Invasive macroalgae in native seagrass beds: vectors of spread and impacts.

BACKGROUND AND AIMS: Worldwide, invasive species are spreading through marine systems at an unprecedented rate with both positive and negative consequences for ecosystems and the biological functioning of organisms. Human activities from shipping to habitat damage and modification are known vectors of spread, although biological interactions including epibiosis are increasingly recognized as potentially important to introduction into susceptible habitats. METHODS: We assessed a novel mechanism of spread - limpets as transporters of an invasive alga, Sargassum muticum, into beds of the seagrass Zostera marina - and the physiological impact of its invasion. The association of S. muticum with three limpet species and other habitats was assessed using intertidal surveys on rocky shores and snorkelling at two seagrass sites in the UK. A 4-year field study tested the effect of S. muticum on Z. marina shoot density, dry weight and phenolic compounds (caffeic and tannic acid) content, and a laboratory experiment tested the impact of S. muticum on nutrient partitioning (C/H/N/P/Si), photosynthetic efficiency (Fv/Fm) and growth of Z. marina. RESULTS: On rocky shores 15 % of S. muticum occurrences were attached to the shells of live limpets. In seagrass beds 5 % of S. muticum occurrences were attached to the shells of dead limpets. The remainder were attached to rock, to cobblestones, to the seagrass matrix or embedded within the sand. Z. marina density and phenolics content was lower when S. muticum co-occurred with it. Over 3 years, photosynthetic responses of Z. marina to S. muticum were idiosyncratic, and S. muticum had no effect on nutrient partitioning in Z. marina. CONCLUSIONS: Our results show limpets support S. muticum as an epibiont and may act as a previously unreported transport mechanism introducing invaders into sensitive habitats. S. muticum reduced production of phenolics in Z. marina, which may weaken its defensive capabilities and facilitate proliferation of S. muticum. The effect of S. muticum on Z. marina photosynthesis requires further work but having no effect on the capacity of Z. marina to sequester nutrients suggests a degree of resilience to this invader.

Design of an electron cyclotron emission diagnostics suite for COMPASS Upgrade tokamak.

COMPASS Upgrade is a medium size and high field tokamak that is capable of addressing key challenges for reactor grade tokamaks, including power exhaust and advanced confinement scenarios. Electron cyclotron emission will be available among the first diagnostics to provide measurements of high spatial and temporal resolution of electron temperature profiles and electron temperature fluctuation profiles through a radial view. A separate oblique view at 12° from normal will be utilized to study non-thermal electrons. Both the radial and oblique views are envisioned to be located in a wide-angle midplane port, which has dimensions that enable simultaneous hosting of the front-end of their quasi-optical (QO) designs. Each QO design will have an in situ hot calibration source in the front-end to provide standalone and calibrated Te (R,t) measurements. The conceptual design for each QO system, the Gaussian beam analysis, and the details of the diagnostic channels are presented.

Modular robotic platform for precision neurosurgery with a bio-inspired needle: System overview and first in-vivo deployment.

Over the past 10 years, minimally invasive surgery (MIS) has shown significant benefits compared to conventional surgical techniques, with reduced trauma, shorter hospital stays, and shorter patient recovery times. In neurosurgical MIS procedures, inserting a straight tool (e.g. catheter) is common practice in applications ranging from biopsy and laser ablation, to drug delivery and fluid evacuation. How to handle tissue deformation, target migration and access to deep-seated anatomical structures remain an open challenge, affecting both the preoperative planning phase and eventual surgical intervention. Here, we present the first neurosurgical platform in the literature, able to deliver an implantable steerable needle for a range of diagnostic and therapeutic applications, with a short-term focus on localised drug delivery. This work presents the system's architecture and first in vivo deployment with an optimised surgical workflow designed for pre-clinical trials with the ovine model, which demonstrate appropriate function and safe implantation.

The Specificity of ParR Binding Determines the Incompatibility of Conjugative Plasmids in Clostridium perfringens.

