Biomedical subjects
Publications and source records attributed to X N Li.
We report values of R = sigma(e(+)e(-)-->hadrons)/sigma(e(+)e(-)-->mu(+)mu(-)) for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider.
OBJECTIVE: To develop a non-invasive method for evaluating gastric emptying and duodenogastric reflux stroke volumes using three-dimensional (3D) guided digital color Doppler imaging. METHODS: The technique involved color Doppler digital images of transpyloric flow in which the 3D position and orientation of the images were known by using a magnetic location system. RESULTS: In vitro, the system was found to slightly underestimate the reference flow (by average 8.8%). In vivo (five volunteers), stroke volume of gastric emptying episodes lasted on average only 0.69 s with a volume on average of 4.3 ml (range 1.1-7.4 ml), and duodenogastric reflux episodes on average 1.4 s with a volume of 8.3 ml (range 1.3-14.1 ml). CONCLUSION: With the appropriate instrument settings, orientation determined color Doppler can be used for stroke volume quantification of gastric emptying and duodenogastric reflux episodes.
OBJECTIVE: The quantification of flow stroke volume is important for evaluation of patients with cardiac dysfunction and cardiovascular disease. Three-dimensional digital color Doppler flow imaging allows the acquisition of flow data in an orientation approximately parallel to flow and analysis of the Doppler flow velocities perpendicular to flow (cross-sectional flow calculation). This in vitro study assessed the applicability of this method for quantifying cardiac output in a funnel-shaped tube model similar to mitral inflow or the left ventricular outflow tract. METHODS: A new digital three-dimensional color Doppler method was used to acquire Doppler flow information. Raw scan line data with digital velocity assignments were obtained on a conventional Doppler color flow imaging system with a 180 degrees rotating multiplanar transesophageal probe connected to a computer workstation. Nine stroke volumes (20-60 mL) with flow rates ranging from 1.5 to 5.28 L/min in a funnel-shaped pulsatile laminar flow model were studied. Three-dimensional flow rates were compared with standard-of-reference measurements of flow obtained from timed collection in a graduated cylinder and with an ultrasonic flow meter. RESULTS: Within the funnel tube, the flow volumes that were calculated from the first, second, and third depths and the average of all 3 depths correlated well with the actual flow rate (r = 0.97-0.99). Results from the middle and second levels and from the average of all 3 depths provided the closest fit to the actual flow rates (r = 0.99; y = 0.96x + 0.14; and r = 0.98; y = 1.14x - 0.43, respectively). CONCLUSIONS: Although a work in progress, this digital three-dimensional color Doppler flow measurement method is feasible, accurate, and simple, and it may offer in vivo evaluation of blood volume flow given a favorable orientation between the valve orifice and the scanning device.
AIM: To detect chemical components of the essential oil of Schisandra chinensis (Turcz.) Baill.. METHODS: The essential oil was analyzed with GC/MS, heuristic evolving latent projections(HELP) resolution and overall volume integration method. RESULTS: HELP method along with the data from GC/MS can be used to conduct the peak purity examination and resolution of overlapping peaks to obtain pure chromatogram and MS spectrum of each component. Fifty six components were separated and 49 of them were qualitatively and quantitatively analyzed. All the components represent about 98.27% of the total content. CONCLUSION: The resolved pure chromatogram and MS spectrum can greatly enhance the reliability of similar searches in the commercial MS database and thus contribute to the accuracy of the qualitative and quantitative analysis of the essential oil.
