Beta-amyloid (Aâ) remains to be the focus of research interest of the pathogenesis of Alzheimers disease (AD). Aâ is subject to oligomerization and its polymers are cytotoxic. Advanced aggregation leads to formation of senile plaques. Depositions of Aâ surrounding the cerebral vasculature, i.e. cerebral amyloid angiopathy (CAA), occur in most AD patients. The occurrence of Aâ aggregation in AD brains is not due to over-expression of amyloid precursor protein in most cases of AD. Factors influencing Aâ polymerization are yet to be established.<p> Aldehydes are highly reactive. They can cause protein crosslinkage. It is interesting to study whether endogenous aldehydes may be involved in Aâ polymerization process. In order to investigate the potential interaction of endogenous aldehydes with Aâ and their effects on its aggregation, various techniques including thioflavin T fluometry, dynamic light scattering, circular dichroism and atomic force microscopy were employed to assess Aâ aggregation at different stages. Formaldehyde, methylglyoxal, malondialdehyde and 4-hydroxyl-nonenal were found to enhance Aâ â-sheets formation, oligomerization and fibrillogenesis in vitro. The sizes of the oligomers are increased after interaction with the aldehydes. Lysine residues of Aâ were identified to be the primary site of interaction with aldehydes by forming Schiff bases, which may subsequently lead to intra- and inter-molecular crosslinkage. Aldehydes can also crosslink Aâ with other proteins such as apolipoprotein E and á2-macroglobulin (á2M), to form large complexes. Results suggest that aldehydes substantially increase the rate of Aâ oligomerization at each stage of fibrillogenesis.<p> The native and formaldehyde-modified Aâ oligomers were isolated by size exclusion chromatography and their cytotoxic effects towards SH-SY5Y neuroblastoma cells were assessed using MTT, LDH and caspase-3 activity assays. The aldehyde-modified oligomers are slightly but significantly more cytotoxic compared to the native oligomers. Since aldehydes significantly increase the production of Aâ oligomers, an increase in aldehydes would enhance the total cytotoxicity, suggesting that aldehydes may potentially exacerbate neurovascular damage and neurodegeneration caused by Aâ.<p> Low-density lipoprotein receptor related protein-1 (LRP-1) plays a crucial role in Aâ clearance via the cerebral vasculature. Semicarbazide-sensitive amine oxidase (SSAO) and LRP-1 are both richly expressed on the vascular smooth muscle cells (VSMCs). We demonstrated that SSAO-mediated deamination affects LRP-1 function using isolated VSMCs. Formaldehyde at low concentrations decreases LRP-1-mediated uptake of á2M, a substrate of LRP-1 and a carrier for Aâ. Methylamine, an SSAO substrate that is converted to formaldehyde, also inactivates LRP-1 function, but not in the presence of an SSAO inhibitor. Increased SSAO-mediated deamination can potentially impair Aâ clearance via LRP-1.<p> In conclusion, aldehydes derived from oxidative stress and SSAO-mediated deamination induce Aâ aggregation, enhance Aâ cytotoxicity and impair Aâ clearance. The exclusive localization of SSAO on the cerebral vasculature may be responsible for the perivascular deposition of Aâ, i.e. CAA, which is associated both with vascular dementia and with AD. Vascular surface SSAO may be a novel pharmacological target for the treatment of AD.

Hormone replacement therapy (HRT) has been studied as a protective factor for cognitive decline and dementia. However, study findings have been inconsistent. Variation in study findings may be due to differences in study designs, small sample size, exposure ascertainment, diagnostic procedures, and inclusion of relevant risk and confounding factors. Moreover, there may be significant differences between the characteristics of women choosing to use HRT and those opting not to use the therapy. Using a large-scale, population-based, cohort study, we examined the relationship between HRT and cognition while paying particular attention to moderating and confounding factors. The main outcomes of interest were to assess differences in risk for cognitive impairments and dementia between HRT user and never user groups; examine HRTs impact on age of onset of dementia; and explore the relationship between duration of HRT and cognitive decline. Logistic regression and Cox Proportional Hazards models were used to test HRT as a predictor for cognitive impairments, Alzheimers disease and vascular dementia, as well as to assess the effect of duration. Linear regression was used to consider the putative relationship between age at onset of dementia and HRT status. HRT use was found to be a statistically significant predictor for Alzheimers disease and vascular dementia. Overall, HRT use did not significantly predict for milder cognitive impairments, although significant interaction effects indicate that HRT may be protective at least for specific sub-groups of women. No durational effect was found for any of the outcomes. Neither did HRT appear to predict for age at onset of dementia. Notably, a large proportion of women in the current study reported using estrogen-only hormone supplements, and therefore generalizations regarding the findings are likely limited to estrogen-only preparations, not combination estrogen-progestin therapies. These findings must be considered within the context of the other known and potential risks and benefits that HRT may afford.

