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 on the HOPES site.
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.
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.
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 - Describes a single stand of DNA whose bases can match up with other bases on the same strand of DNA, forming a loop or a hairpin. A single strand of DNA that curls back onto itself is described as self-complementary.
self-renewal - The ability of a cell to divide continuously to produce more copies of itself.
semantic memory - Memory we use to store facts and concept-based knowledge with no respect to the specific experiences or settings where we learned the facts.
sequencing - The process of determining the order of nucleotide "letters" making up a segment of DNA
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 a person’s sex chromosomes.
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 gene disabling techniques to prevent the translation of genes to protein. Also known as small interfering RNA
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 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 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.
sirtuins - A group of enzymes that may play a role in lifespan extension and the aging process.
sister chromatid - A double helix of DNA, tightly coiled and compacted into a rod-like form. Two identical chromatids are sister chromatids. See Figure B-9.
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.
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 many other nerve cells. Some scientists consider the substantia nigra to be a part of the basal ganglia.
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.
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 - "Allows the transmission of nerve impulses."
Last Modified: 05/22/2009
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