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W Zhang

Publications and source records attributed to W Zhang.

At least 451 records · Page 25Linked to original sources
PubMed2000

Fruit-specific lectins from banana and plantain.

One of the predominant proteins in the pulp of ripe bananas (Musa acuminata L.) and plantains (Musa spp.) has been identified as a lectin. The banana and plantain agglutinins (called BanLec and PlanLec, respectively) were purified in reasonable quantities using a novel isolation procedure, which prevented adsorption of the lectins onto insoluble endogenous polysaccharides. Both BanLec and PlanLec are dimeric proteins composed of two identical subunits of 15 kDa. They readily agglutinate rabbit erythrocytes and exhibit specificity towards mannose. Molecular cloning revealed that BanLec has sequence similarity to previously described lectins of the family of jacalin-related lectins, and according to molecular modelling studies has the same overall fold and three-dimensional structure. The identification of BanLec and PlanLec demonstrates the occurrence of jacalin-related lectins in monocot species, suggesting that these lectins are more widespread among higher plants than is actually believed. The banana and plantain lectins are also the first documented examples of jacalin-related lectins, which are abundantly present in the pulp of mature fruits but are apparently absent from other tissues. However, after treatment of intact plants with methyl jasmonate, BanLec is also clearly induced in leaves. The banana lectin is a powerful murine T-cell mitogen. The relevance of the mitogenicity of the banana lectin is discussed in terms of both the physiological role of the lectin and the impact on food safety.

Amino Acid Sequence↗
PubMed2000

Isolation and characterization of a jacalin-related mannose-binding lectin from salt-stressed rice (Oryza sativa) plants.

A novel plant lectin was isolated from salt-stressed rice (Oryza sativa L.) plants and partially characterized. The lectin occurs as a natural mixture of two closely related isoforms consisting of two identical non-covalently linked subunits of 15 kDa. Both isoforms are best inhibited by mannose and exhibit potent mitogenic activity towards T-lymphocytes. Biochemical analyses and sequence comparisons further revealed that the rice lectins belong to the subgroup of mannose-binding jacalin-related lectins. In addition, it could be demonstrated that the lectins described here correspond to the protein products of previously described salt-stress-induced genes. Our results not only identify the rice lectin as a stress protein but also highlight the possible importance of protein-carbohydrate interactions in stress responses in plants.

Amino Acid Sequence↗
PubMed2000

Expression of Egr-1 in late stage emphysema.

The transcription factor early growth response (Egr)-1 is an immediate-early gene product rapidly and transiently expressed after acute tissue injury. In contrast, in this report we demonstrate that lung tissue from patients undergoing lung reduction surgery for advanced emphysema, without clinical or anatomical evidence of acute infection, displays a selective and apparently sustained increase in Egr-1 transcripts and antigen, compared with a broad survey of other genes, including the transcription factor Sp1, whose levels were not significantly altered. Enhanced Egr-1 expression was especially evident in smooth muscle cells of bronchial and vascular walls, in alveolar macrophages, and some vascular endothelium. Gel shift analysis with (32)P-labeled Egr probe showed a band with nuclear extracts from emphysematous lung which was supershifted with antibody to Egr-1. Egr-1 has the capacity to regulate genes relevant to the pathophysiology of emphysema, namely those related to extracellular matrix formation and remodeling, thrombogenesis, and those encoding cytokines/chemokines and growth factors. Thus, we propose that further analysis of Egr-1, which appears to be up-regulated in a sustained fashion in patients with late stage emphysema, may provide insights into the pathogenesis of this destructive pulmonary disease, as well as a new facet in the biology of Egr-1.

Aged↗
PubMed2000

In vivo adenovirus-mediated endothelial nitric oxide synthase gene transfer ameliorates lung allograft ischemia-reperfusion injury.

