First, this is a thoery that explains the observable results, but I am not 
sure it has ever been proven formally.

The word "dense" in this context can heve two different meanings, and it is 
possible that your difficulty is related to that.

Meaning 1:  (Chemical) More foci at which the dye can attach in an amount of 
stainable material, i.e. more strongly acidophil.

Meaning 2:  (Physical) More stainable material contained in a given space.

In addition there is the question of "permeability", i.e. whether there is a 
barrier of some kind (lipid, cell membrane).

With meaning 1, the dye will take longer to be replaced because there is 
more of it in an equal amount of material.

In meaning 2, the dye has less accessiblity but when it does stain the 
polyacids will have the same accessibility problem or may be too large to 
gain access to remove it.  Sometimes it is so physically dense it does not 
stain at all.

A given structure could also be "dense" in both meanings.

Fibrin is generally considered dense in the chemical meaning and tendon in 
the physical.
Cytoplasm is thought of as less chemically dense than fibrin.

It is covered in some detail on StainsFile at the URLs below.  Follow all 
the links in the second one, about trichrome staining.  It may help to use 
the BabelFish translator below the adverts on the right hand side.  The 
translation is not perfect, but reading the translation and the English may 
help.

http://stainsfile.info/StainsFile/theory/massact.htm
http://stainsfile.info/StainsFile/theory/tri_gen.htm

Bryan Llewellyn


----- Original Message ----- 
From: "Gudrun Lang" 
To: "Histonetliste (Histonetliste)" 
Sent: Saturday, November 11, 2006 12:17 PM
Subject: [Histonet] fixation-density


> Hi all,
>
> I'm still dealing with trichrome staining. There is the theory of
> diffusion-ratio of smaller and bigger dyes. I have a problem of
> understanding:
>
> Why is the fixed cytoplasma, formerly filled with more or less soluble
> proteins beside the cytokeratins, more dense than the fibrillar and 
> twisted
> collagenfibers. Are the spaces between the helices bigger than the mesh of
> the crosslinked proteins? There is much water in a cell (yes?) and the
> proteins are sticked together through fixation.
>
> Can someone bring light into my darkness?
>
>
>
> Gudrun Lang
>
>
>
> Histo-BMA
>
> Linz, Austria
>
>
>
> _______________________________________________
> Histonet mailing list
> Histonet@lists.utsouthwestern.edu
> http://lists.utsouthwestern.edu/mailman/listinfo/histonet
> 


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