Biomedical subjects

Yongjian Liu

Publications and source records attributed to Yongjian Liu.

10 recordsLinked to original sources

PubMed2006

Dok5 is substrate of TrkB and TrkC receptors and involved in neurotrophin induced MAPK activation.

Tropomyosin-related kinase (Trk) family receptors are a group of high affinity receptors for neurotrophin growth factors, which have pivotal functions in many physiological processes of nervous system. Trk receptors can dimerize and autophosphorylate upon neurotrophin stimulation, then recruit multiple adaptor proteins to transduct signal. In this report, we identified Dok5, a member of Dok family, as a new substrate of TrkB/C receptors. In yeast two-hybrid assay, Dok5 can interact with intracellular domain of TrkB and TrkC receptor through its PTB domain, but not with that of TrkA receptor. The interaction was then confirmed by GST pull-down assay and Co-IP experiment. Dok5 co-localized with TrkB and TrkC in differentiated PC12 cells, providing another evidence for their interaction. By using mutational analysis, we characterized that Dok5 PTB domain bound to Trk receptor NPQY motif in a kinase-activity-dependent manner. Furthermore, competition experiment indicated that Dok5 competed with N-shc for binding to the receptors at the same site. Finally, we showed that Dok5 was involved in the activation of MAPK pathway induced by neurotrophin stimulation. Taken together, these results suggest that Dok5 acts as substrate of TrkB/C receptors and is involved in neurotrophin induced MAPK signal pathway activation.

Adaptor Proteins, Signal Transducing↗

PubMed2005

[Single visual-evoked potential estimation based on sparse decomposition].

Iterative weighted sparse decomposition is a method to determine the weight coefficients of the minimum l1 norm optimization in accord with the two-scale relationship of the white noise in the multiresolution wavelet structure and to gradually suppress the influence of the strong noises through an iteration operation. The single-trial Visual Evoked Potential(VEP) estimation results confirmed the effectiveness of the method, and thus supported the viewpoint that the results of the single VEP estimation were different.

Evoked Potentials↗

PubMed2004

Determination of trace-level haloacetic acids in drinking water by ion chromatography-inductively coupled plasma mass spectrometry.

A new method for the determination of nine haloacetic acids (HAAs) with ion chromatography (IC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) was developed. With the very hydrophilic anion-exchange column and steep gradient of sodium hydroxide, the nine HAAs could be well separated in 15 min. After suppression with an ASRS suppressor that was introduced in between IC and ICP-MS, the background was much decreased, the interference caused by sodium ion present in eluent was removed, and the sensitivities of HAAs were greatly improved. The chlorinated and brominated HAAs could be detected as 35ClO and 79Br without interference of the matrix due to the elemental selective ICP-MS. The detection limits for mono-, di-, trichloroacetic acids were between 15.6 and 23.6 microg/l. For the other six bromine-containing HAAs, the detection limits were between 0.34 and 0.99 microg/l. With the pretreatment of OnGuard Ag cartridge to remove high concentration of chloride in sample, the developed method could be applied to the determination of HAAs in many drinking water matrices.

Acetates↗

PubMed2004

Electrochemical monitoring of transport by a vesicular monoamine transporter expressed in Xenopus oocytes.

Xenopus laevis oocytes were injected with synthetic mRNA coding for a rat VMAT2 mutant (rVMAT2-I483A/L484A) shown previously to be retained on the plasma membrane as a result of a presumed reduction of endocytosis. Binding of the specific VMAT inhibitor [3H]dihydrotetrabenazine indicated that expression did occur at a level of approximately 3 fmol per oocyte. To determine if rVMAT2-I483A/L484A expressed in oocytes was capable of substrate transport, oocytes were placed in buffer at pH 6.0, dopamine substrate was injected into the cell, and egress of substrate was monitored by fast scan cyclic voltammetry using a carbon fiber microelectrode. Under these conditions, transport by oocytes injected with RNA coding for rVMAT2-I483A/L484A ranged from approximately 0.5 to more than 2.5 pmol/min. Water-injected and uninjected control oocytes did not exhibit appreciable transport activity. Transport by rVMAT2-I483A/L484A-injected oocytes was reduced to control levels by tetrabenazine, a known inhibitor of VMAT transport activity. Comparison of subtracted voltammograms obtained from transport assays with those for calibration experiments confirmed that the transported species was dopamine. These results suggest that expression of VMATs in oocytes may provide a useful model system for mechanistic and regulatory studies that would not be feasible using traditional methods.

Animals↗

PubMed2004

Determination of bromate and chlorinated haloacetic acids in bottled drinking water with chromatographic methods.

Disinfection by-products of interest such as bromate, chlorate and chlorinated haloacetic acids in 10 representative brands of bottled drinking water were investigated with ion chromatography. With the developed method, the detection limits of the disinfection by-products were in sub-microgl(-1) level. It was observed that bromate, chlorate and dichloroacetic acid could be detected in some water samples. In the bottled natural water, the concentrations for the three compounds were 0.1, 0.9 and 0.6 microgl(-1), respectively. The total concentration of disinfection by-products in the natural water sample was the highest among all the bottled drinking waters. The concentrations for the sum of disinfection by-products in the four types of bottled drinking water investigated were natural water > mineral water > spring water > purified water. The generation of disinfection by-products was much influenced by the original components and process procedure of the source water. The concentrations of bromate and chlorate in the bottled water samples hardly degraded with the increasing storage time. For dichloroacetic acid, with the prolonging of storage time, the concentration was much decreased.

