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At least 775 records · Page 43Linked to original sources
PubMed1985

Rapid effects of insulin on the cycling of the insulin receptor in a human monocyte cell line (U-937).

The insulin receptor and its regulation by insulin was studied in U-937 monocytes, a human cell line with properties similar to those of normal peripheral blood monocytes. Treatment of this cell with insulin for 8-16 h produced an overall loss in the insulin receptor, i.e., a loss of receptors from the cell surface and internal pools. In contrast, short-term insulin treatment (15-30 min) caused a reduction in cell surface receptors but an increase in the internal receptors, as judged by pronase treatment at 4 degrees C to distinguish receptor location. After the removal of insulin and pronase, the internalized receptors were rapidly reinserted back into the cell surface after warming to 37 degrees C. Further studies showed an insulin-mediated increase in fluid-phase pinocytosis as measured by horseradish peroxidase (HRP) uptake. The amount of HRP accumulation and the time course for this stimulation were similar to those for receptor internalization. These features plus other results suggest that the insulin-stimulated internalization of insulin receptors may require an acceleration in the rate of pinocytic vesicle formation.

Cell Line↗
PubMedDate not supplied

Macromolecular transport by the middle ear and its lymphatic system.

The macromolecular transport in the middle ear mucosa of the guinea pig was investigated by means of light and electron microscopy using tracer substances such as Evans blue, India ink, and horseradish peroxidase (HRP). HRP particles were readily taken up by the middle ear mucosa and Eustachian tube. They were absorbed by all cell types, including ciliated, secretory and nonsecretory cells. The particles were first taken up by the pinocytotic vesicles and then transported into the intercellular spaces by reverse pinocytosis. These particles were transported toward the connective tissue through the basilar membrane. Some of the tracer particles were engulfed by the tissue histiocytes, but most of the particles entered into lymphatic and blood capillaries. By Evans blue instillation of the bulla, the retroauricular and junctional lymph nodes were positively identified as those draining the middle ear and the Eustachian tube. When HRP was used, the tracer particles were detected in the ipsilateral retroauricular and junctional lymph nodes as early as 5 minutes following the tympanic instillation. HRP in these lymph nodes were mainly found in the specific granules of the macrophages.

Animals↗
PubMed1982

Cerebral vasoactivity of heme proteins in vitro. Some mechanistic considerations.

The dose responses of canine basilar arteries to human hemoglobin, rabbit hemoglobin, horse-heart myoglobin, and human methemoglobin and cyanomethemoglobin are compared in this paper. The in vitro arterial segments responded similarly to the hemoglobins and myoglobin when doses were based on the hemoglobin dimer rather than on the tetramer. Superoxide free radicals produced by the autoxidation of hemoglobin to methemoglobin do not seem to be involved in the mechanism of hemoglobin-induced vasocontraction as the contraction cannot be blocked by superoxide dismutase or other agents known to react with superoxide-generated products. Nonspecific uptake of hemoglobin into the smooth-muscle cells by pinocytosis is also discounted.

Animals↗
PubMed2006

[Mechanism of oligochitosan-induced macrophage activation].

OBJECTIVE: To study the mechanism of oligochitosan-induced macrophage activation. METHODS: Oligochitosan was chemically modified with fluorophore 2-aminoacridone (2-AMAC). The cellular events of 2-AMAC-oligochitosan-macrophage interaction were analyzed with confocal laser microscopy and the fluorescence intensity of cells was analyzed by BD LSR flow cytometer. The mechanism of oligochitosan uptake by macrophages was studied by competitive inhibition test and the effect of calcium, trypsin and colchicine on oligochitosan recognition and internalization were also determined. RT-PCR was performed to investigate the level of TNF-alpha secretion. RESULT: Macrophage could bind and uptake oligochitosan, which was dependent on the temperature: the uptake proceeded rapidly at 37 degrees C and at 4 degrees C macrophage could only bind oligochitosan. EDTA decreased oligochitosan uptake. Trypsin treatment significantly reduced the internalization, and uptake was recovered by trypsin termination. Colchicine significantly inhibited the internalization process and was dose dependent. 0.1 mol/L mannose inhibited TNF-alpha expression induced by oligochitosan. CONCLUSION: Macrophage could uptake oligochitosan via mannose receptor mediated pinocytosis. Mannose receptor is crucial for the oligochitosan-induced macrophages activation.

