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Scholarship & Creativity

Overfishing threatens inland waters
Overfishing of inland waters is a neglected crisis, say members of a team of freshwater ecologists and fishery scientists led by a U-M professor. Although overfishing widely is recognized, freshwater species rarely are mentioned because most of the focus is on marine species, they say.

“There are many parallels,” says David Allan, professor of conservation biology and ecosystem management in the School of Natural Resources and Environment. “Both marine and freshwater harvests have increased dramatically since the middle of the 20th century and now show signs of reaching their upper limit. Fishers first depleted larger, more valued or easily captured species and then shifted their efforts to remaining species, often lower in the food web.”

An article, “Overfishing in Inland Waters,” appears in the current issue of BioScience, produced by the American Institute of Biological Sciences.

The article notes that because fishers are able to deplete a succession of species, yields appear constant while biodiversity declines and the overall fishery is pushed to its limits.
As a result, the precarious state of the fishery is not immediately apparent. Heavily exploited fisheries of the Mekong River are a good example, Allan says.

The Great Lakes provide an early case study in sequential overfishing of a series of species. Cisco (Coregonus artedi) experienced a collapse in the mid-1920s, and then lake whitefish (Coregonus clupeaformis) were exploited severely throughout the 1930s. Typical of overfishing of more than one species, overall catch increased even while regional populations of both species were depleted, the report says.

But there are important differences between freshwater and marine species, the study says. Species-level records are rare for the capture fisheries of fresh waters, so it is difficult to document declines in individual species. Catches often are dispersed and unrecorded—especially when fishing is illegal—for local markets or for sustenance. And overfishing is not as dominant a threat as in the oceans because dams, pollution and habitat degradation pose additional challenges to the fisheries of inland waters and to the ecosystems that sustain them.

Old test offers new hope for back pain
A test that has been around since World War II is providing the baby boomer generation with a more definitive diagnosis for the back aches and pains that commonly come with age.

Results from a U-M Health System (UMHS) study show that the electromyogram (EMG) test can diagnosis spinal stenosis, reducing misdiagnosis of low back pain and other common neuromuscular conditions that have similar symptoms to avoid unnecessary back surgery.

The findings were published in the December issue of Spine.

An estimated 400,000 Americans have spinal stenosis, a narrowing of spaces in the spine that results in pressure on the spinal cord and nerves that can lead to debilitating back pain or even paralysis if left untreated.

The problem, however, is that the symptoms of spinal stenosis are shared by many other diseases, including peripheral nerve disease and even arthritis in the joints, which can lead to costly misdiagnoses and unnecessary back surgery, says study lead author Dr. Andrew Haig, associate professor in the Department of Physical Medicine and Rehabilitation at the Medical School.

“EMG plays an important role in the diagnosis of back pain because, unlike MRI (magnetic resonance imaging), EMG is more than a picture of a nerve—it can test nerve function and show if there is actual nerve damage,” Haig says. “The EMG is really going to help doctors to avoid unnecessary procedures because it proves that there is nerve damage in the people who clearly have it and can accurately diagnosis spinal stenosis.”

The study found that EMG identified nerve or muscle disease in five participants whom medical experts believed to have spinal stenosis. In all, the results from the EMG show a substantial difference between the spinal stenosis patients and the two control groups, allowing experts to clearly distinguish spinal stenosis from low back pain.

Additionally, EMG successfully detected common neuromuscular disease that can mimic spinal stenosis.

Along with Haig, UMHS co-authors were Dr. Henry Tong, assistant professor in the Medical School; Karen Yamakawa, a research associate in the Spine Program; Dr. Douglas Quint, professor of neuroradiology and MRI; Dr. Julian Hoff, professor and chair of neurosurgery; Dr. Anthony Chiodo, associate professor of physical medicine and rehabilitation; Jennifer Miner, a research area specialist associate in Physical Medicine and Rehabilitation; Dr. Vaishali Choksi, clinical lecturer in radiology; and Michael E. Geisser, associate professor of physical medicine and rehabilitation.

Who understands math well enough to teach it to 3rd graders?
More than 15 years of research shows most Americans and most teachers lack sound mathematical skills, leaving U.S. 12th-grade math students trailing their peers in 21 other nations.

Many teachers lack what a group of U-M researchers calls mathematical knowledge for teaching. Knowing mathematics for teaching is more than the ability to solve a problem or to tell a pupil to move the decimal point. Effective mathematics teaching also requires knowing why a procedure works, being able to interpret what led to a student error, or choosing a model that accurately shows an idea, the researchers say.

