Friday, February 12, 2010

NEW ON-OFF 'SWITCH' TRIGGERS AND REVERSES PARALYSIS IN ANIMALS WITH A BEAM OF LIGHT

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In an advance with overtones of Star Trek phasers and other sci-fi ray guns, scientists in Canada are reporting development of an internal on-off "switch" that paralyzes animals when exposed to a beam of ultraviolet light. The animals stay paralyzed even when the light is turned off. When exposed to ordinary light, the animals become unparalyzed and wake up. Their study appears in the Journal of the American Chemical Society (JACS). It reports the first demonstration of such a light-activated switch in animals.

Neil Branda and colleagues point out that such "photoswitches" — light-sensitive materials that undergo photoreactions — have been available for years. Scientists use them in research. Doctors use light-sensitive materials and photoreactions in medicine in photodynamic therapy to treat certain forms of cancer. Those light-sensitive materials, however, do not have the reversibility that exists in photoswitching.

The JACS report describes development and successful testing of a photoswitch composed of the light-sensitive material, dithienylethene. The scientists grew transparent, pinhead-sized worms (C. elegans) and fed them a dithienylethene. When exposed to ultraviolet light, the worms turned blue and became paralyzed. When exposed to visible light, the dithienylethene became colorless again and the worms' paralysis ended. Many of the worms lived through the paralyze-unparalyze cycle. Scientists were not sure how the switch causes paralysis. The study demonstrates that photoswitches may have great potential in turning photodynamic therapy on and off, and for other applications in medicine and research, they indicate.

(Photo: American Chemical Society)

American Chemical Society

NEW RESEARCH REJECTS 80-YEAR THEORY OF 'PRIMORDIAL SOUP' AS THE ORIGIN OF LIFE

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For 80 years it has been accepted that early life began in a 'primordial soup' of organic molecules before evolving out of the oceans millions of years later. Today the 'soup' theory has been over turned in a pioneering paper in BioEssays which claims it was the Earth's chemical energy, from hydrothermal vents on the ocean floor, which kick-started early life.

"Textbooks have it that life arose from organic soup and that the first cells grew by fermenting these organics to generate energy in the form of ATP. We provide a new perspective on why that old and familiar view won't work at all," said team leader Dr Nick lane from University College London. "We present the alternative that life arose from gases (H2, CO2, N2, and H2S) and that the energy for first life came from harnessing geochemical gradients created by mother Earth at a special kind of deep-sea hydrothermal vent – one that is riddled with tiny interconnected compartments or pores."

The soup theory was proposed in 1929 when J.B.S Haldane published his influential essay on the origin of life in which he argued that UV radiation provided the energy to convert methane, ammonia and water into the first organic compounds in the oceans of the early earth. However critics of the soup theory point out that there is no sustained driving force to make anything react; and without an energy source, life as we know it can't exist.

"Despite bioenergetic and thermodynamic failings the 80-year-old concept of primordial soup remains central to mainstream thinking on the origin of life," said senior author, William Martin, an evolutionary biologist from the Institute of Botany III in Düsseldorf. "But soup has no capacity for producing the energy vital for life."

In rejecting the soup theory the team turned to the Earth's chemistry to identify the energy source which could power the first primitive predecessors of living organisms: geochemical gradients across a honeycomb of microscopic natural caverns at hydrothermal vents. These catalytic cells generated lipids, proteins and nucleotides giving rise to the first true cells.

The team focused on ideas pioneered by geochemist Michael J. Russell, on alkaline deep sea vents, which produce chemical gradients very similar to those used by almost all living organisms today - a gradient of protons over a membrane. Early organisms likely exploited these gradients through a process called chemiosmosis, in which the proton gradient is used to drive synthesis of the universal energy currency, ATP, or simpler equivalents. Later on cells evolved to generate their own proton gradient by way of electron transfer from a donor to an acceptor. The team argue that the first donor was hydrogen and the first acceptor was CO2.

"Modern living cells have inherited the same size of proton gradient, and, crucially, the same orientation – positive outside and negative inside – as the inorganic vesicles from which they arose" said co-author John Allen, a biochemist at Queen Mary, University of London.

"Thermodynamic constraints mean that chemiosmosis is strictly necessary for carbon and energy metabolism in all organisms that grow from simple chemical ingredients [autotrophy] today, and presumably the first free-living cells," said Lane. "Here we consider how the earliest cells might have harnessed a geochemically created force and then learned to make their own."

This was a vital transition, as chemiosmosis is the only mechanism by which organisms could escape from the vents. "The reason that all organisms are chemiosmotic today is simply that they inherited it from the very time and place that the first cells evolved – and they could not have evolved without it," said Martin.

"Far from being too complex to have powered early life, it is nearly impossible to see how life could have begun without chemiosmosis", concluded Lane. "It is time to cast off the shackles of fermentation in some primordial soup as 'life without oxygen' – an idea that dates back to a time before anybody in biology had any understanding of how ATP is made."

John Wiley & Sons, Inc

EXCESSIVE INTERNET USE IS LINKED TO DEPRESSION

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People who spend a lot of time browsing the net are more likely to show depressive symptoms, according to the first large-scale study of its kind in the West by University of Leeds psychologists.

