Biomedical subjects

Jun Chen

Publications and source records attributed to Jun Chen.

At least 145 records · Page 8Linked to original sources

PubMed2005

Activation of spinal extracellular signaling-regulated kinases by intraplantar melittin injection.

Intraplantar injection of melittin, a major toxic peptide of whole bee venom, has been proved to cause alteration in both behavioral and spinal neuronal responses in rats. To see whether extracellular signaling-regulated kinases (ERK) in the spinal cord dorsal horn are activated and involved in induction and maintenance of persistent ongoing nociception, pain hypersensitivity and inflammation, three doses of U0126 (1,4-diamino-2,3-dicyano-1, 4-bis-[o-aminophenylmercapto]butadiene), a widely used specific MAP kinase kinase (MEK) inhibitor, were administered through chronic intrathecal catheterization prior to or after intraplantar injection of melittin. We found that: (1) the induction of melittin-induced persistent spontaneous nociception (PSN), mechanical and heat hypersensitivity could be suppressed by U0126 in a dose-related manner; (2) specific inhibition of ERK pathway suppressed the maintenance of melittin-induced PSN and heat hypersensitivity, while established mechanical hypersensitivity could not be reversed; and (3) intrathecal administration of U0126 had no effects on peripheral inflammation induced by melittin. This result suggests that spinal ERK pathway might be a common factor involved in inducing and maintaining pathophysiological processes of ongoing pain and heat hyperalgesia, while the role of ERK pathway in generation of the mechanical hypersensitivity is not consistent and remains to be further clarified.

Animals↗

PubMed2005

The responses of Ht22 cells to oxidative stress induced by buthionine sulfoximine (BSO).

BACKGROUND: glutathione (GSH) is the most abundant thiol antioxidant in mammalian cells. It directly reacts with reactive oxygen species (ROS), functions as a cofactor of antioxidant enzymes, and maintains thiol redox potential in cells. GSH depletion has been implicated in the pathogenesis of neurological diseases, particularly to Parkinson's disease (PD). The purpose of this study was to investigate the change of cellular antioxidant status and basic cell functions in the relatively early stages of GSH depletion. RESULTS: in this study, GSH was depleted by inhibition of glutamylcysteine synthetase using buthionine sulfoximine (BSO) treatment in Ht22, a neuronal cell line derived from mouse hippocampus. Treatment with BSO produced dose-dependent decreases in total GSH level, Fe3+-reducing ability (FRAP assay), Cu2+-reducing ability (Antioxidant Potential, AOP assay), and ABTS free radical scavenging ability (ABTS assay) of the cells, but the sensitivity of these indicators to dosage varied considerably. Most of the changes were completed during the first 8 hours of treatment. Cell viability was tested by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromid) assay, and cells at lower density in culture were found to be more sensitive to GSH depletion. The activity of antioxidant enzymes, such as glutathione peroxidase (GPx), glutathione reductase (GR), and copper/zinc superoxide dismutase (Cu/Zn-SOD) were affected by GSH depletion. A cDNA expression array assay of the effects of BSO treatment showed significantly decreased mRNA level for 3 genes, and significantly increased mRNA level for 10 genes, including the antioxidant enzymes Cu/Zn-SOD and thioredoxin peroxidase 2 (TPxII). CONCLUSIONS: the study suggests that there are BSO-sensitive and BSO-resistant pools of GSH in Ht22 cells, and that different categories of antioxidant react differently to GSH depletion. Further, the effect of GSH status on cell viability is cell density dependent. Finally, the alterations in expression or activity of several antioxidant enzymes provide insight into the various cellular responses to GSH depletion.

Animals↗

PubMed2005

Conversion of large-amplitude vibration to electron excitation at a metal surface.

