scholarly journals A morphological study of plasma and phagosome membranes during endocytosis in Acanthamoeba.

1980 ◽  
Vol 84 (2) ◽  
pp. 246-260 ◽  
Author(s):  
B Bowers
Keyword(s):  
Plasma Membrane ◽  
Morphological Study ◽  
Direct Evidence ◽  
Particle Density ◽  
Early Stage ◽  
Chemical Analyses ◽  
Surface Separation ◽  
Phospholipid Ratio ◽  
Major Route ◽  
Particle Ingestion

Particle ingestion by Acanthamoeba is rapid. Within 40 s bound particles can be surrounded by pseudopods, brought into the cytoplasm, and released as phagosomes into the cytoplasmic stream. In electron micrographs the phagosome appears as a flasklike invagination of the surface. Separation from the surface occurs by fragmentation of the attenuated "neck+ of the invagination. The separated phagosome membrane has a three- to fourfold greater density of intramembrane particles than the plasma membrane from which it derives. This change is evident within 15 min of ingestion and is detectable while the membrane is still tightly apposed to the particle. There is no direct evidence for the mechanism of this increase; no increase in particle density was seen in the membrane at an early stage in the forming phagosomes still connected to the surface. These morphological observations are consistent with chemical analyses, to be reported in a separate communication, that show that the phagosome membrane has a higher protein to phospholipid ratio and a higher glycosphingolipid content than the plasma membrane. Enlarged phagosomes (presumptive phagolysosomes) show multiple small vesiculations of characteristic morphology. The small vesicles are postulated to be the major route of membrane return to the cell surface.

Exterior and Interior Events in Early Stage of Thrombin-induced Platelet Aggregation

1977 ◽  
Vol 38 (03) ◽  
pp. 0630-0639 ◽  
Author(s):  
Shuichi Hashimoto ◽  
Sachiko Shibata ◽  
Bonro Kobayashi
Keyword(s):  
Molecular Weight ◽  
Enzyme Activity ◽  
Plasma Membrane ◽  
Platelet Aggregation ◽  
Early Stage ◽  
Adenyl Cyclase ◽  
Cellular Component ◽  
Primary Event ◽  
Rabbit Platelets ◽  
Membrane Bound

SummaryTreatment of washed rabbit platelets with 1 u/ml of thrombin at 37° C resulted in a disappearance from platelets of a protein with 250,000 dalton molecular weight which was shown to be originated from plasma membrane. Parallel loss of adenyl cyclase was noted, and both reactions were complete within 30 sec. From the patterns of disc electrophoretograms, the importance of quick suppression of thrombin action in demonstrating the primary event was stressed.Thrombin induced an apparent activation of membrane bound phosphodiesterase. This reaction was also complete within 30 sec. The cellular component which contained the enzyme activity was distinct from plasma membrane. Soluble phosphodiesterase was not influenced by thrombin at all.These reactions required intact platelet cells to react with thrombin, and no reaction was detected when subcellular preparations were treated with thrombin.Possibility of collaboration of changes in externally located synthetic enzyme with those in internally located degrading enzyme in the early phase of thrombin action on platelets was suggested.

scholarly journals The polymerization of actin: II. how nonfilamentous actin becomes nonrandomly distributed in sperm: evidence for the association of this actin with membranes

1976 ◽  
Vol 69 (1) ◽  
pp. 51-72 ◽  
Author(s):  
LG Tilney
Keyword(s):  
Plasma Membrane ◽  
Nuclear Envelope ◽  
Thin Section ◽  
Actin Filaments ◽  
Early Stage ◽  
Mature Sperm ◽  
Vacuole Membrane ◽  
Other Substances ◽  
Associated Proteins ◽  
Basal Half

At an early stage in spermiogenesis the acrosomal vacuole and other organelles including ribosomes are located at the basal end of the cell. From here actin must be transported to its future location at the anterior end of the cell. At no stage in the accumulation of actin in the periacrosomal region is the actin sequestered in a membrane-bounded compartment such as a vacuole or vesicle. Since filaments are not present in the periacrosomal region during the accumulation of the actin even though the fixation of these cells is sufficiently good to distinguish actin filaments in thin section, the actin must accumulate in the nonfilamentous state. The membranes in the periacrosomal region, specifically a portion of the nuclear envelope and the basal half of the acrosomal vacuole membrane, become specialized morphologically in advance of the accumulation of actin in this region. My working hypothesis is that the actin in combination with other substances binds to these specialized membranes and to itself and thus can accumulate in the periacrosmoal region by being trapped on these specialized membranes. Diffusion would then be sufficient to move these substances to this region. In support of this hypothesis are experiments in which I treated mature sperm with detergents, glycols, and hypotonic media, which solubilize or lift away the plasma membrane. The actin and its associated proteins remain attached to these specialized membranes. Thus actin can be nonrandomly distributed in cells in a nonfilamentous state presumably by its association with specialized membranes.

