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