Biomedical subjects

Ke Chen

Publications and source records attributed to Ke Chen.

29 records · Page 2Linked to original sources

PubMed2005

Differences in biological features of gastric dysplasia, indefinite dysplasia, reactive hyperplasia and discriminant analysis of these lesions.

AIM: To investigate the differences in biological features of gastric dysplasia (Dys), indefinite dysplasia (IDys) and reactive hyperplasia (RH) by studying the biomarker alterations in cell proliferation, cell differentiation, cell cycle control and the expression of house-keeping genes, and further to search for markers which could be used in guiding the pathological diagnosis of three lesions. METHODS: Expressions of MUC5AC, MUC6, adenomatous polyposis coli (APC), p53, Ki-67, proliferation cell nuclear antigen (PCNA) and EGFR were studied by immunohistochemistry with a standard Envision technique in formalin-fixed and paraffin-embedded specimens from 43 RH, 35 IDys, 35 Dys and 36 intestinal type gastric carcinomas (IGC). In addition, Bayes discriminant analysis was used to investigate the value of markers studied in differential diagnosis of RH, IDys, Dys and IGC. RESULTS: The MUC5AC and MUC6 antigen expressions in RH, IDys, Dys and IGC decreased gradually (MUC5AC: 86.04%, 77.14%, 28.57%, 6.67%; MUC6: 65.15%, 54.29%, 20.00%, 25.00%, respectively). The expressions of the two markers had no significant difference between RH and IDys, but were all significantly higher than those of the other two lesions (MUC5AC: chi2=27.607, 38.027 and 17.33, 26.092; MUC6: chi2=16.54, 12.665 and 9.282, 6.737, P<0.01). There was no significant difference between RH and IDys, Dys and IGC in MUC6 expression. The APC gene expression in the four lesions had a similar decreasing tendency (RH 69.76%, IDys 68.57%, Dys 39.39%, IGC 22.86%), and it was significantly higher in the first two lesions than in the last two (chi2=7.011, 16.995 and 14.737, 19.817, P<0.05). The p53 expression in RH, IDys, Dys and IGC was 6.98%, 20%, 57.14% and 50%, respectively. There was no significant difference between RH and IDys or Dys and IGC, but the p53 expression in RH and IDys was significantly lower than that in Dys and IGC (chi2=7.011, 16.995 and 14.737, 19.817, P<0.01). The Ki-67 label index was significantly different among four lesions (RH: 0.298+/-8.92%, IDys: 0.358+/-9.25%, Dys: 0.498+/-9.03%, IGC: 0.620+/-10.8%, P<0.001). Positive immunostaining of PCNA was though observed in all specimens, significant differences were detected among four lesions (F=95.318, P<0.01). In addition, we used Bayes discriminant analysis to investigate molecular pathological classification of the lesions, and obtained the best result with the combination of MUC5AC, Ki-67 and PCNA. The overall rate of correct classification was 67.4% (RH), 68.6% (IDys), 70.6% (Dys) and 84.8% (IGC), respectively. CONCLUSION: Dys has neoplastic biological characteristics, while RH and IDys display hyperplastic characteristics. MUC5AC and proliferation-related biomarkers (Ki-67, PCNA) are more specific in distinguishing Dys from RH and IDys.

Biomarkers↗

PubMed2005

An electrochemical stripping metalloimmunoassay based on silver-enhanced gold nanoparticle label.

A novel, sensitive electrochemical immunoassay has been developed based on the precipitation of silver on colloidal gold labels which, after silver metal dissolution in an acidic solution, was indirectly determined by anodic stripping voltammetry (ASV) at a glassy-carbon electrode. The method was evaluated for a noncompetitive heterogeneous immunoassay of an immunoglobulin G (IgG) as a model. The influence of relevant experimental variables, including the reaction time of antigen with antibody, the dilution ratio of the colloidal gold-labeled antibody and the parameters of the anodic stripping operation, upon the peak current was examined and optimized. The anodic stripping peak current depended linearly on the IgG concentration over the range of 1.66 ng ml(-1) to 27.25 microg ml(-1) in a logarithmic plot. A detection limit as low as 1 ng ml(-1) (i.e., 6 x 10(-12) M) human IgG was achieved, which is competitive with colorimetric enzyme linked immuno-sorbent assay (ELISA) or with immunoassays based on fluorescent europium chelate labels. The high performance of the method is attributed to the sensitive ASV determination of silver (I) at a glassy-carbon electrode (detection limit of 5 x 10(-9) M) and to the catalytic precipitation of a large number of silver on the colloidal gold-labeled antibody.

Biosensing Techniques↗

PubMed2005

Adaptive smoothing via contextual and local discontinuities.

