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851.
Exposure to Bordetella pertussis adenylate cyclase toxin affects integrin‐mediated adhesion and mechanics in alveolar epithelial cells 下载免费PDF全文
852.
Shunhui Wei Stephanie Li‐Ying Soh Julia Xia Wei‐Yi Ong Zhiping P. Pang Weiping Han 《Journal of neurochemistry》2014,129(2):328-338
Gain‐of‐toxic‐function mutations in Seipin (Asparagine 88 to Serine (N88S) and Serine 90 to Leucine (S90L) mutations, both of which disrupt the N‐glycosylation) cause autosomal dominant motor neuron diseases. However, the mechanism of how these missense mutations lead to motor neuropathy is unclear. Here, we analyze the impact of disruption of N‐glycosylation of Seipin on synaptic transmission by over‐expressing mutant Seipin in cultured cortical neurons via lentiviral infection. Immunostaining shows that over‐expressed Seipin is partly colocalized with synaptic vesicle marker synaptophysin. Electrophysiological recordings reveal that the Seipin mutation significantly decreases the frequency, but not the amplitudes of miniature excitatory post‐synaptic currents and miniature inhibitory post‐synaptic currents. The amplitude of both evoked excitatory post‐synaptic currents and inhibitory post‐synaptic current is also compromised by mutant Seipin over‐expression. The readily releasable pool and vesicular release probability of synaptic vesicles are both altered in neurons over‐expressing Seipin‐N88S, whereas neither γ‐amino butyric acid (GABA) nor α‐Amino‐3‐hydroxy‐5‐methyl‐4‐ isoxazolepropionic acid (AMPA) induced whole cell currents are affected. Moreover, electron microscopy analysis reveals decreased number of morphologically docked synaptic vesicles in Seipin‐N88S‐expressing neurons. These data demonstrate that Seipin‐N88S mutation impairs synaptic neurotransmission, possibly by regulating the priming and docking of synaptic vesicles at the synapse.
853.
Component and state separation in DMPC/DSPC lipid bilayers: a Monte Carlo simulation study 下载免费PDF全文
In this paper a two-state, two-component, Ising-type model is used to simulate the lateral distribution of the components and gel/fluid state acyl chains in dimyristoylphosphatidylcholine/distearoylphosphatidylcholine (DMPC/DSPC) lipid bilayers. The same model has been successful in calculating the excess heat capacity curves, the fluorescence recovery after photobleaching (FRAP) threshold temperatures, the most frequent center-to-center distances between DSPC clusters, and the fractal dimensions of gel clusters (Sugar, I. P., T. E. Thompson, and R. L. Biltonen, 1999. Biophys. J. 76:2099-2110). Depending on the temperature and mole fraction the population of the cluster size is either homogeneous or inhomogeneous. In the inhomogeneous population the size of the largest cluster scales with the size of the system, while the rest of the clusters remain small with increasing system size. In a homogeneous population, however, every cluster remains small with increasing system size. For both compositional and fluid/gel state clusters, threshold temperatures-the so-called percolation threshold temperatures-are determined where change in the type of the population takes place. At a given mole fraction, the number of percolation threshold temperatures can be 0, 1, 2, or 3. By plotting these percolation threshold temperatures on the temperature/mole fraction plane, the diagrams of component and state separation of DMPC/DSPC bilayers are constructed. In agreement with the small-angle neutron scattering measurements, the component separation diagram shows nonrandom lateral distribution of the components not only in the gel-fluid mixed phase region, but also in the pure gel and pure fluid regions. A combined diagram of component and state separation is constructed to characterize the lateral distribution of lipid components and gel/fluid state acyl chains in DMPC/DSPC mixtures. While theoretical phase diagrams of two component mixtures can be constructed only in the case of first-order transitions, state and component separation diagrams can be constructed whether or not the system is involved in first-order transition. The effects of interchain interactions on the component and state separation diagrams are demonstrated on three different models. The influences of state and component separation on the in-plane and off-plane membrane reactions are discussed. 相似文献
854.
The aim of this work was to investigate the alkaloid patterns of Lapiedra martinezii and their relation to biogeography and phenology focused in a phylogenetic comparison. Plants from 14 populations of L. martinezii, covering almost its entire distribution area, were subjected to morphological, ecological, and phytochemical analysis. Experiments for different alkaloid‐type content are proposed as a new tool for analysis of plant distribution. Several plants were transplanted for weekly observation of their phenological changes, and alkaloids from different plant organs were extracted, listed, and compared. The alkaloid pattern of L. martinezii comprises 49 compounds of homolycorine, lycorine, tazettine, haemantamine, and narciclasine types. The populations located in the north and south margins of the distribution area displayed alkaloid patterns different from those of the central area. Changes in these patterns during their phenological cycle may be related to a better defence for plant reproduction. L. martinezii is an old relict plant, and it has maintained some of the more primitive morphological features and alkaloid profiles of the Mediterranean Amaryllidaceae. The variations in alkaloid content observed could be interpreted in a phylogenetic sense, and those found in their phenological changes, in an adaptive one. 相似文献
855.
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857.
