Category: Medicine & health

Why porcupine quills slide in with ease but come out with difficulty

By Ed Yong | December 11, 2012 8:00 am

A shorter version of this story appears at Nature News.

In August of this year, Allison Noles rushed her bulldog Bella Mae to the vet. The dog’s face looked like a pincushion, with some 500 spines protruding from her face, paws and body. The internet is littered with such pictures, of Bella Mae and other unfortunate dogs. To find them, just search for “porcupine quills”.

North American porcupines have around 30,000 quills on their backs. While it’s a myth that the quills can be shot out, they can certainly be rammed into the face of a would-be predator. Each one is tipped with microscopic backwards-facing barbs, which supposedly make it harder to pull the quills out once they’re stuck in. That explains why punctured pooches need trips to the vet to denude their faces.

But that’s not all the barbs do. Woo Kyung Cho from Harvard Medical School and Massachusetts Institute of Technology has found that the barbs also make it easier for the quills to impale flesh in the first place. “This is the only system with this dual functionality, where a single feature—the barbs—both reduces penetration force and increases pull-out force,” says Jeffrey Karp, who led the study.

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Will we ever… make a safe cigarette?

By Ed Yong | November 26, 2012 9:00 am

Here’s the 13th piece from my BBC column

There’s an old saying among people who work in public health: Tobacco is the only legal product that, when used as intended, will kill you. Decades of research have thoroughly documented the health problems that result from inhaling tobacco smoke – more than a dozen different types of cancer, heart disease, stroke, emphysema and other respiratory diseases, among others. Are these risks an inevitable part of smoking? Or is there a way of creating safe cigarettes without any of these hazards?

“I think it’s very unlikely,” says Stephen Hecht from the University of Minnesota Cancer Center, who studies tobacco carcinogens – substances that cause cancer. Tobacco smoke is a complex cocktail of at least 4,000 chemicals including at least 70 known carcinogens. No one has made a “cigarette that is significantly decreased in all of these [chemicals] and is still something people would want to smoke, even though the industry has worked on this for around 50 years,” says Hecht. “There’s no indication that it’s possible.”

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CATEGORIZED UNDER: Medicine & health

Gangs of corrupted proteins spread through mouse brains and cause Parkinson’s-like symptoms

By Ed Yong | November 15, 2012 4:00 pm

This post contains material from an older one, updated based on new discoveries.

There are many things you don’t want gathering in large numbers, including locusts, rioters, and brain proteins. Our nerve cells contain many proteins that typically live in solitude, but occasionally gather in their thousands to form large insoluble clumps. These clumps can be disastrous. They can wreck neurons, preventing them from firing normally and eventually killing them.

Such clumps are the hallmarks of many brain diseases. The neurons of Alzheimer’s patients are riddled with tangles of a protein called tau. Those of Parkinson’s patients contain bundles, or fibrils, of another protein called alpha-synuclein. The fibrils gather into even larger clumps called Lewy bodies.

Now, Virginia Lee from the University of Pennsylvania School of Medicine has confirmed that the alpha-synuclein fibrils can spread through the brains of mice. As they spread, they corrupt local proteins and gather them into fresh Lewy bodies, behaving like gangs that travel from town to town, inciting locals into forming their own angry mobs. And as these mobs spread through the mouse brains, they reproduce two of the classic features of Parkinson’s disease: the death of neurons that produce dopamine, and movement problems.

This is the clearest evidence yet that alpha-synuclein can behave like prions, the proteins that cause mad cow disease, scrapie and Creutzfeld-Jacob disease (CJD). Prions are also misshapen proteins that convert the shape of normal peers. But there is a crucial distinction: prions are infectious. They don’t just spread from cell to cell, but from individual to individual. As far as we know, alpha-synuclein can’t do that.

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MORE ABOUT: Lewy, Parkinson's, synuclein

When competition is intense, viruses spill over into new hosts

By Ed Yong | October 16, 2012 7:00 pm

When you think about viruses, you might wonder how they infect, how they spread, and how they kill. These questions are of natural interest—you, after all, could play host to a grand variety of lethal viruses. But do remember: it’s not all about you.

A virus’ world contains not just potential hosts, but other viruses. It has competition. This simple fact is often ignored but it has profound implications. In a new study, Lisa Bono from the University of North Carolina has shown that competition between viruses can drive them to spill over into new hosts, imperilling creatures that they never used to infect.

