Sarcoma: Tumors of bones and connective tissue cells. Schistosomiasis: The state of being infected with flukes of the genus Schistosoma. Schwann cell: Large nucleated cell whose cell membrane covers the axons (the process of a nerve cell by which impulses travel away from the cell body) of special nerve cells (myelinated) and produce myelin, substance containing protein and lipid. SCID: Severe combined immunodeficiency, a group of rare congenital disorders characterized by gross immune deficiency. Scleroderma: Chronic hardening and thickening of the skin, which may be a finding in several different diseases, occurring in a localized or focal form and as a systemic disease. Secretagogues: Substances that induces secretion from cells, originally applied to peptides inducing gastric and pancreatic secretion. Secretin: A strongly basic polypeptide hormone secreted by the duodenum and upper jejunum when acid chyme enters the intestine. It stimulates the pancreas to release bicarbonate and water thus changing the pH from acid to alkaline required for the digestive enzymes. Selenium: Essential trace element that must be provided as a supplement in serum free culture media for most animal cells and is thought to prevent prostate cancer. Sentinel lymph node: The first lymph node where the cancerous tissue drains Sepsis: The condition produced by the presence of pathogenic microorganisms or their toxins in blood or other tissues. Sera: Serum is the clear liquid that separates from blood on clotting. Serine proteases: One of a group of endoproteases from both animal and bacterial sources that share a common reaction mechanism based on formation of an acyl enzyme intermediate on a specific active serine residue. Sertoli cells: Tall columnar cells found in the mammalian testis closely associated with developing spermatocytes and spermatids. Probably provide appropriate microenvironment for sperm differentiation and phagocytose degenerate sperm. Signal transduction: The process by which information from one cell is transferred to another. Somatic cell: Usually any cell of a multicellular organism that will not contribute to the production of gametes, i.e. most cells of which an organism is made: not a germ cell. Somatostatin: A cyclic tetradecapeptide primarily produced by the hypothalamus and by the pancreatic islet cells. It inhibits the secretion of several hormones including secretin. S-phase: The synthetic phases in the cell cycle when synthesis of various molecules, especially of DNA takes place. See cell cycle. Sphingomyelin: A general designation of a group of phospholipids, which on hydrolysis yield phosphoric acid, choline, sphingosine, and fatty acid. They occur primarily in nervous tissue and generally in membrane. Spirometry: Measurement of volume of air inhaled or exhaled by the lung. Spleen: A large ductless gland like organ situated in the upper left of the abdominal cavity. It is a part of the lymphoid system, produces lymphocytes and has other functions such as reservoir of red blood cells. Sporadic: Neither endemic nor epidemic; occurring occasionally in a random or isolated manner. Sputum: Matter ejected from the lungs, bronchi, and trachea, through the mouth. Squamous Cell: Long flat cells that make up most part of the epidermis. Squamous Cell Carcinoma (SCC) antigen: Protein expressed in cancerous squamous cell (flat, scalelike epithelial cell). Staging: Careful evaluation to determine the extent of disease. Statins: Statins are a class of drugs that lowers the level of cholesterol in the blood by reducing the production of cholesterol by the liver. Statins block the enzyme in the liver that is responsible for making cholesterol. This enzyme is called hydroxy-methylglutaryl-coenzyme A reductase (HMG-CoA reductase). Scientifically, statins are called HMG-CoA reductase inhibitors. Stem cell: A blood cell progenitor, or mother cell, having the capacity for both replication and differentiation, and giving rise to different blood cell lines, such as the proerythrocytes and myeloblast, which cannot self-replicate and must differentiate into more mature daughter cells. Stenosis: Narrowing of duct or canal. Stent: A tube made of metal or plastic that is inserted into a vessel or passage to keep the lumen open and prevent closure due to a stricture or external compression. Stomatitis: Inflammation of the oral mucosa, due to local or systemic factors which may involve the buccal and labial mucosa, palate, tongue, floor of the mouth and the gingivae. Stricture: Decrease in the caliber of a canal, duct or other passage, as a result of contraction or deposition of abnormal tissue. Stromal layer: Supporting layer of cells or matrix of an organ, as distinguished from its functional elements. Substrate: A substance upon which an enzyme acts. Superoxide dismutases: Any of a range of metalloenzymes that catalyses the formation of hydrogen peroxide and oxygen from superoxide (HO2(.).) and thus protects against superoxide induced damage. Suppressor T cells: Differentiated T lymphocytes that suppress antibody synthesis or cell-mediated immunity. They may be activated in response to antigen. Sympathetic nervous system: One of the two divisions of the vertebrate autonomic nervous system, the other being the parasympathetic nervous system. The autonomic nervous system regulates key functions including the activity of the cardiac (heart) muscle, smooth muscles (e.g., of the gut), and glands. The sympathetic nervous system accelerates the heart rate, constricts blood vessels, and raises blood pressure. The parasympathetic nervous system slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles. Syngeneic: In transplantation biology, denoting individuals or tissues that have identical genotypes, that is, identical twins or animals of the same inbred strain. Called also isogenic. Systemic: Pertaining the body as a whole.