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Z A Cohn

Publications and source records attributed to Z A Cohn.

At least 199 records · Page 11Linked to original sources
PubMed1974

Effects of concanavalin A on mouse peritoneal macrophages. I. Stimulation of endocytic activity and inhibition of phago-lysosome formation.

Concanavalin A (Con A) binds to saccharide residues on the mouse peritoneal macrophage plasma membrane and stimulates extensive pinocytic interiorization of the membrane. The overall pinocytic rate is increased 3.5-4.5 times by the addition of Con A, and the surface marker enzyme adenosine triphosphatase can be identified histochemically in association with the cytoplasmic vesicles generated after exposure of the cells to Con A. Once formed, these pinocytic vesicles may persist for several days and fail to show morphologic evidence of fusion with primary or preformed secondary lysosomes. There is no apparent effect on the capacity of the macrophage to ingest either latex particles or IgG-coated SRBC administered either simultaneously with or subsequent to the Con A.

Acid Phosphatase↗
PubMed1974

Effects of concanavalin A on mouse peritoneal macrophages. II. Metabolism of endocytized proteins and reversibility of the effects by mannose.

The half-time for the degradation of horseradish peroxidase (HRP) is increased from 14 h to 37 h in Con A-treated cells, while the half-time for the degradation of [(125)I]BSA is increased from 5.4 h to 14.8 h. This supports prior microscopic observations which suggested that Con A pinosomes showed a marked impairment in their ability to form phagolysosomes. Artifacts due to anomalous behavior of HRP-Con A complexes, or to inhibition of lysosomal hydrolases by Con A, could be excluded. These indications of impaired phagolysosome formation, as well as those described in the preceding paper, could be reversed by postincubation of the cells in mannose, but not in galactose. This reversal is accompanied by a dissociation of Con A-FITC from the inner surface of the pinosome membrane, into the vesicle contents. These observations may be relevant to the ability of Con A to affect several membrane characteristics, and are also of interest in relation to the impaired formation of phagolysosomes which has been described in certain in vitro parasitic infections of macrophages or other cells.

Animals↗
PubMed1974

Induction of macrophage plasminogen activator by endotoxin stimulation and phagocytosis: evidence for a two-stage process.

The injection of thioglycollate medium into the peritoneal cavity of the mouse induces high levels of macrophage fibrinolytic activity due to the production and secretion of a plasminogen activator, a trypsinlike serine protease, which is absent in unstimulated macrophages. Intraperitoneal injection of endotoxin or mineral oil can stimulate only a fraction (<10%) of the fibrinolytic activity of thioglycollate cells, similar to the partial stimulation (<10%) seen 1-2 days after phagocytosis of latex or SRBC by unstimulated macrophages. The endotoxin-stimulated macrophages contain and release relatively low levels of plasminogen activator, but these primed cells can be triggered to produce and secrete high levels of enzyme, by phagocytosis of latex. Under conditions where the plasminogen activator is induced and secreted, there are no effects on the production and/or release of lysozyme or intracellular acid hydrolases, Discovery of a two-stage procedure for inducing macrophage plasminogen activator made it possible to study the role of cell priming and phagocytosis separately. Endotoxin was a more effective priming agent, weight for weight, than lipid A:BSA complex. Secretion of the plasminogen activator was induced only by thioglycollate, or endotoxin and latex. In situ fibrinolysis was induced by these agents and mineral oil, BCG, and fetal calf serum, in decreasing order of effectiveness. Phagocytosis of latex in all cases except thioglycollate stimulation, increased fibrinolytic activity from three- to sixfold. Latex and a variety of other particles such as M. lysodeikticus, aggregated gamma-globulin and immune complexes showed dose-dependent stimulation of fibrinolysis by endotoxin-primed macrophages. Although the initial phagocytic trigger was not specific for the substance employed, the ability to induce a sustained response depended on the persistence of the phagocytized particle within the cell. Fibrinolysis and secretion of plasminogen activator continued at high levels for at least 9 days after uptake of latex, a nondigestible particle, whereas plasminogen activator was secreted only transiently after ingestion of rapidly digested M. lysodeikticus. The induction of plasminogen activator secretion provides a mechanism by which the activated macrophage can exert a selective effect on its extracellular environment.

Animals↗
PubMed1974

Identification of a novel cell type in peripheral lymphoid organs of mice. 3. Functional properties in vivo.

