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Lin Xu

Publications and source records attributed to Lin Xu.

At least 73 records · Page 4Linked to original sources
PubMed2005

Coupling between NMDA receptor and acid-sensing ion channel contributes to ischemic neuronal death.

Acid-sensing ion channels (ASICs) composed of ASIC1a subunit exhibit a high Ca(2+) permeability and play important roles in synaptic plasticity and acid-induced cell death. Here, we show that ischemia enhances ASIC currents through the phosphorylation at Ser478 and Ser479 of ASIC1a, leading to exacerbated ischemic cell death. The phosphorylation is catalyzed by Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) activity, as a result of activation of NR2B-containing N-methyl-D-aspartate subtype of glutamate receptors (NMDARs) during ischemia. Furthermore, NR2B-specific antagonist, CaMKII inhibitor, or overexpression of mutated form of ASIC1a with Ser478 or Ser479 replaced by alanine (ASIC1a-S478A, ASIC1a-S479A) in cultured hippocampal neurons prevented ischemia-induced enhancement of ASIC currents, cytoplasmic Ca(2+) elevation, as well as neuronal death. Thus, NMDAR-CaMKII cascade is functionally coupled to ASICs and contributes to acidotoxicity during ischemia. Specific blockade of NMDAR/CaMKII-ASIC coupling may reduce neuronal death after ischemia and other pathological conditions involving excessive glutamate release and acidosis.

Acid Sensing Ion Channels↗
PubMed2005

Rationally designed, polymeric, extended metal-ciprofloxacin complexes.

Reactions of the antimicrobial fluoroquinolone ciprofloxacin (cfH) with metal salts in the presence of aromatic polycarboxylate ligands or under basic conditions produce fourteen new metal-cfH complexes, namely, [Ba2(cf)2(1,4-bdc)(H2O)2] x H2O (1), [Sr6(cf)6(1,4-bdc)3(H2O)6] x 2H2O (2), [M2(cfH)2(bptc)(H2O)2] x 8H2O (M = Mn3 and Cd4), [M(cfH)(1,3-bdc)] (M = Mn5, Co6, and Zn7), [Zn2(cfH)4(1,4-bdc)](1,4-bdc) x 13H2O (8), [Ca(cfH)2(1,2-Hbdc)2] x 2H2O (9) and [M(cf)2] x 2.5H2O (M = Mn10, Co11, Zn12, Cd13, and Mg14) (1,4-bdc = 1,4-benzenedicarboxylate, bptc = 3,3',4,4'-benzophenonetetracarboxylate, 1,3-bdc = 1,3-benzenedicarboxylate, 1,2-bdc = 1,2-benzenedicarboxylate). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric analyses. The structures of 1 and 2 consist of unique two-dimensional arm-shaped layers. Compounds 3 and 4 are isostructural and feature one-dimensional structures formed from the interconnection of [M2(cfH)2(H2O)2] dimers with bptc ligands. Compounds 5-7 are isostructural and contain double-chain-like ribbons constructed from [M2(cfH)2(CO2)2] dimers and 1,3-bdc. Compound 8 consists of a pair of [Zn(cfH)2]2+ fragments bridged by a 1,4-bdc into a dinuclear dumbbell structure. Compound 9 is a neutral monomeric complex. To the best of our knowledge, compounds 1-9 are the first examples of metal-quinolone complexes that contain aromatic polycarboxylate ligands. Compounds 10-14 are isostructural and exhibit interesting two-dimensional rhombic grids featuring large cavities with dimensions of 13.6x13.6 A. Up to now, polymeric extended metal-cfH complexes have never been reported.

Ciprofloxacin↗
PubMed2005

Layer-by-layer assembly of polyoxometalates into microcapsules.

The polyoxometalate (POM) chemistry world has been experiencing an unparalleled development of rapid synthesis of new compounds and slow development of POM-based functional materials and devices. Meanwhile, researchers in the microcapsule world, encouraged by the introduction of the layer-by-layer method, are pursuing good components for constructing functional capsule devices. Here, in view of the versatile properties that POM-based microcapsules may possess, various types of POM-polyelectrolyte composite microcapsules were constructed using the layer-by-layer method. Microscopy reveals that polyoxometalates form nanoparticles on the shell in the presence of cationic polyelectrolytes. These nanoparticles connected with polyelectrolytes constitute the shell and support the microcapsule from collapse after drying, and this is an interesting characteristic different from those of common composite and polyelectrolyte capsules. Fourier transform infrared (FTIR), UV-vis absorption, and X-ray photoelectron spectroscopy (XPS) were used to examine the properties of the POMs in the microcapsules. The obtained microcapsules exhibit higher thermal stability than polyelectrolyte microcapsules. Furthermore, the functions of POMs were maintained when they were assembled into microcapsules. It is proved that microcapsules bearing POMs with redox activity can provide a reduction environment, which can lead to the realization of in situ synthesis of materials, and that microcapsules with photoluminescent POMs as a component can also have a photoluminescent property, providing a way to develop functional capsule devices. This work may provide an opportunity to enrich both the polyoxometalate chemistry and the capsule field.

