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Search Results: 1 - 10 of 3418 matches for " Nicola Horstmann "
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Dual-Site Phosphorylation of the Control of Virulence Regulator Impacts Group A Streptococcal Global Gene Expression and Pathogenesis
Nicola Horstmann,Miguel Salda?a,Pranoti Sahasrabhojane,Hui Yao,Xiaoping Su,Erika Thompson,Antonius Koller,Samuel A. Shelburne III
PLOS Pathogens , 2014, DOI: doi/10.1371/journal.ppat.1004088
Abstract: Phosphorylation relays are a major mechanism by which bacteria alter transcription in response to environmental signals, but understanding of the functional consequences of bacterial response regulator phosphorylation is limited. We sought to characterize how phosphorylation of the control of virulence regulator (CovR) protein from the major human pathogen group A Streptococcus (GAS) influences GAS global gene expression and pathogenesis. CovR mainly serves to repress GAS virulence factor-encoding genes and has been shown to homodimerize following phosphorylation on aspartate-53 (D53) in vitro. We discovered that CovR is phosphorylated in vivo and that such phosphorylation is partially heat-stable, suggesting additional phosphorylation at non-aspartate residues. Using mass spectroscopy along with targeted mutagenesis, we identified threonine-65 (T65) as an additional CovR phosphorylation site under control of the serine/threonine kinase (Stk). Phosphorylation on T65, as mimicked by the recombinant CovR T65E variant, abolished in vitro CovR D53 phosphorylation. Similarly, isoallelic GAS strains that were either unable to be phosphorylated at D53 (CovR-D53A) or had functional constitutive phosphorylation at T65 (CovR-T65E) had essentially an identical gene repression profile to each other and to a CovR-inactivated strain. However, the CovR-D53A and CovR-T65E isoallelic strains retained the ability to positively influence gene expression that was abolished in the CovR-inactivated strain. Consistent with these observations, the CovR-D53A and CovR-T65E strains were hypervirulent compared to the CovR-inactivated strain in a mouse model of invasive GAS disease. Surprisingly, an isoalleic strain unable to be phosphorylated at CovR T65 (CovR-T65A) was hypervirulent compared to the wild-type strain, as auto-regulation of covR gene expression resulted in lower covR gene transcript and CovR protein levels in the CovR-T65A strain. Taken together, these data establish that CovR is phosphorylated in vivo and elucidate how the complex interplay between CovR D53 activating phosphorylation, T65 inhibiting phosphorylation, and auto-regulation impacts streptococcal host-pathogen interaction.
Sacred Networks and Struggles among the Karen Baptists across the Thailand-Burma Border Réseaux sacrés et conflits parmi les Baptistes karen de part et d’autre de la frontière birmano-tha landaise
Alexander Horstmann
Moussons : Recherche en Sciences Humaines sur l’Asie du Sud-Est , 2011,
Abstract: In this article, I provide a case study of a moving border between Thailand and Burma. Emphasizing the agency of people who become refugees, the article is concerned to point out the important role of religious networks in providing humanitarian assistance, shelter and mobility to stateless Karen refugees. I argue that Christian and Buddhist literate networks- realigned in political exile, develop competing visions of a Karen “homeland.” Arguing that membership in the network is crucial for survival, the article follows the social organization and religious practices in Baptist networks. I examine how the Baptist church network in close partnership with the Karen National Union is able or not able to mobilize refugees for proselytization. Karen refugee leaders and KNU-pastors find analogies in the bible to find an explanation to the suffering of the Karen civil population in the war. The article is