Alexander Mikhailovich Zakharov and his works on the venom apparatus and venoms of some poisonous snakes

The article gives brief biographical information about a very talented herpetologist Alexander M. Zakharov, and describes the general results of his works on the structure and function of venom glands of some poisonous snakes and their venoms. In his studies, he got the results, which are fundamentally different from the conventional concept of 30s - 70s of the XX century. Unfortunately, among physicians this concept has not changed up today. At that time it was thought that the poisons of Viperidae snakes are almost completely hemotoxic, and poisons of Elapidae (cobra) are almost neurotoxic. But A.M.Zaharov found out, that poisons of both types of snakes (Viperidae and Elapidae) include three groups of substances: hemotoxins, neurotoxins and non-toxic component – hyaluronidase. Each of these groups of substances is produced by independent part of venom glands and has its own special effect. Neurotoxins act on the central nervous system (mainly the respiratory center), but are greatly destroyed by means of the blood antigen properties and cannot pass through the hematoencephalic barrier. Hyaluronidase, connecting with neurotoxins, has an important property – to "smuggle" neurotoxins through the hematoencephalic barrier exactly into the target organ – the respiratory center in the central nervous system. In this case, neurotoxin enters the respiratory center not through the blood and lymph vessels, but directly through the nerve channel, through synapsis. The main function of hemotoxins is not to kill the victim, but to protect neurotoxins and hyaluronidase from the destructive activity of the victim's blood. Therefore, the target of the poisons of Viperidae and Elapidae snakes is the central nervous system of victims, but Elapidae has almost no hemotoxins. That’s why their striking effect can be achieved only by a strong increase in the amount of neurotoxins and hyaluronidase. Hemotoxins of Viperidae venoms permits to reduce the amount of main active ingredient – neurotoxin with hyaluronidase. In the 30 - 70 years of the twentieth century, researches were carried out mainly on dried and then diluted in saline poisons. But A.M.Zaharov showed that when drying, the hyaluronidase loses its activity, as well as neurotoxins. Therefore, dried, and then diluted viper venoms when injected to experimental animals, showed only hemotoxic activity, that differs greatly from the action of native poisons, demonstrating also strong neurotoxic effects.