Plasmids that encode the same replication machinery are generally unable to coexist in the same bacterial cell. However, Clostridium perfringens strains often carry multiple conjugative toxin or antibiotic resistance plasmids that are closely related and encode similar Rep proteins. In many bacteria, plasmid partitioning upon cell division involves a ParMRC system; in C. perfringens plasmids, there are approximately 10 different ParMRC families, with significant differences in amino acid sequences between each ParM family (15% to 54% identity). Since plasmids carrying genes belonging to the same ParMRC family are not observed in the same strain, these families appear to represent the basis for plasmid compatibility in C. perfringens. To understand this process, we examined the key recognition steps between ParR DNA-binding proteins and their parC binding sites. The ParR proteins bound to sequences within a parC site from the same ParMRC family but could not interact with a parC site from a different ParMRC family. These data provide evidence that compatibility of the conjugative toxin plasmids of C. perfringens is mediated by their parMRC-like partitioning systems. This process provides a selective advantage by enabling the host bacterium to maintain separate plasmids that encode toxins that are specific for different host targets. IMPORTANCE Toxins produced by the Gram-positive pathogen Clostridium perfringens are primarily encoded by genes found on different conjugative plasmids. These plasmids encode highly similar replication proteins and therefore should be incompatible, but they are often found to coexist within the same isolate. In this study, we showed that a series of phylogenetically related ParMRC plasmid partitioning systems, structures that are normally responsible for ensuring that plasmids segregate correctly at cell division, dictate which toxin plasmid combinations can coexist within the same bacterial cell. We dissected the recognition steps between the DNA-binding ParMRC component, ParR, and the plasmid-derived centromere, parC. Our data suggested a mechanism by which plasmids encoding ParMRC systems from the same family are incompatible, whereas plasmids encoding ParMRC systems from distinct families are compatible. This work provides insight into how these cells can maintain multiple highly similar toxin plasmids, which is a critical first step in understanding how to limit the disease-causing potential of C. perfringens.

Bivalirudin as a Systemic Anticoagulant and Flush Solution Additive for Sequential Mitral and Tricuspid Valve Percutaneous Edge-to-Edge Repair in a Patient With Heparin-Induced Thrombocytopenia.

Herein the case of a patient with a prior history of heparin-induced thrombocytopenia who underwent percutaneous mitral valve edge-to-edge repair that was followed by a tricuspid edge-to-edge repair two months later is presented. Recommendations exist for systemic anticoagulant alternatives for percutaneous mitral valve edge-to-edge repair with the MitraClip device (Abbott, Chicago, IL), but minimal guidance and experience are present regarding alternative systemic anticoagulation during the performance of right-sided interventions, including tricuspid edge-to-edge repair (TriClip; Abbott). Notably, there is no clear consensus regarding the use of an alternative anticoagulant in the catheter flush solution for the delivery systems used during these procedures, particularly for right-sided interventions.

Successful Mechanical Aspiration of Embolized Vessel Fragment During TAVR With Penumbra Indigo Cat Rx Catheter.

An 81-year-old female with severe aortic valve stenosis underwent TAVR using the right femoral approach. Shortly after successful deployment of a 29 mm Evolut Pro valve (Medtronic), the patient became hypotensive and ST depressions were noted on telemetry. Selective left coronary angiography revealed coronary embolism to the left anterior descending/ first diagonal bifurcation. Mechanical aspiration was performed and a small piece of debris was retrieved. We believe it was a broken-off fragment of the femoral artery that migrated on the tip of the TAVR delivery system. This is the first reported case of such a complication.

Percutaneous Closure of Iatrogenic VSD and Paravalvular Leak: Two Complications of TAVR.

TAVR is increasingly becoming a common treatment for severe symptomatic aortic stenosis. Although there has been marked reduction in intra-procedural complications with evolution in the TAVR technology, these complications remain a challenge. We present a unique case of paravalvular leak (PVL) and iatrogenic ventricular septal defect as a result of closing attempts of PVL. We aim to highlight our procedural approach to percutaneously repair the aforementioned complications using our heart team approach for decision making.

