Biomedical subjects

Xu Liu

Publications and source records attributed to Xu Liu.

36 records · Page 2Linked to original sources

PubMed2005

Homoeologous cloning of omega-secalin gene family in a wheat 1BL/1RS translocation.

Wheat 1BL/1RS translocations are widely planted in China as well as in most of the wheat producing area in the world for their good qualities of disease resistance and high yield. 1BL/1RS translocations are however poor in bread making, partially caused by a family of small monomeric proteins, omega-secalins, which are encoded by genes on 1RS. Based on published sequence of a rye omega-secalin gene we designed a pair of primers to cover the whole mature protein coding sequence. A major band could be amplified from 1BL/1RS translocations but not from euploid wheat. Using this primer set we conducted PCR amplification by using high fidelity Pfu polymerase on the genomic DNAs and cDNAs purified from a 1BL/1RS translocation Lankao 906. Sequencing analysis indicated that this gene family contains several members of 1150 bp, 1076 bp, 1075 bp, 1052 bp and 1004 bp genes, including two pseudogenes and three active genes. The gene transcripts were differentially expressed in developing seeds.

Amino Acid Sequence↗

PubMed2005

Effects of timosaponins on learning and memory abilities of rats with dementia induced by lateral cerebral ventricular injection of amyloid beta- peptide.

OBJECTIVE: To investigate the effects of timosaponins, one group of the two major components of Anemarrhean asphodeloides Bge, on the learning and memory capacities of rats with dementia induced by amyloid beta-peptide (25-35) [Abeta (25-35)]. METHODS: Sixty SD rats were randomized into 6 groups (n=10) and except for those in the control group, all other rats were subjected to lateral cerebral ventriclar injection of aggregated Abeta (25-35) to prepare rat models of dementia. Twenty- four hours after the injection, the rats received intragastric administration of timosaponins at 3 different doses (treatment group) or Ginkgo biloba extract EGB761 on a daily basis for 14 consecutive days. From postoperative days 8 to 14 after Abeta (25-35) injection, Morris water maze test was performed to evaluate the effects of Abeta (25-35) and the therapeutic agents timosaponins on the learning and memory capacity of the rats. On day 14, the level of malonaldehyde (MDA), superoxide dismutase (SOD) activity and total antioxidation capacity in the brain tissue of the rats were measured. RESULTS: Abeta (25-35) induced significant learning and memory impairment in the rats, which had lowered SOD activity and total antioxidation capacity (P<0.01) with elevated MDA level (P<0.05). Compared with the rats in dementia model group, those receiving timosaponin treatment at different doses all manifested alleviation of learning and memory impairment (P<0.05), with enhanced SOD activity (P<0.05) and total antioxidation capacity (P<0.01) and reduced MDA level (P<0.05) in the brain tissue. CONCLUSION: Timosaponins can remarkably enhance the learning and memory capacities in rats with Abeta (25-35)-induced dementia, presumably in relation to their actions to promote the scavenging of the free radicals.

Alzheimer Disease↗

PubMed2005

[Dual chamber pacing for vasovagal syncope].

OBJECTIVE: To investigate the effect of DDD pacing on vasovagal syncope (VVS). METHODS: Eleven patients diagnosed VVS (7 with heart inhibiton type, 4 with combination type)by tilt table test (TTT) in Shanghai Chest Hospital were selected into the study. They all were implanted DDD pacemaker in whom 9 with rate-drop response (RDR) function. All of them were prescribed beta-receptor blocker. The patients were followed-up at 1, 3, 6, 12, 24 months after being discharged. RESULTS: All the 11 patients with pacemaker implantation were free from syncope, in whom 4 still had pre-syncope discomfort, but the symptoms were slightly. Six patients took TTT again after pacemaker implantation. It was observed that pacing at an elevated rate started immediately when heart rate dropping to the lower threshold, and as a result syncope were prevented. CONCLUSION: In the VVS patients with recurrent syncope and severe heart inhibition, DDD pacing with RDR function could prevent from syncope efficiently.

Adult↗

PubMed2005

[Preparation and evaluation of 3,5-dinitrobenzoyl-bonded silica gel stationary phase for high performance liquid chromatography].

