Biomedical subjects

Zhigang Xie

Publications and source records attributed to Zhigang Xie.

At least 19 recordsLinked to original sources

PubMed2007

Synergistic antileukemia effect of genistein and chemotherapy in mouse xenograft model and potential mechanism through MAPK signaling.

We investigated the antiproliferative effect of genistein, and its antileukemia effect in combination with cytosine arabinoside (ara-C) in acute myeloid leukemia (AML). Optimal dosage of genistein as single agent and in combination with ara-C was first determined in vitro. Genistein demonstrated a dose- and time-dependent inhibition of cell proliferation, induction of apoptosis, and cell-cycle arrest at G(2)/M phase. Gene-expression profiles revealed mitogen-activated protein kinase (MAPK) signaling as one of the most affected biological pathways. Phosphatidylinositol 3 kinase, protein kinase A, protein kinase C, MAPK kinase 4, KIT, PIM1, and transforming growth factor-beta receptor 1, were significantly downregulated by genistein. To test whether genistein could augment the antiproliferation activity of ara-C, two groups of severe combined immunodeficient mice were inoculated with NB4 and HL-60 cells, respectively, followed by treatment with either genistein or combination of genistein and ara-C. The combination treatment significantly inhibited tumor growth, and improved survival of NB4 (p = 0.0031) and HL-60 (p = 0.0007) xenograft mice. Our present study highlighted the schedule-dependent synergistic antileukemia effect of genistein with chemotherapy in both in vitro and in vivo models. This novel combination could potentially be a promising regimen for treatment of AML.

Animals↗

PubMed2006

A novel polymer-paclitaxel conjugate based on amphiphilic triblock copolymer.

A novel amphiphilic polymer-paclitaxel conjugate P(LGG-paclitaxel)-PEG-P(LGG-paclitaxel) has been prepared. It was derived from its parent polymer P(LGG)-PEG-P(LGG), poly{(lactic acid)-co-[(glycolic acid)-alt-(l-glutamic acid)]}-block-poly(ethylene glycol)-block-poly{(lactic acid)-co-[(glycolic acid)-alt-(l-glutamic acid)]}, which was prepared by ring-opening copolymerization of l-lactide (LLA) with (3s)-benzoxylcarbonylethyl-morpholine-2,5-dione (BEMD) in the presence of dihydroxyl PEG with molecular weight of 4600 as a macroinitiator using stannous octoate (Sn(Oct)(2)) as catalyst, and by subsequent catalytic hydrogenation. It could self-assemble into micelles in an aqueous system with P(LGG-paclitaxel) block in the core and PEG in the shell. ESEM and DLS analysis of the micelles revealed a homogeneous spherical morphology and a unimodal size distribution. In vitro release of paclitaxel from the conjugate micelles showed that its release rate depended on pH value and was higher at lower pH than in neutral condition. In vitro antitumor activity of the paclitaxel conjugate against rat brain glioma C6 cells was evaluated by MTT method. The results showed that the paclitaxel can be released from the conjugate without losing cytotoxicity.

Animals↗

PubMed2006

Dietary ascorbic acid may be necessary for enhancing the immune response in Siberian sturgeon (Acipenser baerii), a species capable of ascorbic acid biosynthesis.

Siberian sturgeon (Acipenser baerii Brandt) is one of few fish species capable of synthesizing ascorbic acid (AA); however, it is unknown whether dietary AA is still necessary for this species to generate an optimal non-specific immune response, as is found in most teleostean species that do not synthesize AA. Sturgeon fed either 0 or 500 mg AA (AA polyphosphate) equivalent kg(-1) diets for 2 weeks were then either sham or experimentally injected with Aeromonas hydrophila lipopolysaccharide (LPS) to mimic infection and therefore instigate a non-specific immune response. No significant differences were found in growth and survival throughout the duration of the experiment between sham and LPS groups and between both diets. Two and eight days after injection, serum lysozyme levels were elevated in both LPS and non-LPS groups. Respiratory burst was not affected by dietary AA and significantly higher in LPS groups over non-LPS groups; however, dietary AA may have enhanced the effects seen in the LPS injected fish fed the AA supplemented diet. There were no significant differences in renal l-gulono-1, 4-lactone oxidase (GLO) activity between dietary and LPS treatments, but fish exposed to LPS without dietary AA demonstrated an inter-organ transfer of AA from posterior kidney to liver. Our results indicate that dietary AA may be conditionally necessary for Siberian sturgeon to achieve optimal immune response, particularly in early developmental stages, information imperative to developing successful aquaculture programs for sturgeon species.

