Glossary in Plain English
(Note: This glossary will never be complete, and it will never be perfectly worded. These definitions are mostly my own somewhat analogy-heavy way of thinking about scientific terms. I try to find a balance between telling just enough to get the idea across but not so much that it gets lost in yet more incomprehensible jargon. I seriously welcome your thoughts about other terms that should be included here, along with any corrections or suggestions you have for this list. Thank you!)
adeno-associated virus (AAV): extremely tiny critter that serves as a delivery truck for genes. Scientists cleverly switch out the virus’s native genes for others (sort of like changing the nature of the engine in the truck). Teams of AAVs then get deployed into the bodies of patients who need the new genes. Os Steward explained at w2w 2012 (video here, Chapter Two in the book) that his team had used AAV-shPTEN to switch out the gene that prevents certain axons from re-growing after spinal cord injury in human beings. Wired magazine recently ran a good piece, by the way, that tells the story of what happens when you don’t use the right virus.
Americans with Disabilities Act (ADA): awesome law passed in the USA in the summer of 1990. Among other things, that law forced hotels built after 1992 to make their public spaces accessible to people in chairs — and that would include this year’s conference hotel, which was built in 2006. Thank you, ADA activists! We really appreciate these ramps, bathrooms, and accessible rooms.
amyotrophic lateral sclerosis (ALS, Lou Gehrig’s Disease): wretched illness. ALS attacks motor neurons, which are what let healthy people move their arms, legs, fingers, etc. whenever they feel like it. ALS is progressive, which means it keeps getting worse and worse over time, until the patient finally dies. Some of the therapies now under construction for ALS will also benefit people with spinal cord injuries, which is good news. Check out this very recent success story.
amino acid: chain-making molecule. There are about 50 different kinds, but only 20 that matter to us humans. Chains of different combinations of those 20 different amino acids form into proteins.
ASIA scale: score sheet for spinal cord injury. It turns out that defining the exact sort of injury any paralyzed person has is a very tricky business. The people whose job it is to draw boundaries naming levels of suckiness in spinal cord injury have come up with a way to decide where the lines between worst – least bad should be drawn. They go from A to D, and you can read the definitions here. (The ASIA isn’t about geography, by the way. It’s just an acronym for American Spinal Injury Association.)
astrocytes: one of the three kinds of cells in the brain and spinal cord. (The others are neurons and oligodendrocytes, also discussed in this glossary) Astrocytes are called that because they’re vaguely star-shaped (astro!). They’re sort of like worker bees in the healthy brain and cord, buzzing around delivering nourishment to other cells, keeping transmission of electrical impulses orderly, and secreting molecules that help synapses function properly. Unfortunately, they also produce the dreaded proteoglycans that prevent damaged axons from growing through an injury site.
axon: sort of like a single thread (scientists call it a “process,” for mysterious reasons of their own) that extends of out a neuron. Sometimes it’s called a nerve fiber. The basic job of an axon is to carry information from one cell to another. In your brain there are somewhere around 100 billion neurons. Each one sends out an axon. Some of those axons bundle together into tracts, which grow down from your brain and form the white matter of your spinal cord. Broken axons = broken communication between brain and body. Bummer.
brain-derived neurotrophic factor (BDNF): good stuff. This is a happy little protein that acts like fertilizer for neurons (trophiccomes from a Greek word that means nourishing). Sometimes called a growth factor, BDNF was found in the brains of adult pigs back in 1982. All of us humans had lots of it in our in-utero phase of life, where its role was to help produce brain cells at the rate of 250,000/minute, according to The Brain: A Neuroscience Primer. It’s still in our adult bodies, but in very limited quantities. We care about BDNF because getting neurons to grow would be a lot easier if we could make their world more like it was in the good old days when they were multiplying like gangbusters — and that means providing them with lots of BDNF, or something very like it.