Biological tissues were studied with synchrotron infrared (IR) microspectroscopy, a technique that allows the spatially resolved determination and mapping of multiple components in situ at high spatial resolution. The first project involved studying brain tissue from TgCRND8 mice, a transgenic model of Alzheimer’s disease (AD). AD is the main cause of dementia in the ageing population, marked by the deposition of plaques composed of the Aβ peptide. Dense-cored and diffuse plaques were IR mapped and the results correlated with histochemistry and immunostaining. Spectral analysis confirmed that congophilic plaque cores were composed of highly aggregated protein in a β-sheet conformation. The amide I maximum of plaque cores was 1623 cm-1; there was no evidence of the high frequency (1680-1690 cm-1) peak seen in in vitro Aβ fibrils and attributed to anti-parallel β-sheet. A significant elevation in phospholipids was found around dense-cored plaques in TgCRND8 mice ranging in age from 5 to 21 months. This was due to an increase in cellular membranes from dystrophic neurites and glial cells around the core, but could also contribute to Aβ aggregation through the interaction of newly secreted Aβ with phospholipids. In contrast, diffuse plaques were not associated with infrared detectable changes in protein secondary structure or relative concentrations of other tissue components. In addition, focally elevated deposits of creatine, a molecule with a crucial role in energy metabolism, were discovered in AD brain tissue with IR microspectroscopy. The creatine deposits may be a previously undiscovered disease marker. A second project was part of a larger Natural Sciences and Engineering Research Council Collaborative Health Research Project (NSERC-CHRP) to test the hypothesis that treatment with anti-oxidants, L-2-oxo-thiazolidine-4-carboxylate (OTC) and quercetin, following spinal surgery may reduce oxidative stress, inflammation, and scarring. The effect of OTC and quercetin on scar tissue formation was evaluated in rats that had undergone laminectomy. Synchrotron IR microspectroscopy data were collected on scar tissue from OTC, quercetin and saline (control) treated animals, sacrificed at 3 and 21 days post-surgery. Spectral differences could be correlated with the stages of wound healing. / May 2007

We have recently established that aberrant alkylacylglycerophosphocholine metabolism results in the increased tissue concentration of platelet activating factors (PAFs) in the temporal cortex of Alzheimer Disease (AD) patients and in TgCRND8 mice over-expressing mutant human amyloid precursor protein. PAF lipids activate a G-protein coupled receptor (PAFR) reported to be expressed by microglia and subsets of neurons in rat. It is not known whether this same expression pattern is recapitulated in mice however, as the expression has only been inferred by use of pharmacological PAFR antagonists, many of which impact on both PAFR-dependent and PAFR-independent signalling pathways. PAFR plays a role in long term potentiation (LTP) induction in rats. PAFR has also been implicated in behavioural indices of spatial learning and memory in rats. Contradictory reports using mice provide ambiguity regarding the role of PAFR in LTP induction in mice. To assess whether PAFR is expressed in murine neurons, I localized PAFR mRNA in wild-type C57BL/6 mice using PAFR KO mice as a negative control. I further showed that the loss of PAFR did not impair learning and memory although this assessment must be considered preliminary as the behavioural test employed was not optimized to detect changes in learning and memory of C57BL/6 mice over time adequately.Finally, I showed that the loss of PAFR in TgCRND8 mouse model of AD had no impact upon Aβ plaque number. My observations suggest that PAFR is restricted to microglial-like cells in mouse hippocampus and as such, it may not play a role in learning and memory.

