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Erridge, Clett. "Immune responses to lipopolysaccharide." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/23334.
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Samai, Hakim. "Caractéristiques cellulaires et moléculaires de la réponse inflammatoire chez le poisson exposé à des substances d'origines bactériennes dans un contexte écotoxicologique." Thesis, Reims, 2018. http://www.theses.fr/2018REIMS044/document.
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Dans le cadre de l’évaluation du risque immunotoxique de composés glycolypidiques d’origine bactérienne, cette thèse a portée sur l’évaluation de toxicité d’endotoxines d’E.coli de deux sérotype différents : LPS O55:B5 utilisé couramment en comme immunostimulant et le LPS O157:H7 dont la réalité environnementale a soulevé notre questionnement scientifique quant à son impact sur le système immunitaire du poisson et son caractère potentiellement pro-inflammatoire. Les différents procédés employés ont compris l’évaluation des paramètres cellulaires (production d’espèces réactives d’oxygène et phagocytose) ainsi que la caractérisation et la quantification de l’expression de gènes de cytokines (TGFβ et IL-10) et facteurs immuno-associés (MARCO, HSP60 et vitellogénine) chez le modèle gardon (Rutilus rutilus).Les approches expérimentales se sont déroulées tout d’abord en ex vivo sur des leucocytes isolés d’organes lymphoïdes (Rein antérieur, rate et sang) de gardon et ont montré une tolérance endotoxique vis-à-vis de ces LPS à de 1µg/mL même combinés au diclofénac à 0,1 µM. ce travaill a été suivi par une évaluation du risque potentiel d’autres composés glycolipidiques d’origine bactérienne (rhamnolipides).Les approches in vivo qui ont suivies ont été réalisées sur : (i) sur modèle poisson-zèbre (Danio rerio) au laboratoire et (ii) sur modèle gardon par encagement sur terrain. Les résultats obtenus sur danios au laboratoire ont montré une toxicité du sérotype O157 :H7 et une influence sur les paramètres comportementaux par les LPS (Sickness behaviour). Sur terrain, l’approche in vivo par encagement a révélé – au niveau de la rate et du rein antérieur – des réponses cellulaires et moléculaires, sérotype, organe et sexe dépendante avec une immunomodulation prédominante chez les mâles d’autant plus que la période d’étude s’est déroulée durant la maturation sexuelle des gardons. Ce travail fait état du caractère inflammatoire et toxique du LPS peu étudié d’E.coli O157 :H7, évalué par des immunomarqueurs cellulaires bien maitrisés et moléculaires néo-développésIn the context of immunotoxic risk evaluation of glycolypidic compounds of bacterial origin, this thesis focused on the evaluation of E.coli endotoxin toxicity of two different serotypes: LPS O55: B5 commonly used as an immunostimulant et LPS O157: H7, whose environmental reality has raised our scientific questioning about its impact on the fish's immune system et its potentially pro-inflammatory nature. The various methods used included the evaluation of cellular parameters (production of reactive oxygen species et phagocytosis) as well as the characterization of cytokines (TGFβ et IL-10) et immune-realted factors (MARCO, HSP60 et vitellogenin) genes et the quantification of their expression in the roach model (Rutilus rutilus).The experimental approaches were first carried out ex vivo on leukocytes isolated from lymphoid organs (anterior kidney, spleen et blood) roach et showed an endotoxic tolerance at 1μg / mL even combined with 0.1 μM diclofenac. This work was followed by an evaluation of the potential risk of other glycolipidic compounds of bacterial origin (rhamnolipids).The in vivo approaches that followed were performed on: (i) zebrafish (Danio rerio) model in the laboratory et (ii) on roach model by field caging. The results obtained on danios in the laboratory showed a toxicity of the serotype O157: H7 et an influence on the behavioral parameters by the LPS (Sickness behavior). On the field, the caging approach revealed - at spleen et the anterior kidney level - cellular et molecular responses, serotype, organ et sex-dependent with a predominant immunomodulation in males, especially since the study period took place during the sexual maturation of roaches. This work reports the inflammatory et toxic nature of the less studied E.coli O157: H7 LPS serotype, evaluated by well-mastered cellular et neo-developed molecular immunomarkers
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Rose, Robert Edward. "Calpain and lipopolysaccharide mediated hepatitis." Thesis, [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1806.
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Gibb, Alan Patrick. "Cross-reactive antibodies to lipopolysaccharide." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/28093.
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Lipopolysaccharide (LPS), also known as endotoxin, is a constituent of the outer membrane of gram-negative bacteria which is toxic for humans and other animals. LPS probably plays a key part in the pathogenesis of Gram-negative bacteraemia and sepsis syndrome in humans. Cross-reactive antibodies to LPS may play a part in natural host defences, and may also be useful in the treatment of Gram-negative bacteraemia and sepsis syndrome. The structure of LPS, its toxicity, its role in Gram-negative bacteraemia and sepsis syndrome in humans, and the potential value of cross-reactive antibodies to LPS are reviewed. The antibody response in recipients of typhoid vaccine was studied, with particular reference to the possibility that typhoid vaccine might induce the production of antibodies to the core region of LPS (LPS-core). In most recipients however the response observed was directed against specific antigens. Urine samples from patients with suspected UTI were tested for IgG antibodies to LPS-core. Such antibodies were found to be associated with the presence of bacteriuria, although the association was not strong enough for antibody assay to be useful as a diagnostic test. Total urinary IgG was equally strongly associated with bacteriuria. This suggested that the antibodies were probably present because of non-specific leakage of serum components into the urine as a result of inflammation. A large number of murine monoclonal antibodies (MAbs) to LPS-core had been produced by a collaborative group in Edinburgh and Basel, in the hope of producing a cross-reactive MAb which would be useful therapeutically. The binding of some of these MAbs to a collection of blood-culture isolates of Gram-negative bacteria was studied.
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Zhao, Yun. "Immunomodulatory properties of Brucella lipopolysaccharide." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0229/document.
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Le lipopolysaccharide (LPS) de la bactérie à gram-négatif Brucella ne permet pas une reconnaissance efficace par le système immunitaire par l’expression de motifs agissant comme boucliers en vers le système immunitaire. Nous avons déjà constaté qu'un mutant de Brucella dans le gène wadC présentait un défaut dans la région du core du LPS sans modifier la structure de la chaîne oligosaccharidique et le lipide A. Tout d'abord, nous avons constaté que, contrairement au dogme, le LPS de type sauvage de Brucella melitensis (Bm-wt) active sélectivement les sous-ensembles DC dans un modèle BMDC induit par FL-DC mais pas GM-DC. Le LPS du mutant Brucella melitensis wadC (Bm-wadC) induit la maturation des cellules dendritiques et la sécrétion de cytokines pro-inflammatoires in vitro. Et in vivo, nous avons découvert que, en plus de l'activation dans les sous-types de cellules dendritiques conventionnelles spléniques, le LPS de Bm-wadC induit également le recrutement des cellules dendritiques DC-SIGN/CD64+ dans la rate. Dans la cavité péritonéale de la souris, contrairement au LPS de Bm-wt, qui n'a aucun effet sur l'activation des macrophages, le mutant wadC a eu un effet significatif sur la polarisation fonctionnelle des grands macrophages péritonéaux avec un phénotype M1 de manière dépendante de TLR4. Les trois LPS (Bm-wt, Bm-wadC et E. coli LPS) ont provoqué une disparition de macrophages dans le péritoine. De plus, les LPS de Bm-wt et Bm-wadC favorisent un afflux péritonéal important transitoire de neutrophiles après injection. Ces résultats encouragent une amélioration de la génération de nouveaux vaccins contre la brucelloseThe lipopolysaccharide (LPS) of the gram-negative bacterium Brucella lacks a marked pathogen-associated molecular pattern. We had previously found that a Brucella mutant in the wadC gene deletion displayed a disrupted LPS core while keeping both the LPS O-polysaccharide and lipid A. Currently, we continue to carry out an in-depth characterization of the immunomodulatory properties of Brucella wild type and wadC mutant LPS. Firstly, we found that, unlike the dogma, Brucella melitensis wild type (Bm-wt) LPS selectively activates DC subsets in a BMDC model induced by FL-DC but not GM-DC. Brucella melitensis wadC LPS (Bm-wadC) induced both GM-DC and FL-DC maturation and secretion of pro-inflammatory cytokines in vitro. And in vivo, using an intraperitoneal injection model, we discovered that, Bm-wadC LPS also induced the recruitment of DC-SIGN/CD64+ dendritic cells into the spleen. In the mouse peritoneal cavity, unlike Bm-wt LPS, which has no effect on activation of macrophages, wadC mutant displayed a significant effect on the functional polarization of large peritoneal macrophages with a M1 phenotype in a TLR4-dependent manner. In addition, all three LPS (Bm-wt, Bm-wadC and E.coli LPS) induced a transient macrophage disappearance in the peritoneal cavity. Moreover, both Bm-wt and Bm-wadC LPS favored a significant transient peritoneal influx of neutrophils, which was much higher than E. coli LPS especially at early time points after injection. These results encourage for an improvement in the generation of novel vaccines against brucellosis
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Dauphinee, Shauna Marie. "Lipopolysaccharide signaling in endothelial cells." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/23033.
