Biomedical subjects

Rong Gao

Publications and source records attributed to Rong Gao.

At least 37 records · Page 2Linked to original sources

PubMed2005

[Cytokines secretion by peripheral blood mononuclear cells from hepatitis C patients after stimulation with synthetic peptides at the highly variable region].

OBJECTIVE: Test the cytokines secretion by peripheral blood mononuclear cells (PBMC) from hepatitis C patients after stimulation with highly variable region (HVR1) synthetic peptides. METHODS: ELISA was used to test the cytokines secretion, flow cytometry to group the proliferated cells, and the antigenicity of synthetic peptide was predicted by the computer modeling. RESULTS: (1)There were PBMC proliferation when stimulated by HVR1 antigen synthetic peptides. (2) There was a rise of IFN-gamma, IL-4 and IL-10. But no rise of IL-2 and TNF-gamma was found. (3) The proliferated cells were mainly CD4+ lymphocytes. CONCLUSION: PMBC from hepatitis C patients tend to secret Th2 cytokines after stimulation with HVR1 designed by the authors.

Amino Acid Sequence↗

PubMed2005

[The effect of entrapment of CpG sequence with cationic PLG nanoparticles on the immune responses of mice to pig paratyphoid vaccine].

Cationic PLG nanoparticles and liposome were prepared and used as package molecules to pack up pUC18-CpG. The effects of the packed pUC18-CpG on the cellular and humoral immune responses were detected in the mice that were inoculated with pig paratyphoid vaccine. The results showed that compared with the control, the amount of IgG and the titre of specific antibody were significantly increased in the sera of mice immunized with the CpG plasmid entrapped by cationic PLG nanoparticles; the proliferation and induced IL-2 bioactivity of lymphocytes were significantly enhanced in the spleen of the immunized mice; the stimulatory effect of cationic PLG nanoparticles was similar to or stronger than that of cationic liposome. These indicated that cationic PLG nanoparticle could be employed as an effective package molecule to promote the immunostimulatory effect of pUC18-CpG.

Adjuvants, Immunologic↗

PubMed2004

Synthesis and topoisomerase I inhibitory properties of luotonin A analogues.

Luotonin A, a naturally occurring pyrroloquinazolinoquinoline alkaloid, has been previously demonstrated to be a topoisomerase I poison. A number of luotonin A derivatives have now been prepared through the condensation of anthranilic acid derivatives and 1,2-dihydropyrrolo[3,4-b]quinoline-3-one in the presence of phosphorus oxychloride. When dichloromethane was used as solvent the reaction proceeded to a single product. In contrast when the reaction was carried out in tetrahydrofuran or in phosphorus oxychloride, an additional isomeric product was obtained. The luotonin A analogues were evaluated for their ability to effect stabilization of the covalent binary complex formed between human topoisomerase I and DNA, and for cytotoxicity toward a yeast strain expressing the human topoisomerase I.

DNA↗

PubMed2004

Integrating input from multiple signals: the VirA/VirG two-component system of Agrobacterium tumefaciens.

Bacteria, fungi, and plants exploit histidine sensor kinase/response regulators to mobilize complex responses to inputs as diverse as environmental stimuli and hormonal regulation. More than 50 such two-component systems are found in many organisms, yet the mechanisms of signal perception, phosphotransfer regulation, and even the nature of the activating signals remain poorly defined. Here we resolve each phosphate transfer event in vivo for the Agrobacterium tumefaciens virulence two-component system VirA/VirG. The input signals for this system are known, and the complex autocatalytic regulation of the signaling components has been removed. Two separate and independent phosphotransfer events are resolved, an initial ATP-->sensorHis approximately PO(4)-->receiver approximately PO(4), that may be activated by xenognostic sugar/low pH, and a subsequent ATP-->His approximately PO(4)-->VirG approximately PO(4) that requires xenognostic phenol activation. The identification of these separate pathways places biochemical limits on the regulated steps in this two-component signal transduction module and further extends the model of how a single sensor is able to integrate multiple input stimuli.

Agrobacterium tumefaciens↗

PubMed2004

Identification of specific nonbridging phosphate oxygens important for DNA cleavage by human topoisomerase I.

Methylphosphonate-bearing oligonucleotides are characterized by the replacement of one of the nonbridging oxygen atoms with a methyl group. While neutralizing the negative charge associated with the phosphodiester at the point of substitution, the methyl group also imparts chirality to the phosphorus atom. Herein we report the synthesis of a number of oligonucleotides containing isomerically pure S(p) and R(p) methylphosphonates at single positions for the purpose of investigating the hydrogen-bonding contacts necessary for human topoisomerase I function. It was possible to correlate these data to the recent X-ray crystal structure of a truncated form of the enzyme and demonstrate a severe decrease of cleavage efficiency when any of the nonbridging oxygen atoms upstream from the cleavage site was removed. Also observed was increased cleavage for oligonucleotides substituted with methylphosphonates downstream from the cleavage site. These effects were shown to be due primarily to alteration of the binding of the modified DNA substrates by human DNA topoisomerase I.

