This advance ultimately will assist efforts to prevent and treat taste loss or impairment due to infection, radiation, chemotherapy and chemical exposures.

"People who undergo chemotherapy or radiation therapy for oral cancer often lose their sense of taste, leading to decreased interest in food, weight loss, and malnutrition," said lead author M. Hakan Ozdener, M.D., Ph.D., M.P.H., a cellular biologist at Monell. "The success of this technique should provide hope for these people, as it finally provides us with a way to test drugs to promote recovery."

Taste cells are found in papillae, the little bumps on our tongues. These cells contain the receptors that interact with chemicals in foods to allow us to sense sweet, salty, sour, bitter, and umami. They also are among the few cells in the body with the special capacity to regenerate, with new taste cells maturing from progenitor 'stem' cells every 10-14 days.

For many years it was believed that taste cells needed to be attached to nerves in order to both function properly and regenerate. For this reason, scientists thought that it was not possible to isolate and grow these cells in culture, which limited the scope of studies to understand how human taste cells function.

"It had become engrained in the collective consciousness that it wouldn't work," said Monell cellular biologist Nancy E. Rawson, Ph.D

To dispel the long-held belief, the Monell scientists first demonstrated in 2006 that taste cells from rats could successfully be maintained in culture. In the current study, published online in the journal Chemical Senses, they then applied that methodology to a more clinically relevant population – humans.

Taking tiny samples of tongue tissue from human volunteers, the researchers first adapted existing techniques to demonstrate that the human taste cells indeed can regenerate in culture.

They went on to show that the new taste cells were functional, maintaining key molecular and physiological properties characteristic of the parent cells. For example, the new cells also were activated by sweet and bitter taste molecules.

"By producing new taste cells outside the body, our results demonstrate that direct stimulation from nerves is not necessary to generate functional taste cells from precursors," said Ozdener.

The establishment of a feasible long-term taste cell culture model opens a range of opportunities to increase understanding of the sense of taste.

"Results from these cells are more likely to translate to the clinic than those obtained from other species or from systems not derived from taste tissue," said Rawson.

The cells also can be used to screen and identify molecules that activate the taste receptors; one such example might be a salt replacer or enhancer.

"The model will help scientists identify new approaches to design and establish cell culture models for other human cells that previously had resisted viable culture conditions," said Ozdener.

» Read More...

At the American Association for Cancer Research (AACR) 102nd Annual Meeting 2011, however, researchers from Georgetown Lombardi Comprehensive Cancer Center, a part of Georgetown University Medical Center, demonstrate how cigarette smoke produces different "metabolites" or active biological compounds, in individual smokers, compared to non-smokers.

In their pilot study, they analyzed hundreds of metabolites found in the blood and urine of nine smokers and 10 non-smokers. The researchers narrowed their focus to the top 50 metabolites in smokers and non-smokers, which differed by group. In the smokers group, the levels of nicotine-related metabolites varied. In addition, overall metabolomic profiles varied among male and female. The researchers validated the reproducibility of the methodology to ensure the experiments were giving low variability.

"This gives us an idea of how people produce metabolites differently when smoking cigarettes, which is based on their particular genetic profile and other biological and environmental factors," says the study's lead investigator, Ping-Ching Hsu, a doctoral student who works in the laboratory of oncology researcher Peter Shields, M.D., who specializes in tobacco carcinogenesis, and occasionally serves as an expert witness against cigarette manufacturers in tobacco related litigation. Shields is the senior author.

This study is designed to identify the "metabolome" of individual smokers, which can provide clues as to both the specific effect that cigarette smoking has on human biology, as well as how individuals vary in their internal response to the smoke.

The ultimate goal of this study, which is part of extensive research project, is to find biomarkers in smokers that predict for development of disease in smokers, Hsu says. It can also help in the development of blood tests that will allow researchers to assess the harmfulness of one tobacco product compared to another.

A metabolite is produced when anything taken into the body – such as food, tobacco smoke, alcohol, or medicine – is metabolized, or broken down into chemicals that produce a biological function via metabolic pathways. The global metabolome is the network of metabolic reactions, and metabolomics is analysis of the metabolome at any given time.

Comparatively, cigarette manufacturers have only been required to use machines that "smoked" cigarettes to derive the chemical content of potential carcinogens. "Metabolomics provides a broad picture of what is happening in the body of smokers," Hsu says.

This is the second study Hsu has presented at an AACR conference. In November, she reported the findings of a study that examined the blood "metabolomics" profile of light versus heavy smokers, and found that smoking behavior could alter several biological pathways.

» Read More...

