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Search Results: 1 - 10 of 4580 matches for " Klaus Dreisewerd "
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Male-Specific Transfer and Fine Scale Spatial Differences of Newly Identified Cuticular Hydrocarbons and Triacylglycerides in a Drosophila Species Pair
Joanne Y. Yew,Klaus Dreisewerd,Cássia Cardoso de Oliveira,William J. Etges
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016898
Abstract: We analyzed epicuticular hydrocarbon variation in geographically isolated populations of D. mojavensis cultured on different rearing substrates and a sibling species, D. arizonae, with ultraviolet laser desorption/ionization mass spectrometry (UV-LDI MS). Different body parts, i.e. legs, proboscis, and abdomens, of both species showed qualitatively similar hydrocarbon profiles consisting mainly of long-chain monoenes, dienes, trienes, and tetraenes. However, D. arizonae had higher amounts of most hydrocarbons than D. mojavensis and females of both species exhibited greater hydrocarbon amounts than males. Hydrocarbon profiles of D. mojavensis populations were significantly influenced by sex and rearing substrates, and differed between body parts. Lab food–reared flies had lower amounts of most hydrocarbons than flies reared on fermenting cactus substrates. We discovered 48 male- and species-specific hydrocarbons ranging in size from C22 to C50 in the male anogenital region of both species, most not described before. These included several oxygen-containing hydrocarbons in addition to high intensity signals corresponding to putative triacylglycerides, amounts of which were influenced by larval rearing substrates. Some of these compounds were transferred to female cuticles in high amounts during copulation. This is the first study showing that triacylglycerides may be a separate class of courtship-related signaling molecules in drosophilids. This study also extends the kind and number of epicuticular hydrocarbons in these species and emphasizes the role of larval ecology in influencing amounts of these compounds, many of which mediate courtship success within and between species.
Dietary Effects on Cuticular Hydrocarbons and Sexual Attractiveness in Drosophila
Tatyana Y. Fedina, Tsung-Han Kuo, Klaus Dreisewerd, Herman A. Dierick, Joanne Y. Yew, Scott D. Pletcher
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0049799
Abstract: Dietary composition is known to have profound effects on many aspects of animal physiology, including lifespan, general health, and reproductive potential. We have previously shown that aging and insulin signaling significantly influence the composition and sexual attractiveness of Drosophila melanogaster female cuticular hydrocarbons (CHCs), some of which are known to be sex pheromones. Because diet is intimately linked to aging and to the activity of nutrient-sensing pathways, we asked how diet affects female CHCs and attractiveness. Here we report consistent and significant effects of diet composition on female CHC profiles across ages, with dietary yeast and sugar driving CHC changes in opposite directions. Surprisingly, however, we found no evidence that these changes affect female attractiveness. Multivariate comparisons among responses of CHC profiles to diet, aging, and insulin signaling suggest that diet may alter the levels of some CHCs in a way that results in profiles that are more attractive while simultaneously altering other CHCs in a way that makes them less attractive. For example, changes in short-chain CHCs induced by a high-yeast diet phenocopy changes caused by aging and by decreased insulin signaling, both of which result in less attractive females. On the other hand, changes in long-chain CHCs in response to the same diet result in levels that are comparable to those observed in attractive young females and females with increased insulin signaling. The effects of a high-sugar diet tend in the opposite direction, as levels of short-chain CHCs resemble those in attractive females with increased insulin signaling and changes in long-chain CHCs are similar to those caused by decreased insulin signaling. Together, these data suggest that diet-dependent changes in female CHCs may be sending conflicting messages to males.
Insulin Signaling Mediates Sexual Attractiveness in Drosophila
Tsung-Han Kuo equal contributor,Tatyana Y. Fedina equal contributor,Ingrid Hansen,Klaus Dreisewerd,Herman A. Dierick,Joanne Y. Yew,Scott D. Pletcher
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1002684
Abstract: Sexually attractive characteristics are often thought to reflect an individual's condition or reproductive potential, but the underlying molecular mechanisms through which they do so are generally unknown. Insulin/insulin-like growth factor signaling (IIS) is known to modulate aging, reproduction, and stress resistance in several species and to contribute to variability of these traits in natural populations. Here we show that IIS determines sexual attractiveness in Drosophila through transcriptional regulation of genes involved in the production of cuticular hydrocarbons (CHC), many of which function as pheromones. Using traditional gas chromatography/mass spectrometry (GC/MS) together with newly introduced laser desorption/ionization orthogonal time-of-flight mass spectrometry (LDI-MS) we establish that CHC profiles are significantly affected by genetic manipulations that target IIS. Manipulations that reduce IIS also reduce attractiveness, while females with increased IIS are significantly more attractive than wild-type animals. IIS effects on attractiveness are mediated by changes in CHC profiles. Insulin signaling influences CHC through pathways that are likely independent of dFOXO and that may involve the nutrient-sensing Target of Rapamycin (TOR) pathway. These results suggest that the activity of conserved molecular regulators of longevity and reproductive output may manifest in different species as external characteristics that are perceived as honest indicators of fitness potential.
