Anti-fibrillogenic and fibril destabilizing effects of metal ions on cystatin fibrils

Metals such as Cu²⁺, Fe³⁺, and Zn²⁺ are major contributors to the biology of a brain in stages of health, aging, and disease because of their unique effects on both protein structures (misfolding) and oxidative stress. The relationship between metal ions and neurodegenerative diseases is very complicated. Our study highlights how metal ions influence amyloid formation at low pH and on preformed amyloid fibrils. By using thioflavin T assay, ANS fluorescence, Congo red assay, circular dichroism, and microscopy to elucidate the effects of Cu²⁺, Fe³⁺, and Zn²⁺ on goat brain cystatin (GBC) aggregation at low pH. Results showed that Cu²⁺ and Fe³⁺ inhibit fibril formation of GBC by promoting amorphous aggregates. However, Zn²⁺ exclusively promotes fibril formation at low pH, leading to the formation of more ordered aggregates. Furthermore, the combined results of these complementary methods also suggested that Cu²⁺ and Fe³⁺ destabilize the β-sheet secondary structure of preformed amyloid fibrils of GBC.     

Recommended gas transport properties of argon at low density using ab initio potential

The most important transport properties of argon have been calculated using classical kinetic theory expressions in conjunction with high-quality ab initio potential energy values computed by Patkowski and Szalewicz. Dilute gas transport properties have been calculated for the viscosity, thermal conductivity, self-diffusion coefficient and thermal diffusion factor from 83 to 10,000 K. Comparisons between experimental transport property data and values presently calculated indicate that the present theoretical predictions may be employed as recommended values for this set of transport properties over a wide temperature range.     

Electron Paramagnetic Resonance investigation of the interaction of nitroxyl spin labels with photosynthetic membranes

The interactions of four nytroxyl spin labels with photosynthetic membranes (thylakoids and liposomes) have been investigated by the Electron Paramagnetic Resonance technique (EPR). The obtained data (shapes of EPR spectra and kinetics of light induced reactions) allow us to localize the interactions between the markers and photosynthetic membranes. The pH influence on the reaction kinetics has also been investigated. On the basis of these experimental data, a theoretical model of the interaction between spin labels and the photosynthetic electron transport chain is proposed.     

Interaction between atmospheric and pedospheric nitrogen nutrition in spruce (Picea abies L. Karst) seedlings

The effect of NO₂ fumigation on root N uptake and metabolism was investigated in 3-month-old spruce (Picea abics L. Karst) seedlings. In a first experiment, the contribution of NO₂ to the plant N budget was measured during a 48 h fumigation with 100mm³m^?3 NO₂. Plants were pre-treated with various nutrient solutions containing NO₂ and NH₄⁺, NO₃^? only or no nitrogen source for 1 week prior to the beginning of fumigation. Absence of NH₄⁺ in the solution for 6d led to an increased capacity for NO₃^? uptake, whereas the absence of both ions caused a decrease in the plant N concentration, with no change in NO₃^? uptake. In fumigated plants, NO₂ uptake accounted for 20–40% of NO₃^? uptake. Root NO₃^? uptake in plants supplied with NH₄⁺plus NO₃^? solutions was decreased by NO₂ fumigation, whereas it was not significantly altered in the other treatments. In a second experiment, spruce seedlings were grown on a solution containing both NO₂ and NH₄⁺ and were fumigated or not with 100mm³m^?3 NO₂ for 7 weeks. Fumigated plants accumulated less dry matter, especially in the roots. Fluxes of the two N species were estimated from their accumulations in shoots and roots, xylem exudate analysis and ¹⁵N labelling. Root NH₄⁺ uptake was approximately three times higher than NO₃^? uptake. Nitrogen dioxide uptake represented 10–15% of the total N budget of the plants. In control plants, N assimilation occurred mainly in the roots and organic nitrogen was the main form of N transported to the shoot. Phloem transport of organic nitrogen accounted for 17% of its xylem transport. In fumigated plants, neither NO₃^? nor NH₄⁺ accumulated in the shoot, showing that all the absorbed NO₂ was assimilated. Root NO₃^? reduction was reduced whereas organic nitrogen transport in the phloem increased by a factor of 3 in NO₂-fimugated as compared with control plants. The significance of the results for the regulation of whole-plant N utilization is discussed.     

