Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2019 ( 145 )

2018 ( 320 )

2017 ( 295 )

2016 ( 456 )

Custom range...

Search Results: 1 - 10 of 297756 matches for " Jürgen Krieger "
All listed articles are free for downloading (OA Articles)
Page 1 /297756
Display every page Item
A receptor and binding protein interplay in the detection of a distinct pheromone component in the silkmoth Antheraea polyphemus
Maike Forstner, Heinz Breer, Jürgen Krieger
International Journal of Biological Sciences , 2009,
Abstract: Male moths respond to conspecific female-released pheromones with remarkable sensitivity and specificity, due to highly specialized chemosensory neurons in their antennae. In Antheraea silkmoths, three types of sensory neurons have been described, each responsive to one of three pheromone components. Since also three different pheromone binding proteins (PBPs) have been identified, the antenna of Antheraea seems to provide a unique model system for detailed analyzes of the interplay between the various elements underlying pheromone reception. Efforts to identify pheromone receptors of Antheraea polyphemus have led to the identification of a candidate pheromone receptor (ApolOR1). This receptor was found predominantly expressed in male antennae, specifically in neurons located beneath pheromone-sensitive sensilla trichodea. The ApolOR1-expressing cells were found to be surrounded by supporting cells co-expressing all three ApolPBPs. The response spectrum of ApolOR1 was assessed by means of calcium imaging using HEK293-cells stably expressing the receptor. It was found that at nanomolar concentrations ApolOR1-cells responded to all three pheromones when the compounds were solubilized by DMSO and also when DMSO was substituted by one of the three PBPs. However, at picomolar concentrations, cells responded only in the presence of the subtype ApolPBP2 and the pheromone (E,Z)-6,11-hexadecadienal. These results are indicative of a specific interplay of a distinct pheromone component with an appropriate binding protein and its related receptor subtype, which may be considered as basis for the remarkable sensitivity and specificity of the pheromone detection system.
The Olfactory Co-receptor Orco from the Migratory Locust (Locusta migratoria) and the Desert Locust (Schistocerca gregaria): Identification and Expression pattern
Ying Yang, Jürgen Krieger, Long Zhang, Heinz Breer
International Journal of Biological Sciences , 2012,
Abstract: In locusts, olfaction plays a crucial role for initiating and controlling behaviours, including food seeking and aggregation with conspecifics, which underlie the agricultural pest capacity of the animals. In this context, the molecular basis of olfaction in these insects is of particular interest. Here, we have identified genes of two orthopteran species, Locusta migratoria and Schistocera gregaria, which encode the olfactory receptor co-receptor (Orco). It was found that the sequences of LmigOrco and SgreOrco share a high degree of identity to each other and also to Orco proteins from different insect orders. The Orco-expressing cells in the antenna of S. gregaria and L. migratoria were visualized by in situ hybridization. Orco expression could be assigned to clusters of cells in sensilla basiconica and few cells in sensilla trichoidea, most likely representing olfactory sensory neurons. No Orco-positive cells were detected in sensilla coeloconica and sensilla chaetica. Orco expression was found already in all nymphal stages and was verified in some other tissues which are equipped with chemosensory hairs (mouthparts, tarsi, wings). Together, the results support the notion for a decisive role of Orco in locust olfaction.
Antennal expression pattern of two olfactory receptors and an odorant binding protein implicated in host odor detection by the malaria vector Anopheles gambiae
Danuta Schymura, Maike Forstner, Anna Schultze, Thomas Kr?ber, Luc Swevers, Kostas Iatrou, Jürgen Krieger
International Journal of Biological Sciences , 2010,
Abstract: Odor-detection in the malaria mosquito Anopheles gambiae involves large families of diverse proteins, including multiple odorant binding proteins (AgOBPs) and olfactory receptors (AgORs). The receptors AgOR1 and AgOR2, as well as the binding protein AgOBP1, have been implicated in the recognition of human host odors. In this study, we have explored the expression of these olfactory proteins, as well as the ubiquitous odorant receptor heteromerization partner AgOR7, in the thirteen flagellomeres (segments) of female and male antenna. Expressing cells were visualized by adapting a whole mount fluorescence in situ hybridization method. In female mosquitoes, AgOR1-expressing olfactory receptor neurons (ORNs) were almost exclusively segregated in segments 3 to 9, whereas AgOR2-expressing ORNs were distributed over flagellomeres 2 to 13. Different individuals comprised a similar number of cells expressing a distinct AgOR type, although their antennal topography and number per flagellomere varied. AgOBP1-expressing support cells