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Jing Chen

Publications and source records attributed to Jing Chen.

At least 145 records · Page 8Linked to original sources
PubMed2005

Simultaneous determination of palladium, platinum, rhodium and gold by on-line solid phase extraction and high performance liquid chromatography with 5-(2-hydroxy-5-nitrophenylazo)thiorhodanine as pre-column derivatization regents.

In this paper, 5-(2-hydroxy-5-nitrophenylazo)thiorhodanine (HNATR) was synthesized. A new method for the simultaneous determination of palladium, platinum, rhodium and gold ions as metal-HNATR chelates was developed using a rapid analysis column high performance liquid chromatography equipped with on-line solid phase extraction technique. The samples (Water, human urine, geological samples and soil) were digested by microwave acid-digestion. The palladium, platinum, rhodium and gold ions in the digested samples were pre-column derivatized with HNATR to form colored chelates. The Pd-HNATR, Pt-HNATR, Rh-HNATR and Au-HNATR chelates can be absorbed onto the front of the enrichment column when they were injected into the injector and sent to the enrichment column [Zorbax Stable Bound, 10 mm x 4.6 mm, 1.8 microm] with a buffer solution of 0.05 mol L(-1) phosphoric acid as mobile phase. After the enrichment had finished, by switching the six ports switching valve, the retained chelates were back-flushed by mobile phase and travelling towards the analytical column. These chelates separation on the analytical column [Zorbax Stable Bound, 10 mm x 4.6 mm, 1.8 microm] was satisfactory with 72% acetonitrile (containing 0.05 mol L(-1) of phosphoric acid and 0.1% of Triton X-100) as mobile phase. The palladium, platinum, rhodium and gold chelates were separated completely within 2.5 min. Compared to the routine chromatographic method, more then 80% of separation time was shortened. By on-line solid phase extraction system, a large volume of sample (10 mL) can be injected, and the sensitivity of the method was greatly improved. The detection limits (S/N=3, the sample injection volume is 10 mL) of palladium, platinum, rhodium and gold in the original samples reaches 1.4, 1.8, 2.0 and 1.2 ng L(-1), respectively. The relative standard deviations for five replicate samples were 2.4-3.6%. The standard recoveries were 88-95%. This method was applied to the determination of palladium, platinum, rhodium and gold in human urine, water and geological samples with good results.

Chromatography, High Pressure Liquid↗
PubMed2005

The small molecule tyrosine kinase inhibitor AMN107 inhibits TEL-PDGFRbeta and FIP1L1-PDGFRalpha in vitro and in vivo.

AMN107 is a small molecule tyrosine kinase inhibitor developed, in the first instance, as a potent inhibitor of breakpoint cluster region-abelson (BCR-ABL). We tested its effectiveness against fusion tyrosine kinases TEL-platelet-derived growth factor receptorbeta (TEL-PDGFRbeta) and FIP1-like-1 (FIP1L1)-PDGFRalpha, which cause chronic myelomonocytic leukemia and hypereosinophilic syndrome, respectively. In vitro, AMN107 inhibited proliferation of Ba/F3 cells transformed by both TEL-PDGFRbeta and FIP1L1-PDGFRalpha with IC50 (inhibitory concentration 50%) values less than 25 nM and inhibited phosphorylation of the fusion kinases and their downstream signaling targets. The imatinib mesylate-resistant mutant TEL-PDGFRbeta T681I was sensitive to AMN107, whereas the analogous mutation in FIP1L1-PDGFRalpha, T674I, was resistant. In an in vivo bone marrow transplantation assay, AMN107 effectively treated myeloproliferative disease induced by TEL-PDGFRbeta and FIP1L1-PDGFRalpha, significantly increasing survival and disease latency and reducing disease severity as assessed by histopathology and flow cytometry. In summary, AMN107 can inhibit myeloid proliferation driven by TEL-PDGFRbeta and FIP1L1-PDGFRalpha and may be a useful drug for treatment of patients with myeloproliferative disease who harbor these kinase fusions.

Animals↗
PubMed2005

Effect of soybean protein on blood pressure: a randomized, controlled trial.

