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Scientists Create 'Endurance' Mouse

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    NHNE News List Current Members: 668 Subscribe/unsubscribe/archive info at the bottom of this message. ... SCIENTISTS CREATE ENDURANCE MOUSE By Kate Tobin CNN
    Message 1 of 1 , Aug 15, 2002
      NHNE News List
      Current Members: 668
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      By Kate Tobin
      CNN Sci-Tech
      August 14, 2002

      BOSTON, Massachusetts (CNN) -- Mighty Mouse lives, and the "new age" version
      is downright buff.

      Researchers say they have created a transgenic mouse with muscles like a
      marathoner, capable of enduring rigorous exercise for extended periods of

      While so far the research has only been conducted on mice, scientists say
      they expect the techniques they've developed to treat the mouse muscle will
      also work on humans. Doctors say the discovery may one day lead to new
      treatments for people who are bedridden or have degenerative muscle disease,
      and could prove to be a wonder drug for endurance athletes like long
      distance runners or cross country skiers.

      Bruce Spiegelman and colleagues at the Dana-Farber Cancer Institute
      identified a biochemical called PGC-1 that operates as a molecular switch,
      converting so-called "fast-twitch" muscle, which is strong but tires
      quickly, into high-endurance "slow-twitch" muscle.

      "PGC-1 appears to be the switch, or a major component of it, that enables
      your body's muscles to adjust to the demands being put on them," said
      Spiegelman. "Understanding how this system works could make it possible to
      develop a drug to manipulate this system."

      Muscle is made up of a combination of different types of fibers. Endurance
      athletes train long and hard to build up slow-twitch muscle fibers, called
      Type I fibers, which are long and lean and can keep pumping for long periods
      of aerobic exercise. Sprinters or weightlifters, on the other hand, have
      muscle rich in fast-twitch, Type II fibers. These muscles are bulkier and
      stronger but tire quickly.

      Further studies

      To create the endurance mouse, Spiegelman's group bioengineered PGC-1 into
      mouse muscle tissue. They expected that it would promote the development of
      cellular power plants called mitochondria, which fuel the growth and
      development of slow-twitch muscle fiber. But they were surprised to find
      that PGC-1 appeared to be converting Type II fast-twitch fibers into Type I
      slow-twitch fibers.

      The muscle itself actually changed color, taking on a reddish hue
      characteristic of oxygen-rich tissue. Further, in an endurance test at a
      Texas laboratory, the bioengineered muscle turned out to contract
      efficiently two and a half times longer than regular muscle.

      Spiegelman cautions that there is still five to 10 years of work to be done
      before PGC-1 based treatments will be available.

      The research is published in this week's edition of the journal Nature.


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