Topic: New ways to aid in nerve regeneration. General Purpose: To informSpecific Purpose: To inform the audience about news techniques and mechanismsthat aid in nerve regeneration.
Central Idea Statement: The new techniques fornerve regeneration involving magnetic, electrical, and chemical mechanisms lookvery promising. INTRODUCTION I. The site is rather common: someone in a wheelchair unable to use their lower body, or worse, unable to function from theirneck down because of an accident. You may even know one of these people. Theyall have one thing in common: spinal nerve injury.
To the majority of us, one ofthe more famous and recent cases involving spinal trauma is that of ChristopherReeve, known to most of us as Superman. Reeve was riding his horse when he felloff, landed on the back of his head and twisted his neck. His spine was damagednear the second cervical vertebrae; that being two vertebrae away from the baseof the skull. He states that after his accident he saw a handbook written in1990 that “didn’t even mention anyone higher than because 70 percent of them didn’t live longer than five days. I amvery lucky my injury happened at a time when treatment and surgery hadimproved. ” Dr.
Cotman from UCI, who worked with Reeve says that Reeveremains optimistic that a cure is only a few million dollars away. II. Prior tothe end of the Second World War, if a person survived a severe spinal cordinjury, the injury still usually resulted in their early death. This was becauseof complications that accompanied the injury, such as infections to the kidneysand lungs.
Though the development of new antibiotics has greatly improved lifeexpectancy, until recently medical science had not been able to restore nervefunction. III. According to researchers at the University of Alabama using datafrom the regional SCI Centers, there are 7,800 traumatic spinal cord injurieseach year in the US. Yet these numbers do not represent accurate figures since4,860 per year, die before reaching the hospital.
Current estimates are that250,000-400,000 individuals live with spinal cord injury or dysfunction;forty-four percent of these occur in motor vehicle accidents. More than half ofthese injuries occur to individuals who are single, and more than 80% of theseindividuals are male. IV. Within the last five years, a great many things havebeen happening in the area of neurological research.
Research and treatmentinvolving spinal and nerve injury has progressed considerably. In this speech Iwill inform you on the new and promising techniques that are currentlyundergoing testing for human treatment, in terminology that we will be able tounderstand. BODY I. The nervous system consists of the brain, spinal cord, andall 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 andspinal cord, while the PNS involves all the nerves that branch off from thespinal cord to the extremities. A. When the spine is crushed or bent in anextreme 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 electricalinsulation, or myelin, over the very short distance of the injury zone.
Nerveimpulses are blocked at this point. 1. The myelin is the part of the nerve thatactually transfers the electrical signal that enables your muscles to move whenyou 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 primeexample) 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 theydon’t regenerate over very long distances. D. The big problem with treatingspinal injuries is the fact that mature nerve tissue does not spontaneouslyregenerate.
II. The three basic ways to treat nerve damage are: first, produceregeneration of the remaining segment of a nerve fiber, or make new connectionson the other side of the injury. Second, prevent or rescue the damaged nervefiber from proceeding on to separation, or perhaps even functionally reunite thetwo segments, so that both portions of the fiber survive. Or third, facilitatenerve impulse traffic to cross the region of injury in intact fibers where theyhave lost their electrical insulation. III.
The techniques that are being usedto do this involve magnetic, electrical, chemical, or a combination of these tostimulate the damaged nerve. A. At present surgeons take a nerve from a lessimportant part of the body and transfer it to the site of the injury. Generallythe nerve is taken from the lower leg, but then sensation is lost in thatportion of the body.
Next, the surgeons attempt to repair the nerves by sewingthe proximal and distal ends of the nerves together. However, the results areoften disappointing. Even with the operation microscope, surgeons are unable toprecisely match the thousands of minute axons, each being approximately 1/100the diameter of a human hair. B.
Arthur Lander, a molecular neurobiologist whocame to UCI in 1999 from MIT, does research specifically on neural growth andrepair. What scientists currently want to learn, he said, is “thefundamental mechanisms that control whether nerve fibers grow and where theygrow. It’s not good enough just to get them to grow, you’ve got to get them toconnect to the right targets. ” C. Dr. Schmidt, Ph.
D. from the University ofIllinois further states, “Imagine the end of a damaged nerve as a smallchild lost in a forest. The child is resilient and will seek a way out, but sheneeds the help of a flashlight and a path. ” 1.
Dr. Schmidt recentlyreceived a grant from the Whitaker Foundation to research ways to useelectricity and an electrically conducting polymer material to stimulate nervecell growth. Dr. Christine Schmidt’s goal is to give the nervous system’snatural healing mechanism the help it needs in repairing cells. This may meansupplying a tiny burst of electricity to stimulate the growth of a damagednerve. It also means a pathway or tunnel the growing nerve can follow from thesite of the injury to its destination.