Investigation of the role of microtubules in protein secretion from lactating mouse mammary epithelial cells

1992 ◽  
Vol 102 (2) ◽  
pp. 239-247 ◽  
Author(s):  
M.E. Rennison ◽  
S.E. Handel ◽  
C.J. Wilde ◽  
R.D. Burgoyne
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Protein Secretion ◽  
Secretory Pathway ◽  
Mammary Epithelial Cells ◽  
Early Stage ◽  
Major Effect ◽  
Vesicle Transport ◽  
Mammary Epithelial ◽  
Mammary Cells

Disruption of microtubules has been shown to reduce protein secretion from lactating mammary epithelial cells. To investigate the involvement of microtubules in the secretory pathway in these cells we have examined the effect of nocodazole on protein secretion from mammary epithelial cells derived from the lactating mouse. Mouse mammary cells have extensive microtubule networks and 85% of their tubulin was in a polymeric form. Treatment with 1 micrograms/ml nocodazole converted most of the tubulin into a soluble form. In a continuous labelling protocol it was found that nocodazole did not interfere with protein synthesis but over a 5 h period secretion was markedly inhibited. To determine whether the inhibition was at the level of early or late stages of the secretory pathway mammary cells were pulse-labelled for 1 h to label protein throughout the secretory pathway before nocodazole treatment. When secretion was subsequently assayed it was found to be slower and only partially inhibited. These findings suggest that the major effect of nocodazole is on an early stage of the secretory pathway and that microtubules normally facilitate vesicle transport to the plasma membrane. An involvement of microtubules in vesicle transport to the plasma membrane is consistent with an observed accumulation of casein vesicles in nocodazole-treated cells. Exocytosis stimulated by the calcium ionophore ionomycin was unaffected by nocodazole treatment. We conclude from these results that the major effect of nocodazole is at an early stage of the secretory pathway, one possible target being casein vesicle biogenesis in the trans-Golgi network.

Evidence for microtubule nucleation at plasma membrane-associated sites in Drosophila

1987 ◽  
Vol 88 (1) ◽  
pp. 95-107 ◽  
Author(s):  
M.M. Mogensen ◽  
J.B. Tucker
Keyword(s):  
Plasma Membrane ◽  
Cell Differentiation ◽  
Cross Section ◽  
Plasma Membranes ◽  
Early Stage ◽  
Apical Cell ◽  
Apical Plasma Membrane ◽  
Cell Surfaces ◽  
Microtubule Organizing Centres ◽  
Oriented Parallel

This report is concerned with the nucleation and organization of microtubule bundles that assemble after ‘conventional’ centrosomal microtubule-organizing centres have been lost. The microtubule bundles in question span the lengths of wing epidermal cells. Bundles extend between hemidesmosomes at the apical cuticle-secreting surfaces of cells and basal attachment desmosomes that unite the dorsal and ventral epidermal layers of developing wing blades. Furthermore, each bundle includes up to 1500 microtubules and most of the microtubules are composed of 15 protofilaments. Individual cells were serially cross-sectioned at an early stage of bundle assembly. The number of microtubule profiles/cell cross-section decreased progressively by up to 59% of the most apical values in section sequences cut from fairly apical to more basal levels in the cells. The apical ends of microtubules were associated with numerous small dense plaque-like sites (diameter 0.1-0.2 micron), which were specialized regions of plasma membranes at the apical surfaces of cells. Many of the microtubules near apical plaques were not well aligned with each other; they ‘radiated away’ from cell apices. This was in contrast to the situation at more basal levels where most microtubules were oriented parallel to the longitudinal axes of cells. These findings indicate that the relatively dispersed arrays of apical plasma membrane-associated plaques act as microtubule-nucleating sites to initiate basally directed elongation of bundle microtubules. Apical cell surfaces and their plaques seem to operate as microtubule-nucleating and -organizing regions that functionally replace the centrosomal microtubule-organizing centres lost earlier in cell differentiation.

scholarly journals Plant Hormones Differentially Control the Sub-Cellular Localization of Plasma Membrane Microdomains during the Early Stage of Soybean Nodulation