Base Pairing↗

PubMed2004

Synthesis and biochemical properties of E-ring modified luotonin A derivatives.

Luotonin A is a cytotoxic pyrroloquinazolinoquinoline alkaloid that has been shown to stabilize the human topoisomerase I-DNA covalent binary complex in the same fashion as the antitumor alkaloid camptothecin. A study of the structural elements in luotonin A required for binary complex stabilization has revealed key differences relative to those required for camptothecin.

Enzyme Inhibitors↗

PubMed2004

Water-soluble camptothecin derivatives that are intrinsic topoisomerase I poisons.

[structure: see text] In an effort to improve the water solubility of camptothecin, four 20-O-phosphate and phosphonate analogues have been prepared. These analogues are freely water soluble, stable at physiological pH, and stabilize the human topoisomerase I-DNA covalent binary complex with the same sequence selectivity as camptothecin itself. All four compounds inhibited the growth of yeast expressing human topoisomerase I in an enzyme-dependent fashion.

Camptothecin↗

PubMed2004

Insecticidal activity of deoxypodophyllotoxin, isolated from Juniperus sabina L, and related lignans against larvae of Pieris rapae L.

In the course of screening for naturally occurring insecticides from plants from the northwestern part of China, a petroleum ether extract of Juniperus sabina L was found to show insecticidal activity against fifth-instar larvae of Pieris rapae L. From the extract, an insecticidal compound was isolated by bioassay-guided fractionation. The compound was identified as deoxypodophyllotoxin (1) by comparison of its spectroscopic characteristics with literature data. In bioassays, 1 showed antifeedant activity against fifth-instar larvae of P rapae at 0.05-1.00 g litre(-1) and its AFC50 (concentration for 50% antifeedant activity) values at 12 and 48h were 0.170 and 0.060 g litre(-1), respectively. In that concentration range, all treated insects died within 48 h after treatment and compound 1 showed delayed insecticidal activity. At 0.015-0.100 g litre(-1), 1 showed insecticidal activity, with an LC50 of 0.020 g litre(-1). The related compound deoxypicropodophyllotoxin (2), however, showed lower antifeedant and insecticidal activities than 1 in bioassay. This indicated that the trans-lactone ring is an important moiety for enhancing activity in these compounds. Comparison of the insecticidal activities of 1 and another related compound, podophyllotoxin (3), suggested that varying the substituent at C-4 is an exciting possibility for synthesizing more potent analogues.

Animals↗

PubMed2004

Regulating effects of porcine interleukin-6 gene and CpG motifs on immune responses to porcine trivalent vaccines in mice.

In order to develop novel immunoadjuvants to boost immune response of conventional vaccines, experiments were conducted to investigate the regulating effects of porcine interleukin-6 gene and CpG motifs as the molecular adjuvants on immune responses of mice that were co-inoculated with trivalent vaccines against Swine fever, the Pasteurellosis and Erysipelas suis. Synthetic oligodeoxynuleotides containing CpG motifs were ligated into pUC18, forming recombinant pUC18-CpG plasmid. Eukaryotic plasmid expressing porcine interleukin-6 (VPIL-6) were also constructed as molecular adjuvants in an attempt to enhance levels of immune responses of mice co-administered with the trivalent vaccines in this paper. The cellular and humoral immune responses of mice were systematically analysed, and the experimental results were observed that the number of white blood cells, monocytes, granuloytes and lymphocytes significantly increased, respectively, in the mice immunized with VPIL-6, compared with those of the control; the IgG content and titre of specific antibodies to the trivalent vaccine mounted remarkably in the sera from the VPIL-6 vaccinated mice; the proliferation of lymphocytes and induced IL-2 activities were significantly increased in the vaccinated groups. The above-mentioned immune responses of mice co-inoculated with pUC18-CpG plasmid were significantly stronger than those of co-inoculated with pUC18 plasmid, suggesting that the immunostimulatory effect of oligodeoxynuleotides CpG is closely connected with the number of CpG motifs. These results suggest that the porcine IL-6 gene and CpG motifs could be employed as effective immunoadjuvants to elevate immunity to conventional vaccines.

Adjuvants, Immunologic↗

PubMed2004

The immunoregulation of mice by somatic transgenic expression of porcine interleukin-6 gene and CpG sequence.

