Experimental Sequence Test, Part 2

...And we're back!  So last we left off, our team had just finished our isolation and had a nice fresh batch of purified T-Cells.  After a well-deserved lunch break (and more coffee) we began the second half of our day -- loading the experimental containers that will carry our cells into space.

Diagram of Experimental Container

Each experimental container (pictured above) has four chambers, and each of these chamber has three compartments. The bottom compartment in the chamber holds one of our isolated T-cell samples.  The middle compartment has a mixture of activator beads that are used to activate the cells during the experiment - you can think of them as mimicking an infection.  The top compartment holds a chemical fixative that preserves the cells after the experiment is complete.

Experimental Container in action

Importantly, this fixative stabilizes all of the messenger RNA (mRNA)  molecules in the cell, essentially freezing them at a moment in time. As you may recall from biology class, mRNA is the intermediate between genes and proteins.  Under different environmental conditions, cells express different genes -  that is, they will make different types and amounts of mRNA in response to changes in the environment -- and the expression (or lack thereof) of these genes influences the cell's function.

When our fixed cells are returned to us after the experiment, we will compare the expression of thousands of genes between T-cells activated in microgravity and T-cells activated in normal earth gravity (1g) and look for differences between the two conditions.

One very cool thing about our experiment is that we will have samples in both microgravity and 1g onboard the ISS.  The European Space Agency has an onboard centrifuge named KUBIK that our samples go into. A portion of the samples will be centrifuged (spun) so that they experience a 1g force.

KUBIK - outside

KUBIK - inside

Now you may be wondering, "We already have 1g conditions right here on earth, why do you need to send samples all the way to space and put them at 1g?" An excellent question!  And one that hits at the heart of a very basic idea in science -- the importance of controls.

What would happen if we tried to compare a 1g control on earth to a sample that went up into space?  We might see a difference between the samples, but how would we know that the difference was due to one sample being at 1g and the other at microgravity?  It could be that the difference was caused by vibrations from the rocket launch.  Or maybe from the higher cosmic radiation onboard the ISS.  With the 1g sample on earth, it is impossible to conclude if any changes seen were due to a difference in gravity alone.

However, if we have our 1g samples onboard, all conditions will be identical to the microgravity samples, with the exception of gravity.  That is to say, we control all variables except gravity.  This way, we can make the comparison between the samples and know that the changes are due to differences in gravity.  So those 1g onboard samples are very important for our experiment!

We'll be back in our third EST installment with more details about our afternoon filling cassettes. And more pictures!  Stay with us...