Reversible phagocytosis in rabbit polymorphonuclear leukocytes.

Berlin, Richard D.; Fera, Judith P.; Pfeiffer, Janet R.

doi:10.1172/jci109407

Cited by 14 publications

(3 citation statements)

References 10 publications

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“…However, as no temperature-dependent modification on the ob mRNA levels was detected by RT-PCR, the effect of temperature does not appear to be part of a long-term physiological regulatory system of leptin secretion, but rather a non-specific effect of temperature on the secretory pathway. Both the intracellular transport of proteins to the cell surface and the fusion of secretory granules with the plasma membrane are temperature dependent (35,36). In fact, the vesicular forward transport events that take place along all the steps of the secretory pathway can be completely blocked at 20ЊC.…”

Section: Discussionmentioning

confidence: 99%

Cold exposure inhibits leptin secretion in vitro by a direct and non-specific action on adipose tissue

Peinó

Piñeiro²,

Gualillo³

et al. 2000

European Journal of Endocrinology

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Objective: Leptin secretion is reduced by low temperatures in experimental animals, and this effect has been explained as an adaptive mechanism to cold environments. This study investigated the in vitro effects of cold exposure on human white adipose tissue. Design: To understand whether the low temperature action is a direct or a mediated effect, leptin secretion was assessed in vitro in human omental adipose tissue incubated at varied temperatures, from 38 donors. As an internal control, the effect of reduced temperatures on in vitro GH secretion by GH3 cells was assessed. Methods: Measurement of hormones secretion was carried out with an RIA, while human ob gene mRNA expression was assessed with reverse transcription PCR. Results: Compared with the standard temperature of 37 ЊC, leptin secretion by human adipose tissue was significantly (P < 0.05) reduced when the incubations were carried out at 34.5 ЊC (41% inhibition), and 32 ЊC (68% inhibition), with no parallel changes in the ob mRNA expression. At these reduced temperatures, glucocorticoid-mediated leptin secretion was well preserved. When the effect of reduced temperatures was assessed on in vitro GH secretion, a superimposable reduction was observed. Conclusions: These results indicate: (i) that low temperatures reduce leptin secretion by acting directly on the adipose tissue and (ii) that the similar reduction in a hormone unrelated to energy metabolism, such as GH, suggests that the observed reduction is a mechanical perturbation of leptin secretion, which may be devoid of physiological implications.

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Section: Discussionmentioning

confidence: 99%

Cold exposure inhibits leptin secretion in vitro by a direct and non-specific action on adipose tissue

Peinó

Piñeiro²,

Gualillo³

et al. 2000

European Journal of Endocrinology

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“…Extensive bidirectional flow of membrane takes place between the plasma membrane and the lysosomal apparatus during endocytosis (7). Recent evidence has suggested that solutes pass through at least one intracellular compartment before reaching the lysosome (2-6) and representative portions of endocytic markers (2,4,6,8) are returned to the cell surface.We now report the existence of a distinct, intermediate vacuolar compartment in the parasitic amoeba, Entamoeba histolytica. This is the primary pinocytic route in this organism.…”

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confidence: 99%

Endocytosis in Entamoeba histolytica. Evidence for a unique non-acidified compartment.

Aley¹,

Cohn²,

Scott³

1984

The Journal of Experimental Medicine

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Endocytosis by mammalian cells leads to the rapid uptake of exogenous solutes within plasma-membrane-derived vesicles. In general, fusion of these vesicles with primary or secondary iysosomes occurs and most biological macromolecules are degraded to small molecular weight components (1). Extensive bidirectional flow of membrane takes place between the plasma membrane and the lysosomal apparatus during endocytosis (7). Recent evidence has suggested that solutes pass through at least one intracellular compartment before reaching the lysosome (2-6) and representative portions of endocytic markers (2,4,6,8) are returned to the cell surface.We now report the existence of a distinct, intermediate vacuolar compartment in the parasitic amoeba, Entamoeba histolytica. This is the primary pinocytic route in this organism. It is equilibrated with the pH of the ambient milieu and allows for the flow of solutes into and out of the cytoplasm. Only after many hours of intraceilular residence are the solutes detected in a separate, acidified lysosomelike compartment. Materials and MethodsCulture ofE. histolytica. E. histolytica trophozoites, strain HM 1 :IMSS, were generously provided by Dr. L. Diamond, the National Institute for Allergy and Infectious Diseases, and were maintained in axenic culture in TYI-S medium (9). For studies on internalization of fluid phase markers, fluorescein-labeled dextran (fluorescein isothiocyanate [FITC] ~-dextran, average molecular weight 70,000, Sigma Chemical Co., St. Louis, MO) or horseradish peroxidase (HRP, Sigma) was added directly to the culture medium at concentrations ranging between 1 and 10 mg/ml. After incubation for the indicated times, amoebae were harvested by chilling followed by centrifugation at 500 g for 5 min. Trophozoites were then washed by resuspension in cold 19 mM phosphate buffer, pH 7.2, containing 0.27 mM NaCI (PD), or in TYI-S medium and centrifugation. For studies on reincubation of amoebae, trophozoites were harvested and washed with TYI-S medium, resuspended in TYI-S medium, and gently spun (50 g) onto the sides of culture tubes. The cultures were then carefully transferred to a 37 °C water bath and incubated on their sides. These manipulations were necessary to insure rapid warming of amoebae on reincubation.

