Here are 3 references.
On Mon, 9 Jul 2001, Debra Dunlap wrote:
> when I meant 'fluorochrome" in my original message.  I am certainly
> interested in the references that you mentioned.  Thank you again,

The earliest use of OsO4 to quench autofluorescence (that
I know about) is: 
  Ornstein L, Mautner W, Davis BJ, Tamura R: New horizons in
fluorescence microscopy. Journal of the Mount Sinai Hospital 
24:1066-1078, 1957.
  They used 2% OsO4 with only a brief wash, but they were
using a tremendously powerful fluorochrome. I've done their
method (a fluorescent PAS variant, using acriflavine); you
can see some photomicrographs in J. Anat. 99:926-928.

For use of weaker OsO4 solutions and longer washes:
  Stoddart RW, Kiernan JA: Histochemical detection of the
`-D-arabinopyranoside configuration using fluorescent-labelled
concanavalin A. Histochemie 33:87-94, 1973.
[The ` in the title should be the greek letter alpha.]
  Kiernan JA, Stoddart RW: Fluorescent-labelled aprotinin: a 
new reagent for the histochemical detection of acid
mucosubstances. Histochemie 34:77-84, 1973.

----------------------------------------
John A. Kiernan
Department of Anatomy & Cell Biology
The University of Western Ontario
London,  Canada   N6A 5C1
   kiernan@uwo.ca
   http://publish.uwo.ca/~jkiernan