Plasmalemmal vesicles

The structure of the blood capillary wall is complex and varies in different organs and tissues. It consists of a single layer of endothelial cells joined together by intercellular junctions. Each endothelial cell, on an average, is 20-40 pm long, 10-15 pm wide, and 0.1-0.5 pm thick, and contains 10,000-15,000 uniform, spherical vesicles called plasmalemmal vesicles. These vesicles range in size between 60 and 80 nm in diameter. About 70% of these vesicles open on the luminal side of the endothelial surface, and the remaining open within the cytoplasm. Plasmalemmal vesicles are believed to be involved in the pinocytic transport of substances across the endothelium. The transition time of pinocytic vesicles across the cell is... 

E. J. Smart, K. Estes, and R. G. Anderson. Inhibitors that block both the internalization of caveolae and the return of plasmalemmal vesicles. Cold Spring Harb. Symp. Quant. Biol. 60 243-248 (1995). 

Hirst, W. D., Price, G. W., Rattray, M., and Wilkin, G. P. (1998). Serotonin transporters in adult rat brain astrocytes revealed by [3H]5-HT uptake into glial plasmalemmal vesicles. Neurochem. Int. 33, 11-22. 

Nakamura, Y., Iga, K., Shibata, T., Shudo, M., and Kataoka, K. (1993). Glial plasmalemmal vesicles A subcellular fraction from rat hippocampal homogenate distinct from synaptosomes. Glia 9, 48-56. 

Nakamura, Y., Kubo, H., and Kataoka, K. (1994). Uptake of transmitter amino acids by glial plasmalemmal vesicles from different regions of rat central nervous system. Neurochem. Res. 19, 1145-1150. 

PMN binding to and migration across endothelium initiates a sequence of events that resembles that following histamine treatment [14,30], namely, an increase in the permeability of the EC monolayer. For anionic plasma macro-molecules, theplasmalemmal vesicles and bansendothdial channels are suitable candidates for exit from the vessel lumen. Indeed, receptor-mediated tranacytosis of insulin and transferrin has been identified for brain capillaries [31—33], The insulin curriers have nut yet been idoitified, but it is speculated that they could be coaled vesicles and/or plasmalemmal vesicles. Transferrin [341 as well as ceruloplasmin [33,36] binding has been localized to coated pits and vesicles in the endothelium of bone marrow and liver capillary endothelium, respectively. 

L. Ghitescu, A. Fixman, M. Simionescu, and N. Simionescu. Specific binding sites for albumin restricted to plasmalemmal vesicles of continuous capillary endothelium receptor-mediated transcytosis. J. Cell Biol. 102 1304 (1986). 

The density of plasmalemmal vesicles as well as stability of the transendothelial channels varies in different tissues, and is accompanied by a variation of the permeability of the vascular endothelium for polymers, which is, in general, inversely de-... 

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