were present in segments 3 to 13 of the female antenna, with increasing numbers towards the distal end. In male mosquitoes, total numbers of AgOR- and AgOBP1-expressing cells were much lower. While AgOR2-expressing cells were found on both terminal flagellomeres, AgOR1 cells were restricted to the most distal segment. High densities of AgOBP1-expressing cells were identified in segment 13, whereas segment 12 comprised very few. Altogether, the results demonstrate that both sexes express the two olfactory receptor types as well as the binding protein AgOBP1 but there is a significant sexual dimorphism concerning the number and distribution of these cells. This may suggest gender-specific differences in the ability to detect distinct odorants, specifically human host-derived volatiles.
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.
The Co-Expression Pattern of Odorant Binding Proteins and Olfactory Receptors Identify Distinct Trichoid Sensilla on the Antenna of the Malaria Mosquito Anopheles gambiae
Anna Schultze, Pablo Pregitzer, Marika F. Walter, Daniel F. Woods, Osvaldo Marinotti, Heinz Breer, Jürgen Krieger
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069412
Abstract: The initial steps of odorant recognition in the insect olfactory system involve odorant binding proteins (OBPs) and odorant receptors (ORs). While large families of OBPs have been identified in the malaria vector A. gambiae, little is known about their expression pattern in the numerous sensory hairs of the female antenna. We applied whole mount fluorescence in Situ hybridization (WM-FISH) and fluorescence immunohistochemistry (WM-FIHC) to investigate the sensilla co-expression of eight A. gambiae OBPs (AgOBPs), most notably AgOBP1 and AgOBP4, which all have abundant transcripts in female antenna. WM-FISH analysis of female antennae using AgOBP-specific probes revealed marked differences in the number of cells expressing each various AgOBPs. Testing combinations of AgOBP probes in two-color WM-FISH resulted in distinct cellular labeling patterns, indicating a combinatorial expression of AgOBPs and revealing distinct AgOBP requirements for various functional sensilla types. WM-FIHC with antisera to AgOBP1 and AgOBP4 confirmed expression of the respective proteins by support cells and demonstrated a location of OBPs within sensilla trichodea. Based on the finding that AgOBP1 and AgOBP4 as well as the receptor type AgOR2 are involved in the recognition of indole, experiments were performed to explore if the AgOBP-types and AgOR2 are co-expressed in distinct olfactory sensilla. Applying two-color WM-FISH with AgOBP-specific probes and probes specific for AgOR2 revealed a close association of support cells bearing transcripts for AgOBP1 and AgOBP4 and neurons with a transcript for the receptor AgOR2. Moreover, combined WM-FISH/-FIHC approaches using an AgOR2-specific riboprobe and AgOBP-specific antisera revealed the expression of the “ligand-matched” AgOBP1, AgOBP4 and AgOR2 to single trichoid hairs. This result substantiates the notion that a specific response to indole is mediated by an interplay of the proteins.
Sex-Specific Odorant Receptors of the Tobacco Hornworm Manduca Sexta
Ewald Gro?e-Wilde,Regina Stieber,Maike Forstner,Jürgen Krieger,Dieter Wicher,Bill S. Hansson
Frontiers in Cellular Neuroscience , 2010, DOI: 10.3389/fncel.2010.00022
Abstract: As odor information plays a vital role in the life of moths, their olfactory sense has evolved into a highly specific and sensitive apparatus relevant to reproduction and survival. The key players in the detection of odorants are olfactory receptor (OR) proteins. Here we identify four OR-encoding genes differentially expressed in the antennae of males and females of the sphingid moth Manduca sexta. Two male-specific receptors (the previously reported MsexOR-1 and the newly identified MsexOR-4) show great resemblance to other male moth pheromone ORs. The putative pheromone receptors are co-expressed with the co-receptor involved in general odorant signal transduction, the DmelOr83b homolog MsexOR-2. One female-specific receptor (MsexOR-5) displays similarities to BmorOR-19, a receptor in Bombyx mori tuned to the detection of the plant odor linalool.
Sleep apnoea and driving: how can this be dealt with?
J. Krieger
European Respiratory Review , 2007,
