Biomedical subjects

L Wang

Publications and source records attributed to L Wang.

At least 235 records · Page 13Linked to original sources

PubMed2003

Prospective evaluation of the immunobead assay for the diagnosis of adult chronic immune thrombocytopenic purpura (ITP).

Chronic immune thrombocytopenic purpura (ITP) is an autoimmune disease characterized by antibody-induced platelet destruction. To better define the role of antigen-specific assays in adult chronic ITP, we prospectively measured platelet-associated autoantibody against either glycoprotein (GP) IIb/IIIa or GPIb/IX in 282 patients with chronic ITP and 289 patients with thrombocytopenia of other causes. We divided chronic ITP into four subgroups: presplenectomy, mild (platelet count >30 000 micro (L-1) requiring no therapy), presplenectomy, severe (platelet count <30 000 micro L(-1) requiring therapy but not splenectomy), postsplenectomy, remission (postsplenectomy partial or complete remission without further therapy) and postsplenectomy refractory (required therapy after splenectomy failure). Positive results: total ITP group, 55.4%; presplenectomy, mild, 31.1%; presplenectomy, severe, 42.6%; postsplenectomy, remission, 50.0%; and postsplenectomy, refractory, 87.8%. In addition, the degree of positivity increased with the severity of the patient's disease. The assay had a minimum specificity of 84.4% if clinical factors, consistent with immune thrombocytopenia, were not considered in patients with thrombocytopenia associated with other diseases. However, if clinical factors consistent with immune thrombocytopenia were considered and only patients with questionable immune thrombocytopenia and patients 'lost to follow-up' were included in the false-positive group the specificity was 93.1%. We conclude that the presence of immune thrombocytopenia is highly probable if the immunobead assay is positive and that antigen-specific assays are diagnostically useful in adult chronic ITP.

Adult↗

PubMed2003

A catalogue of molecular, physiological and symbiotic properties of soybean-nodulating rhizobial strains from different soybean cropping areas of China.

We have analysed 198 fast-growing soybean-nodulating rhizobial strains from four different regions of China for the following characteristics: generation time; number of plasmids; lipopolysaccharide (LPS), nodulation factors (LCOs) and PCR profiles; acidification of growth medium; capacity to grow at acid, neutral, and alkaline pH; growth on LC medium; growth at 28 and 37 degrees C; melanin production capacity; Congo red absorption and symbiotic characteristics. These unbiased analyses of a total subset of strains isolated from specific soybean-cropping areas (an approach which could be called "strainomics") can be used to answer various biological questions. We illustrate this by a comparison of the molecular characteristics of five strains with interesting symbiotic properties. From this comparison we conclude, for instance, that differences in the efficiency of nitrogen fixation or competitiveness for nodulation of these strains are not apparently related to differences in Nod factor structure.

Bacterial Proteins↗

PubMed2003

Predicting toxicity of benzene derivatives by molecular hologram derived quantitative structure-activity relationships (QSARS).

Holographic quantitative structure-activity relationship (HQSAR) is an emerging QSAR technique with the combined application of molecular hologram, which encodes the frequency of occurrence of various molecular fragment types, and the subsequent partial least squares (PLS) regression analysis. Based on molecular hologram, alignment-free QSAR models could be rapidly and easily developed with highly statistical significance and predictive ability. In this paper, the toxicity data for a series of 83 benzene derivatives to the autotrophic Chlorella vulgaris (IGC50, negative logarithmic form of 6-h 50% population growth inhibition concentration in mmol/l) were subjected to HQSAR analysis and this resulted in a model with a high predictive ability. The robustness and predictive ability of the model were validated by "leave-one-out" (LOO) cross-validation procedure and an external testing set. The influence of fragment distinction parameters and fragment size on the quality of the HQSAR model have been also discussed.

Benzene Derivatives↗

PubMed2003

CoMFA of the acute toxicity of phenylsulfonyl carboxylates to Vibrio fischeri.

From the Comparative Molecular Field Analysis (CoMFA) method, the paper describes a three-dimentional quantitative structure-activity relationship (3D-QSAR) model for the acute toxicity logEC50 (15min-EC50 in micromol l(-1)) of 56 phenylsulfonyl carboxylates on Vibrio fischeri. The achievement of a high leave-one-out (LOO) cross-validated correlation coefficient q2 of 0.790 with four optimum components indicates the significance of the correlation of the steric and electrostatic fields with the biological activities. The key features in the CoMFA contour maps are critical to trace the important properties and gain insight into the toxic mechanism of the tested phenylsulfonyl carboxylates.

