scholarly journals Cell shape and plasma membrane alterations after static magnetic fields exposure

10.4081/840 ◽  
2009 ◽  
Vol 47 (4) ◽  
pp. 299 ◽  
Author(s):  
A Chionna ◽  
M Dwikat ◽  
E Panzarini ◽  
B Tenuzzo ◽  
EC Carlà ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Magnetic Fields ◽  
Cell Surface ◽  
Cell Shape ◽  
Biological Effects ◽  
Human Lymphocytes ◽  
Cell Types ◽  
Continuous Exposure ◽  
U937 Cells ◽  
Static Magnetic Fields

The biological effects of static magnetic fields (MFs) with intensity of 6 mT were investigated in lymphocytes and U937 cells in the presence or absence of apoptosis-inducing drugs by transmission (TEM) and scanning (SEM) electron microscopy. Lectin cytochemistry of ConA-FITC conjugates was used to analyze plasma membrane structural modifications. Static MFs modified cell shape, plasma membrane and increased the level of intracellular [Ca++] which plays an antiapoptotic role in both cell types. Modifications induced by the exposure to static MFs were irrespective of the presence or absence of apoptotic drugs or the cell type. Abundant lamellar-shaped microvilli were observed upon 24 hrs of continuous exposure to static MFs in contrast to the normally rough surface of U937 cells having numerous short microvilli. Conversely, lymphocytes lost their round shape and became irregularly elongated; lamellar shaped microvilli were found when cells were simultaneosly exposed to static MFs and apoptosis-inducing drugs. In our experiments, static MFs reduced the smoothness of the cell surface and partially impeded changes in distribution of cell surface glycans, both features being typical of apoptotic cells. Cell shape and plasma membrane structure modifications upon static MFs exposure were time-dependent. Lamellar microvilli were clearly observed before the distortion of cell shape, which was found at long times of exposure. MFs exposure promoted the rearrangement of F-actin filaments which, in turn, could be responsible for the cell surface modifications. Here we report data that support biological effects of static MFs on U937 cells and human lymphocytes. However, the involvement of these modifications in the onset of diseases needs to be further elucidated.

Biological effects of 6 mT static magnetic fields: A comparative study in different cell types

2006 ◽  
Vol 27 (7) ◽  
pp. 560-577 ◽  
Author(s):  
Bernadette Tenuzzo ◽  
Alfonsina Chionna ◽  
Elisa Panzarini ◽  
Remigio Lanubile ◽  
Patrizia Tarantino ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Comparative Study ◽  
Biological Effects ◽  
Cell Types ◽  
Static Magnetic Fields ◽  
Different Cell Types

scholarly journals β-blockers Reverse Agonist-Induced β2-AR Downregulation Regardless of Their Signaling Profile

2020 ◽  
Vol 21 (2) ◽  
pp. 512
Author(s):  
Sonia Maccari ◽  
Vanessa Vezzi ◽  
Federica Barbagallo ◽  
Tonino Stati ◽  
Barbara Ascione ◽  
...  
Keyword(s):  
Cell Surface ◽  
Human Lymphocytes ◽  
Cell Types ◽  
Hek293 Cells ◽  
Enzyme Linked Immunosorbent Assay ◽  
Mrna Levels ◽  
Receptor Density ◽  
Biased Agonism ◽  
Β Blocker ◽  
Β Blockers

Altered β-adrenergic receptor (β-AR) density has been reported in cells, animals, and humans receiving β-blocker treatment. In some cases, β-AR density is upregulated, but in others, it is unaffected or even reduced. Collectively, these results would imply that changes in β-AR density and β-blockade are not related. However, it has still not been clarified whether the effects of β-blockers on receptor density are related to their ability to activate different β-AR signaling pathways. To this aim, five clinically relevant β-blockers endowed with inverse, partial or biased agonism at the β2-AR were evaluated for their effects on β2-AR density in both human embryonic kidney 293 (HEK293) cells expressing exogenous FLAG-tagged human β2-ARs and human lymphocytes expressing endogenous β2-ARs. Cell surface β2-AR density was measured by enzyme-linked immunosorbent assay (ELISA) and flow cytometry. Treatment with propranolol, carvedilol, pindolol, sotalol, or timolol did not induce any significant change in surface β2-AR density in both HEK293 cells and human lymphocytes. On the contrary, treatment with the β-AR agonist isoproterenol reduced the number of cell surface β2-ARs in the tested cell types without affecting β2-AR-mRNA levels. Isoproterenol-induced effects on receptor density were completely antagonized by β-blocker treatment. In conclusion, the agonistic activity of β-blockers does not exert an important effect on short-term regulation of β2-AR density.

scholarly journals The distinguishing characteristics of the plasma membrane are its exposed proteins

1975 ◽  
Vol 147 (2) ◽  
pp. 373-376 ◽  
Author(s):  
R E Gates ◽  
D R Phillips ◽  
M Morrison
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
Gel Electrophoresis ◽  
Human Lymphocytes ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Cell Types ◽  
Distinguishing Characteristic ◽  
Probe System ◽  
Normal Human

The exposed proteins of the plasma membrane of normal human lymphocytes and platelets were labelled by using the lactoperoxidase macromolecular probe system. The labelled components were separated into molecular-weight classes by sodium dodecyl sulphate--polyacrylamide-gel electrophoresis. In contrast with the report by Tanner et al. (1974), a comparison of the two cell types showed that the major labelled components in both cell types were glycoproteins and were not identical. It is concluded that the exposed proteins are probably the most distinguishing characteristic of the plasma membrane of differentiated cell types.

