Paraffin to EM the FAST way (was :Electron microscope)

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From:Tim Morken <> (by way of histonet)
To:histonet <>
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You can skip all the reprocessing from paraffin to EM resin by using 1
percent osmium in xylene to deparaffinize. This was pioneered by Kai
Chien of Cedars-Sinai in L.A.

1) Cut paraffin tissue in 1mm cubes.
2) deparaffinize in 1 percent osmium in xylene for several changes.
3) Clear in pure xylene
4) Infiltrate in a xylene/resin mix for several changes.
5) Infiltrate in pure resin
6) embed

This will save hours and many of those tedious solution changes.

As mentioned by all the others the morphology isn't the best. In a
diagnostic lab it is useful for distinguishing lymphomas from carcinomas
(lack of or presence of desmosomes), finding neurosecretory granuals in
carcinoids and pre-melanosomes in melanomas. It is really only useful as
a "Hail Mary" attempt to get information after the specimen was wrongly
submitted and all other tests fail to give answers.

Tim Morken, B.A., EMT(MSA), HTL(ASCP)

Infectious Disease Pathology

Centers for Disease Control


1600 Clifton Rd.

Atlanta, GA 30333



FAX:  (404)639-3043

----Original Message Follows----
Date: Wed, 03 Feb 1999 16:07:26 -0500 (EST)
Subject: Re: electron microscope

In a message dated 99-02-03 11:06:28 EST, writes:

<< Can anyone tell me about the issue sriking my mind ..
 Can Electron microscopy be done on formalin fixed paraffin emebedded


Yes, you can do this, but the ultrastructural preservation in the
will probably not be very good.  It all depends on the quality of
during the initial paraffin embedding, which is usually quite rapid.  If
is the case, you will likely only see remains of membranes, cellular
and nuclear "ghosts," and not much intracellular detail.  Extracellular
materials may survive the process well enough to distinguish collagen,
elastin, etc.

1.  Cut away as much of the paraffin from the specimen as possible.

2.  Remove the remaining paraffin by incubating in xylene.  Use several
changes of xylene over 3-4 hours or overnight.

3.  Incubate in 100% alcohol, 3-4 changes, 20 minutes each to remove the
At this point you can cut up the specimen if necessary into the sizes
that are
normally used for EM (0.5-1.0mm cubes, or as small as possible).

4.  Partially rehydrate the specimen by using stepwise alcohol
returning to about 50% or 70% alcohol in water.

5.  Re-dehydrate and process into plastic as you normally do.

Good luck, hope this helps.

Robert (Bob) Chiovetti, Ph.D.
Microimaging Technologies, Inc.
Tucson, Arizona USA
Tel./Fax (520) 546-4986
Manufacturers' Representatives
Systems Integrators
Analog & Digital Imaging Systems
Clinical & Research Microscopy

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