Cajal, Ramon y: our Founding Father. Seriously. Cajal was a Spanish scientist who spent his career first defining the structure of the central nervous system and then exploring barriers to regeneration after injury. He was — in modern terms — kind of a character. If your image of a scientist is someone who speaks fussily and spends his time bent over a lab bench, think of Cajal saying this about the behavior of some of his rivals: “It became fashionable to execrate and even smile at the neuron concept and at the theory of connection by contact. In the face of this crushing tide of error . . . I found myself compelled to . . . descend into the arena.” His rivals, see, didn’t buy his theory that neurons have axons, or that axons are how nervous system communication happens. He clearly took this personally. The nerds among you will be glad to know there’s a club you can join where his 21st century fans get together for news and entertainment and gloating.
California Institute of Regenerative Medicine (CIRM): guys with money. The CIRM was formed in 2004/2005 after the citizens of California decided they wanted to place a very big bet on stem cell-based research as a sound public investment. The law they passed (Proposition 71) authorized the distribution of $3 billion over ten years. That’s a lot of research. CIRM’s website is wonderland of information about how they’ve gone about spending it in the years since.
central nervous system (CNS): your brain and spinal cord. Your cord hangs down off the back of your brain like a long skinny pigtail; they’re not two separate things but two parts of the same thing, made of the same three kinds of cells. Both are also protected by bone — your skull and your vertebrae.
central pattern generator: example of how amazing your body is. Inside the spinal cord in your lower back is a collection of neural networks — basically millions of neurons linked one to another that can generate the movements of walking even without any instructions from the brain. The key to this mechanism is that walking is a rhythmic activity. It follows a pattern: left, right, left, right. This is why re-learning to walk while suspended over a moving treadmill works so much better than doing so while clinging to a walker. The treadmill makes natural rhythm possible; the central pattern generator recognizes the process and kicks in. Here’s a PT Journal paper that goes into detail about why and how it happens.
cervical injury: rotten kind of spinal cord injury. This injury happens somewhere at the top of the cord, in the cervical section. It’s rotten because the higher the injury, the more kinds of function that get compromised.
chondroitin sulfate proteoglycan (CSPG, sometimes shortened to proteoglycan): they’re the devil. Okay, not really, but in terms of chronic spinal cord injury, they’ve been holding up the cure project for a long time. These are the molecules inside the injury site that stop growing axons in their tracks and prevent paralyzed people from regaining function. For a full discussion of how that works, have a look at Jerry Silver’s Working 2 Walk 2012 talk about peptides (or Chapter 7 in my book, which covers that material.)
chondroitinase ABC (chABC): our hero. Ch’ase, is it’s usually called, is a monster molecule that loves to chew up proteoglycans (CSPGs, see above). And because proteoglycans are part of the reason axons don’t grow past the injury site in a damaged spinal cord, it’s good to see them destroyed. Yay, Ch’ase!
chromosome: a huge library full of recipes. Physically, a chromosome is a long, long twisty molecule unique to you (but still almost exactly like that of all other humans!) called DNA. You have a set of 23 pairs of those twisty molecules, that full set is sitting deep inside each of the 60-90 trillion cells that make up your body. It’s a library of recipes because little chunks of DNA (known as genes) are almost always recipes for some kind of protein.
complete injury: as you might guess, the most severe kind. The devastation, so to speak, is complete. There is no sensation and no movement anywhere on the body below where the injury is, because no signals whatsoever are getting through the damaged place in the spinal cord.
contusion injury: smushed like an over-ripe strawberry. This is the most common kind of injury in people. It’s also one of the reasons that — as we’ve all heard about a million times — every injury is different. It all depends on not just how high up or down on the cord the injury happens, but on exactly where within that space the damage is. Center? Mostly on one side or the other? Mostly on the front or the back? Lots of bleeding or not much? Contusions are messy by definition, and the outcomes for any ten people who all have injuries at the exact same level of the cord can vary pretty dramatically.
corticospinal tract: the collection of axons that originate from neuron cell bodies in a specific part of your brain (the motor cortex!). We care a lot about this tract because the motor cortex is the section of your brain that controls voluntary movement. To use my friend Bob Yant’s analogy, it’s like the neuron cell bodies are tennis balls, and the axons are strings hanging down from each one. After an injury, the tennis balls are perfectly okay, but the strings have been damaged or broken. Repairing or restoring those strings is the key to recovering movement.
dendrite: the part of a neuron that receives information. They’re called dendrites because the Greek word for tree is dendros, and they really do look like little trees.
