The anti-sigma factor RsrA responds to oxidative stress by reburying its hydrophobic core

Redox-regulated effector systems that counteract oxidative stress are essential for all forms of life. Here we uncover a new paradigm for sensing oxidative stress centred on the hydrophobic core of a sensor protein. RsrA is an archetypal zinc-binding anti-sigma factor that responds to disulfide stress in the cytoplasm of Actinobacteria. We show that RsrA utilizes its hydrophobic core to bind the sigma factor σ R preventing its association with RNA polymerase, and that zinc plays a central role in maintaining this high-affinity complex. Oxidation of RsrA is limited by the rate of zinc release, which weakens the RsrA-σ R complex by accelerating its dissociation. The subsequent trigger disulfide, formed between specific combinations of RsrA's three zinc-binding cysteines, precipitates structural collapse to a compact state where all σ R-binding residues are sequestered back into its hydrophobic core, releasing σ R to activate transcription of anti-oxidant genes

Status Update and Interim Results from the Asymptomatic Carotid Surgery Trial-2 (ACST-2)

Objectives: ACST-2 is currently the largest trial ever conducted to compare carotid artery stenting (CAS) with carotid endarterectomy (CEA) in patients with severe asymptomatic carotid stenosis requiring revascularization. Methods: Patients are entered into ACST-2 when revascularization is felt to be clearly indicated, when CEA and CAS are both possible, but where there is substantial uncertainty as to which is most appropriate. Trial surgeons and interventionalists are expected to use their usual techniques and CE-approved devices. We report baseline characteristics and blinded combined interim results for 30-day mortality and major morbidity for 986 patients in the ongoing trial up to September 2012. Results: A total of 986 patients (687 men, 299 women), mean age 68.7 years (SD ± 8.1) were randomized equally to CEA or CAS. Most (96%) had ipsilateral stenosis of 70-99% (median 80%) with contralateral stenoses of 50-99% in 30% and contralateral occlusion in 8%. Patients were on appropriate medical treatment. For 691 patients undergoing intervention with at least 1-month follow-up and Rankin scoring at 6 months for any stroke, the overall serious cardiovascular event rate of periprocedural (within 30 days) disabling stroke, fatal myocardial infarction, and death at 30 days was 1.0%. Conclusions: Early ACST-2 results suggest contemporary carotid intervention for asymptomatic stenosis has a low risk of serious morbidity and mortality, on par with other recent trials. The trial continues to recruit, to monitor periprocedural events and all types of stroke, aiming to randomize up to 5,000 patients to determine any differential outcomes between interventions. Clinical trial: ISRCTN21144362. © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved

Second asymptomatic carotid surgery trial (ACST-2): a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86–1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91–1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable. Funding: UK Medical Research Council and Health Technology Assessment Programme

CFU bacterial fraction in the estuarine upwelling ecosystem of Ría de Vigo, Spain: variability in abundance and their ecophysiological description

15 pages, 8 figures, 4 tables.Between October 1990 and August 1991 colony-forming unit (CFU) bacteria at the centre of the Ría de Vigo, Spain, comprised on average 1% of total bacterioplankton, with a maximum of 6.8% in mid-April. In contrast to relatively small fluctuations in total bacterioplankton, fluctuations in CFUs were considerable, with the coefficient of variation ranging from 112 to 233%. Over 40% of the variance in CFU abundance in the surface layer during the whole period of observations (winter and summer) could be explained through an equation relating logCFU to incoming solar radiation, and during the summer months through another equation relating logCFU to upwelling. Both physical factors enhanced CFU concentrations. Biological variables, such as total bacterioplankton, chlorophyll and heterotrophic flagellates, had no further effect on the explained variance. At the bottom of the photic zone, runoff and upwelling accounted for between 29 and 50% of the variance in CFU counts. In this layer, biological variables had a great influence on CFU abundance, increasing the explained variance to 61% for the whole period studied. In this case, chlorophyll was negatively related to logCFU suggesting that the CFU bacterial fraction was more abundant in the water column after the decline of the phytoplankton blooms and after the corresponding release of bacteria attached to particles. At the bottom of the water column, seawater temperature was the only important factor in explaining the variance in CFU counts (36%), with logCFU and temperature being positively related. We hypothesise that 3 factors are prominent in controlling the CFU standing stock: solar radiation and upwelling stimulate the synthesis of particulate organic matter in surface waters, providing a food source for CFU bacteria, and terrestrial runoff which dilutes bacterial numbers. Based on cluster analyses of physiological tests, on pure bacterial isolates from 2 contrasting sampling dates, we show that prevailing hydro- and meteorological conditions select for different bacterial species in the CFU community. Lower CFU counts and diversity within the population, plus lower frequencies of positive responses in physiological tests arose through very high upwelling and NW winds which introduced CFU-poor water masses from the Atlantic Ocean into the Ría de Vigo. Conversely, terrestrial runoff and NE winds enhanced diversity within this population at the centre of the estuary, through the introduction of terrestrial bacteria or those from shallow waters; these were characterised by higher numbers of positive responses in physiological tests.This study was supported by the European Union's MAST project, contract MAST-CT90-0017 M.K.Z. thanks the 'Ministerio de Educación y Ciencia and Ministerio de Asuntos Exteriores' in Spain for the financia1 support that enabled him to conduct this research in Vigo during 1990-1991.Peer reviewe

Relationships between the abundance of bacteria and other biota and the hydrographic variability in the Ría de Vigo, Spain

11 pages, 6 figures, 5 tables.Hydrographic variability driven by changes in wind speed and direction and by meteorological parameters, such as incoming solar radiation, fluvial discharges, and temperature, affects biological standing stocks (e.g. of bacteria) in the marine environment. We studied the effects of such parameters in the Ría de Vigo (Galicia, Spain), between October 1990 and August 1991, where downwelling in winter results from predominantly poleward winds, whilst in summer upwelling is driven by winds travelling towards the equator. Total bacterial abundance was strongly affected by physical factors in the Ría de Vigo. Almost 60% of the variance in bacterial abundance in the surface layer could be explained by an equation relating logTC [log(total count of heterotrophic bacterioplankton)] to incoming solar radiation, water temperature, run-off and coastal upwelling, where solar radiation, water temperature and moderate upwelling are all positive terms, while run-off and strong upwelling act negatively. Consideration of biological variables such chlorophyll, ciliates and heterotrophic flagellates did not further explain the variance. Physical factors, however, only accounted for 40% of the total variance in bacterial abundance at the bottom of the photic layer. The inclusion of biological variables in the regression equations increased the explained variance to 55%; chlorophyll was the most important of these variables and was positively related to logTC. This indicates that bacterial populations in the surface layer are mainly controlled by physical factors with a weak phytoplankton influence; however, a stronger coupling between primary production and bacterial growth must exist at the bottom of the photic layer. Physical variables also explained 60 to 65% of the variance in cultivable spore-forming saprophytic bacteria, but, in contrast to effects on total bacterial numbers, run-off had a positive effect while moderate upwelling had a negative influence on spore-forming numbers. This suggests that terrestrial run-off has some ecological importance through the enrichment of nearshore bacterial populations with cells of terrestrial origin.This study has been supported by the European Union's MAST project, contract MAST-CT90-0017 M.K.Z. thanks 'Ministerio de Educacion y Ciencia and Ministerio de Asuntos Exteriores' in Spain for all financial support and for enabling him to conduct this research in Vigo during 1990-1991.Peer reviewe