scholarly journals Involvement of Raft-Like Plasma Membrane Domains of Entamoeba histolytica in Pinocytosis and Adhesion

2004 ◽  
Vol 72 (9) ◽  
pp. 5349-5357 ◽  
Author(s):  
Richard C. Laughlin ◽  
Glen C. McGugan ◽  
Rhonda R. Powell ◽  
Brenda H. Welter ◽  
Lesly A. Temesvari
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Entamoeba Histolytica ◽  
Fluid Phase ◽  
Cell Types ◽  
Cysteine Proteases ◽  
Membrane Domains ◽  
Cell Surface Molecule ◽  
Physiological Relevance ◽  
Plasma Membrane Domains

ABSTRACT Lipid rafts are highly ordered, cholesterol-rich, and detergent-resistant microdomains found in the plasma membrane of many eukaryotic cells. These domains play important roles in endocytosis, secretion, and adhesion in a variety of cell types. The parasitic protozoan Entamoeba histolytica, the causative agent of amoebic dysentery, was determined to have raft-like plasma membrane domains by use of fluorescent lipid analogs that specifically partition into raft and nonraft regions of the membrane. Disruption of raft-like membrane domains in Entamoeba with the cholesterol-binding agents filipin and methyl-β-cyclodextrin resulted in the inhibition of several important virulence functions, fluid-phase pinocytosis, and adhesion to host cell monolayers. However, disruption of raft-like domains did not inhibit constitutive secretion of cysteine proteases, another important virulence function of Entamoeba. Flotation of the cold Triton X-100-insoluble portion of membranes on sucrose gradients revealed that the heavy, intermediate, and light subunits of the galactose-N-acetylgalactosamine-inhibitible lectin, an important cell surface adhesion molecule of Entamoeba, were enriched in cholesterol-rich (raft-like) fractions, whereas EhCP5, another cell surface molecule, was not enriched in these fractions. The subunits of the lectin were also observed in high-density, actin-rich fractions of the sucrose gradient. Together, these data suggest that pinocytosis and adhesion are raft-dependent functions in this pathogen. This is the first report describing the existence and physiological relevance of raft-like membrane domains in E. histolytica.

The formation and function of the extraacrosomal layer and modification of the plasma membrane in spermiogenesis of Acrida lata motschulsky (Orthoptera)

1978 ◽  
Vol 36 (2) ◽  
pp. 570-571
Author(s):  
Gonpachiro Yasuzumi ◽  
Toshikatsu Asai
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Cell Surface ◽  
Membrane Structure ◽  
Early Stage ◽  
Cell Types ◽  
Unit Membrane ◽  
Sharp Point ◽  
Specific Proteins ◽  
And Function

Receptor-specific proteins are now being widely and usefully applied to the study of cell-surface topography. We have been actively interested in this field from the standpoint of spermiogenesis of the grasshopper. The surface of developing spermatids is in contact with other cells or with their environment, and in addition to carrying on metabolic processes necessary for maturation they must also exhibit the specificity that distinguishes cells from the same cell types from different individuales. The cell bodies of the grasshopper, Acrida lata Motschulsky, spermatids are spherical in the early stage of metamorphosis, but later they become conical and more and more elongate until they are long slender rods, rounded at the base and tapering at the tip to a sharp point. Concurrently with these changes in the spermatid cell bodies, the remarkable trans formation occurs in the fine structure of the cell-surface. In the early stage of maturation of spermatids, the cell-surface is smooth and consists of the unit membrane structure.

Fas ligand is targeted to secretory lysosomes via a proline-rich domain in its cytoplasmic tail

2001 ◽  
Vol 114 (13) ◽  
pp. 2405-2416 ◽  
Author(s):  
Emma J. Blott ◽  
Giovanna Bossi ◽  
Richard Clark ◽  
Marketa Zvelebil ◽  
Gillian M. Griffiths
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Fas Ligand ◽  
Cytoplasmic Tail ◽  
Cell Types ◽  
Cell Surface Receptor ◽  
Cell Surface Expression ◽  
Rich Domain ◽  
Secretory Lysosomes ◽  
In Cells

Fas ligand (FasL) induces apoptosis through its cell surface receptor Fas. T lymphocytes and natural killer cells sort newly synthesised FasL to secretory lysosomes but, in cell types with conventional lysosomes, FasL appears directly on the plasma membrane. Here, we define a proline-rich domain (PRD) in the cytoplasmic tail of FasL that is responsible for sorting FasL to secretory lysosomes. Deletion of this PRD results in cell surface expression of FasL in cells with secretory lysosomes. Positively charged residues flanking the PRD are crucial to the sorting motif and changing the charge of these residues causes mis-sorting to the plasma membrane. In cells with conventional lysosomes, this motif is not recognised and FasL is expressed at the plasma membrane. The FasL PRD is not required for endocytosis in any cell type, as deletion mutants lacking this motif are endocytosed efficiently to the lysosomal compartment. Endogenous FasL cannot internalise extracellular antibody, demonstrating that FasL does not transit the plasma membrane en route to the secretory lysosomes. We propose that an interaction of the PRD of FasL with an SH3-domain-containing protein, enables direct sorting of FasL from the Golgi to secretory lysosomes.

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