Biomedical subjects

Jun Gao

Publications and source records attributed to Jun Gao.

At least 55 records · Page 3Linked to original sources

PubMed2005

[Cloning of Human canstatin gene and expression of its recombinant protein].

OBJECTIVE: To clone human canstatin gene and express its recombinant protein. METHODS: The total RNA was extracted from human placenta. The canstatin gene fragment was synthesized and amplified from the total RNA by RT-PCR. The resulting product was cloned into pUCm-T vector and transformed into E.coli DH5alpha through electroporation. The gene was sequenced by the Sanger Dideoxy-mediated chain-termination method, and then the canstatin cDNA was cloned into the BamHI and HindIII sites of plasmid pET-22b (+) and transformed into E.coli BL21 where it was induced to express proteins by isopropyl-1-thio-b-Dgalactopyranoside (IPTG). RESULTS: The extracted total RNA was separated into three clear bands indicating 28S, 18S, and 5S after electrophoresis. The canstatin gene fragment was synthesized and amplified from the total RNA by RT-PCR. The resulting products were cloned into pUCm-T vectors, and then were transformed into E.coli DHSa. After an over night culture, both blue and white colonies were found on the agar plate. Six white colonies were selected and cut by BamHI and HindIII. The plasmids DNA in one white colony showed one band near the location of primary plasmid after digested by BamHI and two bands near the locations of primary plasmid and objective gene fragment after digested by HindIII. The cloned gene in this white colony was sequenced and demonstrated to have the same sequence as that of canstatin gene in GenBank. Then canstatin cDNA was cut down from pUCm-T with BamHI and HindIII and ligated into the vector pET-22b (+). The resultant plasmid pET-22b (+)/canstatin was then transformed into E.coli BL21. White colonies were found on LB agar plate. Seven of them were selected and their plasmids were digested with both BamHI and HindIII. After electrophoresis, all selected colonies showed two specific bands, one was found near the location of primary plasmids, and the other near that of objective gene fragment. After IPTG induction, there was a new protein band about Mr 24 000 on SDS-PAGE. As estimated by densitometry, the percentage of the expressed product over total bacterial proteins was 18.2%, 18.8%, 23.0% and 23.4%, respectively, 1, 2, 3, and 4 hours after induction. CONCLUSION: Human canstatin gene was successfully cloned and its recombinant proteins were expressed in this study.

Base Sequence↗

PubMed2004

Time-dependent four-component relativistic density functional theory for excitation energies.

Time-dependent four-component relativistic density functional theory within the linear response regime is developed for calculating excitation energies of heavy element containing systems. Since spin is no longer a good quantum number in this context, we resort to time-reversal adapted Kramers basis when deriving the coupled Dirac-Kohn-Sham equation. The particular implementation of the formalism into the Beijing density functional program package utilizes the multipolar expansion of the induced density to facilitate the construction of the induced Coulomb potential. As the first application, pilot calculations on the valence excitation energies and fine structures of the rare gas (Ne to Rn) and Group 12 (Zn to Hg) atoms are reported. To the best of our knowledge, it is the first time to be able to account for spin-orbit coupling within time-dependent density functional theory for excitation energies.

Journal Article↗

PubMed2004

Properties of the proton-evoked currents and their modulation by Ca2+ and Zn2+ in the acutely dissociated hippocampus CA1 neurons.

