Wednesday, March 31, 2010


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Doctors have a clearer picture than ever before of how much radiation reaches sensitive tissues during routine X-rays and similar imaging, thanks to sophisticated models of the human body being developed at the University of Florida.

“We’re building a rich library of computer simulation tools and 3-D patient models that will make dose estimates much more accurate and patient-specific,” said Wesley E. Bolch, a professor in the UF departments of nuclear and radiological engineering and biomedical engineering, and a member of the UF Shands Cancer Center.

In the March 5 issue of Physics in Medicine and Biology, Bolch and researchers in his lab discuss how they used three-dimensional microCT imaging to describe cartilage, bone marrow and two types of mineral bone in 20 different skeletal sites from two newborns. It is the second in a series of planned articles that will describe variations in tissue and bone that can affect how much radiation is absorbed by the body.

They discovered that children have a greater percentage of total mineral bone in direct contact with sensitive bone marrow than do adults. This has implications for radiation treatments and types of chemotherapy used to treat cancer patients, especially therapies targeting pediatric bone cancers.

In contrast to existing models, the study also found that a large amount of the electron and beta particle energy once believed to stay contained within the bone marrow of children actually escapes to surrounding tissue, said Deanna Pafundi, a UF researcher and lead author of the paper, now a research fellow at the Mayo Clinic in Rochester, Minn. This finding is being used in existing UF research calculating the impact of radiation to the skeletal surrounding tissues, she said.

Radiation epidemiologists can use the revised model to look back in time, estimating doses of radiation associated with leukemia risk, Bolch said. He pointed to the case of unusually high rates of leukemia among a Russian population exposed to river discharges of bone-seeking radionuclides during the Soviet’s nuclear weapons program in the 1950s. UF’s newborn skeletal model suggests that radiation doses to newborn bone marrow have been overestimated by existing clinical skeletal models.

Most current estimates of bone marrow radiation dose are obtained from two-dimensional images acquired from seven skeletal sites in a 44-year-old adult male during the late 1960s, Bolch said. UF’s current work seeks to replace these widely used estimates from the University of Leeds by using three-dimensional imaging and extending the work to the pediatric and prenatal skeleton. The work will illustrate how bone marrow radiation dose can vary with patient size, whether a patient has osteoporosis, and marrow health.

“Wes Bolch is doing research that will give clinicians the tools to reduce the level of patients’ radiation exposure. It’s very important work,” said George Xu, a professor in the department of mechanical, aerospace and nuclear engineering at Rensselaer Polytechnic Institute in Troy, N.Y.

The models are being created at a time when the medical community is sounding the alarm about the potential for harm from excessive radiation exposure. According to the National Council on Radiation Protection and Measurements, the average annual radiation exposure in the United States increased about 75 percent between 1982 and 2006. During that time, the proportion of exposure due to medical interventions rose from 15 percent to 48 percent.

“The current philosophy is that there is a small but perceptible risk of cancer with every radiation exposure. Consequently, you want to maximize the dose delivered to the tumor in radiation therapy, while minimizing the dose and thus additional cancer risk to surrounding healthy tissues,” Bolch said.

Children are at particular risk from radiation exposure, Bolch said, as the carcinogenic effects of radiation have more time to develop in children than in adults. In response to these concerns, professionals involved in pediatric imaging have launched a campaign, dubbed Image Gently, to highlight opportunities to lower radiation dosing when imaging children.

“The risk in using ionizing radiation for both therapy and imaging is never going to be zero, but it can be reduced through proper guidelines and patient modeling of these procedures,” Bolch said.

(Photo: U. Florida)

University of Florida


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Since its development in China thousands of years ago, silk from silkworms, spiders and other insects has been used for high-end, luxury fabrics as well as for parachutes and medical sutures. Now, National Science Foundation-supported researchers are untangling some of its most closely guarded secrets, and explaining why silk is so super strong.

Researchers at the Massachusetts Institute of Technology's Center for Materials Science and Engineering say the key to silk's pound-for-pound toughness, which exceeds that of steel, is its beta-sheet crystals, the nano-sized cross-linking domains that hold the material together.

Markus Buehler, the Esther and Harold E. Edgerton Associate Professor in MIT's department of civil and environmental engineering, and his team recently used computer models to simulate exactly how the components of beta sheet crystals move and interact with each other. They found that an unusual arrangement of hydrogen bonds--the "glue" that stabilizes the beta-sheet crystals--play an important role in defining the strength of silk.

