatocytes. Such hepatocytes showed decreased Annexin V binding and increased the expression of anti-apoptotic and/or cytoprotective molecules, including Ku70, NF-kappaB, IKAP, hILP/XIAP, IkappaB, and CAS. Transplantation of the cloth containing the monkey hepatocytes significantly improved blood levels of glucose and ammonia and encephalopathy score and prolonged the survival of the mice with ALF. CONCLUSIONS: The present work clearly demonstrates the usefulness of V5 for maintaining the functions of monkey hepatocytes in tissue culture.

Ammonia↗
PubMed2006

Surface plasmon resonance of silver nanoparticles on vanadium dioxide.

The localized surface plasmon resonance (SPR) spectrum of silver nanoparticles fabricated on a thermochromatic film, vanadium dioxide (VO2), is studied in this paper. Owing to the temperature-dependent dielectric function of VO2, the SPR band dramatically exhibits temperature dependence in the range of 30-80 degrees C. The peak extinction wavelength, lambda(SPR), blueshifts as temperature increases and reversibly redshifts as temperature decreases. The shift magnitude (DeltalambdaSPR) is strongly dependent on the silver mass thickness, dm; a value of 50 nm of DeltalambdaSPR is achieved for particles (mean diameter 51 nm) with dm=2 nm while a value of 250 nm is achieved for particles (mean diameter 133 nm) with dm=10 nm. Beyond the SPR band, it is interesting to find that the spectral line shape of silver particles is dominated by the imaginary part of the dielectric function of VO2. These results can be interpreted based on dynamical Maxwell-Garnett theory.

Journal Article↗
PubMed2006

GEC1 interacts with the kappa opioid receptor and enhances expression of the receptor.

We identified a truncated form (38-117) of GEC1 that interacts with the C-tail of the human kappa opioid receptor (hKOR) by yeast two-hybrid screening. GEC1-(38-117) did not interact with the C-tail of the mu or delta opioid receptors. GEC1, a 117-amino acid protein (Pellerin, I., Vuillermoz, C., Jouvenot, M., Ordener, C., Royez, M., and Adessi, G. L. (1993) Mol. Cell Endocrinol. 90, R17-R21), is highly homologous to GABARAP, GATE-16, and Apg8/aut7, all members of the microtubule associated protein (MAP) family. In pull-down assays, GST-GEC1 interacted directly with the hKOR C-tail, full-length hKOR, and tubulin. When expressed in Chinese hamster ovary (CHO) cells, GEC1 co-immunoprecipitated with FLAG-hKOR. Expression of GEC1 greatly increased total and cell-surface KOR but not mu or delta opioid receptors. GEC1 expression slightly reduced U50,488H-promoted down-regulation, without affecting ligand binding affinity, receptor-G protein coupling, or U50,488H-induced desensitization and internalization. HA-GEC1 expressed in CHO cells was localized in the Golgi apparatus and endoplasmic reticulum (ER). When cells were pulsed with [35S]Met/Cys, GEC1 expression enhanced the level of the mature form (55-kDa band) of FLAG-hKOR at 4, 8, and 22 h after pulse without affecting the precursors (39- and 45-kDa bands), indicating that GEC1 facilitates trafficking of FLAG-hKOR from the ER/Golgi to plasma membranes. GEC1 interacted with N-ethylmaleimide-sensitive factor (NSF) in pull-down assays and co-immunoprecipitated with NSF in rat brain extracts. The interaction with NSF may contribute to GEC1 effects. This is the first report on biological functions of GEC1 and the first demonstration that a GPCR interacts with a protein of the MAP family. The interaction is important for trafficking of the receptor in the biosynthesis pathway.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed2006

PKA-mediated protein phosphorylation regulates ezrin-WWOX interaction.

The ezrin-radixin-moesin proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton, and also participate in signal-transduction pathways. Ezrin is localized to the apical membrane of parietal cells and couples the cAMP-dependent protein kinase activation cascade to the regulated HCl secretion in gastric parietal cells. Our recent studies have mapped the PKA-mediated phosphorylation site to Ser(66) and established its functional role in parietal cell activation [R. Zhou et al., Characterization of protein kinase A-mediated phosphorylation of ezrin in gastric parietal cell activation, J. Biol. Chem. 278 (2003) 35651-35659], but the underlying basis for this regulation is not known. Here, we provide the first evidence that PKA-mediated phosphorylation of Ser(66)regulates the interaction of ezrin with WWOX, a WW domain-containing protein. Our biochemical study reveals that ezrin directly binds to the first WW domain of WWOX via its C-terminal tyrosine-containing polyproline sequence (470)PPPPPPVY(477). Mutational analyses further demonstrate that tyrosine(477) is essential for the ezrin-WWOX interaction. In addition, our study shows that PKA-mediated phosphorylation of ezrin is essential and sufficient for the apical localization of WWOX protein as disruption of ezrin-WWOX interaction eliminated the apical localization of WWOX. Finally, our study demonstrates the essential role of ezrin-WWOX interaction in the apical membrane remodeling associated with H,K-ATPase recruitment. Taken together, these results define a novel molecular mechanism underlying phospho-regulation of ezrin function by PKA in parietal cell activation.

