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Tuesday, February 7, 2017

Why large dogs live fast—and die young.

For most mammals, size is a significant factor as Large ones, such as elephants and whales, live far longer than small ones like rodents. This rule is reversed in the dog kingdom as the tiny Chihuahuas, for example, can live up to 15 years which is 8 years longer than their much larger cousins, Great Danes. Now, a team of undergraduates may be closer to figuring out why this is so and the most likely reason is the more harmful oxygen free radicals in fast-growing, fuel-burning puppies. When an organism grows, its cells break down food to make the molecular fuel they need. But generating this energy can also generate an unwelcome visitor: renegade molecules called oxygen free radicals. These molecules are missing electrons, and as they try to poach them from other cells in the body, they can quickly damage cell membranes and eventually contribute to cancer and other diseases. Molecules known as antioxidants neutralize these free radicals. But ultimately, the more energy a body produces, the more free radicals it makes, and consequently, the more antioxidants it needs. Some scientists think that escaped free radicals contribute to aging, although this is hotly debated. To find out whether that might be true in canines, undergraduates Josh Winward and Alex Ionescu from Colgate University in Hamilton, New York, asked veterinarians for the ear clips, dewclaws, and cut-off tails of puppies and the ear clips from old dogs that had recently died. Altogether, they collected about 80 samples from large and small breeds. Working with Colgate animal physiologist Ana Jimenez, the students isolated cells from those tissues, grew the cells in a lab dish for a few weeks, and then analyzed them. continue