Monday, December 13, 2010

PRIMATES ARE MORE RESILIENT THAN OTHER ANIMALS TO ENVIRONMENTAL UPS AND DOWNS

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What sets mankind's closest relatives — monkeys, apes, and other primates — apart from other animals? According to a new study, one answer is that primates are less susceptible to the seasonal ups and downs — particularly rainfall— that take their toll on other animals. The findings may also help explain the evolutionary success of early humans, scientists say.

The study appeared online in the November 30 issue of American Naturalist.

"Wild animals deal with a world that's unpredictable from year to year," said study lead author Bill Morris, a biologist at Duke University. "The weather can change a lot; there can be years with plenty of food and years of famine," he explained.

To find out how well primates cope with this unpredictability compared with other animals, researchers working at the National Evolutionary Synthesis Center (NESCent) in Durham, N.C. analyzed decades of birth and survival data for seven species of wild primates: muriqui monkeys and capuchin monkeys in Central and South America, yellow baboons, blue monkeys, chimpanzees and gorillas in Africa, and sifakas (lemurs) in Madagascar.

Collecting this data was no small effort. Nearly every day for more than 25 years, seven research teams working around the world have monitored the births, lives, and deaths of thousands of individual primates.

Thanks to a new database developed at NESCent, the scientists were able to pool their painstakingly-collected data and look for similarities across species.

When they compared year-to-year fluctuations in primate survival to similar data for other animals — namely, two dozen species of birds, reptiles, and mammals — they found that primate survival remained more stable despite seasonal variation in rainfall.

"Primates appear to be well buffered against fluctuations in weather and food availability relative to a lot of other animals," said co-author Susan Alberts, a biologist at Duke University and associate director at NESCent.

A number of traits may help shield primates from seasonal ups and downs. "For one thing, they're social," said co-author Karen Strier, an anthropologist at the University of Wisconsin-Madison. Primates live in groups and share information with each other, so they're better able to find food and water in times of scarcity, Strier explained.

Primates also owe their adaptability to broad, flexible diets that enable them to adjust to seasonal shortages of their favorite foods. "Primates will eat leaves, grasses, fruits, flowers, bark, and seeds. They're generalists," said Alberts.

In the distant past, similar traits may have also buffered other primates — namely, humans — against environmental ebbs and flows, scientists say.

"Modern humans have all the same traits these primate species have: we're smart, we have social networks, and we have a broad diet," said Morris. "Modern humans also arose during a period when Africa's climate was changing," Morris added. "So the same traits that allow non-human primates to deal with unpredictable environments today may have contributed to the success of early humans as well."

If primates are good at coping with environmental ups and downs, then why are so many of them now endangered? Despite being well buffered from changing weather, human activities still take their toll, the scientists say. With nearly half of the world's primates now in danger of becoming extinct due to hunting and habitat loss, continued monitoring will be key, Strier added.

"Everything we can learn about them now will help prevent their extinction in the future."

(Photo: Fernando A. Campos ©)

National Evolutionary Synthesis Center

U OF M RESEARCHER HELPS UNLOCK 30 NEW GENES RESPONSIBLE FOR EARLY-ONSET PUBERTY

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University of Minnesota School of Public Health researcher Ellen Demerath, Ph.D., is among an international group of researchers that has identified 30 new genes responsible for determining the age of sexual maturation in women. Many of these genes are also known to influence body fatness, obesity, and energy metabolism. Prior to the multi-institutional study, only four genes had been identified as contributing to the process.

The findings, which were reported in Nature Genetics, help to explain why girls who are obese tend to have earlier puberty: some of the same genes are involved in both outcomes. Early menarche, or the first menstrual cycle, is linked to a variety of chronic adulthood diseases, including breast cancer, cardiovascular diseases, and type 2 diabetes.

As a result of these discoveries, Demerath suggests that health care providers and other professionals pay particularly close attention to girls with a high risk of obesity (those who are overweight in childhood or who have a parental history of obesity) and intervene with them, as those girls are also genetically more susceptible to early menarche.

