Pathologic Peri-Implant Proximal Femur Fracture: Takeaways from Our Experience.

Pathologic fractures of the distal femur secondary to bone metastases are not as common as those in the proximal femur, and they are rarely reported on in the literature. Even in the absence of current metastatic lesions in the femoral neck, traditional orthopaedic teaching has stressed the importance of protecting the entire femur, while recent studies have shown that it may not be necessary to stabilize the entire femur in the event of future metastases. Thus, there is no consensus regarding optimal surgical treatment, making the choice of fixation often based on the experience of the surgeon. In this paper, we reported on a patient who presented with a pathologic fracture of the distal femur who was stabilized with a retrograde intramedullary nail and then subsequently suffered a pathologic fracture of the proximal femur. To our knowledge, there have been no cases reported on a peri-implant pathologic fracture proximal to a retrograde intramedullary nail in the setting of metastatic bone disease. We would like to share our experience on how to surgically manage this and discuss the literature around management of distal femoral bone metastases.

Intelligent design: stablecoins (in)stability and collateral during market turbulence.

How does stablecoin design affect market behavior during turbulent periods? Stablecoins attempt to maintain a "stable" peg to the US dollar, but do so with widely varying structural designs. The spectacular collapse of the TerraUSD (UST) stablecoin and the linked Terra (LUNA) token in May 2022 precipitated a series of reactions across major stablecoins, with some experiencing a fall in value and others gaining value. Using a Baba, Engle, Kraft and Kroner (1990) (BEKK) model, we examine the reaction to this exogenous shock and find significant contagion effects from the UST collapse, likely partially due to herding behavior among traders. We test the varying reactions among stablecoins and find that stablecoin design differences affect the direction, magnitude, and duration of the response to shocks. We discuss the implications for stablecoin developers, exchanges, traders, and regulators.

Study Quality and Patient Inclusion in Geriatric Orthopaedic Trauma Research: A Scoping Review.

OBJECTIVES: To evaluate the quality of evidence published in geriatric traumatology, to investigate how many studies include patients with cognitive impairment, and to investigate which methods are used to determine cognitive impairment. DATA SOURCES: A search was conducted in PubMed for all publications in English in 154 selected journals between 01/01/2017 and 01/01/2020. STUDY SELECTION: Clinical studies investigating patients 65 years of age and older with fractures in the appendicular skeleton or pelvis were included. DATA EXTRACTION: Two independent reviewers performed full-text screening and data extraction for all articles. DATA SYNTHESIS: A comparative analysis was performed for prospective cohort studies and RCTs. The results are discussed in a narrative review. CONCLUSIONS: A total of 2711 publications were screened for eligibility, and after exclusion, a total of 723 articles were included. There is a focus on retrospective studies investigating mortality and complications. Studies are often small in sample size, and there are relatively few prospective studies, RCT studies, patient-reported outcomes, and quality of life. Patients with cognitive impairment are selectively excluded from clinical studies, and no consensus exists on how cognitive impairment is diagnosed. This review identified pitfalls and provides recommendations to navigate these issues for future studies. Many studies exclude cognitively impaired patients, which may result in selection bias and inability to extrapolate results. The lack of use of objective measures to define cognitive impairment and lack appropriate outcome measures for the cognitively impaired is an important issue that needs to be addressed in future research.

Specific Nucleic AcId Ligation for the detection of Schistosomes: SNAILS.

