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Search Results: 1 - 10 of 1466 matches for " Cordula Schulz "
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Control of Germline Stem Cell Division Frequency – A Novel, Developmentally Regulated Role for Epidermal Growth Factor Signaling
Benjamin B. Parrott, Alicia Hudson, Regina Brady, Cordula Schulz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0036460
Abstract: Exploring adult stem cell dynamics in normal and disease states is crucial to both better understanding their in vivo role and better realizing their therapeutic potential. Here we address the division frequency of Germline Stem Cells (GSCs) in testes of Drosophila melanogaster. We show that GSC division frequency is under genetic control of the highly conserved Epidermal Growth Factor (EGF) signaling pathway. When EGF signaling was attenuated, we detected a two-fold increase in the percentage of GSCs in mitotic division compared to GSCs in control animals. Ex vivo and in vivo experiments using a marker for cells in S-phase of the cell cycle showed that the GSCs in EGF mutant testes divide faster than GSCs in control testes. The increased mitotic activity of GSCs in EGF mutants was rescued by restoring EGF signaling in the GSCs, and reproduced in testes from animals with soma-depleted EGF-Receptor (EGFR). Interestingly, EGF attenuation specifically increased the GSC division frequency in adult testes, but not in larval testes. Furthermore, GSCs in testes with tumors resulting from the perturbation of other conserved signaling pathways divided at normal frequencies. We conclude that EGF signaling from the GSCs to the CySCs normally regulates GSC division frequency. The EGF signaling pathway is bifurcated and acts differently in adult compared to larval testes. In addition, regulation of GSC division frequency is a specific role for EGF signaling as it is not affected in all tumor models. These data advance our understanding concerning stem cell dynamics in normal tissues and in a tumor model.
A Temporal Signature of Epidermal Growth Factor Signaling Regulates the Differentiation of Germline Cells in Testes of Drosophila melanogaster
Alicia G. Hudson, Benjamin B. Parrott, Yue Qian, Cordula Schulz
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0070678
Abstract: Tissue replenishment from stem cells follows a precise cascade of events, during which stem cell daughters first proliferate by mitotic transit amplifying divisions and then enter terminal differentiation. Here we address how stem cell daughters are guided through the early steps of development. In Drosophila testes, somatic cyst cells enclose the proliferating and differentiating germline cells and the units of germline and surrounding cyst cells are commonly referred to as cysts. By characterizing flies with reduced or increased Epidermal Growth Factor (EGF) signaling we show that EGF triggers different responses in the cysts dependent on its dose. In addition to the previously reported requirement for EGF signaling in cyst formation, a low dose of EGF signaling is required for the progression of the germline cells through transit amplifying divisions, and a high dose of EGF signaling promotes terminal differentiation. Terminal differentiation was promoted in testes expressing a constitutively active EGF Receptor (EGFR) and in testes expressing both a secreted EGF and the EGFR in the cyst cells, but not in testes expressing either only EGF or only EGFR. We propose that as the cysts develop, a temporal signature of EGF signaling is created by the coordinated increase of both the production of active ligands by the germline cells and the amount of available receptor molecules on the cyst cells.
