From the DEC/JAN 2006 issue of Seed:
CHEMICALS CAN CURE ADDICTION
Credit: Elizabeth Huey
With health and social costs of more than $500 billion a year, drug and alcohol addiction is among the most damaging diseases in the U.S. While neuroscience has made great strides in understanding the basis of addiction (it involves floods of dopamine), that knowledge has yet to yield practical results.
This is beginning to change. Two papers published in Neuron show that addiction—at least in rats—is a treatable medical problem. Each took an unconventional approach, focusing not on the addictive urge itself but on disrupting the memory of the addiction, the theory being that you can’t be addicted to that which you can’t remember.
The first study, by John Marshall and Courtney Miller of the University of California at Irvine,
attempted to eradicate the memories of rodents with a taste for cocaine. After being administered a drug that inhibits production of the protein extracellular signal-regulated kinase, the rats forgot in which cage they received their fix. The unfortunate rodents had gone clean, and they didn’t even need 12 steps.
The second study, by Dr. Jonathan Lee of Cambridge University, focused on the amygdala, the part of the brain that learns to pair the pleasurable feeling of intoxication with a certain stimulus (say, the neon sign of a favorite bar or the sight of an ashtray). He wanted to see whether turning off a particular neuronal gene could erase the amygdala’s memory. It did. Rats with the silenced gene no longer remembered which environmental cues signaled the presence of drugs.
HUMAN CLONING IS MORE THAN JUST A HYPOTHETICAL
The headline was alarming: “South Korea Makes Strides in Human Cloning” The reality was not so Huxleyan. Dr. Woo Suk Hwang’s lab had come up with an extremely efficient method of producing stem cells. First, they created embryos that were exact genetic matches of individuals. After letting the embryo divide a few times, they extracted its stem cells. This method—known as therapeutic cloning—is one of the most promising approaches in the stem-cell field. Researchers believe that therapeutic cloning will one day be used to create replacement tissues for a variety of diseases. Hwang made it look easy.
Three months later, Hwang made headlines again: After working for more than 900 consecutive days, his lab announced they had cloned man’s best friend, the dog (an Afghan hound named Snuppy). At first glance, that may not seem like such a big deal; after all, scientists cloned Dolly the sheep a decade ago. But for a variety of reasons, dogs had been notoriously difficult to clone. (Dogs ovulate unpredictably, their eggs require surgery to extract, and their embryos won’t grow outside the uterus.) Nevertheless, Hwang says, “Dogs can be good models for human diseases. Dogs [can contract] more than 50 diseases that are similar to human diseases.”
The fear is that Hwang’s techniques may open the door to human cloning before the many ethical issues it raises have been adequately addressed. Hwang himself is unapologetic. Regardless, his technical brilliance showed that it’s no longer just a theoretical possibility.
AT THE DAWN OF TIME, THERE WAS A PERFECT LIQUID
Credit: Brian Ulrich
In the timeless time after the big bang, when the universe was as new as it was empty, there were only quarks and gluons. Atoms had to yet to coalesce. But what was this proto-universe like? In the nanosecond before there was matter, what was there?
There was a perfect liquid. Experiments at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory have demonstrated that quarks and gluons, when freed from their workaday reality as the building blocks of nuclei, become a liquid without viscosity, a fluid that flows easier than water.
RHIC proved this by accelerating gold nuclei to 99.7% the speed of light (RHIC scientists actually believe it was 99.9%, but can only conclusively establish the average of “closer to 99.7%,” according to a spokesman—a difference of 600,000 meters per second), then smashing them together in an explosion so powerful it generated temperatures close to those of the big bang. An interpretation of the resulting atomic debris—which disappeared in less than a hundredth of a billionth of a trillionth of a second—showed the clear presence of a liquid.
To most, this was a complete surprise. After all, things that are a trillion degrees hot are normally gases or plasmas, not frictionless liquids. But not all physicists were so flabbergasted. String theorists—hitherto best known for believing in the existence of 10 dimensions—have argued in their own work that the big bang immediately gave way to a sloshy quark-gluon soup. The Brookhaven data tenuously confirms their expectations.
