From spiders to breast cancer: Leslie Brunetta talks candidly about her cancer diagnosis, treatment, and follow-up

According to Leslie Brunetta, she now has much more hair than she had last July.

We became aware of Leslie Brunetta because of her book, Spider Silk: Evolution and 400 Million Years of Spinning, Waiting, Snagging, and Mating, co-authored with Catherine L. Craig. Thanks to a piece Leslie wrote for the Concord Monitor (and excerpted here), we also learned that she is a breast cancer survivor. Leslie agreed to an interview about her experience, and in her emailed responses, she candidly talks about her diagnosis, treatment, and follow-up for her cancers, plural: She was diagnosed simultaneously with two types of breast cancer. 

DXS: In your Concord Monitor piece, you describe the link between an understanding of the way evolution happens and some of the advances in modern medicine. What led you to grasp the link between the two?

LB: I think, because I’m not a scientist (I’m an English major), a lot of things that scientists think are obvious strike me as revelations. I somehow had never realized that the search for what would turn out to be DNA began with trying to explain how, in line with the theory of evolution by natural selection, variation arises and traits are passed from generation to generation. As I was figuring out what each chapter in Spider Silk would be about, I tried to think about the questions non-biologists like me would still have about evolution when they got to that point in the book. By the time we got past dragline silk, I realized that we had so far fleshed out the ways that silk proteins could and have evolved at the genetic level. But that explanation probably wouldn’t answer readers’ questions about how, for example, abdominal spinnerets—which are unique to spiders—might have evolved: the evolution of silk is easier to untangle than the evolution of body parts, which is why we focused on it in the first place.

I decided I wanted to write a chapter on “evo-devo,” evolutionary developmental biology, partly because there was a cool genetic study on the development of spinnerets that showed they’ve evolved from limbs. Fortunately, my co-author, Cay Craig, and editor at Yale, Jean Thomson Black, okayed the idea, because that chapter wasn’t in the original proposal. Writing that chapter, I learned why it took so long—nearly a century—to get from Darwin and Mendel to Watson and Crick and then so long again to get to where we are today. If we non-scientists understand something scientific, it’s often how it works, not how a whole string of people over the course of decades building on each other’s work discovered how it works. I knew evolution was the accumulation of gene changes, but, until I wrote that chapter, it hadn’t occurred to me that people began to look for genes because they wanted to understand evolution.

So that was all in the spider part of my life. Then, a few months into the cancer part of my life, I was offered a test called Oncotype DX, which would look at genetic markers in my tumor cells to develop a risk profile that could help me decide whether I should have chemotherapy plus tamoxifen or just tamoxifen. The results turned out to be moot in my case because I had a number of positive lymph nodes, although it was reassuring to find out that the cancer was considered low risk for recurrence. But still—the idea that a genetic test could let some women avoid chemo without taking on extra risk, that’s huge. No one would want to go through chemo if it wasn’t necessary. So by then I was thinking, “Thank you, Darwin!”

And then, coincidentally, the presidential primary season was heating up, and there were a number of serious candidates (well, serious in the sense that they had enough backing to get into the debates) who proudly declared that they had no time for the theory of evolution. And year after year these stupid anti-evolution bills are introduced in various state legislatures. While I was lying on the couch hanging out in the days after chemo sessions, I started thinking, “So, given that you don’t give any credence to Darwin and his ideas, would you refuse on principle to take the Oncotype test or gene-based therapies like Gleevec or Herceptin if you had cancer or if someone in your family had cancer? Somehow I don’t think so.” That argument is not going to convince hard-core denialists (nothing will), but maybe the cognitive dissonance in connection with something as concrete as cancer will make some people who waver want to find out more.

DXS: You mention having been diagnosed with two different forms of cancer, one in each breast. Can you say what each kind was and, if possible, how they differed?

LB: Yes, I unfortunately turned out to be an “interesting” case. This is one arena where, if you possibly can, you want to avoid being interesting. At first it seemed that I had a tiny lesion that was an invasive ductal carcinoma (IDC) and that I would “just” need a lumpectomy and radiation. Luckily for me, the doctor reading my mammogram is known as an eagle eye, and she saw a few things that—given the positive finding from the biopsy—concerned her. She recommended an MRI. In fact, even though I switched to another hospital for my surgery, she sent emails there saying I should have an MRI. That turned up “concerning” spots in both breasts, which led to more biopsies, which revealed multiple tiny cancerous lesions. The only reasonable option was then a double mastectomy.

The lesions in the right breast were IDCs. About 70% of breast cancers are diagnosed as IDCs. Those cancers start with the cells lining the milk ducts. The ones in the left breast were invasive lobular carcinomas (ILCs), which start in the lobules at the end of the milk ducts. Only about 10% of breast cancers are ILCs.

Oncologists hate lobular cancer. Unlike ductal cancers, which form as clumps of cells, lobular cancers form as single-file ribbons of cells. The tissue around ductal cancer cells reacts to those cells, which is why someone may feel a lump—she’s (or he’s) not feeling the cancer itself but the inflammation of the tissue around it. And because the cells clump, they show up more readily on mammograms. Not so lobular cancers. They mostly don’t give rise to lumps and they’re hard to spot on mammograms. They snake their way through tissue for quite a while without bothering anything.

In my case, this explains why last spring felt like an unremitting downhill slide. Every time someone looked deeper, they found something worse. It turned out that on my left side, the lobular side, I had multiple positive lymph nodes, which was why I needed not just chemo but also radiation (which usually isn’t given after a mastectomy). That was the side that didn’t even show up much on the mammogram. On the right side, the ductal side, which provoked the initial suspicions, my nodes were clear. I want to write about this soon, because I want to find out more about it. I’ve only recently gotten to the place emotionally where I think I can deal with reading the research papers as opposed to more general information. By the way, the resource that most helped us better understand what my doctors were talking about was Dr. Susan Love’s Breast Book.  It was invaluable as we made our way through this process, although it turned out that I had very few decisions to make because there was usually only one good option.   

DXS: As part of your treatment, you had a double mastectomy. One of our goals with this interview is to tell women what some of these experiences with treatment are like. If you’re comfortable doing so, could you tell us a little bit about what a double mastectomy entails and what you do after one in practical terms?

