Biomedical subjects

Ning Wang

Publications and source records attributed to Ning Wang.

144 records · Page 8Linked to original sources

PubMed2002

BEACH family of proteins: phylogenetic and functional analysis of six Dictyostelium BEACH proteins.

The beige and Chediak-Higashi syndrome (BEACH)-domain containing proteins constitute a new family of proteins found in all eukaryotes. The function of these proteins, which include the Chediak-Higashi syndrome (CHS) protein, Neurobeachin, LvsA, and FAN, is still poorly understood. To understand the diversity of this novel protein family, we analyzed a large array of BEACH-family protein sequences from several organisms. Comparison of all these sequences suggests that they can be classified into five distinct groups that may represent five distinct functional classes. In Dictyostelium we identified six proteins in this family, named LvsA-F, that belong to four of those classes. To test the function of these proteins in Dictyostelium we created disruption mutants in each of the lvs genes. Phenotypic analyses of these mutants indicate that LvsA is required for cytokinesis and osmoregulation and LvsB functions in lysosomal traffic. The LvsC-F proteins are not required for these or other processes such as growth and development. These results strongly support the concept that BEACH proteins from different classes have distinct cellular functions. Having six distinct BEACH proteins, Dictyostelium should be an excellent model system to dissect the molecular function of this interesting family of proteins.

Amino Acid Sequence↗

PubMed2002

Non-homogeneous infinite sites model under demographic change: mathematical description and asymptotic behavior of pairwise distributions.

We developed a mathematical model, which makes possible to predict joint distributions of numbers of mismatches in two or more linked regions of the genome, based on the Infinite Sites Models, under mutation-drift equilibrium as well as under various patterns of population growth. With mutation rates varying in the region, one of the predictions is different correlation between numbers of mismatches in the two regions, depending on the pattern of the past population growth (constant, slowly growing, or rapidly growing). Also, for slower growth patterns of population sizes, the coalescence tree is not necessarily 'starlike'. Thus, the joint distribution of mismatches, predicted by the model, provides additional insights into the demographic history of the populations. We also developed expectations and variances of sample statistics under different growth scenarios. As an application we used a sample of mitochondrial sequences from hypervariable regions 1 and 2 (HV1 and HV2), representing major world populations (Europeans, Asians and Africans). The patterns of joint distributions of numbers of mismatches differ markedly from one population to another. In addition, there is a considerable variability in the proportion of numbers of mismatches between HV1 and HV2 sequences. The patterns of bivariate distributions from the HV1 and HV2 data in these data are consistent with those generated by the model involving a stepwise change in population size.

Asian People↗

PubMed2002

High efficiency transgene segregation in co-transformed maize plants using an Agrobacterium tumefaciens 2 T-DNA binary system.

For regulatory issues and research purposes it would be desirable to have the ability to segregate transgenes in co-transformed maize. We have developed a highly efficient system to segregate transgenes in maize that was co-transformed using an Agrobacterium tumefaciens 2 T-DNA binary system. Three vector treatments were compared in this study; (1) a 2 T-DNA vector, where the selectable marker gene bar (confers resistance to bialaphos) and the beta-glucuronidase (GUS) reporter gene are on two separate T-DNA's contained on a single binary vector; (2) a mixed strain treatment, where bar and GUS are contained on single T-DNA vectors in two separate Agrobacterium strains; (3) and a single T-DNA binary vector containing both bar and GUS as control treatment. Bialaphos resistant calli were generated from 52 to 59% of inoculated immature embryos depending on treatment. A total of 93.4% of the bialaphos selected calli from the 2 T-DNA vector treatment exhibited GUS activity compared to 11.7% for the mixed strain treatment and 98.2% for the cis control vector treatment. For the 2 T-DNA vector treatment, 86.7% of the bialaphos resistant/GUS active calli produced R0 plants exhibiting both transgenic phenotypes compared to 10% for the mixed strain treatment and 99% for the single T-DNA control vector treatment. A total of 87 Liberty herbicide (contains bialaphos as the active ingredient) resistant/GUS active R0 events from the 2 T-DNA binary vector treatment were evaluated for phenotypic segregation of these traits in the R1 generation. Of these R0 events, 71.4% exhibited segregation of Liberty resistance and GUS activity in the R1 generation. A total of 64.4% of the R0 2 T-DNA vector events produced Liberty sensitive/GUS active (indicating selectable-marker-free) R1 progeny. A high frequency of phenotypic segregation was also observed using the mixed strain approach, but a low frequency of calli producing R0 plants displaying both transgenic phenotypes makes this method less efficient. Molecular analyses were then used to confirm that the observed segregation of R1 phenotypes were highly correlated to genetic segregation of the bar and GUS genes. A high efficiency system to segregate transgenes in co-transformed maize plants has now been demonstrated.

