Biomedical subjects

Li Liu

Publications and source records attributed to Li Liu.

At least 73 records · Page 4Linked to original sources

PubMed2006

Dynamic changes of HBV DNA in serum and peripheral blood mononuclear cells of chronic hepatitis patients after lamivudine treatment.

AIM: To study the dynamic changes of hepatitis B virus (HBV) DNA in serum and peripheral blood mononuclear cells (PBMCs) of patients after lamivudine therapy. METHODS: A total of 72 patients with chronic HBV infection were included in this study. All patients were confirmed to have the following conditions: above 16 years of age, elevated serum alanine aminotransferase (ALT), positive hepatitis B e antigen (HBeAg), positive HBV DNA in serum and PBMCs, negative antibodies against HAV, HCV, HDV, HEV. Other possible causes of chronic liver damages, such as drugs, alcohol and autoimmune diseases were excluded. Seventy-two cases were randomly divided into lamivudine treatment group (n = 42) and control group (n = 30). HBV DNA was detected both in serum and in PBMCs by fluorescence quantitative polymerase chain reaction (PCR), during and after lamivudine treatment. RESULTS: In the treatment group, HBV DNA became negative both in serum and in PBMC, of 38 and 25 out of 42 cases respectively during the 48 wk of lamivudine treatment, the negative rate was 90.5% and 59.5% respectively. In the control group, the negative rate was 23.3% and 16.7% respectively. It was statistically significant at 12, 24 and 48 wk as compared with the control group (P<0.005). The average conversion period of HBV DNA was 6 wk (2-8 wk) in serum and 16 wk (8-24 wk) in PBMC. CONCLUSION: Lamivudine has remarkable inhibitory effects on HBV replication both in serum and in PBMCs. The inhibitory effect on HBV DNA in PBMCs is weaker than that in serum.

Adolescent↗

PubMed2006

Development of an analytical method for organotin compounds in fortified flour samples using microwave-assisted extraction and normal-phase HPLC with UV detection.

The normal high-performance liquid chromatography with UV detection was applied for the determination of tributyltin chloride (TBT), triphenyltin chloride (TPhT), tetraphenyltin (TrPhT), triethyltin chloride (TET) and tetraethyltin (TrET) from flour samples. The separation was performed in the isocratic mode on cyanopropyl column with a mobile phase of hexane-acetonitrile-THF (97/1/2). Under the experimental conditions used, quantitative limit of TBT, TPhT, TrPhT, TET and TrET are 0.95, 0.46, 0.97, 0.75 and 0.96 microg/ml, respectively. Microwave-assisted extraction of organotin (OT) compounds at 100 degrees C with an extraction time of 3 min was described. The extraction of organotin can be finished in acetic acid-hexane (20/80) medium. The quantitative extraction of five organotin compounds was achieved with recoveries ranging from 88 to 101% R.S.D. 3-8%.

Analytic Sample Preparation Methods↗

PubMed2006

Imaging beta-galactosidase activity using 19F chemical shift imaging of LacZ gene-reporter molecule 2-fluoro-4-nitrophenol-beta-D-galactopyranoside.

2-Fluoro-4-nitrophenol-beta-D-galactopyranoside (OFPNPG) belongs to a novel class of NMR active molecules (fluoroaryl-beta-D-galactopyranosides), which are highly responsive to the action of beta-galactosidase (beta-gal). OFPNPG has a single 19F peak (-55 ppm relative to aqueous sodium trifluoroacetate). Upon cleavage by beta-gal, the pH sensitive aglycone 2-fluoro-4-nitrophenol (OFPNP) is observed at a chemical shift of -59 to -61 ppm. The chemical shift response is sufficient to observe beta-gal activity using chemical shift imaging (CSI). 19F CSI studies of enzyme activity and lacZ gene expression in 9L-glioma and MCF7 breast cancer cells are presented, providing further evidence for the utility of OFPNPG as a gene-reporter molecule for future in vivo studies.

Breast Neoplasms↗

PubMed2006

Controlled hydrothermal synthesis and growth mechanism of various nanostructured films of copper and silver tellurides.

