To Histonetters,
I thought It would be useful to post the message sent to me on the Histonet
where this discussion started.
I do not have information at the moment about preons in our filter system,
but I will make every effort to get the answer.
Bernice
schiller@instrumedics.com

Dear Bernice,

Thanks for sending the very informative reply regarding the above subject
to the Histonette.  You seem to have researched this problem thoroughly and
come up with a good system.  It is an area I have been concerned with for
some time and have not been able to obtain any clear cut information on it
despite a couple of previous requests to the Histonette.  I work for the
Medical Devices Agency here in the UK and it is my job to evaluate, report
and either recommend or not histology and cytology instruments for our
National Health Service.  Vacuum systems on cryostats are not common in the
UK and I was concerned regarding their safety should they become available
on the market place here.

Have you done any research into their suitability for filtering out prions
in relation to mad cow disease?

Best regards,

Jim

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At 12:24 23/08/99 -0400, you wrote:
>Dear Histonetters,
>Several people have raised questions of concern about the safety of
cryostat
>vacuum systems. Instrumedics had the very same concerns when it developed
>the Cryo-Vac-Away vacuum system for the cryostat. The Cryo-Vac-Away had a
>nozzle at the blockface which suctions away trimming debris AS IT IS
>GENERATED. It passes through a closed system and is finally captured in the
>primary filter canister that contain both a fine and coarse filter medium.
>The trimming debris is contained in the primary filter. Since the filter
>canister is inside the cryostat the trimming debris freeze dries over time
>which reduces the volume of the debris and keeps it porous and  prevents
>clogging the filter. This makes it possible to maintain the air flow.
>
>However, because we were concerned about the possibility that viral and
>bacterial particles  might escape the trimming debris, a viral/bacterial
>filter is installed  downstream of the primary filter. The manufacturer of
>the filter material offers the following specs:
>Bacterial Filter Efficiency (BF): 99.999+%
>Viral Filtration Efficiency(FE): 99.99+%
>
>With that Cryo-Vac-Away installed the cryostat remains virtually spotless
>and the operator does not have work all day with possibly infectious
>trimming inside the chamber!
>
>We recognize that the system does not provide 100% protection, but we feel
>is goes a very long way to reducing the biohazards associated with
>sectioning infectious material.
>
>If you are interested please contact us for more information.
>
>Bernice
>schiller@instrumedics.com
>
>