Nerve Regeneration Essay, Research Paper
Topic: New ways to aid in nerve regeneration. General Purpose: To inform
Specific Purpose: To inform the audience about news techniques and mechanisms
that aid in nerve regeneration. Central Idea Statement: The new techniques for
nerve regeneration involving magnetic, electrical, and chemical mechanisms look
very promising. INTRODUCTION I. The site is rather common: someone in a wheel
chair unable to use their lower body, or worse, unable to function from their
neck down because of an accident. You may even know one of these people. They
all have one thing in common: spinal nerve injury. To the majority of us, one of
the more famous and recent cases involving spinal trauma is that of Christopher
Reeve, known to most of us as Superman. Reeve was riding his horse when he fell
off, landed on the back of his head and twisted his neck. His spine was damaged
near the second cervical vertebrae; that being two vertebrae away from the base
of the skull. He states that after his accident he saw a handbook written in
1990 that "didn’t even mention anyone higher than [the fourth cervical
vertebrae] because 70 percent of them didn’t live longer than five days. I am
very lucky my injury happened at a time when treatment and surgery had
improved." Dr. Cotman from UCI, who worked with Reeve says that Reeve
remains optimistic that a cure is only a few million dollars away. II. Prior to
the end of the Second World War, if a person survived a severe spinal cord
injury, the injury still usually resulted in their early death. This was because
of complications that accompanied the injury, such as infections to the kidneys
and lungs. Though the development of new antibiotics has greatly improved life
expectancy, until recently medical science had not been able to restore nerve
function. III. According to researchers at the University of Alabama using data
from the regional SCI Centers, there are 7,800 traumatic spinal cord injuries
each year in the US. Yet these numbers do not represent accurate figures since
4,860 per year, die before reaching the hospital. Current estimates are that
250,000-400,000 individuals live with spinal cord injury or dysfunction;
forty-four percent of these occur in motor vehicle accidents. More than half of
these injuries occur to individuals who are single, and more than 80% of these
individuals are male. IV. Within the last five years, a great many things have
been happening in the area of neurological research. Research and treatment
involving spinal and nerve injury has progressed considerably. In this speech I
will inform you on the new and promising techniques that are currently
undergoing testing for human treatment, in terminology that we will be able to
understand. BODY I. The nervous system consists of the brain, spinal cord, and
all branching nerves. There are two parts: the central nervous system, or CNS,
and the peripheral nervous system, or PNS. The CNS, consists of the brain and
spinal cord, while the PNS involves all the nerves that branch off from the
spinal cord to the extremities. A. When the spine is crushed or bent in an
extreme accident, the spinal cord inside is severely bruised and compressed,
causing localized injury and death to many of the nerve cells and their fibers.
Some of injured nerves fibers survive intact, but lose their electrical
insulation, or myelin, over the very short distance of the injury zone. Nerve
impulses are blocked at this point. 1. The myelin is the part of the nerve that
actually transfers the electrical signal that enables your muscles to move when
you want them to move. B. Nerves regenerate at the rate of about a cm a month.
Keep in mind that not all nerves can regenerate (the spinal cord is a prime
example) and if a nerve is too damaged or is severed it cannot come back C.
Peripheral nerves will regenerate to a certain extent on their own, but they
don’t regenerate over very long distances. D. The big problem with treating
spinal injuries is the fact that mature nerve tissue does not spontaneously
regenerate. II. The three basic ways to treat nerve damage are: first, produce
regeneration of the remaining segment of a nerve fiber, or make new connections
on the other side of the injury. Second, prevent or rescue the damaged nerve
fiber from proceeding on to separation, or perhaps even functionally reunite the
two segments, so that both portions of the fiber survive. Or third, facilitate
nerve impulse traffic to cross the region of injury in intact fibers where they
have lost their electrical insulation. III. The techniques that are being used
to do this involve magnetic, electrical, chemical, or a combination of these to
stimulate the damaged nerve. A. At present surgeons take a nerve from a less
important part of the body and transfer it to the site of the injury. Generally
the nerve is taken from the lower leg, but then sensation is lost in that
portion of the body. Next, the surgeons attempt to repair the nerves by sewing
the proximal and distal ends of the nerves together. However, the results are
often disappointing. Even with the operation microscope, surgeons are unable to
precisely match the thousands of minute axons, each being approximately 1/100
the diameter of a human hair. B. Arthur Lander, a molecular neurobiologist who
came to UCI in 1999 from MIT, does research specifically on neural growth and
repair. What scientists currently want to learn, he said, is "the
fundamental mechanisms that control whether nerve fibers grow and where they
grow. It’s not good enough just to get them to grow, you’ve got to get them to
connect to the right targets." C. Dr. Schmidt, Ph.D. from the University of
Illinois further states, "Imagine the end of a damaged nerve as a small
child lost in a forest. The child is resilient and will seek a way out, but she
needs the help of a flashlight and a path." 1. Dr. Schmidt recently
received a grant from the Whitaker Foundation to research ways to use
electricity and an electrically conducting polymer material to stimulate nerve
cell growth. Dr. Christine Schmidt’s goal is to give the nervous system’s
natural healing mechanism the help it needs in repairing cells. This may mean