The characterization of acid-sensing ion channel (ASIC)-like currents has been reported in hippocampal neurons in primary culture. However, it is suggested that the profile of expression of ASICs changes in culture. In this study, we investigated the properties of proton-activated current and its modulation by extracellular Ca(2+) and Zn(2+) in neurons acutely dissociated from the rat hippocampal CA1 using conventional whole-cell patch-clamp recording. A rapidly decaying inward current and membrane depolarization was induced by exogenous application of acidic solution. The current was sensitive to the extracellular proton with a response threshold of pH 7.0-6.8 and the pH(50) of 6.1, the reversal potential close to the Na(+) equilibrium potential. It had a characteristic of acid-sensing ion channels (ASICs) as demonstrated by its sensitivity to amiloride (IC(50)=19.6+/-2.1 microM). Either low [Ca(2+)](o) or high [Zn(2+)](o) increased the amplitude of the current. All these characteristics are consistent with a current mediated through a mixture of homomeric ASIC1a and heteromeric ASIC1a+2a channels and closely replicate many of the characteristics that have been previously reported for hippocampal neurons cultured for a week or more, indicating that culture artifacts do not necessarily flaw the properties of ASICs. Interestingly, we found that high [Zn(2+)](o) (>10(-4) M) slowed the decay time constant of the ASIC-like current significantly in both acutely dissociated and cultured hippocampal neurons. In addition, the facilitating effects of low [Ca(2+)](o) and high [Zn(2+)](o) on the ASIC-like current were not additive. Since tissue acidosis, extracellular Zn(2+) elevation and/or Ca(2+) reduction occur concurrently under some physiological and/or pathological conditions, the present observations suggest that hippocampal ASICs may offer a novel pharmacological target for therapeutic invention.

Acid Sensing Ion Channels↗

PubMed2004

Characterization of acid-sensing ion channels in dorsal horn neurons of rat spinal cord.

Acid-sensing ion channels (ASICs) are ligand-gated cation channels activated by extracellular protons. In periphery, they contribute to sensory transmission, including that of nociception and pain. Here we characterized ASIC-like currents in dorsal horn neurons of the rat spinal cord and their functional modulation in pathological conditions. Reverse transcriptase-nested PCR and Western blotting showed that three ASIC isoforms, ASIC1a, ASIC2a, and ASIC2b, are expressed at a high level in dorsal horn neurons. Electrophysiological and pharmacological properties of the proton-gated currents suggest that homomeric ASIC1a and/or heteromeric ASIC1a + 2b channels are responsible for the proton-induced currents in the majority of dorsal horn neurons. Acidification-induced action potentials in these neurons were compatible in a pH-dependent manner with the pH dependence of ASIC-like current. Furthermore, peripheral complete Freund's adjuvant-induced inflammation resulted in increased expression of both ASIC1a and ASIC2a in dorsal horn. These results support the idea that the ASICs of dorsal horn neurons participate in central sensory transmission/modulation under physiological conditions and may play important roles in inflammation-related persistent pain.

Acid Sensing Ion Channels↗

PubMed2004

[Expression and significance of Toll-like receptor 4 of splenic macrophage in patients with hypersplenism due to portal hypertension].

OBJECTIVE: To observe the change in expression of Toll-like receptor 4 (TLR4) of splenic macrophage in patients with hypersplenism due to portal hypertension (PH), and investigate the role of TLR4 of splenic macrophage in hypersplenism. METHODS: Splenectomy was performed on 20 patients with hypersplenism due to PH (hypersplenism group) and 6 patients with rupture of spleen by trauma (control group) and the specimens of spleen were collected. The splenic macrophages were isolated by adhibit wall method. The expression of TLR4 of splenic macrophage was detected by immunohistochemical method (SABC), and the result was analyzed by the image analysis system. The phagocytosis of splenic macrophage was measured by chicken red blood cell (CRBC) phagocytosis assay. The level of serum endotoxin was detected before the operation by limulus assay. The results of these 2 groups were compared, and correlation analysis was made among different results of the hypersplenism group. RESULTS: The expression of TLR4 of splenic macrophage was 109 +/- 32 in the hypersplenism group, significantly higher than that of the control group (62 +/- 5, P < 0.01). The rate of phagocytosis and index of phagocytosis of splenic macrophage in the hypersplenism group were 12.6% +/- 3.0% and 0.146 +/- 0.035 respectively, both significantly higher than those of the control group (6.9% +/- 0.5% and 0.076 +/- 0.008 respectively, both P < 0.01) The level of endotoxin of the hypersplenism group was 0.28 EU/ml +/- 0.21 EU/ml, significantly higher than that of the control group (0.054 EU/ml +/- 0.014 EU/ml, P < 0.05). The rate of phagocytosis and the index of phagocytosis of splenic macrophage were notably positively correlated with the expression of TLR4 (r = 0.601, P < 0.01 and r = 0.553, P < 0.05), and the level of endotoxin (r = 0.724 P < 0.01 and r = 0.506, P < 0.05). The expression of TLR4 of splenic macrophage was positively correlated with the level of endotoxin (r = 0.525, P < 0.05). CONCLUSION: The expression of TLR4 of splenic macrophage in patients with hypersplenism due to PH was increased significantly. It may be one of the important factors of hypersplenism due to PH that "endotoxemia-->increase of expression of TLR4 of splenic macrophage (activation of TLR of splenic macrophage)-->increased destruction of red blood cells by macrophage".

