Endocytosis/phagocytosis

With animal cells, the whole virus particle penetrates the cell, being carried inside by endocytosis (phagocytosis or pinocytosis), an active cellular process. We describe some of these processes in detail later in this chapter. 

Endocytosis / Phagocytosis Active Transport Cellular Proliferation Intracellular Cytokine Production Intracellular Signal Transduction Intracellular Free Ions (e.g., Na, K, Ca)... 

Previous work has shown that the majority of cells internalize liposomes through an endocytic pathway (4,5). There are multiple pathways for internalization involving vesicles of 50 300 nm in diameter. These include clathrin-mediated endocytosis, caveolae-mediated endocytosis, phagocytosis, macropinocytosis, and nonclathrin- noncaveolae-dependent endocytosis (6). 

In contrast, myosin I, which is not present in muscle, possesses only one head region and a short tail. Its role in cells may be involved in movement associated with membranes (endocytosis, phagocytosis). 

It is well established that size, charge, and chemical composition of liposomes affect their fate in vivo [306], To manipulate their biodistribution and/or drug release, liposomes of different structures have been prepared, including those sensitive to changes in pH [307, 308] or temperature [309,310]. Compared to soluble polymers discussed in previous chapters, liposomes, when applied i.v., are captured by a substantially greater extent by the specialized cells (macrophages) of the reticuloendothelial system (RES) [311]. The removal of liposomes from the bloodstream takes place by nonspecific endocytosis (phagocytosis) [312],... 

Endocytosis (phagocytosis/pinocytosis requires energy large, insoluble molecules). 

Intracellular movement None Cytoplasmic streaming, endocytosis, phagocytosis, mitosis, vesicle transport... 

As opposed to endocytosis, phagocytosis is more cell-specific and results in the ingestion of particulate as well as whole microorganisms. The cells involved in phagocytosis include monocytes and macrophages, neutrophils and dendritic cells. Furthermore, fibroblasts and epithelial cells can also be induced to assume phagocytic activity. 

Surface functionalization of dendrimer nanoparticles with suitable ligands, size, surface groups, and surface charge plays a key role on the cellular internalization by endocytosis, phagocytosis, miCTopinocytosis, or fluid-phase endocytosis. 

B. I Chemical transport. Passage across membranes may be by passive diffusion, active trans-port fecilitated diffusion, or endocytosis (phagocytosis), and each mechanism is defined by certain principles and characteristics. 

Endocytosis (phagocytosis) is a relatively uncommon specialized system at the cell sur- ce, useful fbr some large molecules that may not pass membranes by other mechanisms. 

Macromolecules and large particles penetrate the impermeable barrier by the process called endo-cytosis in which material to be absorbed is engulfed by an area of the plasma membrane which forms an enclosed vesicle. There are three mechanisms of endocytosis phagocytosis, pino-cytosis and receptor-mediated endocytosis (Figure 9.5). 

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