Functional mechanism study of the allelochemical myrigalone A identifies a group of ultrapotent inhibitors of ethylene biosynthesis in plants.

Allelochemicals represent a class of natural products released by plants as root, leaf, and fruit exudates that interfere with the growth and survival of neighboring plants. Understanding how allelochemicals function to regulate plant responses may provide valuable new approaches to better control plant function. One such allelochemical, Myrigalone A (MyA) produced by Myrica gale, inhibits seed germination and seedling growth through an unknown mechanism. Here, we investigate MyA using the tractable model Dictyostelium discoideum and reveal that its activity depends on the conserved homolog of the plant ethylene synthesis protein 1-aminocyclopropane-1-carboxylic acid oxidase (ACO). Furthermore, in silico modeling predicts the direct binding of MyA to ACO within the catalytic pocket. In D. discoideum, ablation of ACO mimics the MyA-dependent developmental delay, which is partially restored by exogenous ethylene, and MyA reduces ethylene production. In Arabidopsis thaliana, MyA treatment delays seed germination, and this effect is rescued by exogenous ethylene. It also mimics the effect of established ACO inhibitors on root and hypocotyl extension, blocks ethylene-dependent root hair production, and reduces ethylene production. Finally, in silico binding analyses identify a range of highly potent ethylene inhibitors that block ethylene-dependent response and reduce ethylene production in Arabidopsis. Thus, we demonstrate a molecular mechanism by which the allelochemical MyA reduces ethylene biosynthesis and identify a range of ultrapotent inhibitors of ethylene-regulated responses.

Two-Year Outcomes After Pediatric In-Office Tympanostomy Using Lidocaine/Epinephrine Iontophoresis and an Automated Tube Delivery System.

OBJECTIVE: Evaluate 2-year outcomes after lidocaine/epinephrine iontophoresis and tympanostomy using an automated tube delivery system for pediatric tube placement in-office. STUDY DESIGN: Prospective, single-arm. SETTING: Eighteen otolaryngology practices. METHODS: Children age 6 months to 12 years indicated for tympanostomy were enrolled between October 2017 and February 2019. Local anesthesia of the tympanic membrane was achieved via lidocaine/epinephrine iontophoresis and tympanostomy was completed using an automated tube delivery system (the Tula® System). An additional Lead-In cohort of patients underwent tube placement in the operating room (OR) under general anesthesia using only the tube delivery system. Patients were followed for 2 years or until tube extrusion, whichever occurred first. Otoscopy and tympanometry were performed at 3 weeks, and 6, 12, 18, and 24 months. Tube retention, patency, and safety were evaluated. RESULTS: Tubes were placed in-office for 269 patients (449 ears) and in the OR for 68 patients (131 ears) (mean age, 4.5 years). The median and mean times to tube extrusion for the combined OR and In-Office cohorts were 15.82 (95% confidence interval [CI]: 15.41-19.05) and 16.79 (95% CI: 16.16-17.42) months, respectively. Sequelae included ongoing perforation for 1.9% of ears (11/580) and medial tube displacement for 0.2% (1/580) observed at 18 months. Over a mean follow-up of 14.3 months, 30.3% (176/580) of ears had otorrhea and 14.3% (83/580) had occluded tubes. CONCLUSION: In-office pediatric tympanostomy using lidocaine/epinephrine iontophoresis and automated tube delivery results in tube retention within the ranges described for similar grommet-type tubes and complication rates consistent with traditional tube placement in the OR.

Treatment and Prevention of Cardiovascular Implantable Electronic Device (CIED) Infections.

An expanded role for cardiac implantable electronic devices (CIEDs) in recent decades reflects an aging population and broader indications for devices, including both primary prevention and management of dysrhythmias. CIED infection is one of the most important device-related complications and has a major impact on mortality, quality of life, healthcare utilization, and cost. Unfortunately, the investigation and management of CIED infection remain complex, often necessitating complete and timely removal of the device and leads in order to eradicate the infection. In addition, the translation of knowledge from an extensive literature to a disparate group of medical practitioners has often been inadequate. This review of CIED infection management highlights the significant advances made during the past decade, including diagnostic criteria, advanced imaging, and next-generation sequencing for culture-negative cases or those in which uncertainty remains. We also outline the role and indication for powered lead extraction, the process of antibiotic choice and treatment duration, considerations related to the timing and location for reimplantation, and preimplantation risk stratification and associated interventions to reduce the risk of CIED infection.

