Amyloid forms when a protein mistolds and aggregates into insoluble fibril. Amyloidosis is featured in a great varicty of human aliments including Alzheimer's diseases. Parkinson's disease. type II diabetes and prionoses.

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A transgenic animal model in which tau protein aggregation is expected to produce behavioural symptoms similar to those observed in certain tauopathies in humans has been examined in this thesis. The transgenic mouse lines, when tested in a heterozygous genetic background, showed no cognitive deficit although non-associative learning was impaired. Fine motor learning and motor coordination, however, were severely compromised suggesting disruption of cerebellar and/or basal ganglia function. This model can be used to test tau aggregation inhibitors, that may be effective in preventing, or even reversing the behavioural symptoms caused by tau-aggregation. Since the cholinergic deficit is a feature of Alzheimer’s disease, the effect of the inhibitors described above was tested on the cholinergic system. This was examined using a pharmacological model in which cholinergic deficit was induced by treatment of mice with scopolamine, a competitive antagonist at M1 muscarinic acetylcholine receptors. For the four tau aggregation inhibitors tested in the present work, there were differing efficacies in reversing the scopolamine-induced cognitive deficit. TRx0014 (methylene blue) was the most effective and more so than rivastigmine, a marketed cholinesterase inhibitor. Co-administration of TRx0014 and rivastigmine at sub-effective doses showed a synergistic effect on the reversal of cholinergic deficits. In conclusion, the present work provided a novel transgenic animal model that closely mimics certain behavioural traits typical of some tauopathies. These animals thus provide a valuable model to test novel tau aggregation inhibitors with potentially disease-modifying consequences. The study also demonstrates that such inhibitors, in addition, are able to reverse the symptoms due to cholinergic disruption in normal mice.

No description available.

The principal aim of this research project has been the utilisation of various proteomic techniques in the investigation of the Alzheimer's disease amyloid precursor protein (APP) isoforms, namely APP[695], APP[751] and APP[770]. One of the most noticeable pathological characteristics of Alzheimer's disease is the presence of neuritic plaques in brain tissue. The chief protein constituent of neuritic plaques is the beta amyloid peptide. This peptide is proteolytically cleaved from APP, as such the interest in APP isoforms is great and a rapid detection method for the presence of each isoform would be a huge advantage to the research effort with regards to the determination and concentration in both diseased and non-diseased states. Two-dimensional gel electrophoresis and peptide mass fingerprinting are two of the most important techniques in the proteomics arena and both are investigated fully in this work. Retinoic acid induced Ntera 2 cells, derived from a human teratocarcinoma cell line, were the in vitro source of APP. Initial isolation of APP was performed by immunoprecipitation, using a monoclonal antibody raised to amino acids 1-17 of the beta-amyloid peptide sequence, which is present in all three alpha secretase cleaved isoforms of interest. The next step was to separate whole APP into its isoform components by two-dimensional gel electrophoresis. The resulting protein spots were then subjected to peptide mass fingerprinting employing the different digest reagents, trypsin, endoproteinase Asp-N and formic acid. Initial distinction between the APP isoforms could be seen upon examination of theoretical in silica digests using the various digest reagents mentioned. The in silica digests revealed peptides unique to each isoform that in theory could be used as indicators of isoform presence.

The perineuronal net (PN) is a specialised region of extracellular matrix around some neurons, particularly GABAergic neurons that contain the calcium binding protein, parvalbumin (PV). The negatively charged glycosaminoglycan side chains of chondroitin sulphate proteoglycans, a major constituent of the PN, create a polyanionic environment around neurons that is thought to be important in the buffering of ions. Maintaining ion homeostasis around the inhibitory PV-positive neurons is critical in order to sustain their fast-firing rates. Loss or disruption of inhibitory input, particularly to glutamatergic cells could result in excitotoxicity and cell death. The PN is also important in the development, stabilisation and remodelling of synapses, in maintaining the trophic microenvironment around neurons and in synaptic plasticity. Neurodegeneration, the considerable loss of synapses and the inflammatory reaction that occurs in Alzheimer's disease (AD) is likely to affect the PN. Glial cells, activated as part of the inflammatory response to the deposition of β-amyloid (Aβ) and formation of neurofibrillary tangles, release matrix metalloproteinases (MMPs) that are capable of degrading the PN. This thesis describes studies of PN N-acetylgalactosamine and PV-positive neurons in AD, and their relationship to parenchymal tau, Aβ, microglia, astrocytes, and MMPs-2, -3 and -9. The outcome of these studies showed that the PV-positive neurons tend to be spared in AD but there is degradation of surrounding PNs.

