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Biomedical subjects

Z C Hua

Publications and source records attributed to Z C Hua.

At least 19 recordsLinked to original sources
PubMed2005

Selecting peptide ligands of microcystin-LR from phage displayed random libraries.

In the present study, we investigated to find novel ligands for low molecular weight environmental toxin, microcystin-LR (MC-LR) by using phage display technology. Two random libraries, displaying linear 12-mer peptides and cyclic 7-mer peptides, were screened against the immobilized target respectively. After three rounds of panning, phage clones that recognized microcystin-LR specifically were obtained from both the linear and the constrained libraries, proved by enzyme-linked immumosorbent assays and immunoprecipitation assays. DNA sequencing indicated that peptides displayed on some of the selected clones shared consensus sequences. Compared with traditional methods, this approach provided a cheaper and more rapid alternative to screen specific ligands for microcystin-LR. Moreover, since it is rather difficult to take small molecules as targets of phage display libraries, the success of this experiment expanded the applications of phage display technology, and provided a new avenue to study environmental small molecular toxins.

Bacterial Toxins↗
PubMed2004

Expression modulation of multiple cytokines in vivo by cyanobacteria blooms extract from Taihu Lake, China.

Cyanobacterial blooms that generate microcystins (MCs) are being increasingly recognized as a potent health hazard in aquatic ecosystems. However, immunomodulation induced by cyanotoxins has not been well documented. This paper reports the in vivo data on the immune disorder caused by crude microcystin (MC) extract of cyanobacteria blooms collected from Taihu Lake, China, with respect to cytokine mRNA levels. Using reverse-transcriptional polymerase chain reaction (RT-PCR), the expression of multiple cytokines, including proinflammatory (IL-1beta, TNF-alpha, and IL-6) and Th1/Th2-related cytokines (IL-2, IL-4 and IL-10), was evaluated following the cyanobacteria blooms extract containing MCs (CBE) exposure at four doses of 23, 38, 77, 115 mg lyophilized algae cells/kg body weight. The results showed that the mRNA levels of TNF-alpha, IL-1beta, IL-2 and IL-4 decreased significantly following injection of all doses as compared to the control (LPS or ConA only), while the IL-6 level was unaffected. Contrast to this decrease, the level of IL-10 mRNA was, however, transiently up regulated following injection of the lowest dose of CBE. The distinct patterns of expression of these cytokines suggested a modulation of cytokine network, the essential component of the host immune system. We further developed a mathematical model to simulate the interaction of T helper cell subsets and related cytokines, which proved to be a good approach to study the kinetics of the interaction of cells and cytokines in microcystin immunosuppression.

Animals↗
PubMed2004

Targeted gene silencing by small interfering RNA-based knock-down technology.

RNA interference (RNAi) has emerged as a powerful tool for the silencing of gene expression in animals and plants. RNAi is mediated by approximately 21-nt small interfering RNAs (siRNAs), which are originally produced from larger double stranded RNAs (dsRNAs) in vivo through the action of Dicer. Recently, many groups have reported systems designed to express siRNAs in mammalian cells through transfection of either oligonucleotides or plasmids encoding siRNAs. Although the use of siRNAs to silence genes in vertebrate cells was only reported three years ago, the emerging literature indicates that most vertebrate genes can be studied with this technology. This review summarizes some approaches to generate siRNAs, the delivery and application of siRNAs to target cells and the utility of siRNAs as analytical and potential therapeutic tools.

Animals↗
PubMed2003

Effects of cyanobacteria bloom extract on some parameters of immune function in mice.

Microcystis aeruginosa is a common cyanobacterium in water blooms that appear world widely in eutrophic freshwaters, and its toxic blooms have caused many death and illness cases. This paper presents the first data on the immunotoxicity of a microcystin (MC) extract of cyanobacteria bloom collected from Taihu Lake, China to BALB/c mice. The cyanobacteria bloom extract (CBE) containing MCs was administered by i.p. injection for 14 days at three sublethal doses of 16, 32, 64 mg lyophilized algae cells/kg body weight. Exposure to CBE decreased body weights dose-dependently. Meanwhile, liver body weight ratios were markedly increased. The significant differences were also observed in spleen and thymus body ratios upon the elevation of treatment dose comparing to control. CBE was also found to reduce the phagocytosis evaluated using phagocytic index of peritoneal phagocyte; this suppression was not evident in percentage phagocytosis. Treatment of CBE produced the inhibition of lipopolysaccharide-induced lymphoproliferation and the dose-dependent decrease of the numbers of antibody-forming cells in mice that were immunized by using T-dependent antigen sheep red blood cells. However, CBE did not affect concanavalin A-induced T cell proliferation. Our results demonstrate that exposure to CBE resulted in immunosuppression in mice.

Adjuvants, Immunologic↗
PubMed2003

Analysis of microcystins in cyanobacteria blooms and surface water samples from Meiliang Bay, Taihu Lake, China.

