992 research outputs found
Plasmalemmal Na+/Ca2+ exchanger modulates Ca2+-dependent exocytotic release of glutamate from rat cortical astrocytes
Astroglial excitability operates through increases in Ca2+cyt (cytosolic Ca2+), which can lead to glutamatergic gliotransmission. In parallel fluctuations in astrocytic Na+cyt (cytosolic Na+) control metabolic neuronal-glial signalling, most notably through stimulation of lactate production, which on release from astrocytes can be taken up and utilized by nearby neurons, a process referred to as lactate shuttle. Both gliotransmission and lactate shuttle play a role in modulation of synaptic transmission and plasticity. Consequently, we studied the role of the PMCA (plasma membrane Ca2+-ATPase), NCX (plasma membrane Na+/Ca2+ exchanger) and NKA (Na+/K+-ATPase) in complex and coordinated regulation of Ca2+cyt and Na+cyt in astrocytes at rest and upon mechanical stimulation. Our data support the notion that NKA and PMCA are the major Na+ and Ca2+ extruders in resting astrocytes. Surprisingly, the blockade of NKA or PMCA appeared less important during times of Ca2+ and Na+ cytosolic loads caused by mechanical stimulation. Unexpectedly, NCX in reverse mode appeared as a major contributor to overall Ca2+ and Na+ homoeostasis in astrocytes both at rest and when these glial cells were mechanically stimulated. In addition, NCX facilitated mechanically induced Ca2+-dependent exocytotic release of glutamate from astrocytes. These findings help better understanding of astrocyte-neuron bidirectional signalling at the tripartite synapse and/or microvasculature. We propose that NCX operating in reverse mode could be involved in fast and spatially localized Ca2+-dependent gliotransmission, that would operate in parallel to a slower and more widely distributed gliotransmission pathway that requires metabotropically controlled Ca2+ release from the ER (endoplasmic reticulum)
Colour response in western flower thrips varies intraspecifically
Discrepancies in the published research as to the attraction of the economically important pest western flower thrips (WFT) to different colours confounds the optimisation of field traps for pest management purposes. We considered whether the different experimental conditions of independent studies could have contributed to this. Therefore, the behavioural response (i.e., landings) to different colour cues of two WFT laboratory populations from Germany (DE) and The Netherlands (NL), which had previously been independently shown to have different colour preferences, were tested in the same place, and under the same experimental conditions. Single-choice wind tunnel bioassays supported previous independent findings, with more of a NL population landing on the yellow LED lamp (588 nm) than the blue (470 nm) (p = 0.022), and a not-statistically significant trend observed in a DE population landing more on blue compared to yellow (p = 0.104). To account for potential original host rearing influences, both populations were subsequently established on bean for ~20 weeks, then yellow chrysanthemum for 4–8 and 12–14 weeks and tested in wind tunnel choice bioassays. Laboratory of origin, irrespective of the host plant rearing regime, remained a significant effect (p < 0.001), with 65% of the NL WFT landing on yellow compared to blue (35%), while 66% of the DE WFT landed on blue compared to yellow (34%). There was also a significant host plant effect (p < 0.001), with increased response to yellow independent of laboratory of origin after rearing on chrysanthemum for 12–14 weeks. Results suggest that differing responses of WFT populations to colour is, in this case, independent of the experimental situation. Long-term separate isolation from the wild cannot be excluded as a cause, and the implications of this for optimising the trap colour is discussed
The International-Trade Network: Gravity Equations and Topological Properties
This paper begins to explore the determinants of the topological properties
of the international - trade network (ITN). We fit bilateral-trade flows using
a standard gravity equation to build a "residual" ITN where trade-link weights
are depurated from geographical distance, size, border effects, trade
agreements, and so on. We then compare the topological properties of the
original and residual ITNs. We find that the residual ITN displays, unlike the
original one, marked signatures of a complex system, and is characterized by a
very different topological architecture. Whereas the original ITN is
geographically clustered and organized around a few large-sized hubs, the
residual ITN displays many small-sized but trade-oriented countries that,
independently of their geographical position, either play the role of local
hubs or attract large and rich countries in relatively complex
trade-interaction patterns
The Mechanisms of Codon Reassignments in Mitochondrial Genetic Codes
Many cases of non-standard genetic codes are known in mitochondrial genomes.