Alzheimer’s disease (AD) has long been associated with altered activity of the serine/threonine kinases, Glycogen Synthase Kinase-3 (GSK3) isozymes, which are proposed to contribute to both neurofibrillary tangles and amyloid plaque formation. While the molecular links between GS3K and tau pathology are well established, the molecular basis by which GSK3 affects the formation of amyloid-β (Aβ) remains unknown. The aim of this investigation was to identify the underlying mechanisms by which inhibition of GSK3 affects the processing of the amyloid precursor protein (APP). To this end various methods were employed to alter the basal activity of the GSK3 enzyme in N2a cells, a mouse neuroblastoma cell-line, overexpressing the Swedish variant of APP. Specific perturbation of GSK3 activity leads to an alteration in APP processing and Aβ production, something that until now, was seen as controversial. Specific pharmacological inhibition of GSK3 resulted in a decrease in activity, expression and transcription of BACE1, which is the main enzyme responsible for Aβ generation. Activation of the canonical Wnt pathway, which is associated with negative regulation of GSK3, reproduced the previous findings and led to reduction in transcription and expression of BACE1. Furthermore, specific pharmacological GSK3 inhibition and GSK3α/β knockdown enhanced full-length APP degradation via an increase in the number of lysosomes. This induction of the lysosomal/autophagy pathway was associated with the effect of specific GSK3 inhibition on the nuclear translocation of transcription factor EB (TFEB), which is a master regulator of lysosomal biogenesis. All together, GSK3, in addition to being associated with hyperphosphorylation of tau, can also influence Aβ generation through regulating BACE1 expression and the homeostatic turnover of APP. This data reinforces the hypothesis that GSK3 could be a therapeutic target for AD as it is shown to be a central signalling node in the pathogenesis of the disease.

No description available.

This thesis consists of a literature review, a research paper and a critical review which investigates the experience of dementia with a specific focus on the perceptions of cause and control in people with Alzheimer's disease. The literature review is a meta-synthesis of nine qualitative studies that investigated the experience of dementia. The synthesis identified three overarching constructs of: "the consequences of dementia", "resistance and maintenance" and "acceptance and integration". The lines-of-argument synthesis suggested that individuals can be in a circular process of moving between resistance and maintenance, or can be in a state or both resisting and accepting dementia. Subsequently, it was recommended that health professionals consider that this process is a part of the experience of dementia and support individuals with dementia with this. The research paper explored the cause and control illness representation of six. individuals with Alzheimer's disease by completing semi-structured interviews and conducting an interpretative phenomenological analysis. The analysis identified three themes including theme one: "It is something that creeps on isn't it and you don't notice it creeping on"; idiosyncrasies of Alzheimer's disease and impact on understanding; theme two: "I'm not saying that I haven't got it I might have it but I don't know"; graded engagement with diagnosis of Alzheimer's disease; theme three: "I think it's good not to worry about it"; pragmatic emotional response to Alzheimer's disease. Indeed, causal attributions were identified and participants discussed different forms of control. Consequently, clinical implications were discussed and future research suggested. The critical review includes reflections on a number of pertinent issues that arose during the completion of the research.

The objective of this dissertation was to characterise the relative contribution of genetic influences to individual differences in cross sectional performance and decline of semantic-lexical abilities and to investigate whether these linguistic effects indicating semantic degradation are sensitive indicators of medial temporal atrophy in early Alzheimer's disease and in patients with mild cognitive impairment of amnestic type (aMCI). The effect of ApoE status in the genetic profile of these groups on deterioration of semantic abilities was studied to verify whether there was any relationship between variation in lexical factors and genetic variability. Oral generation of words belonging to two categories (animal and fruits) during a fluency tasks was required. In AD patients there was an effect of genotype but, although strong, this was diluted by the advanced cognitive deterioration and could only be seen as a tendency to be stronger in ε4 carriers. The words produced by the aMCI carriers were significantly earlier acquired than those of non-carriers and controls. These behavioural findings confirmed evidence from other recent studies and showed that a significant proportion of phenotype variability in performance on fluency tasks was influenced by genetic factors. Impairments in semantic tasks in the ε4 allele carrier population might indicate either that individuals who will develop AD never fully develop semantic skills, or that the neuroanatomical substrate of semantic abilities is selective sensitive to the earliest effects of the AD neuropathology. On the basis of this result it seemed reasonable to hypothesise that the presence of the “semantic endophenotype” in people carriyng the ApoE vulnerability mutation might be associated with atrophy in areas early affected by neuropathology due to AD and involved in semantic memory retrieval. Using lexical semantic competency in aMCI carriers as an endophenotype, grey matter volume loss in aMCI ε4 carriers/non-carriers and in controls was compared and the residual volume correlated with allele burden and with age of acquisition values for words produced in a category fluency task. Direct group comparisons showed that carriers had grey matter volume loss which was generally confined to limbic regions and medial temporal structures, and non-carriers had greater atrophy in temporal and parieto-occipital neocortex. aMCI subjects had significantly impoverished lexical semantic output compared to controls, more marked in aMCI carriers. A voxel based correlation analysis showed that greater volume loss in parahippocampal gyrus and thalamus was associated with a tendency to retrieve earlier acquired words in the category fluency task. The results suggest a relatively specific impact of ApoE 4 burden and underline the value of linguistic assessment in preclinical diagnosis. The detrimental role of this mutation found in aMCI individuals was also assessed at the larger stage in the disease process by direct comparisons in minimal to mild AD ε4 carriers/non-carrier patients. VBM comparison analysis confirmed the observation done in the genetically determined aMCI subgroups. AD ε4- carriers showed greater atrophy in mediotemporal structures compared to non-carriers whose grey matter volume loss was more widespread in more neocortical areas. Finally, an age, gender and education based norms for AoA, Typicality and Familiarity was built up in order to create a valid psychometric instrument able to detect and monitor subtle semantic deficits in ApoE ε4 carriers over time.