“If we argue that there is professional knowledge for teaching mathematics, then we have to show that improving this knowledge also enhances student achievement,” says Deborah Lowenberg Ball, dean of the School of Education, who authored the article with colleagues Heather Hill and Hyman Bass.

The better teachers are at understanding mathematics in ways that give them flexibility and insight, the more their students learn, the researchers argue in the fall issue of the journal American Educator, drawing on work developed at U-M over eight years.

Ball, who helped organize the Center for Proficiency in Teaching Mathematics, notes that it’s not the same set of math skills required to be a successful accountant, carpenter or engineer.

The teacher not only must know how to solve problems but how to translate that knowledge into the language of a small child, and how to understand the logic of students who use unconventional self-invented methods that might work to solve some problems but not others, she says.

Ball and her colleagues have shown that teachers’ ability to help students understand and succeed with math depends on their ability to hear and understand what students are thinking, and to explain or show ideas in ways that are accessible to the students. This, in turn, depends on the teachers’ own understanding.

“Our finding indicates that, while teachers’ mathematical knowledge would not by itself overcome the existing achievement gap, it could prevent that that gap from growing,” Ball says.

Glacial pace of erosion was not so slow
Glaciers, rivers and shifting tectonic plates have shaped mountains over millions of years, but Earth scientists have struggled to understand the relative roles of these forces and the rates at which they work.

Using a new technique, researchers at U-M, California Institute of Technology and Occidental College now have documented how fast glaciers eroded the spectacular mountain topography of the Coast Mountains of British Columbia.

Their work was described in the Dec. 9 issue of the journal Science.

U-M Assistant Professor of Geological Sciences Todd Ehlers has been working in a remote region of the Coast Mountains for the past three years, studying rates of glacial erosion and topographic change. Using a new geochemical tool developed by Caltech researchers, he and his collaborators were able to quantify the rates and magnitude of glacial erosion across a major valley. They found that glaciers radically altered the landscape around 1.8 million years ago, about the time that Earth began to experience a number of ice ages.

The erosion rates documented in the study suggest glaciers eroded the mountains six times faster than rivers and landslides had before glaciation began. The researchers also found that glaciers scraped at least two kilometers (about 1.2 miles) of rock from the mountains.

“These results are exciting,” Ehlers says, “because they clearly document that glaciers are the most efficient method for sculpting the topography of the range. They also demonstrate the utility of a new geochemical tool that can be applied to study erosion in other mountain ranges.”

The study relied on a technique called helium-helium thermochronometry, developed by Caltech’s Ken Farley and his former student David Shuster, now at Berkeley (Calif.) Geochronology Center.

The technique rests on three facts: 1) rocks on the surface often have come from beneath the surface; 2) the ground gets steadily warmer as depth increases; and 3) helium leaks out of a warm rock faster than a cold one. By determining how fast the helium leaked out of a rock, it’s also possible to determine how fast the rock cooled and, ultimately, how deeply it was buried, as well as when and how fast it got uncovered.

The team showed that the cooling of the rock happened very quickly and that the entire valley was carved out in about 300,000 years.

Research: Modeling cell’s messengers

Humans have millions of cells to conduct the business of the body. By exchanging chemical signals, cells talk to one another to perform functions like regulating blood pressure, converting food into nutrition and sensing pain or danger.

Along this superhighway of communication the family of G proteins is one of the most consequential messengers. G proteins have been implicated in the signaling for dozens of metabolic functions including blood pressure, blood clotting, sight and smell. Despite their centrality to the basic systems of life, many aspects of the G proteins’ structure and function remain a mystery.

John Tesmer, Life Sciences Institute research associate professor and associate professor in the Department of Pharmacology, has captured a picture of these messengers in their active state—when they are conveying signals at the cell membrane.

Tesmer’s study, which provides high-resolution models of one G protein involved in blood clot formation, heart disease and blood pressure, is the first molecular view of how these important proteins can be arranged at the cell membrane. Researchers now can target these protein complexes to try to develop new tools and therapeutic drugs for treating conditions like cardiovascular disease.

Using X-Ray crystallography, Tesmer determined that the atomic structure of a G protein interacts with an important signaling switch called GRK2. Defects in either the protein or the switch could lead to severe heart development defects. The atomic structure of these multiple molecular complexes are extremely difficult to obtain and this work represents an important step forward for capturing nature in action.

The paper, “Snapshot of Activated G proteins at the Membrane: Structure of the G a q -GRK2-G bg Complex” by Tesmer, appears in the journal Science Dec. 9.

Gene variation affects tamoxifen’s benefit for cancer

One of the most commonly prescribed drugs for breast cancer, tamoxifen, may not be as effective for women who inherit a common genetic variation, according to researchers at U-M and the Mayo Clinic. The genetic variation affects the level of a crucial enzyme that activates tamoxifen to fight breast cancer.