Taihu Lake is the third largest freshwater lake in China. In recent years, the water pollution of cyanobacteria blooms has become a severe problem in this area. Microcystins (MCs) are an important group of toxic compounds mainly produced by some cyanobacteria species and have both acute and chronic hepatotoxic effects on animals and humans. This paper presents the first data on the identification and detection of MCs in both natural occurring cyanobacteria blooms and surface water samples (0-0.5 m), collected from Meiliang Bay, Taihu Lake, China. A conventional method for extraction and isolation of MCs from cyanobacteria blooms was applied. High-performance liquid chromatography (HPLC) analysis showed that the main toxic component in the cyanobacteria materials was MC-LR. The monoclonal antibody (mAb) against MC-LR produced by hybridoma technique was employed for direct competitive ELISA to detect the concentrations of MCs in bloom and water samples collected in 2001. The results not only revealed the presence of MCs but also temporal variations of MCs levels of three sampling stations in Meiliang Bay in 1 year. It is obvious that the MC contents were relatively higher during warm months and related with the status of eutrophication. Our study indicates the threat associated with MCs in water body of Taihu Lake. To prevent the MCs potential hazard on public health in this area, some necessary measures of monitoring and control of growth of cyanobacteria are urgently needed.

Bacterial Toxins↗
PubMed2001

Expression of anti-neuroexcitation peptide (ANEP) of scorpion Buthus martensii Karsch in Escherichia coli.

According to the cDNA sequence of anti-neuroexcitation peptide of scorpion Buthus martensii Karsch, the putative mature anti-neuroexcitation peptide (ANEP) encoding DNA fragment was obtained by a PCR method, then was cloned into expression plasmid pET28a, fused with His tag at its 3' end. When expressed in E. coli BL21 (DE3), the expression of recombinant ANEP was 15% of total cellular proteins, while most recombinant ANEP products existed in the form of insoluble inclusion bodies. Coexpression of molecular chaperones or protein disulfide isomerase could not improve its solubility. The recombinant ANEP in the cell lysate was purified to homogeneity by metal chelating affinity chromatography and Superdex 30 chromatography. In bioassay with convulsive mice model induced by thiosemicarbazide, recombinant ANEP could apparently delay the convulsion seizure of model animals by 18% and showed anti-neuroexcitatory activity.

Animals↗
PubMed2000

Expression of human cardiac-specific homeobox protein in Escherichia coli.

Human cardiac-specific homeobox protein cDNA (hCsx) was cloned into expression plasmid pET32a and fused with Escherichia coli thioredoxin (Trx). The Trx-Csx fusion protein was under the control of bacteriophage T7 promoter. When expressed in E. coli BL21(DE3), about half of the recombinant Trx-Csx products existed in the form of insoluble inclusion bodies. When coexpressed with human protein disulfide isomerase, more than 90% of Trx-Csx products accumulated in the soluble form in the cell lysate. The recombinant Csx fusion protein was purified by one-step metal-chelating affinity chromatography.

Chromatography, Affinity↗
PubMed2000

Expression and purification of recombinant human annexin V in Escherichia coli.

Human annexin V cDNA was cloned into plasmid pET19b and fused to a ten consecutive histidine tag at N-terminal. When expressed in E. coli BL21(DE3) LysS, the recombinant His10-annexin V accumulated in soluble form in the cytoplasm. By two-step chromatography, i.e., metal chelate affinity chromatography and anion exchange chromatography, recombinant His10-annexin V was purified to homogeneity on silver-stained SDS-PAGE gel. Recombinant annexin V, 7.4 mg, was obtained from a 1 litre flask culture.

Annexin A5↗
PubMed1999

[The manufacture and clinical use of the auto-sialographic instrument by remote controlling]

OBJECTIVE:The purpose of this article is to realize the auto-control of the injection of radiographic drugs in terms of the principle in remote controlling.METHODS:30 cases of sialaden diseases was studied using the auto sialographic instrument by remote controlling,compared to 67 cases studied using sialography by hand-controlling.RESULTS:The auto-sialographic instrument by remote controlling realize the telecontrol of the injection of the sialographic drugs and auto-injection,simplify the working procedure,and prevent medical staffs from X-ray radiation at work.CONCLUSION:The auto sialographic instrument by remote controlling can not only bring much convenience to medical staffs,but also improve the conformation to clinical diagnosis.

Journal Article↗
PubMed1998

Increased solubility of glutathione S-transferase-P16 (GST-p16) fusion protein by co-expression of chaperones groes and groel in Escherichia coli.

Human cdk (cyclin dependent kinase) inhibitor p16 was fused with glutathione S-transferase (GST) and the GST-p16 fusion protein is under the control of T7 promoter. When expressed in E. coli BL21(DE3), most products existed in the form of insoluble inclusion bodies. When co-expressed with molecular chaperones E. coli GroESL, most GST-p16 products accumulated in the soluble form with a 5-6 fold increase in solubility. When coproduced with human protein disulfide isomerase (PDI), there was no improvement in the solubility of GST-p16 fusion protein.