Gaining insight into the nature and dynamics of the transition state is the essence of mechanistic investigations of chemical reactions, yet the fleeting configuration when existing chemical bonds dissociate while new ones form is extremely difficult to examine directly. Adiabatic potential-energy surfaces--usually derived using quantum chemical methods that assume mutually independent nuclear and electronic motion--quantify the fundamental forces between atoms involved in reaction and thus provide accurate descriptions of a reacting system as it moves through its transition state. This approach, widely tested for gas-phase reactions, is now also commonly applied to chemical reactions at metal surfaces. There is, however, some evidence calling into question the correctness of this theoretical approach for surface reactions: electronic excitation upon highly exothermic chemisorption has been observed, and indirect evidence suggests that large-amplitude vibrations of reactant molecules can excite electrons at metal surfaces. Here we report the detection of 'hot' electrons leaving a metal surface as vibrationally highly excited NO molecules collide with it. Electron emission only occurs once the vibrational energy exceeds the surface work function, and is at least 10,000 times more efficient than the emissions seen in similar systems where large-amplitude vibrations were not involved. These observations unambiguously demonstrate the direct conversion of vibrational to electronic excitation, thus questioning one of the basic assumptions currently used in theoretical approaches to describing bond-dissociation at metal surfaces.

Journal Article↗

PubMed2005

Feasibility of reflectance spectroscopy for the assessment of soil mercury contamination.

Conventional methods for investigating soil Hg contamination based on raster sampling and chemical analysis are time-consuming and relatively expensive. The objective of this study was to develop a rapid method for investigating Hg concentration in suburban agricultural soils of the Nanjing region using reflectance spectra within the visible-near-infrared (VNIR) region. Several spectral pretreatments (absorbance, Kubelka-Munk transformations and their derivatives) were applied to the reflectance spectra to optimize the accuracy of prediction. The prediction of Hg concentration was achieved by univariate regression and principal component regression (PCR) approaches. The optimal model (R= 0.69, RMSEP = 0.15) for predicting Hg was achieved using the PCR method with the Kubelka-Munktransformation asthe spectral predictor. Comparison of three wavelength ranges (0.38-1.1, 1.0-2.5, and 0.38-2.5 microm) on the effect of prediction accuracy showed that the best results were acquired using the 1.0-2.5 microm spectral region. Correlation analysis revealed that Hg concentration was negatively correlated with soil reflectance while positively correlated with the absorption depths of goethite at 0.496 microm and clay minerals at 2.21 microm, suggesting that Hg-sorption by clay-size mineral assemblages in soils was the mechanism by which to predict spectrally featureless Hg. These results indicate that it is feasible to predict Hg levels in agricultural soils using the rapid and cost-effective reflectance spectroscopy. Future study with operational remote sensing techniques and field measurements is strongly recommended.

Absorption↗

PubMed2005

A novel potassium channel encoded by Ectocarpus siliculosus virus.

Kcv, the first identified viral potassium channel encoded by the green algae Paramecium bursaria chlorella virus (PBCV-1), conducted K(+) selective currents when expressed in heterologous systems. This K(+) channel was proposed to be important for PBCV-1 infection and replication. In the present study, we identified and functionally characterized a novel K(+) channel Kesv, encoded by Ectocarpus siliculosus virus that infects filamentous marine brown algae. Kesv encodes a protein of 124 amino acids and is 21.8% identical and 37.1% homologous to Kcv. Membrane topology programs predicted that Kesv consists of three transmembrane domains. When expressed in Xenopus oocytes, Kesv induced largely instantaneous, K(+) selective currents that were sensitive to block by Ba(2+) and amantadine. Thus, Kesv along with Kcv, constitutes an emerging family of viral potassium channels, which may play important roles in the life cycle of viruses.

Animals↗

PubMed2005

[Hand-assisted laparoscopic renal surgery: report of 45 cases].

OBJECTIVE: To evaluate the effect and clinical application of hand-assisted laparoscopic renal surgery. METHODS: Forty-five patients with urologic diseases underwent hand-assisted laparoscopic renal surgery: radical nephrectomy was performed on 23 cases, simple nephrectomy on 9 cases, nephroureterectomy on 8 cases, excision of cysts of kidney on 3 cases, partial nephrectomy on 1 case, and upper pole heminephrectomy in duplex kidney on 1 case. The operation was performed by transperitoneal approach in 38 cases and by underwent and by retroperitoneal approach in 7 cases. RESULTS: Hand-assisted laparoscopic renal surgery were performed successfully on all patients. The mean operation time was 154.7 minutes (40 approximately 300 min), and the mean estimated blood loss was 100.4 ml (15 approximately 300 ml). CONCLUSION: With the advantages of minimal invasion, less blood loss, faster recovery, hand-assisted laparoscopic renal surgery is worth popularizing in urologic clinical practice.

