Copper and zinc as modulators of neuronal excitability in a physiologically significant concentration range

Evidence from several areas of neuroscience has led to the notion that copper and zinc could be modulators of neuronal excitability. In order to contribute to test this idea, we characterized the changes induced by these divalent metal ions on the extracellularly recorded action potential firing rates of undissociated olfactory epithelium neurons. Our main finding is that at low concentrations, 1-100 nM for Cu(2+) and 1-50 microM for Zn(2+), they induced a concentration dependent increase in the neuronal firing rate. In contrast, at higher concentrations, 1-5 microM for Cu(2+) and 100-500 microM for Zn(2+), they decreased the firing rate. Based on these and previous results of our laboratory we propose that the biphasic effect of Cu(2+) and Zn(2+) exposure on neuronal firing may be explained by the interaction of these ions with high and low affinity sites in sodium channels whose occupancy leads to activation or inhibition of the sodium current, which is consistent with the proposed modulatory role of these metal ions on neuronal excitability.     

A new approach to the induction and recovery of Synechococcus leopoliensis CPD-photolyase for cosmetic applications

Journal of Applied Phycology - Ultraviolet (UV) radiation generates cyclobutane pyrimidine dimer (CPD) photoproducts in the DNA of skin cells, causing photoaging and non-melanoma skin cancer....     

Tsunami impact on the population development of a critically endangered hummingbird species of a Pacific island

It is a long-standing question how tsunamis can influence wild populations of animals and plants. Here, we assessed short-term changes in the population of the critically endangered Juan Fernández Firecrown (Sephanoides fernandensis) by using abundance data recorded 1 year before and 1 year after the 2010 Chilean tsunami. We tested that the abundance of Firecrowns declined in the areas where the tsunami caused the massive loss of Cabbage Trees, an important seasonal nectar source for Firecrowns. The abundance of Juan Fernández Firecrowns decreased after the tsunami, but also was affected by the habitat type, altitude, and the abundance of Cabbage Trees. Firecrowns tended to be more abundant in settlement areas than in native forest whereas the reduction in Firecrown abundance after the tsunami was more intense in settlement areas than in native forest. As expected, this habitat effect was dependent on the massive loss of Cabbage Trees in settlement areas following the tsunami. In spite of the short-term nature of our data, our results are conclusive in showing that the loss of an important food source causes short-term changes in the distribution and abundance of Firecrowns, which, in turn, could contribute to population decline.     

A character‐based approach in the Mexican cycads supports diverse multigene combinations for DNA barcoding

A DNA barcoding study was conducted to determine the optimal combination of loci needed for successful species‐level molecular identification in three extant cycad genera—Ceratozamia, Dioon, and Zamia—that occur in Mexico. Based on conclusions of a previous multigene study in representative species of all genera in the Cycadales, we tested the DNA barcoding performance of seven chloroplast coding (matK, rpoB, rpoC1, and rbcL) and non‐coding (atpF/H, psbK/I, and trnH‐psbA) regions, plus sequences of the nuclear internal transcribed spacer. We analysed data under the assumptions of the “character attributes organization system” (CAOS), a character‐based approach in which species are identified through the presence of ‘DNA diagnostics’. In Ceratozamia, four chloroplast regions and one nuclear region were needed to achieve > 70% unique species identification. In contrast, the two‐gene combination atpF/H + psbK/I and the four‐gene combination atpF/H + psbK/I + rpoC1 + ITS2 were needed to reach 79% and 75% unique species identification in Dioon and Zamia, respectively. The combinations atpF/H + psbK/I and atpF/H + psbK/I + rpoC1 + ITS2 include loci previously considered by the international DNA barcoding community. However, none of the three combinations of potential DNA barcoding loci found to be optimal with a character‐based approach in the Mexican cycads coincides with the ‘core barcode’ of chloroplast markers (matK + rbcL) recently proposed for universal use in the plant kingdom.     

Polymerization of hemoglobins in Arctic fish: Lycodes reticulatus and Gadus morhua

In vitro, and possibly in vivo, hemoglobin polymerization and red blood cell sickling appear to be widespread in codfish. In this article, we show that the hemoglobins of the two Arctic fish Lycodes reticulatus and Gadus morhua also have the tendency to polymerize, as monitored by dynamic light scattering experiments. The elucidation of the primary structure of the single hemoglobin of the zoarcid L. reticulatus shows the presence of a large number of cysteyl residues in α and β chains. Their role in eliciting the ability to produce polymers was also addressed by MALDI-TOF and TOF-TOF mass spectrometry. The G.morhua globins are also rich in Cys, but unlike in L. reticulatus, polymerization does not seem to be disulfide driven. The widespread occurrence of the polymerization phenomenon displayed by hemoglobins of Arctic fish supports the hypothesis that this feature may bea response to stressful environmental conditions.     