Schistosomiasis, also known as bilharzia or snail fever, is a debilitating neglected tropical disease (NTD), caused by parasitic trematode flatworms of the genus Schistosoma, that has an annual mortality rate of 280,000 people in sub-Saharan Africa alone. Schistosomiasis is transmitted via contact with water bodies that are home to the intermediate host snail which shed the infective cercariae into the water. Schistosome lifecycles are complex, and while not all schistosome species cause human disease, endemic regions also typically feature animal-infecting schistosomes that can have broader economic and/or food security implications. Therefore, the development of species-specific Schistosoma detection technologies may help to inform evidence-based local environmental, food security and health systems policy making. Crucially, schistosomiasis disproportionally affects low- and middle-income (LMIC) countries and for that reason, environmental screening of water bodies for schistosomes may aid with the targeting of water, sanitation, and hygiene (WASH) interventions and preventive chemotherapy to regions at highest risk of schistosomiasis transmission, and to monitor the effectiveness of such interventions at reducing the risk over time. To this end, we developed a DNA-based biosensor termed Specific Nucleic AcId Ligation for the detection of Schistosomes or 'SNAILS'. Here we show that 'SNAILS' enables species-specific detection from genomic DNA (gDNA) samples that were collected from the field in endemic areas.

Addressing Gender Disparity: Increase in Female Leadership Increases Gender Equality in Program Director and Fellow Ranks.

INTRODUCTION: Women make up 15% of the total number of practicing gastroenterology (GI) physicians in the US. Despite this disparity, only 33% of the current GI fellows are female. Increasing female GIs is a major goal of all four GI societies. It is known that gender disparity exists in the field of gastroenterology, and women are underrepresented in the leadership ranks and trainee level at academic programs. Whether an increase in female leadership in academic medicine is associated with an increase in female program directors and trainees is unknown. The aim of this study was to assess this relationship in GI. MATERIALS AND METHODS: Data were collected via a standardized protocol from all 173 US gastroenterology fellowship programs up until October 2018 from program websites and supplemented by online surveys completed by program coordinators. Any missing information was collected by calling the program coordinators. Data were collected on gender and academic rank of the program director, associate program director, division chief, chair of medicine, program size, academic center affiliation, number, and academic rank of female faculty and geographic region. The association was assessed using a Chi-square test or independent samples t test. RESULTS: In leadership positions, men were listed as comprising 86% of chairs, 82% of division chiefs, 76% of program directors and 63% of associate program directors. Forty-three percent of programs did not have female representation at any leadership level. The presence of a female program director or female associate program director was associated with an increase in the number of female fellows (4.03 vs 3.20; p = 0.076; 4.26 vs 3.36; p = 0.041), respectively. Overall, the presence of a female in any leadership position led to an increase in the number of female fellows (4.04 females vs 2.87 females; p = 0.007) enrolled in a program. If a GI division chief was male, the program director was more likely to be male as well (81% male vs. 18.8% female). Conversely, having a female division chief was likely to lead to a more equitable program director representation, 54% female to 48% male (p value < 0.0001, OR 5.03 95% CI 2.04-12.3). Furthermore, if either the internal medicine department chair or GI chief was female, the proportion of female program directors increased to 41% as compared to 19% if both were male (p value < 0.0001, OR 2.99 95% CI 1.34-6.6). CONCLUSION: Women are significantly underrepresented in the number of practicing gastroenterologists, at all levels of leadership in GI fellowship programs, and at the fellow level. Increasing the number of women in fellowship leadership positions is associated with an increase in female program directors and trainees. Per our knowledge, this is the first study to examine the relationship between female leadership in fellowship programs and the gender of trainees. Increasing female representation in leadership positions would not only address current gender disparity, but it may also increase the number of female future GI trainees.

Biological Materials: The Next Frontier for Cell-Free Synthetic Biology.

Advancements in cell-free synthetic biology are enabling innovations in sustainable biomanufacturing, that may ultimately shift the global manufacturing paradigm toward localized and ecologically harmonized production processes. Cell-free synthetic biology strategies have been developed for the bioproduction of fine chemicals, biofuels and biological materials. Cell-free workflows typically utilize combinations of purified enzymes, cell extracts for biotransformation or cell-free protein synthesis reactions, to assemble and characterize biosynthetic pathways. Importantly, cell-free reactions can combine the advantages of chemical engineering with metabolic engineering, through the direct addition of co-factors, substrates and chemicals -including those that are cytotoxic. Cell-free synthetic biology is also amenable to automatable design cycles through which an array of biological materials and their underpinning biosynthetic pathways can be tested and optimized in parallel. Whilst challenges still remain, recent convergences between the materials sciences and these advancements in cell-free synthetic biology enable new frontiers for materials research.

