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Yan Li

Publications and source records attributed to Yan Li.

At least 289 records · Page 16Linked to original sources
PubMed2005

Erk associates with and primes GSK-3beta for its inactivation resulting in upregulation of beta-catenin.

Beta-catenin is upregulated in many human cancers and considered to be an oncogene. Hepatocellular carcinoma (HCC) is one of the most prevalent human malignancies, and individuals who are chronic hepatitis B virus (HBV) carriers have a greater than 100-fold increased relative risk of developing HCC. Here we report a mechanism by which HBV-X protein (HBX) upregulates beta-catenin. Erk, which is activated by HBX, associates with GSK-3beta through a docking motif ((291)FKFP) of GSK-3beta and phosphorylates GSK-3beta at the (43)Thr residue, which primes GSK-3beta for its subsequent phosphorylation at Ser9 by p90RSK, resulting in inactivation of GSK-3beta and upregulation of beta-catenin. This pathway is a general signal, as it was also observed in cell lines in which Erk-primed inactivation of GSK-3beta was regulated by IGF-1, TGF-beta, and receptor tyrosine kinase HER2, and is further supported by immunohistochemical staining in different human tumors, including cancers of the liver, breast, kidney, and stomach.

Amino Acid Motifs↗
PubMed2005

Rapid and highly sensitive determination of trace proteins using dibromomethyl carboxyazo-Pb(II) complex as a spectroscopic reagent.

BACKGROUND: The concentration of protein in body fluids is an important measure in disease diagnosis and in analytical biochemistry. Searching for a sensitive and rapid method for proteins is an ongoing subject of investigation. We describe the reaction of dibromomethyl carboxyazo-Pb(II) with proteins found in urine. METHODS: In a buffer containing of HCl and KCl at pH 1.80, dibromomethyl carboxyazo-Pb(II) complex combined with proteins to form a colored compound. The reaction was completed in 2 min and remained stable for 80 min. Under optimum conditions, the product of reaction between protein and dibromomethyl carboxyazo-Pb(II) absorbed at 530 nm and was linear in the range of 0-50 microg/ml of BSA. Moreover, the maximum binding number was defined to express the binding ability of dibromomethyl carboxyazo-Pb(II) to protein under a given set of conditions. RESULTS: The method was applied to the determination of urine proteins. The recovery of protein from human urine was 97.6-103% and the precision was <4.8%. Results compared favorably to the Biuret and Bradford protein methods on 50 urine samples. CONCLUSIONS: This method had high sensitivity and specificity and may be applicable to clinical analysis.

Animals↗
PubMed2005

[Measurement of morphological parameters of Cryptosporidium muris oocysts by digital image processing technology].

OBJECTIVE: To establish and analyze the morphological parameters of the oocysts of Cryptosporidium muris for defining their morphological change. METHODS: Oocysts were collected from KM mice (immunodepressed by dexamethasone for 10 days) and examined with modified acid-fast staining. Images of 1 190 oocysts were acquired by photograph system. The length, width, perimeter, area and equivalent diameter of the oocysts were obtained by computer digital image processing system and analyzed by SPSS software (Version 11.0). RESULT: The average length of the oocysts was 5.93 microm, ranging from 3.36 microm to 8.51 microm in 95% confidence interval of them. The average width was 4.96 microm, ranging from 3.26 microm to 6.66 microm in 95% confidence interval of them. The average perimeter was 18.03 microm and the average area was 16.08 microm2. CONCLUSION: Data obtained from the computer system are objective and precise, offering scientific foundation for measuring the oocysts and for identifying Cryptosporidium spp.

Animals↗
PubMed2005

Use of electrokinetic measurements for characterization of columns used in capillary electrochromatography.

