melatonin

melatonin A hormone that is produced by the pineal gland and is intimately involved in regulating the sleeping and waking cycles, among other processes. Some people who have chronic insomnia use melatonin supplements. However, melatonin is not recommended for all patients with sleep problems, so one should consult a physician before taking it.

MELAS syndrome

MELAS syndrome Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes syndrome, a rare form of dementia caused by mutations in the genetic material (DNA) in the mitochondria. Most DNA is in the chromosomes in the cell nucleus, but another important cell structure that carries DNA is the mitochondrion. Much of the DNA in the mitochondrion is…

melanosis coli

melanosis coli A benign, reversible condition that is usually, but not always, associated with longterm use of laxatives in which pigment deposition in the lamina propria of the large intestine results in a brown to black discoloration of the mucosa (lining) of the large intestine. Melanosis coli is sometimes called pseudomelanosis coli because the pigment…