Science  18 Mar 2011:
Vol. 331, Issue 6023, pp. 1372

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  1. Getting to the Guts of Malnutrition


    VANCOUVER, CANADA—A roomful of mice in St. Louis, Missouri, may offer a surprising explanation for why some starving children are susceptible to malnutrition while others fare better: variations in gut bacteria.

    Microbiologist Michelle Smith of Washington University in St. Louis fed germ-free mice stool samples from a set of twins in Malawi, one of whom, despite eating the same food as the other twin, suffers from a form of malnutrition called kwashiorkor in which a child's belly and face become bloated. Once the children's gut bacteria had taken hold in the rodents' intestines, Smith and her colleagues manipulated their diets, checking for changes in the gut bacteria and weighing the rodents every few days.

    Boosting and then cutting back their diet caused mice with gut bacteria from the child with kwashiorkor to lose and then gain more weight than mice with bacteria from the healthier twin, Smith reported at the International Human Microbiome Congress here. The composition of the gut flora, and the makeup and abundance of bacterial enzymes, also fluctuated far more in the mice with bacteria from the child with kwashiorkor.

  2. Microbes Give Mice Intestinal Fortitude

    VANCOUVER, CANADA—Infect some strains of lab mice with the pathogen Citrobacter rodentium and they die, yet other strains survive. You might think the difference is due to genetics, but it's not: The survivors can thank their gut bacteria.

    Microbiologist B. Brett Finlay of the University of British Columbia, Vancouver, and colleagues used a high dose of antibiotics to kill all the native gut bacteria in a susceptible strain of mice and then fed those mice fecal material from a resistant strain. Microbes in the fecal material took up residence in a susceptible mouse's gut for about a month. When infected with Citrobacter, the once vulnerable rodents lived to tell the tale, Finlay reported at the International Human Microbiome Congress here last week.

    Finlay and colleagues then turned the tables. They gave resistant mice low doses of an antibiotic that altered the relative abundance of various gut microbes but didn't kill them altogether. Citrobacter caused severe diarrhea in these rodents. The researchers found that the shift in the microbial makeup reduced by half the thickness of the mucous layer that typically lines the gut. “By thinning this mucous [layer], we increased the susceptibility to infection,” Finlay said at the meeting.

  3. High-Tech Hat for Brain-Scanning Rats

    The RatCAP imager (bottom) produced this PET scan (top) from a moving rat.


    Rats don't like having their brains scanned any more than humans do, so studying their brains with positron emission tomography (PET) usually requires that they be asleep. Now researchers at Brookhaven National Laboratory in New York state have developed a device called a Rat Conscious Animal PET (Rat-CAP) imager, which allows a rat to wear a scanner even while it moves around. The imager, described online in Nature Methods this week, will allow behavioral neuroscientists to study metabolic activity in the brain without using anesthesia, which alters brain chemistry and could misdirect experiments.

    The RatCAP imager, equipped with miniature solid-state photosensor arrays, sits on a rat's head and is attached to a readout system that encircles the animal's head like a very high-tech flea collar. A flexible arm relieves the weight of the scanner and allows the rats to run about their cage, move their heads up and down, and turn 360°.

    When the researchers injected rats with a mildly radioactive tracer to measure dopamine levels in the brain—first in a conventional PET scanner under anesthesia, then when wearing a RatCAP—they found that the patterns of dopamine activity differed, suggesting that anesthesia could be having more of an effect on brain metabolism than previously thought. The researchers are in the process of commercializing the technology so that others can use it to study the neuro biology of disorders such as depression, anxiety, and seizures.

  4. New Doping Test Means Cyclists Can't Pull a Fast One


    A new technique for detecting blood doping in athletes has received a vote of confidence in the sports world. The Court of Arbitration for Sport—considered the world's authority in sports disputes—last week upheld the decision by the International Cycling Union (UCI) to bar Italian cyclists Franco Pellizotti (pictured) and Pietro Caucchioli from competing for 2 years. The two cyclists tested positive for doping using UCI's new Athlete Biological Passport (ABP), approved by the World Anti-Doping Agency in 2009. Developed by researchers at the Swiss Laboratory for Doping Analyses in Lausanne, ABP ties an athlete's sex, age, ethnicity, and exposure to altitude to several blood measurements, such as levels of oxygen-binding hemoglobin, which athletes sometimes increase by illegal blood transfusions or hormone injections. Using previous measurements to establish a personalized baseline, the test flags athletes who have abnormal readings as suspected doping cases.