61.   This is because chemotherapy is toxic to healthy cells as well as cancerous ones.

62.   Thurmond said he shared the belief of many scientists that embryonic stem cells could produce a supply of healthy cells to replace damaged tissue.

63.   Using gene chips, researchers can compare samples of healthy cells against samples of sick cells to discern which genes are off key.

64.   While turning off telomerase could control the uncontrolled replication of cells in cancer, cloning telomerase could also lead to ways of synthesizing the enzyme in healthy cells.

65.   Attacking only telomerase, however, said Harley, can focus specifically and directly on cancer cells alone, leaving healthy cells unaffected.

66.   Besides exposing the HIV for destruction, he said, the drug seems to prevent the AIDS virus from entering healthy cells.

67.   He said the proteasome function is essential for healthy cells, and a drug that blocks that function could affect every cell in the body.

68.   In a laboratory experiment on mice, researchers have shown that a genetically altered herpes virus can knock out brain cancer cells without affecting healthy cells.

69.   In a healthy cell, the gene produces a protein that helps signal cells to grow normally and multiply.

70.   In serious cases, it can attack the DNA and proteins in the healthy cells of kidneys and other vital organs.