BACKGROUND: Epidemiologic studies suggest that vegetable protein intake is inversely related to blood pressure. OBJECTIVE: To examine the effect of soybean protein supplementation on blood pressure in persons with prehypertension or stage 1 hypertension. DESIGN: Randomized, double-blind, controlled trial. SETTING: Three communities in the People's Republic of China. PATIENTS: 302 participants 35 to 64 years of age with an initial untreated systolic blood pressure of 130 to 159 mm Hg, diastolic blood pressure of 80 to 99 mm Hg, or both. INTERVENTION: Study participants were randomly assigned to receive 40 g of isolated soybean protein supplements per day or complex carbohydrate control for 12 weeks; 91.4% completed the intervention. MEASUREMENTS: Blood pressure measurements were obtained by using random-zero sphygmomanometers at baseline and at 6 and 12 weeks. RESULTS: At baseline, the mean systolic and diastolic blood pressures were 135.0 mm Hg (SD 10.9) and 84.7 mm Hg (SD 6.9), respectively. Compared with the control group, the net changes in systolic blood pressure and diastolic blood pressure were -4.31 mm Hg (95% CI, -2.11 to -6.51 mm Hg; P < 0.001) and -2.76 mm Hg (CI, -1.35 to -4.16 mm Hg; P < 0.001), respectively, after the 12-week intervention. The net changes in systolic and diastolic blood pressure reductions were -7.88 mm Hg (CI, -4.66 to -11.1 mm Hg) and -5.27 mm Hg (CI, -3.05 to -7.49 mm Hg), respectively, in persons with hypertension and -2.34 mm Hg (CI, 0.48 to -5.17 mm Hg) and -1.28 mm Hg (CI, 0.52 to -3.07 mm Hg), respectively, in those without hypertension. LIMITATIONS: This trial did not examine whether the blood pressure reduction was due to protein or isoflavones in soybean. CONCLUSIONS: Soybean protein supplementation resulted in a reduction in systolic and diastolic blood pressure. These findings suggest that increased intake of soybean protein may play an important role in preventing and treating hypertension.

Adult↗
PubMed2005

Cyclodextrins as carriers for cinchona alkaloids: a pH-responsive selective binding system.

A series of cyclodextrin-cinchona alkaloid inclusion complexes were prepared from beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and four cinchona alkaloids in ca. 90% yields, and their inclusion complexation behavior was investigated at pH 7.2 and 1.5 by means of fluorescence, UV/Vis and 2D NMR spectroscopy. The results showed that the cinchona alkaloids can be efficiently encapsulated in the cyclodextrin cavity in an acidic environment and sufficiently released in a neutral environment, which makes these cyclodextrin derivatives the potential carriers for cinchona alkaloids. The binding ability and molecular selectivity of cyclodextrins toward cinchona alkaloids were discussed from the viewpoint of the size-fit concept and multiple recognition mechanism between host and guest.

Binding Sites↗
PubMed2005

High-throughput SNP genotyping on universal bead arrays.

We have developed a flexible, accurate and highly multiplexed SNP genotyping assay for high-throughput genetic analysis of large populations on a bead array platform. The novel genotyping system combines high assay conversion rate and data quality with >1500 multiplexing, and Array of Arrays formats. Genotyping assay oligos corresponding to specific SNP sequences are each linked to a unique sequence (address) that can hybridize to its complementary strand on universal arrays. The arrays are made of beads located in microwells of optical fiber bundles (Sentrix Array Matrix) or silicon slides (Sentrix BeadChip). The optical fiber bundles are further organized into a matrix that matches a 96-well microtiter plate. The arrays on the silicon slides are multi-channel pipette compatible for loading multiple samples onto a single silicon slide. These formats allow many samples to be processed in parallel. This genotyping system enables investigators to generate approximately 300,000 genotypes per day with minimal equipment requirements and greater than 1.6 million genotypes per day in a robotics-assisted process. With a streamlined and comprehensive assay, this system brings a new level of flexibility, throughput, and affordability to genetic research.

