Biomedical subjects

Feng Li

Publications and source records attributed to Feng Li.

At least 37 records · Page 2Linked to original sources

PubMed2006

[Application of carbon fiber dressing on burn wounds].

OBJECTIVE: To observe the effects of carbon fiber dressing on burn wounds. METHODS: Two hundreds and seventy seven burn patients were randomly divided into treatment group (group T) and control group (group C). The burn wounds were covered with carbon fiber dressing in T group, and with povidone iodine gauze in C group, respectively. The absorption capability of the dressing, inflammatory reaction and bacteria quantitation of wound tissues and wound healing time were observed, and biopsy of wounds were performed. RESULTS: The absorption capability of the dressing was higher, the wound inflammatory reaction was milder, and bacteria quantitation of wound tissues was lower in the group T than that in group C. The wound healing time in the group T was shorter than that in group C. CONCLUSIONS: Carbon fiber dressing is a new model dressing, it can absorb wound exudation, lessen inflammatory reaction and improve wound healing.

Adolescent↗

PubMed2006

The c-Myc target gene network.

For more than a decade, numerous studies have suggested that the c-Myc oncogenic protein is likely to broadly influence the composition of the transcriptome. However, the evidence required to support this notion was made available only recently, much to the anticipation of an eagerly awaiting field. In the past 5 years, many high-throughput screens based on microarray gene expression profiling, serial analysis of gene expression (SAGE), chromatin immunoprecipitation (ChIP) followed by genomic array analysis, and Myc-methylase chimeric proteins have generated a wealth of information regarding Myc responsive and target genes. From these studies, the c-Myc target gene network is estimated to comprise about 15% of all genes from flies to humans. Both genomic and functional analyses of c-Myc targets suggest that while c-Myc behaves as a global regulator of transcription, groups of genes involved in cell cycle regulation, metabolism, ribosome biogenesis, protein synthesis, and mitochondrial function are over-represented in the c-Myc target gene network. c-Myc also consistently represses genes involved in cell growth arrest and cell adhesion. The overexpression of c-Myc predisposes cells to apoptosis under nutrient or growth factor deprivation conditions, although the critical sets of genes involved remain elusive. Despite tremendous advances, the downstream target genes that distinguish between physiologic and tumorigenic functions of c-Myc remain to be delineated.

Animals↗

PubMed2006

One-pot preparation of silica-supported hybrid immobilized metal affinity adsorbent with macroporous surface based on surface imprinting coating technique combined with polysaccharide incorporated sol--gel process.

A simple and reliable one-pot approach using surface imprinting coating technique combined with polysaccharide incorporated sol-gel process was established to synthesize a new organic-inorganic hybrid matrix possessing macroporous surface and functional ligand. Using mesoporous silica gel being a support, immobilized metal affinity adsorbent with a macroporous shell/mesoporous core structure was obtained after metal ion loading. In the prepared matrix, covalently bonded coating and morphology manipulation on silica gel was achieved by using one-pot sol-gel process starting from an inorganic precursor, -glycidoxypropyltrimethoxysiloxane (GPTMS), and a functional biopolymer, chitosan (CS) at the atmosphere of imprinting polyethylene glycol (PEG). Self-hydrolysis of GPTMS, self-condensation, and co-condensation of silanol groups (Si-OH) from siloxane and silica gel surface, and in situ covalent cross-linking of CS created an orderly coating on silica gel surface. PEG extraction using hot ammonium hydroxide solution gave a chemically and mechanically stabilized pore structure and deactivated residual epoxy groups. The prepared matrix was characterized by using X-ray energy dispersion spectroscopy (EDX), scanning electron microscopy (SEM) and mercury intrusion porosimetry. The matrix possessed a high capacity for copper ion loading. Protein adsorption performance of the new immobilized metal affinity adsorbent was evaluated by batch adsorption and column chromatographic experiment using bovine serum albumin (BSA) as a simple model protein. Under the optimized coating conditions, the obtained macroporous surface resulted in a fast kinetics and high capability for protein adsorption, while the matrix non-charged with metal ions offered a low non-specific adsorption.

Adsorption↗

PubMed2006

[Effects of Yunnan Baiyao on peri-operative bleeding of patients undergoing cervical open-door laminoplasty: a multi-center randomized double-blind placebo-control trial].