Determining the viability of Schistosoma mansoni cercariae using fluorescence assays: An application for water treatment.

BACKGROUND: Schistosome cercariae are the human-infectious stage of the Schistosoma parasite. They are shed by snail intermediate hosts living in freshwater, and penetrate the skin of the human host to develop into schistosomes, resulting in schistosomiasis infection. Water treatment (e.g. filtration or chlorination) is one way of cutting disease transmission; it kills or removes cercariae to provide safe water for people to use for activities such as bathing or laundry as an alternative to infested lakes or rivers. At present, there is no standard method for assessing the effectiveness of water treatment processes on cercariae. Examining cercarial movement under a microscope is the most common method, yet it is subjective and time-consuming. Hence, there is a need to develop and verify accurate, high-throughput assays for quantifying cercarial viability. METHOD: We tested two fluorescence assays for their ability to accurately determine cercarial viability in water samples, using S. mansoni cercariae released from infected snails in the Schistosomiasis Collection at the Natural History Museum, London. These assays consist of dual stains, namely a vital and non-vital dye; fluorescein diacetate (FDA) and Hoechst, and FDA and Propidium Iodide. We also compared the results of the fluorescence assays to the viability determined by microscopy. CONCLUSION: Both fluorescence assays can detect the viability of cercariae to an accuracy of at least 92.2% ± 6.3%. Comparing the assays to microscopy, no statistically significant difference was found between the method's viability results. However, the fluorescence assays are less subjective and less time-consuming than microscopy, and therefore present a promising method for quantifying the viability of schistosome cercariae in water samples.

Transition-Metal-Functionalized DNA Double-Crossover Tiles: Enhanced Stability and Chirality Transfer to Metal Centers.

The double crossover junction (DX) is a fundamental building block for generating complex and varied structures from DNA. However, its implementation in functional devices is limited to the inherent properties of DNA itself. Here, we developed design strategies to generate the first metal-DX DNA tiles (DXM ) by site-specifically functionalizing the tile crossovers with tetrahedral binding pockets that coordinate CuI . These DX junctions bind two CuI ions independently at distinct sites, display greater thermal stability than native DX tiles upon metalation, and melt in a cooperative fashion. In addition, the right-handed helical chirality of DNA is transferred to the metal centers. Our tiles display high metal ion selectivity, such that CuII is spontaneously reduced to CuI in situ. By modifying our design over three generations of tiles, we elucidated the thermodynamic and geometric requirements for the successful assembly of DXM tiles, which have direct applicability in developing robust, stable DNA-based materials with electroactive, photoactive, and catalytic properties.

Cell-free prototyping strategies for enhancing the sustainable production of polyhydroxyalkanoates bioplastics.

