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This week I got to catch up with Kari, a 2nd year grad student in the lab. Kari has worked on many projects in the lab to date including a TEM (transmission electron microscopy) project, where we are trying to visualize the protein titin (filament in muscle). She has also worked on jumping mice with muscular dystrophy with myositis (mdm). These mice have a deletion in the titin gene, and so have lost a valuable muscle component. By comparing jumping abilities of the mdm mice and healthy mice, we get to learn more about how this condition affects locomotion and more importantly how we can fix this in human via prosthesis applications.

For her thesis, Kari is working to further pinpoint titin’s role in muscles. Unfortunately, because of other elastic components, like collagen (connective tissue) and other cell filaments, it is difficult to pinpoint what are actually titin’s attributes compared to the other cellular components. To try and solve this, Kari is shivering mice. Why? because we think of active titin as a spring and therefore has a spring constant. Kari wants to find that spring constant. If she takes the shivering frequency of mice, and plug that into the spring equation with the mice weight, she can find the spring constant of titin.

The trick lies in sorting out titin from the other elements (as we just talked about). To do this, she is going to find the spring constants from healthy mice and mdm mice (missing titin). She will then subtract the mutant mice (missing titin) from the healthy mice (have all components) and be left with just the constant for titin itself.

Now there are a lot of other factors to consider, like the previously researched fact that there is more collagen in mutant mice then healthy mice. There has to be a way to naturalize that out if she wants her data to be meaningful. Other problems include the experiment themselves. The frequency of the shiver is recorded by tiny accelerometers that have been placed on the backs of mice. These guys are so sensitive that air-conditioning, cars outside, footsteps and a vibrating cell phone can all be picked up and so make it difficult to actually pinpoint the mouse shivering from all other ambient vibrations within the data. Kari is working hard right now to trouble shoot these problems, and hopes to have some solid data in within the next couple months.

If you would like to find out more about Kari’s work, you can contact her at kt375@nau.edu

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