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Biomedical subjects

Wei Liu

Publications and source records attributed to Wei Liu.

At least 433 records · Page 24Linked to original sources
PubMed2003

[Construction and expression of retroviral vector containing bone morphogenetic protein-7].

AIM: To achieve stable and long-term expression of BMP-7 gene in bone marrow stem cells (BMSCs). METHODS: Retrovirus expression vector containing BMP-7 gene was constructed and transfected into packaging cells PT67. After puromycin selection and cells cloning, cell clones producing high level of recombinant virus were obtained. The viruses were used to infect directly BMSCs and the expression of BMP-7 gene in BMSCs was analyzed by immunohistochemical staining. RESULTS: Retrovirus vector containing BMP-7 gene was successfully reconstructed and BMP-7 was expressed in the BMSCs.The transfection rates was about 30%-40%. CONCLUSION: The construction of recombinant retrovirus vector containing BMP-7 gene can provide a reliable tool for the formation of bone or cartilage seed cells in the research of tissue engineering.

Bone Marrow Cells↗
PubMed2003

[Detection and identification of emergence of HBV YMDD motif mutation during lamivudine treatment by hybridization to an oligonucleotide array].

OBJECTIVE: Gene chip technology was set up to quickly and accurately detect and identify the HBV P gene YMDD motif mutation during the chronic hepatitis treated with lamivudine. METHODS: DNA microarrays were prepared by spotting fluorescence labeled probes of target genes onto specially lattice glass slides with robotics. The serum samples from 30 patients with hepatitis B after 68-week treatment with lamivudine were detected double-blind by gene chips and by nucleotide sequences assay technique to identify the rate of emergence of HBV P gene YMDD motif mutation. RESULTS: Twenty-one patients were found HBV P gene YMDD motif mutation by the gene chips including 11 cases with YVDD and 10 cases with YIDD motif mutation. By direct sequencing of the PCR products, 11 cases were found to have YVDD with adenine741 changed into cytidine resulted in methionine552 changed into valine in which 6 cases with adenine669 changed into cytidine and leucine changed into methionine, 10 cases had YIDD motif mutation with guanosine743 altered thymidine methionine552 changed into isoleucine, including 3 cases with thymidine281 changed into cytidine and leucine565 altered proline. CONCLUSION: The gene chip can be used to test HBV YVDD,YIDD motif mutation compared with nucleotide sequences assay technique, the accuracy rate was 100%.

Antiviral Agents↗
PubMed2002

[Difference in action sites between mecamylamine and hexamethonium on nicotinic receptors of sympathetic neurons].

To compare the difference in action sites between mecamylamine (MEC) and hexamethonium (HEX) on nicotinic receptors of sympathetic neurons, we investigated the effects of MEC and HEX on the nicotine-induced currents in cultured superior cervical ganglion neurons by whole-cell patch clamp technique. The IC(50) of MEC and HEX for antagonizing the effect of 0.08 mmol/L nicotine was 0.0012 and 0.0095 mmol/L, respectively. Both MEC and HEX accelerated the desensitization of nicotinic receptors. Furthermore, by comparing their effects at holding potentials 30, 70 and 110 mV, it was indicated that their suppressing effect on the nicotine-induced currents was voltage-dependent. However, different from that of HEX, the inhibitory effect of MEC increased with administering the mixture of MEC and nicotine at intervals of 3 min, indicating a use-dependent effect of MEC. It is concluded that the action site of MEC on nicotinic receptors of sympathetic neurons is different from that of HEX.

Animals↗
PubMed2002

[Culture and identification of nanobacteria in bile].