OBJECTIVE: Nitric oxide regulates vascular tone, inhibits platelet aggregation, and inhibits leukocyte adhesion, all of which are important modulators of ischemia-reperfusion injury. This study aimed to determine the effects of endothelial constitutive nitric oxide synthase gene transfer on ischemia-reperfusion injury in a rat lung transplant model. METHODS: In group I, donor animals were injected intravenously with 5 x 10(9) pfu of adenovirus-encoding endothelial constitutive nitric oxide synthase. Groups II and III served as controls, whereby donor animals were injected with either 5 x 10(9) pfu of adenovirus encoding beta-galactosidase or saline solution, respectively. Twenty-four hours after injection, left lungs were harvested and preserved for 18 hours at 4 degrees C, then implanted into isogeneic recipients, which were put to death 24 hours later. Recombinant endothelial constitutive nitric oxide synthase gene expression was evaluated by Western blotting and immunohistochemistry. Lung grafts were assessed by measuring arterial oxygenation, myeloperoxidase activity, and wet/dry weight ratios. RESULTS: Western blotting confirmed the overexpression of endothelial constitutive nitric oxide synthase in lungs so transfected compared with controls. Twenty-four hours after reperfusion, mean arterial oxygenation was significantly improved in group I compared with group II and III controls (189.4 +/- 47.1 mm Hg vs 71.7 +/- 8.9 mm Hg and 67.8 +/- 12.2 mm Hg, P =.02, P =.01, respectively). Myeloperoxidase activity, a reflection of tissue neutrophil sequestration, was also significantly reduced in group I compared with groups II and III (0.136 +/- 0.038 DeltaOD/mg/min vs 0. 587 +/- 0.077 and 0.489 +/- 0.126 DeltaOD/mg/min, P =.001, P =.01, respectively). CONCLUSION: Adenovirus-mediated gene transfer with endothelial constitutive nitric oxide synthase ameliorates ischemia-reperfusion injury as manifested by significantly improved oxygenation and decreased neutrophil sequestration in transplanted lung isografts. Endothelial constitutive nitric oxide synthase gene transfer may reduce acute lung dysfunction after lung transplantation.

Adenoviridae↗
PubMed2000

Effects of MK801 and neuroleptics on prepulse inhibition: re-examination in two strains of rats.

Disruption of prepulse inhibition (PPI) induced by NMDA receptor antagonists, such as MK801, has been used as an animal model of positive and negative symptoms of schizophrenia. Previous studies suggested that atypical, but not typical, neuroleptics can selectively restore MK801-induced PPI disruption and that such selectivity may depend on strain differences. The present study re-examined PPI disruption by systemic MK801 in Wistar (WS) and Sprague-Dawley (SD) strains, and addressed the issue whether clozapine (atypical), compared to haloperidol (typical), effectively antagonizes MK801-induced PPI disruption. In addition, we tested the effects of bilateral microinfusion of MK801 into the ventral hippocampus in WS. Systemic MK801 disrupted PPI in both strains. Neither clozapine nor haloperidol antagonized MK801-induced PPI in either strain. Our clozapine data do not agree with previous reports of clozapine's ability to antagonize MK801-induced PPI disruption. Similar to previous results with SD, MK801 infusion into the ventral hippocampus failed to affect PPI in WS. In our view, the selective ability of atypical neuroleptics to restore PPI disruption by NMDA antagonists, and to serve as a tool for identifying possible atypical neuroleptics, requires further examination. PPI disruption with systemic MK801 may be due to the blockade of NMDA receptors in multiple brain sites.

Animals↗
PubMed2000

Synergistic effects of olanzapine and other antipsychotic agents in combination with fluoxetine on norepinephrine and dopamine release in rat prefrontal cortex.

