Biomedical subjects

Dongsheng Wang

Publications and source records attributed to Dongsheng Wang.

At least 19 recordsLinked to original sources

PubMed2007

Na+-H+ exchanger regulatory factor 1 is a PDZ scaffold for the astroglial glutamate transporter GLAST.

Glutamate is a key neurotransmitter and its levels in the synaptic cleft are tightly regulated by reuptake mechanisms that primarily involve transporters in astrocytes. This requires that the glutamate transporters be spatially constrained to effect maximum glutamate transport. GLAST (EAAT1) is the predominant astroglial transporter and contains a class I PDZ-binding consensus (ETKM) in its C-terminus. The epithelial Na(+)/H(+) exchanger regulatory factors NHERF1 and NHERF2 are PDZ proteins that contain two tandem PDZ domains and a C-terminal domain that binds members of the ERM (ezrin-radixin-moesin) family of membrane-cytoskeletal adaptors. NHERF proteins have been extensively characterized in renal epithelia and their expression in brain has recently been reported; however, their function in the brain remains unknown. The aims of the current study were to (1) determine the distribution of NHERF1/2 in the rodent brain and (2) investigate whether GLAST was a physiological ligand for NHERF1/2. Immunohistochemistry revealed that NHERF1 expression was widespread in rat brain (abundant in cerebellum, cerebral cortex, hippocampus, and thalamus) and primarily restricted to astrocytes whereas NHERF2 expression was primarily restricted to endothelial cells of blood vessels and capillaries. Importantly, NHERF1 distribution closely matched that of GLAST and confocal imaging demonstrated co-localization of the two proteins. Co-immunoprecipitation demonstrated that GLAST, NHERF1, and ezrin associate in vivo. In vitro binding assays showed that GLAST bound directly to the PDZ1 domain of NHERF1 via the C-terminal ETKM motif of GLAST. These findings implicate the GLAST-NHERF1 complex in the regulation of glutamate homeostasis in astrocytes.

Animals↗

PubMed2007

Polarization multiplexing and demultiplexing for appearance-based modeling.

Polarization has been used in numerous prior studies for separating diffuse and specular reflectance components, but in this work we show that it also can be used to separate surface reflectance contributions from individual light sources. Our approach is called polarization multiplexing and it has a significant impact in appearance modeling where the image as a function of illumination direction is needed. Multiple unknown light sources can illuminate the scene simultaneously, and the individual contributions to the overall surface reflectance are estimated. Polarization multiplexing relies on the relationship between the light source direction and the intensity modulation. Inverting this transformation enables the individual intensity contributions to be estimated. In addition to polarization multiplexing, we show that phase histograms from the intensity modulations can be used to estimate scene properties including the number of light sources.

Algorithms↗

PubMed2006

Optimized coagulation of high alkalinity, low temperature and particle water: pH adjustment and polyelectrolytes as coagulant aids.

The Yellow River in winter as source water is characterized as high alkalinity, low temperature and low particle concentrations, which have brought many difficulties to water treatment plants. This study fully examines the optimized coagulation process of the Yellow River by conventional and pre-polymerized metal coagulants, pH adjustment and polyelectrolytes as the primary coagulants or coagulant aids. For all the metal coagulants, polyaluminum chlorides are superior to traditional metal coagulants due to their stable polymeric species and low consumption of alkalinity. The removal of natural organic matter by monomeric metal coagulants can be improved through pH adjustment, which is in accordance with the higher concentration of polymeric species formed at corresponding pH value. With the addition of polyelectrolytes as coagulant aids, the coagulation performance is significantly improved. The effective removal of dissolved organic matter is consistent with high charge density, while molecular weight is relatively important for removing particles, which is consistent with polyelectrolytes as primary coagulants. These results suggest that the coagulation mechanisms in the removal of dissolved organic matter and particles are different, which may be exploited for optimized coagulation for the typical source water in practice.

Alkalies↗

PubMed2006

Removal of direct dyes by coagulation: the performance of preformed polymeric aluminum species.

