[Histonet] question of the day - embedding

[Thomas Jasper]

Tracy,

I used to work at the same (nameless) place with Mr. Saby and I concur.  In my opinion your colleagues are potentially causing harm to the tissue specimens (especially small, delicate ones) while you are not.  Hot paraffin, specimens of various tissue types (particularly animal) and the resultant heat transfer is less than optimal.  Consider...why is it so important to get your specimens off the processor(s) shortly after the run(s) have been completed?  Answer...you don't want to "cook" them in liquid paraffin on the final station.  So why cook them in a holding tank full of liquid paraffin while you embed?  Also, the tissues (ideally) have been properly fixed, processed and infiltrated.  No harm will befall them without liquid paraffin, until they are embedded.

Good luck,
Tom Jasper

Thomas Jasper HT (ASCP) BAS
Histology Supervisor
Central Oregon Regional Pathology Services
Bend, OR 97701
541/693-2677
tjasper <@t> copc.net

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Joseph Saby
Sent: Tuesday, February 17, 2009 3:04 PM
To: Tracy Bergeron; histonet <@t> lists.utsouthwestern.edu
Subject: Re: [Histonet] question of the day - embedding

Tracy-

Where I used to work (at a place that shall remain nameless), we always kept our tissue being embedded in hot paraffin in the holding chamber.  Most of my work has been with animal tissues.

Where I work now, we don't.  And I do bellieve you are right.  If the tissues remain in hot paraffin, the heat transfer rate is very high, and the tissues continue to "cook" even when the chamber temperature has been reduced (as close as feasible) to the melting point of the paraffin.  I have seen little effect on the tissues of longer-than-I-would-like time in the holding chamber without paraffin.  Without the paraffin, the tissues do not get that direct heat from the melted paraffin and survive delay much better.

In short, I agree with you.  Not keeping the tissue in hot paraffin does not only not damage those tissues, it allows more flexiblity in your embedding times.

Joe Saby, BA HT




________________________________
From: Tracy Bergeron <tracy.bergeron <@t> biogenidec.com>
To: histonet <@t> lists.utsouthwestern.edu
Sent: Tuesday, February 17, 2009 4:14:46 PM
Subject: [Histonet] question of the day - embedding

Hi all question/dilemma of the day.

        I have been of the view that the longer tissue sat in melted paraffin the harder it got, especially animal tissue.  So with that said, for the past nearly 10 years I have not used melted paraffin in the holding chamber of the embedding center.  I just keep the chamber warm, and work that way.  Thus keeping the tissue from continuing to cook and harden in the wax.

        Everyone else I am currently working with has never seen the method I use, and firmly believe that this causes harm to the tissues if they are not in paraffin.

        Thoughts ideas etc.  I am dying to know if I am the only one that worries about length of time that animal tissue sits in paraffin.

Thanks.

Sincerely,
Tracy E. Bergeron, B.S., HT, HTL (ASCP)
Associate Scientist III, Pathology
Comparative Pathology Laboratory
Biogen Idec
14 Cambridge Center
Cambridge, MA 02142
Direct:  617-914-1115
Fax:  617-679-3208
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