Bernice -
Although your point was not in reply to my previous contribution to this 
discussion, it does impinge on it.
I had described requirements essential to achieve vitrification: glasslike 
freezing without ice-crystals. This methods is essential for high resolution 
TEM and would be preferable for much light microscopy.
For SEM and some light microscopy a slower freezing method which results in 
some fine crystals is often acceptable and very commonly practiced.

Now to your point: A cryoprotectant which only surrounds and not infiltrates 
the specimen can only be useful for the second method, since such a medium 
contributes to the bulk of the specimen and does not lower the freezing point 
of the specimen itself. To be effective during vitrification the cryoprotectant 
must infiltrate the specimen.
Cheers
Jim Darley
ProSciTech                 Microscopy PLUS
PO Box 111, Thuringowa  QLD  4817  Australia
Ph +61 7 4774 0370  Fax:+61 7 4789 2313  service@proscitech.com.au
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                      www.proscitech.com.au

On Saturday, July 03, 1999 1:19 AM, Instrumedics, Inc. 
[SMTP:info@instrumedics.com] wrote:
> It has been suggested that the CryoGel embedding medium has cryoprotectant
> properties. If true It might be useful for freezing muscle
>
> We have had success freezing muscle using the Gentle Jane method. The
> freezing is very rapid
> (8-10 sec.) The heat extractor  stored in LN2 is equilibrated to -196C.  In
> addition the heat extractor is 3/4lb with a mirror finish providing good
> thermal exchange. The combination leads to the formation of amorphous ice,
> minimizing ice-crystal artifact.
>
> Bernice
> schiller@instrumedics.com
>