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“…THE JOURNAL OF CELL Biorocv " VOLUmt 86, 1980 was prepared according to Stossel and co-workers (43) using oil containing the fluorochrome, perylene (6). Two particles whose binding and uptake is mediated by the macrophage Fc receptor were also studied.…”

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Polarization of endocytosis and receptor topography on cultured macrophages.

Walter¹,

Berlin²,

Pfeiffer³

et al. 1980

The Journal of Cell Biology

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In the J774 .2 macrophage cell line, microtubule disassembly by colchicine causes the polarization of membrane functions and structure. Colchicine-treated cells develop a bulge or protuberance that is bordered by microvillous membrane . The protuberance is the site of concanavalin A cap formation. The fluid pinocytosis of horseradish peroxidase and of fluorescein-and rhodamine-conjugated high molecular-weight dextrans, the adsorptive pinocytosis of concanavalin A, and the concentration and phagocytosis at 37°C of a range of phagocytic particles (IgG-and complement-opsonized erythrocytes, complement-opsonized zymosan, latex spheres, albumin-stabilized oil droplets) are all similarly restricted to the protuberance . A reduction in the rate of dextran pinocytosis, determined by fluorimetry, and reductions in phagocytic rates for oil emulsion and IgG-opsonized erythrocytes accompany the polarization of endocytic activity in colchicine-treated J774 .2 macrophages.Membrane receptors for phagocytic particles are not confined to the protuberance but rather may display their own unique topographical asymmetry. The inherent topography of receptors was inferred from particle distribution under conditions that limit particle-receptor redistribution (after labeling at 4°C or a very brief incubation at 37°C) . Under these restrictive conditions, latex binding sites were detected over the whole membrane whereas receptors for IgGopsonized erythrocytes, aggregated IgG, complement-opsonized erythrocytes, and complement-opsonized zymosan were excluded from the protuberance . Thus, functional (endocytosis) and structural (inherent receptor distribution) analyses of membrane topography define different patterns of asymmetry in protuberant cells .The asymmetry induced in J774 .2 macrophages by colchicine is highly analogous to the functional and structural polarity of epithelial cells . Exploration of this analogy may provide insight into the development of polarized epithelia and, more generally, into mechanisms by which specialized areas of membrane are established .In a variety of leukocytes and macrophages, microtubule disassembly by colchicine leads to development of a ruffled protuberance underlain by microfilaments at one pole of the cell . We and others have shown that the protuberance provides a focus for the movement at 37°C of concanavalin A (Con A)-receptor complexes from their inherently dispersed distribution into a surface cap (1) . In the course of this earlier work, we also noted the similar shapes and ultrastructure of colchicinetreated leukocytes and polarized epithelial cells . In particular, the microfilamentous meshwork that underlies the protuberance of microtubule-depleted leukocytes is reminiscent of the terminal web and brush border of intestinal epithelium (23). It is well known that many surface functions and enzymatic activities are polarized to the microvillous border of epithelial TFiE JOURNAL Of CELL BIOLOGY " VOLUME 86 JULY 1980 199-211 © The Rockefeller University Press -0021-9525/80/07/0199...

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Reversible phagocytosis in rabbit polymorphonuclear leukocytes.

Cited by 14 publications

References 10 publications

Cold exposure inhibits leptin secretion in vitro by a direct and non-specific action on adipose tissue

Cold exposure inhibits leptin secretion in vitro by a direct and non-specific action on adipose tissue

Endocytosis in Entamoeba histolytica. Evidence for a unique non-acidified compartment.

Polarization of endocytosis and receptor topography on cultured macrophages.

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