supplying a tiny burst of electricity to stimulate the growth of a damaged
nerve. It also means a pathway or tunnel the growing nerve can follow from the
site of the injury to its destination. The path or tunnel Schmidt is hoping will
help nerve growth is just that: a minute tube composed of a black-colored
material that somewhat resembles Teflon coating. Called polypyrrole, it is a
polymer that conducts electricity and can be filled with nutrients that help
nerves grow. The chief drawback at present is that polypyrrole is not
biodegradable. Schmidt is trying to modify pol
into the body and disappear as the nerve regenerates, like biodegradable sutures
used in surgery. D. A recent study performed at Cornell University Medical
College has demonstrated that exposure to magnetic fields can result in growth
and regeneration of nerves. Dr. Saxena, who was in charge of the research used
low-level magnetic fields to trigger growth and regeneration of nerve sections
in a culture medium (basically a petri dish). The study also found that those
nerves that were not exposed to the magnetic fields experienced nerve
degeneration. 1. Dr. Saxena said "At the end of the year, we found that
included in the new growth was the myelin sheath, a structure responsible for
normal nerve conduction of impulses. These findings are especially important
because the myelin sheath is the part of the nerve cell that actually conducts
the electrical impulses." E. Another means to restore nerve impulse traffic
in both directions through the injured spinal cord is to allow these impulses to
cross the regions on the nerve fibers that have been stripped of their
insulation, or myelin. The electrical conduction of nerve impulses are blocked
at these regions, and though the fiber may be intact, it is still
"silent." If nerve impulses do not decay in this damaged region, but
are conducted to the other side, then they are carried through the rest of the
nervous system in a normal fashion. The drug 4 aminopyridine (4 AP) can allow
this to happen. The drug was administered by injection, and behavioral
improvements could be observed sometimes within 15 minutes. This break through
was subsequently moved to limited human testing in two Canadian medical centers
with colleagues Dr. Keith Hayes and Dr. Robert Hanseboiut. Their results
extended the utility of 4 AP in human quadriplegic and paraplegics. 1. Richard
B. Bargains, Director for the Center of Paralysis Research who was present for
the administration of the drug said, "I particularly remember one man, 5
years after his injury who began to breathe again more normally within ? hour
of the administration of the drug." Several more clinical trials of the
drug have been completed in the US and Canada. F. MIT scientists and colleagues
have recently discovered a gene that is capable of promoting nerve fiber
regeneration. For the first time, they were able to fully reestablish lost
connections in the mature brain of a mammal. Although the research was conducted
on mice, they believe that it opens the door for the functional repair of brain
and spinal cord damage in humans. The scientists have shown that intrinsic
genetic factors, not just the tissue environment, are of crucial importance.
Brain tissue in adults contains factors that inhibit fiber growth and it lacks
growth-promoting hormones. By culturing brain tissue, the scientists determined
that genes that cause the growth of nerve fibers shut down at a very young age.
G. Purdue University’s Center for Paralysis Research in conjunction with the
School of Veterinary Science are using paraplegic dogs, with their owners
consent, to test some new techniques of their own. What researchers do is induce
spinal nerve fiber regeneration and to some extent guide it, through the use of
an applied electrical field. Very weak electrical fields are a natural part of
embryonic development, particularly in the nervous system, and a inherent part
of wound healing in animals. In experimental treatment for paraplegic dogs,
researchers reverse the polarity of the applied electrical field imposed over
the region of the injury every 15 minutes; using an electronic circuit which is
implanted securely to the outside of the spine. H. In the US the use of fetal
tissue is a very controversial subject-leading to a presidential ban on any use
of human embryonic derived material. Researchers at Purdue University have
developed an alternative. They’ve shown that nerve cells removed from the gut
and grafted to a spinal cord injury in the same animal can survive. Another
interesting and potentially breakthrough technology involves the repair of
individual nerve fibers using special chemicals that can both repair and cover
holes in nerve membranes and even fuse the two segments of a cut nerve back
togther. One may think of this as a molecular-chemical "band-aid" that
prevents injured fibers from preceding on to separation and death. I. British
scientists are developing a pioneering technique for reconnecting severed
nerves. But it will only work with peripheral nerves. Researchers at the Royal
Free Hospital in London have found a way to persuade the severed ends of damaged
nerves to grow though a special tube implanted to bridge the gap. The tiny
tubes-a single millimeter in diameter are glued or stitched between the cut
nerve ends. The inside of the tubing is coated with special cells, called
Schwann cells, which release proteins that encouraged nerve growth. Once the
nerve fibers have grown and reconnected the polymer tubing simply dissolves
away. The Schwann cells would be grown from the patients’ own cells, taken from
a tiny sample of nerve, to avoid rejection problems. Doctors hope to begin
implants into patients within a year. CONCLUSION: I. The three basic techniques
that are currently being used to treat damaged nerves concern electrical,
magnetic, and chemical stimulation. II. Rapid progress is being made in the area
of research and treatment involving injured nerves. Within ten years, common
place treatment will be available for what is presently deemed to be
irreversible spinal cord damage.
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