reticuloendothelial Vre-.tik-yo-lo-.en-do-'the-le-olN system or macrophage \ , mak-r9- 1 faj\ system or mononuclear phago¬ cyte system Part of the body’s defenses, consisting of a class of cells widely distributed in the body. Reticuloendothelial cells filter out and destroy bacteria, viRUSes, and foreign substances and destroy worn-out or abnormal cells and tissues. Precursor cells in bone marrow develop into monocytes (see leukocyte), which are released into the bloodstream. Most enter body tissues, developing into much larger cells called macrophages, with different appearances in various locations. Some roam through the circulation and between cells and can coalesce into a single cell around a foreign object to engulf it. Reticuloendothelial cells also interact with lym¬ phocytes in immune reactions. Cells in the spleen destroy old red blood cells and recycle their hemoglobin; uncontrolled, this process causes ane¬ mia. Tumours of the reticuloendothelial system can be localized or wide¬ spread throughout the body. See also lymphatic system.
retina Vre-Cn-oV Layer of nerve tissue covering the back two-thirds of the eyeball. Light focused onto the retina by the lens of the eye stimulates two types of light-sensitive cells: rods, which are sensitive to low light levels, and cones, which provide detailed vision and colour perception. Chemical changes in these cells trigger nerve impulses, which are assembled by complex connections among retinal nerves into a pattern to be carried through the optic nerve to the visual centres of the brain. Dis¬ orders affecting the retina or the macula in its centre decrease vision and can cause blindness. See also DETACHED RETINA; MACULAR DEGENERATION.
retriever Any of several dog breeds, bred to retrieve game, that have a thick, water-resistant coat, keen sense of smell, and “soft” mouth that does not damage game. Retrievers are 22-24 in. (55-62 cm) tall and weigh 55-75 lbs (25-34 kg). The golden retriever has a golden- brown coat that is long on the neck.
Golden retriever.
SALLY ANNE THOMPSON
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1612 I retrograde motion ► revenue sharing
legs, and tail. The Labrador retriever has a short black or brown coat. Both are often used as guide dogs, and both are highly popular as pets. Other retriever breeds include the Chesapeake Bay, curly-coated, and flat-coated retrievers.
retrograde motion In astronomy, the actual or apparent motion of a body in a direction opposite to that of the predominant (direct or prograde) motions of similar bodies. Observationally and historically, retrograde motion refers to the apparent reversal of the planets’ motion through the stars for several months in each synodic period. This required a complex explanation in Earth-centred models of the universe (see Ptolemy) but was naturally explained in heliocentric models (see Copernican system) by the apparent motion as Earth passed by a planet in its orbit. It is now known that nearly all bodies in the solar system revolve and rotate in the same coun¬ terclockwise direction as viewed from a position in space above Earth’s North Pole. This common direction probably arose during the formation of the solar nebula. The relatively few objects with clockwise motions (e.g., the rotation of Venus, Uranus, and Pluto) are also described as retrograde.
retrovirus \ l re-tro-'vI-r9s\ Any of a group of viruses that, unlike most other viruses and all cellular organisms, carry their genetic blueprint in the form of RNA. Retroviruses are responsible for some cancers and viral infections of animals, and they cause at least one type of human cancer. The retrovirus HIV is the cause of AIDS in humans. The name signifies that they use RNA to synthesize DNA, the reverse of the usual cell pro¬ cess. This process makes it possible for genetic material from a retrovi¬ rus to enter and become a permanent part of the genes of an infected cell.
Retton, Mary Lou (b. Jan. 24, 1968, Fairmont, W.Va., U.S.) U.S. gymnast. Retton began studying dance and acrobatics at age 4. At the 1984 Olympic Games she received perfect scores in her final two events to win a dramatic victory in the combined exercises, becoming the first Ameri¬ can woman gymnast to win an individual Olympic gold medal. Her style, exhibiting speed, accuracy, and power, served to transform women’s gym¬ nastics. She was the first gymnast inducted into the U.S. Olympics Hall of Fame (1985).