L'élargissement du rôle des dispositifs électroniques cardiaques implantables (DECI) au cours des dernières décennies reflète le vieillissement de la population et les indications plus vastes des dispositifs, notamment dans la prévention primaire et la prise en charge des dysrythmies. Les infections liées aux DECI sont l'une des plus importantes complications liées aux dispositifs et ont des conséquences majeures sur la mortalité, la qualité de vie, l'utilisation et les coûts des soins de santé. Malheureusement, le dépistage et la prise en charge des infections liées aux DECI demeurent complexes et nécessitent souvent le retrait complet et rapide du dispositif et des sondes en vue d'éradiquer l'infection. De plus, l'application des connaissances issues d'une vaste littérature à un groupe disparate de médecins praticiens a souvent été inadéquate. La présente revue sur la prise en charge des infections liées aux DECI illustre les avancées importantes réalisées au cours de la dernière décennie, notamment les critères diagnostiques, l'imagerie avancée et le séquençage de prochaine génération des cas à culture négative ou de ceux pour lesquels des incertitudes demeurent. Nous avons aussi décrit le rôle et les indications d'extraction des sondes fonctionnelles, le processus du choix des antibiotiques et de la durée du traitement, les considérations relatives au moment et au lieu de la réimplantation, et la stratification du risque en préimplantation et les interventions associées afin de réduire le risque d'infections liées aux DECI.

Developmental constraints enforce altruism and avert the tragedy of the commons in a social microbe.

Organisms often cooperate through the production of freely available public goods. This can greatly benefit the group but is vulnerable to the "tragedy of the commons" if individuals lack the motivation to make the necessary investment into public goods production. Relatedness to groupmates can motivate individual investment because group success ultimately benefits their genes' own self-interests. However, systems often lack mechanisms that can reliably ensure that relatedness is high enough to promote cooperation. Consequently, groups face a persistent threat from the tragedy unless they have a mechanism to enforce investment when relatedness fails to provide adequate motivation. To understand the real threat posed by the tragedy and whether groups can avert its impact, we determine how the social amoeba Dictyostelium discoideum responds as relatedness decreases to levels that should induce the tragedy. We find that, while investment in public goods declines as overall within-group relatedness declines, groups avert the expected catastrophic collapse of the commons by continuing to invest, even when relatedness should be too low to incentivize any contribution. We show that this is due to a developmental buffering system that generates enforcement because insufficient cooperation perturbs the balance of a negative feedback system controlling multicellular development. This developmental constraint enforces investment under the conditions expected to be most tragic, allowing groups to avert a collapse in cooperation. These results help explain how mechanisms that suppress selfishness and enforce cooperation can arise inadvertently as a by-product of constraints imposed by selection on different traits.

The genetic architecture underlying prey-dependent performance in a microbial predator.

Natural selection should favour generalist predators that outperform specialists across all prey types. Two genetic solutions could explain why intraspecific variation in predatory performance is, nonetheless, widespread: mutations beneficial on one prey type are costly on another (antagonistic pleiotropy), or mutational effects are prey-specific, which weakens selection, allowing variation to persist (relaxed selection). To understand the relative importance of these alternatives, we characterised natural variation in predatory performance in the microbial predator Dictyostelium discoideum. We found widespread nontransitive differences among strains in predatory success across different bacterial prey, which can facilitate stain coexistence in multi-prey environments. To understand the genetic basis, we developed methods for high throughput experimental evolution on different prey (REMI-seq). Most mutations (~77%) had prey-specific effects, with very few (~4%) showing antagonistic pleiotropy. This highlights the potential for prey-specific effects to dilute selection, which would inhibit the purging of variation and prevent the emergence of an optimal generalist predator.

Dictyostelium discoideum: An Alternative Nonanimal Model for Developmental Toxicity Testing.

A critical aspect of toxicity evaluation is developmental and reproductive toxicity (DART) testing. Traditionally, DART testing has been conducted in vivo in mammalian model systems. New legislation aimed at reducing animal use and the prohibitive costs associated with DART testing, together with a need to understand the genetic pathways underlying developmental toxicity means there is a growing demand for alternative model systems for toxicity evaluation. Here we explore the potential of the eukaryotic social amoeba Dictyostelium discoideum, which is already widely used as a simple model system for cell and developmental biology, as a potential nonanimal model for DART testing. We developed assays for high-throughput screening of toxicity during D. discoideum growth and development. This allowed the toxicity of a broad range of test compounds to be characterized, which revealed that D. discoideum can broadly predict mammalian toxicity. In addition, we show that this system can be used to perform functional genomic screens to compare the molecular modes of action of different compounds. For example, genome-wide screens for mutations that affect lithium and valproic acid toxicity allowed common and unique biological targets and molecular processes mediating their toxicity to be identified. These studies illustrate that D. discoideum could represent a predictive nonanimal model for DART testing due to its amenability to high-throughput approaches and molecular genetic tractability.