The path or tunnel Schmidt is hoping willhelp nerve growth is just that: a minute tube composed of a black-coloredmaterial that somewhat resembles Teflon coating. Called polypyrrole, it is apolymer that conducts electricity and can be filled with nutrients that helpnerves grow. The chief drawback at present is that polypyrrole is notbiodegradable. Schmidt is trying to modify polypyrrole so that it will dissolveinto the body and disappear as the nerve regenerates, like biodegradable suturesused in surgery. D. A recent study performed at Cornell University MedicalCollege has demonstrated that exposure to magnetic fields can result in growthand regeneration of nerves.
Dr. Saxena, who was in charge of the research usedlow-level magnetic fields to trigger growth and regeneration of nerve sectionsin a culture medium (basically a petri dish). The study also found that thosenerves that were not exposed to the magnetic fields experienced nervedegeneration. 1. Dr. Saxena said “At the end of the year, we found thatincluded in the new growth was the myelin sheath, a structure responsible fornormal nerve conduction of impulses.
These findings are especially importantbecause the myelin sheath is the part of the nerve cell that actually conductsthe electrical impulses. ” E. Another means to restore nerve impulse trafficin both directions through the injured spinal cord is to allow these impulses tocross the regions on the nerve fibers that have been stripped of theirinsulation, or myelin. The electrical conduction of nerve impulses are blockedat these regions, and though the fiber may be intact, it is still”silent. ” If nerve impulses do not decay in this damaged region, butare conducted to the other side, then they are carried through the rest of thenervous system in a normal fashion. The drug 4 aminopyridine (4 AP) can allowthis to happen.
The drug was administered by injection, and behavioralimprovements could be observed sometimes within 15 minutes. This break throughwas subsequently moved to limited human testing in two Canadian medical centerswith colleagues Dr. Keith Hayes and Dr. Robert Hanseboiut.
Their resultsextended the utility of 4 AP in human quadriplegic and paraplegics. 1. RichardB. Bargains, Director for the Center of Paralysis Research who was present forthe administration of the drug said, “I particularly remember one man, 5years after his injury who began to breathe again more normally within ? hourof the administration of the drug. ” Several more clinical trials of thedrug have been completed in the US and Canada. F.
MIT scientists and colleagueshave recently discovered a gene that is capable of promoting nerve fiberregeneration. For the first time, they were able to fully reestablish lostconnections in the mature brain of a mammal. Although the research was conductedon mice, they believe that it opens the door for the functional repair of brainand spinal cord damage in humans. The scientists have shown that intrinsicgenetic factors, not just the tissue environment, are of crucial importance. Brain tissue in adults contains factors that inhibit fiber growth and it lacksgrowth-promoting hormones.
By culturing brain tissue, the scientists determinedthat 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 theSchool of Veterinary Science are using paraplegic dogs, with their ownersconsent, to test some new techniques of their own. What researchers do is inducespinal nerve fiber regeneration and to some extent guide it, through the use ofan applied electrical field. Very weak electrical fields are a natural part ofembryonic development, particularly in the nervous system, and a inherent partof wound healing in animals. In experimental treatment for paraplegic dogs,researchers reverse the polarity of the applied electrical field imposed overthe region of the injury every 15 minutes; using an electronic circuit which isimplanted securely to the outside of the spine.
H. In the US the use of fetaltissue is a very controversial subject-leading to a presidential ban on any useof human embryonic derived material. Researchers at Purdue University havedeveloped an alternative. They’ve shown that nerve cells removed from the gutand grafted to a spinal cord injury in the same animal can survive. Anotherinteresting and potentially breakthrough technology involves the repair ofindividual nerve fibers using special chemicals that can both repair and coverholes in nerve membranes and even fuse the two segments of a cut nerve backtogther.
One may think of this as a molecular-chemical “band-aid” thatprevents injured fibers from preceding on to separation and death. I. Britishscientists are developing a pioneering technique for reconnecting severednerves. But it will only work with peripheral nerves.
Researchers at the RoyalFree Hospital in London have found a way to persuade the severed ends of damagednerves to grow though a special tube implanted to bridge the gap. The tinytubes-a single millimeter in diameter are glued or stitched between the cutnerve ends. The inside of the tubing is coated with special cells, calledSchwann cells, which release proteins that encouraged nerve growth. Once thenerve fibers have grown and reconnected the polymer tubing simply dissolvesaway.
The Schwann cells would be grown from the patients’ own cells, taken froma tiny sample of nerve, to avoid rejection problems. Doctors hope to beginimplants into patients within a year. CONCLUSION: I. The three basic techniquesthat are currently being used to treat damaged nerves concern electrical,magnetic, and chemical stimulation. II.
Rapid progress is being made in the areaof research and treatment involving injured nerves. Within ten years, commonplace treatment will be available for what is presently deemed to beirreversible spinal cord damage. BibliographyHibasami H. , Hirata H.
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