Medical Related Highlights Of The 157th ASA Meeting, May 18-22, Portland, Ore.

Main Category: Neurology / Neuroscience
Also Included In: Conferences;  Vascular;  Genetics
Article Date: 27 Apr 2009 - 1:00 PDT

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WIMPS HEAR DANGEROUS NOISES DIFFERENTLY

Scrawnier people are more likely to perceive an approaching sound as closer than it actually is. This connection between physical fitness and the brain's auditory system may have evolved to help the weak get out of the way of approaching danger.

That's the latest finding of evolutionary psychologist John Neuhoff and colleagues at The College of Wooster in Ohio, who study "looming" sounds. Participants in their study listened to a tone moving toward them and pressed a button when they thought the sound had arrived directly in front of them. Nearly everyone pushed the button too early, which Neuhoff interprets as an adaptation that helps human beings to anticipate and avoid danger.

The team also tested the fitness levels of the listeners and found that those better equipped to handle danger allowed the sound get closer. Individuals with greater upper body strength and/or stronger cardiovascular systems waited longer to push the button, while subjects in poorer physical shape gave themselves a greater "margin of safety."

The research expands upon previous work showing that women respond to looming sounds sooner than their typically larger, stronger male counterparts -- though both groups perceive receding sounds equally. Rhesus monkeys also spend less time looking at receding sounds than approaching sounds. "These reactions are influenced by evolutionary forces; it's a good thing to respond a little bit early and, evolutionarily, it doesn't cost much," says Neuhoff.

The talk "Strength and cardiovascular fitness predict time-to-arrival perception of looming sounds" (4aPP7) by John Nuehoff is at 11:00 a.m. on Thursday, May 21. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa840.html

SUPPLE WAVES IN CHEESE AND SKIN

When acoustic waves propagate through a given material, the ocean for instance, the sound waves respond to the properties of the fluid. Scientists can use these responses to probe the characteristics of the medium -- the ocean or the atmosphere, for instance -- and one particularly powerful way of doing this employs a technique called "time reversal." In time reversal, signals are played backwards to cancel out interfering noise. The technique is used in astronomy to remove atmospheric blurring and in medical imaging to focus ultrasonic beams. It is also being developed for underwater communication in the ocean.

Now a group of scientists in Grenoble, France and Montevideo, Uruguay have developed a method based on time reversal that can reveal the characteristics of soft solids. In a pair of presentations, the team will report how they measure the elastic properties of soft solids by using surface or bulk acoustic waves. This allows them to characterize the tenderness of beef and monitor the ripening process of soft cheese.

Their approach is a promising low cost technique for future applications in food production and other industries. In medicine, for instance, measuring shear elasticity is a hot topic in neuromusclular disease, and it may be relevant to diseases in the brain or for monitoring changes in moving organs, such as the heart. Their method can also allow determination of the human skin elasticity.

The talk "Tissue shear elasticity assessment using time reversal" (1pBB9) by Thomas Gallot et al is at 3:35 p.m. on Monday, May 18 in room Pavilion East. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa134.html

The talk "Time-reversal Rayleigh wave for soft solid characterization" (1pBB10) by Javier Brum et al is at 3:50 p.m. on Monday, May 18 in room Pavilion East. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa135.html

GENE-LADEN BUBBLES GROW NEW BLOOD VESSELS

Progress in human gene therapy -- the insertion of therapeutic DNA into tissues and cells in the human body -- has been slower than expected since the first clinical trials in 1990. One of the biggest challenges for this technology is finding ways to safely and effectively deliver genes only to the specific parts of the body that they are meant to treat. Cardiologist Jonathan Lindner of Oregon Health and Science University will discuss his latest experiments in gene therapy, which use microscopic bubbles chemically modified to stick to the cells that line blood vessels.

This technique, ultrasound-mediated gene delivery (UMGD), exploits the properties of contrast agents, microparticles that are normally injected into the body to improve the quality of ultrasound images. In UMGD, the tiny particles are microbubbles composed of pockets of gas encapsulated by thin membranes that are coated with DNA before injection. A targeted pulse of ultrasound energy "rings" the bubbles like a bell, popping them in a specific location and releasing the DNA into the surrounding tissue.

To improve the specificity of this targeting, Lindner grafts long arm-like molecules to the outside of the bubbles. These arms, which do not interfere with the DNA attached to surface, are designed to recognize and bind to molecules on the outside of specific cells in the body, allowing the bubbles to attach to a tissue before being popped. In theory, this should improve both the specificity and efficiency of the gene therapy.

Lindner created an arm designed to attach to endothelial cells lining blood vessels. He will present data evaluating the behavior of these "targeted" bubbles in living tissue. The ability to stick these gene-laden microbubbles to the lining of blood vessels increased the amount of gene transfection. This strategy may be particularly important for delivering therapeutic DNA to the walls of blood vessels. For example, Dr. Lindner and collaborators have successfully stimulated the growth of new blood vessels using UMGD with microbubbles carrying a gene for vascular endothelial growth factor. This therapeutic use could be important for treating ischemia in patients who have had a heart attack, peripheral artery disease, or stroke.

The team is also investigating using the bubbles to transport small doses of drugs. "If you're trying to deliver a nasty drug to part of the body, this may be a way to improve safety," says Lindner.

The talk "Targeted microbubble technology and ultrasound-mediated gene delivery" (4aBB2) by Jonathan Lindner is at 8:20 a.m. on Thursday, May 21, 2009. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa791.html

EXPLODING BUBBLES TRIM THE PROSTATE

In the traditional treatment for prostate growths, a rigid instrument is inserted through the penis and used to scrape away cells lining the walnut-sized gland. Urologist William Roberts and a team at the University of Michigan, Ann Arbor, are developing a less invasive way to remove tissue using focused pulses of ultrasound. Their technique, histotripsy, has now been used to safely trim the interiors of aging prostates in the body.

Unlike other therapeutic ultrasound technologies in development, which create heat to boil pathogenic tissue, histotripsy mechanically breaks apart tissue with shorter, strong pulses of ultrasound. These pulses create tiny bubbles out of dissolved gas in prostate tissue. As the bubbles violently collapse, they release tiny shock waves, a phenomena called acoustic cavitation. Over tens of thousands of pulses, the combined force of these cavitations liquefies nearby tissue into slurry that is eliminated through the urine. This tissue excavation can be monitored and targeted in real time with acoustic imaging.

"Historically, no one believed that cavitation could be controlled like this. We're the only group doing this kind of work," says Roberts. His team used the technique to dissolve marble-sized chunks of cells in the walls of prostates. Side effects common in traditional prostrate treatments -- bleeding and inflammation -- were minimal after histotripsy treatment, as were signs of discomfort. Roberts hopes to develop histotripsy into a clinical treatment for early-stage cancer and enlarged prostate (BPH).

The talk "Histotripsy: Urologic applications" (3pBB3) by William Roberts is at 1:15 p.m. on Wednesday, May 20, 2009. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa718.html

Source:
Jason Bardi
American Institute of Physics