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Herpetological Neurotoxins A herpetological neurotoxin, more commonly known as snake venom, is essentially modified saliva. It s primary functions are to slow down (or kill depending on the potency of the venom) the prey of the snake, and to help in the early stages of digestion. Three types of venomous snake: Opisthoglyphs, Proteroglyphs, andSolenoglyphs; and many types of snake venom: hemotoxic and neurotoxic venoms are some of those that will be discussed in this paper. The first type of venomous snake, the Opisthoglyphs, contains rear fanged snakes. These rear fanged snakes have enlarged back teeth, each with a small groove that allows venom to flow down the tooth and into the prey. Most Opisthoglyphs are harmless, although two, the Boomslang (Dispholidus types) and the Twig snake (Thelotorniskirtlandi) have killed humans before.
Other examples of rear fanged snakes are the Mangrove (B. dendrophilia) and the Hognose snakes (Heterodon ssp. ). The second type of venomous snakes are the fixed front fanged snakes, orProteroglyphs. These snakes have small non-movable front fangs. When they bite they hang on and chew to envenom ate the prey.
Obvious examples of this type of snake arete cobras (Naja), kraits (Bungarus), mambas (Dendroaspis), and coral (Micrurus) snakes. These are some of the deadliest snakes in the world. The third type of venomous snake is the Solenoglyph. These snakes have movable front fangs. The fangs fold back into the mouth until they are needed. This is what makes these snakes more dangerous to work with then any of the previously mentioned ones.
They can grab on to your hand like a cobra would but they can also open their mouth almost 180 degrees with the fangs extended straight out. This enables them to strike any portion of your body because it is more of a stab than a bite. Examples include rattlesnakes (Crotalus), eyelash vipers (Bothriechis), gaboon vipers (Bits), cottonmouths and copperheads (Agkistrodon). Snake venom is made up of about 20 different enzymes. Each species usually has 6 - 12 of these enzymes. These enzymes determine the toxicity of the snake s venom, and whether it is hemotoxic or neurotoxic.
Venoms that are referred to as hemotoxic a recalled so because they primarily affect the blood. Almost all American pit vipers fall into this category. A hematosis venom destroys tissue and is very painful, having been compared to placing lit cigarettes on your skin. Neurotoxic venoms attack the nervous system and brain. These may cause almost no pain, but shut down the respiratory systems and interfere with heart functions. Good examples of these types of snakes are the cobra and the beautiful coral snakes.
All of the snakes mentioned so far have come from various places such as the United States, and Africa. While research on non-Australian snake venoms has been intensive with several major toxin classes being characterized at the molecular level, Australian snake toxin research is in its infancy. So far only three toxin classes have been identified: Procoagulants, Phospholipase A 2 s, and Neurotoxins. Also, few researchers in Australia have taken up the challenge with the result that of the 35 Australian snake toxins with complete amino acid sequences identified to date 28 of them have been b overseas researchers (Australian Venom and Toxin Database). Most procoagulants are prothrombin activating enzymes. None have been fully characterized at the molecular level.
Procoagulants lead to disseminated intravascular coagulation with defibrinationwith the net effect being hypo-coagulable blood. The use of these activators are well documented and they are to diagnosedysprothrombin aerial, to determine prothrombin concentration, and are excellent tools activate prothrombin to thrombin. They are also useful in activatingdescarboxyprothrombin. A recent use is to make FDA approved fibrin film for surgical procedures, Taipan activator is used to activate recombinant pre thrombin to alpha thrombin.
An extremely interesting, and useful, aspect of venom components from Australian elapids is in the characterization of lupus using the procoagulants texturing fromthe eastern brown snake (Pseudonaja textiles). Lupus anticoagulants (LA) are secretory IgA, or serum IgG and IgM, immunoglobulins which characteristically interfere with phospholipid dependent in vitro coagulation tests. A sensitive and rather specific confirmatory test has been developed using texturing in conjunction with earn from these-scaled viper (Echo carina tus). In the presence of LA the activation time of prothrombin by texturing is prolonged but that of earn is unaffected, thus the test consists of a useful comparative ratio between texturing / earn (Pubmed online). Snake venoms, no matter the type, are potentially dangerous to humans. Medical emergencies are created when humans are envenomed.
Most venoms are different batman have common toxins. Most venoms contain either neurotoxin's, hemorrhagic toxins or both. In the past toxicity was measured by injecting test animals (mainly mice) with venom; however, many different types of animals have been used. Mice were the universally accepted test animal and comparative toxicity was expressed as an LD 50 (lethal dose that kills 50 % of test animals). The LD 50 is usually determined by injecting the crude venom (by various routes) into mice at varying concentrations.
Today, these types of experiments are not generally performed because of animal welfare concerns, however they have been valuable in understanding the toxicity of snake venom. Therefore other specific tests that look at the effect of single toxins. These can be clotting assays to measure the effect of coagulants, nerve-muscle preparations to measure neurotoxic activity, phospholipase and phosphodiesterase assays which measure these respective agents in the venoms. Even muscle or my oblast preparations to measure the myotoxicactivity of venoms have been used. These tests are very useful to investigate the relative toxicity of the venoms. No matter the type of snake, or the type of venom, when bitten a person should seek immediate medical help.
If bitten by a very venomous snake, antivenin will usually be given to the patient. Most types of snake-venom poisoning can be treated with the use antivenins, serums that neutralize specific venoms. Because some persons may have a potentially fatal allergic reaction to these serums, however, it is generally advised that antivenins be administered only by medically trained personnel. Antivenins a redeveloped by injecting small amounts of snake venom into animals (usually horses) until the animals become immune. The antivenin is then prepared from the animals blood (World Book Encyclopedia).
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