while I agree with most of your comments here, I am not sure about the shrinkage
that you quoted. Was this measured and/or is this personal experience. I have
not processed a lot of brains in celloidin but have processed several other
tissues and the sort of shrinkage that was seen and those in the literature are
well below 10%, usually around 5%. It has been stated somewhere that a 12 micron
celloidin section contains the same volume of tissue as a 7 micron paraffin
section, this difference due to the differences in shrinkage between the two
processing methods necessary.
Perhaps this shrinkage is specific to the brain?
As an aside, celloidin can also be dissolved in amyl acetate instead of
Celloidin and LVN (Low Viscosity Nitrocellulose) blocks as has been mentioned
are slow to infiltrate, difficult to prepare and process and technically
difficult to section and to stain. We estimated cost to be around $200 plus for
block of 2 teeth in a dog jaw.
You do not state why you are considering this embedding medium?
"McMeekin, Bill" wrote:
> 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.
> Bill McMeekin
> Senior Chief Biomedical Scientist
> Newcastle General Hospital
> Phone: +44 191 256 3830
> Fax: +44 191 256 3196
> E-mail: firstname.lastname@example.org
> -----Original Message-----
> From: Billie Zimmerman [mailto:email@example.com]
> Sent: 03 December 2001 15:29
> To: firstname.lastname@example.org
> Subject: Celloidin
> Does anyone have a procedure for using celloidin an embedding media?
> Billie Zimmerman
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