Ultrastructure and histochemistry of the protonephridial system of juvenile Paramphistomum epiclitum and Fischoederius elongatus (Paramphistomidae: Digenea) during migration in Indian ruminants.

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and 1992. Ultrastructure and histochemistry of the protonephridial system of juvenile Paramphistomum epiclitum and Fischoederius elongatus (Paramphistomidae: Digenea) during migration in Indian ruminants. International Journal for Parasitology 22: 1103–1115. The protonephridial system of juvenile Paramphistomum epiclitum and Fischoederius elongatus consists of a bilaterally symmetrical arrangement of primary, secondary and tertiary ducts which connect individual flame cells with a simple common bladder. Primary and secondary ducts are formed from columns of adjoining cells which provide an epithelial lining, whose luminal surface is elaborated with either short tubercles or lamellae. Groups of cilia project from the luminal surface at frequent intervals along secondary ducts. By contrast, the tertiary ducts and bladder are lined with a nucleated syncytium which ends at a junctional complex formed with the terminal canal. The latter is continuous with the tegumental syncytium and opens at a nephridiopore on the postero-dorsal surface. Tertiary ducts of mature cercariae contain concretions which are voided by migrating juveniles in whose tertiary ducts lipids are progressively accumulated. Evidence for the role of protonephridia in excretion and possibly in osmoregulation and ionic balance is currently examined.     

Coordinating Anions “to the Rescue” of the Lithium Ion Mobility in Ternary Solid Polymer Electrolytes Plasticized With Ionic Liquids

Lithium salts with low coordinating anions such as bis(trifluoromethanesulfonyl)imide (TFSI) have been the state-of-the-art for polyethylene oxide (PEO)-based “dry” polymer electrolytes for 3 decades. Plasticizing PEO with TFSI-based ionic liquids (ILs) to form ternary solid polymer electrolytes (TSPEs) increases conductivity and Li⁺ diffusivity. However, the Li⁺ transport mechanism is unaffected compared to their “dry” counterparts and is essentially coupled to the dynamics of the polymer host matrix, which limits Li⁺ transport improvement. Thus, a paradigm shift is hereby suggested: the utilization of more coordinating anions such as trifluoromethanesulfonyl-N-cyanoamide (TFSAM), able to compete with PEO for Li⁺ solvation, to accelerate the Li⁺ transport and reach a higher Li⁺ transference number. The Li–TFSAM interaction in binary and ternary TFSAM-based electrolytes is probed by experimental methods and discussed in the context of recent computational results. In PEO-based TSPEs, TFSAM drastically accelerates the Li⁺ transport (increases Li⁺ transference number by a factor 6 and the Li⁺ conductivity by 2–3) and computer simulations reveal that lithium dynamics are effectively re-coupled from polymer to anion dynamics. Last, this concept of coordinating anions in TSPEs is successfully applied in LFP||Li metal cells leading to enhanced capacity retention (86% after 300 cycles) and an improved rate performance at 2C.     

On the special role of NCX in astrocytes: Translating Na+-transients into intracellular Ca2+ signals

As a solute carrier electrogenic transporter, the sodium/calcium exchanger (NCX1-3/SLC8A1-A3) links the trans-plasmalemmal gradients of sodium and calcium ions (Na⁺, Ca²⁺) to the membrane potential of astrocytes. Classically, NCX is considered to serve the export of Ca²⁺ at the expense of the Na⁺ gradient, defined as a “forward mode” operation. Forward mode NCX activity contributes to Ca²⁺ extrusion and thus to the recovery from intracellular Ca²⁺ signals in astrocytes. The reversal potential of the NCX, owing to its transport stoichiometry of 3 Na⁺ to 1 Ca²⁺, is, however, close to the astrocytes’ membrane potential and hence even small elevations in the astrocytic Na⁺ concentration or minor depolarisations switch it into the “reverse mode” (Ca²⁺ import/Na⁺ export). Notably, transient Na⁺ elevations in the millimolar range are induced by uptake of glutamate or GABA into astrocytes and/or by the opening of Na⁺-permeable ion channels in response to neuronal activity. Activity-related Na⁺ transients result in NCX reversal, which mediates Ca²⁺ influx from the extracellular space, thereby generating astrocyte Ca²⁺ signalling independent from InsP₃-mediated release from intracellular stores. Under pathological conditions, reverse NCX promotes cytosolic Ca²⁺ overload, while dampening Na⁺ elevations of astrocytes. This review provides an overview on our current knowledge about this fascinating transporter and its special functional role in astrocytes. We shall delineate that Na⁺-driven, reverse NCX-mediated astrocyte Ca²⁺ signals are involved neurone-glia interaction. Na⁺ transients, translated by the NCX into Ca²⁺ elevations, thereby emerge as a new signalling pathway in astrocytes.     

