bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular and electrophysiological features of spinocerebellar ataxia type seven in induced pluripotent stem cells
Authors: Burman RJ , Watson LM , Smith DC , Raimondo JV , Ballo R , Scholefield J , Cowley SA , Wood MJA , Kidson SH , Greenberg LJ 
Published: March 2018

AbstractSpinocerebellar ataxia type 7 (SCA7) is an inherited neurodegenerative disease caused by a polyglutamine repeat expansion in the ATXN7 gene. Patients with this disease suffer from a degeneration of their cerebellar Purkinje neurons and retinal photoreceptors that result in a progressive ataxia and loss of vision. As with many neurodegenerative diseases, studies of pathogenesis have been hindered by a lack of disease-relevant models. To this end, we have generated induced pluripotent stem cells (iPSCs) from a cohort of SCA7 patients in South Africa. First, we differentiated the SCA7 affected iPSCs into neurons which showed evidence of a transcriptional phenotype affecting components of STAGA (ATXN7 and KAT2A) and the heat shock protein pathway (DNAJA1 and HSP70). We then performed electrophysiology on the SCA7 iPSC-derived neurons and found that these cells show features of functional aberrations. Lastly, we were able to differentiate the SCA7 iPSCs into retinal photoreceptors that also showed similar transcriptional aberrations to the SCA7 neurons. Our findings demonstrate that iPSC-derived neurons and photoreceptors from SCA7 patients express molecular and electrophysiological differences that are indicative of impaired neuronal health. We hope that these findings will contribute towards the ongoing efforts to establish the cell-derived models of neurodegenerative diseases that are needed to develop patient-specific treatments.
Checkpoint signaling abrogation after cell cycle reentry reveals that differentiated neurons are mitotic cells
Authors: Walton Chaska C , Zhang Wei , Patiño-Parrado Iris , Barrio-Alonso Estíbaliz , Garrido Juan-José , Frade José M 
Published: March 2018

SUMMARYMitotic activity associated to neuron cell-death instead of cell-division is reported in neurodegenerative diseases. However, why mitotic activity can take place in supposedly postmitotic neurons and how it is associated to cell-death remains largely unexplained. To address these questions, we have studied the response of primary neurons to oncogenic deregulation using a fusion protein based on truncated Cyclin E and Cdk2. Oncogenic Cyclin E/Cdk2 elicits mitotic checkpoint signaling, resulting in cell-cycle arrest and cell-death. However, as in mitotic cells, checkpoint suppression enables oncogenic cell-cycle progression and neuronal division. Further, neurons actively adapt to the cell-cycle by losing and reforming the axon initial segment, which integrates synaptic inputs to sustain action potentials. We conclude that neurons are mitotic cells in a reversible quiescent-like state, which is falsely portrayed as irreversible by mitotic checkpoints. In extension, neuronal death in lieu of cell-division reflects oncosuppressive checkpoint signaling.
Benfotiamine reduces pathology and improves muscle function in mdx mice
Authors: Woodman Keryn G. , Coles Chantal A. , Toulson Su L , Gibbs Elizabeth M. , Knight Matthew , McDonagh Matthew , Crosbie-Watson Rachelle H. , Lamandé Shireen R. , White Jason D. 
Published: March 2018

AbstractDuchenne Muscular Dystrophy (DMD) is a progressive and fatal neuromuscular disease which arises from mutations in the dystrophin gene (DMD) that result in the absence or severe reduction of the cytoskeletal protein dystrophin. In addition to the primary dystrophin defect, secondary processes such as inflammation, calcium influx, dysregulated autophagy and fibrosis exacerbate dystrophic pathology and thus increase disease progression. While therapies to restore dystrophin deficiency are being developed, strategies which target these secondary processes could be of benefit to patients. Benfotiamine is a lipid soluble precursor to thiamine that can reduce secondary processes such as inflammation and oxidative stress in diabetic patients. As such we tested it in the mdx mouse model of DMD and found that benfotiamine reduced multiple markers of dystrophic pathology and improved grip strength. In addition, members of the utrophin and dystrophin glycoprotein complexes were significantly increased at the sarcolemma which could improve cell adhesion. We also demonstrated that benfotiamine treatment lowered the expression of macrophage markers and pro-inflammatory cytokines suggesting that benfotiamine is reducing dystrophic pathology by acting on inflammatory processes.
Past selection impacts the strength of an aquatic trophic cascade
Authors: Ousterhout Brittany H. , Graham Savannah R. , Hasik Adam Z. , Serrano Mabel , Siepielski Adam M. 
Published: March 2018

Abstract

In complex food webs, interactions among species in different trophic levels can generate cascading indirect effects that couple top predators with primary producers, thereby affecting ecosystem functioning. Natural selection imposed by top predators on intermediate predators may play a role in shaping the strength of these trophic cascades, but this conjecture remains largely untested.

