scholarly journals Initial events during phagocytosis by macrophages viewed from outside and inside the cell: membrane-particle interactions and clathrin.

1982 ◽  
Vol 94 (3) ◽  
pp. 613-623 ◽  
Author(s):  
J Aggeler ◽  
Z Werb
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Plasma Membranes ◽  
Cell Attachment ◽  
High Resolution Electron Microscopy ◽  
Peritoneal Macrophages ◽  
Coated Pits ◽  
Thin Sections ◽  
Particle Uptake ◽  
Freeze Dried

The initial events during phagocytosis of latex beads by mouse peritoneal macrophages were visualized by high-resolution electron microscopy of platinum replicas of freeze-dried cells and by conventional thin-section electron microscopy of macrophages postfixed with 1% tannic acid. On the external surface of phagocytosing macrophages, all stages of particle uptake were seen, from early attachment to complete engulfment. Wherever the plasma membrane approached the bead surface, there was a 20-nm-wide gap bridged by narrow strands of material 12.4 nm in diameter. These strands were also seen in thin sections and in replicas of critical-point-dried and freeze-fractured macrophages. When cells were broken open and the plasma membrane was viewed from the inside, many nascent phagosomes had relatively smooth cytoplasmic surfaces with few associated cytoskeletal filaments. However, up to one-half of the phagosomes that were still close to the cell surface after a short phagocytic pulse (2-5 min) had large flat or spherical areas of clathrin basketwork on their membranes, and both smooth and clathrin-coated vesicles were seen fusing with or budding off from them. Clathrin-coated pits and vesicles were also abundant elsewhere on the plasma membranes of phagocytosing and control macrophages, but large flat clathrin patches similar to those on nascent phagosomes were observed only on the attached basal plasma membrane surfaces. These resulted suggest that phagocytosis shares features not only with cell attachment and spreading but also with receptor-mediated pinocytosis.

scholarly journals Specialization of the macrophage plasma membrane at sites of interaction with opsonized erythrocytes.

1983 ◽  
Vol 96 (5) ◽  
pp. 1227-1233 ◽  
Author(s):  
R Montesano ◽  
A Mossaz ◽  
P Vassalli ◽  
L Orci
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Cell Types ◽  
Peritoneal Macrophages ◽  
Receptor Interaction ◽  
Coated Pits ◽  
Electron Dense Material ◽  
Functional Studies ◽  
Structural Specialization ◽  
Mouse Peritoneal Macrophages

We incubated mouse peritoneal macrophages for 3-8 min at 37 degrees C with antibody-coated sheep erythrocytes and examined regions of close interaction between the two cell types by electron microscopy. At sites of focal macrophage-erythrocyte contact we observed a distinctive specialization of the macrophage plasma membrane consisting of a prominent subplasmalemmal band of electron-dense material, approximately 25-35 nm in thickness. In many instances, this band showed a periodic substructure similar to that seen in clathrin coats. Moreover, many slender erythrocyte processes penetrated into invaginations of the macrophage surface which were bristle-coated at their blind extremity. As previously shown for clathrin-coated pits, the segments of the macrophage plasma membrane beneath which the defense material was found were selectively resistant to the membrane-perturbing effect of the antibiotic, filipin. This structural specialization of the macrophage plasma membrane at sites of ligand-receptor interaction during immune phagocytosis of antibody-coated erythrocytes may represent the morphological counterpart of the zipper mechanism of phagocytosis previously demonstrated by functional studies.

scholarly journals Redistribution of alpha-granules and their contents in thrombin-stimulated platelets.

1984 ◽  
Vol 98 (2) ◽  
pp. 748-760 ◽  
Author(s):  
P E Stenberg ◽  
M A Shuman ◽  
S P Levine ◽  
D F Bainton
Keyword(s):  
Plasma Membrane ◽  
Tannic Acid ◽  
Extracellular Space ◽  
Plasma Membranes ◽  
Platelet Factor 4 ◽  
Platelet Factor ◽  
Thin Sections ◽  
Immunocytochemical Techniques ◽  
Morphologic Changes ◽  
Stimulation Of

The redistribution of beta-thromboglobulin (beta TG), platelet Factor 4 (PF4), and fibrinogen from the alpha granules of the platelet after stimulation with thrombin was studied by morphologic and immunocytochemical techniques. The use of tannic acid stain and quick-freeze techniques revealed several thrombin-induced morphologic changes. First, the normally discoid platelet became rounder in form, with filopodia, and the granules clustered in its center. The granules then fused with one another and with elements of the surface-connected canalicular system (SCCS) to form large vacuoles in the center of the cell and near the periphery. Neither these vacuoles nor the alpha granules appeared to fuse with the plasma membrane, but the vacuoles were connected to the extracellular space by wide necks, presumably formed by enlargement of the narrow necks connecting the SCCS to the surface of the unstimulated cell. The presence of fibrinogen, beta TG, and PF4 in corresponding large intracellular vacuoles and along the platelet plasma membrane after thrombin stimulation was demonstrated by immunocytochemical techniques in saponin-permeabilized and nonpermeabilized platelets. Immunocytochemical labeling of the three proteins on frozen thin sections of thrombin-stimulated platelets confirmed these findings and showed that all three proteins reached the plasma membrane by the same pathway. We conclude that thrombin stimulation of platelets causes at least some of the fibrinogen, beta TG, and PF4 stored in their alpha granules to be redistributed to their plasma membranes by way of surface-connected vacuoles formed by fusion of the alpha granules with elements of the SCCS.

