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101.
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Claudia Siegl Patricia Hamminger Herbert Jank Uwe Ahting Benedikt Bader Adrian Danek Allison Gregory Monika Hartig Susan Hayflick Andreas Hermann Holger Prokisch Esther M. Sammler Zuhal Yapici Rainer Prohaska Ulrich Salzer 《PloS one》2013,8(10)
Neuroacanthocytosis (NA) refers to a group of heterogenous, rare genetic disorders, namely chorea acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington’s disease-like 2 (HDL2) and pantothenate kinase associated neurodegeneration (PKAN), that mainly affect the basal ganglia and are associated with similar neurological symptoms. PKAN is also assigned to a group of rare neurodegenerative diseases, known as NBIA (neurodegeneration with brain iron accumulation), associated with iron accumulation in the basal ganglia and progressive movement disorder. Acanthocytosis, the occurrence of misshaped erythrocytes with thorny protrusions, is frequently observed in ChAc and MLS patients but less prevalent in PKAN (about 10%) and HDL2 patients. The pathological factors that lead to the formation of the acanthocytic red blood cell shape are currently unknown. The aim of this study was to determine whether NA/NBIA acanthocytes differ in their functionality from normal erythrocytes. Several flow-cytometry-based assays were applied to test the physiological responses of the plasma membrane, namely drug-induced endocytosis, phosphatidylserine exposure and calcium uptake upon treatment with lysophosphatidic acid. ChAc red cell samples clearly showed a reduced response in drug-induced endovesiculation, lysophosphatidic acid-induced phosphatidylserine exposure, and calcium uptake. Impaired responses were also observed in acanthocyte-positive NBIA (PKAN) red cells but not in patient cells without shape abnormalities. These data suggest an “acanthocytic state” of the red cell where alterations in functional and interdependent membrane properties arise together with an acanthocytic cell shape. Further elucidation of the aberrant molecular mechanisms that cause this acanthocytic state may possibly help to evaluate the pathological pathways leading to neurodegeneration. 相似文献
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104.
Synaptic clustering on dendritic branches enhances plasticity, input integration and neuronal firing. However, the mechanisms guiding axons to cluster synapses at appropriate sites along dendritic branches are poorly understood. We searched for such a mechanism by investigating the structural overlap between dendritic branches and axons in a simplified model of neuronal networks - the hippocampal cell culture. Using newly developed software, we converted images of meshes of overlapping axonal and dendrites into topological maps of intersections, enabling quantitative study of overlapping neuritic geometry at the resolution of single dendritic branch-to-branch and axon-to-branch crossings. Among dendro-dendritic crossing configurations, it was revealed that the orientations through which dendritic branches cross is a regulated attribute. While crossing angle distribution among branches thinner than 1 µm appeared to be random, dendritic branches 1 µm or wider showed a preference for crossing each other at angle ranges of either 50°–70° or 80°–90°. It was then found that the dendro-dendritic crossings themselves, as well as their selective angles, both affected the path of axonal growth. Axons displayed 4 fold stronger tendency to traverse within 2 µm of dendro-dendritic intersections than at farther distances, probably to minimize wiring length. Moreover, almost 70% of the 50°–70° dendro-denritic crossings were traversed by axons from the obtuse angle’s zone, whereas only 15% traversed through the acute angle’s zone. By contrast, axons showed no orientation restriction when traversing 80°–90° crossings. When such traverse behavior was repeated by many axons, they converged in the vicinity of dendro-dendritic intersections, thereby clustering their synaptic connections. Thus, the vicinity of dendritic branch-to-branch crossings appears to be a regulated structure used by axons as a target for efficient wiring and as a preferred site for synaptic clustering. This synaptic clustering mechanism may enhance synaptic co-activity and plasticity. 相似文献
105.
The structure of a two-dimensional film formed by adsorbed polymer chains was studied by means of Monte Carlo simulations. The polymer chains were represented by linear sequences of lattice beads and positions of these beads were restricted to vertices of a two-dimensional square lattice. Two different Monte Carlo methods were employed to determine the properties of the model system. The first was the random sequential adsorption (RSA) and the second one was based on Monte Carlo simulations with a Verdier-Stockmayer sampling algorithm. The methodology concerning the determination of the percolation thresholds for an infinite chain system was discussed. The influence of the chain length on both thresholds was presented and discussed. It was shown that the RSA method gave considerably lower thresholds for longer chains. This behavior can be explained by a different pool of chain conformations used in the calculations in both methods under consideration. Figure
The percolation cluster (in red) in the system consisting of long flexible chains 相似文献
106.
Marcus Bär Joachim Klaer Lothar Weinhardt Regan G. Wilks Stefan Krause Monika Blum Wanli Yang Clemens Heske Hans‐Werner Schock 《Liver Transplantation》2013,3(6):777-781
The surface properties of CuInS2 (CIS) thin‐film solar cell absorbers are investigated by a combination of electron and soft X‐ray spectroscopies. Spatially separated regions of varying colors are observed and identified to be dominated by either CuS or Cu2S surface phases. After their removal by KCN etching, the samples cannot be distinguished by eye and the CIS surface is found to be Cu‐deficient in both regions. However, a significantly more pronounced off‐stoichiometry in the region initially covered by Cu2S can be identified. In this region, the resulting surface band gap is also significantly larger than the EgSurf of the initially CuS‐terminated region. Such variations may represent a hidden parameter which, if overlooked, induces irreproducibility and thus prevents systematic optimization efforts. 相似文献
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109.
Michal Ciolkowski Monika Rozanek Maria BryszewskaBarbara Klajnert 《Biochimica et Biophysica Acta - Proteins and Proteomics》2013,1834(10):1982-1987
In this study the ability of three polyamidoamine (PAMAM) dendrimers with different surface charge (positive, neutral and negative) to interact with a negatively charged protein (porcine pepsin) was examined. It was shown that the dendrimer with a positively charged surface (G4 PAMAM-NH2), as well as the dendrimer with a neutral surface (G4 PAMAM-OH), were able to inhibit enzymatic activity of pepsin. It was also found that these dendrimers act as mixed partially non-competitive pepsin inhibitors. The negatively charged dendrimer (G3.5 PAMAM-COOH) was not able to inhibit the enzymatic activity of pepsin, probably due to the electrostatic repulsion between this dendrimer and the protein. No correlation between changes in enzymatic activity of pepsin and alterations in CD spectrum of the protein was observed. It indicates that the interactions between dendrimers and porcine pepsin are complex, multidirectional and not dependent only on disturbances of the secondary structure. 相似文献
110.
Thomas Jans Erika Graf Christian Jacob Ulrike Zwanzger Silke Groß-Lesch Swantje Matthies Evgeniy Perlov Klaus Hennighausen Melanie Jung Michael Rösler Monika Schulte-Altedorneburg Alexander von Gontard Susann Hänig Esther Sobanski Barbara Alm Luise Poustka Lucia Bliznak Michael Colla Laura Gentschow Roland Burghardt Harriet Salbach-Andrae Katja Becker Martin Holtmann Christine Freitag Andreas Warnke Alexandra Philipsen 《Attention deficit and hyperactivity disorders》2013,5(1):29-40