RE: [Histonet] Microwave Processing

From:"Marshall Terry Dr, Consultant Histopathologist"

Kemlo asks:

"Am I talking a load of..........."

Inevitably:-)

Kemlo,

You talk as if formalin was the only fixative. What about the group called, oddly enough, coagulative fixatives? 
Now .... I wonder how they work. Let me see ......
Furthermore, you flit between the several different subjects in an unstructured way.

When you say :
"Its job is also that of preventing putrefaction both by endogenous and exogenous means
(lysosomes and bugs)."

You are wrong on 2 counts.
Its effect may be to prevent putrefaction, but hardly its job. (I realise that some books list this, but a dehydrated specimen in wax is more at risk from mice than bacteria).
Furthermore, the action you refer to, attributed to lysosomes, is autolysis, not putrefaction.

Furtherfurthermore, a fixed egg will only elude putrefaction by virtue of the retained/residual fixative fixing any bacteria with ungodly thoughts toward the egg, wouldn't it?
That is to say, "resistance to putrefaction" will be a property that resides in the fixative not in the fixed egg.

Yours lovingly, 

Confused from Rotherham

Dr Terry L Marshall, B.A.(Law), M.B.,Ch.B.,F.R.C.Path
 Consultant Pathologist
 Rotherham General Hospital
 South Yorkshire
 England
        terry.marshall@rothgen.nhs.uk

-----Original Message-----
From: Kemlo Rogerson [mailto:kemlo@tiscali.co.uk]
Sent: 21 April 2004 15:16
To: Marshall Terry Dr, Consultant Histopathologist; 'Steven E. Slap';
'kevin williams'; histonet@pathology.swmed.edu
Subject: RE: [Histonet] Microwave Processing


Um....... A boiled egg is stabilized but not fixed; does that help? A
fixative is designed not only to stabilize proteins by coagulation, but
in most cases it links chemically to the proteins. Its job is also that
of preventing putrefaction both by endogenous and exogenous means
(lysosomes and bugs). A boiled egg will rot by putrefaction, but if you
fixed it, then it wouldn't; would it? Heat stabilizes by coagulating
protein doesn't it, formalin forms links between reactive sites on the
proteins, doesn't it? 



Mr Kemlo Rogerson MSc DMS MIBiol CBiol FIBMS
Tel: 0208 970 8414
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-----Original Message-----
From: histonet-bounces@lists.utsouthwestern.edu
[mailto:histonet-bounces@lists.utsouthwestern.edu] On Behalf Of Marshall
Terry Dr,Consultant Histopathologist
Sent: 21 April 2004 12:48
To: Steven E. Slap; kevin williams; histonet@pathology.swmed.edu
Subject: RE: [Histonet] Microwave Processing

My confusion has not been dispelled.

Steven writes:

"The saline will not work 
alone as a fixation step, except in the case of 
very small biopsies (as written up in an article 
by Tony Leong)- ..." 

In the next post, we get:

"Yes, in the Leong method for biopsies, the specimens are heat 
stabilized in the microwave in saline, and not really chemically 
fixed.  They get fixed in the ethanol in a traditional processor ..."

These statements are mutually incompatible.

Moreover, what is the difference between "stabilisation" and "fixation".

A further muddle is introduced by:

"not really chemically fixed."

Well, hell, are they fixed or no? Heat fixation is fixation - who cares
whether chemically fixed?

Of course, the major problem is that mechanisms of fixation are varied
(with the fixative) and not well understood.
(Speak for yourself do I hear someone say?)

Dr Terry L Marshall, B.A.(Law), M.B.,Ch.B.,F.R.C.Path
 Consultant Pathologist
 Rotherham General Hospital
 South Yorkshire
 England
        terry.marshall@rothgen.nhs.uk

-----Original Message-----
From: Steven E. Slap [mailto:siksik03@comcast.net]
Sent: 17 April 2004 22:54
To: Marshall Terry Dr, Consultant Histopathologist; kevin williams;
histonet@pathology.swmed.edu
Subject: RE: [Histonet] Microwave Processing


Hi Terry & HistoNetters

I have done lots of successful large organ 
stabilization in saline at 65C for 20-35 minutes 
(depending on the size of the organ.  However, it 
is important to emphasize that the purpose of 
this step usually is to firm up the tissue so 
that it can be subsequently cut up into thinner 
pieces for processing, which must include a 
fixation step, either in the microwave or on a 
conventional processor, in formalin or some 
non-formalin fixative.  The saline will not work 
alone as a fixation step, except in the case of 
very small biopsies (as written up in an article 
by Tony Leong)-  a procedure I have not tried 
myself.

best regards,
Steven Slap
Microwave Consultant


At 3:58 PM +0100 4/16/04, Marshall Terry Dr,
	Consultant Histopathologist wrote:
>Sorry to but in - but on a related question - 
>does anyone do microwave fixation in saline as 
>described by for instance the Melbourne group, 
>which involves bringing up to 65C in saline?
>Have tried it this week and the sections are even crummier than usual.
>When I was in Tasmania, a local private lab. did 
>it and their sections were fine.


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