Alzheimers

Alzheimer 's Disease

I . Introduction

Alzheimer 's disease is a progressive , irreversible , degenerative neurologic disease that beings insidiously and is characterized by gradual losses of cognitive function and disturbances in behavior and affect . Alzheimer 's disease is not found exclusively in the elderly in 1 to 10 of cases , its onset occurs in middle age . A family history of Alzheimer 's disease and the presence of Down syndrome are two established risk factors for Alzheimer 's disease (Mayo , pp . 125-136 2005 . If family members have at least one other relative with

br Alzheimer 's disease , then a familial component , which nonspecifically includes both environmental triggers and genetic determinants , is said to exist . Genetic studies show that autosomal-dominant forms of Alzheimer 's disease are associated with early onset and early death

In 1987 , chromosome 21 was first implicated in early-onset familial Alzheimer 's disease . Soon after , the gene coding for amyloid precursor protein (APP ) was also found to be on chromosome 21 . Not until 1991 was an actual mutation in association with familial Alzheimer 's disease found in the APP gene of chromosome 21 . For those with is gene , onset of Alzheimer 's disease begun in their 50s (Mayo , pp . 125-136 / 2005 . Only a few of the cases of familial Alzheimer 's disease have been found to involve this genetic mutation . In 1992 , chromosome 14 was found to contain an unidentified mutation also linked to familial Alzheimer 's disease . Since 1995 , molecular biologists have been discovering even more-specific genetic information about the various forms of Alzheimer 's disease , including genetic differences between early- and late-onset Alzheimer 's disease . These genetic differences are helping to pinpoint risk factors associated with the disease , although the genetic indicators are not specific enough to be used as reliable diagnostic markers (Mayo , pp . 125-136 / 2005

II . Background

A . Pathophysiology

Specific neuropathologic and biochemical changes are found in patients with Alzheimer 's disease . These include neurofibrillary tangles (a tangled mass of nonfunctioning neurons ) and senile or neuritic plaques (deposits of amyloid protein , part of a larger protein , APP ) in the brain . This neuronal damage occurs primarily in the cerebral cortex and results in decreased brain size . Similar changes are found to a lesser extent in the normal brain tissue of older adults . Cells that use the neurotransmitter acetylcholine are the ones principally affected by this disease . Biochemically , the enzyme active in producing acetylcholine which is specifically involved in memory processing , is decreased (Mayo pp . 125-136 / 2005

Several theories are currently being tested to explain what predisposes an individual to develop the plaques and neurotangles that can be seen at autopsy on biopsy of the brains of Alzheimer 's patients (Mayo , pp 125-136 / 2005 . Scientists continue to increase their understanding of the complex ways in which aging and genetic and nongenetic factors affect and damage brain cells over time and eventually lead to Alzheimer 's disease . Researchers have recently discovered how and why amyloid plaques from and cause neuronal death , as well as the possible relationship between various forms...