Chaperonin 10↗
PubMed1998

Fusion expression of human pro-urokinase with E. coli thioredoxin.

Human pro-urokinase (pro-UK) was cloned into plasmid pET32b and fused to the E. coli thioredoxin (trxA). When expressed in E. coli AD494(DE3), the fusion protein Trx-pro-UK accumulated as insoluble inclusion bodies and amounted to 35% of total cellular proteins. When co-expressed with molecular chaperones human protein disulfide isomerase (PDI) and E. coli GroESL, all the expressed products still existed in the form of insoluble inclusion bodies.

Bacterial Proteins↗
PubMed1997

Renaturation and purification of recombinant tissue-type plasminogen activator expressed in E. coli.

Under the control of trp promoter, human tissue-type plasminogen activator was expressed in E. coli in the form of inclusion body. The recombinant t-PA was recovered for renaturation from preparative native PAGE, gel by zinc acetate staining and electroelution. After renaturation in vitro, the recombinant t-PA was purified by benzamidine affinity chromatography and lysine affinity chromatography. The purified t-PA showed homogeneous on silver-stained SDS-PAGE gel, with a specific activity of 240,000 I.U./mg protein.

Chromatography, Affinity↗
PubMed1996

Characterization of a recombinant chimeric plasminogen activator composed of Gly-Pro-Arg-Pro tetrapeptide and truncated urokinase-type plasminogen activator expressed in Escherichia coli.

A chimeric plasminogen activator, GPRP-u-PA (144-411), consisting of the Gly-Pro-Arg-Pro tetrapeptide fused to the N-terminal of a truncated urokinase-type plasminogen activator (comprising Leu 144 through Leu 411), was produced by expression of the corresponding chimeric cDNA in Escherichia coli cells. After renaturation, the chimera was purified to homogeneity with specific amidolytic activity of 100,000 IU/mg protein. The chimera showed 6-fold greater affinity for fibrin clots than native low molecular weight urokinase (LUK) and 1.5-fold greater affinity than a chemical conjugate, GPRP-LUK, generating via coupling Gly-Pro-Arg-Pro tetrapeptide to native low molecular weight urokinase. The chimera had 2 to 3 fold greater fibrinolytic potency than native LUK in vitro. Fibrinogen had no influence on fibrinolysis of the chimera. The chimera consumed much less fibrinogen than native LUK.

Base Sequence↗
PubMed1996

Renaturation of recombinant human pro-urokinase expressed in Escherichia coli.

A synthetic gene encoding human pro-urokinase (pro-UK) with E. coli-favored codon usage was cloned into plasmid pET-3d and expressed in E. coli BL21(DE3) LysS strain. The expressed products, which accumulated as inactive inclusion bodies, were denatured and renatured in vitro. A broad range of parameters such as pH, protein concentration, denaturant concentration, the use of cosolvent polyethylene glycol and presence of basic or acidic amino acid was examined. At optimal renaturation condition, pro-UK activity of more than 1000I.U was obtained from 1 milliliter cell culture.

Cloning, Molecular↗
PubMed1996

Enhancement of in vitro renaturation of recombinant human pro-urokinase by ampicillin.

Ampicillin was used in in vitro renaturation process of recombinant human prourokinase and it can obviously improve the yield of the renaturation, although not as well as arginine. When ampicillin was used together with arginine or lysine, it decreased the yield of the renaturation comparing with the yield when arginine or lysine used alone.

Ampicillin↗
PubMed1996

Chemical conjugation of Gly-Pro-Arg-Pro. Tetrapeptide to low molecular weight urokinase.

Two low molecular weight urokinase derivatives were obtained by covalent coupling of a synthetic Gly-Pro-Arg-Pro tetrapeptide to peptide A of low molecular weight urokinase and exchanging the native peptide A of low molecular weight urokinase with Gly-Pro-Arg-Pro-peptide A to obtain derivative I or direct conjugation of Gly-Pro-Arg-Pro tetrapeptide to low molecular weight urokinase to obtain derivative II. In caseinolytic assay, fibrin can stimulate the two derivatives to activate plasminogen. But the two derivatives showed different kinetic behaviors. The derivative I displayed immediate onset of lysis and derivative II displayed a lag phase.

Caseins↗
PubMed1996

A low molecular weight urokinase derivative with enhanced fibrin affinity.

A Gly-Pro-Arg-Pro tetrapeptide, homologous to amino-terminal segment of the human fibrin alpha chain after the release of the fibrinopeptide A, was covalently coupled to peptide A of low molecular weight urokinase. The resulting derivative gained increased affinity for fibrin. In caseinolytic assay, fibrin can stimulate the derivative to activate plasminogen. The derivative had two-fold greater fibrinolytic potency than native low molecular weight urokinase and its affinity for fibrin clot was 3.9-fold higher than that of low molecular weight urokinase.

Chromatography, Affinity↗