Removal of three direct dyes (Direct Black 19, Direct Red 28, and Direct Blue 86) by coagulation with three different Al based coagulants was investigated. The main purpose of this paper is to examine the coagulation features of polymeric aluminum coagulants in treatment of dye-polluted waters and the emphasis was placed on the roles of preformed Al species, particularly Al(13). The performance of Al(13) in coagulation of dyes was observed through jar tests by comparing traditional Al salt, polyaluminum chloride (PACl), and purified Al(13). The results showed that under most cases Al(13) had significantly higher efficiency in removal of direct dyes than traditional Al salt and commercial PACl with the exception of Direct Red 28 removal under high pH range. The coagulation of direct dyes could be greatly affected by pH. Reducing pH was favorable for preformed Al species in a broad pH range. For traditional Al coagulant, efficient dye removal only occurred in a relatively narrow pH range of near 6.0. The outstanding coagulation behavior of Al(13) could be ascribed to its high charge neutralization ability, relative stability and potential self-assembly tendency.

Aluminum Compounds↗

PubMed2006

Acute activation of NHE3 by dexamethasone correlates with activation of SGK1 and requires a functional glucocorticoid receptor.

Glucocorticoids stimulate the intestinal absorption of Na(+) and water partly by regulation of the Na(+)/H(+) exchanger 3 (NHE3). Previous studies have shown both genomic and nongenomic regulation of NHE3 by glucocorticoids. Serum and glucocorticoid-inducible kinase 1 (SGK1) has been shown to be part of this cascade, where phosphorylation of NHE3 by SGK1 initiates the translocation of NHE3 to the cell surface. In the present work, we examined a series of changes in SGK1 and NHE3 induced by glucocorticoids using human colonic Caco-2 and opossum kidney cells. We found that dexamethasone rapidly stimulated SGK1 mRNAs, but a significant change in protein abundance was not detected. Instead, there was an increase in SGK1 kinase activity as early as at 2 h. An increase in NHE3 protein abundance was not detected until 12 h of dexamethasone exposure, although the transport activity was significantly stimulated at 4 h. These data demonstrate that the changes of SGK1 precede those of NHE3. Chronic regulation (24 h) of NHE3 was blocked completely by prevention of protein synthesis with cycloheximide or actinomycin D and by the glucocorticoid receptor blocker RU486. The acute effect of dexamethasone was similarly abrogated by RU486, but was insensitive to cycloheximide and actinomycin D. Similarly, the stimulation of SGK1 activity by dexamethasone was blocked by RU486 but not by actinomycin D. Together, these data show that the acute effect of glucocorticoids on NHE3 is mediated by a glucocorticoid receptor dependent mechanism that activates SGK1 in a nongenomic manner.

Caco-2 Cells↗

PubMed2006

Enhanced coagulation in a typical North-China water treatment plant.

The characteristics of typical source waters in northern China and their enhanced coagulation features were studied in this paper. Through bench scale tests, a composite coagulant (HPAC) was selected for this kind of high alkalinity and pH water. It can be 30% more efficient in organic matter (OM) removal than the traditional coagulants (AlCl(3), FeCl(3)), and polyaluminum chloride (PACl), especially more efficient in removing high SUVA, hydrophobic and high molecular weight dissolved organic matter (DOM). It is found that some DOM with low SUVA has precedence over that with high SUVA to be removed at conventional dosages in some seasons, and that the priority of DOM removal is in the same sequence for all the coagulants. DOM with high SUVA is not always more easily removed. When applying HPAC as coagulant, flotation process can remove hydrophobic OM more efficiently than sedimentation process in pilot scale tests.

Aluminum Chloride↗

PubMed2006

MAGI-3 regulates LPA-induced activation of Erk and RhoA.