Cells, Cultured↗
PubMed2005

Innate immune collectin surfactant protein D enhances the clearance of DNA by macrophages and minimizes anti-DNA antibody generation.

Dying microbes and necrotic cells release highly viscous DNA that induces inflammation and septic shock, and apoptotic cells display DNA, a potential autoantigen, on their surfaces. However, innate immune proteins that mediate the clearance of free DNA and surface DNA-containing cells are not clearly established. Pulmonary surfactant proteins (SP-) A and D are innate immune pattern recognition collectins that contain fibrillar collagen-like regions and globular carbohydrate recognition domains (CRDs). We have recently shown that collectins SP-A, SP-D, and mannose binding lectin recognize DNA and RNA via their collagen-like regions and CRDs. Here we show that SP-D enhances the uptake of Cy3-labeled fragments of DNA and DNA-coated beads by U937 human monocytic cells, in vitro. Analysis of DNA uptake by freshly isolated mouse alveolar macrophages shows that SP-D, but not SP-A, deficiency results in reduced clearance of DNA, ex vivo. Analysis of bronchoalveolar lavage fluid shows that SP-D- but not SP-A-deficient mice are defective in clearing free DNA from the lung. Additionally, both SP-A- and SP-D-deficient mice accumulate anti-DNA Abs in sera in an age-dependent manner. Thus, we conclude that collectins such as SP-A and SP-D reduce the generation of anti-DNA autoantibody, which may be explained in part by the defective clearance of DNA from the lungs in the absence of these proteins. Our findings establish two new roles for these innate immune proteins and that SP-D enhances efficient pinocytosis and phagocytosis of DNA by macrophages and minimizes anti-DNA Ab generation.

Adjuvants, Immunologic↗
PubMed1976

Histochemical study of lipid absorption in two teleost fishes.

Absorption of lipid in the different regions of the intestine of two teleost fishes has been studied histochemically at different time intervals of 4, 10 and 20 h. All the three portions of the intestine have the absorptive capacity. However, it varies from one region to another. The lipid has been absorbed in the form of lipoid particles and lipoid goblets. It is also recorded here that some lipoid droplets are absorbed by pinocytosis across the brush border membrane. The lipid absorbed was localized in the brush border cells, in intercellular spaces of connective tissue, in submucosa, in between serosa and muscularis, in the lumen of blood capillaries and mesentric lymphatic vessels but was absent in muscularis and serosa.

Animals↗
PubMed1999

MHC class II antigen processing in B cells: accelerated intracellular targeting of antigens.

Processing and presentation by Ag-specific B cells is initiated by Ag binding to the B cell Ag receptor (BCR). Cross-linking of the BCR by Ag results in a rapid targeting of the BCR and bound Ag to the MHC class II peptide loading compartment (IIPLC). This accelerated delivery of Ag may be essential in vivo during periods of rapid Ag-driven B cell expansion and T cell-dependent selection. Here, we use both immunoelectron microscopy and a nondisruptive protein chemical polymerization method to define the intracellular pathway of the targeting of Ags by the BCR. We show that following cross-linking, the BCR is rapidly transported through transferrin receptor-containing early endosomes to a LAMP-1+, beta-hexosaminadase+, multivesicular compartment that is an active site of peptide-class II complex assembly, containing both class II-invariant chain complexes in the process of invariant chain proteolytic removal as well as mature peptide-class II complexes. The BCR enters the class II-containing compartment as an intact mIg/Igalpha/Igbeta complex bound to Ag. The pathway by which the BCR targets Ag to the IIPLC appears not to be identical to that by which Ags taken up by fluid phase pinocytosis traffick, suggesting that the accelerated BCR pathway may be specialized and potentially independently regulated.