To determine the effects of natural selection on the strength of trophic cascades, we conducted a two‐part experiment in a four‐level aquatic trophic system involving a top predator (fish), an intermediate predator (damselflies), herbivores (zooplankton) and primary producers (algae). We first quantified how predation by fish generated selection on damselfly activity levels after controlling for phenotypic plasticity. We then measured the indirect effects of this selection on primary production (phytoplankton biomass). In both experiments, we varied the density of predators, allowing us to elucidate both trait‐mediated and density‐mediated indirect effects.

We found that as fish density increased, damselfly survivorship declined, which generated natural selection favouring less active damselflies. These results are robust after taking into account latent effects of plasticity in response to fish predator cues. The surviving damselflies likely foraged less, freeing herbivores from predation, which in turn reduced primary production. This selection‐driven trait‐mediated indirect effect was only apparent at low damselfly densities, because the consumptive effect of damselflies at high densities overwhelmed the effects of past selection.

These results demonstrate how the past action of natural selection imposed by predators affects the phenotypes of prey that consume herbivores, which ultimately influences primary productivity—a selective trophic cascade. Natural selection can therefore act as a mechanism coupling ecological dynamics across trophic levels, which ultimately influences ecosystem functioning.

A plain language summary is available for this article.
Metabolic scaling across succession: Do individual rates predict community‐level energy use?
Authors: Ghedini Giulia , White Craig R. , Marshall Dustin J. 
Published: March 2018

Abstract

A major goal of metabolic ecology is to make predictions across scales such that individual metabolic rates might be used to predict the metabolic rates of populations and communities, but the success of these predictions is unclear given the rarity of tests.

Given that older communities tend to have species with slower life histories and larger body sizes, we hypothesized that the metabolism of whole communities should scale allometrically with their mass across successional stages.

We created experimental chronosequences of sessile marine invertebrate communities in the field. We then (1) determined the metabolic scaling of these whole communities across successional stages of different mass and (2) tested whether the sum of individual metabolic rates for the dominant species could predict overall community metabolism.

Contrary to what we expected based on metabolic theory and succession theory, community metabolism scaled isometrically with mass across succession, despite the mean body size of dominant individuals within the communities increasing over time. We resolved this paradox by estimating community metabolism based on individual metabolic rates for the dominant species in the community. We show that non‐random changes in the membership of the species maintain mass‐specific metabolic rates of the whole community invariant across succession despite changes in size structure.

These results suggest that simple assumptions about how community‐level processes scale up from species are unlikely to be correct, because community turnover is non‐random with respect to metabolic rate. Nevertheless, with the appropriate parametrization, the sum of individual species rates can predict the function of the community as a whole.

A plain language summary is available for this article.
Drivers of power line use by white storks: A case study of birds nesting on anthropogenic structures
Authors: Moreira Francisco , Martins Ricardo C. , Catry Inês , D'Amico Marcello 
Published: March 2018

Abstract

Anthropogenic structures are mainly known to have negative impacts on wildlife populations but they can be beneficial. Power lines are a main driver of bird mortality through collision or electrocution, but electricity pylons are also commonly used for nest building by some species. Birds and nests cause power outages that need to be tackled by electricity companies. However, the use of pylons by threatened species provides an opportunity for conservation purposes.

In this study, we describe an empirical modelling approach to predict the circumstances under which nesting birds use electricity pylons. We focused on white storks Ciconia ciconia, a species that has been increasingly using electricity pylons for nesting across Europe.

In a country‐level census in Portugal, we found a total of 1,348 white stork nests in 668 of the 8,680 very high‐tension power line pylons occurring in the distribution range of this colonial species, with spatial clustering in pylon occupation up to a distance of 30 km. The number of nests in each used pylon ranged from 1 to 21 (M ± SD = 2.2 ± 2.06).

The main drivers of pylon use by nesting storks were distance to major feeding areas (rice fields, landfills and large wetlands), with more intensive use closer to these features, followed by land cover type surrounding each pylon. Pylon type and age, and stork population density in the region, had comparatively less importance.

Synthesis and applications. We developed an approach to predict the use of anthropogenic structures by nesting birds that can be used both for species conservation and minimising damage to infrastructures. For power lines, applications include: (1) planning power line routes to take account of the probability of pylon use; (2) applying nesting deterrent devices (to reduce bird mortality and power outage risk) and providing nesting platforms (to promote bird use) on suitable pylons and (3) selecting adequate pylon types to promote or inhibit nesting.
Spatial, temporal and experimental: Three study design cornerstones for establishing defensible numeric criteria in freshwater ecosystems
Authors: Taylor Jason M. , Back Jeffrey A. , Brooks Bryan W. , King Ryan S. 
Published: March 2018

Abstract

Nutrient over‐enrichment increasingly threatens global water resources. Stressor‐response studies specifically designed to identify levels of nutrients strongly associated with undesirable ecological conditions are needed to inform numeric nutrient criteria that protect inland waters.

