Localization of neuronal Ca2+ buffering near plasma membrane studied with different divalent cations

1983 ◽  
Vol 3 (4) ◽  
pp. 297-310 ◽  
Author(s):  
Douglas L. Tillotson ◽  
Anthony L. F. Gorman
Keyword(s):  
Plasma Membrane ◽  
Divalent Cations

scholarly journals Studies on the mechanism of expression of secreted fibrinogen on the surface of activated human platelets

Blood ◽  
1989 ◽  
Vol 73 (5) ◽  
pp. 1226-1234 ◽  
Author(s):  
C Legrand ◽  
V Dubernard ◽  
AT Nurden
Keyword(s):  
Monoclonal Antibody ◽  
Plasma Membrane ◽  
Synthetic Peptides ◽  
Divalent Cations ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Plasma Fibrinogen ◽  
Fab Fragments ◽  
Polymer Formation ◽  
Activated Platelets

Abstract Affinity purified anti-fibrinogen (anti-Fg) Fab fragments were used to study the mechanism of expression of alpha-granule fibrinogen on activated platelets. Low amounts of the radiolabeled anti-Fg Fab bound to unstimulated or adenosine diphosphate (ADP)-stimulated cells. They readily bound to platelets stimulated with collagen, alpha-thrombin or gamma-thrombin in the presence of divalent cations. At 1 n mol/L alpha- thrombin or 25 nmol/L gamma-thrombin, platelet fibrinogen was expressed on the surface of the cells notwithstanding the presence of AP-2, a monoclonal antibody to the glycoprotein (GP) IIb-IIIa complex, or the synthetic peptides Arg-Gly-Asp-Ser and gamma 400–411, all substances that prevented the binding of plasma fibrinogen to platelets. These results suggest that platelet fibrinogen may interact with its receptors during its translocation from the alpha-granules to the plasma membrane and, thus, not occupy the same sites as those available for plasma fibrinogen on the surface of the cell. Furthermore, we found that platelet fibrinogen was expressed on the thrombin-stimulated platelets of a Glanzmann's thrombasthenia variant that failed to bind plasma fibrinogen. Normal platelets stimulated with 5 nmol/L alpha- thrombin bound increased amounts of the anti-fg Fab, the additional expression being inhibited by the anti-GP IIb-IIIa monoclonal antibody or by Gly-Pro-Arg-Pro, an inhibitor of fibrin polymer formation. This suggests that rebinding to externally located GP IIb-IIIa complexes becomes important once fibrin is formed.

scholarly journals Murine fetal liver macrophages bind developing erythroblasts by a divalent cation-dependent hemagglutinin.

1988 ◽  
Vol 106 (3) ◽  
pp. 649-656 ◽  
Author(s):  
L Morris ◽  
P R Crocker ◽  
S Gordon
Keyword(s):  
Plasma Membrane ◽  
Divalent Cation ◽  
Plasma Membranes ◽  
Fetal Liver ◽  
Divalent Cations ◽  
Membrane Receptors ◽  
Erythroid Cells ◽  
Mammalian Development ◽  
Trypsin Treatment ◽  
Plasma Membrane Receptors

During mammalian development the fetal liver plays an important role in hematopoiesis. Studies with the macrophage (M phi)-specific mAb F4/80 have revealed an extensive network of M phi plasma membranes interspersed between developing erythroid cells in fetal liver. To investigate the interactions between erythroid cells and stromal M phi, we isolated hematopoietic cell clusters from embryonic day-14 murine fetal liver by collagenase digestion and adherence. Clusters of erythroid cells adhered to glass mainly via M phi, 94% of which bound 19 +/- 11 erythroblasts (Eb) per cell. Bound Eb proliferated vigorously on the surface of fetal liver M phi, with little evidence of ingestion. The M phi could be stripped of their associated Eb and the clusters then reconstituted by incubation with Eb in the presence of divalent cations. The interaction required less Ca++ than Mg++, 100 vs. 250 microM for half-maximal binding, and was mediated by a trypsin-sensitive hemagglutinin on the M phi surface. After trypsin treatment fetal liver M phi recovered the ability to bind Eb and this process could be selectively inhibited by cycloheximide. Inhibition tests showed that the Eb receptor differs from known M phi plasma membrane receptors and fetal liver M phi did not bind sheep erythrocytes, a ligand for a distinct M phi hemagglutinin. We propose that fetal liver M phi interact with developing erythroid cells by a novel nonphagocytic surface hemagglutinin which is specific for a ligand found on Eb and not on mature red cells.

