Dehydroepiandrosterone: Also DHEA; a steroid hormone made by the adrenal glands, that acts on the body much like testosterone and is converted into testosterone and estrogen. The blood levels of DHEA decline with age. DHEA is sold in the US without a prescription as a ‘nutritional supplement.’ It has been claimed to improve mood, boost the immune system, sharpen memory, and combat aging.
- Deinococcus radiodurans
Deinococcus radiodurans: A bacterium that can survives extremely high levels of radiation and therefore has high potential for radioactive waste cleanup. The genome of Deinococcus radiodurans has been sequenced. It is composed of two chromosomes, a megaplasmid, and a small plasmid. The total genome contains 3,284, 156 base pairs. Deinococcus radiodurans is an organism in […]
- Deja vu
Deja vu: (In French, dejà vu means “already seen.” and the word dejà has an acute accent on the e and a grave accent on the à but we have omitted the accents from the entry term for the sake of the English-speaking search engine.) Dejà vu is a disquieting feeling of having been somewhere […]
- Delay, developmental
Delay, developmental: A condition in which a child is behind schedule in reaching milestones of early childhood development. This term is often used as a euphemism for mental retardation, which can be less a delay than a permanent limitation of a child’s ability to progress.
Deletion: Loss of a segment of DNA from a chromosome. A chromosome deletion can cause disease. An example is the cri du chat (cat cry) syndrome, which is due to loss of part of chromosome 5. The opposite of duplication.
Delirium: A sudden state of severe confusion and rapid changes in brain function, sometimes associated with hallucinations and hyperactivity, during which the patient is inaccessible to normal contact. Delirium can be due to a number of conditions, including infection, drug toxicity or withdrawal, seizures, brain tumor, poisoning, head injury, and metabolic disturbances.