DNA Methylation↗
PubMed2005

Age-dependent brain activation during forward and backward digit recall revealed by fMRI.

In this study, brain activation associated with forward and backward digit recall was examined in healthy old and young adults using functional MRI. A number of areas were activated during the recall. In young adults, greater activation was found in the left prefrontal cortex (BA9) and the left occipital visual cortex during backward digit recall than forward digit recall. In contrast, the activation in the right inferior frontal gyrus (BA 44/45) was more extensive in forward digit recall than in backward digit recall. In older adults, backward recall generated stronger activation than forward recall in most areas, including the frontal, the parietal, the occipital, and the temporal cortices. In the backward recall condition, the right inferior frontal gyrus (BA44/45) showed more activation in the old group than in the young group. These results suggest that different neural mechanisms may be involved in forward and backward digit recall and brain functions associated with these two types of recall are differentially affected by aging.

Adult↗
PubMed2005

Caveolin-1 interacts directly with dynamin-2.

Caveolin is the principal component of caveolae in vivo. In addition to a structural role, it is believed to play a scaffolding function to organize and inactivate signaling molecules that are concentrated on the cytoplasmic surface of caveolar membranes. The large GTPase dynamin has been shown to mediate the scission of caveolae from the plasma membrane, although it is unclear if dynamin interacts directly with caveolin or via accessory proteins. Therefore, the goal of this study was to test whether dynamin associates with caveolae via a direct binding to the caveolin 1 (Cav1) protein. Immunoelectron microscopy of lung endothelium or a cultured hepatocyte cell line stained with antibodies for Dyn2 and Cav1 shows that these proteins co-localize to caveolae. To further define this interaction biochemically, in vitro experiments were performed using glutathione-S-transferase (GST)-Dyn2 and GST-Cav1 fusion proteins, which demonstrated a direct interaction between these proteins. This interaction appears to be mediated by the proline-arginine-rich domain (PRD) of Dyn2, as a GST-PRD fragment binds Cav1 while GST-Dyn2DeltaPRD does not. Further, in vitro binding studies using two Dyn2 spliced forms and Cav1 peptides immobilized on paper identify specific domains of Cav1 that bind Dyn2. Interestingly, these Cav1-binding domains differ markedly between two spliced variant forms of Dyn2. In support of these distinctive physical interactions, we find that the different Dyn2 forms, when expressed as GTPase-defective mutants, exert markedly different inhibitory effects on caveolae internalization, as assayed by cholera toxin uptake. These studies provide the first evidence for a direct interaction between dynamin and the caveolin coat, and demonstrate a selectivity of one Dyn2 form toward the caveolae-mediated endocytosis.

Amino Acid Sequence↗
PubMed2005

Hydrogen peroxide preconditioning protects PC12 cells against apoptosis induced by oxidative stress.

Oxidative stress can induce significant cell death by apoptosis. We explore whether prior exposure to H2O2 (H2O2 preconditioning) protects PC12 cells against the apoptotic consequences of subsequent oxidative damages and what role the ATP-sensitive potassium (K(ATP)) channels play in the preconditioning protection. PC12 cells were preconditioned with 90 min exposure to H2O2 at 10 micromol/L, followed by 24-h recovery and subsequent exposures to different concentrations (20, 30, 50 and 100 micromol/L) of H2O2 for 24 h respectively. We used PI staining flow cytometry (FCM) to observe the apoptosis of PC12 cells. It was shown that 24-h exposures to H2O2 at 20, 30, 50 and 100 micromol/L respectively induced substantial cell apoptosis, which was greatly prevented in the preconditioning cells, indicating that H2O2 preconditioning protected PC12 cells against apoptosis induced by H2O2. Administration of pinacidil (10 micromol/L), an K(ATP) channel activator, significantly attenuated the apoptosis of PC12 cells induced by H2O2 at 30 and 50 micromol/L for 24 h respectively. Glybenclamide (10 micromol/L), a K(ATP) channel inhibitor, significantly suppressed or abolished the protective effects caused by the pinacidil but not by H2O2 preconditioning. However, when both H2O2 preconditioning and pinacidil were co-applied, their protection against the apoptosis of PC12 cells was much stronger than that of the individual one of them. These results suggest that H2O2 preconditioning protects PC12 cells against apoptosis and that the activation of K(ATP) channels is not involved in, but synergetically enhances adaptive protection of H2O2 preconditioning.

