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Biomedical subjects

Q Chen

Publications and source records attributed to Q Chen.

At least 55 records · Page 3Linked to original sources
PubMed2005

B-type natriuretic peptide in patients with clinical hyperthyroidism.

AIMS: To investigate the level and clinical significance of plasma B-type natriuretic peptide (BNP) in patients with hyperthyroidism. METHODS: Plasma BNP was measured in 32 healthy subjects and 67 patients with clinical hyperthyroidism. Left ventricular anatomy and function was assessed with echocardiography. RESULTS: The average BNP in hyperthyroid patients was higher than that in healthy subjects (186+/-140 vs 34+/-17 ng/l, p =0.001). The increase in BNP was mainly found in hyperthyroid patients who had clinical and echocardiographic evidence of left ventricular dysfunction (250+/-190 ng/l). The BNP level in patients with hyperthyroidism, but with normal left ventricular function, was similar to that of the controls (37+/-17 vs 34+/-17, ng/l, p>0.05). Multi-regression analysis showed that left atrial diameter and left ventricular ejection fraction were independently associated with the plasma levels of BNP. CONCLUSIONS: there is a significant elevation in plasma BNP in patients with hyperthyroidism; the increase is largely due to hyperthyroidism-induced left ventricular dysfunction. Measurements of plasma BNP may help to detect heart failure in patients with clinical hyperthyroidism.

Adult↗
PubMed2005

Systolic and diastolic heart failure are associated with different plasma levels of B-type natriuretic peptide.

Previous studies have found that plasma B-type natriuretic peptide (BNP) is elevated during left ventricular systolic or diastolic dysfunction. It is unclear whether the ventricular systolic and diastolic function is associated with different levels of plasma BNP. Plasma BNP was measured in 149 heart failure patients by a rapid point-of-care assay. The patients were divided into left ventricular diastolic dysfunction (n = 48), left ventricular systolic dysfunction (n = 62) and right ventricular systolic dysfunction group (n = 39). The mean BNP level in the left ventricular diastolic dysfunction, left ventricular systolic dysfunction and right ventricular systolic dysfunction was 115 +/- 80 pg/ml, 516 +/- 445 pg/ml and 345 +/- 184 pg/ml, respectively (p < 0.05). We concluded that ventricular systolic and diastolic dysfunction increases plasma BNP levels to a different extent. Left and right ventricular systolic dysfunction is associated with a higher level of plasma BNP than left ventricular diastolic dysfunction.

Adult↗
PubMed2005

Detection of alien chromatin introgression from Thinopyrum into wheat using S genomic DNA as a probe--a landmark approach for Thinopyrum genome research.

The introduction of alien genetic variation from the genus Thinopyrum through chromosome engineering into wheat is a valuable and proven technique for wheat improvement. A number of economically important traits have been transferred into wheat as single genes, chromosome arms or entire chromosomes. Successful transfers can be greatly assisted by the precise identification of alien chromatin in the recipient progenies. Chromosome identification and characterization are useful for genetic manipulation and transfer in wheat breeding following chromosome engineering. Genomic in situ hybridization (GISH) using an S genomic DNA probe from the diploid species Pseudoroegneria has proven to be a powerful diagnostic cytogenetic tool for monitoring the transfer of many promising agronomic traits from Thinopyrum. This specific S genomic probe not only allows the direct determination of the chromosome composition in wheat-Thinopyrum hybrids, but also can separate the Th. intermedium chromosomes into the J, J(S) and S genomes. The J(S) genome, which consists of a modified J genome chromosome distinguished by S genomic sequences of Pseudoroegneria near the centromere and telomere, carries many disease and mite resistance genes. Utilization of this S genomic probe leads to a better understanding of genomic affinities between Thinopyrum and wheat, and provides a molecular cytogenetic marker for monitoring the transfer of alien Thinopyrum agronomic traits into wheat recipient lines.

Chromatin↗
PubMed2004

Interaction of Jar choriocarcinoma cells with endothelial cell monolayers.