Various nanostructured films of copper and silver tellurides were hydrothermally grown on the corresponding metal substrates through reactions between metal foils and tellurium powder in different media. Interesting morphologies including nanowires, nanorods, nanobelts, nanosheets, and hierarchical dendrites were obtained. The nanostructured films were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). A growth mechanism was proposed based on the characterization results. This study provides a low-temperature, solution-phase approach to grow low-dimensional, nanostructured metal tellurides with controllable morphologies.

Journal Article↗

PubMed2006

Structural analysis of water-soluble glucans from the root of Angelica sinensis (Oliv.) Diels.

Two water-soluble glucans (designated APS-1cI and APS-1cII) were extracted from the roots of Angelica sinensis (Oliv.) Diels and further purified by anion-exchange and gel-filtration chromatography. Their molecular weights were determined to be 1.7 x 10(5) and 3.9 x 10(4)Da, respectively. The structures of the purified glucans were investigated by a combination of chemical and instrumental analysis, such as methylation analysis, periodate oxidation, GC-MS, as well as FTIR and NMR spectroscopy ((1)H, (13)C, H-H COSY, HSQC, HMBC, TOCSY and NOESY). The data obtained indicated that APS-1cI was a linear alpha-glucan composed of only (1-->6)-alpha-D-Glcp, and APS-1cII had a repeating unit consisting of (1-->4)-alpha-D-Glcp and (1-->6)-alpha-D-Glcp in a molar ratio of 4:1. Such glucans isolated from A. sinensis (Oliv.) Diels have not been previously reported.

Angelica sinensis↗

PubMed2006

Double-responsive polymer brushes on the surface of colloid particles.

Well-defined poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes were synthesized on the surface of polystyrene latex particles by atom transfer radical polymerization (ATRP). It was found that the surface-initiated polymerization of DMAEMA catalyzed by CuCl/CuCl(2)/bpy was under good control in the solvent of acetone/water at ambient temperature (35 degrees C). High-density PDMAEMA brushes with low polydispersity (PDI 1.21) were obtained. TEM results demonstrate that the PDMAEMA-grafted particles have core-shell structure. Dynamic light scattering studies indicate that the particles with PDMAEMA brushes are both pH and temperature responsive.

Journal Article↗

PubMed2006

Voltammetric determination of mefenamic acid at lanthanum hydroxide nanowires modified carbon paste electrodes.

Lanthanum hydroxide nanowires modified carbon paste electrode (LNW/CPE) exhibiting an electrocatalytic response toward the oxidation of mefenamic acid (MFA) is described. The catalytic action of the LNW/CPE on the oxidation of MFA via one-electron and one-proton transfer is attributed to the formation of the porous construction and the increase of efficient surface of the electrode due to the adulteration of LNW with carbon powders. Using the LNW/CPE, a linear sweep voltammetric method for the determination of MFA and other drugs with diphenylamine parent is proposed. A linear range of 2.0 x 10(-11) to 4.0 x 10(-9)mol L(-1) is obtained along with a detection limit of 6.0 x 10(-12)mol L(-1).

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2006

Cell aggregation-induced FGF8 elevation is essential for P19 cell neural differentiation.

FGF8, a member of the fibroblast growth factor (FGF) family, has been shown to play important roles in different developing systems. Mouse embryonic carcinoma P19 cells could be induced by retinoic acid (RA) to differentiate into neuroectodermal cell lineages, and this process is cell aggregation dependent. In this report, we show that FGF8 expression is transiently up-regulated upon P19 cell aggregation, and the aggregation-dependent FGF8 elevation is pluripotent stem cell related. Overexpressing FGF8 promotes RA-induced monolayer P19 cell neural differentiation. Inhibition of FGF8 expression by RNA interference or blocking FGF signaling by the FGF receptor inhibitor, SU5402, attenuates neural differentiation of the P19 cell. Blocking the bone morphogenetic protein (BMP) pathway by overexpressing Smad6 in P19 cells, we also show that FGF signaling plays a BMP inhibition-independent role in P19 cell neural differentiation.

Animals↗

PubMed2006

Interaction of Skp1 with CENP-E at the midbody is essential for cytokinesis.

