RE: [Histonet] VIR question - finfish tags
Such a project depends largely on the chemical composition of the synthetic
material. We section a variety of synthetics here since we are a core
facility serving a large number of different researchers in various fields.
Most synthetics can be sectioned in paraffin - once you get them into
paraffin - but that can be tricky. In order to embed them in paraffin, you
first have to make sure that the particular synthetic is chemically
resistant to your dehydrant and your clearing agent, and is not harmed by
the temperature of your processing paraffin.
We routinely section sponge implants that have been removed from animals
after several months duration. These are highly resistant chemically, and
can be processed on a normal processing schedule using ethanol and xylene.
We also work with resorbable vessel grafts, and these again can be processed
normally. However, in another project we are sectioning bone containing a
fine resorbable polymer screen, and xylene is not suitable for these. It
makes the material soft and gummy. We found that tetrahydrofuran works well
as a clearing agent for that project.
More recently we have been doing work on an implantable device which
contains synthetic tubules. Before we began work on this, I did what I
always do in such cases - asked the researcher to send me samples of the
synthetic material to test against various solvents before we started
processing specimens. This one proved to be challenging. Xylene caused the
material to shrink to a third its former size, and adjacent tubules to fuse
into a solid mass. A few other solvents had a similar effect.
Tetrahydrofuran, chloroform, toluene, and several other solvents dissolved
the tubules completely within seconds. After trying over different 15
clearing agents, and rapidly running out of options, I tried carbon
tetrachloride. It worked beautifully, rapidly clearing the tubules without
causing any distortion at all. But carbon tetrachloride is very expensive
and also very toxic, so I kept looking. Finally I discovered that a
clearing agent called "SafeClear" by Fisher worked virtually as well as
carbon tetrachloride, so that's what we are now using on this project. The
blocks cut beautifully.
Then of course we also have to use SafeClear to deparaffinize the slides
before staining, and to clear them after staining. And, we had to find a
coverslip mounting medium that is xylene and toluene free, and compatible
with both the clearing agent and the synthetic material. Fortunately,
VectaMount by Vector Laboratories proved suitable. So now we have our
protocol in place for this specific project.
One other consideration. Since most synthetics do not have a net negative
charge like most tissues do, + charged slides do not hold them in place.
Therefore you have to use a chemical adhesive of some sort. Depending on the
particular synthetic, I usually use either PVA (polyvinyl acetate) or
"Sta-On", a chrome gelatin product sold by Surgipath.
> From: email@example.com on behalf of
> McCollough, Carol
> Sent: Friday, September 30, 2005 8:34 AM
> To: Histonet (E-mail 2)
> Subject: [Histonet] VIR question - finfish tags
> Greetings Histonetters:
> We have had a request from a researcher at Woods Hole for embedding and
> sectioning of monkfish that have been tagged. The investigator is
> interested in the interface between the living tissue and the tag. I
> believe that these are Floy-type spaghetti tags, which are flexible soft
> plastic, maybe latex. I have no experience with sectioning non-biological
> materials. We do 99.999% paraffin here, but do have the capability to do
> methacrylates and resins. Suggestions?
> Regards -
> Carol B. McCollough, HT/HTL(ASCP)
> Aquatic Animal Research Pathologist
> Oyster Disease Research Project
> Fisheries Service
> Maryland Department of Natural Resources
> Cooperative Oxford Laboratory
> 904 S. Morris Street
> Oxford, Maryland 21654
> 410-226-5193 x124
> Histonet mailing list
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