During human pregnancy the uterine spiral arteries are invaded by placental trophoblasts which replace the endothelial cells that line the non-pregnant spiral arteries and transform these vessels into large-bore conduits enabling adequate perfusion of the placenta with maternal blood. Failure of this process may predispose to preeclampsia and fetal growth restriction [Brosens I, Robertson WB, Dixon HG. The physiological response of the vessels of the placental bed to normal pregnancy. Journal of Pathology and Bacteriology 1967;93:569-79; Khong TY, De Wolf F, Robertson WB, Brosens I. Inadequate maternal vascular response to placentation in pregnancies complicated by pre-eclampsia and by small-for-gestational age infants. British Journal of Obstetrics and Gynaecology 1986;93:1049-59]. There is a paucity of data on the role of maternal endothelial cells in this process. In this study we investigated the cellular interactions between trophoblast-derived Jar cells and endothelial cells (HUVECs and HMEC-1). The effect of coculturing Jar cells with endothelial cell monolayers was determined by confocal microscopy, DNA fragmentation assay and flow cytometry. We demonstrated that Jar cells migrate into focal areas in endothelial cell monolayers, where they induce endothelial cell death and, then phagocytose the dead endothelial cells. Our results suggest that endothelial cells may not simply be passive targets for invading trophoblasts during the remodeling of the spiral arteries.

Adult↗
PubMed2004

Millimeter wave exposure reverses TPA suppression of gap junction intercellular communication in HaCaT human keratinocytes.

The effect of 30.16 GHz millimeter wave (MMW) exposure at 1.0 and 3.5 mW/cm2 on gap junction intercellular communication (GJIC) was studied in cultured HaCaT keratinocytes, using the fluorescence recovery after photobleaching (FRAP) technique and laser confocal scanning microscopy to follow the intracellular movement of 5,6-carboxyfluorescein diacetate dye. While MMW exposure alone for 1 h at either 1.0 or 3.5 mW/cm2 did not affect GJIC, MMW exposure in combination with 5 ng/ml TPA treatment reversed TPA induced suppression of GJIC. Exposure at 1.0 mW/cm2 resulted in a partial reversal, and exposure at 3.5 mW/cm2 resulted in essentially full reversal of the TPA suppression.

Cell Communication↗
PubMed2004

Performing probe experiments in the SEM.

A four nanoprobe system has been installed inside a FEI XL30 F scanning electron microscope (SEM), and shown to be fully compatible with the normal functions of the SEM and also a Gatan cold stage (model C1003, -185-400 degrees C). With some selected examples of applications, we have shown that this nanoprobe system may be used effectively for gripping, moving and manipulating nanoobjects, e.g. carbon nanotubes, setting up electric contacts for electronic measurements, tailoring the structure of the nanoobject by cutting, etc. and even for making unexpected nanostructures, e.g. a nanohook. Applications in other areas have also been speculated, limitations or disadvantages of the current design of the probe system were discussed, and methods for possible improvement were suggested.

Journal Article↗
PubMed2004

A simple scheme for probehead background suppression in one-pulse 1H NMR.

A very simple method for reducing probehead background signal in one-pulse 1H nuclear magnetic resonance (NMR) spectra is presented. Two one-pulse spectra are recorded, the first with pulse length tp1, the second with an L-times longer pulse, e.g. with L = 2. The second spectrum scaled by 1/L is subtracted from the first. Since the weak pulses experienced by spins outside the coil are in the linear regime, the background from outside the coil is effectively subtracted out. The background suppression efficiency is approximately 1.5b2, where b is the ratio of the B1 field inside the coil relative to that outside the coil. Experimentally, background suppression by at least a factor of 10 was achieved. Examples of background suppression in 1H wideline as well as 1H fast magic-angle spinning (MAS) one-pulse spectra of clay and polymer samples are shown.

Algorithms↗
PubMed2004

Antiphospholipid antibodies bind to activated but not resting endothelial cells: is an independent triggering event required to induce antiphospholipid antibody-mediated disease?

