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Search Results: 1 - 10 of 665 matches for " Silke Sachse "
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Atypical Membrane Topology and Heteromeric Function of Drosophila Odorant Receptors In Vivo
Richard Benton,Silke Sachse,Stephen W. Michnick,Leslie B. Vosshall
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0040020
Abstract: Drosophila olfactory sensory neurons (OSNs) each express two odorant receptors (ORs): a divergent member of the OR family and the highly conserved, broadly expressed receptor OR83b. OR83b is essential for olfaction in vivo and enhances OR function in vitro, but the molecular mechanism by which it acts is unknown. Here we demonstrate that OR83b heterodimerizes with conventional ORs early in the endomembrane system in OSNs, couples these complexes to the conserved ciliary trafficking pathway, and is essential to maintain the OR/OR83b complex within the sensory cilia, where odor signal transduction occurs. The OR/OR83b complex is necessary and sufficient to promote functional reconstitution of odor-evoked signaling in sensory neurons that normally respond only to carbon dioxide. Unexpectedly, unlike all known vertebrate and nematode chemosensory receptors, we find that Drosophila ORs and OR83b adopt a novel membrane topology with their N-termini and the most conserved loops in the cytoplasm. These loops mediate direct association of ORs with OR83b. Our results reveal that OR83b is a universal and integral part of the functional OR in Drosophila. This atypical heteromeric and topological design appears to be an insect-specific solution for odor recognition, making the OR/OR83b complex an attractive target for the development of highly selective insect repellents to disrupt olfactory-mediated host-seeking behaviors of insect disease vectors.
Atypical Membrane Topology and Heteromeric Function of Drosophila Odorant Receptors In Vivo
Richard Benton,Silke Sachse,Stephen W Michnick,Leslie B Vosshall
PLOS Biology , 2006, DOI: 10.1371/journal.pbio.0040020
Abstract: Drosophila olfactory sensory neurons (OSNs) each express two odorant receptors (ORs): a divergent member of the OR family and the highly conserved, broadly expressed receptor OR83b. OR83b is essential for olfaction in vivo and enhances OR function in vitro, but the molecular mechanism by which it acts is unknown. Here we demonstrate that OR83b heterodimerizes with conventional ORs early in the endomembrane system in OSNs, couples these complexes to the conserved ciliary trafficking pathway, and is essential to maintain the OR/OR83b complex within the sensory cilia, where odor signal transduction occurs. The OR/OR83b complex is necessary and sufficient to promote functional reconstitution of odor-evoked signaling in sensory neurons that normally respond only to carbon dioxide. Unexpectedly, unlike all known vertebrate and nematode chemosensory receptors, we find that Drosophila ORs and OR83b adopt a novel membrane topology with their N-termini and the most conserved loops in the cytoplasm. These loops mediate direct association of ORs with OR83b. Our results reveal that OR83b is a universal and integral part of the functional OR in Drosophila. This atypical heteromeric and topological design appears to be an insect-specific solution for odor recognition, making the OR/OR83b complex an attractive target for the development of highly selective insect repellents to disrupt olfactory-mediated host-seeking behaviors of insect disease vectors.
Role of histamine as a putative inhibitory transmitter in the honeybee antennal lobe
Silke Sachse, Philipp Peele, Ana F Silbering, Martin Gühmann, C Giovanni Galizia
Frontiers in Zoology , 2006, DOI: 10.1186/1742-9994-3-22
Abstract: We optically recorded the representation of odors before, during and after histamine application at the input level (estimated from a compound signal), and at the output level (by selectively measuring the projection neurons). For both, histamine led to a strong and reversible reduction of odor-evoked responses.We propose that histamine, in addition to GABA, acts as an inhibitory transmitter in the honeybee AL and is therefore likely to play a role in odor processing.The antennal lobe (AL) of insects is the functional analogue of the olfactory bulb (OB) in mammals, which is the first central neuropil where information from the olfactory sensory neurons (OSNs) is processed. Both the AL and OB, consist of different neuron types that modulate and optimize the afferent input in a complex network. It has been shown that intrinsic inhibitory circuits within the olfactory bulb and the AL shape temporal and spatial aspects of the odor-evoked patterns to improve odor detection and discrimination [1-4]. However, little is known about the synaptic interactions among the olfactory neurons involved in odor processing in insects.In the honeybee, approx. 60,000 OSNs [5] convey olfactory information to two categories of AL neurons, namely approx. 