toxin

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Properly, a poisonous protein, especially of bacterial origin. However, nonproteinaceous poisons, such as fungal aflatoxins and plant alkaloids, are often called toxins. See also Aflatoxin; Alkaloid.

Bacterial exotoxins are proteins of disease-causing bacteria that are usually secreted and have deleterious effects. Several hundred are known. In some extreme cases a single toxin accounts for the principal symptoms of a disease, such as diphtheria, tetanus, and cholera. Bacteria that cause local infections with pus often produce many toxins that affect the tissues around the infection site or are distributed to remote organs by the blood. See also Cholera; Diphtheria; Staphylococcus.

Toxins may assist the parent bacteria to combat host defense systems, to increase the supply of certain nutrients such as iron, to invade cells or tissues, or to spread between hosts. Sometimes the damage suffered by the host organism has no obvious benefit to the bacteria. For example, botulinal neurotoxin in spoiled food may kill the person or animal that eats it long after the parent bacteria have died. In such situations it is assumed that the bacteria benefit from the toxin in some other habitat and that the damage to vertebrates is accidental. See also Food poisoning.

Certain bacterial and plant toxins have the unusual ability to catalyze chemical reactions inside animal cells. Such toxins are always composed of two functionally distinct parts termed A and B, and they are often called A-B toxins. The B part binds to receptor molecules on the animal cell surface and positions the toxin upon the cell membrane. Subsequently, the enzymically active A portion of the toxin crosses the animal cell membrane and catalyzes some intracellular chemical reaction that disrupts the cell physiology or causes cell death. See also Immunologic cytotoxicity.

A large group of toxins breach the normal barrier to free movement of molecules across cell membranes. In sufficient concentration such cytolytic toxins cause cytolysis, a process by which soluble molecules leak out of cells, but in lower concentration they may cause less obvious damage to the cell's plasma membrane or to its internal membranes. See also Cell permeability.

Tetanus and botulinal neurotoxins block the transmission of nerve impulses across synapses. Tetanus toxin blockage results in spastic paralysis, in which opposing muscles contract simultaneously. The botulinal neurotoxins principally paralyze neuromuscular junctions and cause flaccid paralysis.

Gram-negative bacteria, such as Salmonella and Hemophilus, have a toxic component in their cell walls known as endotoxin or lipopolysaccharide. Among other detrimental effects, endotoxins cause white blood cells to produce interleukin-1, a hormone responsible for fever, malaise, headache, muscle aches, and other nonspecific consequences of infection. The exotoxins of toxic shock syndrome and of scarlet fever induce interleukin-1 and also tumor necrosis factor, which has similar effects. See also Endotoxin; Fever; Scarlet fever; Toxic shock syndrome.

Toxoids are toxins that have been exposed to formaldehyde or other chemicals that destroy their toxicities without impairing immunogenicity. When injected into humans, toxoids elicit specific antibodies known as antitoxins that neutralize circulating toxins. Such immunization (vaccination) is very effective for systemic toxinoses, such as diphtheria and tetanus. See also Antibody; Immunity; Vaccination.

A term applied to poisons which are toxic to the human body. Many come from microorganisms — for example, cholera toxin and tetanus toxin are derived respectively from Vibrio cholera and Clostridium tetani. Some toxins are derived from higher organisms — the deadly tetrodotoxin, which blocks nerve conduction, is derived from the liver and ovaries of the puffer fish. Yet others are of fungal origin, such as the liver toxic substance aflatoxin, from a fungus which grows on groundnuts.

— Alan W. Cuthbert

See immunization; microorganisms; poisons; toxicology.

noun

Anything that is injurious, destructive, or fatal: bane, canker, contagion, poison, venom, virus. See help/harm/harmless.

A poisonous protein made by specific animals, higher levels of plants, and diseasecausing bacteria.

A poisonous protein formed by bacteria, plants, and animals. Toxins act as antigens in the body.

Toxins are compounds that are produced and released by a variety of microorganisms and other organisms. Toxins can be fast-acting and, because they are already preformed, do not require the growth of a microorganism in the host. State-sanctioned weaponization programs for various toxins have occurred in the past in many countries, and may be ongoing. As well, toxins are a potent weapon for terrorists.