A new preparation method of 3,5-dinitrobenzoyl-bonded silica gel stationary phase (DNB) for high performance liquid chromatography has been developed by using N-(beta-aminoethyl)-gamma-aminopropyl-methyldimethoxy silane as coupling reagent. Its structure was characterized by elemental analysis, diffuse reflectance Fourier transform infrared spectroscopy and thermal analysis. The surface concentration of 3,5-dinitrobenzoyl ligand was 2.08 micromol/m2 according to the carbon content from elemental analysis. The chromatographic performance of the new packing was evaluated by using different solute probes, such as polycyclic aromatic hydrocarbons (PAHs), phenols, naphthalene derivatives, nitrophenol positional isomers and sulfonamides. The results show that comparing with ODS, DNB has weaker hydrophobicity and more versatile chromatographic properties. The charge-transfer between the dinitrobenzoyl ligand and the analytes plays a significant role in the separation of phenols and naphthalene derivatives. In addition, static electric, hydrogen-bonding and dipole-dipole interactions are responsible for the above separations and improve the selectivity of DNB for solutes. An advantage of DNB is that it is suitable for the separation of the basic compounds containing nitrogen atoms without capped process because the spacer containing nitrogen atoms can shield the residual silanols on DNB.

Chromatography, High Pressure Liquid↗

PubMed2005

[Study on the interaction of water-soluble p-(N,N-dimethylaminomethyl) calix[8] arene with DNA by fluorescent spectrometry].

The interaction of water-soluble p-(N, N-dimethylaminomethyl) calix [8] arene (CX8) with DNA was studied using adriamycin(ADM) as a probe by fluorescent spectrometry. The effect factors such as, pH of solution, salt effect and unlinking DNA on the spectra were also investigated. The interaction mechanism was proposed. The authors observed that the fluorescence of ADM was quenched by calf thymus DNA, and the fluorescence intensity of DNA-ADM enhanced with the increasing of the CX8 gradually. The result indicates that the strong electrostatic interaction between the oxyphosphate anion of DNA and the CX8 existed. According to the plot of scatchard, the results imply that the influence of CX8 on interaction of DNA-ADM belongs to mixed model, on the one hand, in the condition of neutral and acidity, the oxyphosphate anion of DNA can be neutralized by CX8 partially, which induced the contraction of DNA and the conformational change of DNA, which led to release ADM from DNA partially, on the other hand, the CX8 can also compete the electrostatic sites with ADM directly.

Algorithms↗

PubMed2005

[Electroanatomical systems guided circumferential pulmonary veins ablation for atrial fibrillation: initial experience from comparison between the EnSite-NavX and CARTO system].

OBJECTIVE: The circumferential pulmonary vein ablation (CPVA) has been proved effective for atrial fibrillation (AF) and is becoming more widely accepted. This study aims to evaluate the effectiveness of the CARTO and the EnSite-NavX system and to compare between them on procedural parameters and clinical characteristics. METHODS: Seventy-five patients with paroxysmal or persistent symptomatic AF were randomly assigned to CPVA procedure guided by either the EnSite-NavX system (group I, n = 40) or the CARTO system (group II, n = 35). After successful transseptal procedure, a geometry of left atrium was created under the guidance of the two systems. Radiofrequency energy was applied to circumferential tissues out of pulmonary veins (PVs) ostia. In cases with persistent AF, linear ablation was applied to modify the substrate of LA. The endpoint of the procedure was complete PVs isolation. RESULTS: Seventy-four cases underwent a successful procedure. The total procedure and fluoroscopic time in group II was significantly shorter than those in group I (150 min +/- 23 min and 18 min +/- 17 min vs 170 min +/- 34 min and 25 min +/- 16 min, P = 0.03 and 0.04, respectively). There was no significant difference in the fluoroscopic and procedure durations for geometry creation between the groups I and II (8 min +/- 4 min and 16 min +/- 11 min vs 5 min +/- 4 min and 14 min +/- 8 min, respectively). The fluoroscopic time for CPVA was 15 min +/- 5 min in group I vs 10 min +/- 6 min in group II (P = 0.05), and the CPVA procedural durations were significantly shorter in group II than those in group (86 min +/- 11 min vs 110 min +/- 15 min, P = 0.04). AF was terminated by RF delivery in 14 cases (35%) in group Ivs 5 cases (14%) in group II (P = 0.04). Complete PV isolation was obtained in 26 cases (65%) in group Ivs 11 cases (31%) in group II (P = 0.004). During a mean follow-up of 7 months, 32 (80%) cases in group I and 24 (69%) cases in group II were arrhythmia-free (P = 0.06). One case developed pericardial tamponade and 1 case was found to have intestinal artery thrombosis in group II. One case had moderate hemothorax in group I. All the complications were cured and no PV stenosis was observed. CONCLUSIONS: The CPVA procedure for atrial fibrillation is effective and safe. Although there is a difference between the CARTO and the EnSite-NavX system, the CPVA procedure guided by either of them yields similar clinical results.

