Saturday, February 27, 2010


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Since the dawn of the biological sciences, mankind has struggled to comprehend the relationships among the major groups of "jointed-legged" animals — the arthropods. Now, a team of researchers, including Dr. Joel Martin and Dr. Regina Wetzer from the Natural History Museum of Los Angeles County (NHM), has finished a completely new analysis of the evolutionary relationships among the arthropods, answering many questions that defied previous attempts to unravel how these creatures were connected.

Now, for the first time, science has a solid grasp of what those relationships are, and a framework upon which to build. The new study makes a major contribution to our understanding of the nature and origins of the planet's biodiversity. The paper's other researchers are Jerome C. Regier, Andreas Zwick and April Hussey from the University of Maryland Biotechnology Institute; Jeffrey W. Shultz of the University of Maryland's Department of Entomology; and Bernard Ball and Clifford W. Cunningham from Duke University's Department of Biology.

There are millions of distinct species of arthropods, including all the insects, crustaceans, millipedes, centipedes, spiders, and a host of other animals, all united by having a hard external shell and jointed legs. They are by far the most numerous, and most diverse, of all creatures on Earth — in terms of the sheer number of species, no other group comes close. They make up perhaps 1.6 million of the estimated 1.8 to 1.9 million described species, dominating the planet in number, biomass, and diversity.
The economic aspects of arthropods are also overwhelming. From seafood industries worth billions of dollars annually to the world's economy, to the importance of insects as pollinators of ornamental and agriculturally important crops, to the medical role played by arthropods (e.g. as disease vectors and parasites), to biological control of introduced species, to their role in every known food web, to toxicology and biopharmaceuticals, arthropods are by far the planet's most important group of animals.

"We've never really known how arthropods, the most successful animals on Earth, evolved into the diversity we see today," said research scientist and co-author Dr. Regina Wetzer. "For me, what makes this study really exciting is getting such a solid understanding of how these animals are related, so that now we can better understand how they evolved."

Because of their amazing diversity, deciphering the evolutionary history and relationships among the major subgroups of arthropods has proven difficult. Scientists have tried using various combinations of features, in recent years including DNA sequences, to try to understand which groups are related through common ancestors. To date, those attempts have been stymied by the sheer number of species and wild shape variations between the various groups.

One of the most important results of this new study is support for the hypothesis that the insects evolved from a group of crustaceans. So flies, honeybees, ants, and crickets all branched off the arthropod family tree from within the lineage that gave rise to today's crabs, shrimp, and lobsters. Another important finding is that the "Chelicerata" (a group that includes the spiders, scorpions, ticks, and mites) branched off very early, earlier than the millipedes, centipedes, crustaceans, and insects. That means that the spiders, for example, are more distantly related to the insects than many researchers previously thought.

This team approached the problem of illuminating the arthropod family tree by using genetic data (DNA sequences) obtained from 75 species carefully selected to sample the range of arthropod diversity. Many previous analyses were based on the sequences of a handful of genes. The researchers in this study, knowing the daunting diversity they faced, used DNA sequence information from as many genes as they could. In the end, they were able to apply data from 62 protein-coding genes to the problem, leading to an extremely well-supported analysis.

"The Museum's collection of arthropods, and in particular its collection of crustaceans, are what made a study like this possible in the first place," says Dr. Joel W. Martin, NHM Curator of Crustacea and one of the authors who designed the study nearly eight years ago. "The wealth of stored biodiversity information contained in it, both in terms of specimens and in terms of the data, theories, and research related to those specimens, are why natural history museums exist, and why they play such a critical role in explaining the world's diversity. Studies like this confirm the incredible value, not only of existing natural history museum collections, but of continuing to add to these collections every year."