Review of Published Cases of Syncope and Sudden Death in Patients With Severe Aortic Stenosis Documented by Electrocardiography.

The ECG findings during sudden collapse (syncope or sudden death) in severe aortic stenosis (AS) are not well defined. We conducted a comprehensive review of the literature for ECG data during sudden collapse in patients with AS and provided a case report of our own. There were 37 published cases of syncope or sudden death in patients with severe AS which were documented by ECG. Brady- or ventricular arrhythmias were documented in 34 cases (92%). Bradyarrhythmia (n = 24; 71%) was more common at the time of collapse than ventricular tachyarrhythmia (n = 10; 29%). There was slowing of the sinus rate before bradyarrhythmia in the vast majority of patients with bradyarrhythmia but not in those presenting with ventricular tachyarrhythmia (75% vs 0%; p <0.001). ECG evidence of ischemia (ST-segment depression or elevation) was present in most patients with bradyarrhythmia but not in those with ventricular tachyarrhythmia (75% vs 0%; p = 0.011). In conclusion, our findings suggest that left ventricular baroreceptor activation plays a dominant role in the pathophysiology of sudden collapse in patients with severe AS and suggest that ischemia may play a role as well.

Utility of transesophageal echocardiography to assess real time left atrial pressure changes and dynamic mitral regurgitation following placement of transseptal multistage venous cannula for systemic venous drainage and indirect left ventricular venting in venoarterial extracorporeal membrane oxygenation.

A patient with heart failure due to nonischemic cardiomyopathy presented as a transfer to our institution following peripheral (femoral) venoarterial (VA) extracorporeal membrane oxygenation (ECMO) placement. With peripheral VA ECMO cannulation, the patient continued to have unstable ventricular tachyarrhythmias. Echocardiography demonstrated left ventricular (LV) dilation and severe mitral regurgitation (MR) with clinical and chest X-ray evidence of pulmonary edema. To provide venous drainage and simultaneous decompression of the left atrium (LA) and thereby indirect LV venting, a single multistage venous cannula was placed across the inter-atrial septum (IAS) using the previously described left atrial venoarterial (LA-VA) ECMO cannulation technique. Two- and three-dimensional (3D) transesophageal echocardiography (TEE) demonstrated utility in guiding cannula placement into the appropriate position and providing real time assessment of ventricular decompression and MR severity. There was subsequent improvement in pulmonary edema. This case is thought to be the first demonstration of real time resolution of pulmonary venous flow reversal in a patient undergoing LA-VA ECMO cannulation. This demonstration offers important mechanistic insight into some of the potential benefits of such an approach.

Path Replanning for Orientation-Constrained Needle Steering.

INTRODUCTION: Needle-based neurosurgical procedures require high accuracy in catheter positioning to achieve high clinical efficacy. Significant challenges for achieving accurate targeting are (i) tissue deformation (ii) clinical obstacles along the insertion path (iii) catheter control. OBJECTIVE: We propose a novel path-replanner able to generate an obstacle-free and curvature bounded three-dimensional (3D) path at each time step during insertion, accounting for a constrained target pose and intraoperative anatomical deformation. Additionally, our solution is sufficiently fast to be used in a closed-loop system: needle tip tracking via electromagnetic sensors is used by the path-replanner to automatically guide the programmable bevel-tip needle (PBN) while surgical constraints on sensitive structures avoidance are met. METHODS: The generated path is achieved by combining the "Bubble Bending" method for online path deformation and a 3D extension of a convex optimisation method for path smoothing. RESULTS: Simulation results performed on a realistic dataset show that our replanning method can guide a PBN with bounded curvature to a predefined target pose with an average targeting error of 0.65  ± 0.46 mm in position and 3.25  ± 5.23 degrees in orientation under a deformable simulated environment. The proposed algorithm was also assessed in-vitro on a brain-like gelatin phantom, achieving a target error of 1.81  ± 0.51 mm in position and 5.9  ± 1.42 degrees in orientation. CONCLUSION: The presented work assessed the performance of a new online steerable needle path-planner able to avoid anatomical obstacles while optimizing surgical criteria. SIGNIFICANCE: This method is particularly suited for surgical procedures demanding high accuracy on the desired goal pose under tissue deformations and real-world inaccuracies.

