The Battle Against Aging/Mother Nature's Menders; The Quest to Beat Aging; Scientific American Presents; by Mike May; 6 Page(s)

In the 1970s The Six Million Dollar Man television program opened each week by showing a terrible accident that turned astronaut Steve Austin into "a man barely alive." Then we heard: "Gentlemen, we can rebuild him. We have the technology." The idea intrigued us but seemed centuries away. It's not. An explosion of work surrounding stem cells, which can differentiate into many other cell types, raises hope for medical repairs beyond our imagination-mending a damaged heart, fixing a failing liver, improving a forgetful brain and, most exciting, significantly extending life. Instead of using bionic parts, like the ones that made Steve Austin stronger and faster, this technology could provide us with longer and healthier lives by enabling us to control our natural repair mechanisms.

This emerging field takes advantage of a cell that may emerge from the moment of conception. When a sperm cell works its way into an egg during fertilization, some scientists consider the result to be a stem cell. Other researchers consider stem cells to appear after several cell divisions that turn a fertilized egg into a hollow sphere of cells called a blastocyst. That sphere includes a region called the inner cell mass, consisting of a group of stem cells. Wherever stem cells first arise, they can branch out in many directions. A stem cell holds all the information it needs to make bone, blood, brain-any part of a human body. It can also copy itself to maintain a stock of stem cells.