scholarly journals Membrane Properties Involved in Calcium-Stimulated Microparticle Release from the Plasma Membranes of S49 Lymphoma Cells

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Lauryl E. Campbell ◽  
Jennifer Nelson ◽  
Elizabeth Gibbons ◽  
Allan M. Judd ◽  
John D. Bell
Keyword(s):  
Plasma Membranes ◽  
Calcium Ionophore ◽  
Membrane Properties ◽  
Positive Trend ◽  
Lymphoma Cells ◽  
Potassium Efflux ◽  
Significant Positive Trend ◽  
Cytoskeletal Disruption ◽  
Lymphocyte Cell ◽  
Lymphocyte Cell Line

This study answered the question of whether biophysical mechanisms for microparticle shedding discovered in platelets and erythrocytes also apply to nucleated cells: cytoskeletal disruption, potassium efflux, transbilayer phospholipid migration, and membrane disordering. The calcium ionophore, ionomycin, disrupted the actin cytoskeleton of S49 lymphoma cells and produced rapid release of microparticles. This release was significantly inhibited by interventions that impaired calcium-activated potassium current. Microparticle release was also greatly reduced in a lymphocyte cell line deficient in the expression of scramblase, the enzyme responsible for calcium-stimulated dismantling of the normal phospholipid transbilayer asymmetry. Rescue of the scrambling function at high ionophore concentration also resulted in enhanced particle shedding. The effect of membrane physical properties was addressed by varying the experimental temperature (32–42°C). A significant positive trend in the rate of microparticle release as a function of temperature was observed. Fluorescence experiments with trimethylammonium diphenylhexatriene and Patman revealed significant decrease in the level of apparent membrane order along that temperature range. These results demonstrated that biophysical mechanisms involved in microparticle release from platelets and erythrocytes apply also to lymphocytes.

scholarly journals The Greening and Wetting of the Sahel Have Leveled off since about 1999 in Relation to SST

2020 ◽  
Vol 12 (17) ◽  
pp. 2723
Author(s):  
Tiexi Chen ◽  
Shengjie Zhou ◽  
Chuanzhuang Liang ◽  
Daniel Fiifi Tawia Hagan ◽  
Ning Zeng ◽  
...  
Keyword(s):  
Piecewise Linear ◽  
Vegetation Indices ◽  
Positive Trend ◽  
Causality Analysis ◽  
Area Index ◽  
Piecewise Linear Regression ◽  
Significant Positive Trend ◽  
Tropical Oceans ◽  
Regression Approach

The Sahel, a semi-arid climatic zone with highly seasonal and erratic rainfall, experienced severe droughts in the 1970s and 1980s. Based on remote sensing vegetation indices since early 1980, a clear greening trend is found, which can be attributed to the recovery of contemporaneous precipitation. Here, we present an analysis using long-term leaf area index (LAI), precipitation, and sea surface temperature (SST) records to investigate their trends and relationships. LAI and precipitation show a significant positive trend between 1982 and 2016, at 1.72 × 10 −3 yr −1 (p < 0.01) and 4.63 mm yr−1 (p < 0.01), respectively. However, a piecewise linear regression approach indicates that the trends in both LAI and precipitation are not continuous throughout the 35 year period. In fact, both the greening and wetting of the Sahel have been leveled off (pause of rapid growth) since about 1999. The trends of LAI and precipitation between 1982 and 1999 and 1999–2016 are 4.25 × 10 − 3 yr −1 to − 0.27 × 10 −3 yr −1, and 9.72 mm yr −1 to 2.17 mm yr −1, respectively. These declines in trends are further investigated using an SST index, which is composed of the SSTs of the Mediterranean Sea, the subtropical North Atlantic, and the global tropical oceans. Causality analysis based on information flow theory affirms this precipitation stabilization between 2003 and 2014. Our results highlight that both the greening and the wetting of the Sahel have been leveled off, a feature that was previously hidden in the apparent long-lasting greening and wetting records since the extreme low values in the 1980s.

Wasserstruktur und Permeation: Die Aktivierungsenergie und der molekulare Mechanismus der Wasserpermeation

1967 ◽  
Vol 22 (8) ◽  
pp. 885-890 ◽  
Author(s):  
Josef Weigl
Keyword(s):  
Membrane Proteins ◽  
Hydrogen Bonds ◽  
Water Permeability ◽  
Plasma Membranes ◽  
Water Structure ◽  
Activation Energies ◽  
Membrane Properties ◽  
Pure Liquid ◽  
Tissue Water ◽  
Prolonged Contact

The exchange of tissue water of corn roots with ambient water was investigated using D2O, a gaschromatographic method, and a technique which avoids prolonged contact of tissue water with atmospheric water.The exchange experiments were performed at 10°, 20°, and 25 °C and the activation energies for different exchange phases were calculated by a method involving a graphical determination of the relative exchange rates at certain H2O/D2O gradients. Log10 of the rates were plotted versus 1/T as usual and the activation energies were calculated from the slopes of the straight lines. The energy of activation of the exchange process increased from 4.4 kcal-mol-1 in an initial phase (exchange of surface water and free space water) to 6.3 kcal·mol-1 in later phases which represent the processes of permeation through plasma and plasma membranes. This suggests that the hydrogen bonds of permeating water have a mean energy of 6 —7 kcal·mol-1 resulting from interaction with membrane (and plasma) constituents.The theory is proposed that cell membranes contain water phases with hydrogen bonds stronger than those in pure liquid water. These water phases are assumed to be located mainly within apolar portions of globular membrane proteins. Not solely a continous lipid layer, but a specific arrangement of polar and apoiar portions of globular membrane proteins is regarded to be essential for semipermeability and other membrane properties. Results from various authors were considered in establishing the general working hypothesis that agents like apoiar compounds which increase water structure decrease water permeability, and agents like salts which disrupt water structure increase water permeability.

scholarly journals Isoxazolidine Conjugates of N3-Substituted 6-Bromoquinazolinones—Synthesis, Anti-Varizella-Zoster Virus, and Anti-Cytomegalovirus Activity

Molecules ◽  
2018 ◽  
Vol 23 (8) ◽  
pp. 1889 ◽  
Author(s):  
Magdalena Grabkowska-Drużyc ◽  
Graciela Andrei ◽  
Dominique Schols ◽  
Robert Snoeck ◽  
Dorota Piotrowska
Keyword(s):  
Antiviral Activity ◽  
Rna Viruses ◽  
Dipolar Cycloaddition ◽  
Wild Type ◽  
Varicella Zoster ◽  
Dna And Rna ◽  
Varizella Zoster Virus ◽  
Lymphocyte Cell ◽  
Lymphocyte Cell Line ◽  
Virus Strains

1,3-Dipolar cycloaddition of N-methyl C-(diethoxyphosphoryl) nitrone to N3-substituted 6-bromo-2-vinyl-3H-quinazolin-4-ones gave (3-diethoxyphosphoryl) isoxazolidines substituted at C5 with quinazolinones modified at N3. All isoxazolidine cycloadducts were screened for antiviral activity against a broad spectrum of DNA and RNA viruses. Several isoxazolidines inhibited the replication of both thymidine kinase wild-type and deficient (TK+ and TK−) varicella-zoster virus strains at EC50 in the 5.4–13.6 μΜ range, as well as human cytomegalovirus (EC50 = 8.9–12.5 μΜ). Isoxazolidines trans-11b, trans-11c, trans-11e, trans-11f/cis-11f, trans-11g, trans-11h, and trans-11i/cis-11i exhibited moderate cytostatic activity towards the human lymphocyte cell line CEM (IC50 = 9.6–17 μM).

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