Journal Article↗
PubMed2005

Association of the C-344T polymorphism of CYP11B2 gene with essential hypertension in Hani and Yi minorities of China.

BACKGROUND: Aldosterone synthase (CYP11B2) is a key enzyme in the biosynthesis of aldosterone. Recently, a C-344T polymorphism in the promoter region of the CYP11B2 gene has been reported to be in association with high blood pressure. We investigated the association between this polymorphism and essential hypertension in Hani (n=305 individuals) and Yi (n=233 individuals) minorities of China. METHODS: CYP11B2 genotyping with polymerase chain reaction-restriction fragment length polymorphism was performed in 267 normotensive subjects and 271 essential hypertensive subjects. At the same time, the T(-344)C polymorphism detection in 33 subjects was also performed by sequencing. RESULT: The frequency of CYP11B2 C-344T genotype in normotensive controls and essential hypertensive cohort in Hani population were TT: 0.729 vs. 0.610; CT + CC: 0.271 vs. 0.390, respectively. The frequency of CYP11B2 C-344T genotype in normotensive controls and essential hypertensive cohort in Yi population were TT: 0.612 vs. 0.475; CT + CC: 0.388 vs. 0.525, respectively. The frequency of CC + CT genotype in the essential hypertensive group was significantly higher than that in the normotensive controls in both Hani and Yi populations (P<0.05). CONCLUSION: The -344C allele of the CYP11B2 may play a role in genetic predisposition to developing essential hypertension in Hani and Yi minorities of China.

Adult↗
PubMed2005

Self-assembly of a series of extended architectures based on polyoxometalate clusters and silver coordination complexes.

Three unusual compounds based on polyoxometalate building blocks, [(H2O)5Na2(C6NO2H4)(C6NO2H5)3Ag2][Ag2IMo6O24(H2O)4] x 6.25H2O (1), [(H2O)4Na2(C6NO2H5)6Ag3][IMo6O24] x 6H2O (2), and (C6NO2H6)2[(C6NO2H5)2Ag][Cr(OH)6Mo6O18] x 4H2O (3), have been synthesized and characterized by elemental analysis; IR, XPS, and ESR spectroscopy; TG analysis; and single-crystal X-ray diffraction. Compound 1 is constructed from the cationic two-dimensional (2D) coordination polymer sheets which are constituted of [(H2O)5Na2(C6NO2H4)(C6NO2H5)3Ag2]3+ and anionic [Ag2IMo6O24(H2O)4]3- chains as pillars, forming a three-dimensional (3D) supramolecular framework via weak Ag-O interactions. Compound 2 is composed of the well-defined [IMo6O24]5- building blocks, which are linked through trinuclear Ag-pyridine-3-carboxylic acid, [(C6NO2H5)6Ag3]3+, fragments into a one-dimensional (1D) hybrid chain; adjacent chains are further connected by sodium cations to yield a novel 2D network. Compound 3 has a 1D chainlike structure constructed from [Cr(OH)6Mo6O18]3- building blocks and Ag-pyridine-4-carboxylic acid coordination units. The crystal data for these compounds are the following: 1, triclinic, P1, a = 13.280(3) A, b = 13.641(3) A, c = 16.356(3) A, alpha = 89.68(3) degrees, beta = 88.31(3) degrees, gamma = 75.87(3) degrees, Z = 2; 2, triclinic, P1, a = 11.978(2) A, b = 12.008(2) A, c = 13.607(3) A, alpha = 116.14(3) degrees, beta = 108.85(3) degrees, gamma = 93.86(3) degrees, Z = 1; 3, triclinic, P1, a = 10.458(2) A, b = 10.644(2) A, c = 12.295(3) A, alpha = 97.40(3) degrees, beta = 112.38(3) degrees, gamma = 113.59(3) degrees, Z = 1.

Journal Article↗
PubMed2005

Functional polymorphisms of matrix metalloproteinase-9 are associated with risk of occurrence and metastasis of lung cancer.