The separation mechanism in capillary electrochromatography (CEC) is a hybrid differential migration process, which entails the features of both high-performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE), i.e., chromatographic retention and electrophoretic migration. The focus of this paper is on the use of electrokinetic data, such as current, electroosmotic flow (EOF) and column efficiency measurements, that are readily available, for an improved understanding of CEC separations. A framework is presented here for the use of this data for evaluation of a variety of performance parameters including, conductivity ratio, interstitial EOF mobility, porosity, and zeta potential. This framework is applied for characterization of two monolithic columns with different chemistry that were manufactured in-house. The above-mentioned performance parameters were calculated for the two columns and it is found that the poly(VBC-EGDMA-SWNT) monolithic column with the GPTMS-PEI coating offers a significantly improved flow distribution in comparison to the poly(VBC-EGDMA) monolithic column. This observation is confirmed by performing separation of peptides on the two columns and height equivalent of a theoretical plate (HETP) measurements on the resulting peaks. It is shown that following our approach leads to an improved understanding of the separations achieved with the columns and to better column design.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2005

Single nucleotide polymorphism in DNA methyltransferase 3B promoter and its association with gastric cardiac adenocarcinoma in North China.

AIM: To investigate the association between single nucleotide polymorphism (SNP) in promoter of the DNA methyltransferase 3B (DNMT3B) gene and risk for development and lymphatic metastasis of gastric cardiac adenocarcinoma (GCA). METHODS: The hospital based case-control study included 212 GCA patients and 294 control subjects without overt cancer. The DNMT3B SNP was genotyped by PCR and restriction fragment length polymorphism (RFLP) analysis. RESULTS: The C/C genotype was not detected in both GCA patients and controls. In control subjects, the frequency of T/T and C/T genotypes was 94.9% and 5.1% respectively, and that of T and C alleles was 97.4% and 2.6%, respectively. The genotype and allelotype distribution in the GCA patients was not significantly different from that in controls (P=0.34 and 0.33, respectively). When stratified by smoking status and family history of upper gastrointestinal cancer, significant difference in the genotype distribution was not observed between GCA patients and controls. The distribution of DNMT3B genotypes in GCA patients with or without lymphatic metastasis did not show significant difference (P=0.42). CONCLUSION: The distribution of DNMT3B SNP in North China is distinct from that in Caucasians. Although this SNP has been associated with susceptibility to lung, head, neck and breast cancer, it may not be used as a stratification marker to predict susceptibility and lymphatic metastasis of GCA, at least in the population of North China.

Adenocarcinoma↗
PubMed2005

[c-kit and PDGFRA mutations in 60 cases of gastrointestinal stromal tumors (GISTs)].

OBJECTIVE: To explore the status of activating mutations of c-kit and PDGFRA in GIST of Chinese patients. METHODS: Sixty GISTs, confirmed by immunoreactivity of CD117, CD34, SMA, S-100 and Desmin, were evaluated for the presence of c-kit exons 9, 11, 13 and 17 mutations, and PDGFRA exons 12 and 18 mutations. The PCR products were sequenced directly for mutations, using DNA extracted from paraffin-embedded tissue. RESULTS: 53% of the tumors were located in the stomach, 22% in the small bowel, 8% in the colo rectum, 2% in the esophagus and 15% in the extragastrointestinal tract. Immunohistochemical demonstrations of c-kit (CD117) were seen in 90% cases. Overall, c-kit mutations were detected in 63.3% of patients as follows: 58.3% in exon 11, 3.3% in exon 9, 1.7% in exon 13 and none in exon 17. The types of c-kit exon 11 mutations were mostly heterogeneous and clustered in the classic "hot spot" at the 5' end of exon 11, 42.9% being point mutation and in-frame deletion at Codon 557-560. 14.3% of cases showed internal tandem duplications (ITD) at the 3' end of exon 11 in a region of a second hot spot for c-kit mutations. Interestingly, these cases were associated with female predominance, stomach location and occurrence in older patients. The present study failed to identify a significant association between c-kit mutation status and risk of aggressive behavior in GISTs. Exon 9 mutations consisted of ITP of six nucleotides encoding Ala-Tyr. A new point mutation of L641P was revealed in exon 13. PDGFRA mutations were found in 5% of all the 60 cases with none of the positive cases expressed detectable KIT protein. The type of mutation was the commonest point mutation of D842V of exon 18. CONCLUSION: Most KIT expressing GIST show c-kit mutations that are preferentially located within the classic hot spot of exon 11. A second hot spot -ITD at the 3' end of exon 11 seems to associate with a subgroup of gastric GISTs in older females. c-kit exons 9, 13 and 17 mutations are rare events in GIST of China. PDGFRA oncogenic mutations are more likely seen in KIT-negative GISTs arising in the peritoneal surface and have an unfavorable clinical course.