We carry out analysis of phylogeny and codon usage of organisms for which the
complete mitochondrial genome is available, and we determine the most likely
mechanism for codon reassignment in each case. Reassignment events can be
classified according to the gain-loss framework. The gain represents the
appearance of a new tRNA for the reassigned codon or the change of an existing
tRNA such that it gains the ability to pair with the codon. The loss represents
the deletion of a tRNA or the change in a tRNA so that it no longer translates
the codon. One possible mechanism is Codon Disappearance, where the codon
disappears from the genome prior to the gain and loss events. In the
alternative mechanisms the codon does not disappear. In the Unassigned Codon
mechanism, the loss occurs first, whereas in the Ambiguous Intermediate
mechanism, the gain occurs first. Codon usage analysis gives clear evidence of
cases where the codon disappeared at the point of the reassignment and also
cases where it did not disappear. Codon disappearance is the probable
explanation for stop to sense reassignments and a small number of reassignments
of sense codons. However, the majority of sense to sense reassignments cannot
be explained by codon disappearance. In the latter cases, by analysis of the
presence or absence of tRNAs in the genome and of the changes in tRNA
sequences, it is sometimes possible to distinguish between the Unassigned Codon
and Ambiguous Intermediate mechanisms. We emphasize that not all reassignments
follow the same scenario and that it is necessary to consider the details of
each case carefully.Comment: 53 pages (45 pages, including 4 figures + 8 pages of supplementary
information). To appear in J.Mol.Evo
Production of Magnetic Arsenic–Phosphorus Alloy Nanoribbons with Small Band Gaps and High Hole Conductivities
Quasi-1D nanoribbons provide a unique route to diversifying the properties of their parent 2D nanomaterial, introducing lateral quantum confinement and an abundance of edge sites. Here, a new family of nanomaterials is opened with the creation of arsenic–phosphorus alloy nanoribbons (AsPNRs). By ionically etching the layered crystal black arsenic–phosphorus using lithium electride followed by dissolution in amidic solvents, solutions of AsPNRs are formed. The ribbons are typically few-layered, several micrometers long with widths tens of nanometers across, and both highly flexible and crystalline. The AsPNRs are highly electrically conducting above 130 K due to their small band gap (ca. 0.035 eV), paramagnetic in nature, and have high hole mobilities, as measured with the first generation of AsP devices, directly highlighting their properties and utility in electronic devices such as near-infrared detectors, quantum computing, and charge carrier layers in solar cells
Comparison of bacterial communities of conventional and A-stage activated sludge systems
The bacterial community structure of 10 different wastewater treatment systems and their influents
has been investigated through pyrosequencing, yielding a total of 283486 reads. These bioreactors
had different technological configurations: conventional activated sludge (CAS) systems and very
highly loaded A-stage systems. A-stage processes are proposed as the first step in an energy producing
municipal wastewater treatment process. Pyrosequencing analysis indicated that bacterial community
structure of all influents was similar. Also the bacterial community of all CAS bioreactors was similar.
