To clarify methylmethacrylate versus glycol methacrylate

From:Gayle Callis

JB-4 is NOT methylmethacryate, it is glycol methacrylate (GMA) and you are
correct that you cannot reembed once polymerized, although Cathy Mayton has
a publication on doing this in J of Histotechnology.  In fact, you cannot
remove the plastic after sectioning, whereas MMA (see description below)
can be totally removed from thin sections with warm xylene, other solvents
(Neil Hand publication, J of Histotechnology) for immunostaining purposes. 

Methylmethacrylate, commonly called PMMA or MMA can be dissolved away with
methacrylate monomer, allowing a specimen to be reembedded.  Been there,
done that. 

As for GMA polymerization, it happens so fast, and hard to control, that
once we put chuck on top of GMA embedded tissues, excluded air, we had to
place molds, etc on block of ice (in metal cake pan) to slow it down. We
also kept the embedding mixture on ice, and never mixed more than 25 mls at
at time.  You can also slow down GMA polymerization by using less
nndimethylaniline.  Double embedding a block in GMA is also possible for
reorientation, even getting rid of bubbles. 

As for MMA, we had all the time in the world to embed before
polymerization, that took place much more slowly, very controlled.  

 At 09:00 AM 11/21/02 -0600, you wrote:
>Hi Myriam,
>This topic has come up before and, in my (and others)experience, you
>can't re-embed methylmethacrylate very well (in my case JB-4). You can
>fill in the bubbles if they are on a surface by placing the whole block
>into a new mold with fresh embedding media, but the media won't
>penetrate into the block.
>Often, bubbles will form if the block has over heated during 
>polymerization. If this is your case, you will also see that the tissue
>looks a bit "cooked".  There isn't anything you can do for it except 
>make sure that the molds are in some sort of a heat sink the next time
>you embed.  We use ice water around the molds and place the molds into
>the refrigerator as soon as the molds are ready. You can also place
>empty molds, weighted down with something into water so that it comes 
>about half way up the side of the mold. Then place the whole set-up 
>into the frezzer to freeze the molds in place.  This is a little easier
>for manipulation of the tissue media and mold and embedding time.
>Good luck,
>Karen Pawlowski, Ph.D.
>Research Scientist
>UT Dallas
> wrote:
>> hello histonetters,
>> I have methylmetacrylate embedded samples which need to be re-embedded
due to uneven polymerization leading to air bubbles captured in the blocks.
>> can somebody give me a procedure to perform this re-embedding ?
>> thanks in advance
>> best regards
>> Myriam baali
>> marseille
>> France
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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