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Biomedical subjects

Jun Chen

Publications and source records attributed to Jun Chen.

At least 37 records · Page 2Linked to original sources
PubMed2006

Nociceptive stimulus modality-related difference in pharmacokinetic-pharmacodynamic modeling of morphine in the rat.

Pharmacokinetics (PK)-pharmacodynamics (PD) modeling, the mathematical description of the relationship between PK and PD, can estimate and predict relevant parameters associated with onset, magnitude and time courses of dose-concentration-effect of a drug. In this report, we introduce a new nonsteady-state and time-dependent PK-PD modeling of a single dose of morphine in which time courses of concentration of unconjugated and estimated conjugated morphine in compartments of either plasma or biophase (cerebrospinal fluid, CSF) and multiple anti-nociceptive effects across thermal and mechanical stimulus modalities in rats were studied. The results showed that: (1) both intragastric and intraperitoneal administration of a single dose of morphine resulted in a differential anti-nociceptive effect in both magnitude and time course of the drug between thermal and mechanical painful stimuli (anti-mechanical pain effect was 2-3 fold stronger than anti-thermal pain effect, P < 0.01); (2) the PK data showed that the area under concentration-time curves of conjugated morphine was 4.5 and 2.0 fold bigger than unconjugated morphine in either plasma and biophase compartments, suggesting that the PK processes of unconjugated morphine are different from that of conjugated morphine; (3) the PD data also showed a change in PD characteristics of unconjugated and conjugated morphine across systemic and biophasic compartments for anti-mechanical pain effect, while there was no change at all for anti-thermal pain effect; (4) the difference in analgesia of a single dose of morphine across thermal and mechanical stimulus modalities was well reflected by the difference in the nonsteady-state and time-dependent PK-PD modeling, namely, the clockwise hysteresis loop model well represents the relationship of the time course between unconjugated/conjugated morphine concentration (both plasma and biophase) and anti-thermal pain effect, while the counter-clockwise hysteresis loop model well represents that between conjugated morphine concentration (mainly in biophase) and anti-mechanical pain effect. Taken together, the multiple PD-PK modeling is more useful in estimation and prediction of onset, magnitude and time courses of concentration-multiple pharmacological effects of morphine than simple PK or PD models, and establishment of various multiple PD-PK modeling might also be more useful in optimizing clinical use of existing drugs as well as new drugs for analgesia or treatment of other diseases.

Analgesics, Opioid↗
PubMed2006

Protein kinase D 3 is localized in vesicular structures and interacts with vesicle-associated membrane protein 2.

Protein kinase D localizes in the Golgi and regulates protein transport from the Golgi to the plasma membrane. In the present study, we found that PKD3, a novel member of the PKD family, and its fluorescent protein fusions localized in the Golgi and in the vesicular structures that are in part marked by endosome markers. Fluorescent recovery after photobleaching (FRAP) showed that the PKD3-associated vesicular structures were constantly forming and dissolving, reflecting active subcellular structures. FRAP on plasma membrane-located PKD3 indicated a slower recovery of PKD3 fluorescent signal compared to those of PKC isoforms, implying a different targeting mechanism at the plasma membrane. VAMP2, the vesicle-localized v-SNARE, was later identified as a novel binding partner of PKD3 through yeast two-hybrid screening. PKD3 directly interacted with VAMP2 in vitro and in vivo, and colocalized in part with VAMP2 vesicles in cells. PKD3 did not phosphorylate VAMP-GFP and the purified GST-VAMP2 protein in in vitro phosphorylation assays. Rather, PKD3 was found to promote the recruitment of VAMP2 vesicles to the plasma membrane in response to PMA, while the kinase dead PKD3 abolished this effect. Thus, the kinase activity of PKD3 was required for PMA-induced plasma membrane trafficking of VAMP2. In summary, our findings suggest that PKD3 localizes to vesicular structures that are part of the endocytic compartment. The vesicular distribution may be attributed in part to the direct interaction between PKD3 and vesicle-associated membrane protein VAMP2, through which PKD3 may regulate VAMP2 vesicle trafficking by facilitating its recruitment to the target membrane.