Carboxylic Acids↗

PubMed2003

Ni2+ removal and recovery from electroplating effluent by Pseudomonas putida 5-x cell biomass.

Ni2+ and Cu2+ are the major heavy metal ions in electroplating wastewater of Hong Kong. In the present study, Pseudomonas putida 5-x cell biomass was used to remove Ni2+ from electroplating effluent. Ni2+ adsorption capacity of P. putida 5-x cell biomass cultured in sulphate-limiting medium was found to be minimum in early logarithmic growth phase, and maximum of 28.1 mg g(-1) in late stationary growth phase. Pretreated cells by 0.1 mol L(-1) HCl could greatly enhance the Ni2+ adsorption capacity of cell biomass from 28.1 to 36.7 mg g(-1) and had no significant effect on biomass loss. The adsorption process of P. putida 5-x fresh cells and pretreated cell all could be expressed with Freundlich isotherm. TEM analyses indicated that acidic pretreatment degraded the superficial layer-capsule outside of the fresh cell to improve the adsorption capacity of cell to Ni2+. The Ni2+ bound by P. putida 5-x cell biomass could be efficiently recovered using 0.1 mol L(-1) HCl, and the cell biomass could be reused at least five cycles for Ni2+ removal and recovery with 93% above removal efficiency and 98% above recovery rate. Owing to the Cu2+ presented in electroplating wastewater inhibiting Ni2+ adsorption process by P. putida 5-x cell biomass, two-stage biosorption processes should be designed to remove and recover Cu2+ and Ni2+ sequentially from electroplating effluent.

Adsorption↗

PubMed2003

The biodegradation of 1,3-dichlorobenzene by an adapted strain Bacillus cereus PF-11 derived from town-gas industrial effluent.

In the present study, an adapted bacterium PF-11 with high 1,3-dichlorobenzene degradation capability was isolated from town-gas industrial effluent through continuous introducing of N-methyl-N'-nitro-N-nitrosoquanidine (NTG). In suitable condition, a degradation rate of 32 mg L(-1) d(-1) of 1,3-dichlorobenzene was obtained by strain PF-11 with effective chlorion release. Strain PF-11 was tentatively identified as gram-positive Bacillus cereus. The substrate specificity of the strain PF-11 was relatively low, and the degradation rate for different chlorobenzenes was in the order of monochlorobenzene > 1,3-dichlorobenzene > 1,2-dichlorobenzene. Initial oxidation step was molecular oxygen attacking chlorobenzene ring catalyzed by dioxygenase.

Adaptation, Physiological↗

PubMed2003

Beam and phase effects in angle-beam-through-transmission method of ultrasonic velocity measurement.

The accuracy of a plane wave approximation for phase velocity measurements in isotropic and anisotropic material using the angle-beam-through-transmission method has been investigated numerically and experimentally. In this method the velocity is measured in different propagation directions as a function of incidence angle. The effect of two factors on the measurement accuracy have been discussed: intrinsic phase shift of the transmitted signal through a fluid-solid interface and beam diffraction due to the finite beam size of receiver and transmitter. It is shown that the interface-induced phase shift can introduce an error in time delay measurements of the shear wave after the first critical angle and that this time delay error can be accurately corrected for. Numerical results obtained by a time-domain beam model show that except at the critical angles, the finite width of the transmitter and receiver only affects the amplitudes of the transmitted signals and has almost no effect on the measured zero-cross time delay; therefore the plane wave approximation for obtaining phase velocity from the measured time delay data by this method and the plane wave interface-induced phase correction are fully applicable.

Journal Article↗

PubMed2003

Inverse ultrasonic determination of imperfect interfaces and bulk properties of a layer between two solids.

A method for determination of the complete set of physical, geometrical, and interfacial properties of an isotropic layer embedded between two known solids is discussed. These properties are: Lamé elastic moduli, density and thickness of the layer, and complex normal and transverse interfacial stiffnesses between the layer and the substrates. The properties are combined in the form of eight nondimensional parameters, which are determined from experimental reflection spectra at two incident angles: normal and oblique. The conditions for simultaneous determination of bulk layer properties and the interface normal and transverse springs with losses and the stability of the inversion method against data scatter are addressed. The inversion model is validated by experiment on normal and angular ultrasonic reflectivity from a layer between two semispaces in dry mechanical contact and from an environmentally degraded adhesive joint. The layer properties were measured independently, showing good agreement with the reconstructed results.

