This disrupts the work of the brain cells affected and triggers a toxic cascade, ultimately leading to cell death and later brain shrinkage.Alzheimers disease is believed to occur when abnormal amounts of amyloid beta (Aβ), accumulating extracellularly as amyloid plaques and tau proteins, or intracellularly as neurofibrillary tangles, form in the brain, affecting neuronal functioning and connectivity, resulting in a progressive loss of brain function. This altered protein clearance ability is age-related, regulated by brain cholesterol, and associated with other neurodegenerative diseases.Advances in brain imaging techniques allow researchers to see the development and spread of abnormal amyloid and tau proteins in the living brain, as well as changes in brain structure and function. Beta-amyloid is a fragment of a larger protein. When these fragments cluster together, a toxic effect appears on neurons  and disrupt cell-to-cell communication. Larger deposits called amyloid plaques are thus further formed.Tau proteins are responsible in neurons internal support and transport system to carry nutrients and other essential materials. In Alzheimers disease, the shape of tau proteins is altered and thus organize themselves into structures called neurofibrillary tangles. The tangles disrupt the transport system and are toxic to cells. The cause for most Alzheimers cases is still mostly unknown, except for 1–2% of cases where deterministic genetic differences have been identified.
Epidemiological studies found that Dow had been adding cobalt sulfate to the beer for foam stability since July 1965 and that the concentration added in the Quebec city brewery was ten times that of the same beer brewed in Montreal where there were no reported cases. A 1972 paper noted that several dozen cases were also identified over a similar time period in Omaha, Nebraska; Minneapolis, Minnesota; and Belgium. Cobalt in the environment
Plants, animals, and humans can all be affected by high cobalt concentrations in the environment. For plants, the uptake and distribution of cobalt is entirely species-specific. In some species of plants, the overaccumulation of cobalt can lead to an iron deficiency. This in turn leads to poor growth of the plant as well as leaf loss which overall decreases the amount of oxygen produced by plants during photosynthesis. Eventually the deficiency would lead to plant death. One such example was seen in an experiment involving the effects of increased cobalt concentration on tomato plants. As the dosage of cobalt in the soil surrounding the plants increased, so too did the rate of necrosis of the leaves of the tomato plant. Over time this led to an inability of the plant to produce fruit and eventually the plant died. References


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