To understand the mechanism of the clinical efficacy of olanzapine and fluoxetine combination therapy for treatment-resistant depression (TRD), we studied the effects of olanzapine and other antipsychotics in combination with the selective serotonin uptake inhibitors fluoxetine or sertraline on neurotransmitter release in rat prefrontal cortex (PFC) using microdialysis. The combination of olanzapine and fluoxetine produced robust, sustained increases of extracellular levels of dopamine ([DA](ex)) and norepinephrine ([NE](ex)) up to 361 +/- 28% and 272 +/- 16% of the baseline, respectively, which were significantly greater than either drug alone. This combination produced a slightly smaller increase of serotonin ([5-HT](ex)) than fluoxetine alone. The combination of clozapine or risperidone with fluoxetine produced less robust and persistent increases of [DA](ex) and [NE](ex). The combination of haloperidol or MDL 100907 with fluoxetine did not increase the monoamines more than fluoxetine alone. Olanzapine plus sertraline combination increased only [DA](ex). Therefore, the large, sustained increase of [DA](ex), [NE](ex), and [5-HT](ex) in PFC after olanzapine-fluoxetine treatment was unique and may contribute to the profound antidepressive effect of the olanzapine and fluoxetine therapy in TRD.

Animals↗
PubMed2000

Calcineurin inhibitors cause renal afferent activation in rats: a novel mechanism of cyclosporine-induced hypertension.

Inhibition of calcineurin-mediated signaling in T lymphocytes is a major mechanism of cyclosporine A (CsA)-induced immunosuppression, and previous rat studies have suggested that inhibition of calcineurin-mediated signaling in central neuronal pools involved in blood pressure regulation plays an important role in causing acute CsA-induced hypertension. However, a central neural mechanism is difficult to reconcile with other data suggesting that CsA-induced hypertension is due to activation of renal and other subdiaphragmtic visceral afferents that reflexively increase efferent sympathetic nerve activity. Accordingly, we now have revised our hypothesis to suggest that CsA stimulates renal afferents by a calcineurin-dependent process. To test this new hypothesis, in anesthetized rats we recorded arterial pressure and multifiber afferent renal nerve activity from the cut distal end of the renal nerve before, during, and after intravenous infusion of either CsA (5 mg/kg over 20 min, n = 8), FK506 (0.15 mg/kg, n = 7), another potent calcineurin inhibitor that is structurally unrelated to CsA, or rapamycin (0.15 mg/kg, n = 4), a structural analog of FK506 that has no effect on calcineurin. We found that renal afferent discharge was increased markedly by intravenous FK506, as well as CsA, but unaffected by rapamycin (or vehicle), indicating calcineurin mediation. After infusion of either calcineurin inhibitor, afferent renal nerve activity remained elevated for up to 2 h, paralleling the prolonged increase in blood pressure. Thus, the major new conclusion of this study is that, in contrast to what has been assumed previously, calcineurin inhibitors enhance sympathetic neurotransmission by a novel action localized to visceral sensory nerve endings rather than to nerve cell bodies or central synapses. In the rat, calcineurin-dependent activation of renal afferents appears to be the primary mechanism producing the large blood-pressure-raising effect of CsA. Because the data suggest that the major side-effect of CsA and FK506--hypertension--is inexorably linked to calcineurin inhibition in extralymphoid tissue, development of agents that selectively inhibit calcineurin only in T lymphocytes could eliminate this important secondary form of hypertension.

Animals↗
PubMed2000

Xotx5b, a new member of the Otx gene family, may be involved in anterior and eye development in Xenopus laevis.

We describe the cloning, expression pattern and functional overexpression analysis of Xotx5b, a new member of the Otx gene family in Xenopus laevis. Early expression of Xotx5b resembles that of Xotx2, being detected in the organizer region at early gastrula stage, and, shortly after, also in anterior neuroectoderm. During neurula stages Xotx5b exhibits a changing and dynamic pattern of expression. After neural tube closure, Xotx5b is expressed in the eye and pineal gland, both involved in photoreception. Overexpression of Xotx5b has a similar effect to that of Xotx2, producing posterior truncations and inducing ectopic cement gland and neural tissue in whole embryos. In animal cap assays, Xotx5b and Xotx2 are both able to activate XAG, to strongly suppress the expression of the epidermal marker XK81, and to reciprocally activate each other. Finally, in einsteck transplantation assays, Xotx5b is able to respecify a tail/trunk organizer to a head organizer.

