31.   The spread of sex-change chemicals in the environment could soon be tracked with a test that uses tadpoles and liver cells of frogs.

32.   The toxins in turn destroy liver cells.

33.   The solution is then checked for vitellogenin-mRNA, the first in a series of compounds produced after an estrogen receptor in a liver cell has been activated.

34.   The virus kills liver cells, which are then replaced by scar tissue.

35.   They work by inhibiting an enzyme called HMG CoA reductase that is necessary for cholesterol production, resulting in a cholesterol deficit within liver cells.

36.   This signal is recognized only by liver cells, so that Factor IX is made only in the liver.

37.   This signal is recognized only by liver cells, so that Factor IX gets made only in the liver.

38.   Weeklong experiments so far indicate that the hepatocytes are acting like normal liver cells.

39.   When the scaffold melts away, patients would be left with a functioning mass of liver cells fed by its own blood supply.

40.   Peterson said research using the lab rats proves the bone marrow is the source of these new liver cells.