DNA: the incredibly long twisty molecule that forms chromosomes. Its sections are called genes, and those genes are almost always recipes for the proteins that make everything in your body happen. A DNA molecule is shaped like a twisted ladder with lots and lots of rungs. It’s made of just four bases: adenine, cytosine, guanine, and thymine. (A, C, G, and T) Your particular arrangement of those four bases is almost exactly like that of every other human on the planet. A few tiny changes in the order of certain bits of it are unique to you alone; they determine things like your hair, eye, and skin color, along with your predisposition to many other kinds of inherited traits.
dorsal: towards the back. This is an example of what can make it so hard to follow scientific presentations; a lot of the words aren’t used much in ordinary speech. It can be like listening to something half in a foreign language, which it sort of is. This word comes from a Latin word (dorsum) that means “back.”
dura mater: one of three protective coverings around the spinal cord. It’s the outermost layer, and the thickest one. What was I saying about a foreign language? Dura mater is Latin for tough mother.
enzyme: a great big molecule, usually a protein. Our favorite enzyme is chondroitinase (Ch ABC), described above. Enzymes are super-finely-targeted catalysts; they make specific reactions happen and happen fast. I think of them like sheep dogs, in the sense that they’re focused on very specific things (like a single straggling sheep) and because they make things move. Laundry detergent often has enzymes in it; they find, attack and quickly break down the molecules that make certain kinds of stains.
Food and Drug Administration (FDA): target of many love/hate feelings. It’s a federal agency in the USA, and one of its tasks is to make sure that any new drugs or devices are safe before they get put on the market. Sometimes they seem ridiculously cautious, asking for study after study with more and more data before they’ll say yes to anything. On the other hand, they protect us from quacks trying to get rich without making us better. Love ‘em, hate ‘em, whatever — we have to deal with them.
fibrin: filler for the hole in a damaged spinal cord. The scientists who are trying to get axons to cross that cavity have to have something for those axons to be on while they’re growing, in the same way that ivy needs something to crawl up. In the experiments Os Steward’s team did, they used fibrin taken from salmon.
gene: a chunk of DNA. Almost every gene is a do-it-yourself kit for creating a particular protein. It’s an amazing kit, because in a way it comes with built-in timers that tell it when the conditions are perfect for making that protein, and when it would be better not to make it. One of the things scientists have been trying to figure out is which of the many thousands of genes in our bodies are the ones that control axon growth. Those genes must have been switched from ON (grow axons now!) to OFF (don’t grow axons anymore!) at some point during development, right? We want to find them and switch them back ON.
genome: the full set of human genes. Here’s a good analogy, stolen directly from Matt Ridley’s excellent Genome. “Imagine that the genome is a book. There are 23 chapters, called chromosomes. Each chapter contains several thousand stories, called genes . . . ” Those stories are written with just four letters, which are the four bases A, C, G and T. Reading for 8 hours a day, it would take a century to read the whole genome out loud at the rate of one word per second. There’s a good timeline here if you want to marvel at how quickly science can move forward.