LB: A mastectomy is a strange operation. In a way, it’s more of an emotional and psychological experience than a physical experience. My surgeon, who was fantastic, is a man, and when we discussed the need for the mastectomies he said that I would be surprised at how little pain would be involved and how quick the healing would be. Even though I trusted him a lot by then, my reaction was pretty much, “Like you would know, right?” But he did know. When you think about it, it’s fairly non-invasive surgery. Unless the cancer has spread to the surrounding area, which doesn’t happen very often now due to early detection, no muscle or bone is removed. (Until relatively recently, surgeons removed the major muscle in the chest wall, and sometimes even bone, because they believed it would cut the risk of recurrence. That meant that many women lost function in their arm and also experienced back problems.) None of your organs are touched. They don’t go into your abdominal cavity. Also, until recently, they removed a whole clump of underarm lymph nodes when they did lumpectomies or mastectomies. Now they usually remove just a “sentinel node,” because they know that it will give them a fairly reliable indicator of whether the cancer has spread to the other nodes. That also makes the surgery less traumatic than it used to be.

I opted not to have reconstruction. Reconstruction is a good choice for many women, but I didn’t see many benefits for me and I didn’t like the idea of a more complicated surgery. My surgery was only about two hours. I don’t remember any pain at all afterwards, and my husband says I never complained of any. I was in the hospital for just one night. By the next day, I was on ibuprofen only. The bandages came off two days after the surgery.

That’s shocking, to see your breasts gone and replaced by thin red lines, no matter how well you’ve prepared yourself. It made the cancer seem much more real in some way than it had seemed before. In comparison, the physical recovery from the surgery was fairly minor because I had no infections or complications. There were drains in place for about 10 days to collect serum, which would otherwise collect under the skin, and my husband dealt with emptying them twice a day and measuring the amount. I had to sleep on my back, propped up, because of where the drains were placed, high up on my sides, and I never really got used to that. It was a real relief to have the drains removed.

My surgeon told me to start doing stretching exercises with my arms right away, and that’s really important. I got my full range of motion back within a couple of months. But even though I had my surgery last March, I’ve noticed lately that if I don’t stretch fully, like in yoga, things tighten up. That may be because of the radiation, though, because it’s only on my left side. Things are never quite the same as they were before the surgery, though. Because I did have to have the axillary nodes out on my left side, my lymph system is disrupted. I haven’t had any real problems with lymphedema yet, and I may never, but in the early months I noticed that my hands would swell if I’d been walking around a lot, and I’d have to elevate them to get them to drain back. That rarely happens now. But I’ve been told I need to wear a compression sleeve if I fly because the change in air pressure can cause lymph to collect. Also, I’m supposed to protect my hands and arms from cuts as much as possible. It seems to me that small nicks on my fingers take longer to heal than they used to. So even though most of the time it seems like it’s all over, I guess in those purely mechanical ways it’s never over. It’s not just that you no longer have breasts, it’s also that nerves and lymph channels and bits of tissue are also missing or moved around.

The bigger question is how one deals with now lacking breasts. I’ve decided not to wear prostheses. I can get away with it because I was small breasted, I dress in relatively loose clothes anyway, and I’ve gained confidence over time that no one notices or cares and I care less now if they do notice. But getting that self-confidence took quite a while. Obviously, it has an effect on my sex life, but we have a strong bond and it’s just become a piece of that bond. The biggest thing is that it’s always a bit of a shock when I catch sight of myself naked in a mirror because it’s a reminder that I’ve had cancer and there’s no getting around the fact that that sucks.    

DXS: My mother-in-law completed radiation and chemo for breast cancer last year, and if I remember correctly, she had to go frequently for a period of weeks for radiation. Was that you experience? Can you describe for our readers what the time investment was like and what the process was like?

LB: I went for radiation 5 days a week for about 7 weeks. Three days a week, I’d usually be in and out of the hospital within 45 minutes. One day a week, I met with the radiology oncologist and a nurse to debrief, which was also a form of emotional therapy for me. And one day a week, they laid on a chair massage, and the nurse/massage therapist who gave the massage was great to talk to, so that was more therapy. Radiation was easy compared to chemo. Some people experience skin burning and fatigue, but I was lucky that I didn’t experience either. Because I’m a freelancer, the time investment wasn’t a burden for me. I’m also lucky living where I live, because I could walk to the hospital. It was a pleasant 3-mile round-trip walk, and I think the walking helped me a lot physically and mentally.

DXS: And now to the chemo. My interest in interviewing you about your experience began with a reference you made on Twitter to “chemo brain,” and of course, after reading your evolution-medical advances piece. Can you tell us a little about what the process of receiving chemotherapy is like? How long does it take? How frequently (I know this varies, but your experience)?

LB: Because of my age (I was considered young, which was always nice to hear) and state of general good health, my oncologist put me on a dose-dense AC-T schedule. This meant going for treatment every two weeks over the course of 16 weeks—8 treatment sessions. At the first 4 sessions, I was given Adriamycin and Cytoxan (AC), and the last 4 sessions I was given Taxol (T). The idea behind giving multiple drugs and giving them frequently is that they all attack cancer cells in different ways and—it goes back to evolution—by attacking them frequently and hard on different fronts, you’re trying to avoid selecting for a population that’s resistant to one or more of the drugs. They can give the drugs every two weeks to a lot of patients now because they’ve got drugs to boost the production of white blood cells, which the cancer drugs suppress. After most chemo sessions, I went back the next day for a shot of one of these drugs, Neulasta.

The chemo clinic was, bizarrely, a very relaxing place. The nurses who work there were fantastic, and the nurse assigned to me, Kathy, was always interesting to talk with. She had a great sense of humor, and she was also interested in the science behind everything we were doing, so if I ever had questions she didn’t have ready answers for, she’d find out for me. A lot of patients were there at the same time, but we each had a private space. You’d sit in a big reclining chair. They had TVs and DVDs, but I usually used it as an opportunity to read. My husband sat through the first session with me, and a close friend who had chemo for breast cancer 15 years ago sat through a few other sessions, but once I got used to it, I was comfortable being there alone. Because of the nurses, it never felt lonely.

I’d arrive and settle in. Kathy would take blood for testing red and white blood counts and, I think, liver function and some other things, and she’d insert a needle and start a saline drip while we waited for the results. I’ve always had large veins, so I opted to have the drugs administered through my arm rather than having a port implanted in my chest. Over the course of three to four hours, she’d change the IV bags. Some of the bags were drugs to protect against nausea, so I’d start to feel kind of fuzzy—I don’t think I retained a whole lot of what I read there! The Adriamycin was bright orange; they call it the Red Devil, because it can chew up your veins—sometimes it felt like it was burning but Kathy could stop that by slowing the drip. Otherwise, it was fairly uneventful. I’d have snacks and usually ate lunch while still hooked up.

