21.   This step, for some unknown reason, has so far proved impossible for biologists who have followed the same trail with mouse cells.

22.   To confirm that the mouse cells were cleared of prions, the researchers stopped treatment to see what would happen.

23.   To grow the lines in Petri dishes, scientists have nourished them with mouse cells that have been killed with radiation.

24.   Also, many of those cell lines were cultured with the help of irradiated mouse cells.

25.   Blau is confident the adult mouse bone marrow cells did convert into brain cells.

26.   Both drugs have shown promise in mouse cells infected with prions, abnormally shaped proteins that cause variants of Creutzfeldt-Jakob disease.

27.   But the idea of introducing mouse cells into a human body did not appeal to many.

28.   But the new work is an advance because researchers developed a line of mouse cells that is far more useful for genetic testing, Vogelstein said.

29.   Human embryonic stem cells are nurtured in lab dishes with the help of irradiated mouse feeder cells.

30.   In addition, human embryonic stem cells are nurtured in lab dishes with the help of irradiated mouse feeder cells.