http://dailynews.yahoo.com/headlines/hl/story.html?s=v/nm/19980903/hl/nerv11_1.html
Growth factors may repair nerve damage
NEW YORK, Sep 03, 1998 (Reuters) -- Researchers have discovered that the
same nerve growth factors that cause the tips of regenerating nerves to
turn away from each other can be manipulated so that the nerves attract
other growing nerve tips. The findings uncover a ``new therapeutic
approach to treating nerve cell injury,'' according to Dr.
Mu-ming Poo of the University of California at San Diego and colleagues
writing in the journal Science. The findings
``may have implications for repairing nerve damage,'' according to a
statement issued by the journal.
Nerves in the central nervous system are covered with a myelin sheath,
similar conceptually to the insulating coating applied to electrical
wires. Although these sheaths are essential to the efficient
transmission of nervous impulses throughout the body, they are also the
``main cause of lack of regeneration in the nervous system,'' Poo told
Reuters Health.
He and colleagues in California and Canada explain in their report that
two myelin-associated factors -- Collapsin-1/Semaphorin III/D and
myelin-associated protein -- stimulate the repulsion of neuronal growth,
causing growth cones at the ends of regenerating spinal neurons to turn
away.
But these same factors that are repulsive during nerve growth can be
converted to attractive factors by cyclic nucleotides, Poo and his team
found. By manipulating the levels of two compounds called cyclic
nucleotides -- guanosine 3',5'-monophosphate (cGMP) and adenosine
3',5'-monophosphate (cAMP) -- the scientists were able to
manipulate the direction of growth of frog spinal neurons growing in
culture dishes.
The findings add a new concept to the understanding of the biology of
nervous system development, Poo said in an interview. They also suggest
a new approach to the treatment of nerve injury through the local
application of drugs containing nucleotide analogs to the sight of
injury.
``The next step is to do animal model experiments to show that this
actually works,'' Poo told Reuters Health. ``Then we might apply this in
humans.''
In an editorial, Dr. Pico Caroni of the Friedrich Miescher Institute in
Basel, Switzerland, speculates that similar ''switch'' mechanisms may be
involved in other types of nerve growth, both during the development of
the nerve system and later in response to nerve injury.
``Clearly, the most exciting possibility raised by these findings is
that the inhibitory signals that prevent nerve regeneration in the adult
central nervous system could be attenuated by pharmacological
interventions... thus promoting their regeneration,'' he writes.
SOURCE: Science 1998;281:1465-1466, 1515-1518.
--
Judith Richards, London, Ontario, Canada
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