Tuesday, September 21, 2010

MOONSTRUCK PRIMATES: OWL MONKEYS NEED MOONLIGHT AS MUCH AS A BIOLOGICAL CLOCK FOR NOCTURNAL ACTIVITY

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An international collaboration led by a University of Pennsylvania anthropologist has shown that environmental factors, like temperature and light, play as much of a role in the activity of traditionally nocturnal monkeys as the circadian rhythm that regulates periods of sleep and wakefulness.

The study also indicates that when the senses relay information on these environmental factors, it can influence daily activity and, in the case of a particular monkey species, may have even produced evolutionary change. It is possible, according to the study results, that changes in sensitivity to specific environmental stimuli may have been an essential key for evolutionary switches between diurnal and nocturnal habits in primates. The study also provides data to better understand all life cycles.

Researchers set out to examine the hypothesis that masking, the chronobiology term for the stimulation or inhibition of activity, was largely caused by changing environmental factors that affected the Azara’s owl monkeys’ internal timing system, or synchronized circadian rhythm. Put simply, changes in temperature and light make Azara’s owl monkeys the only anthropoid primate (monkeys, apes and humans) with a propensity for both early bird and night owl behavior.

The observational nature of field studies has generally limited science’s understanding of the mechanisms responsible for the change in activity patterns of these species, whose behavior traditionally takes place in the dimmest of light. Researchers monitored the activity of these wild owl monkeys continually for as long as 18 months using actimeter collars fitted to them.

The results represent the first long-term study of wild primates providing direct evidence for environmental masking, according to researchers.

The data indicate that, although regular daytime activity is represented by the output of a circadian clock, nocturnality is the result of fine-tuned masking of circadian rhythmicity by environmental light and temperature.

Specifically, date showed that nocturnal activity was more consolidated during the relatively warmer months of September to March than during the colder months of April to August, when temperatures in the Argentine province of Formosa regularly fall below 10ºC. Throughout the year, nocturnal activity was higher during full-moon nights than during new-moon ones, and these peaks of nocturnal activity were consistently followed by mornings of low activity. Conversely, new-moon nights were usually followed by mornings of higher diurnal activity than mornings following full-moon nights.

“The behavioral outcome for these owl monkeys is nocturnal activity maximized during relatively warm, moonlit nights,” said Eduardo Fernández-Duque, lead investigator and an assistant professor in the Department of Anthropology in Penn’s School of Art and Sciences.

“While laboratory studies have pointed to the importance of masking in determining the environmental factors that cause animals to switch from nocturnal activity patterns to diurnal ones or vice versa, our study underscores the importance of masking in determining the daily activity patterns of animals living in the wild. It also suggests that moonlight is a key adaptation for the exploitation of the nocturnal niche by primates,” he said.

Conclusive evidence for the direct masking effect of light was provided when three full lunar eclipses completely shadowed moonlight, coinciding with diminished monkey activity. Temperature also negatively masked locomotor activity, and this masking was manifested even under optimal light conditions.

“If there was a biological clock that they were depending on to regulate this activity, you could expect the activity to continue even in the absence of lunar light,” said Horacio de la Iglesia of the Department of Biology at the University of Washington.
Primates — even humans — conduct their daily tasks in patterns ranging from nocturnality to diurnality, with a few species showing activity both during day and night. Among anthropoids (monkeys, apes and humans), nocturnality is only present in the Central and South American owl monkey genus Aotus. But unlike other tropical Aotus species, the Azara’s owl monkeys (A. azarai) of the subtropics, and this study, have actually switched their activity pattern from strict nocturnality to one that also includes regular daytime activity. The phenomenon led researchers to question the causes of such a behavioral change.

“Harsher climate, food availability and the lack of predators or daytime competition have all been proposed as factors favoring evolutionary switches in primate activity patterns,” Fernández-Duque said.

“The lunar day has not been a stable force as much as the solar day to evolutionarily select for a clock,” de la Iglesia said. “We still have to prove it in the lab, but the evidence in this paper points to a lack of a lunar biological clock.”

The article appears in the current issue of the journal PLoS ONE.

The study was conducted by Fernández-Duque, de la Iglesia and Hans G. Erkert of the University of Tübingen.

(Photo: U. Penn)

University of Pennsylvania

UCSF UNVEILS MODEL FOR IMPLANTABLE ARTIFICIAL KIDNEY TO REPLACE DIALYSIS

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UCSF researchers today unveiled a prototype model of the first implantable artificial kidney, in a development that one day could eliminate the need for dialysis.

The device, which would include thousands of microscopic filters as well as a bioreactor to mimic the metabolic and water-balancing roles of a real kidney, is being developed in a collaborative effort by engineers, biologists and physicians nationwide, led by Shuvo Roy, PhD, in the UCSF Department of Bioengineering and Therapeutic Sciences.