Agrobacterium tumefaciens↗

PubMed2002

Mechanics of vimentin intermediate filaments.

It is increasingly evident that the cytoskeleton of living cells plays important roles in mechanical and biological functions of the cells. Here we focus on the contribution of intermediate filaments (IFs) to the mechanical behaviors of living cells. Vimentin, a major structural component of IFs in many cell types, is shown to play an important role in vital mechanical and biological functions such as cell contractility, migration, stiffness, stiffening, and proliferation.

Animals↗

PubMed2002

Separation of ephedrine stereoisomers by molecularly imprinted polymers--influence of synthetic conditions and mobile phase compositions on the chromatographic performance.

Separation of ephedrine stereoisomers by molecularly imprinted polymers was performed to study the factors that affect the selectivity and column efficiency. The polymer synthesized with pentaerythritol triacrylate as the cross-linker and chloroform as the porogen was found to have the best overall separation performance. Investigation of the recognition mechanism by NMR and chromatographic analysis revealed that the major binding forces between the polymer stationary phase and ephedrine are the ionic and hydrogen bonding interactions. Studies of the influence of mobile phase compositions on the HPLC analysis have shown that a methanol-aqueous buffer was the suitable mobile phase for the separation in which pH, ionic strength and water content can be adjusted to optimize the chromatographic analysis.

Adrenergic Agents↗

PubMed2002

Dictyostelium LvsB mutants model the lysosomal defects associated with Chediak-Higashi syndrome.

Chediak-Higashi syndrome is a genetic disorder caused by mutations in a gene encoding a protein named LYST in humans ("lysosomal trafficking regulator") or Beige in mice. A prominent feature of this disease is the accumulation of enlarged lysosome-related granules in a variety of cells. The genome of Dictyostelium discoideum contains six genes encoding proteins that are related to LYST/Beige in amino acid sequence, and disruption of one of these genes, lvsA (large volume sphere), results in profound defects in cytokinesis. To better understand the function of this family of proteins in membrane trafficking, we have analyzed mutants disrupted in lvsA, lvsB, lvsC, lvsD, lvsE, and lvsF. Of all these, only lvsA and lvsB mutants displayed interesting phenotypes in our assays. lvsA-null cells exhibited defects in phagocytosis and contained abnormal looking contractile vacuole membranes. Loss of LvsB, the Dictyostelium protein most similar to LYST/Beige, resulted in the formation of enlarged vesicles that by multiple criteria appeared to be acidic lysosomes. The rates of endocytosis, phagocytosis, and fluid phase exocytosis were normal in lvsB-null cells. Also, the rates of processing and the efficiency of targeting of lysosomal alpha-mannosidase were normal, although lvsB mutants inefficiently retained alpha-mannosidase, as well as two other lysosomal cysteine proteinases. Finally, results of pulse-chase experiments indicated that an increase in fusion rates accounted for the enlarged lysosomes in lvsB-null cells, suggesting that LvsB acts as a negative regulator of fusion. Our results support the notion that LvsB/LYST/Beige function in a similar manner to regulate lysosome biogenesis.

Animals↗

PubMed2002

Directional control of lamellipodia extension by constraining cell shape and orienting cell tractional forces.

Directed cell migration is critical for tissue morphogenesis and wound healing, but the mechanism of directional control is poorly understood. Here we show that the direction in which cells extend their leading edge can be controlled by constraining cell shape using micrometer-sized extracellular matrix (ECM) islands. When cultured on square ECM islands in the presence of motility factors, cells preferentially extended lamellipodia, filopodia, and microspikes from their corners. Square cells reoriented their stress fibers and focal adhesions so that tractional forces were concentrated in these corner regions. When cell tension was dissipated, lamellipodia extension ceased. Mechanical interactions between cells and ECM that modulate cytoskeletal tension may therefore play a key role in the control of directional cell motility.

3T3 Cells↗

PubMed2002

Optimization of single-phase, unidirectional transducers using three fingers per period.

