Here’s another question I received recently via Slack:
Them: We have ~120 [lizard] heads that we removed post euthanasia from captive born offspring of 4 different populations... The animals were euthanised in liquid nitrogen and then the heads were persevered in 10%NBF [neutral buffered formalin] 24hrs, then 70% EtoH [ethanol]. I am using the heads for scale counts.... However, post that I was wondering if there is the possible application of looking at their brain morphology? I have had a brief look at the literature, and suspect that we probably haven’t preserved them in an appropriate manner. Similarly, I think the liquid nitrogen euthanasia may cause some issues. I thought I’d ask for your thoughts as it seems like a waste if we could apply it to brain morphology questions. … I thought there may be question around relative sizes of different regions of the brain, … etc. This is all out of my wheelhouse so I could be totally off on this one! Any thoughts on if there is anything that can be done with them?
Me: Does "euthanized in liquid nitrogen" involve freezing them [Edit: This seems obvious in retrospect, but I thought it might have been via asphyxiation]? If not it might be worth a go. The 70% ethanol is not great but 24 hrs in neutral buffered formalin might be enough to prevent the EtOH-induced shrinkage, and 70% EtOH is better than 100%... It might be worth a go for MRI but I don't think you're going to have any success with histological methods after the EtOH.
Them: The whole lizard was frozen solid in liquid N.
Me: Ok then no chance.
So this is probably the most common problem I encounter with offers of brains to study: the brains on offer have been frozen. If you think there is any chance that you’ll want to use a brain for research DO NOT FREEZE IT. Put the whole head in a sealed, humid container in the fridge, and contact your nearest local neuroscientist immediately. If you have access to formalin, put the head in formalin for 24 hours and then, again if you have access, put it in saline until you can get it to a neuroscientist. If you don’t have access to saline, still remove the head from the formalin, rinse it in water, and store it in a sealed container wrapped in paper towel moistened with water.
I remembered to post this today because of this tweet. It seems like this freezing thing is not just a me-problem!
Andrew’s Twitter is here if you have any (never frozen) extra bird brains.
If you have any comments or suggestions on what I’ve said here, please don’t hesitate to get in touch. I’d love to hear from you.
And if you have an extra bird brain lying around, please get in touch with Andrew, and DON’T FREEZE THEM FIRST!