PURPOSE: Matrix metalloproteinase 9 (MMP-9) plays critical roles in cancer development and aggression. Nonsynonymous single-nucleotide polymorphisms (SNP) in the functional domain of the MMP-9 gene may influence substrate and inhibitor binding and contribute to cancer predisposition and aggression. PATIENTS AND METHODS: To test our hypothesis that common nonsynonymous SNPs, R279Q, P574R, and R668Q, in MMP-9 are associated with lung cancer development and metastasis, we conducted a case-control study of 744 patients with incident lung cancer and 747 cancer-free controls in Southeast China. Multivariate logistic regression analysis was used to calculate adjusted odds ratio (OR) and 95% confidence interval (95% CI). RESULTS: We found that compared with the 279QQ genotype, the 279RR genotype was associated with significant elevated risk of lung cancer with metastasis (adjusted OR, 1.79; 95% CI, 1.03-3.08), whereas the 574PR heterozygote and 574PP homozygote had 1.46-fold (95% CI, 0.94-2.26) and 1.69-fold elevated risk (95% CI, 1.10-2.60), respectively, compared with the 574RR genotype. When we examined the combined effect of R279Q and P574R and used the 279R and 574P as the risk alleles, a significantly increased risk of lung cancer was associated with both the genotypes containing "1 to 2 risk alleles" (adjusted OR, 2.16; 95% CI, 1.30-3.59) and containing ">2 risk alleles" (adjusted OR, 2.44; 95% CI, 1.48-4.03), and it was more pronounced in 290 lung cancer cases with metastasis [adjusted OR, 2.30 (95% CI, 1.09-4.85) for the 1 to 2 risk alleles subgroup and adjusted OR, 2.82 (95% CI, 1.35-5.88) for the >2 risk alleles subgroup], compared with those without any risk alleles. However, no overall significant associations were observed between R668Q and lung cancer risk in this study population. CONCLUSION: These findings indicate that the potentially functional polymorphisms, MMP-9 P574R and R279Q, may confer the biomarker in the occurrence and metastasis of primary lung cancer. Further functional studies including these two genetic variants are warranted to confirm our findings.

Adult↗
PubMed2005

Amplitude/frequency of spontaneous mEPSC correlates to the degree of long-term depression in the CA1 region of the hippocampal slice.

Prior synaptic or cellular activity influences degree or threshold for subsequent induction of synaptic plasticity, a process known as metaplasticity. Thus, the continual synaptic activity, spontaneous miniature excitatory synaptic current (mEPSC) may correlate to the induction of long-term depression (LTD). Here, we recorded whole-cell EPSC and mEPSC alternately in the Schaffer-CA1 synapses in brain slice of young rats, and found that this recording configuration affected neither EPSC nor mEPSC. Low frequency stimulation (LFS) induced variable magnitudes of LTD. Remarkably, larger magnitudes of LTD were significantly correlated to smaller amplitude/lower frequency of the basal mEPSC. Furthermore, under the conditions reduced amplitude/frequency of the basal mEPSC by exposure to behavioral stress immediately before slice preparation or low concentration of calcium in bath solution, the magnitudes of LTD were still inversely correlated to mEPSC amplitude/frequency. These new findings suggest that spontaneous mEPSC may reflect functional and/or structural aspects of the synapses, the synaptic history ongoing metaplasticity.

Animals↗
PubMed2005

Allele 2 of the interleukin-1 receptor antagonist gene (IL1RN*2) is associated with a decreased risk of primary lung cancer.

IL-1 receptor antagonist (IL-1ra), a structural variant of IL-1, binds to the same IL-1 receptor and acts as a competitive inhibitor of IL-1 bioactivity. IL-1ra protein has been widely investigated and found to be associated with different human malignancies. In the second intron of the IL-1RN gene, there is a functional polymorphism of a variable number of tandem repeats (VNTR), which is characterized as having an importance role in regulating the serum IL-1ra levels, human immune response and cancer risk. We genotyped this VNTR of IL-1RN in a case-control study of 885 histologically confirmed lung cancer patients and 1024 cancer-free controls frequency-matched to the cases on age and sex in a Chinese population to evaluate the association of this variant and lung cancer risk. We found that the presence of the allele 2 of IL-1RN (IL-RN*2) was associated with a 32% significantly decreased risk of lung cancer (adjusted OR, 0.68; 95% CI, 0.52-0.89). Stratified analyses revealed that the reduced risks associated with the genotypes with IL-RN*2allele (I/II and II/II) were more evident in non-smokers (adjusted OR, 0.53; 95% CI, 0.35-0.79) and in subjects with squamous cell carcinoma (adjusted OR, 0.49; 95% CI, 0.31-0.76). These findings support our priori hypothesis that the IL1RN*2 allele may contribute to lung cancer risk in the Chinese population. More functional data for this IL1RN polymorphism are warranted to explore its role in lung carcinogenesis.

