April 21, 1989

LEAD: FROM mousy beginnings 27 years ago in a walk-up on West 53d Street, the Museum of American Folk Art has finally achieved a place in the glitzy world of big-league museums. Not only is it planning a $40 million headquarters, to be opened on West 53d Street in 1992, but also, as a kind of preview of coming attractions, it has just opened an elegant ''branch'' on boutique-y Columbus Avenue, at 65th Street, a storefront space where a respectable slice of its collection is handsomely displayed.

LEAD: A new test is highly effective in detecting a type of viral hepatitis that is the last major threat to blood supplies, medical researchers report.

LEAD: Raising hopes that the United States can become a major player in the next generation of television technology, researchers at the David Sarnoff Research Center here today demonstrated the world's first broadcast system for high-definition television that is compatible with existing sets.

LEAD: One of New York's most powerful judges appeared before the State Commission on Judicial Conduct yesterday to defend himself against charges that he had improperly interfered in disciplinary proceedings against prominent lawyers.

LEAD: To people like Cookie, who describes herself as a housewife who shot heroin, the new AIDS nursing unit at the Terence Cardinal Cooke Health Care Center - the first hospital in New York City to open a comprehensive-care ward for AIDS patients - is a place where the dying can try to make a better life day by day ''For what we go through, we truly earn our lives,'' said Cookie, who is 37 years old, the mother of a 7-year-old son and the widow of a man who had a penchant for prostitutes.