A key problem that the research team had to solve was obtaining specimens of some of rare and obscure organisms whose DNA was needed for the analysis. Because of their extensive experience in field biology, this was a major contribution to the project from NHM scientists. Dr. Wetzer recalls lying on the beach with a microscope at Woods Hole, Massachusetts. She was hunting for specimens of a tiny, little-known crustacean that lives between grains of sand. "I got the mystacocarids we needed, but I think I also provided pretty good entertainment to the families at the beach that day," Dr. Wetzer said.

(Photo: Simon Richards)

Natural History Museum of Los Angeles County


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New research suggests that the act of voluntarily sharing something with another may not be entirely exclusive to the human experience. A study published in the March 9th issue of Current Biology, a Cell Press publication, observed that bonobos—a sister species of chimpanzees and, like chimps, our closest living relatives—consistently chose to actively share their food with others.

"It has been suggested that only humans voluntarily share their food," says lead study author Brian Hare from Duke University in North Carolina. "However, the food sharing preferences of the unusually tolerant bonobos have never been studied experimentally." Dr. Hare and Suzy Kwetuenda from the Lola ya Bonobo Sanctuary for orphaned bonobos in the Democratic Republic of the Congo conducted a study with unrelated pairs of hungry bonobos.

In the study, bonobos had to choose whether to eat some food by themselves or to give another bonobo access to it. The test subjects had the opportunity to immediately eat the food or to use a "key" to open a door to an adjacent empty room or a room that had another bonobo in it. The test subjects could easily see into the adjacent rooms, so they know which one was empty and which was occupied.

"We found that the test subjects preferred to voluntarily open the recipient's door to allow them to share highly desirable food that they could have easily eaten alone—with no signs of aggression, frustration, or change in the speed or rate of sharing across trials," explains Dr. Hare. "This stable sharing pattern was particularly striking since in other, nonsharing contexts, bonobos are averse to food loss and adjust to minimize such losses."

The authors point out that it is possible that the bonobos in their study chose to share in order to obtain favors in the future. Additional studies are needed to gain further insight into why bonobos and humans share. "Given the continued debate about how to characterize the motivation underlying costly sharing in humans, it will certainly require future research to probe more precisely what psychological mechanisms motivate and maintain the preference we observe here in bonobos for voluntary, costly sharing," concludes Dr. Hare.

Cell Press


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Besides the 92 elements that occur naturally, scientists were able to create 20 additional chemical elements, six of which were discovered at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt. These new elements were produced artificially with particle accelerators and are all very short-lived: they decay in a matter of a split second. However, scientists predict the existence of even heavier elements with an extreme longevity, leaving them to only decay after years. These elements form an island of stability. Scientists at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt have developed and applied a measuring apparatus that might allow them to discover such long-lived elements, reports the renowned scientific journal "Nature".

An international team of scientists headed by Michael Block was able to trap atoms of the element 102, nobelium, in an ion trap. This is the first time in history that a so-called super heavy element had been trapped. Trapping the element allowed the research team to measure the atomic mass of Nobelium with unprecedented accuracy. The atomic mass is one of the most essential characteristics of an atom. It is used to calculate the atom’s binding energy, which is what keeps the atom together. The atom’s binding energy determines the stability of an atom. With the help of the new measuring apparatus, scientists will be able to identify long-lived elements on the so called islands of stability that can no longer be assigned by their radioactive decay. The island of stability is predicted to be located in the vicinity of the elements 114 to 120.

“Precisely measuring the mass of nobelium with our Shiptrap device was a successful first step. Now, our goal is to improve the measuring apparatus so that we can extend our method to heavier and heavier elements and, one day, may reach the island of stability”, says Michael Block, head of the research team at the GSI Helmholtz Centre.

For their measurements, Michael Block and his team built a highly complex apparatus, the ion trap “Shiptrap”, and combined it with “Ship”, the velocity filter which was already used in the discovery of six short-lived elements at GSI. To produce nobelium, the research team used the GSI accelerator to fire calcium ions onto a lead foil. With the help of Ship, they then separated the freshly produced nobelium from the projectile atoms. Inside the Shiptrap apparatus, the nobelium was first decelerated in a gas-filled cell, then the slow ions were trapped in a so-called Penning trap.