INTRODUCTION: Antiphospholipid antibodies (aPL) cause thrombotic disease and recurrent pregnancy loss. Despite their name it is now clear that the antigen for most antiphospholipid antibodies is the phospholipid-binding protein beta(2) glycoprotein I (beta(2)GPI). However, beta(2) glycoprotein I is only antigenic for antiphospholipid antibodies when the protein is immobilised on a suitable surface such as phosphatidyl serine. It has been suggested that antiphospholipid antibodies bind to beta(2) glycoprotein I on the surface of resting endothelial cells and this in turn leads to endothelial activation and the initiation of thrombosis. However, as phosphatidyl serine is absent from resting endothelial cell membranes, we questioned this hypothesis. MATERIALS AND METHODS: The ability of human antiphospholipid antibody-containing sera and monoclonal antiphospholipid antibodies to interact with endothelial cells was examined using cell-based ELISAs employing human umbilical vein endothelial cells (HUVECs) as the antigen. The expression of adhesion molecules in response to treatment with antiphospholipid antibodies was also measured by a cell-based ELISA. Activation of NF kappa beta was examined using electrophoretic mobility shift assays (EMSAs). RESULTS: Neither monoclonal antiphospholipid antibodies nor human sera containing antiphospholipid antibodies bound to resting endothelial cells. In contrast, one monoclonal antiphospholipid antibody did bind to both activated and apoptotic endothelial cells. CONCLUSIONS: Antiphospholipid antibodies do not bind to resting endothelial cells nor do antiphospholipid antibodies activate resting endothelial cells. Rather, an independent triggering event is required to activate endothelial cells and subsequently some antiphospholipid antibodies may then bind to the activated endothelial cells and initiate a thrombogenic process.

Antibodies, Antiphospholipid↗
PubMed2004

Semiautomated thermal lesion segmentation for three-dimensional elastographic imaging.

Several studies have demonstrated that lesion volumes computed from multiple planar slices through the region-of-interest (ROI) are more accurate than volumes estimated assuming simple shapes and incorporating single or orthogonal diameter estimates. However, manual delineation of boundaries on multiple planar 2-D images is tedious and labor-intensive. Automatic extraction of lesion boundaries is, therefore, attractive and imperative to remove subjectivity and reduce assessment time. This paper presents a semiautomated segmentation algorithm for thermal lesions on 3-D elastographic data to obtain both area and volume information. The semiautomated segmentation algorithm is based on thresholding and morphologic opening of both 2-D and 3-D elastographic data. Results obtained on 44 thermal lesions imaged in vitro using elastography were compared to manual delineation of both elastographic and pathology images. Results obtained using semiautomated segmentation demonstrate a close correspondence with manual delineation results. However, area and volume estimates obtained using both manual and semiautomated segmentation of lesions seen on elastograms slightly underestimate areas and volumes measured from pathology.

Algorithms↗
PubMed2004

Testosterone increases osteoprotegerin mRNA expression in mouse osteoblast cells.

The role that androgens play in the regulation of bone metabolism has been substantiated in animals and humans. We previously demonstrated that testosterone inhibits osteoclast differentiation stimulated by parathyroid hormone through the androgen receptor in mouse bone-cell cultures. However, the details of this mechanism are still unknown. The present study was aimed at examining whether testosterone would affect the mRNA levels of osteoprotegerin (OPG) and receptor activator of Nf kappa B ligand (RANKL) in mouse bone-cell cultures as well as mouse osteoblastic cell-line, MC3T3-E1 cells by employing semi-quantitative RT-PCR. Testosterone increased OPG mRNA expression in both mouse bone-cell cultures and MC3T3-E1 cells. 10-8 M PTH-(1-34) as well as 10-8M 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] inhibited OPG mRNA expression in mouse bone cells. 10-8 M testosterone antagonized OPG mRNA expression inhibited by 10-8 M PTH-(1-34), but failed to affect OPG mRNA expression inhibited by 10-8 M 1,25(OH)2D3. 10-8 M alpha-dehydrotestosterone, a non-aromatizable androgen, increased OPG mRNA expression. On the other hand, testosterone did not affect RANKL mRNA expression in MC3T3-E1 or mouse bone cells. In conclusion, the present study demonstrated that testosterone increased OPG mRNA expression in mouse bone-cell cultures and the osteoblastic cell line. These effects are likely to take place through the androgen receptor.

