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The amyloid cascade hypothesis provides an economical mechanistic explanation for Alzheimer's disease (AD) dementia and correlated neuropathology. However, some nonagenarian individuals (high pathology controls, HPC) remain cognitively intact while enduring high amyloid plaque loads for decades. If amyloid accumulation is the prime instigator of neurotoxicity and dementia, specific protective mechanisms must enable these HPC to evade cognitive decline. We evaluated the neuropathological and biochemical differences existing between non-demented (ND)-HPC and an age-matched cohort with AD dementia. The ND-HPC selected for our study were clinically assessed as ND and possessed high amyloid plaque burdens. ELISA and Western blot analyses were used to quantify a group of proteins related to APP/Aβ/tau metabolism and other neurotrophic and inflammation-related molecules that have been found to be altered in neurodegenerative disorders and are pivotal to brain homeostasis and mental health. The molecules assumed to be critical in AD dementia, such as soluble or insoluble Aβ40, Aβ42 and tau were quantified by ELISA. Interestingly, only Aβ42 demonstrated a significant increase in ND-HPC when compared to the AD group. The vascular amyloid load which was not used in the selection of cases, was on the average almost 2-fold greater in AD than the ND-HPC, suggesting that a higher degree of microvascular dysfunction and perfusion compromise was present in the demented cohort. Neurofibrillary tangles were less frequent in the frontal cortices of ND-HPC. Biochemical findings included elevated vascular endothelial growth factor, apolipoprotein E and the neuroprotective factor S100B in ND-HPC, while anti-angiogenic pigment epithelium derived factor levels were lower. The lack of clear Aβ-related pathological/biochemical demarcation between AD and ND-HPC suggests that in addition to amyloid plaques other factors, such as neurofibrillary tangle density and vascular integrity, must play important roles in cognitive failure.
Pubmed ID: 22087282 RIS Download
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THIS RESOURCE IS NO LONGER IN SERVICE. Documented on January 4, 2023.Consortium that developed brief, standardized and reliable procedures for the evaluation and diagnosis of patients with Alzheimer's disease (AD) and other dementias of the elderly. These procedures included data forms, flipbooks, guidebooks, brochures, instruction manuals and demonstration tapes, which are now available for purchase. The CERAD assessment material can be used for research purposes as well as for patient care. CERAD has developed several basic standardized instruments, each consisting of brief forms designed to gather data on normal persons as well as on cognitively impaired or behaviorally disturbed individuals. Such data permit the identification of dementia based on clinical, neuropsychological, behavioral or neuropathological criteria. Staff at participating CERAD sites were trained and certified to administer the assessment instruments and to evaluate the subjects enrolled in the study. Cases and controls were evaluated at entry and annually thereafter including (when possible) autopsy examination of the brain to track the natural progression of AD and to obtain neuropathological confirmation of the clinical diagnosis. The CERAD database has become a major resource for research in Alzheimer's disease. It contains longitudinal data for periods as long as seven years on the natural progression of the disorder as well as information on clinical and neuropsychological changes and neuropathological manifestations.
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