Search PubMed⌕ Search

Biomedical subjects

Jie Chen

Publications and source records attributed to Jie Chen.

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

Excluded volume effect on confined polymer translocation through a short nanochannel.

We simulated the translocation process of a polymer chain from a source container to a drain container through a short nanochannel. We utilized the bond fluctuation model coupled with Monte Carlo dynamics in our simulations. The calculation results show that the excluded volume effect significantly affects the polymer's translocation time tau. This time depends nonmonotonically on the polymer length N. For a fixed nanochannel length, tau decreases when the polymer length increases. tau, however, increases when the polymer length exceeds a certain threshold. This observation differs from those predicated for a Gaussian chain. In this paper, we will further present our findings to explain this phenomenon. The knowledge we gain from this research can enhance the understanding of complex transport processes in many biological systems.

Journal Article↗
PubMed2006

Removal of Cr(VI) and Cr(lll) from aqueous solutions and industrial wastewaters by natural clino-pyrrhotite.

This paper introduced a simple method of treating Cr(Vl)-bearing toxic wastewaters using a natural mineral: clino-pyrrhotite. Laboratory bench-scale mixing experiments were carried out in both Cr(VI)-bearing artificial solutions and industrial wastewaters under controlled conditions. The effects of solution pH, Cr(VI) concentration, mineral grain size, mineral/solution ratio, and reaction time on the Cr(VI) removal were studied. Chromium was effectively removed from the solutions and wastewaters. After the treatment, the liquid was clean enough to be discharged directly into the natural environment. The Cr(VI) removal process involved sequentially the adsorption of Cr(VI), in the form of Cr2O7(2-) or CrO4(2-), onto the mineral surface, the reduction of the adsorbed Cr(VI) to Cr(lll), catalyzed at the vacant Fe sites of the mineral, and finally the precipitation of Cr(lll) as Cr2S3, Cr2O3, and Cr(OH)3 solid phases. Conditions such as a fine mineral grain size, an excessive quantity of clino-pyrrhotite and a weak acidic media, favored the removal process. For clino-pyrrhotite with a restricted grain size, the minimum required quantity of the mineral was proportional to the total quantity of Cr(VI) to be removed. Quantitatively, one cubic meter of industrial wastewater that contained approximately 1 mmol dm(-3) of Cr(VI) and had a pH value between 1 and 10 would be effectively treated after it was in contact with 220 kg of 145 +/- 28 microm clino-pyrrhotite for an hour. Furthermore, the quantity of the final solid waste byproduct was small, and the solid residue of clino-pyrrhotite could be reused after a simple rinse with water. Compared to the previous Cr(VI)-bearing wastewater treatment schemes, this method was simple, effective, economical, and environmentally sound. It has great potential for use in industrial-scale applications.

Adsorption↗
PubMed2006

[Current status of primary hypertension in China: an epidemiological study of 12 provinces, 1 autonomous regions, and 1 municipality].

OBJECTIVE: To investigate the current prevalence of primary hypertension in China in 2002 so as to lay a foundation for further control of hypertension in future. METHODS: Physical examination, including measurement of the blood pressure using international standardized methods especially, was conducted among 29,076 persons aged 35 - 85, 13,555 males (46.6%) and 15,521 females (53.4%), by cluster sampling in Tianjin, Inner Mongolia, Shanxi, Henan, Shandong, Hubei, Hunan, Sichuan, Guangdong, Jiangxi, Yunnan, and Shaanxi. RESULTS: The prevalence of hypertension was 27.9% in general. The prevalence increased along with the age. The rate of awareness of being ill with hypertension was 60.71% in general (9872/29,076), and was 55.64% among the males, significantly lower than that among the females (65.42, P < 0.001). The treatment rate 49.65% (4901/9872) in general, and was significantly higher among the females than among the males (P < 0.01). The control rate was 5.7% (562/9872). In general, the prevalence of hypertension was higher in the North than in the South, and was becoming lower and lower from the North to the South. CONCLUSION: The prevalence of hypertension is high, while the rates of awareness, treatment and control are low in China.