Bacterial toxins. Toxins are the main disease-causing factor for a number of bacteria. Some examples include Corynebacterium diphtheriae (diptheria), Vibrio cholerae (cholera), Bacillus anthracis (anthrax), Clostridium botulinum (botulism), certain strains of Escherichia coli (hemolytic uremic syndrome), and Staphylococcus aureus (toxic shock syndrome).

Certain species of these bacteria are of particular concern in biological warfare and biological terrorism. As the events of 2001 in the United States demonstrated, powdered preparations of Bacillus anthracis spores was easily delivered to a target through the mail. The dispersal of the spores in the air and the inhalation of the spores can cause a form of anthrax that develops quickly and, without treatment, is almost always fatal. The bacteria in the genus Clostridium also form spores. Additionally, during the 1990s, a strain of Staphylococcus aureus emerged that is resistant to almost all known antibiotics.

Bacterial toxins have a wide variety of activity. Some toxins damage the cell wall of host cells, either by dissolving the wall or by chemically punching holes through the wall. Examples of such toxins are the alpha toxin of Clostridium perfringens, hemolysin of Escherichia coli, and streptokinase of Streptococcus pyogenes. The damage to the host cells allows the bacteria to spread rapidly through the host. This can cause an overwhelming infection.

Other bacterial toxins kill host cells by stopping the manufacture of protein in host cells or by degrading the proteins. Examples of protein blockers include exotoxin A of Pseudomonas aeruginosa and the Shiga toxins produced by both Escherichia coli and Shigella dysenteriae. Protein degrading toxins include those produced by Bacillus anthracis and Clostridium botulinum

Still other toxins stimulate an immune response of the host that is so strong that it can damage the host. Staphylococcus aureus produces at least three different toxins that have this effect (i.e., toxic shock syndrome).

Marine toxins. Microorganisms called dinoflagellates can produce toxins when they grow in species of shellfish. Usually, the toxins are a concern when the contaminated seafood is inadvertently eaten. But, the toxins can be isolated in pure form. The purified toxins will produce illness when deliberately used.

Aflatoxin. Aflatoxin is produced by two species of mold—Aspergillus flavus and Aspergillus parasiticus. The toxin is especially a concern when potatoes are contaminated by the mold. Ingestion of the contaminated potatoes can cause serious, even fatal illness. This toxin is of particular concern for food supplies. Storehouses of produce like potatoes are susceptible to the malicious release of the molds.

Ricin. Ricin is a toxin that is produced by the castor bean. It is the third most deadly toxin that is known, after the toxins produced by Clostridium botulinum and Clostridium tetani. The symptoms of ricin toxin include nausea, muscle spasms, severe lung damage, and convulsions. These symptoms appear within hours, and, without treatment, death from pulmonary failure can result within three days. There is no vaccine or antidote for the toxin.

Ricin has long been a weapon of espionage and terrorism. The most famous use of ricin occurred in 1978, when Georgi Markov—a recently defected Bulgarian official—was killed by KGB agents on a bridge in London. An umbrella tip was used to inject a capsule of ricin into one of his legs.

The planned use of ricin by al-Qaeda has been alleged. Traces of ricin have been found in caves in Afghanistan that were used by al-Qaeda. Iraq is also suspected of using ricin in its weaponization program of the 1990s. Also, in January 2003, British antiterrorism officers seized a quantity of ricin in London from a group of Algerian men suspected of being terrorists.

Toxoid vaccines. Some toxins that are capable of causing much harm are also a source of protection. Because of its potency, a toxin cannot be used protectively in its unaltered form. Toxins can be altered, however, so that they do not produce the undesirable effects, but which still stimulate the immune system to produce antibodies to a critical part of the toxin molecule. The weakened version of a toxin is called a toxoid.

The anthrax vaccine that is currently licensed for use contains two toxoids in addition to other immune stimulating molecules. The immune response will produce antibodies to the two toxins of the anthrax bacterium.

Further Reading

Periodicals

Schmitt, C. K., K. C. Meysick, and A. D. O'Brien. "Bacterial Toxins: Friends or Foes?" Emerging Infectious Diseases no. 5 (1999): 224–34.

Electronic

Centers for Disease Control and Prevention. "Marine Toxins." Division of Bacterial and Mycotic Diseases. June 10, 2002. <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/marinetoxins_g.htm>(29 January 2003).