The Plasma Membrane ATPase of Dunaliella parva

1989 ◽  
Vol 44 (1-2) ◽  
pp. 128-138 ◽  
Author(s):  
Hartmut Gimmler ◽  
Lothar Schneider ◽  
Rosemarie Kaaden
Keyword(s):  
Plasma Membrane ◽  
Higher Plants ◽  
Divalent Cations ◽  
Gradient Centrifugation ◽  
Anion Transport ◽  
Hypersaline Environment ◽  
Plasma Membrane Atpase ◽  
Dunaliella Parva ◽  
Membrane Atpases ◽  
Membrane Atpase

Abstract Plasma membrane Mg2+, Ca2+ ATPases were isolated from Dunaliella parva by differential centrifugation and subsequent sucrose gradient centrifugation and analyzed for their properties with special emphasis on ecophysiological requirements of this extremely salt-tolerant alga. Most properties (Vmax- and KM-values, substrate specificity, vanadate and DES sensitivity, resistance against ouabain) indicate that the ATPases of the plasma membrane of D. parva are basically of the same type as that found in the plasma membrane of other algae or higher plants. However, some interesting deviations from the normal characteristics of plasma membrane ATPases of plants were observed for the Dunaliella ATPases. These modifications partially may reflect adaptations of the ATPase and/or the microenvironment of the ATPase to the highly saline environment of this alga; 1) The plasma membrane ATPase of D. parva requires unusually high concentrations of divalent cations (up to 100 mM Mg2+ or Ca2+) for maximal activity. Both cations can substitute for each other. 2) The plasma membrane ATPase of D. parva is extremely resistant against salt. It was stimulated by NaCl or KC1 at concentrations up to 800 mM , whereas at higher salt concentrations the enzyme was inhibited. However, about 2.5 M NaCl was required for halfmaximal inhibition of ATPase activity. 3) The ATPase was inhibited by inhibitors of anion transport such as SITS and D ID S . which suggests direct or indirect involvement of ATPase in anion transport. The possible functions of the plasma membrane ATPases are discussed with special emphasis on problems related to the hypersaline environment of this alga.

A novel form of host defence: Membrane protection by Ca2+ and Zn2+

1987 ◽  
Vol 7 (2) ◽  
pp. 81-91 ◽  
Author(s):  
C. A. Pasternak
Keyword(s):  
Plasma Membrane ◽  
Divalent Cations ◽  
Host Defence ◽  
Cytotoxic Agents ◽  
Biological Role ◽  
Cell Plasma Membrane ◽  
Prosthetic Group ◽  
Dietary Requirement ◽  
Cell Plasma ◽  
Membrane Protection

This review focusses on two questions: (1) How can the intracellular toxicity of ions such as Ca2+ or Zn2+ be reconciled with their extracellular benefit? (2) Why is the dietary requirement for Zn2+ so high when its documented biological role is that of a tightly-bound prosthetic group of certain enzymes? An answer to both questions is provided by the observation that extracellular cations such as Ca2+ and Zn2+ protect the plasma membrane of cells against non-specific leakage, including an influx of Ca2+ or Zn2+. It is suggested that such protection, against leakage induced by microbial and other toxins, may contribute to the high dietary requirement for zinc. These arguments lead to the proposal that a previously unrecognized form of host defence is one of protection of the cell plasma membrane by divalent cations against damage induced by cytotoxic agents of environmental origin.

Physiological and Ultrastructural Studies on the Longitudinal Retractor Muscle of a Sea Cucumber Stichopus Japonicus: I. Factors Influencing the Mechanical Response

1982 ◽  
Vol 97 (1) ◽  
pp. 101-111
Author(s):  
H. SUGI ◽  
S. SUZUKI ◽  
T. TSUCHIYA ◽  
S. GOMI ◽  
N. FUJIEDA
Keyword(s):  
Plasma Membrane ◽  
Sea Cucumber ◽  
Mechanical Response ◽  
Divalent Cations ◽  
Smooth Muscles ◽  
Retractor Muscle ◽  
Stichopus Japonicus ◽  
Ultrastructural Studies ◽  
Physiological Properties ◽  
After Effect