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The endothelium plays a critical role in coordinating the innate immune response through the regulation of vascular tone, leukocyte recruitment and transmigration, and hemostasis. These functions are mediated, in part, by the signaling cascades initiated upon recognition of bacterial and viral products by a family of transmembrane receptors known as Toll-like receptors (TLRs). In endothelial cells, exposure to lipopolysaccharide (LPS), a major cell wall constituent of Gram negative bacteria, results in endothelial activation through TLR4. Recruitment of the adapter protein, MyD88, to the receptor facilitates association of serine threonine kinases of the IL-1 receptor associated kinase (IRAK) family. The IRAKs initiate a phosphorylation cascade through TNFR-associated factor 6 (TRAF6) culminating in activation of proinflammatory signaling pathways including NF-κB and c-Jun NH2-terminal kinase (JNK) pathways. This thesis investigates signaling molecules and pathways downstream of TLR4 in endothelial cells. Specifically, contained herein is a description of the role of heterotrimeric G proteins in endothelial TLR signaling. This thesis identifies for the first time the function of these proteins in multiple TLR signaling pathways. In addition, the work presented here describes the identification and characterization of a novel TLR4 signaling molecule, SAM and SH3 domain containing protein 1 (SASH1). SASH1 promotes LPS-induced NF-κB and JNK, by functioning as a scaffold molecule to bind TRAF6, transforming growth factor-β-activated kinase (TAK1) and IκB-kinase (IKK), thereby increasing proinflammatory cytokine production. The distinct functions of the endothelium in innate immunity highlight the need for an understanding of the signaling cascades initiated by LPS in endothelial cells and will be crucial to our understanding of the pathophysiology of sepsis in the clinic.
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Young, Rosanna E. B. "The lipopolysaccharide of Haemophilus parainfluenzae." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:fc7b7bcc-ea89-4ded-bb65-a1f2879236ca.
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Haemophilus parainfluenzae (Hp) and H. influenzae (Hi) are closely related members of the Pasteurellaceae family and are common commensal bacteria of the human nasopharynx. Whilst Hi is frequently implicated in meningitis, otitis media and respiratory tract infections, reports of pathogenic behaviour by Hp are very rare. Lipopolysaccharide (LPS) is a key component of the Gram negative cell wall, and its structure influences the ability of Haemophilus to interact with the host and evade immune clearance. A better understanding of the differences in LPS structure between Hi and Hp could help to ascertain which parts of the molecule are important for commensal and pathogenic behaviour. Hi LPS comprises lipid A, a conserved oligosaccharide inner core, and an oligosaccharide outer core that differs between strains. The latter is partly phase variable by the slipped strand mispairing during replication of DNA repeat tracts within several LPS biosynthesis genes. Very little was known about LPS in Hp so we investigated its biosynthesis and structure in a panel of 20 Hp carriage isolates. Using PCR, DNA sequencing and Southern analysis we demonstrated that Hp possesses homologues of the Hi lipid A and inner core LPS synthesis genes and a few of the genes for outer core synthesis; however, homologues of the Hi phase variable outer core genes were largely absent and did not contain repeat tracts. The results of immunoblotting and collaborative structural analysis were consistent with this data. Phosphocholine, a phase variable Hi LPS epitope that has been implicated in otitis media, was found to be absent in Hp LPS due to the lack of four genes required for its biosynthesis and incorporation. The introduction of these genes into Hp led to the phase variable addition of phosphocholine to the LPS, indicating that there is no fundamental reason why Hp could not use a similar mechanism of variation to Hi if it was advantageous to do so. SDS-PAGE data suggested the presence of O-antigens (repeated chains of sugars) in many of the Hp strains, an unusual feature for Haemophilus, and all of the strains were found to contain a potential O-antigen synthesis locus. Each locus encodes homologues of several glycosyltransferases in addition to either the Wzy polymerase- or ABC transporter-dependent mechanisms of O-antigen synthesis and transport. Comparisons of wild type and isogenic mutant strains showed that the O-antigen enhances resistance to complement-mediated killing and appears to affect adhesion to epithelial cells in vitro. Hp is a successful commensal organism but lacks the flexibility of adapting its LPS using repeat-mediated phase variation, potentially limiting its range of host niches.
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Smith, David G. E. "Activities of anti-lipopolysaccharide immunoglobulins." Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/19300.
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Ranc, Anne-Gaëlle. "Phenol Soluble Modulins et lipopolysaccharide de Legionella pneumophila : rôle dans la réponse immunitaire innée." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1010/document.
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Legionella pneumophila (Lp) est une bactérie ubiquitaire dans les environnements aqueux et responsable d’une pneumopathie potentiellement sévère : la légionellose. La majorité des souches impliquées appartiennent au sérogroupe 1 (Lp1) et à un sous- groupe spécifique de souches portant un épitope particulier dites mAb3/1+. Cependant, la différence de distribution entre les souches retrouvées dans l’environnement et celles impliquées en clinique n’est pas clairement élucidée. Notre travail a porté sur la détection de deux facteurs de virulence de Lp. Nous avons voulu mettre en évidence l’existence de Phenols Soluble Modulines (PSMs), peptides uniquement décrit chez Staphylocoques et avons ainsi pu démontrer l’activité de peptides prédits par analyse in silico chez Lp capables d’activer la réponse inflammatoire par la voie du NF-?B et sont dotés d’une action cytotoxique. Notre deuxième axe d’étude a porté sur le lipopolysaccharide (LPS) de Lp. Afin de vérifier si la prédominance de certaines souches était liée à un biais diagnostique, nous avons voulu tout d’abord vérifier la sensibilité de 3 tests urinaires diagnostiques envers le LPS extrait de souches de différents sous- groupes de Lp1 et sérogroupes de Lp et avons ainsi pu montrer que ces tests sont capables de détecter tous les LPS de Lp1. La sensibilité envers le LPS des autres sérogroupes est très variable mais reste insuffisante pour permettre leur détection. Nous avons ensuite utilisé ces LPS extraits pour vérifier la réponse immunitaire innée en fonction des souches de Lp1. Ainsi les souches mAb3/1+ activent moins le système immunitaire que les souches mAb3/1-, ce qui pourrait expliquer alors une moins bonne clairance de ces souches permettant leur multiplication à l’origine d’une infection. Au final, notre travail a permis d’étudier deux facteurs de virulence potentiels au sein de Lp, pouvant expliquer partiellement la prédominance de certaines souches en pathologie humaineLegionella pneumophila (Lp) is a ubiquitous intracellular bacterium found widely in the environment and is the cause of an opportunistic infection named legionellosis. The majority of the strains involved belong to serogroup 1 (Lp1) and to a specific subgroup named mAb3/1+, linked to a specific epitope expressed at the cell membrane. However the distribution difference between the strains found in the environment and the ones involved in pathology is not fully understood. We here studied two virulence factors of Lp. We first demonstrated the existence of Phenols Soluble Modulines (PSMs), smalls peptides that only have been described for Staphylococcus and found that the peptides that were predicted for Lp by in silico analysis were able to activate the innate immune response by NF-?B pathway and were able to have a cytotoxic activity. We also studied the lipopolysaccharide (LPS) of Lp. To found out if the predominance of some strains was linked to a diagnosis biais, we first evaluated the sensitivity of 3 urinary antigens tests against extracted LPS of strains belonging to all the sous-groups of Lp1 and serogroups of Lp. We then demonstrated that those tests are able to detect all LPS of Lp1, independently of mAb3/1 character. The sensitivities of the 3 tests were very variable for the other serogroups of Lp, but were too low to be able to detect those LPS in practice. We then used these extracted LPS to evaluate the innate immune response for different strains of Lp1. We demonstrated that mAb3/1- strains needed lower dose of LPS to activate the innate immune response than mAb3/1+ strains, which could be linked to a better clearance of the bacteria from the host, which doesn’t develop an infection. This work has studied two potentially virulent factors of Lp, which could partially explain the predominance of some strains of Lp in human pathology
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Andres, Dorothee. "Biophysical chemistry of lipopolysaccharide specific bacteriophages." Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2012/5926/.