Several properties of lymphoid dendritic cells in situ have been determined, and contrasted to information previously established for lymphocytes and mononuclear phagocytes. Dendritic cells are not found in newborn mice, and their concentration in both spleen and mesenteric lymph node does not reach adult levels until 3-4 wk of age. Dendritic cells largely disappear from adherent populations following administration of steroids (2.5 mg hydrocortisone acetate s.c.) and ionizing radiation (D(o) of 100 rads for Co(60)). Splenic dendritic cells can originate from precursors located in both bone marrow and spleen itself, probably the red pulp. The mature splenic population does not actively divide (pulse labeling index with [(3)H]thymidine of 1.5-2.5%), but does turnover at substantial rate, 10+% of the total pool per day. The influx of new cells appears to be derived from a proliferating precursor compartment, but the mechanism for efflux or turnover is not known. Dendritic cells in spleen and node undergo little or moderate increase in numbers during development of a primary immune response. These in vivo characteristics, taken together, further distinguish dendritic cells as a novel cell type, distinct from mononuclear phagocytes and lymphocytes.

Animals↗
PubMed1974

In vitro synthesis and secretion of lysozyme by mononuclear phagocytes.

Pure cultures of three types of mononuclear phagocytes-mouse peritoneal macrophages, unstimulated or after thioglycollate stimulation, and human monocytes-synthesize and secrete large amounts of lysozyme in vitro. The macrophage lysozyme is indistinguishable from authentic lysozyme in its ability to lyse M. lysodeikticus, inhibition by specific antisera, a similar size of 14,000 and cationic charge. Lysozyme secretion in culture is characterized by a large net increase in total lysozyme, 4-20-fold in 3 h, 75-95% of which is in the medium, and its continued extracellular accumulation over at least 2 wk in culture. Lysozyme is the major (14)C-labeled protein secreted into the medium by both unstimulated and thioglycollate-stimulated macrophages and the 0.75-1 microg produced per 1 x 10(6) cells/day represents 0.5-2.5% of the total cell protein. Lysozyme is a cell-specific marker for mononuclear phagocytes and the PMN, which contains preformed enzyme, since it is absent in lymphoid cells and a variety of fibroblast and epithelioid cell lines. Lysozyme production is also a useful measure of mononuclear phagocyte cell number. The rate of lysozyme production and secretion is remarkably constant for all cell types under a variety of culture conditions. Production by the mouse macrophage increases threefold on the 2nd day in culture and then remains linear with time. Production is optimal at a relatively low serum concentration, but can be maintained, in the absence of serum, in lactalbumin hydrolysate or, at a reduced level in basal media. The production and secretion of lysozyme are independent of the production of macrophage acid hydrolases. Net increase and secretion of lysozyme occur under conditions where acid hydrolases like N-acetyl beta-glucosaminidase, beta-glucuronidase, beta-galactosidase, and cathepsin D are neither accumulated nor secreted. Massive phagocytosis of latex particles has no effect on lysozyme production and secretion. Lysozyme production can be rapidly inhibited by treatment with cycloheximide (0.4 microg/ml) whereas inhibition of its production by colchicine (10(-6) M) occurs only after a lag period of more than 8 h, and is probably due to a secondary effect. These results show that mouse macrophages provide a simple in vitro system to measure lysozyme secretion and its control. These studies also indicate the possible importance of mononuclear phagocytes in the secretion of a variety of biologically active products and in the modification of their environment.

Amino Acids↗
PubMed1974

Identification of a novel cell type in peripheral lymphoid organs of mice. II. Functional properties in vitro.

Dendritic cells are morphologically distinct cells isolated in vitro from peripheral lymphoid organs of mice. They have a buoyant density of less than 1.082 and can be enriched 7-20-fold by isopycnic centrifugation in albumin columns. Surface adherence of enriched populations may yield cultures containing 50% dendritic cells-preparations which can then be studied in more detail. By functional tests, dendritic cells do not represent morphological variants of either lymphocytes or macrophages. They lack lymphocyte surface differentiation markers and do not exhibit the endocytic capacities of macrophages. In tissue culture, they do not differentiate into macrophages. Dendritic cells have a low labeling index in vitro (1.5-2.5%) following administration of [(3)H]thymidine, and this property distinguishes them from large lymphocytes and promonocytes. Dendritic cells also do not possess the functional properties of other types of reticular cells proposed to exist in lymphoid organs, i.e., they do not synthesize collagen-like macromolecules, they are not stem cells for erythroid and myeloid colony formation, and they do not retain antigens or immune complexes on their cell surface. Dendritic cells thus represent a novel cell type on both functional and morphological grounds.

Animals↗
PubMed1974

Pinocytosis in fibroblasts. Quantitative studies in vitro.

