7.13.
THICK SECTIONS FOR CONVENTIONAL MICROSCOPY
257
ing, a suitably small piece of cover slip may serve to pick up sections
directly from the fluid surface of the trough. The sections are simply
allowed to dry upon this, and subsequently inverted and mounted on a
standard slide.
Sections also can be transferred directly from the trough to a standard
1 X 3 in. microscope slide as indicated in Chapter 5.26, or even with a
toothpick. If the glass is clean, it can be assumed that the sections will
stick to it so vigorously after drying that no adhesive will be necessary
no matter what is to be done to them subsequently.
Phase and dark field images usually are improved if the embedment
is extracted insofar as is reasonable and possible. There are no difficulties
in doing this with methacrylate sections, but it is not usually practical
with the various cross-linked plastics, although the partial extraction
(and perhaps some swelling) that results from soaking in a ketone such
as amyl acetate often helps. Organic solvents such as xylene and trichloroethylene also have some effect. Thus, in just a few minutes one can
obtain much information about the contents of the section. Mayor et al.
(1961) have indicated that epoxy resins formulated with dodecenyl
succinic anhydride can be dissolved in a mixture of sodium methoxide,
benzene, and methyl alcohol (Chapter 7.13), which probably will prove
useful for phase microscopy.
Many staining reactions can be carried out even without removing
plastic embedments, although if methacrylate has been used, more vivid
results will follow its extraction. Then, almost any staining reaction will
work reliably. If the embedding medium must be left in place, staining
becomes much more of a problem. The stain which will work with one
embedment will not necessarily with another. In part, no doubt, these
variations relate to the wettability of embedded tissues, and anything
which improves the penetration of the stain can be expected to improve
its reaction.
Heat is perhaps the most effective way of improving staining reactions
in epoxy or polyester resins. Often temperatures of 60°-85°C and even
more can be applied safely. Flooded sections thus can be put on a hot
plate for a few minutes. In at least some instances it will not matter if
the stain actually dries down, for crystal deposits will be redissolved in
clearing and mounting steps. Often, too, a very brief exposure to high
heat will be satisfactory, and a flooded slide can be warmed over a small
burner until a few bubbles start to appear.
It also has become evident that decidedly alkaline stains with a pH of
THICK SECTIONS FOR CONVENTIONAL MICROSCOPY
257
ing, a suitably small piece of cover slip may serve to pick up sections
directly from the fluid surface of the trough. The sections are simply
allowed to dry upon this, and subsequently inverted and mounted on a
standard slide.
Sections also can be transferred directly from the trough to a standard
1 X 3 in. microscope slide as indicated in Chapter 5.26, or even with a
toothpick. If the glass is clean, it can be assumed that the sections will
stick to it so vigorously after drying that no adhesive will be necessary
no matter what is to be done to them subsequently.
Phase and dark field images usually are improved if the embedment
is extracted insofar as is reasonable and possible. There are no difficulties
in doing this with methacrylate sections, but it is not usually practical
with the various cross-linked plastics, although the partial extraction
(and perhaps some swelling) that results from soaking in a ketone such
as amyl acetate often helps. Organic solvents such as xylene and trichloroethylene also have some effect. Thus, in just a few minutes one can
obtain much information about the contents of the section. Mayor et al.
(1961) have indicated that epoxy resins formulated with dodecenyl
succinic anhydride can be dissolved in a mixture of sodium methoxide,
benzene, and methyl alcohol (Chapter 7.13), which probably will prove
useful for phase microscopy.
Many staining reactions can be carried out even without removing
plastic embedments, although if methacrylate has been used, more vivid
results will follow its extraction. Then, almost any staining reaction will
work reliably. If the embedding medium must be left in place, staining
becomes much more of a problem. The stain which will work with one
embedment will not necessarily with another. In part, no doubt, these
variations relate to the wettability of embedded tissues, and anything
which improves the penetration of the stain can be expected to improve
its reaction.
Heat is perhaps the most effective way of improving staining reactions
in epoxy or polyester resins. Often temperatures of 60°-85°C and even
more can be applied safely. Flooded sections thus can be put on a hot
plate for a few minutes. In at least some instances it will not matter if
the stain actually dries down, for crystal deposits will be redissolved in
clearing and mounting steps. Often, too, a very brief exposure to high
heat will be satisfactory, and a flooded slide can be warmed over a small
burner until a few bubbles start to appear.
It also has become evident that decidedly alkaline stains with a pH of