The ever-expanding tcp conjugation locus of pCW3 from Clostridium perfringens.

The spore-forming, anaerobic Gram positive pathogen Clostridium perfringens encodes many of its disease-causing toxins on closely related conjugative plasmids. Studies of the tetracycline resistance plasmid pCW3 have identified many of the genes involved in conjugative transfer, which are located in the tcp conjugation locus. Upstream of this locus is an uncharacterised region (the cnaC region) that is highly conserved. This study examined the importance in pCW3 conjugation of several highly conserved proteins encoded in the cnaC region. Conjugative mating studies suggested that the SrtD, TcpN and Dam proteins were required for efficient pCW3 transfer between C. perfringens cells from the same strain background. The requirement of these proteins for conjugation was amplified in matings between C. perfringens cells of different strain backgrounds. Additionally, the putative collagen adhesin protein, CnaC, was only required for the optimal transfer of pCW3 between cells of different strain backgrounds. Based on these studies we postulate that CnaC, SrtD, TcpN and Dam are involved in enhancing the transfer frequency of pCW3. These studies have led to a significant expansion of the tcp conjugation locus, which now encompasses a 19 kb region.

Utility of three-dimensional transesophageal echocardiography to guide transseptal positioning of a single multistage venous cannula to provide both venous drainage and indirect left ventricular venting in veno-arterial extracorporeal membrane oxygenation.

A patient with heart failure due to dilated ischemic cardiomyopathy presented in cardiogenic shock for institution of veno-arterial extracorporeal membrane oxygenation as a bridge to cardiac transplantation. To provide adequate venous drainage and simultaneous decompression of the left atrium (indirect left ventricular venting), a single venous cannula was placed across the interatrial septum so that the distal orifice and side ports were located within the left atrium and the proximal set of side ports were positioned at the cavoatrial junction. Three-dimensional transesophageal echocardiography demonstrated utility in guiding cannula placement and appropriate positioning within the left atrium.

An Early Pandemic Analysis of SARS-CoV-2 Population Structure and Dynamics in Arizona.

In December of 2019, a novel coronavirus, SARS-CoV-2, emerged in the city of Wuhan, China, causing severe morbidity and mortality. Since then, the virus has swept across the globe, causing millions of confirmed infections and hundreds of thousands of deaths. To better understand the nature of the pandemic and the introduction and spread of the virus in Arizona, we sequenced viral genomes from clinical samples tested at the TGen North Clinical Laboratory, the Arizona Department of Health Services, and those collected as part of community surveillance projects at Arizona State University and the University of Arizona. Phylogenetic analysis of 84 genomes from across Arizona revealed a minimum of 11 distinct introductions inferred to have occurred during February and March. We show that >80% of our sequences descend from strains that were initially circulating widely in Europe but have since dominated the outbreak in the United States. In addition, we show that the first reported case of community transmission in Arizona descended from the Washington state outbreak that was discovered in late February. Notably, none of the observed transmission clusters are epidemiologically linked to the original travel-related case in the state, suggesting successful early isolation and quarantine. Finally, we use molecular clock analyses to demonstrate a lack of identifiable, widespread cryptic transmission in Arizona prior to the middle of February 2020.IMPORTANCE As the COVID-19 pandemic swept across the United States, there was great differential impact on local and regional communities. One of the earliest and hardest hit regions was in New York, while at the same time Arizona (for example) had low incidence. That situation has changed dramatically, with Arizona now having the highest rate of disease increase in the country. Understanding the roots of the pandemic during the initial months is essential as the pandemic continues and reaches new heights. Genomic analysis and phylogenetic modeling of SARS-COV-2 in Arizona can help to reconstruct population composition and predict the earliest undetected introductions. This foundational work represents the basis for future analysis and understanding as the pandemic continues.

Suprasternal Approach to Transcatheter Aortic Valve Replacement in a Complex Congenital Pediatric Patient Presenting With Cardiogenic Shock.

