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Afican cobra venom and necrosis
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by Parcelmouth on May 6, 2003
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Hello again and thanks for the responses to my last question.Now on to my next question.As most people say that cobra venom is mostly neurotoxic(sorry for the venom stereotype Most books I have read say no venom is all neurotoxic or hemotoxic),but as a general guideline most elapid venoms are less rich in enzymes particularly proteases than vipers.I have recently read that the most common effect of elapid envenomation in Africa is local tissue necrosis.The hypothesis stated in the reading(Clinical Toxicology of Animal Venoms and Poisons)With African spitting cobras(genus listed were Naja and Hemachatus) was of cytotoxins or sometimes cardiotoxins in the venom.Also the presence of phospholipases A2.Another hypothesis was amount of venom injected and another was Cobra venom factor which activates the compliment system by alternative pathway.Also one other species was mentioned N. nigricollis that was stated to have PLA2 like anticoagulant that caused clot retraction in vitro.If anyone would be kind enough to explain this further or give additional information it would be most helpful.Thank you for your response.
J.S.
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RE: Afican cobra venom and necrosis
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by BGF on May 6, 2003
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Hi mate
The venoms can vary quite widely in any groups of snakes and there are many ways to be each of the actions.
The elapids have quite a number of ways to be neurotoxic but the vipers have a couple too and viper neurotoxicity is much more common than widely appreciated. Neither use the same pathways as the other.
Localised tissue destruction in vipers is due largely to the various proteases, happy little pac-mans gobbling up the cellular glue. In the few elapids that do it, they do it in different ways. The mulga snake (Pseudechis australis) from Australia (coincidently) is one of the few Australian elapids that can cause local tissue death. It does it through an abundance of myotoxic PLA2s. If they can get concentrated enough in an area, the tissue damage justs gets more concentrated too. The fact that mulgas have the highest venom yield for any snake in the world (1.4 grams!) probably helps.
In the African (and many Asian too as a matter of fact!) cobras, the local tissue death is largely due to a three finger toxin group called the cytotoxins. Cytotoxins and cardiotoxins are the same molecular group (we have a molecular phylogenetics paper on the elapid three finger toxins coming out soon that goes into all that). Ones man cytotoxin was another mans cardiotoxin. While it hasn't been proven yet, its quite likely that the cytotoxins are binding to a receptor somewhere on a cell surface.
The venom action of CVF (cobra venom factor) is still poorly understood. There is some good work being done in that area by a Ph.D. student in Singapore I helped get going and it should be interesting to see what she comes out with. She's a good researcher so it will turn out very well.
Cheers
BGF
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