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.

 

 

T
  • target site - A specific sequence of amino acids in a protein that serve as the point at which the protein interacts with other specific proteins.
  • tau pathologies - neurodegenerative diseases related to problems with the tau protein found in nerve cells. Tau pathologies include Alzheimer's disease and myotonic dystrophy, among others.
  • tauroursodeoxycholic acid (TUDCA) - An acid found in large quantities in bear bile and small amounts in human bile. It helps in preventing programmed cell death, possibly by protecting mitochondria.
  • temporal lobe - A part of the brain associated with memory, hearing, and perception.
  • teratogenic - A substance that disturbs the development of the embryo or fetus
  • tertile - This term is often used in explaining the distribution of scores on a test. A tertile is one-third of the total number of scores. For instance, the highest tertile is the one-third of scores that have the highest scores on the test.
  • terpenoids - A constituent of Ginkgo biloba extract that includes the ginkgolides and the bilobalides.
  • testosterone - A steroid hormone produced primarily in the testes and responsible for the development and maintenance of male secondary sex characteristics. It is also produced synthetically for use in medical treatment.
  • tetrabenazine (TBZ) - A dopamine depletor used to treat chorea.
  • Tetracycline - an antibiotic drug that is used for medicine and for research. In some cases it can serve to regulate the production of certain proteins in the cell, by starting or stopping transcription for a certain target gene
  • TFC - See total functional capacity.
  • TGase - An abbreviation for transglutaminase.
  • thalamus - A collection of nerve cells in the brain. Although it performs many functions, the primary role of the thalamus is to relay sensory information from other parts of the brain to the cerebral cortex.
  • thivoflavine S - A compound that is believed to both decrease the presence of beta-amyloid fibrils, and decrease huntingtin protein aggregation.
  • thivoflavine T - A compound that is believed to decrease the presence of beta-amyloid fibrils, but has little or no success in inhibiting huntingtin protein aggregation.
  • thymine - One of the four nitrogenous bases found in DNA; pairs with the base adenine; often abbreviated as the letter "T"; see Figure B-3.
  • thymus gland - The thymus gland lies at the root of the neck behind the breastbone. It grows from birth to puberty and then starts to diminish in size but remains active. Its main function is the formation of T-lymphocytes which are an essential part of the immune system.
  • thyroid gland - A small organ located near the neck that produces several hormones.
  • Tibetan Buddhism - A branch of Buddhism, which traveled to Tibet from India sometime after Buddhism had traveled to eastern China from India. This resulted in some additional sophisticated techniques for understanding ultimate truth.
  • tissue culture - A technique used to grow body tissue outside the body on a culture medium.
  • tolerability - The potential of a drug to be endured. A drug with good tolerability produces few side effects in the subject.
  • tonic-clonic - Seizures that involve both tonic and clonic phases. During the tonic phase the body is rigid, but during the clonic phase the individual often suffers from rhythmic jerking movements. When tonic-clonic seizures are generalized, they are referred to as grand mal seizures.
  • total functional capacity (TFC) - A standardized scale used to assess capacity to work, handle finances, perform domestic chores and self-care tasks, and live independently. The TFC scale ranges from 13 (normal) to 0 (severe disability).
  • total homocysteine (tHcy) - The sum of all forms of homocysteine, usually measured from blood plasma.
  • totipotent - The ability to give rise to all cell types (including the placenta, other supporting tissues, and the body of the organism itself); having unlimited capability.
  • toxic soluble oligomers - Small, harmful molecules believed to trigger cell damage in HD and related diseases.
  • trachea - (a.k.a. the "windpipe") the main trunk of the system of tubes by which air passes between the mouth and the lungs.
  • trait - A physical characteristic brought about by the expression of a gene or many genes. Examples of traits are height, eye color, and the ability to roll your tongue. Variations in these characteristics are dependent upon the particular alleles an individual has for the genes determining the trait.
  • trans fat - A highly damaging type of fat which is produced when unsaturated fat is subjected to the process of hydrogenation.
  • trans-sulfuration pathway - A two-reaction pathway which degrades homocysteine.
  • transcribe - To undergo transcription. In order for the DNA code of a gene to result in the production of a specific protein, the gene must first be transcribed.
  • transcript - A sequence of RNA produced by transcription from a DNA template.
  • transcription - One part of the process that uses the DNA code to make a protein.
  • transcription factor - A protein that aids in transcription.
  • transcriptional dysregulation - A disease mechanism that disrupts the expression of certain genes, which affects when essential proteins are produced by the cell. Transcriptional dysregulation plays a major role in HD.
  • transfer RNA (tRNA) - An important player in the translation of mRNA to protein; it binds to a specific mRNA codon on one end and a specific amino acid on the other end.
  • transgene - A foreign piece of DNA that has been inserted into the germ line of an organism. Since germ cells give rise to the reproductive cells, an organism that contains a transgene will pass it down to all of its descendents. An organism that contains a transgene is known as "transgenic."
  • transgenic - An organism that has had DNA from another organism introduced into it. For example, if jellyfish DNA is introduced into a mouse, the mouse is then called a transgenic mouse. Transgenic animals are generated by introducing the outside DNA into the developing embryo and then implanting the embryo into a host mother until the animal is born.
  • transglutaminase - An enzyme that helps produce huntingtin protein aggregates.
  • translation - The process by which the protein molecule is formed from the mRNA blueprint.
  • transmissible spongiform encephalopathy (TSE) - A family of human and animal diseases characterized by spongy deterioration of the brain with severe and fatal neurological symptoms.
  • transposable element - Segment of DNA that can move around within a chromosome or between chromosomes in the same cell. Can also be called a transposon.
  • trehalose - A disaccharide made out of two glucose molecules that has been shown to stabilize proteins. Trehalose is used as a sweetener and preservative, and can be found in foods such as lobster, shrimp, honey, and mushrooms.
  • tremor - A quivering, involuntary movement of a part or parts of the body.
  • triglyceride - A fat-like substance found in the blood.
  • trimer - A molecule that is made of three monomers bound together.
  • trinucleotide repeat - Another term for triplet repeat.
  • trinucleotide repeat disorder - An illness in which there is an abnormally large number of repeats of a specific codon of DNA. In addition to Huntington's disease, other trinucleotide repeat disorders include fragile X syndrome and spinobulbar muscular atrophy. In HD, the repeated codon is C-A-G, which codes for the amino acid glutamine.
  • triplet repeat - A three letter sequence of bases (codon) that is repeated consecutively in a section of DNA. In HD, the repeated sequence is C-A-G. Also referred to as a trinucleotide repeat or a codon repeat.
  • tryptophan - One of the amino acids found in our bodies. It can be converted into niacin.
  • tryptophan hydroxylase (TPH) - The rate-limiting enzyme in the synthesis of serotonin. It is very susceptible to free radical damage.
  • tumor - An abnormal mass of tissue that is not inflammatory, possesses no real function, and is the result of uncontrolled cell growth.
  • tumor suppressor - A protein that inhibits the uncontrolled cell growth that leads to formation of tumors.