Adult↗
PubMed2006

A testis-specific and testis developmentally regulated tumor protein D52 (TPD52)-like protein TPD52L3/hD55 interacts with TPD52 family proteins.

Tumor protein D52-like proteins (TPD52) are small coiled-coil motif bearing proteins that were first identified in breast cancer. TPD52 and related proteins have been implicated in cell proliferation, apoptosis, and vesicle trafficking. To date, three human TPD52 members had been identified, named hD52 (TPD52), hD53 (TPD52L1), and hD54 (TPD52L2). The most important characteristic of the protein family is a highly conserved coiled-coil motif that is required for homo- and heteromeric interaction with other TPD52-like proteins. Herein, we identified a novel TPD52-like sequence (TPD52L3, or hD55) in human testis using cDNA microarray. Sequence analysis of the deduced protein suggests that hD55 contains a coiled-coil motif and is highly conserved compared with other TPD52-like sequences. Yeast two-hybrid and GST pull-down assays revealed that hD55 interacts with hD52, hD53, hD54, and itself. cDNA microarray detection found that hD55 was expressed at 5.6-fold higher levels in adult testis than in fetal testis. Additionally, the expression profile shows that hD55 is testis-specific, indicating a potential role for hD55 in testis development and spermatogenesis.

Aging↗
PubMed2006

Enzymatic hydrolysis of microcrystalline cellulose in reverse micelles.

The activities of cellulases from Trichoderma reesei entrapped in three types of reverse micelles have been investigated using microcrystalline cellulose as the substrate. The reverse micellar systems are formed by nonionic surfactant Triton X-100, anionic surfactant Aerosol OT (AOT), and cationic surfactant cetyltrimethyl ammonium bromide (CTAB) in organic solvent media, respectively. The influences of the molar ratio of water to surfactant omega0, one of characteristic parameters of reverse micelles, and other environmental conditions including pH and temperature, on the enzymatic activity have been studied in these reverse micellar systems. The results obtained indicate that these three reverse micelles are more effective than aqueous systems for microcrystalline cellulose hydrolysis, and cellulases show "superactivity" in these reverse micelles compared with that in aqueous systems under the same pH and temperature conditions. The enzymatic activity decreases with the increase of omega0 in both AOT and Triton X-100 reverse micellar systems, but reaches a maximum at omega0 of 16.7 for CTAB reverse micelles. Temperature and pH also influence the cellulose hydrolysis process. The structural changes of cellulases in AOT reverse micelles have been measured by intrinsic fluorescence method and a possible explanation for the activity changes of cellulases has been proposed.

Biochemistry↗
PubMed2006

Interaction of cellulase with sodium dodecyl sulfate at critical micelle concentration level.

The interactions between Trichoderma reesei cellulase and an anionic surfactant, sodium dodecyl sulfate (SDS), at critical micelle concentration level have been investigated using isothermal titration calorimetry, fluorescence spectroscopy, and circular dichroism. SDS micelles have dual interactions with cellulase: electrostatic at first and then hydrophobic interactions. When the concentration of SDS is smaller than 45.0mM, SDS micelles cause a partial loss in the hydrolytic activity together with a steep decrease in the alpha-helical content of cellulase. With further increasing the concentration of SDS, however, a re-formation of the alpha-helical structure and a partial recovery of the hydrolytic activity of cellulase induced by SDS micelles are observed. Taken together, these results indicate that SDS micelles exert dual effects on cellulase through binding as both a denaturant and a recovery reagent.

Calorimetry↗
PubMed2006

Conversion of intramolecular singlet electron transfer at room temperature into triplet energy transfer at 77 K: photoisomerization in norbornadiene- and carbazole-labeled poly(aryl ether) dendrimers.