Adolescent↗

PubMed2005

Construction of recombinant eukaryotic expression plasmid containing murine CD40 ligand gene and its expression in H22 cells.

AIM: To construct a recombinant murine CD40 ligand (mCD40L) eukaryotic expression vector for gene therapy and target therapy of hepatocellular carcinoma (HCC). METHODS: mCD40L cDNA was synthesized by RT-PCR with the specific primers and directly cloned into T vector to generate middle recombinant. After digestion with restriction endonuclease, the target fragment was subcloned into the multi-clone sites of the eukaryotic vector. The constructed vector was verified by enzyme digestion and sequencing, and the product expressed was detected by RT-PCR and immunofluorescence methods. RESULTS: The full-length mCD40L-cDNA was successfully cloned into the eukaryotic vector through electrophoresis, and mCD40L gene was integrated into the genome of infected H22 cells by RT-PCR. Murine CD40L antigen molecule was observed in the plasma of mCD40L-H22 by indirect immunofluorescence staining. CONCLUSION: The recombined mCD40L eukaryotic expression vector can be expressed in H22 cell line. It provides experimental data for gene therapy and target therapy of hepatocellular carcinoma.

Animals↗

PubMed2005

The cry3Aa gene of Bacillus thuringiensis Bt886 encodes a toxin against long-horned beetles.

This report describes the identification of a new toxigenic strain of Bacillus thuringiensis specific for long-horned beetles. B. thuringiensis Bt866 encodes a cry3Aa-like gene (Bt886cry3Aa) that is 1,956 bp in length and is predicted to encode an 85.78-kDa protein. The gene is highly similar to cry3Aa1, differing in only six nucleotides and four amino acids. The four disparate amino acids occur within the conserved domains of the Cry3Aa toxin. The expression of Bt866cry3A in Escherichia coli cells resulted in a high level of toxicity toward Apriona germari Hope larvae. More than 75% of the larvae were killed; and the remaining survivors exhibited slower growth. These results indicate that the toxigenic strain Bt886cry3Aa encodes a protein that is specific against long-horned beetles. Genetic engineering of the Bt866cry3Aa gene into poplar plantations may provide resistance to long-horned beetles.

Amino Acid Sequence↗

PubMed2005

ALARM NMR: a rapid and robust experimental method to detect reactive false positives in biochemical screens.

High-throughput screening (HTS) of large compound collections typically results in numerous small molecule hits that must be carefully evaluated to identify valid drug leads. Although several filtering mechanisms and other tools exist that can assist the chemist in this process, it is often the case that costly synthetic resources are expended in pursuing false positives. We report here a rapid and reliable NMR-based method for identifying reactive false positives including those that oxidize or alkylate a protein target. Importantly, the reactive species need not be the parent compound, as both reactive impurities and breakdown products can be detected. The assay is called ALARM NMR (a La assay to detect reactive molecules by nuclear magnetic resonance) and is based on monitoring DTT-dependent (13)C chemical shift changes of the human La antigen in the presence of a test compound or mixture. Extensive validation has been performed to demonstrate the reliability and utility of using ALARM NMR to assess thiol reactivity. This included comparing ALARM NMR to a glutathione-based fluorescence assay, as well as testing a collection of more than 3500 compounds containing HTS hits from 23 drug targets. The data show that current in silico filtering tools fail to identify more than half of the compounds that can act via reactive mechanisms. Significantly, we show how ALARM NMR data has been critical in identifying reactive compounds that would otherwise have been prioritized for lead optimization. In addition, a new filtering tool has been developed on the basis of the ALARM NMR data that can augment current in silico programs for identifying nuisance compounds and improving the process of hit triage.

Autoantigens↗

PubMed2005

Negative feedback loop formed by Lunatic fringe and Hes7 controls their oscillatory expression during somitogenesis.