Transcatheter aortic valve replacement (TAVR) offers well established benefit for adults with severe aortic stenosis, although applications in the pediatric population remain limited. We describe a case of a 15-year-old male with complex congenital heart disease presenting with cardiogenic shock in the setting of mixed severe aortic stenosis (AS) and severe aortic insufficiency (AI). Self-expanding TAVR was performed via suprasternal approach with robust clinical improvement. At one month follow up, he had resolution of clinical heart failure with improvement in ejection fraction and no symptoms of valvulopathy. To our knowledge, there have been no described cases of suprasternal TAVR in a pediatric patient.

A near full-length HIV-1 genome from 1966 recovered from formalin-fixed paraffin-embedded tissue.

With very little direct biological data of HIV-1 from before the 1980s, far-reaching evolutionary and epidemiological inferences regarding the long prediscovery phase of this pandemic are based on extrapolations by phylodynamic models of HIV-1 genomic sequences gathered mostly over recent decades. Here, using a very sensitive multiplex RT-PCR assay, we screened 1,645 formalin-fixed paraffin-embedded tissue specimens collected for pathology diagnostics in Central Africa between 1958 and 1966. We report the near-complete viral genome in one HIV-1 positive specimen from Kinshasa, Democratic Republic of Congo (DRC), from 1966 ("DRC66")-a nonrecombinant sister lineage to subtype C that constitutes the oldest HIV-1 near full-length genome recovered to date. Root-to-tip plots showed the DRC66 sequence is not an outlier as would be expected if dating estimates from more recent genomes were systematically biased; and inclusion of the DRC66 sequence in tip-dated BEAST analyses did not significantly alter root and internal node age estimates based on post-1978 HIV-1 sequences. There was larger variation in divergence time estimates among datasets that were subsamples of the available HIV-1 genomes from 1978 to 2014, showing the inherent phylogenetic stochasticity across subsets of the real HIV-1 diversity. Our phylogenetic analyses date the origin of the pandemic lineage of HIV-1 to a time period around the turn of the 20th century (1881 to 1918). In conclusion, this unique archival HIV-1 sequence provides direct genomic insight into HIV-1 in 1960s DRC, and, as an ancient-DNA calibrator, it validates our understanding of HIV-1 evolutionary history.

Portable Microfluidic Biosensing System for Real-Time Analysis of Microdialysate in Transplant Kidneys.

Currently, there is a severe shortage of donor kidneys that are fit for transplantation, due in part to a lack of adequate viability assessment tools for transplant organs. This work presents the integration of a novel wireless two-channel amperometric potentiostat with microneedle-based glucose and lactate biosensors housed in a 3D printed chip to create a microfluidic biosensing system that is genuinely portable. The wireless potentiostat transmits data via Bluetooth to an Android app running on a tablet. The whole miniaturized system is fully enclosed and can be integrated with microdialysis to allow continuous monitoring of tissue metabolite levels in real time. We have also developed a wireless portable automated calibration platform so that biosensors can be calibrated away from the laboratory and in transit. As a proof of concept, we have demonstrated the use of this portable analysis system to monitor porcine kidneys for the first time from organ retrieval, through warm ischemia, transportation on ice, right through to cold preservation and reperfusion. The portable system is robust and reliable in the challenging conditions of the abattoir and during kidney transportation and can detect clear physiological changes in the organ associated with clinical interventions.

Virulence Plasmids of the Pathogenic Clostridia.

The clostridia cause a spectrum of diseases in humans and animals ranging from life-threatening tetanus and botulism, uterine infections, histotoxic infections and enteric diseases, including antibiotic-associated diarrhea, and food poisoning. The symptoms of all these diseases are the result of potent protein toxins produced by these organisms. These toxins are diverse, ranging from a multitude of pore-forming toxins to phospholipases, metalloproteases, ADP-ribosyltransferases and large glycosyltransferases. The location of the toxin genes is the unifying theme of this review because with one or two exceptions they are all located on plasmids or on bacteriophage that replicate using a plasmid-like intermediate. Some of these plasmids are distantly related whilst others share little or no similarity. Many of these toxin plasmids have been shown to be conjugative. The mobile nature of these toxin genes gives a ready explanation of how clostridial toxin genes have been so widely disseminated both within the clostridial genera as well as in the wider bacterial community.

pCP13, a representative of a new family of conjugative toxin plasmids in Clostridium perfringens.