Held inside the trap by electric and magnetic fields, the nobelium ion spun on a minuscule spiral course at a specific frequency. This frequency was used to calculate the atomic mass. With an uncertainty of merely 0,000005 per cent, this new technique allows determining the atomic mass and binding energy with unprecedented precision and, for the first time, directly without the help of theoretical assumptions.

(Photo: G. Otto, GSI Helmholtzzentrum für Schwerionenforschung)

GSI Helmholtzzentrum für Schwerionenforschung GmbH


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Manchester scientists have identified the genes that make plants grow fatter and plan to use their research to increase plant biomass in trees and other species – thus helping meet the need for renewable resources.

“The US has set the ambitious goal of generating a third of all liquid fuel from renewable source by the year 2025. Estimates suggest to reach their goal they would need 1 billion tonnes of biomass, which is a lot,” says Professor Simon Turner, one of the University of Manchester researchers whose BBSRC-funded study is published in Development (Wednesday 10th February 2010).

“Our work has identified the two genes that make plants grow outwards. The long, thin cells growing down the length of a plant divide outwards, giving that nice radial pattern of characteristic growth rings in trees. So you get a solid ring of wood in the centre surrounded by growing cells. Now we have identified the process by which the cells know how to grow outwards, we hope to find a way of making that plants grow thicker quicker, giving us the increased wood production that could be used for biofuels or other uses.

“And there is an added benefit. There are concerns that the growing of biofuel products competes with essential food production. However, the part of the plant we have studied is the stalk – not the grain – so there will be no competition with food production.”

Professor Turner and Dr Peter Etchells, at the Faculty of Life Sciences, studied the plant Arabidopsis which does not look like a tree but has a similar vascular system, (which carries water and sugar around the plant). They investigated growth in the vascular bundles and found that the genes PXY and CLE41 directed the amount and direction of cell division. Furthermore, they found over-expression of CLE41 caused a greater amount of growth in a well-ordered fashion, thus increasing wood production.

Professor Turner explained: “We wanted to know how the cells divided to produce this pattern, how they ‘knew’ which side to divide along, and we found that it was down to the interaction of these two genes.

“Trees are responsive to a lot of things. They stop growing in winter and start again in spring and this changes according to the amount of light and the day length. It might take a tree 150 years to grow in Finland and only ten years in Portugal.

“Now we know what genes are dictating the growth process, we can develop a system of increasing growth so that it is orientated to produce more wood – increasing the essential biomass needed for our future.”

The team are now growing poplar trees in the lab – to see if they fit the Arabidopsis model. They will use these results to develop a system of increasing wood production.

(Photo: U. Manchester)

University of Manchester


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Nicotine in third-hand smoke, the residue from tobacco smoke that clings to virtually all surfaces long after a cigarette has been extinguished, reacts with the common indoor air pollutant nitrous acid to produce dangerous carcinogens. This new potential health hazard was revealed in a multi-institutional study led by researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab).

“The burning of tobacco releases nicotine in the form of a vapor that adsorbs strongly onto indoor surfaces, such as walls, floors, carpeting, drapes and furniture. Nicotine can persist on those materials for days, weeks and even months. Our study shows that when this residual nicotine reacts with ambient nitrous acid it forms carcinogenic tobacco-specific nitrosamines or TSNAs,” says Hugo Destaillats, a chemist with the Indoor Environment Department of Berkeley Lab’s Environmental Energy Technologies Division. “TSNAs are among the most broadly acting and potent carcinogens present in unburned tobacco and tobacco smoke.”

Destaillats is the corresponding author of a paper published in the Proceedings of the National Academy of Sciences (PNAS) titled “Formation of carcinogens indoors by surface-mediated reactions of nicotine with nitrous acid, leading to potential third-hand smoke hazards.”