OBJECTIVE: To study the distribution and identification of nanobacteria in bile and to evaluate the identifying methods of nanobacteria. METHODS: RPMI1640 culture or RPMI1640 culture with 10% heat-inactivated gamma-FBS was added into 75 samples of cystic bile from gallbladders resected in operation. Nanobacteria were identified by immunohistochemical staining, transmission electron microscopy (TEM), and calcific staining. RESULTS: Nanobacteria were found in 45 bile samples with a positive rate of 61.3%. The positive rate of nanobacteria was 75.7% among 37 bile samples with white precipitate adhering to the tube, and was 47.4% among the samples with flocculent precipitate or without precipitate (P < 0.05). The immunohistochemically confirmed presence of nanobacteria was re-confirmed by TEM in all the positive samples. The positive rate, sensitivity, specificity, false positive rate and false negative rate of calcific staining were 38.7%, 58.7%, 93.1%, 6.9% and 41.3% respectively. CONCLUSION: Immunohistochemistry with monoclonal antibody of nanobacteria associated with TEM is useful in identifying nanobacteria. Calcific staining is of great value to identification of nanobacteria. Precipitation of white floccules adhering to the tube is an important microbiological characteristic of nanobacteria.

Adult↗
PubMed2002

Association of MHC class I and class II gene polymorphisms with vaccine or challenge response to Salmonella enteritidis in young chicks.

Salmonella enteritidis (SE) is a worldwide source of salmonellosis in humans, caused mainly by consumption of contaminated poultry products. The major histocompatibility complex (MHC) class I and class II molecules, which function as antigen-presentation structures, are involved in both macrophage and dendritic cell immune response to Salmonella and may, therefore, play an important role in host resistance to infections. The chicken MHC class I and class II were investigated as candidate genes for immune response to SE. We characterized the complete MHC class I cDNA sequences for an outbred broiler line and four diverse highly inbred lines: two MHC-congenic Leghorn (G-B2 and G-B1), one Egyptian Fayoumi (M15.2), and one Spanish (Sp21.1), to define the allelic sequences within these lines, so that we might study the association between particular MHC polymorphisms and response to SE. The F1 offspring of outbred broiler sires crossed with three inbred lines (G-B1, G-B2, and Fayoumi) were evaluated as young chicks for either bacterial load in spleen and cecum after pathogenic SE inoculation or antibody level after SE vaccination. Alleles defined by a Lys(148)-->Met(148) polymorphism in the MHC class I alpha(2) domain were associated with spleen bacterial load after SE challenge. These results suggest that particular MHC haplotypes may contribute to control of responses to SE, and that particular polymorphisms may serve as markers for genetic resistance to SE in the chicken.

Animals↗
PubMed2002

Purification, crystallization and preliminary X-ray diffraction analysis of a novel mannose-binding lectin from Gastrodia elata with antifungal properties.

A plant antifungal protein, Gastrodia antifungal protein (GAFP-1) has been isolated from terminal corms of the orchid Gastrodia elata B1 f. elata, purified to homogeneity and crystallized by means of the hanging-drop vapour-diffusion method. The best quality crystals grew over several months at 277 K. The crystal used for data collection belongs to the space group P2(1)2(1)2, with unit-cell parameters a = 61.087, b = 91.488, c = 81.132 A. Using a synchrotron-radiation source, the resolution limit of the data reached 2.0 A, with an overall R(merge) of 0.097 and a completeness of 99.8%. Four independent molecules were estimated to be present in the asymmetric unit, with a solvent content of 46.3%. This data will help to solve the first structure of a monomeric monocot mannose-binding lectin.

Amino Acid Sequence↗
PubMed2002

[Genotyping of hepatitis C virus by hepatitis gene diagnosis microarray].