I was lucky I never had any reactions to any of the drugs, so actually getting the chemo was a surprisingly pleasant experience just because of the atmosphere. On the one hand, you’re aware of all these people around you struggling with cancer and you know things aren’t going well for some of them, so it’s heartbreaking, and also makes you consider, sometimes fearfully, your own future no matter how well you’re trying to brace yourself up. But at the same time, the people working there are so positive, but not in a Pollyannaish-false way, that they helped me as I tried to stay positive. The social worker stopped in with each patient every session, and she was fantastic—I could talk out any problems or fears I had with her, and that helped a huge amount.

DXS: Would you be able to run us through a timeline of the physical effects of chemotherapy after an infusion? How long does it take before it hits hardest? My mother-in-law told me that her biggest craving, when she could eat, was for carb-heavy foods like mashed potatoes and for soups, like vegetable soup. What was your experience with that?

LB: My biggest fear when I first learned I would need chemo was nausea. My oncologist told us that they had nausea so well controlled that over the past few years, she had only had one or two patients who had experienced it. As with the surgeon’s prediction about mastectomy pain, this turned out to be true: I never had even a single moment of nausea.

But there were all sorts of other effects. For the first few days after a session, the most salient effects were actually from the mix of drugs I took to stave off nausea. I generally felt pretty fuzzy, but not necessarily sleepy—part of the mix was steroids, so you’re a little hyped. There’s no way I’d feel safe driving on those days, for example. I’d sleep well the first three nights because I took Ativan, which has an anti-nausea effect. But except for those days, my sleep was really disrupted. Partly that’s because, I’m guessing, the chemo hits certain cells in your brain and partly it’s because you get thrown into chemical menopause, so there were a lot of night hot flashes. Even though I’d already started into menopause, this chemo menopause was a lot more intense and included all the symptoms regularly associated with menopause.

By the end of the first session, I was feeling pretty joyful because it was much less bad than I had thought it would be. By the second week in the two-week cycle, I felt relatively normal. But even though it never got awful, the effects started to accumulate. My hair started to fall out the morning I was going to an award ceremony for Spider Silk. It was ok at the ceremony, but we shaved it off that night. I decided not to wear a wig. First, it was the summer, and it would have been hot. Second, I usually have close to a buzz cut, and I can’t imagine anyone would make a wig that would look anything like my hair. My kids’ attitude was that everyone would know something was wrong anyway, so I should just be bald, and that helped a lot. But it’s hard to see in people’s eyes multiple times a day their realization that you’re in a pretty bad place. Also, it’s not just your head hair that goes. So do your eyebrows, your eyelashes, your pubic hair, and most of the tiny hairs all over your skin. And as your skin cells are affected by the chemo (the chemo hits all fast-reproducing cells), your skin itself gets more sensitive and then is not protected by those tiny hairs. I remember a lot of itching. And strange things like my head sticking to my yoga mat and my reading glasses sticking to the side of my head instead of sliding over my ears.

I never lost my appetite, but I did have food cravings during the AC cycles. I wanted sushi and seaweed salad, of all things. And steak. My sense of taste went dull, so I also wanted things that tasted strong and had crunch. I stopped drinking coffee and alcohol, partly because of the sleep issues but partly because it didn’t taste very good anyway. I drank loads of water on the advice of the oncologist, the nurses, and my acupuncturist, and I think that helped a lot.

During the second cycle, I developed a fever. That was scary. I was warned that if I ever developed a fever, I should call the oncologist immediately, no matter the time of day or day of week. The problem is that your immune response is knocked down by the chemo, so what would normally be a small bacterial infection has the potential to rage out of control. I was lucky. We figured out that the source of infection was a hemorrhoid—the Adriamycin was beginning to chew into my digestive tract, a well-known side effect. (Having to pay constant attention to yet another usually private part of the body just seemed totally unfair by this point.) Oral antibiotics took care of it, which was great because I avoided having to go into the hospital and all the risks entailed with getting heavy-duty IV antibiotic treatment. And we were also able to keep on schedule with the chemo regimen, which is what you hope for.

After that, I became even more careful about avoiding infection, so I avoided public places even more than I had been. I’m very close to a couple of toddlers, and I couldn’t see them for weeks because they were in one of those toddler constant-viral stages, and I really missed them.

The Taxol seems to be much less harsh than the AC regimen, so a lot of these side effects started to ease off a bit by the second 8 weeks, which was certainly a relief.

I was lucky that I didn’t really have mouth sores or some of the other side effects. Some of this is, I think, just because besides the cancer I don’t have any other health issues. Some of it is because my husband took over everything and I don’t have a regular job, so I had the luxury of concentrating on doing what my body needed. I tried to walk every day, and I slept when I needed to, ate when and what I needed to, and went to yoga class when my immune system was ok. I also went to acupuncture every week. I know the science is iffy on that, but I think it helped me with the side effects, even if it was the placebo effect at work (I’m a big fan of the placebo effect). We also both had extraordinary emotional support from many friends and knew we could call lots of people if we needed anything. That’s huge when you’re in this kind of situation.

Currently, I’m still dealing with some minor joint pains, mostly in my wrists and feet. I wasn’t expecting this problem, but my oncologist says it’s not uncommon: they think it’s because your immune system has to re-find its proper level of function, and it can go into overdrive and set up inflammation in the joints. That’s gradually easing off, though.

Most people don’t have it as easy as I did in terms of the medical, financial, and emotional resources I had to draw on. I’m very mindful of that and very grateful.

DXS: You say that you had “few terrible side effects” and a “very cushy home situation.” I’m sure any woman would like to at least be able to experience the latter while dealing with a full-body chemical attack. What were some factors that made it “cushy” that women might be able to talk to their families or caregivers about replicating for them?

LB: As I’ve said, some of it is just circumstance. For example, my kids were old enough to be pretty self-sufficient and old enough to understand what was going on, which meant both that they needed very little from me in terms of care and also that they were less scared than they might have been if they were younger. My husband happens to be both very competent (more competent than I am) around the house and very giving. I live in Cambridge, MA, where I could actually make choices about where I wanted to be treated at each phase and know I’d get excellent, humane care and where none of the facilities I went to was more than about 20 minutes away.