Genes ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 1012 ◽  
Author(s):  
Zhenzhen Qiao ◽  
Prince Zogli ◽  
Marc Libault
Keyword(s):  
Plasma Membrane ◽  
Cellular Localization ◽  
Fluorescent Protein ◽  
Early Stage ◽  
Cellular Level ◽  
Infection Thread ◽  
Membrane Microdomains ◽  
Symbiotic Interaction ◽  
Green Fluorescent ◽  
Plasma Membrane Microdomains

Phytohormones regulate the mutualistic symbiotic interaction between legumes and rhizobia, nitrogen-fixing soil bacteria, notably by controlling the formation of the infection thread in the root hair (RH). At the cellular level, the formation of the infection thread is promoted by the translocation of plasma membrane microdomains at the tip of the RH. We hypothesize that phytohormones regulate the translocation of plasma membrane microdomains to regulate infection thread formation. Accordingly, we treated with hormone and hormone inhibitors transgenic soybean roots expressing fusions between the Green Fluorescent Protein (GFP) and GmFWL1 or GmFLOT2/4, two microdomain-associated proteins translocated at the tip of the soybean RH in response to rhizobia. Auxin and cytokinin treatments are sufficient to trigger or inhibit the translocation of GmFWL1 and GmFLOT2/4 to the RH tip independently of the presence of rhizobia, respectively. Unexpectedly, the application of salicylic acid, a phytohormone regulating the plant defense system, also promotes the translocation of GmFWL1 and GmFLOT2/4 to the RH tip regardless of the presence of rhizobia. These results suggest that phytohormones are playing a central role in controlling the early stages of rhizobia infection by regulating the translocation of plasma membrane microdomains. They also support the concept of crosstalk of phytohormones to control nodulation.

scholarly journals Species-dependent protoplast enlargement involves different types of vacuole generation in bacteria

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Sawako Takahashi ◽  
Marin Mizuma ◽  
Satoshi Kami ◽  
Hiromi Nishida
Keyword(s):  
Plasma Membrane ◽  
Enterococcus Faecalis ◽  
Bacterial Cell ◽  
Early Stage ◽  
Cell Enlargement ◽  
Gram Positive ◽  
Gram Negative ◽  
Different Types ◽  
Spherical Structures ◽  
Vacuolar Membranes

Abstract Vacuole generation occurs frequently during the enlargement of bacterial protoplasts and spheroplasts. Gram-positive Enterococcus faecalis protoplasts and gram-negative Lelliottia amnigena spheroplasts had large and small vacuoles inside the cytoplasm, respectively. Although no vacuoles were found at the early stage of cell enlargement, all enlarged cells used in the microinjection procedures had vacuoles. The plasma membrane of L. amnigena was more flexible than that of E. faecalis. In addition, E. faecalis protoplasts had unique discoidal structures as well as spherical structures in the cytoplasm. Our findings showed that the number of vacuoles increased as the L. amnigena plasma membrane expanded and that the size of vacuoles increased as the E. faecalis plasma membrane expanded, suggesting that bacterial cell enlargement involved vacuole generation. Thus, biosynthesis of the plasma and vacuolar membranes was synchronous with the bacterial cell enlargement. Differences in the plasma membrane flexibility might influence the different types of vacuole generation.

scholarly journals Studies on the mechanism of phagocytosis. I. Requirements for circumferential attachment of particle-bound ligands to specific receptors on the macrophage plasma membrane.

1975 ◽  
Vol 142 (5) ◽  
pp. 1263-1282 ◽  
Author(s):  
F M Griffin ◽  
J A Griffin ◽  
J E Leider ◽  
S C Silverstein
Keyword(s):  
Plasma Membrane ◽  
Sheep Erythrocyte ◽  
Peritoneal Macrophages ◽  
Membrane Receptors ◽  
Macrophage Receptors ◽  
Specific Receptors ◽  
Particle Ingestion ◽  
Plasma Membrane Receptors ◽  
Mouse Peritoneal Macrophages

