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Past Shows
February 17, 2007
 Download an MP3 of the entire program (22MB) (available Saturday, two hours after broadcast).
Bugs and the Bulge
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Obese mice - Courtesy, Baylor College of Medicine |
Obesity rates around the world have risen dramatically over the last 25 years. In fact, obesity is now considered a worldwide epidemic. Diseases like diabetes, heart disease and other illnesses that are a direct result of weight gain are costing the health care system millions of dollars.
The standard argument is that obesity is a disease of affluence -- too much food, and not enough exercise are behind the problem. But there are researchers who argue that the story is more complicated than that; that lifestyles haven't changed enough to explain the big picture.
One of these researchers is Dr. Richard Atkinson. Dr. Atkinson is a clinical professor of pathology at Virginia Commonwealth University. He's seen patients who are morbidly obese, yet eat very little. He's also seen other people who can consume huge numbers of calories without gaining significant amounts of weight. He thinks there are a number of factors we haven't really considered when it comes to understanding obesity. As the editor of the International Journal of Obesity, he recently reviewed a paper that listed birth weight, reduction in smoking, increased age of the mother at a baby's birth and air-conditioning as reasons why obesity levels are on the rise.
Dr. Jeffrey Gordon, from the Washington University School of Medicine in St. Louis, is also looking for factors that contribute to obesity. He's been studying microbes that live in the gut, and has found that the types of bacteria found in the stomach vary between obese and lean mice. Not only that, but by transferring these bacteria into other mice, he can influence whether they'll turn out skinny or fat.
In a similar vein, Dr. Nikhil Dhurandhar from Louisiana State University, is also looking at microbes. But he's studying viruses. He's found a virus that infects chickens, and makes them gain weight. He's tested humans and found that some obese people carry the same virus, suggesting it may be infecting us, too.
All these different factors may be making us fatter, but Dr. Dianne Finegood, Director of the Institute of Nutrition, Metabolism and Diabetes at the Canadian Institutes of Health Research, thinks this is only of limited value to the public. She argues that we also need to come up with solutions for solving the obesity epidemic, regardless of whether we understand all the mechanisms.
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Cloacal Cooling
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Inca Dove - Courtesy, Patricia Velte |
The need to get rid of excess body heat in hot weather is a problem
shared by most land animals. And we've all come up with slightly
different ways of doing it. Humans sweat though their skin. Dogs sweat
through their mouths. But while Inca doves can certainly do both
of these, they also seem to have another, much more unusual way of
perspiring: through their posterior. Birds, like reptiles and amphibians,
have a slightly different anatomy than other land animals in that they
have a single orifice for urine, waste and reproductive fluids. Other animals have a separate orifice for each of these functions.
And as Dr. Ty Hoffman, a biology instructor
at Phoenix College, has discovered, it appears that at least some
members of these families can use their cloaca as a back-up cooling
mechanism, as well.
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Plight of the Peregrines
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Peregrine falcon - Courtesy, Dr. Gordon Court |
For a few decades, DDT was the pesticide of choice in North America. But it nearly killed off several species of birds of prey, among them, the peregrine falcon. However, some swift action and dedicated conservation efforts have now brought this large bird back from the brink of extinction, and their recovery is one of the greatest success stories of conservation biology in North America. The health of a population is not just about the numbers, though. That’s why Joseph Brown, a former biology student at Queen's University, decided to look at the genetic health of the new peregrine population in Canada. Mr. Brown is now a PhD student at the University of Michigan, and he expected to find that the population bottleneck caused by the near-extirpation would have resulted in reduced genetic variability among Canadian peregrines. Reduced variability means reduced ability to withstand environmental and evolutionary pressure. Quite surprisingly, the genetic variability is at the same level or even higher than it was before. Mr. Brown attributes this to the fact that the US breeding programs used not just remaining local birds but also birds imported from Europe and South America. It would appear that some of these birds are making it across the border to Canada and mixing with the local population here, and adding to the genetic mix in a positive way.
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Moth Manoeuvres
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Tobacco Hornworm moth - Courtesy, Armin Hinterwirth, University of Washington, Dept. of Biology |
Moths don't get the respect they deserve when it comes to their flying ability. They've got a reputation for flying into screen doors and the occasional flame. But, in reality, they're capable of some pretty extraordinary aerobatics and precision flying. They're like miniature helicopters: they can hover, fly backwards and forwards, avoid getting eaten by bats and pull the kind of hairpin turns that make Top Gun pilots look like amateurs. And they do all this in the dark. Scientists have been trying to figure out how a creature with a brain that would fit under your baby fingernail manages to execute such extraordinary feats. Dr. Mark Willis, a professor of biology at Case Western Reserve University in Cleveland, has been studying the Tobacco Hornworm moth and accidentally figured out the secret to its flight control system. It turns out the moth uses it's antennae (which it also uses to smell with) like an airplane's gyroscope.
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Question of the Week: Freezing Liquid
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This week, we have a surprisingly popular question. No fewer than 3 different people wrote in with the same puzzle.
Bob Barclay from Beresford, New Brunswick, Dale Basler from Appleton, Wisconson, and Paul Terech from Courtice, Ontario all wrote in, wanting to know the same thing:
Why is it that you can put pop or beer in the freezer and when you take it out, it’s still liquid, but as soon as you open it, it begins to freeze?
Dr. Doulas Goff is a professor in the Department of Food Science at the University of Guelph and he’s going help us answer this really cool question.
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