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221.
Sabine Hauert Laurent Winkler Jean-Christophe Zufferey Dario Floreano 《Swarm Intelligence》2008,2(2-4):167-188
Swarming without positioning information is interesting in application-oriented systems because it alleviates the need for sensors which are dependent on the environment, expensive in terms of energy, cost, size and weight, or unusable at useful ranges for real-life scenarios. This principle is applied to the development of a swarm of micro air vehicles (SMAVs) for the deployment of ad hoc wireless communication networks (SMAVNETs) between ground users in disaster areas. Rather than relying on positioning information, MAVs rely on local communication with immediate neighbors and proprioceptive sensors which provide heading, speed and altitude. To solve the challenging task of designing agent controllers to achieve the swarm behavior of the SMAVNET, inspiration is taken from army ants which are capable of laying and maintaining pheromone paths leading from their nest to food sources in nature. This is analogous to the deployment of communication pathways between multiple ground users. However, instead of being physically deposited in the air or on a map, pheromone is virtually deposited on the MAVs using local communication. This approach is investigated in 3D simulation in a simplified scenario with two ground users. 相似文献
222.
Hsp60 regulation of tumor cell apoptosis 总被引:2,自引:0,他引:2
Molecular chaperones may promote cell survival, but how this process is regulated, especially in cancer, is not well understood. Using high throughput proteomics screening, we identified the cell cycle regulator and apoptosis inhibitor survivin as a novel protein associated with the molecular chaperone Hsp60. Acute ablation of Hsp60 by small interfering RNA destabilizes the mitochondrial pool of survivin, induces mitochondrial dysfunction, and activates caspase-dependent apoptosis. This response involves disruption of an Hsp60-p53 complex, which results in p53 stabilization, increased expression of pro-apoptotic Bax, and Bax-dependent apoptosis. In vivo, Hsp60 is abundantly expressed in primary human tumors, as compared with matched normal tissues, and small interfering RNA ablation of Hsp60 in normal cells is well tolerated and does not cause apoptosis. Therefore, Hsp60 orchestrates a broad cell survival program centered on stabilization of mitochondrial survivin and restraining of p53 function, and this process is selectively exploited in cancer. Hsp60 inhibitors may function as attractive anticancer agents by differentially inducing apoptosis in tumor cells. 相似文献
223.
Bellezza G Colella R Sidoni A Del Sordo R Ferri I Cioccoloni C Cavaliere A 《Histology and histopathology》2008,23(9):1127-1130
Granular cell tumor (GCT) is a relatively rare neoplasm, usually located in the upper aerodigestive tract, skin and soft tissue. Because of its uncertain histogenesis, GCT has been the object of many immunohistochemical and ultrastructural studies that have suggested a Schwann cell origin. Our recent observation of a case of GCT immunoreactive for Galectin-3 and HBME-1 led us to further investigate the immunohistochemical profile of these neoplasms. We evaluated the immunohistochemical expression of the traditional markers for GCT (S-100, CD68) along with new markers (Galectin-3, HBME-1, Calretinina and Inhibin-alpha) in 22 granular cell tumors. Our results showed, in all cases, a constant diffuse positivity for S-100 protein, CD68 and Galectin-3. HBME-1 was positive in 95% of cases. The present study gives a new immunophenotypic profile for GCT, which could help pathologists in distinguishing morphologically ambiguous granular lesions in unusual sites. 相似文献
224.
225.
Ricchiuto P Rocco AG Gianazza E Corrada D Beringhelli T Eberini I 《Journal of molecular recognition : JMR》2008,21(5):348-354
Chicken liver bile acid binding protein (cL-BABP) crystallizes with water molecules in its binding site. To obtain insights on the role of internal water, we performed two 100 ns molecular dynamics (MD) simulations in explicit solvent for cL-BABP, as apo form and as a complex with two molecules of cholic acid, and analyzed in detail the dynamics properties of all water molecules. The diffusion coefficients of the more persistent internal water molecules are significantly different from the bulk, but similar between the two protein forms. A different number of molecules and a different organization are observed for apo- and holo-cL-BABP. Most water molecules identified in the binding site of the apo-crystal diffuse to the bulk during the simulation. In contrast, almost all the internal waters of the holo-crystal maintain the same interactions with internal sidechains and ligands, which suggests they have a relevant role in protein-ligand molecular recognition. Only in the presence of these water molecules we were able to reproduce, by a classical molecular docking approach, the structure of the complex cL-BABP::cholic acid with a low ligand root mean square deviation (RMSD) with respect to its reference positioning. Literature data reported a conserved pattern of hydrogen bonds between a single water molecule and three amino acid residues of the binding site in a series of crystallized FABP. In cL-BABP, the interactions between this conserved water molecule and the three residues are present in the crystal of both apo- and holo-cL-BABP but are lost immediately after the start of molecular dynamics. Copyright (c) 2008 John Wiley & Sons, Ltd. 相似文献
226.
