Following Genetic Footprints out of Africa: First Modern Humans Settled in Arabia

Following Genetic Footprints out of Africa: First Modern Humans Settled in Arabia

  9:18:00 PM    Science Lover

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A new study, using genetic analysis to look for clues about human migration over sixty thousand years ago, suggests that the first modern humans settled in Arabia on their way from the Horn of Africa to the rest of the world.

A new study, using genetic analysis to 
look for clues about human migration 
over sixty thousand years ago, suggests 
that the first modern humans settled in 
Arabia on their way from the Horn of 
Africa to the rest of the world. 
(Credit: © photoromano / Fotolia)

Led by the University of Leeds and the University of Porto in Portugal, the study is recently published in American Journal of Human Genetics and provides intriguing insight into the earliest stages of modern human migration, say the researchers.

"A major unanswered question regarding the dispersal of modern humans around the world concerns the geographical site of the first steps out of Africa," explains Dr Luísa Pereira from the Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP). "One popular model predicts that the early stages of the dispersal took place across the Red Sea to southern Arabia, but direct genetic evidence has been thin on the ground."

The international research team, which included colleagues from across Europe, Arabia and North Africa, analysed three of the earliest non-African maternal lineages. These early branches are associated with the time period when modern humans first successfully moved out of Africa.

Using mitochondrial DNA analysis, which traces the female line of descent and is useful for comparing relatedness between different populations, the researchers compared complete genomes from Arabia and the Near East with a database of hundreds more samples from Europe. They found evidence for an ancient ancestry within Arabia.

Professor Martin Richards of the University of Leeds' Faculty of Biological Sciences, said: "The timing and pattern of the migration of early modern humans has been a source of much debate and research. Our new results suggest that Arabia, rather than North Africa or the Near East, was the first staging-post in the spread of modern humans around the world."

The research was funded by the Portuguese Foundation for Science and Technology, the Leverhulme Trust, and the DeLaszlo Foundation.

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Why Alcohol Is Addicting: Endorphins in Brain

Why Alcohol Is Addicting: Endorphins in Brain

  9:51:00 PM    Science Lover

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Drinking alcohol leads to the release of endorphins in areas of the brain that produce feelings of pleasure and reward, according to a study led by researchers at the Ernest Gallo Clinic and Research Center at the University of California, San Francisco (UCSF).

New research shows that drinking alcohol leads to the
release of endorphins in areas of the brain that produce
feelings of pleasure and reward. (Credit: iStockphoto)

The finding marks the first time that endorphin release in the nucleus accumbens and orbitofrontal cortex in response to alcohol consumption has been directly observed in humans.

Endorphins are small proteins with opiate-like effects that are produced naturally in the brain.

"This is something that we've speculated about for 30 years, based on animal studies, but haven't observed in humans until now," said lead author Jennifer Mitchell, PhD, clinical project director at the Gallo Center and an adjunct assistant professor of neurology at UCSF. "It provides the first direct evidence of how alcohol makes people feel good."

The discovery of the precise locations in the brain where endorphins are released provides a possible target for the development of more effective drugs for the treatment of alcohol abuse, said senior author Howard L. Fields, MD, PhD, a professor of neurology and Endowed Chair in Pharmacology of Addiction in Neurology at UCSF and director of human clinical research at the Gallo Center.

The study appears on January 11, 2012, in Science Translational Medicine.

The researchers used positron emission tomography, or PET imaging, to observe the immediate effects of alcohol in the brains of 13 heavy drinkers and 12 matched "control" subjects who were not heavy drinkers.

In all of the subjects, alcohol intake led to a release of endorphins. And, in all of the subjects, the more endorphins released in the nucleus accumbens, the greater the feelings of pleasure reported by each drinker.

In addition, the more endorphins released in the orbitofrontal cortex, the greater the feelings of intoxication in the heavy drinkers, but not in the control subjects.

