2.2.
POST-MORTEM CHANGE
15
possible (Chapter 2.6). Fortunately, aldehyde fixatives perfuse easily and
hold tissue fine-structure in place until it can be secondarily fixed with
osmium tetroxide. So now we have available a variety of approaches to
the problem of getting fixative to the tissue. These are discussed in the
following sections.
2.2. Post-Mortem Change
Until very recently, electron microscopists have been almost obsessed
with the thought that tissues must be fixed within minutes or seconds of
an animal's death to achieve as nearly perfect preservation as possible.
There seems to be good practical reason as well as some theoretical considerations for this attitude. However, the recent study of post-mortem
change by Ito (1962a,b), emphasizes that many significant morphological
changes do not necessarily occur very rapidly after all. Obviously when
we speak of the death of a vertebrate we are talking of a change at a
complex organismal level which does not have much to do immediately
with cellular death. It is evident that although some cells may die
quickly, others are capable of relatively long survival, hours at least,
when, for example, they might still prove viable in tissue culture explants.
Ito's (1962a) study concerned itself with the time course of post-mortem
changes, particularly in rat liver cells, over a 48 hour period. Tissues were
kept at room temperature until fixed. Even after 2 hours most of the fine
features were almost indistinguishable from those in freshly fixed tissue.
Even after 6 and 12 hours, although there was some rounding up of
formerly elongated mitochondria, and some distortion of their cristae,
these changes were surprisingly small. At 24 hours the characteristic
features of mitochondrial fine structure were still preserved, although
now markedly distorted. Mitochondria could at least be recognized 35
hours after death, and it was only after 48 hours that positive identification
of mitochondria became difficult. The Golgi complex proved to be less
stable than the mitochondria, and vesiculated within a few hours. The
cisterns of the endoplasmic reticulum remained intact for several days.
The plasma membrane was found to be relatively fragile. After delayed
fixation disruption of the latter at times produced myelin-like figures.
Ito (1962b) studied a variety of tissues which were allowed to remain
unfixed at various temperatures for varying periods of time. He points
POST-MORTEM CHANGE
15
possible (Chapter 2.6). Fortunately, aldehyde fixatives perfuse easily and
hold tissue fine-structure in place until it can be secondarily fixed with
osmium tetroxide. So now we have available a variety of approaches to
the problem of getting fixative to the tissue. These are discussed in the
following sections.
2.2. Post-Mortem Change
Until very recently, electron microscopists have been almost obsessed
with the thought that tissues must be fixed within minutes or seconds of
an animal's death to achieve as nearly perfect preservation as possible.
There seems to be good practical reason as well as some theoretical considerations for this attitude. However, the recent study of post-mortem
change by Ito (1962a,b), emphasizes that many significant morphological
changes do not necessarily occur very rapidly after all. Obviously when
we speak of the death of a vertebrate we are talking of a change at a
complex organismal level which does not have much to do immediately
with cellular death. It is evident that although some cells may die
quickly, others are capable of relatively long survival, hours at least,
when, for example, they might still prove viable in tissue culture explants.
Ito's (1962a) study concerned itself with the time course of post-mortem
changes, particularly in rat liver cells, over a 48 hour period. Tissues were
kept at room temperature until fixed. Even after 2 hours most of the fine
features were almost indistinguishable from those in freshly fixed tissue.
Even after 6 and 12 hours, although there was some rounding up of
formerly elongated mitochondria, and some distortion of their cristae,
these changes were surprisingly small. At 24 hours the characteristic
features of mitochondrial fine structure were still preserved, although
now markedly distorted. Mitochondria could at least be recognized 35
hours after death, and it was only after 48 hours that positive identification
of mitochondria became difficult. The Golgi complex proved to be less
stable than the mitochondria, and vesiculated within a few hours. The
cisterns of the endoplasmic reticulum remained intact for several days.
The plasma membrane was found to be relatively fragile. After delayed
fixation disruption of the latter at times produced myelin-like figures.
Ito (1962b) studied a variety of tissues which were allowed to remain
unfixed at various temperatures for varying periods of time. He points