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<P><FONT size=2>My thoughts below<BR></FONT></P><FONT size=2>
<P><FONT face=Arial size=2>Tony Henwood JP, B</FONT><FONT face=Arial size=2>A</FONT><FONT face=Arial size=2>ppSc, GradDipSysAnalys, CT(ASC)</FONT>
<BR><FONT face=Arial size=2>Laboratory Manager</FONT> <BR><FONT face=Arial
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<P><BR>-----Original Message-----<BR>From: louise renton [<A
href="mailto:louise_renton@hotmail.com">mailto:louise_renton@hotmail.com</A>]<BR>Sent:
Tuesday, 30 September 2003 18:50<BR>To:
histonet@lists.utsouthwestern.edu<BR>Subject: [Histonet] over vs
underprocessing<BR><BR><BR>Dear All,<BR><BR>There have been numerous posts
and replies over time regarding the quality<BR>of processed tissues, with under
or over dehydration, fixation or processing<BR>being cited as the cause. I would
lke some clarification and correction on<BR>my personal viewpoints on this
issue as the case may be.<BR><BR>To my understanding:<BR>a) Fixation and
dehydration have an absolute end result, ie one cannot<BR>"over" dehydrate, as
once the water is gone, it's gone. However, residual<BR>water is immiscible with
clearing agents or wax, and would thus produce a<BR>soft poorly processed tissue. Thus "under" dehydration is a real entity.<BR>However, anecdotal evidence has stated that these tissues may become<BR>'alcohol-fixed" thus making
them difficult to cut. What is the rationale<BR>behind this?<BR><BR><FONT color=#ff0000>Alcohol is a fixative as well, so inadequately formalin fixed
tissues will fix in alcohols</FONT><BR><BR>b) "Over" processing, is the result
of excessive or prolonged heat<BR>coagulating proteins rendering the tissue into
hard nasty uncuttable little<BR>nodules. I seem to recall this demonstrated in
cookery class where eggs were<BR>fried to extinction and thus became an
indigestible mass (there are many<BR>proceses and regents used in histology that
bear resemblance to cooking<BR>school)</P>
<P><FONT color=#ff0000>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.<BR></FONT><BR>I realise that
this might be an oversimplified version of the real<BR>processes, but I am interested in what the experts have to say.<BR><BR>Best regards<BR><BR>Louise
Renton<BR>Bone Research Unit<BR>MRC<BR>Johannesburg<BR>South Africa<BR>Tel &
fax +27 11 717 2298<BR>"Time flies like an arrow, fruit flies like a
banana"<BR><BR><BR><BR>----Original Message Follows----<BR>From: " Katri
Tuomala" <katri@cogeco.ca><BR>To: "Kelly
Salceies"<BR><KSalceies@salud.unm.edu>,<Histonet@lists.utsouthwestern.edu><BR>Subject:
Re: [Histonet] Paraffin Embedding of Mice Tissue<BR>Date: Mon, 29 Sep 2003 20:03:35 -0400<BR><BR>Hi Kelly,<BR><BR>What is your fixative for these mice
tissues and how long? How big (read<BR>thick) are your sections to be
processed?<BR>These two things will determine your routine processing
protocol.<BR>I'm not familiar with microwave processing, so I won't comment on
that.<BR>If the tissue is well fixed, there really isn't a chance to "over process"<BR>it. The problems arise with inadequate fixation, which then leads
to<BR>alcohols and xylene drying out the tissue, and hot paraffin then
causes<BR>further damage.<BR>Just something to think
about....<BR><BR>Katri<BR><BR>Katri Tuomala<BR>Anatomic Pathology<BR>St.Joseph's
Health Care<BR>Hamilton, Ontaorio, Canada<BR><BR><BR>----- Original Message -----<BR>From: "Kelly Salceies" <KSalceies@salud.unm.edu><BR>To:
<Histonet@lists.utsouthwestern.edu><BR>Sent: Monday, September 29, 2003
10:01 AM<BR>Subject: [Histonet] Paraffin Embedding of Mice
Tissue<BR><BR><BR> > Hi Everyone,<BR> ><BR> > I am a
brand new Tech and am having trouble preping some mouse tissue<BR> > for
paraffin embedding. I have all different tissues (liver, heart,<BR> >
quads, brain, lung, and gastroc) and would like to prep all tissues
(if<BR> > possible) under the same conditions. I have been using
the Shandon<BR> > Hypercenter XP or the Shandon Histowave (microwave
tissue processor...).<BR> > Does anybody have a good protocol for mouse
tissues on either of these<BR> > instruments?? I have tried a number of
protocols, but all my tissue has<BR> > been really dry in
cutting...<BR> ><BR> > Any suggestions would be greatly
appreciated!!<BR> ><BR> ><BR> >
Thanks,<BR> ><BR> > Kelly Salceies<BR> > University of
New Mexico<BR> > Health Sciences Center<BR> > Dept. of
Pathology<BR> ><BR> >
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