Some things that women might have some control over and that their families might help nudge them toward:

• Find doctors you trust. Ask a lot of questions and make sure you understand the answers. But don’t get hung up on survival or recurrence statistics. There’s no way to know for sure what your individual outcome will be. Go for the treatment that you and your doctors believe will give you the best chance, and then assume as much as possible that your outcome will be good.
• Make sure you talk regularly with a social worker or other therapist who specializes in dealing with breast cancer patients. If you have fears or worries that you don’t want to talk to your partner or family about, here’s where you’ll get lots of help.
• Find compatible friends who have also had cancer to talk to. I had friends who showed me their mastectomy scars, who showed me their reconstructions, who told me about their experiences with chemo and radiation, who told me about what life after treatment was like (is still like decades later…). And none of them told me, “You should…” They all just told me what was hard for them and what worked for them and let me figure out what worked for me. Brilliant.
• Try to get some exercise even if you don’t feel like it. It was often when I felt least like moving around that a short walk made me feel remarkably better. But I would forget that, so my husband would remind me. Ask someone to walk with you if you’re feeling weak. Getting your circulation going seems to help the body process the chemo drugs and the waste products they create. For the same reason, drink lots of water.
• Watch funny movies together. Laughter makes a huge difference.
• Pamper yourself as much as possible. Let people take care of you and help as much as they’re willing. But don’t be afraid to say no to anything that you don’t want or that’s too much.

Family members and caregivers should also take care of themselves by making some time for themselves and talking to social workers or therapists if they feel the need. It’s a big, awful string of events for everyone involved, not just the patient.

DXS: In the midst of all of this, you seem to have written a fascinating book about spiders and their webs. Were you able to work while undergoing your treatments? Were there times that were better than others for attending to work? Could work be a sort of occupational therapy, when it was possible for you to do it, to keep you engaged?

LB: The book had been published about 6 months before my diagnosis. The whole cancer thing really interfered not with the writing, but with my efforts to publicize it. I had started to build toward a series of readings and had to abandon that effort. I had also started a proposal for a new book and had to put that aside. I had one radio interview in the middle of chemo, which was kind of daunting but I knew I couldn’t pass up the opportunity, and when I listen to it now, I can hear my voice sounds kind of shaky. It went well, but I was exhausted afterwards. Also invigorated, though—it made me feel like I hadn’t disappeared into the cancer. I had two streams of writing going on, both of which were therapeutic. I sent email updates about the cancer treatment to a group of friends—that was definitely psychological therapy. I also tried to keep the Spider Silk blog up to date by summarizing related research papers and other spider silk news—that was intellectual therapy. I just worked on them when I felt I wanted to. The second week of every cycle my head was usually reasonably clear.

I don’t really know whether I have chemo brain. I notice a lot of names-and-other-proper-nouns drop. But whether that’s from the chemo per se, or from the hormone changes associated with the chemically induced menopause, or just from emotional overload and intellectual distraction, I don’t know. I find that I’m thinking more clearly week by week.

DXS: What is the plan for your continued follow-up? How long will it last, what is the frequency of visits, sorts of tests, etc.?

LB: I’m on tamoxifen and I’ll be on that for probably two years and then either stay on that or go onto an aromatase inhibitor [Ed. note: these drugs block production of estrogen and are used for estrogen-sensitive cancers.] for another three years. I’ll see one of the cancer doctors every three months for at least a year, I think. They’ll ask me questions and do a physical exam and take blood samples to test for tumor markers. At some point the visits go to every six months.

For self-care, I’m exercising more, trying to lose some weight, and eating even better than I was before.

DXS: Last…if you’re comfortable detailing it…what led to your diagnosis in the first place?

LB: My breast cancer was uncovered by my annual mammogram. I’ve worried about cancer, as I suppose most people do. But I never really worried about breast cancer. My mother has 10 sisters and neither she nor any of them ever had breast cancer. I have about 20 older female cousins—I was 50 when I was diagnosed last year--and as far as I know none of them have had breast cancer. I took birth control pills for less than a year decades ago. Never smoked. Light drinker. Not overweight. Light exerciser. I breastfed both kids, although not for a full year. Never took replacement hormones. Never worked in a dangerous environment. Never had suspicious mammograms before. So on paper, I was at very low risk as far as I can figure out. After I finished intensive treatment, I was tested for BRCA1 and BRCA2 (because mutations there are associated with cancer in both breasts) and no mutations were found. Unless or until some new genetic markers are found and one of them applies to me, I think we’ll never know why I got breast cancer, other than the fact that I’ve lived long enough to get cancer. There was no lump. Even between the suspicious mammogram and ultrasound and the biopsy, none of the doctors examining me could feel a lump or anything irregular. It was a year ago this week that I got the news that the first biopsy was positive. In some ways, because I feel really good now, it’s hard to believe that this year ever happened. But in other ways, the shock of it is still with me and with the whole family. Things are good for now, though, and although I feel very unlucky that this happened in the first place, I feel extremely lucky with the medical care I received and the support I got from family and friends and especially my husband.

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More about Leslie:

Leslie Brunetta's articles and essays have appeared in the New York Times, Technology Review, and the Sewanee Review as well as on NPR and elsewhere. She is co-author, with Catherine L. Craig, of Spider Silk: Evolution and 400 Million Years of Spinning, Waiting, Snagging, and Mating (Yale University Press).

How fluorescent lights work: quantum mechanics in the home

We have a tendency to think that "quantum mechanics" is synonymous with "out of the ordinary." I do that, too, since there's so much strange to talk about: the blurring of particles and waves, the apparent randomness that drove Einstein crazy, and so forth. It's easy to forget that quantum mechanics also is an everyday matter. The odds are pretty good you're reading this post on a computer screen (as opposed to a printout), and possibly the light you're using is fluorescent.


The three major types of lights you can buy are incandescent bulbs, fluorescent lights (including compact fluorescent lights), and light-emitting diodes. Incandescent bulbs are the "normal" type (though they are becoming less so): They light up when an electric current runs through a thin wire made of tungsten, which heats up. The wattage of an incandescent is a measure of how much power it consumes, and most of that power goes to heat, not light, which is why you can burn your hand if you touch a bulb that's been on any length of time. Because of the wasteful nature of that kind of bulb, a lot of people have made the switch to compact fluorescent lights (CFLs), which don't run hot and use a lot less power for the same amount of light. And they work by using quantum mechanics!


