NBC has become manager of health and medical programming provider American Medical Television, which also has through a separate deal become a major shareholder in Pyramed Networks Inc., the Physicians Interactive Network.The first arrangement increases NBC’s interest in American Medical TV — a partnership of the network, the American Medical Assn., “Home” show’s Dr. Art Ulene and Orbis Broadcast Group — and provides the network with daily management of the venture, with the AMA remaining a programming resource. Pyramed, meanwhile, picks up the resources of Lifetime Medical TV, a weekly service that was recently discontinued by Lifetime partners ABC, Hearst and Viacom. That service is scheduled to launch early next year. AMT will be supervised through NBC Cable, with AMT prez Wendy Borow now reporting to NBC officials. The service is currently cablecast by NBC’s cable subsidiary, CNBC, on Saturdays and Sundays from 10 a.m. to 3 p.m. Plans for AMT include expanding its activity in CD-ROM and interactive programming as well as the production of specials on health-policy issues, with a program already under way examining the Clinton administration’s overhaul of the health-care system.