Journal Article↗

PubMed2003

Ultrasonic wave interaction with multidirectional composites: modeling and experiment.

Phenomena of wave transmission through a multidirectional composite laminate immersed in a fluid have been investigated. Based on a recently-developed recursive stiffness matrix method time-domain beam models have been developed to simulate the problem. Experimental and theoretical results at frequency 2.25 MHz show that the transmission amplitude is highly dependent on lamina orientation and angle of incidence. Large transmission amplitude appears at small (<10 degrees) and large incident angles (45 degrees-60 degrees). At intermediate incident angles (16 degrees-40 degrees) the transmission amplitude is almost zero. At high frequency, the residue epoxy layers between each lamina become important and corresponding resonances may be observed. These transmission phenomena have been interpreted in terms of Floquet waves. It shows that the pass and stop bands of the three Floquet waves obtained from the unit cell stiffness matrix determine the transmission amplitude distribution in frequency, incident angle and rotation angle domains. The effect of random deviation of the laminated structure periodicity has also been assessed. At normal incidence, the variation of the thickness of the epoxy residual layer between composite lamina has little effect on the overall stop and pass band structures but introduces random reverberation and scattering in the pass bands. It is shown that for oblique incidence the transmittivity spectrum of a composite with random lamina lay-up converges with increase of randomness to that of a [0/-45/90/45]2s quasi-isotropic composite. Randomization of lamina lay-up produces a small effect in the transmittivity spectrum for a quasi-isotropic composite.

Journal Article↗

PubMed2003

Tempero-spatial dissociation between the expression of Fas and apoptosis after coronary occlusion.

AIMS: To explore the role of Fas in cardiomyocytic apoptosis induced by ischaemia through determining the histological relation between Fas expression and apoptosis in rat myocardium during ischaemia/infarction. METHODS: The myocardial ischaemia model was produced by ligating the left coronary artery in Sprague-Dawley rats. The rats were killed from 10 minutes to seven days after surgery. Apoptotic myocardial cells were detected by the in situ terminal deoxynucleotidyl transferase mediated nick end labelling method, and the expression of Fas by immunohistochemistry and western blotting. RESULTS: Cardiomyocytic apoptosis appeared from three to 36 hours after ischaemia. The expression of Fas could be detected by western blot from before surgery to seven days of ischaemia. Apoptosis and the expression of Fas in the cardiomyocytes appeared in different regions of the myocardium: apoptosis in the ischaemic region, Fas in the regions surrounding ischaemic myocardium. CONCLUSION: These results suggest that there is a tempero-spatial dissociation between the expression of Fas and apoptosis after coronary occlusion. Fas might not directly regulate the apoptosis of cardiomyocytes induced by ischaemia.

Animals↗

PubMed2003

Synthetic studies on nonthrombogenic biomaterials 14: synthesis and characterization of poly(ether-urethane) bearing a Zwitterionic structure of phosphorylcholine on the surface.

A new Zwitterionic compound of the phosphorylcholine analogue, 4-hydroxylbutyl phosphorylcholine (HBPC), was synthesized and characterized. HBPC was chemically tethered onto the surface of poly(ether-urethane) (PEU) films with hexamethylene diisocyanate (HDI) as a coupling agent. The existence of a phosphorylcholine structure on the PEU surface was demomstrated by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FT-IR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. The nonthrombogenicity of the modified films was evaluated by platelet-rich plasma (PRP) assay. The results showed that films grafted with HBPC have excellent platelet adhesion resistance.

Biocompatible Materials↗

PubMed2003

Pro-inflammatory cytokines up-regulate MUC1 gene expression in oral epithelial cells.

The membrane-bound mucin MUC1 is expressed ubiquitously on epithelial surfaces and is thought to provide protection from bacterial and chemical injury. The present study was undertaken to determine whether MUC1 was expressed in cultured oral epithelial cells and whether expression is modulated by pro-inflammatory mediators released as part of the host response to infection by oral pathogens. Northern and Western blotting experiments showed that KB cells express MUC1 mRNA and protein. When cells were treated with interleukins (IL-1beta, IL-6), tumor necrosis factor-alpha (TNF-alpha), or interferon-gamma (IFN-gamma), or combinations of these, real-time PCR demonstrated that MUC1 mRNA increased 1.4- to 3.2-fold. Interestingly, a significant increase in levels of MUC1 protein was also observed. While no effect was observed when KB cells were incubated with LPS from Porphyromonas gingivalis, infection of KB monolayers with this oral pathogen caused a 2.85-fold increase in MUC1 transcript levels. These results suggest that increased MUC1 synthesis may be a key element in the host response to infection with oral pathogens.