United States Department of Agriculture. "Aflatoxin." USDA Grain Inspection, Packers and Stockyards Administration. September 17, 1998. <http://www.usda.gov/gipsa/newsroom/backgrounders/b-aflatox.htm>(29 January 2003).

University of Wisconsin at Madison. "Mechanisms of Bacterial Pathogenicity: Protein Toxins." Bacteriology at UW-Madison. 2002. <http://www.bact.wisc.edu/Bact330/lecturept>(30 January 2003).

Poisonous substances, consisting mainly of protein, that are a by-product of metabolism in certain organisms. Toxins that enter the body through a bacterial infection can be very harmful and can result in diseases such as tetanus and botulism.

A poison, especially a protein or conjugated protein produced by certain animals, some higher plants, and pathogenic bacteria. Antigenic toxins, produced by bacteria or helminths, stimulate production of antitoxins. Exotoxins are produced by bacteria and diffuse into surroundings, e.g. tetanus toxin, or can be ingested preformed, e.g. botulinum toxin. Endotoxins are released into the surrounding tissue only when the bacteria break down. They are lipopolysaccharides and form part of the cell wall, e.g. coliform endotoxins. Metabolic toxins, e.g. toxic amines absorbed from damaged intestine, ketones, lactic acid from carbohydrate engorgement, ammonia in liver damage, creatinine in renal dysfunction. See also metabolic toxins.

• dermonecrotic t. — an exotoxin produced by certain bacteria that causes extensive local necrosis on intradermal inoculation.
• extracellular t. — exotoxin.
• intracellular t. — endotoxin.
• tetanus t. — the potent neurotoxic exotoxin produced by Clostridium tetani. Called also tetanospasmin.

See toxin agent.

This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (November 2006)

For other uses, see Toxin (disambiguation).

For a list of biologically injurious substances, including toxins and other materials, as well as their effects, see poison.

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Toxicology and Poison

General Toxicology (Forensic) Toxinology History of poison

Concepts Poison Venom Toxicant (Toxin) Acceptable daily intake Acute toxicity Bioaccumulation Biomagnification Fixed Dose Procedure LD50 Lethal dose Toxic capacity Toxicity Class

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v • d • e

Universal warning symbol used to indicate toxic substances or environments

A toxin (Greek: τοξικόν, toxikon) is a poisonous substance produced by living cells or organisms^[1][2] (although humans are technically living organisms, man-made substances created by artificial processes usually aren't considered toxins by this definition).

For a toxic substance not produced by living organisms, "toxicant" is the more appropriate term, and "toxics" is an acceptable plural.

Toxins can be small molecules, peptides, or proteins that are capable of causing disease on contact with or absorption by body tissues 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).

Contents 1 Terminology 2 Biotoxins 3 Environmental toxins 4 Non-technical usage 5 See also 6 References 7 External links

Terminology

Toxins are often distinguished from other chemical agents by their method of production- the word toxin does not specify method of delivery (compare with venom and (the narrower meaning of) poison). It simply means it is a biologically produced poison. There was an ongoing dispute between NATO and the Warsaw Pact over whether to call a toxin a biological or chemical agent, in which the former opted for the latter, and vice versa.

According to a International Committee of the Red Cross review of the Biological Weapons Convention, "Toxins are poisonous products of organisms; unlike biological agents, they are inanimate and not capable of reproducing themselves." and "Since the signing of the Convention, there have been no disputes among the parties regarding the definition of biological agents or toxins..."^[3]

According to Title 18 of the United States Code, "...the term "toxin" means the toxic material or product of plants, animals, microorganisms (including, but not limited to, bacteria, viruses, fungi, rickettsiae or protozoa), or infectious substances, or a recombinant or synthesized molecule, whatever their origin and method of production..."^[4]

A rather informal terminology of individual toxins relate them to the anatomical location where their effects are most notable:

• Hemotoxin, causes destruction of red blood cells (hemolysis)
• Phototoxin, causes dangerous photosensitivity

On a broader scale, toxins may be classified as either exotoxins, being excreted by an organism, and endotoxins, that are released mainly when bacteria are lysed.

Related terms are:

• Toxoid, weakened or suppressed toxin
• Venom, toxins in the sense of use by certain types of animals

Biotoxins

The term "biotoxin" is sometimes used to explicitly confirm the biological origin.^[5][6]

Toxins produced by microorganisms are important virulence determinants responsible for microbial pathogenicity and/or evasion of the host immune response^[7].

