Re: congo red

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Rick Strogen wrote:
Yes. Any chance that these amyloids are from a LARGE deposit?

We have found that amyloid from large, old deposits seems to
not stain with the polarizing amyloid stains, such as
Congo red or toluidine blue. We think that the beta pleats
are "warped" in thes large old deposits, so the linear
polarizing stains can not fit into the beta pleats.

Any chance that the blood vessels contain amyloid, and
are displaying some birefringence under polarization?
The blood vessels may contain "newer" amyloid.

However, this same "warped" amyloid will stain with other
amyloid stains, because these other stains react differently
with the amyloid.

Crystal violet and methyl violet bind to the carboxyl ions
attached to the amyloid. Thioflavin T and Thioflavin S
bind to the P component attached to amyloid. Sulfonated
alcian blue is somewhat dependent upon the beta pleats,
so large, old deposits will stain a less intense green.

So sometimes it is better to do several types of stains
for amyloid.

Also, for your control, any chance that these were cut
a long time ago an have been setting around in the lab?
We have found that amyloid control slides seem to not
stain as well with the polarizing dyes if they have been
cut more than 6 months ago. ?Possibly due to the oxidation
of the beta pleats? is our best ?guess?. However, these
same controls will stain OK with the other types of
non-polarizing stains.

Or, is your control from another case of old large deposits?
Again, check the blood vessels, or use another stain.

Hope this helps.

> One of our pathologists wanted me to post this question:
> We have a spleen that is amyloid positive and crystal violet positive.
> Our Congo Red is negative.  All reagents are new and the control is also
> either negative or weak staining.  Does anyone out there have any ideas
> or help in this matter?
> Robin Strogen
> The Valley Hospital
> Ridgewood, NJ

Peggy A. Wenk, HTL (ASCP)
Anatomic Pathology
Wm. Beaumont Hospital
3601 W. 13 Mile Rd.
Royal Oak, MI 48073-6769

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