I'd like to add a bit to this good information from Ms. Callis. Using
osmium tetroxide for lipid staining is discussed in most any electron
microscopy text, since it's a standard EM "stain" (quotes because for EM,
OsO4 isn't staining lipids in the sense that a stain functions in light
microscopy).

Secondly, the best way to dispose of used osmium or osmium-containing
fluids, is to dump them into a tightly sealable jar of kitty litter or
vermiculite soaked with corn oil (or canola, as long as there's lots of
double bonds) and a few inches of the oil. Then give to the hazardous waste
people. Note: fumes will still escape from this, and the fumes are nasty.
Good way to fix your corneas, nasal mucosa, and the like. So put Parafilm
under (or over) the jar lid.

But. OsO4 binds mostly to double bonds in lipids, and it really isn't all
that good a stain for saturated lipids. It works, but not as well as some
or most traditional light microscopy lipid stains.

Phil

>There is one way to stain and get a permanent stain for soluble lipids in
>tissuse.  You postfix the tissue in osmium tetroxide, process and section.
>Osmium tetroxide is not fun to work with, however, requires a good fume hood,
>plus gloves, and should not be drain dumped (we can't, have to collect the
>heavy metal!)  However lipids are black, an H&E stain can be applied, sections
>dehydrated and coverslipped normally.  I knew one diagnostic lab who used this
>routinely, but the choice is whether you want to handle and use osmium
>tetroxide.  If interested I will dig the reference out of the J
>Histotechnology, many years back!
>
>Gayle Callis

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