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Search Results: 1 - 10 of 11827 matches for " Andreas Mayer "
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Identification of Genes Affecting Vacuole Membrane Fragmentation in Saccharomyces cerevisiae
Lydie Michaillat, Andreas Mayer
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0054160
Abstract: The equilibrium of membrane fusion and fission influences the volume and copy number of organelles. Fusion of yeast vacuoles has been well characterized but their fission and the mechanisms determining vacuole size and abundance remain poorly understood. We therefore attempted to systematically characterize factors necessary for vacuole fission. Here, we present results of an in vivo screening for deficiencies in vacuolar fragmentation activity of an ordered collection deletion mutants, representing 4881 non-essential genes of the yeast Saccharomyces cerevisiae. The screen identified 133 mutants with strong defects in vacuole fragmentation. These comprise numerous known fragmentation factors, such as the Fab1p complex, Tor1p, Sit4p and the V-ATPase, thus validating the approach. The screen identified many novel factors promoting vacuole fragmentation. Among those are 22 open reading frames of unknown function and three conspicuous clusters of proteins with known function. The clusters concern the ESCRT machinery, adaptins, and lipases, which influence the production of diacylglycerol and phosphatidic acid. A common feature of these factors of known function is their capacity to change membrane curvature, suggesting that they might promote vacuole fragmentation via this property.
From molecular signatures to predictive biomarkers: modeling disease pathophysiology and drug mechanism of action
Andreas Heinzel,Gert Mayer,Rainer Oberbauer,Arno Lukas,Bernd Mayer
Frontiers in Cell and Developmental Biology , 2014, DOI: 10.3389/fcell.2014.00037
Abstract: Omics profiling significantly expanded the molecular landscape describing clinical phenotypes. Association analysis resulted in first diagnostic and prognostic biomarker signatures entering clinical utility. However, utilizing Omics for deepening our understanding of disease pathophysiology, and further including specific interference with drug mechanism of action on a molecular process level still sees limited added value in the clinical setting. We exemplify a computational workflow for expanding from statistics-based association analysis toward deriving molecular pathway and process models for characterizing phenotypes and drug mechanism of action. Interference analysis on the molecular model level allows identification of predictive biomarker candidates for testing drug response. We discuss this strategy on diabetic nephropathy (DN), a complex clinical phenotype triggered by diabetes and presenting with renal as well as cardiovascular endpoints. A molecular pathway map indicates involvement of multiple molecular mechanisms, and selected biomarker candidates reported as associated with disease progression are identified for specific molecular processes. Selective interference of drug mechanism of action and disease-associated processes is identified for drug classes in clinical use, in turn providing precision medicine hypotheses utilizing predictive biomarkers.
Mouthpart Morphology of Three Sympatric Native and Nonnative Gammaridean Species: Gammarus pulex, G. fossarum, and Echinogammarus berilloni (Crustacea: Amphipoda)
Gerd Mayer,Andreas Maas,Dieter Waloszek
International Journal of Zoology , 2012, DOI: 10.1155/2012/493420
Abstract: In the last 20 years several nonnative amphipod species have immigrated inland waters of Germany and adjacent central European countries. Some of them have been very successful and could establish stabile populations. In some places, they have even replaced native or earlier established species. The gammarid Echinogammarus berilloni originates from the Atlantic region of France and the north-western part of Spain and coexists in some central European waters with the native Gammarus pulex and G. fossarum. Here, we describe and compare the mouthparts and other structures involved in food acquisition of these three sympatric gammaridean species. Our hypothesis was that differences in the mode of feeding of the three species could be the reason for their coexistence and that these differences would be expressed in differences in mouthpart morphology. The results of our SEM study demonstrate that there are indeed interspecific differences in details of the morphology of the feeding structures. This is especially true for the setation of antennae, maxillulae, gnathopods, and third uropods, which can be interpreted as adaptations to special modes of feeding. Generally, all three species are omnivorous, but specializations in details point to the possibility to use some food resources in a