The Micromolecular Fibrinogen Derivatives: Fractionation by Ultrafiltration and Cation-Exchange Chromatography

The micromolecular fibrinogen derivatives were fractionated by successive ultrafiltrations through the Araicon membranes UM10, UM2 and UM05 into three fractions which represented approx. 9%, 2% and 1.5% of the weight of fibrinogen. Assuming that the fragments behaved as spherical molecules, fraction 10-2 contained mainly fragments with mol. weights of 1,000–10,000; fraction 2–05 contained fragments with mol. weights of 500–1,000 and the 05 fraction contained fragments with mol. weights smaller than 500. Cation exchange chromatography on the aminex resin Spinco PA-35 at a high sensitivity range indicated that there were 19–21 fragments in the 10-2 fraction, 10–12 fragments in the 2–05 fraction and 20–22 fragments in the 05 fraction. Relative to fibrinogen, all three fractions were poor in amino acids absorbing light at 280 mu. The two larger fractions were able to prolong the thrombin, prothrombin and partial thromboplastin times of plasma and could also delay the generation of plasma thromboplastin.     

Significantly Enhanced Actuation Performance of IPMC by Surfactant-Assisted Processable MWCNT/Nafion Composite

The performance of Ionic Polymer Metal Composite (IPMC) actuator was significantly enhanced by incorporating surfactant-assisted processable Multi-Walled Carbon Nanotubes (MWCNTs) into a Nafion solution. Cationic surfactant Cetyl Trimethyl Ammonium Bromide (CTAB) was employed to disperse MWCNTs in the Nafion matrix, forming a homogeneous and stable dispersion of nanotubes. The processing did not involve any strong acid treatment and thus effectively preserved the excellent electronic properties associated with MWCNT. The as-obtained MWCNT/Nafion-IPMC actuator was tested in terms of conductivity, bulk and surface morphology, blocking force and electric current. It was shown that the blocking force and the current of the new IPMC are 2.4 times and 1.67 times higher compared with a pure Nafion-based IPMC. Moreover, the MWCNT/IPMC performance is much better than previously reported Nafion-IPMC doped by acid-treated MWCNT. Such significantly improved performance should be attributed to the improvement of electrical property associated with the addition of MWCNTs without acid treatment.     

Ionic strength-dependent alterations of membrane structure of red blood cells

Electron paramagnetic resonance (EPR) measurements using various fatty acid spin labels were performed on membranes of intact human erythrocytes at physiological, and at low ionic strength. In the case of spin probes bearing the nitroxide near the polar head group, a less restricted motion at low ionic strength was seen than with those labels with a nitroxide deeper within the hydrophobic tail of the membrane. Although these data clearly show an influence of ionic strength on membrane structure, and possibly a modified protein-lipid interaction, they cannot be simply discussed in terms of an altered membrane fluidity.     

Sodium and potassium currents recorded during an action potential

A simple method was used to measure directly sodium and potassium currents underlying the action potential in single nerve fibres of Xenopus laevis. A short rectangular stimulus under current-clamp conditions elicited an action potential which was digitally stored and later used as command when voltageclamping the same fibre. The currents thus obtained nearly reproduced the original rectangular stimulus. Adding first 100 nM TTX and subsequently 100 nM TTX plus 10 mM TEA to the extracellular Ringer solution revealed the sodium and the potassium currents during an action potential. They were converted to permeabilities by use of the constant-field equation and are in good agreement with the curves which had been calculated from conventional voltage-clamp data. Thus experimentally determined currents and permeabilities are shown as they are changing during an action potential.     

Adhesion of Azospirillum brasilense to polystyrene: Influence of ionic strength through protein adsorption

The influence of ionic strength on the adhesion of Azospirillum brasilense to polystyrene has been examined by comparing water and phosphate buffer saline (PBS) as suspending media. Polystyrene supports analysed by X‐ray photoelectron spectroscopy (XPS) after adhesion in PBS for 2 h or 24 h and detachment of adhering cells showed a higher protein surface concentration, reflected by the N/C atomic concentration ratio, compared to supports analysed after adhesion in water. It was shown that PBS both favours protein release by the cells into the solution and enhances the tendency of proteins to adsorb at the support surface.

After 2 h contact time, the increase in the concentration of adsorbed proteins in PBS was related to an increase in adhesion density. However, the observation that the adhesion density after 24 h was lower in PBS than in water indicated that the amount of proteins adsorbed at the support surface controls cell adhesion in a complex way. In PBS, a thick layer of proteinaceous material retaining the bacterial cells is formed; this leads to underestimation of the density of adhering cells as well as to a heterogeneous adhesion pattern and to a relatively low adhesion density due to detachment of pellicles upon rinsing.

The ionic strength thus influences bacterial adhesion in a more subtle way than simply through double layer interactions between the cells and the support.     

Structural Modelling of Vanadium Pentoxide

Abstract

Computational techniques, based on the minimization of the crystal energy with respect to atomic coordinates, are shown to predict correctly the complexity of the V₂O₅ crystal structure. Two main types of potential are derived, both fitted to the experimentally determined structure. One is based on integral ionic charges, the other uses partial charges. In all cases the deviations of the observed structures from the ideal model based on regular VO₆ octahedra is correctly reproduced by the energy-minimization techniques. We also qualitatively reproduce some of the important macroscogic properties of this material.