Findings

Science  20 May 2011:
Vol. 332, Issue 6032, pp. 901
  1. Is That Fish Worth Chasing?

    Harbor seals in the murky North Sea rely on their whiskers to follow the wake a fish leaves behind. A new study reveals that whiskers can also gather detailed information about what the seal is hunting.

    Biologist Wolf Hanke of the University of Rostock in Germany and colleagues worked with a harbor seal named Henry, a veteran research participant. First, they created wakes in a box of still water at the bottom of a pool using motorized paddles of different sizes; Henry waited outside the box wearing noise-blocking headphones and a blindfold. Once the paddle stopped, Henry dunked his front half inside and let the eddies swirl around his whiskers. He then pressed one of two buttons with his nose, indicating whether the wake had been made by one of three paddle sizes he'd been trained to recognize or by an unfamiliar one.

    CREDIT: MARINE SCIENCE CENTER, ROSTOCK

    Henry chose correctly more than 90% of the time, as long as the familiar and unfamiliar paddles differed in width by at least 4 cm, the team reported last week in The Journal of Experimental Biology. Laser-aided analysis of the eddies revealed that he could “read” information such as the width of the wake and its velocity—clues to the size of a passing fish, Hanke says, and whether it's worth chasing.

    http://scim.ag/chase-fish

  2. Mice Reject Reprogrammed Cells

    Scientists have high hopes that stem cells called induced pluripotent stem (iPS) cells can be turned into replacement tissues for patients with injury or disease. Derived from a patient's own cells, scientists had assumed they wouldn't be rejected—a common problem with organ transplants. But a new study suggests otherwise.

    Dark-brown T cells, a sign of immune rejection, invade tissue formed by iPS cells.

    CREDIT: YANG XU/UC SAN DIEGO

    Immunologist Yang Xu of the University of California, San Diego, and his colleagues implanted iPS cells, which are reprogrammed from adult cells, into mice that were genetically identical to the iPS cell donor. To the scientists' surprise, the cells were attacked by the recipients' immune systems and were rejected, the team reported online last week in Nature. The culprit seems to be incomplete reprogramming that leaves some genes in iPS cells misexpressed, Xu says.

    The results add to a series of findings that iPS cells differ in subtle but potentially important ways from more controversial embryonic stem cells. Meanwhile, dozens of labs are working on ways to improve the reprogramming process so that the stray gene expression is eliminated.

    http://scim.ag/iPSC-problems

  3. HIV Treatment Prevents Heterosexual Transmission

    HIV-infected people who start antiretroviral (ARV) treatment at earlier stages of the disease lowered their risk of transmitting the virus to their sexual partners by 96%, according to a multicountry study that ended abruptly last week.

    The $73 million study by the U.S. National Institute of Allergy and Infectious Diseases recruited 1763 couples (97% heterosexual) in which only one partner was infected with the AIDS virus at the start. Half the participants received ARVs immediately, while the other half waited until their infections caused serious immune damage.

    An analysis 6 years into the study, which was planned to last 10 years, found that 39 people had become infected, 28 from their regular partners. Of those 28, all but one had a partner in the group that waited to start treatment.

    The dramatic result mirrors findings from less-rigorous earlier studies. Still, says Michel Sidibé, who heads the Joint United Nations Programme on HIV/AIDS, “it's a game-changer in the AIDS response.” Some HIV/AIDS advocates caution that the good news will have an impact only if the world massively scales up distribution of ARVs to people who can't afford them, which there are no plans to do.

    http://scim.ag/NIAID-study

  4. Lizard Lairs Are All in the Family

    The great desert skink is the homebody of the lizard world. The Australian reptiles (Liopholis kintorei) dig elaborate burrows, which, scientists have now discovered, shelter closely related family members and can be occupied for up to seven consecutive years.

    By trapping lizards and snipping off a tiny portion of their tails for DNA analysis, Steve McAlpin and his colleagues at Macquarie University in Sydney, Australia, found that adult desert skinks live in the same burrow with multiple generations of their children. Both parents and siblings pitch in to build and maintain their home, the team reported online 11 May in the journal PLoS ONE. These complex tunnel networks, which measure up to 13 meters across, feature multiple entrances and designated outside latrine areas where the lizards go to defecate.

    Desert skinks build elaborate nests that house multiple generations.

    CREDIT: ADAM STOW/MACQUARIE UNIVERSITY

    Although many species of birds and mammals exhibit such cooperative behavior, this is the first report of lizards constructing a family house. Desert skinks are fairly faithful lovers, which could help explain why families stick together. The finding may bolster the hypothesis that cooperation evolved in groups of genetically related individuals.

  5. Swimming on a Full Stomach

    If you've ever been too full to move after a large meal, envy the leech, which can squirm away even when bloated up to 10 times its normal size on a bloody feast. Now it appears that the signaling molecule serotonin is behind the talent.

    CREDIT: SHANNON P. GERRY AND DAVID J. ELLERBY

    When leeches swell up, they stretch their muscles to their limit. This should prevent the muscles from expanding and contracting. Yet leeches wriggle around just fine, says Shannon Gerry, a biomechanist at Wellesley College in Massachusetts.

    To find out why, Gerry and fellow Wellesley biomechanist David Ellerby chopped leeches into segments and soaked the chunks in a solution containing serotonin, which stimulates feeding in leeches, or in saline. After stretching the segments to lengths that would simulate swimming after feeding, they used electricity to make them contract. Segments exposed to serotonin exerted more force than did the control segments, no matter how strained they were.

    Serotonin, it seems, allows the taxed muscles to push past the strain, the researchers reported online in Biology Letters last week. They suggest that serotonin might relax molecules that crosslink muscle fibers so that the muscles can move more easily. http://scim.ag/leech-swim

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