Re: [Histonet] fixatives

From:Lesley Weston

If you're not interested in membrane, you can dehydrate small samples in a
water-miscible resin such as Aquembed from Ladd, rather than alcohols,
before embedding in epoxy. This preserves fat. If you do need to see the
membrane, OsO4 is your best bet (possibly as well as Aquembed) but be sure
to use it in a fume hood and with gloves. It's nasty stuff, and I would
agree that you shouldn't use it in a processor but that you can use it
safely if you're careful.

Lesley Weston.

on 28/08/2004 3:56 PM, Philip Oshel at wrote:

> Pam,
> There isn't a very good substitute for osmium tetroxide, but
> Maunsback and Aufzelius, "Biomedical Electron Microscopy" shows
> various fixitive alternatives, and is a good place to look. It is for
> TEM, though, and not light microscopy.
> DON'T use OsO4 in a tissue processor unless it is in a **very** well
> vented fume hood and will continue so. I wouldn't use OsO4 in a
> processor period, but there are processors for EM work that do use
> it. It can be used safely, though, so I wouldn't worry about having
> in the lab, just use it properly. It does do a reasonable job
> preserving fat, but it won't prevent extract in the dehydration
> steps, especially of the unsaturated fats -- OsO4 likes to bind to
> C=C double bonds, and isn't that great a fixative for unsaturated
> lipids. Cryostat sections and no dehydration would be better.
> K or NaMnO4 can work, and in the TEM it does a nice job of preserving
> membranes -- the cells can look like line drawings of the membrane
> systems. But this is because the cytoplasm is heavily extracted. Not
> what you want, I think.
> Sorry I can't help with the sections-stuck-to-coverslip-tape problem,
> I've only used glass.
> Phil
>> Hi all:  I know this has been asked before, is there a
>> quick fix for removing tissue from coverslipping tape,
>> reattaching to the slide, covering with a new glass
>> coverslip so the tissue can be photographed?  Also,
>> does anyone know a good alertnate fixative for osmium
>> tetroxide?  We are trying to keep it out of the lab.
>> We have been asked to use it for a post-fix for fatty
>> tissue and on an EM processor.  Thanks, Pam

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