Nucleoporin98-96 Function Is Required for Transit Amplification Divisions in the Germ Line of Drosophila melanogaster
Benjamin B. Parrott, Yuting Chiang, Alicia Hudson, Angshuman Sarkar, Antoine Guichet, Cordula Schulz
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0025087
Abstract: Production of specialized cells from precursors depends on a tightly regulated sequence of proliferation and differentiation steps. In the gonad of Drosophila melanogaster, the daughters of germ line stem cells (GSC) go through precisely four rounds of transit amplification divisions to produce clusters of 16 interconnected germ line cells before entering a stereotypic differentiation cascade. Here we show that animals harbouring a transposon insertion in the center of the complex nucleoporin98-96 (nup98-96) locus had severe defects in the early steps of this developmental program, ultimately leading to germ cell loss and sterility. A phenotypic analysis indicated that flies carrying the transposon insertion, designated nup98-962288, had dramatically reduced numbers of germ line cells. In contrast to controls, mutant testes contained many solitary germ line cells that had committed to differentiation as well as abnormally small clusters of two, four or eight differentiating germ line cells. This indicates that mutant GSCs rather differentiated than self-renewed, and that these GSCs and their daughters initiated the differentiation cascade after zero, or less than four rounds of amplification divisions. This phenotype remained unaffected by hyper-activation of signalling pathways that normally result in excessive proliferation of GSCs and their daughters. Expression of wildtype nup98-96 specifically in the germ line cells of mutant animals fully restored development of the GSC lineage, demonstrating that the effect of the mutation is cell-autonomous. Nucleoporins are the structural components of the nucleopore and have also been implicated in transcriptional regulation of specific target genes. The nuclear envelopes of germ cells and general nucleocytoplasmic transport in nup98-96 mutant animals appeared normal, leading us to propose that Drosophila nup98-96 mediates the transport or transcription of targets required for the developmental timing between amplification and differentiation.
Off-target effects of siRNA specific for GFP
Cordula Tschuch, Angela Schulz, Armin Pscherer, Wiebke Werft, Axel Benner, Agnes Hotz-Wagenblatt, Leticia Barrionuevo, Peter Lichter, Daniel Mertens
BMC Molecular Biology , 2008, DOI: 10.1186/1471-2199-9-60
Abstract: We tested the most widely used control siRNA directed against GFP for off-target effects and found that it deregulates in addition to GFP a set of endogenous target genes. The off-target effects were dependent on the amount of GFP siRNA transfected and were detected in a variety of cell lines. Since the respective siRNA molecule specific for GFP is widely used as negative control for RNAi experiments, we studied the complete set of off-target genes of this molecule by genome-wide expression profiling. The detected modulated mRNAs had target sequences homologous to the siRNA as small as 8 basepairs in size. However, we found no restriction of sequence homology to 3'UTR of target genes.We can show that even siRNAs without a physiological target have sequence-specific off-target effects in mammalian cells. Furthermore, our analysis defines the off-target genes affected by the siRNA that is commonly used as negative control and directed against GFP. Since off-target effects can hardly be avoided, the best strategy is to identify false positives and exclude them from the results. To this end, we provide the set of false positive genes deregulated by the commonly used GFP siRNA as a reference resource for future siRNA experiments.RNA interference (RNAi) is a powerful method to specifically suppress gene expression and is therefore widely used for experimental as well as therapeutic purposes. Since the initial characterization of RNAi in the nematode C. elegans [1], the field of RNAi has expanded remarkably. The essentials of RNAi can be summarized as specific degradation of target mRNA mediated by small, double stranded RNAs [2,3]. Meanwhile, different mechanisms of RNAi were discovered in mammalian cells comprising post-transcriptional gene silencing by siRNAs, transcriptional silencing by siRNAs in the nucleus and the microRNA pathway [4,5]. It has been shown that exogenously introduced siRNA duplexes and endogenously processed miRNA duplexes are taken up by the RNA-ind
Der Topos der Zeit als argumentative Ressource in Konfliktgespr chen The Topos of Time as an Argumentative Resource in Conflict Talk Los topos del tiempo como un recurso argumentativo en el habla de conflicto