Diatoms are important components of aquatic life, which support higher trophic levels and are sensitive to nutrient enrichment. We tested a framework that relies on stressor‐response modelling of phosphorus (P) enrichment and stream diatom assemblages across many field locations, multiple years and seasons within years, and under controlled experimental conditions to inform nutrient criteria development.

Diatom species composition was nonlinearly correlated with total phosphorus (TP) throughout the 2‐year field study. This occurred despite temporal shifts in species composition between two hydrologically distinct years and over eight seasons.

Species assemblages on rocks transplanted from a low P stream to mesocosms representing a P enrichment gradient (8, 20 and 100 μg/L) shifted into two groups over time. Species composition on rocks in low (20 μg/L) and high (100 μg/L) P mesocosms was consistent with assemblages at P‐enriched field sites, whereas rocks in control (8 μg/L) mesocosms had significantly different species composition, consistent with low P field sites. Species composition on rocks transplanted from high P streams did not shift as dramatically and were not significantly different after exposure to different P treatments in mesocosms.

Threshold Indicator Taxa Analysis identified synchronous declines in several diatom species that culminated in assemblage thresholds associated with TP concentrations >20 and 25 μg/L for 2006 and 2007 respectively.

Synthesis and applications. Diatom assemblages show consistent responses to nutrient enrichment despite temporal shifts associated with confounding factors common in stream ecosystems. Regulators should include diatom assemblage responses when developing numeric nutrient criteria. We present a framework that includes spatial, temporal and experimental components, and has broad applicability for use in different ecological settings to evaluate ecological endpoints and set limits for a variety of contaminants threatening freshwater ecosystems throughout the world.
The cover uncovered: Bark control over wood decomposition
Authors: Dossa Gbadamassi G. O. , Schaefer Douglas , Zhang Jiao‐Lin , Tao Jian‐Ping , Cao Kun‐Fang , Corlett Richard T. , Cunningham Anthony B. , Xu Jian‐Chu , Cornelissen Johannes H. C. , Harrison Rhett D. 
Published: March 2018

Abstract

Woody debris (WD) represents a globally significant carbon stock and its decomposition returns nutrients to the soil while providing habitat to microbes, plants and animals. Understanding what drives WD decomposition is therefore important.

WD decomposition rates differ greatly among species. However, the role of bark in the process remains poorly known.

We ask how, and how much, interspecific variation in bark functional traits related to growth and protection have afterlife effects on the decomposition of wood, partly mediated by animals. We examine the roles of bark cover and bark traits throughout the wood decomposition process.

Synthesis. We find that: (1) bark effects on WD decomposition are species‐ and wood size‐specific, (2) bark can enhance coarser WD decomposition but slows twig decomposition in some species, and (3) bark acts as an environmental filter to faunal assemblages in the early stage of wood decomposition.

We highlight the need to account for bark effects on WD decomposition and offer an important complementary contribution to including woody species identity effects in biogeochemical and climate‐change models via species bark traits.
Multi‐dimensional patterns of variation in root traits among coexisting herbaceous species in temperate steppes
Authors: Zhou Meng , Bai Wenming , Zhang Yushi , Zhang Wen‐Hao 
Published: March 2018

Abstract

Characterizing patterns of variation in plant traits across species and environmental gradients is critical for understanding performance of species in ecosystems. One‐dimensional pattern of variation has been demonstrated in leaf traits, which is known as the leaf economic spectrum. However, it is unclear whether such a spectrum exists for root traits.

For roots of 15 species from temperate grasslands, we determined respiration rate, relative growth rate, life span and 10 morphological, chemical and anatomical root traits. We further evaluated pairwise and multiple‐trait relationships by Pearson's correlation and principle component analysis including phylogenetic contrasts.

We found that root functions were related to three clusters of variation. Root respiration rate and relative growth rate were positively correlated with average root diameter (AD), but they were negatively correlated with specific root length (SRL). In contrast, root life span was not correlated with AD, but it was positively correlated with SRL. These results are inconsistent with the presumption of the root economic spectrum.

The principle components analysis revealed a multi‐dimensional pattern of variation in root traits among the 15 coexisting herbaceous species. Moreover, species within the same phylogenetic clades tended to have similar root trait syndromes. Most of the root traits exhibited a significant phylogenetic signal.