The polyhydroxyalkanoates (PHAs) are microbially-produced biopolymers that could potentially be used as sustainable alternatives to oil-derived plastics. However, PHAs are currently more expensive to produce than oil-derived plastics. Therefore, more efficient production processes would be desirable. Cell-free metabolic engineering strategies have already been used to optimize several biosynthetic pathways and we envisioned that cell-free strategies could be used for optimizing PHAs biosynthetic pathways. To this end, we developed several Escherichia coli cell-free systems for in vitro prototyping PHAs biosynthetic operons, and also for screening relevant metabolite recycling enzymes. Furthermore, we customized our cell-free reactions through the addition of whey permeate, an industrial waste that has been previously used to optimize in vivo PHAs production. We found that the inclusion of an optimal concentration of whey permeate enhanced relative cell-free GFPmut3b production by approximately 50%. In cell-free transcription-translation prototyping reactions, gas chromatography-mass spectrometry quantification of cell-free 3-hydroxybutyrate (3HB) production revealed differences between the activities of the Native ΔPhaC_C319A (1.18 ± 0.39 µM), C104 ΔPhaC_C319A (4.62 ± 1.31 µM) and C101 ΔPhaC_C319A (2.65 ± 1.27 µM) phaCAB operons that were tested. Interestingly, the most active operon, C104 produced higher levels of PHAs (or PHAs monomers) than the Native phaCAB operon in both in vitro and in vivo assays. Coupled cell-free biotransformation/transcription-translation reactions produced greater yields of 3HB (32.87 ± 6.58 µM), and these reactions were also used to characterize a Clostridium propionicum Acetyl-CoA recycling enzyme. Together, these data demonstrate that cell-free approaches complement in vivo workflows for identifying additional strategies for optimizing PHAs production.

Ultrastable Gold Nanoparticles Modified by Bidentate N-Heterocyclic Carbene Ligands.

Highly stable gold nanoparticles (Au NPs) functionalized by bidentate N-heterocyclic carbene (NHC) ligands have been synthesized by top-down and bottom-up approaches. A detailed study of the effect of alkylation, denticity, and method of synthesis has led to the production of NHC-stabilized nanoparticles with higher thermal stability than bi- and tridentate thiol-protected Au NPs and than monodentate NHC-stabilized NPs. Importantly, bidentate NHC-protected NPs also displayed unprecedented stability to external thiol, which has been an unsolved problem to date with all nanoparticles. Thus, multidentate NHC ligands are an important, and as yet unrecognized, step forward for the preparation of high stability nanomaterials.

Development of a Bacillus subtilis cell-free transcription-translation system for prototyping regulatory elements.

Cell-free transcription-translation systems were originally applied towards in vitro protein production. More recently, synthetic biology is enabling these systems to be used within a systematic design context for prototyping DNA regulatory elements, genetic logic circuits and biosynthetic pathways. The Gram-positive soil bacterium, Bacillus subtilis, is an established model organism of industrial importance. To this end, we developed several B. subtilis-based cell-free systems. Our improved B. subtilis WB800N-based system was capable of producing 0.8µM GFP, which gave a ~72x fold-improvement when compared with a B. subtilis 168 cell-free system. Our improved system was applied towards the prototyping of a B. subtilis promoter library in which we engineered several promoters, derived from the wild-type Pgrac (σA) promoter, that display a range of comparable in vitro and in vivo transcriptional activities. Additionally, we demonstrate the cell-free characterisation of an inducible expression system, and the activity of a model enzyme - renilla luciferase.

Identification of a Lipoteichoic Acid Glycosyltransferase Enzyme Reveals that GW-Domain-Containing Proteins Can Be Retained in the Cell Wall of Listeria monocytogenes in the Absence of Lipoteichoic Acid or Its Modifications.

