Stem Cells Cure Blind Man(gizmodo.com)
gizmodo.com
Stem Cells Cure Blind Man
http://gizmodo.com/5433391/stem-cells-cure-blind-man
2 comments
One thing I don't fully understand is why the human body doesn't do this process on its own.
Indeed. Furthermore, it seems that there is an inverse relationship between how "advanced" an organism is in the phylogenic tree and its ability to regenerate--especially to regenerate nervous tissues.
One of the major cutoffs seems to be between mammals and other vertebrates. Frogs and amphibians can regrow their nerves if they are cut or damaged [1] and fish can completely regrow their cochlear hair cells, regaining hearing in a mere matter of weeks following deafening from exposure to very loud sounds [2].
The "reason" for the loss of regeneration in mammals could have something to do with the fact that mammals are more able to undergo plastic changes to their existing neurons (learning new skills, for example) at the putative cost of being less able to regenerate new cells. Ultimately, being able to learn and exhibit complex behaviors may be much more evolutionarily advantageous than being able to regenerate damaged nerves.
1. There is actually a clever experiment you can do using this knowledge. You transect the frog optic nerve and rotate the orb of the eye upside-down. Then you ask the question: will it reconnect as before, with each axon in the nerve fiber reconnecting to its now rotated mate and the frog consequently now seeing the world upside-down -or- will each axon reconnect to the closest axon (which would have originally been the incorrect one resulting in the frog still seeing the world the right way up? The answer is that the frog acts as if its vision is inverted, providing evidence for chemical signals being used to guide nerve regrowth. As an aside to this aside, note that people and most mammals can adapt to prism glasses (glasses that invert their vision) in a matter of hours. Amphibians, however, will never learn to use prism glasses no matter how long you let them practice.
2. There is work underway to identify which genes are responsible for allowing fish to regenerate their hearing with the ultimate hope of being able to transiently "turn on" the human gene homologues.
Indeed. Furthermore, it seems that there is an inverse relationship between how "advanced" an organism is in the phylogenic tree and its ability to regenerate--especially to regenerate nervous tissues.
One of the major cutoffs seems to be between mammals and other vertebrates. Frogs and amphibians can regrow their nerves if they are cut or damaged [1] and fish can completely regrow their cochlear hair cells, regaining hearing in a mere matter of weeks following deafening from exposure to very loud sounds [2].
The "reason" for the loss of regeneration in mammals could have something to do with the fact that mammals are more able to undergo plastic changes to their existing neurons (learning new skills, for example) at the putative cost of being less able to regenerate new cells. Ultimately, being able to learn and exhibit complex behaviors may be much more evolutionarily advantageous than being able to regenerate damaged nerves.
1. There is actually a clever experiment you can do using this knowledge. You transect the frog optic nerve and rotate the orb of the eye upside-down. Then you ask the question: will it reconnect as before, with each axon in the nerve fiber reconnecting to its now rotated mate and the frog consequently now seeing the world upside-down -or- will each axon reconnect to the closest axon (which would have originally been the incorrect one resulting in the frog still seeing the world the right way up? The answer is that the frog acts as if its vision is inverted, providing evidence for chemical signals being used to guide nerve regrowth. As an aside to this aside, note that people and most mammals can adapt to prism glasses (glasses that invert their vision) in a matter of hours. Amphibians, however, will never learn to use prism glasses no matter how long you let them practice.
2. There is work underway to identify which genes are responsible for allowing fish to regenerate their hearing with the ultimate hope of being able to transiently "turn on" the human gene homologues.
Why would evolution favor this, by the time this helped the individual he'd already have had all his children. Evolution optimizes more babies, not healthier individuals with long lifespans. A naturally blind person probably wouldn't have survived childhood for most of human evolution.
The value of an individual to the evolution of a species doesn't stop when they have their offspring. Long lifespans or intelligence may allow the formation of culture and society, which improves the chances of survival of the group as it works together. Even individuals that have already had offspring still have value to the group in that they may allow the group to operate more effectively as a unit, increasing the likelihood that it (and thus the species) will thrive.
I guess what I'm trying to say is that 'evolution' doesn't care about the individual... it 'cares' about the species. We think of 'evolving' in terms of mutations to individuals that get passed on via reproduction, but it's just as valid to look at 'mutations' in group behavior that make any given group more fit for survival. These mutations aren't passed on via genes... they are passed on as cultural norms within the group, with the aid of both intelligence and sufficient lifespans that allow offspring to learn from their parents.
Groups with better cultural norms will enjoy more success than other groups. These other groups will either adapt the ideas, or they will be at a disadvantage and eventually lose out. Either way, the species will have 'evolved' in such a way as to improve it's chances of survival, even though no physical improvement was made and handed to offspring via genes.
With this in mind, it's almost as if we are evolving more rapidly than ever. The sweeping changes to human culture (and technology, which is another vector to improve fitness of a group) over the last few centuries (new forms of government/economies/law/freedoms) has been extremely beneficial to the survival of the human species.
I guess what I'm trying to say is that 'evolution' doesn't care about the individual... it 'cares' about the species. We think of 'evolving' in terms of mutations to individuals that get passed on via reproduction, but it's just as valid to look at 'mutations' in group behavior that make any given group more fit for survival. These mutations aren't passed on via genes... they are passed on as cultural norms within the group, with the aid of both intelligence and sufficient lifespans that allow offspring to learn from their parents.
Groups with better cultural norms will enjoy more success than other groups. These other groups will either adapt the ideas, or they will be at a disadvantage and eventually lose out. Either way, the species will have 'evolved' in such a way as to improve it's chances of survival, even though no physical improvement was made and handed to offspring via genes.
With this in mind, it's almost as if we are evolving more rapidly than ever. The sweeping changes to human culture (and technology, which is another vector to improve fitness of a group) over the last few centuries (new forms of government/economies/law/freedoms) has been extremely beneficial to the survival of the human species.
Absolutely. Comparing the evolution of ideas to the evolution of genes is like comparing a programmable chip to a hardwired circuit. I remember reading about this in The Science of the Discworld, a hilarious yet informative book where the authors described these concepts in terms of "memes" (a word coined by Dawkins, I think, to refer to the mental analog of genes) and "extelligence" (knowledge that lives outside you head, like Wikipedia).
Even though we haven't evolved the ability to regrow eyes automatically, we've evolved enough intelligence to approach the level of civilization where, by playing with our own biology, we can make eyes regrow. How's that for a hack!
Even though we haven't evolved the ability to regrow eyes automatically, we've evolved enough intelligence to approach the level of civilization where, by playing with our own biology, we can make eyes regrow. How's that for a hack!
Excellent points.
Because a baby with a father who lost an eye hunting and was able to regenerate it would have a better chance of living long enough to reproduce.
Cross reference: http://searchyc.com/stem+cells+blind
Very similar reports from both very recently and from 2 years ago, with some discussion.
Very similar reports from both very recently and from 2 years ago, with some discussion.
One thing I don't fully understand is why the human body doesn't do this process on its own. If the cells can indeed be regrown or "incubated" using byproducts of the human donor her/himself and reintroduced into the body with little chance of rejection, you wonder why the infinite genius of the human body hasn't evolved to do this naturally. I suppose one might argue that the healing we ARE capable of is a form of this process and you might be right (I'm no doctor), but are their cases of something as grand a scale as restoring your own eyesight happening naturally?