Amino Acid Sequence↗
PubMed2000

Recent developments in cryo-electron microscopy reconstruction of single particles.

Cryo-electron microscopy and single-particle 3D image reconstruction techniques have been used to examine a broad spectrum of samples ranging from 500 kDa protein complexes to large subcellular organelles. The attainable resolution has improved rapidly over the past few years. Structures of both symmetric and asymmetric assemblies at approximately 7.5 A have been reported. Together with X-ray crystallography, three-dimensional cryo-electron microscopy reconstruction has provided important insights into the function of many biological systems in their native biochemical contexts.

Automation↗
PubMed2000

para-Substituted N-nitroso-N-oxybenzenamine ammonium salts: a new class of redox-sensitive nitric oxide releasing compounds.

N-Nitroso-N-oxybenzenamine ammonium salts with -OMe, -Me, -H, -F, -Cl, -CF3, and -SO2Me substituents at the para position of the phenyl ring constitute a new class of-redox sensitive nitric oxide (NO) releasing compounds. These compounds yield nitric oxide and the corresponding nitrosobenzene derivatives by a spontaneous dissociation mechanism after undergoing a one electron oxidation. Oxidation of these compounds can be achieved through chemical, electrochemical and enzymatic methods. It was observed electrochemically that the amount of NO generated was dependent on the substituent effect and the applied oxidation potential. Electron-withdrawing substituents increase the oxidation potential of the compound. A linear correlation was observed when the peak potentials for the oxidation were graphed versus the Hammett substituent constant. Density functional theory calculations were also performed on this series of compounds. The theoretical oxidation energies of the corresponding anions show a strong linear correlation with the experimental potentials. Furthermore, enzymatic oxidation using horseradish peroxidase showed a similar substituent effect. These results indicate that substitution at the para position of the phenyl ring has a profound effect on the stability, oxidation potential and enzymatic kinetic properties of the compounds. Thus para-substituted N-nitroso-N-oxybenzenamine salts comprise a new class of redox-sensitive nitric oxide releasing agents.

Electrochemistry↗
PubMed2000

Rapidly switchable matrix-assisted laser desorption/ionization and electrospray quadrupole-time-of-flight mass spectrometry for protein identification.

We describe a new interface for a prototype quadrupole-quadrupole-time-of-flight (TOF) mass spectrometer (Centaur, Sciex) that allows rapid switching between electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) modes of operation. Instrument performance in both modes is comparable (i.e., resolution approximately 10,000 FWHM, mass accuracy <10 ppm, sensitivity approximately 1 fmol) because the ion source is decoupled from the TOF mass analyzer by extensive gas collisions in the quadrupole stages of the instrument. The capacity to obtain side-by-side high quality ESI and MALDI mass spectra from a single proteolytic mixture greatly facilitates the identification of proteins and elucidation of their primary structures. Improved strategies for protein identification result from this ability to measure spectra using both ionization modes in the same instrument and to perform MS/MS on singly charged as well as multiply charged ions. Examples are provided to demonstrate the utility and performance of the modified instrument.

Amino Acid Sequence↗
PubMed2000

LAT is essential for Fc(epsilon)RI-mediated mast cell activation.

The linker molecule LAT is a substrate of the tyrosine kinases activated following TCR engagement of T cells. LAT is also expressed in platelets, NK, and mast cells. Although LAT-deficient mice contain normal numbers of mast cells, we found that LAT-deficient mice were resistant to IgE-mediated passive systemic anaphylaxis. LAT-deficient bone marrow-derived mast cells (BMMC) showed normal growth and development. Whereas tyrosine phosphorylation of Fc(epsilon)RI, Syk, and Vav was intact in LAT-deficient BMMCs following Fc(epsilon)RI engagement, tyrosine phosphorylation of SLP-76, PLC-gamma1, and PLC-gamma2 and calcium mobilization were dramatically reduced. LAT-deficient BMMCs also exhibited profound defects in activation of MAPK, degranulation, and cytokine production after Fc(epsilon)RI cross-linking. These results show that LAT plays a critical role in Fc(epsilon)RI-mediated signaling in mast cells.