Mutant resources for functional genomics in Dictyostelium discoideum using REMI-seq technology.

BACKGROUND: Genomes can be sequenced with relative ease, but ascribing gene function remains a major challenge. Genetically tractable model systems are crucial to meet this challenge. One powerful model is the social amoeba Dictyostelium discoideum, a eukaryotic microbe widely used to study diverse questions in the cell, developmental and evolutionary biology. RESULTS: We describe REMI-seq, an adaptation of Tn-seq, which allows high throughput, en masse, and quantitative identification of the genomic site of insertion of a drug resistance marker after restriction enzyme-mediated integration. We use REMI-seq to develop tools which greatly enhance the efficiency with which the sequence, transcriptome or proteome variation can be linked to phenotype in D. discoideum. These comprise (1) a near genome-wide resource of individual mutants and (2) a defined pool of 'barcoded' mutants to allow large-scale parallel phenotypic analyses. These resources are freely available and easily accessible through the REMI-seq website that also provides comprehensive guidance and pipelines for data analysis. We demonstrate that integrating these resources allows novel regulators of cell migration, phagocytosis and macropinocytosis to be rapidly identified. CONCLUSIONS: We present methods and resources, generated using REMI-seq, for high throughput gene function analysis in a key model system.

Inferring Adaptive Codon Preference to Understand Sources of Selection Shaping Codon Usage Bias.

Alternative synonymous codons are often used at unequal frequencies. Classically, studies of such codon usage bias (CUB) attempted to separate the impact of neutral from selective forces by assuming that deviations from a predicted neutral equilibrium capture selection. However, GC-biased gene conversion (gBGC) can also cause deviation from a neutral null. Alternatively, selection has been inferred from CUB in highly expressed genes, but the accuracy of this approach has not been extensively tested, and gBGC can interfere with such extrapolations (e.g., if expression and gene conversion rates covary). It is therefore critical to examine deviations from a mutational null in a species with no gBGC. To achieve this goal, we implement such an analysis in the highly AT rich genome of Dictyostelium discoideum, where we find no evidence of gBGC. We infer neutral CUB under mutational equilibrium to quantify "adaptive codon preference," a nontautologous genome wide quantitative measure of the relative selection strength driving CUB. We observe signatures of purifying selection consistent with selection favoring adaptive codon preference. Preferred codons are not GC rich, underscoring the independence from gBGC. Expression-associated "preference" largely matches adaptive codon preference but does not wholly capture the influence of selection shaping patterns across all genes, suggesting selective constraints associated specifically with high expression. We observe patterns consistent with effects on mRNA translation and stability shaping adaptive codon preference. Thus, our approach to quantifying adaptive codon preference provides a framework for inferring the sources of selection that shape CUB across different contexts within the genome.

Cutting-Edge Microscopy Systems as Remote Teaching and Research Tools for Undergraduate Students.

Whether due to illness, weather, safety, or other concerns, it is very difficult for biology students to gather meaningful and timely data without access to campus. This has been especially evident during the COVID-19 pandemic, in which most laboratory exercises have been conducted as a simulation. Simulated experiments provide a stopgap for certain courses, but for upper-level and research courses, they are often insufficient. Many new microscopy tools now on the market can be adapted to allow students to generate and analyze novel data with little aid from instructors. Remote brightfield-based systems like the CytoSMART Lux2 can be used to gather real-time insight into the progression of cell growth, cell migration, and cell viability over time. The data from these systems can be viewed via the Internet or downloaded for later analysis. Confocal microscopy also offers unique remote-learning opportunities. Because these fluorescence-based microscopes are controlled almost exclusively by a computer, free "remote desktop" software can allow students to learn how to use this cutting-edge technology and can also allow for the generation and analysis of novel data. While these systems can be expensive, they offer a variety of benefits for undergraduate students and researchers, whether they are in the laboratory or working remotely.

In-Office Tympanostomy Tube Placement in Children Using Iontophoresis and Automated Tube Delivery.

