Biomedical subjects

Chen Lu

Publications and source records attributed to Chen Lu.

10 recordsLinked to original sources

PubMed2007

Telomerase subunits expression variation between biopsy samples and cell lines derived from malignant glioma.

Although scientific advances have recognised the prognostic power of telomerase activity in different cancers, as yet there has been no investigation regarding the expression variation of telomerase subunits in glioma tissues and cell lines. In this study, a recurrent anaplastic ependymoma and seven glioblastoma biopsy samples, four cell lines and four controls including two normal brain tissues were analysed for telomerase subunit expression profiles together with telomerase activity. Since telomerase activity is linked to tumourgenesis, the genes were analysed with respect to their expression variation. TEP1 was expressed in all glioma cell lines and 70% of glioblastoma tissues, in addition to the control brain tissues. Tankyrase was expressed in 85% of the glioblastoma tissues and was down-regulated in the recurrent anaplastic ependymoma tissue control cell lines. However, it was expressed in the control tissues. Dyskerin was expressed in all cell lines and tissues apart from U87-MG and NHA cells and the recurrent anaplastic ependymoma tissue. As expected, PARP1 and GAPDH showed constitutive expression throughout all cell lines and tissues since both are known to be housekeeping genes. hTERT was expressed in all glioma cell lines and tissues but was absent in the control cells and tissues. Telomerase activity was absent in IPDDC-A2 cells and 57% of the glioblastoma tissues. These results suggest that hTERT expression and not telomerase activity possibly represents a simple and reliable biological diagnostic tool.

Biomarkers, Tumor↗

PubMed2006

Hsp70 inhibits lipopolysaccharide-induced NF-kappaB activation by interacting with TRAF6 and inhibiting its ubiquitination.

Inducible heat shock protein 70 (Hsp70) is one of the most important HSPs for maintenance of cell integrity during normal cellular growth as well as pathophysiological conditions. Tumor necrosis factor receptor-associated factor 6 (TRAF6) is a crucial signaling transducer that regulates a diverse array of physiological and pathological processes and is essential for activating NF-kappaB signaling pathway in response to bacterial lipopolysaccharide (LPS). Here we report a novel mechanism of Hsp70 for preventing LPS-induced NF-kappaB activation in RAW264.7 macrophage-like cells. Our results show that Hsp70 can associate with TRAF6 physically in the TRAF-C domain and prevent TRAF6 ubiquitination. The stimulation of LPS dissociates the binding of Hsp70 and TRAF6 in a time-dependent manner. Hsp70 inhibits LPS-induced NF-kappaB signaling cascade activation in heat-shock treated as well as Hsp70 stable transfected RAW264.7 cells and subsequently decreases iNOS and COX-2 expression. Two Hsp70 mutants, Hsp70DeltaC(1-428aa) with N-terminal ATPase domain and Hsp70C(428-642aa) with C-terminal domain, lack the ability to influence TRAF6 ubiquitination and TRAF6-triggered NF-kappaB activation. Taken together, these findings indicate that Hsp70 inhibits LPS-induced NF-kappaB activation by binding TRAF6 and preventing its ubiquitination, and results in inhibition of inflammatory mediator production, which provides a new insight for analyzing the effects of Hsp70 on LPS-triggered inflammatory signal transduction pathways.

Animals↗

PubMed2006

Polyvinylamine boronate adhesion to cellulose hydrogel.

The adhesion of polyvinylamine to wet cellulose was significantly enhanced by the presence of pendant phenylboronic acid groups. It is proposed that adhesion results from boronate ester formation with cellulose at pH > 8. Experiments with phenol derivatized polyvinylamine gave low adhesion supporting the fact that the boronate moiety was responsible for strong adhesion to never-dried cellulose surfaces.

Biocompatible Materials↗

PubMed2005

Hydroxypropyl guar-borate interactions with tear film mucin and lysozyme.

The interactions of hydroxypropyl guar (HPG) with boric acid, lysozyme, and mucin were characterized by rheology, light scattering, electrophoresis, and isothermal titration calorimetry to help understand how HPG interacts with tear film components. Borate binds to guar under pH, temperature, and ionic strength conditions representative of those found in the eye. The HPG-borate complexes behave as anionic polyelectrolytes and thus interact with cationic lysozyme, a major tear film protein, whereas HPG-borate does not appear to bind to mucin, an anionic glycoprotein. The interactions of HPG, borate, lysozyme, and mucin can be explained by two physical interactions: (1) pH-dependent binding of borate to carbohydrates and (2) the electrostatic attraction of oppositely charged macromolecules.

Animals↗

PubMed2005

Flocculation with poly(ethylene oxide)/tyrosine-rich polypeptide complexes.

New insights into the mechanism for the flocculation of aqueous colloids by the sequential addition of a water-borne phenolic polymer, called cofactor, followed by very high molecular poly(ethylene oxide) (PEO) are presented. It is proposed that PEO/cofactor complexes form in the aqueous phase and adsorb onto the surfaces of the target colloidal particles. Flocculation will occur if PEO/cofactor complex on one particle will bind to adsorbed complex on a second particle; i.e., if the complexes are sticky. The proposed mechanism was illustrated by flocculation experiments with precipitated calcium carbonate, very high molecular weight PEO, and a polypeptide cofactor called PEY1 which was a 1:1 random copolymer of l-glycine and l-tyrosine. Independent measurements of the PEO/PEY1 complex properties, in the absence of calcium carbonate, were used to support the mechanism. In order for PEO/PEY1 complexes to be sticky, they must simultaneously have unbound PEY1 and polymer segments. With time the complexes deactivate (i.e., lose their stickiness) by a reconfiguration process which results in elimination of either unbound PEY1 or PEO segments.