OBJECTIVE: To investigate the effects of Yunnan Baiyao on peri-operative bleeding of the patients undergoing cervical open-door laminoplasty. METHODS: 197 patients undergoing cervical open-door laminoplasty were randomly divided into 2 groups Yunnan Baiyao group (receiving Yunnan Baiyao 500 mg three times daily for 5 days) and placebo group. The amounts of intra-operative and post-operative bleeding were compared, and the side effect of Yunnan Baiyao was also analyzed. RESULTS: Statistical analysis showed that the amount of intra-operative bleeding of the Yunnan Baiyao was 350 ml +/- 190 ml, significantly lower than that of the placebo group (443 ml +/- 266 ml, P < 0.05). There were no statistical differences in the amount of postoperative bleeding and side effect rate between the two groups. CONCLUSION: Yunnan Baiyao is effective and safe in reducing the amount of intra-operative bleeding of cervical open-door laminoplasty.

Adult↗

PubMed2006

Sensitivity of a Lamb wave sensor with 2 microm AlN membrane.

Anti-symmetrical Lamb wave mode A0 presents a large sensitivity to mass loading and can be used in contact with liquids with a small attenuation. The advantages of this system are the possibility to get a large mass sensitivity. The sensitivity increases when the thickness of membrane decreases. Therefore the problem is to obtain thin piezoelectric membranes. A membrane of AlN with a thickness of 2 microm has been made. The measured mass sensitivity with a fluid is 200 cm(2) g(-1). In a practical use point of view, the problem in this kind of sensor is its temperature sensitivity. In order to reduce effective temperature sensitivity, a device with thin metallic strips is presented. On the same membrane two different waves with perpendicular propagating directions are produced. Experimentally, temperature sensitivity is rather different depending on the propagation direction but mass sensitivity is almost the same, this allows distinguishing temperature effects from those due to mass loading on the frequency shift measurements.

Acoustics↗

PubMed2006

Conditional deletion of c-myc does not impair liver regeneration.

The oncogene c-myc encodes a transcription factor that has long been considered essential to liver regeneration, the process by which fully differentiated hepatocytes proliferate in an attempt to maintain a normal functional mass in response to hepatic injury. Experimental liver regeneration can be induced upon 70% partial hepatectomy and is accompanied by an increase in c-myc expression accompanying the synchronous entry of remaining hepatocytes into the cell cycle. Because liver regeneration is an essential process for achieving liver homeostasis, therapies directed at reducing MYC expression in hepatocellular carcinoma are fraught with the theoretical possibility of injuring adjacent noncancerous liver cells, thereby restricting the liver's normal regenerative response to injury. To determine if intact c-myc is required for liver regeneration, we reduced hepatic c-myc in c-myc(fl/fl) mice using an adenoviral vector that expresses Cre recombinase. Despite a 90% decrease in hepatic expression of c-myc, restoration of liver mass 7 days later was not compromised. Reconstituted liver retained the same decrease in hepatic c-myc, indicating that hepatocytes deficient in c-myc were able to proliferate in response to partial hepatectomy. Although c-myc is required for embryonic development, our findings indicate that it is not required for the maintenance of the adult liver.

Alleles↗

PubMed2006

Recombinant baculovirus containing the diphtheria toxin A gene for malignant glioma therapy.

Insect baculoviruses are capable of infecting mammalian glial cells in the central nervous system. We investigated in the current study the feasibility of using the viruses as toxin gene vectors to eliminate malignant glioma cells in the brain. We first confirmed that glioma cells were permissive to baculovirus infection, with variable transduction efficiencies at 100 viral particles per cell and ranging between 35% and 70% in seven human and rat glioma cell lines. We then developed a recombinant baculovirus vector accommodating the promoter of glial fibrillary acidic protein (GFAP) to minimize possible side effects caused by overexpression of a therapeutic gene in sensitive neurons. We placed the GFAP promoter into a baculovirus expression cassette, in which the enhancer of human cytomegalovirus immediate-early gene and the inverted terminal repeats of adeno-associated virus were employed to improve the relatively low transcriptional activity of the cellular promoter. This recombinant baculovirus significantly improved transduction in glioma cells, providing the efficiency in C6 rat glioma cells up to 96%. When used to produce the A-chain of diphtheria toxin intracellularly in a rat C6 glioma xenograft model, the baculovirus effectively suppressed tumor development. The new baculovirus vector circumvents some of the inherent problems associated with mammalian viral vectors and provides an additional option for cancer gene therapy.

Animals↗

PubMed2006

Some advances in plant stress physiology and their implications in the systems biology era.

