[Histonet] Congo Red problems

[Wheelock, Timothy R.]

Hi All:

Lately, I have been having problems with my Congo Red staining too lightly.
The Bielschowsky silver stain shows lots of amyloid in the cerebral blood vessels and the cores of the senile plaques.
However,  the Congo Red stain is pretty faint, although you can still see it.
I have just bought a new bottle of Congo red from Sigma, in case it was the particular batch of dye.
My protocol, which I have always used, is as follows:

1. Deparaffinize sections and bring down to 95% ethanol
2. Stain in 1% Congo Red solution for 10 minutes.
3. Differentiate in Potassium Hydroxide solution; 3 dips
4. Rinse in 4-5 changes of tap water.
5. Counter-stain in Harris Hematoxylin for 1 minute.
6. Differentiate in Acid Alcohol; 10 dips or so.
7. Blue Hematoxylin in running tap water for 10 minutes.
8. 95% ethanol for only 3 dips, then right into absolute ethanol.
9. 20 dips in first absolute ethanol
10. 1 minute in absolute ethanol
11. Clear and mount.

Any suggestions would be really appreciated,

Tim Wheelock
Harvard Brain Bank
Mclean Hospital
Belmont, MA


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