Liver Shake

Yeah, that sounds really appetizing, doesn't it? But that is pretty much what I made yesterday. Today I made abdominal fat pad shakes. Tomorrow it's thigh meat shakes. Mmm, mmm!

How does one make a liver shake, and why do you want to do it? The why is easy: making a liver (or heart or thigh) shake is the first step in a total lipid extraction of our tissue samples. From there we can do all sorts of fancy analyses of different types of lipid (AKA fats). 

The how is a bit more complicated. Fats are typically extracted using organic solvents. I am using a mixture of chloroform and methanol, a fairly standard mixture for lipid extraction from biological samples. I took a piece from each of our sample livers, chopped it up, weighed it, added the solvent, ran it through a "homogenizer"--an expensive, lab-bench-top puree device (the end result is the liver shake), and let it sit overnight. 

I then filtered out the solid bits (bits of cell walls, proteins, fibrous bits--the liver is full of nasty fibrous bits), pretty much anything in the liver that wasn't dissolved by the solvent.

The next step is pretty cool. What we really want is lipids and chloroform. But the chloroform and methanol are mixed. To separate out the methanol, we add a weak salt (sodium chloride, table salt) solution. Some tidy organic chemistry happens, and the less dense methanol/salt/water separates to form a white, cloudy layer above the clear yellow chloroform/lipids layer.

   
We did this exact same procedure, minus the lipids, in the organic chemistry lab I took last summer. I was pretty excited to see my advisor demonstrate the procedure on one sample--I could have written out the balanced equation for the reaction since separating two organic solvents by adding a salt is standard stuff. She was pleased that I was able to put it all together so quickly. Anyway, she's told me that her goal is to turn me into an organic chemist for the summer! So far, so good. 

Our goal is to complete all of the lab work for both feeding trials by the end of August. Then we can focus on the numerical analysis of everything in the fall, I can start writing it all up over the winter break, and maybe even finish up by April or May. That would be setting a land speed record for a master's research project, especially one involving live animals.

And no, I haven't lost sight of the end game. I took the GRE last week, and started my online vet school application over the weekend. I'll be posting about that soon. I totally understand now why I was told, over and over, that it would take weeks to complete (I never doubted this information, but it's good that I have confirmed it for myself).