Adaptor Proteins, Signal Transducing↗
PubMed2000

The effects of high-dose epinephrine combined with isoprenaline on isolated rabbit heart and cardiomyocytes after cardioversion of ventricular fibrillation.

The effects of high-dose epinephrine (HDE) combined with isoprenaline (Iso) on myocardial hemodynamics of isolated rabbit heart were studied. The electrophysiology and L-type Ca2+ channel of single ventricular myocyte after cardioversion of ventricular fibrillation were determined. The results suggest that parameters of hemodynamics were significantly enhanced by HDE+Iso than that of HDE (p < 0.01). The OS and Vmax of HDE+Iso increased 83.7 and 10.15% respectively compared to HDE alone. The APF of HDE+Iso is much more rapid than that of HDE (138.38 +/- 9.96 vs. 55.58 +/- 8.63 min(-1), p < 0.001). The APD50 and APD90 of HDE+Iso were significantly decreased; HR was increased (134.16 +/- 1.48 vs 62.20 +/- 6.25 min(-1)); and the amplitude current of through L-type Ca2+ channel was reduced but was significantly higher than the control. We conclude that HDE+Iso can improve the hemodynamics and improve electrophysiology of cardiomyocytes after cardioversion of ventricular fibrillation which is likely interrelated with I(Ca). The combined use of epinephrine and isoprenaline for cardiopulmonary resuscitation of primary ventricular fibrillation may be beneficial when employed in clinical situations.

Action Potentials↗
PubMed2000

Structural basis of the recognition of the dishevelled DEP domain in the Wnt signaling pathway.

The DEP domain of Dishevelled (Dvl) proteins transduces signals to effector proteins downstream of Dvl in the Wnt pathway. Here we report that DEP-containing mutants inhibit Wnt-induced, but not Dvl-induced, activation of the transcription factor Lef-1. This inhibitory effect is weakened by a K434M mutation. Nuclear magnetic resonance spectroscopy revealed that the DEP domain of mouse Dvl1 comprises a three-helix bundle, a beta-hairpin 'arm' and two short beta-strands at the C-terminal region. Lys 434 is located at the tip of the beta-hairpin 'arm'. Based on our findings, we conclude that DEP interacts with regulators upstream of Dvl via a strong electric dipole on the molecule's surface created by Lys 434, Asp 445 and Asp 448; the electric dipole and the putative membrane binding site are at two different locations.

3T3 Cells↗
PubMed2000

Enhanced antitumoral effect of adenovirus-mediated cytosine deaminase gene therapy by induction of antigen-presenting cells through stem cell factor/granulocyte-macrophage colony-stimulating factor gene transfer.

Suicide gene therapy has been studied intensively for the treatment of cancer. A limited antitumoral effect was obtained by intratumoral injection of adenovirus harboring Escherichia coli cytosine deaminase gene (AdCD) in tumor-bearing mice followed by continuous administration of 5-fluorocytosine (5FC). To address the drawbacks of the limited potential for the induction of antitumoral immunity by CD suicide gene therapy, we hypothesized that antigen-presenting cells (APCs) might contribute to the efficient induction of an antitumoral immune response in tumor-bearing mice undergoing suicide gene therapy. We preinjected the mice with murine stem cell factor (SCF)-encoding adenovirus (AdSCF) and murine granulocyte-macrophage colony-stimulating factor (GM-CSF)-encoding adenovirus (AdGM-CSF); after 7 days, the mice were inoculated with CT26 colon adenocarcinoma. AdCD was injected intratumorally into tumor-bearing mice followed by 5FC administration. The results showed that AdSCF/AdGM-CSF treatment could increase the number, surface molecule expression, and function of APCs efficiently. A more significant growth inhibition of established tumors and a prolongation of the survival period were observed in tumor-bearing mice after AdSCF/AdGM-CSF pretreatment in combination with AdCD/5FC therapy when compared with mice treated with AdSCF or AdGM-CSF in combination with AdCD/5FC, or AdCD/5FC alone (P < .01). Cytotoxic T-lymphocyte activity was induced efficiently after the combined therapy, and mRNA of tumor necrosis factor-alpha, interleukin-4, interferon-gamma, and interleukin-2 was present in the tumor mass after combined therapy, suggesting that a more potent antitumoral response was induced by enhanced APCs. Our results demonstrated that AdSCF/AdGM-CSF pretreatment could activate APCs, and that these APCs could present the tumor antigens released from AdCD/5FC-killed tumor cells and activate the antitumoral response of the host, thus increasing the therapeutic efficiency of suicide gene therapy.

