240
7.
"STAINING"
the edge of a paraffin-coated microscope slide immediately before using
it. We have not been convinced that this accomplishes much.
After the staining is presumed to be complete, the grids should be
rinsed in running distilled water for a few seconds. They are then
immersed and agitated in a solution consisting of 1 drop of 5% citric acid
in 1 ml of distilled water for 30 seconds to 1 minute. This is followed by
yet another rinse in distilled water before drying the grids.
Potassium permanganate appears to stain nearly all of the tissue components when used in the manner described. In most respects, therefore,
the stain gives much the same impression as alkaline lead hydroxide
stain. Stained sections of material fixed in osmium tetroxide or aldehyde
in no way resemble the appearance of permanganate-fixed material.
In our own laboratory we have had only limited experience with this
stain, and have had a good deal of trouble with "dirt." At times we have
had the impression that this has resulted from interaction with the copper
grids when naked sections were stained. Thus it may be that sections
should always be mounted on coated grids as Lawn originally proposed.
We have also noted a further difficulty, that textural irregularities on the
surface of the sections seemed to become particularly prominent after the
use of this stain. Thus the embedment may be observed as having a
granular appearance that is undesirable and, indeed, might interfere with
the observation of cytoplasmic fine structure at high resolution. It seems
evident that the background granularity is not always seen, and therefore,
apparently depends in part upon the character of the section, and perhaps
upon the embedment.
On numerous occasions when we have tried to stain naked sections with
potassium permanganate there has been an undue loss. Sections which
survived the staining also seemed to be particularly sensitive to electron
bombardment. Thus we have come to believe that the permanganate
treatment alters the character of at least some plastic embedments,
presumably by oxidizing components. It is quite probable that this effect
would be limited to particular plastics, but we have not systematically
explored this question. Therefore, in starting a project with this stain,
supporting films should be used with at least some of the sections until
it is certain that naked ones can be successfully handled.
I have learned of barium permanganate being substituted for the
potassium salt, and I have seen some micrographs excellently stained
with it. I do not know to whom to attribute this variant procedure, and
I have no comparative information on whether or not the barium salt
7.
"STAINING"
the edge of a paraffin-coated microscope slide immediately before using
it. We have not been convinced that this accomplishes much.
After the staining is presumed to be complete, the grids should be
rinsed in running distilled water for a few seconds. They are then
immersed and agitated in a solution consisting of 1 drop of 5% citric acid
in 1 ml of distilled water for 30 seconds to 1 minute. This is followed by
yet another rinse in distilled water before drying the grids.
Potassium permanganate appears to stain nearly all of the tissue components when used in the manner described. In most respects, therefore,
the stain gives much the same impression as alkaline lead hydroxide
stain. Stained sections of material fixed in osmium tetroxide or aldehyde
in no way resemble the appearance of permanganate-fixed material.
In our own laboratory we have had only limited experience with this
stain, and have had a good deal of trouble with "dirt." At times we have
had the impression that this has resulted from interaction with the copper
grids when naked sections were stained. Thus it may be that sections
should always be mounted on coated grids as Lawn originally proposed.
We have also noted a further difficulty, that textural irregularities on the
surface of the sections seemed to become particularly prominent after the
use of this stain. Thus the embedment may be observed as having a
granular appearance that is undesirable and, indeed, might interfere with
the observation of cytoplasmic fine structure at high resolution. It seems
evident that the background granularity is not always seen, and therefore,
apparently depends in part upon the character of the section, and perhaps
upon the embedment.
On numerous occasions when we have tried to stain naked sections with
potassium permanganate there has been an undue loss. Sections which
survived the staining also seemed to be particularly sensitive to electron
bombardment. Thus we have come to believe that the permanganate
treatment alters the character of at least some plastic embedments,
presumably by oxidizing components. It is quite probable that this effect
would be limited to particular plastics, but we have not systematically
explored this question. Therefore, in starting a project with this stain,
supporting films should be used with at least some of the sections until
it is certain that naked ones can be successfully handled.
I have learned of barium permanganate being substituted for the
potassium salt, and I have seen some micrographs excellently stained
with it. I do not know to whom to attribute this variant procedure, and
I have no comparative information on whether or not the barium salt