Kenzaburo Oe, a Nobel laureate whose intense novels and defiant politics challenged a modern Japanese culture that he found morally vacant and dangerously tilted toward the same mind-set that led to catastrophe in World War II, died on March 3. He was 88. His publisher, Kodansha, announced the death on Monday. It did not specify a cause or say where he had died. Mr. Oe (pronounced OH-ay) was award