The team studied the mechanisms all animal cells use to repair damage to their membranes and focused on invertebrates, which have a superior ability to regenerate nerve axons
compared to mammals.
To properly form neural circuits, developing axons
(long extensions of neurons that make the nerves) need molecules to guide them towards their target, in the same way that road signs guide us when we drive," Pierre Fabre, doctoral student in Charron's team and first co-author of the article, said.
The scientists exposed the axons
of isolated mouse neurons to nicotine, which mimics a natural chemical messenger in the brain called acetylcholine.
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Paradoxically, a surplus of oligodendrocytes early in brain development may lead to a dearth later, because if there are proportionally fewer neurons, many oligodendrocytes cannot wrap an axon
Also important are neurotrophic factors, often provided by glial cells, other axons
, and glycoproteins located throughout the brain.
On electron microscopy, distinct abnormalities were observed in the myelination of axons
with the vestibular nerves; the most common abnormalities were cleavage, splitting, and fragmentation of the myelin lamellae (figures 2, A, and 2, B).
Waxman's research has also revealed that damaged axons
can reorganize themselves and establish new sodium channels, even in areas that have been stripped of their myelin.
They are well known to stimulate axon
regeneration by making proteins that promote nerve growth either on contact, or at a distance (by secreting growth factors).
All but the smallest axons
have a special covering of a fatty substance called myelin that acts as insulation to preserve and speed these nerve signals, much like the insulating cover of an electrical cord helps preserve the transmission of electricity.
Amputating the tail boosted axon
growth and allowed axons
to penetrate regions of the skin that normally repel them.
Like most neurons in the central nervous system, those that form the bundle that connects each eye to the brain don't regrow their long, spindly axons
, which carry electrical signals, if they become injured.
The issue is a growing concern as new findings continue to show that permanent damage to axons
can take place early in MS.
The motor axons
leave the ambiguous and retrofacial nuclei, combine, and form one or two rostral roots for the vagus nerve.
Despite the success of the bridging strategies, a barrier awaits the regrowing axons
at the point where the bridges end.