Johns Hopkins Medicine

Alzheimer's Disease Research Center

Glossary of Terms

Acetylcholinesterase
An enzyme that helps degrade the nerve transmitter substance "acetylcholine". Acetylcholinesterase is normally found at the point at which two nerves communicate.
Amyloid
An abnormal substance deposited between and within cells. Amyloid stains with the Congo Red stain. In Alzheimer's disease amyloid is abnormally deposited in neuritic plaques and in small blood vessels.
APP
Amyloid Precursor Protein (APP) is a protein of uncertain function that is normally found in the brain. In Alzheimer's disease, APP is abnormally degraded resulting in the formation of amyloid.
Knock-out mice
An experimental strain of mice that has been genetically engineered in the laboratory such that a specific gene is deleted from the DNA of the mouse. Knock-out mice are extremely useful tools that scientists use to study the function of the gene that has been "knocked-out" of the DNA.
Mutation
An abnormal permanent change in the DNA sequence. Mutations can be thought of as "typographical errors" in the DNA code.
Neuritic plaques
Abnormal collections of nerve processes surrounding a central core of amyloid. Neuritic plaques, together with neurofibrillary tangles, are the hallmarks of Alzheimer's disease.
Neurodegenerative
An abnormal deterioration of the nervous system.
Neurofibrillary tangles
Abnormal bundles of filaments in nerve cells in the brain. These filaments contact on protein tau and are of the typical features of Alzheimer's disease.
NSAIDs
Non-steroidal anti-inflammatory drugs.
PS1
Presenilin-1 (PS1) is a protein produced in brain cells. Inherited mutations of the PS1 gene on chromosome 14 are a cause of Familial Alzheimer's Disease.
PS2
Presenilin-2 (PS2)
Secretase
A group of enzymes found in brain cells (alpha-secretase, beta-secretase, and gamma-secretase. The secretases function to degrade APP. The abnormal degradation of APP can result in the accumulation of amyloid in the brain and the development of Alzheimer's disease.
Transgenic mice
An experimental strain of mice that has been genetically engineered in the laboratory such that a specific gene is added to the DNA of the mouse. Transgenic mice are an invaluable resource for scientists who wish to study the function of a specific gene.