OBJECTIVES: To compare mitral annular shape and motion throughout the cardiac cycle in patients with normal hearts versus those with functional mitral regurgitation (FMR). BACKGROUND: The causes of mitral regurgitation without valvular disease are unclear, but the condition is associated with changes in annular shape and dynamics. Three-dimensional (3D) imaging provides a more comprehensive view of annular structure and allows accurate reconstructions at high spatial and temporal resolution. METHODS: Nine normal subjects and 8 patients with FMR undergoing surgery underwent rotationally scanned transesophageal echocardiography. At every video frame of 1 sinus beat, the mitral annulus was manually traced and reconstructed in 3D by Fourier series. Annular projected area, nonplanarity, eccentricity, perimeter length, and interpeak and intervalley spans were determined at 10 time points in systole and 10 points in diastole. RESULTS: The mitral annulus in patients with FMR had a larger area, perimeter, and interpeak span than in normal subjects (P <.001 for all). At mid-systole in normal annuli, area and perimeter reach a minimum, nonplanarity is greatest, and projected shape is least circular. These cyclic variations were not significant in patients with FMR. Annular area change closely paralleled perimeter change in all patients (mean r = 0.96 +/- 0.07). CONCLUSIONS: FMR is associated with annular dilation and reduced cyclic variation in annular shape and area. Normal mitral valve function may depend on normal annular 3D shape and dimensions as well as annular plasticity. These observations may have implications for design and selection of mitral annular prostheses.
AIMS: Evaluation of the accuracy of direct computation of multiple three-dimensional (3D) flow convergence (FC) isovelocities by using digital reconstruction of colour Doppler data of the flow convergence region. METHODS AND RESULTS: We used a conventional ultrasound system (ATL HDI 3000) connected to a computer workstation via Ethernet link. The digital 3D datasets were directly transferred to a Silicon Graphic Imaging Octane workstation for later measurement. We generated nine pulsatile flows (20-60 ml/beat), with peak flow rates (67-180 ml/s), through three orifices (circular, rectangular and triangular, S=0.24 cm(2)). The 3D reconstructions of FC surface areas from multi-threshold velocities, including aliasing velocities were analysed to quantify the peak flow rate. For all orifices, linear regression demonstrated excellent correlation between the 3D calculated and electromagnetic flow meter recorded data. While there was a high correlation for 3D computation of flow rate from the single best Nyquist of 24 cm/s (r=0.97-0.98, SEE=7 .75-12.58 ml/s), the ability to average three threshold velocities (15, 18 and 24 cm/s) yielded an improved correlation (r=0.98-0.99, SEE=5.70-7.73 ml/s). CONCLUSIONS: Direct computation of multiple 3D FC isovelocities from digital reconstruction of colour Doppler data of the FC region provides the potential to accurately quantify the complex asymmetric spatial flow events at any selected velocity.
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BACKGROUND: Conventional 2-dimensional Doppler large vessels are prone to inaccuracy. Three-dimensional (3D) volume imaging provides the opportunity to make cross-sectional flow calculations through digital spatiotemporal integration of flow velocity, area, and profile. METHODS: A new digital 3D color Doppler reconstruction method was used to generate radially acquired flow data sets. Raw scanline data with digital velocity assignments, obtained by scanning parallel to flow, were transferred from a specially programmed but otherwise conventional ultrasonographic system, which controlled a multiplane transesophageal probe, to a computer workstation via an Ethernet link for assimilation into color 3D data sets. This configuration was used to study 20 pulsatile laminar flows (stroke volumes 30 to 70 mL and peak flow rates 65 to 205 mL/s) in a curved tube model with an oval cross-sectional geometry. After generation of the color 3D data set, flow velocity values from cross sections perpendicular to the tubes were analyzed to determine flow rate and stroke volume. RESULTS: The flows from 3D digital velocity profiles showed close correlation with peak instantaneous flow rates (r = 0.99, y = 1.01x-0.9, standard error of estimate 4.1 mL/s). When interpreted with pulsed wave Doppler data obtained through the cardiac cycle, they also allowed computation of stroke volume (r = 0.98, y = 1.44x-2.5, standard error of estimate 3.8 mL). CONCLUSION: The ability to compute laminar flows from 3D digital data sets obtained parallel to the direction of flow and without the need for geometric assumptions represents an important opportunity for and advantage of 3D color Doppler echocardiography.