The study for biointerfaces at different scales in the past years has pricked up the march of biological sciences, in which biomembrane concept and its characteristics, receptor proteins, ion channel proteins, LEA proteins, calcium and newly recognized second messengers, ROS, MAPKs and their related sensors and new genes in osmoregulation, signal transduction, and other aspects have been understood fully, widening area of understanding the extensive interactions from biosystem and biointerfaces. The related discipline, plant stress physiology, especially, crop stress physiology has gained much attention world widely, the important reason of which is from the reducing quality of global ecoenvironment and decreasing food supply. This short review will place a stress on the recent progresses in plant stress physiology, combined with the new results from our State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau.

Adaptation, Physiological↗

PubMed2006

Purification of multiwalled carbon nanotubes by annealing and extraction based on the difference in van der Waals potential.

The potential energies of van der Waals interactions between two multiwalled carbon nanotubes (MWNTs) as well as two carbon nanoparticles (CNPs) were calculated and compared on the basis of the continuum Lennard-Jones model. The well depth of the potential is 1 order of magnitude higher for MWNTs than for CNPs, indicating that MWNTs and CNPs can be separated from each other through polymer-induced steric stabilization. On the basis of this prediction, a novel method for the purification of MWNTs was proposed. The method involves a high-temperature annealing (2600 degrees C, 1 h) followed by an extraction treatment with a selected dispersing agent. While the annealing process evaporates the metal particles, the extraction treatment removes CNPs. The quality of the nanotubes obtained after purification was examined by laser Raman, thermogravimetric analysis, and electron microscopy observations.

Journal Article↗

PubMed2006

On-line hyphenation of flow injection, miniaturized capillary electrophoresis and atomic fluorescence spectrometry for high-throughput speciation analysis.

A hyphenated technique was developed for high-throughput speciation analysis by on-line coupling of flow injection (FI), miniaturized capillary electrophoresis (CE) and atomic fluorescence spectrometry (AFS). Two interfaces were used to couple all three systems: the first to couple FI and CE and the second to couple miniaturized CE and AFS. The first interface was a modified flow through chamber, connected to the FI valve with a piece of PTFE tube (0.1mm i.d.x 20 cm long). The capillary outlet was coupled to the AFS by using the second concentric "tube-in-tube" interface. Split sampling was achieved in the electrokinetic mode. Inorganic mercury (Hg(II)) and methylmercury (MeHg(I)) were taken as model analytes to demonstrate the performance of the developed hyphenated technique. A volatile species generation (VSG) technique was employed to convert the analytes from the CE effluent into their respective volatile species. Baseline separation of Hg(II) and MeHg(I) was achieved by CE in a 50 microm i.d.x 8 cm long capillary at 3.0 kV within 60s. The precisions (RSD, n=12) were in the range of 0.7-0.9% for migration time, 3.8-4.2% for peak area, and 2.1-3.5% for peak height. The detection limits were 0.1 and 0.2 microgmL(-1) (as Hg) for Hg(II) and MeHg(I) with a sample throughput of 60 samples h(-1). The recoveries of both mercury species in the water samples studied were in the range of 93-106%.

Electrophoresis, Capillary↗

PubMed2006

Effect of pore packing defects in 2-d ordered mesoporous carbons on ionic transport.

Ordered mesoporous materials show great importance in energy, environmental, and chemical engineering. The diffusion of guest species in mesoporous networks plays an important role in these applications, especially for energy storage, such as supercapacitors based on ordered mesoporous carbons (OMCs). The ion diffusion behavior in two different 2-D hexagonal OMCs was investigated by using cyclic voltametry and electrochemical impedance spectroscopy. In addition, transmission electron microscopy, small-angle X-ray diffraction, and nitrogen cryosorption methods were used to study the pore structure variations of these two OMCs. It was found that, for the OMC with defective pore channels (termed as pore packing defects), the gravimetric capacitance was greatly decayed when the voltage scan rate was increased. The experimental results suggest that, for the ion diffusion in 2-D hexagonal OMCs with similar mesopore size distribution, the pore packing defect is a dominant dynamic factor.

Journal Article↗

PubMed2006

Progenitors systemically transplanted into neonatal mice localize to areas of active bone formation in vivo: implications of cell therapy for skeletal diseases.

