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ABSTRACT: Dopaminergic and glutamatergic afferents simultaneously innervate median spiny neurons (MSNs) and interact to mediate basal ganglia functions. However, the association between dopaminergic and glutamatergic axons is not clear. In the present study, nigrostriatal, corticostriatal, and thalamostriatal axons were anterogradely traced with biotinylated dextran amines (BDA) in rats, and MSNs were labeled with chloromethylbenzamido-DiI for neurogeometric analysis. Results showed that nigrostriatal, but not corticostriatal or thalamostriatal, axons were biased to a target on dendritic spines of the MSNs. In addition, the MSN dendritic spines, which were innervated by tyrosine hydroxylase-immunoreactive (TH-IR) axons and vesicular glutamate transporter 1 or 2-immunoreactive (VGluT-IR) terminals, were significantly larger than dendritic spines innervated by VGluT-IR terminals alone. Under electron microscopy, glutamatergic synapses on the dendritic spines were located with TH-IR terminals and displayed longer postsynaptic density. In addition, these synapses were more perforated than those on dendritic spines lacking innervated TH-IR terminals. These results demonstrated that dopaminergic axons were biased to a target and preferred to innervate dendritic spines with hyperactive and high-efficacy glutamatergic synapses in the striatum.
Brain research 09/2012; · 2.46 Impact Factor
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ABSTRACT: Parkinson's disease (PD) is a common neurodegenerative disease, characterized by a selective loss of midbrain Dopaminergic (DA) neurons. To address this problem, various types of stem cells that have potential to differentiate into DA neurons are being investigated as cellular therapies for PD, including cells derived from embryonic or adult donor tissue, and embryonic stem cells. These cell sources, however, have raised certain questions with regard to ethical and rejection issues. Recent progress in adult stems has further proved that the cells derived from adult tissue could be expanded and differentiated into DA precursor cells in vitro, and cell therapy with adult stem cells could produce a clear improvement for PD models. Using adult stem cells for clinic application may not only overcome the ethical problem inherent in using human fetal tissue or embryonic stem cells, but also open the possibility for autologous transplantation. The patient-specific adult stem cell is therefore a potential and prospective candidate for PD treatment.
CNS & neurological disorders drug targets 06/2011; 10(4):509-16. · 3.57 Impact Factor
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ABSTRACT: The orientation (vertical or horizontal) of cell division is known to be critical for neural cell fate determination during neurogenesis. At the onset of neurogenesis, neurogenic progenitor cells are dividing with the cleavage plane parallel to the ventricular surface (horizontal division), which would lead to critical apical components being unequally distributed to both their two daughter cells. The daughter cells lack of inheritance is going to differentiate into the neuron. Recent studies have shown that GAP-43 is highly expressed in horizontally dividing neural progenitor cells in the forebrain of mammals. Based on findings from in vivo studies, GAP-43 is locally associated with the centrosome and is required for centrosome positioning, suggesting that GAP-43 may be involved in neurogenesis through regulating the orientation of cell division. With a fibroblast cell model, our results show that both GFP expressing and control cells had the same potential (p>0.05) with regard to dividing orientation (either vertical or horizontal to the cells long axis). On the other hand, we found that GAP-43 was localized on the membrane instead of the centrosome during all phases of mitosis within GAP-43 transgenic cells, but expressing of GAP-43 could make the cells dividing more likely along their long axis (p<0.05). Our observations suggest that GAP-43 might link the cell membrane and spindle pole and consequently participate in controlling cleavage orientation during cell division.
International journal of developmental neuroscience: the official journal of the International Society for Developmental Neuroscience 02/2011; 29(4):469-74. · 2.03 Impact Factor
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Xin Li,
Kunlun Hong,
Yun Liu,
Chwen-Yang Shew,
Emily Liu,
Kenneth W Herwig,
Gregory S Smith, Junpeng Zhao,
Guangzhao Zhang,
Stergios Pispas,
Wei-Ren Chen
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ABSTRACT: We develop an experimental approach to analyze the water distribution around a core-shell micelle formed by polystyrene-block-poly[styrene-g-poly(ethylene oxide (PEO)] block copolymers in aqueous media at a fixed polymeric concentration of 10 mg/ml through contrast variation small angle neutron scattering (SANS) study. Through varying the D(2)O/H(2)O ratio, the scattering contributions from the water molecules and the micellar constituent components can be determined. Based on the commonly used core-shell model, a theoretical coherent scattering cross section incorporating the effect of water penetration is developed and used to analyze the SANS I(Q). We have successfully quantified the intramicellar water distribution and found that the overall micellar hydration level increases with the increase in the molecular weight of hydrophilic PEO side chains. Our work presents a practical experimental means for evaluating the intramacromolecular solvent distributions of general soft matter systems.