"This indicates that the brains of heavy or problem drinkers are changed in a way that makes them more likely to find alcohol pleasant, and may be a clue to how problem drinking develops in the first place," said Mitchell. "That greater feeling of reward might cause them to drink too much."

Results Suggest Possible Approach to Treat Alcohol Abuse

Before drinking, the subjects were given injections of radioactively tagged carfentanil, an opiate-like drug that selectively binds to sites in the brain called opioid receptors, where endorphins also bind. As the radioactive carfentanil was bound and emitted radiation, the receptor sites "lit up" on PET imaging, allowing the researchers to map their exact locations.

The subjects were then each given a drink of alcohol, followed by a second injection of radioactive carfentanil, and scanned again with PET imaging. As the natural endorphins released by drinking were bound to the opioid receptor sites, they prevented the carfentanil from being bound. By comparing areas of radioactivity in the first and second PET images, the researchers were able to map the exact locations -- areas of lower radioactivity -- where endorphins were released in response to drinking.

The researchers found that endorphins released in response to drinking bind to a specific type of opioid receptor, the Mu receptor.

This result suggests a possible approach to improving the efficacy of treatment for alcohol abuse through the design of better medications than naltrexone, said Fields, who collaborated with Mitchell in the design and analysis of the study.

Fields explained that naltrexone, which prevents binding at opioid receptor sites, is not widely accepted as a treatment for alcohol dependence -- "not because it isn't effective at reducing drinking, but because some people stop taking it because they don't like the way it makes them feel," he said.

"Naltrexone blocks more than one opioid receptor, and we need to know which blocking action reduces drinking and which causes the unwanted side effects," he said. "If we better understand how endorphins control drinking, we will have a better chance of creating more targeted therapies for substance addiction. This paper is a significant step in that direction because it specifically implicates the Mu opioid receptor in alcohol reward in humans."

Co-authors of the study are James P. O'Neill and Mustafa Janabi of Lawrence Berkeley Laboratory and Shawn M. Marks and William J. Jagust, MD, of LBL and the University of California, Berkeley.

The study was supported by funds from the Department of Defense and by State of California Funds for Research on Drug and Alcohol Abuse.

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Leaping Lizards and Dinosaurs Inspire Robot Design

Leaping Lizards and Dinosaurs Inspire Robot Design

  10:48:00 PM    Science Lover

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Leaping lizards have a message for robots: Get a tail! University of California, Berkeley, biologists and engineers -- including undergraduate and graduate students -- studied how lizards manage to leap successfully even when they slip and stumble. They found that lizards swing their tails upward to prevent them from pitching head-over-heels into a rock.

An Agama lizard next to Tailbot, a toy car with an attached tail 
and a toy figure. Sensors detect Tailbot's orientation and swing 
the tail upward to keep the robot from pitching forward, similar 
to the way the lizard uses its tail. 
(Credit: Photo by Robert Full lab, UC Berkeley.)

But after the team added a tail to a robotic car named Tailbot, they discovered that counteracting the effect of a slip is not as simple as throwing your tail in the air. Instead, robots and lizards must actively adjust the angle of their tails just right to remain upright.

"We showed for the first time that lizards swing their tail up or down to counteract the rotation of their body, keeping them stable," said team leader Robert J. Full, UC Berkeley professor of integrative biology. "Inspiration from lizard tails will likely lead to far more agile search-and-rescue robots, as well as ones having greater capability to more rapidly detect chemical, biological or nuclear hazards."

Agile therapod dinosaurs like the velociraptor depicted in the movie Jurassic Park may also have used their tails as stabilizers to prevent forward pitch, Full said. Their tail movement is illustrated in a prescient chase sequence from the 1993 movie in which the animated animal leaps from a balcony onto a T. rex skeleton.

"Muscles willing, the dinosaur could be even more effective with a swing of its tail in controlling body attitude than the lizards," Full said.

Student involvement crucial to research

Full and his laboratory colleagues, including both engineering and biology students, will report their discoveries online on Jan. 5 in advance of publication in the Jan. 12 print edition of the journal Nature. The paper's first author, mechanical engineering graduate student Thomas Libby, also will report the results on Jan. 7 at the annual meeting of the Society for Integrative and Comparative Biology in Charleston, S.C.

