TY - JOUR AB - Fast synaptic transmission is important for rapid information processing. To explore the maximal rate of neuronal signaling and to analyze the presynaptic mechanisms, we focused on the input layer of the cerebellar cortex, where exceptionally high action potential (AP) frequencies have been reported invivo. With paired recordings between presynaptic cerebellar mossy fiber boutons and postsynaptic granule cells, we demonstrate reliable neurotransmission upto ~1 kHz. Presynaptic APs are ultrafast, with ~100μs half-duration. Both Kv1 and Kv3 potassium channels mediate the fast repolarization, rapidly inactivating sodium channels ensure metabolic efficiency, and little AP broadening occurs during bursts of up to 1.5 kHz. Presynaptic Cav2.1 (P/Q-type) calcium channels open efficiently during ultrafast APs. Furthermore, a subset of synaptic vesicles is tightly coupled to Ca2+ channels, and vesicles are rapidly recruited to the release site. These data reveal mechanisms of presynaptic AP generation and transmitter release underlying neuronal kHz signaling. AU - Ritzau Jost, Andreas AU - Delvendahl, Igor AU - Rings, Annika AU - Byczkowicz, Niklas AU - Harada, Harumi AU - Shigemoto, Ryuichi AU - Hirrlinger, Johannes AU - Eilers, Jens AU - Hallermann, Stefan ID - 1898 IS - 1 JF - Neuron TI - Ultrafast action potentials mediate kilohertz signaling at a central synapse VL - 84 ER - TY - JOUR AB - In this paper, we introduce a novel scene representation for the visualization of large-scale point clouds accompanied by a set of high-resolution photographs. Many real-world applications deal with very densely sampled point-cloud data, which are augmented with photographs that often reveal lighting variations and inaccuracies in registration. Consequently, the high-quality representation of the captured data, i.e., both point clouds and photographs together, is a challenging and time-consuming task. We propose a two-phase approach, in which the first (preprocessing) phase generates multiple overlapping surface patches and handles the problem of seamless texture generation locally for each patch. The second phase stitches these patches at render-time to produce a high-quality visualization of the data. As a result of the proposed localization of the global texturing problem, our algorithm is more than an order of magnitude faster than equivalent mesh-based texturing techniques. Furthermore, since our preprocessing phase requires only a minor fraction of the whole data set at once, we provide maximum flexibility when dealing with growing data sets. AU - Arikan, Murat AU - Preiner, Reinhold AU - Scheiblauer, Claus AU - Jeschke, Stefan AU - Wimmer, Michael ID - 1906 IS - 9 JF - IEEE Transactions on Visualization and Computer Graphics TI - Large-scale point-cloud visualization through localized textured surface reconstruction VL - 20 ER - TY - JOUR AB - The unprecedented polymorphism in the major histocompatibility complex (MHC) genes is thought to be maintained by balancing selection from parasites. However, do parasites also drive divergence at MHC loci between host populations, or do the effects of balancing selection maintain similarities among populations? We examined MHC variation in populations of the livebearing fish Poecilia mexicana and characterized their parasite communities. Poecilia mexicana populations in the Cueva del Azufre system are locally adapted to darkness and the presence of toxic hydrogen sulphide, representing highly divergent ecotypes or incipient species. Parasite communities differed significantly across populations, and populations with higher parasite loads had higher levels of diversity at class II MHC genes. However, despite different parasite communities, marked divergence in adaptive traits and in neutral genetic markers, we found MHC alleles to be remarkably similar among host populations. Our findings indicate that balancing selection from parasites maintains immunogenetic diversity of hosts, but this process does not promote MHC divergence in this system. On the contrary, we suggest that balancing selection on immunogenetic loci may outweigh divergent selection causing divergence, thereby hindering host divergence and speciation. Our findings support the hypothesis that balancing selection maintains MHC similarities among lineages during and after speciation (trans-species evolution). AU - Tobler, Michael AU - Plath, Martin AU - Riesch, Rüdiger AU - Schlupp, Ingo AU - Grasse, Anna V AU - Munimanda, Gopi AU - Setzer, C AU - Penn, Dustin AU - Moodley, Yoshan ID - 1905 IS - 5 JF - Journal of Evolutionary Biology SN - 1010-061X TI - Selection from parasites favours immunogenetic diversity but not divergence among locally adapted host populations VL - 27 ER - TY - JOUR AB - In the 1960s-1980s, determination of bacterial growth rates was an important tool in microbial genetics, biochemistry, molecular biology, and microbial physiology. The exciting technical developments of the 1990s and the 2000s eclipsed that tool; as a result, many investigators today lack experience with growth rate measurements. Recently, investigators in a number of areas have started to use measurements of bacterial growth rates for a variety of purposes. Those measurements have been greatly facilitated by the availability of microwell plate readers that permit the simultaneous measurements on up to 384 different cultures. Only the exponential (logarithmic) portions of the resulting growth curves are useful for determining growth rates, and manual determination of that portion and calculation of growth rates can be tedious for high-throughput purposes. Here, we introduce the program GrowthRates that uses plate reader output files to automatically determine the exponential portion of the curve and to automatically calculate the growth rate, the maximum culture density, and the duration of the growth lag phase. GrowthRates is freely available for Macintosh, Windows, and Linux.We discuss the effects of culture volume, the classical bacterial growth curve, and the differences between determinations in rich media and minimal (mineral salts) media. This protocol covers calibration of the plate reader, growth of culture inocula for both rich and minimal media, and experimental setup. As a guide to reliability, we report typical day-to-day variation in growth rates and variation within experiments with respect to position of wells within the plates. AU - Hall, Barry AU - Acar, Hande AU - Nandipati, Anna AU - Barlow, Miriam ID - 1902 IS - 1 JF - Molecular Biology and Evolution SN - 0737-4038 TI - Growth rates made easy VL - 31 ER - TY - JOUR AB - In plants, the patterning of stem cell-enriched meristems requires a graded auxin response maximum that emerges from the concerted action of polar auxin transport, auxin biosynthesis, auxin metabolism, and cellular auxin response machinery. However, mechanisms underlying this auxin response maximum-mediated root stem cell maintenance are not fully understood. Here, we present unexpected evidence that WUSCHEL-RELATED HOMEOBOX 5 (WOX5) transcription factor modulates expression of auxin biosynthetic genes in the quiescent center (QC) of the root and thus provides a robust mechanism for the maintenance of auxin response maximum in the root tip. This WOX5 action is balanced through the activity of indole-3-acetic acid 17 (IAA17) auxin response repressor. Our combined genetic, cell biology, and computational modeling studies revealed a previously uncharacterized feedback loop linking WOX5-mediated auxin production to IAA17-dependent repression of auxin responses. This WOX5-IAA17 feedback circuit further assures the maintenance of auxin response maximum in the root tip and thereby contributes to the maintenance of distal stem cell (DSC) populations. Our experimental studies and in silico computer simulations both demonstrate that the WOX5-IAA17 feedback circuit is essential for the maintenance of auxin gradient in the root tip and the auxin-mediated root DSC differentiation. AU - Tian, Huiyu AU - Wabnik, Krzysztof T AU - Niu, Tiantian AU - Li, Hongjiang AU - Yu, Qianqian AU - Pollmann, Stephan AU - Vanneste, Steffen AU - Govaerts, Willy AU - Rolčík, Jakub AU - Geisler, Markus AU - Friml, Jirí AU - Ding, Zhaojun ID - 1901 IS - 2 JF - Molecular Plant TI - WOX5-IAA17 feedback circuit-mediated cellular auxin response is crucial for the patterning of root stem cell niches in arabidopsis VL - 7 ER -