Animals↗

PubMed2006

Biodegradable amphiphilic triblock copolymer bearing pendant glucose residues: preparation and specific interaction with Concanavalin A molecules.

A novel biodegradable amphiphilic block copolymer PLGG-PEG-PLGG bearing pendant glucose residues is successfully prepared by the coupling reaction of 3-(2-aminoethylthio)propyl-alpha-D-glucopyranoside with the pendant carboxyl groups of PLGG-PEG-PLGG in the presence of N,N'-carbonyldiimidazole. The polymer PLGG-PEG-PLGG, i.e., poly{(lactic acid)-co-[(glycolic acid)-alt-(L-glutamic acid)]}-block-poly(ethylene glycol)-block- poly{(lactic acid)-co-[(glycolic acid)-alt-(L-glutamic acid)]}, is prepared by ring-opening copolymerization of L-lactide (LLA) with (3s)-benzoxylcarbonylethylmorpholine-2,5-dione (BEMD) in the presence of dihydroxyl PEG with molecular weight of 2000 as macroinitiator and Sn(Oct)2 as catalyst, and then by catalytic hydrogenation. The glucose-grafted copolymer shows a lower degree of cytotoxicity to ECV-304 cells and improved specific recognition and binding with Concanavalin A (Con A). Therefore, this kind of glucose-grafted copolymer may find biomedical applications.

Biodegradation, Environmental↗

PubMed2006

Cyclin-dependent kinase 5 permits efficient cytoskeletal remodeling--a hypothesis on neuronal migration.

Migration of neurons to their proper position underlies mammalian brain development. To remain on the proper path, a migrating neuron needs to detect various external signals and respond by efficiently remodeling its cytoskeleton. Cyclin-dependent kinase 5 (Cdk5), a member of the cyclin-dependent kinase family, regulates neuronal migration by phosphorylating a number of intracellular substrates. Deficiencies in Cdk5 preferentially cause impairments in radial glia-guided migration, a process that involves complex remodeling of the cytoskeleton, particularly the microtubules. Furthermore, the defined substrates of Cdk5 that are important for migration generally link Cdk5 to the cytoskeleton. Interestingly, none of these phosphorylation events seem to directly control the activity of the substrates. Taken together, these findings support a model in which Cdk5 does not directly control the detection of any specific external signals but instead regulates efficient remodeling of the cytoskeleton through phosphorylation of multiple substrates.

Aging↗

PubMed2005

Synthesis and characterization of novel biotinylated biodegradable poly(ethylene glycol)-b-poly(carbonate-lactic acid) copolymers.

Poly(ethylene glycol)-b-poly(5-benzyloxy-trimethylene carbonate-lactic acid) copolymers (PEG-b-P(BTMC-LA)) were synthesized by ring-opening polymerization of lactide and 5-benzyloxy trimethylene carbonate in the presence of mono-hydroxyl poly(ethylene glycol) with diethyl zinc as catalyst. They were further converted into deprotected copolymers with the pendant hydroxyl groups by hydrogenolysis in the presence of Pd(OH)2/C, and finally conjugated with biotin through the free hydroxyl groups. Gel permeation chromatography, Fourier transform infrared, differential scanning calorimetry and 1H nuclear magnetic resonance studies confirmed the copolymer structures and successful attachment of biotin to the copolymer.

Absorbable Implants↗

PubMed2005

Phosphatidylinositol transfer protein function in the yeast Saccharomyces cerevisiae.

PITPs regulate the interface between lipid metabolism and cellular functions, but the fundamental nature of this regulation is not understood. Yeast and mouse studies demonstrate strict coupling of individual PITPs to specific cellular activities, but the invisibility of these specificities in in vitro models for PITP activity is remarkable. In our opinion, delineation of PITP functions requires the continued application of genetic approaches such as those summarized here. Future studies dedicated to enhancing our understanding of the mechanisms of action of Sec14p-like and metazoan PITPs are worthy goals for three reasons. First, it is becoming abundantly clear that PITPs act at important biological interfaces that involve lipid and protein trafficking, phospholipid biosynthesis and polarized membrane growth. Because these interfaces are critical not only to cellular functions, but also to developmental processes, the function of PITPs in development of multicellular organisms is a particularly attractive area of research that remains essentially untapped. Second, the yeast studies indicate functional linkages between Sec14p-like PITPs and members of ubiquitous but entirely uncharacterized eukaryotic proteins such as OSBP family members. Finally, the link of PITPs to disease is already clear since PITP deficiencies lie at the foundation of novel mechanisms of neurodegenerative, glucose homeostatic and gastrointestinal disorders in mammals. Given that the contribution of Sec14p-like proteins to the PITP complement of mammalian cells is completely uninvestigated, and that the mammalian genome encodes many proteins of this class, we anticipate such advances will directly and positively impact our understanding of the molecular basis of such diseases.