Animals↗
PubMed2004

Estimation of displacement vectors and strain tensors in elastography using angular insonifications.

In current practice, only one out of three components of the tissue displacement vector and one of nine components of the strain tensor are accurately estimated and imaged in ultrasound elastography. Since, only the axial component of both the displacement and strain are imaged, other important elastic parameters, such as shear strains and the Poisson's ratio, also are not imaged. Moreover, reconstruction of the Young's modulus would be significantly improved if all components of the strain tensor were available. In this paper, we describe a new method for estimating all the components of the tissue displacement vector following a quasi-static compression. The method uses displacements estimated from radiofrequency echo-signals along multiple ultrasound beam insonification directions. At each spatial location in the compressed medium, orthogonal tissue displacements in both the axial and lateral direction with respect to the direction of the applied compression are estimated by curve fitting angular displacement vector data calculated for all insonification directions. Following displacement estimation in orthogonal directions, components of the corresponding normal and shear strain tensors are estimated. Simulation and experimental results demonstrate the utility of this technique for the computation of the normal and shear strain tensors.

Algorithms↗
PubMed2004

Temperature dependence of ultrasonic propagation speed and attenuation in excised canine liver tissue measured using transmitted and reflected pulses.

Previous reported data from our laboratory demonstrated the temperature dependence of propagation speed and attenuation of canine tissue in vitro at discrete temperatures ranging from 25 to 95 degrees C. However, concerns were raised regarding heating the same tissue specimen over the entire temperature range, a process that may introduce irreversible and, presumably, cumulative tissue degradation. In this paper propagation speed and attenuation vs temperature are measured using multiple groups of samples, each group heated to a different temperature. Sample thicknesses are measured directly using a technique that uses both transmitted and reflected ultrasound pulses. Results obtained using 3 and 5 MHz center frequencies demonstrate a propagation speed elevation of around 20 m/s in the 22-60 degrees C range, and a decrease of 15 m/s in the 60-90 degrees C range, in agreement with previous results where the same specimens were subjected to the entire temperature range. However, sound speed results reported here are slightly higher than those reported previously, probably due to more accurate measurements of sample thickness in the present experiments. Results also demonstrate that while the propagation speed varies with temperature, it is not a function of tissue coagulation. In contrast, the attenuation coefficient depends on both tissue coagulation effects and temperature elevation.

Animals↗
PubMed2004

Synovectomy reduces stromal-cell-derived factor-1 (SDF-1) which is involved in the destruction of cartilage in osteoarthritis and rheumatoid arthritis.

We have compared the concentrations of stromal-cell-derived factor-1 (SDF-1), matrix metalloproteinase-1 (MMP-1), MMP-9 and MMP-13 in serum before and after synovectomy or total knee replacement (TKR). We confirmed the presence of SDF-1 and its receptor CXCR4 in the synovium and articular cartilage by immunohistochemistry. We established chondrocytes by using mutant CXCR4 to block the release of MMPs. The level of SDF-1 was decreased 5.1- and 6.7-fold in the serum of patients with OA and RA respectively, after synovectomy compared with that before surgery. MMP-9 and MMP-13 were decreased in patients with OA and RA after synovectomy. We detected SDF-1 in the synovium and the bone marrow but not in cartilage. CXCR4 was detected in articular cartilage. SDF-1 increased the release of MMP-9 and MMP-13 from chondrocytes in a dose-dependent manner. The mutant CXCR4 blocked the release of MMP-9 and MMP-13 from chondrocytes by retrovirus vector. Synovectomy is effective in patients with OA or RA because SDF-1, which can regulate the release of MMP-9 and MMP-13 from articular chondrocytes for breakdown of cartilage, is removed by the operation.

