Biomedical subjects

Wei Liu

Publications and source records attributed to Wei Liu.

At least 55 records · Page 3Linked to original sources

PubMed2006

Profilin is an effector for Daam1 in non-canonical Wnt signaling and is required for vertebrate gastrulation.

Non-canonical Wnt signaling plays important roles during vertebrate embryogenesis and is required for cell motility during gastrulation. However, the molecular mechanisms of how Wnt signaling regulates modification of the actin cytoskeleton remain incompletely understood. We had previously identified the Formin homology protein Daam1 as an important link between Dishevelled and the Rho GTPase for cytoskeletal modulation. Here, we report that Profilin1 is an effector downstream of Daam1 required for cytoskeletal changes. Profilin1 interacted with the FH1 domain of Daam1 and was localized with Daam1 to actin stress fibers in response to Wnt signaling in mammalian cells. In addition, depletion of Profilin1 inhibited stress fiber formation induced by non-canonical Wnt signaling. Inhibition or depletion of Profilin1 in vivo specifically inhibited blastopore closure in Xenopus but did not affect convergent extension movements, tissue separation or neural fold closure. Our studies define a molecular pathway downstream of Daam1 that controls Wnt-mediated cytoskeletal reorganization for a specific morphogenetic process during vertebrate gastrulation.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Interactions of tryptophan, tryptophan peptides, and tryptophan alkyl esters at curved membrane interfaces.

Motivated by ongoing efforts to understand the mechanism of membrane protein crystallogenesis and transport in the lipidic cubic phase, the nature of the interaction between tryptophan and the bilayer/aqueous interface of the cubic phase has been investigated. The association was quantified by partitioning measurements that enabled the free energy of interaction to be determined. Temperature-dependent partitioning was used to parse the association free energy change into its enthalpic and entropic components. As has been observed with tryptophan derivatives interacting with glycerophospholipid bilayers in vesicles, tryptophan partitioning in the cubic phase is enthalpy driven. This is in contrast to partitioning into apolar solvents, which exhibits the classic hydrophobic effect whose hallmark is a favorable entropy change. These results with tryptophan are somewhat surprising given the simplicity, homogeneity, and curvature of the interface that prevails in the case of the cubic phase. Nevertheless, the interaction between tryptophan and the mesophase is very slight as revealed by its low partition coefficient. Additional evidence in support of the interaction was obtained by electronic absorption and fluorescence spectroscopy and fluorescence quenching. Partitioning proved insensitive to the lipid composition of the membrane, examined by doping with glycerophospholipids. However, the interaction could be manipulated in meaningful ways by the inclusion in the aqueous medium of salt, glycerol, or urea. The effects seen with tryptophan were amplified rationally when measurements were repeated using tryptophan alkyl esters and with tryptophan peptides of increasing length. These findings are interpreted in the context of the insertion, folding, and function of proteins in membranes.

Esters↗

PubMed2006

Development of a monoclonal antibody-based enzyme-linked immunosorbent assay for the analysis of glycyrrhizic acid.

Glycyrrhizic acid (GL) is a major active compound of licorice. The specific monoclonal antibody (MAb) (designated as 8F8A8H42H7) against GL was produced with the immunogen GL-BSA conjugate. The dissociation constant (Kd) value of the MAb was approximately 9.96x10(-10) M. The cross reactivity of the MAb with glycyrrhetic acid was approximately 2.6%. The conventional indirect competitive enzyme-linked immunosorbent assay (icELISA) and simplified icELISA adapted with a modified procedure were established using the MAb. The IC50 value and the detect range by the conventional icELISA were 1.1 ng mL-1 and 0.2-5.1 ng mL-1, respectively. The IC50 value and the detect range by the simplified icELISA were 5.3 ng mL-1 and 1.2-23.8 ng mL-1, respectively. The two icELISA formats were used to analyze GL contents in the roots of wild licorice and different parts of cultivated licorice (Glycyrrhiza uralensis Fisch). The results obtained with the two icELISAs agreed well with those of the HPLC analysis. The correlation coefficient was more than 0.98 between HPLC and the two icELISAs. The two icELISAs were shown to be appropriate, simple, and effective for the quality control of raw licorice root materials.

