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Biomedical subjects

Jun Chen

Publications and source records attributed to Jun Chen.

At least 55 records · Page 3Linked to original sources
PubMed2006

Observation of two new N* peaks in J/psi-->ppi-n and ppi+n decays.

The decay J/psi-->NNpi provides an effective isospin 1/2 filter for the piN system due to isospin conservation. Using 58x10(6) J/psi decays collected with the Beijing Electromagnetic Spectrometer at the Beijing Electron Positron Collider, more than 100 thousand J/psi-->ppi-n+c.c. events are obtained. Besides the two well-known N* peaks at around 1500 MeV/c2 and 1670 MeV/c2, there are two new, clear N* peaks in the ppi invariant mass spectrum around 1360 MeV/c2 and 2030 MeV/c2 with statistical significance of 11sigma and 13sigma, respectively. We identify these as the first direct observation of the N*(1440) peak and a long-sought missing N* peak above 2 GeV/c2 in the piN invariant mass spectrum.

Journal Article↗
PubMed2006

A large quantity of novel human antisense transcripts detected by LongSAGE.

MOTIVATION: Taking advantage of the high sensitivity and specificity of LongSAGE tag for transcript detection and genome mapping, we analyzed the 632 813 unique human LongSAGE tags deposited in public databases to identify novel human antisense transcripts. RESULTS: Our study identified 45 321 tags that match the antisense strand of 9804 known mRNA sequences, 6606 of which contain antisense ESTs and 3198 are mapped only by SAGE tags. Quantitative analysis showed that the detected antisense transcripts are present at levels lower than their counterpart sense transcripts. Experimental results confirmed the presence of antisense transcripts detected by the antisense tags. We also constructed an antisense tag database that can be used to identify the antisense SAGE tags originated from the antisense strand of known mRNA sequences included in the RefSeq database. CONCLUSIONS: Our study highlights the benefits of exploring SAGE data for comprehensive identification of human antisense transcripts and demonstrates the prevalence of antisense transcripts in the human genome.

Base Sequence↗
PubMed2006

Disposition of flavonoids via enteric recycling: structural effects and lack of correlations between in vitro and in situ metabolic properties.

The purpose of this study is to determine the importance of coupling of efflux transporters and metabolic enzymes in the intestinal disposition of six isoflavones (genistein, daidzein, formononetin, glycitein, biochanin A, and prunetin), and to determine how isoflavone structural differences affect the intestinal disposition. A rat intestinal perfusion model was used, together with rat intestinal and liver microsomes. In the intestinal perfusion model, significant absorption and excretion differences were found between isoflavones and their respective glucuronides (p <0.05), with prunetin being the most rapidly absorbed and formononetin glucuronides being the most excreted in the small intestine. In contrast, glucuronides were excreted very little in the colon. In an attempt to account for the differences, we measured the glucuronidation rates of six isoflavones in microsomes prepared from rat intestine and liver. Using multiple regression analysis, intrinsic clearance (CL(int)) and other enzyme kinetic parameters (V(max) and K(m)) were determined using appropriate kinetic models based on Akaike's information criterion. The kinetic parameters were dependent on the isoflavone used and the types of microsomes. To determine how metabolite excretion rates are controlled, we plotted excretion rates versus calculated microsomal rates (at 10 microM), CL(int) values, K(m) values, or V(max) values, and the results indicated that excretion rates were not controlled by any of the kinetic parameters. In conclusion, coupling of intestinal metabolic enzymes and efflux transporters affects the intestinal disposition of isoflavones, and structural differences of isoflavones, such as having methoxyl groups, significantly influenced their intestinal disposition.

Animals↗
PubMed2006

Inflammatory processes triggered by TCR engagement or by local cytokine expression: differences in profiles of gene expression and infiltrating cell populations.