“PLANET” NEEDS A NEW DEFINITION
Credit: Mark Mahaney
It is the biggest object discovered in our solar system since Neptune, in 1846. It has a faithful moon and is significantly larger in diameter than Pluto. It is the most distant object ever seen orbiting the sun. It is 2003 UB313, and it resides way out there in the Kuiper belt, a vast swath of icy bodies somewhere beyond Neptune.
Caltech astronomer Dr. Mike Brown, who discovered UB313, calls the Kuiper belt “a fossil record of the solar system. Essentially, the objects in the Kuiper belt have been in deep freeze for 4.5 billion years. Things haven’t changed much. So the more we know about the Kuiper belt, the more we know about the formation of our solar system.”
But is it really a planet? The question has dogged Brown and his team since they first glimpsed UB313. “I personally wouldn’t call it a planet,” says Brown. “I only think there are eight planets. If I had my way, I would call UB313 and Pluto Kuiper belt objects, not planets. Of course, they are very significant Kuiper belt objects.”
HUMANS REALLY ARE 98% CHIMP
Credit: Ben Fry
It’s now a fact: We are just hairless chimps. In September, the first analytical comparisons of the chimpanzee and human genomes—led by teams at MIT, Harvard and Washington University School of Medicine, in St. Louis—were published in Nature. The results were unsettling: man is 98.77% chimpanzee (the 98% figure tossed around for years was really just an approximation). In fact, since chimps and humans parted ways on the evolutionary chart about six million years ago, most proteins of Homo sapiens have accumulated a grand total of one unique change.
But even more disquieting is what that 1.23% difference actually describes. The most uniquely human part of the body is not the brain, but the testes. The study’s lead author, Tarjei Mikkelsen, isn’t surprised: “This finding actually makes sense. Sexual selection is a very prominent force in primates. A big guy with the fastest swimming sperm will have the most kids.”
Of course, humans are not merely chimps with sprightly sperm. The human brain underwent a rapid anatomical renaissance, all because of a few flicks of the right developmental switch. The study revealed that natural selection did not go about redesigning us base pair by base pair; that would have taken way too long. Rather, by changing how our genes are expressed—i.e., altering the molecules, called transcription factors, that regulate the activity of other genes—natural selection achieved profound effects with minimal rewriting.
It sounds like a lost chapter of The Lord of the Rings: On a remote tropical island, there lived a species of tiny people, one meter tall, with skulls the size of grapefruits, who hunted Komodo dragons, dwarf elephants and giant rats.
But this is a true story, a finding that completely recasts the range of morphological adaptation and variation for the genus Homo. An archaeological team led by Dr. Peter Brown, of the University of New England in Australia, discovered the remains of this new human species last year on Flores, an island 600km from Bali. More bones were unearthed this year, confirming, for most, Brown’s initial interpretation that this was a new species and not a microencephalic or dwarf Homo sapiens.
“When I first saw the skeleton,” said Brown, “I was speechless. The last time people of this brain size and body size walked the planet was millions of years ago, in Africa. What was it doing on Flores? I would have been less surprised if the team had unearthed an alien spacecraft.” Stranger yet is the age of the skeleton. The little lady was less than 20,000 years old, which means that Homo floresiensis shared the earth with Homo sapiens. This has sent researchers scrambling to rethink the story of human evolution. “Humans are just another mammal,” said Brown. “I’m happy to see a demonstration that they appear to follow the same evolutionary processes on islands as other large-bodied mammals.” In other words, the same island that produced giant rats and small elephants also gave rise to a miniature person.
Credit: Gregory Ryan
GLOBAL WARMING CAUSES STRONGER HURRICANES
Global warming is no longer the apocalypse of the distant future. Last summer, the world learned just how devastating a few degrees of greenhouse warmth can be. Two monstrous hurricanes barreled into the Gulf Coast, and the result was devastating: The ocean swallowed a city.
Global warming does not cause hurricanes. Butterflies flapping their wings in Tokyo cause hurricanes. But three papers, using different statistical approaches, demonstrated the strong correlation between global warming and hurricane intensity. Global warming makes hurricanes worse.
The theory is simple: Rising atmospheric temperatures lead to warmer ocean surface temperatures, causing more water to evaporate, which gives storms more water and energy. The Gulf of Mexico is 2.8°C (5°F) warmer than “normal” this year.
