This episode's headline: One Germany; Medical Mystery; Winter Wonderland. The guests include JUERGEN RUHFUS, Ambassador, West Germany; ANDREAS KABUS, East German Journalist; GEORGE McGHEE, Former U.S. Ambassador, West Germany; ROBERT HORMATS, Investment Banker; FRIEDBERT MALT, General Manager, DG Bank; CORRESPONDENT: FRED DE SAM LAZARO; ESSAYIST: JACK PERKINS. Byline: In New York: ROBERT MacNeil; In Washington: JAMES LEHRER