The Loom » Medicine

Inside Darwin’s Tumor

Carl Zimmer — Thu, 12 Jan 2012 17:04:34 +0000

Cancer evolves. Those two words may sound strange together. Sure, birds evolve. Bacteria evolve. But cancer? The trouble arises from the fact that cancers, unlike birds and bacteria, are not free-living organisms. They start out as cells inside a person’s body and stay there, until they’re either wiped out or the person dies.*

Yet the same forces that drive the evolution of free-living organisms can also drive cancer cells to become more aggressive and dangerous. Evolution becomes our inner foe if mutations disable a cell’s self-restraint. The cell multiplies. Sometimes a new mutation arises in its descendants. If the mutations allow the cancer to grow faster, the cells carrying it will take over the population of cancerous cells. Natural selection and other processes that drive evolution on the outside start driving it on the inside.

Like so many other scientists, researchers who study cancer evolution have jumped on new technology for sequencing genomes on the cheap. They’re now starting to publish fine-grained histories of the disease, tracking individual mutations as they arise and spread. Nature has just published a fine example of this new research. I particularly appreciated the informative pictures they came up with to accompany ...

XMRV takes another step to de-discovery?

Carl Zimmer — Thu, 22 Dec 2011 17:01:54 +0000

I’ve written a few times here about the battle over a virus called XMRV, and its supposed link to chronic fatigue system. I just wanted to point this morning to a few articles by some fine writers about the latest twist: the paper that first claimed a link has been completely retracted.

Ivan Oransky in Reuters

Jon Cohen in Science

Ewen Callaway in Nature

[Image: Wikipedia]

The French Disease, the Italian Disease, the Christian Disease–the New World Disease?

Carl Zimmer — Mon, 19 Dec 2011 22:35:13 +0000

In 1494, King Charles VIII of France invaded Italy. Within months, his army collapsed and fled. It was routed not by the Italian army but by a microbe. A mysterious new disease spread through sex killed many of Charles’s soldiers and left survivors weak and disfigured. French soldiers spread the disease across much of Europe, and then it moved into Africa and Asia. Many called it the French disease. The French called it the Italian disease. Arabs called it the Christian disease. Today, it is called syphilis.

I’ve been intrigued by the murky history of syphilis for a few years now. The text above is from the start of an article I wrote for Science in 2008. At the time, scientists were split between two explanations for sudden appearance of syphilis at the end of the fifteenth century. According to one, it was caused by bacteria that had evolved in the New World and were brought back to Europe by Columbus’s crew. But other researchers found many skeletons with signs of syphilis in Europe, Africa, and Asia that appeared to have been from long before Columbus’s voyage. They argued that it must ...

Holes in the net: A podcast of my Story Collider tale

Carl Zimmer — Tue, 04 Oct 2011 21:13:19 +0000

Story Collider is a monthly performance where people tell stories about science. (Think The Moth in a lab coat.) The organizer, Ben Lillie, invited me to tell a personal story about the place of science writing in my life. I decided to talk about a memorable night in South Sudan, when I wondered what I was living for.

I told the story to a great crowd at Union Hall in Brooklyn last week. And you can hear the podcast at the Story Collider web site. Check it out.

The Penultimate Chapter in the XMRV-Chronic Fatigue Story?

Carl Zimmer — Fri, 23 Sep 2011 15:03:57 +0000

I’ve devoted a few posts (here and here and here) to the saga of a disputed link between chronic fatigue syndrome and a virus called XMRV. This week marks the next chapter in the story, with more evidence that the original results were at least partly due to contamination and a partial retraction of the original paper. Two great writers at Science, Martin Enserink and Jon Cohen, have put together an epic telling of this affair, from the first reports two years ago to the latest developments. The magazine has wisely put the piece out in front of their paywall. Do read it.

As Enserink and Cohen note, this is not the final word. That will probably come early next year, when a larger study led by Ian Lipkin of Columbia. We’ll see then if the link is buried at last, or lives to see another day.

The cell’s changing room: My new profile of Lasker-award winner Arthur Horwich

Carl Zimmer — Mon, 12 Sep 2011 17:36:11 +0000

In tomorrow’s New York Times, I have a profile of Arthur Horwich, a medical geneticist who has spent a quarter century trying to figure out the workings of this beautiful molecular box. Today he won the Lasker Award, a prize for medicine that has often gone to scientists who later won the Nobel. Why all accolades for a little box? Because without it, you’d be dead. And as Horwich and others have discovered what goes on inside, they’ve helped change the way we understand the biology of the cell. Check it out.