The strongest case was made by Kerry Emanuel, a meteorologist at MIT. “What the data shows,” Emanuel says, “is that a measure of the total amount of power generated by hurricanes globally over the past 30 to 50 years has increased by 70 to 80%. That’s a really big increase.” Although some have cautioned against attributing the power of any hurricane to a single cause, the correlation showed by Emanuel and others, and the images of destruction along the Gulf Coast, have indelibly changed the discourse on climate change.
RADIOACTIVE DECAY DATES HUMAN CELLS
In the July issue of Cell, Dr. Jonas Frisen, a biologist at the Karolinska Institute in Stockholm, announced a method for the dating of human cells. His stopwatch is the fallout of the nuclear age.
From 1955 to 1963, thousands of atomic weapons were detonated, dispersing carbon-14 all over the earth. Since carbon-14 decays at a regular rate, Frisen’s creative insight was that the amount of carbon-14 contained in the DNA of a cell, being closely correlated with the amount of carbon-14 in the atmosphere at the time of the cell’s birth, could be used to calculate the age of that cell.
It took Frisen and his team four years experimenting on Swedish pine trees and dead horses to perfect the technique, but the hypothesis played out perfectly. Frisen’s lab began dating cells throughout the body. Intestinal cells, they found, regenerate about every 15 years. And while the cerebellum and the visual cortex are about the same age as the individual (they don’t die until you do), preliminary results suggest that other parts of the brain—such as the hippocampus—undergo constant cellular division. Evidently, your self is always reinventing itself.
Frisen’s notion has an intriguing application: forensics. Frisen’s lab realized that the carbon-14 in tooth enamel can help determine the age of a corpse within 1.6 years’ accuracy. This method has already been used to identify victims of last year’s Indian Ocean tsunami and is currently helping identify victims of Hurricane Katrina and its aftermath.
Credit: Ariel Ruiz i Altaba
STEM CELLS CAN BE MADE FROM ADULT CELLS
A stem cell is a tabula rasa: a living form capable of taking any shape. We, however, are composed almost entirely of adult cells. Our cells have differentiated; their genes have instructed them to become something specific. Until now, no one thought skin could change its mind and go back to become a neuron.
But nothing in life is irrevocable. Harvard biologists led by Kevin Eggan and Chad Cowan made an adult cell turn back into a blank slate. “Our experiment was relatively simple,” says Eggan. “We took a human skin cell, fused it with an embryonic stem cell, and let these two…battle it out.” After a few months, the team made a stem cell deprogram the skin cell.
The experiment’s success has intriguing potential. Eggan cautions his that technique “is complementary to, not a replacement for, research involving embryos—after all, we could never have done this experiment [without] access to embryonic stem cells.” But if the Harvard fusion approach is perfected—it might take a while—will scientists be able to harvest stem cells without using embryos, thus side-stepping the political controversy? Eggan says this is a real possibility.
INFORMATION CAN ESCAPE FROM BLACK HOLES
The fate of information hangs on this question: Do black holes destroy everything they inhale? Stephen Hawking once demonstrated that the radiation emitted by black holes evaporates them. Then in 1976, he published a paper arguing that black holes not only disappear, but all the information they contain—and they can vacuum a galaxy—disappears with them. Poof.
Hawking’s theory was bad news for physics. According to quantum mechanics, information is impossible to destroy. Burn a book and, at least in theory, its text is recoverable from the ashes. But Hawking’s evaporating black holes said otherwise, implying that information is fragile and constantly being annihilated. As a result, physics is ultimately limited in what it can know.
For 20 years, the “information paradox” seemed unavoidable. That all changed in 1997, when Juan Maldacena—an Argentinian research mathematician at Harvard—announced that he had found the “lost” information. It had been hiding in “an equivalent description of reality,” a “holographic” representation that was implied by the laws of negatively curved space.
Despite the surreal elegance of Maldacena’s proof, Hawking denied its implications. Then, last summer, he revealed the groundwork for a proof consistent with Maldacena’s conclusion that black holes do not destroy their information. Knowledge—even obliterated by the gravity of black holes—stubbornly survives.
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Originally published December 27, 2005