interested in the nexus and overlap of humanitarian ideology, Christianity and nationalism in the transitional space between Thailand and Burma. Providing case-studies of individual refugees, the article gives ethnographic sketches from the refugee camp, the countryside and humanitarian assistance to the internally displaced. Cet article est une étude de cas d’une frontière mouvante entre la Tha lande et la Birmanie. Insistant sur l’agency (action) de personnes devenues des réfugiés, l’article souligne le r le important des réseaux religieux qui apportent une assistance humanitaire, des abris et de la mobilité à des réfugiés karen dépourvus d’état. Je soutiens que les réseaux intellectuels chrétiens et bouddhistes, recomposés dans l’exil, développent des visions concurrentes d’une mère-patrie karen. Soutenant que la participation au réseau est cruciale pour la survie, l’article développe plus particulièrement l’organisation sociale et les pratiques religieuses en vigueur dans les réseaux baptistes. J’examine comment le réseau de l’église baptiste, en partenariat étroit avec l’Union Nationale Karen (UNK) est capable – ou pas – de mobiliser les réfugiés pour du prosélytisme. Les dirigeants réfugiés karen et les pasteurs de l’UNK trouvent dans la bible des analogies pour donner une explication aux souffrances de la population civile karen dans la guerre. L’article s’intéresse aux connexions et aux imbrications de l’idéologie humanitaire, du christianisme et du nationalisme dans l’espace de transition entre la Tha lande et la Birmanie. Révélant des études de cas de réfugiés particuliers, l’article donne des éléments ethnographiques du camp de réfugiés, des ca
Sacred Spaces of Karen Refugees and Humanitarian Aid Across the Thailand-Burma Border
Alexander Horstmann
ASEAS : ?sterreichische Zeitschrift für Südostasienwissenschaften , 2011,
Abstract: In this article, I demonstrate that the Karen National Union (KNU) was able to manipulate and politicise humanitarian aid in the Thailand-Burma borderland. I contend that in the context of the civil war in eastern Burma, Protestant Christianity provides a crucial vehicle for political mobilisation. The article shows that refugee camps in the Thai borderland become centres of proselytisation, and that Protestant evangelical and missionary networks open up passages across the Thai-Burmese border. The article thus considers a case where a homeland is constructed in the liminal space between two nations. Illegal emergency aid that doubles as missionary project reinforces the image of a helpless victim being vandalized by evil Burmese army. ----- Dieser Artikel zeigt auf, wie es der Karen National Union (KNU) gelungen ist, die humanit re Hilfe im Grenzgebiet zwischen Thailand und Burma für eigene Ziele zu manipulieren und zu politisieren. Ich argumentiere, dass das protestantische Christentum ein entscheidendes Vehikel zur politischen Mobilisierung im Kontext des Bürgerkriegs in Ost-Burma darstellt. Der Artikel zeigt, dass die Flüchtlingslager im thail ndischen Grenzgebiet als Zentren der Missionierung dienen und dass die protestantisch-evangelikalen und missionarischen Netzwerke territoriale Korridore durch die thail ndisch-burmesische Grenze nen. Wir sehen hier ein Fallbeispiel, wie eine imaginierte Nation in der Grenzerfahrung zweier Nationen konstruiert wird. Soforthilfe, die mit protestantischer Mission doppelt, verst rkt das Bild hil oser Opfer, die von der burmesischen Armee vandalisiert werden.
Editorial: Grenzregionen und Border Studies in Südostasien / Borderlands and Border Studies in South-East Asia
Alexander Horstmann
ASEAS : ?sterreichische Zeitschrift für Südostasienwissenschaften , 2011,
Abstract:
Operative Steinbehandlung: endoskopisch, robotisch oder offen?
Horstmann M
Journal für Urologie und Urogyn?kologie , 2012,
Abstract:
Blasenkrebs: Screening in Risikogruppen oder symptombasierte urologische Diagnostik?