Animals↗
PubMed2006

Utility of large-scale transiently transfected cells for cell-based high-throughput screens to identify transient receptor potential channel A1 (TRPA1) antagonists.

Despite increasing use of cell-based assays in high-throughput screening (HTS) and lead optimization, one challenge is the adequate supply of high-quality cells expressing the target of interest. To this end, cell lines stably expressing targets are often established, maintained, and scaled up by cell culture. These steps require large investments of time and resources. Moreover, significant variability invariably occurs in cell yield, viability, expression levels, and target activities. In particular, stable expression of targets such as transient receptor potential A1 (TRPA1) causes toxicity, cell line degeneration, and loss of functional activity. Therefore, in an effort to identify TRPA1 antagonists, the authors used large-scale transiently transfected (LSTT) cells, enabling rapid establishment of assays suitable for HTS. LSTT cells, which could- be stored frozen for a long period of time (e.g., at least 42 weeks), retained TRPA1 protein expression and could be easily revived to produce robust and consistent signals in calcium influx and electrophysiological assays. Using cells from a single transfection, a chemical library of 700,000 compounds was screened, and TRPA1 antagonists were identified. The use of LSTT circumvented issues associated with stable TRPA1 expression, increased flexibility and consistency, and greatly reduced labor and cost. This approach will also be applicable to other pharmaceutical targets.

Calcium↗
PubMed2006

Glycated Collagen I (GC) impairs angiogenesis in vitro: a study using an innovative chamber for cell research.

Studies of cell-matrix, cell-cell interaction or angiogenesis on different matrices require simultaneous comparison of read-out parameters from differently treated companion cells. The culture conditions (cell number, temperature and volume of culture medium) in different chambers are not completely equalized using conventional methods. It has been reported that cells growing in different environmental conditions may exhibit different proliferation patterns [P. Tracqui, J.W. Liu, O. Collin, J. Clement-Lacroix, E. Planus, Global analysis of endothelial cell line proliferation patterns based on nutrient-depletion models: implications for a standardization of cell proliferation assays, Cell Proliferat. 38(June (3)) (2005) 119-135]. Herein we describe an innovative chamber, which could resolve this problem by significantly improving the standardization of experimental conditions. The chamber was manufactured from a standard cell culture well by its division with a septum into two sections. We utilized the chamber and recently developed topological analysis to examine the effects of glycated matrices on the capillary-like network formation by endothelial cells. Glycated Collagen I resulted in dose-dependent changes to all measured topological characteristics of the capillary-like network, such as the number of branching points, number of meshes and total capillary length. These differences were observed only in neighbored compartments coated with different matrices, but not in the compartments coated with the same matrix. The novel chamber brings an opportunity for better standardization of experimental conditions and simultaneous observation of different experimental groups, reducing the possible effect of any systematic error.

Cell Culture Techniques↗
PubMed2006

Association of vitamin D receptor FokI polymorphism with prostate cancer risk, clinicopathological features and recurrence of prostate specific antigen after radical prostatectomy.

To investigate the effect of vitamin D receptor (VDR) FokI polymorphism on susceptibility to prostate cancer and the outcome of the disease in a Taiwanese population, we genotyped a total of 416 prostate cancer patients, 502 age-matched male controls and 189 non age-matched symptomatic benign prostatic hyperplasia. Although we did not find a significant association between VDR FokI genotypes and overall prostate cancer risk, we found that in men aged less than or equal to the median age of 73 years with VDR FokI F allele specifically had an increased risk of prostate cancer with a marginal significant trend (OR, 2.08; 95% CI, 1.00-4.34, p for trend = 0.056). The FF genotype was also highly associated with more aggressive prostate cancer (Gleason score 8-10) (OR, 2.47; 95% CI, 1.20-5.08) than did the Ff and ff genotypes. After adjusting other covariates, we found that in patients who had localized prostate cancer for which a radical prostatectomy was performed (n = 131), the VDR FokI FF genotype was associated with worse prostate-specific antigen (PSA) recurrence-free survival (hazard ratio = 3.25, 95% CI = 1.32-8.00, p = 0.010). Our findings suggest that the VDR FF genotype may increase the risk of early-onset prostate cancer and is associated with more aggressive disease. Furthermore, the VDR polymorphism could be used as a prognostic marker for localized prostate cancer after radical prostatectomy.

