Genetic Predisposition to Bleeding during Oral Anticoagulant Therapy: Evidence for Common Founder Mutations (FIXVal-10 and FIXThr-10) and an Independent CpG Hotspot Mutation (FIXThr-10)

The recent discovery of five patients with coumarin sensitive FIX-variants due to a missense mutation in the FIX propeptide, either Ala-10Val or Ala-10Thr, has highlighted a novel type of genetic predisposition to bleeding during oral anticoagulant therapy (OAT). In the present study, we report six additional patients with such FIX variants. Haplotype analysis of FIX polymorphisms revealed a founder effect in the five German and Swiss patients with the Val-10 variant. Also, four Thr-10 variants detected in Germany, Switzerland and Great Britain derived from a common founder. Two Thr-10 variants from USA showed an independent de novo origin at a CpG dinucleotide that in general represents a mutation hotspot. These findings implicate the existence of additional subjects with corresponding variants in the populations of various countries. Even though the rare occurrence of these variants does not justify a general aPTT screening during OAT, it is recommended to monitor each bleeding event during OAT in males in order to exclude a genetic predisposition to bleeding by means of the following testing strategy: a) aPTT-testing in each bleeding complication of male patients during OAT, b) if aPTT is disproportionately prolonged, determination of FIX:C, and c) if FIX:C is disproportionately decreased as compared to FII:C, FVII:C and FX:C, sequencing of exon 2 of the FIX gene. This strategy will provide a cost-effective and safe procedure to identify patients that carry the FIX variants. Moreover, such a strategy accumulates data about the prevalence of these FIX mutations in a given population.

The natural history of internalizing behaviours from adolescence to emerging adulthood: findings from the Australian Temperament Project

BACKGROUND

The aims of the study were to describe the patterning and persistence of anxiety and depressive symptoms from adolescence to young adulthood and to examine long-term developmental relationships with earlier patterns of internalizing behaviours in childhood.

METHOD

We used parallel processes latent growth curve modelling to build trajectories of internalizing from adolescence to adulthood, using seven waves of follow-ups (ages 11-27 years) from 1406 participants of the Australian Temperament Project. We then used latent factors to capture the stability of maternal reported child internalizing symptoms across three waves of early childhood follow-ups (ages 5, 7 and 9 years), and examined relationships among these patterns of symptoms across the three developmental periods, adjusting for gender and socio-economic status.

RESULTS

We observed strong continuity in depressive symptoms from adolescence to young adulthood. In contrast, adolescent anxiety was not persistent across the same period, nor was it related to later depressive symptoms. Anxiety was, however, related to non-specific stress in young adulthood, but only moderately so. Although childhood internalizing was related to adolescent and adult profiles, the associations were weak and indirect by adulthood, suggesting that other factors are important in the development of internalizing symptoms.

CONCLUSIONS

Once established, adolescent depressive symptoms are not only strongly persistent, but also have the potential to differentiate into anxiety in young adulthood. Relationships with childhood internalizing symptoms are weak, suggesting that early adolescence may be an important period for targeted intervention, but also that further research into the childhood origins of internalizing behaviours is needed.

Exopolysaccharide biosynthetic glycoside hydrolases can be utilized to disrupt and prevent Pseudomonas aeruginosa biofilms

Bacterial biofilms present a significant medical challenge because they are recalcitrant to current therapeutic regimes. A key component of biofilm formation in the opportunistic human pathogen Pseudomonas aeruginosa is the biosynthesis of the exopolysaccharides Pel and Psl, which are involved in the formation and maintenance of the structural biofilm scaffold and protection against antimicrobials and host defenses. Given that the glycoside hydrolases PelAh and PslGh encoded in the pel and psl biosynthetic operons, respectively, are utilized for in vivo exopolysaccharide processing, we reasoned that these would provide specificity to target P. aeruginosa biofilms. Evaluating these enzymes as potential therapeutics, we demonstrate that these glycoside hydrolases selectively target and degrade the exopolysaccharide component of the biofilm matrix. PelAh and PslGh inhibit biofilm formation over a 24-hour period with a half maximal effective concentration (EC50) of 69.3 ± 1.2 and 4.1 ± 1.1 nM, respectively, and are capable of disrupting preexisting biofilms in 1 hour with EC50 of 35.7 ± 1.1 and 12.9 ± 1.1 nM, respectively. This treatment was effective against clinical and environmental P. aeruginosa isolates and reduced biofilm biomass by 58 to 94%. These noncytotoxic enzymes potentiated antibiotics because the addition of either enzyme to a sublethal concentration of colistin reduced viable bacterial counts by 2.5 orders of magnitude when used either prophylactically or on established 24-hour biofilms. In addition, PelAh was able to increase neutrophil killing by ~50%. This work illustrates the feasibility and benefits of using bacterial exopolysaccharide biosynthetic glycoside hydrolases to develop novel antibiofilm therapeutics.

