Endemic pneumonia of rats See pneumonia virus of rats

endocytosis The process by which extracellular fluid or particles are taken up by eukaryotic cells. Occurs by invagination and pinching off of the plasma membrane so that internalized particles are initially present in vesicles (endosomes) within the cytoplasm. Uptake of large particles is termed 'phagocytosis', and uptake of solutes, fluid and small particles such as viruses is termed 'pinocytosis'. Endocytosis may be a general phenomenon which allows various molecules to enter the cell. Virus entry, however, is usually receptor-mediated and requires a specific cell-surface receptor. The virus-receptor complex accumulates in coated pits of the plasma membrane, which pinch off as intracellu-lar residues. For many enveloped viruses, escape from the vesicle requires acidification within the vesicle, and fusion of the virion lipid envelope and the vesicle membrane occurs as the pH is lowered. The pH at which this fusion occurs is specific for different viruses.

endo-epidemic hemorrhagic fever virus

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