re-embedding of MMA blocks

From:Cathy Mayton

Methlymethacrylate (MMA) is a plastic medium that can be fickle to work with, but a gem when it comes to "saving" tissues that did not polymerize correctly.  Diane and Gayle both put you on the right path for salvaging the blocks that bubbled during polymerization.
Like Gayle, I have done many workshops at NSH on MMA processing  and I believe there is a bit of voo-doo that goes along with MMA processing and it is important to not make the MMA gods angry at you.
There are several things that can "upset" the MMA gods
1) the volume present in the container at the time of polyermization (I have publications that mention polymerizing in layers)
2) vibration (my husband was expanding on my lab this Spring and was pounding nails  and sawing on the new wall) several of the containers "took off" and had to be re-embedded
3) temperature can be a critical factor and as Gayle mentioned do not go over 37 degrees. 
Whenever possible, I embed in plastic containers (don't like breaking the glass).
Diane and Gayle told you what I would have, and that is saw away as much of the MMA as possible.  The specimens can be suspended (I make gauze bags tied with string) in stock MMA (off the shelf) to dissolve away the bubbles or if needed all the way down to the specimen.  If you only need to remove some bubbles the block can be placed right back into new mold with fresh embedding medium.  If, I recover the block down to the specimen I at least go back through the second infiltrating medium and then re-embed the specimen.
Depending on how badly the blocks have bubbled it may take some time but the tissues are not lost.  There are many publications published in the Journal of Histotechnology during the mid-80's to late 90's regarding the processing of MMA.  Not to worry, your blocks can be salvaged.  I have worked with MMA since 1983 and I still sometimes upset the MMA gods. 
Good luck
"Quality Histology with a Personal Touch"
Cathy A. Mayton, HT(ASCP)
Wasatch Histo Consultants, Inc.
Winnemucca, NV   89445

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