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Carbohydrate recognition is a ubiquitous principle underlying many fundamental biological processes like fertilization, embryogenesis and viral infections. But how carbohydrate specificity and affinity induce a molecular event is not well understood. One of these examples is bacteriophage P22 that binds and infects three distinct Salmonella enterica (S.) hosts. It recognizes and depolymerizes repetitive carbohydrate structures of O antigen in its host´s outer membrane lipopolysaccharide molecule. This is mediated by tailspikes, mainly β helical appendages on phage P22 short non contractile tail apparatus (podovirus).
The O antigen of all three Salmonella enterica hosts is built from tetrasaccharide repeating units consisting of an identical main chain with a distinguished 3,6 dideoxyhexose substituent that is crucial for P22 tailspike recognition: tyvelose in S. Enteritidis, abequose in S. Typhimurium and paratose in S. Paratyphi. In the first study the complexes of P22 tailspike with its host’s O antigen octasaccharide were characterized. S. Paratyphi octasaccharide binds less tightly (ΔΔG≈7 kJ/mol) to the tailspike than the other two hosts. Crystal structure analysis of P22 tailspike co crystallized with S. Paratyphi octasaccharides revealed different interactions than those observed before in tailspike complexes with S. Enteritidis and S. Typhimurium octasaccharides. These different interactions occur due to a structural rearrangement in the S. Paratyphi octasaccharide. It results in an unfavorable glycosidic bond Φ/Ψ angle combination that also had occurred when the S. Paratyphi octasaccharide conformation was analyzed in an aprotic environment. Contributions of individual protein surface contacts to binding affinity were analyzed showing that conserved structural waters mediate specific recognition of all three different Salmonella host O antigens.
Although different O antigen structures possess distinct binding behavior on the tailspike surface, all are recognized and infected by phage P22. Hence, in a second study, binding measurements revealed that multivalent O antigen was able to bind with high avidity to P22 tailspike. Dissociation rates of the polymer were three times slower than for an octasaccharide fragment pointing towards high affinity for O antigen polysaccharide. Furthermore, when phage P22 was incubated with lipopolysaccharide aggregates before plating on S. Typhimurium cells, P22 infectivity became significantly reduced.
Therefore, in a third study, the function of carbohydrate recognition on the infection process was characterized. It was shown that large S. Typhimurium lipopolysaccharide aggregates triggered DNA release from the phage capsid in vitro. This provides evidence that phage P22 does not use a second receptor on the Salmonella surface for infection. P22 tailspike binding and cleavage activity modulate DNA egress from the phage capsid. DNA release occurred more slowly when the phage possessed mutant tailspikes with less hydrolytic activity and was not induced if lipopolysaccharides contained tailspike shortened O antigen polymer. Furthermore, the onset of DNA release was delayed by tailspikes with reduced binding affinity. The results suggest a model for P22 infection induced by carbohydrate recognition: tailspikes position the phage on Salmonella enterica and their hydrolytic activity forces a central structural protein of the phage assembly, the plug protein, onto the host´s membrane surface. Upon membrane contact, a conformational change has to occur in the assembly to eject DNA and pilot proteins from the phage to establish infection.
Earlier studies had investigated DNA ejection in vitro solely for viruses with long non contractile tails (siphovirus) recognizing protein receptors. Podovirus P22 in this work was therefore the first example for a short tailed phage with an LPS recognition organelle that can trigger DNA ejection in vitro. However, O antigen binding and cleaving tailspikes are widely distributed in the phage biosphere, for example in siphovirus 9NA. Crystal structure analysis of 9NA tailspike revealed a complete similar fold to P22 tailspike although they only share 36 % sequence identity. Moreover, 9NA tailspike possesses similar enzyme activity towards S. Typhimurium O antigen within conserved amino acids. These are responsible for a DNA ejection process from siphovirus 9NA triggered by lipopolysaccharide aggregates. 9NA expelled its DNA 30 times faster than podovirus P22 although the associated conformational change is controlled with a similar high activation barrier. The difference in DNA ejection velocity mirrors different tail morphologies and their efficiency to translate a carbohydrate recognition signal into action.Kohlenhydraterkennung ist ein fundamentales Prinzip vieler biologischer Prozesse wie z.B. Befruchtung, Embryogenese und virale Infektionen. Wie aber Kohlenhydratspezifität und –affinität in ein molekulares Ereignis übersetzt werden, ist nicht genau verstanden. Ein Beispiel für ein solches Ereignis ist die Infektion des Bakteriophage P22, der drei verschiedene Salmonella enterica (S.) Wirte besitzt. Er erkennt und depolymerisiert die repetitiven Einheiten des O Antigens im Lipopolysaccharid, das sich in der äußeren Membran seines Wirtes befindet. Dieser Schritt wird durch die Tailspikes vermittelt, β helicale Bestandteile des kurzen, nicht kontraktilen Schwanzapparates von P22 (Podovirus). Das O Antigen aller drei Salmonella enterica Wirte besteht aus sich wiederholenden Tetrasacchariden. Sie enthalten die gleiche Hauptkette aber eine spezifische 3,6 Didesoxyhexose Seitenkette, die für die P22 Tailspikeerkennung essentiell ist: Tyvelose in S. Enteritidis, Abequose in S. Typhimurium und Paratose in S. Paratyphi. Im ersten Teil der Arbeit wurde die Komplexbildung von P22 Tailspike mit O Antigen Octasaccharidfragmenten der drei verschiedenen Wirte untersucht. S. Paratyphi Octasaccharide binden mit einer geringeren Affinität (ΔΔG≈7 kJ/mol) an den Tailspike als die beiden anderen Wirte. Die Kristallstrukturanalyse des S. Paratyphi Octasaccharides komplexiert mit P22 Tailspike offenbarten unterschiedliche Interkationen als vorher mit S. Enteritidis und S. Typhimurium Oktasaccharidkomplexen mit Tailspike beobachtet wurden. Diese unterschiedlichen Interaktionen beruhen auf einer strukturellen Änderung in den Φ/Ψ Winkeln der glykosidischen Bindung. Die Beiträge von verschiedenen Proteinoberflächenkontakten zur Affnität wurden untersucht und zeigten, dass konservierte Wasser in der Struktur die spezifische Erkennung aller drei Salmonella Wirte vermittelt. Obwohl die verschiedenen O Antigen Strukturen unterschiedliches Bindungsverhalten auf der Tailspikeoberfläche zeigen, werden alle vom Phagen P22 erkannt und infiziert. Daher wurde in einer zweiten Studie die multivalente Bindung zwischen P22 Tailspike und O Antigen charakterisiert. Die Dissoziationskonstanten des Polymers waren drei Mal langsamer als für das Oktasaccharid allein, was auf eine hohe Affinität des O Antigens schließen lässt. Zusätzlich wurde gezeigt, dass die Aggregate des Lipopolysaccharids in der Lage sind, die Infektiösität vom P22 Phagen zu reduzieren. Ausgehend davon wurde in einer dritten Studie die Bedeutung der Kohlenhydrat Erkennung auf den Infektionsprozess untersucht. Große S. Typhimurium Lipopolysaccharide Aggregate bewirkten die DNA Freisetzung vom P22 Kapsid. Dies deutet darauf, dass der P22 Phage keinen weiteren Rezeptor für die Infektion auf der Oberflächen seines Wirtes verwendet. Zusätzlich moduliert die P22 Tailspike Aktivität den Ausstoss der DNA vom P22 Phagen: Er ist langsamer, wenn der Phage Tailspikes besitzt, die weniger hydrolytisch aktiv sind und wurde nicht induziert, wenn Lipopolysaccharid eingesetzt wurde, dass zuvor mit Tailspike hydrolysiert wurde. Darüber hinaus wurde der Start der DNA Ejektion verzögert, wenn Tailspikes mit verminderter Affinität am Phagen vorhanden waren. Die Ergebnisse führten zu einem Modell für die Infektion von P22: Tailspikes positionieren den Phagen auf Salmonella enterica und ihre Aktivität drückt ein zentrales Strukturprotein des Phagen, das Stöpselprotein, auf die Membranoberfläche. Aufgrund des Membrankontaktes findet eine Konformationsänderung statt die zur Ejektion der Pilotproteine und zur Infektion führt. Vorhergehende Studien haben bisher nur die DNA Ejektion in vitro für Viren mit langen, nicht kontraktilen Schwänzen (Siphoviren) mit Proteinrezeptoren untersucht. In dieser Arbeit wurde das erste Mal die DNA Ejektion für einen Podovirus mit LPS Erkennung in vitro gezeigt. Die O Antigen Erkennung und Spaltung durch Tailspikeproteine gibt es häufig in der Phagenbiosphere, z.B. am Siphovirus 9NA. Die Kristallstrukturanalyse von 9NA Tailspike zeigt eine komplett gleiche Struktur, obwohl beide Proteine nur zu 36% Sequenzidentität besitzen. Zusätzlich hat 9NA Tailspike ähnliche enzymatische Eigenschaften. Diese ist für den DNA Ejektionsprozess im Siphovirus 9NA verantwortlich, der auch durch LPS Agreggate induziert wird. 9NA stößt dabei seine DNA 30 Mal schneller aus als Podovirus P22 obwohl die damit verbundene Konformationsänderung mit einer ähnlich hohen Aktivierungsbarriere kontrolliert wird. Daher spiegeln die Unterschiede in der DNA Ejektionsgeschwindigkeit der verschiedenen Tailmorphologien die Effezienz wieder, mit der die spezifische Kohlenhydraterkennung in ein Signal umgewandelt wird.