They found that hydrogen bonds, which are among the weakest types of chemical bonds, gain strength when confined to spaces on the order of a few nanometers in size. Once in close proximity, the hydrogen bonds work together and become extremely strong. Moreover, if a hydrogen bond breaks, there are still many hydrogen bonds left that can contribute to the material's overall strength, due to their ability to "self-heal" the beta-sheet crystals.

The researchers conclude that silk's strength and ductility--its ability to bend or stretch without breaking--results from this peculiar arrangement of atomic bonds. They say controlling the size of the area in which hydrogen or other chemical bonds act can lead to significantly enhanced properties for future materials, even when the initial chemical bonds are very weak.

(Photo: M.J. Buehler (MIT))

National Science Foundation


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Blind scorpions that live in the stygian depths of caves are throwing light on a long-held assumption, showing that specialized adaptations aren’t always an evolutionary dead-end.

Looking at the phylogenetic relationships among species of the scorpion family Typhlochactidae, endemic to Mexico, Associate Curator Lorenzo Prendini and colleagues found that species currently living closer to the surface (under stones and in leaf litter) evolved independently on more than one occasion from specialized deep-cave ancestors adapted to life further below the surface (in caves). This finding puts a dent in both Cope’s Law of the unspecialized, which assumes that novel evolutionary traits tend to originate from a generalized member of an ancestral taxon, and Dollo’s Law of evolutionary irreversibility, which theorizes that specialized evolutionary traits are unlikely to reverse.

Scorpions are predatory, venomous, nocturnal arachnids related to spiders, mites, and other arthropods. About 2,000 species are distributed throughout the world, but only 23 species found in ten different families are adapted to a permanent life in caves. One of these families is the Typhlochactidae, comprising four genera and nine species.

“Scorpions have been around for 450 million years, and their biology is obviously flexible,” says Prendini. “This unique group of eyeless Mexican scorpions may have started re-colonizing niches closer to the surface from the deep caves of Mexico after their surface-living ancestors were wiped out by the nearby Chicxuluxb impact along with non-avian dinosaurs, ammonites, and other species.”

(Photo: V. Vignoli)

American Museum of Natural History


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Forensic scientists may soon have a valuable new item in their toolkits -- a way to identify individuals using unique, telltale types of hand bacteria left behind on objects like keyboards and computer mice, says a new University of Colorado at Boulder study.

The CU-Boulder study showed that "personal" bacterial communities living on the fingers and palms of individual computer users that were deposited on keyboards and mice matched the bacterial DNA signatures of users much more closely than those of random people. While the development of the technique is continuing, it could provide a way for forensics experts to independently confirm the accuracy of DNA and fingerprint analyses, says CU-Boulder Assistant Professor Noah Fierer, chief author on the study.

"Each one of us leaves a unique trail of bugs behind as we travel through our daily lives," said Fierer, an assistant professor in CU-Boulder's ecology and evolutionary biology department. "While this project is still in its preliminary stages, we think the technique could eventually become a valuable new item in the toolbox of forensic scientists."

The study was published March 15 in the Proceedings of the National Academy of Sciences. Co-authors on the PNAS study included Christian Lauber and Nick Zhou of CU-Boulder's Cooperative Institute for Research in Environmental Sciences, or CIRES, Daniel McDonald of CU-Boulder's department of chemistry and biochemistry, Stanford University Postdoctoral Researcher Elizabeth Costello and CU-Boulder chemistry and biochemistry Assistant Professor Rob Knight.

Using powerful gene-sequencing techniques, the team swabbed bacterial DNA from individual keys on three personal computers and matched them up to bacteria on the fingertips of keyboard owners, comparing the results to swabs taken from other keyboards never touched by the subjects. The bacterial DNA from the keys matched much more closely to bacteria of keyboard owners than to bacterial samples taken from random fingertips and from other keyboards, Fierer said.

In a second test, the team swabbed nine keyboard mice that had not been touched in more than 12 hours and collected palm bacteria from the mouse owners. The team compared the similarity between the owner's palm bacteria and owner's mouse with 270 randomly selected bacterial samples from palms that had never touched the mouse. In all nine cases, the bacterial community on each mouse was much more similar to the owner's hand.

