https://www.youtube.com/watch?v=K0icfVxNHlo
quinta-feira, 3 de julho de 2014
Extinct human cousin gave Tibetans advantage at high elevation
An unusual variant of a gene involved in regulating the body's production of hemoglobin -- the molecule that carries oxygen in the blood -- became widespread in Tibetans after they moved onto the high-altitude plateau several thousand years ago. This variant allowed them to survive despite low oxygen levels at elevations of 15,000 feet or more, whereas most people develop thick blood at high altitudes, leading to cardiovascular problems.
"We have very clear evidence that this version of the gene came from Denisovans," a mysterious human relative that went extinct 40,000-50,000 years ago, around the same time as the more well-known Neanderthals, under pressure from modern humans, said principal author Rasmus Nielsen, UC Berkeley professor of integrative biology. "This shows very clearly and directly that humans evolved and adapted to new environments by getting their genes from another species."
This is the first time a gene from another species of human has been shown unequivocally to have helped modern humans adapt to their environment, he said.
Nielsen and his colleagues at BGI-Shenzhen in China will report their findings online July 2 in advance of publication in the journal Nature.
The gene, called EPAS1, is activated when oxygen levels in the blood drop, triggering production of more hemoglobin. The gene has been referred to as the superathlete gene because at low elevations, some variants of it help athletes quickly boost hemoglobin and thus the oxygen-carrying capacity of their blood, upping endurance. At high altitude, however, the common variants of the gene boost hemoglobin and its carrier, red blood cells, too much, increasing the thickness of the blood and leading to hypertension and heart attacks as well as low-birth-weight babies and increased infant mortality. The variant or allele found in Tibetans raises hemoglobin and red blood cell levels only slightly at high elevation, avoiding the side-effects seen in most people who relocate to elevations above 13,000 feet.
"We found part of the EPAS1 gene in Tibetans is almost identical to the gene in Denisovans and very different from all other humans," Nielsen said. "We can do a statistical analysis to show that this must have come from Denisovans. There is no other way of explaining the data."
Harsh conditions on Tibetan plateau
The researchers first reported the prevalence of a high-altitude version of EPAS1 in Tibetans in 2010, based on sequencing of the genomes of numerous Han Chinese and Tibetans. Nielsen and his colleagues argued that this was the result of natural selection to adapt to about 40 percent lower oxygen levels on the Tibetan plateau. That is, people without the variant died before reproducing at a much higher rate than those with it. About 87 percent of Tibetans now have the high-altitude version, compared to only 9 percent of Han Chinese, who have the same common ancestor as Tibetans.
Nielsen and his colleagues subsequently sequenced the EPAS1 gene in an additional 40 Tibetans and 40 Han Chinese. The data revealed that the high-altitude variant of EPAS1 is so unusual that it could only have come from Denisovans. Aside from its low frequency in Han Chinese, it occurs in no other known humans, not even Melanesians, whose genomes are nearly 5 percent Denisovan. A high quality sequence of the Denisovan genome was published in 2012.
Nielsen sketched out a possible scenario leading to this result: modern humans coming out of Africa interbred with Denisovan populations in Eurasia as they passed through that area into China, and their descendants still retain a small percentage -- perhaps 0.1 percent -- Denisovan DNA. The group that invaded China eventually split, with one population moving into Tibet and the other, now known as Han Chinese, dominating the lower elevations.
He and his colleagues are analyzing other genomes to pin down the time of Denisovan interbreeding, which probably happened over a rather short period of time.
"There might be many other species from which we also got DNA, but we don't know because we don't have the genomes," Nielsen said. "The only reason we can say that this bit of DNA is Denisovan is because of this lucky accident of sequencing DNA from a little bone found in a cave in Siberia. We found the Denisovan species at the DNA level, but how many other species are out there that we haven't sequenced?"
Polyphenols could yield small benefit for people with PAD
In a small study, people with artery problems in their legs walked a little longer and farther when they ate dark chocolate -- a food rich in polyphenols, according to new research in Journal of the American Heart Association.
Peripheral artery disease (PAD) is a narrowing of the peripheral arteries to the legs, stomach, arms, and head -- most commonly in the arteries of the legs. Reduced blood flow can cause pain, cramping or fatigue in the legs or hips while walking.
