March 16, 2009 - Biomedical News from the Largest Physics Meeting of the Year
College Park, MD (March 3, 2009) -- Many of the leading scientists working at the interface of physics and medicine will present their latest research at next month's March Meeting of American Physical Society (APS), which takes place from March 16-20, 2009 at the David L. Lawrence Convention Center in Pittsburgh.
For more than a century, some of the greatest advances in medicine have been born at the intersection of biology and physics. Perhaps many of the most interesting discoveries of tomorrow are being investigated at this crossroads today. Potential examples include: designing advanced imaging and therapeutic techniques for confronting cancer and other diseases deep within the body, inventing advanced materials that help alleviate the suffering of people with particular diseases, creating new materials with useful biomedical properties, and discovering ways of delivering lifesaving drugs to specific parts of the body. Highlights of a few of these discoveries are described below.
Reporters are invited to cover this meeting remotely or in person. Information on how to register as press is contained at the bottom of this email.
HIGHLIGHTS OF BIOMEDICAL NEWS
1) IMMUNE CELLS SHOULDER MICROSCOPIC BACKPACKS
The most obvious advantage of wearing a backpack over briefcases or most other types of book bags, according to Massachusetts Institute of Technology graduate student Al Swiston, is that they free up your hands and do not interfere with your ability to walk around. Now Swiston, with his advisor MIT Professor Michael Rubner and their colleagues, has designed a way to give tiny cells of the immune system the same advantage -- microscopic backpacks that enable these cells to carry loads of foreign materials without interfering with the cell’s ability to interact with their movement.
The packs are actually flexible polymer disks that attach to the membrane of cells. They can carry a wide variety of useful cargo. Swiston and his colleagues envision that the backpacks would enable cells to carry functional molecules that would enhance their action -- antivirals, new vaccines, cancer drugs, contrast agents that show up in MRI scans, fluorescent particles that glow under a microscope, and just about anything that will fit inside.
The idea is to give the immune system new tools for such applications as detecting and imaging cancer cells, delivering drugs to particular sites in the body, and perhaps even delivering particles that can help engineer new tissues. In preliminary tests, which Swiston will describe at the March Meeting, they loaded the backpacks with magnetic and fluorescent particles and traced their movements across a surface. (Talk Y20.3, http://meetings.aps.org/Meeting/MAR09/Event/100256).
2) NEW POLYMER MATERIAL HELPS ACCELERATE BONE GROWTH
As far as materials go, human bones can be both remarkable and frustrating. Their properties are an evolutionary miracle -- steel-like strength, light weight, and the ability to grow continually. But by the same token, these properties can be a medical curse. When treating certain types of severe fractures, for instance, orthopedic surgeons often need to apply grafts that closely mimic real bones. Finding materials that are strong, light, or have the ability to grow is one thing, but finding materials that are all three is a tall order. Titanium, for instance, is terrific for its ability to support heavy loads, but titanium bone grafts may not grow along with healing bones. Once in, these grafts may need to be removed at a later date.
Seeking to design a new type of bone graft, Yizhi Meng of Stony Brook University and her colleagues have been studying the very early stages of bone formation, when a proliferation of cells produce a "matrix" of collagen and other proteins that fits them together tightly. Last year, Meng teamed up with Elaine DiMasi of Brookhaven National Laboratory to probe the mechanical properties of live mouse bone cells as they are laying down a matrix. Over the course of several weeks, calcium and other minerals are deposited into this matrix, which hardens into bones.
What they found was that when cells first lay down their matrix, it needs to be in the correct form in order for mineral deposition to take place. The surface properties are key to this process. On glass, the matrix proteins do not spread out. However, on a specially charged polymer surface designed by a different group of scientists at SUNY Stony Brook and the City University of New York, the proteins unfurl and spread out nicely into a matrix. Meng and her colleagues have found that this special polymer can accelerate bone formation, and they are working on adapting this polymer for making advanced bone grafts. (Talk X39.5, http://meetings.aps.org/Meeting/MAR09/Event/95469).
