[Histonet] Re: Modified Mowry (Long discussion)

[GUTIERREZ, JUAN]

I believe she's referring to 3% Acetic acid.

	-----Original Message----- 
	From: John Kiernan [mailto:jkiernan <@t> uwo.ca] 
	Sent: Tue 9/30/2003 11:32 PM 
	To: Jeannie Heck; Histonet Listserver 
	Cc: 
	Subject: [Histonet] Re: Modified Mowry (Long discussion)
	
	

	gJeannie Heck wrote:
	>
	> I would deeply appreciate a procedure for a modified
	> Mowry Colloidal Iron using 3% as a mordant before the
	> colloidal iron stain. I am currently using the Muller
	> Mowry and I am getting inconsistent results. All help
	> is appreciated. Please post to this list or e-mail me
	> directly at heckj <@t> hhosp.com. Thanks in advance.
	> Jeannie Heck HT (ASCP)
	___________________________________________________
	
	3% what? Nothing in any colloidal iron method involves
	mordanting, because no dye is involved (except as a
	counterstain, which might include a mordant as in
	the case of aluminium-nuclear fast red or brazalum).
	
	Mowry's technique is a modification of Hale's original,
	which wasn't much good. Pearse's Histochemistry reviews
	the various colloidal iron methods. It is the best
	reference, and has been translated into several
	languages.
	
	Is there any reason for using colloidal iron
	instead of an equivalent alcian blue method?
	
	Alcian blue techniques are more reproducible
	and have greater histochemical validity. Certified
	dye is available (tested in the Biological Stain
	Commission's lab, which is a non-profit outfit that
	serves both vendors and users of stains). The solid
	dye powder can deteriorate on the shelf, very
	unpredictably (I've had this happen 3 times). The
	deteriorated dye is insoluble; I have suspicions
	about why. Solutions of alcian blue at pH1 or
	pH3 keep working for a long time (a few years) even
	with repeated use. Alcian blue has its faults, but
	it's a better histochemical reagent than colloidal
	iron.
	
	There are several clever PAS variants developed by
	Scott et al in Britain and by Reid, Culling et al in
	Canada, from the late 1960s to the early 1990s. These
	methods have numerous steps but they stain
	macromolecular carbohydrates with well defined
	chemical specificity. These splendid methods are
	respectfully explained in textbooks but I suspect
	that they are seldom used in labs.
	
	There are also dozens of labeled lectins, which have
	high specificity and have been commercially available
	for 20+ years. There may be a lectin that binds
	specifically to the macromolecular carbohydrate that
	you are trying to stain with colloidal iron. Lectin
	histochemistry is EASY++ but you must do all the
	needed controls or your spectacularly specific
	pictures might be worthless artifacts. Lectins are
	the plant kingdoms's equivalent of antibodies. They
	recognize sugars and oligosaccharide sequences
	rather than the amino acid sequences (epitopes)
	that adhere to antibody molecules.
	--
	-------------------------
	John A. Kiernan
	Department of Anatomy and Cell Biology
	The University of Western Ontario
	London,   Canada   N6A 5C1
	   kiernan <@t> uwo.ca
	   http://publish.uwo.ca/~jkiernan/
	
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