[Image of GroEL from Molecular Chaperone Group, Birkbeck College]

Zooming In On the Cholera Tree of Life (And Death)

Carl Zimmer — Tue, 23 Aug 2011 17:10:05 +0000

In the wake of last year’s earthquake in Haiti, cholera arrived on the island for the first time in 60 years. According to the World Health Organization, 419, 511 Haitians got sick with cholera as of July 31, of which 5,968 died. The infection rate is dropping right now, but the arrival of Hurricane Irene could change that.

As I wrote in December, scientists applied evolutionary biology to find clues to how cholera–or, more precisely, the bacteria Vibrio cholerae– came to Haiti. They compared the DNA in the strain in Haiti to ones that have been found in other parts of the world. From this analysis, they drew a tree, which I’ve reprinted below.

The bacteria in Haiti was more closely related to strains in South Asia than ones from South America. So it was unlikely that cholera came to Haiti floating by water from a nearby country. The evolutionary tree led credence to idea that U.N. peacekeeping troops, some of whom came from Nepal, brought it with them by plane. An outbreak of cholera hit Nepal in September 2010, shortly before a battalion of Nepalese peacekeepers left for Haiti.

This analysis was a bit like a ...

The Mere Existence of Whales: The Scientists Answer Your Questions

Carl Zimmer — Sat, 26 Mar 2011 01:21:49 +0000

Recently I blogged about how the mere existence of whales might be an important clue to treating cancer. That post has drawn many readers, and many questions in the comment thread.

Happily, the authors of the review I described–Carlo Maley of the University of California, San Francisco, and Aleah Caulin of the University of Pennsylvania–have joined the thread. They’ve answered the first set of reader questions and promise to come back to respond to the rest. Further proof of the majesty of blogs…

[Update: Here's their next batch of answers.]

How a pit viper saved millions of lives: Snakes as drug factories

Carl Zimmer — Fri, 11 Mar 2011 17:34:21 +0000

If you’ve just been bitten by a venomous snake and your flesh is starting to rot and you can’t breathe, you may not be in the mood to hear how beautiful snake venom can be. But from a safe distance, it really is a marvel to behold.

Snake venom is a blend of molecules, many of which are exquisitely adapted for wreaking havoc. Some are enzymes that slice muscles apart. Some grab onto proteins that normally form clots, so that a snake’s victim can’t stop bleeding. Many snake venoms attack the nervous system with molecular precision that’s so good that neuroscientists have snakes to thank for some of their biggest discoveries.

In the 1950s, two researchers in Taiwan–CY Lee and CC Chang–decided to study the venom of the banded krait. A bite from the snake, native to Taiwan, caused paralysis and shallow breathing–suggesting to the scientists that the snake’s venom must interfere in an interesting way with the nervous system’s control of muscles.

Nerves trigger muscles to contract by releasing the neurotransmitter acetylcholine. At first Lee and Chang assumed that the snake venom must cut acetylcholine apart, but they found it had ...

The Mere Existence of Whales

Carl Zimmer — Mon, 28 Feb 2011 21:23:02 +0000

Strictly speaking, there should be no blue whales.

Blue whales can weigh over a thousand times more than a human being. That’s a lot of extra cells, and as those cells grow and divide, there’s a small chance that each one will mutate. A mutation can be harmless, or it can be the first step towards cancer. As the descendants of a precancerous cell continue to divide, they run a risk of taking a further step towards a full-blown tumor. To some extent, cancer is a lottery, and a 100-foot blue whale has a lot more tickets than we do.

Aleah Caulin of the University of Pennsylvania and Carlo Maley of the University of California, San Francisco, have done some calculations of the risk of cancer for blue whales thanks to their huge size. We don’t know a lot about cancer in blue whales, because blue whale oncology wards would be a wee bit awkward for everyone involved. So Caulin and Maley extrapolated up from humans.

About thirty percent of all people will get cancer by the end of their life. Scientists have been able to build good models for the odds of developing ...

The Cholera Tree of Life (and Death)

Carl Zimmer — Sat, 11 Dec 2010 02:07:56 +0000

The nightmare that is the cholera epidemic of Haiti (2,100 dead so far) has become a little less mysterious. Haiti has not seen cholera for over a cenutry, and so the emergence of cholera in recent weeks has puzzled scientists and led to riots directed at the U.N. for supposedly bringing Vibrio cholerae to the Caribbean nation. Others have pointed to a New World strain as a potential culprit. It triggered an outbreak in Peru in 1991, and has circulated in Central and South America ever since. Perhaps these bacteria washed up on Haiti’s shores.