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Erwin, Pauline Jessie. "Lipopolysaccharide binding proteins in human serum." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318841.
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Sharma, Dharam Pal. "Non-lipopolysaccharide protective antigens of Vibrio cholerae /." Title page, abstract and contents only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09phs5314.pdf.
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Aubrey, Ruth. "Phase variation of lipopolysaccharide in Haemophilus influenzae." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325985.
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Freinkman, Elizaveta. "Assembly and Regulation of the Lipopolysaccharide Transporter." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10122.
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The hallmark of Gram-negative bacteria is the presence of an outer membrane (OM) surrounding the cytoplasmic membrane (here called the inner membrane [IM]) and the cell wall. The OM is a unique asymmetric bilayer with an inner leaflet consisting of phospholipid and an outer leaflet consisting of lipopolysaccharide (LPS). LPS is a large anionic molecule that typically contains six fatty acyl chains and up to several hundred sugar residues. This chemical structure explains why the OM is relatively impermeable to large hydrophobic molecules, such as detergents, bile salts, and high molecular weight antibiotics, which readily cross a normal phospholipid bilayer. LPS and the OM are essential to the viability of most Gram-negative organisms, including major human pathogens. LPS molecules are biosynthesized at the IM and subsequently exported out of the IM, across the intermembrane space (the periplasm) and through the OM to their final position at the cell surface. In Escherichia coli, the essential LPS transport proteins, LptA-G, are required for this process. This Lpt pathway includes an IM adenosine triphosphate binding cassette (ABC) transporter, LptBFG, which is associated with an additional IM protein, LptC; a periplasmic protein, LptA; and an OM complex consisting of the lipoprotein LptE and the transmembrane \(\beta\)-barrel protein LptD. All seven Lpt proteins associate as a single complex that spans the cell envelope. However, little is known about how these proteins work together to transport LPS. Here, we use in vivo and in vitro biochemical studies to probe the organization, function, and assembly of the Lpt machine. In Chapter 2, we show that LptE forms a plug within the LptD \(\beta\)-barrel and present a model for how this unusual structure can move LPS from the periplasm directly into the outer leaflet of the OM. In Chapter 3, we demonstrate that the Lpt transenvelope bridge consists of a series of structurally homologous domains – LptC, LptA, and the N-terminal domain of LptD – stacked in a head-to-tail orientation, providing a route for LPS from the IM to the OM. Finally, in Chapter 4, we connect these two sets of results by showing how the assembly of the Lpt transenvelope bridge is regulated by that of the LptD/E complex in the OM. Together, these findings explain how the functions of the Lpt proteins are coordinated to ensure delivery of LPS to the correct cellular compartment. A fundamental understanding of LPS biogenesis will contribute to the development of new therapies against Gram-negative infections.
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Chafchaouni-Bussy, Moussaoui Imane. "Etude de l’implication des lipopolysaccharides dans la Symbiose Bactérie-Plante productrice d’azote." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA11T045.
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Nous nous sommes intéressés à la compréhension des mécanismes régissant la symbiose Rhizobium-Acacia dans les conditions de stress salin. Les lipopolysaccharides jouent un rôle important dans les étapes de cette symbiose. Le but était de mettre en évidence les modifications pariétales de la bactérie en réponse au stress salin par l’étude de la structure des lipopolysaccharides des souches isolées du désert marocain tolérant NaCl 7%. Ainsi, une nouvelle méthode d’hydrolyse des lipopolysaccharides sensible, non destructive et compatible avec la spectrométrie de masse a été développée. En présence de stress salin, nous avons montré que la membrane externe devenait plus hydrophobe en augmentant l’acylation de la région lipidique ainsi qu’en réduisant la présence des molécules de LPSs à longues chaînes de sucres.Des essais d’évaluation de l’efficience et de l’infectivité des Rhizobia étudiés ont été mis en œuvre pour déterminer l’impact de ces modifications des LPSs sur la symbiose sous stress salinWe were interested in the understanding of the mechanisms governing Rhizobium-Acacia symbiosis in salt stress conditions. Lipopolysaccharides play an important role in the stages of this symbiosis. The aim of this work was to highlight the changes occurring in the bacterial membrane in response to salt stress by studying the structure of the lipopolysaccharides isolated from Moroccan desert strains tolerating 7% NaCl. Thus, a new method of hydrolysis of the lipopolysaccharide - sensitive, non-destructive and compatible with mass spectrometry- was developed. We studied the LPSs strains grown with or without salt stress and we showed that in salt stress conditions, the outer membrane becomes more hydrophobic by increasing acylation of the lipid region and reducing the number of long sugar chains in LPSs. Tests for evaluating the efficiency and infectivity of the studied rhizobia were carried out to determine the impact of these LPS modifications on symbiosis under salt stress
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Fraysse, Nicolas. "Purification et caractérisation d'un lipopolysaccharide bactérien : modification de composés de surface chez Sinorhizobium SP. NGR234 en conditions symbiotiques." Toulouse 3, 2002. http://www.theses.fr/2002TOU30112.
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Al-Qutub, Montaser Nazmi. "Lipopolysaccharide lipid A structural heterogeneity of Porphyromonas gingivalis /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6383.
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Ren, Lei. "Lipopolysaccharide-binding protein and CD14 in human gingiva." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B31374281.
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Obst, Stefan. "Exponierung von Epitopen bakterieller Lipopolysaccharide und ihrer Aggregate." [S.l.] : [s.n.], 1997. http://darwin.inf.fu-berlin.de/1998/5/index.html.
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Tout, Nancy Lynn. "Construction of recombinant antibodies against Pseudomonas aeruginosa lipopolysaccharide." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24430.pdf.
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Cross-Mellor, Shelley Kathleen. "The effects of lipopolysaccharide and cholecystokinin on ingestion." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0007/MQ42059.pdf.
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Bowen, Jenna Louise. "Detection of lipopolysaccharide pyrogens by molecularly imprinted polymers." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/54444/.