The treatment has been proven to work for the sickest patients using a room-sized external model developed by a team member in Michigan. Roy’s goal is to apply silicon fabrication technology, along with specially engineered compartments for live kidney cells, to shrink that large-scale technology into a device the size of a coffee cup. The device would then be implanted in the body without the need for immune suppressant medications, allowing the patient to live a more normal life.

“This device is designed to deliver most of the health benefits of a kidney transplant, while addressing the limited number of kidney donors each year,” said Roy, an associate professor in the UCSF School of Pharmacy who specializes in developing micro-electromechanical systems (MEMS) technology for biomedical applications. “This could dramatically reduce the burden of renal failure for millions of people worldwide, while also reducing one of the largest costs in U.S. healthcare.”

The team has established the feasibility of an implantable model in animal models and plans to be ready for clinical trials in five to seven years.

End-stage renal disease, or chronic kidney failure, affects more than 500,000 people per year in the United States alone, and currently is only fully treated with a kidney transplant. That number has been rising between 5-7 percent per year, Roy said, in part because of the kidney damage associated with diabetes and hypertension.

Yet transplants are difficult to obtain: a mere 17,000 donated kidneys were available for transplant last year, while the number of patients on the transplant waiting list currently exceeds 85,000, according to the Organ Procurement ant Transplant Network.

Roughly 350,000 patients are reliant on kidney dialysis, Roy explained, which comes at a tremendous cost. The Medicare system alone spends $25 billion on treatments for kidney failure – more than 6 percent of the total budget – while the disease affects only 1 percent of Medicare recipients, he said. That cost includes almost $75,000 per patient each year for dialysis, according to the U.S. Renal Data System.

Dialysis also takes a human toll. A typical dialysis schedule is three sessions per week, for 3 to 5 hours per session, in which blood is pumped through an external circuit for filtration. This is exhausting for patients and only replaces 13 percent of kidney function, Roy said. As a result, only 35 percent of patients survive for more than 5 years.

With the limited supply of donors, that means thousands of patients die each year waiting for a kidney.

The implantable device aims to eradicate that problem. The two-stage system uses a hemofilter to remove toxins from the blood, while applying recent advances in tissue engineering to grow renal tubule cells to provide other biological functions of a healthy kidney. The process relies on the body’s blood pressure to perform filtration without needing pumps or an electrical power supply.

The project exemplifies the many efforts under way at UCSF to build collaborations across scientific disciplines that accelerate the translation of academic research into real solutions for patients, according to Mary Anne Koda-Kimble, PharmD, dean of the UCSF School of Pharmacy.

“This is a perfect example of the work we are doing at UCSF to address some of the most critical medical issues of our time, both in human and financial costs,” Koda-Kimble said. “This project shows what can be accomplished by teams of scientists with diverse expertise, collaborating to profoundly and more quickly improve the lives of patients worldwide.”

The creation of the Department of Bioengineering and Therapeutic Sciences – a joint department in the UCSF schools of Pharmacy and Medicine – was itself an effort to promote translational research at UCSF by forming collaborations across biomedical specialties. Roy is also a founding faculty member of the UCSF Pediatric Device Consortium, which aims to accelerate the development of innovative devices for children health, and a faculty affiliate of the California Institute for Quantitative Biosciences (QB3) at UCSF.

His team is collaborating with 10 other teams of researchers on the project, including the Cleveland Clinic where Roy initially developed the idea, Case Western Reserve University, University of Michigan, Ohio State University, and Penn State University.

The first phase of the project, which has already been completed, focused on developing the technologies required to reduce the device to a size that could fit into the body and testing the individual components in animal models. In the second and current phase, the team is doing the sophisticated work needed to scale up the device for humans. The team now has the components and a visual model and is pursuing federal and private support to bring the project to clinical use.

(Photo: UCSF)

UCSF

PORTABLE LASER BACKPACK REVOLUTIONIZES 3D MAPPING

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A portable, laser backpack for 3D mapping has been developed at the University of California, Berkeley, where it is being hailed as a breakthrough technology capable of producing fast, automatic and realistic 3D mapping of difficult interior environments.

Research leading to the development of the reconnoitering backpack, was funded by the Air Force Office of Scientific Research and the Army Research Office under the guidance of program managers, Dr. Jon Sjogren (AFOSR) and Dr. John Lavery (ARO).

The backpack is the first of a series of similar systems to work without being strapped to a robot or attached to a cart. At the same time, its data acquisition speed is very fast, as it collects the data while the human operator is walking; this is in contrast with existing systems in which the data is painstakingly collected in a stop and go fashion, resulting in days and weeks of data acquisition time.

Using this technology, Air Force personnel will be able to collectively view the interior of modeled buildings and interact over a network in order to achieve military goals like mission planning.

