Neurogenesis

Bernard Marx Bernard at neuro.net
Wed Jan 5 03:11:09 EST 2000


In Spain some scientifics at Valencia University said they met the cells
involved in the adult neurogenesis. They are located in hippocampus. These
cells are said to be gial cells, the same as in embryological neurogenesis.

Brian Scott <brians at interlog.com> escribió en el mensaje de noticias
3872F8E5.2D1C73 at interlog.com...
>
> JoshCahoon wrote:
> >
> > I'd like to get a feel for this controversy. Various publications,
including
> > the NYT today, say that findings indicating neurogenesis in humans have
long
> > been resisted by the neuroscientific community, being contrary to dogma.
On the
> > other hand, my professor at the Salk told me their really isn't a
controversy.
> > Is there? Perhaps just over whether new neurons are functional?
>
>
> Neurogenesis in adult animals had been reported as far back as 30 years
> ago by Joseph Altman and others, but until fairly recently the study of
> adult neurogenesis has been pretty slow.  In the last few years though
> things have really exploded.  The evidence for adult neurogenesis is
> pretty solid in rodents and birds, and there are lots of examples now in
> primates and many other mammals.  Some of the early primate work failed
> to find convincing evidence of adult neurogenesis.  Since this work was
> produced by a big guy (Rakic) in the anatomy field, it was generally
> believed that primates were the exception.  Recent work by Gould and
> Gage's people as well as Rakic have now demonstrated adult neurogenesis
> in several primate species.  It had been said that the production of new
> neurons in adulthood would disrupt existing circuitry and therefore
> memory, and this is why neurogenesis in higher animals stops after
> development.  [Elizabeth Gould is now suggesting that adult neurogenesis
> may actually be important for certain types of memory.]
>
> Kempermann and Gage used essentially the same techniques from the animal
> work to show neurogenesis in the hippocampus of adult cancer patients
> ranging in age from 30s to 70s I think.  It's pretty convincing to me
> but there are still criticisms with respect to the BrdU technique and
> whether it's really labelling new cells.  It's the same criticism of the
> technique since it was invented. Maybe the BrdU is being incorporated
> into dying or injured cells that manage to survive. Some have said that
> maybe this (neurogenesis) is just a phenomenon associated with cancer or
> its treatment.  There's at least one paper I know of since then that
> looked for a marker of cell division in tissue taken from epileptics
> that claimed there was no evidence of a subgranular proliferative
> zone...where the neurogenesis is supposed to occur.  I don't think his
> technique was sensitive enough though.  Anyway, besides the hippocampus
> there's also evidence for neural stem cells which may be generating
> neurons around the ventricles.  I'm less familiar with this though.
> Gould recently reported neurogenesis originating around the ventricles
> and sending neurons to the association cortex of monkeys.  Maybe this is
> happening in humans too.
>
> With respect to the functionality of these cells, they look like the
> other cells nearby and send projections to the same targets and express
> the same marker proteins.  There is evidence of synapses on them too.
> Until someone can actually patch-clamp from a cell which was definately
> born in adulthood, there will always be those that question whether they
> are functional or not.  In animals, their production is very tightly
> regulated by adrenal hormones and probably by input to the dentate
> gyrus.  It's very likely they're being used for something.
>
> --
> Brian Scott           |     Institute of Medical Science &
> brians at interlog.com   |  Bloorview Epilepsy Research Programme
>                       |        University of Toronto
>                       |           Toronto, Canada






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