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Lipopolysaccharide (LPS) is commonly implicated in the development and rapid progression of sepsis however no efficient diagnostic assay currently exists. The over-arching aim of this project was therefore to develop a novel biomimetic peptide-polymer hybrid system capable of recognising and binding LPS in a variety of biologically relevant environments. Target selective peptides (both commercially available and synthesised) have been used as high affinity 'functional monomers' in a molecular imprinting approach. To reduce the concept to practice, a bi-functionalised resin was prepared so as to allow the use of two independent surface attachment strategies. Controlled polymer growth was initiated from surface bound iniferter groups whilst the attachment of the peptide was achieved through amme-amine imidoester linkages or via azide-alkyne "click" chemistry. Polymyxin, a small, conformationally constrained cyclic peptide that possesses high affinity for lipopolysaccharide (LPS) was used to provide proof-of-principle. Polymyxin resins, produced via the immobilisation of alkyne derivitised polymyxin B on the surface of azidomethyl polystyrene via "click" chemistry, were able to efficiently bind LPS from aqueous solutions with an apparent Ka of 0.2 μM. Although the development of the peptide-polymer hybrid system using these resins appeared somewhat unsuccessful, whether the observed reduction in binding is due to changes in the Bmax or the Kd of the resin remains to be elucidated. The assay performed with the polymerisation samples produced using resin displaying polymyxin immobilised via a dimethyl adipimidate linker, suggest that the hypothesised approach is feasible but that optimisation of a number of variables is needed before definitive results can be obtained.
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Ren, Lei, and Ph D. 任蕾. "Lipopolysaccharide-binding protein and CD14 in human gingiva." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B31374281.
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Sherman, David Joseph. "Reconstitution of bacterial lipopolysaccharide transport from purified components." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17465324.
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The surface of Gram-negative bacteria is largely composed of lipopolysaccharide (LPS), a complex glycolipid that contains multiple fatty acyl chains and up to hundreds of sugars. LPS is transported from its site of synthesis at the cytoplasmic inner membrane (IM), across an aqueous compartment (the periplasm), and through the outer membrane (OM) to the cell surface. LPS is essential for the survival of most Gram-negative bacteria. Seven essential and conserved lipopolysaccharide transport (Lpt) proteins in Escherichia coli are responsible for assembling LPS. These proteins form a continuous bridge from the IM to the OM, but it is unknown how they function in LPS transport.
This dissertation describes the development of a reconstitution of LPS transport using purified Lpt proteins. The first two steps of this process are extraction of LPS from the IM by LptBFGC and transport along the periplasmic bridge comprising LptA. We obtained high-resolution crystal structures of the ATPase LptB, which taught us how to overexpress and purify LptBFGC as a stable complex that is highly active in proteoliposomes. Crystallographic snapshots of LptB bound to ATP and ADP provided insight into how energy is used to extract the fatty acyl chains of LPS from the IM. Using site-specific photocrosslinking, we monitored ATP-dependent extraction of LPS from proteoliposomes by LptC and release to LptA. This reconstitution of LptBFGC led to a hypothesis about a role for LptC in regulating the activity of the Lpt IM complex. We also developed methods to reconstitute the late steps of transport by monitoring LPS transit from LptA to the OM components, LptDE, contained in a different proteoliposome. One important observation from this reconstitution is that it appears as though the OM translocon can change activity depending on the amount of LPS in the OM. These studies provide us with the first clues as to how the cell might regulate LPS flux to the cell surface. This reconstitution will allow for mechanistic studies of LPS transport and will aid in the discovery and development of antibiotics targeting this essential process.Chemistry and Chemical Biology
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Bergsma, Mark René. "The effect of alkaline phosphatase upon lipopolysaccharide bioactivity." Thesis, The University of Sydney, 1998. http://hdl.handle.net/2123/4769.
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Pfister, Hélène. "Synthèse d'oligosaccharides représentatifs de l'antigène O de Shigella sonnei." Thesis, Paris 5, 2014. http://www.theses.fr/2014PA05P619.
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Avec 800 000 morts par année, les maladies diarrhéiques sont la seconde cause de mortalité chez les enfants de moins de cinq ans. La shigellose, causée par des bactéries Gram négatif appelées Shigella, est l’une des quatre grandes maladies entériques touchant cette population. L’infection naturelle protège contre la réinfection et la composante polysaccharidique du lipopolysaccharide bactérien est la principale cible de l’immunité humorale. Chez S. sonnei, espèce prévalente dans les pays en développement et développés, ce polysaccharide spécifique, à caractère zwitterionique, a pour unité répétitive un disaccharide composé de deux hexosamines rares : l’acide 2-acétamido-2-désoxy-L-altruronique (A) et le 2-acétamido-4-amino-2,4,6-tridésoxy-D-galactose (B, aussi appelé AAT) associés par des liens glycosidiques 1,2-trans (I). ->4-a-L-AltpNAcA-(1->3)-b-D-FucpNAc4N-(1-> (I). Ces travaux s’intègrent dans un programme visant le développement d’un vaccin issu de sucres de synthèse à couverture large contre les infections par Shigella. Le premier objectif de la stratégie développée contre les infections par S. sonnei est l’identification des épitopes saccharidiques, cibles des anticorps protecteurs. Dans ce but, nous avons entrepris la synthèse d’une diversité de fragments du polysaccharide d’intérêt. Des synthèses multi-grammes de précurseurs orthogonalement protégés des monosaccharides A et B ont été mises au point afin d’accéder aux intermédiaires donneurs et accepteurs impliqués dans les étapes de glycosylation. En particulier, deux voies originales d’accès au précurseur B ont été développées. D’autre part, l’optimisation des conditions de glycosylation et d’oxydation a conduit à un bloc disaccharidique AB compatible avec la synthèse d’oligosaccharides d’ordres supérieurs. Les synthons mono- et disaccharidiques identifiés ont été validés à travers l’obtention de quatre disaccharides portant ou non des modifications de la répartition des charges, de deux trisaccharides ainsi que d’un tétrasaccharide800,000 children die each year of diarrhoeal diseases, making it the second cause of death among children under five. Shigellosis, caused by a Gram negative bacterium, Shigella, is one of the four major forms of diarrhoeal diseases in this population. Natural infection protects against reinfection and the humoral response is primarily directed against the specific polysaccharide moiety of the bacterial lipopolysaccharide. S. sonnei, the prevalent species in developed and transitional countries, displays a zwitterionic polysaccharide, whose disaccharide repeating unit is made of two rare aminosugars: a 2-acetamido-2-deoxy-L-altruronic acid (A) and a 2-acetamido-4-amino-2,4,6-trideoxy-D-galactose (B, AAT) 1,2-trans linked to one another (I). ->4-a-L-AltpNAcA-(1->3)-b-D-FucpNAc4N-(1-> (I). This work is part of the program aimed at the development of a synthetic carbohydrate-based broad coverage vaccine against Shigella infections. In order to define the protective epitopes located on the O-specific polysaccharide of S. sonnei, we tackled the synthesis of fragments thereof. First, multigram-scale syntheses of orthogonally protected precursors to residues A and B were undertaken to access donor and acceptor intermediates in the glycosylation reactions. In particular, two original routes to precursors of residue B were developed. Careful optimisation of the glycosylation and oxidation reaction conditions gave the disaccharide building block AB equipped for the synthesis of chain extension at both ends. Selected mono- and disaccharide building blocks were validated by the synthesis of four disaccharides, bearing modification of the charge pattern or not, two trisaccharides and a tetrasaccharide
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Wells, Christine Anne. "Transcriptional analysis of macrophage signalling in response to lipopolysaccharide /." St. Lucia, Qld, 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18025.pdf.
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Oldfield, Neil J. "The genetic basis of lipopolysaccharide bioynthesis in Campylobacter jejuni." Thesis, University of Leicester, 2000. http://hdl.handle.net/2381/30328.
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Lipopolysaccharide (LPS) and lipooligosaccharide (LOS) molecules are important in the pathogenesis of many Gram negative bacteria. In the enteric pathogen Campylobacter jejuni LPS and LOS molecules are endotoxic, have been suggested as adhesins and are implicated in the development of the auto-immune disorder Guillian Barre syndrome. The aim of this study was to therefore investigate the genetic basis of LPS/LOS biosynthesis, structural variation and function in C. jejuni. A bioinformatic approach was used to identify and characterize LPS/LOS biosynthesis genes in the genome sequence of C. jejuni NCTC 11168 to enable a model of core oligosaccharide biosynthesis to be proposed. Structural variation occurs between LOS/LPS molecules produced by different strains of C. jejuni. The genetic basis of this inter-strain variation was investigated and both conserved and polymorphic genes were identified. Cloning and DNA sequence analysis of some polymorphic genes enabled tentative functions to be proposed. The functions of two genes, one conserved (waaF) and one polymorphic (wlaJ) were further investigated. Studies on wlaJ did not reveal the precise role of this gene in LPS/LOS biosynthesis. However, the function of waaF as encoding a heptosyltransferase involved with inner core biosynthesis was confirmed using complementation and mutational analysis. Significantly, analysis of waaF in C. jejuni NCTC 11828 confirmed that the O-chain molecule produced by this strain is not linked to the core oligosaccharide, and is therefore an independent lipid bound capsular polysaccharide.