OBJECTIVES/HYPOTHESIS: Evaluate technical success, tolerability, and safety of lidocaine iontophoresis and tympanostomy tube placement for children in an office setting. STUDY DESIGN: Prospective individual cohort study. METHODS: This prospective multicenter study evaluated in-office tube placement in children ages 6 months through 12 years of age. Anesthesia was achieved via lidocaine/epinephrine iontophoresis. Tube placement was conducted using an integrated and automated myringotomy and tube delivery system. Anxiolytics, sedation, and papoose board were not used. Technical success and safety were evaluated. Patients 5 to 12 years old self-reported tube placement pain using the Faces Pain Scale-Revised (FPS-R) instrument, which ranges from 0 (no pain) to 10 (very much pain). RESULTS: Children were enrolled into three cohorts with 68, 47, and 222 children in the Operating Room (OR) Lead-In, Office Lead-In, and Pivotal cohorts, respectively. In the Pivotal cohort, there were 120 and 102 children in the <5 and 5- to 12-year-old age groups, respectively, with a mean age of 2.3 and 7.6 years, respectively. Bilateral tube placement was indicated for 94.2% of children <5 and 88.2% of children 5 to 12 years old. Tubes were successfully placed in all indicated ears in 85.8% (103/120) of children <5 and 89.2% (91/102) of children 5 to 12 years old. Mean FPS-R score was 3.30 (standard deviation [SD] = 3.39) for tube placement and 1.69 (SD = 2.43) at 5 minutes postprocedure. There were no serious adverse events. Nonserious adverse events occurred at rates similar to standard tympanostomy procedures. CONCLUSIONS: In-office tube placement in selected patients can be successfully achieved without requiring sedatives, anxiolytics, or papoose restraints via lidocaine iontophoresis local anesthesia and an automated myringotomy and tube delivery system. LEVEL OF EVIDENCE: 2b Laryngoscope, 130:S1-S9, 2020.

Conditional expression explains molecular evolution of social genes in a microbe.

Conflict is thought to play a critical role in the evolution of social interactions by promoting diversity or driving accelerated evolution. However, despite our sophisticated understanding of how conflict shapes social traits, we have limited knowledge of how it impacts molecular evolution across the underlying social genes. Here we address this problem by analyzing the genome-wide impact of social interactions using genome sequences from 67 Dictyostelium discoideum strains. We find that social genes tend to exhibit enhanced polymorphism and accelerated evolution. However, these patterns are not consistent with conflict driven processes, but instead reflect relaxed purifying selection. This pattern is most likely explained by the conditional nature of social interactions, whereby selection on genes expressed only in social interactions is diluted by generations of inactivity. This dilution of selection by inactivity enhances the role of drift, leading to increased polymorphism and accelerated evolution, which we call the Red King process.

Coenzyme A and protein CoAlation levels are regulated in response to oxidative stress and during morphogenesis in Dictyostelium discoideum.

Dictyostelium discoideum (D. discoideum) is a simple eukaryote with a unique life cycle in which it differentiates from unicellular amoebae into a fruiting body upon starvation. Reactive oxygen species (ROS) have been associated with bacterial predation, as well as regulatory events during D. discoideum development and differentiation. Coenzyme A (CoA) is a key metabolic integrator in all living cells. A novel function of CoA in redox regulation, mediated by covalent attachment of CoA to cellular proteins in response to oxidative or metabolic stress, has been recently discovered and termed protein CoAlation. In this study, we report that the level of CoA and protein CoAlation in D. discoideum are developmentally regulated, and correlate with the temporal expression pattern of genes implicated in CoA biosynthesis during morphogenesis. Furthermore, treatment of growing D. discoideum cells with oxidising agents results in a dose-dependent increase of protein CoAlation. However, much higher concentrations were required when compared to mammalian cells and bacteria. Increased resistance of D. discoideum to oxidative stress induced by H2O2 has previously been attributed to high levels of catalase activity. In support of this notion, we found that H2O2-induced protein CoAlation is significantly increased in CatA-deficient D. discoideum cells. Collectively, this study provides insights into the role of CoA and protein CoAlation in the maintenance of redox homeostasis in amoeba and during D. discoideum morphogenesis.

A Seat at the Table.

