122
4.
EMBEDDING
run polymerization tests whenever a new lot is started. Also the manufacturers warn against a fairly rapid decomposition (30 days at 30°C).
Cross-linked methacrylate may be expected to have completed its polymerization in 24 hours at 50°C. Heat polymerization should be employed.
Ultraviolet radiation of the sort we have used without difficulty with
ordinary methacrylate, has proved unsuccessful with the cross-linked
plastic, perhaps because it does not penetrate into the specimen.
We have not recognized specimen "explosion damage" (Chapter 4.8)
when we have used divinyl benzene with ordinary methacrylate monomers. It would be premature, however, to say that this cannot occur
under any circumstances. Thus, the investigator who would cross-link
methacrylate in this simple way should be forewarned, and on the lookout for such artifacts. Hopefully, they will not appear. There is no
apparent reason, however, why divinyl benzene should not be added to
"prepolymerized" methacrylate (Chapter 4.5) which presumably would
obviate any such difficulty. The present writer has not explored this
possibility.
4.16. Water-Soluble Resin Embedding
Investigators originally interested in histochemical applications have
explored the use of several water-soluble resins as embedments in the
hope that the circumvention of ordinary dehydration procedures would
minimize denaturation, and so preserve biochemical activity. To some
extent, this thesis has been justified, and there has appeared at least one
secondary benefit of considerable potential importance. As Bernhard and
Leduc (1962) have shown, aldehyde-fixed tissue embedded in any of these
plastics is not only accessible to enzymatic hydrolysis, but also possesses
unusual numbers of available reactive groups for combination with stains
so that morphological detail can be particularly evident.
The first water-soluble resin to be developed for embedding purposes
was a component of Epon 812, extracted by Gibbons (1959 and 1960),
and named by him, Aquon. This is not available commercially, and the
interested reader should refer to the original papers to learn details of
the relatively simple extraction procedure. After isolation, Aquon is said
to be stable indefinitely.
Staubli (1960) developed procedures for handling the then experimental Ciba Ltd., Basle, epoxy resin called Product X 133/2097. This
4.
EMBEDDING
run polymerization tests whenever a new lot is started. Also the manufacturers warn against a fairly rapid decomposition (30 days at 30°C).
Cross-linked methacrylate may be expected to have completed its polymerization in 24 hours at 50°C. Heat polymerization should be employed.
Ultraviolet radiation of the sort we have used without difficulty with
ordinary methacrylate, has proved unsuccessful with the cross-linked
plastic, perhaps because it does not penetrate into the specimen.
We have not recognized specimen "explosion damage" (Chapter 4.8)
when we have used divinyl benzene with ordinary methacrylate monomers. It would be premature, however, to say that this cannot occur
under any circumstances. Thus, the investigator who would cross-link
methacrylate in this simple way should be forewarned, and on the lookout for such artifacts. Hopefully, they will not appear. There is no
apparent reason, however, why divinyl benzene should not be added to
"prepolymerized" methacrylate (Chapter 4.5) which presumably would
obviate any such difficulty. The present writer has not explored this
possibility.
4.16. Water-Soluble Resin Embedding
Investigators originally interested in histochemical applications have
explored the use of several water-soluble resins as embedments in the
hope that the circumvention of ordinary dehydration procedures would
minimize denaturation, and so preserve biochemical activity. To some
extent, this thesis has been justified, and there has appeared at least one
secondary benefit of considerable potential importance. As Bernhard and
Leduc (1962) have shown, aldehyde-fixed tissue embedded in any of these
plastics is not only accessible to enzymatic hydrolysis, but also possesses
unusual numbers of available reactive groups for combination with stains
so that morphological detail can be particularly evident.
The first water-soluble resin to be developed for embedding purposes
was a component of Epon 812, extracted by Gibbons (1959 and 1960),
and named by him, Aquon. This is not available commercially, and the
interested reader should refer to the original papers to learn details of
the relatively simple extraction procedure. After isolation, Aquon is said
to be stable indefinitely.
Staubli (1960) developed procedures for handling the then experimental Ciba Ltd., Basle, epoxy resin called Product X 133/2097. This