Membrane microdomains, also named lipid rafts ( 1 ), are enriched in glycosphingolipids (GSLs) and cholesterol ( 2 ), and assembled with membrane-integrated proteins, such as caveolins or fl otillins, with affi nity for particular lipid species ( 3 ). Caveolins are cholesterol-binding proteins ( 4 ) and occur in fl ask-shaped invaginations named caveolae ( 5 ). Flotillin proteins, also called reggie proteins, are found in distinct membrane microdomains ( 6 ). Caveolae are particularly abundant in endothelial cells and are involved in many cellular processes, including cholesterol homeostasis, endocytosis, and transcytosis of macromolecules ( 7-9 ). While numerous proteomic studies have been conducted to identify lipid raft-or caveolae-associated proteins of various cell types, including endothelial cells ( 10-12 ), the GSL composition of lipid rafts or caveolae, particularly of endothelial cells, has attracted less attention, despite their outstanding role in membrane microdomain formation
Altenbach, A.V., Heeger, T., Linke, P., Spindler, M. and Thies, A., 1993. Miliolinella subrotunda (Montagu), a miliolid foraminifer building large detritic tubes for a temporary epibenthic lifestyle. In: M.R. Langer (Editor), Foraminiferal Microhabitats. Mar. MicropaleontoL, Live observations, cytological characteristics and biometrical measurements on Miliolinella subrotunda (Montagu, 1803 ) sampled from the northern and southern Atlantic Ocean are presented. M. subrotunda facultatively constructs a long, detritic tube lifting the test several millimeters above the sediment surface. A thickened conical base anchors the construction on the sediment surface and a long, flexible tube protrudes into the velocity profile of the bottom currents. The miliolid test is placed on top, surrounded by the uppermost part of the tube. This construction allows the organisms to feed in the particle stream above the sediment surface. In comparison to species living in and on the surface sediments, M.subrotunda apparently shows higher nutritional values in food ingested and larger amounts of reserve substances. Characteristics of the shape and structure that reduce drag on the tubes include a broadened conical base, a flexible tube, and a rounded top. From biometrical measurements it is concluded, that the tubes are constructed over a short period of their ontogeny.
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