183 research outputs found
Potential climatic transitions with profound impact on Europe
We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize the mechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding. <br/
Morphological and molecular characterization of Curvularia and related species associated with leaf spot disease of rice in Peninsular Malaysia
Curvularia species are important phytopathogens reported worldwide. They are closely related; consist of major destructive pathogens mainly for grasses and cereal plants including rice (Oryza sativa). A leaf spot symptom of rice is one of the common symptoms found in the rice field and caused reduction of rice yield. However, there are no reports on Curvularia species associated with rice leaves showing spot symptoms. The objectives are to isolate and characterize Curvularia and related species from leaf spot of rice by using morphological and molecular characterization and to determine the phylogenetic relationship between the isolated fungi. Fungal isolation was done from diseased rice leaves showing leaf spot symptoms collected throughout Peninsular Malaysia. Thirty-three isolates were recovered and identified based on their morphological characteristics such as conidia morphology, colony appearance, pigmentation and growth rate for species delimitation. Internal transcribed spacer (ITS) region was amplified to confirm the species identification. The 33 isolates were identified as Bipolaris sorokiniana (10 isolates), Curvularia hawaiiensis (8 isolates), C. geniculata (6 isolates), C. eragrostidis (6 isolates), C. aeria (2 isolates) and C. lunata (1 isolate). A phylogenetic tree was constructed based on ITS sequences using neighbour-joining method. The tree grouped members of Curvularia and Bipolaris into different clades. The phylogenetic tree indicated that the presence of two groups of fungi species; highly virulent and mild pathogens. In conclusion, Curvularia species and Bipolaris sorokiniana were present in rice field in Malaysia and associated with leaf spot of rice
Contribution of Somatic Ras/Raf/Mitogen-Activated Protein Kinase Variants in the Hippocampus in Drug-Resistant Mesial Temporal Lobe Epilepsy
Importance: Mesial temporal lobe epilepsy (MTLE) is the most common focal epilepsy subtype and is often refractory to antiseizure medications. While most patients with MTLE do not have pathogenic germline genetic variants, the contribution of postzygotic (ie, somatic) variants in the brain is unknown. Objective: To test the association between pathogenic somatic variants in the hippocampus and MTLE. Design, Setting, and Participants: This case-control genetic association study analyzed the DNA derived from hippocampal tissue of neurosurgically treated patients with MTLE and age-matched and sex-matched neurotypical controls. Participants treated at level 4 epilepsy centers were enrolled from 1988 through 2019, and clinical data were collected retrospectively. Whole-exome and gene-panel sequencing (each genomic region sequenced more than 500 times on average) were used to identify candidate pathogenic somatic variants. A subset of novel variants was functionally evaluated using cellular and molecular assays. Patients with nonlesional and lesional (mesial temporal sclerosis, focal cortical dysplasia, and low-grade epilepsy-associated tumors) drug-resistant MTLE who underwent anterior medial temporal lobectomy were eligible. All patients with available frozen tissue and appropriate consents were included. Control brain tissue was obtained from neurotypical donors at brain banks. Data were analyzed from June 2020 to August 2022. Exposures: Drug-resistant MTLE. Main Outcomes and Measures: Presence and abundance of pathogenic somatic variants in the hippocampus vs the unaffected temporal neocortex. Results: Of 105 included patients with MTLE, 53 (50.5%) were female, and the median (IQR) age was 32 (26-44) years; of 30 neurotypical controls, 11 (36.7%) were female, and the median (IQR) age was 37 (18-53) years. Eleven pathogenic somatic variants enriched in the hippocampus relative to the unaffected temporal neocortex (median [IQR] variant allele frequency, 1.92 [1.5-2.7] vs 0.3 [0-0.9]; P =.01) were detected in patients with MTLE but not in controls. Ten of these variants were in PTPN11, SOS1, KRAS, BRAF, and NF1, all predicted to constitutively activate Ras/Raf/mitogen-activated protein kinase (MAPK) signaling. Immunohistochemical studies of variant-positive hippocampal tissue demonstrated increased Erk1/2 phosphorylation, indicative of Ras/Raf/MAPK activation, predominantly in glial cells. Molecular assays showed abnormal liquid-liquid phase separation for the PTPN11 variants as a possible dominant gain-of-function mechanism. Conclusions and Relevance: Hippocampal somatic variants, particularly those activating Ras/Raf/MAPK signaling, may contribute to the pathogenesis of sporadic, drug-resistant MTLE. These findings may provide a novel genetic mechanism and highlight new therapeutic targets for this common indication for epilepsy surgery
