AT APPROXIMATELY 0400 HOURS E.D.T. PAN AMERICAN FLIGHT #201 FROM NEW YORK TO RIO DE JANEIRO ENCOUNTERED TURBULENCE AT FLIGHT LEVEL 370 IN THE VICINITY OF GEORGETOWN, GUYANA. SEVERAL PASSENGERS AT ROW 50 RECEIVED INJURIES. THE FASTEN SEAT BELT SIGN WAS ON AT THE TIME AND THE CAPTAIN HAD ANNOUNCED THE ILLUMINATION OF THE SIGN OVER THE PA SYSTEM.