Full is enthusiastic about the interplay fostered at UC Berkeley between biologists and engineers in the Center for Interdisciplinary Bio-inspiration in Education and Research (CiBER) lab, within which he offers a research-based teaching lab that provides dozens of undergraduate students with an opportunity to conduct cutting-edge research in teams with graduate students. Each team experiences the benefits of how biologists and engineers approach a problem.

"Learning in the context of original discovery, finding out something that no one has ever know before, really motivated me," said former UC Berkeley integrative biology undergraduate Talia Moore, now a graduate student in the Department of Organismic and Evolutionary Biology at Harvard University. "This research-based lab course … showed me how biologists and engineers can work together to benefit both fields."

"This paper shows that research-based teaching leads to better learning and simultaneously can lead to cutting-edge research," added Full, who last year briefed the U.S. House of Representative's Science, Technology, Engineering and Mathematics (STEM) Education Caucus on this topic. "It also shows the competitive advantage of interdisciplinary approaches and how involvement of undergraduates in research can lead to innovation."

From gecko toe hairs to tails

Full's research over the past 20 years has revealed how the toe hairs of geckos assist them in climbing smooth vertical surfaces and, more recently, how their tails help to keep them from falling when they slip and to right themselves in mid-air.

The new research tested a 40-year-old hypothesis that the two-legged theropod dinosaurs ‑ the ancestors of birds ‑ used their tails as stabilizers while running or dodging obstacles or predators. In Full's teaching laboratory, students noticed a lizard's recovery after slipping during a leap and thought a study of stumbling would be a perfect way to test the value of a tail.

In the CiBER lab, Full and six of his students used high-speed videography and motion capture to record how a red-headed African Agama lizard handled leaps from a platform with different degrees of traction, from slippery to easily-gripped.

They coaxed the lizards to run down a track, vault off a low platform and land on a vertical surface with a shelter on top. When the friction on the platform was reduced, lizards slipped, causing their bodies to potentially spin out of control.

When the researchers saw how the lizard used its tail to counteract the spin, they created a mathematical model as well as Tailbot -- a toy car equipped with a tail and small gyroscope to sense body position ‑ to better understand the animal's skills. With a tail but no feedback from sensors about body position, Tailbot took a nose dive when driven off a ramp, mimicking a lizard's take-off. When body position was sensed and fed back to the tail motor, however, Tailbot was able to stabilize its body in midair. The actively controlled tail effectively redirected the angular momentum of the body into the tail's swing, as happens with leaping lizards, Full said.

Inertial assisted robotics

Tailbot's design pushed the boundaries of control in robotics in an area researchers call inertial assisted robotics, an attention-grabber at last October's meeting of the International Conference on Intelligent Robots and Systems. The UC Berkeley researchers' paper, presented by Libby and fellow mechanical engineering graduate student Evan Chang-Siu, was one of five finalists there among more than 2,000 robot studies.

"Engineers quickly understood the value of a tail," Libby said, noting that when he dropped Tailbot nose-down, it was able to right itself before it had dropped a foot. "Robots are not nearly as agile as animals, so anything that can make a robot more stable is an advancement, which is why this work is so exciting."

Full and his students are now investigating the role of the tail in controlling pitch, roll and yaw while running.

UC Berkeley coauthors include Full and students Moore, Libby and Chang-Siu, along with Department of Integrative Biology undergraduate Deborah Li and graduate students Ardian Jusufi in the Department of Integrative Biology and Daniel Cohen in the Department of Bioengineering.

The work was funded by the National Science Foundation, including the NSF's Integrative Graduate Education and Research Traineeship (IGERT) program, and the Micro Autonomous Systems Technologies (MAST) consortium, a large group of researchers funded in part by the U.S. Army Research Laboratory that is focused on creating autonomous sensing robots.

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