Dietary magnesium, not calcium, prevents vascular calcification in a mouse model for pseudoxanthoma elasticum
Pseudoxanthoma elasticum (PXE) is a heritable disorder characterized by ectopic calcification of connective tissue in skin, Bruch’s membrane of the eye, and walls of blood vessels. PXE is caused by mutations in the ABCC6 gene, but the exact etiology is still unknown. While observations on patients suggest that high calcium intake worsens the clinical symptoms, the patient organization PXE International has published the dietary advice to increase calcium intake in combination with increased magnesium intake. To obtain more data on this controversial issue, we examined the effect of dietary calcium and magnesium in the Abcc6−/− mouse, a PXE mouse model which mimics the clinical features of PXE. Abcc6−/− mice were placed on specific diets for 3, 7, and 12 months. Disease severity was measured by quantifying calcification of blood vessels in the kidney. Raising the calcium content in the diet from 0.5% to 2% did not change disease severity. In contrast, simultaneous increase of both calcium (from 0.5% to 2.0%) and magnesium (from 0.05% to 0.2%) slowed down the calcification significantly. Our present findings that increase in dietary magnesium reduces vascular calcification in a mouse model for PXE should stimulate further studies to establish a dietary intervention for PXE
Recommended from our members
Warming of Central European lakes and their response to the 1980s climate regime shift
Lake surface water temperatures (LSWTs) are sensitive to atmospheric warming and have previously been shown to respond to regional changes in the climate. Using a combination of in situ and simulated surface temperatures from 20 Central European lakes, with data spanning between 50 and ∼100 years, we investigate the long-term increase in annually averaged LSWT. We demonstrate that Central European lakes are warming most in spring and experience a seasonal variation in LSWT trends. We calculate significant LSWT warming during the past few decades and illustrate, using a sequential t test analysis of regime shifts, a substantial increase in annually averaged LSWT during the late 1980s, in response to an abrupt shift in the climate. Surface air temperature measurements from 122 meteorological stations situated throughout Central Europe demonstrate similar increases at this time. Climatic modification of LSWT has numerous consequences for water quality and lake ecosystems. Quantifying the response of LSWT increase to large-scale and abrupt climatic shifts is essential to understand how lakes will respond in the future
Vitamin K supplementation increases vitamin K tissue levels but fails to counteract ectopic calcification in a mouse model for pseudoxanthoma elasticum
Pseudoxanthoma elasticum (PXE) is an autosomal recessive disorder in which calcification of connective tissue leads to pathology in skin, eye and blood vessels. PXE is caused by mutations in ABCC6. High expression of this transporter in the basolateral hepatocyte membrane suggests that it secretes an as-yet elusive factor into the circulation which prevents ectopic calcification. Utilizing our Abcc6−/− mouse model for PXE, we tested the hypothesis that this factor is vitamin K (precursor) (Borst et al. 2008, Cell Cycle). For 3 months, Abcc6−/− and wild-type mice were put on diets containing either the minimum dose of vitamin K required for normal blood coagulation or a dose that was 100 times higher. Vitamin K was supplied as menaquinone-7 (MK-7). Ectopic calcification was monitored in vivo by monthly micro-CT scans of the snout, as the PXE mouse model develops a characteristic connective tissue mineralization at the base of the whiskers. In addition, calcification of kidney arteries was measured by histology. Results show that supplemental MK-7 had no effect on ectopic calcification in Abcc6−/− mice. MK-7 supplementation increased vitamin K levels (in skin, heart and brain) in wild-type and in Abcc6−/− mice. Vitamin K tissue levels did not depend on Abcc6 genotype. In conclusion, dietary MK-7 supplementation increased vitamin K tissue levels in the PXE mouse model but failed to counteract ectopic calcification. Hence, we obtained no support for the hypothesis that Abcc6 transports vitamin K and that PXE can be cured by increasing tissue levels of vitamin K
