PubMed Health⌕ Search

Biomedical subjects

Li Xu

Publications and source records attributed to Li Xu.

At least 127 records · Page 7Linked to original sources
PubMed2004

[Efficiency of combined multiple organs resection in advanced gastric carcinoma].

BACKGROUND & OBJECTIVE: Presently, 26.05% of cases with gastric carcinoma hospitalized in Cancer Center of Sun Yat-sen University were revealed adjacent organs involvement in varying degrees in exploration. There have been many arguments about the issue of surgery therapy on these advanced gastric carcinomas for a long time. This study was designed to demonstrate the feasibility of combined multiple organs resection in such cases. METHODS: Clinical data of 44 advanced gastric cancer patients received combined multiple organs resections from 1985 to 1995 in Cancer Center of Sun Yat-sen University were enrolled retrospectively. Among them, 34 cases received curative resection and 10 cases received palliative resection. The effects of two kinds of operations were analyzed. RESULTS: Median survival time was 588 days (average is 1 676 days) in radical combined multiple organs resection group and 344 days (average is 1 045 days) in palliative resection group respectively (P >0.05). In addition, no serious complication occurred and no patients died of extended resection. CONCLUSION: Combined multiple organs resection is practicable in curative therapy for gastric carcinoma; even palliative resection may have better treatment effect. So, if permission, radical combined multiple organs resection should be top-priority.

Adult↗
PubMed2004

[Genetic polymorphism of short tandem repeat loci D1S549, D3S1754 and D12S375 in Qingdao Han population].

OBJECTIVE: To know the genotype and allele frequency distribution of D1S549, D3S1754 and D12S375 in Chinese Han population in the Qingdao area and to study the three short tandem repeat(STR) loci for genetic application. METHODS: ACD-blood specimens were collected from the unrelated individuals in Qingdao. The DNA samples were extracted with the use of Chelex method and were amplified by polymerase chain reaction (PCR) technique. The PCR products were analyzed by polyacrylamide gel electrophoresis and were visualized by silver staining. RESULTS: Eight alleles were found at D1S549 locus, eight alleles at D3S1754 locus and five alleles at D12S375 locus, and 22, 19 and 14 genotypes were identified respectively. No deviation from Hardy-Weinberg equilibrium was observed in the three loci. The heterozygosities expected of them were 0.7988, 0.7087 and 0.75 respectively. The exclusion probability was calculated as 0.6592 for D1S549, and 0.5605 for D3S1754, and 0.5864 for D12S375. The discriminating power of the three loci were 0.9143, 0.8382 and 0.8861. Comparison of the allelic frequencies in Qingdao area with those in Hans of Chengdu area by chi-square test showed a difference statistically significant at D1S549 locus but no difference at D3S1754 and D12S375 loci. CONCLUSION: This study reveals the structure of the three loci and the obtained data are beneficial to understanding the population genetics in Chinese Han population. All of the three loci have higher chance of exclusion and higher discriminating power, and they will be useful markers for individual identification, paternity test and genetics purposes.

China↗
PubMed2004

[The relationship between a nucleotide substitution of S100A8 gene and aggressive periodontitis].

OBJECTIVES: To screen polymorphisms in the upstream region of S100A8 gene and to detect whether the polymorphisms were associated with aggressive periodontitis. METHODS: Thirty aggressive periodontitis patients and twenty-eight healthy controls were recruited for the study with informed consent. All subjects were of Chinese descent and systemically healthy. The regions about 800 bp upstream from the ATG start codon in exon 2 of the S100A8 gene of 10 patients and 8 controls were amplified by polymerase chain reaction (PCR) and analyzed by direct sequencing. A single nucleotide polymorphism (SNP) at 94 bp upstream from the ATG start codon was selected, and then the shorter regions (about 250 bp upstream from the ATG start codon) of the rest subjects were also amplified by PCR and analyzed by direct sequencing. The frequency of the SNP and the distribution of the genotype were detected and compared between the two groups. RESULTS: A nucleotide substitution (A-->G) at 94 bp upstream from the ATG start codon was demonstrated in Chinese, which was in a cis-acting element, named gamma interferon response element (gamma-IRE) in intron 1 of S100A8 gene. All of the subjects that carried the polymorphism were heterozygous. There was no statistically significant difference in the frequency of allele 2 (corresponding to the nucleotide G) between patients and controls (11.7% vs. 17.9%, chi2 = 0.887, P > 0.05). The prevalence of the heterozygous genotype was 23.2% and 35.7% (chi2 = 1.07, P > 0.05) in patients and controls, respectively. CONCLUSIONS: This is the first report that a nucleotide substitution of S100A8 gene was demonstrated in Chinese. The frequencies of allele 2 and heterozygous genotype were lower in patients, but there is no statistically significant difference between the aggressive periodontitis patients and healthy controls in this preliminary study.

