islet cell tumor A tumor that arises from the islet cells of the pancreas. The islet cells normally produce insulin and other hormones, and so the tumors frequently, but not always, produce one of these hormones. Islet cell tumors can be benign or malignant and generally cause symptoms related to the hormone produced by the…
islet of Langerhans A group of specialized cells in the pancreas that make and secrete hormones, including insulin. These cells sit in groups (islets), with several different types of cells in an islet, including alpha cells that make glucagon, which raises the level of glucose (sugar) in the blood; beta cells that make insulin; and…
isochromosome An abnormal chromosome that has two identical arms due to duplication of one arm and loss of the other. Isochromosomes are found in tumors and in some girls with Turner syndrome.
isodisomy A remarkable situation in which both chromosomes in a pair are from one parent only. Isodisomy causes some birth defects and is suspected to play a role in cancer. Also known as uniparental disomy.
isolate 1 In genetics, a group (for example, the Amish) in which mating is always between members of the group. 2 A single microbe or cell that has been separated from the whole, or a pure culture produced from an isolate. 3 A particular strain of virus, bacteria, or organism taken from a patient.
isotonic solution A solution that has the same salt concentration as cells and blood. Isotonic solutions are commonly used as intravenously infused fluids in hospitalized patients.
intubate To put a tube in, commonly used to refer to the insertion of a breathing tube into the trachea for mechanical ventilation. For example, as a life-saving measure, an emergency room physician might intubate a patient who is not breathing adequately so that the lungs can be ventilated.
intussusception Infolding (prolapse) of a portion of the intestine within another immediately adjacent portion of intestine, which predominantly affects children. Intussusception decreases the supply of blood to the affected part of the intestine and frequently leads to intestinal obstruction. The pressure created by the two walls of the intestine pressing together causes inflammation and swelling,…
invasive cancer Cancer that has spread from the site of origin to deeper tissues or to other parts of the body.
inversion, chromosome See chromosome inversion.
invest In medicine, to envelop, cover, or embed. For example, a dentist might invest a patient’s teeth with a wax material in order to form a mold of it.
involution A retrograde change. After treatment, a tumor may involute; with advancing age, there may be physical and emotional involution.