Re: MSB Trichrome stain.

From:Bryan Llewellyn <>

From: "J. A. Kiernan" <>

>    Lillie did experiments of this kind, and was
>   not impressed with the notion of PMA and PTA as "colourless acid dyes"
>   promoted by J.R.Baker. I think most other investigators would
>   disagree with Lillie on this one.
>   PTA (or PMA) attaches to collagen and displaces medium-size dye
>   anions (usually red) from it, but doesn't do the same for
>   cells (except for certain secretory granules). For reasons that
>   aren't glaringly obvious, PTA allows the largest dye anions of
>   the trichrome mixture (usually aniline blue or fast green FCF)
>   to bind fairly selectively to collagen.

I have always preferred Baker's explanation for this.

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.

I have always assumed from that method that a relatively large molecular
weight acid solution is all that is required.  In fact I remember reading
somewhere, sometime that any acid would do including acetic, citric etc,
although I have never checked it out.

Do you have any comments on this, John?

Bryan Llewellyn

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