The potential of cell or gene therapy to treat skeletal diseases was evaluated through analysis of transplanted osteoprogenitors into neonatal homozygous and heterozygous osteogenesis imperfecta mice (oim). The osteoprogenitors used for transplantation were prepared by injection of mesenchymal stem cells (MSCs) marked with the green fluorescent protein (GFP) into normal mice with the subsequent retrieval of the cells at 35 days. The retrieved cells referred to here as osteoprogenitors were expanded in culture and transplanted into the 2-day-old oim mice via the superficial temporal vein. The recipient mice were evaluated at 2 and 4 weeks after cell transplantation. Four weeks after transplantation, tissue sections made from femurs and tibias of oim mice showed that the GFP-positive (GFP(+)) cells were distributed on the surfaces of the bone spicules in the spongiosa, the area of active bone formation. In the diaphysis, the GFP(+) cells were distributed in the bone marrow, on the endosteal surfaces, and also in the cortical bone. Immunofluorescence localization for GFP confirmed that the fluorescence seen in tissue sections was due to the engrafted donor cells, not bone autofluorescence. Gene expression analysis by polymerase chain reaction of the GFP(+) cells retrieved from the bones and marrow of the recipient mice demonstrated that the cells from bone were osteoblasts, whereas those from bone marrow were progenitors. These data demonstrate that MSCs delivered systemically to developing osteogenesis imperfecta mice engraft in bones, localize to areas of active bone formation, differentiate into osteoblasts in vivo, and may contribute to bone formation in vivo.

Animals↗

PubMed2006

Tumor-suppressor PTEN affects tau phosphorylation, aggregation, and binding to microtubules.

Neurofibrillary tangles (NFTs), consisting of abnormally hyperphosphorylated tau, are implicated in the pathogenesis of several neurodegenerative diseases including Alzheimer's disease (AD). The molecular mechanisms underlying the regulation of tau phosphorylation are largely unknown. While the PI3K/Akt pathway has been shown to regulate multiple cellular events pertinent to AD pathogenesis, potential functions of tumor suppressor phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in AD pathogenesis have not been explored. Here, we examine the effects of PTEN on tau phosphorylation, its microtubule association and formation of aggregates, and consequentially neuronal morphology. In cultured cells, overexpression of wild-type (WT) PTEN alters tau phosphorylation at several sites, increases tau-microtubule association and decreases formation of tau aggregates. In addition, the phosphatase-null PTEN increases tau aggregation and impairs tau binding to microtubule and neurite outgrowth of neurons expressing the mutant PTEN. We also found a significant loss of PTEN in AD patient brains correlated with a dramatically increased concentration of phospho-tau at Ser-214 in NFTs. Together, our results demonstrate that PTEN regulates tau phosphorylation, binding to microtubules and formation of aggregates and neurite outgrowth. These findings suggest a link between malfunction of PTEN and tauopathy, and imply PTEN as a therapeutic target for tauopathy.

Alzheimer Disease↗

PubMed2006

Gene silencing activity of siRNAs with a ribo-difluorotoluyl nucleotide.

Recently, chemically synthesized short interfering RNA (siRNA) duplexes have been used with success for gene silencing. Chemical modification is desired for therapeutic applications to improve biostability and pharmacokinetic properties; chemical modification may also provide insight into the mechanism of silencing. siRNA duplexes containing the 2,4-difluorotoluyl ribonucleoside (rF) were synthesized to evaluate the effect of noncanonical nucleoside mimetics on RNA interference. 5'-Modification of the guide strand with rF did not alter silencing relative to unmodified control. Internal uridine to rF substitutions were well-tolerated. Thermal melting analysis showed that the base pair between rF and adenosine (A) was destabilizing relative to a uridine-adenosine pair, although it was slightly less destabilizing than other mismatches. The crystal structure of a duplex containing rFoA pairs showed local structural variations relative to a canonical RNA helix. As the fluorine atoms cannot act as hydrogen bond acceptors and are more hydrophobic than uridine, there was an absence of a well-ordered water structure around the rF residues in both grooves. siRNAs with the rF modification effectively silenced gene expression and offered improved nuclease resistance in serum; therefore, evaluation of this modification in therapeutic siRNAs is warranted.

Base Pairing↗

PubMed2006

Differences between tethered polyelectrolyte chains on bare mica and hydrophobically modified mica.

This study investigates the structures of layers of amphiphilic diblock copolymers of poly(t-butyl styrene)-poly(styrene sulfonate) (PtBS-PSS) adsorbed on both the bare mica surface (hydrophilic) and an octadecyltriethoxysilane (OTE)-modified mica surface (hydrophobic). When the surface is rendered hydrophobic, the nonsoluble block exhibits stronger interaction with the surface and higher adsorbed masses are achieved. Interaction forces between two such adsorbed layers on both substrates were measured using the surface forces apparatus. The effect of salt concentration (Cs) and molecular weight (N) on the height of the self-assembled layers (L0) was examined in each case. The resulting scaling relationship is in good agreement with predictions of the brush model, L0 proportional to N(1.0) in the low-salt limit and L0N(-1) proportional to (Cs/sigma)(-0.32) in the salted regime, when adsorption takes place onto the hydrophobized mica surface. For adsorption on the bare mica surface, L0N(-0.7) proportional, variant Cs(-0.17) agrees with the scaling prediction of the sparse tethering model. The results suggest that, on the hydrophilic bare mica surface, the adsorbed amount is not high enough to form a brush structure and only very little intermolecular stretching of the tethered chains occurs; in contrast, the presence of the hydrophobic OTE layer increases the tethering density such that the polyelectrolyte chains adopt a brush conformation.

