Biological membranes are quasi two-dimensional self-assembled structure, primarily serving as a barrier to the leakage of cell’s contents. The main constituents of biological membrane are various amphiphilic lipids that form bilayers in an aqueous environment. These lipids carry acidic and/or basic functional groups that ionize in water, giving some of them a net electrical charge. Such a lipid molecule, when integrated into the membrane, experiences electrostatic forces from all other charged objects around it, including ions, surrounding lipids, and other molecules such as cationic peptides. The electrostatic interaction can profoundly influence the membrane, to which many phenomena with physiological significance as well as biophysical interest can be ascribed. In this thesis, we concentrate on investigating the electrostatic properties of lipid membranes. First, we study how the electrostatic interaction affects their preferred structure. To this end, we adopt a coarse-grain model that preserves the dominant characteristics of the lipids, in which the electrostatic interaction is treated within the “renormalized” Debye-H¨uckel theory. In particular, we calculate the spontaneous curvature of a phospholipid monolayer, along with other associated quantities. Our results suggest that such divalent ions as Mg2+ can stabilize HII phases of lipids (inverted hexagonal phases), which would otherwise form lamellar phases. Second,we investigate the competitive binding of ions and cationic peptides onto a monolayer of lipopolysaccharide (LPS) molecules, a class of highly charged bio-molecules found in the outer leaflet of the outer membranes of gram-negative (G-) bacteria. Cationic anti-microbial peptides (AMPs) can selectively kill bacteria, and it is suggested that they destabilize the LPS layer, easing their permeation across it, a process of great physiological and clinical interest. To this end, we model the LPS layer as a collection of charged “binding sites”, based on which we study the binding of cations (monovalent and divalent) and cationic peptides onto the layer. Our calculations suggest that the peptides can compete with divalent ions on the binding to the layer. It has been empirically known that since the stability of an LPS layer relies greatly on the bridging of divalent ions, the substitution of these ions by the peptides significantly compromises its stability. Our results offer a quantitative basis for this observation, thus providing a possible mechanism of an important step in the action of AMPs against G- bacteria.

Hannover, Univ., Diss., 2007

Ulm, Univ., Diss., 2003.

Tübingen, Univ., Diss., 2005.

University, Diss., 2009--Frankfurt (Main). / Dt. Übers. des Hauptsacht.: Die Rolle von APOBEC3G in der angeborenen Immunität gegenüber HIV-Infektionen primärer Zellen.

Regensburg, Univ., Diss., 2009.

Regensburg, Univ., Diss., 2005.

Made available in DSpace on 2014-06-11T19:32:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-12-05Bitstream added on 2014-06-13T21:03:42Z : No. of bitstreams: 1 000742958.pdf: 891454 bytes, checksum: fae2b26d92867ccfdd5068f6db2f14d8 (MD5) / The present study aimed to evaluate the serum cytokine profile and the temperature of the body surface of sheep undergoing experimental endotoxemia. Ten suffolk sheep with approximately four years of age were used. The animals were randomly separated into two groups comprising five animals each: one group was treated with LPS (Escherichia coli 055: B5: Sigma, St. Louis, MO) at a dose of 400 ng/kg, the control group was inoculated with 2 mL of 0.9% physiological solution of sodium chloride (NaCl). We conducted a physical examination of animals at the time of his admission, and blood collection for the profile of cytokines (TNF-α, IL-1β, IL-2 and IL-13), and at 2, 4, 6, 12, 24, 36, 48 and 60 hours after administration of LPS or saline. Cytokines were measured by ELISA. Rectal temperature was measured by a clinical thermometer. The body surface temperature was measured by infrared hand-held and non-contact thermometer and thermography and infrared imaging were done in regions of the forehead, back, underarm, face external and inner thigh, and perineum. Serum levels of cytokines did not change significantly. Rectal temperature peaked at 40.6°C in 4 hours after the LPS inoculation. The body surface temperature, measured by infrared thermography was initially increased at 6 hours after the LPS inoculation, however, the maximum skin temperature was recorded at 12 hours. This situation occurred with the temperature regions of the forehead, back, underarm, face external and internal thigh sheep. This study show for the first time the cytokine profile of sheep submitted to endotoxemia. The results obtained in this study show for the thermography infrared imaging can be used for the analysis of skin temperature of the sheep, so this technique should be incorporated into routine clinical veterinarians as auxiliary tool for early diagnosis of endotoxemia