Aged↗
PubMed2006

Different signaling responses to anti-proliferative agents in human aortic and venous smooth muscle cells.

Proliferation of smooth muscle cells (SMCs) contributes to the stenosis of coronary arteries and vascular grafts. Local delivery of anti-proliferative drugs can prevent vascular stenosis. To understand the cellular responses to anti-proliferative agents, we investigated the signaling events in cultured human aortic SMCs (ASMCs), saphenous venous SMCs (VSMCs), and dermal fibroblasts (DFs) in response to paclitaxel or etoposide. Cellular mitochondrial and proliferative activities were examined with the methylthiazoletetrazolium (MTT) dye reduction and the bromodeoxyuridine (BrdU) incorporation assay, respectively. Cell proliferation was almost completely suppressed by paclitaxel or etoposide, but apoptosis was achieved in only about 50% of cells at the highest drug concentrations, suggesting the presence of compensatory mechanisms to prevent apoptosis. Examination of three important signaling pathways revealed significant differences between ASMCs, VSMCs, and DFs. Treatment with either paclitaxel or etoposide caused a transient phosphorylation/activation of p42 MAPK in ASMCs and DFs, but had no effect on phospho-p42/44 MAPK in VSMCs. High-dose etoposide enhanced p38 MAPK activation in ASMCs, but not in VSMCs. The p38 inhibitor, PD169316, partially inhibited etoposide-induced ASMC apoptosis, but induced apoptosis in VSMCs. The effects of etoposide and paclitaxel on Akt also differed between ASMCs and VSMCs. These observations indicate that ASMCs and VSMCs differ in the response of signaling pathways to anti-proliferative agents. In ASMCs, p42/44 MAPK appears to serve a pro-survival role, whereas p38 MAPK is a pro-apoptotic regulator. In contrast, p38 MAPK is an important pro-survival regulator in VSMCs and p42/44 MAPK appears to play a minor role in responding to anti-proliferative drugs.

Animals↗
PubMed2006

The oncoprotein LMO2 is expressed in normal germinal-center B cells and in human B-cell lymphomas.

We previously developed a multivariate model based on the RNA expression of 6 genes (LMO2, BCL6, FN1, CCND2, SCYA3, and BCL2) that predicts survival in diffuse large B-cell lymphoma (DLBCL) patients. Since LMO2 emerged as the strongest predictor of superior outcome, we generated a monoclonal anti-LMO2 antibody in order to study its tissue expression pattern. Immunohistologic analysis of over 1200 normal and neoplastic tissue and cell lines showed that LMO2 protein is expressed as a nuclear marker in normal germinal-center (GC) B cells and GC-derived B-cell lines and in a subset of GC-derived B-cell lymphomas. LMO2 was also expressed in erythroid and myeloid precursors and in megakaryocytes and also in lymphoblastic and acute myeloid leukemias. It was rarely expressed in mature T, natural killer (NK), and plasma cell neoplasms and was absent from nonhematolymphoid tissues except for endothelial cells. Hierarchical cluster analysis of immunohistologic data in DLBCL demonstrated that the expression profile of the LMO2 protein was similar to that of other GC-associated proteins (HGAL, BCL6, and CD10) but different from that of non-GC proteins (MUM1/IRF4 and BCL2). Our results warrant inclusion of LMO2 in multivariate analyses to construct a clinically applicable immunohistologic algorithm for predicting survival in patients with DLBCL.

Adaptor Proteins, Signal Transducing↗
PubMed2006

In situ studies on the distribution patterns and dynamics of microcystins in a biomanipulation fish--bighead carp (Aristichthys nobilis).

