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The glycocalyx is a glycoprotein-polysaccharide covering that surrounds the cell membranes of some bacteria, epithelia and other cells. Most animal epithelial cells have a fuzz-like coat on the external surface of their plasma membranes. This coating consists of several carbohydrate moieties of membrane glycolipids and glycoproteins, which serve as backbone molecules for support. Generally, the carbohydrate portion of the glycolipids found on the surface of plasma membranes helps these molecules contribute to cell-cell recognition, communication, and intercellular adhesion.〔McKinley, M. & V.D. O’Loughlin. Human Anatomy. McGraw-Hill, 2012. 3rd ed. p. 30-31.〕 The glycocalyx is a type of identifier that the body uses to distinguish between its own healthy cells and transplanted tissues, diseased cells, or invading organisms. Included in the glycocalyx are cell-adhesion molecules that enable cells to adhere to each other and guide the movement of cells during embryonic development.〔Saladin, Kenneth. "Anatomy & Physiology: The unity of form and function." McGraw Hill. 5th Edition. 2010. p. 94-95〕 The glycocalyx plays a major role in regulation of endothelial vascular tissue, including the modulation of red blood cell volume in capillaries.〔Reitsma, Sietze. "The endothelial glycocalyx: composition, functions, and visualization." European Journal of Physiology. 2007. Vol. 454. Num. 3. p. 345-359〕 The slime on the outside of a fish is an example of glycocalyx. The term was initially applied to the polysaccharide matrix coating epithelial cells, but its functions have been discovered to go well beyond that. ==Glycocalyx in vascular endothelial tissue== The glycocalyx is located on the apical surface of vascular endothelial cells which line the lumen. When vessels are stained with cationic dyes such as Alcian blue stain, transmission electron microscopy shows a small, irregularly shaped layer extending approximately 50-100 nm into the lumen of a blood vessel. Another study used cryo-transmission electron microscopy and showed that the endothelial glycocalyx could be up to 11μm thick. It is present throughout a diverse range of microvascular beds (capillaries) and macrovessels (arteries and veins). The glycocalyx also consists of a wide range of enzymes and proteins that regulate leukocyte and thrombocyte adherence, since its principal role in the vasculature is to maintain plasma and vessel wall homeostasis. These enzymes and proteins include: *Endothelial nitric oxide synthase (Endothelial NOS) *Extracellular superoxide dismutase (SOD3) *Angiotensin converting enzyme *Antithrombin-III *Lipoprotein lipase *Apolipoproteins *Growth factors *Chemokines The enzymes and proteins listed above serve to reinforce the glycocalyx barrier against vascular and other diseases. Another main function of the glycocalyx within the vascular endothelium is that it shields the vascular walls from direct exposure to blood flow, while serving as a vascular permeability barrier.〔Van de Berg, Bernard M., Max Nieuwdorp, Erik S.G. Stroes, Hans Vink. "Glycocalyx and endothelial (dys) function: from mice to men." Pharmacological Reports, 2006, 57: 75-80.〕 Its protective functions are universal throughout the vascular system, but its relative importance varies depending on its exact location in the vasculature. In microvascular tissue, the glycocalyx serves as a vascular permeability barrier by inhibiting coagulation and leukocyte adhesion. It is important that leukocytes do not stick to the vascular wall because they are important components of the immune system that must be able to travel to a specific region of the body when needed. In arterial vascular tissue, the glycocalyx also inhibits coagulation and leukocyte adhesion, but through mediation of shear stress-induced nitric oxide (NO) release. Another protective function throughout the cardiovascular system is its ability to affect the filtration of interstitial fluid from capillaries into the interstitial space〔Drake-Holland, Angela & Mark Noble. "The Important New Drug Target in Cardiovascular Medicine – the Vascular Glycocalyx." Cardiovascular & Haematological Disorders-Drug Targets, 2009, 9, p. 118-123〕 Research has shown that the glycocalyx, which is located on the apical surface of endothelial cells, is composed of a negatively charged network of proteoglycans, glycoproteins, and glycolipids.〔Van de Berg, Bernard M., Max Nieuwdorp, Erik S.G. Stroes, Hans Vink. Glycocalyx and endothelial (dys) function: from mice to men. Pharmacological Reports, 2006, 57: 75-80.〕 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「glycocalyx」の詳細全文を読む スポンサード リンク
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