PubMed Health⌕ Search

Biomedical subjects

Yan Wu

Publications and source records attributed to Yan Wu.

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

[Effects of wall shear stress on the morphology and permeability of endothelial cells in stenotic rabbit abdominal aorta].

Stenosis with 55.2% cross section area reduction was introduced into the rabbit aorta. Using Evans blue dye and scanning microscope, we observed the morphology of endothelial cells and the permeability of endothelium to albumin in the stenotic aorta. Numerical simulation of blood flow in the stenotic aorta was performed to obtain the distribution of wall shear rate. The results showed that in the immediately proximal and distal vicinity of stenosis, blood flow was disturbed significantly, resulting in apparent changes in the morphology of endothelial cells and the permeability of endothelium to albumin. These changes were not only attributed to the value of wall shear stress, but also attributed to the flow pattern in the stenosis. The result therefore is in good consistent with the clinical observation that atherosclerosis often occurs in the areas where blood flow is disturbed and flow separation occurs.

Animals↗
PubMed2005

[A pilot survey of the main causes of chronic heart failure in patients treated in primary hospitals in China].

OBJECTIVE: The aim of this investigation is to make clear the main causes of chronic heart failure (CHF) in patients who receive management in primary hospitals in China and to provide scientific evidence for the prevention of CHF in primary hospitals in China. METHODS: The first three main causes of CHF were determined in the way of answering questionnaires by local doctors from 2066 local hospitals (from one hospital at least one doctor) in 17 areas, we got 2100 pieces of valid answer. Input these forms to computer 2 times, check repeatedly till being sure that there were no mistakes in them and then make statistics with SPSS soft kit. RESULTS: In primary hospitals in our country, the first three main causes of CHF are coronary heart disease, hypertension and rheumatic heart disease. In some places chronic pulmonary heart disease is also a main cause of CHF in primary hospitals. CONCLUSIONS: The primary and secondary prevention of coronary heart disease and hypertension is certainly important in the prevention of CHF, but it is equally important to prevent rheumatic heart disease and chronic pulmonary heart disease.

China↗
PubMed2005

[An experimental study on human bitemarks digital analysis and its accuracy].

This experiment was designed to study the method of human bitemarks digital analysis and its accuracy. The human bitemarks were made on the dog skin by human dentition. The related parameters of human bitemarks and suspects criminal dentitions were digitally recorded and managed. The digital picture of human bitemark was obtained, and the dental study model, bite in wax and bitemark on pig skin of suspected criminal were scanned. The overlay was prepared with Adobe Photoshop 5. 5 and the parameters were measured with AutoCAD R14, then their matches were compared. The result shows that the human bitemarks digital analysis is a more accurate approach to human bitemarks identification. Three methods for collecting evidence dental study model, bite in wax and bitemark on pig skin all can be used as aids in forensic sciences. Dental study model is the most accurate one of all the three methods mentioned above.

Animals↗
PubMed2004

Enhanced Dupuytren's disease fibroblast populated collagen lattice contraction is independent of endogenous active TGF-beta2.

BACKGROUND: Dupuytren's disease (DD) is a debilitating fibro-proliferative disorder of the hand characterized by the appearance of fibrotic lesions (nodules and cords) leading to flexion contractures of the fingers and loss of hand function. Although the molecular mechanism of DD is unknown, it has been suggested that transforming growth factor-beta2 (TGF-beta2) may play an important role in the underlying patho-physiology of the disease. The purpose of this study was to further explore this hypothesis by examining the effects of TGF-beta2 on primary cell cultures derived from patient-matched disease and normal palmar fascia tissue using a three-dimensional collagen contraction assay. METHODS: Fibroblast-populated collagen lattice (FPCL) contraction assays using primary cell cultures derived from diseased and control fascia of the same DD patients were studied in response to exogenous TGF-beta2 and neutralizing anti-TGF-beta2 antibodies. RESULTS: Contraction of the FPCLs occurred significantly faster and to a greater extent in disease cells compared to control cells. The addition of TGF-beta2 enhanced the rate and degree of collagen contraction in a dose-dependent fashion for both control and diseased cells. Neutralizing anti-TGF-beta2 antibodies abolished exogenous TGF-beta2 stimulated collagen contraction, but did not inhibit the enhanced basal collagen contraction activity of disease FPCL cultures. CONCLUSIONS: Although exogenous TGF-beta2 stimulated both disease and control FPCL contraction, neutralizing anti-TGF-beta2 antibodies did not affect the elevated basal collagen contraction activity of disease FPCLs, suggesting that the differences in the collagen contraction activity of control and disease FPCL cultures are not due to differences in the levels of endogenous TGF-beta2 activity.