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Ferdous, Farzana. "Thrombocyte response to lipopolysaccharide in stress induced broiler chicks." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1193078990/.
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Jolly, Lisa. "Vascular control mechanisms in normal and lipopolysaccharide-treated rats." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/28882/.
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The development of sepsis is associated with complex cardiovascular changes, some of which can be micmked in animals by administration of lipopolysaccharide (LPS). Animal models have identified a number of mediators important in these changes. The work described within this thesis aimed to investigate the role of adrenomedullin (AM) and adenosine in regulating vascular function in vivo in normal and LPS-treated rats. Integrated haemodynamics were assessed in Sprague Dawley rats following implantation of pulsed Doppler flow probes, allowing changes in renal, mesenteric and hindquarters vascular conductance to be measured across time. Adrenomedullin (AM), a hypotensive peptide involved in cardiovascular regulation, is upregulated in sepsis. Intermedin (IMD) is related to AM and shares some of its functions. However, the in vivo integrated responses to IMD have yet to be determined. In normal rats, both peptides caused marked vasodilatations in all regions, with hypotension and tachycardia. IMD was a more potent vasodilator than equimolar AM. Next, mechanisms involved in IMD signalling were investigated and compared to AM. Both AM and IMD-mediated renal and mesenteric vasodilatation were attenuated by AM22-52 and some components of IMD were sensitive to L-NAME, suggesting IMD causes both endothelial-dependent and -independent vasodilatations. No role for KATP channels was found, but there was an enhanced response to AM in the presence ofU37883A ; this was due to inhibition of the renin-angiotensin system as assessed by the angiotensin II receptor antagonist losartan. To assess whether vascular sensitivity to AM and IMD was affected in an LPS model of endotoxaemia, rats were treated with LPS and responses to peptides were assessed at 1.5 h, 6 hand 25 h. Vascular hyporesponsiveness to both AM and IMD occurred at 1.5 h, but had returned by 25 h regardless of the LPS administration protocol. Thus, vascular hyporesponsiveness appears to be a common phenomenon during the early stages of LPS-induced endotoxaemia. The role of adenosine was then examined in the haemodynamic sequelae of sepsis, since evidence suggests that adenosine-mediated vasodilatations help to maintain regional perfusion in animal models. In control rats, endogenous adenosine caused bradycardia and vasodilatation, whereas there was evidence of regional vasoconstriction in LPS-treated rats. In control animals, exogenous adenosine caused hypotension, tachycardia and vasodilatation, but in LPStreated rats, the adenosine-induced renal (at 1.5 h) and hindquarters (at 6 h) vasodilatations were abolished. As enhanced A1 receptor-mediated vasoconstriction could explain the results in LPS-treated rats, responsiveness to an At-receptor agonist (CCPA) or antagonist (DPCPX) was assessed. There was no evidence for enhanced vasoconstrictor responsiveness to CCP A in LPS-treated rats, but DPCPX caused renal vasodilatation, consistent with endogenous adenosine mediating renal vasoconstriction. Finally, the effects of a subdepressor infusion of adenosine on the haemodynamic responses to AM and IMD were assessed, and vice versa, to determine whether any synergism exists between these agents. No synergism was found between adenosine and AM, but there was functional antagonism between adenosine and IMD in the mesenteric vasculature. Collectively, these studies suggest that the development of novel cardiovascular therapies for treatment of sepsis should be designed to take into account the vascular region, and the time elapsed from onset.
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PEBORDE, JEAN PASCAL. "Etude biochimique et immunologique du lipopolysaccharide d'escherichia coli k12." Toulouse 3, 1989. http://www.theses.fr/1989TOU30074.
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Detection du lipopolyoside (lps) au cours de la purification de proteines issues d'escherichia coli. Mise au point d'une technique elisa par inhibition, application au controle de la purification de l'hormone de croissance humaine (hgh) produite par e. Coli. Comportement chromatographique du lps sur differents supports et au cours de la purification de l'hgh. Etude des interactions lps/proteines dans le cas de la serumalbumine et de l'hgh
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Zimov, Jennifer Laura. "Behavioral and Physiological Responses To Lipopolysaccharide Induced Clinical Mastitis." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1253132975.
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CARDOSO, MENDES MOURA ELISABETE CRISTINA. "TARGETING THE LIPOPOLYSACCHARIDE TRANSPORT TO DEVELOP NOVEL ANTIMICROBIAL DRUGS." Doctoral thesis, Università degli Studi di Milano, 2021. http://hdl.handle.net/2434/789419.
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The emergence of multidrug-resistant strains of Gram-negative pathogens that rapidly spread in the clinic is of great concern, since the range of antibiotics still effective against these organisms is limited and will continue to diminish. Therefore, the identification of novel and unexplored drug targets is an urgent need. Gram-negative bacteria possess an outer membrane (OM) with highly selective permeability properties due to its asymmetric structure with LPS in the outer leaflet and phospholipids in the inner leaflet. Dissecting the biogenesis of the OM and gaining insights into the multiprotein machineries that assemble this structure is vital if we want to succeed in developing novel antibiotic compounds that can target these machineries. This thesis focuses on the machinery that transports lipopolysaccharide (LPS) to the cell surface: the LPS transport (Lpt) machinery. In Escherichia coli, the Lpt system is composed of seven essential proteins spanning the cell envelope: the ABC transporter LptB2FGC powers the LPS extraction from the inner membrane (IM) and its transport along the periplasmic bridge, comprising LptA, to the OM LptDE translocon, which assembles LPS on the cell surface.
Due to its vital role in cell physiology, the Lpt system represents a good target for the development of antibiotics with an innovative mechanism of action. Encouragingly, two promising inhibitors of this machinery have been discovered: murepavadin, which is currently in preclinical development, and thanatin. The research project of this thesis focuses on two main topics: elucidating the mechanism behind thanatin’s antibacterial activity, and the characterization of a mutant six-component Lpt machinery that is functional without LptC.
Thanatin is a host-defence antimicrobial peptide recently shown to cause defects in membrane assembly and to bind to the N-terminal β-strand of LptA in vitro (Vetterli et al., 2018). Since this region is involved in both LptA dimerization and interaction with LptC, we implemented the Bacterial Adenylate Cyclase Two-Hybrid (BACTH) system to detect these interactions in the periplasm and probe which is the target of thanatin. With this technique, we found that thanatin targets both interactions and has a stronger inhibitory effect on the LptC-LptA interaction (Moura et al., 2020: https://doi.org/10.3389/fmicb.2020.00909). Further demonstrating a direct effect upon the LPS transport, we observed in thanatin-treated cells the degradation of LptA and the accumulation of LPS decorated with colanic acid (Moura et al., 2020), both of which have been previously reported to be indicative of LPS transport defects (Sperandeo et al., 2008, 2011). We further explored how thanatin affects the integrity of the cell envelope and observed that it induces promoters regulated by envelope-specific stress response systems (unpublished data).
Although all seven Lpt proteins have been shown to be essential, viable mutants lacking LptC but carrying suppressor mutations at the residue R212 in the periplasmic domain of LptF were isolated by our group (Benedet et al., 2016). Interestingly, LptC was recently proposed to have a regulatory role on the LptB2FGC transporter by modulating its ATPase activity (Owens et al., 2019; Li et al., 2019), thus adding to the mystery of how the suppressor mutants can survive without LptC. In the second part of the project, we elucidated how the cell can bypass the presence of LptC and its regulatory role in the machinery by performing a biochemical characterization of the most representative suppressor mutant (manuscript ready for submission). Moreover, by analysing the interaction networks around the residue R212 of LptF, we also formulated a putative mechanism adopted by the Lpt transporter to regulate LPS transfer from LptB2FGC to LptA.
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Blake, Bertani Robert. "Investigations of the early stages of transport by the transenvelope lipopolysaccharide transporter in E. coli." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563470856804902.
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Venter, P. "Endotoxin residues in food : a review." Interim : Interdisciplinary Journal: Vol 9, Issue 1: Central University of Technology Free State Bloemfontein, 2010. http://hdl.handle.net/11462/348.
