Naum Gabo, 86, the Russian-born Constructivist whose open and transparent sculptures changed the course of modern art, died Tuesday of cancer in Waterbury, Conn.

Other sculptors of his age cast or carbed opaque materials marble, wood or bronze). They thought in terms of mass. Gabo saw, instead, that space could be employes "as a material by itself." He opened up his airy, delicate constructions to emptiness and air. From the start he preferred using new industrial materials - steel wire, nylon thread and clear sheets of plastic. One of the first KInecticists, he also used concealed motors so that his sculptures moved.

Gabo was born Naum Neemia Pevsner in Briansk, Russia. Because his brother, Antoine Pevsner, was a sculptur also, Gabo changed his name when he was 25.

He studied medicine in Munich before turning to art history, which he studied there with Heinrich Wolffin, one of the most important art historians of the time.

Though both Pevsner brothers spent World War I in Norway, they later returned to Moscow to join the revolution that changed the history of Russia - and of abstract art. Like other Russian COnstructivists, they dreamed of a new art, honest, abstract, pure. But where some of their colleagues (Tatlin, Rodchenko, and to some extent, Lissitzky) felt the artist must become a technician-engineer in service to the massed, the Pevsners (and Malevich) called, instead, for art of spirtual significance.

That did not please the commissars."The government hated our art," wrote Gabo, "and one day the work-shops which had been gives to our group were suddenly closed.

Gabo then spent 20 years traveling through Europe. He first moved to Berlin. He lectured at the Bauhaus in 1928. In 1926, Gabo designed sets for Sergei Diaghilev's Ballets Russe. He moved from Germany to France in 1932, and then on to London where he edited an avant garde magazine, "Circle," with the painter Ben Nicholason and the critic Herbert Read.

Gabo, who first visited the United States in 1937, emigrated to this country in 1946 and took U.S. citizenship in 1952. The next year he was named a professor at Harvard University's Graduate School of Architecture.

Gabo's sculptures have not dated. They are unpretentious, clean, and they have been imitated often (most younger artists who employ plexiglas and wire are in Gabo's debt.)

Gabo, who was given an honorary knighthood by Queen Elizabeth II in 1971, has given many of his works to the Tate Gallery in London. His sculptures are on view here both at the Philips Collection and the Hirshhorn Museum and Sculpture Garden.

He is survived by his wife, the former Miriam Israels, and a daughter, Nina.