antidote Remedy to counteract the effects of a poison or toxin. Admin¬ istered by mouth, intravenously, or sometimes on the skin, it may work by directly neutralizing the poison; causing an opposite effect in the body; binding to the poison to prevent its absorption, inactivate it, or keep it from fitting a receptor at its site of action; or binding to a receptor to pre¬ vent the poison’s binding there, blocking its action. Some poisons are not active until converted to a different form in the body; their antidotes inter¬ rupt that conversion.
Antietam \an-'te-t3m. Battle of (Sept. 17, 1862) Decisive and bloody battle of the American Civil War that halted the Confederate advance on Maryland. Following victory in the Second Battle of Bull Run, Gen. Rob¬ ert E. Lee moved his troops into Maryland with an eye to capturing Wash¬ ington, D.C. They were stopped by Union troops under George B. McClellan at Antietam Creek, Md. Confederate casualties numbered some 13,700, and Union losses were about 12,400. McClellan was criticized for allowing Lee’s forces to retreat to Virginia, but the victory encour¬ aged Pres. Abraham Lincoln to issue a preliminary Emancipation Procla¬ mation.
antifreeze Any substance that lowers the freezing point of water, pro¬ tecting a system from the ill effects of ice formation. Antifreezes such as ethylene glycol or propylene glycol commonly added to water in automo¬ bile cooling systems prevent damage to radiators. Additives to prevent freezing of water in gasoline (e.g., Drygas) usually contain methanol or isopropanol. Organisms that must survive freezing temperatures use vari¬ ous chemicals to inhibit ice crystal formation in their cells and tissues: glycerol or dimethyl sulfoxide in insects, glycerol or trehalose in other inver¬ tebrates (nematodes, rotifers), and proteins in Antarctic fishes.
antigen Van-ti-jsnN Foreign substance in the body that induces an immune response. The antigen stimulates lymphocytes to produce antibod¬ ies or to attack the antigen directly (see antibody;immunity). Virtually any large foreign molecule can act as an antigen, including those of bacteria, viruses, parasites, foods, venoms, blood components, and cells and tis¬ sues of various species, including other humans. Sites on the antigen’s surface fit and bind to receptor molecules on the lymphocytes’ surface, stimulating the latter to multiply and initiate an immune response that neutralizes or destroys the antigen.
Antigone \an-'ti-g9-ne\ In Greek legend, the daughter born of the inces¬ tuous relationship between Oedipus and his mother, Jocasta. After Oedi¬ pus had blinded himself in self-punishment, Antigone and her sister Ismene served as his guides, following him into exile. When he died, Antigone returned to Thebes, where her brothers Eteocles and Polyneices were at war. Both were killed, and Creon, the new king, declared that because Polyneices was a traitor, his corpse should remain unburied. Unwilling to let the body be defiled, Antigone buried him; when Creon condemned her to death, she hanged herself. Her story was dramatized by Sophocles and Euripides (in Euripides’ version she escapes and joins her beloved, Haemon).
© 2006 Encyclopaedia Britannica, Inc.
Antigonid dynasty ► antinovel I 83
Antigonid dynasty (306-168) Ruling house of ancient Macedonia. Antigonus I was proclaimed king in 306 bc after his son Demetrius con¬ quered Cyprus, thus giving his father control of the Aegean, the eastern Mediterranean, and most of the Middle East. Under Demetrius II (r. 239- 229 bc), Macedonia was weakened by war with the Greek Achaean and Aetolian leagues. Antigonus III (d. 221) reestablished the Hellenic Alli¬ ance, restoring Macedonia to a strong position in Greece. Under Philip V, Macedonia first clashed with Rome, in 215. Philip’s defeat upset the old balance of power, and Rome became the decisive force in the eastern Mediterranean. The defeat of his successor, Perseus, at Pydna in 168 bc marked the end of the dynasty.