The team sampled private and public computers at CU-Boulder, as well as hand bacteria collected from a variety of volunteers on campus. The study showed the new technique is about 70 to 90 percent accurate, a percentage that likely will rise as the technology becomes more sophisticated, said Fierer, who also is a CIRES fellow.

In an effort to see how persistent the bacteria colonies were, the team also swabbed the skin surfaces of two individuals, freezing one set of samples at minus 4 degrees Fahrenheit and leaving the other room temperature. The results showed room-temperature bacterial colonies remained essentially unchanged after two weeks, pointing up the technique's potential as a forensic tool. "That finding was a real surprise to us," said Fierer. "We didn't know just how hearty these creatures were."

Previous research by Fierer and his colleagues -- which indicated a typical hand carries about 150 bacterial species -- also showed only 13 percent of bacteria species found a single hand were shared by any two people. "The obvious question then was whether we could identify objects that have been touched by particular individuals," Fierer said.

The CU-Boulder team used a "metagenomic" survey to simultaneously analyze all of the bacteria on the fingers, palms and computer equipment, said Knight. The effort involved isolating and amplifying tiny bits of microbial DNA, then building complementary DNA strands with a high-powered sequencing machine that allowed the team to identify different families, genera and species of bacteria from the sample.

"This is something we couldn't have done even two years ago," said Fierer. "Right now we can sequence bacterial DNA from 450 samples at once, and we think the number will be up to 1,000 by next year. And as the cost of the technology continues to drop, even smaller labs could undertake these types of projects."

Another reason the new technique may prove valuable to forensic experts is that unless there is blood, tissue, semen or saliva on an object, it's often difficult to obtain sufficient human DNA for forensic identification, said Fierer. But given the abundance of bacterial cells on the skin surface, it may be easier to recover bacterial DNA than human DNA from touched surfaces, they said. "Our technique could provide another independent line of evidence."

More research needs to done on how human bacterial signatures adhere to different surfaces like metal, plastic and glass, said Fierer. But the new technique may be useful for linking objects to users in cases where clear fingerprints cannot be obtained – from smudged surfaces, fabrics and highly textured materials, he said. The new technique would even be useful for identifying objects touched by identical twins, since they share identical DNA but they have different bacterial communities on their hands.

The new PNAS study was funded by the National Science Foundation, the National Institutes of Health, the Crohn's and Colitis Foundation of America and the Howard Hughes Medical Institute.

"This project is one example of why I got into science," said Fierer. "We go down a lot of different paths trying to answer research questions we have, some of which pan out and some that don't. This particular project is exciting for the whole team."

Fierer said the new technique brings up bioethical issues to consider, including privacy. "While there are legal restrictions on the use of DNA and fingerprints, which are ‘personally-identifying', there currently are no restrictions on the use of human-associated bacteria to identify individuals," he said. "This is an issue we think needs to be considered."

In a related November 2009 CU study led by Knight, the team developed the first atlas of microbial diversity across the human body, charting wide variations in microbe populations from the forehead and feet to noses and navels of individuals. One goal of the human bacterial atlas project is to find out what is normal to healthy people to provide a baseline for studies looking at human disease states, said Knight.

Working with a $1.1 million NIH grant to develop new computational tools to better understand the composition and dynamics of microbial communities, Knight and his colleagues have been developing novel methods to tag DNA samples with error-correcting "barcodes" to obtain more accurate gene sequencing data.

In the 2008 hand bacteria study, the researchers detected and identified more than 4,700 different bacteria species across 102 human hands in the study, only five species of which were shared among all 51 participants. The study also showed that the diversity of bacteria on individual hands was not significantly affected by regular hand washing.

(Photo: Steve Miller, CIRES)

University of Colorado


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Be true to yourself, and better romantic relationships will follow, research suggests.

A new study examined how dating relationships were affected by the ability of people to see themselves clearly and objectively, act in ways consistent with their beliefs, and interact honestly and truthfully with others.

In other words, the ability to follow the words of William Shakespeare: “to thine own self be true,” said Amy Brunell, lead author of the study and assistant professor of psychology at Ohio State University’s Newark campus.

Findings showed that college students who reported being more true to themselves also reported more positive dating relationships.

“If you’re true to yourself, it is easier to act in ways that build intimacy in relationships, and that’s going to make your relationship more fulfilling,” Brunell said.

The study appears online in the journal Personality and Individual Differences and will be published in an upcoming print edition.