A novel adaptive smoothing approach is proposed for noise removal and feature preservation where two distinct measures are simultaneously adopted to detect discontinuities in an image. Inhomogeneity underlying an image is employed as a multiscale measure to detect contextual discontinuities for feature preservation and control of the smoothing speed, while local spatial gradient is used for detection of variable local discontinuities during smoothing. Unlike previous adaptive smoothing approaches, two discontinuity measures are combined in our algorithm for synergy in preserving nontrivial features, which leads to a constrained anisotropic diffusion process that inhomogeneity offers intrinsic constraints for selective smoothing. Thanks to the use of intrinsic constraints, our smoothing scheme is insensitive to termination times and the resultant images in a wide range of iterations are applicable to achieve nearly identical results for various early vision tasks. Our algorithm is formally analyzed and related to anisotropic diffusion. Comparative results indicate that our algorithm yields favorable smoothing results, and its application in extraction of hydrographic objects demonstrates its usefulness as a tool for early vision.

Algorithms↗

PubMed2003

Dissecting the EphA3/Ephrin-A5 interactions using a novel functional mutagenesis screen.

The EphA3 receptor tyrosine kinase preferentially binds ephrin-A5, a member of the corresponding subfamily of membrane-associated ligands. Their interaction regulates critical cell communication functions in normal development and may play a role in neoplasia. Here we describe a random mutagenesis approach, which we employed to study the molecular determinants of the EphA3/ephrin-A5 recognition. Selection and functional characterization of EphA3 point mutants with impaired ephrin-A5 binding from a yeast expression library defined three EphA3 surface areas that are essential for the EphA3/ephrin-A5 interaction. Two of these map to regions identified previously in the crystal structure of the homologous EphB2-ephrin-B2 complex as potential ligand/receptor interfaces. In addition, we identify a third EphA3/ephrin-A5 interface that falls outside the structurally characterized interaction domains. Functional analysis of EphA3 mutants reveals that all three Eph/ephrin contact areas are essential for the assembly of signaling-competent, oligomeric receptor-ligand complexes.

Binding Sites↗

PubMed2003

Adipocyte-selective reduction of the leptin receptors induced by antisense RNA leads to increased adiposity, dyslipidemia, and insulin resistance.

Although recent evidence suggests that leptin can directly regulate a wide spectrum of peripheral functions, including fat metabolism, genetic examples are still needed to illustrate the physiological significance of direct actions of leptin in a given peripheral tissue. To this end, we used a technical knock-out approach to reduce the expression of leptin receptors specifically in white adipose tissue. The evaluation of leptin receptor reduction in adipocytes was based on real time PCR analysis of the mRNA levels, Western blot analysis of the proteins, and biochemical analysis of leptin signaling capability. Despite a normal level of leptin receptors in the hypothalamus and normal food intake, mutant mice developed increased adiposity, decreased body temperature, hyperinsulinemia, hypertriglyceridemia, impaired glucose tolerance and insulin sensitivity, as well as elevated hepatic and skeletal muscle triglyceride levels. In addition, a variety of genes involved in regulating fat and glucose metabolism were dysregulated in white adipose tissue. These include tumor necrosis factor-alpha, adiponectin, leptin, fatty acid synthase, sterol regulatory element-binding protein 1, glycerol kinase, and beta3-adrenergic receptor. Furthermore, the mutant mice are significantly more sensitive to high fat feeding with regard to developing obesity and severe insulin resistance. Thus, we provide a genetic model demonstrating the physiological importance of a peripheral effect of leptin in vivo. Importantly, this suggests the possibility that leptin resistance at the adipocyte level might be a molecular link between obesity and type 2 diabetes.

Adipocytes↗

PubMed2002

Single-chain antibodies produced by phage display against the C-terminal 19 kDa region of merozoite surface protein-1 of Plasmodium yoelii reduce parasite growth following challenge.

Antibodies have the potential to be therapeutic reagents for malaria. Here we describe the production of a novel phage antibody display library against the C-terminal 19kDa region of the Plasmodium yoelii YM merozoite surface protein-1 (MSP1(19)). In vivo studies against homologous lethal malaria challenge show an anti-parasite effect in a dose dependent manner, and analysis by plasmon resonance indicates binding to the antigen is comparable to the binding of a protective monoclonal antibody. The data support the lack of a need for any antibody Fc-related function and hold great significance for the development of a therapeutic reagent for malaria.

Amino Acid Sequence↗

PubMed2002

A dynamically coupled neural oscillator network for image segmentation.

