LEON KASS ON AIR. Professor Milton Rosenberg of the University of Chicago hosts the Extension 720 talk show, 2100-2300 Central Standard Time, on WGN radio, Chicago. Monday's guest is his colleague, Professor Leon Kass, and the topic of conversation will be Kass's new book, Life, Liberty, and the Defense of Dignity: The Challenge for Bioethics. Listeners in most of the United States will be able to pick up this show on the AM band, 720 kHz, or listen online. Professor Rosenberg takes some emails from listeners, particularly listeners at a distance, as well as a few carefully-screened calls.