In this pilot study of patients with PAD (14 men and six women, ages 60-78), study participants increased their ability to walk unassisted after eating dark chocolate, compared to when they ate milk chocolate. The authors suggest that compounds found in cocoa -- polyphenols -- may reduce oxidative stress and improve blood flow in peripheral arteries.
The patients were tested on a treadmill in the morning and again two hours after eating 40 grams of dark and milk chocolate (about the size of an average American plain chocolate bar) on separate days. The dark chocolate in the study had a cocoa content of more than 85 percent, making it rich in polyphenols. The milk chocolate, with a cocoa content below 30 percent, had far fewer polyphenols.
After eating the dark chocolate, they walked an average 11 percent farther and 15 percent longer (almost 12 meters/39 feet farther and about 17 seconds longer) than they could earlier that day. But distance and time didn't improve after eating milk chocolate.
The improvements were modest. Still, the benefit of dark chocolate polyphenols is "of potential relevance for the quality of life of these patients," said Lorenzo Loffredo, M.D., the study's co-author and assistant professor at the Sapienza University of Rome in Italy.
Levels of nitric oxide -- a gas linked to improved blood flow -- were higher when participants ate dark chocolate. Other biochemical signs of oxidative stress were also lower. Based on these observations and other laboratory experiments, the authors suggest that the higher nitric oxide levels may be responsible for dilating peripheral arteries and improving walking independence.
"Polyphenol-rich nutrients could represent a new therapeutic strategy to counteract cardiovascular complications," said, Francesco Violi, M.D., study senior author and professor of internal medicine at the Sapienza University of Rome.
The researchers said the improvements linked to these compounds in dark chocolate need to be confirmed in a larger study involving long-term consumption. The current study lacked a placebo group, and patients knew which kind of chocolate they were given, a factor that could influence the results.
American Heart Association spokesperson Dr. Mark Creager noted that it's far too early to recommend polyphenols or dark chocolate for cardiovascular health.
"Other investigations have shown that polyphenols including those in dark chocolate may improve blood vessel function. But this study is extremely preliminary and I think everyone needs to be cautious when interpreting the findings," said Creager, who is director of the Vascular Center at Brigham and Women's Hospital and a professor of medicine at Harvard Medical School in Boston.
"We know from other studies of antioxidants -- vitamin C and vitamin E for example -- that these interventions have not gone on to show improvement in cardiovascular health."
Chocolate adds calories to the diet. The American Heart Association recommends that men consume no more than 150 calories per day from added sugars (9 teaspoons) and women should consume no more than 100 calories (6 teaspoons) from added sugar per day and 5 percent -6 percent of calories from saturated fat. A typical American chocolate bar provides 94 calories from sugar (24 grams) and 8 grams of saturated fat.
Many other polyphenol-rich foods would offer less added sugar, saturated fats, and calories than dark chocolate, such as cloves, dried peppermint, celery seed, capers, and hazelnuts, to name a few.
Story Source:
The above story is based on materials provided by American Heart Association. Note: Materials may be edited for content and length.
Journal Reference:
- Lorenzo Loffredo; Ludovica Perri; Elisa Catasca; Pasquale Pignatelli; Monica Brancorsini; Cristina Nocella; Elena De Falco; Simona Bartimoccia; Giacomo Frati; Roberto Carnevale; Francesco Violi. Dark Chocolate Acutely Improves Walking Autonomy in Patients With Peripheral Artery Disease. Journal of the American Heart Association, July 2014 DOI: 10.1161/%u200BJAHA.114.001072
The plant that only grows when the going's good
Scientists have identified a new mutant plant that accumulates excessive amounts of starch, which could help to boost crop yields and increase the productivity of plants grown for biofuels.
Researchers from the Max Planck Institute of Molecular Plant Physiology looked for excessive starch accumulators in the model plant Arabidopsis thaliana that had been mutated using Agrobacterium tumefaciens. In one of the mutant plants, the starch granules were significantly larger compared to the controls. Christened NEX1 (meaning NOVEL STARCH EXCESS 1), the researchers believe that the mutation may have affected an enzyme involved in starch degradation. Alternatively, the starch granules themselves may be abnormal and resistant to being broken down for fuel.
Usually, plants that store excessive amounts of starch are much smaller, as less sucrose is available to fuel growth. Remarkably, nex1 mutants are a similar size to normal, non-mutagenised plants.
