11.   Interference in the cell-death process lets damaged cells replicate out of control into cancer tumors.

12.   It cleans up damaged cells and toxic chemicals.

13.   It is then left to another group of specialised cells called fibroblasts to repair the damaged cells and tissues.

14.   It scavenges free radicals, the destabilizing byproducts of oxygen metabolism that also seem to multiply in damaged cells.

15.   Scientists believe they can help these cells to grow into tissues that can replace damaged cells and organs.

16.   Some scientists believe they can prod these cells to grow into tissues that can replace damaged cells and organs.

17.   The central nervous system, which includes the brain and the spinal cord, has erected a biochemical barrier against the agents that repair damaged cells.

18.   Damaged endothelial cells can lead to increased susceptibility to atherosclerosis, which can lead to heart attacks and heart disease.