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Biomedical subjects

Ming Chen

Publications and source records attributed to Ming Chen.

At least 91 records · Page 5Linked to original sources
PubMed2005

An algorithm for linear metabolic pathway alignment.

Metabolic pathway alignment represents one of the most powerful tools for comparative analysis of metabolism. It involves recognition of metabolites common to a set of functionally-related metabolic pathways, interpretation of biological evolution processes and determination of alternative metabolic pathways. Moreover, it is of assistance in function prediction and metabolism modeling. Although research on genomic sequence alignment is extensive, the problem of aligning metabolic pathways has received less attention. We are motivated to develop an algorithm of metabolic pathway alignment to reveal the similarities between metabolic pathways. A new definition of the metabolic pathway is introduced. The algorithm has been implemented into the PathAligner system; its web-based interface is available at http://bibiserv.techfak.uni-bielefeld.de/pathaligner/.

Algorithms↗
PubMed2005

[Infrared spectra analysis of chromium cation biosorbed by biosorbent ZL5-2].

Biosorption of Cr( VI) by the novel biosorbent ZL5-2 produced by Agrobacterium. sp was studied, and infrared spectra of native, absorbing and desorbing ZL5-2 were compared. The initial pH was important for biosorption. The optimum effect on Cr(VI) biosorption was acquired within initial pH 0.5-1.5, then with the pH increasing, the effect on Cr6+ biosorption was reduced. The biosorption for Cr(VI) was a quick process, only within 10 min 65.4% Cr(VI) was biosorbed, and the biosorption was in equilibrium after 60 min, then all the Cr(VI) was biosorbed after 80 min. The absorbed Cr(VI) could be recovered by desorption, and the desorption rate reached 13.6%-67.9%. The absorbance peak around 3 400 cm(-1), which reflected OH stretching vibration, moved about 8 cm(-1), and its absorbance decreased; the absorbance peak around 2 900 cm(-1) decreased, which reflected C-H stretching vibration; and the absorbance peak around 1 600 cm(-1), which reflected amide I group stretching vibration, moved about 13 cm(-1), and its absorbance decreased. After desorption, the absorbance peaks which reflected OH and C-H were increased to the initial degree, and the absorbance peak which reflected NH and amide I group did not increase. Therefore, authors presumed that the process of biosorption was reversible adsorption and irreversible adsorption simultaneously, however the reversible adsorption was more important in the biosorption.

Adsorption↗
PubMed2005

[Rolling friction: a desing of artificial knee joint].

Resorption and osteolysis of periimplant bones resulting from the wear debris of artificial joint will cause long-term loosening. A new type of rolling knee artificial joint without UHMWPE based on the mechanics of rolling friction is designed for alleviating this problem. Because of low friction force, the resistance of extension and flexion is reduced strikingly and the stress on the interface between prosthesis and bone is reduced evidently. In addition, the bio-toxicity caused by the wear debris of UHMWPE will not occur absolutely. In consequence, the rolling artificial joint can prevent the trend of long-term loosening of the prosthesis efficiently.

Animals↗
PubMed2005

[Recombinant adeno-associated viral vector 2-mediated gene transfer of VEGF165 improved porcine chronic myocardial ischemia].

OBJECTIVE: Vectors commonly used for therapeutic angiogenesis such as adenovirus and plasmid had their own limitations. Adenovirus-associated virus (AAV) is a relatively new but probably more ideal vector as it is safe and efficient. We will study the efficiency of recombinant AAV-2 mediated vascular endothelial growth factor165 gene transfer in inducing angiogenesis and arteriogenesis, in improving blood flow and myocardium function in a porcine chronic myocardial ischemic model. METHODS: Chinese experimental minipigs underwent placement of a left circumflex artery aneroid constrictor. Five weeks later, electrocardiogram, coronary angiography and magnetic resonance imaging were performed to confirm occlusion of LCX or ischemia of myocardium in LCX territory. Coronary blood flow, myocardium perfusion and left ventricular wall function were also evaluated. Then the animals were randomized to treatment with rAAV2-VEGF(165) (1 x 10(12) virus genome) or administration of PBS, both by direct myocardial injection. Three and six months after therapy, the animals were evaluated with regard to expression of VEGF(165) Capillary density and arteriole density of the ischemic myocardium, coronary angiography, myocardial perfusion and left ventricular function were also assessed six months after therapy. RESULTS: Five weeks after aneroid occluder implantation, all the animals demonstrated complete or nearly complete occlusion of LCX and perfusion deficiency in LCX territory. Three months after therapy, expression of VEGF(165) mRNA and protein were higher in the VEGF than control group. The difference between the two groups diminished after six months. There was significant increase in capillary density (1404.06 +/- 250.48/mm(2) vs 976.88 +/- 344.79/mm(2), P < 0.05) and arteriole density (167.81 +/- 36.29/mm(2) vs 116.56 +/- 34.48/mm(2), P < 0.05) in VEGF group compared with control. Comparison of myocardial perfusion demonstrated marked differences between the two groups with significant improvement in animals treated with rAAV2-VEGF(165). No significant improvement in left ventricular function was seen in either the VEGF or control group. CONCLUSIONS: Transmyocardial delivery of rAAV2-VEGF(165) resulted in VEGF gene expression for at least three months and stimulated angiogenesis and arteriogenesis in porcine model of chronic myocardial ischemia. Myocardial perfusion was also improved after VEGF gene delivery.