Jose Russo, MD, director of the Breast Cancer Research Laboratory at Fox Chase, will present the new findings at the AACR 102nd Annual Meeting 2011 on Wednesday, April 6.

To investigate how fish oil intensifies the effects of tamoxifen, Russo, in collaboration with a team led by Andrea Manni, MD, from Pennsylvania State University, induced mammary tumors in rats and then divided the animals into four groups. They fed the groups either a 17 percent fish oil diet, with or without tamoxifen, or a 20 percent corn oil diet, with or without tamoxifen, for eight weeks. They then analyzed gene expression patterns in the tumors. Omega-3 fatty acids produced a greater expression of genes related to cellular specialization, or differentiation—a sign of lower cancer severity—compared to corn oil. The combination of fish oil and tamoxifen reduced the expression of genes linked to tumor growth and spreading.

"If a tumor was being treated with tamoxifen, the addition of an omega-3 fatty acid diet seemed to make the tumor, at least at the molecular level, more benign and less aggressive and responsive to tamoxifen," says Russo.

The fish oil diet also boosted the expression of genes related to immune defenses against tumors, more so than did the corn oil diet. But omega-3 fatty acids simultaneously increased the expression of genes that trigger counterproductive immune responses, such as inflammation and allergic reactions, which curtail the ability of cells to fight cancer and can even promote the migration of tumor cells.

More studies are needed to fully understand the effects of fish oil on the immune system, Russo says. Meanwhile, his team is examining whether omega-3 fatty acids can prevent breast cancer in animals and testing the influence of diet on breast cancer risk in women.

» Read More...

What are the signs of spring? They are as familiar as a blooming Daffodil, a songbird at dawn, a surprising shaft of warmth from the afternoon sun.

And, oh yes, don't forget the meteors.

"Spring is fireball season," says Bill Cooke of NASA's Meteoroid Environment Center. "For reasons we don't fully understand, the rate of bright meteors climbs during the weeks around the vernal equinox."

In other seasons, a person willing to watch the sky from dusk to dawn could expect to see around 10 random or "sporadic" fireballs. A fireball is a meteor brighter than the planet Venus. Earth is bombarded by them as our planet plows through the jetsam and flotsam of space--i.e., fragments of broken asteroids and decaying comets that litter the inner solar system.

In spring, fireballs are more abundant. Their nightly rate mysteriously climbs 10% to 30%.

"We've known about this phenomenon for more than 30 years," says Cooke. "It's not only fireballs that are affected. Meteorite falls--space rocks that actually hit the ground--are more common in spring as well1."

Researchers who study Earth's meteoroid environment have never come up with a satisfactory explanation for the extra fireballs. In fact, the more they think about it, the stranger it gets.

Consider the following:

There is a point in the heavens called the "apex of Earth's way." It is, simply, the direction our planet is traveling. As Earth circles the sun, the apex circles the heavens, completing one trip through the Zodiac every year.

The apex is significant because it is where sporadic meteors are supposed to come from. If Earth were a car, the apex would be the front windshield. When a car drives down a country road, insects accumulate on the glass up front. Ditto for meteoroids swept up by Earth.

Every autumn, the apex climbs to its highest point in the night sky. At that time, sporadic meteors of ordinary brightness are seen in abundance, sometimes dozens per night.

Read that again: Every autumn.

"Autumn is the season for sporadic meteors," says Cooke. "So why are the sporadic fireballs peaking in spring? That is the mystery."

Meteoroid expert Peter Brown of the University of Western Ontario notes that "some researchers think there might be an intrinsic variation in the meteoroid population along Earth's orbit, with a peak in big fireball-producing debris around spring and early summer. We probably won't know the answer until we learn more about their orbits2."

To solve this and other puzzles, Cooke is setting up a network of smart meteor cameras around the country to photograph fireballs and triangulate their orbits. As explained in the Science@NASA story What's Hitting Earth?, he's looking for places to put his cameras; educators are encouraged to get involved. Networked observations of spring fireballs could ultimately reveal their origin.

"It might take a few years to collect enough data," he cautions.

Until then, it's a beautiful mystery. Go out and enjoy the night sky. It is spring, after all.

FOOTNOTES

(1) A Study on the Relative Rates of Meteorite Falls on Earth's Surface -- by Ian Halliday and Arthur A. Griffin, Meteoritics, Vol. 17, No. 1, March 31, 1982

(2) Peter Brown notes that the antapex of Earth's way is highest in spring. The antapex is the opposite of the apex. It is the direction Earth is heading away from. Could the sporadic fireballs be coming from the antapex? "There's no evidence for an antapex source of fireballs. Precise details are still unclear, however, in part due to lack of fireball data from different latitudes."