4000 local interneurons (LNs) [6] and 700–800 projection neurons (PNs) [7,8]. LNs branch exclusively within the AL, whereas PNs relay the olfactory information to higher order brain centers. Synaptic contacts between the sensory neurons, LNs and PNs are mostly located in olfactory glomeruli [9]. Each of the approximately 160 glomeruli represents an identifiable morphological and functional subunit, arranged in a single layer around the honeybee AL [10,11]. Similar to the olfactory system of lobsters and moths [4,12], honeybees have anatomically distinct classes of olfactory LNs [13]. The majority of them, heterogeneous LNs (hetero LNs), have a high density of dendrite branches in one particular glomerulus and sparser branches distributed a
Plant odorants interfere with detection of sex pheromone signals by male Heliothis virescens
Pablo Pregitzer,Marco Schubert,Heinz Breer,Bill S. Hansson,Silke Sachse,Jürgen Krieger
Frontiers in Cellular Neuroscience , 2012, DOI: 10.3389/fncel.2012.00042
Abstract: In many insects, mate finding relies on female-released sex pheromones, which have to be deciphered by the male olfactory system within an odorous background of plant volatiles present in the environment of a calling female. With respect to pheromone-mediated mate localization, plant odorants may be neutral, favorable, or disturbing. Here we examined the impact of plant odorants on detection and coding of the major sex pheromone component, (Z)-11-hexadecenal (Z11-16:Ald) in the noctuid moth Heliothis virescens. By in vivo imaging the activity in the male antennal lobe (AL), we monitored the interference at the level of olfactory sensory neurons (OSN) to illuminate mixture interactions. The results show that stimulating the male antenna with Z11-16:Ald and distinct plant-related odorants simultaneously suppressed pheromone-evoked activity in the region of the macroglomerular complex (MGC), where Z11-16:Ald-specific OSNs terminate. Based on our previous findings that antennal detection of Z11-16:Ald involves an interplay of the pheromone binding protein (PBP) HvirPBP2 and the pheromone receptor (PR) HR13, we asked if the plant odorants may interfere with any of the elements involved in pheromone detection. Using a competitive fluorescence binding assay, we found that the plant odorants neither bind to HvirPBP2 nor affect the binding of Z11-16:Ald to the protein. However, imaging experiments analyzing a cell line that expressed the receptor HR13 revealed that plant odorants significantly inhibited the Z11-16:Ald-evoked calcium responses. Together the results indicate that plant odorants can interfere with the signaling process of the major sex pheromone component at the receptor level. Consequently, it can be assumed that plant odorants in the environment may reduce the firing activity of pheromone-specific OSNs in H. virescens and thus affect mate localization.
A New Role of the Complement System: C3 Provides Protection in a Mouse Model of Lung Infection with Intracellular Chlamydia psittaci
Jenny Bode, Pavel Dutow, Kirsten Sommer, Katrin Janik, Silke Glage, Burkhard Tümmler, Antje Munder, Robert Laudeley, Konrad W. Sachse, Andreas Klos
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0050327
Abstract: The complement system modulates the intensity of innate and specific immunity. While it protects against infections by extracellular bacteria its role in infection with obligate intracellular bacteria, such as the avian and human pathogen Chlamydia (C.) psittaci, is still unknown. In the present study, knockout mice lacking C3 and thus all main complement effector functions were intranasally infected with C. psittaci strain DC15. Clinical parameters, lung histology, and cytokine levels were determined. A subset of infections was additionally performed with mice lacking C5 or C5a receptors. Complement activation occurred before symptoms of pneumonia appeared. Mice lacking C3 were ~100 times more susceptible to the intracellular bacteria compared to wild-type mice, with all C3?/? mice succumbing to infection after day 9. At a low infective dose, C3?/? mice became severely ill after an even longer delay, the kinetics suggesting a so far unknown link of complement to the adaptive, protective immune response against chlamydiae. The lethal phenotype of C3?/? mice is not based on differences in the anti-chlamydial IgG response (which is slightly delayed) as demonstrated by serum transfer experiments. In addition, during the first week of infection, the absence of C3 was associated with partial protection characterized by reduced weight loss, better clinical score and lower bacterial burden, which might be explained by a different mechanism. Lack of complement functions downstream of C5 had little effect. This study demonstrates for the first time a strong and complex influence of complement effector functions, downstream of C3 and upstream of C5, on the outcome of an infection with intracellular bacteria, such as C. psittaci.
