Psycho-Babble Medication | about biological treatments | Framed
This thread | Show all | Post follow-up | Start new thread | List of forums | Search | FAQ

Re: Hmmm: my two cents worth

Posted by Sean on November 10, 1999, at 11:46:08

In reply to Re: Hmmm: my two cents worth, posted by Adam on November 10, 1999, at 0:26:56

> >
> > But hey, I'm talking out my ass...
> >
> I guess that never stopped me :).
> I've been thinking more about the implications of increased neural stem cell proliferation
> rates, and the implications could be disturbing.
> Since we're all speculating wildly (as the investigators mentioned above clearly are) here's
> another thing I thought of...
> Stem cells exist all over the body. The paradigm is the hematopoietic stem cell that exists in
> the bone marrow, and neural stem cells from adult tissues have been grown in culture since the
> mid-90s. The first real evidence of a specific stem cell type doing its job in situ was reported
> in the journal Cell last January. They showed that ependymal cells (cells that line the
> ventricals) could divide and give rise to both neurons and glial cells (specifially astrocytes).
> These cells can migrate in response to signals both known and unknown and find their way to where
> they are needed (to form scar tissue in a spinal cord injury, for example, or replenish neurons
> in the olfactory bulb).
> All stem cells have the quality of being "multipotent": they divide and give rise to two new cells.
> One is another stem cell like itself, and the other is a cell that will terminally differentiate
> into a specific cell type. By "terminally differentiated" I mean that even if the cell can divide
> further, it will give rise only to cells just like itself. Neurons are "quiescent"; as far as we
> know, they don't divide at all.
> Stem cells keep dividing as long as they last. Now, all somatic cells (non-germ cells), including
> stem cells, can only divide so many times. All chromosomes in cells contain repetitive, GC-rich
> sequences of DNA stuck on on the ends of the molecule called telomeres. Telomeres are synthesised
> normally in somatic cells only during embryogenesis. Then enzyme that synthesizes them (telomerase)
> isn't active in somatic cells beyond this point. The telomeres function to keep the chromosome
> intact-they provide a sort of glue at the end that prevents it from unravelling and undergoing
> catastrophic rearrangements. The trouble is, every time a cell divides, it loses a bit of the telomere.
> Eventually, the telomere reaches a certain length, which is sensed by the cell. When the cell
> reaches this point, it commits suicide. This is an evolutionary consequence of aging. Every cell
> has this built-in clock, and it leads to death unless telomerase is active (only in germ cells and
> cancerous cells, which are immortal).
> If my understanding of neural stem cells is correct, they divide when needed to give rise to cells
> that go where they're needed (just like hematopoietic stem cells). It could very well be that the
> aging brain starts to decay because our complement of stem cells decreases (as it does in all tissues)
> as time passes and cells reach the end of their life span. This will happen sooner or later depending
> in part on how many times the cell has divided at a given time. If this rate of division is sped up,
> what could this mean? One possibility (and a scary one at that) is that, like the candle burning
> twice as bright half as long, you run out of neural stem cells earlier than you would have otherwise.
> While it's true you may have a few more neurons than the average person when you reach that point,
> if you have fewer stem cells later in life, you might not get the new growth that you need when and
> where you need it. If what these guys are saying about Prozac is true, I see this as a distincly
> possible scenerio, at least as possible as their functional association with antidepressant effect.
> It also could be true of any drug that boosts serotonin levels, if serotonin is in some way the trigger
> of a growth signal. This signal could just be mimicking stress (such as injury), and that's why these
> cells are dividing 60-some-odd% more.
> Kind of creepy, if you ask me.

I think you're right about the telomerase thing.
Basically it's the Hayflick limit being reached
prematurely right?

It is spooky, but not as spooky as killing




Post a new follow-up

Your message only Include above post

Notify the administrators

They will then review this post with the posting guidelines in mind.

To contact them about something other than this post, please use this form instead.


Start a new thread

Google www
Search options and examples
[amazon] for

This thread | Show all | Post follow-up | Start new thread | FAQ
Psycho-Babble Medication | Framed

poster:Sean thread:14806