Combination of dual-energy computed tomography and iterative metal artefact reduction to increase general quality of imaging for radiotherapy patients with high dense materials. Phantom study

PurposeTo evaluate the use of pseudo-monoenergetic reconstructions (PMR) from dual-energy computed tomography, combined with the iterative metal artefact reduction (iMAR) method.MethodsPseudo-monoenergetic CT images were obtained using the dual-energy mode on the Siemens Somatom Definition AS scanner. A range of PMR combinations (70–130 keV) were used with and without iMAR. A Virtual Water™ phantom was used for quantitative assessment of error in the presence of high density materials: titanium, alloys 330 and 600. The absolute values of CT number differences (AD) and normalised standard deviations (NSD) were calculated for different phantom positions. Image quality was assessed using an anthropomorphic pelvic phantom with an embedded hip prosthesis. Image quality was scored blindly by five observers.ResultsAD and NSD values revealed differences in CT number errors between tested sets. AD and NSD were reduced in the vicinity of metal for images with iMAR (p < 0.001 for AD/NSD). For ROIs away from metal, with and without iMAR, 70 keV PMR and pCT AD values were lower than for the other reconstructions (p = 0.039). Similarly, iMAR NSD values measured away from metal were lower for 130 keV and 70 keV PMR (p = 0.002). Image quality scores were higher for 70 keV and 130 keV PMR with iMAR (p = 0.034).ConclusionThe use of 70 keV PMR with iMAR allows for significant metal artefact reduction and low CT number errors observed in the vicinity of dense materials. It is therefore an attractive alternative to high keV imaging when imaging patients with metallic implants, especially in the context of radiotherapy planning.     

Uptake,Transport and Storage of Cardenolides in Foxglove. Cardenolide Sinks and Occurrence of Cardenolides in the Sieve Tubes of Digitalis lanata1

Cardiac glycoside transport was investigated on the organ and whole plant level. Uptake experiments were carried out with shoot and root cultures of Digitalis lanata. In both systems primary cardenolides, i.e., those with a terminal glucose in their oligosaccharide side chain, were taken up against their concentration gradient, whereas the glucose-free secondary cardenolides were not. Active uptake of primary cardenolides was further evidenced by KCN inhibition of uptake. Using plantlets grown in vitro the long-distance transport of primary cardenolides from the leaves to the roots was demonstrated. Cardenolides were also detected in etiolated leaves, induced on plants with green leaves, which are supposed to be unable to synthezise cardenolides de novo, providing further evidence for long-distance transport. Several primary cardenolides were detected in the honeydew excreted by aphids fed on Digitalis lanata leaves, indicating that the phloem is a transporting tissue for cardenolides. On the other hand, the xylem sap obtained by applying the pressure-chamber technique was cardenolide-free. It was concluded that in Digitalis primary cardenolides serve as both the transport and the storage form of cardenolides. After their synthesis they are either stored in the vacuoles of the source tissue or loaded into the sieve tubes, from which they are unloaded at other sites where they are trapped in the vacuoles of the respective sink tissue.     

Selective Alterations in Presynaptic Cytomatrix Protein Organization Induced by Calcium and Other Divalent Cations That Modulate Exocytosis

Rises in intracellular calcium cause several events of physiological significance, including the regulated release of neuronal transmitters. In this study, the effects of divalent cations on the structural organization of cytomatrix in presynaptic terminals was examined. [35S]Methionine-radiolabeled guinea pig retinal ganglion cell cytomatrix proteins were axonally transported [in slow component b (SCb) of axonal transport] to the neuron terminals in the superior colliculus. When the peak of radiolabeled cytomatrix proteins reached the terminals, synaptosomes containing the radiolabeled cytomatrix proteins were prepared. Approximately 40% of each SCb protein was soluble after hypoosmotic lysis of the radiolabeled synaptosomes in the presence of divalent cation chelators. Lysis of synaptosomes in the presence of calcium ions over a range of concentrations, however, caused a dramatic decrease in solubility of the presynaptic SCb proteins. The cytoplasmic effects may result from a calcium-dependent condensation of cytoplasm around presynaptic terminal membrane systems. There are two major presynaptic SCb proteins (at 60 and 35 kDa), that exhibited exceptional behavior: they remained as soluble in the presence of calcium as under control conditions, suggesting that they were relatively unaffected by the mechanism causing the decrease in SCb protein solubility. Also examined were the effects of other alkaline earth and transition metal divalent cations on the presynaptic SCb proteins.     

Do soft drinks affect metal ions release from orthodontic appliances?

ObjectiveThe effect of orange juice and Coca Cola^® on the release of metal ions from fixed orthodontic appliances.Materials and methodsA continuous flow system designed for in vitro testing of orthodontic appliances was used. Orange juice/Coca Cola^® was flowing through the system alternately with artificial saliva for 5.5 and 18.5 h, respectively. The collected samples underwent a multielemental ICP-OES analysis in order to determine the metal ions release pattern in time.ResultsThe total mass of ions released from the appliance into orange juice and Coca Cola^® (respectively) during the experiment was calculated (μg): Ni (15.33; 37.75), Cr (3.604; 1.052), Fe (48.42; ≥156.1), Cu (57.87, 32.91), Mn (9.164; 41.16), Mo (9.999; 30.12), and Cd (0.5967; 2.173).ConclusionsIt was found that orange juice did not intensify the release of metal ions from orthodontic appliances, whereas Coca Cola^® caused increased release of Ni ions.