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e-learning II - Membranes and Ion Channels
In Haitian legend, "bokors", or voodoo witchdoctors, were thought to be able to reanimate the recently deceased and sell them into an existence as a mindless slave - a zombie. In the early 1980's a Ph.D. student at Harvard, by the name of Wade Davis, travelled to Haiti to investigate the basis of such zombie stories. Davis' research brought him into contact with Haitians who told him another variant of the zombie myth. In this version the bokor first selects a living victim and then administers a poison to them that brings them into a death-like trance. Once the victim had been safely buried by their grieving relatives, the bokor could recover the "corpse", revive it, and sell the hapless zombie to its new owner. In these stories, the poison was applied to the victim's skin in the form of a powder and Davis reasoned that there must be some pharmacologically active ingredient present in the powder that could suppress the vital signs and simulate death. Through his contacts with the Haitian voodoo community Davis obtained recipes for zombie powders and was intrigued to find that a vital component was puffer fish. Puffer fish, or fugu, is highly prized as a culinary delicacy in Japan but eating it carries a significant risk: the fish contains a highly potent neurotoxin called tetrodotoxin. If puffer fish is not prepared in a way that removes the organs containing the highest concentrations of tetrodotoxin, "fugu poisoning" can occur, resulting in paralysis,
respiratory failure and often death. In addition to fugu-related fatalities (around 100 per year in
Japan) there have also been sporadic reports of fugu victims coming back to life after having gone into a deep coma that was mistaken for death. For Davis, these cases seemed to hold the key to the zombie legends: he hypothesised that the key active ingredient in zombie powder was in fact tetrodotoxin.
To test his hypothesis, Davis sent samples of the powder for biochemical analysis by Laurent
Rivier at the University of Lausanne, Switzerland who confirmed the presence of tetrodotoxin and to Professor Leon Roizin at Columbia Presbyterian College, New York who tested it on rats. After it had been applied to their skin the animals quickly became immobile and after six hours appeared to be dead. However, EEGs and ECGs revealed low levels of brain and cardiac activity.
Armed with these data, Davis reported his hypothesis to the scientific press and received a flurry of publicity.
Subsequent scientific investigations have poured scorn on Davis' zombie theory. It has been pointed out that the levels of tetrodotoxin in zombie powders are too low to have much effect and that even if higher levels were present it would be extremely difficult to control the dose such that the victim became a zombie rather than a bone fide corpse. Nevertheless, the intriguing possibility remains that zombies may in fact be products of pharmacology rather than over-active imaginations.
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