Adult↗

PubMed2004

A natural vaccinia virus promoter with exceptional capacity to direct protein synthesis.

A survey of vaccinia virus promoters, through a reporter gene approach, has identified the viral I1L promoter as having exceptional activity. The I1L promoter exhibited over 10 times the activity of other vaccinia promoters and even rivaled the activity of the bacteriophage T7 promoter in the hybrid vaccinia/T7 expression system. The I1L promoter had high activity in both transient transfection experiments and in the context of recombinant viruses. The I1L promoter should be useful for high-level protein synthesis and poxvirus studies in general.

Bacteriophage T7↗

PubMed2004

Wavelength-division multiplexed thin-film filters used in tilted incident angles of light.

The properties of wavelength-division multiplexed (WDM) narrowband filters used in tilted collimated light are described. The wavelength shift for s polarization in a low-index-spacer filter is larger than that for p polarization when the filter is tilted, but it is smaller in a high-index-spacer filter. Therefore the passbands of the tilted filter can be centered at the same wavelength for two polarization modes by use of high- and low-index materials, as appropriate, as spacers or by selection of a moderate-index material instead of a spacer. With such spacers, WDM filters used for incident angles of 20 degrees or even greater are constructed. Experimental results agree with the computed ones.

Journal Article↗

PubMed2004

[Prophylactic effect of artesunate against experimental infection of Schistosoma mansoni].

OBJECTIVE: To study the prophylactic effect of artesunate against the infection of Schistosoma mansoni in mice and its optimal scheme for preventing schistosomiasis mansoni. METHODS: BALB/c mice were infected by tail dipping method with S. mansoni cercariae. Mice were administered orally with artesunate at different developmental stage of the parasite, with different regimens. The reduction rates of total and female worms, the number of eggs in the liver and intestine, and the fecundity were calculated and treated statistically. RESULTS: The optimal dosage of artesunate to prevent murine schistosomiasis was 300 mg/kg. The parasite was found to be especially susceptible to artesunate in its schistosomula stage of 14 and 21 d after infection, resulting in worm reduction rate of 84% and 93% respectively compared with control. High protection was reached with worm reduction rate of 99% by the regimens of 300 mg/kg once a week for 4 consecutive weeks beginning 14 d after infection. The fecundity was significantly suppressed, suggesting that the drug inhibited sexual maturation of female worms. The effective protection could also be gained with prolonged interval time of two weeks with worm reduction rate of 97% and 96% beginning 14 or 21 d after infection. CONCLUSION: Artesunate kills schistosomula and reduces the fecundity of females effectively, the infected mice do not develop schistosomiasis mansoni when treated with artesunate. It's proposed that an optimal scheme for field use be the first administration 14 or 21 days after infection with 1 or 2 weeks interval.

Animals↗

PubMed2004

High-throughput imaging of bacterial colonies grown on filter plates with application to serum bactericidal assays.

The ability to accurately enumerate viable bacteria has applications in antibiotic screening assays, toxicology testing, and serological assays for functional antibodies. An impediment to high-throughput bacterial assays is the requirement to grow bacteria as individual colonies on semisolid media containing agar. We have now developed a method for growth, staining, and counting of bacterial colonies in 96-well filter plates. A unique feature of the method is that colony size is inversely proportional to the number of colonies in each well, presumably due to nutrient depletion. As a result, as many as 300 colony-forming units (cfu) can be detected as discrete colonies within a single assay well. The resulting colonies can be counted automatically using an imaging system originally developed for ELISPOT assays. The method has been applied to the measurement of serum bactericidal activity (SBA) in human sera.

Adult↗

PubMed2004

[Content determination of S-citalopram by chiral high-performance liquid chromatography].

