Dolichocolon is an abnormally long large intestine. It should not be confused with an abnormally wide large intestine, which is called a megacolon.Dolichocolon may predispose to abnormal rotation (see volvulus) and interposition between the diaphragm and the liver (see Chilaiditi syndrome). It is more commonly seen in the elderly, some psychiatric patients or in institutionalised individuals. It is not, however, a part of normal aging. The exact cause remains unknown.Dolichocolon is often an incidental finding on abdominal X-rays or colonoscopy. It is not by itself a disease and as such requires no treatment. The term is from ancient Greek dolichos, the long distance in running, and colon. References


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As multi-drug resistant bacteria became more prevalent in the 1990s, colistin started to get a second look as an emergency solution, in spite of toxicity.Colistin has also been used in agriculture, particularly in China from the 1980s onwards. Chinese production for agriculture exceeded 2700 tons in 2015. China banned colistin use for livestock growth promotion in 2016. Biosynthesis
The biosynthesis of colistin requires the use of three amino acids: threonine, leucine, and 2,4-diaminobutryic acid. The linear form of colistin is synthesized before cycliziation. Non-ribosomal peptide biosynthesis begins with a loading module and then the addition of each subsequent amino acid. The subsequent amino acids are added with the help of an adenylation domain (A), a peptidyl carrier protein domain (PCP), an epimerization domain (E), and a condensation domain (C). Cyclization is accomplished by a thioesterase. The first step is to have a loading domain, 6-methylheptanoic acid, associate with the A and PCP domains. Now with a C, A, and PCP domain that is associated with 2,4-diaminobutryic acid. This continues with each amino acid until the linear peptide chain is completed. The last module will have a thioesterase to complete the cyclization and form the product colistin. References
Further reading
Reardon S (December 2015). "Spread of antibiotic-resistance gene does not spell bacterial apocalypse — yet". Nature. doi:10.1038/nature.2015.19037. External links
"Colistimethate sodium". Drug Information Portal. U.S. National Library of Medicine. "Colistin sulfate". Drug Information Portal. U.S. National Library of Medicine. "Colistin topics page (bibliography)". Science.gov.