In the latest issue of the New England Journal of Medicine, Matthew Waldor of Harvard and his colleagues go some distance to settling the debate by finding the Haitian cholera’s place in the tree of life.

“Collectively, our data strongly suggest that the Haitian epidemic began with introduction of a V. cholerae strain into Haiti by human activity from a distant geographic source,” the scientists write. The bacteria belong to a strain that evolved in South Asia. It was probably introduced onto Haiti by a sick person who flew there. We may never ...

A Day Among the Genomes

Carl Zimmer — Fri, 30 Apr 2010 04:25:21 +0000

What will the world be like when your genome sequence costs less than a cell phone? A couple days ago I went to Cambridge, Mass. to find out.

The occasion was a meeting called “Genome, Environments, and Traits,” or GET for short. The history of the meeting is in the upper ranks of my list of meetings with strange histories. In 2006, the Harvard geneticist George Church (arguably the smartest, most influential biologist you never heard of) decided to launch a new kind of human genome project. At the time, scientists had only published the sequence of a single human genome, at a cost of $3 billion. And for all that money, the genome was actually a gap-riddled patchwork from several individuals, and only included the DNA from one copy of each pair of chromosomes. Church declared that he would gather the sequenced genomes of 100,000 individuals, along with information about their health, and make all that information available for scientists to study in order to learn more about human biology. Church issued a manifesto of sorts in Scientific American, called “Genomes for All,” which you can read here (pdf) and also talked ...

The Short History of Measles

Carl Zimmer — Tue, 16 Mar 2010 12:07:39 +0000

Measles looks to be 1000 years old. It jumped from cattle. And you can read more about it here.

I For One Welcome Our Microbial Overlords

Carl Zimmer — Thu, 04 Mar 2010 19:02:06 +0000

Can the bacteria in our bodies control our behavior in the same way a puppetmaster pulls the strings of a marionette? I tremble to report that this wonderfully creepy possibility may be true.

The human body is, to some extent, just a luxury cruise liner for microbes. They board the SS Homo sapiens when we’re born and settle into their assigned quarters–the skin, the tongue, the nostrils, the throat, the stomach, the genitals, the gut–and then we carry them wherever we go. Some of microbes deboard when we shed our skin or use the restroom; others board at new ports when we shake someone’s hand or down a spoonful of yogurt. Just as on a luxury cruise liner, our passengers eat well. They feed on the food we eat, or on the compounds we produce. While the biggest luxury lines may be able to carry a few thousand people, we can handle many more passengers. Although the total mass of our microbes is just a few pounds, the tiny size of their cells means that we each carry about 100 trillion microbes–outnumbering our own cells by more than ten to one.

It’s important to bear in ...

Full-Spectrum Genomes

Carl Zimmer — Wed, 17 Feb 2010 18:38:19 +0000

It’s been nearly ten years since President Bill Clinton stood on the White House lawn with a team of scientists to announce the completion of the first survey of the human genome. “Today, we celebrate the revelation of the first draft of the human book of life,” he said. It’s a pleasing metaphor, but it’s deeply flawed. There is not a single Human Book of Life. If there were, after all, Clinton and the scientists and all the rest of us would all be identical clones.

There is a vast amount of genetic variation from person to person, and from one continent to another. The survey that Clinton was announcing was a cobbling-together of DNA from several individuals. Since then, researchers have produced much higher-quality reads of the genomes of actual people. They’ve learned a lot from those studies, but, in the scope of human genetic diversity, these studies have been timid ventures. If you compare someone from South Korea to someone of northern European descent, you’re only capturing a small sliver of the variation in our species. If you really want to get into the thick of it, there’s really ...

I Am Shiva, Destroyer of Proteins

Carl Zimmer — Mon, 05 Oct 2009 22:41:43 +0000

Deep down, we are all cannibals. In tomorrow’s issue of the New York Times, I take a look at the science of autophagy: how our cells destroy themselves to live again. It turns out that this cellular cannibalism is crucial for our well-being in many ways. Scientists are now trying to improve our ability to destroy ourselves as a potential treatment for diseases like cancer and Huntington disease, and perhaps even to slow the process of aging itself. Check it out.

