Ultrahigh resolution and full-length pilin structures with insights for filament assembly, pathogenic functions, and vaccine potential

Pilin proteins assemble into Type IV pili (T4P), surface-displayed bacterial filaments with virulence functions including motility, attachment, transformation, immune escape, and colony formation. However, challenges in crystallizing full-length fiber-forming and membrane protein pilins leave unanswered questions regarding pilin structures, assembly, functions, and vaccine potential. Here we report pilin structures of full-length DnFimA from the sheep pathogen Dichelobacter nodosus and FtPilE from the human pathogen Francisella tularensis at 2.3 and 1 ? resolution, respectively. The DnFimA structure reveals an extended kinked N-terminal α-helix, an unusual centrally located disulfide, conserved subdomains, and assembled epitopes informing serogroup vaccines. An interaction between the conserved Glu-5 carboxyl oxygen and the N-terminal amine of an adjacent subunit in the crystallographic dimer is consistent with the hypothesis of a salt bridge between these groups driving T4P assembly. The FtPilE structure identifies an authentic Type IV pilin and provides a framework for understanding the role of T4P in F. tularensis virulence. Combined results define a unified pilin architecture, specialized subdomain roles in pilus assembly and function, and potential therapeutic targets.     

The influence of proximal stem geometry and surface finish on the fixation of a double-tapered cemented femoral stem

In this study, the in vitro fixation of four otherwise identical double-tapered stem-types, varying only in surface finish (polished or matte) and proximal stem geometry (with or without flanges) were compared under two conditions. First, four specimens of each stem type were tested with initially bonded stem–cement interfaces, representing early post-operative conditions. Then, simulating conditions a few weeks to months later, stems were implanted in unused synthetic femurs, with a thin layer coating the stem to prevent stem–cement adhesion. Per-cycle motions were measured at both cement interfaces throughout loading. Overall, surface finish had the smallest relative effect on fixation compared to flanges. Flanges increased axial fixation by 22 μm per-cycle, regardless of surface finish (P=0.01). Further, all stems moved under dynamic load at the stem–cement interface during the first few cycles of loading, even without a thin film. The results indicate that flanges have a greater effect on fixation than surface finish, and therefore adverse findings about matte surfaces should not necessarily apply to all double-tapered stems. Specifically, dorsal flanges enhance the stability of a tapered cemented femoral stem, regardless of surface finish.     

Effect of melatonin on incidence of delirium among patients with hip fracture: a multicentre,double-blind randomized controlled trial

Background:

Disturbance of the sleep–wake cycle is a characteristic of delirium. In addition, changes in melatonin rhythm influence the circadian rhythm and are associated with delirium. We compared the effect of melatonin and placebo on the incidence and duration of delirium.

Methods:

We performed this multicentre, double-blind, randomized controlled trial between November 2008 and May 2012 in 1 academic and 2 nonacademic hospitals. Patients aged 65 years or older who were scheduled for acute hip surgery were eligible for inclusion. Patients received melatonin 3 mg or placebo in the evening for 5 consecutive days, starting within 24 hours after admission. The primary outcome was incidence of delirium within 8 days of admission. We also monitored the duration of delirium.

Results:

A total of 452 patients were randomly assigned to the 2 study groups. We subsequently excluded 74 patients for whom the primary end point could not be measured or who had delirium before the second day of the study. After these postrandomization exclusions, data for 378 patients were included in the main analysis. The overall mean age was 84 years, 238 (63.0%) of the patients lived at home before admission, and 210 (55.6%) had cognitive impairment. We observed no effect of melatonin on the incidence of delirium: 55/186 (29.6%) in the melatonin group v. 49/192 (25.5%) in the placebo group; difference 4.1 (95% confidence interval −0.05 to 13.1) percentage points. There were no between-group differences in mortality or in cognitive or functional outcomes at 3-month follow-up.

Interpretation:

In this older population with hip fracture, treatment with melatonin did not reduce the incidence of delirium. Trial registration: Netherlands Trial Registry, NTR1576: MAPLE (Melatonin Against PLacebo in Elderly patients) study; www.trialregister.nl/trialreg/admin/rctview.asp?TC=1576Delirium in older inpatients is associated with a high risk of dementia and other complications that translate into increased mortality and health care costs.^1,2 The antipsychotic haloperidol has historically been the agent of choice for treating delirium, and it has increasingly been administered as a prophylactic for delirium or to reduce symptoms such as hallucinations and aggressive behaviour.^3,4 However, all antipsychotic treatments may induce serious cerebrovascular adverse effects and greater mortality, particularly among patients with dementia.^5,6 These effects led the US Food and Drug Administration to issue a serious warning against their use.⁷ In addition, benzodiazepines are still frequently used to treat delirium, despite their being known to elicit or aggravate delirium.^8,9Disturbances of the circadian sleep–wake cycle represent one of the core features of delirium,¹⁰ leading to the hypothesis that the neurotransmitter melatonin and changes in its metabolism may be involved in the pathogenesis of delirium.^11,12 Objective measurements have shown that melatonin metabolism is disturbed after abdominal and other types of surgery, insomnia, sleep deprivation and stays in the intensive care unit (ICU), all of which are also known to be factors that contribute to delirium.^13–16 These characteristics suggest an association between melatonin abnormalities and delirium.^17–22 Although proof of a causal relation is still lacking, inpatients might nevertheless benefit from melatonin supplementation therapy through postoperative maintenance or restoration of their sleep–wake cycle.^23–25 Although melatonin depletion is thought to be one of the mechanisms of delirium, few studies have investigated the effects of altering perioperative plasma concentrations of melatonin, in particular, the possible effects on postoperative delirium.The primary objective of this study was to assess the effects of melatonin on the incidence of delirium among elderly patients admitted to hospital as an emergency following hip fracture. Secondary outcomes were duration and severity of delirium, length of hospital stay, total doses of haloperidol and benzodiazepines administered to patients with delirium, mortality during the hospital stay, and functional status, cognitive function and mortality at 3-month follow-up.     