Geron: company that first got FDA permission to run trials on people with spinal cord injury using human embryonic stem cells. The Geron Trials, as they’re known, were halted after just a few patients had been given a very small dose of the cells. Why? Because after many years of funding the basic science and working to meet the FDA’s very high bars, the company decided that they needed to put their money into something that would lead to a faster, higher return. The required testing timeline was just too long.
glial cells: the cells in your brain and spinal cord that aren’t neurons, which is about half of them. The rest are either astrocytes or oligodendrocytes, collectively known as glial cells. Back when scientists and doctors didn’t understand that these cells had critical jobs of their own, they thought of them as just a sort of glue — something needed to hold the neurons in place. The word glial is Greek for glue.
glial-restricted precursors: cells on their way to becoming either astrocytes or oligodendrocytes. The video on the menu at the top of this page has a good description of how this works; all our cells started out as one type (embryonic stem cells) and then gradually split off into four different directions, like major branches off the trunk of a maple tree. About halfway along the branch that leads to cells in the brain and spinal cord are these “precursors” — cells that are going to become either astrocytes or oligodendrocytes, but not neurons.
GMP (good manufacturing process): the way you want labs to be set up. Having a GMP lab means, basically, meeting the very highest standards for process and production, as defined by the FDA.
gray matter: neuron cell bodies. In cross sections of spinal cords, the gray matter is the part of the image in the center that looks vaguely like a butterfly. It’s made of neuron cell bodies.
hemisection: an injury type often used on lab rats. It means damaging exactly half (right or left side) of the cord and leaving the other half intact, like taking a sharp knife to make a clean cut through the left half of a French loaf . Scientists use this model because it lets them test their therapies on animals that couldn’t survive complete transections.
human embryonic stem cells (hESC): the first cells in the lifecycle of a human. You have the egg and the sperm, and if fertilization happens, you get a completely new and different thing — a zygote. It has a nucleus with DNA from both the egg and the sperm, and it can replicate itself perfectly. It’s a human embryonic stem cell. Under the right conditions, it can be maintained in that state indefinitely — always a stem cell, never going on to become another cell type. The promise of these cells (first isolated in 1998) is that they can — theoretically — be coaxed into becoming any other kind of cell that’s needed.
human neural stem cells: these can become neurons, oligodendrocytes, or astrocytes, but nothing else. They’re one branching back on the tree from glial precursors.
humanitarian use device (HUD): not a drug, and meant for use in a small number of very desperate people . The most important thing about this FDA designation? The thing under consideration is not a drug and doesn’t need to go through all the expensive, time-consuming animal studies and data-production work that most drugs do. An example would be inVivo’s little scaffold. It’s a device that, if all goes well, can be used to both fill the hole in a damaged cord and serve as a delivery device when filled up with chABC, or BDNF, or neural stem cells, or whatever else can be combined to form a treatment that works.
incomplete injury: what passes for luck in spinal cord injury world. Any movement or sensation, no matter how small or useless, means that the injury is incomplete. There are, of course, levels of incompleteness, which is where the ASIA designations come into play.
interneurons: nerve cells inside the spinal cord that act like relay switches. If your sensation is normal, brushing against a hot surface makes you jump back before your brain even registers that something is wrong. What happens is that a sensory neuron in your hand carries the ouch message into the cord, where it gets heard by an interneuron and transmitted directly to a motor neuron, which causes you to reflexively jerk away. No brain required.
in vitro: in a glass dish. When you hear someone say that this or that experiment worked in vitro, know that this means there’s still a lot of work to be done. The experiment needs to work, eventually, in a person.
in vivo: in a living creature. This is the middle stage between in vitro and in you or me. When the in vitro work goes well, a scientist who has the means to do it will move on to animal experiments. Why? Because the FDA almost always requires lots of animal experiments before it will give the okay for a drug or treatment to be tested on human volunteers. Animal experiments are usually called pre-clinical work. Clinical trials always means carefully controlled experiments on human beings.
investigational new drug (IND): FDA-speak for something never tried before.
induced pluripotent stem cells (iPSC): magic. These are cells that have been taken back in time so that they behave just like embryonic stem cells. Why does this matter? Because it means — theoretically — that it’s possible to take a skin cell off your arm and turn it into an oligodendrocyte that has your own DNA. Your immune system would recognize the reformed cell as part of your body. The cells are “pluripotent” because they’re all-powerful. Many people see these cells as the future of cell-based therapies because they skirt the issue of taking embryonic stem cells from leftover embryos.