Blotting, Northern↗

PubMed2003

Upregulation of Fas and FasL expression in testosterone-induced apoptosis of macrophages.

To the best of the authors' knowledge, there have been few reports on the effect of testosterone on the apoptosis of macrophages. In this report, we studied the effect of testosterone on the apoptosis of bone marrow-derived macrophages (BMMs) and the function of the Fas/Fas ligand (FasL) system in the process. Results showed that testosterone treatment in vitro at the physiological concentration of 10 nM did not induce the apoptosis of BMMs. However, BMMs underwent apoptosis when treated at higher concentrations of testosterone (100, 200 and 400 nM). Testosterone-induced apoptosis was associated with the enhanced expression of Fas, FasL, and caspase-8. These data suggest that the Fas/FasL system may play an important role in the testosterone-induced apoptosis of macrophages.

Animals↗

PubMed2003

Superior mesenteric arterial embolism: a retrospective study of local thrombolytic treatment with urokinase in West China.

Embolism of the superior mesenteric artery (SMA) is a rare disorder. To explore the selective criteria of local thrombolysis, evaluate its efficacy and discuss the therapeutic protocol of SMA embolism, a retrospective case control study was undertaken. Sixteen cases were divided into two groups: nine cases (group A) from May 1995 to April 1999 were given traditional treatment, while seven cases (group B) from November 1999 to June 2002 received comprehensive therapy including local thrombolysis. The local thrombolytic treatment was performed without procedure-related complications and the embolus was successfully lysed in four patients. The time between admission and diagnosis (or treatment) was shorter in group B than in group A (2.3 +/- 1.2 vs 12.3 +/- 9.2 hr, p = 0.013). Gangrenous bowel segments in group A were much longer than in group B (159.4 +/- 87.7 vs 45.7 +/- 61.6 cm, p = 0.009). However, mortality between the two groups was the same (p = 0.282, OR = 0.32, 95% CI = 0.039, 2.618) perhaps because of the small sample size. Angiography could shorten the duration from the onset of SMA embolism to therapy and certainly lowers the risk of mortality. Local fibrinolytic infusion may be an effective alternative to embolectomy in patients with SMA embolism but without intestinal infarction.

Adult↗

PubMed2003

The APC E1317Q variant in adenomatous polyps and colorectal cancers.

Genetic susceptibility may play a role in many colorectal cancers (CRCs). Known syndromes such as familial adenomatous polyposis and hereditary nonpolyposis CRC account for <5% of CRCs. The germ-line missense variant of the APC gene, E1317Q, has been proposed to confer a risk for colonic adenomatous polyps (adenomas), but not for CRCs in the general population. These findings are contradictory and controversial. In the present study, 608 cases (377 patients with CRC, 145 patients with 4-100 lifetime adenomas, and 86 with < or =3 lifetime adenomas), and 679 controls (362 spouses and 317 patients with normal colonoscopy) were screened for the APC E1317Q variant. The frequency of heterozygotes for E1317Q among patients with CRC (2.4%), patients with 4-100 adenomas (1.4%), and < or =3 adenomas (3.5%) did not differ from spouse controls (2.8%). When CRC patients were examined by DNA mismatch repair status, age at onset (< or =age 50 versus >50), or family history of CRC, no differences in the frequency of E1317Q were found. The APC variant E1317Q does not appear to be associated with increased risk for colorectal neoplasia in the general population. However, when we used normal colonoscopy controls (E1317Q carrier frequency = 0.3%), the prevalence of E1317Q was significantly increased in CRC patients, in patients with < or =3 adenomas, and in CRC patients with intact mismatch repair status, suggesting a possible role for E1317Q in colorectal tumorigenesis. These results underscore the importance of carefully defining the controls to be used in comparisons of allele frequencies.

Adenoma↗

PubMed2003

Role of epicardial QT intervals in the assessment of ventricular repolarisation dispersion.

The role of cardiac surface QT intervals (QTI) in assessing ventricular repolarisation dispersion was investigated in 10 pentobarbital-anesthetized, open-chest sheep. Activation-recovery interval (ARI) and QTI were measured from multiple ECGs acquired from left ventricular epicardium, before and after procainamide administration (15 mg/min i.v. for 20 min). Procainamide therapy resulted in a significant prolongation in ARI and corrected QT interval (cQTI). A correlation between QTI, cQTI and ARI was found in only one animal (r = 0.78 and 0.79 respectively, p = 0.01) before procainamide therapy. No correlation was found between pooled QTI and ARI dispersion from the 10 animals at baseline or after procainamide administration (p > 0.05). There was a moderate correlation between pooled cQTI and ARI dispersion (r = 0.69, p = 0.02) before procainamide therapy. In conclusion, epicardial QTI have no significant correlation with the duration of ventricular repolarisation. Epicardial QTI dispersion is not a useful index of repolarisation heterogeneity.