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Patients with non-insulin-dependent diabetes mellitus frequently have been associated with elevation in plasma levels of PAI-1. Part of the variations in individual plasma PAI-1 levels have been attributed to variations in the PAI-1 gene. In order to determine whether insulin regulates PAI-1 expression in a genotype-specific manner, individual human umbilical vein ECs (HUVECs) were genotyped using a Hind III RFLP and incubated in the absence/presence of insulin. Treatment of 1/1 PAI-1 genotype HUVECs with insulin increased secretion of PAI-1 antigen approximately 1.7 to 2.2-fold and mRNA levels were increased approximately 1.8 to 2.8-fold. Treatment of HUVECs with actinomycin D or puromycin completely abolished the induction of PAI-1 by insulin. The nuclear run-on assays indicated approximately 3-4 fold increase in PAI-1 transcription rates. These in vitro studies with the 1/1 PAI-1 genotyped cultured HUVECs, suggests that hyperinsulinemia may be expected to increase EC PAI-1 synthesis in those patients with the responsive 1/1 genotype.
Accurate measurement of left-ventricular (LV) volume and function are important to monitor disease progression and assess prognosis in patients with heart disease. Existing methods of three-dimensional (3-D) imaging of the heart using ultrasound have shown the potential of this modality, but each suffers from inherent restrictions which limit its applicability to the full range of clinical situations. We have developed a technique for image acquisition using a magnetic-field system to track the 3-D echocardiographic imaging planes and 3-D image analysis software including the piecewise smooth subdivision method for surface reconstruction. The technique offers several advantages over existing methods of 3-D echocardiography. The results of validation using in vitro LV's show that the technique allows accurate measurement of LV volume and anatomically accurate 3-D reconstruction of LV shape and is, therefore, suitable for analysis of regional as well as global function.
Plasminogen activator inhibitor-1 (PAI-1) has been shown to be an independent risk factor for coronary artery disease. Variations in plasma PAI-1 levels have been attributed to variations in the PAI-1 gene, and associations between PAI-1 levels and PAI-1 genotypes suggest that PAI-1 expression may be regulated in a genotype-specific manner by insulin, hypertriglyceridemic (HTG) very low density lipoprotein (VLDL), or lipoprotein(a) [Lp(a)]. Polymerase chain reaction-amplified 1106-bp fragments of the promoter of the 1/1 and 2/2 PAI-1 genotypes were sequenced and showed 5 regions of small nucleotide differences in the 1/1 versus 2/2 PAI-1 promoters that consistently occurred with high frequency. These fragments were ligated into the luciferase reporter gene, and 1/1 and 2/2 PAI-1 genotype human umbilical vein endothelial cell (HUVEC) cultures were transiently transfected with their respective p1PAI110/luc and p2PAI110/luc constructs and vice versa. Insulin induced an approximately 12- to 16-fold increase in luciferase activity in both the 1/1 and 2/2 PAI-1 genotype HUVEC cultures transfected with the p1PAI110/luc construct. HTG-VLDL and Lp(a) induced luciferase activity by approximately 14- to 16- and approximately 8- to 11-fold, respectively, in both the 1/1 and 2/2 PAI-1 genotype HUVEC cultures transfected with the p2PAI110/luc construct. The positive control interleukin-1 showed an approximately 7- to 12-fold response in the 1/1 and 2/2 PAI-1 genotype HUVEC cultures transfected with either of the constructs. These cross-over results demonstrate that regulation of either the 1/1 or 2/2 PAI-1 genotype by its respective inducer is due to the promoter itself and not to some factor(s) expressed differently in the 1/1 or 2/2 PAI-1 genotype HUVEC cultures.