Pheromonal and Behavioral Cues Trigger Male-to-Female Aggression in Drosophila
María de la Paz Fernández,Yick-Bun Chan,Joanne Y. Yew,Jean-Christophe Billeter,Klaus Dreisewerd,Joel D. Levine,Edward A. Kravitz
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1000541
Abstract: Appropriate displays of aggression rely on the ability to recognize potential competitors. As in most species, Drosophila males fight with other males and do not attack females. In insects, sex recognition is strongly dependent on chemosensory communication, mediated by cuticular hydrocarbons acting as pheromones. While the roles of chemical and other sensory cues in stimulating male to female courtship have been well characterized in Drosophila, the signals that elicit aggression remain unclear. Here we show that when female pheromones or behavior are masculinized, males recognize females as competitors and switch from courtship to aggression. To masculinize female pheromones, a transgene carrying dsRNA for the sex determination factor transformer (traIR) was targeted to the pheromone producing cells, the oenocytes. Shortly after copulation males attacked these females, indicating that pheromonal cues can override other sensory cues. Surprisingly, masculinization of female behavior by targeting traIR to the nervous system in an otherwise normal female also was sufficient to trigger male aggression. Simultaneous masculinization of both pheromones and behavior induced a complete switch in the normal male response to a female. Control males now fought rather than copulated with these females. In a reciprocal experiment, feminization of the oenocytes and nervous system in males by expression of transformer (traF) elicited high levels of courtship and little or no aggression from control males. Finally, when confronted with flies devoid of pheromones, control males attacked male but not female opponents, suggesting that aggression is not a default behavior in the absence of pheromonal cues. Thus, our results show that masculinization of either pheromones or behavior in females is sufficient to trigger male-to-female aggression. Moreover, by manipulating both the pheromonal profile and the fighting patterns displayed by the opponent, male behavioral responses towards males and females can be completely reversed. Therefore, both pheromonal and behavioral cues are used by Drosophila males in recognizing a conspecific as a competitor.
Rapid metabolic profiling of Nicotiana tabacum defence responses against Phytophthora nicotianae using direct infrared laser desorption ionization mass spectrometry and principal component analysis
Alfredo J Ibá?ez, Judith Scharte, Philipp Bones, Alexander Pirkl, Stefan Meldau, Ian T Baldwin, Franz Hillenkamp, Engelbert Weis, Klaus Dreisewerd
Plant Methods , 2010, DOI: 10.1186/1746-4811-6-14
Abstract: Infrared laser desorption ionization orthogonal time-of-flight mass spectrometry allows rapid and simultaneous detection in both negative and positive ion mode of a wide range of naturally occurring primary and secondary metabolites. An unsupervised principal component analysis was employed to identify correlations between changes in metabolite expression (obtained at different times and sample treatment conditions) and the overall defence response.A one-dimensional projection of the principal components 1 and 2 obtained from positive ion mode spectra was used to generate a Biological Response Index (BRI). The BRI obtained for each sample treatment was compared with the number of dead cells found in the respective tissue. The high correlation between these two values suggested that the BRI provides a rapid assessment of the plant response against the pathogen infection. Evaluation of the loading plots of the principal components (1 and 2) reveals a correlation among three metabolic cascades and the defence response generated in infected leaves. Analysis of selected phytohormones by liquid chromatography electrospray ionization mass spectrometry verified our findings.The described methodology allows for rapid assessment of infection-specific changes in the plant metabolism, in particular of phenolics, alkaloids, oxylipins, and carbohydrates. Moreover, potential novel biomarkers can be detected and used to predict the quality of plant infections.Metabolism consists of a complex network of biosynthetic pathways and comprises a series of biochemical reactions that are catalyzed by enzymes [1,2]. Plants and animals produce a remarkably diverse array of over 100,000 secondary metabolites. In contrast to the primary metabolites, secondary metabolites are normally not directly involved in growth, development, and reproduction, but partly play essential roles in the adaptation of the organisms to their environments [1-5]. The rich diversity of secondary metabolites results f