Adsorption↗

PubMed2004

Fast formation of the P3-P7 pseudoknot: a strategy for efficient folding of the catalytically active ribozyme.

Formation of the P3-P7 pseudoknot structure, the core of group I ribozymes, requires long-range base pairing. Study of the Tetrahymena ribozyme appreciates the hierarchical folding of the large, multidomain RNA, in which the P3-P7 core folds significantly slower than do the other domains. Here we explored the formation of the P3-P7 pseudoknot of the Candida ribozyme that has been reported to concertedly fold to the catalytically active structure with a rate constant of 2 min(-1). We demonstrate that pseudoknot formation occurs during the rapid ribozyme compaction, coincident with formation of many tertiary interactions of the ribozyme. A low physiological concentration of magnesium (1.5 mM) is sufficient to fully support the pseudoknot formation. The presence of nonnative intermediates containing an unfolded P3-P7 region is evident. However, catalysis-based analysis shows these nonnative intermediates are stable and fail to convert to the catalytically active structure, suggesting that rapid pseudoknot formation is essential for folding of the active ribozyme. Interestingly, RNAstructure predicts no stable Alt P3 structure for the Candida ribozyme, but two stable Alt P3s for the Tetrahymena ribozyme, explaining the dramatic difference in folding of the P3-P7 core of these two ribozymes. We propose that rapid formation of the P3-P7 pseudoknot represents a folding strategy ensuring efficient production of the catalytically active structure of group I ribozymes, which sheds new light on the mechanism of effective ribozyme folding in vivo.

Animals↗

PubMed2004

Factors influencing the size of PEO complexes with a tyrosine-rich polypeptide.

Aqueous complexes of PEY1, a 36 100 Da random synthetic peptide of tyrosine (50 mol %) and glutamic acid (50 mol %), with poly(ethylene oxide) (PEO) were studied as functions of PEO molecular weight, mixing ratio of PEO and PEY1, and the presence of calcium ions. Without calcium ions, the complexes were water soluble, with each complex consisting of a single PEO chain with many bound PEY1 chains. In the presence of 1 mM calcium ions, PEY1 formed colloidal aggregates with intermediate molecular weight PEO (10(5) to 10(6) Da). By contrast, very high molecular weight PEO (8 x 10(6) Da) with calcium ions formed large hydrogels when mixed with PEY1. It is proposed that PEY1 molecules completely bind to low molecular PEO and thus are deactivated from causing the coupling of multiple PEO chains, whereas deactivation of PEY1 on very high molecular weight PEO clusters is a slower process, giving an opportunity for cluster-cluster aggregation.

Calcium↗

PubMed2004

[The relationship of temperature and stroke incidence in Beijing: a time-series study].

OBJECTIVE: To study the relationship of temperature and stroke. METHODS: When long time trend, season and relative humidity were under control, the relationship between temperature and incidence rate of acute stroke was explored by generalized additive models (GAMs) for the whole population and stratified by age, sex, disease history and stroke type. RESULTS: Cold appeared to be a risk factor to stroke incidence. The incidence of stroke was higher than the baseline data when the temperature was lower than 8.5 degrees C but the incidence increased along with the decrease of temperature. Cold was more likely to affect females as well as patients older than 65-year-old with first-ever episode. However, heat was more likely to influence females and those over 65-year-old patients having had suffered stroke before. Cold endangered both haemorrhagic and ischaemic stroke while heat only affected ischaemic stroke. CONCLUSION: The interaction between average weekly temperature and stroke was related to the types of stroke. Age, gender and history of stroke in the past had different effects on the relationship between weekly average temperature and stroke incidence.

Adult↗

PubMed2002

PEO flocculation with phenolic microparticles.

Polystyrene latex and precipitated calcium carbonate (PCC) with and without dextran sulfate pretreatment were flocculated by the consecutive addition of high-molecular-weight poly(ethylene oxide) and a novel composite latex microparticle consisting of a polystyrene core and a poly(p-vinylphenol) shell. Good flocculation of polystyrene latex and PCC was obtained, whereas the PCC coated with dextran sulfate was not flocculated. The interaction of the composite microparticle with the target colloids was governed by electrostatic forces, whereas hydrogen bonding and hydrophobic interactions drove the PEO adsorption onto the composite particles.

Journal Article↗

PubMed2002

Reference value of semen quality in Chinese young men.

The purpose of the study was to evaluate semen quality in young Chinese men and to establish reference values. Normal healthy young men from seven geographical areas were enrolled. The study showed that the mean sperm volume was 2.61 mL, and mean percent of sperm with forward progression was 59.89, while median of semen viability was 79.0%, and geometric mean of semen density was 55.45 x 10(6)/mL. Proportion of routine semen indexes that met World Health Organization (WHO) criteria were as follows: 81.9% for semen volume, 91.1% for liquefaction time, 93.4% for viscosity, 90.8% for pH, 81.3% for sperm with forward progression, 65.3% for sperm viability, 93.8% for semen density, 98.8% for normal sperm morphology, and 89.1% for total sperm count. Participants whose sperm met all WHO standard parameters accounted for 42.3%. Because the infertility rate in China is about 10-15%, the fifteenth percentile of semen parameters might be used as the lower limit of reference values, which may be more appropriate for young Chinese men. The fifteenth percentiles of parameters in this study were as follows: 1.5 mL for semen volume, 7.2 for pH value, 45% for proportion of sperm with forward progression, 68% for sperm viability, 30 x 10(6)/mL for semen density, 68% for proportion of sperm with normal morphology, and 50 x 10(6) for total sperm count.

Adult↗