Index of Biomedical Hypertexts Glossary and Index: A
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- abomasum
- The glandular stomach of ruminants such as cattle and sheep.
- acinus
- A small group of cells arranged in a "grape-like" cluster. A classical example is the arrangement of pancreatic exocrine cells, but the term is also applied to larger groups of cells, as in the liver.
- acrocentric
- A chromosome structure in which the centromere is close to one end.
- acromegaly
- A disease state associated with excessive secretion of growth hormone in adults.
- acrosome reaction
- A membrane fusion event that releases enzymes from the head of the sperm to facilitate fertilization.
- ACTH
- Adrenocorticotropic hormone - a peptide hormone secreted from the anterior pituitary that stimulates secretion of glucocorticoids from the adrenal glands.
- Addisons disease
- An endocrine disease resulting from a deficiency of adrenal steroids, particularly aldosterone.
- adenylyl cyclase
- An enzyme and integral membrane protein that converts ATP to cyclic AMP.
- adipocyte
- A fat cell. Adipose tissue is composed predominantly of adipocytes.
- adipose tissue
- Fatty tissue.
- adrenal glands
- A pair of hormone-producing organs located near the kidneys.
- adrenalin
- A trade name for the hormone epinephrine.
- adrenocorticotropic hormone
- A peptide hormone secreted from the anterior pituitary that stimulates secretion of glucocorticoids from the adrenal glands.
- aerobic
- In the presence of oxygen (opposite of anaerobic).
- afferent
- Conveying or carrying toward a center (opposite of efferent). Example: an afferent neuron carries information from the hand toward or to the central nervous system.
- agonist
- In receptor-ligand interactions, an agonist is a molecule that binds receptor and fully induces post-receptor signalling events. The opposite of antagonist.
- aldosterone
- A steroid hormone produced by the adrenal cortex that participates in control of sodium, potassium and water balance.
- amino terminus (amino terminal)
- The end of a polypeptide that carries a free amino group. The first amino acid in a peptide or protein is called the amino terminal or N-terminal amino acid.
- amphipathic
- Having both hydrophilic ("water loving") and hydrophobic ("water hating") regions within the same molecule. Phospholipids and bile salts are good examples of amphipathic molecules.
- amylase
- An hydrolytic enzyme that digests starch into maltose. Produced in abundance by the pancreas.
- ana-
- A prefix meaning upward, backward, excessive or again.
- anabolism (anabolic)
- The process by which organisms build complex molecules from simple molecules by expenditure of energy. The opposite of catabolism.
- anaerobic
- In the absence of oxygen (opposite of aerobic).
- anaplasia
- Loss of a cell's differentiated state, or reversion to a more "primative" cellular phenotype. This usually is seen in association with cancer cells.
- anemia, pernicious
- An anemia caused by reduced ability to absorb vitamin B12 from the intestinal tract due to inability to secrete intrinsic factor from the stomach.
- aneuploid (aneuploidy)
- Having less than or more than the normal diploid number of chromosomes; a common type of cytogenetic abnormality.
- anorexia
- A lack or loss of appetite for food.
- antagonist
- In receptor-ligand interactions, an antagonist is a molecule that binds receptor, blocks the binding of agonist but fails to induce post-receptor signalling events.
- antidiuretic hormone
- A peptide hormone secreted from the posterior pituitary that affects the kidney and vascular system to conserve body water and increase blood pressure. Another name for this hormone is vasopressin.
- apoptosis
- Programmed cell death.
- appendix
- A wormlike extension of the cecum in humans; part of the large intestine.
- aquaporins
- A family of proteins that function as water channels in cell membranes.
- ATPase: Na(+)-K(+)
- The "sodium pump". A membrane protein that pumps 3 sodium ions out of cells in exchange for 2 potassium ions in a reaction that hydrolyzes ATP. Critical in maintaining low intracellular sodium and resting membrane potential.
- autocrine
- The activity of a hormone or growth factors that binds to and affects the same cell that secreted it.
Last updated on 5/21/2000