Cordula Schwarze
Forum : Qualitative Social Research , 2007,
Abstract: Anhand konflikt rer Gespr che im familialen Rahmen werden mittels eines gespr chslinguistischen Zugriffs die Form- und Funktionsbeziehungen des Topos der Zeit als einer argumentativen Ressource aufgezeigt. Der Fokus dieser linguistisch basierten Mikroanalysen liegt insbesondere auf der Interaktivit t und Prozessualit t der Herstellung sowie der funktionalen Zuordnung der Toposverwendung zu rhetorischen Verfahren. Im Artikel wird eine "kleine Ph nomenologie der Zahlen" in konflikt ren Gespr chen zwischen Müttern und ihren adoleszenten T chtern vorgestellt. Es kann gezeigt werden, dass die an der sprachlichen Oberfl che analysierbare Verwendung von Zahlen Ausdruck einer spezifischen Konzeptualisierung von Zeit ist. Zahlen in der konkreten und lokalen Ausfüllung des Topos der Zeit lassen somit Rückschlüsse auf eine Alltagskonzeptualisierung von Zeit zu, und auf diese Weise wird die Kategorie Zeit sichtbar an der Gespr chsoberfl che. URN: urn:nbn:de:0114-fqs0701165 Employing a conversation-analytical approach, this paper describes the form-function relations of the topos of time as an argumentative resource. Linguistically grounded this micro-analysis primarily focuses on the interactivity and processuality of talk-in-interaction as well as on the functional assignment of topoi-uses to rhetorical procedures. The paper provides a ’short phenomenology of numbers’ in conflict talk between mothers and their adolescent daughters. I will argue that the use of numbers on the conversational surface points to a specific conceptualization of time. In their concrete and local realization of the topos of time these numbers lay bare everyday conceptualizations of time. This way time as a category becomes visible on the conversational surface. URN: urn:nbn:de:0114-fqs0701165 Empleando un enfoque analítico de conversación este artículo describe las relaciones forma-función de los topos del tiempo como un recurso argumentativo. Lingüísticamente fundado este microanálisis se enfoca principalmente en la interactividad y procesualidad del habla-en-interacción así como en las tareas funcionales del uso de los topoi en los procedimientos retóricos. Se proporciona una "peque a fenomenología de los números" en el habla de conflicto entre madres y sus hijas adolescentes. Argumentaré que el uso de los números en la superficie conversacional apunta hacia una conceptualización específica del tiempo. En su materialización local y concreta de los topos de tiempo, estos números evidencian conceptualizaciones cotidianas del tiempo. De esta manera el tiempo en tanto categoría se hace visi
Do imputed education histories provide satisfactory results in fertility analysis in the Western German context?
Cordula Zabel
Demographic Research , 2009,
Abstract: In many surveys, information on respondents' education histories is restricted to the level and sometimes the date they attained their highest degree. We compare estimates of education effects on first birth transitions using imputed histories based on this rudimentary information with estimates drawing on complete histories, using the German Life History Study. We find that imputed histories produce relatively reliable estimates for most but not all education categories, especially when information on the date the highest degree was attained is available. We investigate possible explanations for these findings and indicate contexts in which biases may be stronger.
Faire clair et vif avec des éléments complexes
Cordula Reichart
Flaubert : Revue Critique et Génétique , 2010,
Abstract: Avec le roman Salammb et le conte Hérodias, Flaubert se tourne vers l’Antiquité préchrétienne afin de montrer à la modernité, sur le mode clair et vif , sa complexité, son implication dans des discours de pouvoir religieux et historiographiques. C’est en se penchant sur les sources historiographiques et bibliques que Flaubert décline les stratégies d’exclusion et de surécriture, mettant au jour ce qu’elles refoulent, non pas sous forme de signification alternative, explicite, mais en tant que défiguration, réalisation littérale des corps et des signes.Avec Salammb , Flaubert écrit une histoire du salut. Carthage, représentée dès le début par la protagoniste Salammb en tant que pars pro toto, expose les figures cachées de Rome, à laquelle est liée, aussi et surtout, la promesse chrétienne de salut. Dans le nom de Salammb Flaubert réécrit l’origine de cette figure en fait associée à la Rome chrétienne en s’appuyant sur l’exemple de l’histoire