Bacterial community structure of A-stage bioreactors showed a more case-specific pattern. A core
of genera was consistently found for all influents, all CAS bioreactors and all A-stage bioreactors,
respectively, showing that different geographical locations in The Netherlands and Spain did not affect
the functional bacterial communities in these technologies. The ecological roles of these bacteria
were discussed. Influents and A-stage bioreactors shared several core genera, while none of these
were shared with CAS bioreactors communities. This difference is thought to reside in the different
operational conditions of the two technologies. This study shows that bacterial community structure of
CAS and A-stage bioreactors are mostly driven by solids retention time (SRT) and hydraulic retention
time (HRT), as suggested by multivariate redundancy analysis.Department of Civil EngineeringInstitute of Water Research from the University of GranadaDepartment of Environmental Biotechnology of the Delft University of Technolog
Severity of Giardia infection associated with post-infectious fatigue and abdominal symptoms two years after
<p>Abstract</p> <p>Background</p> <p>A high rate of post-infectious fatigue and abdominal symptoms two years after a waterborne outbreak of giardiasis in Bergen, Norway in 2004 has previously been reported. The aim of this report was to identify risk factors associated with such manifestations.</p> <p>Methods</p> <p>All laboratory confirmed cases of giardiasis (n = 1262) during the outbreak in Bergen in 2004 received a postal questionnaire two years after. Degree of post-infectious abdominal symptoms and fatigue, as well as previous abdominal problems, was recorded. In the statistical analyses number of treatment courses, treatment refractory infection, delayed education and sick leave were used as indices of protracted and severe <it>Giardia </it>infection. Age, gender, previous abdominal problems and symptoms during infection were also analysed as possible risk factors. Simple and multiple ordinal logistic regression models were used for the analyses.</p> <p>Results</p> <p>The response rate was 81% (1017/1262), 64% were women and median age was 31 years (range 3-93), compared to 61% women and 30 years (range 2-93) among all 1262 cases. Factors in multiple regression analysis significantly associated with abdominal symptoms two years after infection were: More than one treatment course, treatment refractory infection, delayed education, bloating and female gender. Abdominal problems prior to <it>Giardia </it>infection were not associated with post-infectious abdominal symptoms. More than one treatment course, delayed education, sick leave more than 2 weeks, and malaise at the time of infection, were significantly associated with fatigue in the multiple regression analysis, as were increasing age and previous abdominal problems.</p> <p>Conclusion</p> <p>Protracted and severe <it>giardiasis </it>seemed to be a risk factor for post-infectious fatigue and abdominal symptoms two years after clearing the <it>Giardia </it>infection.</p
miREE: miRNA recognition elements ensemble
Abstract Background Computational methods for microRNA target prediction are a fundamental step to understand the miRNA role in gene regulation, a key process in molecular biology. In this paper we present miREE, a novel microRNA target prediction tool. miREE is an ensemble of two parts entailing complementary but integrated roles in the prediction. The Ab-Initio module leverages upon a genetic algorithmic approach to generate a set of candidate sites on the basis of their microRNA-mRNA duplex stability properties. Then, a Support Vector Machine (SVM) learning module evaluates the impact of microRNA recognition elements on the target gene. As a result the prediction takes into account information regarding both miRNA-target structural stability and accessibility. Results The proposed method significantly improves the state-of-the-art prediction tools in terms of accuracy with a better balance between specificity and sensitivity, as demonstrated by the experiments conducted on several large datasets across different species. miREE achieves this result by tackling two of the main challenges of current prediction tools: (1) The reduced number of false positives for the Ab-Initio part thanks to the integration of a machine learning module (2) the specificity of the machine learning part, obtained through an innovative technique for rich and representative negative records generation. The validation was conducted on experimental datasets where the miRNA:mRNA interactions had been obtained through (1) direct validation where even the binding site is provided, or through (2) indirect validation, based on gene expression variations obtained from high-throughput experiments where the specific interaction is not validated in detail and consequently the specific binding site is not provided. Conclusions The coupling of two parts: a sensitive Ab-Initio module and a selective machine learning part capable of recognizing the false positives, leads to an improved balance between sensitivity and specificity. miREE obtains a reasonable trade-off between filtering false positives and identifying targets. miREE tool is available online at http://didattica-online.polito.it/eda/miREE/</p
Is using the strengths and difficulties questionnaire in a community sample the optimal way to assess mental health functioning?
An important characteristic of a screening tool is its discriminant ability or the measure’s accuracy to distinguish between those with and without mental health problems. The current study examined the inter-rater agreement and screening concordance of the parent and teacher versions of SDQ at scale, subscale and item-levels, with the view of identifying the items that have the most informant discrepancies; and determining whether the concordance between parent and teacher reports on some items has the potential to influence decision making. Cross-sectional data from parent and teacher reports of the mental health functioning of a community sample of 299 students with and without disabilities from 75 different primary schools in Perth, Western Australia were analysed. The study found that: a) Intraclass correlations between parent and teacher ratings of children’s mental health using the SDQ at person level was fair on individual child level; b) The SDQ only demonstrated clinical utility when there was agreement between teacher and parent reports using the possible or 90% dichotomisation system; and c) Three individual items had positive likelihood ratio scores indicating clinical utility. Of note was the finding that the negative likelihood ratio or likelihood of disregarding the absence of a condition when both parents and teachers rate the item as absent was not significant. Taken together, these findings suggest that the SDQ is not optimised for use in community samples and that further psychometric evaluation of the SDQ in this context is clearly warranted
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