Adenoviridae↗
PubMed2005

[Experimental study on the reconstruction of bone defects in vivo and the osteoinduction with degradation products of alpha-tricalcium phosphate cements in vitro].

OBJECTIVE: This study was aimed to clarify the characteristics of alpha-tricalcium phosphate cements in reconstructing bone defects and the action of degradation products of cements in vitro. METHODS: The defect (diameter 1.5 cm) was created in the calvaria of rabbit. Alpha-tricalcium phosphate cements were planted in the treatment groups. All groups were observed by histological examination and roentgenography. Bone marrow stromal cells (BMSc) were cultured in the degradation products of cements in vitro, and were observed by means of cytology and ALP. RESULTS: Degradation of artificial bone, new bone formation, and osteogenesis between artificial bone particles were observed at 12 weeks after implantation. Osteoinduction was observed in vitro. CONCLUSION: Alpha-tricalcium phosphate cements have good biocompatibility, osteoinductivity and degradability, and are ideal bone substitute material for reconstruction.

Animals↗
PubMed2005

[Retrospective analysis of 934 nasopharyngeal carcinoma patients treated with conventional external beam radiotherapy alone].

OBJECTIVE: To analyze the clinical outcome of 934 primary nasopharyngeal carcinoma treated with conventional external beam radiotherapy alone. METHODS: 34 patients were treated from Jan. 1, 1999 to Dec. 31, 1999. The radiation fields were delineated according to the CT/MRI imaging findings on disease extent. Two lateral opposing isocentric portals with customized blockings were used for the nasopharynx and upper neck. The dose delivered to tumor in the nasopharynx was 68-70 Gy/2 Gy fraction/7 weeks. The doses delivered to the neck was 60-70 Gy/6-7 weeks for patients with positive lymph nodes and 50 Gy/5 weeks for the patients with negative lymph node. RESULTS: The 1-, 2-, 3- and 4-year overall survival rate (OS) was 89.5%, 81.9%, 78.1% and 75.7%, and metastasis-free survival rate (MFS) was 84.0%, 77.2%, 74.4% and 72.0%, respectively. The 1-, 2-, 3- and 4-year disease-free survival rate (DFS) was 80.8%, 73.1%, 68.5% and 65.1%, and the relapse-free survival rate (RFS) was 95.5%, 92.7%, 90.3% and 87.3%, respectively. The overall failure rate was 30.9% (289/934). At the end of the radiotherapeutic course, the percentage of residual disease was 14.6%. The 4-year loco-regional recurrence and distant metastasis rates after radiotherapy were 7.2% and 9.2% with a median time of 19.3 months and 12.8 months. CONCLUSION: It may be helpful to improve radiotherapy curative effect when the target is individually designed through improving irradiation technique according to CT/MRI findings and by shortening the overall course time, enhancing irradiation dose and strictly implementing QA/QC measures.

Adolescent↗
PubMed2004

Ringwoodite lamellae in olivine: Clues to olivine-ringwoodite phase transition mechanisms in shocked meteorites and subducting slabs.

The first natural occurrence of ringwoodite lamellae was found in the olivine grains inside and in areas adjacent to the shock veins of a chondritic meteorite, and these lamellae show distinct growth mechanism. Inside the veins where pressure and temperature were higher than elsewhere, ringwoodite lamellae formed parallel to the [101] planes of olivine, whereas outside they lie parallel to the (100) plane of olivine. The lamellae replaced the host olivine from a few percent to complete. Formation of these lamellae relates to a diffusion-controlled growth of ringwoodite along shear-induced planar defects in olivine. The planar defects and ringwoodite lamellae parallel to the [101] planes of olivine should have been produced in higher shear stress and temperature region than that parallel to the (100) plane of olivine. This study suggests that the time duration of high pressure and temperature for the growth of ringwoodite lamellae might have lasted at least for several seconds, and that an intracrystalline transformation mechanism of ringwoodite in olivine could favorably operate in the subducting lithospheric slabs in the deep Earth.

