I use monkey brain tissue perfused with 4% paraformaldyde. The block of brain tissue is maximal 1 cubic centimeter. It usually sinks very fast in 10% sucrose and 20% sucrose (a couple of hours each), but then does not sink to the bottom in 30% sucrose. What am I doing wrong? Or is this what usually happens?
However, it starts floating below the surface after a couple of hours in the 30% sucrose. Is it ok to already use it for doing frozen sections by then? I need to do the sections as soon as possible, as the staining procedure I am aiming for (cytochrome oxidase) needs the brain to be as fresh as possible.
Thanks for any tips!