special effective way. 1. Introduction The gammaridean fauna of middle European inland waters has dramatically changed in the last two decades; particularly, Ponto-Caspian gammarideans arrived in middle European rivers, canals, and lakes [1–11]. Immigration has happened and is still ongoing via three main corridors: (i) along the Danube, Main-Donau Canal and Main into the Rhine system; (ii) via the Pipet-Bug connection from the east, and from the north and along the Baltic coast via ships [12]; (iii) also from the Mediterranean region, freshwater gammarideans have enlarged their range of distribution towards western and middle Europe [5, 13–16]. Some of these nonnative gammaridean species could establish stabile populations and occur in high densities, and several species have a severe impact on the ecology of the invaded regions by reducing and even eliminating native and earlier established gammaridean species (therefore, the immigrants are called invasive). One well-examined example of such invasive species is Dikerogammarus villosus (Sowinsky, 1894) [17]. This species is now the dominant gammaridean species in many rivers, canals, and larger lakes all over central Europe, affecting also other members of the macrozoobenthos [1, 6, 18–20]. But not all nonnative species are
Molecular species identification boosts bat diversity
Frieder Mayer, Christian Dietz, Andreas Kiefer
Frontiers in Zoology , 2007, DOI: 10.1186/1742-9994-4-4
Abstract: A total of at least 1.5 million species of organisms are described, but an estimated number of 10 to 100 million species may live on our planet [1,2]. This huge gap gave rise to search for new technologies to describe the biological diversity. Meanwhile, genetic screening approaches involving a single or a small number of genes – often referred to as DNA barcoding – were started in diverse taxonomic groups for two major aims: (i) to establish a standardized technique to identify species, and (ii) to detect new species in an efficient manner to bring us closer to the true number of species [3-6]. So far, DNA barcodes were primarily used for genetic species identification of taxonomically poorly studied taxa and geographic regions like the tropics [7-11]. Here we tested the applicability of DNA sequencing for species delineation and species identification in one of the best-known taxonomic groups in an intensively sampled geographic region.A recently compiled list of all mammal species of the world specifies a total of 44 vespertilionid bats species for the Western Palaearctic region [12]. One additional species was recently described (Pipistrellus hanaki [13]) and another was given species rank (Plecotus christii [14]). In this study we sequenced 900 base pairs of the mitochondrial nd1 gene [15] of 534 bats from 41 of the 46 described species [see Additional file 1]. This revealed species-specific DNA sequences that differed at least by 4% (uncorrected p distance) from sequences from other species in 816 of 820 pairwise species comparisons. Intraspecific variation was much lower than interspecific variation, which allowed a reliable genetic identification of most species (figure 1). Only four pairs of species showed genetic distances below 2.5% and species did not split in two monophyletic groups in all four pairs of species. Individuals of different species within these four species pairs occasionally shared the same sequence type. This lack of substantial sequence
Behaviour and Perception-based Pedestrian Evacuation Simulation
Tobias Kretz,Georg Mayer,Andreas Muehlberger
Physics , 2010, DOI: 10.1007/978-1-4419-9725-8_82
Abstract: This contribution reports on the research project SKRIBT and some of its results. An evacuation simulation based on VISSIM's pedestrian dynamics simulation was developed, that -- with high time resolution -- integrates results from studies on behavior in stress and crisis situations, results from CFD models for e.g. fire dynamics simulations, and considers visibility of signage and -- adding a psychological model -- its cognition. A crucial issue is the cognition of smoke or fire by the occupant and his / her resulting spontaneous or deliberate reaction to this episode.
Matter-wave scattering from strongly interacting bosons in an optical lattice
Klaus Mayer,Alberto Rodriguez,Andreas Buchleitner
Physics , 2015,
Abstract: We study the scattering of a matter-wave from an interacting system of bosons in an optical lattice, focusing on the strong-interaction regime. Analytical expressions for the many-body scattering cross section are derived from a strong-coupling expansion and a site-decoupling mean-field approximation, and compared to numerically obtained exact results. In the thermodynamic limit, we find a non-vanishing inelastic cross section throughout the Mott insulating regime, which decays quadratically as a function of the boson-boson interaction.
