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.

 

 

R
  • R&D pipeline - See research and development
  • randomized - In the context of a clinical trial, randomized refers to how the different treatments (either the potential drug or the standard treatment) are allocated to the trial subjects. This ensures that the different treatment groups are similar in important characterisitics such as how severe their disease might be and what other conditions they may have along with the disease being studied.
  • range - A set of values that a number can have. A range is usually specified by its maximum and minimum value. Any number that is between these two values is said to be within the range. For example, the range 12-15 has a maximum value of 15 and a minimum value of 12. The numbers 12, 13, 14 and 15 are said to be within the range 12-15.
  • rapamycin - A drug that has been shown to promote the breakdown of huntingtin aggregates by inhibiting the protein mTOR and inducing autophagy.
  • re-methylation - See methylation.
  • reactive oxygen species (ROS) - A highly reactive free radical that can result from excessive levels of iron in the body.
  • receptor - A specialized protein on a cell’s surface that binds to substances that affect the activities of the cell. Specifically, in a nerve cell, neurotransmitters bind to receptors on the surface of the neuron. The binding of a neurotransmitter can have either excitatory or inhibitory effects on the neuron. Once a neurotransmitter is bound to a receptor, changes occur within the neuron that can result in the neuron sending messages to other neurons.
  • recessive - A term used to describe the degree of penetrance of an allele relative to other alleles of the same gene. A recessive trait is only expressed when there are two recessive alleles present. If a dominant allele and recessive allele are both present, the dominant trait will be expressed instead.
  • recombination - An event that occurs during meiosis involving the transfer of segments of DNA from one homologous chromosome to the other.
  • red blood cells - Cells specialized for oxygen transport, having a high concentration of hemoglobin (oxygen-carrying protein) in the cytoplasm.
  • red nucleus - A small part of the brain involved in the control of movement.
  • redox-buffer - Acts to protect against oxidative damage.
  • refined - refers to breads and cereals in which the fibrous bran and germ are removed from the grain by machinery. Refined cereals and breads (such as white bread and pasta) are, thus, less healthy than non-refined cereals and breads.
  • refractory period - In a voltage-gated ion channel, the stage between open and closed. During this time the channel is inactivated, no molecules are allowed in or out, and the channel cannot be excited further.
  • relevant - A protein or molecule is relevant to a disease if it contributes to the disease mechanism or its symptoms in some manner.
  • remacemide - A drug that acts as an NMDA receptor antagonist. It may be helpful in combating glutamate toxicity in people with HD. For the chapter on remacemide, click here.
  • renal system - Part of the metabolic system; responsible for the regulation of bodily fluids and the elimination of wastes.
  • renal dysfunction - Problems with the kidney that detract from the body's ability to adequately retain essential nutrients and clear out toxic substances from the blood.
  • repeat region - The part of DNA where a certain codon is repeated many times. Expansions sometimes occur during replication of repeat regions. In Huntington’s disease, the repeat region involves the CAG codon.
  • replication - The process by which DNA copies itself before cell division. Unless mutation occurs, the new copy of DNA is identical to the original DNA. (Verb form: replicate.)
  • reproductive system - The male and female organs responsible for reproduction.
  • research and development - The process involves the scientific discovery of a mutation, or a pathway or biological target responsible for the disease all the way through to the creation of a therapeutic treatment, such as a drug. It has many stages, takes several years, and costs millions of dollars.
  • respiratory chain - The respiratory chain is composed of mitochondrial complexes that transfer electrons from one complex to another, eventually resulting in the formation of ATP. Also referred to as the electron transport chain.
  • restriction enzymes - Proteins produced by bacteria that break foreign DNA molecules at very specific sites; Enzymes that cut DNA. Different restriction enzymes cut at different sequences of nucleotides. For instance, one restriction enzyme will cut the DNA wherever it sees the sequence ACGGT, while another will cut when it sees CCTAT.
  • resveratrol - A phytoalexin found mainly in red wine that exhibits both antioxidant and anti-inflammatory abilities.
  • retina - A layer of receptors at the back of the eye that forwards information to the optic tract and eventually to the brain.
  • reuptake - The process by which a presynaptic nerve cell takes neurotransmitter out of the synapse and recycles it to prevent too much signaling.
  • Reye's syndrome - A rare and serious brain and liver disorder that is associated with the use of aspirin in children.
  • ribonucleic acid - See RNA.
  • ribose - The particular sugar molecule that is found in RNA.
  • ribosome - A tiny organelle in the cytoplasm of the cell that directs protein synthesis.
  • rifampicin - A compound that is believed to decrease the presence of beta-amyloid fibrils, but has little or no success in inhibiting huntingtin protein aggregation.
  • rigidity - Stiffness or tenseness of muscles; inability to bend or be bent.
  • riluzole - A drug that has been shown to have energy buffering and anti-glutamate properties
  • RNA - Abbreviation for ribonucleic acid; composed of many nucleotide subunits arranged in a long chain and associated with the control of cellular chemical activities; carries the information necessary to make proteins.
  • RNA interference (RNAi) - A technique for gene silencing. RNA is introduced into the cell to disrupt messenger RNA and prevent it from being translated into a protein.
  • RNA polymerase - An enzyme that catalyzes (speeds up) the synthesis of a complementary strand of RNA from a DNA template, or, in some viruses, from an RNA template.
  • RNA world - the RNA world hypothesis proposes that RNA was the basis of the first forms of proto-life, and then later developed into the first cell.
  • rofecoxib - A COX-2 inhibitor.
  • RRS1 - Regulator of ribosome synthesis; a gene that directs the production of ribosomes that, in turn, direct the synthesis of nuclear proteins (proteins found in the nucleus of the cell).