Antibodies, Anti-Idiotypic↗
PubMed2004

Crystal structure of an ATPase-active form of Rad51 homolog from Methanococcus voltae. Insights into potassium dependence.

Homologous gene recombination is crucial for the repair of DNA. A superfamily of recombinases facilitate a central strand exchange reaction in the repair process. This reaction is initiated by coating single-stranded DNA (ssDNA) with recombinases in the presence of ATP and Mg(2+) co-factors to form helical nucleoprotein filaments with elevated ATPase and strand invasion activities. At the amino acid sequence level, archaeal RadA and Rad51 and eukaryal Rad51 and meiosis-specific DMC1 form a closely related group of recombinases distinct from bacterial RecA. Unlike the extensively studied Escherichia coli RecA (EcRecA), increasing evidences on yeast and human recombinases imply that their optimal activities are dependent on the presence of a monovalent cation, particularly potassium. Here we present the finding that archaeal RadA from Methanococcus voltae (MvRadA) is a stringent potassium-dependent ATPase, and the crystal structure of this protein in complex with the non-hydrolyzable ATP analog adenosine 5'-(beta,gamma-iminotriphosphate), Mg(2+), and K(+) at 2.4 A resolution. Potassium triggered an in situ conformational change in the ssDNA-binding L2 region concerted with incorporation of two potassium ions at the ATPase site in the RadA crystals preformed in K(+)-free medium. Both potassium ions were observed in contact with the gamma-phosphate of the ATP analog, implying a direct role by the monovalent cations in stimulating the ATPase activity. Cross-talk between the ATPase site and the ssDNA-binding L2 region visualized in the MvRadA structure provides an explanation to the co-factor-induced allosteric effect on RecA-like recombinases.

Adenosine Triphosphatases↗
PubMed2004

Genomic alterations in the endometrium may be a proximate cause for endometriosis.

OBJECTIVE: To test the hypothesis that endometriosis may originate from genomic alterations in the endometrium by genomic analysis of endometrial tissues in patients with endometriosis and compare them with those from normal controls. METHODS: Endometrial tissue samples were taken from five women with endometriosis. For controls, we used endometrial tissue samples from four women who underwent elective abortions and one sample from placenta. Using array-based comparative genomic hybridization (CGH), we determined the normal range of variation in CGH signals using normal controls. CGH results were further confirmed by real-time quantitative PCR and loss of heterozygosity analysis. RESULTS: We identified several regions of genomic alterations in all five patients. Some of these regions were the same regions identified previously in endometriotic lesions. For select markers, the genomic alterations were confirmed by real-time PCR and LOH analyses. CONCLUSIONS: There is evidence that the endometrium in women with endometriosis has genomic alterations. This is consistent with numerous reports that the endometrium of women with endometriosis differ from those of women without. Our finding suggests that genomic alterations in the endometrium may be a proximate cause for endometriosis.

Adult↗
PubMed2004

Crystal structure of archaeal recombinase RADA: a snapshot of its extended conformation.

Homologous recombination of DNA plays crucial roles in repairing severe DNA damage and in generating genetic diversity. The process is facilitated by a superfamily of recombinases: bacterial RecA, archaeal RadA and Rad51, and eukaryal Rad51 and DMC1. These recombinases share a common ATP-dependent filamentous quaternary structure for binding DNA and facilitating strand exchange. We have determined the crystal structure of Methanococcus voltae RadA in complex with the ATP analog AMP-PNP at 2.0 A resolution. The RadA filament is a 106.7 A pitch helix with six subunits per turn. The DNA binding loops L1 and L2 are located in close proximity to the filament axis. The ATP analog is buried between two RadA subunits, a feature similar to that of the active filament of Escherichia coli RecA revealed by electron microscopy. The disposition of the N-terminal domain suggests a role of the Helix-hairpin-Helix motif in binding double-stranded DNA.

