Methyl methacrylate and automated processors

From:Gayle Callis

I hope this isn't a repeat of any previous messaging, had some strange
can't send messages.

Here goes! 

>You can use any automated processing up through xylene clearing steps for
>PMMA, but automated processors are NOT DESIGNED TO HANDLE METHACRYLATE
>MONOMER.  After clearing, you can remove mineralized bones and do all MMA
>mixture steps by hand.  
>I ran my VIP (older model) for extended large bone processing (huge bones,
>folks!) for 21 days just to see if I could do it.  This went up through
>xylene steps only for final clearing.  Paraffin stations were deleted, of
>course.  Not a good idea if you need to the use the processor for other
>things.  Observed alcohols needed constant replenishing/topping off due to
>evaporation. One could interrupt briefly, top off containers, it really
>uses up charcoal filter, and the water filter needed very frequent changes.
> This was far too long to tie up precious processor time.   
>I know of only one person who had a processor which worked for MMA
>protocols.  Sharon Evander has a Shandon processor, all heat cycles were
>removed from the machine by the company, and she could do monomers in the
>machine.  It required special hoods, etc, handling due to monomer toxicity.
> I don't think anyone else in the world used a Shandon in this manner.
>This was a special arrangement by Shandon, and something about the design
>of their machine permitted this. I would not want to try this with my VIP
>or any other brands, and the Shandon may be different now.  You would have
>to contact them about dedicating a processor for just MMA work as this is
>not what the processor was/is initially designed to do.  Heaven help one,
>if the machine when down in the middle of a monomer cycle, being exposed to
>any fumes would be a health risk one should not take.  
>I find it easier to just do dehydration and xylene clearing steps in VIP,
>no heat added, for extended time, remove dehydrated/cleared bones and do
>all MMA steps inside a hood by hand using vacuum dessicators with inhouse
>waterline vacuum, fumes will eat vacuum pumps too. The worst part about
>large bones is the time it takes to do all processing steps, and if any
>researcher/pathologist/whoever thinks this is going to be a rapid protocol,
>forget it OR let them do the work themselves, they might better appreciate
>what it involves.  Have spent time arguing this point, ad nauseum.    I did
>a whole alligator head (young animal, a small head!) to perfection and it
>took almost three months to do the work, a polymerized block with no
>bubbles.  Some changes of solvents take a week at at time, and then
>embedding is done with layering method for really large bones  Too much MMA
>monomer mixture over the top of a large bone, and you have a bubbly mess
>that is unbelievable. Been there, done that too! 
>I "over-Mother" my large bones, and it pays off, because it is very hard to
>reverse any PMMA bone processing, been there, tried it, and failed. I also
>prefer to do all large bones by hand with a vacuum dessicator system, and
>continue to do other things inbetween. It is also safer, because all
>equipment fits into a chemical fume hood, protect yourself! 
>Contact me for the equipment setup I used, if interested.  I never had
>dried out bone bits, what a bummer!, but I have had bubbled messes and
>undehydrated/poorly cleared bones. Learned from mistakes/failures, and
>patience wins out everytime.
>At 03:25 PM 7/25/01 +0000, you wrote:
>>Hello again
>>Since the episode of the dried out bone bits we are looking to 
>>purchase a new processor. What do those of you dealing with large 
>>pieces of bone use? Enclosed processors? hand processing? 
>>(Bear in mind that we embed in PMMA).
>Gayle Callis
>Histopathology Supervisor
>Veterinary Molecular Biology
>Montana State University - Bozeman
>Bozeman MT 59717-3610
>406 994-6367
>406 994-4303 (FAX)
Gayle Callis
Histopathology Supervisor

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