Adhesion of Phytophthora palmivora zoospores: electron microscopy of cell attachment and cyst wall fibril formation

1975 ◽  
Vol 18 (1) ◽  
pp. 123-132
Author(s):  
V.O. Sing ◽  
S. Bartnicki-Garcia
Keyword(s):  
Electron Microscopy ◽  
Cell Adhesion ◽  
Cyst Wall ◽  
Cell Attachment ◽  
Sodium Dodecyl ◽  
Film Surface ◽  
Phytophthora Palmivora ◽  
Thin Sections ◽  
Electron Dense Deposit ◽  
Dense Deposit

Zoospores of Phytophthora palmivora adhered to a plastic film surface were examined by electron microscopy. Three stages of adhesion were compared: (1) non-adhesive, unencysted zoospores, (2) adhered incipient cysts, and (3) adhered mature cysts. Thin sections of incipient cysts revealed cells attached to the film surface through the partially discharged contents of the so-called peripheral vesicles; this seems to be the first step in cell adhesion. In mature cysts, the adhesive appeared to have been compacted into an electron-dense deposit binding the cyst wall to the plastic surface. The adhesion zone was also examined in face view after lysing attached incipient cysts with sodium dodecyl sulphate. Cyst wall microfibrils were seen together with an amorphous substance (presumably the adhesive material). The microfibrils were in various stages of formation. Seemingly, adhesion and microfibril formation take place concurrently. The possibility was considered that the material contained in the peripheral vesicles serves in both cell adhesion and microfibril elaboration.

scholarly journals Immunofluorescence and electron microscopy of the cytoplasmic surface of the human erythrocyte membrane and its interaction with Sendai virus.

1979 ◽  
Vol 83 (2) ◽  
pp. 338-347 ◽  
Author(s):  
M Büechi ◽  
T Bächi
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Plasma Membranes ◽  
Sendai Virus ◽  
Light And Electron Microscopy ◽  
Distal Portion ◽  
Double Labeling ◽  
Virus Particles ◽  
Viral Antigens ◽  
Cytoplasmic Surface

A method was developed for directly observing the inner surfaces of plasma membranes by light and electron microscopy. Human erythrocytes were attached to cover slips (glass or mica) treated with aminopropylsilane and glutaraldehyde, and then disrupted by direct application of a jet of buffer, which removed the distal portion of the cells, thus exposing the cytoplasmic surface (PS) of the flattened membranes. Antispectrin antibodies and Sendai virus particles were employed as sensitive markers for, respectively, the PS and the external surface (ES) of the membrane; their localization by immunofluorescence or electron microscopy demonstrated that the major asymmetrical features of the plasma membrane were preserved. The fusion of Sendai virus particles with cells was investigated using double-labeling immunofluorescence techniques. Virus adsorbed to the ES of cells at 4 degrees C was not accessible to fluorescein-labeled antibodies applied from the PS side. After incubation at 37 degrees C, viral antigens could be detected at the PS. These antigens, however, remained localized and did not diffuse from the site of attachment, as is usually seen in viral antigens accessible on the ES. They may therefore represent internal viral antigens not incorporated into the plasma membrane as a result of virus-cell fusion.

What Can Epitope Specific Antibodies Tell us About the Organization of Caveolin in Cells?

2001 ◽  
Vol 7 (S2) ◽  
pp. 1030-1031
Author(s):  
J.M. Robinson
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Biochemical Characterization ◽  
Cell Types ◽  
Membrane Microdomains ◽  
Truncated Form ◽  
Coated Pits ◽  
N Terminus ◽  
Plasma Membrane Microdomains

There are three members of the caveolin (CAV) gene family that give rise to four polypeptides. These polypeptides are CAV-1α, CAV-1β, CAV-2, and CAV-3. The CAV-1β isoform is a truncated form of CAV-1α that lacks 31 amino acids at the N-terminus of the molecule. The CAV- 1β molecule arises through an alternative splicing mechanism.Caveolae are specialized plasma membrane microdomains that are expressed at high levels in some cell types (e.g., endothelium, adipocytes, fibroblasts). These specialized regions of the plasma membrane have a characteristic omega-shaped appearance with diameters ranging from 40-90 run. They are distinct from clathrin-coated pits since they lack the characteristic coated appearance in electron microscopy. Caveolae were among the first structures to be discovered by biological electron microscopy. However, biochemical characterization of these structures did not begin in earnest until a marker protein was identified. The initial marker was the 22-kDa protein known as caveolin.

scholarly journals The R-SNARE Endobrevin/VAMP-8 Mediates Homotypic Fusion of Early Endosomes and Late Endosomes

