Scientists announced Monday they have injected mice with human embryonic brain cells in an effort to research Parkinson’s disease and other neurological disorders.

From the AP:

Researchers from the Salk Institute in San Diego injected about 100,000 human embryonic stem cells per mouse into the brains of 14-day-old rodent fetuses. The mice were born with about 0.1 percent of human cells in their heads…

Researchers are … beginning to bump up against what bioethicists call the “yuck factor.” Three top cloning researchers have applied for a patent for fusing a complete set of human DNA into animal eggs in order to manufacture human embryonic stem cells. Scientists say mixing human and animal tissue is vital to ensuring new drugs and tissue replacement therapies are safe.

The “yuck factor” may ultimately become a bigger public relations concern for stem-cell researchers than current opposition from the pro-life camp.

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