Journal Article↗
PubMed2004

Correlation of lymphocyte heat shock protein 70 levels with neurologic deficits in elderly patients with cerebral infarction.

PURPOSE: To assess the association between heat shock protein 70 (HSP70) levels and the severity of ischemic stroke in elderly patients. METHODS: We conducted a case-control study to investigate the changes in lymphocyte HSP70 levels by immunoblot in 65 elderly patients with mild (n = 22), intermediate (n = 21), or severe (n = 22) stroke, and in 34 healthy controls. We analyzed correlations between HSP70 levels and neurologic deficit scores on days 1, 15, and 30 after the onset of stroke. RESULTS: Mean (+/- SD) HSP70 levels were higher in all stroke patients compared with controls (mild stroke: 709 +/- 194 units; intermediate: 585 +/- 165 units; severe: 421 +/- 124 units; controls: 86 +/- 34 units on day 1). Patients with mild stroke had higher levels at day 1 and 15 than did patients with severe stroke. HSP70 levels decreased rapidly from days 1 to 30 in all patients, except in patients with severe stroke, in whom levels decreased slowly between days 15 and 30. There were significant negative correlations between HSP70 levels and neurologic deficit scores in patients on days 1 (r = -0.53, P < 0.001) and 15 (r = -0.54, P < 0.001), but a positive correlation on day 30 (r = 0.49, P < 0.001). CONCLUSION: These data suggest that HSP70 may be a marker for neuroprotection in the early stage of ischemic stroke and a marker for a crisis in the later stages of severe cerebral infarction. Further studies on the use of lymphocyte HSP70 levels in predicting clinical outcomes and underlying mechanisms in cerebral infarction are warranted.

Aged↗
PubMed2004

Prenatal exposure to high level of glucocorticoids increases the susceptibility of renal proximal tubular cells to apoptosis induced by uropathogenic Escherichia coli toxins.

Prenatal exposure to excessive glucocorticoids may alter the developing fetus inducing metabolic and endocrine imbalance in various organs, including the kidney. This study aimed at evaluating whether prenatal exposure to high levels of glucocorticoids adversely affects renal cell survival and predisposes to renal cell death. Pregnant rats were injected with 0.1 mg/kg dexamethasone (DEX) i.p. from day 1 of gestation. Renal proximal tubular cells (PTCs) were prepared from 20-day-old offspring in the DEX (DEX cells) and control groups (CON cells). After 4 days' culture, cells were exposed to uropathogenic Escherichia coli ARD6 toxins at concentrations known to induce apoptotic cell death. We found that cell death rate was significantly higher in DEX than in CON cells. Cells exhibited morphological and biochemical features of apoptosis. Conversely, the activity of the antioxidant enzyme catalase was significantly increased in renal cortex homogenate from 20-day-old DEX rats. The antioxidant vitamin E did not prevent apoptosis. These results indicate that prenatal exposure to high levels of glucocorticoids induces alterations in renal PTCs rendering them more sensitive to E. coli toxins via nonoxidative stress. With the increasing use of multiple doses of glucocorticoids in preterm infants, the possibility that antenatal glucocorticoids may lead to renal adverse consequences is of clinical relevance.

Animals↗
PubMed2004

Ruggedness/robustness evaluation and system suitability test on United States Pharmacopoeia XXVI assay ginsenosides in Asian and American ginseng by high-performance liquid chromatography.

The work of the ruggedness/robustness evaluation and system suitability tests was oriented to profound understand the practicability of using assay methods issued by United States Pharmacopoeia (USP XXVI and XXVII) for ginsenosides in Asian ginseng and American ginseng. The items chosen for the method validation included quantitative related items such as recovery of Rg(1) and Rb(1), respectively, and qualitative related items such as resolution, theoretical plate number, relative retention time of two critical-band-pairs, Rg(1)/Re and Rb(1) with its neighboring peak, respectively. Totally, 16 column types were used for comparison of different vendors, different packing materials, different size, etc. and five sets of LC systems and two laboratories were involved in comparing the data of both quantitative and qualitative items. The results showed that different packing materials of columns used might significantly alters separation. The column packing material Hypersil afforded the preferable separating for the ginsenosides. No significant difference was observed from the different instrumentations and inter-laboratories. Our results suggest a modification of the system suitability test as given in USP26-NF21 and the latest version of USP27-NF22, which was not suitable for most systems. Using resolutions of Rg(1)/Re and Rb(1) with its neighboring peak as critical parameters for the ginsenosides assay and omitting the relative retention time of both Rg(1)/Re and Rb(1) with its neighboring peak is our suggestion for a more reasonable, yet practicable system suitability. Six typical chromatograms gain from different columns were figured out as well.

