Question.

What is the Gallyas Stain, and what is it for?

Answer.

Ferenc Gallyas, in Hungary, has been studying and inventing silver stains for at least 30 years. They all involve the use of "physical developers" (an ancient and obsolete term from photography). A physical developer is a mixture containing silver ions and a reducing agent, made stable for several minutes or even a few hours by other additives. Gallyas introduced silicotungstic acid as a stabilizer. Earlier physical developers used gum arabic, gum mastic, albumen, albumin (no, they aren't the same) and other organic macromolecules.

The name of Gallyas is most often connected with his methods for Alzheimer's neurofibrillary tangles because neuropathologists are, by noble tradition, the biggest users of silver staining. However, there are several other silver staining methods, for a range of tissue components, developed by Gallyas. His work probably forms the rarely acknowledged basis of immunogold-silver amplification for light microscopy and for some of the silver methods used to detect minute amounts of protein in Western blots.

Physical development was discovered, for photography and histology, by Liesegang (1911), and reintroduced to histological practice in 1955 by Alan Peters, who went on to become a great authority on the ultrastructure of nervous tissue, especially that of the cerebral cortex.

I don't know if this really answers the question, but it's interesting to look at the way someone's name gets attached to a method, even if at first there's doubt about _which_ method.

John Kiernan
London, Canada.
(kiernan[AT]uwo.ca)