Re: MSB Trichrome stain.
|From:||"J. A. Kiernan" <firstname.lastname@example.org>|
On Mon, 25 Sep 2000, Bryan Llewellyn wrote:
> There is often an assumption that the tungsten or molybdenum is the culprit,
> although I note you did not say that. In one of his numerous Picro-Mallory
> stains for fibrin (IV, I think) Lendrum used a solution of trichloroacetic
> acid instead of PTA. Results were perfectly satisfactory as I recall.
> ... In fact I remember reading
> somewhere, sometime that any acid would do ...
> Do you have any comments on this, John?
Lillie maintained that the separation of cytoplasmic from
collagen staining could be achieved by low pH alone. He
didn't seem to like trichromes much, especially those with
critical differentiations such as AZAN. He favoured variants
on the van Gieson theme and developed some good methods,
including picro-aniline blue and its "allochrome" combination
with PAS. These are all technically simple and are described
and discussed in "Histopathologic Technic" as well as in
Lillie's many papers.
You certainly cannot replace PTA/PMA with "any acid" in
Heidenhain's AZAN where it's used alone, not mixed with
dyes, to displace the last of the red colour from collagen.
Lillie was well aware of the binding of PMA by collagen
fibres, which is easily demonstrable by reducing to insoluble
molybdenum blue (e.g. with SnCl2). This binding is, in fact,
visible even without making a coloured product. There is
an obvious change in refractility (if that's a word) in
collagen in a section that has been immersed in PTA or PMA.
The most recent mechanistic papers I've seen on connective tissue
staining are by P. Prento (1993) Histochemistry 99:163-174 and
the late P. Reid et al. (1993) Histochem. J. 25:821-829.
Reid came down on the side of a Baker-type explanation,
corresponding to Horobin's rate-controlled and affinity-controlled
general mechanisms of staining, with the molecular weight of
the dyes as an important factor. Prento's approach was different,
and was confined to Van Gieson's picro-fuchsine. He concluded
that picric acid attached principally to hydrophobic sites in
cytoplasm and that hydrogen bonding was important in the binding
of acid fuchsine to collagen. Both papers are well worth reading
because they contain much intelligent discussion.
John A. Kiernan,
Department of Anatomy & Cell Biology,
The University of Western Ontario,
LONDON, Canada N6A 5C1
Phone: (519) 661-2111
FAX (Department): (519) 661-3936
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