BACKGROUND & AIMS: Three-dimensional (3D) ultrasound imaging of the total stomach volume has not yet been achieved. The aim of this study was to investigate whether a magnetic position sensor system for acquisition of 3D ultrasonograms could be used to determine gastric emptying rates and intragastric distribution. METHODS: A system for position and orientation measurement was interfaced to an ultrasound scanner. In vitro accuracy was evaluated by scanning a porcine stomach. Fourteen volunteers, with a median age of 35 years, were scanned fasting and postcibally by two-dimensional (2D) and 3D ultrasound after ingesting a 500-mL soup meal. RESULTS: This 3D system yielded a strong correlation (r = 0.997) between true and estimated volumes in vitro. The limits of agreement were -9.1:70.1 mL in the volume range 1200-1900 mL. The intersubject variability of the total gastric volumes ranged from 12.5% to 46.0%, less than for antral area variability. The average half-emptying time was 22.1 +/- 3.8 minutes. Intragastric distribution of the meal, expressed as proximal distal volume, varied on average from 3.6 +/- 2.1 (5 minutes postpradially) to 2.7 +/- 1.9 (30 minutes postprandially). CONCLUSIONS: This 3D ultrasound system using magnetic scanhead tracking showed excellent in vitro accuracy, calculated gastric emptying rates more precisely than by 2D ultrasound, and enabled estimation of intragastric distribution of a soup meal.
OBJECTIVE: To determine the growth-inhibitory and differentiation-inducing activity of dimethylformamide (DMF) on a human glioma cell line (SHG-44). DMF is a type of polar solvent and a potent differentiation-inducing agent in many kinds of human solid tumors, yet its effect on human glioma remains unclear. METHODS: The effects of DMF on cell proliferation using 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, cell cycle distribution (with flow cytometry), colony-forming efficiency in double-layer soft agar, tumorigenicity in athymic nude mice, morphological changes, and glial fibrillary acidic protein expression were studied. RESULTS: At dose ranges of 0.25, 0.5, 0.75, and 1.0%, DMF caused a dose-dependent proliferation inhibitory effect in monolayers and a marked dose-dependent suppression of colony-forming efficiency in double-layer soft agar with a complete loss of colony-forming ability in cells exposed to 0.75 and 1.0% DMF. Accumulation of cells in G0/G1 phases was observed in DMF-treated (0.5 and 1.0%) cells, also in a dose-dependent manner. SHG-44 cells exposed to DMF (0.5 and 1.0%) for 15 days changed morphologically from small spindle-shaped to large polygonal and flattened stellate cells with multiple slender processes. These cells were still tumorigenic in athymic nude mice, but the growth of xenografts was remarkably reduced, especially in the 1.0% DMF-treated group. The expression of glial fibrillary acidic protein was notably increased by DMF (0.5 and 1.0%). Washout experiments revealed that the effects of DMF on cell proliferation and cell cycle distribution were reversible. CONCLUSION: Our results suggest that DMF drove the SHG-44 cells to a more mature phenotype with inhibited growth.