Co-authoring the PNAS paper with Destaillats were Mohamad Sleiman, Lara Gundel and Brett Singer, all with Berkeley Lab’s Indoor Environment Department, plus James Pankow with Portland State University, and Peyton Jacob with the University of California, San Francisco.

The authors report that in laboratory tests using cellulose as a model indoor material exposed to smoke, levels of newly formed TSNAs detected on cellulose surfaces were 10 times higher than those originally present in the sample following exposure for three hours to a “high but reasonable” concentration of nitrous acid (60 parts per billion by volume). Unvented gas appliances are the main source of nitrous acid indoors. Since most vehicle engines emit some nitrous acid that can infiltrate the passenger compartments, tests were also conducted on surfaces inside the truck of a heavy smoker, including the surface of a stainless steel glove compartment. These measurements also showed substantial levels of TSNAs. In both cases, one of the major products found was a TSNA that is absent in freshly emitted tobacco smoke – the nitrosamine known as NNA. The potent carcinogens NNN and NNK were also formed in this reaction.

“Time-course measurements revealed fast TSNA formation, up to 0.4 percent conversion of nicotine within the first hour,” says lead author Sleiman. “Given the rapid sorption and persistence of high levels of nicotine on indoor surfaces, including clothing and human skin, our findings indicate that third-hand smoke represents an unappreciated health hazard through dermal exposure, dust inhalation and ingestion.”

Since the most likely human exposure to these TSNAs is through either inhalation of dust or the contact of skin with carpet or clothes, third-hand smoke would seem to pose the greatest hazard to infants and toddlers. The study’s findings indicate that opening a window or deploying a fan to ventilate the room while a cigarette burns does not eliminate the hazard of third-hand smoke. Smoking outdoors is not much of an improvement, as co-author Gundel explains.

“Smoking outside is better than smoking indoors but nicotine residues will stick to a smoker’s skin and clothing,” she says. “Those residues follow a smoker back inside and get spread everywhere. The biggest risk is to young children. Dermal uptake of the nicotine through a child’s skin is likely to occur when the smoker returns and if nitrous acid is in the air, which it usually is, then TSNAs will be formed.”

The dangers of mainstream and secondhand tobacco smoke have been well documented as a cause of cancer, cardiovascular disease and stroke, pulmonary disease and birth defects. Only recently, however, has the general public been made aware of the threats posed by third-hand smoke. The term was coined in a study that appeared in the January 2009 edition of the journal “Pediatrics,” in which it was reported that only 65 percent of non-smokers and 43 percent of smokers surveyed agreed with the statement that “Breathing air in a room today where people smoked yesterday can harm the health of infants and children.”

Anyone who has entered a confined space – a room, an elevator, a vehicle, etc. – where someone recently smoked, knows that the scent lingers for an extended period of time. Scientists have been aware for several years that tobacco smoke is adsorbed on surfaces where semi-volatile and non-volatile chemical constituents can undergo reactions, but reactions of residual smoke constituents with atmospheric molecules such as nitrous acid have been overlooked as a source of harmful pollutants. This is the first study to quantify the reactions of third-hand smoke with nitrous acid, according to the authors.

“Whereas the sidestream smoke of one cigarette contains at least 100 nanograms equivalent total TSNAs, our results indicate that several hundred nanograms per square meter of nitrosamines may be formed on indoor surfaces in the presence of nitrous acid,” says lead-author Sleiman.

Co-author James Pankow points out that the results of this study should raise concerns about the purported safety of electronic cigarettes. Also known as “e-cigarettes,” electronic cigarettes claim to provide the “smoking experience,” but without the risks of cancer. A battery-powered vaporizer inside the tube of a plastic cigarette turns a solution of nicotine into a smoky mist that can be inhaled and exhaled like tobacco smoke. Since no flame is required to ignite the e-cigarette and there is no tobacco or combustion, e-cigarettes are not restricted by anti-smoking laws.

