Science Byte

Another late Science Byte - again, due to actual science taking place. I ran a muscle bath this afternoon. I would normally have started early in the morning, but I only found out at noon that the apparatus was free. So that's when I started & I pretty much just got home.

So... what to write about today? Hmmmmm...

Want to know more about this muscle bath experiment that I was doing today? No? Well too bad, that's all that's filling the space in my head right now.

First off - no, I'm not washing my or anyone else's muscles. A muscle bath is a small ... well, bath. It's like a tiny sink that only holds about 3mL (they do come in various sizes too): open at the top & with a valve at the bottom so it can be drained. The bath is made of 2 layers of glass so that hot water can be circulated through to keep the inner bath warm.

This picture explains it a bit better. You can see the inside of the chamber (3mL) is a light gray, and it opens to the bottom left (where there's a valve). The bath walls are open at the top left & bottom right (but not open to the inner chamber). What isn't shown is that the top is open to the inner chamber only. I'm not sure what's poking out the bottom in this schematic. The post on the right is a retort stand; the bath is clamped to this. A typical set-up will have 8 or more baths lined up on a bench.

The #1 points to the force transducer - this is what is going to give us a measurement for our experiment. #2 points to a muscle ring that is suspended on 2 bars tied with string to the force transducer at the top & a rod at the bottom. I don't use rings (like arteries) I use strips of trachea smooth muscle (they come from a slaughterhouse & I dissect out 1mm strips). Instead of the bars, I simply tie a string to each end of the strip - then one string is attached to a glass rod that sticks into the bath & the other string is tied to the force transducer at the top.

Now, we have our piece of muscle strung between a non-moving rod & a force transducer - this will measure any changes in tension in the muscle strip. So I can use certain drugs to cause a contraction & the force transducer will register this - first you'll see a straight line, then it'll rise, making a little hill (or giant peak, depending on the drug). This means that the tension has increased; i.e. the muscle has contracted.

Here's a picture of that trace. You can see a large peak (caused by KCl), then a tiny, sharp peak (caused by me hitting the string as I add in the next treatment) and then a slow, small contraction caused by my treatment.

Actually, this contraction only happened the once. My treatment (the supernatant of my adipocyte cultures - basically, anything that the fat cells produced while I grew them) doesn't do too much - but I've found that it'll cause a small relaxation if I add it while the muscle is contracted with carbachol. I've reproduced it a few times. Now I have to try a different contractile drug (to make sure it isn't specific to carbachol contractions), and then try blocking the relaxation....

So... that's all I can think to say.. any questions?