Immune cell-mediated inflammatory responses are triggered by TCR engagement with the target antigen, the initial event that brings about the complex sequence of events of the inflammatory process. Another form of inflammation is induced by local expression of certain cytokines. Unlike the former form of inflammation, little is known about the basic features of the cytokine-induced responses. Here, we analyzed tissue morphology, the infiltrating cells, and up-regulated, inflammation-related genes in mouse eyes in which inflammation is triggered by local transgenic (Tg) expression of cytokines and compared these features with those in eyes with experimental autoimmune uveitis (EAU), in which inflammation is initiated by engagement of TCR on sensitized T cells with their target antigen, followed by the well-defined, subsequent cytokine production. Eyes of IFN-gamma Tg mice exhibited severe, morphological changes but essentially no inflammation, and intense inflammation was found in eyes of interleukin (IL)-1 or IL-7 Tg mice. The cellular infiltration in eyes of these latter two lines of Tg mice resembled that in eyes with EAU by including many CD4 cells, but unlike in EAU, the infiltration in Tg eyes contained large proportions of B cells and only small numbers of macrophages. Real-time PCR analysis of eye RNA revealed differences among the disease models in the expression profiles of various inflammation-related genes. It is interesting that a bias toward T helper cell type 1 immunity (high IFN-gamma, RANTES/CCL5, MIG/CXCL9, and T-bet but low IL-4, IL-5, and GATA-3 transcripts) was found in EAU eyes but not in eyes of IL-1 and IL-7 Tg mice. The results thus show that similar to TCR engagement, local expression of certain cytokines triggers a complex, subsequent production of numerous inflammation-related molecules, but features of the ensued inflammatory process are determined by the triggering mechanism.

Animals↗
PubMed2006

Generation of high-purity telecom-band entangled photon pairs in dispersion-shifted fiber.

We study the purity of correlated photon pairs generated in a dispersion-shifted fiber at various temperatures. The ratio of coincidence to accidental-coincidence counts greater than 100 can be obtained as the fiber is cooled to liquid-nitrogen temperature (77 K). We then generate polarization-entangled photon pairs by using a compact counterpropagating scheme. Two-photon interference with visibility >98% and Bell's inequality violation by >8 standard deviations of measurement uncertainty are observed at 77 K, without subtracting the accidental-coincidence counts due to background Raman photons.

Journal Article↗
PubMed2006

Shape-controlled synthesis of ternary chalcogenide ZnIn2S4 and CuIn(S,Se)2 nano-/microstructures via facile solution route.

We demonstrated in this paper the shape-controlled synthesis of ZnIn2S4, CuInS2, and CuInSe2 nano- and microstructures through a facile solution-based route. One-dimensional ZnIn2S4 nanotubes and nanoribbons were synthesized by a solvothermal method with pyridine as the solvent, while ZnIn2S4 solid or hollow microspheres were hydrothermally prepared in the presence of a surfactant such as cetyltrimethylammonium bromide (CTAB) or poly(ethylene glycol) (PEG). The mechanisms related to the phase formation and morphology control of ZnIn2S4 are proposed and discussed. The UV-vis absorption spectra show that the as-prepared nano- and micromaterials have strong absorption in a wide range from UV to visible light and that their band gaps are somewhat relevant to the size and morphology. The photoluminescence measurements of the ZnIn2S4 microspheres at room temperature reveal intense excitation at approximately 575 nm and red emission at approximately 784 nm. Furthermore, CuInS2 and CuInSe2 with different morphologies such as spheres, platelets, rods, and fishbone-like shapes were also obtained by similar hydrothermal and solvothermal synthesis.

Journal Article↗
PubMed2006

Efficacy and safety of intraoperative peritoneal hyperthermic chemotherapy for advanced gastric cancer patients with serosal invasion. A long-term follow-up study.