OBJECTIVE: To separate the enantiomers of citalopram and determine the content of S-citalopram using chiral high-performance liquid chromatography (HPLC). METHODS: The chiral column CHIROBIOTIC V was used with the mobile phase using methanol-acetic acid-triethylamine (100:0.1:0.1) at the detection wavelength of 240 nm, column temperature of 20 degrees Celsius and flow rate of 1.0 ml/min. RESULTS: Complete separation of the enantiomers of citalopram was achieved, and S-citalopram exhibited good linearity within the concentration range of 10 to 150 microg/ml (r=0.9991, n=5). CONCLUSION: This method allows accurate quantification of S- and R-citalopram and is well suited for drug interaction investigations.

Chromatography, High Pressure Liquid↗

PubMed2004

[Fingerprinting of Panax notoginseng by high-performance liquid chromatography].

Fingerprinting of Panax notoginseng was performed by high-performance liquid chromatography using Agilent Hypersil C18 (250.0 mm x 4.0 mm, 5 microm) column with the mobile phase of acetonitrile and water and gradient elution. The detection wavelength was set at 203 nm. The method is simple and reliable to identify and evaluate the quality of Panax notoginseng.

Chromatography, High Pressure Liquid↗

PubMed2003

Adjuvant synergy in the response to hepatitis B vaccines.

The adjuvant properties of interleukin-12 (IL-12) and a phosphorothioate oligodeoxynucleotide (S-ODN) hexamer consisting of the sequence, 5'-GACGTT-3', were evaluated in mice using hepatitis B (HBs) protein and DNA vaccines. GACGTT was an effective adjuvant when co-injected with HBs protein intramuscularly or when injected at the same anatomic site within 1 day before or 1 day after injection of the protein. Surprisingly, IL-12 had a negligible adjuvant effect when co-injected with HBsAg; however, when bound to "alum", IL-12 stimulated a dramatic increase in anti-HBs titers and a switch from a TH2 to a TH1 response profile as evidenced by an increase in IgG2a subclass anti-HBs antibodies and the ability to secrete interferon-gamma (IFN-gamma) upon in vitro stimulation with an HBs peptide. Interestingly, aluminum phosphate was a far better co-adjuvant (with IL-12) than was aluminum hydroxide even though both "alums" bound >99% of the IL-12. Finally, the combination of IL-12, GACGTT, and aluminum phosphate was found to elicit a markedly polarized TH1 response. The results indicate that aluminum phosphate is highly effective at delivering an antigen (HBsAg) together with TH1 adjuvants such as IL-12 and GACGTT resulting in a shift from a TH2 to a TH1 response.

Adjuvants, Immunologic↗

PubMed2003

Measurement of cell-mediated immunity with a Varicella-Zoster Virus-specific interferon-gamma ELISPOT assay: responses in an elderly population receiving a booster immunization.

An interferon-gamma ELISPOT assay has been developed for assessment of cellular immune responses to Varicella-Zoster Virus (VZV) in large, multi-center clinical vaccine trials. We show that the assay performed best when testing peripheral blood mononuclear cells (PBMCs) that had been isolated and then frozen on the same day as blood was drawn, and that freezing PBMCs from blood that was stored overnight before processing resulted in dramatically reduced responses. This assay was used to monitor cell-mediated immunity (CMI) in response to a booster immunization with an investigational live, attenuated VZV vaccine in an elderly population that had been vaccinated 8-10 years previously. The booster vaccine elicited a 1.6- to 1.7-fold rise in the VZV-specific cellular immune response as measured by the ELISPOT assay. The increase from pre to post booster vaccination response was more pronounced (approximately 2.2-fold rise) in a subset of subjects who had received two prior immunizations with a live, attenuated vaccine.

Aged↗

PubMed2003

Comparative immunogenicity in rhesus monkeys of DNA plasmid, recombinant vaccinia virus, and replication-defective adenovirus vectors expressing a human immunodeficiency virus type 1 gag gene.

