TOKYO -- The Japanese government on Monday criticized the ethics of a researcher at a Tokyo university who combined a human cell with a cow's egg -- a procedure officials said was too similar to cloning.
Setsuo Iwasaki, professor at the Tokyo University of Agriculture who carried out the research, defended it as unrelated to cloning and merely aimed at studying leukemia blood cells. He warned that Japan would fall behind the United States and other Western nations in basic research on cells.
The controversy, set off by an article on the research in Monday's Yomiuri newspaper, underlines the government's extreme sensitivity to cloning.
The government is studying a law to ban human cloning in Japan. It has already instructed all universities to refrain from research linked to human cloning, Education Ministry official Akifumi Suzuki said.
Gray areas like Iwasaki's research that fused a human blood cell with a cow's egg -- although unlikely to immediately lead to a human clone -- must be approved by the ministry, Suzuki said.
The professor said he used the cow's egg and human blood cell because he wanted to study cell division as part of his work on leukemia. Iwasaki said he knew he could not use exclusively human cells because of the criticism he would face.
"People are very nervous about human cloning and cloning research," he said. "We find this troubling."
Animals can be cloned by fusing a cell from an adult with an egg, allowing the altered egg to divide several times, then putting the cell mass inside a carrier mother's womb until birth.
Scientists in various countries -- including Japan -- have been cloning livestock since the birth in 1996 of the sheep Dolly, the first animal to be cloned from an adult mammal.
Iwasaki said he carried out his experiment to find out the structure of blood cells in leukemia. He stressed he was not trying to produce clones or grow cells. When fused with the cow's egg, the blood cell divided three times and then stopped.
But he admitted he discontinued his research a year ago because he feared it might be misunderstood and criticized.
"The government is stifling research," Iwasaki said in a telephone interview. "If you take that view, you can't do anything."
Yukio Tsunoda, a professor at Kinki University in Nara, who has cloned cows, was outraged by Iwasaki's study.
"We must keep our promise to society in research that has great social impact. We have a social responsibility," Tsunoda said, adding that many cloned cows are born with defects or simply die.
The Yomiuri also criticized Iwasaki's study.
"Research like this that involves manipulation of life requires extreme caution," it said.