Fernández D Bertoldi MV Gómez L Morales A Callegari E Lopez LA 《Biology of reproduction》2008,79(6):1210-1218
In the mammalian testis, peritubular myoid cells (PMCs) surround seminiferous tubules. These cells are contractile, express the cytoskeletal markers of true smooth muscle-alpha-isoactin and F-actin-and participate in the contraction of seminiferous tubules during the transport of spermatozoa and testicular fluid to the rete testis. Myosin from PMCs (PMC-myosin) was isolated from adult rat testis and purified by cycles of assembly-disassembly and sucrose gradient centrifugation. PMC-myosin was recognized by a monoclonal anti-smooth muscle myosin antibody, and the peptide sequence shared partial homology with rat smooth muscle myosin-II, MYH11 (also known as SMM-II). Most PMC-myosin (95%) was soluble in the PMC cytosol, and purified PMC-myosin did not assemble into filaments in the in vitro salt dialysis assay at 4 degrees C, but did at 20 degrees C. PMC-myosin filaments are stable to ionic strength to the same degree as gizzard MYH11 filaments, but PMC-myosin filaments were more unstable in the presence of ATP. When PMCs were induced to contract by endothelin 1, a fraction of the PMC-myosin was found to be involved in the contraction. From these results we infer that PMCs express an isoform of smooth muscle myosin-II that is characterized by solubility at physiological ionic strength, a requirement for high temperature to assemble into filaments in vitro, and instability at low ATP concentrations. PMC-myosin is part of the PMC contraction apparatus when PMCs are stimulated with endothelin 1. 相似文献
227.
Hald S Pribil M Leister D Gallois P Johnson GN 《Biochimica et biophysica acta》2008,1777(9):1173-1183
Photosynthetic electron transport can involve either a linear flow from water to NADP, via Photosystems (PS) II and I or a cyclic flow just involving PSI. Little is known about factors regulating the relative flow through each of these pathways. We have examined photosynthetic electron transport through each system in plants of Arabidopsis thaliana in which either the PSI-D1 or PSI-E1 subunits of PSI have been knocked out. In both cases, this results in an imbalance in the turnover of PSI and PSII, such that PSII electron transport is limited by PSI turnover. Phosphorylation of light-harvesting complex II (LHCII) and its migration to PSI is enhanced but only partially reversible and not sufficient to balance photosystem turnover. In spite of this, cyclic electron flow is able to compete efficiently with PSI across a range of conditions. In dark-adapted leaves, the efficiency of cyclic relative to linear flow induced by far-red light is increased, implying that the limiting step of cyclic flow lies in the re-injection of electrons into the electron transport chain. Illumination of leaves with white light resulted in transient induction of a significant non-photochemical quenching in knockout plants which is probably high energy state quenching induced by cyclic electron flow. At high light and at low CO(2), non-photochemical quenching was greater in the knockout plants than in the wildtype. Comparison of PSI and PSII turnover under such conditions suggested that this is generated by cyclic electron flow around PSI. We conclude that, when the concentration of PSI is limiting, cyclic electron flow is still able to compete effectively with linear flow to maintain a high DeltapH to regulate photosynthesis. 相似文献
228.
Modelling metapopulations with stochastic membrane systems 总被引:2,自引:0,他引:2
Metapopulations, or multi-patch systems, are models describing the interactions and the behavior of populations living in fragmented habitats. Dispersal, persistence and extinction are some of the characteristics of interest in ecological studies of metapopulations. In this paper, we propose a novel method to analyze metapopulations, which is based on a discrete and stochastic modelling framework in the area of Membrane Computing. New structural features of membrane systems, necessary to appropriately describe a multi-patch system, are introduced, such as the reduction of the maximal parallel consumption of objects, the spatial arrangement of membranes and the stochastic creation of objects. The role of the additional features, their meaning for a metapopulation model and the emergence of relevant behaviors are then investigated by means of stochastic simulations. Conclusive remarks and ideas for future research are finally presented. 相似文献
229.
Gentile Francesco Ficetola Dario Furlani Giorgio Colombo Fiorenza De Bernardi 《Biodiversity and Conservation》2008,17(9):2185-2195
Secondary forests constitute a growing portion of forested areas worldwide. They might have a substantial role for the conservation
of biodiversity in tropical areas, but there is little information on their potential to support forest species and the recovery
of faunal communities. We studied two forest frogs (Eleutherodactylus diastema and E. fitzingeri) in an area of Costa Rica composed of a mosaic of primary forest, young secondary forest and pasture, and we compared the
density of calling males in areas with different forest alteration. Autoregressive models were used to compensate for potentially
undesired effects of spatial autocorrelation and pseudoreplication. Both species were most abundant in riparian, primary forest.
However, E. fitzingeri was also abundant in riparian secondary forests, and its density far from the river was similar in primary and secondary
forest, suggesting that river proximity can influence the recovery of secondary forest for amphibians. Conversely, the density
of E. diastema was similar in secondary forest and pasture, stressing interspecific differences for recovery rate. These frogs have a keystone
role in nutrient cycling and food webs, and their prompt recovery might represent an important step for the functional recovery
of forests. Nevertheless, the strong interspecific differences stress the complexity of these processes. 相似文献
230.
Primate copulation calls and postcopulatory female choice 总被引:2,自引:0,他引:2
Females in some species of Old World monkeys and apes vocalizeafter copulation, but the function of these vocalizations isnot clear. In this article, we examine the hypothesis that copulationcalls are a form of postcopulatory female choice. Accordingto this hypothesis, copulation calls are honest signals of fertility(i.e., ovulation) that are used by females to encourage mateguarding by their preferred mating partners and reduce the likelihoodof sperm competition. Evidence in favor of this hypothesis isreviewed and discussed in relation to other hypotheses. We suggestthat the evolution of female copulation calls in primates islinked to the evolution of other female mating signals suchas exaggerated sexual swellings, the potential for sperm competition,and the opportunity for precopulatory female mate choice. 相似文献