The distribution and dynamics of microcystins in various organs of the phytoplanktivorous bighead carp were studied monthly in Lake Taihu, which is dominated by toxic cyanobacteria. There was a good agreement between LC-MS and HPLC-UV determinations. Average recoveries of spiked fish samples were 63% for MC-RR and 71% for MC-LR. The highest MC contents in intestine, liver, kidney and spleen were 85.67, 2.83, 1.70 and 1.57 microg g-1 DW, respectively. MCs were much higher in mid-gut walls (1.22 microg g-1 DW) than in hind- and fore-gut walls (0.31 and 0.18 microg g-1 DW, respectively), suggesting the importance of mid-gut wall as major site for MC absorption. A cysteine conjugate of MC-LR was detected frequently in kidney. Among the muscle samples analyzed, 25% were above the provisional tolerable daily intake level by WHO. Bighead is strongly resistant to microcystins and can be used as biomanipulation fish to counteract cyanotoxin contamination in eutrophic waters.

Animals↗
PubMed2006

Change of sexual function in patients before and after Ho:YAG laser enucleation of the prostate.

The aim of this study is to evaluate the effect of Ho:YAG laser enucleation of the prostate (HOLEP) to the sexual function of patients with benign prostatic hyperplasia (BPH). In the course of the study, 108 patients with BPH were recruited and accepted treatment with HOLEP. The effectiveness of treatment was evaluated by flow rate and the International Prostate Symptom Score (IPSS) before HOLEP and 6 months afterwards. Meanwhile, the sexual functions were evaluated with the Danish Prostate Symptom Score Sexual Function Questionnaire (DanPSS Sex). Before and 6 months after HOLEP treatment, the mean residual urine volume was reduced from 106.0 +/- 51.7 mL to 5.6 +/- 1.7 mL (P<.01), maximum flow rate was improved from 7.2 +/- 3.9 mL/s to 21.7 +/- 1.3 mL/s (P<.01), nocturia frequency was reduced from 5.5 to 1.5 (P<.01), and the mean IPSS score was decreased from 19.4 +/- 5.6 to 7.4 +/- 2.6 (P<.01). The proportion of patients satisfied with their libido was 55% before HOLEP and 57% 6 months afterwards, while 23.5% of the patients had no libido before and after HOLEP; 37% of the patients were satisfied with their erection before HOLEP and 40% after 6 months; 30% of the patients had completely satisfactory sex life before HOLEP, and 32% did 6 months later. The corresponding percentages of fully impotent patients increased from 33% before the procedure to 35% 6 months postoperation. Early morning erections were reported by 45% of the patients before the procedure and by 62% 6 months later (P<.01). In 70% of the patients with normal sex life, ejaculation was retrograde 6 months after HOLEP (P<.01). HOLEP does not affect the sexual function of patients with BPH but does did improve the ability of early morning erection, while causing retrograde ejaculation.

Aged↗
PubMed2006

Signal transducers and activators of transcription 5 contributes to erythropoietin-mediated neuroprotection against hippocampal neuronal death after transient global cerebral ischemia.

The signal transducers and activators of transcription (STAT) proteins are a group of transcriptional factors. Among them, STAT5 initiates a pro-survival signaling cascade. So far, little has been known about the role of STAT5 in cerebral ischemia and reperfusion. This study examines the phosphorylation status of STAT5 in hippocampal CA1 in the early stage after transient global cerebral ischemia in rats. Our data show that the phosphorylation of STAT5 was increased in hippocampal CA1 at 1h and 3h ischemia. Taking advantage of the neuroprotective effect of erythropoietin (EPO) in CA1, we further demonstrated that the administration of EPO enhanced the phosphorylation of STAT5, with SATA5a being phosphorylated earlier. The enhanced phosphorylation of STAT5 in the EPO-treated group was accompanied by the upregulation of STAT5 downstream gene products, Bcl-xL and XIAP. Consequently, ischemic CA1 neuronal damage was attenuated by the administration of EPO. Both the enhancement of STAT5 phosphorylation and the neuroprotection rendered by EPO were blocked by Tyrphostin, a selective inhibitor for Janus kinase 2, which is an upstream kinase of STAT5. These findings suggest an association between the activation of STAT5 and CA1 neuronal survival after cerebral ischemia.