Lysophosphatidic acids (LPA) exert multiple biological effects through specific G protein-coupled receptors. The LPA-activated receptor subtype LPA(2) contains a carboxyl-terminal motif that allows interaction with PDZ domain-containing proteins, such as NHERF2 and PDZ-RhoGEF. To identify additional interacting partners of LPA(2), the LPA(2) carboxyl-terminus was used to screen a proteomic array of PDZ domains. In addition to the previously identified NHERF2, several additional LPA(2)-interacting PDZ domains were found. These included MAGI-2, MAGI-3 and neurabin. In the present work, we demonstrate the specific interaction between LPA(2) and MAGI-3, and the effects of MAGI-3 in colon cancer cells using SW480 as a cell model. MAGI-3 specifically bound to LPA(2), but not to LPA(1) and LPA(3). This interaction was mediated via the fifth PDZ domain of MAGI-3 interacting with the carboxyl-terminal 4 amino acids of LPA(2), and mutational alteration of the carboxyl-terminal sequences of LPA(2) severely attenuated its ability to bind MAGI-3. LPA(2) also associated with MAGI-3 in cells as determined by co-affinity purification. Overexpression of MAGI-3 in SW480 cells showed no apparent effect on LPA-induced activation of Erk and Akt. In contrast, silencing of MAGI-3 expression by siRNA drastically inhibited LPA-induced Erk activation, suggesting that the lack of an effect by overexpression was due to the high endogenous MAGI-3 level in these cells. Previous studies have shown that the cellular signaling elicited by LPA results in activation of the small GTPase RhoA by Galpha(12/13) - as well as Galpha(q)-dependent pathways. Overexpression of MAGI-3 stimulated LPA-induced RhoA activation, whereas silencing of MAGI-3 by siRNA resulted in a small but statistically significant decrease in RhoA activation. These results demonstrate that MAGI-3 interacts directly with LPA(2) and regulates the ability of LPA(2) to activate Erk and RhoA.

Cell Line, Tumor↗

PubMed2006

Morphological characterization of suspended particles under wind-induced disturbance in Taihu Lake, China.

Sediments are disturbed by wind frequently, especially in the shallow lakes. The characteristics of resuspended sediment particles in Taihu Lake were studied under different wind velocities. It showed that sediment particles suspended obviously and particle number in overlying water increased directly under high wind-induced disturbance. Suspended solid (SS) concentration was less than 50 mg/l when the wind velocity was below 3.0 m/s, however, it increased to more than 300 mg/l when the wind velocity was 10.0 m/s. Two methods were used to measure the fractal characteristics of particles. One was light scattering and the other was image analysis. The three-dimensional fractal dimensions of suspended particles, measured by light scattering, were between 2.26 and 2.44; correspondingly, the two-dimensional fractal dimensions, calculated by image analysis, were between 1.44 and 1.77. Moreover, the three-dimensional fractal dimensions were directly proportional to two-dimensional fractal dimensions. The characteristic length of particles was calculated by image analysis. The minimum characteristic length was close to 8.5 microm when the wind velocity was 1.5 m/s at 50 cm beneath lake surface, while, the maximum characteristic length was approximate to 24 microm when the wind velocity was 10 m/s at the depth of 150 cm.

China↗

PubMed2006

Characterization of the phosphate adsorption and morphology of sediment particles under simulative disturbing conditions.

The behavior of nutrient release and adsorption from sediments was influenced by hydrodynamic disturbance significantly. The resuspension/sedimentation processes of sediment particles and phosphate adsorption in Taihu Lake were investigated under different disturbing intensity by utilizing simulative conditions. The effect of morphological characteristics of suspended particles on phosphate adsorption was also studied. In order to elucidate the characteristics of particles suspended by disturbance, the size and structure of particles during different time were monitored on-line by using photometric dispersion and particles image analysis. The method of fractal geometry to explore the morphology characteristics of particles was also used. The results showed that sediments suspended obviously and the phosphate concentration of overlying water decreased rapidly when strong disturbance was applied. Moreover, two different disturbing conditions, one was static condition without wind and the other was weak disturbing intensity with slow wind velocity, following heavy disturbance were compared, and it turned out that the turbidity and phosphate concentration were lower in the latter because the size and the structure of suspended particles were more favorable in the latter disturbing condition. The flocculation index of suspended particles was 0.25 and characteristic length was 30 microm under 100 rpm disturbance; comparatively, when heavy disturbance increased to 120 rpm, the flocculation index grew up to 0.60 and the characteristic length was greater than 60 microm. The fractal dimensions of suspended particles were between 1.65 and 1.92.

