fixation for frozen sections

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From:"Instrumedics, Inc." <>
To:"HistoNet Server" <>
Content-Type:text/plain; charset="iso-8859-1"

Hi Histonetters,
We have devoted a lot of time to fixation issues. Acetone is not a true
fixative. What is does is remove water and ice from the frozen section. This
only stiffens the proteins.  Formaldehyde and glutaraldehyde are hard
fixatives and will maintain the morphology of the frozen section by binding
to  molecular elements.

Good morphology depends on the how rapidly (low temperature and thermal
exchange) the tissue is frozen. Once the tissue is snap frozen the CryoJane
Tape-Transfer process preserves the morphology by keeping the section frozen
until it is immersed in a fixative. The section is not melted in the
mounting step as occurs in conventional frozen section preparation. The
melting degrades the quality of the unfixed tissue!

We fix the section in either an aqueous glutaraldehyde fixative or for the
best results we dissolve the ice in the section in cold acetone(-35deg
C)inside the cryostat, in a process known as freeze substitution, and then
fix the section in an "anhydrous" glutaraldehyde fixative. With this latter
fixation method you preserve red blood cells not normally preserved in a
frozen section and  preserve granules containing enzymes that are not even
preserved in paraffin processing!


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