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

From:"Mikael Niku"

Hello again!

I don't have ANY scientific proof whatsoever of the difference between 10%
formalin and 4% formaldehyde made from PFA. It's just something I think I
have noticed in the lab, clearly enough to make me wonder. But you are right
that the fixation protocols were never specifically controlled to allow real
comparison, so maybe it indeed was some other factor. 

I grew in a developmental biology group and first learnt to use "PFA", and
eventually started to wonder why some use it and some use formalin (often
being the same person, for different applications!). Maybe I should really
investigate it some day. 

With best regards, Mikael

 Mikael Niku, PhD, university lecturer            
 University of Helsinki, Division of Nutrition

 - What do I think of western civilization?
   I think it would be a good idea!                       
-----Original Message-----
From: Tony Henwood [] 
Sent: 22. elokuuta 2008 2:17
To: Mikael Niku;
Subject: RE: [Histonet] (para)formaldehyde (was: in situ question)

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.


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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