7.10.
HISTOCHEMICAL APPLICATIONS
245
normally show metachromasia, and apparently wherever mucopolysaccharides are present, as in glycogen, mucin, elastin and in association with
basement membranes. If sections are oxidized with periodic acid, or
hydrogen peroxide before treatment with the silver solutions, the deposition of silver is limited to the distribution of the mucopolysaccharides.
Indeed, this latter reaction is so specific that probably it can be regarded
as having histochemical import, almost exactly paralleling the response
of the Schiff reaction [see also Movat (1961) for a variant procedure].
Thus it is that we have begun to develop a rational explanation of
some of the important staining reactions currently of interest to electron
microscopists. The importance of reduced osmium tetroxide has been
demonstrated, although the exact role that it plays in the binding of
other heavy metal compounds remains obscure. But the interrelation
between osmium in the section and the intensity of staining reactions
with alkaline lead hydroxide stressed by Marinozzi and by Daems and
Persijn may help explain inconsistencies in staining reactions related to
different embedments and different dehydration procedures. Thus, the
use of highly reactive epoxy monomers, and solvents such as propylene
oxide, may affect the available reduced osmium, and so influence subsequent staining (Chapter 4.3). We can hope also that a rational explanation of the intensification achieved by double staining (Chapter 7.3) will
be forthcoming.
7.10. Histochemical Applications
Important efforts have been and are being made to develop histochemical techniques that are applicable to electron microscopy. No doubt
these efforts will be accelerated now that we have a better understanding
than even a few years ago of aldehyde fixation and how to handle material
preserved in this way (Chapter 3.10). However it is not practical here to
consider particular techniques in their variety of detail for each specific
application would require individual consideration. The
interested
investigator certainly would wish and need to consult the original
literature. But it is perhaps pertinent to make some general remarks, and
refer to a few recent articles which review much of the literature.
The principal approach to enzymatic localization has been to create
in situ a reaction product with adequate electron scattering properties to
be easily identifiable in an electron microscope section. A difficulty has
HISTOCHEMICAL APPLICATIONS
245
normally show metachromasia, and apparently wherever mucopolysaccharides are present, as in glycogen, mucin, elastin and in association with
basement membranes. If sections are oxidized with periodic acid, or
hydrogen peroxide before treatment with the silver solutions, the deposition of silver is limited to the distribution of the mucopolysaccharides.
Indeed, this latter reaction is so specific that probably it can be regarded
as having histochemical import, almost exactly paralleling the response
of the Schiff reaction [see also Movat (1961) for a variant procedure].
Thus it is that we have begun to develop a rational explanation of
some of the important staining reactions currently of interest to electron
microscopists. The importance of reduced osmium tetroxide has been
demonstrated, although the exact role that it plays in the binding of
other heavy metal compounds remains obscure. But the interrelation
between osmium in the section and the intensity of staining reactions
with alkaline lead hydroxide stressed by Marinozzi and by Daems and
Persijn may help explain inconsistencies in staining reactions related to
different embedments and different dehydration procedures. Thus, the
use of highly reactive epoxy monomers, and solvents such as propylene
oxide, may affect the available reduced osmium, and so influence subsequent staining (Chapter 4.3). We can hope also that a rational explanation of the intensification achieved by double staining (Chapter 7.3) will
be forthcoming.
7.10. Histochemical Applications
Important efforts have been and are being made to develop histochemical techniques that are applicable to electron microscopy. No doubt
these efforts will be accelerated now that we have a better understanding
than even a few years ago of aldehyde fixation and how to handle material
preserved in this way (Chapter 3.10). However it is not practical here to
consider particular techniques in their variety of detail for each specific
application would require individual consideration. The
interested
investigator certainly would wish and need to consult the original
literature. But it is perhaps pertinent to make some general remarks, and
refer to a few recent articles which review much of the literature.
The principal approach to enzymatic localization has been to create
in situ a reaction product with adequate electron scattering properties to
be easily identifiable in an electron microscope section. A difficulty has