Horseradish peroxidase (HRP) was used as a marker to determine the rate of ongoing pinocytosis in several fibroblast cell lines. The enzyme was interiorized in the fluid phase without evidence of adsorption to the cell surface. Cytochemical reaction product was not found on the cell surface and was visualized only within intracellular vesicles and granules. Uptake was directly proportional to the administered concentration of HRP and to the duration of exposure. The rate of HRP uptake was 0.0032-0.0035% of the administered load per 10(6) cells per hour for all cells studied with one exception: L cells, after reaching confluence, progressively increased their pinocytic activity two- to fourfold. After uptake of HRP, L cells inactivated HRP with a half-life of 6-8 h. Certain metabolic requirements of pinocytosis were then studied in detail in L cells. Raising the environmental temperature increased pinocytosis over a range of 2-38 degrees C. The Q(10) was 2.7 and the activation energy, 17.6 kcal/mol. Studies on the levels of cellular ATP in the presence of various metabolic inhibitors (fluoride, 2-desoxyglycose, azide, and cyanide) showed that L cells synthesized ATP by both glycolytic and respiratory pathways. A combination of a glycolytic and a respiratory inhibitor was needed to depress cellular ATP levels as well as pinocytic activity to 10-20% of control values, whereas drugs administered individually had only partial effects. In spite of the availability of an accurate quantitative assay for fluid and solute uptake, the function of pinocytosis in tissue culture cells remains unknown.

Adenosine Triphosphate↗
PubMed1973

Peroxidase-mediated mammalian cell cytotoxicity.

Lactoperoxidase, in the presence of hydrogen peroxide and iodide is cytotoxic for human and mouse lymphoid cells, and human erythrocytes. Myeloperoxidase, in amounts equivalent to 1.5 x 10(6) neutrophils, readily replaces lactoperoxidase, and allows the substitution of the iodide ion by chloride. The myeloperoxidase-mediated reaction is rapid, and highly efficient, leading to 85-90% cell death in 90 min, as measured by (51)chromium release and dye exclusion. The mixture of granulocytes. monocytes, and lymphocytes present in an inflammatory exudate, and the intimate cell-to-cell association characteristic of cytotoxic phenomena may provide the in vivo requirements for such a system.

Animals↗
PubMed1973

Identification of a novel cell type in peripheral lymphoid organs of mice. I. Morphology, quantitation, tissue distribution.

A novel cell type has been identified in adherent cell populations prepared from mouse peripheral lymphoid organs (spleen, lymph node, Peyer's patch). Though present in small numbers (0.1-1.6% of the total nucleated cells) the cells have distinct morphological features. The nucleus is large, retractile, contorted in shape, and contains small nucleoli (usually two). The abundant cytoplasm is arranged in processes of varying length and width and contains many large spherical mitochondria. In the living state, the cells undergo characteristic movements, and unlike macrophages, do not appear to engage in active endocytosis. The term, dendritic cell, is proposed for this novel cell type.

Animals↗
PubMed1973

The macrophage.

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Adenosine Triphosphatases↗
PubMed1973

The effect of poly-L-lysine on the uptake of reovirus double-stranded RNA in macrophages in vitro.

The effect of polycations on cultured mouse peitoneal macrophages has been examined. Polycations, at concentrations greater than 5 microg/ml, are toxic for macrophages) as measured by failure of the cells to exclude vital dyes. At toxic concentrations polycations bind in large amounts to nuclei and endoplasmic reticulum, while at nontoxic levels polycations bind selectively to the cell surface. Nontoxic concentrations of polycations stimulate binding of reovirus double-stranded (ds) RNA to the macrophages by forming polycation-dsRNA complexes either in the medium or at the cell surface. These complexes enter the cell in endocytic vacuoles and are concentrated in secondary lysosomes. Despite exposure to the acid hydrolases within this cell compartment, the dsRNA and the polycation (poly-L-lysine) are conserved in a macromolecular form within the vacuolar system. The mechanism(s) by which the uptake of infectious nucleic acids and the induction of interferon by dsRNA are stimulated by polycations are discussed.

Animals↗
PubMed1972

The selective inhibition of macrophage phagocytic receptors by anti-membrane antibodies.

Rabbit antibodies were prepared against purified mouse macrophages, erythrocytes, and liver lysosomes. In the presence of complement each of these reagents was capable of lysing mouse erythrocytes and macrophages. In the absence of complement, all antisera agglutinated mouse erythrocytes and at high concentration produced a cytotoxic effect on macrophages. At IgG concentrations of 100 microg/ml, no morphological evidence of cytotoxicity was evident. These data suggest the presence of common antigens on the erythrocyte and macrophage plasma membrane. Anti-macrophage, anti-erythrocyte, and anti-lysosomal gamma-globulins and IgG, employed at subtoxic concentrations, all inhibited the attachment and ingestion of opsonized erythrocytes and mycoplasma. This occurred without significant reduction in the phagocytosis of polystyrene particles, formalinized erythrocytes, and yeast cell walls. Each of the anti-membrane IgG antibodies was capable of blocking the Fc receptor on the macrophage plasma membrane. Attachment to the macrophage membrane occurred by means of the Fab region. However, a role for the Fc portion of the molecule was suggested since pepsin-digested IgG was unable to block the receptor. Each of the IgG antibodies produced a partial blockade of the complement receptor and reduced the ingestion of EAC1,4,2,3 by approximately 50%.

