Download TITLE?? The central nervous system ( , or CNS )

TITLE??
The central nervous system (CNS)-be efficient is composed of the spinal cord and brain. Humans
have a CNS that is unable to recover and regenerate damaged nerve cells, also named neurons
(Brosamle, et al., 2000).-too much info in this sentence (too efficient), only humans? Start
simple…the cells that make up the CNS are not able to divide, therefore… This is caused by
chemicals called proteoglycans that are released by neurons (Cafferty, et al., 2007).-Completely?
This is the only cause? Proteoglycans are proteins that have multiple sugars attached to them,
making them resemble a tangled mess a tangled mess? (Cafferty, et al., 2007; Krekoski, et al.,
2001). Although they are meant to protect the cells, the proteoglycans’ complex structures make
it hard for neurons to regenerate.-how do they protect the cells? Be specific. Tell the story. They
encase the damaged cells and restrain them from growing through the “wall” of proteoglycans-is
this about neurons not being able to grow or not being able to divide and replace ones that have
died? Make this more clear in the beginning, which is meant to close the damaged site and
prevent further injury.-prevent injury? How so? Though it is helpful, it also prevents further
growth past this sealed site. Another molecule, myelin, also gets tangled around the cell,
blocking it off from more space to grow into-awkward wording, rephrase (Brosamle, et al.,
2000). Luckily-don’t say luckily, you don’t know this…, recent experiments have shown that
regeneration is possible.-make sure the reader knows what regeneration means exactly By
genetically altering, electrically stimulating, and exposing chemicals to cells, proteoglycan and
myelin levels can be lowered.-Rephrase this sentence. It is not clear. These methods may
possibly promote and guide neuronal regeneration (Al-Majed, et al., 2000; Cafferty, et al., 2007;
Davies, et al., 1999).-Not bad, just make it more clear that neurons, when damaged, need to find
their conncections again. You need to discuss what a neuron is in general…a wire and that they
are connected to other wires etc… and that these connections, if lost, will need to be reformed.
Give some analogies. Make it clear to the general audience.
New research has shown that lowering proteoglycan and myelin levels can promote
regeneration.-did you talk about myelin in this paragraph at all? Also, did you discuss what
myelin is in the intro? Does it have the same function as the proteoglycans you are discussing in
terms of preventing further damage? By reducing the number of proteoglycans around the cells,
neurons should then be able to grow into the new available space. One way to achieve this is by
genetically altering the DNA for specific enzymes-general audience will need clarification,
which are molecules that can break proteoglycans-this sentence will not be clear to the general
reader (Cafferty, et al., 2007; Krekoski, et al., 2001; Steinmetz, et al., 2005). DNA for this
enzyme was taken from bacteria and implanted in mice.-for what enzyme? You said to alter the
DNA…I am confused. These mice successfully produced chondroitinase ABC, the enzyme that
breaks proteoglycans.-If you are going to give the name, you should give it when you first
mention the enzyme. The sugars were taken off of the proteins, creating a less complex structureAgain, the reader will be confused. Be more general with your description (Cafferty, et al.,
2007). Because the proteoglycans broke into shorter, smaller pieces, neurons were able to grow
into more areas. Reductions of proteoglycans also allowed scars in the nerves to reform and
completely fill in the damaged areas (Krekoski, et al., 2001).-you end the last two sentences with
the same word…”areas”. – also, I do not understand this sentence Scar tissue forming is
important to regeneration, because they-they? are the first stages of development of fully
functional cells.-you will need a better explanation for this scaring Further aid, like that
accomplished with chemicals such as zymosan, can create even better, clearer environments for
the neurons (Steinmetz, et al., 2005).-say what? Did you just jump? You need a more clear
transition. In these experiments, neurons altered to breakdown proteoglycans yielded results of
recovery after injury.-no idea what this sentence is saying to me… why did you just throw the
chemicals in quickly at the end after discussing enzymes the entire time?
Another way to promote regeneration is lowering myelin levels around the cells.-This is
repetitive from what you said in the intro. Myelin is a chemical released by neurons to encase
themselves, acting like armor against the environment.-this is intro material However, the
“armor” of myelin seals the cell inside.intro By lowering the amount of myelin, neurons can
grow back into the open space.intro Lowering myelin levels can be done by using genetically
altered viral enzymes or human anti-bodies (Brosamle, et al., 2000; Tang, et al., 2007).-you need
to transition into this from the previous paragraph…in addition to proteglycan breakdown,
scientists have also discovered… (something like this). The DNA of neurons are altered so that
viral enzymes and human anti-bodies can be made and enhanced, respectively.-no idea what this
means They are able to digest myelin, leaving little restraint on regeneration.-are they putting
these genes into the cells? What are they doing? The reader is lost… In one study, the human IN1 antibody was used to break long chains of myelin around the neurons.-in humans? Injection?