Conjugative transfer is a major contributor to the dissemination of antibiotic resistance and virulence genes in the human and animal pathogen, Clostridium perfringens. The C. perfringens plasmid pCW3 is the archetype of an extensive family of highly related conjugative toxin and antibiotic resistance plasmids found in this bacterium. These plasmids were thought to constitute the only conjugative plasmid family in C. perfringens. Recently, another series of C. perfringens plasmids, the pCP13-like family, have been shown to harbour important toxin genes, including genes that encode the novel binary clostridial enterotoxin, BEC. Based on early bioinformatics analysis this plasmid family was thought to be non-conjugative. Here we demonstrate that pCP13 is in fact conjugative, transfers at high frequency and that the newly defined Pcp conjugation locus encodes putative homologues of a type 4 secretion system (T4SS), one of which, PcpB4, was shown to be essential for transfer. The T4SS of pCP13 also appears to be evolutionarily related to conjugative toxin plasmids from other clostridia-like species, including Paeniclostridium (formerly Clostridium) sordellii, Clostridioides (formerly Clostridium) difficile and Clostridium botulinum. Therefore, it is clear that there are two distinct families of conjugative plasmids in C. perfringens: the pCW3 family and the pCP13 family. This study has significant implications for our understanding of the movement of toxin genes both within C. perfringens, but also potentially to other pathogenic clostridia.

Clostridium sordellii Pathogenicity Locus Plasmid pCS1-1 Encodes a Novel Clostridial Conjugation Locus.

A major virulence factor in Clostridium sordellii-mediated infection is the toxin TcsL, which is encoded within a region of the genome called the pathogenicity locus (PaLoc). C. sordellii isolates carry the PaLoc on the pCS1 family of plasmids, of which there are four characterized members. Here, we determined the potential mobility of pCS1 plasmids and characterized a fifth unique pCS1 member. Using a derivative of the pCS1-1 plasmid from strain ATCC 9714 which had been marked with the ermB erythromycin resistance gene, conjugative transfer into a recipient C. sordellii isolate, R28058, was demonstrated. Bioinformatic analysis of pCS1-1 identified a novel conjugation gene cluster defined as the C. sordellii transfer (cst) locus. Interruption of genes within the cst locus resulted in loss of pCS1-1 transfer, which was restored upon complementation in trans These studies provided clear evidence that genes within the cst locus are essential for the conjugative transfer of pCS1-1. The cst locus is present on all pCS1 subtypes, and homologous loci were identified on toxin-encoding plasmids from Clostridium perfringens and Clostridium botulinum and also carried within genomes of Clostridium difficile isolates, indicating that it is a widespread clostridial conjugation locus. The results of this study have broad implications for the dissemination of toxin genes and, potentially, antibiotic resistance genes among members of a diverse range of clostridial pathogens, providing these microorganisms with a survival advantage within the infected host.IMPORTANCEC. sordellii is a bacterial pathogen that causes severe infections in humans and animals, with high mortality rates. While the pathogenesis of C. sordellii infections is not well understood, it is known that the toxin TcsL is an important virulence factor. Here, we have shown the ability of a plasmid carrying the tcsL gene to undergo conjugative transfer between distantly related strains of C. sordellii, which has far-reaching implications for the ability of C. sordellii to acquire the capacity to cause disease. Plasmids that carry tcsL encode a previously uncharacterized conjugation locus, and individual genes within this locus were shown to be required for conjugative transfer. Furthermore, homologues on toxin plasmids from other clostridial species were identified, indicating that this region represents a novel clostridial conjugation locus. The results of this study have broad implications for the dissemination of virulence genes among members of a diverse range of clostridial pathogens.