(Note to link-lovers: the article takes you directly to some of the primary literature. Progress!)

[Image: Royal Academy of Arts]

Nobel For Telomeres

Carl Zimmer — Mon, 05 Oct 2009 12:22:54 +0000

Congratulations to Elizabeth Blackburn, Carol Greider, and Jack Szostak, who just won the Nobel Prize in Physiology or Medicine this morning. They won for their discovery of telomeres, the caps on the ends of chromosomes that keep them from degrading and ward off aging. The Nobel site has posted some useful information about why this was such a profound discovery.

Genomes In Newsweek: Futures Near and Far

Carl Zimmer — Mon, 29 Jun 2009 01:46:35 +0000

As a science writer, I often find it sobering to read scientific history. Science works slowly, even though we wish it would work in nanosecond breakthroughs.

In 1913, for example, a Russian scientist named Nikolai Anichkov ran an experiment in which he had egg yolks fed to rabbits. On this cholesterol-heavy diet the rabbits developed atherosclerosis. The more cholesterol the rabbits ate, the bigger the deposits on their blood vessels became. It was a tremendous discovery, considered by some one of the greatest in medical history.

But it did not lead overnight to a treatment for heart disease. In fact, it did not even lead, on its own, to a clear understanding of how cholesterol ends up in the blood vessels. Instead, it focused the attention of later scientists on the question of cholesterol. It took many years for scientists to figure out the steps by which enzymes produce cholesterol molecules. Then scientists began searching for drugs that might interfere with those enzymes.

In 1971, six decades after Anichkov ran his egg-yolk experiments, Akira Endo of Tokyo Noko University and his colleagues, decided to see if microbes made natural cholesterol-fighting compounds (free ...

Swine Flu Science: First Wiki, Then Publish

Carl Zimmer — Thu, 11 Jun 2009 13:38:38 +0000

Here’s a vision of how science may work in the future.

Last month I scrambled to write a story about the evolution of swine flu for the New York Times. I talked to some of the top experts on the evolution of viruses who were, at that very moment, analyzing the genetic material in samples of the virus isolated around the world. One scientist, whom I reached at home, said, “Sure, I’ve got a little time. I’m just making some coffee while my computer crunches some swine flu. What’s up?”

All of the scientists were completely open with me. They didn’t wave me off because they had to wait until their results were published in a big journal. In fact, they were open with the whole world, posting all their results in real-time on a wiki. So everyone who wanted to peruse their analysis could see how it developed as more data emerged and as they used different methods to analyze it.

Now, a little over a month later, they’re publishing their results in the journal Nature. Normally we press folks would get a press release about the paper a week before publication, and ...

Hate the Science Writing, Not the Science

Carl Zimmer — Tue, 20 Jan 2009 14:12:40 +0000

3quarkdaily just picked up my little rant about an awful piece of science writing. They accompanied their post with a picture of the scientist profiled in the article, Hina Chaudhry. That juxtaposition made me a bit queasy–let me just make clear that I was not criticizing Dr. Chaudhry, just the article about her. Dr. Chaudhry is doing what scientists should: running experiments and getting her results published in peer-reviewed journals. Here’s a free link to a 2007 paper of hers on regenerating heart tissue. It’s up to us science writers in turn to find a better way to describe a scientist than as a “a pretty lady.”

Cancer’s Sex Appeal

Carl Zimmer — Wed, 10 Sep 2008 16:27:47 +0000

Cancer is not just a terrible disease but a strange one. Tumor cells must switch on certain genes in order to thrive and multiply. You might expect that natural selection would have eliminated those genes, because they kill off their owners. Far from it. A number of cancer genes, known as oncogenes, have actually been favored by natural selection over the past few million years. Oncogenes, in other words, have boosted the reproductive success of their owners, and have even been fine-tuned by evolution.

Humans are not alone in getting cancer. In fact, it seems to be a pretty inescapable risk of being an animal. As cells divide and mutate, some mutations may make cells ignore the needs of the body and multiply madly. That’s too bad for other animals, but there’s a silver lining for us: by studying other animals, scientists can get some clues to how cancer evolves in us.

The delicate swordtail (Xiphophora cortezi) is particularly prone to getting melanomas (the bottom picture here shows a fish with a tumor in its tail). When Andre Fernandez and Molly Morris of Ohio University went fishing for delicate swordtails in mountain streams in Mexico, they ...