Extreme drought pushes stream invertebrate communities over functional thresholds

Functional traits are increasingly being used to predict extinction risks and range shifts under long‐term climate change scenarios, but have rarely been used to study vulnerability to extreme climatic events, such as supraseasonal droughts. In streams, drought intensification can cross thresholds of habitat loss, where marginal changes in environmental conditions trigger disproportionate biotic responses. However, these thresholds have been studied only from a structural perspective, and the existence of functional nonlinearity remains unknown. We explored trends in invertebrate community functional traits along a gradient of drought intensity, simulated over 18 months, using mesocosms analogous to lowland headwater streams. We modelled the responses of 16 traits based on a priori predictions of trait filtering by drought, and also examined the responses of trait profile groups (TPGs) identified via hierarchical cluster analysis. As responses to drought intensification were both linear and nonlinear, generalized additive models (GAMs) were chosen to model response curves, with the slopes of fitted splines used to detect functional thresholds during drought. Drought triggered significant responses in 12 (75%) of the a priori‐selected traits. Behavioural traits describing movement (dispersal, locomotion) and diet were sensitive to moderate‐intensity drought, as channels fragmented into isolated pools. By comparison, morphological and physiological traits showed little response until surface water was lost, at which point we observed sudden shifts in body size, respiration mode and thermal tolerance. Responses varied widely among TPGs, ranging from population collapses of non‐aerial dispersers as channels fragmented to irruptions of small, eurythermic dietary generalists upon extreme dewatering. Our study demonstrates for the first time that relatively small changes in drought intensity can trigger disproportionately large functional shifts in stream communities, suggesting that traits‐based approaches could be particularly useful for diagnosing catastrophic ecological responses to global change.     

Exploration of Ellsworth Subglacial Lake: a concept paper on the development, organisation and execution of an experiment to explore, measure and sample the environment of a West Antarctic subglacial lake

Antarctic subglacial lakes have, over the past few years, been hypothesised to house unique forms of life and hold detailed sedimentary records of past climate change. Testing this hypothesis requires in situ examinations. The direct measurement of subglacial lakes has been considered ever since the largest and best-known lake, named Lake Vostok, was identified as having a deep water-column. The Subglacial Antarctic Lake Environments (SALE) programme, set up by the Scientific Committee on Antarctic Research (SCAR) to oversee subglacial lakes research, state that prior exploration of smaller lakes would be a “prudent way forward”. Over 145 subglacial lakes are known to exist in Antarctica, but one lake in West Antarctica, officially named Ellsworth Subglacial Lake (referred to hereafter as Lake Ellsworth), stands out as a candidate for early exploration. A consortium of over 20 scientists from seven countries and 14 institutions has been assembled to plan the exploration of Lake Ellsworth. An eight-year programme is envisaged: 3 years for a geophysical survey, 2 years for equipment development and testing, 1 year for field planning and operation, and 2 years for sample analysis and data interpretation. The science experiment is simple in concept but complex in execution. Lake Ellsworth will be accessed using hot water drilling. Once lake access is achieved, a probe will be lowered down the borehole and into the lake. The probe will contain a series of instruments to measure biological, chemical and physical characteristics of the lake water and sediments, and will utilise a tether to the ice surface through which power, communication and data will be transmitted. The probe will pass through the water column to the lake floor. The probe will then be pulled up and out of the lake, measuring its environment continually as this is done. Once at the ice surface, any water samples collected will be taken from the probe for laboratory analysis (to take place over subsequent years). The duration of the science mission, from deployment of the probe to its retrieval, is likely to take between 24 and 36 h. Measurements to be taken by the probe will provide data about the following: depth, pressure, conductivity and temperature; pH levels; biomolecules (using life marker chips); anions (using a chemical analyzer); visualisation of the environment (using cameras and light sources); dissolved gases (using chromatography); and morphology of the lake floor and sediment structures (using sonar). After the probe has been retrieved, a sediment corer may be dropped into the lake to recover material from the lake floor. Finally, if time permits, a thermistor string may be left in the lake water to take time-dependent measurements of the lake’s water column over subsequent years. Given that the comprehensive geophysical survey of the lake will take place in two seasons during 2007–2009, a two-year instrument and logistic development phase from 2008 (after the lake’s bathymetry has been assessed) makes it possible that the exploration of Lake Ellsworth could take place at the beginning of the next decade.     

