A xenobiotic is a chemical which is found in an organism but which is not normally produced or expected to be present in it. A chemical substance is a Material with a definite chemical composition. It can also cover substances which are present in much higher concentrations than are usual. In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance

Specifically, drugs such as antibiotics are xenobiotics in humans because the human body does not produce them itself nor would they be expected to be present as part of a normal diet. Medication, also referred to as medicine, can be loosely defined as any substance intended for use in the diagnosis cure mitigation treatment or prevention of disease In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa However, the term is also used in the context of pollutants such as dioxins and polychlorinated biphenyls and their effect on the biota. Pollution is the introduction of contaminants into an environment that causes instability disorder harm or discomfort to the physical systems or living organisms they are in Not to be confused with Dioxane or Digoxin. Dioxin is a heterocyclic, organic, antiaromatic compound Polychlorinated biphenyls ( PCB s are a class of Organic compounds with 1 to 10 Chlorine atoms attached to Biphenyl which is a molecule composed Natural compounds can also become xenobiotics if they are taken up by another organism, such as the uptake of natural human hormones by fish found downstream of sewage treatment plant outfalls, or the chemical defenses produced by some organisms as protection against predators.

Some xenobiotics can induce apoptosis at lower doses and necrosis at higher doses. Xenobiotics at low concentration can induce precommited reversible apoptotic phase which is followed by irreversible apoptotic phase.

Contents 1 Xenobiotic metabolism 2 Xenobiotics in the environment 3 Inter-species organ transplantation 4 See also 5 References 6 External links

Xenobiotic metabolism

Main article: Xenobiotic metabolism

The body removes xenobiotics by xenobiotic metabolism. Xenobiotic metabolism is the set of Metabolic pathways that modify the chemical structure of Xenobiotics which are compounds foreign to an organism's normal biochemistry This consists of the deactivation and the secretion of xenobiotics, and happens mostly in the liver. Secretion routes are urine, feces, breath, and sweat. Hepatic enzymes are responsible for the metabolism of xenobiotics by first activating them (oxidation, reduction, hydrolysis and/or hydration of the xenobiotic), and then conjugating the active secondary metabolite with glucuronic or sulphuric acid, or glutathione, followed by excretion in bile or urine. An example of a group of enzymes involved in xenobiotic metabolism is hepatic microsomal cytochrome P450. Cytochrome P450 (abbreviated CYP, P450, infrequently CYP450) is a very large and diverse superfamily of Hemoproteins found in all Domains These enzymes that metabolize xenobiotics are very important for the pharmaceutical industry, because they are responsible for the breakdown of medications.

Organisms can also evolve to tolerate xenobiotics. eVolution is the third Album by eLDee, it was due to be released in 2008 An example is the co-evolution of the production of tetrodotoxin in the rough-skinned newt and the evolution of tetrodotoxin resistance in its predator, the common garter snake. In a broad sense biological co-evolution is "the change of a biological object triggered by the change of a related object" Tetrodotoxin (anhydrotetrodotoxin 4-epitetrodotoxin tetrodonic acid TTX is a potent Neurotoxin with no known antidote which blocks Action potentials in Nerves The rough-skinned newt ( Taricha granulosa) is a North American Newt known for its strong poison The common garter snake ( Thamnophis sirtalis) is a Snake indigenous to North America. In this predator-prey pair, an evolutionary arms race has produced high levels of toxin in the newt and correspondingly high levels of resistance in the snake. In Evolutionary biology, an evolutionary arms race is an Evolutionary struggle between competing sets of co-evolving Genes that develop adaptations ^[1] This evolutionary response is based on the snake evolving modified forms of the ion channels that the toxin acts upon, so becoming resistant to its effects. Ion channels are pore-forming Proteins that help establish and control the small Voltage Gradient across the Plasma membrane of all living ^[2]

Xenobiotics in the environment

Xenobiotic substances are becoming an increasingly large problem in Sewage Treatment systems, since they are relatively new substances and are very difficult to categorize. Sewage treatment, or domestic wastewater treatment, is the process of removing Contaminants from Wastewater, both Runoff ( Effluents Antibiotics, for example, were derived from plants originally, and so mimic naturally occurring substances. In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa This, along with the natural monopoly nature of municipal Waste Water Treatment Plants makes it nearly impossible to remove this new pollutant load. Natural monopoly is a term used in Economics to refer to two different things

Some xenobiotics are resistant to degradation. For example, they may be synthetic organochlorides such as plastics and pesticides, or naturally occurring organic chemicals such as polyaromatic hydrocarbons (PAHs) and some fractions of crude oil and coal. Applications The simplest form of organochlorides are chlorinated Hydrocarbons These consist of simple Hydrocarbons in which one or more hydrogen atoms have However, it is believed that microorganisms are capable of degrading all the different complex and resistant xenobiotics found on the earth.

Inter-species organ transplantation

Main article: Xenotransplantation

The term xenobiotic is also used to refer to organs transplanted from one species to another. Xenotransplantation ( xeno- from the Greek meaning "foreign" is the transplantation of living cells tissues or organs In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. For example, some researchers hope that hearts and other organs could be transplanted from pigs to humans. The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic Pigs, also called hogs or' swine', are Ungulates which have been domesticated as sources of food leather and similar products since ancient times Many people die every year whose lives could have been saved if a critical organ had been available for transplant. Kidneys are currently the most commonly transplanted organ. The kidneys are complicated organs that have numerous biological roles Xenobiotic organs would need to be developed in such a way that they would not be rejected by the immune system. Immunity is a material term that describes a state of having sufficient biological defenses to avoid Infection, Disease, or other unwanted biological invasion With the development of vitrification transplantable organs could be stored in organ banks for long periods. Vitrification is a process of converting a material into a Glass -like Amorphous solid that is free from any Crystalline structure either by the quick removal

See also

• Artificial organ
• Organ donation
• Medical grafting
• Drug metabolism

References

External links

• Re-engineering the toilet for sustainable wastewater management
• International Society for the Study of Xenobiotics

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