Adenocarcinoma↗
PubMed2005

The Putative RNA-dependent RNA polymerase RDR6 acts synergistically with ASYMMETRIC LEAVES1 and 2 to repress BREVIPEDICELLUS and MicroRNA165/166 in Arabidopsis leaf development.

The Arabidopsis thaliana ASYMMETRIC LEAVES1 (AS1) and AS2 genes are important for repressing class I KNOTTED1-like homeobox (KNOX) genes and specifying leaf adaxial identity in leaf development. RNA-dependent RNA polymerases (RdRPs) are critical for posttranscriptional and transcriptional gene silencing in eukaryotes; however, very little is known about their functions in plant development. Here, we show that the Arabidopsis RDR6 gene (also called SDE1 and SGS2) that encodes a putative RdRP, together with AS1 and AS2, regulates leaf development. rdr6 single mutant plants displayed only minor phenotypes, whereas rdr6 as1 and rdr6 as2 double mutants showed dramatically enhanced as1 and as2 phenotypes, with severe defects in the leaf adaxial-abaxial polarity and vascular development. In addition, the double mutant plants produced more lobed leaves than the as1 and as2 single mutants and showed leaf-like structures associated on a proportion of leaf blades. The abnormal leaf morphology of the double mutants was accompanied by an extended ectopic expression of a class I KNOX gene BREVIPEDICELLUS (BP) and high levels of microRNA165/166 that may lead to mRNA degradation of genes in the class III HD-ZIP family. Taken together, our data suggest that the Arabidopsis RDR6-associated epigenetic pathway and the AS1-AS2 pathway synergistically repress BP and MIR165/166 for proper plant development.

Arabidopsis↗
PubMed2005

Three-dimensional mesomeric networks assembled from helix-linked sheets: syntheses, structures, and magnetisms.

Two new three-dimensional nickel coordination polymers, [Ni3(BTC)2(4,4'-bpy)2(H2O)5].1.5H2O (1) and [Ni(PDB)(4,4'-bpy)].0.5H2O (2)(4,4'-bpy = bipyridine, BTC = 1,2,4-benzenetricarboxylate, PDB = pyridine-3,4-dicarboxylate), have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR, TGA, and single crystal X-ray diffraction. Both compounds contain 2D scaffolding motifs, and most interestingly adjacent scaffolds are connected by infinite helical chains into unique three-dimensional mesomeric networks. Moreover, temperature-dependent magnetic susceptibilities for the two compounds were studied, and ferromagnetic interactions through syn-anti carboxylate bridges between Ni sites have been observed.

Crystallography, X-Ray↗
PubMed2005

(-)-Clausenamide potentiates synaptic transmission in the dentate gyrus of rats.

The effect of clausenamide on synaptic transmission in the dentate gyrus of rats in vivo and its possible mechanism of action were investigated in this study. Four of 16 enantiomers showed potentiating effects on basal synaptic transmission in anesthetized animals. By comparing one pair of enantiomers, (-)-clausenamide and (+)-clausenamide, we can report three primary findings: (1) (-)-clausenamide potentiated synaptic transmission in both anesthetized and freely moving animals while (+)-clausenamide showed no or little effect; (2) (-)-clausenamide increased the magnitude of long-term potentiation (LTP) induced by high-frequency stimulation (HFS) in anesthetized animals whereas (+)-clausenamide had no effect; (3) voltage-dependent calcium channels (VDCCs) calcineurin and calpain are involved in (-)-clausenamide-induced potentiation of synaptic transmission. Because hippocampal LTP is thought to reflect a cellular mechanism involved in learning and memory, our findings may provide the pharmacological basis for understanding the nootropic mechanisms of (-)-clausenamide, which is the first chiral nootropic agent developed in China.

Animals↗
PubMed2005

Electrochemistry of ITO electrode modified by multilayer ultrathin films based on crown-shaped polyoxomolybdate.

The electrochemical multilayer films of crown-shaped polyoxomolybdate Na21{[Na5(H2O)14] intersection[Mo(V)(20)Mo(VI)(26)O134(OH)10(mu-CH3COO)4]}.CH3COONa.90H2O (Mo46) and polyelectrolytes by layer-by-layer assembly were investigated. The stable multilayer films were assembled by alternate adsorption of negatively charged POM and positively charged polyelectrolytes is from their aqueous dispersions. UV-vis spectroscopy and cyclic voltammetry were used to monitor the regular growth of the multilayer films. The multilayer films-modified ITO electrode was used for the detection of electrocatalytic activity toward the reduction of nitrite, bromate, and hydrogen peroxide. The proposed novel immobilized method exhibited good stability, reproducibility and high sensitivity for the determination of electrocatalytic, which is important for practical application.