AIMS: This study was undertaken to investigate the clinical effects and safety of intraoperative peritoneal hyperthermic chemotherapy (IPHC) for advanced gastric cancer (AGC) patients. METHODS: A total of 118 AGC patients with serosal invasion were enrolled in this study from 1998 to 2001, 52 underwent IPHC after gastrectomy and 66 were treated with gastrectomy only. Among these cases, 96 patients without macroscopic peritoneal metastases were selected for the prophylactic study, 22 with peritoneal metastases were selected for the therapeutic study. Postoperative survival, recurrence pattern and incidences of postoperative complications between patients with and without IPHC were analyzed and compared. RESULTS: For the prophylactic study, the IPHC procedure improves postoperative survival rate and decrease the incidence of peritoneal recurrence, and is an independent prognostic factor for these patients. For the therapeutic study, postoperative survival times were longer if IPHC was undertaken. No surgery-related death occurred. The incidence of renal dysfunction was higher in the IPHC group, but all patients recovered without hemodialysis. CONCLUSION: IPHC is a safe procedure that improves the survival prognosis for AGC patients with serosal invasion. It is especially beneficial for patients without peritoneal metastasis due to the reduction of postoperative peritoneal recurrence.

Chemotherapy, Cancer, Regional Perfusion↗
PubMed2006

Growth of large-area aligned molybdenum nanowires by high temperature chemical vapor deposition: synthesis, growth mechanism, and device application.

Large-area aligned Mo nanowires have been grown on stainless steel substrates by high-temperature chemical vapor deposition with the use of Mo metal. The detailed physical and chemical growth processes regarding the formation of the nanowires have been investigated using mass spectroscopy, thermogravimetry, and differential scanning calorimetry analysis, as well as structure analysis by electron microscopy. In reference to Gibbs energy calculation, our study reveals that the growth relies on the decomposition of MoO2 vapors through condensation of its vapor at high substrate temperatures. The aligned growth is a result of competing growth with the nanowires normal to the substrate surface reaching the final growth front. The field emission measurement and the vacuum luminescent tube study show that the Mo nanowires have potential application as electron emitters.

Journal Article↗
PubMed2006

Association of Catsper1 or -2 with Ca(v)3.3 leads to suppression of T-type calcium channel activity.

Sperm-specific CatSper1 and CatSper2 proteins are critical to sperm-hyperactivated motility and male fertility. Although architecturally resembling voltage-gated ion channels, neither CatSper1 nor CatSper2 alone forms functional ion channels in heterologous expression systems, which may be related to the absence of yet unidentified accessory subunits. Here we isolated CatSper1- and CatSper2-associated protein(s) from human sperm and analyzed their identities by a multidimensional protein identification technology approach. We identified the T-type voltage-gated calcium channel Ca(v)3.3 as binding to both CatSper1 and CatSper2. The specificity of their interactions was verified by co-immunoprecipitation in transfected mammalian cells. Electrophysiological studies revealed that the co-expression of CatSper1 or CatSper2 specifically inhibited the amplitude of Ca(v)3.3-evoked T-type calcium current without altering other biophysical properties of Ca(v)3.3. Immunostaining studies revealed co-localization of CatSper1 and Ca(v)3.3 on the principal piece of human sperm tail. Furthermore, fluorescence resonance energy transfer analysis revealed close proximity and physical association of these two proteins on the sperm tail. These studies demonstrate that CatSper1 and CatSper2 can associate with and modulate the function of the Ca(v)3.3 channel, which might be important in the regulation of sperm function.

Calcium Channels↗
PubMed2006

Laparoscopic adrenalectomy for potentially malignant adrenal tumors greater than 5 centimeters.