A single blind randomised controlled trial of the impact on patient-reported pain of arm elevation versus exsanguination prior to tourniquet inflation

AIMS

The aim of this study was to compare the pain caused by the application of a tourniquet after exsanguination of the upper limb with that occurring after simple elevation.

PATIENTS AND METHODS

We used 26 healthy volunteers (52 arms), each of whom acted as their own matched control. The primary outcome measure was the total pain experienced by each volunteer while the tourniquet was inflated for 20 minutes. This was calculated as the area under the pain curve for each individual subject. Secondary outcomes were pain at each time point; the total pain experienced during the recovery phase; the ability to tolerate the tourniquet and the time for full recovery after deflation of the tourniquet.

RESULTS

There was a significant difference in the area under the pain curves in favour of exsanguination (mean difference 8.4; 95% confidence interval (CI) 3.0 to 13.7, p = 0.004). There was no difference between the dominant and non-dominant arms (mean difference -0.2; 95% CI -23.2 to 22.8, p = 0.99). The area under both recovery curves were similar (mean difference 0.7; 95% CI -6.0 to 4.6, p = 0.78). There was no statistical difference in recovery time, the actual mean difference being 30 seconds longer in the elevation group (p = 0.06).

CONCLUSION

Many orthopaedic and plastic surgery procedures are done under local anaesthetic or regional block where a bloodless field and a motionless patient are essential. Optimising patient comfort during surgery with the tourniquet inflated is thus a priority. This study is useful in that it compares two common methods of preparation of the upper limb prior to tourniquet inflation and which have not previously been compared in this context. Following on the results of this study, we can confidently conclude that exsanguinating the upper limb before inflating a tourniquet is more comfortable than simply elevating the arm for patients undergoing a procedure under local or regional block, both during the procedure and in the recovery phase.

TAKE HOME MESSAGE

Exsanguination rather than elevation is recommended in order to minimise patient discomfort and optimise the surgical field.

Thrombomodulin Expression in Tissues From Dogs With Systemic Inflammatory Disease

Thrombomodulin (TM) is a membrane glycoprotein expressed on endothelial cells, which plays a major role in the protein C anticoagulation pathway. In people with inflammation, TM expression can be down-regulated on endothelial cells and a soluble form released into circulation, resulting in increased risk of thrombosis and disseminated intravascular coagulation. TM is present in dogs; however, there has been minimal investigation of its expression in canine tissues, and the effects of inflammation on TM expression in canine tissues have not been investigated. The objective of this study was to evaluate endothelial TM expression in tissues from dogs with systemic inflammatory diseases. A retrospective evaluation of tissue samples of lung, spleen, and liver from dogs with and without systemic inflammatory diseases was performed using immunohistochemistry (IHC) and a modified manual IHC scoring system. TM expression was significantly reduced in all examined tissues in dogs diagnosed with septic peritonitis or acute pancreatitis.

Progressive radiolucent lines following the implantation of the cemented Rimfit acetabular component in total hip arthroplasty using the rimcutter technique: cause for concern?

AIMS

The highly cross-linked polyethylene Exeter RimFit flanged cemented acetabular component was introduced in the United Kingdom in 2010. This study aimed to examine the rates of emergence of radiolucent lines observed when the Rimfit acetabular component was implanted at total hip arthroplasty (THA) using two different techniques: firstly, the 'rimcutter' technique in which the flange sits on a pre-prepared acetabular rim; and secondly, the 'trimmed flange' technique in which the flange is trimmed and the acetabular component is seated inside the rim of the acetabulum.

PATIENTS AND METHODS

The radiographs of 150 THAs (75 'rimcutter', 75 'trimmed flange') involving this component were evaluated to assess for radiolucencies at the cement/bone interface by three observers.