Dr Maria Grazia Annunziata, who led the study says: "In appearance, the nex1 mutant does not differ from normal plants however the starch granules are generally larger." It also appears that nex1 plants restrict their growing period to the daytime, allowing them to retain their starch reserves. Normally, plants draw on their starch reserves at night, causing the granules to shrink. In the nex1 mutant, the starch granules remain the same size throughout the night, suggesting that growth is suspended until the daytime. Combining high growth rates with large starch reserves is highly desirable for crops that are used both as silage and to feed humans, such as maize.
The researchers are currently investigating the secret of the nex1 mutant by comparing the expression of genes involved in starch metabolism in nex1 and normal plants.
This research was presented at the Society for Experimental Biology Annual Meeting 2014 held at Manchester University, UK, from the 1st - 4th of July.
Desert design: Scorpions are master architects
This is a large-clawed scorpion (Scorpio maurus palmatus).
Israeli scientists have discovered that scorpion burrows have a platform on which to warm up before the evening hunt.
The researchers, represented by Dr Amanda Adams (Ben-Gurion University of the Negev, Israel), investigated the burrows of wild Large-Clawed Scorpions (Scorpio maurus palmatus) in the Negev Desert of Israel. After trapping the scorpions, they prepared replica casts of their burrows by filling them with molten aluminium. Once the casts had solidified, they were then dug out to be analysed by a 3D laser scanner and computer software. Rather than being simple holes in the ground, it was found that the burrows followed a very sophisticated design. Each burrow began with a short, vertical entrance shaft that flattened out a few centimetres below the surface into a horizontal platform. The researchers believe that this provides a safe, warm place for the scorpions to increase their body temperature before they leave the burrow to forage at night. As ectothermic animals, scorpions rely on energy from the environment to regulate their internal temperature.
The burrows then turn sharply downwards, descending further below ground to form a dead-ended chamber. Being cool and humid, this chamber provides a refuge for the scorpions to rest during the heat of the day, where evaporative water loss is minimal. As the design was common to all the burrows studied, this suggests that burrow building in scorpions has evolved by natural selection to meet the animals' physiological needs.
"Very little is known about burrow environments" says Dr Adams. "We plan to expand our studies to more scorpion species around the world to test how burrow structure is shaped to be part of the burrow builder's extended physiology." Understanding the relationship between environmental conditions and burrow structures, meanwhile, could help to predict how burrow-builders will respond to climate change.
This research was presented at the Society for Experimental Biology Annual Meeting 2014 held at Manchester University, UK, from the 1st -- 4th of July.
Story Source:
The above story is based on materials provided by Society for Experimental Biology. Note: Materials may be edited for content and length.
More people means more plant growth, NASA data show
This astronaut photograph, acquired Feb. 10, 2011, illustrates the diverse agricultural landscape in Brazil. In the study in Remote Sensing, plant growth has increased over large areas where intensification of agriculture has occurred.
Ecologist Thomas Mueller uses satellite data to study how the patterns of plant growth relate to the movement of caribou and gazelle. The research sparked an idea: Would the footprint of human activity show up in the data?
Mueller, of the University of Maryland in College Park (now at the Biodiversity and Climate Research Center in Frankfurt) teamed up with university and NASA colleagues to find out. Their new analysis shows that on a global scale, the presence of people corresponds to more plant productivity, or growth.
Specifically, populated areas that have undergone intensive land use showed increasing plant greenness and productivity during the study period from 1981 to 2010. The research was published June 18 in Remote Sensing.
"Earth's land surface has been changed across very broad scales," Mueller said. "Human intervention has increased plant growth over large areas where intensification of agriculture has occurred."
The finding doesn't imply that relatively small areas with massive populations like New York City, with a high population density, are necessarily flourishing in increasingly abundant greenery. Rather, the study uses an existing classifications of the planet's land surface based on how it's impacted by people, including the dense settlements, villages and croplands that compose 28 percent of Earth's ice-free land surface. The rest of the land surface is categorized as forested, rangelands or wildlands.
The researchers used data from NOAA's Advanced Very High Resolution Radiometers (AVHRR), onboard a series of polar-orbiting satellites, and NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) instruments, on the Terra and Aqua satellites, which produce a vegetation index that allows scientists to track changes in plant growth over large areas.
"We are fortunate to have 30 years of global vegetation greenness data from satellites to perform studies such as these," said Compton Tucker a co-author on the study at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The researchers found that the magnitude of changes in plant growth over the 29-year study period was different depending on the size of nearby population. Near areas defined as dense settlements -- with about 500 people per square kilometer -- the vegetation index increased by 4.3 percent. That's less than near villages, where the vegetation index increased by almost 6 percent. "More intensive agriculture occurs in these rural areas," Tucker added.