Amino Acid Sequence↗

PubMed2005

Multiple organ infection and the pathogenesis of SARS.

After >8,000 infections and >700 deaths worldwide, the pathogenesis of the new infectious disease, severe acute respiratory syndrome (SARS), remains poorly understood. We investigated 18 autopsies of patients who had suspected SARS; 8 cases were confirmed as SARS. We evaluated white blood cells from 22 confirmed SARS patients at various stages of the disease. T lymphocyte counts in 65 confirmed and 35 misdiagnosed SARS cases also were analyzed retrospectively. SARS viral particles and genomic sequence were detected in a large number of circulating lymphocytes, monocytes, and lymphoid tissues, as well as in the epithelial cells of the respiratory tract, the mucosa of the intestine, the epithelium of the renal distal tubules, the neurons of the brain, and macrophages in different organs. SARS virus seemed to be capable of infecting multiple cell types in several organs; immune cells and pulmonary epithelium were identified as the main sites of injury. A comprehensive theory of pathogenesis is proposed for SARS with immune and lung damage as key features.

Adult↗

PubMed2005

A novel PCR strategy for high-efficiency, automated site-directed mutagenesis.

We have developed a novel three-primer, one-step PCR-based method for site-directed mutagenesis. This method takes advantage of the fact that template plasmid DNA cannot be efficiently denatured at its reannealing temperature (T(ra)), which is otherwise a troublesome problem in regular PCR. Two flanking primers and one mutagenic primer with different melting temperatures (T(m)) are used together in a single PCR tube continuously without any intervention. A single-stranded mutagenic DNA (smDNA) is synthesized utilizing the high T(m) mutagenic primer at a high annealing temperature, which prevents the priming of the low T(m) primers (i.e. the two flanking primers). A megaprimer is then produced using this smDNA as the template at a denaturing temperature that prevents wild-type template DNA activity. The desired mutant DNA is then obtained by cycling again through these first two steps, resulting in a mutagenic efficiency of 100% in all tested cases. This highly automated method not only eliminates the necessity of any intermediate manipulation and accomplishes the mutagenesis process in a single round of PCR but, most notably, enables complete success of mutagenesis. This novel method is also both cost and time efficient and fully automated.

DNA Primers↗

PubMed2005

Controlled growth of Chinese hamster ovary cells and high expression of antibody-IL-2 fusion proteins by temperature manipulation.

Growth and the expression of the anti-ErbB2 scFv-Fc-IL2 fusion protein in Chinese hamster ovary (CHO) cells were in association at 37 degrees C. The expression of the fusion protein was no more than 25 microg/ml. At 30 degrees C the cell growth was arrested but the cells continued to produce the fusion protein up to 60-80 microg/ml. About 50% of CHO cells were rapidly blocked in G2/M phase after the temperature was shifted from 37 to 30 degrees C. Lowering temperature resulted in cell growth arrest, but maintained cell viability for a longer time and enhanced the production of the antibody-IL-2 fusion protein in CHO cells.

Animals↗

PubMed2005

Severe acute respiratory syndrome associated coronavirus is detected in intestinal tissues of fatal cases.

