[Histonet] (para)formaldehyde (was: in situ question)

[Tony Henwood]

Why would it be different?
I am intrigued as to why IPX and ISH would reaxct differently in tissues
fixed in either.
Do you have any references?
Or please write up your results and publish them (J Histotechnology or
Biotechnic & Histochem are definitely worth considering).

Often there will be differences but my experience indicates that it is
often due to the fixation time. 10% buffered formalin is usually used at
room temp, overnight at least, where as researchers for some reason
often use 4% formaldehyde (made from polyformaldehyde) at 4oC for only a
few hours at best. So often fixation occurs in the ethanols in
processing.
For valid comparisons fixation conditions must be standardised.

Regards

Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC)
Laboratory Manager & Senior Scientist
Tel: 612 9845 3306
Fax: 612 9845 3318
the children's hospital at westmead 
Cnr Hawkesbury Road and Hainsworth Street, Westmead 
Locked Bag 4001, Westmead NSW 2145 




-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Mikael
Niku
Sent: Thursday, 21 August 2008 6:50 PM
To: histonet <@t> lists.utsouthwestern.edu
Subject: RE: [Histonet] (para)formaldehyde (was: in situ question)


This has probably been discussed 1000s of times, but....

I'm wondering to what extent dissolved paraformaldehyde really is
equivalent to 4% formaldehyde or 10% formalin. In my experience, samples
fixed in formalin and "4% PFA" as we tend to say are different when one
does immunostaining or especially in situ hybridization. Formalin is of
course traditionally used in pathology, whereas many labs doing immunos
or ISH use "PFA".

But what really causes the differences? Is it incomplete
de-polymerization of paraformaldehyde, or perhaps the methanol typically
included in formalin?

-----------------------------------------------------
 Mikael Niku, PhD, university lecturer            
 University of Helsinki, Division of Nutrition
 URL: mikael.nikunnakki.info

 - What do I think of western civilization?
   I think it would be a good idea!                       
                                            Gandhi
-----------------------------------------------------
-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Tony
Henwood
Sent: 20. elokuuta 2008 4:42
To: Lee Crosby; histonet <@t> lists.utsouthwestern.edu
Subject: RE: [Histonet] in situ question

Which the becomes 4% formaldehyde or equivalent to 10% formalin. Not 4%
paraformaldehyde.

Regards

Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC) Laboratory
Manager & Senior Scientist
Tel: 612 9845 3306
Fax: 612 9845 3318
the children's hospital at westmead
Cnr Hawkesbury Road and Hainsworth Street, Westmead Locked Bag 4001,
Westmead NSW 2145 


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