Adenoviridae↗
PubMed2000

Identification and genetic mapping of four novel genes that regulate leaf development in Arabidopsis.

Molecular and genetic characterizations of mutants have led to a better understanding of many developmental processes in the model system Arabidopsis thaliana. However, the leaf development that is specific to plants has been little studied. With the aim of contributing to the genetic dissection of leaf development, we have performed a large-scare screening for mutants with abnormal leaves. Among a great number of leaf mutants we have generated by T-DNA and transposon tagging and ethyl-methae sulfonate (EMS) mutagenesis, four independent mutant lines have been identified and studied genetically. Phenotypes of these mutant lines represent the defects of four novel nuclear genes designated LL1 (LOTUS LEAF 1), LL2 (LOTUS LEAF 2), URO (UPRIGHT ROSETTE). and EIL (ENVIRONMENT CONDITION INDUCED LESION). The phenotypic analysis indicates that these genes play important roles during leaf development. For the further genetic analysis of these genes and the map-based cloning of LL1 and LL2, we have mapped these genes to chromosome regions with an efficient and rapid mapping method.

Arabidopsis↗
PubMed2000

Adenovirus-mediated lymphotactin gene transfer improves therapeutic efficacy of cytosine deaminase suicide gene therapy in established murine colon carcinoma.

Lymphotactin (Ltn) is the sole member of C chemokines which attracts T cells and NK cells specially. Ltn gene was transferred in vivo to improve the antitumor efficacy of cytosine deaminase (CD) gene therapy. Upregulation of CD80 and CD54 on murine CT26 colon carcinoma cells was observed after combined transfection with adenovirus encoding CD (AdCD) and adenovirus encoding murine Ltn (AdLtn) followed by administration of 5-fluorocytosine (5FC) in vitro. AdCD/5FC treatment also increased the expression of CD95 and induced obvious apoptosis of CT26 cells. After combined treatment with AdLtn and AdCD/5FC, the pre-established murine model with subcutaneous CT26 colon carcinoma exhibited most significant tumor growth inhibition, and four of eight tumor-bearing mice were tumor free, while tumors in other mice grew more progressively. Examination of lymphocyte infiltration and cytokine gene expression in tumor tissue revealed that tumors from AdLtn/AdCD/5FC-or AdLtn-treated mice were heavily infiltrated with CD4+, CD8+ T cells and NK cells, and IL-2 and IFN-gamma mRNA expression were present in parallel with T cell and NK cell infiltration. Splenic NK and CTL activities increased significantly after the combination therapy. In vivo depletion analysis showed that NK cells, CD4+ T cells and CD8+T cells participated in the antitumor effect of the host with CD8+T cells being the main T cell subset responsible for the enhanced antitumor immune response. These findings suggested that increased immunogenicity and induction of apoptosis of the tumor cells, and efficient induction of local and systemic antitumor immunity of the host might contribute to the enhanced antitumor effects of the combined Ltn and CD suicide therapy. Gene Therapy (2000) 7, 329-338.

Adenoviridae↗