The Journal of chemical physics 10/2010; 133(14):144912. · 3.09 Impact Factor
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ABSTRACT: Thermoresponsive brush copolymers with poly(propylene oxide)-block-poly(ethylene oxide) side chains were synthesized via a “grafting from” technique. Near-monodisperse poly(p-hydroxystyrene) was used as the backbone, and the brush copolymers were prepared by sequential metal-free anionic ring-opening polymerization of the oxyalkylene monomers, using the phosphazene base (t-BuP4) and the phenolic hydroxyl groups in the backbone to generate the complex multifunctional initiating system. The length and composition of the side chains were varied by changing the feed ratios of the backbone and the side-chain monomers. By inverting the sequence of the monomer addition, two different molecular structures were achieved, with either poly(propylene oxide) or poly(ethylene oxide) linked to the backbone. In all cases, brush copolymers with high molecular weights and low molecular weight distributions were synthesized. The thermoresponsive behavior of the brush copolymers in dilute aqueous solutions was investigated by dynamic/static light scattering and fluorescence measurements. Temperature-induced intramolecular chain contraction/association and intermolecular aggregation could both be observed at different stages of the heating process. Intermolecular aggregation was more pronounced for the sample with the poly(propylene oxide) blocks located at the periphery. The results from fluorescence spectroscopy indicate the incompletely solvated state of the brush copolymer in aqueous solution at low temperature and the absence of compact hydrophobic domains in some of the aggregates due to the core−shell brushlike molecular structure of the copolymers.
01/2010;
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ABSTRACT: This work presents the synthesis of polystyrene-block-poly(p-hydroxystyrene-graft-ethylene oxide), PS-b-(PHOS-g-PEO), amphiphilic block−graft copolymers. The backbone diblock copolymers (PS-b-PHOS) were prepared by lithium-based anionic polymerization, followed by postpolymerization acid hydrolysis of the poly(p-tert-butoxystyrene), PtBOS, precursor block. The PEO side chains were synthesized by metal-free anionic ring-opening polymerization of ethylene oxide (EO), using the phosphazene base (t-BuP4) and the phenolic hydroxyl groups (PhOH) in the backbones as the complex multifunctional initiating system. In all cases, starlike block−graft copolymers with high molecular weights and low polydispersities were synthesized. Well-controlled polymerization was achieved even with the molar ratio of t-BuP4 to PhOH being equal to 0.2. Dynamic and static light scattering and fluorescence spectroscopy studies were carried out to investigate the solution behavior of the amphiphilic block−graft copolymers, including the critical micelle concentration and structural characteristics of the aggregates formed in aqueous solutions. Because of the high PEO content and the starlike macromolecular architecture, the PS-b-(PHOS-g-PEO) block−graft copolymers form highly swelled aggregates with low aggregation numbers, having nanostructures resembling hyperbranched clusters.
11/2009;
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ABSTRACT: It has been demonstrated that during neurogenesis in the mammalian brain, cell-cycle lengthening in neuronal progenitors may cause them to switch from proliferation to neuron-generating division. However, little is known about the cellular mechanisms involved in lengthening of the cell cycle. Growth-associated protein-43 (GAP-43) is a nervous system-specific protein whose expression in proliferating neuroblasts is related to neurogenesis. In this study, we investigated the effect of GAP-43 on cell-cycle progression in transgenic fibroblast cells. Using cumulative bromodeoxyuridine labeling, cell-cycle kinetics in GAP-43-transgenic and control NIH 3T3 cells were analyzed. Our data demonstrate that expression of GAP-43 in fibroblasts results in lengthening of the cell cycle compared to control fibroblasts. The mechanism by which GAP-43 mediated this effect appeared to involve increasing the time spent by the cells in the G(1) phase of the cell cycle.
