HD Glossary

Note: Some words can have differing definitions depending on the context in which they are used. The definitions presented here are the ones that best apply to the words as they are used. HDSA is grateful to the Stanford Hopes website for their contribution and maintenance of this glossary.

 

 

S
  • SAHA - Abbreviation for suberoylanilide hydroxamic acid.
  • salicylates - A group of drugs to which aspirin belongs.
  • saturated fat - A type of fat found mainly in meats, butter, and dairy products which, due to its chemical structure, tends to pack very tightly and raise levels of unhealthy cholesterol.
  • schizophrenia - a psychiatric disorder that usually involves problems with perceptions or expressions of reality, significant social or occupational problems, disorganized thinking, and delusions or hallucinations.
  • scientific method - The principles and empirical processes governing investigation into the truth or falsity of a scientific question.
  • scrapie - A common transmissible spongiform encephalopathy (TSE) in sheep and goats.
  • screening assay - A test for potential drugs that are available from biotechnology companies and academic laboratories under contract. Once researchers have figured out the appropriate target for a drug (such as nerve cell machinery clogged by mutated huntingtin protein aggregates), they can test these chemical compounds to see which one of them really goes after the target.
  • second-generation - The modified form of a naturally occurring protein or molecule that has been biologically or chemically manipulated in order to enhance its function to use for drug development.
  • seizure - A convulsion caused by electrical activity in the brain. Physical manifestations of a seizure can include shaking, twitching, staring, or a loss of consciousness.
  • selective serotonin reuptake inhibitors (SSRIs) - A class of drugs that is used to increase the amount of serotonin in the brain. These drugs are commonly used to treat depression.
  • selenium - A mineral essential to the mammalian diet and the central element in glutathione peroxidase (GPx). It has antioxidant properties and is normally obtained through foods such as yeast, whole grains, and seafood.
  • self-complementary - A single strand of DNA that curls back onto itself is described as self-complementary.
  • self-renewal - The ability of a self to divide continuously to produce more copies of itself.
  • self-replication - See self-renewal.
  • serotonin - A neurotransmitter that is a powerful vasoconstrictor (constricts the blood vessels) and is found especially in the brain, blood serum, and gastric mucous membrane of mammals; also called 5-HT or 5-hydroxytryptamine.
  • sex-linked - Used to describe a gene or disease whose inheritance is related to sex in some way.
  • sex chromosome - Sex chromosomes determine the sex of an individual. In humans, the two sex chromosomes happen to make up the last (23rd) pair of chromosomes. See Figure B-10.
  • short interference RNA (siRNA) - A small molecule that is used in the gene disabling technique to prevent the translation of genes to protein.
  • side effects - Problems that occur when treatment causes undesired effects, too much of the desired effect, or other problems occuring in addition to the desired therapeutic effect.
  • signal - when one protein in a molecular pathway can activate or deactivate another protein, it is a signal to the affected protein.
  • signal transduction - A basic process in molecular cell biology involving the conversion of a signal from outside the cell to a functional change within the cell.
  • silent mutation - A point mutation that has no effect on the organism involved.
  • single nucleotide polymorphism (SNP) - A variation of a gene that differs by one base pair. An example would be substituting an “A” where there is usually a “C” in the genetic code.
  • sirolimus - Another name for the drug rapamycin, which has been shown to promote breakdown of huntingtin aggregates by inducing autophagy.
  • sirtuins - A group of enzymes that may play a role in lifespan extension.
  • sister chromatid - A double helix of DNA, tightly coiled and compacted into a rod-like form. See Figure B-9.
  • small interfering RNA (siRNA) - See short interference RNA (A small molecule that is used in the gene disabling technique to prevent the translation of genes to protein).
  • sodium butyrate - An HDAC inhibitor.