KLF7: one of the genes that tells corticospinal axons whether to grow or not. (The others identified so far are PTEN, SOCS3 and SOX11). Murray Blackmore talked about this one at Working 2 Walk in 2012. The video is here, or you can read about in Chapter 3 of my book.
lower motor neuron injury: damage to the bridge. I think of the spinal cord as a sort of massively complex superhighway that has a collection of exit ramps going off from its sides. Some of those exit ramps are there to send instructions to the muscles in the legs and feet; those are called lower motor neurons. In this kind of injury, the cord itself is okay, but the bridge has taken a hit. People with complete LMN injuries have rag doll legs, because there’s no signal of any kind getting to the muscles.
lumbar injury: a spinal cord injury in the lower back area.
Miami Project to Cure Paralysis (Miami Project): largest collection of people working together on curing spinal cord injury in the world. Formed in 1985, the Miami Project was intended to be a version of the Manhattan Project — a very focused effort to solve a particular difficult problem in the shortest possible time. Their website is a warehouse of detail about their progress and plans.
motor neuron: final link in the chain. A motor neuron’s axon grows out of the cord and ends to up right on a muscle fiber; its nucleus is in the gray matter inside the cord. That nucleus in the cord gray matter got its instructions in turn from a different axon that comes from another neuron — one that sits up in the brain. It’s a communication system that happens constantly and at lightning speed.
myelin: protective coating for an axon. Axons can’t carry messages efficiently without myelin, and many strategies to help restore function after spinal cord injury have to do with replacing myelin on axons that have survived. One of the important jobs of the glial cells called oligodendrocytes is to produce myelin and wrap it tightly around nearby axons. The Geron trials involved a scheme to take human embryonic stem cells, nurture them into becoming oligodendrocyte precursors, take those precursors and inject them into a damaged cord, and watch while they restored communication by “insulating” surviving axons. We still don’t know if that would have worked, because the trials were stopped while the dose was too low to be effective. We do know that there was no negative effect from those cells in the few people who volunteered for the treatment.
nerve cell: another name for neuron. If you’re a fan of video-based learning, go here now and spend 6 minutes of your life. It will be worth it.
neuron: the body’s communication device. Neurons are such weird cells. There’s the cell body, and then the lonely axon with its bundle of terminals, and then a collection of dendrites like dense little twigs. The way one neuron talks to another — say, a neuron in your brain talking to another neuron inside your spinal cord — is that the brain neuron’s axon hooks up with the spinal cord neuron’s dendrite. The two parts exchange some charged molecules through a vanishingly tiny space in a vanishingly small time . . . and that’s communication.
neuronal restricted precursors: cells still in a development stage that can only become neurons. They’re like vice-presidents, just waiting around to take on the one job they’re allowed to have.
neurotransmitter: better living through chemistry. Neurotransmitters are very specific molecules that travel the tiny, tiny space between a neuron that’s sending information and another neuron that’s receiving it. In a certain sense, neurotransmitters are the information.
National Institutes of Health (NIH): biggest funder of medical research on earth. NIH started off as a one-room lab in 1798; today it’s got dozens of focus areas called institutes, one of which is NINDS. NINDS stands for National Institute of Neurological Disorders and Stroke. The NIH conducts some research of its own, but mostly they hand out their budgeted money (around $30 billion in 2013, depending on congress) in the form of grants to scientists working on promising projects. Here’s my favorite bullet from the NINDS vision statement:
- To seize opportunities to focus our resources to rapidly translate scientific discoveries into prevention, treatment, and cures.
nucleus: the part of a cell that holds its DNA. Cells are amazing things, and if you’re like me (untrained in biology, thanks to a pathetic experience in high school), I really recommend that you spend 21 minutes letting the good folks at Kahn Academy show you the basics. Seriously, best instruction anywhere.