Horstmann M
Journal für Urologie und Urogyn?kologie , 2011,
Abstract:
Distinct Single Amino Acid Replacements in the Control of Virulence Regulator Protein Differentially Impact Streptococcal Pathogenesis
Nicola Horstmann,Pranoti Sahasrabhojane,Bryce Suber,Muthiah Kumaraswami,Randall J. Olsen,Anthony Flores,James M. Musser,Richard G. Brennan,Samuel A. Shelburne III
PLOS Pathogens , 2011, DOI: 10.1371/journal.ppat.1002311
Abstract: Sequencing of invasive strains of group A streptococci (GAS) has revealed a diverse array of single nucleotide polymorphisms in the gene encoding the control of virulence regulator (CovR) protein. However, there is limited information regarding the molecular mechanisms by which CovR single amino acid replacements impact GAS pathogenesis. The crystal structure of the CovR C-terminal DNA-binding domain was determined to 1.50 ? resolution and revealed a three-stranded β-sheet followed by a winged helix-turn-helix DNA binding motif. Modeling of the CovR protein-DNA complex indicated that CovR single amino acid replacements observed in clinical GAS isolates could directly alter protein-DNA interaction and impact protein structure. Isoallelic GAS strains that varied by a single amino acid replacement in the CovR DNA binding domain had significantly different transcriptomes compared to wild-type and to each other. Similarly, distinct recombinant CovR variants had differential binding affinity for DNA from the promoter regions of several virulence factor-encoding genes. Finally, mice that were challenged with GAS CovR isoallelic strains had significantly different survival times, which correlated with the transcriptome and protein-DNA binding studies. Taken together, these data provide structural and functional insights into the critical and distinct effects of variation in the CovR protein on GAS pathogenesis.
Serial Block-Face Scanning Electron Microscopy to Reconstruct Three-Dimensional Tissue Nanostructure
Winfried Denk,Heinz Horstmann
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0020329
Abstract: Three-dimensional (3D) structural information on many length scales is of central importance in biological research. Excellent methods exist to obtain structures of molecules at atomic, organelles at electron microscopic, and tissue at light-microscopic resolution. A gap exists, however, when 3D tissue structure needs to be reconstructed over hundreds of micrometers with a resolution sufficient to follow the thinnest cellular processes and to identify small organelles such as synaptic vesicles. Such 3D data are, however, essential to understand cellular networks that, particularly in the nervous system, need to be completely reconstructed throughout a substantial spatial volume. Here we demonstrate that datasets meeting these requirements can be obtained by automated block-face imaging combined with serial sectioning inside the chamber of a scanning electron microscope. Backscattering contrast is used to visualize the heavy-metal staining of tissue prepared using techniques that are routine for transmission electron microscopy. Low-vacuum (20–60 Pa H2O) conditions prevent charging of the uncoated block face. The resolution is sufficient to trace even the thinnest axons and to identify synapses. Stacks of several hundred sections, 50–70 nm thick, have been obtained at a lateral position jitter of typically under 10 nm. This opens the possibility of automatically obtaining the electron-microscope-level 3D datasets needed to completely reconstruct the connectivity of neuronal circuits.
La contradicción en Hegel
Horstmann,Rolf-Peter;
Revista latinoamericana de filosof?-a , 2009,
Abstract: in this paper, i argue against the idea of dealing with hegel's philosophy as if it were based on obscure and inexplicable principles that can only be accepted as a fact for which no rational or philosophical explanation is available. in order to do it, i consider the aspect of hegel's method which is connected with the concept of contradiction. hegel's own conceptions of contradiction and objects can be considered as criticism of traditional metaphysics. the shortcomings of traditional metaphysics are seen by hegel as a consequence of its incautious use of the subject-predicate structure of language which, as he holds, is inappropriate to express something true about objects as they really are; nevertheless, hegel is convinced, at the same time, that this way of speaking about objects is unavoidable. hegel tries to solve the resulting dilemma by introducing the concept of contradiction as a methodological rule by means of which the deficiencies of traditional metaphysics could be avoided.
überlegungen zu einer Rechtsgeschichte staatlichen Wissens
Peter Collin,Thomas Horstmann
Forum Historiae Iuris , 2003,
Abstract:
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