Biomedical subjects

Yi Fan

Publications and source records attributed to Yi Fan.

26 records · Page 2Linked to original sources

PubMed2003

Effects of calycosin on the impairment of barrier function induced by hypoxia in human umbilical vein endothelial cells.

The purpose of the present study was to examine the effects of calycosin, an isoflavonoid isolated from Astragali Radix, on the impairment of barrier function induced by hypoxia in cultured human umbilical vein endothelial cells. Hypoxia induced an increase in endothelial cell monolayer permeability, indicating endothelial cell barrier impairment. Endothelial barrier dysfunction induced by hypoxia was accompanied by decreases in cytosolic ATP concentration and cAMP level, the development of actin stress fibers and intercellular gap formation, suggesting that the decreases in cytosolic ATP and cAMP levels and rearrangements of F-actin could be associated with an increase in permeability of endothelial monolayers. Application of calycosin inhibited the hypoxia-induced increase in endothelial permeability in a dose-dependent fashion, which is compatible with inhibition of lactate dehydrogenase release, decrease of the fall in ATP and cAMP contents, and improvement of F-actin rearrangements. These findings indicate that calycosin protected endothelial cells from hypoxia-induced barrier impairment by increasing intracellular energetic sources and promoting regeneration of the cAMP level, as well as improving cytoskeleton remodeling.

Actin Cytoskeleton↗

PubMed2003

Evaluation of beta-cyclodextrin bonded silica as a selective sorbent for the solid-phase extraction of 4-nitrophenol and 2,4-dinitrophenol.

A beta-cyclodextrin bonded silica was synthesized by using a convenient method, and was evaluated as a selective sorbent for the solid-phase extraction of 4-nitrophenol and 2,4-dinitrophenol. When double-distilled water was used as the sample matrix, the sorbent showed a strong capacity to adsorb 4-nitrophenol and 2,4-dinitrophenol; the recoveries were found to be 96% and 99%, respectively, with a 1 L water sample. The selectivity of the sorbent was investigated by using a washing step with methanol. Most of the phenols were washed out with 5 mL of methanol, while 4-nitrophenol and 2,4-dinitrophenol still gave recoveries of 94% and 90%. The solution for efficiently eluting the analytes was optimized and the effect of the inorganic salt on the extraction was examined. In order to investigate the potentiality of the sorbent in dealing with real water samples, water from Donghu lake (Wuhan, China) spiked with nine phenolic compounds at microgram per liter levels were preconcentrated on this cartridge.

Journal Article↗

PubMed2003

[Quasispecies and mutation of hepatitis B virus polymerase gene in lamivudine- treated patients].

OBJECTIVE: To study the quasispecies and mutation features of hepatitis B virus polymerase (HBV P) gene in chronic hepatitis B patients before and after lamivudine treatment. METHODS: The HBV P gene was amplificated with PCR and cloned, then single strand conformation polymorphism / heteroduplex analysis (SSCP/HDA) was applied to analyze the quasispecies complexity and mutation characters of HBV P gene. RESULTS: The quasispecies number of HBV P gene before treatment was larger than that after treatment (7 to 14 vs. 4 to 8, t = 3.98, P < 0.05). Six patients had one or two predominant quasispecies before therapy, but the percentages of predominant quasispecies were lower than those after therapy (33.3% to 81.8% vs. 78.8% to 90.9%, t = 3.42, P < 0.05). By sequencing the predominant clones, there were 2 patients with M550V/L528M mutation, 3 patients with M550I mutation and 1 patient with wild type after lamivudine therapy. Additionally, there were individualization mutations which had no obvious tender. CONCLUSION: Quasispecies of hepatitis B virus are changed under the selection of lamivudine, meanwhile, the mutation at YMDD motif emerges.

Antiviral Agents↗

PubMed2003

Expression, purification, and characterization of recombinant Saccharomyces cerevisiae adenosine kinase.

Adenosine kinase (AK), a key enzyme in the regulation of the cellular concentrations of adenosine (A), is an important physiological effector of many cells and tissues. In this article, we reported that ak, which encoded adenosine kinase, was cloned from Saccharomyces cerevisiae, sequenced, and overexpressed in E. coli using the pET16b expression system, and the recombinant protein was purified to apparent homogeneity using conventional protein purification techniques. Kinetic analysis of S. cerevisiae AK revealed K(m) values of (3.5+/-0.2) micromol/L for adenosine and (100.0+/-11.0) micromol/L for ATP, with k(cat) of (1530+/-20) min(-1) for adenosine and (1448+/-25) min(-1) for ATP. The determination of the K(m) value for other nucleosides and deoxynucleoside indicated that the nucleoside specificity of this enzyme from yeast was quite high.

