Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references. Also available in electronic version.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 6 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 6 uppsatser.

Diss. (sammanfattning) Umeå : Univ., 2005. / Härtill 4 uppsatser.

Konstanz, Univ., Diss., 2006.

Berlin, Freie Universiẗat, Diss., 2000. / Dateiformat: zip, Dateien im PDF-Format.

Chronic inflammation in response to Aß peptide deposits is a pathological hallmark of Alzheimer's disease (AD). The inflammatory environment includes populations of reactive and proliferating microglia and astrocytes and perturbed vasculature. However, the association between activated glial cells and cerebrovascular dysfunction remain largely unknown. This study has used Aß1-42 intrahippocampal injection as an animal model of inflamed AD brain to characterize mechanisms of glial-vasculature responses as a basis for chronic inflammation. Preliminary findings suggested Aß1-42-injected brain demonstrated vascular remodeling including evidence for formation of new blood vessels (angiogenesis). This result led to study of the effects of the anti-angiogenic/anti-inflammatory compound, thalidomide on activated glial cells and perturbations in the vasculature in an Aß1-42 peptide-injected rat model. First, Aß1-42 injection was found to cause perturbations in vasculature including new blood vessel formation and increased BBB leakiness. Second, thalidomide decreased the vascular perturbations and the glial reactivity and conferred neuroprotection. Overall, these results suggest that altered cerebral vasculature is integral to the overall inflammatory response induced by peptide. Experiments then examined the level of parenchymal plasma proteins in brain tissue from AD and nondemented (ND) individuals. AD, but not ND, brain tissue demonstrated high levels of fibrinogen immunoreactivity (ir). Aß1_42 injection into the rat hippocampus increased the level of parenchymal fibrinogen, which was reduced by treatment with the defibrinogenating agent, ancrod. In addition, ancrod also attenuated microglial activation and prevented neuronal injury. Overall, these results demonstrate that extravasation of blood protein and a leaky BBB are important in promoting and amplifying inflammatory responses and causing neuronal damage in inflamed AD brain. Microglial chemotactic responses to VEGF (vascular endothelial growth factor) receptor Flt-1 were next studied. Treatment with a monoclonal antibody to Flt-1 (anti-Flt-1 Ab) in the peptide-injected hippocampus diminished microglial reactivity and provided neuroprotection. Secondly, anti-Flt-1 Ab inhibited the AI3142-induced migration of human microglia. These results suggest critical functional roles for Flt-1 in mediating microglial chemotaxis and inflammatory responses in AD brain. The overall conclusion from my work is that AP deposits induce microglial reactivity which subsequently causes vascular remodeling resulting in an amplified inflammatory microenvironment which is damaging to bystander neurons. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

Amyloid proteins are found in all domains of life, and have a number of defining characteristics, including considerable β-sheet secondary structure and the ability to self-assemble into large, insoluble fibers. These insoluble aggregates are often deleterious to the cell, evidenced by amyloid proteins being involved in Alzheimer’s, Parkinson’s, and Huntington’s disease. Remarkably however, some organisms have found ways to circumvent the toxicity of amyloid proteins, and instead co-opt them as beneficial aspects of their development and survival. An example of this can be seen in the bacteria genus Streptomyces. Streptomyces bacteria have a complex, multicellular life cycle that involves progressing through a number of distinct developmental stages. The reproductive phase of the life cycle requires the activity of amyloid-forming proteins known as chaplins - hydrophobic proteins that polymerize on the cell surface, ultimately promoting reproductive development. Due to limitations in other model Streptomyces, key questions regarding the function of chaplins have not yet been addressed. The emerging model species Streptomyces venezuelae is unique given its rapid growth, its ability to develop in liquid, and its potential to adopt two distinct life cycle programs. This work sought to characterize how chaplins influence these processes. We created a number of chaplin mutants, and determined that chaplins contribute to these process in mostly redundant ways, but when deleted in bulk cause significant phenotypic changes. We have also shown that the requirement of chaplins in development goes beyond what was previously understood - as their loss affects development in all classical life cycle stages, and further impacts alternative life cycle programs. To understanding how chaplins are regulated in S. venezuelae, mutagenesis screens were conducted to identify mutants with altered chaplin regulation. These yielded promising candidates for further investigation. Collectively, this work has advanced our understanding of chaplin proteins, specifically how they are regulated, and how they affect various modes of Streptomyces growth and development. / Thesis / Master of Science (MSc)

Alzheimer-Demenz ist eine Erkrankung, die durch den demografischen Wandel immer mehr an Bedeutung gewinnt. Eine effektive und frühzeitige Diagnostik ist daher entschei-dend. Da die neuropsychiatrische Testung mit einer diagnostischen Unsicherheit von 10% bis 30% zu ungenau ist und auch erst bei Ausbruch der Symptomatik eine Alzheimer-Demenz diagnostiziert werden kann, wurde auf Parameter wie Beta-Amyloid zurückgegrif-fen. Beta-Amyloid stellt einen Hauptbestandteil der Alzheimer-Demenz Pathologie dar und ist bereits vor Ausbruch der Symptome nachweisbar. Da die visuelle Analyse, welche die Beta-Amyloid Hirn-PET-Daten auswertet, durch ihren hohen Zeitaufwand im Alltag nicht einsetzbar ist, wurden automatische Auswerteverfahren entwickelt. Das BRASS zeigt sich mit einer Sensitivität von 78,4% und einer Spezifität von 80,5% im Bezug zur visuellen Analyse als gut geeignet in der Differenzierung zwischen Probanden mit und ohne Anreicherung von Beta-Amyloid. Eine weitere Verbesserung der Ergebnisse ist durch eine ROC-Analyse im Bezug zu den histopathologischen Befunden vorstellbar, welches in Phase 3 der Studie überprüft wird. Innerhalb des BRASS sind bei der Testung einige Schwierigkeiten aufgetreten, die bei der Weiterentwicklung der Software berücksichtigt und verbessert werden müssen. Auch dadurch ist mit einer weiteren Erhöhung der Sensitivität und Spezifität zu rechnen, sodass der Einsatz des BRASS als ein Standardver-fahren in der Alzheimer-Demenz Diagnostik realistisch ist.