PURPOSE: Laparoscopic adrenalectomy (LA) is controversial for large, potentially malignant tumors. We report a series of LA or hand-assisted LA for large (>5 cm) adrenal tumors. PATIENTS AND METHODS: Among 210 LAs performed in 6 yr, 39 patients had potentially malignant tumors greater than 5 cm in diameter. Their perioperative and follow-up data were retrospectively analyzed. RESULTS: All 39 patients had successful LAs without perioperative mortality, conversion to open surgery, or capsular disruption during dissection. The mean tumor size was 6.2 cm (range, 5-12 cm), operative time 207 min (115-315 min), and blood loss 75 ml (minimal-1400 ml). Complications included one intraoperative diaphragmatic perforation, three mild wound infections, and one pneumonia. Preoperatively there were 27 nonfunctioning tumors, seven pheochromocytomas, three cortisol-secreting tumors, and two virilizing tumors. Final pathology revealed eight malignant (four adrenocortical carcinomas and four metastatic carcinomas) and 31 benign tumors (14 cortical adenomas, eight pheochromocytomas, six myelolipomas, and three ganglioneuromas). Median follow-up was 39 months. Four patients (two adrenocortical carcinomas, one metastatic hepatoma, and one lymphoma) died 24, 10, 9, and 3 months after surgery, respectively. A hand-assisted device was used in 10 patients. Only the tumor size was larger and length of postoperative hospital stay longer for those in the hand-assisted group. CONCLUSIONS: LA is a reasonable option for selected large adrenal tumors when complete resection is technically feasible and there is no evidence of local invasion. Hand-assisted LA is a good alternative to open conversion if a difficult dissection is encountered intraoperatively.

Adenoma↗
PubMed2006

An efficient method of sorting liver stem cells by using immuno-magnetic microbeads.

AIM: To develop a method to isolate liver stem cells fast and efficiently. METHODS: Fetal mouse liver cells were characterized by cell surface antigens (c-Kit and CD45/TER119) using flow cytometry. The candidate liver stem cells were sorted by using immuno-magnetic microbeads and identified by clone-forming culture, RT-PCR and immunofluorescence assays. RESULTS: The c-Kit-(CD45/TER119)- cell population with 97.9% of purity were purified by immuno-magnetic microbeads at one time. The yield of this separation was about 6% of the total sorting cells and the cell viability was above 98%. When cultured in vitro these cells had high clone-forming and self-renewing ability and expressed markers of hepatocytes and bile duct cells. Functionally mature hepatocytes were observed after 21 d of culture. CONCLUSION: This method offers an excellent tool for the enrichment of liver stem cells with high purity and viability, which could be used for further studies. It is fast, efficient, simple and not expensive.

Animals↗
PubMed2006

Erythropoietin protects CA1 neurons against global cerebral ischemia in rat: potential signaling mechanisms.

Erythropoietin (EPO) is a hormone that is neuroprotective in models of neurodegenerative diseases. This study examined whether EPO can protect against neuronal death in the CA1 region of the rat hippocampus following global cerebral ischemia. Recombinant human EPO was infused into the intracerebral ventricle either before or after the induction of ischemia produced by using the four-vessel-occlusion model in rat. Hippocampal CA1 neuron damage was ameliorated by infusion of 50 U EPO. Administration of EPO was neuroprotective if given 20 hr before or 20 min after ischemia, but not 1 hr following ischemia. Coinjection of the phosphoinositide 3 kinase inhibitor LY294002 with EPO inhibited the protective effects of EPO. Treatment with EPO induced phosphorylation of both AKT and its substrate, glycogen synthase kinase-3beta, in the CA1 region. EPO also enhanced the CA1 level of brain-derived neurotrophic factor. Finally, we determined that ERK activation played minor roles in EPO-mediated neuroprotection. These studies demonstrate that a single injection of EPO ICV up to 20 min after global ischemia is an effective neuroprotective agent and suggest that EPO is a viable candidate for treating global ischemic brain injury.

Animals↗
PubMed2006

Conducting poly(aniline) nanotubes and nanofibers: controlled synthesis and application in lithium/poly(aniline) rechargeable batteries.

The primary aim of this work was to synthesize aligned perchloric-acid-doped poly(aniline) (HClO(4)-doped PANI) nanotubes by a simple alumina template method and to investigate their application in lithium/poly(aniline) rechargeable batteries. Powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) analysis were used to characterize the nanostructures obtained. The second aim addressed the preparation of HClO(4)-doped PANI microspheres and nanofibers on a large scale through a modified spraying technique, since the template synthesis has limitations in mass production. The present synthesis methods are simple and can be extended to the preparation of a broad range of one-dimensional conductive polymers. Furthermore, electrochemical measurements showed that the as-prepared HClO(4)-doped PANI nanotubes exhibit better electrode performances than their commercial counterparts because they possess more active sites, higher conductivity, and relative flexibility. This indicates that HClO(4)-doped poly(aniline) nanomaterials are promising in the application of lithium/polymer rechargeable batteries.