OBJECTIVE: To study the preparation of hepatitis C virus (HCV) diagnosis microarray and its accuracy in diagnosis of gene type of hepatitis C virus. METHODS: Probe and primer and primers were designed in 5'-untranslated region and C region of hepatitis C virus gene. The probes were synthesized by DNA synthesizer. Solutions of probe of the final concentration of 50 micromol/L were made by dissolving the probes into sodium carbonate buffer. Hepatitis C virus genotype array spotting was performed by pin-based spotting robot PixSys5500 with CMP3 pin. The gene chips were prepared by spotting the probes onto the specially treated glass sliders. Sixty HCV RNA positive serum samples were obtained from the in-patients of the Nanjing Second Hospital (experimental group), and 60 HCV RNA negative serum samples were obtained from the healthy people undergoing physical examination (control group). Quantitative examination of serum HCV RNA was made by fluorescent quantitation PCR. The HCV RNA in the serum specimens of the experimental group (with the HCV RNA concentration of more than 500 copies/ml) and of the control group (with the HCV RNA concentration of less than 500 copies/ml) was isolated and purified, underwent reversed transcription and nested PCR to be amplified, and then genotyped by gene microarray and HCV RNA sequencing. During the experiment, double blind method was used. RESULTS: Tested by the gene microarray, the serum specimens in the experimental group were all HCV RNA positive, out of which 46 cases were 1b type, 3 cases were 3a type, 3 cases were 3b type, 2 cases were 2a type, 2 cases were 2b type, 2 cases were 1b + 2a type, and 2 cases were 3a type. Tested by nucleotide sequencing assay, 50 cases were 1b type, 3 cases were 3a type, 3 cases were 3b type, 2 cases were 2a type, and 2 cases were 2b type. The double-blind test results showed a coincidence rate of 93.3% in genotyping HCV by these two methods. CONCLUSION: Hepatitis gene microarray can be used in detection of serum HCV RNA and in diagnostic genotyping with great accuracy.

Genotype↗
PubMed2002

Sugar interaction with metal ions. The coordination behavior of neutral galactitol to Ca(II) and lanthanide ions.

The crystal structures of CaCl(2).galactitol.4 H(2)O and 2EuCl(3).galactitol.14 H(2)O were determined to compare the coordination behavior of Ca and lanthanide ions. The crystal system of the Ca-galactitol complex, CaCl(2).C(6)H(14)O(6).4 H(2)O, is monoclinic, Cc space group. Each Ca ion is coordinated to eight oxygen atoms, four from two galactitol molecules and four from water molecules. Galactitol provides O-2, -3 to coordinate to one Ca(2+), and O-4, -5 with another Ca(2+), to form a chain structure. The crystal system of the Eu-galactitol complex, 2EuCl(3).C(6)H(14)O(6).14 H(2)O, is triclinic, P1; space group. Each Eu ion is coordinated to nine oxygen atoms, three from an alditol molecule and six from water molecules. Each galactitol provides O-1, -2, -3 to coordinate with one Eu(3+) and O-4, -5, -6 with another Eu(3+). The other water molecules are hydrogen-bonded in the structure. The similar IR spectra of Pr-, Nd-, Sm-, Eu-, Dy-, and Er-galactitol complexes show that those lanthanide ions have the same coordination mode to neutral galactitol. The Raman spectra also confirm the formation of metal ion-carbohydrate complexes.

Calcium Chloride↗
PubMed2002

[Tissue engineered tendon with skin fibroblasts as seed cells, a preliminary study].

OBJECTIVE: To investigate the effect of tissue engineered tendon using autologous dermal fibroblasts in repairing tendon damage. METHODS: Skin tissues were resected from abdomen of 5 pigs. Fibroblasts were isolated from the skin pieces and cultured in vitro. Bundles of polyglycolic acid (PGA) were arranged in parallel and mixed with the suspension of fibroblasts to form a cell-scaffolded construct, which was further cultured in vitro for 1 week. The tendon of musculus flexor digitorum superficialis of pig's right leg was cut with a defect 3 cm long and then bridged with the cultured construct. Six weeks later, specimens of the regenerated tendon of right musculus flexor digitorum superficialis and specimens of corresponding left leg were taken for gross examination, microscopy and biomechanical analysis. RESULTS: After implantation of the fibroblast-biomaterial complex the wounds healed up and the pigs moved well. The histology of the implanted tendon was similar to that of natural tendon. The breaking strength and maximum tensile force were 173.0 +/- 18.2 N and 18.9 +/- 1.9 MPa, reaching 57.4% and 51.9% of those of normal tendon respectively. CONCLUSION: Skin fibroblasts can be used as seed cells to regenerate tendon with normal structure and function.