“Early menarche is caused by both genetics and environmental factors,” said Demerath. “We already knew that diet and physical exercise play a role in menarche, but now that we’ve identified more of the specific genes involved, this gives us clues about how to intervene on the process. By showing how hereditary and biological factors contribute to early menarche, we hope to one day allow health care providers to identify girls with increased risk of early menarche, and help them avoid the complications of early-onset puberty.”

In the large-scale, NIH-funded study, researchers from 104 institutions collected data from more than 100,000 women from the United States, Europe, and Australia. This includes women from the Twin Cities area enrolled in the Atherosclerosis Risk in Communities (ARIC) study. Not only were researchers able to identify these new genes, but they also found that many of them play a role in body weight regulation or biological pathways related to fat metabolism. The study findings also suggest that menarche is a result of a complex range of biological processes.

Today, girls are menstruating earlier than ever before. In the mid-1900s, the average age of menarche was 14-15 years. The average age today is 12-13 years.

“We now know that hormone regulation, cell development, and other mechanisms are related to menarche,” said Demerath.

According to Demerath, the next step for researchers is to examine whether some of these genes also influence sexual development in males, whether the genes are related to general growth in size as well as development, the points in the life cycle when the genes are most powerfully expressed, and how environmental factors such as diet and physical activity can modify their effects.

University of Minnesota

A FOUNTAIN OF YOUTH IN YOUR MUSCLES

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Working out can help you shed pounds — but that's just the beginning. New research from Tel Aviv University has found that "endurance exercises," like a Central Park jog or a spinning class, can make us look younger. The key, exercise, unlocks the stem cells of our muscles.

Prof. Dafna Benayahu and her team at Tel Aviv University's Sackler School of Medicine say their findings explain for the first time why older people who have exercised throughout their lives age more gracefully. They have discovered how endurance exercise increases the number of muscle stem cells and enhances their ability to rejuvenate old muscles. The researchers hope their finding can lead to a new drug to help the elderly and immobilized heal their muscles faster.

The results of the study were recently published in the journal PLoS ONE.

The muscles and skeleton in our bodies work together, explains Prof. Benayahu. "When we age, we experience sarcopenia, a decline in mass and function of muscles, and osteopenia referrers to bone loss," she says. As a result, our musculoskeletal system is more susceptible to daily wear and tear, which also explains the increased risk of falling in the elderly.

Investigating a rat population, Dr. Gabi Shefer from the research team says that the finding shows that exercise increased the number of satellite cells (muscle stem cells) — a number which normally declines with aging. The researchers believe that a decline in the number of these cells and their functionality may prevent proper maintenance of muscle mass and its ability to repair itself, leading to muscle deterioration.

Comparing the performance of rats of different ages and sexes, they found that the number of satellite cells increased after rats ran on a treadmill for 20 minutes a day for a 13-week period. The younger rats showed a 20% to 35% increase in the average number of stem cells per muscle fiber retained — and older rats benefited even more significantly, exhibiting a 33% to 47% increase in stem cells.

Endurance exercise also improved the levels of "spontaneous locomotion" — the feeling that tells our bodies to just get up and dance — of old rats. Aging is typically associated with a reduced level of spontaneous locomotion.

The combination of aging and a sedentary lifestyle significantly contributes to the development of diseases such as osteoporosis, obesity, diabetes and cardiovascular diseases, as well as a decline in cognitive abilities. If researchers can discover a method to "boost" satellite cells in our muscles, that could simulate the performance of young and healthy muscles — and hold our aging bones in place.

"We hope to understand the mechanisms for the activation codes of muscle stem cells at the molecular level," says Prof. Benayahu. "With this advance, we can let ourselves dream about creating a new drug for humans — one that could increase muscle mass and ameliorate the negative effects of aging."

Tel Aviv University

ROUGH MATCH CAN SIDELINE TENNIS PLAYERS' PERCEPTIONS

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Tennis players who "ace" a match are more likely to see the ball as moving slowly and view the net as lower to the ground, according to new research from Purdue University.

"It is not unusual for tennis players who played well or poorly to comment on their perception of the ball's speed," said Jessica K. Witt, an assistant professor of psychological sciences who studies perception in sports. "If they played well, they often say the game seemed to move in slow motion. And we found that, yes, when a person is playing well, they are likely to perceive the ball as moving slower."

