Ad : An Unidentified Mystery

This specific gene codes for amyloid beta peptides. The amyloid beta peptides are found in the plaques associated with AD and also in the neurofibrillary tangles. Accumulation of this peptide may cause AD. There is usually too much accumulation of amyloid beta in the brain and not enough clearance. The build up then causes the plaques and tangles. It is believed that a missense mutation in the precursor for this peptide is what causes an imbalance between accumulation and clearance. Also, when the amyloid beta forms deposits in the neurons, it is believed to stimulate activity of microglial cells. When these cells are stimulated, it causes the production of more amyloid beta, accounting for the progression of the disease. This theory is known as the amyloid beta cascade hypothesis. Although there are many supporters of this theory, there still is not enough evidence to prove it and there is some evidence against it. Firstly, there is not a mutation in the amyloid gene that increases the risk of familial AD. Amyloid beta has also been shown to be non toxic, so it alone can not account for the death of neurons in the brain associated with AD. However, the stimulation of the microglial cells also results in the production of tau proteins, which when in excess, may be the cause of neuronal death. Also, the microglial activation might cause the release of other neurotoxic molecules, such as IL-1b, IL-6, TNFa, nitric oxide, and many other

Alzheimer’s disease (AD) is a progressive and fatal form of dementia, frequently seen in the elderly altering their cognition, thought process and behavior. AD is reported in about half of patients that have a dementia diagnosis; one study states that about 10.3% of the population over 65 years is affected by dementia with an increase to almost 50% over the age of 8 (Beattie, 2002). Alzheimer’s disease is not a normal part of the aging process in humans, but rather found in a group of diseases that affect the brain leading to a decline in mental and physical control. AD when diagnosed has a very slow and gradual course, initially affecting the individual’s short term memory (Beattie, 2002). Alzheimer’s disease is the 6th leading cause of death, affecting more than five million people in the United States and is also one of the most common forms of dementia. Dementia can be defined as a disorder of progressive cognitive impairment severe enough to affect daily functions of an individual’s life (Fillit, et al., 2002).

Alzheimer 's disease (AD) is a progressive degenerative disease of the brain from which there is no recovery. There are three brain abnormalities that are the hallmarks of the Alzheimer’s disease is initially caused by plaques buildup in the brain’s neurons as illustrated in figure 1. The support structure that allows the flow of the nutrients through the neurons gets damaged and ultimately there is loss of connection among the neurons and they die off (National Institute of Health, 2015). This causes the brain tissue to shrinks, which is called atrophies. All this ultimately lead the victim of this disease to face difficulties in governing emotions, recognize errors and patterns, coordinate movement, and remember. Ultimately, a person with AD loses all memory and mental functioning.

The loss of cognitive function is associated with fewer nerve cells and synapses than the normal brain. The neurons demise is thought to be from the formation of plaques and tangles. The formation of these plaques and tangles can begin many years before the person becomes symptomatic of AD. The formation of plagues comes from the breaking down of a protein in the cell membrane into protein fragments called beta-amyloid. The YouTube video, NIH: Unraveling the Mystery of Alzheimer's Disease, provides a clear animation how the beta-amyloid plaques are formed as these sticky fragments begin to clump together. (National Institutes of Health, 2011) The video shows another protein called tau, involved with formation of tangles. The tau protein is instrumental in the transport of food molecules, parts of cells, and key building materials and is compared to a railroad track system. The tracks become unraveled and form tangles. In the earliest stages of the disease, the plaques, and tangles form deep inside the brain in the medial areas where learning and memory are formed, then progresses toward areas where thinking and planning occur as the neurons begin to die. Because of the billions and billions of cells in the neuron forest, the damages caused by the plaques and tangles may go undetected and be asymptomatic for

The brain changes in size and weight as a person ages. There is also a narrowing of the gyri, enlargement of the ventricles, and widening of the cerebral sulci. In AD, these changes are accelerated, causing issues such as atrophy of the cerebral cortex and loss of cortical neurons. In addition, the pre-central gyrus of the frontal lobe, superior temporal gyrus, hippocampus, and substantia nigra are all affected. Changes in neurofibrillary tangles (tangled masses of fibrous tissue throughout the neurons) , amyloid-rich senile or neuritic plague (degenerating nerve terminals in the hippocampus which contain proteins that form neurotoxic plague in the brain) and granulovascular degeneration can all occur as well.