oligodendrocyte: one of the three kinds of cells present in the brain and spinal cord. Their name is descriptive, if you understand Greek. Oligo means few; dendro means tree, and cyte means cell. So, these are cells that look vaguely like a small collection of branches. (They actually do.) Oligodendrocytes produce the white stuff called myelin that wraps around axons, which makes them very important in any recovery scenario, because axons without myelin aren’t going to be able to communicate. A single oligodendrocyte can myelinate dozens of nearby axons.
oligodendrocyte progenitor cell (OPC): a cell that’s fully committed to becoming an oligodendrocyte, but isn’t actually one yet. The cells that were injected into a few patients in the Geron trials were OPCs that had been cultivated in a lab all the way along the development route from embryonic stem cells to ectoderm cells to neural stem cells to oligodendrocyte progenitors. Quite incredible, when you think about it.
peptide: receptor turner-offer. Well, actually a peptide is just a really short chain of amino acids, which is what keeps it from being a protein. (Proteins are long chains of amino acids.) At Working 2 Walk in 2012, Jerry Silver did a terrific presentation about how his team had used a couple of custom-made peptides to “un-stick” axons that had gotten bogged down in the injury site. The axons were doing what axons do — looking for some cozy receptors to form synapses with. It turned out that one reason proteoglycans were like flypaper to axons was that they had these receptor molecules. The axons hooked up with them and then sat there doing nothing. Jerry’s peptides acted like a turn-off switch to those receptor molecules, and voila, the axons moved on. Video here, Chapter 7 in the book.
peripheral nervous system: all the nerves that aren’t part of the brain/spinal cord system. The word “nerve” in this context means a sort of long tube that holds bundles of axons. You have sensory tubes, which gather up news about both what’s happening outside you (sun on your arms, someone pulling on your big toe) and what’s happening inside you (sore muscle, hunger). Then there are motor tubes, which take instructions from inside your spinal cord outside to your fingers, toes, and all the rest of you. These bundles of axons, under the right conditions, can and do regenerate all the time.
pluripotent: full of possibilities. In the world of spinal cord injury research, we usually see that word used to describe cells that are way at the beginning of the differentiation process, like embryonic stem cells. They can become any other kind of cell. A neural stem cell can only become one of three kinds of cell, so it’s described as multipotent. Pluri beats multi, in terms of optional uses, but multi beats pluri, in terms of scientific wizardry required to get it to do what you need it to do.
protein: we’re not talking about eating steak here. We’re talking about the specific and complicated little gizmos that construct and form the machinery that runs your cells. Proteins also deliver the signaling that sets the timing and pace of how that machinery functions. And they’re made out of chains of amino acids. The end.
proteoglycan: a molecule with a protein (proteo!) core surrounded by sugar chains (glycans!). The word is — in our context — interchangeable with chondroitin sulfase proteoglycan and its acronym, CSPG. Have a look at the description under that name.
PTEN: one of the genes that tells corticospinal axons whether to grow or not. (The others identified so far are KLF7, SOCS3 and SOX11).
receptor: structure that knows how to say hello and come on in. When one neuron’s axon is forming a synapse with the dendrite of another neuron, what it’s doing is sending some molecules (neurotransmitters) across the microscopic space between them. Those molecules can’t land unless the dendrite has receptors open and ready to receive them. I think of them like little docking stations, because the shape of the receptor has to match the shape of the molecule coming at it.
rehab: absolutely necessary component of anything resembling a cure. What the scientists and doctors have to do is restore communication through or around the injury site. They need to get axons across, and those axons need to make connections that eventually lead to muscles. After that, patients are going to have to work like crazy to bring those muscles up to strength.
scar, glial: red brick wall all around the injury site that prevents axons from growing on to the other side. Okay, it’s not brick and it’s not red, and it’s really not so much a wall as a collection of proteoglycans, together with oligodendrocyte progenitor cells. There’s a very strange thing going on in that mess, as Jerry Silver explained to us at Working 2 Walk 2012. (Video here, Chapter 7 in thebook). The thing to know is that the “scar” is not at all like what forms on your knee that you skinned badly when you were nine. It’s far mushier, and far more complex, and it must be dealt with.