RESULTS

Rimfit acetabular components implanted using the rimcutter technique had significantly higher rates of radiolucency than those introduced using the 'trimmed flange' technique one year post-operatively (one zone: 63/75 (84%) vs 17/75 (23%); two zones 42/75 (56%) vs 0/75 (0%); all three zones 17/75 (23%) vs 0/75 (0%):(all p < 0.001).

CONCLUSION

On the basis of these findings, we have stopped using the 'rimcutter' technique when implanting the Rimfit acetabular component and have reverted to the 'trimmed flange' technique.

TAKE HOME MESSAGE

Surgeons should be vigilant of the performance of the Rimfit acetabular component when used alongside the rim cutter device due to an observed higher rate of progressive radiolucencies with this combination of component / technique.

Characterization of the Pseudomonas aeruginosa Glycoside Hydrolase PslG Reveals That Its Levels Are Critical for Psl Polysaccharide Biosynthesis and Biofilm Formation

A key component of colonization, biofilm formation, and protection of the opportunistic human pathogen Pseudomonas aeruginosa is the biosynthesis of the exopolysaccharide Psl. Composed of a pentameric repeating unit of mannose, glucose, and rhamnose, the biosynthesis of Psl is proposed to occur via a Wzx/Wzy-dependent mechanism. Previous genetic studies have shown that the putative glycoside hydrolase PslG is essential for Psl biosynthesis. To understand the function of this protein, the apo-structure of the periplasmic domain of PslG (PslG(31-442)) and its complex with mannose were determined to 2.0 and 1.9 Å resolution, respectively. Despite a domain architecture and positioning of catalytic residues similar to those of other family 39 glycoside hydrolases, PslG(31-442) exhibits a unique 32-Å-long active site groove that is distinct from other structurally characterized family members. PslG formed a complex with two mannose monosaccharides in this groove, consistent with binding data obtained from intrinsic tryptophan fluorescence. PslG was able to catalyze the hydrolysis of surface-associated Psl, and this activity was abolished in a E165Q/E276Q double catalytic variant. Surprisingly, P. aeruginosa variants with these chromosomal mutations as well as a pslG deletion mutant were still capable of forming Psl biofilms. However, overexpression of PslG in a pslG deletion background impaired biofilm formation and resulted in less surface-associated Psl, suggesting that regulation of this enzyme is important during polysaccharide biosynthesis.

Sph3 Is a Glycoside Hydrolase Required for the Biosynthesis of Galactosaminogalactan in Aspergillus fumigatus

Aspergillus fumigatus is the most virulent species within the Aspergillus genus and causes invasive infections with high mortality rates. The exopolysaccharide galactosaminogalactan (GAG) contributes to the virulence of A. fumigatus. A co-regulated five-gene cluster has been identified and proposed to encode the proteins required for GAG biosynthesis. One of these genes, sph3, is predicted to encode a protein belonging to the spherulin 4 family, a protein family with no known function. Construction of an sph3-deficient mutant demonstrated that the gene is necessary for GAG production. To determine the role of Sph3 in GAG biosynthesis, we determined the structure of Aspergillus clavatus Sph3 to 1.25 Å. The structure revealed a (β/α)8 fold, with similarities to glycoside hydrolase families 18, 27, and 84. Recombinant Sph3 displayed hydrolytic activity against both purified and cell wall-associated GAG. Structural and sequence alignments identified three conserved acidic residues, Asp-166, Glu-167, and Glu-222, that are located within the putative active site groove. In vitro and in vivo mutagenesis analysis demonstrated that all three residues are important for activity. Variants of Asp-166 yielded the greatest decrease in activity suggesting a role in catalysis. This work shows that Sph3 is a glycoside hydrolase essential for GAG production and defines a new glycoside hydrolase family, GH135.