Asia↗
PubMed2004

Usefulness of a hand-carried cardiac ultrasound device for bedside examination of pericardial effusion in patients after cardiac surgery.

To identify the incidence of pericardial effusion in patients after cardiac surgery using a hand-carried cardiac ultrasound device, 200 patients were assessed on postoperative day 3. If a pericardial effusion was found, patients were monitored for 3 consecutive days with a hand-carried cardiac ultrasound device. Within 72 hours after surgery, 43 patients (21.5%) had developed an effusion, of whom 2 patients had cardiac tamponade and 41 patients (21%) had a small pericardial effusion. No difference was found in the incidence of effusion based on the type of cardiac surgery. Of patients with a small pericardial effusion on day 3 after surgery, an additional 2 of 41 (5%) developed cardiac tamponade.

Cardiac Surgical Procedures↗
PubMed2004

Homology building as a means to define antigenic epitopes on dihydrofolate reductase (DHFR) from Plasmodium falciparum.

BACKGROUND: The aim of this study was to develop site-specific antibodies as a tool to capture Plasmodium falciparum-dihydrofolate reductase (Pf-DHFR) from blood samples from P. falciparum infected individuals in order to detect, in a sandwich ELISA, structural alterations due to point mutations in the gene coding for Pf-DHFR. Furthermore, we wanted to study the potential use of homology models in general and of Pf-DHFR in particular in predicting antigenic malarial surface epitopes. METHODS: A homology model of Pf-DHFR domain was employed to define an epitope for the development of site-specific antibodies against Pf-DHFR. The homology model suggested an exposed loop encompassing amino acid residues 64-100. A synthetic peptide of 37-mers whose sequence corresponded to the sequence of amino acid residues 64-100 of Pf-DHFR was synthesized and used to immunize mice for antibodies. Additionally, polyclonal antibodies recognizing a recombinant DHFR enzyme were produced in rabbits. RESULTS AND CONCLUSIONS: Serum from mice immunized with the 37-mer showed strong reactivity against both the immunizing peptide, recombinant DHFR and a preparation of crude antigen from P. falciparum infected red blood cells. Five monoclonal antibodies were obtained, one of which showed reactivity towards crude antigen prepared from P. falciparum infected red cells. Western blot analysis revealed that both the polyclonal and monoclonal antibodies recognized Pf-DHFR. Our study provides insight into the potential use of homology models in general and of Pf-DHFR in particular in predicting antigenic malarial surface epitopes.

Amino Acids↗
PubMed2004

Activation of extracellular signal-regulated kinase mediates apoptosis induced by uropathogenic Escherichia coli toxins via nitric oxide synthase: protective role of heme oxygenase-1.

Pyelonephritis is a risk factor for renal tubular epithelial cell damage in children. The inter- and intracellular regulator nitric oxide (NO) plays a role in the modulation of cellular viability in urinary tract infections, but the role of the NO pathway in renal proximal tubular-cell death remains unclear. The present study demonstrates that, in renal epithelial cells undergoing death mediated by Escherichia coli strain ARD6 serotype O6K13H1 (O6), levels of the phosphorylated extracellular signal-regulated kinase (ERK) 1/2 and inducible NO synthase (iNOS) proteins are up-regulated, but levels of endothelial NO synthase are down-regulated. When NO synthase (NOS) activity is inhibited by the specific inhibitor of NOS or mitogen-activated protein kinase kinase, cells are prevented from death. Moreover, down-regulating protein 53 (p53) does not prevent the cells from dying, although p53 is up-regulated in O6-exposed cells. Up-regulation of heme oxygenase (HO)-1 by sodium nitroprusside or by the specific activator hemin inhibits cell death. In conclusion, the activation of ERK mediates O6 toxin-mediated renal cell death via induction of iNOS. Stimulation of HO-1 protects cells against death.

Animals↗
PubMed2004

Stimulation of beta-amyloid precursor protein alpha-processing by phorbol ester involves calcium and calpain activation.

