[Histonet] Re:Plastic sectioning

[Gayle Callis]

Sunny,

You have a tough problem here.  30 um thick GMA sections may be too thick 
for this embedding media.  GMA plastic was initially designed for doing 
THIN sections at 1 to 3 micrometers.  It tends to be brittle when cutting 
thick sections and one might have to use a very sharp tungsten carbide 
tipped knife in order to get any thick section off a GMA block.  One could 
try to adjust the plasticizer by increasing its concentration to make the 
GMA more pliable.  The knife, no matter how sharp, may not actually slice 
through the plastic, but force its way through in such a way that the 
plastic shatters i.e. a shearing effect and not really have a clean cut.

Patsy Ruegg published an inhouse method for GMA, rather than buy kits - 
that way she could adjust the ingredients accordingly for softer or harder 
GMA.

If the tissues are thicker than 1 to 2 mm when processing and embedding, 
infiltration may be a problem unless extended time is used and done at 4C ( 
refrigerator) and polymerization might have to controlled with cold 
temperatures in order to slow it down for continuous or steady progression 
of polymerizing.  That can be done at 4C also.

At 12:58 AM 1/5/2006, you wrote:
>Dear Sunny,
>
>First about the knife marks. To me it seems that you are using a blunt 
>knife. Try a new/sharp one.
>About the shattering: I don't know how youre blocks look like. Is the GMA 
>well impregnated into the brain-tissue, for else this could explain the 
>problem. If this is not the case (I don't think, else you would have 
>mentioned it) then perhaps you can try to use some sort of tape. Stick it 
>onto the block and then cut you're slice. I've tried it and it worked in 
>my case. The only problem then is how to remove the tape without damaging 
>the slice (unless you stain the slices when still sticked to the tape). 
>There are also commercial tapes specially for this technique (see for 
>instance this link:  http://www.alphelys.com/site/us/pHGP_CoupesParaffine.htm).

Gayle Callis
Research Histopathology Supervisor
Veterinary Molecular Biology
Montana State University - Bozeman
PO Box 173610
Bozeman MT 59717-3610
406 994-6367
406 994-4303 (FAX)