Adenosine Triphosphatases↗
PubMed2004

Targeting autocrine and paracrine VEGF receptor pathways inhibits human lymphoma xenografts in vivo.

The role of angiogenesis in lymphoproliferative diseases is not well established. We demonstrate here that human lymphoma cells secrete vascular endothelial growth factor (VEGF) and express VEGF receptor 1 (VEGFR-1) and VEGFR-2. Proliferation of non-Hodgkin lymphoma (NHL) cells under serum-free conditions was enhanced by the addition of VEGF and was blocked by VEGFR-1- and VEGFR-2-specific antibodies. To differentiate between VEGF-mediated autocrine and paracrine effects on lymphoma growth, NOD/SCID mice engrafted with human diffuse large B-cell lymphoma (DLBCL) were treated with species-specific antibodies against human VEGFR-1 (6.12), human VEGFR-2 (IMC-1C11), murine VEGFR-1 (MF-1), or murine VEGFR-2 (DC101). Treatment with 6.12 or DC101 (targeting tumor VEGFR-1 and host VEGFR-2) reduced established DLBCL xenograft growth, whereas treatment with IMC-1C11 or MF-1 (targeting tumor VEGFR-1 and host VEGFR-1) had no effect. Decreased tumor volumes after 6.12 and DC101 treatment correlated with increased tumor apoptosis and reduced vascularization, respectively, supporting the presence of autocrine VEGFR-1- and paracrine VEGFR-2-mediated pathways in lymphomagenesis. Inhibition of paracrine VEGF interactions (DC101) in these models was equivalent to their inhibition with rituximab. Combining DC101 with therapeutic agents (rituximab, 6.12, methotrexate) consistently improved tumor responses over those of single-agent therapy. These data support the further clinical development of VEGFR-targeted approaches for the therapy of aggressive DLBCL.

Animals↗
PubMed2004

Suppression of leukemia expressing wild-type or ITD-mutant FLT3 receptor by a fully human anti-FLT3 neutralizing antibody.

FMS-like tyrosine kinase 3 (FLT3), a class III receptor tyrosine kinase, is expressed at high levels in the blasts of approximately 90% of patients with acute myelogenous leukemia (AML). Internal tandem duplications (ITDs) in the juxtamembrane domain and point mutations in the kinase domain of FLT3 are found in approximately 37% of AML patients and are associated with a poor prognosis. We report here the development and characterization of a fully human anti-FLT3 neutralizing antibody (IMC-EB10) isolated from a human Fab phage display library. IMCEB10 (immunoglobulin G1 [IgG1], kappa) binds with high affinity (KD=158 pM) to soluble FLT3 in enzyme-linked immunosorbent assay (ELISA) and to FLT3 receptor expressed on the surfaces of human leukemia cell lines. IMC-EB10 blocks the binding of FLT3 ligand (FL) to soluble FLT3 in ELISA and competes with FL for binding to cell-surface FLT3 receptor. IMC-EB10 treatment inhibits FL-induced phosphorylation of FLT3 in EOL-1 and EM3 leukemia cells and FL-independent constitutive activation of ITD-mutant FLT3 in BaF3-ITD and MV4;11 cells. Activation of the downstream signaling proteins mitogen-activated protein kinase (MAPK) and AKT is also inhibited in these cell lines by antibody treatment. The antibody inhibits FL-stimulated proliferation of EOL-1 cells and ligand-independent proliferation of BaF3-ITD cells. In both EOL-1 xenograft and BaF3-ITD leukemia models, treatment with IMC-EB10 significantly prolongs the survival of leukemia-bearing mice. No overt toxicity is observed with IMC-EB10 treatment. Taken together, these data demonstrate that IMC-EB10 is a specific and potent inhibitor of wild-type and ITD-mutant FLT3 and that it deserves further study for targeted therapy of human AML.

Animals↗
PubMed2004

Induction of cutaneous delayed-type hypersensitivity reactions in VEGF-A transgenic mice results in chronic skin inflammation associated with persistent lymphatic hyperplasia.