Adult↗

PubMed2004

Selective activation of central NPY Y1 vs. Y5 receptor elicits hyperinsulinemia via distinct mechanisms.

Central administration of neuropeptide Y (NPY) stimulates hyperphagia and hyperinsulinemia. Recent evidence has suggested that the Y1 and Y5 receptor subtypes may both mediate NPY-stimulated feeding. The present study attempts to further characterize the role of central NPY receptor subtypes involved in hyperinsulinemia. NPY and peptide analogs of NPY that selectively activated the NPY Y1 or Y5 receptor subtype induced feeding and hyperinsulinemia in satiated Long Evans rats, whereas NPY analogs that selectively activated the NPY Y2 or Y4 receptor subtype did not. To determine whether NPY-induced hyperinsulinemia is secondary to its hyperphagic effect, we compared the plasma insulin levels in the presence and absence of food after a 1-min central infusion of NPY and its analogs at 15, 60, and 120 min postinfusion. Our data suggest that selective activation of central NPY Y1 receptor subtype induced hyperinsulinemia independent of food ingestion, whereas the NPY Y5 receptor-induced hyperinsulinemia was dependent on food ingestion. Central administration of the selective Y1 receptor agonist D-Arg25 NPY eventually decreased plasma glucose levels 2 h postinfusion in Long Evans rats.

Animals↗

PubMed2004

Controlled drug release from hydrogel nanoparticle networks.

Monodisperse nanoparticles of poly-N-isopropylacrylamide-co-allylamine (PNIPAM-co-allylamine) and PNIPAM-co-acrylic acid (PNIPAM-co-AA) were synthesized. The close-packed PNIPAM-co-allylamine and PNIPAM-co-AA nanoparticles were converted to three-dimensional gel networks by covalently crosslinking neighboring particles at room temperature and neutral pH using glutaric dialdehyde and adipic acid dihydrazide, respectively. Controlled release studies were conducted using dextran markers of various molecular weights as model macromolecular drugs. Release was quantified under various physical conditions, including a range of temperatures and dextran molecular weights. Dextran, entrapped in cavities in the nanoparticle network, was released with a rate regulated by their molecular weights and cavity size. No release from a conventional bulk PNIPAM gel, with high crosslinking density, was observed. The rate of release from the PNIPAM-co-allylamine network was temperature-dependent, being much faster at room temperature than that at human body temperature. In contrast, release of low molecular weight dextrans from the PNIPAM-co-AA network showed a temperature-independent release profile. These nanoparticle networks have several advantages over conventional bulk gels for controlling the release of high molecular weight biomolecules.

Acrylic Resins↗

PubMed2004

Electronic gel protein transfer and identification using matrix-assisted laser desorption/ionization-mass spectrometry.

