This episode's headline: Toughest Opponent; Coming Apart; Circle of Life. The guests include MATHILDE KRIME, American Foundation For AIDS Research; DR. REED TUCKSON, Charles Drew University of Medicine; Kathleen Sullivan, Abstinence Education Advocate; LAWRENCE EAGLEBURGER, Deputy, Secretary of State; CORRESPONDENTS: JEFFREY KAYE; ANNE TAYLOR FLEMING. Byline: In New York: ROBERT MacNeil; In Washington: JAMES LEHRER