[Histonet] Soaking paraffin blocks

[Kemlo Rogerson]

"What am I concerned with is the claim of poor processing - how does one
know that it is poor processing, particularly if you haven't seen the
blocks or attempted to cut them?  What is poor about it - insufficient
wax penetration, lack of dehydration?  Processing is essentially quite a
straight forward process and apart from varying timings in alcohols,
xylene and wax, I can't understand how it could go so wrong?!!  I have a
Leica TP1020 without vacuum and run overnight schedule based on what
I've read up - reagents are changed regularly always erring on the side
of caution.  

I am a self-taught histologist (and there may lay your accusations -
LOL) and have been "practicing" for over 5 years now, but I have only
learnt by reading up on what the experts say and do (including Histonet
- which I have found to be a fantastic tutor) and by practice.  I am
always keen to learn from my more experienced peers so please expand on
pharses such as "poor processing" and "poor fixation"."
Nicola

Poor fixation could mean not enough or too much fixation. Some fixatives
harden tissue when 'overexposed' some fixative take some time to
penetrate and to fix. Bluntly, IMHO, you can't process properly unless
you've fixed 'properly'. Fixation puts the tissue in the correct state
to resist the effects of processing and to allow the fluids to
penetrate. 

If the processing fluids are left on too long, tissue goes hard, too
little and water or alcohol isn't removed. If the tissue isn't clear in
xylene then it's not dehydrated, if it's not dehydrated then you won't
get the wax in properly, if you don't get the xylene out then you make
the wax and the tissue 'soggy'. Overprocess and you harden the tissue
(usually the heat from the wax) and you have to use reclamation
techniques such as ice/ water IMHO. You build a house from the
foundations up; fixation is your foundation without which nothing
underpins the processing.

What does your Company do in the UK?

Kemlo Rogerson
Pathology Manager
DD   01934 647057 or extension 3311
Mob 07749 754194; Pager 07659 597107;
Never does nature say one thing and wisdom another. --Juvenal 

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