Multivesicular vesicles

Suv, small unilamellare vesicles luv, large unilamellare vesicles mlv, multilamellare vesicles mvv, multivesiculare vesicles (Fig. 4 from [1.34]). 

Fig. 5. Types of liposomes SUV, small unilamellar vesicle LUV, large unilamellar vesicle MLV, multilamellar vesicle MW, multivesicular vesicle...

Fig. 3.18. Morphology of different liposome vesicles mvv, multivesicular vesicles (Figure 4... 

Fig. 9 Transmission electron micrographs of freeze fractured liquid crystals. (A) lamellar with confocal defects, bar 100 nm (B) hexagonal, bar lOOnm (C) cubic of type I, bar lOOnm (D) multilamellar vesicle consisting of dodecyl-PEG-23-ether, cholesterol and water, bar 200 nm (E) multivesicular vesicle, bar 1 pm. (A and B Adapted from Ref C Adapted from Ref. ° D Adapted from Refs. l)...

FIGURE 39.1 Approximate size ranges for the commonly used colloidal dmg delivery systems. SUV = small unilamellar vesicle LUV = large unilamellar vesicle MLV = large multilamellar vesicle MW = multivesicular vesicle. 

Laser Scanning Confocal Microscopy Number average molecular weight Multivesicular vesicles Weight average molecular weight Near infrared Poly(2-vinylpyridine)... 

The distributions of the vesicle diameters obtained for the two samples are shown in Fig. 11. For the gel-like sample J3 a distinction is made between unilamellar (ULV), multilameller (MLV) and multivesicular vesicles (MW). In Table 2 the average diameters of the different types of vesicles and their relative abundance for a total vesicle count of 903 (J3) and 357 (J6) are summarized. The average vesicle diameters are consistent with the position of the weak shoulder... 

While most vesicles are formed from double-tail amphiphiles such as lipids, they can also be made from some single chain fatty acids [73], surfactant-cosurfactant mixtures [71], and bola (two-headed) amphiphiles [74]. In addition to the more common spherical shells, tubular vesicles have been observed in DMPC-alcohol mixtures [70]. Polymerizable lipids allow photo- or chemical polymerization that can sometimes stabilize the vesicle [65] however, the structural change in the bilayer on polymerization can cause giant vesicles to bud into smaller shells [76]. Multivesicular liposomes are collections of hundreds of bilayer enclosed water-filled compartments that are suitable for localized drug delivery [77]. The structures of these water-in-water vesicles resemble those of foams (see Section XIV-7) with the polyhedral structure persisting down to molecular dimensions as shown in Fig. XV-11. 

Details of the mechanisms by which endocytosed material moves from the early to the late and lysosomal compartment are still poorly understood. However, portions of the EEs tubulovesicular structures may be actively transported along microtubules towards the perinuclear region of the cell in both neurons and non-neuronal cells. These endosomes on the move may enclose invaginated membranes and also internally bud off vesicles. For that reason, these complex structures are called multivesicular bodies (MVBs) [76]. Material returning by retrograde axonal transport to the neuronal cell body includes many MVBs [67]. The eventual fate of these structures may vary. Some MVBs may fuse with LEs or they may fuse with each... 

Early endosomes are the main sorting station in the endocytic pathway. In their acidic interior (pH 5.9-6.0), the receptor and its ligand can be released. The receptor may be recycled to the surface by vesicles that fuse with the plasma membrane. Material that cannot escape from the early endosomes is further transported via multivesicular bodies to late endosomes and digesting lysosomes that contain a broad spectrum of peptidases and hydrolases in an acidic surrounding [for reviews on endocytosis see Refs. (10-12), for review on clathrin uptake see Refs. (9,13)]. 

Green fluorescent protein-RhoB GFP-RhoB is localized in endocytic vesicles and has been shown to highlight early endosomes, recycling endosomes, and multivesicular bodies, but is absent from lysosomes (123). Because RhoB is toxic when applied for long periods of time, the cells should be analyzed within 24 hours of transient transfection. 

Liposomes consist of many phospholipid bilayers of only few, or just one bilayer (Fig. 5). Therefore multilamellar vesicles (MLV), oligolamellar vesicles (OLV), small unilamellar (SUV), and large unilamellar vesicles (LUV) have to be distinguished. Furthermore, multivesicular liposomes (MVL) may be formed. 

Liposomes (see Section 5.3.1), even small unilamellar vesicles, are usually too large to cross the BBB. Multivesicular liposomes of the order of 0.3-2 wm in diameter are retained by brain following systemic administration however, this is due to embolization of these large structures within the brain microvasculature. Since 40-80 nm liposomes do not undergo significant transport through the BBB, it is expected that nanoparticles, which typically have diameters of 140-300 nm, would also have insignificant... 

Heijnen, H.F., SchiefA.E., Fijnheer, R., Geuze, H.J. and Sixma, J.J. (1999)Activatedplatelets release two types of membrane vesicles microvesicles by surface shedding and exosomes derived from exocytosis of multivesicular bodies and alpha-granules. Blood 94, 3791-3799. 

Exosomes are released upon fusion of a multivesicular structure with the plasma membrane. Such multivesicular structures are generally described for endosomal carrier vesicles/late endosomes which allow sorting of transmembrane proteins for delivery into lysosomes for degradation. Proteins that are not sorted into the lumenal vesicles of late endosomes recycle back to the plasma membrane or remain on the limiting membrane, thereby escaping dowmegulation. 

Dendritic cells, depending on their degree of maturation, may or may not secrete the contents of the MVE. Rather than being released in the extracellular medium, intralumenal vesicles contained in MIIC compartment can fuse back with the limiting membrane of the multivesicular structure (Kleijmeer et al. 2001). The tetraspanins CD9 and CD81, which have been shown to be involved in cell fusion regulation (Rubinstein etal. 2006), could participate in this cellular event. Moreover, this process of back fusion is related to activation and maturation of dendritic cells. As a consequence, the intracellular exosomal pool of MHC class II molecules (>50% of the total pool in immature DC) rapidly redistributes to the plasma membrane (Kleijmeer et al. 2001). Thus in both cases, dendritic cells and red cells use exosomes to remodel their surface as a function of their differentiation requirements. 

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