Cell-Glass Separation Depends on Salt Concentration and Valency: Measurements on Dictyostelium Amoebae by Finite Aperture Interferometry

1982 ◽  
Vol 54 (1) ◽  
pp. 299-310
Author(s):  
DAVID GINGELL ◽  
SHEILA VINCE
Keyword(s):  
Ionic Strength ◽  
Cell Membrane ◽  
Divalent Cations ◽  
Optical Measurements ◽  
Surface Glycoprotein ◽  
Monovalent Cations ◽  
Cell Surface Glycoprotein ◽  
Cellular Slime ◽  
Finite Aperture ◽  
Interacting Surfaces

Using pre-aggregation amoebae of the cellular slime mould Dictyostelium discoideum we have investigated the influence of cation concentration and valency on cell-glass separation. For computing the separation we used interference reflection microscopy and converted measured image irradiance to distance by finite aperture theory. Alterations in ionic strength caused virtually instantaneous reversible changes in the interference image due to changes in cell membrane-glass separation. In solutions containing monovalent cations, a change in ionic strength from 20 mM to 0.5 mM increased the separation of the plasmalemma from the glass by 60 nm. Divalent cations were better than monovalent cations at maintaining a small separation. Our results show that both divalent and trivalent cations adsorb to one or both of the interacting surfaces, in addition to acting as electrostatic double-layer counterions. The optical measurements also show that the cell membrane-glass gap is not reduced to zero by counterion screening; this is apparently due to the presence of a cell surface glycoprotein coat.

The influence of aggregation on the redox chemistry of humic substances

2009 ◽  
Vol 6 (2) ◽  
pp. 178 ◽  
Author(s):  
Noel E. Palmer ◽  
Ray von Wandruszka
Keyword(s):  
Ionic Strength ◽  
Humic Substances ◽  
Reduction Potential ◽  
Divalent Cations ◽  
Redox Chemistry ◽  
Fulvic Acids ◽  
Monovalent Cations ◽  
Fluorescence Excitation ◽  
Reduction Potentials ◽  
Fluorescence Excitation Emission Matrices

Environmental context. The ability of humic substances (decaying plant and animal matter) to partake in redox reactions in the environment depends on the extent to which the various humic polymers aggregate in solution to form larger particles. This aggregation, in turn, is predicated on the solution conditions, especially ionic strength, the pH, and the types of cations present. Abstract. Aggregation and conformation play an important role in the aqueous redox chemistry of humic substances (HS). The reduction potentials of dissolved humic and fulvic acids vary with pH, ionic strength, and type of humate used, and depending on the solution conditions, they can abiotically reduce various species. Changes in HS reduction potential ranged from 60 to 140 mV on addition of divalent cations, whereas no significant changes were observed with equivalent additions of monovalent cations. Dynamic light scattering measurements showed that this behaviour paralleled the size changes obtained with humic aggregates under the same conditions. The effect was more pronounced at higher pH, where divalent cations caused a significant decrease in the average hydrodynamic radius, whereas monovalent cations did not. At pH 4, neither mono- nor divalent cations substantially affected aggregate sizes. Quinoid moieties, which are known to play an important role in the redox chemistry of HS, displayed fluorescence excitation–emission matrices with features related to changes in the reduction potential of HS. An increase in the reduction potential (Eh) induced by the addition of Ca2+, for instance, caused a red shift in the excitation–emission matrix maximum.

scholarly journals Dominating Role of Ionic Strength in the Sedimentation of Nano-TiO2in Aquatic Environments

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Guang’an He ◽  
Rui Chen ◽  
Shushen Lu ◽  
Chengchun Jiang ◽  
Hong Liu ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Natural Organic Matter ◽  
Divalent Cations ◽  
Environmental Water ◽  
Orthogonal Experimental Design ◽  
Aquatic Environments ◽  
Monovalent Cations ◽  
Sedimentation Behavior ◽  
Low Levels

Various factors affect the sedimentation behavior of nanotitanium dioxide (n-TiO2) in water. Accordingly, this study aimed to select the dominating factor. An index of sedimentation efficiency related to n-TiO2concentration was applied to precisely describe the n-TiO2sedimentation behavior. Ionic strength (IS), natural organic matter (NOM) content, and pH were evaluated in sedimentation experiments. An orthogonal experimental design was used to sequence the affecting ability of these factors. Furthermore, simulative sedimentation experiments were performed. The n-TiO2sedimentation behavior was only affected by pH and NOM content at low levels of IS. Moreover, divalent cations can efficiently influence the n-TiO2sedimentation behavior compared with monovalent cations at fixed IS. Seven different environmental water samples were also used to investigate the n-TiO2sedimentation behavior in aquatic environments. Results confirmed that IS, in which divalent cations may play an important role, was the dominating factor influencing the n-TiO2sedimentation behavior in aquatic environments.

scholarly journals Deficiency of lymphocyte function-associated antigen 3 (LFA-3) in paroxysmal nocturnal hemoglobinuria. Functional correlates and evidence for a phosphatidylinositol membrane anchor.