Adult↗
PubMed2005

Empirical nanotube model for biological applications.

An empirical model is developed to capture the electrostatics of finite-length single-walled armchair carbon nanotubes for biological applications. Atomic partial charges are determined to match the electrostatic potential field computed at the B3LYP/6-31G* level of density functional theory, and a tight-binding Hamiltonian is selected which permits one to reproduce the dielectric properties in good agreement with density functional theory results. The new description is applied to study movement of a water molecule through a finite-length nanotube channel in order to demonstrate the method's feasibility. We find that atomic partial charges on the tube edges dominate the interaction between the nanotube and the entering water molecule, while the polarization of the nanotube lowers the electrostatic energy of the water molecule inside the tube.

Electrons↗
PubMed2005

Suppression of pancreatic tumor progression by systemic delivery of a pancreatic-cancer-specific promoter driven Bik mutant.

Pancreatic cancer is highly aggressive with extremely poor prognosis. Developing a pancreatic cancer specific promoter (PCSP) is one approach for pancreatic cancer gene therapy. We have modified the promoter of cholecystokinin type A receptor (CCKAR), named CCK/Mpd, which possesses a relatively high activity in pancreatic cancer cells as compared with normal cells. The CCK/Mpd promoter-driven luciferase exhibits a better tumor specific tissue distribution than the CMV promoter-driven luciferase when systemically administered in vivo. Notably, we demonstrate a treatment efficacy by using CCK/Mpd-Bik-DD/liposome in a nude mice xenograft model, suggesting the feasibility of PCSP-based gene therapy in pancreatic cancer treatment.

Animals↗
PubMed2005

[Change of glucose transporter 4 and its influence on glucose and fatty-acid metabolism in type 2 diabetic myocardium].

OBJECTIVE: To investigate the relationship between sarcolemmal content of glucose transporter 4 (GLUT4) and the myocardial glucose and fatty acid utilization in type 2 diabetes. METHODS: Twenty-four Sprague-Dawley rats were randomized into four groups: control, HFD/STZ, control/RSG and HFD/STZ/RSG. Sprague-Dawley rats were fed with high-fat diet (40% of the calories was supplied by fat) for 4 weeks, intraperitoneally injected with 35 mg/kg streptozotocin to establish type 2 diabetes model, and 24 diabetic rats were randomized into four groups: HFD/STZ/RSG group [fed with high fat food and given rosiglitazone (3 mg.kg(-1).d(-1)) for 2 weeks], HFD/STZ group (fed with high fat food and given normal saline), control/RSG [fed with normal food and given rosiglitazone (3 mg.kg(-1).d(-1)) for 2 weeks], and control group (fed with normal food and given normal saline). Then the rats were killed and their hearts were taken out to be mounted onto a Langendorff perfusion apparatus to be perfused with Krebs-Henseleit buffer in the presence of 5 mmol/L glucose and 0.4 mmol/L (3)H labeling palmitate. Glucose uptake and (3)H2O collection were used to evaluate the rate of carbohydrate and fatty acid oxidation. The sarcolemmal content of GLUT4 protein was detected by Western blotting method. RESULTS: Compared with the control group, the diabetic rats had a significantly depression of glucose uptake of the heart [(55 +/- 6) micromol/g dry weight vs (69 +/- 6) micromol/g dry weight, P < 0.01], the oxidation rate of glucose decreased from 25% to 18% and the oxidation rate of palmitate increased from 75% to 82%, and the sarcolemmal GLUT4 content was decreased by 53% after 30 minutes' perfusion. In the HFD/STZ/RSG group the glucose uptake level was (64 +/- 6) micromol/g dry weight, significantly higher than that of the HFD/STZ group (P < 0.05), the proportions of glucose oxidation and fatty acid oxidation were 24% and 76% respectively, and the GLUT4 expression was 92% that of the normal rats, significantly higher than that of the HFD/STZ group (47%, P < 0.01). CONCLUSION: The sarcolemmal GLUT4 content in the type 2 diabetic myocardium is obviously decreased, which may be associated with the decrease of glucose uptake and increase of fatty acid oxygen. Rosiglitazone treatment may exert beneficial effects on the energy substrate utilization by increasing the expression of GLUT4.