Journal Article↗
PubMed2006

In vivo research in astrocytoma cell proliferation with 1H-magnetic resonance spectroscopy: correlation with histopathology and immunohistochemistry.

INTRODUCTION: Assessment of brain tumor proliferative potential provides important prognostic information that supplements standard histopathologic grading. Proton magnetic resonance spectroscopy ((1)H-MRS) gives completely different information, relating to cell membrane proliferation, neuronal damage, energy metabolism and necrotic transformation of brain or tumor tissues. The aim of this study was to investigate the relationship between (1)H-MRS and tumor proliferative potential in astrocytomas. METHODS: We studied 34 patients with histologically verified astrocytomas using the (1)H-MRS protocol following routine MRI preoperatively. The tumor in 26 of these patients was classified as grade I/II (low grade), and the tumor in the remaining patients as grade III/IV (high grade) according to the World Health Organization classification criteria of nervous system tumors (2000). The tumor in 21 patients was homogeneous astrocytoma, and of these 17 were classified as low grade and 4 as high grade. Expression of proliferating cell nuclear antigen (PCNA) was determined immunohistochemically using streptavidin-biotin-peroxidase complex (SP) staining. RESULTS: The ratios of choline (Cho) to N-acetylaspartate (NAA) and Cho to creatine (Cr) in those with high-grade astrocytomas (n=4) were significantly higher than in those with low-grade astrocytomas (n=17) (t=2.899, P=0.009; t=3.96, P=0.001, respectively), and were found to be significantly correlated with the expression of PCNA in 21 patients with homogeneous astrocytomas (r=0.455, P=0.038; r=0.633, P=0.002, respectively). CONCLUSIONS: We conclude that (1)H-MRS may be a valuable method for predicting preoperatively the degree of malignancy of homogeneous astrocytomas by enabling the calculation of the Cho/NAA and Cho/Cr ratios in vivo, and indirect evaluation of the tumor proliferative potential and prognosis, which are not available using conventional magnetic resonance imaging (MRI).

Adolescent↗
PubMed2006

Molecular phenotypes of notochordal cells purified from immature nucleus pulposus.

The immature nucleus pulposus (NP) is populated by cells of notochordal-origin that are larger and contain an extensive cytoskeletal network and numerous vacuoles. The disappearance of these cells with age is believed important in regulating metabolic shifts that may contribute to age-related disc degeneration. The precise biological function of these notochordal cells in the immature NP remains unclear, however, because of challenges in studying the mixed cell population in the NP. In this study, notochordal-like cells were purified from immature NP cells using a new fluorescence-activated cell sorting (FACS) protocol with auto-fluorescence and size analysis. The unique molecular phenotypes of sorted notochordal-like cells were characterized by the mRNA expression pattern for key matrix proteins and modulators, and by the expression of cell-matrix receptor integrin subunits. An FACS analysis showed that the immature NP contained a majority of cells that were larger than anulus fibrosus (AF) cells and with fluorescence higher than AF cells. In comparison with the small NP cells separated by the FACS protocol, sorted notochordal-like cells expressed lower mRNA levels of type I collagen, biglycan, TIMP1, HSP70 and c-fos, and did not express detectable mRNA levels of decorin, lumican, multiple MMPs or IL-1beta via real-time quantitative RT-PCR. A greater number of these notochordal-like cells also expressed the higher levels of alpha6, alpha1 and beta1 integrin subunits as compared to small NP cells. Together, our results point towards a unique molecular phenotype for these notochordal-like cells of NP, characterized by the absence of gene expression for specific small proteoglycans and higher protein expression of integrin subunits that regulate interactions with collagens and laminin. Future studies will be important for revealing if this unique molecular profile is coordinated with functional differences in pericellular matrix regions and/or integrin-mediated cell-matrix interactions for these notochordal-like cells within the NP.