A series of Fréchet-type poly(aryl ether) dendrimers (CZ-Gn-NBD, n = 1-3) with carbazole (CZ) chromophores and a norbornadiene (NBD) group attached to the periphery and the core, respectively, were synthesized, and their photophysical and photochemical properties were investigated. Selective excitation of the carbazole units in CZ-Gn-NBD resulted in a singlet electron transfer from CZ to NBD at room temperature, and an intersystem crossing followed a triplet-triplet energy transfer from CZ to NBD in glassy 2-methyltetrahydrofuran at 77 K. Both singlet electron transfer and triplet energy transfer processes lead to the isomerization of the norbornadiene group into the quadricyclane (CZ-Gn-QC). The efficiencies and the rate constants for singlet electron transfer are approximately 88, 80, and 74% and 1.8 x 10(9), 6.1 x 10(8), and 4.0 x 10(8) s(-1) for generations 1-3, respectively. The quantum yields of the intramolecular photosensitized isomerization are measured to be approximately 0.013, 0.012, and 0.011, and the efficiencies of triplet norbornadiene formation via singlet electron transfer are approximately 0.070, 0.065, and 0.059 for generations 1-3, respectively. The light-harvesting ability of CZ-Gn-NBD increases with the generation due to an increase of the number of peripheral chromophores. In glassy 2-methyltetrahydrofuran at 77 K, the triplet-triplet energy transfer proceeds with efficiencies of approximately 0.86, 0.64, and 0.36 and rate constants of 0.96, 0.25, and 0.08 s(-1) for generations 1-3, respectively. The intramolecular singlet electron transfer and triplet energy transfer in CZ-Gn-NBD proceed mainly via a through-space mechanism involving the proximate donor (folding back conformation) and acceptor groups.

Journal Article↗
PubMed2006

Direct observation of the intramolecular triplet-triplet energy transfer in poly(aryl ether) dendrimers.

A series of benzophenone (BP) and naphthalene (NA) labeled poly(aryl ether) dendrimers (BP-Gn-NA), generations 1-4, were synthesized, and their photophysical properties were examined. Flash photolysis demonstrates that the triplet energy in BP-Gn-NA can be transferred from the peripheral BP chromophores to the core NA group with the efficiencies of ca. 0.97, 0.96, 0.88, and 0.54 and with the rate constants of 1.4x10(8), 1.2x10(8), 9.5x10(7), and 1.3x10(7) s-1 at room temperature for generations 1-4, respectively. The transient absorption spectra of BP-Gn-NA show clearly the formation of the triplet NA absorption along with the decay of the triplet BP one with an isosbestic point at 475 nm, which gives direct evidence of the triplet energy transfer from the periphery BP chromphores to the core NA group. The phosphorescence of the NA group attached to the focal point was observed when the periphery BP chromophores were selectively irradiated in BP-G1-NA at 77 K. The triplet energy transfer occurs at 77 K with the efficiencies of 1.0, 0.16, 0.17, and 0.21 for generations 1-4, respectively. The intramolecular triplet energy transfer is proposed to proceed mainly via a through space mechanism.

Journal Article↗
PubMed2006

The tyrosine kinase inhibitor imatinib fails to inhibit pancreatic cancer progression.

Imatinib targets KIT and platelet-derived growth factor receptors (PDGFR) and is highly effective in the treatment of CML and GIST patients. Pancreatic cancers express KIT and PDGFRs. Therefore, 26 patients with unresectable pancreatic cancer were randomized to either gemcitabine (1000 mg/m2 weekly) or imatinib (2x400 mg po) treatment daily. Pancreatic adenocarcinoma was confirmed histologically and expression of KIT and PDGFRbeta was determined immunohistochemically in the biopsy specimens. Quality of life was assessed with two standard questionnaires. No objective responses were seen in either group. Median time to progression was 77 and 29 days (P=0.411) and median survival time was 140 and 60 days (P=0.517) for gemcitabine and imatinib, respectively. Survival and treatment responses were independent of KIT and PDGFRbeta expression in patients treated with imatinib. Grade 3/4 toxicities of imatinib treatment were anemia, elevated liver enzymes, vomiting, and dyspnea. Patients treated with imatinib reported diarrhoea and/or altered bowel function more frequently, which were treatable symptomatically. Quality of life was similar in both groups. In this small series of pancreatic cancer patients, treatment with imatinib was not associated with a significant control of cancer progression.