Amino Acid Sequence↗
PubMed2006

Cell distribution of stress fibres in response to the geometry of the adhesive environment.

Cells display a large variety of shapes when plated in classical culture conditions despite their belonging to a common cell type. These shapes are transitory, since cells permanently disassemble and reassemble their cytoskeleton while moving. Adhesive micropatterns are commonly used to confine cell shape within a given geometry. In addition the micropattern can be designed so as to impose cells to spread upon adhesive and nonadhesive areas. Modulation of the pattern geometry allows the analysis of the mechanisms governing the determination of cell shape in response to external adhesive conditions. In this study, we show that the acquisition of cell shape follows two stages where initially the cell forms contact with the micropattern. Here, the most distal contacts made by the cell with the micropattern define the apices of the cell shape. Then secondly, the cell borders that link two apices move so as to minimise the distance between the two apices. In these cell borders, the absence of an underlying adhesive substrate is overcome by stress fibres forming between the apices, which in turn are marked by an accumulation of focal adhesions. By inhibiting myosin function, cell borders on nonadhesive zones become more concave, suggesting that the stress fibres work against the membrane tension in the cell border. Moreover, this suggested that traction forces are unevenly distributed in stationary, nonmigrating, cells. By comparing the stress fibres in cells with one, two, or three nonadherent cell borders it was reasoned that stress fibre strength is inversely proportional to number. We conclude that cells of a given area can generate the same total sum of tractional forces but that these tractional forces are differently spaced depending on the spatial distribution of its adherence contacts.

Actins↗
PubMed2006

Picoliter-volume aqueous droplets in oil: electrochemical detection and yeast cell electroporation.

An electrochemical detection method was introduced for aqueous droplet analysis in oil phase of microfluidic devices. This method is based on the electrochemical signal difference between aqueous and oil. Applying a low alternating current (AC) voltage to a couple of Au microelectrodes, this method can offer size information and ion concentration range from 0.02 mmol/L to 1 mol/L of tens of picoliter to nanoliter aqueous droplets. Alternatively, applying a relative high AC voltage (18 Vpp) at a frequency of 1 kHz leads to electroporation of yeast cells encapsulated into picoliter droplets. We believe that this simple technique is useful for a number of aqueous droplet-based chemical and biological analyses as well as cell electroporation.

Electrochemistry↗
PubMed2006

Proteomics-based generation and characterization of monoclonal antibodies against human liver mitochondrial proteins.

Monoclonal antibodies (mAbs) have the potential to be a very powerful tool in proteomics research to determine protein expression, quantification, localization and modification, as well as protein-protein interactions, especially when combined with microarray technology. Thus, a large amount of well-characterized and highly qualified antibodies are needed in proteomics. Purified antigen, which is not always available, has proven to be one of the rate-limiting steps in mAb large-scale generation. Here we describe our strategies to establish a murine hybridoma cell bank for human liver mitochondria using unknown native proteins as the immunogens. The antibody-recognized mitochondrial proteins were identified by MS following immunoprecipitation (IP), and by screening of human liver cDNA expression library. We found that the established antibodies reacted specifically with a number of important enzymes in mitochondria. The subcellular localization of these antigens in mitochondria was further confirmed by immunohistocytochemistry. A panel of antibodies was also tested for their ability to capture and deplete the targeting proteins and complexes from the total mitochondrial proteins. We believe these well-characterized antibodies would be useful in various applications for Human Liver Proteome Project (HLPP) when the scale of this hybridoma cell bank is enlarged significantly in the near future.

Antibodies, Monoclonal↗
PubMed2006

Gene expression profile in immunologically injured liver cell of mice.

To study the gene expression profiles between immunologically injured liver cell and normal liver cell of mice and to screen on a large scale the differentially expressed genes associated with the formation of liver injury, the experimental mice were randomly divided into the normal group for controlling and the immunologically liver-injured group induced by BCG and LPS. The liver mRNA of the two groups were extracted respectively and reversely-transcribed to cDNA with the incorporation of different fluorescence (Cy3, Cy5) labeled dUTP as the hybridization probes. The mixed probes were hybridized to the cDNA microarray chips. The fluorescent signal results were acquired by scanner ScanArray 4000 and analyzed with software GenePix Pro 3.0. Among the 14112 target genes, 293 genes were found to be significantly differentially expressed, in which 188 genes were up-regulated and 105 genes were down-regulated. Based on the analysis of biological functions of those differentially expressed genes, it was indicated that the occurrence and development of mouse liver damage induced by BCG and LPS were highly correlated with the processes of immune reactions, cell synthesis, metabolism, apoptosis and transportation in liver cell, which might be quite important for elucidating the regulatory network of gene expression associated with the liver damage, also important for finally discovering the pathogenic mechanisms of immunological liver damage.