Of course even incandescent bulbs are quantum-mechanical underneath: after all, everything is quantum if you examine it closely enough. The everyday stuff of our lives is made of atoms, which are built up of protons, neutrons, and electrons, governed by the laws of quantum mechanics. However, the details of quantum mechanics often get blurred out, since we are big (relatively speaking) and atoms are small. We can't ignore quantum effects for fluorescent lights, though: The structure of atoms is what enables them to be higher efficiency than their incandescent cousins.

As you probably remember from school, atoms consist of a nucleus (containing protons and neutrons, which are relatively heavy) and electrons orbiting the nucleus. Electrons can only orbit at certain distances in specific patterns, which are dictated by the kind of atom: Hydrogen is different from helium, both of which are different from oxygen or mercury or sodium. I like to use a bookshelf analogy: The books can only lie on shelves, not at arbitrary points in midair. Different bookshelves may have different numbers and configurations of shelves. Lifting a book from a low shelf to a high shelf requires energy from you, just as moving an electron from a lower energy orbit to a higher energy orbit requires energy from outside the atom.

In a real atom, the outside energy can come from collisions with other atoms, or from bombardment by photons (particles of light) or electrons. The difference between a bookshelf and an atom lies in how the electron behaves once it is in a higher-energy orbit: If there is any available space left in a lower “shelf”, the electron jumps back down, emitting a photon. A lot of quantum mechanics involves calculating exactly what energies are involved in making those transitions: which ones are allowed and which are forbidden. We won't worry about that! All we care about is that atoms can absorb and emit only certain quantities (which is where the quantum in quantum mechanics comes from) of energy, and those quantities are determined by the type of atom. Big jumps in energy will correspond to ultraviolet light, while moderate jumps are visible light, and small jumps involve infrared light.

That's a lot of quantum mechanics in two short paragraphs, but it's most of what we need to understand fluorescent lights. Inside a fluorescent bulb (whether a big tube or a CFL), there's a very small amount of mercury, which is liquid at room temperatures. Electrodes at either end of the tube boil off electrons that collide with the mercury atoms, turning the liquid into a gas and kicking electrons into higher-energy states. Mercury produces a lot of photons in the ultraviolet and blue-light parts of the spectrum: a bare mercury bulb appears blue. Fluorescent lights have a coating called the phosphor, which absorbs that ultraviolet light and glows with visible light instead, losing the extra energy to heat (though a lot less than in incandescents).

I'm skipping over a lot of details (mostly involving how the bulbs regulate the flow of electrons through the tube – that's where the “ballast” comes in) but that's the basic idea. Fluorescent lights are more efficient than incandescents because the energy mostly goes directly into making the mercury glow, not into heating up a filiment. By using the quantum-mechanical properties of atoms, fluorescent lights are less hot, more energy efficient, and last longer. Quantum mechanics isn't just weird--it's practical!

By Matthew Francis, DXS physics editor 

Biology Xplainer: Evolution and how it happens

Evolution: a population changes over time

First of all, in the context of science, you should never speak of evolution as a "theory." There is no theory about whether or not evolution happens. It is a fact.

Scientists have, however, developed tested theories about how evolution happens. Although several proposed and tested processes or mechanisms exist, the most prominent and most studied, talked about, and debated, is Charles Darwin's idea that the choices of nature guide these changes. The fame and importance of his idea, natural selection, has eclipsed the very real existence of other ways that populations can change over time.

Evolution in the biological sense does not occur in individuals, and the kind of evolution we're talking about here isn't about life’s origins. Evolution must happen at least at the population level. In other words, it takes place in a group of existing organisms, members of the same species, often in a defined geographical area.

We never speak of individuals evolving in the biological sense. The population, a group of individuals of the same species, is the smallest unit of life that evolves.

To get to the bottom of what happens when a population changes over time, we must examine what's happening to the gene combinations of the individuals in that population. The most precise way to talk about evolution in the biological sense is to define it as "a change in the allele frequency of a population over time." A gene, which contains the code for a protein, can occur in different forms, or alleles. These different versions can mean that the trait associated with that protein can differ among individuals. Thanks to mutations, a gene for a trait can exist in a population in these different forms. It’s like having slightly different recipes for making the same cake, each producing a different version of the cake, except in this case, the “cake” is a protein.

Natural selection: One way evolution happens

Charles Darwin, a smart, thoughtful,
observant man. Via Wikimedia.

Charles Darwin, who didn't know anything about alleles or even genes (so now you know more than he did on that score), understood from his work and observations that nature makes certain choices, and that often, what nature chooses in specific individuals turns up again in the individuals' offspring. He realized that these characteristics that nature was choosing must pass to some offspring. This notion of heredity--that a feature encoded in the genes can be transmitted to your children--is inherent now in the theory of natural selection and a natural one for most people to accept. In science, an observable or measurable feature or characteristic is called a phenotype, and the genes that are the code for it are called its genotype. The color of my eyes (brown) is a phenotype, and the alleles of the eye color genes I have are the genotype.

What is nature selecting any individual in a population to do? In the theory of natural selection, nature chooses individuals that fit best into the current environment to pass along their "good-fit" genes, either through reproduction or indirectly through supporting the reproducer. Nature chooses organisms to survive and pass along those good-fit genes, so they have greater fitness.

Fitness is an evolutionary concept related to an organism's reproductive success, either directly (as a parent) or indirectly (say, as an aunt or cousin). It is measured technically based on the proportion of an individual's alleles that are represented in the next generation. When we talk about "fitness" and "the fittest," remember that fittest does not mean strong. It relates more to a literal fit, like a square peg in a square hole, or a red dot against a red background. It doesn't matter if the peg or dot is strong, just whether or not it fits its environment.

One final consideration before we move onto a synthesis of these ideas about differences, heredity, and reproduction: What would happen if the population were uniformly the same genetically for a trait? Well, when the environment changed, nature would have no choice to make. Without a choice, natural selection cannot happen--there is nothing to select. And the choice has to exist already; it does not typically happen in response to a need that the environment dictates. Usually, the ultimate origin for genetic variation--which underlies this choice--is mutation, or a change in a DNA coding sequence, the instructions for building a protein.

Don't make the mistake of saying that an organism adapts by mutating in response to the environment. The mutations (the variation) must already be present for nature to make a choice based on the existing environment.

