Hi Ray,

I make my GMA fairly soft and I would guess that when I section at 1 -2
microns, I may have a 1 micron variance within a block, but I usually
place 5 sections on one slide and stain.  I know from intentionally
"thick/thin" sectioning on some of these slides that it is easy to tell a
5 micron section from the 1 - 2 micron sections and usually I can see a
staining density difference between the 1 and the 2 micron sections.  I
think as long as you cut all of it in one sitting, and keep your
section rate constant, your variance from section to section will be low.
The GMA protocol I use (actually JB-4) makes a soft block that is subject
to distortions from changes in temp. and humidity.

I have less problems with distortion from spurr's and other EM plastics.


The other question is whether you have the same thickness from block to
block. I would think this variation would be greater.

Hope this helps.

Karen Pawlowski


On Tue, 25 Apr 2000 MarikoKoe@aol.com wrote:

> Would anyone with some fairly extensive GMA (or other plastics) viewing 
> experience care to briefly discuss the following?  What is your comfort level 
> with being assured of the thickness of the section?  That is, if you are 
> looking at a well-processed, well sectioned, well-stained kidney biopsy, how 
> confident are you to state that this section is 1.5 microns versus 2.0 
> microns thick by microscopic viewing alone.  Note I am not talking about 
> cutting one at 1.5 and another at 2.0 and then guessing which might look a 
> little thinner.  But what about viewing a single slide and stating with 
> confidence that this section is at 1.0 or 1.5 or 2.0 microns?  Where is your 
> comfort level for making this assessment?  In addition,  what is your idea of 
> slide readability for diagnostic purposes?  If something is requested at 1.0 
> to 2.0 microns, is 2.5 microns "too thick" to read?  Obviously this may have 
> to do with the specimen and the pathology involved, but how precisely crucial 
> do you consider the thickness of the section to within a micron or so of the 
> requested value? 
> 
> Thanks,
> 
> Ray in Seattle
> 
>