3) IMAGING NEURONAL ACTIVITY DIRECTLY WITH MRI
The technique of functional Magnetic Resonance Imaging (fMRI) has changed the field of neuroscience because it allows scientists to image living brains in action, revealing which distinct regions of the brain control particular mental processes. Typically fMRI studies are done using the big, expensive high-field MRI instruments you might find in a large urban hospital (they are called "high-field" because of the large 1.5 or 3.0 Tesla superconducting electromagnets they employ). High-field MRI studies do not measure neuronal activity directly, however. Instead they measure the effect of the local blood flow on the MRI signal -- a good but inexact proxy of neuronal activity.
Scientists have tried for years to directly measure the signal from firing neurons, since doing so would allow more precise mapping of brain function. Using high-field MRI to do this seems impossible, however, partially because neuronal activity produces an extremely weak signal that gets completely masked by the overwhelmingly strong MRI signal change generated by the blood flow. Detecting the weaker signal would be like trying to hear a whisper above a roaring jet engine.
Karlene Maskaly and her colleagues at Los Alamos National Laboratory are taking a different approach towards directly measuring the signal from firing neurons. Using a technique called ultra-low field MRI, they employ a small, inexpensive magnet that is 10,000 times weaker than a typical hospital MRI. They hypothesize that this less powerful magnet will cause the roaring signal from the blood flow to be 10,000 times smaller, which will reveal the comparatively whispering signal of the neuronal activity. The use of a small magnet may also allow for the possibility of a resonant interaction between the neural currents and the MRI signals that would act to amplify the whisper as well. They have tested their technique in various settings, including the activation of nerve cells in a human arm placed in the apparatus. Although these results have been inconclusive thus far, they are looking to achieve more definitive results through detection of the neuronal currents in the brain of an epileptic rat. This work was funded by the National Institute of Biomedical Imaging and BioEngineering, and the National Eye Institute, both components of the NIH. (Talk Y40.5, http://meetings.aps.org/Meeting/MAR09/Event/100510).
4) MEASURING THE FLEXIBILITY OF HUMAN EYE LENSES AS WE AGE
The lens of the human eye serves a purpose much like the lens on the front of a digital camera-they both bring light coming from distant objects into focus. Unlike the hard glass lens on the front of your digital camera, the lens of a young human eye is soft and deformable. Attached to a sphincter muscle by tiny ligaments around its edge, human lenses dynamically adjust their focus on objects at different distances by changing its shape. As we age, the ability of our eye lenses to change shape decreases, which is one of the reasons why so many people over the age of 40 wear glasses for reading.
There is no clear scientific consensus as to why the lens' ability to change shape diminishes with age. One theory is that the muscles attached to it grow weaker. Another is that the material properties of the lens itself change, stiffening with age. Now Professor Sooryakumar and his colleagues at Ohio State University and the University of Houston have done light scattering studies on human and bovine eye lenses in order to measure their elasticity. By observing tiny changes in the frequency of light scattered off the lenses, they can calculate variations in lens elasticity. What they found, both in cow eyes and in a group of human lenses obtained from OSU's organ donor program, was consistency. While there was some variation in the elastic properties of the lenses with age, the stiffness of the lenses did not significantly change. This contradicts earlier data (obtained using a different technique) that suggests lenses stiffen dramatically as we age. More studies are needed, says graduate student Sheldon Bailey, but for now the question of how time affects our eye lenses is wide open. (Talk A39.14, http://meetings.aps.org/Meeting/MAR09/Event/93636).
5) UNRAVELING THE PROTEINS AT THE HEART OF PARKINSON'S DISEASE
Parkinson's Disease, which affects some 1.5 million people in the United States, is a progressive brain disorder for which there is currently no cure. One of the leading theories about what causes Parkinson's is that it arises due to the toxic accumulation of protein plaques within certain neurons in the brain. The plaques inhibit neurotransmitter uptake and release in neurons necessary to control movement, and the loss of this neuronal function leads to the characteristic movement disorders and other symptoms that are hallmarks of this disease.
Francis Rose and Miroslav Hodak of North Carolina State University are investigating the early events that may lead to the formation of these plaques -- beginning with the misfolding of a mysterious protein called alpha-synuclein, which is the key component of the toxic plaques. Based on computations they performed, they are proposing a mechanism that explains the early misfolding events that lead to plaque formation. Understanding this initial process is critical for drug development, they say, and their proposed mechanism may help in the design of drugs to stop, slow, or reverse Parkinson's. (Talk X39.9, http://meetings.aps.org/Meeting/MAR09/Event/100013).
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