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CATEGORIZED UNDER: Evolution, Medicine & health, Viruses

Jumping DNA rides aboard a virus, which targets a giant virus, which infects an amoeba, which infected a woman's eye

By Ed Yong | October 15, 2012 3:00 pm

Earlier this year, a 17-year-old French woman arrived at her ophthalmologist with pain and redness in her left eye. She had been using tap water to dilute the cleaning solution for her contact lenses, and even though they were meant to be replaced every month, she would wear them for three. As a result, the fluid in her contact lens case had become contaminated with three species of bacteria, an amoeba called Acanthamoeba polyphaga that can caused inflamed eyes.

The mystery of the woman’s inflamed eyes was solved, but Bernard La Scola and Christelle Desnues looked inside the amoeba, they found more surprises.

It was carrying two species of bacteria, and a giant virus that no one had seen before—they called it Lentille virus. Inside that, they found a virophage—an virus that can only reproduce in cells infected by other viruses—which they called Sputnik 2. And in both Lentille virus and Sputnik 2, they found even smaller genetic parasites – tiny chunks of DNA that can hop around the genomes of the virus, and stow away inside the virophage. They called these transpovirons.

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CATEGORIZED UNDER: Medicine & health, Viruses

Why type 2 diabetes is a bit like The Bourne Identity

By Ed Yong | September 14, 2012 11:21 am

In The Bourne Identity, the eponymous hero is presumed dead by his former employers, but turns out to have merely lost his memory. Thus unburdened, he attempts to change his fate.

Which reminds me of diabetes.

People with type 2 diabetes face two problems, both related to insulin – the hormone that regulates the levels of sugar in our blood. They don’t respond properly to it (they become insulin resistant), and they don’t make enough of it. As a result, the levels of sugar in their blood become too high. Insulin resistance is fairly steady throughout a person’s lifetime, but the failure to make insulin gets progressively worse. The typical explanation is that the beta-cells – a type of insulin-making cells within the pancreas – die off.

But Domenico Accili from Columbia University has a different idea. By studying diabetic mice, he has found beta-cells do indeed disappear over time, but not because they die. Instead, they revert back to a more basic type of cell that doesn’t produce insulin. Like Jason Bourne, they lose their former specialised identities and become more of a tabula rasa. In the film, it’s simple memory loss. In the cells, it’s known as “dedifferentiation”.

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CATEGORIZED UNDER: Medicine & health

New virulent strain of flu found in healthy Korean pigs

By Ed Yong | September 12, 2012 9:00 am

That'll do, pig. That'll doIf flu viruses have favoured hook-up spots, then pig pens would be high on the list. Their airways contain molecules that both bird flu viruses and mammalian flu viruses can latch onto. This means that a wide range of flu strains can infect pigs, and if two viruses infect the same cell, they can shuffle their genes to create fresh combinations.

This process is called reassortment. In 2009, it created a strain of flu that leapt from pigs to humans, triggering a global pandemic. If we needed proof that pigs are “mixing vessels” for new and dangerous viruses, the pandemic was it.

Now, scientists have found a new strain of flu in Korean pigs that remphasises the threat. It’s an H1N2, subtly different to the H1N1 virus behind the recent pandemic. But it’s got all the makings of a serious problem. It can kill ferrets – the animal of choice for representing human flu infections. And it spreads through the air between them. I’ve written about this new strain for Nature News, so head over there for more details.

Image by US Dept of Agriculture

CATEGORIZED UNDER: Medicine & health, Viruses
MORE ABOUT: flu, H1N2, influenza, Korea, pigs, virus

Evolutionary trees of traditional medicine plants provide hints for drug-makers

By Ed Yong | September 11, 2012 9:00 am

There’s a bizarre mindset that divides medicine into “natural” (made from plants; untainted by villainous pharmaceutical companies; delivered to your veins by forest animals) and everything else (“man-made” pills fashioned from profits and poisons). The reality, of course, is that many of the drugs used in our hospitals and pharmacies come from plants. Willow bark contains salicylic acid, the main ingredient in aspirin. Paclitaxel (taxol) was isolated from the bark of the Pacific yew tree; today, it is used to stop cancer cells from dividing.  The rose periwinkle has given us vinblastine and vincristine, both used to treat leukaemia.