Recent studies show that the cyclic expression of Lfng in the presomitic mesoderm (PSM) is controlled at the transcription level by Notch signal through the CBF1 binding site for activation and periodic repression on the Lfng promoter. Here we provide genetic evidence that the oscillatory expression is controlled by a negative feedback mechanism. We also show that Hes7, another cyclically expressed protein, can bind to the N-boxes on both Lfng and its own promoters and repress their activity. In addition, we demonstrate that the 3' untranslated region (3'-UTR) is important for rapid degradation of Lfng mRNA.

3' Untranslated Regions↗

PubMed2005

Dynamic Gd-DTPA enhanced MRI as a surrogate marker of angiogenesis in tissue-engineered bladder constructs: a feasibility study in rabbits.

PURPOSE: To evaluate the potential of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to assess angiogenesis in tissue-engineered bladder constructs in a blinded animal study, and compare different analysis approaches and their correlation with microvessel density (MVD). MATERIALS AND METHODS: Constructs fortified with vascular endothelial growth factor (VEGF) for enhanced vascularity were grafted onto the bladder in nine rabbits. DCE-MRI of Gd-DTPA uptake was performed and analyzed using Tofts' model, the area under the concentration time curve (AUC), and the uptake slope. DCE-MRI parameters were compared to MVD determined with CD31 immunohistochemistry. RESULTS: Significantly increased MVD was found in the high VEGF group (20 ng/g of tissue) but not at low VEGF (10 ng/g) (2.3x increase, P = 0.035 vs. 1.1x over control). Enhanced permeability at low VEGF was suggested by elevated K(trans), but overall correlation to MVD was poor. Significant correlation to MVD was obtained with AUC(8min) (r = 0.705, P = 0.034). Furthermore, AUC(8min) provided the most precise discrimination between different VEGF preparations and was the only parameter to show a significant increase (P = 0.0058) consistent with MVD changes at high VEGF. CONCLUSION: Findings support DCE-MRI for evaluating angiogenesis in bladder constructs and suggest vessel changes other than density. Future studies should incorporate larger contrast agents and permeability assessment to devise an optimal DCE-MRI strategy.

Animals↗

PubMed2005

Qualitative and quantitative analysis of active flavonoids in Flos Lonicerae by capillary zone electrophoresis coupled with solid-phase extraction.

Flavonoids are an important bioactive group in the commonly used herbal medicine Flos Lonicerae. A new method of capillary zone electrophoresis (CZE) coupled with solid-phase extraction (SPE) was developed for simultaneous assay of flavonoid aglycones and glycosides in Flos Lonicerae. Optimum CZE separation was achieved with a background electrolyte (BGE) solution consisting of 80 mM boric acid and 20 mM phosphate acid, adjusted to pH 8.1, with 15% acetonitrile (v/v) added, and applying a separation voltage of 28 kV. The SPE method was used for pretreating the complex matrix of botanical materials and good reproducibility was obtained when avicularin was used as internal standard. Linearity of the method was excellent with correlation coefficients (r2) in the range of 0.9995-0.9999 and detection limits were lower than 0.6 microg/mL for the four flavonoids. The obtained recoveries varied between 93 to 104% while the relative standard deviations (RSDs) were below 4.4% (n=3). The developed CZE method was successfully used for the separation of eight flavonoids and the quantification of the four flavonoids in five species of Flos Lonicerae.

Animals↗

PubMed2005

Seasonal dynamics of the hepatotoxic microcystins in various organs of four freshwater bivalves from the large eutrophic lake Taihu of subtropical China and the risk to human consumption.

So far, little is known on the distribution of hepatotoxic microcystin (MC) in various organs of bivalves, and there is no study on MC accumulation in bivalves from Chinese waters. Distribution pattern and seasonal dynamics of MC-LR, -YR and -RR in various organs (hepatopancreas, intestine, visceral mass, gill, foot, and rest) of four edible freshwater mussels (Anodonta woodiana, Hyriopsis cumingii, Cristaria plicata, and Lamprotula leai) were studied monthly during Oct. 2003-Sep. 2004 in Lake Taihu with toxic cyanobacterial blooms in the summer. Qualitative and quantitative determinations of MCs in the organs were done by LC-MS and HPLC. The major toxins were present in the hepatopancreas (45.5-55.4%), followed by visceral mass with substantial amount of gonad (27.6-35.5%), whereas gill and foot were the least (1.8-5.1%). The maximum MC contents in the hepatopancreas, intestine, visceral mass, gill, foot, and rest were 38.48, 20.65, 1.70, 0.64, 0.58, and 0.61 microg/g DW, respectively. There were rather good positive correlation in MC contents between intestines and hepatopancreas of the four bivalves (r=0.75-0.97, p<0.05). There appeared to be positive correlations between the maximum MC content in the hepatopancreas and the delta13C (r=0.919) or delta15N (r=0.878) of the foot, indicating that the different MC content in the hepatopancreas might be due to different food ingestion. A glutathione (GSH) conjugate of MC-LR was also detected in the foot sample of C. plicata. Among the foot samples analyzed, 54% were above the provisional WHO tolerable daily intake (TDI) level, and the mean daily intakes from the four bivalves were 8-23.5 times the TDI value when the bivalves are eaten as a whole, suggesting the high risk of consuming bivalves in Lake Taihu.