Electrode width controlled (EWC) single-phase, unidirectional transducers (SPUDT) is widely used for low loss surface acoustic wave (SAW) filters. The insertion loss and fractional bandwidth of the filters are strongly related to the reflectivity of EWC cells. In order to achieve wide band and low loss simultaneously, it is necessary to obtain higher reflectivity. The relationship between geometrical configuration of EWC cells and reflection coefficient, (and transduction coefficient as well) is studied. Simulation results indicate that the reflectivity of the EWC SPUDT cell could exceed 5% on a 128 degrees Y-X lithium niobate (LiNbO3) substrate. Using such structure, low loss SPUDT test filters without weighting are fabricated. The measured 3 dB bandwidth is 3.9% and the insertion loss is 2.9 dB. The theoretical calculation is verified by the experiment.

Acoustics↗

PubMed2002

Fast, precise, and full extraction of the COM parameters for multielectrode-type gratings by periodic Green's function method.

It is very important to extract all four coupling-of-modes (COM) parameters of the electrode cells for the simulation and optimal design of a low loss surface acoustic wave (SAW) filter. A new approach for fast and full extraction of the COM parameters for multielectrode-type grating is proposed. The field distribution of the wave under the periodic shorted grating is calculated by periodic Green's function method. The phase of the reflection is determined from the positions of the standing wave node. The transduction coefficient and its phase are determined by the charge distribution at low frequency. The COM parameters of the commonly used electrode width controlled (EWC) single phase unidirectional transducer (SPUDT) is computed. It shows that this is a simple and direct way to extract all the COM parameters for SPUDT and, accordingly, is a powerful tool for the optimization of the filter structure.

Acoustics↗

PubMed2002

Spatial and temporal traction response in human airway smooth muscle cells.

Tractions that cells exert on their substrates are essential in cell spreading, migration, and contraction. These tractions can be determined by plating the cells on a flexible gel and measuring the deformation of the gel by using fluorescent beads embedded just below the surface of the gel. In this article we describe the image correlation method (ICM) optimized for determining the displacement field of the gel under a contracting cell. For the calculation of the traction field from the displacement field we use the recently developed method of Fourier transform traction cytometry (FTTC). The ICM and FTTC methods are applied to human airway smooth muscle cells during stimulation with the contractile agonist histamine or the relaxing agonist isoproterenol. The overall intensity of the cell contraction (the median traction magnitude, the energy transferred from the cell to the gel, and the net contractile moment) increased after activation with histamine, and decreased after treatment with isoproterenol. Cells exhibited regional differences in the time course of traction during the treatment. Both temporal evolution and magnitude of traction increase induced by histamine varied markedly among different cell protrusions, whereas the nuclear region showed the smallest response. These results suggest that intracellular mediators of cell adhesion and contraction respond to contractile stimuli with different rates and intensities in different regions of the cell.

Adrenergic beta-Agonists↗

PubMed2002

Cell prestress. I. Stiffness and prestress are closely associated in adherent contractile cells.

The tensegrity hypothesis holds that the cytoskeleton is a structure whose shape is stabilized predominantly by the tensile stresses borne by filamentous structures. Accordingly, cell stiffness must increase in proportion with the level of the tensile stress, which is called the prestress. Here we have tested that prediction in adherent human airway smooth muscle (HASM) cells. Traction microscopy was used to measure the distribution of contractile stresses arising at the interface between each cell and its substrate; this distribution is called the traction field. Because the traction field must be balanced by tensile stresses within the cell body, the prestress could be computed. Cell stiffness (G) was measured by oscillatory magnetic twisting cytometry. As the contractile state of the cell was modulated with graded concentrations of relaxing or contracting agonists (isoproterenol or histamine, respectively), the mean prestress ((t)) ranged from 350 to 1,900 Pa. Over that range, cell stiffness increased linearly with the prestress: G (Pa) = 0.18(t) + 92. While this association does not necessarily preclude other interpretations, it is the hallmark of systems that secure shape stability mainly through the prestress. Regardless of mechanism, these data establish a strong association between stiffness of HASM cells and the level of tensile stress within the cytoskeleton.

Acrylic Resins↗

PubMed2002

Cell prestress. II. Contribution of microtubules.

