3.2.
PALADE (1952) FIXATIVE
35
commonly as "Palade pickle," and which is used by many laboratories
with little or no modification of the original formula.
In that year F. S. Sjostrand brought from Sweden to the national
meeting of the Electron Microscope Society of America the most impressive collection of electron micrographs of ultrathin sections that had been
seen. At that time Sjostrand was using Palade's fixative, and obviously he
applied it with considerable skill. It should be added, though, that the
excellence of his demonstration depended not only upon preservation but
also upon his superior sectioning and skilled microscopy. The net effect
was to set standards which, from then on, had to be met by every laboratory to consider itself successful in this field.
Within the past few years there has been an accelerating realization
that some aldehydes also can serve as excellent cytological fixatives. Proteins and some macromolecular carbohydrates are well preserved. In
general, however, lipids are not rendered insoluble in organic solvents.
Hence the latter are extracted during embedding procedures unless a
secondary fixation with osmium tetroxide is applied. When this is done,
the final result is much as though the tissue was originally fixed in osmium tetroxide. There are advantages, though, in using aldehydes as
primary fixatives for these can be relied upon to penetrate through tissue
much more effectively than osmium tetroxide, and they easily can be
perfused. Aldehyde fixation also permits histochemical studies which
would be quite impossible if we had to rely upon osmium tetroxide alone.
The only other fixative which has proved to be of value for electron
microscopists relies on the oxidative properties of the permanganate ion.
This was introduced as a fixative by Luft (1956). In a sense it compliments
the aldehydes in oxidizing and rendering insoluble the complex lipids of
cytomembranes, so that these are preserved while almost all else is lost.
It has to be regarded as a special purpose fixative without general application.
These three categories of fixatives, and their variations, are discussed
in the sections which follow.
3.2. Palade (1952) Fixative, Buffered Osmium Tetroxide
There is an extraordinary unanimity amongst experienced electron
microscopists that osmium tetroxide fixatives are the general purpose
fixatives of choice for most cytological morphology. As such they can be
used successfully as excellent primary fixatives, or secondarily after an
PALADE (1952) FIXATIVE
35
commonly as "Palade pickle," and which is used by many laboratories
with little or no modification of the original formula.
In that year F. S. Sjostrand brought from Sweden to the national
meeting of the Electron Microscope Society of America the most impressive collection of electron micrographs of ultrathin sections that had been
seen. At that time Sjostrand was using Palade's fixative, and obviously he
applied it with considerable skill. It should be added, though, that the
excellence of his demonstration depended not only upon preservation but
also upon his superior sectioning and skilled microscopy. The net effect
was to set standards which, from then on, had to be met by every laboratory to consider itself successful in this field.
Within the past few years there has been an accelerating realization
that some aldehydes also can serve as excellent cytological fixatives. Proteins and some macromolecular carbohydrates are well preserved. In
general, however, lipids are not rendered insoluble in organic solvents.
Hence the latter are extracted during embedding procedures unless a
secondary fixation with osmium tetroxide is applied. When this is done,
the final result is much as though the tissue was originally fixed in osmium tetroxide. There are advantages, though, in using aldehydes as
primary fixatives for these can be relied upon to penetrate through tissue
much more effectively than osmium tetroxide, and they easily can be
perfused. Aldehyde fixation also permits histochemical studies which
would be quite impossible if we had to rely upon osmium tetroxide alone.
The only other fixative which has proved to be of value for electron
microscopists relies on the oxidative properties of the permanganate ion.
This was introduced as a fixative by Luft (1956). In a sense it compliments
the aldehydes in oxidizing and rendering insoluble the complex lipids of
cytomembranes, so that these are preserved while almost all else is lost.
It has to be regarded as a special purpose fixative without general application.
These three categories of fixatives, and their variations, are discussed
in the sections which follow.
3.2. Palade (1952) Fixative, Buffered Osmium Tetroxide
There is an extraordinary unanimity amongst experienced electron
microscopists that osmium tetroxide fixatives are the general purpose
fixatives of choice for most cytological morphology. As such they can be
used successfully as excellent primary fixatives, or secondarily after an