Animals↗

PubMed2005

Effects of ligustrazine on the contraction of isolated rabbit corpus cavernosum strips.

To investigate the role of ligustrazine on relaxation of the isolated rabbit corpus cavernosum tissue in vitro, the effects of ligustrazine on the corpus cavernosum were observed by using experimental method of smooth muscle strips. Concentration-responses to phenylephine (PE) and KCl were recorded. The results showed that ligustrazine concentration-dependently depressed the contraction response of smooth muscle strips induced by PE. The maximum percentage relaxation of cavernosal strips by ligustrazine was 74.1% +/- 6.2% (compared with control: 21.9% +/- 5.6%, P < 0.01). Ligustrazine concentration-dependently reduced the amplitude of the contraction induced by cumulative doses of PE or KCl, shifted the cumulative concentration response curves of PE and KCI to the right and depressed their maximal responses. It was concluded that ligustrazine could significantly relax the cavernosal muscle contraction induced by PE in vitro. The results suggested that ligustrazine inhibited calcium ion influx.

Animals↗

PubMed2005

Osmolarity regulates gene expression in intervertebral disc cells determined by gene array and real-time quantitative RT-PCR.

Intervertebral disc (IVD) cells experience a broad range of physicochemical stimuli under physiologic conditions, including alterations in their osmotic environment. Cellular responses to altered osmolarity have been documented at the transcriptional and post-translational level, but mainly for extracellular matrix proteins. In this study, the gene expression profile of human IVD cells was quantified with gene array technology following exposure to increased osmolarity in order to capture the biological responses for a broad set of targets. A total of 42 genes were identified in IVD cells as significantly changed following culture under hyper-osmotic conditions. Gene expression patterns were verified using RT-PCR. Genes identified in this study include those related to cytoskeleton remodeling and stabilization (ephrin-B2, muskelin), as well as membrane transport (ion transporter SLC21A12, osmolyte transporter SLC5A3, monocarboxylic acid SLC16A6). An unexpected finding was the differential regulation of the gene for the neurotrophin, brain-derived neurotrophic factor, by hyper-osmotic stimuli that suggests a capability of IVD cells to respond to physicochemical stimuli with factors that may regulate discogenic pain.

Cells, Cultured↗

PubMed2005

Individual C1 domains of PKD3 in phorbol ester-induced plasma membrane translocation of PKD3 in intact cells.

Protein kinase D3 is a novel member of the serine/threonine kinase family PKD. The regulatory region of PKD contains a tandem repeat of C1 domains designated C1a and C1b that bind diacylglycerol and phorbol esters, and are important membrane targeting modules. Here, we investigate the activities of individual C1 domains of PKD3 and their roles in phorbol ester-induced plasma membrane translocation of PKD3. Truncated C1a of PKD3 binds [(3)H]phorbol 12, 13-dibutyrate with high affinity, but no binding activity is detected for C1b. Meanwhile, mutations in C1a of truncated C1ab of PKD3 lead to the loss of binding affinity, while these mutations in C1b have little impact, indicating that C1a is responsible for most of the phorbol ester-binding activities of PKD3. C1a and C1b of the GFP-tagged full length PKD3 are then mutated to assess their roles in phorbol ester-induced plasma membrane translocation in intact cells. At low concentration of phorbol 12-myristate 13-acetate (PMA), the plasma membrane translocations of the C1a and C1ab mutants are significantly impaired, reflecting an important role of C1a in this process. However, at higher PMA concentrations, all C1 mutants exhibit increased rates of translocation as compared to that of wild-type PKD3, which parallel their enhanced activation by PMA, implying that PKD3 kinase activity affects membrane targeting. In line with this, a constitutive active PKD3-GFP translocates similarly as wild-type PKD3, while a kinase-inactive PKD3 shows little translocation up to 2 muM PMA. In addition, RO 31-8220, a potent PKC inhibitor that blocks PMA-induced PKD3 activation in vivo, significantly attenuates the plasma membrane translocation of wild-type PKD3 at different doses of PMA. Taken together, our results indicate that both C1a and the kinase activity of PKD3 are necessary for the phorbol ester-induced plasma membrane translocation of PKD3. PKC, by directly activating PKD3, regulates its plasma membrane localization in intact cells.