We propose a dynamically coupled neural oscillator network for image segmentation. Instead of pair-wise coupling, an ensemble of oscillators coupled in a local region is used for grouping. We introduce a set of neighborhoods to generate dynamical coupling structures associated with a specific oscillator. Based on the proximity and similarity principles, two grouping rules are proposed to explicitly consider the distinct cases of whether an oscillator is inside a homogeneous image region or near a boundary between different regions. The use of dynamical coupling makes our segmentation network robust to noise on an image, and unlike image processing algorithms no iterative operation is needed for noise removal. For fast computation, a segmentation algorithm is abstracted from the underlying oscillatory dynamics, and has been applied to synthetic and real images. Simulation results demonstrate the effectiveness of our oscillator network in image segmentation.

Algorithms↗

PubMed2002

Application of Nd-Yag laser for gingivoplasty during orthodontic treatment.

OBJECTIVE: To study the tissue's reaction and gingival healing after pulsed Nd-Yag laser surgery during orthodontic treatment. METHOD: Pulsed Nd-Yag laser was applied to 18 patients for gingivoplasty with an energy output of 140 mJ (25 Hz). Orthodontic brackets were bonded immediately after the laser surgery. RESULT: Gingivoplasty and brackets bonding were finished within a single surgery in all the 18 patients. The application of pulsed Nd-Yag laser yielded faster healing with less bleeding and infections. CONCLUSION: Nd-Yag laser is applicable and effective in gingivoplasty during orthodontic treatment, with many advantages over other treatment methods.

Adolescent↗

PubMed2002

[Determination of trace palladium in medicament by electric-heated AAS with molybdenum-coated graphite tube].

This paper reports a new method for the determination of palladium in exported medicament doxycycline hydrochloride by graphite furnace atomic absorption spectrometry. The optimum conditions for the determination of trace Pd were investigated in details. When the graphite tube was coated with molybdenum, the sensitivity was enhanced and when EDTA was used as the matrix modifier the matrix interference was eliminated efficiently. The result indicates that the detection limit for Pd is 4.6 x 10(-10) g and the relative standard deviation is 4.3%. The method is accurate and rapid and can be used successfully to determine actual samples. The recovery rate of palladium is in the range of 97.1% to 103.3%.

Doxycycline↗

PubMed2002

[Determination of trace barium in environmental samples by electric-heated AAS with lanthanum-coated graphite tube].

In this paper a new method was established for determination of trace barium in environmental samples by graphite furnace atomic absorption spectrometry. In the presence of matrix modifier magnesium nitrate, the matrix inference was eliminated efficiently. To avoid producing barium carbide, the graphite tubes were coated differently with lanthanum, zirconium, tungsten, molybdenum, and tantalum. Results showed that the tube with lanthanum was the best. The atomization temperature was diminished. The sensitivity was improved, and the tube with lanthanum gave the longest service life. So we used the tube to determine trace barium. The trace barium in Geodchemical Standard Reference Sample Soil-1 (GSS-1) was determined by the new method, the test results showed that the method was reliability and accurate. The method has been used for the determination of trace barium in environmental samples and in water of Yellow River. The detection limit for Ba was 2.1 x 10(-12) g and the relative standard deviation(RSD) was 5.4% for 15 ng.mL-1 Ba.

Barium↗

PubMed2000

Primary porcine hepatocytes with portal vein serum cultured on microcarriers or in spheroidal aggregates.

AIM:To develop a culture mode providing durable biomaterials with high yields and activities used in bioartificial liver.METHODS:Hepatocytes were isolated from a whole pig liver by Seglen s method of orthotopic perfusion with collagenase. In culture on microcarriers, primary porcine hepatocytes were inoculated at a concentration of 5center dot10(7)/mL into the static culture systems containing 2g/L Cytodex-3, then supplemented with 100mL/L fetal calf serum (FCS) or 100mL/L porcine portal vein serum (PPVS) respectively. In spheroidal aggregate culture hepatocytes were inoculated into 100mL siliconized flasks at a concentration of 5.0center dot10(6)/mL.RESULTS:In culture on microcarriers hepatocytes tended to aggregate on Cytodex-3 obviously after being inoculated. Typical multi-cellular aggregated spheroids could be found in the two systems 24h-48h after hepatocytes were cultured. The morphological charact-eristics and synthetic functions were maintained for 5wk in FCS culture system and 8wk in PPVS culture system. In spheroidal aggregate culture about 80%-90% isolated hepatocytes became aggregated spheroids 24h after cultured in suspension and mean diameter of the spheroids was 100&mgr;m. The relationship among the hepatocytes resembled that in the liver in vivo. Synthetic functions of albumin and urea of the spheroids were twice those of hepatocytes cultured on monolayers.CONCLUSION:As high-yields and high-activity modes of culture on microcarriers or in spheroidal aggregate culture with portal vein serum are promising to provide biomaterials for bioartificial liver (BAL) efficiently.

Journal Article↗