Neurogenesis

kenneth Collins kpaulc at earthlink.net
Wed Jan 5 16:31:01 EST 2000


kenneth Collins wrote:
> 
> hi Brian, Thank You for posting this excellent 'review'.
> 
> i hope my comments, below, will be received as adding 'light'.
> 
> Brian Scott wrote:
> 
> >[...]
> 
> > 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
> 
> with respect to which (and probably with respect to all of the Genesis
> of the current neural-genesis work), Fernando Nottebahm Deserves the
> =main= credit. in the face of what was, Nottebahm's efforts were
> Truly-Heroic.
> 
> >, 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.]
> 
> the question of 'disruption' is only correlated with 'transplant'
> methodologies.
> 
> neural genesis is =Necessarily= governed by the same mechanisms that
> govern all non-neural-genesis trophic dynamics, so, except in instances
> of organic damage (disease & mechanical lesions) it's flat-out
> impossible for neural genesis to 'disrupt' anything.

while out on a job hunt this morning, i stopped into a good Library and
read a bit.

one of the things i skimmed was "Functional integration of neural grafts
in Parkinson's Disease", by R. A. Barker and S. B. Dunnett, _Nature
Neuroscience_, vol 2, no. 12, Dec, 1999, p 1047.

this article discusses how it's been confirmed that, in one case, 10
years after grafting of aborted-fetal tissue, the grafted tissue does
possess synaptic functionality.

the tissue was transplanted unilaterally into one basal 'ganglion'.
since, as is discussed in AoK, Ap5, the basal ganglia are a supersystem
configuration mechanism, transplant into them is correlated to the
dynamics of supersystem configuration.

it would be interesting to know, in detail, about pre-transplant and
post-transplant "memory" retrieval, and post-transplant functionality
'ramping', if any.

because the basal ganglia are supersystem configuration mechanisms,
which function in accord with global TD E/I-minimization, NDT holds that
there should've been an observable 'ramping-up' to TD E/I-minimized
supersystem configurations, as what was intact within the supersystem
(AoK's term for the collection of 'systems' that is the nervous system)
exerted its 'biological mass' (AoK, Ap5) upon basal ganglia neural
activation 'states'.

such would gradually bring the transplanted tissue's functioning 'up to
speed' relative to organically-'normal' (non-operated) tissue, as the
'normal' 'state' is converged upon ('replicated'), as is discussed in
AoK, Ap9.

i'll comment further, if i've anything to add, after a thorough reading
of the paper.

K. P. Collins

> 
> >
> > 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.
> 
> differentiation with respect to disease processes is one of those
> Necessary things.
> 
> cheers, Brian, ken (K. P. Collins)
> 
> >  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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