O reparo ósseo é um processo que consiste na restauração dos tecidos. Ele pode ser facilitado através de enxertos, estimulação bioquímica e estimulação física. Por outro lado, pode ser retardado por endotoxina (lipopolissacarídeo; LPS). O exercício físico exerce efeito benéfico para o osso, porém não é reconhecido o efeito sobre a reparação óssea. Assim, investigamos o efeito do exercício físico sobre a ação do LPS no reparo ósseo, por meio, de dosagens de citocinas plasmáticas, densitometria óssea, análise histológica quantitativa do tecido ósseo neoformado e marcadores imuno-histoquímicos, em animais sedentários e treinados. Os ratos foram divididos em quatro grupos: sedentário salina, sedentário LPS, exercício salina e exercício LPS. O exercício consistiu no treinamento físico na esteira durante quatro semanas. Após o treinamento, os ratos foram submetidos à cirurgia para confecção do defeito ósseo na tíbia direita e 24 horas após a cirurgia o LPS foi administrado na dose de 100 ?g/kg ou 1 ml/kg de salina, intraperitoneal. Finalmente, após 10 dias o sangue e as tíbias direitas foram obtidos para as análises, período em que os animais não foram submetidos ao treinamento físico. Os ratos treinados tiveram menor peso corporal do que os ratos sedentários (P<0,001). O exercício físico exerceu efeito positivo na reparação óssea, aumentando a densidade mineral óssea (P<0,005), o conteúdo mineral ósseo (P<0,005), a neoformação óssea (P<0,005), o colágeno tipo I (P<0,05) e a expressão de osteocalcina (P<0,05). As citocinas plasmáticas não foram detectadas na análise. Esses parâmetros não foram afetados pela administração sistêmica de LPS. Assim, os dados são consistentes com o conceito de que o exercício físico exerce um importante efeito osteogênico, que é mantido durante a inflamação sistêmica aguda induzida por uma única dose de LPS. / Bone repair is a process involved in the restoration of injured tissues. It can be facilitated by grafting, biochemical and physical stimulation. On the other hand, may be delayed by endotoxin (lipopolysaccharide; LPS). Physical exercise exerts beneficial effects on the bone, but is not known its effect on bone repair. Thus, we investigated the effect of exercise on the LPS action on bone repair through plasma cytokine measurements, bone densitometry, quantitative histological analysis for new bone tissue and immunohistochemical markers in sedentary and exercised animals. Rats were divided into four groups: sedentary saline, sedentary LPS, exercise saline and exercise LPS. Exercise consisted in physical training on the treadmill for four weeks. After training, rats underwent surgery for making the bone defect in the right tibia and 24 hours after the surgery LPS was administered at a dose of 100 g/kg or 1 ml/kg saline, intraperitonial. Eventually, blood and right tibias were obtained for analysis after 10 days when rats were not submitted to physical training. Exercised rats had lower body weight than the sedentary rats (P<0,001). The physical exercise had a positive effect on bone repair, increased bone mineral density (P<0,005), bone mineral content (P<0,005), bone formation (P<0,005), type I collagen (P<0,05) and osteocalcin expression (P<0,05). Plasma cytokines were not detected in the analysis. These parameters were not affected by systemic administration of LPS. Thus, our data are consistent with the notion that physical exercise has an important osteogenic effect, which is maintained during acute systemic inflammation induced by exposition to a single dose of LPS.

Research in our lab has predicted hundreds of bacterial genes that influence nine different traits in the fruit fly, Drosophila melanogaster. As a practical alternative to creating site-directed mutants for each of the predicted genes, we created an arrayed transposon insertion library using a strain of Acetobacter fabarum DsW_054 isolated from fruit flies. Creation of the Acetobacter fabarum DsW_054 gene knock-out library was done through random transposon insertion, combinatorial mapping and Illumina sequencing. Successful mapping of transposon insertion was achieved for 6418 mutants with hits within 63% of annotated genes within Acetobacter fabarum DsW_054. Insertion sites were verified in 40 mutants through arbitrary PCR and sequencing. To test the utility of the library, genes were selected from MGWAS results on host colonization which show LPS pathway enrichment in the significant gene predicctions. Genes upstream of Lipid-A creation show significant differences in host colonization whereas downstream genes show no effect. In addition, genes were selected from MGWAS results on Drosophila starvation resistance which show Methionine/Cysteine synthesis, Cobalamin synthesis, and Biotin synthesis pathway enrichment. Under our experimental conditions we could not verify influence of these pathways on host starvation resistance. However, they do appear to influence host colonization abundance. This transposon insertion mutant library will be useful for ongoing research in our lab as well as any field studying Acetobacter species, such as other insect microbiome and fermentation research.