Reuchlin Vr6ik-lin\, Johannes (b. Feb. 22, 1455, Pforzheim, Wiirttemberg—d. June 6, 1522, Bad Liebnzell) German humanist. After obtaining his law degree in 1481, he held court and judicial posts in Wiirttemberg and its capital, Stuttgart, from the 1480s until 1512. Second only to Desiderius Erasmus among the German humanists, Reuchlin was a pioneer in the scientific study of Classical Greek and translated many Classical texts. His grammar and lexicon, On the Fundamentals of Hebrew (1506), revolutionized Hebrew studies and advanced Old Testa¬ ment research. His opposition to the Dominicans’ plan to destroy all Hebrew literature was one of the great controversies prior to the outbreak of the Reformation, and in 1516 he was acquitted of heresy by a papal commission. Philipp Melanchthon was his nephew.
Reunion \re-'yun-y3n\ Island (pop., 2005 est.: 780,000) and French overseas department, Mascarene Islands, western Indian Ocean. Located 425 mi (684 km) east of Madagascar, Reunion is about 40 mi (65 km) long and 30 mi (50 km) wide and has an area of 968 sq mi (2,507 sq km). Its capital is Saint-Denis. It consists mainly of rugged mountains dissected by torrential rivers. Most of the population is of mixed ancestry, with African descent predominant. Reunion was settled in the 17th century by the French, who brought slaves from eastern Africa to work on coffee and sugar plantations. It was a French colony until 1946, when it became an overseas department of France. Its economy is based largely on the export of sugar. Other products include meat and milk products, rum, molasses, tobacco, geranium essence, and vanilla.
Reuter Vroi-tsrX, Paul Julius, Baron von Reuter orig. Israel Beer Josaphat (b. July 21, 1816, Kassel, Electorate of Hesse—d. Feb. 25, 1899, Nice, France) German founder of the news agency Reuters. He was a bank clerk and partner in a small publishing concern before initi¬ ating a prototype news service in Paris in 1849, using electric telegraphy and carrier pigeons in his network. He moved to England in 1851 and opened a telegraph office serving banks, brokerage houses, and leading business firms. He steadily extended his commercial news service, acquir¬ ing his first subscribing newspaper client in 1858. Undersea cables enabled him to expand the service to other continents.
Reuters Vroi-tsrzV British cooperative news agency. Founded in 1851 by Paul Julius Reuter, it was initially concerned with commercial news but began to serve a growing newspaper clientele after the London Morning
Advertiser subscribed in 1858. After a period of competition, Reuters and two rival agencies agreed on a division of territory and for many years held a virtual monopoly on world press services. The company remained in pri¬ vate hands until 1925, when its structure began moving toward a coopera¬ tive of British and Australasian press interests. By the late 20th century Reuters was a world leader in business and financial market coverage. In 1984 it became a public company under the name Reuters Group PLC.
Reuther Vru-thoA, Walter (Philip) (b. Sept. 1, 1907, Wheeling, W.Va., U.S.—d. May 9, 1970, Pellston, Mich.) U.S. labour leader. He became an apprentice tool- and diemaker at age 16. He traveled around the world in the 1930s, developing a lifelong distaste for communism after spending two years in a Soviet auto factory. He became a local union leader in Detroit, Mich., and helped organize sit-down strikes—during which he suffered brutal physical attacks—that made the United Automo¬ bile Workers (UAW) a power in the auto industry. As president of the UAW from 1946 until his death, he was an effective negotiator of wages-and- hours gains. He became president of the Congress of Industrial Organi¬ zations (CIO) in 1952 and was an architect of the AFL-CIO merger in 1955. He was second in power to George Meany at the AFL-CIO; how¬ ever, their repeated clashes, partly stemming from Reuther’s strong sup¬ port for civil rights and opposition to the Vietnam War, resulted in Reuther’s leading the UAW out of the AFL-CIO in 1968 and forming a short-lived federation with the Teamsters Union. He died in a plane crash.