Researchers found striking evidence that some users have developed a compulsive internet habit, whereby they replace real-life social interaction with online chat rooms and social networking sites. The results suggest that this type of addictive surfing can have a serious impact on mental health.

Lead author Dr Catriona Morrison, from the University of Leeds, said: "The internet now plays a huge part in modern life, but its benefits are accompanied by a darker side.

"While many of us use the internet to pay bills, shop and send emails, there is a small subset of the population who find it hard to control how much time they spend online, to the point where it interferes with their daily activities."

These 'internet addicts' spent proportionately more time browsing sexually gratifying websites, online gaming sites and online communities. They also had a higher incidence of moderate to severe depression than non-addicted users.

"Our research indicates that excessive internet use is associated with depression, but what we don't know is which comes first – are depressed people drawn to the internet or does the internet cause depression?

"What is clear, is that for a small subset of people, excessive use of the internet could be a warning signal for depressive tendencies."

Incidents such as the spate of suicides among teenagers in the Welsh town of Bridgend in 2008 led many to question the extent to which social networking sites can contribute to depressive thoughts in vulnerable teenagers. In the Leeds study, young people were more likely to be internet addicted than middle-aged users, with the average age of the addicted group standing at 21 years.

"This study reinforces the public speculation that over-engaging in websites that serve to replace normal social function might be linked to psychological disorders like depression and addiction," added Dr Morrison. "We now need to consider the wider societal implications of this relationship and establish clearly the effects of excessive internet use on mental health."

This was the first large-scale study of Western young people to consider the relationship between internet addiction and depression. The internet use and depression levels of 1,319 people aged 16-51 were evaluated for the study, and of these, 1.2% were classed as being internet addicted. While small, this figure is larger than the incidence of gambling in the UK, which stands at 0.6%. The research will be published in the journal Psychopathology on 10th February.

(Photo: U. Leeds)

University of Leeds

NOVEL STUDIES OF DECOMPOSITION SHED NEW LIGHT ON OUR EARLIEST FOSSIL ANCESTRY

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Decaying corpses are usually the domain of forensic scientists, but palaeontologists have discovered that studying rotting fish sheds new light on our earliest ancestry.

The researchers, from the Department of Geology at the University of Leicester, devised a new method for extracting information from 500 million year old fossils -they studied the way fish decompose to gain a clearer picture of how our ancient fish-like ancestors would have looked. Their results indicate that some of the earliest fossils from our part of the tree of life may have been more complex than has previously been thought.

Dr Rob Sansom, lead author of the paper explains: "Interpreting fossils is in some ways similar to forensic analysis – we gather all the available clues to put together a scientific reconstruction of something that happened in the past. Unlike forensics, however, we are dealing with life from millions of years ago, and we are less interested in understanding the cause or the time of death. What we want to get at is what an animal was like before it died and, as with forensic analysis, knowing how the decomposition that took place after death altered the body provides important clues to its original anatomy."

This is something that palaeontologists sometimes overlook, according to Sansom, "probably because spending hundreds of hours studying the stinking carcasses of rotting fish is not something that appeals to everyone." But the rewards are worth the discomfort.

Fish-like fossils from half a billion years ago are recognised as being part of our evolutionary history because they possess characteristic anatomical features, such as a tail, eyes and the precursor of a backbone. Sansom continues: "It seems contradictory, but decomposition is an important part of the process by which animals become preserved and fossilized, so by knowing how these important anatomical features change as they rot, we are better able to correctly interpret the most ancient fossils representing the lowest branches of our part of the evolutionary tree."

"These fossils provide our only direct record of when and how our earliest vertebrate ancestors evolved" adds Dr Mark Purnell, one of the leaders of the study. "Did they appear suddenly, in an evolutionary explosion of complexity, or gradually over millions of years? What did they look like? – in what ways did they differ from their worm-like relatives and how did this set the stage for later evolutionary events? Answers to these fundamental questions - the how, when and why of our own origins - remain elusive because reading the earliest vertebrate fossil record is difficult."

The scarcity of branches in this part of the evolutionary tree could reflect rapid, explosive evolution or the simple fact that, because they lacked bones or teeth, the earliest vertebrates left few fossils.

This is the area in which Dr Sarah Gabbott, who with Purnell conceived the Leicester study, is an expert: "Only in the most exceptional circumstances do soft-tissues, such as eyes, muscles and guts, become fossilized, yet it is precisely such remains that we rely on for understanding our earliest evolutionary relatives: half-a-billion years ago it's pretty much all our ancestors had."

The results published in Nature, show that some of the characteristic anatomical features of early vertebrate fossils have been badly affected by decomposition, and in some cases may have rotted away completely. Knowing how decomposition affected the fossils means our reconstructions of our earliest ancestors will be more scientifically accurate.