Cellular immune responses, particularly those associated with CD3(+) CD8(+) cytotoxic T lymphocytes (CTL), play a primary role in controlling viral infection, including persistent infection with human immunodeficiency virus type 1 (HIV-1). Accordingly, recent HIV-1 vaccine research efforts have focused on establishing the optimal means of eliciting such antiviral CTL immune responses. We evaluated several DNA vaccine formulations, a modified vaccinia virus Ankara vector, and a replication-defective adenovirus serotype 5 (Ad5) vector, each expressing the same codon-optimized HIV-1 gag gene for immunogenicity in rhesus monkeys. The DNA vaccines were formulated with and without one of two chemical adjuvants (aluminum phosphate and CRL1005). The Ad5-gag vector was the most effective in eliciting anti-Gag CTL. The vaccine produced both CD4(+) and CD8(+) T-cell responses, with the latter consistently being the dominant component. To determine the effect of existing antiadenovirus immunity on Ad5-gag-induced immune responses, monkeys were exposed to adenovirus subtype 5 that did not encode antigen prior to immunization with Ad5-gag. The resulting anti-Gag T-cell responses were attenuated but not abolished. Regimens that involved priming with different DNA vaccine formulations followed by boosting with the adenovirus vector were also compared. Of the formulations tested, the DNA-CRL1005 vaccine primed T-cell responses most effectively and provided the best overall immune responses after boosting with Ad5-gag. These results are suggestive of an immunization strategy for humans that are centered on use of the adenovirus vector and in which existing adenovirus immunity may be overcome by combined immunization with adjuvanted DNA and adenovirus vector boosting.

AIDS Vaccines↗

PubMed2002

[Municipal wastewater treatment using the up-biological aerated filter].

Up Biological Aerated Filter(UBAF) was used for the advanced wastewater treatment. The average removal rate of CODCr, BOD5, SS, NH4(+)-N and turbidity was 22.2%, 55%, 84.4%, 49%, 75.6% respectively. The hydraulic and COD load of influent influenced directly the quality of effluent.

Aerobiosis↗

PubMed2002

Sustained peptide-specific gamma interferon T-cell response in rhesus macaques immunized with human immunodeficiency virus gag DNA vaccines.

We examined the influence of dose and method of antigen delivery on the dynamics and durability of T-cell responses to candidate human immunodeficiency virus (HIV) vaccines. Codon-optimized sequences from the HIV gag gene were inserted into alternative DNA vaccine vectors to express the coding sequence with or without the tissue plasminogen activator leader sequence. We delivered the vaccines by intramuscular injection as plasmid DNA without adjuvant or as plasmid DNA formulated with a novel block copolymer adjuvant (CRL8623) and then monitored the ensuing T-cell responses by using a gamma interferon enzyme-linked immunospot assay. We demonstrated persistence of the cell-mediated immune (CMI) response in rhesus macaques for at least 18 months following a four-dose vaccination regimen. The plasmid vaccine, with or without CRL8623, was immunogenic in macaques; however, the form coadministered with adjuvant exhibited improved T-cell responses, with a bias toward more antigen-specific CD8(+) T cells. Finally, we examined the fine specificity of the T-cell response to the gag vaccines by testing the response of 23 vaccinated macaques to individual Gag 20-mer peptides. Collectively, the monkeys responded to 25 epitopes, and, on average, each monkey recognized a minimum of 2.7 epitopes. The results indicate that a broad and durable CMI response to HIV DNA vaccines can be induced in a relevant nonhuman primate model.

AIDS Vaccines↗

PubMed2002

[Effects of hydrogen peroxide on intracellular free Ca2+ content in rat liver oval cells].

OBJECTIVE: To study the effects and mechanism of hydrogen peroxide (H2O2) of low concentration on dynamic changes of intracellular free calcium contents ([Ca2+]i) in cultural rat liver oval cells (WB-F344 cells). METHODS: Using Fluo-3/Am as fluorescent indicator of [Ca2+]i and it was measured by laser scanning confocal microscope system. RESULTS: The results showed that: (1) A rapid transient spiking of [Ca2+]i occurred after the stimulation of H2O2 of low concentration (800 nmol/L). (2) The [Ca2+]i increase was abolished by pretreated with catalase (CAT) or by incubated in D-Hank's solution containing EGTA, the chelate of extracellular Ca2+. (3) The [Ca2+]i increase was not inhibited by pretreated nifedipine, Ca2+ channel blocker, but was abolished by pretreated with anthracere-9-cardoxylic acid (A9C), the Cl-channel blocker and which also blocked calcium activated non-selective cation channel (CAN). CONCLUSIONS: These results suggest that the increase of [Ca2+]i induced by H2O2 of low concentration may be due to the influx of extracellular Ca2+ through CAN.

Animals↗