Animals↗
PubMed1999

Polyriboinosinic polyribocytidylic acid (poly(I:C)) induces stable maturation of functionally active human dendritic cells.

For vaccination strategies and adoptive immunotherapy purposes, immature dendritic cells (DC) can be generated from adherent monocytes using GM-CSF and IL-4. Presently, the only clinically applicable method to induce stable maturation of DC is the use of supernatants of activated monocytes (monocyte-conditioned medium (MCM)). MCM contains an undefined mixture of cytokines and is difficult to standardize. Here we report that stable maturation of DC can be simply induced by the addition of polyriboinosinic polyribocytidylic acid (poly(I:C)), a synthetic dsRNA clinically applied as an immunomodulator. Poly(I:C)-treated DC show a mature phenotype with high expression levels of HLA-DR, CD86, and the DC maturation marker CD83. This mature phenotype is retained for 48 h after cytokine withdrawal. In contrast to untreated DC, poly(I:C)-treated DC down-regulate pinocytosis, produce high levels of IL-12 and low levels of IL-10, induce strong T cell proliferation in a primary allo MLR, and effectively present peptide Ags to HLA class I-restricted CTL. In conclusion, we present a simple methodology for the preparation of clinically applicable mature DC.

Antigen Presentation↗
PubMed2000

Altered membrane trafficking in activated bone marrow-derived macrophages.

Activation of macrophages with interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) leads to increased intracellular resistance to microbes and increased major histocompatibility complex class II-restricted antigen presentation, processes that both use the vacuolar compartment. Despite the requirement of the macrophage vacuolar compartment for microbicidal activities and antigen processing, the rates of endocytosis and membrane trafficking in activated macrophages are not clearly defined. In this study, vacuolar compartment dynamics were analyzed in murine bone marrow-derived macrophages activated with LPS and/or IFN-gamma, conditions that increased macrophage nitric oxide production and resistance to infection by Listeria monocytogenes. Relative to nonactivated cells, activated macrophages showed diminished rates of fluid-phase pinocytosis and phagocytosis and delayed progression of macropinosomes and phagosomes to late endosomes and lysosomes. In contrast to the slowing of membrane trafficking, rates of macropinosome acidification were similar between activated and nonactivated cells. One consequence of this slowed membrane trafficking in activated macrophages was a prolonged exposure of incoming molecules to an acidic nonlysosomal compartment, a condition which may facilitate microbicidal chemistries or antigen processing.

Animals↗
PubMed1975

[Ultrastructural changes in the capillaries of the renal glomeruli and parenchyma following acute ischemia].

The ultrastructural changes of the capillaries of the renal glomerule and the parenchyma of the kidney were studied in 20 albino rats after clamping the vascular peduncle of the left kidney for 30 minutes, 1, 2 and 3 hours without a following recovery of the blood flow. In 30 minutes pinocytosis was increased in the cytoplasm of endothelial cells of glomerule capillaries. In the cytopodia there appeared vacuoles. The brush border was swallen, its separate growings acquired a bulb-like shape. Microplasmatosis of the internal plasmolemma of the endothelium appeared after 1--2--3-hour ischemia. The basal layer of capillaries became wider, with uneven contours and partly homogenized. Cytopodia became deformed and more close. The brush border was rejected in some places. Mitochondria were swallen, crists lost their parallelism, their amount became less.

Acute Disease↗
PubMed1975

An ultrastructural study of sinuatrial node cells in the embryonic rat heart.

Sinuatrial nodal tissue, obtained from rat embryos of 15, 16 and 17 days, was examined with the electron microscope. Embryonic nodal cells were generally similar to adult cells except that (1) they showed thick prolongations of the cytoplasm which insinuated themselves between neighbouring cells; (2) they possessed osmiophilic granules with a predeliction for the region of the Golgi complex; (3) they exhibited a lesser and variable degree of pinocytosis.