Age-related self-overestimation of step-over ability in healthy older adults and its relationship to fall risk
The Cysteine Rich Necrotrophic Effector SnTox1 Produced by Stagonospora nodorum Triggers Susceptibility of Wheat Lines Harboring Snn1
The wheat pathogen Stagonospora nodorum produces multiple necrotrophic effectors (also called host-selective toxins) that promote disease by interacting with corresponding host sensitivity gene products. SnTox1 was the first necrotrophic effector identified in S. nodorum, and was shown to induce necrosis on wheat lines carrying Snn1. Here, we report the molecular cloning and validation of SnTox1 as well as the preliminary characterization of the mechanism underlying the SnTox1-Snn1 interaction which leads to susceptibility. SnTox1 was identified using bioinformatics tools and verified by heterologous expression in Pichia pastoris. SnTox1 encodes a 117 amino acid protein with the first 17 amino acids predicted as a signal peptide, and strikingly, the mature protein contains 16 cysteine residues, a common feature for some avirulence effectors. The transformation of SnTox1 into an avirulent S. nodorum isolate was sufficient to make the strain pathogenic. Additionally, the deletion of SnTox1 in virulent isolates rendered the SnTox1 mutated strains avirulent on the Snn1 differential wheat line. SnTox1 was present in 85% of a global collection of S. nodorum isolates. We identified a total of 11 protein isoforms and found evidence for strong diversifying selection operating on SnTox1. The SnTox1-Snn1 interaction results in an oxidative burst, DNA laddering, and pathogenesis related (PR) gene expression, all hallmarks of a defense response. In the absence of light, the development of SnTox1-induced necrosis and disease symptoms were completely blocked. By comparing the infection processes of a GFP-tagged avirulent isolate and the same isolate transformed with SnTox1, we conclude that SnTox1 may play a critical role during fungal penetration. This research further demonstrates that necrotrophic fungal pathogens utilize small effector proteins to exploit plant resistance pathways for their colonization, which provides important insights into the molecular basis of the wheat-S. nodorum interaction, an emerging model for necrotrophic pathosystems
Global Pyrogeography: the Current and Future Distribution of Wildfire
Climate change is expected to alter the geographic distribution of wildfire, a complex abiotic process that responds to a variety of spatial and environmental gradients. How future climate change may alter global wildfire activity, however, is still largely unknown. As a first step to quantifying potential change in global wildfire, we present a multivariate quantification of environmental drivers for the observed, current distribution of vegetation fires using statistical models of the relationship between fire activity and resources to burn, climate conditions, human influence, and lightning flash rates at a coarse spatiotemporal resolution (100 km, over one decade). We then demonstrate how these statistical models can be used to project future changes in global fire patterns, highlighting regional hotspots of change in fire probabilities under future climate conditions as simulated by a global climate model. Based on current conditions, our results illustrate how the availability of resources to burn and climate conditions conducive to combustion jointly determine why some parts of the world are fire-prone and others are fire-free. In contrast to any expectation that global warming should necessarily result in more fire, we find that regional increases in fire probabilities may be counter-balanced by decreases at other locations, due to the interplay of temperature and precipitation variables. Despite this net balance, our models predict substantial invasion and retreat of fire across large portions of the globe. These changes could have important effects on terrestrial ecosystems since alteration in fire activity may occur quite rapidly, generating ever more complex environmental challenges for species dispersing and adjusting to new climate conditions. Our findings highlight the potential for widespread impacts of climate change on wildfire, suggesting severely altered fire regimes and the need for more explicit inclusion of fire in research on global vegetation-climate change dynamics and conservation planning
Assessing ecological resilience to human induced environmental change in shallow lakes
Sudden unpredictable changes in ecosystems are an increasing source of concern because of
their inherent unpredictability and the difficulties involved in restoration. Our understanding
of the changes that occur across different trophic levels and the form of this change is lacking.