» Read More...

An international team of scientists published new research this week on the origins of flies and, and despite popular belief, the common ancestry house flies have with mosquitoes.

Researchers, publishing a paper in the Proceedings of the National Academy of Sciences of the USA, said the mosquito branched off the same evolutionary tree as the house fly about 220 million years ago, while the house fly branched off about 170 million years later.

While only a few species of flies are commonly known and considered pests, there are more than 152,000 named species of flies, which account for close to 10 percent of all species on Earth.

Flies evolved to thrive in almost any nutrient-rich substrate and in nearly every corner of the globe.

The new research “provides an evolutionary framework for future comparative work on species that are critically important to both society and science,” said one of the paper’s co-authors, Dr David Yeates from CSIRO Ecosystem Sciences.

“What this research shows us is that the Fly Tree of Life went through three periods of fast diversification, with many different groups experimenting with ways to be a fly,” Yeates said in a statement.

“The mosquito, March fly and common house fly are everyday members of these bursts of evolution, which occurred during unstable periods of Earth’s history when dramatic environmental change created new habitats for these ‘experimental’ flies,” he added.

“The really interesting thing is that living representatives of these early branching groups, such as mosquitoes and March flies, are still with us,” Yeates said.

March flies branched off the evolutionary tree around 175 million years ago.

The research conducted by 27 scientists from six countries.

» Read More...

As the Dawn spacecraft continues on its way to Vesta, which it will reach in July, mission controllers have been putting it through its paces with a series of maneuvers that test the vehicle’s capabilities, a rehearsal for the high- and low-altitude mapping orbits it will operate in. It’s interesting to consider Dawn’s ion thrusters, which after more than 2.2 years of powered flight, continue to work flawlessly, now with a bit less than half of the original supply of xenon propellant (the spacecraft started with 425 kilograms of xenon). The velocity change in this period has been 5.7 kilometers per second, marking a record for on-board propulsion systems.

Dawn’s approach to Vesta is slow and spiraling, closing in on the asteroid at 0.7 kilometers per second as the orbital paths of target and spacecraft become more and more similar. In this mission report, chief engineer Marc Rayman (JPL) describes the trajectory, which is made possible by the high fuel efficiency of the ion propulsion system and the long periods of thrusting:

    Designing the spiral trajectories is a complex and sophisticated process. It is not sufficient simply to turn the thrust on and expect to arrive at the desired destination, any more than it is sufficient to press the accelerator pedal on your car and expect to reach your goal. You have to steer carefully (and if you don’t, please don’t drive near me), and so does Dawn. As the ship revolves around Vesta in the giant asteroid’s gravitational grip, it has to change the pointing of the xenon beam constantly to stay on precisely the desired winding route to the intended science orbits.

Interestingly, Rayman says that from Dawn’s perspective, Vesta is already the brightest object in the sky other than the Sun, about as bright as Jupiter appears to us in the evening skies on Earth. I keep calling Vesta an asteroid but the differences between it and other main belt asteroids are profound. Vesta is about 530 kilometers across, compared to the much smaller objects that travel with it in their orbits between Mars and Jupiter. Moreover, Vesta has undergone differentiation, meaning its structure is layered, showing a core, mantle and crust.

Image: This image shows a model of the protoplanet Vesta, using scientists’ best guess to date of what the surface of the protoplanet might look like. It was created as part of an exercise for NASA’s Dawn mission involving mission planners at NASA’s Jet Propulsion Laboratory and science team members at the Planetary Science Institute in Tuscon, Ariz. The images incorporate the best data on dimples and bulges of the protoplanet Vesta from ground-based telescopes and NASA’s Hubble Space Telescope. The cratering and small-scale surface variations are computer-generated, based on the patterns seen on the Earth’s moon, an inner solar system object with a surface appearance that may be similar to Vesta. Credit: NASA/JPL-Caltech/UCLA/PSI.

It was back in 1972 that Tom McCord (now at the Bear Fight Institute, WA) and colleagues discovered the signature of basalt on Vesta, an indicator that the object had melted at some time in the past. We now believe that Vesta had enough radioactive material inside when it coalesced that rock could melt and the lighter layers could float to the outside, a process we normally think of in planetary rather than asteroid terms. That makes Vesta interesting as a ‘protoplanet,’ a dense, layered body that never fully developed by merging with other objects of the same category.

