Amyloid precursor protein (APP)

The protein from which beta-amyloid is derived. APP is expressed on the surface of many different cell types in the body. In the brain it is involved in processes including adhesion, growth, and protection of neurons; recycling of synaptic vesicles, regulating programmed cell death, inhibiting proteases, metabolizing calcium, and transcribing genes.

Amyloid

A general term for an abnormal protein folding causing stickiness and a tendency to aggregate and form clumps which are toxic to cells. Beta-amyloid is a specific example of an abnormally folding protein fragment that accumulates in the brains of Alzheimer's patients. Beta-amyloid is derived by metabolic processing of a much larger protein which is expressed on the surface of many cell types in the body, called the amyloid precursor protein (APP).

Amyloid plaques

Insoluble clumps on the surface of nerve cells in which the chief constituent is beta-amyloid. Diffuse plaques forming early in the disease convert to more solid neuritic plaques in later stages.

Alzheimer's Disease (AD)

A lethal progressive neurodegenerative disorder resulting in the death of nerve cells (neurons) in the brain. The hallmark neurpathological feature of AD is the appearance of amyloid plaques in the brain, particularly in regions associated with learning and memory functions. The symptoms of the disease are cognitive changes, for example, loss of memory as well as psychiatric changes such as depression and hallucinations.

The average duration of the disease from the onset of symptoms is 8-10 years until death results usually because of loss of mobility.

Antibody

A type of protein, called an immunoglobulin, that recognizes and binds to an antigen. Antibodies are produced by white blood cells called B lymphocytes, or B cells. Each B cell produces only one type of antibody that is specific for a single site (called an epitope or antigenic determinant) on a molecule (called an antigen).

Antigen

A molecule that induces an immune response.

Antioxidant

An organic molecule that can counteract the damaging effect of oxygen in tissues. Although the term technically applies to molecules reacting with oxygen, it is often applied to molecules that protect from any free radical i.e., molecule with unpaired electron.

APP

See Amyloid precursor protein.

Antibodies

See antibody.

Antioxidants

An organic molecule that can counteract the damaging effect of oxygen in tissues. Although the term technically applies to molecules reacting with oxygen, it is often applied to molecules that protect from any free radical i.e., molecule with unpaired electron.

beta amyloid

see Amyloid

Beta-pleated-sheet

A common secondary structure of proteins that in some cases can cause abnormal folding such as in beta-amyloid.

Blood-brain barrier (BBB)

The layer of endothelial cells lntellecting blood-vessel walls that are packed more tightly together in the brain, than in other parts of the body, thus forming a semi-permeable barrier that allows some materials to diffuse through but not others. Molecules that are large, highly electrically charged, and/or not lipid-soluble cannot pass through; if needed, such molecules are actively transported by the endothelial cells. Most drugs cannot pass the BBB. The primary function of the BBB is probably to protect it from the hormones and neurotransmitters that are circulated through the bloodstream (areas of the brain where these are needed to not have a BBB) and maintain a constant environment (it works both ways, also keeping things in that are necessary for brain functioning). It also serves, however, to protect the brain from foreign substances, such as most drugs, and from most infectious organisms.

Dementia

The loss, usually progressive, of cognitive and intellectual functions without impairment of perception of consciousness.

Fibrils

A minute fiber or component of a fiber. A fiber is an extracellular filamentous structure such as connective tissue.

Free radicals

One of a type of chemical species called reactive oxygen species (ROS), capable of independent existence and having one or more unpaired electrons. The unpaired electron(s) makes it highly unstable because it "wants" to replace the lost electron(s), which it accomplishes by reacting with organic molecules (e.g., lipids, proteins, DNA). The organic molecule is said to be oxidized, and the free radical is the oxidant. Oxidation of these biological molecules can damage them, which disturbs their normal functions. Free radicals are produced by oxidation-reduction reactions, which are fundamental to cellular metabolism and, thus, to life itself.

Immunization

Protection of susceptible individuals from communicable diseases by administration of a living modified agent (e.g., yellow fever vaccine), a suspension of killed organisms (e.g., pertussis vaccine), or an inactivated toxin (e.g., tetanus vaccine). Synonym: vaccination.

Immunoglobulin

A type of protein commonly referred to as antibodies; there is a slight technical difference that is not relevant here.

Inflammation

A pathologic process that occurs in the blood vessel and nearby tissues in response to injury or abnormal stimulation of white blood cells. The cardinal signs of inflammation are redness, heat, swelling, and pain.

In vitro

Literally, "in the glass"; in culture or a test tube.

In vivo

Literally, "in life"; applies to studies conducted in animals (usually non-human).

Monoclonal antibodies

A pure population of immunoglobulins with identical structure and specificity that is derived from a single clone of B cells.

Neurofibrillary tangles

Twisted fragments of protein within nerve cells consisting primarily of a protein called tau, which forms part of a structure called a microtubule. The microtubule helps transport nutrients and other important substances from one part of the nerve cell to another. In Alzheimer's disease, however, the tau protein is abnormal, the microtubule structures collapse, and the tangles clog up the cell.

Neurons

Nerve cell; consists of a cell body and 2 types of extensions: dendrites receive signals, and axons send signals. The human brain contains on the order of 100 billion neurons.

Neuronal

Of or pertaining to a neuron.

Oxidant

A molecule or compound that can act as the electron.

Oxidative stress

A collective term for the production of free radicals and the damage that they cause to cells.

Pathogen

A disease-causing substance, organism, or virus.

Pathogenesis

The mechanism (pathologic, physiologic, or biochemical) that results in a disease.

Phase I

Usually a preliminary trial in fewer than 100 healthy volunteers to determine the adverse effects, pharmacokinetics, and/or appropriate dose and route of administration of an investigational drug.

Secondary structure

The sequence of amino acids of a protein is called its primary structure. Proteins do not generally exist in the body as long, straight chains of amino acids; rather, they bend and fold into forms that are called their secondary structures. Proteins that exist primarily as helixes or pleated sheets are the fibrous proteins that play an important structural role in organisms.