Centromere-associated protein E (CENP-E) is a kinesin-related microtubule motor protein that is essential for chromosome congression during mitosis. Our previous studies show that microtubule motor CENP-E represents a link between attachment of spindle microtubules and the mitotic checkpoint signaling cascade. However, the molecular function of CENP-E at the midbody had remained elusive. Here we show that CENP-E interacts with Skp1 at the midbody and participates in cytokinesis. CENP-E interacts with Skp1 in vitro and in vivo via its coiled-coil domain. Our yeast two-hybrid assays mapped the binding interfaces to the central stalk region of CENP-E (955-1571 aa) and the C-terminal 33 amino acids of Skp1, respectively. Our immunocytochemical studies revealed that CENP-E targets to the midbody prior to Skp1 and the midbody localization of CENP-E becomes diminished as Skp1 arrives at the midbody. Suppression of Skp1 in mitotic HeLa cells by siRNA resulted in accumulation of telophase cells with elongated inter-cell bridges and with midbodies stretched 2-3 times longer than that of normal cells. These Skp1-eliminated or -suppressed cells accumulate higher level of CENP-E, suggesting that spatiotemporal regulation of CENP-E degradation at the midbody is essential for cytokinesis. Over-expression of Skp1 lacking the CENP-E-binding domain confirmed that Skp1-CENP-E interaction is essential for faithful cytokinesis. We hypothesize that CENP-E degradation is essential for faithful mitotic exit and the proteolysis of CENP-E is mediated by SCF via a direct Skp1 link.

Cell Cycle Proteins↗

PubMed2006

Dynamics study of the reaction OH- + C2H2-->C2H- + H2O with crossed beams and density-functional theory calculations.

The proton transfer reaction between OH- and C2H2, the sole reactive process observed over the collision energy range from 0.37 to 1.40 eV, has been studied using the crossed beam technique and density-functional theory (DFT) calculations. The center of mass flux distributions of the product C2H- ions at three different energies are highly asymmetric, characteristic of a direct process occurring on a time scale much less than a rotational period of any transient intermediate. The maxima in the flux distributions correspond to product velocities and directions close to those of the precursor acetylene reactants. The reaction quantitatively transforms the entire exothermicity into internal excitation of the products, consistent with an energy release motif in which the proton is transferred early, in a configuration in which the forming bond is extended. This picture is supported by DFT calculations showing that the first electrostatically bound intermediate on the reaction pathway is the productlike C2H- H2O species. Most of the incremental translational energy in the two higher collision energy experiments appears in product translational energy, and provides an example of induced repulsive energy release characteristic of the heavy+light-heavy mass combination.

Journal Article↗

PubMed2006

Preparation of chitosan derivative with polyethylene glycol side chains for porous structure without specific processing technique.

The graft copolymer, chitosan-g-polyethylene glycol (PEG), was prepared through graft polymerization of PEG chains to chitosan due to the esterification reaction between PEG and 6-O-succinate-N-phthaloyl-chitosan (PHCSSA). The graft copolymer with porous structure was observed from scanning electron micrographs. It is a potential method to combine chitosan with the hydrophilic synthetic polymers. The graft reaction was carried out in homogeneous system and yielded copolymers with high grafting content. FTIR, NMR, XRD, DSC, spectrofluorophotometer and SEM were detected to characterize the copolymer.

Biocompatible Materials↗

PubMed2006

Sustained FVIII expression and phenotypic correction of hemophilia A in neonatal mice using an endothelial-targeted sleeping beauty transposon.

Hemophilia A, deficiency of coagulation factor VIII (FVIII), is an attractive candidate for gene therapy as expression of modest amounts of FVIII can provide therapeutic benefit. Most gene transfer approaches for hemophilia have focused on the liver, as this is the major source of endogenous FVIII; however, increasing evidence suggests that endothelial cells are capable of synthesis and release of FVIII. Here the Sleeping Beauty (SB) transposon is employed to target long-term expression of the human B-domain-depleted FVIII gene (approved gene symbol F8) within lung endothelia of hemophilic mice. As the formation of inhibitory antibodies to FVIII has been a significant impediment toward achieving therapeutic plasma levels after gene or protein therapy, we chose to perform gene transfer in neonatal mice, which are more likely to be immune tolerant. Using this approach, low therapeutic levels of FVIII ( approximately 10%), as well as phenotypic correction of the bleeding disorder, were achieved in all animals that received the FVIII transposon and functional transposase throughout the duration of the study (24 weeks). Rechallenge of these animals with additional gene transfer did not result in significant increases in FVIII levels, due mainly to increases in inhibitory antibodies. These studies demonstrate the feasibility of using endothelial-targeted SB transposons for the treatment of hemophilia A.