Increasing relevance of spring temperatures for Norway spruce trees in Davos,Switzerland, after the 1950s

Key message

Relevance of spring temperatures for tree-ring growth steadily increased since 1950s. Closely linked tree-ring growth and net CO ₂ exchange driven by spring temperatures.

Abstract

We investigated long-term (over 100 years) tree-ring width (TRW) variabilities as well as short-term (10 years) variations in net ecosystem productivity (NEP) in response to climate to assess the driving factors for stem growth of Norway spruce in a subalpine forest at Davos in Switzerland. A tree-ring width index (TRWi) chronology for the period from 1750 to 2006 was constructed and linked with climate data from 1876 to 2006, and with NEP available for the period from 1997 to 2006. Based on TRWi, we found that only two out of the 257 years exhibited extreme negative TRWi, compared to 29 years with extreme positive anomalies, observed mainly in recent decades. Annual temperature, annual precipitation, as well as autumn and winter temperature signals were well preserved in the TRWi chronology over the last 130 years. Spring temperatures became increasingly relevant for TRWi, explaining less than 1 % of the variation in TRWi for the period from 1876 to 2006, but 8 % for the period from 1950 to 2006 (p = 0.032), and even 47 % for 1997–2006 (p = 0.028). We also observed a strong positive relationship between annual TRWi and annual NEP (r = 0.661; p = 0.037), both strongly related to spring temperatures (r = 0.687 and r = 0.678 for TRWi and NEP, respectively; p = 0.028; p = 0.032). Moreover, we found strong links between monthly NEP of March and annual TRWi (r = 0.912; p = 0.0001), both related to March temperatures (r = 0.767, p = 0.010 and r = 0.724, p = 0.018, respectively). Thus, under future climate warming, we expect stem growth of these subalpine trees and also ecosystem carbon (C) sequestration to increase, as long as water does not become a limiting factor.     

Anterograde and Retrograde Regulation of Nuclear Genes Encoding Mitochondrial Proteins during Growth,Development, and Stress

Mitochondrial biogenesis and function in plants require the expression of over 1000 nuclear genes encoding mitochondrial proteins （NGEMPs）. The expression of these genes is regulated by tissue-specific, developmental, internal, and external stimuli that result in a dynamic organelle involved in both metabolic and a variety of signaling processes. Although the metabolic and biosynthetic machinery of mitochondria is relatively well understood, the factors that regu- late these processes and the various signaling pathways involved are only beginning to be identified at a molecular level. The molecular components of anterograde （nuclear to mitochondrial） and retrograde （mitochondrial to nuclear） signaling pathways that regulate the expression of NGEMPs interact with chloroplast-, growth-, and stress-signaling pathways in the cell at a variety of levels, with common components involved in transmission and execution of these signals. This positions mitochondria as important hubs for signaling in the cell, not only in direct signaling of mitochondrial function per se, but also in sensing and/or integrating a variety of other internal and external signals. This integrates and optimizes growth with energy metabolism and stress responses, which is required in both photosynthetic and non-photosynthetic cells.     

SSRIs Increase Risk of Blood Transfusion in Patients Admitted for Hip Surgery

Background

Recent studies have shown that an increased bleeding tendency can be caused by Selective Serotonin Reuptake Inhibitors (SSRI) use. We aimed to investigate the occurrence and risk of blood transfusion in SSRI users compared to non-SSRI users in a cohort of patients admitted for hip-surgery.

Methods

We conducted a retrospective cohort study of patients who underwent planned or emergency hip surgery from 1996 to 2011 in the Academic Medical Center in Amsterdam. Primary outcome measure was risk of blood transfusion. Secondary outcome measures were pre- and postoperative hemoglobin level. Multivariate logistic regression was used to adjust for potential confounders.

Results

One-hundred and fourteen SSRI users were compared to 1773 non-SSRI users. Risk of blood transfusion during admission was increased for SSRI users in multivariate analyses (OR 1.7 [95% CI 1.1–2.5]). Also, pre-operative hemoglobin levels were lower in SSRI users (7.8±1.0 mmol/L) compared to non-SSRI users (8.0±1.0 mmol/L) (p = 0.042)), as were postoperative hemoglobin levels (6.2±1.0 mmol/L vs. 6.4±1.0 mmol/L respectively) (p = 0.017)).

Conclusions

SSRI users undergoing hip surgery have an increased risk for blood transfusion during admission, potentially explained by a lower hemoglobin level before surgery. SSRI use should be considered as a potential risk indicator for increased blood loss in patients admitted for hip surgery. These results need to be confirmed in a prospective study.