Witt and Mila Sugovic (pronounced MEE-la SHU-go-vich), a third-year doctoral student in cognitive psychology, published their findings in the current issue of Perception. They also found that those who performed well perceived the net to be lower.

"In other studies, when the person performs better, like at softball, they perceive the ball to be bigger," Sugovic said. "This is the first finding where we are showing that something looks smaller or lower, and it matters in this case because the net is something the person is trying to avoid. Viewing it as smaller or lower turned out to be a good thing."

The findings are based on the performance of 36 tennis players who were students in beginner, intermediate and advanced classes. They hit tennis balls at various spins and speeds, from 50-80 mph, from a ball machine. After each hit, they estimated the ball's approaching speed using a computer tool. The players, across all skill levels, judged the ball to be moving slower when they successfully returned the ball compared to when they hit it out-of-bounds. The players who played well also reported the net's height as appearing lower.

This was reinforced by additional experiments in which 26 people played virtual tennis in the lab. By manipulating the size of the racket, the researchers observed that when people played with a larger one, which was easier to control in this game, they perceived the ball as moving slower. When people played with a smaller racket, which was more difficult to control, they perceived the ball as moving faster.

The findings are similar to Witt's previous work in softball, golf and football. For example, in football, she found that people who kick field goals perceive the goal as smaller when unsuccessful and the goal posts as farther apart and the crossbar lower to the ground after a good kick.

The findings challenge traditional views of perception, Witt said.

"Most people consider perception just to be about optical information in the eye, so the same optical information should look the same. What we are finding instead is that what you see relates to your abilities," she said. "This explains moment-to-moment performance. It is not just about your overall skill but how you are able to wield those skills, so to speak. If you are on a hot streak, then you are going to see the world accordingly, and if you are in a slump and struggling, then you are going to see the world according to your performance at that time and not your overall skill."

Witt's research team also will look at the role that streaks and slumps play in an athlete's long-term performance as related to perception, as well as the influence of factors such as fear, pressure or motivation. Other experiments will focus on the perception of fans or onlookers as they watch someone who is playing and how that perception changes if the athlete is playing well or poorly.

(Photo: Purdue University/Andrew Hancock)

Purdue University

ANCIENT WIND HELD SECRET OF LIFE AND DEATH

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The mystery of how an abundance of fossils have been marvellously preserved for nearly half a billion years in a remote region of Africa has been solved by a team of geologists from the University of Leicester’s Department of Geology.

They have established that an ancient wind brought life to the region – and was then instrumental in the preservation of the dead.

Sarah Gabbott, Jan Zalasiewicz and colleagues investigated a site near the Table Mountains in South Africa. Their findings are published in the latest issue of the journal Geology.

Sarah Gabbott said: “Near Table Mountain in South Africa lies one of the world’s most mysterious rock layers. Just a few metres thick, and almost half a billion years old, it contains the petrified remains of bizarre early life-forms, complete with eyes and guts and muscles.

“We investigated why these animals are so marvellously preserved, when most fossils are just fragments of bone and shell? The answer seems to lie in a bitter wind, blowing off a landscape left devastated by a massive ice-cap.”

Gabbott and Zalasiewicz added that microscopic analysis of the shale layers using a specially designed ‘Petroscope’, obtained with funding from the Royal Society, revealed remarkable and so far unique structures – myriads of silt grains, neatly wrapped in the remains of marine algae.

The authors state: “The silt grains are sedimentary aliens - much bigger than the marine mud flakes in which they are embedded. They could only have been blown by fierce glacial winds on to the sea surface from that distant landscape. Arriving thick and fast, they carried nutrients into the surface waters, fuelling its prolific life. The deep waters, though, were overwhelmed by rotting, sinking vegetation, becoming stagnant and lifeless – ideal conditions to preserve the animal remains, down to their finest details. A cold wind, here, was key to both life and death.”