UNLABELLED: Listeria monocytogenes is a foodborne Gram-positive bacterial pathogen, and many of its virulence factors are either secreted proteins or proteins covalently or noncovalently attached to the cell wall. Previous work has indicated that noncovalently attached proteins with GW (glycine-tryptophan) domains are retained in the cell wall by binding to the cell wall polymer lipoteichoic acid (LTA). LTA is a glycerol phosphate polymer, which is modified in L. monocytogenes with galactose and d-alanine residues. We identified Lmo0933 as the cytoplasmic glycosyltransferase required for the LTA glycosylation process and renamed the protein GtlA, for glycosyltransferase LTA A Using L. monocytogenes mutants lacking galactose or d-alanine modifications or the complete LTA polymer, we show that GW domain proteins are retained within the cell wall, indicating that other cell wall polymers are involved in the retention of GW domain proteins. Further experiments revealed peptidoglycan as the binding receptor as a purified GW domain fusion protein can bind to L. monocytogenes cells lacking wall teichoic acid (WTA) as well as purified peptidoglycan derived from a wild-type or WTA-negative strain. With this, we not only identify the first enzyme involved in the LTA glycosylation process, but we also provide new insight into the binding mechanism of noncovalently attached cell wall proteins. IMPORTANCE: Over the past 20 years, a large number of bacterial genome sequences have become available. Computational approaches are used for the genome annotation and identification of genes and encoded proteins. However, the function of many proteins is still unknown and often cannot be predicted bioinformatically. Here, we show that the previously uncharacterized Listeria monocytogenes gene lmo0933 likely codes for a glycosyltransferase required for the decoration of the cell wall polymer lipoteichoic acid (LTA) with galactose residues. Using L. monocytogenes mutants lacking LTA modifications or the complete polymer, we show that specific cell wall proteins, often associated with virulence, are retained within the cell wall, indicating that additional cell wall polymers are involved in their retention.

A forward-design approach to increase the production of poly-3-hydroxybutyrate in genetically engineered Escherichia coli.

Biopolymers, such as poly-3-hydroxybutyrate (P(3HB)) are produced as a carbon store in an array of organisms and exhibit characteristics which are similar to oil-derived plastics, yet have the added advantages of biodegradability and biocompatibility. Despite these advantages, P(3HB) production is currently more expensive than the production of oil-derived plastics, and therefore, more efficient P(3HB) production processes would be desirable. In this study, we describe the model-guided design and experimental validation of several engineered P(3HB) producing operons. In particular, we describe the characterization of a hybrid phaCAB operon that consists of a dual promoter (native and J23104) and RBS (native and B0034) design. P(3HB) production at 24 h was around six-fold higher in hybrid phaCAB engineered Escherichia coli in comparison to E. coli engineered with the native phaCAB operon from Ralstonia eutropha H16. Additionally, we describe the utilization of non-recyclable waste as a low-cost carbon source for the production of P(3HB).

Developments in the tools and methodologies of synthetic biology.

Synthetic biology is principally concerned with the rational design and engineering of biologically based parts, devices, or systems. However, biological systems are generally complex and unpredictable, and are therefore, intrinsically difficult to engineer. In order to address these fundamental challenges, synthetic biology is aiming to unify a "body of knowledge" from several foundational scientific fields, within the context of a set of engineering principles. This shift in perspective is enabling synthetic biologists to address complexity, such that robust biological systems can be designed, assembled, and tested as part of a biological design cycle. The design cycle takes a forward-design approach in which a biological system is specified, modeled, analyzed, assembled, and its functionality tested. At each stage of the design cycle, an expanding repertoire of tools is being developed. In this review, we highlight several of these tools in terms of their applications and benefits to the synthetic biology community.

Temperature dependence of electrical transport in a pressure-sensitive nanocomposite.

Printed nanocomposites are of significant application potential in numerous technologies, such as touch-sensitive sensors and surfaces. Here, temperature dependent electrical transport measurements were undertaken on a recently developed screen-printed, multicomponent, nanocomposite ink to develop a detailed understanding of the electrical transport mechanisms. A theoretical model combining contributions from linear percolative conduction and nonlinear conduction attributed to field-assisted quantum tunneling successfully describes the temperature dependent conduction observed.

Ultra stable self-assembled monolayers of N-heterocyclic carbenes on gold.