1987 ◽  
Vol 166 (4) ◽  
pp. 1011-1025 ◽  
Author(s):  
P Selvaraj ◽  
M L Dustin ◽  
R Silber ◽  
M G Low ◽  
T A Springer
Keyword(s):  
Cell Membrane ◽  
Cell Surface ◽  
Cell Line ◽  
Paroxysmal Nocturnal Hemoglobinuria ◽  
Lymphoma Cell ◽  
Surface Glycoprotein ◽  
Thymic Epithelial Cells ◽  
Lymphocyte Function ◽  
Lymphoma Cell Line ◽  
Cell Surface Glycoprotein

Lymphocyte function-associated antigen 3 (LFA-3) is a widely distributed cell surface glycoprotein that binds to the T lymphocyte CD2 surface glycoprotein. This interaction mediates CTL-target cell conjugate formation and adhesion of thymocytes to thymic epithelial cells. CD2 is also the E rosette receptor of T lymphocytes and mediates rosetting with autologous E by binding to LFA-3. We describe deficient expression of LFA-3 on E from paroxysmal nocturnal hemoglobinuria (PNH) patients. PNH is an acquired defect affecting phosphatidylinositol-anchored membrane proteins, of which decay-accelerating factor (DAF) is most important in the clinical symptoms of PNH. LFA-3-negative, weakly positive, and positive populations were found among PNH E. There was a good correlation with DAF deficiency. PNH E exhibited decreased binding of 125I-CD2 and rosetting with a human T lymphoma cell line. PNH E readily incorporated purified LFA-3, restoring LFA-3 expression and the CD2 binding and rosetting activity to normal levels. The expression of DAF was not restored after the incorporation of purified LFA-3 into PNH E, showing that LFA-3 and DAF are different molecules. Phosphatidylinositol-specific phospholipase C (PIPLC) treatment of a B lymphoma cell line released 35% of the cell surface LFA-3 and 62% of DAF. LFA-3 on E was resistant to PIPLC. However, when LFA-3 purified from human E was reconstituted in sheep E or human E and subjected to PIPLC treatment, 40-50% of LFA-3 was released from the cell membrane. The results show that LFA-3 is attached to the cell membrane by a phosphatidylinositol glycolipid moiety, and confirm previous findings (37-41) that LFA-3 is a cell adhesion molecule that mediates adhesion by interacting with CD2 antigen.

scholarly journals Hyaluronate-CD44 Interactions Can Induce Murine B-Cell Activation

Blood ◽  
1997 ◽  
Vol 89 (8) ◽  
pp. 2901-2908 ◽  
Author(s):  
Asimah Rafi ◽  
Mitzi Nagarkatti ◽  
Prakash S. Nagarkatti
Keyword(s):  
T Cells ◽  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Critical Role ◽  
Surface Glycoprotein ◽  
B Cell Differentiation ◽  
B Cell Activation ◽  
Cell Surface Glycoprotein ◽  
Immunodeficient Mice

Abstract CD44 is a widely distributed cell surface glycoprotein whose principal ligand has been identified as hyaluronic acid (HA), a major component of the extracellular matrix (ECM). Recent studies have demonstrated that activation through CD44 leads to induction of effector function in T cells and macrophages. In the current study, we investigated whether HA or monoclonal antibodies (MoAbs) against CD44 would induce a proliferative response in mouse lymphocytes. Spleen cells from normal and nude, but not severe combined immunodeficient mice, exhibited strong proliferative responsiveness to stimulation with soluble HA or anti-CD44 MoAbs. Furthermore, purified B cells, but not T cells, were found to respond to HA. HA was unable to stimulate T cells even in the presence of antigen presenting cells (APC) and was unable to act as a costimulus in the presence of mitogenic or submitogenic concentrations of anti-CD3 MoAbs. In contrast, stimulation of B cells with HA in vitro, led to B-cell differentiation as measured by production of IgM antibodies in addition to increased expression of CD44 and decreased levels of CD45R. The fact that the B cells were responding directly to HA through its binding to CD44 and not to any contaminants or endotoxins was demonstrated by the fact that F(ab)2 fragments of anti-CD44 MoAbs or soluble CD44 fusion proteins could significantly inhibit the HA-induced proliferation of B cells. Also, HA-induced proliferation of B cells was not affected by the addition of polymixin B, and B cells from lipopolysaccharide (LPS)-unresponsive C3H/HeJ strain responded strongly to stimulation with HA. Furthermore, HA, but not chondroitin-sulfate, another major component of the ECM, induced B-cell activation. It was also noted that injection of HA intraperitoneally, triggered splenic B cell proliferation in vivo. Together, the current study demonstrates that interaction between HA and CD44 can regulate murine B-cell effector functions and that such interactions may play a critical role during normal or autoimmune responsiveness of B cells.