Porcine IL-6 gene and CpG sequences were used to enhance some indirect indicators of the immune response of mice. An indirect ELISA was used to quantify the amount of IgG in the sera from mice that had been inoculated with VPIL-6, a recombinant VR1020 vector into which had been inserted the porcine IL-6 gene cloned in our laboratory, or with CpG, pUC18 or VR1020. The induced bioactivity of IL-2 of lymphocytes in the spleen was assayed by the MTT method, and the proliferation of lymphocytes stimulated with ConA was tested to identify the immune response of the experimental mice. The amount of IgG in the immunized mice was significantly higher than that in the control group. Among the immunized groups, inoculation with VPIL-6 induced the highest content of IgG (p < 0.05), the greatest bioactivity of IL-2 and the greatest proliferation of lymphocytes from the spleen of the mice. These results suggest that inoculation with porcine IL-6 gene and CpG sequences may enhance the immune response of mice, and might be used as an immunoadjuvant.

Adjuvants, Immunologic↗

PubMed2004

Chemical biology of multi-host/pathogen interactions: chemical perception and metabolic complementation.

The xenognostic mechanisms of two multi-host pathogens, the causative agent of crown gall tumors Agrobacterium tumefaciens and the parasitic plant Striga asiatica, are compared. Both organisms are general plant pathogens and require similar information prior to host commitment. Two mechanistic strategies, chemical perception and metabolic complementation, are used to ensure successful host commitment. The critical reactions at host-parasite contact are proton and electron transfer events. Such strategies may be common among multi-host pathogens.

Agrobacterium tumefaciens↗

PubMed2004

[Construction and expression of DNA-binding domain plasmid with hepatitis B virus e antigen in yeast double hybrid system].

BACKGROUND: Using hepatitis B virus e antigen (HBeAg) gene to construct the DNA-binding domain vector, which can express HBeAg in yeast cell, and can be used in yeast double hybrid as "bait plasmid" to look for the gene from the cDNA library, which expresses the protein that can interact with HBeAg. METHODS: PCR was performed to amplify the HBeAg gene from a sera of hepatitis B patient. The product of the amplification was inserted into T-vector and was verified by sequencing. Then it was inserted into the "bait" plasmid pGBKT7 after the digestion with the restricted endonuclease of EcoR I and Sal I. The plasmid was transformed into the yeast cell. PCR was used to verify whether the plasmid was transformed into yeast. The HBeAg protein expressed in the cell was confirmed by Western blot. Using nutrition selection assay to verify the constructed plasmid alone could not activate the reporter gene in the yeast cell. RESULTS: Sequenced and digested by two endonucleases, the recombined vectors pGBKT7-eAg produced anticipated fragment. PCR verified that there was HBeAg fragment in the yeast. Having assayed by Western blotting, it was shown that the yeast cell transformed with pGBKT7-eAg vector had positive signal which could not be seen in the control. Tested by the nutrition selection assay, the recombined vectors pGBKT7-eAg could not activate LacZ reporter gene in the yeast. CONCLUSION: DNA-binding domain plasmid was successfully constructed and could express HBeAg proteins in the yeast cell but could not activate transcription of LacZ reporter gene alone. The recombined plasmid can be used in yeast double hybrid.

Genetic Vectors↗

PubMed2004

[Effects of entrapment of murine interleukin-2 gene with chitosan nanoparticles on expression of mIL-2 gene and on regulation of immune response in mice].

The experiment was conducted to prepare chitosan nanoparticles (CNP), to entrap VRMIL-2 with CNP, the eukaryotic VR1020 expression plasmid containing murine IL-2 gene (mlL-2), and to investigate the expression in vivo and the regulatory effect of mIL-2 on immune-response and immuno-protection in mice inoculated muscularly with CNP entrapped VMIL-2 at 21 days old. The results showed that IgG, IgM and IgA contents increased to different degrees in the sera from the inoculated mice, which were remarkably higher than those of the controls inoculated VR1020 packed with CNP (P<0.05); so were the IL-2, IL-4 and IL-6 contents in the sera of the immunized mice. The number of white blood cells and lymphocytes significantly increased respectively in the vaccinated mice, compared with those of controls. These mice were orally challenged with virulent E. coli 35 days post-inoculation, and all the immune responses were significantly higher than those of the control except the number of neutrophils. The mice inoculated with VRMIL-2 survived healthily, while the mice of control group were ill with the evident lesions. Although there are no remarkable differences between the cellular and humoral immune indexes of mice inoculated with CNP-VRMIL-2 and nude VRMIL-2 (P>0.05), the dosage of CNP-VRMIL-2 is only one fifth of the VRMIL-2. These indicated that entrapment of mIL-2 gene with chitosan nanoparticles could remarkably enhance the expression of mIL-2 in vivo, and significantly raise the levels of cellular and humoral immune, and increase the resistance of mice against E. coli infection. The results suggested that chitosan nanoparticles and IL-2 gene could be used as an effective immunoenhancer to increase the immunity of animals against infection.