Animals↗
PubMed1979

Alterations in human monocyte structure and function induced by incubation with gold sodium thiomalate.

The effect of in vitro indubation with gold sodium thiomalate (GST) on the morphology and functional activity of human mononuclear phagocytes (Mphi) was examined. Human peripheral blood Mphi that had been incubated with GST (25 micrograms/ml) for 4 days developed large intracytoplasmic vacuoles. Similar vacuolization developed after incubation with gold chloride but not with thiomalic acid. GST pre-incubation also induced a number of functional alterations in Mphi. GST incubation had little effect on glass adherence or FC receptor-mediated particle binding but markedly diminished pinocytosis of horseradish peroxidase and phagocytosis of IgG opsonized erythrocytes. These data indicate that the action of GST in rheumatoid arthritis may result from its capacity to alter the functional capability of Mphi.

Cell Survival↗
PubMed1983

Membrane shuttle between plasma membrane, phagosomes, and pinosomes in Dictyostelium discoideum amoeboid cells.

The intracellular redistribution of membrane internalized during endocytosis was studied quantitatively by a biochemical approach and by a morphometric analysis of autoradiographs in electron microscopy. Plasma membrane glycoconjugates, enzymatically labelled with radioactive galactose, were used as a membrane marker. In cells labelled at their surface either before or after the phagocytotic uptake of latex beads, subsequent endocytosis led to a redistribution of label between the plasma membrane and endosomal membranes until a steady-state was reached after about 1 h with 43% of the label on the plasma membrane. The steady-state resulted when all participating membranes carried the same surface density of label. During phagocytosis or pinocytosis the equivalent of the plasma membrane was internalized and recycled once every 20 min or 40 min, respectively. Compared to this rate a very rapid and complete mixing of membranes was observed between newly formed phagosomes and preexisting digestive vacuoles or between newly formed pinosomes and preexisting phagosomes. Due to this rapid mixing, the membranes enclosing undigestible latex beads remained fully linked to the shuttle of membrane to and from the cell surface.

Animals↗
PubMed1976

Peroxidase activity of alveolar macrophages.

Peroxidase activity was studied in alveolar macrophages and compared to the peroxidase activity in polymorphonuclear leukocytes using cytochemical techniques. A dense reaction product for peroxidase was observed in the primary lysosomes of polymorphonuclear leukocytes, but no significant peroxidase or peroxidative enzymes could be detected in rabbit alveolar macrophages. Furthermore, following vigorous phagocytosis of zymosan particles by alveolar macrophages in vitro, no peroxidase could be detected in association with the phagocytic vacuole. Exogenous horseradish peroxidase was ingested readily by alveolar macrophages so that abundant reaction product was demonstrated in pinocytotic vesicles and phagocytic vacuoles. The uptake of exogenous peroxidase by pinocytosis appeared to be more vigorous in alveolar macrophages than in polymorphonuclear leukocytes. These studies demonstrate that alveolar macrophages do not contain significant quantities of peroxidase and suggest that, it contrast to polymorphonuclear leukocytes, peroxidative metabolism does not contribute in a major way to microbial killing by alveolar macrophages.

Animals↗
PubMed1975

The changes of thyroglobulin in the lysosomal particles of thyroid during the postnatal period in rats.