Animals↗
PubMed2002

The reduction potential of nitric oxide (NO) and its importance to NO biochemistry.

A potential of about -0.8 (+/-0.2) V (at 1 M versus normal hydrogen electrode) for the reduction of nitric oxide (NO) to its one-electron reduced species, nitroxyl anion (3NO-) has been determined by a combination of quantum mechanical calculations, cyclic voltammetry measurements, and chemical reduction experiments. This value is in accord with some, but not the most commonly accepted, previous electrochemical measurements involving NO. Reduction of NO to 1NO- is highly unfavorable, with a predicted reduction potential of about -1.7 (+/-0.2) V at 1 M versus normal hydrogen electrode. These results represent a substantial revision of the derived and widely cited values of +0.39 V and -0.35 V for the NO/3NO- and NO/1NO- couples, respectively, and provide support for previous measurements obtained by electrochemical and photoelectrochemical means. With such highly negative reduction potentials, NO is inert to reduction compared with physiological events that reduce molecular oxygen to superoxide. From these reduction potentials, the pKa of 3NO- has been reevaluated as 11.6 (+/-3.4). Thus, nitroxyl exists almost exclusively in its protonated form, HNO, under physiological conditions. The singlet state of nitroxyl anion, 1NO-, is physiologically inaccessible. The significance of these potentials to physiological and pathophysiological processes involving NO and O2 under reductive conditions is discussed.

Electrochemistry↗
PubMed2002

Soluble syndecan-1 promotes growth of myeloma tumors in vivo.

Syndecan-1 (CD138) is a transmembrane heparan sulfate-bearing proteoglycan expressed by most myeloma plasma cells that regulates adhesion, migration, and growth factor activity. In patients with myeloma, shed syndecan-1 accumulates in the bone marrow, and high levels of syndecan-1 in the serum are an indicator of poor prognosis. To test the effect of soluble syndecan-1 on tumor cell growth and dissemination, ARH-77 B-lymphoid cells were engineered to produce a soluble form of syndecan-1. Controls included vector only (neo)-transfected cells and cells transfected with full-length syndecan-1 complementary DNA that codes for the cell surface form of syndecan-1. Assays reveal that all 3 transfectants have similar growth rates in vitro, but cells expressing soluble syndecan-1 are hyperinvasive in collagen gels relative to controls. When injected into the marrow of human bones that were implanted in severe combined immunodeficient mice, tumors formed by cells expressing soluble syndecan-1 grow faster than tumors formed by neo-transfected cells or by cells expressing cell surface syndecan-1. In addition, cells bearing cell surface syndecan-1 exhibit a diminished capacity to establish tumors within the mice as compared with both neo- and soluble syndecan-1-transfected cells. Tumor cell dissemination to a contralateral human bone is detected significantly more often in the tumors producing soluble syndecan-1 than in controls. Thus, high levels of soluble syndecan-1 present in patients with myeloma may contribute directly to the growth and dissemination of the malignant cells and thus to poor prognosis.

Animals↗
PubMed2002

Thermally invariant dielectric coatings for micromirrors.

Thermal expansion-induced curvature becomes a major effect in micromirrors as the mirror diameter exceeds 100 microm. Such mirrors are used for optical switching, scanning, and many other applications. By using multilayer coatings instead of a single metal reflector, one can use the mechanical properties of the multilayer to create mirrors with zero curvature across temperature. We demonstrate the fabrication of such thermally invariant mirrors using dielectric coatings. A semianalytic model based on free-plate elastic theory is developed that uses empirical parameters in place of the true thermal expansion coefficients of the coating materials. Micromirrors are demonstrated that maintain their design curvature to within lambda/60 for lambda = 633 nm across an operating range from 21 degrees C to 58 degrees C.

Journal Article↗
PubMed2002

[Repair of meniscal defects with autologous tissue-engineered fibrocartilage].