spinal cord injury (SCI): ugh. Damage to the cord that results in loss of sensation and movement, along with screwed up bowel, bladder, and sexual function. Also sometimes comes with involuntary spasms, fragile skin, lots of pain, frequent hospitalizations, and need for personal assistants. Oh, and don’t forget difficulties in traveling and navigating public spaces. Plus expensive rehab that may or may not be helpful. Like I said: ugh.
SOCS3: another one of the genes that tells corticospinal axons whether to grow or not. (The others identified so far are PTEN, KLF7 and SOX11).
SOX11: and yet another one of the genes that tells corticospinal axons whether to grow or not. (The others identified so far are PTEN, SOCS3 and SOX11). How many of these are there, anyway? We don’t know. How many of them will need to be shut off in order for axons to grow? We don’t know that either.
suspended gait training: looks weird, seems crazy, but it works. The word, “gait” means “a particular way of moving.” Each of us has that — a particular way of moving. Sometimes a way of walking is shared by family members; I have a set of cousins whose head-down, long-stride, shoulders-hunched gait can be tagged from 50 yards away. Suspended gait training is called that because it makes use of a suspension system (usually a harness over a treadmill) to help a partially paralyzed person recover their natural way of walking. It works, or at least it worked in one case I know of. My husband was in a clinical trial (long thread about it here) that tested one form of suspended gait training. He looked very odd in his elaborate harness, strung like a large human puppet over a highly sensitive treadmill . . . but after ten weeks of the training, he could walk far more naturally than when it began.
synapse: the giver and the taker and the space in between. The synapse is the magical point of connection between a pair of neurons — the place and structure where one neuron’s axon can pass information to another neuron’s dendrite.
synaptic cleft: most important tiny space in the universe. If you can imagine splitting off 1/20,000th of a human hair, you’ve got a feel for the distance between an axon and a dendrite when they’re in the midst of communicating. The cleft isn’t empty space either; it’s filled with molecules called neurotransmitters.
thoracic injury: spinal cord injury to the part of the cord that lies between the shoulder blades and the bottom of the rib cage.
transcription: copying the recipe. Remember when I said that the genome is like a book, and that genes are like recipes for specific proteins? Let’s stick with that analogy. The genome isn’t just any book, it’s a cookbook full of recipes, but it’s the kind of book you can’t check out of the library — a reference book. If you want to get one of those recipes out of it and make yourself a nice new protein, you have to have a way to copy the recipe and get it to a kitchen. Transcription is the process by which the recipe gets copied. The copied-out recipe is called messenger RNA (mRNA). After that comes translation, which is where the recipe gets turned into lunch — where the new protein gets built.
transection: clean cut all the way through. When scientists are trying to show beyond all shadow of a doubt that they’ve succeeded in getting axons to grow across an injury site, they sometimes start by giving the experimental animals a complete transection injury. The spinal cord is cut into two pieces that do not touch one another at any point. (Sorry, animals.) The other kinds of injuries used in labs are called hemisection and contusion. Both are defined above.
ventral: towards the front. It comes from the Latin word venter, which means belly or paunch. Suck in your venters, people.
virus: most abundant life form on earth. Really. A small bundle of genes inside a snug protein coat, the virus has only one purpose, and that is to find a nice fat cell to occupy. Once a virus gets inside a cell, it gets to work making thousands of copies of itself, each of which in turn goes off to find other cells, invade them, and repeat the process.
white matter: bundles of axons in their white myelin coats. In the cross section of a spinal cord, there’s the gray-matter-butterfly shape in the center, surrounded by white stuff. That white stuff is actually made of bundles (usually called tracts) of myelin-coated axons coming down from neuron cell bodies that originate up in the brain.