Adenocarcinoma↗
PubMed2006

Effects of autoantibodies removed by immunoadsorption from patients with dilated cardiomyopathy on neonatal rat cardiomyocytes.

INTRODUCTION: Immunoadsorption has been shown to improve cardiac performance and reduce mortality in patients with dilated cardiomyopathy. In this study, the underlying mechanism for these beneficial effects was investigated in cultured rat cardiomyocytes. METHODS AND RESULTS: Immunoadsorption was performed in patients with dilated cardiomyopathy (n=7). Antibody-induced complement-dependent cytotoxicity was investigated by colorimetric MTT. Autoantibodies against the beta(1)-adrenoceptor were detected by ELISA and purified. Column eluent from six patients exhibited a cytotoxic effect, three patients were positive for the beta(1)-adrenoceptor autoantibodies. The purified autoantibodies were able to visualize the beta(1)-adrenoceptors by immunocytofluorescence on rat cardiomyocytes, and also displayed partial agonist properties and induced a positive chronotropic effect, which were blocked by the beta(1)-selective antagonist bisoprolol and the peptide corresponding to the beta(1)-adrenoceptor. Column eluent from one patient induced apoptosis in nick end labelling test (8.1+/-1.7% vs. 2.9+/-1.2% in control, p<0.05). CONCLUSION: Autoantibodies removed by immunoadsorption from patients with dilated cardiomyopathy have a pathophysiological role, as shown by the complement-dependent cytotoxicity and chronotropic action on rat cardiomyocytes. This implies that removal of circulating autoantibodies might be part of the underlying mechanism for improved cardiac function.

Adrenergic beta-Antagonists↗
PubMed2006

Optical properties of thermally responsive amphiphilic gold nanoparticles protected with polymers.

Amphiphilic thermally responsive gold nanoparticles have been prepared by protecting the particles with both polystyrene, PS, and poly(N-isopropylacrylamide), PNIPAM, chains. Particles form a monolayer on a water surface in a Langmuir trough, and according to in situ spectroscopic measurements, the surface plasmon resonance, SPR, band undergoes a blue-shift during the monolayer compression. The compression-induced blue-shift is related to a change in the conformation of tethered PNIPAM chains; the phenomenon is discussed on the basis of Mie-Drude theory. In contrast, a red-shift in the SPR of the multilayers of the same nanoparticles transferred at different temperatures has been observed with increasing the deposition cycle, attributed to the presence of a weak interparticle coupling in the multilayer.

Journal Article↗
PubMed2006

A nuclear transport signal in mammalian target of rapamycin is critical for its cytoplasmic signaling to S6 kinase 1.

The mammalian target of rapamycin (mTOR) regulates nutrient-dependent cell growth and proliferation through cytoplasmic targets, such as S6 kinase 1 (S6K1). Consistent with its main function in the cytoplasm, mTOR is predominantly cytoplasmic. However, previously we have found that mTOR shuttles between the nucleus and cytoplasm, and we have proposed that the nucleocytoplasmic shuttling of mTOR is required for the maximal activation of S6K1. The intrinsic signals directing mTOR nuclear transport and the underlying mechanisms are unknown. In this study we initially set out to identify nuclear export signals in mTOR. A systematic scan of the mTOR sequence revealed 16 peptides conforming to the canonical leucine-rich nuclear export signal, of which 3 were found by reporter assays to contain leptomycin B-sensitive and leucine-dependent nuclear export activity. Unexpectedly, mTOR proteins with those conserved leucines mutated to alanines were unable to enter the nucleus. Further investigation revealed that the L982A/L984A and L1287A/L1289A mutations likely induced a global structural change in mTOR, whereas the L545A/L547A mutation directly impaired the nuclear import of the protein, potentially regulated by a nucleocytoplasmic shuttling signal. The loss of nuclear import was accompanied by the significantly reduced ability of the L545A/L547A mutant to activate S6K1 in cells. Most importantly, when nuclear import was restored in the L545A/L547A mutant by the addition of an exogenous nuclear import signal, signaling to S6K1 was rescued. Taken together, our observations suggest the existence of a nuclear shuttling signal in mTOR and provide definitive evidence for the requirement of mTOR nuclear import in its cytoplasmic signaling to S6K1.