Journal Article↗

PubMed2006

Staging of nasopharyngeal carcinoma investigated by magnetic resonance imaging.

BACKGROUND AND PURPOSE: To investigate the American Joint Commission on Cancer (AJCC) sixth edition staging system of nasopharyngeal carcinoma (NPC) by Magnetic Resonance Imaging (MRI). PATIENTS AND METHODS: One hundred and fifty-nine non-disseminated biopsy-proven NPC patients were studied with MRI before treatment. Retrieval of MRI information enabled us to restage all patients accurately according to the sixth edition of the AJCC staging system. Splitting the respective T and N stages by the significant defining factors identified, the cancer death hazard ratios were modeled by the Cox model in SPSS 10.0 for windows (SPSS Inc, Chicago, IL). RESULTS: Single site of skull base abnormality (HR = 3.91, 95% CI: 0.74-20.56) has a superior result to others involved in T3 (HR = 5.83, 95% CI: 1.24-27.29). Involvement of either anterior or posterior cranial nerves solely (HR = 6.02, 95% CI: 1.55-35.60) was not found to be as a poor prognostic indicator as others involved in T4 (HR = 7.81, 95% CI: 1.81-33.63). Less than or equal to 3 cm of N1 (HR = 4.01, 95% CI: 0.48-33.83) and N2 (HR = 4.72, 95% CI: 0.62-35.78) have a better result than >3 cm of N1 (HR = 8.09, 95% CI: 0.95-68.97) and N2 (HR = 10.58, 95% CI: 1.32-84.62), respectively. CONCLUSIONS: Perhaps, it is better to down-stage single site of skull base abnormality from T3 to T2, and involvement of either anterior or posterior cranial nerves solely from T4 to T3, meanwhile, < or =3 cm of N2 down-stage to N1, >3 cm of N1 up-stage to N2.

Adolescent↗

PubMed2006

[An analysis of failure factors in treatment of femoral shaft fracture with interlocking intramedullary nailing].

OBJECTIVE: To analyze the failure factors treating femoral shaft fracture with interlocking intramedullary nailing, and to offer the measures for prevention. METHODS: From April 1999 to September 2002, among the 213 cases of femoral shaft fracture treated by interlocking intramedullary nailing, 18 were failure. The data of these cases were analyzed. RESULTS: The failure cases were divided into 6 types: 3 cases with nail break-down, 7 with distal screw backing out, 3 with proximal screw backing out, 3 with fibrous ankylosis of knee, 2 with late infection. Failure relative factors were regarded to operation technique, incorrect rehabilitation choice of operative indication, quality of interlocking intramedullary nailing. CONCLUSIONS: An appropriate indication should be chosen as using interlocking intramedullary nailing for femoral shaft fracture. The skills should be mastered well. The suitable materials should be chosen carefully. And the rehabilitation exercises should be directed properly. All these are important measures for prevention.

Adult↗

PubMed2006

2'-Fluoroarabino- and arabinonucleic acid show different conformations, resulting in deviating RNA affinities and processing of their heteroduplexes with RNA by RNase H.

2'-Deoxy-2'-fluoro-arabinonucleic acid (FANA) and arabinonucleic acid (ANA) paired to RNA are substrates of RNase H. The conformation of the natural DNA/RNA hybrid substrates appears to be neither A-form nor B-form. Consistent with this, the conformations of FANA and ANA were found to be intermediate between the A- and B-forms. However, FANA opposite RNA is preferred by RNase H over ANA, and the RNA affinity of FANA considerably exceeds that of ANA. By investigating the conformational boundaries of FANA and ANA residues in crystal structures of A- and B-form DNA duplexes at atomic resolution, we demonstrate that FANA and ANA display subtle conformational differences. The structural data provide insight into the structural requirements at the catalytic site of RNase H. They also allow conclusions with regard to the relative importance of stereoelectronic effects and hydration as modulators of RNA affinity.

Arabinonucleotides↗