Severed Optical Nerves Can Be Made To Grow Again 187
Anonymous Coward writes: "It is being hailed as one of the most significant advances in nerve regeneration in a decade. After severing an optic nerve in rats, neurologists have found a way to reconnect it to the brain so that it once again transmits normal electrical signals. As reported in the New Scientist this achievement is a first in mammals, and may hint at ways of reversing some types of blindness in people. Scientists also hope to use a version of the technique to treat people with spinal cord injuries.
What about other nerves? (Score:3, Interesting)
How long until human trials? (if ever) (Score:3, Interesting)
Research like this, when it might potentially spark a break-thru that could help someone close to you, is always great to see. I hope they make serious progress with this one.
Interesting, semi-on-topic Oliver Sacks tidbit (Score:5, Interesting)
His eyes, it turned out, were functioning perfectly. But because he has been blind during infancy, the visual parts of his brain had never developed -- he had never learned to see.
He did slowly learn, but it was agonizing for him. His newfound sight was overwhelming and sent his brain into chaos. After a long time, with tremendous effort, he could shave for a minute or two in front of the mirror -- but it was absolutely exhausting, and had to finish with the lights off.
Eventually, an unrelated optical infection threatened to take his sight, and he chose to let it run its course. Returning to blindness was a tremendous relief.
Perhaps slightly off-topic, but fascinating!
Crystallins or Immune Sys? (Score:4, Interesting)
The article said that it was just inflammation that induced growth. I somehow doubt that, since everyone who's ever had irritated eyes has felt the fun of histamines and the primary immune response in action. If that sort of thing could make the blind see again, I'd be really surprised, even if it is on a larger scale.
If it is the immune system, I'd bet on cytokines released by helper T cells (those things that HIV targets) simply because these cells release a ton of stimulants. This may be triggered by the nonspecific inflammation like the author suggested, but I'd bet on the helper T as actually secreting growth signal.
If it is possible to use the immune system to regrow neurons, it's very likely applicable in other parts of the body too.
Re:Interesting, semi-on-topic Oliver Sacks tidbit (Score:2, Interesting)
Re:What about other nerves? (Score:3, Interesting)
However, if you cut the axon of the cell (the bit which connects to other cells put very simply) it can regrow, but don't expect it to take the same function. The part of the axon which is cut off will die, and the cell should make new synapses. As I said these might not be of the same function.
The technique described could work for spinal axons, but there are a lot more of these than in the eye. So you would have to get each cell to connect to its exact axon in the first place and then stimulate them to reconnect. I would think it would be quite difficult to do the above.
Anyway after this the patient would have to learn to regain control of their body. Note how they said it only partially regenerates the nerve. You're still not going to get all sensation or motor control - the potential for damage to a person who undergoes this and cannot control themselves properly is massive. I can't see this working for a time, and then there will have to be years of trials (after persuading ethics committees that this is a good ides). I think they'll have to find a way of improving the technique first.
I have no clue who Rush Limbaugh is - is he metaphorically deaf? His deafness might not be due to damage to nervous tissue anyway, but could be due to damage to the actual ear.
(Some of the above is IMHO, and some of the facts may be wrong - or oversimplified - as science moves very fast; try searching biomedical databases for yourself to see how hard it is. Correct me if i've got anything wrong please)
I have to wonder... (Score:5, Interesting)
When I was 15 years old, I put my hand through an old glass door while trying to open it. The glass sliced through my right wrist, severing pretty much everything (apart from about half of one tendon). I probably don't have to mention the large quantities of blood that went everywhere.
Six hours of microsurgery, and it was put back together again...followed by three months of three hours a day physiotherapy.
The thing I found fascinating was that when the median nerve [0] (the nerve that runs up the middle of your wrist and supplies your index finger to thumb and half your palm) is that some of the nerves went the wrong way. I could stroke part of one finger, and the sensation would come out somewhere else - like a different finger, or a different side of the finger. It was...well...very weird.
