25 years ago I worked in a neuropathology lab where we used celloidin
embedding for large brain sections. We could obtain 2 concentrations of
necoloidine solution (8% and 14% from memory) at that time and prepared a
graded series from these in ether/alcohol (1:1). Fixed tissue was processed
to absolute alcohol followed by ether alcohol and then infiltrated with
increasing strengths of celloidin solutions up to the 14% max. The
viscosity of the thicker celloidin solutions necessitated a very slow
process (changes at weekly intervals). Embedding was then carried out in
large flat-bottomed, circular glass troughs with a glass plate for a lid.
After placing blocks in fresh 14% celloidin in the trough (poured to a depth
of perhaps 4-5cm) they were allowed to settle. The celloidin had to be
allowed to thicken very gradually by sliding the lid aside to create a small
vent, letting the ether/alcohol evaporate slowly. Periodically, gas bubbles
had to be encouraged from under the blocks (to avoid distortion) by
judicious use of pressure and lifting. Care was required to prevent a
'skin' forming on the surface (by overzealous venting of solvent), leaving a
soft underside which was difficult to recover. When the celloidin had
reached a firm, rubbery consistency, throughout its depth (assessed by
probing), it could be removed from the trough in one piece and individual
blocks trimmed using a scalpel. Preparations were elegant and very
satisfying to produce.
Some of the drawbacks: The process was very time consuming and costly.
Shrinkage is significant (25-30% ?). Ether is highly flammable and
explosive as a vapour (and you can get rather attached to it). Blocks need
to be kept under 70% alcohol to limit hardening and this needs to be
regularly topped up if storing long term. The blocks remain highly
flammable and make for bulky storage.
We do not use it in my current lab and I would be loathe to introduce it for
some of the reasons stated.
Senior Chief Biomedical Scientist
Newcastle General Hospital
Phone: +44 191 256 3830
Fax: +44 191 256 3196
From: Billie Zimmerman [mailto:email@example.com]
Sent: 03 December 2001 15:29
Does anyone have a procedure for using celloidin an embedding media?
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