h a l f b a k e r yNot so much a thought experiment as a single neuron misfire.
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shredded nerve
A different surgical cut into increase nerve to nerve contact. | |
If the nerve is analogous to a forest of trees then a fire break might be analogous to a scalpel cut. This cut would leave very little nerve on nerve contact for signally to help regrowth and scarring would seal off any rejoin capability.
I suggest a shredding of nerve lengthways to produce a frayed
rope type scenario. Then two nerve frays could then be weaved together and compressed with the opposite of a stent. Hopefully more surface area of each nerve can be brought closer together.
With the right injected feed solutions, the natural rewiring and regrowth ability may be coaxed out of the severed nerves. May be a treatment with glial cells may also help.
If this joining procedure is possible then it would open the door for the transfer of sections of living nerve.
Transfer of sections of living nerve
http://nerve.wustl...._graft_brachial.php
yes! [bungston, Sep 26 2015]
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Imagining deeper, what is needed is a cell or vessicle that sacrifices
itself to merge bridging nerve axons. |
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Inspired by that terrible The Thing horror, 2011. |
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It would be nice if the two severed ends were magnetic, like the north and south attraction. Are there two separate molecules that, with enzyme activity, could create a selective attraction of cut axon pipes? |
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So the process would be soak each shredded axon bundle in its part solution, weave, compress together and wash with linking enzyme. A growing solution, cells and brain rewiring would hopefully regrow the connection to full health. |
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I'm pretty sure the correct model of a nerve is plumbing, not
rope. There is a single correct path, and if that path isn't
rejoined, no nerve function. |
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I'm not a neurologist, but my understanding is that
when nerves are severed, the distal part (the
axon) dies - it has no cell body to sustain it. The
proximal part can (I think) grow a new axon.
Whether this new axon is helped to grow by signals
from the remains of the old axon, I'm not sure. I
am pretty sure, though, that it's not a question of
the severed axon remaking its connection. |
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With the nerve grafts in the link, they seem to be
transferring nerve bundles just to act as guides to
help regrowth of the original nerves. |
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My former boss had the nerves in his right arm
severed (in an assault). It took many months
before there was any significant nerve regrowth,
and I think a year or more to get any function
back. |
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But they reconnect the surrounding tissue so that the
regrowth occurs along the same path to make the new
connection. And any extra tension (such as from a longer
overlap from fraying the tissue) is detrimental to possible
regrowth. |
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[MechE] //model of a nerve is plumbing// True, it all comes down to scale. An active miss-matched path would still be worked by the brain and could be 'software' altered. The paramount is making and keeping paths through the cut. |
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Isn't the problem with those large nerves is the the axon is so long that regrowth can't be the same as a lifetime? Keeping those distal axon bundles alive, as long as possible, for re-linking, as quickly as possible, is probably the only way to go. |
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[wjt], the nerve that operates your big toe has its
cell body in your spine - it's a single nerve (actually a
bundle of nerves). So, if it's severed in your thigh, it
has to regrow from there; there's no cell body distal
to your spine to keep alive. |
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Human nerves regrow at rates of mm per day. Large
nerves, up to 5mm per day. Given that, a nerve running all
the way from the head to the foot (and no, there aren't any
quite that long), you're looking at a year-ish to complete
growth. So months for most cases. |
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[Max] we want to try and keep that severed axon without it's cell body active and working so no exceptional nerve growth travel is necessary. |
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[MechE] Think of the scale and complexity, of the growth path needed from the CNS. Always smarter to build with what is there. |
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if a CNS injury is in the parameters of the medical emergency then electrical stimulation (prickly foot/hand feeling) would be great to keep those orphaned axons, at risk, active and responsive to repair. |
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//we want to try and keep that severed axon
without it's cell body active and working so no
exceptional nerve growth travel is necessary.
// |
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Yes, but the point is that a severed axon can't
survive. A severed axon is not a living cell - it has
none of the machinery needed for long-term
survival. Eventually, some sort of nanosurgical
technique might, perhaps, be able to repair the
break in individual axons (and we're talking
thousands of axons in a nerve bundle), but it's way
beyond what we can do with technology as it
stands right now. |
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Interesting question. If the axon was sealed then would it act like a cell with no nucleus? Axons transport mitochondria. There is some indication that axon degradation is due to an active clean up cascade rather than it's own falling apart. |
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Bridging a CNS cut is still going to need a substantial more linking neurons than a one to one ratio because die off is paramount in training pathways. Probably why head transplants are a current no go. Not enough sacrificial neurons for rewiring. |
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// If the axon was sealed then would it act like a
cell
with no nucleus?// |
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Probably yes, i.e. it would die. With no nucleus,
it's
only going to continue making proteins until its
current stock of mRNA has degraded. This would
be
anywhere from minutes to hours depending on the
mRNA in question. After that, no new proteins,
and
protein turnover will quickly lead to cell death. |
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(And yes, mammalian red blood cells have no
nuclei but survive for 3 or 4 months. But they
don't
do much, and have specifically evolved to not
require protein turnover.) |
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Brings out data on starvation cell dynamics, doesn't it, an axon rupture. Probably bleeding to death is like starvation, though time relative. |
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I wonder how long it will be before computation will simulate cellular environment such that the nucleus environment opens different sections of DNA with initiation sections, ready for transcription?
Being able to co-op one of the glial /auxiliary cells as a surrogate nerve cell body would be, in my opinion, the best. |
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