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.

Biotoxins in nature have two primary functions:

• Predation (spider, snake, scorpion, jellyfish, wasp)
• Defense (bee, ant, termite, honeybee, wasp, poison dart frog)

Some of the more well known types of biotoxins include:

• Cyanotoxins, produced by cyanobacteria
• Hemotoxins target and destroy red blood cells, and are transmitted through the bloodstream. Organisms that produce hemotoxins include:
  • Pit vipers, such as rattlesnakes
• Necrotoxins cause necrosis (i.e., death) in the cells they encounter and destroy all types of tissue^{[citation needed]}. Necrotoxins spread through the bloodstream^{[citation needed]}. In humans, skin and muscle tissues are most sensitive to necrotoxins^{[citation needed]}. Organisms that possess necrotoxins include:
  • The brown recluse or "fiddle back" spider
  • The "Puff Adder" - Bitis arietans
  • Necrotizing fasciitis (the "flesh eating" bacteria)
• Neurotoxins primarily affect the nervous systems of animals. Organisms that possess neurotoxins include:
  • The Black Widow and other widow spiders
  • Most scorpions
  • The box jellyfish
  • Elapid snakes
  • The Cone Snail
• Cytotoxins are toxic at the level of individual cells, either in a non-specific fashion or only in certain types of living cells:
  • Ricin is a plant toxin found in the castor bean plant
• Apitoxin, the honey bee venom

Environmental toxins

The term "environmental toxin" is often used.^[8][9][10]

In these contexts, it can sometimes explicitly include contaminants that are man-made, ^[11] which contradicts most formal definitions of the term "toxin". Because of this, when encountering the word "toxin" outside of microbiological contexts, it is important to confirm what the researcher means by the use of the term.

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. Many non-technical and lifestyle journalists also follow this usage to refer to toxic substances in general, though some specialist journalists at publishers such as the BBC^{[citation needed]} and The Guardian^[12] maintain the distinction that toxins are only those produced by living organisms.

In the context of alternative medicine the term is often used non-specifically to refer to any substance claimed to cause ill health, ranging anywhere from trace amounts of pesticides to common food items like refined sugar or additives like artificial sweeteners and MSG.^{[citation needed]}

See also

• Insect toxins
• List of fictional toxins
• List of highly toxic gases
• Microbial toxins
• Toxicophore, feature or group within a chemical structure that is thought to be responsible for the toxic property

References

1. ^ toxin at Dorland's Medical Dictionary
2. ^ "toxin - Definition from the Merriam-Webster Online Dictionary". http://www.merriam-webster.com/dictionary/toxin. Retrieved 2008-12-13. 
3. ^ "The Biological Weapons Convention - An overview". http://www.icrc.org/web/eng/siteeng0.nsf/html/57JNPA. Retrieved 2008-12-13. 
4. ^ "U.S. Code". http://law2.house.gov/uscode-cgi/fastweb.exe?getdoc+uscview+t17t20+235+1++()%20%20AND%20((18)%20ADJ%20USC)%3ACITE%20AND%20(USC%20w/10%20(209))%3ACITE. Retrieved 2008-12-13. 
5. ^ "biotoxin - Definition from the Merriam-Webster Online Dictionary". http://www.merriam-webster.com/dictionary/biotoxin. Retrieved 2008-12-13. 
6. ^ biotoxin at Dorland's Medical Dictionary
7. ^ Proft T (editor) (2009). Microbial Toxins: Current Research and Future Trends. Caister Academic Press. ISBN 978-1-904455-44-8. 
8. ^ Lanphear BP, Vorhees CV, Bellinger DC (March 2005). "Protecting children from environmental toxins". PLoS Med. 2 (3): e61. doi:10.1371/journal.pmed.0020061. PMID 15783252. PMC 1069659. http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0020061. 
9. ^ Grollman AP, Jelaković B (November 2007). "Role of environmental toxins in endemic (Balkan) nephropathy. October 2006, Zagreb, Croatia". J. Am. Soc. Nephrol. 18 (11): 2817–23. doi:10.1681/ASN.2007050537. PMID 17942951. http://jasn.asnjournals.org/cgi/pmidlookup?view=long&pmid=17942951. 
10. ^ Cohen M (December 2007). "Environmental toxins and health--the health impact of pesticides". Aust Fam Physician 36 (12): 1002–4. PMID 18075622. http://www.racgp.org.au/afp/200712/21201. 
11. ^ Grigg J (March 2004). "Environmental toxins; their impact on children's health". Arch. Dis. Child. 89 (3): 244–50. PMID 14977703. PMC 1719840. http://adc.bmj.com/cgi/pmidlookup?view=long&pmid=14977703. 
12. ^ Corrections and clarifications, The Guardian, 30 May 2005.