Animals↗

PubMed2006

Catalytic properties of carboxylic acid functionalized-polymer microsphere-stabilized gold metallic colloids.

Polymer-microsphere-stabilized gold metallic colloids have been prepared by a novel strategy of simple and convenient reduction of the metallic salt through the stabilization of the active carboxylic acid group on the gel and surface layer of the microsphere. The nature of the interaction between the carboxylic acid and Au nanoparticles was studied in detail by XPS. Preliminary results indicate that polymer-microsphere-stabilized gold colloids are active catalysts for the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride as reductant. The catalytic properties of the stabilized catalyst for recycling were also investigated.

Adsorption↗

PubMed2006

Functional characterization of nucleoside transporter gene replacements in Leishmania donovani.

Leishmania donovani express two nucleoside transporters of non-overlapping ligand selectivity. To evaluate the physiological role of nucleoside transporters in L. donovani, homozygous null mutants of the genes encoding the LdNT1 adenosine-pyrimidine nucleoside transporter and the LdNT2 inosine-guanosine transporter were created singly and in combination by single targeted gene replacement followed by selection for loss-of-heterozygosity. The mutant alleles were verified by Southern blotting, and the effects of gene replacement on transport phenotype were evaluated by rapid sampling transport measurements and by drug resistance profiles. The Deltaldnt1, Deltaldnt2, and Deltaldnt1/Deltaldnt2 mutants were all capable of proliferation in defined culture medium supplemented with any of a spectrum of purine nucleobases or nucleosides, except that a Deltaldnt2 lesion conferred an inability to efficiently salvage exogenous xanthosine, a newly discovered ligand of LdNT2. Each of the three knockout strains was viable as promastigotes and axenic amastigotes and capable of maintaining an infection in J774 and bone marrow-derived murine macrophages. These genetic studies demonstrate: (1) that L. donovani promastigotes, axenic amastigotes, and tissue amastigotes are viable in the absence of nucleoside transport; (2) that nucleoside transporters are not essential for sustaining an infection in mammalian host cells; (3) that the phagolysosome of macrophages is likely to contain purines that are not LdNT1 or LdNT2 ligands, i.e., nucleobases. Furthermore, the Deltaldnt1, Deltaldnt2, and Deltaldnt1/Deltaldnt2 knockouts offer a unique genetically defined null background for the biochemical and genetic characterization of nucleoside transporter genes and cDNAs from phylogenetically diverse species and of genetically manipulated LdNT1 and LdNT2 constructs.

Adenosine↗

PubMed2006

Expression of Six3 Opposite Strand (Six3OS) during mouse embryonic development.

Recently, sequence analyses have identified a large number of opposite strand transcripts in the vertebrate genome. Although the transcripts appear to be spliced and polyadenylated, many of them are predicted to represent noncoding RNAs. High levels of noncoding transcripts of the Six3 Opposite Strand (Six3OS) were recently identified in the embryonic and postnatal retina of the mouse. In this study, we expanded those initial expression analyses, elucidated in detail the developmental expression profile of mouse Six3OS in the brain and visual system, and compared it with that of Six3. Our results show that Six3OS expression overlaps extensively with that of Six3 and is not altered in Six3-null embryos.

Animals↗

PubMed2006

Preparation of anti-pefloxacin antibody and development of an indirect competitive enzyme-linked immunosorbent assay for detection of pefloxacin residue in chicken liver.

