This episode's headline: Perils of Perestroika; On the Stump; Texas Showdown; Showdown. The guests include ABEL AGANBEGYAN, Gorbachev Adviser; PADMA DESAI, Columbia University; ED HEWETT, Brookings Institution; VICE PRESIDENT GEORGE BUSH, GOP Presidential Candidate; CORRESPONDENT: MARY ANN BOWSER. Byline: In New York: ROBERT MacNeil; In Washington: JAMES LEHRER