Since the first report of thiol-based self-assembled monolayers (SAMs) 30 years ago, these structures have been examined in a huge variety of applications. The oxidative and thermal instabilities of these systems are widely known, however, and are an impediment to their widespread commercial use. Here, we describe the generation of N-heterocyclic carbene (NHC)-based SAMs on gold that demonstrate considerably greater resistance to heat and chemical reagents than the thiol-based counterparts. This increased stability is related to the increased strength of the gold-carbon bond relative to that of a gold-sulfur bond, and to a different mode of bonding in the case of the carbene ligand. Once bound to gold, NHCs are not displaced by thiols or thioethers, and are stable to high temperatures, boiling water, organic solvents, pH extremes, electrochemical cycling above 0 V and 1% hydrogen peroxide. In particular, benzimidazole-derived carbenes provide films with the highest stabilities and evidence of short-range molecular ordering. Chemical derivatization can be employed to adjust the surface properties of NHC-based SAMs.

A multi-component nanocomposite screen-printed ink with non-linear touch sensitive electrical conductivity.

Printable electronics is an innovative area of technology with great commercial potential. Here, a screen-printed functional ink, comprising a combination of semiconducting acicular particles, electrically insulating nanoparticles and a base polymer ink, is described that exhibits pronounced pressure sensitive electrical properties for applications in sensing and touch sensitive surfaces. The combination of these components in the as-printed ink yield a complex structure and a large and reproducible touch pressure sensitive resistance range. In contrast to the case for some composite systems, the resistance changes occur down to applied pressures of 13 Pa. Current-voltage measurements at fixed pressures show monotonic non-linear behaviour, which becomes more Ohmic at higher pressures and in all cases shows some hysteresis. The physical basis for conduction, particularly in the low pressure regime, can be described in terms of field assisted quantum mechanical tunnelling.

Effect of clathrate hydrate formation and decomposition on NMR parameters in THF-D2O solution.

The NMR spin-lattice relaxation time (T(1)), spin-spin relaxation time (T(2)) and the diffusion coefficient D were measured for (1)H in a 1:17 mol % solution of tetrahydrofuran (THF) in D(2)O. The aim of the work was to clarify some earlier points raised regarding the utility of these measurements to convey structural information on hydrate formation and reformation. A number of irregularities in T(1) and T(2) measurements during hydrate processes reported earlier are explained in terms of the presence of interfaces and possible temperature gradients. We observe that T(1) and T(2) in solution are exactly the same before and after hydrate formation, thus confirming that the solution is isotropic. This is inconsistent with the presence of memory effects, at least those that may affect the dynamics to which T(1) and T(2) are sensitive. The measurement of the diffusion coefficient for a number of hours in the subcooled solution before nucleation proved invariant with time, again suggesting that the solution remains isotropic without affecting the guest dynamics and diffusion.

Two-enzyme systems for glycolipid and polyglycerolphosphate lipoteichoic acid synthesis in Listeria monocytogenes.

Lipoteichoic acid (LTA) is an important cell wall polymer in gram-positive bacteria and often consists a polyglycerolphosphate backbone chain that is linked to the membrane by a glycolipid. In Listeria monocytogenes this glycolipid is Gal-Glc-DAG or Gal-Ptd-6Glc-DAG. Using a bioinformatics approach, we have identified L. monocytogenes genes predicted to be involved in glycolipid (lmo2555 and lmo2554) and LTA backbone (lmo0644 and lmo0927) synthesis. LTA and glycolipid analysis of wild-type and mutant strains confirmed the function of Lmo2555 and Lmo2554 as glycosyltransferases required for the formation of Glc-DAG and Gal-Glc-DAG. Deletion of a third gene, lmo2553, located in the same operon resulted in the production of LTA with an altered structure. lmo0927 and lmo0644 encode proteins with high similarity to the staphylococcal LTA synthase LtaS, which is responsible for polyglycerolphosphate backbone synthesis. We show that both proteins are involved in LTA synthesis. Our data support a model whereby Lmo0644 acts as an LTA primase LtaP and transfers the initial glycerolphosphate onto the glycolipid anchor, and Lmo0927 functions as LTA synthase LtaS, which extends the glycerolphosphate backbone chain. Inactivation of LtaS leads to severe growth and cell division defects, underscoring the pivotal role of LTA in this gram-positive pathogen.