Organized medicine and psychiatry have a long tradition of governmental advocacy and public engagement. The American Academy of Psychiatry and the Law (AAPL), since its founding 50 years ago, has made some forays into these fields. However, its involvement has been less substantial than other similarly situated professional organizations. With its increasing membership and expertise, AAPL now possesses the capacity to dedicate some of its organizational attention, energy, and resources to educating policymakers and the public on current and future topics related to forensic mental health. In addition, an increasing number and type of professional activities related to this discipline are affected by governmental regulation and public opinion. Therefore, the need to become involved in shaping policy is more urgent, particularly in light of the fact that other forensic mental health organizations have been actively involved in governmental advocacy for decades. Finally, as a field and in the near future, we likely will deal with life-changing technological innovations related to the practice of forensic psychiatry. AAPL and its members are perhaps uniquely qualified and have a responsibility to help ensure that these innovations are developed, implemented, and utilized appropriately. This can only be accomplished by having a proverbial seat at the table in the process.

Cell Cycle Heterogeneity Can Generate Robust Cell Type Proportioning.

Cell-cell heterogeneity can facilitate lineage choice during embryonic development because it primes cells to respond to differentiation cues. However, remarkably little is known about the origin of heterogeneity or whether intrinsic and extrinsic variation can be controlled to generate reproducible cell type proportioning seen in vivo. Here, we use experimentation and modeling in D. discoideum to demonstrate that population-level cell cycle heterogeneity can be optimized to generate robust cell fate proportioning. First, cell cycle position is quantitatively linked to responsiveness to differentiation-inducing signals. Second, intrinsic variation in cell cycle length ensures cells are randomly distributed throughout the cell cycle at the onset of multicellular development. Finally, extrinsic perturbation of optimal cell cycle heterogeneity is buffered by compensatory changes in global signal responsiveness. These studies thus illustrate key regulatory principles underlying cell-cell heterogeneity optimization and the generation of robust and reproducible fate choice in development.

Strategic investment explains patterns of cooperation and cheating in a microbe.

Contributing to cooperation is typically costly, while its rewards are often available to all members of a social group. So why should individuals be willing to pay these costs, especially if they could cheat by exploiting the investments of others? Kin selection theory broadly predicts that individuals should invest more into cooperation if their relatedness to group members is high (assuming they can discriminate kin from nonkin). To better understand how relatedness affects cooperation, we derived the ?Collective Investment" game, which provides quantitative predictions for patterns of strategic investment depending on the level of relatedness. We then tested these predictions by experimentally manipulating relatedness (genotype frequencies) in mixed cooperative aggregations of the social amoeba Dictyostelium discoideum, which builds a stalk to facilitate spore dispersal. Measurements of stalk investment by natural strains correspond to the predicted patterns of relatedness-dependent strategic investment, wherein investment by a strain increases with its relatedness to the group. Furthermore, if overall group relatedness is relatively low (i.e., no strain is at high frequency in a group) strains face a scenario akin to the "Prisoner's Dilemma" and suffer from insufficient collective investment. We find that strains employ relatedness-dependent segregation to avoid these pernicious conditions. These findings demonstrate that simple organisms like D. discoideum are not restricted to being ?cheaters" or ?cooperators" but instead measure their relatedness to their group and strategically modulate their investment into cooperation accordingly. Consequently, all individuals will sometimes appear to cooperate and sometimes cheat due to the dynamics of strategic investing.

Curcumin and derivatives function through protein phosphatase 2A and presenilin orthologues in Dictyostelium discoideum.

Natural compounds often have complex molecular structures and unknown molecular targets. These characteristics make them difficult to analyse using a classical pharmacological approach. Curcumin, the main curcuminoid of turmeric, is a complex molecule possessing wide-ranging biological activities, cellular mechanisms and roles in potential therapeutic treatment, including Alzheimer's disease and cancer. Here, we investigate the physiological effects and molecular targets of curcumin in Dictyostelium discoideum We show that curcumin exerts acute effects on cell behaviour, reduces cell growth and slows multicellular development. We employed a range of structurally related compounds to show the distinct role of different structural groups in curcumin's effects on cell behaviour, growth and development, highlighting active moieties in cell function, and showing that these cellular effects are unrelated to the well-known antioxidant activity of curcumin. Molecular mechanisms underlying the effect of curcumin and one synthetic analogue (EF24) were then investigated to identify a curcumin-resistant mutant lacking the protein phosphatase 2A regulatory subunit (PsrA) and an EF24-resistant mutant lacking the presenilin 1 orthologue (PsenB). Using in silico docking analysis, we then showed that curcumin might function through direct binding to a key regulatory region of PsrA. These findings reveal novel cellular and molecular mechanisms for the function of curcumin and related compounds.