Animals↗
PubMed2005

Actin and Arf1-dependent recruitment of a cortactin-dynamin complex to the Golgi regulates post-Golgi transport.

Cortactin is an actin-binding protein that has recently been implicated in endocytosis. It binds directly to dynamin-2 (Dyn2), a large GTPase that mediates the formation of vesicles from the plasma membrane and the Golgi. Here we show that cortactin associates with the Golgi to regulate the actin- and Dyn2-dependent transport of cargo. Cortactin antibodies stain the Golgi apparatus, labelling peripheral buds and vesicles that are associated with the cisternae. Notably, in vitro or intact-cell experiments show that activation of Arf1 mediates the recruitment of actin, cortactin and Dyn2 to Golgi membranes. Furthermore, selective disruption of the cortactin-Dyn2 interaction significantly reduces the levels of Dyn2 at the Golgi and blocks the transit of nascent proteins from the trans-Golgi network, resulting in swollen and distended cisternae. These findings support the idea of an Arf1-activated recruitment of an actin, cortactin and Dyn2 complex that is essential for Golgi function.

ADP-Ribosylation Factor 1↗
PubMed2005

The nucleocapsid protein of SARS coronavirus has a high binding affinity to the human cellular heterogeneous nuclear ribonucleoprotein A1.

The nucleocapsid (N) protein of SARS coronavirus (SARS_CoV) is a major structural component of virions, which appears to be a multifunctional protein involved in viral RNA replication and translation. Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is related to the pre-mRNA splicing in the nucleus and translation regulation in the cytoplasm. In this report, based on the relevant biophysical and biochemical assays, the nucleocapsid protein of SARS_CoV (SARS_N) was discovered to exhibit high binding affinity to human hnRNP A1. GST pull-down results clearly demonstrated that SARS_N protein could directly and specifically bind to human hnRNP A1 in vitro. Yeast two-hybrid assays further indicated in vivo that such binding relates to the fragment (aa 161-210) of SARS_N and the Gly-rich domain (aa 203-320) of hnRNP A1. Moreover, kinetic analyses by surface plasmon resonance (SPR) technology revealed that SARS_N protein has a specific binding affinity against human hnRNP A1 with K(D) at 0.35 +/- 0.02 microM (k(on) = 5.83 +/- 0.42 x 10(3) M(-1)s(-1) and k(off) = 2.06 +/- 0.12 x 10(-3)s(-1)). It is suggested that both SARS_N and hnRNP A1 proteins are possibly within the SARS_CoV replication/transcription complex and SARS_N/human hnRNP A1 interaction might function in the regulation of SARS_CoV RNA synthesis. In addition, the determined results showed that SARS_N protein has only one binding domain for interacting with human hnRNP A1, which is different from the mouse hepatitis virus (MHV) binding case where the nucleocapsid protein of MHV (MHV_N) was found to have two binding domains involved in the MHV_N/hnRNP A1 interaction, thereby suggesting that SARS_N protein might carry out a different binding mode to bind to human hnRNP A1 for its further function performance in comparison with MHV_N.

Clone Cells↗
PubMed2005

Constitutively activated FGFR3 mutants signal through PLCgamma-dependent and -independent pathways for hematopoietic transformation.