The study, co-led by researcher James Rae at the Comprehensive Cancer Center (CCC) and Dr. Matthew Goetz, an oncologist at the Mayo Clinic, tested the most common genetic variant responsible for lowering the CYP2D6 enzyme, and found that women with this genetic variant were almost twice as likely to see their breast cancer return. Up to 10 percent of women inherit this genetic trait.

Their findings were published in the Dec. 20 issue of the Journal o Clinical Oncology.

“Our group has shown that CYP2D6 is responsible for activating tamoxifen to a metabolite called endoxifen that is nearly 100 times more potent as an anti-estrogen than tamoxifen itself,” says Rae, research assistant professor of internal medicine at the Medical School.

“Our study suggests that women who inherit a genetic variant in the CYP2D6 gene appear to be at higher risk of relapse when treated with five years of tamoxifen.”

CCC researchers were among the group to discover CYP2D6 metabolizes tamoxifen, and they are leading ongoing work looking at how genetic differences affect women’s response to tamoxifen. Their research also has found the antidepressant drug Paxil can prevent tamoxifen from being activated, while the antidepressant drug Effexor does not. These drugs, selective serotonin reuptake inhibitors or SSRI’s, often are used to treat hot flashes, a common side effect of tamoxifen.

Rae and Dr. Daniel Hayes, CCC director of breast oncology, are part of the Pharmacogenetics Research Network, a multidisciplinary research group conducting a prospective clinical trial to confirm whether genetic testing can be used to identify patients likely to respond to endocrine therapy, including tamoxifen.

Super-fast quantum search achieved with atoms
U-M researchers have been able to use a small quantum computer consisting of two atoms to do a super-fast database search. This same system could someday be scaled to a much larger quantum computer that could outperform any conventional computer for certain applications

The super-fast search is called Grover’s Quantum Search Algorithm, and it can be used to search unsorted databases for specific information. If a person wanted to find a name belonging to a phone number in the phonebook, Grover’s algorithm could be used to search for the corresponding name much faster than using a normal computer. For example, a phone book with 1 million names would only take 1,000 “looks” to find the right match—the square root of 1 million—instead of an exhaustive search over all 1 million entries in the phone book.

The search was implemented using two atoms, each of which stores a single bit of information, for a total of four possible states. It’s a system that increases exponentially, so by adding one atom the memory doubles, says Christopher Monroe, professor of physics and co-author of a paper on the topic, “Implementation of Grover’s Quantum Search Algorithm in a Scalable System,” which appeared in the November issue of Physics Review.

“You don’t have to add too many atoms before you have a huge system,” he says. The research was led by graduate student Kathy-Anne Brickman in Monroe’s research group in the Department of Physics and the FOCUS Ultrafast Optics Center.

Using the hypothetical phonebook analogy, researchers used four numbers and tried to find the corresponding name. After looking only once, the algorithm was successful in finding the correct answer 60 percent of the time, better than the maximum possible success rate of 50 percent using a normal computer.

Sweet tooth may really be in brain’s ‘pleasure hotspot’
As many people try to recover from holiday overeating, U-M researchers offer insight into why those now-forbidden candies and cookies look so tempting. Neuroscientists have discovered a pleasure spot in the brains of rats, helping them understand where and how pleasure is generated in humans.

Psychology researchers Susana Peciña and Kent Berridge detail their study in the latest issue of the Journal of Neuroscience, explaining a pleasure spot in the brains of rats that makes sweet tastes more highly ‘liked’ using natural heroin-like chemicals in the nucleus accumbens (lower front of the brain).

“It’s basically a tiny brain pleasure cube that chemically doubles rats’ liking for sweets, and makes them eat six times more,” Berridge says. “It’s tucked into a larger appetite cube that increases eating many times above normal, but doesn’t make the sweetness any more liked.”

Sweetness by itself is merely a sensation, they note, and its pleasure arises within the brain where neural systems actively paint pleasure onto the sensation to generate a “liking” reaction—as a sort of “pleasure gloss.”

“These results also show how brain circuits that make you like a tasty food are different from the circuits that make you want to eat more of it,” Berridge says.

The study revealed the brain nucleus pleasure spot as an island of liking in a sea of wanting for the same reward, both of which also may be involved in causing human eating disorders and drug addictions.

The researchers note that sweet tastes elicit positive liking expressions such as lip licking. In contrast, bitter tastes instead bring out disliking reactions such as gapes. The study found the pleasure hotspot in the nucleus accumbens caused a sweet taste encountered minutes later to elicit even more than the normal number of positive facial liking reactions.

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