The hypothesized relationships between plasminogen activator inhibitor (PAI-1) genotypes, PAI-1 levels, and their potential regulation by hypertriglyceridemic (HTG) very low density lipoprotein (VLDL) and lipoprotein(a) [Lp(a)] was examined in a PAI-1 genotyped human umbilical vein endothelial cell (HUVEC) culture model system. Individual human umbilical veins were used to obtain cultured ECs and were genotyped for PAI-1 by using the HindIII restriction fragment length polymorphism (RFLP) as a marker for genetic variation. Digested genomic DNA, examined by Southern blot analysis and probed with an [alpha-32P]dCTP-labeled 2.2-kb PAI-1 cDNA, yielded three RFLPs designated 1/1 (22-kb band only), 1/2 (22-plus 18-kb bands), and 2/2 (18-kb band only). Individual PAI-1 genotyped HUVEC cultures were incubated in the absence or presence of HTG-VLDL (0 to 50 micrograms/mL) or Lp(a) (0 to 50 micrograms/mL) at 37 degrees C for various times (4 to 24 hours), followed by analyses of PAI-1 antigen (by ELISA) and mRNA (by ribonuclease protection assay) levels, EC surface-localized plasmin generation assays, and nuclear run-on transcription assays. Secreted PAI-1 antigen levels were increased approximately 2- to 3-fold by HTG-VLDL and approximately 1.6 to 2-fold by Lp(a); mRNA levels were increased approximately 3- to 4.5-fold by HTG-VLDL and approximately 2.5- to 3.2-fold by Lp(a) compared with medium-incubated controls, primarily in the 2/2 PAI-1 genotype HUVEC cultures. Increases in PAI-1 mRNA induced by HTG-VLDL or Lp(a) could be abolished by coincubation with actinomycin D (2 x 10(-6) mol/mL) or puromycin (1 microgram/mL). In addition, nuclear transcription run-on assays typically demonstrated that HTG-VLDL increased PAI-1 gene transcription rates by approximately 5- to 6-fold and approximately 4- to 5-fold, respectively, primarily in the 2/2 PAI-1 genotype HUVEC cultures compared with 1/1 PAI-1 genotype HUVEC cultures or medium-incubated controls. The positive control interleukin-1 increased both 2/2 and 1/1 PAI-1 mRNA levels by approximately 5- to 6-fold. Increased PAI-1 antigen and mRNA expression were associated with a concomitant 50% to 60% decrease in plasmin generation. These combined results demonstrate the genotype-specific regulation of PAI-1 expression by HTG-VLDL and Lp(a) and further indicate that these risk factor-associated components regulate PAI-1 gene expression at the transcriptional level in cultured HUVECs. Results from these studies further suggest that individuals with this responsive 2/2 PAI-1 genotype may reflect the additional inherent potential for later HTG-VLDL- or Lp(a)-induced fibrinolytic dysfunction, resulting in the early initiation of thrombosis, atherogenesis, and coronary artery disease.
The effect of normo (NTG)- and hypertriglyceridemic (HTG)-VLDL on cultured human umbilical vein endothelial cell (HUVEC) surface-localized fibrinolysis was examined following pre-incubation with NTG-, HTG-VLDL, LDL (1-20 micrograms/mL) or buffer (control). Ligand binding assays, using 125I-labeled tcu-PA, t-PA, or Glu-plasminogen (Glu-Pmg) were carried out in the absence/presence of lipoproteins. Scatchard analyses showed that HTG-VLDL decreased the Bmax for 125I-labeled Glu-Pmg ligand binding approximately 35% [(2.11 +/- 0.39)-(1.40 +/- 0.32) x 10(6) sites/cell, p < 0.005] and increased the Kd, app approximately 5-fold (0.32 +/- 0.03 to 1.74 +/- 0.08 microM, p < 0.01), while NTG-VLDL, LDL, and buffer had no effect. 125I-labeled PA ligand binding was unaffected by these lipoproteins. Receptor-bound PA activation of cell-bound 125I-labeled Glu-Pmg was measured by quantitation of either the M(r) 20 kDa light- or M(r) 60 kDa heavy-chain of 125I-labeled plasmin, following SDS-PAGE. Kinetic analysis of these data (HTG-VLDL vs controls) indicated that HTG-VLDL decreased the V(max) of tcu-PA- and t-PA-mediated activation of plasminogen approximately 2.7-fold (0.317 +/- 0.023 vs 0.869 +/- 0.068 nM s-1, p < 0.01) and approximately 2.9-fold (0.391 +/- 0.098 vs 1.152 +/- 0.265 nM s-1, p < 0.01), respectively. Increasing concentrations of the HTG-VLDL increased 1/V(max), yielding a series of parallel plots, typical for uncompetitive inhibition with a Ki for inhibition of approximately 10 micrograms/mL. The combined ligand binding and kinetic data best fit an uncompetitive inhibition model in which the binding of the large HTG-VLDL particle to the EC surface may directly affect Glu-Pmg binding and activation, thus contributing to early fibrin deposition and the increased thrombotic risk associated with HTG.