The Modern Synthesis

When Darwin presented his ideas about nature's choices in an environmental context, he did so in a book with a very long title that begins, On the Origin of Species by Means of Natural Selection. Darwin knew his audience and laid out his argument clearly and well, with one stumbling block: How did all that heredity stuff actually work?

We now know--thanks to a meticulous scientist named Gregor Mendel (who also was a monk), our understanding of reproductive cell division, and modern genetics--exactly how it all works. Our traits--whether winners or losers in the fitness Olympics--have genes that determine them. These genes exist in us in pairs, and these pairs separate during division of our reproductive cells so that our offspring receive one member or the other of the pair. When this gene meets its coding partner from the other parent’s cell at fertilization, a new gene pair arises. This pairing may produce a similar outcome to one of the parents or be a novel combination that yields some new version of a trait. But this separating and pairing is how nature keeps things mixed up, setting up choices for selection.

Ernst Mayr, via PLoS.

With a growing understanding in the twentieth century of genetics and its role in evolution by means of natural selection, a great evolutionary biologist named Ernst Mayr (1904--2005) guided a meshing of genetics and evolution (along with other brilliant scientists including Theodosius Dobzhansky, George Simpson, and R.A. Fisher) into what is called The Modern Synthesis. This work encapsulates (dare I say, "synthesizes?") concisely and beautifully the tenets of natural selection in the context of basic genetic inheritance. As part of his work, Mayr distilled Darwin’s ideas into a series of facts and inferences.

Facts and Inferences

Mayr’s distillation consists of five facts and three inferences, or conclusions, to draw from those facts.

1. The first fact is that populations have the potential to increase exponentially. A quick look at any graph of human population growth illustrates that we, as a species, appear to be recognizing that potential. For a less successful example, consider the sea turtle. You may have seen the videos of the little turtle hatchlings valiantly flippering their way across the sand to the sea, cheered on by the conservation-minded humans who tended their nests. What the cameras usually don't show is that the vast majority of these turtle offspring will not live to reproduce. The potential for exponential growth is there, based on number of offspring produced, but…it doesn't happen.
2. The second fact is that not all offspring reproduce, and many populations are stable in size. See "sea turtles," above.
3. The third fact is that resources are limited. And that leads us to our first conclusion, or inference: there is a struggle among organisms for nutrition, water, habitat, mates, parental attention…the various necessities of survival, depending on the species. The large number of offspring, most of which ultimately don't survive to reproduce, must compete, or struggle, for the limited resources.
4. Fact four is that individuals differ from one another. Look around. Even bacteria of the same strain have their differences, with some more able than others to with stand an antibiotic onslaught. Look at a crowd of people. They're all different in hundreds of ways.
5. Fact five is that much about us that is different lies in our genes--it is inheritable. Heredity undeniably exists and underlies a lot of our variation.

So we have five facts. Now for the three inferences:

1. First, there is that struggle for survival, thanks to so many offspring and limited resources. See "sea turtle," again.
2. Second, different traits will be passed on differentially. Put another way: Winner traits are more likely to be passed on.
3. And that takes us to our final conclusion: if enough of these "winner" traits are passed to enough individuals in a population, they will accumulate in that population and change its makeup. In other words, the population will change over time. It will be adapted to its environment. It will evolve.

Other mechanisms of evolution

A pigeon depicted in Charles Darwin's
Variation of Animals and Plants
Under Domestication, 1868. U.S.
public domain image, via Wikimedia.

When Darwin presented his idea of natural selection, he knew he had an audience to win over. He pointed out that people select features of organisms all the time and breed them to have those features. Darwin himself was fond of breeding pigeons with a great deal of pigeony variety. He noted that unless the pigeons already possessed traits for us to choose, we not would have that choice to make. But we do have choices. We make super-woolly sheep, dachshunds, and heirloom tomatoes simply by selecting from the variation nature provides and breeding those organisms to make more with those traits. We change the population over time.

Darwin called this process of human-directed evolution artificial selection. It made great sense for Darwin because it helped his reader get on board. If people could make these kinds of choices and wreak these kinds of changes, why not nature? In the process, Darwin also described this second way evolution can happen: human-directed evolution. We're awash in it today, from our accidental development of antibiotic-resistant bacteria to wheat that resists devastating rust.

Genetic drift: fixed or lost

What about traits that have no effect either way, that are just there? One possible example in us might be attached earlobes. Good? Bad? Ugly? Well…they don't appear to have much to do with whether or not we reproduce. They're just there.

When a trait leaves nature so apparently disinterested, the alleles underlying it don't experience selection. Instead, they drift in one direction or another, to extinction or 100 percent frequency. When an allele drifts to disappearance, we say that it is lost from the population. When it drifts to 100 percent presence, we say that it has become fixed. This process of evolution by genetic drift reduces variation in a population. Eventually, everyone will have it, or no one will.

Gene flow: genes in, genes out

Another way for a population to change over time is for it to experience a new infusion of genes or to lose a lot of them. This process of gene flow into or out of the population occurs because of migration in or out. Either of these events can change the allele frequency in a population, and that means that gene flow is another was that evolution can happen.

If gene flow happens between two different species, as can occur more with plants, then not only has the population changed significantly, but the new hybrid that results could be a whole new species. How do you think we get those tangelos?

Horizontal gene transfer

One interesting mechanism of evolution is horizontal gene transfer. When we think of passing along genes, we usually envision a vertical transfer through generations, from parent to offspring. But what if you could just walk up to a person and hand over some of your genes to them, genes that they incorporate into their own genome in each of their cells?

Of course, we don't really do that--at least, not much, not yet--but microbes do this kind of thing all the time. Viruses that hijack a cell's genome to reproduce can accidentally leave behind a bit of gene and voila! It's a gene change. Bacteria can reach out to other living bacteria and transfer genetic material to them, possibly altering the traits of the population.

Evolutionary events

Sometimes, events happen at a large scale that have huge and rapid effects on the overall makeup of a population. These big changes mark some of the turning points in the evolutionary history of many species.

Cheetahs underwent a bottleneck that
has left them with little genetic variation.
Photo credit: Malene Thyssen, via
Wikimedia. 

Bottlenecks: losing variation

The word bottleneck pretty much says it all. Something happens over time to reduce the population so much that only a relatively few individuals survive. A bottleneck of this sort reduces the variability of a population. These events can be natural--such as those resulting from natural disasters--or they can be human induced, such as species bottlenecks we've induced through overhunting or habitat reduction.

