In what situations is a cryostat
better than regular paraffin processing, and why?
Faster to get the sections under the microscope and
lipids are not lost with dehydration and clearing and
some immunoreactivity may be lost with fixation (depending on the antigen).
However, morphology is worse with fresh frozen sections and
some enzymes and antigens may diffuse without fixation giving less precise
localization.
So "better" is relative to what you want to do.
How do you get cryostat sections
to stick to a slide for staining?
In my (limited) experience the proteins from tissue fluids allow for good
adhesion even on plain glass slides. Your mileage may vary. For long proceedures
I would use coated (gelatin, silane) slides.
Do you need to fix tissue for
cryostat in paraformaldhyde/sucrose solution?
You can, depending on the goal. You can also fix tissue first, then freeze
and cut on a cryostat or a sliding microtome. The latter gives much better
morphology.
Can
you section fresh/frozen tissue?
Yes. You can section fresh, unfrozen tissue down to about 20 microns with
an instrument called a Vibratome. This does take some practice. For thicker
sections you can use a "Stadie-Riggs" tissue slicer.
You can freeze fresh tissue with dry ice or liquid nitrogen and section it
with a cryostat.