Toxin: Encyclopedia - Toxin

Toxin

A toxin (Gk. toxikon "(poison) for use on arrows,") is a poisonous substance produced by living cells or organisms. Toxins are nearly always proteins that are capable of causing disease on contact or absorption with body tissues by interacting with biological macromolecules such as enzymes or cellular receptors. Toxins vary greatly in their severity, ranging from usually minor and acute (as in a bee sting) to almost immediately deadly (as in botulinum toxin).

Biotoxins vary greatly in purpose and mechanism, and can be highly complex (the venom of the cone snail contains dozens of small proteins, each targeting a specific nerve channel or receptor), or relatively small protein.

Toxin - Use

Biotoxins are used in nature for two primary reasons:

• Predation (spider, snake, jellyfish, wasp)
• Defense (poison dart frog, deadly nightshade, honeybee, wasp)

Some of the more well known biotoxins include:

• Hemotoxin targets and destroys red bloodcells, and is transmitted through the bloodstream.
• Necrotoxin causes necrosis (i.e., death) in the cells it encounters and destroys all types of tissue. Necrotoxin spreads through the bloodstream, but infects all tissues. In humans, skin and muscle tissues are most sensitive to necrotoxin. Organisms that possess necrotoxin include:
  • The brown recluse or "fiddle back" spider.
  • Necrotizing fasciitis (the "flesh eating" bacteria)
• Neurotoxin primarily affects the nervous systems of animals. Organisms that possess neurotoxin include:
  • The black widow and other widow spiders.
  • The box jellyfish.
  • Elapid snakes.

When toxins are generated by bacteria, they are called toxoids. The toxins may be produced either in the living body during infection (for instance, by tetanus) or by bacteria in dead biological material.

In the context of complementary medicine the term is often used as a broader category of any harmful substance claimed to cause ill health, though mainstream scientists argue that the nature of such substances is usually unproven. Many publishers of non-technical material, such as the BBC, also follow this usage to refer to toxic substances in general, though some such as The Guardian maintain the distinction that toxins are only those produced by living organisms.

Toxin - Non-technical usage

When used non-technically, the term "toxin" is often applied to any toxic substances. Toxic substances not of biological origin are more properly termed poisons.

Practitioners of alternative medicine often apply the term in a non-specific manner to refer to a broad category of harmful substances claimed to cause ill health.

See also

• Apitoxin
• Hemotoxin
• Neurotoxin

Adapted from the Wikipedia article "Toxin", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki