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Articles by J Tan
Total Records ( 5 ) for J Tan
  Y Yuan , J Tan , Y Wang , C Qian and M. Zhang

Chitosan (CS), a biocompatible and biodegradable material, can act as a non-viral delivery vehicle with low toxicity. In this study, plasmid DNA (pDNA) and siRNA were encapsulated in CS nanoparticles (NPs) to prepare CS–DNA and CS–siRNA NPs using a complex coacervation process. The CS–DNA particle size was within the range of 180–370 nm with a surface charge ranging from 0 to 18 mV at pH 5.5. The stability of pDNA in CS–DNA was investigated by pDNA release study and DNase I protection assay. The release of pDNA from NPs was studied in pH 7.4 phosphate-buffered saline at 37°C and the CS–DNA NPs could delay the DNA release. Results of DNase I protection assay showed that CS–DNA NPs could protect the encapsulated pDNA from nuclease degradation. In the transfection study, it was found that the transfection efficiency in vitro was dependent on the molecular weight, charge ratio, and DNA concentration of the CS–DNA NP as well as the type of cell transfected. Moreover, the morphology of HeLa cells transfected with CS–siRNA complexes was studied using atomic force microscopy. The results suggest that CS may be more capable than liposome in delivering siRNA to target cells. In summary, our analysis suggests that pDNA and siRNA can be encapsulated in CS NPs without being damaged.

  T Melkamu , X Zhang , J Tan , Y Zeng and F. Kassie

MicroRNAs (miRNAs) are small, non-protein-coding RNAs that can function as tumor suppressors or oncogenes. Deregulation of miRNA expression has been reported in lung cancer. However, modulation of miRNA expression by chemopreventive agents remains to be defined. In the present study, we examined if the chemopreventive agent indole-3-carbinol (I3C) reversed vinyl carbamate (VC)-induced deregulation of miRNA levels in lung tissues of female A/J mice. Lung tissues were obtained from a previous chemoprevention study, in which mice were treated with VC and given I3C in the diet for 15 weeks. Microarray studies revealed alterations in the expression of a number of miRNAs in lung tumors relative to that of normal lungs. miR-21, mir-31, miR-130a, miR-146b and miR-377 were consistently upregulated, whereas miR-1 and miR-143 were downregulated in lung tumors relative to normal lungs. In mice treated with VC and given I3C in the diet, levels of miR-21, mir-31, miR-130a, miR-146b and miR-377 were reduced relative to the level in mice treated with the carcinogen only. The results of the microarray study were confirmed by quantitative reverse transcription–polymerase chain reaction and gel analysis of polymerase chain reaction products. Further studies with miR-21 indicated that phosphatase and tensin homolog, programmed cell death 4 and rich protein with Kazal motifs are potential targets for the oncogenic effect of miR-21 and the chemopreventive activity of I3C. Taken together, we showed here that miRNAs are deregulated during VC-induced mouse lung tumorigenesis and their levels are modulated by I3C. Therefore, miRNAs and their target genes are promising biomarkers for the diagnosis of lung cancer and efficacy of chemopreventive/chemotherapeutic agents.

  C Tian , J Tan , X Wu , W Ye , X Liu , D Li and H. Yang

To describe the variation in bacterioplankton diversity within a large hypertrophic freshwater lake, as well as changes in the diversity that occurred with time, PCR- (denaturing gradient gel electrophoresis) DGGE was utilized to study water samples collected from Lake Taihu in China. To accomplish this, water samples were collected from different locations and during different months. The trophic status of these sampling sites ranged from eutrophic to hypertrophic. Cluster and multidimensional scaling analyses revealed that the temporal transition in the diversity of the bacterioplankton occurred primarily in response to a cyanobacterial bloom, and that all samples could be divided into normal-bloom, peak-bloom and winter period groups. Spatial differences in the bacterial diversity were also detected among the three sampling sites, with diversity being found to be strongly correlated with the gradient of the trophic status of the three sampling sites. In addition, these temporal and spatial changes could be characterized by several specific DGGE bands. The results were further analyzed by canonical correspondence analysis, which revealed that the bacterioplankton diversity of Lake Taihu was primarily associated with temperature, pH, total nitrogen (TN), total phosphorus (TP) and dissolved oxygen. Of these factors, TN and TP were only shown to be significant influencing factors at Wuxi, which had the highest trophic level.

  C. K Cheung , J Tan , R. A Lowe , D Gouldesbrough and J. Stoves

We present a case of myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA)-associated vasculitis with the rare complication of haemoperitoneum due to mesenteric vessel involvement. Initial investigations demonstrated typical renal features including haematoproteinuria and a focal segmental necrotising glomerulonephritis. The patient then developed haemoperitoneum and required an emergency hemicolectomy. Subsequent histology revealed ileo-colic arteritis with aneurysm formation and rupture. A sustained remission was achieved with corticosteroids and mycophenolate mofetil followed by azathioprine. This case demonstrates the need for a high degree of vigilance in patients with ANCA-associated vasculitis who develop abdominal symptoms.

  Y Wang , B. R Weil , J. L Herrmann , A. M Abarbanell , J Tan , T. A Markel , M. L Kelly and D. R. Meldrum

Human bone marrow mesenchymal stem cells (MSCs) are a potent source of growth factors, which are partly responsible for their beneficial paracrine effects. We reported previously that transforming growth factor- (TGF-), a putative mediator of wound healing and the injury response, increases the release of vascular endothelial growth factor (VEGF), augments tumor necrosis factor- (TNF-)-stimulated VEGF production, and activates mitogen-activated protein kinases and phosphatidylinositol 3-kinase (PI-3K) pathway in human MSCs. The experiments described in this report indicate that TGF- increases MSC-derived hepatocyte growth factor (HGF) production. TGF--stimulated HGF production was abolished by inhibition of MEK, p38, PI-3K, or by small interfering RNA (siRNA) targeting TNF receptor 2 (TNFR2), but was not attenuated by siRNA targeting TNF receptor 1 (TNFR1). Ablation of TNFR1 significantly increased basal and stimulated HGF. A potent synergy between TGF- and TNF- was noted in MSC HGF production. This synergistic effect was abolished by MEK, P38, PI-3K inhibition, or by ablation of both TNF receptors using siRNA. We conclude that 1) novel cross talk occurs between tumor necrosis factor receptor and TGF-/epidermal growth factor receptor in stimulating MSC HGF production; 2) this cross talk is mediated, at least partially, via activation of MEK, p38, and PI-3K; 3) TGF- stimulates MSCs to produce HGF by MEK, p38, PI-3K, and TNFR2-dependent mechanisms; and 4) TNFR1 acts to decrease basal TGF- and TNF--stimulated HGF.

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