Acetates↗

PubMed2004

[Molecular genetic diversity of phytoplankton rbcL gene in Jiaozhou Bay].

The variants of a 500 base pair fragment of RubisCo large subunit gene (rbcL) from the phytoplanktonic DNA of Jiaozhou Bay surface seawater were amplified by using polymerase chain reaction and cloned. Twenty-eight clones were randomly selected and sequenced, which were further used to determine the molecular genetic diversity of the phytoplankton of Jiaozhou Bay surface seawater. Systematic analysis showed that the clones representing cryptophyta counted for 28.6%, Stramenopiles 32.1%, Haptophyta 28.6%, Rhodophyta 3.6% and Chlorophyta 7.1%. The sequences from Cryptophyta, Stramenopiles, Haptophyta and Rhodophyta belonged to type D of Form I rbcL and Chlorophyta to type B, indicating that the dominant phytoplankton were those represented by type D rbcL. The genetic diversity index and the reversely translated amino acid sequence diversity of Jiaozhou Bay phytoplankton were 2.85 and 0.20, which were determined by the abundances of operational taxonomy units and the reversely translated amino acid sequences respectively.

Amino Acid Sequence↗

PubMed2003

Determination of trace levels of haloacetic acids and perchlorate in drinking water by ion chromatography with direct injection.

Disinfection by products of haloacetic acids and perchlorate pose significant health risks, even at low microg/l levels in drinking water. A new method for the simultaneous determination of nine haloacetic acids (HAAs) and perchlorate as well as some common anions in one run with ion chromatography was developed. The HAAs tested included mono-, di-, trichloroacetic acids, mono, di-, tribromoacetic acids, bromochloroacetic acid, dibromochloroacetic acid, and bromodichloroacetic acid. Two high-capacity anion-exchange columns, a carbonate-selective column and a hydroxide-selective hydrophilic one, were used for the investigation. With the carbonate-selective column, the nine HAAs as well as fluoride, chloride, nitrite, nitrate, phosphate and sulfate could be well separated and determined in one run. With the very hydrophilic column and a gradient elution of sodium hydroxide, methanol and deionized water, the nine HAAs, fluoride, chloride, nitrite, nitrate as well as perchlorate could be simultaneously determined in one run within 34 min. The detection limits for HAAs were between 1.11 and 9.32 microg/l. For perchlorate, it was 0.60 microg/l.

Acetates↗

PubMed2002

Separation methods for taurine analysis in biological samples.

Taurine plays an important role in a variety of physiological functions, pharmacological actions and pathological conditions. Many methods for taurine analysis, therefore, have been reported to monitor its levels in biological samples. This review discusses the following techniques: sample preparation; separation and determination methods including high-performance liquid chromatography, gas chromatography, ion chromatography, capillary electrophoresis and hyphenation procedures. It covers articles published between 1990 and 2001.

Chromatography↗

PubMed2002

Determination of trace level bromate and perchlorate in drinking water by ion chromatography with an evaporative preconcentration technique.

A simple sample preconcentration technique employing microwave-based evaporation for the determination of trace level bromate and perchlorate in drinking water with ion chromatography is presented. With a hydrophilic anion-exchange column and a sodium hydroxide eluent in linear gradient, bromate and perchlorate can be determined in one injection within 35 min. Prior to ion chromatographic analysis, the drinking water sample was treated with an OnGuard-Ag cartridge to remove the superfluous chloride and concentrated 20-fold using a PTFE beaker in a domestic microwave oven for 15 min. The recoveries of the anions ranged from 94.6% for NO2- to 105.2% for F-. The detection limits for bromate, perchlorate, iodate and chlorate were 0.1, 0.2, 0.1 and 0.2 microg/l, respectively. The developed method is applicable for the quantitation of bromate and perchlorate in drinking water samples.

Bromates↗

PubMed2002

[Losartan in the rat model of bleomycin-induced pulmonary fibrosis and its impact on the expression of monocyte chemoattractant protein-1 and basic fibroblast growth factor].

OBJECTIVE: To study the effect of losartan on bleomycin-induced pulmonary fibrosis in rats and its possible mechanism. METHODS: Pulmonary fibrosis was induced in Wistar rats by intratracheal instillation of bleomycin. Then the rats received daily losartan 10 mg/kg (group L), prednisone 20 mg/kg (group P), or normal saline (group B) orally. Normal controls received normal saline both intratracheally and orally. Six rats in each group were sacrificed 3, 7, 14, 28 and 56 days after intratracheal instillation. Histological changes of the lungs were evaluated by HE stain, Masson's trichrome stain and sirius red stain. Collagen content of the lung tissue was assessed by hydroxyproline concentration. The mRNAs of monocyte chemoattractant protein-1 (MCP-1) and basic fibroblast growth factor (bFGF) were detected by reverse transcription-polymerase chain reaction (RT-PCR). Lung expression of MCP-1 and bFGF proteins was assessed by immunohistochemistry and the level of MCP-1 protein was further measured by ELISA. RESULTS: Pulmonary fibrosis of group L and group P was improved as compared with that of group B. Hydroxyproline concentrations of group L and group P were lower than that of group B. Protein expression of MCP-1 and bFGF in group L was lower than that in group B. CONCLUSION: Losartan alleviates bleomycin-induced pulmonary fibrosis in rats. Inhibiting the expressions of MCP-1 and bFGF in lung tissues may be one of the mechanisms.

Administration, Oral↗