Animals↗

PubMed2002

Rodent model for investigating the effects of estrogen on bone and muscle relationship during growth.

It has been reported that in humans from about 11-12 years of age, bone mass begins to increase faster in girls than in boys with the same muscle mass, and by 14-15 years of age, bone mass per unit mass of muscle was found to be significantly higher in girls than in boys. Because around 15 years is the beginning of reproductive age in women, it was suggested that estrogen was involved in the higher bone mass in women during puberty. The present study was undertaken to determine if bone mass per unit muscle mass is higher in female than in male Sprague Dawley (SD) rats during growth, as has been reported in humans during growth and consequently, whether these SD rats are suitable for studying the musculoskeletal effects of estrogen, as may occur in humans during growth. L-4 vertebra of female and male SD rats aged 1-6 months were studied using peripheral quantitative computed tomography (pQCT). Muscle cross-sectional area was measured as a surrogate for muscle mass and bone mineral content (BMC) was measured as a surrogate for bone mass. From 1 to 6 months of age, total BMC, cortical BMC, and cancellous BMC increased faster in females than in males with similar muscle area, and at 3 and 6 months of age, the above vertebral indices of bone mass were significantly higher in female than in male rats. Since one of the main differences between female and male rats is the level of serum estrogen, the higher bone mass per unit muscle area seen at the L-4 vertebra in these female SD rats is similar to what has been reported in humans during puberty when serum estrogen level is high in females. The findings from this study indicate that female and male SD rats aged 1-6 months can be used as appropriate model for studying the effects of serum estrogen on the skeletal response of voluntary muscle forces, as has been reported in humans during growth.

Animals↗

PubMed2002

Potent and long-acting corticotropin releasing factor (CRF) receptor 2 selective peptide competitive antagonists.

We present evidence that members of the corticotropin releasing factor (CRF) family assume distinct structures when interacting with the CRF(1) and CRF(2) receptors. Predictive methods, physicochemical measurements, and structure-activity relationship studies have suggested that CRF, its family members, and competitive antagonists such as astressin [cyclo(30-33)[DPhe(12),Nle(21),Glu(30),Lys(33),Nle(38)]hCRF((12-41))] assume an alpha-helical conformation when interacting with their receptors. We had shown that alpha-helical CRF((9-41)) and sauvagine showed some selectivity for CRF receptors other than that responsible for ACTH secretion(1) and later for CRF2.(2) More recently, we suggested the possibility of a helix-turn-helix motif around a turn encompassing residues 30-33(3) that would confer high affinity for both CRF(1) and CRF(2)(2,4) in agonists and antagonists of all members of the CRF family.(3) On the other hand, the substitutions that conferred ca. 100-fold CRF(2) selectivity to the antagonist antisauvagine-30 [[DPhe(11),His(12)]sauvagine((11-40))] did not confer such property to the corresponding N-terminally extended agonists. We find here that a Glu(32)-Lys(35) side chain to side chain covalent lactam constraint in hCRF and the corresponding Glu(31)-Lys(34) side chain to side chain covalent lactam constraint in sauvagine yield potent ligands that are selective for CRF(2). Additionally, we introduced deletions and substitutions known to increase duration of action to yield antagonists such as cyclo(31-34)[DPhe(11),His(12),C(alpha)MeLeu(13,39),Nle(17),Glu(31),Lys(34)]Ac-sauvagine((8-40)) (astressin(2)-B) with CRF(2) selectivities greater than 100-fold. CRF receptor autoradiography was performed in rat tissue known to express CRF(2) and CRF(1) in order to confirm that astressin(2)-B could indeed bind to established CRF(2) but not CRF(1) receptor-expressing tissues. Extended duration of action of astressin(2)-B vs that of antisauvagine-30 is demonstrated in the CRF(2)-mediated animal model whereby the inhibition of gastric emptying of a solid meal in mice by urocortin administered intraperitoneally at time zero is antagonized by the administration of astressin(2)-B but not by antisauvagine-30 at times -3 and -6 h while both peptides are effective when given 10 min before urocortin.

Animals↗