Calcium dynamics in the secretory granules of neuroendocrine cells

Cellular Ca(2+)signaling results from a complex interplay among a variety of Ca(2+) fluxes going across the plasma membrane and across the membranes of several organelles, together with the buffering effect of large numbers of Ca(2+)-binding sites distributed along the cell architecture. Endoplasmic and sarcoplasmic reticulum, mitochondria and even nucleus have all been involved in cellular Ca(2+) signaling, and the mechanisms for Ca(2+) uptake and release from these organelles are well known. In neuroendocrine cells, the secretory granules also constitute a very important Ca(2+)-storing organelle, and the possible role of the stored Ca(2+) as a trigger for secretion has attracted considerable attention. However, this possibility is frequently overlooked, and the main reason for that is that there is still considerable uncertainty on the main questions related with granular Ca(2+) dynamics, e.g., the free granular [Ca(2+)], the physical state of the stored Ca(2+) or the mechanisms for Ca(2+) accumulation and release from the granules. This review will give a critical overview of the present state of knowledge and the main conflicting points on secretory granule Ca(2+) homeostasis in neuroendocrine cells.     

Lower Bashkirian conodonts from the Iraty Formation in the Alduides-Quinto Real Massif (Pyrenees,Spain)

The stratigraphy of the Carboniferous Iraty Formation is described in several sections from the southwestern Alduides-Quinto Real Massif (western Pyrenees), and biostratigraphy is updated based on conodont occurrences. The Ochaverri Member yields upper Serpukhovian conodonts, whereas the lower part of the overlying Asturreta Member is assigned to the lower Bashkirian, according to the occurrences of Declinognathodus noduliferus bernesgae and D. n. noduliferus, respectively. The upper beds of the formation (Baserdi Member) are correlated with the Kinderscoutian to lowermost Marsdenian English substages (lower Bashkirian), and new conodont occurrences are the oldest species of Neognathodus and Idiognathodus known in Spain. We discuss the status of Idiognathoides macer, several species related to I. sinuatus, I. sulcatus and Lochriea glaber. Conodont diversity is related to stratigraphic distribution of species and conodont biofacies. Finally, the lowermost Marsdenian to upper Bashkirian age of the siliciclastic rocks overlying the Iraty Formation is also discussed and compared with known data from localities in the western Pyrenees.     

The effects of drying on sediment nitrogen content in a Mediterranean intermittent stream: a microcosms study

Mediterranean climates predispose aquatic systems to both flood and drought periods, therefore, stream sediments may be exposed to desiccation periods. Changes in oxygen concentrations and sediment water content influence the biotic processes implicated in nitrogen dynamics. The objectives of this study were to identify (1) the changes of inorganic nitrogen in stream sediments during the transition from wet to dry conditions, and (2) the underlying processes in N dynamics and its regulation. Extractable sediment NO₃ ⁻-N and NH₄ ⁺-N, organic matter and extractable organic carbon content were assessed during natural desiccation in microcosms with sediments from an intermittent Mediterranean stream. In agreement with our initial hypothesis, our results showed how the NO₃ ⁻-N content of the sediment was enhanced during the first 10 days of sediment drying, whereas NH₄ ⁺-N was lost by 14 days post-drying. During the first 10 days, sediment desiccation seemed to stimulate the net N-mineralization and net nitrification from sediments. Afterwards, the extractable NO₃ ⁻-N concentration sharply dropped, which may be attributed to lower ammonium-oxidation rates as ammonium and organic matter are depleted, and to an increase in NO₃ ⁻-N consumption by microbial populations. Denitrification was inhibited, with a significant decrease as % water-filled pore space lowered. We hypothesize that the sediment inorganic N content enhanced during sediment desiccation could be released as part of the N pulse observed after sediment rewetting. However, the stream N availability after rewetting dried sediments would differ depending on desiccation period duration.     