External links

• Society of Toxicology
• The Journal of Venomous Animals and Toxins including Tropical Diseases
• Special Issue on "Marine Toxins"
• ATDB: A animal toxin database

v • d • e Toxins (enterotoxin/neurotoxin/hemotoxin/cardiotoxin) Bacterial toxins Exotoxin Gram positive Bacilli Clostridium: tetani (Tetanospasmin) · perfringens (Alpha toxin, Enterotoxin) · difficile (A, B) · botulinum (Botox) other: Anthrax toxin · Listeriolysin O Cocci Streptolysin · Leukocidin (Panton-Valentine leukocidin) · Staphylococcus (Staphylococcus aureus alpha/beta/delta, Exfoliatin, Toxic shock syndrome toxin, SEB) Actinobacteria Cord factor · Diphtheria toxin Gram negative Shiga toxin · Verotoxin/shiga-like toxin (E. coli) · E. coli heat-stable enterotoxin/enterotoxin · Cholera toxin · Pertussis toxin · Pseudomonas exotoxin · Extracellular adenylate cyclase By mechanism type I (Superantigen) · type II (Pore forming toxins) · type III (AB toxin/AB5) Endotoxin Lipopolysaccharide (Lipid A) · Bacillus thuringiensis delta endotoxin Virulence factor Clumping factor A · Fibronectin binding protein A Mycotoxins Aflatoxin · Amatoxin (alpha-amanitin, beta-amanitin, gamma-amanitin, epsilon-amanitin) · Citrinin · Cytochalasin · Ergotamine · Fumonisin (Fumonisin B1, Fumonisin B2) · Gliotoxin · Ibotenic acid · Muscimol · Ochratoxin · Patulin · Sterigmatocystin · Trichothecene · Vomitoxin · Zeranol · Zearalenone Invertebrates arthropod: scorpion: Charybdotoxin, Maurotoxin, Agitoxin, Margatoxin, Slotoxin, Scyllatoxin, Hefutoxin, Lq2 · spider: Latrotoxin (Alpha-latrotoxin) · Stromatoxin · PhTx3 mollusca: Conotoxin · Eledoisin · Onchidal · Saxitoxin Vertebrates fish: Ciguatera · Tetrodotoxin amphibian: (+)-Allopumiliotoxin 267A · Batrachotoxin · Bufotoxins (Arenobufagin, Bufotalin, Bufotenin · Cinobufagin, Marinobufagin) · Epibatidine · Histrionicotoxin · Pumiliotoxin 251D · Tarichatoxin reptile/snake venom: Bungarotoxin (Alpha-Bungarotoxin, Beta-Bungarotoxin) · Calciseptine · Taicatoxin · Calcicludine · Cardiotoxin III note: some toxins are produced by lower species and pass through intermediate species

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Dansk (Danish)
n. - toksin

Nederlands (Dutch)
gif, giftige stof

Français (French)
n. - toxine

Deutsch (German)
n. - Toxin, Gift(stoff)

Ελληνική (Greek)
n. - (χημ.) τοξίνη

Italiano (Italian)
tossina

Português (Portuguese)
n. - toxina (f)

Русский (Russian)
токсин, яд

Español (Spanish)
n. - toxina

Svenska (Swedish)
n. - toxin

中文（简体）(Chinese (Simplified))
毒素, 毒质

中文（繁體）(Chinese (Traditional))
n. - 毒素, 毒質

한국어 (Korean)
n. - 독소

日本語 (Japanese)
n. - 毒素

العربيه (Arabic)
‏(الاسم) ألتوكسين, ألذيفان, السمين‏

עברית (Hebrew)
n. - ‮רעלן (רעל הנוצר בגוף של בעל-חיים)‬

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