Aggressive Periodontitis↗
PubMed2004

Effect of combination of extracts of ginseng and ginkgo biloba on acetylcholine in amyloid beta-protein-treated rats determined by an improved HPLC.

AIM: To determine the concentration of acetylcholine (ACh) in amyloid beta-protein (Abeta) treated rats and offer a method determining ACh as well. METHODS: A 1-month combination of extrats of ginseng and ginkgo biloba (Naoweikang) ig administration to rats was performed daily after bilateral injection of Abeta(1-40) (4 g/L, 1 microL for each side) into hippocampus. After decollation, homogenizing, and centrifuging and extracting, a high pressure liquid chromatographic (HPLC) method using electrochemical detection (ECD) combined with two immobilized enzyme reactors was used to determine ACh in rat whole brain. RESULTS: With a mobile phase consisting of disodium hydrogen orthophosphate, tetramethylammonium chloride (TMACl), octanesulfonic acid sodium salt (OSA) and "Reagent MB" at a final pH of 8.0, ACh was determined while removing the interfering choline in less than 10 min at a flow rate of 0.35 mL/min on a platinum (Pt) working electrode at a potential of +300 mV vs a solid-state palladium (Pd) reference electrode. Linear regression analysis of peak area vs concentration demonstrated linearity in the 28.01 to 1400.06 microg/L injection range. The r-value was 0.9978. The limit of detection (LOD) is 0.28 ng on column. ACh in whole brain decreased by 20.34 % (from 162.1+/-32.7 to 134.7+/-14.0 microg/L, P<0.05) after bilateral injection of Abeta into rat hippocampus. After Naoweikang administration (31 and 15.5 mg/kg, respectively), ACh increased by 19.97 % (from 134.7+/-14.0 to 161.6+/-26.2 microg/L, P<0.05) and 18.56 % (from 134.7+/-14.0 to 159.7+/-22.9 microg/L, P<0.05), respectively. CONCLUSION: Naoweikang significantly increased the level of ACh in whole brain of Abeta treated rats. And a sensitive, selective and reliable method for routinely determining ACh in rat whole brain was established in this study.

Acetylcholine↗
PubMed2004

Interannual variability of carbon cycle implied by a 2-d atmospheric transport model.

A 2-dimensional atmospheric transport model is deployed in a simplified CO2 inverse study. Calculated carbon flux distribution for the interval from 1981 to 1997 confirms the existence of a terrestrial carbon sink in mid-high latitude area of North Hemisphere. Strong interannual variability exists in carbon flux patterns, implying a possible link with ENSO and other natural episodes such as Pinatubo volcano eruption in 1991. Mechanism of this possible link was investigated with statistic method. Correlation analysis indicated that in North Hemisphere, climatic factors such as temperature and precipitation, to some extend, could influence the carbon cycle process of land and ocean, thus cause considerable change in carbon flux distribution. In addition, correlation study also demonstrated the possible, important role of Asian terrestrial ecosystems in carbon cycle.

Atmosphere↗
PubMed2004

[Two new triterpenoid saponins from Lysimachia capillipes Hemsl].