INTRODUCCIÓN: El envejecimiento es un factor de riesgo para enfermedades neurodegenerativas como la Enfermedad de Alzheimer (EA), que constituye la demencia más frecuente. Uno de los objetivos de la comunidad científica, actualmente, es el diagnóstico precoz de la EA en fases previas de la demencia, es decir, detectar muy tempranamente el daño cerebral que inicialmente se manifiesta como un síndrome de la memoria y que con el tiempo evolucionará a un síndrome de demencia. Esta tesis se centrado en la EA y su fase prodrómica que se manifiesta como el síndrome denominado Deterioro Cognitivo Leve (DCL), y especialmente, en el estudio de las características cerebrales que confieren a determinadas personas una resistencia a la manifestación del daño cerebral asociado al envejecimiento o a los estadios iniciales de la demencia, ya que es un área de máximo interés en investigación en neurociencia, ya que si se consiguen comprender los mecanismos específicos, podrán mejorarse las estrategias dirigidas a paliar el impacto del deterioro cognitivo en la edad avanzada. METODOLOGÍA: La presente tesis consiste en cuatro estudios, prospectivos transversales, que examinan cómo las bases neuroanatómicas y neurofuncionales de la RC modulan tanto la estructura cómo la función cerebral en envejecimiento sano y patológico. Para la realización de los estudios se ha utilizado una muestra y diversas aproximaciones neuropsicológicas y de resonancia magnética estructural y funcional. OBJETIVO: Investigar los correlatos neuroanatómicos y neurofuncionales de la reserva cognitiva o cerebral en CTR, DCL-a y EA. RESULTADOS:En el envejecimiento sano, los sujetos con altos índices de RC, volumétricamente, muestran una mayor preservación de la integridad de la SB. Funcionalmente, se observa utilización de menos recursos cerebrales durante el procesamiento de tareas cognitivas de comprensión lingüística y percepción visual compleja.En la patología, altos índices de RC comportan una mayor atrofia cerebral y daño en la sustancia blanca. Funcionalmente, correlacionan positivamente con la intensidad de activaciones y negativamente con las desactivaciones del ‘patrón de activación por reposo’ o ‘default mode network’ (DMN) durante el procesamiento cognitivo. Altos índices de RC permite a los pacientes con DCL-a el uso de redes cerebrales alternativas.CONCLUSIONES: Los estudios descritos en esta tesis aportan evidencia de que el nivel de implicación a lo largo de la vida en actividades de tipo mental o intelectual, social y físico modula la estructura y función del cerebro. En definitiva, el concepto de RC permite explicar la resistencia y compensación que muestran algunos cerebros a manifestar clínicamente un proceso patológico subyacente.

Purpose: The purpose of this project was to look at the costs of individuals with Alzheimer’s disease and related dementias (ADRD), ALS, and MS in long stay home care in Ontario, Canada. The specific goals were to produce estimates of costs for these individuals, as well as identify clinical and personal characteristics associated with these costs. This project also tested the effectiveness of the Resource Utilization Group for home care case-mix system for use in these special populations. Methods: This project was conducted using a secondary analysis of assessment data from the Canadian Staff Time Resource Intensity Verification Project, a 13-week study of home care costs (N=435 141). The project was guided by the Andersen and Newman (1973) framework for healthcare resource utilization. Descriptive characteristics and mean costs were produced using bivariate frequency and means procedures for each of three conditions. Predictors of costs were identified for each of the three neurological conditions through multivariate regression analysis conducted separately for each condition. In total 41 independent variables were included into the bivariate and multivariate analyses. The dependent variable was the total weekly formal and informal home care costs across all multivariate analyses. Results: In total, ADRD, ALS, or MS diagnoses were present in 16% of the assessments. The mean costs for the three conditions combined were $594.81. The mean costs for ADRD, ALS, and MS were $593.32, $898.41, and $574.92, respectively. Characteristics that were predictive of cost across all conditions included the Resource Utilization Group for home care case-mix system, ADL functionality, IADL functionality, cognitive performance, unsteady gait, stair use, difficulty swallowing, respiratory challenges, and bowel incontinence. The Resource Utilization Group for home care case-mix system had the highest level of explained variance of any single item tested in this project across all conditions. However, other clinical characteristics also contributed substantial levels of explained variance to the models for each of the three conditions. Conclusions: The findings from this project suggest that although diagnosis of ADRD, ALS, and/or MS can describe cost, clinical characteristics are the most important predictors of costs for individuals with these conditions. In addition, the Resource Utilization Group for home care case-mix system can adequately predict costs of individuals with these conditions. The addition of some clinical characteristics would likely improve the predictive abilities of the Resource Utilization Group for home care case-mix system.

