Glossary

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L

l-dopa:
Drug used to alleviate some of the symptoms of Parkinson's disease , particularly trembling, rigidity, and slow movements; the drug is also called levodopa. Parkinson's disease results when the concentration of dopamine in the brain is depleted (see catecholamine ). Medical administration of dopamine itself is ineffective since that chemical apparently does not enter the brain from the blood. A metabolic precursor of dopamine, l-dopa does enter the brain via the bloodstream and is probably converted into dopamine there. Because there are many brain disorders with similar symptoms, many patients do not show any improvement when treated with the drug. Furthermore, virtually all patients on l-dopa experience side effects including nausea, loss of appetite, cardiac irregularities, and psychological changes.

Lafora's disease:
A progressive myoclonic encephalopathy (PME) that is inherited as an autosomal recessive trait. Associated symptoms typically begin in childhood or early adolescence and include frequent seizures characterized by loss of consciousness and rhythmic contraction and relaxation of all muscle groups (generalized tonic-clonic seizures); sudden, involuntary, "shock-like" muscle jerks (myoclonus); and rapidly progressive deterioration of thought processing and acquired intellectual abilities (dementia). Removal and microscopic examination of minute tissue samples (e.g., muscle fibers, liver cells, etc.) reveal abnormal, characteristic deposits of complex proteins and carbohydrates within the fluid portion of cells (intracytoplasmic inclusions known as "Lafora bodies").

Lance-Adams syndrome:
Also known as "posthypoxic" or "postanoxic action myoclonus," this condition is characterized by the development of chronic action myoclonus due to a temporary lack or inadequate supply of oxygen to the brain (cerebral hypoxia or anoxia). Patients with action myoclonus experience sudden, involuntary, "shock-like" muscle contractions that may be triggered or aggravated by voluntary movement. Lance-Adams syndrome is also often associated with cerebellar ataxia or lack of coordination, postural imbalance, and other associated findings.

Lassitude:
Weakness characterized by a lack of interest, vitality, and energy. Its cause in MS is unknown. It doesn’t seem to be related to exertion or time of day, and sleep does not always help.

Lateral:
Sideways; of, on, from, or toward the side.

Leucine:
An essential amino acid.

LDL:
See Lipoproteln.

Leigh disease:
A disorder of mitochondrial function that typically becomes apparent during infancy. Also known as subacute necrotizing encephalomyelopathy, the disorder may be characterized by feeding and swallowing difficulties, vomiting, muscle weakness, low muscle tone (hypotonia), and delayed acquisition of motor and language skills. Affected infants and children may also develop seizures; an impaired ability to coordinate voluntary movements (ataxia); involuntary, rapid, rhythmic eye movements (nystagmus); tremor; dystonia; and/or other abnormalities. The disorder, which has a number of underlying causes, may occur randomly for unknown reasons (sporadically) or be transmitted as an autosomal recessive or X-linked trait. Leigh disease is associated with characteristic changes of the central nervous system (CNS), including symmetric regions of localized tissue loss (necrosis) and neurodegenerative changes of the basal ganglia, thalamus, brainstem, spinal cord, and other regions of the CNS.

Lenticular nucleus:
This group of cells along with the caudate nucleus form the Striatum or Corpus Striatum.

Leukocyte:
A type of white blood cell that manufactures proteins to reduce inflammation in the body and aid healing.

Levodopa:
Levodopa is a drug used to treat Parkinson's disease. It is also called L-dopa and, in the United States, is sold as one of the ingredients in Sinemet. Levodopa crosses the blood-brain barrier and is converted by the body to dopamine. A loss of dopamine-producing nerve cells in the part of the brain that controls movements leads to the symptoms of Parkinson's disease.

Levodopa-Induced Dyskinesias:
A side effect of medication which may occur with prolonged use. These abnormal, involuntary movements may be alleviated by reducing the amount of medication.

Lewy Body:
A pink-staining sphere (a mass of protein), found in the bodies of dying cells in the brain, that is considered to be a marker for Parkinson's disease.

Lewy Body Disease:
Also called diffuse Lewy body disease, Lewy body dementia. Lewy body disease is a common cause of dementia, accounting for approximately 15%-20% of all cases. The age of onset is typically in the late 50s through the 70s. It is more common in men than women. Lewy Body Disease is characterized by more daily fluctuations in symptoms than Alzheimer's disease, as well as more prominent psychosis. Patients are prone to have adverse reactions to antipsychotics. Patients also have parkinsonian features early in the disease, including slowed movements and rigidity, though usually without tremor. The Lewy body is a protein aggregate found in dying neurons in the brain. In Lewy body disease, the Lewy bodies are most prominently found in the cortex, or surface of the brain, versus in the midbrain for Parkinson's disease.