“Nicotine, the addictive substance in tobacco smoke, has until now been considered to be non-toxic in the strictest sense of the term,” says Kamlesh Asotra of the University of California’s Tobacco-Related Disease Research Program, which funded this study. “What we see in this study is that the reactions of residual nicotine with nitrous acid at surface interfaces are a potential cancer hazard, and these results may be just the tip of the iceberg.”

The Berkeley Lab researchers are now investigating the long-term stability in an indoor environment of the TSNAs produced as a result of third-hand smoke interactions with nitrous acid. The authors are also looking into the development of biomarkers to track exposures to these TSNAs. In addition, they are conducting studies to gain a better understanding of the chemistry behind the formation of these TSNAs and to find out more about other chemicals that are being produced when third-hand smoke reacts with nitrous acid.

“We know that these residual levels of nicotine may build up over time after several smoking cycles, and we know that through the process of aging, third-hand smoke can become more toxic over time,” says Destaillats. “Our work highlights the importance of third-hand smoke reactions at indoor interfaces, particularly the production of nitrosamines with potential health impacts.”

In the PNAS paper, Destaillats and his co-authors suggest various ways to limit the impact of the third hand smoke health hazard, starting with the implementation of 100 percent smoke-free environments in public places and self-restrictions in residences and automobiles. In buildings where substantial smoking has occurred, replacing nicotine-laden furnishings, carpets and wallboard might significantly reduce exposures.

(Photo: Roy Kaltschmidt, Berkeley Lab Public Affairs)

Lawrence Berkeley National Laboratory


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Neuroscientists at the California Institute of Technology (Caltech) and their colleagues have tied the human aversion to losing money to a specific structure in the brain—the amygdala.

The finding, described in the latest online issue of the journal Proceedings of the National Academy of Sciences (PNAS), offers insight into economic behavior, and also into the role of the brain's amygdalae, two almond-shaped clusters of tissue located in the medial temporal lobes. The amygdala registers rapid emotional reactions and is implicated in depression, anxiety, and autism.

The research team responsible for these findings consists of Benedetto de Martino, a Caltech visiting researcher from University College London and first author on the study, along with Caltech scientists Colin Camerer, the Robert Kirby Professor of Behavioral Economics, and Ralph Adolphs, the Bren Professor of Psychology and Neuroscience and professor of biology.

The study involved an examination of two patients whose amygdalae had been destroyed due to a very rare genetic disease; those patients, along with individuals without amygdala damage, volunteered to participate in a simple experimental economics task.

In the task, the subjects were asked whether or not they were willing to accept a variety of monetary gambles, each with a different possible gain or loss. For example, participants were asked whether they would take a gamble in which there was an equal probability they'd win $20 or lose $5 (a risk most people will choose to accept) and if they would take a 50/50 gamble to win $20 or lose $20 (a risk most people will not choose to accept). They were also asked if they'd take a 50/50 gamble on winning $20 or losing $15—a risk most people will reject, "even though the net expected outcome is positive," Adolphs says.

Both of the amygdala-damaged patients took risky gambles much more often than subjects of the same age and education who had no amygdala damage. In fact, the first group showed no aversion to monetary loss whatsoever, in sharp contrast to the control subjects.

"Monetary-loss aversion has been studied in behavioral economics for some time, but this is the first time that patients have been reported who lack it entirely," says de Martino.

"We think this shows that the amygdala is critical for triggering a sense of caution toward making gambles in which you might lose," explains Camerer. This function of the amygdala, he says, may be similar to its role in fear and anxiety.

"Loss aversion has been observed in many economics studies, from monkeys trading tokens for food to people on high-stakes game shows," he adds, "but this is the first clear evidence of a special brain structure that is responsible for fear of such losses."

California Institute of Technology (Caltech)




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