Mathematical modeling of neuronal connexin-36 channels

Neurotransmission through electrical synapses play an important role in the spike synchrony among neurons and oscillation of neuron networks. Connexin36 (Cx36) is the principal gap junction protein of electrical synapses between inhibitory interneurons in vertebrates. Coupling strength between coupled neurons is modulated, among other factor, by the voltage difference between cell interiors, termed transjunctional voltage (Vj), in a complex manner; with the Vj gradient junctional conductance of Cx36 channels first increases instantaneously (+ 20% for + 100 mV) and then it decreases slowly to half for a similar range of Vj. The significance of this regulation by voltage, a stimulus always presents and changing, in the firing properties of coupled neurons is unknown

Giant barocaloric effect in all-d-metal Heusler shape memory alloys

We have studied the barocaloric properties associated with the martensitic transition of a shape memory Heulser alloy Ni50Mn31.5Ti18.5 which is composed of all-d-metal elements. The composition of the sample has been tailored to avoid long range ferromagnetic order in both ausenite and martensite. The lack of ferromagnetism results in a weak magnetic contribution to the total entropy change thereby leading to a large transition entropy change. The combination of such a large entropy change and a relatively large volume change at the martensitic transition gives rise to giant barocaloric properties in this alloy. When compared to other shape memory Heusler alloys, our material exhibits values for adiabatic temperature and isothermal entropy changes significantly larger than values reported so far for this class of materials. Furthermore, our Ni50Mn31.5Ti18.5 also compares favourably to the best state-of-the-art magnetic barocaloric materials.Peer ReviewedPostprint (author's final draft

Experimental and topological determination of the pressure-temperature phase diagram of morniflumate, a pharmaceutical ingredient with anti-inflammatory properties

The pressure-temperature phase diagram of morniflumate (niflumic acid ß-morpholinoethyl ester) has been obtained by high-pressure thermal analysis. In addition, calorimetric melting data (TI¿L = (348.1 ± 0.4) K and ¿HI¿L = (89 ± 2) J·g-1) and the specific volumes of the solid and the liquid state have been obtained under normal pressure. Comparison of the measured high-pressure melting data with the equilibrium curve obtained through the Clapeyron equation indicates that the initial slopes are the same (dP/dT = (2.96 ± 0.06) MPa·K-1) at the melting point under normal pressure. The fact that the Clapeyron equation can be used to construct topological phase diagrams may be of interest for the food and pharmaceutical industries.Peer ReviewedPostprint (author's final draft

Long-term dynamics of somatosensory activity in a stroke model of distal middle cerebral artery oclussion

A constant challenge in experimental stroke is the use of appropriate tests to identify signs of recovery and adverse effects linked to a particular therapy. In this study, we used a long-term longitudinal approach to examine the functional brain changes associated with cortical infarction in a mouse model induced by permanent ligation of the middle cerebral artery (MCA). Sensorimotor function and somatosensory cortical activity were evaluated with fault-foot and forelimb asymmetry tests in combination with somatosensory evoked potentials. The stroke mice exhibited both long-term deficits in the functional tests and impaired responses in the infarcted and intact hemispheres after contralateral and ipsilateral forepaw stimulation. In the infarcted hemisphere, reductions in the amplitudes of evoked responses were detected after contralateral and ipsilateral stimulation. In the intact hemisphere, and similar to cortical stroke patients, a gradual hyperexcitability was observed after contralateral stimulation but no parallel evidence of a response was detected after ipsilateral stimulation. Our results suggest the existence of profound and persistent changes in the somatosensory cortex in this specific mouse cortical stroke model. The study of evoked potentials constitutes a feasible and excellent tool for evaluating the fitness of the somatosensory cortex in relation to functional recovery after preclinical therapeutic intervention

Effect of Charge Substitutions at Residue His-142 on Voltage Gating of Connexin43 Channels

AbstractPrevious studies indicate that the carboxyl terminal of connexin43 (Cx43CT) is involved in fast transjunctional voltage gating. Separate studies support the notion of an intramolecular association between Cx43CT and a region of the cytoplasmic loop (amino acids 119–144; referred to as “L2”). Structural analysis of L2 shows two α-helical domains, each with a histidine residue in its sequence (H126 and H142). Here, we determined the effect of H142 replacement by lysine, alanine, and glutamate on the voltage gating of Cx43 channels. Mutation H142E led to a significant reduction in the frequency of occurrence of the residual state and a prolongation of dwell open time. Macroscopically, there was a large reduction in the fast component of voltage gating. These results resembled those observed for a mutant lacking the carboxyl terminal (CT) domain. NMR experiments showed that mutation H142E significantly decreased the Cx43CT-L2 interaction and disrupted the secondary structure of L2. Overall, our data support the hypothesis that fast voltage gating involves an intramolecular particle-receptor interaction between CT and L2. Some of the structural constrains of fast voltage gating may be shared with those involved in the chemical gating of Cx43