Founder effect: starting small

Sometimes, the genes flow out of a population. This flow occurs when individuals leave and migrate elsewhere. They take their genes with them (obviously), and the populations they found will initially carry only those genes. Whatever they had with them genetically when they founded the population can affect that population. If there’s a gene that gives everyone a deadly reaction to barbiturates, that population will have a higher-than-usual frequency of people with that response, thanks to this founder effect.

Gene flow leads to two key points to make about evolution: First, a population carries only the genes it inherits and generally acquires new versions through mutation or gene flow. Second, that gene for lethal susceptibility to a drug would be meaningless in a natural selection context as long as the environment didn't include exposure to that drug. The take-home message is this: What's OK for one environment may or may not be fit for another environment. The nature of Nature is change, and Nature offers no guarantees.

Hardy-Weinberg: when evolution is absent

With all of these possible mechanisms for evolution under their belts, scientists needed a way to measure whether or not the frequency of specific alleles was changing over time in a given population or staying in equilibrium. Not an easy job. They found--“they" being G. H. Hardy and Wilhelm Weinberg--that the best way to measure this was to predict what the outcome would be if there were no change in allele frequencies. In other words, to predict that from generation to generation, allele frequencies would simply stay in equilibrium. If measurements over time yielded changing frequencies, then the implication would be that evolution has happened.

Defining "Not Evolving"

So what does it mean to not evolve? There are some basic scenarios that must exist for a population not to be experiencing a change in allele frequency, i.e., no evolution. If there is a change, then one of the items in the list below must be false:

·       Very large population (genetic drift can be a strong evolutionary mechanism in small populations)

·       No migrations (in other words, no gene flow)

·       No net mutations (no new variation introduced)

·       Random mating (directed mating is one way nature selects organisms)

·       No natural selection

In other words, a population that is not evolving is experiencing a complete absence of evolutionary processes. If any one of these is absent from a given population, then evolution is occurring and allele frequencies from generation to generation won’t be in equilibrium.

Convergent Evolution

Arguably the most famous of the
egg-laying monotremes, the improbable-
seeming platypus. License.

One of the best examples of the influences of environmental pressures is what happens in similar environments a world apart. Before the modern-day groupings of mammals arose, the continent of Australia separated from the rest of the world's land masses, taking the proto-mammals that lived there with it. Over the ensuing millennia, these proto-mammals in Australia evolved into the native species we see today on that continent, all marsupials or monotremes.

Among mammals, there's a division among those that lay eggs (monotremes), those that do most gestating in a pouch rather than a uterus (marsupials), and eutherians, which use a uterus for gestation (placental mammals).

Elsewhere in the world, most mammals developed from a common eutherian ancestor and, where marsupials still persisted, probably outcompeted them. In spite of this lengthy separation and different ancestry, however, for many of the examples of placental mammals, Australia has a similar marsupial match. There's the marsupial rodent that is like the rat. The marsupial wolf that is like the placental wolf. There's even a marsupial anteater to match the placental one.

How did that happen an ocean apart with no gene flow? The answer is natural selection. The environment that made an organism with anteater characteristics best fit in South America was similar to the environment that made those characteristics a good fit in Australia. Ditto the rats, ditto the wolf.

When similar environments result in unrelated organisms having similar characteristics, we call that process convergent evolution. It’s natural selection in relatively unrelated species in parallel. In both regions, nature uses the same set of environmental features to mold organisms into the best fit.

By Emily Willingham, DXS managing editor

Note: This explanation of evolution and how it happens is not intended to be comprehensive or detailed or to include all possible mechanisms of evolution. It is simply an overview. In addition, it does not address epigenetics, which will be the subject of a different explainer.

For Dad: A guide on strokes, including a glossary of terms

A scanning electron micrograph of a blood clot.  Image credit: Steve Gschmeissner/Science Photo Library (http://www.sciencephoto.com/media/203271/enlarge#) 

On Monday January 1^st, I overheard my dad telling my mom how his left arm was numb and that he had no strength in his left hand.  I immediately ran into the medicine cabinet, grabbed two aspirin, practically shoved them down my dad’s throat, and told him to get his coat.  He was going to the ER. 

As it turns out, my dad was having a stroke, which is basically the cessation of blood flow to an area in the brain.  Luckily, my dad only suffered a very mild stroke, and after several days of monitoring and a battery of tests, he was released from the hospital. 

While we are all relieved that he dodged what could have been a fatal bullet, I came to realize that there was only a superficial understanding of what was actually happening.  So, to help demystify the process for my dad (and anyone else in this situation), I’ve decided to write a mini-guide on strokes.  Below you will find some handy information about strokes, including what they are, as well as a glossary of relevant terms.   

Why we need blood flow in the brain

Before I get into what happens to the brain when a stroke occurs, it is important to first understand why unrestricted blood flow in blood vessels in the brain is important.  The brain is a type of tissue, and like all tissues in our body, it needs a constant access to nutrients and oxygen.  Furthermore, tissues produce waste, and this waste needs to be removed.

The human cardiovascular system. Image Credit: Wikipedia.

Evolution’s solution to this problem is the development of a vast network of blood vessels existing within our tissues.  For instance, take a good look at your very own eyeballs.  Especially when we are tired, we can see tiny blood vessels called capillaries, which help to deliver key nutrients and oxygen, keeping our organs of sight healthy and happy.  Now consider that this type of blood vessel network exists in all tissues in our bodies (because it does).  Depending on the needs of the tissue, these vessels vary in size and number.  Sometimes the blood vessels are large, like the aorta, and sometimes they are super tiny, like the capillaries in our eyes.  However, all serve the same function: to make sure that cells can breath, eat, and get rid of waste.

When blood is prevented from traveling to a specific area within a tissue, the cells in that area will not get enough fuel and oxygen and will begin to die.  For instance, the restriction of blood flow to the heart leads to the death of heart tissue, causing a heart attack.  Similarly, the interruption of normal blood flow within the brain causes the affected cells in the brain to essentially starve, suffocate, and die, resulting in a stroke.  The medical term for a lack of oxygen delivery to tissues due to a restriction in blood flow is ischemia.  In general, the heart, brain, and the kidneys are the most sensitive to ischemic events, which, when occurring in these organs, can be fatal.      

So, what exactly is a stroke?