  • sodium (Na+) channels - Gated ion channels that are necessary for glutamate release. Riluzole and lamotrigine interfere with these channels.
  • sodium selenite - A chemical form of selenium used for its antioxidant effects.
  • solution - A homogenous mixture of two or more substances.
  • soma - See nerve cell body.
  • specialized cells - Cells that are committed to a specific function (e.g., muscles cells, skin cells).
  • spermatogonia (singular: spermatogonium) - Primitive male germ cells; precursors to sperm cells.
  • spider cell - A type of neuroglial cell in the central nervous system that helps support other nerve cells. Also referred to as an astrocyte.
  • spinal cord - The major pathway for information traveling between the brain and the skin, muscles, and joints of the body.
  • Spinobulbar muscular atrophy (SBMA) - A C-A-G trinucleotide repeat disorder that occurs predominantly in males in which weakness and atrophy of the proximal muscles occurs. For more information, click here.
  • spinocerebellar ataxias (SCAs) - A family of disorders involving variable degeneration of the cerebellum, spinal cord, and brain stem. Symptoms such as loss of coordination and difficulty articulating speech are common to all SCAs. There are 7 SCAs described on the HOPES site: SCAs 1, 2, 3, 6, 7, 8, and 12.
  • sporadic - Occurring in a random or isolated manner.
  • ST14A cell line - Cells that exhibit quite accurately many of the properties of striatal nerve cells and can be engineered to express either normal or mutant huntingtin.
  • stem cells - Cells that have the ability to divide for an indefinite time and to give rise to specialized cells.
  • stereotactic lesions - highly specific damage done to a part of the brain
  • sterol regulatory element-binding proteins (SREBPs) - Sterol regulatory element-binding proteins; proteins involved in regulating cholesterol biosynthesis.
  • stimulus - Something causing a response; something in the environment detected by a receptor. Ex: a chemical that causes a nerve impulse.
  • stress - The effects of psychosocial and environmental factors on physical and mental well-being.
  • stress response - A set of nerve cell and endocrine responses that are elicited in response to a stressor to help restore homeostasis.
  • stressor - Any agent that causes stress to an organism.
  • striatal nerve cells - see striatal neurons.
  • striatal neurons - Nerve cells that make up the striatum. See striatum.
  • striatonigral pathway - pathway of cell communication from the striatum to the substantia nigra and back
  • striatum - Term that refers to the part of the brain consisting of both the caudate and the putamen. Also referred to as the corpus striatum.
  • stroke - Occurs when brain cells die because of inadequate blood flow to the brain.
  • stromal cells - Bone marrow cells that can be the source of other kinds of tissues.
  • suberoylanilide hydroxamic acid (SAHA) - An HDAC inhibitor.
  • substance P - a kind of neurotransmitter, known as a neuropeptide, which serves in particular regions of the brain
  • substantia nigra - A group of nerve cells at the base of the midbrain that receives input from a number of nerve cells. Some scientists consider the substantia nigra to be a part of the basal ganglia.
  • substrate - A molecule that an enzyme binds and acts upon.
  • subthalamic nuclei / subthalamic nucleus - A group of nerve cells that receives input from the caudate and putamen and participates in the modulation of motor control.
  • sugar - One of the molecular components of a nucleotide; sugars are a class of molecules made up of carbon, oxygen, and hydrogen arranged in a ringed structure.
  • suicide ideation - Thoughts about fatally harming one's self
  • SUMO-1 - A protein that is responsible for making the mutated huntingtin protein significantly more toxic to nerve cells in the brain.
  • superoxide [An unstable molecule that is very reactive and has the potential to do damage to nerve cells; O 2 - is a common one.
  • superoxide anion - A type of free radical.
  • sympathetic nervous system - A subdivision of the body's nervous system that is automatic (not consciously controlled) and is involved in preparing the body for physical activity.
  • symptoms - Changes in the body or its functions, experienced by the patient and indicative of disease.
  • synapse [The narrow gap between the end of one neuron and the beginning of another where neurotransmitters are passed. Very important for communication between neurons - "subserves the transmission of nerve impulses."