The tensegrity model hypothesizes that cytoskeleton-based microtubules (MTs) carry compression as they balance a portion of cell contractile stress. To test this hypothesis, we used traction force microscopy to measure traction at the interface of adhering human airway smooth muscle cells and a flexible polyacrylamide gel substrate. The prediction is that if MTs balance a portion of contractile stress, then, upon their disruption, the portion of stress balanced by MTs would shift to the substrate, thereby causing an increase in traction. Measurements were done first in maximally activated cells (10 microM histamine) and then again after MTs had been disrupted (1 microM colchicine). We found that after disruption of MTs, traction increased on average by approximately 13%. Because in activated cells colchicine induced neither an increase in intracellular Ca(2+) nor an increase in myosin light chain phosphorylation as shown previously, we concluded that the observed increase in traction was a result of load shift from MTs to the substrate. In addition, energy stored in the flexible substrate was calculated as work done by traction on the deformation of the substrate. This result was then utilized in an energetic analysis. We assumed that cytoskeleton-based MTs are slender elastic rods supported laterally by intermediate filaments and that MTs buckle as the cell contracts. Using the post-buckling equilibrium theory of Euler struts, we found that energy stored during buckling of MTs was quantitatively consistent with the measured increase in substrate energy after disruption of MTs. This is further evidence supporting the idea that MTs are intracellular compression-bearing elements.

Acrylic Resins↗

PubMed2002

Effect of the cytoskeletal prestress on the mechanical impedance of cultured airway smooth muscle cells.

We investigated the effect of the cytoskeletal prestress (P) on the elastic and frictional properties of cultured human airway smooth muscle cells during oscillatory loading; P is preexisting tensile stress in the actin cytoskeleton generated by the cell contractile apparatus. We oscillated (0.1 Hz, 6 Pa peak to peak) small ferromagnetic beads bound to integrin receptors and computed the storage (elastic) modulus (G') and the loss (frictional) modulus (G") from the applied torque and the corresponding bead rotation. All measurements were done at baseline and after cells were treated with graded doses of either histamine (0.1, 1, 10 microM) or isoproterenol (0.01, 0.1, 1, 10 microM). Values for P for these concentrations were taken from a previous study (Wang et al., Am J Physiol Cell Physiol, in press). It was found that G' and G", as well as P, increased/decreased with increasing doses of histamine/isoproterenol. Both G' and G" exhibited linear dependences on P: G'(Pa) = 0.20P + 82 and G"(Pa) = 0.05P + 32. The dependence of G' on P is consistent with our previous findings and with the behavior of stress-supported structures. The dependence of G" on P is a novel finding. It could be attributed to a variety of mechanisms. Some of those mechanisms are discussed in detail. We concluded that, in addition to the central mechanisms by which stress-supported structures develop mechanical stresses, other mechanisms might need to be invoked to fully explain the observed dependence of the cell mechanical properties on the state of cell contractility.

Actins↗

PubMed2002

[Case control study on the risk factors of primary open angle glaucoma in China].

OBJECTIVE: The purpose of this study is to comprehensively explore the risk factors of primary open angle glaucoma (POAG) in China. METHODS: Two groups of data based on distinct resources were analyzed to explore the risk factors of POAG. One group of data was based on hospital records between 1995 and 2000 which composed of 107 patients with POAG and 149 controls without POAG. The other group of data was based on 40 patients with POAG and 120 matched controls without POAG. The former was designed by non-matched case control study, the latter was done by 1:3 matched case control study. The relationships between POAG and the factors such as age, sex, family history, diabetes, hypertension, intraocular pressure (IOP), cardiovascular diseases, smoking, drinking and mutation of TIGR gene were studied by logistic regression analysis. RESULTS: The simple factor analysis showed that the risk of POAG was related to age, family history, hypertension, IOP, cardiovascular diseases, smoking, drinking and the mutation of TIGR gene (T353I). However, logistic regression analysis confirmed that POAG mainly related to IOP, family history, hypertension, smoking, alcohol intake and the mutation of TIGR gene. CONCLUSION: The most important risk factor of POAG was IOP. Family history, hypertension, smoking and the mutation of TIGR gene were also important risk factors of POAG. However, alcohol intake was a protective factor for POAG.

Adolescent↗

PubMed2002

[Antibacterial effect of niaoluqing oral liquid on clinical drug-resistant strains and different serotype strains of Ureaplasma urealyticum in vitro].