Animals↗
PubMed2005

The functional polymorphism in the matrix metalloproteinase-7 promoter increases susceptibility to esophageal squamous cell carcinoma, gastric cardiac adenocarcinoma and non-small cell lung carcinoma.

An A to G transition at the 181 base pair position upstream of the transcription initiation site of the matrix metalloproteinase-7 (MMP-7) gene (-181A/G) may modify the development and progression of some diseases via influencing the transcription activity of the promoter. To assess the effects of the functional single nucleotide polymorphism on cancer susceptibility and progression, the MMP-7 -181A/G genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism analysis among 258 patients with esophageal squamous cell carcinoma (ESCC), 201 patients with gastric cardiac carcinoma (GCA), 243 patients with non-small cell lung carcinoma (NSCLC) and 350 healthy individuals without cancer. The result showed that the frequency of the -181G allele in ESCC, GCA and NSCLC patients was significantly higher than that in healthy controls (P = 0.019, 0.023 and 0.004, respectively). Compared with the A/A genotype, genotypes with the -181G allele (A/G + G/G) significantly increased susceptibility to all three tumors, with adjusted odds ratio of 1.83 (95% CI = 1.12-2.99) for ESCC, 1.96 (95% CI = 1.17-3.29) for GCA and 2.00 (95% CI = 1.23-3.24) for NSCLC. Stratification analysis showed that smoking did not significantly influence the association between the MMP-7-181A/G and GCA or NSCLC, while the -181G allele only significantly increased susceptibility to ESCC among smokers. In addition, association between the -181G allele and susceptibility to ESCC and GCA showed significance only among individuals with family history of upper gastrointestinal cancer. The correlation of the MMP-7-181A/G polymorphism with potential of lymphatic metastasis was not observed in all three tumors. The study suggested that, the MMP-7-181A/G polymorphism might be a candidate marker for predicting individuals who are at higher risk to certain tumors but might not be used to predict potential of lymphatic metastasis in ESCC, GCA and NSCLC.

Adenocarcinoma↗
PubMed2005

No association of the matrix metalloproteinase 1 promoter polymorphism with susceptibility to esophageal squamous cell carcinoma and gastric cardiac adenocarcinoma in northern China.

AIM: To investigate association of the 2G or 1G single nucleotide polymorphism (SNP) in matrix metalloproteinase 1 (MMP1) promoter with susceptibility to esophageal squamous cell carcinoma (ESCC) and gastric cardiac adenocarcinoma (GCA) in a population of North China. METHODS: MMP1 promoter SNP was genotyped by polymerase-chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analysis in 417 cancer patients (234 ESCC and 183 GCA) and 350 healthy controls. RESULTS: The genotype frequencies of the MMP1 promoter SNP in healthy controls were 55.4% (2G/2G), 30% (1G/2G) and 14.6% (1G/1G), respectively. The genotype and allelotype distribution in ESCC and GCA patients was not significantly different from that in healthy controls (all P values were above 0.05). Compared with the 1G/1G genotype, neither the 2G/2G nor in combination with the 1G/2G genotype significantly modified the risk of developing ESCC and GCA, the adjusted odds ratio was 1.28 (95%CI = 0.78-2.09), 1.23 (95%CI = 0.38-2.05) in ESCC and 1.39 (95%CI = 0.80-2.41), 1.34 (95%CI = 0.74-2.40) in GCA, respectively. When stratified by smoking status and family history of upper gastrointestinal cancer, the 2G/2G genotype alone or in combination with the 1G/2G genotype also did not show any significant influence on the risk of ESCC and GCA development. In addition, influence of the MMP1 SNP on lymphatic metastasis in ESCC and GCA was also not observed. CONCLUSION: The 2G or 1G SNP in the MMP1 promoter might not modify the risk of ESCC and GCA development and might not be used as a stratification marker to predict the potential of lymphatic metastasis in these two tumor types.

