Re: paraffin and microtome blades for mouse tissue

From:Gayle Callis

WE have worked and/or tried every paraffin we could access for mouse
tissues, and all work. We adjust our processing for size and organ/tissue
type from the mouse, i.e. custom processing.  The processing schedule is
probably just as important as any particular paraffin. Surgipath
infiltration/embedding medias, Tissue Prep, etc, etc. and have used many
others over the last 22 years.   

As for knives, high or low profile disposable blades, and once again -
tried everyone we can access, available on the market, and they work.  

The knife marks (we call them ski tracks) you have are probably due to
brush bristles or some other thing that is putting nicks in knife edge.
Take care in HOW you clean paraffin off blade, do not touch the knife edge
with anything other than tissue being cut, and be careful how pick ribbon
off blade and inserting blade in holder.  If you get nicks, move knife
over, or change blade.  Disposable blades are wonderful, the best invention
since chocolate!  BUT you need to protect knife edge from damage or it
shows up as tears in the tissue - usually where you want to see things!
You need to clean the back of you knife holder, do not use xylene or
substitutes for removing paraffin, these will ruin the lubricants in your
knife holder/screws, etc.  We use rough cloth, rubbing paraffin off rather
than dissovling paraffin away.  Jan Minshew enlightened me on cleaning
knife holders.     

It is not necessary to clean or "dull" a blade, and if you do that, that
may be the source of your nicks.  Dulling a blade can be accomplished by
cutting a blank (no tissue) paraffin block before you cut your tissue
block.  This removes some of (commonly teflon) coating placed on blades. 


Gayle Callis
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
S. 19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (lab with voice mail)
406 994-4303 (FAX)


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