The word "xenotransplant" generally brings to mind the transplantation of whole animal organs into humans. But the use of cells may be at least as important.

The latest example is Diacrin Inc.'s Phase I trial of fetal pig brain cells in the brains of patients with intractable epilepsy. If it works, the therapy could prove highly attractive, as the only other therapy for these patients is lobectomy, which removes the portion of the brain in which the seizures are seated.