Under the direction of Dr. Avideh Zakhor, lead researcher and UC Berkeley professor of electrical engineering, the scientists have been able to use this more portable method of mapping by way of sensors or lightweight (less than eight ounces) laser scanners.

"We have also developed novel sensor fusion algorithms that use cameras, lasers range finders and inertial measurement units to generate a textured, photo-realistic, 3D model that can operate without GPS input and that is a big challenge," said Zakhor.

There are many basic research issues to achieve a working system, including calibration, sensor registration and localization. Using multiple sensors facilitates the modeling process, though the data from various sensors do need to be registered and precisely fused with each other in order to result in coherent, aligned, and textured 3D models. Localization is another technical challenge since without it; it is not possible to line up scans from laser scanners in order to build the 3D point cloud, which is the first step in the modeling process.

"It is fair to say that embarking on such a hands-on project, to make indoor 3D modeling a matter of routine, a number of research questions of a fundamental nature came up," said Sjogren. "It is typical of the work that Prof. Zakhor has done for AFOSR/Air Force Research Laboratory over the years, that she meets these challenges head-on, and in most cases solves the problem sufficient to demonstrate a prototype system."

Sjogren noted that what is left for others is to examine the approach that was taken, and extend the techniques that were brought in, to a wider context.

"We are gratified to see how technology can drive science in a domain of critical relevance to practical defense implementations," he said.

Even though they don't have all the answers yet, the scientists are boldly looking ahead to how this technology can be used in the future when they plan to model entire buildings and develop interactive viewers that allow users to virtually walk through buildings before they are there in person.

In the meantime, the cutting-edge technology is being successfully implemented on campus.

"We have already generated 3D models of two stories of the electrical engineering building at UC Berkeley, including the stairway and that is a first," said Zakhor.

(Photo: John Kua, University of California, Berkeley)

Wright-Patterson Air Force Base

THE SMALLEST POSSIBLE REFRIGERATOR

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When it comes to refrigerators, size matters. Who hasn’t at least once in their life wished for a bigger fridge? However, who can say they’ve wished for the extreme opposite – the smallest conceivable one? But this is exactly what experts in quantum mechanics from the University of Bristol have done.

It’s not a question of engineering, of how small can one build a refrigerator, but about the fundamental limitations that Nature may impose on the size of refrigerators. Is there a minimum size below which no refrigerator can work?

The Bristol team – Professor Noah Linden, Professor Sandu Popescu and Paul Skrzypczyk – found there is no minimum size, and, using quantum mechanics, designed what is arguably the smallest possible refrigerator. It works extremely well too: it can cool as close as you like towards absolute zero.

One model refrigerator is made from just three two-level quantum systems – the simplest possible physical systems, known as qubits. Two of the qubits make up the refrigerator – one in a hot heat bath, the other in a heat bath at “room temperature”; the third is the object to be cooled. In addition to their interaction with their local heat baths, the qubits interact with each other. As the hot qubit absorbs energy from its bath, it causes the tepid qubit to siphon energy from the third qubit, thus cooling it.

According to Nicolas Gisin, a theoretical and experimental physicist at the University of Geneva, who was not involved with the work, this result is “extremely elegant. It opens a totally new avenue for interesting questions, combining thermodynamics and quantum information science in a very original way.”

And an article about the work in the online news section of Science quotes physicist David Wineland from the U.S. National Institute of Standards and Technology in Boulder, Colorado, saying he believes such schemes can actually be implemented using “trapped ions”.

So while the main motivation behind this research was understanding fundamental limitations of Nature and not possible applications, as high-tech devices get smaller and smaller – nano-technology, quantum computers and so on – the smallest possible refrigerator may still find its way into your home.

(Photo: Bristol U.)

University of Bristol

BALANCING THE RISKS OF GREENLANDS MELTING ICE SHEET

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Scientists investigating the geophysical and hydrological conditions beneath the Greenland ice sheet say their analysis will be vital for helping understand how the ice sheet will respond to climate change.

Researchers from the University of Bristol, who have carried out extensive fieldwork in Greenland over the past few years, are to lead a series of new experiments, which could yield important information about the wider risks to global sea levels.

Members of the Bristol Glaciology Centre and colleagues from the University’s Faculty of Engineering will work with partners from the universities of Aberystwyth, Cambridge, Edinburgh, Texas, Woods Hole Oceanographic Institution, NASA-Jet Propulsion Laboratory and the Greenland Geological Survey to collate new geophysical data in two complementary projects, the first using ground-based tracers and the second, a suite of airborne observations.

The Bristol-led tracers project will reveal how meltwater generated on the surface of the ice sheet is routed at its base. They will work alongside colleagues from the universities of Edinburgh and Aberystwyth, to tackle the challenging task of tracing water flow over 100 km and in sub-surface rivers with double the discharge of the River Thames. The huge volumes of water generated on the surface of the Greenland Ice Sheet makes it challenging to detect any artificial tracers injected in the water exported as runoff.