Animals↗

PubMed2005

Tissue distributions and seasonal dynamics of the hepatotoxic microcystins-LR and -RR in a freshwater snail (Bellamya aeruginosa) from a large shallow, eutrophic lake of the subtropical China.

Tissue distributions and seasonal dynamics of the hepatotoxic microcystins-LR and -RR in a freshwater snail (Bellamya aeruginosa) were studied monthly in a large shallow, eutrophic lake of the subtropical China during June-November, 2003. Microcystins (MCs) were quantitatively determined by High-Performance Liquid Chromatography (HPLC) with a qualitative analysis by a Finnigan LC-MS system. On the average of the study period, hepatopancreas was the highest in MC contents (mean 4.14 and range 1.06-7.42 microg g(-1)DW), followed by digestive tracts (mean 1.69 and range 0.8-4.54 microg g(-1)DW) and gonad (mean 0.715 and range 0-2.62 microg g(-1)DW), whereas foot was the least (mean 0.01 and range 0-0.06 microg g(-1)DW). There was a positive correlation in MC contents between digestive tracts and hepatopancreas. A constantly higher MC content in hepatopancreas than in digestive tracts indicates a substantial bioaccumulation of MCs in the hepatopancreas of the snail. The average ratio of MC-LR/MC-RR showed a steady increase from digestive tracts (0.44) to hepatopancreas (0.63) and to gonad (0.96), suggesting that MC-LR was more resistant to degradation in the snail. Since most MCs were present in the hepatopancreas, digestive tracts and gonad with only a very small amount in the edible foot, the risk to human health may not be significant if these toxic parts are removed prior to snail consumption. However, the possible transference of toxins along food chains should not be a negligible concern.

Animals↗

PubMed2005

Tissue distributions and seasonal dynamics of the hepatotoxic microcystins-LR and -RR in two freshwater shrimps, Palaemon modestus and Macrobrachium nipponensis, from a large shallow, eutrophic lake of the subtropical China.

So far no information is available on microcystin (MC) contents in shrimps, prawns or crayfish from natural freshwaters. Tissue distributions and seasonal dynamics of the hepatotoxic MC-LR and -RR in two freshwater shrimps, Palaemon modestus and Macrobrachium nipponensis were studied monthly (during June-November, 2003) in a Chinese lake containing toxic cyanobacterial blooms. The shrimps P. modestus and M. nipponensis accumulated high MCs not only in the hepatopancreas (mean 4.29 and 0.53 microg g(-1) DW, respectively) but also in the gonad (mean 1.17 and 0.48 microg g(-1) DW, respectively), and the crayfish Procambarus clarkii accumulated as much as 0.93 microg g(-1) DW in the gonad. This indicates that gonads of these invertebrates are the second important target organ of MCs. P. modestus apparently accumulated more MCs in their organs than M. nipponensis, which might be a reflection of their difference in trophic niche. Eggs of the shrimps accumulated 8.4% (M. nipponensis, 0.27 microg g(-1) DW) and 29.0% (P. modestus, 2.34 microg g(-1) DW) of total toxin burden, indicating that MCs had been transferred into offspring from their adults. Among the shrimp muscle samples analyzed, 31% were above the provisional WHO TDI level, suggesting the risk of consuming shrimps in Lake Chaohu.

Animals↗