Pefloxacin has been increasingly used in veterinary medicine to treat microbial infections. To avoid using a labor-intensive instrumental method to detect the residue of pefloxacin in food, a simple and convenient indirect competitive enzyme-linked immunosorbent assay method has been developed in this study. The antibody generated from immunogen cationized bovine serum albumin-pefloxacin showed high sensitivity toward pefloxacin with an IC50 value of 6.7 ppb in buffer and was suitable for a screening assay to detect the residue of pefloxacin in food products. The antibody has been assessed using rapid enzyme immunoassays to exploit its specificity. The antibody prepared shows cross-reactivity with a few other (fluoro)quinolones including fleroxacin (116%), enrofloxacin (88%), and ofloxacin (10%). The assay measured drug residue in chicken liver spiked with pefloxacin with an interassay coefficient of variation of 13.6% or less and an intra-assay coefficient of variation of 10.9% or less. The average recovery rates at 0.5, 5, 10, 50, and 100 ppb were in the range of 86-106% for interassay and in the range of 87-103% for intra-assay, respectively.

Animals↗

PubMed2006

Tumor necrosis factor alpha blocking peptide loaded PEG-PLGA nanoparticles: preparation and in vitro evaluation.

Nanoparticles prepared from polyethyleneglycol-modified poly(d,l-lactide-co-glycolide) (PEG-PLGA-NPs) are being extensively investigated as drug carriers due to their controlled release, biodegradable and biocompatibility. The purpose of this study was to evaluate the in vitro characteristics of PEG-PLGA-NPs loading tumor necrosis factor alpha blocking peptide (TNF-BP). PEG-PLGA copolymer was synthesized by ring-opening polymerization of d,l-lactide, glycolide and methoxypolyethyleneglycol (mPEG) (Mw = 5000). Blank PEG-PLGA-NPs, with particle size within the range of 79.7 to 126.1 nm and zeta potential within the range of -12.91 to -24.55 mV, were prepared by the modified-spontaneous emulsification solvent diffusion (modified-SESD) method. PEG-PLGA-NPs uptake by murine peritoneal macrophages (MPM) was lower than that of PLGA-NPs. TNF-BP was loaded on the blank nanoparticles by electrostatic interactions, and TNF-BP loading capacity of PEG-PLGA-NPs was found to be dependent on the characteristics of blank nanoparticles, peptide concentration and incubation medium. In vitro release experiments showed the peptide release rate affected by the drug loading and ionic strength, and approximately 60.2% of TNF-BP released from nanoparticles still possessed bioactivity. These experimental results indicate that PEG-PLGA-NPs could be used to develop as drug carriers for TNF-BP.

Animals↗

PubMed2006

Extracellular signal-regulated kinases are not involved in activity-dependent survival or apoptosis in cerebellar granule neurons.

Cerebellar granule neurons (CGNs) depend on potassium depolarization for survival and undergo apoptosis when deprived of depolarizing concentration of potassium. Extracellular signal-regulated kinases (ERK1/2) are thought to be activated in response to potassium depolarization and responsible for the activity-dependent survival in CGNs, but one recent study has revealed that ERK1/2 is activated by potassium deprivation and is required for apoptosis of CGNs. In this study we showed that ERK1/2 was inactivated, rather than activated, by potassium deprivation, indicating a lack of ERK1/2 involvement in potassium deprivation-induced apoptosis. Furthermore, suppression of potassium depolarization-induced activation of ERK1/2 with chemical inhibitor U0126 or PD98059 had no influence on the pro-survival effect of potassium depolarisation. Thus, ERK1/2 was not required for potassium depolarization-dependent survival of CGNs. Taken together, our findings suggest that ERK1/2 is not involved in activity-dependent survival or apoptosis of CGNs.

Animals↗

PubMed2006

Insights into COPI coat assembly and function in living cells.

Eukaryotic cells use an elaborate machinery involving the COPI coat complex to control protein trafficking in the secretory pathway. Although individual components of this complex are well known and their roles in deforming lipid membranes into coated carriers are well described, the precise sequence of molecular events by which these components assemble into and release from the COPI coat lattice remains unclear. Here, we present images and movies characterizing the dynamics of protein components of the COPI coat in living cells. We discuss the self-assembly of these coat components into a molecular machine for sorting and trafficking membranes.

ADP-Ribosylation Factor 1↗

PubMed2006

Depth profiles of radiocarbon and carbon isotopic compositions of organic matter and CO2 in a forest soil.