Letter↗
PubMed2005

Electrochromic multilayer films of tunable color by combination of copper or iron complex and monolacunary dawson-type polyoxometalate.

Electrochromic multilayer films consisting of polyoxometalate (POM) cluster alpha-K(10)[P(2)W(17)O(61)].17H(2)O (P(2)W(17)), copper(II) complex [Cu(II)(phen)(2)](NO(3))(2) (phen = 1,10-phenithroline), and iron complex [Fe(II)(phen)(3)](ClO(4))(2) were fabricated on silicon, quartz and ITO substrates by layer-by-layer self-assembly method. The multilayer films, PSS/Cu(II)(phen)(2)/[(P(2)W(17)/Cu(II)(phen)(2))](n) and PSS/Fe(II)(phen)(3)/[(P(2)W(17)/Fe(II) (phen)(3))](n) were characterized by UV-vis spectra, X-ray photoelectron spectra, cyclic voltammetry (CV), chronoamperometric (CA) and in-situ spectral electrochemical measurements. The interesting feature of the electrochromic film is its adjustable color by reduction of both transition metal complex and polyoxometalate at different potentials. The multilayer films also exhibit high optical contrast, suitable response time and low operation potential due to the presence of mono-lacunary-substituted polyoxometalate and transition metal complex. This is the first example that the color of electrochromic film can be adjustable, which gives valuable information for exploring new electrochromic materials with tunable colors.

Journal Article↗
PubMed2005

Propofol effects on excitatory synaptic efficacy in the CA1 region of the developing hippocampus.

The anesthetic, propofol, effectively suppresses excitatory synaptic transmission and facilitates long-term depression (LTD) in the CA1 region of the hippocampus. Here, we have examined whether these effects are different in the developing hippocampus. We found that propofol in suppressing whole-cell excitatory postsynaptic currents (EPSC) was more effective in 21 day old rats than either in 7 day old rats or under the condition of high intracellular chloride concentration in 21 day old rats. Furthermore, the propofol concentration to facilitate the NMDA receptor-dependent LTD was lower at postnatal day 21 than at postnatal day 7. Interestingly, the decay time of EPSC was decreased during the development from postnatal day 7 to 21, but it was increased by the recording condition of high intracellular chloride concentration or by propofol administration. All these effects of propofol were dependent on the chloride channel opening. These observations suggest that propofol may induce differential anesthetic effects in the developing hippocampus, at least partially, depending on the intracellular chloride concentration.

Age Factors↗
PubMed2005

Roles for nicotinic acetylcholine receptor subunit large cytoplasmic loop sequences in receptor expression and function.

To evaluate possible physiological roles of the large cytoplasmic loops (C2) and neighboring transmembrane domains of nicotinic acetylcholine receptor (nAChR) subunits, we generated novel fusion constructs in which human nAChR alpha4, beta2, or beta4 subunit C2 or C2 and neighboring sequences were replaced by corresponding sequences from the mouse serotonin type 3A (5-HT3A) receptor subunit. Following stable expression in human SH-EP1 cells, we found that extensive sequence substitutions involving third and fourth transmembrane domains and neighboring "proximal" C2 sequences (e.g., beta2 H322-V335 and V449-R460) did not allow functional expression of nAChR containing chimeric subunits. However, expression of functional nAChR was achieved containing wild-type alpha4 subunits and chimeric beta2 (beta2chi) subunits whose "nested" C2 domain sequences K336-S448 were replaced with the corresponding 5-HT3A subunit sequences. Whereas these findings suggested indispensable roles for M3/M4 transmembrane and/or proximal C2 sequences in alpha4beta2-nAChR function, nested C2 sequences in the beta2 subunit are not essential for functional receptor expression. Ligand-binding analyses also revealed only subtle differences in pharmacological profiles of alpha4beta2-nAChR compared with alpha4beta2chi-nAChR. Nevertheless, there was heightened emergence of agonist-mediated self-inhibition of alpha4beta2chi function, greater sensitivity to functional blockade by a number of antagonists, and faster and more complete acute desensitization of alpha4beta2chi-nAChR than for alpha4beta2-nAChR. These studies are consistent with unexpected roles of nested C2 sequences in nAChR function.

Amino Acid Sequence↗