AIM: To study the triterpenoid saponins in the whole plants of Lysimachia capillipes Hemsl.. METHODS: Column chromatography (including AB-8 macroporous resin, silica gel and ODS) was used to separate triterpenoid saponins whose structures were elucidated by ESI-MS, NMR (1D and 2D) and hydrolysis methods. RESULTS: Two new triterpenoid saponins were isolated and established as 3beta, 22alpha-dihydroxy-16alpha-angeloyloxy-28-->13-lactone-oleanane-3-O-[beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinpyranosyl]-22-O-(6-acetyl)-beta-D-glucopyranoside (I), 3beta, 13beta, 22alpha-trihydroxy-16alpha-acetyloxyoleanane-28-oic acid Na-3-O-[beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinpyranosyl]-22-O-beta-D-glucopyranoside (II). CONCLUSION: Compounds I and II are new compounds and named as capilliposide I and capilliposide J.

Flavonoids↗
PubMed2004

[Comparision of high dose impulsion and low dose density chemotherapeutic regimens with paclitaxel plus cisplatin in advanced NSCLC].

OBJECTIVE: To explore high effective and low toxic chemotherapeutic regimens in the treatment of non-small-cell lung cancer (NSCLC). METHODS: A total of 126 patients with advanced NSCLC (Stage III, IV) were randomly divided into two groups: high dose impulsion chemotherapy group (HDIC group) and low dose density chemotherapy group (LDDC group) with 54 patients in HDIC group who received paclitaxel 135-175 mg/m2 on day 1, DDP 80-100 mg/m2 on day 1 and BCNU 125 mg given for brain metastasis on days 1-3 in a 4-6 weeks cycle. Seventy-two patients in LDDC group were given paclitaxel 60-80 mg/m2 on day 1, DDP 40-80 mg/m2 on day 1 repeated weekly and BCNU 125 mg given for brain metastasis with an interval of 2 weeks, in a 4-6 weeks cycle. Antiemetic agent and fluid were administered routinely in HDIC group whereas LDDC group was given antiemetic agent only. RESULTS: Of 157 courses in HDIC group, an average of 2.9 courses per patient, CR 3, PR 23, SD 17 and PD 11 were observed. The effective remission rate was 48.1%, the median effective remission period was 4.5 months and the 1-year survival rate was 46.3%. Of 184 courses in LDDC group, an average of 2.6 courses per patient, CR 9, PR 30, SD 24 and PD 9 were observed. The effective remission rate was 54.2%, the median effective remission period was 6 months and the 1-year survival rate was 56.9%. The effective remission rate and the 1-year survival rate were higher in HDIC group than those in LDDC group, but there was no statistical difference between the two groups (P > 0.05). Severe toxicity was higher in HDIC group than in LDDC group. Two patients in HDIC group died of treatment-related complications (3.7%). Quality of life was better in LDDC group (70.8%) than in HDIC group (51.9%). CONCLUSION: When comparing with high dose impulsion, low dose density regimen of paclitaxel plus cisplatin is more effective and better tolerated with improvement of quality of patients' life in the treatment of NSCLC due to its low dose and short interval duration.

Adult↗
PubMed2004

[Study on cucurbit[ 7] uril-mediated capillary electrophoresis].

The use of a novel macrocyclic molecule, cucurbit[7] uril (CB[7]), as an additive in capillary electrophoresis (CE) for the separation of several neutral nitrobenzenes is reported. Disodium hydrogen phosphate-hydrochloric acid was used as the buffer solvent with the UV detection at 254 nm. During the running process, CB [7] bore positive charge under the studied pH range (pH 2 - 6.5) and was adsorbed onto the inner wall of fused silica capillary, leading to a reversal of the electroosmotic flow (EOF). The effects of buffer pH and CB [7] concentration on the EOF behavior were investigated. The influences of the CB [7] concentration on electrophoretic behaviors of nitrobenzenes were also studied, and it was found that the selectivity increased with CB[7] concentration. The results showed that CB [7] provided good selectivity for nitrobenzenes and successful separation was obtained under optimum condition (10 mmol/L Na2HPO4 (pH 2.47, adjusted by HCl)-methanol (90 : 10, v/v), containing 5 mmol/L CB[7]). Possible explanation is also proposed.

