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At least 271 records · Page 15Linked to original sources
PubMed1977

A quantitative study of pinocytosis and intracellular proteolysis in rat peritoneal macrophages.

A method for the culture of rat peritoneal macrophages in vitro is described, in which pinocytic uptake of colloidal [198 Au]gold, 125I--labelled poly(vinylpyrrolidone) and [14C]sucrose proceeds at contant and fairly reproducible rates for several hours. The rat of uptake of colloidal [198 Au]gold, which wxhibited some inter-batch variation, was approx. 100 times that of the other two substrates. Colloidal gold did not affect the rate of uptake of 125I-labelled poly(vinylpyrrolidone) and therefore its own high rate of uptake could not be attributed to a stimulation of the formation of pinocytic vesicles. It conclude that uptake of collodial gold is highly dependent on adsorption on binding sites on the plasma membrane. Uptake of formaldehyde-treated 125I-labelled bovine serum albumin was followed by the release of [125I]iodo-L-tyrosine into the culture medium and took place at a rate intermediate between those of collodial [198Au]gold and the other two non-digestible substrates, 125I-labelled poly(vinylpyrrolidone) and [14C]sucrose.

Animals↗
PubMed1979

Effects of temperature, metabolic inhibitors and some other factors on fluid-phase and adsorptive pinocytosis by rat peritoneal macrophages.

Low temperature, NaF and 2,4-dinitrophenol could each abolish the pinocytic uptake of 125I-labelled poly(vinylpyrrolidone) or colloidal [198Au]gold by rat peritoneal macrophages cultured in vitro. Cytochalasin B caused only partial inhibition, even at 10 microgram/ml, and colchicine (10 or 25 microgram/ml) inhibited uptake of colloidal [198Au]gold much more than that of 125I-labelled poly(vinylpyrrolidone). Dibutyryl cyclic AMP and ouabain were without effect on uptake of 125I-labelled poly(vinylpyrrolidone), and slight stimulation was seen with ATP and theophylline. Uptake of 125I-labelled poly(vinylpyrrolidone) was abolished by EGTA (5mM), but restored by adding CaCl2 (5mM). The results appear not to support the conventional criteria for the division of pinocytic phenomena into macropinocytosis, requiring a metabolic energy supply and cytoskeletal components, and micropinocytosis, requiring neither.

Adsorption↗
PubMed1992

Clathrin heavy chain is required for pinocytosis, the presence of large vacuoles, and development in Dictyostelium.

To investigate the intracellular role of the clathrin heavy chain in living cells, we have used "antisense" RNA to engineer mutant Dictyostelium discoideum cells that are severely deficient in clathrin heavy chain expression. Immunoblots stained with an anti-clathrin heavy chain antiserum revealed that mutant cells contained undetectable amounts of clathrin heavy chain protein. Similarly, Northern blots showed an absence of clathrin heavy chain mRNA. Clathrin heavy chain-deficient Dictyostelium cells were viable, but exhibited growth rates twofold slower than parental cells. Whereas many morphological features of the mutant cells were normal, mutant cells lacked coated pits and coated vesicles. Clathrin-deficient cells were also missing large translucent vacuoles that serve as endosomes and contractile vacuoles. In the absence of clathrin heavy chain, mutant cells displayed three distinct functional defects: (a) impairment in endocytosis of fluid phase markers, but competence in another endocytic pathway, the phagocytosis of solid particles; (b) defects in osmoregulation; and (c) inability to complete the starvation-induced development cycle.

Animals↗
PubMed1976

Membrane flow during pinocytosis. A stereologic analysis.

HRP has been used as a cytochemical marker for a sterelogic analysis of pinocytic vesicles and secondary lysosomes in cultivated macrophages and L cells. Evidence is presented that the diaminobenzidine technique (a) detects all vaculoes containing encyme and (b) distinguishes between incoming pinocytic vesicles and those which have fused with pre-existing lysosomes to form secondary lososomes. The HRP reactive pinocytic vesicle spaces fills completely within 5 min after exposure to enzyme, while the secondary lysosome compartment is saturated in 45--60 min. The size distribution of sectioned (profile) vaculoe diameters was measured at equilibrium and converted to actual (spherical) dimensions using a technique modified from Dr. S. D. Wicksell. The most important findings in this study have to do with the rate at which pinocytosed fluid and surface membrane move into the cell and on their subsequent fate. Each minute macrophages form at least 125 pinocytic vesicles having a fractional vol of 0.43% of the cell's volume and a fractional area of 3.1% of the cell's surface area. The fractional volume and surface area flux rates for L cells were 0.05% and 0.8% per minute respectively. Macrophages and L cells thus interiorize the equivalent of their cell surface area every 33 and 125 min. During a 3-period, the size of the secondary lysosome compartment remains constant and represents 2.5% of the cell volume and 18% of the surface area. Each hour, therefore, the volume and surface area of incoming vesicles is 10 times greater than the dimensions of the secondary lysosomes in both macrophages and L cells. This implies a rapid reduction in vesicle size during the formation of the secondary lysosome and the egress of pinocytosed fluid from the vacuole and the cell. In addition, we postulate that membrane components of the vacuole are subsequently recycled back to the cell surface.

Histocytochemistry↗
PubMed1967

The regulation of pinocytosis in mouse macrophages. IV. The immunological induction of pinocytic vesicles, secondary lysosomes, and hydrolytic enzymes.

Bovine sera contain factors which are capable of agglutinating mouse erythrocytes and stimulating the pinocytic activity of cultivated mouse macrophages. The hemagglutinating and vesicle-inducing activities of sera increase with the age of the animal and are absent in fetal calf serum. The majority of this material is recovered in globulin fractions prepared with Na(2)SO(4)-(NH(4))(2)SO(4) and is absent in bovine fraction II. It behaves as a macroglobulin in studies employing zone electrophoresis, Sephadex G-200 filtration, sucrose density gradient centrifugation, and in its sensitivity to 2-mercaptoethanol and heat. Absorption of bovine sera with either mouse erythrocytes or spleen cells removes the hemagglutinating and pinosome-inducing properties of the sera. The addition of small quantities of bovine macroglobulin to mouse macrophages results in a stimulation of pinocytic activity, phase-dense granule formation and the cellular content of three acid hydrolases. In the presence of heat-labile factors, the macroglobulin initiates the hemolysis of mouse erythrocytes and the cytolysis of mouse macrophages. This material is thought to represent an interspecies gammaM-type antibody directed against common antigenic determinants on the mouse erythrocyte and macrophage surface.

Agglutination↗