Synthesis. Our results do not support a one‐dimensional root economic spectrum in the coexisting herbaceous species of temperate grasslands. In contrast, the pattern of variation in root traits was multi‐dimensional. We further demonstrated that species in different phylogenetic clades possess diverse root trait syndromes for efficient resource acquisition. Our findings provide a next step in understanding root functions and plant strategies in temperate grasslands.
Temporal variation in plant–pollinator networks from seasonal tropical environments: Higher specialization when resources are scarce
Authors: Souza Camila S. , Maruyama Pietro K. , Aoki Camila , Sigrist Maria R. , Raizer Josué , Gross Caroline L. , de Araujo Andréa C. 
Published: March 2018

Abstract

The temporal dynamics of plant phenology and pollinator abundance across seasons should influence the structure of plant–pollinator interaction networks. Nevertheless, such dynamics are seldom considered, especially for diverse tropical networks.

Here, we evaluated the temporal variation of four plant–pollinator networks in two seasonal ecosystems in Central Brazil (Cerrado and Pantanal). Data were gathered on a monthly basis over 1 year for each network. We characterized seasonal and temporal shifts in plant–pollinator interactions, using temporally discrete networks. We predicted that the greater floral availability in the rainy season would allow for finer partitioning of the floral niche by the pollinators, i.e. higher specialization patterns as previously described across large spatial gradients. Finally, we also evaluated how sampling restricted to peak flowering period may affect the characterization of the networks.

Contrary to our expectations, we found that dry season networks, although characterized by lower floral resource richness and abundance, showed higher levels of network‐wide interaction partitioning (complementary specialization and modularity). For nestedness, though, this between‐seasons difference was not consistent. Reduced resource availability in the dry season may promote higher interspecific competition among pollinators leading to reduced niche overlap, thus explaining the increase in specialization.

There were no consistent differences between seasons in species‐level indices, indicating that higher network level specialization is an emergent property only seen when considering the entire network. However, bees presented higher values of specialization and species strength in relation to other groups such as flies and wasps, suggesting that some plant species frequently associated with bees are used only by this group.

Our study also indicates that targeted data collection during peak flowering generates higher estimates of network specialization, possibly because species activity spans longer periods than the targeted time frame. Hence, depending on the period of data collection, different structural values for the networks of interactions may be found.

Synthesis. Plant–pollinator networks from tropical environments have structural properties that vary according to seasons, which should be taken into account in the description of the complex systems of interactions between plants and their pollinators in these areas.
Nitrogen fixer abundance has no effect on biomass recovery during tropical secondary forest succession
Authors: Lai Hao Ran , Hall Jefferson S. , Batterman Sarah A. , Turner Benjamin L. , van Breugel Michiel 
Published: March 2018

Abstract

Nitrogen‐fixing trees (N2 fixers) provide new nitrogen critical for rapid biomass accumulation of tropical forests during early secondary succession, but it remains unclear how the abundance of N2 fixers in the forest community affects the growth of non‐fixers or the primary productivity of the whole forest.

On the one hand, N2 fixers may enhance forest productivity by providing a facilitative effect through the provision of plant‐available nitrogen to non‐fixing trees. On the other hand, N2 fixers may suppress the growth of non‐fixers by growing faster and competing more vigorously for light and other resources. A third alternative is that the growth of N2 fixers themselves accumulate biomass rapidly, while having a neutral effect on non‐fixers, leading to an overall increase in forest biomass.

We examine these alternative hypotheses using 5‐year tree census data from 88 plots in 44 seasonal tropical moist secondary forests (3–32 years old) across a human‐modified landscape in central Panama. We examined whether N2 fixers accumulated biomass more rapidly than non‐fixers, and how relative biomass of N2 fixers as a functional group and as individual species influenced the growth of non‐fixer and whole stand primary productivity.

Surprisingly, we found no evidence for either a net competitive or a facilitative effect of N2 fixers as a functional group or individual species on the biomass recovery in these young forests. N2 fixers did not grow faster than non‐fixers. Individual mortality rates were lower among N2 fixers, but biomass losses due to mortality were similar between the two groups. Overall, we found no relationship between the relative abundance of N2 fixers and stand primary productivity during succession.

Synthesis. Nitrogen‐fixing trees may be critical for reducing nitrogen limitation and accelerating biomass growth during tropical secondary forest succession, thereby impacting the global carbon cycle. However, our findings indicate that, in early successional seasonal tropical moist forests, nitrogen fixers provide neither a net competitive nor a facilitative effect on non‐fixing trees or the whole forest stand, likely because tropical nitrogen fixers utilize facultative fixation and hence abundance poorly approximates the ecosystem function of fixation. Our results indicate that models should not simply scale symbiotic fixation and its effects from nitrogen‐fixing tree abundance.