Bridged-Ring Compounds↗
PubMed2004

[The effect of Baicalin on gene expression profile in rat brain of focal cerebral ischemia].

OBJECTIVE: To explore the difference of genes expression profiles between focal cerebral ischemia tissue and that treated with Baicalin using cDNA microarray. METHOD: The total RNAs were isolated from rat brains of sham-operation, vehicle (focal cerebral ischemia of rat brain) and baicalin-treated groups. mRNAs were reversely transcribed to cDNA with incorporation of fluorescent dUTP (Cy5 or Cy3 dUTP) to prepare hybridization probes. The PCR products of 4096 genes were spotted on the chip after a serial of treatment. The mixed probes were hybridized to the cDNA microarray. Axon Genepix 4000B and GenePixPro 3.0 software were used to scan and analyze the fluorescent signals. RESULT: The expressions of 199 and 12 genes were found up-regulated and down-regulated, respectively, in the vehicle group compared with the sham-operation one. But the numbers of genes whose expressions were up-regulated and down-regulated were 89 and 88, respectively, when comparing the gene expression in the Baicalin-treated rat brain with that in the vehicle group. Moreover, one down-regulated and three up-regulated genes in the vehicle group were up-regulated and down-regulated in the Baicalin-treated group, respectively. Expressions of three up-regulated genes in the vehicle group were further reinforced in the Baicalin-treatment group. CONCLUSION: Multiple pathways and nodes may be involved in the pharmacological effect of Baicalin on brain ischemia.

Animals↗
PubMed2003

Across-site variation in detection thresholds and maximum comfortable loudness levels for cochlear implants.

In cochlear implants, variation across stimulation sites in psychophysical detection thresholds (T levels) and maximum comfortable loudness levels (C levels) can be large when narrow-bipolar (BP) stimulation is used. This across-site variation is typically smaller when monopolar (MP) stimulation is used. At least two models can account for across-site variation and the effects of electrode configuration on the magnitude of the variation. According to one model, across-site variation reflects site-to-site differences in the distances between the stimulating electrodes and the sites of action-potential initiation. Under this model, the lower across-site variation with MP stimulation is due to shallower current versus distance gradients. An alternative model assumes that T and C levels depend on integration of activity across the whole population of neurons and that MP stimulation activates neurons over a larger spatial extent than does BP stimulation. If T and C levels are determined by integration of activity across large overlapping populations of neurons, then their values at adjacent sites should be more similar than if these levels result from integration across smaller, more independent populations. We tested the models by examining the effects on across-site variation of three variables believed to affect the spatial extent of activation: electrode configuration, stimulus level within the dynamic range, and electrode-array design. T levels and C levels were measured in 13 subjects with Nucleus CI24M (straight array) and 9 subjects with Nucleus CI24R(CS) (Contour) cochlear implants using bipolar (BP) and monopolar (MP) electrode configurations. Site-to-site variation in T and C levels for BP stimulation was 2.1-3.3 times larger than that for MP stimulation. Contrary to the across-neuron integration hypothesis, no significant differences were found between across-site variation for T levels and that for C levels for the BP configuration. There was considerable overlap in site-to-site variation values for the two types of implants but mean site-to-site variation in C levels for CI24M implants was significantly lower than that for CI24R(CS) implants. Control studies suggested that these results were not an artifact of the scale, and not due to differences in inherent variability of the psychophysical measures, or to the method of quantifying across-site variation.

Adult↗
PubMed2003

In vivo mucosal delivery of bioactive human interleukin 1 receptor antagonist produced by Streptococcus gordonii.