Animals↗
PubMed2006

Bcl-2 enhances neurogenesis and inhibits apoptosis of newborn neurons in adult rat brain following a transient middle cerebral artery occlusion.

To determine whether Bcl-2 could influence adult neurogenesis and prevent apoptosis of newborn neurons, we injected Bcl-2 expressing plasmid into the lateral ventricle of rat brain immediately following a 30-min occlusion of the middle cerebral artery (MCAO). We found that Bcl-2 increased neural progenitor cells (BrdU+-DCX+) in the ipsilateral striatum, newborn immature neurons (BrdU+-Tuj-1+) and newborn mature neurons (BrdU+-MAP-2+) in the ipsilateral striatum and frontal cortex at 1 to 4 weeks following MCAO. Bcl-2 overexpression promoted development of newborn neurons into GABAergic and cholinergic neurons in the ipsilateral striatum. Moreover, Bcl-2 significantly decreased the apoptosis of newborn neurons, determined by double staining of Tuj-1 and activated caspase-3 (Tuj-1+-Casp+). These results indicate that overexpression of Bcl-2 in adult rat brain enhances neurogenesis and survival of newborn neurons. Increasing neurogenesis and preventing the death of newborn neuron may be a strategy to aid in the repair of adult brain after stroke.

Animals↗
PubMed2006

Catalpol protects dopaminergic neurons from LPS-induced neurotoxicity in mesencephalic neuron-glia cultures.

Inflammation plays an important role in the pathogenesis of Parkinson's disease (PD). Microglia, the resident immune cells in the central nervous system, are pivotal in the inflammatory reaction. Activated microglia can induce expression of inducible nitric-oxide synthase (iNOS) and release significant amounts of nitric oxide (NO) and TNF-alpha, which can damage the dopaminergic neurons. Catalpol, an iridoid glycoside, contained richly in the roots of Rehmannia glutinosa, was found to be neuroprotective in gerbils subjected to transient global cerebral ischemia. But the effect of catalpol on inflammation-mediated neurodegeneration has not been examined. In this study, microglia in mesencephalic neuron-glia cultures were activated with lipopolysaccharide (LPS) and the aim of the study was to examine whether catalpol could protect dopaminergic neurons from LPS-induced neurotoxicity. The results showed that catalpol significantly reduced the release of reactive oxygen species (ROS), TNF-alpha and NO after LPS-induced microglial activation. Further, catalpol attenuated LPS-induced the expression of iNOS. As determined by immunocytochemical analysis, pretreatment by catalpol dose-dependently protected dopaminergic neurons against LPS-induced neurotoxicity. These results suggest that catalpol exerts its protective effect on dopaminergic neurons by inhibiting microglial activation and reducing the production of proinflammatory factors. Thus, catalpol may possess therapeutic potential against inflammation-related neurodegenerative diseases.

Animals↗
PubMed2006

Laparoscopic partial adrenalectomy for aldosterone-producing adenomas with needlescopic instruments.

INTRODUCTION: Laparoscopic total adrenalectomy is the treatment of choice for aldosterone-producing adenomas (APAs). There have not been many reports of laparoscopic partial adrenalectomy, although this procedure offers benefits to patients with suspected bilateral APAs or an APA in a solitary adrenal gland. We describe the feasibility of a novel technique of laparoscopic partial adrenalectomy for APA solely using 2-mm working instruments and a 5 to 10-mm telescope. TECHNICAL CONSIDERATIONS: Six unilateral and two bilateral partial adrenalectomies were performed laparoscopically. Only one umbilical 12-mm port for the telescope and two (for left adenomas) or three (for right adenomas) subcostal 2-mm working ports were used. Hemostasis and transection of adrenal tissues were performed using a 2-mm mini-bipolar coagulator and 2-mm scissors. RESULTS: All laparoscopic operations were successfully performed using only 2-mm working instruments and a 5 or 10-mm 30 degree telescope with no intraoperative or postoperative complications. Blood loss was minimal, and the operative times were comparable to those of previous reports. All patients had low pain scores, required minimal amounts of narcotics postoperatively, and reported excellent cosmetic results for the wounds. The pathologic examinations confirmed complete excision of all adenomas with intact capsules. The plasma aldosterone concentrations and renin activities returned to normal ranges postoperatively in all patients. At a mean follow-up of 25 months (range 13 to 48), 7 (87.5%) were cured of their hypertension and 1 had the hypertensive medications significantly reduced. CONCLUSIONS: Laparoscopic partial adrenalectomy for APAs using 2-mm working instruments and a 5 to 10-mm telescope is a safe and effective treatment alternative.

