Quote Originally Posted by Raistlin
Quote Originally Posted by DarkLadyNyara
...but they can be used. If you need brain cells, you get the adult stem cell which can form brain cells.
Not always. Some cells cannot be derived from adult stem cells. Do people just assume that we want to kill babies for the hell of it? 'Cause if so, theres no point in attempting intellegent debate.
Unless I'm vastly mistaken(it has been well over two years since my last biology class), ALL cells can be derived from adult stem cells(by definition), as long as you have all of the different kinds of adult stem cells.
No, not all cells can be derived from adult stem cells.

The most relevant example lies in the brain. There are two areas in the brain that continue to produce neurons during adulthood: the sub-ependymal zone (SEZ) and the sub-granular zone (SGZ). The neurons generated in the SEZ travel along the rostral migratory stream bound for the olfactory bulb where there is a modest amount of neuronal turn-over (read: there are neurons dying that need to be replaced--unlike most other areas of the brain). Those generated in the SGZ are bound for the granular zone of the hippocampus (they have a much shorter "trip" to take). There are some interesting theories out there detailing why the SGZ would need to produce more neurons, but at this point there is little empirical support for said theories.

[to summarize the bulk of them: the hippocampus has been demonstrated to be necessary for encoding new declarative memories--for an interesting case study, check out the hippocampectomy patient H.M., and it is thought that these new neurons might be needed as someone acquires more knowledge/information/mental pornographic images/etc.]


But it is important to remember that the neurons produced in these areas are not generic neurons that could simply be placed anywhere in the brain. They are intended to fill a very small subset of restricted areas in the brain. So you couldn't take some adult stem cells from the SEZ, place them in primary motor cortex, and expect them to differentiate into Betz neurons, or put them in the cerebellum and expect them to differentiate into basket neurons, and so on.

The take home message here is that neuronal adult stem cells are probably not incredibly useful throughout the brain (though this is not to say they are not at all useful, just rather restricted in meaningful application). I'm also not saying that other adult stem cells aren't useful.


If you have moral objections to using embryos as a source for embryonic stem cells, that's you're prerogative. However, don't blindly claim that adult stem cells (and you can go ahead and lump umbilical cord stem cells into this group--the only real distinction is that all other types of stem cells are pluripotent or multipotent, and NOT totipotent) are just as "useful" as ES cells (because that's just wrong, not to mention uninformed).