Endothelia
The inner lining of blood and lymphatic vessels is a simple, squamous epithelium, designated as “endothelium.” The endothelium performs multiple tasks and is diversely developed according to the different functions in the various segments of the macro- an
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the coagulation system, are stored and, upon disturbance, are promptly delivered to the surface of the cells. By this mechanism, endothelial cells are able to change the microenvironment of perturbed regions and modulate and control inflammatory and hemostasis processes. The insets in panel B show endothelial cell-specific storage vesicles, the Weibel-Palade bodies, in cross section and longitudinal section (insets 1 and 2, respectively). In both, the typical tubular substructures are visible. WeibelPalade bodies represent the storage compartments for von Willebrand factor, which has a pivotal role in controlling adhesion and aggregation of platelets at sites of vascular injury. Recently, new insights into the biogenesis of Weibel-Palade bodies, mechanisms of their release from the endothelial cells, and remodeling of von Willebrand factor during exocytosis have been provided by advanced microscopic technologies, including cryo-methods and three-dimensional analyses.
References Berriman JA, Li S, Hewlett LJ, Wasilewski S, Kiskin FN, Carter T, Hannah MJ, Rosenthal PB (2009) Structural organization of WeibelPalade bodies revealed by cryo-EM of vitrified endothelial cells. Proc Natl Acad Sci USA 106:17407 Minshall RD, Tiruppathi C, Vogel SM, Malik AB (2002) Vesicle formation and trafficking in endothelial cells and regulation of endothelial barrier function. Histochem Cell Biol 117:105 Mourik JA, Valentijn JA, Voorberg J, Koster AJ, Valentijn KM, Eikenboom J (2013) Von Willebrand factor remodeling during exocytosis from vascular endothelial cells. J Thromb Haemost 11:2009 Reininger AJ (2008) Function of von Willebrand factor in haemostasis and thrombosis. Haemophilia 14:11 Valentijn KM, Valentijn JA, Jansen KA, Koster AJ (2008) A new look at Weibel-Palade body structure in endothelial cells using electron tomography. J Struct Biol 161:447 Weibel ER, Palade GE (1964) New cytoplasmic components in arterial endothelia. J Cell Biol 23:101 Van Hooren KWEM, Spijkers LJA, van Breevoort D, Fernandez-Borja M, Bierings R, van Buul JD, Alewijnse AE, Peters SLM, Voorberg J (2014) Sphingosine-1-phosphate receptor 3 mediates sphingosine-1phosphate induced release of Weibel-Palade bodies from endothelial cells. PLoS ONE 9:e91346 Zenner HL, Collinson LM, Micheaux G, Cutler DF (2007) Highpressure freezing provides insights into Weibel-Palade body biogenesis. J Cell Sci 120:2117
Magnification: ×16,000 (A), ×29,500 (B), ×65,000 (inset 1), ×90,000 (inset 2) M. Pavelka, J. Roth, Functional Ultrastructure: Atlas of Tissue Biology and Pathology, Third Edition, DOI 10.1007/978-3-7091-1830-6_20, © Springer-Verlag Vienna 2015
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Endothelia
HYALINE ARTERIOLOSCLEROSIS Hyaline arteriolosclerosis is a common pathological lesion of arterioles and results in a thickening of the vessel wall. The deposition of hyaline material begins as a focal process that eventually involves the entire circumference of the vessel and may extend into the media. The hyaline material is composed of precipitated plasma proteins, a major comp
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