Aposematism increases acoustic diversification and speciation in poison frogs

Multimodal signals facilitate communication with conspecifics during courtship, but they can also alert eavesdropper predators. Hence, signallers face two pressures: enticing partners to mate and avoiding detection by enemies. Undefended organisms with limited escape abilities are expected to minimize predator recognition over mate attraction by limiting or modifying their signalling. Alternatively, organisms with anti-predator mechanisms such as aposematism (i.e. unprofitability signalled by warning cues) might elaborate mating signals as a consequence of reduced predation. We hypothesize that calls diversified in association with aposematism. To test this, we assembled a large acoustic signal database for a diurnal lineage of aposematic and cryptic/non-defended taxa, the poison frogs. First, we showed that aposematic and non-aposematic species share similar extinction rates, and aposematic lineages diversify more and rarely revert to the nonaposematic phenotype. We then characterized mating calls based on morphological (spectral), behavioural/physiological (temporal) and environmental traits. Of these, only spectral and temporal features were associated with aposematism. We propose that with the evolution of antipredator defences, reduced predation facilitated the diversification of vocal signals, which then became elaborated or showy via sexual selection. © 2014 The Author(s) Published by the Royal Society. All rights reserved

Biometrical analysis reveals major differences between the two subspecies of the European rabbit

The climatic oscillations that have occurred in the last few million years have strongly affected species distribution ranges. Highly divergent genetic lineages arose, some of which correspond to recognized subspecies that currently occupy small geographical areas. Understanding the implications of the genetic differences between these subspecies is crucial for proper conservation of Evolutionarily Significant Units. We use the two European rabbit subspecies, Oryctolagus cuniculus cuniculus and O. c. algirus, in the Iberian Peninsula as a model to investigate the repercussions at the biometric level of their largely recognized genetic differentiation. To accomplish this we analysed the ear and hind foot length, and the body mass of 999 adult rabbits from 27 locations across the distribution range of both subspecies in their native range, the Iberian Peninsula. Our results show biometric differences between the two subspecies, also explained by geographical location and sex, O. c. algirus being lighter and having shorter ear and hind foot lengths. We examine these findings under an evolutionary framework, and discuss their implications for current conservation efforts. Future research should focus on the ecological implications of these biometric differences, namely potential different habitat use and anti-predatory strategies in the species' native range.This study was partially funded by Projects PAI06-170, VP-0119-07,POII09-0099-2557, CGL2009-11665, 2012-30E060, CGL2013-43197, CGL2013-43197-R, FCT research project (PTDC/BIA-EVF/111368/2009), and ‘Genomics Applied to Genetic Resources’ co-funded by North Portugal Regional Operational Programme 2007/2013 (ON.2 – O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF). C.F. was supported by a PhD grant (Ref. SFRH/BD/22084/2005) and a postdoctoral grant (Ref. SFRH/BPD/88643/2012), and J.B.-A. by a postdoctoral grant (Ref. SFRH/BPD/65464/2009) all from the Fundaçao para a Ciência e Tecnologia of the Ministêrio da Ciência, Tecnologia e Ensino Superior, Portuguese government. C.F. is currently supported by a Marie Curie Out going International Fellowship for Career Development (PIOF-GA-2013-621571) within the 7th Framework Programme of the European Union. M.D.-M. is currently funded by Consejería de Economía, Innovación, Ciencia y Empleo of Junta de Andalucía, and the European Union’s SeventhFramework Programme for research, technological development and demonstration under grant agreement 267226. C.A.R.-S. was supported by a doctoral grant from the National Council of Science and Technology of Mexico (CONACyT). P.C.A. was supportedby an FCT sabbatical grant (SFRH/BSAB/1278/2012) and by FLAD (Luso-American Foundation).Peer Reviewe

Linking changes in species composition and biomass in a globally distributed grassland experiment