Integrifolin,a guaianolide from Andryala integrifolia

Integrifolin, the major constituent of Andryala integrifolia, has been isolated and characterized as 3β,8β-dihydroxy-4(15),10(14),11(13)-trien-(1αH), (5αH) guaian-6,12-olide (8-epi-desacylcynaropicrin).     

Putative ClC-2 Chloride Channel Mediates Inward Rectification in <Emphasis Type="Italic">Drosophila </Emphasis>Retinal Photoreceptors

We report that Drosophila retinal photoreceptors express inwardly rectifying chloride channels that seem to be orthologous to mammalian ClC-2 inward rectifier channels. We measured inwardly rectifying Cl⁻ currents in photoreceptor plasma membranes: Hyperpolarization under whole-cell tight-seal voltage clamp induced inward Cl⁻ currents; and hyperpolarization of voltage-clamped inside-out patches excised from plasma membrane induced Cl⁻ currents that have a unitary channel conductance of ∼3.7 pS. The channel was inhibited by 1 mM Zn²⁺ and by 1 mM 9-anthracene, but was insensitive to DIDS. Its anion permeability sequence is Cl⁻ = SCN⁻> Br⁻>> I⁻, characteristic of ClC-2 channels. Exogenous polyunsaturated fatty acid, linolenic acid, enhanced or activated the inward rectifier Cl⁻ currents in both whole-cell and excised patch-clamp recordings. Using RT-PCR, we found expression in Drosophila retina of a ClC-2 gene orthologous to mammalian ClC-2 channels. Antibodies to rat ClC-2 channels labeled Drosophila photoreceptor plasma membranes and synaptic regions. Our results provide evidence that the inward rectification in Drosophila retinal photoreceptors is mediated by ClC-2-like channels in the non-transducing (extra-rhabdomeral) plasma membrane, and that this inward rectification can be modulated by polyunsaturated fatty acid. G. Ugarte and R. Delgado contributed equally to this work.     

Kinetic properties of DM-nitrophen binding to calcium and magnesium

Caged-Ca(2+) compounds such as nitrophenyl-EGTA (NP-EGTA) and DM-nitrophen (DMn) are extremely useful in biological research, but their use in live cells is hampered by cytoplasmic [Mg(2+)]. We determined the properties of Ca(2+) release from NP-EGTA and DMn by using Oregon green BAPTA-5N to measure changes in [Ca(2+)] after ultraviolet flash photolysis in vitro, with or without Mg(2+) present. A large fraction (65%) of NP-EGTA, which has a negligible Mg(2+) affinity, uncages with a time constant of 10.3 ms, resulting in relatively slow increases in [Ca(2+)]. Uncaging of DMn is considerably faster, but DMn has a significant affinity for Mg(2+) to complicate the uncaging process. With experimentally determined values for the Ca(2+) and Mg(2+) binding/unbinding rates of DMn and NP-EGTA, we built a mathematical model to assess the utility of NP-EGTA and DMn in rapid Ca(2+)-uncaging experiments in the presence of Mg(2+). We discuss the advantages and disadvantages of using each compound under different conditions. To determine the kinetics of Ca(2+) binding to biologically relevant Ca(2+) buffers, such as Ca(2+)-binding proteins, the use of DMn is preferable even in the presence of Mg(2+).     

Quantitative evaluation of mammalian skeletal muscle as a heterologous protein expression system

The production of mammalian proteins in sufficient quantity and quality for structural and functional studies is a major challenge in biology. Intrinsic limitations of yeast and bacterial expression systems preclude their use for the synthesis of a significant number of mammalian proteins. This creates the necessity of well-identified expression systems based on mammalian cells. In this paper, we demonstrate that adult mammalian skeletal muscle, transfected in vivo by electroporation with DNA plasmids, is an excellent heterologous mammalian protein expression system. By using the fluorescent protein EGFP as a model, it is shown that muscle fibers express, during the course of a few days, large amounts of authentic replicas of transgenic proteins. Yields of approximately 1mg/g of tissue were obtained, comparable to those of other expression systems. The involvement of adult mammalian cells assures an optimal environment for proper protein folding and processing. All these advantages complement a methodology that is universally accessible to biomedical investigators and simple to implement.