BACKGROUND: Interleukin-1 (IL-1) is a cytokine involved in the initiation and amplification of the defence response in infectious and inflammatory diseases. IL-1 receptor antagonist (IL-1ra) is an inactive member of the IL-1 family and represents one of the most potent mechanisms for controlling IL-1-dependent inflammation. IL-1ra has proven effective in the therapy of acute and chronic inflammatory diseases in experimental animal models and also in preliminary clinical trials. However, optimisation of therapeutic schedules is still needed. For instance, the use of drug delivery systems targeting specific mucosal sites may be useful to improve topical bioavailability and avoid side effects associated with systemic administration. RESULTS: In order to develop systems for the delivery of IL-1ra to mucosal target sites, a Streptococcus gordonii strain secreting human IL-1ra was constructed. The recombinant IL-1ra produced by S. gordonii was composed of the four amino acid residues RVFP of the fusion partner at the N-terminus, followed by the mature human IL-1ra protein. RFVP/IL-1ra displayed full biological activity in vitro in assays of inhibition of IL-1beta-induced lymphocyte proliferation and was released by recombinant S. gordonii in vivo both at the vaginal and the gastrointestinal mucosa of mice. RFVP/IL-1ra appeared beneficial in the model of ulcerative colitis represented by IL-2-/- mice (knock-out for the interleukin-2 gene), as shown by the body weight increase of IL-2-/- mice locally treated with S. gordonii producing RFVP/IL-1ra. CONCLUSIONS: These results indicate that recombinant S. gordonii can be successfully used as a delivery system for the selective targeting of mucosal surfaces with therapeutic proteins.

Animals↗
PubMed2003

A one-dimensional zigzag coordination polymer: catena-poly[[diaquapyridinenickel(II)]-mu-pyridine-2,3-dicarboxylato-kappa3N,O2:O3].

The asymmetric unit of the title one-dimensional coordination polymer, [Ni(C(7)H(3)NO(4))(C(5)H(5)N)(H(2)O)(2)](n), contains a quinolinate dianion, a nickel(II) ion, two water molecules and a pyridine molecule. The pyridine-2,3-dicarboxylate (quinolinate) ligands connect the nickel(II) ions in a head-to-tail fashion, resulting in the formation of a one-dimensional zigzag chain. Adjacent chains form pairs via an extensive network of hydrogen-bonding interactions. A weak C--H...O intermolecular hydrogen bond links neighboring pairs of chains, thus generating two-dimensional double-sheet layers that are stabilized via pi-pi-stacking interactions between adjacent quinolinate pyridyl rings.

Journal Article↗
PubMed2003

Resolving the unresolved complex mixture in petroleum-contaminated sediments.

Comprehensive two-dimensional gas chromatography (GC x GC) was used to investigate the chemical composition of the unresolved complex mixture (UCM) of hydrocarbons in petroleum-contaminated marine sediments. The UCM hydrocarbons were extracted and separated with silica and silver-impregnated silica gel chromatography to yield four fractions (branched alkanes and cycloalkanes, monoaromatics, naphthalenes, and multi-ring PAHs) prior to GC x GC analysis. GC x GC separations used a poly-(dimethylsiloxane) stationary phase for volatility selectivity on the first dimension and a 14% cyanopropylphenyl polysiloxane phase for polarity selectivity on the second dimension to fully resolve monoaromatic, naphthalene, and multi-ring PAH compounds from the UCM. A chiral gamma-cyclodextrin phase was used for shape selectivity on the second GC x GC dimension to resolve individual branched alkanes and cycloalkanes in the saturates fraction of the UCM. The ability of GC x GC to resolve thousands of individual chemical components from the UCM will facilitate an understanding of the sources, weathering, and toxicity of UCM hydrocarbons.

Chromatography, Gas↗
PubMed2003

Platelet-derived growth factor-B enhances glioma angiogenesis by stimulating vascular endothelial growth factor expression in tumor endothelia and by promoting pericyte recruitment.

