A

Adrenoleukodystrophy (ALD): A rapidly progressive X-linked genetic disorder marked by the accumulation of saturated very long chain fatty acids (VLCFA) in all tissues and body fluids, with a preference for the brain and the adrenal glands. This buildup leads to inflammation of the brain and erosion of the white matter of the central nervous system and the adrenal glands. It affects only boys; while there is a neonatal form, it typically strikes between the ages of 6 and 10.

Adrenomyeloneuropathy (AMN): The adult form of ALD, milder and more slowly progressive than the childhood form; it affects the spinal cord and peripheral nervous system.

Alexander Disease:  A rapidly progressive and usually fatal disease.  The destruction of white matter is accompanied by the formation of Rosenthal fibers, which are abnormal clumps of protein that accumulate in non-neuronal cells of the brain called astrocytes.  Rosenthal fibers are sometimes found in other disorders, but not in the same amount or area of the brain that are featured in Alexander disease.  The infantile form is the most common type of Alexander disease.  It has an onset during the first two years of life.

Arylsulfatase: The lack of this enzyme results in the toxic accumulation of sulfatide deposits in metachromatic leukodystrophy, leading to demyelination of the CNS.

Astrocyte: See Glia.

Asymptomatic: Having a disease without manifestation of symptoms.

Axon: Myelin-ensheathed tail of the neuron that is responsible for carrying impulses away from the neuron cell body. Nerves are made up of several interwoven axons.

B

Biopsy: The removal and microscopic examination of a tissue sample taken from the living body to establish an exact diagnosis, check for signs of disease, or assess the results of a surgical or pharmacological intervention.

Blood-brain barrier: A selectively permeable, protective barrier that limits the passage of substances in the bloodstream into brain tissue. It is believed to be formed by astrocytes and blood vessels.

Bone marrow: A soft tissue occurring in certain large bones that is responsible for manufacturing most of the body's blood cells.

C

Canavan disease: A neurodegenerative disease of infancy in which the lack of the enzyme aspartoacyclase results in the buildup of N-acetyl aspartate, leading to demyelination in the CNS, as well as increased brain volume and weight and spongy degeneration in the subcortical white matter.

Central nervous system (CNS): Consisting of the brain and the spinal cord.

D

Demyelination: The destruction, loss or removal of the protective myelin sheath coating the axons, resulting in their inability to transmit impulses. Usually caused by diseases such as multiple sclerosis or the leukodystrophies.

Dysmyelination: Congenital absence of or defective formation of the myelin sheath that results in abnormal, delayed, or inadequate myelination of the nerves. Example: Pelizaeus-Merzbacher Disease.

E

Experimental allergic encephalomyelitis (EAE): A disease induced in laboratory rodents that produces symptoms similar to human multiple sclerosis.

Enzyme: A protein molecule produced by living organisms able to catalyze, or facilitate, a specific chemical reaction involving other substances without itself being destroyed or changed in any way.

Erucic acid: One of the active components of Lorenzo's Oil, it is a 22-carbon monounsaturated fatty acid present in the seeds of the nasturtium flower and of several Cruciferae species (rape, mustard, and wallflower).

Estrogen: A steroidal hormone produced in both males and females that has a variety of functions. In women, it is released during menstruation to form a hospitable environment for embryo fertilization and implantation in the womb.

G

Gene: The basic unit of inheritance on a chromosome. Genes determine the structure and function of all components of the body.

Gene therapy: A novel approach to treat, cure, or ultimately prevent disease by changing or repairing defective genes.

Glia/glial cells: They make up the supportive tissue of the brain and CNS. There are two main types of glial cells in the CNS: Oligodendrocytes, which produce, maintain and repair the myelin sheath of the axons, and astrocytes, named for their characteristic star-like shape, which lend both mechanical and metabolic support to neurons. Other types of glia exist outside the CNS, including Schwann cells.

Gray matter: Otherwise known as the cerebral cortex, or the "thinking matter" of the brain, it is composed of nerve cells and blood vessels. Growth factors: Substances produced by the body to control growth, division and maturation of cells and tissues.

Growth factors: Substances produced by the body to control growth, division and maturation of cells and tissues.

I

Immortalized cell line: Cells, maintained in culture, that are capable of continuously renewing themselves.

Interferons: A group of naturally occurring proteins that act as chemical messengers between cells. Three have so far been discovered, alpha, beta and gamma, all of which have immune-modulating effects. Interferons are used in the treatment of cancer and autoimmune diseases, such as MS.

In vitro: Latin for "in glass," it refers to experiments done in the lab in a test tube, petri dish, etc.

In vivo: Literally, within the living body.

K

Krabbe disease (or globoid cell leukodystrophy): An inherited disorder characterized by a deficiency of the enzyme galactosylcereamidase, resulting in destruction of myelin.