An electronic protein transfer technique is described for achieving the rapid and efficient recovery of sodium dodecyl sulfate (SDS)-protein complexes from polyacrylamide gels. This process involves the use of small-dimension capillaries in physical contact with a resolved protein band within the polyacrylamide gel, providing a large potential drop and high electric field strength at the capillary/gel interface. Several factors controlling the electronic protein transfer, including the applied electric field strength, the electrophoresis buffer concentration, and the capillary dimension, are studied to further enhance the use of field-amplification for sample stacking of extracted SDS-protein complexes. As a result of sample stacking, the extracted proteins from a 50 ng gel loading are present in a narrow ( approximately 80 nL) and highly concentrated (0.46 mg/mL or 3.3 x 10(-5) M for cytochrome c) solution plug. Three model proteins with molecular mass ranging from 14 kDa (cytochrome c) to 116 kDa (beta-galactosidase) are stained by Coomassie blue and electrophoretically extracted from gels with protein loadings as low as 50 ng. The capillary format of the electronic protein transfer technique allows direct deposition of extracted proteins onto a matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) target. Various matrices and solvent compositions are evaluated for the analysis of extracted and concentrated SDS-protein complexes using MALDI-MS. The electronic protein transfer technique, when operated under optimized conditions, is demonstrated for the effective (>70% recovery), speedy (less than 5 min), and sensitive MS identification of gel resolved proteins (as low as 50 ng).

Cytochromes c↗

PubMed2004

Purification, folding, and characterization of Rec12 (Spo11) meiotic recombinase of fission yeast.

Meiotic recombination is initiated by controlled dsDNA breaks (DSBs). Rec12 (Spo11) protein of fission yeast is essential for the formation of meiotic DSBs in vivo, for meiotic recombination, and for segregation of chromosomes during meiosis I. Rec12 is orthologous to Top6A topoisomerase of Archaea and is likely the catalytic subunit of a meiotic recombinase that introduces recombinogenic DSBs. However, despite intensive effort, it has not been possible to produce Rec12 protein in a soluble form required to permit biochemical analyses of function. To obtain purified Rec12 protein for in vitro studies, a rec12(+) cDNA was generated, cloned into vector pET15b(+), and expressed in Escherichia coli. Rec12 protein was produced at moderate levels and it partitioned into insoluble fractions of whole-cell extracts. The protein was enriched based upon its differential solubility in two different denaturants and was further purified by column chromatography. A combinatorial, fractional, factorial approach was used to identify conditions under which Rec12 protein could be refolded. Four parameters were most important and, following optimization, soluble Rec12 protein was obtained. Gel filtration demonstrated that refolded Rec12 protein exists as a monomer in solution, suggesting that additional proteins may be required to assemble biologically-active Rec12 dimers, as inferred previously from genetic data [Cell Chromosome 1 (2002) 1]. The production of refolded Rec12 in a soluble form will allow for characterization in vitro of this key meiotic recombination enzyme.

Chromatography, Gel↗

PubMed2004

DNA vaccine of SARS-Cov S gene induces antibody response in mice.

The spike (S) protein, a main surface antigen of SARS-coronavirus (SARS-CoV), is one of the most important antigen candidates for vaccine design. In the present study, three fragments of the truncated S protein were expressed in E.coli, and analyzed with pooled sera of convalescence phase of SARS patients. The full length S gene DNA vaccine was constructed and used to immunize BALB/c mice. The mouse serum IgG antibody against SARS-CoV was measured by ELISA with E. coli expressed truncated S protein or SARS-CoV lysate as diagnostic antigen. The results showed that all the three fragments of S protein expressed by E.coli was able to react with sera of SARS patients and the S gene DNA candidate vaccine could induce the production of specific IgG antibody against SARS-CoV efficiently in mice with seroconversion ratio of 75% after 3 times of immunization. These findings lay some foundations for further understanding the immunology of SARS-CoV and developing SARS vaccines.

Animals↗

PubMed2004

High-performance liquid chromatographic method for the determination and pharmacokinetic study of mangiferin in plasma of rats having taken the traditional Chinese medicinal preparation Zi-Shen pill.

A high-performance liquid chromatographic method for the determination and pharmacokinetic study of mangiferin in the plasma of rats that have been orally administered the traditional Chinese medicinal preparation Zi-Shen pill is established. Plasma samples taken from rats are pretreated by protein precipitation with acetonitrile. Separation of the main effective constituent mangiferin is accomplished on a C18 stationary phase and a mobile phase of methanol&-water (25:75, v/v) with 0.6% glacial acetic acid. The UV detection wavelength is set at 320 nm, and the detection limit for mangiferin in plasma is 0.163 micro g/mL. After validation, the method is used to take a limited view of pharmacokinetic profiles of the traditional Chinese medicinal preparation Zi-Shen pill.