Depth profiles of the specific activities of (14)C and carbon isotopic compositions (Delta(14)C, delta(13)C) in soil organic matter and soil CO(2) in a Japanese larch forest were determined. For investigating the transport of CO(2) in soil, specific activities of (14)C, Delta(14)C and delta(13)C in the organic layer, and atmospheric CO(2) in the same forest area were also determined. The specific activity of (14)C and Delta(14)C in the soil organic matter decreased with the increase in depth of 0-60cm, while that of soil CO(2) did not vary greatly at a soil depth of 13-73cm and was more prevalent than that of atmospheric CO(2). Peaks of specific activities of (14)C appeared at the depth of 0-4cm and Delta(14)C values were positive in the depth range from 0 to 15cm. These results suggest that the present soil at a depth of 0-4cm had been produced from the mid-1950s up until 1963, and the bomb C had reached the depth of 15cm in the objective soil area. The delta(13)C in the soil organic matter increased at the depth of 0-55cm, while that of soil CO(2) collected on 8 November 2004 decreased rapidly at the depth of 0-13cm and only slightly at the depth of 53-73cm. By combining the Delta(14)C and delta(13)C of the respective components and using the Keeling plot approach it was made clear that the entering of atmospheric CO(2) showed a large contribution to soil CO(2) at the depth of 0-13cm and a negligible contribution at the depth of 53-73cm for soil air collected on 8 November 2004. Respiration of live roots was presumed to be the main source of soil CO(2) at the depth of 53-73cm on 8 November 2004.

Carbon Dioxide↗

PubMed2006

[Therapeutic experience of fulminant acute pancreatitis in acute response stage].

OBJECTIVE: To investigate therapeutic strategy of fulminant acute pancreatitis (FAP) in acute response stage. METHODS: Sixty-four patients were divided into Death group (27 patients) and Survival group (37 patients). The time course of shock and recovery of enteral function, parameters of fluid resuscitation, PaO(2)/FiO(2) and AaDO(2) at 24 hours prior to mechanical ventilation, rate of continuous venovenous hemofiltration (CVVH) and abdominal compartment syndrome (ACS), severity of the disease in the acute response stage were investigated. And the effect of surgical manner and time on the prognosis was also analyzed. RESULTS: Compared with Survival group, the time course of shock and recovery of enteral function in Death group were prolonged significantly (P < 0.05). Between the groups, there was no difference in the amount of crystal fluid infused from admission to 72 hours after, but the amount of colloid fluid infused and ratio of amount of colloid and crystal fluid in Survival group were higher (P < 0.05). The amount of fluid retention in third space from admission to 72 hours after in Death group was higher than that of Survival group significantly (P < 0.05). The fluid infusing rate in Survival group in the first day of admission was faster than Death group (P < 0.05). PaO(2)/FiO(2) and AaDO(2) in 24 hours prior to mechanical ventilation in Death group were negatively changed significantly. Within 72 hours after the onset of the disease, the rate of CVVH in Survival group was higher than Death group. Incidence rate of ACS and the APACHEII scores within 72 hours after admission in Death group were higher than in Survival group. The cure rate of the patients operated in the day 7 to day 14 after admission was higher than that of patients operated prior and post this period. Time for the first operation in operated patients was earlier than patients received minimally invasive drainage (MID) and its cure rate was lower than that of MID Group. CONCLUSIONS: It is the key point to shorten the time course of ischemia, to control persistent systemic inflammatory response syndrome (SIRS) and to adopt reasonable surgical intervention in acute response stage for FAP.

Acute Disease↗

PubMed2006

IL-10 gene modified dendritic cells induced antigen-specific tolerance in experimental autoimmune myocarditis.