OBJECTIVE: To repair critical-sized meniscal defects in an immunocompetent mammal by tissue engineering approach. METHODS: 15 45-day-old Changfeng crossbred pigs were selected as experimental animals. Autologous fibrochondrocytes were obtained from left knee menisci by modified Klagsbrun's method and were proliferated in vitro to a proper amount. A 1-cm-long full-layer defect of right medial meniscus was created anterior to the medial collateral ligament. PGA-fibrochondrocyte-Pluronic complex, fibrochondrocyte-Pluronic complex or PGA only was respectively implanted into the defects. We used intact menisci and untreated meniscal defects as controls. Samples respectively obtained in 9 w, 16 w and 25 w were appraised by general observation, histology, biochemistry and biomechanics. RESULTS: From the sights of general morphology, histological structure and Young's Modulus (59.7% of that in normal meniscus at 25 w), the PGA-cell-Pluronic complex can form the best quality tissue, which can stabilize the GAG ratio (74.5% of that in normal cartilage at 25 w) of femoral entocondyle cartilage. CONCLUSION: Autologous tissue-engineered fibrocartilage is a promising feasible method to regenerate or reconstruct menisci so as to hold back the degenerative changes of the knee.

Animals↗
PubMed2002

Maintaining low HIV type 1 env genetic diversity among injection drug users infected with a B/C recombinant and CRF01_AE HIV type 1 in southern China.

HIV-1 outbreaks in Guangxi Province, southern China were initiated from two separate border cities in 1996 and 1997. Drug users in Pingxiang City, which borders Vietnam, were infected with CRF01_AE HIV-1, and drug users in Baise City, which borders Yunan Province, were infected with a novel B/C recombinant HIV-1. Since 1997, HIV-1 has been rapidly spreading in Guangxi, including its capital city Nanning. Survey data indicated that HIV-1 prevalence among IDUs in new outbreak regions increased 8 to 42% within 1 year. The B/C recombinants obtained from five separate regions in Guangxi, which span a 4-year time frame, were remarkable for their low intersubject env V3 diversity, less than 0.2%. Similarly, the CRF01_AE from IDUs over a 3-year time frame had low intersubject env V3 diversity of less than 1.6%. Different patterns of sequence variations in the V3 and V4 regions were observed for the B/C recombinant and the CRF01_AE HIV1. The rapid spreading of homogeneous HIV-1 strains in Guangxi may have important implications for HIV transmission as well as vaccine development and evaluation.

Amino Acid Sequence↗
PubMed2002

Kinetic thermal response and damage in laser coagulation of tissue.

BACKGROUND AND OBJECTIVES: Laser induced interstitial coagulation has become a method of treating different types of tumors. Theoretical modeling and analysis may be used to better understand the complex process involved in the laser coagulation and optimized the dosimetry of laser thermotherapy. STUDY DESIGN/MATERIALS AND METHODS: A full dynamic theoretical model was developed to simulate the dynamic evolution of coagulation in tissue, which accounted for the dynamics of the temperature and damage dependence of optical properties, thermal properties, and blood-perfusion rate. The simulation of the temperature distribution, coagulation depth and its hysteresis during laser thermotherapy for full-dynamic model are compared with the calculations from other models. RESULTS: Increased scattering in the near surface of applicator prevents light penetration into deeper region. Moreover, rise in temperature increases both blood flow at the periphery of coagulation region and thermal properties, which reduces the damage depth and its hysteresis. It results in a considerable overestimation of the temperature distribution and damage depth ignoring the dynamic of optical properties. The coagulation would be limited in a smaller region and there is no hysteresis if blood perfusion is regarded as a constant. In contrast, the hysteresis is overestimated if blood perfusion is ignored. Ignoring the dynamics of thermal parameters, there is also overestimation of the rise in temperature and damage depth. CONCLUSIONS: Mathematical modeling techniques that simulate laser coagulation may not provide reliable information unless they take into account these dynamic parameters.