Participating in the study were 62 heterosexual couples, all of whom were college students. The participants completed a long list of questionnaires in three separate sessions that took place about two weeks apart.

The first set of questionnaires probed how true participants were to themselves, a characteristic that psychologists call “dispositional authenticity.” This was measured through the answers to questions like “For better or for worse, I am aware of who I truly am.”

In the second phase, participants answered questions examining various aspects of their relationship functioning, including their willingness to discuss their emotions with their partner, and whether they kept secrets.

The third phase involved measures of relationship satisfaction and personal well-being.

Overall, the study found that both men and women who reported being more true to themselves also behaved in more intimate and less destructive ways with their partner, and that led to them feeling their relationship was more positive. In addition, they also reported greater personal well-being.

But the study revealed an interesting gender difference in how authenticity in men and women affected their partners, Brunell said.

Men who were more true to themselves had partners who showed more healthy relationship behaviors. However, there was no significant relationship between women being true to themselves and men’s relationship behaviors.

That finding may be the result of relationship gender roles in our society, she said.

“Typically in dating and marital relationships, the women tend to be ‘in charge’ of intimacy in the relationship,” Brunell explained.

“So when men have this dispositional authenticity, and want to have an open, honest relationship, it makes women’s job easier – they can more easily regulate intimacy,” she said.

But since men have less of a role in developing relationship intimacy, they were not affected as much by whether their partners were true to themselves or not.

The study also confirmed findings from other studies that show that when men or women act in constructive, healthy ways in a relationship, it increases their partners’ satisfaction with the relationship.

Brunell said being true to yourself doesn’t mean that you should accept all of your flaws and not try to make positive changes in your life. But you should be aware of both your limitations and areas where you can improve. One payoff could be better romantic relationships.

“It shouldn’t be a surprise, but being true to yourself is linked to having healthier and happier relationships for both men and women,” she said.

(Photo: OSU)

Ohio State University


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Although most people think of slavery as a matter of racial oppression, new research has suggested that, between 1500 and 1800, human bondage was often based on religion rather than on race.

Long-running hostilities between Muslims and Christians in Europe, Africa, and the Middle East during these three centuries resulted in the enslavement of at least 3 million people of both faiths, according to Robert C. Davis, professor of history at Ohio State University.

Davis examined this “faith slavery” – a term he coined -- in his new book, Holy War and Human Bondage: Tales of Christian-Muslim Slavery in the Early-Modern Mediterranean (Praeger).

As a result of his research, Davis estimated that during these centuries more than 1 million Muslims were enslaved in Europe and another 2 million Christians suffered the same fate in North Africa and the Near East.

“Faith slavery had huge economic and social consequences at the time but most people today don’t even know about it,” Davis said.

Though we are familiar with the clash between Christianity and Islam today, in early-modern times the balance of forces was much different from what it is now, according to Davis.

“During this period, both sides, Muslims and Christians, had nearly equal power,” Davis said. “It was really a clash of empires and taking slaves was part of the conflict.”

If people today are familiar with faith slavery at all, it is because of novels and films about Muslim corsairs who used Christians as their galley slaves and about Turkish harems including Christian slave women.

But in reality Mediterranean slavery was much more extensive, and much more brutal, than these fictional versions might suggest, Davis says.

Muslim corsairs would capture ships and raid seaside towns in the Mediterranean and Atlantic, in search of men, women and children for slaves.

Once captured, men were made to row galleys, work in heavy construction, at stone quarries, or on private farms. Women were typically sold into harems, for either household or sexual duties.

But faith slavery went both ways: many thousands of Muslims were also captured and enslaved, in Italy, Spain, and Malta.

Davis first explored faith slavery in his 2004 book, Christian Slaves, Muslim Master: White Slavery in the Mediterranean, the Barbary Coast, and Italy, 1500-1800 (Palgrave MacMillian).

To calculate how many Europeans were enslaved on Africa’s Barbary Coast, Davis developed a unique methodology in that book. Taking the best contemporary estimates of how many slaves were at each location at a given time, he then calculated how many new slaves it would take to replace the ones who died, escaped or were ransomed.

He felt that this is the best way available to make enslavement estimates, given the limited records.

In his new book, he expanded this research methodology to calculate how many Christians were enslaved in the Near East, as well as the extent of Islamic slavery in Christian Europe.