L

Leukodystrophy: A group of genetic disorders characterized by the imperfect development or maintenance of myelin. Diseases in this class include adrenoleukodystrophy, Alexander disease, Canavan disease, Krabbe disease, metachromatic leukodystrophy, Pelizaeus-Merzbacher disease, Refsum disease, and phenylketonuria.

Lorenzo's Oil: Used as a therapy for adrenoleukodystrophy, it is a 4:1 mix of erucic acid and oleic acid, extracted from rapeseed oil and olive oil, respectively.

M

Metachromatic leukodystrophy: In this disease the lack of an enzyme, Arylsufatase-A (ASA), causes the accumulation of sulfatide deposits in the brain, which in turn leads to myelin breakdown.

MRI: An acronym for magnetic resonance imaging, it is a non-invasive method of obtaining images of internal soft bodily tissue such as the brain and the spinal cord through the use of powerful magnets and radio waves.

Multiple sclerosis: A disorder of the central nervous system of unknown cause in which the body's immune system attacks myelin in the brain and spinal cord. Whether the disease manifests in repeated episodes of inflammation or as a chronic condition, it results in multiple scars, or scleroses, on the myelin sheath, leading to impairment or loss of nerve function.

Murine: Pertaining to rats and mice.

Myelin: The fatty tissue covering the axons of the nerves that allows efficient conduction of impulses. Myelin is produced by oligodendrocytes in the CNS and by Schwann cells in the peripheral nervous system.

N

Nerve: A cordlike structure made up of nerve fibers that conducts impulses to and from the CNS and other parts of the body.

Neuron: The main actors in the brain, neurons are cells that issue and receive electrical signals to and from other parts of the body, and control all functions in humans and animals. Signals to other parts of the body are carried by axons (see Axon).

O

Olfactory ensheathing cells (OECs): Glial cells covering the nerves involved in the sense of smell. Recent studies suggest that OECs transplanted into the CNS may facilitate axonal regeneration and remyelination.

Oligodendrocyte: See Glia.

Oncogene: Any of several genes that control cell growth, division, and normal cell death, which can become mutated and cause cells to grow out of control, leading to cancer. These genes can be used to maintain stem cells as a self-renewing cell line in culture.

P

Peripheral nervous system (PNS): Nerves that conduct impulses outside the brain and spinal cord i.e., outside the CNS. However, the cell bodies of PNS nerves reside in the CNS, with their lengths extending out to peripheral parts of the body.

Pelizaeus-Merzbacher disease is an X-linked recessive dysmyelinating disorder of the central nervous system in which myelin is not formed properly  PMD is characterized clinically by nystagmus, spastic quadriplegia, ataxia, and developmental delay

Phenylketonuria (PKU): An inherited, metabolic disorder that can result in mental retardation and other neurological problems. People with this disease have difficulty breaking down and using the amino acid phenylalanine. PKU can be managed by a diet restricted in foods that contain this amino acid.

Presymptomatic: Having a disease, but prior to the appearance of symptoms.

Progesterone: A female steroid hormone secreted by the ovary; it is produced by the placenta in large quantities during pregnancy.

S

Schwann cell: These cells form myelin sheaths in the peripheral nervous system.

Sclerosis: Literally, "scar"; the hardening of tissue. In multiple sclerosis it refers to the body's replacement of lost myelin around axons with scar tissue.

Stem cell: Cells that can give rise to other types of cells; they are produced both during embryonic development and in the adult body. Embryonic stem cells begin with the ability to become any cell type, and quickly differentiate into cells committed toward a certain type of tissue, e.g., blood, skin, or neural stem cells. These are termed multipotential stem cells, because they further divide into cells with a particular function, such as red and white blood cells and platelets. Multipotential cells are also present in adults. Stem cells are capable of dividing for indefinite periods in culture.

T

Translational research: Intended to translate knowledge derived from laboratory work (basic research) into clinical applications.

U

Umbilical cord blood stem cell: Blood stem cells left within the umbilical cord post-partum, which can be collected and preserved; they are an alternative to cells from bone marrow for transplantation in a variety of disorders.

V

Vector: A carrier, or vehicle, that transfers a substance from one host to another. In gene therapy, a disabled virus is commonly used as a means of efficiently inserting genetic material, such as the code for a normal gene, into the body, because viruses can infect most cells.

Ventricles: The four connected cavities of the brain that contain cerebrospinal fluid. Ventricles also refers to two of the chambers of the heart.

Very long chain fatty acids (VLCFA): Compounds with a long hydrocarbon chain; because of a defective gene and the malfunction of the corresponding enzyme, they accumulate in adrenoleukodystrophy.

X

X-linked: A trait or disease tied to genes on the X chromosome, which is one of the sex chromosomes that determine gender of an organism. Males have one X and one Y chromosome, while females have two X's. Thus if a defective gene that is X-linked is passed on by one parent to a female child, she will become a carrier, but in many cases will not develop symptoms, because the other gene is normal. When a defective X-linked gene is inherited by a boy, he typically will develop symptoms, because there is only one gene to do the job.