These examples scratch the surface of what the botanical world has given us, and what it might still offer. Of the tens of thousands of plants used in “traditional medicine”, a piddling proportion has been tested for chemicals with medical benefits. How do we find the rest? How do we go about the business of “bioprospecting”? One solution is to tap the knowledge of indigenous populations, who still rely on plants for traditional medicine. When they get sick, how do they heal themselves?

But this approach has problems. Traditional use doesn’t always imply an actual medical benefit, and the chosen plants might not yield interesting chemicals any more readily than the species around them. Many attempts to follow such leads have ended in the drug-development cul-de-sac. To make matters worse, collating traditional knowledge involves fieldwork and training, and is both expensive and time-consuming.

Meanwhile, the tools of molecular biology have become faster and cheaper. Companies can afford to gather large collections of plants, and screen their constituent chemicals en masse. Why filter them any further when you can test thousands of samples at once? But Haris Saslis-Lagoudakis from Imperial College London thinks that this scattershot approach to bioprospecting is a mistake. To him, traditional knowledge still has great value in honing our search for tomorrow’s drugs.

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Reading your body clock with a molecular timetable, inspired by flowers

By Ed Yong | August 28, 2012 9:00 am

What time is it? That’s easy to check: Just look at a watch or a clock. What time is it inside your body? That’s a harder question.

Your body keeps its own time. It has an internal 24-hour “circadian clock” that drives the rise and fall of many molecules. Everything from brain activity to hormone levels waxes and wanes according to these molecular metronomes, which dictate how hungry, hot and sleepy we are.

They also affect how well we respond to medicine. Since the late 1980s, scientists have shown that drugs work better at certain times of the day. For example, the cancer drug cisplatin is more effective and less toxic if it’s given in the evening. Adriamycin is more of a morning drug. In another cancer trial, tailoring chemotherapy to these daily rhythms—a practice known as chronotherapy—made the same drugs more effective and reduced the frequency of toxic side effects.

Chronotherapy would seem to be a no-brainer but it hasn’t caught on widely. That may be partly due to scepticism, but there’s a more practical reason: it’s hard to read a person’s body clock. Some people are larks, others are owls. The ticks and tocks of the clock vary depending on age, sex, health, employment, and more. The clocks of two people can be half a day apart. How do you administer a drug at the right time if you can’t tell that time?

The conventional way would be to take blood samples every hour or so for 24 hours, and measure the concentrations of melatonin—a hormone that rises in darkness and falls in light. Melatonin can be detected in saliva samples but because the hormone is found in such low concentrations, the process can’t be automated. As such, it’s labour-intensive work that takes days and tightly controlled environmental conditions. If you have patients to treat, you rarely have such luxuries.

Takeya Kasukawa and Masahiro Sugimoto from the RIKEN Center for Developmental Biology have a better way. Their team have developed a “metabolite timetable”  that plots how dozens of molecules rise and fall in relation to one another. With this timetable, they could accurately read a person’s internal clock with just two blood samples, taken 12 hours apart.

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CATEGORIZED UNDER: Medicine & health, Select

Antibiotics fuel obesity by creating microbe upheavals

By Ed Yong | August 23, 2012 9:00 am

We aren’t single individuals, but colonies of trillions. Our bodies, and our guts in particular, are home to vast swarms of bacteria and other microbes. This “microbiota” helps us to harvest energy from our food by breaking down the complex molecules that our own cells cannot cope with. They build vitamins that we cannot manufacture. They ‘talk to’ our immune system to ensure that it develops correctly, and they prevent invasions from other more harmful microbes. They’re our partners in life.

What happens when we kill them?

Farmers have been doing that experiment in animals for more than 50 years. By feeding low doses of antibiotics to healthy farm animals, they’ve found that they could fatten up their livestock by as much as 15 percent. You can put the antibiotics in their feed or in their water. You can give the drugs to cows, sheep, pigs or chickens. You can try penicillins, or tetracyclines, or many other classes of antibiotics. The effect is the same: more weight.

Consistent though this effect is, no one really understands why it works. The safe bet is that the drugs are exerting their influence by killing off some of the microbiota. Now, Ilseung Cho from the New York University School of Medicine has confirmed that hypothesis. By feeding antibiotics to young mice, he has shown that the drugs drastically change the microscopic communities within their guts, and increase the amount of calories they harvest from food. The result: they became fatter.

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