Adenocarcinoma↗
PubMed2005

Inhibition of Hepatitis B virus gene expression by single and dual small interfering RNA treatment.

RNA interference (RNAi) has been successfully applied in suppression of Hepatitis B virus (HBV) replication. To circumvent the problem that mutation in HBV genome may result in resistance when siRNA is further developed as an anti-viral drug, in this study, we established a dual small interfering RNA (siRNA) expression system, which could simultaneously express two different siRNA molecules that can specifically target two genes. To test the effectiveness of this system, we applied this new approach to express simultaneously two different 21-bp hairpin siRNA duplexes that specifically attack the HBs and HBx genes of HBV, respectively, in Bel-7402 and HepG2.2.15 cells. Results indicated that dual siRNA could simultaneously inhibit the expression of HBs and HBx gene by 83.7% and 87.5%, respectively, based on luciferase assays. In addition, dual siRNA molecules were able to significantly reduce the amount of HBV core associated DNA, which is considered as an intracellular replicative intermediate, and the viral DNA in culture supernatant. Therefore, this dual siRNA system provides a more powerful tool for the study of gene function and implicates a potential application in the treatment of viral infection.

Cell Line, Tumor↗
PubMed2005

Preferential growth of single-walled carbon nanotubes on silica spheres by chemical vapor deposition.

The preferential growth of single-walled carbon nanotubes (SWNTs) on silica spheres with various diameters was realized for the first time by chemical vapor deposition (CVD) of methane. SWNTs tend to wrap the silica spheres to form a new superstructure of uniform SWNT nanoclaws when the diameters of the silica spheres are larger than 400 nm. The SWNTs obtained on silica spheres have highly graphitic tubular walls as characterized by Raman spectroscopy and HRTEM. This is a new method to obtain tunable uniform elastic deformation of SWNTs, which may act as the model for the study about the effect of delocalized bending on the properties of SWNTs. In addition, the combination of SWNTs with monodispersed silica spheres could conveniently integrate SWNTs into photonic crystals.

Journal Article↗
PubMed2005

Molecular cytogenetic characteristics of the human hepatocellular carcinoma cell line HCCLM3 with high metastatic potential: comparative genomic hybridization and multiplex fluorescence in situ hybridization.

The HCCLM3 cell line was established at the authors' institute from the lung metastatic lesions of BALB/c nude mice bearing human hepatocellular carcinoma (HCC) from the metastatic HCC cell line MHCC97-H. It has been shown to have a high potential for lung metastases and extensive metastases when the cells are inoculated subcutaneously or orthotopically in athymic nude mice. In the present study, the molecular cytogenetic characteristics of this cell line were evaluated with conventional G-banding, comparative genomic hybridization, and multiplex fluorescence in situ hybridization. A hyperdiploid karyotype of 53-58 chromosomes with 10 marker chromosomes was identified. The chromosomal aberrations such as i(X)(q10), der(Y)t(Y;18)(q12;p11), der(3)t(3;20) (p25;q13), der(4)t(4;8)(q31;q22)5, der(9)t(9;13)(p21;q22), der(14)t(14;22)(p13;q13), and der(15) t(15;21)(q11;q22) were described for the first time in human HCC cells. The analysis of this cell line through a combination of molecular cytogenetic techniques provides information on the possible molecular mechanisms involved in the metastatic process of HCC.