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Published ArticleThe initial section of this manuscript focus on the ultra-structure of a unique class of heat stable cell-bound lipopolysaccharides (endotoxin) produced by Gram-negative bacteria. Subsequently, this paper summarises literature on the human body's response when challenged with endotoxins present in food and further explores the influence of food manufacturing and storage practices on endotoxin production and release by bacteria commonly isolated from food. Finally, this paper presents a brief description on the methods applied by the food industry to quantify endotoxins.
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Al-Hawi, Mohammad Abdullah Mubarak. "Lipopolysaccharide of different bacteria : extraction methods, signalling and cytokine production." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/24453.
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Different LPS extraction methods were utilized to investigate the differences between them in terms of producing proinflammatory immune response. A further application of a repurification method was to eliminate any possible protein contaminants. These purified LPS preparations were used for the other main approach this study in which different unpurified and repurified Bacteroides fragilis LPSs together with different heat killed B. fragilis populations were examined to elucidate their Toll-like receptor (TLR) specificity. Four different extraction methods were chosen to extract LPS from Escherichia coli O18K-, Pseudomonas aeruginosa Pa-O1, B. fragilis NCTC 9343 and Rhodobacter sphaeroides NCIMB 8253. All of these species, except of R. sphaeroides, were able to simulate the production of proinflammatory cytokines TNF-α and IL-1β with differences apparent between different LPS preparations according to their extraction methods. R. sphaeroides LPS was able to inhibit the ability of these LPSs to induce TNF-α production except for B. fragilis LPS which was not effected by R. sphaeroides LPS. All different B. fragilis LPSs showed the ability to exert an antagonist effect on different E. coli on production of TNF-α or IL-1β from both human monocytes and THP-1 cell lines, which indicated that there was not such a profound effect of the extraction method in totally changing the bioactivity of specific LPS. Moreover, unpurified or purified LPSs of B. fragilis on the one hand and heat killed bacteria of B. fragilis from different capsular polysaccharide populations on the other hand all showed an obvious TLR2 signalling specificity but not TLR4 specificity. This adds further evidence that different LPS extraction methods with or without applying a repurification procedure do not change the TLR specificity of the B. fragilis LPS.
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Mo, Anthony John. "Effect of NaOH solutions on planktonic bacteria, biofilms, and lipopolysaccharide." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58354.
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Background: Eradicating bacteria, biofilms and harmful by-products such as LPS from the root canal system is important in providing successful endodontic treatment. To date no irrigant or medicament used in endodontics has been able to completely eradicate bacteria in the root canal system or detoxify all LPS. Aim: It is proposed that a novel solution containing NaOH (Sodium hydroxide), Sodium dodecyl sulfate (SDS) and an alcohol may have unique disinfective properties against bacterial factors highly relevant in endodontic treatment. Materials and Methods: Combinations of the proposed solution were tested and compared to NaOCl (sodium hypochlorite) against 1- Planktonic E. faecalis in direct contact and quantified by CFU counts 2 - Polymicrobial biofilms in an open model exposed to solutions and visualized with CLSM (Confocal Laser Scanning Microscopy) 3 – LPS using a biofunctional assay, stimulating IL-1ß production in RAW 264.7 macrophages with treated LPS aliquots and analyzed by ELISA. Results: Planktonic killing tests with E. faecalis showed that NaOCl was more effective than NaOH solutions. With potency from highest to lowest as follows: 6% NaOCl, 2% NaOCl, NaOH/SDS/Propanol, NaOH/Propanol. Biofilm tests showed that NaOCl killed more biofilm bacteria, however NaOH/SDS combinations removed more biofilm mass. Results showed that LPS samples treated with either 6% or 2% NaOCl produced no IL-1ß. Samples treated with NaOH/SDS combinations produced inconsistent results regarding IL-1ß release due to inefficient dialysis removal of toxic irrigants. Conclusions: Results suggest that NaOCl remains the irrigant of choice as it is most effective in killing bacteria either planktonically or within biofilm systems. The results of this study suggest that NaOCl is indeed effective in LPS detoxification which is contrary to suggestions by several previous studies. NaOH/SDS combinations while less effective in killing, appear to remove more biofilm mass when compared to NaOCl. This may be attributed to the surfactant properties of SDS.Dentistry, Faculty of
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De, Wilde Virginie. "Dialogue entre l'immunité innée et acquise en réponse au lipopolysaccharide." Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210371.
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Le système immunitaire nous protège contre les infections et les cancers. Cependant, des réponses immunitaires excessives ou incontrôlées peuvent causer des pathologies potentiellement mortelles comme le choc endotoxinique, des maladies auto-immunes, ou le rejet d’allogreffe. Une compréhension claire des mécanismes de régulation des réponses immunes permettrait d’envisager de nouvelles thérapeutiques plus ciblées. Dans ce travail réalisé chez la souris, la modulation de la réponse inflammatoire à une toxine bactérienne, le lipopolysaccharide (LPS), a été utilisée comme archétype de la régulation immunitaire. Ceci nous a permis de démontrer que la régulation de la prolifération homéostatique de lymphocytes T CD4+CD25- par des lymphocytes T régulateurs naturels tempère la réponse inflammatoire au LPS. Cet effet est notamment dépendant d’une diminution de la sécrétion d’IFN-γ par les lymphocytes activés par la prolifération induite par la lymphopénie. Nous avons aussi observé, que la désensibilisation du système immunitaire inné vis-à-vis du LPS, suite à des injections répétées d’endotoxine, induit le développement de cellules myéloïdes suppressives (myeloïd-derived suppressor cells MDSC) capables de réguler des réponses lymphocytaires T in vitro et in vivo. Nous avons pu mettre en évidence que l’effet suppresseur des MDSC est dépendant de leur expression de l’enzyme hème oxygénase-1 et de leur production d’IL-10. Le dialogue constant entre les cellules de l’immunité innée et de l’immunité acquise assure donc à la fois l’activation et la régulation du système immunitaire. Dans la majorité des cas, ceci permet aux réponses immunitaires d’être efficaces sans être excessives. La mise en évidence de ces processus identifie les lymphocytes T régulateurs et les cellules myéloïdes suppressives comme des éléments clefs de la régulation d’un processus inflammatoire. Les traitements immunosuppresseurs, les thérapies cellulaires et les greffes de moelle ont des effets variables et mal connu sur ces populations de cellules régulatrices. Tenir compte de ces interférences thérapeutiques avec les processus naturels de régulation de notre système immunitaire permettra certainement d’optimaliser l’utilisation de ce type de traitements. D’autre part, l’utilisation thérapeutique de ces deux types de cellules régulatrices pourrait être envisagé dans de nouvelles stratégies d’immuno-modulation plus « physiologique ».
Doctorat en Sciences médicales
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Jersmann, Hubertus Paul Anton. "Bacterial lipopolysaccharide and tumour necrosis factor- alpha synergism in inflammation." Title page, contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phj56.pdf.
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Bibliography: leaves 152-194. This thesis has contributed to the knowledge of how the bacteriokine-cytokine network operates by demonstrating how two major proinflammatory mediators interact in modulating the inflammatory response. Furthermore the discovery of CD14 expression on endothelial cells not only provides greater insight in the pathogenesis of bacterial infection, sepsis and perhaps atherosclerosis, it is also likely to influence the future development of new treatment strategies for those conditions.
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Zhou, Yuchen. "Isolation and characterization of lipopolysaccharide-like substances from Spirochaeta aurantia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq20719.pdf.
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Frey, Elizabeth Ann. "Lipopolysaccharide induced apoptosis of a bovine pulmonary endothelial cell line." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25049.pdf.
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Langley, Roger Sean. "Metal binding by Pseudomonas aeruginosa PAO1 and isogenic lipopolysaccharide mutants." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ33244.pdf.
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Rocchetta, Heather Lynn. "Molecular analysis of a-band lipopolysaccharide synthesis in Pseudomonas aeruginosa." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ33319.pdf.
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Farah, Abdullah O. "Changes of lipopolysaccharide of Salmonella enterica grown under different conditions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0032/MQ64422.pdf.
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Williams, Lynn Michelle. "A comparison of interleukin-10 and lipopolysaccharide signalling in monocytes." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264968.
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Wilson, Susan. "Lipopolysaccharide-activated signal transduction in cardiac and vascular smooth cells." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367047.
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Royle, Matthew Charles James. "Early responses of macrophages to Salmonella typhimurium and its lipopolysaccharide." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620488.