Antigonus I Monophthalmus \an- , tig-3-n9s...- I man-3f- , thal-m9s\ or Antigonus I Cyclops Latin "One-Eyed" (b. 382—d. 301 bc,
Phrygia, Asia Minor) Founder of the Macedonian dynasty of the Anti- gonids. He served as a general under Alexander the Great. From the plots, alliances, and wars among Alexander’s successors, he emerged in control of Asia Minor and Syria, though he soon relinquished the lands east of the Euphrates to Seleucus I Nicator. In 307 his son Demetrius I ousted the governor of Athens and conquered Cyprus, giving Antigonus control of the eastern Mediterranean, the Aegean, and Asia Minor. In 306 he was proclaimed king of the empire by the assembled army. In 302 he and his son renewed the Panhellenic League (consisting of all the Hellenic states except Sparta, Messenia, and Thessaly), in order to ensure peace in Hel¬ las and protect Antigonus. His dreams of taking Macedonia itself and Alexander’s entire former empire died with him at the Battle of Ipsus (301), the only battle he ever lost.
Antigonus II Gonatas \'gan-ot-3s\ (b. c. 320—d. 239 bc) King of Macedonia (276-239 bc). The son of Demetrius I Poliorcetes, he defeated the Gauls in Greece (279) and in Asia Minor (277), occupied key cities, and made alliances. He defeated Pyrrhus of Epirus in Greece (272) to solidify his control in Macedonia. In the Chremonidean War (267-261), he achieved lasting victory over Egypt, Sparta, and Athens. He allied with the Aetolian League and local tyrants to stave off incursions of the Achaean League. His defeat of the Egyptian fleet at Andros (244?) assured Mace¬ donian hegemony in the Aegean.
Antigua and Barbuda \an- , t9-g3...bar- , byu-do\ Island country, Lesser Antilles, Caribbean Sea. It consists of three islands: Antigua, Bar¬ buda, and Redonda. Area: 171 sq mi (442 sq km). Population (2005 est.): 77,800. Capitaclass="underline" St. John's (on Antigua). The majority of the population are descendants of African slaves brought in during colonial times. Lan¬ guage: English (official). Religion: Christianity (mostly Protestant; also Roman Catholic). Currency: Eastern Caribbean dollar. The largest of the islands is Antigua (108 sq mi [280 sq km]), which lacks forests, moun¬ tains, and rivers and is subject to droughts. The main anchorage is the deepwater harbour of St. John’s. Barbuda—25 mi (40 km) north of Anti¬ gua, 62 sq mi (161 sq km) in area, and mostly uninhabited—is home to a large bird sanctuary; its only human settlement is Codrington, on the western coast. Redonda, an uninhabited rock (0.5 sq mi [1.3 sq km]), lies southwest of Antigua. Tourism is the mainstay of the country’s economy; offshore banking is growing. Christopher Columbus visited Antigua in 1493 and named it after a church in Sevilla, Spain. It was colonized by English settlers in 1632, who imported African slaves to grow tobacco and sug¬ arcane. Barbuda was colonized by the English in 1678. In 1834 the islands’ slaves were emancipated. Antigua (with Barbuda) was part of the British colony of the Leeward Islands from 1871 until that colony was defederated in 1956. The islands achieved full independence in 1981. See map opposite.
antihistamine V.an-ti-'his-to-.men, .an-ti-'his-to-monV Synthetic drug that counteracts the effects of released histamine in the body. Antihista¬ mines compete with histamine at one of the three types of histamine receptors, preventing allergic attacks (see allergy) or inflammation. Some antihistamines also prevent motion sickness and vertigo. Drowsiness is a frequent side effect. H 2 antihistamines, which bind to the second recep¬ tor type, are used to control gastric-acid secretion (see stomach) and treat PEPTIC ULCERS.
Antilles \an-'til-ez. Greater and Lesser Two groups of islands in the West Indies, bounding the Caribbean Sea on the north and east, respec¬ tively. The Greater Antilles include the largest islands (Cuba, Jamaica, Hispaniola, and Puerto Rico), the Lesser Antilles all being much smaller. The name Antilia originally referred to semimythical lands located some¬ where west of Europe across the Atlantic. After Christopher Columbus’s