Normal processing of Alzheimer's beta-amyloid precursor protein (APP) is markedly stimulated by phorbol esters, but the underlying mechanisms have yet to be fully understood. In this study, we observed that: (a) Phorbol 12,13-dibutyrate (PDBu)-stimulated APP secretion in cultured SH-SY5Y neuroblastoma and fibroblast cells was blocked by EGTA and calpain inhibitors in a concentration-dependent manner, but not by other protease inhibitors. (b) Secretion of fibronectin, another secretory protein tested for comparison, was enhanced by PDBu, but insensitive to calpain inhibitors. (c) PDBu stimulated intracellular calpain activity as measured by the hydrolysis of a fluorogenic calpain substrate. (d) PDBu also induced rapid proteolysis of two endogenous substrates of calpains, i.e., tau and microtubule-associated protein-2 (MAP-2) and the proteolysis was blocked by EGTA and calpain inhibitors. Taken together, these results suggest that stimulation of APP alpha-processing by PDBu is through a mechanism that involves the activation of Ca(2+) and, most notably, calpain. The implications of the findings are discussed in relation to the regulatory mechanism of APP alpha-processing.

Amyloid beta-Protein Precursor↗
PubMed2004

Characterization of synaptogyrin 3 as a new synaptic vesicle protein.

Synaptogyrins comprise a family of tyrosine-phosphorylated proteins with two neuronal (synaptogyrins 1 and 3) and one ubiquitous (cellugyrin) isoform. Previous studies have indicated that synaptogyrins are involved in the regulation of neurotransmitter release. Synaptogyrin 1 is a synaptic vesicle protein; cellugyrin, by contrast, is absent from synaptic vesicles. In an effort to further characterize the synaptogyrin family, we studied the distribution of the synaptogyrin 3 protein in the nervous system. Subcellular fractionation and immunoprecipitation of synaptic vesicles from mouse brain showed that synaptogyrin 3 is associated with synaptic vesicles and that synaptogyrins 1 and 3 can reside on the same synaptic vesicle. Immunofluorescent staining of cultured hippocampal neurons confirmed the synaptic localization of synaptogyrin 3. Analysis of the relative distributions of synaptogyrins 1 and 3 in mouse brain revealed a more restricted expression pattern for synaptogyrin 3 compared to the ubiquitous distribution of synaptogyrin 1. Strong synaptogyrin 3 labeling was observed in the mossy fiber region of the hippocampus, substantia nigra pars reticulata, pallidum, and deep cerebellar nuclei. By comparison, the striatum and reticular and ventral posterolateral thalamic nuclei, which all showed synaptogyrin 1 labeling, contained significantly less synaptogyrin 3. Finally, we used in situ hybridization experiments to correlate synaptogyrin 3 mRNA in cell bodies with synaptogyrin 3 protein at synapses. Altogether, our data indicate that neuronal synaptogyrins are differentially expressed protein isoforms that may represent functionally distinct populations of synapses and/or synaptic vesicles.

Animals↗
PubMed2004

A novel piezoelectric quartz micro-array immunosensor based on self-assembled monolayer for determination of human chorionic gonadotropin.

A novel multi-channel 2 x 5 model of piezoelectric quartz micro-array immunosensor has been developed for quantitative detection of human chorionic gonadotropin (hCG) in serum or urine samples. Every crystal unit of the fabricated piezoelectric hCG micro-array immunosensor can oscillate independently without interfering each other. A 2 x 5 model of micro-array immunosensor as compared with a one-channel immunosensor can provide eight times higher detection speeds for hCG assay. The anti-hCG antibody is deposited on the gold electrode's surface of 10 MHz quartz AT-cut crystal by self-assembled technique using sulfosuccinimidyl 6-[3'-(2-pyridyldithio) propionamido] hexanoate (Sulfo-LC-SPDP), and serves as an antibody recognizing layer. The highly ordered self-assembled monolayers (SAM) ensure well-controlled surface structure and offer many advantages to the performance of the sensor. Compared with conventional antibody immobilization methods, the amount and the reaction activity of antibody monolayer coated by the SAM binding are bigger than those by the SPA method, and less non-specific binding caused by other analytes in sample is found. Under the optimized experimental conditions, the results showed that micro-array immunosensor quantitatively detected serum or urine hCG in the range of 2.5-500 mIU/ml with high precision (CV<5%); other hormones in human serum and urine did not interfere with the determination markedly. Serum and urine samples of 60 patients were detected by the micro-array immunosensor, and the results agreed well with those given by the commercial radioimmunoassay test kit, with correlation coefficient of 0.92. After regeneration with urea solution the coated immunosensor can be reused five times without appreciable loss of activity.

Biosensing Techniques↗