DENVER -- In research that seems to blur the line between fact and fiction, scientists have discovered it is possible to use dead sperm to create live offspring.
Such experiments are fundamentally changing the definition of "fertility." The new technology means that in some cases -- where reproduction was not possible -- healthy offspring can now be born.
According to reproductive physiologist Kazufumi Goto of Kagoshima University in Japan, his experiments have succeeded in producing live, normal calves by injecting single, dead sperm cells directly into mature eggs.
The sperm cells, purposely killed by repeated cycles of freezing and thawing, show no signs of metabolism, cannot move their whip-like tails, cannot swim, and cannot penetrate the egg. They are, as one scientist put it, dead by every definition.
The work is aimed at understanding the intimate details of fertilization and at overcoming some of nature's most formidable barriers to reproduction.
If a man's sperm is too weak, unable to swim up the reproductive tract to meet the waiting egg, for example, normal fertilization cannot occur. Or if the sperm is for some reason unable to penetrate the egg, fertilization also fails.
Mr. Goto and others have found that one solution to male infertility -- caused by weak or inactive sperm -- is to inject the DNA-laden sperm through the egg's semirigid outer shell directly into the egg's watery cytoplasm.
Scientists had already shown that sperm injected directly into the egg can work properly.
But what Mr. Goto, in collaboration with Akira Iritani at Kyoto University, have shown is that the sperm can be completely dead and still work.