antique de Carthage.Dans Hérodias, Flaubert reprend le thème du triomphe de l’Orient annoncé par Renan et redouté par l’église catholique. Un danger, pourrait-on dire, qui se réalise dans la figure d’Hérodias et qui est conjuré avec la décapitation de Jean. Dans son rapport inversé avec les textes de référence, Hérodias démasque les ambitions et la volonté hégémonique du modèle de pouvoir propre à l’église en Orient. La translatio de l’empire romain est radicalisée au moyen de la figure d’Aulus. Aulus peut faire l’objet d’une lecture performative en tant que début et fondement de l’histoire fran aise du salut comme histoire romaine de la perversion. In the novel Salammb and the short story Hérodias, Flaubert turns to pre-Christian antiquity in order to present modernity its complexity, its entwinement in religious and historiographical discourses of power, in a clair et vif manner. In Salammb , Flaubert re-writes the story of salvation. In Salammb ’s name, Flaubert construes the origin of a figure which is actually linked to Christian Rome as the ancient story of Carthage. In Hérodias, Flaubert takes up the triumph of the Orient as proclaimed by Renan and feared by the Catholic Church. This danger is realized in the figure of Hérodias and averted by the decapitation of John the Baptist. In its perverted relationship to the historical texts of reference, Hérodias unmasks the claim to supremacy of the rising clerical model of power, while the translatio of the Roman Empire gets radicalized in the figure of Aulus. Aulus can be read performatively as beginning and foundation of the French story of salvation as
Optimization of Formaldehyde Cross-Linking for Protein Interaction Analysis of Non-Tagged Integrin 1
Cordula Klockenbusch,Juergen Kast
Journal of Biomedicine and Biotechnology , 2010, DOI: 10.1155/2010/927585
Abstract: Formaldehyde cross-linking of protein complexes combined with immunoprecipitation and mass spectrometry analysis is a promising technique for analysing protein-protein interactions, including those of transient nature. Here we used integrin 1 as a model to describe the application of formaldehyde cross-linking in detail, particularly focusing on the optimal parameters for cross-linking, the detection of formaldehyde cross-linked complexes, the utility of antibodies, and the identification of binding partners. Integrin 1 was found in a high molecular weight complex after formaldehyde cross-linking. Eight different anti-integrin 1 antibodies were used for pull-down experiments and no loss in precipitation efficiency after cross-linking was observed. However, two of the antibodies could not precipitate the complex, probably due to hidden epitopes. Formaldehyde cross-linked complexes, precipitated from Jurkat cells or human platelets and analyzed by mass spectrometry, were found to be composed of integrin 1, 4 and 6 or 1, 6, 2, and 5, respectively.
Praktische Sonografie und Echokardiografie im Selbststudium für Studierende der Tiermedizin: ein modernes Unterrichtsmodell für das 4. bis 9. Semester []
Poulsen Nautrup, Cordula
GMS Zeitschrift für Medizinische Ausbildung , 2008,
The ultimate tactics of self-referential systems
Christine Cordula Dantas
Physics , 2015,
Abstract: Mathematics is usually regarded as a kind of language. The essential behavior of physical phenomena can be expressed by mathematical laws, providing descriptions and predictions. In the present essay I argue that, although mathematics can be seen, in a first approach, as a language, it goes beyond this concept. I conjecture that mathematics presents two extreme features, denoted here by {\sl irreducibility} and {\sl insaturation}, representing delimiters for self-referentiality. These features are then related to physical laws by realizing that nature is a self-referential system obeying bounds similar to those respected by mathematics. Self-referential systems can only be autonomous entities by a kind of metabolism that provides and sustains such an autonomy. A rational mind, able of consciousness, is a manifestation of the self-referentiality of the Universe. Hence mathematics is here proposed to go beyond language by actually representing the most fundamental existence condition for self-referentiality. This idea is synthesized in the form of a principle, namely, that {\sl mathematics is the ultimate tactics of self-referential systems to mimic themselves}. That is, well beyond an effective language to express the physical world, mathematics uncovers a deep manifestation of the autonomous nature of the Universe, wherein the human brain is but an instance.
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