In short, areas with a human footprint have seen plant productivity increase. In contrast, areas with a minimal human footprint -- rangelands and wildlands -- saw close to no change.
Next, the team used a statistical analysis to estimate the relative importance of the various causes of changes in productivity. They showed that human-caused factors such as land use, nitrogen fertilization and irrigation accounted for much of the growth changes since 1981 in the areas studied.
The study follows on the heels of related research that showed the impact of climate on land plants at higher northern latitudes, where winter temperatures restrict the growing season, which researchers called the "warmer Earth, greener north" phenomenon. Agricultural areas were excluded from the higher northern latitude studies. "We now know that in addition to warmer climate at higher northern latitudes, human land use at lower latitudes also has a detectable, global footprint on Earth's vegetation growth," Tucker said.
Story Source:
The above story is based on materials provided by NASA. Note: Materials may be edited for content and length.
Journal Reference:
- Thomas Mueller, Gunnar Dressler, Compton Tucker, Jorge Pinzon, Peter Leimgruber, Ralph Dubayah, George Hurtt, Katrin Böhning-Gaese, William Fagan. Human Land-Use Practices Lead to Global Long-Term Increases in Photosynthetic Capacity. Remote Sensing, 2014; 6 (6): 5717 DOI: 10.3390/rs6065717
Plants respond to leaf vibrations caused by insects' chewing
This is a cabbage butterfly caterpillar feeding on an Arabidopsis plant where, on an adjacent leaf, a piece of reflective tape helps record vibrations.
Previous studies have suggested that plant growth can be influenced by sound and that plants respond to wind and touch. Now, researchers at the University of Missouri, in a collaboration that brings together audio and chemical analysis, have determined that plants respond to the sounds that caterpillars make when eating plants and that the plants respond with more defenses.
"Previous research has investigated how plants respond to acoustic energy, including music," said Heidi Appel, senior research scientist in the Division of Plant Sciences in the College of Agriculture, Food and Natural Resources and the Bond Life Sciences Center at MU. "However, our work is the first example of how plants respond to an ecologically relevant vibration. We found that feeding vibrations signal changes in the plant cells' metabolism, creating more defensive chemicals that can repel attacks from caterpillars."
Appel collaborated with Rex Cocroft, professor in the Division of Biological Sciences at MU. In the study, caterpillars were placed on Arabidopsis, a small flowering plant related to cabbage and mustard. Using a laser and a tiny piece of reflective material on the leaf of the plant, Cocroft was able to measure the movement of the leaf in response to the chewing caterpillar.
Cocroft and Appel then played back recordings of caterpillar feeding vibrations to one set of plants, but played back only silence to the other set of plants. When caterpillars later fed on both sets of plants, the researchers found that the plants previously exposed to feeding vibrations produced more mustard oils, a chemical that is unappealing to many caterpillars.
"What is remarkable is that the plants exposed to different vibrations, including those made by a gentle wind or different insect sounds that share some acoustic features with caterpillar feeding vibrations did not increase their chemical defenses," Cocroft said. "This indicates that the plants are able to distinguish feeding vibrations from other common sources of environmental vibration."
Appel and Cocroft say future research will focus on how vibrations are sensed by the plants, what features of the complex vibrational signal are important, and how the mechanical vibrations interact with other forms of plant information to generate protective responses to pests.
"Plants have many ways to detect insect attack, but feeding vibrations are likely the fastest way for distant parts of the plant to perceive the attack and begin to increase their defenses," Cocroft said.
"Caterpillars react to this chemical defense by crawling away, so using vibrations to enhance plant defenses could be useful to agriculture," Appel said. "This research also opens the window of plant behavior a little wider, showing that plants have many of the same responses to outside influences that animals do, even though the responses look different."
The study was funded in part by the National Science Foundation and was published in Oecologia.
Video: http://vimeo.com/99635253
Story Source:
The above story is based on materials provided by University of Missouri-Columbia. Note: Materials may be edited for content and length.
Journal Reference:
- H. M. Appel, R. B. Cocroft. Plants respond to leaf vibrations caused by insect herbivore chewing. Oecologia, 2014 DOI: 10.1007/s00442-014-2995-6
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