OBJECTIVES: To study the antibacterial effect of Niaoluqing Oral Liquid (NOL) on clinical drug-resistant strains and 14 serotype strains Ureaplasma Urealyticum (UU). METHODS: Sixty-three clinical strains of UU were detected to determine their serology and antibiotic susceptibilities by the metabolic inhibition test (MIT). Mininum inhibitory concentration (MIC) was used to evaluate the sensitivity of NOL to different serotypes of UU. The sensitivity of NOL, erythromycin and tetracycline to 63 clinical strains of UU was also studied. RESULTS: In 63 clinical strains of UU, the range of MIC to NOL was from 0.48 mg/ml to 15.63 mg/ml, MIC50 < or = 1.95 mg/ml, MIC90 < or = 3.91 mg/ml. Among them, 31 strains were resistant to tetracycline and 31 were resistant to erythromycin. No obvious correlation between the sensitivity of NOL to UU clinical strains and that of erythromycin and tetracycline to UU clinical strains (P > 0.05). Clinical strains of UU in this experiment contains all of its serotypes, also having a higher sensitivity to NOL (MIC < or = 3.91 mg/ml) except serology 1, 2, 3 and 11 (MIC > or = 7.81 mg/ml). CONCLUSIONS: NOL exerts a strong in vitro antibacterial effect on erythromycin-resistant and tetracycline-resistant clinical strains of UU. All kinds of serotype strains had a higher sensitivity to NOL, too. Chinese medicinal herbs are of momentous significance in the treatment of UU infection.

Anti-Bacterial Agents↗

PubMed2002

[Experimental study on anti-thrombus effect of different extracts from Semen Persicae].

OBJECTIVE: To observe the effects of anti-thrombus of different extracts from Semen Persicae and provide experimental basis for finding and defining effective fraction of Semen Persicae. METHODS: The effects of different extracts from Semen Persicae on clotting time in mice, pulmonary embolism in mice and electro-irritate thrombosis in rats were observed. RESULT: Ethyl acetate extract from Semen Persicae could prolong clotting time in mice, markedly relieve respiratory difficult due to pulmonary embolism in mice induced by ADP-Na, obviously retard the generation of thrombosis induced by electrical injury of carotid artery in rats. CONCLUSION: Ethyl acetate extract from Semen Persicae possesses evidently anti-thrombotic effect.

Animals↗

PubMed2002

[Relationship between amount of HBV DNA in serum/liver tissue and hepatitis G virus (HGV) infection in patients with chronic hepatitis B].

OBJECTIVE: To observe the relationship between the amount of HBV DNA in serum/liver tissue and HGV infection in patients with chronic hepatitis B (CH-B) for exploring the effect of HGV infection on hepatitis B virus (HBV) replication of CH-B. METHODS: HGV RNA in serum, HGV nonstructural region 5 (NS5) antigen (HGV Ag) in liver tissue and the amount of HBV DNA in serum, liver tissue were detected for 56 patients with CH-B by reverse transcription-polymerase chain reaction (RT-PCR) assay, peroxidase antiperoxidase (PAP) immunohistochemical method and fluorescence quantitative PCR assay, respectively. Then the relationship between HGV Ag expression in liver tissue and HGV RNA expression in serum was analysed and the amount of HBV DNA in serum and liver tissues from the serum HGV RNA or liver tissue HGV Ag positive patients were compared with those of the serum HGV-RNA or liver tissue HGV Ag negative patients, respectively. RESULTS: Ten (17.9%) and eight (14.3%) patients were positive for serum and liver tissues,respectively.HGV RNA expression in serum was closely related to HGV Ag expression in liver tissues, but there was HGV RNA in serum from some of the liver tissues HGV Ag negative patients ?cases of HGV RNA and HGV Ag positive or negative,HGV RNA positive but HGV Ag negative, HGV RNA negative but HGV Ag positive, respectively: 5,43,5,3,(P<0.01). There was no significant difference in the amount of HBV DNA in serum and liver tissues between HGV RNA or HGV Ag positive and negative patients (P>0.05). CONCLUSIONS: HGV infection may not affect HBV replication. Liver is the site of HGV replication, but HGV probably also replicates in extrahepatic tissues. HGV hepatic pathogenicity is probably mild and further studies are still needed.

Adult↗

PubMed2002

[The adjustable, folding and multi-function mount].

An adjustable folding mount is presented in this paper. It is a multi-functional device for one or more patient's infusions, continuous traction and functional training, and life nursing etc.

Equipment and Supplies↗