Some strokes can be categorized as being ischemic.  As mentioned above, an ischemic stroke occurs when blood flow (and the associated oxygen supply) is restricted in an area within the brain, leading to tissue death.  A major cause of ischemic strokes is a progressive disease called atherosclerosis, which can be translated to mean “the hardening of the arteries.” 

Severe atherosclerosis of the aorta.
Image Credit: Wikipedia.

Affecting the entire cardiovascular system, atherosclerosis is the result of cholesterol build-up inside of our blood vessels, causing their openings to become narrower.  These cholesterol plaques can eventually burst, leading to the formation of a blood clot.  Ischemic strokes occur as a result of a blood clot, medically known as a thrombus, that blocks the flow of blood to the brain, a phenomenon often related to complications from atherosclerosis.  A ruptured cholesterol plaque and resulting blood clot can occur in the brain, or it can occur elsewhere in the body, such as in the carotid arteries, and then travel to the brain.  Either way, the blood clot will block blood flow and oxygen delivery to sensitive brain tissue and cause a stroke.           

Strokes that result from the bursting of a blood vessel in the brain can be categorized as being hemorrhagic.  In this situation, there may be a pre-existing condition rendering the blood vessels in the brain defective, causing them to become weak and more susceptible to bursting.  More often than not, a hemorrhagic stroke is the result of high blood pressure, which puts an awful lot of stress on the blood vessels.  Hemorrhagic strokes are less common than ischemic strokes, but still just as serious. 

How do you know if you’ve had a stroke?

The symptoms of a stroke can vary depending on which part of the brain is affected and can develop quite suddenly.  It is common to experience a moderate to severe headache, especially if you are hemorrhaging (bleeding) in the brain.  Other symptoms can include dizziness, a change in senses (hearing, seeing, tasting), muscle tingling and/or weakness, trouble communicating, and/or memory loss.  If you are experiencing any of these warning signs, it is important to get to the hospital right away.  This is especially important if the stroke is being caused by a blood clot since clot-busting medications are only effective within the first few hours hours of clot formation. 

Once in the hospital, the caregiver will likely give anyone suspected of having a stroke a CT scan.  From this test, doctors will be able to determine if you had a stroke, what type of stroke you had (ischemic versus hemorrhagic), or if there is some other issue.  However, as was the case with my dad, a CT scan may not show evidence for a stroke.  This issue can arise as a result of timing (test performed before brain injury set in) or size of affected area (too small to see).  When not in an emergency situation, doctors may also or instead choose to prescribe an MRI test to look for evidence of a stroke.    

If a stroke has been confirmed, the next steps will be to try and figure out the underlying cause.  For ischemic strokes, it is important to find out if there is a blood clot and where it originated.  Because my dad had an ischemic stroke, he had to undergo a series of tests that searched for a blood clot in his carotid arteries though ultrasound, as well as in the heart, using both an electrocardiogram (EKG) and an echocardiogram (ultrasound of the heart).  The patient might also be asked to wear a Holter Monitor, which is a device worn for at least 24 hours and can detect potential heart abnormalities that may not be obvious from short-term observations, like those obtained via an EKG.  If a stroke is due to a hemorrhagic event, an angiogram would be performed to try an pinpoint the compromised blood vessel.  

A stroke you did have.  Now what?

Once a stroke has been confirmed and categorized, the patient will most likely be transferred to the stroke unit of the hospital for both treatment and further observation.  If a clot has been detected, a patient will receive clot-busting medications (assuming this detection occurs within several hours of clot formation).  Alternatively, a clot can be mechanically removed with surgery (animation of clot removal, also known as a thrombectomy).  Patients might also be given blood-thinning medications to either ensure that clots do not increase in size or to prevent new clots from forming.   As for secondary prevention, meaning preventing another stroke from happening, patients might be given blood pressure and cholesterol lowering medications. 

If a disability arises due to stroke, a patient might need to undergo rehabilitation.  The type and duration of stroke rehabilitation is dependent on the area of brain that was affected, as well as the severity of the injury.  

Major risk factors and predictors of stroke

There are many situations that could predispose one to having a stroke, and many of these conditions are treatable.  The absolute greatest predictor of a stroke is blood pressure.  High blood pressure, also known as hypertension, will significantly raise your risk of having a stroke.   Other modifiable stroke risk factors include blood cholesterol levels, smoking, type 2 diabetes, diet, alcohol/drug use, and a sedentary life style.  However, there are also risk factors that you cannot change including family history of stroke, age, race, and gender.  But that shouldn’t stop one from practicing a healthy lifestyle!

In conclusion, strokes are no joke.  I am glad that my dad is still here (yes, dad, if you are reading this, we are in fact friends) and that he escaped with relatively no real consequences.  Let’s just not do this again, ok?  

Stroke Glossary

Anti-coagulants: These are medications that help to reduce the incidence of blood clotting.  The repertoire includes aspirin, Plavix, Warfarin, and Coumadin.  Also called blood thinners.

Atherosclerosis: Literally translated as “hardening of the arteries,” this condition is hallmarked by the build-up of cholesterol inside of blood vessels.  Atherosclerosis can lead to many complications including heart disease and stroke.

Atherosclerotic Plaque: The build of fatty materials, cholesterol, various cell types, and calcium.

Cardiovascular System: The network of blood vessels and heart that works to distribute blood throughout the body. 

Carotid Arteries: Arteries that carry blood away from the heart toward the head, neck, and brain.

CT Scan: Cross sectional pictures of the brain using X-rays.

Echocardiogram: An ultrasound of the heart.  In stroke vicitms, electrocardiography is used to detect the presence of a blood clot in the heart.

Electrocardiogram (EKG or ECG): The measurement of the electrical activity of the heart.  It is performed by attaching electrodes to a patient at numerous locations on the body, which function to measure electrical output of the heart.

Embolic Stroke: A type of ischemic stroke, an embolic stroke occurs when a blood clot forms (usually in the heart) and then travels to the brain, blocking blood flow and oxygen delivery to brain tissue.

Hemorrhagic Stroke: A type of stroke that results form the bursting of a blood vessel in the brain.

Hypertension: High blood pressure, defined as having 140/90 mmHg or above.

Ischemic Stroke: The restriction of blood flow to an area within the brain.

Magnetic Resonance Imaging (MRI): An imaging technique employing a magnetic field that can contrast different soft tissues in the body.

Thrombolytic Medications: Medications that are approved to dissolve blood clots.  Also called “clot-busting” medications.

Thrombus: Blood clot.