Animals↗
PubMed2006

Weekly cisplatin plus infusional high-dose 5-fluorouracil and leucovorin (P-HDFL) for metastatic urothelial carcinoma: an effective regimen with low toxicity.

BACKGROUND: Conventional systemic chemotherapy for metastatic urothelial carcinoma (UC) such as methotrexate, vinblastine, doxorubicin, and cisplatin (M-VAC) or cisplatin, methotrexate, and vinblastine (CMV) is associated with significant dose-limiting toxicities and even treatment-related death. The authors developed a regimen that was designed to maintain efficacy, while reducing toxicities. METHODS: Between January 1998 and July 2003, 35 patients (median age, 71 yrs) with metastatic UC were treated with 4-week cycles of P-HDFL (cisplatin 35 mg/m(2), high-dose 5-fluorouracil [5-FU] 2,600 mg/m(2), and leucovorin 300 mg/m(2), on Days 1 and 8, all given by 24-hr infusion). On Day 15, only HDFL was given again. RESULTS: Among the 32 patients treated with > or = 2 cycles, 9 (28.1%) and 11 (34.4%) were complete and partial responders, respectively, with an overall response rate of 62.5% (95% confidence interval [CI], 45.9-79.2%). The median overall and progression-free survival was 12.3 months (95% CI, 8.2-16.4 mos) and 10.5 months (95% CI, 8.4-12.6 mos), respectively. Toxicity in a total of 121 courses (mean, 3.5 per patient) was modest, with WHO Grade 3 or 4 leukopenia and thrombocytopenia noted in only 1 and 0 patients, respectively. Grade 3 or 4 nausea, vomiting, mucositis, and diarrhea were noted in 3, 2, 0, and 2 patients, respectively. In general, patients tolerated the regimen very well. CONCLUSIONS: P-HDFL is a moderately active and considerably low-toxic regimen for metastatic UC. The excellent toxicity profile makes it a viable option for patients with poor general conditions. To reach any conclusion, randomized trials comparing P-HDFL with traditional cisplatin-based regimens are necessary.

Aged↗
PubMed2006

Neuroprotection against focal ischemic brain injury by the peroxisome proliferator-activated receptor-gamma agonist rosiglitazone.

Peroxisome proliferator-activated receptor gamma (PPAR-gamma) is a nuclear membrane-associated transcription factor that governs the expression of various inflammatory genes. PPAR-gamma agonists protect peripheral organs from ischemic injury. In the present study, we investigated whether the PPAR-gamma agonist rosiglitazone is neuroprotective against focal ischemic brain injury. C57/B6 mice underwent 1.5-h middle cerebral artery occlusion, and received either vehicle or rosiglitazone treatment of 0.75, 1.5, 3, 6 or 12 mg/kg (n = 9 per group). Cerebral infarct volume, neurological function, expression of pro-inflammatory proteins and neutrophil accumulation were assessed after ischemia and reperfusion. At 48 h after ischemia, infarct volume was significantly decreased with 3-12 mg/kg of rosiglitazone, with a time window of efficacy of 2 h after ischemia at the optimal dose (6 mg/kg). Neutrophil accumulation was significantly decreased in the brain parenchyma of rosiglitazone-treated mice. Ischemia-induced expression of several inflammatory cytokines and chemokines was markedly reduced in rosiglitazone-treated brains, as determined using proteomic-array analysis. Rosiglitazone treatment improved neurological function at 7 days after ischemia. Moreover, in cultured cortical primary microglia, rosiglitazone attenuated inflammatory responses by decreasing lipopolysaccharide-induced release of tumor necrosis factor-alpha, interleukin (IL)-1beta and IL-6. These results suggest that the PPAR-gamma agonist rosiglitazone has neuroprotective properties that are at least partially mediated via anti-inflammatory actions, and is thus a potential novel therapeutic agent for stroke.

Anilides↗