Predators marked with chemical cues from one prey have increased attack success on another prey species 下载免费PDF全文
GEORGE BROUFAS PAULIEN DE JONG ERNESTINA AGUILAR‐FENOLLOSA ALEXANDRA REVYNTHI MAURICE W. SABELIS ARNE JANSSEN 《Ecological Entomology》2015,40(1):62-68
1. To reduce the risk of being eaten by predators, prey alter their morphology or behaviour. This response can be tuned to the current danger if chemical or other cues associated with predators inform the prey about the risks involved. 2. It is well known that various prey species discriminate between chemical cues from predators that fed on conspecific prey and those that fed on heterospecific prey, and react stronger to the first. It is therefore expected that generalist predators are more successful in capturing a given prey species when they are contaminated with chemical cues from another prey species instead of cues from the same prey species. 3. Here, a generalist predatory mite was studied that feeds on thrips larvae as well as on whitefly eggs and crawlers. Mites were marked with cues (i.e. body fluids) of one of these two prey species and were subsequently offered thrips larva. 4. Predators marked with thrips cues killed significantly fewer thrips than predators marked with whitefly cues, even though the predator's tendency to attack was the same. In addition, more thrips larvae sought refuge in the presence of a predatory mite marked with thrips cues instead of whitefly cues. 5. This suggests that generalist predators may experience improved attack success when switching prey species. 相似文献
858.
Flavodoxin has been recently recognized as an essential protein for a number of pathogenic bacteria including Helicobacter pylori, where it has been proposed to constitute a target for antibacterial drug development. One way we are exploring to screen for novel inhibitory compounds is to perform thermal upshift assays, for which a detailed knowledge of protein thermostability and cofactor binding properties is of great help. However, very little is known on the stability and ligand binding properties of H. pylori flavodoxin, and its peculiar FMN binding site together with the variety of behaviors observed within the flavodoxin family preclude extrapolations. We have thus performed a detailed experimental and computational analysis of the thermostability and cofactor binding energetics of H. pylori flavodoxin, and we have found that the thermal unfolding equilibrium is more complex that any other previously described for flavodoxins as it involves the accumulation of two distinct equilibrium intermediates. Fortunately the entire stability and binding data can be satisfactorily fitted to a model, summarized in a simple phase diagram, where the cofactor only binds to the native state. On the other hand, we show how variability of thermal unfolding behavior within the flavodoxin family can be predicted using structure-energetics relationships implemented in the COREX algorithm. The different distribution and ranges of local stabilities of the Anabaena and H. pylori apoflavodoxins explain the essential experimental differences observed: much lower Tm1, greater resistance to global unfolding, and more pronounced cold denaturation in H. pylori. Finally, a new strategy is proposed to identify using COREX structural characteristics of equilibrium intermediate states populated during protein unfolding. 相似文献
859.
Bogácsi-Szabó E Kalmár T Csányi B Tömöry G Czibula A Priskin K Horváth F Downes CS Raskó I 《Human biology; an international record of research》2005,77(5):639-662
The Cumanians were originally Asian pastoral nomads who in the 13th century migrated to Hungary. We have examined mitochondrial DNA from members of the earliest Cumanian population in Hungary from two archeologically well-documented excavations and from 74 modern Hungarians from different rural locations in Hungary. Haplogroups were defined based on HVS I sequences and examinations of haplogroup-associated polymorphic sites of the protein coding region and of HVS II. To exclude contamination, some ancient DNA samples were cloned. A database was created from previously published mtDNA HVS I sequences (representing 2,615 individuals from different Asian and European populations) and 74 modem Hungarian sequences from the present study. This database was used to determine the relationships between the ancient Cumanians, modern Hungarians, and Eurasian populations and to estimate the genetic distances between these populations. We attempted to deduce the genetic trace of the migration of Cumanians. This study is the first ancient DNA characterization of an eastern pastoral nomad population that migrated into Europe. The results indicate that, while still possessing a Central Asian steppe culture, the Cumanians received a large admixture of maternal genes from more westerly populations before arriving in Hungary. A similar dilution of genetic, but not cultural, factors may have accompanied the settlement of other Asian nomads in Europe. 相似文献
860.
László?K?lesEmail author Erzsébet?Kató Adrienn?Hanuska Zoltán?S.?Zádori Mahmoud?Al-Khrasani Tibor?Zelles Patrizia?Rubini Peter?IllesEmail author 《Purinergic signalling》2016,12(1):1-24
Glutamate is the main excitatory neurotransmitter of the central nervous system (CNS), released both from neurons and glial cells. Acting via ionotropic (NMDA, AMPA, kainate) and metabotropic glutamate receptors, it is critically involved in essential regulatory functions. Disturbances of glutamatergic neurotransmission can be detected in cognitive and neurodegenerative disorders. This paper summarizes the present knowledge on the modulation of glutamate-mediated responses in the CNS. Emphasis will be put on NMDA receptor channels, which are essential executive and integrative elements of the glutamatergic system. This receptor is crucial for proper functioning of neuronal circuits; its hypofunction or overactivation can result in neuronal disturbances and neurotoxicity. Somewhat surprisingly, NMDA receptors are not widely targeted by pharmacotherapy in clinics; their robust activation or inhibition seems to be desirable only in exceptional cases. However, their fine-tuning might provide a promising manipulation to optimize the activity of the glutamatergic system and to restore proper CNS function. This orchestration utilizes several neuromodulators. Besides the classical ones such as dopamine, novel candidates emerged in the last two decades. The purinergic system is a promising possibility to optimize the activity of the glutamatergic system. It exerts not only direct and indirect influences on NMDA receptors but, by modulating glutamatergic transmission, also plays an important role in glia-neuron communication. These purinergic functions will be illustrated mostly by depicting the modulatory role of the purinergic system on glutamatergic transmission in the prefrontal cortex, a CNS area important for attention, memory and learning. 相似文献