(Photo: Alan Male)

University of Leicester

NEUROSCIENCE OF INSTINCT: HOW ANIMALS OVERCOME FEAR TO OBTAIN FOOD

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When crossing a street, we look to the left and right for cars and stay put on the sidewalk if we see a car close enough and traveling fast enough to hit us before we're able to reach the other side. It's an almost automatic decision, as though we instinctively know how to keep ourselves safe.

Now neuroscientists have found that other animals are capable of making similar instinctive safety decisions. In a study published online the week of Nov. 29 in the Proceedings of the National Academy of Sciences, University of Washington researcher Jeansok Kim demonstrates that rats weigh their odds of safely retrieving food pellets placed at varying distances from a perceived predator.

"When animals go out to forage, they're taking a risk," said Kim, a UW psychology professor. "They're leaving the safety of their nests, venturing out where there may be predators that could eat them."

But staying in the nest is not a safe option either, rats need to get out and find food. How do they decide whether it's safe to leave the nest? Kim and co-author June-Seek Choi, a visiting professor in the UW psychology department from Korea University, studied how the amygdala -- known to be an important brain area for perceiving and reacting to fear -- was involved in the rats' decisions to risk their safety for food.

In humans, impaired amygdala activity has been linked to risky decision-making, such as gambling. And an overactive amygdala could explain anxiety disorders, including post-traumatic stress disorder and phobias.

Kim and Choi trained male rats to retrieve a food pellet placed at varying distances from a safety zone, or nest. The rats, hungry from a restricted food supply for several days, quickly learned to retrieve the food pellets.

The researchers introduced a "predator," an alligator-shaped robot that was programmed to snap its jaws and surge at the rats. With a body made of gray LEGO blocks and fangs of bright orange LEGOS, the LEGO Mindstorms Robogator was about twice the size of the rats. The researchers programmed the robot to lurch forward about 9 inches, open and shut its mouth and then return to its resting spot far away from the rats' nest.

With the robot in place, the rats began foraging as usual. When they neared the food, the Robogator quickly moved toward the rats and snapped its jaws. The rats scurried back to the safety of the nest and then momentarily froze -- a typical fear response.
Still hungry, the rats paced back in forth in the nest areas, hidden from the Robogator (see video "Robot encounter day 1: Pre-amygdalar lesion"). Slowly they re-emerged and cautiously approached the food, while the Robogator continued its aggressive movements whenever the rats neared the food pellet. Most rats learned that they could safely retrieve the food pellet placed closest, 10 inches, from their nest and not intersect the robot's path. None of the rats obtained the pellet nearer the Robogator, about 30 inches from the nest.

Kim compared the rats' decision-making process to the classic math problem that asks when two trains leaving at different times from different places and traveling at different speeds will pass each other. With a predator nearby, Kim said, rats gauge how quickly they can run to the food, how quickly the predator moves and how far away the pellet is from the rat and from the predator. If they judge that there's a chance the rat and robot will cross paths, they don't attempt to get the food.

"Like when people cross the street, we just tend to automatically have a sense of what is safe," Kim said. "I think that most animals have that capability in their nervous system. Through our amygdala, we instinctively know what keeps us safe."

Overactive amygdala could explain anxiety disorders and irrational fears in humans, Kim said. Brain imaging studies show heightened amygdala activity in patients with post-traumatic stress disorder. Underactive amygdala could be linked to risk-taking and impulsive behaviors.

To study this in rats, the researchers created amygdala lesions and observed the rats' subsequent interactions with the robot. Rats with lesions were unperturbed by the Robogator, and when food was placed near the predator the rats ran straight for the food, barely flinching when the Robogator lunged and snapped (see video "Robot encounter day 2: Post-amygdalar lesion"). The same was true when the researchers inactivated the amygdala with the chemical muscimol.

When Kim and Choi increased the amygdala activity, the rats showed greater fear. Even when the food was at a safe distance from the robot, rats treated with the drug bicuculline, which increases neural activity, were too afraid to venture out for the pellet.

"Because humans share many biological and behavioral features with animals, experimental studies with rats provide valuable information toward understanding the physiological as well as the psychological aspects of fear," Kim said.

(Photo: June-Seek Choi and Jeansok Kim)

University of Washington

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