Vascular endothelial growth factor-A (VEGF-A) expression is up-regulated in several inflammatory diseases including psoriasis, delayed-type hypersensitivity (DTH) reactions, and rheumatoid arthritis. To directly characterize the biologic function of VEGF-A in inflammation, we evaluated experimental DTH reactions induced in the ear skin of transgenic mice that overexpress VEGF-A specifically in the epidermis. VEGF-A transgenic mice underwent a significantly increased inflammatory response that persisted for more than 1 month, whereas inflammation returned to baseline levels within 7 days in wild-type mice. Inflammatory lesions in VEGF-A transgenic mice closely resembled human psoriasis and were characterized by epidermal hyperplasia, impaired epidermal differentiation, and accumulation of dermal CD4+ T-lymphocytes and epidermal CD8+ lymphocytes. Surprisingly, VEGF-A also promoted lymphatic vessel proliferation and enlargement, which might contribute to the increased inflammatory response, as lymphatic vessel enlargement was also detected in human psoriatic skin lesions. Combined systemic treatment with blocking antibodies against VEGF receptor-1 (VEGFR-1) and VEGFR-2 potently inhibited inflammation and also decreased lymphatic vessel size. Together, these findings reveal a central role of VEGF-A in promoting lymphatic enlargement, vascular hyperpermeability, and leukocyte recruitment, thereby leading to persistent chronic inflammation. They also indicate that inhibition of VEGF-A bioactivity might be a new approach to anti-inflammatory therapy.

Animals↗
PubMed2004

Age-related alterations in cytochrome c-mediated caspase activation in rhesus macaque monkey (Macaca mulatta) brains.

Age-related changes and regional differences in caspase expression were determined in the primate brain. Using immunoblot analysis, the levels of endogenous caspase-3, caspase-9 and cytochrome c-triggered activated caspase-3 were examined in brain homogenates from the prefrontal, motor and visual cortices, cerebellum, hippocampus and amygdala of 4-year-old and 20-year-old rhesus macaques. Procaspase-3 was detected in similar quantities in all brain regions of both young and aging macaques. Being found in all brain regions, caspase-9 was significantly elevated in old macaques as compared to young ones. After incubation with cytochrome c, active forms of caspase-3 were detected in all brain regions of young and old macaques. In almost all brain regions of old monkeys, the levels of cytochrome c-dependent caspase-3 activation were higher than those of young macaques. These results suggest that the aging rhesus macaque brain has a lower threshold to apoptotic stimuli.

Adenosine Triphosphate↗
PubMed2004

Deregulation of Flk-1/vascular endothelial growth factor receptor-2 in fibroblast growth factor receptor-1-deficient vascular stem cell development.

We have employed embryoid bodies derived from murine embryonal stem cells to study effects on vascular development induced by fibroblast growth factor (FGF)-2 and FGF receptor-1, in comparison to the established angiogenic factor vascular endothelial growth factor (VEGF)-A and its receptor VEGF receptor-2. Exogenous FGF-2 promoted formation of morphologically distinct, long slender vessels in the embryoid bodies, whereas VEGF-A-treated bodies displayed a compact plexus of capillaries. FGF-2 stimulation of embryonal stem cells under conditions where VEGF-A/VEGFR-2 function was blocked, led to formation of endothelial cell clusters, which failed to develop into vessels. FGFR-1(-/-) embryoid bodies responded to VEGF-A by establishment of the characteristic vascular plexus, but FGF-2 had no effect on vascular development in the absence of FGFR-1. The FGFR-1(-/-) embryoid bodies displayed considerably increased basal level of vessel formation, detected by immunohistochemical staining for platelet-endothelial cell adhesion molecule (PECAM)/CD31. This basal vascularization was blocked by neutralizing antibodies against VEGFR-2 or VEGF-A and biochemical analyses indicated changes in regulation of VEGFR-2 in the absence of FGFR-1 expression. We conclude that VEGF-A/VEGFR-2-dependent vessel formation occurs in the absence of FGF-2/FGFR-1, which, however, serve to modulate vascular development.

Animals↗
PubMed2004

Fluorinated aminoglycosides and their mechanistic implication for aminoglycoside 3'-phosphotransferases from Gram-negative bacteria.

