#acl 3191E,3305E,3239E:read,write Default
= Pathogenesis of the Main Neurodegenerative Diseases: Alzheimer’s and Parkinson’s Diseases =
Project by: <
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Pirounaki, Styliani <
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Vadamootoo, Shanya <
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Aoun, Lea <
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Supervisor: <
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Dr. Bárány Zoltán <
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Physiology Department, <
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University of Veterinary Medicine, Budapest <
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Spring Term, 2017 <
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<>
== Introduction to Alzheimer’s disease ==
Alzheimer's disease (AD) is the most common type of dementia, it is caused by parts of the brain shrinking (atrophy), which affects the structure and function of particular brain areas. AD and dementia are often used interchangeably as many people believe that one means the other. According to the national institute on aging (NIA), Dementia is a brain disorder that affects communication and performance of daily activities(impaired thinking and memory) and AD is a form of dementia that specifically affects parts of the brain that control thought, memory and language.
AD is not a reversible disease. It is degenerative and incurable at this time. Some forms of dementia, such as a drug interaction or a vitamin deficiency, are actually reversible or temporary.<
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Atypical AD: Atypical AD is the type of AD where a different area in the brain is affected. Although this type of AD results because of the same underlying cause (plaques and tangles), its first symptom is not memory loss. The atypical forms of AD are as follows:
* Posterior cortical atrophy (PCA) occurs when there is damage to the parietal lobes (Ross S, 1996).These are areas that process visual information and deal with spatial awareness. This means the early symptoms of PCA are often problems identifying objects or reading, even if the eyes are healthy. <
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* Logogenic aphasia involves damage to the areas in the left side of the brain(frontal lobes) that is responsible for speech. The person’s conversation becomes labored with long pauses. <
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* Frontal variant AD involves damage to the Frontal lobes. The symptoms are problems with planning and decision-making. The person may also behave in socially inappropriate ways or seem not to care about the feelings of others (Krishnan, 2014).
== Types and stages of Alzheimer’s disease ==
Types:
* Early onset AD:
* Early-onset AD occurs in people age 30 to 60 and represents less than 5 percent of all people with Alzheimer's. Most cases are caused by an inherited mutation in one of three
genes. For others, the disease develops without any genetic or other known cause.
*Early-onset AD is caused by a single-gene mutation on chromosomes 21, 14, or 1. Due to these mutations, abnormal proteins are formed. Mutations on chromosome 21 cause the formation of abnormal amyloid precursor protein (APP). A mutation on chromosome 14 leads to the production of abnormal presenilin 1(PS1) (a core protein that forms amyloid beta from APP), and a mutation on chromosome 1 leads to abnormal presenilin 2(PS2); which processes proteins that transmit chemical signals from the cell membrane to the nucleus.
*Mutations in the genes for APP, PS1 and PS2 were observed in AD families and all these mutations induced an increase of Ab production (Puzzo & al, 2015); on the other hand, a mutation in the APP gene that results in a reduction in the formation of amyloidogenic peptides was found to protect against cognitive decline in the elderly (Jonsson et al., 2012)
* Late-onset AD:
* Most people with AD have this form of the disease, in which symptoms become apparent in the mid-60s and later. A specific gene has not yet been found to cause late-onset AD. However, one genetic risk factor—having one form of the apolipoprotein E (APOE) gene on chromosome 19—increases the risk of late on-set AD(Corder E. H. et al, 1993). APOE comes in several different forms, or alleles:
*APOE e2 — the least common — appears to reduce the risk of Alzheimer's.
*APOE e4 — a little more common — appears to increase the risk of Alzheimer's.
* Having at least one APOE e4 gene increases the risk of developing Alzheimer's disease. If you have two APOE e4 genes (one on each chromosome), the risk is even higher. But not everyone who has one or even two APOE e4 genes develops Alzheimer's disease. The disease also occurs in many people who don't even have an APOE e4 gene, suggesting that the APOE e4 gene affects risk but is not a cause.
Stages: The different stages of AD are summarized in table 1.
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