On Thu, 2 Aug 2001, Dalefield, Rosalind wrote:

> Can anyone suggest something that will permanently stain keratin?
> This is actually for keratin in the living animal; I want to mark ...
> ... hooves of Merino sheep so I can track rate of hoof growth.

If this means something to draw a line that won't wash off,
on the outside of the hoof, then here are some suggestions.
I'm assuming you need a thinnish (0.5-1.0 mm) line that can
be applied from a fine brush or very thin glass tube.

1. Silver nitrate. Use a strong solution (10% at least). If
   it dries before a black mark develops, cover it with
   varnish, to prevent difusion of unreduced silver ions
   by water.
2. Scribe grooves in the hooves (yes, I know that's not quite
   write, but it sownds OK), apply a bit of some permanent
   pigment such as Indian ink or house paint, wipe off the
   stuff that hasn't lodged in the groove, and cover the
   area with some transparent varnish.
3. This is if you've _must_ be histochemical. Place a line
   of acidified potassium permanganate solution to mark
   the current level of hoof-keratin; wash it off and then
   apply an alcian blue solution, which will bind to
   cysteic acid formed by oxidation of cystine. Wash in
   water, and then treat briefly with ammonia-water to
   ensure that all the alcian blue is changed to completely
   insoluble copper phthalocyanine. If you seriously
   consider this option, consult a psychiatrist before
   asking by email for detailed technical instructions
   from people you don't know.   

You will get many answers to your unusual and interesting 
query. Please tell Histonet what you eventualy decide is
the best answer.
----------------------------------------
John A. Kiernan
Department of Anatomy & Cell Biology
The University of Western Ontario
London,  Canada   N6A 5C