| From: | Tony Henwood |
My thoughts below
Tony Henwood JP, BAppSc, GradDipSysAnalys, CT(ASC)
Laboratory Manager
The Children's Hospital at Westmead,
Locked Bag 4001, Westmead, 2145, AUSTRALIA.
Tel: 612
9845 3306
Fax: 612 9845 3318
http://www.histosearch.com/homepages/TonyHenwood/default.html
http://us.geocities.com/tonyhenwoodau/index.html
-----Original Message-----
From: louise renton [mailto:louise_renton@hotmail.com]
Sent:
Tuesday, 30 September 2003 18:50
To:
histonet@lists.utsouthwestern.edu
Subject: [Histonet] over vs
underprocessing
Dear All,
There have been numerous posts
and replies over time regarding the quality
of processed tissues, with under
or over dehydration, fixation or processing
being cited as the cause. I would
lke some clarification and correction on
my personal viewpoints on this
issue as the case may be.
To my understanding:
a) Fixation and
dehydration have an absolute end result, ie one cannot
"over" dehydrate, as
once the water is gone, it's gone. However, residual
water is immiscible with
clearing agents or wax, and would thus produce a
soft poorly processed tissue. Thus "under" dehydration is a real entity.
However, anecdotal evidence has stated that these tissues may become
'alcohol-fixed" thus making
them difficult to cut. What is the rationale
behind this?
Alcohol is a fixative as well, so inadequately formalin fixed
tissues will fix in alcohols
b) "Over" processing, is the result
of excessive or prolonged heat
coagulating proteins rendering the tissue into
hard nasty uncuttable little
nodules. I seem to recall this demonstrated in
cookery class where eggs were
fried to extinction and thus became an
indigestible mass (there are many
proceses and regents used in histology that
bear resemblance to cooking
school)
Over processing (a cooked look to tissues) seems to be
more pronounced in under-fixed tissue. Tissues fixed in formalin for longer than
24 hours rarely show this change. This is based on microwave processing
experience where tissues are regularly under-fixed.
I realise that
this might be an oversimplified version of the real
processes, but I am interested in what the experts have to say.
Best regards
Louise
Renton
Bone Research Unit
MRC
Johannesburg
South Africa
Tel &
fax +27 11 717 2298
"Time flies like an arrow, fruit flies like a
banana"
----Original Message Follows----
From: " Katri
Tuomala" <katri@cogeco.ca>
To: "Kelly
Salceies"
<KSalceies@salud.unm.edu>,<Histonet@lists.utsouthwestern.edu>
Subject:
Re: [Histonet] Paraffin Embedding of Mice Tissue
Date: Mon, 29 Sep 2003 20:03:35 -0400
Hi Kelly,
What is your fixative for these mice
tissues and how long? How big (read
thick) are your sections to be
processed?
These two things will determine your routine processing
protocol.
I'm not familiar with microwave processing, so I won't comment on
that.
If the tissue is well fixed, there really isn't a chance to "over process"
it. The problems arise with inadequate fixation, which then leads
to
alcohols and xylene drying out the tissue, and hot paraffin then
causes
further damage.
Just something to think
about....
Katri
Katri Tuomala
Anatomic Pathology
St.Joseph's
Health Care
Hamilton, Ontaorio, Canada
----- Original Message -----
From: "Kelly Salceies" <KSalceies@salud.unm.edu>
To:
<Histonet@lists.utsouthwestern.edu>
Sent: Monday, September 29, 2003
10:01 AM
Subject: [Histonet] Paraffin Embedding of Mice
Tissue
> Hi Everyone,
>
> I am a
brand new Tech and am having trouble preping some mouse tissue
> for
paraffin embedding. I have all different tissues (liver, heart,
>
quads, brain, lung, and gastroc) and would like to prep all tissues
(if
> possible) under the same conditions. I have been using
the Shandon
> Hypercenter XP or the Shandon Histowave (microwave
tissue processor...).
> Does anybody have a good protocol for mouse
tissues on either of these
> instruments?? I have tried a number of
protocols, but all my tissue has
> been really dry in
cutting...
>
> Any suggestions would be greatly
appreciated!!
>
>
>
Thanks,
>
> Kelly Salceies
> University of
New Mexico
> Health Sciences Center
> Dept. of
Pathology
>
>
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