“Even rough calculations make it clear that Mediterranean faith slaving was not some minor phenomenon, a petty problem for people at the time, as has been assumed by many historians today,” Davis said.

“Rather, it was a huge business and a vital part of the economy and the social fabric at the time.”

Entire villages along the coast of Italy and Spain were abandoned after raids by Muslim corsairs, Davis said.

In addition, ransoming back a slave was expensive – a year’s income or more for many Europeans.

“The sheer expense of getting their loved ones back represented an enormous transfer of wealth from Europe to Africa,” he said (Muslim slaves were more rarely ransomed).

And while faith slaving was concentrated in the Mediterranean, its reach extended far beyond, Davis found.

In 1627, for instance, a corsair raid on Iceland brought about 400 Icelandic slaves to Algiers. Similar attacks were carried out in Ireland and all along the English coast in the 1630s and 1640s. Most of the captives died in slavery.

Nor was the United States immune. One of the many personal stories that Davis used to give a human face to the statistics is that of the American seaman John Foss. Captured by Algerian corsairs near Spain in 1793, Foss and his fellow crew members labored as slaves for two years before the fledgling American government finally ransomed them.

In his journal, Foss recalled how he, together with 130 fellow Americans and a thousand or more other slaves quarried and hauled enormous stone blocks under the overseers’ lash.

Faith slavery was different in one significant way from the more familiar race slavery, Davis said. Faith slaves, both Christian and Muslim, could convert to their masters’ religion.

For Christians, conversion to Islam was simple: all they had to do was swear there was one God, and his name was Allah.

But the results of their conversion were mixed. Though now Muslims, such “renegades” were still slaves, even if their masters usually gave them easier work. On the other hand, such converts had a much lower chance of being ransomed.

“A Muslim slave owner who let a Muslim slave be ransomed was essentially abandoning someone from the faith, which was punishable by death,” Davis said.

Consequently, many Muslim slave owners didn’t want their Christians slaves to convert. Davis told of one master who beat a would-be renegade until the slave recanted his conversion.

Given the historical magnitude and impact of faith slavery, Davis said he is often asked why more people don’t know about it and why it isn’t taught in schools.

Davis admitted he is not entirely sure. One reason, he said, may be that faith slavery “does not fit the historical master narrative that people in the United States and Europe tend to assume.”

“This narrative holds that from Columbus’ time until the 20th century, history was largely about European colonial expansion, with the imposition of white, European, Christian power on much of the world,” Davis said.

“This story of faith slavery does not fit that narrative. The idea that triumphant Europeans were not everywhere inflicting their dominance on others seems counter-intuitive,” Davis said.

“But in fact, during this centuries-long struggle between nearly equal empires, millions of European Christians ended up enslaved in Muslim hands.”

Some historians have minimized faith slavery by calling victims “captives” rather than “slaves,” as if they were simply prisoners of war. They argue that since some of those captured were eventually ransomed, they were never really slaves.

“That ignores the fact that more than half of the Christian slaves, and almost all of the Muslims, were never ransomed,” Davis said.

Moreover, these faith slaves were treated very much like the more familiar African slaves, Davis said: made to work long days in difficult, dangerous jobs, poorly fed and brutally beaten.

“Some people assume that faith slavery, because it was not based on race, was less brutal or dehumanizing. Nothing could be further from the truth,” he said.

“Just as with black Africans, faith slaves were considered commodities to be bought and sold. If anything, religious intolerance justified extremely cruel and harsh treatment of both Christian and Muslim slaves.”

Davis noted that race slavery ensnared more victims than faith slavery. About 10 to 12 million black Africans were brought to the Americas as slaves, over three times the number he has calculated for Mediterranean faith slaves.

“But that shouldn’t minimize the huge impact that 3 or 4 million faith slaves had on history.”

Davis said he hopes his research encourages people to remember an historical reality that is often forgotten or ignored.

“Faith slavery played an important role in both American and European history. It deserves more attention,” Davis said.

Yet Davis has taken issue with the argument that the slavery of white Europeans somehow mitigates or diminishes the enslavement of black Africans in the Americas.

“That doesn’t make sense to me. Though faith and race slavery were both pervasive in these centuries, the enslavement of some white Christians can hardly balance the moral wrong of the slavery other whites inflicted on Africans,” he said. “Two such enormous wrongs don’t make anything right.”

(Photo: OSU)

Ohio State University




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