Animals↗

PubMed2006

Distinct memory traces for two visual features in the Drosophila brain.

The fly Drosophila melanogaster can discriminate and remember visual landmarks. It analyses selected parts of its visual environment according to a small number of pattern parameters such as size, colour or contour orientation, and stores particular parameter values. Like humans, flies recognize patterns independently of the retinal position during acquisition of the pattern (translation invariance). Here we show that the central-most part of the fly brain, the fan-shaped body, contains parts of a network mediating visual pattern recognition. We have identified short-term memory traces of two pattern parameters--elevation in the panorama and contour orientation. These can be localized to two groups of neurons extending branches as parallel, horizontal strata in the fan-shaped body. The central location of this memory store is well suited to mediate translational invariance.

Adenylyl Cyclases↗

PubMed2006

Specialization of phonological and semantic processing in Chinese word reading.

The purpose of this study was to examine the neurocognitive network for processing visual word forms in native Chinese speakers using functional magnetic resonance imaging (fMRI). In order to compare the processing of phonological and semantic representations, we developed parallel rhyming and meaning association judgment tasks that required explicit access and manipulation of these representations. Subjects showed activation in left inferior/middle frontal gyri, bilateral medial frontal gyri, bilateral middle occipital/fusiform gyri, and bilateral cerebella for both the rhyming and meaning tasks. A direct comparison of the tasks revealed that the rhyming task showed more activation in the posterior dorsal region of the inferior/middle frontal gyrus (BA 9/44) and in the inferior parietal lobule (BA 40). The meaning task showed more activation in the anterior ventral region of the inferior/middle frontal gyrus (BA 47) and in the superior/middle temporal gyrus (BA 22,21). These findings are consistent with previous studies in English that suggest specialization of inferior frontal regions for the access and manipulation of phonological vs. semantic representations, but also suggest that this specialization extends to the middle frontal gyrus for Chinese. These findings are also consistent with the suggestion that the left middle temporal gyrus is involved in representing semantic information and the left inferior parietal lobule is involved in mapping between orthographic and phonological representations.

Acoustic Stimulation↗

PubMed2006

TGF-betal transgenic mouse model of thoracic irradiation: modulation of MMP-2 and MMP-9 in the lung tissue.

To investigate the effects of TGF-beta1 on the two gelatinases (MMP-2 and MMP-9), and their roles in lung remodeling after irradiation-induced lung injury. Expressions of TGF-beta1 were measured with western blot, and expressions of MMP-2 and MMP-9 were analyzed with zymography in a -TGF-beta1 transgenic mouse model after thoracic irradiation with 12 Gy. We found expressions of TGF-beta1 in the lung from the transgenic mice were three folds as compared to those from control mice. With densitometrical analysis, we found a significant decrease in MMP-9 activity in lung homogenates from the transgenic mice as compared with those from non-transgenic control mice 8 weeks after sham-irradiation (relative MMP-9 activity: C: 1.000 0.1091; TG: 0.4772 +/- 0.470 (n = 8, P < 0.05). But MMP-2 was constitutively expressed in the lung homogenates from the transgenic mice as compared to those from control mice 8 weeks after sham-irradiation (relative MMP-2 activity 8 weeks after sham-irradiation: C: 1.000 +/- 0.1556, TG: 1.0075 +/- 0.1472). Eight weeks after thoracic irradiation with 12 Gy, we observed a significant increase of MMP-2 and MMP-9 activity in lung homogenates from both transgenic and normal mice. In TGF-beta1 transgenic mice relative MMP-9 activity was increased to 1.5321 +/- 0.2217 folds 8 weeks after thoracic irradiation with 12 Gy as compared to those after sham-irradiation (1.000 +/- 0.2153), and relative MMP-2 activity was increased to 1.7142 +/- 0.4231 folds. Our results show that TGF-beta1 itself down-regulates activity of MMP-9, thereby decreases ECM degradation in lungs of TGF-beta1 transgenic mice. Also we find that ionizing irradiation upregulates both MMP-2 and MMP-9 activity. Over-expressions of MMP-9 and MMP-2 after lung irradiation are involved in the inflammatory response associated with radiation-induced lung injury, and maybe further in radiation-induced lung fibrosis.

