Embedding molds for MMA

From:Gayle Callis <uvsgc@msu.oscs.montana.edu>

Buy Histoplex specimen containers, unfilled, from Fisher or contact Erie
Scientific about their plastic specimen containers. Both are polypropylene
plastic, and safer than glass. Cathy Sanderson (Mayton) wrote an article in
J of Histotechnology on embedding molds for PMMA, 13:131-133, 1990.  

You will have to shape the blocks after polymerization IF microtoming, but
can be cut easily on saws.  These come in 40, 60, and 90 ml sizes, with a
lid that has an inner built-in O ring design on the lid for a good seal.
You should not have an open embedding mold with PMMA, it needs to be capped
or in a container for good polymerization as evaporation of monomer messes
up polymerization process, and changes the texture and total volume of
block you need. 

If the UV light causes rapid polymerization (bubbling) you can let the
blocks polymerize tightly capped at RT, it may take a few days, but works
fine.  You can make prepolymerized layers, to keep specimen from contacting
bottom of a container,
makes for better support during cutting and grinding.  The concept of UV
light polymerization is not a new one.  Sanderson, J of Histotechnology,
18(4):323, 1995 Polymerization of mineralized bone specimens embedded in
methymethacrylate using ultraviolet irradiation.  She also warns about
doing this outside of a fume hood. If aspecimen is placed in sunlight, some
UV wavelengths could be blocked by window glass, but certain wavelengths
must get through.  Artificial UV light sources could be contained in a hood
and far safer, similar to the EXAKT light polymerization method.   

I know of two people who have been badly poisoned by methyl methacrylate
fumes, it is a sensory motor neuron toxin, and if you can detect the odor
during handling, YOU ARE AT GREAT RISK.  Just ask Cathy Mayton (Sanderson)
she is an expert on handling MMA, and had a terrible experience with it at
one time, she is extremely careful now.  There have been articles published
on the toxicity methylmethacrylate, in my file somewhere.  If my lab did
not have an adequate fume hood, MMA (and GMA!) would be banned.  I would
refuse to work with either- it's as simple as that.  

If they try to force you to use MMA without proper ventilation, you should
refuse until an outside fume hood is installed.  If you think your formalin
problems are bad, you are in for equal or worse problems.  You will live

Gayle Callis
Veterinary Molecular Biology
Montana State University
Bozeman MT 59717-3610
406 994-4705
406 994-4303

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