International journal of developmental neuroscience: the official journal of the International Society for Developmental Neuroscience 08/2009; 27(6):531-7. · 2.03 Impact Factor
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ABSTRACT: Low-molecular-weight cationic surfactants, dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB), were introduced to dilute aqueous solutions of thermosensitive poly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PEO-b-PNIPAM) block copolymers at concentrations (C(s)) either lower or higher than the critical micelle concentrations (cmc) of the surfactants. The copolymer/surfactant mixtures were investigated by dynamic and static light scattering at different temperatures. At temperature lower than the aggregation temperature (T(agg)), the disaggregation of the copolymers from the loose associations was observed upon addition of the surfactants(.) The thermo-induced aggregation behavior was found to be profoundly influenced with the cooperation of cationic surfactants in terms of T(agg) and the structural characteristics of the aggregates formed at high temperature. In general, T(agg) was increased together with the decrease in the size and molecular weight of the aggregates. These were attributed to the copolymer/surfactant interactions and the electrostatic repulsion coming from the ionic head groups of the surfactants within the mixed aggregates. These changes were much more pronounced at higher C(s). CTAB, which has a longer hydrophobic tail, displayed higher influences compared to DTAB. The formation of vesicles, by one of the copolymers, was suppressed in the presence of CTAB. At the higher CTAB concentration, only small mixed aggregates with very low mass were observed even at the highest temperature investigated.
The Journal of Physical Chemistry B 08/2009; 113(31):10600-6. · 3.70 Impact Factor
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Journal of Polymer Science Part A Polymer Chemistry 07/2009; 47(16):4099 - 4110. · 3.92 Impact Factor
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ABSTRACT: The effects of temperature, pH, and salt concentration on the layer-by-layer (LBL) deposition of sodium poly(styrene sulfonate) (PSS)/poly[2-(dimethylamino)ethyl methacrylate] (PDEM) were investigated by use of a quartz crystal microbalance with dissipation (QCM-D). At pH 4, the frequency change (Deltaf) gradually decreased to a constant, indicating that the polyelectrolyte complexes of the layer were not dissolved. As the layer number increased, the -Deltaf oscillatedly increased, indicating that the thickness of the multilayer increased. At the same time, the dissipation change (DeltaD) oscillatedly increased with the layer number, indicating the chain interpenetration or complexation that led to the alternative swelling-and-shrinking of the outermost layer. For the same layer number, as the temperature increased, the amplitude of DeltaD increased, indicating that the chain interpenetration increased. The thickness also increased with temperature. Further increasing the pH to 7 led to a thicker layer, reflected in the larger amplitude of DeltaD. At pH 10, the polyelectrolytes no longer formed multilayers on the surface because of the lack of electrostatic interactions. On the other hand, the addition of NaCl also led to a thickness increase. The amplitude in DeltaD increased with NaCl concentration, indicating that the chain interpenetration increased. Our experiments indicated that the LBL deposition of polyelectrolytes was dominated by the chain interpenetration. Also, the polyelectrolyte complexes in the layer can redissolve into solution from the surface at a high temperature or a high salt concentration.
The Journal of Physical Chemistry B 04/2008; 112(11):3333-8. · 3.70 Impact Factor
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ABSTRACT: Microporous polypropylene (PP) hollow fiber (PPHF) membranes with surface-grafted block copolymer brushes of poly(ethylene glycol) monomethacrylate (PEGMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) (PPHF-g-(PPEGMA-b-PDMAEMA)) were prepared via consecutive surface-initiated atom transfer radical polymerization (ATRP). The effective pore size of the surface modified PPHF membranes could be adjusted by controlling the graft chain length, or the ATRP time. Quaternization of the tertiary amine groups of the PDMAEMA block with 1-bromododecane gave rise to a high concentration of quaternary amine salt (QAS) on the PPHF membrane surface. The antibacterial effect of the quaternized PPHF-g-(PPEGMA-b-PDMAEMA) membrane was assayed with Escherichia coli (E. coli, a Gram-negative bacterium) and Staphylococcus aureus (S. aureus, a Gram-positive bacterium) cultures. In addition to bactericidal properties, the functionalized membrane surface also exhibited anti-fouling effect for bacteria due to the hydrophilic nature of the P(PEGMA) block on the PPHF-g-(PPEGMA-b-PDMAEMA) membrane. The permanence of antibacterial effect of the functionalized PPHF membrane was also demonstrated in repeated applications of the quaternized PPHF-g-(P(PEGMA)-b-PDMAEMA) membrane.
Journal of Membrane Science.
