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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

The production and characterization of murine monoclonal antibodies against Salmonella lipopolysaccharide

陸滿淸, Luk, Moon-ching, John. January 1987 (has links)
published_or_final_version / Microbiology / Master / Master of Philosophy
22

Changes of lipopolysaccharide of Salmonella enterica grown under different conditions

Farah, Abdullah O. January 1999 (has links)
The incidence of foodborne disease caused by Salmonella enterica is increasing yearly, despite the growing body of information regarding these most common pathogens. We examined the growth of, and lipopolysaccharide (LPS) expression of three Salmonella species (S. typhimurium, S. enteritidis , and S. blockley) grown at different pH values and temperatures and to different stages of the growth cycle. Growth conditions were found to affect the compositions of the LPS molecules produced by the organisms. The Tricine-SDS-PAGE and immunoblot profiles of LPS from the three Salmonella species were in accordance with the chemical data. Altered LPS profiles at different growth conditions were noted. Such differences among the profiles include variations within core oligosaccharides and the presence of O-side chains. The results also show that S. enteritidis and S. blockley grown to their exponential and stationary phases of the growth cycle produced longer O antigens and greater amounts of O antigens than did S. typhimurium grown at different growth stages. Tricine-SDS-PAGE allowed excellent resolution of low molecular weight LPS and the core region of LPS.
23

Cytokine production by cultured bovine mammary epithelial cells (MAC-T) upon stimulation with lipopolysaccharide

Chan-Tang, Hoi-Sing. January 1998 (has links)
Cytokines are known to be involved in mastitis, yet their production by bovine epithelial cells has so far not been reported. In this research a bovine mammary alveolar cell line (MAC-T) was used as a simplified model for mammary glands. Cultured MAC-T cells were stimulated with 1, 10 and 20 mug/ml of a bacterial cell wall component (lipopolysaccharide) to verify the production of epithelially derived bovine cytokines. Cytokine mRNA production was assessed by reverse transcriptase polymerase chain reaction (RT-PCR) using RNA samples isolated during the first 24 hrs of lipopolysaccharide stimulation. Interleukin-1alpha/beta, interleukin-6 and interleukin-8 mRNA production seemed to be time and dose dependent. Restriction enzyme analysis of PCR products confirmed the identity of the cytokines. Enzyme linked immunosorbent assays for interleukin-1 and interleukin-8 showed that the respective mRNA's were translated into proteins. Interleukin-8 protein was detectable 6 hrs after lipopolysaccharide stimulation; maximal levels of approximately 55 pg/ml were reached at 48 hrs post stimulation. Interleukin-1 was detected 1hr after stimulation; concentrations peaked between 500 and 600 pg/ml at 2, 5 and 12 hrs for 20, 10 and 1 mug/ml of lipopolysaccharide respectively. The amount of protein produced by the MAC-T cell line was relatively low and required high concentrations of lipopolysaccharide. Nevertheless, this model demonstrated a time and dose dependent cytokine production. These results suggest that bovine epithelial cells could be a source of cytokine production during mammary infection.
24

Inducible tolerance to Bacillus thuringiensis (Bt) endotoxins based on cell-free immune reactions.

Rahman, Mohammad Mahbubur January 2006 (has links)
Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / The use of Bacillus thuringiensis (Bt) endotoxins to control insect vectors of human diseases and agricultural pests is threatened by the possible evolution of resistance in major pest species. Despite the use of Bt-endotoxins in transgenic crops covering about 80 million hectares, the precise details of how endotoxins bind to gut cells to kill insects are poorly understood. This limitation impedes our understanding of potential mechanisms of insect resistance to Bt-endotoxins other than the loss or modification of receptors. We explored a novel mechanism, where tolerance to Bt-endotoxins is correlated with an elevated immune status involving cell-free immune reactions in the gut lumen. The thesis project is based on investigations of a laboratory culture of the flour moth Ephestia kuehniella, which showed induction of hemolymph melanization a sign of immune induction, after feeding sub-lethal concentrations of a Bt-formulation. Since the elevated immune status was transmitted to subsequent generations by a maternal effect, an increase of toxin in the food by increments was possible every generation. Investigations of strains exposed to various toxin levels revealed a correlation between systemic immune induction and Bt-tolerance. Molecular analysis revealed a possible mechanism of immune mediated inactivation of Bt-endotoxins in the gut lumen. To gain more specific information about the effector pathways involved in the protection against the toxin, we studied the effects of Bt-toxin formulations in susceptible (non-induced) and tolerant (immune-induced) larvae after natural (parasitism-mediated) and chemical (tropolone-mediated) suppression of defence reactions. Although melanization in hemolymph was significantly reduced, there was no significant effect on susceptibility to the toxin in parasitised or tropolone-treated larvae. This suggests that melanization of hemolymph is correlated with an elevated immune status but not responsible for the observed tolerance to Bt-toxin. This leaves coagulation as a likely mechanism for Bt-tolerance in the gut lumen. To examine whether hemolymph proteins exist in the gut lumen were they could function as pro-coagulants to inactivate the toxin; we compared gut and plasma proteins of immune-induced larvae with those of non-induced larvae. This analysis revealed that the lipid carrier lipophorin represents a major component in the gut lumen and interacts with mature Bt-toxin like an oligomeric lectin that may inactivate the toxin in a cell free coagulation reaction in the gut lumen before it can reach the brush border membrane. Further analysis showed that lipophorin particles are the regulatory and effector components in innate immune defence reactions, which are involved in the recognition and inactivation of lipopolysaccharides (LPS) and bacteria even in the absence of hemocytes. Examination of proteins from lipophorin particles separated by low-density gradient centrifugation have shown that in immuneinduced insects sub-populations of lipophorin particles are associated with pattern recognition proteins, phenoloxidase and regulatory proteins that activate prophenoloxidase. Moreover, interactions with lectins resulted in the assembly of lipophorin particles into cage-like coagulation products, effectively protecting the surrounding tissues and cells from the potentially damaging effects of pathogens and phenoloxidase products. This cell-free immune reaction mediated by lipophorin particles may potentially involve in detoxification of poreforming toxins (Bt-endotoxins) in the gut lumen. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1259896 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2006
25