Evaluation of a point-of-care blood test for identification of Ebola virus disease at Ebola holding units, Western Area, Sierra Leone, January to February 2015

Current Ebola virus disease (EVD) diagnosis relies on reverse transcription-PCR (RT-PCR) technology, requiring skilled laboratory personnel and technical infrastructure. Lack of laboratory diagnostic capacity has led to diagnostic delays in the current West African EVD outbreak of 2014 and 2015, compromising outbreak control. We evaluated the diagnostic accuracy of the EVD bedside rapid diagnostic antigen test (RDT) developed by the United Kingdom's Defence Science and Technology Laboratory, compared with Ebola virus RT-PCR, in an operational setting for EVD diagnosis of suspected cases admitted to Ebola holding units in the Western Area of Sierra Leone. From 22 January to 16 February 2015, 138 participants were enrolled. EVD prevalence was 11.5%. All EVD cases were identified by a positive RDT with a test line score of 6 or more, giving a sensitivity of 100% (95% confidence interval (CI): 78.2-100). The corresponding specificity was high (96.6%, 95% CI: 91.3-99.1). The positive and negative predictive values for the population prevalence were 79.0% (95% CI: 54.4-93.8) and 100% (95% CI: 96.7-100), respectively. These results, if confirmed in a larger study, suggest that this RDT could be used as a 'rule-out' screening test for EVD to improve rapid case identification and resource allocation.

P. aeruginosa SGNH hydrolase-like proteins AlgJ and AlgX have similar topology but separate and distinct roles in alginate acetylation

The O-acetylation of polysaccharides is a common modification used by pathogenic organisms to protect against external forces. Pseudomonas aeruginosa secretes the anionic, O-acetylated exopolysaccharide alginate during chronic infection in the lungs of cystic fibrosis patients to form the major constituent of a protective biofilm matrix. Four proteins have been implicated in the O-acetylation of alginate, AlgIJF and AlgX. To probe the biological function of AlgJ, we determined its structure to 1.83 Å resolution. AlgJ is a SGNH hydrolase-like protein, which while structurally similar to the N-terminal domain of AlgX exhibits a distinctly different electrostatic surface potential. Consistent with other SGNH hydrolases, we identified a conserved catalytic triad composed of D190, H192 and S288 and demonstrated that AlgJ exhibits acetylesterase activity in vitro. Residues in the AlgJ signature motifs were found to form an extensive network of interactions that are critical for O-acetylation of alginate in vivo. Using two different electrospray ionization mass spectrometry (ESI-MS) assays we compared the abilities of AlgJ and AlgX to bind and acetylate alginate. Binding studies using defined length polymannuronic acid revealed that AlgJ exhibits either weak or no detectable polymer binding while AlgX binds polymannuronic acid specifically in a length-dependent manner. Additionally, AlgX was capable of utilizing the surrogate acetyl-donor 4-nitrophenyl acetate to catalyze the O-acetylation of polymannuronic acid. Our results, combined with previously published in vivo data, suggest that the annotated O-acetyltransferases AlgJ and AlgX have separate and distinct roles in O-acetylation. Our refined model for alginate acetylation places AlgX as the terminal acetlytransferase and provides a rationale for the variability in the number of proteins required for polysaccharide O-acetylation.

Bacteria utilize many defense strategies to protect themselves against external forces. One mechanism used by the bacterium Pseudomonas aeruginosa is the production of the long sugar polymer alginate. The bacteria use this polymer to form a biofilm – a barrier to protect against antibiotics and the host immune response. During its biosynthesis alginate undergoes a chemical modification whereby acetate is added to the polymer. Acetylation of alginate is important as this modification makes the bacterial biofilm less susceptible to recognition and clearance by the host immune system. In this paper we present the atomic structure of AlgJ; one of four proteins required for O-acetylation of the polymer. AlgJ is structurally similar to AlgX, which we have shown previously is also required for alginate acetylation. To understand why both enzymes are required for O-acetylation we functionally characterized the proteins and found that although AlgJ exhibits acetylesterase activity – catalyzing the removal of acetyl groups from a surrogate substrate – it does not bind to short mannuornic acid polymers. In contrast, AlgX bound alginate in a length-dependent manner and was capable of transfering acetate from a surrogate substrate onto alginate. This has allowed us to not only understand how acetate is added to alginate, but increases our understanding of how acetate is added to other bacterial sugar polymers.