Ammonium Sulfate↗
PubMed1972

The interaction of soluble horseradish peroxidase with mouse peritoneal macrophages in vitro.

The in vitro interaction of soluble horseradish peroxidase (HRP) with homogeneous mono layers of mouse macrophages has been studied using sensitive biochemical and cytochemical techniques. The compartmentalization of HRP in extracellular and intracellular sites has been quantitatively evaluated. A significant fraction is bound to a serum-derived layer, which coats the surface of culture vessels and may be removed by appropriate washes. Macrophages interiorize HRP as a solute in pinocytic vesicles without appreciable binding of the glycoprotein to the plasma membrane. Uptake is directly proportional to the concentration of HRP in the culture medium. 1 x 10(6) cells ingest 0.0025% of the administered load per hr over a wide range of concentrations. Cytochemically, all demonstrable HRP is sequestered within the endocytic vesicles and secondary lysosomes of the vacuolar apparatus. After uptake, the enzymatic activity of HRP is inactivated exponentially with a half-life of 7-9 hr, until enzyme is no longer detectable. When macrophages have pinocytosed trace-labeled HRP-(125)I, cell-associated isotope disappears with a t (1/2) of 20-30 hr and they release monoiodotyrosine-(125)I into the culture medium. We were unable to obtain evidence that significant amounts of HRP (>2%) can be exocytosed after uptake, can exist intact on the cell surface, or can be digested extracellularly. It is difficult to reconcile these observations with several of the postulated mechanisms whereby macrophages are thought to play a prominent role in the induction of an immune response.

Animals↗
PubMed1972

The enzymatic iodination of the red cell membrane.

An enzymatic iodination procedure utilizing lactoperoxidase (LPO), radioactive iodide, and hydrogen peroxide generated by a glucose oxidase-glucose system has been described and utilized for a study of the red cell membrane. 97% of the incorporated isotope is in the erythrocyte ghost and 3% is associated with hemoglobin. No significant labeling of the red cell membrane occurs in the absence of LPO or by the deletion of any of the other reagents. A 6 million-fold excess of chloride ions inhibits iodination by no more than 50%. Incorporation of up to 1 x 10(6) iodide atoms into a single erythrocyte membrane results in no significant cell lysis. The incorporated label is exclusively in tyrosine residues as monoiodotyrosine. 10-15% of the trichloroacetic acid-precipitable radioactivity can be extracted with lipid solvents but is present as either labeled protein or (125)I. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of solubilized membrane proteins reveals only two labeled protein bands out of the 15 present, and the presence of 50-1 x 10(6) iodide atoms per ghost does not alter this pattern. Component a has a molecular weight of 110,000, is carbohydrate poor, and represents 40% of the total label. Component b has an apparent molecular weight of 74,000, contains all of the demonstrable sialic acid, and accounts for 60% of the total label. Trypsinization of iodinated, intact red cells results in the disappearance of only component b, the appearance of labeled glycopeptides in the medium, and the absence of smaller, labeled peptides remaining in the membrane. Pronase treatment hydrolyzes component b in a similar fashion, but also cleaves component a to a 72,000 mol wt peptide which is retained in the membrane. A combination of protease treatment and double labeling with (125)I and (131)I does not reveal the appearance of previously unexposed proteins.

Cell Membrane↗
PubMed1972

The interaction of particulate horseradish peroxidase (HRP)-anti HRP immune complexes with mouse peritoneal macrophages in vitro.

The uptake, distribution, and fate of particulate horseradish peroxidase (HRP)-anti HRP aggregates has been studied in homogeneous monolayers of mouse macrophages in vitro. Macrophages rapidly interiorize the immune complexes after binding to the cell surface. The rate of interiorization is maximal for complexes formed in a broad zone of 4-fold antibody excess to equivalence and corresponds to a rate of 10% of the administered load/10(6) cells per hour. This rate is 4000-fold greater than the uptake of soluble HRP. The binding and endocytosis of HRP-anti HRP by macrophages is mediated by the trypsin insensitive F(c) receptor. Cytochemically, intracellular HRP is localized within membrane bound vacuoles. After uptake of HRP, the enzymatic activity is degraded exponentially with a half-life of 14-18 hr until enzyme is no longer detectable. This half-life is twice as long as that previously observed for soluble uncomplexed HRP and is related to the combination of HRP with anti-HRP rather than the absolute amounts of enzyme or antibody ingested. The half-life of HRP-(125)I was 30 hr. Exocytosis of cell associated enzyme or TCA precipitable counts was not detected, nor were persistent surface complexes demonstrable. The extensive capacity of macrophages to interiorize and destroy large amounts of antigen after the formation of antibody illustrates a role of this cell in the efferent limb of the immune response.

Animals↗