Ectopic expression of fibroblast growth factor receptor 3 (FGFR3) associated with t(4;14) has been implicated in the pathogenesis of human multiple myeloma. Some t(4;14) patients have activating mutations of FGFR3, of which a minority are K650E (thanatophoric dysplasia type II [TDII]). To investigate the role of autophosphorylated tyrosine residues in FGFR3 signal transduction and transformation, we characterized a series of FGFR3 TDII mutants with single or multiple Y-->F substitutions. Phenylalanine substitution of Y760, essential for phospholipase Cgamma (PLCgamma) binding and activation, significantly attenuated FGFR3 TDII-mediated PLCgamma activation, as well as transformation in Ba/F3 cells and a murine bone marrow transplant leukemia model. In contrast, single substitution of Y577, Y724, or Y770 had minimal to moderate effects on TDII-dependent transformation. Substitution of all 4 non-activation loop tyrosine residues significantly attenuated, but did not abolish, TDII transforming activity. Similar observations were obtained in the context of a constitutively activated fusion TEL-FGFR3 associated with t(4;12)(p16;p13) peripheral T-cell lymphomas. Moreover, 2 independent EmuSR-FGFR3 TDII transgenic mouse lines developed a pro-B-cell lymphoma, and PLCgamma was highly activated in primary lymphoma cells as assessed by tyrosine phosphorylation. These data indicate that engagement of multiple signaling pathways, including PLCgamma-dependent and PLCgamma-independent pathways, is required for full hematopoietic transformation by constitutively activated FGFR3 mutants.

Amino Acid Substitution↗
PubMed2005

A helical structure with Z' = 10.

The structure of N''-cyano-N,N-diisopropylguanidine, a push-pull nitrile that includes the H(2)N-C=N-CN fragment, has been determined. Although the number of molecules in the asymmetric unit is exceptionally high (Z' = 10), there were no special crystallographic difficulties associated with data collection, structure solution or structure refinement because the individual molecules are small (12 non-H atoms) and because there is no important crystallographic pseudosymmetry. A complete set of N-H...N bonds is formed. Pairs of molecules form dimers, which associate to form ribbons that twist into a helix having five dimers per turn. The helices lie parallel to [101] and fit together with close contacts in three different directions perpendicular to that axis. The problems with optimizing so many different intermolecular contacts lead to a loosely packed structure.

Journal Article↗
PubMed2005

Synthesis and activity of 4,5-diarylimidazoles as human CB1 receptor inverse agonists.

Structure-activity relationship studies directed toward the optimization of 4,5-diarylimidazole-2-carboxamide analogs as human CB1 receptor inverse agonists resulted in the discovery of the two amide derivatives 24a and b (hCB1 IC50 = 6.1 and 4.0 nM) which also demonstrated efficacy in overnight feeding studies in the rat for reduction in both food intake and overall body weight.

Animals↗
PubMed2005

A dynamin-3 spliced variant modulates the actin/cortactin-dependent morphogenesis of dendritic spines.

Immature dendrites extend many actin-rich filopodial structures that can be replaced by synapse-containing dendritic spines as the neuron matures. The large GTPase dynamin-3 (Dyn3) is a component of the postsynapse in hippocampal neurons but its function is undefined. Here, we demonstrate that a specific Dyn3 variant (Dyn3baa) promotes the formation of immature dendritic filopodia in cultured neurons. This effect is dependent upon Dyn3 GTPase activity and a direct interaction with the F-actin-binding protein cortactin. Consistent with these findings, Dyn3baa binds to cortactin with a 200% higher affinity than Dyn3aaa, a near identical isoform that does not induce dendritic filopodia when expressed in cultured neurons. Finally, levels of Dyn3baa-encoding mRNA are tightly regulated during neuronal maturation and are markedly upregulated during synaptogenesis. Together, these findings provide the first evidence that an enhanced interaction between a specific Dyn3 splice variant and cortactin modulate actin-membrane dynamics in developing neurons to regulate the morphogenesis of dendritic spines.

Actins↗
PubMed2005

Electrochemical antitumor drug sensitivity test for leukemia K562 cells at a carbon-nanotube-modified electrode.