Active Transport, Cell Nucleus↗
PubMed2006

Atm-haploinsufficiency enhances susceptibility to carcinogen-induced mammary tumors.

Ataxia-telangiectasia (A-T), which is due to mutations in the ATM gene, is a rare autosomal recessive genomic instability syndrome characterized by radiosensitivity and predisposition to cancer. Epidemiological studies have suggested that relatives of A-T patients (A-T carriers) have increased risks of developing breast cancer. We propose that increased breast cancer risks in A-T carriers may be due to exposure to various environmental carcinogens and/or dietary consumption. To test this hypothesis, we treated a congenic strain of Atm+/- mice with DMBA (7,12-dimethylbenz(alpha)anthracene), a mammary carcinogen, and observed mammary tumor incidence. It was found that Atm+/- mice have a 2-fold increase, as well as early onset, in mammary tumor incidence relative to wild-type mice (P<0.005). The increased mammary tumor development is correlated with a 3-fold increase in the development of mammary dysplasia in Atm+/- compared with wild-type mice (P<0.05). We also found that Ras signaling pathway was not activated in DMBA-induced mammary tumors irrespective of the Atm status. At the cellular level, Atm-haploinsufficiency confers increased cellular stress manifested by an increased p53 expression and a slightly enhanced survival of mammary epithelial cells in response to radiation. Our results demonstrate that Atm heterozygotes are predisposed to mammary tumor development and support the hypothesis that exposure to environmental carcinogens contributes to the increased rate of breast cancer development in A-T carriers. Given that 1% of the general population are ATM heterozygotes (A-T carriers), this study has great implications in breast cancer development in this population.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2006

Identification of metastasis candidate proteins among HCC cell lines by comparative proteome and biological function analysis of S100A4 in metastasis in vitro.

Widespread metastasis of hepatocellular carcinoma (HCC) was a complex cascade of events, which is still beyond full appreciation. Screening key proteins, which play a critical role in metastasis, using high-throughput proteomics approach help discover valuable biomarkers and elucidate the mechanism of metastasis. This study was to find out some metastasis candidate proteins among HCC cell lines with various metastatic potential by comparative proteomics, and then further validate the biological function of these proteins in metastasis in vitro. The protein profiles of metastatic HCC cell lines (MHCC97H and MHCC97L) displayed obvious differences compared with nonmetastatic ones (Hep3B). Twenty-six metastasis candidate proteins, which were identified by on-line LC-ESI-MS/MS, such as S100 calcium-binding protein A4 (S100A4), annexin 1, etc., might have much application in diagnostic procedures and prognosis evaluation. S100A4, as a leading different metastasis candidate protein, which overexpressed only in the metastatic cells, was selected for further investigation. A series of assays related to invasion and metastasis in vitro, including cell motility, invasion, and matrix metalloproteinases (MMPs) secretion, were performed in MHCC97H/antisense recombinant plasmid to S100A4 (pcDNA3.1(+) AS S100A4) and the mock controls. All the data in the present study suggested that S100A4 might contribute to HCC invasion and metastasis through two paths of matrix metalloproteinase (MMP9) secretion regulation and strengthened motility and invasion properties.

Apoptosis↗
PubMed2006

Identification and analysis of altered alpha1,6-fucosylated glycoproteins associated with hepatocellular carcinoma metastasis.

