[Histonet] NFB vs. Paraformaldehyde

[Morken, Tim - Labvision]

Jo-Ann,

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. While
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
paraformaldehyde. 

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

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
www.labvision.com

Free webhosting for US State Histotechnology Societies:
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-----Original Message-----
From: jo-ann-e.bader <@t> staff.mcgill.ca [mailto:jo-ann-e.bader <@t> staff.mcgill.ca]

Sent: Tuesday, November 09, 2004 6:51 AM
To: histonet <@t> lists.utsouthwestern.edu
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
histology.

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

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.

Jo-Ann

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