1. The physiological properties of contraction and the ultrastructure of the longitudinal retractor muscle (LRM) of a sea cucumber Stichopus japonicus were studied to give information about the sources of activator Ca in echinoderm somatic smooth muscles. 2. The magnitude of ACh- and K-induced contractures was dependent on [Ca]0, and both contractures were eliminated in Ca-free solution, while they were not markedly influenced by Mn ions (10 mM) and low pH (4.0). 3. Procaine (5 mM) decreased ACh-contracture tension with a long lasting after-effect, which was removed by the application of high [K]0. 4. ACh-contractures were markedly potentiated shortly after the termination of mechanical response to the removal of external Na. 5. The LRM could also be made to contract by caffeine (10 mM), the removal of external divalent cations and hypertonic solutions, indicating the presence of intracellularly stored Ca available for the activation of the contractile mechanism. 6. The LRM fibres contain poorly developed intracellular membranous structures. The inner surface of the plasma membrane and small vesicles located underneath the plasma membrane seem to be two of the sources of activator Ca.

Plasma membrane vesiculation in 3T3 and SV3T3 cells. II. Factors affecting the process of vesiculation

1979 ◽  
Vol 35 (1) ◽  
pp. 245-252
Author(s):  
R.E. Scott ◽  
P.B. Maercklein
Keyword(s):  
Plasma Membrane ◽  
Divalent Cations ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Hypertonic Medium ◽  
Factors Affecting ◽  
Low Concentrations ◽  
Membrane Vesiculation ◽  
Membrane Shedding ◽  
Energy Dependent

Plasma membrane vesicles are shed from monolayer cell cultures during incubation in low concentrations of formaldehyde and other sulphydryl blocking reagents. In both 3T3 and SV3T3 cells disulphide reducing agents, including dithiothreitol and mercaptoethanol, potentiate formaldehyde-induced vesiculation. Plasma membrane vesiculation is shown to be a temperature-dependent phenomenon which occurs optimally between 22 and 37 degrees C and at pH 7.0 to 7.5. Membrane shedding is an energy-dependent phenomenon, requiring monovalent and divalent cations and slightly hypertonic medium. Plasma membrane vesiculation is not affected by pretreatment of cells with inhibitors of protein synthesis, i.e. cycloheximide, nor by agents which disrupt the cytoskeleton.

scholarly journals Regulation of Connexin Hemichannels by Monovalent Cations

2005 ◽  
Vol 127 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Miduturu Srinivas ◽  
D. Paola Calderon ◽  
Jack Kronengold ◽  
Vytas K. Verselis
Keyword(s):  
Cell Death ◽  
Plasma Membrane ◽  
Divalent Cations ◽  
Signaling Molecules ◽  
Primary Effect ◽  
Monovalent Cations ◽  
Modest Increase ◽  
Monovalent Ions ◽  
The Difference ◽  
Connexin Hemichannels

Opening of connexin hemichannels in the plasma membrane is highly regulated. Generally, depolarization and reduced extracellular Ca2+ promote hemichannel opening. Here we show that hemichannels formed of Cx50, a principal lens connexin, exhibit a novel form of regulation characterized by extraordinary sensitivity to extracellular monovalent cations. Replacement of extracellular Na+ with K+, while maintaining extracellular Ca2+ constant, resulted in >10-fold potentiation of Cx50 hemichannel currents, which reversed upon returning to Na+. External Cs+, Rb+, NH4+, but not Li+, choline, or TEA, exhibited a similar effect. The magnitude of potentiation of Cx50 hemichannel currents depended on the concentration of extracellular Ca2+, progressively decreasing as external Ca2+ was reduced. The primary effect of K+ appears to be a reduction in the ability of Ca2+, as well as other divalent cations, to close Cx50 hemichannels. Cx46 hemichannels exhibited a modest increase upon substituting Na+ with K+. Analyses of reciprocal chimeric hemichannels that swap NH2- and COOH-terminal halves of Cx46 and Cx50 demonstrate that the difference in regulation by monovalent ions in these connexins resides in the NH2-terminal half. Connexin hemichannels have been implicated in physiological roles, e.g., release of ATP and NAD+ and in pathological roles, e.g., cell death through loss or entry of ions and signaling molecules. Our results demonstrate a new, robust means of regulating hemichannels through a combination of extracellular monovalent and divalent cations, principally Na+, K+, and Ca2+.

Sign in / Sign up

Export Citation Format

Share Document