Tumor metastasis might be associated with the expression levels of cellular glycoproteins and the alteration of their glycan parts. In order to screen the aberrantly alpha1,6-fucosylated glycoproteins related to hepatocellular carcinoma (HCC) metastasis, a high-throughput glycomic approach which consisted of 2-DE, electronic transfer of proteins, lectin affinity blot and precipitation, and MALDI-TOF-MS/MS, was established. Lens culinaris agglutinin (LCA) affinity glycoprotein profiles of higher and lower metastatic HCC cell lines were compared and analyzed. Seven out of 34 identified glycoproteins were differentially displayed; they were cytokeratin 8 (CK8), annexin I, annexin II, heterogeneous nuclear ribonucleoprotein A/B, PDZ and LIM domain 1, RNA-binding motif protein 4, and poly(rC)-binding protein 1. On comparison with Hep3B, CK8 showed a higher affinity to Ricinus communis agglutinin 1 (RCA-I) and LCA, and annexin I presented a higher affinity to LCA and Con A by the lectin-binding assay. Furthermore, the up-regulation of CK8, annexin I, and annexin II were found by Western blot and immunofluorescence analysis in higher metastatic HCC cell lines. This implied that the alteration of CK8, annexin I, and annexin II both in their expression levels and their glycan parts might be related to metastatic ability, and play a critical role in the process of HCC metastasis.

Annexin A1↗
PubMed2006

The effects of first- and second-order gable bends on forces and moments generated by triangular loops.

INTRODUCTION: Triangular loops are frequently used for space closure. Studies of this loop have focused on dimensional and in-plane (second-order) gable-bend influences on the generated forces and moments, but there have been no investigations into the effects of out-of-plane (first-order) gable bends. Both bends are generally needed to accomplish tooth translation. The primary purpose of this project was to ascertain whether first- and second-order bend effects were uncoupled. METHODS: Ninety triangular loops were divided into 9 groups with combinations of 0 degrees and 30 degrees first- and second-order gable bends in the anterior and posterior positions. Forces (F(x), F(y), F(z)) and moments (M(x), M(y), M(z)) generated along 3 mutually perpendicular axes-x (mesiodistal), y (occlusogingival), and z (buccolingual)-were measured, and moment/force ratios (M(z)/F(x), M(y)/F(x)) were calculated. Statistical comparisons were made between the 9 groups and between activation distances. The Sidak multiple-comparison adjustment method was used to control the overall confidence level at 95%. RESULTS: It was shown that the magnitude of M(z)/F(x) increased significantly with second-order gable bends but did not change with first-order bends. The opposite was found for M(y)/F(x). CONCLUSIONS: Thus, in triangular springs, first- and second-order gable bends produce the desired effects without interfering with each other.

Biomechanical Phenomena↗
PubMed2006

Numerical investigation of the non-Newtonian pulsatile blood flow in a bifurcation model with a non-planar branch.

The pulsatile flow of non-Newtonian fluid in a bifurcation model with a non-planar daughter branch is investigated numerically by using the Carreau-Yasuda model to take into account the shear thinning behavior of the analog blood fluid. The objective of this study is to deal with the influence of the non-Newtonian property of fluid and of out-of-plane curvature in the non-planar daughter vessel on wall shear stress (WSS), oscillatory shear index (OSI), and flow phenomena during the pulse cycle. The non-Newtonian property in the daughter vessels induces a flattened axial velocity profile due to its shear thinning behavior. The non-planarity deflects flow from the inner wall of the vessel to the outer wall and changes the distribution of WSS along the vessel, in particular in systole phase. Downstream of the bifurcation, the velocity profiles are shifted toward the flow divider, and low WSS and high shear stress temporal oscillations characterized by OSI occur on the outer wall region of the daughter vessels close to the bifurcation. Secondary motions become stronger with the addition of the out-of-plane curvature induced by the bending of the vessel, and the secondary flow patterns swirl along the non-planar daughter vessel. A significant difference between the non-Newtonian and the Newtonian pulsatile flow is revealed during the pulse cycle; however, reasonable agreement between the non-Newtonian and the rescaled Newtonian flow is found. Calculated results for the pulsatile flow support the view that the non-planarity of blood vessels and the non-Newtonian properties of blood are an important factor in hemodynamics and may play a significant role in vascular biology and pathophysiology.

Animals↗