Experimental autoimmune myocarditis (EAM) in rats is a T-cell-mediated disorder, and the involvement of Th1/Th2 unbalance has been demonstrated. The induction of antigen-specific tolerance is critical for the treatment of EAM and maintenance of immune tolerance. IL-10 is a pleiotrophic immunomodulatory cytokine that functions at different levels of the immune response, so it has emerged as a promising therapeutic factor for the treatment of autoimmune/inflammatory diseases. This study was designed to explore the effects of IL-10 gene modified bone-marrow-derived immature dendritic cells (iDCs) on the in vitro and in vivo immune response to cardiac myosin in EAM. EAM was induced using the classic methods of cardiac myosin immunization on day 0 and day 7. 2 x 10(6)/per rat mature DC (mDC), immature DC (iDC), pcDNA3 transfected iDC, pcDNA3-IL-10 transfected iDC or PBS were injected intravenously for treatment 5 days after the first immunization. On day 21, transthoracic echocardiogram and HE staining were performed to detect the cardiac function and myocardial inflammation. Th1/Th2 cytokines were detected by ELISA and MHC-II molecules, costimulatory molecules were identified by flow cytometry. In vitro T lymphocyte proliferation assay and adoptive transfer of DCs were performed to determine the antigen-specific tolerance induced by IL-10 gene modified iDCs. IL-10 gene modified iDC-treated EAM rats showed improved cardiac function and reduced infiltration of inflammatory cell into myocardium. Serum cytokines data indicated lower Th1 while higher Th2-type responses were induced in the pcDNA3-IL-10-iDC-treated group, suggesting a Th2 polarization. Moreover, IL-10 gene modified iDCs down-regulated MHC-II and costimulatory molecules on the surface of splenocytes and inhibited the antigen-specific immunological responses towards cardiac myosin. Adoptive transfer of IL-10 producing DCs prevented EAM induction. IL-10 gene modified iDCs ameliorates EAM histopathologically and functionally. The underlying mechanisms may be related to the IL-10 induced Th2 polarization and down-regulation of MHC-II molecules and costimulatory molecules expression.

Adoptive Transfer↗

PubMed2006

Dissipative particle dynamics study on the morphology changes of diblock copolymer lamellar microdomains due to steady shear.

The morphology changes of linear diblock copolymer lamellar microdomains under uniform simple shear are studied via the dissipative particle dynamics technique. The parallel and perpendicular reorientations of the lamellae are observed in the simulations, and two different reorientation mechanisms, under small and large shear rates respectively, are proposed. The parallel-to-perpendicular transition is also observed and the kinetics is discussed. Sinusoidal and chevron instabilities due to the shear are found. After relaxation the peculiar "bidirectionally undulating" instability is obtained.

Journal Article↗

PubMed2006

Sustained production of the labile pheromone component, (Z,Z)-6,9-heneicosadien-11-one, from a stable precursor for monitoring the whitemarked tussock moth.

The principal sex pheromone component of the whitemarked tussock moth (WMTM), Orgyia leucostigma, was recently identified as (Z,Z)-6,9-heneicosadien-11-one (Z6Z9-11-one-21Hy). However, it is thermally unstable and quickly degrades under field conditions so that baited traps are effective for only one night. We have developed a solution to this problem that combines two techniques: (1) the use of a stable pheromone precursor, (Z,Z)-6,9-heneicosadien-11-one ethylene ketal, which is hydrolyzed to the dienone by an acidic aqueous solution (2% p-toluenesulfonic acid in 35% aqueous sorbitol), and (2) use of a small, off-the-shelf, autonomous pump (the Med-e-Cell Infu-disktrade mark) to deliver the precursor continuously to a suitable substrate where it is converted rapidly into the attractive dienone pheromone component. The pump and hydrolysis substrate fit inside sticky traps and because generation and release of pheromone is continuous, the instability of the pheromone is not an issue. In electroantennogram bioassays, dose-dependent responses were obtained with 1 to 1000 ng of hydrolyzed ketal on filter paper, but no response was obtained to 1000 ng of the ketal itself. In wind tunnel bioassays, males were attracted to lures emitting the dienone pheromone component generated from 0.1 to 100 ng of the hydrolyzed ketal. Field tests in 2004 and 2005 showed that sticky traps fitted with the pump delivering the ketal (0.1-1 microg/microL in heptane) at 10 microL/hr to a cotton pad soaked with the hydrolyzing solution were attractive to male WMTM. No moths were caught in controls or traps baited with (Z)-6-heneicosen-11-one. An average of 0.51 moths per trap night was caught over an 18-night period in 2005. The results represent a first step toward developing a sensitive and practical monitoring tool for the WMTM by using a ketal precursor of its unstable dienone pheromone component.

