[Histonet] Soaking artifact

[Lee & Peggy Wenk]

One slight amendment - this applies to human tissue.

Animal tissue has far less bound and unbound water to start with, so no 
matter how it's processed, it always ends up "dry". Therefore, longer 
soaking in water is needed.

Peggy A. Wenk, HTL(ASCP)SLS

-----Original Message----- 
From: Lee & Peggy Wenk
Sent: Monday, January 06, 2014 8:07 AM
To: Deanna Leslie ; histonet <@t> lists.utsouthwestern.edu
Subject: Re: [Histonet] Soaking artifact

The only "soaking" artifacts that I can think of would be caused by:
- soaking too long in water (minutes instead of a few seconds)
- soaking under-processed tissue in water

In both cases, the tissue is supposed to be "protected" by the wax, and if
it is not (under-processed), or if the faced block is in water too long, the
tissue can start re-absorbing water. The tissue then turns white and swells
out of the block. So all that "swelled out" tissue is cut away and lost when
the tissue is put back on the microtomy for sectioning the ribbon.

If you soak for just a few seconds, such as a gauze with water being held
against the block on the microtome, after it has been faced, then you will
get a little bit of water absorbed into just a few layers of cells. Just
enough to cut 2-4 sections. And you won't see that swelling artifact.

For those of you saying - "but I have to face all the blocks, put them back
on ice and/or water while I cut a bunch more blocks, and then go back and
cut each block" - that is an artifact also. You have over-dehydrated your
tissue during processing, and you are putting back the water that you should
not have taken out. Processing is supposed to remove the unbound water (not
attached to proteins), and some of the bound water (attached to proteins),
and leave some of the bound water (attached to proteins) in the tissue. If
you HAVE to soak EVERY block for more than a couple of seconds, then you are
wasting time rehydrating and wasting time while microtoming. Cut down the
time in the alcohols on the tissue processor, to leave a little bound water
in the tissues. And you can NOT processing little biopsies on the same long
processing cycle as the larger pieces of tissue (uterus, breast, etc.).
Those little biopsies will be over-dehydrated. They HAVE to be run on a
separate cycle of much shorter time intervals (10-20 minutes in each
solution (once fixed), instead of 45-60 minutes in each solution).

You should be able (on nearly every tissue block) to rough trim the tissue,
and immediately start cutting ribbons. Possibly, you will need to put an ice
cube on some of the harder tissue (cervix, uterus, bone, lens, etc.) just to
get the paraffin hardness to match the hardness of the tissue. That being
said, some tissues are naturally brittle or crumbly, and always need some
water put back in the tissue, such as spleen or bloody tissue, but again,
some wet gauze on the faced block for a few seconds should be enough time to
get 2-4 sections. And that's all the tissue we usually need from those
blocks. If you need more for IHC, put the wet gauze back on the faced block,
and cut a few more sections.

Peggy A. Wenk, HTL(ASCP)SLS

-----Original Message----- 
From: Deanna Leslie
Sent: Sunday, January 05, 2014 4:42 PM
To: histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] Soaking artifact

Has anybody in histoland ever heard of this?  I have been cutting tissue
for 25 yrs and until recently I had never heard of this!
I am under contract to a facility and the supervisor there does not want
anybody to soak their tissue or use ice!  Your are supposed to use the cold
plate, because as I have stated soaking them causing an artifact. I have
not disputed this because it is not my place or in my job discription as a
traveler.  I am not even sure what it is supposed to look like or what type
of problems it causes.

Thanks for listening!
Deanna Leslie HT ASCP
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