Aminoglycoside 3'-phosphotransferases [APH(3')s] are important bacterial resistance enzymes for aminoglycoside antibiotics. These enzymes phosphorylate the 3'-hydroxyl of these antibiotics, a reaction that inactivates the drug. A series of experiments were carried out to shed light on the details of the turnover chemistry by these enzymes. Quench-flow pre-steady-state kinetic analyses of the reactions of Gram-negative APH(3') types Ia and IIa with kanamycin A, neamine, and their respective difluorinated analogues 4'-deoxy-4',4'-difluorokanamycin A and 4'-deoxy-4',4'-difluoroneamine were carried out, in conjunction with measurements of thio effect and viscosity studies. The fluorinated analogues were shown to be severely impaired as substrates for these enzymes. The magnitude of the effect of the impairment of the fluorinated substrates was in the same range as when the D198A mutant APH(3')-Ia was studied with nonfluorinated substrates. Residue 198 is the proposed active site base that promotes the aminoglycoside hydroxyl for phosphorylation. These findings collectively argue that the Gram-negative APH(3')s show significant nucleophilic participation in the transition state for the phosphate transfer reaction.

Aminoglycosides↗
PubMed2004

Essential roles of a dynamic loop in the catalysis of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase.

6-Hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) catalyzes the transfer of pyrophosphoryl group from ATP to 6-hydroxymethyl-7,8-dihydropterin (HP) following an ordered bi-bi mechanism with ATP as the first substrate. The rate-limiting step of the reaction is product release, and the complete active center is assembled and sealed only upon the binding of both ATP and HP. The assembly of the active center involves large conformational changes in three catalytic loops, among which loop 3 undergoes the most dramatic and unusual changes. To investigate the roles of loop 3 in catalysis, we have made a deletion mutant, which has been investigated by biochemical and X-ray crystallographic analysis. The biochemical data showed that the deletion mutation does not have significant effects on the dissociation constants or the rate constants for the binding of the first substrate MgATP or its analogues. The dissociation constant of HP for the mutant increases by a factor of approximately 100, which is due to a large increase in the dissociation rate constant. The deletion mutation causes a shift of the rate-limiting step in the reaction and a decrease in the rate constant for the chemical step by a factor of approximately 1.1 x 10(5). The crystal structures revealed that the deletion mutation does not affect protein folding, but the catalytic center of the mutant is not fully assembled even upon the formation of the ternary complex and is not properly sealed. The results together suggest that loop 3 is dispensable for the folding of the protein and the binding of the first substrate MgATP, but is required for the assembling and sealing of the active center. The loop plays an important role in the stabilization of the ternary complex and is critical for catalysis.

Adenosine Triphosphate↗
PubMed2004

Halting the interaction between vascular endothelial growth factor and its receptors attenuates liver carcinogenesis in mice.

It has been shown that angiogenesis plays an important role not only in tumor growth, but also in early carcinogenesis. The expression of a potent angiogenic factor, vascular endothelial growth factor (VEGF), increased during the early stage of carcinogenesis. In this study, the effects of the neutralizing monoclonal antibodies R1 mAb and R2 mAb of the VEGF receptors Flt-1 (VEGFR-1) and KDR/Flk-1 (VEGFR-2), respectively, on murine hepatocarcinogenesis induced by diethylnitrosamine (DEN) were examined. The effects of R1 mAb and R2 mAb on spontaneous lung metastasis from hepatocellular carcinoma (HCC) were also investigated. VEGF expression and neovascularization in the tumor increased stepwise during hepatocarcinogenesis. Treatment with both R1 mAb and R2 mAb markedly inhibited the development of HCC and adenoma in the liver. The inhibitory effect of R2 mAb was more potent than that of R1 mAb, and the combination treatment with both mAbs almost completely attenuated hepatocarcinogenesis. Both R1 mAb and R2 mAb treatment significantly suppressed the development of angiogenesis in HCC. The suppressive effects against angiogenesis R1 mAb and R2 mAb were similar in magnitude to their inhibitory effects against hepatocarcinogenesis. Furthermore, spontaneous lung metastasis from HCC was also significantly suppressed by R1 mAb and R2 mAb treatment. In conclusion, these results suggest that VEGF and receptor interaction plays an important role in hepatocarcinogenesis and in spontaneous lung metastasis from HCC.

Animals↗