Adsorption↗

PubMed2006

Regulation of albumin endocytosis by PSD95/Dlg/ZO-1 (PDZ) scaffolds. Interaction of Na+-H+ exchange regulatory factor-2 with ClC-5.

The constitutive reuptake of albumin from the glomerular filtrate by receptor-mediated endocytosis is a key function of the renal proximal tubules. Both the Cl- channel ClC-5 and the Na+-H+ exchanger isoform 3 are critical components of the macromolecular endocytic complex that is required for albumin uptake, and therefore the cell-surface levels of these proteins may limit albumin endocytosis. This study was undertaken to investigate the potential roles of the epithelial PDZ scaffolds, Na+-H+ exchange regulatory factors, NHERF1 and NHERF2, in albumin uptake by opossum kidney (OK) cells. We found that ClC-5 co-immunoprecipitates with NHERF2 but not NHERF1 from OK cell lysate. Experiments using fusion proteins demonstrated that this was a direct interaction between an internal binding site in the C terminus of ClC-5 and the PDZ2 module of NHERF2. In OK cells, NHERF2 is restricted to the intravillar region while NHERF1 is located in the microvilli. Silencing NHERF2 reduced both cell-surface levels of ClC-5 and albumin uptake. Conversely, silencing NHERF1 increased cell-surface levels of ClC-5 and albumin uptake, presumably by increasing the mobility of NHE3 in the membrane and its availability to the albumin uptake complex. Surface biotinylation experiments revealed that both NHERF1 and NHERF2 were associated with the plasma membrane and that NHERF2 was recruited to the membrane in the presence of albumin. The importance of the interaction between NHERF2 and the cytoskeleton was demonstrated by a significant reduction in albumin uptake in cells overexpressing an ezrin binding-deficient mutant of NHERF2. Thus NHERF1 and NHERF2 differentially regulate albumin uptake by mechanisms that ultimately alter the cell-surface levels of ClC-5.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Coagulation behavior of aluminum salts in eutrophic water: significance of Al13 species and pH control.

The coagulation behavior of aluminum salts in a eutrophic source water was investigated from the viewpoint of Al(III) hydrolysis species transformation. Particular emphasis was paid to the coagulation effect of Al13 species on removing particles and organic matter. The coagulation behavior of Al coagulants with different basicities was examined through jar tests and hydrolyzed Al(III) speciation distribution characterization in the coagulation process. The results showed that the coagulation efficiency of Al coagulants positively correlated with the content of Al13 in the coagulation process ratherthan in the initial coagulants. Aluminum chloride (AICl3) was more effective than polyaluminum chloride (PACI) in removing turbidity and dissolved organic matter in eutrophic water because AlCl3 could not only generate Al13 species but also function as a pH control agent in the coagulation process. The solidstate 27Al NMR spectra revealed that the precipitates formed from AlCl3 and PACl were significantly different and proved that the preformed Al13 polymer was more stable than the in situ formed one during the coagulation process. Through regulating Al speciation, pH control could improve the coagulation process especially in DOC removal, and AlCl3 benefited most from pH control.

Aluminum↗

PubMed2005

Coexpression of MAST205 inhibits the activity of Na+/H+ exchanger NHE3.