Inducible tolerance to Bacillus thuringiensis (Bt) endotoxins based on cell-free immune reactions.

Rahman, Mohammad Mahbubur January 2006 (has links)
Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / The use of Bacillus thuringiensis (Bt) endotoxins to control insect vectors of human diseases and agricultural pests is threatened by the possible evolution of resistance in major pest species. Despite the use of Bt-endotoxins in transgenic crops covering about 80 million hectares, the precise details of how endotoxins bind to gut cells to kill insects are poorly understood. This limitation impedes our understanding of potential mechanisms of insect resistance to Bt-endotoxins other than the loss or modification of receptors. We explored a novel mechanism, where tolerance to Bt-endotoxins is correlated with an elevated immune status involving cell-free immune reactions in the gut lumen. The thesis project is based on investigations of a laboratory culture of the flour moth Ephestia kuehniella, which showed induction of hemolymph melanization a sign of immune induction, after feeding sub-lethal concentrations of a Bt-formulation. Since the elevated immune status was transmitted to subsequent generations by a maternal effect, an increase of toxin in the food by increments was possible every generation. Investigations of strains exposed to various toxin levels revealed a correlation between systemic immune induction and Bt-tolerance. Molecular analysis revealed a possible mechanism of immune mediated inactivation of Bt-endotoxins in the gut lumen. To gain more specific information about the effector pathways involved in the protection against the toxin, we studied the effects of Bt-toxin formulations in susceptible (non-induced) and tolerant (immune-induced) larvae after natural (parasitism-mediated) and chemical (tropolone-mediated) suppression of defence reactions. Although melanization in hemolymph was significantly reduced, there was no significant effect on susceptibility to the toxin in parasitised or tropolone-treated larvae. This suggests that melanization of hemolymph is correlated with an elevated immune status but not responsible for the observed tolerance to Bt-toxin. This leaves coagulation as a likely mechanism for Bt-tolerance in the gut lumen. To examine whether hemolymph proteins exist in the gut lumen were they could function as pro-coagulants to inactivate the toxin; we compared gut and plasma proteins of immune-induced larvae with those of non-induced larvae. This analysis revealed that the lipid carrier lipophorin represents a major component in the gut lumen and interacts with mature Bt-toxin like an oligomeric lectin that may inactivate the toxin in a cell free coagulation reaction in the gut lumen before it can reach the brush border membrane. Further analysis showed that lipophorin particles are the regulatory and effector components in innate immune defence reactions, which are involved in the recognition and inactivation of lipopolysaccharides (LPS) and bacteria even in the absence of hemocytes. Examination of proteins from lipophorin particles separated by low-density gradient centrifugation have shown that in immuneinduced insects sub-populations of lipophorin particles are associated with pattern recognition proteins, phenoloxidase and regulatory proteins that activate prophenoloxidase. Moreover, interactions with lectins resulted in the assembly of lipophorin particles into cage-like coagulation products, effectively protecting the surrounding tissues and cells from the potentially damaging effects of pathogens and phenoloxidase products. This cell-free immune reaction mediated by lipophorin particles may potentially involve in detoxification of poreforming toxins (Bt-endotoxins) in the gut lumen. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1259896 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2006
26

Systemic bacterial endotoxin plus MPTP as a model of Parkinson's disease in C57BL/J6 mice

Byler, Stefanie Lynn. January 2007 (has links) (PDF)
Thesis (Ph.D.)--Texas Christian University, 2007. / Title from dissertation title page (viewed Apr. 29, 2008). Includes abstract. Includes bibliographical references.
27

B-1 and B-2 B cell responses to lipopolysaccharide putative roles in the pathogenesis of periodontitis /

Philips, Julia Rachel. January 2006 (has links)
Thesis (M. Sc. Dent.)--Discipline of Oral Biology, Faculty of Dentistry, University of Sydney, 2006. / Title from title screen (viewed July 11, 2007). Submitted in fulfilment of the requirements for the degree of Master of Science in Dentistry to the Discipline of Oral Biology, Faculty of Dentistry. Includes bibliographical references. Also issued in print.
28

Investigating bacterial lipopolysaccharides and interactions with antimicrobial peptides

Strauss, Joshua. January 2009 (has links)
Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: QCM-D; AFM; bacterial adhesion; E. coli; antimicrobial peptides Includes bibliographical references (leaves 135-157).
29

The interaction between Newcastle disease virus and E. coli or its endotoxin

El Tayeb, Amna Bashir. January 1983 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 66-75).
30

Biochemistry of virulence in Brucella

Goodfellow, Steven James, January 1965 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 69-74.

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