Complete genome sequence of Bifidobacterium breve CECT 7263, a strain isolated from human milk

Bifidobacterium breve is an actinobacterium frequently isolated from colonic microbiota of breastfeeding babies. Here, we report the complete and annotated genome sequence of a B. breve strain isolated from human milk, B. breve CECT 7263. The genome sequence will provide new insights into the biology of this potential probiotic organism and will allow the characterization of genes related to beneficial properties.     

The Interconversion between a Flexible β-Sheet and a Fibril β-Arrangement Constitutes the Main Conformational Event during Misfolding of PSD95-PDZ3 Domain

The temperature-induced misfolding pathway of PDZ3, the third PDZ domain of the PSD95 neuronal protein, is populated by a trimeric β-sheet-rich intermediate state that leads to a stepwise and reversible formation of supramacromolecular structures. Using FTIR, we have found that misfolding of this pathway is not due to different ensembles of a variety of precursors, but comes mainly from the interconversion of a flexible β-sheet of the domain to wormlike fibrils. The appearance of the wormlike fibril FTIR component is also accompanied by a slight decrease of the band that corresponds to loops in the native state, whereas the rest of the regular elements of secondary structure are fairly well maintained upon misfolding. Transmission electron microscope micrographs have confirmed the presence of wormlike fibrils upon heating at 60°C, where the trimeric intermediate is maximally populated. Toxicity assays in the human neuroblastoma cell line SH-SY5Y show that cytotoxicity increases as the aggregation pathway proceeds. NMR analysis of chemical shifts as a function of temperature has revealed, as one of the main conformational aspects of such an interconversion at the residue level, that the β-sheet arrangement around strand β3 promotes the change that drives misfolding of the PDZ3 domain.     

Herbivores modify selection on plant functional traits in a temperate rainforest understory

There is limited evidence regarding the adaptive value of plant functional traits in contrasting light environments. It has been suggested that changes in these traits in response to light availability can increase herbivore susceptibility. We tested the adaptive value of plant functional traits linked with carbon gain in contrasting light environments and also evaluated whether herbivores can modify selection on these traits in each light environment. In a temperate rainforest, we examined phenotypic selection on functional traits in seedlings of the pioneer tree Aristotelia chilensis growing in sun (canopy gap) and shade (forest understory) and subjected to either natural herbivory or herbivore exclusion. We found differential selection on functional traits depending on light environment. In sun, there was positive directional selection on photosynthetic rate and relative growth rate (RGR), indicating that selection favors competitive ability in a high-resource environment. Seedlings with high specific leaf area (SLA) and intermediate RGR were selected in shade, suggesting that light capture and conservative resource use are favored in the understory. Herbivores reduced the strength of positive directional selection acting on SLA in shade. We provide the first demonstration that natural herbivory rates can change the strength of selection on plant ecophysiological traits, that is, attributes whose main function is resource uptake. Research addressing the evolution of shade tolerance should incorporate the selective role of herbivores.     

Habitat distribution of migratory and sedentary blackcaps Sylvia atricapilla wintering in southern Iberia: a morphological and biogeochemical approach

In migratory species, the way in which conspecifics from different breeding populations are distributed during the non‐breeding period is important from and ecological, evolutionary and conservation perspective, but such knowledge is still limited for most species. Migratory and sedentary blackcaps Sylvia atricapilla wintering in southern Spain can occupy two habitat types: forests and shrublands. According to earlier studies, blackcaps prefer forests over shrublands, and residents remain nearly restricted to forests. However, whether migrants with different breeding origin occupy the two habitats differently is unknown. We used morphological and biogeochemical data (hydrogen isotope ratios measured on feathers: δ²H_f), which show variation along the breeding range of the species, to answer this question. Isotope analyses supported the reliability of morphology as a method for distinguishing between migratory and sedentary blackcaps in sympatry, showing that sedentary individuals are rare in shrublands while migratory ones are abundant in both habitat types. However, migratory blackcaps scored similar δ²H_f values in forests and shrublands, and neither did vary in structural size or flight morphology between habitats. Our study suggests that migrants from a wide range of breeding origins end up mixing between forests and shrublands, which may explain the patterns of variation in space and time in the abundance of blackcaps in this area, and supports the view that inequalities may arise among migrants with the same origin but wintering in different habitats. Such inequalities might carry over into other stages of blackcaps’ life cycle contributing to the regulation of its migratory populations.     

