Life of a Lab Rat

If you're as old as me, you might remember sometime in the early '90s being completely blown away by Tim Springer's wonderful videos of leucocyte extravasation. For some reason I seem to have a lot of non-science types reading these ramblings and I reckon I've probably just lost half my readership, so I'll step back a bit and put things into plain(er) English.

If you happened to pick up, say Jandl's Blood: Pathophysiology, you might find an opening paragraph that reads something like

Blood is a complex suspension in plasma of nondividing differentiated cells which continuously perfuses the vasculature. It contains a mixture of several very different kinds of cells, all of which stem from an oligarchy of progenitors that originate in marrow or lymph follicles.

Which is a rather complicated way of describing the red stuff that leaks out when you get a real bad paper cut. Essentially, blood is made up of red cells, white cells and little bitty things called platelets, all floating round in a kind of white wine sauce. And it gets everywhere. The red cells are the little fellas that carry oxygen and nutrients around, platelets help stop the red stuff leaking out, and white cells, like knights of old on armour'd chargers, fight infection. Depending on the sort of white cell you are, you can throw chemicals or antibodies at nasties, or actually muscle up and eat invading bacteria and other bits and pieces. Yummy.

Leucocytes (or leukocytes, depending on your education I guess) are a subset of white cells, and the term is generally used to refer to a further subset called macrophages. These guys, normally floating around in the blood in the same way that NSW cops hang around in corner cafés, are recruited to sites of infection/inflammation in the body by certain chemical signals. What happens is that these free-flowing leucocytes detect a signal on the wall of the blood vessel and briefly stick to it. Because the blood itself is flowing relatively fast and the initial interaction is somewhat weak, the leucocytes roll along the internal wall, sensing for further signals. If they find these signals, that is if it really is a blue light situation, then they suddenly stick, and squeeeeze between vessel cells into the tissue in order to find the bad guys. This is extravasation.

In the fifteen years since Tim Springer first showed his videos, we've come a fair way in understanding the molecular mechanisms behind leucocyte extravasation. And some two-bit polytechnic in the US has got together with a scientific animation company to make a simply gorgeous video of the internals of the process, the secret life of the cell.

The imagination and scope of the animation — from the long shot of the inside of the capillary, through past the lipid rafts and the microtubule zipping and unzipping, messenger RNA shooting up through the nuclear pores, protein extruding from the microscopic pasta maker that is the ribosome, the kinesin trudging along with its vesicle on its back, right through to the final schloop as the leucocyte disappears into the tissue — is breathtaking. And it's amazing to think that this is going on in all our bodies all the time.

The video is much simplified, of course — the cell is much more crowded than the impression given here and there are bits of protein and fluff covering everything (RNA and DNA are never that 'naked') — and there are parts where the scientific jury is still out if not actually at war (cough lipid rafts cough), but it's well worth the few minutes it takes to download and watch it.

So if you die and are reincarnated as a bacterium, and you see a big angry macrophage bearing down on you, you'll be able to wave your flagellum in wild wonder at this remarkable process, just as it gobbles you up. Even if you are an arts graduate.

(Thanks to Alex)