RE: [Histonet] NFB vs. Paraformaldehyde

From:"Favara, Cynthia (NIH/NIAID)"

To All,

I also work with many different researchers and they all have their own idea
as to what fixative should be used.

My solution:

I provide NBF freshly made from 37% formaldehyde if requested. I make small
quantities as that seems to be to most researchers liking. I have a SOP for
paraformaldehyde if a researcher chooses to go to the trouble. I know very
few of them take the time to make this properly and you can only imagine the
variation. I do not make paraformaldehyde because I have never been able to
convince myself it makes any difference for the stains I do. Most of the
staining variability I see is a result of a researcher insisting on their
own brand of fixative without any normal controls fixed and processed the
same way.

Just some ramblings! Creative procrastination!

Cynthia Favara
903 South 4th Street
Hamilton, MT 59840

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-----Original Message-----
From: Barry R Rittman [] 
Sent: Tuesday, November 09, 2004 10:41 AM
To: histonet
Subject: RE: [Histonet] NFB vs. Paraformaldehyde

Actually not to detract from the references below but a lot of the work in
this area was carried out by Karlsson and Schultze in 1965. They were
working with different fixatives for studying the electron microscopy of the
brain and found that indeed the buffer made a significant difference to the
final image. They also compared immersion via perfusion fixation.

-----Original Message-----
[] On Behalf Of Morken, Tim
- Labvision
Sent: Tuesday, November 09, 2004 10:42 AM
To: '';
Subject: RE: [Histonet] NFB vs. Paraformaldehyde


Way back in 1973 (ref below) Frieda Carson showed that when comparing
quality of fixation between formaldehyde and paraformaldehyde, the buffer is
the critical factor, not the source of the formalin.

Paraformaldehyde is the solid form of formaldehyde. Once dissolved in water
there is no difference between formalin from formaldehyde gas dissolved in
water (what most of us use) and formalin made from paraformaldehyde.
commercial formalin has methanol included to prevent polymerization of the
formaldehyde, that does not affect the fixative properties. 

So, in short,  it would be much better to have the students pay attention to
the buffers that are used than the source of the formalin. Of course, making
the formalin will be much easier with concentrate than having to dissolve

In fact, a good class experiment would be to compare the two with the same

Carson, FL, Lynn JA, Martin JN: Formalin fixation for electron
microscopy: A
re-evaluation. Am J Clin Pathol 59:365, 1973.

Carson FL, Lynn JA, Martin JN: Ultrastuctural effect of various buffers,
osmolality, and temperature on paraformaldehyde fixation of the formed
elements of blood and bone marrow.  Texas Rep Miol Med 30: 125, 1972

Tim Morken
Lab Vision - Neomarkers

Free webhosting for US State Histotechnology Societies:

-----Original Message-----

Sent: Tuesday, November 09, 2004 6:51 AM
Subject: [Histonet] NFB vs. Paraformaldehyde

Good Morning Histonetters,

I would like to get an idea from those histotechs that work with mouse
tissue if they prefer NFB or Paraformaldehyde as a fixative for routine

I work for a group of 6 researchers, most of who do mouse work.   Their
do the necropsies, remove and block the tissue, make up their own
paraformaldehyde, fix and submit the cassettes to me from processing and

I would like everyone to change to NFB to standarize the fixation.  I can
guarentee that no one makes Paraformaldehyde the same.  Some make it the
same day, some the day before, 2-3 days before  etc.

I am meeting with the big bosses this afternoon and would like some
ammunition if possible.

Thanks for the assistance.


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