X-Message-Number: 3026
From: Ralph Merkle <>
Subject: CRYONICS: Quote about the effects of postmortem delay on neurons
Date: 	Sat, 27 Aug 1994 11:49:14 PDT


"Effects of postmortem delay. Some brain functions are damaged
irreversibly within minutes of the cessation of blood
flow to the tissue.  This led to the widespread belief that
it would be impossible to isolate metabolically active and
responsive preparations very long after death and use them to study
neurotransmission.  However, this is a misconception; many groups
have successfully obtained functional preparations from normal
(Table 1) and pathological (Table 2) human brain tissue
from autopsies carried out up to 24 h or more postmortem.  This
is perhaps less surprising when the stability of enzymes, receptors,
and nucleic acids is taken into consideration (see Hardy and Dodd, 1983).
With very few exceptions, the brain retains the metabolic machinery
to reconstitute tissue metabolite and neurotransmitter pools.  It also
appears that sufficient structural integrity is retained to allow
the various tissue compartments to remain relatively intact and
distinct."

"Experiments with both animal and human brain have shown that viable
preparations can be isolated routinely up to at least 24 h postmortem,
a time scale within which a sufficient number of autopsies
is carried out to allow extensive neurochemical studies.
When the human subject has died suddenly (see below),
such preparations exhibit the same range of
characteristics as preparations made from fresh animal
tissue, or from fresh human tissue obtained at biopsy
or neurosurgery.  Thus incubated synaptosomes and brain
slices from postmortem human brain respire, accumulate tissue
potassium, maintain membrane potentials, release neurotransmitters
in a calcium-dependent fashion, and possess active, sodium -
dependent uptake systems (see Table 1 for references).
Electron microscopic examination of synaptosome
preparations from postmortem human brain showed them to be
only slightly less pure than preparations from fresh tissue, although
some degree of damage is evident (Hardy et al., 1982)."

>From "A Comparison of Methodologies for the Study of
Functional Transmitter Neurochemistry in Human Brain,"
by Peter R. Dodd, John W. Hambley, Richard F. Cowburn and John A. Hardy;
Journal of Neurochemistry, 1988, pages 1133-1345.

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3026