Shiga Toxin Receptor Gb3Cer/CD77: Tumor-Association and Promising Therapeutic Target in Pancreas and Colon Cancer
Ute Distler, Jamal Souady, Marcel Hülsewig, Irena Drmi?-Hofman, J?rg Haier, Alexander W. Friedrich, Helge Karch, Norbert Senninger, Klaus Dreisewerd, Stefan Berkenkamp, M. Alexander Schmidt, Jasna Peter-Katalini?, Johannes Müthing
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006813
Abstract: Background Despite progress in adjuvant chemotherapy in the recent decades, pancreatic and colon cancers remain common causes of death worldwide. Bacterial toxins, which specifically bind to cell surface-exposed glycosphingolipids, are a potential novel therapy. We determined the expression of globotriaosylceramide (Gb3Cer/CD77), the Shiga toxin receptor, in human pancreatic and colon adenocarcinomas. Methodology/Principal Findings Tissue lipid extracts of matched pairs of cancerous and adjacent normal tissue from 21 pancreatic and 16 colon cancer patients were investigated with thin-layer chromatography overlay assay combined with a novel mass spectrometry approach. Gb3Cer/CD77 was localized by immunofluorescence microscopy of cryosections from malignant and corresponding healthy tissue samples. 62% of pancreatic and 81% of colon adenocarcinomas showed increased Gb3Cer/CD77 expression, whereas 38% and 19% of malignant pancreas and colon tissue, respectively, did not, indicating an association of this marker with neoplastic transformation. Also, Gb3Cer/CD77 was associated with poor differentiation (G>2) in pancreatic cancer (P = 0.039). Mass spectrometric analysis evidenced enhanced expression of Gb3Cer/CD77 with long (C24) and short chain fatty acids (C16) in malignant tissues and pointed to the presence of hydroxylated fatty acid lipoforms, which are proposed to be important for receptor targeting. They could be detected in 86% of pancreatic and about 19% of colon adenocarcinomas. Immunohistology of tissue cryosections indicated tumor-association of these receptors. Conclusions/Significance Enhanced expression of Gb3Cer/CD77 in most pancreatic and colon adenocarcinomas prompts consideration of Shiga toxin, its B-subunit or B-subunit-derivatives as novel therapeutic strategies for the treatment of these challenging malignancies.
Pheromonal and Behavioral Cues Trigger Male-to-Female Aggression in Drosophila
María de la Paz Fernández equal contributor ,Yick-Bun Chan equal contributor,Joanne Y. Yew,Jean-Christophe Billeter,Klaus Dreisewerd,Joel D. Levine,Edward A. Kravitz
PLOS Biology , 2010, DOI: 10.1371/journal.pbio.1000541
Abstract: Appropriate displays of aggression rely on the ability to recognize potential competitors. As in most species, Drosophila males fight with other males and do not attack females. In insects, sex recognition is strongly dependent on chemosensory communication, mediated by cuticular hydrocarbons acting as pheromones. While the roles of chemical and other sensory cues in stimulating male to female courtship have been well characterized in Drosophila, the signals that elicit aggression remain unclear. Here we show that when female pheromones or behavior are masculinized, males recognize females as competitors and switch from courtship to aggression. To masculinize female pheromones, a transgene carrying dsRNA for the sex determination factor transformer (traIR) was targeted to the pheromone producing cells, the oenocytes. Shortly after copulation males attacked these females, indicating that pheromonal cues can override other sensory cues. Surprisingly, masculinization of female behavior by targeting traIR to the nervous system in an otherwise normal female also was sufficient to trigger male aggression. Simultaneous masculinization of both pheromones and behavior induced a complete switch in the normal male response to a female. Control males now fought rather than copulated with these females. In a reciprocal experiment, feminization of the oenocytes and nervous system in males by expression of transformer (traF) elicited high levels of courtship and little or no aggression from control males. Finally, when confronted with flies devoid of pheromones, control males attacked male but not female opponents, suggesting that aggression is not a default behavior in the absence of pheromonal cues. Thus, our results show that masculinization of either pheromones or behavior in females is sufficient to trigger male-to-female aggression. Moreover, by manipulating both the pheromonal profile and the fighting patterns displayed by the opponent, male behavioral responses towards males and females can be completely reversed. Therefore, both pheromonal and behavioral cues are used by Drosophila males in recognizing a conspecific as a competitor.
