Akinetic mutism: A state of complete physical unresponsiveness caused by damage to the base of the brain.

Amyloid: extracellular, proteinaceous deposit exhibiting cross-beta structure due to mis-folding of unstable proteins.

Autonomic nervous system (or visceral nervous system): the nervous system that controls many of the involuntary functions of the body, such as heart rate and perspiration.

BASE (bovine amyloidotic spongiform encephalopathy): L-type (low molecular weight) BSE.

Bovinized or ovinized transgenic mice: mice expressing bovine or ovine prion protein genes.

Brain biopsy: The removal of a small piece of brain tissue through an operation for the diagnosis of brain abnormalities.

Cerebellar ataxia: Shaky movements, unsteady gait and clumsiness caused by damage to the cerebellum, a part of the brain which controls movement.

Downer animal: A "downer" or non-ambulatory animal is generally defined as livestock that cannot rise from a recumbent position or that cannot walk.

Electroencephalogram (EEG): The record obtained through the recording and analysis of the electrical activity of the brain.

ELISA (Enzyme-Linked Immunosorbent Assay): A process in which brain tissue is homogenized, normal prion protein is destroyed by a protease enzyme, and any remaining abnormal prion protein is bound to the surface of a clear, microtiter well. Abnormal proteins are detected immunologically using antibodies linked to an enzyme and exposed to a chemical substrate, which provides a signal in the form of a color change or light emission. An electronic instrument called a spectrophotometer picks up the signal. In the United States, non-negative test results for TSE using the ELISA method are confirmed through Immunohistochemistry and Western Blot testing. ELISA tests for TSE typically can be completed in about four hours.

Encephalopathy: Any disease in which the functioning of the brain is affected without the brain showing an inflammatory response.

Histopathology: Examination of sections of brain tissue under a microscope to detect spongiform patterns characteristic of specific types of TSE. Histopathology tests take from two to five days to complete and are best performed on fixed tissue.

Immunoblot/Western Blot: A biochemical technique in which brain tissue is homogenized and treated with a protease enzyme that destroys normal prion protein but not the abnormal protein. The brain sample is separated by gel electrophoresis (a method that separates protein molecules based on size, electric charge and other physical properties). Abnormal prion protein molecules can be detected using antibodies linked to an enzyme that results in a chemical reaction (staining). Immunoblot tests typically take two to three days to complete and can only be performed on frozen tissue. A modified Western Blot is approved for use in Europe and other countries and takes six to eight hours to complete.

Immunohistochemistry (IHC): A laboratory method that involves microscopic examination of brain tissue that has been reacted with antibodies for proteins. The antibodies are linked to enzymes that show a chemical reaction (called staining) that can detect the abnormal form of prion protein found in TSE. Immunohistochemistry testing requires two to three days to complete and can be performed on fixed or frozen tissue.

Inconclusive test: In the United States, any test result from the conduct of an ELISA rapid test that is not categorically negative and requires additional confirmatory tests (Immunohistochemistry and Western Blot) to determine if the sample is negative or positive for BSE.

Isoform: any of the three forms of the abnormal prion protein as distinguished in Western Blots: unglycosylated, mono-glycosylated or di-glycosylated isoforms.

Lumbar puncture (Spinal Tap): The insertion of a hollow needle beneath the arachnoid membrane of the spinal cord in the lumbar region to withdraw cerebrospinal fluid for diagnostic purposes or to administer medication.

Magnetic Resonance Imaging (MRI): a noninvasive diagnostic technique that produces computerized images of internal body tissues and is based on nuclear magnetic resonance of atoms within the body induced by the application of radio waves.

Myoclonus: Jerking movements of the limbs caused by sudden muscle spasms.

Nucleic acid: The molecules used to encode genetic information in living organisms, of which there are two important types: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

Pathogen: a disease-producing microorganism.

Peripheral nerves: nerves that lie outside of the brain and spinal cord.

Peyers Patches: aggregated lymphoid nodules of the small intestine.

Plasmid: a mobile, self-replicating segment of DNA that exists outside of the chromosome in bacterial cells.

Polysaccharides: a carbohydrate made up of many simple sugars.

PrPc (prion protein cellular): a naturally occurring protein found in cells of the central nervous system (the brain and the spinal cord) and other tissues.

PrPSc: When the PrPC molecule (see above) refolds into an aberrant shape it becomes pathogenic. The disease-causing form of the normally occurring prion protein is designated as protease resistant protein (PrPRes) or PrP Scrapie (PrPSc ).

Somatic mutation: A mutation that occurs in a non-reproductive cell of an organism. These mutations cannot be passed on to offspring.

Spongiform change: Brain damage characterized by a spongy appearance of brain tissue seen under the microscope.

Transmissible Spongiform Encephalopathies (TSE): A rare group of brain diseases that affect mammals, both humans and animals. TSE are associated with the accumulation of abnormal prion protein in the brain. Animal TSE include scrapie, bovine spongiform encephalopathy (BSE) and chronic wasting disease. Human TSE include Creutzfeldt-Jakob disease (CJD), variant Creutzfeldt-Jakob disease (vCJD), Gerstmann-Sträussler-Scheinker disease, Kuru, fatal familial insomnia (FFI), sporadic fatal insomnia (SFI) and Alpers’ disease.

Unglycosylated: a protein chain without any sugar side chains.

Unusual or atypical BSE: a BSE case that does not follow the typical pattern of classic BSE disease.

Vagus nerve: the 10th cranial nerve.

Viroid: an infectious particle similar to but smaller than a virus consisting of a single strand of RNA. Viroids are agents of plant disease; whether they occur in animals is uncertain.

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