osteoarthritis V.as-te-o-ar-'thri-tosX or osteoarthrosis or degen¬ erative joint disease Most common joint disorder, afflicting over 80% of those who reach age 70. It does not involve excessive inflamma¬ tion and may have no symptoms, especially at first. Cartilage softens and wears away, and bone grows in its place, distorting the joint’s surface and causing pain, stiffness, and limited movement, usually in weight-bearing joints (vertebrae, knees, hips). Treatment may include analgesics, rest, weight loss, corticosteroids, and/or physical medicine and rehabilitation or an exercise program. Hip or knee replacement or surgical removal of unhealthy tissue may be needed.
osteogenesis imperfecta V.as-te-o-'je-no-sos-.im-por-'fek-toN Group of connective-tissue diseases in which the bones are very fragile. Several forms probably reflect different degrees of expression of the same disor¬ der. Persons with osteogenesis imperfecta type I are normal at birth, but fractures occur easily; in van der Hoeve syndrome the sclerae are bluish, bone deformities in the skull cause deafness, double-jointedness occurs, and skin is abnormally thin. Babies with osteogenesis imperfecta type II, if not stillborn, are born with fractures, and fractures continue to occur, causing severe crippling; survival to adulthood is rare.
osteopathy \,as-te-'a-p3-the\ Health-care profession founded by the U.S. physician Andrew Taylor Still (1828-1917) as a reform movement against the rather primitive 19th-century drugs and surgical techniques. It emphasizes the relationship between musculoskeletal structure and organ function. Osteopathic physicians learn to recognize and correct structural problems through manipulative and other therapies. Osteopathic hospitals provide general or specialized health care, including maternity and emergency care.
osteoporosis \,as-te-6-p3-'ro-s9s\ Generalized loss of bone density, causing skeletal weakness. Around age 40, the rate of bone resorption in humans starts to exceed the rate of bone formation. Women experience accelerated bone loss after menopause, when the estrogen level decreases. When the amount of bone falls below a certain threshold, fractures occur with little or no trauma. Prevention begins with adequate calcium intake in youth, when bone mass is built, and then throughout life. Weight¬ bearing exercise and vitamin D are important at all ages. Medications can inhibit bone resorption or prevent bone loss in patients who are at risk for developing osteoporosis.
Ostia \'a-ste-o\ Ancient Roman town. Originally at the mouth of the Tiber River, it would now be about 4 mi (6 km) upstream. The modern seaside resort of Ostia, Italy, is near the ancient city. It was probably founded in the 4th century bc and developed as a naval station, major port, and cen¬ tre of the grain trade. It reached the height of its prosperity in the 2nd century ad, when it had a population of about 50,000. It suffered from the decline of the Roman economy in the 3rd century and from barbarian raids in the 5th century. Its Roman ruins were quarried for building materials in the Middle Ages and for sculptors’ marble during the Renaissance. Excavations began in the 19th century, and about two-thirds of the Roman town can now be seen.
ostomy Vas-t3-me\ Surgical opening in the body, or the operation cre¬ ating it, usually to allow discharge of wastes through the abdominal wall. It may be temporary, to relieve strain on damaged organs, or permanent, to replace normal channels congenitally missing or surgically removed (usually to treat cancer). A loop of bowel (the colon in colostomy and the ileum in ileostomy) is cut and the end brought through to the abdominal
surface. Waste usually exits into a self-adhering bag worn over the open¬ ing, or an internal pouch may be made from body tissue.
Ostpolitik Vost-po-li-.tekX (German: “Eastern Policy”) West German foreign policy begun in the late 1960s. Initiated by Willy Brandt as for¬ eign minister and then chancellor, the policy was one of detente with Soviet-bloc countries, recognizing the East German government and expanding commercial relations with other Soviet-bloc countries. Trea¬ ties were concluded in 1970 with the Soviet Union, renouncing the use of force in their relations, and with Poland, recognizing Germany’s 1945 losses east of the Oder-Neisse Line. The policy was continued by Chancel¬ lor Helmut Schmidt.
Ostrasia See Austrasia
Ostrava Vo-stro-vsX City (pop., 2001 prelim.: 319,293), northeastern Czech Republic, at the confluence of the Opava and Oder rivers near the Moravian Gap. It was founded c. 1267 as a fortified town by Bruno, bishop of Olomouc, to protect the entry to Moravia from the north. Its castle was demolished in 1495. Historic buildings include a 13th-century church.
ostrich Two-toed, long-necked ratite ( Struthio camelus, family Struthionidae) found in Africa, the largest living bird. An adult male ostrich may be nearly 9 ft (2.75 m) tall and weigh more than 330 lb (150 kg). Males are black, with white wing and tail plumes; females are brown. Ostriches live in flocks of 5-50, usually among grazing animals, and eat plants and an occasional small animal. Roaring, hissing males fight for three to five hens, which lay 15-60 eggs in a communal nest scraped in the ground. The male sits at night; the females take turns by day. One- month-old chicks can run with adults, at 40 mph (65 km/hr). To escape detection, an ostrich may lie on the ground with its neck outstretched, a habit that may have given rise to the notion that ostriches bury their heads in the sand.
Ostrogoth Vas-tro-.gathV Member of a division of the Goths (Ostrogoth means “Eastern Goth”) who built an empire north of the Black Sea in the 3rd century and established a kingdom in Italy in the late 5th century. At its zenith in the 4th century, the Ostrogoth empire stretched from the Don to the Dniester (in present-day Ukraine) and from the Black Sea to southern Belarus. The Ostrogoths were conquered by the Huns c. 370 and remained part of the Huns’ empire until the mid 5th century. When the Hun empire collapsed (455), the Ostrogoths emerged as an independent people once again. Their greatest ruler, Theodoric, led the Ostrogothic invasion of Italy and declared himself king (493). Theodoric maintained good relations with the native population, especially the senatorial class, throughout most of his reign and promoted a cultural revival. The turmoil in Italy following his death provided the Byzantine emperor Justinian I with the opportunity to invade the peninsula. The ensuing war lasted almost 20 years (c. 535-54) and ended the national existence of the Ostrogoths.
Ostrovsky V.o-'strof-skeV, Aleksandr (Nikolayevich) (b. April 12, 1823, Moscow, Russia—d. June 14, 1886, Shchelykovo) Russian playwright. His second play, The Bankrupt (1850), exposed bogus bank¬ ruptcy cases and led to his dismissal from the civil service. Most of his plays treat characters from the Russian merchant class; they include the comedies Poverty Is No Disgrace (1853), The Thunderstorm (1859), and The Snow Maiden (1873), adapted as an opera by Nikolay Rimsky- Korsakov. With his 47 plays Ostrovsky created a Russian national reper¬ toire, and he is considered the greatest representative of the Russian realistic period.
Ostwald \'6st-,valt\, (Friedrich) Wilhelm (b. Sept. 2, 1853, Riga, Latvia—d. April 4, 1932, near Leipzig, Ger.) Russian-German physical chemist. He moved to Germany in 1887. He wrote the influential Text¬ book of General Chemistry, 2 vol. (1885-87). With Jacobus H. van't Hoff in 1887 he founded the Zeitschrift fur physikalische Chemie, which became for many years the most important journal in the field. His work at the University of Leipzig (1887-1906) established it as a great school of physical chemistry. In 1888 he discovered Ostwald’s law of dilution of an electrolyte. He gave the first modem definition of a catalyst in 1894 and was awarded the Nobel Prize in 1909 for his work on catalysis. His process for the conversion of ammonia to nitric acid proved of great industrial importance. He is regarded as one of the founders of the field of physical chemistry.