Alanine Transaminase↗
PubMed2006

Cooperative binding and multiple recognition by bridged bis(beta-cyclodextrin)s with functional linkers.

Possessing two beta-cyclodextrin cavities in close vicinity and a functional linker with good structural variety in a single molecule, bridged bis(beta-cyclodextrin)s can significantly enhance the original binding ability and molecular selectivity of native beta-cyclodextrin and thus be successfully utilized in drug carriers, solubilizers, catalysis, photochemical materials, etc. This Account describes recent developments in the intramolecular cooperative binding and multiple recognition of bridged bis(beta-cyclodextrin)s with functional linkers in solution, as well as their molecular assembly behaviors through the intermolecular cooperative binding. It also gives a description of unique properties and wide applications of bis(beta-cyclodextrin)s and their assemblies.

Binding Sites↗
PubMed2006

Bundle-shaped cyclodextrin-Tb nano-supramolecular assembly mediated by C60: intramolecular energy transfer.

A bundle-shaped nano-supramolecular assembly possessing numerous luminescent cyclodextrin-Tb polyads and photosensitizing C(60) units has been constructed through the end-to-end inclusion complexation of cyclodextrin cavities with C(60)s, and its properties have been comprehensively characterized. Further investigations on the luminescence properties of the cyclodextrin-Tb polyad and the bundle-shaped assembly demonstrate that a pyridine --> Tb --> C(60) intramolecular energy transfer process is operative when a solution of the assembly is exposed to UV light.

Crystallization↗
PubMed2006

The identification of a new actin-binding region in p57.

The actin-binding protein p57 is a member of mammalian coronin-like proteins. The roles of this protein in phagocytic processes conceivably depend on its interactions with F-actin. Two regions, p57(1-34) and p57(111-204), were previously reported to be actin-binding sites. In this study, we found that the C-terminal region of p57, p57(297-461), also possessed F-actin binding activity. Furthermore, the leucine zipper domain at the C-terminus of p57(297-461) was essential for this actin-binding activity. The F-actin cross-linking assay revealed that the region contained in p57(297-461) was sufficient to cross-link actin filaments. Our results strongly suggested that there was a new actin-binding region at the C-terminus of p57.

Actins↗
PubMed2006

Nociceptin and its receptor in rat dorsal root ganglion neurons in neuropathic and inflammatory pain models: implications on pain processing.

Nociceptin (NC), by activating its receptor, the opioid receptor-like 1 (ORL1) receptor, exerts an effect on a number of functions in the nervous system including locomotion, learning and memory, and processing of pain signals. Data on the expression of NC and ORL1 receptor in dorsal root ganglion (DRG) neurons and on its modulation after nerve injury and inflammation are controversial. We therefore sought to investigate the immunoreactivity (IR) of NC and ORL1 receptor in DRG neurons in two pain models, a pure neuropathic pain model, namely partial sciatic nerve transection (PST), and an inflammatory pain model, complete Freund's adjuvant (CFA) injection into the hindpaw. In intact DRG neurons, both NC and ORL1 receptor IR were present in mainly small- and medium-sized neurons, NC IR in 31% and ORL1 receptor IR in 33% of all neuronal profiles. Both NC and ORL1 receptor IR were upregulated 7 days after nerve injury (to 56 and 55%) and inflammation (to 53 and 48%), respectively. Activating transcription factor 3 (ATF3), a neuronal marker of nerve injury, was induced in DRG neurons 7 and 14 days after PST and 7 days after CFA injection. Double labeling with ATF3 revealed expression of NC and ORL1 receptor in intact as well as in injured primary afferent neurons. Thus, NC and the ORL1 receptor may be involved in the modulation of neuropathic and inflammatory pain at the level of the primary afferent neuron.

Activating Transcription Factor 3↗
PubMed2006

Atomic force microscopic examination of chromosomes treated with trypsin or ethidium bromide.

Trypsin treatment is frequently used during chromosome preparation for removal of cellular contaminants, and ethidium bromide (EB) staining of bands is often used to facilitate high-resolution observations by optical microscopy. However, conventional optical microscopy is unable to visualize potential aberrations of chromosome structures caused by these physicochemical treatments. In this article, we use atomic force microscopy (AFM) in the tapping mode to obtain and analyze high-resolution images of chromosome surface structure damage associated with trypsinization and EB treatment. According to our results, the trypsin-based digestion effects became more severe as incubations increased across a range from 10 to 40 s; a digestion time of 10 to 20 s appeared to be most suitable for observation by AFM. In terms of chromosomal damage induced by EB treatment, addition of EB into the media of cultured human blood cells induced chromosomal breakage in a dose-dependent fashion, and the results indicate centromeric region damnifyed severer than arms. Together, these results indicate that EB staining and the standard chromosomal preparative techniques of trypsinization can induce chromosomal damage that may affect the observed results.

Blood Cells↗