Drosophila Avoids Parasitoids by Sensing Their Semiochemicals via a Dedicated Olfactory Circuit
Shimaa A. M. Ebrahim?,Hany K. M. Dweck?,Johannes St?kl?,John E. Hofferberth?,Federica Trona?,Kerstin Weniger?,Jürgen Rybak?,Yoichi Seki?,Marcus C. Stensmyr?,Silke Sachse
PLOS Biology , 2015, DOI: 10.1371/journal.pbio.1002318
Abstract: Detecting danger is one of the foremost tasks for a neural system. Larval parasitoids constitute clear danger to Drosophila, as up to 80% of fly larvae become parasitized in nature. We show that Drosophila melanogaster larvae and adults avoid sites smelling of the main parasitoid enemies, Leptopilina wasps. This avoidance is mediated via a highly specific olfactory sensory neuron (OSN) type. While the larval OSN expresses the olfactory receptor Or49a and is tuned to the Leptopilina odor iridomyrmecin, the adult expresses both Or49a and Or85f and in addition detects the wasp odors actinidine and nepetalactol. The information is transferred via projection neurons to a specific part of the lateral horn known to be involved in mediating avoidance. Drosophila has thus developed a dedicated circuit to detect a life-threatening enemy based on the smell of its semiochemicals. Such an enemy-detecting olfactory circuit has earlier only been characterized in mice and nematodes.
A Deformed Poincaré Algebra On A Cubic Lattice
Sebastian Sachse
Physics , 1992,
Abstract: Replacing the continuous space by a cubic lattice we find a deformation of the Poincar\'e algebra. A deformation of the relativistic mass operator is shown to be a Casimir of the algebra. The real structure is preserved.
A Categorical Formulation of Superalgebra and Supergeometry
Christoph Sachse
Mathematics , 2008,
Abstract: We reformulate superalgebra and supergeometry in completely categorical terms by a consequent use of the functor of points. The increased abstraction of this approach is rewarded by a number of great advantages. First, we show that one can extend supergeometry completely naturally to infinite-dimensional contexts. Secondly, some subtle and sometimes obscure-seeming points of supergeometry become clear in light of these results, e.g., the relation between the Berezin-Leites-Kostant and the de Witt-Rogers approaches, and the precise geometric meaning of odd parameters in supergeometry. In addition, this method allows us to construct in an easy manner superspaces of morphisms between superobjects, i.e., the inner Hom objects associated with the sets of such morphisms. The results of our work rely heavily and were inspired by the ideas of V. Molotkov, who first outlined the approach extensively expounded here.
Global Analytic Approach to Super Teichmueller Spaces
Christoph Sachse
Mathematics , 2009,
Abstract: In this thesis we investigate a new formalism for supergeometry which focuses on the categorical properties of the theory. This approach is our main tool in the subsequent investigation of a global analytic approach to the construction of super Teichmueller spaces. These results should be of importance to various other fields, in particular, superstring theory and superconformal field theory. This new approach, which was actually first proposed by Molotkov and Schwarz and Voronov already in the mid-80s, is based on a consequent use of the functor of points. Apart from clarifying various issues of supergeometry which sometimes remain obscure in the standard (ringed-space) approach, its main achievement is that it makes infinite-dimensional supermanifolds available. We use this to define the supermanifold of all almost complex structures on a given finite-dimensional supermanifold and show that it actually carries a complex structure itself. Moreover we succeed in giving an explicit definition and construction of the diffeomorphism supergroup of a finite-dimensional supermanifold. We then combine these results to show that one can construct a slice for the action of the diffeomorphism supergroup on the subspace of integrable almost complex structures on a smooth closed oriented 2|2-dimensional supersurface. This slice represents a local patch of super Teichmueller space. We also investigate how this construction changes if one instead looks at N=1 superconformal structures on such a surface and show that one obtains an analogous result.
Sylvester-t' Hooft generators of sl(n) and sl(n|n), and relations between them
Christoph Sachse
Mathematics , 2006, DOI: 10.1007/s11232-006-0119-0
Abstract: Among the simple finite dimensional Lie algebras, only sl(n) possesses two automorphisms of finite order which have no common nonzero eigenvector with eigenvalue one. It turns out that these automorphisms are inner and form a pair of generators that allow one to generate all of sl(n) under bracketing. It seems that Sylvester was the first to mention these generators, but he used them as generators of the associative algebra of all n times n matrices Mat(n). These generators appear in the description of elliptic solutions of the classical Yang-Baxter equation, orthogonal decompositions of Lie algebras, 't Hooft's work on confinement operators in QCD, and various other instances. Here I give an algorithm which both generates sl(n) and explicitly describes a set of defining relations. For simple (up to center) Lie superalgebras, analogs of Sylvester generators exist only for sl(n|n). The relations for this case are also computed.
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