If one does not have a sliding microtome, then you can rig a rotary
microtome to make it work. One of the problems with large blocks is to get
total clearance of the whole block face past the knife - during sectioning.
You can, with a bit of ingenuity, and using a rotary microtome, a universal
knife holder and a c profile square back steel knife make this type of large
block sectioning possible.
You need to raise the blade so it sits higher in the knife holder, and that
can be achieved by using two diamond pens that are hexagonal (?) in shape -
the diamond pencils we used to label plain glass slides. By stacking one
diamond pencil on top of the other so flat sides from each pen touch in the
middle,you place the knife on top of the upper pencil. The metal pencils are
very sturdy and help prevent chatter. Then as you section, the block face
clears the knife edge, so a ribbon can form. I have seen this done on an
old AO 820 rotary microtome, and it should work as long as one has the
universal knife holder, pens and a c profile knife. I am not sure this
would work with a blade holder insert for disposable, high profile blade,
but it may as long as one raises the insert in the same way.
As for molds, the L shaped (embedding blocks from Electron Microscopy
Sciences) are wonderful, still available, and reusable. To shape a block so
it is smaller, merely melt the edges to "square up a block" using a tilted
hot plate paraffin runs off into a pan). To embed, you need to have add a
block holder so you can clamp the block into the microtome.
You can mount wooden block squares into the back to the embedded tissue,
preferably with a spacer under the wooden block above the tissue, put the
hot block on top of that, and let everything cool. Hard wood is better as
soft wood soaks up water if you need to soak a block. Keep some pre cut
blocks hot in the embedding center, after embedding, let everything harden
together. Our favortie was Electron Microscopy Sciences resin blocks - that
work very well in a screw clamp holder. Once again, keep these hot until
tissue and block are embedded, let all harden in place. Leica should have
a block clamp for their microtomes or a used equipment dealer. We could
remove these by heating but it may not be worth it.
If sectioning is a really hassle, I know of a delightful tape transfer using
packaging tape that is excellent for cutting eyes to maintain all structures
intact on a slide. This was published by Diane Sterchi in Journal of
Histotechnology approx 1988 or so. We used it for really horrible bone
blocks and tried it with large eyes. It does not require Instrumedics
setup, and was totally inexpensive and effective.
Gayle M. Callis
Bozeman MT 59715
----- Original Message -----
From: "Rene J Buesa"
To: "Bull, Jennifer L." ;
Sent: Monday, January 21, 2008 1:57 PM
Subject: Re: [Histonet] Whole Mount Slides
> The regular Minot type (rotary) microtomes usually have a maximum of 2.5
> inches block travel. For larger blocks you will need a horizontal
> microtome, they are just what is needed for this type of specimen.
> René J.
> "Bull, Jennifer L." wrote:
> I am looking for any information on Whole Mount Slides. Our pathologists
> would like to start doing them on Prostate and Bladder tissue. I have
> researched and located
> a microtome attachment from Leica and SurgiPath carries oversized
> cassettes and embedding molds. Does anyone have any information to add?
> Processing/cutting issues? Supplies? I would like to be as informed as
> possible before taking the plunge............ Thank You in advance!
> Jennifer Bull
> Histology Supervisor
> NW Pathology
> Bellingham, WA
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