A New Mint1 Isoform, but Not the Conventional Mint1, Interacts with the Small GTPase Rab6
Anika Thyrock, Edith Ossendorf, Martin Stehling, Mark Kail, Tanja Kurtz, Gottfried Pohlentz, Dieter Waschbüsch, Simone Eggert, Etienne Formstecher, Johannes Müthing, Klaus Dreisewerd, Stefan Kins, Bruno Goud, Angelika Barnekow
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0064149
Abstract: Small GTPases of the Rab family are important regulators of a large variety of different cellular functions such as membrane organization and vesicle trafficking. They have been shown to play a role in several human diseases. One prominent member, Rab6, is thought to be involved in the development of Alzheimer’s Disease, the most prevalent mental disorder worldwide. Previous studies have shown that Rab6 impairs the processing of the amyloid precursor protein (APP), which is cleaved to β-amyloid in brains of patients suffering from Alzheimer’s Disease. Additionally, all three members of the Mint adaptor family are implied to participate in the amyloidogenic pathway. Here, we report the identification of a new Mint1 isoform in a yeast two-hybrid screening, Mint1 826, which lacks an eleven amino acid (aa) sequence in the conserved C-terminal region. Mint1 826, but not the conventional Mint1, interacts with Rab6 via the PTB domain. This interaction is nucleotide-dependent, Rab6-specific and influences the subcellular localization of Mint1 826. We were able to detect and sequence a corresponding proteolytic peptide derived from cellular Mint1 826 by mass spectrometry proving the absence of aa 495–505 and could show that the deletion does not influence the ability of this adaptor protein to interact with APP. Taking into account that APP interacts and co-localizes with Mint1 826 and is transported in Rab6 positive vesicles, our data suggest that Mint1 826 bridges APP to the small GTPase at distinct cellular sorting points, establishing Mint1 826 as an important player in regulation of APP trafficking and processing.
An Enduring Concept for Security Council Reform  [PDF]
Klaus Schlichtmann
Beijing Law Review (BLR) , 2011, DOI: 10.4236/blr.2011.22010
Abstract: UN Security Council reform has been lingering over the years, since it was first seriously considered in the 1990s, after the collapse of the Soviet Union. This paper argues that enlarging the Security Council by adding new permanent and non-permanent members, while many of the Charter provisions vital for the maintenance of international peace and security and disarmament are not in effect, would be counterproductive. Instead, the composition of the Council should be reshuffled and expanded by giving a seat to a prominent member of the Global South, i.e. India, and replacing the seats of France and Britain with a single European representation. While there would be no increase or change in the number of permanent and non-permanent members, the result will be a dramatic increase in the numbers of people represented by the Permanent Five, which then will, in effect, comprise half of the world’s population projected for 2012. The underlying logic is that increasing the number of permanent members (P5) would make the Security Council not only less effective, but also prevent the realization of a fundamental purpose of the United Nations, i.e. the transition from an armed to an unarmed peace. By maintaining the number 5, the effective operation of the consensus principle required for the maintenance of international peace and security during the transition is ensured. It is maintained that the changes proposed in this paper may be regarded as “purely procedural” under Article 27 paragraph 2 of the Charter. It will be seen, however, that to trigger the process of the transition, UN Member states (other than the P5, who bear responsibility under the Charter to guarantee safe passage during the transition) must begin, one by one, to delegate “Security Sovereignty” to the Council.
Digital Technology to Support the Trade Union Movement  [PDF]
Klaus Schoemann
Open Journal of Social Sciences (JSS) , 2018, DOI: 10.4236/jss.2018.61005
Abstract:
New digital technologies have a potential to bypass traditional forms of labour organization. We summarize the academic and trade union literature on the potential of new digital technologies for trade unions. Building on the literature of the social construction of technology and democracy at work we present the concept of the technology-supported construction of the social sphere. A review of digital technologies allows us to identify the potential innovator role of trade unions and work councils in digital forms of employee participation. Digital technologies are an important way to attract younger generations of trade union members. For experienced members, bridging the digital divide becomes a vital issue, too. Finally, we highlight the active interplay and mutually reinforcing effect of online and offline communication in networking.
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