(Photo: Mark Purnell, Rob Sansom, Sarah Gabbott, University of Leicester)

University of Leicester

DNA TESTING ON 2,000-YEAR-OLD BONES IN ITALY REVEALS EAST ASIAN ANCESTRY

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Researchers excavating an ancient Roman cemetery made a surprising discovery when they extracted ancient mitochondrial DNA (mtDNA) from one of the skeletons buried at the site: the 2,000-year-old bones revealed a maternal East Asian ancestry.

The results will be presented in the Journal of Roman Archaeology.

According to Tracy Prowse, assistant professor of Anthropology, and the lead author on the study, the isotopic evidence indicates that about 20% of the sample analyzed to-date was not born in the area around Vagnari. The mtDNA is another line of evidence that indicates at least one individual was of East Asian descent.

"These preliminary isotopic and mtDNA data provide tantalizing evidence that some of the people who lived and died at Vagnari were foreigners, and that they may have come to Vagnari from beyond the borders of the Roman Empire," says Prowse. "This research addresses broader issues relating to globalization, human mobility, identity, and diversity in Roman Italy."

Based on her work in the region, she thinks the East Asian man, who lived sometime between the first to second centuries AD—the early Roman Empire—was a slave or worker on the site. His surviving grave goods consist of a single pot (which archaeologists used to date the burial). What's more, his burial was disturbed in antiquity and someone was buried on top of him.

Prowse's team cannot say how recently he, or his ancestors, left East Asia: he could have made the journey alone, or his East Asian genes might have come from a distant maternal ancestor. However, the oxygen isotope evidence indicates that he was definitely not born in Italy and likely came here from elsewhere in the Roman Empire.

During this era, Vagnari was an Imperial estate owned by the emperor in Rome and controlled by a local administrator. Workers were employed in industrial activities on the site, including iron smelting and tile production. These tiles were used for roofing buildings on the site and were also used as grave covers for the people buried in the cemetery. Fragmentary tiles found in and around Vagnari are marked "Gratus Caesaris", which translates into "slave of the emperor."

In addition to the mystery the find uncovers, Prowse sees the broader scientific impact for archaeologists, physical anthropologists, and classicists: The grave goods from this individual's burial gave no indication that he was foreign-born or of East Asian descent.

"This multi-faceted research demonstrates that human skeletal remains can provide another layer of evidence in conjunction with archaeological and historical information," says Prowse.

(Photo: McMaster U.)

McMaster University

WHY THE MIRROR LIES

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Everyone checks themselves in the mirror now and then, but that experience can be horrifying for individuals suffering from body dysmorphic disorder, or BDD, a psychiatric condition that causes them to believe, wrongly, that they appear disfigured and ugly. These people tend to fixate on minute details — every tiny blemish looms huge — rather than viewing their face as a whole.

Now researchers at UCLA have determined that the brains of people with BDD have abnormalities in processing visual input, particularly when examining their own face. Further, they found that the same systems of the brain are overactive in both BDD and obsessive-compulsive disorder, suggesting a link between the two. The research appears in the February issue of the journal Archives of General Psychiatry.

"People with BDD are ashamed, anxious and depressed," said Dr. Jamie Feusner, an assistant professor of psychiatry and lead author of the study. "They obsess over tiny flaws on their face or body that other people would never even notice. Some refuse to leave the house, others feel the need to cover parts of their face or body, and some undergo multiple plastic surgeries. About half are hospitalized at some point in their lifetimes, and about one-fourth attempt suicide."

Despite its prevalence — BDD affects an estimated 1 to 2 percent of the population — and severe effects, little is known about the underlying brain abnormalities that contribute to the disease.

To better understand its neurobiology, Feusner and colleagues examined 17 patients with BDD and matched them by sex, age and education level with 16 healthy people. Participants underwent functional magnetic resonance imaging (fMRI) while viewing photographs of two faces — their own and that of a familiar actor — first unaltered, and then altered in two ways to parse out different elements of visual processing.

One altered version included only high–spatial frequency information, which would allow detailed analysis of facial traits, including blemishes and hairs. The other showed only low–spatial frequency information, conveying the general shape of the face and the relationship between facial features.

Compared to the control participants, individuals with BDD demonstrated abnormal brain activity in visual processing systems when viewing the unaltered and low–spatial frequency versions of their own faces. They also had unusual activation patterns in their frontostriatal systems, which help control and guide behavior and maintain emotional flexibility in responding to situations.

Brain activity in both systems correlated with the severity of symptoms. In addition, differences in activity in the frontostriatal system varied based on participant reports of how disgusting or repulsive they found each image. Basically, how ugly the individuals viewed themselves appeared to explain abnormal brain activity in these systems.

The abnormal activation patterns, especially in response to low-frequency images, suggest that individuals with body dysmorphic disorder have difficulties perceiving or processing general information about faces.

"This may account for their inability to see the big picture — their face as a whole," Feusner said. "They become obsessed with detail and think everybody will notice any slight imperfection on their face. They just don't see their face holistically."

Some of the patterns, said Feusner, also appear to be similar to those observed in patients with obsessive-compulsive disorder, supporting hypotheses that the two conditions share similar neural pathways. However, future studies are needed to further elucidate the causes and development of body dysmorphic disorder.

(Photo: UCLA)

UCLA

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