Animals↗

PubMed2004

Characterization of plutonium aerosol collected during an accident.

This study determined the plutonium particle size distribution and dissolution rate of PuO2 aerosol collected during the 16 March 2000 release of an undetermined amount of PuO2 in a room within a plutonium facility at Los Alamos National Laboratory. The facility has been in operation since 1978 to support the development, fabrication, and testing of Pu heat sources for the U.S. Department of Energy. Several workers were in the room at the time of the release and in vivo study of five of the workers began the day after the exposure event. Four of the subjects subsequently received chelation therapy. Over 30 fixed air filter samplers (FASs) and four continuous air monitors (CAMs) were operating in the room during the radiological release. One 47-mm-diameter glass fiber FAS filter and one 25-cm-diameter mixed cellulose ester CAM filter containing Pu aerosol from the incident were examined in the study described here. Total alpha radioactivity on the filters was determined by gross alpha counting. Isotopic identification of the Pu was made by alpha spectrometry. Film autoradiography was used to characterize the spatial distribution of alpha-emitting particles on the filters. Track-etch autoradiography was used to estimate the distribution of alpha radioactivity in individual plutonium particles on the filters for particle size measurement. The glass fiber filter was then cut into six sections. Particles from two sections were resuspended in alcohol, dispersed as an aerosol using a Lovelace nebulizer, and characterized by aerodynamic diameter using a Lovelace Multi-jet cascade impactor. The measured activity median aerodynamic diameter from the cascade impactor was 4.8 mum with a geometric standard deviation of 1.5. That agreed with the size distribution obtained from the alpha track detection technique. The remaining four filter sections were used in an in vitro dissolution study with synthetic serum ultrafiltrate. The retention of undissolved Pu was consistent with a biphasic exponential function. The majority of the Pu dissolved with a half-time of 900 d. The information on particle size distribution and solubility from this study was useful in assigning a radiation dose to the exposed workers, supporting the decision to administer chelation therapy, and providing a model for characterizing accident-associated aerosols in the future.

Aerosols↗

PubMed2003

Hypothalamus-brain stem circuitry responsible for vagal efferent signaling to the pancreas evoked by hypoglycemia in rat.

Circulating glucose levels significantly affect vagal neural activity, which is important in the regulation of pancreatic functions. Little is known about the mechanisms involved. This study investigates the neural pathways responsible for hypoglycemia-induced vagal efferent signaling to the pancreas and identifies the neurotransmitters involved. Vagal pancreatic efferent nerve activities were recorded in anesthetized rats. Insulin-induced hypoglycemia, a decrease of blood glucose levels from 114 +/- 5 to 74 +/- 6 mg dl(-1), stimulated an increase in pancreatic efferent nerve firing from a basal rate of 1.1 +/- 0.3 to 19 +/- 3 impulses 30 s(-1). In contrast, vagal primary afferent neuronal discharges recorded in the nodose ganglia were unaltered by systemic hypoglycemia. Vagal afferent rootlet section plus splanchnicotomy had no effect on hypoglycemia-induced vagal efferent firing, suggesting a central site of action. Decerebration reduced the increase in nerve firing stimulated by hypoglycemia from 21 +/- 4 to 9.6 +/- 2 impulses 30 s(-1). Chemical ablation of the lateral hypothalamic area, but not the arcuate nucleus, inhibited pancreatic nerve firing evoked by hypoglycemia. Microinjection of the orexin-A receptor antagonist SB-334867 into the dorsal motor nucleus of the vagus (DMV) inhibited pancreatic nerve firing evoked by insulin-induced hypoglycemia by 56%. In contrast, injection of orexin-A (20 pmol) into the DMV elicited a 30-fold increase in pancreatic nerve firing. We concluded that systemic hypoglycemia stimulates pancreatic efferent nerve firing through a central mechanism. Full expression of pancreatic nerve activities during hypoglycemia requires both the forebrain and the brain stem. In addition to activating neurons in the brain stem, central neuroglucopenia activates subpopulations of neurons in the lateral hypothalamic area that contain orexin. The released orexin acts on DMV neurons to stimulate pancreatic efferent nerve activities and thus regulate pancreatic functions.