Elucidating the ticking of an in vitro circadian clockwork

A biochemical oscillator can be reconstituted in vitro with three purified proteins, that displays the salient properties of circadian (daily) rhythms, including self-sustained 24-h periodicity that is temperature compensated. We analyze the biochemical basis of this oscillator by quantifying the time-dependent interactions of the three proteins (KaiA, KaiB, and KaiC) by electron microscopy and native gel electrophoresis to elucidate the timing of the formation of complexes among the Kai proteins. The data are used to derive a dynamic model for the in vitro oscillator that accurately reproduces the rhythms of KaiABC complexes and of KaiC phosphorylation, and is consistent with biophysical observations of individual Kai protein interactions. We use fluorescence resonance energy transfer (FRET) to confirm that monomer exchange among KaiC hexamers occurs. The model demonstrates that the function of this monomer exchange may be to maintain synchrony among the KaiC hexamers in the reaction, thereby sustaining a high-amplitude oscillation. Finally, we apply the first perturbation analyses of an in vitro oscillator by using temperature pulses to reset the phase of the KaiABC oscillator, thereby testing the resetting characteristics of this unique circadian oscillator. This study analyzes a circadian clockwork to an unprecedented level of molecular detail.     

Bog breathing: the extent of peat shrinkage and expansion on blanket bogs in relation to water table,heather management and dominant vegetation and its implications for carbon stock assessments

Wetlands Ecology and Management - Peatlands represent a globally important carbon stock. Peat soil carbon stock assessments rely on measurements of carbon concentration, bulk density and soil...     

Reproductive factors and the risk of incident dementia: A cohort study of UK Biobank participants

BackgroundWomen’s reproductive factors have been associated with the risk of dementia; however, these findings remain uncertain. This study aimed to examine the risk of incident all-cause dementia associated with reproductive factors in women and the number of children in both sexes and whether the associations vary by age, socioeconomic status (SES), smoking status, and body mass index (BMI) in the UK Biobank.Methods and findingsA total of 273,240 women and 228,957 men without prevalent dementia from the UK Biobank were included in the analyses. Cox proportional hazard regressions estimated hazard ratios (HRs) for reproductive factors with incident all-cause dementia. Multiple adjusted models included age at study entry, SES, ethnicity, smoking status, systolic blood pressure, BMI, history of diabetes mellitus, total cholesterol, antihypertensive drugs, and lipid-lowering drugs. Over a median of 11.8 years follow-up, 1,866 dementia cases were recorded in women and 2,202 in men. Multiple adjusted HRs ((95% confidence intervals (CIs)), p-value) for dementia were 1.20 (1.08, 1.34) (p = 0.016) for menarche <12 years and 1.19 (1.07, 1.34) (p = 0.024) for menarche >14 years compared to 13 years; 0.85 (0.74, 0.98) (p = 0.026) for ever been pregnant; 1.43 (1.26, 1.62) (p < 0.001) for age at first live birth <21 compared to 25 to 26 years; 0.82 (0.71, 0.94) (p = 0.006) for each abortion; 1.32 (1.15, 1.51) (p = 0.008) for natural menopause at <47 compared to 50 years; 1.12 (1.01, 1.25) (p = 0.039) for hysterectomy; 2.35 (1.06, 5.23) (p = 0.037) for hysterectomy with previous oophorectomy; and 0.80 (0.72, 0.88) (p < 0.001) for oral contraceptive pills use. The U-shaped associations between the number of children and the risk of dementia were similar for both sexes: Compared with those with 2 children, for those without children, the multiple adjusted HR ((95% CIs), p-value) was 1.18 (1.04, 1.33) (p = 0.027) for women and 1.10 (0.98, 1.23) (p = 0.164) for men, and the women-to-men ratio of HRs was 1.09 (0.92, 1.28) (p = 0.403); for those with 4 or more children, the HR was 1.14 (0.98, 1.33) (p = 0.132) for women and 1.26 (1.10, 1.45) (p = 0.003) for men, and the women-to-men ratio of HRs was 0.93 (0.76, 1.14) (p = 0.530). There was evidence that hysterectomy (HR, 1.31 (1.09, 1.59), p = 0.013) and oophorectomy (HR, 1.39 (1.08, 1.78), p = 0.002) were associated with a higher risk of dementia among women of relatively lower SES only. Limitations of the study include potential residual confounding and self-reported measures of reproductive factors, as well as the limited representativeness of the UK Biobank population.ConclusionsIn this study, we observed that some reproductive events related to shorter cumulative endogenous estrogen exposure in women were associated with higher dementia risk, and there was a similar association between the number of children and dementia risk between women and men.

In a cohort study, Jessica Gong and colleagues investigate associations between reproductive factors, number of children, and dementia among individuals in the UK Biobank.     

