[Histonet] congo red featuring thioflavin-S

[Bryan Hewlett]

While fluorescence of Thioflavine-T(NOT Thioflavine-S) can provide a high 
contrast for demonstration of small amyloid deposits,
providing that the excitation/barrier filter set is optimized to obtain a 
fully dark field, the staining per se is not specific for amyloid (other 
basophilic structures can stain even at low pH).
Neither is Congo red however, the dichroism and green/red birefringence is 
specific for B pleated sheets.
A carefully optimized polarization microscope, using a monocular head with 
stress free optics (no tape coverslips!!) to provide a completely dark 
field,
is incredibly sensitive and will reveal even fine reticular fibers coated 
with amyloid.
A literature search will provide several papers comparing the two methods 
(check Burns 1967, Mowry&Scott 1967, Puchler 1983).

Bryan


----- Original Message ----- 
From: "Rene J Buesa" <rjbuesa <@t> yahoo.com>
To: "Delatour Benoît" <benoit.delatour <@t> ibaic.u-psud.fr>; 
<histonet <@t> lists.utsouthwestern.edu>
Sent: Tuesday, October 10, 2006 1:11 PM
Subject: Re: [Histonet] congo red featuring thioflavin-S


> Neither would I, and you can add that thiflavin preparations will fade and 
> are not permanent, something to consider also when deciding on the 
> procedure.
>  René J.
>
> Delatour Benoît <benoit.delatour <@t> ibaic.u-psud.fr> wrote:
>
> Dear Histoneters,
>
> Does anyone knows the true difference (in terms of 
> specificity/sensitivity)
> between Congo red and Thioflavin stains for amyloid deposits (eg Abeta
> plaques in the brain of Alzheimer's patients or genetically-modified mice
> that develop cerebral amyloidosis). In a recent publication I used Congo
> red to quantify agregated Abeta deposits but one of the reviewers claimed
> that thioflavin was, per sure, more efficient "to provide high contrast to
> detect even the smallest plaques". From my personal experience I would not
> share the same conclusions. Has anyone has a bibliographic reference
> dealing with differences between the two stains?
> Thanks!
>
> Benoît
>
>
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