Processed foods and the nutrition transition: evidence from Asia

This paper elucidates the role of processed foods and beverages in the 'nutrition transition' underway in Asia. Processed foods tend to be high in nutrients associated with obesity and diet-related non-communicable diseases: refined sugar, salt, saturated and trans-fats. This paper identifies the most significant 'product vectors' for these nutrients and describes changes in their consumption in a selection of Asian countries. Sugar, salt and fat consumption from processed foods has plateaued in high-income countries, but has rapidly increased in the lower-middle and upper-middle-income countries. Relative to sugar and salt, fat consumption in the upper-middle- and lower-middle-income countries is converging most rapidly with that of high-income countries. Carbonated soft drinks, baked goods, and oils and fats are the most significant vectors for sugar, salt and fat respectively. At the regional level there appears to be convergence in consumption patterns of processed foods, but country-level divergences including high levels of consumption of oils and fats in Malaysia, and soft drinks in the Philippines and Thailand. This analysis suggests that more action is needed by policy-makers to prevent or mitigate processed food consumption. Comprehensive policy and regulatory approaches are most likely to be effective in achieving these goals.

Clinical trial networks in orthopaedic surgery

The aim of this study was to review the role of clinical trial networks in orthopaedic surgery. A total of two electronic databases (MEDLINE and EMBASE) were searched from inception to September 2013 with no language restrictions. Articles related to randomised controlled trials (RCTs), research networks and orthopaedic research, were identified and reviewed. The usefulness of trainee-led research collaborations is reported and our knowledge of current clinical trial infrastructure further supplements the review. Searching yielded 818 titles and abstracts, of which 12 were suitable for this review. Results are summarised and presented narratively under the following headings: 1) identifying clinically relevant research questions; 2) education and training; 3) conduct of multicentre RCTs and 4) dissemination and adoption of trial results. This review confirms growing international awareness of the important role research networks play in supporting trials in orthopaedic surgery. Multidisciplinary collaboration and adequate investment in trial infrastructure are crucial for successful delivery of RCTs.

Cite this article: Bone Joint Res 2014;3:169–74.

How do anaesthetists in New Zealand disseminate critical airway information?

The communication of information concerning patients with difficult airways is universally recognised as an important component in avoiding future airway management difficulties. A range of options is available to impart this information; little is known however, about the follow-up patterns of anaesthetists following the identification and management of a difficult airway. In this study, 158 anaesthetists were contacted and asked to comment on their follow-up patterns regarding a number of difficult airway scenarios. This was followed by a retrospective survey of 124 patients with known difficult airways. A wide discrepancy was found between stated follow-up preferences by anaesthetists and the actual use of options such as postoperative visits, notes in the clinical record, letters to the patient and family doctor, and entries in hospital, national and MedicAlert™ databases. Of the patients with an airway difficulty noted on their anaesthetic record, only 14% of them also had a pertinent comment on their clinical record; even fewer were referred to hospital warning systems (12%) or national (6%) and MedicAlert (7%) databases. Comments from our survey were critical of multiple difficult airway databases and alert systems, which are not linked and do not lead automatically to a single source of information. We suggest that a custom-designed MedicAlert New Zealand difficult airway/intubation registry could be established, with easy access for medical practitioners and patients. This registry could be accessed through the National Health Index database and linked to the MedicAlert international registry and their nine international affiliates.

Structural and functional characterization of Pseudomonas aeruginosa AlgX: role of AlgX in alginate acetylation

The exopolysaccharide alginate, produced by mucoid Pseudomonas aeruginosa in the lungs of cystic fibrosis patients, undergoes two different chemical modifications as it is synthesized that alter the properties of the polymer and hence the biofilm. One modification, acetylation, causes the cells in the biofilm to adhere better to lung epithelium, form microcolonies, and resist the effects of the host immune system and/or antibiotics. Alginate biosynthesis requires 12 proteins encoded by the algD operon, including AlgX, and although this protein is essential for polymer production, its exact role is unknown. In this study, we present the X-ray crystal structure of AlgX at 2.15 Å resolution. The structure reveals that AlgX is a two-domain protein, with an N-terminal domain with structural homology to members of the SGNH hydrolase superfamily and a C-terminal carbohydrate-binding module. A number of residues in the carbohydrate-binding module form a substrate recognition "pinch point" that we propose aids in alginate binding and orientation. Although the topology of the N-terminal domain deviates from canonical SGNH hydrolases, the residues that constitute the Ser-His-Asp catalytic triad characteristic of this family are structurally conserved. In vivo studies reveal that site-specific mutation of these residues results in non-acetylated alginate. This catalytic triad is also required for acetylesterase activity in vitro. Our data suggest that not only does AlgX protect the polymer as it passages through the periplasm but that it also plays a role in alginate acetylation. Our results provide the first structural insight for a wide group of closely related bacterial polysaccharide acetyltransferases.