Re: AL vs AA amyloid

From:Andrew Kennedy

Hi Jill,

We use an acidified permanganate solution as pretreatment for the Congo Red
stain to distinguish secondary amyloid (composed predominantly of protein
AA) from other forms.

2 control sections and 2 sections from test case are used - one control and
one test slide is kept in water until step 5.

1.     Acidified permanganate solution:
            0.25% sulphuric acid - 25 mL
            5% Potassium permanganate - 25 mL
2.    5% Oxalic Acid
3.    Congo Red in 50% EtOH
4.    0.2% KOH in 80% EtOH

1.    Take sections to water
2.    Place in acidified permanganate solution 2.5 to 3 mins
3.    Wash in water
4.    Clear in Oxalic acid
5.    Wash well in water
6.    Stain in Haematoxylin, differentiate and blue
7.    Wash well in water
8.    Stain in Congo Red - 15 min
9.    Differentiate in KOH - 10-15 sec
10.  Rinse in water, dehydrate, clear and mount

The secondary amyloid loses Congo Red affinity and polarisation

The reference quoted in our manual for this is: Wright et al, (1977). Lab
Invest 36(3); 274-281.

Hope this helps you out....

Andrew Kennedy

Senior Science Officer in charge - Histopathology.
Department of Anatomical Pathology
Concord Repatriation General Hospital
Hospital Road
Concord, NSW, Australia
Phone: +612 9767 6115
Fax: +612 9767 8427

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