Resulting fragments of myelin could not encase the damaged neurons, allowing them to grow
longer (Brosamle, et al., 2000).-more explanation, details please These severed nerves were able
to grow out into damaged areas and reattach to other nerves.-nerves or neurons? Using
genetically altered viruses that release certain enzymes that-repeated “that” facilitate growth is
also possible.-enzymes that facilitate growth? How? Are these myelin breakdown enzymes?
These were injected around neurons, so that their enzymes could be near the nerves.-neurons?
Nerves? Look up the difference. The enzymes caused parts of neurons to break through and grow
out of the myelin casing without any myelin covering them-without any myelin covering them?
(Tang, et al., 2007). Without any myelin-repeated “without any myelin” holding the neurons
back, they were able to branch out and connect with other neurons.-This is a repeat.
Transition? Transplanting neurons and surrounding material from another source to the
injured area has also been shown to promote regeneration.-how does this relate to the breaking
down of myelin/proteoglycans. Reader is lost. Neurons from other nerves were surgically
removed and placed into the damaged site.-in the same individual? Human? Details… In the new
environment, the neurons grew and connected to pre-existing broken ones resulting in severed
nerves being reconnected (Davies, et al., 1999).-was the person able to use these neurons
effectively now? What is the outcome of this? The problem with this is that transplanted nerves
grow and attach to any other nerve. In other words, the wrong nerves will regenerate into the
wrong areas.-the wrong nerves? Or just the wrong attachments… Nerves that communicate with
muscles may grow into the skin, while nerves that interact between the brain and skin may grow
into muscle. Surprisingly, electrical stimulation has been shown to guide nerves during
regeneration and allow them to function correctly. In this approach, nerves are continuously
shocked with pulses of electricity. Any amount of stimulation caused nerves to extend and grow
into the correct areas. With this treatment, sensory nerves grew toward the skin and motor nerves
grew toward muscles successfully (Al-Majed, et al., 2000). – I have no idea what this paragraph
has to do with proteoglycan breakdown. Your intro implied that this was the main point of the
paper.
All of these methods may aid large scale human CNS recovery; while on the other hand,
they also have some disadvantages. By genetically altering the nerves, enzymes that break
proteoglycans and myelin will continuously do so. Proteoglycans and myelin are needed by
healthy neurons to protect themselves from injury. If too many are lost, the neurons will be
extremely vulnerable and will not function correctly. The enzymes will have to be modified so
that they can be deactivated/activated when needed. Transplanting neurons from other hosts may
also lead to the rejection of these nerve cells. The body may misjudge them as foreign invaders
and attack them. Even if the neurons are taken from the same host, the surgery to remove them
will cause another area of the body to be damaged. Electrical stimulation may also cause further
damage. If your hands are shocked by static, you feel pain (your response to damage). This
creates the possibility that prolonged electrical shock may injure other neurons. Despite the
setbacks, these new treatments for neuronal regeneration are a huge step for researchers. They
will soon be able to “cure” people with damaged CNS’s and problems like memory loss,
concussions, and paralysis.
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References:
Al-Majed, A. A., Neumann, C. M., Brushart, T. M., & Gordon, T. (2000). Brief electrical
stimulation promotes the speed and accuracy of motor axonal regeneration. Journal of
Neuroscience, 20, 2602-2608.
Brosamle, C., Huber, A. B., Fiedler, M., Skerra, A., & Schwab, M. E. (2000). Regeneration of
lesioned corticospinal tract fibers in the adult rat induced by a recombinant,
humanized IN-1 Antibody fragment. Journal of Neuroscience, 20, 8061-8068.
Cafferty, W. B. J., Yang, S. H., Duffy, P. J., Li, S., & Strittmatter, S. M. (2007).
Functional axonal regeneration through astrocytic scar genetically modified to
digest chondroitin sulfate proteoglycans. Journal of Neuroscience, 27, 2176-2185.
Davies, S. J. A., Goucher, D. R., Doller, C., & Silver, J. (1999). Robust regeneration of adult
sensory axons degenerating white matter of the adult rat spinal cord. Journal of
Neuroscience, 19, 5810-5822.
Krekoski, C. A., Neubauer, D., Zuo, J., & Muir, D. (2001). Axonal regeneration into acellular
nerve grafts is enhanced by degradation of chondroitin sulfate proteoglycan. Journal
of Neuroscience, 21, 6206-6213.
Steinmetz, M. P., Horn, K. P., Tom, V. J., Miller, J. H., Busch, S. A., Nair, D., Silver, D. J., &
Silver, J. (2005). Chronic enhancement of the intrinsic growth capacity of sensory
neurons combined with the degradation of inhibitory proteoglycans allows functional
regeneration of sensory axons through the dorsal root entry zone in the mammalian
spinal cord. (2005). Journal of Neuroscience, 25, 8066-8076.
Tang, X. Q., Heron, P., Mashburn, C., & Smith, G. M. (2007). Targeting sensory axon
regeneration in adult spinal cord. Journal of Neuroscience, 27, 6068-6078.