Animals↗
PubMed2005

Functional and structural comparisons of cysteine residues in the Val108 wild type and Met108 variant of human soluble catechol O-methyltransferase.

Catechol O-methyltransferase (COMT) plays an important role in the inactivation of biologically active and toxic catechols. This enzyme is genetically polymorphic with a wild type and a variant form. Numerous epidemiological studies have shown that the variant form is associated with an increased risk of developing estrogen-associated cancers and a wide spectrum of mental disorders. There are seven cysteine residues in human S-COMT, all of which exist as free thiols and are susceptible to electrophilic attack and/or oxidative damage leading to enzyme inactivation. Here, the seven cysteine residues were systematically replaced by alanine residues by means of site-directed mutagenesis. The native forms and cysteine/alanine mutants were assayed for enzymatic activity, thermal stability, methylation regioselectivity, and reactivity of cysteine residues to thiol reagent. Our data showed that although there is only one encoding base difference between these two COMT forms, this difference might induce structural changes in the local area surrounding some cysteine residues, which might further contribute to the different roles they might play in enzymatic activity, and to the different susceptibility to enzyme inactivation.

Catechol O-Methyltransferase↗
PubMed2005

Active tolerance induction and prevention of autoimmune diabetes by immunogene therapy using recombinant adenoassociated virus expressing glutamic acid decarboxylase 65 peptide GAD(500-585).

Tolerance induction of autoreactive T cells against pancreatic beta cell-specific autoantigens such as glutamic acid decarboxylase 65 (GAD65) and insulin has been attempted as a method to prevent autoimmune diabetes. In this study, we investigate whether adenoassociated virus (AAV) gene delivery of multiple immunodominant epitopes expressing GAD(500-585) could induce potent immune tolerance and persistently suppress autoimmune diabetes in NOD mice. A single muscle injection of 7-wk-old female NOD mice with rAAV/GAD(500-585) (3 x 10(11) IU/mouse) quantitatively reduced pancreatic insulitis and efficiently prevented the development of overt type I diabetes. This prevention was marked by the inactivation of GAD(500-585)-responsive T lymphocytes, the enhanced GAD(500-585)-specific Th2 response (characterized by increased IL-4, IL-10 production, and decreased IFN-gamma production; especially elevated anti-GAD(500-585) IgG1 titer; and relatively unchanged anti-GAD(500-585) IgG2b titer), the increased secretion of TGF-beta, and the production of protective regulatory cells. Our studies also revealed that peptides 509-528, 570-585, and 554-546 in the region of GAD(500-585) played important roles in rAAV/GAD(500-585) immunization-induced immune tolerance. These data indicate that using AAV, a vector with advantage for therapeutic gene delivery, to transfer autoantigen peptide GAD(500-585), can induce immunological tolerance through active suppression of effector T cells and prevent type I diabetes in NOD mice.

Animals↗
PubMed2005

Molecularly imprinted solid-phase extraction of (-)-ephedrine from Chinese Ephedra.

Method of molecularly imprinted solid phase extraction (MISPE) of (-)-ephedrine from Chinese Ephedra has been developed in the research. The molecularly imprinted polymer (MIP) with good selectivity and affinity for (-)-ephedrine was synthesized with (-)-ephedrine as the template, methacrylic acid as the functional monomer. The washing and elution conditions in MISPE were selected and optimized for efficient analyte extraction and sample clean-up. A clean analytical HPLC base line of ephedra extract was obtained after MISPE, which indicated that the sample pre-treatment was efficient. Good recovery and precision were obtained in the assessment for the MISPE-HPLC procedure, which demonstrated it is a reliable method and can be used for the determination of (-)-ephedrine in herbal ephedra.

Chromatography, High Pressure Liquid↗