The change in electrochemical behavior of tumor cells induced by antitumor drugs was detected by using a multiwall carbon nanotubes (MWNTs)-modified glass carbon electrode (GCE). Based on the changes observed, a simple, in vitro, electrochemical antitumor drug sensitivity test was developed. MWNTs promoted electron transfer between the electroactive centers of cells and the electrode. Leukemia K562 cells exhibited a well-defined anodic peak of guanine at +0.823 V at 50 mV s(-1). HPLC assay with ultraviolet detection was used to elucidate the reactant responsible for the electrochemical response of the tumor cells. The guanine content within the cytoplasm of each K562 cell was detected to be 920 amol. For the drug sensitivity tests, 5-fluorouracil (5-FU) and several clinical antitumor drugs, such as vincristine, adriamycin, and mitomycin C, were added to cell culture medium. As a result, the electrochemical responses of the K562 cells decreased significantly. The cytotoxicity curves and results obtained corresponded well with the results of MTT assays. In comparison to conventional methods, this electrochemical test is highly sensitive, accurate, inexpensive, and simple. The method proposed could be developed as a convenient means to study the sensitivity of tumor cells to antitumor drugs.

Antineoplastic Agents↗
PubMed2005

C/EBP{beta} and its binding element are required for NF{kappa}B-induced COX2 expression following hypertonic stress.

NFkappaB plays a critical role mediating COX2 expression in renal medullary interstitial cells (RMICs). The trans-activating ability of NFkappaB can be modified by another nuclear factor C/EBPbeta that can physically bind to NFkappaB and regulate its activity. Because the COX2 promoter also contains a C/EBPbeta site adjacent to the NFkappaB site, the present study examined whether these two transcription factors cooperate to induce COX2 expression following hypertonic stress. Hypertonicity markedly induced COX2 expression in cultured medullary interstitial cells by immunoblot analysis. The tonicity-induced COX2 expression was suppressed by mutant IkappaB (IkappaBm) that blocks NFkappaB activation, demonstrating that tonicity-induced COX2 expression depends on NFkappaB activation. However, mutation of the NFkappaB site in the COX2 promoter failed to abolish tonicity-induced COX2 reporter activity. IkappaB kinase-1 (IKK1) significantly induced COX2-luciferase activity by 2.3-fold (n = 10, p < 0.01); mutation of the NFkappaB site also failed to abolish IKK1-stimulated COX2 reporter activity (86 +/- 3.1% of wild type, p > 0.05, n = 4). Interestingly, mutation of the C/EBPbeta site of the COX2 gene significantly reduced both IKK1 and hypertonicity-induced COX2 reporter activity (p < 0.01). To further examine the potential role of C/EBPbeta in tonicity-induced COX2 expression, a dominant negative C/EBPbeta-p20 was transduced into RMICs. C/EBPbeta-p20 markedly suppressed hypertonic (550 mOsm) induction of COX2 (immunoblot) to a similar extent as IkappaBm. No additional suppression was observed when both NFkappaB and C/EBPbeta were simultaneously blocked by IkappaBm and C/EBPbeta-p20. Interestingly, IKK-induced COX2 expression was not only blocked by IkappaBm, but also completely abolished by C/EBPbeta-p20. Further studies demonstrated physical association of C/EBPbeta to NFkappaB p65 by coimmunoprecipitation. Importantly, this interaction between C/EBPbeta and NFkappaB was greatly enhanced following hypertonic stress. These studies indicate C/EBPbeta is required for the transcriptional activation of COX2 by NFkappaB, suggesting a dominant role for the C/EBPbeta pathway in regulating induction of RMIC COX2 by hypertonicity.

Animals↗
PubMed2005

Synthesis of Ag/BSA composite nanospheres from water-in-oil microemulsion using compressed CO2 as antisolvent.

In this work, a novel route to synthesize biomolecule/metal composite nanospheres is proposed. This method combines the advantages that the silver nanoparticles and bovine serum albumin (BSA) can be precipitated simultaneously from water-in-oil microemulsion by the easy control of CO2 pressure, which was revealed by our high-pressure UV-VIS spectra. The Ag/BSA nanocomposites were successfully prepared using this method. The transmission electronic microscopy (TEM) if the obtained nanocomposites shows that the small-sized Ag nanaoparticles are immobilized by the BSA nanospheres, and the phase structure was characterized by X-ray diffraction (XRD). The Ag/BSA nanocomposites show absorption properties at a wavelength around 435 nm.

Biocompatible Materials↗