Catherine,

You don't say whether you are embedding for EM or LM. I've done both and
never had any problems.

For LM, using methylmethacrylate, we streched the nerve on a stiff card
for two minutes before fixation. This takes care of the tendancy for the
nerve to contract. The card with the nerve is put nerve-side down in a
petri dish of formalin. Alternatively, you can tie sutures to each end
of the nerve, attach a weight of some sort (we used fishing split shot)
to one suture, and suspend the nerve (weight-end down) in a screw-top
tube of fixative with the opposite suture held by the tube cap.

Let either prep fix for two days.

For LM plastics be certain the nerve is fully infiltrated, as seen by
the biopsy dropping to the bottom of the 100 percent plastic mixture.

For EM we took part of the above prep after it was fixed in formalin and
put it 1% osmium for 24 hours. Then it was processed as usual for EM and
embedded in a Chein two-way mold. A portion of the osmium-fixed piece
was kept for nerve teasing.

Tim Morken, B.S., EMT(MSA), HTL(ASCP)
Infectious Disease Pathology
Centers for Disease Control
MS-G32
1600 Clifton Rd.
Atlanta, GA 30333
USA

email: tim9@cdc.gov
       timcdc@hotmail.com

FAX:  (404)639-3043





----Original Message Follows----
Date: Mon, 05 Oct 1998 13:20:02 -0500
From: Catherine Johnson <johns373@maroon.tc.umn.edu>
Subject: Plastic Embedded Nerve
To: HistoNet@Pathology.swmed.edu

Dear Histonetters:

We've had a problem with our plastic embedded nerve biopsies on and off.
The tissue sections are stained with MAB or Toluidine blue.  Often
times,
it looks like there has been poor penetration of the fixative or
possibly
other solutions during processing.  Sometimes the sections are difficult
to
read because there is so much artifact.  Artifacts include poor
penetration
of the stain, distorted cross sections of myelinated fibers, and
wrinkles.
Our EM technician has a tendency to always blame it on the fixative, so
she
makes an effort to make sure the fixative is always fresh.  We've also
started slitting the perineurium with a razor blade before dropping the
specimen into fixative in hopes of improving penetration, but these
methods
have not helped consistently.  I'd appreciate any recommendations all
you
plastics experts might have to remedy this frustrating problem.

Thanks in advance,

Catherine Johnson
University of Minnesota Neuromuscular Lab








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