Animals↗

PubMed2006

CD4+CD25high regulatory cells in peripheral blood of NSCLC patients.

The proportion and changes of CD4+CD25high regulatory T cells (Trs) in peripheral blood of non-small cell lung cancer (NSCLC) patients were analyzed and their clinical significance explored. The peripheral blood was collected from 61 patients with NSCLC and 15 healthy controls. By using monoclonal antibodies, the blood samples were evaluated with the flow cytometry for lymphocyte subsets (CD3+, CD4+ and CD8+) and CD4+CD25high Tr cells. The results showed that the proportion of CD4+CD25high Tr cells in NSCLC group was significantly higher than in control group [(4.36 +/-2.07) % vs (2.04+/-1.03) %, P<0.01]. The proportion of CD4+CD25 high Tr cells in late stage was higher than that in early stage [stages I +II (2.26+/-0.6) %; stage III (3.28+/-1.38) %; stage IV (6.06 +/-4.08) %] (P<0.05). Kaplan-Meier survival analysis revealed that the prognosis of the patients who had higher proportion of CD4+CD25high Tr cells in peripheral blood was worse (P=0.0026). In conclusion, the relative increase in CD4+CD25high Tr cells in peripheral blood may be related to immunosuppression and tumor progression in patients with NSCLC. This finding suggests that CD4+CD25+high Tr cells in peripheral blood of NSCLC may be positive for prognosis analysis. The use of depletion of the CD4+CD25high Tr cell therapy to treat NSCLC patients may be an effective strategy.

Adult↗

PubMed2006

[Three-step column chromatographic method for separation and purification of thrombin-like enzyme from venom of Agkistrodon halys pallas].

A three-step column chromatographic method, utilizing CM Sepharose CL-6B, DEAE Sepharose Fast Flow and Sephadex G-75 in sequence, for the separation and purification of thrombin-like enzyme from crude venom of Agkistrodon halys pallas was developed. Based on the separation results on lab-scale chromatographic column, this isolation and purification process was amplified according to the diameter of the chromatographic columns used in labscale. It was found that when the amount of the sample loaded on the large-scale columns was 25 times as that loaded on the lab-scale columns, the quality level of the thrombin-like enzyme obtained with the large-scale columns was almost the same as that obtained with lab-scale columns. The relative molecular mass of thrombin-like enzyme obtained was about 33500, and its purity was about 96%. When using this method to isolate thrombin-like enzyme from crude venom of Agkistrodon halys pallas, the total protein yield and total activity yield of thrombin-like enzyme were about 0.3% and 64% respectively, and specific activity was more than 2000 U/mg.

Agkistrodon↗

PubMed2006

Synthesis and in vitro sorption properties of PAA-grafted cellulose beads for selective binding of LDL.

Poly(acrylic acid) (PAA)-grafted cellulose copolymer beads were synthesized and tested in vitro as an adsorbent for selective removal of low-density lipoprotein (LDL) from human plasma. The copolymers were prepared by graft copolymerization of acrylic acid (AA) onto porous cellulose beads using cerium ammonium nitrate (CAN) as an initiator. The effect of initiator concentration, monomer amount and reaction time on the grafting was examined, and it revealed that the extent of grafting could be controlled by setting the appropriate reaction conditions. In vitro batch-wise adsorption tests were conducted to evaluate the lipoprotein sorption properties of the resulted copolymer beads, and the effect of grafting conditions on the adsorption performance was investigated. It was shown that the binding capacities of the best adsorbent derived from the appropriate reaction conditions could reach 4.96 mg/g total cholesterol (TC) and 4.46 mg/g LDL cholesterol (LDL-C) from human plasma, respectively, without significantly affecting the contents of beneficial constitutes such as high-density lipoprotein (HDL) and total proteins (TP). The influences of plasma amount and adsorption period on the adsorption properties were also determined and analyzed. It appears that this kind of copolymer is worthy of being developed as an alternative LDL adsorbent.

Acrylates↗