Translational repression mediates activation of nuclear factor kappa B by phosphorylated translation initiation factor 2

Numerous stressful conditions activate kinases that phosphorylate the alpha subunit of translation initiation factor 2 (eIF2alpha), thus attenuating mRNA translation and activating a gene expression program known as the integrated stress response. It has been noted that conditions associated with eIF2alpha phosphorylation, notably accumulation of unfolded proteins in the endoplasmic reticulum (ER), or ER stress, are also associated with activation of nuclear factor kappa B (NF-kappaB) and that eIF2alpha phosphorylation is required for NF-kappaB activation by ER stress. We have used a pharmacologically activable version of pancreatic ER kinase (PERK, an ER stress-responsive eIF2alpha kinase) to uncouple eIF2alpha phosphorylation from stress and found that phosphorylation of eIF2alpha is both necessary and sufficient to activate both NF-kappaB DNA binding and an NF-kappaB reporter gene. eIF2alpha phosphorylation-dependent NF-kappaB activation correlated with decreased levels of the inhibitor IkappaBalpha protein. Unlike canonical signaling pathways that promote IkappaBalpha phosphorylation and degradation, eIF2alpha phosphorylation did not increase phosphorylated IkappaBalpha levels or affect the stability of the protein. Pulse-chase labeling experiments indicate instead that repression of IkappaBalpha translation plays an important role in NF-kappaB activation in cells experiencing high levels of eIF2alpha phosphorylation. These studies suggest a direct role for eIF2alpha phosphorylation-dependent translational control in activating NF-kappaB during ER stress.     

Effects of ethanol on lipid bilayers with and without cholesterol: the distearoylphosphatidylcholine system

Differential scanning calorimetry (DSC) and fluorescence spectroscopy are useful techniques for investigating the phase transitions of phospholipid bilayers. In this study, these methods have been extended to determine the effects of ethanol on DSPC and DSPC/2 mol.% cholesterol bilayers. The biphasic effect of the main transition was observed on the DSC heating scans above 0.60 M ethanol. In addition, the concentration at which the biphasic effect occurs is not significantly changed in the presence of 2 mol.% cholesterol. For the fluorescence studies, 1,6-diphenyl-1,3,5-hexatriene (DPH) has been incorporated into the bilayer to monitor the phase transitions through the displacement of DPH. This fluorescent probe is used to directly determine the onset of interdigitation in the bilayer systems as indicated by a large decrease in the DPH fluorescence intensity. The addition of cholesterol lowered and broadened the transition temperatures of the phosphatidylcholine (PC) system. However, 2 mol.% cholesterol did not have a significant effect on the induction of the interdigitated phase in DSPC as observed from the small difference in ethanol threshold concentration for the two systems. This suggests that DSPC forms a more stable interdigitated gel phase than other PCs with shorter acyl chains.     

Amperometric determination of lactate with novel trienzyme/poly(carbamoyl) sulfonate hydrogel-based sensor

A novel trienzyme sensor for the amperometric determination of lactate was constructed by immobilizing salicylate hydroxylase (SHL, E.C. 1.14.13.1), l-lactate dehydrogenase (LDH, E.C. 1.1.1.27), and pyruvate oxidase (PyOD, E.C. 1.2.3.3) on a Clark-type oxygen electrode. The enzymes were entrapped by a poly(carbamoyl) sulfonate (PCS) hydrogel on a Teflon membrane. LDH catalyzes the specific dehydrogenation of lactate consuming NAD(+). SHL catalyzes the irreversible decarboxylation and the hydroxylation of salicylate in the presence of oxygen and NADH produced by LDH. PyOD decarboxylates pyruvate using oxygen and phosphate. SHL and PyOD force the equilibrium of dehydrogenation of lactate by LDH to the product side by consuming NADH and pyruvate, respectively. Dissolved oxygen acts as an essential material for both PyOD and SHL during their respective enzymatic reactions. Therefore, an amplified signal, caused by the consumptions of dissolved oxygen by the two enzymes, was observed in the measurement of lactate. Regeneration of cofactor was found in the trienzyme system. A Teflon membrane was used to fabricate the sensor in order to avoid interferences. The sensor has a fast response (2s) and short recovery times (2 min). The total test time for a measurement by using this lactate sensor (4 min) was faster than using a commercial lactate testing kit (up to 10 min). The sensor has a linear range between 10 and 400 microM lactate, with a detection limit of 4.3 microM. A good agreement (R2 = 0.9984) with a commercial lactate testing kit was obtained in beverage sample measurements.     

Familial non-syndromic clear cell renal cell carcinoma

The diagnosis of familial non-syndromic clear cell renal cell carcinoma is one of exclusion. In families presenting with clear cell RCC a germline VHL mutation and a constitutional translocation of chromosome 3 must be excluded before familial non-syndromic clear cell RCC can be diagnosed. Large familial non-syndromic clear cell RCC kindreds are uncommon and a predisposing gene has not been identified. However inheritance is autosomal dominant in most cases and age at onset is earlier than in sporadic cases. Recognition and appropriate screening of familial non-syndromic clear cell RCC cases will reduce morbidity and mortality. Large scale collaborative linkage studies may provide a basis for the identification of familial non-syndromic clear cell RCC susceptibility gene(s).