MeOH form & paraform

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This is obviously an important question. Many folks think that methanol
does matter for EM, and since many of the people I've worked with believe
this, and are very good, I tend to be in the "use paraformaldehyde" camp.
But! testing is what matters.

The commercial formaldehyde I used contains 15% MeOH. Whether that extra
0.5% matters, I don't know. But the problem wasn't MeOH's toxicity, but
that it distorts -- "crinkles" --  cells, and renders them useless for

Freida Carson's article is obviously important, but it's curious that it
was published in 1973, yet the EM community still uses paraformaldehyde
instead of commercial formaldehyde. Good workers, who are critical of
techniques, including theirs. Is this a case of an ignored publication
(perhaps because of the journal?) or what?


>  Does the methanol really make all that difference? Conc. formalin
>  contains about 10%, so there's only 1% in NBF. Back in 1968 or so,
>  I remember seeing some pretty good EM pictures of human thyroid
>  that had been surgically removed and had sat in NBF for some time.
>  It was then osmicated etc. The work was done by my PhD supervisor,
>  the late Brian A. Young, in Birmingham (UK) and a student called
>  David Kill, who went on to become a dentist. I'm pretty sure they
>  published it - almost certainly in J. Anat. They also examined
>  bits of thyroid fixed in glutaraldehyde and in Karnovsky-type
>  mixtures, which were better, but not impressively so.
>  *** Has anyone done a severe comparison of 4% formaldehyde made from
>  formalin vs paraformaldehyde, for EM or LM?  There are lots of
>  anecdotes; mine is that I can't tell the difference for several
>  LM applications. Others will surely disagree, but is this because
>  of having made a controlled comparison?
>  1% methanol might well be toxic to living (cultured) cells, but
>  that's hardly a fault in a fixative. 1% ethanol would be below
>  physiological levels; beer is 4% to 5%.
> John A. Kiernan,
> Department of Anatomy & Cell Biology,
> The University of Western Ontario,
> LONDON,  Canada  N6A 5C1

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