3.12.
PERMANGANATE FIXATIVE OF LUFT (1956)
63
plasmic proteins. Thus, at fairly high magnification in Figs. 12 and 28
the background is conspicuously stippled. If osmium tetroxide had been
used alone, perhaps this would not have been so obvious. The granularity
after the formaldehyde is not necessarily an artifact, however, for it might
indeed represent an improved preservation of globular proteins, better
than with osmium tetroxide alone. The other effect that we have noted is
the tendency for membrane bounded cavities to be mildly enlarged
beyond what we ordinarily think of as most desirable preservation.
Usually this has shown up most significantly in the cisterns of the endoplasmic reticulum. Thinking that this might be a simple osmotic effect,
we have varied the sucrose content of the Millonig vehicle, but so far the
small variations we have employed have not convincingly altered the
patterns we have seen.
3,12. The Permanganate Fixative of Luft (1956)
In 1956 Luft demonstrated that the oxidative potential of potassium
permanganate could be usefully applied to certain problems of cytological
preservation. Luft recognized, however, that the buffered mixture of
potassium permanganate that he advocated was in no sense a general
purpose fixative. In fact, its useful oxidative properties are largely confined to preserving lipoprotein complexes which occur in the membrane
systems of a cell. Almost all other parts of a cell are destroyed. The net
effect is that cell membranes appear as a tracery of thin but very dark
lines against a pale background. This extreme contrast is a particularly
useful property when tissue is embedded and sectioned in epoxy or
polyester resins as discussed in the next chapter. To a certain extent this
fixative differentiates structures within biological membranes, and has
been particularly useful in studying myelin (cf. Robertson, 1957, 1958).
Figure 5 indicates the general characteristics of the fixation. Whaley et al.
(1959) have demonstrated that this fixative can be employed with advantage in studying endoplasmic reticulum in botanical material.
Luft prepared the permanganate fixative with the same buffer that
Palade had used with osmium tetroxide, as follows:
Stock permanganate solution:
Potassium permanganate (store in refrigerator
in glass-stoppered bottles)
1.2%
PERMANGANATE FIXATIVE OF LUFT (1956)
63
plasmic proteins. Thus, at fairly high magnification in Figs. 12 and 28
the background is conspicuously stippled. If osmium tetroxide had been
used alone, perhaps this would not have been so obvious. The granularity
after the formaldehyde is not necessarily an artifact, however, for it might
indeed represent an improved preservation of globular proteins, better
than with osmium tetroxide alone. The other effect that we have noted is
the tendency for membrane bounded cavities to be mildly enlarged
beyond what we ordinarily think of as most desirable preservation.
Usually this has shown up most significantly in the cisterns of the endoplasmic reticulum. Thinking that this might be a simple osmotic effect,
we have varied the sucrose content of the Millonig vehicle, but so far the
small variations we have employed have not convincingly altered the
patterns we have seen.
3,12. The Permanganate Fixative of Luft (1956)
In 1956 Luft demonstrated that the oxidative potential of potassium
permanganate could be usefully applied to certain problems of cytological
preservation. Luft recognized, however, that the buffered mixture of
potassium permanganate that he advocated was in no sense a general
purpose fixative. In fact, its useful oxidative properties are largely confined to preserving lipoprotein complexes which occur in the membrane
systems of a cell. Almost all other parts of a cell are destroyed. The net
effect is that cell membranes appear as a tracery of thin but very dark
lines against a pale background. This extreme contrast is a particularly
useful property when tissue is embedded and sectioned in epoxy or
polyester resins as discussed in the next chapter. To a certain extent this
fixative differentiates structures within biological membranes, and has
been particularly useful in studying myelin (cf. Robertson, 1957, 1958).
Figure 5 indicates the general characteristics of the fixation. Whaley et al.
(1959) have demonstrated that this fixative can be employed with advantage in studying endoplasmic reticulum in botanical material.
Luft prepared the permanganate fixative with the same buffer that
Palade had used with osmium tetroxide, as follows:
Stock permanganate solution:
Potassium permanganate (store in refrigerator
in glass-stoppered bottles)
1.2%