Venomous snake

Turning now to chemical attack, many predators immobilize their prey by injecting toxins, often neurotoxins, into them. Examples include venomous snakes, spiders, and scorpions. Some spider toxins (Quick and Usherwood 1990 Figure 1.3) are neurotoxic through antagonistic action upon glutamate receptors. The venom of some scorpions contains polypeptide neurotoxins that bind to the sodium channel. 

Administration of preformed anhbodies, taken from animals, flxm pooled human serum, or flom human cell-lines is often used to treat an existing infechon (e.g. tetanus, diphtheria) or condition (venomous snake-bite). Pooled human serum may also be administered prophylachcally, within a slow-release vehicle, for those persons entering parts of the world where diseases such as hepatitis A are endemic. Such administrations confer no long-term immunity and will interfere with conciurent vaccinalion procedures. 

Lizards that prey on snakes hut are also eaten hy larger snakes discriminate skin chemicals of snakes very well. Monitor lizards, Varanus albigularis, fall in this group. Hatchling monitors attacked harmless snakes but avoided venomous species. However, they accepted meat of all snakes if carefully skinned. The hatchlings tongue flicked to invertebrate prey covered with skin from venomous snakes and rejected these samples (Phillips and Alberts, 1992). 

Phillips, J. A. and Alberts, A. C. (1992). Naive ophiophagus lizards recognize and avoid venomous snakes using chemical cues. Journal of Chemical Ecology 18, 1775-1783. 

Williams, B. L., Brodie, E. D., Jr., and Brodie E. D., Ill (2004). A resistant predator and its toxic prey persistence of newt toxin leads to poisonous (not venomous) snakes. Journal of Chemical Ecology 30,1901-1919. 

Snakes occupy a unique place in our collective imagination. The primary function of snake venom is to immobilize or kill prey for food. A secondary function of the venom is defensive or protective, but clearly snakes are not capable of eating large animals, such as humans. Often venomous snakes will strike but not release venom, which conserves a valuable resource. Approximately 400 of the more than 3500 species of snake are sufficiently venomous to be a threat to humans and other large animals. 

The second most common venomous snakes are the Elapidae, of which cobras and coral snakes are well known. These snakes deliver their venom from fixed fangs and must hold onto the victim while the venom is released. These snakes tend to... 

Warrell DA. Treatment of bites by adders and exotic venomous snakes. BMJ 2005 331(7527) 1244-7. 

Presynaptic snake neurotoxins endowed with PLA2 activity (SPANs) are major components of the venom of four families of venomous snakes (Crotalidae, Elapidae, Hydrophiidae, and Viperidae). These neurotoxins play a crucial role in envenomation of the prey (Harris 1997) by causing a persistent blockade of neurotransmitter release from nerve terminals with a peripheral paralysis very similar to that of botulism (Connolly et al. 1995 Gutidrrez et al. 2006 Kularatne 2002 Prasampun et al. 2005 Theakston et al. 1990 Trevett et al. 1995 Warrell et al. 1983). 

Snakes belong to the phylum Chordata, Class Rept-ilia. Two major families of venomous snakes are Crotalidae and Elapidae. 

See also Animals, Poisonous and Venomous Snake, Elapidae Snakes. 

All venomous snake species occur within the superfamily Colubroidea advanced snakes , a large and ecologically diverse group distributed worldwide. Within Colubroidea there are five families that have species (all or in part), which are considered venomous Elapidae, Viperidae, Hydrophiidae, At-ractaspididae, and Colubridae. 

Venomous snakes and venom have always been of interest to biologists. Historically, snake venoms were viewed as a valuable aid and were frequently used in early medical therapies. Ancient Egyptian and Chinese physicians utilized snake venoms as treatment for a variety of ailments and diseases. For over a century, snake venom has been used to develop antivenoms to treat snakebite envenomation. Currently, there are over 30 facilities worldwide that produce 120 different commercially available antivenoms. These antivenoms include both monovalent forms (effective for a specific species) and polyvalent forms (generally effective for several species that occur... 

Venomous snakes have developed various features that warn off would-be predators. The coral snakes have venom sufficiently powerful to harm a human being and are brightly colored with bands of black, yellow and red. Some harmless snakes have developed similar body markings which send the same messages to local predators and people alike. In southern North America and tropical South America there are many species of snake that mimic the genuinely dangerous coral snakes. 

Agistrodon Piscivorus Most poisous snakes in the United States and tropical regions are pit vipers. Pit vipers are a group of venomous snakes that have deep depressions on each side of the face between the nostril and the eye. These are associated with a membrane that is incredibly sensitive to changes in temperature and serves to detect the presence of infra-red heat. Equipped with the most efficient natural heat receptors in the animal world, these pits allow the snake to sense the heat difference between a small animal and the cooler rocks, plants and other objects in the area. When a warm-blooded animal ventures closer than 20", the snake can detect the prey entirely... 

Photo courtesy of Munhy. "Venomous Snakes of Medical Impunance in India (Part At." In Snakes of Metlictil Imporiancc tAsia-Pui ifii Region p. 29 (i990), P. Gopalaknishnakone and L. M, Chou, eds. 

There is a bioreaction engineering home problem in virtually every chapter. Bio-related web modules include physiological-based-pharmacokinetic (PBPK) models of ethanol metabolism, of drug distribution, and of venomous snake bites by the Russels viper and the cobra. 

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