scholarly journals Pharmacological inactivation of the prion protein by targeting a folding intermediate

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Giovanni Spagnolli ◽  
Tania Massignan ◽  
Andrea Astolfi ◽  
Silvia Biggi ◽  
Marta Rigoli ◽  
...  
Keyword(s):  
Prion Protein ◽  
Prion Diseases ◽  
Cellular Prion Protein ◽  
Surface Glycoprotein ◽  
Folding Intermediate ◽  
Biological Regulation ◽  
Cell Surface Glycoprotein ◽  
Folding Intermediates ◽  
Protein Levels ◽  
Small Molecule Ligands

AbstractRecent computational advancements in the simulation of biochemical processes allow investigating the mechanisms involved in protein regulation with realistic physics-based models, at an atomistic level of resolution. These techniques allowed us to design a drug discovery approach, named Pharmacological Protein Inactivation by Folding Intermediate Targeting (PPI-FIT), based on the rationale of negatively regulating protein levels by targeting folding intermediates. Here, PPI-FIT was tested for the first time on the cellular prion protein (PrP), a cell surface glycoprotein playing a key role in fatal and transmissible neurodegenerative pathologies known as prion diseases. We predicted the all-atom structure of an intermediate appearing along the folding pathway of PrP and identified four different small molecule ligands for this conformer, all capable of selectively lowering the load of the protein by promoting its degradation. Our data support the notion that the level of target proteins could be modulated by acting on their folding pathways, implying a previously unappreciated role for folding intermediates in the biological regulation of protein expression.

scholarly journals Clinical and Biological Characteristics of Medullary and Extramedullary Plasma Cell Dyscrasias

Biology ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 629
Author(s):  
Snjezana Janjetovic ◽  
Philipp Lohneis ◽  
Axel Nogai ◽  
Derya Balci ◽  
Leo Rasche ◽  
...  
Keyword(s):  
Plasma Cell ◽  
Molecular Mechanisms ◽  
Biological Characteristics ◽  
Surface Glycoprotein ◽  
Cell Surface Glycoprotein ◽  
Similar Frequency ◽  
Cytogenetic Aberrations ◽  
A Cell ◽  
Plasma Cell Dyscrasias ◽  
Extramedullary Plasmocytoma

Background: Extramedullary plasma cell (PC) disorders may occur as extramedullary disease in multiple myeloma (MM-EMD) or as primary extramedullary plasmocytoma (pEMP)/solitary osseous plasmocytoma (SOP). In this study, we aimed to obtain insights into the molecular mechanisms of extramedullary spread of clonal PC. Methods: Clinical and biological characteristics of 87 patients with MM-EMD (n = 49), pEMP/SOP (n = 20) and classical MM (n = 18) were analyzed by using immunohistochemistry (CXCR4, CD31, CD44 and CD81 staining) and cytoplasmic immunoglobulin staining combined with fluorescence in situ hybridization (cIg-FISH). Results: High expression of CD44, a cell-surface glycoprotein involved in cell-cell interactions, was significantly enriched in MM-EMD (90%) vs. pEMP/SOP (27%) or classical MM (33%) (p < 0.001). In addition, 1q21 amplification by clonal PC occurred at a similar frequency of MM-EMD (33%), pEMP/SOP (57%) and classical MM (44%). Conversely, del(17p13), t(4;14) and t(14;16) were completely absent in pEMP/SOP. Besides this, 1q21 amplification was identified in 64% of not paraskeletal samples from MM-EMD or pEMP compared to 9% of SOP or paraskeletal MM-EMD/pEMP and 44% of classical MM samples, respectively (p = 0.02). Conclusion: Expression of molecules involved in homing and cytogenetic aberrations differ between MM with or without EMD and pEMP/SOP.

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