Animals↗

PubMed2006

Functional studies of a novel oncogene TGM3 in human esophageal squamous cell carcinoma.

AIM: To investigate the role of transglutaminase 3 (TGM3) gene in human esophageal squamous cell carcinoma (ESCC), and analyze its relationship with clinicopathological parameters. METHODS: Gene expression of TGM3 in fresh esophageal cancer tissues and their corresponding normal mucosas was detected immunohistochemically (IHC) by means of tissue microarray (TMA). Its correlation with clinical characteristics was evaluated and analyzed by univariate analysis. All statistical analyses were performed by SPSS version 10.0. RESULTS: Expression rate of TGM3 was reduced to 81.8% in ESCC. Expression of TGM3 was significantly inversely correlated with histological grade of esophageal carcinoma (in grade I, II and III tumors, the reduced expression was 4/7, 57/71, and 20/21, respectively, P < 0.05), whereas it had no obvious correlations with lymph node metastasis and depth of invasion. CONCLUSION: Reduced expression of TGM3 may play an important role in esophageal carcinogenesis.

Adult↗

PubMed2006

Pitx2 regulates cardiac left-right asymmetry by patterning second cardiac lineage-derived myocardium.

Current models of left-right asymmetry hold that an early asymmetric signal is generated at the node and transduced to lateral plate mesoderm in a linear signal transduction cascade through the function of the Nodal signaling molecule. The Pitx2 homeobox gene functions at the final stages of this cascade to direct asymmetric morphogenesis of selected organs including the heart. We previously showed that Pitx2 regulated an asymmetric pathway that was independent of cardiac looping suggesting a second asymmetric cardiac pathway. It has been proposed that in the cardiac outflow tract Pitx2 functions in both cardiac neural crest, as a target of canonical Wnt-signaling, and in the mesoderm-derived cardiac second lineage. We used fate mapping, conditional loss of function, and chimera analysis in mice to investigate the role of Pitx2 in outflow tract morphogenesis. Our findings reveal that Pitx2 is dispensable in the cardiac neural crest but functions in second lineage myocardium revealing that this cardiac progenitor field is patterned asymmetrically.

Animals↗

PubMed2006

Comprehensive examination of charged intramembrane residues in a nucleoside transporter.

Permeases of the equilibrative nucleoside transporter family mediate the uptake of nucleosides and/or nucleobases in a diverse array of eukaryotes and transport a host of drugs used for treatment of cancer, heart disease, AIDS, and parasitic infections. To identify residues that play central roles in transport function, we have systematically substituted by site-directed mutagenesis all the charged residues located within predicted transmembrane domains of the Leishmania donovani nucleoside transporter 1.1, LdNT1.1, which transports adenosine and the pyrimidine nucleosides. Substitution of three of these ten residues by uncharged amino acids resulted in loss of >95% transport activity, and we hence designated them "key" residues. These amino acids were Glu94, Lys153, and Arg404 located in transmembrane domains 2, 4, and 9, respectively. In addition, previous studies on the related LdNT2 inosine/guanosine transporter identified the highly conserved Asp389 and Arg393 (equivalent to Asp374 and Arg378 in LdNT1.1) in transmembrane domain 8 as key residues. Among these residues, the mutants in Arg393 (LdNT2) and Arg404 were strongly impaired in trafficking to the plasma membrane, but the other mutants were expressed with high to moderate efficiency at the cell surface, indicating that their mutation impaired transport activity per se. A conservative K153R substitution exhibited a change in substrate specificity, acquiring the ability to transport inosine, a nucleoside that is not a substrate for the wild-type LdNT1.1 permease. These results imply that the Glu94, Lys153, and Asp374 residues may play central roles in the mechanism of substrate translocation in LdNT1.1.

Animals↗