Bristol’s Dr Jemma Wadham, who is leading the project said: “We know little about how water flows beneath the Greenland Ice Sheet because the toolkit available to scientists to trace waters under such challenging conditions has been very limited. We aim to employ a new suite of highly sensitive tracing methods, developed in Bristol, to solve this mystery.”

The airborne geophysics project, lead by the University of Cambridge, will focus on ten major outlet glaciers across the ice sheet and will use radar, gravity and magnetic data to characterize the subglacial environment of the glaciers and, in particular, the presence of water and sediment at the bed.

“Together these two projects will provide important insights and new information on the factors that control basal processes and motion beneath the 1-3 km thickness of ice that covers most of Greenland,” said Prof Jonathan Bamber from Bristol.

Greenland’s ice sheet extends across 1.7 million km2 and contains enough water to cause a global sea level rise of seven metres. The ice sheet is divided into a series of major drainage basins, each typically about 50-100,000 km2 in area. Many of these basins drain into coastal fjord systems via relatively narrow and heavily crevassed outlet glaciers that dissect the mountains fringing the island.

Over the past 15 years, rising temperatures have led to increasing mass loss from the ice sheet and subsequent increase in global sea level. This increased loss has been due to a roughly equal increase in the speed of glaciers flowing into the ocean and increased melting at the surface.

Results from the new studies will enable the team of researchers to describe essential information about the internal structure of the ice sheet and the conditions at the bed, including basal melting and the routing of basal water. That information will make a fundamental contribution to computer modelling of the ice sheet, and how it may respond to changes in air and ocean temperature over the coming decades.

(Photo: Bristol U.)

University of Bristol

TERMITES FORETELL CLIMATE CHANGE IN AFRICAS SAVANNAS

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Using sophisticated airborne imaging and structural analysis, scientists at the Carnegie Institution’s Department of Global Ecology mapped more than 40,000 termite mounds over 192 square miles in the African savanna. They found that their size and distribution is linked to vegetation and landscape patterns associated with annual rainfall. The results reveal how the savanna terrain has evolved and show how termite mounds can be used to predict ecological shifts from climate change. The research is published in the September 7, 2010, advanced online edition of Nature Communications.

Mound-building termites in the study area of Kruger National Park in South Africa tend to build their nests in areas that are not too wet, nor too dry, but are well drained, and on slopes of savanna hills above boundaries called seeplines. Seeplines form where water has flowed belowground through sandy, porous soil and backs up at areas rich in clay. Typically woody trees prefer the well-drained upslope side where the mounds tend to locate, while grasses dominate the wetter areas down slope.

“These relationships make the termite mounds excellent indicators of the geology, hydrology, and soil conditions,” commented lead author Shaun Levick at Carnegie. “And those conditions affect what plants grow and thus the entire local ecosystem. We looked at the mound density, size, and location on the hills with respect to the vegetation patterns.”

Most research into the ecology of these savannas has focused on the patterns of woody trees and shorter vegetation over larger, regional scales. Work at the smaller, hill-slope scales has, until now, been limited to 2-dimensional studies on specific hillsides. The Carnegie research was conducted by the Carnegie Airborne Observatory (CAO)–a unique airborne mapping system that operates much like a diagnostic medical scan. It can penetrate the canopy all the way to the soil level and probe about 40,000 acres per day. The CAO uses a waveform LiDAR system (light detection and ranging) that maps the 3-dimensional structure of vegetation and, in this case, termite mounds and combines that information with spectroscopic imaging—imaging that reveals chemical fingerprints of the species below. It renders the data in stunning 3-D maps.

“We looked at the vegetation and termite mound characteristics throughout enormous areas of African savanna in dry, intermediate, and wet zones,” explained Levick. “We found that precipitation, along with elevation, hydrological, and soil conditions determine whether the area will be dominated by grasses or woody vegetation and the size and density of termite mounds.”

The advantage of monitoring termite mounds in addition to vegetation is that mounds are so tightly coupled with soil and hydrological conditions that they make it easier to map the hill slope seeplines. Furthermore, vegetation cover varies a lot between wet and dry season, while the mounds are not subject to these fluctuations.

“By understanding the patterns of the vegetation and termite mounds over different moisture zones, we can project how the landscape might change with climate change,” explained co-author Greg Asner at Carnegie. “Warming is expected to increase the variability of future precipitation in African savannas, so some areas will get more, while others get less rain. The predictions are that many regions of the savanna will become drier, which suggests more woody species will encroach on today’s grasslands. These changes will depend on complex but predictable hydrological processes along hill slopes, which will correspond to pattern changes in the telltale termite mounds we see today from the air.”

(Photo: Nature Communications and Shaun Levick)

Carnegie Institution

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