OBJECTIVES: A significant percentage of confirmed severe acute respiratory syndrome (SARS) patients experienced gastrointestinal symptoms, and the viral sequence was detectable in the stool of most patients. At present, the knowledge of the pathology of the digestive system in SARS patients is limited. Because a resurgence of the SARS epidemic is constantly possible, there is an urgent need to understand the involvement of the digestive system in this new disease. METHODS: We performed seven SARS autopsies in which samples of alimentary tract and digestive glands were examined with routine pathology, electron microscopy (EM), in situ hybridization (ISH), immunohistochemistry, and real-time polymerase chain reaction (PCR). RESULTS: The main histopathological finding was atrophy of the mucosal lymphoid tissue. A few mucosal epithelial cells and lymphocytes in the intestine were positively stained for coronavirus with ISH. SARS-coronavirus (CoV)-like particles were found in the mucosal epithelial cells under EM and mild focal inflammation was detected in the alimentary tract. One patient who experienced severe diarrhea had pseudomembranous enteritis of the ileum. Fatty degeneration and central lobular necrosis were observed in the liver. No evidence of direct viral infection was found in the esophagus, the stomach, the salivary gland, the liver, or the pancreas. CONCLUSIONS: In addition to the lungs, the gastrointestinal tract is another target of SARS-CoV infection, as the intestinal epithelial cells and mucosal lymphoid tissue are infected. The findings provide possible explanations for the gastrointestinal symptoms and the presence of virus in the stool of SARS patients.

Adult↗

PubMed2004

A new format of bispecific antibody: highly efficient heterodimerization, expression and tumor cell lysis.

Bispecific antibodies (BsAbs) have been considered as potential therapeutics for cancer. A major obstacle in the development of BsAb has been the difficulty in producing a heterodimer with two different arms and in sufficient quantity for clinical application by the traditional methods. We describe a new format of BsAb that consists of two single-chain variable fragment of antibodies (scFvs), one for human epidermal growth factor receptor 2 (HER2)/neu and the other for CD16, heterodimerized by a "knobs-into-holes" device from the CH3 domains of the human IgG1 Fc fragment. The two chains were functionally expressed in CHO cells and assembled into heterodimers with dual antigen-binding specificity. Compared with other types of engineered BsAbs expressed in mammalian cells, the yield of this BsAb was relatively high (12-14 mg/l). In vitro experiments demonstrated that the BsAb was able to recruit human peripheral blood mononuclear cells (PBMC) to kill SK-BR-3 cells more effectively than the commercial anti-HER2/neu antibody Herceptin (Roche, Shanghai). This new format of BsAb possesses properties that support its potential as a new antitumor agent.

Animals↗

PubMed2004

Ndel1 operates in a common pathway with LIS1 and cytoplasmic dynein to regulate cortical neuronal positioning.

Correct neuronal migration and positioning during cortical development are essential for proper brain function. Mutations of the LIS1 gene result in human lissencephaly (smooth brain), which features misplaced cortical neurons and disarrayed cerebral lamination. However, the mechanism by which LIS1 regulates neuronal migration remains unknown. Using RNA interference (RNAi), we found that the binding partner of LIS1, NudE-like protein (Ndel1, formerly known as NUDEL), positively regulates dynein activity by facilitating the interaction between LIS1 and dynein. Loss of function of Ndel1, LIS1, or dynein in developing neocortex impairs neuronal positioning and causes the uncoupling of the centrosome and nucleus. Overexpression of LIS1 partially rescues the positioning defect caused by Ndel1 RNAi but not dynein RNAi, whereas overexpression of Ndel1 does not rescue the phenotype induced by LIS1 RNAi. These results provide strong evidence that Ndel1 interacts with LIS1 to sustain the function of dynein, which in turn impacts microtubule organization, nuclear translocation, and neuronal positioning.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2004

Highly efficient selection of the stable clones expressing antibody-IL-2 fusion protein by a dicistronic expression vector containing a mutant neo gene.

To increase the selection efficiency and productivity of stable clones expressing recombinant antibody-IL-2 fusion protein, a dicistronic expression vector containing the anti-erbB2 scFv-Fc-IL-2 fusion gene followed by a weakened neo gene, was constructed to allow for the concurrent translation of the recombinant protein and mutated neomycin phosphotransferase from a single mRNA. The presence of the mutant enzyme in the transfectomas resulted in a decreased resistance of cells in the presence of an elevated level of G418 and retarded cell growth. The transfectomas containing the mutant enzyme expressed considerably higher levels of the fusion protein than those containing the normal enzyme. Furthermore, these positive clones had an almost identical level of recombinant gene expression, which was very stable even when the concentration of G418 was significantly increased. Thus, the selection efficiency of strongly positive producers was remarkably increased. Our results demonstrate that the dicistronic expression vector is useful for the selection of highly expressing clones. Combined with an amplification system, this vector may have potential usage for the expression of recombinant antibody and the yield may be further improved by this expression system.

Animals↗

PubMed2004

The difference of binding epitopes on human CD16 (FcgammaRIII) interacted with hIgG1 and monoclonal antibody B88-9.