Action Potentials↗

PubMed2003

Notch and the amyloid precursor protein are cleaved by similar gamma-secretase(s).

Gamma-secretase is an intramembrane-cleaving protease whose substrates include Notch and the amyloid precursor protein (APP). On the basis of initial genetic and pharmacologic data, the gamma-secretase activity responsible for cleavage of both proteins appears to be identical. However, apparent differences in the cleavage site and in sequence specificity raise questions about the degree of similarity between Notch and APP gamma-like proteolysis. In an effort to resolve this issue directly, we established an in vitro gamma-secretase activity assay that cleaves both APP- and Notch-based substrates, C100Flag and N100Flag. Analysis with specific gamma-secretase inhibitors, dominant-negative gamma-secretase preparations, and antibody co-immunoprecipitations all demonstrated identical cleavage of these substrates. Most importantly, we found that these substrates prevented cleavage of each other, indicating that the same gamma-secretase complex can cleave either protein. Finally, we provide evidence that both substrates are cut at two distinct regions in the transmembrane domain. These data resolve some of the apparent conflicts and strongly indicate that Notch and APP are proteolyzed by the same enzyme(s).

Amino Acid Sequence↗

PubMed2003

Growth of hyperthermophilic archaeon Pyrococcus furiosus on chitin involves two family 18 chitinases.

Pyrococcus furiosus was found to grow on chitin, adding this polysacharide to the inventory of carbohydrates utilized by this hyperthermophilic archaeon. Accordingly, two open reading frames (chiA [Pf1234] and chiB [Pf1233]) were identified in the genome of P. furiosus, which encodes chitinases with sequence similarity to proteins from the glycosyl hydrolase family 18 in less-thermophilic organisms. Both enzymes contain multiple domains that consist of at least one binding domain and one catalytic domain. ChiA (ca. 39 kDa) contains a putative signal peptide, as well as a binding domain (ChiA(BD)), that is related to binding domains associated with several previously studied bacterial chitinases. chiB, separated by 37 nucleotides from chiA and in the same orientation, encodes a polypeptide with two different proline-threonine-rich linker regions (6 and 3 kDa) flanking a chitin-binding domain (ChiB(BD) [11 kDa]), followed by a catalytic domain (ChiB(cat) [35 kDa]). No apparent signal peptide is encoded within chiB. The two chitinases share little sequence homology to each other, except in the catalytic region, where both have the catalytic glutamic acid residue that is conserved in all family 18 bacterial chitinases. The genes encoding ChiA, without its signal peptide, and ChiB were cloned and expressed in Escherichia coli. ChiA exhibited no detectable activity toward chitooligomers smaller than chitotetraose, indicating that the enzyme is an endochitinase. Kinetic studies showed that ChiB followed Michaelis-Menten kinetics toward chitotriose, although substrate inhibition was observed for larger chitooligomers. Hydrolysis patterns on chitooligosaccharides indicated that ChiB is a chitobiosidase, processively cleaving off chitobiose from the nonreducing end of chitin or other chitooligomers. Synergistic activity was noted for the two chitinases on colloidal chitin, indicating that these two enzymes work together to recruit chitin-based substrates for P. furiosus growth. This was supported by the observed growth on chitin as the sole carbohydrate source in sulfur-free media.

Amino Acid Sequence↗

PubMed2003

Excessive expression of the scavenger receptor class A type I can significantly affect the serum lipids.