Autumn fertilization with nitrogen improves nutritional status,cold hardiness and the oxidative stress response of Holm oak (<Emphasis Type="Italic">Quercus ilex</Emphasis> ssp. <Emphasis Type="Italic">ballota</Emphasis> [Desf.] Samp) nursery seedlings

Holm oak (Quercus ilex ssp. ballota [Desf.] Samp) is one of the most important species in forest communities of the western Mediterranean Basin, but is very vulnerable to environmental stress during the first years of its life. In particular, summer drought and winter frosts limit the distribution, survival, and growth of Holm oak. These two stress factors can lead to plasmolysis and/or oxidative stress. We hypothesized that autumn fertilization with nitrogen (N) can improve plant tolerance to these abiotic stress factors and improve plant quality and therefore reforestation success. A 12-week autumn application of 30 or 60 mg N (plus 70 mg N applied to both treatments during the previous 28 weeks in the nursery, i.e. 100 and 130 mg N in total, respectively) improved overall growth, root growth capacity, frost tolerance, and nutritional status of plants relative to plants given 0.0 and 1.5 mg autumnal N, and had no negative effect on seedling response to water stress. A very small increment in N doses during the autumn (1.5 vs. 0.0 mg N) improved some morphological parameters, such as stem diameter (D) and shoot dry weight, and physiological parameters, such as total antioxidant activity. The highest autumnal N dose (60 mg) increased leaf nutrient content without decreasing the concentration, but had a tendency to reduce frost tolerance relative to seedlings given a lower autumnal N dose (30 mg).     

Quantification of extraradical soil mycelium and ectomycorrhizas of Boletus edulis in a Scots pine forest with variable sporocarp productivity

The availability of most edible ectomycorrhizal mushrooms depends on their natural fructification. Sporocarp formation of these fungi is linked to habitat characteristics and climate conditions, but these data alone do not explain all the trends of fungal fruiting and dynamics. It could be hypothesized that the amount of soil mycelia could also be related to the production of carpophores. Soil samples (five cylinders of 250 cm³ per plot) were taken monthly, from September to November, in five fenced permanent plots (5 × 5 m) in Pinar Grande (Soria, Spain), a Pinus sylvestris stand situated in the north of the Sistema Ibérico mountain range. Plots were chosen to establish a gradient of Boletus edulis productivity from 0 to 38.5 kg/ha year, according to the mean fresh weight of sporocarps collected during the last 10 years. B. edulis ectomycorrhizal root tips were identified in each soil sample according to its morphology and counted. DNA extractions were performed with the PowerSoil^TM DNA Isolation Kit and quantification of extraradical soil mycelium by real-time polymerase chain reaction using specific primers and a TaqMan? probe. The concentration of soil mycelium of B. edulis (mg mycelium/g soil) did not differ significantly between plots (p = 0.1397), and sampling time (p = 0.7643) within the fructification period. The number of mycorrhizal short roots per soil volume showed significant differences between the plots (p = 0.0050) and the three sampling times (p < 0.0001). No significant correlation between the number of mycorrhizas and the productivity of the plot (kg of B. edulis/ha year) was detected (p = 0.615). A statistically significant positive correlation (p = 0.0481) was detected between the concentration of mycelia of B. edulis in the soil samples and the presence of short roots mycorrhizal with B. edulis in these samples. The productivity of the plots, in terms of sporocarps produced during the last 10 years, was not correlated either with the concentration of soil mycelium or with the presence or abundance of ectomycorrhizas.