250
7.
"STAINING"
to develop an embedment which does not have this unfortunate characteristic which presumably depends upon nonionic hydrophobic interactions. McLean and Singer (1964) report promising success with a polyampholyte (Chapter 4.16). This polymer has a large total ionic charge,
but only a small net charge. The plastic is hydrophilic. It must be admitted, however, that these efforts are still in a developmental stage.
7.12. Autoradiography
Autoradiography at electron microscopic levels of resolution is an
established technique now that reasonably satisfactory material and
methods have been proven. It is interesting to note that 1961 was the
decisive year when at least a half-dozen different groups of investigators,
largely independently, achieved resolution extending into the fractional
micron range. At this time, too, fairly "clean" preparations were seen for
the first time, presenting good images of cellular structure. The work of
Revel and Hay (1961), Caro (1961), and Przybylski (1961) was particularly
outstanding. The work of Harford and Hamlin (1961) and Pelc, Coombes,
and Budd (1961) also achieved good radiographic localization but the
micrographs suffered somewhat from what presumably were the remains
of the gelatin of the original emulsion. As might be expected, these several
laboratories used different commercially available photographic emulsions, and of course their technique varied in its details. In the same year
Silk, Hawtrey, Spence, and Gear (1961) attempted the interesting experiment of evaporating a layer of silver directly upon the specimen, and
then converting this with bromine vapor to silver bromide. Thus they
formed their own very dense emulsion in immediate contact with the
specimen. However, they were unable to overcome some technical difficulties relating to photographic sensitivity, and their results were not
particularly successful, although perhaps they point the way to future
developments. Subsequently time and experience have encouraged Caro
(1962), Pelc (1963), and Granboulan (1963) to consider theoretical aspects
underlying the application of radiographic techniques to electron microscopy. In the subsequent years, too, reports dealing importantly with
methodology have been published by Caro and van Tubergen (1962) and
Hay and Revel (1963). What follows is drawn largely from these latter
sources.
It should be realized from the outset that autoradiographic resolution
7.
"STAINING"
to develop an embedment which does not have this unfortunate characteristic which presumably depends upon nonionic hydrophobic interactions. McLean and Singer (1964) report promising success with a polyampholyte (Chapter 4.16). This polymer has a large total ionic charge,
but only a small net charge. The plastic is hydrophilic. It must be admitted, however, that these efforts are still in a developmental stage.
7.12. Autoradiography
Autoradiography at electron microscopic levels of resolution is an
established technique now that reasonably satisfactory material and
methods have been proven. It is interesting to note that 1961 was the
decisive year when at least a half-dozen different groups of investigators,
largely independently, achieved resolution extending into the fractional
micron range. At this time, too, fairly "clean" preparations were seen for
the first time, presenting good images of cellular structure. The work of
Revel and Hay (1961), Caro (1961), and Przybylski (1961) was particularly
outstanding. The work of Harford and Hamlin (1961) and Pelc, Coombes,
and Budd (1961) also achieved good radiographic localization but the
micrographs suffered somewhat from what presumably were the remains
of the gelatin of the original emulsion. As might be expected, these several
laboratories used different commercially available photographic emulsions, and of course their technique varied in its details. In the same year
Silk, Hawtrey, Spence, and Gear (1961) attempted the interesting experiment of evaporating a layer of silver directly upon the specimen, and
then converting this with bromine vapor to silver bromide. Thus they
formed their own very dense emulsion in immediate contact with the
specimen. However, they were unable to overcome some technical difficulties relating to photographic sensitivity, and their results were not
particularly successful, although perhaps they point the way to future
developments. Subsequently time and experience have encouraged Caro
(1962), Pelc (1963), and Granboulan (1963) to consider theoretical aspects
underlying the application of radiographic techniques to electron microscopy. In the subsequent years, too, reports dealing importantly with
methodology have been published by Caro and van Tubergen (1962) and
Hay and Revel (1963). What follows is drawn largely from these latter
sources.
It should be realized from the outset that autoradiographic resolution