Uranium nitrate (uranyl nitrate) is used in a few histologic stains, in 
particular silver impregnation stains, including a recently discussed stain 
for Helicobacter. Questions are often raised about its radiotoxicity and 
chemical toxicity. A recent editorial in The Lancet is informative.

Toxicity of depleted uranium - by N.D. Priest (School of Health, Biological 
and Environmental Sciences, Middlesex University, London N11 2NQ, UK - 
n.priest@mdx.ac.uk) The Lancet 27 Jan 2001; 357: 244-6. (I suppose it's on 
the Web, but I've got a paper copy.)

Priest describes depleted uranium as uranium from which 70-80% of the highly 
radioactive U-235 and U-234 have been removed. Depleted uranium has come into 
commercial use in several settings, including X-ray shielding in hospitals, 
but it has recently gained notoriety because of its use in armor-piercing 
munitions in the former Yugoslavia (and in fact earlier, in the Gulf War).

Of histologic interest is the statement that "Depleted uranium has replaced 
uranium of 
natural isotopic composition as a less radioactive substitute for some uses - 
e.g., laboratory chemicals." Is this substitution stated on labels? I don't 
have a recent label to check. - The substitution is not sufficient to affect 
computations at the level of precision needed in histologic work.

Priest's review suggests that the need for chemical or radiologic precautions 
with handling uranyl salts is not very great from a practical viewpoint - 
though what keeps the Herrn Inschpektors happy is another question.

(Parenthetically, some bottles of lithium carbonate note that the lithium has 
been depleted of lithium 6 - used in making tritium for hydrogen bombs - and 
this substitution might actually be of soposition.)

I've cross posted this note to the pathologists' PATHO-L list and to the 
histologists' Histonet.

Bob Richmond
Samurai Pathologist
Knoxville TN