Life Lines

Experimental Biology – Tuesday

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Today’s symposia included a session on “Integrative Cardiovascular and Respiratory Physiology of Non-model Organisms” as well as the August Krogh Distinguished Lecture.

This year’s Krogh lecture was given by Dr. Stan Lindstedt from Northern Arizona University. Dr. Lindstedt is arguably best known for publishing work showing that the metabolic rate of an animal is negatively correlated with body mass. In other words, smaller animals have a higher metabolic rate than larger animals. Knowing that relationship could have saved Tusko the elephant from a whopping dose of LSD (1962, prior to the requirement for all studies involving animals to be approved by an institutional animal care and use committee). Dr. Lindstedt related the history of how past researchers at The University of Oklahoma and LJ West from the CIA had known what dose of LSD would cause rage in a cat and just increased the dose to match the body mass of the elephant without taking into consideration that the elephant’s metabolism is much slower than a cat’s. Regardless of the questionable ethics of giving an elephant LSD, the dose was apparently over 5 times the amount that would have been equivalent to what was administered to the cat. As you can see from the headline below, the outcome was not good:

Had the researchers working with Tusko known what Dr. Lindstedt later discovered about scaling, Tusko may have lived through this ridiculous historical experiment. Dr. Lindstedt also presented data that body size is also negatively related to shivering frequency and the frequency of taking strides. Therefore, a mouse has a faster stride than a cow. Could you imagine seeing a cow scurry?

Dr. Lindstedt is also known for studying the mitochondria of species with muscles that are capable of produce really fast contractions: hummingbirds  and rattlesnakes. The mitochondria is a structure within cells that makes energy. In hummingbirds, the mitochondria are specially structured to allow them to make even more energy than a mammal to help support their super-fast wingbeats. For the rattlesnake’s rattle, their muscles release calcium (needed to produce muscle contraction) more efficiently since they have large stores of calcium within the muscle.

More recently, his work has focused on developing the Eccentron. This is a specialized exercise machine that uses eccentric muscle contractions (lengthening) to build strength. You are probably most familiar with this type of exercise from walking downhill. Eccentric muscle contraction can produce high force with very little energy, so his research showed that it was great for elderly people at risk for falling. After gradually training with an Eccentron machine, their fall risk was dramatically reduced.

Image of Eccentron from: www.morphopedics.wikidot.com

 Congratulations Dr. Stan Lindstedt on being this year’s August Krogh lecturer!

Other highlights included: 

 J. Eme, T. Rhen, K. B. Tate, K. Gruchalla, Z. F. Kohl, C. E. Slay, D. A. Crossley II. Univ. of North Texas, Univ. of North Dakota and Univ. of California, Irvine. Dr. Eme, from Univ North Texas, presented work on turtle embryos that were shown to develop larger hearts, increased heart rate, decreased blood pressure and weigh less when developing in an oxygen-poor environment (hypoxic; 10% oxygen) as compared to turtle embryos growing up in a normal oxygen-rich environment (21% oxygen). With the ever-changing natural environment, this is a concern as the developing embryos can be exposed to hypoxic conditions in the wild. Dr. Crossley expanded on this research and talked about the effects of hypoxia exposure on developing alligators. In contrast to the turtle, developing alligators exposed to hypoxia have decreased heart mass, blood pressure, and heart rate compared to those developing in normal oxygen environments. What this means is that the effects of hypoxia on developing embryos is species-specific. Their most recent work on this topic was just published (PMID: 23552497). These findings are of interest especially in areas that raise these animals for food (fried gator or turtle soup, anyone?).

J. U. Meir, W. Jardine, J. York, B. Chua, W. K. Milsom. Harvard Med. Sch. and Univ. of British Columbia. Dr. Meir presented her work on bar-headed geese. She had actually raised the geese from hatching so they would imprint on her. She showed some really neat photos riding a scooter alongside the birds as they learned to fly next to her. The whole point of these exercises was to train the birds to eventually fly in a wind tunnel and to get them used to wearing a mask that could be used to manipulate the oxygen concentrations the geese were breathing. The bar-headed geese are spectacular flyers and are probably best known for flying over Mount Everest. Extreme hypoxic conditions, to say the least! Her research is really novel in that she was able to measure the amount of oxygen in the bird’s blood and their temperature during flight! Her preliminary analyses of the data suggest that the tissues of the birds are able to adequately extract the much-needed oxygen from the blood very well even while breathing in oxygen concentrations that mimic ~5500 m (10.5% oxygen) or 9000 m above sea level (7% oxygen).

You can watch the development of her research here:

 

What a great day for comparative physiology!