Matter-wave scattering from interacting bosons in an optical lattice
Klaus Mayer,Alberto Rodriguez,Andreas Buchleitner
Physics , 2014, DOI: 10.1103/PhysRevA.90.023629
Abstract: We study the scattering of matter-waves from interacting bosons in a one-dimensional optical lattice, described by the Bose-Hubbard Hamiltonian. We derive analytically a formula for the inelastic cross section as a function of the atomic interaction in the lattice, employing Bogoliubov's formalism for small condensate depletion. A linear decay of the inelastic cross section for weak interaction, independent of number of particles, condensate depletion and system size, is found.
New and revised parameters for several southern OB binaries
Pavel Mayer,Horst Drechsel,Andreas Irrgang
Physics , 2014, DOI: 10.1051/0004-6361/201423455
Abstract: Using ESO FEROS archive spectra of several southern OB-type binaries, we derived periods for three SB2 spectroscopic binaries, HD 97166, HD 115455, and HD 123590, and two SB1 systems, HD 130298 and HD 163892. It was also possible to use new FEROS spectra to improve the parameters of the known binaries, KX Vel and HD 167263. For KX Vel, we determined a dynamic mass of the primary of 16.8 M$_{\odot}$, while the evolutionary model suggests a higher value of 20.2 M$_{\odot}$. We derived an improved period for HD 167263, and in its spectra, we recognized contributions of both of its interferometric components.
A Cambrian micro-lobopodian and the evolution of arthropod locomotion and reproduction
Andreas Maas,Georg Mayer,Reinhardt M. Kristensen,Dieter Waloszek
Chinese Science Bulletin , 2007, DOI: 10.1007/s11434-007-0515-3
Abstract: The evolutionary success of arthropods, the most abundant and diverse animal group, is mainly based on their segmented body and jointed appendages, features that had evolved most likely already before the Cambrian. The first arthropod-like animals, the lobopodians from the Early Cambrian, were unsclerotized and worm-like, and they had unjointed tubular legs. Here we describe the first three-dimensionally preserved Cambrian lobopodian. The material presented of Orstenotubulus evamuellerae gen. et sp. nov. is the smallest and youngest of a lobopodian known. O. evamuellerae shows strikingly detailed similarities to Recent tardigrades and/or onychophorans in its cellular-structured cuticle and the telescopic spines. It also shows similarities to other, longer known lobopodians, but which are ten times as large as the new form. These similarities include the finely annulated body and legs, which is characteristic also for Recent onychophorans, and paired humps continuing into spines situated dorsally to the leg insertions, a feature lacking in the extant forms. The morphology of O. evamuellerae not only elucidates our knowledge about lobopodians, but also aids in a clearer picture of the early evolution of arthropods. An example is the single ventral gonopore between a limb pair of O. evamuellerae, which indicates that a single gonopore, as developed in onychophorans, tardigrades, pentastomids, myriapods and insects, might represent the plesiomorphic state for Arthropoda, while the paired state in chelicerates and crustaceans was convergently achieved. Concerning life habits, the lateral orientation of the limbs and their anchoring spines of the new lobopodian imply that early arthropods were crawlers rather than walkers.
Diversity of immune strategies explained by adaptation to pathogen statistics
Andreas Mayer,Thierry Mora,Olivier Rivoire,Aleksandra M. Walczak
Quantitative Biology , 2015,
Abstract: Biological organisms have evolved a wide range of immune mechanisms to defend themselves against pathogens. Beyond molecular details, these mechanisms differ in how protection is acquired, processed and passed on to subsequent generations -- differences that may be essential to long-term survival. Here, we introduce a mathematical framework to compare the long-term adaptation of populations as a function of the pathogen dynamics that they experience and of the immune strategy that they adopt. We find that the two key determinants of an optimal immune strategy are the frequency and the characteristic timescale of the pathogens. Depending on these two parameters, our framework identifies distinct modes of immunity, including adaptive, innate, bet-hedging and CRISPR-like immunities, which recapitulate the diversity of natural immune systems.
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