pinocytosis


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pinocytosis:

see endocytosisendocytosis
, in biology, process by which substances are taken into the cell. When the cell membrane comes into contact with a suitable food, a portion of the cell cytoplasm surges forward to meet and surround the material and a depression forms within the cell wall.
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Pinocytosis

 

the engulfing by the cell surface of fluid and substances that the fluid contains. Pinocytosis is one of the principal mechanisms by which high-molecular-weight compounds enter the cell, particularly proteins and carbohydrate-protein complexes. The phenomenon of pinocytosis was discovered by the American scientist W. Lewis in 1931. During pinocytosis short, slender outgrowths on the plasma membrane surround a drop of fluid. Then the region of the plasma membrane that contains these outgrowths invaginates and pinches off to form a bubble inside the cell. The formation of pinocytotic bubbles, whose diameters do not exceed 2 microns (μ), has been traced by phase-contrast microscopy and microcinematography. With the aid of the electron microscope, bubbles with diameters that range from 0.07 to 0.1 μ can be discerned. Pinocytotic bubbles are capable of freely moving within the cell or of merging with each other or with other intracellular membranous structures. The most active pinocytosis is observed in amoebas, in epithelial cells of the intestines and renal tubules, and in the endothelium of blood vessels and growing oocytes. The level of pinocytotic activity depends on the physiological state of the cell and on the environment. Active inducers of pinocytosis are γ-globulin, gelatin, and certain salts.

T. B. AIZENSHTADT

pinocytosis

[¦pin·ō·sī′tō·səs]
(cell and molecular biology)
Deprecated term formerly used to describe the process of uptake or internalization of particles, macromolecules, and fluid droplets by living cells; the process is now termed endocytosis.
References in periodicals archive ?
Bulk-phase endocytosis (pinocytosis) is the nonspecific uptake of extracellular fluids and occurs at a constitutive level within the cell via mechanisms, which are independent of ligand binding [156].
Like IgGs, a Ibumin is taken up by cells through nonspecific pinocytosis and is protected from intracellular degradation through pH-dependant binding to the FcRn in acidic endosomes.
(7.) Gonzalez-Noriega A, Grubb JH, Talkad V and WS Sly Chloroquine inhibits lysosomal enzyme pinocytosis and enhances lysosomal enzyme secretion by impairing receptor recycling.
Once the EB attaches to the columnar epithelial cell it is incorporated into the cell by a process of pinocytosis, in which the organism is surrounded with a phagosome membrane (Friss 1972).
It has been reported that the ingestion of small particles by cells occurs by endocytosis or pinocytosis for nanometersized particles (less than 150 nm).
Essentially all of the filtered Cd-MT is reabsorbed by pinocytosis into proximal tubule cells in the renal cortex, and MT is catabolized by lysosomes, releasing the free [Cd.sup.+2] ion.
Alphaviruses enter host cells by pinocytosis and they replicate in the cytoplasm.
In the proposed regulatory mechanism (3, 4), FcRns, predominantly localized intracellularly in endothelial cells that cover the bloodstream, capture circulating IgG and HSA taken up by fluidphase pinocytosis, after the ligands enter acidified endosomal compartments.
(7,8) Substances with a molecular weight of more than 1,000 (e.g., human serum albumin, ferritin, and endotoxins) can be transported via pinocytosis. Steroids have been shown to diffuse through the RWM.
The transport of nutrients from the lumen into the epithelial cells lining the lumen and then into the blood or lymph may occur by simple diffusion, active transport (requiring energy), or pinocytosis (engulfing large particles in a way similar to the way an Amoeba obtains its food).
Cells use pinocytosis to take up TCII hydroxocobalamin.
Normally, more than 99% of the filtered protein is reabsorbed by pinocytosis in the proximal convoluted tubule [6].