Scavenger receptor (SR) is characterized by its ability to bind negatively charged macromolecules, particularly the modified lipoproteins that are pertinent to the development of vascular disease. To determine the role of excessive scavenger receptor A in the serum lipoprotein metabolism, transgenic mice lines with mouse scavenger receptor A gene type I (SR-AI) under the control of human SR-AI enhancer and metallothionein gene promotor were established. After zinc induction, the expression of SR-AI in transgenic mice was a little higher than the controls, but the serum lipids levels were significantly different from the controls, especially the cholesterol. These results demonstrated that overexpression of SR-AI significantly affected the serum lipids levels.

Animals↗

PubMed2003

[Establishment of a SCID mouse model for synergistic anti-tumor effect of human IL-12 and B7-1].

Human IL-12(hIL-12) has weak effect on mouse immunity cells, so the practical animal model is not available for the study of hIL-12 anti-tumor activity. In this work, the improved Winn assay was applied to evaluate the synergistic anti-tumor effects of hIL-12 and human costimulatory molecule B7-1(hB7-1) on human tumor in HuPBL-SCID mouse model. Three gene transferring solutions hIL-12, hB7-1 and their mixture(1:1) were prepared using the nonliposome transgene reagent and the expressing vectors, and hIL-12, hB7-1 or their mixture were transferred into tumor cell A375 respectively. Then A375 were co-injected into SCID mice with HuPBL, and rhIL-2 were injected i.p. as an anti-tumor agitator. On the other hand, LoVo and SPC tumor cells were also used to test the inhibitory effect of the mixture of hIL-12 and hB7-1. The anti-tumor effect of transferred genes was estimated by detecting tumor inhibition rate. Furthermore, the histochemical change of A375 implanting tumor tissue was also observed. Results showed that, to A375, the tumor inhibition rate of hIL-12, hB7-1, or their mixture were 74.06%, 66.98%, and 93.40%, respectively (P<0.01); and the mixture showed a good synergistic effect according to the Webb s fraction multiplication law. The tumor inhibition rate of the mixture in LoVo and SPC implanted mice were 98.37% and 97.39% respectively, also showing a good synergistic effect. Histochemical study in A375 implanted mice showed that in gene transfected mice, tumor cells were greatly inhibited and fully intruded by HuPBL cells; while in control group, tumor cells grew very well and HuPBL showed a conglomeration. At last, the human IgG and T cells in PBL of HuPBL-SCID mice were higher than non-HuPBL-SCID mice implanted A375; which showed that HuPBL-SCID mice could be applied for the evaluation of the anti-tumor effect of human IL-12 and B7-1. All data indicated that the combination of hIL-12 and hB7-1 gene might be a promising approach for in vivo cancer therapy.

Animals↗

PubMed2003

Antigen-expressed recombinant Salmonella typhimurium driven by an in vivo-activated promoter is capable of inducing cellular immune response in transgenic mice.

To explore the approaches and mechanisms for reversing the immune tolerance in transgenic mouse, and the pathogenicity of hepatitis G virus (HGV), the promoter of phoP-activated gene (P(pagC)) of Salmonella typhimurium was used as a transcriptionally regulating element to construct an attenuated S. typhimurium expressing HGV NS3. The recombinant S. typhimurium was orally administered to HGV transgenic mice. As the results, HGV antigen in serum and liver as well as HGV mRNA in liver were decreased significantly, although the serum anti-HGV NS3 remained undetectable as the control transgenic mice. The spleen cell proliferation, in vitro HGV NS3 specific CTL, and IFN-gamma assays with the primed cultured splenocytes indicated the induction of Th1 immune responses in those administered transgenic mice. Adoptive transfer of fractionated primed spleen cells to the transgenic mice showed that T lymphocytes were responsible for, maybe through IFN-gamma, the down-regulation of HGV mRNA transcription. Histological examination found no significant inflammatory changes in liver of the transgenic mice. These findings suggested that the oral inoculation of the HGV NS3-expressed attenuated S. typhimurium driven by an in vivo-activated promoter should be a simple and effective approach for potential treatment of chronic viral infection.

Adoptive Transfer↗