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A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to research human disease when human experimentation would be unfeasible or unethical.〔Griffiths, E. C. (2010) (What is a model? )〕 This strategy is made possible by the common descent of all living organisms, and the conservation of metabolic and developmental pathways and genetic material over the course of evolution. Studying model organisms can be informative, but care must be taken when extrapolating from one organism to another.〔Slack, J.M.W. (2013) Essential Developmental Biology. Wiley-Blackwell, Oxford.〕 In researching human disease, model organisms allow for better understanding the disease process without the added risk of harming an actual human. The species chosen will usually meet a determined taxonomic equivalency to humans, so as to react to disease or its treatment in a way that resembles human physiology as needed. Although biological activity in a model organism does not ensure an effect in humans, many drugs, treatments and cures for human diseases are developed in part with the guidance of animal models. There are three main types of disease models: homologous, isomorphic and predictive. Homologous animals have the same causes, symptoms and treatment options as would humans who have the same disease. Isomorphic animals share the same symptoms and treatments. Predictive models are similar to a particular human disease in only a couple of aspects, but are useful in isolating and making predictions about mechanisms of a set of disease features. ==History== The use of animals in research dates back to ancient Greece, with Aristotle (384–322 BCE) and Erasistratus (304–258 BCE) among the first to perform experiments on living animals.〔Cohen and Loew 1984.〕 Discoveries in the 18th and 19th centuries included Antoine Lavoisier's use of a guinea pig in a calorimeter to prove that respiration was a form of combustion, and Louis Pasteur's demonstration of the germ theory of disease in the 1880s using anthrax in sheep. Research using animal models has been central to most of the achievements of modern medicine. It has contributed most of the basic knowledge in fields such as human physiology and biochemistry, and has played significant roles in fields such as neuroscience and infectious disease.〔Hau and Shapiro 2011: * *〕 For example, the results have included the near-eradication of polio and the development of organ transplantation, and have benefited both humans and animals.〔 From 1910 to 1927, Thomas Hunt Morgan's work with the fruit fly ''Drosophila melanogaster'' identified chromosomes as the vector of inheritance for genes.〔(【引用サイトリンク】url=http://nobelprize.org/nobel_prizes/medicine/laureates/1933/index.html )〕〔(【引用サイトリンク】url=http://www.nobelprize.org/nobel_prizes/medicine/laureates/1933/morgan-article.html )〕 ''Drosophila'' became one of the first, and for some time the most widely used, model organisms,〔Kohler, ''Lords of the Fly'', chapter 5〕 and Eric Kandel wrote that Morgan's discoveries "helped transform biology into an experimental science."〔Kandel, Eric. 1999. ("Genes, Chromosomes, and the Origins of Modern Biology" ), ''Columbia Magazine''〕 ''D. melanogaster'' remains one of the most widely used eukaryotic model organisms. During the same time period, studies on mouse genetics in the laboratory of William Ernest Castle in collaboration with Abbie Lathrop led to generation of the DBA ("dilute, brown and non-agouti") inbred mouse strain and the systematic generation of other inbred strains. The mouse has since been used extensively as a model organism and is associated with many important biological discoveries of the 20th and 21st centuries. In the late 19th century, Emil von Behring isolated the diphtheria toxin and demonstrated its effects in guinea pigs. He went on to develop an antitoxin against diphtheria in animals and then in humans, which resulted in the modern methods of immunization and largely ended diphtheria as a threatening disease.〔(Bering Nobel Biography )〕 The diphtheria antitoxin is famously commemorated in the Iditarod race, which is modeled after the delivery of antitoxin in the 1925 serum run to Nome. The success of animal studies in producing the diphtheria antitoxin has also been attributed as a cause for the decline of the early 20th-century opposition to animal research in the United States.〔(Walter B. Cannon Papers, American Philosophical Society )〕 Subsequent research in model organisms led to further medical advances, such as Frederick Banting's research in dogs, which determined that the isolates of pancreatic secretion could be used to treat dogs with diabetes. This led to the 1922 discovery of insulin (with John Macleod)〔(Discovery of Insulin )〕 and its use in treating diabetes, which had previously meant death.〔(Thompson bio ref )〕 John Cade's research in guinea pigs discovered the anticonvulsant properties of lithium salts,〔() John Cade and Lithium〕 which revolutionized the treatment of bipolar disorder, replacing the previous treatments of lobotomy or electroconvulsive therapy. Modern general anaesthetics, such as halothane and related compounds, were also developed through studies on model organisms, and are necessary for modern, complex surgical operations.〔Raventos J (1956) ''Brit J Pharmacol'' 11, 394〕〔Whalen FX, Bacon DR & Smith HM (2005) ''Best Pract Res Clin Anaesthesiol'' 19, 323〕 In the 1940s, Jonas Salk used rhesus monkey studies to isolate the most virulent forms of the polio virus,〔() Virus-typing of polio by Salk〕 which led to his creation of a polio vaccine. The vaccine, which was made publicly available in 1955, reduced the incidence of polio 15-fold in the United States over the following five years.〔() Salk polio virus〕 Albert Sabin improved the vaccine by passing the polio virus through animal hosts, including monkeys; the Sabin vaccine was produced for mass consumption in 1963, and had virtually eradicated polio in the United States by 1965.〔() History of polio vaccine〕 It has been estimated that developing and producing the vaccines required the use of 100,000 rhesus monkeys, with 65 doses of vaccine produced from each monkey. Sabin wrote in 1992, "Without the use of animals and human beings, it would have been impossible to acquire the important knowledge needed to prevent much suffering and premature death not only among humans, but also among animals."〔()〕 Other 20th-century medical advances and treatments that relied on research performed in animals include organ transplant techniques,〔Carrel A (1912) ''Surg. Gynec. Obst.'' 14: p. 246〕〔Williamson C (1926) ''J. Urol.'' 16: p. 231〕〔Woodruff H & Burg R (1986) in ''Discoveries in Pharmacology'' vol 3, ed Parnham & Bruinvels, Elsevier, Amsterdam〕〔Moore F (1964) ''Give and Take: the Development of Tissue Transplantation''. Saunders, New York〕 the heart-lung machine,〔Gibbon JH (1937) ''Arch. Surg.'' 34, 1105〕 antibiotics,〔() Hinshaw obituary〕〔() Streptomycin〕〔Fleming A (1929) ''Brit J Exper Path'' 10, 226〕 and the whooping cough vaccine.〔Medical Research Council (1956) ''Br. Med. J.'' 2: p. 454〕 Treatments for animal diseases have also been developed, including for rabies,〔''A reference handbook of the medical sciences''. William Wood and Co., 1904, Edited by Albert H. Buck.〕 anthrax,〔 glanders,〔 feline immunodeficiency virus (FIV), tuberculosis,〔 Texas cattle fever,〔 classical swine fever (hog cholera),〔 heartworm, and other parasitic infections. Animal experimentation continues to be required for biomedical research,〔Sources: * * * *〕 and is used with the aim of solving medical problems such as Alzheimer's disease, AIDS,〔(AIDS Reviews 2005;7:67-83 Antiretroviral Drug Studies in Nonhuman Primates: a Valid Animal Model for Innovative Drug Efficacy and Pathogenesis Experiments )〕〔(PMPA blocks SIV in monkeys )〕〔(PMPA is tenofovir )〕 multiple sclerosis, spinal cord injury, and other conditions in which there is no useful ''in vitro'' model system available. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Model organism」の詳細全文を読む スポンサード リンク
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