Animals↗
PubMed2002

Vitamin D arrests thyroid carcinoma cell growth and induces p27 dephosphorylation and accumulation through PTEN/akt-dependent and -independent pathways.

We investigated the effects of 1,25-dihydroxycholecalciferol vitamin D(3) (VD) and its noncalciomimetic analog EB1089 on thyroid carcinoma cell growth. VD and EB1089 exhibited anti-proliferative effects in a dose-dependent manner as determined by [(3)H]thymidine incorporation and MIB-1 immunolabeling. VD or EB1089 resulted in similar G(1)-phase arrest. Neither apoptosis nor differentiation was affected. VD and EB1089 induced increased nuclear protein expression of the cyclin-dependent kinase inhibitor, p27(kip1) (p27). VD/EB1089 effects paralleled but were not additive to those of the proteasome inhibitor LLnL, consistent with reduced p27 degradation. As p27 phosphorylation and association with Skp2 is a key step in its degradation, we examined the effects of VD/EB1089 on this reaction. Despite increased total p27, the pThr content of p27 remained unaffected, an effect confirmed by diminished association with Skp2 as well as in situ phosphorylation. Moreover, phosphatase inhibition abrogated the effect of VD/EB1089 on p27 accumulation consistent with a role for phosphatase action in mediating this VD effect. Although VD/EB1089 resulted in comparable increases in p27 in WRO and NPA cells, only WRO but not NPA cells demonstrated a change in the phosphatase PTEN and its downstream target pAkt/PKB in response to VD/EB1089. Transfection of PTEN resulted in p27 accumulation and was partially additive to the effect of VD/EB1089. Moreover, treatment with PI-3 kinase inhibitors decreased pAkt/PKB and increased p27 in both WRO and NPA cells highlighting the potential role of this downstream pathway in regulating p27 in the thyroid. These findings point to a novel mechanism of action for VD/EB1089 inhibition of thyroid carcinoma cell growth by p27 hypophosphorylation, diminished association with Skp2, and consequent accumulation. This effect can be mediated but is not essentially dependent on the phosphatase PTEN/Akt/PKB pathway. These properties support the potential utility of VD analogs in the treatment of thyroid carcinomas irrespective of their PTEN/pAkt status.

Antineoplastic Agents↗
PubMed2002

Comparison of helix interactions in membrane and soluble alpha-bundle proteins.

Helix-helix interactions are important for the folding, stability, and function of membrane proteins. Here, two independent and complementary methods are used to investigate the nature and distribution of amino acids that mediate helix-helix interactions in membrane and soluble alpha-bundle proteins. The first method characterizes the packing density of individual amino acids in helical proteins based on the van der Waals surface area occluded by surrounding atoms. We have recently used this method to show that transmembrane helices pack more tightly, on average, than helices in soluble proteins. These studies are extended here to characterize the packing of interfacial and noninterfacial amino acids and the packing of amino acids in the interfaces of helices that have either right- or left-handed crossing angles, and either parallel or antiparallel orientations. We show that the most abundant tightly packed interfacial residues in membrane proteins are Gly, Ala, and Ser, and that helices with left-handed crossing angles are more tightly packed on average than helices with right-handed crossing angles. The second method used to characterize helix-helix interactions involves the use of helix contact plots. We find that helices in membrane proteins exhibit a broader distribution of interhelical contacts than helices in soluble proteins. Both helical membrane and soluble proteins make use of a general motif for helix interactions that relies mainly on four residues (Leu, Ala, Ile, Val) to mediate helix interactions in a fashion characteristic of left-handed helical coiled coils. However, a second motif for mediating helix interactions is revealed by the high occurrence and high average packing values of small and polar residues (Ala, Gly, Ser, Thr) in the helix interfaces of membrane proteins. Finally, we show that there is a strong linear correlation between the occurrence of residues in helix-helix interfaces and their packing values, and discuss these results with respect to membrane protein structure prediction and membrane protein stability.

Amino Acid Sequence↗