The 3-D complex structures of extracellular domain of human CD16 (FcgammaRIII) and hIgG1 or B88-9 were obtained by means of computer-guided molecular modeling, respectively. The binding epitopes were predicted and binding energy was calculated theoretically. The epitopes of human CD16 interacted with hIgG1 and B88-9 were different and the binding energy of B88-9 was stronger than hIgG1. The computer competing simulation results showed that B88-9 could bind to CD16 when CD16 was also bound by hIgG1, while IgG1 could not bind to CD16 after CD16 was bound by B88-9. By flow cytometry analysis, the competitive binding activity of B88-9 to CD16 with hIgG1 was evaluated. With the increasing concentrations of hIgG1, the binding activity of B88-9 was not interfered markedly. It suggested that hIgG1 could not inhibit the interaction of CD16 and B88-9 and the binding domain of hIgG1 and B88-9 on CD16 was different.

Antibodies, Monoclonal↗

PubMed2004

Cdk5 phosphorylation of FAK regulates centrosome-associated miocrotubules and neuronal migration.

Cdk5 is a member of the cyclin-dependent kinase (Cdk) family. Unlike other Cdks that promote cell cycle, Cdk5 is activated in postmitotic neurons and critically regulates neuronal migration by phosphorylating its substrates during brain development. Recently, we found that Cdk5 phosphorylates focal adhesion kinase (FAK) at Serine 732 in vitro and is responsible for this phosphorylation in the developing brain. Our experiments using a phospho-specific antibody and an S732-unphosphorylatable mutant FAK suggest that S732 phosphorylation may regulate a centrosome-associated microtubule structure to promote nuclear translocation, a critical step in neuronal migration. S732 phosphorylation does not directly impact on the kinase activity of FAK, but appears to prevent the accumulation of FAK at the centrosome. Our study reveals a similarity between Cdk5 and Cdk1 in the regulation of neuronal migration and cell division, respectively. In addition, our study implicates FAK in a signaling pathway that directly regulates microtubules.

Animals↗

PubMed2003

[Integrin alpha6 beta4 and experimental allergic neuritis].

OBJECTIVE: To explore the relationship between integrins alpha6,beta4 and the process of the injury and repair of the myelin, their expressions in experimental allergic neuritis were analyzed. METHODS: Experimental allergic neuritis (EAN) models were induced in Lewis rats. The expressions of integrins alpha6 and beta 4 and their receptor laminin, both in the acute phase and recovery phase of EANs, were analyzed by in situ hybridization and immunohistochemistry. RESULTS: The expression of beta4 decreased in the acute phase P<0.05 and showed no significant changes in the recovery phase(P=0.6840). There were no significant changes of the expression of alpha6 and laminin both in the acute phase and recovery phase of EANs by immunohistochemistry (alpha6 P=0.0751;laminin P=0.2047). The similar results were obtained by in situ hybridization (beta4 in acute phase P<0.05;beta4 in recovery phase P=0.823;alpha6 P= 0.81). CONCLUSION: The expressions of integrins of Schwann cells were affected by inflammation injury, and their patterns of expression were similar to those of integrins alpha6, beta1 and beta4 during embryogenesis. It is inferred that integrin beta4 and the reformation of myelin have a more imitate relationship. The expression changes of alpha6 and beta4 correlate with the injury and repair of myelin during EAN.

Animals↗

PubMed2003

A trivalent anti-erbB2/anti-CD16 bispecific antibody retargeting NK cells against human breast cancer cells.

Bispecific antibody (BsAb) can physically cross-link immune cells to tumor cells, circumventing the proper structures for tumor cell-immune cell interactions and activating the cellular cytotoxic mechanisms. The optimal BsAb should target tumor cells with high affinity, but activate trigger molecules on cytotoxic cells by monovalent binding of Fab fragments. In the present study, a trivalent anti-erbB2/anti-CD16 BsAb was produced. This BsAb possesses bivalent arms specifically binding to the extracellular domain of erbB2 and monovalent Fab fragment redirecting NK cells. The recombinant protein could be expressed and purified from Escherichia coli as native proteins without refolding. It was fully functional in bispecific binding to SKBR3 and NK cells. The molecular size of this trivalent BsAb protein is larger than diabody and smaller than whole antibody and expected to have advantages for both high penetration of small antibody fragments and the slow circulation clearance of whole antibody. This novel protein may be an attractive target for further improvement and evaluation.

Antibodies, Bispecific↗