Vesta is, in other words, a window into the remote past, one we can study by looking at the hundreds of meteorites that make up some of Vesta’s debris following ancient collisions with space rocks, and now by orbiting the distant object itself. Dawn principal investigator Christopher Russell (UCLA) describes Vesta’s significance:

    “This gritty little protoplanet has survived bombardment in the asteroid belt for over 4.5 billion years, making its surface possibly the oldest planetary surface in the solar system. Studying Vesta will enable us to write a much better history of the solar system’s turbulent youth.”

We’ll have a year at Vesta to study these matters, with Dawn arriving in July at a time when the south pole will be in full sunlight and the huge crater at the pole will be completely visible. Vesta’s evolution may be put on display if we get a good enough view of the layered materials inside the crater. In any case, Dawn will be able to give us high-resolution data on the asteroid’s surface composition, topography and texture as we probe its internal and external features. More on Vesta as protoplanet in this JPL news release.

» Read More...

The fascination of the so-called ‘Pioneer anomaly’ is that it offers the possibility of new physics, an apparently constant acceleration on the Pioneer 10 and 11 probes with a value of (8.74 ± 1.33) × 10−10 m/s2 being something that we can’t easily explain. Equally useful is the chance the Pioneer anomaly gives us to validate current physical models by figuring out how we might explain this acceleration through hitherto unsuspected processes, perhaps aboard the spacecraft itself. Either way you look at it, the Pioneer anomaly has deserved the attention it has received, and now a new paper emerges to take a crack at resolving the issue once and for all.

Frederico Francisco (Instituto Superior Técnico, Lisbon) and colleagues have revisited the question of whether heat that is emitted and reflected aboard the spacecraft could account for the anomalous acceleration. Francisco’s team had accounted for between 33% and 67% of the acceleration in a thermal model they developed in 2008. The new paper builds on this earlier work, with a methodology based on a distribution of point-like radiation sources that can model the thermal radiation emissions of the spacecraft. The authors then deploy a method called ‘Phong Shading’ that is commonly used to render the illumination of surfaces in 3D computer graphics. This allows them to study how heat effects can be reflected off the various parts of the spacecraft.

Image: An artist’s rendition of one of the Pioneer probes. Credit: NASA.

I referred to the acceleration as ‘apparently constant’ above, but the authors take pains to note that we haven’t fully characterized the acceleration. In fact, one analysis of the flight data shows that, given the data we have, both a constant acceleration and one with a linear decay of a period greater than fifty years are compatible with the data. This comes into play as the team tests for the constancy of the acceleration, as discussed in the paper:

    … a so-called “jerk term” is found to be consistent with the expected temporal variation of a recoil force due to heat generated on board… This is essential if the hypothesis of a thermal origin for the Pioneer anomaly is to be considered, as such [a] source would inevitably lead to a decay with at least the same rate as the power available onboard. Possible causes for an enhanced decay include e.g. degradation of thermocouples, stepwise shutdown of some systems and instruments, etc.

With this in mind, the authors go to work looking at thermal radiation and the force it can bring to bear on a surface, using Phong Shading to model the reflection of this radiation off the various other surfaces of the Pioneer probes. Radiation facing outwards, for example, radiates directly into space with an effect that cancels out. But radiation emitted toward the center of the spacecraft is reflected by the high-gain antenna and the main equipment compartment. The trick is to weigh these effects in terms of the acceleration. The method gives “a simple and straightforward way of modeling the various components of reflection…,” according to the paper, and one that accounts for the effect of thermal radiation on different parts of the spacecraft.

The result: The Phong shading method confirms earlier work suggesting that the Pioneer anomaly results from heat effects aboard the spacecraft. It also offers a method with which to study similar effects aboard other spacecraft. The authors explain:

    …the acceleration arising from thermal radiation effects has a similar order of magnitude to the constant anomalous acceleration reported [in a study of the anomaly published in 2002]. We believe that the chosen approach is most adequate for the study of this particular problem, taking into account all its specific characteristics. Moreover, this Phong shading method is well suited for future studies of radiation momentum transfer in other spacecraft.

And the paper concludes:

    With the results presented here it becomes increasingly apparent that, unless new data arises, the puzzle of the anomalous acceleration of the Pioneer probes can finally be put to rest.

This is a useful result, and one that will now be scrutinized by the wider community. If its conclusions are accepted, we will have made a step forward in identifying an effect that may need to be taken into account in future spacecraft operations. Just as important, we’ll have been able to rule out a line of investigation that seemed to open a door into new physics, meaning that the analysis of the Pioneer Anomaly, now more than a decade old, has born fruit. This is exactly what good science should do, and while we might hope for breakthroughs into new theories, anomalies like these are just as valid as ways of testing and verifying accepted physical laws.

» Read More...