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Bauwens, Ciara. "Shigella flexneri Lipopolysaccharide Modifications in the Presence of Bile Salts." Thesis, Boston College, 2019. http://hdl.handle.net/2345/bc-ir:108501.
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Thesis advisor: Christina FahertyShigella, a Gram-negative bacterial pathogen, induces inflammation and diarrhea by invading the colonic epithelium. Annually, millions of Shigella infections occur globally, mainly in malnourished children. Despite extensive research, no effective vaccine exists. This work explores the mechanisms of Shigella proliferation before colonic infection, where an adverse environment is encountered, including bile salts exposure. One means of bile salts evasion is possibly lipopolysaccharide (LPS) modification. LPS—O-antigen, the polysaccharide core, and the lipid A—is a crucial outer membrane component for virulence. Transposon mutant analysis suggested a role of LPS in bile salts resistance; thus, the goal of this study was to define Shigella LPS modifications following bile salts exposure. LPS mutants were investigated to distinguish crucial components of the LPS structure for bile salts resistance. Mutants were analyzed relative to wild type for growth in bile salts and biofilm formation. The LPS from all strains was purified and analyzed by polyacrylamide gel electrophoresis. Stained gels show modifications in the Oag, lipid A, and core components. Key bands were sent for mass spectrophotometry sequencing. Results indicate that the O-antigen regulates Shigella bile salts resistance, as the complete O-antigen deletion mutant and partial deletion mutants exhibited slow growth in bile salts and failed to form a biofilm in the presence of bile salts. This work highlights the importance of bile salts exposure for Shigella in future targeted antibodies against the pathogen
Thesis (BS) — Boston College, 2019
Submitted to: Boston College. College of Arts and Sciences
Discipline: Departmental Honors
Discipline: Biology
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Rideau, Aline. "Dysfonction glutamatergique et GABAergique dans l'hippocampe après un stress immuno-inflammatoire prénatal chez le rat." Thesis, Montpellier 1, 2012. http://www.theses.fr/2012MON1T011.
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Introduction: L'injection ip de lipopolysaccharide (LPS) d'E.coli à la rate gestante aboutit à un phénotype cognitivo-comportemental de pathologies neuropsychiatriques chez la progéniture mâle. L'objectif principal était de vérifier l'hypothèse d'une atteinte structurelle et d'un déséquilibre entre excitation et inhibition dans l'hippocampe. L'objectif secondaire était de dégager des stratégies thérapeutiques ciblées.Méthodes: 500 μg/kg de LPS d'E.coli de sérotype O55:B5 ou 2 ml/kg de sérum physiologique étaient injectés ip à la rate au 19e jour de gestation. La progéniture mâle était étudiée à différents stades du développement. L'étude structurelle reposait sur de l'immunohistochimie, l'étude fonctionnelle sur des enregistrements électro-physiologiques de l'activité des cellules pyramidales de l'aire CA1. L'effet protecteur de la N-acétylcystéine (NAC) donnée po à la rate gestante après l'injection de LPS était testé. Résultats: Les animaux soumis à un stress prénatal par le LPS présentaient une désorganisation durable de la couche pyramidale de l'aire CA3, un déficit transitoire de neurones exprimant la reeline, une altération de la dépression à long terme des synapses glutamatergiques (LTDe) liée à un déficit des récepteurs NMDA et du système GABAergique. Un inhibiteur de la recapture du GABA parvenait à corriger les anomalies de la LTDe. La NAC prévenait les anomalies cyto-architecturales.Conclusion: Cette thèse confirme l'impact d'un stress immuno-inflammatoire maternel sur la structure et la fonction hippocampique. Elle démontre l'intérêt d'un traitement prénatal par la NAC et de la modulation du tonus GABAergique pour corriger les troubles cognitifs associésIntroduction: A late gestational exposure to lipopolysaccharide (LPS) leads to a behavioral and cognitive phenotype of neuropsychiatric disorders in male offspring. The main goal was to test the hypothesis of structural damage and imbalance between excitation and inhibition in the hippocampus. The secondary goal was to identify targeted therapeutic strategies.Methods: Pregnant rats were ip injected with either 500 μg/kg LPS from E.coli O55:B5 or 2 ml/kg saline vehicle on gestational day 19. Male offspring were studied at different developmental stages. The structural study was based on immunohistochemistry, the functional study on electrophysiological recordings of the activity of pyramidal cells in the CA1 area. The protective effect of N-acetylcysteine (NAC) given to pregnant rats after LPS injection was tested.Results: In male offspring, LPS induced late gestational immune challenge led to sustainable disarray of the pyramidal layer in the CA3 area, transient deficit of reelin expressing neurons, impaired long term depression of glutamatergic synapses (LTDe), due to NMDA receptor and GABAergic system dysfunction. An inhibitor of GABA reuptake completely restored plasticity lost after prenatal stress. NAC prevented cyto-architectural abnormalities.Conclusion: This thesis confirms the impact of a late prenatal immune challenge on hippocampal structure and function. It demonstrates that prenatal treatment with NAC and GABAergic tone modulation are valuable therapeutic strategies for the cognitive impairment associated with prenatal immune challenge
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Vidovic, Aleksandar. "Die quantitative Limulus-Amoebozyten-Lysat-Endotoxin-bestimmung bei Pferden mit Magen-Darm-Kolik unter besonderer Berücksichtigung der Endotoxämieentwicklung im Krankheitsverlauf." Doctoral thesis, Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-96972.
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Pferde als Pflanzenfresser benötigen für die Verdauungsvorgänge im Magen-Darm-Kanal eine Vielzahl von Mikroorganismen. In der Pathogenese der equinen Kolikerkrankungen spielen die aus einem Teil dieser Bakterien stammenden Endotoxine (Lipopolysaccharide, LPS) eine wichtige Rolle. Das Caecum und das Colon ascendens scheinen der Ort einer pathologischen Endotoxinabsorption beim Pferd zu sein. Mit Hilfe von Limulus-Amoebozyten-Lysat-Tests (chromogenes Substrat, Endpunkt Methode) wurden die Endotoxinkonzentrationen bei 52 gesunden Pferden und 105 an Magen-Darm-Kolik erkrankten Pferde bestimmt. Durch wiederholte Messungen wurde die Entwicklung der Endotoxinkonzentration bei Kolikpferden im Krankheitsverlauf untersucht. Im Plasma aller gesunden Pferde wurden Endotoxine nachgewiesen, mit einem Mittelwert von = 5,90 pg/ml ± 2,78 pg/ml. Bei 90,5% der Pferden mit Kolik lag die Endotoxinkonzentration in der ersten Probe nach Einlieferung in die Klinik über 10 pg/ml. Kolikformen mit grundsätzlich hohen Endotoxinkonzentrationen konnten herausgefunden werden. In dieser Untersuchung waren das die Hernia foraminis omentalis mit einem LPS-Mittelwert von 91,57 pg/ml, die Dünndarmstrangulation durch Lipoma pendulans mit einem LPS-Mittelwert von 89,32 pg/ml und die Torsio coli totalis 360° mit einem LPS-Mittelwert von 88,21 pg/mlEndotoxaemia in colic illnesses in horses; Quantitative analysis and clinical relevance Horses as herbivores require a multitude of micro-organisms for the digestive processes in the gastrointestinal tract. The endotoxins (lipopolysaccharides, LPS) originating from a part of the bacteria play an important role in the pathogenesis of equine colic illnesses. The caecum and the colon ascendens appear to be the site of a pathological absorption of endotoxins in horses. With the aid of limulus-amoebocyte-lysate tests (chromogeneous substrate, end-point method) the endotoxin concentrations were analysed in 52 healthy horses and 105 horses suffering from gastrointestinal colic. The development of the endotoxin concentration in the case of horses suffering from colic was investigated through repeated measurements throughout the course of the illness. Endotoxins were identified in the plasma of all healthy horses at a mean value of = 5.90 pg/ml ± 2.78 pg/ml. In 90.5% of the horses with colic, the concentration of endotoxins in the first sample subsequent to admission to the clinic was over 10 pg/ml. It was possible to determine specific forms of colic accompanied by fundamentally high concentrations of endotoxins. In this investigation these were omental foramen hernia with a mean LPS value of 91.57 pg/ml, small intestinal strangulation by lipoma pendulans with a mean LPS value of 89.32 pg/ml and colon torsion 360° with a mean LPS value of 88.21 pg/ml