These experiments were designed to evaluate the role of macrophage plasma membrane receptors for the third component of complement (C) and for the Fc portion of IgG in the ingestion phase of phagocytosis. Sheep erythrocyte (E) were coated with anti-E IgG [E(IgG)]; these E(IgG) were then attached to cultivated monolayers of mouse peritoneal macrophages under conditions which reversibly inhibit ingestion of E(IgG). The E(IgG)-macrophage complexes were further incubated under similar conditions with an antimacrophage IgG fraction which blocks Fc receptor-mediated ingestion but has no effect upon ingestion mediated by other phagocytic receptors. When these cultures were subsequently incubated under conditions optimal for particle ingestion, phagocytosis of the IgG-coated erythrocytes did not occur; the erythrocytes remained bound to the Fc receptors of the macrophage plasma membrane. To determine whether ligands must cover the entire surface of an attached particle to permit ingestion of that particle, C-coated E [E(IgM)C] were bound to the C receptors of thioglycollate-induced (activated) macrophages at 4 degrees C. E(IgM)C-macrophage complexes were then trypsinized at 4 degrees C, a procedure which resulted in cleavage of erythrocyte-bound C3b molecules to a form of C3 not recognized by the macrophage receptors for C3b. Under the conditions used, trypsin did not affect the attachment of E(IgM)C to the macrophage surface or the macrophage receptors for C3b. When these trypsin treated E(IgM)C-macrophage complexes were incubated at 37 degrees C, the bound E(IgM)C were not ingested; the erythrocytes remained attached to the macrophage plasma membrane via the macrophage's C receptors. These results indicate that attachment of a particle to specific receptors on the macrophage plasma membrane is not sufficient to trigger ingestion of that particle. Rather, ingestion requires the sequential, circumferential interaction of particle-bound ligands with specific plasma membrane receptors not involved in the initial attachment process.

scholarly journals Alterations of new methylated phospholipid synthesis in the plasma membranes of macrophages exposed to chemoattractants.

1981 ◽  
Vol 91 (1) ◽  
pp. 221-226 ◽  
Author(s):  
M C Pike ◽  
R Snyderman
Keyword(s):  
Plasma Membrane ◽  
Guinea Pig ◽  
Plasma Membranes ◽  
Total Phospholipid ◽  
Peritoneal Macrophages ◽  
Phospholipid Synthesis ◽  
Directed Migration ◽  
Phospholipid Ratio ◽  
Chemotactic Factors ◽  
Biophysical Changes

Chemotactic factors have been shown to inhibit the methylation of phosphatidylethanolamine in macrophages without affecting total phospholipid synthesis. It would thus be anticipated that newly synthesized membranes of macrophages exposed to chemoattractants would have an increased ratio of phosphatidylethanolamine to its methylated derivatives. These ratios were measured directly in newly synthesized phospholipids of plasma membranes isolated from guinea pig peritoneal macrophages. The phosphatidylethanolamine: methylated phospholipid ratio in such plasma membranes was increased by 53 to 111% upon exposure of the cells to chemotactic factors. This increase was due to decreased synthesis of methylated phospholipids and not to altered formation of phosphatidylethanolamine or activation of phospholipases. Methylated phospholipid ratios were also studied in the leading front lamellipodia isolated from macrophages migrating under chemotactic and nonchemotactic conditions. The phosphatidylethanolamine:methylated phospholipid ratios were increased up to fourfold in lamellipodia of macrophages migrating towards chemotactic agents when compared to those from cells migrating randomly. Biophysical changes in the plasma membrane produced by an increase in the ratio of phosphatidylethanolamine:methylated phospholipids as a result of exposure of cells to chemoattractants may be required for sustained directed migration.

scholarly journals Injury to the Endothelial Surface Layer Induces Glomerular Hyperfiltration Rats with Early-Stage Diabetes

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Chunyang Zhang ◽  
Yao Meng ◽  
Qi Liu ◽  
Miao Xuan ◽  
Lanyu Zhang ◽  
...  
Keyword(s):  
Surface Layer ◽  
Particle Density ◽  
Early Stage ◽  
Diabetic Rats ◽  
Mesangial Matrix ◽  
Sprague Dawley ◽  
Endothelial Surface Layer ◽  
Sprague Dawley Rats ◽  
Endothelial Surface

Glomerular endothelial surface layer (ESL) may play a role in the mechanisms of albuminuria in diabetic nephropathy, which lack evidencein vivo. The effects of high glucose on the passage of albumin across the glomerular ESL were analysed in streptozotocin-induced diabetic Sprague-Dawley rats for 4 weeks. Albuminuria and glomerular mesangial matrix were significantly increased in diabetic rats. The passage of albumin across the ESL, as measured by albumin-colloid gold particle density in the glomerular basement membrane (GBM), was increased significantly in diabetic rats. The thickness of the glomerular ESL, examined indirectly by infusing Intralipid into vessels using an electron microscope, was significantly decreased and the GBM exhibited little change in diabetic rats. In summary, the glomerular ESL may play a role in the pathogenesis of albuminuria in rats with early-stage diabetes.

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