Recent studies have shown that accessory proteins that interact with the apical Na(+)/H+ exchanger NHE3 are a vital part of the dynamic nature of the Na(+)/H+ exchanger regulation. We have identified MAST205, a microtubule-associated serine/threonine kinase with a molecular mass of 205 kDa that interacts with NHE3. MAST205 contains a S/T kinase domain and a PDZ domain that mediates interaction with NHE3. Northern blot analysis showed that MAST205 is highly expressed in human and rat kidney. Expression in opossum kidney (OK) cells showed that MAST205 is predominantly expressed in the apical membrane of the cells. Immunohistochemical studies demonstrated the presence of MAST205 at the apical region of the renal proximal tubules. Heterologous expression of MAST205 in OK cells inhibited endogenous NHE3 activity, and this inhibition required the presence of the kinase domain of MAST205, since deletion of the kinase domain or a dominant-negative mutant of MAST205 did not affect the activity of NHE3. Consistent with these results, we found that MAST205 phosphorylated NHE3 under in vitro conditions. However, overexpression of MAST205 did not affect expression of NHE3 proteins, suggesting that the effect of MAST205 was not mediated by a decrease in NHE3 expression. These findings suggest that MAST205 regulates NHE3 activity and, although the precise mechanism is yet to be determined, MAST205 appears to inhibit NHE3 activity through a phosphorylation-dependent mechanism.

Animals↗

PubMed2005

Activation of NHE3 by dexamethasone requires phosphorylation of NHE3 at Ser663 by SGK1.

Glucocorticoids stimulate Na+ absorption by activation of the epithelial Na+/H+ exchanger NHE3 in the kidney and intestine. It has been thought that glucocorticoid-induced activation of NHE3 is solely dependent on transcriptional induction of the NHE3 gene. While the transcriptional regulation remains an essential part of the chronic effect of glucocorticoids, a previous study by us identified the serum- and glucocorticoid-inducible kinase 1 (SGK1) as an important component of the activation of NHE3 by glucocorticoids. In this work, we have demonstrated phosphorylation of NHE3 by SGK1 as the key mechanism for the stimulation of the transport activity by glucocorticoids. By using in vitro SGK1 kinase assay and site-directed mutagenesis, we have identified Ser663 of NHE3 to be the major site of phosphorylation by SGK1. Ser663 is invariantly conserved in all NHE3 proteins from several species, and the mutation of Ser663 to Ala blocks the effect of dexamethasone, demonstrating the importance of phosphorylation at Ser663. We also show that phosphorylation of NHE3 precedes the changes in NHE3 activity, and the increased activity is associated with an increased amount of NHE3 proteins in the surface membrane. These data reveal that dexamethasone activates NHE3 activity by phosphorylating the NHE3 protein, which initiates trafficking of the protein into the plasma membrane.

Amino Acid Sequence↗

PubMed2005

LPA2 receptor mediates mitogenic signals in human colon cancer cells.

Lysophosphatidic acid (LPA) is a mediator of multiple cellular responses. LPA mediates its effects predominantly through the G protein-coupled receptors LPA1, LPA2, and LPA3. In the present work, we studied LPA2-mediated signaling using human colon cancer cell lines, which predominantly express LPA2. LPA2 activated Akt and Erk1/2 in response to LPA. LPA mediated Akt activation was inhibited by pertussis toxin (PTX), whereas Erk1/2 activation was completely inhibited by a blocker of phospholipase Cbeta, U-73122. LPA also induced interleukin-8 (IL-8) synthesis in the colon cancer cells by primarily activating LPA2 receptor. We also found that LPA2 interacts with Na+/H+ exchanger regulatory factor 2 (NHERF2). Activation of Akt and Erk1/2 was significantly attenuated by silencing of NHERF2 expression by RNA interference, suggesting a pivotal role of NHERF2 in LPA2-mediated signaling. We found that expression of LPA2 was elevated, whereas expression of LPA1 downregulated in several types of cancers, including ovarian and colon cancer. We conclude that LPA2 is the major LPA receptor in colon cancer cells and cellular signals by LPA2 are largely mediated through its ability to interact with NHERF2.

Caco-2 Cells↗

PubMed2005

Phosphorus adsorption on natural sediments: modeling and effects of pH and sediment composition.

