[Histonet] why do we use xylene? was - Peloris Processor and
barbara.bublava <@t> meduniwien.ac.at
Fri Apr 6 00:53:58 CDT 2007
Dear Histonetters, Hallo Gudrun,
In 1968 Romeis (german book about Microscopic Techiniques) named
Isopropanol as an Intermedium when used at 56°C.
In a later edition ( I dont have it by hand right now) he once more
mentions the potential of Isopropanol.
Searching Histonet archives or Google also gives some results
One protocol suggested isopropanol with 50°C at the last
change and then going directly to paraffin. I did try that and neither
me nor my pathologist could see differences to usual xylene processing
(on autopsy material; HE, Trichrome; Chloroacetate Esterase, Prussian Blue).
For me it sounds too good to be true. I am afraid of missing something
important because IF it is that easy - why do we all use hazardous
xylene or expensive and smelly substitutes on our processors?
Maybe someone out there can tell us why isopropanol isn´t the
intermedium of choice?
Dep. of Forensic Medicine
Gudrun Lang wrote:
> Yes, I've been told, that it works. But what is the histochemical background?
> Proper fixed tissue would'nt suffer too much from high temperatures, I think. What is about too thick, underfixed tissue? Wouldn't it become hard and tough, difficult to cut? What about shrinkage?
> What about collagen-rich tissue? I don't want to produce glue.
> Is the whole process sensitiv to the duration in the high temp.? What is the recommandation for the maximum duration in 80 degrees?
> What are the critical points?
> Many questions, I know. But I don't like black boxes.
> Gudrun Lang
> Biomed. Analytikerin
> Akh Linz
> Krankenhausstr. 9
> 4020 Linz
> -----Ursprüngliche Nachricht-----
> Von: Phil McArdle [mailto:pmcardle <@t> ebsciences.com]
> Gesendet: Montag, 02. April 2007 20:30
> An: gu.lang <@t> gmx.at
> Cc: histonet <@t> lists.utsouthwestern.edu
> Betreff: Re: AW: [Histonet] Peloris Processor and isopropanol
> I'm with a laboratory microwave vendor:
> Never mind 74˚ C - some microwave protocols call for temperatures as
> high as 82˚ or 84˚ C (!) in order to exceed the boiling point of
> isopropanol, facilitating its replacement with paraffin. Naturally, this
> caused some concern and resistance in the anatomic pathology community.
> However, look at your own question about IHC: when you consider antigen
> retrieval protocols call for 100˚C, even 84˚ pales by comparison. Of
> course, there are many reasons you want to minimize the amount of time
> spent at high temperatures, but there is no problem with the majority of
> tissue types for the relatively short timeframes involved in microwave
> Also, by the paraffin step, the tissue has already been fixed,
> dehydrated, and defatted; while it is in a sense still "tissue," it's
> radically different from the tissue as received. You certainly don’t
> want to burn or "cook" anything, but 82°C isn’t really extreme in this
> context. (I'd be at least as concerned about how a given paraffin and
> additives hold up at high temperatures, so it's always a good idea to
> check with the manufacturer.) There also is the issue of vacuum; since
> the purpose of high temperature is to get above the boiling point of
> isopropanol, and vacuum causes BP depression, vacuum should allow you to
> lower the temperature to something you're more comfortable with.
> More information may be found at
> Very best regards,
> Phil McArdle
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