[Histonet] tissue fixation-formaldehyde concentrations which is best.

[John Kiernan]

 Dear Peter, 
 
Some of the information you mention as "anecdotal" is wrong. Formaldehyde and paraformaldehyde are well documented in original peer-reviewed papers and in all textbooks in the fields of histotechnology and histochemistry.  
 
Your anecdote about "high concentrations of formaldehyde quickly form a 'shell' in the tissue and will stop good penetration and fixation to the deeper tissues" has no basis in published work.  Paraformaldehyde is an insoluble polymer, not "non polymerized formaldehyde".  There is no such thing as "4% paraformaldehyde"! 
 
It is a sad fact that many labs do not contain even one book about histotechnology. Nearly all books in the field (and there are many) have plenty of references to review articles and original literature about the techniques. There are also several websites that provide links to useful papers.  Check out some of the "useful links" on the Biological Stain Commission's site:  http://biologicalstaincommission.org/useful-links/  
 
As a graduate student, you  need to  work from primary sources or reliable secondary sources. When you defend your thesis, you won't want to justify your fixation or staining method by saying "I got the method by asking on an internet listserver". 
 
John Kiernan
Professor Emeritus
Anatomy & Cell Biology
University of Western Ontario
London,Canada
= = = 

On 05/06/15, Peter Noyce <pwnoyce at gmail.com> wrote: 
>  Formaldehyde 37% (commonly called 100% formalin) compared to 4% ( commonly
> known as 10% neutral buffered formalin)-in theory the 37% should fix quicker
> and better BUT anecdotally it is said that high concentrations of
> formaldehyde quickly form a "shell" in the tissue and will stop good
> penetration and fixation to the deeper tissues AND over the years it has
> been said anecdotally that 4%  concentration is the quickest and most
> complete for all sample (mammal and plant) fixation and preservation-are
> these true. Please do discuss the methanol or buffers that is in the
> formaldehyde, or discuss paraformaldehyde (which is non polymerized
> formaldehyde with no methanol, in water).
> 
> Regards Peter Noyce PhD student.
> 
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