Abstract Background: Home care is an important care setting for those with Alzheimer’s disease (AD). It provides support that allows individuals with AD to remain at home and may delay the transition to long-term care homes. Many clients with AD receive medications that are used for managing the symptoms of AD: cholinesterase inhibitors (ChEIs) and memantine. Ontario’s provincial drug benefit plan (ODB) provides subsidies for some of these medications based on specific clinical criteria. These AD medications are costly and can have significant side effects, so it is important to understand how they are being used in practice. Objectives: The objectives of this study were to report the proportion taking AD medications and which types were taken, show the change in receipt of AD medications over time, and show the covariates that were independently associated with receiving AD medications. Methods: Analysis of secondary data was performed on the provincial home care dataset. All home care clients receiving long-term home care services were assessed using the RAI-Home Care (RAI-HC), which is a comprehensive and standardized assessment. One assessment from each individual over the age of 65 who was assessed between January 2004 and September 2008 was used, for a final sample size of 321,013. Results: Overall, 65% of clients with a diagnosis of AD were receiving an AD medication. Logistic regression analysis among those diagnosed with AD showed that increased physical impairment and clinical complexity were associated with decreased odds of receiving AD medication. Contraindicating diagnoses such as congestive heart failure, lack of medical oversight and needing to make economic tradeoffs were also associated with decreased odds of receiving AD medication. Conclusions: The multivariate model showed trends of rational prescribing, such as clients with contraindicating diagnoses or very high clinical complexity having decreased odds of receiving AD medications. At the same time, evidence of structural barriers to receiving the medications was shown. There is debate about the cost-effectiveness of these medications. The provincial government could consider expanding ODB guidelines to include all AD medications for those with all levels of cognitive impairment, but further analyses involving longitudinal outcomes available in this dataset should be performed to ensure it would be in the public interest.

A 20 weeks project at Karolinska Institutet (KI), Huddinge, Sweden is in this master thesis summarized. Alzheimer’s disease is the most common form of dementia in the world. One of the pathological hallmarks seen in AD patients consists of amyloid plaques assembled of beta amyloid (Aβ) peptide aggregates. A lot of research has been done on Aβ40 and Aβ42 but not on the longer variant with 43 residues. An earlier study by Welander et al, quantified the Aβ43 peptide from amyloid plaque cores with high-performance liquid chromatography coupled to mass-spectrometry (HPLC-MS/MS)1. Here, I present the initial development of an enzyme-linked immunosorbent assay (ELISA) with the goal to quantify Aβ43 peptides in soluble fractions of human brain tissue. An ELISA method with the possibility to quantify Aβ43 peptides from cerebral spinal fluid might have the prospect to serve as a diagnostic tool for AD in the future. Commercial ELISA kits coated with antibodies against all Aβ species was not suitable for detecting Aβ43 in soluble brain tissue from human AD patients. This is due to the high amount of Aβ40 (and in some extent Aβ42) in the samples, which will bind to the same epitope as Aβ43 on the capturing antibody. These shorter Aβ species will be in excess and bind to the capturing antibody thereby ousting Aβ43 from binding in. A better way for quantifying Aβ43 with ELISA might instead be to coat a polystyrene plate with α-Aβ43 antibodies, which are c-terminal specific to Aβ43. This will abolish the competition between the different Aβ species and function as an immunoprecipitation of unwanted species. This yielded adequate quantification of Aβ43 (2.64 pM) from tris-buffer saline (TBS) fractions from a human brain sample from AD.