Aged↗
PubMed2004

Comparison of hyperkalemic cardioplegia with altered [CaCl2] and [MgCl2] on [Ca2+]i transients and function after warm global ischemia in isolated hearts.

AIM: [MgCl(2)] and [CaCl(2)] may modify the cardioprotective effects of hyperkalemic cardioplegia (CP). We changed [MgCl(2)] and [CaCl(2)] in a CP solution to examine their effects on [Ca(2+)]i transients and cardiac function before and after global normothermic ischemia. METHODS: After stabilization and loading of indo 1-AM in Kreb's solution (KR), each heart was perfused with either KR or 1 of 4 CP solutions before 37 degrees C, 30 min ischemia followed by reperfusion with KR. The KR solution contained, in mM, 4.5 KCl, 2.4 MgCl(2) and 2.5 CaCl(2); the CP solutions had in addition to 18 KCl: CP 1 (control CP): 2.4 MgCl(2), 2.5 CaCl(2); CP 2: 7.2 MgCl(2), 2.5 CaCl(2); CP 3, 7.2 MgCl(2), 1.25 CaCl(2); CP 4: 2.4 MgCl(2), 1.25 CaCl(2). RESULTS: In the KR group [Ca(2+)]i markedly increased on early reperfusion while functional return (LVP, dLVP/dt((max and min))) was much reduced; each CP group led to reduced [Ca(2+)]i loading and improved function. The rates of cytosolic Ca(2+) fluxes (d[Ca(2+)]/dt(max) and d[Ca(2+)]/dt(min)) increased significantly compared to baseline in the KR group, but were mostly suppressed in the CP groups, and d[Ca(2+)]/dt(min) was lower after CP 4 compared to CP 1 on reperfusion. At 60 min reperfusion, LVP area to [Ca(2+)] area and cardiac efficiency to phasic [Ca(2+)] relationships were shifted after KR, but not after CP 1-4. With similar functional recovery, [Ca(2+)] transient and [Ca(2+)] area were significantly lower after CP 4 than after CP 1. CONCLUSION: Increasing [MgCl(2)] (CP 2 and 3) did not improve cardiac function or reduce Ca(2+) transients on reperfusion better than the other CP groups, but reducing [CaCl(2)] (CP 3 and 4) was more effective in reducing [Ca(2+)] transients on reperfusion after global ischemia.

Animals↗
PubMed2004

Level set based auto segmentation of the tagged left ventricle MR images.

To facilitate automatic segmentation, we adopt SVM (Support Vector Machine) to localize the left ventricle, and the segmentation is then carried out with narrow band level set. The method of generating the narrow band is improved such that the time used is reduced. Based on the imaging characteristics of the tagged left ventricle MR images, BPV (block-pixel variation) and intensity comparability are introduced to improve the speed term of level set and to increase the precision of segmentation. Our method can perform the segmentation of the tagged left ventricle MR images accurately and automatically.

Heart Ventricles↗
PubMed2003

Formation mechanism of H2Ti3O7 nanotubes.

Formation mechanism of H2Ti3O7 nanotubes by single-step reaction of crystalline TiO2 and NaOH has been investigated via transmission electron microscopy examinations of series specimens with different reaction times and extensive ab initio calculations. It was found that the growth mechanism includes several steps. Crystalline TiO2 reacts with NaOH, forming a highly disordered phase, which recrystallized into some H2Ti3O7 thin plates. H-deficiency on the top surface leads to an asymmetrical environment for the surface Ti3O2-7 layer. The calculations of the surface tension, elastic strain energy, interlayer coupling energy, and Coulomb force indicated that the asymmetrical environment is the principal driving force of the cleavage of the single sheets of H2Ti3O7 from the plates and the formation of the multiwall spiral nanotubes.

Journal Article↗