Adenosine Kinase↗

PubMed2002

Electrochemical and Raman studies of the biointeraction between Escherichia coli and mannose in polydiacetylene derivative supported on the self-assembled monolayers of octadecanethiol on a gold electrode.

Here, we describe a new method to study the biointeraction between Escherichia coli and mannose by using supramolecular assemblies composed of polydiacetylene supported on the self-assembled monolayer of octadecanethiol on a gold electrode. These prepared bilayer materials simply are an excellent protosystem to study a range of important sensor-related issues. The experimental results from UV-vis spectroscopy, resonance Raman spectroscopy, and electrochemistry confirm that the specific interactions between E. coli and mannose can cause conformational changes of the polydiacetylene backbone rather than simple nonspecific adsorption. Moreover, the direct electrochemical detection by polydiacetylene supramolecular assemblies not only opens a new path for the use of these membranes in the area of biosensor development but also offers new possibilities for diagnostic applications and screening for binding ligands.

Acetylene↗

PubMed2002

Metabolic responses induced by thrombin in human umbilical vein endothelial cells.

Metabolic responses induced by thrombin in human umbilical vein endothelial cells (HUVECs) were investigated by using the cytosensor technique. Thrombin increased the extracellular acidification rate of endothelial cells, measured as an index of metabolic activity with a cytosensor microphysiometer, in a concentration-dependent fashion with an EC(50) of 1.27+/-0.59 IU/ml, which was abolished by the MAP kinase inhibitor PD98059. When intracellular Ca(2+) was chelated or PKC was inactivated, PD98059 failed to abolish the thrombin-induced acidification rate response in HUVECs. In addition, the tyrosine kinase inhibitor genistein, PKC inhibitor calphostin C, and Na(+)/H(+)exchanger antagonist MIA also partly inhibited thrombin-induced acidification rate responses. It is suggested that thrombin stimulated rapid metabolic responses via MAP kinase in HUVECs, which are calcium- and PKC-dependent.

Calcium Signaling↗

PubMed2002

Mouse restin inhibits bovine aortic endothelial cell proliferation and causes cell apoptosis.

Restin, a homologous protein of endostatin, was found by Ramchandran et al. It was the C-terminal fragment of type XV collagen. To analysis the inhibition activity of mouse restin on the proliferation of endothelial cells, the cDNA of restin was amplified from the total RNA of the mouse muscle and cloned into the prokaryotic expression plasmid pQE32. The recombinant protein was expressed in inclusion body with a yield about 60%--70% of total protein. After refolding, the purified recombinant protein specifically inhibits bovine aortic endothelial (BAE) cell proliferation stimulated by basic fibroblast growth factor (bFGF) in a dose-dependent manner, but the activity of restin was weaker than that of endostatin. Treatment of BAE cell with recombinant restin caused G(1) arrest and apoptosis in BAE cells.

Amino Acid Sequence↗

PubMedDate not supplied

Erianin induces a JNK/SAPK-dependent metabolic inhibition in human umbilical vein endothelial cells.

BACKGROUND: Erianin is a natural product derived from Dendrobium chrysotoxum, with promising antitumor activity. MATERIALS AND METHODS: To evaluate the metabolic effect of erianin, a cytosensor assay for acidification rate, MTT assay, measurement of lactate, glucose and ATP were performed in human umbilical vein endothelial cells (HUVECs) exposed to 1-100 nM erianin. JNK/SAPK activity was detected by Western blot. RESULTS: Twelve- or 24- hour incubation with erianin induced a dose-dependent metabolic inhibition, as indicated by reduced acidification rate and cell viability, with an endothelium-selectivity. Erianin caused decreases in lactate production, glucose consumption and intracellular ATP level. Pretreatment with the JNK/SAPK inhibitor SP600125 significantly abolished these inhibitory responses, and especially restored the erianin-induced decreases in ATP and the erianin-induced phosphorylation of JNK/SAPK with dose- and time- dependence. CONCLUSION: Erianin inhibited endothelial metabolism in a JNK/SAPK-dependent manner. This mechanism may be involved in the potential antitumnor and antiangiogenic actions of erianin.

Adenosine Triphosphate↗