2000 ◽  
Vol 11 (10) ◽  
pp. 3289-3298 ◽  
Author(s):  
Wolfram Antonin ◽  
Claudia Holroyd ◽  
Ritva Tikkanen ◽  
Stefan Höning ◽  
Reinhard Jahn
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Subcellular Fractionation ◽  
Immunogold Electron Microscopy ◽  
Fusion Reactions ◽  
Coated Pits ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Golgi Network

Endobrevin/VAMP-8 is an R-SNARE localized to endosomes, but it is unknown in which intracellular fusion step it operates. Using subcellular fractionation and quantitative immunogold electron microscopy, we found that endobrevin/VAMP-8 is present on all membranes known to communicate with early endosomes, including the plasma membrane, clathrin-coated pits, late endosomes, and membranes of thetrans-Golgi network. Affinity-purified antibodies that block the ability of endobrevin/VAMP-8 to form SNARE core complexes potently inhibit homotypic fusion of both early and late endosomes in vitro. Fab fragments were as active as intact immunoglobulin Gs. Recombinant endobrevin/VAMP-8 inhibited both fusion reactions with similar potency. We conclude that endobrevin/VAMP-8 operates as an R-SNARE in the homotypic fusion of early and late endosomes.

The fine structure of Sphaerotilus nutans

1973 ◽  
Vol 19 (3) ◽  
pp. 309-313 ◽  
Author(s):  
Judith F. M. Hoeniger ◽  
H.-D. Tauschel ◽  
J. L. Stokes
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Lateral Position ◽  
Thin Sections ◽  
Liquid Cultures ◽  
Sphaerotilus Natans ◽  
Stationary Liquid ◽  
Basal Disk ◽  
Polar Organelle

Sphaerotilus natans developed sheathed filaments in stationary liquid cultures and motile swarm cells in shaken ones. Electron microscopy of negatively stained preparations and thin sections showed that the sheath consists of fibrils. When the filaments were grown in broth with glucose added, the sheath was much thicker and the cells were packed with granules of poly-β-hydroxybutyrate.Swarm cells possess a subpolar tuft of 10 to 30 flagella and a polar organelle which is usually inserted in a lateral position and believed to be ribbon-shaped. The polar organelle consists of an inner layer joined by spokes to an accentuated plasma membrane. The flagellar hook terminates in a basal disk, consisting of two rings, which is connected by a central rod to a second basal disk.

High-Resolution Electron Microscopy on Thin Sections of Monodisperse CdS Particles

1996 ◽  
Vol 183 (1) ◽  
pp. 295-298 ◽  
Author(s):  
Jun-Mo Yang ◽  
Daisuke Shindo ◽  
Grace E. Dirige ◽  
Atsushi Muramatsu ◽  
Tadao Sugimoto
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Thin Sections ◽  
Resolution Electron

scholarly journals Receptor-mediated endocytosis of transferrin and recycling of the transferrin receptor in rat reticulocytes.

1983 ◽  
Vol 97 (2) ◽  
pp. 329-339 ◽  
Author(s):  
C Harding ◽  
J Heuser ◽  
P Stahl
Keyword(s):  
Plasma Membrane ◽  
Transferrin Receptor ◽  
Intracellular Membrane ◽  
Coated Pits ◽  
Surface Receptors ◽  
Receptor Mediated Endocytosis ◽  
Freeze Dried ◽  
Inner Surface ◽  
Multivesicular Endosomes ◽  
Rat Reticulocytes

At 4 degrees C transferrin bound to receptors on the reticulocyte plasma membrane, and at 37 degrees C receptor-mediated endocytosis of transferrin occurred. Uptake at 37 degrees C exceeded binding at 4 degrees C by 2.5-fold and saturated after 20-30 min. During uptake at 37 degrees C, bound transferrin was internalized into a trypsin-resistant space. Trypsinization at 4 degrees C destroyed surface receptors, but with subsequent incubation at 37 degrees C, surface receptors rapidly appeared (albeit in reduced numbers), and uptake occurred at a decreased level. After endocytosis, transferrin was released, apparently intact, into the extracellular space. At 37 degrees C colloidal gold-transferrin (AuTf) clustered in coated pits and then appeared inside various intracellular membrane-bounded compartments. Small vesicles and tubules were labeled after short (5-10 min) incubations at 37 degrees C. Larger multivesicular endosomes became heavily labeled after longer (20-35 min) incubations. Multivesicular endosomes apparently fused with the plasma membrane and released their contents by exocytosis. None of these organelles appeared to be lysosomal in nature, and 98% of intracellular AuTf was localized in acid phosphatase-negative compartments. AuTf, like transferrin, was released with subsequent incubation at 37 degrees C. Freeze-dried and freeze-fractured reticulocytes confirmed the distribution of AuTf in reticulocytes and revealed the presence of clathrin-coated patches amidst the spectrin coating the inner surface of the plasma membrane. These data suggest that transferrin is internalized via coated pits and vesicles and demonstrate that transferrin and its receptor are recycled back to the plasma membrane after endocytosis.

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