The distribution of radioactivity and protein-SH groups was studied in neonatal rats injected with 125-I- in the 15,000 g pellets of thyroid glands to obtain information about the colloid which undergoes phagocytosis by lysosomes. The 15,000 g pellet was solubilized in Triton X--100. The soluble portion was enhanced on the 16th day of age, whereas the portion of the insoluble fraction remained almost unchanged. The content of protein-SH groups in the insoluble fraction decreased with age and was increased in the soluble fraction. The concentration of immunoreactive thyroid stimulating hormone (TSH) in the pituitary and in the blood of rats during ontogenesis was higher on the first day after delivery, then decreased within the first seven days and again markedly increased during the third postnatal week. It was concluded that higher amounts of Triton soluble thyroglobulin occurring during the postnatal period in rats reflects the availability of more substrate, i.e. thyroglobulin for pinocytosis and partially depends upon the TSH level. These findings also support the suggestion on maturation of the pituitary-thyroid system during the postnatal period in rats.

Animals↗
PubMed2002

Inhibition of endocytotic functions in Dictyostelium discoideum treated with a carbamate pesticide.

Administration of a carbamate pesticide carbaryl (1-Naphthyl-N-methyl carbamate) at a concentration of 60 and 100 ppm greatly inhibits the endocytotic functions during growth of the cellular slime mold D. discoideum. The ingestion of fluorescien isothiocynate (FITC) labeled E. coli is reduced between 30 and 40% in the treated cells as compared to controls. Similarly, the uptake of FITC-labeled dextran, which has been used as fluid-phase marker for pinocytosis also show 40-50% inhibition in the treated cells. 3H-leucine uptake and incorporation are also inhibited in the treated cells. SDS-PAGE analysis of cytoskeletal proteins shows a higher actin association with the membrane of treated cells. The results demonstrate the detrimental effects of Carbamate on the soil microbe even at a very low concentration and the efficacy of the slime mold cells as a biosensor for the carbamate-induced cytotoxicity.

Actins↗
PubMedDate not supplied

[The dynamic morphology of the endothelial cells of aortocoronary vessels cultured in vitro].

The morphologic and functional meaning of the endothelial cell, as the first cellular element between blood and tissues, has been investigated since the earliest histological knowledge of the vascular tree. Although there have been multiple attempts for its study, through different biological branches, very little has been comprehended in its dynamic biology, due to technical difficulties and to the apparent simplicity of this extraordinary cellular type. In this research we pretend to establish a morphodynamic pattern of the endothelial cells from the aortocoronary segment, using the particular advantages of tissue culture. Our results, have been obtained through careful observations with light microscopy under different optical systems and the help provided by spaced microcinematography. Our results showed the reality of the images in the different cellular phenomena, particularly, endocytotic pinocytosis, the dynamic of the cellular membrane, and the cell-cell linkages established in vitro.

Animals↗
PubMed1992

Protein phosphatase inhibitors okadaic acid and calyculin A alter cell shape and F-actin distribution and inhibit stimulus-dependent increases in cytoskeletal actin of human neutrophils.

The phosphatase inhibitors okadaic acid and calyculin A were found to elicit or to modify several neutrophil responses, suggesting that dephosphorylation plays a regulatory role. The concentrations of okadaic acid (> or = 1 mumol/L) that were effective on neutrophil functions (shape changes and marginal stimulation of pinocytosis) were shown to stimulate the incorporation of 32PO4 into many neutrophil proteins several-fold. Calyculin A was effective at 50-fold lower concentrations. In the presence of the inhibitors, the cells exhibited a nonpolar shape and the polarization response induced by chemotactic peptide was inhibited. Both phosphatase inhibitors also induced the association of F-actin with the cell membrane. A steady-state phosphatase activity is thus involved in maintaining shape and F-actin localization of resting cells. Inhibitors alone had no significant effect on the amount of cytoskeleton-associated actin. The increase in cytoskeletal actin observed at 30 minutes of stimulation with phorbol ester or 5 to 30 minutes of stimulation with chemotactic peptide, however, was abolished by okadaic acid or calyculin A, suggesting an important role of a phosphatase. In contrast, the early increase in cytoskeleton-associated actin observed at 1 minute of stimulation with peptide was not affected. This finding indicates that the increased association of actin with the cytoskeleton in the early and the later stages of neutrophil activation may be mediated by different signalling pathways.

Actins↗