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Rodney · 04-02-2004, 09:54 AM

Well, glomming together info from a dozen hazily-remembered newspaper articles...

There are at least two factors (at _least_) at work here. One that scientists are pretty sure of is genetic damage, caused both by the environment and by the cell copying mechanism (y'know, like making a xerox of a xerox; the next copy just isn't as good). The human cellular mechanism for copying itself is pretty good at error checking, which is why we leave 70+ years instead of 10-15 for most dogs and cats. But it's not perfect. Over time, the genes in more and more cells get degraded enough that they work imperfectly, stop serving a useful purpose but don't exactly die (called "senecscent cells," which is like calling thems senile), or go wrong in a spectacularly bad way (cancer). All of which causes bodily system to lose efficiency and fail, eventually causing death.

Now there are some people in the world, particularly Okinawa for some reason, who have really, really good cellular repair systems. There's one guy in particular whose genes are as undamaged as most people's are at 20. And except for having really terrible skin (sun damage, moles), he's built like a fit 25-year-old. He's a diver -- one of those fishermen who keep nets and traps under the water, and dive down 30-40 feet to load and unload them _without tanks_. He does this every day, even now.

But he's still going to die within 40 years or so because of each cell's built-in suicide switch, the telomeres.

The DNA molecule which holds the genes itself is described as a double helix: two "ropes" of genes wrapped around each other and attached to one another at matching genes. The ends of these ropes (which don't hold functioning genes) are called the telomeres. They're literally the shoelaces of the DNA. The telomeres of each strand loop around each other in a sort of knot and hold the DNA together.

Each time the DNA replicates itself in cell division, it loses a little bit off the end of each telomere. When the telomeres become too short to form the knot during cell replication, the cell commits suicide. I'm not sure why, and I'm not sure if anybody is. But at any rate, in human beings this usually happens after 50-55 cell replications. And since cells generally replicate themselves approximately every two years, that's why practically no one lives past 120, and not past much that ever.

Some people have done experiments in which they were able to extend the telomeres of genes in animal cells and keep them going on past the usual number of replications for that creature. So I suppose it'd be possible, at some point in the medium to distant future, to renew everybody's telomeres.

Like I said, these are two factors that people think account for aging and death. Who wants to bet there are many more?

04-02-2004, 09:54 AM	#4 (permalink)
Rodney Observant Ruminant Location: Rich Wannabe Hippie Town	Well, glomming together info from a dozen hazily-remembered newspaper articles... There are at least two factors (at _least_) at work here. One that scientists are pretty sure of is genetic damage, caused both by the environment and by the cell copying mechanism (y'know, like making a xerox of a xerox; the next copy just isn't as good). The human cellular mechanism for copying itself is pretty good at error checking, which is why we leave 70+ years instead of 10-15 for most dogs and cats. But it's not perfect. Over time, the genes in more and more cells get degraded enough that they work imperfectly, stop serving a useful purpose but don't exactly die (called "senecscent cells," which is like calling thems senile), or go wrong in a spectacularly bad way (cancer). All of which causes bodily system to lose efficiency and fail, eventually causing death. Now there are some people in the world, particularly Okinawa for some reason, who have really, really good cellular repair systems. There's one guy in particular whose genes are as undamaged as most people's are at 20. And except for having really terrible skin (sun damage, moles), he's built like a fit 25-year-old. He's a diver -- one of those fishermen who keep nets and traps under the water, and dive down 30-40 feet to load and unload them _without tanks_. He does this every day, even now. But he's still going to die within 40 years or so because of each cell's built-in suicide switch, the telomeres. The DNA molecule which holds the genes itself is described as a double helix: two "ropes" of genes wrapped around each other and attached to one another at matching genes. The ends of these ropes (which don't hold functioning genes) are called the telomeres. They're literally the shoelaces of the DNA. The telomeres of each strand loop around each other in a sort of knot and hold the DNA together. Each time the DNA replicates itself in cell division, it loses a little bit off the end of each telomere. When the telomeres become too short to form the knot during cell replication, the cell commits suicide. I'm not sure why, and I'm not sure if anybody is. But at any rate, in human beings this usually happens after 50-55 cell replications. And since cells generally replicate themselves approximately every two years, that's why practically no one lives past 120, and not past much that ever. Some people have done experiments in which they were able to extend the telomeres of genes in animal cells and keep them going on past the usual number of replications for that creature. So I suppose it'd be possible, at some point in the medium to distant future, to renew everybody's telomeres. Like I said, these are two factors that people think account for aging and death. Who wants to bet there are many more?