of post-synaptic membrane (complete with neurotransmitter receptors and other apparatus). Synaptosome are living structures, and it is possible to test them for viability after freezing and thawing, which is just what the authors of this report (John A. Hardy et al.) have done. Both human and rat synaptosomes were isolated after thawing and their activities compared. Histologically normal human cerebral cortex was removed from patients during surgery for brain tumors or aneurysms to allow access to these structures. The following results were obtained by freezing 1-5 gram pieces of brain immersed in 0.32 M sucrose. (Freezing homogenates gave poorer results.) The cooling rate (not measured) was slow and the warming rate (not measured) was fast; other cooling rate/warming rate combinations gave poor results. Measurement made -------------------------------------------number of synaptosomes recovered (for homogenates, the results were rat 66%, man 64%) amount of protein recovered oxygen uptake/100 mg of protein stimulation of oxygen uptake by veratrine potassium accumulated/100 mg protein loss of potassium caused by veratrine retention of neurotransmitters stimulated transmitter release (amount, selectively, and drug modulation)
species ------rat man rat man rat man rat man rat man rat man rat man rat man
% recovery* ----------80 not done 70 91 59 78 86 86 70 86 85 39 good good good good
* recovery compared to unfrozen control samples It is apparent that rat and human brain tissue frozen to -70øC with essentially no cryoprotection has synapses "closely comparable to. . . fresh tissue," as the authors conclude. It is also apparent that human and rat synapses are about equally resistant to freezing damage (although the authors mentioned less uptake of glutamate by the human synaptosomes). These results are very similar to those of Haan and Bowen (J. Neurochem. 37: 243-246, 1981), who froze rat and human cerebral cortex with 10% DMSO and measured uptake of norepinephrine (94-95% recovery for both rat and man) and incorporation of glucose into acetylcholine (89-100% recovery for rat, 85% recovery for human) and into CO2 (86-100% recovery for rat, 78% recovery for man), and attributed most of this activity to synapses. These two papers, together with others in which rat brain (Life Sci. 28: 11471154, 1981) or rat superior cervical ganglion (Proc. Roy. Soc., Ser. B, 510519, 1957) was studied, clearly establish beyond much doubt that the synaptic connections in the human brain will substantially withstand cryonic suspension. If nerve ends also remain connected to their neurons of origin, then the brain's "wiring" pattern (the blueprint for identity?) will also survive. We will be awaiting the final word on that question with some anxiousness! ---------------------------------------------------------------------(18)
AIDS:
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