Adenoma↗
PubMed2006

Fiber-based telecom-band degenerate-frequency source of entangled photon pairs.

We demonstrate the generation of polarization-entangled photon pairs of degenerate frequency for the first time, to the best of our knowledge, in standard optical fiber using a novel dual-pump, counterpropagating configuration. Two-photon interference with >97% visibility is obtained. The purity of the photon source, as characterized by the ratio of coincidence to accidental-coincidence counts, is shown to be as high as 116 under suitable operating conditions.

Journal Article↗
PubMed2006

Active participation of antigen-nonspecific lymphoid cells in immune-mediated inflammation.

The pathogenic process of tissue-specific autoimmune disease depends to a large extent on recruitment of Ag-nonspecific cells into the target tissue. Little is known, however, about the recruitment process and the features that characterize the recruited cells. In this study, we analyzed the recruitment of Ag-nonspecific lymphoid cells into an inflammatory site by using an experimental system in which TCR-transgenic Th1 cells are adoptively transferred to induce ocular inflammation in recipient mice that express the target Ag in their eyes. A sharp increase in number of all host cell populations was observed in the recipient spleen, reaching a peak on day 4 postcell transfer and declining thereafter. A large portion of the host's spleen CD4 cells underwent phenotypic changes that facilitate their migration into the target organ, the eye. These changes included increased expression of the chemokine receptor CXCR3, and the adhesion molecule CD49d, as well as a decline in expression of CD62L. The host lymphocytes migrated into the recipient mouse eye more slowly than the donor cells, but became the great majority of the infiltrating cells at the peak of inflammation on day 7 postcell injection. Interestingly, the mass migration of host T cells was preceded by an influx of host dendritic cells, that reached their peak on day 4 postcell injection. The eye-infiltrating host CD4 lymphocytes underwent additional changes, acquiring a profile of activated lymphocytes, i.e., up-regulation of CD25 and CD69. Our results thus provide new information about the active participation of Ag-nonspecific lymphoid cells in immune-mediated inflammation.

Animals↗
PubMed2006

Transient simulation of kinetics of electric-sensitive hydrogels.

Kinetics of the hydrogels responsive to electric stimulus due to an externally applied electric field is modeled for the first time through transient simulation. The mathematical model employed is called the multi-effect-coupling electric-stimulus (MECe) model, which is developed with consideration of multi-phases and multi-physics. Transient simulation by the MECe model is examined with available experimental data and good agreement is achieved. The kinetics of ionic concentration of diffusive species is simulated. The simulation also predicts the influences of several important parameters on the hydrogel deformation, including the externally applied electric voltage, initially fixed charge density and surrounding bath solution concentration.

Biosensing Techniques↗
PubMed2006

Mutational analysis of the GDD sequence motif of classical swine fever virus RNA-dependent RNA polymerases.

To define the function of the GDD motif of the RNA-dependent RNA polymerase (RdRp) of classical swine fever virus (CSFV), single amino acid substitutions were introduced into the CSFV NS5B. All substitutions within the GDD motif were detrimental to the polymerase activity, the binding activity and the terminal nucleotidyl transferase activity of the NS5B protein. It was also found that the wild-type NS5B had higher RdRp activity with Mg(+2) than with Mn(+2) whereas some mutants worked better with Mn(+2) than with Mg(+2), suggesting that substitutions within the GDD motif modified the enzyme cation preferences and the GDD sequence of CSFV NS5B might be involved in polymerase-metal interaction. Therefore, the GDD amino acid sequence is important for the function of CSFV RdRp.

Amino Acid Motifs↗