Amyloid plagues are extracellular accumulations of soluble oligomeric form of amyloid beta (Aβ) protein in the brain that result from failure to process and clear amyloid precursor protein (Lista & Hampel 2017). The soluble Aβ oligomers are highly toxic to the brain, leading to dysfunction and loss of neuronal synapses (or connections between neurons), and death of neurons (Boss & Huether 2014). In AD pathology, the tau protein, which maintains cellular structure by binding microtubules in neurons, becomes detached from the microtubules and causes them to become twisted in a helical structure, forming abnormal aggregates called neurofibrillary tangles (NFTs) (Lewis 2017). The formation of NFTs contributes to synaptic degeneration and neuronal cell death (Lista & Hampel 2017). Amyloid plaques and NFTs are also found in the brains of individuals without cognitive impairment; however, they are more abundant and particularly concentrated in the hippocampus and neocortex in the brains of individuals with AD, which are responsible for memory and cognition (Spires-Jones & Hyman 2014).

There are many Neuropsychological assessments used to differentiate AD from other dementia diseases such as Wechsler Memory Scale, Rey Auditory verbal learning test (RAVLT),Figure copying which used to test spatial skills ,Digit Span Forward

AD is the second most dreaded sickness in the United States, after disease. By 2011, more than five million Americans have been diagnosed with AD, and the number will climb quickly at the point when the time of increased birth rates era starts to achieve retirement age. It is evaluated that the number

Alzheimer’s Disease (AD) affects individuals and families mentally, emotionally and physically. The signs and symptoms are progressive in nature, and can significantly impact the quality of life of those who are affected. Early symptoms of AD are often not detected, and therefore may lead to delayed treatment and support.

Advancing age is the biggest risk for AD, with every decade after 65 years of age doubling the risk for AD. Family history is the second strongest risk factor following age. Studies conducted over the last three decades have shown that the genetic factors leading to AD are complex and heterogeneous, meaning, AD risk is attributed to a complex interaction of heritable (e.g. genetic) and non-heritable (e.g. education, life-style) factors. Although environmental factors do affect AD risk, population and twin studies estimate up to 80% of the AD cases are attributable to genetic risk factors (Gatz et al., 2006).

The research into Alzheimer's Disease has come a long way since 1906 when it is was discovered by Alois Alzheimer. He detected microscopic brain tissue changes called senile and neuritic plaques in deceased patients. These are chemical deposits consisting of protein molecules called Amyloid Precursor Protein(APP) that are fundamental components of a normal brain. However in the brain of an Alzheimer patient, an enzyme cuts the APP apart and leaves fragments in the brain tissue. These combined with degenerating nerve cells cause the plaques or lesions. These lesions are found in many sections of the brain including the hippocampus which regulates emotion and memory, the basal forebrain, and especially the basal nucleus of Meynert and the cortex, where the memory function is located.(2) Another sign of a diseased brain are neurofibrillary tangles, which are malformations within nerve cells.

There are two important physiological abnormalities that define the disease: amyloid plaques and tau tangles. Abnormal protein deposits throughout the brain form amyloid plaques and tau tangles. Amyloid is a normally harmless protein that appears throughout the body. Cleavage of the amyloid precursor protein by β-secretase and γ-secretase leads to the formation of beta-amyloid, a toxic version of the protein, which leads to the death of neurons. While the mode of action of beta amyloid is still not definitively known, a 2012 study by the University of Michigan supports the idea that it damages neuronal membranes (Moore). According to this theory, the plaques poke tiny holes in the membrane, allowing calcium to flow into the neuron uncontrollably, leading to the eventual death of the neuron. Another theory is that the beta amyloid breaks down to form free radicals that attack the neurons. The degenerated neurons and the amyloid protein combine to form sticky clumps, known as amyloid plaques, that the body is incapable of breaking down naturally. As a result, these plaques build up throughout the brain, leading to the loss of connections between neurons. According to research, plaque formation first occurs in the hippocampus, which plays a vital role in memory formation. Overtime, additional brain structures are affected, and significant brain tissue shrinkage

Another clue may be the effects the aging process has on the brain as it is harming the neurons in the brain causing the disease (NIA, 2012). Regardless of the cause, AD is a life altering disease in every aspect of the victim’s life.

In Alzheimer’s two things have been shown to cause this disease in people; tangles and tau plaques. Plaques are sticky deposits of protein called beta amyloid; however, normal cells make this protein. It is formed from another protein called amyloid precursor protein, or as it is commonly known as APP. Cells use enzymes on their surface to make beta amyloid out of APP. The enzymes act like scissors, cutting beta amyloid from the bigger APP molecules. Usually, beta amyloid proteins dissolve after it drifts away from the nerve cell, but when the abnormal enzyme “ships” the APP to a different location, they begin to form into insoluble clumps: fibrils. Fibrils cluster together creating the plaques seen in AD

Alzheimer 's disease (AD) the commonest form of dementia (70 %). It is a complex disease which is characterized by an accumulation of β-amyloid (Aβ) plaques and neurofibrillary tangles composed of tau amyloid fibrils associated with synapse loss and