Abstract Background: Home care is an important care setting for those with Alzheimer’s disease (AD). It provides support that allows individuals with AD to remain at home and may delay the transition to long-term care homes. Many clients with AD receive medications that are used for managing the symptoms of AD: cholinesterase inhibitors (ChEIs) and memantine. Ontario’s provincial drug benefit plan (ODB) provides subsidies for some of these medications based on specific clinical criteria. These AD medications are costly and can have significant side effects, so it is important to understand how they are being used in practice. Objectives: The objectives of this study were to report the proportion taking AD medications and which types were taken, show the change in receipt of AD medications over time, and show the covariates that were independently associated with receiving AD medications. Methods: Analysis of secondary data was performed on the provincial home care dataset. All home care clients receiving long-term home care services were assessed using the RAI-Home Care (RAI-HC), which is a comprehensive and standardized assessment. One assessment from each individual over the age of 65 who was assessed between January 2004 and September 2008 was used, for a final sample size of 321,013. Results: Overall, 65% of clients with a diagnosis of AD were receiving an AD medication. Logistic regression analysis among those diagnosed with AD showed that increased physical impairment and clinical complexity were associated with decreased odds of receiving AD medication. Contraindicating diagnoses such as congestive heart failure, lack of medical oversight and needing to make economic tradeoffs were also associated with decreased odds of receiving AD medication. Conclusions: The multivariate model showed trends of rational prescribing, such as clients with contraindicating diagnoses or very high clinical complexity having decreased odds of receiving AD medications. At the same time, evidence of structural barriers to receiving the medications was shown. There is debate about the cost-effectiveness of these medications. The provincial government could consider expanding ODB guidelines to include all AD medications for those with all levels of cognitive impairment, but further analyses involving longitudinal outcomes available in this dataset should be performed to ensure it would be in the public interest.

Background: Dementia is a disease known to cause chronic deterioration of intellectual functions severe enough to interfere with the ability to perform activities of daily living. Alzheimer’s disease (AD) is the most frequent cause of dementia and is expected to have a substantial impact on the health care system as the Canadian population ages. Current therapies are ineffective at halting disease progression; thus, investigations examining risk factors for AD have become a popular avenue of research. A relationship between cerebrovascular disease and the risk of AD has been established, but the underlying mechanisms on how these morbidities are related remain unclear. The apolipoprotein E gene (ApoE) influences the development of AD with the apolipoprotein E-e4 allele (ApoE-e4) conferring increased risk. The underlying mechanism by which the ApoE-e4 allele influences AD is unclear. Since the ApoE-e4 allele is related to both AD and stroke, the impact of cerebral infarcts on AD may vary by ApoE-e4 allele status. Objective: The objective of this study was to assess if ApoE-e4 allele status modified the relationship between cerebral infarcts and AD. Methods: Secondary data from the Nun Study, a longitudinal clinico-pathologic study of aging representing 678 female participants 75+ years were used for this investigation. AD was diagnosed using criteria for clinical dementia and AD pathology. Dementia was diagnosed using standard criteria, including the Consortium to Establish a Registry for Alzheimer’s Disease battery of neuropsychological tests and performances on activities of daily living. AD pathology was diagnosed using a modified version of the National Institute on Aging and Reagan Institute criteria. Infarcts were identified during gross neuropathologic assessment at autopsy. Logistic regression was used to assess the relationship between AD and the presence, location, and size of cerebral infarcts. Regression models were then stratified by ApoE-e4 allele status to determine if this variable was a significant effect modifier. The relationship of ApoE-e4 allele status with AD, as well as presence of cerebral infarcts, was also explored. All regression models were adjusted for age at death, educational level, and, when appropriate, ApoE-e4 allele status. A sensitivity analysis using different definitions for the outcome AD was performed and showed that varying criteria for AD pathology did not change study results; however, the use of clinical dementia (regardless of pathology) as an outcome did produce significantly different results. Thus, the research questions were repeated using clinical dementia as an outcome. Results: The presence of cerebral infarcts was not significantly associated with AD; this relationship did not change when location and size of infarcts were examined. ApoE-e4 was significantly associated with an increased risk of AD. ApoE-e4 was not associated with presence of cerebral infarcts. ApoE-e4 did not modify the relationship between presence of cerebral infarcts and AD. When the outcome clinical dementia was investigated, presence of cerebral infarcts significantly increased the risk of dementia. This relationship remained when location and size of infarcts were analyzed. ApoE-e4 allele status slightly modified the relationship between presence of cerebral infarcts and dementia. Conclusions: The findings from this study suggest that individuals with severe AD pathology are unlikely to be affected by cerebral infarcts. Future studies should focus on examining levels of severity of AD pathology in relation to cerebral infarcts. Cerebral infarcts appear to have an impact on dementia and this relationship was found to slightly vary by ApoE-e4 status. Future studies are recommended to examine how ApoE interacts with a variety of age-related risk factors to increase the risk of AD.