This is especially true of large shallow lakes, where characteristics such as fetch and depth
are close to theoretical boundary values for hysteretic behaviour. The development of
reliable indicators capable of predicting these changes has been the focus of much research
in recent years. The success of these early warning indicators (EWIs) has so far been mixed.
There remain many unknowns about how they perform under a wide variety of conditions
and parameters. Future climate change is predicted to have a wide range of impacts through
the interaction of combined pressures, making the understanding of EWIs and the in-lake
processes that occur during regime shifts imperative. Loch Leven, Scotland, UK, is a large
shallow lake with a history of eutrophication, research and management and as such is an
ideal study site to better understand resilience and regime shifts under a range of interacting
stressors.
The objectives of this research are to: (1) analyse long term data to identify the occurrence
of common tipping points within the chemical (water column nutrient concentrations) and
biological (macrophytes, phytoplankton, zooplankton) components of the loch, then test
these tipping points using five statistical early warning indicators (EWIs) across multiple
rolling window sizes; and (2) quantify the changes in lake ecology using a before/after
analysis and testing for non-linearity, combined with modelling using the aquatic ecosystem
process model PCLake to determine the level of resilience following a regime shift during
recovery from eutrophication; (3) using PCLake, examine the sensitivity of Loch Leven to
regime shifts in the face of predicted environmental change (e.g. climate change, nutrient
pollution).
Statistical analysis identified tipping points across all trophic levels included, from physical
and chemical variables through to apex predators. The success of EWIs in predicting the
tipping points was highly dependent on the number of EWIs used, with window size having
a smaller impact. The 45% window size had the highest overall accuracy across all EWIs but
only detected 16.5% more tipping points than the window size with the lowest overall
accuracy. Differences between individual EWI performance and usage of them as a group
was substantial with a 29.7% increase between the two. In both individual and group use of
EWIs, false positives (early warning without a tipping point) were more common than true
positives (tipping point preceded by EWI), creating significant doubts about their reliability
as management tools.
Significant change was seen across multiple variables and trophic levels in the before/after
analysis following sudden recovery from eutrophication, with most variables also showing
evidence of non-linear change. Modelling of responses to nutrient loading for chlorophyll,
zooplankton and macrophytes, under states from before and after the shift, indicate
hysteresis and thus the presence of feedback mechanisms. The modelling of responses to
nutrient loading and predicted climate change in temperature and precipitation
demonstrated that increases in temperature and decreases in summer precipitation
individually had large impacts on chlorophyll and zooplankton at medium to high phosphorus
(P) loads. However, modelling of the combined effects of these changes resulted in the
highest lake chlorophyll concentrations of all tested scenarios. At low P loads higher
temperatures and increased winter precipitation had the greatest impact on system
resilience with a lower Critical Nutrient Load (CNL). The difference between chlorophyll and
zooplankton as opposed to macrophytes was in the presence of a lower CNL for the increased
winter precipitation-only scenarios which was not seen in the macrophytes. This highlights
the potential role of high winter inputs potentially loaded with particulate matter in reducing
resilience at lower P loads.
This research has highlighted the vulnerability and low resilience of Loch Leven to
environmental change. The presence of multiple tipping points and high levels of EWI activity
show a high level of flexibility in the system. Coupled with the occurrence of widespread
trophic change during a sudden recovery and a small level of hysteresis and high levels of
sensitivity to climate change, the low levels of resilience become clear. The impact of lake-specific
characteristics such as moderate depth, large fetch and a heterogeneous bed
morphology is particularly evident in the limitations on macrophyte cover and the reliance
on zooplankton to determine the hysteresis offset (amount of phosphorus (P) loading
between the two CNL). The presence of these characteristics can be used to identify other
lakes vulnerable to change. Improving the predictive capabilities of resilience indicators such
as EWIs, and better understanding of the ecological changes that occur during non-linear
change in response to recovery and climate change, can help target relevant ecosystem
components for preventative management. These actions may become necessary under
even the most conservative estimates of environmental change
- …