I got to watch surgery on a live mouse today!
The mice are tricked into thinking they're pregnant (they're "plugged" or "sechsed" [second word my own choosing] by male mice who have had a vasectomy). Mice, it seems, do not have access to pregnancy testing kits and so assume they're pregnant. This causes a psychosomatic response in that the mouse goes into pregnancy mode.
The mice are then given an injection to knock them out for around an hour (in labs with more space, the mice are given gas through a little mousey gas mask, but it's too cramped where I was). The injection doesn't kick in right away, so the mice stagger about drunkenly for a bit, and then collapse. They can still be awake - you check this by tickling their feet. If they're awake, they'll twitch.
Anyway, then ethanol is sprayed on their back (this helps keep fur out of the cut), and they're cut open. The oviduct is fished out and embryos are inserted. (I also got to watch embryo modification; fragments of DNA are pushed into an egg cell with a needle, and injected in the cytoplasm in the pronuclear membrane. The nucleus of an egg and sperm are haploid, containing half the information required. So they divide and then fuse; one division is discarded, leading to a "polar orbital" or something, which looks like a lump on the side of a cell. Anyway, the DNA fragments are inserted within the pronuclear membrane, and the pronucleus will then just weave the strands into the rest of the DNA. Truly amazing!). The mice need to be less pregnant than the embryos; the embryos can hang around in the oviduct while the surrogate mother catches up with her body clock, but it doesn't work the other way around - the mother won't wait, but piddle them out instead. The first mouse was a bit too pregnant, so she was put down. The second one was ok, so the wound was sutred (the sutre is made of a fibre that will just be absorbed) and then clamped shut with a little clip. She's then put into a recovery chamber at thirty degrees, wrapped in paper like a little mousey sleeping bag. The mouse is kept seperate for several days, in case her cage mates try and groom her and accidentally rip her open.
I then got to see the pregnant mice, as well as some male mice. The male mice are pretty much killed once they stop mating; if they won't mate but stay in the cage with nobody doing anything until they dont produce any good sperm, the line of mice is effectively dead.
I also did a polymerase chain reaction, like they do on CSI. More on that tomorrow!