The modulation effects of hexamethylene bisacetamide (HMBA), a differentiation-inducing agent, on growth and differentiation of cells from human malignant glioma cell line SHG-44 were studied. At cytostatic doses (2.5 mM, 5 mM, 7.5 mM, and 10 mM for 15 days), HMBA exerted a marked inhibitory effect on cell proliferation. Exposure to HMBA (5 mM and 10 mM for 12 days) also resulted in an accumulation of cells in G0/G1 phase and a decrease of cells in S phase as analyzed by flow cytometry. The reversible effects of 7.5 mM HMBA and 10 mM HMBA on cell proliferation and 10 mM HMBA on disruption of cell cycle distribution were observed when HMBA was removed from culture media on Day 6 and replaced with HMBA-free media. Colony-forming efficiency (CFE) in soft agar was remarkably decreased by HMBA (2.5 mM, 5 mM, 7.5 mM, and 10 mM for 14 days), and in 7.5 mM HMBA- and 10 nM HMBA treated cells, the CFEs were reduced to 25% and 12.5%, respectively, of that in untreated cells. Cells treated with HMBA (5 mM and 10 mM for 15 days) remained tumorigenic in athymic nude mice, but the growth rates of the xenografts were much slower than those in the control group. The effects of HMBA on cell proliferation, cell cycle distribution, CFE, and growth of xenografts were dose dependent. A more mature phenotype was confirmed by the morphological changes from spindle shape to large polygonal stellate shape and remarkably elevated expression of glial fibrillary acidic protein in cells exposed to HMBA (5 mM, 10 mM for 15 days). Our results showed that a more differentiated phenotype with marked growth arrest was induced in SHG-44 cells by HMBA.
To determine whether inherent fibrinolytic differences may exist in racial groups (black americans, BA vs. white americans, WA), 55 different individual racially-derived human umbilical vein endothelial cell (HUVEC) cultures (35 BA and 20 WA) were analyzed in terms of their fibrinolytic protein (t-PA, u-PA and PAI-1) antigen and mRNA levels. Values (mean +/- SD) for measured fibrinolytic component levels include: cell-associated t-PA antigen (ELISA), 1.14 +/- 0.82 ng/ml/8.6 x 10(5) cells/24 hr in BA and 0.70 +/- 0.85 ng/ml in WA (p = 0.0624); secreted t-PA antigen, 18.65 +/- 17.06 ng/ml in BA and 10.37 +/- 6.38 ng/ml in WA (p = 0.0422); t-PA/cyclophilin mRNA ratios (Northern blot analysis), 1.90 +/- 1.34 in BA and 1.32 +/- 0.70 in WA (p = 0.0776); cell-associated PAI-1 antigen, 71.10 +/- 30.16 ng/ml/8.6 x 10(5) cells/24 hr in BA and 108.85 +/- 56.89 ng/ml in WA (p = 0.0022); secreted PAI-1 antigen, 1,582.13 +/- 612.67 ng/ml in BA and 1,992.17 +/- 711.50 ng/ml in WA (p = 0.0285); 2.4 kb PAI-1/cyclophilin mRNA ratios, 0.59 +/- 0.39 in BA and 0.79 +/- 0.31 in WA (p = 0.1085); 3.4 kb PAI-1/cyclophilin mRNA ratios, 0.70 +/- 0.47 in BA and 0.77 +/- 0.54 in WA (p = 0.6322). These combined data suggest that cultured HUVECs from BA express significantly higher levels of t-PA, lower levels of PAI-1 and approximately 1.72-fold lower molar ratio of PAI-1/t-PA antigen (183.99 +/- 168.81 vs. 315.92 +/- 164.99) (p < 0.05) than cultured HUVECs from WA, presumably reflecting an apparent inherent increased fibrinolytic potential in cultured HUVEC derived from BA.