Abstract: Excessive daytime sleepiness has long been known to be associated with an increased risk of often particularly severe traffic accidents. Obstructive sleep apnoea (OSA) is among the most prevalent conditions leading to excessive daytime sleepiness, in addition to impaired cognitive function, both of which are likely to impair driving ability. An increased risk of traffic accidents has been demonstrated repeatedly, in association with OSA, as well its normalisation with effective treatment. However, it seems that not all patients are at equal risk, but it is not clear how to identify when and how at-risk patients can be identified. Nevertheless, some European countries have made specific regulations concerning OSA and/or excessive daytime sleepiness and the capacity to obtain or to keep a driving license. Most countries have the general rule that "a driving license should not be given or renewed to any candidate or license holder suffering from a disorder ... likely to compromise safety on the road", without a specific mention of sleepiness and/or sleep apnoea. However, the way in which such a statement is applied and the measures taken to identify unfit drivers vary greatly from country to country. In addition, in those countries that have made specific regulations, no evaluation of their efficacy in reducing sleepiness-related accidents is available. In practice, it is the physician's responsibility to inform the untreated obstructive sleep apnoea patient about the risk associated with their condition, and about the regulations that prevail in their country, if relevant; only in a few countries, is the physician allowed (or compelled) to report the unfit patient to the licensing authorities. Although it is generally accepted that the treated patient may be allowed to drive, the specific treatment conditions that eliminate the risk are not clearly established.
Shifts in sensory neuron identity parallel differences in pheromone preference in the European corn borer
Fotini A. Koutroumpa,Zsolt Kárpáti,Christelle Monsempes,Sharon R. Hill,Bill S. Hansson,Emmanuelle Jacquin-Joly,Jürgen Krieger,Teun Dekker
Frontiers in Ecology and Evolution , 2014, DOI: 10.3389/fevo.2014.00065
Abstract: Pheromone communication relies on highly specific signals sent and received between members of the same species. However, how pheromone preference is determined in moth olfactory circuits remains unknown. Here we describe a potential mechanism that generates preference differences in Ostrinia nubilalis. In Ostrinia nubilalis it was found that a single locus causes strain-specific, diametrically opposed preferences for a 2-component pheromone blend. Previously we found that pheromone preference was correlated with strain and hybrid-specific relative antennal response to both pheromone components. Here we detail the underlying mechanism of this differential response, through chemotopical mapping of the pheromone detection circuit in the antenna. We found that both strains and their hybrids have swapped the neuronal identity of the pheromone-sensitive neurons co-housed within a single sensillum. Furthermore, neurons that mediate behavioral antagonism surprisingly co-express up to five pheromone receptors, mirroring the concordantly broad tuning to heterospecific pheromones. Co-expression appears evolutionarily advantageous as it prevents cross attraction to a range of heterospecific signals, while keeping the pheromone detection system to its simplest tripartite setup.
Male Circumcision Does Not Reduce Sexual Function, Sensitivity or Satisfaction  [PDF]
Brian J. Morris, John N. Krieger
Advances in Sexual Medicine (ASM) , 2015, DOI: 10.4236/asm.2015.53007
Abstract: We disagree with Boyle’s recent article questioning our systematic review in Journal of Sexual Medicine in 2013 (Volume 10, pages 2644-2657). In particular, he disputed the quality ranking we assigned to 7 of the 36 articles that met our inclusion criteria. These had been ranked for quality by the Scottish Intercollegiate Guidelines Network (SIGN) grading system. We found that, “the highest-quality studies suggest that medical male circumcision has no adverse effect on sexual function, sensitivity, sexual sensation or satisfaction.” This conclusion was supported by two randomized controlled trials, regarded as high-quality (1++) evidence and the majority of surveys and studies involving physiological measurements comparing uncircumcised and circumcised men. Here we explain why the 2 randomized controlled trials merit a 1++ ranking and why 4 reports that Boyle believes merit a higher ranking only meet the criteria set down for low quality (2?) evidence according to the SIGN system. We therefore stand by our conclusions. These are supported by a meta-analysis of sexual dysfunctions and by a recent detailed systematic review of the histological correlates of male sexual sensation.
Operator Splitting Method for Coupled Problems:Transport and Maxwell Equations  [PDF]
Jürgen Geiser
American Journal of Computational Mathematics (AJCM) , 2011, DOI: 10.4236/ajcm.2011.13019
Abstract: In this article a new approach is considered for implementing operator splitting methods for transport problems, influenced by electric fields. Our motivation came to model PE-CVD (plasma-enhanced chemical vapor deposition) processes, means the flow of species to a gas-phase, which are influenced by an electric field. Such a field we can model by wave equations. The main contributions are to improve the standard discretization schemes of each part of the coupling equation. So we discuss an improvement with implicit Runge- Kutta methods instead of the Yee’s algorithm. Further we balance the solver method between the Maxwell and Transport equation.
Page 1 /297756
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.