Adjuvants, Immunologic↗

PubMed2004

[Preparation of contraceptive pill microcapsule and its anti-fertility effect].

The main component of this pill is 2-Octadecanoic acid-4-Palmitic acid-2, 4-Pentanediyl ester separated from chloroform extract of neem oil. The microcapsules coated by the re-curdle method were fabricated with an average particle size of 100-180 microm. The morphological characteristics, incorporation efficiency, carrier reclamation efficiency of the microcapsule were investigated. Kunming mice were used in the experiment, and the anti-fertility effect of the microcapsule on the histology and apoptosis was studied by light and electron microscopy and the flow cytometry. The data obtained clearly indicated that the microcapsule could lead to the payload of medicine, the incorporation efficiency being 90%. After the microcapsules were given to the male mice orally, its anti-fertility effect came into being and could keep the mice in a state of reversible infertility for a long time. The results of histological study and flow cytometry indicate that the mechanism of its anti-fertility effect involves mainly the inhibition of sperm motility and the arrest of spermatogenic process.

Animals↗

PubMed2003

Luotonin A. A naturally occurring human DNA topoisomerase I poison.

Luotonin A is a pyrroloquinazolinoquinoline alkaloid isolated from the Chinese herbal medicinal plant Peganum nigellastrum. Although previously shown to exhibit cytotoxicity against the murine leukemia P-388 cell line, the mechanism of action of luotonin A is unknown. Presently, we demonstrate that luotonin A stabilizes the human DNA topoisomerase I-DNA covalent binary complex, affording the same pattern of cleavage as the structurally related topoisomerase I inhibitor camptothecin. Luotonin A also mediated topoisomerase I-dependent cytotoxicity toward Saccharyomyces cerevisiae lacking yeast topoisomerase I, but harboring a plasmid having the human topoisomerase I gene under the control of a galactose promoter. This finding identifies a putative biochemical locus for the cytotoxic action of luotonin A and has important implications for the mechanism of action of camptothecin and the design of camptothecin analogues.

Alkaloids↗

PubMed2003

3'-modified oligonucleotides by reverse DNA synthesis.

Reverse DNA oligonucleotide synthesis (i.e. from 5'-->3') is a strategy that has yet to be exploited fully. While utilized previously for the construction of alternating 3'-3'- and 5'-5'-linked antisense oligonucleotides, the use of nucleoside 5'-phosphoramidites has not generally been used for the elaboration of (modified) oligonucleotides. Presently, the potential of reverse oligonucleotide synthesis for the facile synthesis of 3'-modified DNAs is illustrated using a phosphoramidite derived from tyrosine. The derived oligonucleotide was shown to have chromatographic and electrophoretic properties identical with the modified oligonucleotide resulting from the proteinase K digestion of the vaccinia topoisomerase I-DNA covalent complex. The results confirm the nature of the structure previously assigned to this product, and establish the facility with which proteinase K is able to complete the digestion of the polypeptide backbone of the DNA oligonucleotide-linked topoisomerase I.

DNA↗

PubMed2003

[Cloning and expressing the E2 subunit of pyruvate dehydrogenase complex].

OBJECTIVES: To construct the expression vector of the pyruvate dehydrogenase complex E2 subunit gene (PDC-E2). METHODS: The PDC-E2 gene was amplified from human lymphocytes with RT-PCR, and was cloned into pExSecI vector to induce the PDC-E2 expression. The products were identified with western blot and ELISA. RESULTS: The expression vector pExSecI/PDC-E2 was successfully constructed. The products could be identified by the specific self-antibodies in the sera from the primary biliary cirrhosis patients. CONCLUSION: High efficient expression vector of PDC-E2 lays the foundation for serum assay of primary biliary cirrhosis patients with prokaryotic expressing PDC-E2.

Cloning, Molecular↗

PubMed2002

A novel prothrombin activator from the venom of Micropechis ikaheka: isolation and characterization.

A novel prothrombin activator, Mikarin, has been isolated from Micropechis ikaheka venom. It is a single polypeptide chain metalloproteinase with the apparent molecular weight of 47kDa. Mikarin exhibits Ca(2+)-independent prothrombin activation, but no effects on other blood coagulation factors, such as factor X and fibrinogen. Mikarin is the first member of group I prothrombin activators from elapid venom. Like other high-molecular-weight snake venom proteinases, it has three structural domains, metalloproteinase and disintegrin-like and Cys-rich domains, and belongs to the P-III class of snake venom metalloproteinases. The N-terminal of Mikarin exhibits 76% sequence identity with Cobrin, a metalloproteinase identified from Naja naja venom, but very lower identities were found when compared with those from viperid and crotalid venom. In addition, the presence of disintegrin-like and Cys-rich domains in snake venom metalloproteinases with diverse biological activities suggests that these domains may be important for their function.

Amino Acid Sequence↗