The classic Langmuir isotherm equation was modified to describe phosphorus (P) adsorption on P-polluted sediments. The P adsorption characteristics of six sediment samples from Chinese Taihu Lake were studied by short-term isotherm batch experiments and related to sediment composition. The maximum P adsorption capacities (PAC) and P-binding energy constant (k) were obtained by nonlinearly fitting sorption data using the modified Langmuir isotherm model. Native adsorbed exchangeable phosphorus (NAP), the zero equilibrium P concentration value (EPC(0)), and partitioning coefficients (K(p)) were subsequently calculated by corresponding formulae. K(p) and PAC were linearly related to the contents of active Fe and Al in sediments by least squares regression analyses (R(2) approximately 0.9 for both). The effect of pH in a wide range on adsorption process was investigated and H2PO4- was presumed to be the preferential sorption species in overall sorption process. The fact that the amount of P sorbed and zeta potential of sediment particles have no necessary relationship reveals that a strong contribution to the P binding still comes from a ligand-exchange process on the Me-OH(2+) and Me-OH sites rather than electrostatic attraction. In addition, the influence of oxidation-reduction potential (ORP) was investigated and discussed and the dual nature of sediments as a pool or source of P in natural waters was evaluated in site T1-T4.

Adsorption↗

PubMed2005

Removal of earthy-musty odorants in drinking water by powdered activated carbon.

The removal of four earthy-musty compounds, 2-methylisoborneol (MIB), 2,4,6-trichloroanisole (TCA), 2-isopropyl-3-methoxy-pyrazine (IPMP), and 2-isobutyl-3-methoxy-pyrazine (IBMP), by powdered activated carbon (PAC) were investigated under the simulative condition of Xicun water plant, Guangzhou. The adsorption kinetics of odor compounds by two PACs show that main removal of odor compounds occurs within contact time of 1 h. Compared with the wood-based PAC, the coat-based PAC evidently improves the removal efficiency of poorly adsorbed compounds like MIB. The effects on removal efficiency such as optimum PAC dosage, initial concentration of the organics, chlorine residual, background organics, and changes of water quality were investigated. The percent removal of trace odorants at any given time for a particular carbon dosage is irrelative to the initial concentration of the odor compounds. Adsorptive capacity of PAC for target compounds is reduced by chlorine residual and background organics. Characteristics of raw water have vast influence on the removal of target compounds by PAC.

Adsorption↗

PubMed2004

Formation of PCDD/Fs and PCBs in the process of production of 1,4-dichlorobenzene.

The occurrence and distribution of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) in a typical process of production of 1,4-dichlorobenzene (p-DCB) were investigated systematically in this study. P5CDFs and H6CDFs were the main congeners of PCDD/Fs, while only low levels of other PCDD/Fs were detected in the samples. The concentrations of PCBs were up to 4614 ng/g in the semi-manufactured products, and 1797 ng/g in the product p-DCB. It was also found that high chlorinated PCB congeners increased with the further chlorination. The levels of PCDD/Fs decreased obviously in the purification process, while PCBs could not be removed effectively. Polychlorophenols and other important dioxin precursors (1,4-dichloro-2-phenoxybenzene and 2-phenyl-2',5,5'-trichlorophenol) were also analyzed. Polychlorophenols which ortho- and para-positions of the hydroxyl were substituted by chlorine were the main congeners. In addition, a possible pathway of the formation of PCDD/Fs and PCBs in the production of p-DCB was presented. The results of this article suggest that re-estimation on the risk of using p-DCB products, especially the products for daily use such as mothballs, is expected.

Benzofurans↗

PubMed2003

[The application of polyferric chloride in micro-flocculation deep bed filtration].

Compared with polyaluminium chloride (PAC), the application efficiency of polyferric chloride (PFC) were investigated by pilot micro-flocculation deep bed filtration. The results show that, under the condition of lower dosage (Fe:Al = 3:5), the headloss cycle of PFC was 63 h, and its output in a cycle was 1504 m3/m2, but PAC headloss cycle was 53 h with its output 1266 m3/m2. It is concluded that PFC was benefit to prolong operation cycle and improve output. The research on particle removal mechanism shows that PFC could enhance the floc growth, and the PFC flocs could be effectively entrapped and dehydrated. Therefore PFC is more suitable for the micro-flocculation deep bed filtration process than PAC.

Aluminum Chloride↗