Updated: I’ve written a follow-up on research ethics to make up for some problems in this post.
Yes, that title does in fact include the phrase “pureed bee heads”. While on vacation, I was doing some reading on basic stuff related to neonicotinoids, my favorite pesticide class1. One paper that came up was a 2001 toxicity study done by researchers at Bayer AG on the effects of imidacloprid on honey bees. The results are not terribly surprising to anyone who knows anything about the (acute) effects of neonicotinoids on bees (neonics kill bees at high doses, make them behave funny at lower doses). Even though the results are unsurprising, the methods were interesting to me. Partly this is because I just don’t know that much about the field. But bonus for you is that you get to learn about interesting (but gruesome!) methods for find stuff out.
When I was reading that book on pesticide metabolism, there were a lot of passing methods to interesting methods. One method involved taking rabbit or other animal skin and spreading it thin to test skin absorption of a pesticide. A bit “ewww”, right? But, neat that they can figure things out using it, right? In this study2, two of the things they wanted to study were if proteins in the brain bound to imidacloprid or chemicals that are by-products of organism reactions with imidacloprid (called metabolites) and if neurons in the presence of those chemicals reacted differently to electrical signals. To study this, they cut off bee heads and pureed them.
For biochemical studies, worker honeybees were carefully collected from hive combs (collection site: Burscheid, Germany) and directly frozen using dry ice. Bee heads were then separated from other body parts by vigorous shaking and recovered by sieving. The heads were then frozen at -40°C (usually not longer than 6 weeks) until use.
Bee heads weighing 10g were homogenized in 200 ml ice-cold 0.1 M [molar] potassium phosphate buffer, pH 7.4 containing 95mM sucrose using a motor-driven Ultra Turrax blender. The homogenate was then centrifuged for 10 min at 1200*g* and the resulting supernatant was filtered through five layers of cheesecloth and then used without prior purification.
In short, they froze bees, separated their heads by shaking and tossing thru (probably) a small mesh, then later pureed them using a fancy science blender device and mixed it with sugar solution and other chemicals. Then they did some tests to see if anything in there reacted with imidacloprid or with common metabolites of it. In a related experiment they separated neurons out of those bee heads and ran electrical currents thru them when they were floating in solutions containing different amounts of chemicals that might interfere with electrical activity.
This is gruesome. While doing more population based studies is useful — for example, feed bees the chemicals of interest and see what happens over time — it’s also necessary to find out exactly what is going on at the physical level rather than just correlations. In this case, they are trying to see if and how imidacloprid affects bees in the brain by directly extracting the relevant parts and doing experiments on them. One result they got which would be much harder to tease out using what I would think as an obvious way to test toxicity (feed the chemical to bees, see which ones die), is that there are different forms of the same brain receptors that are reacting to imidacloprid and to different degrees. To do that, they had to puree bee heads. No doubt these are obvious methods to someone in the field, but to me they are gruesome (but neat!) science methods3.
Gruesome Science Methods might become a series. We’ll see. Pesticide studies definitely lend themselves to it.
I had, shall we say, slightly better access to scholarly works than I normally have and slurped down a bunch. ↩
I apologize for linking to a closed access article. I’m not really sure how to handle this honestly. It’s not really reasonable to just ignore all science not published as open access… ↩
I may have excitedly told everyone I possibly could while on vacation if the subject was at all relevant to conversation. I may have even talked about it over dinner. ↩