Complete and utter bullshit
Posted by Thermus aquaticus on Oct 18, 2003 at 10:25
(63.189.208.91)Re: genetics and long life (Uncle Al)
Uncle Al: “At this very moment we could trivially brew up a 500-year life expectancy human.”Complete 100% crap. We can do no such thing, trivially or otherwise.
Look who’s been Googling again in an effort to convince us all that he knows more about absolutely everything. As they say, a little knowledge is a dangerous thing. These wild claims of yours are typical of many know-it-all types that you find on internet science forums who seem to think that telomerase is the universal answer to all questions regarding lifespan, aging and senescence. It’s not. There are a number of different telomerase-independent ways to immortalize cell lines (SV40 T-antigen, v-myc etc etc), and these indicate that senescence is a complex system that we do not fully understand. There is zero evidence that overexpressing telomerase in a human will create a 500 year lifespan. Unless you want to embarrass yourself further and try to offer some?
Uncle Al: “Switch on general somatic telomerase and every cell in your body can reproduce forever.”
There are varieties of cell lines that can indeed be immortalized by overexpression of telomerase. But these are in vitro experiments, not in vivo situations. Cells living in a dish don’t mind dividing indefinitely. Scientists have been culturing cancer cell lines for decades through thousands of cell divisions. However, with cells that are part of an organism, it’s a completely different story. The physiology of a human is totally dependant on cell senescence. Cells must die in order to avoid accumulating mutations. Cells must die and be replaced in order to achieve normal tissue turnover. When cells manage to avoid senescence, a disease known as “cancer” develops. Have you come across that disease in your Google searches? If every cell in a human being suddenly escaped senescence, I expect the person would die well before the current average life span.
Now, there is some in vivo evidence that telomerase-expressing cells that are transplanted into recipients can repopulate diseased organs and restore functioning of the organ in question. But we are talking about transplanting specific telomerase-overexpreesing cells into specific organs, not ubiquitous expression of telomerase in all tissues. These experiments may restore organ function but they do nothing to increase lifespan.
It is possible to extend the lifespan of various developmental model organisms (eg. DAF mutant C.elegans and various Drosophila mutants). Mice can be engineered to live longer, such as the Ames mice, p66 knockout mice and MGMT transgenic mice. The incidence of spontaneous tumors in these mice is similar to normal. However, you don’t need to genetically engineer vertebrates at all to increase lifespan. Calorie restriction is all it takes. But with all these incidences, it’s a case of deceleration of the aging process, not that the cells have escaped senescence. These observations are in agreement with an earlier established positive correlation between tumor incidence and the rate of tumor incidence increase associated with aging and the aging rate in a population. However, these experiments don’t even come close to extending lifespan >600% as you have made up off the top of your head (ie. humans living to 500 years).