7.3.
ALKALINE LEAD HYDROXIDE STAINS
231
(1960) proposed a method of achieving lead intensification in which
alkaline lead hydroxide was presumed to be formed directly within the
section. This involved floating the sections on the surface of a saturated
solution of lead acetate for sufficient time to allow as much of the salt to
be incorporated in the sections as possible. The grids then were touched
to absorbent paper to drain off excess lead acetate, and immediately
washed vigorously in 3-4 changes of boiled, distilled water in separate
beakers. Following this, the grids were thoroughly dried. The incorporated
lead acetate finally was converted to lead hydroxide by waving the grids,
section side down, in the vapors of 1-5% ammonium hydroxide. The
grids were held a minimum of 5 cm from the liquid surface. Several
passes, or a total exposure of about 5 seconds, usually was found to be
appropriate. Overexposure was apt to damage the sections.
This simple method often works very effectively with methacrylate
embedments. We have had difficulty getting adequate stain with some
epoxy sections.
Dalton and Zeigel (1960) also have suggested using a saturated solution
of monobasic lead acetate (lead subacetate) as a stain. While this works
effectively upon methacrylate sections, it by no means yields the intense
staining of the alkaline lead hydroxides when used with epoxy or
polyester resins.
Lead hydroxide
as a secondary
stain. Under most circumstances the
intensity of lead staining that can be achieved does not seem to depend
greatly upon the particular stain employed. One usually is about as
effective as another, and thus the reaction seems generally to go to completion. The time it takes to achieve maximum staining also does not
seem to depend particularly on the stain, but rather upon the embedment and the specimen. Thus, there are only small quantitative differences at best to select from if one is seeking maximum intensification.
However, there is a very simple and effective way of achieving an image
intensification significantly greater than lead stains will produce by themselves. This involves pretreating the sections with a uranyl stain (Chapter
7.4) and then secondarily staining with lead hydroxide. The effect seems
to be more than just an additive one [Figs. 28(c) and (d)]. Moreover,
staining times can be greatly reduced from what would be necessary to
achieve a maximum effect if either stain were used separately. Images with
truly great contrast can be expected to result even when the embedding
medium is dense, as Araldite.
In our own laboratory we have had the best success when uranyl
ALKALINE LEAD HYDROXIDE STAINS
231
(1960) proposed a method of achieving lead intensification in which
alkaline lead hydroxide was presumed to be formed directly within the
section. This involved floating the sections on the surface of a saturated
solution of lead acetate for sufficient time to allow as much of the salt to
be incorporated in the sections as possible. The grids then were touched
to absorbent paper to drain off excess lead acetate, and immediately
washed vigorously in 3-4 changes of boiled, distilled water in separate
beakers. Following this, the grids were thoroughly dried. The incorporated
lead acetate finally was converted to lead hydroxide by waving the grids,
section side down, in the vapors of 1-5% ammonium hydroxide. The
grids were held a minimum of 5 cm from the liquid surface. Several
passes, or a total exposure of about 5 seconds, usually was found to be
appropriate. Overexposure was apt to damage the sections.
This simple method often works very effectively with methacrylate
embedments. We have had difficulty getting adequate stain with some
epoxy sections.
Dalton and Zeigel (1960) also have suggested using a saturated solution
of monobasic lead acetate (lead subacetate) as a stain. While this works
effectively upon methacrylate sections, it by no means yields the intense
staining of the alkaline lead hydroxides when used with epoxy or
polyester resins.
Lead hydroxide
as a secondary
stain. Under most circumstances the
intensity of lead staining that can be achieved does not seem to depend
greatly upon the particular stain employed. One usually is about as
effective as another, and thus the reaction seems generally to go to completion. The time it takes to achieve maximum staining also does not
seem to depend particularly on the stain, but rather upon the embedment and the specimen. Thus, there are only small quantitative differences at best to select from if one is seeking maximum intensification.
However, there is a very simple and effective way of achieving an image
intensification significantly greater than lead stains will produce by themselves. This involves pretreating the sections with a uranyl stain (Chapter
7.4) and then secondarily staining with lead hydroxide. The effect seems
to be more than just an additive one [Figs. 28(c) and (d)]. Moreover,
staining times can be greatly reduced from what would be necessary to
achieve a maximum effect if either stain were used separately. Images with
truly great contrast can be expected to result even when the embedding
medium is dense, as Araldite.
In our own laboratory we have had the best success when uranyl