Platelet-derived growth factor (PDGF)-B and its receptor (PDGF-R) beta are overexpressed in human gliomas and responsible for recruiting peri-endothelial cells to vessels. To establish the role of PDGF-B in glioma angiogenesis, we overexpressed PDGF-B in U87MG glioma cells. Although PDGF-B stimulated tyrosine phosphorylation of PDGF-Rbeta in U87MG cells, treatment with recombinant PDGF-B or overexpression of PDGF-B in U87MG cells had no effect on their proliferation. However, an increase of secreted PDGF-B in conditioned media of U87MG/PDGF-B cells promoted migration of endothelial cells expressing PDGF-R beta, whereas conditioned media from U87MG cells did not increase the cell migration. In mice, overexpression of PDGF-B in U87MG cells enhanced intracranial glioma formation by stimulating vascular endothelial growth factor (VEGF) expression in neovessels and by attracting vessel-associated pericytes. When PDGF-B and VEGF were overexpressed simultaneously by U87MG tumors, there was a marked increase of capillary-associated pericytes as seen in U87MG/VEGF(165)/PDGF-B gliomas. As a result of pericyte recruitment, vessels induced by VEGF in tumor vicinity migrated into the central regions of these tumors. These data suggest that PDGF-B is a paracrine factor in U87MG gliomas, and that PDGF-B enhances glioma angiogenesis, at least in part, by stimulating VEGF expression in tumor endothelia and by recruiting pericytes to neovessels.

Animals↗
PubMed2003

Synthesis and hydrolysis of a phenylalanyl adenylate pentacoordinated phosphorane.

Amino acid-nucleotide conjugates have important biological functions and therapeutic applications. For example, aminoacyl adenylates are key intermediates in aminoacyl tRNA synthetase reactions. They may also be involved in the prebiotic synthesis of polypeptides. Finally, various amino acid carbomethoxy aryl phosphoramidates of nucleotide prodrugs may be activated through a mechanism involving a pentacoordinated phosphorane intermediates. In order to understand better the chemistry of these compounds, a phenylalanyl adenylate pentacoodinated phosphorane has been synthesized in 72% yield and its decomposition in aqueous solution studied. Hydrolysis gave 2('),3(')-O-isopropylidene adenosine 5(')-monophosphate, 2('),3(')-O-isopropylidene adenosine, and phenylalanine. The results provide model chemistry for the enzymatic degradation mechanism of antiviral aryl amino acid phosphodiester amidates in cells, which leads to their activation.

Adenosine Monophosphate↗
PubMed2003

Lipase-catalyzed synthesis of precursor dipeptides of RGD in aqueous water-miscible organic solvents.

PPL-catalyzed synthesis of the precursor dipeptides of RGD as a cellular adhesion factor, Benzyl-Arg-Gly-NH2 and CBZ-Gly-Asp-NH2, was conducted in water-organic cosolvents systems. Five water-miscible organic solvents, which have some advantage over the water-immiscible organic solvent systems or the anhydrous organic solvent systems used often in protease-catalyzed synthesis of a peptide bond, were tested. The reaction condition of PPL-catalyzed synthesis of the dipeptides was optimized by examining the main factors affecting the product yield. The optimal reaction condition for the synthesis of Benzyl-Arg-Gly-NH2 was set up as pH 8.0, 15 degrees C in 40% MeOH for 10 h with the maximum yield of 73.6%. The optimum condition for the synthesis of CBZ-Gly-Asp-NH2 was pH 7.0, 15 degrees C in 50% MeOH for 10h with the maximum yield of 67.0%.

Catalysis↗
PubMed2003

Identification of a transmission chain of HIV type 1 containing drug resistance-associated mutations.

We have investigated a potential transmission chain of HIV-1 with drug resistance-associated mutations between three individuals over a period of 5 years by use of cloning and sequencing of viral genes, and phenotypic characterization. Viruses containing reverse transcriptase drug resistance-associated mutations were transmitted sequentially between three homosexual men (A, B, and C), and persisted in one individual for at least 4 years, despite intermittent therapy and reduced viral replicative capacity compared with wild-type strains. Clonal analysis of the envelope gene from semen and blood virus showed that the virus transmitted to patient C was more closely related to virus from the semen than the blood of patient B. Our data suggest that HIV variants with drug resistance-associated mutations can persist following primary infection, despite intervening antiretroviral therapy, and subsequently sexually transmitted. We provide "proof of principle" that such mutations can therefore become "fixed" within the circulating virus pool.

Anti-HIV Agents↗