Libido:
Sex drive.

Lipid:
A fat-soluble substance.

Lipoatrophy:
The loss of the fatty tissue under the skin.

Lipofuscin:
"Wear-and-tear" brown pigment granules consisting of lipid-containing residues of metabolism. These granules can be found in liver, brain, and heart muscle, and are a sign of aging.

Lipopolysaccharide:
A lipopolysaccharide is a molecule made up of a lipid (a fat) with a polysaccharide (a complex sugar). In most circumstances, the terms lipopolysaccharide and endotoxin can be used interchangeably.

Lipoproteins:
Compounds that contain lipids and proteins. Almost all of the lipids in blood, including cholesterol, are transported as lipoprotein complexes. There are a number of these lipoproteins in blood. The two best known by the public are HDL (high density lipoproteins, the "good" cholesterol) and LDL (low density lipoproteins, the "bad" cholesterol).

Lithium:
Lithium affects the flow of sodium through nerve and muscle cells in the body. Sodium affects excitation or mania. Medically it is used to treat the manic episodes of manic depression. Manic symptoms include hyperactivity, rushed speech, poor judgment, reduced need for sleep, aggression, and anger. Lithium also helps to prevent or lessen the intensity of manic episodes.

Livido Reticularis:
A purplish or bluish mottling of the skin seen usually below the knee and sometimes on the forearm in persons under treatment with the drug amantadine (Symmetrel).

Lumbar Puncture:
(Also called spinal tap.) A special needle is placed into the lower back, into the spinal canal. This is the area around the spinal cord. The pressure in the spinal canal and brain can then be measured. A small amount of cerebral spinal fluid (CSF) can be removed and sent for testing to determine if there is an infection or other problems. CSF is the fluid that bathes the brain and spinal cord.

Lordosis (Also called sway-back):
An exaggeration of the forward curve of the lower part of the back.

LRKK2:
LRRK2 (pronounced as lark-two) stands for leucine-rich repeat kinase 2. It is the name of a gene that is responsible for providing instructions for making a protein called dardarin. The gene is thought to be active in the brain. Although little is known about the LRRK2 gene or dardarin protein, researchers do know that part of the LRRK2 gene provides instructions to make a protein segment that is rich in a protein building block (amino acid) called leucine. Proteins with leucine-rich regions appear to play a role in activities that require protein-protein interactions, such as transmitting signals or helping to assemble the cell's structural framework (cytoskeleton). Other parts of dardarin, such as a region called the WD40 domain, also indicate that dardarin is capable of multiple protein-protein interactions. Researchers also suspect that the dardarin protein has an enzyme activity known as kinase. Proteins with kinase activity assist in the transfer of a phosphate group (a cluster of oxygen and phosphate atoms) from the energy molecule ATP to amino acids in certain proteins. This phosphate transfer is called phosphorylation, and it is a necessary step in turning on and off many cell activities.

Lumbar puncture:
A procedure during which a sample of fluid (i.e., cerebrospinal fluid [CSF]) is removed from the spinal canal for diagnostic or therapeutic purposes. During the procedure, CSF is obtained via a hollow needle inserted between two bones of the spinal column within the lower back (i.e., usually the third and fourth lumbar vertebrae). Laboratory analysis conducted on CSF may help to diagnose central nervous system infections, certain tumors, or particular neurologic disorders. In some cases, lumbar puncture may also be performed to inject certain medications into the CSF, such as particular anticancer (chemotherapeutic) agents.

Lymphocyte:
A type of white blood cell that fights infections. Two major types are B lymphocytes and T lymphocytes.

Lymphokine:
A substance released by lymphocytes to help with immune function. Interferon is a type of lymphokine.

Lysosomal:
Referring to lysosomes, which are membrane-bound bodies (organelles) outside the nuclei of cells that contain various enzymes engaged in intracellular digestion.

Lysosomal storage diseases:
Inborn errors of metabolism in which deficiency or impaired functioning of particular lysosomal enzymes leads to an abnormal accumulation of certain substances (e.g., fats, complex carbohydrates) within particular cells, progressively affecting multiple bodily tissues and organs. (Lysosomes are membrane-bound, enzyme-containing bodies within cells that engage in digestive processes; enzymes are proteins that accelerate the rate of certain chemical reactions in the body.) Most lysosomal storage disorders (e.g., mucolipidoses, mucopolysaccharidoses, lipidoses, etc.) are thought to be inherited as autosomal recessive traits.

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Document last modified:06/16/08 09:43:08 AM