Global change drivers, such as anthropogenic nutrient inputs, are increasing globally. Nutrient deposition simultaneously alters plant biodiversity, species composition and ecosystem processes like aboveground biomass production. These changes are underpinned by species extinction, colonisation and shifting relative abundance. Here, we use the Price equation to quantify and link the contributions of species that are lost, gained or that persist to change in aboveground biomass in 59 experimental grassland sites. Under ambient (control) conditions, compositional and biomass turnover was high, and losses (i.e. local extinctions) were balanced by gains (i.e. colonisation). Under fertilisation, the decline in species richness resulted from increased species loss and decreases in species gained. Biomass increase under fertilisation resulted mostly from species that persist and to a lesser extent from species gained. Drivers of ecological change can interact relatively independently with diversity, composition and ecosystem processes and functions such as aboveground biomass due to the individual contributions of species lost, gained or persisting.EEA Santa CruzFil: Ladouceur, Emma. German Centre for Integrative Biodiversity Research (iDiv); AlemaniaFil: Ladouceur, Emma. Helmholtz Centre for Environmental Research – UFZ. Department of Physiological Diversity; AlemaniaFil: Ladouceur, Emma. University of Leipzig. Department of Biology; AlemaniaFil: Ladouceur, Emma. Martin Luther University Halle-Wittenberg. Institute of Computer Science; AlemaniaFil: Blowes, Shane A. German Centre for Integrative Biodiversity Research (iDiv); AlemaniaFil: Blowes, Shane A. Martin Luther University Halle-Wittenberg. Institute of Computer Science; AlemaniaFil: Chase, Jonathan M. German Centre for Integrative Biodiversity Research (iDiv); AlemaniaFil: Chase, Jonathan M. Martin Luther University Halle-Wittenberg. Institute of Computer Science; AlemaniaFil: Clark, Adam T. German Centre for Integrative Biodiversity Research (iDiv); AlemaniaFil: Clark, Adam T. Helmholtz Centre for Environmental Research – UFZ. Department of Physiological Diversity; AlemaniaFil: Clark, Adam T. Karl-Franzens University of Graz. Institute of Biology; Austria.Fil: Garbowski, Magda. German Centre for Integrative Biodiversity Research (iDiv); AlemaniaFil: Garbowski, Magda. Helmholtz Centre for Environmental Research – UFZ. Department of Physiological Diversity; AlemaniaFil: Alberti, Juan. Universidad Nacional de Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Laboratorio de Ecología. Mar del Plata; Argentina.Fil: Alberti, Juan. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Arnillas, Carlos Alberto. University of Toronto. Department of Physical and Environmental Sciences; Canadá.Fil: Bakker, Jonathan D. University of Washington. School of Environmental and Forest Sciences; Estados UnidosFil: Barrio, Isabel C. Agricultural University of Iceland. Faculty of Environmental and Forest Sciences; IslandiaFil: Bharath, Siddharth. Atria University; India.Fil: Peri, Pablo Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santa Cruz; Argentina.Fil: Peri, Pablo Luis. Universidad Nacional de la Patagonia Austral; Argentina.Fil: Peri, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Harpole, Stanley. German Centre for Integrative Biodiversity Research (iDiv); AlemaniaFil: Harpole, Stanley. Helmholtz Centre for Environmental Research – UFZ. Department of Physiological Diversity; AlemaniaMartin Luther University Halle-Wittenberg. Institute of Computer Science; Alemani

Nutrient enrichment increases invertebrate herbivory and pathogen damage in grasslands

1- Plant damage by invertebrate herbivores and pathogens influences the dynamics of grassland ecosystems, but anthropogenic changes in nitrogen and phosphorus availability can modify these relationships. 2- Using a globally distributed experiment, we describe leaf damage on 153 plant taxa from 27 grasslands worldwide, under ambient conditions and with experimentally elevated nitrogen and phosphorus. 3- Invertebrate damage significantly increased with nitrogen addition, especially in grasses and non-leguminous forbs. Pathogen damage increased with nitrogen in grasses and legumes but not forbs. Effects of phosphorus were generally weaker. Damage was higher in grasslands with more precipitation, but climatic conditions did not change effects of nutrients on leaf damage. On average, invertebrate damage was relatively higher on legumes and pathogen damage was relatively higher on grasses. Community-weighted mean damage reflected these functional group patterns, with no effects of N on community-weighted pathogen damage (due to opposing responses of grasses and forbs) but stronger effects of N on community-weighted invertebrate damage (due to consistent responses of grasses and forbs). 4- Synthesis. As human-induced inputs of nitrogen and phosphorus continue to increase, understanding their impacts on invertebrate and pathogen damage becomes increasingly important. Our results demonstrate that eutrophication frequently increases plant damage and that damage increases with precipitation across a wide array of grasslands. Invertebrate and pathogen damage in grasslands is likely to increase in the future, with potential consequences for plant, invertebrate and pathogen communities, as well as the transfer of energy and nutrients across trophic levels.EEA Santa CruzFil: Ebeling, Anne. University of Jena. Institute of Ecology and Evolution; AlemaniaFil: Strauss, Alex T. University of Minnesota. Department of Ecology, Evolution, and Behavior; Estados UnidosFil: Strauss, Alex T. University of Georgia. Odum School of Ecology; Estados UnidosFil: Adler, Peter B. Utah State University. Department of Wildland Resources and the Ecology Center; Estados UnidosFil: Arnillas, Carlos Alberto. University of Toronto —Scarborough. Department of Physical and Environmental Sciences; CanadáFil: Barrio, Isabel C. Agricultural University of Iceland. Faculty of Environmental and Forest Sciences; IslandiaFil: Biederman, Lori A. Iowa State University. Department of Ecology, Evolution, and Organismal Biology; Estados UnidosFil. Borer, Elizabeth T. University of Minnesota. Department of Ecology, Evolution, and Behavior; Estados UnidosFil: Bugalho, Miguel N. University of Lisbon. Centre for Applied Ecology (CEABN-InBIO). School of Agriculture; Portugal.Fil: Caldeira, Maria C. University of Lisbon. Forest Research Centre. School of Agriculture; Portugal.Fil: Cadotte, Marc W. University of Toronto Scarborough. Department of Biological Sciences; CanadáFil: Peri, Pablo Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santa Cruz; Argentina.Fil: Peri, Pablo Luis. Universidad Nacional de la Patagonia Austral; Argentina.Fil: Peri, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Blumenthal, Dana M. USDA-ARS, Rangeland Resources & Systems Research Unit; Estados Unido