In NATURE (Oct. 15), Professor Isamu Suda (Kobe University, Japan) and associates, reported a study on the Viability of Long Term Frozen Cat Brain in Vitro. This paper has been reprinted by the Cryonics Society of New York. It describes a method for cooling an entire cat brain to -20 degrees C.
The brain was thoroughly perfused with glycerol solution, and removed from the cat along with its surrounding case of bone. Torso, neck, skin, jaw bones, and facial muscle & nerves were cut away. After re-warming to body temperature, evidence of electrical brain wave activity (EEG) was recorded.
The following aspects of the study need further clarification, discussion, and experimentation.
The Japanese group did not specify what per cent of the brains were revived. It is important to know how often success can be expected using the Suda technique.
Cooling curves were not published. This data would be valuable to clarify procedure and to give positive evidence that the brains were actually frozen. Also, a number of organs frozen without glycerol would have been useful in evaluating the cryoprotective effect of this chemical.
The most important question is whether the EEG’s of the revived brains represent organized cerebral functioning. Brain activity can be quite disorganized. The generation of EEG’s is not necessarily an indication of organized, coherent activity. To illustrate, it has been observed that with suitable cryoprotective agents, hearts frozen to -70 degrees C. will exhibit electrical activity (EKG), despite the absence of any evidence of mechanical activity. The EEG tracings obtained by Suda probably could have been generated even if a large number of the cells were damaged.
The fact that the brain tissue appeared normal under the light microscope is of little help in evaluating capacity to function. Severe cellular damage does not necessarily show under this instrument.
If a brain was frozen in a whole head preparation, with some nerve and muscle attached, incontrovertible proof might be obtained. If the pupils of the eyes contraced in response to bright light after re-warming, at least some of the normal complex physiological functioning of the brain would be demonstrated.
The significance of the Suda report lies in its implications. He has demonstrated that a re-warmed cat’s brain will resume EEG activity after cooling to -20 degrees C. The next step is to demonstrate the preservation of normal physiology.
Cryonics Reports, Vol. 2, No. 1, January 1967