However, it didn't take long for the brain to fix it. After a short while, the brain learned the error, and sensations came out in the expected place.
It's one thing when this happens to fingers - but I wonder if you'd need some kind of "optotherapy" to coach the brain to fix the image problems you'd get with optical connections wired differently to how they were before.
[0] Movement of the fingers is controlled by the muscles in the forearm. The median nerve does sensation.
Re:What about other nerves? (Score:3, Interesting)
Actually, the formation of new nerve cells in the adult human brain has been observed for several years now. Your statement would have been taken as correct some years ago but is now known to be incorrect. As you noted yourself:
science moves very fast
Cheers,
Tim
Seen it happen... (Score:3, Interesting)
I know of quite a few stories about people in areas outside of the united states received advanced medical treatment; this is the first I actually know personally.
The really amazing thing about Jedi is that he could actually shoot a very good game of pool while blind. He would have his friend use a cue tapper and tap on the X/Y axis of the table to tell him where the object balls were at. I met him after he got his sight, but none-the-less an impressive feat.
I would recommend to anyone interested in alternate surgies than what america has to offer to check into the european medical field and you may be surprised. I wish I had more information about him, if anyone is interested in any further information post in my journal and I'll get a hold of him.
Nothing particularly new... (Score:3, Interesting)
The increased length is a bonus but not particularly important: They proved that the nerves formed synapses with the other nerves in the brain by shining light on the eye tissue and oberving the rats' pupils shrink in response.
Otherwise, the article is excellent.
Elgon
Fingers (Score:3, Interesting)
There was a recent incident here in Australia where an accident victims fingers were transplanted [smh.com.au] from one hand onto the other...
One hand was severed during the accident, the other hand was crushed, they took the good fingers from the severed hand and put them on place of the crushed fingers. Wow.
Re:I thought 'optic nerves' were actually brain ce (Score:3, Interesting)
Close again... The retina is probably most accurately described as part of the brain. A strong argument for this description comes from looking at how the eye develops embryologicaly. Also, there are four layers of neurons in the retina, just as there are four layers of neurons in areas of brain cortex which are phylogenicaly old. (hence the term neocortex for cerebral cortex, which has six layers of neurons and is a recent evolutionary design.) The cell bodies of the neurons making up the optic nerve are in layer four of the retina and synapse with neurons in the thalamus, another phylogenicaly old brain structure. So, it is "brain all the way down."
So, should we call cranial nerve II (you wrote III, but you meant to say II) a "nerve?" or should we call it a "tract?"
Glad you asked. The real distinction is between central nervous system and periphrial nervous system. PNS neurons tend to heal, while CNS nerves do not. It is believed that this has much to do with the differences among the cells which provide support for the CNS vs PNS. For example, the myelin in PNS is provided by schwan cells, while the myelin in the CNS is provided by oligodendricytes, and there are many other differences in the "support staff" between CNS and PNS.
So, you ask, is CN II really a nerve or is it a tract? Well, if you look at it closely, it is realy part of the brain, and therfore properly called a tract, but the convention is to call it a nerve until it reaches the optic chiasma, then call it a nerve. But whatever you call it, it is very differant than the sort of nerve which gets cut when one, say, puts their hand through an old glass door.
crystallin theory doubtful (Score:2, Interesting)
It is a long story, but the crystallins in the eye serve an essentially structural role. They're present in an absurdly high concentration in order to up the refractive index of the lens tissue. The proteins that evolution recruited to the lens were selected because they resist unfolding and aggregation at high concentration (and, one set of crystallins are thought to help with preventing aggregation of the other crystallins...).
In any case, that tissue is just barely metabolically active (mature lens cells are non-nucleated), and the proteins present have, at most, only vestigal enzymatic activity. From everything we know about crystallins, there is no reason to think that they could ilicit this kind of response. They are highly stable, rather inactive proteins that evolved to last a long time and not mess with stuff.
I don't dispute the study. I just think that the immune system response is a much more plausible explanation.
!splut